Nonwoven fabric: manufacturing and applications 9781536175875, 1536175870

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MATERIALS SCIENCE AND TECHNOLOGIES

NONWOVEN FABRIC MANUFACTURING AND APPLICATIONS

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MATERIALS SCIENCE AND TECHNOLOGIES

NONWOVEN FABRIC MANUFACTURING AND APPLICATIONS

REMBRANDT ELISE EDITOR

Copyright © 2020 by Nova Science Publishers, Inc. All rights reserved. No part of this book may be reproduced, stored in a retrieval system or transmitted in any form or by any means: electronic, electrostatic, magnetic, tape, mechanical photocopying, recording or otherwise without the written permission of the Publisher. We have partnered with Copyright Clearance Center to make it easy for you to obtain permissions to reuse content from this publication. Simply navigate to this publication’s page on Nova’s website and locate the “Get Permission” button below the title description. This button is linked directly to the title’s permission page on copyright.com. Alternatively, you can visit copyright.com and search by title, ISBN, or ISSN. For further questions about using the service on copyright.com, please contact: Copyright Clearance Center Phone: +1-(978) 750-8400 Fax: +1-(978) 750-4470 E-mail: [email protected].

NOTICE TO THE READER The Publisher has taken reasonable care in the preparation of this book, but makes no expressed or implied warranty of any kind and assumes no responsibility for any errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising out of information contained in this book. The Publisher shall not be liable for any special, consequential, or exemplary damages resulting, in whole or in part, from the readers’ use of, or reliance upon, this material. Any parts of this book based on government reports are so indicated and copyright is claimed for those parts to the extent applicable to compilations of such works. Independent verification should be sought for any data, advice or recommendations contained in this book. In addition, no responsibility is assumed by the Publisher for any injury and/or damage to persons or property arising from any methods, products, instructions, ideas or otherwise contained in this publication. This publication is designed to provide accurate and authoritative information with regard to the subject matter covered herein. It is sold with the clear understanding that the Publisher is not engaged in rendering legal or any other professional services. If legal or any other expert assistance is required, the services of a competent person should be sought. FROM A DECLARATION OF PARTICIPANTS JOINTLY ADOPTED BY A COMMITTEE OF THE AMERICAN BAR ASSOCIATION AND A COMMITTEE OF PUBLISHERS. Additional color graphics may be available in the e-book version of this book.

Library of Congress Cataloging-in-Publication Data ISBN: 978-1-53617-587-5

Published by Nova Science Publishers, Inc. † New York

CONTENTS Preface

vii

Chapter 1

Natural Fibre Nonwovens Subhankar Maity

Chapter 2

Potential of Jute Based Needle-Punched Nonwoven: Properties and Applications Surajit Sengupta

Chapter 3

Chapter 4

Chapter 5

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37

Development of Needle Punched Nonwovens for Thermal Insulation Applications N. Muthukumar and G. Thilagavathi

101

Development of Thermal Bonded Nonwoven Fabrics Made from Reclaimed Fibers for Sound Absorption Behaviour S. Sakthivel, S. Senthil Kumar and Seblework Mekonnen

121

Boric Acid Based Fire-Retardants and Nonwoven Fabric Surface Coatings for Safety in the Automotive Industry Nazan Avcioğlu Kalebek and Emel Çinçik

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vi Chapter 6

Index

Contents Nonwoven Geotextiles in Civil and Environmental Engineering José Ricardo Carneiro, Filipe Almeida, David Miranda Carlos and Maria de Lurdes Lopes

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PREFACE Nonwoven industry plays an important role in economy and society. Nonwoven Fabric: Manufacturing and Applications addresses important data on both natural and synthetic fibres that are used in the industry to develop products for different purposes. Though synthetic fibres are extensively used in the nonwoven industry for the manufacture of various products, natural fibres are steadily occupying the market due to some of their obvious merits. In this respect, a review of the various manufacturing techniques for nonwoven fabric derived from natural fibres such as cotton, jute, flax and hemp is given in this book. Next, the authors assess the structure, property, evaluation and applications of jute and jute blended needle-punched nonwoven fabric, in an effort to aid those who work with natural lingo-cellulosic fibre-based needle punched nonwovens. In addition, flax/low melting point polyester needle punched nonwoven fabrics were manufactured and characterized for thermal insulation applications. The test results show a decrease in thermal resistance value with an increase in low melt PET % and needle penetration depth. Six types of recycled nonwovens samples were developed using thermal bonding and aero dynamic methods, and these samples are

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characterized by their physical properties such as areal density, bulk density, thickness, porosity, air permeability and thermal resistance. The authors assess the way in which the increased use of fire retardant materials in industries has put considerable pressure on the scientific community to develop new polymer materials, chemicals, and fiber combinations for such applications. This compilation concludes with an overview of the history, common raw materials, manufacturing processes, properties, functions and applications of nonwoven geotextiles. The potential use of recycled nonwoven geotextiles towards a more sustainable construction is also discussed. Chapter 1 - Though synthetic fibres are extensively used in nonwoven industry for manufacturing various products, natural fibres are steadily gearing up occupying the market due to some of their obvious merits. This paper reviews various manufacturing techniques of nonwoven fabric from natural fibres such as cotton, jute, flax, hemp etc. It has been observed that carding, air-laying, and wet-laid techniques could be used for web formation, and needlepunching, hydroentangling, stitch bonding, and thermal bonding could be used for web bonding of the natural fibres. Carding and needlepunching process has been mostly used for manufacturing of the natural fibre nonwovens. A huge scope of potential applications of these nonwovens in various field of geotextiles, filtration, automotive, upholstery, acoustic insulation, thermal insulation etc. have been discussed here. Chapter 2 - Uses of nonwoven fabric in domestic and industrial areas are increasing day by day. Now-a days, research is going on to apply natural fibre in different uses in the form of nonwoven either alone or blended with synthetic fibres. The chapter presents with an idea regarding the structure, property, evaluation and application of jute and jute blended needle-punched nonwoven fabric. Knowing well about the effect of various factors on the needle-punched jute nonwoven, the proper and effective design can be made of such fabrics for a particular use. This chapter is intended to present an overview and potential — most of which are based on ideas and conclusions presented in published literature during

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the last 40 years, the rest representing the author’s concepts developed through extensive research. It will help to those who will deal with natural lingo-cellulosic fibre-based needle punched nonwoven in both industry and academia especially to teachers, students and technologists. Chapter 3 - Today the nonwoven technology, is considered as the most modern method, constitutes for the low cost substitutes for producing textiles. Among textile applications, nonwovens, one of the fastest growing sector constitutes about one-third of the fiber industry. Nonwoven materials are porous materials consisting of fibres and interconnected voids. Due to their unique fibre orientation and porous structure, nonwovens are ideal materials for insulation applications. Needle punching is one of the simplest and oldest methods of nonwoven fabrication. In this work, flax/low melting point polyester needle punched nonwoven fabrics were manufactured and characterized for thermal insulation applications. Nonwovens were developed by blending flax fibers with low melt PET at 3 blend ratios (10%, 20% & 30%) with 7mm & 10 mm needle penetration depth. The influence of blend ratio and needle penetration depth on the performance of the nonwovens was studied. The test results showed that there was a decrease in thermal resistance value with increase in low melt PET % and needle penetration depth. Also the performance of the developed nonwovens compared with commercial product. Chapter 4 - Recycled fibers are commonly used in different applications, sound absorption being one of the most important applications. Recycled fiber nonwovens are currently high in demand in industries because of their advantages such as low cost, biodegradability, acceptable mechanical and physical properties and so on. Sound absorption materials such as renewable and eco-friendly thermal bonded nonwoven have been developed using recycled cotton and polyester fibers. Six types of recycled nonwovens samples were developed using thermal bonding and aero dynamic methods. The blending ratio of cotton and polyester fibers was 60:40. Sound absorption coefficient was measured by impedance tube method (ASTM E 1050). The recycled fiber nonwoven samples are characterized by their physical properties such as areal density, bulk density, thickness, porosity, air permeability and thermal resistance

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was determined for all the samples according to the ASTM standards. The results exposed that recycled cotton/polyester nonwoven samples with its physical properties showed superior sound absorption at 4000 Hz, lower thermal resistance, lower air permeability. Then compared with recycled cotton/polyester are corresponding to the achieved level but it was lower in recycled cotton/polyester nonwoven samples. But, at superior frequencies (4000 Hz), there was a decrease from the achieved level in all the nonwoven samples which might be enhanced by increasing the thickness of the nonwovens. The average sound resistance percentages of these three decibel values were calculated and compared for all the samples. Chapter 5 - Nonwoven fabrics are porous webs which are produced directly from fibers. Not only natural fibers but also man-made fibers are used in web production and bonding. Nonwoven fabrics continue to be one of the fastest growing material types being used in the textile industry. They are considered to be engineered fabrics with excellent performance properties. Over the past two decades, increasing uses are being found for nonwoven fabrics in many fields due to the ease of the manufacturing process, high production speeds, and lower production costs. Nonwovens are used almost everywhere including in the military, agriculture, construction, clothing, home furnishings, travel and leisure, healthcare, personal care and for household applications. These fabrics demonstrate much functionality such as strength, resilience, absorbency, liquid repellency, softness and etc. One primary functionality is as a flame retardant. Flame retardants are important for personal safety and for reducing losses caused by fire. Most recently established federal regulations on the flammability of the fabric indicate that the use of FR textiles will steadily increase in the near future. The increasing use of FR materials in industry has put considerable pressure on the scientific community to develop new polymer materials, FR chemicals, and fiber combinations to a wide range of end use applications. Boric acid has recently been used in textile materials as a flame retardant. Boric acid (commercially known as Optibor®) is a white triclinic crystal in water (5.46 wt.%), alcohols, and glycerin. It has the chemical formula H3BO3 (sometimes written B(OH)3), and exists in the form of colorless crystals or

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a white powder that dissolves in water. Boric acid is found naturally in its free state in some volcanic regions. Flame retardant chemicals only minimize fire risk however they are not completely non-flammable. With flame retardancy, people have time to escape, ignition times are reduced and the release of toxic gases is minimized. In this study, polyester (PES) based nonwoven fabrics produced by air layering and spunlace techniques were used as samples. They have been used for interior car roofs and interior door linings. Boric acid (BA) was applied to nonwoven fabrics as a finishing operation by spraying and brushing at the completion of the spunlace production systems. The applied amount of 2.58 g boric acid was mixed with 250 ml of warm water at 32ºC based on the chemical properties as written in the information chart for the chemicals. The flammability test was evaluated according to the ASTM D2863 standard under controlled conditions. The Limiting Oxygen Index (LOI) is a test method for evaluating the ignition and ease of flame extinction in samples. Fabrics having an LOI value of 21 or below ignite easily and burn rapidly in air. LOI values above 21 ignite and burn more slowly. When LOI values are above 26-28, the fabric may be considered to be flame retardant. As a result, the LOI value of untreated PES nonwoven fabrics were measured at 16.2 for 45 g/m2. The LOI value of PES fabrics treated with the solution increased to 26.8 for 200 g/m2. This result confirms that the boric acid had a great influence on the flammability resistance of nonwoven fabrics. Chapter 6 - Geotextiles are polymeric materials widely used in the construction of many civil and environmental engineering structures, such as waste landfills, roads, railways, dams, reservoirs or coastal protection structures. These materials can perform many different functions and are able to be employed in a wide range of applications. The advantages of using geotextiles (as replacement for other construction materials) typically include: ease of installation, low cost, high efficiency and versatility, and low environmental impact. According to their structure, the geotextiles can be divided into three types: woven, nonwoven or knitted, nonwoven being the most used type. This chapter addresses many aspects about nonwoven geotextiles, including their history, common raw materials, manufacturing process, properties, functions and applications. The potential use of

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recycled nonwoven geotextiles towards a more sustainable construction will also be discussed.

In: Nonwoven Fabric Editor: Rembrandt Elise

ISBN: 978-1-53617-587-5 © 2020 Nova Science Publishers, Inc.

Chapter 1

NATURAL FIBRE NONWOVENS Subhankar Maity Department of Textile Technology, Uttar Pradesh Textile Technology Institute, Souterganj, Kanpur, India

ABSTRACT Though synthetic fibres are extensively used in nonwoven industry for manufacturing various products, natural fibres are steadily gearing up occupying the market due to some of their obvious merits. This paper reviews various manufacturing techniques of nonwoven fabric from natural fibres such as cotton, jute, flax, hemp etc. It has been observed that carding, air-laying, and wet-laid techniques could be used for web formation, and needlepunching, hydroentangling, stitch bonding, and thermal bonding could be used for web bonding of the natural fibres. Carding and needlepunching process has been mostly used for manufacturing of the natural fibre nonwovens. A huge scope of potential applications of these nonwovens in various field of geotextiles, filtration, automotive, upholstery, acoustic insulation, thermal insulation etc. have been discussed here.



Corresponding Author’s E-mail: [email protected].

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Keywords: natural fibre, nonwovens, needlepunching, spunlace, jute, flax, cotton

1. INTRODUCTION Traditionally fabrics have been produced by weaving and knitting, which involve conversion of fibres into yarns and subsequently yarns into two-dimensional fabric structures. Nonwoven technologies are latest fabric formation techniques and principally different from weaving and knitting technologies. The actual time of evolution of the nonwoven technology is not clear but it is suspected that adhesive bonded fibre webs were first produced in 1942 in United States and termed as “nonwoven fabrics.” The first written definition of nonwoven fabrics was proposed in 1962 by American Society for Testing and Materials as “the textile fabrics made of carded web or fibre web held together by adhesives.” Henceforth, INDA defined nonwovens as “sheet or web structures bonded together by fibre entanglement or filaments (and by perforating films) mechanically, thermally or chemically.” Nonwovens are flat and porous sheets made directly from either separate fibres or from molten plastic or plastic film. The nonwoven manufacturing process is fundamentally different from weaving and knitting and do not require converting the fibres to yarn.” Nonwoven manufacturing processes such as; fibre selection, web formation, bonding, and finishing techniques can be altered to manipulate fabric properties based on functional requirements. Due to its diversity in achievable characteristics, nonwoven fabrics penetrate a wide range of markets including medical, automotive, apparel, filtration, civil, geotextiles, fibre reinforced composites and protective applications. Due to these reasons nonwovens are becoming a fastest growing sector in textile market throughout the world [1]. Majority of the nonwoven products are used by consumers either as single or one-time use or short life products. As a result, disposability is becoming a big issue. In these situations, natural fibres such as cotton, wool, jute, flax, hemp etc. become the fibre of choice. Their

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biodegradation properties make them more and more appealing in the context of new regulations for environment protection. Also, it need to mention here that the natural fibres like cotton, jute, flax and other natural fibres might enjoy more favourable market conditions in the future on account of increasing concern with environmental issues all over the world. It has been found in study that these natural fibres are more environmentally sound and less costly to society than its competing synthetic material. Even in the life-cycle, the disposal stage of synthetic material is most harmful to the environment causing highest direct economic and social costs [2-3].

2. RAW NATURAL FIBERS (OR FIBER PREPARATION) FOR NONWOVEN FABRICS MANUFACTURING 2.1. Cotton Thought cotton is mostly used natural fibre in textile sector, its share in the nonwoven market at present time is insignificant. However, the potential for its growth is impressive. Cotton is a durable, breathable and soft fibre. Bleached cotton fibres have high levels of absorbency, soft to the touch, breathable and biodegradable [4]. The issues with cotton such as consistency in quality, processability and cost, limit its share in nonwoven market. Trash content, fibre length and colour variation, linting, nep formation etc. are the common complaints with cotton fibre nonwovens. However, with recent advances in science and technology, it is possible to prepare lint-free cotton nonwovens at a cheaper price. Furthermore, with increasing cost of petroleum products, and constriction in polymer and fibre supply market, synthetic fibres are becoming expensive. As a result, the future of cotton looks brighter as nonwoven raw material with increasing opportunities for growth. Cotton nonwovens are used in various products in medial textile sector for hygiene applications. The cotton nonwoven products that go into hygiene applications generally require

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bleached cotton are raw material. Many of the such cotton nonwoven products such as surgical sponges, sanitary napkins, tampons and cosmetic pads and puffs can also be satisfactorily made from by-product cotton fibre, i.e., gin motes, comber noils and other cotton mill waste. The methods of producing nonwovens, especially those applicable to cotton fibres, their application potential, the nonwoven market, and recent research in different areas for cotton nonwovens have been favouring cotton as a vital raw material for manufacturing nonwovens [1, 5].

2.2. Jute Jute is probably mostly explored natural fibres for nonwoven manufacturing. Raw jute is to be cut in short staple form is used for nonwoven production and various products are already available in market. Utilization of mill wastes of jute or jute caddies are also suitable for making nonwoven. Various techniques like needle punching, stitch bonding, hot calendaring, hot-air thermal bonding, hydro entanglement etc. are successfully employed for manufacturing jute-nonwovens [3]. The prime reasons of growing market of jute-nonwovens is due to its various technical applications due to their promising properties such as, high strength, high modulus, good dimension stability, high frictional property, moderate stiffness or draping, coarseness, high moister absorption, good breathability, good bleachability, dyeability, printability and many more [6-7].

2.3. Flax Main constrictions of usage of flax fibre as textile raw material is the hard processability in conventional methods and cost of production. In this regard, nonwoven technologies are very suitable for manufacturing functional products. The raw flax fibres are highly contaminated with harl and as a result do not produce good quality fabric. The amount of

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contamination is typically ranges from 10 to 80 percent. A contamination level of lesser than 10 percent is required for nonwoven fabric production. Short flax fibres for manufacturing nonwoven fabrics are mechanically produced from flax straw, predecorticated flax, flax pluckings, and cut flax. They have high dust content and are either smooth or stiff. Most flax waste, therefore, requires additional purification through cleaning [8]. Webs are prepared by carding or aerodynamically. Bonding of web can be done by water jet, needle punching, stitch bonding, adhesive bonding etc. [2, 9-12]. Applications of flax nonwovens include carpet backings, upholstery felts, insulation for apparel, composites etc. [11]. Blends of flax with synthetic fibres such as polyester, polypropylene, etc are also used for manufacturing nonwovens [8]. These days, traditional natural fibres, including cotton, jute, and flax have been achieving more demand internationally, while other fibres such as hemp, kapok, milkweed etc. are starting to emerge into more nonwovens areas, especially due to their natural origin and biodegradability.

3. CONCEPT OF NONWOVEN FABRIC MANUFACTURING PROCESS In general, the nonwoven formation processes consists of two basic steps, web formation followed by bonding. The web formation in nonwoven production is a critical contributor of the end-use product performance. There are three basic methods of web formation: dry laid; wet laid; and polymer laid. The latter one classified as spun laid and melt blown web formations which are particularly applicable for synthetic polymers and out of scope in this chapter. There are three basic types of bonding: chemical, thermal, and mechanical. The natural fibre webs can be successfully bonded by mechanical process without any additives. Additional binder polymer or synthetic fibre is required for the chemical or thermal bonding.

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4. WEB FORMATION PROCESS 4.1. Dry Laid or Air Laid Conventional staple fibres are used are raw material in the dry-laid process, which are usually 12 to 100 mm in length. Classical textile carding or air laying machines are used to separate and orient the staple fibre mechanically for formation of fibre web. The objective of carding is to separate the fibre stock into individual fibres with minimum fibre breakage and opening and blending of different species of fibres thoroughly. In a normal carding process, the fibres are more oriented along the machine direction than the cross direction. More random web structures can be obtained by cross lapping. In the air laying process a lap or plied card webs are fed by a feed roller. The fibres are separated by a licker-in or spiked roller and introduced into an air stream. Finally, the fibres are collected on the condenser screen to form a web after desired fibre orientation. A conveyor is used for transporting the web from condenser to the bonding area. The length of fibres used in air laying is ranging from 20 to 60 mm. A higher production speeds can be achieved with shorter fibre as they are transported easily in the air stream with larger amount of fibres per unit volume of air and deposited on the condenser. Higher air volume is required for longer fibres to avoid entanglement. The limitations associated with this air laying are speed, web uniformity and weight. It is difficult to prepare isotropic webs lighter than 30 g/m2 by the air laid process. However, voluminous, isotropic and uniform web can be successfully prepared from a wide variety of fibres such as natural, synthetic, glass, steel, carbon, etc., by this method. This will allow the production of webs from blends of cotton with other staple fibres. The air-laid webs usually have basis weights ranging from 30 to 2500 g/m2[1]. Typical end uses for air-laid nonwoven fabrics are the fabrics for apparel and upholstery backings, carpet backing, interlinings for garments, linings, filter media, medical fabrics, diaper coverstock, wipes, insulation, geotextiles and personal hygiene products [1].

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4.2. Wet Laid In wet-laid nonwoven manufacturing process the fibres are mixed with chemicals and then suspended in water to make the slurry. Then, specialized paper machines are used to drain the water off the fibres to form a uniform sheet of material like web, which is then bonded and dried. Fibres shorter than 10 mm are suitable for wet-laid process and the resulting fabric has a basis weight ranging from 10 to 540 g/m2. The wetlaid process has merits of high productivity, high uniformity at low basis weight and control of fibre orientation of properties, as compared to airlaid process. Typical applications for wet-laid nonwovens include wipes, surgical gowns, drapes, towels, tea bags, etc. [1].

5. WEB BONDING TECHNIQUES The web bonding techniques are generally classified into three categories, mechanical, chemical, and thermal bonding, based on raw material fibres, end-use applications and web formation technology. Often, a combination of different bonding methods is used to achieve a products with certain properties. Mechanical bonding can be further classified as needle punching, stitch bonding, and spunlacing (or hydroentangling). In the needle punching process, fibre web is bonded by mechanically interlocking the fibres by punching with barbed needles. As the unbonded web moves through the needle loom, the web is consolidated and becomes stronger because of the fibre interlocking. The level of consolidation is controlled by the needle punching density and depth of needle penetration. It is the only bonding method suitable for heavyweight nonwoven fabrics. The needlepunched fabrics are extensible, bulky, conformable, distortable and extremely absorbent. Both dry laid and polymer laid webs can be needle punched. Stitch bonding is the process of bonding a web by stitching with yarns, filaments, or fibres. Spunlacing is a process of entangling individual fibres with each other using high-pressure water jets, which cause the fibres to migrate and entangle. The water jets create

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turbulence inside the web which causes enough interlocking between fibres to produce strong fabrics. Spunlace fabrics have more appealing properties than the needle punched fabrics. The typical applications of spunlace fabrics are wipes, medical gowns, dust cloths, garment and leather interlining etc. Faster rate of production can be achieved with spunlacing process than that of needlepunching as there is no reciprocating mechanical part. Other methods of bonding such as chemical bonding and thermal bonding are generally used for synthetic fibres.

5.1. Natural Fibre Needlepunched Nonwovens Cotton, jute and flax fibres are mostly used by various researchers and manufacturers for preparation of needlepunched nonwovens. Regular length staple cotton should be considered for needle punching since longer fibres perform better. Needles of 36–42 gauges have been found appropriate for the production of cotton needlepunched nonwovens. Needle fineness has probably the most effect on fabric properties. Good length and length uniformity in a cotton sample is required for good quality fabrics. Bleached cotton with good lubricity is required to prevent fibre damage during needling and also needle breakage. Raw cotton fibres (unbleached) are also suitable and needles extremely well subject to proper needle selection. Needlepunched cotton nonwovens are highly efficient filter media due to the irregular fibre shape and absorption properties. Increased tenacity in the wet condition is an important advantage with such cotton filters. To improve strength of bed blankets and industrial fabrics their scrim materials are made of needlepunched cotton. Needlepunching is mostly used technique for manufacturing of jute nonwovens [7, 13]. The raw jute fibres do not produce good quality fabric because they are stiff and have no crimp [14]. These fibres are treated with 18% (w/v) sodium hydroxide solution at 30℃ for 45 min maintaining the liquor-to-material ratio 10:1 for the development of crimp. This process is called woollensation of jute fibre [14-15]. However, certain precautions are required during web manufacturing steps which are different from cotton

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fibre. At first, a softening treatment is necessary after jute fibres are extracted by removing root and tip portion. The softener is applied by spraying emulsion of any commercial grade hydrocarbon based mineral oil. The emulsion should contain about 1.5% oil and sprayed at 35% weight of jute fibre. After softening, the fibres are kept in a bin for conditioning. The well softened and conditioned jute fibres become suitable for web formation by carding. [13, 16]. It has been observed that the needle punching made without the support of a reinforcing material are much bulkier in nature, and can be compressed easily under the same pressure range to a much higher extent. A better entanglement among the fibres and better reinforcing material is achieved when needlepunched fabrics are produced with reinforcing material, [17-18]. Appropriate technology of manufacturing jute needlepunched nonwovens not only produces the diversified products from jute but also creates the value addition. Jute needlepunched nonwoven products offer cost effective and market oriented diversification for jute. Thick nonwoven fabrics also can be producing from flax fibres by needle punching method. The retted, scutched, and hackled flax fibres are suitable for needlepunching with or without any chemical treatment. Thick web of flax fibre is prepared by carding and cross lappers are used for fibre randomization. Fibre web is bonded by needlepunching for the preparation of nonwoven fabrics [11, 19]. A series of nonwoven fabrics composed of different ratios of cotton to flax are manufactured using a drylaid needle punching system by Annis, et al., (2005)[20]. They vary the proportion of cotton during web formation to determine the effect of blend composition and fibre quality on several different physical properties. Blending cotton with flax fibre increases tensile, tearing and bursting strength of resulted nonwoven fabric, whereas, stiffness and resilience of the fabric are affected by a high percentage of flax fibre. These improved characteristics of blended product contribute to greater industrial use of lower grades of cotton and flax fibres and boost the potential for developing markets for these two bio-based fibres.

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5.2. Natural Fibre Spunlace Nonwovens The nonwovens market is steadily growing with hydroentangled or spunlace nonwovens. This technology can produce nonwoven fabrics which truly have a textile quality in terms of hand, softness and comfort. The main raw materials explored for spunlacing are viscose, cotton, polyester, polypropylene and lyocell fibres. This nonwoven technology is gaining popularity with cotton fibre due to its low wet modulus which allow it to easily respond to water jets. Additionally, the kidney shaped cross-section and twisted ribbon structure of cotton fibres are helpful for additional frictional resistance leading to better adhesion and entanglement of fibres. It is also advantageous in using unbleached cotton as it is cheaper and water jets can remove some of the oils or wax from the fibre. Hydroentangled cotton fabrics are softer in feel, good hand, good strength, high absorbency, permeability and can be easily dyed and finished using conventional textile methods. Years ago, processing of bast fibres such as jute, flax, hemp etc. in hydroentanglement system was unthinkable, but this also is possible today [21-22]. Norafin GmbH, a Switzerland based company is involved in manufacturing of flax nonwovens and products. It is demanded that flax fibre as an environmentally responsible alternative to glass and other hightech fibres for various technical applications and realized that spunlace process has advantages over needlepunching [23]. Because, needlepunching is harsher mechanical process as the needles can break the fibres. Whereas, the water jets used in spunlacing process are gentler to the fibre. Also, a multilayer composite structure composed of same or different fibres blends can be prepared by spunlacing technique after configuring the manufacturing line in a state of art technology. It is a cost effective process yielding improved and uniform quality of fabric. Also, the process enables production of three dimensional fabrics, fabrics with apertures, embossed or custom patterned structures. Flaxline, a product of spunlace flax is commercially available which is described as durable, light weight, waterproof, hard-wearing, tear-resistant suitable for roofing membrane that is offered in Europe by a France-based company Soprema. The

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antibacterial, UV-resistant, and anti-slip property of flax fibres contribute a great virtue to its performance [10, 23]. Flax/PP blend spunlace nonwoven is produces in 50/50 ratio and studied for 2D and 3D auto interior composites, acoustical and fogging properties [24-25]. The blended spunlace product is prepared in an AquaJet spunlace line. It is further thermally bonded by a panel press and a stampforming press. Major benifits of spunlace technique processing with flax fibres are significant increase of tensile strength, flexural strength and flexibility. Also, a large reduction in nonwoven thickness is possible without increase in weight of nonwoven which is an added advantage. Howevere, decrease in impact strength is a negative effect of the spunlace process as stated by Chen, Y, et al., (2008) [24]. Other non-composite applications include biodegradable bags and covers, for which moisture absorption is a desirable property, and sunshades and sunscreens, for which flax’s UV resistance and natural appearance are attractive [23]. A green and biodegradable hemp/cotton spunlaced nonwoven was developed to research oil flowing property and practical application for filtration. Due to the stiffness of hemp fibre, it is difficult to manufacture 100% hemp fibre spunlaced nonwoven by existed equipment. So, 40% soft cotton fibre is used to prepare hemp/cotton blended spunlaced nonwoven on the basis of easily producing requirement. The average diameter and length of hemp fibres used were 14.306 µm and 27.88 mm respectively [26].

5.3. Natural Fibre Stich Bonded Nonwovens In this nonwoven technique fibre web is stitched like sewing. The performance of the product depends on area weight of web, stitch density and quality of sewing threads. Typically, a filament yarn is used for stitching purposes. However, cotton yarn in counts from 18 to 30 Ne (295– 177 denier) are also found suitable for stitching a cotton web. Arachne and Maliwatt type of warp knitting machines are generally used for stitching to produce stitchbonded nonwovens. As with some of the other bonded webs,

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wet processing of stitchbonded nonwovens can be possible in fabric form like conventional textiles. Nonwoven materials are prepared from flax straw, predecorticated flax, flax pluckings, and cut flax fibres by first needling and then stich bonding [10]. Two variations of stitch bonding such as Malivlies and Kunit methods are employed to produce nonwoven flax fabrics by Boettcher, P., et al., (1993) [9]. The stitching process makes the fabric stronger in a very short while with low energy consumption. Malivlies nonwovens are porous with a surface consisting of partial fibre stitches and a horizontal fibre arrangement in unstitched areas. Whereas, Kunit nonwovens are porous with one elastic face and one pile face. Applications for flax nonwoven fabrics included multipurpose mats, composite moulds and preforms, soil embankment fabrics etc. [9].

5.4. Natural Fibre Chemical Bonded Nonwovens This is an easiest way of fabric formation where fibre webs are bonded using some adhesive binders that may be applied by spraying, foaming, padding or printing. A wide range of adhesive or chemical binders are available in market. Among these methods, printed patterns provide sufficient fabric bonding without imparting objectionable stiffness on it. Nonwovens wipes are manufactured using the print bonding technique.

5.5. Natural Fibre Thermal Bonded Nonwovens This process is suitable for thermoplastic fibres where fibre webs with blends of natural fibres are passed between two hot rollers (calender rollers). The thermoplastic fibre melts or partially melts and bonds the natural fibre web. Low melt bi-component polyester or polyolefin fibres are also can be blended with natural fibres. By this method lightweight coverstock fabrics are prepared for top sheets of diapers. The exact bonding conditions are dependent on the melting temperature of the binder

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fibre, pressure and mass of the web. The calendar pressure need to be increased with increase in fabric mass to get efficient heat transfer and efficient bonding. The calendar temperature is kept close to the melting temperature of the binder or low melt fibre. When sheath-core bicomponent fibres are used as binder, the temperature is set above the melting temperature of the sheath, but well below that of the core polymer. The strength of the nonwoven fabric increases with the increase in binder fibre content. Because, with more binders, there is sufficient amount of binder to melt and flow to form good bond points. Typically, 30 to 50% binder fibres are blended with cotton fibre to produce stronger thermobonded cotton nonwovens. Though a bond area of about 15% is generally used for the majority of thermoplastic fibre nonwovens, an embossed calendar roll with about 30% contact area is required to achieve good mechanical properties. Alternatively, one can use hot air-through bonding, where the web containing a proportion of thermoplastic binder is passed through a hot air oven. Inside the oven a sufficient residence time is required in the order of several seconds to minutes for achieving good bonding due to the melting and flow of the binder around the cotton fibres. Flax nonwovens fabrics can be manufactured by thermal bonding of wetlaid web blended with different contents of polypropylene (PP), polyvinyl alcohol (PVA) and bi-component polyamide 6/copolyamide (PA6/CoPA) fibres in 10–30% of blending range [27-28].

6. APPLICATIONS OF NATURAL FIBRE NONWOVENS These nonwoven technologies are useful for the development of novel materials and products in shorter and comparatively faster rate than those attainable in conventional weaving and knitting. Furthermore, nonwoven techniques engineer the final product with superior specific properties. Owing to their specific properties, lower costs of manufacture, nonwovens open up new markets in numerous household, industrial and technical enduse applications [7, 29-32].

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6.1. Application of Natural Fibre Nonwovens in Filtration The nonwovens have been used as filter media since the birth of nonwoven technology. The performance of nonwoven fabrics in dry and wet filtration is mainly determined by its pore size and its distribution. The selection of the fibres for preparation of filter media is important. The appropriate pore size is a design consideration for filter fabrics for a particular application corresponding to particle size. The micro-pores should be smaller than the minimum particle size to ensure the desired filtration efficiency. This should be achieved with the minimum pressure drop across the filter media and without causing any disturbance to the pore geometry [33]. It is desirable that pore size distribution should be as uniform as possible and that the values at extremities should well controlled. Too small and too large pores than the required average value of the particulates are undesirable. Needle-punched nonwoven fabrics show superior filtration efficiency with good dust particle separation and dust holding ability. A calendaring process has been found to further increase in filtration efficiency of the fabrics by regulating their density and permeability. Calendaring makes the fibres more tightly packed, thus making it more difficult for particles to pass through the filtre fabric. With the increase in consolidation, the fabric density increases with the resultant increase in dust arrestance and holding capacity without increase in pressure drop [33]. Jute needlepunched nonwovens are suitable for coarse and medium filtration application and suitable for textile, tobacco dust, wood flour, paper shreds etc. [34]. Nonwoven mats made of biodegradable, natural fibres of flax and cotton are used for remediation of a ubiquitous pollutant of water and wastewater, namely, copper ion. The nonwoven mats were treated with citric acid in order to enhance the amount of negative charge on the mats and improve their ability to sequester copper ion. Treated flax fibre mats and flax/cotton fibre mats represent a potentially fast and convenient method for removal of metal ions from water and wastewater streams [35]. Different hemp-based mono-layer and composite nonwovens are prepared to study the oil filtration properties [26, 36]. The Reynolds number of hemp/cotton spunlace nonwoven at different

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fluxes is small (Re < 1), which decreases as the increasing of filtration area while increases as the increasing of flux at the state of laminar flow. Hemp/cotton spunlace nonwoven, hemp/viscose spunlace nonwoven, hemp/viscose spunlaced nonwoven etc. are impregnated with polyacrylic adhesive to prepare composites [36]. Those composites are explored for filtration application in practical application.

6.2. Applications in Medical Textiles Spunlace cotton nonwovens are extensively used in various medical and healthcare application [37]. Tencel/Cotton Nonwoven Fabric Coated with Chitosan was explored for Wound Dressing [38]. The flax fibre cloth used in medical purpose like cancer and wound healing etc. Air-laid and we-laid nonwoven structure made of flax fibres and its blends could be used as disposables in medical use [39-40]. As An antimicrobial material flax fibres coated with silver nanoparticles could be of interest not only in fabrication of sanitary and medical articles, but also industrial materials. Manufacturing of medicinal products, health care apparels, and cosmetology aids is becoming one of the most developing segments in the global market of nonwovens production in near future.

6.3. Applications in Automotive Textiles Jute and flax nonwovens are recently used extensively in automotive industries [41-42]. The reasons influencing the steady growth of use of these nonwovens in this sector are many. Comparative weight reduction of 10–30% in automobile parts can be achieved in addition of Good mechanical properties. Composite structure can be formed in a single machine passage with relatively good impact performance, with high stability and minimal splintering. The nonwoven end products are having no health hazard during handling or use, no emissions of toxic fumes when subject to heat. The sustainable and renewable raw material resource and

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superior environmental balance during material and energetic use, recycling possibilities and relative cost advantages make them attractive alternative to synthetic fibre nonwovens. Researchers found that the flax/polypropylene nonwoven prepared by spunlacing are suitable auto interiors with particular technical merits of enhancing tensile and flexural strengths, reducing thickness with controlled ultimate weight, increasing noise absorption coefficient and transmission loss and improving nonwoven moldability and fogging performance[2425]. Compared with glass fibre, flax has significantly lower density, thereby enabling a lighter-weight composite that offers comparable performance. This is key for the automotive industry, where it is used for sound absorption, strengthening and structural reinforcement. Door panels of Opel Vectra are now made of flax-based nonwovens. All BMW and Mercedes models now use natural fibre nonwoven composites for door liners, boot liners and parcel shelves. There are now making more sophisticated modifications like blending of flax with extra strong sisal fibres for strengthening or and lightweight headliner and rest of the automobile body. Present market is remarkably open to approach from new nonwoven suppliers, and equally open–minded in respect of which fibre they may consider using – flax, hemp or jute.

