Bamboo Fibres: Processing, Properties and Applications 0323857825, 9780323857826

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BAMBOO FIBRES

The Textile Institute Book Series Incorporated by Royal Charter in 1925, The Textile Institute was established as the professional body for the textile industry to provide support to businesses, practitioners, and academics involved with textiles and to provide routes to professional qualifications through which Institute Members can demonstrate their professional competence. The Institute’s aim is to encourage learning, recognize achievement, reward excellence, and disseminate information about the textiles, clothing and footwear industries and the associated science, design and technology; it has a global reach with individual and corporate members in over 80 countries. The Textile Institute Book Series supersedes the former “Woodhead Publishing Series in Textiles” and represents a collaboration between The Textile Institute and Elsevier aimed at ensuring that Institute Members and the textile industry continue to have access to high calibre titles on textile science and technology. Books published in The Textile Institute Book Series are offered on the Elsevier website at: store. elsevier.com and are available to Textile Institute Members at a substantial discount. Textile Institute books still in print are also available directly from the Institute’s website at: www. textileinstitute.org To place an order, or if you are interested in writing a book for this series, please contact Matthew Deans, Senior Publisher: [email protected] Recently Published and Upcoming Titles in the Textile Institute Book Series: Handbook of Natural Fibers: Volume 1: Types, Properties and Factors Affecting Breeding and Cultivation, 2nd Edition, Ryszard Kozlowski Maria Mackiewicz-Talarczyk, 978-0-12-818398-4 Handbook of Natural Fibers: Volume 2: Processing and Applications, 2nd Edition, Ryszard Kozlowski Maria Mackiewicz-Talarczyk, 978-0-12-818782-1 Advances in Textile Biotechnology, Artur Cavaco-Paulo, 978-0-08-102632-8 Woven Textiles: Principles, Technologies and Applications, 2nd Edition, Kim Gandhi, 978-0-08102497-3 Auxetic Textiles, Hong Hu, 978-0-08-102211-5 Carbon Nanotube Fibers and Yarns: Production, Properties and Applications in Smart Textiles, Menghe Miao, 978-0-08-102722-6 Sustainable Technologies for Fashion and Textiles, Rajkishore Nayak, 978-0-08-102867-4 Structure and Mechanics of Textile Fiber Assemblies, Peter Schwartz, 978-0-08-102619-9 Silk: Materials, Processes, and Applications, Narendra Reddy, 978-0-12-818495-0 Anthropometry, Apparel Sizing and Design, 2nd Edition, Norsaadah Zakaria, 978-0-08-102604-5 Engineering Textiles: Integrating the Design and Manufacture of Textile Products, 2nd Edition, Yehia Elmogahzy, 978-0-08-102488-1 New Trends in Natural Dyes for Textiles, Padma Vankar Dhara Shukla, 978-0-08-102686-1 Smart Textile Coatings and Laminates, 2nd Edition, William C. Smith, 978-0-08-102428-7 Advanced Textiles for Wound Care, 2nd Edition, S. Rajendran, 978-0-08-102192-7 Manikins for Textile Evaluation, Rajkishore Nayak Rajiv Padhye, 978-0-08-100909-3 Automation in Garment Manufacturing, Rajkishore Nayak and Rajiv Padhye, 978-0-08-101211-6 Sustainable Fibers and Textiles, Subramanian Senthilkannan Muthu, 978-0-08-102041-8 Sustainability in Denim, Subramanian Senthilkannan Muthu, 978-0-08-102043-2 Circular Economy in Textiles and Apparel, Subramanian Senthilkannan Muthu, 978-0-08-102630-4 Nanofinishing of Textile Materials, Majid Montazer Tina Harifi, 978-0-08-101214-7 Nanotechnology in Textiles, Rajesh Mishra Jiri Militky, 978-0-08-102609-0 Inorganic and Composite Fibers, Boris MahltigYordan Kyosev, 978-0-08-102228-3 Smart Textiles for In Situ Monitoring of Composites, Vladan Koncar, 978-0-08-102308-2 Handbook of Properties of Textile and Technical Fibers, 2nd Edition, A. R. Bunsell, 978-0-08101272-7 Silk, 2nd Edition, K. Murugesh Babu, 978-0-08-102540-6

The Textile Institute Book Series

BAMBOO FIBRES Processing, Properties and Applications

K. MURUGESH BABU S.M. CHANDRASEKHARA

Introduction This book highlights bamboo fibre extraction, properties and applications. It is a comprehensive collection of detailed chapters ranging from bamboo fibre history, its growth characteristics to its applications and technoeconomics. The book provides an overview of bamboo fibre extraction and its processing. The book commences with a chapter on introduction to bamboo fibres and the history of bamboo, growth characteristics of bamboo such as types of bamboo and morphology of bamboo are discussed in detail. This is followed by chapters providing comprehensive information on bamboo fibre extraction; its characterization and its physical, comfort, thermal and low-stress properties as well as detailing the production of yarns and fabrics. The book concludes with chapters on the antimicrobial properties of bamboo fibres, chemical processing of bamboo fibres, yarns and fabrics and the application and techno-economics of bamboo fibre production and processing aspects. Bamboo Fibres: Processing, Properties, and Applications is an essential book for all those concerned with bamboo fibre extraction, its processing aspects and properties, its production and extension, its research and development and its application in textile and other industries. It will serve as a valuable material for textile and fashion industry professionals, research scientists, and academia. It is a comprehensive resource material for students and academicians.

xv

Foreword Nowadays, when pollution by synthetic microfibres is one of the biggest plastic pollution issues, we are returning to biodegradable, natural fibres to save our environment. The family of fibrous cellulosic raw materials, such as cotton, jute, flax, hemp, kenaf, sisal, ramie, coir and bamboo, and recently discovered many other lignocellulosic natural fibrous resources can be extracted, processed, modified, specially functionalized and applied in the production of the textiles: woven, knitted, nonwoven, technical, 3D textiles and also used as reinforcement of more friendly composites. Now the future of natural fibrous resources, new trends in their production, processing, wider application and their competition with manmade fibres in the 21st century is very important for decreasing pollution and CO2 emissions. Bamboo has a short reproduction time, grows with solar energy and water, extracts CO2 from air and releases oxygen. It is a lignocellulosic plant that grows very fast, with high structural organization and with many advantages. It helps millions of global people to live. At the end of 20th century, on the base of bamboo biomass, bamboo fibre was developed as a textile fibre, similar to viscose and cotton. In the book, “Bamboo Fibres: Processing, Properties and Applications,” the authors have compiled the current knowledge including an introduction and history of bamboo fibres; the growth characteristics of bamboo: types of bamboo, morphology of bamboo; the extraction methods for bamboo fibres—various extraction methods, different types of bamboo fibres; the characterization of bamboo fibres: physical and chemical composition, characterization of bamboo using X-ray, IR and other techniques; the properties of bamboo fibres—physical, performance, comfort thermal and low stress mechanical properties; the production and properties of bamboo yarns and fabrics; the investigation and comparison of antibacterial property of bamboo plants, natural bamboo fibres and commercial bamboo viscose textiles; the chemical processing of bamboo and bamboo products and the applications and techno-economics of bamboo fibres.

xiii

xiv

Foreword

This book provides comprehensive knowledge about these new emerging fibres, and the target readers may be scientists, students, industrial people, policy makers and consumers. Prof. Dr. Ryszard Kozlowski Prof. Dr. Ryszard M. Kozłowski, F.T.I. (Hon) Editor-in-Chief, Journal of Natural Fibers (Taylor & Francis Group, Philadelphia, USA) Former Director, Institute of Natural Fibres, Pozna´n, Poland Professor Honoris Causa, Pontifical Catholic University Ibarra (Ecuador) Coordinator, ESCORENA Network (European Cooperative Research Network on Flax and Other Bast Plants) Coordinator, ESCORENA Focal Point Editor, Handbook of Natural Fibres, 1st (ed.) (2012) and 2nd (ed.) (2020), ELSEVIER Honorary Fellow, Textile Institute, Manchester, UK Member, American Chemical Society Member, ICOMOS (International Council on Monuments and Sites)

Woodhead Publishing is an imprint of Elsevier 50 Hampshire Street, 5th Floor, Cambridge, MA 02139, United States The Boulevard, Langford Lane, Kidlington, OX5 1GB, United Kingdom Copyright © 2023 Elsevier Ltd. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions. This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein). Notices Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary. Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility. To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. ISBN: 978-0-323-85782-6 (print) ISBN: 978-0-323-90926-6 (online) For information on all Woodhead Publishing publications visit our website at https://www.elsevier.com/books-and-journals

Publisher: Matthew Deans Acquisitions Editor: Brian Guerin Editorial Project Manager: Fernanda A. Oliveira Production Project Manager: Prasanna Kalyanaraman Cover Designer: Christian Bilbow Typeset by MPS Limited, Chennai, India

Contents About the authors Foreword Introduction

1. Introduction and history of bamboo fibres 1.1 Introduction to bamboo and bamboo fibres 1.1.1 History of bamboo and bamboo fibres 1.1.2 Taxonomy and geographical distribution 1.1.3 Prospects of bamboo fibres References Further reading

2. Growth characteristics of bamboo: types of bamboo, morphology of bamboo 2.1 2.2 2.3 2.4 2.5 2.6

World distribution of bamboo Bamboo growth habitat Growth process Bamboo growing areas in India Morphology of bamboo Types of bamboo 2.6.1 Running bamboo 2.6.2 Clumping bamboos 2.7 Other varieties of bamboo (Chinese varieties) 2.7.1 Ornamental bamboo 2.7.2 Modern bamboo varieties 2.8 Chemical composition of bamboo References

3. Extraction methods for bamboo fibres: various extraction methods, different types of bamboo fibres 3.1 Introduction 3.2 Bamboo fibre extraction methods 3.2.1 Extraction of natural bamboo fibres 3.3 Types of mechanical extraction methods 3.3.1 Steam explosion method 3.3.2 Crushing

xi xiii xv

1 1 5 9 15 18 21

23 24 25 27 27 28 31 31 33 34 34 37 41 43

47 47 47 47 50 50 52

v

vi

Contents

3.3.3 Grinding 3.3.4 Rolling mill 3.3.5 Retting 3.4 Bamboo fibre process by chemical methods 3.4.1 Chemical retting 3.4.2 Alkali or acid retting 3.5 Biological methods 3.5.1 Microbial culture 3.6 Combined mechanical and chemical extraction methods 3.7 Extraction of fibres from bamboo shoot shell 3.8 Production of regenerated (pulp) bamboo fibres 3.8.1 Rayon process 3.8.2 Lyocell process (eco-friendly process to produce bamboo fibre) 3.9 Types of bamboo fibres 3.9.1 Natural bamboo fibres 3.9.2 Bamboo (viscose) rayon fibres 3.9.3 Bamboo charcoal fibre 3.9.4 Natural bamboo fibre from LITRAX 3.10 Summary References

4. Characterisation of bamboo fibres 4.1 Introduction 4.2 The chemical composition of bamboo fibres 4.3 Cellulose 4.4 Hemicellulose 4.5 Lignin 4.6 Structure of the bamboo fibre at the macro- and microlevel 4.7 Morphology of the elementary bamboo fibres 4.8 Studies on characterisation of structure of bamboo fibres 4.9 X-ray diffraction studies 4.10 Degree of crystallinity 4.11 FTIR studies 4.12 Summary References

5. Properties of bamboo fibres: physical, performance, comfort, thermal, and low stress mechanical properties 5.1 Introduction 5.2 Physical properties of natural bamboo fibres

52 52 53 53 54 55 56 57 58 58 59 59 61 62 62 62 63 66 67 67

71 71 72 73 74 74 75 78 79 85 86 91 95 96

101 101 102

Contents

vii

5.2.1 Moisture absorption 5.2.2 Length and linear density 5.3 Tensile properties 5.4 Stress relaxation behaviour 5.5 Physical properties of bamboo viscose (pulp) fibres 5.6 Thermal properties 5.7 Low stress mechanical properties of bamboo and bamboo blended fabrics 5.7.1 Tensile properties (tensile tester KES-FB1) 5.7.2 Shear properties 5.7.3 Bending properties 5.7.4 Compression properties 5.7.5 Fabric compressibility 5.7.6 Surface properties 5.7.7 Fabric weight and thickness 5.7.8 Primary and total hand values 5.8 Summary References

102 103 105 112 117 118

6. Production and properties of bamboo yarns and fabrics

137

6.1 Introduction 6.2 Production and properties of bamboo and bamboo blended yarns 6.2.1 Methodology used for yarn production 6.2.2 Testing of yarns 6.3 Physical properties of bamboo and bamboo blended yarns 6.3.1 Yarn liner density 6.3.2 Twist in the yarn 6.3.3 Twist multiplier 6.4 Mechanical properties of yarns 6.4.1 Tensile properties 6.5 Yarn evenness testing 6.6 Yarn hairiness 6.6.1 Uster yarn hairiness tester 6.7 Production and properties of bamboo and bamboo blended fabrics 6.7.1 Fabric production 6.7.2 Fabric testing 6.8 Tensile strength and tearing strength 6.9 Abrasion resistance 6.10 Pilling 6.11 Crease recovery

123 124 126 127 128 128 129 129 130 133 133

137 138 140 141 141 141 142 142 142 142 143 144 144 148 149 150 153 155 156 157

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Contents

6.12 Flammability 6.13 Fabric stiffness 6.14 Drape 6.15 Permeability 6.16 Moisture content and moisture regain 6.17 Fabric wetting 6.18 Summary References

7. Antimicrobial properties of bamboo, bamboo fibres, and fabrics

157 158 160 160 161 162 167 167

169

7.1 Introduction 7.2 Antibacterial properties of bamboo extract 7.3 Antimicrobial properties of bamboo fibres and fabrics 7.3.1 Bamboo plant extraction 7.3.2 Bacterial strains 7.3.3 Methodology used 7.3.4 Antimicrobial activity of fabrics 7.3.5 Evaluation of antimicrobial activity (qualitative agar diffusion test AATCC 147-2004) 7.3.6 Antimicrobial activity of cotton fabric treated with bamboo extract 7.4 Summary References

169 171 173 174 175 175 176

8. Chemical processing of bamboo and bamboo products

195

8.1 Introduction 8.1.1 Chemical processing of bamboo products 8.1.2 Chemical treatment of bamboo 8.1.3 Dyeing of blends 8.1.4 Measurement of colour fastness properties of the fabrics 8.1.5 Measurement of colour strength (K/S) 8.1.6 Fabric fastness properties 8.1.7 Colour strength (K/S) 8.2 Summary References

9. Applications and technoeconomics of bamboo fibres 9.1 Applications in the textile industry 9.1.1 Bamboo medical textiles and healthcare products

177 180 191 191

195 196 196 205 205 206 206 207 209 209

213 215 216

Contents

9.1.2 Textile clothing 9.2 Bamboo fibres in fashion 9.3 Bamboo fibres in paper production 9.4 Bamboo fibres in the construction industry 9.5 Bamboo fibre in composites 9.6 Future trends and technoeconomics of bamboo fibres 9.7 Summary References Index

ix 217 217 218 219 220 222 224 226 231

About the authors Dr. K. Murugesh Babu has more than 30 years of teaching and research experience in the field of textile science and technology. Dr. Babu, a doctorate from IIT, Delhi, has a rich experience in teaching and research in the areas of silk technology, textile dyeing, printing and finishing, natural fibre processing, textile fibre composites, and textile polymer science. He is a recipient of the prestigious Commonwealth Fellowship by the Association of Commonwealth Universities. Dr. Babu has published more than 100 research papers in various national and international textile and polymer-related research journals and has contributed 11 book chapters in textbooks published by Wood Head Publishing and Elsevier and has supervised 6 PhD theses. He has also published three textbooks: Silk— Processing, Properties and Applications - Ist Edition, Silk—Processing, Properties and Applications - IInd Edition, and Abstract Pattern Illustrations for Textile Printing.

Dr. S.M. Chandrasekhara is working as an associate professor in the Department of Textile Technology at Bapuji Institute of Engineering & Technology, Davangere, Karnataka, India. He has more than 20 years of rich teaching and research experience. His expertise includes bamboo fibre processing, natural fibre processing and applications, fabric manufacturing technologies, garment manufacturing and textile science. He has guided a number of undergraduate and postgraduate students in textile and garment technology areas.

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CHAPTER EIGHT

Chemical processing of bamboo and bamboo products

8.1 Introduction Bamboo has been recently considered as a promising textile fibre for the production of bamboo yarns, woven and knitted fabrics because it is lightweight, durable, hardy, flexible, strong, and renewable. Bamboo fibres that are suitably treated have been widely used in construction, reinforcement, and composite materials (Li et al., 1995; Sathitsuksanoh et al., 2010; Shin and Yipp, 1989). In addition, the bamboo fibres are also a promising alternative source for textile fibres due to their attractive properties such as rapid growth rate, astounding reproduction rate (asexual reproduction yearly), widespread distribution, unique structure, great diversity of uses, and high tensile strength (Amada et al., 1997; Gritsch et al., 2004; Nugroho and Ando, 2000; Shao et al., 2008; Shin and Yipp, 1989; Steinfeld, 2001). Bamboo fibres and its blends have wide prospects in the field of medical suppliers and hygiene products, such as household wipes, sanitary napkin, wet wipe, baby diaper, medical bandage, base cloth, inside lining, disposable sheet, nonwoven textiles, and nanotechnology products (Sahinbaskan, 2012). Bamboo yarn is made out of 100% bamboo fibre or blended with other material. Because of its many unique properties, bamboo fibre has gained attention towards its use for textiles specially apparels (Xu et al., 2007). Bamboo yarn can then be made into other final products such as garment, underwear, towel, etc. fabric made of bamboo fibre and bamboo yarn is characterized by its good hygroscopility, excellent permeability, soft feel, easiness to straighten and dye, and splendid colour effect of pigmentation. Cloth has been made from bamboo fibre mixed with cotton or ramie or nylon or polyester having same superior property. Many kinds of knitting and weaving fabrics are made (piece dyed, yarn dyed, or printed). Due to high fibre porosity, the bamboo textiles produce higher colour yields when dyed. Bamboo Fibres. DOI: https://doi.org/10.1016/B978-0-323-85782-6.00004-0

© 2023 Elsevier Ltd. All rights reserved.

195

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Bamboo Fibres

8.1.1 Chemical processing of bamboo products In general, chemical processing of bamboo textiles follow similar route as any other cellulosic fibre fabrics. However, the all the processes need to be done under mild conditions, that is, light singeing, enzymatic desizing, moderate bleaching, and semimercerizing before dyeing and finishing operations. Any drastic conditions must be avoided and moderate tension must be applied on yarns and fabrics during wet processing operations. Due to the lack of research on pretreatment processes for pure bamboo fabrics, some researchers have attempted to undertake works on pretreatment of bamboo and its blended fabrics by different methods. Various studies have been focused on scouring and bleaching of either pure bamboo fibres or regenerated bamboo viscose fibres and their blends with cotton, viscose, silk, and polyester fibres.

8.1.2 Chemical treatment of bamboo 8.1.2.1 Effect of alkali on bamboo Bamboo has a compact structure when compared to other materials (Muhammad et al., 2011; Callum et al., 1998), a mechanical beetling treatment may be required to open the culms, to enable the penetration of chemicals easily when it is exposed to the wet processing for the extraction of fibres. A severe alkaline treatment (using solutions of NaOH) which is generally used in paper and pulp industries is generally recommended to remove noncellulosic substances, that is, lignin and gummy substances (Grosser and Liese, 1971). In this way lignin can be removed/dissolved in sodium hydroxide solution followed by subsequent washing and neutralization. Other alkalis used are aqueous alkaline solutions of sodium carbonate (Na2CO3), potassium hydroxide (KOH), and lithium hydroxide (LiOH) (Grosser and Liese, 1971; Farrelly, 1984). Sodium hydroxide (NaOH) being a popular alkali, acts as a swelling agent, enhances the dissolution and removal of lignin along with other noncellulosic materials. Alkali treatment cleans the surface of fibre bundles, enhances the regularity of fibres in the bundles, and thus increasing the fibre productivity. It may be observed that at lower temperatures, it is possible to extract excellent fibres with good mechanical properties (Peng et al., 2014; Cai and Zhang, 2005; Khuhwaha and Kumar, 2009). But at higher concentrations of caustic soda, physical, and chemical changes occur and a soft appearance is observed at a concentration of 16% due to formation of a high degree of twist and shrinkage, due to longitudinal

Chemical processing of bamboo and bamboo products

197

shrinkage of fibres, a phenomenon termed as “mercerization” of bamboo (Das and Chakraborty, 2006) resulting in some partial conversion of native cellulose-I to cellulose-II as a result of partial loss of crystallinity due to lateral swelling effect (Liu and Hu, 2008; Stout, 1985). The efficiency of this treatment depends on the decrystallisation and the degree of lattice conversion (Jones, 1994). The aim of this process of mercerization of bamboo is entirely different from well-established mercerization of cotton. A low degree of softness is achieved below 15% concentration and thermal stability, weight loss and softening increase with increase in concentration of caustic soda solution up to 17.5%
20%. The reaction of bamboo materials with alkali is usually accomplished within short time. But an immersion time 20
30 minutes is generally recommended for effective decrystallisation (Das and Chakraborty, 2008). A good crystal lattice conversion and decrystallisation with good softness can be produced at 20 C without tension applied to the fibres with 16% alkali. However, the mercerization of bamboo is normally done at the ambient temperature (Yueping et al., 2010). Mercerisation of bamboo improves its handle and appearance which can be further enhanced by subsequent bleaching and dyeing processes. In addition, bamboo fibres which undergo mercerization can further be blended with other natural fibres to enhance their usage (Kaur et al., 2019; Trotman, 2008). 8.1.2.2 Bleaching of bamboo fibres It is a general practice to skip scouring before bleaching of regenerated bamboo viscose fibres owing to their chemical composition and alkali sensitivity and hence they are bleached directly. Bleaching is an important operation in the processing of bamboo and its blends to produce white shade. Bamboo being a lignocellulosic fibre has a tendency to show pale brownish yellow colour after bleaching when exposed to sunlight due the presence of residual lignin of high molecular weight and hydrophobic nature (Kaur et al., 2019; Trotman, 2008). Bamboo fibres can be bleached by controlled treatment with selected oxidizing type of bleaching agents such as sodium hypochlorite, hydrogen peroxide (HP) in an alkaline pH, potassium permanganate, and sodium chlorite under neutral or slightly acidic pH in aqueous medium. Reducing bleaching agents like sodium hydrosulfite, sodium sulphite, sulphur dioxide, sodium bisulphate, etc. are less used due to drawbacks of

198

Bamboo Fibres

nonpermanency of whiteness. The chemical reaction with lignin must be slow enough for complete diffusion of bleaching chemical into the interstices of fibres. Different bleaching agents used have their own level of effect on the environment. For good lignin removal, chemical reaction with lignin must be slow enough to allow time for diffusion of chemical into interstices of fibres. Different bleaching agents engender different levels of concern for environment (Kushwaha and Kumar, 2011; Rao, 2007). 8.1.2.3 Bleaching with sodium hypochlorite Sodium hypochlorite can be used to obtain bleached bamboo fibres with improved whiteness. Delignified bamboo fibres strands can be bleached with sodium hypochlorite having 5
8 g/L available chlorine at room temperature for 1
2 hours. Sodium carbonate can be used to maintain alkaline pH in the range 10
10.5. It is then thoroughly washed with water and antichlored with 0.2% sodium sulphate for 15 minutes at 60 C. The fibres are then finally washed and dried. It is extremely important to choose correct parameters such as pH, time, and temperature for an optimized bleaching action. Hypochlorite bleaching is generally not considered an eco-friendly process due to the presence of chlorine in hypochlorite. 8.1.2.4 Bleaching with sodium chlorite Bamboo fibres can be successfully bleached with sodium chlorite solution (Subramanian et al., 2005; Sengupta and Radhakrishnan, 1972). Its strands can be bleached using 4% (mass/volume) sodium chlorite at boil, at a pH 3
4.5 for 90 minutes using a material to liquor ratio of 1:20. Formic acid can be used to maintain an acidic pH of the bleaching bath. It is then thoroughly washed and finally dried. However, the acidified sodium chloride solution is very reactive and causes environmental pollution. 8.1.2.5 Bleaching with hydrogen peroxide HP is considered as an eco-friendly bleaching agent and can be successfully used for bleaching bamboo fibres as the reaction products obtained are nonionic, resulting in fewer effluent problems (Biagiotti et al., 2004; Changhai et al., 2010). A general recipe for bleaching of bamboo can be H2O2 (50%), 3%
8% (owf), sodium silicate 6%
8% (owf), caustic soda 0.5%
0.7% (owf), nonionic detergent 0.2%
0.5% (owf), temperature 85 C
90 C, pH 105
11, and time 1.5
2 hours.

Chemical processing of bamboo and bamboo products

199

A research study on the pretreatment processes for fabrics from cotton, bamboo, polylactic acid (PLA), and soybean protein fibres has been ˇ cka et al., 2015). This study focused on enzymatic scouring reported (Spiˇ and the bleaching performance of different peracetic acid (PAA) bleaching processes, which were compared with each other and with the conventional HP process. Enzymatic scouring and bleaching with PAA were chosen to minimize fibre damage and to perform the processes under more benign conditions. The fabrics were bleached by the following three PAA bleaching processes: with PAA, with PAA in combination with tetraacetylethylenediamine (TAED) (peroxide activator), and with HP in combination with arylesterase enzymes (gentle power bleach). The conventional bleaching process with HP was performed at 90 C in highly alkaline pH media, and the bleaching processes with PAA were performed at 65 C in neutral to slightly alkaline pH media. Measurements of whiteness, water drop absorbency, tenacity at maximum load, along with fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) spectra and scanning electron microscope (SEM) micrographs were evaluated for the fabrics enzymatically scoured and bleached by the different processes. The results revealed that after the enzymatic scouring, the hydrophilicity of the fabrics was adequate. The regenerated bamboo and especially the poly(lactic) acid and soy protein fibres were found significantly damaged during conventional HP bleaching compared to cotton fibres. The bleaching process with PAA treatment resulted in a strong whitening ability that was comparable to that of conventional bleaching with HP but with substantial reduction fibre damage. The whiteness and yellowness indices values of the desized, enzymatically scoured, and differently bleached fabric samples are presented in Table 8.1. It may be observed from the results that the enzymatic scouring removes the noncellulosic components to a certain extent from the cellulosic fibres resulting in slightly higher WIs and lower YIs of all of the scoured samples. Further, after bleaching, the increase in the WIs and the decrease in the YIs were significant. In the case of the CO, CO/BAM, and CO/PLA samples, the whiteness levels obtained increased in the following order: HP/ENZ (enzyme) , PAA , PAA/TAED , HP. For CO/ SPF (soy protein fibre), the highest WI was measured after the PAA/ TAED process. Based on the whiteness results, the authors concluded that the PAA/TAED process was the most efficient among the lowtemperature PAA bleaching processes.

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Bamboo Fibres

Table 8.1 Whiteness and yellowness Indices Sample Desized Scoured Bleached with with PAA pectinases

of various pretreated fabrics. Bleached Enzymatically Bleached with PAA catalysed HP with bleaching hydrogen and TAED peroxide

Whiteness indices (WI) Cotton Cotton/ bamboo Cotton/ PLA Cotton/ SPF

26.61 25.76

30.72 31.52

74.93 72.46

77.22 73.06

73.41 68.59

80.29 73.40

43.15

49.06

81.94

82.37

80.99

85.90

20.67

23.20

51.36

54.3

49.86

51.37

Yellowness indices (YI) Cotton Cotton/ bamboo Cotton/ PLA Cotton/ SPF

19.51 20.74

18.65 18.68

4.49 5.18

3.80 4.92

4.94 6.33

3.00 5.44

15.20

13.04

2.25

1.92

2.38

1.01

22.76

21.56

12.62

11.80

13.18

10.36

ˇ cka, N., Zupin Z., ˇ Kovaˇc J., Tavˇcer P.E.F., 2015. Enzymatic scouring and Source: Adapted from Spiˇ low-temperature bleaching of fabrics constructed from cotton, regenerated bamboo, poly(lactic acid), and soy protein fibers. Fibers Polym. 16 (8), 1723
1733.

The tenacity of treated samples after the enzymatic scouring (ES) and the different PAA bleaching processes was retained, whereas after the HP bleaching, the tenacity values of the bamboo, PLA and SPF samples significantly decreased. Hence, it was confirmed that compared with the conventional HP bleaching, the ES and different PAA bleaching processes did not deteriorate the strength of the fabrics. From the above study it was proved that mild enzymatic treatments must be used for bamboo fibres in order to retain the essential properties and to obtain maximum level of whiteness after bleaching. In addition it was observed that cotton fibres could withstand HP bleaching, but fibres such as bamboo, PLA, and SPF could be significantly damaged during conventional HP bleaching. Further, in order to maintain a high tenacity in bamboo and other fibres, enzymatic scouring, and low-temperature PAA bleaching can be recommended in place of conventional HP bleaching as the bleaching processes with PAA compared with the conventional HP bleaching process operate at lower temperatures and result in final

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Chemical processing of bamboo and bamboo products

bleaching baths with a near neutral pH resulting in an environmentfriendly process. Similarly, in another study, a weft-knitted fabric from regenerated bamboo fibres was bleached with four different PAA bleaching processes: with only PAA, with PAA or H2O2 in combination with TAED (tetraacetylethylenediamine) (peroxide activator), and with H2O2 (hydrogen ˇ cka and Tavˇcer, peroxide) in combination with arylesterase enzymes (Spiˇ 2015). The knit fabric was also bleached conventionally with H2O2 for comparison purposes. Whereas the conventional H2O2 process was carried out at 90 C and in highly alkaline pH media, the bleaching processes with PAA were carried out at 65 C and in neutral to slightly alkaline pH media. It was found that with PAA bleaching processes, bamboo knit fabrics demonstrated a high degree of whiteness, high water absorbency, and high tenacity with low water and energy consumption. The knit fabric produced from regenerated bamboo fibres was bleached with five different bleaching processes, that is, bleaching with PAA, bleaching with PAA and TAED, bleaching with H2O2 and TAED, enzymatically catalysed bleaching (gentle power bleach), and bleaching with H2O2. The results of bleaching are summarized in Table 8.2. Overall, all bleaching processes, with the exception of the H2O2/TAED process, yield similar whiteness, yellowness, and tint levels. In addition, all the bleached samples showed higher moisture absorption values (10.37
10.63) compared to the unbleached sample (10.22)

Table 8.2 Whiteness indices (WI), yellowness indices (YI), and tint values (TV) of the bleached samples. Sample Whiteness Yellowness Tint value index (WI) index (YI) (TV)

Unbleached fabric Bleached with PAA Bleached with PAA and TAED Bleached with H2O2 and TAED Bleached with enzyme and H2O2 Bleached with H2O2

43.47 70.01 71.17 58.01 68.97 70.26

14.46 5.41 5.05 9.50 5.77 5.20

22.62 20.37 20.34 21.09 20.40 20.39

ˇ cka, N., Tavˇcer P.E.F., 2015. Low-temperature bleaching of knit fabric from Source: Adapted from Spiˇ regenerated bamboo fibers with different peracetic acid bleaching processes. Text. Res. J. 85 (14) 1497
1505.

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with a very small difference between the treated samples which confirmed the fact that the absorption properties of differently PAA-bleached knitted bamboo fabrics that were carried out in milder conditions were still comparable to that of conventionally H2O2 bleached fabric samples. Interestingly, all bleached samples exhibited higher tenacity and elongation values at the maximum load than the unbleached sample (Table 8.3). This was attributed to fabric contraction during the bleaching processes, because all bleached samples showed higher wale and row density and thickness values than the raw sample resulting in a strong and more compact fabric after bleaching. It was noted that the sample bleached with H2O2, recorded the lowest tenacity and elongation values as compared with differently PAA-bleached samples making the lowtemperature PAA bleaching processes very suitable for producing stronger knitted fabrics with minimum damage to fibres. 8.1.2.6 Dyeing of bamboo textiles Textile dyeing process is an important step which adds value to textile by improving its aesthetics, comfort and functional properties. Today textiles, not only satisfy human needs for clothing but it is also a fashion statement. Earlier the purpose of colouring of textile was initiated by natural source until the introduction of synthetic dyes. The coloured material may originate from animals or plants and the dyes used for coloration of textiles, plastic etc. are organic chemicals and the dyes used for ceramics, glasses, rocks, jewels, etc. are inorganic substances (Choudhury, 2006). The natural dyes have dominated the world market in the beginning of the 19th century. The only synthetic dye which was known at that time was picric acid. The second half of the 19th century saw the Table 8.3 Tenacity at the maximum load (Fmax) and elongation (E) of bleached fabrics. Sample Fmax (N) E (%)

Unbleached fabric Bleached with PAA Bleached with PAA and TAED Bleached with H2O2 and TAED Bleached with enzyme and H2O2 Bleached with H2O2

66.35 78.55 80.82 74.42 72.00 69.20

241.11 312.55 317.23 298.96 294.70 284.18

ˇ cka, N., Tavˇcer P.E.F., 2015. Low-temperature bleaching of knit fabric from Source: Adapted from Spiˇ regenerated bamboo fibers with different peracetic acid bleaching processes. Text. Res. J. 85 (14) 1497
1505.

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introduction of many new classes of dyes by British chemists. Since then, very few chromogens have been added to the range of available dyestuffs. Traditionally synthetic dyes available were organic raw material containing six-membered ring structures of carbon atoms. Commercially products must be standardized to give acceptable consistent shades, depth of shade, and other physical properties. Bamboo fibre is a regenerated cellulosic fibre lighter in weight, soft, with smooth handle, and has excellent wicking properties. The microgaps present in the fibre and high porosity of bamboo fibre structure produce higher colour yield when dyed (Larik et al., 2015). Bamboo viscose fabrics are usually dyed with reactive dyes and show better colour performance than cotton, modal, and viscose (Han et al., 2008). A study on dyeing of bamboo and its blends was undertaken by Chandrasekhara (2019). In this study, five different varieties of fabrics, viz., bamboo/cotton bamboo/polyester, 100% bamboo, 100% cotton, 100% polyester fabrics were dyed and evaluated for colour fastness, rubbing fastness, and colour strength (k/s) properties. Scouring and bleaching was carried out only for cotton, bamboo, and bamboo/cotton blended fabrics. bamboo, cotton, and bamboo/cotton blended fabrics were dyed with reactive HE-brands. Polyester fabrics were dyed using disperse dyes and bamboo/polyester blended fabrics were dyed with reactive (HE) and disperse dyes. Scouring, bleaching, and dyeing of all the fabrics were carried out using standard procedures in the laboratory. 8.1.2.7 Dyeing of bamboo, cotton, and bamboo/cotton fabrics Bamboo and cotton are cellulosic materials and were dyed using reactive dyes (hot brand, Procion-HE). Reactive dyes are the important dye classes for cellulosic materials. The reactive class of dyes offer a wide range of dyes with varying shades, fastness properties, easy applicability, reproducibility, and low cost with brilliancy. Bamboo and bamboo blended fabric varieties were dyed using the standard procedure in the laboratory. Bamboo/cotton, 100% bamboo fabric, and 100% cotton fabric samples were dyed by preparing the dye bath with 3% reactive dye (hot brand procion—HE) with a liquor ratio of 1:40. The fabric samples were entered into the dye bath at room temperature. The temperature of the dye bath was raised gradually to about 90 C
95 C. Common salt was used as an exhausting agent to exhaust the dye bath. Dyeing was carried out at the above temperature for about 90 minutes. Sodium carbonate

204

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was used as a fixing agent. After dyeing, soaping was done with a soap solution of 15 gpl to remove surface adhered dye. The dyeing recipe is shown in Table 8.4. Dyeing of polyester was done using carriers at 100 C using standard procedure in the laboratory. The recipe used for dyeing of polyester fabrics is given in Table 8.5. In the first instance the fabric was treated in the bath containing carrier at 60 C for 15 minutes. In a separate container the disperse dye was prepared with a small quantity of water and acetic acid. The contents were then transferred to the main bath and dyeing was continued. The temperature of the bath was gradually raised up to boil and the fabric was dyed at this temperature for 90 minutes. 1. Reduction clearing: this treatment was done to remove excess dye from the fabric using the following recipe. 2. Na2C03: 2 gpl 3. Hydrose: 2.5 gpl 4. M:L: 1:30 The dyed fabric is treated in the reduction clearing bath at a temperature of 60 C for about 15 minutes. Then the material was taken out and washed thoroughly and then dried. Table 8.4 Dyeing conditions. M:L ratio

1:40

Reactive dye Sodium chloride (NaCl) Sodium carbonate (Na2CO3) Wetting agent Temperature Time

3% shade 40 gpl 20 gpl 2
3 drops 90 C 90 min

Table 8.5 Dyeing conditions for polyester fabrics. M:L ratio

1:40

Dye Carrier Dispersing agent Acetic acid Na2CO3 Temperature Time

3% shade 10 gpl 02 gpl 2
3 drops 2 gpl 90 C 90 min

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8.1.3 Dyeing of blends Dyeing of bamboo/polyester blended fabrics is a little complicated because one component of these is hydrophilic and the other is hydrophobic. In order to dye the blended fabric, reactive dye for cotton and disperse dye polyethylene terephthalate (PET) were used. A two-step dyeing method was used. Bamboo/polyester blended fabrics were dyed first with disperse dyes using carrier dyeing methods, and then dyed with reactive dye to dye the cotton portion (Choudhury, 2006).

8.1.4 Measurement of colour fastness properties of the fabrics Colour is one of the most important factors in consumer acceptance of textiles. When a consumer shops for a new garment, colour plays an important role in the purchase decision. Retention of colour is equally important to consumer and is often a determining factor in the serviceability of a textile item. It is therefore important to test any dyed or printed fabrics for the fastness of the colours that have been used for different applications. Colour parameters were assessed using instruments such as (1) RBE (R.B. Electronic & Engineering Private Limited, India) Laundrometer to test wash fastness property, (2) Paramount Crockmeter to test rubbing fastness property, and (3) Minolta spectrophotometer for the determination of K/s values. 8.1.4.1 Wash fastness The dyed and undyed sample pieces to be tested were colour fastness are cut to a size of 10 3 4 cm each. Dyed fabric sample was sandwiched between the two undyed bleached sample and they were sewn longitudinally. The sample was weighed and kept in the container with M: L ratio of 1:40 and soap solution of 0.5% on the weight of material. The material was treated for 30 minutes and then washed with cold water and dried. The samples were tested using RBE laundrometer following ISO 63301984 E standards and compared with the colour staining grey scales and graded accordingly. 8.1.4.2 Rubbing fastness The fabric samples to be tested were conditioned in standard testing atmosphere for 24 hours. The fabric samples were tested for rubbing

206

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fastness using Paramount crock metre following IS 766-1956 standards. Ten readings were taken and their mean was found out.

8.1.5 Measurement of colour strength (K/S) The calorimetric characteristics of bamboo and bamboo blended fabrics were measured using Minolta Spectro-photometer. The spectrophotometer is integrated with a computer in terms of CIEL a b colour coordinates (L , a , b , c , h) and colour strength value (K/S). The colour strength value (K/S) in the visible region of the spectrum (400
700 nm) was calculated using the Kubelka
Munk equation following ASTM E284 standards. K ð12RÞ2 5 S 2R where R is reflectance value of the dyed fabric at max absorption, K is absorption coefficient, and S is scattering coefficient.

8.1.6 Fabric fastness properties The fastness properties like washing, rubbing, and colour fastness properties that were evaluated are listed in Table 8.6. 8.1.6.1 Fabric fastness properties From the results it was observed that 100% bamboo fabrics shows good fastness to washing and rubbing (grey scale rating of 4.0) compared to other four varieties of fabrics. The bamboo/cotton, bamboo/polyester, 100% cotton, and 100% polyester fabrics show average wash and rubbing fastness ratings (grey scale rating of 3
4). Compared to 100% bamboo fabric, 100% polyester fabrics show poor fastness and rubbing fastness properties (grey scale rating of 3.0) compared to other four varieties of fabrics. Table 8.6 Fastness properties of bamboo and bamboo blended fabrics. Fabric Bamboo/ Bamboo/ 100% 100% 100% properties cotton polyester Bamboo Cotton Polyester

Fastness to washing Fastness to rubbing

3
4

3
4

4

3

3

3
4

3
4

4

3
4

3

1, Very poor; 2, poor; 3, average; 4, good; 5, excellent.

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8.1.7 Colour strength (K/S) The colour strength values of bamboo and bamboo blended fabrics are presented in the Table 8.7. The 100% bamboo fabrics showed higher K/S (13.42) compared to bamboo/polyester, bamboo/cotton, 100% cotton, and 100% polyester blended fabrics (K/S values 12.64, 10.22, 6.22, and 4.33, respectively). The higher K/S values of 100% bamboo, bamboo/polyester, and bamboo/cotton fabrics were due to better dye uptake of bamboo fibre. This showed that the light reflectance was lowest for these fabrics. Thus, the bamboo viscose and its blended fabrics showed better dyeing behaviour and fastness properties to washing, rubbing, and higher K/S values. From the results it was also observed that bamboo viscose and its blended fabrics showed the maximum dye saturation and the colours obtained were the brightest. The difference in these values was attributed to the difference in the molecular structure of the fibres. It is known that the diffusion of dye molecule into fibres mainly depends on the size and distribution of crystalline and amorphous regions. Lower crystallinity and higher amorphous region of the fibre increases dye diffusion (Shen et al., 2004). The crystallinity of bamboo fibre compared to cotton and polyester was lower. Therefore, it would be easier for dye molecule to diffuse into bamboo viscose fibre than into cotton and polyester which leads to the higher K/S values for bamboo and its blended fabrics. In addition to crystallinity, voids in a fibre structure also influence the dyeing and colour fastness properties of fibres. Voids in the fibre increases the ability of fibre to absorb more water and dye molecule. The results of the structural and thermal properties of bamboo fibre (Shen et al., 2004) shows many voids in the fibre cross section. Therefore, voids in the fibre structure may lead to an increase in the dye uptake of bamboo fibre, resulting in the deepest colour of the fabrics. In addition, the presence of voids in the fibre structure increase the depth of colour by the mechanism of decreasing the surface reflection of light. Owing to lower crystallinity, the greater amount of amorphous region, and the presence of voids in the cross section, bamboo fibres result in higher K/S values compared to cotton and polyester. Table 8.7 Colour strength (K/S). Fabric Bamboo/ Bamboo/ properties cotton polyester

100% Bamboo

100% Cotton

100% Polyester

K/S values

13.42

6.22

4.33

10.22

12.64

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Bamboo Fibres

After the study the authors concluded that the bamboo fabrics showed good fastness to wash and rubbing (grey scale rating of 4.0) compared to cotton, polyester, and other blended fabrics. Bamboo/cotton, bamboo/polyester, cotton, and polyester fabrics showed average wash and rubbing fastness properties (grey scale rating of 3.0
4.0). Polyester fabrics results in poor fastness and rubbing fastness properties (grey scale rating 3.0) compared to bamboo and cotton fabrics. From the K/S results it was observed that the bamboo fabrics shows higher colour strength values (K/S 13.42) compared to cotton polyester and bamboo blended fabrics. The colour strength values (K/S) of bamboo/ polyester, bamboo/cotton, and cotton were 12.64, 10.22, 6.22, and 4.33, respectively. The better wash, rubbing, and colour strength (K/S) of bamboo fabrics was due to many voids in the fibre structure and this leads to increase in the dye uptake resulting in the deep shades and higher colour strength values. Some attempts have been made to modify bamboo viscose fibres by different methods to enhance their dyeing behaviour. The dyeing characteristics of raw bamboo fabric and modified by oxidation and sericin treatment have been reported by Chu and Chen (2012). The dyeing was carried out by constant temperature staining method using reactive dyes and to improve the reactivity, bamboo fibres were oxidized by sodium and sericin protein cross-linking. The dyeing performance, whiteness, and absorbency tests were carried out and evaluated before and after the modification of bamboo fabric after sericin treatment. The fabrics were dyed by reactive dyes such as reactive dyes (Reactive Violet A-5RV, Reactive Red A-EF, Reactive Yellow A-4GLN, Reactive Dark Blue A-2GLN, and Reactive Turquoise Blue A-6GLN). The K/S values of raw bamboo fabric (unmodified) and treated with sericin have been presented in Table 8.8. It was observed from the dyeing Table 8.8 K/S values of dyed bamboo fabrics. Bamboo fabric Reactive dye used Reactive Reactive turquoise yellow A-4GLN blue A-6GLN K/S K/S

Unmodified Modified by sericin (5 g/L) Modified by sericin (25 g/L) Modified by sericin (35 g/L)

Reactive red A-EF K/S

9.01 11.68

9.58 12.19

12.04 11.83

12.42

14.73

10.59

11.83

15.67

12.18

Source: Adapted from Chu, Y.M., Chen, Y.Y., 2012. Study on modification of raw bamboo fabric and dyeing properties. Adv. Mater. Res. 502, 277
281.

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studies that the sericin treatment of bamboo fabrics results in an increase in dye uptake, showing higher K/S values. The authors also observed an increased washing and rubbing fastness ratings for the dyed fabrics after the modification. Similarly, in a study, the bamboo rayon fabric was grafted with acrylamide using potassium persulfate (KPS) as an initiator by optimising the grafting conditions in terms of temperature, time, initiator, and monomer concentrations. The ungrafted and grafted fabrics were dyed using acid dyes and tested for colour strength and fastness properties. An increase in the dyeability of the order of 150%
230% was observed on grafting of bamboo rayon. The bamboo rayon which was otherwise not dyeable with acid dyes could be rendered acid dyeable by grafting technique (Teli and Sheikh, 2012).

8.2 Summary In this chapter an attempt has been made to describe the chemical processing of bamboo and bamboo fibre products. Various pretreatment methods such as scouring and bleaching carried out for bamboo textiles using various methods have been explained in detail. Different methods of dyeing of bamboo fabrics have also been explained. Dyeing methods used after modification of bamboo fabrics in order to improve their dyeing behaviour have also been described in detail.

References Amada, S., Ichikawa, Y., Munekata, T., Nagase, Y., Shimizu, H., 1997. Fibre texture and mechanical graded structure of bamboo. Compos. B Eng. 28B, 13
20. Biagiotti, J., Puglia, D., Torre, L., Kenny, J., 2004. A systematic investigation on the influence of the chemical treatment of natural fibers on the properties of their polymer matrix composites. Poly Compos. 25, 470
479. Cai, J., Zhang, L., 2005. Rapid dissolution of cellulose in LiOH/urea and NaOH/urea aqueous solutions. Macromol. Biosci. 5, 539
548. Callum, A.S., Hill, H.P.S., Khalil, A., Hale, M.D., 1998. A study of the potential of acetylation to improve the properties of plant fibres. Indust Crop. Prod. 8, 53
63. Chandrasekhara, S.M., 2019. Studies on Production, Properties and Techno-Economics of 100% Pure Bamboo and Bamboo/Cotton Blended Fabrics (Ph.D. thesis). Visvesvaraya Technological University, Belgaum, Karnataka, India. Changhai, X., Shamey, R., Hinks, D., 2010. Activated peroxide bleaching of regenerated bamboo fiber using a butyrolactam-based cationic bleach activator. Cellulose 17, 339
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Choudhury, A.K.R., 2006. Textile Preparation and Dyeing. Science Publishers, UK/ USA, p. 245. Chu, Y.M., Chen, Y.Y., 2012. Study on modification of raw bamboo fabric and dyeing properties. Adv. Mater. Res. 502, 277
281. Das, M., Chakraborty, D., 2006. Influence of alkali treatment on the fine structure and morphology of bamboo fibers. J. Appl. Poly Sci. 102, 5050
5056. Das, M., Chakraborty, D., 2008. Thermogravemetric analysis and weathering study by water immersion of alkali treated bamboo fibres. BioRes 3, 1051
1062. Farrelly, D., 1984. The Book of Bamboo. Sierra Club Books, San Francisco, CA. Gritsch, C.S., Kleist, G., Murphy, R.J., 2004. Developmental changes in cell wall structure of phloem dibres of the Bamboo Dendrocalamus asper. Ann. Bot. 94, 497
505. Grosser, D., Liese, W., 1971. On the anatomy of Asian bamboos, with special reference to their vascular bundles. Wood Sci. Technol. 5, 290
312. Han, G., Lei, Y., Wu, Q., Kujima, Y., Suzuki, S., 2008. Bamboo-fiber filled high density polyethylene composites: effect of coupling treatment and nano-clay. J. Environ. Polym. Degrad. 16 (2), 123
130. Jones, F.R., 1994. Hand Book of Polymer-Fibre Composites. Longman Scientific & Technical, New York. Kaur, V., Chattopadhyay, D.P., Satindar, K., Sachin, K.G., Sanyog, S., Simran, K., et al., 2019. A review on preparatory processes of bamboo fibres for textile applications. J. Text. Sci. Eng. 9, 398. Khuhwaha, P., Kumar, P., 2009. Enhanced mechanical strength of BFRP composite using modified bamboos. J. Reinfor Plast. Compos. 28, 2851
2859. Kushwaha, P.K., Kumar, R., 2011. Influence of chemical treatments on the mechanical and water absorption properties of bamboo fibre composites. J. Reinfor Plast. Compos. 30, 73
85. Larik, S.A., Awais, K., Shamsad, A., Seong, H.K., 2015. Batchwise dyeing of bamboo cellulose fabric with reactive dye using Ultrasonic energy. Ultrason. Sonochem. 24, 178
183. Li, S.H., Zeng, Q.Y., Xiao, Y.L., Fu, S.Y., Zhou, B.L., 1995. Biomimicry of bamboo bast fibre with engineering composite materials. Mat. Sci. Eng. C3, 125
130. Liu, Y., Hu, H., 2008. X-ray diffraction study of bamboo fibres treated with NaOH. Fibre Polym. 9, 735
739. Muhammad, N., Bustam, M.A., Mutalib, M.I.A., Cecilia, D., 2011. Dissolution and delignification of bamboo biomass using amino acid-based ionic liquid. Appl. Biochem. Biotechnol. 165, 998
1009. Nugroho, N., Ando, N., 2000. Development of structural composite products made from bamboo I: Fundamental properties of bamboo zephyr board. J. Wood Sci. 46, 68
74. Peng, W.X., Xue, Q., Ohkoshi, M., 2014. Immune effects of extractives on bamboo biomass self-plasticization. Pak. J. Pharm. Sci. 27, 991
999. Rao, K.M.M., 2007. Extraction and tensile properties of natural fibers: vakka, date and bamboo. Compos. Struct. 77, 288
295. Sahinbaskan, B.Y., 2012. Dyeing properties of bamboo/cotton blended yarns by singlebath combined process. Asian J. Chem. 24 (4), 1638
1642. Sathitsuksanoh, N., Zhu, Z., Ho, T., Bai, M., Zhang, Y.P., 2010. Bamboo saccharification through cellulose solvent-based biomass pretreatment followed by enzymatic hydrolysis at ultra-low cellulase loadings. Bioresour. Technol. 101, 4926
4929. Sengupta, A.B., Radhakrishnan, T., 1972. The diversification of jute decorative fabrics in new ways to produce textile. Text. Inst. Manche 112
114. Shao, S., Wen, G., Jin, Z., 2008. Changes in chemical characteristics of bamboo (Phyllostachys pubescens) components during steam explosion. Wood Sci. Technol. 42, 439
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Shen, Q., Liu, D.S., Gao, Y., Chen, Y., 2004. Surface properties of bamboo fiber and a comparsion with cotton linter fibres. Colloids Surf. B: Biointerfaces 35 (3
4), 193
195. Shin, F.G., Yipp, M.W., 1989. Analysis of the mechanical properties and microstructure of bamboo-epoxy composites. J. Mater. Sci. 10, 3483
3490. ˇ cka, N., Tavˇcer, P.E.F., 2015. Low-temperature bleaching of knit fabric from regenerSpiˇ ated bamboo fibers with different peracetic acid bleaching processes. Text. Res. J. 85 (14), 1497
1505. ˇ cka, N., Zupin, Z., ˇ Kovaˇc, J., Tavˇcer, P.E.F., 2015. Enzymatic scouring and lowSpiˇ temperature bleaching of fabrics constructed from cotton, regenerated bamboo, poly (lactic acid), and soy protein fibers. Fibers Polym. 16 (8), 1723
1733. Steinfeld, C.A., 2001. Bamboo Future. January 25. [cited 2011 October 10]; Available from: http://www.carol-steinfeld.com/bamboofuture.html. Stout, H.P., 1985. Fibre chemistry. Hand Book of Fibre Science and Technology. Marcel Dekker, New York, p. 4. Subramanian, K., Kumar, S.P., Jeypal, P., Venkatesh, N., 2005. Characterization of lingocellulosic seed fibre from Wrightia Tinctoria plant for textile applicationsan exploratory investigation. Eur. Poly J. 41, 853
861. Teli, M.D., Sheikh, J., 2012. Graft copolymerization of acrylamide onto bamboo rayon and fibre dyeing with acid dyes. Iran. Polym. J. 21, 43
49. Trotman, E.R., 2008. Dyeing and chemical technology of textile fibres, Textile Scouring and Bleaching, fourth ed. Hodder Arnold, England. Xu, Y., Lu, Z., Tang, R., 2007. Structure and thermal properties of bamboo viscose, Tencel and conventional viscose fiber. J. Therm. Anal. Calorim. 89, 197
201. Yueping, W., Ge, W., Haitao, C., Xiaojun, T., Xushan, G., 2010. Structure of bamboo fiber for textiles. Text. Res. J. 80, 334
343.

CHAPTER FIVE

Properties of bamboo fibres: physical, performance, comfort, thermal, and low stress mechanical properties

5.1 Introduction Bamboo is a fast growing, inexpensive, and available natural resource in most developing countries and it has outstanding material qualities. In general, bamboo fibres have good properties of moisture adsorption, moisture desorption, and air permeability. Being natural fibres, they are available in abundance, have high strength, are biodegradable and renewable. Bamboo fibres, which possess high mechanical properties, can be used as a sustainable material for application in textile clothing manufacture and fibre-reinforced polymer composites. The cultivation and industrial processing of bamboo and the unique microstructural properties of natural bamboo with respect to its mechanical properties make it a suitable renewable material for composites in high-performance applications and offer huge potential for a new generation of building materials fabricated through embedding natural bamboo fibres into a resin matrix for applications in architecture and construction. The mechanical strength of bamboo fibres is higher compared to certain other natural fibres, such as wood, jute, coir, and straw. Therefore, bamboo fibres have been proposed as reinforcements in plastics, cement and concrete, rubber, and even aluminium. The mechanical properties of bamboo increase with the age of the plant, reaching a peak value at 3 6 years’ time and then decreasing, resulting in the overall mechanical performance being strongly dependent on age (Low and Che, 2006). Hence, the properties of the bamboo fibres are inconsistent with respect to time owing to the decrease in their cellulose content with aging (Khalil et al., 2012). Moreover, the properties of bamboo fibres are also greatly affected by their method of extraction. Bamboo Fibres. DOI: https://doi.org/10.1016/B978-0-323-85782-6.00003-9

© 2023 Elsevier Ltd. All rights reserved.

