Industrial applications of natural fibres : Structure, Properties and Technical Applications

In the past, when synthetics became used as alternative construction materials instead of metals, a lot of damage happened to different components. This resulted in a very negative estimation of the performance of synthetics. Soon it became clear that metals could not simply be replaced by synthetics and the designer had to learn how to deal with these new materials. This time of apprenticeship was injurious to the image and the reputation of synthetics, and as a consequence similar developments have to be avoided, if new materials like natural fibres are to be technically applied in the future. Thus, knowledge of structure and properties as well as interconnection with shaping is necessary for material selection. The main argument against the industrial use of natural fibres is often that the quality of the fibres depends on the year in which they were grown. It is nevertheless possible to obtain fibres of consistent quality, as well as reliable data, enhancing the predictability of the properties of natural fibre products by using a quality management system that starts for plant fibres at the cultivation stage and that is based on reproducible proof of origin and harvesting parameters. This document will combine the different steps of processing, from agriculture, fibre separation and fibre processing to the manufacture of the final product. Each step will be linked to the fibre properties, the possibilities to characterise them, and how the different natural fibres will influence the product properties.

Industrial Applications

of Natural Fibres

Wiley Series in Renewable Resources

Series Editor

Christian V Stevens, Department of Organic Chemistry, Ghent University, Belgium

Titles in the Series

Wood Modification: Chemical, Thermal and Other Processes

Callum A.S Hill

Renewables-Based Technology: Sustainability Assessment

Jo Dewulf & Herman Van Langenhove

Introduction to Chemicals from Biomass

James H Clark & Fabien E.I Deswarte

Biofuels

Wim Soetaert & Erick J Vandamme

Handbook of Natural Colorants

Thomas Bechtold & Rita Mussak

Surfactants from Renewable Resources

Mikael Kjellin & Ingeg¨ard Johansson

Industrial Applications of Natural Fibres: Structure, Properties and Technical Applications

J¨org M¨ussig

Forthcoming Titles

Thermochemical Processing of Biomass

Robert C Brown

This edition first published 2010

C

2010 John Wiley & Sons, Ltd

Registered office

John Wiley & Sons, Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, United Kingdom

For details of our global editorial offices, for customer services and for information about how to apply for permission to reuse the copyright material in this book please see our website at www.wiley.com

The right of the author to be identified as the author of this work has been asserted in accordance with the Copyright, Designs and Patents Act 1988.

All rights reserved No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by the UK Copyright, Designs and Patents Act 1988, without the prior permission

of the publisher.

Wiley also publishes its books in a variety of electronic formats Some content that appears in print may not be available in electronic books.

Designations used by companies to distinguish their products are often claimed as trademarks All brand names and product names used in this book are trade names, service marks, trademarks or registered trademarks of their respective owners The publisher is not associated with any product or vendor mentioned in this book This publication is designed to provide accurate and authoritative information in regard to the subject matter covered It is sold on the understanding that the publisher is not engaged in rendering professional services If professional advice or other expert assistance is required, the services of a competent professional should be sought.

The publisher and the author make no representations or warranties with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties, including without limitation any implied warranties of fitness for a particular purpose This work is sold with the understanding that the publisher is not engaged in rendering professional services The advice and strategies contained herein may not be suitable for every situation In view of ongoing research, equipment modifications, changes in governmental regulations, and the constant flow of information relating

to the use of experimental reagents, equipment, and devices, the reader is urged to review and evaluate the information provided in the package insert or instructions for each chemical, piece of equipment, reagent, or device for, among other things, any changes in the instructions or indication of usage and for added warnings and precautions The fact that an organization or Website is referred to in this work as a citation and/or a potential source of further information does not mean that the author or the publisher endorses the information the organization or Website may provide or recommendations it may make Further, readers should be aware that Internet Websites listed in this work may have changed or disappeared between when this work was written and when it is read No warranty may be created or extended by any promotional statements for this work Neither the publisher nor the author shall be liable for any damages arising herefrom.

Library of Congress Cataloging-in-Publication Data

Industrial applications of natural fibres: structure, properties and technical applications / edited by J¨org M¨ussig.

p cm – (Wiley series in renewable resources)

Includes bibliographical references and index.

In recent years, natural fibres have become increasingly popular for use in industrial applications, e.g

as reinforcement for plastics This approach is also of growing interest in light of the discussion aboutsustainability and environmental issues These aspects are commonly not included in the regular universityeducation for engineers and natural scientists This book will examine the value-added chain of natural fibres

in order to bring more detailed information about this complex topic to students as well as to industry andresearch The book will enable the reader to gain a fundamental understanding of the sometimes complextransformation of a natural fibre to final technical product

This book is dedicated to professional industrial researchers working in production processing (from fibreseparation to the final product – textiles and composites), in fibre characterisation and in standardisation andharmonisation, to academics researching in the field of technical applications of natural fibres, as well as topostgraduates on specific courses and research projects in the above areas

Fenella G France

Danny E Akin

Michaela Eder and Ingo Burgert

J¨org M¨ussig and Tanja Slootmaker

Axel Drieling and J¨org M¨ussig

Nina Graupner and J¨org M¨ussig

Stephan Piotrowski and Michael Carus

Danny E Akin

Stefano Amaducci and Hans-J¨org Gusovius

6 Jute – A Versatile Natural Fibre Cultivation, Extraction and Processing 135

Md Siddiqur Rahman

Friedhelm G¨oltenboth and Werner M¨uhlbauer

Rajesh D Anandjiwala and Maya John

Chitrangani Jayasekara and Nalinie Amarasinghe

Muhammed Rafiq Chaudhry

Anja Gliˇsovi´c and Fritz Vollrath

12 Wool – Structure, Mechanical Properties and Technical Products based on Animal

Crisan Popescu and Franz-Josef Wortmann

13 Testing Methods for Measuring Physical and Mechanical Fibre Properties (Plant and

J¨org M¨ussig, Holger Fischer, Nina Graupner and Axel Drieling

Tanja Slootmaker and J¨org M¨ussig

Ingo Burgert and Michaela Eder

16 DNA-Analytical Identification of Species and Genetic Modifications in Natural Fibres 345

Lothar Kruse

Axel Drieling and Jean-Paul Gourlot

Danny E Akin

Tuomas H¨anninen and Mark Hughes

Erwin Baur and Frank Otremba

Tim Huber, Nina Graupner and J¨org M¨ussig

Eugen Pr¨omper

19.5 Composites Based on Natural Resources 437

Martien van den Oever and Harri¨ette Bos

Sanchita Bandyopadhyay-Ghosh, Subrata Bandhu Ghosh and Mohini Sain

Franz Neubauer

Gero Leson, Michael V Harding, and Klaus Dippon

Series Preface

Renewable resources, their use and modification are involved in a multitude of important processes with amajor influence on our everyday lives Applications can be found in the energy sector, chemistry, pharmacy,the textile industry, paints and coatings, to name but a few