6.4. Applications for Thermal Insulation Jute and flax needlepunched nonwoven can be used for effective thermal insulation. Thick and porous needlepunched structure contains evenly dispersed void or air pockets which provide thermal insulation. Also, inherent thermal conductivity of jute and flax is very poor. Woollenization of jute fibre improves the bulk of the nonwoven structure which improves thermal insulation further. In addition to industrial uses these nonwoven fabrics can be used as filler of warm garment like jackets [32]. The thermal conductivity (λ) of air-laid flax nonwoven of 10 mm thickness is evaluated using one sample panel apparatus for evaluation of materials for building industry. The nonwoven has exhibited excellent

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insulation performance with λ = 0.043 W/m K, which resulted in reduction of energy needed to heat the building. This result fits in the requirements for insulation materials of natural origin [43]. Thermal conductivity and thermal resistance of thermal bonded flax:PVA blend and flax: PA6/CoPA bi-component blend fibres is reported as shown in Table 1[28]. Both flax:PVA and flax:PA6/CoPA nonwovens offer interesting properties but, flax/PVA nonwovens possess lower thermal conductivity and good thermal resistance. Table 1. Thermal resistance of blended flax nonwovens Weight % Flax/binder fibre

90/10 80/20 70/30

Flax/PVA fibre nonwovens Thermal Thermal conductivity resistance [W(m K)-1] [m2KW-1] 0.020 0.065 0.024 0.075 0.023 0.060

Flax/PA6/CoPA fibre nonwovens Thermal Thermal conductivity resistance [W(m K)-1] [m2KW-1] 0.093 0.018 0.109 0.012 0.090 0.016

6.5. Applications for Acoustic Insulation Nonwoven fabrics of ideal materials are used as acoustical insulation products because they have high total surface area. The nonwoven composites consists of cotton fibre with three surface layers (glass fiber, cotton and activated carbon fibre) are explored for their acoustic properties. The nonwoven composites with cotton as a surface layer has significantly higher sound absorption coefficients than the glassfiber layered composites. It is also found that carbonization and activation of the cotton nonwoven further improves sound absorption ability. The effect of blend proportion of cotton, kapok and milkweed fibres with cotton, fabric GSM, bulk density and distance of fabric from sound source on sound reduction of needlepunched nonwoven fabrics is investigated [43-49]. A nonwoven

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fabric of cotton/milkweed 40/60 shows the highest sound reduction potential. A positive correlation between fabric GSM and sound reduction and negative correlation between bulk density and sound reduction were found by them as shown in Figure 1. Jute needlepunched nonwovens also exhibit superior sound insulation characteristics. When sound energy passes through the jute needlepunched nonwoven there is significant sound transmission loss [42, 47-49]. When the nonwoven structure is as sound barrier its structural parameters such as punch density, depth of needle penetration and mass per unit area affect the sound transmission loss. It has been reported that decorated jute needlepunched nonwoven or sandwich blended synthetic and jute needlepunched nonwoven can be used as sound absorbent medium successfully. The porous and irregular surface and resiliency of the needlepunched nonwoven structure are mainly responsible for the sound absorbency. Such nonwoven structure can be used as wrapper of a sound source or it can be used in the wall as wall mount or cover to reduce the reverberations. For acoustic absorption in car interiors floor coverings are made of nonwoven fabrics using natural fibres (kenaf, jute, waste cotton, and flax) and their blends with polypropylene and polyester fibres [42, 4749].

Figure 1. Effect of Bulk Density of needlepunched nonwoven on acoustic insulation.

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Nonwoven acoustic insulation materials made from flax fibres by needlepunching technology are tested for applications in family houses and bungalows [43]. The nonwoven materials are found possessing strong ability to absorb sound waves. In another study by Fages, et al., (2013), flax fibres are blended with synthetic binder fibres and nonwoven structures are prepared by wet-laid and subsequent thermal bonding [28]. The plot of the acoustic absorption coefficient in terms of the sound frequency for flax:PVA and flax:PA6/CoPA thermal bonded nonwovens are shown Figure 2. Figure 2 depicts low acoustic absorption at low frequencies (below 300Hz), with absorption coefficients in the range of 0.05–0.2. With respect to flax: PVA nonwovens, the absorption coefficient increases up to values of about 0.4–0.5 in the 300Hz–2kHz frequency range, indicating interesting and quite homogenous acoustic insulation properties in this range. At about 500–600Hz, a remarkable increase in absorption coefficient is observed up to almost 0.6 in case of flax: PA6/CoPA nonwovens, however, it decreases up to values around 0.2–0.3 in the 1–2 kHz range. This slight decrease in acoustic absorption properties in this frequency range could be due to internal structure and resonance phenomena that could be more intense in this range.

Figure 2. Plot evolution of the absorption coefficient of flax nonwovens thermally bonded with polyvinyl alcohol (PVA) and polyamide 6/copolyamide (PA6/CoPA) fibres.

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Figure 3. Sound absorption behavior of flax/low melt PET nonwovens.

Acoustic and fogging properties of the felt and panel of flax spunlace nonwoven are evaluated in accordance with the industrial standards of Alpha Cabin, ASTM, and DIN. The both impedance tube test and Alpha Cabin test indicate that the sound absorption coefficient approached to 1.0 for the spunlace flax/polypropylene nonwoven felts (before hot-pressing). For the panels (after hot-pressing) the sound absorption coefficient is found to be always below 0.3 within the whole testing range of sound frequency [25]. Flax/low melting point polyester needle punched nonwoven fabrics are manufactured and characterized for sound and thermal insulation applications as shown in Figure 3. It can be seen that the developed nonwovens has better sound insulation value at medium and high frequency and that is better for flax enriched nonwovens[50].

6.6. Application in Nonwoven Composites Recently, vegetable fibres such as jute, flax, hemp etc. have been increasingly used as reinforcement in polymer composites. Due to the low cost and good mechanical properties these natural fibres aided with good, renewable and biodegradable resources they are successful alternative to the most common synthetic reinforcement, i.e., glass or carbon fibres. The

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main drawbacks with these natural reinforcement are their hydrophilicity and lack of adhesion with most common thermoplastic matrices. Several ways are now established to overcome this drawbacks. Typically, physical and chemical modifications of these fibres are available to improve the adhesion with matrices as well as suitable matrix materials are also developed. Cotton, jute, flax, hemp, sisal, and broom are the fibres most commonly used fibres and suitable matrix polymers are polyolefins, polystyrene, epoxy resins and unsatured polyesters. In present days, the application areas of these composites are in the automotive sector and include composite parts produced by means of thermo-forming or thermocompression moulding techniques [12, 24]. Needlepunched nonwoven may be a successful reinforcing agent for composites [49]. It is reported that nonwoven composites show better properties than that of woven composites and cross laid nonwovens is better in compare to parallel laid considering its mechanical strength in both machine and cross direction [41]). Jute nonwovens made from caddies are successful alternative of glass fibres as reinforcing materials of composites [7]. Chair, table, wash basin, serving tray, tool box, rain pipe, signal casing, corrugated sheet, speaker box, fan blade, country boat etc. have been successfully prepared from jute needlepunched nonwoven based composite. Jute needlepunched fabrics can be used for decoration, bags, home furnishing, soft luggage, hat, apron, gloves, handicraft items, file cover, sports equipment etc.[16, 51]. As a reinforcement layer in tennis racquets spunlaced flax is lightweight and absorbs vibrations. The UV resistance quality and natural wood-like appearance of flax nonwovens make them attractive as construction material for boats and canoes. Other applications include reinforcement in foot bridges, and in wind turbine blades, which provide high strength to weight ratio [23, 52-53]. Flax nonwoven composites can be used as roofing membranes with hard-wearing, high breathability and long lasting. In this way, it is established as a valuable alternative to synthetically manufactured membranes in the roofing sector. The nonwoven material made of 100% flax, has tensile strength of 220 N/5 cm. If a scrim made of natural fibres, PET, or fibreglass is included into the nonwoven material then the strength in cross and machine direction of the

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180 gsm fabric increased upto 450 N/5 cm and 600 N/5 cm correspondingly. Flax composites are valuable alternative in the filtration industry, and packaging industry such as biodegradable bags and covers. Biocomposites of flax reinforced polylactic acid (PLA) are made using a new technique incorporating an air-laying nonwoven process followed by thermal consolidation [33]. Flax fibre content is the most significant factor influencing the biodegradation and water absorption. Hemp/polypropylene, kenaf/polypropylene, ramie/polypropylene, bagasse/polypropylene nonwovens are produced by carding and needlepunching techniques and is thermo-bonded to form composites. These composites are explored for automotive interior application [54-55]. Flax and hemp fibres are blended with PP and maleic anhydride-grafted PP (MAPP) are manufactured by needlepunching and composite structures are formed by their compression hot moulding [12, 56]. These composites show sound mechanical properties as shown in Figure 4. These hybrid natural fibre nonwoven composites are prepared by blending of synthetic fibres which provide high product quality. By mixing the two fibre components before the consolidation, a proportionate distribution and a good wetting of the reinforcing fibres could be ensured. Short fibre reinforced and nonwoven flax/polypropylene blend composites are prepared by carding and needle punching [19, 57]. The effect of water uptake on their mechanical properties is investigated. A strong effect of water is found on the dimensional and mechanical properties. Influence of manufacturing parameters on the properties of flax/polypropylene blend needlepunched nonwoven fabrics are studied by Kohler, E et al., (2000) [19]. In another study, nonwovens comprising of flax and polypropylene are prepared by needle punching process and carbon black is added as filler in varying proportions 1, 3, and 5%. The addition of carbon black to the nonwoven would pave the way for achieving improved mechanical properties if it is used as a precursor for preparing thermoplastic composites [58].

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Figure 4. Tensile properties of hemp, flax, PP and maleic anhydride-grafted PP (MAPP) composites.

6.7. Application in Geotextiles Now-a-days, properly designed needlepunched nonwovens made of bast fibres are used in erosion control in highway embankment and cut slops, river bank protection, ground separation functions, filtration in road, reinforcement applications in temporary unpaved roads etc.[16, 19, 32, 5964]. The main advantages of these fibres are their ecofriendliness and renewability. As ecofriendly fibres, jute, flax, hemp etc. have a great compatibility with soil and degrades after few months helping in soil stabilization, cake formation, and vegetation to grow. Though these nonwovens have low strength and biodegradable, they improves the performance of the unpaved road as the soft subgrade attains strength over the time [17]. Presently, application of natural fibre-synthetic blended fabrics may produce a long-term effect in geotextiles [65-67]. A comparison has been made between the properties of the needlepunched nonwoven geotextiles prepared from polyester fibre and that of flax fibres. The properties of geotextiles studied are density, pore size and air permeability. Variation in length and diameter of the flax fibre is hound to be the cause of loss of tensile strength of materials. Nevertheless, flax fibre-based geotextiles have a great potential in various civil engineering applications as they are isotropic, compact and permeable to air. Flax nonwoven reinforced cement composites are prepared as sustainable

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materials for building envelopes [68-70]. Nonwovens are even explored for water proofing and geotechnical applications. It is found that jute, jute caddies (unspinable jute fibre) in 1:1 proportion suitable for water proofing treatments [71].

6.8. Application as Floor Covering Natural fibre nonwovens are successfully explored for reducing automotive interior noise and floor covering [48]. Jute and jute blended needlepunched nonwoven fabric are successfully used as floor covering and carpets [17, 72]. Jute blended needlepunched nonwovens prepared by sandwich blending technique provides both the aesthetic and functional properties for specific applications and are substantially cheaper than commercially available woolen materials. In some cases, woven sacking or hessian fabric is used at the backside for reinforcement of jute based nonwoven fabrics to enhance the mechanical performance and coarse denier polypropylene/ acrylic fibre is used on top to bring aesthetic appeal and smooth appearance. Kenaf nonwovens are used as substrates for laminations and explored universally in the manufacture of furniture, kitchen cabinets, fixtures, wall-coverings, displays, and various other products [73]. Nonwoven mats are manufactured from kenaf fibres [7778]. Now jute-nonwovens and its composites are used in making of door liners, boot liners parcel shelves etc.

6.9. Natural Fibre Nonwoven Oil Sorbents Needlepunched nonwoven fabrics are prepared from cotton, milkweed, kapok, wool, and kenaf fibres and explored for sea water oil sorbents. Except kenaf, oil sorption capacity of these natural sorbents are found much higher than that of polypropylene in a simulated seawater bath ad shown in Figure 5 [76]. More oil adsorption is demonstrated by wool fibre due to the presence of large amount of oleophilic waxes on surface (10-

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20%) [76]. The hydrophobic and scaly surface of wool provides large and readily accessible surface pores for oil adsorption. When wool fibre is present in nonwoven structure the structure itself contributes to easier formation of capillary bridges of oil in fibres interstices [77-78].

Figure 5. Oil sorption capacities of natural fibre sorbents.

Needlepunched nonwovens are prepared from waste recycled wool fibres which are found to be a good sorbent for Pb2+ ions, and it seemed that they do not require any modification to improve this ion absorption property [79]. The kapok/polypropylene blend needlepunched nonwovens are investigated as oil sorbent and reported that 50/50 blend ratio of kapok and polypropylene is having higher oil sorption [88]. Choi, Kwon and Moreau (1993) have investigated cotton/polypropylene blend needlepunched nonwovens as oil sorbent and reported that increase in cotton content increases the oil sorption capacity. A needlepunched cotton nonwoven is produced as a precursor for making activated carbon material [80]. The study exhibited that the carbonized and activated cotton nonwoven is a special type of renewable and biodegradable material featuring lightweight, high microporosity, and high performance of chemical adsorption and separation [81]. The activated carbon nonwoven exhibited the potential for use as high adsorbent and absorbent materials. They are light weight and bulky, advantageous in protective clothing applications and other consumer and industrial applications [82]. Hence, natural fibre nonwoven structure is one of the best choice where accessible

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fibre surface area is nearer to loose fibres due to structural openness and the nonwovens can be easily collected after usage[83].

CONCLUSION Natural fibres such as cotton, wool, jute, flax, hemp etc. become the fibre of choice for manufacturing various nonwoven fabrics. Their biodegradation properties make them more and more appealing in the context of new regulations for environment protection. The natural fibre nonwovens are becoming the fastest growing sectors occupying technical textile market around all over the world. The nonwovens are manufactured by web formation (carding, air laying and wet laying) followed by fibre bonding. Most widely used fibre bonding process is needlepunching followed by spunlacing, thermal bonding and chemical bonding. Some chemical modification are required to natural bast fibre such as jute, flax etc. to make them to feel softer in nonwoven form which is a demand in many applications. Cotton fibre nonwovens are occupying the market of hygiene and healthcare sector more prominently while jute nonwovens are found more suitable positions in the field of applications of filtration, geotextiles, automobile interiors, household products, composite reinforcements and other appliances. Flax and hemp nonwovens are used suitably for reinforcing application in composites, geotextiles, mats, panels etc. All these nonwovens have tremendous potential for various other functional application such as for insulation from heat and sound, sea water oil sorption, metal ion removal from wastewater and many more. On account of these discussions, it is concluded that the natural fibres like cotton, jute, flax and others will occupy a more favourable market conditions in near future due to the increasing concern with environmental issues all over the world. It has been found in study that these natural fibres are more environmentally sound and less costly to society than its competing synthetic material. Even in the life-cycle, the disposal stage of synthetic material is most harmful to the environment causing highest direct economic and social costs.

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[31] Sevost’yanov, P. A. and Seryakova, T. V. (2009). Study of deformation of nonwoven fibre material during needle-punching. Fiber Chemistry 41:38-40. [32] Debnath, S. and Madhusoothanan, M. (2010) ‘Water Absorbency of Jute--Polypropylene Blended Needle-punched Nonwoven,’ Journal of Industrial Textiles, 39(3), pp. 215–231. doi: 10.1177/1528083 709347121. [33] Anandjiwala, R. D. and Boguslavsky, L. (2008) ‘Development of Needle-punched Nonwoven Fabrics from Flax Fibers for Air Filtration Applications,’ Textile Research Journal, 78(7), pp. 614– 624. doi: 10.1097/IAE.0000000000000647. [34] Sengupta, S., Chattopadhyay, S. N., Samajpati, S. and Day, A. (2008a). Use of Jute Needle-Punched Nonwoven Fabric as Reinforcement in Composite, Indian Journal of Fibre and Textile Research 33:.37-44. [35] Marshall, E. W., et al, (2007), Citric acid treatment of flax, cotton and blended nonwoven mats for copper ion absorption, Industrial Crops and Products, 26: 8–13. [36] Jianyong, F. and Jianchun, Z. (2015) ‘Preparation and filtration property of hemp-based composite nonwoven,’ Journal of Industrial Textiles, 45(2), pp. 265–297. doi: 10.1177/1528083714529807. [37] Edwards, J. et al., (2017) ‘Induction of Low-Level Hydrogen Peroxide Generation by Unbleached Cotton Nonwovens as Potential Wound Dressing Materials’ Journal of Functional Biomaterials, 8(1), p. 9. doi: 10.3390/jfb8010009. [38] Lou, C. W. et al., (2008) ‘Properties Evaluation of Tencel/Cotton Nonwoven Fabric Coated with Chitosan for Wound Dressing,’ Textile Research Journal, 78(3), pp. 248–253. doi: 10.1177/ 0040517507089747. [39] Alimuzzaman, S., Gong, R. H. and Akonda, M. (2014) ‘Biodegradability of nonwoven flax fiber reinforced polylactic acid biocomposites,’ Polymer Composites, 35(11), pp. 2094–2102. doi: 10.1002/pc.22871.

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[40] Sen, T., et al., (2011), Various Industrial Applications of Hemp, Kinaf, Flax and Ramie Natural Fibres, International Journal of Innovation, Management and Technology, 2(3): 192-198. [41] Sengupta, S., (2010). Modelling on sound transmission loss of jute needle-punched nonwoven fabrics using central composite rotatable experimental design. Indian Journal of Fibre and Textile Research 35: 293-297. [42] Thilagavathi, G., Pradeep, E., Kannaian, T., Sasikala, L. (2010). Development of Natural Fiber Nonwovens for Application as Car Interiors for Noise Control. Journal of Industrial Textiles 39: 267278. [43] Kozłowski, R., et al., (2008), Development of Insulation Composite Based on FR Bast Fibers and Wool, International Conference on Flax and Other Bast Plants, ID number: 68, pp 353-363. [44] Ganesan, P. and Karthik, T. (2016) ‘Development of acoustic nonwoven materials from kapok and milkweed fibres,’ Journal of the Textile Institute, 107(4), pp. 477–482. doi: 10.1080/00405000. 2015.1045251. [45] Ogunbowale, W. O. et al., (2012) ‘Acoustical Absorptive Properties of Cotton, Polylactic Acid Batts and Fabrics,’ American International Journal of Contemporary Research, 2(11). [46] Zhu, W. B., Nandikolla, V. and George, B. (2015) ‘Effect of Bulk Density on the Acoustic Performance of Thermally Bonded Nonwovens,’ Journal of Engineered Fibers and Fabrics, 10(3), pp. 39–45. doi: 10.1259/bjr/44936440. [47] Parikh, D. V., Chen, Y. and Sun, L. (2006) ‘Reducing Automotive Interior Noise with Natural Fiber Nonwoven Floor Covering Systems,’ Textile Research Journal, 76(11), pp. 813–820. doi: 10.1177/0040517506063393. [48] Sengupta, S., Majumdar, K. P., Ray, P. (2008b). Tensile deformation of jute-needlepunched nonwoven geotextiles under compressive load. Indian Journal of Fibre and Textile Research 33: 139-145. [49] Sengupta, S., (2010a). Sound reduction by needlepunched nonwoven fabrics. Indian Journal of Fibre and Textile Research 35: 237-242.

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[50] Muthukumar, N. et al., (2017) ‘Sound and thermal insulation properties of flax/low melt PET needle punched nonwovens,’ Journal of Natural Fibers, pp. 1–8. doi: 10.1080/15440478. 2017.1414654. [51] Sengupta, S., Chattopadhyay, N. S., Samajpati, S., Day, A. and Bhattacharyya, K. S. (2005), Jute Based Composite Products. Asian Textile Journal 14:.70-72. [52] Habibi, M. et al., (2018) ‘Effect of surface density and fiber length on the porosity and permeability of nonwoven flax reinforcement,’ Textile Research Journal, 88(15), pp. 1776–1787. doi: 10.1177/ 0040517517708542. [53] Niu, H. et al., (2010) ‘Direct manufacturing of flax fibers reinforced low melting point PET composites from nonwoven mats,’ Fibers and Polymers, 11(2), pp. 218–222. doi: 10.1007/s12221-010-0218-2. [54] Chen, Y. et al., (2007) ‘Comparative study of hemp fiber for nonwoven composites,’ Journal of Industrial Hemp, 12(1), pp. 27– 45. doi: 10.1300/J237v12n01_04. [55] Merotte, J. et al., (2016) ‘Impact of porosity level on of nonwoven flax/PP composite properties,’ Materiaux et Techniques, 104(4). doi: 10.1051/mattech/2016017. [56] Miao, M. and Shan, M. (2011) ‘Highly aligned flax/polypropylene nonwoven preforms for thermoplastic composites,’ Composites Science and Technology, 71(15), pp. 1713–1718. doi: 10.1016/ j.compscitech.2011.08.001. [57] Hargitai, H., et al., (2005), Development of hemp fibre-PP nonwoven composites, Proceeding of the 8th Polymers for Advanced Technologies International Symposium, Budapest, Hungary,13-16 September 2005. [58] Dhanakodi, A. K. P. and Giri Dev, V. R. (2017) ‘Effect of Carbon Fillers on Mechanical Properties of Heat-Treated Needle-Punched Nonwoven Preforms,’ Polymer - Plastics Technology and Engineering, 56(2), pp. 195–201. doi: 10.1080/03602559.2016. 1211688.

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[59] Sao, K. P. and Jain, A, K. (1995), Mercerization and crimp formation in jute. Indian Journal of Fibre and Textile Research 20: 185-191. [60] Roy, A. N. and Ray, P. (2005). Physical Properties of Jute-Viscose Blended Needle Punched Nonwoven, Part-II: Compressibility and Bending Stiffness, Manmade Textiles India 48: 435-439. [61] Sengupta, S., Ray, P., Majumder, P. K. (2005). Ranking of Important Parameters Affecting Compressionof Jute Based Needle Punched Nonwoven Fabrics. Asian Textile Journal 14: 69-72. [62] Debnath, S., Nag, D., De, S. S., Ganguly, P. K. and Ghosh, S. K. (2006). Studies on mechanical and hydraulic properties of JGT for geo-technical applications. Journal of Institute of Engineers (India) TX86: 46-49. [63] Elbadry, E. A., Aly-Hassan, M. S. and Hamada, H. (2012). Mechanical Properties of Natural Jute Fabric/Jute Mat Fiber Reinforced Polymer Matrix Hybrid Composites. Advanced Mechanical Engineering 1-12. doi:10.1155/2012/354547. [64] Elbadry, E. and Hamada, H. 2012b. Impact Properties of Natural Jute Fabric/Jute Mat Fiber Reinforced Polymer Matrix Hybrid Composites. Journal of Mechanical Engineering and Automation 2: 381-388. [65] Samajpati, S. and Sensupta. S. (2006). Wetting characteristics of long vegetable fibres. Indian Journal of Fibre and Textile Research 32: 262-266. [66] Rawal, A. and Sayeed, M. M. A. (2013) ‘Mechanical properties and damage analysis of jute/polypropylene hybrid nonwoven geotextiles,’ Geotextiles and Geomembranes, 37, pp. 54–60. doi: 10.1016/ j.geotexmem.2013.02.003. [67] Rawal, A. and Sayeed, M. M. A. (2014) ‘Tailoring the structure and properties of jute blended nonwoven geotextiles via alkali treatment of jute fibers,’ Materials and Design, 53, pp. 701–705. doi: 10.1016/j.matdes.2013.07.073. [68] Claramunt, J. et al., (2016) ‘Natural fiber nonwoven reinforced cement composites as sustainable materials for building envelopes,’

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[78] Choi, H. M., Kwon, H. J. and Moreau, J. P. (1993) ‘Cotton Nonwovens as Oil Spill Cleanup Sorbents,’ Textile Research Journal, 63(4), pp. 211–218. doi: 10.1177/004051759306300404. [79] Radetić, M. M. et al., (2003) ‘Recycled wool-based nonwoven material as an oil sorbent,’ Environmental Science and Technology, 37(5), pp. 1008–1012. doi: 10.1021/es0201303. [80] Lee, Y. H., Kim, J. S., Kim, D. H., Shin, M. S., Jung, Y. J., Lee, D. J. and Kim, H. D., (2013). Effect of blend ratio of PP/kapok blend nonwoven fabrics on oil sorption capacity. Environmental technology, 34(24), pp.3169-3175. [81] Chen, J. Y. and Jiang, N. (2014) ‘Fabrication and characterization of carbonized and activated cotton nonwovens,’ Journal of Industrial Textiles, 43(3), pp. 338–349. doi: 10.1177/1528083712454153. [82] Chen, Y. et al., (2006) ‘Activated Carbon Nonwoven as Chemical Protective Materials,’ Research Journal of Textile and Apparel, 10(3), pp. 1–7. [83] Renuka, S., Rengasamy, R. S. and Das, D. (2016) ‘Studies on needlepunched natural and polypropylene fiber nonwovens as oil sorbents,’ Journal of Industrial Textiles, 46(4), pp. 1121–1143. doi: 10.1177/ 1528083715613630.

In: Nonwoven Fabric Editor: Rembrandt Elise

ISBN: 978-1-53617-587-5 © 2020 Nova Science Publishers, Inc.

Chapter 2

POTENTIAL OF JUTE BASED NEEDLE-PUNCHED NONWOVEN: PROPERTIES AND APPLICATIONS Surajit Sengupta*, PhD Mechanical Processing Division, ICAR-National Institute of Natural Fibre Engineering and Technology, Kolkata, West Bengal, India

ABSTRACT Uses of nonwoven fabric in domestic and industrial areas are increasing day by day. Now-a days, research is going on to apply natural fibre in different uses in the form of nonwoven either alone or blended with synthetic fibres. The chapter presents with an idea regarding the structure, property, evaluation and application of jute and jute blended needle-punched nonwoven fabric. Knowing well about the effect of various factors on the needle-punched jute nonwoven, the proper and effective design can be made of such fabrics for a particular use. This chapter is intended to present an overview and potential — most of which are based on ideas and conclusions presented in published literature during the last 40 years, the rest representing the author’s concepts *

Corresponding Author’s E-mail:[email protected].

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Surajit Sengupta developed through extensive research. It will help to those who will deal with natural lingo-cellulosic fibre-based needle punched nonwoven in both industry and academia specially to teachers, students and technologists.

Keywords: jute and allied fibres, needle-punched nonwoven, structure, properties, application

INTRODUCTION Among the textiles applications, nonwovens are one of the fastestgrowing segments of the textile industry and constitute roughly one-third of the fibre industry. An estimate shows that the global consumption of nonwovens in 2018 is 11.2 million tonnes or 307.0 billion square meters (m2), valued at $46.8 billion (URL 1, 2019).The market is concentrated in three regions; Asia, Europe, and North America account for approximately 87% of world consumption in 2017. Demand growth during 2017–22 will be the highest in Other Asia, China, and the Middle East/Africa. China is the largest single participant in the global nonwoven fabrics market, accounting for nearly 28% of consumption, 34% of production, and 35% of exports in 2017(URL 2, 2019). The nonwoven fabric has proved its potential mainly in the synthetic arena. Nonwoven machinery has reached a high level of engineering quality and design. The continued development of the process and its product has allowed the nonwoven fabric to become widely used in both domestic and industrial applications. Nonwovens have many fold advantages, e.g., high production rate, short manufacturing line eliminating series of machines in conventional spinning-weaving, a wide range of products, the possibility of value addition to inferior quality fibres, low manufacturing cost etc, with having their particular specific properties (Kozlowski et al., 1999). A nonwoven machine usually consists of fibre blending and opening unit (to break, to clean the fibre strands and to mix with other fibres or qualities), suitable card according to fibre (individualisation, parallelisation and levelling of fibres), butt former (fibre orientation by multiple laying)

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and needle loom (entanglement) (Figure 1A). In the process of nonwoven making, a web (a thin semi-transparent layer of fibres where fibres are attached by surface cohesion only) is prepared in a card and then several webs are laid one above another, which enters directly to make bond formation by mechanical, chemical, thermal or solvent means in a single process. The fibre orientation in the batt is of three types; parallel laying, cross laying and random laying according to the orientation of fibre (Russell, 2007). Figure 1B shows the schematic diagram of needle loom.

(A)

(B)

Figure 1. (A) Needle punched nonwoven system with (B) Schematic diagram of loom.

Now-a days, research is going on to apply natural fibre in different uses in the form of nonwoven either alone or blended with synthetic fibres. In this regard, the application of jute and allied fibres is scanty. Nonwoven technology appears to be particularly relevant to the jute industry because of its high productivity and low wage component of the production cost associated with it. Besides, this offers a means of diversifying into various value-added products which would fetch better returns to the industry using even waste fibres. Today, production of jute nonwoven fabrics are limited to a few thousand tons of needled felts used mainly for packaging, cushioning, and carpet under-laying. The research is continued in following broad areas: (a) use of un-spinnable fibre wastes, (b) to identify and characterise the different uses, (c) blending of jute with other natural or synthetic fibres, (d) to study the structure-property relations. Jute (mainly Tossa and white varieties, i.e., Corchorus olitorius L and Corchorus capsularies L), a ligno-cellulosic technical fibre, is the second

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most important fibre after cotton because of production and uses. Presently, it is grown mainly in India, Bangladesh, China, Myanmar, Nepal and Thailand. India and Bangladesh account for more than 93% of world production. Figure 2A shows the jute plant. In 2017, about 3,000,000 tonnes of jute were produced and used in making ‘sackcloth’ and carpetbacking fabric. It is a bast fibre and is extracted from the inner bark of plants of the genus Chochorus. It is extracted by a retting process facilitating to ferment the non-cellulosic material binding of fibres and remove it by washing in water. Jute fibre generally has a rough feel; however, the best quality fibres are smooth and soft. A single jute fibre cell (ultimate) has an average length of 2.5 mm and a mean diameter of 12 μ. There are usually 6 to 20 ultimates in each cross-section of a fibre. The strand length varies approximately from 1.5 to 3.5 m. The average weight per unit length of individual fibres varies from 1.9 to 2.2 tex. The average length of a single fibre is 0.5 to 80 cm. The individual fibre shows nodes and cross-markings in the longitudinal view, and polygonal shapes in the cross-section. Jute fibre varies greatly in strength (40 –70 g/tex). It has an elongation at break of approximately 1.7%. Jute is highly hygroscopic (moisture regain at 65% R.H. is 12.8%). The specific gravity of jute fibre is 1.48. The fibres in the strand are organized in a meshy structure (Figure 2B). During processing, this meshy structure is opened to form fibres. Besides having many industrial applications, finer quality jute fibres are utilized in furnishing and curtain fabrics (Frank R. R., 2005).

(A) Figure 2. (A) Jute plant, (B) Messy fibre above stick.

(B)

Potential of Jute Based Needle-Punched Nonwoven

(A)

41

(B)

Figure 3. (A) Jute reed, (B) Nonwoven fabric.

During the process, jute reeds (Figure 3A) are sprayed with castor oil emulsified in water. The wet fibres are kept in stacked condition for better and uniform absorption of oil emulsion.Then removing from the bin, it is processed in the softener, jute breaker card and finisher card to individualise the fibres. These fibres are fed to the carding machine of nonwoven preparation system, butts are produced by parallel lapping, cross lapping or air lapping system in case of natural fibres and finally, a preneedled fabric has been made. This pre-needled fabric is laid one over another to get required g/m2 in layers followed by needling by 20-25 gauge needles (Sengupta et al., 2008d). Bonding of jute butt can be made using needling punching (Figure 3B), stitch bonding and chemical bonding, thermal bonding. Out of these, the most successful for jute is needle punching system which has been commercialised in the Indian subcontinent. It is not only used for domestic purposes but also exported to advanced countries. The main criteria in this process are thick fabric with some special properties can be made; and in that sense, it has no competition with woven or knitted fabric. Finer the fabric lower is the uniformity. Such fabrics are usually used in paddings, insulation media, reinforcing material, packaging etc.

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JUTE NONWOVEN STRUCTURE The structure of jute needle-punched fabric is very complex due to inherent properties of the jute fibre with a wide variation in length, fineness along with meshyness, brittleness and presence of gummy material. It is formed by the penetration of barbed needles which during the inward journey, create fibre loop or peg along with some fibre breakage due to inextensible and brittle nature and entanglement during the outward journey and also some. (Sengupta et al. 2008d), According to Debnath (1979d), the vertical structure of jute needled fabric is associated with the entanglement of the vertical fibres around neighbouring fibres and consequently the formation of fibre loops (Figure 4A). The amount of reorientation or interlacement of the fibres increases gradually as the needling density is increased and simultaneously the resultant fabric becomes denser with the reduction in thickness. The length of the loops increases for the higher depth of penetration of the needle and consequently the depth of penetration of the needle changes the degree of entanglement of the fibre assembly. A coarse gauge needle has a greater influence on the transfer and interlacement of a very large number of fibres and consequently the formation of thicker loops in comparison to a fine gauge of the needle. High barb protrusion influences the fibre in such a way that the fibrous mass is not bound as fairly and firmly as a standard protrusion barb. Again, the interlacements of the fibres are associated with fibrous strands and fibre reversals around the greater neighbouring fibres and as a result, a large number of fibres are closely associated with multiple entanglement centres. The number of fibres of the loops in the vertical structures of the fabrics is increased with the higher web weight. In a study by Sengupta et al. (1985e), a ratio recording spectrophotometer was used to estimate the percentage of fibres transferred during needling from top to the bottom layer of a two-layer bolt. The ratio of transmittance of the face and the back after punching, expressed as a percentage, is the transfer index. The transfer index of jute reinforced needle-punched nonwoven with 14.3 mm depth of needle penetration is 40%. As needling density increases, the fibre transfer also increases and it

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was verified experimentally using jute. As jute is a rigid, brittle and inextensible fibre, controlled needling is important otherwise the harse action of needles will break the fibre and broken fibres are not building the loops or contributing in strength (Sengupta et al., 1985a). The horizontal structure results from the sideways disturbance of the web fibres that do not come into contact with needle barbs (Figure 4B). Scanning electron microscopic observation was made by Das et al. (1987). It revealed that fibres, in the jute needle punched fabric, formed the layered structure and their arrangement depended on the type of fibres and mode of needling. The sideways disturbance during the needle penetration is mostly irreversible due to low extensibility of jute (Sengupta, 2017).

(A)

(B)

(c) Figure 4. Structure of needle punched nonwoven, (A) Vertical Structure -50X, (B) Horizontal- 50 X, (C) Fabric surface (Purdy, 1980).

A study (Debnath, 1979d) showed that the horizontal structure of the fabric was changed significantly with a higher amount of needling. The longitudinal paths of the parallel laid fibre on the surface of the web tended to change to a circular area by the transferred fibres and gauges. The

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degree of smoothness and surface uniformity of the jute needle-punched fabric gradually increased if the total needling density distributed in a higher number of passages of the web movement (Figure 4C). These two structures are not necessarily distinct. Many fibres, that are reoriented, remain partly in the horizontal plane. Such behaviour is important in the realisation of fabric strength. (Debnath, 1986). The length of the fibrous loops and the number of loops of jute are directly influenced by the variation of loom parameters. Debnath (1979f) observed that a higher depth of penetration of the needle or needling density generally achieved a longer and a greater number of fibrous loops, respectively. But, beyond their optimum levels, the fibrous loops were broken. The tenacity of the jute needled fabric increased by 47% with an increment of the fibrous loop length at 25% higher depth of penetration of the needle. It was suggested the tenacity of the jute needled fabric gradually increased with an increase in the value of the fibrous loop length multiplied by the number of the fibrous loops, irrespective of the needling density or depth of penetration of the needle. The needling action produces a force on the needle that acts as a measure of the resistance to needle passage. The punching force of felting needles of gauge 40, 32 and 21 respectively was estimated separately with the help of a model needling assembly attached to an Instron Tensile Strength Tester while needling parallel laid webs of white jute, tossa jute and mesta of web weights varying from 600 to 3600 g/m2 with a constant rate of traverse of 10 cm/min. (Debnath, 1979c). It was found that the punching force increased with increase in the coarseness of fibre and needle, and with an increase in the weight of web. The proportion of the needle damage was lower with the coarse needle. For each of the three varieties of fibre, the increase in punching force due to decrease in needle gauge from 40 to 32 and from 32 to 21 was found to be rough of the order of 25%. The average percentage increase in punching force, due to change from white to tossa jute, was somewhat greater than that from tossa jute to mesta fibre. The average percentage increase of punching force due to change from white to tossa jute or from tossa jute to mesta fibre appeared to be greater with a finer needle than with coarse needle.

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0.1 20

0. 12 4

0.1 22

Oil applied, %

0.1 26

4.91

0. 12 8

6.00

0. 13 0.13 2 0

PHYSICAL PROPERTIES

3.00

0.115 1.22

0

0.117 10.0

11.6

14.0

16.4

18.0

Depth of needle penetration, mm

Figure 5. Effect on bulk density of fabric with 160 punches/cm 2 (Sengupta, 2009).

