High Performance Technical Textiles 9781119325055, 9781119325031, 9781119325017, 1119325056
An authentic resource for thefundamentals, applied techniques, applicationsand recent advancements of all the main areas
426 115 16MB
English Pages 504 [489] Year 2019
Cover......Page 1
Front page......Page 3
Copyright......Page 4
Contents......Page 5
List of Contributors......Page 10
1.2 Application Areas of Technical Textiles......Page 13
1.3 Technical Textiles by Functional Finishing......Page 14
1.4.1 Household and Packaging Textiles......Page 15
1.4.3 Medical Textiles......Page 16
1.4.5 Personal Protective Clothing......Page 17
1.4.8 Geotextiles and Environmental Protection Textiles......Page 18
1.4.10 Building and Construction Textiles......Page 19
1.4.12 Marine Textiles......Page 20
1.5 Conclusion......Page 21
2.2 Textile Materials, Properties, and Manufacturing......Page 23
2.2.1.1 Types and Properties......Page 24
2.2.1.2 Manufacturing......Page 26
2.2.2.1 Types and Properties......Page 28
2.3.1 Household Textiles......Page 32
2.3.2 Packaging Textiles......Page 33
2.4.1 Household Textiles......Page 35
2.4.2 Packaging Textiles......Page 37
2.5.1 Household Textiles......Page 38
2.5.2 Packaging Textiles......Page 42
References......Page 44
3.2 Textile Fibres......Page 49
3.2.1 Natural Fibres......Page 50
3.2.2 Regenerated Fibres......Page 51
3.2.3 Synthetic Fibres......Page 52
3.2.4 Special Fibres......Page 53
3.3 Developments in Yarns......Page 54
3.4 Developments in Fabric Structures......Page 55
3.5 Special Finishes......Page 57
3.6.2 Desirable Attributes of Functional Sportswear......Page 58
3.6.4 Requirements for an Active Sportswear......Page 60
3.6.5 Moisture Management......Page 62
3.6.6.1 Thermal Insulation......Page 63
3.6.6.2 Cold Protective Clothing......Page 64
3.6.6.4 Layered Clothing......Page 65
3.6.6.5 Comfort......Page 66
3.6.9 Multiple Criteria Decision Making......Page 67
3.7.3 Patterning......Page 69
3.8.1 Wearable Technology......Page 70
3.9 Testing Methods and Quality Control......Page 73
References......Page 74
4.1.1 Medtech Definition......Page 80
4.2 Textile Materials, Structures, and Processes......Page 81
4.3 High Performance Applications of Medical Textiles......Page 83
4.4 Nanotechnology in Medicine and Healthcare......Page 87
4.4.1 Blood Vessels......Page 89
4.4.2 Wound Healing......Page 90
4.4.3 Drug Delivery......Page 91
4.5 Thermo‐Physiological Comfort of Medical Textiles......Page 92
4.6 Biocompatibility – Bioresorbability – Biostability......Page 94
4.7 Intelligent Medical and Healthcare Textiles......Page 96
4.8 Antimicrobial Textiles......Page 104
4.9 Testing Methods and Quality Control......Page 106
4.10 Sustainability and Ecological Aspects......Page 109
References......Page 111
5.1 Introduction......Page 117
5.2 Performance Requirements of Protective Textiles......Page 119
5.3 High Performance Fibres......Page 120
5.4.1 Protection Against Cold......Page 125
5.4.1.1 Feather and Down Fibres......Page 126
5.4.1.2 Kapok......Page 128
5.4.1.4 Synthetic Insulative Materials......Page 129
5.4.1.5 Other Thermal Insulative Materials......Page 130
5.4.2 Protection Against Mechanical Cut Hazards......Page 131
5.4.3 Protection Against Flame and Heat [80]......Page 132
5.5.1 Thermal Burden from Protective Clothing......Page 141
5.5.2 Materials for Improving Thermo‐Physiological Comfort......Page 143
5.5.3 Phase Change Materials (PCMs)......Page 144
5.5.4 Smart Structure for Protection and Thermal Comfort......Page 146
5.5.5 Active Cooling System for Clothing Comfort......Page 147
5.6.1 Protective Clothing and Gloves Against Cold......Page 148
5.6.3 Protective Clothing Against Radiation......Page 149
5.6.6 Protective Clothing Against Mechanical Hazards......Page 150
5.6.8 Other Standards......Page 151
5.8 Conclusion......Page 158
References......Page 159
6.1 Introduction......Page 168
6.2 General Aspects of Textile Based PPC......Page 169
6.3.1 Natural Fibres......Page 171
6.3.2 Synthetic Fibres......Page 172
6.3.3 Dyed Fibres......Page 175
6.4 Yarns for PPC......Page 176
6.4.1 Ring‐Spun Yarns......Page 177
6.4.2.1 Rotor‐Spun Yarn......Page 179
6.4.2.3 Air‐Jet‐Spun Yarn......Page 180
6.4.3 Dyed Yarn......Page 181
6.5 Fabrics for PPC......Page 182
6.5.2 Knitted Fabrics......Page 183
6.5.3 Nonwoven Fabrics......Page 184
6.5.5 Dyed and Printed Fabrics......Page 186
6.5.6 Finished Fabrics......Page 187
6.5.7 Fabric Testing......Page 188
6.6 PPC Fabrication......Page 192
6.7.1 Development of New High Performance Fabric Materials......Page 196
6.7.2 Ecologically Sustainable Processing Techniques and Materials......Page 197
References......Page 198
7.2 Ballistic and Sharp Weapon Protection......Page 205
7.2.1 Protective Materials......Page 207
7.2.2 Test Methods......Page 210
7.3.2 Mechanisms of Injury......Page 211
7.4 Chemical, Biological, Radiological, and Nuclear (CBRN)Protective Clothing......Page 214
7.6 Conclusion......Page 218
References......Page 219
8.1 Introduction......Page 222
8.2.1 High Performance Synthetic Fibres......Page 223
8.2.2.2 Pollutant Capture Mechanism of Fibrous Filters......Page 224
8.2.2.3 Synthetic Polymers for Technical Nanofibres......Page 225
8.3 Natural Fibres for Technical Applications......Page 226
8.3.2 Technical Applications of Natural Fibres......Page 227
8.4.1 Electrospinning for Technical Textiles......Page 228
8.4.2.1 Fibre Diameter......Page 229
8.4.3.1 Monofilaments......Page 230
8.4.3.3 Fibrillated Tape Yarns......Page 231
8.5.1 Heat‐Setting Process......Page 232
8.5.4 Calendering Technique......Page 233
8.6 Textile Reinforced Composite Materials......Page 234
8.7.2 Needlefelts......Page 235
8.8.1 General Quality Control Tests......Page 236
8.8.4.1 Geometrical Characterization......Page 237
8.8.4.2 Chemical Characterization......Page 238
8.9 Sustainability and Ecological Aspects......Page 239
8.10 Conclusion......Page 240
References......Page 241
9.1 Introduction......Page 245
9.2 Structure and Performance......Page 246
9.3 Fibres for Geotextiles......Page 249
9.3.1 Natural Fibres......Page 250
9.3.2 Synthetic Fibres......Page 257
9.3.3 Nonpolymeric Fibres......Page 259
9.4 Geotextiles and Soil......Page 260
9.5 Manufacturing Techniques......Page 266
9.5.1 Two‐Dimensional Woven Fabric......Page 267
9.5.2 Triaxial Fabrics......Page 270
9.5.4 Nonwovens......Page 272
9.5.4.1 Standard Nonwovens......Page 273
9.5.4.2.1 Mechanical Fixation of Surfaces of Nonwoven Structures......Page 274
9.5.4.2.2 Principle of Quasi‐Yarn Formation......Page 275
9.5.4.2.3 ROTIS Principle of Nonwoven Structures Production......Page 276
9.6 Sustainability and Ecological Aspects......Page 278
9.6.2 Environmental Impacts of Geotextiles......Page 279
9.7 Conclusion......Page 280
References......Page 281
10.1 Introduction......Page 285
10.2.1 Natural Fibres......Page 286
10.2.3 Biopolymers......Page 288
10.2.4 Nanofibres......Page 289
10.3 Textile Structures for Agrotextiles......Page 290
10.4.1 Nets and Protection Barriers for Crops......Page 291
10.4.2 Fishing Nets......Page 293
10.4.5 Crop Covers, Floating Row Covers, Row Covers......Page 297
10.5 Testing Standards Applicable to Agrotextiles......Page 301
10.5.1 Mechanical Properties......Page 304
10.5.1.1 Tensile Strength......Page 307
10.5.2 Optical and Radiative Properties......Page 310
10.5.3 Biodegradability......Page 312
10.5.5 Measurement of Air Permeability......Page 314
10.5.6 Fabric Weight......Page 316
10.6 Sustainability and Ecological Aspects......Page 317
10.7 Conclusion......Page 318
References......Page 319
11.1 Introduction......Page 325
11.2 Architectural Textiles......Page 326
11.2.1.1 Air Supported Structure......Page 328
11.2.3 Material Requirements......Page 329
11.2.3.1 Mechanical Properties......Page 331
11.2.3.3 Thermal Behaviour......Page 332
11.3 House Wraps......Page 333
11.3.1.1 Water Resistance......Page 335
11.3.1.2 Durability......Page 336
11.3.1.4 Drainage......Page 337
11.3.2 House Wrap Materials......Page 339
11.4 Insulation......Page 340
11.4.1 Types of Insulating Materials......Page 341
11.4.3 Fibrous Insulating Materials......Page 342
11.4.3.1.1 Fibreglass......Page 344
11.4.3.2 Organic Fibres......Page 345
11.5 Textile Reinforced Concrete......Page 347
11.5.1 Requirements for Textile Reinforcement Materials......Page 348
11.5.2 Types of Reinforcing Fibrous Materials......Page 349
11.5.3 Applications of Textile Reinforced Concrete......Page 352
11.6 Sustainability and Ecological Issues......Page 353
References......Page 355
12.1 Introduction......Page 359
12.2.2 Classification of Automotive Textiles......Page 360
12.3.1 Seat Covers and Upholstery......Page 361
12.3.1.2 Properties......Page 362
12.3.1.4 Utility Performance of Seats......Page 363
12.3.2 Carpets......Page 365
12.3.3 Roof Headliner......Page 366
12.3.4.1 Manufacturing Process......Page 367
12.3.4.2 Seatbelt Material Properties......Page 368
12.3.5 Airbags......Page 369
12.3.5.1 Fabrics for Airbags......Page 370
12.3.5.2 Future Trends......Page 371
12.3.10 Tyre Cord Fabric......Page 372
12.3.12 Filters and Engine Compartment Items......Page 373
12.3.13 Acoustic Textiles......Page 374
12.4 Textile Composites for Automobiles......Page 375
12.4.1 Textile Structural Composites......Page 376
12.4.3 An Engineered Alternative......Page 377
12.5 3D Fabrics for Automotive Applications......Page 378
12.5.1 Applications Areas......Page 379
12.5.2 3D Woven Structures for Reinforcements......Page 380
12.5.3 Advantages of 3D Woven Preforms......Page 381
12.6 Comfort Properties of Automotive Interior......Page 382
12.6.2 Warmth Sensation......Page 383
12.6.3 Moisture Sensation......Page 384
12.7 Conclusion......Page 385
References......Page 386
13.2 Textiles for Marine Applications......Page 390
13.2.1.2 Glass Fibre......Page 391
13.2.1.6 Carbon Fibre......Page 392
13.2.2.2 Vinyl Ester Resin......Page 393
13.2.3.1 Balsa......Page 394
13.2.3.7 FRP Planking......Page 395
13.2.4.2 Reinforcement Fabric......Page 396
13.2.4.2.1 Woven Reinforcement Structure......Page 397
13.2.4.2.3 Omnidirectional Reinforcement Structure......Page 398
13.3.1 Antifouling......Page 399
13.3.2 Flame‐Retardant Nature......Page 400
13.4.1 Furnishing Fabrics......Page 402
13.4.3 Hovercrafts Skirts......Page 403
13.4.5 Naval Ships and Submarines......Page 404
13.4.7 Oil–Water Separation......Page 405
References......Page 408
14.1 Introduction......Page 412
14.2 Synthetic and Nanotechnical Fibres......Page 413
14.2.1 Carbon Fibre......Page 414
14.2.3 Glass Fibre......Page 415
14.2.4 Vectran Fibre......Page 416
14.2.6 Graphene......Page 417
14.3.1 Flax......Page 418
14.3.3 Jute......Page 419
14.4.1 Spinning......Page 420
14.4.2 Electrospinning......Page 421
14.4.4 Three‐Dimensional Weaving......Page 422
14.4.5 Knitting......Page 423
14.4.7 Nonwoven/Stitching......Page 424
14.5.1 Hand Lay‐Up Technique......Page 425
14.5.2 Vacuum Bagging Technique......Page 426
14.5.4 Injection Moulding......Page 427
14.5.5 Autoclave......Page 428
14.5.6 Pultrusion......Page 429
14.6 Textile Composite Material Finishing......Page 430
14.7.2 Textile Composites in the Aerospace Industry......Page 431
14.7.2.3 Wing......Page 432
14.8 Testing Methods and Quality Control......Page 433
14.8.2 Compression Testing......Page 434
14.8.3 Shear Testing......Page 435
14.9 Self‐Healing of Composite Materials......Page 436
14.11 Conclusion......Page 437
References......Page 438
15.1 Introduction......Page 443
15.3.1 Shape Memory Materials......Page 444
15.3.2 Optical Textiles......Page 445
15.3.3 Wearable Electronics......Page 447
15.3.3.1 Piezoelectric Sensors......Page 449
15.3.3.2 Diapers and Incontinence Products with Sensors......Page 450
15.3.7 Warfare Protective Clothing......Page 451
15.3.8 Phase Change Materials......Page 454
15.3.9 Chromic Textiles......Page 456
15.4 Application of Smart Textiles......Page 457
15.4.1.2 On the Patient......Page 459
15.4.1.3 In the Patient......Page 460
15.4.2 Healthcare Applications......Page 462
15.4.3 Sports and Fitness......Page 463
15.4.5 Conductive Ink on Textiles......Page 464
15.5 Sustainability and Ecological Aspects......Page 466
References......Page 468
Index......Page 478
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High Performance Technical Textiles
High Performance Technical Textiles Edited by Roshan Paul
University of Beira Interior, Portugal
This edition first published 2019 © 2019 John Wiley & Sons Ltd All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by law. Advice on how to obtain permission to reuse material from this title is available at http://www.wiley.com/go/permissions. The right of Roshan Paul to be identified as the author of the editorial material in this work has been asserted in accordance with law. Registered Offices John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USA John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK Editorial Office The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK For details of our global editorial offices, customer services, and more information about Wiley products visit us at www.wiley.com. Wiley also publishes its books in a variety of electronic formats and by print‐on‐demand. Some content that appears in standard print versions of this book may not be available in other formats. Limit of Liability/Disclaimer of Warranty In view of ongoing research, equipment modifications, changes in governmental regulations, and the constant flow of information relating to the use of experimental reagents, equipment, and devices, the reader is urged to review and evaluate the information provided in the package insert or instructions for each chemical, piece of equipment, reagent, or device for, among other things, any changes in the instructions or indication of usage and for added warnings and precautions. While the publisher and authors have used their best efforts in preparing this work, they make no representations or warranties with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties, including without limitation any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives, written sales materials or promotional statements for this work. The fact that an organization, website, or product is referred to in this work as a citation and/or potential source of further information does not mean that the publisher and authors endorse the information or services the organization, website, or product may provide or recommendations it may make. This work is sold with the understanding that the publisher is not engaged in rendering professional services. The advice and strategies contained herein may not be suitable for your situation. You should consult with a specialist where appropriate. Further, readers should be aware that websites listed in this work may have changed or disappeared between when this work was written and when it is read. Neither the publisher nor authors shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages. Library of Congress Cataloging‐in‐Publication Data Names: Paul, Roshan. Title: High performance technical textiles / edited by Roshan Paul, University of Beira Interior, Portugal. Description: First edition. | Hoboken, NJ, USA : Wiley, [2019] | Includes bibliographical references and index. | Identifiers: LCCN 2018049413 (print) | LCCN 2018050917 (ebook) | ISBN 9781119325055 (AdobePDF) | ISBN 9781119325031 (ePub) | ISBN 9781119325017 (hardcover) Subjects: LCSH: Industrial fabrics. | Geotextiles. | Synthetic fabrics. Classification: LCC TS1770.I53 (ebook) | LCC TS1770.I53 H54 2019 (print) | DDC 677/.6–dc23 LC record available at https://lccn.loc.gov/2018049413
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Contents
List of Contributors xi
1
High Performance Technical Textiles: An Overview 1 Roshan Paul
1.1 Introduction 1 1.2 Application Areas of Technical Textiles 1 1.3 Technical Textiles by Functional Finishing 2 1.4 High Performance Technical Textiles 3 1.5 Conclusion 9 2
Household and Packaging Textiles 11 Pelagia Glampedaki
2.1 Introduction 11 2.2 Textile Materials, Properties, and Manufacturing 11 2.3 High Performance Applications 20 2.4 Testing Methods and Quality Control 23 2.5 Sustainability and Ecological Aspects 26 2.6 Conclusion 32 References 32 3
Sports Textiles and Comfort Aspects 37 Ali Harlin, Kirsi Jussila, and Elina Ilen
3.1 Introduction 37 3.2 Textile Fibres 37 3.3 Developments in Yarns 42 3.4 Developments in Fabric Structures 43 3.5 Special Finishes 45 3.6 High Performance Applications 46 3.7 Active Textiles 57 3.8 Smart Textiles and Garments 58 3.9 Testing Methods and Quality Control 61 3.10 Sustainability and Ecological Aspects 62 3.11 Conclusion 62 References 62
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Contents
4
Medical and Healthcare Textiles 69 Nuno Belino, Raul Fangueiro, Sohel Rana, Pelagia Glampedaki, and Georgios Priniotakis
4.1 Introduction 69 4.2 Textile Materials, Structures, and Processes 70 4.3 High Performance Applications of Medical Textiles 72 4.4 Nanotechnology in Medicine and Healthcare 76 4.5 Thermo‐Physiological Comfort of Medical Textiles 81 4.6 Biocompatibility – Bioresorbability – Biostability 83 4.7 Intelligent Medical and Healthcare Textiles 85 4.8 Antimicrobial Textiles 93 4.9 Testing Methods and Quality Control 95 4.10 Sustainability and Ecological Aspects 98 4.11 Conclusion 100 References 100 5
Textile Materials for Protective Textiles 107 Ningtao Mao
5.1 Introduction 107 5.2 Performance Requirements of Protective Textiles 109 5.3 High Performance Fibres 110 5.4 High Performance Textile Materials 115 5.5 Thermal Burden and Thermo‐Physiological Comfort 131 5.6 Testing Methods and Standards 138 5.7 Sustainability and Ecological Issues 148 5.8 Conclusion 148 References 149 6
Personal Protective Textiles and Clothing 159 Sumit Mandal, Simon Annaheim, Martin Camenzind, and René M. Rossi
6.1 Introduction 159 6.2 General Aspects of Textile Based PPC 160 6.3 Fibres for PPC 162 6.4 Yarns for PPC 167 6.5 Fabrics for PPC 173 6.6 PPC Fabrication 183 6.7 Key Issues Related to PPC 187 6.8 Conclusion 189 References 189 7
Textiles for Military and Law Enforcement Personnel 197 Christopher Malbon and Debra Carr
7.1 Introduction 197 7.2 Ballistic and Sharp Weapon Protection 197 7.3 Protection from Heat and Flames 203 7.4 Chemical, Biological, Radiological, and Nuclear (CBRN) Protective Clothing 206
Contents
7.5 Functional Finishing 210 7.6 Conclusion 210 References 211 8
Industrial and Filtration Textiles 215 Tawfik A. Khattab and Hany Helmy
8.1 Introduction 215 8.2 Synthetic and Nanotechnical Fibres 216 8.3 Natural Fibres for Technical Applications 219 8.4 Manufacture of Technical Textiles 221 8.5 Functional Finishing 225 8.6 Textile Reinforced Composite Materials 227 8.7 High Performance Applications 228 8.8 Testing Methods and Quality Control 229 8.9 Sustainability and Ecological Aspects 232 8.10 Conclusion 233 References 234 9
Geotextiles and Environmental Protection Textiles 239 Jiří Militký, Rajesh Mishra, and Mohanapriya Venkataraman
9.1 Introduction 239 9.2 Structure and Performance 240 9.3 Fibres for Geotextiles 243 9.4 Geotextiles and Soil 254 9.5 Manufacturing Techniques 260 9.6 Sustainability and Ecological Aspects 272 9.7 Conclusion 274 References 275 10
Agrotextiles and Crop Protection Textiles 279 Adriana Restrepo‐Osorio, Catalina Álvarez‐López, Natalia Jaramillo‐Quiceno, and Patricia Fernández‐Morales
10.1 Introduction 279 10.2 Fibres for Agrotextiles 280 10.3 Textile Structures for Agrotextiles 284 10.4 High Performance Applications 285 10.5 Testing Standards Applicable to Agrotextiles 295 10.6 Sustainability and Ecological Aspects 311 10.7 Conclusion 312 References 313 11
Building and Construction Textiles 319 Jordan Tabor and Tushar Ghosh
11.1 Introduction 319 11.2 Architectural Textiles 320 11.3 House Wraps 327 11.4 Insulation 334
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Contents
11.5 Textile Reinforced Concrete 341 11.6 Sustainability and Ecological Issues 347 11.7 Conclusion 349 References 349 12
Automotive Textiles and Composites 353 Bijoy K. Behera
12.1 Introduction 353 12.2 Mobiltech 354 12.3 Application Areas of Automotive Textiles 355 12.4 Textile Composites for Automobiles 369 12.5 3D Fabrics for Automotive Applications 372 12.6 Comfort Properties of Automotive Interior 376 12.7 Conclusion 379 References 380 13
Marine Textiles and Composites 385 Chi‐wai Kan and Change Zhou
13.1 Introduction 385 13.2 Textiles for Marine Applications 385 13.3 Properties of Textiles for Marine Applications 394 13.4 Marine Textiles and Quality Standards 397 13.5 Sustainability and Ecological Aspects 403 13.6 Conclusion 403 Acknowledgement 403 References 403 14
Aeronautical and Space Textiles 407 Sadaf A. Abbasi, Lijing Wang, Mazhar H. Peerzada, and Raj Ladani
14.1 Introduction 407 14.2 Synthetic and Nanotechnical Fibres 408 14.3 Natural and Bast Fibres for Technical Applications 413 14.4 Manufacture of Technical Textiles 415 14.5 Textile Reinforced Composite Materials 420 14.6 Textile Composite Material Finishing 425 14.7 High Performance Applications 426 14.8 Testing Methods and Quality Control 428 14.9 Self‐Healing of Composite Materials 431 14.10 Sustainability and Ecological Aspects 432 14.11 Conclusion 432 References 433 15
Wearable and Smart Responsive Textiles 439 Lihua Lou, Weijie Yu, and Seshadri Ramkumar
15.1 Introduction 439 15.2 Characterization of Smart Textiles 440 15.3 Smart Textiles Grouped by Function 440
Contents
15.4 Application of Smart Textiles 453 15.5 Sustainability and Ecological Aspects 462 15.6 Conclusion 464 Acknowledgements 464 References 464 Index 475
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List of Contributors Sadaf A. Abbasi
Debra Carr
School of Engineering RMIT University Melbourne Australia
Defense and Security Accelerator, Dstl Wiltshire United Kingdom
Catalina Álvarez‐López
Raul Fangueiro
Universidad Pontificia Bolivariana Medellín Colombia
University of Minho Guimarães Portugal
Simon Annaheim
Patricia Fernández‐Morales
Laboratory for Biomimetic Membranes and Textiles Empa - Swiss Federal Laboratories for Materials Science and Technology St Gallen Switzerland
Universidad Pontificia Bolivariana Medellín Colombia
Bijoy K. Behera
Indian Institute of Technology Delhi New Delhi India Nuno Belino
University of Beira Interior Covilhã Portugal Martin Camenzind
Laboratory for Biomimetic Membranes and Textiles Empa - Swiss Federal Laboratories for Materials Science and Technology St Gallen Switzerland
Tushar Ghosh
North Carolina State University Raleigh North Carolina USA Pelagia Glampedaki
Social Fashion Factory – SOFFA Athens Greece Ali Harlin
VTT Technical Research Centre of Finland Ltd Espoo Finland
xii
List of Contributors
Hany Helmy
Christopher Malbon
Textile Research Division National Research Centre Cairo Egypt
Centre for Defence Engineering Cranfield University Shrivenham United Kingdom
Elina Ilen
Sumit Mandal
School of Arts, Design and Architecture Aalto University Espoo Finland
Laboratory for Biomimetic Membranes and Textiles Empa - Swiss Federal Laboratories for Materials Science and Technology St Gallen Switzerland
Natalia Jaramillo‐Quiceno
Universidad Pontificia Bolivariana Medellín Colombia Kirsi Jussila
Finnish Institute of Occupational Health Oulu Finland Chi‐wai Kan
Institute of Textiles and Clothing The Hong Kong Polytechnic University Kowloon Hong Kong
Ningtao Mao
School of Design University of Leeds Leeds United Kingdom Jiří Militký
Department of Material Engineering Faculty of Textile Engineering Technical University of Liberec Liberec Czech Republic Rajesh Mishra
Textile Research Division National Research Centre Cairo Egypt
Department of Material Engineering Faculty of Textile Engineering Technical University of Liberec Liberec Czech Republic
Raj Ladani
Roshan Paul
School of Engineering RMIT University Melbourne Australia
University of Beira Interior Covilhã Portugal
Lihua Lou
Department of Textile Engineering Mehran University of Engineering & Technology Jamshoro Pakistan
Tawfik A. Khattab
Nonwovens & Advanced Materials Laboratory Texas Tech University Lubbock USA
Mazhar H. Peerzada
List of Contributors
Georgios Priniotakis
Jordan Tabor
Technological Education Institute of Piraeus Egaleo Greece
North Carolina State University Raleigh North Carolina USA
Seshadri Ramkumar
Mohanapriya Venkataraman
Nonwovens & Advanced Materials Laboratory Texas Tech University Lubbock USA
Department of Material Engineering Faculty of Textile Engineering Technical University of Liberec Liberec Czech Republic
Sohel Rana
Lijing Wang
University of Minho Guimarães Portugal
School of Fashion and Textiles RMIT University Brunswick Australia
Adriana Restrepo‐Osorio
Universidad Pontificia Bolivariana Medellín Colombia René M. Rossi
Laboratory for Biomimetic Membranes and Textiles Empa - Swiss Federal Laboratories for Materials Science and Technology St Gallen Switzerland
Weijie Yu
Nonwovens & Advanced Materials Laboratory Texas Tech University Lubbock USA Change Zhou
College of Textile & Clothing Jiangnan University Wuxi China
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1
1 High Performance Technical Textiles: An Overview Roshan Paul University of Beira Interior, Covilhã, Portugal
1.1 Introduction Technical textiles provide technical, functional, and performance properties, unlike textiles used in the fashion, artistic, or decorative sectors. These include textiles for households, packaging, sports, medical, protection, military, filtration, geotextiles, agriculture, construction, automotive, marine, aeronautic, and other smart applications. Synthetic as well as nanofibres – like aramid, polyolefin, polyamide, polyester (PES), viscose, glass, and ceramic fibres – are widely used for the manufacture of technical textiles. Nanofibre nonwovens can also improve the properties of textiles designed for technical applications. Natural and bast fibres like jute, flax, hemp, coir, ramie, kenaf, and abaca are also finding applications as technical textiles for environmental reasons. They are gaining increasing importance particularly as fibre reinforced composites in automotive, construction, aerospace, and packaging industries. This is mainly due to the fact that bast fibres offer good tensile strength and stiffness compared to synthetic fibres such as polyamide, carbon, and aramid. Besides, they originate from renewable natural resources and are environmentally friendly.
1.2 Application Areas of Technical Textiles In general, application areas of technical textiles are classified as: ●●
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Hometech. Carpet components, furniture components, consumer and industrial wipes, air and water filtration, interior design, drapes, covers, ticking, composites, etc. Packtech. Bulk packaging with a predefined three‐dimensional (3D) structure, scrap and disposable, spacer and tying, absorbent food pads, etc. Sporttech. Luggage components, sports equipment, sportswear, wipes, covers, disposable, and camping equipment, etc. Medtech. Drapes and gowns, sterile wrap, swabs and dressing, cleaning products, cover stock, wound care, protective apparel, bedding and sheets and masks, etc.
High Performance Technical Textiles, First Edition. Edited by Roshan Paul. © 2019 John Wiley & Sons Ltd. Published 2019 by John Wiley & Sons Ltd.
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Protech. Chemical and biological protection, particulate protection, flame retardant, cut resistant, shields and gowns worn in emergency situations, chemical handling, hazardous waste control, cleaning, filtration, etc. Clothtech. Cleanroom garments, shoe components, insulation and structure, sewing products, interlining, leather goods applications, etc. Indutech. Electrical components, filtration and separation, satellite dishes, clothing surfacing tissues/veils, conveyor belts, reinforced plastics, polyvinyl chloride (PVC) substrates, flame barriers, noise absorbents, battery separators, antislip matting, lifting and pulling, etc. Geotech. Asphalt overlay, soil stabilization, drainage, sedimentation and erosion control, pond liner, impregnation base, drainage channel liners, separation, reinforcement, filtration, offshore land reclamation, roadside, railside, river and canal banks, reservoirs, etc. Oekotech. Environmental protection, exhaust air and waste water filtration, dust collection, oil and fuel absorbent, gas and odour removal, etc. Agrotech. Crop covers, seed blankets, weed control fabrics, greenhouse shading, root bags, biodegradable plant pots, capillary matting cover, protection and collection, fishing, etc. Buildtech. Roofing and tile underlay, underslating, thermal and noise insulation, house wrap, facings for plaster board, pipe wrap, concrete moulding layers, foundations and ground stabilization, vertical drainage, protection and display, textile construction, building components, reinforcements, high quality wallpapers, etc. Mobiltech. Boot liners, parcel shelves, heat shields, shelf trim, moulded bonnet liners, boot floor covering, fuel/oil filters, headliners, rear parcel shelves, airbags, cabin air filters, engine intake and exhaust air filters, silencer pads, insulation materials, car covers, under padding, car mats, tapes, backing for tufted carpets, seat covers, door trim and insulation, floor coverings, protection, composites, etc.
1.3 Technical Textiles by Functional Finishing It is a general concept that technical textiles are manufactured using technical fibres, with inherent technical properties. But innovative functional finishes are creating possibilities for developing functional technical textiles by a simple finish application at the end of the textile manufacturing process. The modification of commodity fibre and fabric properties by innovative finishes can be a cheaper route to high performance than by using high cost fibres with inherent built in performance properties. In a textile industry, finishing is usually done in the final stage of textile processing. A wide variety of functional properties can be created on textiles by means of chemical or bio finishing and also it is possible to develop multifunctional textiles. With the advent of nanotechnology, a new area has developed in the realm of textile finishing. Nanotechnology is opening new avenues in chemical finishing, resulting either in improved processes or in helping to achieve new functional properties, which were not possible with conventional finishes. Thus, the application of nanotechnology creates an expanded array of functional properties enabling textiles to be used in novel materials and products. Unlike in conventional finishing, the nanometric size of the coating will not affect negatively the hand and feel of the finished fabric.
1.4 High Performance Technical Textiles
The low temperature sol–gel techniques, as well as the new generation of polymeric resins, are offering new possibilities in textile chemical finishing. Another important development is the plasma enhanced chemical vapour deposition (PECVD) technique. It is a finishing process which can be used to deposit thin solid polymeric films from a gas state to a solid state on a textile substrate to achieve the desired properties. The advantage of such plasma treatments is that the modification turns out to be restricted to the uppermost layers of the substrate, thus not affecting the overall bulk properties. In general, plasma treatment can be considered as a dry alternative to the wet chemical treatments and so they are environmentally friendly. Layer by layer (LbL) assembly method is another new finishing technique by which ultrathin composite films can be developed on solid surfaces like textiles. It involves an LbL adsorption of polycations and polyanions to build a multilayer ultrathin polyelectrolyte coating on a textile substrate.
1.4 High Performance Technical Textiles This book on high performance technical textiles covers almost all the important areas of technical textiles. The book starts with household and packaging textiles, hi‐tech sports textiles, and medical textiles. Further, it focuses on the protective aspects, with chapters on protective textiles, personal protective clothing, and military textiles. Industrial and filtration textiles, geotextiles, and agrotextiles are dealt with in the subsequent chapters. Important application areas like construction, automotive, marine, aeronautic, and space are covered in the following chapters. The last chapter talks exclusively about smart and responsive textiles. 1.4.1 Household and Packaging Textiles Textiles have become an integral part of the home, both in daily use and in household installations. Household textiles include carpets, sheets, pillow cases, pillows, blankets and quilts, bedspreads, table linens, bathroom and kitchen towels, bathmats, shower curtains, readymade and custom made curtains, draperies, slipcovers, and other furniture protectors. They make life more comfortable and give home interiors a defined aesthetic characteristic. Technological innovations have converted conventional household textiles into high performance textiles by improving their durability and by adding multiple functionalities, thus allowing them to follow trends in line with e‐textiles, combining sustainable materials for easier disposal and reuse, and incorporating nanotechnology into everyday personal items. Hollow fibres with good insulation properties are broadly employed in bedding and sleeping bags. Other categories of fibre are increasingly being utilized to substitute foams in furniture because of the fear of fire and of health hazards created by such materials. Packaging textiles include all textile packing material for industrial, agricultural, and other goods. Lightweight nonwoven and knitted materials are widely used for various wrapping and protection purposes, particularly in foodstuff industries. Growing environmental concern over reusable packages and containers is opening new opportunities for textile products in this area. Textiles have helped high performance packaging
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to advance as they can be engineered to have very strong weaving structures while being lightweight and more sustainable than conventional packaging materials. High performance textiles along with modern materials handling methods have permitted the innovation of more proficient handling, storing, and distribution of various powdered and granular merchandise varying from fertilizers, sand, cement, sugar, and flour to dyes and pigments. Packaging textiles have also entered a new era of active and intelligent systems which interact with their content and inform the consumer about spoilage risks or products’ nonconformity. 1.4.2 Sports Textiles Traditional applications of sports textiles are in high activity outdoor athletics, team sports, as well in less active games, for example golf. Further, they are also used in highly visible applications, including textiles for balloons, parachutes, paragliders, and sailcloth. Sportswear has also become leisure and casual clothing. High performance sports textiles are widely used in shoes, sports equipment, winter and summer sports, flying and sailing sports, climbing, angling, and cycling. Functional sportswear has a new look as lifestyle wear, and accordingly sportswear is functionally modified and fashion elements are added to meet these new requirements. High performance sports textiles are manufactured using sophisticated raw materials and technology. The performance fibres, yarns, fabrics, and functional finishes developed for the sports sector are increasingly transferring the sportswear to the mass market in the high street. Sports textiles are also specially designed to take moisture away from the body, and attached with sensors to identify high impact stresses on joints, heart rate, temperature, and other physiological data. All these developments have made the choice of materials more pronounced and selection of them more complicated. This leads to balancing properties and functionalities with user and maintenance friendliness. 1.4.3 Medical Textiles Medical textiles are one of the important areas within technical textiles and the use of textile materials for medical and healthcare products ranges from simple uniforms or gauze or bandage materials to scaffolds for tissue culturing and a large variety of prostheses for permanent body implants. It should provide barrier properties, comfort and water vapour transmission, along with the required mechanical properties. Disposability is the main reason hospitals and operating rooms prefer nonwovens over woven fabrics. Generally, medical nonwovens offer unique antimicrobial solutions and provide increased protection for the user and have less potential for cross‐contamination. Nonwovens used in gauze swab should absorb exudates, protect from external contamination, cushion from further trauma and have good air permeability. High performance medical textiles are in constant demand, owing to their major expansion into fields like wound healing and controlled release, bandaging and pressure garments, implantable devices, as well as medical devices, and development of new intelligent textile products. Medical textiles are clearly driving the emergence of new and improved raw materials and processes, leading to new technological solutions specifically designed to tackle the problems medical professionals and patients are daily
1.4 High Performance Technical Textiles
faced with. At present, high performance medical textiles have the potential to substantially change the way patients receive medical assistance/services. Despite not being very common, the awareness of these intelligent textile systems is rising along with the number of marketed medical products. 1.4.4 Protective Textiles Protective textiles are the technical textile materials used in the manufacturing of a wide variety of protective clothing (personal protective equipment [PPE]) for people working in hazardous situations. The diversity of protective textiles includes safety against cuts, impacts, abrasion, stabs, explosions, flame, foul weathering, severe high or low temperatures, high voltage, harmful dust and particles, and nuclear, biological, chemical, and hazardous materials. Natural fibres, specific synthetic fibres, high performance fibres, nanofibres, and other functional materials all demonstrate excellent performances in either protection or comfort of protective clothing in various environmental conditions. A combination of those high performance functional textile materials in engineered structures would help achieve desirable functionalities in specific applications. Protective textile products have been in constant demand and the main driving force is the increasing emphasis on the reduction of occupational hazards and assurance of the health, safety, and protection of the workforce. The constant revision of legislation, governmental policies, and standards has encouraged stakeholders to take initiatives to introduce accountable measures and equipment in the prevention of hazardous events and accidents at worksites. 1.4.5 Personal Protective Clothing Protective clothing is generally designed to enhance the worker’s safety, by complying to the requirements stipulated by international regulatory bodies. Clothing plays an important role in protecting human beings from their surrounding environments. High performance PPE is widely used as advanced protective clothing – like coats, trousers, vests, etc. and body armour products like helmets, masks, aprons, gloves, socks, shoes, etc. – to protect the human body from environmental hazards. The hazards addressed by protective equipment include physical, electrical, heat, chemical, biohazards, and airborne particulate matter. PPE is also required to protect human beings from various natural hazards such as wind, cold air, rain, flash fire, etc. Protective equipment may be worn for job related occupational safety and health purposes, as well as for sports and other recreational activities. Thus, the main purpose of PPE is to reduce human exposure to hazards when engineering controls and administrative controls are not feasible or effective to reduce these risks to acceptable levels. PPE is expected to possess high thermal protective performance under a thermal or fire hazard. At the same time, it should effectively regulate the metabolic heat and sweat vapour from the wearer’s body to their surrounding environment, and this regulation will provide high thermo‐physiological comfort to the wearer. Along with this functional performance, it should also possess some aesthetic features like appropriate colours and printed designs.
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1.4.6 Military Textiles Textiles for military uniforms face a complex set of challenges as they must provide protection, durability, and comfort in a wide range of hostile environments. Military and police forces are two sectors where protection and performance are paramount, as they are faced with diverse threats routinely in their employment. The main threats are ballistic, sharp weapon, flame, and chemical, biological, radiological, and nuclear (CBRN). Clothing and uniforms in these lines of work must offer a large variety of essential properties, from flexibility and breathability, to fire retardancy and body armour level protection. There is always a compromise between the protection offered by a clothing system and the ability to complete the task, i.e. between survivability and mobility. The optimum design of high performance protective clothing systems requires subject matter expert knowledge of the threats faced, the tasks to be completed, the anthropometric properties of the persons to be protected, the fabrics that might be used, integration with other fabrics and equipment, and knowledge of appropriate clothing manufacturing techniques and test methods. 1.4.7 Industrial and Filtration Textiles Industrial textiles are widely used for chemical, mechanical, and electrical engineering purposes, such as filtration, plasma screens, lifting machines, transportation, sound proofing, roller covering, grinding equipment, insulation, and fuel cells. These textiles are generally strongly woven with high tenacity PES and/or polyamide yarns. This area of technical textiles offers solutions and products for different industries like paper, carbon, metal, ceramic, glass fibre, plastic, etc. High performance industrial textiles play a major role in filtration media and are widely employed to separate and clean industrial goods, gases, and effluents. A wide variety of fibres, DREF yarns, nonwoven fabrics, multifilament and monofilament woven fabrics, and in some cases blends or combinations of more than one of the above are used in filtration applications. Depending on the filtration purpose, several requirements and standards must be fulfilled for the production of filters. Sometimes it is required to merge different filtration media to better fit the application’s requirements, such as filter fabric and membrane. 1.4.8 Geotextiles and Environmental Protection Textiles Geotextiles are permeable fabrics, and when used in association with soil have the ability to separate, filter, reinforce, protect, or drain. They are widely used in supporting embankments, bridges, and drainage systems. They are also employed for soil reinforcement, erosion control, and filters. Typically made from polypropylene (PP) or PES, geotextile fabrics come in three basic forms: woven, needle punched, or heat bonded. Geotextile composites have also been developed, and products such as geogrids and meshes are available commercially. A woven geotextile could be manufactured from monofilament, multifilament, or fibrillated fibres. A nonwoven geotextile could be fabricated from either continuous filaments or staple fibres. Nonwovens resistant to tear, soil chemicals, puncture, UV light exposure, mildew, rot, freeze/thaw conditions, etc. are an ideal choice for high performance geotextile applications.
1.4 High Performance Technical Textiles
Each configuration of geotextiles like geonets, geosynthetic clay liners, geogrids, geotextile tubes, etc. are able to yield benefits in geotechnical and environmental engineering design. The three main properties which are required and specified for geotextiles are mechanical responses, filtration ability, and chemical resistance. They should be able to withstand several high stress situations, be durable, and be able to soften an undesired fall. The environmental protection textiles are widely used for protection of environment and ecology. This is not a well‐defined sector yet, though it overlaps with numerous other application areas of technical textiles. They are also used for environmental protection such as floor sealing, erosion protection, oil spill management, air and water filters, and waste handling. 1.4.9 Agrotextiles Agrotextiles offer advantages like flexibility, breathability, and greater ease of installation as compared to polymer films and are widely used for crop protection and for promoting crop development. The most important requirements of agrotextiles are weather resistance and resistance to microorganisms, in order to protect the plants against temperature extremes by day and by night. They are characterized by strength, elongation, stiffness, porosity, sunlight and toxic environment protection, and biodegradation. The use of agrotextiles to improve the conditions under which crops are grown or developed is increasing. They include all the woven, nonwoven, and knitted fabrics applied for agricultural and horticultural uses including livestock protection, shading, weed and insect control, and extension of the growing season. Lightweight spunbonded fleeces are employed for a range of products such as shading, thermal insulating, and weed suppression. Heavyweight nonwoven, knitted, and woven textiles are used for wind and hail shelters. Capillary nonwoven mats are employed for horticulture to spread moisture to rising plants. The type of fibre used in the development of high performance agrotextiles is important to ensure that the textile fulfils its protective functions efficiently and that it will withstand the environmental conditions. As the synthetic fibres such as PP, polyethylene (PE), polyethylene terephthalate (PET), and polyamide (PA) comply with these requirements, these fibres have been for many years the primary option for producing agrotextiles; however, these fibres are not biodegradable and have a significant impact on the environment once their useful life ends. New production techniques, the advancement of modern materials, and the use of ecological bast fibres have led to the development of sustainable high performance agrotextiles. These additional performance features can increase the productivity and quality of agricultural goods and thus help to effectively tackle the growing challenges currently experienced by the agricultural sector. 1.4.10 Building and Construction Textiles Textiles in fibre, yarn, or fabric form combine excellent strength, resilience, and flexibility with low weight, resulting in desirable construction materials for multitudinous functions and appearances. They should offer mechanical properties such as lightness, strength, and resilience as well as resistance to many factors such as creep, degradation
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by chemicals and pollutants in the air or rain, and other construction material, as well as the effects of sunlight and acid. Construction textiles are widely employed in building construction, including textile reinforced concrete, house wrap, frontispiece, interior structures, sun protection, heat and noise insulation, water‐ and fireproofing, air conditioning, wall reinforcement, aesthetic, safety, sewer and pipe, and linings. They are also used for temporary constructions such as tents, marquees, and awnings. Such temporary use textile materials should be characterized by lightweight, strength, rot resistance, sunlight protective, flame retardant, and weatherproof. The application of new sustainable materials with high performance properties, together with a better understanding of textile structures and their mechanics, has led to new applications of these materials in construction. Architectural fabric structures are becoming an integral part of commercial construction, because of their energy efficiency and potential for creating a form of architecture. Similarly, insulation and house wraps are being improved to offer more efficient, comfortable, and sustainable structures. 1.4.11 Automotive Textiles Automotive textiles are that area of technical textiles which are widely used in transportation vehicles and systems, including cars, trains, buses, ships, and aeroplanes. These textiles range from seats, carpets, belts, tyres, hose reinforcement, and air bags to reinforced composites for automotive and aircraft bodies, filters, battery separators, wings, and engine components, etc. Among all these applications, the major part constitutes seat upholstery and roof covering. They should not only cover isolation and safety aspects but also focus on comfort, style, and a wide range of functionalities. Other applications include solutions for engineering problems in the form of composites, tyre reinforcement, sound insulation, and vibration control. Textile reinforced composites and 3D woven solid structures are now widely used in the automotive sector replacing metallic parts, thus leading to weight reduction and fuel efficiency. Increasing complexity of product specifications and the requirement of high performance end uses have led to the adoption of sustainable, lightweight, durable, low cost, and more accurately engineered yarns, textiles, and nonwovens in the automotive sector. 1.4.12 Marine Textiles As in other application areas, textiles are used in functional as well as decorative applications in the marine industry. Marine textiles play an integral role on every vessel, from protection to upholstery. They are the preferred choice for making hoods, tarpaulins, protective covers, rear closures, but also for decorating and boat furnishings. Textile reinforced composites are being increasingly used for navigational aids. Marine textiles are specialized technical textiles because of the high performance specifications and special properties required. Marine textiles have to withstand a much higher exposure to sunlight, seawater, and potential damage from ultraviolet radiation. In addition, safety features like flame retardant behaviour are crucial, and weight reduction and antifouling are also other important technical requirements. Owing to the
1.5 Conclusion
highly aggressive environment, marine textiles developed from natural and synthetic materials are then reinforced with different functional materials and techniques. In a marine environment, the comfort, design, and appearance of textiles are important for providing users with a relaxing atmosphere. In order to satisfy the high performance requirements, numerous advanced materials and technologies are being developed for marine applications. 1.4.13 Aeronautic and Space Textiles From clothing to complicated aeroplane parts, textiles are found everywhere in aircraft. Aeronautic and space textiles include specially crafted lightweight structures as well as engineered textiles. The application of high performance textile composites in space shuttles and other aerospace products needs to be completely defect free. The use of textile reinforced composites reduces fuel consumption in aircraft and space shuttles, without any compromise on the strength. These products are mainly manufactured with high performance textile fibres, which require additional properties as compared to conventional fibres. Apart from aircraft applications, textile structures are widely used in the manufacturing of specialized space suits. Various new materials are used for making the space suit, including fabrics made from different functional polymers. Typically, the innermost layer of the suit is made up of a nylon tricot material, the second layer is manufactured with spandex which gives elasticity in the suit, and the next layer is made up of urethane coated nylon. Thermo‐physiological comfort aspects are also considered while designing the spacesuits. 1.4.14 Smart and Responsive Textiles Active and responsive textile materials providing functional and high performance properties are generally termed smart textiles. Smart textiles are thus the textile materials or products that can discern and deduce changes in their surroundings and respond appropriately. Smart textiles act as both sensors and actuators and thus stand differently from the other existing multifunctional textiles that behave as mere passive materials with enhanced properties. Major end uses of high performance smart textiles include architecture, automotive, fashion, entertainment, military or protection, healthcare, sport or fitness, and others. Developments in smart and responsive textiles have made a great impact on human lives in recent years. They have a wide range of applications like wearable electronics, shape memory materials, barrier membranes, phase change materials, optical materials, and other functional textiles, which provide convenience and comfort required for a smart life.
1.5 Conclusion A wide variety of high performance technical textiles can be developed either from technical fibres or through the functional finishing of conventional fibres. Technical textiles, textile reinforced composites, and 3D woven solid structures have a wide range of applications in different industrial sectors, offering multifunctional properties which
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are not possible to achieve by using conventional materials. On the other hand, smart and responsive textiles are contributing towards a smarter way of life. Sustainability and recyclability of technical textiles is becoming a significant concern in every area of its application. A major reason for reduced recyclability of technical textiles is the use of nonbiodegradable fibres. Hence, there is a great research focus to develop sustainable and biodegradable technical textile materials, which should be far simpler to recycle and reuse.
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2 Household and Packaging Textiles Pelagia Glampedaki Social Fashion Factory – SOFFA, Athens, Greece
2.1 Introduction In a constantly technologically advancing world, homes are continuously turning ‘smarter’ and often ‘greener’, equipped with high performance household materials. Textiles are integral part of a household’s built and daily dynamics as they are sensed by the whole body and are related to every basic human need. Towels are used to dry the hands, cleansing wipes to clean the face, bed linen and duvets to cover the body, carpets to step on with the feet, food in textile packaging to alleviate the feeling of hunger, tents as a roof above the head to sleep in outdoors or as protective shades from excessive sun at home, and of course homewear clothing to shield oneself against weather conditions. As people worldwide become more educated and have access to opportunities for realizing a higher income, the information, knowledge, and financial independence that they have acquired drive their will to turn their houses into homes with high technology products which offer higher living standards and enhance performance, durability, comfort, hygienic conditions, and even aesthetics. Therefore, smart design solutions combined with high performance attributes are part of the package of modern‐day household and packaging textiles. This chapter offers an overview of the types of such textiles, as well as of their proper ties, engineering processes, testing methods, and applications. Sustainability aspects are also discussed before the chapter concludes.
2.2 Textile Materials, Properties, and Manufacturing Like in any other category of high performance textiles, both natural and synthetic fibres are used in household and packaging textile‐based materials. Such fibres origi nate from the same sources used for common fabrics, such as wool (e.g. for carpets), cotton (e.g. for towels), jute (e.g. for food sacks), polyester (e.g. for curtains), and poly amide (e.g. for packaging bags). The key to their advanced properties is the type of fin ish and coating, the type of combination in composites, and even the structural High Performance Technical Textiles, First Edition. Edited by Roshan Paul. © 2019 John Wiley & Sons Ltd. Published 2019 by John Wiley & Sons Ltd.
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engineering of the textiles produced. Bast (i.e. woody, cellulosic, plant) fibres, for instance, have been used for decades in the manufacturing of wrapping and bagging materials from hemp, ramie, and flax. Nowadays, they are used in polymer matrix com posites which exhibit improved mechanical properties, such as tensile and flexural strength. Examples include the use of bamboo, kenaf, and sisal fibres combined with glass fibres in epoxy matrices to produce hybrid materials that are lighter with an increased impact energy [1]. Altering the layering sequence of bast fibre plies or varying the fibre content with different weight ratios are techniques to manufacture such high performance textile‐based composites. Lamination with various stacking sequences can be achieved by using regular vacuum bagging methods and post‐curing of compos ite laminates in an autoclave. A representative example of exploiting textile structures to achieve high performance is a recent study performed on woven polyester fabrics used to manufacture curtains as sound absorbers [2]. Four types of fabrics were investigated, all lightweight, contrary to the old practice of heavy velvet curtains used for sound absorption. Three to five differ ent types of yarns with various linear mass densities and different weaving patterns were employed to produce fabrics of increasing area density, specific airflow resistance, and cut‐off frequency. The fabrics were tested, both folded and unfolded, as well as with and without a rigid backing material (a wall), to distinguish among good or poor sound absorbance. 2.2.1 Household Textiles 2.2.1.1 Types and Properties
In the global market of technical textiles, household textiles contribute with a share of 7% [3]. Examples include soft furnishings (carpets, rugs, upholstered furniture, cush ions, curtains, blinds, bed linen, blankets, duvets, and pillows); bath towels and kitchen cloths (oven gloves, tea towels, etc.); fibrefill (e.g. polyester staple fibres); nonwoven wipes for house cleaning and personal hygiene; and textile‐based filters for vacuum cleaners, heating, ventilation, and air‐conditioning systems, mosquito nets, even stuffed toys (Figure 2.1). Home products like impregnated fabric wipes have been developed decades ago [4] but technological progress has broadened the field of textile‐for‐house applications to uses beyond imagination. Knitted fabrics can be used to reinforce wall coverings, both outside and inside, as a lighter material than steel [5]. Solar textiles, inspired by biological archetypes such as polar bear fur, are used for the translucent thermal insulation of buildings. The sun shines through a transparent front sheet and warms up a dark absorber sheet lying behind. The absorber convects the heat to the brick wall and thus into the house. Insulation is achieved through a coated flexible spacer textile with smooth foils on both sides, the top one for self‐cleaning purposes functioning according to the lotus effect and the bottom one in the form of a black pigmented coating to absorb sunlight and transform it into heat [6]. Insulating textiles are becoming an integral part of wall constructions as they are flexible and lightweight. Novel systems, such as aerogel impregnated textiles that can act as the insulating core, can easily be installed in combination with suitable fabric finishes [7]. Even though such textiles (solar and wall covers) do not fall strictly under the category ‘household’ or ‘home’ but rather under ‘construction building’ textiles, it is evident that hundreds of square metres could be covered by textiles in a house.
2.2 Textile Materials, Properties, and Manufacturing
Sleepwear Robes/Slippers Cleansing wipes -
Homewear & Personal care
Carpets
Curtains
HOME TEXTILES
Ventilating Mosquito nets Vacuum cleaning -
- Roller blinds - Drapes - Window panels
Upholstery
Towels Bedding
Filters
-Rugs - Insulating floor coverings - Anti-slip substrates
- Sofa fabrics - Dining chairs - Wall covers
- Kitchen - Bathroom - Cleaning wipes
- Blankets/duvets (thermal) - Bed linen - Mattresses
Figure 2.1 An overview of household or home textiles.
Owing to the large impact a home has on daily life, choosing household textiles is dictated by very concrete parameters, such as cost, durability, ease of cleaning, func tional properties, and of course colour and fashion style. For instance, curtains play an important multiple role in a house – they provide privacy, they retain warmth, they protect from the sun, and they add to the decoration – so choosing them is a matter not just of taste but also of functionality. Lined curtains have better drape, provide insula tion, and are less likely to fade with time and under the effect of sunlight so they may be preferred over nonlined ones. At the same time, it is good if they are also fire‐resistant. The same general attributes apply to upholstery fabrics, i.e. the outer fabrics which cover furniture. Duvets consist of an insulating material, such as down, feathers, or polyester wadding, to be warm but light. Carpets should be durable, fire‐resistant, moth proofed, and easy to clean, be able to absorb sound, and also add warmth. Therefore, the general properties of household textiles are mechanical strength, elasticity to avoid deformation, antistatic properties, hypoallergenic properties, soil releasing, flame retardancy, and insect repellence [8]. Particularly in the case of fire resistance and flame retardation, depending on the type of fibre used, each textile has different grades of flammability. Wool, for example, does not burn that easily, but synthetic fabrics like polyester could easily catch fire. To enhance their performance and safety features, flame‐retardant agents are used, especially for products like carpets and curtains. The new generation of such agents is halogen‐free, owing to environmental and health considerations. Silicon, nitrogen, and phosphorus based compounds are mainly employed with the ideal aim to produce only char and no toxic fumes while burning [9]. The burning behaviour of commercial polyester curtains treated with flame retardants has been reported in a study [10]. Fabrics had various weights in the range of 300–550 g m−2 and their flammability was investigated using cone
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calorimetry. Apart from the efficiency of the flame retardant itself, the physical charac teristics of the fabrics, such as the weight per unit area, were found to be of importance influencing the rate of heat and smoke release, among other parameters [11]. Last but not least, fashion design and decoration are integral components of house hold textiles, particularly for furniture and drapes. Furnishing fabric designers use fancy yarns for decorative purposes but there are certain practical aspects to consider, such as formability and risk of deformation from daily usage, abrasion resistance, soft handle, insect repellence, etc. A material often used for furniture by designers is che nille yarn for its shiny appearance, reflection effect, and softness. A study on the per formance of chenille for upholstery fabrics showed that pile length is one of the properties of the chenille yarn which affects resistance to abrasion [12]. As the pile length increases, the pile loss decreases because it is harder to remove long fibres incorporated into the twists of the chenille yarns than short fibres. Also, the appear ance rate of chenille yarns on the surface of upholstery fabrics due to abrasion is related to weaving constructions [12]. 2.2.1.2 Manufacturing
One of the most modern types of high performance household textiles is that which offers protection from electromagnetic radiation. Such an attribute can be achieved by using electroconductive covers which can generate and transport free charges. There are two main paths for the production of such covers: (i) metallization of textile materials and (ii) coating textiles with conductive polymers. The most widely used metals are silver, copper, and stainless steel. However, conductive polymers, such as polypyrrole or polyaniline, and dispersed additives, such as carbon nanotubes or gra phene, can be also used to increase conductivity. Traditionally, sewing or stitching metallic yarns was used to create conductive patterns. More recent application tech niques include metal fibre staple spinning, vapour deposition, sputter deposition, plasma‐assisted coating, sol–gel processes, and even inkjet printing with conductive inks, which enable the production of stable coatings in the nanoscale [13–15]. Particularly for sample collections, inkjet printing is cost‐effective (very accurate usage of colour pastes) and time saving (production from two months down to two weeks) while it offers high pattern repeatability [8]. Another method is electroless metal plating which is a nonelectrolytic method of deposition of metal from solution and has some advantages such as coherent metal deposition, excellent conductivity, and shielding effectiveness [13]. In the case of coating with conductive polymers, there are various techniques, includ ing in situ chemical polymerization, in situ electrochemical polymerization in a one‐ compartment cell with two electrodes connected with an external power supply, in situ vapour phase polymerization, solution coating process, and in situ polymerization in a supercritical fluid. The conductive polymer coated composites manufactured by these methods function on the principle of absorption of electromagnetic rays rather than reflection [14]. A commercial example of conductive polymer coated yarn is the E‐glass/ polypropylene commingled yarn produced by the P‐D FibreGlass Group (Germany) and used for the production of poly(3,4‐ethylenedioxythiophene): poly(styrene sul fonate) (PEDOT: PSS)‐coated yarns as strain sensors [16]. Also, it has been reported that an increasing number of laminating layers increases the electromagnetic shielding effectiveness of woven polyester fabrics with stainless steel staple blended yarns and
2.2 Textile Materials, Properties, and Manufacturing
far‐infrared‐emissive polyester filaments produced with various structures, densities, lamination layers, and warp/weft arrangements [10]. The incorporation of small‐sized and lightweight electronic components, such as display screens and LED lights, into hidden parts of textiles is another easy way to pro duce e‐textiles for household applications. More advanced applications include GPS devices and antennas for wearable indoor location awareness systems [13]. Detachable functional elements, like electronic components, fastened onto or into home textile products can be in the form of buttons, zippers, ribbons, etc. for decorative purposes as well as for functional reasons, e.g. bearing a LED monitor or a light applied to bed linen, curtains, towels, even a textile cupboard [9]. Fire‐resistant textiles are manufactured to create a barrier preventing heat and flame from penetrating the substrate, whereas flame‐retardant textiles are designed to reduce the ease of ignition and the flame propagation rate [17]. As they are used for a number of household items such as sleepwear, bed linen, blankets, mattresses, upholstered fur niture covers, carpets, textile wallpapers, and curtains, it is crucial that they are engi neered to inhibit or suppress the combustion process during the heating, decomposition, ignition, or flame spreading stage. Organohalogen and inorganic compounds are nowa days the most predominant flame retardants used, although there are significant con cerns with their decomposition products (e.g. brominated and chlorinated furans and dioxins) as well as with their environmental impact in terms of safe disposal. Therefore, the focus has now shifted towards the development of halogen‐free additives, one group of which is inorganic aluminosilicates (clays). The most common application methods to impart flame retardation and fire resistance involve chemical finishing through the pad‐dry‐cure process which results in deposition, condensation, or polymerization of the additives on the textile surface. Compounds include ammonium polyphosphate and organophosphorus‐ and nitrogen‐containing monomers or oligomers. The back‐ coating treatment is another way to manufacture flame‐retardant textiles, particularly those used for upholstery furnishes. Antimony–halogen systems (e.g. decabromodi phenyl oxide, hexabromocyclododecane) are mainly used in this case and they are incorporated with a resin on the back of the fabric [17]. As in most functionalization cases, flame‐retardant additives can be either covalently bonded to the fibres during polymerization or fibre extrusion or physically incorporated, which is also the fastest and most cost‐effective way. In the former case, fibres and textiles are inherently fire resistant and flame retardant, whereas in the latter case they are rendered post‐produc tion as such. Commercial examples of flame‐retardant and fire‐resistant textiles and fibres include the Pyrovatex®CP cotton, the Ultem® 9011 polyimide, the Basofil® mela mine, the Visil® rayon fibres, and the Tes‐firESD® series of fabrics which are both flame retardant and antistatic. For curtains, roller‐blinds, and even tents, fabrics with the ability to protect against ultraviolet (UV) radiation are essential. A fabric’s sun protection factor (SPF) is deter mined by the chemical structure of its constituent fibres, the substances present on and in them (additives, coatings), and by the fabric structure (porosity, thickness, surface roughness, etc.). Cotton, silk, polyamide, and polyamide/elastane fabrics with low delustrant content, particularly in pale shades, were found to be inefficient against intense UV radiation. Their performance can be markedly improved by treatment with UV absorbers, especially if the fabric porosity is low and its thickness high [18]. An example of UV blocking cotton fabrics are those developed by coating with ZnO and
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TiO2 nanoparticles. The ZnO nanoparticles applied on cotton yarns were found to withstand the knitting operation. On the other hand, the TiO2 nanoparticles applied on bleached and dyed cotton fabrics by sol–gel and linking agent methods exhibited wash ing durability even after various cycles of domestic washing. Knitted fabrics treated with ZnO nanoparticles showed moderate to high values of ultraviolet protection factor (UPF), whereas 50+ UPF values were measured for the TiO2‐coated samples [19]. A very efficient technique to manufacture fabrics with antifouling and soil‐repellent properties, thus particularly relevant to upholstery and other household fabrics, is reported by Gotoh et al. [20]. Surface coating by atmospheric pressure plasma jet (APPJ) polymerization was employed, with hexamethyldisiloxane as a precursor, for depositing silicon oxide layers on the fibre surface of plain woven polyester and rayon filament fabrics. It was found that the APPJ polymerization remarkably prevented soil deposi tion of model particulate soils, carbon black and red clay, as compared to the treatment with two fluorochemical resins. In the spirit of novelty combined with sustainability, household linen manufacturers have turned to natural dyes for natural fibres, exploiting their lower toxicity and anti bacterial, antiallergic, even deodorizing properties which are quite rare for natural fab rics [21, 22]. Examples include the use of myrrh and gallnut extracts for cotton, silk, and wool, following common extraction and dyeing protocols, such as grinding and pro longed immersion in water at 90 °C for dye extraction, and exhaustion without auxilia ries at a specific liquor‐to‐goods ratio and 80 °C in a dye bath for fabric dyeing. Reported results show that the natural dyed fabrics have a good to excellent deodorizing function against ammonia, trimethyl amine, and acetaldehyde, and outstanding antibacterial activities (bacteriostatic reduction rate: 99.9%) against Staphylococcus aureus and Klebsiella pneumonia [21, 22]. Often, the high performance of household textiles can be achieved mechanically rather than chemically, especially when toxic emissions from, for example, coatings are consid ered on a daily basis in a home with possibly elderly people and children. An example where design and performance are paired in a more physical way is the reversible textile furnishing, a product that has no true inside out since either side can be used to give a different appearance or an alternative decorative surface [23]. A study was carried out to discover the existing reversible textile products and to explore the different ways of reversing a textile furnishing product. Reversible techniques were introduced to provide several possible looks within one item with a finished appearance. Apart from designing innovations, the possibility to reverse the faces of a furnishing fabric results in mitigating abrasion and weathering effects to both sides, prolonging the fabric’s life. 2.2.2 Packaging Textiles 2.2.2.1 Types and Properties
Product packaging is part of the 4P marketing matrix: price, product, place, and promo tion. It is designed to give consumers awareness, product recognition, and helps build the manufacturer’s reputation. The factors taken into account in packaging decisions are the concept of product to structure the visual element of style, mood, and tone; the target group; the identity factor; the element of graphic design to strengthen product packaging; the aesthetic factor in terms of visual communication; the added value; the appeal to encourage consumers’ desire or need for consumption; the structure factor
2.2 Textile Materials, Properties, and Manufacturing
related to the product’s characteristics and product protection; the form of packaging matching the product type or environmental or legal issues that require consideration for sustainability, environmental responsibility, and applicable environmental and recy cling regulations; and of course the cost–profit relation [24]. It is not an easy task to produce packaging materials that fulfil all the above criteria, especially when the product to be contained is susceptible to spoilage, like food. Traditional food packaging was meant for protection, communication, convenience, and containment. The package was used to protect the product from the deteriorative effects of external conditions like heat, light, moisture, microorganisms, and gaseous emissions, so traditional packaging materials needed to be inert. A lot has changed in food packaging since the 1930s, when a fabric bag for fruits and vegetables was designed [25]. Not only chemically active and electronically intelligent systems are integrated into packaging but also the actual textile materials to build the packaging body have been reinvented. New types coated with antimicrobial agents have been developed, e.g. scoured jute fabrics treated with chitosan and chitosan–metal complexes [22]. It was actually found that the latter (i.e. jute fabrics treated with chi tosan–metal complexes) show better antimicrobial properties than fabrics treated only with chitosan or metal salts [26]. Nonwoven textiles are also rapidly developing as packaging materials that could replace plastic bags. As an example, a film based on gas‐permeable nonwoven fabric was engineered to prolong the shelf life of fresh fruits, vegetables, and vase flowers. The film has high permeability of oxygen and carbon dioxide providing a suitable atmos phere for the perishable products. At the same time, the reduced levels of oxygen inside the packaging decrease the respiration rate of the living item, leading to moisture loss and an increase in the metabolic heat while reducing ethylene levels [27]. Ethylene is a ripening agent, which is produced naturally in fresh fruits and vegetables as they respire. Reduced oxygen levels cause increased metabolic activity and hence reduction in shelf life, and increased carbon dioxide levels lead to tissue softening, fungal and bacterial growth. With 50% polyester‐50% rayon and a thin polymer layer, the nonwoven packag ing is both strong and permeable [27]. In the same aspect, a packaging material comprising a textile substrate impregnated with a solution of zeolite, a cross linker and a binder, has been developed to prolong the shelf life of fresh produce [28]. The packaging consists of a gas‐permeable container and an atmosphere‐modifying device within the container, with a carbon dioxide emitter, an oxygen scavenger, and an optional ethylene scavenger of CaO2, zeolite impregnated with permanganate, activated carbon, and combinations thereof. The packaging is suit able for home use (e.g. in a refrigerator), energy‐saving, cost‐effective, washable, reus able, simple in construction, and user friendly. The textile substrate could be woven, nonwoven, or knitted polyester, or blends of polyester with viscose, cotton, or acrylic fibres. To test its performance, fruits and vegetables were covered with the textile pack aging and were stored in uncontrolled atmosphere of 20–30 °C and 55–70% relative humidity. Mangoes covered with the engineered textile packaging were found to soften and blacken after eight days, while mangoes kept in a polyethylene bag for comparison under the same atmospheric conditions started softening and blackening in just three days. Similar experiments with other fruits and vegetables confirmed their shelf‐life extension (pomegranates six days, lemons seven days, tomatoes three days, and oranges four days) [28].
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Another invention relates to thermoplastic textile packaging with cyclodextrin as adsorbent in at least a monolayer coating and in combination with an effective amount of polyethylenimine [27]. Plastic fabrics with a metalized surface, which is also anti static, are another type of storage or transport container. Their development was based on the fact that fabrics for packaging need to be stronger and more durable than regular fabrics made of natural fibres. Also, when powder, granular, or liquid materials are poured into containers, static electric charge is developed through friction, and may lead to an explosion or fire if the container is not discharged [29]. In the group of bio‐based materials and, in particular, of fibrous cellulosic for packag ing, cellulose‐nanomaterial‐based foams are being studied for packaging applications in order to replace polystyrene based foams. Replacing a polymer produced from fossil fuel with a renewable material that decreases weight is an advantage of using webs of cellulose nanomaterials in packaging [30]. As most materials used today are nonde gradable and raise environmental and health concerns, the demand for exploring advanced and eco‐friendly packaging materials with superior physical, mechanical, and barrier properties is increasing. A study on totally green composites based on bamboo fabric and polypropylene and bamboo fabric and poly(lactic acid) was conducted to compare the performance of the green composites used for packaging as opposed to conventional thermoplastics. Results based on a number of analyses – such as drop weight impact tests, thermogravimetric analysis, differential scanning calorimetry, and heat deflection temperature analy sis – have shown that the addition of bamboo fabric improved the thermal resistance of the composites while providing mechanical reinforcement of the material. A shortcom ing of these packaging materials is that high humidity levels should be avoided [31]. It is self‐evident that there is a plethora of materials used for textile based packaging in combination with metals, glass, wood, paper, plastics, or composites. Most of these materials enter municipal waste streams at the end of their service life. Over 67 million tonnes of packaging waste are generated annually in the EU, comprising about o ne‐third of all municipal solid waste [32]. A large number of different types of polymers, each of which may contain different additives – such as fillers, colourants, and plasticizers – are used for packaging applications, and this complex composition makes recycling expen sive compared with disposal in landfill. These facts have given ground to the develop ment of biodegradable plastics for sustainable packaging applications, typically from renewable raw materials such as starch or cellulose, and with waste management by composting or anaerobic digestion. 2.2.2.2 Manufacturing
Active packaging can be designed to modify the atmospheric concentration inside the package through selective absorbance of gaseous compounds, achieved by coating, lamination, microperforation, co‐extrusion, and polymer blending techniques. Depending on their protective mechanism, various active packaging can be categorized as oxygen scavengers; ethylene scavengers; carbon dioxide absorbers and emitters; anti microbial, moisture control systems; antioxidant release systems; and flavour or odour absorbers and releasers [33]. In the case of innovative packaging, materials have been produced from a mixture of textile dust fibre (i.e. waste from mechanical recycling of textiles) and paper fibre (recovered or virgin wood fibre) [34]. The technology required to produce this novel textile/paper material is of an existing infrastructure available in
2.2 Textile Materials, Properties, and Manufacturing
the paper making industry and at the same time it valorizes waste products as second ary raw materials. A third angle is that such a textile/paper material is further eco‐ designed to reduce its environmental impact and add to the category of sustainable packaging. Initially, the textile dust fibre needs to undergo the pulping process where the fibres are suspended in water. Then, this suspended dust fibre solution is refined with the fibres disintegrated into smaller ones ( 40 corresponding to fabrics that provide excellent protection [48]. For example, a UPF value of 50 means that only 1/50 (or 2%) of the biologically effective UV radiation will be able to pass through a piece of fabric. On the other hand, UV resistance is defined as the ability of a material to resist UV light or sunlight. UV irradiation will cause nonresistant materials and surfaces to fade or discolour. To be tested, fabric samples are conditioned and then exposed to UV rays for a defined period of time in an accelerated UV‐ageing tester. In fact, the UV acceler ated weathering tester reproduces the damage caused by sunlight over time. In other words, after exposure of a piece of textile to UV light for a few days or weeks, the tester can assess the effect that the sun will have on that textile in months or years of exposure. In practice, if a material after ageing has a UV resistance value of less than or equal to 2, it is considered UV‐resistant.
2.5 Sustainability and Ecological Aspects 2.5.1 Household Textiles With petroleum resources rapidly depleting, the textile industry is shifting gradually from conventional processes to more sustainable solutions and raw materials. Con sidering, also, that synthetic fibre manufacturing is not a closed‐loop process, in that by‐products are not be fed back into the system, air and water pollution is another major issue, which makes way for the use of traditional fibres as sustainable alternatives. Such an example is reported in the study of Lambert et al. (2017) [43] for furniture applica tions, in which hemp fibres are compared with cotton in terms of performance, including colour fastness, resistance to abrasion, etc. It was found that hemp fabrics were compa rable to cotton with respect to mechanical properties meeting the minimum require ments for breaking and tearing strength of upholstery fabrics. Moreover, hemp fabrics performed somewhat better in colourfastness‐to‐water tests showing negligible resist ance to cleaning, i.e. very little dye loss and stain presence, particularly important if steam cleaners are used. However, hemp exhibited great colour changes upon exposure to light, limiting its use to indoor furniture, unless modified with suitable finishes [43]. In product manufacturing, planned obsolescence is a purposely implemented eco nomic and industrial strategy that ensures the current version of a given product will become obsolete or useless within a planned time period. This strategy guarantees that consumers will demand replacements sooner or later, supporting demand and sales.
2.5 Sustainability and Ecological Aspects
The phenomenon is evident especially in electronics, where new versions of products are launched every few months, but the textile industry has its own share of responsibility in that respect. In fact, ‘fast fashion’ was coined as a term to designate low‐cost clothing which imitates luxury fashion and feeds unscrupulous disposability. In much the same way, the term ‘fast furnishings’ has been introduced to describe the design and production of low‐cost home/soft furnishings in very short manufacturing and consuming cycles of residential textile products such as upholstery, carpets, curtains, bedding, and decorative pillows. As a result, fast furnishings contribute to the nonsustainability of the textile industry with respect to the overuse of natural resources, escalating pollution and waste production, the presence of harmful substances like toxins and carcinogens in fabrics, and the growing volume of textile goods that end up in landfills or incinerators [49]. The environmental impacts of textile consumption and use in the European Union are both supply and demand driven. Supply factors include agricultural practices, pro duction processes, product design and functionalities of washing/drying/ironing appli ances, and the existence of sorting and recycling schemes, while demand factors (which are mostly driven by social parameters) include choice of products/fibres, care practices (washing, drying, ironing), lifetime of product in a context of fast fashion, and disposal practices [50]. A study conducted to identify, map, and discuss LCA methodological issues in the textile sector focused on ranking three fabric types for a sofa – cotton, polyester, and wool/polyamide – and more specifically for a surface covering of a three‐seat sofa for private use during 10 years [51]. The results of the study revealed that with all assump tions and boundaries the polyester type of fabric has a lower environmental impact than the fabric made of natural fibres such as cotton. The significant issues addressed with respect to sustainability were: the production phase, yield (e.g. regarding cotton cultivation), air emissions of methane and ammonia from sheep or sheep manure, fossil energy extraction and use, type of electricity used, and system expansion/allocation choice. The system expansion/allocation choice in sheep farming, where oddments were assumed to replace first‐class wool, had most influence. Fuel replacement in the incinerator and recycling of packaging material had less influ ence. Less significant issues were: use phase, production of drinking water, freighter and truck transports, business trips, waste management of used fabrics or fibre waste, and type of heating value used. Issues not or not fully assessed were: the effects of chemicals discharged to water, inclusion of a wastewater treatment plant, eutrophying discharges to water, land use, human health impacts from the working environment, the effects of lubri cants, production of packaging materials, and production of chemicals [51]. Aspects of the negative impact of interior (home) textiles include contamination of indoor air quality, chemical usage, and energy and water consumption, calculated for the total lifecycle of the product. In fact, studies on interior spaces with a lot of furniture like schools and offices revealed that poor indoor air quality can cause ‘sick building syndrome’, which is a physical reaction expressed with fatigue and respiratory prob lems. Further to the emissions of harmful volatiles from home textiles, wall coverings and carpets can trap allergens such as mites and moulds and may contain trace amounts of formaldehyde, contributing to poor indoor air quality, especially in combination with poor ventilation. In the case of chemicals use, conventional cotton production, for example, involves the use of large amounts of pesticides and insecticides, some of which remain in the
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finished textile product throughout its lifecycle. Chemical finishes such as soil repel lents and flame retardants may be released into the environment during the later stages of product use, maintenance, and disposal. For example, a common flame retardant such as decabromodiphenyl ether is a hazardous chemical used for interior furnishings and, if disposed in a landfill at its end of life, it can contaminate the ground during its slow decomposition affecting human health and wild life. Moreover, such chemicals may pose health risks to the workers who handle them, unload the shipment, and place the products for retail display. Also, the transportation of materials from one factory (or country) to another contributes to greenhouse gas emissions. The use of potentially harmful chemicals during the laundering process (e.g. softeners and dry cleaning sol vents) is another stage of environmental impact of household textiles post‐production. In a study about chemical toxicity [52], 14 commonly used household textile dyes and two colour removers were tested for their oral toxicity in mice and they were categorized as ‘moderately toxic’ compounds. Toxic symptoms appeared rapidly and consisted of marked respiratory difficulties and convulsions. Most deaths occurred within hours. The five most toxic dyes of the study and one colour remover were tested for oral toxicity also in dogs and, in this case, they were all characterized as ‘very toxic’. Symptoms resembled those seen in mice. In general, the dark dyes were more toxic than the pastel shades [52]. It is evident that sustainability aspects in the field of household and packaging textiles are not very different from those in the field of clothing textiles, and they reflect the deleterious impact of fast furnishings and single‐use packaging on the environment and on human health (Figure 2.3). Such a realization was the drive for some companies to embrace more holistic and sustainable approaches to interior textile design and manu facturing. Design for the environment (DfE) is such an approach. It is a process which
• Laundered micro-plastics • E-textiles in landfill • Sick building syndrome
Pollution
Education • • • •
Designers Manufacturers Policy makers Consumers
Product Life Cycle Assessment
• Planned obsolescence • Fast fashion • Fast furnishing • Single use packaging
Circular Economy • Sustainable resources • Waste/package valorisation • Recycle/Reuse
Figure 2.3 Schematic summary of the key parameters that describe or influence the environmental impact of household and packaging textiles.
2.5 Sustainability and Ecological Aspects
takes into consideration the economic, health, and environmental impact associated with a product across its lifecycle, emphasizing the use of safe and sustainable materials, features, and processes, and with the understanding that environmental concerns need to be addressed during the initial design stage of the process [49]. Establishing long‐term relationships with various stakeholders – suppliers, govern ments, NGOs, consumers, and communities – can support efforts towards sustainabil ity. In the context of interior textile design, all levels of stakeholders may influence a product’s lifecycle and sustainability, including product designers and developers, mar keting managers, production experts, third‐party organizations (e.g. the Global Organic Textile Standard [GOTS] organization), government agencies, consumers, dry cleaners, and product recyclers [49, 53]. In that context, a product LCA model with respect to environmental design criteria specifically for interior textiles was developed (Environmental Design 2013). The model is based upon three propositions about environmentally responsible or ecologically sustainable organizations (ESOs). First, designers are given environmental objectives and goals for product design. Second, ESOs employ systems to assess environmental objectives or criteria at key points throughout the product design process. Third, ESOs integrate environmental considerations into the design process by measuring environ mental outcomes and incorporating outcomes into strategic planning. In a five‐step process of concept, product design, process design, package design, and product launch, sustainability can rise through product specifications, raw material selection, and end‐ of‐life planning (e.g. selecting materials that can easily be recycled), waste management during production, choosing a more ecological transportation manner, and evaluation of environmental outcomes using LCA, reports of regulatory experts, and cost analyses. Studies have shown that the application of sustainable design, development, and pro duction methods is limited in the textile industry for interior textiles, owing to indus trial standards and regulation, availability of products, production methods, and company size and resources. Furthermore, product performance and quality were per ceived to be more important to achieve than reduced impacts to human health and the environment [49]. However, in the framework of circular economy, choice of materials in product design plays an important role for sustainability, along with standardized parts, products designed to last, end‐of‐life sorting, product reuse, and closed‐loop manufacturing which valorizes by‐products and waste [34]. Taking into consideration that contemporary textile waste comes also in the form of e‐waste, three main concerns arise: (i) the e‐waste mountain piles, (ii) the toxic load from their constituents, and (iii) resource depletion for their manufacturing [13]. Even if e‐textiles enter municipal solid waste streams that lead to either landfill or incinera tion, they will be co‐processed with all other solid waste. Released pollutants would add to the overall environmental issues, plus no recovery of valuable materials would be expected. Upon dispersion within low‐grade wastes, valuable materials, such as metals, would be lost. However, if e‐textiles entered an e‐waste recycling scheme, the recycled fibres could be agglomerated to flocks or manufactured into nonwoven fabrics with applications in mattresses and upholstery (66%) or carpet underlay (11%), as well as in paper pulp (5%) and the automotive industry (8.7%). It is still not known whether it would be possible to maintain the ‘intelligence’ of e‐textiles for re‐use. It can be assumed that repairing e‐ textiles would hardly be possible during textile recycling, either technically or
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economically. However, old e‐textiles could provide classical textile functions. Therefore, a large part of them could be categorized as second‐hand clothes [13]. But it is not just solid waste that ends up in landfills. A new and more alarming source of marine contamination has been identified in micro‐ and nanosized plastic fragments. Microplastics are difficult to see with the naked eye and as they do not biodegrade in aquatic environments, they can be ingested by plankton or other marine organisms. Microplastics reach the sea through sewage contaminated by synthetic fibres from washing clothes and household textiles. In a relevant study [54], the highest release of microplastics was recorded for the wash of woven polyester and this phenomenon was correlated to the fabric characteristics. The number of microfibres released from a typi cal 5 kg wash load of polyester fabrics was estimated to be over 6 000 000 depending on the type of detergent used. The usage of a softener during washes reduces the amount of microfibres released by more than 35%. The amount and size of the released micro fibres confirm that they could not be totally retained by wastewater treatments plants, and potentially affect the aquatic environment [54]. A way to minimize or at least contain this environmentally unfriendly effect is to substitute synthetic components with natural ones, wherever possible. In this context, research has been conducted to substitute harsh chemical finishing agents with more benign and natural ones. For instance, vegetable oils from rapeseed, olive, coconut, saf flower, and linseed have been applied in the form of aqueous emulsions to investigate the wrinkle recovery of 100% cotton fabrics [55]. It was found that spraying such emul sions on cotton results in the formation of a thin microdroplet layer on the fibres, fila ments, and yarns, without any chemical bonding taking place. The performance and effectiveness of these natural antiwrinkling agents lie in the reduction of the friction coefficient which in turn promotes fibre relaxation after deformation. Another interesting approach is the use of bio‐binders for nonwovens. Researchers have tested soy‐protein‐based binders applied on viscose nonwoven textiles in the form of foam [56]. The same type of textiles treated with acrylic binders in a conventional pad‐dry‐cure method were used as a reference. The results of the study showed that foam‐applied biobinder‐treated nonwovens have comparable mechanical and thermal properties with conventional ones. Studies have also shown that the impregnation of personal care and household poly ester and cellulose wipes with solutions of natural components such as rosewater and olive oil, treated with sodium alginate and natural antibacterial agents of cinnamalde hyde and geraniol, can result in products with good liquid absorption and antibacterial performance [57]. Thus, they can substitute conventional commercial household wipes produced with synthetic means. 2.5.2 Packaging Textiles In the case of packaging textiles, they emerged, among other materials, as sustainable alternative to bad practices of the past when storage life of perishable articles like fruit and vegetables was prolonged by spraying antibacterial and antifungal chemical agents (silver nitrate, sorbic acid anhydride, chlorinated hydrocarbon, potassium permanga nate) on the fruits and vegetables causing serious health hazards for the consumers [28]. Biodegradable textile based bioplastics are most suitable as sustainable packaging in such cases. Apart from their safer use, their end of life can take place by biological
2.5 Sustainability and Ecological Aspects
composting and potentially in anaerobic digestion systems. They should ideally be separated at the household level from other, nonbiodegradable materials and collected with organic waste, including food waste. By using biological waste treatments, the total waste sent to landfill would be reduced and the composts generated could be used as valuable soil improvers [32]. An example of creating a new value from the waste stream of textile recyclers in a sustainable way that promotes circular economy is the case of dust fibre valorization. Even though the quantity of dust fibre produced per tonne of discarded textile is still low, there is a high potential of around 60% to generate large amounts of dust fibre when the discarded textiles are diverted from incineration and landfill [34]. The dust fibre waste from textile recycling can find better use in packaging or other applications as a circular material. A textile paper bag has a lower environmental impact than virgin and recycled paper bags, and has lower operating costs, owing to the lower cost of the textile dust fibre [34]. Furthermore, even Tetra Pak® packaging waste can be reused in combination with wool fibre waste or glass/jute woven fabrics to produce thermo‐insulating bio‐based composite materials [58], increasing also their sustainability features. In fact, the new materials exhibit improved thermal conductivity and thermal resistance compared to control samples made of plain Tetra Pak. Also, applications of composite plastic materials reinforced with natural fibres such as from flax, hemp, and various wood origins gain ground in many industries, including packaging boxes manufacturing. The main advantages are the low weight and the renewability of such fibres, while major disadvantages pertain to high water absorption, degradation in wet environments as well as under ultraviolet light, and high smoke emission in the presence of flame. Reportedly [59], the water absorbed by a flax/epoxy composite until saturation is more than 12 times greater than the water absorbed by a glass/epoxy composite. Also, accelerated UV weathering tests performed for 1500 hours led to decreased tensile and flexural strength of composite flax fabrics, according to the same report. But apart from traditional bast fibres from jute, flax, hemp, etc. that are combined with synthetic polymeric ones to increase biodegradability and induce sus tainability, lesser‐known natural sources have drawn attention owing to their valuable properties. Seaweeds are such a source, increasingly investigated for their use in medi cal and healthcare textiles thanks to their bioactive constituents [60], and they could find use also in naturally antimicrobial textile packaging. Pigments aside, which could be applied as natural dyes, seaweeds comprise a plethora of antioxidants and antimicro bial agents. In fact, most seaweeds contain carotenoids, phenolics, alkaloids, and orga nosulfur compounds, including a‐carotene, b‐carotene, lutein, and zeaxanthin, the antioxidant pigments of both red and green algae, as well as fucoxanthin and fucoidan found in brown seaweed. The analysis of possible improvement options in the sense of sustainability in house hold and packaging textiles indicates consumer education and awareness as fundamen tal to any change (Figure 2.4). In fact, some of these options would require small behavioural changes, such as reducing washing temperature, washing at full load, avoiding tumble drying when possible, purchasing eco‐friendly home textiles, donating textiles not being used any more, upcycling or downcycling clothes to create household textiles, and refusing to utilize single‐use packages. Education on ecolabels and promo tion of best practices could be used as tools for the overall improvement of
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Design for the Environment
Choice of materials (sustainable, biodegradable)
Closed loop manufacturing
End-of-life product valorisation
Sustainability
Figure 2.4 Basic steps to sustainability in the household and packaging textile industry.
environmental performance. Consumers may exhibit greater support for sustainability if they consciously evaluate the consequences of their actions [61].