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102

Bamboo fibres are the primary load-carrying members in bamboo, and are extremely soft, comfortable, and cool possessing a bright colour. The fibres demonstrate high elastic resilience, moisture absorption, good drapability, wearability, and excellent spinnability (Jain et al., 1992). In addition, the production of bamboo pulp fibres is similar to viscose production, and it is easy to predict the properties of bamboo fibres. A number of researchers have studied the mechanical properties of various types of bamboo fibres for textile and composite manufacture. Studies have reported on the properties of bamboo culm, natural bamboo fibres, and bamboo viscose (pulp) fibres. The physical and mechanical properties of several bamboo species have also been studied extensively. An attempt has been made in this chapter to provide detailed information on the physical, mechanical, and thermal properties of natural bamboo and bamboo viscose fibres.

5.2 Physical properties of natural bamboo fibres Natural bamboo fibres are generally extracted from bamboo culm by different extraction methods, such as mechanical, chemical, and biological techniques. Normally inexpensive equipment is used in chemical methods which consume less energy. However, these methods have better control over fibre properties compared to steam explosion (SEP) and mechanical methods (Phong et al., 2012). Therefore, different methods have different potential to remove lignin, which contributes to the stiffness and yellowing of bamboo fibres. Further, fibre properties like strength, density, moisture absorbency, and flexibility are also affected by the presence of noncellulosic components (Li et al., 2010). Hence, the fabrics produced from natural bamboo fibres have a rough and stiff feel compared with the fabrics produced from bamboo pulp fibres. The mechanically processed fibres demonstrate higher strength and durability than the chemically processed fibres due to the change in physical form, molecular orientation, and degree of polymerisation within the fibres.

5.2.1 Moisture absorption One of the most important characteristics of bamboo fibres is their hygroscopicity, to the level of absorbing three times their weight of water.

Properties of bamboo fibres

103

The moisture absorption of bamboo fibres is observed to be 13%, which is more than that of cotton, lyocell, viscose rayon, modal, and soybean (Erdumlu and Ozipek, 2008). Large voids are observed in bamboo fibres resulting in very good hygroscopicity. Therefore, the moisture content is also an important factor affecting the mechanical properties of bamboo fibres (Chen et al., 2021). The process of moisture absorption in bamboo is observed to follow the kinetics described in Fick’s theory (Kushwaha and Kumar, 2010). Bamboo fibre provides a reservoir of moisture, which usually diffuses into interfacial regions and decreases the shear strength (Chen, 2014). Bamboo possesses very high moisture content; green bamboo has 100% moisture with innermost layers having 155% moisture (Li, 2004). Phyllostachys bambusoides is found to have a moisture content of 138%. Owing to the presence of microgaps and microholes in the fibres, the fabrics produced from bamboo fibres possess excellent wickability, so that the moisture is instantly taken away from the skin to be quickly evaporated, thus providing a cooling sensation. In addition, some striated cracks are also observed, which are distributed over the length of bamboo viscose fibres, and many voids in their cross section, both of which are suggestive of good water retention capacity (Xu et al., 2007).

5.2.2 Length and linear density Generally, natural bamboo fibres are finer and shorter than other natural fibres such as ramie fibres. The length of individual natural bamboo fibre varies between 1 and 5 mm (average 2.8 mm) and diameter is 14 27 µm (average 20 µm). Ten to twenty individual fibres are packed into bundles (Majumdar and Arora, 2015). These fibres are used in the manufacture of nonwoven fabrics. They are characterised with a rough surface and a circular cross section with a small round lumen. Several researchers have tried to investigate the properties of pure bamboo fibres and the fabrics made out of them. Lengths of the natural bamboo fibres range from 1.2 to 21.5 cm and the minimum average length is 1.73 cm (Rocky and Thompson, 2018). The size of single bamboo fibres are 10 30 mm in diameter and 1 4 mm in length (Wang et al., 2011; Yu et al., 2014a). The length of fibres varies according to the age of the bamboo. The average length of fibres obtained from different horizontal layers of 1-, 3-, and 5-year-old bamboo is presented in Table 5.1 (Li, 2004). The length varies from 1.6 to 3.1 mm, but can go up to 6.4 mm. Compared to 1-year-old bamboo,

Bamboo Fibres

104

Table 5.1 Average fibre length from 1-, 3-, and 5-year-old bamboo. Age (years old) Layer Fibre length (mm) Fibre number measured

1

3

4

Outer Middle Inner Outer Middle Inner Outer Middle Inner

2.16 2.27 2.19 2.08 2.32 2.26 2.03 2.32 2.39

484 401 294 321 301 292 456 431 307

3- and 5-year-old bamboo show a higher percentage of fibres less than 1.6 mm. Generally, the outer layer shows a significant shorter fibre length than the middle and inner layers. Rocky and Thompson (2018) reported the fibre length and linear densities of natural bamboo fibres by different extraction methods. They extracted the fibres by using SEP, high-temperature chemical processes, enzymatic process, and a combined process to analyse the length of fibres and their linear density. Fifteen specimens were chosen for length and weight measurement. These 15 selected samples were among the prospective fibres in each process. At least 20 fibres were selected randomly from each of the produced fibres in the 15 specimens. Fibres that were very small and expected to be removed by carding or combing action in spinning were not considered for length or weight measurement. The quantity of discarded fibres was not large, roughly less than 5%. The weight of fibres with respect to their lengths was measured by a microbalance. Linear density, which is an alternative to fibre fineness, was calculated by conditioning the fibres at 21 C 6 1 C for 72 hours, according to standard ASTM method D1776 04 before measurement. The average length and fineness values are presented in Table 5.2. It may be observed that the average lengths of the fibres range from 2.73 to 10.2 cm amongst the samples (Table 5.2), which means that all the fibres had very good spinnable average lengths, which need to be at least 1.9 cm for cotton spinning processes in industry. The results presented in Table 5.2 show that the average length of the fibres from different processes is different as would be expected. For example, sample 3 with an average length of 8.06 cm shows a fineness of 305.58 dtex but sample 12 with almost the same average length (8.3 cm) has 266.27 dtex.

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105

Table 5.2 Average length and linear density of extracted natural bamboo fibres. Specimen Average length (cm) Fineness (dtex)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

2.73 6.4 8.06 7.4 7.79 5.73 6.93 7.3 2.9 4.34 4.81 8.3 10.2 5.61 7.2

232.6 225.0 305.58 294.40 389.27 316.99 218.98 307.95 262.76 292.17 134.10 266.27 293.14 341.04 223.43

Source: Adapted from Rocky, B.P., Thompson, A.J., 2018. Production of natural bamboo fibres-1: experimental approaches to different processes and analyses. J. Text. Inst., 109 (90): 1 11.

This indicates that the amount of the weight loss of the fibres differs with different processes as the removal of lignin, pectin, and other extractable components, and the number of fibres in the bundle differ. In general, the fineness decreases with the increase of length for most of the processes. This indicates that the higher the average length of the fibres, the less delignification occurred and/or the number of fibres decreases along the length as the length increases.

5.3 Tensile properties A number of researchers have studied the tensile properties of bamboo fibres. The tensile properties of single bamboo fibres isolated by chemical and mechanical extraction methods have been reported by Chen et al. (2015). Single bamboo fibres and bamboo fibre bundles obtained from both chemical retting and mechanical retting were tested. The tensile properties of single bamboo fibres isolated by different methods are presented in Table 5.3. From the Table 5.3, it may be observed that the extraction methods have a significant effect on the tensile properties of bamboo fibres. The

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Table 5.3 Tensile properties of single bamboo fibres. Single bamboo Tensile strength, GPa Tensile modulus, GPa Elongation, % fibres (CV) (CV) (CV)

Chemically extracted Mechanically extracted

1.77 (0.15)

26.85 (0.06)

2.89 (0.16)

0.93 (0.19)

34.62 (0.17)

4.30 (0.17)

From Chen, H., Cheng, H., Wang, G., Yu, Z., Shi, S. Q., 2015. Tensile properties of bamboo in different sizes. J. Wood Sci., 61: 552 561.

tensile strength of chemically extracted fibres show a higher value than that of mechanically extracted fibres, whereas the modulus and elongation are lower (Xu and Tang, 2006; Guimarães et al., 2009). Similarly, tensile strength, modulus, and elongation of chemically extracted bamboo fibre bundles were all higher than for mechanically extracted bamboo fibre bundles (Table 5.4). In the chemical extraction method, the alkali used removes a large part of the lignin and hemicellulose surrounding the cellulose, resulting in higher tensile properties. In addition, the alkali treatment helps in removing a part of the lignin-rich middle lamella, thus reducing the damage caused by the combing process in the preparation of bamboo fibre bundles. In contrast, mechanically extracted fibre bundles (peeled with tweezers from fibrillated bamboo strips) were found to be damaged more in the middle lamella. It was also observed that mechanically extracted fibre bundles failed near the glue droplet compared to chemically extracted bundles. Moreover, mechanical extraction caused more damage due to stress concentration. The chemically extracted fibre bundles show higher strain indicating the introduction of ductility into fibres after the alkali treatment, which was in line with the results reported by others (Chen, 2014; Hossain et al., 2014). The tensile properties of bamboo strips are presented in Table 5.5. It may be seen from the values in Table 5.5 that the tensile strength and modulus along the grain direction of samples made from outer portion of bamboo were higher compared to those made from the inner portion of bamboo. However, the tensile strength and modulus of bamboo strips were lower than that of samples made from outer portion of the bamboo but higher than that of samples made from inner portion of the bamboo. It was opined that the density of vascular bundles, the amount, and the thickness of fibres may be the factors affecting the tensile properties of bamboo fibres (Xian and Xian, 1990). The higher tensile strength of the

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Table 5.4 Tensile properties of bamboo fibre bundles. Bamboo fibre Tensile strength, GPa Tensile modulus, GPa Elongation, % bundles (CV) (CV) (CV)

Chemically extracted Mechanically extracted

0.61 (0.37)

23.56 (0.06)

2.61 (0.32)

0.29 (0.71)

16.50 (0.42)

1.68 (0.31)

From Chen, H., Cheng, H., Wang, G., Yu, Z., Shi, S. Q., 2015. Tensile properties of bamboo in different sizes. J. Wood Sci., 61: 552 561.

Table 5.5 Tensile properties of bamboo strips. Samples Tensile strength, GPa Tensile modulus, GPa (CV) (CV)

Bamboo strips Bamboo outer layer Bamboo inner layer

0.30 (0.02) 0.33 (0.04)

19.85 (0.05) 25.51 (0.06)

0.26 (0.01)

18.53 (0.05)

Elongation, % (CV)

From Chen, H., Cheng, H., Wang, G., Yu, Z., Shi, S. Q., 2015. Tensile properties of bamboo in different sizes. J. Wood Sci., 61: 552 561.

outer layer than the inner one has been attributed to the differences in the structure. Being a natural composite, cells in bamboo can be classified as the cells in (1) basic tissues for transmitting load which have high tensile strength, but low modulus, and low density; and (2) vascular tissues, structurally consisting of fibres and lignified vessels. The mechanical properties of bamboo can be attributed to the fibres in vascular tissue having high tensile strength, modulus, and density (Liu, 2008). The differences in the structure are mainly responsible for the phenomenon that the tensile strength of the outer layer is greater than that of the inner layer. The amount of vascular bundles determines the mechanical properties of bamboo. The higher the vascular bundle content, the greater the tensile strength and modulus for the bamboo (Amada et al., 1997). The higher amount of fibres in the outer layer of the vascular bundle was also responsible for the higher tensile strength and modulus of bamboo strips obtained from the outer layer. Tensile properties of fibres from bamboo strips treated with different concentrations of NaOH have been reported (Das and Chakraborty, 2008). Bamboo strips treated with caustic solutions of different concentrations, for example, 5%, 10%, 15%, 20%, 25%, and 50%, were subjected to

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Ultimate tensile strength Flexural strength

Alkali Concentration (%)

Figure 5.1 Tensile and flexural strength of alkali-treated bamboo fibres.

Flexural Strength (MPa)

Ultimate tensile strength (MPa)

mechanical testing giving stresses on tensile strength, per cent elongation at break, flexural strength, flexural modulus, and toughness. Tensile and flexural tests were performed on an Instron tensile tester 4304. For tensile testing, five specimens of bamboo strips with the dimension of 10 3 1 3 (0.01 0.015) cm3 were tested for each type of sample with a crosshead speed of 5 mm/min and a gauge length of 4 cm. For the purpose of flexural test, three-point bend tests were performed on bamboo strip samples [10 3 1 3 (0.01 0.015) cm3] using a crosshead speed of 1.2 mm/min and a span length of 4 cm. The mechanical properties of bamboo fibres treated with NaOH solutions are presented in Figs 5.1 5.3. The tensile strength of bamboo fibres was maximum at 20% concentration of alkali, whereas flexural strength was maximum at 15% concentration (Fig. 5.1). Similarly, the toughness value follows the same trend as that of flexural strength (Fig. 5.3). Flexural and tensile modulus increase up to 20% alkali concentration and then decrease (Fig. 5.2). However, the per cent elongation at break shows a decreasing trend, as expected with a corresponding increase in tensile strength (Fig. 5.3). It may be observed that the alkali-treated bamboo fibres demonstrate superior mechanical properties up to 20% alkali concentration, after which an increase in alkali concentration leads to a drastic reduction. This was attributed to the rupture of alkali-sensitive bonds existing in different components of bamboo due to the penetration and swelling and a reduction in hemicellulose content. The mechanical properties of bamboo fibres are affected by many factors, such as growth environment, growth years, and fibre extraction

Properties of bamboo fibres

Flexural Modulus (MPa)

Tensile Modulus (MPa)

109

Alkali Concentration (%)

Toughness (MPa)

Elongation-at-break (%)

Figure 5.2 Tensile and flexural modulus of alkali-treated bamboo fibres.

Alkali Concentration (%)

Figure 5.3 Toughness and elongation of alkali-treated bamboo fibres.

method (Osorio et al., 2011). Properties of untreated and bamboo single fibres treated with different concentrations of NaOH have been reported (Zhang et al., 2018). Bamboo fibres were manually sized into lengths of 5, 10, and 15 mm, respectively, and single fibre tensile testing was conducted on a Z-Wick Testing Machine. The stress strain curves for bamboo fibres are presented in Fig. 5.4 and the mechanical property parameters are shown in Table 5.6. The untreated bamboo fibres shows an average tensile strength of 262 MPa and a Young’s modulus of 9.8 GPa. Compared to untreated fibres, 2 wt.% NaOH treatment demonstrated a minor effect on the tensile properties of bamboo fibres. However, after 6 wt.% NaOH treatment, the tensile strength and the Young’s modulus of bamboo fibres increase by 38% and 14%, respectively. It may be noted that moderate alkalitreatment can effectively remove the hemicellulose and lignin in bamboo fibres, so that cellulose crystallinity can be increased, which usually

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Figure 5.4 Typical stress strain curves of natural bamboo single fibres. Table 5.6 Mechanical properties of single bamboo fibres. Conc. of NaOH Tensile strength Young’s modulus (wt.%) (MPa) (GPa)

Untreated 2 6 10

262 6 75 283 6 71 363 6 103 235 6 67

9.8 6 1.6 9.2 6 1.3 11.2 6 2.4 6.1 6 0.9

Strain at break (%)

0.7 0.8 0.5 1.1

improves both fibre tensile strength and modulus (Bledzki and Gassan, 1999; Sydenstricker et al., 2003). Several extraction methods produce different forms of bamboo fibres and the properties of fibres thus vary, especially the strength parameter. Table 5.7 shows the physical and mechanical properties of fibres extracted by different methods. It may be observed from the values in Table 5.6 that the rolling method produces bamboo fibres of the lowest strength (270 MPa). However, several other methods produce fibres of considerably higher tensile strength. The bamboo fibre shows slightly lower strength compared to other natural fibres, such as kenaf, ramie, and flax. However, the strength of bamboo demonstrated in the range of 615 862 MPa is considered high compared to other fibres (Shah et al., 2016). Another study reported the tensile properties of fibres from different bamboo species (Waite, 2010). The tensile properties of different fibres are presented in Table 5.8.

Table 5.7 Mechanical and physical properties of bamboo fibres extracted by different methods (Zakikhani et al., 2014). Fibre Extraction procedure Tensile strength Young’s modulus Fibre length Fibre diameter (µm) (MPa) (GPa) (mm)

Density (g/cm3)

Bamboo Mechanical Steam explosion Steam explosion Steam explosion Steam explosion Steam explosion Steam explosion Rolling mill Grinding Retting Crushing

516 441 6 220 383 441 615 862 308 6 185 270 450 800 503 420 6 170

17 36 6 13 28 35.9 35.45 25.7 6 14.0

Chemical Chemical Chemical Alkaline Alkaline

341 450 329 419 395 6 155

19.67 18 22 30 26.1 6 14.5

15 210 0.8 125

220 270 18 30 35.91 38.2 6 16

195 6 150 100 600 262 6 160

1.4 0.91

Chemical 10

270

0.89 1.3

230 6 180

Combined mechanical and chemical Chemical 1 Compression Chemical 1 roller mill

645 Max: 1000

. 10

370 Max: 480

120 170

50 400 HC:150 250 HC: 50 100

0.8 0.9

Source: Adapted from Zakikhani, P., Zahari, R., Sultan, M.T.H., Majid, D.L., 2014. Extraction and preparation of bamboo fibre-reinforced composites. Mater. Des., 63: 820 828.

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Table 5.8 Tensile properties fibres from different bamboo species. Bamboo Extraction Fibre Average Average breaking species method specification breaking force tenacity (CN/dtex) (CN)

Bambusa emeiensis

Chemical (thick pulp) Chemical

Bambusa emeiensis Phyllostachys Chemical edulis Phyllostachys Mechanical edulis

Varied

406 6 106

Varied

1.56 dtex

13.7 6 2.1

8.75 6 1.36

1.56 dtex

17.7 6 2.8

11.4 6 1.8

5.88 dtex

146 6 20

24.9 6 3.64

It can be observed that the mechanically extracted bamboo fibres demonstrate higher fibre breaking force and breaking tenacity than chemically extracted fibres. Among the varieties, mechanically extracted Phyllostachys edulis fibres show the highest breaking tenacity (24.9 CN/Tex). Chiu and Young (2020) reported a study on the tensile properties of dry and wet bamboo fibres that were used as preforming for manufacturing fibre-reinforced composites. The single bamboo fibre preforming test and stress relaxation test were conducted to study the formability. Table 5.9 shows the tensile properties of the alkali-treated dry and wet bamboo fibres. The wet fibres with 58% moisture content were obtained by water spray for 1 minute. The result shows that the tensile strength of bamboo fibre reduces significantly after the wet treatment and is only 56% of that of the dry bamboo fibres. The decrease in Young’s modulus was also observed for the wet fibres, which results in easy deformation of these fibres compared to dry fibres. Figs 5.5 and 5.6 shows the corresponding stress strain curves of tensile tests. While, the dry bamboo fibres demonstrated brittle fracture behaviour, the wet bamboo fibres showed more ductility due to the softening of the cellulose, the hemicellulose, and lignin.

5.4 Stress relaxation behaviour Chiu and Young (2020) also conducted stress relaxation tests on single bamboo fibres to study the relaxation behaviour under a constant

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Table 5.9 Tensile properties of wet and dry bamboo fibres. Moisture Tensile strength Failure strain content (%) (MPa) (%)

0 58

430.85 1 41.17 32.41 242.57 1 22.90 27.42

2.00 1 0.27 0.19 1.27 1 0.17 0.21

Young’s modulus (GPa)

25.62 1 1.64 2.58 23.36 1 4.33 4.33

Source: Adapted from Chiu, H.-H., Young, W.-B., 2020. Characteristic study of bamboo fibres in preforming. J. Composite Mater., 54 (25): 3871 3882.

Figure 5.5 Stress strain curves of dry bamboo fibres (moisture content 5 0%). Adapted from Chiu, H.-H., Young, W.-B., 2020. Characteristic study of bamboo fibres in preforming. J. Composite Mater., 54 (25): 3871 3882.

applied strain of 0.002. The results are presented in Figs 5.7 and 5.8. Both the dry and wet fibres were tested at room temperature and at 140 C. At room temperature, the wet bamboo fibres demonstrate faster stress relaxation, attaining a constant residual stress of about 36 MPa. The dry fibres also show the relaxation behaviour as well, but with a lower rate. Both the wet and dry fibres do not relax completely and have a residual stress after about 60 minutes. The stress was decreased to zero for both the wet and dry fibres when the testing temperature was raised to 140 C. At high temperature, the plastic deformation occurs, which compensates for the applied strain and causes the stress to decrease. Due to a high Young’s modulus of fibres at high temperature, upon loading, the bamboo fibres

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Figure 5.6 Stress strain curves of wet bamboo fibres (moisture content 5 58%). Adapted from Chiu, H.-H., Young, W.-B., 2020. Characteristic study of bamboo fibres in preforming. J. Composite Mater., 54 (25): 3871 3882.

Figure 5.7 Stress relaxation behaviour of a single bamboo fibre under a constant strain. Adapted from Chiu, H.-H., Young, W.-B., 2020. Characteristic study of bamboo fibres in preforming. J. Composite Mater., 54 (25): 3871 3882.

acquire lower stress at higher temperature, resulting in a complete relaxation with a certain amount of plastic deformation. The amount of plastic deformation may be associated with the moisture content of the bamboo fibre.

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Figure 5.8 Stress relaxation behaviour of a single bamboo fibre under different strain. Adapted from Chiu, H.-H., Young, W.-B., 2020. Characteristic study of bamboo fibres in preforming. J. Composite Mater., 54 (25): 3871 3882.

It was noted that the dry fibres demonstrated a complete relaxation at high temperature under a 0.002 applied strain as shown in Fig. 5.7. Fig. 5.8 shows the stress relaxation of dry bamboo fibres under different applied strains. As the applied strain was higher than 0.004, a residual stress was seen due to the insufficient relaxation. The authors opined that it was difficult to perform experiments for stress relaxation of bamboo fibres at a high temperature and wet conditions due to the variation in the humidity. However, they concluded that the wet bamboo fibres demonstrate a large plastic deformation under an external load. Heating of the bamboo fibres will facilitate the plastic deformation and allow a complete stress relaxation under a certain prescribed strain. But the dry bamboo fibres only show limited strain relaxation at a temperature of 140 C. Hot and wet conditions promote the relaxation behaviour which will allow the plastic deformation to occur during the preforming process. The morphological structure and properties of the extracted bamboo shell fibre have been investigated by Ni et al. (2017). The mechanical properties of the bamboo shell fibres were tested on an Instron 5565 tensile tester at an extension rate of 10 mm/min with a clamping distance of 10 mm and pretension of 0.1 cN. Fifty readings were recorded to obtain

116

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Figure 5.9 The typical strain stress curves of bamboo shell fibres. From Ni, H., Li, Y., Fu, S., 2017. Morphological structure and properties of bamboo shell fibre. J. Nat. Fibres, 15 (4): 1 10.

the mean values of tensile strength and elongations at breakage, as well as initial modulus. Strain stress curves of the bamboo shell fibre are presented in Fig. 5.9. It may be observed that the strain stress curves of bamboo shell fibre are different from those of the regular bamboo fibres. The curve is linear with no significant bending phase, indicating that the bamboo shell fibre has high tenacity and low elongation at break. Moreover, the strain stress curve of the bamboo shell fibre exhibits a distinct brittle fracture trend. The tenacity and elongation at break of fibres were lower in their wet state compared with those in their dry state. The results suggested that the as-prepared bamboo shell fibres have good mechanical stability. The average breaking tenacity, elongation at breakage, and initial modulus of the bamboo shell fibres are summarised in Table 5.10. It was noted that the tenacity and initial modulus of the bamboo shell fibres were remarkably affected by moisture absorption and were found to be lower in their wet state than in their dry state. However, there was no

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Table 5.10 Tensile properties of bamboo shell fibres. Status Breaking tenacity Elongation at average value break average (cN/dtex) (CV%) value (%) (CV%)

Initial modulus average value (cN/dtex) (CV%)

Dry Wet

214.32 30.47 143.37 37.71

3.21 28.11 1.97 35.84

2.01 3.56 1.93 3.71

significant difference in the elongation at break between dry and the wet state. It was concluded that the bamboo shell fibres demonstrated excellent tenacity, low elongation, and brittle fracture.

5.5 Physical properties of bamboo viscose (pulp) fibres Physical properties of bamboo viscose fibres have been reported by Chandrasekhara (2019). In this study, the author compared the physical characteristics and tensile properties of bamboo, cotton, and polyester fibres. The Fibre strength and elongation of bamboo, cotton, and polyester fibres were measured as per ASTMD1445 05 standards for all the fibres using an Eureka stelometer which works on the Constant Rate of Loading (CRL) principle. Fibre strength and elongation were recorded to the nearest 0.01 kg and 0.5%, respectively. Ten readings were taken and the average was calculated. The moisture content and moisture regain of bamboo, cotton, and polyester fibres were measured using a Statex Moisture Tester. The moisture content and moisture regain of all the fibres were calculated using the formula: Moisture content: W =D 3 100 Moisture regain: W =D 3 100 where W 5 weight of moisture present, and D 5 dry weight of fibres. The density of bamboo, cotton, and polyester was determined using the method of immersing the fibre in an organic liquid. In this case benzene was used to determine the density of the fibre sample. Ten readings were taken and the average was calculated using the formula: ρ5

Mf Vf

where ρ 5 density of fibre, Mf 5 mass of the fibre, and Vf 5 volume of the fibre

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Table 5.11 Properties of bamboo, cotton, and polyester fibres. Sample Bamboo Cotton

Polyester

Fibre length (mm) Fibre fineness (denier) Fibre strength (gpd) Elongation at break (%) Moisture regain (%) Moisture content (%) Density (g/cm3)

35.5 1.71 4.0 10 0.4 0.3 1.38

35 1.81 2.48 15.5 12.5 11 1.51

32 1.5 2.4 5.7 7 6.6 1.53

The physical properties of bamboo fibres, that is, fibre length, fineness, tenacity, elongation at break, moisture regain, moisture content, and density, are presented in Table 5.11. From the results it was observed that the fibre lengths of bamboo, cotton, and polyester are in a similar range, that is, 35, 30.25, and 35.5 mm, respectively. The cotton fibre was finer (1.5 d) compared to polyester (1.71 d), whereas bamboo viscose fibres showed a fineness value of 1.81 d. The polyester fibre was stronger (4.0 gpd) compared to bamboo viscose (2.48 gpd) and cotton (2.4 gpd). This was due to the difference in the physical and chemical structure of polyester. The elongation of bamboo fibre was highest (15.5%) compared to polyester and cotton (10% and 5.7%) and this showed that the bamboo fibre is more flexible compared to polyester and cotton. Similarly, bamboo fibres showed the highest moisture regain and content (12.5% and 11%, respectively) compared to cotton and polyester (7% and 6.6% and 0.4% and 0.3%, respectively). This was due to the presence of voids and microgaps in the bamboo fibre compared to the cotton and polyester fibres.

5.6 Thermal properties Thermal analysis is conducted to understand the thermal stability, glass transition, melting temperature and other properties as a function of temperature of polymers and fibres. Chandrasekhara (2019) carried out studies on the thermal behaviour of bamboo, cotton, and polyester fibres

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119

using TGA. Thermo analyser SDTQ600 was used for this purpose. The fibre sample of 3 4 mg was taken and evenly and loosely distributed on the sample pan. The fibre samples were subjected to an increasing temperature regime over the range of ambient to 800 C at a heating rate of 10 C/min. All the tests were conducted under dry and pure nitrogen atmosphere. TGA and derivative (DTG) traces were obtained for all the fibres. Table 5.12 shows the results of thermogravimetric analysis of bamboo, cotton, and polyester fibres. The respective TGA and DTG are presented in Figs 5.10 5.12. From the results it was observed that in the first stage, moisture evaporation takes place in a temperature region of 38.71 C 76.03 C for bamboo, the same occurs at 81.18 C 84.03 C for cotton, and this stage Table 5.12 TGA results of bamboo, cotton, and polyester fibres. Fibre Thermal Maximum temperature of Final temperature samples stability ( C) decomposition ( C) ( C)

Residue (%)

Bamboo 297.96 Cotton 319.77 Polyester 405.78

6 14 15

520.94 370.84 448.48

Weight (%)

Deriv. Weight (%/°C)

333.74 352.30 431.78

Temperature (°C)

Figure 5.10 TGA and DTG traces of bamboo fibres.

Bamboo Fibres

Weight (%)

Deriv. Wt. (%/°C)

120

Temperature (°C)

Weight (%)

Deriv. Wt. (%/°C)

Figure 5.11 TGA and DTG traces of cotton fibres.

Temperature (°C)

Figure 5.12 TGA and DTG traces of polyester fibres.

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121

was not found in polyester fibres as its fibres are highly hydrophobic in nature. The weight loss in this stage was 10.01% for bamboo and 4.7% for cotton. Bamboo exhibits lower thermal stability at a temperature of 297.96 C compared to cotton (319 C) and polyester (405 C). The second stage, decomposition, continues in the temperature range of 297 C 520 C for bamboo, 319.9 C 370.84 C for cotton, and 405.95 C 448.48 C for polyester. Residue left was 6% for bamboo fibre, 14% for cotton, and 15% for polyester fibres. Among the three fibres, the polyester fibres showed the maximum thermal stability with a residue of 15%. The TGA studies on natural bamboo fibres have been reported by Wu et al. (2021). The effects of heat treatment at various temperatures on mechanically separated bamboo fibres and parenchyma cells were examined by the authors in terms of colour, microstructure, chemical composition, crystallinity, and thermal properties. Bamboo fibres and parenchyma cells mechanically isolated from each other were treated at various heating temperatures in an oven and the thermal behaviour of fibres was investigated by TGA technique. Typical TGA and DTG curves of the untreated and treated bamboo fibres are shown in Figs 5.13 and 5.14. Three distinct weight-loss stages were

Figure 5.13 Typical TGA curves of bamboo fibres. From Wu, J., Zhong, T., Zhang, W., Shi, J., Fei, B., Chen, H., 2021. Comparison of colors, microstructure, chemical composition and thermal properties of bamboo fibres and parenchyma cells with heat treatment. J. Wood Sci., 67: 56.

122

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Figure 5.14 Typical DTG curves of bamboo fibres. From Wu, J., Zhong, T., Zhang, W., Shi, J., Fei, B., Chen, H., 2021. Comparison of colors, microstructure, chemical composition and thermal properties of bamboo fibres and parenchyma cells with heat treatment. J. Wood Sci., 67: 56.

observed at 30 C 100 C, 200 C 350 C, and 315 C 400 C. The first stage was mainly attributed to the evaporation of water, the second to the decomposition of hemicellulose and lignin, and the third to the decomposition of cellulose. The shoulder peak observed at about 300 C was caused by the thermal decomposition of hemicellulose. There was no significant change in the shoulder when the heat treatment temperature was below 220 C, but it was reduced obviously in fibres at 220 C. This indicated the decrease of hemicellulose content. One may observe a main peak at about 360 C which could be caused by the thermal decomposition of cellulose in fibres (Fig. 5.14). The cellulose chains in bamboo fibres demonstrate close packing with smaller dspacing. After the treatment at temperatures of 200 C and 220 C, the main peak of the fibres shifts to a lower temperature. Lignin is a complex aromatic polymer composed of phenylpropane structural units connected by C C bonds and C O C bonds and was more difficult to decompose than hemicellulose and cellulose (Yang et al., 2007; Li et al., 2013). The pyrolysis of lignin almost takes place during the entire process as the bond energy was widely distributed (Zhang et al., 2021), but the main

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degradation of lignin occurred at above 350 C. The results of this study revealed that the thermal stability of bamboo fibres remained almost unchanged at low treatment temperatures but decreased at 200 C or 220 C. The heat treatment at temperature 220 C resulted in the most pronounced decrease in thermal stability.

5.7 Low stress mechanical properties of bamboo and bamboo blended fabrics The quality and performance of fabrics and garments are of great importance and are influenced by the mechanical properties of fabrics. Fabric handle is dependent on complex interactions between tensile, bending, shear, and compressive deformation at low stress. Handle properties are assessed subjectively by sliding the fabric between finger and thumb, which gives some idea about stiffness, softness, smoothness, bulkiness, and crispiness of the fabric. However, the concept of fabric handle measurement has been completely transformed with the invention of the Kawabata evaluation system (KES) (Gerick and Pol, 2010), which measures the low stress mechanical properties (tensile, shear, bending and compression) of fabrics and predicts the fabric hand value. Quality has become of prime importance in every aspect of life in today’s competitive environment. In 1930 Pierce carried out the research work on the objective measurement of mechanical properties of fabrics like bending and compression. He started his work at Sevenska Textile for Skinning Institute and in the late 1950s and 1960s he started the evaluation of low-stress mechanical properties of apparel fabrics. The research was focused mainly on mechanical properties such as tensile, shear, buckling, bending, and compression for the tailorability and formability of fabric into garments. Lindberg et al. (1961) were the first to apply the theory of buckling to fabrics in a garment manufacturing process. Fabric compression in longitudinal direction is an important property in tailoring and this is related to fabric formability, which is a measure of the degree of longitudinal compression. Mishra et al. (2012) produced 100% cotton, viscose rayon, regenerated bamboo viscose, and cotton/bamboo blended (60/40) fabrics and characterised these fabrics for various healthcare applications. The studies revealed that the fabrics made from 100% bamboo viscose fabrics showed

124

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better results compared to 100% cotton and 100% viscose fabrics in terms of ultraviolet protection factor (UPF), absorbency, static characteristics, moisture vapour permeability, and fabric handle. The total hand values (THVs) of bamboo and cotton fabric were higher compared to cotton fabric. The study revealed that breaking load and elongation of bamboo gauze bandages were higher than cotton gauge bandages. From the studies it was observed that 100% bamboo fabrics were showing better resistance to microbial growth compared to 100% cotton and viscose rayon fabrics. Some important properties like mechanical, surface, and frictional properties of fabric are identified as important from the point of view of fabric handle. Kawabata established some standards regarding the handle of a fabric considering the subjectively assessed hand values. The fabric properties considered for Kawabata evaluation are tensile, shearing, bending, compressional, surface, weight, and thickness. Chandrasekhara (2019) conducted detailed studies on low-stress mechanical properties of bamboo and bamboo blended fabrics. Five varieties of fabrics: 100% bamboo, bamboo/cotton (65:35), bamboo/polyester (65:35), 100% cotton, and 100% polyester fabrics, were chosen for the study. Four different instruments were used to measure the low stress mechanical properties of bamboo and bamboo blended fabrics by the KES-W at CIRCOT (Central Institute For Research on Cotton Technology) Mumbai, India. Tensile and shear properties of fabrics were measured using KES-FB1, bending behaviour by KES-FB2, compression by KES-FB3, and surface characteristics by KES-FB4 tester. The mechanical properties of fabrics at low stress were measured with high sensitivity.

5.7.1 Tensile properties (tensile tester KES-FB1) The tensile properties of bamboo and bamboo blended fabrics are presented in Table 5.13. It may be observed from the results that the tensile linearity (LT) of 100% polyester fabric was highest (0.857) compared to bamboo/polyester, 100% cotton, bamboo/cotton, and 100% bamboo fabrics (0.802, 0.760, 0.736, and 0.727, respectively). The tensile energy (WT) of 100% bamboo fabric was higher (0.83 gf. cm/cm2) compared to bamboo/cotton, 100% cotton, bamboo/polyester, and 100% polyester (0.53, 0.52, 0.37, and 0.195 gf. cm/cm2 respectively). This was attributed to lower

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Table 5.13 Tensile properties of bamboo and bamboo blended fabrics. Sl. no. Sample LT WT gf. cm/cm2 RT%

1

Bamboo/cotton (65/35)

2

Bamboo/polyester (65/35)

3

100% Bamboo

4

100% Cotton

5

100% Polyester

Side 1 Side 2 Avg. Side 1 Side 2 Avg. Side 1 Side 2 Avg. Side 1 Side 2 Avg. Side 1 Side 2 Avg.

0.823 0.816 0.820 0.756 0.848 0.802 0.727 0.726 0.727 0.872 0.839 0.855 0.743 0.777 0.760

0.60 0.46 0.53 0.38 0.34 0.37 1.00 0.65 0.83 0.54 0.50 0.52 0.19 0.19 0.19

64.63 79.36 72.00 62.33 63.10 62.71 71.57 79.03 75.30 62.69 61.14 61.91 60.92 57.98 59.45

EMT%

2.89 2.26 2.57 2.04 1.61 1.83 5.48 3.60 4.54 2.50 2.37 2.43 1.02 0.98 1.00

LT, linearity of load extension curve; WT, tensile energy; RT, tensile resilience; EMT, tensile strain.

molecular weight and lower crystallinity of bamboo compared to cotton. The low tensile energy of fabric causes a low extension at low stress level. One hundred per cent polyester and 100% cotton fabrics showed lower tensile energy (WT) as it was difficult to extend these fabrics. This was caused by the higher initial modulus of cotton and polyester fibres than bamboo. One hundred per cent bamboo fabric showed higher tensile resilience (RT% 75.30) followed by bamboo/cotton (72%), bamboo/polyester (62.71%), cotton (61.91%), and polyester fabrics (59.45%). The polyester fabrics demonstrate minimum tensile resilience compared to other varieties of fabrics. The resilience property of fabric represents its recovery from tensile deformation; the higher the tensile resilience of the fabric, the better is the fabric handle property. Tensile strain (EMT %) of bamboo fabrics was highest (4.54%) followed by bamboo/cotton (2.57%), cotton (2.43%), bamboo/polyester (1.83%), and polyester (1.00%). The 100% polyester fabrics showed less tensile strain compared to other varieties of fabrics. Higher EMT (%) value of 100% bamboo viscose fabric also signifies the greater comfortness compared to cotton, polyester, and other fabrics. The results also showed that the ability to recover from tensile deformation was higher in the case of 100% bamboo fabrics.

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5.7.2 Shear properties The shear properties of all the fabrics are presented in the Table 5.14. From the results of shear properties, it was observed that the shear rigidity (G gf/cm. deg) of 100% cotton fabrics (2.05) was highest followed by 100% polyester (1.46), bamboo/cotton (1.27), bamboo/polyester (1.18), and 100% bamboo fabrics (0.56). The sheer force (2HG) of 100% cotton fabric was highest (3.72), followed by 100% polyester (2.64), bamboo/cotton (1.77), bamboo/polyester (1.67), and 100% bamboo fabrics (0.49). The sheer force (2HG5 gf/cm) was highest for 100% polyester fabrics (6.19) followed by 100% cotton, bamboo/polyester, bamboo/cotton, and bamboo fabrics (5.60, 4.40, 3.88, and 1.36 respectively). The shear rigidity of fabrics depends on the mobility of cross threads at the intersection points, which in turn depends on weave, yarn diameter, and the surface characteristic of both yarn and fibres. From the handle characteristic point of view, the lower the shear rigidity, the better is the fabric handle. One hundred per cent bamboo fabrics showed low shear rigidity and low hysteresis of shear force both at 0.5 and 5 degrees shear angle. From this it was concluded that the fabrics made from 100% bamboo are more comfortable compared to 100% cotton fabrics. Table 5.14 Shear properties of bamboo and bamboo blended fabrics. Sl. no. Sample Side G gf/cm. deg 2HG gf/cm 2HG5 gf/cm

1

2

3

4

5

Bamboo/cotton (65/35)

Side 1 Side 2 Avg. Bamboo/polyester Side 1 (65/35) Side 2 Avg. 100% Bamboo Side 1 viscose Side 2 Avg. 100% Cotton Side 1 Side 2 Avg. 100% Polyester Side 1 Side 2 Avg.

1.33 1.21 1.27 1.24 1.13 1.18 0.43 0.68 0.56 1.95 2.15 2.05 1.47 1.45 1.46

1.95 1.59 1.77 1.91 1.42 1.67 0.44 0.54 0.49 3.51 3.94 3.72 2.86 2.41 2.64

4.09 3.66 3.88 4.49 4.31 4.40 1.36 1.36 1.36 5.14 6.06 5.60 6.25 6.13 6.19

G, shear rigidity; 2HG, hysteresis of shear force at 0.5 shear angle; 2HG5, hysteresis of shear force at 5 degrees shear angle.

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5.7.3 Bending properties Bending properties of bamboo and bamboo blended fabrics, that is, bending rigidity (B gf. cm2/cm) and bending hysteresis (2HB gf. cm/cm) are presented in Table 5.15. Bending rigidity of a fabric is a measure of ease with which the fabric bends on its own weight. The bending rigidity of the fabrics depends on the bending rigidity of constituent fibres and yarns from which the fabric is produced. From the results of bending rigidity of all the five varieties of fabric tested, the 100% cotton fabrics showed the highest bending rigidity and bending hysteresis (0.0997 and 0.1012) followed by polyester (0.0845 and 0.0787), bamboo/cotton (0.0746 and 0.0512), bamboo/polyester (0.0641 and 0.0604), and 100% bamboo (0.0541 and 0.0265). The higher stiffness of the cotton fabrics compared to bamboo and other varieties of fabrics was attributed to the higher density of cotton fibre (1.52 1.54) compared to bamboo fibre (1.43 1.48). Bending rigidity is an important parameter for handle of fabric; the bamboo fabrics showed low bending rigidity compared to all the other varieties of fabrics tested and demonstrated a good handle property.

Table 5.15 Bending properties of bamboo and bamboo blended fabrics. Sl. no. Sample Side B gf. cm2/cm 2HB gf. cm/cm

1

Bamboo/cotton (65/35)

2

Bamboo/polyester (65/35)

3

100% Bamboo

4

100% Cotton

5

100% Polyester

B, bending rigidity; 2HB, bending hysteresis.

Side 1 Side 2 Avg. Side 1 Side 2 Avg. Side 1 Side 2 Avg. Side 1 Side 2 Avg. Side 1 Side 2 Avg.

0.0763 0.0730 0.0746 0.0626 0.0656 0.0641 0.0536 0.0547 0.0541 0.1005 0.0989 0.0997 0.0824 0.0866 0.0845

0.0593 0.0431 0.0512 0.0603 0.0604 0.0604 0.0271 0.0259 0.0265 0.1110 0.0914 0.1012 0.0755 0.0820 0.0787

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5.7.4 Compression properties The results of compression properties of bamboo and bamboo blended fabrics are presented in Table 5.16.

5.7.5 Fabric compressibility The fabric compressibility character contributes to a feeling of bulkiness and sponginess. The compressibility character of a fabric depends on the yarn packing density and yarn spacing arrangements in the fabric. In fabric compression first the protruding fibres get compressed, then the yarns, and finally the fibres get compressed and are intended to change the crosssectional shape. A higher value of linearity of compression (LC) in the fabric is an indication of the hard feeling of material. The cotton fabric showed the highest LC with LC of (0.599), WC of (0.101), and RC of (40.14), followed by bamboo/cotton (0.533, 0.070, and 36.94), polyester (0.503, 0.051, and 44.56), bamboo/polyester (0.492, 0.0465, and 41.43), and bamboo fabrics (0.461, 0.052, and 44.26). The higher the thickness of the fabric, the higher is the compressibility and it relates to the primary hand values (fukurami or fullness) of the fabric. The thickness of the cotton fabric was more (0.549 mm at 5 gf/cm2) compared to bamboo/cotton, bamboo/ polyester, 100% bamboo, and 100% polyester fabrics (0.527, 0.467, 0.462, and 0.405 mm at 5 gf/cm2 respectively). The other reason given was that the cotton yarn also had lower packing density and higher hairiness compared to 100% bamboo yarns. The cross-sectional shape and noncircular shape of the fibre plays an important role in enhancing the compressional energy. From the results it was also observed that the fabrics made from 100% polyester and 100% bamboo fabrics possessed higher compression resilience (RC% 44.56 and 44.26, respectively) compared to the fabrics made from 100% cotton (RC% 40.14) fabrics. Table 5.16 Compression properties of bamboo and bamboo blended fabrics. Sl. no. Sample LC WC g. cm/cm2 RC%

1 2 3 4 5

Bamboo/cotton (65/35) Bamboo/polyester (65/35) 100% Bamboo 100% Cotton 100% Polyester

0.533 0.492 0.461 0.599 0.503

0.070 0.046 0.052 0.101 0.051

LC, linearity of compression-thickness curve; WC, compressional energy; RC, compressional resilience.

36.94 41.43 44.26 40.14 44.56

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5.7.6 Surface properties The surface properties of bamboo and bamboo blended fabrics are presented in Table 5.17. The surface characteristics of fabric, yarn, and fibre will have greater influence on the fabric handle, comfort, and aesthetic properties. The surface properties, that is, the coefficient of friction (MIU), the deviation in the coefficient of friction (MMD), and geometrical roughness (SMD), of bamboo and bamboo blended fabrics are presented in Table 5.17. From the results it was observed that the 100% bamboo fabrics had higher coefficient of friction (MIU 0.207), followed by cotton, bamboo/polyester, bamboo/cotton, and polyester fabrics (0.194, 0.193, 0.192, and 0.191, respectively). The deviation in the coefficient of friction characteristics in the case of polyester fabrics was higher (MMD 0.0372) followed by bamboo/polyester (0.0320), 100% bamboo (0.0312), bamboo/cotton (0.0267), and 100% cotton fabrics (0.0229). The 100% polyester fabrics showed higher geometrical roughness (SMD 7.87) followed by bamboo/ polyester, bamboo/cotton, 100% bamboo, and 100% cotton fabrics (7.14, 7.00, 6.99, and 6.91 MMD, respectively).

5.7.7 Fabric weight and thickness Fabric weight and thickness of bamboo and bamboo blended fabrics are listed in Table 5.18. From the data given in the table, one can observe Table 5.17 Surface properties of bamboo and bamboo blended fabrics. Sl. no. Sample Side MIU MMD

1

Bamboo/cotton (65/35)

2

Bamboo/polyester (65/35)

3

100% Bamboo

4

100% Cotton

5

100% Polyester

Side 1 Side 2 Avg. Side 1 Side 2 Avg. Side 1 Side 2 Avg. Side 1 Side 2 Avg. Side 1 Side 2 Avg.

0.188 0.196 0.192 0.184 0.202 0.193 0.204 0.211 0.207 0.194 0.193 0.194 0.176 0.206 0.191

0.0372 0.0162 0.0267 0.0511 0.0129 0.0320 0.0447 0.0177 0.0312 0.0240 0.0219 0.0229 0.0548 0.0197 0.0372

SMD (µm)

8.42 5.58 7.00 8.37 5.91 7.14 8.42 5.57 6.99 7.82 6.00 6.91 10.53 5.22 7.87

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Table 5.18 Fabric weight and thickness of bamboo and bamboo blended fabrics. Sl. no. Sample Fabric thickness Fabric thickness at max. Fabric wt. (To) (mm) pressure (Tm) (mm) (mg/cm2)

1 2 3 4 5

Bamboo/cotton (65/35) Bamboo/polyester (65/35) 100% Bamboo 100% Cotton 100% Polyester

0.791

0.527

22.59

0.657

0.467

22.81

0.693 0.889 0.609

0.462 0.549 0.405

23.38 19.43 18.99

To, thickness at 0.5 gf/cm2; Tm, thickness at 5 gf/cm2.

that there is no major difference in the thickness and weight of the fabrics. The thickness of the fabrics both at 0.5 and 5 gf/cm2 was measured and from the data it was observed that the thickness of the 100% cotton fabrics was more (0.549 mm at 5 gf/cm2) followed by bamboo/cotton, bamboo/ polyester, bamboo, and polyester (0.527, 0.467, 0.462, and 0.405, respectively) fabrics. The fabric weight (mg/cm2) of bamboo viscose was higher (23.38 mg/cm2), followed by bamboo/polyester, bamboo/cotton, cotton, and polyester fabrics (22.81, 22.59, 19.43, and 18.99, respectively).

5.7.8 Primary and total hand values Primary and THVs of bamboo and bamboo blended fabrics are presented in Table 5.19. From the results it was observed that the stiffness property (koshi) of 100% bamboo fabric was lower (6.86) compared to bamboo/polyester, bamboo/cotton, 100% cotton, and 100% polyester fabrics (7.42, 7.51, 7.73, and 7.81, respectively). The smoothness property (numeri) of 100% polyester fabrics was lower (3.69) compared to bamboo/polyester, bamboo/cotton, 100% bamboo, and 100% cotton fabrics (4.02, 4.32, 4.50, and 4.68, respectively). The lower smoothness property of polyester fabrics was due to the higher surface roughness characteristic of polyester fibre. On the other hand, bamboo viscose fabrics show lower values of smoothness compared to cotton and possess smooth surface characteristics properties. From the table it can also be observed that the fullness and softness (fukurami) property of 100% cotton fabrics (6.45) shows higher values followed by 100% bamboo, bamboo cotton, bamboo/polyester, and 100% polyester fabrics (5.91, 5.85, 5.37, and 5.30, respectively).

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Table 5.19 Primary and total hand values of bamboo and bamboo blended fabrics. Sl. no. Sample Koshi Numeri Fukurami THV (stiffness) (smoothness) (fullness KN-302 and softness)

1 2 3 4 5

Bamboo/cotton (65/35) Bamboo/polyester (65/35) 100% Bamboo 100% Cotton 100% Polyester

7.51

4.32

5.85

2.32

7.42

4.02

5.37

2.28

6.86 7.73 7.81

4.50 4.68 3.69

5.91 6.45 5.30

2.83 2.28 1.86

THVs of all the five varieties of fabric are presented in Table 5.19. The THVs of all five varieties of fabrics were estimated using the primary hand values using the Kawabata Niwa equation by the KES system (Kawabata and Niwa, 1991). The fibre structure influences the fabric handle and its suitability to various applications for summer seasons. 100% bamboo viscose fabrics exhibited good THV (2.83) compared to bamboo/cotton, bamboo/polyester, 100% cotton, and 100% polyester fabrics (2.32, 2.28, 2.28, and 1.86, respectively). The reason for better hand values of bamboo fabrics was due to higher extensibility and noncircular cross section of bamboo viscose fibre. The THVs were also better for bamboo/cotton and bamboo/polyester blended fabrics and this was due to the presence of more bamboo fibre component which has a lower bending rigidity and good surface characteristics. Thus the fabrics made from 100% bamboo fabrics showed better comfort characteristics compared to cotton and polyester and can be used for apparel manufacture. Low stress mechanical properties of fabrics woven from bamboo viscose blended yarns have been reported by Majumdar and Pol (2014). Three blends (100% cotton, 50:50 cotton:bamboo, and 100% bamboo) were used to produce three yarn counts (20, 25, and 30 Ne). Each of these yarns was used to make fabrics with different pick densities (50, 60, and 70 picks per inch). Ring spun yarns of 20, 25, and 30 Ne linear density were spun from 100% cotton, 50:50 cotton:bamboo viscose, and 100% bamboo viscose fibre. Plain woven fabric samples were produced on a sample weaving machine with a warp sett of 50, keeping same warp and weft yarn counts for all the fabric specimens. Three yarn counts (20, 25, and 30 Ne), three fibre blends (100% cotton, 50:50 cotton:bamboo, and 100% bamboo) and three pick densities or picks per inch (50, 60, and 70)

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were used for producing a total of 27 (3 3 3 3 3) fabric specimens. All the fabrics were then desized using the standard recipe and tested for low stress mechanical properties on KES. The authors found that the bending rigidity, bending hysteresis, shear rigidity, shear hysteresis, and compressibility was lower for bamboo fabrics compared to those of 100% cotton fabrics. On the other hand, extensibility, tensile energy, and compressional resilience were higher for 100% bamboo fabrics than 100% cotton fabrics. Higher pick density increased the linearity of load elongation curve, bending rigidity, shear rigidity, and compressional resilience. Shear and bending rigidities showed very good correlation with the respective hysteresis values. The hand properties of fabrics produced from 100% cotton, 100% viscose rayon, 100% regenerated bamboo viscose fibres, and cotton/bamboo viscose blend (60/40) have been reported by Mishra et al. (2012) using KES. From their studies, it was found that the bamboo fabric showed better tensile extensibility than cotton and the cotton/bamboo blended fabric due to the higher extensibility of viscose and bamboo yarn and fibres. Tensile linearity of bamboo and viscose fabric was almost the same. But cotton fabric showed slightly lower tensile linearity. The bamboo and viscose fibres exhibited a comparatively higher tensile energy than cotton. Shear rigidity was higher in the case of cotton and cotton/bamboo blend fabric than viscose and bamboo fabric in both warp and weft directions. Hence, the hand value as well as comfort were noted to be less in the case of cotton fabric than other samples. Similarly, the overall bending rigidity was higher in the case of cotton fabric due to the higher stiffness of the material and higher diameter of constituent yarn than that of bamboo and viscose yarn. In addition, cotton fibre had slightly higher density than bamboo and viscose fibre, resulting in the lower stiffness of 100% bamboo and viscose fabrics. The compressibility results indicated that the ability of recovering from compressional deformation was higher in the case of cotton and cotton/bamboo blend fabric samples. The surface characteristics of the samples showed that the coefficient of surface friction (MIU) was slightly higher in the viscose and bamboo fabrics due to the presence of many serrations on bamboo and viscose fibre surfaces. The geometrical roughness of the fabric was also higher for bamboo and cotton/bamboo blend fabrics compared to cotton and viscose fabrics due to their differences in fabric construction particulars with respect to yarn diameter.

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The results of primary hand values showed that stiffness (koshi) of viscose and bamboo fabric was lower than the other two samples due to the lower modulus and density of viscose and bamboo fibres than that of cotton fibres. In the case of smoothness (numeri), bamboo and viscose fabric had lower values due to the higher surface roughness. On the other hand, viscose and bamboo fabric showed higher values of fullness and softness (fukurami) than cotton fabric. Antidrape property (hari) was lower in the case of viscose and bamboo fabrics due to the lower bending rigidity of these fabrics. Similarly, bamboo (100%) and 100% viscose fabrics exhibited good THV values, which was attributed to the low modulus, higher extensibility, and noncircular cross section. THV of cotton/bamboo blend was also higher than that of 100% cotton fabric due to the lower bending rigidity of the bamboo component, resulting in better comfort of viscose and bamboo than cotton fabrics.