Density and thickness govern many functional properties of nonwovens, e.g., insulation, absorbency etc.due to its pore properties and tortuosity. Study has been conducted to find out influential process parameters, which governs the density of needle-punched nonwoven (Sengupta, 2009). The contour diagrams (Figure 5) show the effect of depth of needle penetration and softening oil percent on the bulk density of needle-punched nonwoven. For a given depth of needle penetration, bulk density increases with the increase in percent oil applied and for a given oil percent, it decreases with the increase in depth of needle penetration. Debnath and Madhusoothanan (2007) studied the effect of fabric weight and needling density on thickness of fabric. As needling density increases there is a minor change in thickness, but increase in fabric weight, decreases the thickness. In another study, effect of jute content in jute/polypropylene-blended nonwoven fabric on its thickness and density is studied. It is found that the thickness of jute/polypropylene needle-punched fabric increases with the increase in jute content. At lower fabric weight

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(250 g/m2), with the increase in jute content, the fabric density decreases (Debnath and Madhusoothanan, 2010).

Figure 6. Effect of fabric weight and needle density on thickness (Debnath and Madhusoothanan, 2007).

TENSILE PROPERTY The tensile properties of the nonwoven fabrics, in the machine direction or cross direction, were determined (ASTM D5035) on an Instron Tensile Testing Machine (model number 5567) after conditioning at standard atmosphere, i.e., 65% RH and 21oC. The test conditions (Sengupta et al., 2008a) were: test length, 10 cm; cross-head speed, 5 cm/min; and strip width, 2.5 cm. The fabric tenacity and elongation-atbreak were determined as follows: Tenacity (cN/tex) =Breaking load (cN)/(Specimen width (mm) x Fabric mass per unit area (g/m2)) Extension-at-break, % = Elongation-at-break (cm) x 100/Gauge length (cm)

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Energy to break, which represents the toughness, data was available in the machine report calculating the area under the load-elongation curve. Initial modulus was measured as the modulus between 0% and 1% tensile extension of the sample. The factors responsible for structural imperfections of needled jute fabric were analysed theoretically by Debnath (1986) about the fabric tensile strength. The jute web had very poor strength and dimensional stability but the tensile strength of jute nonwovens improved with a higher fibre-loop length. A detailed study was carried out by Debnath (1978a, 2001) regarding the effect of various parameters on jute fabric tenacity. It was reported that an effective needling action, with better entanglement of fibres, could be achieved either by an increase in the needling density up to an optimum level with a constant depth of penetration of the needle or vice-versa. The breaking load of the fabric, made with a different number of passages of the web through the needle loom, appeared to be greater than that of the fabric made with its one passage only. In general, the fabric made with a low protrusion, finer gauge, 9-barbed needle or a needle of closer barb spacing showed higher values of both stress and strain. The value of tenacity of the fabric made by needling on one surface only was higher than that of the fabric made by needling on both top and bottom surfaces. Table 1. Physical properties of jute needle punched nonwoven textiles with or without reinforcement Jute needle punched Nonwoven Without reinforcement Hessian reinforcement Polyethelene reinforcement

Fabric weight g/m2 10001500 270570 210990

Thickness cm

Density g/cm2

0.90-0.14

0.100.14 0.070.08 0.040.13

0.35-0.70 0.35-0.90

Ganguly and Samajpati, 1996

Breaking load kg 2.5-6.5

Tenacity g/tex 0.06-0.12

Thermal insulation Marsh % -

18.0-32.5

0.70-1.70

29.36

1.3-7.1

1.30-7.10

-

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Some physical properties of jute nonwoven fabric with or without reinforcement have been shown in Table 1. It was also reported (Debnath 1979a) that the tenacity of jute needled fabrics, with the least percentage of jute batching emulsion (5%), applied either on the fibrous webs before needling or on fabric, was higher than that of the untreated jute needled fabric. The tenacity values of the needled fabrics increased with an increase in the batching emulsion or binning period (both for web and fabric) up to a certain level, and the optimum conditions were found to be (10%, 30%) and (48hrs, 72 hrs) respectively. In the cross-laid nonwoven, the majority of fibres are oriented in an angle with the cross direction of the fabric. Hence, for the tensile test in cross-direction of fabric, the fibres can easily be reoriented much closer to the test direction (in the direction of application of load during tensile testing); but if the testing is carried out in machine direction the majority of fibres cannot be oriented in the test direction. Hence, the contribution of fibres toward the load-bearing is much higher during the testing of cross direction than that of in machine direction. The stress development during extension is always higher in cross direction than that of in machine direction. Moreover, the rupture of fabric in the cross direction shows higher step breaks which are the evidence of breakage of taut fibres and subsequent increase in stress due to other fibres. The same fabric in wet condition shows improved tensile properties due to increased cohesion between the fibres and more compact structure in swelling and shrinkage. In another study, it is reported that the tensile strength of the fabric made of multiple numbers of passages of the web through the needle loom is found greater than that of the fabric made with its one passage only. The fabric made with a low protrusion, finer gauge, needle of closer barb spacing showed higher values of both stress and strain. The value of tenacity of the fabric made by needling on one surface only is higher than that of the fabric made by needling on both top and bottom surfaces. It is also reported that if jute batching oil is applied on the web before needling, then the tensile strength of the needled fabric is increased. The tenacity value is increased with an increase in the batching oil percentage or binning period up to a certain level. Afterwards, no improvements are

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found (Roy and Ray, 2005). With the increase in fabric weight, the tenacity, initial modulus, and work of rupture initially increase, but at greater fabric weight, though the tenacity becomes steady, initial modulus and work of rupture have a declining trend. Elongation at break is reduced with an increase in fabric weight, punch density, and depth of penetration (Roy and Ray, 2005; 2009a). The amount of compressive load is also important along with fibre orientation in the fabric for its tensile behavior during crack or void generation (Sengupta et al., 2008a). The tensile and flexural properties of jute needle-punched nonwoven composites increased by increasing the jute fibre weight content and by adding the jute fabric as skin layers (Sengupta et al., 2008b). The stress-strain diagram of reinforcing material, needled web without reinforcing material and with reinforcing material have been shown in Figure 7. In another Figure (Figure 8), the stress-strain diagram of nonwoven in different direction and wet condition has been shown.

Figure 7. Stress-strain diagram of (a) Reinforcing material, (b) Needled web without reinforcing material, (c) needled web with reinforcing material (Sengupta et al., 1985a).

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Figure 8. Stress-strain diagram of jute needle punched nonwoven,a - test in cross direction, b - test in machine direction, c – test in cross direction and wet condition, d – 2-ply fabric in cross direction, e – 3-ply fabric in cross direction(Sengupta et al.,2008a).

Extensive work had been carried out (Ganguly et al., 1999) to understand the mechanical behaviour of jute and polypropylene blended needle-punched fabrics. It included the effects of jute/PP blend composition, jute fibre cut length, punch density, depth of needle penetration, PP fibre fineness and web laying technique on the properties of needle punched nonwoven. The blending of polypropylene with jute made the fabrics bulkier, stronger, tougher and more flexible. With the increase in punch density and depth of needle penetration, the mechanical properties improved initially and after attaining the optimum value they deteriorated. Jute fibre cut-length of 80 mm showed the optimum mechanical properties of the fabric. Fabrics prepared using finer polypropylene fibre and randomly laid webs exhibited better tensile and bending properties in the machine direction compared to those made out of coarser fibre and cross laid webs. The fabrics made out of random laid webs are bulkier, stronger, tougher and more flexible in the machine direction compared to those made out of cross laid webs. The effects of punch density and blend composition on the tensile properties, relaxation behaviour and response to cyclic loading of woollenised jute and polypropylene blended cross-laid nonwoven fabrics having wollenised jute

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as a major constituent had been studied (Ganguly et al.,1997; Sengupta et al. 1999). Physical, mechanical, tensile, relaxation and elasticity characteristics of the wollenised jute and polypropylene blended (20%, 30% and 40%) needle punched nonwoven fabrics largely depended on the punch density employed in preparing the fabrics. For 20% and 30% of PP blended fabrics, the best results were obtained at 120 punches/cm2, while for 40% PP blended fabric, at the 160 punches/cm2. This was apparently due to the increase in the number of fibres per unit volume of fibrous webswith an increase in PP component in the web, which in turn, necessitates increasing level of punch density to achieve the desired consolidation of the fibrous web. The blending of PP with woollenised jute improved the tenacity, initial modulus and extension at break of the nonwoven fabric at all levels of punch density. Stress decay suffered by the fabric subjected to stress relaxation was higher for the blended fabric in comparison to the woollenised jute fabric at both high and low extension levels. Extension cycling lowered the tenacity of woollenised jute and 80:20 woollenised jute/polypropylene fabrics. Permanent set suffered by the blended fabrics was generally lower in comparison to woollenised jute fabric. Physical properties of needle punched nonwoven textiles from jute, woollenised jute and their blends with polypropylene have been shown in Tables 2 and 3. Table 2. Physical properties of jute and jute polypropylene blended needle punched nonwoven textiles Fabric type

Bulk density g/cc 0.117 0.091

Tenacity cN/tex

Breaking strain % 20 86

Jute 0.160 Jute/PP 0.967 =60:40 WJ 0.114 0.110 25 WJ/PP= 0.103 1.020 67 60:40 Ganguly et al., 1999, Ganguly et al., 1997

Work of rupture cN 1.145 3.536

Initial Modulus cN/tex 1.124 1.132

Bending modulus N/cm2 1.825 1.638

Flexural rigidity mg/tex -

-

0.770 1.240

-

4.83 4.98

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Table 3. Functional properties of jute and jute polypropylene blended needle punched nonwoven textiles Fabric type

Stress decay %

Permanent set %

Dynamic loading for 500 cycles Thickness Thickness loss, % gain, % 58.52 4.81 66.10 5.93

SAP cc/s/cm

Thermal conductivity cal/deg/cm/s

Fibre shredding mg/m2

Jute 51.20 2.56x10-4 950 Jute/PP= 44.60 60:40 WJ 27.2 41.5 6.41 2.42x10-4 WJ/PP= 39.7 33.4 13.64 60:40 Sengupta et al. 1985b, Sengupta et al. 1985d, Ganguly et al. 1997, Sengupta et al. 1999, Sengupta et al. 2005

The Instron Tensile Tester was used to measure the amount of force needed to break down a loop of a single fibre (Debnath 1979e). The tenacity of jute single fibre loops is much lower (470%) than that of viscose single fibre loops. The tensile strength of jute single fibre loops is reduced by 84% in comparison with the respective single fibre tensile strength, whereas the strength of viscose single fibre loops is reduced by 2% only. The load-extension curve of a jute needle-punched nonwoven fabric was characterized by two deformation regions. The initial region shows negligible resistance to deformation and this is followed by a jammed, stiff region. In the initial stage of extension, fibres are pulled straight, helped by slippage at crossover points, with only a nominal development of tension. This is followed by the building up of transverse forces from the fibres under tension passing round and into fibre pegs, resulting in a steep rise in load with a small increase in extension. The presence of pegs and their extended parts in both the surfaces alone is sufficient to generate resistance to deformation. It pointed out that the pegs act to allow the build-up of transverse forces within the structure. Adjacent pegs are pushed close together, and individual pegs are squeezed to an elliptical shape along the direction of extension. Eventually, as the fabric density increased as a result of the changes caused by stretching, fibres are locked together in

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frictional contact and substantial resistance is evident as the stress rises sharply with small increments of extension. As frictional forces are overcome, slippage and breakage of fibres occur, the ultimate result being fabric breakdown. (Hearle et al. 1972)

Empirical Models to Predict Tensile Property The effects of jute nonwoven fabric weight and needling density on tenacity, elongation at break and initial modulus was reported (Debnath et al. 2000) using Box and Behnken factorial Design. Tenacity values were found to increase with increased needling density and fabric weight whilst breaking elongation values were found to decrease with increased fabric weight due to better consolidation of the fabric structure. Initial modulus values of nonwoven fabrics were found to increase with fabric weight and needling density due to an increase in the number of fibres per unit area. In another study, using same factorial design Debnath and Majumder (2001) studied on fabric weight, needling density and blend proportion in polypropylene-woollenised jute blends on tenacity, breaking elongation and initial modulus. It concluded that the breaking elongation decreased with increasing fabric weight due to better consolidation of the fabric structure with increasing weight. The initial modulus in the transverse direction was higher than in the machine direction, possibly due to use of the cross-laid web. The initial modulus increased with increase in fabric weight. In a study on jute/viscose blended needle punched nonwoven (Roy et al., 2005a, Roy et al. 2005b, Roy et al. 2005c, Roy et al. 2006) studied the tensile response, stress decay, cyclic loading and bursting strength using statistical experimental designing technique and subsequent response surfaces. It was depicted that with the increase in fabric weight, punch density and depth of needle penetration, the tenacity, initial modulus and work of rupture of fabric initially increases and after reaching an optimum value starts decreasing with further increase in those variables, whereas the extensibility of fabric reduced continuously with the increase in fabric

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weight, punch density and depth of needle penetration. The increase in jute percentage in the fabric, tenacity, extensibility, initial modulus and work of rupture was reduced. The tenacity of needled fabric was improved on stress relaxation except in fabric having low area density, very high punch density and depth of penetration. Both stress decay and permanent set on the cyclic extension were initially reduced and then show an upward trend with the increase in fabric weight, punch density and depth of penetration. Permanent set on cyclic extension, stress decay and tenacity after stress relaxation increased with the increase in jute percentage in the jute-viscose blended fabric but a very high percentage of jute in the fabric tended to show a slight reduction in stress relaxation. Blending of viscose fibre with jute increased fabric bursting strength. The predicted response surface equations for various properties of jute/viscose blended needle punched nonwoven agreed well with the experimental data as evident from the high value of coefficients of multiple correlations.

Figure 9. Effect of punch density and mass/area of jute nonwoven on tenacity.

The modelling of tensile properties of needle-punched nonwoven fabrics produced from the blends of jute and polypropylene fibres with varying fabric weight, needling density and blend ratio has been reported (Debnath et al., 2000). The tenacity and initial modulus values of needlepunched nonwoven fabrics have been predicted with the help of empirical model (using multiple regression analysis) and artificial neural networks and compared with the experimental values. The artificial neural network

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model was found to be much better and more accurate than an empirical model. The experimental verification of the predicted values for extrapolated input variables was made. The prediction by the artificial neural network model showed better results than that by empirical model even for the extrapolated input variables. Effects of punch density/needle penetration and mass per unit area on jute nonwoven tenacity, extension at break, energy-to-break have been shown in Figures 9, 10 and 11 respectively.

Figure 10. Effect of needle penetration and mass/area of jute nonwoven on extensionat-break.

Figure 11. Effect of punch density and mass/area of jute nonwoven on energy-to-break (Ref. For Figures 9,10,11- Sengupta et al., 2008b).

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Sandwich blending: Needling of jute-cotton, jute-viscose and jute nylon fibrous webs laid in sandwiched form and the resultant fabrics were investigated (Debnath, 1978b) for the optimum proportion of blends as well as the critical condition of needling density for the tensile properties of the fabrics. Jute fabric was stronger than nylon, followed by viscose and cotton respectively. The critical jute viscose, jute nylon blend proportions were found to exist at 25:75 and 75:25, respectively, at which the fabric tenacity was the minimum. The value of rupture strain increased with the proportion of viscose, nylon or cotton. Whenever the coarser and stronger jute fibres were on the top surface of the sandwiched blends, a higher tenacity and a higher initial modulus were found in comparison with other arrangements of fibrous layers of the sandwiched webs. This holds good for jute viscose or jute cotton sandwiched blended webs.

Woven Fabric Reinforced Nonwoven

Figure 12. Stress-strain diagram of jute nonwoven reinforced with different material, (a) Jute hessian, (b) Cotton bandage cloth, (c) Cotton gauge cloth, (d) Polyethylene film.

Debnath (1979b) investigated the effect of jute hessian reinforcement in needle punched nonwoven varying the web weight and quality of hessian used as a base or in centre. Jute caddis and woollenised jute were used as nonwoven. The jute needled fabric with reinforcement had good

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dimensional stability and the value of breaking load of the fabrics were mainly influenced by the tensile properties of the reinforcement fabric, which increased with an increase in warp/weft sett or higher count of yarns or varying warp yarn tension of the reinforced fabric. Longer and finer fibres were more suitable for the formation of better interlocked fibrous structures by the needling process, causing a higher value of stress and strain of the fabric. Stress-strain diagram of jute nonwoven reinforced with different material has been shown in Figure 12.

Figure 13. Stress strain diagram of hessian reinforced jute nonwoven,x-x-x: Hessian at centre, _____: Hessian at base.

Figure 14. Stress strain diagram of reinforced nonwoven, (A) Jute, (B) Woollenised jute, (3) Woollenised in fabric form(Ref. Figures 12,13,14- Sengupta et al., 1985a).

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In another work (Sengupta et al. 1985a), it was reported that batching oil emulsion treatment on jute fibres and woollenized jute was found to give improved processability and tensile properties to nonwovens. Reinforcing fabric placed at centre shows better tensile property than that at the base (Figure 13). Figure 14 shows that woollenisation in the fabric form gives much higher extensibility than nonwoven fabric made from woollenised jute fibre.

BURSTING STRENGTH The nonwoven fabric samples were tested in the Bursting Strength Tester with diaphragm expansion principle following the BIS standard IS: 1966. The effects of various factors on the bursting strength of jute needlepunched nonwoven were studied. It is observed that the bursting strength of fabric increases with the increase in fabric weight, needle punch density, and depth of needle penetration. However, but beyond some optimum punch density and depth of needle penetration bursting strength of fabric shows a declining trend (Roy and Ray, 2005b; 2009b). Effect of punch density and mass/area of jute nonwoven on bursting strength has been shown in Figure 15.

Figure 15. Effect of punch density and mass/area of jute nonwoven on bursting strength (Sengupta et al., 2008b).

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FABRIC RIGIDITY The flexural rigidity of the fabric samples (150 mm x 25 mm) was determined by measuring the bending length following the standard cantilever principle (ASTM D 5732). Flexural rigidity was calculated from the following formula (Debnath et al., 2006): Flexural Rigidity, G (N.cm) =WC3 x 9.81/104 where W - fabric area density (g/m2); and C- bending length in cm. Bending Modulus (N/cm2) = 12G/g3 where, g = thickness (cm) measured by following ASTM D5199-917 In the case of thick and semi-rigid nonwoven fabric, a computerised bending behaviour tester (Sengupta et al., 2016) was developed working in loop principle. The nonwoven strip of 5 cm width and 40 cm length is mounted as a loop and the load on bending of 10 mm of that loop along the radius at the rate of 10 mm/min defines the bending resistance. Ganguly et al.(1997) studied the effects of punch density and blend composition on the flexural property of chemically texturised (woollenised) jute and polypropylene blended cross-laid nonwoven fabrics. Bending modulus of the fabric increases with the increase of fabric weight, whereas modulus after attaining a maximum value, it starts declining with the increase in punch density and depth of needle penetration (Sengupta et al., 1985a; Sengupta et al., 2008b). In a study (Roy and Ray, 2005c) on jute/viscose blended needle punched nonwoven using statistical experimental design stated that bending modulus of fabric increased with the increase in fabric weight whereas fabric bending modulus after attaining a maximum value started declining with the increase in punch density and depth of needle penetration. Blending of viscose fibre with jute in needle punched nonwoven fabric reduced fabric bending modulus. Another study on bending rigidity of jute/viscose blended needle-punched nonwoven using statistical experimental designing technique has been

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reported. This study also says that bending modulus of fabric increased with the increase in fabric weight. However as the proportion of viscose fibre is increased in the blend proportion, the bending modulus decreases (Debnath and Madhusoothanan, 2000).Bending property of jute needlepunched nonwoven has been shown in Table 4. Table 4. Bending property of jute needle punched nonwoven Direction Thickness Area (mm) density (g/m2) Machine 1.68 250 Machine 3.12 500 Cross 3.12 500 Machine 5.06 850 Sengupta et al., 2016

Load CV (cN) (%) 51 121 135 196

2.31 1.85 1.67 1.28

Stress (cN/tex x 10-3) 4.080 4.840 5.400 4.612

Modulus(cN/tex Flexural x 10-3) rigidity Nm x 10-6 18.378 0.0112 21.802 0.0265 24.324 0.0295 20.774 0.0429

Bending modulus N/m2 28.22 10.45 11.66 3.97

THERMAL INSULATION For thermal insulation testing, (Debnath, 2011) the fabric sample is held between two metal discs. In steady condition, the temperature drop across the metal disc with known thermal resistance and across the material under test is measured, and from these two values, the thermal resistance of the sample is determined. The area of the test specimen is 706.85 cm2 (diameter 30 cm) and kept under pressure of 0.3352 kPa. Assuming constant rate of flow of heat, (t1-t2)/TRk = (t2-t3)/TRs So, Thermal resistance of sample in tog (TRs) = x (t2-t3)/(t1-t2), where, TRk- thermal resistance of the known disc, t1,t2and t3- temperature at the lower surface of the known disc, the lower surface of the sample and the upper surface of the sample. Specific thermal resistance, K m2/W = TRs/T0, where T0 - the mean thickness in the meter at 1.55 kPa pressure of the fabric sample.

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Alternately, the cooling method (Sengupta 2018) has been used to measure the thermal insulation. In this method, a hot body is wrapped with the fabric sample and its rate of cooling is measured. A brass cylinder (45 cm length, 5 cm external diameter and 2 mm thickness) closed at one end with a cork was filled with distilled water heated to about 50oC. The other end of the cylinder was closed with a cork through which a thermometer was inserted. A rectangular specimen of the needle punched nonwoven sample was used to cover the whole of the outer surface of the brass tube. The lengthwise edges of the specimen were made to touch each other closely avoiding overlapping to kept in position by sticking cello-tape over the joint running parallel to the length of the cylinder. Repeatability and reliability of the instrument have been checked by repeated testing of the same sample under the similar thermal conditions and also under a different range of temperatures respectively. The experiment was started when the temperature of the water was exactly 48oC. The time taken to cool the fabric from 48oC to 38oC was found. Average of ten such readings was considered and used for calculation of thermal insulation value. The same experiment was repeated without sample under identical atmospheric condition. All the tests have been performed in the same atmospheric condition. This data was also used for calculation of thermal insulation value in the following way: The thermal insulation value (TIV) was calculated as TIV = (1-(Heat lost by covered hot body/Heat lost by the uncovered hot body)) x 100. = (1- (Fall in temperature of the covered hot body/Fall in temperature of the uncovered hot body)) x 100. As the temperature range through which the covered and uncovered hot body cools (48o – 38oC) is the same. TIV will vary with the time and its value is chosen for calculation. TIV = (1- (Time taken by the uncovered body to cool through a certain temperature range/Time taken by the covered body to cool through the same temperature range)) x 100.

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The thermal insulator is defined as a material that is used to reduce the flow of heat. The thermal conductivity of needle-punched nonwovens can be measured by the Lees disc method (Sengupta et al. 1985c). This property of parallel laid and randomly laid needle punched nonwoven fabrics using jute, jute blends with synthetic fibres, jute caddis (mill waste) and wollenised (alkali-treated) jute was investigated (Debnath and Roy, 2001). The maximum area density and thickness of the nonwoven was 950 g/m2 and 0.65 cm. The parallel-laid needle punched nonwoven has shown better thermal insulation behaviour than random laid nonwoven. Nonwoven from jute caddies can also be used as thermal insulator due to its low conductivity. The blending of woollenised jute improves the thermal insulation property when blended with pineapple leaf and ramie fibre. Needle punched nonwovens, made out of woollenised jute/wool blend, shows better thermal insulation than those made out of woollenised jute/polypropylene or woollenised jute/acrylic blend. A sandwich (layered) blending of polypropylene or acrylic with woollenised jute appears to be better than homogeneous blending as far as needle punched nonwoven thermal insulation is concerned. Crimp in fibres has a significant contribution towards thermal insulation. A study (Debnath and Madhusoothanan, 2000a), using jute-polypropylene blend, with 150 and 250 punches/cm2 needle-punched non-woven textiles, has shown that thermal insulation value was increased with an increase in the proportion of PP in the blend. Sengupta et al. (1985c) studied the thermal conductivity of hessian reinforced jute and woollenised jute nonwoven. It shows that the thermal conductivity of jute nonwoven woollenised in fabric form is much higher, which was due to its higher density than nonwoven fabric, made from jute or woollenised jute. The thermal conductivity decreases with the decrease in the ratio of the reinforcing material weight to web weight and the increase in the thickness of the fabric. It is increased with the increase of punch density and depth of needle penetration. These studies explored the possibility of utilization of needle-punched jute based nonwovens as thermal insulation medium with advantageous cost-benefit ratio.

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Figure 16. Effect of punch density and mass/area of jute nonwoven on thermal insulation (Sengupta et al., 2008b).

The blending of woollenized jute improved the thermal insulation property when it is used with pineapple leaf and ramie fibre in blends. Needle-punched nonwovens made of woollenized jute and wool blend show better thermal insulation than those made of woollenized jute and polypropylene or woollenized jute and acrylic blend. The needlepunched nonwoven made of jute caddies can also be used as a thermal insulator (Sengupta et al., 1999). In another study, the effect of fabric weight and needling density on the thermal resistance of jute-polypropylene blend needle-punched nonwoven is examined by employing experimental design (Debnath, 2011). It is reported that the thermal resistance increases with the increase in fabric weight and it is found prominent at lower needling density. Its effect is negligible at higher needling density. With the increase in fabric weight, the number of fibres unit area of the fabric increases. This causes an increase in fabric thickness and tortuosity in fabric structure, causing an increase in thermal resistance. However, with the increase in needling density, thermal resistance decreases because the fabric structure tends toward a higher degree of consolidation and hence reduces the amount of pores in the structure. Effect of punch density and mass/area of jute nonwoven on thermal insulation has been shown in Figure 16.

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AIR PERMEABILITY Air permeability or the airflow through the sample was calculated (ASTM D737 – 04)by dividing the flow meter reading in cc/s at 10 mm pressure drop by the test area 5.07 cm2. The results were expressed as the units of volume of air in cubic centimetre passed per sec through 1 cm2 of fabric at a pressure difference of 10 mm head of water. Sectional air permeability (cm3/s/cm) = Air permeability (cm3/cm2/s) x T0, where, T0 - the mean thickness in the meter at 1.55 kPa pressure of the fabric sample. The air permeability of fabric is of fundamental significance from the points of view both of its structure and end-use. It depends on several simultaneously varying characteristics. Its modelling and structureproperty relationship has been discussed here. The artificial neural network (ANN) and empirical models have been developed (Debnath and Madhusoothanan, 2000b) to predict the air permeability of needled fabrics with varying jute-polypropylene blend ratio, fabric weight and needling density. The fabrics were produced as per a statistical factorial design. The predicted air permeability values from both the models were compared statistically. The correlation was found in an artificial neural network with three hidden layers. The neural network model with three hidden layers showed less prediction error followed by ANN with two hidden layers, empirical model and ANN with one hidden layer. Roy and Ray (2005b) used statistical experimental design and suggested that with the increase in fabric weight, punch density and depth of needle penetration, air permeability of needle punched nonwoven fabric was first reduced due to better consolidation of fibres in the fabric and then showed an upward trend due to channel or hole formation in the fabric. Roy et al.(2005b) observed that blending of viscose fibre with jute had reduced air permeability compared to jute nonwoven fabric Sengupta et al. (1999) studied the cross laid needle punched nonwoven fabrics from jute, woollenised jute and their blends with polypropylene. Here, the effects of texturisation, blend composition, punch density, depth of needle penetration and jute fibre cut length on fabric thickness, fabric density and

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air permeability was studied. The resistance offered to the flow of air through the fabric was much higher for the fabrics made from woollenised jute and its blends compared to the fabrics made from jute and its blends. The air permeability of fabrics made from woollenised jute and its blends decreased with the increase in punch density, whereas the air permeability of fabrics made from jute and its blends having low polypropylene content (10%, 20%) increased with the increase in punch density. As the polypropylene content was increased to 30% and 40%, the trend was reversed. With the increase in needle penetration and jute fibre cut length, the air permeability decreased with slight deviation for 100% jute fabric. Random-laid jute/polypropylene (60:40) blended fabric exhibited higher thickness, lower density and higher air permeability compared to its cross laid counterpart. Good correlation between sectional air permeability and reciprocal of fabric density was observed in most of the fabrics. However, it was found to be highly significant for fabrics made from jute, woollenised and their blends with 30% and 40% polypropylene. The air permeability of jute needle punched nonwoven with reinforcing jute cloth was studied by Sengupta et al.(1985d). It was observed that at lower needle penetration, for both jute and woollenised jute, the air permeability was higher and it reduced with higher needle penetration up to a certain limit. Too deep a needle penetration resulted in fibre rupture and damaged to the reinforcing fabric and also created channels in the nonwovens. Batching oil emulsion treatment did not affect the air permeability of the nonwoven fabric. Air permeability increased with the increase in the reinforcing material weight by web weight ratio and when the reinforcing material is used at the centre of the web instead of the base. The more open was the construction of the reinforcing fabric, the more was the air permeability. In this context, scrim cloth was better. Successive increases in the needling density increased the fabric consolidation correspondingly and thereby reduced sectional air permeability. Reduction in air permeability was usually more in woollenised jute nonwovens. Effect of needle penetration and mass/area of jute nonwoven on air permeability has been shown in Figure 17.

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Figure 17. Effect of needle penetration and mass/area of jute nonwoven on air permeability (Sengupta et al., 2008b).

The air permeability of needle-punched material is a function of its structural parameters. Some studies have been reported the air permeability of jute needle-punched nonwovens. It is reported that with the increase in fabric weight, punch density, and depth of penetration, air permeability of the fabric is initially reduced due to better consolidation of fibres in the fabric and then shows an upward trend due to channel or near-hole formation in the fabric (Roy and Ray, 2005). The air permeability of nonwoven fabric made from woollenized jute and its blends is reported much lowers compared to the fabrics made of jute and its blends. As punch density increases air permeability of jute-nonwoven made of woollenized jute and its blends decreases. But air permeability of fabrics made of jute and its blends having low polypropylene content increases with the increase in punch density. As the polypropylene content is increased, the trend is reversed. With the increase in needle penetration and jute fibre cut length, the air permeability decreases (Debnath and Madhusoothanan, 2007; Sengupta et al., 1999). The effect of fabric weight and punched density on air permeability is shown in the contour diagram in Figure 3 (Subramanium et al. 1992). The air permeability decreases prominently with the increase in fabric weight for all levels of jute contents. With the increase in needling density, the air permeability decreases at higher fabric weight, but its influence is negligible at a lower level of fabric weight.

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COMPRESSION AND RECOVERY Compression means a force squashing, squeezing or pressing down on an object. Compression tends to change the shape of an object and reduce its volume. The extent of recovery from the compressed state on the removal of external force is important because it shows the resilience of structure and product. In a detailed study (Sengupta et al. 2005a; 2005b; 2005c) on compressional characteristics of needle punched nonwoven made from jute and its blends, the compressional and recovery behaviour was characterised with the help of two dimensionless parameters α and β. Higher the value of α, higher is the compressibility. Empirical equations for compression and recovery curves of needle punched nonwoven fabrics was suggested. For compression:

For recovery:

Where,

a) In case of second compression cycle of jute needle-punched nonwoven or jute-polypropylene blended (1:1) nonwoven or 100% PP nonwoven or jute nonwoven in wet condition: T/To = 1- α.log e (P/Po) b) Jute needle-punched nonwoven (first compression cycle) follows: T/To = α/log e (P) where,Po ≥ 10 kPa T/To = 1- α.log e (P/Po) for any value ofPo a) In case of jute (first compression cycle) or jutepolypropylene blend (1:1) or polypropylene needle punched nonwovenT/Tf = (P/Pf)- β b)Jute (second compression cycle) or wet jute needle-punched nonwoven follows T/Tf = 1- β.log e (P/Pf) T = Thickness at any pressure P, To and Tf = Initial and final thickness, Po and Pf = Initial and final pressure,

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α = Compressional pressure, a dimensionless parameter, β = Recovery parameter, a dimensionless parameter. Hence, knowing α, β, initial thickness (To) and pressure range one would be able to get the compression-recovery hysteresis curve and related parameters. The parameter α represented the compressibility and higher the value of α, higher would be the compressibility of fabrics. The parameter β represented the extent of recovery from the compressed thickness. Using these two parameters and initial thickness of a fabric, one can calculate thickness at any pressure and all other behaviours of the compressionrecovery cycle. Sengupta et al. (2005a) were ranked different important parameters which may affect compression of fabric, using statistical method and found that needling density, depth of needle penetration and fabric area density are three most significant parameters for compressional behaviour expressed by the percent loss in thickness. Taking these parameters, they fabricated a composite rotatable factorial design and proposed the statistical model (Sengupta et al., 2005b) describing the interactions between those parameters (independent variables) and compressional parameters. From the contour diagrams, it was found that 15-16 mm depth of needle penetration, 170 punches/cm2 needling density and 650-700 g/m2 area density was a very critical combination and which might be considered as optimum for minimum compressibility because deviation from any of the variable might be responsible for the deterioration compressional parameters. Thickness reduction of jute nonwoven fabric due to application of compressive load has been shown in Figure 18. The effect of needling density and penetration on compressional and recovery parameter has been shown in Figure 19. Roy et al. (2005c) studied the compressibility on jute/viscose blended fabric and reported that the compressibility of fabric in terms of thickness loss or energy loss was initially reduced with the increase in fabric weight, punch density and depth of penetration and after attaining a minimum value, thickness started increasing if the increase in those variables was continued further. The

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changes in jute-viscose blend proportion in needle punched nonwoven fabric did not have much effect on changes in fabric compressibility. They also observed (Roy and Debnath, 1996) that in the compression and recovery tests, both the thickness loss and energy loss of jute viscose blended nonwoven were found to be lower than that of all jute and jutepolypropylene blended needle punched nonwovens.

Figure 18. Thickness reduction of jute nonwoven fabric due to application of compressive load (Sengupta et al., 2008a).

Figure 19. Effect of needling density and penetration on (a) compressional and (B) recovery parameter (Sengupta et al., 2008b).

A good correlation (Table 5) was observed (Sengupta et al., 2005b) between compressional parameter (α) or recovery parameter (β) and the properties, i.e., tenacity, elongation-at-break, energy to break, air permeability and thermal insulation, of jute needle punched nonwoven fabrics. It depicted that with the help of measurement of α and β, the other

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properties of the needle punched nonwoven could be approximately predicted. Table 5. Correlation coefficient between compressional behaviour and properties of mesta nonwoven fabrics Compressional behaviour

Compressional parameter (α) Recovery parameter (β)

Tenacity cN/tex

Properties of jute nonwoven fabrics Extension at Energy to Air break break permeability % J cc/s/cm2

Thermal insulation Value %

-0.7540

0.7696

-0.8028

0.8028

0.9327

-0.7603

0.7478

-0.8000

0.7921

0.9047

Sengupta, 2017

In the repeated compression recovery cycles, it was observed (Sengupta et al., 2005c) that most of the changes in the compressional properties took place between the first and second compression cycles. After that, the compressional behaviour of the fabric remained all most unchanged. As the rate of compressional deformation increased, the compressional parameter, recovery parameter and percentage energy loss decreased. There was no significant effect of ultimate compressional pressure on different compressional and related parameters. When needle punched nonwoven was used in the plied condition, compressional and related parameters increased with increase in the number of plies, tested up to three. When compressional pressure of 200 kPa was applied on needle punched fabric, there was an instantaneous compression and after that thickness-loss increased with time in diminishing rate. The thickness-loss stabilized after reaching to the maximum. Recovery for that load also followed a similar trend. Approximately, jute took 30-40s whereas polypropylene and jute-polypropylene blend needed 120-140s time for stabilization in thickness value in the tested configuration of needlepunched fabric. The effect of dynamic loading is explained by the compression caused by persons walking on a carpet or repeated loading by moving vehicles on

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a geotextile laid under the road or rail track. The suitability of nonwoven fabrics in those areas depends upon the ability to absorb energy applied by dynamic loads. Dynamic loading is very important when the fabric will be used as a carpet, floor covering and sports mat. Studies (Sengupta et al., 2005c) showed that with an increase in cycles of dynamic loading, thickness loss increased. As needling density, depth of needle penetration and area density increased, thickness loss reduced caused by dynamic loading, but there was an optimum needling density/depth of needle penetration/area density beyond which thickness loss increased. The optimum values for jute were: needling density-250 punches/cm2, depth of needle penetration-15 mm and area density-600 g/m2. The extent of recovery decreased with the increase of needling density and depth of needle penetration and increased with area density. As the proportion of polypropylene fibre increased in the blended needle-punched nonwoven with jute, thickness loss due to dynamic loading increased. 100% polypropylene showed the highest relaxation from compression. Sengupta et al.(1985b) observed dynamic loading behaviour of jute and woollenised jute needle punched nonwoven along with hessian reinforcing material and reported lower deformation compare to nonwoven without reinforcing the material. A study on the effect of compressional pressure on tensile behaviour of different needle punched nonwoven was reported (Sengupta et al., 2008a). There are a large number of applications, where needle-punched nonwoven fabrics are subjected to compressional deformation and tensile deformation simultaneously. With the increase in compressional pressure on jute needle-punched nonwoven, tenacity and elongation-at-break cv%, tensile modulus decreased drastically whereas fabric tenacity increased up to an optimum value and then decreased. This optimum tenacity was increased when polypropylene fibre was blended with jute or wetting of jute needlepunched nonwoven. It was increased initially with the increase in needling density or depth of needle penetration or area density, and beyond a certain value, it decreased. Debnath and Madhusoothanan, (2008) applied the artificial neural network to propose a model for compression property. Needling density,

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depth of needle penetration, and fabric area density are found as three most important parameters that affect compression behaviour of jute needlepunched nonwoven (Debnath and Madhusoothanan, 2007; 2013; Roy and Ray, 2009a; 2009b; Saleh, 2011; Sengupta et al., 2005b). The compressibility of fabric in terms of thickness loss is initially reduced with the increase in fabric weight, punch density, and depth of penetration, and after attaining a minimum value, it starts increasing if the increase in these variables is continued further (Roy and Ray, 2009b; Sengupta et al., 2005b). The application of compressive load on jute needle-punched nonwoven fabric reduces its thickness and makes it more compact, which may affect its properties. Figure 4 shows the gradual thickness reduction of 600 g/m2 jute nonwoven fabric ontheapplication of compressive pressure up to 39.2 kPa. It reveals that the thickness reduction is less significant in case of wet fabric than that of conditioned fabric (Sengupta et al., 2008b). It is proposed that the compression of needle-punched nonwovens takes place in two stages (Elbadry et al., 2012a). The first stage deformation is due to the horizontal disposition of fibres in nonwovens of low surface density. In the second stage, the vertically positioned fibres bear the load. The compression behaviour of jute/polypropylene blend needle punched nonwoven shows increase of thickness with increase of fabric weight as shown in Figure 5 (Debnath and Madhusoothanan, 2007). This study also says that fabric thickness reduces with the increase in the needing density and the percentage compression resilience of the fabric increases with the increase in polypropylene content in the blend.