2.6 Conclusion Household textiles are second after apparel in production volume worldwide and they comprise a large part of our living utilities. They are directly related to our basic func tions and needs (sleep, food, hygiene) in the form of soft furnishings, bed linen, carpets, towels, and even packaging. Technological developments have increased the perfor mance of home textiles in terms of durability and added functionalities, allowing them to follow trends in line with e‐textiles, combining sustainable materials for easier dis posal and reuse, embedding nanotechnology into everyday personal items. Packaging textiles, on the other hand, have entered a new era of active and intelligent systems which interact with their content and inform the consumer about spoilage risks or products’ nonconformity. Bio‐ and chemical sensors and indicators advert and at the same time educate the user about a product’s story, identity, and properties. Textiles have helped high performance packaging to advance, as they can be engineered to have very strong weaving structures while being lightweight and more sustainable than con ventional packaging materials. A lot needs to be done still to tackle environmental issues in this particular textile sector but there is preliminary evidence that textiles could be turned into circular materials in household textile and packaging production.
References 1 Sanjay, M.R. and Yogesha, B. (2017). Studies on hybridization effect of jute/kenaf/E‐glass
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3 Sports Textiles and Comfort Aspects Ali Harlin1, Kirsi Jussila 2, and Elina Ilen3 1
VTT Technical Research Centre of Finland Ltd, Espoo, Finland Finnish Institute of Occupational Health, Oulu, Finland 3 Aalto University, School of Arts, Design and Architecture, Espoo, Finland 2
3.1 Introduction During the last many years, sportswear has taken on a new look as lifestyle wear, and accordingly function required for sportswear on the whole has changed to meet these new requirements [1]. Textile materials are an essential part of all sports as sportswear, and in many games as sports equipment and sports footwear. The sports textiles sector includes specialist apparel for specific sports each with its own particular functions. The performance fibres, yarns, fabrics, and finishes developed for this specialist sector are increasingly transferring to the mass market in the high street. The increasing cultural importance of sportswear in fashion means that only 25% of sportswear finds use in active sports or during exercise [2]. Emerging sports like yoga and winter sports are changing sportswear tradition. This chapter emphasizes the requirements and applications of different sport textile materials in hi‐tech applications, with very good wear comfort properties. Comfort describes especially through thermal comfort and relates to moisture management.
3.2 Textile Fibres The evolution of fibre developments has gone through the phases of conventional fibres, highly functional fibres, and high‐performance fibres. Polyester (PES) is the single most common fibre for sport and active wear. Other fibres suitable for activewear are polyamide, polypropylene, acrylic, and elastane. Wool and cotton fibres find application in leisurewear and in increasing comfort required, e.g. in yoga. Synthetic fibres can be modified, e.g. by producing hollow fibres and fibres with irregular cross‐sections, or optimally blended with natural fibres to improve their thermo‐physiological and sensory properties [3]. The performance space model of different materials is illustrated in Figure 3.1. High Performance Technical Textiles, First Edition. Edited by Roshan Paul. © 2019 John Wiley & Sons Ltd. Published 2019 by John Wiley & Sons Ltd.
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Thermal protection Comfort
KillatN
Lycra
Feathers
Dagron
Lyocel
Kevlar
Wool
Mechanical protection
Casual
Weight
Cotton Polyester
Nylon Coolmax Coretex
Breathability Figure 3.1 Fibre materials enabling required performances.
3.2.1 Natural Fibres Cotton was a traditional solution for sport clothes, but synthetic fibres have replaced it, because of its easier maintenance and faster drying, and because it is a lighter product, especially when wet. This does not mean cotton is replaced entirely. Cotton and polyamide blends find use in sports clothing because they perform better than cotton. Cotton can be blended with regenerated fibres like Tencel for performance wear and sports garments to achieve relatively less absorbent and ‐drying garments [4]. Bast fibres like hemp, jute, or kenaf are used as reinforcements in sport equipment. However, the soft hemp fibre is suitable for t‐shirts and underwear. In these applications, it replaces the cotton. Their particular benefits vis‐à‐vis sustainability include the absence of any genetic modification and the possibility of organic farming and hence they represent low to no risk to the environment. Hemp provides the same breathability as cotton but is more stain repellent and especially more wear resistant. Wool has good wicking ability, high moisture regain, and is a good insulator even when wet. However, wool is slow to dry. Superfine Merino wool possesses superior water vapour permeability and quick drying properties. Merino wool can be blended with a range of other fibres, including silk, viscose, Tencel, PES, and polyamide. In addition, very fine Merino wool is convenient as an inner face of the fabric with an outer face of polyamide. Sportswool, a trademark of the Woolmark Company, is an example of a fabric which has been engineered to manage moisture. It is a hybrid material composed of a fine Merino wool sublayer for insulation and a PES exterior, which draws moisture away from the wool layer to the outer surface. The wool fibre next to the skin attracts perspiration vapour molecules, before they have the chance to condense into liquid, and disperses them into the atmosphere. The fabric has attracted the attention of top Australian
3.2 Textile Fibres
athletes and the Manchester United football team. Its major drawback, however, is that it takes longer to dry because of its wool content. The Merino wool content is normally limited to 25% and the other 75% of the garment is CoolMax® PES yarn. Silk is a luxurious material with the most versatile, breathable, durable, and exquisitely comfortable natural fibre. The material is very suitable for winter underwear and is also easy to care for. Benefit in use is also the low friction of the materials. Owing to its natural elastic properties, it can stretch up to 20%. In addition, its high tenacity allows lightweight clothes to be designed. Silk is able to absorb one‐third of weight moisture before it feels wet. It also enables regulation of body heat through its breathability and moisture balancing properties. It is a hypoallergenic and repels mould and mildew. 3.2.2 Regenerated Fibres Regenerated fibres (man‐made cellulosic fibres) are derived from natural sources, and tend to be absorbent. Tencel is the registered trade name for a type of lyocell by Lenzing, made from wood pulp cellulose. It has a very high absorption capability, a unique nanofibril structure, and a very smooth surface. It is a soft fibre that is stronger than cotton, both wet and dry, which is resistant to wear and tear for clothing. As a result, all these physiological functions pronounce markedly more for Tencel than for other cellulosic fibres. Lyocell‐type fibres are textile fibres, which – both in 100% applications and as a part in textile blends – have a clearly positive influence on the comfort in wear of textiles. The nanofibrillary structure of lyocell, the resulting ability to perfect moisture management, its smooth surface, and the purity of the fibre, which is due to the environmentally friendly production process, result in superior properties regarding wearing physiology. Lyocell satisfies the requirements for the temperature regulation of the human body, for skin sensitivity, hygiene and electrostatic behaviour, because of its natural construction and the associated properties, when compared to other fibre materials [5]. Recently, researchers at Helsinki University and Aalto University were successful in developing a novel cellulose spinning solvent. This two component ionic liquid consisting of a super base/acid ion pair, revealed excellent, spin stability resulting in outstanding fibre properties. The optimum rheological properties of the cellulose dope for spinning are attained at moderate temperatures, thus reducing the risk of uncontrolled cellulose degradation that may compromise rheological properties. The mechanical properties of the resulting fibres are outstanding and reach the highest level known for commercial regenerated cellulose fibres (tensile strength 700–870 MPa, elastic modulus 25–35 GPa) [6]. Bamboo fabrics originate from pure bamboo fibre yarns, which have excellent wet permeability, moisture vapour transmission property, soft hand, better drape, easy dyeing, and splendid colours [7]. However, the fibre is simply just another type of viscose fibre, and suitable for underwear, tight T‐shirts, and socks [8]. The cellulosic fibre material should have antibacterial properties, especially viscose. Misleading statements have been published, for example that natural bamboo fibre has no natural antibacterial property. The shape could not affect the natural antibacterial property of natural bamboo fibre but the hygroscopic and extractives influence that [9]. However, the viscose‐ like fibres can be modified to possess antibacterial properties by means of adding silver,
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e.g. an in situ incorporation technique was used for coloration and acquiring excellent antibacterial properties for viscose fibres by silver nanoparticles (AgNPs) [10]. Recently antibacterial and antifungal materials based on cellulose carbamate have been invented [11]. The carbamate pathway provides a simple and environmentally friendly method, offering an alternative to the environmental drawbacks of the viscose process. The tenacity of the fibres was determined in the range of 1.7–2.4 cN/dtex, which was comparable with that of commercial viscose rayon. Furthermore, the regenerated cellulose carbamate fibres filaments showed improved dye properties compared with viscose rayon [12]. 3.2.3 Synthetic Fibres Synthetic fibres are a frequent choice for sportswear. PES has outstanding dimensional stability and offers excellent resistance to dirt and alkalis, and has a comfortable smooth feel. It is the fibre used most commonly in base fabrics for activewear because of its low moisture absorption, easy care properties, and low cost. PES is essentially hydrophobic and does not absorb moisture. However, most base layer are PES yarns chemically treated to wick moisture. High tenacity and good durability make PES the choice for high‐stress outdoors use too. PES is also a strong fibre that is hydrophobic in nature. It is thus ideal clothing for wet and damp environments. The water‐resistant finish of the fabric intensifies further its hydrophobic nature. By creating hollow fibre it is also possible to build insulation into the PES fibre. Air traps inside the fibre and insulates the body heat. This keeps the body warm in cold weather. Another method to build insulation is to use crimped PES in a fibrefill. The crimp helps keep the warm air in. PES is an ideal fabric for this kind of insulation because it retains its shape. Cotton and wool tend to flatten with use and lose their warming effect [13]. PES is also wrinkle resistant in everyday clothing, like trousers, shirts, tops, skirts, and suits. Used either by itself or as a blend, it is also stain resistant and hence very popular. Owing to its increasing consumption and nonbiodegradability, PES waste disposal has created serious environmental and economic concerns. Indeed, the management of PES waste has become an important social issue. In view of increasing environmental awareness in society, recycling remains the most viable option for the treatment of waste PES. Among the various methods of recycling (primary or ‘in‐plant’, secondary or mechanical, tertiary or chemical, quaternary involving energy recovery), only chemical recycling conforms to the principles of sustainable development because it leads to the formation of the raw materials from which PES is originally made [14]. Most synthetic fibres (approximately 70%) are made from PES, and the PES most often used in textiles is polyethylene terephthalate (PET). The majority of the world’s PET production – about 60% – is for textiles; and the rest makes bottles (30%) and other packaging materials (10%). Recycled PES (often written rPET) is a green option in textiles, for two main reasons: ●●
●●
The energy needed to make the rPET is less than for virgin PES in the first place, so we save energy. Moreover, we are keeping bottles and other plastics out of landfill.
3.2 Textile Fibres
It is true that recycling PES uses less energy than creating virgin PES. Various studies agree that it takes from 33 to 53% less energy [15]. The rPET materials have been available since 1993 [16]. Recently, the chemical recycling of PES (as monomers back to polymeric fibres) has become a more prominent alternative, owing to improved yields and the ability to benefit lower quality of fractions. Teijin Eco Circle, a Japanese company, has developed a closed‐loop recycling system for used PES products that employs the world’s first chemical recycling technology. With this technology, chemically decomposed PES is first converted to monomers and then back to new PES [17]. Polypropylene (PP) fibres find increasing use in the sportswear market, although its market share is still small. The fibres have a very low moisture absorbency but excellent moisture vapour permeability and wicking capabilities. PP has the advantage of providing insulation when wet. Insensible and liquid perspiration transportation from the skin without being absorbed makes it an ideal fibre for sportswear. PP claims to be a proved performer in moisture management, owing to its hydrophobic nature, and it has very good thermal characteristics, keeping the wearer warm in cold weather and cold in warm weather [18]. Because PP does not absorb moisture into the fibre, drying time is minimal. The fabric will dry while you wear it. Therefore, the athlete stays drier longer and dries faster. Bacteria, mould, and mildew cannot grow on PP, and will not damage the fibre. A PP garment washed regularly will not retain body odours. However, PP is an olefin material: it has high oleic properties and so absorbs fat and grease, which makes it essential to wash PP clothes properly [19]. 3.2.4 Special Fibres Owing to recent inventions in design and production, today’s new sports textiles use both synthetic and natural fibres. Natural fibres are often unsuitable for high performance, while synthetics have been the top choice. However, natural fibres combined with synthetics give sophisticated finishing treatments to improve their performance. Customers like this new group of ‘techno‐naturals’ or ‘super naturals’, because of their familiar look and handle. The slow‐to‐dry and cold‐when‐wet characteristics of cotton make this an unsuitable fibre for use against the skin during strenuous activity. Table 3.1 lists some of the common types of sports textiles. Phase change materials (PCMs) take advantage of latent heat that can be stored or released from a material over a narrow temperature range. PCMs possess the ability to change their state within a certain temperature range. These materials absorb energy during the heating process as phase change takes place and release energy into the environment during a reverse cooling process. The insulation effect reached by the PCM depends on temperature and time. Recently, the incorporation of PCM in textiles by coating or encapsulation to make thermoregulated smart textiles has become an area of increasing research interest, to review the working principles of PCMs and their applications for smart, temperature‐regulated textiles. Different types of PCMs are available and have been incorporated into cooling textile structures. PCMs found in contemporary consumer products were originally used in spacesuits and gloves to protect astronauts from extreme temperature fluctuations in space. The use of innovative new materials and the integration of PCMs into garments requires, for example, the development of new types of testing methods and standards. Furthermore,
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Table 3.1 A comparison of sports textiles. Name
Type
Method
Property
Hygra™ (unitika ltd.)
Sheath‐core‐type filament yarn
Water‐absorbing Superior antistatic polymer and nylon properties even under low wet conditions
Killat N™ (kanebo ltd)
Hollow nylon filament
Hollow portion is about 33% of the cross‐section
Lycra®
At least 85% segmented polyurethane
Gives it stretch and Comfort and recovery fit‐to‐order
Roica™ (asahi chemical)
Polyether‐type spandex
Knitted with soft nylon 66 yarn (Leofeel™)
Good water absorbency and warmth retentive property
Knitted tricot fabric gives a soft touch and excellent stretch
Use
Apparel applications include sportswear like athletic wear, skiwear, golfwear, etc. Superior fabric, for wicking action, drying time, moisture absorption, and transport Swimwear, active sportswear, and floor gymnastics Practical in swimwear
the development of materials, such as their mechanical properties, durability, or functionality in various conditions, may take a long time. The main challenge in developing textile PCM structures concerns the method of their application. The encapsulation of PCMs in a polymeric shell is an obvious choice but it adds dead weight to the active material. Efficient encapsulation, yield of encapsulation, stability during use, and integration of capsules onto fabric structures are important technological issues to be considered. Another important challenge for this innovative textile in practical use concerns the durability of PCM‐incorporated textiles following repeated use [20].
3.3 Developments in Yarns Fabrics made from staple fibre yarns absorb more than fabrics made from filament yarns of the same content and yarn size, owing to the looser packing of the yarn. A looser packing in the yarn increases the fibre surface area for absorption and by increasing the gaps between the yarns increases moisture vapour permeability. Staple fibre yarns also provide better thermal insulation, owing to the increased volume of air contained in the yarn. They may also improve the sensorial comfort through a warmer feeling to the touch and the yarns have slightly lower areas of contact with the skin. However, the strength of the continuous filament yarns is better. Crimping of synthetic yarns can improve their water vapour permeability by increasing the bulk of the fibres in yarns and yarns in fabrics, thus improving their thermo‐physiological comfort. However, staple fibre yarns do not shed soil as well as filament yarns and they have a greater tendency to pill or shed lint. Filament yarns are useful in windbreaker jackets
3.4 Developments in Fabric Structures
and in the shell and lining of skiwear, where a combination of dense weave and low surface coefficient of friction is desirable [21].
3.4 Developments in Fabric Structures The performance of the fabric/garment is enhanced or achieved by a number of processes, like selection of fibres and blending of the performance fibres during spinning and weaving, along with other yarns like cotton, viscose, bamboo, PES, acrylic, nylon, and elastane, and also by processing and finishing with chemicals (also known as functional finishes) [22]. On the one hand, existing functionality can be improved using nanotechnology and, on the other, it could make possible the manufacture of textiles with entirely new properties or a combination of different functions in one textile material [23]. Knitted fabrics are preferred for sportswear, as these fabrics have greater elasticity and stretchability as compared to woven fabrics, which provide unrestricted freedom of movement and transmission of body vapours to the next textile layer in the clothing system [24]. For warmth and comfort in adverse conditions, brushed, bonded, padded, quilted, or wadded textile fabrics give lightweight volume with little excess bulk [25]. Liquid transporting and drying rate are two vital factors affecting the physiological comfort of sports garments. In a study, plated knitted fabrics produced with functional fibre yarns in the back of the knit (close to the body) combined with PP or PES in the face (outer surface) were tested in terms of their wicking behaviour and drying rate capacity. Functional knitted fabrics provide attractive properties in vertical and horizontal wicking tests. The drying capability was assessed by drying rate tests under two different conditions, namely at 20 ± 2 °C and 65 ± 3% relative humidity and, in an oven, at 33 ± 2 °C, in order to simulate the human body temperature [26]. The fabric structure is an important factor in the design of sportswear garments. A study on the effect of warp‐knitted structures on thermo‐physiological comfort properties showed that most open‐construction 3D Eyelet provided the best moisture vapour permeability but had poor thermal insulation. Micromesh structure, which has much smaller openings or holes than 3D Eyelet does, but is relatively more open than the Pique and Mock Rib structures, yielded the most favourable combination of comfort properties. Dense pile fabrics play a big part in sports clothing and clothes with a high pile trap air for insulation and are highly absorbing. Brushed surfaces apply as an inner lining where the wearer feels comfortable, as the brushed surface against the skin does not cling to the skin’s surface. Wadding of fabrics is for insulation. PES wadding or synthetic foam is sandwiched between fabrics. Some wadding originates from synthetic microfibres, making it waterproof and breathable. The real three‐dimensional (3D) cloth structures are still rare. One reason may be the cost to produce these multilayered structures. However, combinations of novel automation and 3D manufacturing technologies may provide adaptable insulation structures. Knitted fabrics with a foam backing can be very soft, and when blended with elastane have good stretch and recovery characteristics, making them suitable for extreme sports. Technical knitted fabrics that are moisture wicking tend to be more open in structure on the back than on the face. In such open structures, moisture from perspiration passes more quickly through them. Examples of this include Aertex, a traditional
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sports fabric, which is widely used. These specific fabric structures have been developed with the specific requirements of sports textiles in mind, including temperature regulation [27] and moisture management [28]. DuPont CoolMax is a high‐performance fabric that can help the performance of the athletes who wear it. CoolMax moves sweat away from the body to the outer layer of the fabric, where it dries faster than any other fabric. In moisture management tests, garments made with CoolMax dried almost completely in 30 minutes. Cotton, by comparison, remained wet nearly 50% longer. Better evaporation means you spend less energy to cool your body, which increases your performance and endurance. CoolMax fabrics are specially designed not only to provide superior moisture management but also to enhance the wearer’s comfort. All of the benefits of these fabrics are permanent and built into the fibre, requiring no chemical treatments. CoolMax fabric originally developed for clothing intended for use during extreme physical exertion – sweat can evaporate quickly so the wearer remains dry. Other useful properties include resistance to fading, shrinking, and wrinkling. The fibres are now often woven with other materials like cotton, wool, Spandex® and Tencel. As a result, CoolMax is found in a wide variety of garments from mountain climbing gear to casual sportswear and underwear. The fibres are not round but oblong and in cross‐section with grooves running lengthwise along the threads. They are either tetra channel or hex channel style. The series of closely spaced channels creates capillary action that wicks moisture through the core and out to a wider area on the surface of the fabric. This increases evaporation. Toray Industries Inc. developed a series of waterproof/breathable fabrics. The Entrant® fabrics series intended for active wear, and there are many variations that used advanced finishes. Entrant‐DT is a lightweight, waterproof, and breathable microporous coated fabric. It is soft, with a dry smooth texture, and is intended for cycling, running, and hiking. Entrant GII‐XT is a microporous coated fabric made of two polyurethane resin components that produce a ‘pumped‐up’ effect and rapidly wick away sweat. It is wind‐, rain‐, and snow‐proof and so suitable for many outdoor winter sports. Entrant Dermizax EV is a lightweight fabric having a feather smooth texture with excellent waterproof/moisture permeability and durable water repellence (i.e. 20 000 mm of water pressure resistance and moisture permeability of 30 000 g m−2 /24 h). It is an excellent and original active sportswear fabric with globally top class waterproof/ moisture permeability, as well as excellent durable water repellence. It has a water repellent membrane with improved moisture permeability, making it especially suitable for snow sports and climbing. Entrant HB is a new‐generation fabric with a hybrid structure that synergistically integrates the advantages offered by a coating (balanced moisture permeability) and lamination (high waterproofness). It has high resistance to water pressure and high durability against repeated washings (80 points or higher after 20 wash cycles). Its main application is outdoor wear. Toray has developed also H2OFF™ made up of PES microfibre fabric with a unique high‐density weave structure, comprising millions of microcrimped fibre loops. It also features superb and durable water repellence, superior breathability, wind‐chill resistance, and attractiveness with a soft hand. Unitika developed Naiva by combining Naiva yarn with a nylon microfibre. Naiva™ is an Eval/nylon bi‐component filament yarn and Eval is nothing but a copolymer resin
3.5 Special Finishes
of ethylene vinyl alcohol. Naiva yarn composition is 55% Eval (23% ethylene + 32% vinyl alcohol) and 45% nylon. In the Naiva fabrics there are many nylon microloops on the surface, which are formed by making use of the high thermal shrinkage property of Naiva yarn. Naiva fabric not only has good moisture permeability but also has some other positive features, such as being lightweight with a soft hand. It is successfully used in mountaineering wear and other active sportswear. Field Sensor™ is a very popular high‐performance fabric from Toray, which employs a multilayer structure that not only absorbs perspiration quickly but also transports it up to the outer layer of fabric very rapidly using the principle of capillary action. It is composed of coarser denier yarn on the inside surface (in direct contact with skin) and fine denier hydrophobic PES yarn in a mesh construction on the outer surface to accelerate the evaporation of sweat.
3.5 Special Finishes Finishes can transform textiles and give them an array of sports applications. The latest finishes give textiles a new aesthetic, a ‘good to wear’ experience, and superior performance. A fabric could not be weatherproof and breathable before, but sophisticated membrane technologies in the form of new coatings and laminates have altered this. Both visible and invisible coatings make it possible for a fabric to carry sweat away from, and for air to circulate around, the body. Ultrafine and superlight treatments make textiles rain‐, wind‐, and fireproof, and breathable (Figure 3.2). An ultrafine treatment on the face of the fabric does not hide the underlying textile, and appearance, texture, and drape are less affected. Generally, there are two methods of creating breathable, waterproof textiles: by using either (i) microporous or (ii) hydrophilic technologies. The first work by means of very fine holes in the membrane that allow perspiration to escape as water vapour and move quickly from inside to outside but completely block the passage of water. The second
Rain
Wind
Waterproof Drops of water (10 000–2 000 000 Å) are too big to penetrate the membrane
Moisture-permeable Perspiration vapour (3.5 Å) passes through membrane’s inter molecular openings Figure 3.2 Semipermeable cloth structure.
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3 Sports Textiles and Comfort Aspects
attracts water molecules and allows warmer water vapour to move through the membrane to the cooler temperature outside the garment [4].
3.6 High Performance Applications 3.6.1 Sportswear Sports textile is one of the branches of technical textiles. Further, sophisticated technologies find ways for technical textiles to produce sportswear. Hi‐tech textiles in sports are nothing new. In recent years, fabrics have been designed to perform specific tasks – to take moisture away from the body; patches on all jerseys so that the players can dry their hands for better grip; fabrics that sense high‐impact stresses on the joints of players; and fabrics that can sense heart rate, temperature, and other physiological data. Sportswear (or active attire) is clothing, including footwear, worn for sport or exercise. Typical garments include shorts, tracksuits, t‐shirts, polo shirts, and trainers. Specialized garments include wetsuits and salopettes. It also includes some underwear, such as the jockstrap. Sportswear includes more often replacements of casual fashion clothing. The best athleticwear for some forms of exercise, for example cycling, should not create drag or be too bulky. On the other hand, it should be loose enough so as not to restrict movement [3]. Beyond the traditional sports, there are an increasing number of new sports and so novel requirements accordingly. Snow sports apparel plays a crucial role in comfort by ensuring that the wearer does not become cold or wet when spending many hours exposed to temperatures below freezing. However, consumers are now demanding garments which will not only keep them warm and dry but also have enhanced performance properties such as improved breathability, lightweight, softness, and stretch. Furthermore, consumers are demanding snow sports clothing for other outdoor sports and even for day‐to‐day wear [29]. 3.6.2 Desirable Attributes of Functional Sportswear PES is the single most common fibre material used in sportswear. Also, polyamide, PP, acrylics, and elastane are also used for active wears. The fabric used in sports jerseys must be both breathable and stretch. In active and endurance sports, the performance of a sportswear is synonymous with its comfort characteristics. It should be capable of maintaining the heat balance between the excess heat produced by the wearer due to increased metabolic rate, on the one hand, and the capacity of the clothing to dissipate body heat and perspiration, on the other. Today’s sports demand high‐performance equipment and apparel. The lightweight and safety features of sport‐tech have become important in their substitution for other materials. These high‐functional and smart textiles are increasingly adding value to the sports and leisure industry by combining utilitarian functions with wearing comfort that leads to achieving high levels of performance [30]. Technological developments have enabled the production of materials that are tougher than wood, which breathe like skin, are waterproof like rubber, and at the same
3.6 High Performance Applications
Function of clothing Demands of the sport
Duration of activity Safety/Survival Range of sporting conditions
Demands of the body Protection Anthropometry Thermo-physiological regulation Psychological considerations
Figure 3.3 Different factors involved in designing functional clothing.
time are eco‐friendly and highly economical. The augmentations in the sports and leisure industry have resulted in the use of technical textiles in different sports. Figure 3.3 shows the different factors involved in the designing of a functional clothing, such as a sports jersey. ●●
●●
●●
The fabric needs to be able to hold throughout the duration of the activity and support the safety of the user. For instance, cotton clothing does not have any elasticity. This leads to restrictions in movement and it cannot hold well against the harshness of the sports environment. The fabric is good in hot climates, where the sweat transfers through capillary action to the fabric surface and evaporates. Nevertheless, the conditions for a sport are not always cold and the metabolic rate (the sweating rate) is not the same as normal conditions. PES on the other hand wicks away the sweat from the surface faster in high metabolic rate sports and nowadays we see dry‐fit, which efficiently keeps the sports person dry. The literature gives several different listings of sport textiles requirements [31].
●● ●●
●● ●●
●● ●●
●●
●●
●●
Sports textile must have comfort ability, be easy to wear, and enjoy ease of handling. Sports textiles fabrics have a very high electrical conductivity, so they can permit the effectual dissipation of electrical charge. It should be as light as best as possible. Highly effective in moisture management, wick the moisture from the body and keep it dry. Sports textile should have good perspiration fastness. It is well known that sports fabric must have a heat conductive property that makes the wearer feel cool in summer and warm in winter. Garments manufactured from sports textiles fabrics keep the normal stability of body comfort, because these fabrics are ultra‐breathable, fast drying, and possess outstanding moisture managing properties, which rapidly wick moisture away from the body. These garments are also lighter and feature elasticity properties, which provides immense comfort and independence of movement. Keeping a normal level of bacteria on the skin offers a high level of comfort and personal hygiene, especially during athletic activities.
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3 Sports Textiles and Comfort Aspects ●●
●●
Sports textiles fabrics remove UVA and UVB rays that are dangerous to the skin, and guarantees an improved level of defence compared to the majority of general natural and man‐made fibres. It also provides superior strength and durability.
It is not possible to achieve all of these properties in a simple structure of any single fibre or even a blend of them. Certain optimizations will be needed so that the sportswear can enhance the performance of the wearer. Thermal comfort is essential for body performance: low temperatures reduce muscular performance and accuracy, while high temperatures limit physiological resilience (see Figure 3.4). 3.6.3 Differentiation of Requirements When sportswear is adapted to leisure and casual wear, the need to balance hi‐tech performance with comfort aspects becomes more pronounced. The spread of a desire for a healthy lifestyle and an understanding of sports versus leisurewear varies from country to country. Yet the general trend is for the incorporation of sports and technological components into nonsportswear clothing. The schematic view expressed in Figure 3.5 differentiates the requirements of sport textiles in different sports. The figure groups together available materials with their technologies. 3.6.4 Requirements for an Active Sportswear Sportswear should support performance in an ambient condition and during an activity. The dependences between body performance and environment are complex and physiological aspects in respect of environment are not the only issues surrounding performance, but they may become limiting factors in certain cases. Ambient air may vary from mild and moist to dry and extremely cold and so thermal protective clothing has to vary accordingly. Environmental factors, such as wind, convey heat away from
36°C 34°C 32°C 30°C 28°C Figure 3.4 Temperature distribution over the body at 20 °C and 35 °C ambient temperature.
3.6 High Performance Applications
Thermal protection Comfort
Yoga Extreme sports
Winter sports
Weight
Mechanical protection
Casual Athletics
Contact sports
Breathability Figure 3.5 Schematic view for different requirements of sports textiles.
the clothing and compress the air layers underneath outer garments, whereas water and dirt block fabric construction, increase thermal conductivity, and evaporate heat away from clothing. Figure 3.6 presents both environmental and human physiological factors influencing clothing properties and microclimatic conditions, which create a feeling of comfort and support the performance, health, and safety of the user.
Thermal comfort Performance Safety Health
Environment Coldness Wind
Rain Heat radiation Snow and sleet Impurities
Clothing
Microclimate
Thermal insulation
Temperature
Air permeability
Humidity
Water vapour permeability
Air movement
Clothing design
Skin contact
Human
Dry heat loss
Evaporative heat loss
Behaviour and postures
nce
tena
Main
Figure 3.6 Effects of environmental and human physiological factors on textile properties and microclimatic conditions.
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Table 3.2 General requirements and standards for their valorization. Property
Requirements
Reference
Long period at +10 °C, light activity
0.170
EN 14058
Short period cold exposure (−15 °C), light activity
0.310
EN 342
Long period cold exposure (−15 °C), light activity
0.470
EN 342
Thermal insulation, Icler (m2K W−1)
−1
Protection against wind, air permeability (AP) (mm s )
EN 342/ EN 14058
High activity
100 > AP
Moderate activity
5 300
93
T* represents the temperature for the fibre to be frequently used for continuous operation. ++ means very good or excellent, + means mild or good, − means poor.
PBI (polybenzimidazole) fibre has excellent thermal resistant properties. It has one of the greatest LOI (limiting oxygen index; 41%), resistant to ignition and hydrolysis, nei ther burn in air nor melt or drip. PBI fabric can withstand dangers associated with firefighting, arc flash, and flash fire [85]. However, PBI has relatively low tensile strength, does not resist acids [86] or UV radiation exposure [87, 88], and degrades in moist environments. The PBI fibres used in firefighters’ clothing loses its mechanical proper ties in environments having a high RH [89]. It was reported that PBI fibres lost 30% tensile strength after exposure to the environment of 500 °C, RH 60% for 84 days, and 600 °C, RH 37% for 73 days [90]. Four forms of PBI fabrics (PBI Gold, PBI Matrix, PBI TriGuard, and PBI BaseGuard) are available on the market [91]. PBI Gold, which is available as PBI Gold knits, PBI Gold Ripstop, and PBI Gold Twill fabrics, has been widely used as an outer shell in firefighters’ clothing (e.g. Bristol Uniform) since 1978. It blends 40% thermal‐resistant PBI fibres with 60% p‐polyaramid fibres, resulting in a fabric which does not shrink,
5.4 High Performance Textile Materials
become brittle, or break open under extreme heat and flame exposure. PBI Matrix, which was introduced into the market in 2003, employs a durable matrix of high strength aramid filaments woven into the PBI Gold fabric to enhance and reinforce its resistance to wear and tear while retaining its superior flame and heat protection. PBI TriGuard fabric, a blend of three types of high performance fibres including PBI, Lenzing FR, and micro Twaron, is designed for flame protection, comfort, and durabil ity. It is certified for use in wildland firefighters’ clothing, special operations, and mot orsports applications, as well as petrochemical, gas utility, and electric utility industries. PBI TriGuard and PBI Gold knits are also in use at several major motorsport racetracks. PBI BaseGuard is a type of lightweight, soft, and flexible knitted fabric designed to be as a next‐to‐skin base layer in a firefighter’s clothing system to provide fire‐resistant pro tection with the consideration of moisture management and durability. PBI fibres is also used in military flame protection, automotive braking systems, and fire blocking layers in aircraft seats. A summary of some outer shell fabrics used in the turnout gear of structural firefighters’ clothing are shown in Table 5.5. The other reactive protective materials for flame and heat protection are also engi neered to provide minimal insulation during normal wear, and maximum insulation when the heat threat impinges. For example, intumescent treatments which normally are in the form of thin, low‐insulation coatings on a lining fabric: when activated by excessive heat or flames the formulation swells instantly to form an inert insulative char, protecting the wearer. Superior flame‐retardant PTFE or expandable polytetrafluoroethylene (ePTFE) membrane barrier is laminated to a thin polyaramid woven or nonwoven backing sub strate (Kevlar fabrics) to form waterproof and breathable moisture barrier fabrics that have superior mechanical properties [94]. The moisture barrier is typically the middle layer between the outer shell and thermal liner in firefighters’ clothing to prevent water, high temperature water vapour, chemicals, and other pathogens from the environment penetration into the firefighters’ clothing. One of the most significant fabrics is the Gore‐Tex based bi‐component polymeric membrane made of ePTFE porous structure embedded in a continuous polyurethane film to prevent the skin of the wearer to be burned by the hot‐water vapour to inversely penetrate through the moisture barrier. PTFE porous membrane could also be formed into 3D innovative functional bar rier materials (e.g. Gore‐Tex Airlock) to provide still air space between the moisture barrier and outer shell fabrics for firefighting clothing to make the clothing combine the functions of protection, comfort, and heat insulation [95]. The above high performance fire‐resistant fibres are also widely used in making ther mal insulation liners in firefighters’ clothing and flame‐retardant workwear (see Tables 5.6 and 5.7). The thermal liner layer provides primarily thermal protection and is usually engineered as a highly porous padding or nonwoven insulating structure fixed between an inner layer of woven fabric. The still air that remains in the nonwoven insu lating padding between the inner layer of woven fabric and the moisture barrier pro vides thermal protection. While a thicker thermal liner provides better heat protection, it might be heavier and less breathable and thus less thermal comfortable (Tables 5.6 and 5.7). In addition, other flame‐retardant treated natural and regenerated fibres such as wool and cellulosic fibres might also be used to produce thermal insulation liner materials. Wool is the only natural fibre having inherent flame‐retardant properties,
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and wool fabric has been used as a fire‐resistant layer in various products [99]. Owing to its r elatively high nitrogen content (16%) and strong disulfide bond network in the microstructure of wool fibres, it has a high ignition temperature at 570–600 °C and an LOI [100] of 25–26% with low heat of combustion (4.9 kcal g−1) and low heat release [101]. There are durable flame‐retardant treatments [102, 103] based on different fire‐ retardant mechanisms developed for wool and its blend fabrics, including the treat ments based on phosphorous compounds [104–106] and intumescent agents [107]. The treatment based on phosphorous compounds tends to lower the thermal decomposi tion temperature of wool fabrics, allowing the volatile fuel to escape before the ignition temperature is reached, and the intumescent agent [107] combines the attributes of flame retardancy with the formation of a high thermal resistance insulating char layer and thus enhances the natural flame‐resistant and char formation properties of wool. However, wool fabrics treated by using both phosphorous compounds and intumescent agents have limited market size so far. The flame‐retardant treatments for wool fibres by introducing halogen donors [108] into wool treatment, although highly effective in interfering free radical process, have unavoidable associated environmental problems and their use is thus restricted. Zirpro wool (or wool with Zirpro treatment) [109–114] has been the most popular wool fabric used in firefighters’ clothing to date. It is developed by Benisek at the International Wool Secretariat and it involves a treatment with either hexafluorotitan ate or hexafluorozirconate. Zirpro treatments are based on the exhaustion of negatively charged zirconium or titanium salts onto positively charged wool, resulting in the depo sition of about 3% of flame‐retardant inside the fibre and causes the formation of intu mescent char during the burning process [115]. Zirpro wool has an LOI of 27–33% without decomposition temperature found. Benisek and Craven also showed that the combination of Zirpro and tetrabromophthalate has a synergistic effect in fire‐resist ance, although tetrabromophthalic acid or its salts are conducive to smoke on burning and are not durable to washing [116]. It has been claimed that Zirpro wool fabric assemblies show a relatively longer time to reach pain (first‐degree burn) and blister (second‐degree burn) thresholds, as well as the longer pain alarm time (the time available to the wearer to withdraw from the flame heat source before serious injuries occur) [117]. It is also claimed that, compared to other fibres including aramid and Novoloid fibres, Zirpro wool fabric assemblies have one of the lowest residual heat transfers after a limited flame exposure to the pain threshold and thus reduce the possibility of causing second‐ degree burns [20]. When used in firefighters’ clothing, it was found that a woven Zirpro wool fabric of high density over a bulky knitted Zirpro wool underwear fabric offered significantly better protection than a single layer of a woven or knitted fabric or a double layer of a woven fabric of the same total weight [20]. However, the Zirpro wool treatment process and Zirpro wool products have certain problems. First of all, both the zirconium and titanium hexafluorozirconate salts used in the Zirpro wool treatment have associated potential environmental problems and maybe affected by government legislations and directives, such as Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH). In addition, Zirpro wool fibres tend to be brittle, which may lead to problems in yarn spinning and fabric
5.5 Thermal Burden and Thermo‐Physiological Comfort
weaving. However, research into developing new chemical treatments utilizing the syn ergic effects of phosphorous and nitrogen elements to achieve wool fibres of improved flame‐retardant properties are reported [118]. The use of a phosphorus additive [119] in viscose rayon (e.g. Clariant 5060) developed by Sandoz and Lenzing AG and silicic acid‐containing rayon fibres [120] developed in Finland by Sateri (formerly Kemira) are two typical fire‐resistant viscose rayon fibres potentially used as a blend in firefighters’ clothing. Remarkably, the phosphorus addi tives can be added to the highly alkaline cellulose xanthate ‘dope’ before fibre spinning. It survives the acidic coagulating bath and survives alkaline laundering. Visil [121] and other similar viscose fibres [122] are inherently flame‐retardant silicic acid‐containing viscose rayon fibres used as a blend component. Visil is made by wet spinning alkaline cellulose xanthate (viscose) containing a sodium silicate (equivalent to about 30–33% SiO2) with some aluminosilicate component [22]. During fire combus tion, flame retards by both endothermic water release and char formation. Halogen‐containing fibres such as modacrylic fibres [123] (e.g. Saran fibres [124]) are also used as a flame‐retardant component in blends of fire protection equipment [125, 126]. Modacrylic fibres are typically copolymers of vinyl chloride or vinylidene dichlo ride and acrylonitrile. However, while modacrylic fibres are nonflammable and do not melt‐flow or drip, they shrink rapidly when exposed to the fire and thus are rarely used in firefighters’ clothing. Polyphenylene sulfide (PPS) fibres (e.g. Torcon™ (Toray), Procon™ (Evonik) and Diofort™ (Diolen)) have inherently fire‐resistant, chemical‐resistant, and high tenacity properties. They are widely used in high temperature filtration applications and chemi cal protective clothing. New materials and designs have been developed for improved thermal insulation. For example, nonwovens made with thin hollowed fibres can be made thermo‐adaptive with two‐way shape memory alloys like nickel‐titanium [127].
5.5 Thermal Burden and Thermo‐Physiological Comfort Clothing comfort is a human feeling of satisfaction towards clothing when the clothing is seen, touched, or worn by the user. Thermal stress is an especial concern for all types of protective clothing [128]. The three characteristics of thermal stress in protective clothing are: ●● ●● ●●
human body metabolic heat; weight of protective clothing; impermeability of the fabrics to water vapour.
5.5.1 Thermal Burden from Protective Clothing The quantity of heat produced by a human being depends very much on their physical activity and can vary from 100 W while resting to over 1000 W during maximum physi cal performance [129]. Particularly during the cooler seasons (approx. 0 °C), the recom mended thermal insulation is defined to ensure that the body is sufficiently warm when resting.
131
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Some protective clothing is very heavy (e.g. body armour, CBRN clothing). Currently, the majority of available bulletproof vests are very heavy and bulky, the weight of such a bulletproof vest for US police uses ranges from 2.5 kg for US National Institute of Justice (NIJ) level III protection up to 10 kg when including ceramic plates for US NIJ level IV protections [130]. For some special military purposes, the weight of body armour could be up to 20 kg. It is found that weight of clothing is linearly related to metabolic energy consumed by the human body [131, 132], and the relationship between the metabolic energy consumed during loaded walking, Mw, and the load carried by the walker, L, is proposed by Givoni and Goldman as [133]:
Mw = T (W + L)(2.3 + 0.32(V − 2.5)1.65 + G (0.2 + 0.07(V − 2.5))
Mw =Metabolic energy consumed during walking (watts) W =Body mass (kg) L = Load mass (kg) T = Terrain factor V = Velocity or walking rate (m s−1) G = Slope or grade (%) Pandolf et al. expanded on the work of Givoni and Goldman to develop an equation to predict the energy cost of load carriage [134]: 2
(
L Mw = 1.5W + 2.0 (W + L) + T (W + L) 1.5V 2 + 0.35VG W
)
where T = Terrain Factor (1.0 = black top road; 1.1 = dirt road; 1.2 = light brush; 1.5 = heavy brush; 1.8 = swampy bog; 2.1 = loose sand; snow, dependent on depth of depression (T = 1.30 + 0.082*D, where D = depression depth in cm2)) [135]. As the thermal burden is proportional to the clothing weight, it thus requires more metabolic energy to be transported away from the human body within the microclimate of the heavier protective clothing in order to keep the wearer comfortable. Many differ ent technologies rarely used in traditional clothing systems have been invented to achieve thermo‐physiological comfort in protective clothing. One example technology is to place humidity‐absorbing modules containing hygroscopic endothermic salts within the protective clothing to reduce the RH, which increases the wearer’s comfort and allows more sweat to evaporate, leading to additional cooling [136]. In chemical protective clothing, especially for clothing against the penetration of haz ards in the forms of gas, liquid, and mist, the thermal burden usually comes from a lack of breathability of the clothing due to the impermeability of the fabrics to water vapour. A serious challenge associated with body armour and chemical protective clothing, apart from its excessive weight, is the heat caused by the lack of effective perspiration, eliminating the body’s natural ability to dissipate and dispose of metabolic heat. Increasing heat stress exhausts the human body within a short time, even under normal conditions, let alone the extreme heat encountered in the Middle East and Central Asia. Examples of individual protective clothing include body armour (e.g. bulletproof clothing, stab‐proof clothing, cut‐proof gloves, etc.); firefighters’ clothing; chemi cal, biological, radiological and nuclear (CBRN) protective clothing; and chemical
5.5 Thermal Burden and Thermo‐Physiological Comfort
protective clothing; etc. These garments usually need to bear certain labelling (e.g. the UL (Underwriters Laboratories) mark in the US or the CE mark and Wheel mark in the EU) to demonstrate compliance with legislative requirements (e.g. UL standards and 46 CFR US regulations in the US, EU Directive 89/686/EEC Protective Equipment Annex II Health & Safety Requirements (the new PPE Regulation [EU] 2016/425 shall apply from 21 April 2018 to replace Directive 89/686/EEC). Different types of protective clothing need to withstand the attack of specific environ mental hazards presented and thus require the constituent textile materials to have high performance in some specific properties. For example, body armour systems require the textile materials used to have superior mechanical properties; firefighters’ clothing requires its component materials to have exceptional fire‐resistant properties; and chemical protective clothing requires the materials to be resistant to the attacks of chemical agents. All of these clothing systems require the guarantee of clothing comfort in the envi ronment of their application. Clothing comfort includes tactile comfort and thermal comfort. Tactile comfort is one of the key requirements to the clothing/equipment next to the skin and the thermal comfort of clothing is required for all of these clothing sys tems. The thermal homeostasis of the body is a result of the balance between heat pro duction and heat dissipation. The primary factors influencing this thermal balance are energy metabolism, clothing thermal properties, and ambient climatic conditions. Several models or thermal indices – for example PMV (predicted mean vote), PPD (pre dicted percentage of dissatisfaction), DR (draught rate) – taking into account all of these factors have been developed to compute thermal interactions and their effect on the body. Protective clothing serves the purpose of eliminating or reducing the effects of environmental stress factors. High performance textiles, which include fibres, yarns, fabrics, and composite struc tures made from functional organic polymers and inorganic materials with remarkable functions and properties unmatched by conventional textile materials are widely used in protective clothing systems. The required special properties in protective clothing include mechanical properties (tensile strength and modulus, abrasion, puncture, and flex durability), thermal and electrical insulation properties, resistance to heat, flame and chemical agents, liquid absorption and diffusion properties, optical, and radioac tive absorption properties. Such exceptional properties are frequently integrated together in one protective clothing system to achieve both desirable protection and human comfort while wearing the clothing. 5.5.2 Materials for Improving Thermo‐Physiological Comfort Both smart materials and structures can be used to achieve physiological comfort of protective clothing. In this chapter, three groups of typical examples of incorporating smart textile technologies into protective clothing to achieve clothing comfort are discussed. ●●
The typical examples of using smart materials to achieve clothing comfort are heat storage and thermo‐regulating materials including PCMs [137, 138], temperature‐ sensitive materials [139] including shape memory polymer/alloy (SMP) [140]; smart polyurethane film for moisture transport and evaporative cooling technologies.
133
134
5 Textile Materials for Protective Textiles ●●
●●
The typical examples of using smart structure to achieve clothing comfort are Hainsworth® TI‐TECHNOLOGY and clothing having forced ventilation system. A range of active and proactive systems used in protective clothing to control the temperature and humidity of clothing microclimate such as active cooling system using ice, water, and Peltier plate are discussed.
5.5.3 Phase Change Materials (PCMs) Better thermoregulation inside a garment is sought with using PCMs [141, 142], either encapsulated [143] or incorporated in a matrix [144]. PCMs are able to absorb, store, and release latent heat through undergoing one of the four types of phase transforma tions (solid–solid, solid–liquid, liquid–gas, and solid–gas phase transformations) in a nearly isothermal process within a certain range of environmental temperature. Solid– gas and liquid–gas transformations have relatively higher latent heat but can hardly be used in smart textiles, owing to the complex storing technique requirement with a pres surized container. Solid–liquid PCM is among the most favourable, owing to its rela tively large energy storage with acceptable volume change (≤ 10%) over small temperature variations. The latest development of solid–solid PCMs [145, 146], changing their crys talline structure from one lattice configuration to another, has some irreplaceable advantages, such as simple to use, small erosion, no leakage, no contaminant, longer lifespan, little change in appearance, no need of nucleation to prevent supercoiling, and their phase changing temperature remains between 25 °C (77 °F) and + 180 °C (356 °F). In general, PCMs can be grouped into three categories: organic, inorganic, and eutec tics materials. Organic materials used as PCMs include aliphatic compounds or poly mers with long chain molecules composed primarily of carbon and hydrogen (e.g. paraffin waxes (or n‐alkanes), oils, fatty acids, and polyglycols (polyethylene glycols, or PEGs)). They tend to exhibit high orders of crystallinity when freezing and mostly change phase above 0 °C (32 °F). Currently, crystalline alkyl hydrocarbons are used exclusively for textile applications, owing to their large latent heat, good thermal and chemical stability, low vapour pressure, and self‐nucleating behaviour [147]. Inorganic PCMs include salt hydrates, metallic, and ice. The typical inorganic PCMs are Glauber’s salt. Eutectic materials are a mixture of chemical compounds or elements (e.g. solutions of salts in water) that have a single chemical composition that solidifies at a lower tem perature (eutectic temperature) than any other composition made up of the same ingre dients. It is known that the phase change temperature of salt‐hydrates‐based eutectics could be below 0 °C (32 °F) or above 0 °C (32 °F) depending on the formula of the mix ture. Some of those water based eutectics can change phase at temperatures of up to 117 °C (242.6 °F) [148]. The PCMs having the most suitable phase change temperature for clothing are organic compounds such as paraffins or linear alkyl hydrocarbon and nonparaffinic materials (e.g. hydrocarbon alcohol, hydrocarbon acid, polyethylene or polytetramethylene glycol, and aliphatic polyester), and inorganic compounds such as hydrated inorganic salts, eutectics, or polyhydric alcohol‐water solution [136]. Table 5.8 shows the latent heat of selected waxes and stearates. Table 5.9 shows the latent heat and melting point of salt hydrates. PCM microcapsules were initially developed in textile structures and clothing in the early 1980s by NASA to provide improved thermal protection in textile and clothing, having smart acclimatizing properties for astronauts’ spacesuits against the extreme temperature fluctuations in outer space [155, 156]. PCM can be incorporated into
5.5 Thermal Burden and Thermo‐Physiological Comfort
Table 5.8 Latent heat of adsorption, emission, and crystallization temperature of selected waxes [141, 149] and stearates [150].
Hydrocarbons
No of C atoms
Latent heat of adsorption (ΔH) in J g−1
Latent heat of emission (−ΔH) in J g−1
Melting point
Cystallization temperature (Tc, °C) Reference
n‐Hexadecane
16
235.2
236.6
12.2
[151]
n‐Heptadecane
17
176.4
182.6
16.5
[150]
n‐Octadecane
18
244.8
246.4
22.0
[150]
n‐Nonadecane
19
177.6
182.6
26.4
[150]
n‐Eicosane
20
242
230
30.4
[152]
Butyl stearate
120
19
21
[141]
Vinyl stearate
122
27
29
[141]
Isopropyl stearate
142
14
18
[141]
Table 5.9 Latent heat and melting point of selected salt hydrates [147, 153, 154]. Material
Melting point (°C)
Heat of fusion (kJ kg−1)
Latent heat (MJ m−3)
MgCl2.6H2O
117
169
242
Mg(NO3)2.6H2O
89
163
252
CH3COONa.3H2O
58
226
287
MgCl2.6 H2O – Mg(NO3)2.6H2O 58
132
201
Urea – Acetamide [154]
53
224
263
Na2HPO4.12H2O
34
265
379
LiBr2.2H2O [153]
34
124
/
KFe(SO4)2.12H2O
33
173
/
Na2SO4.10H2O [154]
32
180
295
Na2CO3.10H2O
32
233
340
Urea – CH3COONa.3H2O [154]
30
200
266
LiNO3.2H2O [153]
30
296
/
CaCl2.6H2O [154]
30
127
230
Waxes
28 to 4
220 to 245
170 to 195
Polyethylene glycols
28 to 15
146 to 155
165 to 175
Glauber’s salt (Na2SO4·10H2O) + additives
24 to 4
wide range
wide range
Mn(NO3)2.6H2O [153]
25.5
148
/
CaCl2.(H2O)6 – MgCl2.6H2O (67 : 33) [154]
25
127
205
FeBr3.6H2O [153]
21.0
105
/
CaCl2.6H2O – CaBr2.6H2O
15
140
249
K2HPO4.6H2O [153]
14.0
109
/
Water
0
335
335
135
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5 Textile Materials for Protective Textiles
various fibres [157–159], nonwovens [10], polyurethane foams [160], and coated on fabrics [161] in original form, microcapsulated PCMs [11, 12] or nanocapsulated PCMs [162]. Fabrics [163] incorporating PCMs were used in protective clothing [164–166] to achieve the desired thermo‐regulating functions for clothing comfort. When the pro tective clothing is in use, PCMs absorb human body metabolic heat in clothing micro climate during its melting process to give a cooling effect to the wearer and release the stored energy to the environment during a reverse solidifying process to give the wearer a warming effect [167]. Outlast fibre is a bi‐component fibre, including both staple fibres and filaments, con taining patented tiny microcapsules (ca. 1–3 μm in diameter) of paraffin‐like PCMs, Outlast Thermocules™ [168]. It is claimed that the new fibre with temperature manage ment can align particularly well with underwear and other products worn next to skin ,such as socks, t‐shirts, shirts, and trousers. Outlast technology used in firefighters’ clothing was made from 60% MAC Protex™ and 40% CV Outlast [169]. In this bicom ponent yarn structure, the flame‐retardant Protex fibre stops the flame from spreading by producing minute amounts of inert noncombustible gases which ‘seal’ the fabric surface from oxygen. After the removal of the flame source, the flame is stopped from spreading. The Outlast fibre provides a high level of comfort, temperature regulation, and moisture management not normally associated with protective clothing. Beginn [170] reported an ultra‐high‐molecular‐weight polyethylene (UHMW‐PE) paraffin waxes (PW) composite gel structure having superior heat capacities (up to 200 J g−1 of enthalpies at the melting temperature of the paraffin waxes) to microencap sulated paraffin PCMs. Even with the cheap paraffin wax PW42, the melting enthalpies could be up to 120 J g−1, while commercial polyurethane PCM foams [171] only carry a latent heat of 60–65 J g−1. Another example of phase‐change technology used in protective clothing is utilizing evaporative cooling technology. Cooling fibres introduce water‐retaining fibres into the fabric structure [172], and these are sandwiched between breathable outer fabrics (e.g. cotton and Nomex). The inner layer containing cooling fibres conducts heat and moisture away from the body through the evaporation of water. 5.5.4 Smart Structure for Protection and Thermal Comfort Outer shell textile materials for firefighting clothing have frequently been manufactured from 100% m‐aramid or polyamide‐imide, blends of m‐aramid, and p‐aramid fibres or by use of core spun yarns or staple mixtures with p‐aramid copolymer or fibres compris ing p‐aramid cores with m‐aramid or polyamide‐imide covers. However, m‐aramid and polyamide‐imide fibres shrink, consolidate, and thicken when exposed to a high tem perature heat source. The presence of p‐aramid or p‐aramid copolymer in either the fibre blend or as a core can be used to lessen fibre shrinkage and consequent breaking open of the garment. However, the inclusion of p‐aramid fibre in the blend has been found to be insufficient in tightly woven fabrics to prevent breaking open. Hainsworth TI‐Technology™ [173–175] is a double‐layer spacer fabric construction that combines the high performance of Nomex and Kevlar fibres in an intelligent way by keeping them as separate layers to maximize the benefits of each fibre. Nomex is on the face of the fabric, with the high strength of Kevlar protected from the effects of UV degradation and abrasion on the back. When the fabric assembly is hit by extreme heat,
5.5 Thermal Burden and Thermo‐Physiological Comfort
the Nomex layer consolidates, while the Kevlar layer remains unchanged. The different thermal shrinkage of the two fibres means that the two layers move and react against each other. The dynamic nature of the fabric means that the open, breathable construc tion required for everyday activities moves to form air pockets between the two layers, thereby increasing thermal protection only when it is most needed. Temperature‐dependent permeability to moisture could be provided by polyurethane based shape memory polymer [176]. Better comfort is also provided by pulling humid ity and sweat away from the surface of the skin, either with hydrophilic linings [177] or by the use of channelled cross‐section fibres with reinforced wicking properties. 5.5.5 Active Cooling System for Clothing Comfort Various smart textiles have been used to actively control clothing comfort for protective clothing. They include being able to sense the wearer’s physiological condition [5], their posture and activity [6], outside environment [7], as well as their responsive action [8]. Conductive yarns can be produced by coating with conductive polymers or by embed ded conductive fillers like carbon nanotubes [4]. Electrically active structures can then be formed, e.g. through specially patterned knitting [2] and ‐responsive materials for clothing [3]. However, numerous challenges remain, in particular with contactless sen sors, interconnects, electronic reliability, data and power transmission lines, and shield ing [178]. Other solutions use external power, e.g. for liquid coolant circulation [179] or with Peltier cells [180] embedded in the textiles. A personal cooling system sustains a microclimate circulating dry, fresh air, liquid, ice, or wax to draw and absorb heat from the wearer’s body. One example is a light weight ‘spacer vest’ for interceptor body armour (IBA), designed to assist the natural cooling through perspiration [181]. The spacer vest system could increase the evapora tive cooling potential by up to 20% in comparison with wearing standard IBA. Another example is a lightweight cooling system known as Breeze [182], which utilizes a light weight battery‐powered ventilation system that feeds fresh air beneath the body armour to re‐establish natural cooling through perspiration. The Breeze vest facilitates cooling by wicking moisture from the body and cooling through the natural phase change pro cess. A more advanced cooling system in the Future Force Warrior (FFW) project [183] was developed to provide microclimate control within the standard FFW suit or a full CBRN protected gear to support soldiers’ operation. The Body Ventilation System (BVS) [184] developed by Global Secure Safety Corporation uses a battery‐powered blower to circulate air through an air distribution device worn beneath the interceptor body armour and battledress uniform (BDU) to gain natural body cooling and improved physiological comfort. The Microclimate Cooling System (MCS) [185] is provided as part of the US Army’s Air Warrior program, for helicopter crews, operating in the hot climate of Southwest Asia. The microclimate cooling garment is connected to a con denser unit which chills water and pumps it through small tubes embedded in the vest. It is worn as an undergarment. Cooling can also be achieved by applying thermal regulation elements into the body armour [185]. This concept, eliminating the need for a liquid coolant or PCMs, uses high thermal‐conductivity channels embedded into the body armour itself. The heat conductors are applied over a moisture‐wicking layer pulling moisture from the body and dispersing the moisture to the outer surface, where it can evaporate.
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Protective suits for firefighters and others working in extremely hot conditions with a built‐in cooling system [186] is developed to provide a high quality thermal and mois ture management layer based on a 3D warp‐knitted fabric coated with a water‐binding polymer. Its structure will mimic the physical mechanisms for thermoregulation in the human body. A 3D textile structure is used for the thermal and moisture management layer with a cooling tubing system inserted into cavities in the 3D textile structure. The tubes have liquid circulating through them and remove heat in a similar manner to blood vessels in the body.
5.6 Testing Methods and Standards Various EN ISO standards have been established for the rational assessment of protec tion requirements and subsequent selection of appropriate clothing suitable for vari ous environments. For example, protective clothing used in food, drink, pharmaceutical, cosmetics, medical, electronic manufacture, and healthcare industries is required to have further properties in order to protect not only the wearer from environmental hazards but also the product from contamination (e.g. linting, pilling, dissolved mono mer) or cross‐infection between the wearer and the protective clothing itself. In the engineering design of textile materials to meet those specific performance require ments of clothing set in the CE marking scheme together with other additional func tions, the composition of fibres, membrane, coating, and accessory materials (such as seals, tapes, and zips) used in the garment, together with the microstructure of fabrics, yarns, and fibres employed to construct the clothing, need to correspond to a hazard ous environment, physiological comfort, durability, and other special requirements (e.g. product hygiene) in order to reach the functions, properties, and performance of the clothing. 5.6.1 Protective Clothing and Gloves Against Cold Major ISO standards for determining performance requirements and testing perfor mance of protective clothing and gloves are shown below. EN 340: 2003 – Protective clothing, general requirements specifies ergonomic requirements (comfort, weight, and design considerations), durability requirements (colour fastness and dimensional change after ageing), and sizing requirements (against wearer height, chest, and weight circumference). EN 342: 2004 – Protective clothing, ensembles, and garments against cold speci fies the requirements and test methods for performance of clothing ensembles (i.e. salopettes and jackets) to determine if adequate protection is provided by the protec tive clothing at temperatures lower than −5 °C. Performance of selected clothing ensemble can be tested by measuring the insulation value on a moveable, thermal manikin. BS EN 343:2003+A1: 2007 – Protective clothing. Protection against rain. This stand ard specifies protective clothings resistant to water penetration, including rain, precipi tation, fog, and ground humidity, as well as its level of breathability.
5.6 Testing Methods and Standards
BS EN 511: 2006 – Protective gloves against cold. Designed for testing any glove which claims protection against cold environments. The performance of protective gloves against cold are tested with a heated hand model. BS EN ISO 11079: 2007 – Ergonomics of the thermal environment. Determination and interpretation of cold stress when using required clothing insulation (IREQ) and local cooling effects. This standard specifies methods and strategies for assessing the thermal stress associated with exposure to cold environments, and will help determine required resultant clothing insulation for given conditions by using an IREQ index. These methods apply to continuous, intermittent, as well as occasional exposure and type of work (indoors and outdoors). BS EN 14058: 2004 – Protective clothing. Garments for protection against cool envi ronments. It specifies requirements and test methods for the performance of single garments (e.g. waistcoats, jackets, coats, or trousers and/or separable thermal linings) for protection against cooling of the body in cool environment. BS EN 13537: 2012 – Sleeping bag testing. A standard aiming to make sleeping bag testing and temperature rating more consistent. While this standard arguably still has flaws, it has largely achieved its objective. However, this standard does not apply to sleeping bags for use in extreme climates. 5.6.2 Protective Clothing Against Thermal and Fire Hazards Protection against heat and flame EN ISO 11612 EN ISO 14116 | EN 1486 EN 407: 2004 – Protective gloves against thermal risks (heat and/or fire). EN 469: 2005 – Protective clothing for firefighters. Performance requirements for protective clothing for firefighting. EN 659: 2003 – Protective gloves for firefighters. BS EN ISO 6942: 2002 – Protective clothing – Protection against heat and fire. Method of test: evaluation of materials and material assemblies when exposed to a source of radiant heat. BS EN ISO 9151: 2016 – Protective clothing against heat and flame. Determination of heat transmission on exposure to flame. BS EN ISO 11612:2015 – Clothing for protection against heat and flame. Test meth ods and performance requirements for heat‐protective clothing. BS ISO 13506 part 1 and part 2 – 2008 Protective clothing against heat and flame. Test method for complete garments. Prediction of burn injury using an instrumented manikin. BS EN ISO 15025: 2016 – Protective clothing. Protection against flame. Method of test for limited flame spread. BS ISO 16073: 2011 – Wildland firefighting personal protective equip ment. Requirements and test methods. ISO 17492: 2003 – Clothing for protection against heat and flame. Determination of heat transmission on exposure to both flame and radiant heat. 5.6.3 Protective Clothing Against Radiation X‐ray protection clothing for the individual using radiation is governed by a new EU directive regarding PPE 2016/425. X‐ray protection clothing for patients is governed by
139
140
5 Textile Materials for Protective Textiles
the EU directive for medical devices (MDD) 93/42/EWG. In order to comply with PPE, the article must be marked with a CE logo and a four‐digit number that correlates to the notified certification office. In the US, some radiative protective clothing must meet the burn safety criteria of OSHA Rule 29CFR Part 1910.269 and be compliant with National Fire Protection Association (NFPA) standards 2112 and NFPA 70E. EN 421: 2010 – Protective gloves against ionizing radiation and radioactive contamination. BS EN 1073‐1: 2016 – Protective clothing against solid airborne particles including radioactive contamination. BS EN 1073‐2: 2002 – Protective clothing against radioactive contamination. 5.6.4 Protective Clothing Against Microbial Hazards BS EN 14126: 2003 – Protective clothing. Performance requirements and tests meth ods for protective clothing against infective agents. ISO 16603: 2004 – Clothing for protection against contact with blood and body fluids. Determination of the resistance of protective clothing materials to penetration by blood and body fluids. Test method using synthetic blood. ISO 16604 – Clothing for protection against contact with blood and body flu ids. Determination of resistance of protective clothing materials to penetration by blood‐borne pathogens. Test method using Phi‐X 174 bacteriophage (‘virus’ penetra tion simulation). ISO 22610: 2006 – Surgical drapes, gowns and clean air suits, used as medical devices, for patients, clinical staff, and equipment. Test method to determine the resistance to wet bacterial penetration (wet bacterial penetration). ISO/DIS 22611 – Resistance to penetration by biologically contaminated liquid aerosols. ISO 22612: 2005 – Clothing for protection against infectious agents. Test method for resistance to dry microbial penetration. 5.6.5 Protection Against Chemicals Protection against chemicals EN 943‐1 | EN 943‐2 | EN 13034 EN 14605 | EN 13982‐1 EN ISO 5630 – Penetration test results at one minute of exposure to the hazardous substance. EN ISO 6529 – Permeation test assesses long‐term response, up to eight hours. 5.6.6 Protective Clothing Against Mechanical Hazards EN 381: 1999 – Protection against chainsaws. EN 388: 2003 – Protective gloves against mechanical risks. BS EN 510: 1993 – Specification for protective clothing for use where there is a risk of entanglement with moving parts. EN 1082‐1: 1997 – Protective clothing. Gloves and arm guards protecting against cuts and stabs by hand knives. Chainmail gloves and arm guards.
5.6 Testing Methods and Standards
BS EN ISO 13998: 2003 – Protective clothing. Aprons, trousers, and vests protecting against cuts and stabs by hand knives. EN 14328: 2005 – Gloves and armguards protecting against cuts by powered knives. BS EN ISO 14877: 2002 – Protective clothing for abrasive blasting operations using granular abrasives. BS EN 1522: 1999 – Windows, doors, shutters, and blinds. Bullet resistance. Requirements and classification. BS EN 1523: 1999 – Windows, doors, shutters, and blinds. Bullet resistance. Test method. 5.6.7 Ballistic Resistance and Stab/Cut Resistance NIJ Standard 0101.06 – Ballistic Resistance of Body Armour. NIJ Standard 0115.00 – Stab Resistance of Personal Body Armour. NIJ Standard 0104.02 – Riot Helmets and Face Shields. NIJ Standard 0106.01 – Ballistic Helmets. NIJ Standard 0117.00 – Public Safety Bomb Suit Standard. NIJ Standard 0108.01 – Ballistic Protective Materials. FBI Body Armour Test Protocol 2008. HP White 401‐01B Bullet Resistant Helmet Testing Procedure. HOSDB Body Armour Standards for UK Police (2007) Part 1: General Requirements (39/07/A). HOSDB Body Armour Standards for UK Police (2007) Part 2: Ballistic Resistance (39/07/B). HOSDB Body Armour Standards for UK Police (2007) Part 3: Knife and Spike Resistance (39/07/C). 5.6.8 Other Standards EN 50237: 2000 – Gloves and mitts with mechanical protection for electrical purposes. EN ISO 11611 – Protective clothing used during welding operations. BS EN 1149‐1‐8: 2006 – Protective clothing. Electrostatic properties. EN ISO 20471 – High visibility protective clothing (equipment) Some typical examples of the performance of protective clothing set in the CE mark ing scheme and defined by various associated BS EN ISO standards were summarized in Table 5.10. All the standards for CE marking clothing are based on the other EN and ISO standards for the examination of the fabric properties, which are decisive for the clothing functions including protection (e.g. heat, cold, electricity, cut, stab, etc), com fort (thermal and tactile comfort properties such as moisture transport resistance, smoothness, and softness), mobility (heaviness, flexibility, and conformability), durabil ity (protection properties and strength properties after washing, flex cracking, and age ing), and others (environmental impact, toxicity, etc.).
141
148
5 Textile Materials for Protective Textiles
5.7 Sustainability and Ecological Issues Single‐use items of protective equipment – such as gloves, aprons, and masks – are usually disposed of after each procedure or activity to prevent cross‐transmission of microorganisms. Manufacture of most of the high performance fibres could be harmful to environ ment. For example, one of the main solvents used in the process of spinning Kevlar fibres is sulphuric acid, which is very toxic to animals and plants if disposed of or used incorrectly and is dangerous to workers when used in operation, thus the production process could be a problem in sustainability. Most high performance fibres used in protective textile products are not biodegrad able. They barely decompose in a landfill, even over a very long period. Currently, the only way to reduce the environmental impact of these products is to reuse and recy cle them. When recycling, the disposed product made from filament could be made into yarns and nonwovens after being chopped into staple fibres and pulps. Lifecycle assessment of the environmental impact of three types of protective cloth ing – including emergency operations under extreme weather conditions (floods, hail, etc.), firefighters’ clothing for fighting wild land fires, and medical protective clothing for first aid – has been conducted [188]. As most protective clothing for emergency operations, which is mainly made from conventional fibres (e.g. nylon, polyester and cotton) and membranes, can be either reused or recycled, it was found that its major environmental impact came from its uses and maintenance processes (e.g. laundry and disinfections, etc). However, for protective clothing for firefighters and medical first aid which are mainly made from flame‐retardant materials (e.g. chemicals used in Proban® flame‐retardant agents) and high performance fibres (e.g. Kevlar and Nomex), the manufacturing process is more polluting than its maintenance and use phase. Apparently, the disposal of contaminated protective clothing is still a challenge in terms of sustainability, although the reuse and recycling of used protective textiles is currently common practice.
5.8 Conclusion Textile materials are employed in various protective textile products for the protection of wearers from cold, thermal, fire, water, oil, radiation, acoustic, and microbial hazards while maintaining comfort. Natural fibres, specific synthetic fibres, high performance fibres, and other functional materials all demonstrate excellent performances in either protection or comfort of protective clothing in various environmental conditions; engi neering design of their microstructures, hierarchy architectures, and properties play a great role in achieving the required performance. A combination of those functional textile materials in engineered structures would help achieve desirable functionalities in specific applications. The disposal of contaminated protective clothing is still a chal lenge in terms of sustainability, although the reuse and recycling of used protective textiles is currently common practice.
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6 Personal Protective Textiles and Clothing Sumit Mandal, Simon Annaheim, Martin Camenzind, and René M. Rossi Empa - Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Biomimetic Membranes and Textiles, St Gallen, Switzerland
6.1 Introduction Clothing plays an important role in protecting human beings from their surrounding environments [1–3]. For centuries, human beings have used regular clothing (jacket, windcheater) to protect themselves from light rain, cold, and/or windy environments. In recent times, specialized clothing is considered significantly important for the per‑ sonal protection of working human beings from their occupational hazards [4]. In some occupations, workers are exposed to various hazards, namely chilled air, extreme cold air/water, heavy rain, high heat (e.g. flash fires, hot liquids splash, steam, electric arc), bullets or knives, chemical substances (e.g. flammable materials, acids), biological matters (e.g. bacteria, viruses), radiological threatening agents, and/or nuclear elements [5–8]. For example, food processing unit operators, pilots of capsized vessels, navy personnel, police officers, and flood rescuers can occasionally be exposed to chilled air, cold water, and/or heavy rain; cooks/chefs, firefighters, and industry (forg‑ ing, oil, and gas) workers can often be exposed to high heat; police officers and military personnel can be exposed to bullets or knives; and, laboratory technicians, healthcare staff, and military personnel can be exposed to chemical, biological, radiological, and/ or nuclear hazards. In order to get protection from the hazardous working environments, employees (e.g. police officers, military personnel, firefighters, healthcare staff ) need to wear textile based personal protective clothing (PPC) [9, 10]. PPC acts as a barrier between hazard‑ ous environments and wearers, which actually provides them with protection and safety [11]. It is also required that PPC should effectively regulate the metabolic heat and sweat vapour generated by wearers’ bodies [12, 13]. This effective regulation of meta‑ bolic heat and sweat vapour should provide thermo‐physiological comfort to wearers. Along with functional performance (hazards protective performance and thermo‐ physiological comfort performance), PPC should also possess some aesthetic features like appropriate colour (e.g. dark blue or tan coloured PPC is mainly worn by police officers) and printed design (e.g. camouflage designs are generally printed on military PPC). These aesthetic features are especially required to ensure the visual presence of High Performance Technical Textiles, First Edition. Edited by Roshan Paul. © 2019 John Wiley & Sons Ltd. Published 2019 by John Wiley & Sons Ltd.
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the on‐duty employees. However, PPC should have both functional performance (pro‑ tection and comfort) as well as aesthetic features (colour and printed design) for its effective use by a wearer. To achieve the desired functional performance and aesthetic features, it is necessary to thoroughly understand the various aspects of textile based PPC (e.g., textile materials, manufacturing processes). Considering this, various aspects of textile based PPC are discussed in the following section. Furthermore, some key issues related to various aspects of PPC are indicated before concluding this chapter. By resolving these key issues, high quality PPC could be manufactured in future which could provide more effective functional performance and aesthetic features for the wearers.
6.2 General Aspects of Textile Based PPC Generally, PPC is commercially manufactured through different stages, as shown in Figure 6.1. As per Figure 6.1, the basic raw material for manufacturing the PPC is textile fibre. After the selection of suitable fibres (e.g. natural, synthetic, or a blend of natural and/or synthetic fibres), they are spun into different types of yarns (e.g. ring‐spun, other‐spun) using various spinning techniques (e.g. ring spinning, rotor spinning) [14]. Then, these spun yarns are used in the weaving or knitting process to produce the woven or knitted fabrics, respectively [15, 16]. Sometimes, the fibres or filaments of the synthetic fibres are directly used in the nonwoven process (e.g. chemical bonding, mechanical bonding, electrospinning) to produce nonwoven fabrics [17]. Finally, the fabrics (woven, knitted, and/or nonwoven) are used in the garmenting process (cutting, sewing) to fabricate the PPC. Depending upon the requirements, the intermediate materials (fibres, yarns, and fab‑ rics) for PPC can be processed through different dyeing, printing, and/or finishing techniques (Figure 6.1) [18, 19]. For example: colours can be imparted on these materi‑ als using different dyes into the dyeing processes such as loose stock fibre dyeing, high temperature high pressure (HTHP) fibre, yarn dyeing, and continuous fabric dyeing. These dyes can also be used to print a design on fabrics by applying different printing techniques such as roller printing and screen printing. Furthermore, fabrics can be mechanically (by sanforizing with moisture and dryer) and/or chemically (by padding with finishing agents) finished in order to enhance their properties, such as dimensional stability, flame retardancy, water repellency, etc. The above discussion shows how different processing techniques (spinning, weaving, knitting, nonwoven, dyeing, finishing, garmenting) can help to manufacture PPC with the required functional performance and aesthetic features. It is further notable that these techniques can generate a huge amount of waste materials (fibres, yarns, fabrics), chemicals (dyes, finishing agents), energy (thermal, electrical), and water (during wet processing, namely dyeing and finishing) [20, 21]. There is an estimate that nearly 200 l of waste water can be generated during wet processing of 1 kg material [22]. This indi‑ cates that water is the largest waste product during the manufacturing of PPC. All this waste can affect the ecology by polluting the environment of the inhabitants of this earth. Hence, it is necessary to use ecologically sustainable approaches for PPC manu‑ facturing through proper waste management (e.g. waste water recycling, workers train‑ ing and awareness, monitoring waste generation and disposal) (Figure 6.1). Additionally,
Dyed Fibre
Spinning
Spinning
(e.g. ring, rotor)
Dyeing
Dyed Yarn Weaving/ Knitting
Weaving/ Knitting
Fabric (e.g. woven, nonwoven)
Finishing, Dyeing, Printing
Finished, dyed, printed fabrics
Personal Protective Clothing
Garmenting
Spun Yarn
bonding, electrospinning)
Dyeing
(e.g. ring-spun, other-spun)
Garmenting
bonding, electrospinning)
Nonwoven process (e.g. chemical bonding, mechanical
Textile Fibre
(e.g. natural, synthetic)
Nonwoven process (e.g. chemical bonding, mechanical
6.2 General Aspects of Textile Based PPC
(e.g. for hazards like extreme cold, high heat)
Figure 6.1 Manufacturing of PPC.
PPC should not contain any harmful substances (e.g. textiles, finishes) that can affect the wearer’s health and damage the environment; so, the materials used for PPC should also be ecologically sustainable. According to Figure 6.1, PPC can be manufactured through the technical processing of different materials. Eventually, the types (e.g. natural fibres, ring‐spun yarns, woven fabrics) and processing techniques (e.g. spinning, weaving, dyeing) of these materials can significantly affect the manufacturing of the PPC [23]. It is recommended to sys‑ tematically and intermittently monitor the properties (e.g. tenacity, strength, colour fastness) of these materials to effectively achieve the desired quality of the manufac‑ tured PPC, especially in terms of its required functional performance and aesthetic features [24]. Notably, this continuous monitoring of the properties can also help to minimize the re‐processing of any material, which ultimately makes the textile busi‑ ness profitable (by reducing the extra cost of purchasing and re‐processing of materi‑ als) and ecologically sustainable (by reducing the textile waste). For this monitoring, the properties of materials can be measured using different test methods developed by standard organizations, namely the International Organization for Standardization
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(ISO), American Society for Testing Materials (ASTM), American Association of Textile Chemists and Colorists (AATCC), European Committee for Standardization (CEN), and National Fire Protection Association (NFPA). This suggests that a thorough understanding of materials is essential in order to manufacture PPC with proper quality (i.e. functional performance and aesthetic fea‑ tures). Therefore, the following sections discuss each of the materials (fibres, yarns, fabrics) used in PPC manufacturing. In these sections, the types, processing techniques, ecological sustainability, and/or testing of the materials are scientifically explained. Thereafter, the fabrication process of the PPC from fabrics is highlighted.
6.3 Fibres for PPC Two different types of fibres – natural and/or synthetic – are usually selected for the industrial manufacturing of PPC [11, 25, 26]. Commonly, it is expected that the tenacity (i.e. the ratio of the load required to break a fibre and the linear density of that fibre) and elasticity (i.e. the ability of a fibre to return to its original length after the removal of stress) of the selected fibres should be adequate enough to maintain the integrity of the PPC under any hazardous environment. Depending upon the type of hazardous envi‑ ronment, moisture regain (MR; i.e. the weight of water in a fibre as a percentage of its oven dry weight), ignition, or glass transition temperature (i.e. the temperature at which a natural fibre ignites or a hard synthetic fibre is transferred to a soft rubbery fibre), and limiting oxygen index (LOI, i.e. the minimum amount of oxygen required to support the combustion of the fibres) of the fibres could be substantially important to achieve the required quality of the PPC. Although the MR and ignition/glass transition temperature mainly depend upon the polymer composition of the fibres, it is notable that LOI values of the artificially produced fibres (e.g. regenerated natural fibre viscose, synthetic fibre polyester) could be enhanced by doping the phosphorous based flame‐retardant (FR) chemicals (e.g. bis(2‐thiono‐5,5‐dimethyl‐l,3,2‐dioxaphosphorinayl)oxide, n‐propoxyphosphazene, n‐methylol‐3‐dimethylphosphonopropionamide, red phosphorous) within their poly‑ mer compositions. The enhancement of LOI could help to convert an originally unsuitable non‐FR fibre (viscose, polyester) for PPC into a suitable FR fibre (FR vis‑ cose, FR polyester). Furthermore, fibre structure (e.g. surface topography, cross‐section) can substantially control some of its properties (e.g. colour fastness at fabric stage, tenacity, elasticity). Hence, fibre structure is important to consider for the manufacture of good‐quality PPC. 6.3.1 Natural Fibres Considering the properties (tenacity, elasticity, MR, combustion temperature, and LOI), two natural fibres – ‘plant/cellulosic fibre cotton’ and ‘animal/protein fibre wool’ – are commonly used for PPC (Table 6.1). Recently, some other natural fibres (such as ‘plant fibre flax’ and ‘animal fibre silk’) have also been introduced for the manufacture of PPC (Figure 6.2). Contextually, it is notable that these natural fibres are relatively expensive. Hence, cost‐efficient regenerated natural (cellulosic) fibre ‘viscose’ is preferred nowadays for the manufacture of PPC. Along with natural or
6.3 Fibres for PPC
Table 6.1 Properties of natural fibres used in PPC.