The area interconnects several scientific disciplines (agriculture, biochemistry, chemistry, technology,environmental sciences, forestry, ), which makes it very difficult to have an expert view on the complicatedinteraction Therefore, the idea to create a series of scientific books, focussing on specific topics concerningrenewable resources, has been very opportune and can help to clarify some of the underlying connections inthis area

In a very fast changing world, trends are not only characteristic of fashion and political standpoints, alsoscience is not free from hypes and buzzwords The use of renewable resources is again more importantnowadays; however, it is not part of a hype or a fashion As the lively discussions among scientists continueabout how many years we will still be able to use fossil fuels, with opinions ranging from 50 years to 500years, they do agree that the reserve is limited and that it is essential not only to search for new energy carriersbut also for new material sources

In this respect, renewable resources are a crucial area in the search for alternatives for fossil-based rawmaterials and energy In the field of energy supply, biomass and renewable-based resources will be part

of the solution, alongside other alternatives such as solar energy, wind energy, hydraulic power, hydrogentechnology and nuclear energy

In the field of material sciences, the impact of renewable resources will probably be even greater Integralutilisation of crops and the use of waste streams in certain industries will grow in importance, leading to amore sustainable way of producing materials

Although our society was much more (almost exclusively) based on renewable resources centuries ago,this disappeared in the Western world in the nineteenth century Now it is time to focus again on this field

of research However, this should not mean a ‘retour `a la nature’ but should be a multidisciplinary effort

on a highly technological level to perform research into the development of new crops and products fromrenewable resources This will be essential to guarantee a level of comfort for a growing number of people

living on our planet It is the challenge for the coming generations of scientists to develop more sustainable

ways to create prosperity and to fight poverty and hunger in the world A global approach is certainly favoured.This challenge can only be dealt with if scientists are attracted to this area and are recognised for their efforts

in this interdisciplinary field It is therefore also essential that consumers recognise the fate of renewableresources in a number of products

Furthermore, scientists do need to communicate and discuss the relevance of their work The use andmodification of renewable resources may not follow the path of the genetic engineering concept in view ofconsumer acceptance in Europe In this regard, the series will certainly help to increase the visibility of theimportance of renewable resources

Being convinced of the value of the renewables approach for the industrial world, as well as for developingcountries, I was myself delighted to collaborate on this series of books focusing on different aspects ofrenewable resources I hope that readers become aware of the complexity, the interaction and interconnectionsand the challenges of this field, and that they will help to communicate the importance of renewable resources.

I certainly wish to thank the people at John Wiley & Sons, Chichester, especially David Hughes, JennyCossham and Lyn Roberts, in seeing the need for such a series of books on renewable resources, for initiatingand supporting it and for helping to carry the project through to the end

Last but not least, I would like to thank my family, especially my wife Hilde and my children Paulien andPieter-Jan, for their patience and for giving me the time to work on the series when other activities seemed to

What makes natural fibres so fascinating? Representatives of different professional disciplines, like biologists,chemists, agrononomical scientists, process engineers or preservation scientists, would certainly each answerthis question quite differently, according to their own scientific interest and research As a material scientist,

I would like to describe my own perception and at the same time outline the leading thoughts of this book.Material discoveries and material developments have in the history of mankind led to great progress ininnovation, with far-reaching consequences for technology, economy and culture The periodical division ofprehistory and early history of mankind is mainly determined by the materials used in these periods (StoneAge, Bronze Age and Iron Age) Although the utilisation of natural fibres is verifiable in early archaeologicalcultures, it has not resulted in the naming of an epoch There is no ‘natural fibre age’, although in history theusage of natural fibre has been quite varied and has repeatedly generated culturally significant innovations.Clothing textiles as well as technical textiles (e.g nets) or composite materials (e.g natural fibre compoundedclay) are examples of such innovations In this book these historical aspects of natural fibre usage are combinedwith possible future products

In our progressively globalised world with unforeseeable demographic, economic and ecological lenges, management of resources and sustainability are increasingly becoming the focus of debate and dis-cussion The utilisation of materials is a key factor, and natural fibres in particular, being a natural resource,provide opportunities for technical innovation and sustainability

chal-The use of natural fibres, e.g in technical applications, needs to be in line with the three essential pillars

of sustainability – economy, ecology and society To ensure that this remains so now and in the future, theworldwide raw material turnaround and its effects on the selection of materials must be critically examined

on the basis of sustainability criteria

The main argument against the industrial use of natural fibres is often that the quality of the fibres depends

on the year in which they were grown It is nevertheless possible to obtain fibres of consistent quality, aswell as reliable data, enhancing the predictability of the properties of natural fibre products by using a qualitymanagement system that starts for plant fibres at the cultivation stage and that is based on reproducibleproof of origin and harvesting parameters This book will combine the different steps of processing, fromagriculture, fibre separation and fibre processing to the manufacture of the final product Each step will belinked to the fibre properties, the possibilities to characterise them, and how the different natural fibres willinfluence the product properties

In order to understand why and how a natural fibre influences a product property, their chemical aswell as structural qualities are thoroughly described The fundamental understanding of the hierarchy andconstruction of natural fibre structures allow for a specific and selective design of natural fibre products.However, natural fibres and their function in biological systems also offer an exceedingly interesting modelfor the development of biomimetic and bio-inspired materials Here, also, a fundamental understanding ofthe functions enhances the transfer from biological system to technological appliance

The subject of natural fibres is an interdisciplinary field of research and, among others, touches the fields

of cultivation, biochemistry, agricultural science, biology, material science and engineering The aim andobjective of writing this book was to provide a substantiated overview of the status of current research on thesubject of natural fibres and technical natural fibre usage, including the perspectives of other disciplines

I would like to thank the authors, who have shown great interest in this interdisciplinary book project