5.8 Summary This chapter described the various properties of bamboo fibres in detail. The properties of both natural bamboo fibres and bamboo (pulp) viscose fibres were discussed separately. Physical properties of bamboo fibres such as length, linear density, etc. have been presented for various natural fibres from different species, for fibres extracted via different extraction methods. A detailed discussion on the tensile properties of various types of natural and bamboo viscose fibres is also presented. In addition, studies conducted on thermal properties, low-stress mechanical properties of bamboo, cotton, polyester, and viscose blended fabrics by various researchers have also been presented in detail.

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Chen, H., Cheng, H., Wang, G., Yu, Z., Shi, S.Q., 2015. Tensile properties of bamboo in different sizes,”. J. Wood Sci. 61, 552 561. Chen, C., Li, H., Dauletbek, A., Shen, F., Hui, D., Gaff, M., et al., 2021. Properties and applications of bamboo fibre-A current-state-of-the art. J. Renew. Mater. 10 (3), 605 624. Chiu, H.-H., Young, W.-B., 2020. Characteristic study of bamboo fibres in preforming. J. Composite Mater. 54 (25), 3871 3882. Das, M., Chakraborty, D., 2008. Evaluation of improvement of physical and mechanical properties of bamboo fibres due to alkali treatment. J. Appl. Polym. Sci. 107, 522 527. Erdumlu, N., Ozipek, B., 2008. Investigation of regenerated bamboo fiber and yarn characteristics. Fibre Text. East. Eur. 16 (4), 43 47. Gerick, A., Pol, J.V., 2010. A comparative study of regenerated bamboo, cotton and viscose rayon fabrics. Part I selected comfort properties. J. Family Ecol. Consum. Sci. 38, 63 73. Guimarães, J., Frollini, E., Da, S.C., Wypych, F., Satyanarayana, K., 2009. Characterization of banana, sugarcane bagasse and sponge gourd fibres of Brazil. Ind. Crop. Prod. 30, 407 415. Hossain, M.K., Karim, M.R., Chowdhury, M.R., Imam, M.A., Hosur, M., Jeelani, S., et al., 2014. Comparative mechanical and thermal study of chemically treated and untreated single sugarcane fibre bundle. Ind. Crop. Prod. 58, 78 90. Jain, S., Kumar, R., Jindal, U.C., 1992. Mechanical behavior of bamboo and bamboo composites. J. Mater. Sci. 27 (17), 4598 4604. Kawabata, S., Niwa, M., 1991. Objective measurement of fabric mechanical property and quality: its application to textile and clothing manufacturing. Int. J. Cloth. Sci. Technol. 3 (1), 7 18. Khalil, H.A., Bhat, I., Jawaid, M., Zaidon, A., Hermawan, D., Hadi, Y., 2012. Bamboo fibre reinforced biocomposites: a review. Mater. Des. 42 (1), 353 368. Kushwaha, P.K., Kumar, R., 2010. Effect of silanes on mechanical properties of bamboo fibre-epoxy composites. J. Reinf. Plast. Compos. 29 (5), 718 724. Li, X., 2004. Physical, chemical, and mechanical properties of bamboo and its utilization potential for fibreboard manufacturing. Master’s Thesis, Louisiana State University, p. 866. Li, L.J., Wang, Y.P., Wang, G., Cheng, H.T., Han, X.J., 2010. Evaluation of properties of natural bamboo fibre for application in summer textiles. J. Fibre Bioeng. Inform. 3 (2), 94 99. Li, Y., Du, L., Kai, C., Huang, R., Wu, Q., 2013. Bamboo and high density polyethylene composite with heat-treated bamboo fibre: thermal decomposition properties. BioResources 8, 900 912. Lindberg, J., Sandelius, M., 1961. 8-Optimum discount rate for cloth of sub-standard width—Part II. J. Text. Inst. Trans. 52 (3), T109 T121. Liu, B., 2008. Formation of cell wall in development culms of Phyllostachys pubescens. PhD dissertation. Chinese Academy of Forestry, Beijing, pp. 159 161. Low, I., Che, Z., 2006. Mapping the structure, compositions and mechanical properties of bamboo. J. Mater. Res. 21 (8), 1969 1976. Majumdar, A., Arora, S., 2015. Bamboo fibres in textile applications. Text Book: Bamboos in India. ENVIS Centre on Forestry, India, pp. 285 304. Majumdar, A., Pol, S.B., 2014. Low stress mechanical properties of fabrics woven from bamboo viscose blended yarns. Fibres Polym. 15 (9), 1985 1991. Mishra, R., Behera, B.K., Bishnu, P.P., 2012. Novelty of bamboo fabric. J. Text. Inst. 103 (3), 320 329.

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Ni, H., Li, Y., Fu, S., 2017. Morphological structure and properties of bamboo shell fibre. J. Nat. Fibres 15 (4), 1 10. Osorio, L., Trujillo, E., Van Vuure, A.W., Verpoest, I., 2011. Morphological aspects and mechanical properties of single bamboo fibres and flexural characterization of bamboo/epoxy composites. J. Reinf. Plast. Compos. 30, 396 408. Phong, N.T., Fujii, T., Chuong, B., Okubo, K., 2012. Study on how to effectively extract bamboo fibres from raw bamboo and wastewater treatment. J. Mater. Sci. Res. 1 (1), 144 155. Rocky, B.P., Thompson, A.J., 2018. Production of natural bamboo fibres-1: experimental approaches to different processes and analyses. J. Text. Inst. 109 (90), 1 11. Shah, A.U.M., Sultan, M.T.H., Jawaid, M., Cardona, F., Abu Talib, A.R., 2016. A review on the tensile properties of bamboo fibre reinforced polymer composites. Bioresources 11 (4), 10654 10676. Sydenstricker, T.H., Mochnaz, S., Amico, S.C., 2003. Pull-out and other evaluations in sisal-reinforced polyester biocomposites. Polym. Test. 22, 375 380. Waite, M., 2010. Sustainable textiles: the role of bamboo and a comparison of bamboo textile properties (part II). J. Text. Appar. Technol. Manag. 6 (3), 1 23. Wang, G., Yu, Y., Shi, S.Q., Wang, J.W., Cao, S.P., Cheng, H.T., 2011. Microtension test method for measuring tensile properties of individual cellulosic fibres. Wood Fibre Sci. 43 (3), 251 256. Wu, J., Zhong, T., Zhang, W., Shi, J., Fei, B., Chen, H., 2021. Comparison of colors, microstructure, chemical composition and thermal properties of bamboo fibres and parenchyma cells with heat treatment. J. Wood Sci. 67, 56. Xian, X.J., Xian, D.G., 1990. The relationship of microstructure and mechanical properties of bamboo. J. Bamboo Res. 9 (3), 10 23. Xu, Y., Lu, Z., Tang, R., 2007. Structure and thermal properties of bamboo viscose, tencel and conventional viscose fibre. J. Therm. Anal. Calorim. 89 (1), 197 201. Xu, W., Tang, R.C., 2006. Extracting natural bamboo fibres from crude bamboo fibres by caustic treatment. Biomass Chem. Eng. 40 (3), 1 5. Yang, H., Yan, R., Chen, H., Lee, D.H., Zheng, C., 2007. Characteristics of hemicellulose, cellulose and lignin pyrolysis. Fuel 86, 1781 1788. Yu, Y., Wang, H.K., Lu, F., 2014a. Bamboo fibres for composite applications: a mechanical and morphological investigation. J. Mater. Sci. 49, 2559 2566. Zakikhani, P., Zahari, R., Sultan, M.T.H., Majid, D.L., 2014. Extraction and preparation of bamboo fibre-reinforced composites. Mater. Des. 63, 820 828. Zhang, K., Wang, F., Liang, W., Wang, Z., Duan, Z., Yang, B., 2018. Thermal and mechanical properties of bamboo fibre reinforced epoxy composites. Polymers 10 (6), 608. Zhang, Y., Yu, Y., Lu, Y., Yu, W., Wang, S., 2021. Effects of heat treatment on surface physicochemical properties and sorption behavior of bamboo (Phyllostachys edulis). Constr. Build. Mater. 282, 122683.

CHAPTER FOUR

Characterisation of bamboo fibres

4.1 Introduction Bamboo fibres are promising alternatives to synthetic fibres because of their sustainability, low environmental footprint, and their specific properties that are desirable for a wide range of technical engineering applications. They are also an attractive alternative to reinforced polymers in the new era of green composite materials. Bamboo fibre can be divided into natural bamboo fibre, bamboo pulp fibre, and bamboo charcoal fibre. Natural bamboo fibre is a fibre directly extracted from bamboo using physical or microbial degumming (Chen et al., 2021). Bamboo raw fibres, bamboo pulp fibres and bamboo charcoal fibres made from bamboo are widely used in the textile industry. However, due to the low spinnability and poor fibre holding power of bamboo fibres themselves, there is a need to explore improved forms of bamboo fibres in order to develop bamboo spinning fibres with better performance in all aspects (Zeng, 2017). Bamboo fibre has a complex natural structure but offers excellent mechanical properties, which are utilised in the textile, papermaking, construction, and composites industry. The industrial implementation of fine grade natural bamboo fibres, including technical (100
200 μm) and elementary fibres (,30 μm) has been of increasing interest in recent times because these fibres offer a unique set of properties including high tensile strength, antibacterial activity, and UV absorption. The cross section of bamboo fibre presents a hollow structure offering excellent moisture absorption ability and air permeability. Being a natural lignocellulosic fibre obtained from bamboo culm, its chemical composition is similar to other bast fibres, hence, its structure and properties are often compared with other bast fibres such as flax and jute. However, bamboo fibre’s content of hemicelluloses and particularly lignin are greater than that of flax and a little less than that of jute fibre. Many structural parameters of bamboo fibres have been found to affect their mechanical properties, moisture Bamboo Fibres. DOI: https://doi.org/10.1016/B978-0-323-85782-6.00009-X

© 2023 Elsevier Ltd. All rights reserved.

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content, etc. For example, noncellulosic substances such as pectin and hemicelluloses show a significant effect on moisture absorption and density as well as fibre properties such as strength and flexibility. The remarkable performance of bamboo and its fibres can be explained from its microstructure and has attracted the attention of many researchers. Throughout evolution, bamboos have developed a structurally intelligent plant: the fibres are oriented along the bamboo’s culm, whereas in the nodes the fibres become entangled in a complicated manner to produce nodes with isotropic properties that provide additional reinforcement to the culm (Wang et al., 2015; Amada, 1997). A number of research studies have been reported on the analysis of the structure of bamboo culm, natural bamboo fibres, and bamboo viscose (pulp) fibres. In this chapter, details from studies on the chemical composition of bamboo fibres, microstructure, cross section/longitudinal sections using scanning electron microscope (SEM), crystal structure and crystallinity by X-ray diffraction, and functional group analysis by FTIR techniques have been presented.

4.2 The chemical composition of bamboo fibres Bamboo is a very sustainable source of cellulose fibres: its primary constituents are cellulose, hemicellulose, and lignin (approx. 90% of its composition). The minor constituents found are soluble polysaccharides, waxes, resins, tannins, proteins, and ashes. The macroscopic and microscopic appearance show bamboo to be a natural nanocomposite, possessing multinodes and functional gradient structures. The fibres are distributed densely in the outer surface region and sparsely in the inner surface region (Rao and Rao, 2005). It is designed to have uniform strength at all positions in both the radial direction on the transverse section and the lengthwise direction (Nogata and Takahashi, 1995). It was shown that the thick-walled bamboo fibres have a polylamellate structure with alternating broad and narrow lamellae. The narrow lamellae exhibits a higher concentration of lignin and xylan than the broad ones (Parameswaran and Liese, 1976). It possesses a high-volume fraction of cellulose fibres—approx. 48% by mass (Moradbak et al., 2015) compared to, for example, wood (39%
45%) by mass (Mohamed and Hassabo, 2015) and grass (33%
45%) by mass (Prasad et al., 2007). Bamboo monofilament consists of four layers where crystallised cellulose microfibrils are

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aligned longitudinally with reference to the axis of the fibre. These cellulose microfibrils are bonded together with lignin and hemicellulose (Fukushima et al., 2003). Lignin is a hydrophobic substance and is responsible for the formation of fibres in the form of matrix whilst cellulose microfibrils provide the reinforcement. It (a typical grass lignin) is a polymer of phenyl-propane units (p-hydroxyphenyl) (H), guaiacyl (G) and syringyl (S) in a molar ratio of 10:68:22 (Wahab et al., 2013; Liese and Tang, 2015). The overall structure has a hydrophilic surface with a hydrophobic lignin core (Jain et al., 1992). According to a report, bamboo fibre contains more than 70% cellulose in the bamboo species, Neosinocalamus affinis, largely found in China (Li et al., 2010). N. affinis, now known as Bambusa emeiensis ‘Chrysotrichus’ was used to provide chemical bamboo samples by a manufacturing company based in Shanghai and Sichuan, China. N. affinis has a sympodial and tufted rhizome system. It is cultivated at less than 1900 m in altitude, and is widespread in the southwest of China (Kanglin, 1998). Cellulose and hemicelluloses are carbohydrate polymer constituents of simple sugar monomers. Cellulose, like other plant cellulose, consists of linear chains of β-1
4linked glucose anhydride units. In addition, bamboo consists of xylan (4-Oacetyl-4-O-methyl-D-glucuronoxylan, a relatively short polymer with a degree of polymerisation of 200) (Liese, 1987; Liese and Tang, 2015). It has been reported that, the growth condition, age, and the part of the culm affects the chemical composition of fibres. The proportion of lignin and carbohydrates varies as the culm tissue matures within a year when the soft and fragile sprout becomes hard and strong. But once the culm matures fully, the chemical composition tends to remain rather constant (Liese, 1987, 1992). The main chemical constituents of bamboo fibre are cellulose, hemicellulose, and lignin (Zhang et al., 2014; Chokshi et al., 2020).

4.3 Cellulose Cellulose mainly consists of three elements: carbon, hydrogen, and oxygen, and it is mainly responsible for the formation of the cell wall of the bamboo fibres (Takahashi and Matsunaga, 1991; Zhang et al., 2014). Like other plant cellulose, it consists of linear chains of β-1
4-linked glucose anhydride units. It remains in the form of microfibrils within the cell wall of the plant (Gardner and Blackwell, 1974). The extracted bamboo

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74

fibres show a cellulose content of approximately 74% (Wang et al., 2010), although it depends on the age of bamboo. Its presence affects properties such as tensile strength, elongation, etc. Interestingly, the cellulose content of the same bamboo material decreases with the increasing age of bamboo (Zhang et al., 2014).

4.4 Hemicellulose Hemicellulose is an amorphous substance which exists between the fibres that offers a low degree of polymerisation (Zhang et al., 2014). It is a complex polysaccharide with xylan as the main chain, and the branches mainly include 4-O-methyl-D-glucuronic acid, L-arabinose, and D-xylose (Xu, 2006). In a study, it was reported that the polysaccharide fraction of Phyllostachys makinoi extracted with 5% and 17.5% NaOH showed arabinoxylan as its main component and the ratio of xylose to arabinose was observed to be 17
18:1 (Fengel and Shao, 1984). Further it was observed that bamboo polysaccharide extracted by different methods with distilled water showed glucose to be its main component, whereas the content of xylose was higher after extraction with alkali (Sun et al., 2012).

4.5 Lignin Lignin is a kind of polymer with complex structures, mainly composed of guaiacyl, syringyl monomers, and p-hydroxyphenyl monomers (Xu, 2006). Ether and carbon
carbon single bonds connect the above structural units in lignin (Zhang et al., 2014). Its distribution in the secondary wall of bamboo fibre is not even. Generally, the concentration in the broad layer is lower, whereas its concentration is higher in the narrow layer (Xu, 2006). Its presence in the bamboo gives bamboo materials a certain degree of stability. Even the lignin content also varies with the age of the bamboo (Zhang et al., 2014). In addition to the above three main components, lignin often contains various sugars, fats, and protein substances and a small amount of ash elements which not only affect the properties of bamboo, but also the application of bamboo fibres in various

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fields (Zhang et al., 2014; Chokshi et al., 2020; Xu, 2006). It has been reported that bamboo fibres containing a large amount of lignin are rough, stiff, and do not meet the requirements of textile fibres, hence the removal of lignin becomes necessary to improve the properties of bamboo fibre. It may be noted that the single fibres that are not bound by pectin and lignin are short in length and have low spinnability (He et al., 2008).

4.6 Structure of the bamboo fibre at the macro- and microlevel The microstructure of bamboo fibres (Fig. 4.1) show oriented fibres along the culm of bamboo, whereas they are entangled in the nodes in a complicated way to produce nodes with isotropic properties that provide additional reinforcement to the culm (Amada, 1997; Shao et al., 2010). The microstructure of a single bamboo fibre, as shown in Fig. 4.2, is a multilayered wall structure that is in concentric circles. The layers consist of a thick cell wall, a small lumen, a few pits, and a small microfibril angle. The size of a single bamboo fibres is 10
30 μm in diameter and 1
4 mm in length (Wang et al., 2011; Yu et al., 2014). The cells of bamboo are mainly composed of fibre cells, parenchyma cells, ducts, epidermal cells, sieve tubes, companion cells, and some other cells (Xu, 2006). The cell structure is shown in Fig. 4.3. It has also been reported that the inner wall is absent in bamboo fibre cells but the middle layer of the secondary wall has a multilayer structure (Osorio et al., 2011; Liese, 1998a,b), and different types of bamboo show different orientations of microfibrils between various layers of bamboo cell walls (Zhang et al., 2014; Xu, 2006; Osorio et al., 2011; Liese, 1998a,b).

Figure 4.1 Microstructure of bamboo (moso) fibre.

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Figure 4.2 Typical emission scanning electron microscope (ESEM) images of a longitudinal section of a single fibre.

Figure 4.3 The model of polylamellae structure: the wide layer (L1
L4), the narrow layer (N1
N4), the primary wall (P), and the external sheet of the secondary wall (O) (Osorio et al., 2011; Liese, 1998a,b).

Bamboo has more than 10 cellular layers in its cell structure, with each dissimilar microfibril orientation with thick layers and thin layers in alternate arrangements on the cell wall of bamboo fibres. The direction of microfibres in the narrow layer is a near-horizontal spiral arrangement, whilst the direction of microfibres in the wide layer is a near-axial spiral arrangement. Bamboo exhibits anisotropic behaviour due to the different fibre orientations of the narrow layer and the wide layer. The different distribution of vascular bundles leads to the different longitudinal permeability of bamboo fibres, which in turn affects the penetration of chemical reagents and has a certain impact on the composition analysis and production of bamboo fibres.

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The main structural component of the bamboo culm is the elementary fibres and they exhibit a hexagonal or pentagonal shape. The small hole in the centre of each elementary fibre is called the lumen (Fig. 4.4F). The bamboo fibres are a bundle of elementary fibres that are cemented together by middle lamellae. The fibres are aligned and have the shape of tube-like cells with thickened cell walls composed generally of four different layers surrounding a central lumen. Generally, each layer consists of semicrystalline cellulose microfibrils embedded in a hemicellulose/lignin matrix at a defined angle (Mohanty et al., 2005). The layers are divided into two groups, namely the primary and secondary wall. While the primary wall, being the outermost layer, represents about 8% of the total thickness, the secondary wall is the thickest layer consisting of 80% of the total thickness and is responsible for most of the mechanical properties. The microfibrils are spirally wound around the lumen in this region. The bamboo

Figure 4.4 (A) Distribution of vascular bundles in the bamboo wall (G. angustifolia). Morphology of the vascular bundles of G. angustifolia. (B) Outer, (C) middle and (D) inner section of the bamboo wall. Vascular bundle parts: vessels 1, phloem 2, protoxylem 3, fibre bundles 4, and parenchyma tissue 5. (E) Bamboo fibre bundle; the bean-shaped bundle breaks up into a few technical fibres upon extraction. (F) Elementary bamboo fibres.

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elementary fibre walls exhibit a unique structure referred to as a polylamellate structure (Liese, 1998a,b). This complex structure is composed of several thick and thin layers of lignin reinforced with cellulose microfibrils of different orientations (Parameswaran and Liese, 1976; Murphy and Alvin, 1992). The cellulose microfibrils are oriented inside the thick wall layers at a small angle to the fibre axis, whereas the thin ones show mostly a more transverse orientation to the fibre axis. Different studies have reported different results for the number of lamellae due to the position of the fibre bundles, the relative location of the fibres within the bundles, and the state of maturity of the fibres. High tensile strength of the fibres and the culm has been attributed to these alternating lamellae (Gritsch, 2004). At the macrolevel, bamboo has a structure of a hollow section and a thin wall with a certain tapering shape (Liu et al., 2012) and the bamboo culm can be observed as a typical UD fibre-reinforced composite with the fibres as the reinforcing phase and the supporting tissue (parenchyma) as the matrix material. The rule of mixtures with a simple model has been used to describe aligned continuous fibre composites, to characterise the bamboo structure (Shao et al., 2010). Bamboo consists of unidirectional fibres that are reinforced by parenchymatous ground tissue that functions as a matrix. The nonuniform distribution of vascular tissue along the radius direction indicates the feature of functionally graded materials for bamboo. At the meso-level, in the cross section of the bamboo culm wall, the fibre bundles that form a protecting sheath around the vascular bundles are distributed densely in the outer region of the wall and sparsely in the inner region, and are more concentrated in the upper part of the culm compared with the base (Osorio et al., 2011; Liese, 1998a,b); this has also a positive influence on the mechanical properties of the culm.

4.7 Morphology of the elementary bamboo fibres The morphology of the elementary fibre wall as well as the development of the polylamellar structure has been reported. The multilayered structure does not show a defined pattern or a relation with the thickness of the cell wall (Murphy and Alvin, 1992; Gritsch and Murphy, 2005). In addition, the number of layers varies between individual fibres. The polylamellation is observed to be influenced by the position in the fibre bundle and a majority of the fibres do not possess any layering of their walls. Each

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elementary bamboo fibre wall possesses a unique multilayer configuration called the polylamellate structure which contributes to the strength and modulus of the bamboo culm. The fibre lumen fraction (ratio of the lumen area to the fibre cross section) is on average 4% and was calculated for both elementary fibres present in the periphery (outer layer) and in the inner part (inner layer) of the fibre bundle. The number of layers is bigger in fibres adjacent to either vascular elements or at the periphery of the fibre bundles (Liese, 1998a,b; Gritsch, 2004; Gritsch and Murphy, 2005; Lybeer et al., 2006). It has been found that the multilayered structure of fibre cell walls is formed mainly during the first year of growth and there is no significant overall increase in wall thickness of fibre and parenchyma cells of bamboo culms older than 1 year (Gritsch, 2004; Lybeer et al., 2006). Characterisation of the fibre bundle is not only important in taxonomic research, but also in the fibre processing, since the shape and size of the fibre bundle have a strong influence on the difficulty of extraction and the dimensions and quality of the extracted technical fibres (Fig. 4.4E). The elementary fibres represent the main structural component of the bamboo culm and they exhibit a hexagonal or pentagonal shape; the small hole in the centre of each elementary fibre is called the lumen (Fig. 4.4F). These fibres are observed to be long, tapered at both ends, and sometimes forked. The peripheral layer of the culm wall show shorter and smaller fibres. There exists a strong correlation between the fibre length, fibre diameter, cell wall thickness (number of layers), and internode diameter, but not with the lumen diameter and internode length. The elementary fibre diameter has been found to vary between 11 and 19 mm, the lumen diameter between 2 and 4 mm, and the cell wall thickness between 4 and 6 mm (Liese, 1998a,b). It is observed that the length-to-diameter ratio plays an important role in processing and mechanical properties in the short fibre-reinforced composites and pulping industry (Liese and Grosser, 1972; Trujillo et al., 2014).

4.8 Studies on characterisation of structure of bamboo fibres A number of studies on the characterisation of natural bamboo fibres and bamboo viscose fibres using SEM, WAXD, and FTIR have been reported. Lifang et al. (2011) characterised the natural bamboo fibres for textile applications. The fibres were treated with NaoH alkali at different

80

Bamboo Fibres

concentrations to study the changes in longitudinal section and cross section, chemical composition, linear density, and tenacity of fibres. The longitudinal and cross-sectional views of bamboo fibres observed by SEM are presented in Figs 4.5 and 4.6. A large quantity of gum was observed in the raw fibres without any alkali treatment (Fig. 4.5A). But after the alkali treatment, the fibres show clear fibrils and become clear. The longitudinal views show that the fibrils are straight with striations on the surface (Fig. 4.5D). The natural bamboo fibres exhibit an irregular hollow polygonal cross section (Fig. 4.6A
D). The number of elementary fibres reduces after the intensity of the treatment making the fibres finer. The inner structure shows loose fibres after treatment with additive agents. Clear cracks were observed in the cross section of the fibres, indicating that the fibres could be easily separated into small bundles. The cross section and longitudinal sections of bamboo viscose fibres have been reported (Xu et al., 2007). The bamboo viscose fibre shows an irregular cross section (Fig. 4.7). The cross section and longitudinal

Figure 4.5 Longitudinal views of natural bamboo fibres treated with alkali: (A) untreated; (B) 20 g/L NaOH; (C) 20 g/L NaOH, 3 g/L Na5P3O10, 5 g/L Na2SO3, and 3 g/L penetrating agent, and (D) optimal parameters (Lifang et al., 2011).

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Figure 4.6 Cross section of natural bamboo fibres treated with alkali: (A) untreated; (B) 20 g/L NaOH; (C) 20 g/L NaOH, 3 g/L Na5P3O10, 5 g/L Na2SO3, and 3 g/L penetrating agent; and (D) optimal parameters (Lifang et al., 2011).

Figure 4.7 (A) Cross section and (B) longitudinal views of bamboo viscose fibres. Modified from Xu, Y., Lu, Z., Tang, R., 2007. Structure and thermal properties of bamboo viscose, tencel and conventional viscose fibre. J. Therm. Anal. Calorim., 89 (1): 197
201.

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Bamboo Fibres

morphology are fairly similar to these of regular viscose rayon fibre. Some striated cracks distributed over the length of bamboo viscose fibres and many voids in their cross section were observed. These structural observations suggest that bamboo fibres exhibit good water retaining capacity (Erdumulu and Ozipek, 2008; Hardin et al., 2009). The differences in surface morphology among various bamboo fibres were studied using SEM analysis by Waite (2010). Standard test procedures for live specimens were used to observe the differences in surface morphology among various bamboo fibres. The four varieties of bamboo fibres showed many similarities and differences in their SEM images. While the longitudinal surface of chemical bamboo fibre displayed a tubular and ribbed (celery-like) image, the cross sections of both species showed voids (Fig. 4.8). The thick pulp shows a rough and very porous surface as expected, because it is closest to the actual bamboo plant among all of the fibre types (Fig. 4.9). Interestingly, the mechanical bamboo fibre shows a

Figure 4.8 SEM images of chemical bamboo fibres of (A) Phyllostachys edulis longitudinal view and (B) cross section; and (C) Bambusa emeiensis longitudinal view and (D) cross section. Adapted from Waite, M., 2010. Sustainable textiles: the role of bamboo and a comparison of bamboo textile properties (part II). J. Text. Appar. Technol. Manag., 6 (3): 1
23.

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Figure 4.9 SEM images of Bambusa emeiensis chemical bamboo fibre (thick pulp): (A) longitudinal view and (B) cross section. Adapted from Waite, M., 2010. Sustainable textiles: the role of bamboo and a comparison of bamboo textile properties (part II). J. Text. Appar. Technol. Manag., 6 (3): 1
23.

Figure 4.10 SEM images of Phyllostachys edulis mechanical bamboo fibres: (A) longitudinal view and (B) cross section. Adapted from Waite, M., 2010. Sustainable textiles: the role of bamboo and a comparison of bamboo textile properties (part II). J. Text. Appar. Technol. Manag., 6 (3): 1
23.

tubular longitudinal section with nodes and a cross section with some voids though much fewer than the chemical bamboo fibres (Fig. 4.10). The surface morphology of bamboo fibres using SEM has been reported (Chandrasekhara, 2019). The SEM Tescan Vega 3LMU with a voltage setting of 5 kV and a specimen to detector distance ranging between 8 and 12 mm was used to investigate the longitudinal view of bamboo fibres. Before observation the samples were coated with gold for 5 minutes by ion sputtering. The longitudinal section of bamboo fibres for different magnification, viz, 3 200, 3 500, 3 1000, and 3 5000 are presented in Fig. 4.11. From the SEM images it can be observed that the

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84

X200

X1000

X500

X5000

Figure 4.11 Longitudinal view of bamboo fibres.

(A) Bamboo

(B) Jute

(C) Flax

Figure 4.12 Cross sections of bamboo, jute and flax fibres. (A) Bamboo; (B) jute; (C) flax.

(A) Bamboo fibre bundle

(B) Bamboo single fibre

(C) Flax

Figure 4.13 Longitudinal view of bamboo, jute and flax fibres. (A) Bamboo fibre bundle; (B) bamboo single fibre; (C) flax.

longitudinal section of bamboo fibre is similar to the conventional viscose fibre. The bamboo fibre bundles were gummed by 15
20 single fibres. There were no nodes in the longitudinal surface of the bamboo fibre. The surface of the fibre becomes rough and consists of many microgaps which make the fibre more hygroscopic. The surface morphology of various bast fibres such as bamboo, jute, and flax fibres has been reported by Yueping et al. (2010). The crosssectional and longitudinal views of bamboo, jute, and flax fibres are presented in Figs 4.12A
C and 4.13A
C respectively.

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From the SEM image shown in Fig. 4.12A, it is evident that the single bamboo fibre shows a round cross section with a small round lumen. Most of the bamboo fibres show multilamellate cell walls with various layers. However, the jute fibre has a large, round lumen or thinner wall. Therefore, the bamboo fibre is quite different from jute and ramie fibres (Fig. 4.12B,C) in the cross section. Although the shape of a bamboo single fibre is similar to that of flax, the width and length of a bamboo single fibre (6
12 μm, 2
3 mm, respectively) is far smaller than that of flax (12
20 μm, 17
20 mm, respectively). As a result, a single bamboo fibre can be identified according to the characteristics of cross section and size. The longitudinal views of the bamboo fibres are shown in Fig. 4.13. Normally the bamboo fibres exist in the form of bundles of 10
20 single fibres cemented with gum. After bleaching they are separated into single fibres. It may be observed that a node is absent in the longitudinal surface of the bamboo fibre (Fig. 4.13B), which is different from ramie and flax fibres (Fig. 4.13C). In addition, the bamboo single fibre shows a rough surface, with tree-bark stripes. A small, thin lumen is also present in the longitudinal direction.

4.9 X-ray diffraction studies The crystalline structure and crystallinity of various bamboo fibres have been reported by many researchers. Yueping et al. (2010) have reported the crystallinity and crystal size of N. affinis bamboo fibre using WAXD technique. The crystallinity and crystal size were determined by wide angle X-ray diffraction (XRD; 2θ 5 4
40 degrees), using a D/ max-B X-ray diffractometer made by Japan Rigaku Electronic Machine Company. Fibres were ground into powders as measuring samples. The scanning velocity was 5 degrees/min, the voltage was 40 kV, and the electric current was 50 mA. The rotational target was a Cu target, which produced X-rays with a wavelength of 1.5418 Å. The crystallite dimensions were calculated from the half-peak width of diffraction peak (002) according to the Scherrer equation. The X-ray diffraction patterns for different bast fibres are presented in Fig. 4.14. From the peaks it may be observed that, the bamboo fibres shows the same XRD as jute. Two diffraction peaks were shown at the

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86

Figure 4.14 XRD patterns of bast fibres.

angles of 15
16 and 22 degrees for the bamboo fibre and jute fibre, and the peak width at an angle of 15
16 degrees was widened in half of the peak. This is quite different from that of viscose, and not quite the same as that of the cotton, but quite similar to that of wood (Jian, 2003).

4.10 Degree of crystallinity Cellulosic fibres from various plants differ considerably in their degree of crystallinity, as evidenced by a large number of investigative methods. The degree of crystallinity values are shown in Table 4.1. It may be observed that the degree of crystallinity of the bamboo fibres and jute fibres are lower than those of flax and cotton. The ramie fibre has the highest degree of crystallinity among the six fibres. The low degree of crystallinity for the bamboo fibre was attributed to the disturbance of the formation of the cellulose crystalline structure during the growth of bamboo by a lot of substances grown with cellulose concomitantly and the

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Table 4.1 Degree of crystallinity of bast fibres. Sl. no. Fibre type

Degree of crystallinity (%)

1 2 3 4

52.54 53.80 67.43 72.02

Bamboo Jute Flax Ramie

Source: Adapted from Yueping, W., Ge, W., Haitao, C., Genlin, T., Zheng, L., Feng, X. Q., et al., 2010. Structures of bamboo fibre for textiles. Text. Res. J., 80 (4): 334
343.

effect of about 20% of lignin and hemicellulose residuals in fibres on the testing results to some extent. It was opined that the degree of crystallinity for the bamboo fibre in the study was a relative value, because some noncellulose substances exist in the fibre. Because of its unique crystalline structure, bamboo fibres show differences in characteristics such as density, moisture regain, tenacity, dyeing, and thermal properties compared to ramie, flax, cotton, and viscose fibres. Studies on comparative investigations of bamboo viscose fibre, cotton, and polyester fibres were undertaken by Chandrasekhara (2019) to analyse the differences and similarities in their molecular structure and fine structures. WAXD analysis was carried out on these fibres. The results revealed that bamboo viscose fibres showed a lower degree of crystallinity compared to other fibres. The percentage crystallinity of bamboo fibre was determined using wide angle X-ray diffraction (XRD; 2θ 5 4 2 40degrees), using D/max B diffractometer spectroscopy D8advanced (Bruker, USA). The bamboo fibre powdered sample was scanned with a scanning velocity of 5 degrees/min, with voltage 40 kV, and current of 50 mA. The rotational target was a Cu target which produced X-rays with a wavelength of 1.5418 Å. The observed equatorial X-ray scattering date in the 2θ 5 10
35 degrees range was corrected and resolved using a well-established curve fitting procedure. The peak widths at half-height were been corrected using the Stoke’s deconvolution procedure. The apparent crystallite size of a given reflection was evaluated using the Scherrer equation: LðhklÞ 5

k λ:cosðθÞ β

where θ 5 Braggs angle λ 5 wave length, β 5 integral breadth, k 5 Scherrer parameter, and L(hkl) 5 mean length of the crystallite perpendicular to the planes.

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88

The crystallinity of the fibre was calculated by finding the total area of I v/s 2θ curve and the area under the crystalline region of the I v/s 2θ curve. Crystallinity (X%) was found using the following equation. X% 5

Ac 3 100 Ac 1 Aa

Intensity in arbitrary units

Ac 5 area under crystallinity region Aa 5 area under amorphous region The X-ray diffraction pattern of the bamboo fibres is shown in Fig. 4.15. It is known that regenerated cellulosic fibres with a cellulose II structure have peaks at 2θ 5 15
16 and 21.8 degrees assigned to (101) and (102) reflection, respectively. From the figures it may be observed that bamboo and cotton fibres have a cellulose II structure. The intensity of peak at 2θ 5 21.8 degrees is much higher than that of 2θ 5 15
16. The X-ray crystallinity of bamboo was found to be 35.48% which was less compared to cotton and polyester fibres. The crystallinity index (CI), crystallinity %, and crystallite size of the raw bamboo and the enzyme-treated bamboo fibres have been reported by Noor (2020). The powdered fibres were examined between angles (2θ) 5 and 70 degrees to obtain the equatorial reflections using X-ray diffractometer (XRD) (Bruker AXS D8) with CuKα radiation (λ
1.5418 Å). The generator was utilised at 40 kV, 30 mA at

20

30

40 50 60 Diffractometer angle 2θ degrees

Figure 4.15 XRD graph of bamboo fibre.

70

80

Characterisation of bamboo fibres

89

a scanning level of 1.2 degrees/1 min. The CI was determined by using the following equation: CI% 5

I2002Iam 3 100 I200

where I200 is the intensity of the peak from 200 lattice plane (2θ 5 22.4 degrees) representing the crystalline material, while Iam is the diffracted intensity peak at 2θ 5 18 degrees indicating the amorphous material of bamboo fibres. The per cent crystallinity of the raw and treated bamboo fibres of each 30 C, 40 C, and 50 C was evaluated using the equation below: Crystalline% 5

I22 3 100 I22 1 I18

where I22 and I18 are the 2θ scale of 22 and 18 degrees representing the crystalline and amorphous intensities, respectively. The crystallite size of the fibres samples was evaluated using the Scherrer formula: L 5 Kλ=βcosθ where L is the crystallite size; K is the shape factor (0.94); λ is the X-ray wavelength used; β is the half-width maximum of the equatorial reflections; and θ is the Bragg angle related to the 200 plane. The CI (%), crystallinity (%), and crystallite size values are presented in Table 4.2. The authors revealed that the temperature and concentration of the enzyme 100% had a significant effect on the CI of bamboo fibres. At 30 C treatment temperature, the CI, crystallinity, and crystallite size parameters showed a marginal improvement after enzyme treatment, whereas at higher temperatures, there was a significant increase in these parameters. XRD of bamboo shell fibres has been reported by Haiyan et al. (2017). The degree of crystallinity of the fibres was measured by XRD7000 X-ray diffractometer using parameters such as Cu target Ka radiation Table 4.2 CI (%), crystallinity (%), and crystallite size of bamboo fibres. Bamboo Temperature CI Crystallinity fibre ( C) (%) (%)

Crystallite size (nm)

Control Treated Control Treated Control Treated

2.31 2.97 2.82 3.91 2.62 3.11

30 40 50

48 49 41 57 51 55

65 66 63 72 67 69

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90

Diffraction Intensity

(X-ray wavelength 0.154 nm), and the diffraction direction θ
2θ linkage scan mode. The tube voltage, tube current, scanning angle, and scanning speed were set at 40 kV, 30 mA, 5
50 degrees, and 5 degrees/min, respectively. The XRD pattern of bamboo shell fibre is shown in Fig. 4.16. It may be observed that the bamboo shell fibre shows three strong diffraction

2θ

Intensity

Figure 4.16 XRD pattern of bamboo shell fibre.

2θ

Figure 4.17 X-ray diffractograms of natural bamboo fibres (A) without treatment and (B) after optimum treatment.

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91

peaks at about 2θ 5 15.1, 22.6, and 34.7 degrees corresponding to the 101, 002, and 040 surfaces, respectively. They are also similar to those of cotton demonstrating typical cellulose I structure. The calculated degree of crystallinity was about 68.2% higher than that of cotton. In another study, XRD patterns of modified bamboo fibres have been reported (Liu et al., 2011). The X-ray diffraction pattern for bamboo strips and optimally treated bamboo fibres has been presented in Fig. 4.17. Both the fibres show similar diffraction peaks, but with different intensity. The degree of crystallinity calculated were 67.5% and 70.3% for bamboo strip and optimally treated bamboo fibres, respectively. Swelling in NaOH introduced considerable changes in the crystallinity of natural bamboo fibres, which was mainly due to the removal of the noncellulosic material that led to a better packing of cellulose chains.

4.11 FTIR studies The infrared spectroscopy provides the complete information about fibre structure considering the characteristic vibrational energy of the different chemical groups present in the fibre molecule. A number of studies have been reported on the characterisation of bamboo fibres using IR spectroscopy. Chandrasekhara (2019) conducted a comparative study on the chemical composition of regenerated bamboo, cotton, and polyester fibres. A Bruker Alpha FT-IR which works on attenuated total reflectance (ATR-A537) was used for the study. The frequency range used was 4000
600 cm
1. FTIR spectra of regenerated bamboo fibres are presented in Fig. 4.18. From the FT-IR traces, it may be observed that different absorption bands in the spectra can be assigned from 4000 to 650 cm
1. The absorption bands around 3500
3200 cm
1 are due to hydroxyl O
H stretching vibration (Sowmya et al., 2017; Saville, 1999). From the observation, the O
H stretching are associated with absorbed alcohols found in cellulose, hemicelluloses, lignin, extractives, and carboxylic acids. The absorption band around 3100
2850 cm
1 is due to C
H stretching (Table 4.3), which is characteristic of any natural fibre. The presence of a band at about 2150 cm
1 could not be identified with any molecular origin. The bands at 1740 cm
1 and around 1670 cm
1 were related to C 5 O stretching observed in bamboo fibres. The characteristic wavelengths around 1374 cm
1 shared by hemicelluloses,

Bamboo Fibres

04 02

3500

3000

2500

2000

1500

662.89

893.56

1322.35 1251.49 1154.23 992.54

1438.81 1374.41

1597.23

1724.28

1816.34

2380.71

2887.39

2977.96

3301.38

00

Transmittance (%)

06

08

92

1000

Wavenumber (cm-1)

Figure 4.18 FTIR spectra of bamboo fibres.

Table 4.3 Assignment of FTIR bands of bamboo fibre. Band position Assignment (cm
1)

3500
3200 3100
2850 1760
1754 1650
1640 1597
1585 1420
1410 1374
1365 1261
1255 1154
1145 1110
1100 ,1055

O
H stretch vibration (bonded) C
H stretch vibration C 5 O stretch vibration (unconjugated) H
O
H deformation vibration of adsorbed water and conjugated C 5 O stretch vibration Aromatic skeletal and C 5 O stretch vibration C
H deformation (asymmetric) C
H deformation (symmetric) C
O stretch vibration in lignin, acetyl and carboxylic vibration in xylan C
O
C asymmetric stretch vibration in cellulose and hemicelluloses O
H association band in cellulose and hemicelluloses C
O stretch vibration in cellulose and hemicelluloses

cellulose, and lignin, correspond to C
H stretching and deformation of
CH3. The band at 1261
1255 cm
1 is due to possible C
O stretch vibration in lignin, acetyl and carboxylic vibration in xylan. On the other hand, 1154
1145 cm
1 C
O
C is due to asymmetric stretch vibration in cellulose

Characterisation of bamboo fibres

93

and hemicelluloses. The absorption band at ,1080 cm
1 is due to C
O deformation band in bamboo fibre (Sekerden, 2011). FTIR studies on bamboo shell fibres have been reported (Haiyan et al., 2017). The bamboo shell fibres were ground into powder, and then mixed with KBr powder to prepare the samples for the FTIR (Nexus670) investigation with the wavenumber ranging from 400 to 4000 cm21. The FT-IR spectrum of the bamboo shell fibre is shown in Fig. 4.19. It may be observed from the spectrum that the bamboo shell fibre is characterised by two characteristic absorption peaks at the wave numbers of 3410.42 and 2905.01 cm21 resulting from the stretching vibration of
OH and
CH groups. The absorption band at 1715.38 cm21 was associated with the stretching vibration of a seminonconjugated cellulose ester group. The absorption peak at 1647.35 cm21 belongs to the adsorbed water of samples. Moreover, the absorption peaks at 1432.56, 1376.87, and 1063.75 cm21 were assigned to the lignin aromatic ring bending vibration of C 5 C, the bending deformation of
CH and a cyclic C
O
C stretching vibration of C
O, respectively. The two absorption peaks at 993.87 and 891.72 cm21 correspond to the characteristic peaks of fibre ether linkages, annular inner surface C
O
C asymmetric stretching vibration, and CH2 (CH2OH) nonplanar rocking. The absorption peak at 583.45 cm21 was regarded as the outer
OH plane deformation vibration. The authors concluded that the absorption peaks of the as-prepared bamboo shell fibres are almost similar to

100 90

10 4000

3500

891.72 1095.23 1063.75

20

3410.42

30

3000

2500 2000 1500 Wave number (cm-1)

Figure 4.19 FTIR spectra of bamboo shell fibres.

993.87

1376.87

40

1152.17

1432.56

50

583.45

1715.38

60

1647.35

70

2905.01

Transmittance (%)

80

1000

500

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those of the cotton, which indicates that both the bamboo shell fibre and cotton belong to the same typical cellulose I. In another study, the microstructure of N. affinis bamboo fibres was determined by FT-IR spectroscopy (Yueping et al., 2010). Thermo Nicolet Nexus 670 micro-FTIR spectrometer was used for the experiment with a resolution of 8000 cm
1, the number of samples scanned was 64 min
1, and the wave number used was from 675 to 4000 cm
1 using a KBr beam splitter, placing the sample in the OMNI-Sampler ATR Smart Accessory. They also compared the IR spectra of bamboo, jute, and flax fibres (Fig. 4.20). The wave numbers of the main characteristic peaks along with their corresponding chemical bonds and moving modes are presented in Table 4.4. From Fig. 4.20, it is very clear that the peak of expanding and contracting vibration of O
H corresponding to wave number of about 3340 cm
1 that is clearly shown for the fibres is a functional group region. However, the bamboo and jute fibres demonstrate incomplete characteristic absorbency peaks of cellulose corresponding to wavenumber of about 1050 cm
1, which is a fingerprint region, compared with those of flax and ramie. The characteristic peaks of lignin appear in the 1500
1750 cm
1 wavenumber range, except for the absorbency peaks of water in the wavenumber at 1640 cm
1 (Jingbo et al., 2005). Characteristic absorbency peaks of lignin in the

Figure 4.20 IR spectra of bamboo, jute and flax fibres.

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Table 4.4 Chemical bonds and their behaviours of bamboo, jute, and flax fibres. Wave numbers (cm21) Chemical bonds and their behaviour Bamboo

Jute

Flax

3351.24 2918.42 1639.22

3368.90 2921.21 1640.05

3342.79 2902.66 1640.78

1427.09 1322.72 1160.28

1038.98 1600.25


1424.11 1322.95 1158.23

1037.32 1596.80 1736.30

1426.89 1316.56 1158.52 1106.16 1955.37 1032.61



O
H, expanding and contracting vibration C
H, expanding and contracting vibration H
O
H, expanding and contracting vibration (absorbing water) C
H, bending vibration in plane O
H, bending vibration in plane Circular C
O
C stretching and contracting asymmetric motion Circular C
O
C stretching and contracting asymmetric motion Skeletal vibration of aromatic ring from lignin Nonconjugated carbonyl vibration from lignin

Source: Adapted from Yueping, W., Ge, W., Haitao, C., Genlin, T., Zheng, L., Feng, X. Q., et al., 2010. Structures of bamboo fibre for textiles. Text. Res. J., 80 (4): 334
343.

wavenumber range 1500
750 cm
1 can also be observed for both bamboo and jute fibres. The corresponding chemical bonds and their behaviours of absorbency peaks from the infrared spectrum of the bamboo fibres appear almost the same as that of jute (Table 4.4). However, bamboo fibre shows two differences in the characteristic absorption band, compared with other typical cellulosic fibres; the first being the peak of skeletal vibration of an aromatic ring at about 1600 cm
1 indicating the existence of lignin in the bamboo fibre, and the other is a series of characteristic peaks in the wave numbers from 1032 to 1158 cm
1. The bamboo and jute fibres show weak absorption in the wave numbers between 1106 and 1055 cm
1. This was related to lower DP of the fibres. It was opined by the authors that the fibres had defects in the C
O
C chain, and in addition the peak of nonconjugated carbonyl vibration from lignin at 1736 cm
1 indicated more lignin content in jute fibre (Yueping et al., 2010).

4.12 Summary This chapter presented the various studies related to the physical and chemical composition and characterisation of bamboo fibres. The surface

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morphology of fibres characterised using SEM has also been presented. Various studies related to the analysis of longitudinal and cross-sectional views of different types of bamboo fibres are discussed in detail. Further, discussion on various studies on microstructure and macrostructure of bamboo fibres using WAXD and FTIR studies have been presented. Bamboo is a very sustainable source of cellulose fibres: its primary constituents are cellulose, hemicellulose, and lignin (approx. 90% of its composition). The minor constituents found are soluble polysaccharides, waxes, resins, tannins, proteins, and ashes. As per SEM studies, the natural bamboo fibres and the bamboo viscose fibres exhibit an irregular hollow polygonal cross section. The cross section and longitudinal morphology are fairly similar to those of regular viscose rayon fibre. These structural observations suggest that bamboo fibres exhibit good water retaining capacity. The longitudinal views show that normally the bamboo fibres exist in the form of bundles of 10
20 single fibres cemented with gum. After bleaching they are separated into single fibres. The node is absent in the longitudinal surface of the bamboo fibre, which is different from ramie and flax fibres. In addition, the bamboo single fibre shows a rough surface, with tree-bark stripes. A small, thin lumen is also present in the longitudinal direction. The X-ray diffraction peak patterns of bamboo fibres are similar to jute fibres. The degree of crystallinity varies from 50%
60% but is lower than other bast fibres such as jute and flax. Because of its unique crystalline structure, bamboo fibres show a difference in characteristics such as density, moisture regain, tenacity, dyeing, and thermal properties compared to ramie, flax, cotton, and viscose fibres. The infrared spectrum of the bamboo fibres appears to be almost the same as that of jute fibres.

References Amada, S., 1997. Fibre texture and mechanical graded structure of bamboo. Comp. Part. B Eng. 28, 13. Chandrasekhara, S.M., 2019. Studies on production, properties and techno-economics of 100% pure bamboo and bamboo/cotton blended fabrics, Ph.D. Thesis, Visvesvaraya Technological University, Belgaum, Karnataka, India. Chen, C., Haitao, L., Assima, D., Feng, S., David, H., Milan, G., et al., 2021. Properties and applications of bamboo fibre - a current-state-of-the art. J. Renew. Mater. 10 (3), 605
624. Chokshi, S., Parmar, V., Gohil, P., Chaudhary, V., 2020. Chemical composition and mechanical properties of natural fibres. J. Nat. Fibres 1
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Fengel, D., Shao, D., 1984. A chemical and ultrastructural study of the bamboo species Phyllostachys makinoi Hay. Wood Sci. Technol. 18 (2), 103
112. Fukushima, F., Funada, R., Sugiyama, J., Takebe, K., Umezawa, T., Yamamoto, H., 2003. Secondary Xylem Formation - Introduction to Biomass Science. Kaiseisha Press, p. 65. Gardner, K.H., Blackwell, J., 1974. The structure of native cellulose. Biopolymers 13 (10), 1975
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1540. Kanglin, W., 1998. Ecology and Habitats of Bamboos in Yunnan, China. Biodiversity International, Rome. Li, L.J., Wang, G., Cheng, H.T., Han, X.J., 2010. Evaluation of properties of natural bamboo fibre for application in summer textiles. J. Fibre Bioeng. Inform. 3 (2), 94
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14, 1985. In: Recent Research on Bamboo. Chinese Academy of Forestry, Beijing, and IDRC, Canada, 1987, 196
208. Liese, W., 1992. The structure of bamboo in relation to its properties and utilization. In: Bamboo and Its Use. Proceedings International Symposium on Industrial Use of Bamboo, Beijing, China, 7
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100. Liese, W., 1998a. The anatomy of bamboo culms. NBAR Technical Report No. 18. International Network for Bamboo and Rattan. Liese, W., 1998b. The anatomy of bamboo culms. Technical Report. International Network for Bamboo and Rattan. Liese, W., Tang, T.K.H., 2015. Properties of the bamboo culm. In: Liese, W., Kohl, M. (Eds.), Tropical Forestry, Bamboo: The Plant and Its Uses. Springer International Publishing, Switzerland, pp. 227
256. Lifang, L., Qianli, W., Longdi, C., Jingfang, Q., Jianyong, Y., 2011. Modification of natural bamboo fibres for textile applications. Fibres Polym. 12 (1), 95
103. Liu, D.G., Song, J.W., Anderson, D.P., Chang, P.R., Hua, Y., 2012. Bamboo fibre and its reinforced composites: structure and properties. Cellulose 19 (5), 1449
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103. Lybeer, B., Koch, G., Acker, J.V., Goetghebeur, P., 2006. Lignification and cell wall thickening in nodes of Phyllostachys viridiglaucescens and Phyllostachys nigra. Ann. Bot. 97 (4), 529
539. Lybeer, B., Acker, J.V., Goetghebeur, P., 2006. Variability in fibre and parenchyma cell walls of temperate and tropical bamboo culms of different ages. Wood Sci. Technol. 40 (6), 477
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Mohamed, A.L., Hassabo, A.G., 2015. Flame retardant of cellulosic materials and their composites. Flame Retardants. Springer International Publishing, pp. 247
314. Mohanty, A.K., Misra, M., Drzal, L.T., 2005. Natural Fibres, Biopolymers, and Biocomposites. CRC Press. Moradbak, A., Tahir, P., Mohamed, A., Halis, R., 2015. Alkaline sulfite anthraquinone and methanol pulping of bamboo (Gigantochloa scortechinii). BioResources 11 (1), 240. Murphy, R.J., Alvin, K.L., 1992. Variation in fibre wall structure in bamboo. IAWA J. 13 (4), 403
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751. Noor, T.H., 2020. “Investigation of crystallinity characterization of bamboo fibres using xylanase from Aspergillus nidulans. Syst. Rev. Pharm. 11 (7), 06
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408. Parameswaran, N., Liese, W., 1976. On the fine structure of bamboo fibres. Wood Sci. Technol. 10, 231
246. Prasad, S., Singh, A., Joshi, H.C., 2007. Ethanol as an alternative fuel from agricultural, industrial and urban residues. Resour. Conserv. Recycling 50 (1), 1
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295. Saville, B.P., 1999. Physical Testing of Textiles. Textile Institute, Wood Head Publishing Ltd., p. 85. Sekerden, F., 2011. Investigation on the unevenness, tenacity and elongation at break properties of bamboo/cotton blended yarns. Fibres Text. East. Europe 86 (3), 26
29. Shao, Z.-P., Fang, C.H., Huang, S.X., Tian, G.L., 2010. Tensile properties of Moso bamboo (Phyllostachys pubescens) and its components with respect to its fibre-reinforced composite structure. Wood Sci. Technol. 44, 655
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CHAPTER NINE

Applications and technoeconomics of bamboo fibres In the era of sustainability, the development and utilisation of natural fibres (Ramesh et al., 2017; Bousfield et al., 2018; Senthilkumar et al., 2018) has become a research interest. The usage of bamboo in china dates back to ancient times. In addition to making decorative items, musical articles, and construction purpose it also offered people abundant resource for their daily life use (Zhoe et al., 2008). All over the world the wide application of bamboo for various activates has been thought much by consumers. Bamboo fibres were used earlier in construction materials, composites and decorating items such as furniture for years together. The latest applications of bamboo fibres are in textile products such as yarns, fabrics and garments (Nazan and Bulent, 2015). In recent years, bamboo fibres have attracted great attention as the most abundant renewable biomass materials that can be used in textiles (Xu et al., 2006) and composite reinforcement (Das et al., 2006). Bamboo is a naturally grown renewable material that offers excellent environmental performance based on the Life Cycle Assessment and will decompose if discarded after end-of-life (Van der Lugt et al., 2006). Due to the abundant availability of bamboo fibres and its resources and owing to its renewable short natural growth cycle, bamboo fibre has attracted greater attention compared with other natural fibres. Bamboo fibre constitutes a kind of natural material that has a huge application possibilities in the textile field due to some of its unique properties (Liu and Hu, 2008). For example, it has a unique structure that makes it superior to other natural lignocellulosics (Ray et al., 2004). Bamboo fibre has a complex natural structure and possess excellent mechanical properties, which are utilised in the textile, papermaking, construction, and composites industry. The fibres possess many excellent properties when used as textile materials such as high tenacity, excellent thermal conductivity, resistance to bacteria, and high water and perspiration adsorption. Natural bamboo fibres

Bamboo Fibres. DOI: https://doi.org/10.1016/B978-0-323-85782-6.00001-5

© 2023 Elsevier Ltd. All rights reserved.