Fibres
Polymer composition
Tenacity Elasticity (gm/denier) (%)
MR (%)
Ignition Temperature LOI (°C) (%)
Cotton
Cellulose
4
52
7.5
~400 (burn freely)
15
Wool
Protein
1.6
69
13.6
~600 (do not burn freely)
25
Flax
Cellulose
4–5
Very low
12
~400 (burn freely)
18
Silk
Protein
4
52
11
~600 (do not burn freely)
20
Viscose
Regenerated cellulose
Varies, as artificially produced
Varies, as artificially produced
11
~100
19
Glass, Ceramic
A compound of silica, sodium, potassium, magnesium, calcium, strontium, barium
Varies, as artificially produced
Varies, as artificially produced
0
~1500
70
regenerated organic fibres (cotton, wool, flax, silk, viscose), a few regenerated natural inorganic fibres (eco‐friendly glass, ceramic fibres) have also been used for PPC manu‑ facturing [27–29]. According to Table 6.1, the properties of these fibres (cotton, wool, flax, silk, viscose, glass, ceramic) can vary in a certain range at a standard atmospheric condition (21 °C temperature and 65% relative humidity). Additionally, their tenacity could change in wet conditions, such as at high relative humidity (e.g. wet tenacity of cotton and flax is higher and lower, respectively). It is further notable from Figure 6.2 that the surface topographic views of these fibres are different in scanning electron microscopy (SEM). As a result, the uptake of dyes and finishing agents of these fibres is different, which ultimately varies the colour fastness of fabrics. Altogether, it reflects that PPC with varied quality can be manufactured by using different types of natural fibres. Finally, as any type of natural fibre is ecologically sustainable (because they are bio‑ degradable and require less industrial processing to produce), it is required to investi‑ gate the usability of other natural organic fibres (e.g. jute, hemp, ramie) for PPC manufacturing apart from the existing cotton, wool, flax, silk, and viscose [30]. Notably, it is very difficult to consistently achieve the required properties of natural organic fibres from one lot to the other lot even though they are cultivated at the same place. Therefore, commercial markets nowadays are more interested in synthetic‐fibres‐ based PPC [27]. 6.3.2 Synthetic Fibres A set of synthetic fibres (e.g. polyester, nylon, acrylic, aramid, polyimide, polybenzi‑ midazole, polybenzoxazoles, melamine formaldehyde, chlorinated, fluorinated, poly‑ phenylene sulfide, semi‐carbon) are widely used for manufacturing PPC (Table 6.2)
163
Cotton
Gossypium hirsutum Ginning
SEM View
Wool
Ovis aries Scouring and Bleaching
Linum usitatissimum
Retting
SEM View
Flax SEM View
Bombyx mori
Silk Boiling and Demineralizing
SEM View
Figure 6.2 Natural fibres for PPC (cotton, wool, flax, silk). Source: Ms. Mary Ankeny (Vice President – Product Development and Implementation Operations, Cotton Incorporated, USA), Mr. Andy Cooper (Science Impact Leader − Wool Products & Supply, AgResearch Limited, New Zealand), Ms. Patty Grossman (President, Two Sisters Ecotextiles, USA), Prof. (Dr) Ryszard Kozłowski (Deputy Director, Institute of Natural Fibres and Medicinal Plants, Poland), Dr Hariraj Gopal (Scientist, Central Silk Technological Research Institute, India).
6.3 Fibres for PPC
Table 6.2 Properties of the synthetic fibres used in PPC.
Spinning techniques
MR (%)
Glass transition temperature LOI (%) (%)
Fibres
Polymer composition
Polyester
Terephthalic acid and ethylene glycol
Melt
0.4
250
20
Nylon
Adipic acid and hexamythelenediamine
Melt
4.5
250
20
Acrylic
Acrylonitrile
Wet‐solution
1.5
100
18
Aramid
Aromatic diamines and diacids or diacids chlorides
Wet‐solution
5–7
300
45
Polyimide
Aromatic tetracarboxylic dianhydride and aromatic diamine
Wet‐solution
3.5
380
45
Polybenzimidazole
Tetra‐aminobiphenyl and diphenylisophthalate
Dry‐solution
13
420
40
Polybenzoxazoles
Benzoxazoles
Wet/ Dry‐solution
1.5
500
65
Melamine formaldehyde
Melamine and formaldehyde
Dry‐solution
5
315
32
Chlorinated (polyvinyl chloride)
Chloride
Melt
0
80
40
Fluorinated Fluoride (polytetrafluoroethylene)
Melt
0
115
95
Polyphenylene sulfide
Phenylene sulfide
Melt
0.1
80
40
Semi‑carbon
Acrylonitrile
Wet‐solution
0
300
55
[11, 27]. These fibres are artificially manufactured from a group of polymers using different spinning techniques, namely melt spinning, dry‐solution spinning, or wet‐ solution spinning (Figure 6.3). By adjusting the drawing or stretching process in these spinning techniques, it is possible to control the tenacity and elasticity of these fibres as per the requirements of further use. Depending upon the polymeric compositions, the MR, melting temperature, and LOI of these fibres can be varied in a wide range to achieve the required quality of PPC. Nevertheless, the cross‐sectional view of con‑ ventional synthetic fibres is usually solid‐circular with very high diameter (≥ 5 μm). Therefore, they possess some properties (e.g. tenacity, elasticity, dye uptake) in a limited range. In order to overcome this limitation, some fibres have been recently developed with different cross‐sectional views (e.g. hexalobular, scalloped oval, hol‑ low‐circular) and/or lower diameters (50–500 nm). The latest development in this context is a hollow nanofibre, such as carbon nano tube (CNT), which can be used in PPC [31, 32].
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6 Personal Protective Textiles and Clothing Polymer Container
Polymer Hopper Molted Polymer
Polymer Solution Spinning Pump
Spinning Pump
Spinning Nozzle
Warm Air
Spinning Nozzle Cold Air
Blade
Blade Fibre
Fibre Drawing Roller Stretching
Drawing Roller Stretching
Filament
Filament
Dry-solution Spinning
Melt Spinning
Polymer Container Polymer Solution Spinning Pump Chemical Bath
166
Spinning Nozzle Blade
Fibre Drawing Roller Stretching
Filament
Wet-solution Spinning
Figure 6.3 Fibre spinning techniques.
6.3.3 Dyed Fibres Natural and synthetic fibres are generally dyed using the loose stock and HTHP fibre dyeing machines, respectively (Figure 6.4) [33]. The working principles of the loose stock and HTHP machines are similar; however, as the name suggests, the HTHP machine can be operated at high temperature and high pressure depending upon the types of synthetic fibres being used for the dyeing. In this machine, a carrier with a removable perforated lid and base is loaded with fibres and its lid is closed with two screws. Through its base, dye liquor is circulated within the carrier from a storage tank for a certain duration (depending upon the type of fibre, e.g. natural wool or synthetic aramid, and dye, e.g. direct, disperse, sulfur, pigment, mordant, vat, reactive, macromo‑ lecular, metalized, azo, aniline, anthraquinonoid). And, the temperature of the dye liq‑ uor is adjusted depending upon the types of fibres and dyes. After the circulation, the dye liquor is drained from the carrier and fibres are taken out of the carrier (by opening
6.4 Yarns for PPC
Lid
Lid Closing Screw Fibre inside the carrier Dye-liquor Storage
Fibre Carrier
Reversible Pump and Valve
Dye-liquor circulation system
Draining
Figure 6.4 Working principle of loose stock or HTHP fibre dyeing machine. Table 6.3 Test standards for measuring fibre properties. Fibre properties
Test standards
Tenacity
ISO 5079:1995; ASTM D 3217 M:2015
Elasticity
ISO 5079:1995; ASTM D 1774:1994
MR
ISO 6741‐4:1987; ASTM D629:2015
Combustion/Melting temperature
ISO 11357‐1:2016; ASTM D 7138:2016
LOI
ISO 4589‐2:1996; ASTM D 2863:2013
Structures
ISO 11827:2012; ASTM D 276:2012
the lid). The advantage of this technique is that the colour fastness of the dyed fibres is very high. However, it is very difficult to achieve the required colour of the PPC from the dyed/coloured fibres because they need further processing to manufacture the PPC. 6.3.4 Fibre Testing The above discussion indicates that some fibre properties are very important for manufacturing the PPC with quality. These properties are mainly tenacity, elasticity, MR, combustion/melting temperature, LOI, and structure. In order to measure these properties, standard test methods developed by ISO and ASTM are used. Specific test standards along with corresponding fibre properties are presented in Table 6.3 [34–44].
6.4 Yarns for PPC It is notable that the filament can be directly used as a yarn, by removing the blading process of converting filament into fibre (Figure 6.3) [45]. The direct use of filament yarns escapes all the processing stages involved in converting fibres into yarns, and thus makes it a cost‐effective (less production cost) and ecologically sustainable approach (it generates less soft fibres, hard yarns, and energy waste). However, the
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surface of filament yarns is very smooth, which makes it difficult to use them during the weaving/knitting/garmenting process to manufacture the fabrics and PPC with quality. Owing to the smooth surface topography, the uptake of dyes and finishing agents of these filament‐yarns‐based fabrics is very low, which also ultimately affects the quality of PPC. Owing to this limitation, the use of spun yarns in PPC manufactur‑ ing has gained popularity over filaments yarns [14, 46]. Broadly, spun yarns are pro‑ duced from fibres and can be categorized into ‘ring‐spun’ and ‘other‐spun’ (e.g. rotor, air‐jet, friction) yarns. In general, ring‐spun yarns are produced through numerous stages, whereas fewer stages are involved in the production of other‐spun yarns. Therefore, the production of the ring‐spun yarn and its production cost are very high and low, respectively. Nevertheless, any type of fibres can be used in the production of ring‐spun yarns and their properties (e.g. breaking strength, evenness) are much better controlled than the other‐spun yarns. Because of the versatility of ring‐spun yarns, they are generally used for the manufacture of PPC. Notably, by using a suitable yarn dyeing machine and dyes, both ring‐ and other‐spun yarns can be coloured as per the con‑ sumer’s requirements. And, the properties of the undyed or dyed yarns can be meas‑ ured by various ISO and ASTM standard methods. 6.4.1 Ring‐Spun Yarns Ring‐spun yarns are generally produced through different processing stages, as indi‑ cated in Figure 6.5 [14]. At first, the fibres supplied in the bale form (Figure 6.6a) are opened and cleaned by a bale opening machine (Figure 6.7a) in the blow room process. Then, these opened fibres are individualized to produce sliver (Figure 6.6b) in the
Fibre Bale
Ring-spun Yarn Package
Blowroom
Winding
Opened Carding and Cleaned Fibres
Ring-spun Yarn Bobbin
Ring Spinning
Carded Combing Sliver
Roving
Roving Yarn
Combed Sliver Drawing
168
Draw-framed Sliver
Figure 6.5 Processing of ring‐spun yarns.
(a)
(b)
(c)
(d)
(e)
Figure 6.6 Materials used for producing yarn: (a) fibre bale, (b) sliver, (c) roving yarn package, (d) yarn bobbin, and (e) yarn package. Source: Mr Nityanada Kundu (Manager, Vardhaman Spinning Mills, India).
6.4 Yarns for PPC
carding process by a carding machine (Figure 6.7b). Next, the carded sliver is passed through a lap former (Figure 6.7c) and short fibres are subsequently removed from the formed lap (as the presence of only long fibres enhances the strength of produced yarns) in the combing process by a combing machine (Figure 6.7d). And then, the combed slivers are drawn in the drawing process by a draw frame machine (Figure 6.7e) to make the parallel orientation of the long fibres within the slivers (as the parallel orientation of fibres enhances the strength and evenness of the yarns). Thereafter, draw‐framed slivers are processed by a speed frame machine (Figure 6.7f ) for drawing and twisting them to produce the package of roving yarns (Figure 6.6c). Finally, roving yarns are re‐drawn and re‐twisted by a ring spinning machine (Figure 6.7g and h) to produce the ring‐spun yarns and to wrap them onto small bobbins (Figure 6.6d). The ring‐spun yarns from these bobbins are re‐winded on plastic cones in the winding process by a winding machine (Figure 6.7i) to produce the yarn packages (Figure 6.6e). The evenness of the conventional ring‐spun yarns is generally low, owing to their high hairiness. However, the more even (i.e. less hairiness) and compact ring‐spun yarns can also be produced
(a)
(b)
(c)
(d)
(e)
(f)
(g)
Figure 6.7 Machinery for producing yarn packages: (a) bale opening, (b) carding, (c) combing, (d) draw frame, (e) speed frame, (f ) ring spinning, and (g) winding. Source: Mr Nityanada Kundu (Manager, Vardhaman Spinning Mills, India).
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6 Personal Protective Textiles and Clothing
nowadays in the ring‐spinning machine by condensing (e.g. aerodynamic condensing, mechanical condensing, and magnetic condensing) the drawn roving yarns before twisting them to produce ring‐spun yarns. 6.4.2 Other‐Spun Yarns Apart from ring‐spun yarns, some other‐spun yarns are also widely used in PPC manu‑ facturing. As other‐spun yarns are directly produced from fibres/slivers, their produc‑ tion is cost‐effective and ecologically sustainable. Depending upon the processing technique, the other‐spun yarns can be primarily categorized into rotor‐spun, friction‐ spun, and air‐jet‐spun [47–50]. 6.4.2.1 Rotor‐Spun Yarn
Rotor‐spun yarn technology was developed in 1963 by Cotton Research Institute, Czechoslovakia [47]. This technology involves direct feeding of a draw‐framed fibre sliver (Figure 6.8) into a rotor‐spinning machine to produce the yarn packages (Figure 6.9). These yarns comprise looped, hooked, and/or disoriented fibres in their structures; eventually, the breaking extension, hairiness, and abrasion resistance of these yarns are much higher than the ring‐spun yarns. Nowadays, rotor‐spun yarns are widely used after ring‐spun yarns.
Fibre Bale
Blowroom
Opened Carding and Cleaned Fibres
Carded Combing Sliver
Rotor-spun Yarns
Rotor Spinning
Combed Sliver Drawing
170
Draw-framed Sliver
Figure 6.8 Processing of rotor‐spun yarns.
Trash Yarn to Package
Feed Plate
Transport Channel
Sliver Opening Roller
Doffing Tube Rotor
Figure 6.9 Working principle of rotor‐spinning machine.
Feed Roller
6.4 Yarns for PPC
Blowroom
Opened Carding and Cleaned Fibres
Carded Combing Sliver
Friction-spun Yarns
Friction Spinning
Combed Sliver Drawing
Fibre Bale
Draw-framed Sliver
Figure 6.10 Processing of friction‐spun yarns.
Slivers
Drafting Rollers
Air Flow Device
Fibre Opening Rollers
Yarn to Package
Friction Rollers Drafting Rollers Figure 6.11 Working principle of friction spinning machine.
6.4.2.2 Friction‐Spun Yarn
The technique to produce friction‐spun yarn was developed by Dr Ernst Fehrer in 1975 and is called DREF friction spinning technology [50]. This technology was further improved by Dr Fehrer and is called DREF‐II and DREF‐III friction spinning technolo‑ gies. These technologies involve feeding a draw‐framed fibre sliver into a DREF friction spinning machine (Figure 6.10). This machine first drafts the sliver and then opens it by an opening roller (Figure 6.11). The opened fibres are thereafter passed through friction rollers with the help of air flow. Owing to the friction in the friction rollers, the yarns are formed and winded on a package. The friction‐spun yarns are bulky and thermally insu‑ lative in nature, which makes them suitable for the production of PPC. However, the low strength of the friction‐spun yarns could be one of the concerns about their suita‑ bility to use in PPC. 6.4.2.3 Air‐Jet‐Spun Yarn
The technology to produce air‐jet‐spun yarns was commercially introduced in the mar‑ ket by Murata Machinery Limited, Japan in 1990 [48, 49]. In 2003, Rieter Group of Switzerland introduced its own spinning technology to produce the air‐jet‐spun yarns. As Rieter’s air‐jet spinning machine has high productivity, flexibility, simple settings, ease of operation, and low downtimes for maintenance, this technology quickly gained popularity in the market for producing air‐jet‐spun yarns. As per this technology, a strand of draw‐framed fibre sliver is directly fed into the air‐jet spinning machine (Figure 6.12). Next, the sliver is drafted by drafting rollers and then passed through air nozzles to produce the yarn (Figure 6.13). The core of this yarn has parallel fibre strands
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6 Personal Protective Textiles and Clothing
Blowroom
Opened Carding and Cleaned Fibres
Carded Combing Sliver
Air-jet-spun Yarns
Air-jet Spinning
Combed Sliver Drawing
Fibre Bale
Draw-framed Sliver
Figure 6.12 Processing of air‐jet‐spun yarns.
Drafting Rollers Air Nozzles
Slivers
Sheath with Twisted Fibres Yarn Core with Parallel Fibres
Drafting Rollers Figure 6.13 Working principle of air‐jet spinning machine.
and its sheath is wrapped by fibres. The air‐jet‐spun yarns possess the least hairiness and abrasion resistance in comparison to the rotor‐spun and friction‐spun yarns, which makes air‐jet‐spun yarns more suitable for the production of a knitted fabric. 6.4.3 Dyed Yarn An undyed yarn package can be dyed using the loose stock or HTHP yarn dyeing machine, depending upon the types of fibres used in the yarn (Figure 6.14) [51]. In this machine, yarn packages are loaded onto a perforated spool within a carrier having removable perforated lid and base. Next, the lid of the carrier is closed by closing screws, Lid
Lid Closing Screw Perforated Spool Packages
172
Dye-liquor Storage
Yarn Package Carrier
Dye-liquor Circulation System
Figure 6.14 Working principle of a yarn dyeing machine.
Reversible Pump and Valve Draining
6.5 Fabrics for PPC
Table 6.4 Test standards for measuring yarn properties. Yarn Properties
Test Standards
Breaking strength and extension
ISO 2062:2009; ASTM D 2256M:2010
Evenness
ISO 16549:2004; ASTM D 1425M:2014
Hairiness
ASTM D 5647: 2007
Abrasion resistance
ASTM D 6611:2007
and dye liquor from a storage tank is circulated within the carrier through its base. The temperature of the dye liquor can be adjusted depending upon the types of fibres, yarns, and dyes. After dyeing, the dye liquor is drained off from the carrier and yarn packages are taken out of the carrier (after opening the lid). This technique has the advantage that the customized colour and shade matching of the small lot yarns packages is possible. However, the poor colour uniformity and fastness of the dyed yarns ultimately affect the quality of the PPC. 6.4.4 Yarn Testing Based on the above discussion, it is clear that some yarn properties – such as breaking strength, breaking extension, evenness, hairiness, and abrasion resistance – are impor‑ tant in order to produce a suitable fabric for PPC [52]. To measure these properties, the standard test methods developed by ISO and ASTM can be used (Table 6.4) [53–58].
6.5 Fabrics for PPC In general, four types of fabrics are used for the PPC: woven fabrics, knitted fabrics, nonwoven fabrics, and composite fabrics [59–62]. Considering different fabric proper‑ ties (weight, thickness, air permeability, thermal resistance, evaporative resistance, and/ or colour fastness), the selection of a particular type of fabric depends upon the end use of the PPC. For example, as underwear is always in close contact with a wearer’s skin, it is necessary that the fabric used for it should have good extensibility and strength. Considering this, knitted fabrics are preferred for the manufacturing of underwear to be worn by wearers under their PPC. Also, as strength and thermal insulation are the key fabric properties to consider, an assembly of woven, nonwoven, and/or composite fab‑ rics is generally preferred for the manufacturing of PPC for firefighters/military person‑ nel. Sometimes, the electrostatic propensity (EP) of the fabric becomes very important for the manufacturing of PPC, and the EP is primarily dependent on the MR, polymer composition, and electrical resistance of the fibres. The EP of a natural‐fibre‐based fab‑ ric is very low as it has high MR and low electrical resistance (e.g. electrical resistance of cotton is 6.8 Ω), whereas the EP of a synthetic‐fibre‐based fabric is very high, owing to its low MR and high electrical resistance (e.g. electrical resistance of polyester/acrylic is 14 Ω). A fabric with high EP could make a cling PPC, and also makes it difficult to remove soil from the PPC during its washing and dry cleaning. Notably, by using a suit‑ able fabric dyeing machine and dyes, all types of fabrics can be coloured as per the
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6 Personal Protective Textiles and Clothing
Heddle
Reed Weft Insertion Device Cloth Fell Front Rest
Back Rest
Fabric
Warp Warp Beam Cloth Beam
Figure 6.15 Working principle of a power loom weaving machine.
Weft Warp
Figure 6.16 Plain weave fabric.
consumer’s requirements. And, the properties of the fabrics can be measured by various ISO and ASTM standard methods. 6.5.1 Woven Fabrics Woven fabrics for PPC are generally produced on a power loom (shuttle loom, projec‑ tile loom, rapier loom, air‐/water‐jet loom) machine by proper interlacement of warp and weft yarns (Figure 6.15) [63]. This loom involves dividing a set of warp yarn (on a warp beam) lengthwise into two sets (upper positions and lower positions) by using two heddles, and the up and down movement of these heddles can help to interchange the positions of these two sets of warp yarns. Then, a weft yarn is cross‐wisely inserted in between the two sets of warp yarns by a device/technique (shuttle, projectile, rapier, air jet, or water jet) and a traverse‐motioned reed helps to securely push the weft yarn into the cloth fell to produce the fabric. Then, this fabric is winded onto a cloth beam. By varying the movements of the two sets of warp yarns at different time intervals, it is possible to produce the woven fabric with different interlacement of warp and weft yarns. These fabrics can be categorized into plain weave fabrics (1 warp up and 1 weft down), twill weave fabrics (2 warp up and 1 weft down), etc. (Figures 6.16 and 6.17). 6.5.2 Knitted Fabrics Although woven fabrics are produced by interlacing two different yarns (lengthwise warp yarns and crosswise weft yarns), knitted fabrics are produced by interlacing only one yarn [64]. The yarn in the knitted fabric follows a meandering path and forms
6.5 Fabrics for PPC
Weft Warp
Figure 6.17 Twill weave fabric.
Figure 6.18 Working principle of a circular knitting machine.
Yarn Guide Yarn Yarn Package YarnTensioner Feeder
Yarn Guide
Needle Fabric Take Down Roller Cloth Beam
symmetric loops above and below the mean path of the yarn. If these loops run across the length and width of the fabric, this is called warp and weft‐knitted fabrics, respec‑ tively. In general, weft‐knitted fabrics are used in the garment manufacturing. The weft‐ knitted fabric can be manufactured by a circular knitting machine or flatbed knitting machine. The cost of the circular knitting machine is lower than the flatbed knitting machine; therefore, circular knitting machines are widely used in the production of knitted fabrics (Figure 6.18). In the circular knitting machine, the yarns from the pack‑ ages are passed through a tensioner and feeder before reaching the needle. These nee‑ dles help to form loops in the knitted fabric and then the knitted fabric is passed through the take down roller and winded onto a cloth beam. 6.5.3 Nonwoven Fabrics As indicated earlier, nonwoven fabrics are produced directly from a filament or bunch of fibres [65]. The filaments or fibres are laid together in the form of a sheet or web, and then they are bonded in the sheet or web form mechanically (by interlocking the fibres with serrated needle), chemically (by applying the adhesives to interlock the fibres), and/or thermally (by applying and heating the binder on the sheet or web). Based on the filament or fibres laying techniques (by laying the melt spun filament of Figure 6.3 onto a solid collector or by blowing the melt spun filament of Figure 6.3 through the spin‑ neret and then laying onto a solid collector, or by laying the dry fibres from carding to a solid collector, or by laying the mixture of fibres and water onto a wire mesh), the
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6 Personal Protective Textiles and Clothing Nonwoven Fabrics
Filament Web
Spun-Laid Web
Fibre Web
Dry Laid Web
Melt Blown Web Parallel-Laid
Wet Laid Web
Cross-Laid Random-Laid
Figure 6.19 Classification of nonwoven fabrics.
nonwoven fabrics can be classified as per Figure 6.19. Among these classifications, the production of spun‐laid nonwoven fabrics is most economical; therefore, it is widely used commercially for the manufacturing of PPC. Recently, nanofilament based spun‐ laid nonwoven fabrics have also been commercially used especially for the manufac‑ turing of PPC. For these fabrics, filaments are generally manufactured by an electrospinning machine and laid onto an electric field supported collector (Figure 6.20). As nanofibres based nonwoven fabrics are lightweight, these fabrics are becoming more popular in the production of PPC; this lightweight PPC can be used for providing chemical, biological, and thermal protection to wearers.
Syringe Pump
Polymer Solution in Syringe
Voltage
Needle Needle Tip
Bended or Whipped Jet Nano Filament
Splaying Collector Voltage
Figure 6.20 Working principle of an electrospinning machine to produce nanofilament based nonwoven fabrics.
6.5 Fabrics for PPC
6.5.4 Composite Fabrics The fabrics produced by the above methods can be reinforced with different high strength fibres (glass, carbon, aramid) in order to produce composite fabrics [66]. This fibre reinforcement can add strength to the fabric even though the fabric remains light‑ weight. For example, aramid‐fibre‐based woven fabric can be reinforced with glass and carbon fibres in order to enhance its ballistic and stab protective performance. Many researchers compared the ballistic and/or stab protective performance of fibre rein‑ forced fabrics with ordinary fabrics. They found that fibre reinforced fabrics possess much higher strength and protective performance than the ordinary woven/knitted/ nonwoven fabrics. 6.5.5 Dyed and Printed Fabrics A fabric can be dyed in a batch or continuous process. In the batch process, a certain length of fabric can be dyed by different dyeing machines (e.g. beck, jet, jig) [18]. These machines mainly move the fabric through the dye liquor or move the dye liquor through the fabric or both (fabric as well as dye liquor). As the exhaustion of dyes within the fabric materials is very high in the batch‐dyeing process, the colour fastness of the batch‐dyed fabrics is very high. However, the production rate of dyed fabrics by these machines is very low, whereas the production rate of continuous dyeing machine is high. Therefore, the continuous dyeing process is preferred for industrial use (Figure 6.21). Nevertheless, the colour variation across the length and width of the continuous dyed fabric may occur, owing to its high production speeds and large num‑ ber of process variables (e.g. dye padding time, steaming time). By applying suitable dyes, a fabric can be printed using different processes: (i) block printing (by transferring a design engraved on a wooden block to the fabrics using dyes), (ii) roller/cylinder printing (by passing the fabrics over an engraved dye containing roller), (iii) stencil printing (by passing the dyes through the interstices of a designed stout paper sheet onto the fabric), (iv) screen printing (by squeezing the printing paste through the opening of a screen onto the fabric). Among all these processes, screen printing is widely used because of its high productivity and print quality. This type of printing is usually carried out by flatbed screen printing machines (Figure 6.22) or rotary screen printing machines (Figure 6.23).
Guide Roller Drying Undyed Fabric Roll
Steaming Dyed Fabric Roll
Padding of Fabrics with Dye
Padding of Fabrics with Chemical (e.g. salt, alkali)
Washing
Figure 6.21 Working principle of continuous fabric dyeing machine.
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Squeezer Dyes
Designed Screen
Printed Design on Fabrics Fabric
Moving Fabric Holder
Figure 6.22 Working principle of flatbed screen printing machine.
Rotating Screen Squeezer Dyes
Printed Fabrics
Figure 6.23 Working principle of rotary screen printing machine.
Impression Cylinder
Unprinted Fabrics
6.5.6 Finished Fabrics After dyeing and printing, a fabric is mechanically and/or chemically finished to improve its properties, such as dimensional stability, fire retardancy, water repellency, antimicrobial, ballistic and stab protection, and thermo‐regulation (i.e. total heat loss (THL) from the body through proper metabolic heat and sweat vapour dissipation) [67–69]. Notably, both mechanical and chemical processing techniques can comple‑ ment each other to improve a property. To improve dimensional stability of a fabric by mechanical finishing, the fabric is passed through a sanforizing machine (Figure 6.24). In this machine, the fabric is first wetted in a moistening device to shrink and then pressed against a heated rubber band to relax and re‐shrink. Next, the fabric is passed through a dryer to stabilize the shrinkage by removing the moisture from it. After pro‑ ducing the antishrink fabric, it is generally finished through chemical processing. During this processing, chemical substances are generally finished on the fabric surface through padding, exhaustion, coating, spraying, and foam formation. For example, phosphorous and fluorinated based chemical substance are finished on the fabric sur‑ face by a padding machine to improve its flame retardancy and water repellency, respectively (Figure 6.25). Similarly, a coating of shear thickening agents may improve the ballistic and stab‐protection properties of the fabric. During this stage, it is
6.5 Fabrics for PPC Dimensionally Stable Anti-shrink Fabric Roll Dimensionally Unstable Fabric Roll
Dryer
Moistening Device
Heated Rubber Band Assembly
Figure 6.24 Working principle of sanforizing machine for improving the dimensional stability (antishrink) of a fabric.
Unfinished Guide Roller Drying Fabric Roll
Finished Fabric Roll Padding of Fabrics with Chemicals (Phosphorous, Fluorine) Figure 6.25 Working principle of padding machine for improving the flame retardancy and water repellency of a fabric.
necessary to remember that the finishing agents should not contain any harmful chemi‑ cal substances that could affect the wearer’s health. For example, the halogen based chemical substances could also improve the flame retardancy of a fabric, but these halo‑ gen substances are carcinogenic and are illegal to use for imparting flame retardancy to the fabric. 6.5.7 Fabric Testing The above discussion shows that many fabric properties are substantially important to measure before fabrication of the PPC [70, 71]. These properties are: weight, thick‑ ness, air permeability, thermal resistance, evaporative resistance, EP, colour fastness, shrinkage, fire retardancy, water repellency, antimicrobial, ballistic and stab‐protection, and thermo‐regulatory. These properties can be measured by various test standards developed by ISO, ASTM, and the National Institute of Justice (NIJ) (Table 6.5) [72–95]. Contextually, some bench‐scale tests are available to evaluate the protective per formance of fabrics under different hazards. For example, ISO 9151:2016 and ISO 12127‐1:2015 test standards are available for evaluating the protective performance of fabrics under flame and hot surface contact hazards, respectively [96, 97]. Never theless, these bench‐scale tests for fabrics may not holistically/accurately represent
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Table 6.5 Test standards for measuring fabric properties. Fabric properties
Test standards
Weight
ASTM D 3776:2013
Thickness
ASTM D 1777:2015
Air permeability
ASTM D 737:2016
Thermal resistance
ISO 11092:2014; ASTM F 1868:2014; ASTM D 1518:2014
Evaporative resistance
ISO 11092:2014; ASTM F 1868:2014
Electrostatic propensity
ISO 18080‐1:2015; ASTM D 4238:1990 (withdrawn in 1996)
Colour fastness
ISO 105:2013; AATCC TM6:2016; AATCC TM23:2015; AATCC TM61:2013; AATCC TM125:2009
Dimensional stability
ISO 3005:1978; ASTM D 6207:2015
Fire retardancy
ISO 15025:2016; ASTM E 1321:2013
Rainwater repellency
ISO 9865:1991; ASTM D 7017:2014
Antimicrobial
ISO 20743:2013; ASTM E 2149:2013
Ballistic and stab protection
NIJ 0108.00:1985; NIJ 0115.0:2000
Thermo‐regulatory
ISO 18640‐1:2018; ASTM F 1868:2014
the protective performance of whole PPC (made from the same fabrics) under these hazards. Hence, it is recommended to use the full‐scale instrumented manikin tests for evaluating the hazard protective performance of whole PPC (which discussed in the next section). According to Table 6.5, ASTM F 1868:2014 standard can be used for evaluating three fabric properties: thermal resistance, evaporative resistance, and thermo‐regulatory. Actually, thermal and evaporative resistance values are used for evaluating the thermo‐ regulatory property of the fabric in terms of THL (i.e. equivalent to the total amount of heat transferred through a fabric by the combined dry metabolic heat and sweat vapour evaporative heat exchanges). Eventually, this THL can explain the thermo‐regulatory property of the fabric. Historically, ISO 11092 standard was developed by the Hohenstein Institute of Germany for evaluating thermal and evaporative resistances. Thereafter, the NFPA developed a method to determine the THL of thermal protective fabrics using the ISO 11092 standard, and this THL method was included in several standards (e.g. NFPA 1971, NFPA 1977, NFPA 1951, NFPA 1999). Later, the members of the ASTM F23 committee decided to compile the evaluation procedures for measuring thermal resistance, evaporative resistance, and THL in one document, which resulted in the ASTM F 1868:2014 standard. The ASTM F 1868:2014 standard uses the sweating guarded hot plate device for evaluating thermal and evaporative resistances (Figure 6.26); and then, a mathematical equation is used for predicting the THL from the thermal and evaporative resistances. As per the ASTM F 1868:2014 standard, a fabric specimen is placed on a sweating guarded hot (35 °C) plate (to simulate human skin); and, the ambient air temperature, relative humidity, and ambient air velocity are controlled at 25 °C, 65%, and 0.5–1 m s−1, respectively. When the specimen and hot plate reach the steady‐state condition, the amount of heat flow per unit area of the specimen is measured. By using the
6.5 Fabrics for PPC
Figure 6.26 Sweating guarded hot plate tester at Empa, Switzerland.
temperature difference between the hot plate surface (Ts) and ambient air (Ta), heat flow (Hc) per unit area (A), and the thermal resistance of the boundary air layer of the hot plate (Rcb), the thermal resistance of the fabric (Rcf ) is calculated in m2 K/W (Eq. 6.1). In order to evaluate the evaporative resistance, the temperatures of the sweating guarded hot plate and ambient air are set at 35 °C (please note: this isother‑ mal condition can prevent the dry heat exchange between the hot plate and ambient air, but the evaluation of evaporative resistance is also possible under nonisothermal conditions). And the relative humidity and velocity of the ambient air are set at 40% and 0.5–1 m s−1, respectively. Then, water is fed to the surface of the plate‐guard sec‑ tion (to simulate the sweating on wearers’ bodies) and covered with a liquid barrier having a permeability index greater than 0.7. Thereafter, the fabric specimen is placed on the liquid barrier covered plate. When the fabric specimen reaches the steady‐state condition, water vapour pressure on the plate (at 35 °C temperature and 100% relative humidity) and fabric surface (at 25 °C temperature and 40% relative humidity) are cal‑ culated by using the internationally recognized water vapour saturation tables. By using the vapour pressure difference between the hot plate surface (Ps) and ambient air (Pa), heat flow (He) per unit area (A) and the evaporative resistance of the boundary air layer of the hot plate (Reb), the evaporative resistance of the fabric (Ref ) is calculated in m2 Pa/W (Eq. [6.2]). Rcf and Ref values obtained from Eqs. (6.1) and (6.2) are used to calculate the THL through the fabric using Eq. (6.3). Many organizations also used this method to standardize the THL requirement of a fabric used in PPC. For example: NFPA 1971:2007 recommends that the THL of multi‐layered fabrics used in firefight‑ ers’ PPC should be at least 205 W m−2; the fulfilment of this requirement could provide better thermo‐regulation to on‐duty firefighters.
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Rcf = (TS − Ta ) A / H c − Rcb (6.1)
Ret = ( PS − Pa ) A / H e − Reb (6.2)
THL =
10 °C Rcf + 0.04
+
3.57kPa (6.3) Ref + 0.0035
Although the ASTM F 1868:2014 standard procedure possesses high reproducibility and repeatability for evaluating thermo‐regulatory property in terms of THL, it does have some shortcomings and limitations. For example, reaching the steady‐state con‑ dition of the thick fabric specimen and hot plate is often quite difficult while evaluating thermal and evaporative resistances. At the high ambient air velocity, the fabric speci‑ men may also lift off from the hot plate; this situation could result in high thermal resistance, high evaporative resistance, and low THL. The calculation procedure of the THL is also tedious and time‐consuming. Finally, many researchers found that the individual evaluation of thermal and evaporative resistances could be unrealistic because dry and evaporative heat losses occur simultaneously from the human body to the ambient environment. Therefore, this method of THL calculation could not realis‑ tically represent the thermo‐regulatory property of the fabric. Considering this, a group of researchers from Empa in Switzerland have contributed to the development of a torso test device that can realistically evaluate the thermo‐regulatory property of the fabric, by considering the combined heat and vapour/moisture transfer through fabric [98–100]. Presently, this torso test method has been approved by the ISO and documented in ISO 18640‐1:2018 standard. Although the torso method of this stand‑ ard is presently applicable for evaluating the thermo‐regulatory property of fabrics used in firefighters’ PPC, this method could also be used for developing the standard for fabrics used in other types of PPC (e.g. chemical protective clothing or rain protec‑ tive clothing). The sweating torso device mentioned in ISO 18640‐1:2018 standard has an upright standing heated cylinder, representing the surface of a human trunk, with the ability for perspiration through nozzles (Figure 6.27). As per this standard, a fabric specimen is wrapped around the torso (surface temperature of the torso is 35 °C) that is placed in a climatic chamber at controlled air temperature (20 °C), relative humidity (50%), and air velocity (1 m s−1). Then, the torso device is run through three consecutive phases of 60 minutes each (Phase 1 condition: at constant torso surface temperature of 35 °C without sweating; Phase 2 condition: apply constant heating power of 125 W to torso with a sweat rate of 100 g h−1; Phase 3 condition: apply constant heating power of 25 W to torso without any sweating) to measure dry thermal insulation, dry and wet heat transfer, and the drying properties of the fabrics. These measurements together could holistically explain the thermo‐regulatory property of a fabric in a complete simulated situation where firefighters first wear the dry clothing (Phase 1 of the torso test), then they start sweating while performing activities (Phase 2 of the torso test), and finally no sweating after their activities (Phase 3 of the torso test). As an air gap (microclimate region) always exists between the PPC and firefighters, the torso test can be conducted by considering the air gap between the torso surface and tested fabric. This test can also
6.6 PPC Fabrication
Figure 6.27 Sweating torso tester at Empa, Switzerland.
be conducted in combination with underwear to more realistically analyse the thermo‐ regulatory property of the fabric.
6.6 PPC Fabrication PPC is usually fabricated through the cut‐and‐sew garmenting process [101, 102]. First, fabrics (single‐layered or multilayered) are cut into the pattern of different body parts (e.g. sleeve, back body panel, front body panel). And then, these patterned parts are sewn together by different types of stitches (e.g. chain‐stitch, lock‐stitch, zigzag‐stitch) and seams (e.g. plain‐seam, flat‐seam, lapped‐seam) using an industrial sewing machine. For the stitching, a thread is inserted via needle to seam the fabric parts together for fabricating the PPC. After fabricating the PPC, various trims and accessories (e.g. front panel closing fasteners, flaps, reflective tape) are attached to it. In some cases, a single coloured PPC can be dyed using a paddle garment dyeing machine. In this machine, the PPC is first immersed in dye liquor within a steam‐heated dye bath and then moved through the padding roller within the dye liquor (Figure 6.28). If required, PPC can also be printed using a newly developed digital inkjet printing machine. Overall, PPC can be fabricated in a similar way as regular clothing; however, the fabricator of the PPC should follow some guidelines (related to innocuousness, size des‑ ignation, ageing, compatibility, marking, and ergonomics) provided by ISO 13688:2013 (Protective clothing – general requirements). These guidelines should be applied in combination (strictly not on a stand‐alone basis) with other standards that can measure the specific functional performance. Notably, the functional performance (hazard pro‑ tective and thermo‐physiological comfort) of PPC can be measured against different hazards/environments using various standards, as indicated in Table 6.6 [103–121]. The standards mentioned in Table 6.6 for evaluating the protective performance of PPC mainly use instrumented manikins to simulate an adult‐sized human body. The PPC that needs to be tested is donned on the manikin (with or without underwear) and the clothed manikin is exposed to the hazards to predict the protective performance of
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Rotating Padding Roller
PPC Dye Bath Dye Liquor Dye Liquor Draining
Figure 6.28 Working principle of PPC dyeing machine. Table 6.6 Test standards for measuring functional performance of PPC. Clothing functional performance
Hazard/Environment
Test standard
Protective
Cool/Chilled air
CEN 14058:2004
Cold water
ISO 15027‐3:2012
Cold air
CEN 342:2004
Rain
CEN 14360:2004
Flash fire
ISO 13506:2008; ASTM F 1930:2017
Arc and flame
ASTM F 1891:2012
Hot liquid splash
NFPA 1992
Steam vapour
NFPA 1991
Knife stab
ISO 13998:2003
Chemical substances
ISO 16602:2007; ASTM F 1296:2008; NFPA 1994
Radioactive agents
CEN 1073‐1:2016; CEN 1073‐2:2016
Biological matters
CEN 14126:2003; NFPA 1994
Ambient temperature is similar to or lower (12 °c) than human skin temperature of 35 °C
ISO 9920:2007; ASTM F 1291:2010; ASTM F 2370:2010
Thermo‐physiological comfort
the PPC. For example, as per Figure 6.29, the clothed manikin is exposed to flash fire (at 84 kW m−2) in a fire chamber according to ISO 13506:2008 standard. Thereafter, the time and percentage of burn injury generated on the human body is predicted by more than 100 heat flux sensors that are instrumented on the manikin. PPC that takes a long time or generates a low percentage of burn injury is considered high performance fire pro tective clothing. Similarly, as per Figure 6.30, the clothed manikin is exposed to the rain (cloudburst rain: 450 l (m2 h)−1; drizzle rain: 40 l (m2 h)−1; persistent rain: 100 l (m2 h)−1)
6.6 PPC Fabrication
(a)
(b)
(c)
Figure 6.29 Flash fire manikin ‘Henry’ at Empa, Switzerland: (a) nude instrumented manikin; (b) clothed manikin; (c) clothed manikin engulfed in flash fire.
(a)
(b)
(c)
Figure 6.30 Rain manikin ‘James’ at Empa, Switzerland: (a) nude instrumented manikin; (b) clothed manikin under a rain tower; (c) wet zones on the underwear.
under a rain tower according to CEN 14360:2004 standard. Thereafter, the presence of wet zones on the underwear is detected by 22 conductance sensors that are instrumented on the manikin, and the size of the wet zone is calculated manually by the experimenter. PPC that generates smaller size wet zones is considered high performance rain protective clothing. According to Table 6.6, there exist individual test standards for evaluating the protec‑ tive performance of PPC depending upon the hazard. But, the ISO has also recom‑ mended one single test (ISO 9920:2007) to evaluate the thermo‐physiological comfort performance of all types of PPC. As per the ISO 9920:2007 standard, the thermal and
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Figure 6.31 Clothed sweating thermal manikin ‘Sam’ at Empa, Switzerland.
evaporative resistances of the clothing are measured to explain its thermo‐physiological comfort performance. In order to evaluate the thermal resistance, a sweating thermal manikin (skin tem‑ perature of the manikin is set at 35 °C) is housed in a climatic chamber having ambient air temperature: 23 °C, relative humidity: 50%, and air velocity: 0.4 m s−1 (Figure 6.31). To evaluate evaporative resistance, the temperatures of both manikin skin and ambient air are kept at 35 °C (please note: the evaluation of evaporative resistance can also be possible under nonisothermal conditions). The PPC that needs to be tested is donned on the manikin (with or without underwear) and the skin temperature of the clothed manikin is further stabilized to reach the steady‐state (i.e. the mean skin temperature and electrical heating power input remain constant ±3%). After reaching the steady‐ state, the manikin’s skin temperature and the ambient air temperature are recorded at every one‐minute interval. The average of these records is taken over a period of 30 minutes in order to determine the thermal or evaporative resistance value. Over the test period of 30 minutes, the power input to heat the manikin is also continuously measured at every one‐minute interval. Then, the thermal resistance of the clothing with the manikin’s surface (boundary) air layer is calculated according to Eq. (6.4), where, Rt = total thermal resistance of the clothing and surface air layer around the manikin (°C m2 W−1); Ts = temperature at the manikin’s skin surface (°C); Ta = tempera‑ ture of the ambient air flowing over the clothing (°C); A = area of the manikin’s surface (m2); and, H = power required to heat the manikin (W). Here, it seems that a significant amount of trapped air on the boundary of the manikin’s surface (or around the mani‑ kin) contributes to Rt. Thus, the intrinsic thermal resistance (Rcl) of the clothing can be determined by subtracting the thermal resistance (Ra) of the nude manikin from the Rt
6.7 Key Issues Related to PPC
based on Eq. (6.5), where, Rcl = intrinsic thermal resistance of the clothing (°C m2 W−1); Ra = thermal resistance of the air layer on the surface of the nude manikin (°C m2 W−1); and, fcl = clothing area factor (dimensionless) that can be estimated using the ISO 9920 standard, or a photographic method described by [122]. The evaporative resistance (Ret) of the clothing with the manikin’s surface (boundary) air layer can be determined by Eq. (6.6), where, Ret = total evaporative resistance provided by the clothing with a surface air layer around the manikin (kPa m2 W−1); A = area of the manikin’s sweating surface (m2); Ps = the water vapour pressure at the manikin’s sweating surface (kPa); Pa = the water vapour pressure of the air flowing over the clothing (kPa); He = electrical heating power required for the sweating area (W); Ts = temperature at the manikin’s skin surface (°C); Ta = temperature of the air flowing over the clothing (°C); and Rt = total thermal resistance of the clothing with manikin’s surface air layer measured by Eq. (6.4) (°C m2 W−1). Similar to intrinsic thermal resistance (Rcl), the intrinsic evaporative resistance (Recl) of clothing is also determined by subtracting the evaporative resistance of the air layer on the surface of the nude manikin’s sweating surface (Rea) from the Ret [Eq. (6.7), where Recl = intrinsic evaporative resistance of the clothing (kPa m2 W−1); Rea = the evaporative resistance of the air layer on the surface of the nude manikin’s sweating surface (kPa m2 W−1)].
Rt = (Ts − Ta ) A / H (6.4) Rcl = Rt −
Ra (6.5) f cl
Ret = [( Ps − Pa )]A]/[ H e − (Ts − Ta ) A / Rt ] (6.6) Recl = Ret −
Rea (6.7) f cl
6.7 Key Issues Related to PPC Although PPC has been successfully manufactured over decades, a few key issues still remain that need to be addressed in future. These issues are mainly related to (i) devel‑ oping new high performance fabric materials and (ii) ecologically sustainable process‑ ing techniques and materials. In the following sections, these issues are discussed. 6.7.1 Development of New High Performance Fabric Materials PPC generally employs heavyweight, thick, and/or air‐impermeable fabrics/membrane [11, 23, 123]. This type of fabric is required mainly to provide effective protection to the wearer. However, this type of fabric lowers the thermo‐physiological comfort perfor‑ mance of the PPC by exerting weight on the wearer’s body, restricting the metabolic heat and sweat vapour transmission through the fabric. Considering this, many research‑ ers have put great effort into developing new materials or implementing smart tech nologies (e.g. foamed silicone on vapour permeable membrane, macro‐encapsulated nanoporous gels or aerogels, or nanoclay‐reinforced resin coating on woven/nonwoven
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fabrics, nanofibres in nonwoven fabrics, nano finishes or phase change materials (PCMs), or shape memory alloy in woven/nonwoven fabrics, sensors, gas detectors, safety alarm, cooling devices) in PPC that can give better protection and comfort to wearers [124–129]. Nevertheless, these new materials and smart technologies are not yet very cost‐effective and are confined to laboratory settings and/or are only applied in highly specialized circumstances like aerospace, military, and defence. In future, it will be required to use different cost‐effective technologies (nanotechnology, smart textiles) to manufacture a fabric that can be lightweight and thin, and effectively transmit the metabolic heat and sweat vapour from wearers’ bodies. For example, nanofibre based nonwoven fabrics are lightweight and have good thermal insulation capacity. This type of fabric can be used for the manufacturing of firefighters’ PPC. This will ultimately provide better thermo‐physiological comfort to the wearers. Furthermore, biological and chemical protective clothing mainly comprises a membrane fabric that is air‐imper‑ meable. This air‐impermeable fabric impedes the transfer of sweat vapour from the wearer’s body and thus lowers the thermo‐physiological comfort of the PPC. Instead of using the membrane, some finishing could be applied to the woven fabrics to make them biological and chemical protective. This can also enhance the comfort performance of the fabrics. By incorporating the PCM and moisture management finishes within the fabrics, it is also possible to absorb the metabolic heat and sweat vapour generated from the wearers’ bodies, and provides them better thermo‐physiological comfort. Additionally, some new test methods needs to be developed to realistically evaluate the functional performance (hazards protective performance and thermo‐physiological comfort performance) of PPC by properly simulating the hazards and environments faced by wearers. 6.7.2 Ecologically Sustainable Processing Techniques and Materials The PPC is generally manufactured using wide range of processing techniques. All of these techniques cause a significant amount of air and water pollution. Also, most of the waste textile materials (fibres, yarns, fabrics) generated during the manufactur‑ ing and disposal stage of PPC also involves synthetic petrochemical based materials and such materials do not decompose easily. In fact, an estimate indicates that such materials may take 40 years to degrade naturally [130]. Overall, the air/water pollu‑ tion and nonbiodegradable materials can significantly affect our ecological system. This makes it necessary to focus on different ecologically sustainable processing techniques and materials that can lower the waste and save the environment. For example: use of digital colouring or printing techniques can significantly reduce the water consumption during the manufacturing of PPC. Proper maintenance (wash and care) of PPC can lower its ageing and thus wearers can use it for long time. Additionally, this will considerably reduce the dumping of nonbiodegradable materi‑ als in environment. In this context, it is notable that Hohenstein Institute of Germany has introduced standard certifications (Oeko‐Tex Standard 100/1000) for textile products. These standard certifications mainly control the harmful substances in a textile product (e.g. formaldehyde, pesticides, heavy metals, carcinogenic amines) and/or promote environmental friendly textile productions (e.g. prohibit the uses of harmful technologies, control the wastage of water and energy, reduce the noise and air pollutions). Eventually, the implementation of these certifications in PPC could
References
help to make it more ecologically sustainable and can protect the global people and environment.
6.8 Conclusion PPC is required to protect the human beings from various hazards such as wind, cold air, rain, flash fire. In general, it is necessary that PPC should possess high thermal protective performance under a particular hazard. At the same time, the PPC should effectively regulate the metabolic heat and sweat vapour from wearers’ bodies to their surrounding environment; this regulation will provide high thermo‐physiological com‑ fort to the wearers. Along with these functional performance (hazards protective per‑ formance and thermo‐physiological comfort performance), PPC should also possess some aesthetic features like appropriate colours and printed designs. Notably, various aspects (e.g. materials used, manufacturing process employed) associated with the tex‑ tile based PPC can help to achieve the desired functional performance and aesthetic features. There are different processing techniques (spinning, weaving, knitting, nonwoven, dyeing, finishing, garmenting) to manufacture the PPC from various materials (fibres, yarns, fabrics). Generally, fibres are used as basic raw materials for manufacturing the PPC. These fibres are processed into the spinning process to produce filament‐ or spun‐ yarns. Then, these yarns are used in the weaving/knitting/nonwoven process to produce the fabrics. These fabrics are further dyed and finished in order to impart some proper‑ ties. Finally, these dyed and finished fabrics are used in the garmenting process to fabri‑ cate PPC. There are different standard testing methods available for evaluating the properties of various materials used for the manufacture of PPC. Additionally, the functional per‑ formance (hazard protective performance and thermo‐physiological comfort perfor‑ mance) of whole PPC can also be measured by using various standard methods. In general, sensor instrumented manikins are used for evaluating the protective perfor‑ mance of PPC under various hazards. Additionally, sweating thermal manikins are used for evaluating the thermo‐physiological comfort performance of PPC. Although PPC has been manufactured and tested successfully over the decades, some key issues (development of new high performance materials, ecologically sustainable processing techniques and materials) related to the PPC still remain unaddressed. In future, it will be necessary to resolve these key issues in order to manufacture a high performance PPC that can provide better protection and comfort to the wearers.
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2 Li, Y. (2001). The science of clothing comfort. Textile Progress, 31 (1/2): 1–135. Scott, R.A. (2005). Textiles for Protection. Cambridge: Woodhead Publishing. 3 Raheel, M. (1994). Protective Clothing Systems and Materials. New York: Marcel Dekker. 4
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5 Ceballos, D., Mead, K., and Ramsey, J. (2015). Recommendations to improve employee
thermal comfort when working in 40°F refrigerated cold rooms. Journal of Occupational and Environmental Hygiene 12 (9): D216–D237. 6 Mandal, S., Song, G., Ackerman, M. et al. (2013). Characterization of textile fabrics under various thermal exposures. Textile Research Journal 83: 1005–1019. 7 Mandal, S., Lu, Y., Wang, F., and Song, G. (2014). Characterization of thermal protective clothing under hot water and pressurized steam exposure. AATCC Journal of Research 1: 7–16. 8 Occupational Safety and Health Guidance Manual for Hazardous Waste Site Activities. (1985). Retrieved from: https://www.osha.gov/Publications/complinks/OSHG‐ HazWaste/all‐in‐one.pdf. Accessed 5 January 2017. 9 Bajaj, P. and Sriram (1997). Ballistic protective clothing: an overview. Indian Journal of Fiber and Textile Research 22 (4): 274–291. 10 Rossi, R. (2003). Firefighting and its influence on the body. Ergonomics 46 (10): 1017–1033. 11 Song, G., Mandal, S., and Rossi, R. (2016). Thermal Protective Clothing for Firefighters. Cambridge: Woodhead Publishing. 12 Psikuta, A., Richards, M., Fiala, D. Single‐ and multi‐sector thermophysiological human simulator for clothing research. 7th International Thermal Manikin and Modelling Meeting. Coimbra, Portugal, 3–5 September 2008. 13 Song, G. and Mandal, S. (2016). Testing and evaluating thermal comfort of clothing ensembles. In: Performance Testing of Textiles: Methods, Technology, and Applications (ed. L. Wang), 39–64. Cambridge: Woodhead Publishing. 14 Klein, W. (1987). A Practical Guide to Ring Spinning. London: Textile Institute. 15 Marks, R. and Robinson, A.T.C. (1976). Principles of Weaving. London: Textile Institute. 16 Spencer, D.J. (2001). Knitting Technology. London: Pergamon Press. 17 Albrecht, W., Fuchs, H., and Kittelmann, W. (2006). Nonwoven Fabrics. Hoboken, NJ: Wiley. 18 Clark, M. (2011). Handbook of Textile and Industrial Dyeing. Cambridge: Woodhead Publishing. 19 Gulrajani, M.L. (2013). Advances in the Dyeing and Finishing of Technical Textiles. Cambridge: Woodhead Publishing. 20 Bartle, A. (2011). Textile waste. In: WASTE: A Handbook of Waste Management (ed. T. Letcher and D. Vallero), 167–179. Amsterdam: Elsevier. 21 Wang, Y. (2006). Recycling in Textiles. Cambridge: Woodhead Publishing. 22 Agrawal, R. and Sharan, M. (2015). Municipal textile waste and its management. Research Journal of Family, Community and Consumer Services 3 (1): 4–9. 23 Ko, F. (1999). Textiles and garment for chemical and biological protection. In: Strategies to Protect the Health of Deployed US Forces: Force Protection and Decontamination (ed. Wartell et al.), 182–216. Washington DC: National Academic Press. 24 Dhillon, B.S. (2007). Applied Reliability and Quality. London: Springer. 25 Kilinc, F.S. (2013). Handbook of Fire Resistant Textiles. Cambridge: Woodhead Publishing. 26 Pan, N. and Sun, G. (2011). Functional Textiles for Improved Performance, Protection and Health. Cambridge: Woodhead Publishing.
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Textiles and Their Applications (ed. C.A. Lawrence), 91–143. Cambridge: Woodhead Publishing. Shalev, I. and Barker, R.L. (1983). Analysis of heat transfer characteristics of fabrics in an open flame exposure. Textile Research Journal 53 (8): 475–482. Shalev, I. and Barker, R.L. (1984). Protective fabrics: a comparison of laboratory methods for evaluating thermal protective performance in convective/radiant exposures. Textile Research Journal 54 (10): 648–654. Ali, M.A., Sarwar, M.I. (2010). Sustainable and environmentally friendly fibers in textile fashion. MSct, University of Boras, Sweden. McCann, J.T., Li, D., and Xia, Y. (2005). Electrospinning of nanofibers with core‐sheath, hollow, or porous structures. Journal of Material Chemistry 15 (7): 735–738. Ramakrishna, S., Fujihara, K., Teo, W. et al. (2005). Electrospinning and Nanofiber. Singapore: World Scientific. Kulkarni, S.V. (1986). Textile Dyeing Operations: Chemistry, Equipment, Procedures, and Environmental Aspects. New York: Noyes Publications. ASTM D 1774:1994. Standard test methods for elastic properties of textile fibers. ASTM D 276:2012. Standard test methods for identification of fibers in textiles. ASTM D 2863:2013. Standard test method for measuring the minimum oxygen concentration to support candle‐like combustion of plastics (oxygen index). ASTM D 3217M:2015. Standard test methods for breaking tenacity of manufactured textile fibers in loop or knot configurations. ASTM D629:2015. Standard test methods for quantitative analysis of textiles. ASTM D 7138:2016. Standard test method to determine melting temperature of synthetic fibers. ISO 6741‐4:1987. Textiles – Fibres and yarns – determination of commercial mass of consignments. Part 4: Values used for the commercial allowances and the commercial moisture regains. ISO 5079:1995. Textile fibres – determination of breaking force and elongation at break of individual fibres. ISO 4589‐2:1996. Plastics – determination of burning behaviour by oxygen index. Part 2: Ambient‐temperature test. ISO 11827:2012. Textiles – composition testing – identification of fibres. ISO 11357‐1:2016. Plastics – Differential scanning calorimetry (DSC) – Part 1: General principles. Demir, A. and Behery, H.M. (1997). Synthetic Filament Yarn: Texturing Technology. New York: Prentice Hall. Lawrence, C.A. (2010). Advances in Yarn Spinning Technology. Cambridge: Woodhead Publishing. Lawrence, C.A. and Chen, K.Z. (1984). Rotor Spinning. Textile Progress 13 (4): 1–78. Lord, P.R. (2003). Handbook of Yarn Production. Cambridge: Woodhead Publishing. Oxtoby, E. (1987). Spun Yarn Technology. London: Butterworths. Sinclair, R. (2014). Textiles and Fashion: Materials, Design and Technology. Cambridge: Woodhead Publishing. Roy Choudhury, A.K. (2006). Textile Preparation and Dyeing. Enfield, NH: Science Publishers.
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52 Booth, J.E. (1986). Principles of Textile Testing. London: Butterworths. 53 ASTM D 6611:2007. Standard test method for wet and dry yarn‐on‐yarn abrasion
resistance.
54 ASTM D 5647: 2007. Standard guide for measuring hairiness of yarns by the photo‐
electric apparatus.
55 ASTM D 2256M:2010. Standard test method for tensile properties of yarns by the
single‐strand method.
56 ASTM D 1425M:2014. Standard test method for evenness of textile strands using
capacitance testing equipment.
57 ISO 16549:2004. Textiles – unevenness of textile strands – capacitance method. 58 ISO 2062:2009. Textiles – yarns from packages – determination of single‐end breaking
force and elongation at break using constant rate of extension (CRE) tester.
59 Long, A.C. (2005). Design and Manufacture of Textile Composites. Cambridge:
Woodhead Publishing.
60 Majumdar, A. (2017). Principles of Woven Fabric Manufacturing. New York: CRC Press. 61 Ray, S.C. (2012). Fundamentals and Advances in Knitting Technology. Cambridge:
Woodhead Publishing.
62 Russell, S.J. (2007). Handbook of Nonwovens. New York: CRC Press. 63 Gandhi, K.L. (2012). Woven Textiles: Principles, Developments and Applications.
Cambridge: Woodhead Publishing.
64 Au, K.F. (2011). Advances in Knitting Technology. Cambridge: Woodhead Publishing. 65 Batra, S.K. and Pourdeyhimi, B. (2012). Introduction to Nonwovens Technology.
Lancaster, PA: DEStech Publications.
66 Cherif, C. (2015). Textile Materials for Lightweight Construction. London: Springer. 67 Karmakar, S.R. (1999). Chemical Technology in the Pretreatment Processes of Textiles.
Amsterdam: Elsevier.
68 Paul, R. (2014). Functional Finishes for Textiles: Improving Comfort, Performance, and
Protection. Cambridge: Woodhead Publishing.
69 Roy Choudhury, A.K. (2017). Principles of Textile Finishing. Cambridge: Woodhead
Publishing.
70 Amutha, K. (2016). A Practical Guide to Textile Testing. New Delhi: Woodhead
Publishing India.
71 Collier, B.J. and Epps, H.H. (1998). Textile Testing and Analysis. New York:
Prentice Hall. AATCC TM125:2009. Colorfastness to perspiration and light. AATCC TM61:2013. Colorfastness to laundering. AATCC TM23:2015. Colorfastness to burnt gas fumes. ASTM D 4238:1990. Standard test methods for electrostatic propensity of textiles. ASTM D 3776:2013. Standard test methods for mass per unit area (weight) of fabric. ASTM E 1321:2013. Standard test method for determining material ignition and flame spread properties. 78 ASTM E 2149:2013. Standard test method for determining the antimicrobial activity of antimicrobial agents under dynamic contact conditions. 9 ASTM F 1868:2014. Standard test method for thermal and evaporative resistance of 7 clothing materials using a sweating hot plate. 0 ASTM D 1518:2014. Standard test method for thermal resistance of batting systems 8 using a hot plate. 72 73 74 75 76 77
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81 ASTM D 7017:2014. Standard performance specification for rainwear and all‐
purpose, water‐repellent coat fabrics.
82 ASTM D 1777:2015. Standard test method for thickness of textile materials. 83 ASTM D 6207:2015. Standard test method for dimensional stability of fabrics to
changes in humidity and temperature.
84 ASTM D 737:2016. Standard test method for air permeability of textile fabrics. 85 ISO 3005:1978. Textiles – determination of dimensional change of fabrics induced by
free‐steam.
86 ISO 9865:1991. Textiles – determination of water repellency of fabrics by the
Bundesmann rain‐shower test.
87 ISO 105:2013. Textiles – tests for colour fastness. 88 ISO 20743:2013. Textiles – determination of antibacterial activity of textile products. 89 ISO 11092:2014. Textiles – physiological effects. Measurement of thermal and
water‐vapour resistance under steady‐state conditions (sweating guarded‐ hotplate test). 90 ISO 18080‐1:2015. Textiles – test methods for evaluating the electrostatic propensity of fabrics. Part 1: Test method using corona charging. 91 ISO 15025:2016. Protective clothing – protection against flame – method of test for limited flame spread. 92 ISO DIS 18640‐1.2. Protective clothing for firefighters – physiological impact. Part 1: measurement of coupled heat and moisture transfer with the sweating TORSO. 93 ISO DIS 18640‐2.2. Protective clothing for fire‐fighters – physiological impact. Part 2: determination of physiological heat load caused by protective clothing worn by firefighters. 94 NIJ 0108.00:1985. Ballistic resistant protective materials. 95 NIJ 0115.0:2000. Stab resistance of personal body armor. 96 ISO 9151:2016. Protective clothing against heat and flame − determination of heat transmission on exposure to flame. 97 ISO 12127‐1:2015. Clothing for protection against heat and flame − determination of contact heat transmission through protective clothing or constituent materials. 98 Zimmerli, T. and Weder, M.S. (1997). Protection and comfort: a sweating torso for the simultaneous measurement of protective and comfort properties of PPE. In: Performance of Protective Clothing: STP 19909S (ed. J. Stull and A. Schwope), 271–280. West Conshohocken, PA: ASTM. 99 Keiser, C., Becker, C., and Rossi, R.M. (2008). Moisture transport and absorption in multilayer protective clothing fabrics. Textile Research Journal 78 (7): 604–613. 100 Annaheim, S., Wang, L., Psikuta, A. et al. (2015). A new method to assess the influence of textiles properties on human thermophysiology: part I: thermal resistance. International Journal of Clothing Science and Technology 27 (2): 272–282. 101 Glock, R.E. and Kunz, G.I. (1999). Apparel Manufacturing: Sewn Product Analysis. New York: Prentice Hall. 102 Nayak, R. and Padhye, R. (2015). Garment Manufacturing Technology. Cambridge: Woodhead Publishing. 103 CEN 14058:2004. Protective clothing – garments for protection against cool/chilled environments. 104 ISO 15027‐3:2012. Immersion suits (used for cold water protection). Part 3: test methods.
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105 CEN 342: 2004. Protective clothing – garments and clothing combinations for
protection against cold air.
106 CEN 14360:2004. Protective clothing against rain test method for readymade
garments impact from above with high energy droplets.
107 ISO 13506:2008. Protective clothing against heat and flame – test method for
complete garments – prediction of burn injury using an instrumented manikin.
108 ASTM F 1930:2017. Standard test method for evaluation of flame resistant clothing 109 110 111 112 113 114 115 116
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for protection against fire simulations using an instrumented manikin. ASTM F 1891:2012. Standard specification for arc and flame resistant rainwear. NFPA 1992. Standard on liquid splash‐protective ensemble and clothing. NFPA 1991. Standard on vapor‐protective ensemble and clothing. ISO 13998:2003. Protective clothing – aprons, trousers and vests protecting against cuts and stabs by hand knives. ISO 16602:2007. Protective clothing for protection against chemicals – classification, labelling and performance requirements. ASTM F 1296:2008. Standard guide for evaluating chemical protective clothing. NFPA 1994. Standard on protective ensemble for chemical/biological terrorism incidents. CEN 1073‐1:2016. Protective clothing against radioactive contamination – requirements and test methods for ventilated protective clothing against particulate radioactive contamination. CEN 1073‐2:2016. Protective clothing against radioactive contamination – requirements and test methods for non‐ventilated protective clothing against particulate radioactive contamination. CEN 14126:2003. Protective clothing – performance requirements and tests methods for protective clothing against infective agents. ISO 9920:2007. Ergonomics of the thermal environment – estimation of thermal insulation and water vapour resistance of a clothing ensemble. ASTM F 1291:2010. Standard test method for measuring the thermal insulation of clothing using a heated manikin. ASTM F 2370:2010. Standard test method for measuring the evaporative resistance of clothing using a sweating manikin). McCullough, E.A., Jones, B.W., and Huck, J. (1985). A comprehensive data base for estimating clothing insulation. ASHRAE Transactions 91: 29–47. Bajaj, P. and Sengupta, A.K. (1992). Protective clothing. Textile Progress 22 (2): 1–110. Dadi, H.H. 2010. Literature Overview of Smart Textiles. MSc thesis. University of Borås, Borås, Sweden. Donnelly, M.K., Davis, W.D., Lawson, J.R., Selepak, M.J. 2006. Thermal Environment for Electronic Equipment Used by First Responders, National Institute of Standards and Technology. Technical Note 1474. National Institute of Standards and Technology, USA, 1–36. Hocke, M., Strauss, L., and Nocker, W. (2000). Firefighter garment with non textile insulation. In: Proceedings of NOKOBETEF 6 and 1st European Conference on Protective Clothing, Stockholm, Sweden (ed. K. Kuklane and I. Holmer), 293–295. Denmark: European Society for Protective Clothing. Holme, I. (2004). Innovations in performance clothing and microporous film. Technical Textiles International 13 (4): 26–30.
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the thermal protective performance of firefighter garment. In: Proceedings of TBIS2011, Beijing, China (ed. Y. Li, X.N. Luo and Y.F. Liu), 1010–1014. Hong Kong: Textile Bioengineering and Informatics Symposium Society. 129 Song, G. and Lu, Y. (2013). Structural and proximity firefighting protective clothing: textiles and issues. In: Handbook of Fire Resistant Textiles (ed. F.S. Kilinc), 520–548. Cambridge: Woodhead Publishing. 30 Wool and Biodegradability. (n.d.). Retrieved from: http://www.iwto.org/sites/default/ 1 files/files/iwto_resource/file/Wool%20and%20Biodegradability_IWTO%20Fact %20Sheet_update.pdf. Accessed 21 April 2017.
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7 Textiles for Military and Law Enforcement Personnel Christopher Malbon1 and Debra Carr 2 1 2
Centre for Defence Engineering, Cranfield University, Shrivenham, United Kingdom Defense and Security Accelerator, Dstl, Wiltshire, United Kingdom
7.1 Introduction Military and law enforcement personnel are faced by diverse threats routinely in their employment. Examples of these threats include ballistic, chemical, flame, and environmental threats (e.g. extremes of temperature, precipitation, wind). There is always a compromise between the protection offered by a clothing system and the ability to complete the task (i.e. survivability vs. mobility). The optimum design of protective clothing systems requires expert knowledge of the threats faced, the tasks to be completed, the anthropometric properties of the persons to be protected, the fabrics that might be used, integration with other fabrics and equipment, and knowledge of appropriate clothing and textile sciences manufacturing techniques and test methods. Amongst the threats considered in such an analysis are those that require specialized fabrics and clothing systems to provide protection (e.g. ballistic and sharp weapon; flame retardant; and chemical, biological, radiological, and nuclear). These threats are considered in this chapter and the fabrics and test methods used are summarized.
7.2 Ballistic and Sharp Weapon Protection The primary cause of injury to military personnel in modern warfare is fragmentation, e.g. [1–3]. Fragments originate from traditional munitions such as grenades and artillery shells and from improvised explosive devices (IEDs). Fragments vary in size, shape (preformed cubes, ball bearings, random), and velocity (Figure 7.1) [1, 4, 5]. Military personnel are also injured by bullets: gunshot wounds were the second highest injury suffered by UK personnel in recent conflicts [3]. The rifle ammunition typically of concern is 5.45, 5.56, and 7.62 mm calibre (Figure 7.2). For civilian law enforcement personnel the threat could be both sharp weapon and ballistic albeit of a lower calibre typically than the military. For example, in the UK a police officer is most likely to be threatened by a sharp weapon such as a knife (Figure 7.3) [6]. Sharp weapons vary from weapons High Performance Technical Textiles, First Edition. Edited by Roshan Paul. © 2019 John Wiley & Sons Ltd. Published 2019 by John Wiley & Sons Ltd.
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Figure 7.1 Typical fragmentation from traditional munition.
Figure 7.2 Rifle ammunition: 5.45 × 39 mm, 7.62 × 39 mm, 5.56 mm NATO and 7.62 mm NATO.
7.2 Ballistic and Sharp Weapon Protection
Figure 7.3 Sharp weapons used for testing law enforcement stab‐resistant armour in the UK.
Figure 7.4 Pistol ammunition: 9 mm Luger FMJ, 9 mm Luger HP and .357 Magnum.
of opportunity such as a kitchen knife to a weapon that may be carried by an expert user, e.g. [7–10]. Pistol ammunition is also considered a threat to routine patrol police officers (Figure 7.4), e.g. [11, 12]. Authorised firearms officers (AFOs) and specialist firearms officers (SFOs) can face greater threats than beat officers that may include rifle and carbine ammunition similar to that faced by military personnel. 7.2.1 Protective Materials The materials used in protective equipment are briefly discussed in this section; a more descriptive description of fibres and materials can be found in textbooks such as that edited by Bhatnagar [13]. Protection from the threats summarized in Figures 7.1–7.4 are typically achieved by the use of protective systems such as body armour and helmets [11, 14]. Body armour is usually a waistcoat or tabard style garment that provides protection to the critical organs of the torso (Figures 7.5 and 7.6). Body armour that protects the wearer from
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Figure 7.5 Typical military body armour.
Figure 7.6 Typical police body armour.
7.2 Ballistic and Sharp Weapon Protection
fragments, sharp weapons, and low velocity pistol ammunition typically comprises multiple layers of fabrics; if protection from high velocity rifle ammunition is required then hard plates are added to the body armour (Figure 7.7) [14]. Body armour increases the thermo‐physiological loading on the user because of an increase in mass and thickness (bulk) [15]. Helmets usually have a composite shell and provide protection to the brain and brainstem (Figure 7.8) [16, 17]. The fibre types that are used in modern body armour and helmets are synthetic polymer high performance fibres; two main types are used (i) para‐aramids (e.g. Kevlar® and Twaron®) and (ii) ultra‐high‐molecular‐weight polyethylene (UHMWPE) (e.g. Dyneema® and Spectra®). These fibres are high tenacity and high stiffness products. Military body armour typically provides protection from fragments using plain woven para‐aramid fabrics; the amount of layers in the armour will be adjusted as required by the user with respect to mass and protection offered. Some countries use a cross‐ply UHMWPE multilayered solution, i.e. the fibres are arranged perpendicularly in layers with a low‐molecular‐weight layer of polymer between them. High velocity rifle protection for both military and specialized law enforcement personnel is provided by the use of plates which are usually ceramic faced (alumina, silicon carbide, boron carbide)
Figure 7.7 Typical hard armour plates (rifle protection).
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Figure 7.8 Typical ballistic helmet.
and composite backed (para‐aramid or UHMWPE); in some cases a 100% cross‐ply UHMWPE plate is used [11, 14]. Law enforcement body armour provides protection from sharp weapons by the use of chainmail or ‘laminated’ fabrics, i.e. single layers of (usually) plain woven para‐aramid fabrics impregnated with a polymer [18]. Protection from pistol ammunition can be provided by a wide range of fabrics, including plain woven para‐aramid, noncrimp para‐aramid, and cross‐ply UHMWPE [18]. 7.2.2 Test Methods Most countries have their own requirements in terms of protection offered by body armour. For example, in the UK, military armour is tested according to NATO STANNAG AEP‐2920 and law enforcement armour is tested according to a Home Office Standard [12, 19]. Protection from fragments for military armour is usually
7.3 Protection from Heat and Flames
assessed using standardized steel fragment simulating projectiles (FSPs) because real fragmentation varies in size, shape, and material. The FSP used commonly in the UK is the 1.1 g chisel nosed FSP, but other shapes and masses are defined in AEP‐2920. AEP‐2920 also describes test methods for bullet‐resistant armour. UK police sharp‐ weapon‐resistant armour is typically tested using a standard knife; again, real knives vary in size and shape (including sharpness) (Figure 7.3). Spike‐resistant armour is also available and this is tested using the standard spike (Figure 7.3). Most police officers in the UK wear a sharp‐weapon‐ and ballistic‐resistant armour, the ballistic protection provided is typically from pistol ammunition (e.g. Figure 7.4). Some specialized police officers (e.g. AFOs, SFOs) wear body armour plates that are tested using rifle ammunition (e.g. Figure 7.2).
7.3 Protection from Heat and Flames 7.3.1 Background Both military personnel and police officers can also be faced with the threat of fire, primarily from petrol bombs, more commonly known as a Molotov cocktail. Over the past decade there have been several cases highlighted in the press. There were reports of an attack on a UK patrol in Basra, Iraq by anti‐British protestors, which resulted in an armoured vehicle being hit by a petrol bomb. Images show one of the soldiers jumping from the vehicle on fire [20]. There were similar incidents of police officers involved in public order policing in Northern Ireland, including one where an officer was struck by a petrol bomb resulting in burning fluid covering his overalls [21]. All these incidents point out the importance of donning flame‐retardant garments by the security personnel. 7.3.2 Mechanisms of Injury The human body is covered in skin, which is susceptible to heat, leading to various degrees of damage. The prediction of the response of the skin to burns has been modelled and shown to be exponential [22]. A first‐degree, or superficial, burn is classed as reddening of the skin, and typically happens with a 12 °C rise in surface skin temperature. A second‐degree, or mixed depth, burn is deeper and generally results in blistering of the skin. A third‐degree, or full thickness, burn generally extends through the entire skin layers [23]. Fire can cause injury to the body in three ways: ●●
●●
●●
Direct burning of the skin due to the flames coming into contact with the flesh, generally having burnt through or melted any clothing layers. Heat transfer via either conducted or radiant heat passing through the clothing layers, necessarily holing the clothing. Steam burns, which although caused predominantly by heat transfer through clothing are exacerbated by moisture speeding up the transfer of heat.
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7.3.3 Protective Clothing UK police have been using protective clothing for use in public disorder situations since the 1980s. This clothing was generally a wool barathea overall that had been treated with a flame‐retardant finish. This would have been worn over the officer’s standard beat duty uniform, which consisted of wool trousers and a cotton shirt. The selection of wool was mainly due to the inherent flame‐retardant properties of wool, including a high ignition temperature, a high limiting oxygen index (LOI) of 25–28%, and a tendency for slow burning and self‐extinguishing [24]. In addition, wool has natural insulating properties which when combined with the wool trousers and cotton shirt help reduce the risk of burns due to heat transfer. The main drawback with this type of garment is the requirement to ensure the flame‐retardant treatment applied to the fabric is maintained as it degrades following washing and from wear and tear. In addition, these treatments generally had to be reactivated after washing by heat, either by tumble drying or ironing with a hot iron. In more recent years, wool barathea overalls have been replaced by overalls made from synthetic inherently flame‐retardant materials (Figure 7.9). The most common of these in the UK are Nomex® and Kermel® viscose. Nomex is a flame‐retardant polyamide (meta‐aramid) product produced by DuPont, which has an LOI of 29–30%, making it ideal for flame retardant clothing [24]. It also has benefits over other materials such as glass fibre, which can be woven to produce a garment that has significant issues with skin irritation. Nomex does not burn or melt, but chars, meaning that the flames cannot spread rapidly; however, Nomex can become very brittle, almost paper like, when exposed to high temperatures. Kermel is a polyamide‐imide part of the meta‐aramid family and is designed to withstand very high temperatures (1000 °C) for a few seconds. An alternative version is Kermel Tech® polyimide‐amide fibre which is designed to withstand high temperature for extended periods of time [25]. The combination of Kermel with viscose, commonly at a ratio of 50/50, is done to improve comfort and flexibility of the finished product. The basic requirement for public order overalls in the UK is to provide a minimum of four seconds of protection, before the rise in heat behind the overalls when tested exceeds 12 °C. In addition to providing flame retardancy, another requirement is that these overalls provide a level of resistance to liquids, with the aim being that the majority of any liquid runs off the material and is not absorbed. This is typically done using a chemical treatment which, as with the treatment for wool barathea, has a limited lifespan and needs to be reactivated after washing. The repellency of these overalls to liquids includes hydrocarbons (petrol), chemicals, both alkaline and acids, and water. Current treatments use C8 fluorocarbons, which are being phased out as part of the REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) [26] regulations. Alternatives that are as effective are currently being investigated [27]. Guidance for UK police officers wearing public order overalls is that they should wear them as the outer‐most layer to reduce the risk of creating flammable liquid traps. In addition, they are designed to be loose fitting as this provides an additional air gap between the outer layer of the overall and the body, reducing the rate of heat transfer to the skin, as air is a natural insulator.
7.3 Protection from Heat and Flames
Figure 7.9 Flame‐retardant clothing used by police officers.
Within the UK military sphere, the majority of the Multi‐Terrain Pattern (MTP) combat clothing is not inherently flame retardant, with the main emphasis being on environmental comfort. These uniforms are made from a cotton/polyester blend (typically 65/35 mix). UK military personnel deployed during operations in Afghanistan starting in 2001 were provided with clothing commonly known as The Black Bag [28]. Certain roles within the UK armed forces do use flame‐retardant clothing, e.g. Royal Navy personnel for whom it is mandatory to wear flame‐retardant clothing when at sea. The decision on whether to use flame‐retardant clothing within the armed forces is based on a risk assessment of individual roles. The level of protection in this clothing
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will be dependent on the role, but may have different requirements in general to that used in public order. It should also be noted that many other civil responders and industries use and deploy flame‐retardant clothing, much of which is based on the same technology and materials used for the police and military. 7.3.4 Test Standards There are multiple standards for flame‐retardant material and clothing. Some are bespoke to applications, whereas others are related to test methods and are generally referenced from other standards. A list of some of the British, European, international, and American standards for flame‐retardant material and clothing that are extant at the time of publishing are shown in Table 7.1. In addition to these standards, more exist which relate to materials used in the home or office, such as curtains and flooring materials, which are not detailed in the table.
7.4 Chemical, Biological, Radiological, and Nuclear (CBRN) Protective Clothing Details on the exact protection required for the testing of chemical, biological, radiological, and nuclear (CBRN) clothing worn by law enforcement and military personal are briefly discussed here. A characterization of chemical, biological, and nuclear agents is presented by Turaga, who provides a background understanding of potential threats [29]. The use of CBRN clothing by law enforcement and the military comes with its own issues. The very nature of the role requires the clothing to enable personnel to still perform their required roles, and be operationally effective, e.g. use a firearm or detection equipment. This adds extra challenges when considering the clothing. The challenge of protecting a user from the risk of contamination by liquids or gases chemical, biological, or nuclear in form requires the combination of different types of material properties. An example of where this has been done is with the UK civilian law enforcement CBRN suit, the Civil Responder 1 (CR1). This consists of a multilayer garment, the base layer is known as the Cooler layer, which is designed to help maintain body temperature and encourage the movement of sweat away from the body. The second layer is a one‐piece carbon‐loaded suit with a butyl rubber seal around the neck, wrists, and ankles to provide a tight seal. This second layer is known as the ‘Britannia’. The final and outer layer is another one‐piece permeable layer which is designed to provide a high level of cut, tear, abrasion, and fire resistance. This third layer provides chemical resistance and some vapour protection. It is known as the Peeler [30]. To work as a CBRN protective ensemble, protective boots and gloves are also required, typically made of butyl rubber which forms a seal with the clothing layer. The ensemble is completed with the addition of a suitable respirator, and the whole system is tested to ensure it meets the necessary protection levels (Figure 7.10). The main issues with the CR1 (and all CBRN clothing) are thermo‐physiological loading of the wearer and the time taken to don the suit [31–33]. A newer version of the suit has been developed which is the Swift Responder 3, or ‘quick don’, which is a single‐garment double‐layer fabric which combines the attributes of the CR1 with a decrease in weight and time taken to put on.