As a combination of different areas of research may cause problems of understanding, there has been greatemphasis on using consistent terminology This will enhance understanding across the borders of scientificfields In this context, I would again like to thank the authors, who worked very cooperatively in this project

A special focus was to present the graphic elements in this book consistently and appealingly Using mainlyhandwritten graphics and diagrams, we have attempted a new way of illustration in this book My specialthanks to Tanja Slootmaker and Anja M¨ussig for their creative work

I would like to thank the staff at John Wiley & Sons, Chichester, especially Richard Davies, Sarah Halland Jenny Cossham, for supporting the book project through to the end

I would also like to thank my family and friends for their patience and the time they have given me for theconception and writing of this book

I hope while reading this book you will experience some of the fascination of ‘natural fibres’ that I havebeen experiencing for years now, being engaged in this highly interesting area of research

J¨org M¨ussig

Hochschule Bremen – University of Applied Sciences,

Faculty 5 – Department of Biomimetics,Professorship Biological Materials,

Bremen, Germany

Editor Industrial Applications of Natural Fibres

January 2010

In the past, when synthetics became used as alternative construction materials instead of metals, a lot ofdamage happened to different components This resulted in a very negative estimation of the performance ofsynthetics Soon it became clear that metals could not simply be replaced by synthetics and the designer had

to learn how to deal with these new materials This time of apprenticeship was injurious to the image and thereputation of synthetics, and as a consequence similar developments have to be avoided, if new materials likenatural fibres are to be technically applied in the future Thus, knowledge of structure and properties as well

as interconnection with shaping is necessary for material selection

It is therefore highly appreciated that the publishers John Wiley & Sons, Chichester, have initiated a series

of scientific books on special subjects of renewable resources This particular volume “Industrial Applications

of Natural Fibres” is edited by J¨org M¨ussig, a very active young Professor of Biological Materials He is boththe initiator and scientific head of numerous research projects on the value-added chain of natural fibres inthe field of technical applications, starting from agriculture and ending with the final product

Bulk properties of materials are mainly determined by their chemical composition and atomic structure.Technically, geometrical and test conditions additionally influence parameters of construction materials Asall of them have their own life history, these facts have to be known if materials are to be used sustainably inindustrial applications This means that modern procedures using statistical methods of testing and evaluationare necessary Particularly in the case of natural fibres, the whole distribution of property should be known.Thanks to the thorough and extensive activities of the editor, a great number of internationally well-knownexperts in the field of natural fibres have contributed their expertise, writing articles on this interdisciplinaryfield of research and application, and thus making a comprehensive compendium available Many of thechapters refer to the requirements mentioned above The uniformity of the structure of each chapter, the wellcoordinated contents with links to corresponding chapters and the consistent terminology of the combinedcontributions will be of great advantage for every reader Of particular note are the handwritten graphics anddiagrams They are very informative, and in combination with historical drawings of plants, the informationpresented becomes clear and vivid The reader not only gets general information but also detailed facts on ascientific basis with links to comprehensive lists of well investigated current publications

It was a great pleasure to read the manuscript and hopefully many students, as well as academic andindustrial researchers in the field of technical applications of natural fibres will contribute to the development

of these advanced materials by studying this highly professional compendium

I congratulate and thank the editor and the authors for their ambitious work

Helmuth Harig

Professor of Materials (retired)Universit¨at Bremen/Faserinstitut Bremen

Berlin, January 2010

List of Contributors

Danny E Akin Athens, Georgia, USA

Dr Akin (PhD in Microbiology); retired in January 2008, after a 37 year career with the US Department ofAgriculture; currently associated with the consulting firm Light Light Solutions, LLC, in Athens, Georgia,USA

Stefano Amaducci Istituto di Agronomia, Universit`a Cattolica del Sacro Cuore, Piacenza, Italy

Dr Amaducci; researcher and teaches the course of Field Crops at Universit`a Cattolica del Sacro Cuore;research focus: agronomic evaluation of industrial crops, particularly for fibre and biomass production

Nalinie Amarasinghe Industrial Technology Institute, Colombo, Sri Lanka

MSc Amarasinghe (Diploma in Technology, University of Moratuwa, Sri Lanka; Post Graduate Diploma andMSc in Chemical Engineering, University of Bradford, UK); Project Director at the ITI ‘Coir Processing andQuality Control.’

Rajesh D Anandjiwala CSIR Materials Science and Manufacturing, Port Elizabeth, South Africa, andDepartment of Textile Science, Nelson Mandela Metropolitan University, Port Elizabeth, South Africa

Dr Anandjiwala (Doctor of Philosophy; University of Leeds, UK in Textile Engineering); Chief Researcherand Research Group Leader at the CSIR; Adjunct Professor, Nelson Mandela Metropolitan University

Subrata Bandhu Ghosh Center for Biocomposites and Biomaterials Processing, Faculty of Forestry,University of Toronto, Toronto, Canada

Dr Ghosh (PhD, Department of Engineering Materials, University of Sheffield, UK); currently a Post-doctoralResearch Fellow at the University of Toronto; research focus: biobased foams and biocomposites

Sanchita Bandyopadhyay-Ghosh Center for Biocomposites and Biomaterials Processing, Faculty ofForestry, University of Toronto, Toronto, Canada

Dr Bandyopadhyay-Ghosh (PhD, Department of Engineering Materials, University of Sheffield, UK); rently a Post-doctoral Research Fellow at the University of Toronto; research focus: biopolyol, biofoam andcellulose nanofibres

cur-Erwin Baur M-Base Engineering + Software GmbH, Aachen, Germany

Dr.-Ing Baur (Graduated in Mechanical Engineering, specialised in Plastics Technology, Technical University

of Aachen (RWTH), Aachen, Germany); Managing Director of M-Base Engineering + Software GmbH inAachen

Harri¨ette Bos Wageningen University and Research Centre, Food and Biobased Research, Department ofFibre and Paper Technology, Wageningen, The Netherlands.

Dr Bos (PhD, Eindhoven University; graduated in Physical Chemistry, University of Groningen, The lands); currently responsible for the policy support research program on Biobased Economy from the Ministry

Michael Carus nova-Institut, H¨urth, Germany

Diplom-Physiker Michael Carus (Advanced degree in Physics, University of Cologne, Germany); currentlyManaging Director of nova-Institut and head of the field “Renewable resources/market research.”