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have excellent properties, and therefore they have potential for use in textiles; however, they have not received the attention they deserve owing to their coarse and stiff quality. In addition, bamboo fibre has an unique cross section, presenting a hollow structure that exhibits excellent moisture absorption ability and air permeability. Further, the vascular bundles of bamboo fibres are distributed in the radial direction, which makes them conducive to the classification and utilisation of bamboo fibres (Xian and Xian, 1990; Grosser and Liese, 1971; Mwaikambo, 2006; Dunne et al., 2016; Lou et al., 2020). The 21st century is an era in which the protection of the environment is paramount and bamboo is one new form of ‘green’ environmentfriendly natural fibre that has recently entered the market. Bamboo regenerated cellulose fibre, known as bamboo viscose, has recently entered the market for apparel, home furnishing, sanitary pads, and medical applications such as masks, bandage cloth, surgical cloth, and gowns (Adine and Jani, 2010). In the year 2002, Hebai Jigao Chemical Fibre Company Limited, China introduced bamboo viscose products into the market. Regenerated bamboo fibre is 100% cellulose, biodegradable, and it is claimed to be ‘green’ and environmentally friendly (Erdumlu and Ozipek, 2008). Bamboo viscose products are used for a wide range of end-uses, such as towels, bathrobes, surgical cloths, bedding, food packaging, and hygiene products like sanitary pads, surgical masks, bandages, and mattresses. Bamboo viscose fabrics are known for their comfort, hand, and antimicrobial properties. Their unique properties, such as antibacterial activity, wearability, moisture absorption, ventilation, excellent comfort, quick drying, etc., have made bamboo fabrics more attractive and useful in many textile applications. Bamboo fibre is also considered a breathable fibre as it absorbs sweat quickly allowing it to evaporate and make the wearer feel more comfortable. Bamboo-based fabrics are antibacterial and very soft, with a low amount of pilling and creasing (Karahan et al., 2006). Fabrics made of bamboo fibre have very good physical properties. When compared with cotton fabrics, bamboo fabrics require a lower amount of dye for the same depth of shade. Moreover, the colourant is absorbed better and faster than in cotton fabrics and dyed bamboo fabric appears better than dyed cotton fabric (Wallace, 2005). The inherent characteristics of bamboo fabrics have made them suitable for healthcare, hygiene, and comfort in the medical application of textiles. The various products made from bamboo

Applications and technoeconomics of bamboo fibres

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viscose include disposable and nondisposable items such as surgical gowns, masks, diapers, gloves, napkins, and baby diapers used in hospitals. Bamboo fibre products are natural antibacterial, with good moisture vapour transmission and quick drying property. They are nonallergic to skin, smooth, soft, and are suitable for use in many textile applications. Bamboo clothing is a recent development and the clothes are labelled as biodegradable, green, soft, cool, breathable, and light (Das et al., 2008). Bamboo fabrics often claim that they possess antimicrobial properties (IFAR/INBAR, 1991) and UV protective capability and are used in apparels (undergarments, sports textiles, t-shirts, and socks), healthcare textiles such as hospital masks, surgical gowns, bandage cloths, sanitary napkins, absorbent pads, furnishing textiles, ultraviolet protective clothing, and food packaging bags (Hardin et al., 2009). These outstanding and unique properties of bamboo have been attracting many researchers, academia and industry people to develop new products for specialised applications. Bamboo fibres are currently used in the textile, papermaking, and construction industries in various formats. Recently, bamboo fibres have attracted the attention of composite material researchers and have been gradually making their way into the composite material industry.

9.1 Applications in the textile industry Bamboo fibres for clothes came about in the 20th century. There had been attempts over the years to generate fibre to be turned into apparel. The origins of bamboo fabric can be traced back to Asia. The credit for the first modern process of development of bamboo textile goes to Beijing University. They released the results of usable bamboo apparel in the early 2000s. Around this time, some other manufacturers and organisations were working to create bamboo apparel by using similar methods. Successful extraction and bleaching methods were developed to produce pure white fabrics. The process became commercially available and successful in the American market. Over the years, experts have developed methods of innovations in mixing and blending fabrics to generate the bamboo fabrics. Natural bamboo fibre that has been processed mechanically is environmentally friendly but not yet commercially viable or affordable. Moreover,

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Bamboo Fibres

most bamboo fibres and fabrics in the market are produced by a viscose process which uses chemical solvents that raise environmental concerns, besides being quite different from the original bamboo fibres (Nayak and Mishra, 2016). While bamboo rayon is a good choice relative to other manmade fibre options, a naturally processed bamboo fibre would be far superior and preferable. Bamboo rayon would have a smooth, silky hand like other rayon. On the contrary, natural bamboo fibre, being alike to bast fibre in chemical composition, would produce linen-like fabric, but it might not possess any antibacterial properties as is claimed by many. However, regarding moisture-transport performance properties researchers argue that bamboo fibre has a larger moisture regain capability than other natural fibres, such as cotton, because of its loose structure and existence of disordered noncellulose substances (Li et al., 2010).

9.1.1 Bamboo medical textiles and healthcare products Compared to other fibres, bamboo fibre has good hygroscopicity, can reflect light, and reduce the absorption of heat radiation, and can be used for clothing production (Hu et al., 2019; Li et al., 2010). At the same time, bamboo fibre has a strong antibacterial effect and can be used in the production of medical supplies, such as masks and medical gauze (Zhang et al., 2014). It was also found that the natural antibacterial function of bamboo fibres differs greatly from that of chemical antimicrobials in that bamboo does not cause skin allergies (Quitain et al., 2004; Bamboo-tshirt, 2009). It has been validated by the Japan Textile Inspection Association that even after being washed 50 times bamboo fibre fabrics still possess excellent antibacterial and bacteriostatic functions (Bambrotex, 2008). In the textile industry, bamboo fibre can be utilised on its own or in combination with other materials such as silk and cotton fibres. Bamboo fibres inhibit bacterial growth, absorb peculiar smells, and possess excellent hygroscopicity. Due to these characteristics, bamboo fibres are used as nonwoven medical and hygiene materials (Yi, 2004). Flavones, which can be extracted from bamboo fibres by the leaching method, are used in the preparation of many drugs (Gang et al., 2000). Being bacteriostatic and bacteriolytic (Zhong-Kai et al., 2005) in nature, the consumption of bamboo fibre reduces the rate of intestinal natural flora and pathogens, and, in addition, this property has been used to produce a bamboo drug for gastrointestinal infections (Anping et al., 2005). Bamboo fibre also has particular and natural functions of deodorisation. The deodorisation rate of

Applications and technoeconomics of bamboo fibres

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bamboo is 80% for the NH3 test (Ftcamerica, 2008). Under these circumstances, bamboo fibres have a promising place in sanitary towels, gauze mask, absorbent pads, food packing, surgical clothes, operating coat, and nurse dresses (Kim et al., 2005).

9.1.2 Textile clothing Bamboo fibres are used for the production of socks, underwear, t-shirts, bathing suits, bathing suit cover-ups, towels, sleep wear, face masks, sanitary napkins, bed sheets, pillows, baby diapers, bullet proof vests, table cloth, blinds, and mattresses. Despite the potential and widespread application of bamboo fibres in the textile industry, some of its shortcomings, such as the short length of single bamboo fibre and the easy water absorption of bamboo fibre fabrics, should be addressed through fundamental research. Bamboo fibres are gaining popularity as green fibres and they are found suitable in many applications. The inherent antifungal and antibacterial properties of bamboo fabrics make them suitable for making hygiene products, especially for medical applications such as bamboo intimate apparels (sweaters, bath suits, mats, blankets, towels, t-shirts, socks, etc.), bamboo nonwoven fabrics (sanitary napkins, masks, mattress, and food packaging bags) due to their antibacterial nature, medical applications (bandages, masks, surgical gowns, etc.), bamboo bathroom products, and home furnishing fabrics (cushion covers, table linen, bed linen, curtains, wall papers, etc.).

9.2 Bamboo fibres in fashion Bamboo has received enormous attention from designers around the world due to the growing environmental awareness among consumers. As an alternative to silk, designer Kate O’Connor has used bamboo fabrics as an eco-friendly replacement material. She opined that bamboo gives a similar drape to silk and is perfect for use in a summer collection. Other eco-fashion designers such as Linda Loudermilk, Katherine Hamnett, Miho Aoki, and Thuy Pham frequently incorporate bamboo into their eco-fashions due to its light, soft, and luxurious appeal. Designer Amanda Shi of Avita has some of the most exciting and originally beautiful eco-fashion in bamboo (Organic Clothing, 2008).

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Bamboo Fibres

Being more wrinkle-resistant than cotton, bamboo clothing can be machine washed in cold water with mild soap with a gentle wash treatment. It is recommended to avoid softeners or bleaches for bamboo clothing. Further, bamboo fabrics dries faster than most other fabrics and it is best if garments are hung to dry (Earth Easy, 2009). Bamboo socks, bed sheets, and jackets are very common items among the web-based retailers. Fashion retailers, Target and Sussan are already selling bamboo textile products in the Australian market. Bamboo clothing may create a new dimension in the fashion trend of sunny regions of the world like Australia for its multifunctionality. A famous Chinese quote, ‘Man can live without meat, but he will die without bamboo’ (Ding, 2008) reflects the significant potential of bamboo fibres. It is suggested that bamboo fibres have unique properties such as excellent appearance and feel, natural antibacterial, UV-shielding, and moisture-controlling characteristics. However, these unique properties may largely depend on the manufacturing processes and the policies of the manufacturing companies. In spite of the claims by various companies, the unique properties of bamboo such as ‘cool in summer’ or ‘warm in winter’ would need to be verified in well-controlled experimentation. There is a strong need for unbiased laboratory experiments being conducted in a rigorous manner to elucidate the origin of those unique properties of bamboo fibres and to develop the methods to effectively utilise the properties in the final products.

9.3 Bamboo fibres in paper production Since bamboo fibre has an antibacterial effect and its length is close to coniferous trees, it can be used in the papermaking industry (Zhang, 1984; Chen et al., 2019; Fasake and Dashora, 2018; Wang et al., 2021). China has a long history of using bamboo for papermaking. Bamboo was utilised in the papermaking industry as early as 1700 years ago and the use of bamboo for machine-made paper production in China began in the 1940s (Fasake and Dashora, 2018). In recent years, due to the shortage of wood fibre, bamboo fibre has become an indispensable raw material for papermaking. The shape, chemical composition, and structure of bamboo

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are very suitable for pulping. Pulping performance and pulp strength make bamboo fibres one of the most suitable materials for paper production. The paper production from bamboo results in certain advantages, such as reduction in pressure of wood demand, less pollution, and environmental protection (Kefu, 2002). Bamboo fibre pulp can be used in the manufacture of newsprint, bond paper, toilet tissue, cardboard, cement sacks, and coffee filters (Vena et al., 2010). It should be noted that although bamboo fibre is a good papermaking material, compared to wood, the cost of bamboo planting, storage, and transportation is higher, and the price of bamboo fibre is easily affected by the market (Chen et al., 2019).

9.4 Bamboo fibres in the construction industry Owing to its special properties, such as high specific strength, tensile strength, tensile modulus, hardness, light weight, and other mechanical properties, bamboo can be used for construction purposes (Youngsi, 2007). Not requiring processing or finishing, bamboo constructions exhibit strength and resistance, even to earthquakes (Jayanetti, 2000). Being a functionally gradient material, bamboo can be used for the formation of reinforced concrete composites, which find wide application in the construction of strong buildings (Ghavami, 2005; Aziz et al., 1981). Bamboo fibres are used in concrete reinforcement, bamboo fencing, and housing (Diver, 2001; Lima et al., 2008). They can be used as a reinforcement material as an alternative to steel in concrete. Studies have shown that in the production of some building materials, natural fibres can replace traditional steel (Ashraf et al., 2021) and synthetic fibres (Meng et al., 2020), and improve their mechanical properties (Silva et al., 2017; Wei and Meyer, 2017; Danso, 2017). Bamboo fibre is a natural fibre with excellent mechanical properties, and incorporating it into concrete leads to better physical and mechanical properties (Kumarasamy et al., 2020; Goh and Zulkornain, 2019; Terai and Minami, 2012). The effect of adding 0%, 1%, and 2% (by volume) bamboo fibre on the mechanical properties of concrete was studies and it was found that the flexural strength, tensile strength, and compressive strength of bamboo fibre-reinforced concrete increased with the increase in bamboo

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fibre content. Wahyuni et al. (2014) added 0.50% bamboo fibre based on the weight of cement and compared the splitting tensile strength of concrete at the age of 28 and 90 days; test results showed that the mechanical properties of the new type of concrete mix were comparable to those of ordinary concrete. Ramaswamy et al. (1983) studied the deformation properties of bamboo fibre concrete and reported that the addition of bamboo fibre could reduce the shrinkage deformation of coagulation. Chin et al. (2019) conducted experiments on bamboo fibre composite plate reinforced concrete beams, and the results showed that its structural bearing capacity increased by 10% 12% compared to unreinforced beams. Bamboo fibre can also be added to cement paste to develop bamboo fibre-reinforced cement (Tripura et al., 2020). Studies have shown that adding an appropriate amount of bamboo fibre can enhance the toughness of cement, but if the amount of bamboo fibre is excessive, it can cause fibre agglomeration and hence cannot enhance the maximum flexural strength and impact resistance of the composites (Xie et al., 2019). Akinyemi et al. (2020) studied the effects of different pretreatment methods on bamboo fibre cement composite materials and observed that microwave-assisted alkali treatment enhanced mechanical properties. Sanchez-E et al. (2021) compared the performance of bamboo fibre-reinforced cement made from treated and untreated bamboo fibres and reported that the applied alkali treatment produced enhanced flexural strength. They also observed that after alkali treatment, the impurities on the surface of the bamboo fibre were significantly reduced giving a cleaner surface (Sanchez-E et al., 2021). Huang et al. (2018) analysed the applicability of bamboo fibre and bamboo charcoal resources as building fillers in tropical and subtropical regions through the hygrothermal properties test as well as through simulation of the building component and the enclosed space.

9.5 Bamboo fibre in composites Natural plant-based fibres have an advantage over synthetic fibres because of their light weight and noninvasive, nontoxic, and biodegradable nature. Bamboo fibres have high strength, low cost, and narrow microbial angle and can be used effectively as reinforcement in polymer

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matrix composite, replacing synthetic fibres to some extent. Usage of bamboo fibre composite has increased in recent years even though it has the disadvantage of high moisture absorption and variation in fibre properties. Bamboo fibre is best suited for the reinforcement of rubber, plastic, and biopolymer matrices. Han et al. (2008) investigated the compounding characteristics, clay dispersion, high density polyethylene (HDPE) crystallisation, and mechanical properties of the composites. HDPE/bamboo and pure HDPE composites were prepared using melt compounding and compression moulding. Results showed that the equilibrium torque of both pure HDPE and HDPE/bamboo system was decreased with the addition of the clay master batch, while adding MAPE increased the torque value of HDPE/bamboo systems. The mechanical properties of bamboo glass hybrid composites made from 15:15 ratio were studied. The fibre matrix interfacial morphology of the tensile fractured specimen was observed using scanning electron microscopy (SEM). The crystallisation, melting behaviour, and thermal stability of the hybrid composites were investigated using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). From the results it was observed that the increase in the thermal stability of the matrix polymer increases with the incorporation of bamboo and glass fibre (Sreenivasa Murthy, 2015). The melting and crystallisation process of pure PLA (poly lactic acid) and PLA composites (1% Bamboo fibre/PLA, 1%, Talc/PLA, 1%, bamboo fibre/1% Talc/PLA) were studied with DSC. Single exothermic peaks were observed in the DSC curves during the cooling process. Tc and ΔHc shows decrease in trend with cooling rate. It was observed that bamboo fibre has a minor effect on the crystallisation temperature and the Talc played the significant role in crystallisation temperature of PLA composites (Shi et al., 2010). The composites developed from eco-friendly bamboo and wood fibre cement composite from agriculture wastes were used for the construction of housing and building industries and sustainable infrastructure regeneration (Ding, 2019; Li and Ding, 2007). The bamboo flakes comprise 4.92% which has significant retarding effect on the strength development of the Portland cement matrix. From the results it was observed that the particle boards produced from bamboo:cement ratio 1:2.75 and 2% aluminium sulphate alone or in combination with sodium silicate satisfied the strength and dimensional stability requirements for international standards. Chuanbao and Sanjiu (2014) developed the bamboo fibre/polypropylene (PP) composites, and the effects of bamboo fibre content and the alkali

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treatment of bamboo fibre on morphological, mechanical, thermal, and dynamic mechanical properties, as well as water absorption were studied. The fourier transform infrared spectroscopy (FTIR) results revealed that the hydrophilic nature of raw bamboo fibre was significant by alkali treatment. From the results it was observed that the interaction of fibre matrix was greatly improved by alkali treatment. SEM images showed that the distribution of bamboo fibre was improved by premixing bamboo fibre and PP fibres to make a composite similar to the papermaking process. The composite were developed from bamboo fibre extracted from raw green bamboos by crushing, rolling, and combing techniques using 1,4-butanediol (BDO) as solvent. FTIR, X-ray photoelectron spectroscopy (XPS), and nuclear magnetic resonance (NMR) results showed that 2-(Methacryloyloxy) ethyl isocyanate (IEM) was covalently bonded on to the bamboo fibres. After treatment with IEM the interfacial adhesion between the bamboo fibres and unsaturated polyester resin (UPE) resins was improved (Zhang et al., 2008).

9.6 Future trends and technoeconomics of bamboo fibres Bamboo has served as an important crop for centuries. It is known as a ‘friend of the people’ in China, ‘poor man’s timber’ in India, and the ‘brother’ in Vietnam. The bamboo plant supports an international trade worth over US $2.5 billion (Chaowana, 2013) and also there are over 2.5 billion people (38% of world population) involved in its trade or use (Bystriakova and Kapos, 2006). In 2003 the bamboo forest area was around 22 million hectare and it has been steadily increasing with a speed of 3% per year (Bystriakova and Kapos, 2006). China hosts a bamboo forest area of 7.2 million hectare. Bamboo grows in almost all climates and it is native to every continent except Antarctica and Europe. It grows in temperatures ranging from 20 C to 40 C both in poor and rich soil and with an annual rain fall requirement of 76.2 635 cm/year. Prominent players in the bamboo fibre market include Litrax, Swicofil, Advantage Fibres, America Hoy Technology, Bo Group, TIC Gums, Bambro Textile Co., CFF GmbH & Co. KG, International Fibre Corporation, Wild Fibres, Liahren, Chengdu grace Fibre Co., Suzhou Lifei Textile Co., Shanghai Tenbro Bamboo Textile, and Hebei Jigao Chemical Fibre.

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Natural bamboo fibre is a cellulosic fibre which is soft, naturally breathable, and moisture-wicking produced from the starchy pulp of bamboo plant. The bamboo fibre is widely used in bathroom textile, medical and hygienic clothing, bamboo clothing, and home furnishings among other applications. They are as thin as hairs and have a smooth surface and have antifungal and antibacterial properties. The growing focus on environment-friendly textile production has led to a rise in demand for bamboo fibre amid growing concern about its production volume. Rising awareness among the population regarding environmental sustainability and conservation coupled with growing demand for natural fabrics is likely to propel the market demand over the forecast period. There has been a shift in consumer behaviour, where consumers are more inclined toward quality over quantity, which has boosted the demand for green and sustainable products. Textiles made from bamboo address the aim of sustainable development by utilising a renewable resource to make clothes and other textile applications. Bamboo fabric is widely available in China, India, and Japan. Philadelphia-based Footprint provides socks made of 95% bamboo that offer antibacterial and moisture-wicking properties as well as superior comfort (Textile World, 2008). Bamboo textiles show clear advantages in the realm of sustainable development. There are a few mainstream manufacturing techniques that are currently used for the creation of bamboo textiles. These techniques are inspired by already-existing textile technology, as well as emerging nanotechnology. The main constraints of bamboo textiles are those inherent in the textile industry; these issues, such as energy, water, and chemical use, could be addressed through closed-loop manufacturing, eco-chemicals, water recycling, and economic tools (full pricing). One constraint of bamboo, though not large, is the current cost/price. A bamboo t-shirt costs about $7 and is softer, easier to dye, and better at fighting odour than cotton (Durst, 2006). According to Rich Delano who owns a bamboo textile company, bamboo fabric is ‘not as cheap as cotton yet, but it will be’ (Durst, 2006). The global bamboo products market was valued at USD 53.28 billion in 2020 and is expected to expand at a compound annual growth rate (CAGR) of 5.7% from 2021 to 2028. The European and North American regions are anticipated to show an upward growth in the years to come and the bamboo fibres market in the Asia Pacific region is likely to show remarkable growth during the forecasted period. Cutting-edge technology and innovations are the most important traits of the North

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American region and that is the reason most of the time that the United States dominates the global markets. The bamboo fibres market in South America is also expected to grow in the near future. The drivers that contribute to the growth are growing demand for natural bamboo fibre and increasing investment in clothing and furnishing. Natural bamboo fibre is thinner as compared to hair and has a round and smooth surface which makes it abrasion proof, antifungal, and antibacterial, which features are creating an upsurge in the demand for bamboo fibre. Restraints for the bamboo market are a high cost for processing and stringent regulation on the chemical processing of bamboo fibre. China is the largest producer of bamboo fibre across the globe, followed by India with a significant growth rate. In terms of volume, Asia Pacific is expected to dominate the global bamboo fibre market, owing to the rising demand for furniture with the rapid growth of per capita income of the consumer in the region. Bamboo fibre is prepared from bamboo pulp, which is removed from the bamboo leaves and stems through wet spinning, comprising a procedure of alkaline hydrolysis and multiphase bleaching. The increasing applications of bamboo fibre in the furniture and textile industry are anticipated to drive the global market of bamboo fibre in the forthcoming years. The rising emphasis on eco-friendly textile production has led to an increase in demand for bamboo fibre. Increasing awareness among population about environmental conservation and sustainability along with rising demand for natural fabrics is expected to boost the market demand over the forecast years. There has been a major shift in buyer behaviour, where buyers are more inclined towards good quality fabrics, which is expected to boost the demand for eco-friendly fabrics. The increasing demand for ecofriendly fabrics is anticipated to further aid the growth of the global market of bamboo fibre. The prominent market players operating in the market are embarking upon the launch of bamboo fibre-containing products.

9.7 Summary The versatility of bamboo-based textiles affords the opportunity for sustainable development. Indeed, bamboo fibres have been used for decades in the production of textile materials. Bamboo as a new fibre has

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been introduced recently into the textile industry with claims of some useful unique properties. Bamboo products are being focussed upon and dominate the market because of their compatible price and the ease of the processing conditions. The growth rate of bamboo and its carbonabsorbing properties make it important among the plant fibres. Bamboo plantations do not require any fertilisers or pesticides and bamboo is a renewable and harvestable plant. It does not require replanting after harvesting but immediately regenerates from its rhizome root structure. However, the cultivation and management of bamboo resources should be the top priority and the exploitation of bamboo resource from the industries should be given equal importance for sustainable bamboo cultivation. Nevertheless, the economic objectives should not be achieved at the cost of causing damage to the environment. Natural/pure bamboo fibre processed mechanically is environmentally friendly but not available commercially and not affordable. The bamboo fabrics available in the market are from a viscose process using chemical solvents and raise environmental issues. Bamboo viscose fibre is a better choice compared to other manmade fibre and pure bamboo fibre would be a far superior and preferable option. Bamboo viscose fibres are smooth, soft, have silky hand characteristics, and the fabrics made from bamboo viscose are more attractive. The inherent characteristics of bamboo viscose fibre, that is, antibacterial, UV-resistant, deodorant, highly hygroscopic, and breathable are unique in nature. Recently bamboo fibres have been processed through the lyocell process and presently there are only limited manufacturing plants in China producing bamboo fibres. Lenzing Austria and Litrax companies have already started greener bamboo manufacturing processes. Research in bamboo fabrics and clothing is in full swing for the development of eco-friendly products. With the abundant resource of raw material, the low cost, and some unique properties of bamboo fibre, it is a matter of time until the development of green and pure bamboo textiles. Bamboo blended fabrics possesses better performance, comfort, and low stress mechanical properties compared to cotton and polyester alone. The bamboo/cotton and bamboo/ polyester blended fabrics show excellent tensile, tearing, abrasion, and bursting strength and can be used suitably in apparel production. The prominent players in the global bamboo fibre market include Bambro Textile Co., Shanghai Tenbro Bamboo Textile, Advantage Fibres, Towel Industrial Co. Ltd, China Thrive Industrial Co., Ltd., Xiamen Ebei import & Export Co., Ltd., Wild Fibres, and TIC Gums.

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Bamboo fibre fabrics are anticipated to witness considerable growth in the global market. Asia Pacific is anticipated to be a leading region in the global market of bamboo fibre. The increasing cultivation of bamboo in countries such as China and India is anticipated to create new opportunities for market players. Moreover, bamboo is one of the fastest growing plants and does not require water and replantation. The high profit associated with the cultivation of bamboo plants may increase the area under the cultivation of bamboo plant, which is predicted to boost the production of bamboo fibre within the region. North America is anticipated to witness significant growth in the global market of bamboo fibre. The increasing demand for eco-friendly clothing and bathroom textiles, coupled with the high purchasing power of Americans, is predicted to drive the market within the region. Moreover, the increasing popularity of furniture made of bamboo fibre is expected to further drive the market growth within the region. In a nutshell the bamboo textile industry has the full potential to provide a livelihood for millions across the world. Bamboo fibres and other natural fibres, such as jute, flax, and hemp, are primarily lignocellulosic and are 100% biodegradable, irrespective of whether they are regenerated (e.g., bamboo viscose) or mechanically and/or biologically extracted, thereby reducing their environmental impact as pollutants and contaminants. Hence, bamboo-based textiles present an advantage compared to fossil-based textiles such as polyester, acrylics, nylons, and PP, which have been noted as contributing to microplastic pollution in the environment. Research is ongoing for the development of eco-friendly, natural bamboo fabric. With the abundant sources of raw materials, the relatively low cost, and the unique performance of bamboo fibre it is only a matter of time before the development of green and pure bamboo textiles. Furthermore, the bamboo textile industry has the potential to provide livelihoods for millions of people worldwide.

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CHAPTER ONE

Introduction and history of bamboo fibres

1.1 Introduction to bamboo and bamboo fibres The development of textile fibre and its usage for clothing dates back 4000
5000 years. Nature in its abundance has various kinds of fibrous materials that are needed for making apparel. Twisting of fibres into cords, plaiting, and sewing originate from the Palaeolithic age. Until about last 100 years ago the fibres employed by human being were solely from natural sources (Nayak and Mishra, 2016). The soaring prices of raw materials for textile and clothing, the future sustainability of natural resources, and the threat to environment have forced people to use natural renewable materials for the development of textile products. Natural fibres have served mankind for very many years with a wide range of applications and they compete in the 21st century with manmade fibres, especially in terms of quantity, sustainability, and production costs. Natural fibres possess good moisture absorption properties, permeability, and biodegradability, they dye easily, are naturally antibacterial, have good UV blocking properties, and are easily made flame retardant. Natural fibres grow in multiple geographical locations and their production does not damage the ecosystem. In recent times the natural fibre production has reached 35
40 million tonnes/year and current cotton production has reached 26
30 million tons/year. The textile industry is presently finding alternative green fibres to provide healthy, comfortable, recyclable, and biodegradable fibres. The majority of textile fibres are found in natural forms, such as seed fibres (cotton) or animal hair (wool). Some of the natural fibres are extracted from lignocellulosic fibrous plants, such as flax, jute, hemp, kenaf, sisal, ramie, coir, and bamboo, which are widely used not only for developing products and textile but also as building materials, animal food, agrochemicals, and a source of biopolymers and energy. Bamboo Fibres. DOI: https://doi.org/10.1016/B978-0-323-85782-6.00008-8

© 2023 Elsevier Ltd. All rights reserved.

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With the growing demand in recent years for more comfortable, healthier, and environment-friendly products, the research activities in textile Industry have focussed on the utilisation of renewable and biodegradable resources and environmentally sound manufacturing processes (Erdumlu and Ozipek, 2015). In the beginning of the 21st century environment conservation regulations have given lot of importance to the natural materials (Larik et al., 2015). Nowadays people’s living standards are getting higher and demanding new-generation textile materials with improved properties for higher comfort or industrial use. The environmental regulations when developing new fibres are strict and more stringent than before; the popular petroleum-based synthetic fibres do not meet the criteria because they are ecologically unfriendly. The important synthetic fibres, for example, polyester, polypropylene, and poly-acrylic, are hazardous to the environment. The problems with synthetic polymers are that they are nondegradable and nonrenewable. Recent evidence has proven that polyester is the most frequently used among all fibres, taking over from cotton. The fossil fuels like oil and petroleum are nonrenewable and with the current rate of consumption they are expected to last for another 55
60 years (Zupin and Dimitrovski, 2010). The present petrol consumption rate is estimated to be 100,000 times the natural generation rate (Blackburn, 2005). A material is termed as biodegradable if it is easily broken into simpler substances by naturally available decomposers, essentially anything that can be ingested by an organism without harming the organism. An important thing to be noted here is that the substance should be nontoxic and decomposable in a relatively short period on a human time scale (Blackburn, 2005). Natural cellulosic fibres have received increasing attention because of their biodegradability and renewable resources in comparison to synthetic fibres. Cotton and bast fibres, especially cotton fibres, are important textile materials, primarily because of their more cost-efficient production and nearly universal product possibilities. The natural fibres like cotton, wool, jute, and regenerated bamboo are biodegradable. The biodegradability of fibres depends on their chemical structure, molecular weight, and supermolecular structure. All known natural fibres are biodegradable, however, they have some demerits during the growing and production processes. While growing cotton and other vegetable fibres, large amounts of pesticides and chemical fertilisers are used, which have a negative influence on the environment. Bamboo fibres are a new kind of regenerated fibres introduced into the textile field due to some of their

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unique properties. These fibres belong to bast fibres produced from bamboo pulp similar to viscose rayon. Bamboo as a raw material is remarkably sustainable and versatile and the bamboo fibres are often labelled as being biodegradable, eco-friendly, antibacterial, antimicrobial, with good UV blocking properties, etc. (Liu et al., 2011). Microbial growth is common on textiles under suitable conditions like availability of sufficient water, air, and nutrients (Gerick and Vander Pol, 2010). In such conditions many natural fibres are rapidly colonised by microorganisms, bacteria, and fungi, and metabolised by them as part of their food chain. Natural fibres are more susceptible to biodeterioration, especially in hot humid conditions. Cloths such as undergarments, sportswear, socks, and healthcare textiles such as bedding, gowns, masks, towels, and gauzes are the best examples where microbial growth is rapid. Innovation in textile has brought alternative plant-based fibres such as bamboo into the spotlight and as a replacement to petrochemical-based synthetic fibres. Bamboo has attracted renewed interest from an environment point of view. Bamboo needs no irrigation and fertilisers to grow and its unique rhizome system is responsible for its fast growth rate (Majumdar and Arora, 2015). Bamboo possesses an excellent carbonsequestering property, which makes it more useful. Bamboo as a raw material is a remarkably sustainable and versatile resource. The usage of bamboo in China dates back to ancient times. In addition to making decorative items, musical instruments, and construction purpose, it also offered people abundant resources for use in their daily life. All over the world the wide application of bamboo for various activities has been considered by consumers. Growing knowledge about the dangers of microbial and viral contamination and the spread of diseases has initiated the development of a market for antimicrobial textiles, especially for healthcare products and next to skin garments. Bamboo products can be used successfully for the production of the above textile materials. Bamboos are members of a group of woody perennial, evergreen to deciduous plants of the true grass family Poaceae, which is a subfamily of Bambusoideae, from the tribe Bambuseae. Bamboo comprises over 1500 species, including 87 genera worldwide, and its rhizome structure is responsible for its rapid growth (Majumdar and Arora, 2015). It is a perennial evergreen, the fastest growing plant, and can reach nearly 119 cm height in 24 hours. It is a rich renewable resource for developing many useful products. Probably bamboo is the world’s most abundantly available sustainable resource material. Bamboo does not require fertilizers

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or pesticides and growing bamboo is significantly beneficial to the environment. Bamboo fixes carbon remarkably; a 28-day-old bamboo is able to store 1.83 kg of carbon and can become an important source for controlling global warming. It releases 35% more oxygen and sequesters four times more CO2 per hectare per year (60 tons CO2/ha) than a young tropical forest plant. Bamboo grows naturally in all continents except Europe but is not evenly distributed in humid, tropical, subtropical, and temperate regions (Joselin et al., 2014). China is the largest producer of bamboo products in the world. India is the second largest producing country in the world next to China with a high diversity of bamboo products. In India nearly 18 genera and 136 species are grown and they cover about 8.96 million hectares of land including forest, homesteads, and private plantations; this accounts for nearly half of the total bamboo cultivation in Asia. Textile and clothing manufactures are exploring new natural fibres that are renewable, with unique characteristics, and that add new value and attract customers/consumers. Plant-based fibres are contributing to economic development and sustainability in our day-to-day life and they have applications in many areas. In this way new ideas have been thought of for producing the best materials which balance between the properties sought, cost, and energy used, and that are either biodegradable or recyclable (Rodie, 2008). Presently there has been a great demand for renewable, biodegradable, comfortable, healthier, nonallergic, soft and breathable fabrics (Hardin et al., 2009). These concerns triggered the researchers to develop new fibres from plant sources such as bamboo into spot light as a replacement for synthetic fibres (Devi et al., 2007). Bamboo belongs to the group of woody grasses that readily available and its plays an important role in socioeconomic prosperity (Scurlock et al., 2000). Bamboo is a long grass and a fast-growing plant and grown organically without any fertilisers and pesticides (Munro, 1868). The latest development in fibre research is the use of bamboo fibres in various textile products and it has been used in construction materials, in decorative items such as furniture, and in high-performance composite materials (Erdumlu and Ozipek, 2015). Bamboo is a rich renewable natural resource of cellulosic nature and it originates from the bamboo grass (Larik et al., 2015). The 21st century is an era seeking environment protection, and bamboo fibre is one such kind of new green environment-friendly natural fibre. Bamboo regenerated cellulose fibre, known as bamboo viscose, recently entered the market with the claim that bamboo fabrics are

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eco-friendly and antibacterial (Afrin et al., 2012). Hebai Jigao Chemical fibre Company Limited, China introduced bamboo viscose products into the market in the year 2002. Bamboo fibres exhibit unique natural antibacterial properties, good moisture vapour transmission, and quick drying behaviour. They are comfortable to wear, are nonallergic to the skin, smooth, soft, and can be used in many textile applications. These characteristics have made the fabrics from these fibres more attractive and useful in many textile applications. Bamboo viscose fibre is also known as a breathable fibre as it absorbs sweat quickly, allowing evaporation, and thus makes the wearer feel more comfortable. Bamboo viscose products are used for a wide range of end uses, such as apparel, fabrics for home furnishing (towels, mattresses, and bathrobes), disposable and nondisposable medical products such as sanitary pads, masks, diapers, gloves, napkins, bandage cloth, surgical cloths, and gowns (Gerick and Vander Pol, 2010) used in hospitals, and fabrics for food packaging products. The compound called bamboo Kun is a hydroxyl functional group [ 2 OH] that is responsible for the antibacterial property in bamboo. There are two ways to produce bamboo fibres from bamboo plant. The mechanical means of producing bamboo fibres is crushing the woody parts of bamboo and treating them with natural enzymes to break the bamboo walls into a soft mass which is combed out mechanically and spun into yarn. Regenerated bamboo viscose fibres are produced in a wet spinning process in which natural cellulose (bamboo leaves, stems, and inner pith) is used as a raw material in a hydrolysis alkalisation process (Erdumlu and Ozipek, 2015). Bamboo charcoal is produced using nanotechnology in which bamboo is dried and heated at 800 C until it turns into nanoparticles. These nanoparticles are embedded into cotton, polyester, and nylon fibres.

1.1.1 History of bamboo and bamboo fibres In Asia, bamboo was historically used for the production of paper, weapons, and household articles. Bamboo fabrics only entered into commercial markets in the early 2000s, but the concept is not exactly new. The experimentation and refinement of this invention has been around for more than 100 years. The earliest record of US patents involving bamboo was made by Philipp Lichtenstadt in 1864. His original idea was to create a ‘new and useful process for disintegrating the fibre of bamboo so that it

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may be used in manufacturing cordage, cloth, mats, or pulp for paper’. However, his patent never materialised into popular goods, probably due to the low demand for bamboo and high transport costs from Asia. In 2001, Beijing University became accredited as the first institution to successfully transform bamboo into cloth. During this time, many other organisations also attempted the same process, so it was plausible that any of them could have achieved the same feat. Production involved using modern solvents to dissolve bamboo pulp, followed by a special dying process to turn the fabric white. Bamboo clothing is a recent development and it is labelled as biodegradable, green, soft, cool, breathable, and light (Das et al., 2008). Bamboo fabrics often claim that they possess antimicrobial properties and UV protective capability and are used in apparel (undergarments, sports textiles, t-shirts, and socks), healthcare textiles (such as hospital masks, surgical gowns, bandage cloths, sanitary napkins, absorbent pads), furnishing textiles, ultraviolet protective clothing, and food packaging bags (Hardin et al., 2009). These outstanding and unique properties of bamboo have been attracting many researchers, academia, and industry to develop new products for specialised applications. 1.1.1.1 Bamboo textiles Bamboo textiles have been around for a long time. In fact, the earliest patents involving these materials go back to 1864 by Philipp Lichtenstadt. His original idea was to create a ‘new and useful process for disintegrating the fibre of bamboo so that it may be used in manufacturing cordage, cloth, mats, or pulp for paper’. Yet somehow, despite the availability of the material, it has only been within recent years that commercially viable bamboo clothing has made it into the mainstream. Many attempts have been made over the years to develop bamboo fibre that can be used in cloth. The process detailed in the original patent was a lot like the one used for making paper but, at the time, no one developed a cloth fabric. In 1881, there was another patent that involved mixing bamboo fibre with wool, which would lead to some results that were usable as cloth, but it did not go into mass production for reasons that could include inefficient or expensive processing methods. Bamboo is supposed to be one of the best functionally gradient composite materials available. Bamboo has a few advantages besides the fact that it grows fast, up to 21 cm a day, it is abundant (Londono et al., 2002), and can help with the reforestation of degraded land (Vander

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Lugt, 2017). It is estimated that 15 million hectares of ‘giant bamboo’ is present (Trujillo, 2014) which can be used for fibre extraction. It is a very diverse plant, since over 1600 species are known (Liese and Kohl, 2015) and spread worldwide. Bamboo is native to all continents except for Antarctica and Europe. The natural distribution of bamboo can mostly be found in the tropical and subtropical climate regions (Ohrnberger, 1999) but some bamboo is native to temperate climate zones and can therefore adapt to grow in European regions (Gielis, 2000). Bamboo fibre is a new kind of natural material, which has high potential in the textile field due to some of its specific properties (Liu and Hu, 2008). Bamboo fibres are also known as breathable fibres as they resemble puffballs of light and cotton in an untwisted form (Yao and Zhang, 2011). These fibres are cellulosic in nature and are obtained from the natural, renewable resource of bamboo plants. The fibres are made from pulp of the plant, which are extracted from the plant’s stems and leaves. They are considered as prospective green fibres with outstanding biodegradable properties, having strength comparable to conventional glass fibres. Bamboo fibre is a best example for an eco-friendly natural fibre as it comes from nature and completely returns to nature in the end, retaining carbon-neutral characteristics through the product life cycle (Yu et al., 2003). Natural bamboo, once it is cut, recovers with a growth period of 2
3 years as compared to a normal forest tree which requires at least 60 years. Hence, bamboo fibres are highly regarded as a green fibre and form a basis for a very promising alternative to other natural fibres by virtue of their novel properties. Being naturally more wrinkle-resistant than cotton, bamboo textiles can be machine washed in cold water with a mild soap using a gentle procedure. Garments made of bamboo dry faster than other fabrics. In addition, bamboo has attracted a great deal of attention from designers and fashion retailers around the world due to the growing environmental awareness among consumers (Yu et al., 2003). Generally, 3
4 years old bamboo is used for fibre extraction. The process involves alkaline hydrolysis and multiphase bleaching of bamboo stems and leaves followed by the chemical treatment of starchy pulp. Bamboo fibres show various micropores which make them more comfortable and absorb more moisture compared to other natural fibres such as cotton. They are biodegradable, eco-friendly, and elastic in nature. Other exclusive properties of bamboo fibres are their antimicrobial, bacteriostatic, hypoallergenic, hygroscopic, and UV-resistant properties. Due to these properties, the fibres are used in medical applications for making

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bandages, masks, sanitary napkins, baby’s diapers, etc. In addition, they find wide application in furnishing industry for the manufacture of UV-proof, antibiotic, and bacteriostatic curtains, television covers, and wallpaper, attire, towels, and bathrobes. They are also used for decorative cloth (Imadi et al., 2014). Regenerated bamboo fibres can be obtained from the bamboo plant, which grows in tropical climates and is harvested after 3
4 years. Bamboo fibres used in textile applications are obtained from Phyllostachys heterocycla pubescens, a species known as Moso bamboo. Regenerated cellulosic bamboo fibre were first manufactured in 2002 by Hebei Jigao Chemical Fibre Co. Ltd. in China. Bamboo fibres are extracted from bamboo pulp, which is extracted from the bamboo stem and leaves by wet spinning, with alkaline hydrolysis and multiphase bleaching processes, which are used in the manufacture of viscose rayon fibres (Liu et al., 2004). The first modern example of turning bamboo into usable cloth happened at Beijing University. They released their results in the early 2000s, but it should be mentioned that there were a lot of people and organisations working to manufacture cloth from bamboo at the time, and many of them could have produced something similar, such as a new processing technology that was patented in 2003 by a group of chemists with the Hebei Jigao Chemical Fibre Co. in Shijiazhuang, China. From 2004 to 2010, the market for bamboo cloth expanded rapidly, some say by as much as 5000%. This is due to many reasons, including the new affordability and availability of the fabric, its use in more products, and the new technology that allowed the fabric to be as soft and pliable as cashmere and similar materials. One of the possible reasons that it took so long to develop commercially viable bamboo clothing is that the push for more environmentally sustainable textiles is a relatively recent trend. But now, because of its silky sheen, smooth texture, and the inherent environmental benefits of the material, bamboo clothing has gone beyond the basics and is now seen in some modern, luxury fashions. Producers utilise bamboo to make a variety of products. For instance, the paper industry uses it in paper production. However, bamboo fibres for clothes came about in the 20th century. It is important to note that there had been attempts over the years to generate fibre to be turned into apparel. One can trace the origins of bamboo fabric to Asia and the development of the first modern process of attaining bamboo textile to Beijing

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University. They released the results of usable bamboo apparel in the early 2000s. Around this time, some other manufacturers and organisations were working to create bamboo apparel by using similar methods. This successful extraction was developed, and modern bleaching methods were used to turn the fabric white. It then became commercially available and successful in the American market. Over the years, experts have developed methods of generating the fabric. As a result, we’ve noticed innovations in mixing and blending fabrics. Bamboos that have been earlier used for the purpose of construction, pulp and paper manufacture, and in composites can be used also for extraction of bamboo fibres. Bamboo fibres consist of elementary fibres with a length of 1.9 mm and a width of 15.3 µm, like other bast fibres such as jute, hemp, flax, and ramie. The fibres are cemented together by noncellulosic materials such as lignin, hemicellulose, and pectin. These noncellulosic substances also contribute to the stiff and coarse nature of bamboo fibres. It is necessary to remove these noncellulosic substances partially without disturbing the fibre cellulose for producing bamboo fibres for textile applications (Liu et al., 2011). Bamboo is supposed to be one of the best functionally gradient composite materials available. It is observed that in a piece of bamboo, 1 mm2 area near the outer periphery contains approximately eight fibres and the inner periphery contains two fibres (Ray et al., 2005). Bamboo fibre is a new kind of natural material, which has high potential in the textile field due to some of its specific properties (Liu and Hu, 2008). Bamboo fibres are also known as breathable fibres as they resemble a puffball of light and cotton in untwisted form (Yao and Zhang, 2011). These fibres are cellulosic in nature and are obtained from natural, a renewable resource of bamboo plants. Bamboo fibres are made from the pulp of the plant, which is extracted from the plant’s stems and leaves.

1.1.2 Taxonomy and geographical distribution 1.1.2.1 Taxonomy Bamboos have a unique anatomy and their super productive behaviours are truly interesting to study. The bamboos are classified according to their type, species, and variety. Bamboo belongs to the grass Family Poaceae [Syn. Graminease] and sub-Family Bambusoideae. It is a perennial long grass and woody plant and makes up the largest and most productive member of the grass family (IFAR/INBAR, 1991). All the types of bamboo, such as the cold hardy temperate species fall into a group of

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common characteristics. An example of this would be the Phyllostachys that are grown in Alabama and throughout the United States. Next comes the species such as nigra (Black Bamboo). Then the cultivars of this species such as the Henon (Giant Gray). When a cultivar flowers it may or may not create a stable new variety. This happened fairly recently when the cultivar Phyllostachys vivax ‘Aureocaulis’ started to produce the variety P. vivax ‘Huangwenzhu’ within the groves of ‘Aureocaulis’. The peculiar characteristic of bamboo is its perennial habit, flowering, and seeding behaviour (Scurlock et al., 2000). The bamboo is classified into 170 species within 20 genera (Goyal et al., 2013). Presently bamboo accounts for 1482 species within 119 genera in the world and they grow in a wide range of climates and regions. Nearly half of these species are found on the Asian continent, mostly in the Indo-Burmese region, which is considered to be origin of bamboos place (Clark et al., 2015). Bamboo has the ability to grow in regions that range from the subSarahan deserts of Africa, to the cold mountain terrain of the Himalayas. It has a long and detailed history and is one of the most versatile plants in the world. The majority of species are native to the tropics of Asia, although one variety is native to the United States, Arundinaria gigantea. The sizes of bamboo species vary greatly. The smallest varieties grow to a height of 11 in., while giant timber bamboo can reach heights of over 100 ft. The taxonomy of how bamboo is classified is presented in Table 1.1. The identification of bamboo differs from many plants. It rarely flowers and is not easy to identify. The process of flowering varies from 20 to over 120 years so classification is often difficult. Chinese and Japanese growers have maintained a good record of them and the others have been grouped and identified based on completely vegetation structures. When a species of bamboo does flower, the grove may or may not Table 1.1 Taxonomy of bamboo (botanical classification of bamboo). Kingdom Plantae

Phylum (Division) Class Order Family Subfamily Tribe Subtribe

Magnoliophyta Liliopsida Cyperales Gramineae (Poaceae) Bambusoideae Bambuseae Bambusinae

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establish itself again. The rhizomes (root system) may establish the grove or the flowering process may produce new seedlings. The major division in bamboo occurs in their growing patterns. This is divided into two groups, running and clumping bamboo. Running bamboo has monopodial or leptomorph rhizome (root) systems. It produces vertical axes (canes or culms) and the main vegetative growth can extend underground to produce additional culms. Typically forming a line of growth, clumping bamboo has sympodial or pachmorph rhizome systems. The vertical axis differentiates and produces a terminal vegetative growth, typically producing an expanding spiral growth pattern (http://www.lewisbamboo.com/ pages/bamboo-basics). 1.1.2.2 Geographical distribution of bamboo Bamboos are distinct and fascinating plants, with a wide range of values and uses. Bamboos are native to all continents except Antarctica and Europe and have a latitudinal distribution from 47 S to 50 300 N and an altitudinal distribution from sea level to 4300 m. Bamboos therefore grow in association with a wide variety of mostly mesic to wet forest types in both temperate and tropical regions, but some bamboos have adapted to more open grasslands or occur in more specialised habitats. Although their diversity and their importance are highest in and have been best documented for the Asia-Pacific region, they are also important in continental Africa, Madagascar, and the Americas. Worldwide they are associated with unique elements of biodiversity, many with great conservation significance. Bamboo history dates back to ancient times and China has used bamboo for a very long time. It plays an important role in society economic constructions by providing clothes, food, household articles, and construction materials in tropical countries. Bamboo belongs to a grass family and is a fast-growing plant with rich renewable resource. Bamboo can grow in a wide range of climatic conditions like hot, cold, humid, and rainforests areas (Joselin et al., 2014). The unique rhizome structure is responsible for its growth rate. Bamboos are unevenly distributed in different parts of the world in different climatic conditions. Nearly 40 million hectares of Earth is covered by bamboo and not all species available are used for clothing. ‘Moso’, one of the popular varieties in China is used for bamboo clothing. Bamboo yields up to 60 tons/ha. The price of 1.67 dtex-38 mm bamboo fibre is nearly 2.83 USD/kg and it is high compared to viscose rayon (Erdumlu and Ozipek, 2015).

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Figure 1.1 Distribution of bamboo growth in the world (Janssen, 2000): (A) Herbaceous bamboos; (B) woody bamboos; and (C) temperate woody bamboos.

Bamboo plants are grown in almost all parts of the world except in some extreme cold climates. Some species of bamboo have been recently introduced in mild temperate zones of Europe (Seethalakshmi et al., 1998). The world’s bamboo plantations are spread into three major divisions, namely, Asia-Pacific, America, and Africa. The geographical distribution of bamboo in the world is shown in Fig. 1.1. Bamboos play a significant role in biodiversity conservation and contribute to soil and water management. They are important for biomass production and play an increasing role in local and world economies (Bysthakova et al., 2003). The greatest diversity of bamboo is found in Southeast Asia and South America, where they occur in tropical, subtropical, and temperate regions, while fewer bamboo species are found in Africa in comparison to the other two regions, with the exception of Madagascar which is rich in endemic genera and species. They occur at latitudes from 51 N in Japan to 47 S in South Argentina and from sea level to 4000 m elevation, though the occurrence of herbaceous bamboo never exceeds an altitude of 1500 m. Almost 1000 bamboo species are found in Asia, predominantly indigenous rather than plantation or introductions (Qiu et al., 1992). Bamboo species are classified into three groups, • Arundinarieae: temperate woody bamboos occur in the tropics at high elevation (546 species). • Bambusae: tropical woody bamboos (812 species). • Olyreae: herbaceous bamboos (124 species). According to a recent survey there are 1600 bamboo species around the world and approximately 50 are in commercial use ( Janssen, 2000). The majority of these are spread in Asia, mostly in the Indo-Burmese region. Fig. 1.2 shows the share of world bamboo resources by continent. Asia remains the richest continent, with about 65% of the total world bamboo resources.

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Figure 1.2 World bamboo resource share by continent.

Asia remains the richest continent in the world with 65% of total world bamboo resources, 28% in America, and 7% in Africa. Presently the global climate is encouraging the spread of many species that can bear temperatures of 28 C. Hot countries 3000 m above main sea level (MSL) and the Himalaya Regions 3600 m above MSL are preferred for the luxuriant growth of Bamboo. In Asia, bamboo is integrated in nature and is used in many areas like religion, arts, construction, and daily life. China has more than 400 species spread over 6.8 million hectares (largest-area) and has the world-leading position in producing bamboo products. The total area of bamboo growth exceeds more than 4.21 billion hectares in the world. According to sources available nearly 40,000 tons of bamboo fibre are produced annually. ‘Moso’ bamboo is the popular species used for bamboo fibre production and it covers nearly 3 million hectares. In Asia, bamboos are found in the greatest abundance and the greatest variety are in the Southern and South Eastern border areas of Asia. China is an important country for production of bamboo with the highest diversity in Asia. More than 500 species of bamboo under 39 genera are found in China alone, followed by India, Indonesia, Myanmar, and Malaysia, each with more than 100 species. A good number of species can be found in other Asian countries such as Myanmar with 90 species followed by Japan (84), Philippines (55), Thailand (50), Malaysia (44), Indonesia (31), Nepal (30), and Sri Lanka (30) (Ohrnberger, 1999; Sharma, 1980). In Bangladesh, 33 species in 9 genera have been recorded. China has the highest pure bamboo forest with 5.38 million hectares of land accounting for nearly 25% of the bamboo in the world (Yue, 2012). The American continent is another rich bamboo region with 429 species within 20 genera. Brazil (134 species), followed by Venezuela (68), Columbia (56), Peru (48), and

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Ecuador (42) are the important countries in Latin America with a rich diversity and large number of bamboo species (Fan et al., 2006; Takahashi, 2006). Unfortunately, due to unsuitable growth environmental conditions for bamboo cultivation, African countries show the lowest bamboo diversity. However, as an exception, Ethiopia accounts for 67% of the African bamboo resources and exhibits comparatively good bamboo diversity (Tadesse, 2006). There are many regions in the world which are to be explored for new bamboo species. The bamboo industry generates over $2.4 billion a year. It is native to every continent except Antarctica and Europe (though it was introduced later to Europe) and can survive, or thrive, in areas that would be inhospitable to other plants. It can grow in both rich and poor soils and withstand temperatures that range from
4F to 117F and rain levels from 30 up to 248 in. in a year. In tropical areas, especially Asian countries, bamboo is a basic natural resource that plays an important role in people’s daily lives and cultures because of its rapid growth, excellent flexibility, high strength, weight ratio, excellent specific strength, and high specific modulus. As a raw material, bamboo is one of the most renewable, biodegradable, and fastest-growing resources on the planet. It uses space and water efficiently, has amazing carbon sequestering abilities (it uses up to five times more CO2 than a group of trees the same size would), and it does not need replanting. As a resource, its environmental benefits are unquestionable. Being environmentally friendly, bamboo also contains antibacterial and antifungal properties, so it repels odour for long periods of time. Bamboo materials are highly absorbent because the fibre is covered with microgaps that pull moisture away from your skin. It is extremely soft, is hypoallergenic, and its nonirritant qualities make it a great choice for clothing. Since the original patent in 1864, the process for harvesting bamboo pulp and creating usable bamboo fibres has not changed very much. In basic terms, the bamboo joints are cut and then split into many slivers. These components are then put into an approved solution by the Global Organic Textile Standard, where they’re left to soak for 12
24 hours. From there, the bamboo is milled, combed, and spun into cordage, yard, or other usable forms. As the demand for ethical textiles continues to increase, more modern manufacturing technologies are being used that are more eco-friendly and safer for the people working in the industry. The Lyocell Process, for example, is nontoxic to humans and uses a

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closed-loop chemical manufacturing process that can capture and recycle 99.5% of the chemicals it uses. For almost a decade now, the bamboo clothing industry has continued to grow and expand. While some of this is likely attributed to more affordable and efficient processes, a lot of it is related to the demand for ethical textiles and eco-friendly production methods. Hundreds of millions of dollars of bamboo textiles are sold in the United States alone. Growing retail brands and massive department stores are carrying these popular bamboo products. If the trend continues, we can expect a lot more retail growth and production throughout the industry.