7.4 Chemical, Biological, Radiological, and Nuclear (CBRN) Protective Clothing
Table 7.1 Standards for flame‐retardant clothing and materials for various applications. Document Number
Description
Publisher
Publication Date
BS EN 61482‐1‐1:2009
Live working. Protective clothing against the thermal hazards of an electric arc. Test methods. Method 1. Determination of the arc rating (ATPV or EBT50) of flame resistant materials for clothing
BSI
31/07/2010
BS 4569:1983
Method of test for ignitability (surface flash) of pile fabrics and assemblies having pile on the surface
BSI
28/02/1983
BS 5438:1976
Methods of test for flammability of vertically oriented textile fabrics and fabric assemblies subjected to a small igniting flame
BSI
30/11/1976
BS 7175:1989
Methods of test for the ignitability of bedcovers and pillows by smouldering and flaming ignition sources
BSI
31/07/1989
BS EN ISO 14116:2015
Protective clothing. Protection against flame. Limited flame spread materials, material assemblies and clothing
BSI
31/07/2015
BS EN ISO 15025:2016
Protective clothing. Protection against flame. Method of test for limited flame spread
BSI
31/12/2016
ASTM F1506‐15
Standard performance specification for flame resistant and arc rated textile materials for wearing apparel for use by electrical workers exposed to momentary electric arc and related thermal hazards
ASTM
01/11/2015
ASTM E2573‐12
Standard practice for specimen preparation and mounting of site‐ fabricated stretch systems to assess surface burning characteristics
ASTM
02/01/2012
ASTM E2404‐15A
Standard practice for specimen preparation and mounting of textile, paper or polymeric (including vinyl) and wood wall or ceiling coverings, facings and veneers, to assess surface burning characteristics
ASTM
06/01/2015
ASTM F1930‐15
Standard test method for evaluation of flame resistant clothing for protection against fire simulations using an instrumented manikin
ASTM
02/01/2015
ASTM D6413/ D6413M‐15
Standard test method for flame resistance of textiles (Vertical Test)
ASTM
01/06/2015
ASTM D6545‐10
Standard test method for flammability of textiles used in children’s sleepwear
ASTM
23/08/2010 (Continued )
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Table 7.1 (Continued) Document Number
Description
Publisher
Publication Date
BS EN ISO 6941:2003
Textile fabrics. Burning behaviour. Measurement of flame spread properties of vertically oriented specimens
BSI
08/01/2004
BS EN 1624:1999
Textiles and textile products. Burning behaviour of industrial and technical textiles. Procedure to determine the flame spread of vertically oriented specimens
BSI
15/11/1999
BS EN 16806‐1:2016
Textiles and textile products. Textiles containing phase change materials (PCM). Determination of the heat storage and release capacity
BSI
31/03/2016
BS EN 14878:2007
Textiles. Burning behaviour of children’s nightwear. Specification
BSI
31/07/2007
BS EN ISO 17881‐1:2016
Textiles. Determination of certain flame retardants. Brominated flame retardants
BSI
31/03/2016
BS EN ISO 17881‐2:2016
Textiles. Determination of certain flame retardants. Phosphorus flame retardants
BSI
31/03/2016
BS EN 1103:2005
Textiles. Fabrics for apparel. Detailed procedure to determine the burning behaviour
BSI
14/02/2006
16/30318704 DC
BS EN ISO 18640‐1. Protective clothing for fire fighters physiological impact. Part 1. Measurement of coupled heat and mass transfer with the sweating TORSO
BSI
01/07/2016
16/30318707 DC
BS EN ISO 18640‐2. Protective clothing for fire fighters physiological impact. Part 2. Determination of physiological heat load caused by protective clothing worn by firefighters
BSI
01/07/2016
ISO 15384:2003
Protective clothing for fire fighters. Laboratory test methods and performance requirements for wildland fire fighting
ISO
15/04/2003
BS EN 1486:2007
Protective clothing for fire fighters. Test methods and requirements for reflective clothing for specialized fire‐fighting
BSI
31/03/2008
BS ISO 22488:2011
Ships and marine technology. Shipboard fire fighters’ outfits (protective clothing, gloves, boots and helmet)
BSI
31/07/2011
BS 7971‐10:2014
Protective clothing and equipment for use in violent situations and in training. Coveralls. Requirements and test methods
BSI
28/02/2014
89/08
HOSDB flame retardant overalls standard for UK police (2008)
Home Office
2008
7.4 Chemical, Biological, Radiological, and Nuclear (CBRN) Protective Clothing
Figure 7.10 Police officers working in CR1 (training exercise).
The materials used for chemical and biological clothing typically fall into one of four categories: permeable, semi permeable, selectively permeable, or impermeable [34]. Permeable material allows liquid through at low hydrostatic pressures and is usually treated with a liquid repellent finish and is combined with a sorptive material, such as activated carbon‐impregnated foam or felt to absorb harmful chemical vapours. However, because of its permeability, convective air flow helps with the thermo‐ physiological burden of the wearer. Semi‐permeable materials can be classed as porous or nonporous (solution diffusion membranes). Porous membranes allow for the flow of air and vapours through, but vary depending upon the type of porous membrane: macroporous, microporous, or ultraporous. Nonporous membranes do allow gas vapours to diffuse across it, dependent upon concentration gradient, time, and thickness. An example of a nonporous membrane is Gore‐Tex® (W.L. Gore & Associates). Impermeable materials include butyl and neoprene, which are in common use in CBRN protective clothing. They provide a barrier to liquids and gases and vapours entering the body. However, their being impermeable means convective airflow cannot occur and the thermo‐physiological burden is high. Selectively permeable materials have the combined properties of impermeable and semipermeable materials, providing a high level of protection, allowing sweat to evaporate without the need for the heavy sorptive layer [34].
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7.5 Functional Finishing Finishing chemicals can be used to convert a textile material into a technical textile with functional properties. The modification of commodity fibre and fabric properties by innovative finishes could be a cheaper route to high performance than using a high cost fibre with inherent performance properties. There are different types of functional finishes and the right type of finish should be selected, depending on the fibre type of the textile substrate and the desired end use. It is possible to change the performance of the materials used for ballistic and impact protection by the use of additional treatments. Several technological solutions to protect the persons against impacts by chemical finishing exist. At present, the most promising technology is based on the use of shear thickening fluids, which consist mainly of highly concentrated nanoparticles dispersed in liquids. A shear‐ thickening fluid can harden in a few milliseconds, when it encounters mechanical stress or shear and will start behaving like a solid. Their viscosity and surface tension can be regulated in order to adapt the chemical formulation to conventional finishing technologies available in the textile industry. Some other very interesting alternatives to shear‐thickening fluids include ceramic or metallic spray coatings and silicone based dilatant powders. The future of flame retardancy is hindered greatly by environmental and eco‐toxicological considerations, both of the flame‐retardant chemicals and the toxic nature of the by‐products released upon combustion of textile fabrics. Thus, the new flame‐retardant chemistry is based on phosphorus, silicone, and nitrogen compounds. Flame‐retardant overalls used by police in public order situations are also treated with a liquid‐repellent coating to reduce the probability of liquids being absorbed by the material. There is a great interest to develop multifunctional protective textile materials by finishing techniques to counter CBRN threats. Liquid‐repellent coatings are also applied on CBRN protective materials. Aramids can be coated with a water‐repellent finish to help preserve the longevity of the materials if they come into contact with moisture [35].
7.6 Conclusion Clothing worn by military and law enforcement personnel has to protect the wearer from a wide range of threats faced during their duties. The threats considered in this chapter are ballistic and sharp‐weapon, flame, and CBRN. There is always a compromise between the protection offered to wearers of such personal protective equipment (PPE) and the ability to complete their duties. Optimum design of protective clothing systems requires knowledge of the threats faced, the tasks to be completed, the anthropometric properties of the persons to be protected, the fabrics that might be used, integration with other fabrics and equipment, and knowledge of appropriate clothing and textile sciences manufacturing techniques and test methods.
References
References 1 Ryan, J.M., Cooper, G.J., Haywood, I.R., and Milner, S.M. (1991). Field surgery on a
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future conventional battlefield: strategy and wound management. Annals of the Royal College of Surgeons of England 73: 13–20. Keene, D.D., Penn‐Barwell, J.G., Wood, P.R. et al. (2015). Died of wounds: a mortality review. Journal of the Royal Army Medical Corps 162: 355–360. Penn‐Barwell, J.G., Roberts, S.A.G., Midwinter, M.J., and Bishop, J.R.B. (2015). Improved survival in UK combat casualties from Iraq and Afghanistan 2003–2012. Journal of Trauma and Acute Care Surgery 78: 1014–1020. Hill, P.F., Edwards, D.P., and Bowyer, G.W. (2001). Small fragment wounds: biophysics, pathophysiology and principles of management. Journal of the Royal Army Medical Corps 147: 41–51. Cant, D.S., Ashmore, A., Dray, J., et al. (2016). A comparison of fragment simulating projectiles and real fragments with respect to soft body armour performance. International Symposium on Ballistics 2016. Edinburgh: 982–991. Office for National Statistics (2016). Crime in England and Wales: year ending June 2016. UK Statistics Authority London. Maynard, R. (1986). Tanto: Japanese Knives and Knife Fighting. Glastonbury: Unique Publications. Loriega, J. (1999). Sevillian Steel: The Traditional Knife‐Fighting Arts of Spain. Boulder, CO: Paladin Press. Godhania, K. (2010). Eskrima: Filipino Martial Art. Ramsbury: Crowood Press Limited. Cowper, E., Mahoney, P.F., Godhania, K. et al. (2016). A pilot study examining garment severance damage caused by a trained sharp‐weapon user. Textile Research Journal 87: 1287–1296. Tobin, L. and Iremonger, M. (2006). Modern Body Armour and Helmets: An Introduction. Canberra: Argros Press. Payne, T., O’Rourke, S., and Malbon, C. (2017). Body Armour Standard (2017). London: Home Office http://ped‐cast.homeoffice.gov.uk/standards//Home_Office_Body_ Armour_Standard_[FINAL_VERSION]1.pdf. Accessed 11 October 2018. Bhatnagar, A. (ed.). 2016). Lightweight Ballistic Composites: Military and Law‐ enforcement Applications, 2. Cambridge: Woodhead Publishing. Lewis, E.A. and Carr, D.J. (2016). Personal armour. In: Lightweight Ballistic Composites: Military and Law‐enforcement Applications, 2e (ed. A. Bhatnagar). Cambridge: Woodhead Publishing. Carr, D.J. and Lewis, E.A. (2014). Ballistic protective clothing and body armour. In: Protective Clothing: Managing Thermal Stress (ed. F. Wang and C. Gao). Manchester: Woodhead Publishing / The Textile Institute. Breeze, J., Baxter, D., Carr, D.J., and Midwinter, M.J. (2013). Defining combat helmet coverage for protection against explosively propelled fragments. Journal of the Royal Army Medical Corps 161: 9–13. Carr, D.J., Starling, G., De Wilton, T., and Horsfall, I. (2014). Tensile properties of military chin‐strap webbing. Textile Research Journal 84: 655–661.
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18 Horsfall, I. ((2012). Key issues in body armour: threats, materials and design. In:
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Advances in Military Textiles and Equipment (ed. E. Sparks). Cambridge: Woodhead Publishing / The Textile Institute. The NATO Standardization Office (2015). NATO Standard AEP‐2920: Procedures for the evaluating and classification of personal armour bullet and fragmentation threats Edition A Version 1. Brussels: NATO. BBC. BBC news website 2005. http://news.bbc.co.uk/1/hi/4269672.stm. Accessed 11 October 2018. BBC. BBC news website 2013. http://www.bbc.co.uk/news/uk‐northern‐ ireland‐23378221. Accessed 11 October 2018. Henriques, F.C. and Moritz, A.R. (1946). Studies of thermal injury. The American Journal of Pathology https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1934298/pdf/ amjpathol00501‐0024.pdf. Accessed 11 October 2018. Lee, K.C., Joory, K., and Moiemen, N. (2014). History of burns: The past, present and the future. Burns Trauma 2 (4): 169–180. https://doi.org/10.4103/ 2321‐3868.143620. Cardamone, J. (2013). Flame resistant wool and wool blends. In: Handbook of Fire Resistant Textiles (ed. F. Selcen Kilinic), 245–271. Cambridge: Woodhead Publishing. Kermel (2018). Polyamide‐imide fibres protecting against fire: Kermel. Available at: http://www.kermel.com/fr/Production‐of‐High‐Tech‐non‐flammables‐Fibres‐640. html. Accessed 11 October 2018. HSE (2018). REACH : Registration, Evaluation, Authorisation & Restriction of Chemicals. Available at: http://www.hse.gov.uk/reach/. Accessed 11 October 2018. Blackburn, R. (2015). Sustainable Apparel: Production, Processing and Recycling. https://doi.org/10.1016/C2014‐0‐02597‐X. Accessed 11 October 2018. Defence Clothing Team (DCT) (2018). Clothing for Operations: ‘The Black Bag’. London: Ministry of Defence. Available at: http://anyflip.com/tjtz/klri. Accessed 11 October 2018. Turaga, U., Kendall, R., Singh, V. et al. (2012). Advances in materials for chemical, biological, radiological and nuclear (CBRN) protective clothing. In: Advances in Military Textiles and Personal Equipment (ed. E. Sparks), 260–287. Cambridge: Woodhead Publishing. Remploy (n.d.) Frontliner CBRN Suit. Available at: http://ampsys.com.my/frontliner. pdf. Accessed 11 October 2018. Blacker, S.D. et al. (2013). Physiological responses of police officers during job simulations wearing chemical, biological, radiological and nuclear personal protective equipment. Ergonomics 56 (1): 137–147. https://doi.org/10.1080/00140139.2012. 734335. Ormond, R.B. and Barker, R.L. (2014). Chemical, biological, radiological and nuclear (CBRN) protective clothing. In: Protective Clothing: Managing Thermal Stress (ed. F. Wang and C. Gao), 112–145. Cambridge: Woodhead Publishing / The Textile Institute.
References
33 Potter, A. et al. (2015). Biophysical characteristics of chemical protective ensembles with
and without body armour. Natick, MA: United States Army Medical Research & Materiel Command. 34 Truong, Q. and Wilusz, E. (2008). Chemical and biological protection. In: Military textiles (ed. E. Wilusz), 242–280. Cambridge: Woodhead Publishing. 5 Paul, R. (ed.) (2015). Functional Finishes for Textiles: Improving Comfort, Performance 3 and Protection. Cambridge: Woodhead Publishing.
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8 Industrial and Filtration Textiles Tawfik A. Khattab and Hany Helmy Textile Research Division, National Research Centre, Cairo, Egypt
8.1 Introduction Technical textiles have been used as filter media. Depending on the filtration purpose, several requirements and standards must be fulfilled for the production of filters. Sometimes it is required to merge different filtration media to better fit the application’s requirements, such as filter fabric and membrane. In addition to such requirements and standards, the environmental impacts and structural design of textile filters and their production technologies are also discussed [1, 2]. High performance textiles are usually employed in filtration to separate and clean industrial goods, gases, and effluents. Therefore, textile filters represent a growing global market, as manufacturing and environmental demands increase. There are five major classes of filtration, which can be best classified as solid–gas, solid–liquid, solid–solid, liquid–liquid, and gas–gas separation. Textile permeability can be defined as the degree to which a fabric allows the flow of specific materials through it. This requires engineering precise characteristics into a functional fabric according to a specific desired outcome and the properties of the solids being filtered. The selection of the fibre and textile materials and their assembly properties are critical to the performance of a specified filter cloth and its processing abilities with a specified slurry composition, the properties of which must be obviously identified and understood to reduce any expected problem, such as filter plugging leading to low durability due to the accumulation of the solids being separated [3]. The different chemical, thermal, and pressure circumstances that are usually available in the various applications of filters have profound effects on the type of polymer used, as well as the target product. The solids being separated also have major effects on the sort of fabric structure in use. When selecting the suitable filter for an application, the properties of the fluid surrounding the filter must be considered, such as their chemical composition, temperature, humidity, and mass flow. Also, the particle properties such as particle size and their size distribution must be taken into consideration [4–7].
High Performance Technical Textiles, First Edition. Edited by Roshan Paul. © 2019 John Wiley & Sons Ltd. Published 2019 by John Wiley & Sons Ltd.
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8.2 Synthetic and Nanotechnical Fibres 8.2.1 High Performance Synthetic Fibres A synthetic fibre is a man‐made fibre developed to improve on animal and plant natural fibres. However, all man‐made fibres are not synthetic fibres. For example, nylon and polyester are synthetic fibres, while rayon and cellulose acetate are man‐made fibres but cannot be considered as synthetic fibres. Nylon, modacrylic, olefin, acrylic, and polyester fibres are classified as ‘common synthetic fibres’, while ‘speciality synthetic fibres’ include rayon artificial silk, acrylonitrile rubber, vinyon, vinalon, aramids, Dyneema, polybenzimidazole, polylactic acid, metallic, Zylon, glass, and Derclon. Synthetic fibres are chemically produced by joining monomers into polymers, through a process called polymerization (Figure 8.1). The majority of synthetic and cellulosic based fibres are generated by ‘extrusion’ via forcing such thick, viscous polymer fluid through tiny holes of the spinneret, while cooling, to afford continuous solid thread [8]. In their preliminary state, such fibre forming polymeric materials are in their solid state and therefore must be first transformed into the liquid phase for extrusion. This is generally done by melting, in the case of thermoplastic synthetic polymers, or by applying an appropriate solubilizing solvent to dissolve the polymer, in the case of nonthermoplastic cellulose. If they are not soluble or melted, they have to be chemically functionalized to produce soluble or thermoplastic modified polymer. In the case of polymeric materials that do not melt, dissolve, or afford suitable derivatives, small liquid monomers and additives are mixed in to react to produce these otherwise intractable polymeric materials during the extrusion course. Depending on the synthetic merchandise functional properties, a variety of chemicals can be added to introduce softer, stain‐resistant, wrinkle‐free, flame‐retardant, hydrophobic, or moth‐repellent garments. The above synthetic fibres have been modified and customized for extremely specific end‐users by blending and/or changing specific properties, such as tenacity, length, decitex, surface morphology, finish, etc., to make new hybrid product systems. However, it is the development of the so‐called technical fibres since the early 1980s that has introduced some of the most important and spectacular impulses to the evolution of high performance textiles [9].
O
O
CH3 O
HO
HO O
O
O O
Figure 8.1 Structural formula of cellulose acetate.
CH3
O
CH3
O
CH3
O O
n
8.2 Synthetic and Nanotechnical Fibres
8.2.2 Nanotechnical Fibres Nanofibres have received significant attention in different filtration applications. There are a variety of techniques to develop nanofibres, such as conjugate spinning (sea‐island method), chemical vapour deposition, phase separation, self‐assembly, melt‐blowing, and electrospinning. Among those techniques, the electrospinning method is a versatile and broadly accepted process to manufacture textile filters. Nanofibrous materials created from synthetic polymers are favoured to prepare textile filters, although a number of biopolymers have also been considered. Recently, nanofibres have been functionalized with a number of additives to separate gaseous contaminants [10, 11]. 8.2.2.1 Filters for Air Pollutants
Gaseous pollutants and particulate matter vary in their size and chemical composition. According to inhalable particle diameter, particulate matter is categorized as coarse (between 2.5 and 10 mm), fine (between 0.1 and 2.5 mm), and ultrafine (less than 0.1 mm). A particulate matter filter is thin, light, and highly porous compared to a gas filter, which are usually manufactured from granules of activated carbon with an extremely large surface area. Air filters are typically characterized in terms of their filtration effectiveness, penetration pressure drop, highly penetrating particle size, filter resistance, and quality factor. ‘Filter resistance’ indicates the filter breathability and is mostly related to pressure drop [11]. 8.2.2.2 Pollutant Capture Mechanism of Fibrous Filters
The air filtration mechanism describes the mode by which contaminants are adsorbed, attached, and captured by the filter medium. It mainly depends on the properties of the filter medium and the nature of contaminants. The filtration mechanisms of particulate matter and gaseous pollutants can be similar physically to some degree but chemically completely different. Filtration by micro‐ or nanofibres is usually controlled by physical factors, including contaminant size, filter geometry, and rate of air flow. The micro‐ and nanofibrous materials can hold the particles physically much smaller than its pore size, which is beyond simply sieving [12]. The filtration mechanisms include diffusion, interception, intermolecular interaction, straining, inertial impaction, gravitation, and electrostatic interaction of particles on the filter surface. Both diffusion and interception are the most significant particle capture mechanisms of nanofibrous filters. Diffusion holds fine particles below 0.5 mm diameter that move randomly, owing to Brownian movement. A particle interception with a nanofibre occurs when the distance between the nanofibre surface and the particle centre is equal to or less than the particle radius. The small fibrous diameter enhances the particle interception efficiency. Particle capture by nanofibrous filter depends on Peclet and Knudsen numbers and the nanofibre packing density. The Peclet number stands for the relative strength between interception and diffusion mechanisms, while the Knudsen number is the ratio of mean free path of air molecules to the particle size. Strong diffusion is accompanied by a decreased Peclet number and an increased Knudsen number. However, such strong diffusion results in high air flow (Figure 8.2) [13]. Therefore, the aerosol retention time on nanofibres gets decreased, leading to inefficient diffusion mechanism. Nanofibre packing density is known as the accumulative mass of nanofibres per unit length. It depends on fibre density and filter thickness. High
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Electrostatic attraction Interception Intertial impact
Gravitation
Diffusion
Fiber cross section
van der Waal interaction
Air Stream
Straining Aerosol particle
Figure 8.2 Particle collection mechanism of fibres.
packing density is a sign of efficient particle capture. Straining takes place in a filter when the particles go through passages between two or more fibres that have dimensions lower than the particle diameter. Straining is a significant capture mechanism. However, in the case of a nanofibrous medium, straining along with intertial impact and gravitation may be less efficient than diffusion and interception. The intermolecular attraction mechanism, also known as Van der Waals forces, holds uncharged particles with a diameter of less than 0.5 mm that move with speeds of less than 0.01 m s−1. The electrostatic interaction mechanism separates particulate particles according to Coulomb’s law. This mechanism is favoured for particulate particles with a diameter range of 0.1 to 1 mm [12]. Physisorption and chemisorption are the two essential separation mechanisms of gaseous contaminants. Physisorption refers to separation at the surface pores of the nanofibrous structure as a result of Van der Waals forces. Nanofibres can have strong intermolecular attraction forces with the gaseous units, owing to a higher surface area, which raises the physisorption ability. Therefore, the nanofibrous filter with a large surface area should be aimed to separate gaseous contaminants. Chemisorption converts contaminants into simple materials via catalytic or noncatalytic reduction. Chemisorption is a highly selective technique compared to physisorption. Such selectivity can be enhanced via surface active functionalization of the fibre structure [13]. 8.2.2.3 Synthetic Polymers for Technical Nanofibres
Synthetic polymers are ideal for the formation of nanofibres via electrospinning towards filter membranes. This is due to the outstanding chemical and thermal stability of synthetic polymers along with controllable fluid properties and simplicity of spinning. Filter membranes can be created from polyamide and polyacrylonitrile (formation). Polyamide is easy to spin because of its short length of di‐acid and di‐amine monomer units. Its fibres are characterized as being suitable for air filtration because of their small diameter, narrow diameter distribution, large surface area, and enhanced dirt‐loading capability along with their high electrostatic charge. Polyamide electrospun nanofibres demonstrated outstanding filtration efficiency that was 250% higher than pristine
8.3 Natural Fibres for Technical Applications
clothing, with five times less areal density, and about three times less pressure drop than the marketable glass filter media [14]. Polyacrylonitrile nanomembranes more effectively separated particulate matter and gaseous pollutants than other polymers such as polyamide, polyvinyl pyrrolidine, polystyrene, polyvinyl alcohol, and polypropylene. Its nanofibrous membranes separated pollutants 10 times its own mass, owing to better surface properties, higher single nanofibre separation capacity, and higher dipole moments. Polyacrylonitrile nanofibres are also characterized by high quality tensile strength and moisture vapour transport properties. For other synthetic polymers, the filtration effectiveness and pressure drop of polyvinyl alcohol nanofibrous membranes displayed better characteristics than conventional cotton. Polyurethane based polymers were electrospun to create nanofibres for absorption of volatile organic compounds (VOCs) in air, and were also prepared as protective technical garments against chemical and biological threats [15]. 8.2.2.4 Biopolymers for Technical Nanofibres
Recently, biopolymers gained attention as matrix materials to produce nanofibrous membranes for textile filters. There are some polymers, such as wool keratin, chitosan, and polylactic acid, that have been electrospun to prepare filter membranes. A limited number of biopolymers have been electrospun for textile filters, because of the difficulty in electrospinning biopolymers. Therefore, biopolymers are usually blended, typically with synthetic polymers, such as keratin/polylactic acid and chitosan/ poly(ethylene oxide) blends to get a uniform nanofibrous diameter with a bead‐free structure [16]. Keratin biopolymer absorbs and removes toxic materials in fluids such as formaldehyde in air and other hazardous VOCs, owing to its unique molecular structure and chemical properties. Electrostatic wool based microfibrous filters remove particulate matter via columbic attraction. Nanofibrous membranes made from chitosan biopolymer possess excellent antimicrobial properties. Chitosan can also afford positive charge on filter fibrous surface and can efficiently neutralize air pollutants by unique physical and chemical methods. Polylactic acid can introduce promising applications such as a respiratory filters, owing to its sustainable and carbon‐neutral nature. An optimized nanostructure composition, made up of 5% of polylactic acid in a 10% solvent, provided the highest quality factor. Biopolymer blended from polylactic acid/polyhydroxybutyrate displayed good mechanical strength, high filtration efficiency, low pressure drop, high dust loading, and dust purification regeneration capacity [17].
8.3 Natural Fibres for Technical Applications Natural fibres are produced by plants, animals, and geological processes as follows: ●●
●●
Plant fibres such as cotton are the cell walls that are located in stem and leaf elements and are composed of cellulose, hemicellulose, lignin, aromatic substances, waxes, lipids, ash, and other water‐soluble materials. The chemistry and structural properties of fibres determine their functionalities and processing efficiencies. Animal fibres include catgut, mohair, silk, wool, angora, and alpaca textile fibres. They normally comprise proteins such as collagen, keratin, and fibroin.
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Mineral fibres are produced from mineral resources. They could be used in their natural structure or after slight modification. Mineral fibres include metallic fibres, such as aluminium fibres; asbestos that can be modified into serpentine and amphiboles; or ceramics, such as glass fibres prepared from aluminium oxide, boron carbide, glass wool, quartz, and silicon carbide.
Natural fibres can be employed as a constituent of a composite, where the orientation of fibres influences the properties. They can also be matted into sheets to construct goods such as paper, felt, and fabric. The most primitive proof of humans using fibres is the finding of wool and dyed flax fibres. Natural fibres are used for high tech purposes, such as composites for automobiles. Compared to reinforcement of composites with glass fibres, composites with natural fibres are characterized by having less density, improved thermal isolation, and decreased skin irritation. Furthermore, in contrast to glass fibres, natural fibres are biodegradable by bacteria once they are no longer in use [18]. 8.3.1 Bast Fibres Bast fibres – such as ramie, flax, hemp, jute, kenaf, and abaca – are soft wooded fibres, which are produced from the stems or stalks of dicotyledonous natural plants. The fibres are located in bundles or aggregates. The bundles are of 10–25 elementary fibres, 2–5 mm length, and 10–50 μm diameter. The bundles are linked by lateral ramification, creating three‐dimensional (3D) networks. The basic fibrils and bundles are reinforced by lignin and pectin intercellular matter, which have to be eliminated during the processing of fibre extraction. Bast fibres have been used not only in the textile industry but also for modern eco‐friendly composites for building supplies, insulation panels, geotextiles, foodstuff, cosmetics, medicine, and as a resource for other biopolymers [19]. 8.3.2 Technical Applications of Natural Fibres The most common textile fibres available that have been used for technical and industrial applications are cotton and a range of coarser vegetable fibres, such as flax, jute, and sisal. They have been typically used to produce heavy canvas‐type goods, ropes, and twines. They are characterized by comparatively high weight, low resistance to water, microbial, and fungal attack as well as weak flame retardance. Natural fibres are gaining increasing significance in automotive, aerospace, packaging, fibre reinforced composites, and other high performance textiles applications. Natural fibres present excellent specific tensile strength and stiffness, in some cases even better than glass fibres but somewhat similar to synthetic fibres. In addition, they present other advantages including enhanced energy recovery, carbon dioxide sequestration, production simplicity, and production flexibility, and are eco‐friendly and come from renewable natural resources. However, the market demand for natural fibres is also changing, owing to the availability of newer biodegradable polymers, such as polylactic acid prepared from corn. Currently, some other biopolymers have characteristics comparable to their petroleum origin counterparts. To strike a balance between price, quality, performance, ecological regulations, and supply of natural fibres, a number of composites and high performance fabric producers are developing novel facilities for using alternative
8.4 Manufacture of Technical Textiles
fibres. The automotive division requires rationally durable materials which must be biodegradable at the ending of their service life [3]. In order to explore value‐added products, it is necessary to understand the value addition during each stage of manufacturing. Usually, very little value addition is achieved in the early stage of the processing chain, for example cultivation, harvesting, fibre extraction, and fibre preparation. The value addition increases further up the chain, particularly in the production of products with functional attributes which can satisfy demanding technical specifications, for example woven fabrics for soil erosion and preforms for reinforced composites or nonwoven fabrics for insulation and filtration. Even still, higher levels of value addition can be achieved when producing products with multifunctional attributes, for example composite panels with thermal and acoustic barriers and roofing products with built‐in photovoltaic cells. Semi‐finished and finished components can provide still higher levels of value addition, for example automotive parts and panels, such as parcel trays and door panels. With the increasing added value across the value‐addition chain, obviously, the technical complexity increases, and this requires careful research interventions and investment in the development process [20]. It is often mentioned that the tensile properties of natural fibres are much lower than that of E‐glass, Kevlar, and carbon fibres. However, the advantage of natural fibres lies in their comparatively lower densities. Therefore, an effective comparison of mechanical properties should be in terms of their specific mechanical properties according to which it is apparent that certain tensile strength of some of the natural fibres, such as flax, kenaf, hemp, and Caraua is quite comparable to that of E‐glass fibres. Therefore, natural‐fibre‐based products clearly provide an opportunity to reduce component weight and are therefore widely used in technical textiles and as reinforcements in composite products for the transportation sector [20].
8.4 Manufacture of Technical Textiles 8.4.1 Electrospinning for Technical Textiles Principally, electrospinning is a method to manufacture synthetic textile nanofilaments by applying an electric force on a polymer fluid. The electrospinning process was originally patented by Formhals. Taylor mathematically modelled the electrospinning approach to illustrate the effect of electric force on the fluid droplet creating a cone profile, known as the Taylor cone. Electrospinning received real momentum in 1990s mostly due to knowledge progression in nanoscience. Electrospinning is characterized by simplicity and versatility to afford nanofibres and control their shape [21, 22]. In a typical electrospinning system (Figure 8.3), a capillary tube located on a syringe pump containing viscoelastic polymer fluid which could be a polymer dissolved in a solvent or molten form. A high voltage is applied to the polymer fluid enclosed in the capillary tube. Electrically charged polymer fluid overcomes its surface tension, producing a Taylor cone at the needle tip, which elongates in a jet shape towards the grounded collector. The concurrent effect of the jet stretching and solvent evaporation during the jet travel produces nanofibres characterized by a small pore size and high specific surface area with higher ability to capture dust particles on its surface, and
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Syringe pump Syringe containing polymer solution
High voltage power supply
Fiber
Grounded collector Figure 8.3 Diagram displaying an electrospinning setup.
eventually this enhances filtration efficiency compared to microfibrous membranes. Air filtration is the earliest commercial application of electrospun nanofibres such as pulse filters, turbine air filters, and vacuum bag filters. A thin layer of nanofibrous membrane is appropriate for the preparation of filter media for antimicrobial air filters, cabin air filters, and filters for individual protective textiles. Owing to their efficient ability to capture air contaminants, technical textiles from electrospun nanofibres have strong potential in the clean energy, healthcare, and ecological sectors [22, 23]. 8.4.2 Effect of Nanofibre Parameters on Air Filtration The fibre diameter, pore size, surface area, thickness, mass coverage, and structure of the membrane of an air filter can generally be manipulated. 8.4.2.1 Fibre Diameter
The fibre diameter has a deep effect on the filtration efficiency. The nanofibre diameter up to 300 nm can be appropriate to achieve more than 99% filtration effectiveness of sodium chloride particles up to 300 nm in size. Reducing the fibre diameter from 300 to 120 nm considerably increases the filtration effectiveness at all levels of mass coverage of nanofibres. For instance, the filtration performance of a polyacrylonitrile based nanofibrous filter increased from 48.21 to 98.11% as the fibre diameter decreased from 1000 to 200 nm. Compared to wider distribution of the same fibre diameter, the lower distribution of fibre diameters can affect the filtration efficiency because it may lead to less pressure drop and normalized thickness. It has been reported that the small diameter nanofibres (less than 100 nm) offer improved aerodynamic slip, where air molecules do not collide with the nanofibres. This slip flow decreases the friction effect, and pressure drop was not increased significantly. The small fibre diameter enhances the filtration performance but with a large pressure drop. The small fibre diameter decreases the
8.4 Manufacture of Technical Textiles
pore size by reducing the pore aperture and improves the direct interception effect for particle capture [24]. 8.4.2.2 Pore Size
Nanofibres can form closed, blind, and through pores in their 3D structure. The closed pores are not accessible, while the blind pores terminate within the intertwined structure itself. Through pores are open and therefore significant for air filtration media. The smaller through pore size can accomplish high filtration performance but adversely affects air permeability and pressure drop of the filter media. The nanofibrous membrane containing both high and small through pore size exhibited more efficient air filtration than the one with only a small pore size of the same thickness. This can be attributed to the less twisting path of air flow compared to less porous membrane, and consequently, highly porous membranes can result in a smaller pressure drop [24]. 8.4.2.3 Membrane Thickness and Mass Coverage
Membrane thickness is linearly correlated to the electrospinning time. It is directly proportional to pressure drop and reversely proportional to air permeability. A very thin nanofibrous layer of a few microns’ thickness restricts the air flow of the membrane to a large degree. Nanofibrous membrane of comparable thickness and multilayer system increases the filtration efficiency [24]. 8.4.3 Yarn Types and Fabric Constructions There are different types of manufactured yarns to select from when designing a filter fabric, as described below. 8.4.3.1 Monofilaments
Being produced from thermoplastic polymeric materials, monofilament based yarns are prepared by the extrusion of molten polymer through a precision engineered die nozzle. On emergence from the extruding point, the polymer melt is cooled, generally in a water bath, and drawn over a series of rollers to orient the molecules and to afford the monofilament with the requested stress strain properties. The bath through which the monofilament passes may also include additives such as lubricants to help in weaving and antistatic agents to prevent shocks during high rapidity warping. The diameters of the monofilaments employed range from 0.1 to 1.0 mm, the small diameters being employed mostly in applications related to candle filters, rotary vacuum disc, filter presses, pressure leaf, and rotary vacuum drum filtration systems. On the other hand, the higher diameters are used largely for coarse filtration purposes, including heavy duty vacuum belt filtration systems and multiroll filter presses [25]. Although usually extruded in circular cross‐section, for particular applications they may also be obtained in flat or oval shapes. The major properties of monofilament cloths (Figure 8.4) involves resistance to blinding, elevated filtrate throughput, and effective cake discharge at the end of the filtration cycle. These properties are ascribed to the smooth surface of the yarn and, in the case of cake discharge, weaving in a satin building can further improve this. On the downside, the spaces that are shaped between adjacent threads and at the interweaving points may prove to be extremely large for the capture of very fine particles, such as colourants, even though the warp threads may be
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Figure 8.4 Diagram representing monofilament fabric.
highly dense. For most filtration purposes employing monofilaments, the mostly employed diameters range from 0.15 to 0.35 mm. Heavy‐duty filter belt applications typically use diameters of between 0.3 and 1.0 mm [25]. 8.4.3.2 Multifilaments
Similar to monofilaments, multifilaments are also extruded throughout a precision engineered die nozzle. However, the die in this case involves many nozzles of much smaller sizes. Furthermore, the substance to be extruded may also be in the shape of a molten polymer or dissolved in a solvent which can be evaporated upon extrusion to be recycled for further use. The threads are drawn so as to orient the molecules and develop suitable tenacity. Producers of multifilament yarns introduce several standard linear densities that, for industrial filtration applications, may range in fineness from 120 to 2200 decitex, with single filaments ranging from 6 to 10 decitex. Multifilament garments are distinguished by their high strength and resistance to stretch, these characteristics being improved as the tenacity of the yarn raises. Multifilament yarns are more flexible compared to monofilaments, leading to easier weaving of the tightest and most effective of all woven garments [26]. In regard of the textiles tightness into which they are often woven, multifilament garments are usually substandard to monofilaments for the sake of throughput, and their resistance against blinding will be also decreased. This is due to the reality that, in addition to the filtration which occurs between adjacent threads, particles are also separated and probably permanently trapped and accumulated in the threads leading to swelling of yarns. The light fabrics may necessitate extra support via fabric backing to prevent damage from abrasive filter plates or possibly to prevent the fabric deformation to the indentations of the plate surface where it would hinder escape of the filtrate. Heavier garments will be employed mostly without support for harder and higher stress‐related purposes, such as filtration belts on vertical automatic filtration presses [26]. 8.4.3.3 Fibrillated Tape Yarns
These yarns are manufactured from a narrow width polypropylene film split into some components then given a twist to bind the fibres. They could be seen as rather coarse multifilaments, however, as fibrillated tape yarns are much stiffer than the multifilament yarns. They are not usually employed in filter cloths as such but rather in higher
8.5 Functional Finishing
open‐weave backing textiles. Therefore, their purpose is to afford protection for the more fragile primary filter fabrics from damaging surfaces, while allowing the free flow of filtrate from the filtration compartment as displayed by mock leno weave [27]. 8.4.3.4 Staple‐Fibre Yarns
These yarns are manufactured by a continuous extrusion method, then converted into a short staple length. Cotton affords yarns that are rather lean in nature, whereas those from the wool based textiles are more bulky. In addition to their excellent ability to collect particles, fabrics obtained from wool based spun staple‐fibre yarns are distinguished by their resistance to abrasive forces. For filtration applications, the yarns are typically spun with 3.3 decitex fibres in moderately coarse linear densities from 1.3 to 2.5 decitex. Yarn combinations can be presented in different ways, such as multifilament warp/staple based weft yarns and monofilament warp/multifilament fibre weft yarns to result in an enhancement in filtration efficiency, particularly if it is correctly textured. For fabric constructions, plain weave is the basic weave of all woven assemblies and provides the skeleton for the tightest and most rigid single layer filtration fabric. Other woven structures include twill weaves, satin weaves, needlefelts, duplex and semiduplex weaves, and link fabrics [28].
8.5 Functional Finishing Functional finishing treatments are designed mainly to enhance fabric dimensional stability during use, filtration collection effectiveness, better dust discharge, and resistance to damage due to moisture or chemical agents. A variety of finishing methods are employed to accomplish these objectives, for instance heat setting, singing, raising, calendering, and chemical and plasma treatments. Fabric finishes are designed mainly to guarantee the filtration fabric will exhibit specific characteristics as follows: ●● ●● ●● ●●
Stable dimensions during usage. Afford efficient cake release during the cleaning cycle. Convene the fabric’s designed air permeability. Being protected from any chemicals or environmental circumstances.
8.5.1 Heat‐Setting Process Synthetic fibres and continuous filament yarns usually shrink when subjected to high temperatures. In addition, because of tensions imposed on fibres and yarns during processing or use, additional shrinking is predictable as a result of relaxation effects. Fabric shrinking may lead to too tight filter sleeves on filter cages to result in ineffective cleaning, and in severe cases can yet produce such force as to lift the cages out of the cell plates into which they have been positioned. In order to decrease these effects, textiles are commonly exposed to thermal relaxation or heat‐setting. Enhanced dimensional stability is necessary in order to avoid shrinkage during usage [4]. Fabric shrinking may be caused by the relaxation of tensions applied on fibres and/or yarns during the production process, or could be due to the inherent shrinking properties of the fabric’s raw materials. The thermal circumstances that are frequently found in a dust collector will
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encourage fabric relaxation and, if not effectively addressed during fabric production, could result in severe shrinkage problems during use. For instance, in a pulse collector, lateral shrinking could lead to high fabric tightness on the supporting cage, resulting in ineffective cleaning and eventually an undesirable pressure drop. As heat is the major reason of shrinking, it is reasonable that fabric stability should be accomplished by thermal methods. Such a process is generally referred to as ‘heat setting’, and may be performed by surface contact methods via air equipment or stentering. The latter two are favoured because they enable better penetration of heat. This is especially relevant in the needlefelts fabric construction because the scrim is to some degree insulated by the batt fibres. The heat setting technique also increases the density of the structure via increasing the fibre consolidation, which assists in accomplishing a better level of filtration efficiency [29]. 8.5.2 Singeing Process Filter fabrics, particularly needlefelts, which are manufactured from short staple fibres, usually have a surface with protruding fibre ends. Since such protrusions may reduce cake release efficiency by clinging to the dust, it is ordinary practice to eliminate them. This is accomplished by singeing at relatively high speed on a direct gas flame or on a copper plate heater. The direct flame causes the fibres to contract to the fabric surface, forming, in the case of thermoplastic fibres, small hard polymer beads. Singeing speed and gas pressure are usually set depending on polymer category and end‐use preference [30]. 8.5.3 Raising Finishing Process While the singeing approach is intended to denude the fabric of its protruding fibres, the raising technique is considered to generate a fibrous surface, usually on the outlet side of the filter sleeve, to improve the fabric’s dust collection efficiency. Hence, the raising method is intended fundamentally for woven garments containing staple‐fibre yarns. In the raising technique, the fabric is drawn over a sequence of rotating rollers known as pile and counter‐pile covered by card wire and located concentrically on a cylinder of about 1.5 m diameter. Raised fabrics may contain 100% staple‐fibre yarns or a combination of multifilaments/staple‐fibre yarns. The smooth surface introduced by the multifilaments will assist cake discharge, while the raised staple yarns on the reverse surface will improve particle collection capability [31]. 8.5.4 Calendering Technique The calendering process is used to enhance the fabric’s surface smoothness assisting dust release, and to increase the fabric’s filtration capability by controlling its density and permeability, which leads to higher tightness of yarns and fabrics, making it harder for particles to pass through or even into the fabric. Calenders in industry are mainly composed of at least two bowls, one made from chrome plated steel and another from a more flexible matter such as nylon or highly packed cotton or wool fibres. The steel bowl is set with a heat supply such as gas, electric power components, superheated steam, or circulating hot oil. Thus, by changing the processing temperature, pressure, and speed, the required density and level of surface polish can be achieved [32].
8.6 Textile Reinforced Composite Materials
8.5.5 Chemical Treatments Chemical treatments are usually applied to aid in dust release, particularly where moist sticky dusts, probably containing oil or water vapour, are encountered. Chemical treatments are also used to offer protection from chemically harmful gases. Other chemical treatments are used for more specific applications. For instance, proprietary treatments used to improve yarn‐to‐yarn or fibre‐to‐fibre lubricity during pulse or flex cleaning and likewise, where flammability is a possible risk, padding through commercially available flame‐retardant materials is necessary [33]. 8.5.6 Plasma Treatment Plasma textiles are an innovative category of compressed filters which offer improved submicron particle filtration for particle diameters in the range of 30–300 nm. Unlike conventional inactive respiratory filters, plasma textiles are active filters which can be produced from woven, nonwoven, or knitted garments. Both woven and nonwoven plasma garments offer filtration effectiveness close to 100% for ultrafine particles. Textiles are exposed to plasma in the range from several seconds to a few minutes to afford effective fabrics. Plasma flexible fabrics with embedded electrically conductive wires have been employed as wearable sterile textiles or antiseptic filters. These fabric embedded high voltage electrodes are able to generate in situ room temperature plasma. Well‐designed textiles produce plasma, thus offering reactive species such as free radicals, ions, and excited molecules that are potentially destructive for bacteria [34].
8.6 Textile Reinforced Composite Materials Fibre reinforced composites for high performance textile filters are increasingly utilized in our daily life. Composites are structurally engineered materials with a high modulus of elasticity able to offer materials with stiffness, high strength, and low weight properties. Technical textile fibres with superior mechanical, thermal, and chemical characteristics have presented a novel generation of composite materials. Given increasing pollution, particularly air and water pollution, and its effects on humans, filtration processes have become more significant. Filtration introduces surface adjustment for better healthcare and a cleaner environment [3, 7]. Air and water filters are very significant, and high performance textile structures are broadly employed for the filtration processes of fluids. Technical textile engineering affords 3D networks of fibres for efficient filtration. The surfaces of such textile fibres capture particles, and consequently fibre surface features are critical to filtration efficiency. A technical fibre owes its efficiency to a composite through the boundary between the matrix and the fibre surface [35]. The most commonly utilized technical fibres for filtration are polyester fibres. They illustrate moderately good strength, are inexpensive, and possess high temperature resistance. However, polyester fibres possess weak resistance to alkalis, acids, and steam. On the other hand, polyester fibres of diverse linear densities and cross‐sectional forms can be manufactured easily. Teflon and glass fibres are utilized for
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high‐temperature filtration. Glass fibres are characterized by a strong particle capture capacity, while ceramic fibres are appropriate for hot glass filtration. After polyester, polypropylene is the most broadly used fibre for filtration. It is characterized as a hydrophobic with strong acid, alkali, and abrasion resistance. It is highly appropriate for melt‐ blown and spunbond nonwovens. However, it has a comparatively low melting point [36]. Both Teflon and polypropylene are hydrophobic and possess a nonwettable surface Therefore, they have been used in the filtration of liquid aerosols. These hydrophobic fibres enforce the liquid particles to produce droplets that can be drained and collected. When these droplets reach a critical size they start to oscillate, then break free and pass through the filter. This self‐cleaning feature of the hydrophobic filter surface has significant applications in filtering liquid aerosols because, in the case of wettable surfaces, liquid aerosols adhere to a wettable surface, producing liquid layers around the fibres [36].
8.7 High Performance Applications In air filtration fabrics, there is a growing interest in combating air pollution. Enhanced media filtration efficiency will be needed in order to meet the current demands, and in traditional dust collection, it is anticipated to see greater use of finer fibres, and fibres of irregular cross‐sectional form, used in the form of surface layers. There is also a growing demand for the use of cartridge filter elements which can be installed either in novel filtration tools or as retrofit units in existing filters. There are three essential types of structures found in fabric dust filters involving woven fabrics, needlefelts, and knitted structures. Both woven fabrics and needlefelts are manufactured in flat form and will necessitate slitting to a suitable width and converting into tubular sleeves, while knitted fabrics may be manufactured directly into a tubular shape [4–7]. 8.7.1 Woven Fabrics Woven fabrics are used mainly in shaking mechanism based filters cloths which may consist of twisted continuous filament yarns, short staple‐fibre yarns, or possibly a combination of both. Weave models may be in the shape of elementary twills or possibly simple satin designs, the latter affording higher flexibility and therefore excellent resistance to flex fatigue and a smoother surface for excellent cake release. The area densities of woven fabric are usually between 200 and 500 gsm [37]. 8.7.2 Needlefelts This category of construction is by far the most common in dust filtration processes, affording an infinitely larger number of pores and facilitating significantly higher filtration velocities than woven filter cloths. On the whole, they are manufactured by needle punching a batt of fibre onto both sides of a woven cloth or scrim. This may be performed in a continuous procedure or by attachment of a pre‐needled batt formed in a separate process [38].
8.8 Testing Methods and Quality Control
8.7.3 Nonwoven Fabrics 8.7.3.1 Spunbonded Fabrics
As in synthetic yarn manufacture, spunbonded garments are also formed by extruding molten polymer chip through a spinneret, the difference being that the spinning head or die includes a much larger number of holes. The filaments that come out from the extruder first pass through a quenching region, where they are hardened by jets of cold air. This is followed by high velocity air leading to the orientation of polymer chains and increasing the filament strength [39]. 8.7.3.2 Melt‐blown Fabrics
In parallel vein to spunbonded garments, melt‐blown textiles are also manufactured by extruding molten polymer chip through a die. The distinction being that in this case the emerging filaments are fibrillated and fractured by a jet of high velocity hot air to afford much finer fibres, ideally 0.5–5 μm. The airflow guides the fibres to a vacuum‐supported mandrel where they produce a fibrous batt, being cooled and solidified followed by secondary air that is drawn into the procedure [40, 41]. 8.7.4 Knitted Fabrics Because of their capability of being manufactured in a seamless tubular structure, weft‐ knitted garments afford an attractive and economic substitute to both woven and needled fabrics. By inlaying suitable yarns into the knitted fabric, the elasticity which is usually coupled to such fabrics can also be controlled and the same may be employed to improve the particle filtration ability [42].
8.8 Testing Methods and Quality Control 8.8.1 General Quality Control Tests General quality control measurements are usually performed in normal textile laboratories to guarantee that the materials under examination have been made in accordance with design requirements, and to supervise any short‐, medium‐, or long‐term trends. Such examinations are concerned mainly with area and linear densities, fabric structure and type, air permeability, thickness, tensile properties, fabric set, and dimensional stability. Fabric resistance to stretch is of great significance with respect to tensile properties. Although filtration textiles are rarely exposed to forces that will lead to tensile failure, they may undergo a degree of stretch that could have severe consequences [4–7]. Resistance to stretch at low loads (i.e. less than 100 N per 5 cm) is consequently of particular significance from a control point of view. In addition, since shrinkage is temperature dependent, the capability to perform such tests at high temperatures is also useful [43]. Shrinking tests possess a number of forms depending on whether the end‐use is wet or dry. For dust collection purposes, testing fabric’s free shrinkage in an air circulating oven is the standard technique, the time of exposure and temperature changes being dependent on the particular test procedure. By comparison, since it is familiar in liquid
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filters for cloths to be removed from the filter and exposed to a laundering process, a laboratory examination has to be devised that will reproduce the mechanically stimulated shrinking produced by an industrial tumble washing machine. Such action, by virtue of the weight of cloths included, is unavoidably more severe than a domestic machine. Although examination procedures are available to evaluate the liquid permeability of fabrics (e.g. by calculating the time for a particular volume of water to pass through the fabric), either under gravity (falling column) or at a certain vacuum, it is usually more suitable to quantify the permeability of fabrics by air methods [43, 44]. 8.8.2 Performance Related Tests While the above testing techniques are ideal for regular quality control purposes, they offer very little assistance about the aperture size and consequently the real efficiency of the filter fabric in dealing with particles of identified size. In the case of large mesh monofilament screening cloths, it is likely to determine the aperture size easily via thread diameters and thread spacing. Alternative approaches must be taken with tighter structures. The test of ‘equivalent pore size’ by a bubble point practice is possibly the most popular approach and includes soaking the fabric in an appropriate wetting liquid and then reporting the air pressure that is essential to generate a bubble on the surface. The pore size can be determined from the relationship r = 2 T ¥ 105/sPg, where r is the pore radius (mm), T is the surface tension of the liquid (mNm−1), s is the density of water at the testing temperature (g.cm−3), P is the bubble pressure (mm H2O), and g = 981 cm.s−2 [43, 44]. 8.8.3 Characterization of the Filtration Efficiency of Nonwovens Nonwoven filters have not completely uniform structures as screens. The filtration effectiveness of an ideal filter should be the same at each point of its active surface. It is significant to evaluate uniformity of filtration fabric, particularly in the case of nanofibrous filtration systems. Uniformity of a filter depends on mechanical properties, uniformity of fibres, layer thickness, and uniformity of a fibre deposition. In other words, the filter uniformity is the quality gauge of the filtration material. The examination technique investigates filtration material in processing by artificial seeding particles [4–7]. 8.8.4 Characterization of Electrospun Nanofibres It is required to characterize the properties of nanofibres – such as fibre diameter, pore size, surface area, and surface chemistry – to evaluate their effects on air filtration. Generally, nanofibres can be studied according to their geometrical, chemical, and mechanical properties. 8.8.4.1 Geometrical Characterization
Both fibre diameter and pore size are significant geometrical properties of nanomembranes that can considerably influence air filtration. The fibre diameter, distribution, orientation, cross‐sectional shape, and surface roughness can be measured using electronic microscopes, such as the scanning electron microscope (SEM) as shown in
8.8 Testing Methods and Quality Control
Figure 8.5 Scanning electron microscope image showing the porous structure of random orientation.
Figure 8.5, transmission electron microscopy (TEM), and atomic force microscopy (AFM) followed by image analytical techniques. TEM is most valuable when the nanofibre’s diameter is lower than 300 nm. AFM is a little difficult to be used in the determination of the nanofibre’s diameter precisely, but it is a multipurpose system used to study the surface morphology precisely. Several studies report nanofibre thickness employing SEM images. However, it is hard to prepare a uniform cross‐section of a model from delicate polymer based nanofibrous membrane, unlike microfibres. Therefore, the thickness preciseness determined by SEM is suspicious. Pore size, pore distribution, and porosity can be determined by microscopy and porosimetry techniques. In microscopic systems, SEM, TEM, and AFM images can be employed to determine the pore size on nanofibrous surface. Porosimetric systems involves intrusion (mercury), extrusion (capillary flow), and molecular resolution (known as the Brunauer–Emmett–Teller (BET) analytical technique. The benefit of BET analysis is that it can determine surface area, porosity, pore size, and distribution [45]. 8.8.4.2 Chemical Characterization
Chemical characterization of nanomaterials can recognize the chemical character of such materials before and after being electrospun. Nuclear magnetic resonance (NMR) and Fourier‐transform infrared (FTIR) spectroscopies can identify the molecular structure of polymers, their reaction with other materials, and the existence of specific additives. The identification of macromolecules and crystalline character of nanomaterials can be considered using X‐ray diffraction (XRD). The dissimilarity in the diffraction peaks can chemically determine different materials exist in the nanofibre membrane. Surface chemistry of nanofibrous membrane can be studied using X‐ray photoelectron spectroscopy (XPS) and water contact angle evaluation. X‐ray photoelectron spectroscopy can quantitatively measure the atomic concentration of elements that exist on the surface of the nanofibrous membrane. The water contact angle investigation of the nanofibrous membrane gives details of the hydrophilic/hydrophobic character
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alongside its surface chemistry. The elevated water contact angle of a nanofibrous membrane surface signifies hydrophobic activity which may be valuable in enhancing the antifouling nature of the filter [46]. 8.8.4.3 Mechanical Characterization
For air fabric filters, elevated tensile strength, and elongation of nanofibrous membranes are enviable to guarantee dimensional stability and durability. In general, nanofibrous membranes, unaccompanied by microfibrous substrate support, have poor mechanical properties and fail to resist the macroscopic effects of air flow. Nanofibrous membranes can be mechanically described employing tensile examination and other approaches such as AFM and dynamic mechanical analysis (DMA). The tensile examination investigates the mechanical properties such as mechanical strength and elongation. The elastic modulus is studied using AFM, while dynamic mechanical analysis identifies the different dynamic moduli of polymers. The tensile strength of nanomembranes can be adjusted by changing their polymer concentration and solvent nature. Sometimes, additives used during the electrospinning process can also enhance the tensile stress, Young’s modulus, elongation, and elastic modulus of the nanofibrous membrane [47]. 8.8.5 Standard Testing Methods There are different standard testing methods for filtration systems [48–51]. Testing appliances can be divided into three major categories: Filtration of combustion appliances ●●
●●
Filtration of hot combustion merchandise via filtration materials and self‐cleaning power of filtration elements testing (Standard Methods: ISO 11057, ASTM D6830‐02, VDI/DIN 3926). Testing of hot combustion filtration systems in real circumstances of hot combustion merchandise with no solid particles.
Filtration of air ●●
●● ●● ●●
Small‐grained filters for atmospheric air via highly efficient filtration elements (Standard Method: EN 1822). Small‐grained filters for atmospheric air via respirators (Standard Method: EN 143). Coarse‐grained filters for atmospheric air (Standard Method: EN 779). Air permeability (Standard Method: EN ISO 9237).
Filtration of liquids ●●
●●
Porous size determination through the bubble method (according to the Standard ASTM F316‐A3). Dynamic water permeability.
8.9 Sustainability and Ecological Aspects In the area of air pollution control, there are numerous choices that over the years have become available, such as textile filters whose use has become more significant, owing
8.10 Conclusion
to increasing pollution emission. Textile filtration efficiently controls environmental contaminants in either gaseous or liquid streams. In air pollution control systems, fabric filters remove dry particles from gaseous pollution emissions. In water pollution control, fabric filters remove suspended solid contaminants. In solid‐waste disposal, fabric filters concentrate solids, decreasing the landfill area needed [4–6]. Filtration techniques usually decrease air, water, and solid‐waste pollution concurrently. In an air pollution control system, for instance, a fabric filter can remove particles and/or gases from a pollution emission source and may be composed of a rubbing device that removes particulates by impaction and the gases by chemical absorption. The reaction products of gases and chemical materials can create a crystalline sludge. Textile filters may also be employed to remove solids from liquids so that such liquids can be recycled. As a result, sewage slurry does not represent a water pollution crisis. The efficient optimization of a fabric filter would reduce filter problems with waste disposal. Although textile filters are appropriate to remove solids from both gases and liquids, it is important that the filter stays dry when gases are filtered and, similarly, it is advisable to prevent the filter from drying out in liquid filtration. In gaseous systems, numerous solid materials are deliquescent (i.e. they tend to pick up moisture and dissolve in it to some extent), leading to a mudded filter fabric. It is usually not possible to remove this mudded sludge without washing or scraping the filter fabric. If the cake on the fabric filter is allowed to dry during liquid filtration, a decrease in the porosity of the cake as well as a fractional blinding of the filter could result, which could then decrease the rate of consequent filtration [52, 53]. Although technical textile filtration is very significant for pollution reduction, the textile industry itself causes ecological harm, contamination, and resources exhaustion. Production, finishing, and circulation of fibres, yarns, or fabrics are made with the assistance of huge, complicated, expensive machines, and chemicals. Therefore, there is a high probability that materials such as fibre components or chemicals used in processing will escape, during processing, leading to ecological pollution. In addition, efforts to produce finished goods result in spreading impurities into the air, water, and soil, as well as in undesirable noise or visual ugliness. Both air and water pollution influences human health, machines, and even the final product. There is an increased occurrence of harmful health effects, particularly byssinosis, tuberculosis, and asthma due to air pollution. This may be due to harmful gases such as formaldehyde, warfare nerve agents, or other volatile organic materials. Noise pollution arises in, for instance, twisting, spinning, and weaving machinery and transportation systems, while visual pollution is due to waste accumulation at landfill sites or that which is illegally dumped to become an eyesore [54, 55].
8.10 Conclusion Fabric filters are one of the highly expanding industrial sectors in the technical textile market. The rapid growth of technical textile filtration systems and of their application has generated various opportunities for diverse innovations. Industrial textile filtration processes are found in the manufacture of limitless items that we use in our daily lives, and yet further processes and techniques are emerging which enhance environment protection. This chapter attempts to offer a concise overview of the textile filtration
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techniques that are included in industrial separation processes. The chapter also illustrates the nature of textile filter media that are used in diverse operations, their strengths and weaknesses, and the applied finishes used to improve their efficiency.
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evaluation for use in water filters. Reactive and Functional Polymers 68 (10): 1448–1458. Mishra, M.K., Liu, S., Sweeney, W.R., Lipowicz, P.J. Biopolymer foams as filters for smoking articles. US Patent 9,226,524, issued 5 January 2016. Abou‐Yousef, H., Khattab, T.A., Youssef, Y.A. et al. (2017). Novel cellulose‐based halochromic test strips for naked‐eye detection of alkaline vapors and analytes. Talanta 170: 137–145. Terzopoulou, Z.N., Papageorgiou, G.Z., Papadopoulou, E. et al. (2015). Green composites prepared from aliphatic polyesters and bast fibers. Industrial Crops and Products 68: 60–79. Müssig, J. (ed.) (2010). Industrial Applications of Natural Fibres: Structure, Properties and Technical Applications. Wiley. Taylor, G.I. (1964). Disintegration of water drops in an electric field. Proceedings of the Royal Society of London Series A Mathematical and Physical Sciences 280: 383–397. Abdelmoez, S., Azeem, A., Rehab, A. et al. (2016). Electrospun PDA‐CA nanofibers toward hydrophobic coatings. Zeitschrift für Anorganische und Allgemeine Chemie 642 (3): 219–221. Khattab, T.A., Abdelmoez, S., and Klapötke, T.M. (2016). Electrospun nanofibers from a tricyanofuran‐based molecular switch for colorimetric recognition of ammonia gas. Chemistry: A European Journal 22 (12): 4157–4163. Brown, P. and Stevens, K. (eds.) (2007). Nanofibers and Nanotechnology in Textiles. Elsevier. Tung, K.‐L., Shiau, J.‐S., Chuang, C.‐J. et al. (2002). CFD analysis on fluid flow through multifilament woven filter cloths. Separation Science and Technology 37 (4): 799–821. Benesi, S.C. Woven filter fabric. US Patent 5,477,891, issued 26 December 1995. Lefkowitz, L.R., Henrik Krohn, W. Stitch knitted filters for high temperature fluids and method of making them. US Patent 4,181,514, issued 1 January 1980. Purchas, D. and Sutherland, K. (eds.) (2002). Handbook of Filter Media. Elsevier. Marvin, D.N. (1954). The heat setting of terylene polyester filament fabrics in relation to dyeing and finishing. Coloration Technology 70 (1): 16–21. Horrocks, A.R. and Subhash, C.A. (2000). Handbook of Technical Textiles. Elsevier. Cogan, M.G. (1986). Atrial natriuretic factor can increase renal solute excretion primarily by raising glomerular filtration. American Journal of Physiology: Renal Physiology 250 (4): F710–F714. Tung, K.‐L., Li, Y.‐L., Lu, K.‐T., and Lu, W.‐M. (2006). Effect of calendering of filter cloth on transient characteristics of cake filtration. Separation and Purification Technology 48 (1, 1): –15. Kim, B., Gautier, M., Prost‐Boucle, S. et al. (2014). Performance evaluation of partially saturated vertical‐flow constructed wetland with trickling filter and chemical precipitation for domestic and winery wastewaters treatment. Ecological Engineering 71: 41–47. Chongqi, M., Shulin, Z., and Gu, H. (2010). Anti‐static charge character of the plasma treated polyester filter fabric. Journal of Electrostatics 68 (2): 111–115. Chapman, R.L. Multilayer composite air filtration media. US Patent 5,419,953, issued 30 May 1995.
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36 Yang, Y., Zhang, S., Zhao, X. et al. (2015). Sandwich structured polyamide‐6/
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47 48
49 50
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polyacrylonitrile nanonets/bead‐on‐string composite membrane for effective air filtration. Separation and Purification Technology 152: 14–22. Aydilek, A.H. and Edil, T.B. (2002). Filtration performance of woven geotextiles with wastewater treatment sludge. Geosynthetics International 9 (1): 41–69. Turkson, A. Composite higher temperature needlefelts with woven fiberglass scrims. US Patent Application 11/041,143, filed 27 July 2006. Patel, S.U., Kulkarni, P.S., Patel, S.U., and Chase, G.G. (2012). The effect of surface energy of woven drainage channels in coalescing filters. Separation and Purification Technology 87: 54–61. Hassan, M.A., Yeom, B.Y., Wilkie, A. et al. (2013). Fabrication of nanofiber meltblown membranes and their filtration properties. Journal of Membrane Science 427: 336–344. Khattab, T.A., Rehan, M., Aly, S.A. et al. (2017). Fabrication of PAN‐TCF‐hydrazone nanofibers by solution blowing spinning technique: naked‐eye colorimetric sensor. Journal of Environmental Chemical Engineering 5 (3): 2515–2523. Anand, S.C. and Lawton, P.J. (1991). The development of knitted structures for filtration. Journal of the Textile Institute 82 (3): 297–308. Ahmad, R., Kim, J.K., Kim, J.H., and Kim, J. (2017). Nanostructured ceramic photocatalytic membrane modified with a polymer template for textile wastewater treatment. Applied Sciences 7 (12): 1284. Kulkarni, N. and Muddapur, U. (2014). Biosynthesis of metal nanoparticles: a review. Journal of Nanotechnology 2014: 510246. https://doi.org/10.1155/2014/510246. Kadam, V.V., Wang, L., and Padhye, R. (2016). Electrospun nanofibre materials to filter air pollutants: a review. Journal of Industrial Textiles 47: 2253–2280. Tierney, T.B., Rasmuson, Å.C., and Hudson, S.P. (2017). Size and shape control of micron‐sized salicylic acid crystals during antisolvent crystallization. Organic Process Research & Development 21 (11): 1732–1740. Corrales, T.P., Friedemann, K., Fuchs, R. et al. (2016). Breaking nano‐spaghetti: bending and fracture tests of nanofibers. Langmuir 32 (5): 1389–1395. Weber, C., Altenhofen, U., and Zahn, H. (1988). Basic studies on the stability of filtration fabrics: Part I: the effects of sulphur dioxide and nitrogen oxides on polyacrylonitrile. Textile Research Journal 58 (9): 507–514. Tanaka, S. and Kanaoka, C. (2004). Durability validation of synthetic filter bags. Filtration 4 (4): 287–294. Tanthapanichakoon, W., Furuuchi, M., Nitta, K. et al. (2006). Degradation of semi‐ crystalline PPS bag‐filter materials by NO and O2 at high temperature. Polymer Degradation and Stability 91 (8): 1637–1644. Tanthapanichakoon, W., Furuuchi, M., Nitta, K. et al. (2007). Degradation of bag‐filter non‐woven fabrics by nitric oxide at high temperatures. Advanced Powder Technology 18 (3): 349–354. Potluri, P. and Needham, P. (2005). Technical textiles for protection. In: Textiles for Protection, (ed. R.A. Scott), 151–175. Cambridge: Woodhead Publishing.
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study environmental fate of engineered metallic nanoparticles: Factors affecting filter performance. Journal of Hazardous Materials 322: 105–117. 54 Lo, C.K.Y., Yeung, A.C.L., and Cheng, T.C.E. (2012). The impact of environmental management systems on financial performance in fashion and textiles industries. International Journal of Production Economics 135 (2): 561–567. 5 Fletcher, K.T. (1998). Design, the environment and textiles: developing strategies for 5 environmental impact reduction. Journal of the Textile Institute 89 (3): 72–80.
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9 Geotextiles and Environmental Protection Textiles Jiří Militký, Rajesh Mishra, and Mohanapriya Venkataraman Department of Material Engineering, Faculty of Textile Engineering, Technical University of Liberec, Liberec, Czech Republic
9.1 Introduction Textile use is no longer restricted to apparel and upholstery. Textiles were used in roadway construction in the days of the pharaohs to stabilize roadways and their edges. These early textiles were made of natural fibres, fabrics, or vegetation mixed with soil and used to improve road quality, particularly when roads were made on unstable soil [1]. Geotextiles are one of the fastest‐growing sectors and have proven to be among the most versatile and cost‐effective ground modification materials. Their use has expanded rapidly into nearly all areas of civil, geotechnical, environmental, coastal, and hydraulic engineering. They form the major component in the area of geosynthetics, the others being geogrids, geofoams, etc. Geotextiles are permeable fabrics, which are used to filter, reinforce, and separate when working in association with soil. The term ‘geotextile’ comes from ‘geo‐’ meaning earth and ‘textile’ meaning fabric. The American Society for Testing Materials (ASTM), defines geotextile as a permeable geosynthetic comprised solely of textiles. Geotextiles are used with foundation, soil, rock, earth, or any other geotechnical engineering‐related material as an integral part of human‐made projects, structures, or systems, or more simply a permeable textile materials used in contact with soil, rock, earth, or any other geotechnical‐related material that is an integral part of a civil engineering project, structure, or system. Examples of the use of natural fibre for reinforcement can be traced back 3000 years, when Babylonians constructed the ziggurat in Dur‐Kurigalzu (present‐day Aqar‐Quf ), and the Great Wall of China, completed around 200 BC, used tamarisk branches mixed with clay. The earliest materials which were used as geotextiles are based on natural fibre. The use of synthetic‐fibre‐based geotextiles in the twentieth century was a revolutionary change. One of the earliest documented cases was a waterfront structure built in Florida in 1958. Then, the first nonwoven (needle‐punched) geotextile was developed in 1968 by the Rhône‐Poulenc company in France and was used in dam construction in France in 1970 [2]. Talking about the serious work in this direction vis‐à‐vis geotextiles, in 1977 Rankilor produced the first ‘design manual’ for geotextiles. It was the first manual for the commercial use of geotextiles [3]. In the 1980s, a significant book was High Performance Technical Textiles, First Edition. Edited by Roshan Paul. © 2019 John Wiley & Sons Ltd. Published 2019 by John Wiley & Sons Ltd.
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published by Koerner and Welsh, which was about the work conducted up till then in the United States at an advanced level [3]. This was the time when engineers started doing serious work on geotextiles in their own respective countries. In 1978, the International Geotextile Society was established for the development of geotextile design and its utilization. The society provided a platform for publications, providing exposure of developments to all interested engineers. Once a textile was recognized as a good material for reinforcement, engineers started developing new types of textiles and composites to solve more difficult problems. In 1984–1985, researchers developed the design and use of warp‐knitted fabrics for civil engineering [4]. During the last 20 years, the use of geotextiles increased across the world and advanced developments were made in design for their better performance. The development and usage of geotextiles will only increasing in the coming years.
9.2 Structure and Performance Different types of textile structures are available for a broad range of geotechnical applications. For such applications, an understanding of the dynamic interaction between the textile structure and the geotechnical environment is very important. Two‐ and three‐dimensional (2D and 3D) fabric structures, methods to weave, multiaxial warp‐ knit structures, and braided structures are some important parameters for developing multifunctional structural geotextiles. A novel method of joining geotextiles by robotic one‐side stitching technology is also interesting. The application of emerging nanofibre technologies is leading to the development of the next generation of geotextiles [5]. The main processes used for technical textiles are weaving, nonwoven, braiding, knitting, tufting, etc. Traditional as well as contemporary fabric structures are increasingly gaining acceptance in industries such as defence, transportation, automobile manufacture, energy, and marine, owing to their attractive specific performances and low cost in use for the technical textiles [6, 7]. Biaxial, triaxial, and more sophisticated multiaxial 3D fabric structures are used as structural elements in these areas [8] (Figure 9.1). Geotextiles are a subset of industrial/technical textiles. There are three types of industrial categories (see Table 9.1). Geotextiles fall into the first and the third categories. For many years, industrial textiles were known as mechanical fabrics as described
Figure 9.1 Geotextiles in use.
9.2 Structure and Performance
Table 9.1 Categories of industrial textiles [9]. Composite industrial textiles
Textiles prepared by coating, impregnating, laminating, or other processes not normally undertaken within the textile industry Examples of products in this category include reinforced rubber; reinforced plastics, metal, ceramics and carbon matrices; abrasive fabrics; asphalt impregnates; etc.
Processing industrial textiles
Textile structures used as a component in a manufacturing process Examples include filtration fabrics such as paper‐making felts; polishing fabrics; laundry machine aprons; etc.
Direct use industrial textiles
Textile structures that are manufactured or incorporated directly into the finished products Examples include awnings, tarpaulins, marine equipment, outdoor furniture, sporting goods, canvas bags, shoe linings, etc.
focusing on tyre fabrics, balloon fabrics, and wing fabrics using woven cotton cord as the primary material [10]. Many industrial textiles have traditionally been produced by members of the Canvas Product Association (CPA) in the United States. The diversification of fibre materials and the expansion of applications from awning to geotechnical and other industrial applications, as well as the trend in market globalization in the 1970s, led to the reorganization of the CPA to the Industrial Fabrics Association International (IFAI), which has played an important role in promoting geotextiles [11]. Industrial fibre manufacturers – such as Owens Corning Fiberglas, DuPont, Celanese, Allied, Union Carbide and Dow Corning – played an important role in developing materials and processing technology that supported the growth of the industrial textiles market. According to SANS ISO 10318:2013, geosynthetics are products with several components made from raw material derived from synthetic or natural origins. Components may be in the form of a sheet, a strip, or three‐dimensional structure employed in contact with soil and/or other materials for geotechnical and civil engineering applications. The major members of geosynthetic family are geomats, geonets, geogrids, geocells, geostrips, geoliners, geospacers, geomembranes, geotapes, geotextiles, geocomposites, etc. (see Figure 9.2). WOVEN, NON_WOVEN, KNITTED
GEOMEMBRANES
GEOTEXTILES
GEOGRIDS
GEOSYNTHETICS
it is a general term, involves a broad range of products
GEONETS, GEOMATS, GEOCELLS GEOCOMPOSITES
Figure 9.2 Geosynthetics family [12].
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Main functions of geotextiles are separation, filtration, drainage, and reinforcements. ●●
●●
●●
●●
Separation: defined as the introduction of a flexible porous textile placed between dissimilar materials so that the integrity and the functioning of both the materials can remain intact or be improved [12, 13]. It actually acts as a separator between fine soil and crushed stone. The geotextile prevents mixing of the two materials. Filtration: defined as the equilibrium geotextile‐to‐soil system that allows for adequate liquid flow with limited soil loss across the plane of the geotextile over a service lifetime compatible with the application under consideration. Filtration applications are drainage systems beneath highways, retaining wall drainage, landfill leachate collection systems, as silt fences and curtains, and as flexible forms for bags and tubes. Drainage: a geotextile acts as a drain when it acts as a conduit for the movement of liquids or gases in the plane of the geotextile. Geotextile materials which have good filtration and permittivity characteristics can be used for this purpose. Reinforcements: a geotextile can be used as reinforcement material when the stability of the road is not good. To reinforce embankments and retaining structures, a woven geotextile is recommended because it can provide great strength at small strains.
Although there are numerous textile structures suitable for geotechnical applications, a textile structure is not a geotextile until the interaction of the fabric with soil or the geotechnical environment is considered a total system [12]. Observing the lack of understanding at the time on the importance of soil–fabric interaction, it was pointed out that almost every geotextile application is multifunctional, involving separation, reinforcement, and drainage; and that fabric forming deals with water and its proper dissipation [14, 15]. This feature underscores the necessity of determining a given fabric’s hydraulic properties – more specifically, its flow rate, permeability, or permittivity (permeability divided by thickness). Towards this end, many organizations have recommended test methods and specifications for the laboratory determination of these fabric properties. It should be noted, however, that these procedures are generally for the fabric alone, e.g. ASTM’s Standard Method for Testing the Water Permeability of Geotextiles – Permittivity Method, as proposed by the Subcommittee D13.61 on Geotextiles. While of interest in comparing one fabric to another, these tests have no indication of the hydraulic behaviour of the combined soil–fabric system. Researchers went on to explain that, as soon as soil is placed adjacent to the fabric, it is seen that the soil’s hydraulic properties dominate the initial behaviour of the system [12, 16, 17]. Only after a period of time does the fabric begin to play a role and, ideally, not at all in the long‐term, e.g. when a properly designed configuration exists. In this latter instance, the flow passing through the soil/fabric system becomes constant and an equilibrium situation exists thereafter. To verify and quantify these long‐term hydraulic behaviours, a simple test for various soil/fabric systems was established. This system consists of water at a constant head, flowed downward through the soil, then through the fabric and out of the system where it is collected and a flow rate is calculated [2]. Design of geotextiles is described in many publications [18–24]. The porosity of geotextiles is here one of most important parameters. Fabric performance characteristics are a result of the interaction between fibre (material properties), yarn and fabric geometry, and finishing treatment. Textile structures in fabric form (produced by yarn‐to‐fabric such as woven and knitted fabrics or
9.3 Fibres for Geotextiles
fibre‐to‐fabric processes such as nonwoven fabrics) can be characterized in terms of geometric and performance properties. Performance maps provide an overview of the range of behaviours of various fabrics as a function of four geometric parameters and four performance parameters [25]. The geometric parameters include: ●●
●●
●●
●●
Porosity: the amount of open space in a unit volume of the fabric. As the fibre diameter and yarn diameter increase, the structure tends to be porous. The porosity of a fabric is inversely proportional to the areal coverage or cover factor of a fabric. A porous fabric tends to be lighter and more permeable. The permeability k of nonwoven geotextiles is nonlinear function of their porosity P, k ≈ P3/(1 ‐ P)2 [18]. Woven and knitted structures are generally worse in comparison with nonwovens because some pores are larger, which leads to the unwanted increase of air permeability. Nonwoven structures can be tailor‐made by simple modification of fabrication process. Especially perpendicularly laid structures of the ROTIS (rotary instrument) type can be prepared in huge variation of porosities, owing to the changing density of waves. Surface texture: the surface geometry of a fabric is characterized by the smoothness of the surface, which in turn is governed by fibre and yarn diameter. Modular length of fibre or yarn is the essential geometric repeating unit in fabrics. Voluminosity: a reflection of the bulkiness of a fabric for a given areal density (mass per unit area). A fabric tends to be more voluminous if the fibre/yarn diameter is larger and the freedom of fibre mobility in the geometric repeating unit is high. Voluminosity is directly related to fibre thickness in that a voluminous fabric tends to be thick. Thickness of the fabric: similar to voluminosity, fabric thickness is related to fibre and yarn diameter. The larger the fibre and yarn diameter, the thicker and bulkier the fabric [18].
9.3 Fibres for Geotextiles Polymeric fibres have a typical fibrous structure characterized by the hierarchy of bundles of a long thin element (molecular chains, microfibrils, macrofibrils) oriented preferably in the fibre axis direction and having more or less ordered 3D arrangements (semicrystalline state). Owing to these special structural arrangements, fibres have strong anisotropy of physical and mechanical properties and extraordinary good mechanical/physical properties in fibrous axis direction in comparison with plastics of the same chemical composition. A typical feature of fibres is the cooperative character of deformation where the deformation process acts on the group of molecular chains (elements) together. Textile fibres have special organoleptic properties (lustre, hand), technological properties (length, strength, crimp, surface roughness, etc.), and utility properties (sorption, ability to stabilize form, abrasion resistance, etc.). The majority of these properties are changed, because of ageing, weathering, or environmental degradation, which is important especially when these processes are long term and intensive, as in the case of geotextiles. Here, the soil itself is responsible for the combined chemical, physical, and microbial
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degradation (see Section 9.4). The textile fibres can be divided according to their preparation and source of raw polymers into four groups: ●● ●● ●● ●●
Natural fibres: prepared by nature from natural polymers. Man‐made fibres: prepared artificially from natural polymers. Synthetic fibres: prepared artificially from synthetic polymers. Nonpolymeric fibres: prepared from nonpolymeric materials.
The internal structure of a fibre is determined by the orientation of polymeric chains along the fibre axis. Orientation in natural fibres is caused by biological requirements during their growth. The molecular alignment is an inherent characteristic of fibre (it is often significantly different in different morphological parts of natural fibres) and is commonly stable. Within the groups of cellulosic fibres, ramie and jute both have an extremely high degree of fibrils orientation, whereas that of cotton is much lower. In cotton the chains are helically oriented. The orientation of synthetic fibres is started during the spinning stage. After spinning, fibres are progressively elongated in the fibre axis direction during fibre drawing. Polymeric chains are oriented and partial crystallization occurs, resulting in drawn fibre. Drawing ratio, i.e. ratio between length of drawn and undrawn fibre, is usually 3–5 (standard fibres) or in special cases as much as 10. Spinning ability can be characterized by natural draw ratio λp, which is dependent on temperature and rate of deformation. ●● ●●
●●
●●
Stiff polymers (polystyrene, aramids) have λp = 1.5–2.5 (as for viscose). Semicrystalline polymers with lower stiffness, for example polyamide (PA) and polyester (PES), have λp = 3–5. High crystalline, flexible polymers (polypropylene [PP], polyethylene [PE]) have λp = 5–10. For gel spinning of PE is λp = 50 and more.
Polymeric chains in undrawn fibres are randomly oriented, i.e. only 33% lie in the fibre axis direction. Polymeric chains in drawn fibre are mainly oriented to the fibre axis (around 80–90% of chains are oriented in the fibre axis direction). Drawing is therefore responsible for increasing fibre strength, decreasing deformation at break, and formation of proper fibre structure (fibrillar) structure. For geotextiles the cheaper fibres are commonly used. Durability and degradation in soil aspects are usually not the main issues. 9.3.1 Natural Fibres The commercially important natural fibres for geotextiles are based on cellulose (vegetable fibres) extracted from different part of plants. Typical vegetable fibres are: ●● ●● ●●
●●
Seed fibres (fibres cover seeds): cotton. Fruit fibres (nuts are covered by fibres): kapok, coir. Bast fibres (fibre bundles lie between the outer bark and the woody core of the stem): flax, hemp, jute, ramie, kenaf, nettle, sugar cane, bamboo. Leaf fibres (fibre bundles are located in the leaf ’s tissue): sisal, abaca (Manila hemp), agave, pineapple, aloe, cabuya.