Muhammad Rafiq Chaudhry International Cotton Advisory Committee, Washington, DC, USA

Dr Chaudhry (PhD in Cotton Breeding and Genetics, Uzbekistan); currently head of the Technical InformationSection of the ICAC; author of the book ‘Cotton Facts’ and Editor of the THE ICAC RECORDER

Klaus Dippon Bio-Composites And More GmbH, Ipsheim, Germany

Dr Dippon (PhD in Agricultural Engineering, University of Stuttgart-Hohenheim, Germany); Vice President

to a start-up firm that produced high quality erosion control products from coir; currently Managing Director

of B.A.M

Axel Drieling Faserinstitut Bremen e.V (FIBRE), Bremen, Germany

Dipl.-Ing Drieling (Degree in Production Engineering, University of Bremen, Germany); currently head ofthe Testing Methods Department at FIBRE; research focus: harmonisation of fibre testing (ITMF, CSITC &INTERWOOLLABS)

Michaela Eder Max-Planck-Institute of Colloids and Interfaces, Department of Biomaterials, Potsdam,Germany

Dr Eder (Wood Science and Technology at BOKU University, Vienna, Austria); currently post-doctoral fellow

at the Department of Biomaterials; research focus: mechanical performance of plant cell wall properties

Holger Fischer Faserinstitut Bremen e.V (FIBRE), Bremen, Germany

Dr Fischer (Dr rer nat in Chemistry, University of Bremen, Germany); currently Senior Research Fellow

at the FIBRE; research focus: enzymatic fibre modification, fibre characterisation, fibre surface modification,biocomposites

Fenella G France Preservation Research and Testing Division, Library of Congress, Washington, DC,USA

Dr France (PhD from Otago University, New Zealand); currently preservation scientist in the Library ofCongress Preservation Directorate; research focus: polymer aging, polymer and textile deterioration

Anja Gliˇsovi´c Fraunhofer Institut f¨ur Fertigungstechnik und Angewandte Materialforschung (IFAM),Bremen, Germany

Dr Gliˇsovi´c (PhD in Physics, Georg-August-Universit¨at G¨ottingen, Germany); currently project manager

at the IFAM; research focus: development and industrial application of biopolymers and nature-inspiredbiomaterials

Friedhelm G¨oltenboth Institute for Plant Production and Agroecology in the Tropics and Subtropics,University of Hohenheim, Stuttgart, Germany.

Prof Dr G¨oltenboth (PhD in Genetics, Ruhruniversity Bochum, Germany); Honorary Professor for TropicalAgro-Ecology, University of Hohenheim; research focus: tropical agro-ecology in indonesia, Papua NewGuinea and Philippines

Jean-Paul Gourlot CIRAD PERSYST LTC, Montpellier, France

Dr Gourlot (PhD in Sciences for Engineer); Head of the Cotton Technology Laboratory at CIRAD; researchfocus: cotton testing and standardisation, ‘Commercial Standardized Instrument Testing for Cotton TaskForce.’

Nina Graupner Hochschule Bremen – University of Applied Sciences, Department of Biomimetics,Bremen, Germany

Dipl.-Ing (FH) Graupner (Degree in Renewable Resources, University of Applied Sciences, Hanover,Germany); currently affiliated with the Hochschule Bremen; research focus: biopolymer composites andfibre/matrix interaction

Hans-J¨org Gusovius Leibniz-Institut f¨ur Agrartechnik Potsdam-Bornim e.V., Potsdam, Germany

Dr Gusovius (Dr.-Ing Agriculture, Humboldt-University, Berlin, Germany); currently member of staff atLeibniz-Institute for Agricultural Engineering: research focus: development of highly effective harvestingmachinery for hemp

Tuomas H¨anninen Department of Forest Products Technology, Aalto University, Helsinki, Finland.MSc H¨anninen (Wood Chemistry, Helsinki University of Technology, Finland); currently PhD at the Depart-ment of Forest Products Technology; research focus: ultrastructural characteristics of natural fibres, Ramanspectroscopy

Michael V Harding Great Circle International, Inc., San Diego, CA, USA

Michael Harding (graduate from Purdue University) Director of the San Diego State University Soil ErosionResearch Lab and President of the IECA: research focus: development and implementation of test methodsfor EC products

Tim Huber University of Canterbury, Department of Mechanical Engineering, Christchurch, New Zealand.BSc Tim Huber (University of Applied Sciences, Bremen, Germany); currently PhD at the CanterburyUniversity, Christchurch, New Zealand; research focus: biocomposites and processing of novel all-cellulosecomposites

Mark Hughes Department of Forest Products Technology, Aalto University, Helsinki, Finland

Prof Dr Hughes (PhD in Wood Science); currently Professor of Wood Technology at the Aalto University;research focus: wood and non-wood fibre reinforced composites, experimental mechanics and micro-mechanics

Chitrangani Jayasekara Coconut Research Institute, Lunuwila, Sri Lanka

Dr Jayasekara (PhD University of Queensland, Australia); currently Director of the Coconut ResearchInstitute of Sri Lanka; research focus: retting of coir, development of coir based new products for agriculturalapplications

Maya John CSIR Materials Science and Manufacturing, Port Elizabeth, South Africa, and Department ofTextile Science, Nelson Mandela Metropolitan University, Port Elizabeth, South Africa

Dr John (PhD, Mahatma Gandhi University, India); currently Senior Researcher at the CSIR; research focus:hybrid natural fibre composites, lignocellulosic fibre reinforced composites and biopolymer systems

Lothar Kruse Impetus GmbH & Co Bioscience KG, Bremerhaven, Germany.