ABRASION RESISTANCE It is the weight loss due to 1000 cycles abrasion on 38mm diameter nonwoven fabric sample by the jute hessian abrader in 9 kpa pressure following the standard ASTM D4966-98 in Martindale Abrasion Tester. Abrasion resistance is the ability of a fabric to withstand surface wear and rubbing. The resistance to abrasion is closely related to plucking and friction cutting of fibres during the abrasive action. It was observed

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(Sengupta et al., 1985b) that an increase in the ratio of the reinforcing material to web weight increases the abrasion resistance of the fabric. 18% sodium hydroxide treatment of jute reduces and batching oil emulsion treatment increases the abrasion resistance of nonwoven compared to untreated jute. Jute nonwoven, woollenised (18% sodium hydroxide treatment) in fabric form shows much higher abrasion resistance than raw jute nonwoven and nonwoven made from woollenised jute. Jute hessian reinforcement shows the highest abrasion resistance followed by bandage and gauge cloth respectively. The abrasion resistance is significantly higher when the reinforcing material is used at the centre of the web. It decreases with increase in needling density and increases with increase in depth of needle penetration. The effect of abrasion on nonwoven has been shown in Table 6. Table 6. Effect of abrasion on nonwoven, (Jute hessian in the base 300 g/m2, needles/cm2 36, penetration 14.3 mm) Fibre type Jute Wollenised jute

Fabric weight, g/m2 909 908

Abrasion resistance, Cycles 35.8 29.8

Sengupta et al., 1985b

WATER ABSORBENCY Conditioned (65% RH, 210 C) nonwoven fabrics of 5cm x 5 cm dimension was weighed and then placed gently, but in one continuous smooth motion, on to the surface of a pool of distilled water in a tray (0.4 m  0.3 m  0.2 m) and a timer was started. At the last disappearance of dryness from the upper surface, the timer was stopped. The wet nonwoven was taken out of the water, allowed to drain for 1 min on blotting paper and then reweighed. The extrinsic sorptive capacity (ESC), i.e., the volume of liquid absorbed per unit area and extrinsic rate of sorption (ERS), i.e., the volume of water absorbed by unit area in unit time were calculated

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(Sengupta, 2009) using the following relationships, considering the density of water as 0.997 g/mL at 21oC: ESC (mL/m2) = ((mw– md )/0.997)/(l  w) and ERS (mL/m2/s)= ESC/(tn/n) = ((mw – md )/0.997)/(l  w  tn)

Where md is the mass of dry nonwovens (g); mw, the mass of wet nonwovens (g); l, the length of the sample (m); w, the width of sample (m); and tn, the time to complete sorption (s). Sengupta (2009) studied the absorbency of needle-punched jute nonwoven fabrics with different area densities and punch densities. It was observed that with an increase in area density both the sorptive capacity and rate of sorption increased. However, the fabric with an area density of 300 g/m2 and punch density of 150 punches/cm2 showed the highest absorptive capacity as well as the rate of sorption. It was also observed that the sorptive capacity of the fabric without oil was more than that of the fabric with oil. In case of the rate of sorption, the effect was reversed. The alkali-treated (18% w/v) jute absorbed 2.7 times water of its weight and bleached jute 6.08 times of water. Thus bleaching improves water absorbency of jute remarkably. Studies (Debnath, 1978; Debnath 1979b) showed that the tensile behaviour of wet jute and jute blended fabrics were always higher than those of the respective fabrics tested in standard conditions. As a result of wetting, the stick-slip oscillation of loading curve during extension was eliminated in case of jute blended nonwovens. Wettability of jute fibre is good among all the long vegetable fibres (Samajpati and Sengupta, 2006). The porous nonwoven structure is expected to improve the water-holding capacity of the fabric. Functional properties of jute nonwovens can be quantified by water-sorption capacity and rate of sorption. Sorption capacity can be defined as volume of water absorbed per unit area and rate of sorption is the volume of water absorbed per unit area per unit time.

Potential of Jute Based Needle-Punched Nonwoven

1089

18.0

75 25

03 22

1460

32 18

14.0

32 18

1460

03 22

36 89

33 18

1089

11.6

717

10.0

29 46

16.4

25 75

Depth of needle penetration, mm

75

70

106

160

213

250

Punch density, punches/sq. cm.

Figure 20. Effect of punch density and needle penetration on extrinsic sorptive capacity of jute fabric.

Depth of needle penetration, mm

18.0 8.224 16.4 7.074 14.0

5.924

4.774

3.6

24

11.6

0.1 73

10.0 70

1.3 2

2.4 7

4

106

4

160

213

250

Punch density, punches/ sq. cm.

Figure 21. Effect of punch density and needle penetration on extrinsic rate of sorption of jute fabric.

A study has been reported that for a particular depth of needle penetration or for particular batching oil percentage, with the increase in punch density, the rate of sorption of needle-punched jute-nonwoven

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initially increases and then decreases (Sengupta, 2009).The effect of punch density and needle penetration on extrinsic sorptive capacity and rate of sorption of jute fabric have been shown in Figure 20 and 21 respectively. Initial increase of rate of sorption is due to better entanglement of fibre but afterwards when fibre breaks the rate decreases. For a particular punch density and depth of needle penetration, or with the increase in depth of needle penetration, the increase in batch oil percent will increase the rate of sorption. The increase of oil percentage ensures the less breakage of fibres, which ultimately resulted in low bulk density. Lower will be the bulk density higher will be the sorption capacity as shown in Figure 22 (Sengupta, 2009). The water absorbency of jute/polypropylene needlepunched nonwoven fabrics initially increases, reaching to a maximum value with the increase in jute content, and then with a further increase of jute content (55%), the absorbency decreases (Debnath and Madhusoothanan, 2010). The water absorbency decreases with the increase in fabric weight and needling density.

Bulk density, g/cc

0.130

y = 8E-09x2 - 4E-05x + 0.1611 R² = 0.8399

0.125 0.120 0.115 0.110 0.105 0.100 1000

1500

2000

2500

3000

Extrinsic sorptive capacity, mL/ sq. m

Figure 22. Correlation between bulk density and extrinsic sorptive capacity (Figure 20, 21, 22- Sengupta, 2009).

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ACOUSTIC INSULATION Absorption of acoustic wave energy or transmission loss can be tested using 30 mm diameter BSWA impedance tube (model SW477) following ASTM E1050 and ASTM E2611 respectively. Mathematically, Transmission loss= -20 log |T| where T is the transmission coefficient.(Jung et al., 2008) Absorption co-efficient = 1- (IR/II ) where IR andII are the one-sided intensity of the reflected sound and the one-sided intensity of the incident sound, respectively (ASTM E 1050). The sound reduction has been tested in the indigenous set up (Sengupta, 2010) by measuring the reduction in decibel after passing a sound of fixed frequency and amplitude through a nonwoven barrier. The distance of a barrier from sound source and receiver is 8 cm kept in the opposite direction.

Figure 23. Effect of mass/area and needle penetration on sound loss by jute fabric (Sengupta, 2010a).

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Jute needle-punched nonwovens exhibit superior sound insulation characteristics. The studies (Parikh et al., 2006; Sengupta 2010a, 2010b; Thilagavathi et al. 2010; Sengupta et al., accepted) report that there is significant sound transmission loss when sound energy passes through the jute needle-punched nonwoven. Punch density, depth of needle penetration, and mass per unit area of needle-punched nonwoven significantly affect the sound transmission loss when the nonwoven acts as a sound barrier. With the increase in the needle penetration, sound loss increases initially and after achieving the maximum it decreases. Increase in needle penetration means a higher number of barbs penetrates the web, resulting in more fibre orientation in the vertical position. This may create a bigger hole due to side-wise shifting of web and more compact structure, thus forming a denser fabric. This is the reason for the increase in sound loss with the increase in needle penetration. When the penetration is very high, it may create fibre breakage. This is very much prone in jute-like non-extensible fibre, which, in turn, increases the bulk and deteriorates the structure.

Figure 24. Effect of punch density and needle penetration on electrical resistance of jute nonwoven with 230 V (Sengupta and Sengupta, 2013).

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Hence, sound loss decreases with high penetration. With the increase in punch density, sound loss decreases initially, reaches to a minimum, and then increases. The initial decrease in sound loss is probably due to the higher number of holes in compact structure through which sound can penetrate. At the higher punch density, these holes are not completely formed due to breakage of fibres, which is responsible for an increase in sound loss. As area density increases, there is an initial decrease in sound loss and after attaining minimum, it increases. This is because in this range of needle penetration, a change over takes place from major fibre consolidation to major fibre breakage and it affects the structure. Effect of mass/area and needle penetration on sound loss by jute fabric has been shown in Figure 23.

ELECTRICAL RESISTANCE Fabric electrical resistance tester (Sengupta et al., 2018) can be used to measure this property. Nonwoven fabric samples of (2.54x2.54) cm are placed between two jaws and after the start of the tester, results are available in Mohm/Gohm. Figure 24 shows the effect of punch density and needle penetration on electrical resistance of jute nonwoven with 230 V power supply. As punch density increases, electrical resistance decreases with needle penetration lower than 12 mm. Beyond 12 mm pene tration, resistance increases. Therefore a major structural change takes place with 12 mm needle penetration. With the increase of needle penetration, electrical resistance decreases till 165 punch density. When punch density is higher than 165 punches/cm2, with the increase of needle penetration, resistance increases. Therefore, the critical point is 12 mm needle penetration and 165 punches/cm2.

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TRACKING Tracking is the needle mark on the surface of the nonwoven fabric. In the case of synthetic fibres, such marks are not so visible due to their high extensibility and recovery properties. As jute fibre is inextensible and rigid such marks are distinctly visible. It was observed (Young, 1970) that any fault in the needle produces some abnormal marks on the surface of the fabric. Those faults should be removed immediately to get quality fabric. The study on jute and its blends with polypropylene, acrylic and polyester showed (Sengupta and Roy, 2003) that judicious use of needling parameters, i.e., needle gauge, punch density and depth of needle penetration could minimise the tracking with an insignificant effect on tensile properties. From the results (Sengupta and Roy, 2005a) of tensile behaviour and surface appearance of the fabric, it was observed that almost trackless jute fabric can be made with 250 punches/cm2, 8 mm depth of needle penetration using 30 gauge needles.

A

B

Figure 24. (A) Almost trackless fabric, (B) Highly tracked fabric (Sengupta and Roy, 2005b).

Fabric with maximum tracking was noted at 200 punches/cm2, 12 mm depth of needle penetration and 21 gauge needles. For jute polypropylene (1:1) blended fabric (Sengupta and Roy, 2005b), trackless fabric could be made with 300 punches/cm2, 8 mm depth of needle penetration and 36 gauge needle whereas fabric with the best tracking could be made with 200 punches/cm2, 12 mm depth of needle penetration and 30 gauge needle. Tracking behaviour was also optimized (Sengupta and Roy, 2003) for

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jute/acrylic (1:1) and jute-polyester (1:1) blended needle punched nonwoven textiles. Tracking of jute needle punched fabric has been shown in Figure 24. Using this knowledge, the patterned needled punched fabric was made successfully.

FIBRE SHREDDING A method for measuring fibre shredding in needle-punched jute nonwovens was suggested by Sengupta et al. (1985d). The test was performed with a laboratory flask shaker. A shaking rate of 260/min was used for 2 min. The shredding fibres were collected in a tray and weighed accurately. It was observed that the treatment of jute with batching oil emulsion and woollenisation reduced the fibre shredding. Increase in needling density and depth of needle penetration increased the jute fibre shredding from nonwoven. Table 7. Some properties of jute and woollenised jute needle punched nonwoven (Sengupta et al., 1985b; 1985c; 1985d; Sengupta et al., 1999; Sengupta et al., 2008d; 2005c; Sengupta, 2009)

1 2 3 4 5 6

7

Property

Jute

Thermal conductivity, Cal.deg-1.cm-1.s-1 Sectional air permeability, ml.s-1.cm-1 Fibre shredding, mg.m-2 Dynamic loading (thickness loss in 250 impacts),% Abrasion resistance, cycles Compression & recovery a) Compressional parameter (α) b) Recovery parameter (β) c) Energy loss, % d) Thickness loss, % Wetting, times of water absorbed

2.56 X 10-4 12.55 952 51.5 35.8

Woollenised jute 2.42 X 10-4 10.50 385 62.5 29.8

0.1109 0.1537 76.73 49.52 1.57

2.70

When jute needle punched nonwoven was reinforced by jute hessian fabric, the increase of reinforcing material weight and web weight ratio

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decreased the number of fibres shredded per unit area of the fabric. The trends were similar for jute and woollenised jute; only the magnitudes were different. Some of the property values have been shown in Table 7.

ANISOTROPY IN THE STRUCTURE Anisotropy defines as the variation concerning test direction of fabric sample. In a study (Debnath et al., 1995; Debnath et al., 1996, Ray and Ghosh, 2017), it was measured in parallel laid and cross laid jute nonwovens of mass/unit area373-710 g/m2 and thickness 0.27-0.45 cm and found the anisotropy range of 1-41.97. The range of properties was: bending modulus 0.69-32.95 kg/cm2, breaking strength 0.018-0.89 cN/tex, breaking extension 11.30-60.5%. The testing was made along with different directions varying between 0o and 90o to the machine direction at an interval of 15o. It was found that the values of above-mentioned properties along any direction of fabric are dependent on the degree of fibre inclination in that particular direction. Fabric from card sliver web showed a much lower level of anisotropy than the fabric from drawing sliver web.

POTENTIAL USES 

Floor covering: Needle-punched jute/jute blended nonwoven fabric can be successfully used in the area of floor covering and carpets. Jute blended nonwovens employing sandwich blending technique combine both the aesthetic and the functional properties required in such materials and are substantially cheaper than woollen materials which are the main advantage though performance-wise jute products are slightly inferior to woollen products. In such cases, woven sacking or hessian fabric is used at the backside for reinforcement. and coarse denier polypropylene/ acrylic fibre is used on top for aesthetic appeal and smooth

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appearance, keeping a thick layer of jute fibre in between for resiliency (Sengupta et al., 1985a). Needle-punched jute/juteblended needle-punched nonwoven fabric can be successfully used in the area of floor covering and carpets (Sengupta et al. 1985b; 1985c). Jute-blended needle-punched nonwovens employing sandwich blending technique combine both the aesthetic and the functional properties required in such materials and are substantially cheaper than woollen materials which is the main advantage though performance-wise jute products are slightly inferior to woollen products. In such cases, woven sacking or hessian fabric is used at the backside for reinforcement and coarse denier polypropylene/acrylic fibre is used on top for aesthetic appeal and smooth appearance, keeping a thick layer of jute fibre in between for resiliency. Thermal Insulation medium: Jute needle-punched nonwoven can be used as thermal insulation medium effectively. Thick and porous jute nonwoven contains evenly dispersed void of air which are responsible for thermal insulation. Moreover, the thermal conductivity of jute is very poor (Geopaul et al., 1977). Use of woollenised jute (crimped fibre due to chemical texturisation) improves this property due to the increase in bulk (Sengupta et al., 1985e). In addition to industrial uses, it can be used as the filler of warm garment like jackets (Debnath and Madhusoothanan, 2011). Sound absorbent medium: Decorated jute needle-punched nonwoven or sandwich blended synthetic and jute needle-punched nonwoven can be used as sound-absorbent medium successfully. The porous surface and resiliency in the needle-punched nonwoven products are responsible for the sound absorbency. It can be used as a wrapper of the sound source or it can be used in the wall to reduce the reverberations. Floor coverings using natural fibres (kenaf, jute, waste cotton, and flax) in blends with polypropylene and polyester are developed as carded needlepunched nonwoven for acoustic absorption in car interiors (Parikh et al. 2006; Sengupta 2010a; 2010b; Thilagavathi et al. 2010).

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Geotextiles: Nowadays, properly designed jute needle-punched nonwo-vens are used in erosion control in highway embankment and cut slops, riverbank protection, ground separation functions, filtration in road, reinforcement applications in temporary unpaved roads, etc. (Elbadry and Hamada, 2012b; Majumdar et al., 1999; 2001; Debnath et al., 2006). The main advantages of jute are its eco-friendliness and renewability (Frank, 2005). As the ecofriendly fibre, jute has great compatibility with soil and jute needle-punched nonwoven degrades after few months helping in soil stabilization, cake formation, and vegetation to soil to grow plants. Though they are of low strength and biodegradable material, it improves the performance of the unpaved road as the soft subgrade attains strength over the time (Ghosh et al., 2014; Kumar and Devi, 2011, Sayeedet al., 2014b; Senthil Kumar and Pandiammal Devi, 2011). Presently, the application of jutesynthetic blended fabrics may produce a long-term effect in geotextiles (Rawal and Sayeed, 2013; Rawal and Sayeed, 2014). In a study (Choudhury et al., 2008), seepage control has been investigated using jute nonwoven as canal lining. Moreover, trials also conducted as river bank protection and found encouraging results (Ghosh et al., 2006). Waterproofing: It is used for waterproofing and geotechnical applications. It has been found that jute and jutecaddies (unspinable jute fibre) in 1:1 proportion is suitable for waterproofing treatments (Debnath, 1983) Agrotextiles: Jute needle punched nonwovens can be used (a) for agricultural mulching, (b) irrigation mats for nurseries, (c) pots for seedlings for mail-order packaging and as seed bags etc. (Sengupta, 2013).Studies (Sengupta and Debnath, 2018a; 2018b; Debnath et al., 2010; Nag et al., 2008; 2010a; 2010b; Sengupta and Debnath, 2014) has been conducted to produce, optimise and apply jute needle punched nonwoven as soil cover for strawberry, summer variety tomato, cauliflower, tea, sweet lime and turmeric. It was found that plant health and yield have been improved with

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less water requirement and weed generation. Sengupta and Debnath (2019) suggested that needle punched jute nonwoven can be successfully used as an artificial medium for germination of seed and the effect of bulk density has been reported. Filter media: Proper designing of jute needle punched nonwoven can be used as filter media. Such nonwovens are suitable for coarse and medium filtration application and suitable for textile, tobacco dust, wood flour, paper shreds etc. (Subramanium et al., 1988). A study (Anandjiwala and Boguslavsky, 2008) shows that flax needled punched nonwoven can be used as an air filter. Substrate of composite: Needle-punched nonwoven may be a successful reinforcing agent for the jute-based composites (Sengupta et al., 2008c; Chattopadhyay et al., 2006). It is reported that nonwoven composites show better properties than that of woven composites and cross-laid nonwovens is better in comparison to parallel laid considering its mechanical strength in both machine and cross direction. Jute-nonwovens made from caddies are successful alternative of glass fibres as reinforcing materials of composites (Sharma and Patnaik, 2018) Tabletop, chair, washbasin, toolbox, signal casing, serving tray, rain pipe, corrugated sheet, fan blade, speaker box, and country boat have been successfully made from jute needle-punched nonwovenbased composite products. Jute-based needle-punched fabric can be used in decoration, furnishing, bags, soft luggage, apron, hat, gloves, file cover, handicraft items, etc. (Samajpati et al., 2005; Sengupta et al., 2008; Sayeedet al., 2014a). Applications in automobiles: Jute-nonwovens are recently used extensively in automotive industries (Parikh et al., 2006; Thilagavathi et al., 2010). The main reason for the steady growth of the use of jute-nonwovens in this sector is a weight reduction of 10–30% with good properties. Now jute-nonwovens and its composites are used in making of door liners, boot liners parcel shelves, etc. Floor carpets and interior decorations are also made of these products.

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Household goods: Decoration, furnishing, bags, soft luggage, Apron, hat, gloves, file cover, handicraft items etc. (Maity, 2016).

Figure 25 shows some of the applications.

(A)

(B)

(C)

(D)

Figure 25. Application (A) Floor covering, (B) Geotextile, (C) Agrotextile, (D) Air filter.

CONCLUSION Jute needle punched fabric has a wide range of applications, demanding a variety of fibre utilization and properties. These can be achieved by alterations in the fabric parameters, the needling process parameters etc. It should be remembered that needle-punched fabrics no longer competes with woven fabric in every application but has made certain outlets of its own, where technical characteristics such as smoothness of surface and permeability or economic considerations reign supreme. Jute is the most successful fibre among the lignocellulosic varieties. It’s processing and products can be developed with other

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lignocellulosic fibres by minor modifications. Hence, jute may be considered as the representative of other lignocellulosic fibres. Needle punched nonwoven fabrics are essentially a three-dimensional network of fibres enclosing small air pockets. Air and heat transfer in such textile materials can occur through their complex fibre-air matrix structure. Various applications including filtration and floorcovering of jute needle punched nonwoven fabric demand air permeability as an important property. The comfort property of floor coverings depends on their thermal conductivity. In most of the applications, nonwoven fabric is subjected to various types of compressional loads and the compression-recovery behaviour has an effect on other properties of fabric especially on hydraulic behaviour. In some cases, abrasion property has an important role in fabric wear life. In many process techniques and end-use characteristics, the surface wettability of fabric is a key factor. In dying, finishing and coating processes, the adhesion and wetting properties affect the process parameters and the final characteristics of the material. In the needle-punched nonwoven, the needle penetration, as well as, forward movement of the fibre web, at the time of needling, makes a mark on the surface of the fabric. Uncontrolled needle marks produce a typical surface fault indicating the eye in the direction of the feed, which is called tracking. An ideal trackless needled fabric is one, which has a surface almost completely uniform in its needling and consequently a constant appearance is achieved over its surface, giving a negligible visible indication of needle mark. For various applications, it is important to know the number of fibres loosely held by the fabric, as these is likely to come out easily from the fabric during use. As a majority of these fibres comprise fibres broken or shredded from the batt during needling, it is necessary to know the effect of materials and process variables on the shredding of fibres so that fibre shredding can be kept to a minimum. The information available on the behaviour of jute nonwovens concerning air permeability and thermal insulation are useful in thermal insulation medium, filter fabric, carpets, blankets etc. There are numerous

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applications in which jute nonwovens are called upon to perform under constant or repeated changing compressive loads. Abrasion resistance is essential for an application like floor covering. Wetting behaviour is important when the fabric is used as a substrate of composite, as an absorbent or in any chemical treatment. Tracking and shredding, especially for 100% jute, are the problem for high-quality nonwoven fabric. The jute based needle punched nonwoven is used in floor-covering, insulation medium, geotextiles, agrotextiles, filter media, household goods etc.

REFERENCES Anandjiwala, R. D. and Boguslavsky, L. 2008. “Development of Needlepunched Nonwoven Fabrics from Flax Fibers for Air Filtration Applications.” Text Res J.78 (7):614-624. Chattopadhyay, S. N., Sengupta, S., Samajpati, S., and Dey, A., 2006. “Modification of Jute Fibres for Making Composites.” Asian Textile Journal, 15( 8), 42-51 Choudhury, M. R., Chatterjee, P., Dey, P., Nag, D., Debnath, D., Ghosh, S. K., and Ganguly, P. K. 2008. “Lining of Open Cannel with Jute Geotextile and Its Performance in Seepage Control.” Journal of Agricultural Engineering 45(4):83-86. Das, B. K., Debnath, C. R., and Ray, P. K. 1987. “Scanning Electron Microscope Observations of Nonwoven Fabrics from Jute and Other Textiles.” Text Res J. 57(9): 528-531. Debnath C. R. 1986. “Theoretical Approach to the Tensile Properties of Needled Jute Fabric.” Indian J Text Res. 11 (3): 129-137. Debnat.h, C. R. 1978. “Needle punching of Jute Webs, Part 2.” The Indian Textile Journal. 89 (November): 137-142. Debnath, C. R. 1978. “Needle punching of Jute Webs, Part 3.” The Indian Textile Journal.89 (Dec): 137-151. Debnath, C. R.1979a. “Needle Punching of Jute Webs, Part 4.” The Indian Textile Journal. 89 (January): 151-158.

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Debnath, C. R. 1979b. “Needle Punching of Jute Webs, Part 5.” The Indian Textile Journal. 89 (February): 151-169. Debnath, C. R. 1979c. “Needle punching of Jute Webs, Part 6.” The Indian Textile Journal, 89(March): 135-148. Debnath, C. R., 1979d. “Needle Punching of Jute Webs, Part 7.” The Indian Textile Journal, 89 (April): 122. Debnath, C. R. 1979f. “Needle Punching of Jute Webs, Part 8.” The Indian Textile Journal. 89 (may): 123-126. Debnath, C. R. 1979e. “Needle punching of Jute Webs, Part 9.” The Indian Textile Journal, 89(June): 125-130. Debnath, C. R. 2001. “Influence of Manufacturing Factors on Tensile Behaviour of Acrylan and Acrylan-woollenised Jute Non-wovens.” Manmade Textiles in India. 44 (11): 443-447. Debnath, C. R., and Roy, A. N. 2001. “Thermal Insulation Behaviour of Jute Needle Punched Non woven Textiles.” Manmade Textiles in India. 44 (12): 481-483. Debnath, C. R., Roy, A. N., Ghosh, S. N., and Mukhopadhyay, B. N. 1996. Indian Journal of Fibre and Textile Research 21 (4): 244-255. Debnath, S. 2007. “Compression Behaviour of Jute-polypropylene Blended Needle-punched Nonwoven Fabrics.” Indian Journal of Fibre and Textile Research 32(4): 427–33. Debnath, S., Madhusoothanan, M. 2012a.“Compression Creep Behaviour of Jute-polypropylene Blended Needle-punched Nonwoven.” Text Res J82 (2): 2116-2127. Debnath, S., Madhusoothanan, M. 2012b.“Compression Behaviour of Jute–polypropylene Blended Needle-punched Nonwoven under Wet Condition.” Journal of Textile Institute,103 (6):583-594. Debnath, S., Madhusoothanan, M., Srinivasmoorthy, V. R. 2000. “Modelling of Tensile Properties of Needle-punched Nonwovens using Artificial Neural Networks.” Indian Journal of Fibre and Textile Research. 25 (1): 31-36. Debnath, S., 2011. “Thermal Resistance and Air Permeability Jutepolypropylene Blended Needle-punched Nonwoven.” Indian Journal of Fibre and Textile Research 36 (2): 122–131.

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Debnath, S., and Mazumder, A. K. 2001. “Study of PolypropyleneWoollenised Jute Blended Needle-Punched Non-Wovens Using a Factorial Design Technique: Part 3.” Manmade Textiles in India. 44 (4): 131-136. Debnath, S., and Madhusoothanan, M. 2000a. “Physical Properties of Needle-punched Polypropylene-jute Nonwoven Textiles-Part 4.” Manmade Textiles in India. 43 (4): 220-224. Debnath, S., and Madhusoothanan, M. 2000b. “Physical Properties of Needle-punched Polypropylene-jute Nonwoven Textiles-Part6.”Manmade Textiles India 43(7): 305–309. Debnath, S., and Madhusoothanan, M. 2010. “Water Absorbency of Jutepolypropylene Blended Needle-punched Nonwoven.” Journal of Industrial Textiles 39: 215–31. Debnath, S., and Madhusoothanan, M. 2013. “Studies on Compression Behaviour of Polypropylene Needle punched Nonwoven Fabrics under Wet Condition.” Fibers and Polymers 14: 854–59. Debnath, S., and Mazumder, A. K. 2001. “Study of PolypropyleneWoolenised Jute Blended Needle-Punched Non-Wovens Using a Factorial Design Technique: Part 2.” Manmade Textiles in India. 44 (3): 93-98. Debnath, S., Ganguly, P. K., De, S. S., and Nag, D. 2010. “Control of Soil Moisture and Temperature by Light Weight Jute Fabrics.” Journal of The Institution of Engineers (India)-TX 90(2):16-19. Debnath, S., Madhusoothanan, M., 2008.“Modeling of Compression Properties of Needle-punched Nonwoven Fabrics using Artificial Neural Network.” Indian Journal of Fibre and Textile Research 33(4):392-399. Debnath, S., Nag, D., De, S. S., Ganguly, P. K., and Ghosh, S. K. 2006. “Studies on Mechanical and Hydraulic Properties of JGT for Geotechnical Applications.” Journal of The Institution of Engineers (India)-TX 86(2):46-49. Debnath, S., and Madhusoothanan,M. 2010. “Water Absorbency of Jute— Polypropylene Blended Needle-punched Nonwoven.” Journal of Industrial Textiles, 39 (3): 215-231.

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Elbadry, E. A., Aly-Hassan, M. S., and Hamada, H. 2012a. “Mechanical Properties of Natural Jute Fabric/Jutemat Fiber Reinforced Polymermatrix Hybrid Composites.” Advanced Mechanical Engineering 1-12: 10.1155/2012/354547. Elbadry, E., and Hamada, H. 2012b. “Impact Properties of Natural Jute Fabric/Jute mat Fiber Reinforced Polymer Matrix Hybrid Composites.” Journal of Mechanical Engineering and Automation2: 381–88. Frank, R. R., 2005.Bast and other Plant Fibres. Ed. Robert R Frank, England: Woodhead Publishing Limited. Ganguly P. K., Sengupta, S. and Samajpati, S. 1999. “Mechanical Behaviour of Jute and Polypropylene Blended Needle-punched Fabrics.” Indian Journal of Fibre and Textile Research24 (1): 34-40. Ganguly, P. K., and Samajpati, S. 1996. Nonwoven Technology- A Versatile and Cost Effective Route of Jute Diversification, paper presented at the seminar on Technology Today - Transfer Tomorrow, Calcutta, India, February 2. Ganguly, P. K., Sengupta S., and Samajpati, S. 1997. “Mechanical Behaviour of Texturised Jute and Polypropylene Blended Needlepunched Fabrics.” Indian Journal of Fibre and Textile Research 22 (3): 169-175. Geopaul, N., and Mukhopadhyay, M. 1977. “Thermal Insulation Values of Jute Fabrics and of Its Blends with Other Fibres” Indian J Text Res2 (3): 88-91. Ghosh, S. K., Debnath, S., Nag, D., and Ganguly, P. K. 2006. “Geo-jute for River Bank Protection– A Case Study.” Journal of Agricultural Engineering (India) 43(3):62-65. Ghosh, S.K., Ray Gupta, K., Bhattacharyya, R., Sahu, R.B.,Mandol S. 2014.“Improvement of Life Expectancy of Jute Based Needlepunched Geotextiles through Bitumen Treatment.” Journal of The Institution of Engineers (India): Series E, 95 (2): 111–121. Hearle, J. W. S., and Purdy, A. T. 1972.“Fibre Breakage during Needlepunching.” J Text Inst. 63: 475-476.

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Jung, S. S., Kim, Y. T., Lee, Y. B., Cho, S., Lee, J. K. 2008. “Measurement of Sound Transmission Loss by Impedance Tubes”, Journal of the Korean Physical Society 53 (2): 596-600. Kozlowski, R., Manys, S., and Fibers, G. 1999. Textile industry: Winning strategies for the New Millennium, World Conference, The textile institute.Feburary10-13: 29–41. Kumar, P. S., and Devi, S. P. 2011. “Effect of Needle-punched Nonwoven Coir and Jute Geotextiles on CBR Strength of Soft Subgrade.” ARPN Journal of Engineering Applied Science6: 114–16. Maity, S.2016.“Jute Needle punched Nonwovens: Manufacturing, Properties, and Applications.” Journal of Natural Fibers,13 (4):383396,. Majumdar, A. K., Bhattacharyya, S. K., Saha, S. C., and Goswami, K. 1999. “Use of Jute Nonwoven in Protecting Riverbanks andAgrohorticultural Practices.” Paper presented at National Seminar on Production and Characterisation of Natural and Manmade Fibres, Central Institute of Research on Cotton Technology, Mumbai, India, July 3. Majumdar, A. K., Dey, A., Ghosh, S. K, Saha, S. C., and Bhattacharyya, S. K. 2001. “A Case Study on Rural Road Construction with Geo Jute Nonwovens under Indian Conditions.” Paper presented at National Seminar on Recent Advances in Natural Fibre Research, Central Research Institute of Jute and Allied Fibre, West Bengal, India, December 16. Mitra, B. C., and Majumdar,A. K. 1998. “Jute Nonwoven and Its Potential.” Proceedings of Jute Conference, PSG College of Technology, Coimbatore, India, April 15-16. Nag, D., Choudhury, T. K., Debnath, S., Ganguly, P. K., and Ghosh, S. K. 2008. “Efficient Management of Soil Moisture with Jute Nonwoven as Mulch for Cultivation of Sweetlime and Turmeric in Red Lateritic Zone.” Journal of Agricultural Engineering (India) 46(3):59-62. Nag, D., Debnath, S., Ganguly, P. K., and Ghosh, S. K. 2010. “Efficient Management of Soil Moisture by Jute Geotextile for Cultivation of

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Horticultural Crops in Red Lateritic Zone.” Journal of The Institution of Engineers (India)- AG, 91(1): 21-24. Parikh, D. V., Chen, Y., and Sun, L. 2006. “Reducing Automotive Interior Noise with Natural Fiber Nonwoven Floor Covering Systems. Textile Research Journal 76: 813–820. Purdy, A.T.1980, Needle punching, The Textile Institute. England. Rawal, A., Sayeed, M.M.A. 2013. “Mechanical Properties and Damage Analysis of Jute/Polypropylene Hybrid Nonwoven Geotextiles.” Geotextiles and Geomembranes, 37:54-60. Rawal, A., Sayeed, M.M.A. 2014. “Tailoring the Structure and Properties of Jute Blended Nonwoven Geotextiles via Alkali Treatment of Jute Fibers.” Materials & Design, 53: 701-705. Ray, S. C. and Ghosh, P. 2017.Studies on nature of anisotropy of tensile properties and fibre orientation in cross-laid needle-punched nonwoven fabrics, Indian Journal of Fibre & Textile Research, 42 (2):160-167. Roy, A. N., and Ray, P. 2006. “Tensile Response of Jute-viscose Blended Needle-punched Nonwoven.” Manmade Textiles in India. 49 (5): 190194. Roy, A. N., and Ray, P, 2009a. “Optimization of Jute Needle-Punched Nonwoven Fabric Properties: Part I–Tensile Properties.” Journal of Natural Fibres. 6: 221–235. doi:10.1080/15440470903127901. Roy, A. N., and Ray, P. 2009b. “Optimization of jute needle-punched nonwoven fabric properties: Part 2-Some Mechanical and Functional Properties.” Journal of Natural Fibres. 6: 303–318. doi:10.1080/ 15440470903339514. Roy, A. N., and Ray, P. 2005a. “Jute Viscose Blended Needle-punched Nonwoven: Sress Decay and Cyclic Loading.” Manmade textiles in India. 48 (4): 161-166. Roy, A. N., and Ray, P. 2005b. “Physical Properties of Jute Viscose Blended Needle-punched Nonwoven: Bursting Strength and Airpermeability.” Manmade Textiles in India.48 (10): 386-390. Roy, A. N., and Ray, P. 2005c. “Physical Properties of Jute Viscose Blended Needle-punched Nonwoven: Compressibility and Bending Stiffness.” Manmade textiles in India. 48 (11): 435-439.