1.1.3 Prospects of bamboo fibres Bamboo is a source of natural fibre with abundant availability with limited application to meet needs, such as houses, walls, ornaments, traditional equipment, and even can be consumed in the form of bamboo shoots. Bamboo fibres are considered as one of the eco-friendly fibres as they come from nature and go back to nature at the end. Through its product cycle, it retains carbon-neutral characteristics (Yu et al., 2003). Bamboo fabrics are antibacterial, odour-free, feel and smell fresh, highly sweat absorbent (pulls moisture from skin for evaporation—moisture wicking), highly insulating, naturally UV protectant, and hypoallergenic in nature. They have a softness similar to the softness of silk. Bamboo fibres are naturally smoother and rounder with no sharp spurs to irritate the skin, making bamboo fabrics hypoallergenic and perfect for those who experience allergic reactions to other natural fibres, such as wool or hemp. On that same note, bamboo is also antibacterial and antifungal. This is because bamboo possesses an antibacterial and bacteriostatic bioagent called ‘Bamboo Kun’, allowing it to naturally flourish and grow in the wild without the use of pesticides or fertilisers. Cellulose from bamboo fibres is suitable for processing into viscose rayon, and viscose manufactured from bamboo is promoted as having environmental advantages over wood pulp viscose. Bamboo is also used as an additive in biopolymers for construction and in many other applications. Mechanically processed and extracted bamboo fibre is environmentally friendly, but not yet commercially viable or affordable. Original bamboo fibres differ from those produced by the viscose process using chemical solvents. In fact, most bamboo fibres and fabrics available in the market are produced by this process. Naturally processed bamboo fibres

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are far superior and preferable to bamboo rayon fibres, which are an alternative option to other manmade fibres. Like other rayon fibres, bamboo rayon fibres are very smooth and possess silky hand. Being a bast fibre, chemically similar to other bast fibres can be used to produce linen like textured fabrics. Unlike many of the other fabrics, bamboo textiles are extremely breathable. The natural bamboo plant keeps itself cool in the heat and like its other properties, is also maintained in its fabric form. The cross-section of the bamboo fibre is covered with microgaps giving the fabric better moisture absorption and ventilation. As a result, it is able to keep the wearer almost 2 C cooler in the heat and noticeably warmer in the cold. Bamboo fabric is also antistatic and UV-protective as it cuts out 98% of harmful UV rays, providing the wearer with another beneficial quality from bamboo-made clothing. Bamboo shows great potential as a sustainable structural material as well as for use in textiles due to its shorter maturity cycle and high cellulose content. The versatility of bamboo fabric makes it an excellent choice for clothing designers exploring alternative textiles, and in addition, it can be dyed by many dyes with bright colours as it is made of cellulose and there are many dyes available to dye cellulose. Natural bamboo fibres have excellent properties, suggesting that there is a good potential for them to be used in textiles; however, they have not received the attention that they deserve owing to their coarse and stiff quality. The high lignin content of the fibre is the major cause of its stiffness (Fu et al., 2012; Li et al., 2010). Owing to its open structure and presence of disordered noncellulose substances, bamboo fibres have excellent moisture regain compared with other natural fibres such as cotton (Li et al., 2010). Fabrics produced from bamboo have not yet achieved their full potential, cleaner production methods are being introduced to produce completely eco-friendly fibres. Bamboo, being a type of tropical grass, has an extensive rooting system that grows on average four to six new shoots a year, naturally replenishing itself. It is also 100% biodegradable, the most renewable resource on the planet, and provides an abundance of usable oxygen making it a crucial element in the balance between oxygen and carbon dioxide in the atmosphere. The bamboo industry offers the best opportunity for sustainable economic development for biocomposite fibres, which are produced at minimal cost and will bring a new evolution in the world of supply chain and manufacturing.

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1.1.3.1 Bamboo fibre composites Due to the increasing awareness of eco-friendly biomaterials, natural fibres have gained popularity over synthetic fibres for their applications as prospective alternative reinforcing materials in biocomposites in the construction and automobile industries. Bamboo fibres are important natural fibres and have attracted substantial attention as reinforcement in polymer composites because of their environmental sustainability, relatively high mechanical properties, high toughness, recyclability, simple processing, and performance comparability with those of glass fibres (Zakikhani et al., 2014). As an attractive alternative to reinforced polymers, these fibres can be used as reinforcing materials to develop green composites. The tensile strength of bamboo-fibre reinforced plastic composites (BFRP) may be compared to that of mild steel and the tensile strength of some BFRP composites is more or less equal to the ultimate tensile strength of mild steel; their density is much less compared to that of the mild steel. In addition, the physical and mechanical properties of these composites can be compared to glass fibre-reinforced plastics. New areas of applications have opened up for bamboo fibres for both academicians and industrialists in designing new sustainable materials. Cost-effective and eco-friendly biocomposites can be developed using bamboo fibre-based composites using different matrices and these composites are likely to find wide applications in the near future (Abdul Khalil et al., 2015). Hence, these composites are significant in structural applications (Jindal, 1986). In order to design and develop such composites, it is very much necessary to make a thorough investigation of the basic physical, mechanical, and thermal properties of bamboo fibres. At present, researches are being carried out on bamboo fibre-based composites in terms of either fibre modifications or their mechanophysical, thermal, and other properties. However, efforts are on the way to develop biocomposites and nanobiocomposites from bamboo fibres with improved performance for global applications. The economic value and function of bamboo can be increased through the diversification of natural polymer fibre products into biocomposites for the production of various lightweight structures that may find applications as sound vibration dampers, biofilters, and thermal products (Gaceva et al., 2007; Joshi et al., 2004). Bamboo fibre-based research in composite materials contributes to good design capabilities as it is concerned with the parameters such as aesthetics, safety, functionality, and consumer satisfaction. In addition, it is related to the potential impact on

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the environment. Through technology and research innovations, materials made of bamboo can be an exciting challenge in future leading to the design and development of new products that are both economic and ecologically sustainable. This has become a reality due to the superior mechanical properties of bamboo, such as low density (0.8
1.5 g/cm3), high tensile strength (500
575 MPa), and high elastic modulus (27
40 GPa) (Khalil et al., 2012; Li and Shen, 2011). At present, in China, only a few manufacturing companies are producing natural bamboo fibres. Companies such as Litrax and Lenzing have already engaged in introducing bamboo textiles towards sustainable production and green manufacturing methods. In addition, researchers all over the world are making their best efforts to develop eco-friendly natural bamboo fibres. As bamboo fibres and fabrics are popular in the clothing and fashion industry, the growth and demand for more bamboo plants will increase in the future. This will reduce the amount of greenhouse gases due to an increased amount of photosynthesis. Characterised by abundant sources of raw materials, low cost of production, and excellent performance and aesthetic properties, the production of green and pure bamboo fibre fabrics will be a reality soon and the bamboo textile industry has great potential to emerge as a promising industry to provide livelihoods for millions of people worldwide.

References Abdul Khalil, H.P.S., Alwani, M.S., Islam, M.N., Suhaily, S.S., Dungani, R., H’ng, Y.M., et al., 2015. The use of bamboo fibres as reinforcements in composites. Biofiber Reinf. Composite Mater. 488
524. Available from: https://doi.org/10.1533/ 9781782421276.4.488. Afrin, T., Suzuki, T., Kanwar, R.K., Wang, X., 2012. The origin of the antibacterial property of bamboo. J. Text. Inst. 103, 844
849. Blackburn, R.S., 2005. Biodegradable and Sustainable Fibres. Woodhead Publication, Cambridge, England, ISBN 1
85573-916-X. Bysthakova, N., Kapos, V., Stapleton, C., Lysenko, I., 2003. Bamboo biodiversity, information for planning conservation and management in the Asia-Pacific region, Bamboo Biodiversity UNEP-WCMC/INBAR. Clark, L.G., Londono, X., Ruiz-Sanchez, E., 2015. Bamboo taxonomy and habitat. In: Liese, W., Kohl, M. (Eds.), Tropical Forestry, Bamboo: The Plant and Its Uses. Springer International Publishing, Switzerland, pp. 1
30. Das, M., Bhattacharya, S., Singh, P., Filguerias, T.S., Pal, A., 2008. Bamboo taxonomy and diversity in the era of molecular markers. Adv. Botanical Res. Available from: https://doi.org/10.1016/S0065-2296(08)00005-0. Devi, M.R., Poornima, N., Guptan, P.S., 2007. Bamboo
the natural, green and ecofriendly new
type textile material of the 21st century. J. Text. Assoc. 67, 221
224. Erdumlu, N., Ozipek, Bulent, 2015. Investigation of regenerated bamboo fibre and yarn characteristics. Fibres Text. East. Europe 16, 43
47.

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Fan, S.H., Xiao, F.M., Wang, S.L., Xiong, C.Y., Zhang, C., Liu, S.P., et al., 2006. Carbon storage and spatial distribution in Phyllostachys pubescens and Chinese fir plantation ecosystem. In: Bamboo for the Environment, Development and Trade Abstracts and papers, International Bamboo Workshop, Wuyishan City, Fujian, China, 23 October, 29
39. Fu, J., Li, X., Gao, W., Wang, H., Cavaco-Paulo, A., Silva, C., 2012. Bio-processing of bamboo fibres for textile applications: A mini review. Biocat. Biotransfor. 30, 141
153. Gaceva, G.B., Avella, M., Malinconico, M., Buzarovska, A., Grozdanov, A., Gentile, G., et al., 2007. Natural fiber eco-composites. Polym. Compos. 28 (1), 98
107. Gerick, A., Vander Pol, Jani, 2010. A comparative study of regenerated bamboo, cotton and viscose rayon fabrics. Part
I selected comfort properties. J. Family Ecol. Consum. Sci. 38, 63
73. Gielis, J., 2000. Future possibilities for bamboo in European agriculture. Short report “Bamboo for Europe Project”: Oprins plant, Rijkevorsel, Belgium. Goyal, A.K., Kar, P., Sen, A., 2013. Advancement of bamboo taxonomy in the era of molecular biology: a review. In: Sen, A. (Ed.), Biology of Useful Plant and Microbes. Narosa Publication House. National bamboo Mission, Ministry of Agriculture, Government of India, Shashtri Bhawan, New Delhi, New Delhi, pp. 197
208. Hardin, I.R., Wilson, S.S., Dhandapani, R., Dhende, V., 2009. An assessment of the validity of claims for “Bamboo” fibres. AATCC Rev. 9 (10), 33
36. IFAR/INBAR, Research needs for bamboo and rattan to the year 2000, 1991. Tropical tree crops program, International Fund for Agricultural Research/International Network for Bamboo and Rattan, Singapore. Imadi, S.R., Mahmood, I., Kazi, A.G., 2014. Bamboo fibre processing, properties, and applications, Ch. 2. In: Hakeem, K.R., et al., (Eds.), Biomass and Bioenergy: Processing and Properties. Springer International Publishing, Switzerland, pp. 27
46. Available from: http://doi.org/10.1007/978-3-319-07641-6_2. Janssen, J.J.A., 2000. Designing and building with bamboo. In: Kumar, A. (Ed.), Technical Report No. 20. International Network for Bamboo and Rattan, China. Jindal, U.C., 1986. Development and testing of bamboo fibers reinforced plastic composites. J. Composite Mater. 20, 19
29. Joselin, J., Jenitha, S., Brintha, T.S.S., Jeeva, S., Sukumaran, S., et al., 2014. Phytochemical and FT-IR spectral analysis of certain bamboo species of South India. J. Biodivers. Biopros Dev. 1, 103. Available from: https://doi.org/10.4172/23760214.1000103. Joshi, S.V., Drzal, L.T., Mohanty, A.K., Arora, S., 2004. Are natural fibers composites environmentally superior to glass fiber composites? Compos. Part. A: Appl. Sci. Manuf. 35 (3), 371
376. Khalil, H.P.S.A., Bhat, I.U.H., Jawaid, M., Zaidon, A., Hermawan, D., Hadi, Y.S., 2012. Bamboo fibre reinforced biocomposites: a review. Mater. Des. 42, 353
368. Larik, S.A., Khatri, A., Ali, S., Kim, S.H., 2015. Batchwise dyeing of bamboo cellulose fabric with reactive dye using ultrasonic energy. Ultrason. Sonochem. 24, 178
183. Li, H., Shen, S., 2011. The mechanical properties of bamboo and vascular bundles. J. Mater. Sci. Res. 26 (21), 2749
2756. Li, L.J., Wang, G., Cheng, H.T., Han, X.J., 2010. Evaluation of properties of natural bamboo fiber for application in summer textiles. J. Fiber Bioeng. Inform. 3 (2), 94
99. Available from: https://doi.org/10.3993/jfbi09201006. Liese, W., Kohl, M., 2015. Bamboo: The Plant and Its Uses. Springer International Publishing, Switzerland. Liu, Y., Hu, H., 2008. X-ray diffraction study of bamboo fibers treated with NaOH. Fibre Polym. 9 (6), 735
739.

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Liu, G., Zhang, H., Hu, X., 2004. The dyeing behaviours of bamboo fibre with reactive dyes and the product development. In: Proceedings of the Textile Institute 83rd World Conference, Shanghai, China. Liu, L., Qian, Q.W.L.C.J., Yu, J., 2011. Modification of natural bamboo fibres for textile applications. Fibres Polym. 12 (1), 95
103. Londono, X.C., Camayo, G.C., Riano, N.M., et al., 2002. Characterization of the anatomy of Guadua angustifolia (Poaceae: Bambusoideae) culms. Bamboo Sci. Cult. 16, 18
31. Majumdar, A., Arora, S., 2015. Bamboo fibres in textile applications. Bamboos India, Publisher: ENVIS. Cent. Forestry 286
304. Munro, W., 1868. A monograph of the Bambusaceae, including description of all the species. Trans. Linn. Soc. Lond. 26 (1), 1
157. Nayak, L., Mishra, S.P., 2016. Prospect of bamboo as a renewable textile fibre, historical overview, labeling, controversies and regulation. Fashion and Textiles. Springer Open Journal, pp. 1
23. Ohrnberger, D., 1999. The Bamboos of the World: Bambus Buch. Elsevier Science, Amsterdam, The Netherlands. Qiu, G.X., Shen, Y.K., Li, D.Y., Wang, Z.W., Huang, Q.M., Yang, D.D., et al., 1992. Bamboo in sub-tropical eastern China. In: Long, S.P., Jones, M.B., Roberts, M.J. (Eds.), Primary Productivity of Grass Ecosystems of the Tropics and Subtropics. Chapman and Hall, London, pp. 159
188. Available from: http://www.lewisbamboo. com/pages/bamboo-basics. Ray, A.K., Mondal, S., Das, S.K., Ramachandrarao, P., 2005. Bamboo—a functionally graded composite- correlation between microstructure and mechanical strength. J. Mater. Sci. 40 (19), 5249
5253. Rodie, J.B., 2008. Going green: beyond marketing hype. Text. World November/ December 2008. Available from: http://www.textileworld.com. Scurlock, J.M.O., Dayton, D.C., Hames, B., 2000. Bamboo: an overlooked biomass resource? Environmental Science Division. Publication No. 4963. Prepared for the U.S. Department of Energy, USA. Seethalakshmi, K.K., Muktesh-Kumar, M.S., Pillai, K.S., Sarojam, N., 1998. Bamboos of India, a compendium, Kerala Forest Research Institute, India and International Network for Bamboo and Rattan, China. ISBN 81
86247-25-4. Sharma, Y.M.L., 1980. Bamboo in the Asia-Pacific region. In: G. Lessard, A. Chouinard (Eds.), Bamboo Research in Asia, Proceedings of a Workshop held in Singapore 28
30 May, 1980. International Development Research Centre, International Unit of Forestry Research Organisation, Ottawa, Canada, 99
120. Tadesse, M., 2006. Bamboo and rattan trade development in Ethiopia. In: Proceedings of Bamboo for the Environment, Development and Trade, International Bamboo workshop, 23rd October 2006, Wuyishan City, Fujian, China, pub. INBAR, 17
24. Takahashi, J., 2006. Bamboo in Latin America: past, present and future. In: Proceedings of Bamboo for the Environment, Development and Trade, International Bamboo Workshop, 23rd October 2006, Wuyishan City, Fujian, China, pub. INBAR, 4
12. Trujillo, E., 2014. Polymer composite materials based on bamboo fibres. PhD Thesis, KU Leuven, Leuven. Van der Lugt, P., 2017. Booming bamboo. Naarden. Materia Exhibitions B.V, The Netherlands. Yao, W., Zhang, W., 2011. Research on manufacturing technology and application of natural bamboo fibre. In: Fourth International Conference on Intelligent Computation Technology and Automation, IEEE, vol. 2. Yu, W.K., Chung, K.F., Chan, S.L., 2003. Column buckling of structural bamboo. Eng. Struct. 25, 755
768.

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Yue, Y., 2012. Bamboo value chain in China and the importance of research for value chain development, International Centre for Bamboo and Rattan, SFA China, the 9th WBC, Antwerp, Belgium, April 12. Zakikhani, P., Zahari, R., Sultan, M.T.H., Majid, D.L., 2014. Extraction and preparation of bamboo fibre-reinforced composites. Mater. Des. 63, 20
828. Zupin, Z., Dimitrovski, K., 2010. Mechanical properties of fabrics from cotton and biodegradable yarns bamboo, SPF, PLA in weft. Woven Fabr. Eng. IntechOpen, Polona Dobnik Dubrovski, pp. 25
46.

Further reading Panda, H., 2011. Bamboo Plantation and Utilization Handbook. Asia Pacific Business Press Inc.

CHAPTER SEVEN

Antimicrobial properties of bamboo, bamboo fibres, and fabrics

7.1 Introduction The growing concern of consumers about the dangers of microbes and bacteria and the spreading of diseases has led the development of new markets for antimicrobial textiles particularly in hospitals and skin-contact products. Antimicrobial textiles are functionally active textiles, which may kill the microorganisms or inhibit their growth. These antimicrobial textiles are used in a variety of applications ranging from households to commercial including air filters, food packaging, health care, hygiene, medical, sportswear, storage, ventilation, and water purification systems. Public awareness of antimicrobial textiles and growth in commercial opportunities has been observed during the past few years (Gulati et al., 2021). The large surface area and ability to retain moisture of textile structures enable microorganisms’ growth, which causes a range of undesirable effects, not only on the textile itself, but also on the user. Due to the public health awareness of the pathogenic effects on personal hygiene and associated health risks, over the last few years, intensive research has been promoted in order to minimise microbes’ growth on textiles (Morais et al., 2016). The antimicrobial properties of functional fabrics are valuable for two reasons. They serve as a prophylactic measure to reduce the risk of infection or the spreading of diseases and as preventive measures against the development of odours. Antimicrobial finished fabric is that which inhibits the growth of bacteria or germs and controls the spread of diseases and reduces the chances of infection. Bamboo is well known for its medicinal values as its roots and leaves have been used medicinally. Studies have also revealed that bamboo leaves have antioxidant, anticancer, and antibiotic properties (Lee et al., 2001; Zhang et al., 2008). In these studies, various active compounds were Bamboo Fibres. DOI: https://doi.org/10.1016/B978-0-323-85782-6.00002-7

© 2023 Elsevier Ltd. All rights reserved.

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separated from the leaves, such as flavones, glycosides, phenolic acids, coumarin lactones, anthraquinones, and amino acids (Lu et al., 2005; Jiao et al., 2007; Hasegawa et al., 2008; Zhang et al., 2006; Kurokawa et al., 2006). In addition, 2,6-dimethoxy-p-benzoquinone obtained from the skin of the bamboo was found to have antibiotic activities, as were two chitin-binding peptides: Pp-AMP1 and Pp-AMP2, that were isolated from bamboo shoots (Nishina et al., 1991; Fujimura et al., 2005). Tricin and taxifolin, found in the bamboo sheath, reportedly have antioxidant activity (Katsuzaki et al., 1999). Recently bamboo clothing has entered the clothing industry with claims that bamboo fabrics are antibacterial, antimicrobial, and have antideodorisation properties etc. Regenerated bamboo viscose fibre is produced from natural bamboo through a hydrolysis alkalisation process. The antibacterial agent in the bamboo is identified as “KUN” which belongs to hydroxyl functional group ( OH) (Afrin et al., 2012). Interestingly, bamboo has been reported as naturally antibacterial and this property is expected to be retained if the fibres are extracted in their natural form along with some nonfibrous trace elements. Consequently, bacteria or mildew get killed on a bamboo fabric unlike on other cellulosic cousins of bamboo which facilitate their propagation, leading to foul odour and even fibre degradation in the worse cases. In fact, bamboo was used in ancient Chinese medicine owing to this property. Since most of the existing natural and synthetic fibres do not have antibacterial activity, rather some promote bacteria growth (Budama et al., 2013; Comlekcioglu et al., 2017; Gupta and Bhaumik, 2007; Ibrahim et al., 2011; Morais et al., 2016; Shalini and Anitha, 2016), extraction of NBFs with such activity is of great interest. A study conducted by the National Textile Inspection Association, China (NTIA), Shanghai, Microorganism Research Institute, and Japan Textile Inspection Association showed that even after 50 washes, bamboo fabric possessed a considerable antibacterial property. Moreover, being natural, it has no potential threat of causing skin allergy as in the case of chemical antimicrobial finishes (Das, 2014). Studies have concluded that extracts from bamboo leaves have shown antibacterial activity against some bacteria (Singh et al., 2010). Tanaka et al. (2011) investigated the inhibition of extract from Moso bamboo shoot skins against Staphylococcus aureus and reported that it exhibited antibacterial activity. Moreover, different parts of bamboo plants (roots, leaves, skins) have already been used for manufacturing preservatives and medicinal products (Keski-Saari et al., 2008; Nirmala et al., 2014; Quitain

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171

et al., 2004; Tanaka et al., 2011, 2013, 2014). These studies on multiple bamboo species confirmed that the plants possess antibacterial activity. It was also shown that bamboo culms exhibited very high antibacterial property and fibres are mainly extracted from the culms (Tanaka et al., 2014). Therefore, it can be proposed that natural fibres from bamboo have the potential to retain antibacterial compounds, for example, phenolic compounds and lipids (Gokarneshan et al., 2017; Mishra et al., 2012; Nirmala et al., 2014; Quitain et al., 2004), and thus antibacterial properties. Another justification for the inherent bacterial-resistance of bamboo is the presence of chlorophyll and sodium copper chlorophyllin which perform the function of antibiotics and deodorisation. This too has been verified by the Japan Textile Inspection Association. Some studies have indicated that NBFs extracted from the bamboo will have antibacterial properties (Afrin et al., 2012, 2014; Chen et al., 2015; Waite, 2009; Zupin and Dimitrovski, 2010).

7.2 Antibacterial properties of bamboo extract The most important antibacterial property of bamboo is carried from its plant form to fibre form. Bamboo plant contains a bacteriostasis bioagent, “bamboo-kun”, that is, 2.6-bimethoxy-p-benzoquinone, which imparts the plant natural resistance to microbes; and the protein dendrocin that has highly distinctive fungal resistance (Lipp-Symonowicz et al., 2011). These substances are bound very firmly to the bamboo cellulose molecule and are hence retained even after mechanical processing. A study on the antibacterial activity of plant extracts from Australian-grown bamboo (Phyllostachys pubescens) was undertaken by Afrin et al. (2012). Bamboo extracts were made using water, dimethyl sulfoxide (DMSO), and dioxane and their antibacterial properties were compared against a Gram-negative bacteria, Escherichia coli. The study revealed that the bamboo extracts in water could not inhibit or kill the growth of E. coli. But, bamboo extracts in 20% aqueous DMSO showed the inhibition of bacterial growth. Although the colony size was significantly larger on the control (DMSO) plates than on the bamboo extracts plates, the colony number was higher in the bamboo extracts plates than the control plates (Fig. 7.1). Further, the bamboo extract in an aqueous dioxane solution after removal of dioxane (milled wood lignin, MWL) was diluted with water

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Figure 7.1 Images of bacterial plaques plated with (A) 20% DMSO and (B) bamboo extracts in 20% DMSO. Adapted from Afrin, T., Tsuzuki, T., Kanwar, R.K., Wang, X., 2012. The origin of the antibacterial property of bamboo. J. Text. Inst. 103 (8), 844 849.

Figure 7.2 Images of bacterial plaques that were plated with (A) sterilised deionised water and (B) 100%, (C) 50%, (D) 25%, (E) 10%, and (F) 5% MWL in sterile water. Adapted from Afrin, T., Tsuzuki, T., Kanwar, R.K., Wang, X., 2012. The origin of the antibacterial property of bamboo. J. Text. Inst. 103 (8), 844 849.

into v/v 100% (undiluted), 50%, 25%, 10%, and 5% and their antibacterial properties were tested against E. coli. It was observed that the control plates had a full lawn of bacteria, whereas no bacterial colony was evident on the plates with bamboo extracts (Fig. 7.2). It was demonstrated that at the lowest concentration, 5% of bamboo extract in water was sufficient to achieve 100% sterilisation rate against strong bacteria such as E. coli. Since dioxane was evaporated after extracting bamboo in aqueous dioxane (dioxane:water 5 9:1), there was no effect of dioxane on the antibacterial activity. Therefore, it is evident that the bamboo (P. pubescens) lignin contains strong antibacterial compounds.

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Hence, from the results of the study, the authors proved that the antibacterial agents of P. pubescens were responsible for the antimicrobial activity of bamboo and they were located in lignin, not in hemicelluloses. These antibacterial compounds which are insoluble in water, resided in lignin which is also almost insoluble in water (Walker, 2006). It was also proved from their chemical constituent analysis that bamboo powder contained a high amount of lignin (28%). It may be noted that lignin is an aromatic gummy material composed of guaiacyl, syringyl, and p-hydroxyphenyl functional groups, as well as pcoumaric acid that is esterified in the polymer systems, and many researchers have depicted the antibiotic effects of synthetic compounds having guaiacyl and syringyl structures that are related to the structure of native lignin. As such, the existence of the aromatic and phenolic functional groups in lignin may be responsible for the antibacterial property of P. pubescens (Higuchi, 1969; Zemek et al., 1979). It was strongly opined that lignin components need to be retained in the fibres while processing raw bamboo into fibre in order to produce bamboo fabrics with antibacterial properties (Afrin et al., 2012). However, in the production of regenerated bamboo fibres where bamboo plants are dissolved in solvents like alkali and carbon disulphide to convert celluloserich fibres (Rydholm, 1965), the functional chemical compounds like lignin are lost. Hence, there is a strong need for the development of new fibre production methods that enable the retention of lignin in the final fibre products.

7.3 Antimicrobial properties of bamboo fibres and fabrics It is already known that mechanically processed bamboo fibres can resist pest and fungi-infestation as they maintain the innate antimicrobial property of the bamboo plants due to the presence of bamboo-kun and dendrocin. However, the fibres obtained from regenerated cellulose of bamboo plant fail to retain them. Despite this fact, several researchers still state bamboo viscose fibres exhibit antibacterial, antifungal, and UV proˇ tection properties (Pavko-Cuden and Kupljenik, 2012). An attempt was made to evaluate the antimicrobial property of 100% bamboo fabrics from bamboo viscose fibres and the leaf and stem extract of bamboo for the

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purpose of developing antimicrobial finish for cotton fabrics using agar diffusion method by Chandrasekhara (2019). Bamboo fabric which was manufactured on CCI SEDIT 2, single rigid rapier loom with the geometrical parameters (Table 7.1) was selected for the purpose. Plain bleached cotton fabric was used for the application of antimicrobial finish and its geometrical parameters are presented in Table 7.1.

7.3.1 Bamboo plant extraction The bamboo plants were collected from the garden and were sorted out into stem, leaves, and roots, and then dried in shade for a week. The plant materials were powdered into coarse particles with the help of kitchen blender, as shown in Fig. 7.3.

Table 7.1 Geometrical parameters of bamboo and cotton fabrics. Sl. no. Specification Bamboo fabric

1 2 3 4 5 6 7

EPI 3 PPI Yarn count (Ne) Fabric weight (GSM) Type of weave Fabric condition Cover factor (K) Thickness (mm)

Figure 7.3 Bamboo powder.

68 3 63 26 3 24 233 Plain Bleached 24.85 0.462

Cotton fabric

68 3 60 28 3 28 194 Plain Bleached 23.82 0.549

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Figure 7.4 Microbes: (A) Staphylococcus aureus; (B) Escherichia coli.

7.3.2 Bacterial strains S. aureus ATCC 6538, as a representative of Gram-positive, and E. coli ATCC 11230, as a representative of Gram-negative bacteria (Fig. 7.4A and B), were used for the study; both were reference strains used for antimicrobial susceptibility testing according to AATCC standards. Pure strains were obtained from microbial type culture collection (MTCC), Chandigarh, India, cultured on nutrient agar (Hi-Media, Mumbai, India) and incubated aerobically at 37 C, as shown in Fig. 7.4A and B.

7.3.3 Methodology used 7.3.3.1 Collection of plant material The plant materials were powdered into fine particles with the help of a kitchen blender. The powdered plant materials were used to prepare the plant extract using organic solvents of different polarities. 7.3.3.2 Extraction The bamboo plant leaves and stems were collected and washed in water and dried under shade for 1 week. The dried leaves and stems were collected and made into a fine powder using a kitchen blender. The powder was mixed with water and heated to get the decoction of bamboo extract. The bamboo leaf and stem extracts from water were separated using the evaporation (hot water) method. The solution was filtered off with filter paper and heated up until it turned to powder form.

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7.3.3.3 Process • Powder: 10 g • Water: 100 mL • Time: 1 hour • Temperature: 100 C 7.3.3.4 Finishing The cotton fabric was treated with bamboo plant extract of 10% concentration using the material to liquor ratio of 1:30. Cotton fabric was treated in the temperature range of 40 C 50 C for 15 30 minutes using 8% glutaraldehyde as a cross-linking agent and 2% sodium hypophosphite as a catalyst. Then the temperature was gradually raised to reach 60 C 80 C and the material was treated for another 30 minutes and cured at 100 C 120 C.

7.3.4 Antimicrobial activity of fabrics 7.3.4.1 Preparation of inoculum MTCC strains of E. coli and S. aureus were prepared in respective lysogeny broth (LB) and nutrient broth, followed by the required period of incubation of 24 and 48 hours, respectively, for further studies. The bacterial culture and nutrient agar used for the study are shown in Fig. 7.5A and B.

Figure 7.5 (A) Bacterial culture and (B) nutrient agar.

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7.3.4.2 Inoculation The culture method employed here was the pour plate method. The inoculum was seeded at the centre of the Petri plate and the media was poured and rotated in clockwise and anticlockwise directions. The plate was allowed to stand for solidification. All the steps were carried under sterile conditions.

7.3.5 Evaluation of antimicrobial activity (qualitative agar diffusion test AATCC 147-2004) Evaluation of antimicrobial activity was carried out for untreated and treated fabric samples qualitatively by agar diffusion test AATCC 147-2004 (American Association of Textile Chemists and Colourists). Bacterial cells were inoculated on nutrient agar plates over which textile samples were laid for intimate contact. The plates were then incubated at 37 C for 18 24 hours and examined for growth of bacteria directly underneath the fabrics and immediately around the edges of the fabrics (zone of inhibition). No bacterial growth directly underneath the fabric sample indicates the presence of antimicrobial activity. The inhibition zones were measured in terms of the distance in millimetres from the edge of the disc to the zone edge. Measuring the zone size enables the strain to be categorised as sensitive or resistant. The autoclave and bacteriological incubator used are shown in Figs 7.6 and 7.7. 7.3.5.1 Bacteriological incubator A bacteriological incubator (Fig. 7.7) is similar to an oven. The temperature of the incubator is maintained at the desired level by an automatic device called a thermostat which switches the connection off when the temperature reaches the point for which the thermostat is set and turns it on again when the temperature falls slightly below that point. 7.3.5.2 Laminar air flow unit A laminar air flow system is used for reducing the danger of infection while working with pathogenic microbes, as shown in Fig. 7.8. The laminar air flow works on the principle of the application of fibrous filters in air filtration. In this system, the air of a closed cabinet or room is made to pass through a high efficiency particulate filter.

178

Figure 7.6 Autoclave.

Figure 7.7 Bacteriological incubator.

Bamboo Fibres

Antimicrobial properties of bamboo, bamboo fibres, and fabrics

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Figure 7.8 Laminar air flow unit.

Figure 7.9 Micropipette.

7.3.5.3 Micropipette A pipette is a laboratory tool used to transport a measured volume of liquid. A pipette that dispenses between 1 and 1000 µL is termed as a micropipette, as shown in Fig. 7.9 and Table 7.2. The antimicrobial activity of bamboo fabric and the zone of inhibition are shown in Fig. 7.10 and Table 7.3. From the results it was observed that the bamboo fabrics exhibit excellent antimicrobial activity. The bamboo fabric samples were subjected to several wash cycles (10 cycles). The fabric samples were washed using standard detergent (3% on the weight of fabric (OWF)) at 40 C in an automatic washing machine using method ISO 6330-1948 E. The zone of inhibition of bamboo fabric subjected to S. aureus bacteria treatment showed 20 mm before and after wash, and for E. coli the zone of inhibition measured was 20 mm before and after wash. It was observed that the

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Table 7.2 Zone of inhibition for bamboo fabrics. Sl. no Bamboo fabric

1 2

Before wash After wash

Zone of inhibition (mm) S. aureus

E. coli

20 20

18 18

Figure 7.10 Antimicrobial activity of bamboo fabrics.

Table 7.3 Zone of inhibition of cotton fabrics treated with bamboo extract. Sl. no Fabric Zone of inhibition in mm Leaf

1 2 3.

Untreated bleached cotton fabric Treated (before wash) Treated (after wash)

Stem

S. aureus

E. coli

S. aureus

E. coli

00 15 10

00 12 8

00 20 16

00 18 12

bamboo fabric not only prevented the growth of the microorganism but also retained the antimicrobial property even after multiple washes.

7.3.6 Antimicrobial activity of cotton fabric treated with bamboo extract In the above study the bleached cotton fabric was treated with natural antimicrobial agent extracted from the leaf and stem of bamboo plant. Photographs in Fig. 7.11 show a clear zone of inhibition around the test fabrics and also a complete absence of bacterial growth underneath the fabric specimen. From the test results shown in Table 7.3 it was understood that the antimicrobial activity of the fabrics treated with bamboo stem extract was greater than those treated with the bamboo leaf extract. The active compound applied on cotton fabric samples was attached to

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Figure 7.11 Cotton fabric sample treated with bamboo extract in contact with bacteria culture on nutrient ager.

the fibre successfully by cross linking and this prevented leaching out, due to which a small zone was formed. Results shown in the Table 7.3 and Fig. 7.11 indicated a slight reduction of antimicrobial activity after five washes. For leaf extract the zone was reduced from 15 to 12 mm against S. aureus and 12 to 8 mm against E. coli. Also, for stem extract it was reduced from 20 to 16 mm and 18 to 12 mm. Among the bacterial strains used in this study the Gram-positive bacteria showed less resistance to antibacterial activity than Gram-negative bacteria. From this study, the author revealed that the woven bamboo viscose fabric showed a clear zone of inhibition and confirmed the antimicrobial activity of bamboo fabrics. In addition, a complete absence of microbial growth underneath the treated cotton fabric and clear zone of inhibition around the test fabrics was observed. The antimicrobial activity of the fabrics treated with bamboo stem extract was greater than bamboo leaf extract. The treated cotton fabric which was subjected to multiple wash cycles showed a slight reduction of antimicrobial activity after five washes. Also, it was observed that the cotton fabric not only prevented the growth of the microorganisms but also retained the antimicrobial property through multiple washes (10 cycles) due to the effective bonding of active

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substance to cotton fabric. Gram-negative bacteria (E. coli) were found to be more resistant to antibacterial activity than Gram-positive (S. aureus) bacteria. Chen and Guo (2007) compared the antibacterial properties of a bamboo viscose jersey with that of a common wood pulp jersey and declared the former to possess natural antibacterial effects. However, they attributed this effect to the hollow structure of the bamboo viscose fibres that facilitates absorption of humidity followed by its evaporation. An investigation and comparison of antibacterial properties of bamboo plants, natural bamboo fibres (NBFs), and commercial bamboo viscose fabrics has been reported by Rocky (2019). The researcher conducted a detailed study on the antibacterial activity of 12 commercial bamboo viscose textiles, conventional rayon fabric, raw cotton fibres and fabric, four bamboo plant species, and 12 NBF samples using S. aureus and Klebsiella pneumoniae. The accuracy and efficacy of test methods were investigated and modified for antibacterial assessment. The spectrophotometric method was found to be less effective when bacterial reduction was not very high as bamboo and NBF samples with low antibacterial/antimicrobial activity were tested. The revised viable plate counting technique was very consistent and effective when tested materials were in fibre, fabric or crushed forms and tested in sterilised and nonsterilised states. Percentage reduction of bacteria by bamboo viscose textiles was tested where antibacterial activity was found in only one out of 12 products. A majority of the specimens from bamboo plant species and NBFs showed a measurable percentage reduction of bacteria against K. pneumoniae (8% 95%) but had poor results against S. aureus (3% 50%). These results were interpreted to be due to the presence of both bacteria-killing and -promoting compounds found in the bamboo plant specimens and the NBFs. Overall, NBFs showed higher reduction of bacteria than raw bamboo specimens. However, due to the presence of bacteria from the environment, some NBF specimens showed a greater number of colonies and thus a negative reduction of bacteria when sterilisation of the fibre specimens was not performed prior to the experiment protocol. From this study, the researcher concluded that the antibacterial properties by bamboo viscose were not attributed to the bamboo starting material, rather they were due to special treatments or through processing chemicals. Without these additional treatments, products from bamboo viscose would not offer bacterial protection. On the other hand, microscopic images revealed that there were some nonfibrous elements with

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183

NBFs from four bamboo species. All four bamboo species and their NBFs exhibited antibacterial activity to a certain degree, at least at a low level. The activity was stronger against K. pneumoniae than against S. aureus. Results also suggested that though raw bamboo had antibacterial compounds, it may have bacteria-promoting substances at the same time that caused higher growth of bacteria if nonsterilised samples were tested. The bacterial inhibition was higher for sterilised bamboo and NBF samples. However, the author opined that further investigations were needed to confirm if bamboo species and its NBFs had antibacterial activity and such activity was not contributed to processing chemicals. Moreover, the antibacterial property of such materials needs to be tested against other bacteria species. A study was undertaken to investigate and compare the antimicrobial properties of 100% regenerated bamboo, 100% viscose rayon, and an untreated cotton fabric (used as the control or reference) to determine whether the antimicrobial properties of the two regenerated cellulose fabrics differed from that of the cotton, a fabric well known for not having any antibacterial properties (Gericke and Van der Pol, 2011). Three single jersey knitted fabrics, cotton, viscose rayon, and regenerated bamboo yarns of similar counts were used. The fabrics were finished to a weight of 170 ( 6 2) g/m2 and bleached. The antibacterial properties of the fabrics were compared by measuring antimicrobial activity as per the ASTM Designation E 2149-01 test method. The bacteria used in the study were Staphylococcus epidermidis, a Grampositive bacterium, and the Gram-negative bacterium E. coli. The antimicrobial activity of the three different samples was determined separately for both Gram-positive bacteria and Gram-negative bacteria. The uninhibited microbial growth of each culture on an agar plate after no contact with a fabric sample was recorded (119 colonies for S. epidermidis and 129 colonies for E. coli). The antibacterial properties of the fabrics tested were clearly demonstrated when the average number of colonies counted on the agar plates after incubation was compared to the reference values. A low number demonstrated a strong antibacterial effect. It was found that the average number of E. coli colonies that formed after contact with the regenerated bamboo fabric was 56, for viscose fabric it was 55, and for cotton 164. This indicated an increase in the number of colonies after contact with the cotton (i.e., it had no antibacterial effect) and a reduction of 56.6% and 57.4% in the cases of the regenerated bamboo and viscose rayon fabrics, respectively. Similarly, the average number

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of S. epidermidis colonies counted on the agar plates after incubation following contact with the regenerated bamboo fabric was 30, it was 53 for viscose and 127 for cotton fabric. Here again, the cotton fabric again did not show any antibacterial properties, but there was 74.8% reduction in bacteria in regenerated bamboo and 59.5% reduction in viscose rayon fabrics. The results of the study clearly indicated that cotton fabric did not show any antibacterial activity with no significant difference (or reduction) in the number of colonies formed after exposure, however, the numbers of colonies formed after contact with the regenerated bamboo and viscose rayon fabrics were significantly lower than those counted on the control agar plates. This confirmed the bactericidal effect of the regenerated bamboo fabric and the viscose rayon fabric on the Gram-positive and the Gram-negative bacteria. However, only a percentage of the bacteria was killed suggesting that regenerated bamboo fibres or fabrics prevent the bacterial growth was thus not substantiated by the results obtained in this study. The researchers also did not rule out the presence of residual chemical such as sulphur that might still be present on regenerated-bamboo and viscose rayon fibres after being spun in a hydrogen sulphate bath during fibre manufacturing. As mentioned, sulphur is known to have an antimicrobial effect on microbes (Taj and Baqai, 2007; Usseglio-Tomasset, 2010), the authors were able to identify the traces of sulphur on all three samples, but doubted whether these small amounts were enough to have an antimicrobial effect; this could be a subject for further research. Mishra et al. (2012) also observed the antibacterial property of bamboo viscose fabric to be superior to that of a cotton fabric. They justified this behaviour due to the interaction of phenolic compounds still present in the bamboo viscose fibres with the bacterial membrane. Interestingly, attempts are being made for the antibacterial modification of bamboo viscose fibres using Ag, Cu, or ZnO nanoparticles to ultimately obtain a grafted composite fabric out of it. Chitosan, a natural biopolymer, has also been explored for the same with an intention to have a safe antibacterial agent for the apparel textile material (Sheikh, 2013). A study on antibacterial and antifungal properties of socks made out of bamboo fibres compared with the socks those made from 100% cotton, 100% viscose, and 50%/50% bamboo/cotton (before and after wear of socks) has been reported (Gomathi, 2008). Yarns from 100% bamboo, 100% cotton, 100% viscose, and 50:50 bamboo/cotton blended yarns were knitted into socks and the grey knitted socks were given

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185

pretreatment by using appropriate recipes. After bleaching microbial testing was conducted. In order to assess the resistance to survivability of bacteria, a sample swatch survival test was carried out using two test organisms (E. coli and S. aureus). The survival of test bacterial concentration in all the four samples was assessed over time, every 24 hours from 24 to 120 hours of incubation at 37 C. The survival test was also carried out on used socks. The survival test results are presented in Tables 7.4 and 7.5. The results of the above indicated that the survivability of bacteria on cotton was more prominent compared to rayon and bamboo. The survivability of bacteria on 50%/50% bamboo/cotton was similar to bamboo. The general survivability of E. coli was less compared to S. aureus. Hence, it was opined that bamboo potentially resisted the colonisation of both E. coli and S. aureus from the second day of incubation, which was an indication of antimicrobial resistance characteristics of bamboo towards bacterial growth. To determine the resistance of samples towards the survivability of fungi, a sample swatch survival test was carried out using two test organisms (Aspergillus niger and Trichoderma viridae). Starting from 48 to 260 hours of incubation at 27 C, the survival of the known fungi in all the four samples was assessed over a constant period of time, every 24 hours. The results of this test indicated that the survivability of fungi was more or less the same on all the four test samples (Table 7.6). Hence, it was concluded that the antifungal resistance of bamboo, cotton, and 50%/50% bamboo/cotton were equally efficient, when compared with rayon. All the four samples supported the growth of T. viridae and resisted the growth of A. niger. Further, the growth rate of bacteria (E. coli and S. aureus) and fungi (T. viridae and A. niger) were compared when grown on the four test samples as substrates. The results proved that the growth rate of organisms on bamboo as a substrate was less, when compared with cotton and rayon (Table 7.7). The natural antimicrobial effect of bamboo did not allow the multiplication of bacteria and fungi and ultimately proved to be both bacteriostatic and fungistatic. The growth rate of microorganisms on 100% cotton was the same as on rayon. On 50%/50% bamboo/cotton, the growth rate of organism was less when compared with cotton. The inhibitory effect of bamboo, cotton, rayon, and 50%/50% bamboo/cotton samples towards bacteria (E. coli and S. aureus) and fungi (T. viridae and A. niger) were compared based on a time course analysis,

Table 7.4 Survival of bacteria Escherichia coli (before and after wear of socks). Samples (socks) Initial 0.1 mL No. of colonies (103 cfu/mL) inocula (before wear)

100% Bamboo 21 50%/50% Bamboo/cotton 100% Cotton 100% Viscose TNTC, Too numerous to count. a 5 10 cfu/mL.

a

No. of colonies (103 cfu/mL) (after wear)

Day-1

Day-2

Day-3

Day-4

Day-5

Day-1

Day-2

Day-3

Day-4

Day-5

6 10 57 TNTC

— — 38 220

— — 5 103

— — — 50

— — — 43

TNTC TNTC TNTC TNTC

228 TNTC TNTC TNTC

146 160 200 TNTC

50 70 90 TNTC

— 7 25 250

Table 7.5 Survival of bacteria Staphylococcus aureus (before and after wear of socks). Samples (socks) Initial 0.1 mL No. of colonies (103 cfu/mL) inocula (before wear)

100% Bamboo 33 50%/50% Bamboo/cotton 100% Cotton 100% Viscose TNTC, too numerous to count. a 5 10 cfu/mL.

a

No. of colonies (103 cfu/mL) (after wear)

Day-1

Day-2

Day-3 Day-4 Day-5 Day-1

Day-2

Day-3

Day-4

Day-5

200 250 TNTC TNTC

16 30 280 TNTC

— — 20 230

TNTC TNTC TNTC TNTC

270 280 TNTC TNTC

— 150 220 TNTC

— — 100 TNTC

— — — 140

— — — 28

TNTC TNTC TNTC TNTC

Table 7.6 Survival of fungi Aspergillus niger and Trichoderma viridae. Survival of fungi Aspergillus niger Samples (socks) Initial 0.1 mL No. of colonies (102 cfu/mL) inocula (before wear) Day-1

100% Bamboo 50%/50% Bamboo/ cotton 100% Cotton 100% Viscose a

105 cfu/ml.

7

a

Day-2

Day-3

Day-4

Day-5

5 4

2 —

— —

— —

— —

5 7

1 5

— 8

— 13

— 14

Initial 0.1 mL inocula

19

a

Survival of fungi - Trichoderma viridae No. of colonies (102 cfu/mL) (before wear) Day-1

Day-2

Day-3

Day-4

Day-5

34 29

35 28

28 20

23 19

20 19

38 39

38 30

35 34

35 36

28 20

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Antimicrobial properties of bamboo, bamboo fibres, and fabrics

Table 7.7 Comparison of the growth rate of bacteria and fungi. S. No. Sample Bacterial growth rate Fungal growth rate E. coli bacteria

1 2 3 4

100% Bamboo 100% Cotton 50%/50% Bamboo/ cotton 100% Viscose

1

S. aureus bacteria

2

A. niger Fungi 1

T. viridae fungi 2

1 11 1

11 11 1 11

1 11 1

11 11 1 11 1

11 1

11 1

11

11 1

Note: 1 , moderate growth rate; 11, high growth rate; 11 1 , very high growth rate.

and it was observed that E. coli was able to survive only up to 24 hours on bamboo and 50%/50% bamboo/cotton, whereas on rayon it was able to survive for up to 120 hours. It was also observed that E. coli was able to survive for up to 72 hours on 100% cotton. It was also observed that S. aureus was able to survive on bamboo up to 48 hours and 50%/50% bamboo/cotton, whereas on 100% cotton it was able to survive for up to 72 hours. It was also observed that S. aureus was able to survive on rayon up to 120 hours. On the contrary, some studies have demonstrated that NBFs used in textile manufacturing do not possess any antibacterial activity against the attack by bacteria and fungi. These tendencies were determined with the dynamic test method for evaluating antibacterial activity and were compared with the bacterial and fungal resistance of other textile fibres, such as cotton, jute, flax, ramie, and regenerated bamboo fibre. The bacteria studied were E. coli (8099) and S. aureus (ATCC 6538), and the fungal species was Candida albicans (ATCC 10231). The relationships between the bacteriostatic ability of NBF and its physical state, hygroscopicity, and extractives were tested to explore the possible influencing factors (Xi et al., 2013). NBFs used in the study were produced from Neosinocalamus affinis. The antibacterial activity was tested with a shake flask test. The effect of the bamboo’s physical state on the antibacterial properties of NBF was investigated. Untreated cotton was used as the negative control sample, and the antibacterial cotton was used as the positive control sample. The microbial resistance properties were evaluated by determining the bacteriostatic rate using Eq. (7.1). The effect of extracts on the antibacterial properties of NBFs was also investigated. The bacterial growth condition in the flasks containing the extracted and unextracted NBF was compared. The effect of the extracts was evaluated by determining the antibacterial

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efficiency using Eq. (7.2). Negative numbers in the results were represented as 0, Y 5 Wt

Qt=Wt 3 100%

(7.1)

where Y is the bacteriostatic rate (%), Wt is the average CFU (colonyforming unit) per millilitre for the flask containing the negative control sample after 18 hours contact, and Qt is the average CFU per millilitre for the flask containing the test sample after 18 hours contact.
E 5 1 2 Dt =D0 3 100% (7.2) where E is the antibacterial efficiency (%), Dt is the average CFU per millilitre for the flask containing the extracted NBF after 18 hours contact, and D0 is the average CFU per millilitre for the flask containing the untreated NBF after 18 hours contact. The results of the antibacterial tests are shown in Table 7.8. The untreated cotton as the negative control sample was not effective against bacteria, while the antibacterial cotton was very effective against all test bacteria, with a bacteriostatic rate of over 99% against E. coli and 100% against S. aureus and C. albicans, indicating the dependability of this test. The results showed that NBF was not effective against E. coli, S. aureus, and C. albicans, as the bacteriostatic rate against all of them was 0. From their investigations, the earlier claims that NBF had inherent antibacterial properties as a result of “bamboo-kun” could not be substantiated. By comparison, the bacteriostatic rate of ramie against S. aureus was over 90%, and that of regenerated bamboo fibre was 75.8%. Jute and flax had bacteriostatic rates against C. albicans of 48% and 8.7%, respectively. Table 7.8 Antibacterial activity of bamboo and other fibres. Fibre Type Bacteriostatic rate (%)

Untreated cotton NBF Jute fibre Flax fibre Ramie fibre RBF Antibacterial cotton

E. coli

S. aureus

C. albicans

0 0 (268.9) 0 (215.9) 0 (245.0) 24.3 41.4 .99

0 0 (213.2) 0 (248.4) 0 (288.8) 90.2 75.8 100

0 0 (241.3) 48 8.7 54 0 (212.8) 100

NBF, Natural bamboo fibre; RBF, regenerated bamboo fibre. Source: Adapted from Xi, L., Qin, D., An, X., Wang, G., 2013. Resistance of natural bamboo fibre to microorganisms, and factors that may affect such resistance. Bioresources 8 (4), 6501 6509.

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The authors concluded that NBFs do not exhibit natural antibacterial properties, as compared with natural cotton bacteriostatic rates against the bacteria were all zero. The physical state did not impact the natural resistance of NBF to the bacteria and the fungus. The resistance of the plant fibre could be related to its hygroscopicity, and some extraction methods could improve the ability of natural bamboo to resist microorganisms.

7.4 Summary In this chapter, an attempt has been made to explain the antimicrobial and antibacterial properties of bamboo, bamboo fibres, and the fabrics made of them. It has been demonstrated that bamboo leaves, shavings, and shoots have many components, such as flavonoids, phenolic acids, polysaccharide, anthraquinones, coumarins, and peptides. Anthraquinones and coumarins are two components that exhibit strong antibacterial and bactericidal activities. Various studies conducted on antibacterial characteristics of bamboo extracts, NBFs, and regenerated bamboo fibres have been investigated and their results have been discussed in detail. It was observed in most of the studies that the inherent antimicrobial properties of natural bamboo are undisputed, since the natural bamboo contains bamboo-kun, a bacteriostatic agent unique to bamboo plants, which gives the bamboo fibres a different nature not found in other cellulosic fibres. While most of the studies reveal that both natural and regenerated bamboo fibres possess antibacterial properties, some researchers claim that both natural and regenerated fibres do not contain any type of antibacterial agents in them and the claims made by other researchers is mainly due to the interaction of phenolic compounds still present in the bamboo viscose fibres with the bacterial membrane and presence of residual chemical such as sulphur that might still be present on regenerated-bamboo and viscose rayon fibres after being spun in a hydrogen sulphate bath during fibre manufacturing. In view of the controversial results reported by different workers regarding antibacterial and antimicrobial properties of bamboo, further investigations on these properties are recommended before definite conclusions can be drawn.