Dr Kruse (PhD in Molecular Biology, University of Bremen, Germany); Managing Director of Impetus;research focus: test systems and analyses for the DNA-based identification of species and genetic modifications

in food, feed, seed and fibres

Gero Leson Leson & Associates, Berkeley, CA, USA

Dr Leson (Physicist and Environmental Scientist); project coordinator for the sustainable production oforganic and fair trade raw materials (coconut oil, palm oil) for use in the production of Dr Bronner’s naturalsoaps and as foods

Werner M ¨uhlbauer Institute for Agricultural Engineering, University of Hohenheim, Stuttgart, Germany.Prof Dr.-Ing Dr h.c M¨uhlbauer (Stuttgart University, Germany); Managing Director of the Institute atHohenheim University until his retirement in 2004; initiated and implemented the abac´a PPP-Project withDaimler AG

J¨org M ¨ussig Hochschule Bremen – University of Applied Sciences, Department of Biomimetics, Bremen,Germany

Prof Dr.-Ing J¨org M¨ussig (Dr.-Ing University of Bremen, Germany); currently Professor of BiologicalMaterials at the Hochschule Bremen; research focus: bio-inspired materials, natural fibres and natural fibrecomposites

Franz Neubauer ECOLABOR e.U., Accredited Testing Laboratory and Inspection Agency for Thermal-,Moisture-, Sound- and Fire Protection, Stainz, Austria

Dipl.-Ing Neubauer (University of Technology of Graz, Austria); founder of the ECOLABOR e.U., member

of standardization committees; research focus: thermal conductivity and water-vapour transmission property

Frank Otremba M-Base Engineering + Software GmbH, Aachen, Germany

Dipl.-Ing Otremba (Technical University of Aachen, Germany); 2001–2009 simulation engineer and projectmanager at M-Base, currently simulation specialist (theory group) of Enrichtemnet Technolgy Company Ltd,J¨ulich, Germany

Stephan Piotrowski nova-Institut, Department of Economics and Resource Management, H¨urth, Germany

Dr Piotrowski (PhD Agricultural Economics, University of Stuttgart-Hohenheim); currently working at thenova-Institut; research focus: land use competition between food and energy crops, renewable raw materialsfor material uses

Crisan Popescu DWI an der RWTH Aachen e.V., Aachen, Germany

Prof Dr Popescu (Doctorate in Physical Chemistry, University of Bucharest); Professor of Textile istry, University ‘Aurel Vlaicu’, Arad, Romania; currently scientist at DWI; research focus: keratin fibres,biomaterials and chemistry of proteins

Chem-Eugen Pr¨omper Johnson Controls, Burscheid, Germany

Dr rer nat Pr¨omper (Polymer Chemistry, Technical University of Aachen, Germany); department leader formaterial research and testing at different automotive suppliers; currently associated with Pr¨omper-Consulting,Viersen, Germany

Siddiqur Rahman International Jute Study, Dhaka, Bangladesh

MSc Rahman (Degree in Applied Physics, University of Dhaka, Bangladesh); currently working in theInternational Jute Study Group (IJSG), an intergovernmental group which works for the development ofworld jute economy

Mohini Sain Center for Biocomposites and Biomaterials Processing, Faculty of Forestry, University ofToronto, Toronto, Canada.

Prof Dr Sain is a Professor of the Faculty of Forestry and Director of the Centre for Biocompositesand Biomaterials Processing; research focus: cellulose based micro and nano composite, biomaterials andbiocomposites

Tanja Slootmaker Faserinstitut Bremen e.V (FIBRE), Bremen, Germany

Mrs Slootmaker (physical-technical assistant) at the FIBRE; currently responsible for the administration

of international wool standards and round trials; research focus: identification and differentiation of naturalfibres

Martien van den Oever Wageningen University and Research Centre, Food and Biobased Research,Wageningen, The Netherlands

MSc van den Oever (Chemical Engineering, Eindhoven University, The Netherlands); Project Manager at theResearch Institute F & BR; research focus: fibre reinforced polymers, panel and board materials, fibre basedfoams and films, and textiles

Fritz Vollrath Department of Zoology, Oxford University, Oxford, UK

Prof Dr Vollrath (PhD, University of Freiburg, Germany); currently a Senior Research Fellow at the partment of Zoology, University of Oxford; research focus: silks and silk-structures as well as animaldecision-making

De-Franz-Josef Wortmann Textiles & Paper, School of Materials, University of Manchester, UK

Prof Dr Wortmann (PhD in Polymer Chemistry at DWI, Aachen, Germany) currently Professor of Fibreand Textile Technology at the University of Manchester; research focus: chemical and physical properties ofanimal fibres

List of Illustrators

Anja M ¨ussig schnittreif, Bremen, Germany

Dipl.-Ing (FH) Anja M¨ussig (University of Applied Sciences Niederrhein, Germany); during her industrycareer, strong focus on construction and pattern design; currently free-lancer in the clothing business anddesign of ‘schnittreif.’

Tanja Slootmaker Faserinstitut Bremen e.V (FIBRE), Bremen, Germany

Beside her expertise in identification and differentiation of natural fibres, she has a strong affinity towards artand design She combines the topics fibre technology and fibre science with arts in this publication

PART I

BACKGROUND

1 Historic Usage and Preservation

Histor-of information for textile preservation (France, 2005a) A historical textile consists not only Histor-of the materialitself but also of all the historical evidence collected upon and within it over years of use Scientific analysescan establish whether surface contaminants and soiling have historical significance or are potential sources

of degradation For cultural heritage institutions (including museums, libraries, archives and historic housecollections) this involves additional critical details concerning display, storage, exhibition and treatments,including details about soiling, deterioration and the effects of environmental conditions Techniques such

as scanning electron microscopy, X-ray analysis, confocal microscopy, gas chromatography, mechanicaltesting and chemical analyses allow investigations into internal and external aspects of the fibre structure,identification of surface contaminants and the opportunity to learn about the impact of treatments and dis-play environments on textile deterioration This microscopic-level examination in turn reveals macro-levelinformation pertaining to the condition of the entire textile

1 The views presented in this chapter reflect the opinion of the author and not the Library of Congress.

Industrial Applications of Natural Fibres: Structure, Properties and Technical Applications Edited by J¨org M¨ussig

1.2 Preservation of Cultural Heritage

The historic use of natural fibres is much broader than clothing and tapestries, as they heralded patriotism,sovereignty, peace and all too often war when structured into woven fabrics Finely woven wool fabricswere utilised as banners and large flags, as they were robust and could be dyed to required colours, with theloose-weave structure allowing them to brandish the symbol of the message, even in a large format Preservingour past requires knowledge of the properties of the textiles from which they are formed (France, 2005b).The ubiquitous nature and functionality of textiles give them a unique place in our cultural heritage Unlikeworks of art and other items, textiles are generally made to be functional, so that, after normal wear and tear,they enter our museums already in a fragile state This also has implications for their documentation, or lackthereof Gaining knowledge of the unique natural fibre textile properties and structure can be accomplishedwith a range of scientific analyses and techniques