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Russell, S. J. 2007. Handbook of nonwovens. Woodhead Publishing Limited, England. Saleh, S. S. 2011. “Performance of needle-punching lining nonwoven fabrics and their thermal insulation properties.” Journal of Basic Applied Science Research 1: 3513–3524. Samajpati, S., and Sengupta, S., 2006.“Wetting Characteristics of Long Vegetable Fibres.”Indian Journal of Fibre and Textile Research 31 (2): 262-266. Samajpati, S., Mitra, B. C., Ganguly, P. K., and Sengupta, S.1998. “Development of Jute Nonwoven Geofabrics with Improved Microbial Resistance and Agrotextiles with Improved Hygral Properties.” Annual report of ICAR-NIRJAFT, Kolkata, India. Samajpati, S., Sengupta, S., Chattopadhyay, S.N., Day, A., and Bhattacharyya, S.K. 2005. “Jute Based Composite Products. Asian Textile Journal, 14 (7): 70-72. Sayeed, M.M.A., Rawal,A., Onal,L., Karaduman, Y. 2014a.“Mechanical Properties of Surface Modified Jute Fiber/Polypropylene Nonwoven Composites.” Polymer Composite,35 (6): 1044-1050. Sayeed, M.M.A., Janaki Ramaiah, B., Rawal, A. 2014b.“Interface Shear Characteristics of Jute/Polypropylene Hybrid Nonwoven Geotextiles and Sand using Large Size Direct Shear Test.” Geotextiles and Geomembranes, 42 (1) 63-68. Sengupta,S., and Debnath, D. 2014. “A gro-textile: Use of Jute Nonwoven.” In: Ed. Nag D. Jute and Allied Fibres: Issues and Strategies. The Indian Natural Fibre Society, Kolkata India: 409-401. Sengupta, A. K., Sinha, A. K., and Debnath, C. R. 1985a. “NeedlePunched Non-Woven Jute Floor Coverings: Part I-Influence of Fibre and Process Variables on Tensile Properties of Fabrics.” Indian J Text Res. 10 (3): 91-96. Sengupta, A. K., Sinha, A. K., and Debnath, C. R. 1985b. “Needlepunched Non-woven Jute Floor Coverings: Part II- Dynamic Loading Behaviour and Abrasion Resistance.” Indian Journal of Fibre and Textile Research 10: 141–146.

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Sengupta, A K, Sinha, A K, Debnath, C. R. 1985c. “Needle-Punched NonWoven Jute Floor Coverings: Part III-Air Permeability and Thermal Conductivity.” Indian Journal of Fibre and Textile Research. 10(4): 147-151. Sengupta, A. K., Sinha, A. K., and Debnath, C. R. 1985d. “Fibre Shredding in Needle-Punched Jute Non-Wovens.”Indian Journal of Fibre and Textile Research 10(3): 97-99. Sengupta, A. K., Sinha, A. K., and Debnath, C. R. 1985e. “A New Method of Measuring Fibre Transfer in Needle-Punched Fabrics.” Indian J Text Res. 10 (4): 191-192. Sengupta, A., Debnath, S., and Sengupta, S., 2018. “Design and Development of an Instrument for Testing Electrical Insulation of Technical Textiles.” Indian Journal of Fibre and Textile Research43(4): 402-409. Sengupta, S. 2009. “Water Absorbency of Jute Needle-punched Nonwoven Fabric.” Indian J Fibre Text Res. 34 (4): 345-351. Sengupta, S. 2010a. “Modelling on Sound Transmission Loss of Jute Needle Punched Nonwoven Fabrics using Central Composite Rotatable Experimental Design.” Indian Journal of Fibre and Textile Research 35(4): 293-297. Sengupta, S. 2010b. “Sound Reduction by Needle-punched Nonwoven Fabric”, Indian Journal of Fibre and Textile Research 35(3): 237-242. Sengupta, S. 2013. “Development of Low Cost Dense Jute Non-woven Fabric.” Final report of project under Jute Technology Mission, MiniMissionIV, Scheme 7.1,Govt of India. Sengupta, S. 2017. “Study on Some Functional Properties of Mesta Needle Punched Nonwoven Fabrics Using Central Composite Rotatable Design.” Journal of Natural Fibres, 15(1): 131-145 Sengupta, S., Basu, G., Datta, M., Debnath, S. and Nath, D. “Noise Control Material using Jute (Corchorus olitorius): Effect of Bulk Density and Thickness” Accepted and In press with Journal of Textile Institute. Sengupta, S. 2009. “Water Absorbency of Jute Needle Punched Nonwoven Fabric.” Indian Journal of Fibre and Textile Research. 34 (4): 345351.

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Sengupta, S., and Debnath, S. 2018a. “Organic Soil Cover to Save Environment and Water.” Paper presented in International Conference on Innovative and Emerging Technologies for farming – energy & environment-water, Vellore Institute of Technology, Vellore, India, October 12-14. Sengupta, S., and Debnath, S., 2018b. “Production and Application of Engineered Waste Jute Entangled Sheet for Soil Cover: A Green System.” Journal of Scientific & Industrial Research77 (1): 240-245. Sengupta, S., and Roy, A. N. 2003. Final report of project entitled ‘Development of Jute Needle-punched Patterned Nonwoven Textiles’ under Agricultural Product Cess Funds, Indian Council of Agricultural Research. Sengupta, S., and Roy, A. N. 2005a. “Needle Tacking Behaviour of Jute Polypropylene Blended Needle Punched Nonwoven Fabric.” Manmade Textiles in India. 48 (3): 117-121. Sengupta, S., and Roy, A. N. 2005b. “Studies on Tracking Behaviour of Jute Needle-punched Nonwoven Fabric.” J Inst Engrs(I)-TX86 (1): 1620. Sengupta, S., and Sengupta, A., 2012. “Electrical Resistance of Jute Fabric.” Indian Journal of Fibre and Textile Research, 37(1): 55-59. Sengupta, S., and Sengupta, A., 2013. “Electrical Resistance of Jute Needle Punched Nonwoven Fabric: Effect of Punch Density, Needle Penetration and Area Density.” J Text Inst 104(2):132-139. Sengupta, S., Debnath, S. 2019.“Study on Needle-punched Jute Nonwoven as an Artificial Medium for Germination of Seed: Effect of Bulk Density.” Journal of Natural Fibres 16 (4), 494-502. Sengupta, S., Debnath, S., and Sengupta, A., 2016. “Fabric Bending Behaviour Testing for Technical Textiles.” J of Measurement, 87 (June): 205-215. Sengupta, S., Majumdar, P. K., and Ray, P. 2008a. “Tensile Deformation of Jute Needle-punched Nonwoven Geotextiles under Compressive Load.” Indian Journal of Fibre and Textile Research. 33(2): 139–145. Sengupta, S., Majumdar, P. K., and Ray, P. 2008b. “Study on the Physical Properties of Jute Needle-punched Nonwoven Fabrics using Central

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Composite Rotatable Design.” Journal of Institute of Engineers-TX (I) 89 (August): 16-24. Sengupta, S., Chattopadhyay, S. N., Samajpati, S., and Day A., 2008c. “Use of Jute Needle-punched Nonwoven Fabric as Reinforcement in Composite.” Indian Journal of Fibre and Textile Research 33(1):3744. Sengupta, S., Ray, P., and Majumdar, P. K. 2008d. “Effect of Punch Density, Depth of Needle Penetration and Mass per Unit Area on Compressional Behaviour of Jute Needle Punched Nonwoven Fabrics using Central Composite Rotatable Experimental Design.” Indian Journal of Fibre and Textile Research 33 (4): 411-418. Sengupta, S., Ray, P., and Majumdar, P. K., 2005a. “Ranking of Important Parameters Affecting Compression of Jute-based Needle-punched Nonwoven Fabrics.” Asian Textile Journal, 14(6):69-72. Sengupta, S., Ray, P., and Majumder, P. K. 2005b. “Characterization of compressional behaviour of jute-based needle-punched nonwoven fabrics.” Manmade Textiles in India. 48 (10): 391-395. Sengupta, S., Ray, P., and Majumder, P. K. 2005c. “Effect of Dynamic Loading on Jute-based Needle-punched Nonwoven Fabrics.” Indian Journal of Fibre and Textile Research. 30 (4): 389-395. Sengupta, S., Samajpati, S.and Ganguly, P. K. 1999. “Air Permeability of Jute-based Needle-punched Nonwoven Fabrics.” Indian Journal of Fibre and Textile Research 24 (2): 103-110. Senthil Kumar, P., and Pandiammal Devi,S. 2011. “Effect of Needle Punched Nonwoven Coir and Jute Geotextiles on CBR Strength of Soft Subgrade.” ARPN Journal of Engineering and Applied Sciences 6 (11): 114-116. Sevost’yanov, P. A., and Seryakova, T. V. 2009. “Study of Deformation of Nonwoven Fibre Material during Needle-punching.” Fibre Chemistry 41(1) 38–40. Sharma, A., and Patnaik, A. 2018. “Experimental Investigation on Mechanical and Thermal Properties of Marble Dust Particulate-Filled Needle-Punched Nonwoven Jute Fiber/Epoxy Composite.” The

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Journal of The Minerals, Metals & Materials Society 70(7): 12841288. Subramanium, V., Mathusoothanan, M., and Debnath, C. R. 1988. “Air permeability of blended nonwoven fabrics.” Text. Res. J. 58 (11): 677678. Subramanium, V., Madhusoothanan, M., and Debnath, C. R. 1992. “A Study on the Properties of Needle-punched Nonwoven Fabrics using a Factorial Design Technique.” Indian Journal of Fibre and Textile Research 17 (3): 124–129. Thilagavathi, G., Pradeep, E., Kannaian, T., and Sasikala, L. 2010. “Development of Natural Fiber Nonwovens for Application as Car Interiors for Noise Control.” Journal of Industrial Textiles 39 (3): 267– 278. URL 1:https://www.smithers.com/services/market-reports/nonwovens/thefuture-ofglobal-nonwovens-to-2024, accessed on 5th November, 2019. URL 2:https://ihsmarkit.com/products/nonwoven-fabrics-chemicaleconomics-handbook.html, accessed on 5th November, 2019. Young, G. 1970. “Needle Tracking.” Textile Month (2): 44.

BIOGRAPHICAL SKETCH Surajit Sengupta Affiliation: Mechanical Processing Division, ICAR- National Institute of Natural Fibre Engineering and Technology, Kolkata, India Education: BSc Tech (Textile Technology), MTech. (Textile Engineering), PhD Tech (Textile Technology), PGDFM. Research and Professional Experience: Four years of Industrial Experience, 27 years of Research Experience and 5 years of teaching experience as visiting faculty of post graduate course.

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Professional Appointments:     

Fellow of The Institution of Engineers (India), Patron Member of Textile Association of India, Life member of The Indian Natural Fibre Society, Convener of The Textile Engineering Subcommittee, The Institution of Engineers (India). Moderator and Examiner of Calcutta University

Honors:  

Awaded Dr Triguna Sen Medal from The Institution of Engineers, India in 2009. Published Research Papers: 64, Book Chapter: 6, Popular Article: 8, Books: 4, Patent: 7, Conference Presentation: 36.

Publications from the Last 3 Years: 1. Sengupta, S., Basu, G., Datta, M., Debnath, S. and Nath,D. “Noise Control Material using Jute (Corchorus olitorius): Effect of Bulk Density and Thickness” Accepted and In press with Journal of Textile Institute. 2. Sengupta, S., Debnath, S. 2019. “Study on Needle-punched Jute Nonwoven as an Artificial Medium for Germination of Seed: Effect of Bulk Density”, Journal of Natural Fibres 16 (4), 494502. 3. Sengupta, S., and Debnath, S. 2018. “Production and Application of Engineered Waste Jute Entangled Sheet for Soil Cover: A Green System”, Journal of Scientific & Industrial Research 77 (1): 240245. 4. Sengupta, S. 2017. “Study on Some Functional Properties of Mesta Needle Punched Nonwoven Fabrics Using Central Composite Rotatable Design”. Journal of Natural Fibres, 15(1): 131-145

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5. Roy, S.,Sengupta, A.,Sengupta, S. 2017.“Performance Study of Optical Sensor for Parameterization of Staple Yarn”, Journal of Measurement. 109 (October): 394-407. 6. Sengupta, S., and Debnath, S. 2018. “Development of Sunnhemp Fibre Based Unconventional Fabric”, Industrial Crops and Products, 116: 109-115. 7. Sengupta, S., and Debnath, S. 2019. “Study on Needle Punched Jute Nonwovenas an Artificial Medium for Germination of Seed: Effect of Bulk Density”, Journal of Natural Fibres, 16 (4), 494502. 8. Sengupta, S. 2018. “Effect of Loading Behaviour on Compressional Property of Needle Punched Nonwoven Fabric”, Indian Journal of Fibre and Textile Research. 43(2): 194-202. 9. Sengupta, S., Debnath, S., Ghosh, P., and Mustafa, I. 2019. Development of unconventional fabric from banana fibre for industrial uses, Journal of Natural Fibres, DOI:10.1080/ 15440478.2018.1558153. 10. Sengupta, A., Debnath, S., and Sengupta, S. 2018. “Design and Development of an Instrument for Testing Electrical Insulation of Technical Textiles”. Indian Journal of Fibre and Textile Research. 43(4):402-409.

In: Nonwoven Fabric Editor: Rembrandt Elise

ISBN: 978-1-53617-587-5 © 2020 Nova Science Publishers, Inc.

Chapter 3

DEVELOPMENT OF NEEDLE PUNCHED NONWOVENS FOR THERMAL INSULATION APPLICATIONS N. Muthukumar* and G. Thilagavathi Department of Textile Technology, PSG College of Technology, Coimbatore, India

ABSTRACT Today the nonwoven technology, is considered as the most modern method, constitutes for the low cost substitutes for producing textiles. Among textile applications, nonwovens, one of the fastest growing sector constitutes about one-third of the fiber industry. Nonwoven materials are porous materials consisting of fibres and interconnected voids. Due to their unique fibre orientation and porous structure, nonwovens are ideal materials for insulation applications. Needle punching is one of the simplest and oldest methods of nonwoven fabrication. In this work, flax/low melting point polyester needle punched nonwoven fabrics were manufactured and characterized for thermal insulation applications. Nonwovens were developed by blending flax *

Corresponding Author’s E-mail: [email protected].

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fibers with low melt PET at 3 blend ratios (10%, 20% & 30%) with 7mm & 10 mm needle penetration depth. The influence of blend ratio and needle penetration depth on the performance of the nonwovens was studied. The test results showed that there was a decrease in thermal resistance value with increase in low melt PET % and needle penetration depth. Also the performance of the developed nonwovens compared with commercial product.

Keywords: flax fibers, low melt PET, needle punching, nonwovens, thermal insulation

1. INTRODUCTION Nonwovens are known as engineered fabrics. They are created with a view to targeted structure and properties by applying a set of scientific principles for a variety of applications. Nonwovens are manufactured by high-speed and low-cost processes. As compared to the traditional woven and knitting technology, a larger volume of materials can be produced at a lower cost by using nonwoven technology. The manufacturing principles of nonwovens are manifested in a unique way based on the technologies of creation of textiles, papers, and plastics and, as a result, the structure and properties of nonwovens resemble, to a great extent, those three materials. The Textile Institute defines nonwoven fabrics as ‘textile structures made directly from fiber rather than yarn’. These fabrics normally are made from continuous filaments or from fiber webs or batts strengthen by bonding using various techniques: these include adhesive bonding, mechanical interlocking by needling or fluid jet entanglement, thermal bonding and stitch bonding. The various methods of producing nonwovens are: (i)

Dry process in which the fibers are prepared using traditional opening and carding textile machines adapted for the purpose. The card produces webs which are placed one on top of the other in various geometric arrangements. Names given to some of these

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arrangements are ‘parallel’, ‘cross’, ‘composite’ and ’random’. Each arrangement gives different fiber orientation. Then the fibers in the web are reinforced either by needle punching or by stitch bonding. The principle of the latter is to reinforce the webs by means of yarn stitching, a principle similar to warp knitting (ii) Chemical bonding in which a chemical, typically a rubber-based, thermo reactive or thermoplastic bonding agent in various forms, e.g., solution, powder, and fiber types, is used to reinforce the web. Typical examples are as follows: • Emulsion adhesive: A polymer emulsion such as acrylic latex is used. • Powder type adhesives: The most popular type is a thermoplastic powder. • Fiber type adhesives: Between 5–40% by weight of these fibers is mixed in with the base fibers. The web is then hotcalendered to cause the bond to form. The binder fibers must have a lower melting than the fibers in the web, and are softened or melted by the hot-calendering process, causing the bond to form. (iii) Spun bonded fabrics are those in which a web structure is produced by randomly-oriented continuous filament fibers which self-bond to one another by chemical or heat treatments. A very wide range of spun bonded products are made from them.

1.1. Needle Punching Process In this work, development of nonwovens by the needle-punching method is discussed. The Textile Institute defines needling (or needlepunching, needle felting, needle bonding) as the use of barb needles to entangle a fiber web or batt by mechanical reorientation of some of these fibers within its structure. In the needle loom itself, the reciprocating beam causes barbed needles, mounted on a needle board in a density of 300–

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5000 per meter, to pass through the web or batt which in turn is supported between plates containing holes through which the needles pass. The needle punching operation integrates the fibre lay-down and needling processes continuously to consolidate the structure. The fibre web formed during fibre lay-down is transported on a conveyor belt to the needle punching machine, where fibres are mechanically entangled by the penetration of the needles to form a coherent nonwoven fabric. The barbs on the needles pick up fibres on their downward stroke and carry them into the structure, thereby compacting the web and providing high frictional resistance to fibre withdrawal. The rollers pull the batt through the needle loom, which consists of two plates – a stripper plate on top and a bed plate at the bottom as shown in Figure 1.

Figure 1. Needle punching process.

During processing, the needle beam connected to the needle board mounted with needles moves up and down with the needles carrying the fibres during their downward motion. The fibres are carried downwards by the barbed needles and reoriented from a predominantly horizontal direction to a vertical position to create fibre interlocking. The fibres are released by the barbs during the upward needle stroke. The unhooking and releasing of fibres take place when a part of the tension in the fibre, produced by the downward motion of the needle, is resisted by the equal

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and opposite frictional force built up between fibres within the structure of the web. The performance characteristics of needle punched nonwovens are dependent upon the fiber and structural mechanics of the fabric developed during the manufacturing process. The needle punching parameters can be divided into three categories; material parameters (fibre and web types), needle parameters (needle type, shape, arrangement and number of barbs, etc.) and the machine parameters (depth of needle penetration, stroke frequency, punch density, etc.). These parameters are interrelated and approach limits dictated by process economics and fibre properties [1].

1.2. Factors Influencing the Performance of Needle Punched Nonwovens 1.2.1. Web Parameters The mechanical properties of needle punched nonwovens are dependent upon laying techniques used for the production of web structures or the initial web structure. Depending on the feed rate employed, the web density can be varied, and with higher feed rate thicker and denser nonwovens are formed. The resultant properties of needle punched nonwovens directly relate to the web density; for instance, lower feed rates increases the permeability characteristics of the nonwovens. It is due to the presence of fewer fibres per unit volume. Relatively fewer fibres in the structure result in the formation of larger pores, especially at lower stroke frequencies. However, increases in both feed rate and stroke frequency reduce the permeability of the needle punched nonwovens, as the pore size decreases with the increase in the number of fibres. The isotropy or anisotropy of the subsequent nonwoven is dependent upon the web laying technique. Control of the web is vital in the needle punching process because the fabric’s structural properties, such as thickness, basis weight, bulk density and air permeability, are directly related to the web features, such as fibre orientation, web density, web thickness and web homogeneity [2].

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1.2.2. Depth of Needle Penetration The depth of needle penetration in needle punching refers to the longest distance that the first barb reaches below the lower surface of the web or bed plate. The depth is set by lowering the bed plate to increase the needle penetration or raising it to decrease the depth of penetration. During the needling process the barbs on the needles carry fibres through the web thickness from the surface to the base. An increase in the depth of needle penetration causes an increase in the relative frequency of the fibres oriented in the machine direction for cross-lapped webs, due to the fact that the fibres have to take a longer path because of a higher depth of needle penetration from surface to the thickness direction. In the process, some of the fibres would be released and recover from the stress and strain. On recovery, the fibres, preferentially oriented in the cross-machine during web laying reorient in the machine direction. The depth of needle penetration in the needle punching process is probably the most significant processing variable influencing the mechanical properties, dimensional stability and fabric density. Generally, the mechanical properties, such as tensile strength, improve with the increase in the depth of penetration due to the greater extent of fibre reorientation and contact points. The tensile properties steadily improve with the increase in depth of needle penetration, but reach a limit beyond which it begins to decrease. This decrease with excessive needle penetration is explained by the fibre damage that occurs at those levels resulting in the weakening of the structure. The fabric thickness, on the other hand, decreases with the increase in needle penetration because of the improved consolidation of the structure with greater depth of needle penetration. Needle penetration determines the number of fibres carried on the down stroke; the deeper the needle penetration, the higher is the number of fibres carried by the needle. The needle configuration is also another factor influencing the number of fibres carried on the down stroke. At a higher depth of penetration the lower barbs on the needle carry the fibres through the entire web thickness, which remain protruding beyond the bottom surface, whereas with a low depth of penetration the punched loops do not

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protrude through the web thickness. If the penetration is too great, tufts are punched right through the previous loop to give a pseudo knitted entanglement of fibres. The linkage of such punched fibre tufts results in an increase in the tensile modulus and tenacity, but a reduction in the breaking extension of the fabric. The change in mechanical properties is largely due to the intensity of fibre entanglement [2, 3].

1.2.3. Stroke Frequency Stroke frequency refers to the rate at which the needle board moves per second forcing the needles through the bed plate and penetrating the web. An increase in the stroke frequency results in a higher number of fibres being reoriented from the horizontal to the vertical direction, which significantly reduces the larger pores of the structure. This process parameter also determines fabric density and tensile strength since, at higher stroke frequencies, there is improved consolidation of the web. The frequency of the strokes and linear speed of the web must be balanced to achieve the desired degree of consolidation. The key parameter representing the entanglement of fibres is known as penetration per square inch (PPSI). PPSI is directly proportional to the density of the needles on the needle board and to the frequency of strokes, but inversely proportional to the speed of the web [2, 4]. 1.2.4. Amount of Needling (Punching Density) Punching density is the amount of needling that the web receives from the barbed needles when passing through the needle punching machine. The amount of needling received by the fibrous web determines the degree of entanglement of the fibres, thus influencing such properties as tensile strength, strain and fabric density. With the increasing punching density, fabric breaking strength increases to a maximum and then decreases. The punching density also directly affects the packing factor. An increase in the punching density takes place, resulting in a corresponding increase in the packing factor as more fibres are entangled and a higher level of structural consolidation. This results in an increase in the compressive modulus, and the fabric also becomes stiffer.

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When the punching density is beyond its optimum, the strength of the nonwoven falls due to fibre damage inflicted by the excessive needling. The use of the optimum punching density parameters, at which the nonwoven has maximum tensile strength, is important to obtain the best possible nonwoven structure. The effect of punching was shown to change the mechanical properties and the greater the punching density, the higher will be the tensile strength and modulus, until a maximum is reached. Excessive punching density was shown to result in damage to the fibres, which lowers the mechanical properties, such as fabric tenacity and initial modulus of the fabric. The amount of needling is a parameter that affects the thickness, weight and the strength of the fabric. The needling process results in fibre entanglement and reorientation of the fibres in the thickness direction, thereby binding different fibre layers into a coherent self-locking structure. Needling the fibrous web reduces the web thickness due to a collapse of the spaces between fibrous layers and entanglement of the fibres by the action of the needles. Fibres are pulled from the top layer or surface to the base of the web during the down stroke of the needles. This consolidates the fabric, and its weight decreases with the increase in the needling density due to the drafting and spread of fibres during punching. The web is drafted by the nip rollers when it is drawn through the plates in the needling zone, thereby increasing the length of the structure and reducing its weight. The fabric also experiences recovery of the fibres previously drawn to the base of the structure when needles are withdrawn from the web causing some fibres to be pulled up and recover from compression. Thus, fibre recovery leads to the spreading out of the fibres in the structure and loss in area weight. The amount of needling is varied by altering the rate of web advance, changing the stroke frequency of the needle board, or increasing the number of passes of the nonwoven through the needle punching machine. The stress/strain behavior of the nonwoven produced by needle punching is also influenced by the amount of needling used to produce the structure. Tensile strength and modulus of the fabric increase with the increase in needling, up to a limit, after which further needling tends to decrease the

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modulus and tenacity. This decrease beyond the maximum is caused by the damage to the constituent fibres at high needling intensities [2, 5].

1.2.5. Needle Type Much technical consideration should be taken with regard to needles, as they ultimately influence several properties of needle punched nonwovens. The correct type of needles should be selected to produce any specific type of fabric. For instance, when barbs are close, more fibres are carried across the fibre web, and the C and F types of barb spacing therefore form very compact products. However, the surface of such products is not smooth and does not have a good appearance, because of the penetration holes showing on the surface caused by excessive needling actions. The best surface is obtained with regular and medium barb needles, as they cause relatively small holes on the surface. The closer the barbs are the more fibres they transport during the downward stroke [2, 6].

1.3. Nonwovens for Thermal Insulation Application Thermal insulation is a process of reducing the heat transfer through the surfaces; it prevents the cold air or hot air in the outdoor environment from causing temperature loss or gain in the indoor environments. There are some studies in the literature investigating the thermal insulation properties of nonwovens. Abdel-Rehim et.al studied the thermal insulation properties of 100% polyester and 100% polypropylene nonwovens. They found out that polyester fabric had higher thermal resistance and specific heat resistance than polypropylene. Fabric thickness had a significant effect on the fabric temperature variations [7]. Debnath studied the thermal resistance and air permeability of needle punched nonwovens made from jute and polypropylene blends and observed that the thermal resistance and air permeability were influenced significantly by fabric weight [8].

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Sakthivel and Ramachandran studied the thermal conductivity of nonwoven materials using reclaimed fibres and observed that thermal insulation properties of the nonwoven materials vary significantly, depending on the type of reclaimed fibre [9]. Ghane et.al investigated influence of the effective parameters on thermal conductivity of needle punched nonwovens and found out that porosity was the more significant parameter affecting thermal conductivity of nonwoven in comparison to the mean fiber orientation [10]. Kopitar et.al studied the influence of calendering process on thermal resistance of polypropylene nonwoven fabric structure and observed that a change in structure of the calendered samples caused a considerably lower thermal resistance i.e., better thermal conductivity. With increasing nonwoven fabric mass, the difference between thermal resistances of needled and needled as well as additionally bonded by calendering the nonwoven fabric was reduced [11]. Martin and Lamb studied the measurement of thermal conductivity of nonwovens using a dynamic method and indicated that in agreement with established theory, the conductivity decreases if the nonwoven is compressed or is made with finer fibers or has a reflective coating on the fiber surface, due to the reduction in the radiative component of heat transfer. Fiber shape has no effect on thermal conductivity [12]. We are focusing on natural fibers for their insulation properties [13, 14]. Generally, natural fibres have good specific mechanical properties due to their low density, short span of renewable resource with low energy consumption and recyclability. Among the natural fibers, flax fiber has good mechanical properties and it’s nearly to E-glass fiber. We thought the presence of central canel like free space in the flax fiber, which is referred to as lumen can contribute for thermal insulation. The focus of this work is to manufacture flax/low melt PET needle punched nonwoven fabrics and characterize the developed nonwovens for thermal insulation applications. Nonwoven fabrics were developed by blending flax fibers with low melt PET at 3 blend ratios (10%, 20% & 30%) with 7 mm and 10 mm needle penetration depth. The influence of needle penetration depth and % of low

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melt PET on physical and insulation properties of the developed nonwovens was investigated.

2. EXPERIMENTAL DETAILS 2.1. Sample Preparation The flax fiber and low melting point polyester fibers used in this study were sourced from in and around Coimbatore, India. Their physical properties are given in Table 1. The flax fibers were treated with alkali solution before further processing; then, treated flax fibers were blended with low melt PET fibers and web was formed using lab model carding machine. Then this web was needle punched at needle loom - DI-Loom OUG-II 6 to form nonwoven fabric. Then the nonwoven fabric was passed through the hot calendering machine at the temperature of 120˚C to enhance mechanical or adhesive bond between fibres without any chemical reaction between flax and low melt PET. The microscopic images of the flax/low melt PET nonwovens before and after hot calendering are shown in Figure 2. Due to limitations imposed by the fiber properties and machine capabilities, blend ratio and depth of needle penetration were taken as process variables in the manufacturing of nonwovens. Nonwoven samples were developed by blending flax fibers with low melt PET at 3 blend ratios (10%, 20% & 30%) with 7 mm and 10 mm needle penetration depth. Totally 6 nonwovens were developed and the specifications are given in Table 2. Table 1. Properties of flax and low melt PET fibers Flax Effective fiber length (mm) Mean length(mm) Short fiber content (%) Fiber fineness (dtex) Bundle strength (cN/dtex)

214.00 134.00 71.40 4.60 1.97

Low melt PET Effective length (mm) Moisture regain (%) Breaking strength(cN/dtex) Elongation at break Melting temperature (ºC)

38.00 0.36 3.20 40.60 115.00

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Figure 2.Microscopic image of flax/low melt PET nonwoven a) before calendering b) after calendering.

2.2. Characterization Methods The developed nonwoven fabrics were conditioned in standard testing temperature (20ºC ± 2ºC) and humidity (65% ± 2%) for 24 hours according to ASTM standard before testing. The nonwoven fabrics were tested for the following parameters: The areal density of the developed nonwoven fabrics was tested on an electronic balance with a capacity of 0.001 g

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according to ASTM D-1910 [15]. Fabric thickness gauge was used for measuring the thickness under 2 KN load with capacity of 0.01 mm according to ASTM D-1777 [16]. The air permeability of the developed nonwoven fabrics was tested as per ASTM D 737 using TEXTEST air permeability tester [17].

2.3. Thermal Insulation Characterization The thermal insulation property of the developed flax/low melt PET nonwovens was evaluated by determining the thermal resistance according to the guidelines of ISO 8301:1991 with a heat flow meter apparatus HFM 436 Lambda supplied by NETZSCH (NETZSCH-Geratebau GmbH, Selb, Germany) [18].

2.4. Heat Transfer Mechanisms in Nonwoven Composite Materials The thermo conductive properties of cellulosic-based, needle-punched nonwoven composites depend on the nature and fineness of the fibers, inter-fiber pore size, the distribution of fibers in the composite, the nature and quantity of the binder, and the overall material bulk density. A very porous medium, such as nonwoven composites, can be treated as a combination of various solid substances (fibers and binder matter) and ‘pockets’ of still air that fill its pore space. Notably, these ‘pockets’ of still air have very low thermal conductivity of 0.0245 Wm-1 K-1 at 20–30ºC while that of textile fibers/binder components have one order of magnitude higher conductivity . There are three fundamental ways by which heat energy can be transferred through the finely porous materials such as nonwoven composites – conduction, convection, and radiation. Depending on the fiber’s and binder material’s specific thermal conductivity, and/or the size and configuration of the space between the fibers in the nonwoven sample,

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heat transfer mechanisms – conductive, radiative, and convective – will provide very different contributions to the overall heat transfer throughout the sample. Very complex interactions and contributions of various heat transfer mechanisms in the overall thermal insulation properties of nonwoven composites make the direct instrumental measurement of the thermal conductivity of these materials the only viable option [19].

3. RESULTS AND DISCUSSION 3.1. Physical Properties of Flax/Low Melt PET Nonwovens The thickness of flax/low melt PET nonwovens is in the range of 1.0 1.6 mm as observed in the Table 2. The variation in thickness of nonwovens may be due to random distribution of fibers during nonwoven formation. The density of the developed nonwovens is in the range of 0.300-0.400 (g/cm3). It was observed that the nonwovens developed using 10 mm needle penetration had higher density than nonwovens developed using 7 mm needle penetration. This may be due to the fact that increased needle penetration leads to increased number of barbs penetrating the web which ultimately causes higher consolidation, resulting in higher density. Increased needle penetration may also cause compression of the web and a consequent increase in density. Table 2. Physical properties of flax/low melt PET nonwovens Blend % Flax/ low melt PET 90/10 80/20 70/30

7 mm needle penetration Thickness GSM Density (mm) (g/cm3) 1.19 320 0.270 1.24 404 0.325 1.03 358 0.347

10 mm needle penetration Thickness GSM Density (mm) (g/cm3) 1.62 609 0.376 1.22 481 0.394 1.04 421 0.404

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Figure 3. Influence of low melt PET % on air permeability of nonwovens.

Air permeability is the most important property of nonwoven materials for thermal insulation applications. Figure 3 shows the influence of low melt PET % on air permeability of nonwovens at 7mm and 10mm needle penetration. It was observed that there was a decrease in air permeability value with increase in low melt PET % and depth of needle penetration. This may be due to the fact that consequent increase in compactness of fabrics offers more resistance to airflow [20]. The negative co-efficient value of variable in the equation indicated that increase in low melt PET % decrease the air permeability value. The co-efficient of determination (R2) of the linear regression curve for 7 mm needle penetration and 10 mm needle penetration are 0.958 and 0.994 respectively indicated its goodness of fit.

3.2. Thermal Insulation Properties of Flax/Low Melt PET Nonwovens Figure 4 shows the influence of low melt PET % on thermal resistance value of nonwovens at 7mm and 10mm needle penetration. The negative co-efficient value of variable in the equation indicated that increase in low melt PET % decrease the thermal resistance value of nonwovens. This may be due to the fact that thermal conductivity of synthetic fibres higher than

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natural fibres. Hence, increasing blend % of low melt PET with flax increases the thermal conductivity of nonwovens and reduces its thermal resistance. The co-efficient of determination (R2) of the linear regression curve for 7 mm needle penetration and 10 mm needle penetration are 0.889 and 0.947 respectively indicated its goodness of fit.

Figure 4. Influence of low melt PET % on thermal resistance of nonwovens.

It was also observed that the increase in needle penetration reduces the thermal insulation of nonwovens. Nonwovens developed using 7 mm needle penetration had better thermal insulation value compared to nonwovens developed using 10 mm needle penetration. While increasing needle penetration, the structure becomes more compact and therefore holds less air, which reduces the insulating properties. The thermal resistance value of the developed nonwovens is in the range of 0.025 0.065 m2K/W. This fact is interesting since a thermal insulating material is characterized by thermal resistance values higher than 0.025 m2 K/W. Therefore, the developed flax/low melt PET nonwovens fulfill these requirements and can be used for thermal insulation applications. The performance of the developed flax/low melt PET nonwoven has been compared with commercial product named Autex Cove made of 100

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% polyester fibers manufactured by Autex Industries Ltd, New Zealand and is given in Table 3. It was observed that the commercial product has 20 times higher in thickness value compared to developed flax/low melt PET nonwoven. Thermal resistance converted to unified thickness of 1 mm, it turns out to be 0.034 m2 K/W and 0.027 m2 K/W for the commercial and developed sample respectively which are almost a close value for practical purposes. Further when density is considered, denser the sample lower would be the thermal resistance. Accordingly, the resistance values are unified based on density, the values are obtained as 0.0068/mm and 0.011/mm for the commercial and developed sample respectively, in which case the developed flax/low melt PET appears to stand superior to the commercial product. Table 3. Comparison of flax/low melt PET nonwoven with commercial product Specifications Raw material Thickness (mm) Density (g/cm3) Thermal resistance (m2K/W)

Autex Cove 100% polyester 24.000 0.200 0.820 (0.034 mm)

Flax/low melt PET nonwoven 80% flax/20% low melt PET 1.220 0.394 0.033 (0.027 mm)

CONCLUSION The potential of natural fiber nonwovens opens a wide variety of new applications in the textile industry (for example, as biodegradable wipes). Also, uses in other technical sectors, such as automotive, are attractive. Flexible nonwoven structures can be used as thermal and/or acoustic insulating materials in automotive interior parts. These can provide interesting properties as lining materials because of their ease of handling and shape adaptability. In this work, flax/low melt PET needle punched nonwovens were developed with 3 different low melt PET % with 7mm and 10 mm needle penetration depth. The influence of blend ratio and needle penetration

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depth on insulation properties of nonwovens was investigated. The thermal insulation behavior of the developed nonwovens decreased with increase in low melt PET percentage and needle penetration depth. All the developed nonwovens had better thermal insulation values. The present results showed that flax/ low melt PET nonwovens have very good thermal insulation properties and show replacements for commercially available glass fibrous mat. In our developed products, natural fibers present from 90 to 70%. Even in the lowest limit of natural fibers, 70% of product undergoes bio degradation contributing towards biodegradation of product otherwise made of 100% polyester.

ACKNOWLEDGMENTS The authors thank M/s PSG TECHS COE INDUTECH, Coimbatore for providing facilities to carry out this research.

REFERENCES [1] [2] [3]

[4]

Wang, Y. (2006). Recycling in textiles, Wood head publishing limited, Cambridge, England. Abhijit, M. (2013). ‘Process Control in Textile Manufacturing’, Wood head Publishing limited, Cambridge, England. Muthukumar, N., Thilagavathi, G., Neelakrishnan, S., and Poovaragan, P.T. (2017). ‘Sound and thermal insulation properties of Flax/low melt PET needle punched nonwovens’, Journal of Natural Fibers, doi.org/10.1080/15440478.2017.1414654. Kothari,V.K., Das, A., and Sarkar, A. (2007). “Effect of processing parameters on properties of layered composite needle punched nonwoven air filters. Indian Journal of Fibre and Textile Research, vol.32, no.6, pp.196-201.