9.3 Fibres for Geotextiles
A major part of these fibres is cellulose, one of the most abundant materials in nature. It is a renewable and biodegradable material, available widely and at low cost, with a low‐energy consumption profile and good mechanical properties, such as high modulus. Another advantage of cellulose is the creation of long fibrous cells, which can be aligned and oriented easily [19, 20]. Cellulose is polyalcohol, having one primary and two secondary −OH groups. In backbone are ether bonds (glycoside link) −C−O−C−. Contracted notation is cel −OH or cel − (OH)3. The −OH groups are the sites for creation of hydrogen bonds and some chemical reactions, such as esterification. Cellulose chains are connected by various systems of hydrogen bonds, which have a significant influence on properties (see Figure 9.3). These bonds are responsible for the limited solubility of cellulose in most solvents, the swelling in water, the reactivity of the hydroxyl groups, and morphological features (crystallinity). Cellulose also contains hydrophobic areas (around the C atoms) that have partial influence on the overall solubility. Intermolecular hydrogen bonds are responsible for the strong interaction between cellulose chains. These bonds are produced between adjacent cellulose macromolecules located along the (002) plane in the crystal lattice of cellulose I (native cellulose), mainly between the oxygen atom in C3 and the −OH at C6 [21]. Together, the hydrogen bonding, weak C–H–O bonds, and hydrophobic interactions are responsible for the assembly of cellulose in layers [22]. The density of α‐cellulose is about 1560 kg m−3. Well‐aligned bundles of cellulose chains are creating crystalline nanofibrils [23]. The main building element of vegetable fibres is the cellulose microfibrils aligned mainly along the fibre axis, which ensure maximum tensile and flexural strengths, in addition to improved rigidity (high initial modulus) [24]. The main components of vegetable fibres are cellulose (α‐cellulose), hemicellulose, lignin, pectin, and waxes. These fibres can be considered to be composites of cellulose fibrils held together by a lignin and hemicellulose matrix. The amorphous matrix phase in a cell wall is very complex and consists of hemicellulose, lignin, and in some cases pectin [26]. Schematic structure of these constituents are shown in Figure 9.4. The typical content of these constituents in typical fibres used commonly for geotextiles is shown in Table 9.2. Lignin is a complex thermoplastic hydrocarbon based, 3D copolymer with both aliphatic and aromatic constituents, and is shown in Figure 9.5. Hydroxyl, methoxy, and carbonyl groups have been identified. The density of lignin is about 1260 kg m−3 and the initial modulus is 5.9 GPa [27]. Lignin is fully insoluble in most solvents and cannot be broken down to monomeric units. Lignin is totally amorphous and hydrophobic in nature. It has a glass transition temperature of around 90 °C and a melting point of around 170 °C. It is the compound
H O H
H O O H
O
6
O O
H
5
4
O
3
O 2
H 1
O
O O H O H
H O H O O O O H
Figure 9.3 Cellulosic chain with hydrogen bonds [21].
O
H
O
O O H O H
O H O
O
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CH2OH
O
HO
O O OH
CH2OH
OH
HO
O
O
O
HO
CH2OH O
OH
Cellulose
O
O
OH
HO O
HO
O
O
OH
O
HO
O
OH
Hemicellulose
OH
HO O COOCH3
O
COOH
O
O
HO
OH
HO
OH
O
COOCH3
O
O
Pectin O H3CO
CH=CH—CH2OH H H OCH3
C
O
O OCH3
Lignin Figure 9.4 Schematic structure of vegetable fibres constituents. Table 9.2 Typical composition of selected vegetable fibres. Fibre type
Cellulose (wt. %)
Hemi cellulose (wt. %)
Lignin (wt. %)
Pectin (wt. %)
Bamboo
26–43
15–26
21–31
—
Flax
60–81
14–19
2–3
0.9
Hemp
70–92
18–22
3–5
0.9
Sisal
43–78
10–13
4–12
0.8–2
Jute
51–84
12–20
5–13
0.2
9.3 Fibres for Geotextiles
OH O HC
O
OH
HO
OH
O O
H3C
O
OH
CH3
O
OH
O O
O
HO
O
OH
OH Figure 9.5 Structure of lignin.
that gives rigidity to the plants. One of the basic units of lignin is 3‐(4‐hydroxyphenyl) prop‐2‐methoxy‐eneol group in the ortho position of the phenol ring (Figure 9.6). Lignin can be used also as a replacement for phenol in the preparation of phenol‐ formaldehyde resins. It is not hydrolysed by acids, but soluble in hot alkali, readily oxidized, and easily condensable with phenol. Lignin can be removed from fibres by chlorination forming a complex chloro‐lignin, which is soluble, like hemicellulose in dilute alkalis. In some vegetable fibres there is degradation or removal of lignin accompanied by evolving of very short ultimate fibres in the form of ‘dust’ (e.g. in the case of jute). Lignin is a macromolecular framework that is difficult to degrade, even by microorganisms. Only ligninolytic microorganisms can do it. It is beneficial, especially for geotextiles, because of its durability in soil is longer. Pectin (see Figure 9.7) consisting of polysaccharides is characterized by a high content of glucuronic acid and the corresponding methyl ester, and partially also the acetyl ester. Component D‐galacturonic acid is combined with D‐galactose and L‐arabinose. They give plants flexibility. Pectin can be removed readily in alkalis and it is sensitive to microbial attack and enzymes (pectinases). Soil degradation is easy.
Figure 9.6 Basic unit of lignin.
OH
R1
R2
R1, R2 : OMe, H
OH 3-(4-hydroxy phenyl) prop-2-eneol
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Plant Cell Wall Structure
Middle Lamella
Pectin
Primary Cell Wall
Cross-Linking Glycan Cellulose Microfibrils
Plasma Membrane
Figure 9.7 Schematic arrangement of primary wall [28].
Hemicelluloses (see Figure 9.7) are characterized by irregularities in the chains. They consist mainly of low molecular chains composed of hexoses, pentoses, and parts of uronic acids. Single chains contain D‐xylose portions as well. Branched portions consist of both a D‐xylose component as well as components of glucuronic acid and the corresponding methyl ester. Density of hemicelluloses is about 1450 kg m−3 and the initial modulus is 8.4 GPa [29]. Hemicelluloses differ from cellulose in three aspects: ●●
●●
●●
They contain several different sugar units, whereas cellulose contains only 1,4–β‐d‐ glucopyranose units. They exhibit a considerable degree of chain branching containing pendant side groups giving rise to its noncrystalline nature, whereas cellulose is a linear polymer. The degree of polymerization (DP) of hemicellulose is around 50–200 [30]. This is 10–100 times lower than native cellulose.
Hemicelluloses are very hydrophilic, soluble in alkali, and easily hydrolysed in acids. Waxes make up the last part of fibres and they consist of different types of alcohols. Cotton fibres are in fact single‐cell, while other fibres are multi‐cell connected by natural glues (pectin and lignin). The majority of natural fibres can be then considered as naturally occurring composites of cellulose microfibrils in a matrix of intertwined hemicellulose and lignin or pectin [31]. Hemicellulose and lignin matrix is called lignin–carbohydrate complex (LCC) and cellulose glued by pectin mainly is called pecto‐cellulose complex (PCC). The density of LCC is about 1340 kg m−3 and initial modulus is 6.93 GPa [32]. The average electrostatic energies between cellulose microfibril faces and hemicellulose, LCC and lignin are 38, 57, and 58 mJ m−2, respectively, and the average van der Waals energies between cellulose microfibril faces hemicellulose, LCC, and lignin are 44, 76, and 95 mJ m−2, respectively. Lignin van der Waals energy is therefore around 116% higher than that of hemicellulose, whereas the electrostatic energy is higher by about 50%. The superiority of lignin adhesion energies to cellulose comes from the relatively higher van der Waals energies [33].
9.3 Fibres for Geotextiles
Many plant cells have a primary cell wall, which accommodates the cell as it grows, and a secondary cell wall they develop inside the primary wall after the cell has stopped growing. The main chemical components of the primary plant cell wall are cellulose in the form of organized microfibrils (see Figure 9.7). The cell wall contains two groups of branched polysaccharides, the pectins, and cross‐linking glycans (derivatives of polysaccharides [34]). Cellulose microfibrils cross‐linked by glycans increase the tensile strength of the cellulose, and a network of pectins provides the cell wall with the ability to resist compression. In addition to these networks, a small amount of protein can be found in all plant primary cell walls [35]. In the secondary cell wall additional substances, especially lignin, are often found. Lignin also makes plant cell walls less vulnerable to attack by fungi or bacteria. Bast fibre (e.g. flax, jute, and hemp) bundles are located in the outer layer of the stem. Their cross‐sections consist of 10–40 elementary fibres glued together with pectin and/ or lignin. The length of the elementary fibres varies between 5 and 55 mm and the thickness is about 20 μm. Bast fibres have a thicker cell wall and a smaller lumen. Common features of bast and other vegetable fibres are: ●●
●●
●● ●●
Technical fibres are multi‐cell, consisting of a series of elementary (ultimate) fibres bonded by pectins or lignin. The fibres have a similar chemical composition: cellulose 65–85%; waxes, 2–4%; pectins, hemicelluloses from 2 to 10%; lignin from 1 to 20%; humidity 10%. The fibres have a similar microscopic appearance. The fibres have similar properties. They are strong enough (wet strength is higher), have low deformation at break, and are resistant to both freshwater and saltwater.
The plants, technical fibres bundles and surface structure of fibres for selected vegetable fibres are shown in Figure 9.8. The selected vegetable fibre crystallinity and an average polymerization degree of cellulose of different origin are given in the Table 9.3. Lowest polymerization degree is in case of bamboo fibre. Polymerization degree is directly connected with strength and resistance to external influences. The selected physical parameters of some vegetable fibres are given in Table 9.4. Low fibre density compared with the density of the cellulose 1560 kg m−3 indicates their porosity and the presence of lignin.
(P)
(B)
(P)
(S)
(a)
(B)
(P)
(B)
(S)
(b)
(S)
(c)
Figure 9.8 Plant (P); a bundle (B), and SEM surface (S) for the sisal (a), jute (b), and bamboo (c) fibres [36].
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Table 9.3 Crystallinity and cellulose polymerization degree of selected vegetable fibres. Fibre
Hemp
Sisal
Jute
Flax
Bamboo
Crystallinity (%)
88
71
72
91
70–75
Polymerization degree of cellulose
1170
4500
1123
2801
891
Table 9.4 Selected physical parameters of some vegetable fibres. Fibre
Density (kg m−3)
Moisture regain at 65% RH (%)
Porosity (%)
Flax
1540
12
10
Jute
1500
13.8
14–15
Hemp
1480
12
11
Sisal
1200–1450
14
17
Bamboo
850–1100
6–8
High
It is evident that the highest porosity and content of lignin is to be found in bamboo fibre. The density of fibre without pores ρ composed from weight fraction wC of α‐cellulose (density ρC), weight fraction wH of hemicelluloses (density ρH), weight fraction wL of lignin (density ρL), and weight fraction wP of pectin (density ρP) is in fact weighted harmonic mean, i.e. 1
wC
wH
wL
wP
C
H
L
P
(9.1)
If the density of fibre with pores is equal to ρf, it is simple to calculate the fibre porosity Pf (neglecting the air density around 1 kg m−3) from Eq. (9.1). In the majority of vegetable fibres, technical fibres are composed from many ultimate (elementary) fibres. Especially the bast fibres, where ultimate fibres are glued by pectin mainly and are relatively strong (wet strength is higher) with low deformation at break and better degradation resistance to the normal water and seawater. Ultimate (elementary) vegetable fibres form long elongated cells, sealed at the ends, and have typically lumen, i.e. a central channel. It can be seen that only for flax and hemp are ultimate fibres sufficiently long and soft for textile processing. For other fibres, it is necessary for textile processing (spinning) to use technical fibres (bundles of ultimate fibres glued by pectin or lignin). Lignin (particularly in bamboo and jute) causes an increased stiffness of technical fibres, which limits their use for textile purposes but can be beneficial for some geotextiles. The most abundantly used multicellular cellulose fibre is flax (3–6 cells constitute a fibre cross‐section). Each fibre consists of cells cemented together by wax, pectin, and hemicelluloses (see Figure 9.9). Dimensions of elementary (ultimate) bast fibres are given in Table 9.5. It can be clearly seen from this table that these dimensions are too small for spinning some bast fibres. The elementary flax fibre dimensions are comparable with cotton and therefore can be
9.3 Fibres for Geotextiles
(a)
(b)
Figure 9.9 Bundle of ultimate flax fibres (a) glued by pectin, (b) after removal of pectin. Table 9.5 Ultimate fibre dimensions of some vegetable fibres.
Fibre
Average length (mm)
Range of lengths (mm)
Average width (μm)
Range of widths (μm)
Flax
33
9–70
19
5–38
Jute
2
1–5
20
10–25
Hemp
25
5–55
25
10–51
Sisal
3
1–8
20
8–41
Bamboo
2.7
1.5–4.4
14
7–27
used for direct spinning. The process of preparing elementary flax fibres is called cottonization. The geometrical characteristics of selected technical vegetable fibres are shown in Table 9.6. Mechanical properties of selected vegetable fibres are summarized in Table 9.7. It can be clearly seen from the table that the flax fibres have the best tensile properties. Their application in geotextiles is often limited, owing to relatively quick degradation in soils. Most common fibres in geotextiles are jute, flax, coconut matting, and straw. Every fibre is used with reference to its specific properties. Jute is easily degradable when it absorbs moisture so this is mostly used on seashores to give wind shield to small trees till they are mature. By the time trees grow larger, jute shielding is degraded and the cover of jute is removed automatically to give way to the growing tree. In general, natural fibres are used in geotextiles for short‐term applications only (see Section 9.4). 9.3.2 Synthetic Fibres Geotextiles are commonly made from PP, polyester, polyethylene, polyamide (nylon), polyvinylidene chloride. PP is the most used fibre because its water sorption is approximately equal to zero and its degradation in soil is very slow. For the production of PP fibres, only isotactic PP is suitable. The space helix of polymer chains is here due to presence of voluminous side −CH3 group. Helix unit is composed from three monomer
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Table 9.6 Geometrical characteristics of selected technical vegetable fibres. Fibre
Length (mm)
Diameter (mm)
Fineness (tex)
Flax
200–1400
0.04–0.62
0.18–2
Jute
1500–3600
0.03–0.14
1.4–3
Hemp
1000–3000
0.16
0.34–2.2
Sisal
600–1000
0.1–0.46
2–40
Bamboo
60–80
0.5–0.6
3.5
Table 9.7 Mechanical properties of selected vegetable fibres [37].
Fibre
Strength (MPa)
Deformation at break (%)
Modulus (GPa)
Flax
345–2000
1.6–3
27.5–85
Jute
393–773
1.7
10–30
Hemp
368–800
1.6
17–70
Sisal
350–700
2–7
9–22
Bamboo
140–230
2.8–4
11–17
units (gauche). Glass transition temperature is Tg = −10 to 0 °C, density is 900 kg m−3, and melting temperature is Tm = 165 °C. The moisture content is only 0.05%. Preparation of isotactic PP was first described in 1954 (Natta). The principle involves the coordination stereospecific polymerization of propylene with special catalyst TiCl3, Al(C2 H5)3 (Ziegler – Natta catalyst). Polymerization at 100 °C and pressure 3 MPa leads to highly crystalline isotactic PP. Molecular mass of polymer before spinning Mn = 100 000– 600 000 and the molecular mass of fibre is 50 000–250 000. Industrial production of PP fibre Meraklon IT (Montecatini) started in 1960. Standard process of PP fibres preparation consists of three steps: ●● ●●
●●
Melt spinning in inert atmosphere (PP melt is sensitive to O2). Cooling in the long cooling tube, owing to low temperature conductivity of polypropylene (PP). Undrawn fibre contains about 70% of crystalline phase. Cold drawing (with neck) to draw ratio 3–5.
Crystallinity degree of drawn fibres is about 70–80%. Microvoids may appear depending on the drawing temperature. Drawn fibre is characterized by high orientation of crystalline phase fc = 0.98 but very low orientation of amorphous phase fa = 0.2–0.4. Structural features are microvoids (20%), tie chains (3%), crystalline phase (70%), and amorphous phase (7%). Setting (stabilization) at 130 °C in free‐state (shrinkage till 40%) leads to the improvement of recovery properties. The properties of PP fibres differ substantially from common synthetic fibres. They are hydrophobic and practically do not have any group capable to water bonding. PP fibres show excellent chemical resistance. A low glass transition temperature and melting point is not essential for geotextiles. Bacterial resistance is also excellent for
9.3 Fibres for Geotextiles
PP fibres. PP fibres show brittleness, low mechanical performance, and low impact because of their high crystallinity. Sewing thread for geotextiles is made from Kevlar or any of the above polymers. The physical properties of these materials can be varied by changing the condition of drawing and heat setting or by the use of additives. Yarns may be composed of very long fibres (filaments) or relatively short pieces cut from filaments (i.e. staple fibre). 9.3.3 Nonpolymeric Fibres Some geotextiles are made from fibreglass or basalt mainly, or these materials are used in preparation of hybrid structures in combination with natural fibres (see Section 9.4). Mineral fibres from basalt are not new, but their suitability as reinforcement in composites or in hybrid woven structures is a relatively new issue. Basalt fibres have good physical and chemical properties, as well as good adhesion to metals, epoxies, and glues. Basalts also exhibit excellent thermal, electrical, and acoustic insulation properties. Owing to all these favourable properties, basalt fibre can be used in several applications in technical textiles. Basalt fibre density is 2733 kg m−3 and has a softening temperature of about 960 °C. The diameter of standard fibres is around 9–12 μm. Glass transition temperature from thermomechanical curves is Tg = 596 °C. Axial thermal expansion under Tg is a1 = 4.9·10−6 deg−1 and above Tg is a2 = 19.1·10−6 deg−1. The shear modulus of basalt fibres is about 21.76 GPa. The modulus of elasticity in the axial compression is 112 GPa [38]. From the cross‐section of broken fibres (see Figure 9.10), the brittle fracture caused by structure heterogeneities is evident. Basalt has excellent stability in soil and it is not attacked by microorganisms. Basic physical and mechanical properties of basalt fibres and a comparison with different other commercial fibres are depicted in Table 9.3, which shows that basalt has an excellent tensile strength and also a good modulus. Regarding mechanical properties, basalt fibres are positioned between E‐glass fibres and S2‐glass fibres. Researchers investigated the mechanical properties of glass fibre, short basalt fibre, and continuous basalt fibre from different manufacturers [39]. They concluded that all tested fibres
Figure 9.10 Cross‐section of broken basalt fibre.
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Table 9.8 Physical and tensile properties of basalt, glass, and carbon fibres. Properties
Basalt
E‐Glass
S2‐Glass
Carbon
Density (kg m−3)
2630–2800
2540–2570
2540
1780–1950
Filament diameter (μm)
6–21
6–21
6–21
5–15
Single filament tensile strength (MPa)
3000–4840
3100–3800
4020–4650
3500–6000
Initial modulus (GPa)
93–110
72.5–75.5
83–97/86
230–600
Elongation at break (%)
3.1–6
4.7
5.3
1.5–2.0
have a rigid behaviour, without plastic deformation. The tensile modulus and strength of continuous basalt fibres and glass fibres are quite similar, while short basalt fibres are considerably less stiff. The joint SiO2 and Al2O3 content (denominated as ceramic‐like materials) of basalt fibres shows correlation with the tensile properties of fibres. It was noted that continuous basalt fibres were competitive with glass fibres and short basalt fibres were weaker in terms of mechanical properties. Physical and tensile properties of basalt, glass, and carbon fibres are summarized in Table 9.8. It is known that the fibrous fragments with a diameter of 1.5 μm or less and a length of 8 μm or greater should be handled and disposed of using the widely accepted procedures for asbestos. The experimental data of basalt particle dimensions created by the abrasion of basalt weaves showed that, because the mean value of fibre fragment diameter is the same as the diameter of the fibres, no splitting during fracture occurs [40]. Basalt fibres and fabrics are labelled as safe according to both US and European occupational safety guidelines. Its particles or fibrous fragments due to abrasion are too thick to be inhaled and deposited in the lungs, but care in handling is recommended. Basalt filaments can be used as one component of hybrid fabrics containing natural fibres for the creation of geotextiles with enhanced resistance in soil burial conditions. Influence of fibre type on selected properties of hybrid plain woven fabrics with basalt filaments in the warp and basalt or jute yarns in the weft are shown in Table 9.9. All fabrics were made on the CCI sample loom under the same technological conditions with the same density for all fabrics. The sett was 12 threads cm−1 in warp and 8 threads cm−1 in weft [41]. The presence of basalt yarns is enhancing tensile mechanical properties of fabric and this fabric portion is not degraded in soil.
9.4 Geotextiles and Soil Geotextiles are during their whole service time buried in soil. The majority of soils have a solid phase including inorganic solids and organic solids, a liquid phase including dilute aqueous solution of inorganic and organic compounds, and a gas phase as a mixture of some major (e.g. nitrogen, oxygen) and trace (e.g. carbon dioxide, methane, nitrous oxide) gases (see Figure 9.11) [42].
9.4 Geotextiles and Soil
Table 9.9 Influence of weft and warp composition on mechanical properties of plain fabrics. Material
Basalt/basalt
Basalt/jute
Jute/jute
Tensile modulus (MPa) warp
3912.9
926
369.95
Tensile modulus (MPa) weft
3839.7
466.1
77.41
Shear rigidity (MPa)
0.05
0.372
0.095
Strength (MPa) weft
1154.9
192.9
153.7
Strength warp (MPa)
1403.5
535.1
101.9
Fabric composition
Under optimal conditions for the growth of upland plants, the solid components (inorganic and organic) constitute about 50% of the total volume, while liquids and gases comprise 25% each. Particles that constitute the soil are called sand (2–0.02 mm), silt (0.02–0.002 mm), and clay ( 20 lbf MD, 20 lbf CD
Weathering
UV Exposure/ Accelerated‐Aging
Weathered samples pass strength and water resistance
Cold resistance
AC38 Section 3.3.4: Cold Mandrel Bend Test
No cracking
Boat test
ASTM D779: Standard Test Method for Water Resistance of Paper, Paperboard and Other Sheet Materials by the Dry Indicator Method
10 min – no water passage
Water ponding test
CCMC 07102 (Section 6.4.5): Water Ponding Test
2 h – no water passage
Static and dynamic AATCC Test Method 127: Water Resistance Hydrostatic water pressure Pressure Test resistance
5 h – no water passage
Permeability
Water vapour transmission
ASTM E96: Test Method for Water Vapour Transmission of Materials
> 5 US perms
Air resistance (optional)
Air barrier resistance
ASTM E2178: Standard Test Method for Air Permeability of Building Materials
< 0.02 L/SM2@75 psi [0.004 CFM/ [email protected] psi]
Drainage (optional)
Drainage efficiency
ASTM E2273: Test Method for Determining the Drainage Efficiency of Exterior Insulation and Finish Systems (EIFS) Clad Wall Assemblies
> 90% drainage efficiency
Fire resistance (optional)
Flame spread index and smoke development
ASTM E84: Test Method for Surface Burning Characteristics of Building Materials
Class A
Water resistance
Method 127) [16, 18]. The Boat test and the Hydrostatic Pressure test are most commonly utilized in the US building codes to evaluate house wrap materials [16]. 11.3.1.2 Durability
House wrap materials must be able to withstand the stresses and strains applied during installation without compromising the properties of the material. Weather resistive barriers must be able to withstand potential exposure to harsh UV rays, wind, and
11.3 House Wraps
precipitation for long periods of time prior to cladding installation [16]. Tear resistance is particularly important during installation when the material may be exposed to strong winds [21]. Other important physical properties that should be considered are breaking strength, elongation, shrinkage, and puncture resistance [15]. Durability of a house wrap is generally evaluated by analysing the material’s resistance to UV radiation and cold temperatures as well as its strength in tear and tensile loading. Many house wraps advertise a tolerable 90‐ to 180‐day gap for siding installation, However, it is generally recommended that house wraps are covered within 30 days [18]. House wrap material is not accessible unless the cladding material is removed. Therefore, it is expected that the house wrap remains functional during the entire service life of the wall system [16]. 11.3.1.3 Vapour Permeability
Vapour permeability is a measure of the amount of water vapour transmitted through the barrier membrane per unit time [19]. The presence of water within a wall cavity can be due to many sources, including initial construction moisture, condensation of water vapour within the wall, and weak spots in the house wrap material. Therefore, it is important that the weather resistive material allows drying from the interior of the wall and moves the wetness to the exterior wall [16]. The moisture vapour transmission rate [19], also denoted as the water vapour transmission rate [16], is usually determined through a standard test protocol (e.g. ASTM E96) [16, 19]. This test indicates how much water vapour can pass through a barrier in a 24‐hour period. In Table 11.2, this criterion is indicated as the ‘perm rating’. A higher perm rating indicates a material which possesses higher permeability. Materials with greater perm ratings allow moisture to escape more quickly, resulting in a lower chance of moisture vapour accumulation. However, higher perm ratings do not necessarily indicate a better house wrap. Low tech house wraps often achieve high air perm values with mechanically punched perforations. While these perforations do facilitate vapour transport, they also create a material more susceptible to water leakage. Well‐designed house wraps, such as the HomeWrap and R‐Wrap, discussed in Table 11.2, offer high vapour transmission while preventing the movement of liquid water. Current building codes require a house wrap to meet or exceed grade‐D building paper, meaning house wraps must possess a perm rating of five or higher [19]. Some consider a perm rating of 10–20 to be ideal for house wraps [18]. 11.3.1.4 Drainage
This parameter is widely accepted as one of the best ways to evaluate a house wrap’s ability to reduce moisture, keep walls dry, and minimize structural damage due to rain penetration [18]. House wrap materials are designed to drain water, which can enter through exterior cracks, or accumulate because of condensation or evaporation out of the wall cavity. However, if the siding is applied too tightly to the house wrap, there is insufficient space to allow drainage. To overcome this issue, some house wraps incorporate channels in the barrier material [22] via creping, embossing, weaving, or filament spacers to provide suitable paths for drainage [18]. Additionally, many builders incorporate a 1/4–3/8 in. (0.64–1.9 cm) drainage separation between siding and house wrap material via vertical furring strips. This gap provides adequate space for moisture to dissipate naturally [19].
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Table 11.2 Common house wrap materials [19]. Name
Type
Perm rating
Notes
HomeWrap (DuPont)
Nonwoven polyolefin
58.0
30+ years ago, this was the first house wrap on the market It accounts for more than 70% of the total house wrap sales
PinkWrap (Owens Corning)
Woven perforated 14.0 polyolefin
This incorporates a translucent membrane which makes it simple to see where to nail siding material
Typar (Typar)
Nonwoven polyolefin
11.7
Provides excellent protection against surfactants Ideal for use with stucco siding (which is porous) Guaranteed tear resistance
StuccoWrap (DuPont)
Nonwoven polyolefin
50.0
Designed for use under traditional and synthetic stucco Does not absorb water, expand or contract thus reducing cracking Surface texture allows for channelling of water.
Weathermate (The Dow Chemical Company)
Nonwoven polyolefin
N/A
Translucent and perforated Perforated products are less protective against water intrusion
Weathermate Plus (The Dow Chemical Company)
Woven perforated 6.7 polyolefin
Texture is comparatively more foam like and substantial
Barricade (Barricade Building Products)
Woven perforated N/A polyolefin
Perforated products are less protective against water intrusion UV resistant for 12 mo
R‐Wrap (Barricade Building Products)
Nonwoven polyolefin
59.0
Provides the highest perm rating
GreenGuard Ultra (Kingspan)
Nonwoven polyolefin
48.0
Incorporates a reinforcing scrim which provides high tear resistance Translucent membrane facilitates seeing where to nail siding
Weather Trek (Barricade Building Products)
Perforated polyethylene
6.5
Possesses distinct texture that ensures water drains easily regardless of orientation
Raindrop (Kingspan)
Woven polyolefin
10.0
Drainage channels are woven into the surface which directs water down and out; therefore, channels must run vertically
11.3 House Wraps
11.3.1.5 Air Permeability
Air permeability indicates how well a house wrap prevents unwanted air from moving across a building enclosure. This property is comparatively less critical than other requirements discussed in this section [18]. However, most house wraps provide an air leakage value of between 0.03 and 0.08 CFM/ft2 with higher values indicating greater airflow through the material [21]. 11.3.2 House Wrap Materials Fibrous materials are ideal house wrap materials because they are breathable and capable of preventing moisture infiltration [23]. Early materials utilized for house wraps included asphalt saturated felts and papers (also called kraft papers) [16]. Asphalt saturated felts and papers are two distinct products. ‘Kraft paper’ broadly refers to various types of sulfate paper but the term is most often used to describe basic grades of unbleached sulfate papers. Asphalt saturated felts are made in processes similar to papermaking in order to create fibrous, felt materials. Felts and kraft papers are made waterproof via asphalt saturation [16]. In the 1980s, plastic, polymeric house wraps were developed and gained popularity because of their ease of installation, durability, and ability to block water [16, 18]. The advantages and disadvantages of traditional asphalt based products and polymeric house wrap materials are compared in Table 11.3. As previously mentioned, house wraps are incorporated into buildings to provide a barrier to external environments while also allowing air to pass through the structure. How this is achieved is dependent on the fabric design and the specific wall assembly [17]. Table 11.2 includes some of the available house wrap materials as well as important design characteristics. Most house wraps consist of either woven or nonwoven polyolefin (usually either polyethylene or polypropylene fibres) [18]. Each house wrap product is designed to provide specific, unique properties such as tear or UV resistance. Regardless of the unique characteristics provided, every house wrap must provide a means of moisture management. Some house wrap materials have microperforations to allow moisture vapour to pass through while others are designed to transport water vapour through the fabric itself (microporous). When considering the microperforated approach (which is used in many woven house wrap fabrics), vapour transport is facilitated while water resistance is reduced. On the other hand, microporous materials provide sufficient vapour movement while also providing excellent resistance to water [18]. House wrap materials can potentially come into contact with surface active agents, called surfactants [20]. This is problematic because surfactants reduce the surface tension of water such that a liquid can penetrate deeper into the microscopic openings of a fibrous material. As a result, water may eventually interact with a building’s sheathing. House wrap designers can overcome this issue by applying surfactant‐resistant coatings or primers to the house wrap or by creating drainable house wraps [18, 19]. For example, Typar®, which is described in Table 11.2, possesses superior resistance to surfactants when compared to other house wraps [19].
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Table 11.3 Advantages and disadvantages of asphalt based and polymeric based house wrap materials [16]. Asphalt saturated kraft paper
Material
Asphalt saturated felt
Polymeric products
Potential advantages
Successful applications throughout history under normal exposure Conforms to many model codes Material costs are low Long‐term durability, possibly better than paper based products
Successful applications throughout history under normal exposure Conforms to many model codes Material costs are low Better bending properties than felt based Lower permeance than felt based, less potential for condensation build up
Highly resistant to tearing and breaking Large sheet products meaning joints are minimized Not susceptible to deterioration upon water exposure Can act as a barrier to air movement Possess high water vapour permeance
Potential disadvantages
Not much performance data supporting use as house wrap Relatively high permeance may lead to condensation build up Minimal resistance to tears, breaks, and bending Susceptible to deterioration when exposed to water, air, and/or UV Surfactant exposure reduces water penetration resistance Does not conform to some building codes for application with plaster over wood based sheathing
Tear resistance is low Highly susceptible to deterioration upon exposure to water, air, and/or UV
Relatively expensive compared to other available materials Susceptible to deterioration upon long‐term exposure to UV Water resistance can be negatively impacted by surfactants Can slow down evaporation of excess water
11.4 Insulation Energy use in commercial and residential buildings accounts for a significant part of the world’s total energy use and greenhouse gas emissions. According to the Department of Energy in the United States, an average American home consumes 50–70% of its total energy during heating and cooling [24]. Similarly, the European Union (EU) estimates that 79% of the energy consumed in EU households is utilized for heating alone, while cooling accounts for a much smaller percentage. However, energy requirements for cooling increase as the effects of climate change progress and temperatures rise. The EU has progressive strategies in place to improve both energy efficiency and decrease greenhouse gas emissions 20% by 2020. Part of the EU’s strategy to meet these goals is utilizing high performance insulation materials in new and existing buildings to reduce energy consumption and harmful emissions [25].
11.4 Insulation
Insulation is a thermal barrier layer which reduces heat flow through building components and enhances a building’s energy efficiency. To understand how insulation works, it is beneficial to understand heat flow. Heat flow is achieved via conduction, convection, and/or radiation. Conduction is the manner in which heat moves through materials, convection describes the way heat circulates, while radiation is the movement of heat in the form of electromagnetic waves. Fibrous insulating materials discussed within this section work primarily by minimizing conductive heat flow, and to a lesser extent by reducing convective heat flow [26]. Thermal insulating materials are porous and contain microscopic pockets of stationary or dead air, which suppress heat flow. Inherently, stagnant air is one of the best thermal insulators. Therefore, air trapped within the insulating material is responsible for thermal resistance rather than the fibrous material itself [27]. Insulation materials are incorporated within various building components, including interior or exterior walls, roofs, garages, foundations, unheated garages, band joists, and around windows, doors, and heating systems [2]. The benefits of utilizing thermal insulation include: ●●
●●
●●
●●
●●
●●
Energy cost savings: With little capital expenditure (insulation only accounts for approximately 5% of building costs), dependence on heating/cooling systems can be reduced, which in turn provides energy cost savings. Environmental footprint: Reducing the use of heating/cooling systems, which lowers emitted pollutants and helps to preserve natural resources. Building structural integrity: Insulation helps to minimize temperature fluctuations that could compromise a building’s structural integrity and shorten its lifetime. Acoustic insulation: Thermal insulation can also reduce disturbing noises from outside environments, providing improved acoustical comfort. Vapour condensation prevention: Insulation that is properly designed and installed can help to prevent vapour collection on building surfaces. Fire protection: Some insulations incorporate means to retard heat and prevent flame immigration [27].
11.4.1 Types of Insulating Materials Building insulation materials can be categorized by their form and packaging. The insulation market is dominated by two basic groups of materials: inorganic fibres and organic foams. These could be packaged or installed in the form of blown‐in/loose‐fill insulation, batts, rolls, foam boards/panels, and spray foam. Blanket insulation, as shown Figure 11.9,3 which encompasses batts and rolls, is the most commonly used and widely available type of insulation. It is made with 6 in. (15.24 cm) uninsulated flaps that allow all horizontal and vertical seams to be installed in a shingled fashion. Batts and rolls are available in a variety of widths which are designed to fit the standard spacing of wall studs, attic rafters, and floor joists. Alternatively, continuous rolls are available that can be trimmed to custom fit desired structures [28].
3 Copyright 2017. All rights reserved. DuPont, Tyvek, Tyvek ThermaWrap™, DuPont AirGuard™ are trademarks or registered trademarks of E.I. du Pont de Nemours and Company or its affiliates.
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Figure 11.9 DuPont Tyvek ThermaWrap® R5.0 – an insulated house wrap that provides air and water protection. Source: photo provided by DuPont.
11.4.2 Property Requirements Thermally insulting materials must prevent heat flow. To achieve this, insulating materials should possess high thermal resistance to reduce heat transmission. The key parameter related to this is thermal conductivity. The thermal conductivity of a material is the rate of steady state heat flow through a unit area of the material of unit thickness in a direction perpendicular to the isothermal planes, induced by a unit temperature difference across the sample [29]. Thermal conductivity, indicated by a material’s k‐value, is expressed in units of W m−1 K−1. When considering insulation materials, a low thermal conductivity is desired. A low thermal conductivity allows a relatively thin building envelope to obtain a high thermal resistance [30]. Insulation materials are objectively compared and rated according to their thermal resistance or R‐value. The R‐value is an indicator of a material’s ability to resist heat flow through a given thickness and is expressed in units of (m2K)/W . The higher the R‐value, the better a material is at preventing heat flow. R‐values are dependent on the type of insulation, its thickness, as well as the material’s density. The degree of insulation needed depends on several factors, including climate, location within the building, type of heating/cooling system, and building construction type [2]. The US Department of Energy recommends R‐values based on geographic region and location of installation within a building. As an example, the United States’ geographic zone distinction is shown in Figure 11.10 and the respective R‐value requirements are shown in Table 11.4. This information is specific to new wood framed houses. It is important to note that R‐value requirements vary if the structure is pre‐existing. 11.4.3 Fibrous Insulating Materials Most insulation materials are either fibrous or foam based. Polyurethane and polystyrene foams are common foam based solutions. However, this discussion will focus on fibrous insulation materials, which are the most widely utilized insulating materials today [2].
11.4 Insulation
Figure 11.10 U.S. Department of Energy R‐value zones. Source: Image courtesy of the US Department of Energy.
Table 11.4 US Department of Energy recommended total R‐values for new wood framed houses [26]. Wall Zone
Heating system
1 2
3
4
5
Attic
Cathedral ceiling
Cavity
Insulation sheathing
Floor
All
R30–R49
R22–R38
R13–R15
None
R13
Gas, heat pump, fuel oil
R30–R60
R22–R38
R13–R15
None
R13
Electric
R30–R60
R22–R38
R13–R15
None
R19–R25
Gas, heat pump, fuel oil
R30–R60
R22–R38
R13–R15
None
R25
Electric
R30–R60
R30–R38
R13–R15
R2.5–R5
R25
Gas, heat pump, fuel oil
R38–R60
R30–R38
R13–R15
R2.5–R6
R25–R30
Electric
R38–R60
R30–R38
R13–R15
R5–R6
R25–R30
Gas, heat pump, fuel oil
R38–R60
R30–R38
R13–R15
R2.5–R6
R25–R30
Electric
R38–R60
R30–R60
R13–R21
R5–R6
R25–R30
6
All
R49–R60
R30–R60
R13–R21
R5–R6
R25–R30
7
All
R49–R60
R30–R60
R13–R21
R5–R6
R25–R30
8
All
R49–R60
R30–R60
R13–R21
R5–R6
R25–R30
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Inorganic Fibers
Glass wool Mineral wool PET
Insulating Materials
Cellulose Organic Fibers
Cotton Sheep wool Bast
Figure 11.11 Insulating material types.
As shown in Figure 11.11, fibrous insulation materials can be divided into two categories: inorganic fibre based products and organic fibre based products. Regardless of whether the insulation comprises inorganic or organic fibres, manufacturers typically attach a ‘face’ layer, such as kraft paper, foil‐kraft paper, or vinyl, to act as a vapour and/ or air barrier layer. The ‘facing’ material may also possess flame‐resistant properties and facilitate the installation process [28]. 11.4.3.1 Inorganic Fibres
Fibre based insulation materials are typically produced with inorganic fibres. Over time, inorganic fibres have been developed to provide higher performance compared to organic fibres. Specifically, inorganic fibres provide increased product lifetime and better thermal stability [2]. 11.4.3.1.1 Fibreglass
Fibreglass (glass wool), a material made up of very fine glass fibres, is one of the most dominant insulation materials. It is most often used in blanket (batt and roll) or loose‐ fill form but it can also be found in the form of rigid boards and duct insulation. Fibreglass products are available in various densities and thicknesses to achieve the desired R‐values, as shown in Table 11.5. Lofty glass wool products are applied inside the structural cavities of walls and floors of buildings. When used as loose‐fill insulation, fibreglass is made from molten glass spun or blown into fibres. Glass wool is produced from borosilicate glass heated around 1400 °C, and pulled through rotating nozzles [30]. Loose‐fill fibreglass insulation usually consists of 20–30% recycled glass fibres. In loose‐fill form, fibreglass must be applied using an insulation blowing machine within spaces appropriate for open blowing, such as attics or in closed cavities of inner walls and attic floors [31]. A well‐documented issue regarding fibreglass insulation is the tendency for glass fibres to break. When inhaled, the glass fibres can cause lung damage. Additionally, many fibreglass insulation materials contain carcinogenic substances. So, most manufacturers have developed new processes which eliminate the use of carcinogenic chemicals.
11.4 Insulation
Table 11.5 Fibreglass batt R‐value comparison [28]. Thickness (cm)
R‐value
8.89
11
9.21
13
8.89 (high density)
15
15.24–15.88
19
13.34 (high density)
21
20.32–21.59
25
20.32 (high density)
30
24.13 (standard)
30
30.48
38
11.4.3.1.2 Mineral Wool
The term ‘mineral wool’ can apply generally to two distinct types of insulation: ●●
●●
Rock wool, which is a manufactured material containing natural minerals like basalt or diabase. Slag wool, also a manufactured material, which contains material from blast furnace slag.
Rock wool is produced from melted stone at approximately 1500 °C, using a wheel centrifuge process wherein the heated mass is hurled out from a wheel or disk, thus creating discontinuous fibres [30]. Mineral wool insulation is typically available as a blanket (batt or roll) as well as loose‐fill insulation. Generally, mineral wool insulation contains approximately 75% post‐industrial recycled content [31]. 11.4.3.2 Organic Fibres
Organic fibrous materials are historically significant in the development of insulation. In ancient times, natural fibres like cotton, sheep wool, straw, hemp, and asbestos were used as building insulation. However, the issues associated with organic fibres, such as their low resistance to elevated temperatures and environmental extremes, limit their use in the insulation field [2]. PET (polyethylene terephthalate) based insulation is less readily available when compared to other types of insulation. Insulation containing PET primarily consists of fibres produced from recycled plastic bottles. PET fibres are generally used to form batt insulation products similar to high density fibreglass materials. One positive aspect of this type of insulation is that it is relatively nonirritating to work with and does not cause the health problems associated with glass fibre materials. The R‐values provided by PET based insulation varies based on density. A 1.0 lb ft−3 material reportedly provides an R‐value of 3.8 per in., while a 3.0 lb ft−3 insulation provides an R‐value of 4.3 per in. value [31]. Cellulose insulation is produced from recycled paper products, most often newspapers. This form of insulation generally contains 80–90% recycled material. To produce this material, recycled paper is first shredded to small pieces and then converted to a fibre form. Cellulose insulation may be installed in attics as well as densely
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packed in to building cavities in loose‐fill form. Cellulose based fibrous material is capable of tightly packing into cavities, efficiently inhibiting airflow, and provides an R‐value of 3.6–3.8 per in. More recent methods of application include damp‐spraying. In damp‐spraying, the spray nozzle tip provides the cellulose with a small amount of moisture which activates natural starches and causes the cellulose to adhere to cavities. Dry cellulose fibres may also be applied when dry as loose‐fill insulation within attics [31]. Cotton insulation is available as a loose‐fill material or in batt form. Cotton insulation comes in a few varieties. Some cotton insulation is produced from approximately 85% recycled cotton and 15% plastic fibres treated with borate. Other cotton insulation products are produced from denim scraps and thus require minimal energy to manufacture. Cotton insulation can be nontoxic. Therefore, it can be installed without concern for respiratory issues or skin contact. However, cotton insulation typically costs 15–20% more than fibreglass batt insulation. Cotton insulation can provide an R‐value of approximately 3.4 per in. [31]. Sheep wool may also be used as insulation. Similar to cotton and cellulose, sheep wool requires borate treatment. Wool is capable of high moisture regain which can be problematic because boric acid may leach after repeated wetting and drying cycles. The R‐value provided by sheep wool is approximately 3.5 per in., which is similar to other insulation materials [31]. Recently, the use of bast fibres for insulation has gained interest. The bast fibre group includes natural fibres such as hemp, linseed, and flax. Although flax and hemp have a long history in insulation application, they are often considered new materials in this area, owing to their recent gain in popularity. Hemp and flax are plants which grow on an annual basis and thus are considered renewable materials. As ecological issues become of greater concern in the industry, materials which are recyclable and renewable, and require relatively few resources for production will become increasingly popular. Traditionally, tows of hemp and flax fibres have been utilized in timber houses in the form of tapes. More recently, bast fibre mats and loose‐fill bast insulation have become more commercialized with different thicknesses available for modern structures. The thermal conductivity of bast fibres is comparable to conventionally used insulation Table 11.6 R‐values of fibre assemblies, per centimetre of thickness [24, 31]. Insulation type
R‐value per 2.54 cm of thickness
Fibre glass blanket or batt
2.9–3.8
High performance fibre glass blanket or batt
3.7–4.3
Loose fill fibre glass
2.3–2.7
Loose fill rock wool
2.7–3.0
PET
3.8–4.3
Loose fill cellulose
3.4–3.7
Cotton (type not specified)
3.4
Sheep wool (type not specified)
3.5
Bast fibre (specifically, Hemp)
3.5
11.5 Textile Reinforced Concrete
materials, owing to the porous nature of bast fibres and their low bulk density, which allows the fibres to trap a large amount of air. However, bast fibres make up a very small portion of the market, which may be explained by the twofold price increase when compared to other insulation materials like mineral wool [32]. The R‐values of the materials discussed in this section are shown in Table 11.6.
11.5 Textile Reinforced Concrete Textile reinforcements for concrete can be described as fibrous arrangements which are incorporated within concrete to improve the lifetime and performance of concrete structures. Concrete reinforced with fibres randomly distributed throughout the concrete matrix is termed fibre reinforced concrete (FRC); on the other hand those reinforced with mesh‐like textile arrangements are called textile reinforced concrete (TRC). These concepts are shown schematically in Figure 11.12. While there is extensive literature pertaining to FRCs, this discussion will primarily focus on TRCs. Concrete, or ‘artificial rock’ [33], is one of the most commonly used materials in the construction industry [34]. The components of concrete include cement, stone aggregates, and water. Pure concrete is a material characterized by high compressive strength (about 60 N mm−2), but also very low tensile strength [33]. The low tensile strength of pure concrete can lead to crack propagation and crack growth, which ultimately causes material failure. The concept of TRC is relatively new with research initiatives beginning in the mid‐ 1990s [35] . Historically, the low tensile strength of concrete was mitigated utilizing steel bar reinforcements [33], as shown in Figures 11.12 and 11.13. While steel bar reinforcements do provide advantageous properties like high load capacity, straightforward processing [37], durability, and versatility [36], they are also highly prone to corrosion. Within the reinforced concrete structure, steel bars are protected from corrosion by concrete encapsulation. However, over time, substances can penetrate concrete such that the steel bars are no longer protected and begin to corrode. As the reinforcement corrodes, the concrete begins to break up into smaller components ultimately leading to structural failure [37].
Concrete Reinforcement
(a)
(b)
(c)
Figure 11.12 Schematic of different reinforcement systems: (a) steel reinforced concrete; (b) fibre reinforced concrete; (c) textile reinforced concrete. Source: Redrawn with permission from SGL, German Centre for Textile Reinforced Concrete and JEC Composites Magazine.
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(a)
(b)
Figure 11.13 (a) Carbon fibre roving used for concrete reinforcement; (b) carbon fibre textile structure and its incorporation into concrete. Source: Images from [36] courtesy of SGL, German Centre for Textile Reinforced Concrete and JEC Composites Magazine.
There are many advantages to utilizing textile arrays for concrete reinforcement. Most importantly, textile concrete reinforcements are noncorrosive; however, there are many other advantages, including: ●●
●● ●● ●●
●●
●●
●●
TRC requires far less concrete encapsulation than steel bars. To prevent steel bar degradation, building standards require that steel bars are protected by concrete layers with a minimum thickness of 35 mm, which leads to an overall material thickness of at least 100 mm. This can be compared to TRC products which are typically 20–30 mm thick as they only require 10–15 mm layers of concrete encapsulation. Therefore, TRCs are thinner, lighter, and require less material than steel reinforced materials. Compared to steel reinforced concretes, TRCs require up to 80% less concrete to produce, allowing for significant cost savings [37]. TRC has high specific strength (strength‐to‐weight ratio) [38]. TRC materials are lighter and therefore can be transported at lower costs. Textile reinforcement layers possess much greater surface area when compared to steel bar reinforcements. This creates high bonding forces between the textile reinforcement and the surrounding matrix [36]. TRCs can achieve high tensile strengths, up to 3000 N mm−2 [35]. Their strength properties can be five to six times greater than traditional steel reinforced concrete [37]. TRCs are applicable to structures exposed to high chloride stresses, such as bridges, parking decks, and maritime structures [35]. TRCs can be used as very thin strengthening layers and repair layers. Strengthening layers have been shown to reduce subsequent concrete cracking.
11.5.1 Requirements for Textile Reinforcement Materials Textile materials used in TRCs must carry the tensile forces which occur when concrete cracks [34]. Most continuous fibres are well suited for use as concrete reinforcement materials. However, it is imperative that the fibre type utilized is noncorrosive and that the selected reinforcing material creates a strong bond with the concrete. This means
11.5 Textile Reinforced Concrete
that the fibres should be permanently compatible with the concrete matrix, both chemically and physically. Additionally, it is important that reinforcing fibres are high strength and possess low fracture elongation. More specifically, it is necessary that the Young’s modulus of the reinforcing fibre is sufficiently larger than the concrete matrix to avoid significant strength reduction upon crack development [33]. 11.5.2 Types of Reinforcing Fibrous Materials The fibre types that are most often utilized for TRCs are alkali‐resistant (AR) glass fibres, and carbon fibres. AR glass fibres and carbon fibres are not susceptible to corrosion and also possess high strength [37]. AR glass and carbon fibres are used in the form of filament yarns or rovings, as shown in Figure 11.13. These materials typically provide low material strain under tensile load, which is desirable for reinforced concrete structures. While most TRCs are produced with AR glass or carbon fibres, other fibre types have also been explored, such as polypropylene, polyvinyl alcohol, polyacrylonitrile [33], polyethylene, aramids, and basalt. Recently, basalt fibres have gained significant attention in the area of TRCs, owing to their low cost and environmental friendliness [38]. Table 11.7 provides qualitative comparison of the different reinforcement materials based on corrosion resistance, temperature resistance, bond quality, demand, and production costs. Corrosion resistance indicates a material’s ability to withstand alkaline, neutral, and acidic conditions. Temperature resistance is compared based on the reinforcements’ thermal conductivity and coefficient of thermal expansion. Bond quality comparisons depend heavily on the geometrical properties and surface finishes utilized; therefore, bond quality can significantly vary with design. Demand analysis indicates how easily the reinforcement material can be obtained, while production cost involves the monetary requirements which vary with demand, availability, and production method [39]. A quantitative comparison of the common reinforcement materials can be found in Table 11.8. For the sake of comparison, and owing to the current available data, the yield stress and strain are recorded as the tensile strength and ultimate strain of steel reinforcements. However, the tensile strength and ultimate strain of the AR glass, carbon, and basalt fibres is provided. Using these data, the values were normalized with respect to steel as the reference material. The normalized results are shown in Figure 11.14 [39]. The qualitative and quantitative data provided show that in some areas the common reinforcement materials are comparable in performance. However, steel reinforcements prove insufficient when considering corrosion resistance in realistic environmental settings. In terms of tensile strength, carbon fibres may be the optimal fibre reinforcement material, although carbon fibres can be expensive, difficult to obtain, and possess a comparatively low ultimate strain. AR glass fibres present some issues, such as their poor temperature behaviour and low strength performance but impressive corrosion resistance. Basalt fibres provide greater tensile strength properties than AR‐glass fibres. Overall, the performance of AR glass fibres and basalt fibres is relatively similar [39]. When incorporated into TRCs, fibrous materials are used in the form of yarns or rovings and processed into planar textile structures like those shown in Figure 11.13, with optimal fibre alignment. The fibre alignment achieved in textile materials provides TRCs’ higher load bearing performances when compared to FRCs with equivalent or
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Table 11.7 Qualitative comparison of TRC reinforcement materials. Reinforcement material
Corrosion resistance
Temperature resistance
Bond quality
Demand/ production cost
Conventional steel reinforcement
High resistance to high alkaline solutions Low resistance to low alkaline, neutral, or realistic acidic outdoor conditions
Average High thermal expansion and conductivity
Low to high based on mechanical deformations
High/average, commonly used
AR‐Glass
Average resistance to high alkali attack High resistance to neutral or realistic acidic outdoor conditions
Low Average thermal expansion Low thermal conductivity
Average, depends on density of yarn Improve with coating
Average, particularly produced for alkaline environments
Carbon
High resistance to acid, alkaline and organic solvents (inert)
High Low thermal expansion, shortens when heated Average thermal conductivity
Low to average Smaller filament diameter leads to weaker adhesion Improve with coating
Low/high, compared with all other reinforcement materials
Basalt
Comparable to unsized E‐glass and AR‐glass in high alkaline solutions High resistance to neutral or realistic and alkaline outdoor conditions
High Low thermal expansion Geometrically stable Low thermal conductivity
Unsized filament Low friction coefficient, improve with coatings
Low/average, easily extractable natural resource
Source: Reformatted with permissions from [39] Copyright © 2014, ASCE.
Table 11.8 Comparison of mechanical properties of TRC reinforcement materials. Reinforcement material
Tensile strength (MPa)
Modulus of elasticity (GPa)
Ultimate strain
Conventional steel reinforcement (B500B)
560 (±30)
205
2.0 (±0.2)
AR‐glass
1870 (±127)
70 (±1)
2.7 (±0.2)
Carbon
4348 (±385)
238 (±9)
1.8 (±0.2)
Basalt
2809 (±964)
86 (±8)
3.2 (±0.7)
Source: Reformatted with permissions from [39] Copyright © 2014, ASCE.
reduced fibre content [36]. The textile materials utilized for TRCs are typically open structure configurations, which provide extensive surface contact area for the matrix material. This allows for optimal bonding between the concrete and reinforcing textile material [34].
11.5 Textile Reinforced Concrete
Tensile Strength
Modulus of Elasticity
Ultimate Strain
Basalt 7.8 Carbon
AR-glass
Steel
0
1
2
3
4
5
6
Normalized Value Figure 11.14 Comparison of normalized mechanical properties (tensile strength of steel considered yield stress and ultimate elongation of steel is considered yield strain). Source: Image reprinted with permissions from [39] Copyright © 2014, ASCE. All rights reserved.
Considering the large variety of textile manufacturing methods available, textile reinforcement materials can be configured in a wide range of manners. Fibres may be configured with no specific orientation utilizing nonwoven fabric techniques. Alternatively, yarns in the fabric may be oriented in predetermined manners with unidirectional, biaxial, and multiaxial orientations. Unidirectional reinforcements are typically in the form of pre‐pregs. Similarly, a unidirectional nature can be achieved with woven fabrics containing one yarn set which is significantly weaker than the other such that one direction of the fabric does not significantly contribute to the reinforcement properties. Multiaxial textile materials can be made manufacturing techniques such as weaving, multilayer knitting, multiaxial warp knitting, or braiding. Reinforcing yarn materials can be interlaced with each other in different orientations via woven and braiding methods. Additionally, the textile reinforcement layer can contain many stacked yarn layers in different orientations held together by a binding yarn. This can be achieved with multiaxial warp knitting, multilayer knitting, and multilayer woven fabrics. Alternatively, the reinforcement layer can provide reinforcement in all three axes. With 3D weaving, multilayer weaving, or multiply knitting, z‐axis reinforcements provide additional resistance to impact. In these manners, the properties of the TRC can vary from strongly anisotropic to quasi‐isotropic [33]. TRCs can be manufactured in a number of ways. Textile materials may be incorporated into concrete via processes such as hand lay‐up (shown in Figure 11.15), casting, or laminating. Alternatively, FRC can be manufactured through processes like spraying,
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Figure 11.15 Hand lay‐up of TRC. Source: Images from [36] courtesy of SGL, German Centre for Textile Reinforced Concrete and JEC Composites Magazine.
spinning, and extrusion [40]. The processing method utilized for TRCs will determine the specific materials which can be incorporated and the final properties of the material. 11.5.3 Applications of Textile Reinforced Concrete TRCs are a relatively new class of materials which are noncorrosive, lightweight, thin, and durable. As these materials have developed and emerged, designers have been able to create new and unique structural designs utilizing TRC materials. TRC has been used in a variety of applications, including facades, roofs, balconies, noise barriers, furniture, tanks, bridges, pipes, etc. Examples of structures produced with TRC are shown in Figure 11.16. The Albstadt‐ Ebingen Bridge in Germany was the first bridge in the world to be made entirely from carbon reinforced concrete. The bridge is frost resistant, requires no surface coating, and is capable of supporting a 10‐tonne vehicle [41]. Also shown in Figure 11.16 is the Eastsite VIII building located in Mannheim, Germany, which is the largest textile‐reinforced sandwich facade in the world. The facade is quite thin, thus achieving significant reduction in concrete usage [42]. Another emerging application of TRC is the strengthening and repairing of existing concrete structures. As structures reinforced with steel age and degrade because of corrosion, structural damage, increased loading, design faults, or construction faults, repairing and strengthening methods may be required to maintain the integrity of the structure [36]. By virtue of the noncorrosive nature of textile materials, thin TRC layers can be utilized as additional reinforcement layers while only slightly increasing the overall weight of the structure. TRC materials are easily shaped, thus allowing the layers to easily adapt to most component geometries [33]. For example, textile reinforced composite materials have been used to strengthen masonry structures in the event of seismic activity. TRCs can help to increase the shear and flexural resistance, the in‐ plane and out‐of‐plane strength, and deformation capacity of existing reinforced concrete structures [43].
11.6 Sustainability and Ecological Issues
(a)
(b)
(c)
(d)
Figure 11.16 Applications of textile reinforced concrete: (a, b) the Albstadt‐Ebingen bridge which is made entirely from carbon reinforced concrete; (c, d) the Eastsite VIII sandwich facade in Mannheim, Germany. Source: Images courtesy of solidian® at www.solidian.com.
11.6 Sustainability and Ecological Issues Sustainability in this context means being good stewards of our natural resources to ensure a long‐term ecological balance. The US Environmental Protection Agency describes sustainability as a pursuit ‘to create and maintain the conditions under which humans and nature can exist in productive harmony to support present and future generations’ [44]. The construction industry has a significant impact on both problems as well as potential solutions regarding issues related to sustainability. While the industry is a major consumer of natural resources and energy as well as a producer of solid waste during construction, it also has a long‐term lasting influence on the lifetime carbon footprint of its products through the entire process of design, engineering, and construction. In the United States, the construction industry is reported to be the third‐largest contributor to greenhouse gas emissions [45]. It is estimated that the building/construction sector accounts for 40% of the natural resources utilized in industrialized countries, 70% of electricity, as well as 12% of the portable water available. Additionally, researchers estimate that 45–65% of the construction/building sector’s material waste is disposed in landfills [46, 47]. The United Nations estimates that the global population will reach 8.5 billion by 2030, 9.7 billion by 2050, and 11.2 billion in 2100 [48]. While the
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growth in global population and issues related to climate change are likely to increase demands for resources (materials, energy, etc.) these problems can be mitigated through sustainable practices. Perhaps the most compelling reason to pursue sustainable practices for the industry and society at large is the financial incentives derived from delivering buildings and services at a low cost and with great energy efficiency over their lifetimes. Textiles can play an essential role in realizing these efforts. The EU has initiated various actions to overcome issues related to textiles and sustainability. Reportedly, approximately 5.8 million tonnes of textile products are discarded each year in the EU. About 25% of this waste, or 1.5 million tonnes, is recycled via charities or industrial enterprises. The remaining 4.3 million tonnes of textile waste is sent to landfills or municipal waste incinerators [49]. In order to combat the issues related to excessive waste, the EU has taken action through legislation. One such regulation is called the Waste Framework Directive (Directive 2008/98/EC), which specifically confronts textile related waste issues. In the directive, the EU defines waste, recycling, and recovery while also encouraging adaptation of waste management and waste prevention programs. The EU has set aggressive goals to reduce household related waste by 50% and construction and demolition waste by 70% before 2020 [50, 51]. Similarly, the EU has implemented Regulation (EC) No 1907/2006, also known as REACH (Registration, Evaluation, Authorization, and Restriction of Chemical Substances). This regulation requires that the chemical substances used to produce textiles in Europe are registered and reported. In order to improve transparency and better inform consumers, companies are required to report textile products which contain harmful chemical products in a concentration greater than 0.1% [51, 52]. Further, the EU has developed a voluntary scheme called Ecolabel, in which sustainable products are clearly designated with a particular logo. Businesses are only allowed to place the distinct logo on their product when an independent body recognizes the good as complying with strict ecological criteria. Ecolabel products meet environmental standards throughout their lifecycles from raw material extraction, through production, distribution, and disposal. The labels allow consumers to easily choose sustainable products and provides opportunities for companies to gain recognition for adhering to environmentally friendly standards [52, 53]. While countries like the United States and China are not taking as aggressive a stance on such issues, it is likely that in the near future such policies will be ubiquitous. The construction industry has been slowly embracing the new paradigms of environmental sustainability, including efforts to reduce energy consumption, decrease waste, and lower greenhouse gas emissions. This is being accomplished by methods such as utilizing more environmentally friendly materials, reusing material waste, as well as rehabilitating existing buildings to prevent further waste [49]. Textile materials that are currently used in construction and those that can be potentially designed from improved materials and structural design practices offer many opportunities to advance sustainability. Possibly the most important example is architectural textiles. The fabric membranes used in tension and air structures offer superior area‐to‐weight ratio, specific strength, and environmental and mechanical stability and therefore are suitable for lightweight, long‐span structures that can function under a variety of loading conditions including seismic. Designs with tunable optical transparency of fabric membranes offer savings in energy. The low thermal mass of fabric membranes can be advantageous in certain climatic conditions, including hot and humid tropical climates.
References
Natural fibres – such as flax, hemp, jute, kenaf, and sheep wool – are being examined for their potential as sustainable, natural, and renewable insulation materials. These types of fibres could serve their regional or niche markets. In addition to fibre based insulation, other textile structural components, such as house wraps, do have significant roles to play in energy management and environmental impact in the design and lifecycle of buildings. There is significant untapped potential for reducing the environmental ‘footprint’ of buildings by reusing and recycling these materials. Textiles offer many alternatives to construct lightweight, energy efficient, long‐span structures that are compatible with a sustainable future while maintaining high quality living standards for future generations. Architectural textiles with integrated sensors and actuators are likely to play an integral role in this. In the future, smart and responsive textile materials and structures will offer opportunities to design active structures for safe and comfortable environmental conditions. The construction industry as well as the regulators need to adapt and drive the necessary cultural shift such that the construction industry incorporates new sustainable concepts. Relevant research and regulatory reform (i.e. building codes) could lead the way to a more sustainable efficient future for all.
11.7 Conclusion Textiles used in construction span a wide variety of applications, including architectural membranes, weather‐resistant house wraps, thermal insulation layers, as well as TRC. The use of specific polymer types, fabric structures, or fabric finishes depends on the application environment. Additionally, the material requirements vary depending upon the location of construction, surrounding building components, and regional building codes. Textile based construction solutions offer promising prospects for the future. Architectural fabric structures will become a larger part of commercial construction by virtue of their energy efficiency, and potential in creating a form of architecture that is more organic, natural, and aesthetically pleasing. Similarly, insulation and house wraps are being improved to offer more efficient and comfortable structures. The use of textile materials in construction will evolve with the development of new sustainable materials with improved properties, manufacturing technologies, and analytical techniques as well as design paradigms.
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industry. In: Design and Manufacture of Textile Composites (ed. A.C. Long). Cambridge: Woodhead. Jurg, R. (2011). Architectural textiles: economical and ecological roofing. Textile World 161 (2): 28–29. Stegmaier, T. and Planck, H. (2008). Innovative developments in fiber based materials for construction. In: Textile Composites and Inflatable Structures: II: Electronic Resource (ed. E. Oñate, B. Kröplin and I. Ebrary). Dordrecht, The Netherlands: Springer. Sheth, P.J. Composite breathable housewrap films. 29 May 1990. https://patents.google. com/patent/US4929303A/en. Accessed 11 October 2018. Butt, T. (2005). Water resistance and vapor permeance of weather resistive barriers. Journal of ASTM International, 2 (10): 1–15. White, W.C. and Kuehl, M.H. (2002). The role of construction textiles in indoor environmental pollution. Journal of Industrial Textiles 32 (1): 23–43. Benjamin, O. Understanding Housewraps: A Decision Guide for Selecting the Right Housewrap. 2012. Available at: http://www.benjaminobdyke.com/uploads/resources/ Understanding_Housewrap.pdf. Accessed 10 February 2017. Ruiz, F.P. Making sense of housewraps. Fine Homebuilding, 177 (10 March 2006). Bomberg, M., Pazera, M., and Onysko, D. (2005). The functional requirements for water resistive barriers exposed to incidental water leakage: part 2: testing materials. Journal of Testing and Evaluation 33 (3): 1–7. https://doi.org/10.1520/JTE12583. Weather‐Resistive Barriers. 2000. Available at: http://inspectapedia.com/interiors/ Weather_Resistant_Barriers_DOE.pdf. Accessed 16 February 2017. Cashin, A., Anderson, G, Gelotte, S. Housewrap with drainage channels. 23 October 2003. Horrocks, A.R. and Anand, S.C. Handbook of Technical Textiles. Cambridge: Woodhead Publishing. The US Department of Energy. Insulation fact sheet with addendum on moisture control, DOE/CE‐0180. 2002. Available at: https://www1.eere.energy.gov/library/pdfs/ insulation_fact_sheet.pdf. Accessed 13 April 2017. European Commission. Heating and Cooling. Available at: https://ec.europa.eu/energy/ en/topics/energy‐efficiency/heating‐and‐cooling. Accessed 18 October 2017.
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26 The U.S. Department of Energy. Insulation. Available at: https://energy.gov/
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27 Al‐Homoud, D.M.S. (2005). Performance characteristics and practical applications of
common building thermal insulation materials. Building Environment, 40 (3): 353–366.
28 The US Department of Energy. Types of Insulation. Available at: https://energy.gov/
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29 Schaschke, C. (2014). A Dictionary of Chemical Engineering Electronic Resource.
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30 Jelle, B.P. (2011). Traditional, state‐of‐the‐art and future thermal building insulation
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materials and solutions: properties, requirements and possibilities. Energy and Buildings 43 (10): 2549–2563. The US Department of Energy. Insulation Materials. Available at: https://energy.gov/ energysaver/insulation‐materials. Accessed 13 April 2017. Kymäläinen, H. and Sjöberg, A. (2008). Flax and hemp fibres as raw materials for thermal insulations. Building and Environment, 43 (7): 1261–1269. Cherif, C., Diestel, O., Engler, T. et al. (2016). Processing aspects and application examples. In: Textile Materials for Lightweight Constructions (ed. C. Cherif and T. Dresden), 599. Springer. (2007). Advances in Construction Materials, 2007. Berlin, Heidelberg: Springer Berlin Heidelberg. solidian. Textile‐reinforced concrete is the building material of the future. Available at: https://www.solidian.com/en/textile‐reinforced‐concrete. Accessed 14 October 2017. Plaggenborg, B. and Weiland, S. (2008). Textile‐reinforced concrete with high‐ performance carbon fibre grids. JEC Composites Magazine 44: 32–35. Kulas, C. Actual applications and potential of textile‐reinforced concrete, 2015; Available at: www.grca.org.uk/pdf/congress‐2015/02%20Actual%20applications%20 and%20potential%20of%20textile‐reinforced%20concrete.pdf. Accessed 11 October 2017. Du, Y., Zhang, M., Zhou, F., and Zhu, D. (2017). Experimental study on basalt textile reinforced concrete under uniaxial tensile loading. Construction and Building Materials 138 (Supplement C): 88–100. Williams, P.N., Karin, L., Holger, W., and Katarina, M. (2015). Sustainable potential of textile‐reinforced concrete. Journal of Materials in Civil Engineering, 27 (7): 04014207. Brameshuber, W. (2016). Manufacturing methods for textile‐reinforced concrete. In: Textile Fibre Composites in Civil Engineering (ed. T. Triantafillou), 45–59. Cambridge: Woodhead Publishing. solidian. The Albstadt‐Ebingen bridge. Available at: https://www.solidian.com/en/ references/details/?reference=12&cHash=c38ed0a97235822b3ba5eb5e7ebaf1af. Accessed 14 October 2017. solidian. ‘Eastsite VIII’ sandwich façade, Mannheim. Available at: https://www.solidian. com/en/references/details/?reference=4&cHash=7811ee7c235c4608973964fc30c13e23. Accessed 14 October 2017. Triantafillou, T. (2011). Innovative textile‐based composites for strengthening and seismic retrofitting of concrete and masonry structures. In: Advances in FRP Composites in Civil Engineering: Proceedings of the 5th International Conference on FRP Composites in Civil Engineering (CICE 2010), 27–29 September 2010 (ed. L. Ye, P. Feng and Q. Yue), 3–12. Beijing: Heidelberg: Springer Berlin Heidelberg.
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45 Li, X., Zhu, Y., and Zhang, Z. (2010). An LCA‐based environmental impact assessment
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47 Castro‐Lacouture, D., Sefair, J.A., Flórez, L., and Medaglia, A.L. (2009). Optimization
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model for the selection of materials using a LEED‐based green building rating system in Colombia. Building and Environment, 44 (6): 1162–1170. United Nations Department of Economic and Social Affairs. World population projected to reach 9.7 billion by 2050. Available at: http://www.un.org/en/development/ desa/news/population/2015‐report.html. Accessed 3 May 2017. Briga‐Sá, A., Nascimento, D., Teixeira, N. et al. (2013;). Textile waste as an alternative thermal insulation building material solution. Construction and Building Materials, 1 (38): 155–160. European Commission. Directive 2008/98/EC on waste (Waste Framework Directive). 2016. Available at: http://ec.europa.eu/environment/waste/framework. Accessed 14 December 2017. European Commission. Sustainability of textiles. Available at: http://ec.europa.eu/ environment/industry/retail/pdf/issue_paper_textiles.pdf. Accessed 14 December 2017. European Commission. REACH. Available at: https://ec.europa.eu/growth/sectors/ chemicals/reach_en. Accessed 14 December 2017. European Commission. EU Ecolabel. Available at: http://ec.europa.eu/environment/ ecolabel. Accessed 14 December 2017.
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12 Automotive Textiles and Composites Bijoy K. Behera Indian Institute of Technology Delhi, New Delhi, India
12.1 Introduction The textile industry stemmed from the need of human beings to protect themselves from the changing climatic conditions. Humans first learnt to cover their bodies with leaves and the bark of trees to get protection against adverse environmental conditions. With progress in civilization, various natural fibres from plant and animal sources were discovered and used as the basic raw materials to produce fabric. Textile fabric gradually became a symbol of tradition and culture of various parts of the globe. In subsequent years, textile became the mainstream product dominating the fashion industry all over the world. Today, the trend of textile development is dominated by functionality in addition to the basic need of protection, culture, and fashion. The textile industry is as old as human civilization. Cloth is one of the basic needs of human beings. In ancient times, cloth was made only from cotton, flax, and hemp. At present, cloth is made from silk, rayon, nylon, acrylic, viscose, polyester (PES) staple, and filament yarns. Besides this, cloth is prepared by weaving, knitting, nonwoven, braiding, etc. not only for apparel purpose but also for numerous technical, industrial, and functional applications. Textiles are broadly applied in three different fields: apparel, home textiles, and technical textiles. Among these three categories of applications, technical textiles are an expanding area of textile industries. New yarn and fibre development is one of the driving forces of the modern technical textile industry. Technical textiles are the textile applications in nonconventional areas, such as medicine, agriculture, packaging, civil engineering, automotive design, and many other fields. Technical textiles are gaining fast becoming one of the most dynamic and promising areas for the future of the textile industry for high performance applications. Automotive textiles happen to be one rewarding sector, which extensively uses technical textiles, namely for interior trims, safety devices like seatbelts and airbags, carpets, filters, battery separators, hood liners, hoses, and belt reinforcement. The potential for the growth of the automotive textile business is considered one of the most progressive sectors in over the world, as car production is exponentially increasing in almost all developing countries [1]. High Performance Technical Textiles, First Edition. Edited by Roshan Paul. © 2019 John Wiley & Sons Ltd. Published 2019 by John Wiley & Sons Ltd.
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12.2 Mobiltech Among other sectors, the automotive industry is one of the largest single market for technical textiles and one of the most diverse as well. This market comprises automobiles, trains, marine vehicles, and aeroplanes. Technical textiles that are used in this automotive or transport sector are called Mobiltech. Mobiltech today covers not only isolation and safety aspect but also focuses on comfort, style, and a wide range of functionality. The customers look for aesthetically pleasing interiors, great comfort, and fuel economy. Mobiltech is also known as Mobiltex in some literature. Truck covers like polyvinyl chloride (PVC) coated PES fabrics and restraints are significant textile end‐ uses in the transportation sector. They can range from simple ropes and tarpaulins to highly engineered flexible curtain systems and webbing tie‐downs. Other examples include seat covers (both knitted and woven), denim, pile fabrics, floor coverings, tubes and tapes, tyre cord, filter, seatbelts, nonwovens for cabin air filtration, airbags, parachutes, car boot coverings (often needle felts), lashing belts for cargo tiedowns, seatbelts, nonwovens for cabin air filtration (also covered in Indutech), airbags, parachutes, boats (inflatable), air balloons, aerostats, and airships [2, 3]. 12.2.1 Textile and Automotive Industry The automotive industry is one of the fastest growing industries in the world and the most global of all industries, because of product distribution. The term ‘automobile textile’ means all type of textile components like fibres, filaments, yarns, and the fabrics of various structures used in automotive production. Automobile textiles are nonapparel textiles widely used in vehicles like cars, trains, buses, aircraft, and marine vehicles. Textiles which constitute approximately 20–25 kg in a car are used not only for their enhanced aesthetic value in automotive design but also for sensual comfort and safety. Additionally, few textile products found their applications as design solutions to engineering problems in the form of composites, tyre reinforcement, sound insulation, and vibration control. Apart from woven and knitted constructions, nonwovens also find applications in transport textiles, owing to certain advantages served by them. Normally, the percentage of textile in a motor car amounts to 2% of the overall weight of the car. Car seats are the most important part of the interior, from an aesthetic appeal and customer satisfaction point of view. Almost 45–50 m2 of textile material is used in an average car. Nearly two‐thirds of automobile textiles are for interior trim. The majority of automotive textiles are used for the upholstery and roof covering. The hidden textiles weigh almost 10–12 kg. Textiles for automobiles must satisfy very strong requirements for both security and competing demands [4]. 12.2.2 Classification of Automotive Textiles Automotive textiles can be classified into four major groups based on their functions. The main functions identified are comfort, aesthetics, safety, and speciality in material characteristics. Comfort includes both the physical and the physiological aspects of textiles used in seats and interiors of the vehicle, whereas aesthetics of textiles used in a car include the interior design of carpets, roof liners, and side walls for decoration purpose. Textiles used for safety purposes are seatbelts, airbags, and helmets. These
12.3 Application Areas of Automotive Textiles
products are manufactured using stringent specifications. Several technical textiles are used in modern cars to enhance functional requirements such as noise controllers, filters, battery separators, composite materials, etc. All textiles used in automotive design in the form of fibres, filaments, yarns, and fabrics can also be classified into two different types: visible components and concealed components. Components like upholstery, carpet, seatbelt, roof liner, etc. which have a significant role in the aesthetic appeal of the car are classified under visible components. Components like tyre cord, composite materials, airbag, etc., which have significant functional attributes but do not appear from outside are called concealed components. Although there are more than 30 components made from textiles in a modern car, only the items which have a perceptible effect on the function, comfort, aesthetic appearance, and economics of the vehicle are described in this chapter [5]. Some major technical textile products covered under Mobiltech are listed below: ●● ●● ●● ●● ●● ●● ●●
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Automotive upholstery and other textile fabrics used inside the vehicle. Airbag fabrics. Fabric used as a basis for reduction in weight of body parts. Tyre cord fabrics (including hose and drive belt reinforcements). Tyres (for cord reinforcement material, side and thread walls, carcass piles, etc.). Engine (radiator hoses, power steering, hydraulic lines, filters, etc.). Composites for body and suspension parts (bumpers, wheel covers, door handles, etc.). Comfort and decoration (seating, carpets, interior decoration). Safety (seatbelts, airbags, seat fire barriers, etc.). Car body covers. Headliners. Insulation felts (noise, vibration, and harshness [NVH] components). Sun visors/sun blinds. Helmets. Airline disposables. Webbings for aircrafts. Aircraft upholstery. Railways seating fabrics. Cargo fastening belt. Lifting straps. Composite preforms.
12.3 Application Areas of Automotive Textiles 12.3.1 Seat Covers and Upholstery The car seat constitutes the primary part of the interior decoration. The car seat is perhaps the most important part of the interior, because it is the first element that the customer appreciates when they open the door to look inside and it is the main interface between human and machine in a passenger vehicle. The volume of upholstery varies by region since manufacturers from different regions may prefer different styles of vehicle interiors. An average of 5–6 m2 of fabric is used in cars for upholstery. PES is
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the most widely used material in car seat coverings all over the world. Fabrics produced by weaving and circular and warp knitting are commonly used depending on colour, design, pattern, surface properties, and comfort characteristics demanded by customers. Modern designers try to give a sporty or elegant look to fabric structures by introducing innovative patterns and colour combinations. Computer aided design system supported by electronic dobby and jacquard has brought a spectacular change in introducing innovative designs in seat covers and upholstery. The very initial types of seat cover were made of leather or leather imitation material. As leather was relatively scarce and of limited comfort, it was gradually replaced by copolymers of vinyl and vinylidene chloride in which the pigment was dyed directly into the melt and had high light fastness. These were very easy to clean but still lacked many of the necessary attributes related to mechanical wear and tear, acoustic absorption, and other utility performance aspects. Then PVC coated fabrics were used and subsequently the fabrics made from the threads that were generated from PVC were used that possessed increased mechanical stability but lacked comfort. Modern seat covers started with the use of cotton and viscose, which have lower abrasion resistance than nylon, PES, and acrylic as they are comfort giving, easy to clean, and environment friendly. Acrylics then came along, as they have a very high UV light resistance, which is a major requirement for automobiles as the colour and properties get majorly affected by the action of UV radiations. PES is stronger than acrylics and thus is preferred from a durability point of view. The properties of PES are enhanced through various chemical processes such as mixing a UV light absorbing chemical in the dye bath of the fabric. PES is also cost efficient and has very high abrasion resistance and could be spun dyed. Some people use denim and pile fabrics to upholster their cars [6]. Figure 12.1 shows a typical textile based car seat cover. 12.3.1.1 Types of Seat Covers
Some major seat covers used in the industry are: camo seat covers, canvas seat covers, mesh seat covers, neoprene seat covers, leather seat covers, pet seat covers, and denim seat covers. 12.3.1.2 Properties
Seat cover fabrics are generally woven and engineered to give mechanical and physiological comfort along with having an aesthetic appeal. The major mechanical requirements of the fabric used are durability, UV light resistance, wear and tear resistance, flexibility, stretch ability, waterproofing, and wrinkle resistance. The comfortability and safety attributes are studied by automobile manufacturers, fabric production houses, seat makers, and research centres like universities or independent organizations and the same are followed by automobile industries with the utmost care because of stiff competition amongst the manufacturers. To overcome the two major tribulations of soiling and steam rupturing, the upholstery fabric once fixed in place must last the life of the car without being put in a washing machine. The fabric should have desired wear properties (abrasion and pilling resistance) and seam strength. Functional properties such as wet ability, water repellency, oil and stain resistance, and flammability must meet specific standards [4, 7–11]. One of the most traditional forms of automobile upholstery is plain woven fabric manufactured from air‐jet textured and spun PES yarns. The textured yarns have good
12.3 Application Areas of Automotive Textiles
Figure 12.1 Textile based car seat cover.
abrasion resistance because of their tight loop structure. The yarn contrived from core and effect components can produce fabric covers of very good quality. These types of yarns are based on a central yarn called the core, which gives strength and stability to the yarn structure. 12.3.1.3 Test Methods
Test methods and quality measurement attributes for seat covers are internationally standardized by several institutions like ASTM, SAE, etc. Many different companies have their own testing methods and assessment checks and the results of those tests vary at a certain level. Many attempts are made to harmonize those results. To achieve this, each testing house uses different methodology to do the same property testing. Different abrasion tests, like the Martindale, Schopper, and transversal, are performed and the general trend could be that the results obtained by two methods coincide and differ from the third one or all three results have variation to a certain degree. 12.3.1.4 Utility Performance of Seats
All these aspects relate to the technical characteristics of textiles. Automotive textiles have to fulfil certain technical requirements, which strongly depend on the application. One can divide them into the following groups: [12] Processing Properties ●● ●● ●● ●● ●● ●●
sewability. sewing strength. seam slippage resistance. stiffness. elongation. tensile strength.
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Service Properties ●●
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mechanical behaviour (strength, elongation, bending and folding, tear propagation strength, dimension stability, pressure resistance). ageing behaviour (heat/cold, temperature, humidity, light). colour fastness (friction, light, chemicals, sweating). friction behaviour (brushing‐up, abrasion, pilling, fibre migration). bio‐physiological demands (air permeability, heat and humidity transport in upholstery). emission behaviour (toxic elements, smelling, fogging, total emission). contamination and cleaning behaviour. electrostatic behaviour. flammability. optical, haptic, and design.
Depending on the application, some additional specific requirements may have to be considered. The diversity in textiles for automotive end‐uses offers plenty of opportunities for growth in the automotive textile industry because of the ever‐increasing demand on aesthetics, comfort, and safety of passengers as well as environmental issues such as low weight, lower energy consumption, and recycling at the end of a vehicle’s lifecycle. New designs in automotive construction are increasingly influenced by the legal regulations on emissions and those on the waste from old vehicles, which require the use of materials that can be recycled. These influence nearly all textile developments in the automotive sector. It was required for automobile manufacturers to greatly increase the recyclable products used in vehicles with a target rate of 95% recyclability. The textiles for interior furnishing are primarily made of woven, weft knitted, warp knitted, tufted, and laminated fabrics and nonwovens. Design, aesthetics, feel, and comfort are important considerations for automotive textiles. One future trend for car seats is to replace the foam by a textile material able to match various constraints such as resilience and resistance to fatigue. As a result, the chemical agents used in foam production and the different solvents used during the production process will be avoided, which may lead to a more easily recycled material. The seats of some models used to be stuffed with hair. But, with mass production, it soon became clear that hair fibres require treatment to avoid disintegration or loosening. For that purpose, animal fibres were impregnated and bonded with natural or synthetic rubber latex. More recently, coconut fibres have been used, along or in combination with animal fibres. Today, small volumes with coconut fibres agglomerated with a latex mixture are still produced in Europe. Latex was replaced by polyurethane foam for two main reasons: the production process of polyurethane foam is easier to master and provides a more consistent product, and its cost is lower than that of the latex foam production process. This is why the technology was relatively quickly replaced by polyurethane foam when it came onto the market. Polyurethanes, one of the most versatile group of plastics, are used in a wide range of applications. They are made from two basic raw materials: polyols and polyisocyanates, which are measured and mixed to form solid polyurethanes or various types of foams.