While highly significant and recognisable items such as the United States’ Star-Spangled Banner are noted

to have been present at certain events – in this case the battle at Fort McHenry in Baltimore harbour inSeptember 1814 – detailed knowledge of their history is often sketchy This historic flag was commissioned

by Major George Armistead, commander of Fort McHenry, and was raised over Fort McHenry on the morning

of 14 September 1814 to signal American victory over the British in the Battle of Baltimore It was this eventthat inspired Francis Scott Key to write ‘The Star-Spangled Banner’, the song that became the United States’national anthem The original flag was 9.1 m by 12.8 m (30 ft by 42 ft) and made of high-quality single-weavewool bunting and cotton Each of the fifteen stripes in red and white (undyed) wool were 0.6 m (24 in) wide,the same width for the wool in the blue canton, and the fifteen large cotton stars measured 0.6 m (2 ft) point

to point The history of this woollen flag fabric can be traced back to a cottage industry in Sudbury, Suffolk,England, in the late eighteenth century (France, 2007) This artefact provides us with an excellent example ofthe impact, potential and challenges offered by science and technology for studies into the textile structure andproperties of cultural objects Scientific techniques and new technologies are proving critical for providingpreviously lost information, information that informs us as to both the current state of the artefact and themain sources of degradation, as this information is paramount for establishing the optimum environmentalconditions to ensure the long-term preservation of a historic technical textile such as a flag

The determination of chemical and mechanical properties and fabric, yarn and fibre morphology start

to provide this knowledge A historical textile consists not only of the material itself but also of all thehistorical evidence collected over its years of use Determining the probable source of surface contaminants iscritical, as soiling offers curators evidence linking a textile to a particular geographical location, or can revealtrace elements from a particular historic event, such as the War of 1812 Scientific analysis supported bymicroscopy helps establish whether surface particulates, contaminants and soiling have historical significance,and aids in critical decisions regarding possible degradation from surface contaminants that could reduce theartefact’s life

Assessment of the amino acid content of the wool fibres allows identification of the specific aminoacid composition characteristic of the specific breed of sheep or domestic animal (see Chapters 12 and 16).Historically, many cultural heritage items had pieces removed over the years For example, when soldiers whofought at Fort McHenry died, their widows wrote to the daughter of the commander of the fort, requesting apiece of the Star-Spangled Banner to be buried with their husband Amino acid analyses of samples found later

in various locations were tested to assess and confirm their provenance against the amino acid composition

of the flag keratin Changes in specific amino acid analyses can also confirm the main agent of deterioration(e.g light or temperature), as specific amino acids will degrade under certain conditions while others are leftunchanged

Scanning electron microscopy (SEM) and elemental analysis are pertinent techniques for assessing theeffects of surface deterioration to support curatorial decisions SEM provides insights into fabric, yarnand fibre fracture morphology, which illustrates changes due to photodegradation, through high-resolutionhigh-magnification images At the fibre level, these highly magnified visible changes, linked with specific

Figure 1.1 Scanning electron micrograph of an aged wool fibre dated ca 1800, approximately 47 µm in diameter (2000× magnification).

mechanical and chemical behaviour in the keratin structure, lead to a commensurate decrease in the textile’smechanical strength, as the fibre fracture is a direct manifestation of changes in the internal structure thatreduce the mechanical properties

Changes in fibre surface morphology evident in SEM images provide strong indicators of the effects ofvarious degradative environmental influences – light, relative humidity, biological and soiling This fibredegradation is indicated by the presence of microfractures and cracking from relative humidity fluctuations,abrasion from particulates and/or damage from biological organisms Analyses by SEM allow confirmation

of the high sulphur content characteristic of wool, as well as determination of any surface contaminants thatcan provide further historic information relating to the historic context, sometimes geographical informationand size and composition of degradative particulates and soiling (France, 2003a)

The SEM micrograph in Figure 1.1 shows a relatively smooth fracture surface, indicating light damage,and a lack of scale structure, indicating both age and damage from usage as a technical textile Furthermorphological details illustrate the presence of microfractures in the fibre, probably owing to environmentalfluctuations and the expansion and contraction of organic natural fibres from moisture changes, and thelodging of small particulates in these microfractures, which exacerbates the fracture and leads to breaks anddeterioration of the textile The basic theory regarding fibre fracture in extension involves the propagation of

a crack from a flaw (Andrews, 1964) The influence of flaws on the tensile properties of natural fibres will

be discussed in more detail in Chapter 13 In aged wool fibres, deterioration has already occurred owing tothe effects of use and exposure to the environment Changes in relative humidity cause small changes in fibredimensions, which, when constantly repeated, slowly generate microscopic flaws in the wool fibres Modernfracture mechanics has established that fibre breaks can initiate from a microscopic flaw present in the fibrestructure, with axial shear deformation playing an important role in the initiation and propagation of cracks.Figure 1.2 illustrates the soiling that is prevalent with historic natural wool fibres, but also the fact that,through shielding within the textile yarn structure, some fibres may retain scale formation Therefore, it should

be noted that, while some fibres may be so degraded as to require amino acid analysis or chemical testing toconfirm their substrate, there can be a range of fibre morphologies within natural historic fibre assemblies.However, the microfractures – albeit smaller – are still in evidence, with small particulate material lodging inthe fractures and leading to exacerbated damage and deterioration of the natural fibres

Figure 1.2 Scanning electron micrograph of an aged wool fibre dated ca 1800, approximately 50 µm in diameter (2000× magnification).

For conservation specialists and cultural heritage collections, preventive conservation requires analysesthat include additional critical details about display, storage, exhibition and treatments These investigationsmust include information about soiling, patterns and levels of deterioration and the effects of environmentalconditions – such as relative humidity, light levels and pollution control The application of a range ofscientific techniques to fibre analysis provides a wealth of information for textile preservation Techniquessuch as SEM, elemental analysis, confocal microscopy, light microscopy, gas chromatography (GC-MS),mechanical testing and chemical analyses allow investigations into internal and external aspects of the fibrestructure, identification of surface contaminants and the opportunity to learn about the impact of varioustreatments and display environments on textile deterioration (France, 2004)