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Sengupta, S., Majumdar, P.K., and Ray, P. (2008). ‘Study on the physical properties of jute needle-punched nonwoven fabrics using central composite rotatable design’, Journal of The Institution of Engineers (India): Series E, vol.89, pp. 16–24. Rajesh Anandjiwala, D. and Boguslavsky, L. (2008). ‘Development of needle-punched nonwoven fabrics from flax fibres for air filtration applications’, Textile Research Journal, vol.78, no.7, pp. 614-624. Abdel-Rehim, Z.S., Saad, M.M., El-Shakankery, M., Hanafy, I. (2006). ‘Textile fabrics as thermal insulators’, AUTEX Research Journal, vol.6, no.3, pp.148-616. Debnath, S. (2011). ‘Thermal resistance and air permeability of jutepolypropylene blended needle-punched nonwoven’, Indian Journal of Fibre and Textile Research, vol.36, pp.122-131. Sakthivel, S., Ramachandran, T. (2012). ‘Thermal conductivity of non-woven materials using reclaimed fibers’, International Journal of Engineering Research and Applications, vol. 2, no.3, pp. 29832987. Ghane, M., Pashaei M., Zarrebini, M., Moezzi, M., Saghafi, R. (2014). ‘Investigation of Effective Parameters on Thermal conductivity of Needle Punched Nonwovens Using Multiple Regression’. Journal of Fashion Technology and Textile Engineering, doi:10.4172/2329-9568.1000117. Kopitar, D., Skenderi, Z., Mijovic, B. (2014), ‘Study on the Influence of Calendaring Process on Thermal Resistance of Polypropylene Nonwoven Fabric Structure’, Journal ofFiber Bioengineering and Informatics, vol.7, no.1, pp.1–11. Martin J.R., Lamb, G.E.R. (1987). ‘Measurement of thermal conductivity of nonwovens using a dynamic method’, Textile Research Journal, vol.57, no.12, pp.721-727. Thilagavathi, G., E. Praveen, T. Kannaian, and L. Sasikala. (2010). ‘Development of natural fiber nonwovens for application as car interiors for noise control’, Journal of Industrial Textiles,vol.39, pp.267-278.

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[14] Thilagavathi, G., Muthukumar, N., Neelakrishnan, S., and Senthilram T. ‘Development and characterization of pineapple fiber nonwovens for thermal and sound insulation applications’, Journal of Natural Fibers, doi: 10.1080/15440478.2019. 1569575. [15] ASTM D-1910. (1996). ‘Standard test method for weight of textile fabrics’, ASTM Internationals, West Conshohocken, PA. [16] ASTM D-1777. (1996). Standard test method for thickness of textile materials, West Conshohocken, PA. [17] ASTM D-737. (2004). ‘Standard test method for air permeability of textile fabrics’, ASTM Internationals, West Conshohocken, PA. [18] ISO 8301-1991. (2014). ‘Thermal insulation - Determination of steady-state thermal resistance and related properties - Heat flow meter apparatus’, International Organization for Standardization, Geneva, Switzerland. [19] Yachmenev, V.G., Negulescu, I., and Yan, C. (2006). ‘Thermal insulation properties of cellulosic-based nonwoven composites’, Journal of Industrial Textiles, vol.36, pp.73–86. [20] Midha, V.M., and Mukhopadyay, A. (2005). ‘Bulk and physical properties of needle punched nonwoven fabrics’, Indian Journal Fibre & Textile Research, vol.30, pp.218-229.

In: Nonwoven Fabric Editor: Rembrandt Elise

ISBN: 978-1-53617-587-5 © 2020 Nova Science Publishers, Inc.

Chapter 4

DEVELOPMENT OF THERMAL BONDED NONWOVEN FABRICS MADE FROM RECLAIMED FIBERS FOR SOUND ABSORPTION BEHAVIOUR S. Sakthivel1, S. Senthil Kumar2, and Seblework Mekonnen2 1,2

Department of Textile and Garment Technology, Federal Tvet Institute, Addis Ababa, Ethiopia 2# Department of Handloom and Textile Technology, Indian Institute of Handloom Technology, Salem, Tamilnadu, India

ABSTRACT Recycled fibers are commonly used in different applications, sound absorption being one of the most important applications. Recycled fiber nonwovens are currently high in demand in industries because of their advantages such as low cost, biodegradability, acceptable mechanical and 

Corresponding Author’s E-mail: [email protected].

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S. Sakthivel, S. Senthil Kumar and Seblework Mekonnen physical properties and so on. Sound absorption materials such as renewable and eco-friendly thermal bonded nonwoven have been developed using recycled cotton and polyester fibers. Six types of recycled nonwovens samples were developed using thermal bonding and aero dynamic methods. The blending ratio of cotton and polyester fibers was 60:40. Sound absorption coefficient was measured by impedance tube method (ASTM E 1050). The recycled fiber nonwoven samples are characterized by their physical properties such as areal density, bulk density, thickness, porosity, air permeability and thermal resistance was determined for all the samples according to the ASTM standards. The results exposed that recycled cotton/polyester nonwoven samples with its physical properties showed superior sound absorption at 4000 Hz, lower thermal resistance, lower air permeability. Then compared with recycled cotton/polyester are corresponding to the achieved level but it was lower in recycled cotton/polyester nonwoven samples. But, at superior frequencies (4000 Hz), there was a decrease from the achieved level in all the nonwoven samples which might be enhanced by increasing the thickness of the nonwovens. The average sound resistance percentages of these three decibel values were calculated and compared for all the samples.

Keywords: recycled fiber nonwoven, thermal bonding, aero dynamic web, physical properties and sound absorption coefficient

1. INTRODUCTION The concern over the environment induced a large numbers of companies to start developing manufacturing process using alternative materials for their products and seeking new markets. With the significant production of waste fibrous materials, different companies are looking for applications wherein waste materials may represent an added-value material. This study is about the research where waste fibers are collected and transformed into a fibrous mat of more homogenously mixed and combed fibers, mainly containing natural fibers. The fiber material is processed into a nonwoven fabric. There are many compelling reasons for the recycling of waste from textile products and processes. They include conservation of resources, reduction of the need for landfills and paying

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the associated tipping fees, and provision of low-cost raw materials for products. The reclaimed fiber prepared from the waste fabric has the parameters like span length, uniformity ratio, microniare value and tenacity which are suitable to fabricate the fiber into non-woven. In this chapter, thermal bonded non-woven fabrics using reclaimed fiber have been developed and their characteristics have been critically analyzed for sound absorption behavior. In this research work the non-woven samples were developed by thermal bonded non-woven technique using reclaimed fibers. Characteristics like thickness, areal density, bulk density, porosity, air permeability, thermal conductivity were analyzed for influencing the sound absorption behavior of thermal bonded non-woven fabrics.

2. MATERIALS The materials for the development of thermal bonded nonwoven fabric are a kind of knitted waste from garment industries. Reclaimed fibers are from a secondary cycle of processing. To obtain them, fabric-type or thread-type textile waste is mechanically broken down as far as of fibers. The reclaimed fibers cotton, polyester; cotton polyester blended is segregated in the form of color and white.

3. METHODS The following flow chart shows the method of development of the thermal bonded nonwoven samples.

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Figure 1. Flow chart of the development of the thermal bonded non-woven.

3.1. Web Formation The air or random laying techniques allows fabrics with range of mass per unit area to be produced, in which fiber orientation can be made much more random than in the case with traditional web layering. Short fibers can be processed easily, allowing textile waste materials to be used in nonwovens. Random laid webs are made as a single layer and claimed to have equal properties in all directions. A very open-structured, low-melting-point thermoplastic fabric is placed between the webs and, during thermal bonding between the calendar rolls, the fabric melts completely bonding the webs together. The nonwoven produced by this technique is soft and bulky. Six varieties of web were produced such as color cotton, white cotton, color polyester, white polyester, color cotton polyester blend and white cotton polyester blended materials. This web former produces 138 meters of fibrous layer per hour.

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Figure 2. Showing the schematic representation of web formation.

Figure 3. Schematic representation of thermal bonding non-woven.

3.2. Method of Thermal Bonding Nonwoven In this research six nonwoven samples were developed by thermal bonded nonwoven technique using reclaimed fiber web. Air thermal bonding involves the application of hot air to the surface of the nonwoven fabric. The hot air flows through holes in a plenum positioned just above the nonwoven. However, the air is not pushed through the nonwoven, as in common hot air ovens. Negative pressure or suction, pulls the air through the open conveyor apron that supports the nonwoven as it passes through the oven. Pulling the air through the nonwoven fabric allows much more rapid and even transmission of heat and minimizes fabric distortion. Six varieties of nonwoven were produced such as color cotton, white cotton, color polyester, white polyester, color cotton polyester blend and white cotton polyester blended nonwoven materials.

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Figure 3.1. White and colour thermal bonded nonwoven samples.

4. TESTING METHODS The nonwoven samples of recycled cotton, polyester and cotton/polyester blend reclaimed fiber from cutting waste of garment units produced according to required samples of colour and white, which were tested for sound absorption and physical properties like thickness, areal density, Bulk density, porosity, air permeability, thermal conductivity and sound absorption behavior were critically analyzed.

4.1. Sound Absorption Coefficient by Impedance Tube Method The sound absorption coefficients of the nonwovens were tested by the impedance tube method on ASTM E 1050 at Indian Institute of Technology Chennai. A sound source (loud speaker) is mounted at one end of the impedance tube and at the other end the nonwoven is placed. The loud speaker generates broadband, stationary random sound. This sound propagates as planner waves in the tube, hits the sample and gets absorbed. Thus a standing wave interference pattern results due to superimposition of forward and backward travelling waves inside the tube. The sound pressure at two fixed location is measured and by using the two-channel digital frequency analyzer. From the results it will be possible to determine the complex reflection coefficient, the sound absorption

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coefficient and the normal acoustic impedance of the non-woven. The usable frequency range depends on the diameter of the tube and spacing between the microphone positions. The small tube setup with 29 mm diameter measures the parameters of sound in the frequency range from 500 Hz to 6.4 KHz. Whereas, the larger tube setup with 100 mm diameter measures the parameter of sound in the frequency range from 50 Hz to 1.6 KHz.

4.2. Methods of Testing Physical Properties The standard test procedure followed for determining the physical properties of the thermal bonded nonwoven samples are ASTM D 5736 for thickness of the fabric, ASTM 6242 for areal density and bulk density, ASTM D 737 for its air permeability, ASTM D 6343-10 standard methods for the thermal conductivity, and ASTM E 1294-89 for Porosity. In order to study the influence of fiber type, number of layers areal density, porosity and air permeability on sound absorption, the samples of recycled fiber nonwoven were produced and measured with the above parameters.

5. RESULT AND DISCUSSION The physical properties of the thermal bonded nonwoven of recycled cotton, polyester and cotton polyester blend fabrics are measured and average values of samples are given in Table 1. The sample of white cotton (WP), colour cotton (CC), white polyester (WP), colour polyester (CP), white cotton/polyester (W C/P), colour cotton/polyester (C C/P). From the Table 1, it is observed that the white cotton, polyester and cotton/polyester recycled fiber nonwoven shows similar results in porosity. When the color fibers are used the porosity is increased. This may be due to increase in the thickness and areal density of the fabrics. While comparing the air permeability of the samples, WC, CC, WP, CP, W C/P

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and C C/P shows that CC has more air permeability value of 38.7 CC/S/C m2. These comparisons reveal that the increase in fiber content of the nonwovens decreases the air permeability. This may be due to the fiber properties and their bonding behavior.

5.1. Sound Absorption Performance of WC, CC, WP, CP, W C/P & C C/P Different recycled fiber of natural and synthetic fiber has different properties especially in consideration to the surface and inner bonding properties. These properties influence the density of the nonwovens, which in turn affect the sound absorption by the fabric. Figure 4 shows the sound absorption coefficient of recycled fiber thermal bonded nonwoven made out of cotton, polyester, and cotton/polyester blend. The evaluation has been done with the white and colour samples. From the Figure 6.4 it can be observed that while the frequency increase the sound absorption coefficient (SAC) of all samples WC, CC, WP, CP, W C/P, and C C/P also increases. Similarly while thickness increases the sound absorbing performance also increases. At the highest frequency of 4000 Hz, the SAC values of WC, CC, WP, CP, W C/P, and C C/P are 0.39, 0.6, 0.35, 0.56, 0.48 and 0.64. Table 1. Physical Properties of Thermal Bonded Nonwoven Sample Thickness Areal (mm) density (g/ m2) WC 3.2 323.11 CC 3.3 330.50 WP 3.4 648.03 CP 3.5 653.03 W C/P 3.35 953.00 C C/P 3.4 980.77

Bulk Density (g/ cm3) 0.139 0.141 0.155 0.157 0.157 0.151

Fabric Porosity 0.394 0.387 0.356 0.335 0.378 0.365

Air permeability (CC/S/C m2) 30.5 29.5 27.9 26.7 28.7 29.2

Thermal conductivity (W/mK) 0.13 0.29 0.125 0.123 0.126 0.127

Sound absorption co-efficient 0.123 0.253 0.150 0.281 0.203 0.328

in consideration to the surface and inner bonding properties. These properties influence the density

Development ofaffect Thermal Bonded Nonwoven Fabrics of the nonwovens, which in turn the sound absorption by the fabric.

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S A C

absorption. Frequency (Hz)

5.2 Influence of Thickness on Sound Absorption: FigureFigure 4. Sound absorption performances of WC, CC,CC, WP,WP, CP,CP, W C/P & CC/P. 4 Sound absorption performances of WC, W C/P & CC/P.

Figure 5 Influence of Thickness on Sound Absorption Figure 5. Influence of Thickness on Sound Absorption. From the figure 5 it is observed that the nonwoven WC, WP, W C/P which has 3.2 mm,

The calculated average SAC values of WC, CC, WP, CP, W C/P, and 3.4mm, and 3.35mm thickness is having SAC of 0.123, 0.15, and 0.203; whereas with the increase C C/P which are 0.123, 0.253, 0.15, 0.281, 0.203 and 0.328 also reveal the of .01mm, and .05mm thickness CC,CP, CP,CCC/P C/P shows shows increase SAC of 0.253, 0.281 and same. The.01mm, performance of sample CC, equal values from 00.328. to 1000 Hz; this may be due to the lower frequency, the small increase in thickness or fiber content of this nonwoven does not influence the sound absorption.

S. Sakthivel, S. Senthil Kumar and Seblework Mekonnen 5.3130 Influence of areal density on sound absorption

Figure 6 Influence arealabsorption. density on sound absorption Figure 6. Influence of areal density onofsound

5.2. Influence of Thickness on Sound Absorption From the Figure 5 it is observed that the nonwoven WC, WP, W C/P which has 3.2 mm, 3.4 mm, and 3.35 mm thickness is having SAC of 0.123, 0.15, and 0.203; whereas with the increase of .01 mm, .01 mm, and .05 mm thickness CC, CP, C C/P shows increase SAC of 0.253, 0.281 and 0.328. The colour Cotton/polyester blend nonwoven C C/P with the thickness of 3.4 mm results with average SAC of 0.328 which is higher than WC, WP, CP, W C/P nonwoven fabric. The result reveals that the increase in thickness of the nonwoven fabric increases the sound absorption.

5.3. Influence of Areal Density on Sound Absorption Figure 6 shows when there is an increase in areal density there is an increase in sound absorption coefficient for cotton, polyester and cotton polyester blend nonwovens. The coloured materials have more density than white material due to the dying molecule content in the coloured material.

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The Colour Cotton/polyester nonwoven C C/P with the density of 980.77 g/m2 results with average SAC of 0.328 which is higher than WC, WP, CP, W C/P nonwoven fabric.

5.4. Influence of Bulk Density in Sound Absorption The influence of bulk density on SAC of nonwovens as shown in the Figure 7 reveals that increase in bulk density directly increases the SAC. Coloured nonwoven which has the difference in bulk density of 0.022 g/cm3 with the white nonwoven depicts 18% increase in SAC. Colour and white polyester nonwoven having the difference in bulk density of 0.013 g/cm3 with depicts of 28% increase in mean SAC. Cotton/Polyester nonwoven having the difference in bulk density 0.002 g/cm3 increases in mean SAC of 0.328.

5.5. Influence on Air Permeability on Sound Absorption While increasing thickness of nonwoven fabrics of recycled colour and white cotton, colour and white polyester, and colour and white cotton polyester air permeability Influence of bulk blended, density inthe Sound absorption decreases as in Figure 8.

Figureof7 bulk Influence density in Sound absorption Figure 7. Influence densityofinbulk Sound absorption.

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Figure 8. Influence on air permeability on sound absorption.

The Figure 8 refers the air permeability of cotton, polyester and cotton/polyester based upon the color and white samples. The deviation among the materials can be tested clearly based upon the fiber type and color type. The air permeability of the colour nonwoven is about 26.7-29.2 cc/s/cm2 with SAC of 0.253 to 0.328. The graph also shows that polyester has less air permeability than cotton nonwoven materials. It is clear that where the fabric density increased, the air permeability decreased due to increased resistance to air flow caused by the consolidation of the web. The C C/P has the highest air permeability value with the SAC of 0.328 which is greater than that of WC, CC, WP, CP, and W C/P.

5.6. Influence of Porosity on Sound Absorption Similar to air permeability lower level the porosity higher level the sound absorption must be. From the Figure 9 it is observed that the nonwoven WC, WP, W C/P, CC, CP, C C/P which has 0.394, 0.356, 0.378, 0.387, 0.335 and 0.365 porosity is having SAC of 0.123, 0.151, 0.203, 0.253, 0.281 and 0.328. Less porosity and less air permeability of the

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samples permit the sound frequency lesser amount at low frequency level, but at higher frequency, the sound enters the fine pores and experience friction between the fibers and bond thus performs with higher absorption of sound energy. The above said results are in line with the findings of Shoshani et al. (2000).

5.7. Influence of Sound Absorption on Thermal Conductivity In the Figure 10 the graphical representation shows the influence of sound absorption of the thermal conductivity. There is difference among the thermal conductivity for various thermal bonded nonwoven samples. Cotton (colour and white) non-woven material and polyester (colour and white) non-woven material were assessed for thermal insulation property. The thermal conductivity for the white cotton material is about 0.13 W/mK which has SAC of 0.123 which is higher than that of the CC, WP, CP, W C/P, and C C/P. The same trend was observed by Rahul Vallabh (2008).

Figure 9. Influence of porosity on Sound Absorption.

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Figure 10. Influence of Sound Absorption on Thermal Conductivity.

Figure 11. Sound resistance performances of the thermal bonded nonwovens.

5.8. Sound Resistance Performance of the Thermal Bonded Nonwovens The thermal bonded nonwovens while tested for the sound resistance with 30 dB to 60 dB showed that when the number of layer increases the sound resistance value of the material is also increases. The average sound resistance percentage values for the three decibel values were shown in Figure 11. The nonwoven of recycled colour and white cotton, polyester and cotton polyester blend approximately 21%, 22% and 28% sound

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resistance with fabric to source distance of 25 cm, 50 cm, and 75 cm. The nonwoven of cotton, polyester and cotton/polyester blend showed approximately 15%, 30%, and 38% sound resistance with fabric to source distance of 25 cm, 50 cm, and 75 cm. These results also reveal that the sound resistance increases at the distance between the fabric and the source increases.

CONCLUSION The automotive and building interiors made up of recycled fibers are in potential market growth. The recycled fiber nonwoven as acoustic absorption material are developed by using the fibers recycled from the waste fabrics of cotton (colour and white), polyester (colour and white) and cotton polyester blend (colour and white) collected from the garment industries. The nonwoven are tested for acoustic absorption by ASTM E 1050. It is observed that polyester fiber nonwoven has the highest absorption coefficient in lower frequency levels and higher frequency levels. The recycled polyester nonwoven fabric are having high total surface area, which is influenced by the denier and cross sectional structure of the fibers in the nonwoven fabrics. Similarly while thickness is increases sound absorbing performance of polyester samples WP, CP and C C/P also increases, at the highest frequency of 4000 Hz. Hence it is concluded that the nonwoven made of recycled polyester with its closer structure and higher sound absorbing percentage of 72% is much suited for interiors in building and automotives. The cotton (colour and white), polyester (colour and white) and cotton polyester blend (colour and white) are also having sound absorption percentage of 73% is much suited for interiors in sound absorption of 76% and 82% at 4000 Hz. The major application of these developed nonwoven products may be suggested for floor covering and wall coverings.

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S. Sakthivel, S. Senthil Kumar and Seblework Mekonnen From this chapter the following conclusions were derived;  

     

The Color cotton/polyester nonwoven C C/P with the thickness of 3.4 mm has the higher sound absorption of 0.328 SAC. The recycled fiber nonwoven exhibits higher efficiency of sound absorption due to the following factors: effect of fiber diameter, shortened length of fibers, and variable pore geometry of the fabric. The average sound absorption values of C C/P are 0.328. Where there is an increase in areal density there is an increase in sound absorption The influence of bulk density on SAC of nonwoven reveals that the increase into bulky density directly increases the SAC. Similar to air permeability, lower the porosity level higher the sound absorption. Sample with highest thermal conductivity shows lesser sound absorption behavior. The samples reveal that the sound resistance also increases at the distance between the fabric and the source increases. The reclaimed fiber of thermal bonded nonwoven sound absorbing materials were developed by using the fibers recycled from the waste of cotton, polyester and cotton polyester blend were taken. In total there were 6 samples of cotton colour and white, polyester colour and white and cotton/polyester colour and white have been produced. Among 6 samples colour cotton/polyester nonwoven showed highest average SAC of 0.328.

The sound resistance of thermal bonded nonwoven has been tested using sound decibel meter with different sound level of 30 dB to 60 dB. The colour cotton/polyester showed higher sound resistance of 60%. This is because the nonwoven fabrics of recycled fibers while increasing the no of layers, the areal density and bulk density also increased and thus resulting in higher sound absorption coefficient. Hence colour polyester, white cotton/polyester and colour cotton/polyester nonwovens at 75 cm

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distance from the source showed the sound insulating values of 37%, 44% and 60% respectively. The acoustic characteristics of a room or an auditorium can be controlled by covering the walls, ceiling and floor with materials having suitable acoustic absorptive characteristics. Nonwoven is a kind of material with orientation and random arrangement of fibers bonded by means of thermal are very much suitable for the application as sound absorbing materials. The sound absorption character is different from the sound resistance character of a material. Hence a sound insulation tester has been used to measure sound resisting capacity of the automotive interiors of nonwoven composite materials.

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[3]

[4] [5]

[6]

Andrea Zent et al. “Automative sound absorbing material survey results.” International Conference on Acoustic, 2007. Arbelaiz A, Fernandez B, Cantero G, Llano-Ponte R, Valea A & Mondragon I, 2005, “Mechanical properties of flax fibre/ polypropylene composites. Influence of fibre/matrix modification and glass fibre hybridization,” Applied Science and Manufacturing, vol. 36, no 12, pp. 1637-1644. Allard et al. “Free field surface impedance measurements of soundabsorbing materials with surface coatings.” Applied acoustics, Vol, 26(3), pp. 199-207, 1989. Bartl 2004 & 2005, Characterization of short fibers, Vienna University of Technology, Austria. Bentchikou M, Guidoum A, Scrivener KL, Silhadi K & Hanini S, Effects of cellulose fibers on the thermal and mechanical properties of cement paste. Bernard Castagnèdea, Alexei moussatova, & Viggo Tarnowb, 2001, “Parametric study of the influence of compression on the acoustical anisotropy of automotive felts,” In: International conference of engineering education, Sydney, pp. 720-726.

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S. Sakthivel, S. Senthil Kumar and Seblework Mekonnen Boettcher P & Schilde W, 1994, “Using Reclaimed Fibers in Nonwovens,” In: International Textile Bulletin, no 1, pp. 26-27. Boguslavsky & Tsehloane, 2010, “Spun laced and chemically bonded nonwovens for filtration applications: Performance evaluation and comparison,” In: CSIR international conference, pp. 10. Bohnhoff A & Petershans J, 2001, “Sorting carpets non-centrally,” 28th Aachen Textile Conference, Aachen, DWI Reports, vol. 125, pp. 242-252. Braccesi C and Bracciali A, 1998, “Least Squares estimation of main properties of sound absorbing materials through acoustical measurements,” Appl. Acoust., vol. 54, pp. 59-70. Braun M, Levy AB and Sifniades S, 1999, “Recycling Nylon 6 Carpet to Caprolactam,” Polymer-Plastics Technology & Engineering, vol. 38, No. 3, 471-484. Brown T, 2001, “Infinity Nylon - A Never-ending Cycle of Renewal,” Presentation at 6th Annual Conference on Recycling of Polymer, Textile and Carpet Waste, Dalton, GA. Bula K, Koprowska J & Janukiewicz J, 2006, “Application of Cathode Sputtering for Obtaining Ultra-thin Metallic Coatings on Textile Products,” Fibres & Textiles in EE, vol. 14, no. 5, pp. 75-79. Carvalho R, Rana S, Fangueiro R & Soutinho F, 2012, “Noise reduction performance of thermobonded nonwovens,” In: 12th World Textile Conference AUTEX, Carotia, pp. 597-600. Christian R Koenig & Dieter H Mueller, 2001, Acoustical properties of reinforced composite material basing on natural fibers, BIK University of Bremen, Germany. Davidson WAB, 1994, “Spandex Markets are Heating Up,” America’s Textiles International, pp. 49. Delany, M. E. and Bazley, E. N. “Acoustical properties of fibrous absorbent materials,” Applied Acoustics, Vol. 3, pp. 105-116, 1970. Dias T & Monaragala R, Measurement Science and Technology, vol. 17, no. 9, pp. 2499-2505. Dias T, Monaragala R, Needham P & Lay E, Measurement Science and Technology, vol. 18, no. 8, pp. 2657-2666.

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[20] Diren Mecit & Arzu Marmarah, 2012, “Application of spacer fabrics in composite production,” Usak University Journal of Material Science, vol. 2, pp. 71-78. [21] Dockery A, 1995, “Spandex Moves in the Fast Lane,” America’s Textiles International, pp. 227. [22] ECOTEC Research and Consulting Ltd (1997, Reducing Cost Through Waste Management: Garment and Household Textile Sector.

In: Nonwoven Fabric Editor: Rembrandt Elise

ISBN: 978-1-53617-587-5 © 2020 Nova Science Publishers, Inc.

Chapter 5

BORIC ACID BASED FIRE-RETARDANTS AND NONWOVEN FABRIC SURFACE COATINGS FOR SAFETY IN THE AUTOMOTIVE INDUSTRY Nazan Avcioğlu Kalebek1, and Emel Çinçik2,† 1

Fine Art Faculty, Gaziantep University, Gaziantep, Turkey 2 Engineering Faculty, Erciyes University, Kayseri, Turkey

ABSTRACT Nonwoven fabrics are porous webs which are produced directly from fibers. Not only natural fibers but also man-made fibers are used in web production and bonding. Nonwoven fabrics continue to be one of the fastest growing material types being used in the textile industry. They are considered to be engineered fabrics with excellent performance  †

Corresponding Author’s E-mail: [email protected]. E-mail: [email protected].

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Nazan Avcioğlu Kalebek and Emel Çinçik properties. Over the past two decades, increasing uses are being found for nonwoven fabrics in many fields due to the ease of the manufacturing process, high production speeds, and lower production costs. Nonwovens are used almost everywhere including in the military, agriculture, construction, clothing, home furnishings, travel and leisure, healthcare, personal care and for household applications. These fabrics demonstrate much functionality such as strength, resilience, absorbency, liquid repellency, softness and etc. One primary functionality is as a flame retardant. Flame retardants are important for personal safety and for reducing losses caused by fire. Most recently established federal regulations on the flammability of the fabric indicate that the use of FR textiles will steadily increase in the near future. The increasing use of FR materials in industry has put considerable pressure on the scientific community to develop new polymer materials, FR chemicals, and fiber combinations to a wide range of end use applications. Boric acid has recently been used in textile materials as a flame retardant. Boric acid (commercially known as Optibor®) is a white triclinic crystal in water (5.46 wt.%), alcohols, and glycerin. It has the chemical formula H3BO3 (sometimes written B(OH)3), and exists in the form of colorless crystals or a white powder that dissolves in water. Boric acid is found naturally in its free state in some volcanic regions. Flame retardant chemicals only minimize fire risk however they are not completely non-flammable. With flame retardancy, people have time to escape, ignition times are reduced and the release of toxic gases is minimized. In this study, polyester (PES) based nonwoven fabrics produced by air layering and spunlace techniques were used as samples. They have been used for interior car roofs and interior door linings. Boric acid (BA) was applied to nonwoven fabrics as a finishing operation by spraying and brushing at the completion of the spunlace production systems. The applied amount of 2.58 g boric acid was mixed with 250 ml of warm water at 32ºC based on the chemical properties as written in the information chart for the chemicals. The flammability test was evaluated according to the ASTM D2863 standard under controlled conditions. The Limiting Oxygen Index (LOI) is a test method for evaluating the ignition and ease of flame extinction in samples. Fabrics having an LOI value of 21 or below ignite easily and burn rapidly in air. LOI values above 21 ignite and burn more slowly. When LOI values are above 26-28, the fabric may be considered to be flame retardant. As a result, the LOI value of untreated PES nonwoven fabrics were measured at 16.2 for 45 g/m2. The LOI value of PES fabrics treated with the solution increased to 26.8 for 200 g/m2. This result confirms that the boric acid had a great influence on the flammability resistance of nonwoven fabrics.

Keywords: boric acid (BA), fire retardant, LOI, nonwoven, spraying

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1. INTRODUCTION Raw textile materials such as fibers, yarns and fabrics are flammable, therefore in order to reduce the loss of human life, injury and damage, flame retardants (FR) are applied to them. Fire is one of the most destructive forces on the planet. It is impossible to prevent fire. However, it can be controlled and limited as a hazard by FR chemicals. Much of the research and industry development of new products, methods and processes has focused on extending the wide range and uses of various applications. FR chemicals generally generate smoke, toxic gases and flames while and/or after burning. There are three major products used commercially. These are halogens, metal hydrates, and phosphorus. Halogenated FR chemicals can include bromine, chlorine or both. Specific product examples are Decambromodiphendyl oxide (DECA), Tetrabromobisphend A (TBBA), and Hexabromo cyclododecane (HBCD). These products generally generate halogen acid gas. Halogen FR products are used in polyolefins, nylons, polyester and other materials. The second main FR product is metal hydrates. The best-known FR metal hydrides are aluminum trihydrate (ATH) and magnesium hydroxide (Mg(OH)2). Magnesium hydroxide is considered especially environmentally friendly. Phosphorus based flame retardants are a broad and expanding class of additive or reactive organic or inorganic compounds used to improve the fire safety of materials such as plastics, textiles, wood, paper, and other flammable materials [1-5]. Kowlowski and Wodyko-Przybylak (2008), investigated the most commonly used natural fibers such as flax, hemp, jute, ramie, coir, sisal, cotton, kenaf, bamboo and matrices for composites (thermoplastic polymers including polyolefins, polyethylene (PF) and polypropylene(PP) polyvinyl plastics) and biopolymers (cellulosic plastic, polylactides (PLA), starch plastics, soy-based plastics and microbial synthesized biopolymers). Natural fibers containing composites are manufactured by way of simple techniques including hand layup, spraying, compression, transfer, resin transfer, injection, compression injection and pressure bag molding operations. In order to increase the fire retardancy of composites, there are

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two main methods applied. One of them involves the application of different types of fire retardants during the manufacturing process. The other requires the application of fire retardants at the finishing stage. The HRR (Heat Release Rate) and MLR (Mass Loss Rate) can be detected by a calorimeter. The limited oxygen index (LOI) can be used to determine flammability [6]. Fatima and Mohanty (2011), aimed to study the acoustic and flammability properties of the natural fiber, jute, for use in house hold appliances, and for automotive and architectural applications. Before undertaking the tests, physical properties such as porosity, flow resistivity, tortuosity and length of the natural jute material were investigated. On completion of the flammability test, the limiting oxygen index (LOI), flame propagation and smoke density results were obtained. As a result, the LOI values showed the highest value as 30.2 LOI. The 5% NR latex jute composite showed the least smoke density. This produced a better performance percentage wise in terms of maximum light absorption [7]. Allen et al., (2013), investigated detailed information about flame retardant chemicals used in airplanes to slow the propagation of fire. Firstly, they collected dust samples from 19 commercial airplanes to identify possible sources of fire and to calculate bromine concentrations inside the planes. In the dust collected from the airplanes, BDEs 47, 99, 153, 183 and 209, tris (1-3-dichloro-isopropyl) phosphate (TDCPP), hexabromocyclododecane (HBCD) and bis-(2-ethylhexyl)-tetrabromo-phthalate (TBPH) were detected. This indicates that flame retardants are widely used in all types of airplanes especially commercial ones, where the most commonly identified dust is BDE 209 [8]. Cardoso and Gomes (2009) applied microcapsules to nonwoven materials without using flammable binders. The microcapsule was applied by laboratory machine controlled and pneumatically controlled methods. Three types of microcapsules were used. These were mPCM coated with PMMA-PPBBA co-polymer, mPCM coated with PMMAPMA co-polymer treated with zinc oxide, and mPCM with boric acid. Small quantities of boric acid were sufficient for producing a flame retardant finish [9]. Kozlowski et al., (2002), developed new nonwoven fabrics with natural fibers.

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These nonwoven fabrics were wool+hemp (500 gr/m2, 50/50%), wool+man-made materials (350 g/m2, 30/70%), linen (300 g/m2) and linen FR (700 g/m2, treated with a fire retardant). The flame retardant was based on a mixture of urea polyborates and the sodium salt of alkyl-aryl sulphonic acid. Three flammability tests were applied. These tests were the Limiting Oxygen Index (LOI), Cone Calorimetry and burning behavior according to PN-ISO 3795; 1996. The results show that nonwoven manufactured natural fibers treated with fire retardants can be used as effective barrier materials in bedding systems for home furnishings and for car seats [10]. Reti and et al., (2009), focused on the development of new flame retard nonwoven fabrics through the use of renewable materials. Polylactic acid (PLA), ammonium polyphosphate (APP), pentaerythritol (PER), kraft lignin (LIG) and maize starch (PEG) were applied to nonwoven surfaces as films with a Darragon molding press at 180ºC at a pressure of 1 MPa for 5 min. A horizontal, vertical flame spread test according to the IN ISO 11925-2 standard and a mass loss calorimeter test according to ASTM E-1354-90 were performed. The application of PLA FR created a protective layer on the top surface of the nonwoven samples [11]. Uppal et al., (2010), improved the flame retardancy of high loft nonwoven fabrics used in the manufacture of upholstery, mattresses, pillows, bedclothes, carpets, work clothes, children’s sleep wear and home furnishings. Needle punched cotton nonwoven fabrics were produced with the specifications, 100 m, 228.6 cm wide, 150 g/m2. Diammonium phosphate (DAP) and urea were used as flame-retardants. The most commonly used flammability tests, the LOI and small open chamber tests were applied to the samples. Flame retardant formulations indicated more effective flammability results [12]. This research included a study of the flammable properties of nonwoven fabrics after coating with a flame retardant. The coating was applied with two different methods, spraying and brushing.

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2. MATERIALS AND METHOD 2.1. Materials The present study focused on 100% PES spunlace nonwoven fabrics produced with different fabric mass per unit areas. Spunlace webs were manufactured firstly by dry laying. In the dry laid web formation, the fibers were initially aerodynamically formed by air and technically bonded by mechanical means. The needle punch method was used in the mechanical bonding process. Some technical properties of the nonwoven fabrics are provided in Table 1. The application area of the samples used in this experimental study was undertaken for relevance to the automotive industry. Since, nonwoven fabrics produced from polyester fibers are usually used for cell coverings, interior door coverings and rear coverings for seats in the automotive industry. Cheap prices, accessibility and suitability of the fibers were important factors affecting the choice of material. PES nonwoven fabric is highly flammable. It burns in air and gives off clean flames without any char residue. In the automotive industry, the use of non-flammable materials is necessary for human safety. Different methods can be used to apply flame retardants [12]. A new chemical is widely used for PES. This new chemical more recently used as a flame retardant on PES nonwoven fabric surfaces is boron. It is abundant in nature in the form of BA or borate salts. In Turkey, there are millions of tons of untouched reserves. [13]. Boric acid is added to PES nonwoven fabric surfaces by applying either with a spray and by scrubbing. Boric acid is known as hydrogen borate, boracic acid, or orthoboric acid. Its chemical formula is H3BO3, sometimes written as B(OH)3. It comes as either a colorless crystal or in white powder form. BA is soluble in boiling water (2.52 g/100ml at 0°C, 4.72g/100ml at 20°C, 5.7 g/100 mL at 25°C and 19.10g/100ml at 80°C and 27.53g/100mL at 100°C) (Table 2). BA is often used as an antiseptic, insecticide, flame retardant, neutron absorber or precursor.

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Table 1. Technical properties of nonwoven fabric

1 2 3 4 5

Weight (g/m2)

Thickness (mm)

Density (g/m3)

45 100 120 150 200

0.57 0.75 0.92 1.12 1.78

0.079 0.098 0.130 0.187 0.199

Tensile Strength (N/50 mm) MD/CD 117/128 125/132 323/422 524/459 581/503

Elongation (%) MD/CD 47/60 50/52 53/53 64/59 82/67

Tear Strength (N/50 mm) MD/CD 37/47 81/59 102/98 145/102 135/125

Table 2. Technical Properties of BA Molar Mess (g-mol-1) Density (g/cm3) Melting Point (°C) Boiling Point (°C) Acidity (pKa) Shape Particle Size

61.83 1.435 170.9 300 9.24, 12.4, 13.3 Powder -0.0063 mm

2.2. Method The experimental process was performed in the order given above. 1. A chemical solution was prepared according to the concentrations set out on the packaging of each of the chemicals. 2. Additives were applied to all the samples using two processes; either spraying or brushing. They were then taken out and dried in the open air. 3. The fixing step was undertaken in certain conditions with a 120ºC hot pressing temperature, 2.3 second hot pressing time and 2.8 MPA hot-pressing pressures.