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CHAPTER SIX

Production and properties of bamboo yarns and fabrics

6.1 Introduction Bamboo fabrics are an excellent organic choice over cotton clothing and offer many benefits and advantages over cotton. Bamboo fabrics are softer than cotton and possess a texture similar to silk. Bamboo is a natural antibacterial fibre grown without the use of chemicals or pesticides. The moisture absorption of bamboo fabrics is very good and keeps the body dry and odour free. Moreover, pure bamboo fabrics can dry twice as fast as cotton clothing (Sekerden, 2011). In addition, fabrics made of bamboo fibre have very good physical properties with very good dyeability. Bamboo fabrics require less dyestuff than cotton fabrics in order to be dyed to the level desired, as they absorb the dyestuff better and faster and show the colour better (Sekerden, 2011; Wallace, 2005). Bamboo fabrics have a wide variety of applications in apparel and home furnishings, and are also important in industrial applications; viz., for geotextiles, industrial belts and filters, tyre cord, ornamentation inside vehicles, motorways, building construction, medical implants, and aviation. Similarly, the bamboo fibres, yarns, and fabrics also are widely used for today’s high-tech composite materials, offering lightweight, highperformance alternatives to metals. The fabrics also find uses in many products for environmental protection, ranging from geotextiles for land stabilisation and erosion prevention, such as liquid filtration, to filtration materials that clean air and water. They are also used in special absorbents designed to remove spilled oil from waterways and wetlands (Karahan et al., 2006). Bamboo (pulp) or regenerated bamboo fibre fabrics possess excellent mechanical properties in terms of superior tensile strength, excellent UV protection, antibacterial and biodegradable characteristics, high moisture absorption, softness, brightness, and high flexibility under flexible and compressive loads. With their high moisture absorption capacity, breathability Bamboo Fibres. DOI: https://doi.org/10.1016/B978-0-323-85782-6.00005-2

© 2023 Elsevier Ltd. All rights reserved.

137

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and fast drying behaviour, regenerated bamboo fabrics ensure excellent comfort in various applications. Currently, regenerated bamboo fabrics are used in medical textiles as intimate apparels, hygienic products, and sanitary materials and also in nonwovens and home furnishings (Tyagi et al., 2011; Sekerden, 2011). Production of 100% pure bamboo fabrics is very limited as these fabrics are too soft for skin and hence, these days, the production of bamboo yarns and fabrics and their blends with other regenerated fibres, cotton, silk, and polyester is receiving increasing attention due to the demand for high-quality goods at reasonable price. In addition, many attempts have been made to manufacture bamboo knitted fabrics with blends of other natural and synthetic fibres for a number of applications in medical textiles, thermal, and comfort wear. Owing to the eco-friendly nature of bamboo fibres, the materials made of bamboo are cool and possess the unusual ability to breathe with some special properties (Rathod and Kolhatakar, 2014). Natural fibres, regenerated fibres, and their blends bear valuable properties and presently there are various products made from these fibres used for different applications. The blending of different fibres is generally carried out with a view to achieve and to improve certain characteristics of yarn form or its processing performance. Fabrics produced from blended yarns might have better characteristics than yarns produced from single fibre alone. Blending of different fibres enhances the performance and aesthetic properties of the fabrics (Kandi et al., 2013).

6.2 Production and properties of bamboo and bamboo blended yarns Many researchers have studied the production of bamboo yarns from bamboo viscose fibres and their physical, thermal, comfort, and low stress mechanical properties. Majumdar and Pol (2014) investigated the properties of ring spun yarns made from cotton and regenerated bamboo fibres. Three sets of yarns made from 100% cotton, 50:50 cotton/bamboo, and 100% bamboo yarns were analysed for yarn diameter, tensile, evenness, and hairiness-related properties. The results revealed that the diameter of bamboo blended yarn was lower and the tenacity of yarns spun from 50:50 cotton/bamboo blends was also lower than that

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of 100% cotton and 100% bamboo yarns. It was observed that the large difference in breaking extension between cotton and bamboo led to load-sharing by the bamboo fibre component when the cotton fibre component reached the rupture point. When the bamboo fibre proportion increased, the breaking elongation of yarn increased and initial modulus reduced. Sowmya et al. (2017) investigated the influence of blend and yarn twist on properties of bamboo and its blended yarns. From the studies it was observed that the yarn unevenness characteristic was affected by the blend ratio of cotton, polyester, and regenerated bamboo fibre. The yarn tenacity of blended yarns was decreased due to the lower elongation at break of bamboo/cotton blended yarns and polyester yarns showed the higher yarn friction. A detailed investigation on production of 100% bamboo and its blend with cotton and polyester was carried out (Chandrasekhara, 2019). Bamboo viscose, cotton, and polyester fibres were chosen to develop different varieties of bamboo and bamboo blended yarns. Blending of fibres, the yarn production methodology, and testing of physical and mechanical properties were presented in detail. Materials used for the above study were bamboo, cotton, and polyester fibres. Cotton fibre of 32 mm staple length and strength of 2.4 gpd, bamboo fibres of staple length 35 mm and fibre strength of 1.5 gpd and polyester fibres of 36 mm and fibre strength of 4 gpd were procured from local mills in India. The fibre properties of bamboo viscose, cotton, and polyester used in the study are given in the Table 6.1.

Table 6.1 Properties of bamboo viscose, cotton, and polyester fibres. Sample Bamboo viscose Cotton

Polyester

Fibre length (mm) Fibre fineness (denier) Fibre strength (gpd) Elongation at break (%) Moisture regain (%) Moisture content (%) Density (g/cm3)

35.5 1.71 4.0 10 0.4 0.3 1.38

35 1.81 2.48 15.5 12.5 11 1.51

32 1.5 2.4 5.7 7 6.6 1.53

Source: From Chandrasekhara, S.M., 2019. Studies on production, properties and techno-economics of 100% pure bamboo and bamboo/cotton blended fabrics, Ph.D. Thesis, Visvesvaraya Technological University, Belgaum, Karnataka, India.

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6.2.1 Methodology used for yarn production Bamboo, cotton, and polyester fibres were processed on Laxmi Reiter spinning line (Coimbatore, India) to produce the following five varieties of yarns. Different blended yarns were produced with varying blend composition as mentioned in Table 6.2. The blow room sequence of operations is used is given in Fig. 6.1. The fibres were opened thoroughly and blended homogenously to produce the different sets of yarns. Bamboo, cotton, and polyester staple fibres were processed on a Laxmi Reiter spinning line. The Laxmi Reiter blow room was used for opening and cleaning to remove the trash present in the fibres. The blow room line consisted of five beating points running with a delivery speed of 7 m/min. The fibres were opened thoroughly, trash was removed, and the lap of 0.0012 hanks was produced. Then the lap was fed to LR Crystalline C1/2 card to remove the residual trash present in the fibre and to ensure fibre to fibre separation. The carding machine was running at a speed of 100 m/min with an actual draft of 100 to get a hank of sliver of Table 6.2 Different blend composition. Sl. no Fibres

Blend composition

1 2 3 4 5

65:35 65:35 100% 100% 100%

Bamboo/cotton Bamboo/polyester Bamboo Cotton Polyester

x

Delivery Speed – 7m/min Beating Points - 5

x x

LR Crystallina C1/2 with Crosrol Verga Doffing Planetary Coiler System

Draw frame

x x

Do/2s LR Twin Delivery Draw Frame Delivery Speed – 300m/min

Speed frame

x x x

LF 1400 Speed Frame Spindle Speed – 820 rpm Delivery Speed – 10m/min

Ring frame

x x x

DJ/5 Ring Frame Spindle Speed – 8000 rpm Delivery Speed – 12m/min

Blow room line x Carding

Figure 6.1 Flow chart for converting fibre.

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approximately 0.12 Ne. Then the material was fed to the LR DO/2S draw frame for parallelization of fibres to get an uniform sliver. In the draw frame the material was given eight draft and eight doublings to get 0.12 Ne of draw frame sliver and the drawing machine was run at a speed of 300 m/min. Then the material was fed to the LF1400 speed frame to give a required draft, twist, and winding the strands of material on the bobbin, and the draft of 10 was given to get a roving hank of approximately 1.2 Ne. The material was then fed to a speed frame working with a speed of 820 rpm and front roller speed of 10 m/min. The drafted rovings were then taken to Laxmi Reiter ring frame DJ/5 and given a draft of 25 to spin 30 Ne yarn. The ring frame was running with a spindle speed of 8000 rpm and a front roller delivery speed of 12 m/min. For blending 100% polyester and bamboo viscose fibres with cotton to produce bamboo/cotton (65:35) and bamboo/polyester (65:35) blended yarns, the cotton fibres are separately processed from blow room to card to remove the trash present in the fibres. Then the cotton fibres were homogenously blended with bamboo and polyester fibres to produce bamboo/cotton (65:35) and bamboo/polyester (65:35) blended yarns.

6.2.2 Testing of yarns Yarn takes the intermediate position in the manufacture of fabrics from raw material. Therefore yarn results are very important in estimating the quality of the fabric produced. The important yarn characteristics, viz., linear density, twist/inch, twist multiplier, lea strength (lbs), count strength product (CSP), Resistance per kilometer (RKM), elongation percentage, and yarn imperfections like uniformity percentage (U%), thick and thin places, total imperfections, and hairiness index were tested as per ASTM standards in standard testing atmospheric conditions at a temperature of 20
C 6 2
C and relative humidity of 65% 6 2%.

6.3 Physical properties of bamboo and bamboo blended yarns 6.3.1 Yarn liner density Yarn liner density of all the samples were measured using electronic balance following a standard laboratory procedure as per BS 2010 standards.

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The sample length of 40 m yarn was wound on a wrap reel and weighed accurately by placing it on the weighing plate of an electronic balance and the weight was noted in grams. Ten readings were taken for each set of yarns and their mean was calculated. The English count (Ne) was determined using the relation CountðNeÞ 5 Length in yards 3 453:5=840 3 weight in g:

6.3.2 Twist in the yarn Twist is introduced into a staple yarn to bind the constituent fibres together, thus to give strength to the yarn. Twist (TPI) is expressed as turns per inch or turns per metre. TPI of all the yarn samples were determined on an Eureka Twist Tester using the untwist and twist principle as per ASTMD 142 standards and the TMs for all the yams were also found out. In this method a 10-in. length of the yam was untwisted at a certain tension and then again twisted to the same level of original tension. The number of revolutions gives the TPI of the yam. Averages of 10 readings were taken and the mean was calculated.

6.3.3 Twist multiplier The twist multiplier for all five varieties of yarn was calculated using the relation TPI TM 5 pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi COUNT

6.4 Mechanical properties of yarns 6.4.1 Tensile properties 6.4.1.1 Lea strength The measuring of skein or hank was practiced in earlier days of textile testing. The main advantage of lbs measurement is that it tests a long length of yarn in one set. One lea means 120 yards of yarn length. Strength is a measure of the steady force required to break a material and is expressed in force units. A lbs tester works on the principle of constant

Production and properties of bamboo yarns and fabrics

143

rate of extension (CRE). The machine is designed on the pendulum lever principle and the force applied is directly proportional to sinθ of the deflection of the angle of the weight lever. The lbs of all five varieties was evaluated using the Eureka lbs tester as per ASTMD 1578 standards. Twenty readings were taken and their mean was calculated. 6.4.1.2 Count strength product CSP of the yarns was found out by determining the product of lbs in lbs and count of yarn in Ne. 6.4.1.3 Tensile strength of single yarn (rupture kilometre) During routine testing, the breaking load of yarn and extension are usually considered for assessing the yarn quality. In this experiment a Hounsfield Universal Testing Machine was used to determine the yarn tenacity and breaking elongation. The instrument works on the CRE principle, the application of load is made in such way that the rate of elongation of the specimen is kept constant. A yarn specimen of length 500 mm was clamped between the movable upper jaw and a fixed lower jaw. The upper jaw was traversed at a constant speed of 200 mm/min with a load cell capacity of 1 kg to extend the specimen. This caused the stress to be developed in the yarn. The cross head speed was varied between 50 and 500 mm/min and the maximum capacity of the machine is 500 kg. Ten readings were taken and the mean was calculated as per ASTMD-503590.

6.5 Yarn evenness testing Evenness, unevenness, regularity, and irregularity are common terms used to describe the degree of uniformity of textile products. In the textile field, the uniformity of the products like the lap, sliver, roving, or yarn is expressed in terms of evenness or regularity or in terms of unevenness or irregularity. The Uster Evenness Tester gives an output of the unevenness (U%) of the test strands of sliver, roving, and the imperfections in yarn. The instrument works on the capacitance principle. The textile strand is passed through a parallel plate capacitor. The capacitance of the capacitor varies as the cross section area of the test strand changes. The capacitance

144

Bamboo Fibres

is transformed into signals which are amplified and converted by suitable circuits to give an output of the following information: • U% (Unevenness %). • Imperfections: Neps, thick places and thin places. • CV% (coefficient of variation). • Spectrograph. • Hairiness index. U%, CV%, relative count, evenness, total imperfections, Neps were analysed on Uster Evenness Tester (UT-3) in Saranya Spinning Mills Limited, Coimbatore (India). The testing of all yarns was carried out in standard testing atmospheric conditions.

6.6 Yarn hairiness Yarn hairiness is an undesirable property which causes problems in fabric production. Therefore it is very important to measure the length of hair in order to control it. However, at the same time it is not possible to represent hairiness with a single parameter because the length of hair and number of hairs exceeding 3 mm length as a percentage of the total number of hairs is found to be linearly related to the linear density of yarn. Maturity, micronaire, uniformity ratio of fibres, spinning conditions, and maintenance of spinning machineries are the key factors which influence the yarn hairiness.

6.6.1 Uster yarn hairiness tester This is an optional attachment to Uster Evenness Tester3. This instrument works on the principle of a parallel beam of infrared red light as it runs through the measuring head. The light rays that are scattered by fibres protruding from the main body of the yarn reach the detector. The direct light is blocked from reaching the detector by an opaque stop. The amount of scattered light is then a measure of hairiness and it is converted to an electrical signal by the apparatus. All the yarns were tested for hairiness using the above attachment and the hairiness index was found out. The physical properties of all the five varieties yarns, viz., count, TPI, TM, lbs, CSP, RKM (g/tex), breaking extension (%), U%, CV%, thick

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Production and properties of bamboo yarns and fabrics

places thin places, Neps, TI, and hairiness index values are presented in Table 6.3. From the results of the count parameters of bamboo and bamboo blended yarns, a slight difference was observed between the actual counts of yarn and the nominal count. It was due to unavoidable errors in machine and variation in material. TPI and TM of all the yarn varieties also showed a slight variation, with the 100% cotton yarns showing higher twist and TM (23.5 and 4.30), whereas 100% polyester yarns showed lower TPI and TM (22.5 and 4.10). When mechanical properties of all the five varieties of yarns were compared, it was found that 100% polyester yarns had higher RKM (23.5) and high CSP (3152) and 100% cotton yarns had the lowest RKM (16.5) and CSP (2349). As polyester fibres were having higher tenacity (4.0 gpd), the yarns produced from polyester fibres were stronger. Cotton fibres were weaker (2.4 gpd) compared to polyester and bamboo fibres and the yarns produced from the constituent fibres were also weaker. The yarns produced from 100% bamboo (RKM 17.5, and CSP 2638) were stronger than 100% cotton but weaker than 100% polyester. The tensile

Table 6.3 Physical properties of yarns. Physical Bamboo/ parameters cotton (65:35)

Bamboo/ polyester (65:35)

100% Bamboo

100% Cotton

100% Polyester

Nominal count (Ne) Actual count (Ne) TPI (twist/inch) TM (twist multiplier) Lea strength (lbs) CSP RKM (g/tex) Breaking extension (%) U% CV% Thick places 150% Thin places 250% Neps 1200% TI (total imperfections) HI (hairiness index)

30 s 30.02 22.15 3.91 94.10 2842 18.5 15.7 9.8 12.9 86 16 143 245 4.30

30 s 29.95 22.4 4.22 88.1 2638 17.5 13.2 9.8 12.8 130 17 185 332 5.2

30 s 29.86 23.5 4.30 78.7 2349 16.5 5.3 12.56 16.4 285 22 345 652 6.3

30 s 30.05 22.5 4.10 104.9 3152 23.5 19.5 8.5 11.6 55 14 88 157 4.27

30 s 29.2 22.8 4.22 84.10 2456 16.2 9.8 11 15.7 220 20 286 526 5.8

Source: From Chandrasekhara, S.M., 2019. Studies on production, properties and techno-economics of 100% pure bamboo and bamboo/cotton blended fabrics, Ph.D. Thesis, Visvesvaraya Technological University, Belgaum, Karnataka, India.

146

Bamboo Fibres

properties of blended yarns lay almost in-between 100% polyester, 100% cotton, and 100% bamboo viscose yarns. It was observed from the results of the evenness test that the uniformity ratio (U%), coefficient of variation (CV%), and total imperfections of polyester yarns (U% 8.5, CV 11.6, and TI 157) were least and 100% cotton yarns were maximum (U% 12.56, CV% 16.4, TI 652). One hundred per cent bamboo yarns also showed lower U%, CV%, and TI, (U% 9.8, CV%12.8, TI 332). This was due to the fact that the yarns produced from 100% bamboo and 100% polyester were from cut staple fibres of uniform length and fineness. Hence irregularities in the resulting yarn was lower compared to yarn produced from 100% cotton fibre which is inherently less uniform with respect to fibre length and fibre fineness. From the overall studies, the researchers summarised that the 100% polyester yarns were stronger (23.5 g/tex) and demonstrated good uniformity ratio, lower coefficient of variation, and less imperfections and hairiness (8.5, 11.6, 157, and 4.27, respectively) compared to 100% cotton (12.56, 16.4, 652, and 6.3 respectively) and 100% bamboo yarns (9.8, 12.8, 332, and 5.2 respectively). The bamboo yarns were stronger (17.5 g/tex) than cotton (16.5 g/tex) and weaker than polyester (23.5 g/ tex). The tensile properties of bamboo, cotton, and polyester blended yarns lied almost in between 100% polyester and 100% cotton yarns. When mechanical properties of all the yarns were compared it was found that 100% polyester yarns showed high RKM (23.5) and high CSP (3152) and 100% cotton yarn had lowest RKM (16.5) and CSP (2349). As polyester fibres were having higher tenacity (4.0 gpd), the yarns produced from polyester fibres were stronger. As cotton fibres were weaker (2.4 gpd) compared to polyester and bamboo fibres and the yarns produced from the constituent fibres were also weaker. The yarns produced from 100% bamboo (RKM 17.5, and CSP 2638) were stronger than 100% cotton but weaker than 100% polyester. Tensile properties of blended yarns lay almost in-between 100% polyester and 100% cotton yarns. Uniformity ratio (U%), coefficient of variation (CV%) and total imperfections of polyester yarns (U% 8.5, CV 11.6, and TI 157) were the least and for 100% cotton yarns were maximum (U% 12.56, CV% 16.4, TI 652). One hundred per cent bamboo yarns also showed lower U%, CV%, and TI (U% 9.8, CV%12.8, TI 332). This was due to the fact that the yarns produced from 100% bamboo and 100% polyester were from cut staple fibres of uniform length and fineness. Hence irregularities in the

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Production and properties of bamboo yarns and fabrics

resulting yarn was lower compared to 100% cotton yarns which are inherently less uniform with respect to fibre length and fibre fineness. Hairiness index of 100% polyester and bamboo/polyester yarns was 4.27 and 5.8, respectively, and it was found to be less than yarns made from 100% cotton and bamboo/cotton (65:35) blended yarns (6.3 and 5.8, respectively). This could be due to better packing of polyester and bamboo fibres in the yarns cross section compared to cotton fibres. The tensile properties of regenerated bamboo yarn have also been reported (Li and Yan, 2012). Pure regenerated bamboo yarn (linear density 14.58 tex; twist multiplier 350; and yarn irregularity 17.3%) was selected to investigate the tensile properties. The test length of yarn was 500 mm, the pretension force was 0.5 cN/tex, and the tensile speed was 100, 500, 1000, 2000, 3000, 4000, and 5000 mm/min. The tensile properties of regenerated bamboo yarns are presented in Table 6.4. It was observed that the breaking strength increased with an increase in tensile speed. The breaking strength showed a maximum value at a tensile speed of 3000 mm/min (183.62 cN), then it decreased with increase in tensile speed. However, there was no change in elongation at different tensile speeds. The authors concluded that the distributions of the breaking strength and breaking elongation of regenerated bamboo yarn were normal and the breaking strength had a maximum value at a tensile speed of 3000 mm/min. The breaking elongation demonstrated little change at a tensile speed from 100 to 4000 mm/min. A simple nonlinear three-element viscoelasticity model could be selected to simulate the tensile model of regenerated bamboo yarn at various tensile rates. The specific tensile strength of bamboo yarn could be obtained according to the model with the relative error between the theoretical tenacity and actual tenacity was less than 3%.

Table 6.4 Tensile properties of regenerated bamboo yarns. Value Breaking strength (cN) Tenacity (cN/tex) Elongation at break (%)

Mean Maximum Minimum SD CV (%)

170.04 228.50 125.00 19.60 9.85

11.66 15.67 8.57 1.33 11.37

11.72 15.34 6.43 1.65 12.27

Source: Adapted from Li, L., Yan, H., 2012. Tensile properties of regenerated bamboo yarn. Fibres Textiles East. Europe, 20, 1 (90) 2022.

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Bamboo Fibres

Analysis of quality parameters of ring spun yarns made from different blends of bamboo and cotton fibres has been reported (Ahmad et al., 2012). Bamboo and cotton fibres were processed separately in the blow room and then card slivers of individual components were obtained. Blending was done at draw frame by varying the bamboo and cotton ratio from 1% to 100%, break draft from 1.23 to 1.27, and twist factor from 3.5 to 3.9. The resultant composite roving samples were spun into yarn samples of count Ne 30 seconds at the same spindles of the ring frame by varying break draft and twist levels. Yarn lbs, single yarn strength, and moisture regain were determined using standard test methods. From their results, it was observed that as the cotton content was increased in the blend, the lbs and single yarn strength of blended yarns were also increased. The lbs varied from 72.4 g (for 100% bamboo yarn) to 73.65 g (for 100% cotton yarn). Similarly, single yarn strength was better for 100% cotton yarn (319.15 g) when compared to 100% bamboo yarns (314.22 g). The moisture regain, however, demonstrated a reverse trend. One hundred per cent bamboo yarns showed a value of 13%, and the same for 100% cotton was 7.5% resulting in higher moisture absorption capacity of bamboo yarns. Production of bamboo and bamboo/silk blended yarns was carried out by Geethanjali et al. (2021). In this work, blending was at the sliver stage and the researchers attempted to produce a series of blended yarns of silk/bamboo with blend proportions of 75:25, 50:50, and 25:75 to produce 9.84 tex yarns. Apart from this, 100% bamboo yarn and 100% spun silk yarn were also used for this research. The physical properties of bamboo and bamboo blended yarns are presented in Table 6.5. The silk yarn showed lower imperfections, but this increased with the addition of bamboo fibre and owing to this the thick places, thin places, and Neps/km were also higher in the yarn made with bamboo fibres. These irregularities increased along with the content of bamboo fibres due to the presence of floating fibres in the drafting zone, and it was very difficult to control the bamboo fibres in the drafting zone in order for them to integrate (Mahish et al., 2012).

6.7 Production and properties of bamboo and bamboo blended fabrics Textile and apparel manufacturers are seeking new natural renewable products to draw the attention of the consumers. This concern

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Table 6.5 Physical properties of bamboo and bamboo/silk blended yarns. Properties Bamboo/ Bamboo/ Bamboo/ Bamboo/ Bamboo/ silk silk silk silk silk (100:0) (70:30) (50:50) (30:70) (0:100)

Count (tex) CV% RKM (g/tex) U% Thin places 50% (km) Thick places 150% (km) Neps 1200% (km) Total imperfections (km)

9.99 1.15 18.8 18.8 13 58

9.94 1.43 19.2 18.1 12 38

9.88 1.06 19.4 17.5 10 33

9.83 1.54 19.1 17.2 9 28

9.79 1.33 20.1 16.5 8 23

118 182

87 159

72 124

64 102

61 92

Source: From Geethanjali, T., Prakash, C., Rajwin, A.J., Kumar, M.R., 2021. Thermal comfort properties of bamboo/silk fabrics. Fibres Textiles East. Europe, 29, 2(146): 3640.

focused the research activity onto the development of new fibres and fabrics from agro resources, like bamboo viscose fibre, which is environment-friendly, biodegradable, breathable, has good moisture absorption properties, superior comfort and hand, and exhibits unique antimicrobial property. The demands from fabrics have also changed with developments in technology and the rising living standards. Now the requirement is not only style and durability but also clothing comfort which includes psychological, sensorial, and thermophysiological comfort (Rathod and Kolhatakar, 2014). Consumers when selecting fabrics and garments consider the factors like aesthetic appearance and fashion along with the comfort properties. In this respect, many researchers have reported their studies on the production and properties of bamboo viscose, bamboo/cotton, bamboo/silk, bamboo/polyester, and other bamboo blended fabrics. An attempt was made to produce five different varieties of fabrics, viz., bamboo/cotton (65:35), bamboo/polyester (65:35), 100% bamboo, 100% cotton, and 100% polyester plain fabrics to study their geometrical, performance, and comfort properties (Chandrasekhara, 2019).

6.7.1 Fabric production The five varieties of yarn samples were woven on a sample loom of model CCI SEDIT 2, a single rigid rapier loom running with a speed of 60 picks/min. The loom consisted of 20 heald frames, pneumatic

150

Bamboo Fibres

shedding, and positive electronic let-off and take-off with electronic dobby. The loom had reed width of 25v and the maximum length of the fabric which could be produced was 2.75 m. The bamboo and bamboo blended plain fabrics were produced on the above loom.

6.7.2 Fabric testing Geometrical, performance, and comfort properties of bamboo/cotton, bamboo/polyester, 100% bamboo, 100% cotton, and 100% polyester fabrics were evaluated in the laboratory at standard testing atmospheric conditions as per ASTM standards. 6.7.2.1 Geometrical parameters 6.7.2.1.1 Thread density

Fabric thread density, that is, ends/inch and picks/inch, of the fabrics was found out using a counting glass. Ten readings were taken and the mean was calculated. 6.7.2.1.2 Yarn count

The warp and weft yarn count were found out using Beasley’s balance. The apparatus consisted of a horizontal lever type balance, with a pointer at one end and a hook at other side to support yarn to hang. The template was provided to cut the threads from the fabric sample of required length. This apparatus could be used to determine the yarn count in cotton, worsted, and woollen system as per BS 2010 standards. Ten readings were taken and the mean was calculated. 6.7.2.1.3 Crimp

Crimp percentage is defined as the mean difference between the straightened thread length and the length of thread while in the cloth. WIRA crimp tester was used to find out the warp and weft crimp as per ASTM BS 2863 standards. Crimp (%) of yarn was calculated using the relation:   l2p C5 p 3 100 where C 5 crimp, l 5 uncrimped length, and p 5 crimped length. The rectangular strips on the fabric were marked and each strip was cut into the form of a flap. From each strip 10 threads were taken out and one end was placed in the grip of the tester and the other end was

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removed and placed on the second grip. In this way the threads were transferred from the cloth to the crimp tester without loss of twist. 6.7.2.1.4 GSM (g/m2)

GSM is a metric measurement, which means grams per square metre. It is the measurement of how much one square metre of fabric weighs. The higher the GSM number, the denser the fabric will be. Ounce per square yard (oz/sq2) is the imperial measurement which is commonly used. Ten readings were taken and the mean was calculated. 6.7.2.1.5 Fabric thickness

Fabric thickness determines the dimension between the upper and lower side of the fabric. Thickness measurement of the fabric samples in the laboratory is usually carried out with the help of a precession thickness gauge. To measure the fabric thickness the fabric was kept on a flat anvil and a circular pressure foot was gently pressed on to it from the top under a standard fixed load. The dial indicator gives directly the thickness of the fabric in mm. Ten readings were taken and the mean was calculated. 6.7.2.1.6 Cover factor

Cover factor is a number that indicates the extent to which the area of the fabric is covered by one set of threads. For a woven fabric two cover factors are considered, that is, warp cover factor and weft cover factor. In the cotton system the cover factor is the ratio of the number of threads/ inch to the square root of the cotton yarn count. The cloth cover factor was calculated by adding the warp cover factor and weft cover factor: n Cover factor 5 pffiffiffiffiffi N where n 5 threads/inch, and N 5 cotton count, Cloth cover factor was calculated using the formula,   K1 3 K2 K1 1 K2 2 28

6.7.2.1.7 Tensile strength

The tensile strength of all the five varieties of fabrics was tested on AMIL Universal Tensile Strength Testing Instrument as per ASTM (D-503590)

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Bamboo Fibres

standard. The samples were tested using a gauge length of 20 cm and a cross head speed of 200 m/min. 6.7.2.1.8 Tearing strength

Tearing strength of the bamboo and bamboo blended fabrics was tested using an Elmendorf Tearing Strength Tester as per ASTM D 142496 RG-04 standard. The fabric specimen was cut according to the template size and the force required to tear the fabric was noted down. Five readings were taken and the mean was found. 6.7.2.1.9 Bursting strength

Bursting strength of a fabric is a measure of strength in which the material is stressed in all directions at the same time and it is suitable to test knitted, lace, or nonwoven materials. The fabric samples were tested on MAG Digi bursting strength tester as per ASTM D-3786 standard. The test specimens used were of size 30.5 mm diameter and the capacity of the machine was 370 kg/cm2. Five readings were taken and the mean was found. The geometrical parameters of bamboo and bamboo blended fabrics are presented in Table 6.6. From the results of the geometrical parameters, it was observed that there was no major difference in the geometrical properties of the fabrics produced from bamboo/cotton, bamboo/polyester, 100% bamboo, 100% cotton, and 100% polyester. There was a slight deviation in the yarn count and it was due to unavoidable errors during spinning and doubling processes. When the weight of the fabrics was compared it was found that the weight of 100% polyester and 100% cotton fabrics (189.3 and 194.3 gsm, respectively) showed lower weight than 100% bamboo, bamboo/cotton, bamboo/polyester (233.8, 225.9, and 228.1, respectively). This was due to the presence of finer yarns in 100% polyester and 100% cotton fabrics. It was opined that the fabrics are medium weight and could be used for apparel textiles. Similarly, the thread density (weft direction) of fabrics made from 100% polyester, 100% cotton (epi 3 ppi: 68 3 59 and 68 3 60) was slightly lower than 100% bamboo, bamboo/cotton, and bamboo/polyester (68 3 63, 68 3 60, and 67 3 62) blended fabrics. When the crimp results were observed it could be seen that the crimp (%) of all the fabrics in warp direction (10%, 10%, 12%, 11%, and 12% respectively) was higher

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Production and properties of bamboo yarns and fabrics

Table 6.6 Geometrical parameters of fabrics. Fabric specification Bamboo/ Bamboo/ 100% 100% cotton polyester Bamboo Cotton

Ends/inch (EPI) Picks/inch (PPI) Yarn count Type of yarn Type of weave Crimp Cover factor

Thickness (mm) Fabric weight (GSM)

Warp (N1) Weft (N2) Warp Weft Warp (K1) Weft (K2) Fabric (Kc)

68 60 2/13 s 2/13 s Double Plain 10% 7% 18.85 16.64 24.29 0.527 225.9

67 62 2/13 s 2/13 s Double Plain 10% 8% 18.58 17.22 24.36 0.467 228.1

68 63 2/13 s 2/12 s Double Plain 12% 8% 19.62 17.47 24.85 0.462 233.8

68 60 2/14 2/14 Double Plain 11% 8% 18.18 16.042 23.82 0.549 194.3

100% Polyester

68 59 2/14 s 2/14 s Double Plain 12% 8% 18.85 16.36 24.2 0.405 189.3

Source: From Chandrasekhara, S.M., 2019. Studies on production, properties and techno-economics of 100% pure bamboo and bamboo/cotton blended fabrics, Ph.D. Thesis, Visvesvaraya Technological University, Belgaum, Karnataka, India.

compared to weft direction (7%, 8%, 8%, 8%, and 8%, respectively). As the tension applied on warp yarns during the weaving process was higher, the crimp (%) of warp yarn was higher than weft yarns.

6.8 Tensile strength and tearing strength From the results of fabric tensile and tearing strengths, it was observed that 100% polyester fabrics showed highest tensile and tearing strength (87.5 kg and 2560 g respectively) followed by 100% cotton (30 kg and 1568 g respectively). One hundred per cent bamboo fabrics demonstrated moderate tensile and tearing strength (70 kg and 2416 g respectively) (Table 6.7). Polyester fibres and yarns were stronger than other yarns and these fabrics exhibited higher values. These results were consistent with the results of fibres and yarns (Table 6.1). Bamboo yarns possessed moderate strength and the fabrics made from bamboo yarns showed lower strength values.

Table 6.7 Properties of fabrics. Sample Tensile strength

Bamboo/cotton Bamboo/ polyester 100% Bamboo 100% Cotton 100% polyester

Average tensile strength (kg)

Tearing strength Warp (g)

Weft (g)

Average tearing strength (g)

Bursting strength (kg/cm2)

Abrasion resistance (weight loss %)

Pilling rating

Crease recovery angle (warp 1 weft) (degrees)

Warp (kg)

Weft (kg)

60 85

50 80

55 82.5

2560 2880

2240 2656

2400 2455

9.82 17.65

3.4 2.8

3 3

160 185

75 30 80

65 30 95

70 30 87.5

2368 1568 2624

2464 1568 2496

2416 1568 2560

13.38 7.90 20.1

3.0 4 1.2

4 3 5

153 165 224

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155

Similarly, the tensile and tearing strengths of bamboo/polyester blended fabrics (82.5 kg and 2455 g, respectively) were higher compared to bamboo/ cotton (55 kg and 2400 g, respectively) blended fabrics. This was attributed to the presence of strong polyester fibres in bamboo/polyester blended fabrics. The strength of cotton fibres was less than polyester, hence, the blending of cotton fibre with bamboo reduced the tensile and tearing strengths of these fabrics. From the observations it was also be noted that strength values of all the fabrics was sufficient enough to use them for the production of apparels. From the results of bursting strength it was observed that 100% polyester fabrics showed higher bursting strength (20.1 kg/cm2) compared to 100% bamboo (13.38 kg/cm2) and 100% cotton (7.90 kg/cm2) fabrics. Cotton being brittle and weak compared to polyester showed lower bursting strength. As bamboo fibres were more flexible and stronger than cotton fibres, fabrics made from bamboo fibres resist more bursting pressure than cotton fibres (Table 6.7). Similarly, bamboo/cotton (9.82 kg/cm2) and bamboo/polyester (17.65 kg/cm2) fabrics demonstrated higher bursting strength values. Since, polyester was stronger and flexible, blending polyester with bamboo increased the bursting strength of bamboo blended fabrics, whereas cotton fibres were weak and stiff, blending cotton with bamboo decreased the bursting strength of bamboo/cotton (9.82 kg/cm2) blended fabrics.

6.9 Abrasion resistance The factors which influence the abrasion of fabrics are fibre type, fibre properties, yarn twist, and fabric structure. Abrasion resistance of bamboo and bamboo blended fabrics was determined using the Martindale Abrasion Resistance Tester as per ASTM (D-388401E01) standard. The samples were cut according to the template size and abraded against a rough surface multidirectionally; the difference between initial weight and final weight of the sample was measured. Five readings were taken and the mean was found. Abrasion resistance (weight loss %) of bamboo and bamboo blended fabrics are presented in Table 6.7. It was observed that 100% polyester fabrics were more resistant to abrasion (weight loss 1.2%) and the fabrics made from cotton yarns had the least resistance to abrasion (weight loss 4%). However, fabrics produced from 100% bamboo demonstrated moderate abrasion resistance

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(weight loss, 3%) which was better than that of 100% cotton fabrics. Normally, the abrasion resistance of the fabrics depends on strength, flexibility, and elasticity of yarns used for the production of fabrics. Similarly, the abrasion resistance of bamboo/polyester blended fabrics was lower with a weight loss of 2.8%, compared to bamboo/cotton (3.4%) and was due to the presence of polyester fibre in the blend. Polyester had good abrasion resistance and flexible compared to cotton, blending polyester with bamboo resulted in better abrasion resistance.

6.10 Pilling The pilling tendency of bamboo and bamboo blended fabrics was found out using I.C.I Pilling Tester as per ASTM (D-351205) standard. The samples were cut to a size of 5v 3 5v and stitched to a rubber tube 6v long with 1 l/4v outside diameter and 1/8v thick. The cut ends of the fabric were covered by cello tape and four such tubes were placed in a box of size 9v 3 9v 3 9v. The instrument rotated at a speed of 60 rpm and the samples were kept there for 5 hours. The extent of pilling was assessed visually, by comparing with pilling arbitrary standards (15) and the samples were rated accordingly. Note: Grey scale ratings for pilling test are as follows: 1. Very severe pilling 2. Severe pilling 3. Moderate pilling 4. Slight pilling 5. No pilling From the pilling test, it was observed that the fabrics produced from 100% polyester and 100% bamboo showed better pilling rating (4 and 5, respectively) than 100% cotton (3). As cotton is more hairy with higher hairiness % and with a fuzzy surface, the pilling tendency was greater in these fabrics. Similarly, the pilling ratings of bamboo/cotton and bamboo/polyester, was more (3.0 and 3.0, respectively) in blended fabrics. This was due to the presence of cotton in the cotton/polyester blend and differences in the tensile strength of constituent fibres used for the production of blended yarns. It was opined that due to this difference, the broken fibres (fuzz) would be anchored within the fabrics during the washing and laundering process which appear as

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157

pill on the fabric surface. However, this problem was not observed in case of fabrics made from single type of fibre (Table 6.7).

6.11 Crease recovery The fabrics were tested for warp and weft crease recovery using Eureka Crease Recovery Tester as per ASTMD 1296 standard. The samples were cut to a size of 2v 3 lv in warp and weft way. The tests were conducted both in warp and weft way direction. Five readings were taken and the average was found. Fabric crease recovery angle was found out by adding warp and weft crease recovery angles. From the results of crease recovery tests (Table 6.7), one could observe that crease resistance was moderate in the case of 100% bamboo (153 and 165 degrees) and cotton fabrics, whereas 100% polyester fabrics showed good crease resistance (224 degrees) compared to cotton and polyester fabrics. Similarly, bamboo/polyester blended fabrics demonstrated better crease resistance (185 degrees) compared to bamboo/cotton fabrics (160 degrees) due to the presence of polyester, which had very good crease recovery property. This showed that wash and wear properties of bamboo fabrics were similar to that of cotton fabrics. Crease recovery depends on fibre structure and the tensile property of fibres. The major parameters which influence crease recovery of fabrics are inter- and intramolecular forces in the fibre, initial modulus, strength, and elasticity of fibre. As these properties were poor in the case of bamboo viscose and cotton fibres, fabrics made from these fibres exhibited lower crease recovery angle. It was opined that fabrics made from bamboo fabrics could be subjected to some wrinkle-free finishing treatments for improving their wash and wear properties.

6.12 Flammability The flammability of bamboo and bamboo blended fabrics were tested on the Paramount Flammability Tester as per ASTM D123094R01 standards. The fabric samples were conditioned in a standard atmosphere for 24 hours. The fabric sample was cut according to a standard size, that is,

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50 3 150 mm and then fixed onto the sample holder firmly. After the completion of the burning of the fabric, the stop motion device stops the instrument due to the thread break by flame; the stop motion device gets sensed and the time taken in seconds to burn the fabric was noted down. Five readings were taken and the mean was found. From the tests of flammability it was observed that 100% polyester was more flame retardant with a time of 14.04 seconds, whereas 100% cotton fabric was the least flame retardant with a time of 9 seconds. Interestingly, 100% bamboo fabrics showed better flammability characteristics compared to 100% cotton fabrics (Table 6.8). This property depends on the inherent flame retardant nature of the fibres and since bamboo and cotton are cellulosic materials, they support sustained burning, whereas polyester being a thermoplastic material melts and does not burn continuously. Similarly, the bamboo/polyester showed a better flame retardant property (13.5 seconds) compared to bamboo/cotton (12.2 seconds) and this was due to the presence of polyester in the blend which had good flame retardant property.

6.13 Fabric stiffness The stiffness test is used to measure the bending property of a fabric by allowing a narrow strip of the fabric to bend to a fixed angle under its own weight. Bending length flexural rigidity (G), bending modulus (q) was measured using Eureka Bending Tester as per ASTM 138896 RG02 standards. Bending length is the length of fabric required to bend on its own weight to a definite extent. A rectangular strip of fabric (6v 3 1v size) was mounted on a horizontal platform and was slide until the fabric over hangs like a cantilever. Bending length was measured for five samples and average was found. From these values, flexural rigidity (G) was found using the following formula. Five readings were taken and the mean was found out. Flexural rigidity; G 5 M 3 C 3 3 103 mg=cm where M 5 GSM of fabric, and C 5 bending length in mm The fabrics made from 100% bamboo exhibited good flexibility (37.44 mg/cm), whereas 100% cotton fabrics were stiffer (109 mg/cm) due to the presence of stiffer cotton yarns in the fabrics (Table 6.8). Similarly, among the blended fabrics the bamboo/cotton fabrics were stiffer

Table 6.8 Properties of fabrics. Sample Flammability time (s)

Bamboo/cotton Bamboo/polyester 100% Bamboo 100% Cotton 100% Polyester

12.2 13.5 12.2 09.5 14.04

Flexural rigidity (mg/cm)

Drape coefficient

Air permeability (cc)

Moisture regain (%)

Moisture content (%)

Wetting ratings

74.64 64.12 37.44 109 138.46

0.56 0.52 0.53 0.60 0.54

14.10 13.15 14.60 13.14 12.77

11.10 7.80 12.10 7.50 0.45

9.90 7.23 10.79 9.11 0.45

0 70 0 0 50

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(74.64 mg/cm) compared to bamboo/polyester fabrics (64.12 mg/cm) due to the presence of stiffer cotton fibres and flexible polyester fibres resulting in the higher flexural rigidity of bamboo/cotton blended fabrics.

6.14 Drape The Eureka Drape Tester was used to measure the drape coefficient as per BS 5058 standards. A sample size of 30 cm diameter was taken and the drape coefficient of all the five varieties of bamboo and bamboo blended fabrics was calculated using the standard procedure. Five readings for each sample were taken and their mean was calculated. The drape coefficients of bamboo and bamboo blended fabrics are presented in Table 6.8. From the results of the fabric drape test it was observed that 100% bamboo, cotton, and polyester fabrics showed drape coefficient values of 0.53, 0.60, and 0.54, respectively. Cotton fabrics demonstrated slightly higher drape coefficient (0.60) values compared to bamboo and polyester fabrics. In polyester fabrics, the friction between fibres in yarns is less and hence the 100% polyester fabrics showed less drape coefficient value compared to 100% cotton fabrics. Similarly, bamboo fibres were smooth, soft, and showed less friction between the fibres, resulting in lower drape coefficient compared to cotton and polyester fabrics. However, in cotton yarns the interfibre friction was higer, thus the yarns become stiffer, hence resulting in a higher drape coefficient. In the same way, the drape coefficient of bamboo/cotton and bamboo/polyester blended fabrics were 0.56 and 0.52, respectively. The drape coefficient of bamboo/cotton fabric was higher compared to bamboo/polyester, which was due to the presence of stiff cotton fibres, whereas due to the smooth, soft, and flexible nature of bamboo and polyester fibres, the bamboo/polyester blended fabrics showed a lower drape coefficient value (0.52) compared to bamboo/cotton blended fabrics.

6.15 Permeability Air permeability of a fabric is the volume of air measured in cubic cm passed per sec through 1 cm2 of the fabric at a pressure of 1 cm head

Production and properties of bamboo yarns and fabrics

161

of water. The air permeability of the fabric samples was tested using Paramount Air Permeability Tester as per ASTM D073704 standards. The fabrics were conditioned in standard testing atmosphere for 24 hours. For thick and dense fabrics 10 cm dia, and for light weight fabrics 4 cm dia rings were used. The suction was started to force the air through the fabric and the rate of flow of air was adjusted until pressure drops of 1 cm water head across the fabric were indicated. The air permeability values of 100% bamboo, cotton and polyester fabrics were 14.6, 13.14, and 12.77 (cc), respectively (Table 6.8). The higher permeability of 100% bamboo fabrics was due to the presence of a substantial number of microgaps in the bamboo fibre structure. Polyester fabrics showed lower air permeability and this was due to the compact structure of polyester fibres. The air permeability of 100% cotton fabrics was moderate compared to bamboo fabrics due to the presence of hairiness on the surface of cotton fibre, which obstructs the flow of air through the fabrics. Similarly, the bamboo/cotton (14.1 cc/cm2/s) blended fabrics show higher air permeability compared to bamboo/polyester fabrics (13.15 cc/cm2/s). Good air permeability of bamboo and bamboo blended fabrics was due to the presence of microgaps in the bamboo fibre structure.

6.16 Moisture content and moisture regain The moisture content and regain of fabrics was measured using Eureka moisture oven as per BS 4784 standards. The moisture regain and moisture content were found out using the following formulae: W 3 100 D W 3 100 Moisture content M 5 D1W Moisture regain R 5

where R 5 moisture regain, W 5 amount of water, D 5 oven dry weight, and M 5 moisture content. Fabrics produced from 100% bamboo showed maximum moisture regain and moisture content (12.1% and 10.79%) and 100% polyester showed minimum moisture regain and moisture content (0.45% and 0.45%) whereas, 100% cotton shows moisture regain and moisture content values in between 100% polyester and 100% bamboo (7.5 and 9.11)

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fabrics (Table 6.8). The results were consistent with moisture properties of respective fibres (bamboo 12.5 and 10.79), cotton (7.0 and 6.6) and polyester (0.4 and 0.3). In a similar way, moisture regain and content of bamboo/cotton and bamboo/polyester blended fabrics were better (11.10% and 9.9%, respectively) compared to bamboo/polyester fabrics (7.8% and 7.23%, respectively). It is quite obvious that bamboo and cotton are cellulosic in nature, and bamboo, being highly porous, absorbs more moisture from the atmosphere resulting in better moisture absorption behaviour of bamboo/cotton blended fabrics leading to better comfort and moisture management in apparels.

6.17 Fabric wetting A spray test is generally used to measure the resistance of a fabric surface for wetting but not the penetration of water. Therefore, this test is particularly used for showerproof finished fabrics. It is often the case that waterproof coatings are applied to the inner surface of a material and a water-repellent finish is then applied to the outer fabric surface to stop it absorbing water as it would otherwise become waterlogged. For this test, a test specimen of 180 mm2 was held taut over a 150 mm diameter embroidery hoop which was mounted at 45 degrees to the horizontal. A funnel which was fitted with a standard nozzle containing 19 holes of a specified diameter was held 150 mm above the fabric surface. Distilled water was poured into the funnel to give a continuous shower onto the fabric. After the water spray had finished, the hoop and specimen were removed and tapped twice gently against a solid abject on opposite points of the frame and the fabric was kept horizontal. This removed any large drops of water. Then the fabric was assigned with spray ratings comparing with the AATCC photographic standards. The Grey scale ratings for spray test are: 100: No sticking/wetting of upper surface 90: Slight random sticking or wetting of upper surface 80: Wetting of upper surface at spray point 70: Partial wetting of whole upper surface 50: Complete wetting of whole upper surface 0: Complete wetting of whole upper and lower surface

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The spray test rating for 100% bamboo and cotton was found to be zero. This was because both bamboo and cotton are cellulosic and hydrophilic in nature, thus they absorb moisture quickly and become completely wet, whereas the polyester, being hydrophobic in nature, could not absorb moisture. Thus the spray rating for polyester was 50, which was much higher than the cotton and bamboo fabrics (Table 6.8). The compact structure of PET makes its fabric absorb less moisture from the atmosphere and results in poor spray ratings. Similarly, the spray ratings of bamboo/cotton fabrics were found to be good compared to bamboo/polyester fabrics (0 and 70). This was again due to the inherent characteristics of bamboo and cotton fibres, being hydrophilic in nature, absorbing more moisture quickly from the atmosphere to wet the surface. Although, polyester was hydrophobic, blending it with bamboo resulted in partial wetting of bamboo/polyester fabrics. Production and properties of bamboo/silk blended woven fabrics has been reported by Geethanjali et al. (2021). The woven blended fabrics with different blend ratios were produced from blended yarns with a plain weave. The thermal comfort properties such as, thermal conductivity, thermal resistance, air and water vapour permeability, and wicking ability were determined and analysed. It was identified from their studies that the warp and weft densities remained the same for all the fabrics. The weight and the porosity of the fabrics increased with the content of bamboo fibres. This also resulted in higher air permeability in 100% bamboo fabrics than those produced from 100% silk. The air permeability decreased with an increase in the content of silk fibre due to higher adhesion and cohesive nature of silk resulting in a compact fabric construction (Militky et al., 2004; Verma et al., 2016). In addition, the porous nature of bamboo fibres also resulted in an increased air permeability bamboo fabrics. Bamboo fabrics demonstrated the highest thermal conductivity, while it was lowest for the silk fabrics. This is was due to the higher interyarn space and porosity exhibited by bamboo yarns and fibres in bamboo fabrics, resulting in higher air permeability. Similarly, the silk fabrics exhibited a high thermal resistance, a property which is considered significant for understanding the thermal insulation characteristics of fabrics. Since the porosity of a fabric has a profound effect on its thermal resistance (Aboalasaad et al., 2020), the fabrics made with silk are less porous and thus showed a higher thermal resistance. Thermal resistance decreased with an increase in air permeability for silk/bamboo blended fabrics. It was noted that there was an increase in heat and vapour transfer properties of the fabrics with an increase in the air permeability of the

164

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fabric and hence, a fabric with an open structure resulted in lower thermal resistance and higher air permeability. Another property, that is, water vapour permeability, also showed an increase with the increase in the content of bamboo fibres and decreased with an increase in the content of silk fibres, again due to higher interyarn space and more porosity of bamboo fibres in the fabric allowing the easy passage of water vapour from the fabric to the environment. A similar trend was observed for wickability, that is, as the content of bamboo fibre increased, the wickability of the fabric was also better. Many studies on the production of knitted fabrics from bamboo fibre and its blends have been reported. Bamboo yarns and blended yarns from bamboo/cotton, bamboo/lyocell, bamboo/polyester and bamboo/silk could be used to manufacture woven/knitted fabrics. In a study, single jersey knitted fabrics with different linear densities of yarns, that is, 20, 25, 30 s Nec from 100% cotton, 50/50 cotton/bamboo, and 100% bamboo were produced and their thermal properties were investigated (Prakash et al., 2012). Single jersey knitted fabrics were produced on a MV4 Meyer and Cie single jersey knitting machine, with a gauge 24 GG, having a diameter of 23v, with 30 rpm speed, 74 feeders, and with 1728 needles. Samples were produced with the same loop-length of 2.7 mm with constant machine settings. The results of this study are summarised in Table 6.9. The thermal conductivity and thermal resistance values of 100% bamboo fabrics were found to be lower than those of 100% cotton fabrics for all the constituent yarn linear densities, with the cotton/bamboo blended fabrics showing intermediate values. The authors opined that although bamboo fibre is well-known for its comfort properties, the properties were not as good as those for cotton. Moreover, the known morphological differences between the two fibres and the fact that the bamboo yarn was finer than a cotton yarn of comparable linear density tends to mask the inverse relationship between thermal conductivity and thermal resistance. However, water vapour permeability increased with the bamboo fibre content in the fabric. The water vapour permeability was also higher for the fabrics made from finer yarns. The greater interstitial spaces in the fabric arising as a result contributed to higher water vapour permeability. The water vapour transmission due to diffusion was also higher for bamboo fabrics as the moisture regain of bamboo fibre was higher than that of cotton.

Table 6.9 Thermal properties of bamboo and bamboo/cotton knitted fabrics. Weight Air Linear Blend ratio Fabric (g2) density thickness permeability (mm) (cm3/cm2/s)

20 s Nec 25 s Nec 30 s Nec

100% Cotton 50:50% Bamboo/cotton 100% Bamboo 100% Cotton 50:50% Bamboo/cotton 100% Bamboo 100% Cotton 50:50% Bamboo/cotton 100% Bamboo

0.790 0.666 0.598 0.768 0.628 0.529 0.713 0.609 0.519

189 184 176 152 132 110 131 108.5 94

101 142 304 191 274 402 265 333 542

Relative watervapour permeability (%)

Thermal conductivity (Wm/K 3 103)

Thermal resistance (m2/kW 3 103)

41.03 42.25 43.01 42.19 45.78 46.04 44.15 46.5 49.28

50.01 46.04 42.22 48.23 44.23 40.02 46.35 42.10 38.10

20.22 19.04 18.44 21.33 19.97 18.32 23.26 21.98 19.13

Source: Adapted from Prakash, C., Ramakrishnan, G., Koushik, C.V., 2012. A study of the thermal properties of single jersey fabrics of cotton, bamboo and cotton/bamboo blended-yarn vis-a-vis bamboo fibre presence and yarn count. J. Therm. Anal. Calorim., 110: 11731177.

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Similarly, besides the obvious result that fabric air permeability increases with a reduction in the linear density of the constituent yarn, it was observed that 100% bamboo fabrics had the highest air permeability value. It was clear that irrespective of yarn linear density, the air permeability increased with increasing presence of bamboo fibre. This result was in line with the findings of Majumdar et al. (2010) that the bamboo fibre yarns have smaller diameters than cotton yarns of the same linear density. The thickness and mass per square metre of the fabrics containing bamboo fibre were also therefore lower than those of the corresponding cotton fabrics. The lower hairiness of the bamboo blended yarns was another contributing factor towards better air permeability (Sekerden, 2011). It was also clear from the above results that fabrics made from yarns of the same fibre composition but of finer linear density showed higher air permeability for the three types of fabrics, with the expected reduction in thickness and fabric mass. Production and a comparative study on handle properties of bamboo and cotton fabrics has been reported by Mengüç et al. (2019). In this study 100% cotton and 100% bamboo (regenerated) yarns of 20 Tex count using αm 5 120 twist coefficient were knitted with an interlock structure in the same density (27 wpc and 15 cpc) on a Fouquet 18E gauge knitting machine. After the production, the fabrics were pretreated and dyed and then six different commercial softeners were applied by the padding method. Various characteristics, such as thickness, mass per unit area, drapeability, friction coefficient, and circular bending rigidity, were determined by standard procedures. It was found that the fabric weight and thickness increased after washing processes owing to the shrinkage of the fabric, which occurs during the repeating washing cycles for all fabrics. Shrinkage was highest especially after the first five washing cycles. However, the weight and thickness generally decreased after repeated washings. There was a significant difference in the drapeability of both cotton and bamboo fabrics and the washing cycles had an effect on drape coefficient values. The results indicated that all the bamboo fabrics showed lower drape coefficient values than cotton fabrics (drape coefficient % was well within 15%) indicating their high bending behaviour and softness. It was also observed that washing process caused an increase in the drape coefficient for both cotton and bamboo fabrics, making them stiffer after washing. Cotton fabrics exhibited the highest drape coefficient (drape coefficient % varied from 14% to 33%) within all fabrics compared to the bamboo fabrics.