Linking chemical and mechanical properties allows changes in the fibre properties to be associated withphysical changes in the technical textile While much attention is paid to temperature, organic materials arehighly susceptible to changes in relative humidity, as indicated by the micrograph in Figure 1.2 Wayne (1970)noted the basis for distinguishing between photochemical and thermal effects This can be highlighted by theexample of a bond-breaking reaction that requires energy of 251 kJ/mol, typical of many covalent bonds inwool fibres The excitation energy to break this bond can be induced photochemically by a single quantum

of light of about 450 nm (i.e green light) In contrast, at ambient temperatures the thermal energy availablefor bond cleavage is essentially zero (4 × 10−46) The state of historic wool fibres is dependent upon the

extent to which the textile item has been used, and the conditions to which they have been exposed: light,water, oxygen and temperature A study of keratin fibres taken from tombs in Egypt dated at between 1500and 4000 years old showed that these retained as much as 20% of the strength and 10% of the extensibility

of modern unaged wool fibres (Massa et al., 1980) These values were also comparable with those of wool

fibres only 200 years old from textiles that had been used as working textiles, and that had spent a portion oftheir recent history in museum environments To gain an accurate assessment of the state of deterioration ofhistoric natural fibre assemblies, the use of the ‘energy of rupture’ measure provides a combination of both theloss of strength and the loss of extensibility of the aged fibres As shown in Figure 1.3, pre-Columbian wooltextile fibres (ca 1500) that had been buried under conditions of constant relative humidity, low oxygen and

no light were shown to retain up to 50% of the strength of unaged wool fibres, as compared with textiles from

1800 that had been exposed to environmental fluctuations This shows the significant effect of environmental

Figure 1.3 Energy of rupture degradation curve of wool fibres from ca 1500 AD and 1800 AD after different irradiation times.

parameters on historic wool textiles As is evident from the steep initial portion of the curve, extensivedegradation occurs early in the life of a textile; therefore, as regards the degradation process of natural fibres,the preservation of modern natural textiles needs to be carefully considered in terms of their exposure to

degradative environmental influences (France et al., 2005).

The primary goal of conservation is the preservation of cultural property, with current preventive tion focusing on non-intervention techniques if possible An important consideration is whether stabilisation

conserva-of conditions alone can confer enough conserva-of a benefit to conserva-offset the requirement for treatment to the historictextile artefact If treatment of the textile is required to remove harmful contaminants, an evaluation of thetreatment is necessary to ensure that it both confers a benefit by removing soiling and particulate matterand does no harm through fracturing or decreasing mechanical properties In order to create a baseline formany of these tests, samples that have undergone accelerated ageing are usually utilised to assess the variouspotential environmental conditions and treatments In these cases, removing samples from an already fragilehistoric textile for assessment is an ethical dilemma Very small samples that can directly answer criticalquestions for the long-term preservation of the item may be permitted; however, preservation scientists areconstantly developing non-destructive, non-invasive techniques that can provide the same level of informationwithout any impact on an item of significant cultural heritage (France, 2003b) This assessment of treatmentsand environmental parameters supports critical cost-benefit decisions while providing a more comprehensiveoverview of preservation requirements

Characterisation of natural fibres is a critical component in assessing the overall properties of the product,

as what occurs at a micro level can have a significant impact on the effects observed at a macro level and theapplicability of the fibre for specific uses The determination of chemical and mechanical properties is criticalfor cultural heritage, as often there is little documentation and it is only through scientific analyses of thefibre and fibre structures that a historical profile can be recreated Many techniques in conservation sciencefocus upon microsampling as non-invasively as possible, causing minimal disturbances to an already fragiletextile Changes in chemical properties can give a good assessment of structural damage and deterioration

of the natural fibres, particularly when these are linked with physical markers that integrate this micro-levelinformation with the macro-level manifestation Significant interest is again being shown in the analysis

of both animal and plant natural fibres because of their inherent properties, providing a template for thecreation of man-made fibres These can include bicomponent structures such as wool, or specific moisture,strength and extensibility properties such as those for cellulose and protein fibres The utilisation of thesenatural fibres in long-term applications such as technical textiles will continue to play a significant role in thepreservation and understanding of our cultural heritage as well as in future developments for sustainable andenvironmentally compatible textiles

Figure 1.4 Scanning electron micrograph of ca 1900 AD single bast fibres with a diameter of approximately 20 µm.

As mentioned previously, the stars of the Star-Spangled Banner were made from cotton fabric, and theseexhibited a higher level of acidity than the wool fabric Stabilisation of the cotton fabric was part of theconservation treatment, as well as removal of a linen backing attached in 1913 to stabilise the flag Thelinen backing and Amelia Fowler stitching stabilisation undertaken in 1913 was removed, as the bast fibres(Figure 1.4) were degrading at a different rate to the wool fabric and causing destabilisation of the wool andcotton flag structure It should be noted that all natural fibres have different properties with regard to strengthand extensibility, so composite fabrics – whether historic or modern technical textiles – need careful attention

as to the combination of fibre properties

Studies of the history of historic textiles and their natural fibres provide additional insights into the technicalapplications of the textiles over the years The stewardship of historic textiles, in common with all culturalheritage items, requires the best preservation techniques possible to ensure their longevity based on currentinformation and resources This requires an understanding of the history of the textile in terms of its lifetime

of usage, display and storage environments, technical application and the effects of treatments and conditions.The current state of a natural fibre textile will be entirely dependent upon this history As this is often notdocumented, a range of analytical techniques are essential to provide the missing information, including bytesting the properties of the natural fibres This critical information should include not only the mechanicaland chemical state of the textile, together with fibre and dye analysis and identification, but also the leveland type of environmental degradation that have occurred Identification of soils and contaminants, as well

as an assessment of those treatments that are most beneficial for the preservation and understanding of thistextile, is also important While a wide variety of analytical techniques are available, a clear understanding

of the information required for conservation of each textile should be established, so as to utilise the mostappropriate technique to answer the conservation questions and determine the optimum preservation outcome

or treatment

Conservation requires scientific analyses for conservation specialists and museum collections that providecritical details for identifying a natural historic textile – history, display, storage, exhibition and treatments

These investigations must include information about soiling, patterns and levels of deterioration and the effects

of environmental conditions – light levels, relative humidity and pollution control The application of a range

of scientific techniques to textile fibre analysis provides a wealth of information for textile preservation.The advanced precision in techniques such as mechanical testing, chemical analyses and microscopy allowsinvestigations into internal and external aspects of the fibre structure, identification of surface contaminantsand assessment of textile deterioration linked to environment or treatment In the museum setting, conditionscan be controlled and monitored to minimise the effects of environmental factors

The primary goal of conservation is the preservation of cultural property, with preventive conservationfocusing on non-intervention techniques if possible An important consideration is whether stabilisation ofconditions alone can confer enough of a benefit to offset the requirement for treatment of a historic artefact Iftreatment of a textile is required to remove harmful contaminants, an evaluation of the treatment is necessary

to ensure that it both confers a benefit by removing soiling and particulate matter and does no harm throughfracturing or decreasing mechanical properties Preventive textile conservation extends the life of a textile withthe best care available This involves making decisions about exhibition and storage conditions, monitoringand controlling the environment and treating or cleaning the textile Critical information is necessary tomake these informed decisions The use of available and well-developed scientific techniques provides thoseinvolved in conservation activities with the empirical information needed to understand the properties of thenatural fibres and to make these critical decisions about preservation

References

Andrews, M.W (1964) The fracture mechanism of wool fibers under tension Text Res J., 34, 831–835.