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Nazan Avcioğlu Kalebek and Emel Çinçik 4. Flammability test was performed to evaluate the LOI value of PES nonwoven fabrics. The average for each samples tree value has been given in Table 2.

A flammability test was performed according to international standard ASTM D2863 (Standard Test Method for Measuring Minimum Oxygen Concentrations). In this test, a minimum value of the oxygen index is obtained in response to heat and flame under controlled conditions. The oxygen index is the minimum concentration of oxygen that will support flaming combustion of a material, initially at 23 ± 2ºC, under test conditions. However, these conditions do not occur under actual fire conditions for fire hazard or fire risk materials. It is the responsibility of the user of this standard to ensure safe handling and compliance with standard health practices and determine the applicability of the regularity of limitations prior to use [14]. The sample was prepared manually in 100 mm length, 10 ± 0.5 mm width and 2 ± 0.25 mm thickness. The surface of the samples needed to be clean and free from flaws that could affect the burning behavior, for example, peripheral molding flashing or burrs from machining. The edges of the samples must be smooth and free from fuzz or material burns left by scissors. The sample was mounted vertically in the center of the chimney so that the top of the specimen was at least mm below the open top of the chimney and the lowest exposed part of the specimen was at least 100 mm above the top of the gas distribution device at the base of the chimney. Gas mixing was set to flow controls so that an oxygen/nitrogen mixture was achieved. The gas flow purge was allowed for at least 30 seconds prior to ignition of each specimen, and the flow was maintained without change during the ignition and combustion of each specimen. At the end of the test, the burning behavior was noted as dripping, charring, erratic, burning, glowing combustion, or after-glow [14]. BA was applied to the nonwoven fabric surface in two ways. One of them was by spraying and the other by brushing. They were photographed with a microscope both with and without the applied chemicals. The

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microscopic view identified not only the orientation of the fibers, but also the presence of individual fibers forming aggregates.

3. EXPERIMENTAL RESULTS 3.1. LOI Values Table 3 indicates the change in LOI values before and after the additives at relevant concentrations. This is one of the important indexes to measure FR. It can be seen that the LOI values of the relevant samples were higher without chemicals and reached the maximum of 24.7 for additives applied by spraying and 26.8 for additives applied by brushing. The presence of FR additives resulted in increasingly significant LOI values in each of the samples. Furthermore, it implied that lower LOI values resulted in higher flammability and vice versa. Table 3. LOI Values Mass per unit area (g/m2)

Without Chemicals

With Spraying

45 100 120 150 200

16.2 18.4 18.6 18.9 20.3

20.6 22.5 23.2 24.0 24.7

With Brushing 22.0 24.1 25.5 26.4 26.8

A gradual increase in LOI values was observed as the mass per unit area rose from 45 to 200 g/m2 for all samples, with and without the application of the BA flame retardant. Higher fabric mass per unit area can be obtained with orientation of the greater random distribution of the fibers in the nonwoven construction. Obtaining lower LOI values for flammability behavior is extremely dependent on the adhesion of the lower fibers in the construction of the nonwoven material. If the fiber orientation on the surface of the nonwoven material was low, a low LOI value was

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achieved on completion of the flammability test. In this sense, there is a gradual increase in flammability behavior between 45 and 200 g/m2 confirming the perfect compaction of the PES fibers in web formation during the manufacturing the needle-punch nonwoven fabrics. This indicates that the combination of the textile surfaces of nonwoven fabrics and FR can provide a greater contribution to flame retardancy. Higher LOI values mean that a higher quantity of oxygen is required to generate a flame.

3.2. Microscopic View Polyester nonwoven fabrics are produced by a process of needlepunching directly from the fibers after formation of the web. It is, therefore, not only porous, hairy, and thicker, but it also displays a disordered structure. These structural differences influence the absorption of additives, for example, BA chemicals. In Figure 1, the first sample shown is without BA, the second and third samples are treated by spraying BA and brushing BA, respectively. As can be seen in Figure 1, the samples generally display a rough surface appearance. Surface disorientation is important for greater absorption of chemicals because a more irregular surface is more absorbent and the fabric has a larger surface area.

A

B

C

Figure 1. Nonwoven fabrics a) without chemicals, b) with BA applied by spraying, c) with BA applied by brushing.

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CONCLUSION AND DISCUSSION A chemical solution of boric acid was successfully applied to the surfaces of 100% PES nonwoven fabrics by spraying and brushing. On conclusion of the flammability test, the following results were obtained; 

 





The addition of boric acid prolongs burning time and hence reduces the LOI values as a result of the boric acid based flame retardant. An increase in LOI values with the aid of boric acid is considered an efficient fire retardant. An increase in the mass per unit area simultaneously increased the absorption of the boric acid based flame retardant. More boric acid based FR was absorbed by the impregnated 100% PES nonwoven fabrics by brushing rather than by spraying. Therefore, nonwoven fabrics which had the boric acid applied by brushing show the best flame retardancy results. According to the flammability test results (Table 1), it was found that 100 PES% nonwoven fabrics which had the boric acid based flame retardant applied by either method; spraying or brushing, are considered appropriate for reducing flammability. Over the last few years, green or eco-friendly composites that are reinforced with natural fibers have been developed. because the automotive industry exhibits a high potential due to the need for increased human safety and the search for alternative environmentally green recycled materials.

REFERENCES [1] [2]

Corbman, B. P. (1983). Textiles Fiber to Fabric. 6th ed. McGraw Hill Inc. 594 p. ISBN: 0070131376. Klein, W. (1994). Processing of Man-made Fibres. The Textile Institute. ISBN:1870812611.

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Aydın, D.Y., Gürü, M., Ayar B. and Çakanyıldırım Ç. (2016). Applicability of Boron Compounds as Flame Retardants and High Temperature Resistants, Journal of Boron, 1(I): 33-39. [4] Yang, C. Q., He Q., Lyon R. E. and Hu, Y. (2010). Investigation of the flammability of different textile fabrics using a micro-scale combustion calorimeter, Polymer Degradation and Stability, 95, 108115. [5] Allen, J. G., Stapleton, H. M., Vallarino, J., McNelly, E., McClean M. D., Harrad, S. J., Rauert, C. B. and Spengler, J. D. (2013). Exposure to Flame Retardant Chemicals on Commercial Airplanes. Environmental Health, 12(XVII): 2-12. [6] Kozlowski R., and Wladyka-Przybylak, M. (2008), Flammability and Fire Resistance of Composites Reinforced by Natural Fibers, Polymers for Advanced Technologies, 19: 446-453. [7] Fatima S., and Mohanty, A. R. (2011). Acoustical and Fire-Retardant Properties of Jute Composite Materials. Applied Acoustics, 72: 108114. [8] Allen, J. G., Stapleton, H.M., Vallarino, J., McNeely, E., McClean, M.D., Harrad, S.J., Rauert C.B. and J.D. Spengler, (2013), Exposure to Flame Retardant Chemicals on Commercial Airplanes, Environmental Health, 12:17-29. [9] Cardoso, I. and Gomes, J.R. (2009). The Application of Microcapsules of PCM in Flame Resistant Non-Woven Materials, International Journal of Clothing Science and Technology, 21(II/III): 102-108. [10] Kozlowski, R., Mieleniak, B., Muzyczek M. and Kubacki A. (2002). Flexible Fire Barriers on Natural Nonwoven Textiles, Fire and Materials, 26: 243-246. [11] Uppal, R., Mercemik H. and Bhat, G. (2010). Flame Retardant Cotton Based High Loft Nonwovens, Beltwide Cotton Conference, 47 January 2010. New Orleans. Louisiano, USA. [12] Shi, Z., Fu, R., Agathopoulos, S., Gu, X., Zhao, W. (2012). Thermal conductivity and fire resistance of epoxy molding compounds filled with Si3N4 and Al(OH)3. Materials and Design, 34: 820-824. [3]

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[13] Yang, C. Q., He, Q., Lyon, R. E., Hu, Y. (2010). Investigation of the flammability of different textile fabrics using a micro-scale combustion calorimeter. Polymer Degradation and Stability, 95: 108115. [14] ASTM D2863. (2017). Standard Test Method for Measuring the Minimum Oxygen Concentration (Oxygen Index).

In: Nonwoven Fabric Editor: Rembrandt Elise

ISBN: 978-1-53617-587-5 © 2020 Nova Science Publishers, Inc.

Chapter 6

NONWOVEN GEOTEXTILES IN CIVIL AND ENVIRONMENTAL ENGINEERING José Ricardo Carneiro*, Filipe Almeida, David Miranda Carlos and Maria de Lurdes Lopes Construct-Geo, Faculty of Engineering, University of Porto, Porto, Portugal

ABSTRACT Geotextiles are polymeric materials widely used in the construction of many civil and environmental engineering structures, such as waste landfills, roads, railways, dams, reservoirs or coastal protection structures. These materials can perform many different functions and are able to be employed in a wide range of applications. The advantages of using geotextiles (as replacement for other construction materials) typically include: ease of installation, low cost, high efficiency and versatility, and low environmental impact. According to their structure, the geotextiles can be divided into three types: woven, nonwoven or knitted, nonwoven being the most used type. This chapter addresses many aspects about nonwoven geotextiles, including their history,

*

Corresponding Author’s E-mail: [email protected].

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J. R. Carneiro, F. Almeida, D. M. Carlos et al. common raw materials, manufacturing process, properties, functions and applications. The potential use of recycled nonwoven geotextiles towards a more sustainable construction will also be discussed.

Keywords: geotextiles, nonwoven, civil engineering, environmental engineering, sustainable construction

1. INTRODUCTION Geosynthetics are construction materials widely used in the domains of civil and environmental engineering. Nowadays, many different types of geosynthetics are available (e.g., geotextiles, geomembranes, geogrids, geocomposites, etc.), geotextiles being the most used (in part due to their high versatility and relatively low cost). The main raw materials employed in the manufacture of geotextiles are synthetic polymers (e.g., polypropylene or polyethylene terephthalate), which result from the processing of crude oil. Notwithstanding, natural materials such as cotton, wool, sisal or jute can also be used in the development of geotextiles targeting their application in temporary solutions. The geotextiles can be divided into three main categories: woven, nonwoven or knitted. Woven geotextiles result from a traditional weaving process, typically by interlacing two or more sets of components (e.g., filaments, yarns or tapes). In nonwoven geotextiles (most used type of geotextiles), staple fibres or continuous filaments are bonded by using mechanical, thermal or chemical processes. Finally, in knitted geotextiles, one or more yarns are interloped by a knitting process [1]. This chapter presents relevant information on nonwoven geotextiles, and is divided into five sections. The current section gives a brief overview of geotextiles and describes the contents of the other sections. Section 2 addresses the history, raw materials, manufacturing process and properties of nonwoven geotextiles. Sections 3 and 4 deal with the use of nonwoven geotextiles in civil and environmental engineering, describing their functions and applications. Finally, section 5 approaches the possible

Nonwoven Geotextiles in Civil and Environmental Engineering 157 development of recycled nonwoven geotextiles to achieve a more sustainable construction.

2. NONWOVEN GEOTEXTILES 2.1. Brief History The advent of synthetic polymers in the 1940s had a decisive influence on the development of geotextiles. The woven geotextiles appeared in the 1950s, while the nonwovens appeared in the 1960s [1]. The great success achieved by the nonwoven geotextiles was essentially due to technical (ease of installation, high efficiency and high versatility) and economical (relatively low cost) advantages. The development and expansion of the geotextile market led, in the 1980s, to the emergence of many new geosynthetics. With the extensive use of geotextiles (and other geosynthetics) in civil engineering projects, the academic community and industry fostered forums to discuss a wide range of issues related to these construction materials, including their possible applications, short-term behaviour, service life, durability or sustainability. Within this process, three moments must be highlighted: the International Conference on the Use of Fabrics in Geotechnics held in Paris, France in 1977, the foundation of the International Geotextile Society in Paris in 1983 (which name was changed to International Geosynthetics Society, in 1994) and the release of the international journal Geotextiles and Geomembranes (1987). From the 1990s onward, a series of standards related to geosynthetics have been published by different international organizations, namely the International Organization for Standardization (ISO), the American Society for Testing and Materials (ASTM) or the European Committee for Standardization (CEN).

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2.2. Raw Materials Nonwoven geotextiles can be produced from natural or synthetic sources, the latter being the most common (Figure 1). Natural materials such as cotton, wool, sisal or jute can be used as raw materials. However, due to their biodegradability, they can only be employed for manufacturing geotextiles for short-term applications. In addition, geotextiles produced from natural sources typically have low mechanical strengths (compared with materials made from synthetic polymers).

Nonwoven geotextiles

Chemical additives

Base polymers (Thermoplastics)

Polyolefins

Polyesters

Polyamides

Antioxidants

Ultraviolet stabilisers

Others

Figure 1. Synthetic raw materials used for manufacturing nonwoven geotextiles.

The most used raw materials for manufacturing geotextiles are thermoplastics, which are synthetic polymeric compounds that become soft when heated and hard when cooled down. Polyolefins (e.g., polyethylene or polypropylene), polyesters (e.g., polyethylene terephthalate) and polyamides (e.g., nylon 6 or nylon 66) are the thermoplastics typically used for producing geotextiles. Their base monomer is formed mostly by carbon and hydrogen (polymers are macromolecules formed by the repetition of small units: monomers). Oxygen and nitrogen can also be found in some monomers (Figure 2). Polypropylene is the most commonly used thermoplastic in the manufacture of geotextiles, having a good resistance against acids, alkalis and most solvents, but a relatively low resistance against oxidation and

Nonwoven Geotextiles in Civil and Environmental Engineering 159 ultraviolet radiation. In addition, it has a good microbiological resistance and is relatively inexpensive. Polyethylene terephthalate, which is the second most used thermoplastic in the manufacture of geotextiles, also has a good chemical resistance against acids and many solvents. However, it has a relatively poor resistance against hydrolysis in alkaline conditions and is more expensive than the polyolefins. The main advantages of polyethylene terephthalate over polyolefins include its higher mechanical strength and higher resistance against ultraviolet radiation. H

H

H

H

C

C

C

C

H

H

H

CH3 n

n

(a)

(b) H

O C

O

H C

C

C

C

C

O C

C O

CH2CH2

H

H

n

(c) O C

H (CH2)5

N

n

(d) O

C

(CH2)4

O

H

C

N

H (CH2)6

N

n

(e)

Figure 2. Monomers of: (a) polyethylene; (b) polypropylene; (c) polyethylene terephthalate; (d) nylon 6; (e) nylon 66.

Polyethylene and polyamides (such as nylon 6 or nylon 66) are seldom used in the development of geotextiles. Polyethylene has a good chemical resistance, being more resistant against oxidation than polypropylene. However, it is normally more expensive. Polyamides also have relatively

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good chemical resistances. Their main drawbacks are the limited resistance against acids and weathering. Chemical additives are often added to synthetic polymers in order to improve their properties, processing and performance. The additives are usually classified according to their function. There is a wide range of compounds available for carrying out different functions (e.g., antioxidants, thermal stabilisers, ultraviolet stabilisers, plasticizers or pigments). Antioxidants can be used to protect polymeric products against oxidative degradation induced by heat (thermo-oxidation) or by ultraviolet radiation (photo-oxidation). Thermal stabilisers can contribute to preventing or reducing the degradation of polymers exposed to high temperatures. Ultraviolet stabilisers can enhance the resistance of polymers against solar radiation. Plasticizers are used to increase flexibility and can also contribute to increasing resistance against impact. Pigments are added to provide colour to polymeric products and, in some cases (e.g., carbon black) can also protect them against solar radiation.

2.3. Manufacturing Process The production of nonwoven geotextiles often includes three main phases: the preparation of the polymeric mixture (base polymer plus chemical additives), the development of the components (often continuous filaments or staple fibres), and the use of those components to manufacture the geotextiles. The manufacturers often purchase the base polymers and additives from the chemical industry, which are usually supplied in the form of pellets or granules [2]. The continuous filaments result from the extrusion of the polymeric mixture through a bank of extrusion dies or spinnerets, followed by longitudinal drawing. For producing staple fibres (usually with a length between 20 and 300 mm [1, 3]), continuous filaments are cut. After being prepared, these components are laid down on a conveyor belt (brattice) in the form of a randomly orientated loose web. The final nonwoven structure

Nonwoven Geotextiles in Civil and Environmental Engineering 161 results from the bonding process of the loose web, which can be achieved through a mechanical, chemical or thermal process [2, 3].

2.3.1. Mechanical Bonding The process of mechanical bonding involves passing the loose web (forwarded by the brattice) through a needle loom incorporating thousands of barbed needles that penetrate over the entire thickness of the web, promoting the interlacing of the components (Figure 3). The characteristics of the formed nonwoven structure are influenced by the amount and distribution of the barbed needles. The textile arising from the mechanical bonding process can be submitted to drawing in the machine or crossmachine directions of production using, respectively, godets or tenter frames [2, 3]. Irrespective of the use of continuous filaments or staple fibres as components, the final fabrics are known as needle-punched nonwoven geotextiles (Figure 4).

3 4

2

1

6

7 5 6 Needle detail

8

A 1

Loose web

A Supporting part of the needle

2 Stripping grid

B Barb

3 Needle support

C Needle point

4 Needle 5 Supporting grid

B

6 Draw-off system 7 Delivered needled fabric 8 Feed conveyor

C

Figure 3. Manufacturing process of needle-punched nonwoven geotextiles (based on [3]).

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Figure 4. Scanning electron microscopy image of a needle-punched nonwoven geotextile.

2.3.2. Thermal Bonding Thermal bonding (or heat bonding) is mainly used when continuous filaments are employed to produce the nonwoven geotextiles and involves passing the loose web through hot calenders or linear ovens, depending on the chemical composition of the filaments. Besides single polymer filaments, there are also filaments made with different polymers (e.g., a polypropylene core surrounded by a polyethylene sheath) [3]. The bonding of single polymer filaments is accomplished by submitting the loose web to hot calenders, which allow melting of the filaments’ surface, fostering the fusion of their crossover points. In the case of filaments made from different polymers in which the polymer used in the sheath has a lower melting point than the polymer employed in the core, the principle of the bonding process is similar. However, while passing through a linear oven, the goal is only to melt (and merge) the filaments’ sheating [2, 3]. The fabrics resulting from this bonding process are designated as thermallybonded nonwoven geotextiles (Figure 5).

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Figure 5. Scanning electron microscopy image of a thermally-bonded nonwoven geotextile.

2.3.3. Chemical Bonding The bonding of continuous filaments or staple fibres can be achieved by adding (by spraying or dipping) a chemical binder (e.g., an acrylic resin) to the loose web [2]. This bonding process, which results in the production of chemically-bonded nonwoven geotextiles, is not very common, since it is quite expensive and can lead to rather stiff materials [3]. In some situations, chemical bonding is performed after mechanical bonding to improve the bonds within the nonwoven structure [2].

2.4. Properties The suitability of nonwoven geotextiles to perform certain functions in civil and environmental engineering depends on their properties, which are often divided into physical, mechanical and hydraulic (Figure 6). Durability is also a crucial issue, since the materials must have a good resistance against many different degradation agents.

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Physical    

Mass per unit area Thickness Pore size Etc.

   

Mechanical

Hydraulic

Tensile strength Puncture strength Tearing strength Etc.

 Water permeability normal to the plane  In-plane water permeability

Figure 6. Main properties of nonwoven geotextiles.

2.4.1. Physical Properties 2.4.1.1. Mass Per Unit Area Mass per unit area is expressed in grams per square meter (g.m-2) and, in the case of geotextiles, usually ranges from 100 to 1000 g.m-2 [2, 3]. This property, besides providing an idea about the expected cost of the materials, can also be used as an indicator of mechanical properties, such as tensile and puncture strengths. In general, the higher the mass per unit area, the higher the tensile [2, 3] and puncture strengths [3] of nonwoven geotextiles. The mass per unit area of geotextiles can be determined according to EN ISO 9864 [4] or ASTM D5261 [5]. 2.4.1.2. Thickness Thickness is usually measured in millimetres (mm) and normally falls in the range between 0.25 and 7.5 mm for geotextiles [6]. Considering materials with similar structures, an increase in thickness often results in an increase in mass per unit area, and higher mechanical strengths. Hydraulic properties, such as in-plane water permeability, are also dependent on thickness. The determination of thickness can be performed according to EN ISO 9863-1 [7] or ASTM D5199 [8]. 2.4.1.3. Pore Size The pore sizes of geotextiles, measured in micrometres (µm), usually fall in the range of 1 to 1000 µm [3]. Unlike other geosynthetics with more regular structures, nonwoven geotextiles usually have a wide range of pore sizes and their distribution is irregular. The size and distribution of pores

Nonwoven Geotextiles in Civil and Environmental Engineering 165 are features of utmost importance in applications where geotextiles are used as filters. Due to its relation with the design of filters, the pore size distribution of geotextiles is considered by some authors as an hydraulic property [1, 3, 6]. The characterisation of the pore sizes of geotextiles can be carried out in accordance with EN ISO 12956 [9] and ASTM D4751 [10].

2.4.2. Mechanical Properties 2.4.2.1. Tensile Strength Tensile strength, usually expressed in kilonewtons per linear meter (kN.m-1), is one of the most important mechanical properties of geotextiles, being influenced by the manufacturing process (structure), base polymer and by the presence of some chemical additives, such as carbon black. For nonwoven geotextiles, this property commonly ranges from 5 to 20 kN.m-1, but can achieve values of 50 kN.m-1, with strains at rupture load between 30 and 80% [2, 3]. The tensile behaviour of nonwoven geotextiles can be characterised according to EN ISO 10319 [11] and ASTM D4595 [12]. 2.4.2.2. Puncture Strength Puncture strength, which is usually expressed in Newtons (N), is an important mechanical property, especially for applications in which nonwoven geotextiles are going to perform filtration or protection functions. This property can be evaluated under static or dynamic conditions (impact tests). The static puncture tests can be carried out according to EN ISO 12236 [13] or ASTM D6241 [14], whereas impact tests can be performed following EN ISO 13433 [15]. 2.4.2.3. Tearing Strength Tearing strength represents the capability of a geotextile to support stresses that may lead to the propagation of tears (often induced during installation) and is usually expressed in Newtons (N) [1]. In some applications (e.g., geotextiles included in geosystems used for coastal

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protection), tears may also occur during service life. The tearing strength of geotextiles can be evaluated according to ASTM D4533 [16].

2.4.3. Hydraulic Properties 2.4.3.1. Water Permeability Normal to the Plane Nonwoven geotextiles are permeable materials, being the water permeability normal to the plane a relevant property, for example, when considering the function of filtration. The water permeability behaviour normal to the plane is influenced by the pore sizes of the nonwoven geotextiles (and their distribution), which depend on their manufacturing process. Indeed, for nonwoven geotextiles with similar masses per unit area, those thermally-bonded tend to have a lower water permeability than those needle-punched [3]. The methods included in EN ISO 11058 [17], EN ISO 10776 [18], ASTM D4491 [19] and ASTM D5493 [20] can be used to determine the water permeability normal to the plane of geotextiles. 2.4.3.2. In-Plane Water Permeability In-plane water permeability refers to the ability of nonwoven geotextiles to allow the flow of water in their plane, being relevant for applications in which these materials perform drainage functions. This property is affected by the thickness of the geotextiles, which often depends on the level of normal stresses applied to them and their compressibility [3]. In-plane water permeability behaviour of geotextiles can be characterised by the methods presented in EN ISO 12958 [21], ASTM D4716 [22] and ASTM D6574 [23].

3. FUNCTIONS OF NONWOVEN GEOTEXTILES Nonwoven geotextiles are the most versatile type of geosynthetics considering the wide range of functions that they are able to perform in civil and environmental engineering structures. These materials can carry

Nonwoven Geotextiles in Civil and Environmental Engineering 167 out many different functions, such as filtration, drainage, separation, protection, reinforcement or superficial erosion control. Unlike most of the other geosynthetics, nonwoven geotextiles can perform more than one function simultaneously.

3.1. Filtration To act as a filter, nonwoven geotextiles must have the ability to retain soil, or other particles, when subjected to hydrodynamic actions, besides allowing fluids to pass into or through their structure [24]. Figure 7 illustrates a nonwoven geotextile between a soil and a granular drainage element, in which the geotextile is allowing the flow of water (in the direction normal to its plane) from the soil into the drainage element. This way, the geotextile is preventing the uncontrolled migration of soil particles, i.e., internal erosion of soil, which is commonly known as piping. The most relevant properties of nonwoven geotextiles related to the function of filtration are water permeability normal to the plane, and the size and distribution of pores. It is also important to evaluate if there is a risk of pore clogging during the service life of the materials, restricting the correct water flow. 1 Water flow direction

2

1 Soil 2 Geotextile 3

3 Granular drainage element

Figure 7. Nonwoven geotextile performing the function of filtration.

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3.2. Drainage When performing the drainage function, nonwoven geotextiles must be able to collect and transport rainwater, groundwater and/or other fluids within their plane [24]. Therefore, a balanced soil-geotextile system, in which the fluids flow with limited losses of soil particles, must be achieved [6]. Figure 8 shows a nonwoven geotextile, installed between a concrete element and soil, allowing the drainage of the water that flows through the soil. The water drainage is properly ensured when the nonwoven geotextiles have a water flow capacity in their plane (which highly depends on the thickness and compressibility of the nonwoven structure) compatible with the adjacent soil permeability. In addition, nonwoven geotextiles must guarantee a proper filtration of water when it flows from the soil into the geotextile core. 2 Water flow direction

1

3 1 Soil 2 Geotextile

3 Concrete element

Figure 8. Nonwoven geotextile performing the function of drainage.

3.3. Separation Nonwoven geotextiles can be used to prevent mixing of two adjacent materials (soils and granular materials with different grain size distributions), i.e., to perform the function of separation [24]. Figure 9 illustrates the application of a nonwoven geotextile to separate a granular

Nonwoven Geotextiles in Civil and Environmental Engineering 169 material from a soft soil. In this case, the geotextile avoids both the penetration of the granular material in the adjacent soft soil and the pumping of fine particles from the soil to the granular layer. Thus, the integrity and thickness of the layer of granular material can be preserved during the service life of the application. Many properties of nonwoven geotextiles (e.g., pore size, tensile behaviour or puncture strength) are important considering the function of separation. Their suitability to conduct this function also depends on the characteristics of the soils and aggregates that they are going to contact with. 1

2 3

1 Granular fill 2 Geotextile 3 Soil

Figure 9. Nonwoven geotextile performing the function of separation.

3.4. Reinforcement The reinforcement function consists in using the stress-strain characteristics of the nonwoven geotextiles to improve the mechanical behaviour of soils and granular materials [24] (Figure 10). The geotextiles play the role of reinforcement in two main situations: when they are installed between two layers of soil exposed to different stress levels (geotextiles are submitted to tensile stresses while the different stress levels are withdrawn, leading to the global reinforcement of the structure), and when they are installed inside a soil to withstand tensile stresses, increasing the overall ability of the structure to resist against such stresses [25].

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The short and long-term mechanical properties of geotextiles (e.g., stress-strain behaviour) are of utmost importance when considering the reinforcement function. In addition, the properties of soil-geotextile interaction have also to be taken into account. Indeed, the efficiency in transmitting the tensile stresses from the soil to geotextiles (by friction, adhesion, interlocking or confinement), which affects the behaviour of the reinforced soil structure, depends on those interaction properties. It is important to mention that geotextiles are not the geosynthetics typically used for reinforcement, being that role normally ascribed to geogrids or reinforcement geocomposites. 1

2

T

3

P

F

S S

S T

1 Geotextile 2 Slope 3 Potential failure surface

T - tensile force; S - shear force; P - pullout force; F - friction force

Figure 10. Nonwoven geotextile performing the function of reinforcement.

3.5. Protection A nonwoven geotextile conducts the function of protection when preventing or limiting the occurrence of local damage in the element or material that is expected to be protected [24]. In Figure 11, the two layers of geotextile must have the capability to absorb and distribute the stresses and deformations induced by the geotechnical materials (granular fill and soil) to the geomembrane (the material to be protected). Puncture strength

Nonwoven Geotextiles in Civil and Environmental Engineering 171 and thickness are two relevant properties when considering the function of protection. 1

3 4 3 2

1 Granular fill

2 Soil 3 Geotextile

4 Geomembrane

Figure 11. Nonwoven geotextile performing the function of protection.

3.6. Superficial Erosion Control The function of superficial erosion control consists in preventing or limiting the movement of soil, or other materials, on the surface of geotechnical structures [24]. In these structures, superficial erosion is normally provoked by the action of atmospheric agents. When considering hydraulic structures, hydrodynamic actions are often the main cause of superficial erosion. Nonwoven geotextiles can provide effective filtration and drainage for water flows and prevent the soil particles from washing out, thereby, contributing to avoid soil erosion. As shown in Figure 12, nonwoven geotextiles can be the superficial erosion control element (Figure 12a) or be a part of the superficial erosion control system (Figure 12b). In the latter, they combine the functions of superficial erosion control, filtration and drainage. Therefore, the properties relevant for filtration and drainage are also important for the superficial erosion control function. In addition, for long-term applications, the weathering resistance of the geotextiles can also be a relevant issue to be considered.

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Rain

Rain 2

2

3

1

1

1 Soil

1 Soil

2 Geotextile

2 Geotextile

3 Erosion control element (a)

(b)

Figure 12. Nonwoven geotextile performing the function of superficial erosion control: (a) geotextile as the erosion control element; (b) geotextile as a part of the superficial erosion control system.

4. APPLICATIONS OF NONWOVEN GEOTEXTILES The use of nonwoven geotextiles in civil and environmental engineering structures has become a common practice in the last decades. Their high versatility and efficiency, associated with the ease of installation and relatively low cost, make them suitable construction materials to perform many different functions in various applications. This section will describe the most common uses of these materials in four main different application areas: geotechnical, transportation, hydraulic and environmental engineering. The number of applications of nonwoven geotextiles is very high and in constant growth, therefore, this section presents only the most common applications of these materials.

Nonwoven Geotextiles in Civil and Environmental Engineering 173

4.1. Applications in Geotechnical Engineering Structures Geotextiles can be applied in many geotechnical engineering structures, such as embankments, earth retaining structures, slopes and foundations. The geotextiles are used in these structures to perform functions of filtration, drainage, separation, reinforcement and superficial erosion control. The main limitations found by geotechnical engineers in the construction of embankments are the lack of backfill soils with proper properties and the existence of saturated soft foundation soils. To overcome these limitations, some conventional methods are available, but they are too expensive and time-consuming. The application of geotextiles can help to solve these issues. In Figure 13, two examples of the use of geotextiles in embankments are schematically represented. The embankment over a soft foundation soil shown in Figure 13a has vertical drainage elements, which are usually strips of nonwoven geotextiles (or columns of drainage materials coated with geotextiles) aiming the drainage and/or filtration of the water away from the soft foundation soil (therefore, accelerating its consolidation). In addition, the embankment has a granular drainage layer wrapped around by geotextiles. The main functions of these geotextiles are to filter the water coming from the base of the embankment during the consolidation of the soft foundation soil (and/or the seepage water coming from the embankment), and to keep the granular drainage layer separated from the embankment filling material and the soft foundation soil. The slopes of the embankment can also be protected with geotextiles in order to control superficial erosion (for long service lives, the materials must have a good resistance against solar radiation and other weathering agents). The second example represented in Figure 13b corresponds to an embankment constructed with poor soil. In this case, the embankment has several layers of geotextiles to reinforce the filling material. In addition, the geotextiles can also control superficial erosion in the slopes of the embankment. Despite the possible use of geotextiles for reinforcing poor

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soils, the geosynthetics most commonly used for soil reinforcement are geogrids and geocomposites.

1

1

Embankment 2 Granular drainage layer 2

3 Soft foundation soil

1 Geotextile (erosion control) 2 Geotextile (filtration, drainage, separation) 3 Geotextile strips (vertical drainage)

(a)

1

1 Embankment 2

Foundation soil 1 Geotextile (erosion control) 2 Geotextile (reinforcement)

(b)

Figure 13. Embankments: (a) over a soft foundation soil; (b) made with poor soil.

In earth retaining structures, the geotextiles can be incorporated in the backfill material to obtain a reinforced soil, which behaves like a gravity structure and withstands the pressure imposed by the surrounding unreinforced soil. Figure 14 illustrates some examples of earth retaining structures reinforced with geotextiles.

Nonwoven Geotextiles in Civil and Environmental Engineering 175

1 Backfill/filling material 2

1 Backfill/filling material 2

3

3

Foundation soil

Foundation soil 1

2

1

Wraparound facing geotextile (erosion control, filtration) Geotextile (reinforcement)

3 Geotextile (reinforcement, separation, drainage)

Geotextile (filtration, drainage) Geotextile (reinforcement)

3

Geotextile (reinforcement, separation, drainage)

4

Drainage element

5

Gabion facing

(b)

1 Backfill/filling material 2

Foundation soil 1

4

2

(a)

3

5

1 Backfill/filling material 2

5

3

4

Foundation soil

5

4

1

Geotextile (filtration, drainage)

2 Geotextile (reinforcement)

2

Geotextile (reinforcement)

3

Geotextile (reinforcement, separation, drainage)

3

Geotextile (reinforcement, separation, drainage)

4

Drainage element

4 Drainage element

5

Concrete facing

Geotextile (filtration, drainage)

5 Modular blocks facing

(c)

(d)

Figure 14. Earth retaining structures reinforced with geotextiles: (a) with wraparound geotextile facing; (b) with gabion facing; (c) with concrete panel facing; (d) with modular blocks facing.

The bottom layer of geotextile (nº 3 in Figure 14) can be used to separate the backfill material from the foundation soil. In addition, it can also drain the water from the base of the structure. When the foundation is a soft soil, the bottom layer of geotextile can act in a similar way as described for embankments. Geotextiles can also be applied to ensure the stability of the backfill materials at the back of the facing elements of the earth retaining structures. In structures with wraparound facing (Figure 14a), the geotextile is used to prevent the surface erosion of the structure and to

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filter the water coming from the backfill material. Regarding the structures with gabions, concrete or modular blocks (Figures 14b, 14c and 14d), the geotextile placed at the back of those elements is used to transport the water from the backfill material to the drainage elements (nº 4 in Figures 14b, 14c and 14d). In addition, it can also filter the water that will pass through the gabions, the joints of modular blocks or drains in the concrete facing. The main issues about natural slopes are their global stability (depending on potential failure surfaces in soil) and the local stability of their surface (which is influenced by the erosion of the soil particles caused by the action of atmospheric agents) (Figure 15a). Geotextiles can be used to reinforce slopes (increasing their stability) and to prevent the occurrence of erosion at their surface (Figure 15b). The concept of applying geotextiles in natural slopes is similar to what was described for earth retaining structures. Rain

2

Rain

3

2

1

1

1 Natural soil

1 Geotextile (reinforcement)

2 Potential failure surface

2 Geotextile (erosion control)

3 Erosion of slope surface

(a)

(b)

Figure 15. Slopes: (a) natural slope; (b) slope reinforced with geotextiles.

The characteristics of the foundation soils are very relevant to the safety and serviceability of many civil engineering structures (embankments, earth retaining structures, pavements of transportation structures, dams, footings of buildings or bridges abutments, among

Nonwoven Geotextiles in Civil and Environmental Engineering 177 others). When foundation soils have a bearing capacity unable to withstand the loads imposed by the structures (e.g., soft soils, cohesive soils, soils with low California Bearing Ratios), it is necessary to adopt measures to improve their behaviour. Usually, the improvement of the bearing capacity of poor foundation soils can be accomplished by preloading, dynamic consolidation, lime/cement mixing or by the replacement of a thick superficial layer of soil by a soil of better characteristics (often a goodquality granular material). However, due to financial restrictions or lack of suitable building materials near the construction area, these approaches are not always used. The application of geotextiles can be an alternative to improve the behaviour of poor foundation soils. For that purpose, geotextiles can be used with a layer of a good-quality granular material (as shown in Figure 16). The geotextiles improve the bearing capacity of the foundation soil, reducing its settlements by distributing the loads over a much broader area. These materials can be applied inside the good-quality granular layer (nº 2 in Figure 16) and/or between that layer and the foundation soil (nº 1 in Figure 16). In the latter case, the geotextile performs both reinforcement and separation functions, also being able to drain the water coming from the foundation soil (which is important for the consolidation of soft soils). The drainage of water can also be provided by the inclusion of vertical drains as shown in Figure 13a. 4

3

2 1 Foundation soil 1 Geotextile (reinforcement, separation)

2 Geotextile (reinforcement) 3 Good-quality granular layer 4 Footing of a building or bridge abutment, etc.

Figure 16. Cross-section of a foundation soil reinforced with geotextiles.