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As far as friction properties were concerned, the authors found a significant difference in the friction coefficient between bamboo and cotton fabrics. While softening treatment increased the surface friction in most of the bamboo fabrics, in cotton fabrics the softening treatment resulted in a significant decrease in surface friction. Similarly, for all fabric types, circular bending rigidity becomes higher for all the fabrics after washing. Cotton fabrics showed higher circular bending rigidity than bamboo fabrics and all the softeners had a significant effect on fabric rigidity.

6.18 Summary In this chapter, production and properties of bamboo yarns and fabrics have been described. Studies conducted by various researchers on the production of pure bamboo yarns, bamboo/cotton/bamboo/silk, bamboo/polyester, and other bamboo blended yarns were analysed. It was observed from various studies that most of the research studies focus on the production of yarns from bamboo blends rather than from 100% pure bamboo fibres. Similarly, many studies have reported on fabrics produced from bamboo blended yarns for a number of applications ranging from apparel to composites. In addition to the production of bamboo, bamboo blended yarns, and their fabrics, this chapter also provides an insight into the various properties of yarns and fabrics, such as their geometrical, tensile, thermal, comfort, and friction behaviour.

References Aboalasaad, A.R., Skenderi, Z., Kolcavova, S.B., Khalil, A.A., 2020. Analysis of factors affecting thermal comfort properties of woven compression bandages. Autex Res. J. 20 (2), 178185. Chandrasekhara, S.M., 2019. Studies on production, properties and techno-economics of 100% pure bamboo and bamboo/cotton blended fabrics, Ph.D. Thesis, Visvesvaraya Technological University, Belgaum, Karnataka, India. Ahmad, I, Baig, S.A., Rashid, M.F., 2012. Quality parameters analysis of ring-spun yarns made from different blends of bamboo and cotton fibres. J. Qual. Technol. Manage. 8 (1), 112. Geethanjali, T., Prakash, C., Rajwin, A.J., Kumar, M.R., 2021. Thermal comfort properties of bamboo/silk fabrics. Fibres Textiles East. Europe 29 (2), 3640. 146. Kandi, I.M., Das, K.N., Mahish, S.S., 2013. Thermo-physical comfort properties of P/B blended suiting fabrics. Int. J. Innovative Res. Sci. Eng. Technol. 2, 76207629. Karahan, A., Öktem, T., Seventekin, N., 2006. Natural bamboo fibres. J. Text. Appar. 4, 236240.

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Li, L., Yan, H., 2012. Tensile properties of regenerated bamboo yarn. Fibres Textiles East. Europe 20 (1), 2022. 90. Majumdar, A., Pol, S.B., 2014. Low stress mechanical properties of fabrics woven from bamboo viscose blended yarns. Fibers Polym. 15 (9), 19851991. Majumdar, A., Mukhopadhyay, S., Yadav, R., 2010. Thermal properties of knitted fabrics made from cotton and regenerated bamboo cellulosic fibres. Int. J. Therm. Sci. 40, 20422048. Mahish, S.S., Patra, A.K., Thakur, R., 2012. Functional properties of bamboo/polyester blended knitted apparel fabrics. Indian. J. Fibre Text. Res. 37 (3), 231237. Mengüç, G.S., Dalba¸sı, E.S.N., Özgüney, A.T., Özdil, N., 2019. A comparative study on handle properties of bamboo and cotton fabrics. Industria Textila 70 (3), 278284. Militky, J., Vik, M., Vikova, M., Kremenakova, D., 2004. Influence of fabric construction on their porosity and air permeability. Proc. 2nd Sientex Conf. Int. Symp. Text. Eng. 22 (3), 118. Prakash, C., Ramakrishnan, G., Koushik., C.V., 2012. A study of the thermal properties of single jersey fabrics of cotton, bamboo and cotton/bamboo blended-yarn vis-a-vis bamboo fibre presence and yarn count. J. Therm. Anal. Calorim. 110, 11731177. Rathod, A., Kolhatakar, A., 2014. Analysis of physical characteristics of bamboo fabrics. Int. J. Res. Eng. Technol. 3, 2125. Sekerden, F., 2011. Investigation on the unevenness, tenacity and elongation properties of bamboo/cotton blended yarns. Fibres Textiles East. Europe 19 (3), 2629. Sowmya, R., Raaja, N.V., Prakash, C., 2017. Investigation of relationship between blend ratio and yarn twist on yarn properties of bamboo, cotton, polyester, and its blends. J. Nat. Fibers 14 (2), 228238. Tyagi, G.K., Bhattacharaya, S., Kherdekar, G., 2011. Comfort behaviour of woven bamboo-cotton ring and MJS yarn fabrics. Indian. J. Fibre Text. Res. 36, 4752. Verma, N., Grewal, N., Bains, S., 2016. Evaluation of comfort and handle behavior of mulberry silk waste/wool blended fabrics for end use. J. Nat. Fibers 13 (3), 277288. Wallace, R., 2005. Commercial availability of apparel inputs: effect of providing preferential treatment to apparel of woven bamboo - cotton fabric. United States International Trade Commission, Investigation No: 332465-007, June: 14.

CHAPTER THREE

Extraction methods for bamboo fibres: various extraction methods, different types of bamboo fibres

3.1 Introduction Bamboo fibres are considered to be suitable for substitution for other natural plant fibres, with many advantages, such as being low cost, low density, eco-friendly, sustainable, and biodegradable. Bamboo fibres in the textile industry are used in two different forms: (1) raw/natural bamboo (bast) fibres extracted through physical and chemical treatments; and (2) regenerated (pulp) bamboo fibres obtained through spinning of bamboo pulp (Yueping et al., 2010). Using physical and chemical treatments, bundles of original or pure bamboo fibres of usually 2 mm staple length can be obtained. By the process of spinning of bamboo pulp, regenerated bamboo cellulose or bamboo viscose filaments can be obtained. These bamboo viscose filaments can be further converted into staple fibres for making yarns and fabrics. The bamboo fibre extraction generally begins with the splitting of bamboo strips, which are collected directly from the bamboo clump, so as to remove the diaphragm and node. The hollow portions of the stalks that remain after splitting are taken for either mechanical or chemical treatments (Phong et al., 2012).

3.2 Bamboo fibre extraction methods 3.2.1 Extraction of natural bamboo fibres Natural bamboo fibres are mainly extracted using four actions: (1) mechanical treatment; (2) chemical treatment; (3) biological treatment; Bamboo Fibres. DOI: https://doi.org/10.1016/B978-0-323-85782-6.00007-6

© 2023 Elsevier Ltd. All rights reserved.

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Bamboo Fibres

and (4) combined treatment of 1, 2, and 3. The three routes of production of natural bamboo fibres are presented in Fig. 3.1. 3.2.1.1 Bamboo fibre extraction through mechanical process The mechanical process of bamboo fibre extraction involves the immersion of bamboo strips (prepared from bamboo culms) in water for 3 7 days or, alternatively, boiling at 90 C for 10 15 hours and then beating the strips to loosen the fibre from the outer skin (green exodermis). This soaking and boiling process is followed by several repetitions of scraping with sharp-edged tools and combing to yield bamboo fibres that are suitable for spinning (Rao and Rao, 2007). This method is very labour intensive and has been abandoned by many industrial manufacturers in favour of the less eco-friendly viscose rayon production method. The bamboo fibres extracted through this process are often known as ‘original’ or ‘natural’ bamboo fibres. This process is more or less the same as the ramie fibre extraction process. The following steps are followed in the manufacturing process: 1. The selected bamboo culms are split mechanically into small strands. 2. Crushed bamboo strands are treated with enzymes like cellulase which will break down the bamboo into a soft mushy and spongy mass. 3. Then the fibrous materials are separated and the individual fibre is combed out. 4. Then the fibres are spun into yarns.

Figure 3.1 Different routes to extract natural bamboo fibres (Bahrum and Thompson, 2018).

Extraction methods for bamboo fibres

49

The bamboo fibre produced in this way is considered to be ecofriendly and less used because it is very labour intensive, time consuming, and costly, thus it finds only limited application in the textile industry (Devi et al., 2007). The mechanical processing of bamboo fibres is shown in the Fig. 3.2. The mechanical extraction processes can produce either rough or fine fibres. The steps involved in the preparation of rough and fine bamboo fibres are different. Rough bamboo fibres are produced without the use of harsh treatments, such as bleaching, acid treatments, and soaking in oil. The following steps are involved in the production of bamboo fibres with a rough texture (Fig. 3.3) (Yao and Zhang, 2011). 1. Cutting of the stem 2. Separation 3. Boiling 4. Fermentation with the enzyme The preparation of bamboo fibres with fine texture is very similar to that of rough fibres, but also includes some additional steps (Fig. 3.4). The overall process involves the following steps: 1. Boiling 2. Fermentation with enzyme 3. Wash and bleach 4. Acid treatment 5. Oil soaking 6. Air-drying

Figure 3.2 Bamboo fibre extraction through a mechanical process (Liese and Tang, 2015).

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Bamboo Fibres

Figure 3.3 Steps involved in rough bamboo fibres.

Figure 3.4 Steps involved in fine bamboo fibres.

3.3 Types of mechanical extraction methods The different mechanical extraction methods are steam explosion, crushing, grinding, rolling in a mill, and retting. Suitable bamboo fibres can be extracted from these methods and they find wide application in bamboo fibre-reinforced composites.

3.3.1 Steam explosion method In this method, a steam explosion chamber is used on the bamboo strips, which separates the fibrous and nonfibrous parts of the culms rapidly. The

Extraction methods for bamboo fibres

51

water contained in bamboo is heated under high temperature and pressure, and the pressure is then rapidly released to the atmosphere, so that the water evaporates, shattering the parenchyma inside the bamboo (Ochi, 2012). This is a method often used in biomass production and has been adopted as a potential method for bamboo fibre production, usually for use in composites (Fu et al., 2012a,b; Phong et al., 2012). This method consumes less energy and the pulp is generated by separating the cell walls of the plant. By this method, lignin can be separated easily from the plant surface but the resulting fibres produced are rigid and dark (Shao et al., 2008). In a study, it was revealed that single fibres could not be effectively separated from the fibre bundles. Fibre bundles with 125 210 μm diameter could be produced using a sifter machine and mesh filters. The fibres were then dried at 120 C for 2 hours. This method has been found to be a suitable method to eliminate lignin from the fibres completely. Hence, by removing lignin, fibrous bamboo can be produced (Okubo et al., 2004). Similar trials were conducted on raw bamboo by cutting and overheating it in an autoclave at 175 C for 60 minutes at 0.7 0.8 MPa and then immediately releasing the steam for 5 minutes and repeating this process several times. This procedure was repeated to ensure that the cell walls were fractured. Then ash content from the fibre was removed by washing it in hot water at 90 C 95 C and then dried in an oven at 105 C for 24 hours. This resulted in condensation of most of the lignin content, reducing the adhesion between the resin and extracted fibres (Phong et al., 2012). The steam explosion method results in cracking of fibre cell walls, thus enabling the easy extraction of soft bamboo fibres. Ultrasonic washing was followed to wash the fibres with partly decomposed lignin and treatment of the fibres with isocyanate silane to remove the unexpanded cells. From the results, it was found that the steam explosion method produces bamboo fibres with higher tensile strength than silane-treated fibres (Tung et al., 2004) The interactive forces were weak between the fibres and soft cells, and thus reduce the tensile strength of the fibre-reinforced thermoplastics. Proper surface treatment is needed to achieve strong adhesion between the fibre and the matrix (Ashimori et al., 2004). Witayakran et al. (2013) applied steam explosion by a batch reactor at 205 C and 17 bar pressure for 5 minutes followed by rinsing in water. They were able to extract bamboo fibres of 5 135 mm length from two different species of bamboo (Bambusa beecheyama and Dendrocalamus latiflorus).

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Bamboo Fibres

3.3.2 Crushing In this method, a roller crusher is used to first cut the raw bamboo into small pieces. Then the coarse fibres are extracted from these small pieces by a pin-roller. The fibres are then boiled at 90 C for 10 hours to remove the fat and later dried in a rotary dryer and a dehydrator (Phong et al., 2012). The main disadvantage associated with this method is that it yields only short fibres, and, further, with mechanical overprocessing the fibres get crushed into a powder form (Ashimori et al., 2004).

3.3.3 Grinding In this method, the bamboo culm without any nodes is cut into strips and then soaked in water for 24 hours. Then the drenched strips are cut into smaller pieces with a knife. Wider strips are passed through an extruder and long bamboo strips are cut into small bamboo chips. These small bamboo chips are ground in a high-speed blender for 30 minutes to obtain short bamboo fibres. The fibres are then separated by suitable sieves of different mesh sise. The extracted fibres are finally dried in an oven at 105 C for 72 hours (Thwe and Liao, 2002). Long fibres separated through this process can take up more tensile load due to the increase in transverse length and thus tensile modulus of the composite produced from such fibres can be increased. Researchers have used this method for extracting bamboo fibres and studied the rheological and morphological behaviour of the bamboo fibre composites produced from such extracted fibres (Ying-Chen et al., 2010). This method has also been used in studies where particles from dry bamboo strands are used with nanoclay (Han et al., 2008).

3.3.4 Rolling mill In this method, bamboo culm is cut into small pieces from the nodes and these pieces are cut into strips with 1 mm thickness. In order to separate the fibres from the strips, the strips are soaked in water for 1 hour. They are then passed through a rolling mill under slight pressure at low speed. After soaking these rolled strips in water for 30 minutes, the fibres can be separated from these rolled strips using a razor blade. The obtained fibres are then dried under sunlight for 2 weeks to obtain fibres of lengths ranging from 220 to 270 mm. Alternatively, bamboo strips can be cut from the bamboo culm, pressed between two pairs of steel cylinders and, without soaking in water, fibres can be extracted (Shin et al., 1989). In

Extraction methods for bamboo fibres

53

addition, fibres having lengths ranging from 30 to 60 mm can be extracted from sliced bamboo strips that are steamed and soaked in water to soften the lignin content and then passed through the roller (Yao and Zhang, 2011).

3.3.5 Retting In this procedure, first, the strips are obtained by peeling the cylindrical part of the bamboo culm. Then bundles of strips are soaked in water for 3 days. The fibres are then extracted by beating the wetted strips, scraping using a sharp-edged knife, followed by combing (Rao and Rao, 2007). The process of scraping has a direct effect on the quality of fibres extracted. Alternatively, without scraping or combing, raw bamboo can be simply cut into several longitudinal parts without removing the bamboo node and epidermis. These bamboo strips can then be cleaned with flowing water and then fermented in water at room temperature for 2 months. After fermentation, two different retting types, namely aerobic and anaerobic retting, are used to separate the fibre bundles from the culm. It is possible to extract single fibres of any length using this method (Fu et al., 2012a,b). 3.3.5.1 Properties of pure bamboo fibres extracted by mechanical methods • Good moisture absorption properties because of the presence of microgaps and microholes. • Highly breathable and show good thermoregulating properties. • Lower shrinkage, higher absorption of dyes, better colour absorption, and better lustre. • Better pilling and abrasion resistance. • Antibacterial activity and ultraviolet protection property.

3.4 Bamboo fibre process by chemical methods Bast fibres are generally extracted conventionally using chemicals such as sodium hydroxide (NaOH), sodium triphosphate (Na5P3O10), sodium sulphate (Na2SO4), sodium carbonate (Na2CO3), sodium hydrogen phosphate (Na2HPO4), sodium silicate (Na2SiO3), and sodium citrate (C6H5Na3O7) (Fu et al., 2012a,b). In chemical extraction methods, the

54

Bamboo Fibres

lignin present is removed or reduced through either chemical retting or alkali or acid retting. These methods are not eco-friendly processes and have an adverse effect on important properties of bamboo fibres, such as antibacterial properties, strength, and ultraviolet (UV) protection. These methods also affect the other fibre components such as pectin and hemicelluloses (Deshpande et al., 1999; Kaur et al., 2013; Kushwaha and Kumar, 2009a). However, these methods are inexpensive and consume low energy, and hence the price of chemically extracted bamboo fibres is much lower than mechanically or biologically extracted fibres (Waite, 2010). However, these processes result in a huge volume of wastewaters with high effluent load that require treatment with strong chemicals, such as sulphuric acid, hydrochloric acid, nitric acid, and carbon dioxide.

3.4.1 Chemical retting Chemical-assisted natural (CAN) retting procedure has been used by researchers to reduce lignin and water content in the fibres. The fibres can be separated from the bamboo culm which is cut in a longitudinal direction with a slicer into thin slabs. The manually separated fibres are immersed in a solution of Zn(NO3)2 with varying concentrations of 1% 3% (owf) at 1:20 material:liquor ratio at 40 C for 116 hours in neutral pH in a biological oxygen demand incubator, which is followed by boiling in water for 1 hour. This procedure can remove more lignin than alkali and acid retting, but the treated fibres show a high moisture content (Kaur et al., 2013). Alternatively, bamboo culm can be split into 2 cm chips and the chips are roasted at 150 C for 30 minutes followed by immersion in water for 24 hours at 60 C and air drying prior to removing further impurities. Further, the fibre bundles are cooked in 2% sodium silicate, 2% sodium sulphite, 2% sodium polyphosphate, and 0.5% NaOH (w/v) solutions at 100 C for 60 minutes at 1:20 ML ratio. The fibres can then be washed with hot water and treated with 0.04% xylanase and 0.5% diethylene triamine pentacetic acid at 70 C with pH 6.5 for 60 minutes. The fibres obtained thus are cooked again at 100 C for 60 minutes with the same procedure but using 0.7% NaOH. The fibres are then transferred to a polyethylene bag and bleached in a solution containing 0.5% sodium silicate, 4% H2O2, and 0.2% sodium hydroxide for 50 minutes at pH 10.5. Finally, the fibres can be treated with 0.5% sulphuric acid for 10 minutes and after emulsification for 5 days, refined bamboo fibres can be obtained. This method produces bamboo fibres with a smaller orientation angle for

Extraction methods for bamboo fibres

55

exterior macrofibrils and they are found to be very suitable as reinforcing fibres in composites, in comparison to flax, ramie, and cotton fibres (He et al., 2007).

3.4.2 Alkali or acid retting In the alkali retting procedure, bamboo strips are heated with 1.5 N NaOH solution in a stainless steel container at 70 C for 5 hours. Then the alkali-treated bamboo strips are pressed using a press machine and by using a steel nail, fibres can be separated. These extracted fibres can be washed and dried in an oven. Fibre damage caused in this extraction method is less (Kim et al., 2013). Alternatively, the fibre in the pulp form can be extracted by soaking the bamboo strips in a solution of NaOH (4%) for 2 hours. The procedure can be repeated several times at a certain pressure. The disadvantage of this method is that it produces large fibre bundles (Kumar et al., 2010). Similarly, fibres can be extracted by soaking small bamboo strips in 1 N sodium hydroxide solution for 72 hours (Deshpande et al., 2000). Acids such as trifluoroacetic acid (TFA) can also be used to extract the fibres as lignin content is soluble in acidic conditions. A large portion of lignin present in the middle lamellae can be removed in the TFA process (Fengel et al., 1984). However, by using alkali treatments the interfacial bonding and surface adhesion of composites can be improved as compared to other methods (Takagi and Ichihara, 2004; Kushwaha and Kumar, 2009b). Phong et al. (2012) reported an alkali retting method in which the nodes of raw bamboo (2 4 years old) were first removed and the remaining parts were cleaved by a slicer in a longitudinal direction to thin slabs 20 30 cm in length and 2 3 mm in thickness. These thin slabs were then immersed in NaOH solution at 70 C for 10 hours. The concentrations of NaOH were 1%, 2%, and 3%. The roller looser was used to extract small fibres from the alkali-treated slabs. Finally, they were washed with fresh water to neutralise, and dried in the oven for 24 hours at 105 C. The alkaline retting treatment shows some benefits over steam explosion and mechanical extraction methods. It employs inexpensive equipment, obtains a high ratio of fibre, has relatively low energy consumption, and it is easy to control the fibre property. It has been observed that if the bamboo products are to be used in the automotive industry, the control of fibre properties plays an important role. The fibre properties depend mainly on the relationship between bamboo age and processing conditions,

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Bamboo Fibres

Table 3.1 Properties of bamboo fibres from different extraction et al., 2017). Extraction Tensile Young’s Fibre procedure strength modulus diameter (MPa) (GPa) (µm)

methods (Subash Fibre length (mm)

Fibre density (g/mm3)

Mechanical methods Steam explosion Crushing Grinding Rolling mill Retting

441 6 220 420 6 170 450 6 800 270 503

36 6 13 38.2 6 16 18 6 30

15 210 262 160 100 160

220 270

35.91

0.91

Chemical methods Chemical Alkaline

450 18 270 395 6 155 26.1 6 14.5 230 6 180

10

1.3

Source: Adapted from Subash, S., Stanly, J., Retnam, B., Edwin, R.D.J., 2017. A review on extraction of bamboo fibres and its properties. Int. J. Adv. Chem. Sci. Appl. (IJACSA), 5 (2): 22 27.

such as alkali concentration, temperature, and immersing time (Tokoro et al., 2008; Deshpande et al., 2000; Wakasugi et al., 2010; Chen et al., 2009; Rao and Rao, 2007; Thwe et al., 2003; Tung et al., 2004). In addition, this technique has been found to be suitable in rural areas in Asia where bamboo almost only grows in forest mountain areas with difficulties in the transportation of bamboo strips from harvesting fields to factories for the purpose of extraction of fibres and fabrication of products. The mechanical and physical properties of bamboo fibres extracted by mechanical and chemical extraction methods are presented in Table 3.1.

3.5 Biological methods The most commonly used chemical methods for extraction of bamboo fibres are expensive and cause negative impacts on the environment and human health. Hence, alternative eco-friendly techniques for the extraction of fibres have been introduced. These techniques make use of closed-loop manufacturing strategies, better equipment, and eco-friendly compounds (Fu et al., 2011). Various biological methods for the production of macro-, micro-, and nanosized fibres from raw bamboo have been reported (Liu et al., 2012). In these methods, enzymes like hemicellulases,

Extraction methods for bamboo fibres

57

pectinases, cellulases, xylanases, and lignin-oxidising enzymes, such as manganese peroxidases (MnP), lignin peroxidases (LiP), and laccases, which are produced from indigenous complex bacterial communities, can be used for the extraction of fibres from the bast. They separate the cellulosic fibre bundles from the matrix and affect the quality and the yield of the fibre. Soft and spinnable fibres can be produced by subjecting the split bamboo culms with an autoclave pretreatment to increase protein absorption and enzyme penetration, followed by a greater amount of weight loss by delignification (Fu et al., 2012a,b). One such biological process is a bioretting process of bamboo which is a very gentle pretreatment process and yet as effective as other conventional techniques. Fibres obtained by enzymatic treatments generally yield coarser fibres and cannot be spun without further processing. Enzymatic treatments can produce fibres with length, density, and breaking strength in the range of 27.66 mm (with a range of 8.2 67.9 mm), 66.6 dtex, and 15.76 cN/tex (can be enhanced as high as 48.81 cN), respectively, on average (Fu et al., 2012a,b).

3.5.1 Microbial culture Application of microbial culture has been practiced recently to remove lignin and pectin substances from bast materials for fibre extraction. The microbes consume gummy substances of plants and secrete enzymes that degrade complex substances, for example, lignin, hemicellulose, and pectin, into water-soluble molecules without affecting the cellulose, and thus promote fibre extraction (Fu et al., 2011, 2012a,b; Yu and Yu, 2007). Although, this process is an eco-friendly process, it is slow and lengthy and produces fibres that are too coarse and stiff to spin, and hence it is economically not viable for bamboo fibre extraction. The enzymatic and the microbial or bacterial processes are considered as eco-friendly processes for natural fibre production. However, these processes are extremely slow and not effective for bamboo fibre extraction for textiles. Moreover, the cost of the equipment, microbes/bacteria, and enzymes are very high, making it not be commercially competitive. Research on these processes have not clearly yielded successful results on producing bamboo fibres followed by spinning or weaving for textiles. Therefore, investigation on extracting the natural bamboo fibres by solely using the enzymatic or bacterial treatment is not a productive idea for textile production. Enzymes or bacteria are found to be very effective when applied after the initial extraction of fibres in bundle form.

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Bamboo Fibres

3.6 Combined mechanical and chemical extraction methods Bamboo fibre structure is dominated by its high lignin content, due to which the extraction of fibres becomes difficult using only one technique. Hence, it is sometimes useful to use more than one extraction method in different stages of bamboo fibre extraction (Fu et al., 2012a,b). Thus a combination of different methods results in enhanced fibre extraction with more benefits. For example, a combination of pretreatment or posttreatment of bamboo strips using chemicals or enzymes and steam explosion can be used to extract fibres. Similarly, fibres can be extracted by semiautomatic mechanical treatment (beating and crushing), enzymatic treatment, a series of waterwashings, and bleaching by peroxide. Sometimes, only the steam explosion method can be applied and then extracted fibres can be scoured with alkali and bleached with hydrogen peroxide. In this method, first the bamboo strips are pretreated with chemicals to eliminate lignin and hemicellulose materials to soften the fibre and then this chemical treatment is followed by mechanical processes, such as compression moulding or roller milling. The combination of both mechanical and chemical treatments results in better separation of fibres (Zakikhani et al., 2014). The fibres extracted by this combined method can be used for the processing of isotropic composite materials. This method produces lower fibre yield, requires more chemicals, and the process is complex and expensive (Yao and Zhang, 2011; Deshpande et al., 2000). In a research study by Anyakora (2013) bamboo fibres were impregnated with ‘white liquor’ and the softened sample was converted into fibre by mechanical action, followed by thorough washing, screening, and drying. The extracted fibres were separated, rewashed, and dried in a forced-air circulation type oven.

3.7 Extraction of fibres from bamboo shoot shell Fibres from bamboo shoot shell show high strength, good rigidity, and other excellent properties (Gong et al., 2017). At present, most bamboo shoot shells are abandoned in the bamboo forests and an effective utilisation of bamboo shoot shells is highly advantageous in alleviating the

Extraction methods for bamboo fibres

59

energy crisis and making the rational use of resources. The research on the uses of bamboo shoot shell fibres toward textile applications is still in its infancy as their utilisation at present is restricted in the fields of food, wastewater treatment, and medicine (Chen et al., 2018). However, in order to accelerate the uses of these shoot fibres in textile industry, it is important to extract bamboo shoot shell fibres. An eco-friendly method of extraction of fibres from bamboo shoot shell using sodium percarbonate combined with an alkali oxygen bath has been reported. This method had a good effect on the degumming of bamboo shoot shell fibre, and most of the noncellulose components such as hemicellulose, lignin, and pectin were removed. After treatment, the cellulose content and crystallinity were 73.19% and 61.40%, respectively. The extracted fibres were smooth with a high cellulose content and excellent quality of fibres. Most of the pectin and noncellulosic contents were removed, and the fibres exhibited typical cellulose structure. The thermal stability of fibres was also better. It was revealed that this method is an eco-friendly method and could be widely used in textile, composite materials, medical care, and other fields of application.

3.8 Production of regenerated (pulp) bamboo fibres 3.8.1 Rayon process When it is required to have a regenerated bamboo viscose fibre for the end-use application, the bamboo stalks ought to be freed from lignin and hemicellulose. Several techniques like acid or alkaline pretreatment, wet oxidation, steam pretreatment, and ammonia fibre explosion have been explored by various researchers (Hong et al., 2013). Bamboo fibre obtained from the chemical method is known as bamboo viscose and is almost similar to viscose fibre production method. The process is like conventional viscose manufacturing process; and even the product obtained is similar to rayon or modal fibres. Bamboo viscose or bamboo regenerated fibre obtained from this process is from the bamboo plant, which is a rich, renewable, abundant, cheap, and naturally available resource in tropical regions and widely spread throughout Asian countries. ‘Phyllostachys Heterocycla Pubescens, a species popularly known as ‘moso’’ bamboo is used for the production of bamboo fibre. The 3 4-year-old bamboo

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Bamboo Fibres

stems, leaves, and inner pith of bamboo plant are extracted and crushed, and the fibres are extracted by hydrolysis alkalisation, a multiphase bleaching process that is quite similar to the viscose fibre manufacturing process (Nazan and Bulent, 2015). The following steps have been identified in the production of bamboo viscose fibres. 1. Preparation: In this process 4 5-year-old bamboo is taken and the bamboo leaves and the soft inner pith from the hard bamboo trunk are extracted and crushed. 2. Steeping: In this step the crushed bamboo cellulose is soaked in a solution of 15% 20% NaOH at a temperature between 20 C and 25 C for one to 3 hours to form alkali cellulose. 3. Pressing: Bamboo alkali cellulose is squeezed to remove excess sodium hydroxide. 4. Shredding: To increase the surface area and make the cellulose easier the alkali cellulose is shredded by a grinder. 5. Ageing: The alkali cellulose is kept open for drying for 24 hours in contact with oxygen in ambient air. The partially oxidised cellulose is degraded to a lower molecular weight due to high alkalinity. 6. Sulfarisation: Carbon disulphide is added to the bamboo alkali cellulose to sulfarise the compound and convert it into gel form. 7. Xanthation: In this process the excess carbon disulphide (CS2) is removed by evaporation due to decompression to obtain cellulose sodium xanthogenate. 8. Dissolving: Dilute sodium hydroxide is added to the cellulose sodium xanthogenate to dissolve it to create a viscose solution consisting of 5% NaOH and 7% bamboo fibre cellulose. 9. Spinning: After ripening, filtering, and degassing, the bamboo viscose solution is forced through spinneret nozzles into a large container containing dilute sulphuric acid solution, which will harden the viscose bamboo cellulose sodium xanthate, and converts it into bamboo fibre threads that are further spun into bamboo viscose yarn. The production process of bamboo viscose is shown in Fig. 3.5. Researchers have conducted a number of studies to determine the best mode of retting, that is, acid retting or alkali retting, or CAN retting (Kaur et al., 2013), where the CAN retting route has been found to be most efficient for the pretreatment of bamboo cellulose for its wet spinning. Studies on the optimisation of process parameters, so as to yield a fibre of desired characteristics, have also been documented (Hong et al., 2013; Zakikhani et al., 2014).

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Extraction methods for bamboo fibres

Preparation

Steeping

Pressing

Extract soft, inner pith from hard bamboo trunk and then crush.

Soak crushed bamboo cellulose in NaOH at 2025 ° C for 2-3hrs. Alkali cellulose formed.

Remove excess NaOH solution by pressing the alkali cellulose.

Sulfarization

Ageing

Shredding

Add carbon di sulphide (CS2) to bamboo alkali cellulose for the formation of gel.

Dry alkali cellulose in air for 24 hrs. to oxidise it and degrade it to lower molecular weight so as to have optimum viscosity in spinning solution

Grind the alkali solution to increase the surface area for better processing.

Xanthation

Dissolving

Spinning

Remove excess CS2 by evaporation and decompression and obtain sodium cellulose xanthogenate.

Add to dilute NaOH solution to cellulose sodium xanthogenate and dissolve to create viscose solution to comprising 5% NaOH and 715% bamboo cellulose. 19

Ripen, filter and degas the viscose bamboo cellulose and force it spinneret nozzle into a large container of dilute H2SO4.

Figure 3.5 Production of bamboo viscose fibre through chemical process (Hardin et al., 2009).

3.8.2 Lyocell process (eco-friendly process to produce bamboo fibre) The lyocell process used to produce lyocell fibre from wood cellulose can also be used to manufacture bamboo fibre. Carbon disulphide is known to be toxic, consequently posing a threat to factory workers, as well as polluting the environment via air emissions and wastewater. Its recovery in most industries is only about 50%. One remedy is to opt for a process similar to the lyocell process used for the manufacturing of Tencel. In this process Nmethylmorpholine-N-oxide (NMMO) is used as a solvent to dissolve the bamboo cellulose. H2O2 is used as a stabiliser and the viscose solution is then forced through a spinneret into a coagulation bath, which then causes thin streams of viscose bamboo solutions to harden into bamboo cellulose fibre threads. The hardening bath usually consists of water and methanol or ethanol or a similar alcohol. These fibres are spun into bamboo yarn for weaving into fabric. This process is eco-friendly, NMMO is nontoxic, and the process uses closed loop system, and hence 99.5% of chemicals used in this process are recycled (Yueping et al., 2010).

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Bamboo Fibres

3.9 Types of bamboo fibres 3.9.1 Natural bamboo fibres It is a general practice to use mechanical and chemical methods to extract natural bamboo fibres from the bamboo plants. Natural enzymes are used to prepare the mass from the crushed woody part of the bamboo plant from which the short fibres are combed out. The extracted fibres exhibit a circular cross section and a small circular lumen, similar to other vegetable fibres, with a length ranging from 2 to 5 mm. Bamboo fibres appear similar to cotton in their unspun form. In addition, the fibres are naturally antibacterial, green and biodegradable, ultraviolet protective, cool and breathable, soft, flexible, and strong with a luxurious, shiny appearance (Xiaoling, 2006). Further, the microstructure of the bamboo fibres shows various microgaps and microholes, imparting a good ventilation and moisture absorption behaviour compared with cotton. As a result of this microstructure, warm air gets trapped in microholes providing better warmth next to the skin in cold weather conditions. In addition, the fibres are naturally antifungal and antistatic. Owing to the presence of a distinctive antibacterial and bacteriostatic bioagent called ‘bamboo kun’, which bonds firmly with the bamboo cellulose molecules during bamboo fibre growth, the fibres exhibit good antibacterial and antimicrobial properties (Yueping et al., 2010).

3.9.2 Bamboo (viscose) rayon fibres It has been difficult to extract a fine variety of bamboo fibres such as technical (100 200 μm) or elementary fibres (,20 μm) from the plant culm due to technical hindrances in the extraction procedures (Deshpande et al., 2000; Erdumlu and Ozipek, 2008; Jain et al., 1992; Ogawa et al., 2008; Zakikhani et al., 2014). Hence, efforts were made to produce what is known as ‘bamboo viscose’ fibre, a regenerated cellulosic fibre obtained from bamboo pulp by a wet-spinning method (Erdumlu and Ozipek, 2008); a process which involves the dissolution of bamboo pulp in a solution of NaOH and regenerating the cellulose in a coagulating bath containing sulphuric acid. Regenerated bamboo fibre is obtained from the bamboo plant, which is an abundant and cheap natural resource. Different from natural bamboo fibre, bamboo rayon is an important regenerated cellulosic fibre made

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from the starchy pulp of bamboo plants. The yield of bamboo culms is 10 times that of cotton, without using any fertilisers or pesticides. In addition, even organic cotton uses a massive amount of water for growing, however bamboo grows without any irrigation, normally on hill slopes where nothing else can be grown. Regenerated cellulosic bamboo fibre was first manufactured in 2002 by Hebei Jigao Chemical Fibre Co. Ltd. in China (Liu et al., 2004). The fibres are obtained from bamboo pulp, which is extracted from the bamboo stem and leaves by wet spinning, including a process of hydrolysis alkalisation and multiphase bleaching that is quite similar to that of viscose rayon fibre (Basit et al., 2018). The production process to obtain bamboo rayon fibres from bamboo pulp can be more sustainable if bamboo viscose is produced through a closed loop system where no harmful substances will enter into the ecosystem. This process will have less detrimental effects on the environment and give a reduced amount of carbon emissions. Bamboo viscose is considered as cellulose II with a low degree of crystallinity and high-water retention and release ability. Hence, the fibre exhibits desirable comfort, aesthetic, and processing properties like good moisture absorption, permeability, soft handling, pleasing tactile sensation, excellent dye-ability, etc. Bamboo rayon fibres require a lower amount of dye for obtaining the same depth of shade with better appearance (Xufeng, 2003) and has a silk-like texture. Thus using bamboo rayon fibre as a replacement to cotton can be better for the environment as it requires less dye and consequently less waste is obtained (Erdumlu and Ozipek, 2008; Filiz, 2011; Prakash et al., 2011a,b, 2013). Also, the Organic Crop Improvement Association has certified bamboo rayon fibre to be an organic fibre that can be degraded under the action of microorganisms and sunshine. The products manufactured from bamboo viscose dominate the market because of their considerably lower price and easyto-maintain processing conditions. Hence, these fibres can prove to be a remarkable alternative for those producing bamboo, bamboo textiles and other products for sustainable processing practices (Brady, 2014).

3.9.3 Bamboo charcoal fibre In recent years, with the introduction of nanotechnology, it has become possible to produce a special type of bamboo fibre called ‘bamboo charcoal fibre’ which can be used in improving the performance of textile products. Bamboo charcoal is a porous, adsorptive material that can be

64

Bamboo Fibres

used for a range of purification applications, such as preserving the freshness of fruit and vegetables, in healthcare products, as air filters, and in industrial processes such as sugar processing. A large amount of activated bamboo charcoal is used to dispose of water and waste gas in developed countries. Seventy thousand tons of bamboo charcoal is used every year in the United States and over 50,000 tons in Japan. 3.9.3.1 Production of bamboo charcoal Bamboo charcoal can be produced by heating the pieces of bamboo under a specific controlled temperature range until they become ‘carbonised’, that is, they turn into activated charcoal (Tso, 2009). Traditionally this is done in wood-fired brick kilns, but modern automated kilns are now available and allow more rapid throughput. Today, the technology of producing charcoal from bamboo is a highly specialised process where dried bamboo is carbonised in a kiln at very high temperature (800 C or more, according to the performance desired), reducing it to charcoal. Uniform quality charcoal with good yield and properties can be produced by carbonisation in a brick kiln. The temperature used in the carbonising bamboo charcoal will affect its adsorption capacity of methanol, benzene, methyl benzene, ammonia, and chloroform. The bamboo charcoal exhibits about four times more cavities, three times more mineral constituents, four times better absorption rate, and a large number of small cavities compared with wood charcoal. Interestingly, the surface area of bamboo charcoal is 300 m2/g, which is 10 times more than wood charcoal (30 m2/g). The bamboo charcoal contains different minerals including potassium, magnesium, sodium, and calcium, and when used as filtration material these minerals dissolve during filtration and enrich the mineral content in water (Mahesh and Anitha, 2014). Drying the bamboo before placing it in the kiln and carefully controlling the rise and fall in temperature in the kiln are the main secrets to success. The production of bamboo charcoal involves the following steps: • Cutting the bamboo culms into segments. • Heating the segments under controlled conditions to carbonise them (i.e., to convert them into charcoal). • Checking and packing the charcoal. Fig. 3.6 shows the production of culm charcoal in brick kilns. In the above process, the temperature in the kiln during the heating phase can be divided into three periods: smoking (60 C 100 C), drying (100 C 150 C), and precarbonising (150 C 300 C), and during the

65

Extraction methods for bamboo fibres

Bamboo culms

Unloading kilns

Succeeding

Cut into segments

Cooling

Desiccation

Carbonising

Loading in kilns

Heating

Checking

Figure 3.6 Production of culm charcoal.

Residual

Breaking down

Heating

Loading kilns

Carbonizing

Cooling

Filtering

Drying in a furnace

Forming Sticks

Convey by air

Unloading kilns

Cutting

Packing

Checking

Figure 3.7 Production of stick charcoal.

carbonising phase it can be separated into two periods: carbonising (300 C 450 C) and refining (450 C 1000 C) with actual temperature depending on the final products required (Zhang et al., 2003). In some instances, waste bamboo is pressed together to form sticks that can then be converted into charcoal. This is referred to as ‘stick charcoal’. The production process of bamboo stick charcoal is presented in Fig. 3.7. The formation of bamboo charcoal powder is carried out with an extruder machine with a screw in it at a temperature between 120 C and 140 C. Usually, the mechanical kilns are used to carbonise the bamboo stick charcoal due to their shorter processing cycle compared to brick kilns (Zhang et al., 2003). 3.9.3.2 Production of bamboo charcoal fibre The bamboo charcoal that is produced using the above methods is then processed to be converted into nanoparticles. The charcoal is ground into nanosized particles and this molecular nanocharcoal/carbon powder is then embedded into natural or synthetic polymers to form fibre. The fibres are later spun into yarns that are woven or knitted into fabric form (Sheu, 2007; China Textile Magazine, 2009) (Fig. 3.8). There are two

66

Bamboo Fibres

25 Bamboo burnt at 800oC

Bamboo Charcoal

Bamboo Charcoal Nano-particles

Bamboo Charcoal Fibre

Bamboo Charcoal Yarn

Figure 3.8 Stages in the production of bamboo charcoal fibres.

methods used in making bamboo charcoal fibre. The first method is to add nanobamboo charcoal powder during the spinning solution. The second method is to make bamboo charcoal composite polymer master batch in the stage of synthesising fibre. The charcoal particles are then embedded into existing textile fibres. The amount of charcoal embedded into the fibres is typically 2% or less. Referred to as ‘Black Diamond’ in Japan and Southeast Asia, bamboo charcoal fibre use is an emerging trend in the fashion industry as manufacturers look to combine fashion with function. The bamboo charcoal-infused fabrics have shown enhanced performance properties, such as electromagnetic shielding properties, low surface resistivity, odour absorption, far-infrared emission, thermal regulation, antibacterial and antifungal properties, antistatic behaviour, and so on (Dinsely, 2010; Sheu, 2007; China Textile Magazine, 2009; Kittinaovarat and Suthamnoi, 2009; Lin et al., 2011a,b).

3.9.4 Natural bamboo fibre from LITRAX LITRAX-AG a Hong Kong based company has developed an ecofriendly method of processing raw bamboo culms into natural bamboo fibre. The fibres are produced from bamboo using a high-tech process which includes opening up and refining the culm fibre cells through an enzyme process that separates longitudinal bamboo cells into textile fibre strands ready for further processing through carding and combing. The process involved a series of precisely timed alternate steam-washing and enzyme treatment cycles, which also act on the vertical and horizontally aligned lignin of the resulting fibre bundles. The final step includes a bleaching treatment for fibres with hydrogen peroxide. The fibres extracted by his method show a kidney shaped cross section with a fineness of 5.7 denier and staple length varying between 70 and 150 mm. Later, the fibres can be cut to shorter lengths, that is, 50 or 38 mm for further processing (Nayak and Mishra, 2016).

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3.10 Summary Natural bamboo fibres can be mainly extracted using several methods such as mechanical, chemical, biological, and combined mechanical, chemical, and biological methods. Recently, new techniques have been developed to extract bamboo fibres mechanically, chemically, by steam explosion, or by a combination of mechanical and chemical processes. Importantly, these new processes produce bamboo fibres which retain much of the lignin, hemicellulose, and pectin, and therefore their associated properties and benefits. Some of these characteristic lignocellulosic compounds are claimed to provide fibres with UV absorption and antibacterial properties, opening the way to new fields of applications from smart clothing to composite materials design. Pure bamboo fibre is obtained directly from the bamboo stalk, whereas the viscose form is obtained by regeneration of the raw bamboo cellulose. Bamboo viscose fibres are produced by a viscose process that uses chemical solvents that raise environmental concerns, besides being quite different from the original bamboo fibres. Natural bamboo fibre that has been processed mechanically is environmentally friendly but not yet commercially viable or affordable. While bamboo rayon is a good choice relative to other manmade fibre options, a naturally processed bamboo fibre would be far superior and preferable. Due to faulty labelling, the products made from natural bamboo and from regenerated bamboo fibres are often confused with each other. With the help of nanotechnology, it has become possible to produce bamboo charcoal fibres with enhanced performance properties such as odour absorption, electromagnetic shielding, thermal regulation, and antifungal, antibacterial, and antistatic properties.

References Anyakora, A.N., 2013. Evaluation of mechanical properties of polyester matrix reinforced with bamboo fibre for the production of low strength building products. Int. J. Eng. Appl. Sci. 2 (2), 57 66. Ashimori, M., Katayama, T., Aoyama, E., Nagai, S., 2004. Study on splitting of bamboo fibres due to freezing and tensile strength of FRTP using bamboo fibres. JSME Int. J. Ser. A 47, 566 569. Bahrum, P.R., Thompson, A.J., 2018. Production of natural bamboo fibres-1: experimental approaches to different processes and analyses. J. Text. Inst. 109 (90), 1 11. Basit, A., Latif, W., Baig, S.A., Afzal, A., 2018. The mechanical and comfort properties of sustainable blended fabrics of bamboo with cotton and regenerated fibres. Cloth. Text. Res. J. 36 (4), 267 280.

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Brady, S., 2014. 7 Reasons bamboo is better option than cotton. Retrieved from Cariloha Bamboo website: http://blog.cariloha.com/7-reasons-bamboo-better-option-cotton/. Chen, G., Bu, F., Chen, X., Li, C., Wang, S., Kan, J., 2018. Ultrasonic extraction, structural characterization, physicochemical properties and antioxidant activities of polysaccharides from bamboo shoots (Chimonobambusa quadrangularis) processing by-products. Int. J. Biol. Macromol. 112, 656 666. Chen, H., Miao, M., Ding, X., 2009. Influence of moisture absorption on the interfacial strength of bamboo/vinyl ester composites. Comp. Part. A 40, 2013 2019. China Textile Magazine, 2009. Study on applications of nanotechnology in bamboo charcoal fibre. http://chinatextile.360fashion.net/2009/07/study-on-applications-of-nanot. php. Deshpande, A.P., Bhaskar Rao, M., Lakshmana Rao, C., 2000. Extraction of bamboo fibres and their use as reinforcement in polymeric composites. J. Appl. Polym. Sci. 76 (1), 83 92. Devi, M.R., Poornima, N., Guptan, P.S., 2007. Bamboo the natural, green and ecofriendly new type textile material of the 21st century. J. Text. Assoc. 67, 221 224. Dinsely, J., 2010. The complete handbook of medicinal charcoal and its applications. charcoal remedies.com. GateKeepers Book. Remnant Publications, Michigan, US, ISBN 9780-9738464-0-9, 34 40. Erdumlu, N., Ozipek. B, B., 2008. Investigation of regenerated bamboo fibre and yarn characteristics. Fibres Text. East. Europe 16, 69. Fengel, D., Shao, X., Munchen, 1984. Chemical and ultrastructural study of the Bamboo species Phyllostachysmakinoi Hay. Wood Sci. Technol. 112, 103 112. Filiz, S., 2011. Investigation on the unevenness, tenacity and elongation properties of bamboo/cotton blended yarns. Fibres Text. East. Europe 19, 86. Fu, J., Mueller, H., de Castro, J.V., Yu, C., Cavaco-Paulo, A., Guebitz, G.M., et al., 2011. Changes in the bacterial community structure and diversity during bamboo retting. Biotechnol. J. 6 (10), 1262 1271. Fu, J., Li, X., Gao, W., Wang, H., Cavaco-Paulo, A., Silva, C., 2012a. Bioprocessing of bamboo fibres for textile applications: a mini review. Biocat. Biotrans. 30 (1), 141 153. Fu, J., Zhang, X., Chongwen, Y., Guebitz, G.M., Cavaco-paulo, A., 2012b. Bioprocessing of bamboo materials. Fibres Text. East. Europe 1, 13 19. Gong, W., Ran, Z., Ye, F., Zhao, G., 2017. Lignin from bamboo shoot shells as an activator and novel immobilizing support for α-amylase. Food Chem. 228, 455 462. Han, G., Lei, Y., Wu, Q., Kojima, Y., Suzuki, S., 2008. Bamboo fibre filled high density polyethylene composites: effect of coupling treatment and nanoclay. J. Polym. Env. 16, 123 130. Hardin, I.R., Wilson, S.S., Dhandapani, R., Dhende, V., 2009. An assessment of the validity of claims for bamboo fibres. AATCC Rev. 9 (10), 33 36. He, J., Tang, Y., Wang, S., 2007. Differences in morphological characteristics of bamboo fibres and other natural cellulose fibres: studies on X-ray diffraction, solid state C-CP/ MAS NMR, and second derivative FTIR spectroscopy data. Iran. Polym. J. 16, 807 818. Hong, B., Xue, G., Guo, X., Weng, L., 2013. Kinetic study of oxalic acid pretreatment of moso bamboo for textile fibre. Cellulose 20 (2), 645 653. Jain, S., Kumar, R., Jindal., U.C., 1992. Mechanical behaviour of bamboo and bamboo composite. J. Mater. Sci. 27, 4598 4604. Kaur, V., Chattopadhyay, D.P., Kaur, S., 2013. Study on extraction of bamboo fibres from raw bamboo fibres bundles using different retting techniques. Text. Light. Ind. Sci. Technol. 2, 174 179.

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Kim, H., Okubo, K., Fujii, T., Takemura, K., 2013. Influence of fibre extraction and surface modification on mechanical properties of green composites with bamboo fibre. J. Adhes. Sci. Technol. 27, 1348 1358. Kittinaovarat, S., Suthamnoi, W., 2009. Physical properties of polyolefin/bamboo charcoal composites. J. Metals Mater. Miner. 19 (1), 9 15. Kumar, S., Choudhary, V., Kumar Rakesh, R., 2010. Study on the compatibility of unbleached and bleached bamboo-fibre with LLDPE matrix. J. Therm. Anal. Calorim. 102, 751 761. Kushwaha, P.K., Kumar, R., 2009a. Studies on performance of acrylonitrile pretreated bambooreinforced thermosetting resin composites. J. Reinf. Plast. Compos. 29, 1347 1352. Kushwaha, P.K., Kumar, R., 2009b. The studies on performance of epoxy and polyester based composites reinforced with bamboo and glass fibres. J. Reinf. Plast. Compos. 29, 1952 1962. Liese, W., Tang, T.K.H., 2015. Properties of the bamboo culm. In: Leise, W., Kohl, M. (Eds.), Bamboo: The Plant and Its Uses. Springer International Publishing, pp. 227 256. Lin, C.M., Huang, C.C., Lou, C.W., Chen, A.P., Liou, S.E., Lin, J.H., 2011b. Evaluation of a manufacturing technique of bamboo charcoal polyamide/polyurethane complex yarns and knitted fabrics and assessment of their electric surface resistivity. Fibres Text. East. Europe 19 (2), 28 32. Lin, J.H., Chen, A.P., Hseih, C.T., Lin, C.W., Lin, C.M., Lou, C.W., 2011a. Physical properties of the functional bamboo charcoal/stainless steel core-sheath yarns and knitted fabrics. Text. Res. J. 81, 567 573. Liu, D., Song, J., Anderson, D.P., Chang, P.R., Hua, Y., 2012. Bamboo fibre and its reinforced composites: structure and properties. Cellulose 19 (5), 1449 1480. Liu, G., Zhang, H., Hu, X., 2004. The dyeing behaviours of bamboo fibre with reactive dyes and the product development. In: Proceedings of the Textile Institute 83rd World Conference, Shanghai, China. Mahesh, G., Anitha, D., 2014. Ecofriendly fabrics from bamboo. Indian. Text. J. April 2014. Nayak, L., Mishra, S.P., 2016. Prospect of bamboo as a renewable textile fibre, historical overview, labeling, controversies and regulation. Fash. Text. 3 (1), 1 23. Nazan, E., Bulent, O., 2015. Investigation of regenerated bamboo fibre and yarn characteristics. Fibres Text. East. Europe 16, 43 47. Ochi, S., 2012. Tensile properties of bamboo fibre reinforced biodegradable plastics. Int. J. Comp. Mater. 2, 1 4. Ogawa, K., Hirogaki, T., Aoyama, E., Imamura, H., 2008. Bamboo fibre extraction method using a machining center. J. Adv. Mech. Des. Syst. Manuf. 2, 550 559. Okubo, K., Fujii, T., Yamamoto, Y., 2004. Development of bamboo-based polymer composites and their mechanical properties. Compos. Part A Appl. Sci. Manuf. 35, 377 383. Phong, N.T., Fujii, T., Chuong, B., Okubo, K., 2012. Study on how to effectively extract bamboo fibres from raw bamboo and wastewater treatment. J. Mater. Sci. Res. 1, 144 155. Prakash, C., Ramakrishnan, G., Koushik, C.V., 2011a. Effect of blend ratio on the quality characteristics of bamboo/cotton blended ring spun yarn. Fibres Text. East. Europe 19, 38 40. Prakash, C., Ramakrishnan, G., Koushik, C.V., 2011b. A study of the thermal properties of single jersey fabrics of cotton, bamboo and cotton/bamboo blended-yarn vis-a-vis bamboo fibre presence and yarn count. J. Therm. Anal. Calorim. 110, 1173 1177. Prakash, C., Ramakrishnan, G., Koushik, C.V., 2013. Effect of blend proportion on moisture management characteristics of bamboo/cotton knitted fabrics. J. Text. Inst. 104, 1320 1326.