12.3 Application Areas of Automotive Textiles
Polyurethanes combine lightweight and flexibility with strength and durability. Their versatility is instrumental in achieving the precise mechanical properties required for specific applications. Polyurethane foam is commonly used as padding in car seats despite some problems concerning comfort and recycling. In addition, their thermo‐ physiological comfort properties are poor because they are not breathable. Because of these problems, much research has been carried out and many developments are being made to improve the thermal comfort of car seats. Investigations into the use of textiles as substitutes for polyurethane foam in car seats have been carried out by several European car manufacturers. Today, the three‐ dimensional (3D), stitch‐bonded nonwovens, Multiknit/Caliweb® are used in several types of car [13]. Three‐dimensional spacer fabrics to improve breathability and hence thermal comfort of the seating materials are becoming more popular. There has been a continuous improvement of both the technology and the fabric quality for both the warp and weft knitting sectors over the last two decades. As a result, machines are now capable of producing spacer fabrics to a very high standard for a wide range of applications [12, 14, 15]. 12.3.2 Carpets Carpet is an important part of the automotive interior. Carpets must withstand temperature extremes. Major car producers are using tufted cut‐pile carpets in their cars. Carpets usually have a rubberized backing. The important quality parameters of a carpet used in car include light fastness, mouldability, and soil and abrasion resistance. Carpets are manufactured either by tufting or needle felting. Carpets made by tufting are based upon a supportive backing which is used as a base for the pile yarns which becomes the upper most surface. Carpet backing is usually spunbonded and is made by an integrated process in which polymer chips are melted and filaments are extracted through a die. Mainly PES is used in making this carpet backing where as a blend of nylon and PES is used on some occasions. The process of needling has got the advantage of more productivity at relatively low cost. But carpets produced by needling have the advantage of greater productivity at a relatively low cost. But carpets produced by needling cannot be used to cover sharp‐edged surfaces, especially foot areas and transmission tunnels. Superior needled material has a good filling which is determined by the amount of vertically oriented fibres at a given stitch density. 12.3.2.1 Interior Carpet
It is also placed on the vehicle floor, on top of which is then placed a rubber mat to provide compression resistance to the fabric. Usually, nonwoven textile fibres using polypropylene are used in flooring carpet. Figure 12.2 shows typical flooring carpets. The thickness of the fabric used is around 3 mm and areal density around 500 gsm. The desired characteristics of interior carpets are: ●● ●● ●● ●● ●●
high durability. high abrasion resistance. tensile strength. low inflammability. good compression recovery.
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Figure 12.2 Flooring carpet for automotive applications.
12.3.3 Roof Headliner The hood part comprises almost 18% of the total textile used in an automobile. In the earlier stages of the automobile manufacturing the headliner just consisted of a fabric that was a mere covering to the metal roof. Some basic requirements of the hood covering are lightweight, flexibility, acoustic insulation, antiflex, antivibrational, soft feel, and aesthetically presentable. The evolved version of the headliner consists of multiple layers which may vary from three to eight, depending on the requirements. Each layer serves a defined purpose, such as rigidity, aesthetics, etc. Figure 12.3 shows a nonwoven textile based car roof headliner.
Figure 12.3 Typical nonwoven car roof headliner.
12.3 Application Areas of Automotive Textiles
12.3.3.1 Structure and Properties
The layers used are produced by needle‐punched nonwoven PES bonded with phenolic resins, and are soft and thermoplastic. The face fabric is made up of tricot knit fabric covered by melted polyurethane foam. The areal density varies from 185 to 220 gsm. A layer is formed by PSF (polyester staple fibre) sprayed between two reinforced sheets. The central layer of the multilayer structure is a semi‐rigid polyurethane NVH foam guarded by two layers of chapped fibre glass sheet, each on either side, which imparts stability and rigidity to the structure and helps with acoustic damping and absorption. The next layers are decorative ones and are nonwoven scrimp attached on both sides of the structure, and provide heat insulation and aesthetic properties. The layers are joined by melted adhesives in a plain laminator, and precaution should be taken to ensure the central layers do not become too compressed and thin; otherwise, the decorative aspect of the outer most layers will be adversely affected. Some major types of headliners are brushed nylon, union cloth, perforated vinyl, moonstone, and perforated moonstone‐ type headliners. 12.3.4 Seatbelts The seatbelt, also known as a safety belt, is a vehicle safety device designed to secure the occupant of a vehicle against harmful movement that may result during a collision or a sudden stop. A seatbelt functions to reduce the likelihood of death or serious injury in a traffic collision by reducing the force of secondary impacts with interior strike hazards, by keeping occupants positioned correctly for maximum effectiveness of the airbag (if equipped), and by preventing occupants from being ejected from the vehicle in a crash or if the vehicle rolls over. When in motion, the driver and passengers are travelling at the same speed as the car. If the driver makes the car suddenly stop or crashes it, the driver and passengers continue at the same speed the car was going before it stopped. A seatbelt applies an opposing force to the driver and passengers to prevent them from falling out or making contact with the interior of the car. Seatbelts are known as primary restraint systems (PRSs), because of their vital role in occupant safety. Seatbelts are arguably the single most important safety feature in a vehicle and when properly designed and utilized save countless lives. However, when they fail to perform as intended or malfunction thanks to a defect in their design or manufacturing, tragic results can occur. Figure 12.4 shows typical seatbelts used in automotive industry. 12.3.4.1 Manufacturing Process
In seatbelt manufacture, the yarn specification is a frequently debated issue, especially the linear density of the yarn and its constituent filaments. The debate primarily concerns the threads whose strength is most critical in the event of a crash. The weft yarns have less influence on the mechanical performance of the belt than the finer filaments do, and are more prone to contamination and the incidence of yarn impurities tends to be greater. In comparison, coarser filaments produces webbing with superior abrasion resistance and improved lateral tear strength. Moreover, when the linear density of individual filaments rises, the translational efficiency also rises. The choice between twisted and untwisted yarn is another debatable issue and also equally unsettled. Untwisted yarns yield product and cost advantages over their twisted rivals. The untwisted yarns give softer and more flexible webbing as they are thinner
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Figure 12.4 Typical seatbelts used in automotive industry.
and smoother, because the untwisted filaments pack themselves closer together. Original seatbelt webbing was woven on shuttle looms, around 1959. These looms were capable of delivering up to 200 weft insertions per minute from small weft supplies, which frequently needed replenishing. Since 1975, most seatbelt webbing has been made on needle looms which run at considerably higher speeds. The needle loom is shuttle less and is capable of delivering over 1000 picks per minute or even more. In the needle loom, weft is inserted from one side of the warp sheet and here a selvedge is formed. The other side of the webbing is held by an auxiliary needle which manipulates a binder and a lock thread. Once these threads are combined with the weft yarn, a run‐proof selvedge is created. Special care must be taken when constructing the selvedge to ensure it is abrasion‐resistant. It is equally important to ensure that the selvedge is soft and comfortable to wear. 12.3.4.2 Seatbelt Material Properties
Seatbelt webbing material is normally made of nylon or PES and woven from about 300 warp strands and one weft strand. The width of the webbing is about 48 mm and has a tensile strength sufficient to support approximately three tonnes. Most seatbelt webbing is made from PES because it is a high quality material that has high strength (tenacity almost 10 g/den). They are more than just a strap that passengers wrap on their bodies. The following are some of the qualities that webbing made of PES has: ●● ●● ●● ●● ●●
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Very high strength tenacity: up to 10 g/den. Elongation: up to 25% at break. Abrasion: excellent resistance to abrasion. Moisture: has a very low regain of 0.4%, making it feel damp very quickly. Temperature: the melting point is around 260 °C and will withstand temperatures above 180 °C for some time. It will lose some strength if kept at high temperature for extended periods. PES is very good in low temperatures, increasing in strength and reducing elongation. PES webbing is difficult to ignite, and tightly woven structures do not burn quickly. PES has excellent resistance to sunlight (one of the best for outdoor use). PES is resistant to most common chemicals.
12.3 Application Areas of Automotive Textiles
After the belt is made and finished, it should have certain properties to meet safety standards. These properties are: ●● ●● ●● ●● ●● ●● ●● ●●
Good retraction behaviour. High load bearing capacity (up to 1500 kg). Abrasion resistance. Resistance to heat. Capable of being removed and put back in place. UV resistance. Lightweight. Flexibility and extensibility.
12.3.5 Airbags In an automobile, in addition to comfort, aesthetics, speed, mileage, durability and efficiency, safety is a priority for the passengers. Airbags work as a supplementary safety device for an occupant who is correctly restrained with a seatbelt. In the event of a collision, seatbelts hold the occupant securely in place and the airbags inflate instantly to cushion the passenger with a gas filled pillow. The airbag is a part of an inflatable restraint system known as an air cushion restraint system (ACRS) or airbag supplemental restraint system (ASRS). All modern vehicles incorporate a wide variety of airbags in the form of driver, front passenger, side impact, and rollover airbags in various side and frontal locations. The airbags work as a supplement to other active restraints (i.e. seatbelts). Airbags are passive devices, as no action by the vehicle occupant is required to activate or use them. On the other hand, seatbelts are considered active devices, as the vehicle occupant must act to enable them. Figure 12.5 shows some examples of airbags used in the automotive industry. Airbags constitute about 3.7% of the textiles used in a car. It is made from nylon 6,6 of lighter linear density and is normally coated with silicone. The amount of fabric used per
Figure 12.5 Airbags used in automotive industry.
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airbag is approximately 1.8 m2. It is usually located in both the front and the back side of the vehicle and can be classified into three categories based on positioning: ●● ●● ●●
roof mounted airbags. door mounted airbags. seat mounted airbags.
Nowadays, all airbags (driver, passenger, side, and others) remain either coated or uncoated, like their predecessors. However, the performance criteria are gradually becoming more stringent. The coated or uncoated airbags developed in the last two decades are significantly superior compared to earlier designs, as they are lighter in weight, have improved performance and ageing characteristics, and have better packability. However, the market share of coated airbags is gradually reducing, owing to cost and environmental issues. The cost reduction of uncoated fabrics has been realized by the reduced material content and reduced cost of manufacture. In the industry, the coating process is well known for being extremely cost sensitive, for which reason the traditional coated fabrics are not preferred against alternative materials. Another reason for this can be attributed to technical developments, which enable the specification requirements to be obtained without any coating. In addition, today’s uncoated airbag fabrics are better engineered with respect to the construction and yard utilization, which overcomes the problems of poor seam strength, bulkiness, gas leakage, and variation of permeability [16–23]. One type of airbag material may not be practical for all applications, owing to the associated factors such as steering wheel design (pan size), inflator type (azide, gas assist, or liquid), inflator aggressiveness, and bag type (driver, passenger, side, knee‐bolster, or others). Hence, several airbag designs exist with different automobile manufacturers. 12.3.5.1 Fabrics for Airbags
Almost all the airbags manufactured world‐ide are from woven fabrics of nylon 6,6 yarns. The other structures used are knitted and nonwoven. The airbag fabric is required to have the following properties: ●● ●● ●● ●● ●● ●● ●● ●●
High tensile strength. High tear and bursting strength. Good heat stability. Good ageing characteristics. High energy absorption features. Good coating adhesion. Functionality at extreme hot and cold conditions. Good packability.
The early stage airbag fabrics were coarse and heavy. The surface of the airbag made from this fabric was coated by relatively heavy neoprene coating [17]. In addition, the coated surface was heavily covered with talc to facilitate handling and packaging as well as to prevent the possibility of blocking between fabric layers during folded storage of the airbag. The coated airbag fabric was heavy with a weight as high as 500 gsm. Therefore, the early airbags needed a large module for storage and deployment. The subsequent fabrics were modified to be lighter weight, cheaper, and with improved performance [24–30].
12.3 Application Areas of Automotive Textiles
12.3.5.2 Future Trends
The future of airbags is promising, as there are a wide range of applications ranging from motorcycle helmets to aircraft seating. The airbags in future will be more economical, owing to developments in the technology and availability of advanced materials. The focus of the airbags from the very early stage of development is longer service life, smaller package size, cost reduction, and improved occupant safety. Owing to the sharp increases in the prices of new automobiles, car owners try to keep their vehicles longer before trading them in. As per the legislation, the legal ramifications of failed safety devices can be ruinous. Hence, the safety restraint systems should perform longer even under more adverse conditions. The airbags in most recent cars use and in future will be using a range of intelligent sensing elements to ensure the severity of a crash before the deployment. This reduces the likelihood of airbags deploying in the case of minor crashes. The first‐generation airbags were of a larger size. The design of smaller cars provided a lower amount of interior space to accommodate these airbags. However, technological developments helped to reduce the size of the airbags, while ensuring the same level of protection for the reduced interior. It is an established fact that airbag deployment causes minor injuries, such as bruises, abrasions, scratches, contusions, and burns. However, modern airbags are designed with lighter, softer, and smoother fabrics with a lower surface friction to reduce bruises and abrasions. The main focus is to reduce secondary injury risks while improving primary injury protection. The airbag triggering algorithms used in recent vehicles are becoming much more precise and complex. They try to reduce unnecessary deployments and to adapt the deployment speed to the crash conditions. The algorithms are considered valuable intellectual property. Experimental algorithms may take into account such factors as the weight of the occupant, the seat location, seatbelt use, and even attempt to determine whether a baby seat is present. In future airbags, fuzzy logic controllers should be used to address the complexity of restraint system. The system should include occupant detection sensors, weight sensors both for driver and passenger, a distributed crash sensor arrangement, a dual stage airbag for both the driver and passenger, and a micro‐ controller implementing a fuzzy logic algorithm. Crash sensors can be fitted in several positions on the front and rear of the vehicle, which can monitor the airbag deployment. Future airbags will be smaller and lighter in weight, with more integrated systems and improved sensors. Tomorrow’s airbag systems will be smart adaptive restraint systems that can detect the size and position of the occupant, out‐of‐position conditions, distance between the occupant and the airbag module, as well as the severity of the crash [31]. Depending on these conditions, the airbag deployment (i.e. the height and velocity) can be tailored or the airbag can be completely disabled. The future airbags will focus on the following parameters: ●● ●● ●●
●● ●●
Lighter fabrics with good packability and use of cold inflator technology. New coating polymers. New application for airbags: such as side curtain, rollover protection. external pedestrian protection, and other special areas. Consolidation/integration of supply chain. Combinations of nonwovens and film.
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Newer designs of airbags need to hold the air for longer with a reduced level of coating material. Hence, the coating should provide effective air retention as well as prevent edge combing in order to sufficiently protect the driver and the passenger. 12.3.6 Insulating Felts It is used for acoustic and thermal insulation in automobiles and is often known as an NVH product. It is the main constituent of bonnet lines, outer dash, wheelhouse, and outer floor under shield. It functions as noise reduction both inside and outside the car. Fabric used in this case is made of 100% PES using nonwoven technical textiles. Based on the nonwoven technique used for PES, insulating felts are of three types: ●● ●● ●●
needle‐punched. phenolic resin bonded. thermoplastic.
12.3.7 Sun Visor These are located just above the windscreen in the interior of four‐wheelers. Their main function is to block the sunlight that enters through the windscreen. There are generally two sun visors in a car: one for the driver and the other for the passenger. It is made up of three components: ●● ●● ●●
Synthetic backbone made of polypropylene/kenaf fibres. Scrim composed of coarse woven reinforcement fabric. Upholstery typically made of artificial leather.
12.3.8 Helmet Helmets are used to prevent the shock of a crash. Usually, a motorbike helmet’s internal layer is made up of polystyrene or polypropylene foam with a cushion and the external layer of plastic glass and other synthetic fibres like acrylonitrile butadiene styrene (ABS), which is very hard in nature. The function of the helmet is to absorb the shock of a crash and thus put a stop to major injury to the brain, rather than preventing head and facial injuries. 12.3.9 Car Outer Body Covers The outer body cover is used to cover the whole car, or any kind of vehicle, to protect it from dust and rain, etc. Generally, covers are made from HDPE (high density polyethylene), PVC, reinforced cotton material, nylon and canvas covers. 12.3.10 Tyre Cord Fabric Tyre cord fabric is used to provide strength and support to a tyre. It is prepared from fabric of high tenacity and continuous filament yarn. The fabric is made by twisting and plying the filaments. Both nylon 6 and nylon 6,6 are used to produce tyre cord fabric.
12.3 Application Areas of Automotive Textiles
Some typical denier and ply types of nylon 6 used for this fabric are 840/2, 1260/2, 1260/3, 1680/2, and 1890/2 with a 6 denier per filament (dpf of 6). Typical tyre cord fabric is shown in Figure 12.6. The properties required for fabric of nylon tyre cord are: ●● ●● ●● ●●
high strength. fatigue‐resistant. impact‐resistant. high adhesion.
12.3.11 Tyres Textile materials such as viscose, glass, and steel cords are used as reinforcement materials in the manufacture of tyre cord. They provide dimensional stability as well as reinforcement. Dimensional stability is an essential requirement for tyres. There are many textile components in a tyre such as casting belt breaker fabric, bead wrapping fabric, chafer fabric, filler fabric, tyre cord fabric, etc. The fibres generally used for tyre cords are high tenacity filament yarns of nylon 6, nylon 6,6, PES, and viscose. Nylon 6 is most commonly used in tyre cord manufacturing. Plied cotton yarn was originally used for the manufacture of tyre cord fabric. It was preferred as it had natural compatibility towards rubber. Kevlar, glass, or steel are used in the manufacture of cords for the breaker or belt layer. They are preferred because of their high modulus. Viscose is the commonly used fibre in radial ply tyre casing. Carbon fires are also finding application in the form of reinforcing material. 12.3.12 Filters and Engine Compartment Items The important components of a car engine are its hoses, belts, and linens. They are reinforced with textile materials. Automotive filters are largely made of textiles. The air filter and oil filter are two examples of the types of filters to be found. The function of these filters is to filter the fluid before it enters the engine because certain delicate machine components may be destroyed if dust particles enter the engine.
Figure 12.6 Typical tyre cord fabric.
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Paper is used in many applications, such as the oil filter and carburettor air filter. Nowadays, nonwovens are used in some cars for their filter application. The latest advanced filters combine mechanical filtering through polypropylene nonwoven electret fabric with adsorption by activated carbon. Filter fabric is arranged in a pleated form to maximize the surface area with minimum airflow resistance. The nonwoven filter fabric must be strong. When it is wet, it has to be odour‐free, resistant to microorganisms, and resistant to extremes of temperature. A woven fabric structure is also used in some of the applications, but nonwoven textile fabrics are the most widely used textile filtration media, and they have good filtration efficiency. This is mainly due to their complex structures, which are as a result of a 3D network of fibres and their considerable thickness. Different types of finishing – like calendaring, raising, chemical treatments, and special surface treatments – are used to improve the filter efficiency of the fabric. Type of Filter Media and Applications ●● ●● ●● ●●
●● ●● ●● ●● ●● ●● ●●
Carburettor air filters: wet, dry, needled, or spunbonded. Engine oil filters: resin impregnated wet laid nonwovens. Fuel tank filters: activated carbon. Cabin interior filters: electrostatically charged fibre media, nonwoven, activated carbon. Diesel/soot filters: ceramic materials. ABS wheel/brake filters: metal or fibre woven screens. Power steering filters: mainly screen fabrics. Transmission filters: woven fabrics or needle felts. Wiper washer screen filters: woven fabrics. Air conditioning recirculation filters: nonwoven/activated carbon. Crank case breather filters: nonwovens.
The filtration efficiency of a particular filter depends upon the fibre structure, yarn structure, fabric structure, weight per unit area, porosity, and surface characteristics of the fibre. By making necessary changes in the fibre, yarn, or fabric level, one can alter the filtration efficiency and the properties of the filter fabric. 12.3.13 Acoustic Textiles The use of acoustic textiles in the transportation industry currently represents the most important application of textiles in the world. In general, acoustic textiles are used in the transportation industry to reduce interior noise and vibration and improve the sensation of ride comfort for passengers. Interior noise is currently a competitive quality characteristic of every mode of transport facility, and in particular for automobiles. Although interior noise lowers the comfort feeling inside a vehicle, it also induces fatigue and may reduce driving safety. In the case of automobiles, sound is propagated through the air and by vibration of the car body. There are three basic mechanisms for reducing it: by absorption, by claiming, and by isolation or insulation. In general, a thick piece of material will absorb more sound than a thinner piece of the same material. And various permutations of the
12.4 Textile Composites for Automobiles
number of layers and the type of materials used can be employed to reduce noise and dampen vibrations experienced inside the vehicle. These layers are: ●●
●●
●●
Top decorative layer: tufted bulked continuous filament (BCF) nylon or needle‐ punched PES or polypropylene‐back acrylic. Thermoforming layer: polythene powder. Mouldable fibre ethylene‐vinyl acetate (EVA) or a further thick layer of compounded styrene‐butadiene rubber (SBR) later. Acoustic layers: heavy layers of EPDM (ethylene propylene diene monomer) rubber, shoddy fibres, or polyurethane foam. These layers are generally made up by being filled with lots of small pieces of material, which is a time consuming process and it produces an inferior insulation performance than a continuous layer. In some vehicles this insulation layer is formed directly on the back of the pre‐formed carpet itself by back injection moulding using polyurethane foam.
Eliminating unwanted noise in the passenger compartments of vehicles is important to automobile manufacturers. Several methods are presently employed to reduce noise and its sources. One of the most popular methods uses sound absorbing materials attached to various components such as floor coverings, package trays, door panels, headliners, and trunk liners. Natural fibres are also considered noise absorbing materials that are renewable and biodegradable, making them an attractive choice for the automobile industry. Control of the interior frequency response of a car can be achieved by modifying the cabin geometry so that high acoustic resonance peaks are reduced and the interior frequency response tends to be linear. However, the new design of automobile cabin shapes is usually limited, and the acoustic resonances are often damped through the use of sound absorption. The addition of acoustic damping in the form of a sound absorbing material on the surfaces greatly affects the acoustic character of the passenger space. Research work reveals that the addition of a thick nonwoven textile lining significantly reduces the resonant response peaks of the acoustic modes at mid‐ and high frequencies. The number of cars exceeds by many times the total number of other means of transport produced every year in the world. The need to reduce noise in the passenger cabin of a car is of paramount importance resulting in the widespread use of acoustic textiles. A variety of sources contribute to the interior noise of a vehicle, which can be structure‐ borne or airborne sound. Acoustic textiles used to control noise in vehicles must provide airborne transmission reduction, damping, and sound absorption. However, the use of acoustic textiles in vehicles is not only dependent on their acoustic properties but also on additional characteristics. The selection of a particular material is also determined by its ratio between performance and cost. Acoustic textiles employed to reduce noise and vibrations are used either individually or as components of complex composite materials, which is an interesting area of research [1, 4, 32–36].
12.4 Textile Composites for Automobiles Composite materials have been used for nonstructural car parts since the 1950s. In recent decades, automotive interiors have been increasingly produced from thermoplastics, with semi‐structural parts now widely made from thermoset composites. In
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the aircraft, boat building, and racing/sports car sectors, the use of carbon fibre composites, in particular, has grown rapidly in recent years. In the aerospace industry, for example, carbon fibre based composite parts in the aircraft body now account for more than 50% of the total weight of the latest models, such as the Airbus A380 and Boeing 787 Dreamliner. In general, composite materials are lighter in weight than steel or aluminium, which provides engineers with a lightweight alternative for use in a wide range of automotive structures and components. High strength and lighter weight leading to better fuel efficiency are the key benefits that composites offer the automotive sector; greater design flexibility, enhanced aesthetics, and improved durability are other advantages. Amongst all materials, composite materials have the potential to replace widely used steel and aluminium, and often this will mean better performance. Replacing steel components with composite components can save 60–80% in component weight, and 20–50% weight by replacing aluminium parts. There are many other advantages of using composites over metals in the advanced transport sector, such as in aerospace applications. Monolithic metals and their alloys cannot always meet the demands of today’s advanced technologies. For example, trusses and benches used in satellites need to be dimensionally stable in space during temperature changes between −160 and 93.3 °C. 12.4.1 Textile Structural Composites Textile structural composites (TSCs) are composites reinforced by textile structures dedicated for load bearing applications. These composites must have textile as well as resin, metal, or ceramic components and must be capable of withstanding the primary and secondary load to the basic framework. The primary work in TSCs was initiated in the 1970s and subsequently composite materials became common engineering materials. Today, composites are the materials of choice for many engineering applications, including automobiles, aerospace, marine, and many other advanced fields. The principal objective of structural composites envisages the utilization of textile structures in composite manufacturing in order to achieve: ●● ●● ●●
lightweight composites. load bearing composites. advanced composites.
And the main advantage of TSCs is utilization of advantages of textile structure in addition to textile materials in composites so as to obtain: ●● ●● ●● ●● ●●
High strength (strength/weight ratio). Structural anisotropy. Endless textile structures, such as woven, knitted, braided, etc. Numerous shapes and geometry. Using existing textile manufacturing technologies.
‘Advanced composite materials’ refers to those composite materials developed and used in the aerospace industries. They usually consist of high performance fibres as reinforcing phases and polymers or metals as matrices. But there are several reasons why advanced composites have not been more widely adopted by the automotive industry. The key stumbling block is price, while the availability and future supply of carbon
12.4 Textile Composites for Automobiles
fibres is another issue that is being addressed by fibre producers. Many companies, from carbon fibre suppliers through to original equipment manufacturers (OEMs), are now entering the market, with a wave of partnerships and joint ventures announced recently. Meanwhile, there are ongoing attempts to replace glass fibre with natural fibres, such as flax and hemp. 12.4.2 Application of Structural Composites In the automotive industry, there is an increasing demand for higher quality exterior panels with better functional properties and reduced weight. The weight of an automobile is directly related to fuel efficiency and emissions. Weight reduction is one of the main problems of new vehicle design. In modern daily life, composites are used because they have less weight and more strength than conventional metals. Therefore, TSCs are a good substitute for advanced automotive structural applications, owing to their high specific mechanical properties and other properties like corrosion‐free low maintenance, especially fatigue resistance. Textile composites are widely used in many different areas of transportation applications, such as aircraft, marine, and automotive, and are available in various structures. The most important factor in fabricating these composites is to achieve better structure in automotive design, where aesthetics and weight play an important role. In one study, theoretical analysis was done to examine the advantage of TSCs over conventional metals in terms of their mechanical, weight reduction, and fuel saving properties. A comparative analysis was also done between the mechanical properties of composites with different textile reinforcing structures like chopped fibres, unidirectional (UD) fabric, 2D fabric, and 3D orthogonal fabric. From these analysis, it could be concluded that TSCs have good potential to replace metals in automobile body panels. A comparison has been done between composites with a 3D orthogonal structure preform of various stuffer‐to‐binder ratios. The tensile properties of composite and metal are compared to ensure the potential of TSCs to replace conventional metal [37]. 12.4.3 An Engineered Alternative Recent analysis of the automotive industry has identified that the textile industry is becoming an increasingly important part of the global automotive supply chain, because textile products are now used so widely for interior, exterior, and even suspension parts and components of automobiles. The automotive industry is increasingly demanding higher quality exterior panels with better functional properties and reduced weight. One of the main reasons for this demand is based on the fact that 3D woven composites technology innovations have the potential to replace the existing technology. Light vehicles represent an important market for plastic resins and composites. The new role of the textile industry could make important changes in the automotive supply chain industry, such as changes in the size of the supply chain, the time to market, and the position of the textile industry in the automotive supply chain structure. Textile composites are widely used in many different areas of transportation applications – such as aircraft, marine, and automotive – and are available in various structures. The process of manufacturing thick 3D orthogonal woven composites is capable of weaving thick (up to 7.6 cm) preforms from practically any fibre. The 3D woven preforms are
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conformable and can be easily moulded to complex shapes and made into high performance composite materials. Typically, composites are up to 40% lighter than steel parts of equal strength. Structural composites were first used in a mass‐produced vehicle on the closure panels of the 1953 Corvette, and their use has grown significantly during last decades. The average light vehicle contains 171 kg of plastics and composites (9.4% of total vehicle weight). Lightweight, fibre‐reinforced composites made primarily of polypropylene and fibreglass are steadily being adopted by the automotive market, based on their performance properties, and their lightweight and cost savings characteristics. High performance textiles for automotive applications usually consist of high performance fibres, yarns, or rovings. Typical materials are carbon, glass, and aramid. In most cases, twisted and untwisted multifilaments, the so‐called rovings, are used. Twisting the roving slightly improves its processability significantly and decreases the risk of filament damage. For the use of textile structures as reinforcement in composites, it is often important to realize a yarn position that is as straight as possible, because noncrimped fibres can bear the highest loads and induce the highest stiffness. In other applications fibre crimp is needed, for example to achieve high damage tolerance or high energy absorption. Therefore, each application requires its own textile structure. 12.4.4 Advantages of Composites Composites have many advantages over traditional materials, such as their relatively high strength and low weight, excellent corrosion resistance, thermal properties and dimensional stability, and their greater resistance to impact, fatigue, and other static and dynamic loads that car structures are subjected to. These advantages increase the performance of cars and lead to greater safety and less energy consumption. It should be noted that car performance is affected not only by engine horsepower but also by other important parameters such as the weight‐to‐ horsepower ratio and the good distribution of weight. Moreover, reducing the weight of vehicles reduces their fuel consumption. It has been estimated that fuel economy improves by 7% for every 10% of weight reduction from a vehicle’s total weight. It is reported that using carbon fibre composites instead of traditional materials in the body and chassis car parts could reduce a car’s weight by up to 50%. In addition, it means for every kilogram of weight reduced in a vehicle, there is about 20 kg of carbon dioxide reduction [37].
12.5 3D Fabrics for Automotive Applications Using new possibilities and improved machine technology, spacer fabrics have already become an established feature of many areas. Unlike regular 2D fabrics, spacer uses two separate fabrics, joined by microfilament yarn, to create a breathable, 3D free space between layers. Spacer textiles in upholstery are made from warp knitted (double‐ Raschel machine) or (circular knitting machine) fabrics. Spacers are also made from two separate textile layers which are connected by stiff spacer yarns so as to achieve the desired resilience. Figure 12.7 shows the 3D spacer knitted fabric production.
12.5 3D Fabrics for Automotive Applications
Figure 12.7 3D spacer knitted fabric production.
Monofilaments are mainly used for spacer yarns, also called pile threads. The height of the structure is governed by the distance of the two needle bars of the Raschel machine and by the distance between the cylinder and rib discs in the circular knitting machine. The force that is necessary to keep the two textile layers apart depends on the material, thickness, and structural integration of the spacer yarns (monofilaments) into the basic layers. Spacer structures have an elastic pressure behaviour: by pressing on the surface, they are compressed. When the pressure is released, they relax in an elastic way. The space between the two layers is an air‐filled cavity from which the air is removed during compression, and into which air is sucked during decompression. Unlike foam constructions, these textile constructions are able to breath. Figure 12.8 shows some examples of 3D stitch bonded nonwovens. 12.5.1 Applications Areas Transportation industries are willing to replace metallic materials by composites materials on structural parts subjected to severe mechanical solicitations with equal mechanical performances. Composite materials are proposed because they are able to provide credible answers to the optimization of large and thick structural parts. Their good strength‐to‐weight ratio and especially their anisotropy, which can be adapted to the mechanical solicitation of the structure, are particularly interesting. Three‐dimensional warp interlock fabrics can be used as fibrous reinforcement in composite material. 6 2
5 3
1
4 7 8 Figure 12.8 3D stitch bonded nonwovens. 1. Stitching needle, 2. Closing wire, 3. Knock over bit, 4. Support, 5. Oscillating, stuffing unit, 6. Nonwoven, 7. Fibre loop, 8. Pole fibre fold.
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Recently, a general definition of the 3D warp interlock fabric was proposed for the scientific community in order to take into account all the main parameters of this 3D woven fabric architecture. Thus, the complexity of the 3D warp interlock fabric geometry could be better described and this definition could help designers understand the influence of product parameters on residual mechanical properties. Composite materials made with commingled E‐glass/polypropylene yarns inserted in 3D warp interlock fabric have been one of the studied solutions to cope with fast and low cost production requirements of the European Union (EU) research project MAPICC 3D. To obtain a final 3D shape of the composite part, the forming of the 3D warp interlock preforms made with commingled yarns can be performed at room temperature on dedicated mould. Then a thermo‐compressing step is applied to the 3D formed fabric in order to melt the polypropylene filaments all around the E‐glass filaments to ensure a complete consolidation of the composite material. Different solutions have been developed according to the different transportation area requirements: an oil container for the automotive application (Auto‐Mapicc), a seat reinforcement for the truck application (Truck‐Mapicc), a tubular cross for the rail application (Rail‐Mapicc), and an F‐preform for the aeronautic application (Aero‐Mapicc). All of these solutions tend to replace existing metallic parts by lightweight composite materials, including fibrous reinforcement as a 3D warp interlock fabric. The three ground transportation applications are using commingled E‐glass; polypropylene yarns and aeronautic application is based on qualified carbon yarns and epoxy resin. 12.5.2 3D Woven Structures for Reinforcements Processes for the production of 3D textile structures often allow the realization of textile preforms in one production step. Many production processes to create 3D textiles have been invented over the last two decades and development has not ceased yet. The most relevant technologies are described below [4, 38–44]. Different types of 3D woven solid structures are developed during last decade. Among the solid structures, orthogonal, warp interlock, and angle interlock are most prominent weave architecture, as shown in Figure 12.9a–c, respectively. Table 12.1 gives an overview of some common types of 3D structures with the type of weaving machine and process used to produce them.One kind of 3D fabric structure is the so‐called multi‐layer woven fabric. This is manufactured by the composition of several fabric layers without any spacing between. The layers are fixed by interlocking or warp knitting. The yarns are oriented in a 0° and 90° direction, and yarns in a z‐direction are variable. Multilayer fabrics can be draped well, having very good elongation behaviour and good tensile, compression, and bending stability. True 3D woven fabrics are manufactured by inserting two picks with double shed opening, being perpendicular to each other. The yarns are fed in a 0° and 90° direction and an additional yarn is positioned orthogonally towards the two others in a z‐direction. Three‐dimensional fabrics feature quasi‐isotropic properties, a high tensile and compression strength, as well as a good bending stability and a very good impact behaviour. The distribution of the reinforcement fibres is very uniform in all three dimensions. The drapability and the elongation behaviour of 3D fabrics, however, is very poor. Three‐dimensional fabrics are applied in fibre‐reinforced composites with high thermal impacts as well as for structural parts for cars and aircraft.
12.5 3D Fabrics for Automotive Applications
(a)
(b)
(c)
Figure 12.9 3D solid structures: (a) orthogonal; (b) warp interlock; and (c) angle interlock. Table 12.1 Overview of 3D structures with the type of weaving machine and process. S. No
Name
Weaving device
Set of yarns involved
Weaving process
1
Multilayer interlaced 3D fabric
Conventional 2D waving device
Multilayer warp yarns (Z) Weft yarns (X)
Two orthogonal set of yarns interlaced together Ex: angle and warp interlock
2
Multilayer noninterlaced 3D fabric
Modified 2D weaving machine
Multilayer warp yarns (Z) Weft yarns (X) Binder warp yarns (Y)
Three sets of orthogonal yarns bound together but not interlaced
3
Fully interlaced 3D fabric
Specifically designed 3D weaving machine
Multilayer warp yarns (Z) Weft yarns in row (X) Weft yarns in column (Y)
Three orthogonal sets of yarn are completely interlaced together
4
Nonwoven, noninterlaced 3D fabric Noobing
Specially designed device
Multilayer warp yarns (Z) Weft yarns in row (X) Weft yarns in column (Y)
Three orthogonal sets of yarns together with no interlacing (weaving), interloping (knitting), or intertwining (braiding) The fabric is held together by a special binding process
Woven spacer fabrics also have a 3D structure. They are manufactured by weaving in upright pile warps, and their properties are comparable to those of multilayer fabrics, but their drapability is poor. The distance between the two layers can be adjusted individually. These textiles show a high resistance to perforation. They are applied in sandwich structures, for example in composite lightweight design applications [45, 46]. 12.5.3 Advantages of 3D Woven Preforms In the automotive industry, various kinds of composites have many advantages in comparison with heavy metal materials. The actual material cost of a composite is higher than the cost for a comparable metal material, but lifetime analysis shows that savings in fuel over the life time of the vehicle significantly exceed the extra cost of manufacturing. [4]. There are
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several significant benefits from composites’ use in automotive industry. The main benefits are: less bulk (this creates more useful space), anticorrosion, dent resistance, high rigidity, and strength. Composites also allow more moulding freedom, which is very important in creating aerodynamic shapes and in the integration of many different components (a single composite can replace several individual metal parts which have to be joined together). To perform effectively in the case of a car crash, vehicle components have to have high energy absorption properties. While energy absorption in metal structures is achieved by plastic deformation, in composites it relies on a material’s diffuse fracture. For that reason, composites have a better capacity to absorb kinetic energy compared to metal parts [38]. Three‐dimensional woven composites have many advantages in comparison with different composites technologies. First of all, the thickness of 3D woven preform eliminates multiple plies of 2D woven preforms and at the same time dramatically reduces labour time and decreases the costs associated with building up the desired thickness for constructing a given part. One or a handful of 3D woven thick fabric plies replaces dozens or hundreds of 2D woven fabric plies needed to achieve the required thickness of the material and eliminates every layer’s resin pre‐impregnation process and lamination process. Compared with 2D woven laminated composites, 3D woven composites demonstrate higher through‐ thickness and interlaminar properties because of their integrated structure in the presence of orthogonal constituents. Unlike very thick laminates from multiple 2D woven fabric reinforcements, 3D woven composites can be easily machined into components in the same fashion as aluminium or steel. A thick composite based on a single ply fabric preform will not delaminate and will provide exceptional mechanical performance [39]. The unique reinforcement geometry of 3D orthogonally woven fabric‐reinforced composites (z‐yarns act as capillary channels to transfer resin into the preform interior from the outer surface) creates significantly improved resin infusion and resin transfer moulding methods with much higher resin penetration speeds during composite processing. They wet out faster in both open and closed moulding, improving quality, reducing moulding times, and facilitating migration to vacuum resin infusion. Two‐dimensional woven fabrics have an inherent crimp in the interlaced yarns that is undesirable for maximum composite properties. The absence of interlacing between warp and pick yarns allows 3D orthogonal woven panels to bend and internally shear easily without jamming and buckling within in‐plain reinforcement that allows an easier moulding process for different shaped parts and also leads to stronger and lighter structures. Even 2D woven fabric composites are characterized by superior impact resistance and damage tolerance characteristics and high fracture toughness. However, 3D orthogonal woven composites have an advantage in impact tolerance compared with 2D woven laminates. Z‐yarns, connecting different layers of warps and picks, create higher interlaminar shear strength, and in this way dramatically improve impact damage tolerance. Connected layers eliminate the risk of composite delamination as a failure mode, so a more effective load transfer can be achieved [47, 48].
12.6 Comfort Properties of Automotive Interior Most of the developments of components, parts, pieces, and materials used in a car are primarily governed by comfort, functionality, safety, economy, and ecology. Comfort is the first criterion that values the customer. In the case of a car’s upholstery, both
12.6 Comfort Properties of Automotive Interior
psychological comfort (the aesthetic aspects) and thermo‐physiological comfort (captured by the touch and feel of the fabric) are considered. Thermal comfort while sitting is evaluated by the ‘cold–hot’ sensation. Functionality and material safety criteria are captured during use of the vehicle, by means of wear, seat ventilation, the internal environment, ease of care, etc. In fact, comfort in a car is a complex phenomenon and comprises different aspects, such as noise, driving behaviour, and ease of handling, as well as the most important factor influencing passenger convenience: thermal comfort. A particularly important aspect of vehicle comfort is the seats. Seats do not only have to have an attractive design or meet specific design criteria for safety reasons; they must also have optimum comfort properties. But seat comfort is much more than just passenger convenience. Scientific findings show that the performance of a driver over long distances significantly decreases if the car seats do not support posture and heat balance as required. This leads to exhaustion and loss of concentration, which, in extreme cases, could result in serious accidents. In addition to the ergonomic considerations of comfort, the climatic or thermo‐physiological comfort of the seat is of particular importance. This indicates whether the seat is able to support the thermoregulation of the body via heat and moisture transport [49–52]. 12.6.1 Parameters of Seating Comfort From the thermo‐physiological point of view, seat comfort comprises four parameters: ●●
●●
●●
●●
The initial heat flow following the first contact with the seat, i.e. the sensation of warmth or cold in the first few minutes or even seconds after entering the car. The dry heat flow on long journeys, i.e. the amount of body heat transferred by the seat. The ability, known as breathability, to transfer sweat away from the body. In so‐called normal sitting situations, there is no perceptible perspiration, but, nevertheless, the human body constantly releases moisture (so‐called insensible perspiration), which has to be taken away from the body. In the event of heavy perspiration (a car in summer heat, stressful traffic situations) the ability to absorb perspiration without the seat feeling damp [49].
12.6.2 Warmth Sensation About 25% of human body remains in contact with the car seat and the car seat acts as an extra layer of clothing, thus the parameter of clothing comfort is the same for car seat thermal comfort as well. The passenger has their first thermal impression of a car seat upon entering the vehicle. This initial perception of warmth after sitting depends on the thermal absorptivity of the car seat. It is affected by the heat capacity of the car seat material. Heat capacity is the amount of heat required to raise its temperature by 1 °C. Heat capacity varies with the mass of the cushion and the type of material. Thermal conductivity is also another parameter of thermal absorptivity and it should be as low as possible; otherwise, a car seat feels too cold in winter or too hot in summer. Although this initial feeling may last only a few minutes, it is nevertheless very important for the user’s acceptance, as it is repeated frequently. If a car is used every day during the winter time and each morning the driver is dissatisfied when entering the
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car, acceptance can be significantly decreased. During long journeys, it is favourable if the seat offers a high steady state heat flow, to minimize the tendency to sweat, whereas for the initial perception a low heat flux is required. Hence, a conflict arises between these two scenarios. This conflict can be overcome, because the cover, which determines the initial perception, has only a minor influence over the steady state heat flux, which is mainly determined by the thermal insulation of the seat. Owing to its greater thickness and, hence, higher thermal insulation in comparison to the cover, the cushion becomes the dominant factor. On the other hand, the heat flux is also dependent on the ventilation in the seat and between the seat and the passenger. Ventilation itself is determined by the design of the seat (side supports, surface grooves), the elasticity and air permeability of the cushion, and, if present, a fan to enforce ventilation. For car seats with heating, the dominant seat component is the cover. Other than the thermal properties of the car seat cover, heating power and its position are of great importance. As a common material used in car seats, foams are poor conductors of heat and have a low heat capacity. A thin layer of foam (plus cover) warms up to skin temperature when the driver sits on it but does not draw much heat from the body’s tissues. In warm environments, or during physical exercise, the body attempts to lose heat but is prevented from doing so in the buttocks area and back rest, owing to the insulating foam of the cushion. This region may therefore begin to heat, resulting in uncomfortable dampness. A car seat with an impermeable foam can increase the skin temperature by 10 °C in two hours. And this increase will cause sweating [49, 51–56]. 12.6.3 Moisture Sensation The moisture sensation of the passenger is very important for perceived overall seat comfort. In order to achieve a dry microclimate, the ability, known as breathability, of the seat to transport any perspiration formed away from the body is crucial. Not only under warm summer conditions is good water vapour transport necessary but even when there is no perceptible perspiration. The human body constantly releases moisture, the so‐called insensible perspiration. As the skin is not totally water vapour tight, our body loses at least 30 g of moisture per hour. Because a car seat covers large areas of the body, the seat has to manage a large part of the perspiration formed, and, hence, a considerable amount of moisture. Moisture accumulation results in discomfort and, in some cases, an increased risk of soft tissue damage. Many factors determine the causes and prevention of moisture accumulation. The generation of excessive quantities of heat can cause sweating. Sweat is normally generated to assist in the thermoregulation of the body by the evaporation of moisture to cool the surface of the skin. Normally, sweating is suppressed locally by pressure. However, sweating can occur in an uncontrolled manner, independent of thermoregulation, as in insensible perspiration. Poor air exchange is one of the reasons for moisture accumulation If there is a poor exchange of air in the supported area and the supported area is thermally insulated by the cushion, the interface temperature can exceed 38 °C, whereupon sweating increases rapidly with increasing temperature. So, use of impermeable covers for car seats can increase this moisture accumulation. If materials in close contact with the skin are not breathable, the sweat on the body will not be evaporated so that natural environmental cooling cannot occur, which will result in more heat build‐up and more sweating.
12.7 Conclusion
Methods for preventing moisture build‐up include the use of cushion and cover materials that encourage air exchange between the cushion and the skin. Any impermeable layer of a car seat will be the barrier for moisture transport and will make the complete structure impermeable and so uncomfortable. Cushions with good heat dissipation characteristics help to reduce moisture build‐up; if they include absorbent materials like wool or cotton, it helps to reduce moisture build‐up. Some cushions naturally pump air that is trapped in their structure when compressed. This effect can contribute to maintaining comfortable moisture level at the cushion/skin interface, if the cushion is fitted with an air permeable cover [49]. One solution to reduce passenger discomfort is to improve the ventilation properties of the car seat. This can go a long way towards reducing the problems of uncomfortably high temperatures and levels of moisture. But it is important that the car seat has sufficient air permeability, and air distribution within the car should also be optimized at the design stage. Another important parameter for ventilation is to do with the suction or blowing of air. The insertion of a component blocking the transport of moisture (e.g. polyurethane foam of a thickness greater than 5 mm leather and artificial leather products, flame, and the other adhesive lamination of the layers) inside a package disqualifies the whole package, irrespective of the quality of the remaining components. This is an unwanted situation for seats, be they with or without ventilation systems. In this case the water vapour absorbency is the car seat cover layer is the only source to remove the moisture from microclimate in between human body and the car seat [49, 51, 52, 57–59].
12.7 Conclusion Textiles for automobiles must satisfy very stringent requirements for both security and competing demands. High performance textile materials are widely used in automobiles for interior trim and for ensuring comfort (seat covers, carpets, roof liners, and door liners) as well as for reinforcement (tyre) and filters. Textiles also offer weight reduction, which in turn results in fuel economy. Airbags help to save lives, but at times they can also be a source of serious injury. The search for a uniform smart airbag, which can perceive the size of the passenger or whether the seat is empty and react in that manner, is underway. Such a smart airbag will incorporate sensors to judge the weight, size, and location of the car’s passengers and hence be deployed more appropriately. The trend towards uncoated fabrics is anticipated to continue and so is the improved trend towards more airbags per car and full size bags. The use of acoustic textiles in the transportation industry currently represents the most important application of textiles in the world. In general, acoustic textiles are used in the transportation industry to reduce interior noise and vibration and improve the sensation of ride comfort for passengers. Although interior noise lowers the comfort feeling inside a vehicle, it also induces fatigue and may reduce driving safety. Many factors affect the automotive industry. Government policies, competitive rivalries, safety requirements, and environmental regulations influence the research, design innovations, and changes in the manufacturing processes. The style, reliability, and performance requirements and at a lower cost are driven by consumer requirements and
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preferences. Changes in technology are also very important drivers in the automotive industry. The demand for lighter vehicles leads to replacing metal body parts with lighter composite materials. The body of the vehicle makes up to 28% of its total mass and gives the biggest opportunity to reduce the weight by substituting current materials with lighter weight composites. Replacing a car’s metal body parts with lighter composites will lead to improved fuel efficiently, reduced emissions, and decreased processing time, increased performance, and improved corrosion resistance. The properly selected fibre and resin, and the architecture of the composite will not only reduce automobile weight but also maintain safety standards as their performance characteristics, such as impact resistance and flexural characteristics, will stay the same or even be improved. In addition, tooling for composites parts can be 80% lower than comparable steel parts. The role of the textile industry is significantly increasing in the global automotive supply chain, as new textile composites are aggressively penetrating this market. High performance textile products nowadays can be used not only for interior and exterior components but even for suspension parts of automobiles. The incorporation of 3D woven composites is changing automotive design and the development process; instead of one level, the textile industry will be engaged at all stages of the automotive development process.
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13 Marine Textiles and Composites Chi‐wai Kan1 and Change Zhou 2 1 2
Institute of Textiles and Clothing, The Hong Kong Polytechnic University, Kowloon, Hong Kong College of Textile & Clothing, Jiangnan University, Wuxi, China
13.1 Introduction Textiles can be used for decoration and for providing a warm soft touch to surfaces, thus enhancing human wellbeing and comfort. In this respect, textiles are extensively used in transportation with different technical functions [1]. Fibres are used in several functional applications and most commonly have decorative and technical applications in the marine industry [2]. Textile products in the form of clothing, furniture, carpets, canvas, burlap, ropes, and bedding, etc. are used extensively in the marine environment; others are carried as cargo, besides use as technical textiles for water–oil separation [3, 4]. Textiles in marine applications can be classified as technical because of the very high performance specifications and special properties required [1]. For instance, tex‑ tiles for marine usage have to withstand a much higher exposure to daylight, seawater, and potential damage from ultraviolet (UV) radiation. In addition, safety features like flame‐retardant behaviour are crucial and weight saving and antifouling are also other important technical requirements, especially in racing craft [5–7]. In marine environments, the comfort, design, and appearance of textiles are impor‑ tant for providing users with a relaxing atmosphere [1, 2]. In order to satisfy the high requirements, numerous advanced materials and technologies are being developed for marine applications. For example, reinforcement composites are used to replace tradi‑ tional materials for ship construction and nanotechnology can be used for antifouling of materials in marine environment [2, 8]. This chapter aims to summarize characteris‑ tics of some raw materials and fabrics which can be used for marine textiles. Besides this, certain marine products and manufacturers of marine products are also introduced.
13.2 Textiles for Marine Applications In the very beginning, all textile materials used in marine applications were natural materials, such as fish nets and ropes. These are heavy in weight, absorb water easily, and can be damaged by rot. With the development of material technology, synthetic High Performance Technical Textiles, First Edition. Edited by Roshan Paul. © 2019 John Wiley & Sons Ltd. Published 2019 by John Wiley & Sons Ltd.
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fibres/plastic composites are being used for replacing metallic components and more traditional materials with considerable benefits, especially savings in weight [1]. Materials used in marine products are generally classified into three groups, namely: (i) reinforcement materials, (ii) resin materials, and (iii) core materials [2]. A very good review of materials used in marine applications is provided by [2] and the key issues are summarized in Sections 13.2.1–13.2.3. 13.2.1 Reinforcement Materials 13.2.1.1 Tough Cotton
Normal cotton fabric can be made into tough cotton by coating with carbon nano‑ tubes. The coated fabric will have improved mechanical behaviour, flame retardancy, UV blocking, and water‐repellent properties, etc. when compared with original cotton fabric [9, 10]. Nanotubes, acting as a reinforcement and protective shell, are used for making tough cotton that forms a cross‐linking network with a thickness of about 500 nm surrounding the cotton fibres. The cross‐linking network in the tough cotton is nanoscale and hydrophobic in nature, which can help the original hydrophilic cot‑ ton to repel water win the same way as the lotus leaf [11]. In addition, these cotton fabrics with nanotube networking are stronger and more resistant to tear than the original untreated cotton fabrics. A concentration of nanotubes over 2% in the applied emulsion may make the cotton fabric more difficult to catch fire and can prevent treated fabric from burning by forming a carbonaceous char on the surface of the cot‑ ton. This carbonaceous char can serve as a heat shield to prevent burning. In the case of UV protection, more that 90% of harmful UV radiation can be blocked with just 0.25% addition of nanotubes to the cotton fabric [9]. Fabrics with UV resistance and water‐repellent properties can offer new opportunities for textile products in marine applications [9]. 13.2.1.2 Glass Fibre
Glass fibre generally consists of more than 90% of fibres used in reinforced plastics because they are not expensive to produce but have very good strength properties. Generally speaking, glass fibre can exhibit very good chemical resistance and process‑ ability [12]. Owing to its highly competitive cost and relatively good mechanical proper‑ ties, glass fibre can be widely applied in making reinforced composites in the marine field, such as canoes and fishing trawlers, etc. Glass fibre can also be found in the rein‑ forcement of making the composites for offshore drilling platforms and liquid conduct‑ ing pipes, etc. [13, 14]. Continuous glass fibre can be produced by the extrusion of molten glass into filaments with a diameter of between 5 and 25 μm. For practical use, the individual glass fibre filaments are then coated with a sizing material (serving as a coupling agent during the resin impregnation) to minimize and reduce abrasion and they can be combined into a strand with either 102 or 204 filaments. There are two types of glass fibres: (i) E‐glass and (ii) S‐glass. The E‐glass (lime aluminium borosili‑ cate) is the most commonly used for reinforcing marine laminates, owing to its good strength and resistance to water degradation [2]. The S‐glass (silicon dioxide, alumin‑ ium, and magnesium oxides) can exhibit about a one‐third higher tensile strength, and demonstrates better fatigue resistance than E‐glass. The comparison of E‐glass and S‐glass is shown in Table 13.1 [2].
13.2 Textiles for Marine Applications
Table 13.1 Glass fibre composition [2]. E‐glass (%)
S‐glass (%)
Silicon dioxide
52–56
64–66
Calcium oxide
16–25
0–3
Aluminium oxide
12–16
24–26
Boron oxide
5–10
—
Sodium and potassium oxide
0–2
0–3
Magnesium oxide
0–5
9–11
Iron oxide
0.05–4
0–3
Titanium oxide
0–8
—
Fluorides
0–1
—
13.2.1.3 Spectra
A high strength/modulus extended chain polyethylene fibre called Spectra was devel‑ oped by Allied Corporation and introduced in the market in 1985. At room tempera‑ ture, Spectra has a better specific mechanical properties better than Kevlar, but its performance falls off at elevated temperatures. The chemical and wear resistance per‑ formance of Spectra is superior to the aramid fibres. The comparison between Kevlar and Spectra fibres is also shown in Table 13.1 [2]. 13.2.1.4 Polyester and Nylon
Polyester and polyamide (nylon) are commonly used for making ropes because of their good strength and resistance to corrosion in marine environment [15–18]. Polyester and nylon thermoplastic fibres are used in the marine industry as primary reinforce‑ ments and in a hybrid arrangement with fibreglass [5]. A product called COMPET was developed by Allied Corporation which is based on a finish application on polyester fibres that enhances matrix adhesion properties [2]. Some properties of COMPET are listed in Table 13.1 [2]. 13.2.1.5 Trevira
Trevira is a hi‐tech polyester fibre which is designed as a bulking material and as a gel coat barrier to reduce print‐through [2]. Although original polyester fibres have high strength, their stiffness is considerably below that of glass. This brings the attractive features of Trevira, other than original polyester fibres, which include low density, rea‑ sonable cost, good impact, and fatigue resistance, and potential for vibration damping and blister resistance [2]. 13.2.1.6 Carbon Fibre
All continuous carbon fibre is being produced recently from organic precursors, which in addition to PAN (polyacrylonitrile), include rayon and pitches, with the latter two generally used for low modulus fibres. Carbon fibres can provide the highest strength and stiffness among all commonly used reinforcement fibres. Carbon fibres are not subjected to stress rupture or stress corrosion, and high temperature performance is
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Table 13.2 Comparison of different fibre properties [2].
Fibre
Density (lb./in.3)
Tensile strength Tensile modulus Ultimate (psi ×103) (psi ×103) elongation (%) Cost ($/lb.)
E‐glass
0.094
500
10.5
4.8
0.8–1.2
S‐glass
0.090
665
12.6
5.7
4
Aramid‐Kevlar 49
0.052
525
18.0
2.9
16
Spectra 900
0.035
375
17.0
3.5
22
Polyester‐COMPET
0.049
150
1.4
22.0
1.75
Carbon‐PAN
0.062–0.065
350–700
33–57
0.38–2.0
17–450
particularly outstanding. The major drawback of carbon fibre is due to the cost of PAN based fibres, which is based on the high cost of precursors and an energy intensive manufacturing process [2]. Some properties of carbon fibre (Carbon‐PAN) are shown in Table 13.2 [2]. 13.2.2 Resin 13.2.2.1 Polyester Resin
Polyester resin is the simplest, most economical resin system that is easiest to use and shows good chemical resistance. Unsaturated polyester consists of unsaturated materi‑ als, such as maleic anhydride, which is dissolved in a reactive monomer, e.g. styrene. Most polyesters are air inhibited and do not cure when exposed to air. Typically, in the formulation of resin, paraffin is added for the effect of sealing the surface during the curing process. Moreover, wax film on the surface presents a practical problem for resin bonding or finishing and so the wax film must be completely removed during the appli‑ cation of polyester resin. Non‐air‐inhibited resins do not present this problem and are, therefore, more widely accepted in the marine industry [2]. There are two basic polyester resins that are commonly used in the marine industry: (i) orthophthalic and (ii) isophthalic. Orthophthalic resins are widely used but they have relatively lower thermal stability, chemical resistance, and processability charac‑ teristics when compared with isophthalic resins. Isophthalic resins have generally better mechanical properties and show better chemical resistance when compared with orthophthalic resins. Their increased resistance to water permeation has prompted many builders to apply this resin as a coating in marine laminates [2]. 13.2.2.2 Vinyl Ester Resin
Vinyl ester resin is unsaturated resin prepared by the reaction of a monofunctional unsaturated acid, e.g. methacrylic or acrylic, to a bisphenol diepoxide. The resulting polymer is mixed with an unsaturated monomer, e.g. styrene. Thus, the handling and performance characteristics of vinyl esters are similar to those of polyesters. Some advantages of vinyl ester, other than its higher cost, include good corrosion resistance, superior hydrolytic stability, and excellent physical properties, e.g. impact and fatigue resistance. The vinyl ester resin matrix can provide an excellent permeation barrier that resists blistering in marine laminates [2].
13.2 Textiles for Marine Applications
13.2.2.3 Epoxy Resin
Epoxy resin is a family of materials which contains a reactive functional group in its molecular structure. Epoxy resin has the best performance characteristics among all resins used for marine applications. Other than marine applications, epoxy resin is used exclusively in aerospace applications. However, its high cost of application and handling difficulties limit its usage for large marine structures [2]. 13.2.2.4 Thermoplastic Resin
Thermoplastic resin has two structures: (i) one‐dimensional (1D) or (ii) two‐dimensional (2D) molecular structures, as opposed to three‐dimensional (3D) structures for ther‑ mosets. The thermoplastic resin is generally in the form of moulding compounds that soften at high temperatures. Examples of thermoplastic include polyethylene, polysty‑ rene, polypropylene (PP), polyamide, and nylon. Their marine applications are gener‑ ally limited to small boats and recreational items. Owing to the development of reinforcement technology and the need for advanced materials for marine applica‑ tions [2], reinforced thermoplastic materials have recently been investigated for the possibility of use in the large scale production of structural components. Thermoplastic resin has some attractive features, such as (i) no exothermal reaction upon cure and (ii) enhanced damage tolerance. Figure 13.1 shows a comparison chart of different resin systems used in the marine industry [2]. 13.2.3 Core Materials 13.2.3.1 Balsa
Balsa has a closed‐cell structure which consists of elongated, prismatic cells with a length (grain direction) approximately 16 times the diameter. Material with balsa structure generally exhibits excellent stiffness and bond strength. The stiffness and strength characteristics of balsa are similar to aerospace honeycomb cores. When 0%
10%
Orthopolyester for Hulls Orthopolyester for Decks Orthopolyester for Parts Isopolyester for Hulls Isopolyester for Decks Isopolyester for Parts Vinyl Ester for Hulls Vinyl Ester for Decks Vinyl Ester for Parts Epoxy for Hulls Epoxy for Decks Epoxy for Parts Figure 13.1 Marine industry resin systems [2].
20%
30%
40%
50%
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13 Marine Textiles and Composites
compared with PVC (polyvinyl chloride), a balsa panel has a higher static strength than PVC foam but its impact energy absorption is lower. However, the local impact resist‑ ance of balsa is very good because stress is efficiently transmitted between its sandwich skins. In the market, end‐grain balsa in sheet form is available for constructing flat panels or for conforming complex curves [2]. 13.2.3.2 Thermoset Foams
Foamed plastics – such as cellular cellulose acetate (CCA), polystyrene, and polyure‑ thane – are very light. They can resist water and fungi formation. These materials have very low mechanical properties and so they cannot conform to complex curves. Their uses are generally limited to buoyancy instead of structural applications. Polyurethane is usually a foam material in‐place when used as a buoyancy material [2, 19]. 13.2.3.3 Cross‐Linked PVC Foam
Polyvinyl foam core is manufactured by combining a polyvinyl copolymer with stabiliz‑ ers, plasticisers, cross‐linking compounds, and blowing agents. The mixture is heated under pressure to initiate the cross‐linking reaction and is then submerged in hot water to expand to the desired density with cell diameters ranging from 0.025 to 0.25 cm. The resulting material is thermoplastic, conforming to the compound curves of a hull. PVC foam has almost exclusively replaced urethane foam as a structural core material, except in configurations where the foam is ‘blown’ in place [2]. 13.2.3.4 Linear PVC Foam
In marine applications, linear PVC foam is used because it has good and unique mechanical properties, owing to its nonconnected molecular structure allowing signifi‑ cant displacement before failure happens. When compared with cross‐linked (nonlin‑ ear) PVC foam, the static properties of linear PVC foam are less favourable, but it does have better impact resistance [2]. 13.2.3.5 Honeycomb
Honeycomb cores are used extensively in the aerospace industry which can be fabri‑ cated by different materials such as PP, aluminium, or phenolic resin impregnated fibreglass. Although honeycomb core can be used for fabricating extremely lightweight panels, its applications in the marine environment are limited because of the difficulty of making complex face geometries and its potential to absorb significant amounts of water [2]. 13.2.3.6 PMI Foam
Polymethacrylimide (PMI) foam, for example Rohacell®, is used for composite con‑ struction which requires minimum laminating pressure to develop good peel strength. The most important feature of PMI foam is its ability to withstand curing temperatures in excess of 176 °C, which makes it attractive for use with reinforcements [2, 19]. 13.2.3.7 FRP Planking
FRP (fibreglass reinforced plastic) planking consists of rigid fibreglass rods held together with unsaturated strands of continuous fibreglass rovings and a light fibre‑ glass cloth which can be used to build a cost effective one‐off hull. The self‐supporting
13.2 Textiles for Marine Applications
material conforms to compound curves and a typical application involves a set of male frames as a mould [20, 21]. The planking has more rigidity than PVC foam sheets, which eliminates the need for extensive longitudinal stringers on the male mould [2]. 13.2.4 Fabrics for Marine Applications 13.2.4.1 Core Fabric
Various natural and synthetic materials can be used for manufacturing products to build laminate thickness economically [2, 22]. Plywood is a structural core material, although fibreglass is generally viewed as sheathing when used in conjunction with ply‑ wood. Plywood can be used as a core, because of its low density, to improve the com‑ pressive properties of the laminate. Plywood can sometimes be used as a form for longitudinal, but its continuous exposure to water leads to concerns of moisture absorp‑ tion in a maritime environment. The absorption of moisture will make the wood swell and cause delamination. Thus, there is a decline in the use of plywood and the uneven surface of plywood can make it a poor bonding surface. In addition, the low strength and low strain characteristics of plywood can lead to failures when they are used as a core [2]. 13.2.4.2 Reinforcement Fabric
Reinforcement materials are combined with resin systems in a variety of forms to cre‑ ate structural laminates. Different forms of reinforcement material are graphically shown in Figure 13.2 [2]. Owing to processing and economic considerations, some of the lower strength noncontinuous configurations are limited to fibreglass [2]. Because of their light weight, high strength, stiffness and resistance to high temperature, fabric reinforced composites have been used widely in marine applications [23]. The two
Tubular Braid
Tubular Braid Laid in Warp
Flat Braid
Weft Knit
Weft Knit Weft Knit Weft Knit Laid Square Laid in Weft Laid in Warp in Warp Laid Braid in Weft
Square Braid Laid in Warp
3-D Braid
3-D Braid Laid in Warp
Warp Knit
Warp Knit Weft inserted Weft inserted Fiber Mat Stichbonded Laid in Warp Laid in Warp Warp Knit Warp Knit Laid in Warp
Biaxial Bonded
XYZ Laid in System
Biaxial Woven
High Modulus Multilayer Woven Woven
Triaxial Woven
Figure 13.2 Different forms of reinforcement [2].
Flat Braid Laid in Warp
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13 Marine Textiles and Composites
main advantages of fibre‐reinforced plastics over metals are (i) resistance to the marine environment and (ii) ease of tailoring structures by moulding processes. Glass‐fibre‐reinforced polymer (GRP) composites are generally used in marine craft such as canoes and fishing trawlers, etc. [14]. Fibreglass composites can also be used in offshore drilling platforms for deck grates, low‐pressure pipes, and storage tanks [24–26]. The polymer matrix in almost all GRP composites for seawater applications is based on isophthalic polyester or vinyl ester resin [1]. In marine applications, glass/ polyester and glass/vinyl ester composites must retain their mechanical properties and should not degrade even after remaining immersed in seawater for many years [25]. One disadvantage of using polyester based composites in seawater is that the polymer matrix and fibre/matrix interphase can be degraded by a hydrolysis reaction of unsatu‑ rated groups within the resin. Seawater degradation can cause swelling and plasticiza‑ tion of the polyester matrix and debonding at the fibre–matrix interface, which may weaken the mechanical properties [26–30]. This problem can be alleviated by using vinyl ester based composites that generally have superior chemical stability in seawater [5, 7]. Another disadvantage of using GRP composites in marine structures is the rela‑ tively low Young’s modulus, which makes it difficult to build ultralight marine struc‑ tures with adequate stiffness. For this reason, marine composite structures requiring high stiffness are often built using carbon fibre composites. Carbon/epoxy laminate is occasionally used [31], but the high cost of epoxy resin has led to the increased use of carbon/polyester and carbon/vinyl ester composites in racing yachts and naval patrol vessels [25]. 13.2.4.2.1 Woven Reinforcement Structure
Cloth or woven roving used in marine applications is normally considered woven com‑ posite reinforcements. Such cloths of woven composite reinforcement are light in weight but their usage in the marine sector is limited to the construction of small parts and repairs. The weave patterns used in marine application include (i) plain weave, which is highly interlaced; (ii) basket weave, which has warp and fill yarns that are paired up; and (iii) satin weaves, which exhibit a minimum of interlacing. Some com‑ mercially available weave patterns are summarized and illustrated in Figure 13.3 [2].
Plain weave
Basket weave
Twill
Crowfoot satin
8 harness satin
5 harness satin
Figure 13.3 Commercially available weave patterns [2].
13.2 Textiles for Marine Applications
Other than woven cloth, woven roving reinforcements consist of flattened bundles of continuous strands in a plain weave pattern. This is the most commonly used type of reinforcement for building large marine structures, owing to its heavyweight, which enables the rapid build‐up of thickness. Woven reinforcement structures also have good directional strength properties and the impact resistance is enhanced because the fibres are continuously woven [2]. 13.2.4.2.2 Knitted Reinforcement Structure
When compared with woven reinforcement structures, knitted fabrics for reinforce‑ ment can provide greater strength and stiffness per unit thickness than woven struc‑ ture. The knitted reinforcement structure is constructed by using a combination of unidirectional reinforcements that are stitched together with a nonstructural synthetic, such as polyester, to form a layer of mat in the structure [2]. The manufacturing process provides an advantage that the reinforcing fibre is lying flat when compared with the crimped orientation of fibre in woven reinforcement structures. In addition, knitted reinforcement structures can be oriented along any combination of axes. A comparison of woven roving and knitted constructions is shown in Figure 13.4 [2]. 13.2.4.2.3 Omnidirectional Reinforcement Structure
Omnidirectional reinforcement is generally in the form of a chopped strand mat which can be applied during hand lay‐up as a prefabricated mat or via the spray‐up process. The chopped strand mat contains randomly oriented glass fibre strands which are bonded together with a soluble resin binder. Other than chopped strand mats, continu‑ ous strand mats are also available. They are similar to chopped strand mats, except the fibre is continuous and laid down in a swirl pattern. Both hand lay‐up and spray‐up methods can produce plies with equal properties along the x and y axes with good interlaminar shear strength [32]. The omnidirectional reinforcement structure is an economical way to build up thickness but its mechanical properties are not as good as other reinforcements [2]. End View
Woven Roving
End View Knitted Biaxial
Figure 13.4 Comparison of woven roving and knitted construction [2].
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13 Marine Textiles and Composites
13.2.4.2.4 Unidirectional Reinforcement Structure
Pure unidirectional reinforcement means no structural reinforcement in the fill direc‑ tion. For example, carbon fibre, an ultra‐high‐strength/modulus material, is sometimes used for making pure unidirectional reinforcement structure, owing to its specificity of application. The width of material with unidirectional reinforcement structures is gen‑ erally limited because of the difficulty of handling and wet‐out. In order to produce material with a unidirectional reinforcement structure, the structure is held together with a thermoplastic web binder compatible with thermoset resin systems. A typical application of unidirectional reinforcement structure includes stem and centreline stiff‑ ening. Entire hulls are fabricated from unidirectional reinforcements when an ultra‐ high‐performance laminate is desired [2]. 13.2.4.2.5 Three‐dimensional (3D) Textile Structure
Polymer materials reinforced with a 2D layered fibre structure have been used with outstanding success in maritime applications. Despite the widespread use of 2D mate‑ rials over a long period, their use in many structural applications has been limited because of manufacturing problems and because of some inferior mechanical proper‑ ties. Reinforcement materials with 3D fibre architectures can overcome many of the problems with manufacturing and mechanical properties of materials [33]. Three‐ dimensional textile structural composites possess superior mechanical performance, for example improved structural integrity, enhanced fracture toughness, and through‐ the‐thickness strength against delamination [34, 35]. Three‐dimensional textile com‑ posites can be made by weaving, braiding, stitching, and knitting. Three‐dimensional textile composites include 3D braided composites, 3D woven composites, 3D stitched composites, 3D knitted composites, as well as 3D auxetic textile structures consisting of weft, warp, and stitch yarn systems. The potential of 3D materials is impressive and they have been used in items such as inlet ducts and rotor blades, etc. [33]. Three‐ dimensional textile composites have a vast range of properties that are superior to traditional 2D laminates and, therefore, it is advantageous to exploit them for many applications.
13.3 Properties of Textiles for Marine Applications 13.3.1 Antifouling Marine structures such as platforms and ship hulls are subject to the problem of bio‑ fouling. The inhibition methods for both organic and inorganic growth on wet sub‑ strates are varied but most antifouling systems use the form of protective coatings. Biofouling can negatively affect the hydrodynamics of a hull by increasing its required propulsive power and fuel consumption. Therefore, fouling is also a concern in the case of surfaces exposed to aquatic environments where marine microorganisms can bind to a surface and form a conditioning layer, which then provides an easily accessible plat‑ form for other aquatic species, such as diatoms and algae, to attach and proliferate [36–38]. The critical issues associated with biofouling include increased operational and maintenance cost due to fouling of water conduits and ship hulls and the degradation of abiotic materials [39, 40]. Recently, different strategies for antifouling, antimicrobial as
13.3 Properties of Textiles for Marine Applications
Table 13.3 Requirements for an optimal antifouling finishing [39]. Must be
Must not be
Anticorrosive
Toxic to the environment
Antifouling
Persistent in the environment
Environmentally acceptable
Expensive
Economically viable
Chemically unstable
Long life
A target for nonspecific species
Compatible with underlying system Resistant to abrasion/biodegradation/erosion Capable of protecting regardless of operational profile Smooth
well as marine antifouling, applications have been developed. One of the most common approaches to prevent the surface from adhesion of microbes involves the treatment of polyethylene glycol (PEG) or oligo (ethylene glycol) groups. This treatment will induce surfaces with a low surface energy and give the optimized surface topography with promising results. This promotes the development of new approaches for the func‑ tionalization of surfaces with PEG and the development of alternatives to PEG for resisting microbial adhesion. Other important approaches for killing or degrading bac‑ teria include the design of surfaces that release antibiotics or silver, surfaces functional‑ ized with polycations or antimicrobial peptides (AMPs), etc. Their widespread use, however, results in the emergence of antibiotic‐ or silver‐resistant bacteria. Moreover, antibiotic‐ and silver‐containing coatings act through a release based mechanism and are therefore exhausted over time. Approaches involving the generation of microbicidal coatings based on AMPs and polycationic polymers have gained significant attention and are promising. Meanwhile, activity of these biomolecules upon incorporation into coatings need to be improved by using appropriate linkers and nanomaterials as immo‑ bilization supports [7]. The requirements for an optimal antifouling coating are listed in Table 13.3 [39]. As shown in Table 13.3, most of these strategies are helpful in combating the problem of fouling but several of them are also associated with shortcomings related to stability, toxicity, or the method of fabrication. A comprehensive review about marine antifoul‑ ing coating is provided by [39]. 13.3.2 Flame‐Retardant Nature Conventional polyester and epoxy type organic matrix materials are currently used in shipboard applications but they support combustion and generate large quantities of smoke while burning. Therefore, methods to inhibit fire growth in composites rely on using either (i) a fire‐retardant ingredient in the matrix resin or (ii) resins that can func‑ tion under high temperatures, such as polyimides. Fire resistance and reduced smoke and toxicity can also be achieved by the use of fire barriers, which include ceramic fabric, ceramic coating, intumescent coating, or other high temperature foam insulation
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barriers [5]. An abridged version of fire characteristics to be investigated and the test methods and requirements for qualifying composite materials for use on‐board a naval submarine are presented in Table 13.4 [5]. A comprehensive review of fire safety require‑ ments of products for marine (naval) application is given by [5]. Table 13.4 Some fire performance acceptance criteria [5]. Fire test/characteristics
Oxygen‐ temperature index (%)
Requirement
Oxygen at 25 °C Oxygen at 75 °C
35 Minimum
Oxygen at 300 °C 100 kW m irradiance
Ignitability (s)
−2
50 kW m irradiance
Minimum
90 150
Maximum
20
120
75 kWm−2 irradiance, peak
100
500 kW m−2 irradiance, peak
Maximum
Average for 300 s
100 65
25 kW m irradiance, peak
50
Average for 300 s
50
Ds during 300 s
100
Dmax
200
Combustion gas generation (25 kW m−2)
CO = 200 ppm CO2 = 4%v HCN = 30 ppm
N‐gas model smoke toxicity
ASTM E‐1354
50
−2
Smoke obscuration
ASTM E‐162
150
Average for 300 s
Average for 300 s
ASTM E‐1354
300
100 kW m−2 irradiance, peak
Heat release (kW m−2)
ASTM D‐2863 (modified)
60
25 kW m−2 irradiance Flame spread index
30 21
−2
75 kW m−2 irradiance
Test method
Maximum
ASTM E‐662
ASTM E‐1354
HCL = 100 ppm No deaths
Modified
Screening test
Pass
NBSTTM
Quarter‐scale fire test
No flashover in 10 min
DTRC Quarter‐ scale test
Burn‐through fire test
No burn‐through in 30 min
Burn‐through fire test (DTRC)
13.4 Marine Textiles and Quality Standards
13.3.3 Mechanical Behaviour Marine textiles are exposed to moisture and hydrostatic pressure in the deep sea envi‑ ronment, which may affect its mechanical properties. For example, the moisture absorption of polymer would cause a reduction of the glass transition temperature of the matrix, leading to a loss of stiffness and strength, which causes fibre microbuckling and premature fracturing. Accordingly, the effect of moisture absorption on the com‑ pressive, tensile, and shear behaviours of marine textiles has been investigated by many researchers [13, 24, 31, 41]. The mechanical behaviour of specimens can be tested according to the ASTM E1922, ASTM D2344, ASTM D256, for an edge notched tensile test, a short beam bend test, and impact tests, respectively [24].
13.4 Marine Textiles and Quality Standards The development of textile technology means that hull structures can be produced to meet the demands of higher loads [42] while at the same time using lighter struc‑ tures. And the materials used for this are steadily replacing the natural materials traditionally used for ship construction. Fibre composites of glass reinforced plastic are used extensively in small vessels, patrol boats, and pleasure craft [14]. Polyester fibre is being used to replace some of the heavier and costly glass fibres in compos‑ ites. The advantages are: easy handling, corrosion resistance, and low maintenance. Kevlar (DuPont) is also used, sometimes in combination with glass fibre. Examples of specific cases where metal cannot be used are minesweepers, sonar domes, and cor‑ rosive cargo carriers. Composites are being increasingly used for navigational aids, such as buoys, so that no damage results to the craft in the event of an accidental collision. A very good summary about the textiles for marine application and their quality standard is provided by [2], and the key issues are summarized in the follow‑ ing sections. 13.4.1 Furnishing Fabrics Carpets are necessities for the furnishing of passenger vessels because of their noise and vibration absorbing properties. Meanwhile, carpets should be more pleasant to walk upon than on a hard surface in order to reduce physical stress against hard ground surface. Owing to the special characteristics of passenger vessels (i.e. escape restrictions at sea, narrow corridors, and low ceilings in many vessels, etc.), there is a particular requirement a high degree of flame retardancy for the carpets that are used. In pas‑ senger vessels, fires are frequently caused by careless smokers. Flame retardancy is important and wool carpets are generally treated with flame‐retardant materials, for example Zirpro (IWS). Because of the special service environment, dyes used for marine textiles in passenger vessels must possess good fastness properties to light, rubbing, and saltwater, and durability is also an important consideration for marine textiles [1, 2]. Besides the high requirements of the carpets, furnishing fabrics must also pass rigorous evaluation standards set by the International Maritime Organization (IMO). Such standards of flame retardancy include IMO Resolution A471 (XII), DIN 4102 class B, and BS476 paragraph 6 [1].
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13.4.2 Sails Nylon and polyester are commonly used for making sails because of their good prop‑ erties of lightweight, rot‐resistant, low water absorption, and high sunlight resistance. When polyester and nylon materials are compared, polyester is generally better than nylon. However, in the case of spinnaker sails, nylon material shows a better perfor‑ mance than polyester in terms of stretch and elasticity. Recently, some modern racing sails have been produced from polyester film laminated to woven polyester or nylon fabric. The development of sails has progressed to lighter laminated types where film is bonded to the fabric. Thus, the fabric does not form the surface of the sail but acts as the reinforcing structure. For racing yachts in which fabric weight is a crucial factor in affecting the performance, aramid is used in the reinforcement structure because of its high strength and light weight. However, aramid degrades in sunlight; ultra‐high‐ modulus polyethylene yarns and carbon fibres are now used as an alternative aramid. The polyethylene yarn has also found application in heavy duty ropes [2]. The main requirements for sail cloth are: (i) lightweight, (ii) dimensional stability, (iii) puncture resistance, (iv) high tear strength, (v) high seam strength, (vi) low porosity to wind, (vii) low water absorbency, (viii) good resistance to microbes and UV degradation, and (ix) smoothness [2]. Sails which absorb water will increase the overall weight of the vessel and reduce its efficiency. Also, a sail with a rough surface can increase the frictional drag. The fabric bias stretch will limit the usage of sail cloths, which can be eliminated by calendering with or without a resin coating. In making the sail, the seam will be a source of weak‑ ness and under high stress the sewing holes in the seam may be enlarged, which may affect the porosity of the sail. Under prolonged high stress, the sail fabrics will be dis‑ torted and their shape will change subsequently. In order to retain the sail shape, most sails are laminated with polyester film (has high modulus of elasticity in all directions) and the final sails will have excellent shape retention properties with very little distor‑ tion or stretch. Moreover, the laminated sail must be bonded with an adhesive that can withstand seawater and UV degradation during normal marine application conditions [2, 19, 21, 22]. For modern racing sails, they comprise film laminated to threads of yarn laid on the bias of the sail to produce an article of high dimensional stability that is very lightweight [2]. Spectra, Vectran, and carbon fibre – which all have good UV degradation resistance when compared with nylons, polyesters, and aramids – can be used for making racing sails [2]. As a coin has two sides, laminated sails do not last as long as normal fabric sails, but laminated sails are highly important in terms of speed and performance. When sails are cleaned, any detergent or cleaning agent must be rinsed away because it may affect the laminated bond strength or contribute to UV degradation of the materials. Hot melt adhesive films are generally used, and these factors must be taken into consideration when the adhesive is selected [2]. 13.4.3 Hovercrafts Skirts The skirt material is a nylon fabric coated with a polychloroprene/natural rubber blend or natural rubber/polybutadiene and compounded for oil resistance. PVC blended with nitrile rubber was evaluated but was not found to be as satisfactory. The nylon cords are
13.4 Marine Textiles and Quality Standards
highly twisted in the fabrics (woven) in order to impart fatigue resistance to withstand the rapid and continual flexing during use. The adhesion used for bonding the fibre to the rubber must be of the best standard so that a suitable priming coat can be formed. Nylon is the best overall fibre for this application. Other than nylon, polyester yarns can be used because they are less affected by water. However, coated polyester fabrics do not last as long as nylon. This may be due to the poorer polyester/rubber bonding com‑ pared with nylon/rubber. Cotton and rayon absorb too much water and are not gener‑ ally strong enough and recommended for this application. And although aramids are stronger than both nylon and polyester, they break down quite rapidly because of their low fatigue resistance [2]. 13.4.4 Inflatable Craft Inflatable craft have many advantages over rigid boats and have become widely used since around 1960 [43]. They are used as lifeboats and rescue craft, as freight carrying vessels and as pleasure craft, besides having several military applications. When they are not in use or when they are transported to different locations, they can be deflated, folded, and packed into a relatively small capacity. They are made from individual buoy‑ ancy tubes or several different compartments, so that even if a particular section is damaged the whole craft is still able to float and be capable of supporting weight. There are national standards and minimum performance specifications for the coated fabric and the craft itself but these standards do not actually specify which materials should be used. Different coatings, polychloroprene, polyurethane and PVC, and nylon woven fabric are used. Good tear strength is a required property to prevent propagation of any damage. Although polyester with a higher yarn modulus can be used as an alternative to nylon, it is usually more difficult to bond rubber coatings to polyester, and polyester can be degraded by certain compounding ingredients. In addition, polyester is heavier than nylon. If cost allows, aramid fibre may be used, thus saving a significant amount of weight [2]. 13.4.5 Naval Ships and Submarines A wide range of naval structures are being developed using fibre reinforced polymer composites. Their special structures, such as sandwich composite, provide savings in hull weight for the design of patrol boats. This development is driven by the need to enhance the operational performance (e.g. increased range, stealth, stability, payload) and at the same time reduce the ownership cost (e.g. reduced maintenance, fuel con‑ sumption cost) of warships and submarines. Other new or potential uses for compos‑ ites are in the superstructures, advanced mast systems, bulkheads, decks, propellers, propulsion shafts, and rudders for large surface combatants [44]. They were built with a sandwich composite consisting of glass‐ and carbon‐fibre laminate skins with a PVC core. Use of the sandwich composites simplified the construction of the hull and superstructure and provides a high strength‐to‐weight ratio; good impact prop‑ erties; and low infrared, magnetic, and radar cross‐sectional signatures. The sand‑ wich composites are also used to build mine countermeasure vessels, corvettes, hydrofoils, and hovercrafts to reduce weight, improve damage tolerance, and reduce maintenance [14].