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4.2. Applications in Transportation Engineering Structures Transportation engineering structures, such as roads, railways, airports, parking lots, intermodal facilities, container ports or tunnels, are designed to aid population mobility and ensure freight transport. The use of geotextiles in embankments, earth retaining structures, slopes or foundations, which are engineering projects that are developed in the domain of transportation structures, have been formerly addressed in section 4.1. In addition, when considering transportation structures, geotextiles can also be used in the construction of road pavements, railway tracks, tunnels and drainage systems, being able to perform functions of separation, filtration, drainage, protection, reinforcement and superficial erosion control. The construction of pavements (e.g., in roads, airports, parking lots, intermodal facilities or container ports) follows a well established structure, where the thickness of the constituent layers are a relevant variable. Pavements are formed by one or several layers of good-quality granular materials (base and sub-base coarse layers) placed over the foundation soil (which can be, for example, a natural soil, a stabilised soil or an embankment). At the surface, pavements are usually composed of layers of asphalt (flexible pavement) or a layer of concrete (rigid pavement), or layers of both materials (semirigid pavement) (Figure 17). 1

2

3

Granular base Granular sub-base

4

5

5

Foundation soil

1

Asphalt layers (flexible pavement)

2 Concrete layer (rigid pavement) 3 Asphalt and concrete layers (semi-rigid pavement) 4 Geotextile (separation, reinforcement, drainage) 5 Drainage element, geotextile (filtration)

Figure 17. Representative cross-section of pavements used in transportation structures.

Nonwoven Geotextiles in Civil and Environmental Engineering 179 The main function of geotextiles in pavements is to act as a barrier between the granular materials and the foundation soil (thus, performing separation), avoiding the penetration of the granular materials into the foundation and, simultaneously, preventing the pumping of fine particles from the foundation into the granular layer (the latter, most frequent in soft foundation soils). Geotextiles placed between the foundation and granular sub-base also have to drain (to the side drainage elements represented in Figure 17) the water rising from the foundation or the seepage water. The geotextiles can also contribute to improving the mechanical behaviour of the pavements. Besides their incorporation between the foundation and the sub-base granular layer (as illustrated in Figure 17), geotextiles can be introduced between the base and sub-base granular layers. Regarding railway tracks, the use of geotextiles is mainly to provide separation between: (a) foundation soil and sub-ballast layer, (b) subballast and ballast layers and (c) old contaminated and new clean ballast layers, when rehabilitating railway tracks (Figure 18). In addition, and similar to what was described for pavements, geotextiles can also perform functions of filtration, drainage and reinforcement. 1 2

4 4 6

Granular sub-base course

5

3 6

Foundation soil

1

New ballast layer

2 Old ballast layer 3 Sub-ballast layer 4 Geotextile (separation, filtration, drainage) 5 Geotextile (separation, reinforcement, filtration, drainage) 6 Drainage element, geotextile (filtration)

Figure 18. Representative cross-section of a rehabilitated railway track.

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In the domain of tunnel technology, geotextiles and geomembranes are often used in the construction of waterproof tunnels (Figure 19). Geomembranes act as fluid barriers and, to guarantee the correct performance of their function, they need to be protected from damaging actions, for which geotextiles are used. In addition, the geotextiles can also function as drains by conducting the water coming from the surrounding materials to the drainage elements (nº 5 in Figure 19). Thereby, the development of excess pore water pressures in the concrete coating of the tunnel is avoided.

Rock/soil 3 4 3

1

2

5

5

1

Concrete lining

2 Shotcrete 3 Geotextile (protection, drainage) 4 Geomembrane (fluid barrier) 5 Drainage element, geotextile (filtration)

Figure 19. Representative cross-section of a tunnel vault.

4.3. Applications in Hydraulic Engineering Structures Within hydraulic engineering structures, geotextiles can be used in earth dams, water reservoirs, irrigation and water transport channels, structures for protecting river banks, drainage elements or coastal protection structures. The action of water (hydrostatic or hydrodynamic) may affect these structures by different mechanisms: (a) internal erosion of

Nonwoven Geotextiles in Civil and Environmental Engineering 181 soil particles caused by the flow of water inside the structure, (b) superficial erosion due to the impact of water and (c) development of excess pore water pressures, which may promote the global instability of the structure. In hydraulic structures, geotextiles may be used for performing functions of filtration, drainage, protection (e.g., of geomembranes) or superficial erosion control (on the banks of the structures). Earth dams are artificial barriers developed in watercourses for retaining large volumes of water. The application of geotextiles in these structures (which can be of various types) can have different purposes. Figure 20 illustrates two examples of earth dams in which geotextiles may perform different functions. Regarding earth dams with a core made from a material with a low permeability (e.g., clay soil) (Figure 20a), the geotextiles can be used: (a) to filter the seepage water from the core to the chimney drain (this way, avoiding the internal erosion of the core and, consequently, the clogging of the drain), (b) to prevent superficial erosion of the downstream dam slope and (c) as an element of the superficial erosion control system of the upstream dam slope (with functions of filtration and drainage), installed beneath the rip-rap layer. The homogeneous earth dams include a lining in the upstream slope to provide waterproofing, which is formed, among other materials, by a geomembrane and two geotextiles (for protecting the geomembrane and for water drainage) (Figure 20b). On the opposite slope, geotextiles can be included in the superficial erosion control system, as described for the earth dams with central core and chimney drain. Water reservoirs and channels are used in water supply, irrigation, flood control and recreation facilities. Shukla and Yin [1] state that unlined water reservoirs and channels can lose 20% to 50% of their water to seepage. Other structures made from concrete, masonry or other materials (as liners) and without waterproof systems can also be ineffective due to water leaks (for example, caused by cracking of the liners or by settlements in adjacent materials).

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2 5

1 Water

Clay core

Earthfill/ rockfill Earthfill/rockfill

1

4

3

Geotextile (filtration, drainage)

2 Rip-rap layer (erosion control) 3 Drainage element, geotextile (filtration) 4 Chimney drain

5 Geotextile (erosion control)

(a)

2 Water

Earthfill/rockfill 1

3 1

5

Geotextile (filtration, drainage) 4

2 Rip-rap layer (erosion control)

7

3 Drainage element, geotextile (filtration)

8

4 Concrete slabs 5 Geomembrane (fluid barrier)

6

6 Geotextiles (protection, drainage) 7 Cold premix layer 8 Gravel layer

(b)

Figure 20. Examples of earth dams: (a) zoned earth dam with central core and chimney drain; (b) homogeneous earth dam.

The current building systems of channels normally include a lining material (to prevent the erosion of the banks and channel bed) waterproofed with a fluid barrier (to prevent leakage of fluids) (Figure 21). The waterproofing of channels is usually done with a geomembrane placed between two geotextiles (used to protect the geomembrane).

Nonwoven Geotextiles in Civil and Environmental Engineering 183

Water Soil 3 1

Geotextile (protection)

2

2 Geomembrane (fluid barrier) 3 Lining material (concrete, masonry, soil) 1

Figure 21. Typical cross-section of a water channel.

The solutions used in the construction of channels can also be applied in water reservoirs. However, nowadays, many water reservoirs only have a geomembrane as lining (Figure 22). Geotextiles are employed to protect the geomembrane and to drain water, arising from possible leaks, to the leakage detection drain.

2

Water Soil

1

3

1

3

Geotextile (protection, drainage)

2 Geomembrane (fluid barrier) 3 Leakage detection drain, geotextile (filtration)

Figure 22. Typical cross-section of a water reservoir.

Drains are hydraulic elements commonly included in civil and environmental engineering structures, being used for the drainage of groundwater and/or seepage water. Among others, geotextiles can be employed in the construction of drains in the following situations: (a) drains on the sides and on the base of road pavements (Figure 17) and

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railway tracks (Figure 18), (b) drainage systems in embankments (Figure 13), earth retaining structures (Figure 14), slopes, tunnels (Figure 19), earth dams (Figure 20) and water reservoirs (Figure 22), (c) landfill leachate collection systems (Figure 26) and (d) drains to accelerate the consolidation of soft foundation soils (Figure 13). The drains can be formed by geotextiles, granular materials and pipes, being the geotextiles used for water filtration (Figure 23). Seawalls, bulkheads, jetties, breakwaters or coastal revetments are examples of coastal protection structures. These structures can be built using many different construction materials, such as rock, masonry, concrete (plain or reinforced), steel and/or timber. Geotextiles can also be used in coastal protection structures, being, for example, employed in the manufacture of geosystems (e.g., geobags, geotubes or geocontainers), which are elements filled with sand or other filling materials (Figure 24). In geosystems, the functions of the geotextiles are to contain the filling materials and to act as filters (during the filling stage and service life of the systems).

1 Soil

3 2

3

1 Granular material 2 Porous pipe 3 Geotextile (filtration) Figure 23. Typical cross-section of a drain.

The geotextiles can also be used as filters, for example, in seawalls and coastal revetments, in which they are installed beneath the lining systems (e.g., rip-rap or prefabricated concrete elements) (Figure 25). The solutions described for coastal protection can be adapted for the protection of banks

Nonwoven Geotextiles in Civil and Environmental Engineering 185 of rivers and lakes or other hydraulic structures exposed to aggressive hydrodynamic actions. 2 2

1

1 Water

1

Geobag

2

Geotextile (filtration, containment)

(a) 2 1 Water

1

Geocontainer or geotube

2

Geotextile (filtration, containment)

(b) Pedestrian zone

2 2

1

1 Soil Water

1

Geobag

2

Geotextile (filtration, containment)

(c)

Figure 24. Typical cross-section of some coastal protection structures: (a) breakwater made with geobags; (b) breakwater made with geocontainers or geotubes; (c) beach revetment made with geobags.

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Pedestrian zone

3 1 Water

1

2

Soil 4

Geotextile (filtration)

2 Coastal material 3 Rip-rap or prefabricated concrete elements

4 Concrete wall

Figure 25. Typical cross-section of a coastal revetment with rip-rap and a geotextile.

4.4. Applications in Environmental Engineering Structures Waste landfills (facilities for the final controlled disposal of waste) are the most common environmental engineering structures in which geotextiles are applied. Depending on the stored waste, there are different types of waste landfills, such as municipal solid waste landfills, industrial waste landfills, mining waste landfills or construction and demolition waste landfills. These structures are often formed by a liner system, a leachate collection and removal system, a gas collection system and a final cover system (these elements are typically found in municipal solid waste landfills). The geotextiles are used in waste landfills mainly to protect the geomembranes and for the filtration of leachates. Figure 26 illustrates a representation of a municipal solid waste landfill, in which many important components (e.g., leachate collection and removal system or gas collection system) were not represented to simplify the draft. The geotextiles can also be used in several of these components to perform functions of filtration, drainage or separation.

Nonwoven Geotextiles in Civil and Environmental Engineering 187 1

4

Waste

2 3

5 6

Soil

5

Soil

Waste

7 8

Waste

Soil

1

Geotextile (filtration)

5

Geomembrane (fluid barrier)

2 Geotextile (protection)

6 Bentonite geocomposite (fluid barrier, protection)

3 Compacted clay liner

7 Geotextile (protection, drainage)

4 Drainage layer

8 Geocomposite (gas drainage, protection)

Figure 26. Typical cross-section of a municipal waste landfill.

5. SUSTAINABLE CONSTRUCTION WITH RECYCLED NONWOVEN GEOTEXTILES 5.1. Introducing Circularity to Nonwoven Geotextiles The path towards a sustainable development involves switching from the linear model of economic growth based on the principle “take-makedispose” to a circular paradigm, in which the materials and products have their lifetime extended as much as possible. Circularity has to be introduced within the different industrial sectors, which includes finding noble roles for the generated residues, instead of incineration or landfilling. The textile sector is responsible for the production of a considerable volume of waste that should be forwarded for valorization actions, including reuse or recycling. There are two types of textile waste: preconsumer and post-consumer textile waste. The pre-consumer waste results from the manufacturing process of garments and other textile products, whilst the textile products discarded by the consumers are considered post-

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consumer waste. These wastes contain natural and/or synthetic raw materials (e.g., polyester, nylon, cotton or wool) that can be used for developing recycled nonwoven geotextiles. In addition to textile waste, plastic waste may also be harnessed for the manufacture of recycled nonwoven geotextiles. This section addresses how textile and plastic waste can be used to produce recycled nonwoven geotextiles and in which applications these materials may be used. The exposition follows Carneiro et al. [26].

5.2. Manufacturing Principles The production of recycled nonwoven geotextiles may use exclusively recycled materials (natural or synthetic) or a mix of recycled with virgin materials, this way enhancing the properties of the final products. Taking into account that geotextiles are buried or covered by liquids in most applications, aesthetic requirements are not a concern, which is an important feature when considering the use of textile waste for manufacturing these materials. For the possible use of textile waste as raw material for manufacturing nonwoven geotextiles, some pre-treatment procedures (such as sorting, cutting or shredding) are needed (Figure 27). These procedures aim the preparation of fibres (or pieces of fabrics) to be used in the formation of a web, which will be bonded by mechanical, thermal or chemical processes to form the nonwoven product. During the web formation step, the addition of virgin fibres can be considered to improve the properties of the final product. The polymers used in plastic packaging (e.g., polyolefins and polyesters) and in geotextiles are similar. Therefore, plastic waste may be a valuable material for producing nonwoven geotextiles. For example, polyethylene terephthalate bottles are discarded in high amounts and can be a possible source for manufacturing fibres for nonwoven geotextiles. The use of these bottles (and other types of plastic waste) also requires some pre-treatment actions (e.g., sorting, separation, removal of labels

Nonwoven Geotextiles in Civil and Environmental Engineering 189 and/or size reduction) (Figure 28). The treated bottles are then melted in order to obtain recycled plastic. Prior to the use of the recycled plastic for developing the nonwoven geotextiles (by the common manufacturing processes described in section 2.3), it is necessary to consider the addition of virgin plastic (in order to improve the properties of the recycled geotextiles) and/or chemical stabilisers (to enhance the resistance of the final products against degradation).

Recycled fibres

?

Virgin fibres

Web forming

Pre-treatment

Bonding

Textile waste

Nonwoven structure

Figure 27. Production of recycled nonwoven geotextiles from textile waste (based on [26]).

Melting

Recycled plastic

Pre-treatment

Polyethylene terephthalate bottles

? ? Nonwoven structure

Virgin plastic

Chemical additives

Figure 28. Production of recycled nonwoven geotextiles from polyethylene terephthalate bottles (based on [26]).

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5.3. Applications and Performance Issues The possible applications for recycled nonwoven geotextiles should take into account the nature and composition of these products, i.e., the fact that recycled raw materials were used in their manufacture. Naturally, this circumstance may address some questions about the reliability of these products. The first issue to be addressed is the non-existence of a full traceability of the products used to obtain the recycled raw materials, which prevents knowing the degradation state of their polymers. Furthermore, the presence of contaminants may be also difficult to ascertain. When using textile waste, it is difficult to manufacture products with regular properties, since the recycled fibres (or pieces of fabrics) can be from many different sources (with distinct properties), affecting the quality and homogeneity of the final product. Moreover, the pre-treatment procedures often induce damage on the textile fibres, leading to geotextiles with lower mechanical resistance than materials made from virgin fibres. The use of plastic waste results in more homogeneous nonwoven geotextiles (compared with textile waste), since new components are manufactured by melting and extrusion. In addition, plastic waste is often a much more homogeneous waste stream than textile waste. The geotextiles made from plastic waste are also expected to haver lower mechanical resistance than materials made from virgin plastic. The durability of nonwoven geotextiles is a crucial issue, since these materials are often applied in structures with expected lifetimes of many years. A drawback of using recycled raw materials for manufacturing geotextiles is that they may have already experienced degradation, which can compromise the long-term behaviour of the final products. When using textile waste, the recycled raw materials can be natural (e.g., cotton or wool), which leads to biodegradable geotextiles, therefore unsuitable for long-term applications. Taking into account the previous concerns, it is reasonable to consider the application of recycled nonwoven geotextiles only in temporary or low-demanding structures. Examples of application include their use for erosion control (e.g., protection of slopes until the

Nonwoven Geotextiles in Civil and Environmental Engineering 191 growth of vegetation), rooftop gardens (e.g., as filters) or for agricultural purposes. The use of recycled nonwoven geotextiles can be a valuable contribution for a more sustainable construction and to improve circularity within the textile and the building and construction sectors. The manufacturing of these materials can help boosting the use of textile and plastic waste as raw materials and, simultaneously, reduce the consumption of natural resources.

ACKNOWLEDGMENTS This work was financially supported by project PTDC/ECIEGC/28862/2017, funded by FEDER funds through COMPETE 2020 – “Programa Operacional Competitividade e Internacionalização” (POCI) and by national funds (PIDDAC) through FCT/MCTES.

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Shukla, S. K. & Yin, J. H. (2006). Fundamentals of Geosynthetic Engineering. 1st ed. Leiden, The Netherlands: Taylor & Francis/ Balkema. Ingold, T. S. & Miller, K. S. (1988). Geotextiles Handbook. 1st ed. London, United Kingdom: Thomas Telford Limited, Thomas Telford House. Ingold, T. S. (1994). The Geotextiles and Geomembranes Manual. 1st ed. Oxford, United Kingdom: Elsevier Advanced Technology.

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J. R. Carneiro, F. Almeida, D. M. Carlos et al. European Committee for Standardization. (2005). Geosynthetics Test method for the determination of mass per unit area of geotextiles and geotextile-related products. EN ISO 9864. Brussels, Belgium: CEN. ASTM International. (2018). Standard Test Method for Measuring Mass per Unit Area of Geotextiles. ASTM D5261-10(2018). West Conshohocken, PA, United States of America: ASTM. Koerner, R. M. (2005). Designing with Geosynthetics. 5th ed. Upper Saddle River, New Jersey, United States of America: Pearson Education, Inc. European Committee for Standardization. (2016). Geosynthetics Determination of thickness at specified pressures - Part 1: Single layers. EN ISO 9863-1. Brussels, Belgium: CEN. ASTM International. (2019). Standard Test Method for Measuring the Nominal Thickness of Geosynthetics. ASTM D5199-12(2019). West Conshohocken, PA, United States of America: ASTM. European Committee for Standardization. (2010). Geotextiles and geotextile-related products - Determination of the characteristic opening size. EN ISO 12956. Brussels, Belgium: CEN. ASTM International. (2016). Standard Test Method for Determining Apparent Opening Size of a Geotextile. ASTM D4751-16. West Conshohocken, PA, United States of America: ASTM. European Committee for Standardization. (2015). Geosynthetics Wide-width tensile test. EN ISO 10319. Brussels, Belgium: CEN. ASTM International. (2017). Standard Test Method for Tensile Properties of Geotextiles by the Wide-Width Strip Method. ASTM D4595-17. West Conshohocken, PA, United States of America: ASTM. European Committee for Standardization. (2006). Geosynthetics Static puncture test (CBR test). EN ISO 12236. Brussels, Belgium: CEN. ASTM International. (2014). Standard Test Method for Static Puncture Strength of Geotextiles and Geotextile-Related Products

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INDEX A acid, x, 14, 22, 30, 142, 143, 144, 146, 151 acoustic insulation, viii, 1, 17, 18, 19, 77 activated carbon, 17, 25 additives, 5, 149, 150, 160, 165 adhesion, 10, 21, 87, 149, 170 aero dynamic web, 122 aesthetic, 24, 82, 188 anisotropy, 82, 93, 105, 137 application, viii, 4, 11, 14, 15, 20, 21, 23, 24, 26, 31, 37, 38, 39, 48, 68, 69, 72, 84, 85, 86, 88, 96, 98, 99, 109, 119, 125, 135, 137, 138, 139, 144, 145, 146, 149, 152, 156, 168, 172, 173, 177, 181, 190 automobile parts, 15 automobiles, 85 automotive sector, 21 automotive textiles, 15

B banks, 180, 182, 184 barriers, 180, 181

base, 56, 57, 58, 65, 73, 103, 106, 108, 148, 158, 160, 165, 173, 175, 178, 179, 183 biodegradability, ix, 5, 121, 158 biodegradation, 3, 22, 26, 118 biopolymers, 143 blends, 6, 10, 12, 15, 18, 51, 53, 54, 56, 62, 63, 64, 66, 67, 80, 83, 109 bonding, vii, viii, ix, x, 1, 2, 4, 5, 6, 7, 12, 19, 26, 41, 102, 103, 122, 124, 125, 128, 141, 146, 161, 162, 163 boric acid (BA), v, x, 141, 142, 144, 146, 147, 148, 149, 150, 151 brittle nature, 42 brittleness, 42 broadband, 126 bromine, 143, 144

C carbon, 6, 20, 25, 158, 160, 165 chemical, x, 5, 7, 9, 12, 21, 25, 26, 39, 41, 83, 88, 98, 103, 111, 142, 146, 147, 151, 156, 159, 160, 161, 162, 163, 165, 188, 189 chemical bonded, 12

196

Index

chemical industry, 160 chemical properties, xi, 142 chemicals, viii, x, 7, 142, 143, 144, 147, 148, 149, 150 civil engineering, 23, 156, 157, 176 cleaning, 5 clothing, x, 25, 142 coatings, 137 color, iv, 123, 124, 125, 127, 132 combustion, 148, 152, 153 commercial, ix, 9, 102, 116, 117, 144 community, viii, x, 142, 157 composites, 2, 5, 11, 15, 16, 17, 20, 21, 23, 24, 26, 28, 29, 30, 32, 33, 34, 49, 85, 88, 91, 94, 113, 120, 137, 143, 151, 152 composition, 9, 50, 59, 64, 162, 190 compounds, 143, 152, 158, 160 compressibility, 67, 68, 166, 168 compression, 21, 67, 68, 70, 71, 87, 108, 114, 137, 143 conductivity, 16, 17, 52, 62, 81, 83, 87, 110, 113, 115, 119, 123, 126, 127, 128, 133, 136, 152 conference, 137, 138 configuration, 106, 113 consolidation, 7, 14, 22, 51, 53, 63, 64, 65, 66, 79, 106, 107, 114, 132, 173, 177, 184 construction, viii, x, xi, 21, 65, 142, 149, 155, 156, 157, 172, 173, 177, 178, 180, 183, 184, 186, 191 correlation, 18, 64, 65, 69 cost, ix, xi, 3, 4, 9, 10, 16, 20, 38, 39, 62, 101, 102, 121, 123, 155, 156, 157, 164, 172 cotton, vii, viii, ix, 1, 2, 3, 5, 6, 8, 9, 10, 11, 13, 14, 15, 17, 18, 21, 24, 25, 26, 27, 28, 29, 30, 31, 34, 35, 40, 56, 83, 92, 122, 123, 124, 125, 126, 127, 128, 130, 131, 132, 133, 134, 135, 136, 143, 145, 152, 156, 158, 188, 190 covering, 24, 71, 82, 86, 88, 135, 137 cycles, 52, 70, 71, 72, 81

D decay, 51, 52, 53 decibel, x, 77, 122, 134, 136 deformation, 30, 31, 52, 70, 71, 72 degradation, 118, 160, 163, 189, 190 depth, vii, ix, 7, 18, 42, 44, 45, 47, 49, 50, 53, 58, 59, 62, 64, 66, 68, 71, 72, 73, 75, 78, 80, 81, 102, 105, 106, 110, 111, 115, 117 distribution, 14, 22, 113, 114, 148, 149, 161, 164, 166, 167 drainage, 166, 167, 168, 171, 173, 176, 177, 178, 179, 180, 181, 183, 186 dry laid, 5, 6, 7, 146 durability, 157, 190 dynamic loads, 71

E economic growth, 187 economics, 98, 105 electrical resistance, 78, 79 electron, 43, 162, 163 electron microscopy, 162, 163 elongation, 40, 46, 47, 53, 69, 71 energy, 12, 17, 18, 55, 68, 69, 70, 71, 77, 78, 96, 110, 113, 133 energy consumption, 12, 110 engineering, xi, 23, 38, 137, 155, 156, 157, 163, 166, 172, 173, 176, 178, 180, 183, 186 environment, 3, 26, 96, 109, 122 environmental engineering, vi, xi, 155, 156, 163, 166, 172, 183, 186 environmental impact, xi, 155 erosion, 23, 84, 167, 171, 172, 173, 175, 176, 178, 180, 181, 182, 190 experimental design, 31, 53, 59, 63, 64 extinction, xi, 142 extrusion, 160, 190

Index F fabrication, ix, 15, 101 federal regulations, x, 142 fiber content, 111, 128, 129 filament, 11, 103 filling materials, 184 filters, 8, 118, 165, 184, 191 filtration, viii, 1, 2, 11, 14, 22, 23, 26, 30, 84, 85, 87, 88, 119, 138, 165, 166, 167, 168, 171, 173, 178, 179, 181, 184, 186 fire hazard, 148 fire resistance, 152 fire retardancy, 143 fire retardant, viii, 142, 144, 145, 151 flame, x, 142, 143, 144, 145, 146, 148, 149, 151 flame propagation, 144 flame retardants, 143, 144, 146 flammability, x, 142, 144, 148, 149, 151, 152, 153 flaws, 148 flax, vii, viii, ix, 1, 2, 4, 5, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 23, 26, 27, 28, 29, 30, 31, 32, 34, 83, 85, 88, 101, 102, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 137, 143 flax fiber, ix, 30, 32, 102, 110, 111 flax fibers, ix, 30, 32, 88, 102, 110, 111 formation, viii, 1, 2, 3, 5, 6, 7, 9, 12, 23, 25, 26, 33, 39, 42, 57, 64, 66, 84, 105, 114, 125, 146, 150, 188

G geotextiles, vi, viii, xi, 1, 2, 6, 23, 26, 31, 33, 84, 88, 91, 92, 93, 94, 96, 97, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179,

197

180, 181, 182, 183, 184, 186, 187, 188, 189, 190, 191, 192, 193, 194 groundwater, 168, 183 growth, 3, 15, 38, 85, 135, 172, 191

H health, 15, 84, 148 health care, 15 heat transfer, 13, 87, 109, 110, 114 hemp, vii, viii, 1, 2, 5, 10, 11, 14, 16, 20, 23, 26, 30, 32, 143 hexabromocyclododecane (HBCD), 144 history, viii, xi, 155, 156 homogeneity, 105, 190 human, 143, 146, 151 humidity, 112 hybrid, 22, 28, 33 hybridization, 137 hydrogen, 146, 158 hydrolysis, 159 hydrophilicity, 21 hydroxide, 73, 143

I India, 1, 29, 33, 37, 40, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 101, 111, 119, 121 industrial sectors, 187 industry, vii, viii, ix, x, 1, 16, 22, 27, 38, 39, 92, 101, 117, 141, 143, 146, 151, 157 insulation, vii, viii, ix, 1, 5, 6, 16, 17, 18, 19, 20, 26, 29, 32, 41, 45, 47, 60, 61, 62, 63, 69, 70, 78, 83, 87, 94, 101, 102, 109, 110, 113, 114, 115, 116, 118, 120, 133, 137 interference, 126 interlacements, 42 irrigation, 84, 180, 181 issues, 3, 157, 173, 176

Index

198 J

jute, v, vii, viii, 1, 2, 4, 5, 8, 10, 14, 15, 16, 18, 20, 23, 24, 26, 27, 28, 29, 30, 31, 32, 33, 34, 37, 38, 39, 40, 41, 42, 44, 45, 47, 48, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 99, 100, 109, 119, 143, 152, 156, 158 jute and allied fibres, 38, 39

L landfills, xi, 122, 155, 186 leakage, 182, 183 low melt PET, vii, ix, 20, 32, 102, 110, 111, 112, 113, 114, 115, 116, 117, 118

M manufacturing, vii, viii, x, xi, 1, 2, 4, 7, 8, 10, 22, 26, 28, 32, 38, 102, 105, 111, 122, 142, 144, 150, 156, 158, 165, 166, 187, 188, 190, 191 mass, 13, 18, 42, 46, 54, 55, 58, 63, 65, 66, 74, 77, 78, 82, 110, 124, 145, 146, 149, 151, 164, 192 materials, viii, ix, x, xi, 8, 12, 15, 16, 17, 19, 21, 23, 24, 25, 31, 33, 82, 85, 87, 101, 102, 110, 114, 115, 117, 119, 120, 122, 123, 124, 125, 130, 132, 136, 137, 138, 142, 143, 144, 146, 148, 151, 155, 156, 157, 158, 163, 164, 166, 167, 168, 169, 170, 171, 172, 173, 175, 177, 178, 179, 180, 181, 184, 187, 188, 190, 191 mechanical interlocking by needling or fluid jet entanglement, 102

mechanical properties, 13, 15, 20, 50, 105, 106, 107, 108, 110, 137, 164, 165, 170 media, 6, 8, 14, 41, 85, 88 medical, 2, 6, 8, 15 medical textiles, 15 melt, vii, ix, 5, 12, 20, 32, 102, 110, 111, 112, 113, 114, 115, 116, 117, 118, 162 melting, vii, ix, 12, 20, 32, 101, 103, 111, 124, 162, 190 melting temperature, 12 meter, 60, 64, 104, 113, 120, 136, 164, 165 mixing, 22, 148, 168, 177 modifications, 16, 21, 87 modulus, 4, 10, 47, 49, 51, 53, 54, 56, 59, 60, 71, 82, 107, 108 municipal solid waste, 186

N natural appearance, 11 natural fibre, v, vii, viii, 1, 2, 3, 4, 5, 8, 10, 11, 12, 13, 14, 16, 18, 20, 23, 24, 25, 26, 31, 37, 39, 41, 83, 92, 93, 94, 95, 96, 98, 99, 100, 110, 116 natural resources, 191 needle punching, ix, 4, 5, 7, 8, 9, 22, 28, 41, 88, 89, 93, 101, 102, 103, 104, 105, 106, 107, 108 needlepunched, 7, 8, 9, 14, 16, 17, 18, 21, 23, 24, 25, 27, 28, 31, 34, 63 needle-punched nonwoven, v, vii, viii, 14, 28, 30, 31, 32, 37, 38, 42, 45, 49, 52, 54, 58, 59, 62, 63, 66, 67, 71, 72, 76, 78, 83, 84, 85, 87, 93, 97, 113, 119, 161 needlepunching, viii, 1, 2, 8, 9, 10, 19, 22, 26 novel materials, 13 nylons, 143

Index O oil, 9, 11, 14, 24, 25, 26, 29, 35, 41, 45, 48, 58, 65, 73, 74, 75, 81 oil sorbents, 24, 35 opportunities, 3 oscillation, 74 oxidation, 158, 159, 160 oxygen, 144, 148, 150

P parallel, 21, 39, 41, 43, 44, 61, 62, 82, 85, 103 permeability, viii, ix, 10, 14, 23, 32, 64, 65, 66, 69, 70, 81, 86, 87, 93, 98, 105, 109, 113, 115, 119, 120, 122, 123, 126, 127, 128, 131, 132, 136, 166, 168, 181 physical properties, viii, ix, 9, 48, 111, 119, 120, 122, 126, 127, 144 physical properties and sound absorption coefficient, 122 polymer, viii, x, 3, 5, 7, 13, 20, 103, 142, 144, 160, 162, 165 polymer composites, 20 polymer laid, 5, 7 polymer materials, viii, x, 142 polymeric materials, xi, 155 polymeric products, 160 polymers, 21, 143, 158, 160, 162, 188, 190 polyolefins, 21, 143, 159, 188 polypropylene, 5, 10, 13, 16, 18, 20, 22, 24, 25, 28, 32, 33, 35, 45, 50, 51, 52, 53, 54, 59, 62, 63, 64, 66, 67, 69, 70, 71, 72, 76, 80, 82, 83, 89, 90, 109, 110, 119, 137, 143, 156, 158, 159, 162 polystyrene, 21 polyvinyl alcohol, 13, 19 porosity, viii, ix, 32, 110, 122, 123, 126, 127, 132, 133, 136, 144 porous materials, ix, 101, 113

199

positive correlation, 18 preparation, iv, 8, 9, 14, 41, 160, 188 properties, v, viii, ix, x, xi, 2, 3, 4, 7, 8, 9, 11, 13, 14, 15, 17, 19, 20, 23, 24, 26, 27, 28, 30, 31, 32, 33, 34, 37, 38, 41, 42, 45, 46, 47, 48, 50, 51, 52, 54, 56, 57, 58, 69, 70, 72, 74, 80, 81, 82, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 102, 105, 106, 107, 108, 109, 110, 111, 113, 114, 115, 116, 117, 118, 119, 120, 122, 124, 126, 127, 128, 137, 138, 142, 144, 145, 146, 147, 152, 156, 160, 163, 164, 165, 166, 167, 169, 170, 171, 173, 188, 189, 190, 192 protection, xi, 3, 23, 26, 84, 155, 165, 166, 167, 170, 171, 178, 180, 184, 185, 190

R radiation, 113, 159, 160, 173 raw materials, viii, xi, 10, 123, 156, 158, 188, 190, 191 recovery, 67, 68, 69, 70, 71, 80, 81, 87, 106, 108 recycled fiber nonwoven, ix, 121, 122, 127, 135, 136 reinforcement, 16, 20, 23, 24, 32, 47, 48, 56, 73, 82, 84, 167, 169, 170, 173, 174, 177, 178, 179 requirements, 2, 17, 116, 188 resilience, x, 9, 67, 72, 142 resistance, x, xi, 10, 11, 17, 21, 28, 44, 52, 59, 60, 63, 65, 72, 73, 79, 81, 88, 104, 109, 110, 115, 116, 117, 119, 122, 132, 134, 135, 136, 137, 142, 158, 159, 160, 163, 171, 173, 189, 190 response, 50, 53, 148 restrictions, 177 risk, xi, 142, 148, 167

Index

200 S

safety, x, 142, 143, 146, 151, 176 scanning electron microscopy, 34 soil erosion, 171 soil particles, 167, 168, 171, 176, 181 solid waste, 186 solution, xi, 8, 103, 111, 142, 147, 151 solvents, 158 sorption, 24, 25, 26, 34, 35, 73, 74, 75 soy-based, 143 spraying, xi, 9, 12, 142, 143, 145, 147, 148, 149, 150, 151, 163 spunlace, xi, 2, 8, 10, 11, 14, 15, 20, 142, 146 spunlacing, 7, 10, 16, 26, 29 stitchbonded, 11 stress, 47, 48, 51, 53, 57, 106, 108, 169, 170 stroke, 104, 105, 106, 107, 108, 109 structure, vii, viii, ix, xi, 10, 15, 16, 18, 19, 25, 33, 37, 38, 39, 40, 42, 43, 48, 52, 53, 63, 64, 67, 74, 78, 79, 82, 87, 93, 101, 102, 103, 104, 105, 106, 107, 108, 110, 116, 119, 135, 150, 155, 160, 161, 163, 165, 167, 168, 169, 170, 174, 175, 178, 181 surface area, 17, 26, 135, 150 surface layer, 17 sustainable construction, viii, xii, 156, 157, 187, 191 synthetic fiber, 128 synthetic polymers, 5, 156, 157, 158, 160

T teaching experience, 98 techniques, vii, viii, xi, 1, 2, 4, 7, 13, 21, 29, 87, 102, 105, 124, 142, 143 technology, ix, 2, 3, 7, 9, 10, 14, 19, 27, 35, 39, 101, 102, 180 temperature, 13, 60, 61, 109, 111, 112, 147

tensile strength, 11, 21, 23, 47, 48, 52, 106, 107, 108 tension, 52, 57, 104 test procedure, 127 testing, 20, 48, 60, 61, 82, 112 textiles, ix, x, 12, 29, 38, 47, 51, 52, 62, 81, 93, 101, 102, 118, 142, 143 thermal bonded, v, ix, 12, 17, 19, 121, 122, 123, 124, 125, 126, 127, 128, 133, 134, 136 thermal bonding, vii, viii, ix, 1, 4, 5, 7, 13, 19, 26, 41, 102, 122, 124, 125, 162 Thermal conductivity, 17, 81, 119, 128, 152 thermal insulation, v, vii, viii, ix, 1, 16, 20, 32, 47, 60, 61, 62, 63, 69, 70, 83, 87, 89, 91, 94, 101, 102, 109, 110, 113, 114, 115, 116, 118, 120, 133 thermal resistance, vii, viii, ix, 17, 60, 63, 89, 102, 109, 110, 113, 115, 116, 117, 119, 120, 122 transmission, 16, 18, 31, 77, 78, 125 transport, 109, 168, 176, 178, 180 treatment, 9, 30, 33, 58, 65, 73, 81, 88, 188, 190

U upholstery, viii, 1, 5, 6, 145

V variables, 53, 55, 68, 72, 87, 111 varieties, 39, 44, 86, 124, 125 versatility, xi, 155, 156, 157, 172 viscose, 10, 15, 52, 53, 56, 59, 64, 68, 93

Index W waste, xi, 4, 5, 18, 25, 27, 39, 62, 83, 122, 123, 124, 126, 135, 136, 155, 186, 187, 188, 189, 190, 191 water absorption, 22 water permeability, 164, 166, 167, 193 web, viii, x, 1, 2, 5, 6, 7, 8, 9, 11, 12, 26, 39, 42, 43, 44, 47, 48, 49, 50, 53, 56, 62, 65, 73, 78, 81, 82, 87, 103, 104, 105, 106, 107, 108, 109, 111, 114, 122, 124, 125, 132, 141, 146, 150, 160, 161, 162, 163, 188 web bonding, viii, 1, 7 weight ratio, 21, 65, 81 weight reduction, 15, 85 wet laid, 5, 7

201

wettability, 87 wetting, 22, 71, 74, 87 withdrawal, 104 wood, 14, 21, 85, 143 wool, 2, 24, 25, 26, 35, 62, 63, 145, 156, 158, 188, 190 woollenization, 16 wound healing, 15

Y yarn, 2, 11, 57, 102, 103

Z zinc oxide, 144