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Rao, K., Rao, K.M., 2007. Extraction and tensile properties of natural fibres: vakka, date and bamboo. Compos. Struct. 77, 288 295. Shao, S., Wen, G., Jin, Z., 2008. Changes in chemical characteristics of bamboo (Phyllostachyspubescens) components during steam explosion. Wood Sci. Technol. 42, 439 451. Sheu, R., 2007. The legend of black diamond-how does a research institute create extraordinary economic value for SMEs by bamboo charcoal technology applications. http://www.apec-smeic.org/newsletter/. Shin, F.G., Xian, X.J., Zheng, W.P., Yipp, M.W., 1989. Analyses of the mechanical properties and microstructure of bamboo epoxy composites. J. Mater. Sci. 24. Subash, S., Stanly, J., Retnam, B., Edwin, R.D.J., 2017. A review on extraction of bamboo fibres and its properties. Int. J. Adv. Chem. Sci. Appl. (IJACSA) 5 (2), 22 27. Takagi, H., Ichihara, Y., 2004. Effect of fibre length on mechanical properties of Green composites using a starch-based resin and short bamboo fibres. JSME Int. J. Ser. A 47, 551 555. Thwe, M.M., Liao, K., 2002. Effects of environmental aging on the mechanical properties of bamboo - glass fibre reinforced polymer matrix hybrid composites. Compos. Part A Appl. Sci. Manuf. 33, 43 52. Tokoro, R., Vu, D.M., Okubo, K., Takanaka, T., Fujii, T., Fujiura, T., 2008. How to improve mechanical properties of polylactic acid with bamboo fibres. J. Mater. Sci. 43, 775 787. Tso, L.-D., 2009. Black diamond from green bamboo. http://taiwanreview.nat.gov/tw.mht. Tung, N.H., Yamamoto, H., Matsuoka, T., Fujii, T., 2004. Effect of surface treatment on interfacial strength between bamboo fibre and PP resin. JSME Int. J. Ser. A 47, 561 565. Wakasugi, K., Okubo, K., Fujii, T., 2010. Improvement of strength of bamboo fibre paper by addition of MFC (Micro Fibrillated Cellulose). In: Proceeding of the Sixth International Workshop on Green Composites (IWGC-6), 178 181. Waite, M., 2010. Sustainable textiles: the role of bamboo and a comparison of bamboo textile properties (part II). J. Text. Apparel Technol. Manag. 6 (3), 1 21. Witayakran, S., Haruthaithanasan, M., Agthong, P., Thinnapatanukul, T., 2013. Green production of natural bamboo fibres for textiles. Int. Text. Costume Congr. 1 6. Xiaoling, W., 2006. Recent development and perspective of bamboo fibre. J. Anhui Agric. Sci. 34, 1578. Xufeng, Z., 2003. Dyeing processes of bamboo fibre and bamboo/cotton blended fabrics. Dyeing Finish. 48 50. Yao, W., Zhang, W., 2011. Research on manufacturing technology and application of natural bamboo fibre. In: 4th Intelligent Computation Technology and Automation (ICICTA), vol. 2, Shenzen, 28 29, March 2011, Proceedings. Los Alamitos, IEEE Computer Society, 143 148. Ying-Chen, Z., Hong-Yan, W., Yi-Ping, Q., 2010. Morphology and properties of hybrid composites based on polypropylene/polylactic acid blend and bamboo fibre. Bioresour. Technol. 101, 7944 7950. Yu, H., Yu, C., 2007. Study on microbe retting of kenaf fibre. Enzyme Microb. Technol. 40 (7), 1806 1809. Yueping, W., Ge, W., Haitao, C., 2010. Structure of bamboo fibre for textile. Text. Res. J. 80 (4), 334 343. Zakikhani, P., Zahari, R., Sultan, M.T., Majid, D.L., 2014. Bamboo fibre extraction and its reinforced polymer composite material. Int. J. Chem. Nucl. Metall. Mater. Eng. 8 (4), 284 287. Zhang, Q., Jiang, S., Shuhai, J., Ping, X., 2003. INBAR-Nanjing Forestry University Transfer of Technology Model: Bamboo Charcoal Unit, Nanjing, China, 1 17.

CHAPTER TWO

Growth characteristics of bamboo: types of bamboo, morphology of bamboo Bamboo is one of the fastest growing plants in the world due to its unique rhizome system. It is a naturally occurring composite material which grows abundantly in most of the part of the world. This plant has a role in the economics and culture in East Asia, Southeast Asia, and South Asia where it is used for construction, a food source, and also a versatile raw product (Balakrishnan et al., 2017). Bamboo is found in abundance in Asia and South America. In many Asian countries bamboo has not been explored fully, although it is considered as a natural engineering material. This sustainable material has evolved as a backbone for the socioeconomic status of society as it takes several months to grow (Khalil et al., 2012). As a cheap and fast-grown resource, with superior physical and mechanical properties, bamboo offers great potential as an alternative to wood. Bamboo can widely substitute for not only wood, but also the plastics and other materials in structural and product applications through improvements in processing technologies and product innovation with the application of scientific and engineering skills (Gupta and Kumar, 2008). Bamboo or has 7 10 subfamilies and there are 1575 different species ranging from a type of wood to bamboo herb. However, each particular species of bamboo has different properties and qualities (Mohd et al., 2013). Bamboo offers a vast variety of commercial and domestic products due to its excellent mechanical, physical and chemical properties (Li, 2004). Bamboo is a natural lignocellulosic composite in which cellulose fibres are embedded in the lignin and hemicellulose matrix. Bamboo contains 44.5% cellulose, 0.5% lignin, 32% soluble matter, 0.3% nitrogen, and 2% ash. The average length is 2 m and the average diameter is 10 20 mm (Adamson, 1978). The geometry of bamboo’s longitudinal profile has a macroscopically functionally graded structure, which can withstand extreme wind loads. Fibre distribution in transverse cross-section at any particular height of bamboo is dense in the outer periphery and sparse in the inner periphery. Bamboos mainly consist of

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the roots, culm, and leaves. The culms, being the most useful part in a bamboo, are hollow and vary in sizes, diameters, colours, and textures. The culm is composed of the strands of cellulose fibres and the lignin matrix. Spaces between adjacent strands of fibres are filled with lignin, a type of resin. The number of fibrous strands increases toward the outer surface of the culm. Cellulose fibre is stronger than the lignin matrix and the cross-sectional area of the culm changes from location to location. Hence, the cellulose strand distribution would be different plant species. Bamboo has different mechanical properties in the three dimensions: axial, radial, and tangential. However, bamboo is a biological material and it is subjected to great variability and complexity due to various conditions such as years of growth, soil and environmental conditions, and the location of the bamboo culm within the bamboo. Hence, it is observed that the mechanical properties of bamboos vary enormously (Ray et al., 2005). Bamboos are available in the form of different species and the mechanical and physiochemical properties vary from one species to another.

2.1 World distribution of bamboo Bamboo is grown in different parts of the world and this can be classified into the Asia-Pacific bamboo region, American bamboo region, Table 2.1 Regions of bamboo in different countries (Lobovikov et al., 2007). Bamboo region Countries

1. Asia-Pacific

2. American bamboo region (Latin America, South America and North America) 3. African bamboo region 4. European countries

China, India, Burma, Thailand, Bangladesh, Cambodia, Vietnam, Indonesia, Malaysia, Korea, and Sri Lanka Mexico, Guatemala, Costa Rica, Nicaragua, Honduras, Columbia, Venezuela and Brazil Mozambique, Eastern Sudan England, France, Germany, Italy, Belgium, Holland, United States, and Canada have introduced a large number of bamboo species from Asian and Latin American bambooproducing countries

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Figure 2.1 World distribution of bamboo (Lobovikov et al., 2007).

African bamboo region, and European and North American region (Table 2.1). Amongst these, the Asia-Pacific region is the largest growing area. The bamboo growing area in Asia is largely occupied by the major countries such as India, China, Indonesia, Philippines, Myanmar, and Vietnam. The data of bamboo production provided by FAO at global level is presented in Fig. 2.1. Bamboo is called by different names in Asian countries, such as ‘friend of people’ in China, ‘wood of the poor’ in India, and ‘the brother’ in Vietnam (Waite, 2009; Farrelly, 1984).

2.2 Bamboo growth habitat Bamboo is the largest member of the grass family. It can reach the height of 35 m and one Japanese species can grow up to 1 m/day. The absence of xylem and the unique rhizome dependent system in bamboo is responsible for its rapid growth. Bamboo grows in two distinctly different forms due to the presence of the subterranean rhizome: (1) sympodial or clump forming, and (2) monopodial or nonclump forming, runner bamboo. Monopodial (single stem) bamboos are native to temperate climates with cool, wet winters, and sympodial (clump farming) bamboos like Dendrocalamus strictus and Bambusa bamboo are found in tropical climates with a pronounced dry season (Pande et al., 2012). Bamboo comprises many different species which all have unique growth rates and characteristics. The fastest growing plant on Earth is a bamboo species that grows up to 91 cm/day, which is almost 4 cm/h, or a speed of 0.00003 km/h. These growth rates can be established in shooting season, and when optimal soil and climate conditions are present.

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However, the growth rate is dependent on local soil and climatic conditions, as well as species and a more typical growth rate for many commonly cultivated bamboos in temperate climates is in the range of 3 10 cm (1.2 3.9 in.) per day during the growing period. Primarily growing in regions of warmer climates during the late cretaceous period, vast fields existed in what is now Asia. Some of the largest timber bamboo can grow over 30 m (98 ft) tall, and be as large as 15 20 cm (5.9 7.9 in.) in diameter. However, the size range for mature bamboo is species dependent, with the smallest bamboos reaching only several inches high at maturity. A typical height range that would cover many of the common bamboos grown in the United States is 4.6 12 m (15 39 ft), depending on species. Unlike trees, individual bamboo stems, or culms, emerge from the ground at their full diameter and grow to their full height in a single growing season of 3 4 months. During these several months, each new shoot grows vertically into a culm with no branching out until the majority of the mature height is reached. Then, the branches extend from the nodes and leafing out occurs. In the next year, the pulpy wall of each culm slowly hardens. During the third year, the culm hardens further. The shoot is now considered a fully mature culm. Over the next 2 5 years (depending on species), fungus begins to form on the outside of the culm, which eventually penetrates and overcomes the culm. Around 5 8 years later (species and climate dependent), the fungal growths cause the culm to collapse and decay. This brief life means culms are ready for harvest and suitable for use in construction within about 3 7 years. Individual bamboo culms do not get taller or larger in diameter in subsequent years than they do in their first year, and they do not replace any growth lost from pruning or natural breakage. Bamboos have a wide range of hardiness depending on species and locale. Small or young specimens of an individual species will produce small culms initially. As the clump and its rhizome system mature, taller and larger culms will be produced each year until the plant approaches its particular species limits of height and diameter. Bamboo has the great potential to be used as a solid wood substitute material, especially in manufacturing, design, and construction. Bamboo’s properties of being lightweight and high-strength has attracted researchers to investigate and explore, especially in the field of biocomposite bamboo and is acknowledged as a green-technology responsible for eco-friendly products (Khalil et al., 2012).

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2.3 Growth process The growth process of bamboo is from asexual reproduction to later sexual reproduction, the general cycle is 60 years. There are four stages in the growth of bamboo, namely seedling emergence, long leaf, flowering and fruiting, and dying. Most of the time, bamboo is thriving. But once it bears fruit it dies, completes one of its life cycles, and starts growing again in the next year. The specific characteristics of the growth stage are as follows: 1. Growth of bamboo shoots through root germination as bamboo does not grow out of the ground. 2. After a period of time, in the spring, bamboo shoots will be unearthed, slowly the outer shell will be removed, and then from the middle of the bamboo. 3. Then the bamboo will begin to joint and grow to a height of more than 10 m in just a few months. But in general, the bamboo will only keep rising and will not become thicker. 4. After the bamboo flowers and bears fruit, the stems shed their leaves and do not grow new leaves until they become yellow and die. The majority of bamboos thrive at temperature ranges of 8.8 36 C. Some species, however, grow at high altitudes, as in the case of some Arundinaria species up to 10,000 ft (3050 m) in India. Rainfall is an important factor, and 40 in. (1020 mm) seems to mark the minimum annual precipitation required. The upper limit is not known but bamboos are found in zones with over 250 in. of rain (6350 mm). The most common range is 50 160 in. (1270 4050 mm) per year. Relative humidity is correspondingly high and ranges from 80% upward. Most bamboos grow in a wide range of soil, such as sandy loam to loamy clay soils, derived from river alluvium or frequently from the underlying rock. Yellow, brownish yellow, or light reddish yellow are the soil colours most frequently encountered. Usually bamboo prefers welldrained soils but it is also found in swampy or wet stream beds. No bamboo is reported on saline soils (Khybri et al., 1987).

2.4 Bamboo growing areas in India India holds the second position in terms of the world’s growing areas and nearly 8.96 million hectares of land is covered by bamboo.

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Figure 2.2 Share of bamboo resource in India (Subrata, 2007).

This includes forest land, homesteads and private plantations. Next to China, India is the second largest producer of bamboo with 136 different species. The bamboo growing areas in India are shown in Fig. 2.2. In India bamboo grows in the northeastern states, Western Ghats, Madhya Pradesh, Andhra Pradesh, and Chhattisgarh. Some of the important species of bamboo grown in India are Arundinaria, Cephalostachyum, Dendorcalamus, and Dinchola.

2.5 Morphology of bamboo Morphology has both analytical and interpretative functions, and will always be of great importance in the naming and identification of bamboos. There are 1000 1500 bamboo species (Asia accounts for about 1000 species) within 75 91 genera of bamboo plants and 50 species are now involved in textile production (Fu et al., 2012; Hardin et al., 2009; He et al., 2008; Steffen et al., 2013; Waite, 2009). The morphology of

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bamboo refers to the external structure (form and features) of the bamboo plant’s components. Bamboo does not have a central trunk like other woody plants and its major components include roots, rhizomes, culms, branches, leaves, and flowers (Seethalakshmi et al., 1998: Qisheng et al., 2003). Rhizome is an important part of bamboo which bears roots and this character of rhizome decides whether the plant will be a clumpforming or nonclump-forming type (Li, 2004). The underground part of bamboo is the rhizome, and in well-developed bamboo it spreads and forms shoots or new rhizome from its nodes (Seethalakshmi et al., 1998). The new young shoots are covered by sheaths that fall off as they grow up into mature culms (Li, 2004). Culm is the important aboveground part of bamboo from which bamboo is characterised as a hollow cylindrical tube divided by nodes and internodes (Fengel and Wegener, 1989). Bamboos can be classified into two main types: sympodial (clumping and largely tropical) bamboos, and monopodial (running and largely warm temperate bamboos) (Maoyi and Banik, 1995; Valade and Dahlan, 1991). Monopodial bamboos spread by creeping rhizomes. Climatic conditions influence the differences in rhizome system. Monopodial bamboos are native to temperate climates with cool winters and sympodial bamboos are native to tropical climates with a dominant dry season (Kleinhenz and Midmore, 2001). They will naturally invade and thicken up. They can be very easily propagated by simple cuttings from the rhizomes. It is more difficult to make such cuttings from sympodial bamboo. However, techniques such as soillayering, air-layering, and branch or culm cuttings can be successfully used. Reduced rhizome surface to dehydration during extended dry seasons can be attributed to the tight clumping habit of tropical species (Farrelly, 1984). The genus Phyllostachys, a temperate monopodial one, mainly originates from Central China and Japan (Abd. Razak and bin Mohamad, 1995; Maoyi and Banik, 1995). Species Phyllostachys aurea (André) Rivière & C. Rivière is indigenous to East China (Huxley, 1992) within the genus, Phyllostachys viridiglaucescens; whereas Phyllostachys pubescens Mazel ex Lehaie is native to China, and occurs extensively (Li et al., 1998; Scurlock et al., 2000). Other species, that is, Phyllostachys bambusoides Siebold et Zucc. is native to China, but can thrive better in more colder conditions than P. pubescens (Chao, 1989; Scurlock et al., 2000). Bambusa ventricosa McClure is native to South China (Huxley, 1992) and the genus Bambusa (sympodial one) is found in tropical and subtropical Asia (Sun et al., 2006). Bamboo plants can be as tall as 30 m (98 ft) and as wide as 25 30 cm (10 12 in.) in diameter (“Promoting the Beauty and Utility of Bamboo,”

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2008). Unlike other plants, it initially develops in full diameter from the ground and continues growing up to the maximum height without branching until 3 4 months old and at this point, leaves and branches emerge from nodes. The cavity, diaphragm, node, branch, internode, and wall are the main parts of a bamboo stem. Main parts of a bamboo stem have been shown in Fig. 2.3. Each hollow cylindrical portion between two nodes is called an internode or culm. The outer part of the bamboo stem, the exodermis, comprises the green portion with dense vascular bundles. The inner part of the stem, endodermis, comprises the yellow portion with rare vascular bundles. The main cellulosic part or timber lies between the exodermis and endodermis (Li et al., 2015; “Promoting the Beauty and Utility of Bamboo,” 2008; Waite, 2010). Each bamboo culm can be as long as 10 25 cm between two nodes. The diameter of bamboo fibres varies from 10 to 20 nm. Individual fibre length may vary from 5 to 159 mm depending on species (Hardin et al., 2009; Steffen et al., 2013; Witayakran et al., 2013). He et al. (2008) extracted about 51% cellulose from bamboo as compared to hardwood and softwood trees, which generally yield 42% 51% and 39% 43%, respectively (He et al., 2008). The flowering sequences in bamboo vary according to species and these are classified into three types, namely, annual, irregular, and gregarious. Bambusa tulda and some major species exhibit gregarious flowering that occurs at long intervals with synchronised seed production.

Figure 2.3 Main parts of bamboo stem.

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The whole clump at one point produces flower and then dies over the course of 2 3 years. This cycle repeats every 35 45 years or even up to more than 60 years. All herbaceous bamboos exhibit seasonal flowering, while woody bamboos exhibit gregarious flowering (Tso, 2009). Bamboos grow from sea level, in the tropics, to 4000 m above sea level, in the temperate region. Although, bamboos are more common to the tropics, they also occur naturally in subtropical and temperate zones of the world, except in Europe. The geographical distribution of bamboos is governed largely by the conditions of rainfall, temperature, altitude, and soil. Most of the bamboos require a temperature from 8 C to 36 C, a minimum annual rainfall of 1000 mm, and high atmospheric humidity for good growth. They form an important constituent of many deciduous and evergreen forests. In nature bamboos seldom occur as pure crops, but are generally found as an understorey in tropical evergreen, tropical moist deciduous, tropical dry deciduous, montane subtropical, montane wet temperate, and Himalayan wet temperate forests. Bamboo is considered to be the second largest resource of forestry in the whole world because of its rapid growth potential. Bamboo forests are distributed extensively in tropical and subtropical climates in frigid zones. Bamboo is a multipurpose plant and can substitute for timber in many respects due to its lignified culms. Because of its fast growth, intricate rhizome system, and sustainability, it has become a plant with conservation value, able to mitigate phenomena that result from global climate change.

2.6 Types of bamboo Bamboo has been categorised into two broad regenerative categories.

2.6.1 Running bamboo The varieties shown in Fig. 2.4A are generally grown in temperate regions (hardy) and spread exuberantly. These varieties grow quickly and their stem is hard. Running bamboos exhibit leptomorph or monopodial rhizomes. This is characterised by an independent underground stem from which aerial culms develop.

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Bamboo Fibres

Figure 2.4 (A) Running bamboo and (B) clumping bamboo.

Running bamboos (monopodial or leptomorph) spread through the growth of long, horizontal roots, called rhizomes. They have a distinctively vigorous rhizome root system. The monopodial or leptomorph rhizomes tend to grow horizontally, parallel to the ground, spreading outward and overtaking an area. As the horizontal rhizomes extend outward, they eventually produce fresh shoots, new culms, growing upward. With a little knowledge and proper materials, running bamboos can be effectively contained. There are running species for most all climate zones. From the cold of climate zone 5 to the warmth of the tropics, there are running species suited for all applications. They spread variously, sending out underground runners (rhizomes) which sometimes range far from the parent plant. Runners fill in the spaces between plantings faster, making them ideal for fast screens, hedges, and the popular open grove look. Bamboo runners may be easily contained, since the rhizomes grow sideways at a depth of only about 2 18 in. Most are also very cold-hardy. 2.6.1.1 Types of running bamboo The common species of running bamboo tend to be taller and less coldhardy than the popular clumping types: • Phyllostachys nigra is a black bamboo that stands 20 35 ft high and grows in zones 7 through 10. • Hibanobambusa tranquillans ‘Shiroshima’ is a variegated bamboo reaching 16 ft; it grows in zones 7 through 9.

Growth characteristics of bamboo: types of bamboo, morphology of bamboo

•

33

Phyllostachys bambusoides ‘Allgold’ grows in zones 7 through 10 and can reach a height of 35 ft. It boasts a yellow culm.

2.6.2 Clumping bamboos The varieties shown in Fig. 2.4B are usually grown in tropics (tender) and slowly expand from the original plant. Clumping bamboo usually grows less than 15 ft high (Tso, 2009). Clumping bamboo displays pachymorph or sympodial components to their rhizome structure, meaning that each rhizome turns upward to form a culm. Further, clumping bamboo can be classified as (1) cold hardy clumping species and (2) tropical varieties. The cold hardy clumping species grow in very limited climatic zones and generally take many years to attain a height of 8 12 ft. They usually struggle to survive in climate zones 7 and warmer, and usually die due to the summer heat and humidity. Cold climates are better for their growth and a slow growing bamboo can reach heights up to 12 ft. Tropical clumping bamboos are grown only in very warm climate zones such as zone 8 and 9. They are generally giant plants and can grow very fast like running bamboo. The problem is the limited climate zones and the spacing of the canes within the clumper. The spaces between the culms (canes) are so close that most specimens are very unsightly due to the large amount of dead canes and limbs in the interior of the clump. These dense dead canes and limbs cannot be reached unless some of the outside canes are cut away first. 2.6.2.1 Types of clumping bamboo There are a few commonly grown types of clumping bamboo plants: • Fargesia rufa • Fargesia nitida • Fargesia robusta F. rufa Green Panda is popular because it stays relatively short (8 10 ft high) and is cold-hardy; it can be grown in USDA plant hardiness zones 5 through 9. While is it relatively sun-tolerant, it will do best where it receives some shade in the afternoon, especially if you live at the southern end of the zone range. F. nitida is equally cold-hardy but is taller (12 15 ft). F. robusta ‘Campbell’ also grows to 12 15 high, but it is not as hardy; it can be grown in zones 7 through 9.

Bamboo Fibres

34

2.7 Other varieties of bamboo (Chinese varieties) 2.7.1 Ornamental bamboo 2.7.1.1 Luo Han bamboo (Phyllostachys aurea) This is a tufted type, the culm is not high, the head is big, the upper body is small. It can be used as a handicraft material (Fig. 2.5). 2.7.1.2 Stringed bamboo (Bambusa blumeana) The stringed bamboo is clustered, some are tall, some are short. The stem surface is light yellow in colour with thick and thin green lines on it. It looks like ‘stringed violin’ and hence the name stringed bamboo (Fig. 2.6).

Figure 2.5 Luo han bamboo.

Figure 2.6 Stringed bamboo.

Growth characteristics of bamboo: types of bamboo, morphology of bamboo

35

2.7.1.3 Phoenix bamboo (Oligostachyum hupeheuse) This is a caespitose type bamboo. The culms are thin and short, and the variety has very small branches and leaves, like the phoenix tail (Fig. 2.7). 2.7.1.4 Square bamboo (Chimonobambusa quadrangularis) Bamboo culm is square in nature. The face is light yellow in colour and there is a ring of small thorns on the ring, so it is also known as ‘thorn bamboo’. It can be used for handicraft processing materials (Fig. 2.8). 2.7.1.5 Palm bamboo (Rhapis excelsa) This is a black, leathery, solid, with white bristle veins in the flesh. Palm bamboo not only has high ornamental value, but also has high medicinal

Figure 2.7 Phoenix bamboo.

Figure 2.8 Square bamboo.

36

Bamboo Fibres

value. Eating palm bamboo can play the role of dispelling wind, dehumidification, convergence, and haemostasis (Fig. 2.9). 2.7.1.6 Dragon bamboo (Dendrocalamus giganteus) This is the largest known species of giant tufted bamboo in the world, used locally to make buckets and large utensils (Fig. 2.10). 2.7.1.7 Purple bamboo (Phyllostachys nigra) A year after planting this variety, purple spots gradually appear on the bamboo pole and finally the whole bamboo pole turns purple black in colour. It is mostly used for courtyard viewing. This bamboo is tough and

Figure 2.9 Palm bamboo.

Figure 2.10 Dragon bamboo.

Growth characteristics of bamboo: types of bamboo, morphology of bamboo

37

Figure 2.11 Purple bamboo.

Figure 2.12 Single bamboo.

can be used to make articles such as fishing rods and walking sticks, other handicrafts, as well as musical instruments, such as flutes, etc. (Fig. 2.11).

2.7.2 Modern bamboo varieties 2.7.2.1 Single bamboo (Bambusa cerosissima) This variety of bamboo is delicate and has strong fibre toughness. It can be woven into bamboo strips as thin as cicada wings or hair, and is used in fine bamboo weaving crafts like silk (Fig. 2.12). 2.7.2.2 Four seasons bamboo (Oligostachyum lubricum) This is a fascicular type bamboo variety named after the four seasons bamboo shoots. It is characterised by thick and straight culms and has fine fibres and grows fast. It is a good material for papermaking and has great economic value (Fig. 2.13).

38

Bamboo Fibres

Figure 2.13 Four seasons bamboo.

Figure 2.14 Ci bamboo.

2.7.2.3 Ci bamboo (Neosinocalamus affinis/Bambusa emeiensis) This is a typical representative of bamboo, tall, with a long tube-like structure. It is a good material for weaving bamboo handicrafts (Fig. 2.14). 2.7.2.4 Spotted bamboo (Phyllostachys bambusoides) This refers to several types of bamboo with stems that are mottled by dark spots. It is also known as Concubine Hunan bamboo, with scattered, straight, high stems, with brown spots on the surface. Legend has it that when Emperor Shun died suddenly during a trip to Cangwu, the tears of his two concubines, the Xiang River goddesses Ehuang and Nüying dropped onto the surrounding bamboo and stained it forever, and thus the name ‘spotted bamboo’. This kind of bamboo is mostly used as building and decorative material (Fig. 2.15).

Growth characteristics of bamboo: types of bamboo, morphology of bamboo

39

Figure 2.15 Spotted bamboo.

Figure 2.16 Nan bamboo.

2.7.2.5 Nan bamboo (Phoebe faberi) This is the representative of scattered bamboo. The culms are tall, straight, and hard. It is a good building material. The bamboo heads are good materials for carving handicrafts. Their shoots are the best dish (Fig. 2.16). 2.7.2.6 Cinan bamboo (Category of Nan Bamboo) This is a bamboo of the genus Phyllostachys, a genus of Asian bamboo in the grass family. Many of the species are found in central and southern China, with a few species in northern Indochina and in the Himalayas. It is known for its hard ‘thorns’ on the stems and branches. It has a Caespitose type culm, tall, straight and thick with fewer leaves. It is mostly used for building materials (Fig. 2.17). 2.7.2.7 Water bamboo (Phyllostachys heteroclada) It has scattered, long and hard culms, shaped like steel pipes. It has sparse leaves and the toughness is very good. It is mainly used for bamboo

40

Bamboo Fibres

Figure 2.17 Cinan bamboo.

Figure 2.18 Water bamboo.

furniture-making material, and can be used as a papermaking material when it grows in a large area (Fig. 2.18). 2.7.2.8 Gaojie bamboo (Phyllostachys prominens) This is also known as high joint bamboo and its bamboo rod is the highest among bamboo species. Using the shoots of common joint bamboo as food can not only increase the taste of food, but also increase the nutritional value (Fig. 2.19). 2.7.2.9 Arrow bamboo (Fargesia) This is a variety with straight stalks and smooth walls and it is also called slippery bamboo. It is a favourite food of giant pandas. It is also used for making penholders, chopsticks, and woven basket-scaffolding (Fig. 2.20).

Growth characteristics of bamboo: types of bamboo, morphology of bamboo

41

Figure 2.19 Gaojie bamboo.

Figure 2.20 Arrow bamboo.

There are many kinds of bamboo, and different types of bamboo need different environments. Bamboo likes to grow in high humidity and cannot be exposed to strong sunlight. For example, Luo Han bamboo needs enough light to grow, whereas square bamboo needs to grow in the shade, otherwise their growth forms are affected.

2.8 Chemical composition of bamboo The chemical composition of bamboo is similar to that of wood. Table 2.2 shows the chemical composition of bamboo (Higuchi, 1957). The main constituents of bamboo culms are cellulose, hemicellulose, and lignin, which amount to over 90% of the total mass. The culm comprises

Bamboo Fibres

42

Table 2.2 Chemical composition of bamboo (Higuchi, 1957). Species % % Ethanol toluene % Ash extracts Lignin

Phyllostachys heterocycla Phyllostachys nigra Phyllostachys reticulata

% Cellulose

% Pentosan

1.3

4.6

26.1

49.1

27.7

2.0 1.9

3.4 3.4

23.8 25.3

42.3 25.3

24.1 26.5

60% parenchyma, 40% fibres, and 10% conducting tissues (vessels and sieve tubes). Bamboo culm constitutes 60% 70% of fibre content by weight (Liese, 1992). The minor constituents of bamboo are resins, tannins, waxes, and inorganic salts. Compared with wood, however, bamboo has higher alkaline extractives, ash, and silica content (Tomalang et al., 1980; Chen et al., 1985). Yusoff et al. (1992) studied the chemical composition of 1-, 2-, and 3-year-old bamboo (Gigantochloa scortechinii). The results indicated that the holocellulose content did not vary much among different ages of bamboo. Alpha-cellulose, lignin, extractives, pentosan, ash, and silica content increased with increasing age of bamboo. Bamboo contains other organic composition in addition to cellulose and lignin. It contains about 2% 6% starch, 2% deoxidised saccharide, 2% 4% fat, and 0.8% 6% protein. The carbohydrate content of bamboo plays an important role in its durability and service life. The durability of bamboo against mould, fungal, and borers attack is strongly associated with its chemical composition. Bamboo is known to be susceptible to fungal and insect attack. The natural durability of bamboo varies between 1 and 36 months depending on the species and climatic condition (Liese, 1980). The presence of large amounts of starch makes bamboo highly susceptible to attack by staining fungi and powder-post beetles (Mathew and Nair, 1990). It is noteworthy that even in 12-year-old culms starch was present in the whole culm, especially in the longitudinal cells of the ground parenchyma (Liese and Weiner, 1997). Higher benzene ethanol extractives of some bamboo species could be an advantage for decay resistance (Feng et al., 2002). The ash content of bamboo is made up of inorganic minerals, primarily silica, calcium, and potassium. Manganese and magnesium are two other common minerals. Silica content is the highest in the epidermis, with very little in the nodes and is absent in the internodes. Higher ash content in some bamboo species can adversely affect the processing machinery.

Growth characteristics of bamboo: types of bamboo, morphology of bamboo

43

The internode of solid bamboo has significantly higher ash, 1% NaOH, alcohol toluene, and hot water solubles than the nodes (Mabilangan and Estudillo, 2002). However, differences between the major chemical composition of node and internode fraction of bamboo are small (Scurlock et al., 2000); neither the number of nodes nor the length of internode segments would be critical to the utilisation of bamboo for energy conversion, chemical production, or as a building material. Fujii et al. (1993) investigated the chemistry of the immature culm of a Moso bamboo (P. pubescens Mazel). The results indicated that the contents of cellulose, hemicellulose, and lignin in immature bamboo increased while proceeding down the culm. The increase of cellulose in the lower position was also accompanied by an increase in crystallinity. The culm of the bamboo is covered by its hard epidermis and inner wax layer. It also lacks ray cells as radial pathways. Several results have revealed that bamboo is difficult to treat with preservatives (Liese, 1987; Lee et al., 2001). An oil-bath treatment can successfully protect against fungal attack, but severe losses in strength have to be expected (Leithoff and Peek, 2001). Since the amount of each chemical composition of bamboo varies with age, height, and layer, the chemical compositions of bamboo are correlated with its physical and mechanical properties. Such variation can lead to obvious physical and mechanical properties changes during the growth and maturation of bamboo. This chapter has concentrated on a detailed analysis of chemical composition at different age, height, and horizontal layer of bamboo in order to have a better understanding of the effect of these factors on the chemical composition of bamboo. It can also provide chemical composition data for the pulp and paper industry which may have interest in better utilising bamboo.

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International Bamboo Workshop, Hangzhou, China, 6 14 October. Chinese Academy of Forestry, Beijing China; International Development Research Center, Ottawa, Canada, 110 113. Das, S., 2007. Bamboo 21st century eco fibre: Application in towel sector, Fibre2Fashion.com, World of Garment-Textile-Fashion, 1 5. Farrelly, D., 1984. The Book of Bamboo: A Comprehensive Guide to this Remarkable Plant, Its Uses, and Its History. Thames and Hudson, London, UK. Feng, W.Y., Wang, Z.H., Guo, W.J., 2002. A study on chemical composition and fibre characteristics of two sympodial bamboos. In: Paper for the International Network for Bamboo and Rattan. Chinese Academy of Pulp and Paper Making. Fengel, D., Wegener, G., 1989. Wood: Chemistry, Ultrastructure, Reactions. Walter de Gruyter Publishers, Berlin and New York. Fu, J., Li, X., Gao, W., Wang, H., Cavaco-paulo, A., Silva, C., 2012. Bio-processing of bamboo fibres for textile applications: A mini review. Biocat. Biotrans. 30 (1), 141 153. Available from: https://doi.org/10.3109/10242422.2012.650450. Fujii, Y., Azuma, J., Marchessault, R.H., Morin, F.G., Aibara, S., Okamura, K., 1993. Chemical-composition change of bamboo accompanying its growth. Holzforschung 47 (2), 109 115. Gupta, A., Kumar, A., 2008. Potential of bamboo in sustainable development. Asia-Pac. Bus. Rev. 4 (3), 100 107. Hardin, I.R., Wilson, S.S., Dhandapani, R., Dhende, V., 2009. An assessment of the validity of claims for bamboo fibre. AATCC Rev. 9 (10), 33 36. He, J., Cui, S., Wang, S.Y., 2008. Preparation and crystalline analysis of high-grade bamboo dissolving pulp for cellulose acetate. J. Appl. Polymer Sci. 107 (2), 1029 1038. Available from: https://doi.org/10.1002/app.27061. Higuchi, H., 1957. Biochemical studies of lignin formation, III. Physiol. Plant. 10, 633 648. Huxley, A., 1992. The New Royal Horticultural Society Dictionary of Gardening. Macmillan Press, London. Khalil, H.P.S.A., Bhat, I.U.H., Jawaid, M., Zaidon, A., Hermawan, D., Hadi, Y.S., 2012. Bamboo fibre reinforced biocomposites: a review. Mater. Design 42 (1), 353 368. Khybri, M.L., Nambiar, K.K.M., Niwas, S., Puri, D.N., Saxena, H.C., 1987. Mortality of bamboo (Dendrocalamus strictus) in relation waterlogging and salinity build up in chambal ravine. National Symposium Land and Water Management in Ravines. Abst. No. 38. 34 p. Kleinhenz, V., Midmore, D.J., 2001. Aspects of bamboo agronomy. Adv. Agric. 74, 99 145. Lee, A.W.C., Chen, G., Tainter, F.H., 2001. Comparative treatability of Moso bamboo and Southern pine with CCA preservative using a commercial schedule. Bioresour. Technol. 77, 87 88. Leithoff, H., Peek, R.D., 2001. Heat treatment of bamboo. In: Paper Prepared for the International Research on Wood Preservation 32nd Annual Meeting, Section 4, Nara, Japan. Li, X., 2004. Physical, chemical, and Mechanical properties of bamboo and its utilization potential for fibreboard manufacturing, Master of Science Thesis, Louisiana State University, Available at http://etd.Isu.eduidocs/available/etd-04022004-l44548/unrestricted/Lijhesis.pdf (last accessed 15.09.08.). Li, K., Wang, X., Wang, J., Zhang, J., 2015. Benefits from additives and xylanase during enzymatic hydrolysis of bamboo shoot and mature bamboo. Bioresour. Technol. 192, 424 431. Available from: https://doi.org/10.1016/j.biortech.2015.05.100. Li, R., Werger, M.J.A., During, H.J., Zhong, Z.C., 1998. Biennial variation in production of new shoots in groves of the giant bamboo Phyllostachys pubescens in Sichuan, China. Plant Ecol. 135, 103 112. Li, X.B., 2004. Physical, chemical, and mechanical properties of bamboo and its utilization potential for fibreboard manufacturing, LSU Master’s Theses. 866. Louisiana State University. https://digitalcommons.lsu.edu/gradschool_theses/866.

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Liese, W., 1980. Preservation of bamboos. In: Lessard, G., Chouinard, A. (Eds.), Bamboo Research in Asia. IDRC, Canada, pp. 165 172. Liese, W., 1987. Anatomy and properties of bamboo. In: Rao, A.N., Dhanarajan, G., Sastry, C.B. (Eds.), Recent Research on Bamboos. Chinese Academy of Forestry, China and International Development Research Centre, Canada, pp. 196 208. Liese, W., 1992. The structure of bamboo in relation to its properties and utilization. In: International Symposium on Industrial Use of Bamboo, Beijing, China. Liese, W., Weiner, G., 1997. Modifications of bamboo culm structures due to ageing and wounding. In: Chapman, G. (Ed.), The Bamboos. The Linnean Society, London, pp. 313 322. Lobovikov, M., Shyam, P., Piazza, M., Ren, H., Wu, J., 2007. Non-wood forest products 18 world bamboo resources. A Thematic Study Prepared in the Framework of the Global Forest Resources Assessment. Food and Agriculture Organization of the United Nations, Rome. Mabilangan, F.L., Estudillo, E.C., 2002. Chemical properties of bikal [Schizostachyum lumampao (Blanco) Merr.] and solid bamboo [Dendrocalamus strictus (Roxb) Nees]. 2001. Project of Forest Products Research and Development Institute, Philippines’ Department of Science and Technology. Maoyi, F., Banik, R.L., 1995. Bamboo production systems and their management. In: Fifth International Bamboo Workshop and the IVth International Bamboo Congress, Ubud, Bali, Indonesia, 19 22 June. International Network for Bamboo and Rattan, New Delhi. Mathew, G., Nair, K.S.S., 1990. Storage pests of bamboos in Kerala. In: R. Rao, R. Gnanaharan, C.B. Sastry (Eds.), Bamboos: Current Research. IV. Proceedings of International Bamboo Workshop, KFRI/IDRC, 212 214. Mohd, T.M., Bhat, I.U.H., Mohmod, A.L., Aditiawati, P., Khalil, H.P.S.A., 2013. Thermal and FT-IR characterization of gigantochloa levis and gigantochloa scrotechinii bamboo, a naturally occuring polymeric composite. J. Polym. Environ. 21 (2), 534 544. Pande, V.C., Parandiyalcand, A.K., Kala, S., 2012. Growth of bamboo in ravines, Chapter-7. In: R.S. Kurothe, M.L. Gaur (Eds.), Conservation and Production Potential of Bamboo in Ravine Lands. Promoting the Beauty and Utility of Bamboo, 2008. Retrieved January 3, 2016, from http://www.bamboo.org/GeneralInfo.html. Qisheng, Z., Shenxue, J., Shuhai, J., Ping, X., 2003. International Network for Bamboo and Rattan, Nanjing Forestry University, Nanjing, China. Ray, A.K., Mondal, S., Das, S.K., Ramachandrarao, P., 2005. Bamboo-A functionally graded composite - correlation between microstructure and mechanical strength. J. Mater. Sci. 40 (19), 5249 5253. Scurlock, J.M.O., Dayton, D.C., Hames, B., 2000. Bamboo: An Overlooked Biomass Resource? ORNL/TM-999/264. Oak Ridge National Laboratory, Oak Ridge, Tennessee. Seethalakshmi, K.K., Muktesh-Kumar, M.S., Pillai, K.S., Sarojam, N., 1998. Bamboos of India, a Compendium. Kerala Forest Research Institute, India and International Network for Bamboo and Rattan, China, ISBN 81-86247-25-4. Steffen, D., Marin, A.W., Muggler, I.R., 2013. Bamboo: A holistic approach to a renewable fibre for textile design. In: 10th European Academy of Design Conference Crafting the Future, 1 14. Sun, Y., Xia, N., Stapleton, C.M.A., 2006. Relationships between Bambusa species (Poaceae, Bambusoideae) revealed by random amplified polymorphic DNA. Biochem. Syst. Ecol. 34, 417 423. Tomalang, F.N., Lopez, A.R., Semara, J.A., Casin, R.F., Espiloy, Z.B., 1980. Properties and utilization of Philippine erect bamboo. In: Lessard, G., Chouinard, A. (Eds.),

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International Seminar on Bamboo Research in Asia. International Development Research Center and the International Union of Forestry Research Organization, Singapore, pp. 266 275. , May 28 30. Tso, L.D., 2009. Black diamond from green bamboo, Taiwan Today, September. Valade, I., Dahlan, Z., 1991. Approaching the underground development of a bamboo with leptomorph rhizomes: Phyllostachys viridis (Young) McClure. J. Am. Bamboo Soc. 8, 23 42. Waite, M., 2009. Sustainable textiles: the role of bamboo and a comparison of bamboo textile properties-Part 1. Journal of Textile and Apparel, Technology and Management 6 (2), 1 21. Waite, M., 2010. Sustainable textiles: The role of bamboo and a comparison of bamboo textile properties-Part II. Journal of Textile and Apparel, Technology and Management 6 (3), 1 23. Witayakran, S., Haruthaithanasan, M., Agthong, P., Thinnapatanukul, T., 2013. Green production of natural bamboo fibres for textiles. International Textiles and Costume Congress. pp. 1 6. Yusoff, M.N.M., Abd Kadir, A., Mohamed, A.H.J., 1992. Utilization of bamboo for pulp and paper and medium density fibreboard. In: Mohd, W.R.W., Mohamad, A.B. (Eds.), Proceedings of the Seminar towards the Management, Conservation, Marketing and Utilization of Bamboos. Kuala Lumpur, FRIM, pp. 196 205.

Index Note: Page numbers followed by “f” and “t” refer to figures and tables, respectively.

A AATCC. See American Association of Textile Chemists and Colourists (AATCC) American Association of Textile Chemists and Colourists (AATCC), 177 Antimicrobial properties antimicrobial textiles, 169 bamboo clothing, 169 170 bamboo extract, 171 173, 172f antibacterial and antifungal properties, 184 185 Aspergillus niger, 185, 188t cotton fabric, 180 181, 181f E. coli, 183 185, 186t Gram-negative bacterium, 183 Gram-positive bacterium, 183 NBFs, 182 183, 189 190 S. aureus, 184 185, 187t spectrophotometric method, 182 Staphylococcus epidermidis, 183 Trichoderma viridae, 185, 188t woven bamboo viscose fabric, 181 182 bamboo fibres and fabrics, 173 191 bacterial strains, 175 plant extraction, 174 bamboo plant extraction, 175 finishing, 176 plant material, collection of, 175 process, 176 fabrics, antimicrobial activity of inoculation, 177 inoculum, preparation of, 176 qualitative agar diffusion test AATCC 147-2004, 177 180 autoclave, 177, 178f bacteriological incubator, 177, 178f laminar air flow unit, 177 178, 179f micropipette, 179 180, 179f

Applications and technoeconomics of bamboo fibres bamboo viscose fibre, 214, 225 composites, 220 222 construction industry, 219 220 eco-fashion designers, 217 in fashion, 217 paper production, 218 219 products, 214 215 textile industry, 215 217 bamboo medical textiles and healthcare products, 216 217 natural bamboo fibre, 215 216 origins of, 215 textile clothing, 217 trends and technoeconomics of, 222 224 Arrow bamboo, 40 41, 41f Aspergillus niger, 185, 188t

B Bamboo bamboo fibres. See Bamboo and bamboo fibres charcoal fibre. See Bamboo charcoal fibre chemical composition, 41 43, 42t Chinese varieties modern bamboo varieties, 37 41 ornamental bamboo, 34 37 growth habitat, 25 26 growth process, 27 in India, 27 28, 28f morphology, 28 31 natural antibacterial fibre, 137 regions of, 24 25, 24t types of clumping bamboos, 33 running bamboo, 31 33 Bamboo and bamboo fibres bamboo, usage of, 3 bamboo viscose products, 4 5

231

232 Bamboo and bamboo fibres (Continued) charcoal, 5 cotton fibres, 2 3 cultivation, 4 geographical distribution of bamboo, 11 15 arundinarieae, 12 bambusae, 12 growth rate, 11, 12f olyreae, 12 production, 13 14 raw material, 14 resources, 12 history of bamboo textiles, 6 9 clothing, 6 microbial growth, 3 natural fibres, 1 plant-based fibres, 4 prospects of, 15 18 cellulose, 15 16 composites, 17 18 fabrics, 15 natural, source of, 15 synthetic fibres, 2 taxonomy, 9 11, 10t bamboo, types of, 9 10 botanical classification, 10, 10t monopodial or leptomorph rhizome (root) systems, 10 11 textile fibre, development of, 1 Bamboo charcoal fibre, 63 66 bamboo fibre, 71 72 production of, 64 66 Bamboo fabrics antimicrobial properties. See Antimicrobial properties yarns and fabrics. See Bamboo yarns and fabrics Bamboo-fibre reinforced plastic composites (BFRP), 17 Bamboo fibres antimicrobial properties. See Antimicrobial properties applications and technoeconomics of. See Applications and technoeconomics of bamboo fibres

Index

extraction methods for. See Extraction methods for bamboo fibres properties of. See Properties of bamboo fibres Bamboo viscose fibre, 225 Bamboo yarns and fabrics abrasion resistance, 155 156 applications, 137 crease recovery, 157 drape, 160 eco-friendly nature, 138 fabric stiffness, 158 160 fabric wetting, 162 167 cotton fabrics, 166 167 distilled water, 162 grey scale ratings, 162 163 knitted fabrics, production of, 164, 165t spray test, 162 163 thermal comfort properties, 163 washing cycles, 166 water vapour permeability, 164 flammability, 157 158 mechanical properties bamboo (pulp) or regenerated bamboo fibre fabrics, 137 138 tensile properties, 142 143 medical textiles, 137 138 moisture content and regain, 161 162 permeability, 160 161 physical properties of twist multiplier, 142 twist (TPI), 142 yarn liner density, 141 142 pilling, 156 157 production and properties of, 138 141, 139t fabric production, 149 150 methodology, 140 141 testing, 141, 150 153 tensile strength and tearing strength, 153 155 Uster yarn hairiness tester, 144 148 cotton fibres, 145 146 polyester yarns, 146 147 regenerated bamboo yarns, tensile properties of, 147, 147t

233

Index

silk yarn, 148, 149t single yarn strength, 148 yarn evenness testing, 143 144 Bambusa bamboo, 25 Bambusa blumeana. See Stringed bamboo Bambusa cerosissima. See Single bamboo Bambusa tulda, 30 31 Bambusa ventricosa, 29 BFRP. See Bamboo-fibre reinforced plastic composites (BFRP) Breathable fibres. See Bamboo and bamboo fibres

C CAN. See Chemical-assisted natural (CAN) Category of Nan bamboo. See Cinan bamboo Cellulosic fibre, 223 Characterisation of Bamboo fibres bamboo charcoal fibre, 71 72 bamboo pulp fibre, 71 72 Bambusa emeiensis chemical bamboo fibre, 82 83, 83f cellulose, 73 74 chemical bamboo fibres, SEM images of, 82 83, 82f chemical composition, 72 73 cross-sectional views, 79 84, 80f, 81f, 84f crystallinity, degree of cellulosic fibres, 86 87 XRD pattern, 89 91 elementary bamboo fibres, morphology of, 78 79 FTIR studies, 91 95 assignment of, 91 93, 92t bamboo shell fibre, 93 94, 93f chemical bonds, 94 95, 95t hemicellulose, 74 lignin, 74 75 longitudinal views, 79 84, 80f, 81f, 84f macro- and microlevel, 75 78 ESEM images, 75, 76f microstructure of, 75, 75f polylamellae structure, model of, 75, 76f primary and secondary wall, 77 78

natural bamboo fibre, 71 72 Phyllostachys edulis mechanical bamboo fibres, 82 83, 83f X-ray diffraction, 85 86 Chemical-assisted natural (CAN), 54 Chemical processing of bamboo and bamboo products, 196 bamboo yarn, 195 chemical treatment alkali on bamboo, effect of, 196 197 bamboo/cotton fabrics, 203 204 bamboo, dyeing of, 203 205 bamboo fibres, bleaching of, 197 198 bamboo textiles, dyeing of, 202 203 colour fastness properties, 205 206 colour strength (K/S), 206 209 cotton, 203 204 fabric fastness properties, 206 hydrogen peroxide, bleaching with, 198 202 sodium chlorite, bleaching with, 198 sodium hypochlorite, bleaching with, 198 Chimonobambusa quadrangularis. See Square bamboo Ci bamboo, 38, 38f Cinan bamboo, 39, 40f Concubine Hunan bamboo, 38 Count strength product (CSP), 143 CSP. See Count strength product (CSP) Culm, 28 29

D Dendrocalamus giganteus. See Dragon bamboo Dendrocalamus strictus, 25 Differential scanning calorimetry (DSC), 221 Dimethyl sulfoxide (DMSO), 171 DMSO. See Dimethyl sulfoxide (DMSO) Dragon bamboo, 36, 36f DSC. See Differential scanning calorimetry (DSC)

E Emission scanning electron microscope (ESEM), 76f

234 Escherichia coli, 171, 183 185, 186t ESEM. See Emission scanning electron microscope (ESEM) Eureka Drape Tester, 160 Extraction methods for bamboo fibres advantages, 47 bamboo shoot shell, 58 59 biological methods, 56 57 chemical methods, 53 56 alkali or acid retting, 55 56 chemical retting, 54 55 and combined mechanical, 58 mechanical extraction methods, types of crushing, 52 grinding, 52 retting, 53 rolling mill, 52 53 steam explosion method, 50 51 mechanical process, 48 49, 49f microbial culture, 57 regenerated (pulp) bamboo fibres, production of lyocell process, 61 rayon process, 59 60 types of bamboo charcoal fibre, 63 66 bamboo (viscose) rayon fibres, 62 63 natural bamboo fibres, 47 49, 48f, 62

F Fabric testing, 141, 150 153 bursting strength, 152 153 cover factor, 151 crimp, 150 151 fabric thickness, 151 GSM, 151 tearing strength, 152 tensile strength, 151 152 thread density, 150 yarn count, 150 Fabric wetting, 162 167 cotton fabrics, 166 167 distilled water, 162 grey scale ratings, 162 163 knitted fabrics, production of, 164, 165t spray test, 162 163

Index

thermal comfort properties, 163 washing cycles, 166 water vapour permeability, 164 Fargesia. See Arrow bamboo Four seasons bamboo, 37, 38f

G Gaojie bamboo, 40, 41f

H High joint bamboo, 40 Hydrogen peroxide (HP), bleaching with, 198 202 PAA bleaching processes, 199, 201 pretreatment processes, 199 tenacity and elongation values, 202, 202t whiteness and yellowness indices, 199, 200t, 201t

K Kawabata evaluation system (KES), 123 KES. See Kawabata evaluation system (KES)

L Laminar air flow unit, 177 178, 179f Luo Han bamboo, 34, 34f

M Microbial type culture collection (MTCC), 175 Micropipette, 179 180, 179f Modern bamboo varieties arrow bamboo, 40 41, 41f Ci bamboo, 38, 38f cinan bamboo, 39, 40f four seasons bamboo, 37, 38f gaojie bamboo, 40, 41f nan bamboo, 39, 39f single bamboo, 37, 37f spotted bamboo, 38, 39f water bamboo, 39 40, 40f Monopodial bamboos, 29 Monopodial (single stem) bamboos, 25 Moso bamboo, 8 MTCC. See Microbial type culture collection (MTCC)

235

Index

N

bamboo viscose (pulp) fibres, physical properties of, 117 118 bending properties, 127 compression properties, 128 fabric compressibility, 128 fabric weight and thickness, 129 130 low stress mechanical properties, 123 133 natural bamboo fibres, physical properties of length and linear density, 103 105, 105t moisture absorption, 102 103 primary and total hand values, 130 133, 131t stress relaxation behaviour, 112 117 surface properties, 129 tensile properties, 105 112 alkali-treated bamboo fibre, 108, 108f, 109f bamboo fibre bundles, 106, 107t bamboo strips, 106, 107t flexural and tensile modulus, 108 mechanical properties, 108, 110, 110t, 111t physical properties, 110, 111t single bamboo fibres, 105, 106t wet and dry bamboo fibres, 112, 113f, 113t, 114f tensile properties (tensile tester KESFB1), 124 125, 126t thermal properties, 118 123 natural bamboo fibres, 121 TGA and DTG curves, 121 122, 121f, 122f thermogravimetric analysis, 119 121

Nan bamboo, 39, 39f NaOH. See Sodium hydroxide (NaOH) Natural bamboo fibres (NBFs), 47 49, 48f, 62, 67, 182, 223 LITRAX, 66 mechanical process, 48 49 NBFs. See Natural bamboo fibres (NBFs) Neosinocalamus affinis/Bambusa emeiensis. See Ci bamboo N-methylmorpholine-N-oxide (NMMO), 61

O Oligostachyum hupeheus. See Phoenix bamboo Oligostachyum lubricum. See Four seasons bamboo Ornamental bamboo dragon bamboo, 36, 36f Luo Han bamboo, 34, 34f palm bamboo, 35 36, 36f phoenix bamboo, 35, 35f purple bamboo, 36 37, 37f square bamboo, 35, 35f stringed bamboo, 34, 34f

P PAA. See Peracetic acid (PAA) Palm bamboo, 35 36, 36f Paramount Air Permeability Tester, 160 161 Peracetic acid (PAA), 199 Phoebe faberi. See Nan bamboo Phoenix bamboo, 35, 35f Phyllostachys aurea. See Luo Han bamboo Phyllostachys bambusoides. See Spotted bamboo Phyllostachys heteroclada. See Water bamboo Phyllostachys prominens. See Gaojie bamboo Phyllostachys pubescens, 29 PLA. See Poly lactic acid (PLA) Poly lactic acid (PLA), 221 Polypropylene (PP) fibre, 221 222 PP fibre. See Polypropylene (PP) fibre Properties of bamboo fibres

R Regenerated bamboo fibre, 62 63 Regenerated cellulosic bamboo, 63 Rhapis excelsa. See Palm bamboo Rhizome, 28 29 Rubbing fastness, 205 206

S Single bamboo, 37, 37f Slippery bamboo, 40

236 Sodium hydroxide (NaOH), 196 197 Spotted bamboo, 38, 39f Square bamboo, 35, 35f Staphylococcus aureus, 184 185, 187t Staphylococcus epidermidis, 183 Stringed bamboo, 34, 34f Sympodial bamboos, 29

T TAED. See Tetraacetylethylenediamine (TAED) Tensile properties CSP, 143 lea strength, 142 143 single yarn (rupture kilometre), 143 Tetraacetylethylenediamine (TAED), 199 Thorn bamboo, 35 Trichoderma viridae, 185, 188t

Index

U Uster Evenness Tester-3 (UT-3), 143 145 UT-3. See Uster Evenness Tester-3 (UT-3)

W Warm temperate bamboos, 29 Wash fastness, 205 Water bamboo, 39 40, 40f

X X-ray diffractometer (XRD), 88 89 XRD. See X-ray diffractometer (XRD)

Y Yarn hairiness, 144 148