France, F.G (2003a) Beneath the grime: measuring the effects of preservation treatments for textiles, in Textile Specialty

Group Postprints Textile Specialty Group, American Institute for Conservation, Washington, DC, pp 45–52.

France, F.G (2003b) Creating a standard vocabulary for defining levels of deterioration, in Development of a

Web-Accessible Reference Library of Deteriorated Fibers Using Digital Imaging and Image Analysis, ed by Merritt, J.

Proceedings of Conference, Harpers Ferry, WV, 3–6 April 2003 Harpers Ferry Center, National Park Service, USDepartment of the Interior, pp 77–86; available at: http://www.nps.gov/hfc/products/cons/con-fiber.htm (accessed

17 December 2009)

France, F.G (2004) Preservation of textile cultural heritage, in Quality Textiles for Quality Life Proceedings of the Textile

Institute’s 83rd World Conference, 23–27 May 2004 College of Textiles, Donghua University, Shanghai, China/TextileInstitute, Manchester, UK, pp 1583–1587

France, F.G (2005a) Scientific analysis in the identification of textile materials, in Scientific Analysis of Ancient and

Historic Textiles: Informing Preservation, Display and Interpretation: Postprints, ed by Janaway, R and Wyeth, P.

Archetype Publications, London, UK, pp 3–11

France, F.G (2005b) Andean to banners, in Proceedings of the 11th International Wool Research Conference, University

of Leeds, 4–9 September 2005 Department of Colour and Polymer Chemistry, University of Leeds, Leeds, UK, CDROM

France, F.G (2007), Weaving independence from a distant cottage industry, in Textile Narratives + Conversations, ed.

by Bier, C and Perlman, A.S 10th Biennial Symposium, Textile Society of America, Earleville, MD, CD-ROM.France, F.G., Roussakis, V., Lissa, P., Xanena, M., Santillan, P., Campero de Larran, M., Dona, G and Ammrati, C

(2005) Textile treasures of Llullaillaco, in Recovering the Past: the Conservation of Archaelogical and Ethnographic

Textiles 5th Biennial North American Textile Conservation Conference, Mexico City, Mexico, 9–11 November 2005,

pp 31–34

Massa, E.R., Masali, M and Fuhrman, A.M.C (1980) Early Egyptian mummy hairs: tensile strength tests, optical and

scanning electron microscope observation A paleo-biological research J Hum Evolution, 9, 133.

Wayne, R.P (1970) Photochemistry Butterworth & Co Ltd, London, UK.

2 What Are Natural Fibres?

2.1 Chemistry of Plant Fibres

hemicellu-‘typical’ cell wall with major components and a schematic representation of their organisation

The chemistry and structure of fibres determine their characteristics, functionalities and processing ciencies The following information briefly describes the major components in these natural fibres as it relates

effi-to fibre applications

2.1.2 Cellulose

Cellulose is a linear polymer of glucose (Nelson and Cox, 2000; Ljungdahl, 1990; Focher, 1992) In itssimplest form, cellulose is a linear carbohydrate polymer ofβ-1,4-linked glucose units However, the basic

repeating unit of cellulose is the dimer cellobiose, which comprises two glucose units bound by theβ-1,4

linkage as well as intermolecular hydrogen bonds A typical structure of cellulose is shown in Figure 2.1.2.The structure of how glucose is bound in the linear polymer determines the properties of cellulose Cellulosecan take many forms, a phenomenon that is the basis for numerous in-depth reviews of this important naturalpolymer (Ljungdahl, 1990; Focher, 1992) Briefly, cellulose, which consists of thousands of glucose units,can stack to form crystalline forms with intramolecular hydrogen bonds providing a stable, hydrophobicpolymer with high tensile strength Cellulose occurs in plant cell walls as microfibrils (e.g 2–20 nm diameterand 100–40 000 nm long) providing a linear and structurally strong framework (see Figure 2.1.1) Severalmodels have been proposed of the packing of microfibrils within the cellulosic fibre In addition to the moreordered or crystalline regions of cellulose, there are other regions of less order, or non-crystalline regions.These differences can have enormous influence on characteristics and functionalities

Industrial Applications of Natural Fibres: Structure, Properties and Technical Applications Edited by J¨org M¨ussig

Figure 2.1.1 Schematic diagram of the hierarchy of a ‘typical’ plant cell wall, from cellulose synthesis to a simplified model

of a primary cell wall and from microfibril structure to crystalline cellulose to the cellulose molecule with the monomer unit glucose Adapted with permission from AAAS, C Somerville et al Science, 306, 2206–11 (2004) and U.S Department of Energy Genome Programs, http://genomics.energy.gov.

The structure of cellulose results in a complicated situation for enzymatic degradation Classically, threecellulases are required to degrade cellulose: exocellulase (exocellobiose hydrolase), endocellulase and cel-lobiase (Ljungdahl, 1990) Much detailed work has elucidated some of the complexity of cellulolysis, and ingeneral terms exocellulase knocks off cellobiose units from an end of the polymer, endocellulase randomlybreaksβ linkages and the cellobiase degrades the dimer into glucose units It is known that enzymes can

degrade cellulose by other mechanisms

While a large amount of information exists on this very important polymer, there are characteristics not wellunderstood for particular fibres Such characteristics may be further influenced by various amounts of othersugars or components as integral parts of ‘cellulose’ (Focher, 1992) A practical example of this differentialchemistry is shown in retting of cellulosic bast fibres such as flax In the bast tissues, the cellulosic structure

of the fibre is more resistant than other components, such as the matrix components, to the enzyme tium of retting microorganisms, allowing for a separation of the (primarily) cellulosic fibres (Figure 4.4 inChapter 4)