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13.4.6 Marine Safety Apparatus Coated fabrics are used for life raft buoyancy tubes, canopies, and lifejackets. The base fabric for life rafts is generally woven polyamide with butyl or natural rubber, polychlo‑ roprene, or thermoplastic polyurethane coatings. Natural rubber, polyurethane, or SBR (styrene‐butadiene rubber) coated on woven polyamide fabric is much lighter and suit‑ able for canopies used on life rafts. Lifejackets are generally made from woven polyam‑ ide coated with butyl or polychloroprene rubber. Performance standards for the coated fabrics used for life rafts and lifejackets are usually subject to government controls and specifications. Quality tests of fabrics used for life rafts include air porosity, coating adhesion, and breaking and tear strength both in the warp and weft direction, flexing, antifouling, and waterproofness measured by hydrostatic head test methods. Performance specifications of fabrics used for lifejackets include polymer adhesion, tensile strength, flex cracking, antifouling and elongation‐at‐ break, including testing after immersion in water for 24 hours [1, 2, 7, 8, 36, 45]. The specifications and performance standards for lifejackets and life rafts are subject to dif‑ ferent regulations, such as (i) UL 1123, Marine Buoyant Devices and (ii) UL 1180, Recreational Inflatables. Specifications are also issued by the military in different coun‑ tries. Aircraft survival equipment such as lifejackets, life rafts, and escape chutes are generally made from woven nylon coated with polyurethane or synthetic rubber, but PVC is avoided. This is because PVC may generate toxic gases in the event of fire [18]. 13.4.7 Oil–Water Separation Many textiles can be used for oil–water separation, such as cotton fibre, woven and nonwoven PP, as well as polyethylene terephthalate (PET) [46, 47]. However, the oil containment capacities of samples are inversely proportional to their porosity [4]. Electrospun nanofibrous materials with tunable surface wettability have shown great promise for oil–water separation applications. Based on the different types of separa‑ tion materials, these nanofibrous materials can be divided into three parts (Figure 13.5): nanofibrous sorbents for oil spill clean‐up, nanofibrous membranes for oil–water sepa‑ ration. and nanofibrous aerogels (NFAs) for emulsified oil–water separation. A variety of different nanofibrous materials with tunable surface wettability for oil–water separa‑ tion applications have been developed (Table 13.5). As sorbents, the oil sorption capacity of nanofibrous materials has been proven to be further enhanced because the nanofibrous sorbent can drive the oil not only into the voids between fibres but also into its multi‐pores. Three major categories of nanofi‑ brous sorbents – hydrophobic‐oleophilic polymer nanofibres, composite nanofibres, and carbon nanofibres – have been developed for oil sorption. Nanofibrous membranes used to treat oily wastewater are attributed with high separation efficiency and rela‑ tively simple operational processes. The fabrication of fibrous membranes with selec‑ tive superwetting property can be achieved through manipulating both the surface geometrical structure and the chemical composition. Generally speaking, these separation membranes are classified into three types: oil‐ removing, water‐removing, and smart separation membranes, including superhydro‑ phobic and superoleophilic nanofibrous membranes, superhydrophilic and underwater superoleophobic nanofibrous membranes, nanofibrous ultrafiltration membranes, and smart special wettable nanofibrous membranes. Three‐dimensional functional aerogels
13.4 Marine Textiles and Quality Standards
Figure 13.5 Electrospun nanofibrous materials for oil–water separation [45]. Table 13.5 Electrospun nanofibrous materials for oil–water separation applications [45].
Type
Materials
Nanofibrous PS nanoporous fibres sorbents
Water contact angle/oil contact angle
Oil–water separation performancea)
147.6°/0°
113.87 (motor oil), 111.80 (bean oil), 96.89 (sunflower seed oil)
PS nanoporous fibres
151.3 ± 1.6°/0°
131.63 (motor oil), 112.30 (peanut oil), 81.40 (silicone oil), 7.13 (diesel oil)
PVC/PS composite nanofibres
—
146 (motor oil), 119 (peanut oil), 81 (ethylene glycol), 38 (diesel oil)
PU/PS composite nanofibres
118–138°/0°
30.81 (motor oil), 24.36 (sunflower seed oil)
PVDF/Fe3O4@PS composite nanofibres
~126°/0°
35–45 (sunflower oil, soybean oil, motor oil, diesel oil)
PU‐PS core–shell fibres
~140°/0°
64.40 (motor oil), 47.48 (sunflower seed oil)
Carbon nanofibres
155.3°/0°
138.4 (silicone oil), 94.0 (corn oil), 73.8 (pump oil), 64.0 (mineral oil) (Continued )
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Table 13.5 (Continued)
Type
Materials
Water contact angle/oil contact angle
Oil–water separation performancea)
Nanofibrous F‐PBZ/SiO2 membranes NPs‐CA
161°/3°
Fast separation for a 200 g oil–water (50% v/v) mixture
F‐PBZ/SiO2 NPs‐PMIA
161°/0°
Oil flux of 3311 l m−2 h−1 for oil (dichloromethane) and water (50% v/v) mixtures
F‐PBZ/Al2O3 NPs‐SNM
161°/0°
Oil flux of 892 l m−2 h−1 for a surfactant‐ stabilized (span 80) water‐in‐oil (petroleum ether) emulsion
Aminated PAN‐Ag
162.4 ± 1.9°/0°
Oil flux of 4774.6 ± 45.6 l m−2 h−1 for a 200 ml mixture of oil (1,2‐dibromoethane, 50% v/v) and water
Flexible SiO2‑carbon composite nanofibres
144.2 ± 1.2°/0°
Oil flux of 3032.4 ± 234.6 l m−2 h−1 (petroleum spirit), oil flux of 2648.8 ± 89.7 l m−2 h−1 (hexane)
PS nanofibres/steel mesh
155 ± 3°/0°
Easily separating diesel oil from water
CaCO3 mineralised PAA‐grafted PP
0°/157 ± 2.4°
Can separate oil–water mixtures with high separation efficiency (> 99%) and high water flux (> 2000 l m−2 h−1)
SiO2 NPs‐SNM
0°/161°
Can separate oil‐in‐water emulsions by gravity, with an extremely high water flux of 2237 l m−2 h−1
NiFe2O4 NPs‐SNM
0°/145°
High water flux of 1580 ± 106 l m−2 h−1 for a surfactant‐stabilized (span 80) water‐in‐oil emulsion
PVA hydrogel‐ MWNT/PVA/ Nonwoven
—
High water flux (up to 330 l m−2 h−1 at the feed pressure of 100 psi) for an oil/–water emulsion
Chitosan/PAN/ Nonwoven
—
High water flux (~170 l m−2 h−1 at the feed pressure of 130 psi) and good filtration efficiency (> 99.9%)
PVA/PAN composite membranes
—
High water flux (210 l m−2 h−1 at the feeding pressure of 0.3 MPa) with high rejection rate (99.5%) in oil–water emulsion separation
PMMA‐co‐ PDEAEMA
147°/36° – N2 Oil flux of 17 000 l m−2 h−1 (before CO2 −2 −1 36°/155° – CO2 bubbling), water flux of 9554 l m h (after CO2 treatment) for oil–water mixture separation
Nanofibrous FIBRE NFAs aerogel SiO2 NPs‐FIBRE NFAs
145°/0°
High water flux of 8100 ± 160 l m−2 h−1 for a surfactant‐stabilized water‐in‐oil emulsion
162°/0°
High water flux of 8140 ± 220 l m−2 h−1 for a surfactant‐stabilized water‐in‐oil emulsion
a) Sorbent capacity (g oil/g sorbent); Membrane and aerogel permeate flux (l m−2 h−1).
References
with special wettability – including silica colloid aerogels, carbon nanotube aerogels, graphene monoliths, porous boron nitride, and polymer sponges as demulsification – can be used to realize oil–water separation. This is because they possess versatile poros‑ ity, low density, and high internal surface area properties [45].
13.5 Sustainability and Ecological Aspects Sustainability and ecological aspects are now important issues in the field of material development. Based on the analysis of different information obtained, composite mate‑ rials would be a trend for developing sustainable marine textiles. Owing to the forma‑ bility of the composite materials, we can design them for suiting different purposes, according to their end use.
13.6 Conclusion Because of the aggressive environment, textiles used in marine applications are devel‑ oped from natural and synthetic materials, and are then reinforced with different mate‑ rials and techniques because synergistic interaction between the environment and the applied loads accelerates fatigue damage of materials. The reinforcement materials are designed to resist primary loads that act on the laminate and the resin serves to transmit loads between the plies, primarily via shear. For the purpose of protecting humans against injuries from marine environment and disasters, materials for marine applica‑ tions are finished with advanced technologies and evaluated against strict standards. The use of reinforcement materials enables the building of bigger, lighter, and stronger ships, making it safer for people to work at sea. Another advantage is that the applica‑ tion of reinforcement materials alleviates marine pollution, owing to its long service life. This is beneficial for the sustainable development of the marine industry.
Acknowledgement The authors would like to thank the financial support from The Hong Kong Polytechnic University for this work.
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14 Aeronautical and Space Textiles Sadaf A. Abbasi1, Lijing Wang 2, Mazhar H. Peerzada 3, and Raj Ladani1 1
School of Engineering, RMIT University, Melbourne, Australia School of Fashion and Textiles, RMIT University, Brunswick, Australia 3 Department of Textile Engineering, Mehran University of Engineering & Technology, Jamshoro, Pakistan 2
14.1 Introduction The history of textiles started when human beings began using textiles to cover their bodies and protect them from the environment. Today’s innovations in the textile industry go far beyond what early humans could have conceived of. Amongst many textile applications, one area is space and aeronautical textiles. These days, the design, manufacturing, and application of textile composites in space and aerospace have become a very important and challenging industry. The phrase ‘composite material’ refers to material combining two or more different constituents together in order to get desired properties in an end product. The application of composite techniques in the making of space shuttles and other aerospace products needs to be defect free. Composites help in improving reduction of fuel consumption in aircraft and space shuttles. These products are mainly manufactured with high performance textile fibres, which require additional properties compared to the conventional fibres. High specific modulus and high specific strength are the basic requirements for aerospace structural parts. Good fatigue and stress resistance, good dimensional stability, and conformability are some additional properties. Along with fibres, the preform manufacturing process also requires attention. Fibres – such as carbon, glass, aramid, Kevlar, and many others – are commonly used as composite reinforcement in the manufacture of structural parts of commercial and military aircraft. Recent advances in the composite industry show the use of some natural fibres in the construction of aircraft parts following sustainability concerns. Apart from aircraft applications, textile fibres are used in the manufacture of spacesuits. Various raw materials are used for tailoring the spacesuit, including fabrics made from different synthetic fibres. For example, the innermost layer of a suit is made up of a nylon tricot material; the second layer is manufactured with spandex, which gives elasticity in the suit; and the next layer is made up of urethane coated nylon. Many other materials are also used in the manufacturing process, such as Dacron (a type of High Performance Technical Textiles, First Edition. Edited by Roshan Paul. © 2019 John Wiley & Sons Ltd. Published 2019 by John Wiley & Sons Ltd.
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polyester fibre used as a pressure restraining layer), Neoprene (a type of rubber), aluminized Mylar, Gore‐Tex, Kevlar, and Nomex. Manufacturing processes of composites play a significant part in the aerospace industry. It is necessary to choose cost effective, economical, and sustainable processes for the manufacture of composites. Advances in weaving, knitting, braiding, and nonwoven techniques opened new ideas for getting near net shape preforms, which can reduce the manufacturing time, material wastage, and production cost. This chapter deals with the typical synthetic and natural fibres used in the manufacture of aerospace materials, their characterization, manufacturing techniques, and testing methods. It also covers sustainability issues regarding textiles in the aerospace industry.
14.2 Synthetic and Nanotechnical Fibres Generally, fibres are classified as natural or manufactured (including nanofibres), as shown in Figure 14.1. The raw material for manufactured fibres may be derived from natural sources, like nonfibrous material such as glass fibres, natural polymers such as rubber fibre from latex, synthesized polymers such as polyamides and polyesters, and other manufactured fibres which have undergone further processing and modifications, for example carbon fibres manufactured from acrylic and pitch fibres. Nanofibres are fibre with diameters of less than 100 nm [1]. They are classified as manufactured fibres.
Textile Fibre
Natural
Vegetable Animal Synthetic
Cotton Jute Hemp
Silk
Manufactured
Mineral
Re-Generated
Synthetic
Asbestos
Viscose Rayon
Nylon Polyester Acrylic Carbon
Wool
Rample Linen
Cupramonium Rayon Acetate Rayon Ramie Linen
Aramid Vectran Nanofibres
Figure 14.1 Classification of textile fibres.
14.2 Synthetic and Nanotechnical Fibres
Technical fibres are widely used in various high‐tech applications, owing to their superior properties. They are capable of offering special characteristics to end products (technical textiles), such as mechanical, thermal, conduction, durability, resistance to flame, heat, smoke and chemical, etc. Technical textiles have been defined as ‘textile materials and products manufactured primarily for their technical and performance properties rather than their aesthetic or decorative characteristics’ [1]. The properties of material made by technical fibres can be tailored according to the needs of users by applying a manufacturer’s knowledge. New material characteristics can be developed by employing technical fibres and suitable technologies together. In the last few decades, the aerospace industry has focused on fibrous material to replace conventional material, and to manufacture various parts with fabrics, such as the fuselage, wings, landing gears, tail boom, rotor blades, skin, and thermal insulation tiles of spacecraft and space shuttles [2–7]. Among the fibrous material, natural fibres are irrelevant; however, manufactured fibres have huge potential. During polymerization, the characteristics of manufactured fibres can be modified easily according to a user’s needs. 14.2.1 Carbon Fibre Carbon fibre contains a minimum of 90% carbon which is attained from a controlled pyrolysis process. Carbon fibre is known for its high specific strength in the aerospace industry. Carbon fibre was discovered in 1879 by Edison when he placed a patent for the manufacture of electric lamps from carbon filaments [8]. However, the commercial production of carbon fibre started in the early 1960s. At that time, carbon fibre was used mainly in military aircraft, taking the advantage of its lightweight characteristics [9]. Carbon fibre is manufactured with the help of the controlled pyrolysis of organic precursors in the form of fibrous material by removing the oxygen, nitrogen, and hydrogen from the precursor. The mechanical properties of carbon fibre mainly depend on the polymer orientation in precursor fibre. Therefore, it is important to use highly oriented precursor fibre to manufacture strong and defect‐free carbon fibre. In recent decades, carbon fibre has become prominent in many industries, including aerospace, defence, sports and leisure, automobile, construction and infrastructure, etc. Carbon fibre is mainly used where lightweight property is of primary importance. Along with its lightweight property, carbon fibre composites are used in applications where strength, stiffness, and outstanding fatigue characteristics are required. Occasionally, carbon fibre is used where high temperature, chemical inertness, and high damping are important. There are a wide range of structural applications of carbon fibre in the aerospace industry, such as floor beams, stabilizers, flight controls, primary fuselage, and wing structure [10–16]. Along with its many advantages, there is a disadvantage: lower conductivity than aluminium. This is why lightning protection mesh or coating is essential to improve the conductivity of carbon fibre based materials for the aerospace industry. Advances in carbon fibre manufacturing techniques harness its flexibility and introduce novel types of carbon fibre in terms of improved modulus and strength for the aerospace industry. Research and development of carbon fibre is in two directions: one is to increase the strength (>5 GPa) with concurrent increase of modulus to a moderate level (>300 GPa) and this is for aircraft applications. Another is aimed at high modulus
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(> 500 GPa) with moderate strength (3.5 GPa) for space applications. The higher failure strain for carbon fibre is assumed to be the outcome of composites with improved damage resistance [17, 18]. 14.2.2 Aramid/Kevlar Fibre Aramid fibre was first introduced in the early 1970s, produced by DuPont under the tradename of Kevlar [19]. At the time of its first commercial introduction, aramid fibre had the highest strength‐to‐weight ratio among reinforced fibres. At that time aramid fibre was mainly used as a reinforcement in tyres and plastics, but now there are many applications of aramid fibre in different industries, and especially in the aerospace industry [20]. Aramid fibre is manufactured from the condensation reaction of paraphenylenediamine and terephthaloyl chloride. The structure of aramid fibre is an aromatic ring which contributes high thermal stability, whereas the para position gives stiff, rigid molecules, giving the fibre great strength and a high modulus. Aramid fibre is light in weight, strong, and tough. Kevlar 49 and Kevlar 29 are types of aramid fibres. Kevlar 49 is known in the a erospace industry for its high modulus, high resistance, and high impact resistance. Similarly, Kevlar 29 has a low modulus, is lightweight, and nonflammable. However, Kevlar fibre has disadvantages in compression and hygroscopy. Nevertheless, the remarkable performance of aramid fibre is used to increase fuel efficiency and decrease operating and maintenance costs. The interior parts of aircraft – such as cabin floors, overhead bins, and bulkheads – are manufactured with Kevlar honeycomb cores, which can help to reduce the weight of aircraft [21]. In spite of the weight reduction, a honeycomb structure is known for its low electrical conductivity and high fire resistivity, which are very demanding characteristics for meeting the safety standards. Kevlar fibre is strong enough to last in the extreme forces and temperature variations of space travel. Kevlar is used in communication satellites and also in space shuttles to protect against impact from orbital debris. Some more application examples are given in Table 14.1. 14.2.3 Glass Fibre Glass fibre is the oldest and most common reinforcement material used in the aerospace industry to replace heavier metal parts. Its density is higher than carbon fibre. Glass fibre is not as stiff as carbon fibre but has high impact resistivity and high elongation at break. Continuous glass fibre was manufactured by Owens Corning Textile Products in 1930s for high temperature electrical applications. Raw material for glass fibre involves silicates, soda, clay, limestone, boric acid, fluorspar, or various metallic oxides. These raw materials are mixed thoroughly to form a glass batch which is then melted in a furnace and also refined. The molten glass passes through various heating treatments and then is quickly quenched and attenuated in air into fine fibres ranging from 3 to 35 μm. Finally, winders are used to pass the fibres over the applicator which is used to apply chemical sizing to aid additional processing and performance. Glass fibre is stronger than any other inorganic fibre but it lacks in rigidity in account of its molecular structure [23]. E‐glass, also called borosilicate glass, is mainly used as the composite reinforcement material. Glass fibre has a low density, high resistance to chemicals, and excellent insulation capacity, which makes the fibre fit for the aerospace
14.2 Synthetic and Nanotechnical Fibres
Table 14.1 Applications of aramid fibre in aerospace [22]. Aircraft: exterior
Aircraft: interior
Missiles and space
Wing‐to‐body fairing Landing gear doors Leading and trailing edges of wings and control panels Engine nacelles Crash‐proof helicopter structures Helicopter blades Propellers Aircraft central fuselage (Super Puma MK2) Window reveals Overhead and side panels Cargo liner panels Armoured seats on military helicopters Partitions, lavatories, galleys, and bulkheads Pressure bottles for escape slides Air ducting Passenger seat pedestals Filament‐wound rocket engine cases Pressure bottles Launch tube reinforcement Air ducting
industry. The disadvantages of glass fibre are its low tensile strength when subjected to high tensile stress for long periods, and its brittle nature, which gives little warning before catastrophic failure. Regardless of this, glass fibre can still be used in break resistance parts at higher stress levels but for short timeframes. Secondary parts of aircraft – such as the fairing, radomes, wing tips, and helicopter rotor blades – are manufactured with glass fibre. 14.2.4 Vectran Fibre Vectran is the brand name of a high performance thermoplastic multifilament spun yarn having light crystal polymers (LCPs). It is manufactured with the help of a melt spinning process and also found as a melt spun LCP fibre. Chemically, it is an aromatic polyester produced by the polycondensation of 4‐hydroxybenzoic acid and 6‐hydroxynaphthalene‐2‐carboxylic acid. Vectran fibre possesses extraordinary strength and rigidity and is five times stronger than steel and ten times stronger than aluminium [24]. It has two variants: Vectran HS (high strength reinforcement fibre) and Vectran M (high performance matrix fibre). Vectran fibre was first produced in 1990 by Celanese scientists [25]. At the time of this fibre invention, the usage was limited to specialized military applications. But its unique properties opened new doors to the aerospace industry. In July 1997, airbags made from Vectran fibre were used to cushion the Pathfinder’s successful landing on the surface of Mars [26].
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14.2.5 Carbon Nanotubes The composite manufacturing industry always works to improve mechanical properties and this leads to research in carbon nanofibres. Improvement in crack propagation and fibre defects called for alternative solutions for obtaining ultra‐high‐modulus fibres. In the late 1950s, Roger Bacon found straight, hollow tubes of carbon which consist of graphite layers [27]. In the 1970s, Morinobu Endo produced tubes by gas‐phase and observed that some tubes contain single layer of rolled‐up graphite. Furthermore, in 1991, Sumio Iijima discovered multiwall nanotubes [28]. Carbon nanotubes (CNTs) can be produced with the help of a catalytic chemical vapour deposition technique. This low cost technique is simple and can deposit CNTs at a specific place on a substrate [29]. CNTs have unique nanostructures with remarkable electronic and mechanical properties, which are of prime importance for the aviation industry [30]. CNTs are employed in many scientific applications, including electrical energy management, sensing, conductive textiles, electronics, composite materials, mechanical systems, etc. It is evident that aerospace technology is an emerging discipline for CNTs. The introduction of new commercial aircraft, such as the Boeing 787 and the Airbus A380, opened new doors for CNTs in the aeronautical and space industry [31, 32]. Basic applications of CNTs in the aerospace sector consist of reduction of mass, improvement in functionality, self‐healing and durability, and enhancement in damage tolerance, thermal protection, and control. 14.2.6 Graphene Graphene is a revolutionary material for aerospace technology. It consists of a single atom thick sheet and an allotrope of carbon. Graphene is a flat monolayer of carbon atoms which are compactly packed into a two‐dimensional (2D) honeycomb lattice and is a main component for graphitic materials of all other dimensionalities. Graphene can be wrapped up into 0D fullerenes, rolled into 1D nanotube, or arranged into 2D and 3D graphite. Various efforts were made to synthesize monolayer graphene but were unsuccessful until 2004, when Andre Geim and Konstantin Novoselov used a method to isolate graphene [33]. Since then, a new era of graphene has begun. The graphene has attracted significant attention, owing to its high specific area and novel properties, including thermal, electrical, and mechanical properties. Following recent advances it has become possible to manufacture graphene polymer composites when a graphene sheet was exfoliated from graphite for bulk production. Several methods of preparing ordered graphene fibres were developed, for example hydrothermal and wet spinning of graphite oxide liquid crystal solution. The thermal and mechanical properties of graphene fibres are still unsatisfactory. Attempts have been made to overcome such problems by size selection of graphene oxide and the thermal treatment of graphene fibres. However, these approaches are complex and costly. Nevertheless, graphene is continually finding new applications within the aerospace industry; some recent applications include graphene/epoxy coating as multifunctional material (anticorrosion/hydrophobicity) for aerospace structures, electrically conductive epoxy resins, and aviation electronics.
14.3 Natural and Bast Fibres for Technical Applications
14.3 Natural and Bast Fibres for Technical Applications Nowadays, customers demand more environmentally friendly products and more sustainable technologies to reduce the global waste. This has led to greater attention being given to green products using renewable resources in the polymer industry. It is well accepted that natural fibres are renewable, hence more sustainable and environmental friendly, than synthetic fibres. Therefore, interest in research and development using natural fillers to reinforce polymers is growing in the field of composite materials [34]. Natural fibres offer several advantages over conventional reinforced fibres, such as lower cost, low density, toughness, and biodegradability. Hence, the use of natural fibres in the production of composite materials is well developed. Natural fibres are obtained from plants (such as cotton, flax, ramie, and hemp) and from animals (such as silk and wool). Table 14.2 shows the physical and mechanical properties of different natural fibres in comparison with manufactured fibres that may be used in the aerospace industry. It is obvious that the tensile strength of natural fibres is lower than that of synthetic fibres, but natural fibre reinforced materials still receives research attention because of its low cost and low environmental impact. On a ‘per weight’ basis, flax, jute, and hemp fibres have higher tensile moduli than E‐glass fibres, owing to the low density of natural fibres compared to E‐glass [38]. This is particularly important in applications where weight reduction is a priority. Therefore, it is not surprising that natural fibres are used as reinforcement for polymer matrices to replace conventional glass fibres. 14.3.1 Flax Flax is better known as linen. It is obtained from the stalk of Linum usitatissimum plant, which is 80–120 cm high. Flax was used in ancient Egyptian for mummy wraps, clothing, bed linen, and ships’ sails. Flax is two to three times stronger than cotton fibre but it is not very elastic in nature. Flax fibre is more resistant to wear and abrasion. Table 14.2 Density and tensile properties of different fibres [35–37].
Fibre
Density (g/cm3)
Tensile strength (MPa)
Young’s modulus (GPa)
Elongation at break (%)
Flax
1.50
345–1500
27.6
2.7–3
Hemp
1.48
690
70.0
1.6
Jute
1.3–1.49
393–800
13–26.5
1.2–1.5
Ramie
1.55
400–938
61.4–128
1.2–3.8
Sisal
1.45
468–700
9.4–22
3–7
Cotton
1.5–1.6
287–800
5.5–12.6
7–8
E‐glass
2.55
3400
73
2.5
Kevlar
1.44
3000
70.5–112.4
2.5–3.7
Carbon
1.78
3400–4800
240–425
1.4–1.8
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Materials made from flax do not tend to lose their shape easily. Flax fibre absorbs humidity well, and is also hypoallergenic; hence, it is an excellent choice of fibre for home textiles. In 1941, flax and hemp fibres were used in the manufacture of the bodywork of a new car, nicknamed the Soybean Car, which was claimed to have 10 times more impact strength than a car made with traditional steel [39]. Flax is finding its place in thermoplastic matrix composite panels for the internal structures of aircraft, but because of the high standards of the aviation industry, testing and research are still necessary before the commercial use of flax fibres becomes acceptable in the aviation industry. 14.3.2 Hemp Hemp fibre is obtained from Cannabis sativa L. plant, which is native to central Asia and was grown in China over 4500 years ago [39]. The plant can grow up to 4 m in 12 weeks. It does not require any fertilizer, herbicides, or pesticide to grow, which is why this fibre garnered interest regarding sustainability. Hemp fibre is a fine, lustrous, light‐ coloured, and strong bast fibre. There are grades of hemp fibre. Lower grade fibres are dark cream and have less fibrous material. Higher grade fibres are found in the skin/ stalk of the plant, which contain approximately 70% of the fibres and are long, high in cellulose, and low in lignin. Primary bast fibres are the most valuable part of the stalk, and are generally considered among the strongest part, and are mainly used in aviation applications. Similar to other natural fibres, hemp fibre is also finding its place in thermoplastic matrix composites for internal structures in automotive and aviation applications. Airbus and the South African Council for Scientific and Industrial Research launched a joint project into the research and application of natural and recyclable fibre based materials, including hemp fibre, for the manufacture of internal structures of aircraft, such as sidewall and ceiling panels, insulation blankets, and other less load bearing parts [40]. Hemp fibre is also used to make hybrid sustainable composite materials [41, 42]. 14.3.3 Jute Jute is native to the Asian subcontinent. It is bast fibre and obtained from Corchorus capsularis (white jute) and Corchorus olitorius (dark jute). Jute fibre was spun mechanically in the early 1800s. After cotton, jute is the second most common natural fibre. The plant grows to 2.5–4.5 m. It is mostly grown in Bangladesh, Brazil, China, India, and Indonesia. Jute fibre is for applications where low cost is more important than durability. Jute based thermoplastic matrix composites find a substantial market in the German automotive door panel industry. Jute fibre is being used in fibre reinforced composite materials because of its adequate tensile strength and good specific modulus. Jute composites can thus ensure a very effective and value‐added application avenue for the natural fibre. Ongoing research focuses on using natural fibres in reinforced polymer matrices and as a replacement of glass fibre, but still proper research and development using jute fibre is necessary for finding proper applications of jute fibre in the aerospace industry [43].
14.4 Manufacture of Technical Textiles
14.3.4 Kenaf Kenaf is bast fibre and obtained from Hibiscus cannabinus, a warm seasoned and wild plant, which is native to Africa and Asia. This plant has been cultivated since around 4000 bce, for food and fibre [39]. The plant consists of different lengths of fibres, both long bast and short core fibres with a hollow core. The plant grows to up to 4–6 m in about five months. The properties of kenaf fibre are similar to jute fibre. Kenaf fibre may be used as an alternative of jute fibre. Beyond cordage, bast fibres are beginning to enter the markets of mouldable nonwoven fabrics, reinforced composite materials, and packaging and other industrial fibres. Past research on kenaf fibre includes proper moulding condition for kenaf fibres, mechanical properties of heat treated kenaf fibres, and also the biodegradability of composite material using kenaf fibre [44].
14.4 Manufacture of Technical Textiles Textile fabrics for composite materials are designed and fabricated for load bearing functions. Since textile engineered with the same fibre orientation exhibits maximum tensile properties in the fibre length direction, often fibres are engaged in multiple orientations in a composite material to achieve optimum mechanical properties. In this context, biaxial woven fabrics and knitted fabrics with yarn interlacing and interlooping respectively exhibit high strength in both fabric width and length directions [45], but poor in radial direction. Nonwoven fabrics can be laminated at randomly oriented technical fibres for a degree of quasi‐isotropic properties. Below are most common technical textile fabric manufacturing techniques for composites. 14.4.1 Spinning Technical yarns are used to manufacture technical products to fulfil the requirements of their intended end use. There are many spinning techniques to convert fibres into yarns, as shown in Table 14.3, but this chapter deals with aeronautics and space textiles and most of the yarns used in this industry are synthetic fibres such as carbon, glass, Kevlar, etc. Synthetic fibres are extruded through the melt, dry, or wet spinning process. Apart from these techniques, many other techniques – such as reaction spinning, gel spinning, dispersion spinning, and electrospinning – are also used but only in particular situations. Melt spinning is the process in which a molten polymer is forced through a spinneret to form filaments. The filaments pass from the stretching zone in winding which facilitates orientation in the polymer chains along the fibre axis. Different cross‐sectional shapes of spinneret can be used in the melt spinning process depending on the end‐use application. After leaving the winding zone, a drawing process is used to give strength in the filament and make it suitable for technical applications. Normally, drawing is done with the help of two pairs of rollers, the second of which forwards the filaments at a faster speed than the first. According to their intended use, the filaments are then wound onto a package with or without twist. The untwisted filaments at this stage can form filament tow flat tape. Figure 14.2 shows the melt spinning process and drawing process.
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Table 14.3 Techniques of converting fibres into yarn. Short staple yarn
Synthetic filament yarn
Nanofibre yarn
Ring spinning Rotor spinning Friction spinning Self‐twist spinning Electro‐static spinning Vortex spinning Air‐jet spinning Twistless spinning Melt spinning Dry spinning Wet spinning Reaction spinning Gel spinning Dispersion spinning Electrospinning Bicomponent spinning Melt‐blowing Flash spinning
14.4.2 Electrospinning Nanofibres for textile applications are fibres having diameters of less than 1000 nm. There are a number of techniques for nanofibre production such as drawing, template synthesis, phase separation, self‐assembly, and electrospinning. Amongst all these techniques, electrospinning has become popular and is proven to be the simplest, most convenient, and a relatively cheap method of producing nanofibres. Electrospinning is the spinning technique in which ultrafine polymeric fibres are produced. Such ultrafine fibres are difficult to produce in any other normal spinning technique. Electrospinning was invented in the 1930s, but it was not popular; following the growth in interest in nanotechnology and nanoscience, researchers realized the importance of this spinning technique [46]. Nanofibres with a large surface area and small pore size can be used for nanocomposite and nanocatalytic applications. Development of electrospinning is mainly divided into three sections: the investigation of electrospinnable polymers, alignment control of electrospun nanofibres, and development of nanofibre yarns. Today, many synthetic and natural polymers have been electrospun, including polylactic acid (PLA), polyurethane (PU), polycaprolactone (PCL), polylactic‐co‐glycolic acid, polyethylene‐co‐vinyl acetate, and polylactide‐co‐caprolactone (PLLA‐CL). Amongst natural polymers, collagen, chitosan, hyaluronic acid, and silk fibroin have been successfully electrospun into nanofibres, thus opening up a whole range of application potentials for these fibres [47–50]. More recently, electrospinning has been systematically combined with melt‐blowing technology or flash spinning to mass produce nanofibres. To date, only nonwoven nanofibre materials have been commercially viable to produce. Despite considerable recent progress in electrospinning, fabrication of yarns with controlled nanofibre orientation remains one of the most serious challenges.
14.4 Manufacture of Technical Textiles
Hopper for polymer granulate
Drawing Extruder for cladding material
Spinning extruder
Feed rollers
Blow box for cooling
Stretching and take-up
Drawing rollers
Package Figure 14.2 Melt spinning process and drawing process.
14.4.3 Weaving Weaving, a fabric manufacturing technique, is most widely used to produce woven fabrics. This technique is very suitable for flat panel and 2D laminated composites. In weaving, a set of warp yarns is interlaced with a set of weft yarns at right angles. Warp yarns are oriented at 0° and weft yarns at 90° directions respectively. Plain, twill and satin are common designs for 2D woven preforms, as shown in Figure 14.3. Composites having 2D woven preform exhibit tensile strength and in‐plane shear characteristics. The plain weave has the ability to resist shear deformation at some point because it is the most highly interlaced and tightest woven, though the tight weave can be problematic to saturate with normally used resins in the composite manufacturing process. On the other hand, satin weave contains the least interlacing and as such has less resistance to shear distortion as compared to plain and twill. Hence, satin increases the ability to conform to complex contour shapes (drapeability). Other advantages that make satin weaves important for applications such as in aerospace include their high tensile and flexural strengths and minimum thickness. 14.4.4 Three‐Dimensional Weaving Three‐dimensional weaving is a promising and advanced preform manufacturing technique for engineering materials used in niche applications, such as stiffeners, aircraft wing joints, rocket nose cones, etc. [51]. This technique is similar to 2D woven preform structures except for the addition of a number of layers and binder yarns. During the manufacture of 3D woven preforms, three sets of yarns are interlaced, i.e. warp yarns in 0° direction, weft yarns in 90° direction, and binder yarns (also known as z‐yarns) in the through thickness direction. Three types of preforms can be manufactured: orthogonal, angle interlock, and layer to layer 3D weave designs. Three‐dimensional fabric
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Figure 14.3 Plain, twill, and satin 2D weave constructions.
designs with their shape description are shown in Table 14.4. Composite materials from 3D woven preforms have some impact resistance and damage tolerance [52–54] and are delamination free [52, 55–57]. 14.4.5 Knitting Knitting is a fabric manufacturing process by intermeshing loops of yarns. Generally, two types of knitted preforms are used in composite, i.e. warp knitted and weft knitted preforms. Weft knitted preforms is the utmost designed for their ease and manufacturability. It is considered to offer the most potential and versatile 3D shapes, which is required in the aerospace industry. Warp knitted structures are used to produce elastic or stable, open or closed, or flat or tubular structures. Composites having knitted preforms possess low mechanical properties [58, 59]. Despite the compromised mechanical properties and damage of fibre in preform due to knitting needles, knitted preforms are suited for rapid production of composite components with complex and near‐net
14.4 Manufacture of Technical Textiles
Table 14.4 Three‐dimensional textile structures and weave architectures [52]. Structure
Architecture
Shape
Solid
Multilayer Orthogonal Angle interlock
Compound structure with regular or tapered geometry
Hollow
Multilayer
Uneven surfaces, even surfaces, and tunnels on different level in multi‐directions
Shell
Single layer Multilayer
Spherical shells and open box shells
Nodal
Multilayer Orthogonal Angle interlock
Tubular nodes and solid nodes
shapes, with minimum material wastage. Knitted ceramic composite jet engine vanes impregnated with silicon carbide by chemical vapour deposition [60], rudder tip fairing for mid‐sized jet engine crafts [61], and electrically conductive composites [62] are worth a mention for the application of composite material. 14.4.6 Braiding Braiding is a composite preform manufacturing technique where three (minimum) or more yarns are intertwined to create a desired architecture. During braiding, each yarn crosses over the other yarns at an angle of between 0° and 90°. Tri‐axial braid with axial yarn added along the length of braided preform increases stiffness, tension, and bending strength of composite materials [63–65]. In addition, it also resists shrinkage in radial and in width (during tensile loads) in flat tri‐axial braids. The most common composite applications of braiding preforms are over‐braided fuel lines, rocket launch tubes, braided air ducts, and aircraft structures [66]. Dry and pre‐preg yarns can be used to manufacture braided preforms. The braiding preform manufacturing technique competes well with tape lay‐up, pultrusion, and tape winding, owing to design flexibility, damage tolerance, and low manufacturing cost. Figure 14.4 shows a braided structure. 14.4.7 Nonwoven/Stitching A nonwoven preform is produced by laying up multiaxial layers. The most significant advantage of multiaxial layers is that the end material may have different fibre properties, and the ability to optimize the thickness, weight, and strength at particular load paths. To make a multilayer preform, the layers may be stitched to improve the through thickness strength and damage tolerance of the materials. Stitching can be carried out by high performance fibres such as Kevlar, carbon, or glass. On one hand, stitching is a simple way of fabricating multiaxial layers but, on the other hand, it leads to significant in‐plane fibre damage that can compromise in‐plane mechanical properties. Three‐dimensional nonwoven composites have been largely successful in structural applications, including ceramic based and C based structures. Three‐dimensional
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Figure 14.4 Braided structure.
needle‐punched carbon/carbon (C/C) and carbon/silicon carbide (C/SiC) composites, for instance, have been widely used in Airbus aircraft C/C brakes, automobile brake discs, solid rocket motors, nozzle throats, exit cones, etc. [67].
14.5 Textile Reinforced Composite Materials Textile reinforced composite material is replacing conventional material in several engineering applications, owing to its useful properties such as being lightweight, and having high stiffness, good fatigue resistance, and corrosion resistance. It can be used to manufacture engineering parts with complicated geometries and designs at a low cost compared with conventional manufacturing techniques. The composite material combines two or more different constituents in order to get the desired properties in the end product. There are three main types of composites materials: ●● ●● ●●
metal matrix composites (MMCs). ceramic matrix composites (CMCs). polymer (textile) matrix composites.
Fibre reinforced polymer composites consist of two main components: reinforcement (textile material) and matrix (resin), as shown in Figure 14.5. There are several composite material manufacturing techniques that are widely used for high performance aerospace products. In this chapter, five of the most important techniques are introduced. 14.5.1 Hand Lay‐Up Technique The hand lay‐up technique is the simplest and easiest method of composite manufacturing particularly suitable for making low cost large parts, such as yacht hulls. The infrastructural requirement and processing steps are quite simple and suitable for flat
14.5 Textile Reinforced Composite Materials
Reinforcement
Composite
Matrix
Figure 14.5 Polymer reinforced composite structure.
or curvy shapes. Most aeroplane parts – such as flaps, ailerons, rudder, radomes, etc. – are usually made by the hand lay‐up technique. In the first step of the hand lay‐up composite manufacturing technique, release gel is sprayed on the mould surface, which is necessary to avoid sticking the polymer melt to the surface of mould. Reinforcement such as woven/knitted fabric or chopped fibre mat is cut in the same size of mould and carefully placed on the surface of the mould. Resin (liquid form of thermosetting material) that was mixed carefully in appropriate amount with a prescribed hardener (i.e. curing agent) is applied to the surface of the reinforcement already placed in the mould by pouring, brushing, or spraying. A mild pressure roller or squeegee is used on the reinforcement layers to remove trapped air bubbles. The process is repeated for each layer of reinforcement until the desired thickness is reached. Typically, this lay‐up technique is suitable to manufacture wide variety of composite parts using an open moulding method. Stacked layers are usually cured at room temperature without a vacuum bag. Although using vacuum bags increases costs, the vacuum bag offers better consolidation, uniform thickness, and better surface finishes. Curing time of hand lay‐up depends upon the type of polymers for composite manufacturing, e.g. epoxy based polymers take 24–48 hours curing time at room temperature. The hand lay‐up technique is suitable for thermosetting polymer based composites. This technique requires low capital and infrastructure compared with other techniques. However, the production is low and it is difficult to produce a high volume fraction of reinforcement. The hand lay‐up technique has many applications in the aerospace industry. Table 14.5 shows the raw materials to fabricate composites with the hand lay‐up technique. 14.5.2 Vacuum Bagging Technique A vacuum bagging technique has been developed for fabricating composite material by applying atmospheric pressure to adhere prepregs until the composite is consolidated Table 14.5 Raw materials used in the hand lay‐up technique. Matrix
Epoxy, polyvinyl ester, polyester, phenolic resin, unsaturated polyester, polyurethane resin
Reinforcement
Glass fibre, carbon fibre, aramid fibre, natural plant fibres (sisal, banana, nettle, hemp, flax, etc.)
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through curing. It has been developed for manufacturing various components but mostly for low cost complex shapes, double contours, and large structural parts. This technique involves a sealed bag in which a vacuum is created and an even amount of pressure of up to 1 atm (14 psi) is applied to the laminated material in the mould. This assembly is then placed in an oven for curing. This technique uses low cost equipment and tooling and is able to produce good quality composite components. Manufactured fibres – such as glass, carbon (graphite), and Kevlar – can be used in the vacuum bagging process. This method produces high quality mouldings with minimum or no air bubbles and can also improve the inner surface of the moulding. The controlled curing temperature helps to improve quality and consistency and gives time to allow resin to be used properly, while opening the way to additional quick cure with a quicker turnaround of moulds. 14.5.3 Advantages of Vacuum Bagging Vacuum bagging offers a suitable clamping method for very small to large scale applications, such as aerospace parts, wind turbines, race car components, musical instruments, model boats, etc. It has the following advantages: ●●
●● ●● ●●
●●
●●
The method is simple and produces high quality mouldings with minimum or no air bubbles. A variety of moulds can be used. A variety of fibres can be combined in a single laminate. Materials/polymers can be carefully chosen precisely to match the structural requirements of an end product. Vacuum bagging gives firm and evenly disturbed pressure over an entire surface, whereas mechanical clamping applies pressure only to concentrated areas and may damage fragile core material. The method can achieve optimum amount of adhesive in laminating, resulting in higher fibre volume fraction.
14.5.4 Injection Moulding Injection moulding is similar to metal die casting and is one of most important manufacturing techniques for plastic and plastic composite parts. It can produce fibre reinforced composite parts, especially glass fibre. It is based on Darcy’s law of flow through porous media. This law calculates that the flow rate per unit area (Q/A) is proportional to the preform permeability (k) and pressure gradient (ΔP) and inversely proportional to the viscosity (μ) of the resin and the flow length (L), i.e.:
Q / A = k∆P / µL
In this method, a special reciprocating single screw extrusion machine is used. The fibre filled matrix is fed into a machine, where it is melted within the barrel. This is followed by injection, where it is forced into the cavity of the mould, where it freezes and is ultimately ejected as the finished part, as shown in Figure 14.6. The injection moulding process permits finer part details and can be easily computerized. The
14.5 Textile Reinforced Composite Materials
Mould Injection moulding screw Gas water Pressure controller
Temperature regulator High pressure
Injection unit Figure 14.6 Setup for the injection moulding process.
portion and mould can produce near‐net shape parts. There is a limit to the amount and types of fibre reinforcement that can be included in an injection moulding part. The injection moulding process of thermoplastic is slightly different from thermosets. In the thermoplastic injection moulding process, a melted thermoplastic material is enforced on an orifice into a cold mould, where it solidifies. In thermoset injection moulding, a liquid state material is forced into a warm/hot mould, where the material polymerizes/cross‐links to a solid part. Injection moulding is widely used in the aerospace industry, automotive industry (air intake manifolds, rocker covers, etc.), electronic industries, medical and dental products (heart pump parts, orthopaedic devices, electrocardiograph, and oxygen parts), and household appliances (washing machine cylinders), etc. 14.5.5 Autoclave Autoclave processing is a popular method to manufacture fibre reinforced composites for high performance applications, typically for large complex engineering parts. Autoclave is the technique to manufacture large aircraft components like wings and fuselages. It is also used to produce a wide variety of materials, such as thermoplastics and thermoset composite materials. The aircraft industry has very strict quality standards. Apart from ensuring reliable and consistent processing methods, the industry also focuses on the improvement in the efficiency and cost effectiveness of aircraft structural systems. It is necessary and challenging for the designer to propose a proper autoclave system with controlled heated atmosphere, which produces satisfactory results and fulfils the requirements of the aircraft. An autoclave system is multidisciplinary in nature; it involves mechanical, electrical, electronic, and instrumental engineering and process controls in order to make it a completely automated system with reliable computerized control. In autoclave, pressure bag, moulding, heat and pressure are applied on the lay‐up from pre‐preg materials. The autoclave operating parameters such as temperature and pressure are based on the resin systems used. A vacuum may be applied in the early stages to remove trapped air. Air can be used for pressure, and forced hot air is used for stream heat‐up. The service temperature of these epoxy resin based structural components is restricted to about 120 °C [68]. A typical layout of autoclave is
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Insulated shell
Air distribution shroud
Heating elements
Bagged composites on moulds Quick opening door
Circulating air
Figure 14.7 Schematic diagram of autoclave.
shown in Figure 14.7. In an autoclave process, a number of thin sheets of high modulus fibres are impregnated with moderately cured resin then cut and stacked in sequence to the required shape. Then various layers of different materials (such as breather, bleeder, etc.) are covered to absorb excess resin and remove air and unwanted volatile gases from the stacked layers during the curing process. For a smooth surface, both sides of the laminate are usually covered with a fine polyester fabric which is peeled off after curing. For curing, certain pressures and temperatures are provided to laminate in a determined curing cycle for polymerization reaction. Autoclave technology is considered one of the mature technologies to produce composite materials that have quality, high performance, and the desired fibre volume fraction for high‐end applications. 14.5.6 Pultrusion The pultrusion process is a mature process for manufacturing fibre reinforced composite products. It produces profile shapes of continuous length of fibre reinforced polymer. The word ‘pultrusion’ is generally a combination of the two words ‘pull’ and ‘extrusion’. The pultrusion process involves pulling and drawing high performance fibres and pushing them into a resin liquid which is used to saturate the fibre reinforcement. The most preferred fibre is glass fibre (owing to its cheap price). The fibre and resin mixture allows for multidirectional reinforcement, resulting in the formation of strong material. Types of resins which can be used in pultrusion include polyester resin, vinyl ester resin, polyurethane resin, and epoxy resin. In this method, a surface veil may be used to avoid corrosion and erosion, and resist ultraviolet (UV) radiation. The resin and glass fibre combination is pulled together through a special heating die for a process of polymerization. After that, the mass of reinforced material in the shape of the die leaves to harden and to heat set into a desired shape. Finally, the consolidated composite material is cut into length and is ready for use. Through the pushing process a fixed
14.6 Textile Composite Material Finishing
Ventilation Resin injection
Heating & curing
Pulling device
Saw
Reinforcement Figure 14.8 Schematic diagram of the pultrusion process.
cross‐sectional shape may also be obtained. A schematic diagram of pultrusion is given in Figure 14.8. The pultrusion process is one of the low production cost processes because of minimum scrappage, simple machine, and low cost for the raw material. It is restricted to constant cross‐section, continuous reinforcement, and low viscosity resin. It is often used for high volume production runs of parts for the automotive and transportation industries.
14.6 Textile Composite Material Finishing The term ‘finishing’ refers to improving the serviceability and functionality of the material. Although there are several techniques to improve the aesthetic properties of composite material, there are no such standard finishing methods to finish or polish the material. Over the last couple of decades, a lot of effort has been made to improve durable cosmetic finishes such as smooth and high gloss finishes, etc. The following materials are mostly preferred for finishing the textile composite material, especially for aerospace application: ●● ●●
finishing and covering material. paints.
Finishing to airframe structures (internal as well as external) is done for several reasons including identity, protection from corrosion (where metal parts are used), solar and UV radiation, moisture, and biological attack. Although textile composite parts are free from corrosion, it is very necessary to provide an impermeable surface coating to block moisture from penetrating the laminates. The moisture may lead to delamination or weaken the part. Spraying is the most common method of applying a quality finish. There must be a suitable source of compressed air, a feed tank to hold a finishing material, and a device (like a nozzle) for controlling the combination of the air and finishing material ejected in spray form against the surface to be treated. Paint finishes
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always require time, patience, and a lot of skill. Paint finish involves mostly three ingredients, i.e. binder, pigment, and solvent. After mixing these ingredients, the paint may be applied by brush, roller, or spray.
14.7 High Performance Applications Advances in material engineering facilitated the need of customized engineered materials. Textile composite material is replacing the conventional materials in several fields such as aerospace, automobiles, transportation, sports, and other niche applications, owing to its light weight, superior corrosion resistance, and high strength and stiffness. 14.7.1 Spacesuit Textile composites have extended their boundaries from regular use to aerospace applications. The spacesuit is one such example, and is used for launch and space walks. It has zero tolerance for defects. On earth, nature provides humans with the correct mixture of gases in the environment necessary for our survival, including oxygen, nitrogen, carbon dioxide, and water vapour. However, in space there is no such natural environment, and astronauts encounter harmful radiation, low pressure, and high temperatures. Hence, a spacesuit is made from nonflammable, high performance textile fibre. The spacesuit is designed to protect the astronaut and keep them comfortable by providing cooling, clean air, and pressurizing systems inside the suit. The spacesuit should be lightweight, flexible, strong, thermally insulated, and thermal‐resistant. The suit consists of several layers, and each layer has different functions. The inner layer is manufactured by knitting technique for the comfort of the astronaut. The second and third layers are primarily made of polyurethane elastic fabric and urethane coated nylon fabric for pressure balancing (internal and external). Above these layers, seven layers are placed for thermal insulation. The outer layers are made of Kevlar and Nomex fibres for protection against electrical charges, particles, UV radiation, and meteoroids, which are the main threats that astronauts will encounter in space. Meteoroids are very small pieces of metal and rock. They travel at high velocity and can easily penetrate the body. Therefore, the spacesuit must be able to resist the impact and stress caused by these fragments and particles. 14.7.2 Textile Composites in the Aerospace Industry Excellent specific strength, stiffness properties, and lightweight structures are always the primary material requirements for aerospace and defence applications. The selection of high performance fibres and orientating the fibre in the required direction enable material engineers to tailor fibre reinforced composites with optimum mechanical properties. In addition, compound shapes and excellent fatigue and corrosion resistance have made composite material more significant and favourable through an
14.7 High Performance Applications
appropriate textile composite manufacturing technique. Therefore, commercial aircraft, such as the Boeing 787, Dreamliner, and Airbus A350 XWB, contain large proportions (by weight as well as by volume) of composite parts [60]. In addition, compound shapes and excellent fatigue and corrosion resistance have made composite material more significant and favourable through an appropriate textile composite manufacturing technique. 14.7.2.1 Structural Requirement of Aircraft
According to material definition, any structural component whose failure could endanger the aircraft is known as primary structure. The other structural parts are referred to as secondary structure. Fibre reinforced composites have a very wide variety of usage in different applications such as from air gondolas and gliders to passenger aeroplanes and military aircraft. Every application has a different need of mechanical properties and different area of usage. For example, carbon fibre has different mechanical characteristics (like high modulus) than glass fibre. It has a unique fatigue property, but on the other hand it is brittle. Boeing used 1500 composite components successfully in its helicopter to replace the metal with carbon composites. The aviation industry is increasing the use of composite parts and replacing metal parts to reduce weight and therefore fuel consumption, and carbon products are most widely used reinforced composite in aviation applications for both primary and secondary structures. 14.7.2.2 Fuselage
The fuselage is based on a semi‐monocoque structure containing longitudinal stringers. Conventionally, the fuselage was manufactured by different materials, such as wood and aluminium. However, these days only textile material, for example glass fibre or carbon fibre impregnated with epoxy resin, is preferred, owing to its low weight and superior mechanical properties. There are three areas in a fuselage: the crown, sides, and bottom. The skin of the fuselage holds the pressure and shear loads, while stringers carry longitudinal tension and compression loads. During flight, the fuselage bends because of the loading of the wings. This causes tension in front, shear in the sides, and compression in the bottom. 14.7.2.3 Wing
The wing is an important part of the aircraft and acts like a beam used to transmit the applied air load to the fuselage. Generally, various materials (wood, metals, and textile composites) are used to meet specific properties, such as strength, elasticity, specific weight, and corrosion resistance. The wings consist of wing box, spars, and ribs. The wing box contains top and bottom covers (skin and stringers) and carries the torsion load during flight. The spars work like a beam. The wing materials are designed according to their specific structural function and the right materials should be used for the appropriate parts of the wing. Replacing aluminium alloys, advanced composite materials can be tailored to meet specific design loads, strengths, and tensions for different wings and aircraft models. In past years, the use of nanomaterials has increased in the manufacture of wings. For example, electric conductive nanoparticles were introduced into structural components like wings to protect them against lightning strikes and also to increase damage resistance of the outer wing laminate [69].
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14.7.2.4 Empennage
The tail of an aeroplane is known as the empennage. It is composed of rudders, elevators, a vertical stabilizer, and a horizontal stabilizer. Structural designs of both stabilizers (horizontal and vertical) are as important as the design of the wing. Owing to bending, the upper and lower surfaces of the horizontal stabilizer are usually important in compression. Textile fibre benefits the empennage in different aspects. For example, different textile fibres may be blended in order to make the laminate lighter as well as lower in cost, such as a combination of carbon/glass fibres. In addition, carbon and glass fibres possess excellent fatigue resistance and are free of corrosion, and thus there will be no significant deterioration seen in the material, even after years of continual use. In addition to composites for structural parts, composite materials are also used for interior parts, such as overhead luggage compartments, sidewalls, ceilings, floor, galleys, lavatories, partitions, cargo liners, etc. Interior parts are usually made of fibre reinforced epoxy or phenolic resin. The composite parts include the wing box, forward fuselage, horizontal stabilizer, elevators, rudder, over‐wing surfaces, etc. There are many military aircrafts in which composites are used, such as the B‐B1 Lancer, F‐14A, F16, and the Navy’s V‐22. Almost 90% of the Voyager, which travelled around the world without refuelling, was made up of graphite fibre composites [70]. 14.7.3 Textiles in Space Industry Composite materials also play an important role in manufacturing space structures such as missiles, rockets, and satellites. Space structures require low weight, high stiffness, a low coefficient of thermal expansion, and dimensional stability. These properties are offered by composites. The application areas of composites in missile systems include rocket motor case, nozzle, skirts, and inter‐stage structures, control surfaces, and guidance structural components. E‐glass, S‐glass, aramid, and carbon graphite fibres are widely used in space and missile composite structures.
14.8 Testing Methods and Quality Control The applications of textile composite material increase as more and more industries realize what this material can offer. Aerospace structures made by composite materials requires wide range testing because composite products must face incredibly severe conditions, and it is a prime requirement to test them thoroughly to ensure the safety and reliability of the final product. Composite materials are anisotropic and nonhomogeneous, and a full classification of the material properties must be conducted if they are to be used in structural aerospace situations. The determination of bulk properties requires tension, compression, and shear tests. During qualification and material development, other test types – such as open‐hole tension/compression, interlaminar fracture toughness, compression after impact, and fatigue tests – are used to explore more complex properties. These tests should be conducted according to a test standard set by organizations such as: ●●
International Composites Testing Standards: the American Society for Testing Materials (ASTM), International Organization for Standardization (ISO), and European Committee for Standardization (CEN).
14.8 Testing Methods and Quality Control ●●
●●
Manufacturer Proprietary Standards: Boeing safety standards (BSS) Series and Airbus Industries Test Method (AITM) Series. Obsolete Standards (rarely used): Suppliers of Advanced Composite Materials Association (SACMA), Composites Research Advisory Group (CRAG), and European Association of Aerospace Industries (AECMA).
In most cases, the test procedure is similar in different standards; they only differ in specimen size. The following lists some important and common tests. 14.8.1 Tensile Testing Tensile testing is one of most common mechanical tests used for textile composite materials. A key purpose of this test is to determine the ultimate tensile stress and strain, tensile modulus (E), and maybe Poisson’s ratio with addition instrumentation attached while testing. Details and failure behaviour may be closely observed under controlled conditions. Testing metal is not difficult, owing to its isotropic homogeneous nature, whereas textile composites are anisotropic and complex, owing to fibre direction, diameter irregularity along the length, voids (air gaps), and resin rich area within the structure, etc. Textile composites will show optimum tensile properties if fibres are aligned in load direction; however, they will be weaker if fibres are perpendicular to the load. There are three types of specimen used for tensile testing: dog‐bone, waisted, and bow‐tie. Examples of common standards for the tensile testing of laminates made from high performance textile fibres are: ●●
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●●
●●
●●
Standard test method for tensile properties of polymer matrix composite materials (ASTM D 3039). Carbon fibre reinforced plastics. Undirectional laminates. Tensile test parallel to the fibre direction (EN 2561). Carbon fibre reinforced plastics. Unidirectional laminates. Tensile test perpendicular to the fibre direction (EN 2597). Determination of tensile properties. Test conditions for isotropic and orthotropic fibre‐reinforced plastic composite (ISO 527‐4). Determination of tensile properties. Test conditions for unidirectional fibre‐reinforced plastic composites (ISO 527‐5).
The specimens are parallel sided with bonded tabs to prevent the grip jaws from damaging the material and causing premature failures. Gripping mechanisms include manual and hydraulic wedge grips. 14.8.2 Compression Testing Textile composite materials are mainly manufactured in the form of laminates of mono, double, and sometimes several layers. Compression testing introduces compressive load into a material while preventing it from buckling. Textile composite materials are mostly good in tensile strength. However, some composites have low compressive strength, because their constituent fibre possesses low strain at break. During loading, specimen surfaces must be as flat and parallel as possible. If required, a specimen may be rubbed manually with different grades of emery paper or it may be
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grinded by machine to achieve the desired results. The strain gauges should be affixed on both sides of the specimen in order to measure macro‐buckling. Compressive loads are introduced into a test specimen (often thin and flat) by following the standard methods. Common compression test standards for textile composite materials are: ●●
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Standard test method for compressive properties of rigid plastics/composites (ASTM D695). Standard test method for compressive properties of polymer matrix composite materials with unsupported gage section by shear loading (ASTM D3410). Standard test method for compressive properties of polymer matrix composite materials using a combined loading compression (CLC) test fixture (ASTM D6641). Fibre reinforced plastic composites. Determination of compressive properties in the in‐plane direction (ISO 14126). Carbon fibre thermosetting resin unidirectional laminates. Compression test parallel to fibre direction (EN 2850). The standards can be used for:
●● ●● ●●
End loading: the load is introduced into the flat end of the test specimen. Shear loading: the load is introduced into the wide faces of the test specimen. Combined loading: a combination of shear and end loading is used.
14.8.3 Shear Testing Textile composites are often compromised because of their low shear stiffness and poor strength. Thus, a laminate stacking sequence is arranged in order to increase shear resistance, though this would compromise other properties. Ideally, a test specimen should provide quantitative shear measurements during the linear and nonlinear response regimes. Unfortunately, this is not possible, because of the material’s anisotropic and inhomogeneous nature. This is why there are several national and international test standards. However, no universal method is suitable for the accurate evaluation of a wide range of textile composites that have a variety of architectures. The following test methods are those commonly used for the determination of shear properties. ●● ●● ●● ●●
Uniaxial tension of a ±45° laminate (ASTM D3518/D3518M‐94). Two‐rail and three‐rail shear tests (ASTM D 4255). The V‐notched beam shear specimen (ASTM D7078/D7078M‐05). In‐plane shear test (ASTM D3518 and ISO 14129). Furthermore, there are other ways to determine shear properties:
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In‐plane shear: standard method for in‐plane shear response of polymer matrix composite materials by tensile test of ±45° laminate (ASTM D3518/D3518M‐13 and ISO 14129). Interlaminar shear: standard method for short‐beam strength of polymer matrix composite materials and their laminates (ASTM D2344, EN2563 and ISO 14130). Rail shear: standard method for in‐plane shear properties of polymer matrix composite materials by the rail shear method (ASTM D4255 and ASTM D7078). V‐notched beam: standard method for shear properties of composite materials by the V‐notched beam method (ASTM D5379).
14.9 Self‐Healing of Composite Materials
14.8.4 Fatigue Testing Failure of engineering material due to cyclic loading is known as material fatigue. Compared to metallic materials, textile materials possess excellent fatigue properties, owing to their anisotropic and inhomogeneous natures. Hence, it has been adopted by industries such as the aerospace and automotive industries. The following important variables affect fatigue properties. ●● ●● ●● ●● ●● ●●
Textile fibre type. Resin type. Design structure of reinforcement (unidirectional, woven, knitting, braiding, etc.). Laminate stacking sequence. Environmental conditions (temperature and moisture absorption). Loading condition.
Any test method for static testing may be used for the fatigue testing of textile composite material. Correct gripping and alignment are very important for better results. Failure must occur within gauge length. Generally uniaxial tension–tension cycling is done on composite material. However, tension–compression and compression– compression cycling is rarely used. High cyclic frequency in fatigue testing on polymer composites can cause temperature rises in the specimen being tested. The maximum temperature rise recommended by the ISO 13003 fatigue standard is 10 °C.
14.9 Self‐Healing of Composite Materials Engineering material has always benefited from the latest technological advancements in various applications. Today, it is no longer fanciful to speak of developing material which could repair itself and restore its structural integrity in the event of failure. For example, such material may recover its original shiny body surface, even after being scratched. An example of this would be Scratch Guard Coat, a Nissan product [71]. The original concept is taken from living species whose cuts and wounds heal naturally. In engineering, long‐term degradation can lead to microcracks and ultimately the failure of the material, and so ongoing self‐repair would be indispensable when designers look to increase the lifetime of the material. High performance textile based reinforced composites are the leading contenders for component materials to enhance reliability, efficiency, and the long‐term service life in various applications such as transport, aerospace, building, and many more. They offer immense scope for incorporating multifunctionality, owing to their hierarchical internal architecture. However, their relatively poor performance under impact loading leads to a significant reduction in strength, stiffness, and stability [72], and creates defects and damage by absorbing energy. As a result, the damage often manifests itself internally as matrix cracks and delamination, but it is very difficult to detect visually. Thus, textile fibre reinforced composites could directly benefit from incorporating an added functionality, such as self‐healing. Self‐healing techniques may be categorized into three groups: capsule based, vascular, and intrinsic [73]. In capsule based techniques, small capsules contain a liquid able to heal the crack. When a crack causes capsule damaged, the liquid inside the capsules is released and fills in the gap. In vascular type techniques, the self‐healing material is a
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vascular structure which is similar to a tunnel network. These tunnels are filled with liquid and when the rupture takes place the damaged tunnels break the vascular network and the liquid closes the gap. Conversely, intrinsic self‐healing techniques heal through inherent reversibility of chemical or physical bonding instead of through structural design [74]. Thermally remendable, highly cross‐linked polymeric materials like shape memory polymers are used in this type of self‐repair.
14.10 Sustainability and Ecological Aspects Demand for air transport is continually growing day by day. To meet the demand, society must also accept the costs. With the increase of air transportation, people can also be facing problems of noise, air pollution, climate change, greenhouse gases, etc. It is highly unlikely to achieve 100% sustainability in the aviation industry, but sustainability can be improved. It is believed that the aviation industry is one of the most polluting industries. In a report released by Air Transport Action Group (ATAG) [75], it is estimated that aircraft transport accounts for 12% of the total emission of carbon dioxide globally. The Intergovernmental Panel on Climate Change stated that 2% of global anthropogenic carbon dioxide emission is because of the aviation industry [76]. Increasing awareness of sustainability issues promoted the industry to research not only into the sustainability of biofuels but also into changing manufacturing practices by using natural fibres in composite manufacturing. Future aircraft are supposed to include new and environmentally friendly materials like natural fibres, and use more composite materials instead of metals. For example, Boeing is working on using parts manufactured with composite material in its beta versions of the new 767 in the hope that they will improve lift and reduce the aeroplane’s environmental impact.
14.11 Conclusion Textile material is a promising engineering material that has proved its worth in numerous applications such as aerospace, civil, transportation, medical, and many more. Some high performance textile fibres, such as carbon, possess high specific strength and modulus, good fatigue, and stress resistance, as well as being corrosion free. They are a highly desirable material for aerospace structural parts. Textile fibres may be divided into two categories: natural and manufactured fibres. Nanofibres became popular manufactured fibres because of their high surface area and functional properties. Synthetic fibres are widely used in the aerospace industry as compared to natural fibres because, during polymerization, the characteristics of synthetic fibre can be modified easily according to user needs. Carbon, glass, Kevlar, polyester, and Vectran fibres are some examples of such synthetic fibres with aerospace applications. It is well accepted that natural fibres are renewable, and hence more sustainable and environmentally friendly, than synthetic fibres. Natural fibres are increasingly used, in part because of customer demand for more environmentally friendly products and more sustainable technology to reduce global waste and greenhouse gases.
References
Textile fibres are generally converted into fabrics that can carry out load bearing functions. Fibres and polymers are first of all converted into yarns or filaments through spinning. They can also be used to produce nonwovens directly. The yarns/filaments are then used to manufacture woven, knitted, or braided fabrics through weaving, knitting, and braiding manufacturing techniques. Among all these techniques, weaving is the most widely used to produce fabrics, particularly 3D woven fabrics, for textile reinforced composite material for niche applications such as stiffeners, aircraft wings, joints, and rocket nose cones. Textile reinforced composite materials are replacing conventional metal materials in several engineering applications including aerospace, owing to their desired properties such as lightweight, high strength and stiffness, good fatigue resistance, and good corrosion resistance. In order to test their properties, different testing standards can be used for different structural materials of an aircraft. Fibre reinforced composites consist of two main components, textile reinforcement as core and matrix (resin) for shaping. Textile reinforcement is impregnated with resin to make composite parts and then consolidated according to a suitable composite manufacturing technique such as vacuum infusion, autoclave, pultrusion, etc. The selection for an appropriate technique relies on manufacturing cost, shape complexity, fibre volume fraction, and intended application. Generally, vacuum infusion is widely used for composite parts manufacturing, while autoclave processing is a popular method to manufacture fibre reinforced composites for high performance applications, typically for large complex engineering parts such as aircraft components like wings and fuselages. Autoclave is also used to produce a wide variety of materials such as thermoplastics and thermoset composite materials. Textile composite materials are replacing conventional material in several fields, such as aerospace, transportation, sports, and other niche applications, because of its lightweight, superior corrosion resistance, higher strength, and stiffness properties. The wide deployment of composite materials in commercial aircraft, such as the Boeing 787 Dreamliner, and the Airbus A350 XWB, is an example of the current application of textile composite materials. Today, all major parts of an aircraft – such as the fuselage, wings, empennage, and interior parts – are made using textile composite materials. Space and aeronautical textiles have a bright future.
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15 Wearable and Smart Responsive Textiles Lihua Lou, Weijie Yu and Seshadri Ramkumar Nonwovens & Advanced Materials Laboratory, Texas Tech University, Lubbock, USA
15.1 Introduction Textile materials that provide functional and high performance properties, which make them active, are generally termed smart textiles. Smart textiles, as indicated by their name, suggest materials that do not have the normal characteristics and functions of commodity textiles. In other words, materials when made into some shape or form, could somehow function as a textile material with enhanced functionalities can be conveniently grouped as smart textiles [1]. For example, smart textile is a subcategory within textiles and refers to textiles that can be worn and have electronic components. However, wearable smart textiles are not confined to electronic materials. In the past, wearables were bulky and not very aesthetically pleasing. Since consumers demand comfort and fashion, wearables have become smaller, lighter, and more stylish. Not only do consumers want comfort, they also want a product that is the most technically advanced for their individual lifestyle needs. Electronic components in wearables vary tremendously and include simple monitoring of footsteps to more complicated capabilities, such as monitoring heart rate and body temperature and detecting dangerous levels of air polluting substances, such as carbon dioxide [1]. Smart textiles have been around for about 1000 years, with the earliest wearable eyeglasses dating back to 1282. [2, 3] Throughout history, pioneers in wearables have attempted to create wearable accessories, to enhance the functionality of clothing. A wearable computer in 1962, George, another wearable computer, in 1972, the Pulsar ‘Calculator’ wristwatch in 1975, a wired computer backpack in 1981, digital hearing aids in 1987, the Bluetooth headset in 2000, a full digital pacemaker in 2003, the Fitbit in 2007, and Google Glass in 2013 [2, 3]. The development of smart textiles requires a multidisciplinary approach in which knowledge of circuit design, smart materials, micro‐electronics, and chemistry are fundamentally integrated with a deep understanding of textile fabrication [4]. Smart textiles provide unlimited opportunities to satisfy human imagined and dreamed smart life. Currently, there are more than 100 million wearable devices on the market, with a projected estimate of 600 million by 2020. Thanks to these smart textiles, High Performance Technical Textiles, First Edition. Edited by Roshan Paul. © 2019 John Wiley & Sons Ltd. Published 2019 by John Wiley & Sons Ltd.
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healthcare, medical, fashion, lifestyle, sport, security, and other aspects of future human life can be smarter and simpler than today [3–6]. This chapter provides an overview of the development of smart textiles over the past 20 years, their current status, and future prospects in smart textiles. In particular, this chapter intends to highlight future directions of smart textiles in the market, including challenges and competitiveness.
15.2 Characterization of Smart Textiles Smart textiles can be characterized by function and application. There are seven categories of characterizing smart textiles by function. They are: (i) shape memory textiles/ polymers [7–12], (ii) optical textiles (solar cells, light emitting, photovoltaic textiles) [5, 13–17], (iii) wearable electronics (electrotextile interfaces, textile based sensors, textile based actuators) [18–84], (iv) barrier membranes (waterproof garments, medical textiles, warfare protection) [85–96], (v) phase change materials (PCMs) (thermal energy storage) [97–102], (vi) chromic materials (colour change, photochromic, thermochromic, electrochromic, piezochromic, solvatochromic) [103–107], and (vii) other functional textiles (waterproof textiles, emitting scents textiles, breathable textiles, etc.) [108–115]. Characterizing smart textiles by application can be done as follows: (i) medical and healthcare [6, 12, 116–120], (ii) sport and wellness [121–126], (iii) fashion electronics [12, 124, 127], (iv) defence textiles (military, security) [128, 129], and (v) conductive ink textiles [130–134]. In addition to function and application, a general and broader categorization method has also been proposed by Md. Syduzzaman: (i) aesthetic and (ii) performance enhancing [19]. Matteo Stoppa and Alessandro Chiolerio categorized smart textiles into four groups by their sense and response to external stimuli: passive smart materials, active smart materials, very smart materials, and materials with even higher level of intelligence [18]. Lastly, smart textiles can also be characterized by fibre type, for example metal fibres, nanoparticles, polymers, composites, etc.
15.3 Smart Textiles Grouped by Function 15.3.1 Shape Memory Materials Shape memory materials are one kind of smart material that can change their shapes to temporarily deformed shapes induced by external stimuli (pressure, pH, temperature, electric, magnetic, chemical, ultraviolet light, etc.). [7] Based on the adjustment and control of the material parameters, the shape, permeability, surface tension, and tensile properties of shape memory materials can be controlled. This control has been applied to biomedical and microelectromechanical systems (MEMSs), and the aerospace, automobile, and telecommunication industries, etc. [8]. Shape memory materials are categorized based on the type of material: alloys and polymers. Polymer application seems to have great development prospects compared to relatively developed alloys because polymers are cheap, easily controllable, and have
15.3 Smart Textiles Grouped by Function
a large deformation range. The shape recoverable mechanism of shape memory polymers is due to their ability to transfer energy from thermal energy to mechanical energy, as an example. The extremely extensibility ability (about 400%) is derived from polymer networks’ intrinsic elasticity, viscoelastic, mechanical, and optical properties [9]. Temperature is the major and most commonly used external stimuli for polymers. The temperature at which a polymer shape change occurs is known as the transformation temperature (Ttrans) [9]. If the deformation occurs within the polymer recovery range, the shape of the polymer will return. However, once the unrecoverable deformation has occurred, the shape of polymers cannot be reinstated. Shape memory polymers can be categorized into four groups by transformation temperature: physically cross‐linked noncrystalline thermoplastic polymers, physically cross‐linked semi‐crystalline block copolymers, chemically cross‐linked glassy thermosetting materials, and chemically cross‐linked semi‐crystalline rubbers [11]. In fact, the intrinsic properties and the structural design are two major factors that affect polymer shape recovery behaviours. Many polymers have an increased shape retention performance and high recovery rate, thanks largely to these two factors. One of the parameters to measure the shape recovery behaviours of polymers is the shape memory cycle (strain recovery rate and strain fixity rate) [9]. Commonly used shape memory polymers include cross‐linked poly(cyclooctene), polyurethanes, poly(ester urethane), poly(D,l‐lactide), poly(1,4‐butylene adipate), poly(hexamethylene adipate), poly(ε‐caprolactone), poly(ethylene adipate), poly(ethylene glycol), poly(l‐lactide), poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate), poly(ethylene glycol) dimethacrylate, poly(ethylene oxide), poly(methyl methacrylate), poly(cyclooctene), poly(1,4‐butylene succinate‐co‐1,3‐propylene succinate), etc. [7–12]. Research has shown that 50–70% of patents for shape memory material target medical applications. Commercial polymers, for example New Ortho Polymers, MedShape, and MnemoScience, have been used in custom‐fitted perforated medical casts [12]. As polymers allow for minimum surgery and reduce rejection responses with imbedded drugs, shape memory materials have great potential in future medical applications. Furthermore, there has been an increase in interest for the application of shape memory material in smart textiles (nonwoven materials) in recent years. The material could be used as window treatments, room partitions, smart clothing, and wall hangings, which are triggered by temperature, electric, sunlight, etc., as shown in Figure 15.1 [7–12]. 15.3.2 Optical Textiles Wearable optical textiles produced from optical fibres or electronic wires blended with textiles have been used as electronics, sensors, and optics [13]. Optical textiles are able to carry light and are immune to electromagnetic fields. Park and Jayaraman invented the smart optical shirt, which is flexible, comfortable, wearable, and able to sense a variety of vital signs, such as body temperature, electrocardiogram, heart rate, and pulse oximetry [5]. Optical smart textiles can easily connect to optical devices, for example a photo detector, light source, and connector. The structure of optical fibres consists of the cladding and the core, in which the light is kept in the core and is satisfied with the internal reflection condition: n (core) > n (cladding), where n reflects the refractive indices [14]. Commonly used material for the
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(a) Weaving
Traditional Yarn
Deformation
Shape-memory device Smart energy storage shape memory fabrics
Healing
Shape recovered
Fabrics with original shape (b)
Smart energy storage cloths
Normal temperature
Automatic transformation
Over 35°C
Shape recovering
Easy to deform
Cooling down
Figure 15.1 The application of shape memory materials [10]. Source: Thakur S. Shape Memory Polymers for Smart Textile Applications[M]//Textiles for Advanced Applications. InTech, 2017.) under CC BY 3.0 license. Available from: http: //dx.doi.org/10.5772/intechopen.69742.
core is polystyrene. Polymethyl methacrylate (PMMA), styrene‐methylmethacrylate copolymers, polyethylene, polyvinyl chloride, and polyamide are commonly used materials for the cladding. The major optical fibre polymer suppliers are Toray, AGE, Inc., Asahi Kasei Corporation, and Mitsubishi Rayon [12]. As optical materials are brittle, and may break during textile processing, weaving, and knitting, processing methods need to be carefully selected to prevent breakage and thereby ensure light transmitting over a long distance. Optical fibres can be integrated into either warp or weft directions [15]. During the fabrication process, the fibre bending ratio and radius must be properly designed. Mikwang Dyetech has developed different weaving processes for optical smart textiles production [15]. As yarns in knitted fabric are exposed to severe bending, optical fibre is usually integrated in a straight line during the production process. The application of plasma for optical fabrics surface treatment greatly improves the surface wettability and chemical composition of the surface. Optical smart fabrics are categorized into two classes: smart shirts and photonic textiles [16]. Smart shirts have been designed for soldiers, athletes, and patients for medical monitoring, biofeedback, and clinical trials monitoring. Smart shirts that have been designed for fashion costumes, clothing, curtains, and handbags are called light
15.3 Smart Textiles Grouped by Function
illuminating textiles. Light illuminating textiles are irradiated by light emitting diodes (LEDs) and are battery operated. Photonic textiles consist of flexible displays and light therapy. Flexible displays are capable of displaying graphics and videos on the wearer and portable electronic devices. Light therapy has its application in medicine and can be used to treat skin diseases and nonseasonal depression. The mechanism of light therapy is based on the wavelength of light, 600–900 nm, emitted by the textiles [15]. Optical textile sensors are designed to measure the light transmitted intensity change applied to the textiles. The performance of optical smart fabrics can be enhanced if improved optics and electronics technology are embedded into fabrics and garments. However, signals remain relatively weak, which results in optical smart fabrics with weak durability and poor reliability [17]. Moreover, the bending of optical textiles is unavoidable during the production process, which also weakens the optical signal. It is believed that optical smart fabrics will become competitive in the medical and fashion industries once a new method for weaving optical smart fabrics without fibre breakage is designed. Without breakage, fabric with optimized light emission performance can be produced. 15.3.3 Wearable Electronics Wearable electronic textiles are fabrics interconnected with electronics, which provide flexibility, integration, and low power consumption to electronics. Wearable electronics are further categorized into three subgroups: passive smart textiles, active smart textiles, and highly active smart textiles [18]. All three subgroups need sensors to sense stimuli and react based on the signal’s outcome. Most passive wearable electronics have been used in biomedical fields, such as sensing of biophonic, electroencephalography, electromyography, electrocardiogram, and human muscle movement [19]. For active wearable electronics, they have been used in assistive technology, radio frequency (RF) functionality, human interface elements, and power storage or generation. The power of active wearable electronics is derived from motion or is photovoltaic. One of the materials used for wearable electronics is conductive fibre. Fabrics with conductive fibres could be applied to infrared absorption, protective clothing, electromagnetic interference (EMI) shielding, and antistatic fields. There are several conductive fibres production processes, one of which is wire drawing. Wire drawing, including metal monofilaments and blended fibres, could be directly used in fabric production process (weaving and kitting). Common products include copper clad aluminium (CCA) filaments, silver plated brass (Ms/Ag), aluminium (Al) filaments, silver plated copper (Cu/Ag) filaments, and metal filaments/yarns (cotton, aramids, polyesters, polyamides) [18]. Another method to produce conductive fibres is coating. Coating is relatively easier than fabrication, as metals are sprayed onto the surface of fabrics, yarns, or fibres. Coating technologies used include sputtering, evaporative deposition, and electroless plating [20]. A major advantage of coating is high yield. However, it also has disadvantages, for example poor durability and mechanical properties. Wearable electronics textiles are also produced with conductive inks [21]. The ingredients of conductive ink are highly conductive metal (copper, gold, and silver nanoparticles) and pure water. The technology to produce electronic textiles is called screen‐printing,
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which is versatile and provides high durability and flexibility. The possible disadvantages include low resolution and nozzle clogging caused by high viscosity particles. Wearable antennas are an essential part of the development of autonomous garments, which have controllable electric monitors [22]. The permittivity and mechanical properties of antennas are influenced by the bandwidth and efficiency of the materials used. The major issue facing wearable antennas is shape change due to body movements: bending, or deforming. Designers need to consider this influencing factor during the design process. Wearable electronics textiles can be used as sensors, which react to the environmental stimuli, for example pressure, electrochemical, and stretch [23]. Pressure sensors are mainly used as switches for electronic devices. The operational mechanism of pressure sensors is sensing the planar pressure or capacitance variations. Electrochemical sensors can convert chemical signals into physical measurements. Stretch sensors can sense body temperature, heart rate, blood pressure, respiration, muscle movement, and other body parameters. For example, a comfortable knitted fabric produced by Shu Yang and Randall Kamien’s groups was made which incorporated nano yarn structure [24]. The colour of the knitted fabric would change with the sweat increasing from the wearer, which indicates the health condition of the wearer. Smart textiles also could get energy from sunlight or body motion. A woven solar cell with triboelectric fibrous nanogenerators made by polymeric fibre has been produced by Zhonglin Wang’s team. This smart product could be used to charge cell phones and watches [25]. Qing Wang’s team has produced a wearable cooling vest with nanoarrays made from ferroelectric barium strontium titanite that can run for two hours on a 500 g battery [26]. A flexible and wearable battery has been invented by Yong‐Hee Lee et al., which is made by coating nickel on woven polymer and electroless deposition method. This solar‐charged textile battery can illuminate nine LED bulbs [27]. Nowadays, research is mainly focused on the development of intelligent textiles rather than passive or active electrical textiles. Figure 15.2 shows the basic structure of electric textiles. Interdisciplinary cooperation breaks the barriers between disciplines and Pressure
Shield
Electrode Array
Spacer (foam, textile)
Back Electrode Shield Figure 15.2 Electronic textiles.
15.3 Smart Textiles Grouped by Function
promotes the improved development of smart and intelligent electrical textiles. For example, a group of scientists from Austria, Germany, and Israel incorporated glucose moieties into upland cotton in vitro [28]. Glucose moieties incorporated with magnetic complexes enable cotton fabric to be magnetic. Ultimately, the market and consumer demand are the driving forces. 15.3.3.1 Piezoelectric Sensors
‘Piezoelectricity’ means electric charge that accumulates on materials in response to mechanical pressure or latent heat, and the interaction between the mechanical and electrical state of a material is linear and reversible [29]. Piezoelectricity has been applied to several application fields, such as the generation of high voltages, sound production and detection, microbalances, and electronic frequency generation [30]. The piezoelectric phenomenon was discovered by the Curie brothers in 1880 [31]. At the beginning of the twentieth century, macro‐scale piezoelectric transducers were produced for military application, which were called MEMSs [32]. Inorganic materials are commonly used for MEMS, for example silicon‐ and lead‐containing materials [33]. Since the 1990s, polymeric materials have created great interest, owing to the advantages of flexibility, low cost, and having additional properties [34]. Recently, nanostructured piezoelectric materials have been produced, which are called nanogenerators [35–40]. Ali Gheibi fabricated a one‐step nanogenerator using polyvinylidene fluoride (PVDF) with electrodes, which has an electric output as high as 1 V [35]. Polymer piezoelectric materials can be divided into two types of bulk polymers: (i) voided charged polymers and (ii) composite polymers [41]. Bulk polymers’ molecular structures need to be arranged to have piezoelectric mechanism [36, 37]. Voided charged polymers are polymers with gas voids and internal dipoles to form charges. Composite polymers are polymers integrated with piezoelectric ceramics [42]. Conductive textiles with zinc oxide have excellent piezoelectrical properties, which have proved to be alternative substrates to conventional substrates [43]. There are two common type of bulk polymers: amorphous and semi‐crystalline polymers. Amorphous polymers including polyimide [29] and polyvinylidene chloride [44, 45]. Commonly used semi‐crystalline polymers include polyamides [46], PVDF [47, 48], Parylene C™, and liquid crystal polymers [49, 50]. The mechanism of semi‐crystalline polymers piezoelectric materials is similar with inorganic materials. The negative and positive ions or polar groups of polymers are arranged in crystalline structures which cause polarization change depending on the stress [31]. The structure of voided charged polymers was invented by Gerhard Sessler [31]. The charged voids rather than ion displacement are the reason for the piezoelectric effect. There are several factors affecting charges of voided charged polymers, for example density/shape of voids and type/pressure of gas [31]. Composite polymers with piezoelectric ceramics have several advantages, for example flexibility, higher coupling, low acoustic impedance, few spurious modes, and dielectric constant [51]. Smart Material produces randomly or arranged scattered rods in polymer films. Microscale or nanoscale particles incorporated into a polymer matrix are another way to produce composite polymers piezoelectric materials [52, 53]. There are several applications of piezoelectric materials, including piezoelectric tactile sensors [54, 55], vibration energy harvesters [56, 57], acoustic transducers [58], and inertial sensors [36, 59]. Piezoelectric tactile sensors can be used to measure shape,
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tactile temperature, pressure, softness, and force. Ceramic/PVDF composites and PVDF‐TrFE with improved piezoelectricity flexibility [60] and softness have been designed. Nanograss PVDF sensor with a sensitivity of 0.56 V at 98 mN force is produced, which is 2.8 times higher than regular thin films [60]. Some researchers are using cellular polypropylene (PP) to analyse and identify touch location. [55] Other research has incorporated carbon black and high density polyethylene with PVDF and piezoelectric bicomponent fibre to detect the human heartbeat [61]. Piezoelectric materials with a high voltage of 20 V have also been applied to muscle driven applications [29]. There are many novel products designed using piezoelectric materials for energy harvesting, which could replace batteries [62, 63]. Usually inorganic materials are used because of their high power output [64]; however, polymeric piezoelectric materials provide flexibility and decrease stiffness, which could improve the lifetime of the device [65]. PEDOT/PSS polymer electrodes with PVDF [45], PZT‐epoxy composite harvesters [66, 67] and PMN‐PT nanowire based/PDMS composite are proving to be more robust than indium tin oxide (ITO) or platinum (Pt) electrodes. Polymers could effectively compensate high coupling and flexibility [68]. And, there is already continuous production technology for piezoelectric PVDF electronical textiles [69]. All fibre and environmentally friendly piezoelectric fabrics of ‘3D spacer’ technology have been produced by researchers, which have a power density of 1.10–5.10 μW cm−2 at applied pressure of 0.02–0.10 MPa [70], for an energy harvester and power generator. Besides that, a wearable piezoelectric fibre composite microsystem with a voltage output about 6 V is produced by Swallow et al. [71]. Another application of piezoelectric materials is for acoustic transducers, which are operated within audio, infrasonic, and ultrasonic ranges and could be used for loudspeakers and microphones [31]. It could also be used for medical applications, such as medical automated machinery or medical imaging. Inertial sensors produced by piezoelectric materials can be used to detect material orientation or acceleration and velocity. Edmison et al. applied piezoelectric materials for glove based electronic textiles that could sense hand movement [72]. Seyedin’s group used stretchable conductive knitted textile sensor, which can detect up to 200% strains and up to 500 cyclic stretching compared to the initial sample size [73]. Other research conducted by his group using polyurethane/poly(3,4‐ethylenedioxythiophene)polystyrene sulfonate (PEDOT: PSS) composite fibres showed excellent electrotechnical properties [74]. There is growing interest in making piezoelectric smart textiles, because they do not need to consume power to operate [75]. The polylactic acid (PLLA) piezoelectric braided cord sensor has also been used for fashionable clothes by a group of scientists [76]. More interdisciplinary research and funding focus on this field and its adaptation for consumers can accelerate the practical potential of piezoelectric smart textiles with further advances in their performances [76, 77]. 15.3.3.2 Diapers and Incontinence Products with Sensors
Urinary tract infections are common and usually affect children and the elderly [78]. However, conventional testing methods use urine culture, microscopic examination, and dipsticks [79]. These methods take a long time, and samples may be contaminated and a large number of samples are necessary. Diapers are commonly used for patients with urinary tract infections, thus the detection of urinary discharges on diapers will be a low‐cost and easier method for disease diagnosis.
15.3 Smart Textiles Grouped by Function
There are many existing technologies incorporating wireless and self‐power biosensors [80, 81] in diapers [82]. The power comes from the urine activated battery, which enables free movement and does not interfere with the wearer’s comfort. The connected transmitter will transmit an ID signal over a distance of 5 m at a voltage of 1 V [82]. A paper based device has been invented by Couto and Dong, which is used to analyse biomarkers from urine on diapers. The thickness of the device is 5.3 mm, which is important as it means comfort is guaranteed. Besides that, the results could be obtained within eight hours [84]. A smart diaper with integrated dipsticks is designed for colorimetric analysis of urinary tract infections, which can be used for the elderly and pets [83]. 15.3.4 Barrier Membranes Barrier smart textiles can be used as military protective clothing; medical garments with antibacterial and antifungal properties; or sportswear with protection against water, bacteria, viruses, blood, particulate matter particles, etc. The major advantage of barrier textiles is their breathability, which makes these textiles more comfortable than traditional barrier materials. Barrier smart textiles are categorized as waterproof garments, medical textiles, and warfare protective clothing. 15.3.5 Waterproof Garments Although waterproof garments guard against liquids, they are breathable porous textiles. The pore size and fibre diameter are major factors that determine their performance. Besides that, affinity (chemistry) and surface roughness (morphology) also have an influence on the wetting processes. There are three models to describe the behaviour of waterproof garments: the Wenzel model, the Cassie–Baxter model, and the Young– Laplace Equation [85]. 15.3.6 Medical Textiles Medical textiles are usually single‐use products, for example surgical clothing and medical antibacterial masks or caps. The apparel may also be covered with fluoro compounds or fluoropolymer based coatings and are used to prevent strike through by organic solvents with contaminants [86]. Additionally, multiple layer membranes are used, with each membrane having a different function. The inner layer is typically designed for comfort, while the barrier layer faces the outside. Metal oxides, activated carbon, and small particles have been imbedded into polymers to make composite membranes and provide biomimetic activity to the barrier layer. 15.3.7 Warfare Protective Clothing Warfare protection is the major application of barrier smart textiles. Protective armours have been used for almost five millennia and have gradually evolved from the use of animal skins and furs to metals and fibres [87]. Fibre materials belong to the class of soft body armours that are lightweight and more comfortable than ancient protective armours [88].
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Some of the earlier designs of soft body armours use silk woven fabric, which was later replaced by other fibres, such as aromatic polyamides and nylon 66 [89]. Nowadays, there are newer high performance fibres that are being used for ballistic protection. This includes Zylon [90], Kevlar [91], Technora [92], Spectra [93], and Nomex [94]. The ballistic‐proof ability depends on the absorbing energy performance of the materials, and the ability to distribute energy across the whole structure [89]. Thus, sonic velocity [95], tenacity, modulus, and extension at the break of the materials are important parameters determining the protection level. The detail properties of the materials listed above are described in Table 15.1. Zylon, or poly(p‐phenylene‐2,6‐benzobisoxazole), PBO, trademarked name, is a synthetic fibre manufactured by the Toyobo Corporation and was developed by DRI International in the 1980s [90]. Zylon has a tensile strength of 5.8 GPa, which is about 1.6 times higher than Kevlar [90]. Moreover, Zylon has excellent thermal stability. The modulus of Zylon is twice that of p‐aramid fibres and its decomposition occurs about 100 °C hotter than them [90]. These properties contributed to Zylon gaining wide application in body armour in 1998. However, recently some issues with Zylon have arisen, such as the degradation of the tensile strength under high ultraviolet (UV) radiation [90]. Kevlar, a para‐aramid synthetic fibre, was developed by DuPont in 1965. It is produced from poly‐paraphenylene terephthalamide and consists of long molecular chains [91]. Its high alignment of Kevlar molecular chains results in a high tensile strength (about 3620 MPa), low extension, high modulus/toughness, high chemical resistance, high thermal stability, and low flexibility [90]. The high tensile‐strength‐to‐weight ratio makes Kevlar five times stronger than steel [90]. Kevlar is a well‐known component for ballistic vests and face masks. Table 15.1 Ballistic protection materials. Chemical name/ formula
Tensile strength (MPa)
Extension (%)
Density (g/cc)
1800
3.5
0.97
Poly(p‐phenylene terephthalamide)
3900
3.5
1.44
Diaminodiphenyl ether‐para‐ phenylenediamine‐ terephthaloyl dichloride
3100
4.4
1.39
3000
3.5
0.97
485
35
1.38
Fibre name
Type
Company
Zylon [90]
PBO
Toyobo
poly(p‐ phenylene‐2,6‐ benzobisoxazole)
Kevlar 29 [91]
Paramid
DuPont
Technora [92]
Paramid
Teijin
Spectra [93]
HPPE
Honeywell High performance polyethylene
Nomex [94]
DuPont Ballistic protection materials Meta‐aramid
Poly‐meta‐ phenylene isophthalamide
15.3 Smart Textiles Grouped by Function
Technora is a para‐aramid fibre developed by Teijin. Its high strength and resistance properties make it useful in a number of applications, such as ballistic protection, cables, and ropes. Additionally, this fibre has good fatigue resistance, dimensional stability, and high thermal resistance [91]. Technora is produced by condensation polymerization of terephthaloyl chloride (TCI), p‐Phenylenediamine (PPD), and 3,4‐diaminodiphenyl ether (ODA) [91]. Spectra, a product of Honeywell, is an ultra‐high‐molecular‐weight polyethylene (UHMWPE) fibre, synthesized from the monomer ethylene [92]. Spectra is a thermoplastic polyethylene fibre. This material has a high strength (2.4 GPa) and is abrasion‐ resistant because of its extremely long chains and high molecular mass (3.5 and 7.5 million amu) [92]. Moreover, Spectra has a lower coefficient of friction than nylon, and its strength‐to‐weight ratio is about 8–15 times higher than steel [89]. Spectra is developed to provide arm and leg protection. Nomex is a meta‐aramid polymer developed by DuPont in the 1960s [93]. The aromatic backbones makes this polymer rigid and durable. Nomex is produced by a condensation reaction of m‐Phenylenediamine and isophthaloyl chloride [92]. Moreover, it has excellent thermal, chemical, and radiation resistance. Nomex is a commonly used polymer for protection against fire [92, 93]. The mechanisms of the ballistic proof ability of materials are the absorption of impact energy and redistribution of impact energy [89]. A protective material should absorb the energy before the bullet completely penetrates the material by either stretching, compressing, or destroying the material [92]. The energy spread speed should be quick, as the bullet’s speed is about 900 m s−1 [92]. The protection performance of ballistic materials is attributed to the rapid conversion and dispersion of the kinetic energy to strain energy. The absorption and redistribution of energy can be achieved when: (i) the protective materials decelerate and finally stop the high speed bullet by dissipating the kinetic
Cross-section of the Composite Leather Layer Nylon Nonwoven Anti-ballistic Layer U.S. Patent # 686127
Figure 15.3 Ballistic protection materials [88]. Source: Texas Tech University.
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energy along the plane of the protective material impacted [89], (ii) the protective materials bounce the high speed bullet [96], or (iii) a combination of 1 and 2. The transverse and longitudinal structure of ballistic fabric can be seen in Figure 15.3 [92]. The transverse wave propagates perpendicular to a material, while the longitudinal wave travels in the plane of the material [89]. The major parameters affecting the dissipation of kinetic energy are the tensile strength of the fibre, the number of layers, and the fabric structure. In conclusion, to be considered a ballistic material, the material should completely absorb the kinetic energy of the high speed bullet, to prevent injuries to the body. 15.3.8 Phase Change Materials PCMs are substances capable of storing and releasing energy during the phase change process, for example solid to liquid during the melting process. The NASA research programme was the first to incorporate PCMs in textiles (fibres, yarns, fabrics) in an effort to improve thermal protection for astronauts [97]. Textiles with PCMs react with the change of the body’s microclimate to provide thermal comfort. The mechanism of PCM materials is illustrated in Figure 15.4. For the past 30 years, PCMs have been widely applied in wallboards, walls, floors, and ceilings for active or passive solar heating, shutters, underfloor electric heating systems, night cooling, and textiles [98]. PCMs are essential for reducing dependency on nonrenewable resources and contribute towards an increase in the use of efficient and Heat absorbed PCM solid
PCM liquid Heat emitted
PCM fabric Figure 15.4 Schematic energy exchange process of phase change materials.
15.3 Smart Textiles Grouped by Function
environmentally friendly solar energy. Thermal energy storage of shape change materials can be accomplished by either sensible or latent heat storage processes [98]. Sensible storage processes are a traditional process, which needs a larger volume of material for energy storage than latent storage process. There are two kinds of PCMs: organic and inorganic. The most commonly used organic PCMs are polyethylene glycol (PEG), fatty acids, and paraffins [99]. The use of organic PCMs is advantageous in that they are recyclable, chemically stable, nonreactive, safe, compatible, not segregated, easily cooled, and have a wide temperature range. The possible disadvantages of organic PCMs include flammability, low energy storage capacity, and low thermal conductivity [98]. The commonly used inorganic PCMs are salt hydrates and metallics. The advantages of inorganic PCMs include nonflammability, high thermal conductivity, sharp phase change, low cost, and high energy storage capacity. The possible disadvantages of inorganic PCMs include segregation, super‐cooling, and high volume change [98]. There are three commonly used methods to measure the thermal properties of PCMs: differential scanning calorimetry (DSC), differential thermal analysis (DTA), and T‐history method. DSC measures the difference of heat capacity, melting temperature, solidification temperature, and heat of fusion between the samples and reference during the same heating process [100]. DTA uses the same heat applied to the samples and reference to measure the temperature difference between them. On the other hand, the T‐history method was used to measure thermal conductivity, heat of fusion, degree of super‐cooling, and the melting temperature [100]. For a PCM to be used in textiles, it has to satisfy several demands, including low price, ease of availability, large and effective thermal conductivity, stability for repetition of melting and solidification, be nonflammable, have a low toxicity level, be harmless to the environment, have temperature difference between the melting point and the solidification point, large heat of fusion, and a melting point between 15 and 35 °C [99, 100]. The materials that have satisfied these demands include hydrated inorganic salts, linear long chain hydrocarbons, and PEGs [101]. Hydrated inorganic salt incorporated textiles usually have an absorbing and releasing temperature range of 20–40 °C, for example Glauber’s salts have a melting temperature of 32.4 °C. Hydrophilic linear hydrocarbons absorbing and releasing temperature range depends on the number of n of CnH2n+2 [101]. PEG is one of the most important PCMs for textile applications. Commercial paraffin waxes have a wide melting temperature range and are cheap. Others include fatty acids (stearic acids, palmitic, lauric, and capric) and butyl stearate [101]. PCMs are incorporated into textiles during the liquid state; the diameter of these microcapsules is about 1–30 μm. When the temperature rises, the microcapsule melts and the heat is transferred and stored. When the temperature decreases, the stored heat is released and the microcapsules are solidified [102]. There are many individual differences amongst PCMs. As far as comfort goes, about 80% of the occupants have deemed the comfort of phase change textiles acceptable. The methods used to incorporate PCMs into textiles include fibre technology, coating, and lamination [104]. The fibre technology method involves adding the PCM microcapsules into the liquid polymer solution. The drying of wet spinning methods forms the PCM/fibre composites. Coating composition for textiles – such as PCM microcapsules, a dispersant, a surfactant, a thickening agent, and an antifoam agent – are
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applied directly to the textile substrate. Lastly, the lamination method incorporates PCMs as a thin polymer layer [101]. Although there are many applications of phase change textiles (shoes, accessories, bedding, sportswear, spacesuits, and medical applications), there are many challenges facing this textile. First, no standard testing method currently exists. Second, the mechanical properties of phase change textiles are bad. 15.3.9 Chromic Textiles Chromic materials or chameleon textiles are materials that show a colour change due to the external stimulus [103]. The external stimuli include light (photochromic), temperature (thermochromic), electricity (electrochromic), pressure (piezochromic), and pH (halochromic) [103]. Photochromic materials are materials, which change colour when exposed to UV light or electromagnetic radiation. In the 1960s, there were two significant applications of photochromic materials: photochromic glasses and photochromic micro‐ images [104]. An application in the optical industry is that photochromic glasses change tint, while photochromic micro‐images use an innovate method that allows the storing of images. The mechanism of action from photochromic materials comes from the electronic configuration change under excitation, which induces the change of the absorption spectrum in the visible range [103]. Most compounds switch from a colourless or light colour state to a darker colour state. The thermal activated reaction is called type T, while a photo activated reaction is called type P [104]. Photochromic materials can be organic and inorganic compounds [104]. Inorganic compounds are incorporated into glass, while organic compounds are incorporated into polymer matrices, microcapsules, stabilizers, or barrier polymers. Inorganic compounds have a long life and good resistance to fatigue. Commonly used inorganic compounds are silver salts. The commonly used organic compound comes from the spiropyran family of organic chemical compounds. These compounds can be degraded by UV radiation, oxygen, and free radicals. Some applications of inorganic/organic hybrid composite compounds are also used, for example polyoxometalates [105]. Thermochromic materials when induced by temperature will produce a colour change. The mechanisms of change include physical and chemical (phase transition, decompositions, and thermal dilation), modification of chemical structure, crystalline field, and charge transfer [105]. Thermochromic materials are classified as continuous and discontinuous. Continuous thermochromic materials undergo a gradual temperature change process. Discontinuous thermochromic materials undergo an abrupt change of colour at specific temperatures. There are two main families of thermochromic compounds: irreversible and reversible systems [106]. Electrochromic materials change colour when induced by an electrical current. The change of colour is dependent upon redox reactions, for example Fe+2 is yellow, while Fe+3 is orange [105]. Generally, electrochromic textiles need to have a sandwich structure to carry out the reaction: a support layer that allows for mechanical holding, a conducting layer to supply the system with electricity, an electrolyte layer, an ionic storage layer, a transparent conductive layer, an electrolyte layer, and an upper support layer [106].
15.4 Application of Smart Textiles
There are two families of thermochromic compounds: inorganic and organic. Inorganic compounds include metal oxides and Prussian blue. The commonly used organic compounds include conductive polymers and viologens [107]. Most chromic materials applied in textiles are in the field of fashion and technical and smart textiles. There are also some other possible application areas, for example in wound dressing to indicate the healing process. 15.3.10 Other Textile Products There are also some other types of functional smart textiles, for example waterproof textiles, scent emitting textiles, breathable textiles, etc. Waterproof fabrics could provide protection against rain and wind [108]. Scent emitting textiles can emit scent which could alter the wearer’s memory and mood [109]. Breathable textiles allow water vapour diffusion and prevent the penetration of water [108]. There are two types of waterproof fabrics: hydrophilic fabrics and microporous fabrics [110]. Hydrophilic polymers – for example modified polyurethane, polypropylene, nylon and polyester – are used for the production of hydrophilic fabrics. Microporous fabrics have tiny holes which are smaller than waterdrops and larger than water vapour molecules [111]. The commonly used polymer for the production of microporous fabrics include PVDF and polytetrafluoroethylene (PTFE). Waterproof fabrics can be applied for functional leisurewear and sportswear [110]. Emitting scents textiles are designed for human health regulation. For example, a herbal scented pillow has been designed for revitalizing and soothing the user with herbal aromas. Perfume emitting clothes are also designed for changing human moods and fighting diseases (e.g. Alzheimer’s disease) [113]. Breathable textiles have been used in medical and military fields, because breathability is associated with the comfort of the body in different environmental conditions [114]. One of the important developing trends for breathable textiles is the production of smart waterproof and breathable fabrics. Materials explored are shape memory polymer, such as shape memory polyurethane, cotton/poly(N‐tert‐butylacrylamide‐ran‐ acrylamide: 27: 73), etc. [108, 115].
15.4 Application of Smart Textiles Smart textiles are serving in various fields nowadays since they offer versatile functions for information, assistance, communication, aesthetics, etc. As Figure 15.5 shows, the application of wearable technology is mainly in the sectors of safety and security, medical and wellness, sport and fitness, communication, computing and entertainment [12]. Of these, the most widely used that are related to our daily life are the fields of medicine and sport. Apart from these applications in military and environmental fields, wearables also find applications in fashion sectors. Although, developments in smart clothing technology are highly innovative and advanced, application is only in its starting phase. Some products are on the market, but most of the new products are not in the market yet, which suggests that their potential use is enormous. So is the potential of integration with the electronic and fashion industries [12].
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Figure 15.5 World of wearable technology applications. Source: Beecham Research, UK.
15.4 Application of Smart Textiles
15.4.1 Medical and Healthcare Smart and high performance textiles are widely applied in the medical field, owing to their specific chemical and physical characteristics, quick production, and multiple functionality. Importantly, these textiles can serve as a platform to carry and deliver drugs. Therefore, the research and development of medical textiles is experiencing rapid growth because of their high potential in the world of technology and because of their potentially huge monetary value. Functional nonwoven materials in the medical sector can be classified according to where they are applied: (i) near the patient, (ii) on the patient, or (iii) in the patient. Medical textiles ‘near the patient’ are protective garments and articles that the surgeons need to wear and use while doing the surgery, ‘on the patient’ products are used to treat the wounds on the surface of the patient’s body, and ‘in the patient’ products could be planted inside the patient’s body for medical purposes. 15.4.1.1 Near the Patient
‘Near the patient’ textiles include surgery gowns, hats, and masks that the surgeons wear and the towels, sheets, and covers used in surgeries. Their purpose is to prevent cross‐infection between the surgeon and the patient, and to provide a sanitary environment during surgery. Therefore, the requirements for these materials are that they should have proper barrier capabilities against microbes such as bacteria, viruses, and microparticles; be comfortable to wear; be resistant to abrasion; be able to undergo disinfection treatment; and have a good balance between cost and performance, etc. [116]. Different nonwoven technologies and different new finishing technologies can give the material properties that meet these requirements. The material produced by a single nonwoven method has its limitations in the property and cannot meet all the requirements in medical practice, and hence the combination of two or three types of methods or raw materials is the way forward. For example, the composite fabric of SMS (spunbond melt‐blown spunbond) technology has a good balance of protection and comfort and is widely used in medical clothing. A comparison of the properties of different nonwoven technologies for the production of surgical gowns (spunbond, thermalbond, SMS, and spunlace) has shown that the comfort of spunbond and barrier quality of thermalbond are not good enough for them to serve as surgery gowns. Although spunlace materials have the best comfort and barrier qualities, its cost is the highest. Therefore, SMS technology can achieve a good barrier property and lower cost at the same time [117]. The finishing of surgical gowns usually includes water‐repellency, oil‐repellency, and alcohol‐repellency treatments that ensure the material’s barrier functions by enforcing its leakage‐proof property and sterilizing treatment like steaming process, ethylene oxide gas processing, and radiation sterilization [117]. 15.4.1.2 On the Patient
‘On the patient’ medical materials are those that are used to treat patient wounds, like surgical dressings, bandages, gauzes, suture lines, etc. They should have no toxicity, good absorbency of blood, and good affinity for the wound so that they can facilitate haemostasis and wound healing. They should also provide comfort for the patient, such
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as gas permeability, and no adhesion to the wound so that they will not cause trauma at removal [118]. More advanced requirements include odour management, microbial control, scar reduction, debridement of necrotic tissue, and other properties that accelerate the wound healing process [6, 116]. More and more new materials and technologies have been developed and introduced in the market for the use of dressings and bandages since the 1990s. In addition to maintaining the good absorbency of traditional cotton gauzes, new smart wound care materials have more advanced functions that better meet the requirements of the healing process. For example, bandages made of chitin fibres can accelerate the healing process because the glucosamine structure in the molecules of chitin has good biocompatibility with human tissue and chitin can enter bacteria cells and disturb their metabolism, also the hydrophilic groups in its molecules can retain moisture and make patients feel comfortable. Alginate fibres are ideal materials for wound dressings as their unique ion exchange property can swell the fibres in aqueous conditions. After cellulosic fibres are carboxymethylated, they become high absorbent fibres that absorb fluid near the wound directly into the fibre body instead of holding, which creates an environment of fewer microorganisms and makes dressing changes less painful [117]. In order to achieve multiple functions, modern wound care products adopt different composite structures with different materials in each part according to their uses. As Figure 15.6 shows, the most generally used structure is composed of three layers: the contact layer, the functional layer, and the retention layer. The contact layer provides a nonadherent interface with the wound which allows exudate to pass into the functional layer, and it can be made of polyamide nonwoven, polyurethane foam, etc. The functional layer absorbs and contains wound exudate and controls microbial growth, so it is made of superabsorbent and antimicrobial material. The retention layer secures the dressing onto the wound edge and provides both physical protection and a breathable path for oxygen in and moisture out. Therefore, it is often made of polyurethane films and hydroentangled nonwoven materials [6, 116, 135]. 15.4.1.3 In the Patient
‘In the patient’ textiles are those applications such as artificial skin, artificial blood vessels, and artificial organs that are implanted into the patient’s body. These applications have higher requirements for the materials and technologies. Functional Retention Layer Functional Layer
Contact Layer Figure 15.6 Structure of modern composite wound care products.
15.4 Application of Smart Textiles
nonwoven materials combined with modern chemistries have played a significant role in human tissue engineering and have become an important component in medical smart textiles [116]. One classical example of in the patient medical textile is the artificial blood vessel. It should be biologically safe to the human body and physically stable during application, which means it should have proper porosity, stiffness, and flexibility so that it can be resistant to pressure. Also, it should be easy for suture at implanting surgery. Silk, polyester filament, and PTFE have been used to develop artificial blood vessels. Large artificial blood vessels with an inner diameter of more than 10 mm are usually made by weaving or knitting material and should have good stability and flexibility. The requirements of artificial blood vessels with small diameters (< 6 mm) are better satisfied by nonwoven technology and coating with biocompatible materials [119]. The fabrication of multifunctional blood vessels by electrospinning is currently enjoying a period of rapid development. Artificial organs and tissues include the kidney, pancreas, bones, soft tissues, etc. The textile materials to be implanted into the human body should be biocompatible, nontoxic, and have good strength and chemical stability. The porosity and surface roughness of materials as cell growth media also influence the growth of tissue cells nearby. Hollow fibres from regenerated cellulose, acetate cellulose, polyacrylonitrile (PAN), polysulfone, etc. are used to make artificial kidneys. The substitute materials for soft tissues include ossein, silk protein, cellulose, chitin, hydrogel, carbon fibre, etc. The hard tissue implanting materials for bones are high strength and high modulus composite materials made from carbon fibre, polyester fibre, ceramic fibre, etc. [116]. These days, in‐plant materials are made using micro‐ and nanofibres produced using electrospinning and other techniques. Electrospinning technology produces ultrafine and solid fibres with diameters at the nanometre level which have large surface areas, and so the biochemical characteristics of nanofibre mats are similar to the features of natural tissue. This has resulted in the wide application of polymer nanofibres produced by electrospinning in the field of biomedicine. For example, biocompatible and biodegradable polymers, such as polyglycolic acid (PGA) and polylactic acid (PLA) are often used as the base materials for implant devices and they can provide high efficiency in drug loading [120]. Figures 15.7 and 15.8 show the process of electrospinning and the diameter of nanofibres produced using electrospinning. Collector
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Figure 15.8 SEM images of untreated and treated nanowebs (a) and (b). Fibre diameter distribution histograms of untreated and treated nanowebs (c) and (d). Source: Reprinted with permission from Uday Turaga, Vinitkumar Singh, Rachel Behrens, Carol Korzeniewski, Sudheer Jinka, Ernest Smith, Ronald J. Kendall, and Seshadri Ramkumar. Breathability of Standalone Poly(vinyl alcohol) Nanofiber Webs. Industrial & Engineering Chemistry Research 2014 53 (17), 6951–6958 [121]. Copyright 2014 American Chemical Society.
15.4.2 Healthcare Applications The application of smart textiles for healthcare and hygiene purposes is also very wide as they are necessities in our daily life. As elaborated earlier, there is a large market and huge space for the development of sustainable materials used to make baby or adult diapers, female hygiene products, and personal care wipers. With the development of economies and technology, and also the improvement of life quality, healthcare and hygiene products will not only grow in volume but also become more sophisticated and smart, with diverse functions, even built‐in performance indicators and warnings for disposal or change [118]. The common fibres used for healthcare products like incontinence diaper or wipes are: polyester, polypropylene, wood fluff, and viscose [122].
15.4 Application of Smart Textiles
15.4.3 Sports and Fitness Using smart textiles for sports and fitness involves more than just the fabrication of textile materials. It also means combining woven, knitted, or nonwoven materials with electronic technologies so that the device‐cum‐garment can monitor various aspects of the wearer’s body, such as body temperature, heart rate, blood pressure, or detect various activities, such as sweating, skin pH, moisture levels, etc. Wearable clothes for sports and fitness share some of the goals of healthcare appliances in the hospital, such as the result of the indicator points that reflect a person’s health condition, while the difference is smart textiles are more ‘smart’ and easy to use, which only require the wearer’s simple interaction, like a voice or gesture, instead of the complicated data doctors input in the hospital. Wearable devices also offer the possibility to monitor physiological signals continuously over long periods instead of a brief check only on visits to hospital [124]. Fibres and fabrics with a significant and reproducible change of properties according to specific environmental factor changes have been created using textile materials and processes, so they can be used as sensors or actuators [123]. Strain sensors in wearable outfits may be used in biomechanical analysis to provide interaction of posture detection, movement performance improvement, and injury reduction. For example, the Canadian company Heddoko has designed a set of smart compression clothing with textile embedded sensors that track the movement of body joints and provide live coaching feedback [125]. Chemical sensors could be used to detect the amount of sweat in athletic performance. Modified foams coated with conducting polymer or modified stretch knit fabrics can be incorporated into a garment to measure the breathing rate [126]. Figure 15.9 shows the functions of wearable sensors in sports.
Figure 15.9 Smart textiles system with monitoring functions in sports.
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The application of wearable textile technology in electronics partially overlaps with applications in other areas, such as healthcare, sports, defence, etc. In the medical field, long‐term monitoring and recording of the physiological signals of patients with chronic diseases requires electronic devices. In sports, smart clothes with sensors attached detect the activities of wearers to improve training regimens. For the military, wearable electronic systems can collect, process, and, crucially, give feedback on data pertaining to potential threats to soldiers on operations [124]. With the development of information technology, smart clothes not only serve basic functions like health and safety but also allow personal expression to satisfy the wearer’s fashion requirements. Clothes and other wearable products like handbags integrated with LED electronic parts show different dazzling colours in a dramatic way. For example, Luminex® is a fabric that can be illuminated by LEDs, as it is integrated with fibreoptic strands during the weaving process [124]. Clothes that have an ‘emotional effect’ can interact with their wearer ‘emotionally’. The electronic parts can detect the wearer’s bodily signals and reflect these back, thus ‘reflecting their emotional state’ [12]. Diverse innovative designs of textile based electronics can not only offer people aesthetic value but also provide different new functions by integrating sensors and electronics with numerous types of textile products to improve a person’s lifestyle. The integration of textile technology and electronic technology can greatly facilitate people’s lives and in many different ways. For example, a light and easily portable fabric keyboard that can be rolled up was invented years ago [124]. Smart gloves, socks, and footwear with electronic sensors can control factors like temperature. Curtains or car seats can alert people to environmental changes [127]. 15.4.4 Defence Applications Smart textiles are applied in the military field for the protection of soldiers from chemical, biological, thermal, and additional external threats, such as high velocity projectiles [128]. Figure 15.10 shows the structure of a nonparticulate pad that can be used for chemical warfare decontamination. It is manufactured by needle‐punch technology, bonding three layers of viscose, activated carbon, and polyester fibres together. This dry decontamination pad can absorb a wide range of both liquid and gaseous chemicals, and can be applied to both the human body and a soldier’s equipment [129]. 15.4.5 Conductive Ink on Textiles Smart textiles with electronic parts that have a sensor or communication function to work with the wearer’s body have one major design issue. The hard electronic parts or stiff metallic fibres that have been developed to form the fabrics can compromise a garment’s comfort and/or breathability[130, 131]. One solution is to print functional conductive inks onto the surface of the textiles [130]. The printing of conductive inks on textiles has enjoyed rapid developmental breakthroughs in recent years. The key determiner of this technology’s adoption and growth is ensuring the conducting property of the ink material and the flexibility of both ink and base materials, and to ensure that the ink will maintain a good durability after wearing or washing.
15.4 Application of Smart Textiles
Top absorbent layer Activated carbon fabric Bottom fabric layer Cross section of the three-layered wipe
Figure 15.10 Nonwoven decontamination fabric and its structure [129].
Insulating upper cover layer Conductive wire Insulating lower cover layer Fabric substrate Figure 15.11 Structure of textiles printed with conductive ink.
Two printing methods are used in the production of a whole conductive patch: screen printing and stencil printing. As Figure 15.11 shows, the structure of conductive inks is printed on the textiles in the sequence such as first a lower insulated cover layer is printed, then the conductive layer is printed on top of it, and finally an upper insulated cover layer on top of the conductive wire is printed. Stencil printing is only for the printing of an encapsulation layer with an increased thickness around the electrodes [132]. The textile materials used as the substrate vary from fabrics made of natural or synthetic fibres such as cotton, viscose, polyester, and polyamide to blended fibres like cotton/polyester. Silver, gold, and copper have been used to make conductive wires [133, 134].
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15.5 Sustainability and Ecological Aspects In contrast to the positive and useful aspects smart textiles bring to human beings, they are now facing a critical challenge. There is growing concern about the ecological effects and sustainability of smart textiles [136–137]. Nanomaterials have been applied in smart textiles in different fields, because of their special properties: antibacterial (silver), UV protective (TiO2), electrically conductive (gold, carbon), etc. [140–141]. Some materials are not toxic when they are in their usual bulk state but they become toxic when they have nanostructures like nanoparticles or nanofibres. The small size of nanoparticles allows them to go through the exposure pathways and cross barriers easily, enter the inner organs and tissues, and damage the health of organisms. All aspects of their toxicity should be studied and settled into a series of related standards: mass, diameter, shape, and difference when taken through different pathways [138, 143]. The problems of what to do with the waste generated by manufacturing smart textiles, as well as the excessive energy consumed and the environmental hazards potentially produced during this process, not to mention the various demands of washing and maintaining smart clothes all highlight the sustainability challenge of textiles. Smart textiles promote a new marketing model called fast fashion, whose quick product turnover brings with it an environmental and economic burden [144]. Meadows et al. came up with the idea of holistic sustainability, which considers economic, societal, and environmental sustainability together. Right now, it seems economy wins over the other two [138]. However, in order to reach holistic sustainability, a redefined consumerist culture and economy should be propounded. Moreover, a qualitative risk assessment of nano‐bio‐info‐cogno‐ (NBIC) smart technology has been conducted by Claudia Som and Lorenz M. Hilty [145]. The results assume the NBIC has great impact on traffic, housing, work, and health. Wearable sensors may impact the traffic situation by modifying the individual’s short‐term decision‐ making. The possible impact on housing involves human occupants focusing more on virtual environments than on the actual environment. The possible impact in the world of work is individuals who are not smart tech savvy being treated as though they were disabled. The possible impact on human health is the increased risk of privacy intrusion and ethical dilemmas [145]. Toxic and scarce materials in the electronic smart textiles also will lead to e‐waste, which has a severe environmental burden [141, 146–148]. This e‐waste is normally treated as normal waste right now, which is even worse for the environment. Besides e‐waste, chemical waste during textile production and use is a widespread problem. Most chemicals are not immediately toxic but have chronic effects on human health [149–151]. Researchers are increasingly focusing on monitoring and measuring smart textiles’ environmental impact [152, 153]. They believe the technology embedded in clothes – for example electronic textiles, phase change textiles, chromic textiles, shape memory textiles, and conductive textiles – can be used to encourage those activities that are environmentally sustainable. Fic et al. published a paper about future materials for electrochemical capacitors that suggested using by‐products from the food industry as a carbon precursor, for example coconut shells, various seeds, shells, coffee grounds, etc. [153]. Some other work has already been done to combine wearable technologies and environmental sustainability with textiles, for example clothes responsive to noise, light, and air pollution [154–156].
15.5 Sustainability and Ecological Aspects
Before the issues surrounding sustainability can be tackled, researchers must understand that smart textiles are first and foremost user‐centric. And because of their high energy and raw material consumption, lack of long‐term functional durability (i.e. they become less waterproof, weatherproof, comfortable, easily stored, heat‐resistant, etc., over time) and the difficulty in recycling them, their impact on public health and the environment can be quite significant [136–139]. Niu has suggested several methods of recharging wearable electronics that are convenient for wearers and could elongate battery life: generating power from the wearer’s body movement, using human food as a power source, especially for soldiers, and recovering power from the sun and radio transmissions [157]. Genuinely sustainable smart textiles can have a positive impact on both society and human beings [137]. Many users abandon smart textiles after wearing them only a few times. The main reason for this seems to be designers’ lack of understanding of the requirements of long‐ term usability. Sustainable smart textiles, as the name indicates, means designing smart textiles and applications that have a positive effect on humans, public health, and society at large without causing environmental hazards [137]. The idea of increasing the service life of textiles by creating enriching stories is promoted based on the definition above [137]. Electronics textiles with sensors can contact skin and response with environmental data, which could promote data visualization and experience surrounding environment. Shape memory textiles could sense data and express either positive or negative responses, which would enhance and stimulate the relationship between textile and wearer [137]. The major considerations for sustainability are material selection, possible waste production, and waste treatment. Possible waste production and waste treatment can be improved by changing consumer consumption habits and modifying production processes [136]. Marilyn Waite mentioned using bamboo as a raw materials because it is more environmentally friendly than common polymers and natural fibres, because of its biodegradability and renewability [158]. Moreover, designers should also consider experience based design from the perspective of customers. Usually, five elements should be considered when designing sustainable smart textiles: (i) comfort, (ii) interaction and communication between smart textiles and their surroundings, (iii) to sense change in both the wearer and their surroundings, (iv) respond effectively to visible signals, and (v) functionality [137]. Kristi Kuusk [136] conducted research into sustainable smart textiles. He concluded sustainable smart textiles have eight issues: controlling energy and chemical use, minimizing consumption, caring for longevity, developing constantly, updating the product, supporting meaningful creation, building relationships, and empowering positive emotions. Reducing energy and chemical use means reducing toxins during production and use. Caring for longevity means paying attention to a product’s durability. Supporting meaningful creation is about inspiring consumers’ creativity. Developing constantly means using the same products for different purposes to improve their service life. Building relationships is about creating relationships between consumers and smart textiles. Empowering positive emotions is about enhancing a garment’s use and its wearer’s comfort. Besides that, economy and market sustainability are also important. Irene Pasqualotto’s thesis talked about the circular economy and textile recycling market opportunities.
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‘Circular economy’ means integrating and managing the different aspects of sustainability, for example utilizing renewable energy and waste and avoiding waste generation and clean production [159]. Aparna Sharma conducted a study about eco‐friendly textiles and sustainable textile production processes [160]. It concluded that smart textiles need to be kept in use as long as possible to maximize their value by providing an emotional connection between products and the humans who use them.
15.6 Conclusion Developments in smart and wearable textiles have had a great impact on daily life in recent years. These textiles have a large range of applications, for example wearable electronics, barrier membranes, PCMs, shape memory materials, optical materials, and other functional textiles, which provide convenience, comfort, and sense of technology to satisfy humans’ imagined and dreamed smart life. Areas that use smart textiles include architecture, automotive design, fashion and entertainment, military, healthcare, sport and fitness, among others. From a research point of view, this field has attracted a wide array of groups and funding. Some of the major challenges facing this field are cost, logistics, durability and textile‐like feel and hand. These challenges need to be tackled to make smart textile products a mainstay of the textiles sector. This chapter has analysed the definitions, categories, functions, applications, and sustainability of smart textiles. The topics covered here show that interdisciplinary research is necessary for designing smart textiles, including computer and sensor technology, material research, engineering, fashion design, marketing analysis, etc. To avoid possible waster production, chemical pollution, energy consumption caused by design defects of wearable textiles, an eco‐friendly and sustainable design method should be proposed. In future, new technologies – such as advanced nanotechnologies, electronic technologies, computer technologies, etc. – will play an important role in determining the next generation of smart textiles. In the meantime, empowering positive emotional interactions between smart textiles and their consumers will encourage the longevity of smart textiles and decrease the pollution they cause. Therefore, user‐oriented technology development, ecological design, and fashion design should be integrated for future smart textile design. Acknowledgements The authors would like to acknowledge Abdul‐Hamid Cherissa at TTU Health Sciences Center for her help with some discussions on the chapter.
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Index a Abrasion resistance 14, 24, 107, 113, 121, 122, 126, 128, 145, 170, 172, 173, 228, 243, 290, 324, 356, 357, 359, 361, 363 Absorbents 1, 2, 23, 38, 39, 51, 53, 97, 116, 295, 299, 379, 456 Accidents 5, 107, 290, 301, 377, 397 Acoustic textiles 368–369, 379 Activated carbon 17, 20, 217, 368, 447, 460 Active cooling system 134, 137–138 Active materials 21, 42, 58 Active sportswear 42, 44, 45, 48–50, 57 Active textiles 57–58 Aerogel 12, 20, 116, 120, 187, 400, 402, 403 Aeronautic textiles 1, 9, 407–433 Aeroplanes 8, 9, 354, 421, 427, 428, 432 Aerospace industry 370, 390, 408–414, 418, 421, 423, 426, 432 Agrotech 2 Agrotextiles 3, 7, 279–312 Airbags 2, 353–355, 361, 363–366, 379, 411 Airborne particulate matter 5 Aircrafts 8, 9, 125, 354, 355, 370, 371, 374, 400, 407, 409–412, 414, 417, 419, 420, 423, 426–428, 432, 433 Air filtration 99, 217, 218, 222–223, 228, 230, 354 Air inflated structure 322, 323 Air‐jet‐spun yarns 171–172
Air permeability 4, 50, 97, 115, 144, 173, 179, 180, 223, 225, 229, 232, 243, 285, 298, 308–309, 329, 333, 358, 378, 379 Air pollutants 217, 219 Air structures 322–325, 348 Air supported structure 322–323 Ammunition 197–202 Antennas 15, 60, 444 Antifouling 8, 16, 94, 232, 385, 394–395, 400 Antimicrobial textiles 31, 93–95, 99 Antistatic properties 13, 19, 42 Application areas 1–3, 7, 8, 61, 279, 355–369, 428, 453 Applications 2, 4, 8, 9, 14, 15, 20–23, 29, 31, 39, 46–57, 59–61, 69, 70, 72–76, 84, 86, 87, 90, 93, 94, 125, 133, 206–208, 215, 219–221, 227–229, 240–242, 251, 253, 260, 279–295, 305, 306, 308, 310, 320, 322–325, 346–347, 353–376, 385–403, 407, 409–417, 419–428, 431, 440–443, 445–449, 452–461, 463 Aprons 5, 107, 140, 141, 147, 241 Aramid fibre 111–113, 123, 177, 387, 399, 410, 411, 421 Architectural fabric structures 8, 320–322, 349 Architectural textiles 319–326, 348, 349 Atmospheric pressure plasma jet (APPJ) 16 Autoclave 12, 423–424, 433
High Performance Technical Textiles, First Edition. Edited by Roshan Paul. © 2019 John Wiley & Sons Ltd. Published 2019 by John Wiley & Sons Ltd.
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Index
Automotive industry 29, 354, 361–363, 370, 371, 375, 376, 379, 380, 423 Automotive interior 359, 369, 376–379 Automotive textiles 8, 353–380 Awnings 8, 241
b Ballistic protection 202, 448, 449 Ballistic resistance 141 Balsa 389–390 Barrier membranes 9, 331, 440, 447, 464 Basalt fibres 253, 254, 343 Bast fibres 1, 7, 12, 31, 38, 220, 244, 249, 250, 340, 341, 413–415 Binders 30 Biocompatibility 83–86, 97, 456 Biodegradability 31, 40, 84, 85, 257, 260, 280, 282, 285, 298, 306–308, 413, 415, 463 Biodegradable plastics 18, 306, 307 Biohazards 5 Biopolymers 93, 98, 217, 219, 220, 282–283, 290, 295, 300, 308 Bioresorbability 83–85 Biostability 83–85 Blood vessels 76, 78, 138, 456, 457 Boats 8, 288, 329, 330, 354, 370, 389, 397, 399, 422 Body armour 5, 6, 107, 121, 132, 133, 137, 141, 199–202, 447, 448 Braiding 240, 260, 345, 353, 375, 394, 408, 419, 431, 433 Breathability 6, 7, 38, 39, 44, 46, 81, 82, 87, 128, 132, 138, 217, 312, 359, 377, 378, 447, 453, 458, 460 Bridges 6, 94, 319, 342, 346, 347 Building textiles 12 Buildtech 2 Bulletproof vests 110, 132 Burn 13, 24, 60, 79, 89, 124, 125, 130, 139, 140, 163, 184, 204, 207, 208, 326, 362, 365, 386, 395
c Calendering technique 226 Capillary mats 2, 280, 295, 298, 299
Carbon fibre 108, 110, 112, 115, 124, 127, 177, 221, 254, 342, 343, 370–372, 387–388, 392, 394, 398, 399, 408–410, 421, 427, 429, 430, 457 Carbon nanotubes (CNTs) 14, 108, 116, 137, 165, 386, 403, 412 Car covers 2 Carpets 1–3, 8, 11–13, 15, 19–21, 24, 27, 29, 32, 353–355, 359, 360, 369, 379, 385, 397 Cellulose 18, 20, 30, 39, 40, 78, 118, 131, 163, 216, 219, 244–246, 248–250, 257, 258, 282, 283, 293, 308, 339, 340, 414, 457 Characterization 206, 230–232, 275, 301, 302, 304, 306, 309, 408, 440 Chemical, biological, radiological and nuclear (CBRN) 6, 13, 132, 137, 146, 197, 206–211 Chemicals characterization 231–232 resistance 7, 209, 252, 282, 386, 388, 448 treatments 3, 21, 44, 51, 131, 206, 227, 368 Chemical vapour deposition 3, 217, 412, 439 Chenille yarns 14 Chitosan 17, 80, 93, 98, 219, 282, 402, 416 Chromic textiles 452–453, 462 Classification 22, 70–72, 141, 176, 286, 354–355, 408, 428 Clothing cold protective 51–53 comfort 54, 107–109, 131, 133, 134, 136–138, 377 Clothtech 2 CNTs see Carbon nanotubes (CNTs) Cold weather sports 51–54 Comfort 4–6, 8, 9, 11, 37–62, 69, 70, 81–83, 97, 107–109, 121, 125, 131–138, 141, 148, 159, 160, 183–189, 205, 206, 326, 329, 335, 354–356, 358, 359, 363, 368, 376–379, 385, 426, 439, 447, 450, 451, 453, 455, 460, 463, 464
Index
Composites fabrics 21, 173, 177, 455 material finishing 425–426 materials 373, 420, 432, 433, 457 Compression testing 429–430 Conductive inks 14, 440, 443, 460–461 Conductive polymers 14, 19, 137, 453 Construction textiles 7–8, 319–349 Controlled release 4, 79, 283 Core fabric 391 Core materials 386, 389–391, 422 Cotton 11, 15–17, 19, 20, 23, 26, 27, 30, 37–41, 43, 44, 47, 51, 53, 55, 70, 71, 82, 93, 95, 96, 99, 108, 116, 136, 148, 162–164, 173, 204, 206, 219, 220, 225, 226, 241, 244, 248, 250, 257, 258, 281, 288, 294, 295, 300, 307, 339–341, 353, 356, 366, 367, 379, 386, 399, 400, 413, 414, 443, 445, 453, 456, 461 Crops covers 2, 279, 280, 283, 286, 291, 294–298, 310 protection textiles 279–312 Cross‐linked PVC foam 390 Curtains 3, 11–13, 15, 20, 25, 27, 95, 206, 242, 282, 354, 365, 442, 460 Cut hazards 121–122 Cut resistance 113, 121, 122, 141, 147, 285 Cyclodextrin 18
d Decision making 55–57 Defence applications 426, 460 Degradation 7–8, 31, 39, 84, 86, 99, 108, 110, 112, 113, 136, 243, 244, 247, 250, 251, 256–260, 280–282, 284, 290, 295, 298, 305–307, 311, 342, 386, 392, 394, 398, 431, 448 Design 6, 7, 9, 14, 16, 19, 27, 29, 41, 54, 55, 57, 82, 109, 131, 138, 159, 160, 177, 197, 215, 229, 240, 284, 325, 326, 333, 343, 346–349, 353–356, 358, 364, 365, 369–371, 377–379, 385, 395, 399, 403, 407, 417–420, 427, 428, 431, 432, 439, 441, 444, 448, 460, 463
Development 3, 4, 7, 9, 15, 18, 29, 32, 37, 40–46, 59, 61, 62, 84, 85, 90, 91, 93, 96, 107, 120, 134, 165, 182, 187–188, 212, 221, 240, 261, 269, 272, 273, 279–283, 290, 295, 312, 320, 339, 343, 349, 353, 358, 359, 364, 365, 374, 376, 380, 385, 389, 395, 397–399, 403, 409, 413, 414, 416, 428, 439, 440, 444, 445, 453, 455, 457, 458, 460, 464 Diapers 20, 97, 446–447, 458 Down fibres 116–118, 120 Drainage 2, 6, 242, 266, 267, 308, 329, 332 Drug delivery 76, 80, 86, 95 Durability 3, 6, 11, 13, 16, 25, 32, 40, 42, 44, 48, 93–96, 99, 108, 109, 113, 121, 122, 125, 127, 128, 133, 138, 141, 215, 232, 244, 247, 260, 279, 285, 290, 291, 295, 298, 306, 323–325, 329–331, 333, 341, 356, 359, 363, 370, 397, 409, 412, 414, 443, 444, 460, 463, 464 Duvets 11–13 Dyed fabrics 16, 177 Dyed fibres 166–167 Dyed yarns 168, 172–173
e Ecological aspects 26–32, 62, 98–100, 232–233, 272–274, 311–312, 403, 432, 462–464 Ecological issues 141, 148, 340, 347–349 e‐health system 85, 87, 88, 93 Electromagnetic radiation 14, 305, 452 Electromagnetic shielding 14 Electrospinning 76, 79, 217–219, 221– 223, 232, 283, 415–417, 457 Electrospun nanofibrous 400, 401 Embankments 6, 242, 310 Emergency situations 2 Empennage 428, 433 Energy efficiency 8, 334, 335, 348, 349 Engine compartment items 367–368 Engineered structures 5, 148 Environmental impacts 15, 19, 20, 27–29, 31, 62, 94, 98, 141, 148, 215, 273–274, 291, 295, 312, 349, 413, 432, 462
477
478
Index
Environmental protection textiles 6–7, 239–275 Epoxy resin 374, 389, 392, 412, 423, 424, 427 Erosion control 2, 6, 267, 292, 308, 310 e‐textiles 3, 15, 19, 20, 29–30, 32, 88, 90, 98
f Fabrication 162, 179, 183–187, 243, 395, 400, 416, 439, 442, 443, 457, 459 Fabrics constructions 49, 52, 53, 136, 223–226 structures 8, 15, 23, 42–45, 52, 82, 108, 119, 121, 136, 215, 229, 240, 310, 320–323, 349, 356, 368, 374, 450 weight 126, 127, 296, 310–311, 398 Fatigue testing 431 Feather fibres 115, 118 Fibreglass 253, 325, 338–340, 372, 387, 390–392 Fibreglass reinforced plastic (FRP) planking 390–391 Fibres diameter 21, 78, 115, 118, 222–223, 230, 243, 429, 447, 458 reinforced composites 1, 220, 227, 319, 372, 374, 414, 422–424, 426, 427, 431, 433 Fibrillated tape yarns 224–225 Fibrous filters 217–219, 222 Fibrous insulating materials 335–340 Fibrous materials 70, 115, 280, 319, 320, 326, 333, 335, 339, 340, 343–346, 409, 414 Filters 2, 6, 8, 72, 215, 217–219, 222–228, 230, 232–234, 239, 267, 308, 353–355, 367–368, 379 Filtration efficiency 97, 218, 219, 222, 223, 225–228, 230, 368, 402 Filtration media 6, 215, 223, 368 Filtration textiles 3, 6, 215–234 Finished fabrics 2, 178–179, 189 Fire hazards 5, 139 Fire resistance 13, 15, 130, 209, 324, 326, 330, 395 Fishing nets 284, 285, 287–290, 303, 308, 312
Fitness 9, 453, 459–460, 464 Flame protection 125 Flame‐retardant (FR) 2, 8, 13–15, 28, 108, 122, 123, 125, 130, 131, 136, 148, 162, 197, 204–208, 210, 211, 216, 227, 385 Flax 1, 12, 31, 98, 162–164, 220, 221, 244, 246, 249–252, 258, 281, 291, 340, 349, 353, 371, 413–414, 421 Floating row covers 291–295, 311 Fluorochemical resins 16 Food packaging 17, 19, 25, 93 Friction‐spun yarns 171, 172 Fuel efficiency 8, 370, 371, 410 Functional finishing 2–4, 9, 43, 210–211, 225–227, 325 Functional materials 5, 9, 55, 148, 412 Functional performance 5, 71, 109, 159–162, 183, 184, 188, 189 Functional sportswear 4, 46–48 Furnishing fabrics 14, 16, 397 Fuselage 409, 411, 423, 427, 428, 433
g Geogrids 6, 7, 239, 241 Geometrical characterization 230–231 Geonets 7, 241 Geotech 2 Geotextile composites 6 Geotextiles 1, 3, 6–7, 220, 239–275, 302, 303, 308 Glass fibres 6, 12, 110, 204, 220, 227, 228, 253, 254, 325, 338, 339, 343, 371, 386–387, 393, 397, 408, 410–411, 413, 414, 421, 422, 424, 427, 428 Gloves 5, 12, 41, 107, 115, 119, 132, 138–141, 208, 209, 446, 460 Graphene 14, 403, 412 Ground covers 283, 284, 291, 292, 294 Growing medium 295, 300, 301
h Hand lay‐up technique 420–421 Hazardous situations 5 Hazardous waste control 2 Healthcare textiles 31, 69–100 Heat bonding 6, 267 Heat protection 125
Index
Heat‐setting process 225–226 Helmet 5, 107, 141, 199, 200, 203, 208, 354, 355, 365, 366 Hemp 1, 12, 26, 31, 38, 116, 163, 220, 221, 244, 246, 249–252, 281, 288, 291, 339–341, 349, 353, 371, 408, 413, 414, 421 High activity 4, 50, 55, 62 High performance applications 20–23, 46–57, 72–76, 228–229, 285–295, 353, 423, 426–428, 433 High performance textiles 3, 4, 9, 11, 12, 108, 110, 115–131, 133, 215, 216, 220, 227, 372, 379, 380, 407, 426, 429, 431, 432, 455 Hometech 1 Honeycomb core 389, 390, 410 Horticulture 7, 279, 283, 294, 295, 302, 304, 306, 308 Hot weather 55 Household textiles 3, 12–16, 19–21, 23–32 House wraps 2, 8, 319, 326–334, 336, 349 materials 327, 330–334 Hovercrafts skirts 398–399
i Impact resistance 261, 301–304, 376, 380, 390, 393, 410, 418 Incontinence products 446–447 Industrial textiles 6, 233, 240, 241 Indutech 2, 354 Inflatable craft 399 Injection moulding 369, 422–423 Injury 121, 139, 184, 197, 204, 361, 365, 366, 379, 459 Inkjet printing 14, 19, 183 Inner layer 21, 53, 78, 125, 136, 271, 426, 447 Inorganic fibres 112, 124, 163, 335, 338–339, 410 Insect repellence 13, 14 Insulating felts 366 Insulating materials 13, 335–340 Insulation 2, 3, 6, 8, 12, 13, 21, 38, 40–43, 51–53, 57, 81, 115, 116, 118–122, 125, 131, 133, 138, 139, 173, 182, 188, 220, 221, 253, 319, 320, 323, 326, 334–341, 349, 354, 355, 360, 361, 366, 368, 369, 378, 395, 409, 410, 414, 427
Insulative materials 116, 119–121 Intelligent textiles 4, 5, 61, 444 Interior carpet 359–360 International regulatory bodies 5 Internet of things (IoT) 61, 62
j Jackets 42, 116, 119, 122, 138, 139, 159, 400 Jerseys 46, 47 Jute 1, 11, 17, 31, 38, 163, 220, 244, 246, 247, 249–252, 254, 255, 258, 259, 262, 263, 274, 281, 291, 292, 295, 300, 307, 308, 311, 349, 413–415
k Kapok 115, 116, 118–119, 244 Kenaf 1, 12, 38, 220, 221, 244, 349, 366, 415 Key issues 160, 187–189, 386, 397 Knife 121, 141, 184, 197, 199, 202 Knitted fabrics 7, 12, 16, 23, 43, 119, 125, 130, 160, 172–175, 228, 229, 240, 242, 262, 284, 285, 289, 291, 297, 372, 373, 393, 415, 421, 442, 444 Knitted reinforcement structures 393 Knitting 16, 21, 91, 137, 160, 168, 175, 189, 240, 260, 262, 285, 345, 353, 356, 359, 372–375, 394, 408, 418–419, 426, 431, 433, 442, 457
l Lamination 12, 15, 18, 19, 44, 60, 78, 108, 269, 270, 272, 376, 379, 451, 452 Land reclamation 2 Law enforcement personnel 197–211 Layered clothing 53–55 Lifecycle assessment (LCA) 20, 27, 29, 98, 148 Lightweight 3, 4, 7–9, 12, 15, 22, 23, 32, 39, 43–46, 51, 53, 55, 90, 108, 116, 125, 127, 129, 137, 176, 177, 188, 267, 295, 319, 323, 346, 348, 349, 359, 360, 363, 370, 372, 374, 375, 390, 398, 409, 410, 420, 426, 433, 447 Linear PVC foam 390 Linen 11, 12, 15, 16, 32, 257–259, 413 Low active sports 51–54
479
480
Index
m Manikin 52, 138, 139, 180, 183–187, 189, 207 Manufacture/manufacturing processes 2, 148, 160, 189, 241, 273–275, 361–362, 379, 388, 393, 407, 408, 417, 418 techniques 6, 19, 197, 211, 260–272, 345, 408, 409, 415, 417, 419–422, 426, 433 Marine applications 9, 385–403 Marine composites 392 Marine safety apparatus 400 Marine textiles 8–9, 385–403 Masks 1, 5, 97, 107, 141, 447, 448, 455 Mass coverage 222, 223 Material properties 209, 242, 322, 362–363, 428, 455 Material requirements 323–326, 349, 426 Mattress 15, 24, 29, 91–93, 97 Measurement 24, 26, 50, 52, 60, 87, 88, 91, 96, 182, 208, 229, 308–310, 357, 430, 444 Mechanical behaviour 301, 304, 325, 358, 386, 397 Mechanical characterization 232, 301, 302 Mechanical fixation 268–269 Mechanical hazards 109, 111, 112, 140–141 Mechanical properties 4, 7, 12, 23, 26, 39, 42, 78, 84, 110, 111, 113, 124, 125, 133, 221, 230, 232, 243, 245, 251–255, 262, 285, 298–305, 307, 325, 344, 345, 359, 371, 374, 386–388, 390, 392–394, 397, 409, 412, 413, 415, 418, 419, 426, 427, 443, 444, 452 Mechanism 18, 51, 52, 80, 81, 94, 113, 120, 130, 138, 204, 217–218, 228, 256, 257, 283, 284, 368, 395, 429, 441, 443–445, 449, 450, 452 Medical textiles 3–5, 69–100, 440, 447, 455, 457 Medicine 69, 76–80, 220, 353, 443, 453 Medtech 1, 69–70, 100 Melt‐blown fabrics 229
Membrane 6, 9, 44–46, 53, 54, 79, 94, 110, 113, 115, 120, 125, 127, 138, 148, 187, 188, 210, 215, 218, 219, 222, 223, 230–232, 283, 292, 320, 322–327, 331, 332, 348, 400, 402, 440, 447, 464 Meshes 6 Microbial hazards 108, 140, 148 Microclimate 50, 52, 81, 82, 132, 134, 136, 137, 182, 280, 285, 291, 294, 378, 379, 450 Microorganisms 7, 17, 25, 93–96, 141, 247, 253, 256–258, 260, 280, 281, 283, 307, 368, 394, 456 Mildew 6, 39, 41, 289, 311, 325 Military textiles 3, 6 uniforms 6 Milkweed 116, 119 Mineral fibres 220, 253 Mobility 6, 109, 141, 197, 243 Mobiltech 2, 354, 355 Moisture management 37, 39, 41, 44, 47, 50–51, 108, 115, 116, 118–120, 125, 136, 138, 188, 333 Moisture sensation 53, 378–379 Monofilaments 6, 223–225, 230, 274, 285, 307, 309, 373, 443 Mulch mats 281, 283, 284, 291, 292, 294 Multifilaments 6, 224–226, 274, 288, 290, 372, 411 Multiple criteria 55–57
n Nanofibres 1, 5, 76, 78–80, 82, 165, 176, 188, 217–223, 230–232, 240, 283–284, 400–402, 408, 412, 416, 432, 457, 462 Nanotechnical fibres 216–219, 408–412 Nanotechnology 2, 3, 20, 32, 43, 76–80, 100, 107, 108, 188, 385, 416 Natural fibres 5, 16, 18–20, 27, 31, 37–39, 41, 98, 108, 125, 148, 161–164, 173, 216, 219–221, 239, 244–251, 253, 254, 257, 260, 280–282, 288, 291, 295, 300, 307, 308, 312, 339, 340, 349, 353, 369, 371, 407–409, 413, 414, 432, 463
Index
Naval ships 399 Needlefelts 225, 226, 228 Needle punching 6, 228, 239, 267, 268, 271, 273, 284, 291, 292, 311, 361, 366, 420, 460 Nets 12, 269, 280, 283–291, 298, 303–306, 308–312, 385, 408 Nonpolymeric fibres 244, 253–254 Nonwovens fabrics 6, 17, 29, 108, 119, 160, 173, 175–177, 188, 221, 229, 243, 260, 267, 268, 308, 311, 345, 415 structures 71, 243, 268–272 Nylon 9, 23, 42–45, 81, 93, 107, 114, 119, 121, 122, 148, 163, 165, 216, 226, 251, 282, 353, 356, 359, 361–364, 366, 367, 369, 387, 389, 398–400, 407, 426, 448, 449, 453
o Occupational hazards 5, 107, 159 Occupational safety 5, 254 Oekotech 2 Oil spill management 7 Oil‐water separation 400–403 Omnidirectional reinforcement structures 393 Optical properties 298, 324, 441 Optical textiles 440–443 Organic fibres 163, 338–340
p Packaging textiles 3–4, 11–32 Packtech 1 Parameters 13, 14, 23–25, 27, 28, 56, 60, 88, 89, 92, 94, 97, 99, 222–223, 240, 242, 243, 249, 250, 262, 268, 270–272, 304–306, 309, 325, 326, 331, 336, 359, 365, 372, 374, 377, 379, 423, 440, 441, 444, 448, 450 Patients 4, 5, 69, 70, 72, 82, 87, 89–93, 96, 100, 139, 140, 442, 446, 455–458, 460 Patterning 53, 57 Perception 53, 57, 377, 378
Performance 1, 2, 4–7, 9, 11, 17, 19, 23, 24, 26, 29, 30, 37, 38, 43, 44, 46, 48, 50, 55, 58, 59, 71, 95, 97, 99, 109– 111, 113, 118–122, 125, 131, 133, 136, 138–141, 148, 159, 160, 162, 180, 183–186, 188, 200, 210, 215, 220, 222, 223, 240–243, 253, 279, 283, 290, 295, 298, 305, 306, 323, 325, 329, 330, 338, 340, 343, 356–359, 364, 369, 370, 372, 373, 377, 385, 387–389, 396, 398–400, 409, 410, 420, 424, 426, 429, 431, 441, 443, 446–449, 455, 459 Performance tests 230 Perishable products 17 Permeable fabrics 6, 53, 239 Personal protective clothing (PPC) 3, 5, 159–189 Phase change materials (PCMs) 9, 41, 42, 82, 83, 108, 116, 119, 133–137, 188, 208, 440, 450–452, 464 Photocatalysis 20 Piezoelectric sensors 445–446 Plasma treatment 3, 95, 225, 227, 260 Police 6, 132, 141, 159, 197, 199, 201–206, 208, 209, 211 Pollutant capture 217–218 Polyamide (PA) 1, 6, 7, 11, 15, 27, 37, 38, 46, 51, 71, 84, 107, 108, 204, 218, 219, 244, 251, 282, 283, 311, 387, 389, 400, 408, 442, 443, 445, 448, 456, 461 Polyester 1, 11–17, 20, 23, 27, 30, 37, 71, 84, 93, 107, 108, 114, 115, 119, 121, 134, 148, 162, 163, 165, 173, 206, 216, 227, 228, 244, 251, 258, 274, 282, 320, 324–326, 353, 361, 387, 388, 392, 393, 395, 397–399, 407, 408, 411, 421, 424, 432, 443, 453, 457, 458, 460, 461 Polyester resin 388, 424 Polyethylene (PE) 7, 17, 25, 40, 107, 108, 110, 111, 114, 121, 134, 135, 244, 251, 257–259, 274, 282, 283, 332, 333, 343, 387, 389, 398, 442
481
482
Index
Polymers 9, 14, 18, 69, 80, 84–86, 107, 108, 110, 113, 119, 133, 134, 137, 165, 216–220, 231, 232, 244, 253, 257–259, 282, 283, 290, 291, 293, 295, 307, 312, 319, 365, 370, 395, 407, 408, 413, 416, 421, 422, 432, 433, 440–442, 445–447, 452, 453, 457, 463 Polymethacrylimide (PMI) foam 390 Polypropylene (PP) 6, 14, 18, 37, 41, 71, 96, 107, 108, 219, 224, 228, 244, 252, 282, 333, 343, 359, 366, 368, 369, 372, 374, 389, 446, 453, 458 Polystyrene 18, 219, 244, 326, 336, 366, 389, 390 Pore size 79, 217, 221–223, 230, 231, 275, 416, 447 Porosity 7, 15, 78–80, 82, 115, 231, 233, 242, 243, 249, 250, 262, 283, 285, 305, 309, 368, 398, 400, 403, 457 Principle 14, 40, 41, 45, 87, 88, 92, 166, 167, 170–172, 174–179, 184, 252, 268–272, 295, 322 Printed electronics 22 Printed fabrics 177–178 Production 6, 7, 14, 19–21, 23, 27–29, 39–41, 46, 53, 69, 71, 72, 98, 99, 133, 148, 167, 168, 170–172, 175–177, 215, 220, 221, 225, 226, 233, 251, 252, 261, 270–273, 279, 282–284, 291, 305, 306, 311, 340, 343, 344, 348, 353, 354, 356, 358, 372–374, 389, 408, 409, 412, 413, 416, 418, 421, 425, 442, 443, 445, 446, 453, 455, 461–464 Properties 1, 2, 7, 9, 11–19, 30, 31, 38–41, 43, 46, 49, 50, 52–55, 71, 78, 79, 81–84, 86, 95, 97, 108, 110, 111, 115, 116, 118–121, 124–126, 130, 131, 133, 134, 137, 138, 141–147, 161–163, 165, 167, 168, 173, 174, 178–180, 182, 197, 204, 209, 210, 215–221, 223, 230, 232, 242, 245, 251–254, 256, 260–263, 268, 282–285, 291–306, 311, 322–325, 331, 333, 341, 343–346, 356–359, 361–364, 367–369, 371, 372, 375–379, 385, 386, 388, 390–403, 407, 409, 412, 413, 415, 418–420, 425–433, 440, 441, 443–449, 451, 452, 455, 456, 459, 462
Property requirements 329–333, 336 Protech 2 Protection 6–8, 14, 16, 17, 26, 53, 90, 107–141, 160, 188, 197–206, 209, 210, 225, 227, 239–275, 279–312, 353, 425, 427, 440, 447–450, 453, 455, 456, 460 Protection barriers 285–287 Protective materials 107, 113, 120, 125, 141, 199–201, 211, 449, 450 Protective textiles 3, 5, 107–148, 159–189, 211, 222 Pultrusion 419, 424–425, 433 Puncture 6, 109, 111, 112, 128, 133, 145, 302, 325, 331, 398
q Quality control 23–26, 61–62, 95–98, 229–232, 428–431 Quality standards 397–403, 423 Quasi‐yarn formation 269–270
r Radiation 8, 14, 15, 25, 26, 51, 58, 82, 108, 109, 115, 120, 124, 139–140, 142, 144, 168, 280, 286, 287, 289, 290, 295, 298, 304, 306, 311, 325, 331, 335, 356, 385, 386, 424–427, 448, 449, 452, 455 Radiative properties 304–306 Radiofrequency identification (RFID) systems 22, 23 Raising finishing process 226 Recyclability 10, 62, 99, 358 Regenerated fibres 38–40, 112, 124 Reinforcement fabrics 366, 391–394 Reinforcement materials 242, 342–345, 355, 367, 386–388, 391, 394, 403, 410 Reinforcing fibrous materials 343–346 Renewable natural resources 1, 220 Requirements 4–9, 19, 24–26, 37, 39, 44, 46–56, 62, 78, 98, 109, 121, 126–128, 133, 134, 138–142, 144, 145, 160, 165, 168, 174, 181, 183, 201, 204–206, 208, 215, 229, 244, 269, 275, 279, 280, 284, 288, 304, 312, 323–326, 329–334, 336, 342–343, 349, 354–360, 364, 367, 374, 379, 385, 395–398, 407, 415, 420, 422, 423, 426–428, 455–457, 460, 463
Index
Resin 15, 44–45, 187, 366, 368, 370, 374, 376, 380, 386, 388–395, 398, 403, 420–425, 427–431, 433 Responsive textiles 3, 9, 10, 349, 439–464 Ring‐spun yarns 168–170 Roof headliner 360–361 Root protection 291 ROTIS technology 272 Rotor‐spun yarns 170, 172 Row covers 291, 296, 298, 311 R‐value 336–341
s Sails 398, 413 Seatbelts 353–355, 361–363, 365 Seat covers 3, 354–359, 378, 379 Seating comfort 377 Seawater 8, 109, 250, 288, 385, 392, 398 Self‐cleaning 12, 20, 228, 232, 325 Self‐healing 412, 431–432 Sensors 4, 9, 14, 22, 23, 32, 45, 59–61, 87–93, 137, 184, 185, 188, 349, 365, 379, 440, 441, 443–447, 459, 460, 462–464 Shading 2, 7, 279, 282, 289, 290, 297, 305, 310 Shape memory materials 9, 119, 440–442, 464 Sharp weapon protection 197–203 Shear testing 430 Ships 8, 94, 208, 274, 385, 394, 397, 399, 403, 413 Shoes 2, 4, 5, 107, 241, 452 Silicone 116, 120, 127, 187, 210, 211, 325, 363, 401 Singeing 226 Skiwear 42, 43 Smart garments 58–61 Smart structures 134, 136–137 Smart textiles 9, 41, 46, 58–61, 70, 133, 134, 137, 188, 439–464 Socks 5, 39, 50, 107, 136, 460 Soil reinforcement 6
repellent 16, 28 Space industry 412, 428 Spacesuit 9, 41, 134, 407, 426–428, 452 Space textiles 9, 407–433 Spandex 9, 42, 44, 407 Special fibres 41–42 Special finishes 45–46, 108 Spectra fibre 387 Spinning 14, 20, 39, 43, 82, 97, 110, 130, 131, 141, 160, 161, 165, 166, 168, 169, 171, 172, 189, 217, 218, 229, 233, 244, 250–252, 346, 411, 412, 415–417, 433, 451 Sports 1, 3–5, 9, 37–62, 89, 370, 409, 426, 433, 440, 453, 459–460, 464 Sports textiles 3, 4, 37–62 Sporttech 1 Spunbonded fabrics 229 Stab resistance 141 Standard nonwovens 267 Standards 5, 6, 11, 23–26, 29, 41, 50, 53, 95–97, 107, 121, 133, 138–147, 167, 173, 179, 180, 183–185, 206, 207, 215, 295–312, 329, 342, 348, 349, 356, 363, 380, 397–403, 410, 414, 423, 429, 430, 433, 462 Staple‐fibre yarns 42, 225, 226, 228 Stiffness 1, 7, 113, 200, 220, 227, 244, 250, 264, 285, 290, 301, 321, 324, 325, 357, 372, 387, 389, 391–393, 397, 409, 419, 420, 426, 428, 430, 431, 433, 446, 457 Stitching 14, 183, 240, 261, 373, 394, 419–420 Strength 1, 7–9, 12, 23, 24, 42, 110, 121, 125, 136, 141, 169, 173, 177, 217, 219, 220, 224, 227, 232, 249, 250, 254, 267, 281, 282, 284, 286, 288, 290, 291, 301, 304, 319, 323, 325, 331, 341, 343, 348, 356, 357, 359, 361, 362, 364, 366, 370–372, 374, 376, 386, 387, 391, 393, 398–400, 407, 409–411, 413–415, 417, 419, 426, 427, 429–431, 433, 448–450, 457 Structural requirements 420, 422, 427
483
484
Index
Structure 15, 16, 21, 39, 43–45, 48, 52, 53, 58, 69–72, 82, 108, 110, 115, 116, 119, 121, 125, 126, 133, 134, 136, 167, 170, 222, 226, 230, 231, 239–247, 249, 253, 260–264, 266, 268–272, 280, 284–285, 287, 288, 294, 304, 319–326, 328, 333, 340–344, 346–349, 357, 361, 362, 364, 368–376, 379, 389, 390, 392–394, 397–400, 409, 410, 412, 414, 417–421, 425–432, 441, 444, 445, 448, 450, 452, 456, 460, 461 Submarines 396, 399 Sunlight 7, 8, 12, 13, 26, 109, 279, 281, 282, 315, 362, 366, 398, 441, 444 Sun protection factor (SPF) 15 Sun visor 355, 366 Surfaces 3, 19, 26, 43, 53, 225, 227, 228, 260, 268–269, 321, 325, 335, 359, 369, 385, 394, 395, 419, 428, 429 Sustainability 10, 11, 16, 17, 26–32, 62, 98–100, 141–148, 162, 232–233, 272–274, 280, 281, 311–312, 347–349, 403, 407, 408, 414, 432, 462–464 Sustainable development 40, 273, 312, 403 Sustainable processing 187–189, 408 Sweat 5, 44, 45, 47, 53, 89, 115, 132, 137, 159, 178, 180–183, 186–189, 208–210, 358, 377, 378, 444, 459 Synthetic fibres 1, 5, 7, 11, 26, 30, 37, 38, 40–41, 51, 107, 119, 148, 160, 162–166, 173, 216, 220, 225, 239, 244, 251–253, 274, 280–283, 290, 291, 307, 312, 366, 413, 415, 432, 448, 461
t Tarpaulins 8, 241, 354 Tear resistance 122, 128, 142, 145, 302–304, 325, 331, 332, 334, 356 Technical applications 1, 76, 219–221, 240, 385, 413–415 Technical textiles 1–10, 12, 20, 46, 47, 69, 208, 210, 221–225, 227, 233, 240, 253, 261, 279–281, 293, 295, 353–355, 366, 385, 409, 415–420
Techniques 3, 6, 7, 9, 12, 14, 16, 18, 19, 25, 55, 95, 99, 160–162, 165, 166, 175, 178, 187–189, 197, 211, 230, 231, 233, 234, 260–272, 279, 283, 284, 295, 345, 349, 403, 407–409, 415, 416, 420–422, 425, 431–433, 457 Tensile strength 1, 39, 97, 112, 118, 122, 124, 126, 133, 142–145, 147, 219–221, 232, 249, 253, 254, 281, 284, 287, 301–304, 325, 341–345, 357, 359, 362, 364, 386, 388, 400, 411, 413, 414, 417, 429, 448, 450 Tensile testing 429 Tensioned fabric structures 323 Tents 8, 11, 15, 95, 320 Testing methods 11, 23–26, 41, 61–62, 95–98, 138–147, 209, 249–232, 302, 357, 408, 428–431, 446, 452 Testing standards 95, 295–311, 428, 433 Textile reinforced composite materials 227–228, 346, 420–425, 433 Textile reinforced concrete (TRC) 8, 319, 340–349 Textile reinforcement materials 342–343, 345 Textiles composites 9, 369–372, 380, 394, 407, 425–431, 433 electronics 60, 61 fibres 9, 20, 37–42, 72, 81, 116, 160, 219, 220, 227, 243, 244, 280, 359, 407, 408, 426, 428, 429, 431–433 manufacturing 2, 94, 98, 99, 345, 370 materials 4, 5, 8–19, 25, 37, 43, 57, 61, 70–72, 76, 81, 82, 87, 107–148, 160, 188, 207, 210, 211, 215, 239, 242, 257, 319, 325, 326, 342–346, 348, 349, 354, 358, 367, 370, 379, 385, 409, 420, 427, 431, 432, 439, 457, 459, 461 processes 2, 250, 442 products 3–5, 15, 16, 20, 27, 28, 70, 71, 88, 93, 95, 98, 99, 107, 122, 148, 188, 208, 269, 319, 348, 354, 355, 371, 380, 385, 386, 410, 453, 460, 462, 464 properties 49, 50
Index
structures 8, 9, 12, 41, 58, 69, 87, 134, 138, 227, 240–242, 260, 261, 270, 280, 284–285, 312, 319, 320, 322, 323, 326, 342, 343, 370, 372, 374, 394, 419 Textile structural composites (TSCs) 370–371, 394 Thermal behaviour 326 Thermal burden 131–138 Thermal comfort 37, 48, 54, 55, 108, 109, 125, 133, 136–137, 359, 377, 450 Thermal insulation 12, 42, 43, 50–53, 57, 81, 115, 116, 118–121, 125, 131, 143, 144, 173, 182, 188, 320, 323, 326, 335, 349, 366, 378, 409, 427 Thermo‐physiological comfort 5, 9, 42, 43, 81–83, 108, 131–138, 159, 183–189, 359, 377 Thermoplastic resin 389 Thermoset foams 390 Thickness 15, 19, 51, 52, 55, 82, 113, 115, 118, 173, 179, 180, 200, 204, 210, 217, 222, 223, 229–231, 242, 243, 249, 257, 261–263, 266, 268–270, 290, 301, 309, 336, 338–342, 359, 368, 373, 376, 378, 379, 386, 391, 393, 394, 417, 419, 421, 447, 461 Thick nonwovens 268–273, 369 Three‐dimensional textile structures 394, 419 Three‐dimensional weaving 417–418 Three‐dimensional woven fabrics 266, 376 Tough cotton 386 Toxicity 16, 28, 95, 96, 141, 395, 396, 451, 455, 462 Trains 8, 354 Transportation 6, 8, 28, 29, 41, 50, 51, 70, 221, 233, 240, 273, 274, 294, 354, 368, 371, 373, 374, 379, 385, 425, 426, 432, 433 Trevira 387 Triaxial fabrics 264–265 Two‐dimensional woven fabric 261–264, 376 Tyre cord fabric 355, 366–367 Tyres 8, 241, 354, 355, 366, 367, 379, 410
u Ultraviolet protection factor 16 Unidirectional reinforcement structures 394 Uniforms 4, 6, 25, 95, 122, 124, 204, 206, 219, 230, 231, 295, 301, 325, 374, 379, 421 Upholstery 8, 13–16, 23–27, 29, 239, 354–359, 366, 372, 376 Utility performance 356–359 UV light 26, 31, 142, 280, 311, 356, 440, 452
v Vacuum bagging technique 421–422 Vapour permeability 38, 41–43, 53, 115, 327, 329, 331 Vectran fibre 411, 432 Vehicles 8, 203, 346, 354, 355, 358, 359, 361, 363–366, 368, 369, 371, 372, 375–377, 379, 380 Vinyl ester resin 388, 392, 424 Viscose 1, 17, 30, 38–40, 43, 70, 71, 83, 108, 112, 124, 131, 162, 163, 204, 205, 244, 257, 258, 295, 300, 353, 356, 367, 458, 460, 461
w Warfare protective clothing 447–450 Warmth sensation 377–378 Waterproof garments 440, 447 Water resistance 97, 115, 329–330, 333, 334 Water retention 20, 280, 298, 300, 308 Wearable electronics 9, 440, 443–447, 460, 463, 464 Wearable technology 58–61, 453, 454 Weather resistance 7, 282 Weaving 4, 12, 14, 19, 21, 23, 32, 43, 131, 160, 161, 168, 174, 189, 223, 224, 233, 240, 261, 263, 264, 266, 284, 285, 331, 345, 353, 356, 371, 374, 375, 394, 408, 417–418, 433, 442, 443, 457, 460 Weed suppression 7 Weight reduction 8, 371, 372, 379, 410, 413
485
486
Index
Wings 8, 241, 409, 411, 417, 423, 427, 428, 433 Wool 11, 13, 16, 23, 27, 31, 37–39, 44, 53, 82, 93, 96, 98, 108, 112, 116, 124, 125, 129–131, 162–164, 166, 204, 206, 219, 220, 225, 226, 258, 281, 291, 292, 295, 299, 338–341, 349, 379, 397, 413 Wound healing 4, 76, 79, 455, 456 Woven fabrics 4, 6, 25, 31, 43, 52, 125, 130, 136, 161, 173–175, 177, 188, 221, 228, 254, 260–263, 265, 266, 284, 289, 303, 345, 356, 364, 368, 374, 376, 399, 415, 417, 433, 448 Woven preforms 266, 371, 375–376, 417–419 Woven reinforcement structures 392–393 Woven structures 19, 225, 253, 362, 374–375, 393
x Xanthate 131 X‐rays 109, 231 protection 139
y Yarns 4, 6, 7, 12, 14, 21, 30, 37, 40, 42–43, 45, 51, 52, 71, 91, 121, 133, 148, 160, 167–175, 188, 223–229, 242, 253, 254, 261, 262, 264, 266, 284, 285, 310, 319, 324, 343, 345, 353, 354, 357, 361, 372–374, 376, 398, 415–419, 442, 443, 450 types 223–225
z Zeolite 17, 94 Zippers 15, 60 Zirpro wool 112, 124, 130