Textiles for Hygiene and Infection Control (Woodhead Publishing Series in Textiles)

Textiles for hygiene and infection control

© Woodhead Publishing Limited, 2011

The Textile Institute and Woodhead Publishing The Textile Institute is a unique organisation in textiles, clothing and footwear. Incorporated in England by a Royal Charter granted in 1925, the Institute has individual and corporate members in over 90 countries. The aim of the Institute is to facilitate learning, recognise achievement, reward excellence and disseminate information within the global textiles, clothing and footwear industries. Historically, The Textile Institute has published books of interest to its members and the textile industry. To maintain this policy, the Institute has entered into partnership with Woodhead Publishing Limited to ensure that Institute members and the textile industry continue to have access to high calibre titles on textile science and technology. Most Woodhead titles on textiles are now published in collaboration with The Textile Institute. Through this arrangement, the Institute provides an Editorial Board which advises Woodhead on appropriate titles for future publication and suggests possible editors and authors for these books. Each book published under this arrangement carries the Institute’s logo. Woodhead books published in collaboration with The Textile Institute are offered to Textile Institute members at a substantial discount. These books, together with those published by The Textile Institute that are still in print, are offered on the Woodhead website at: www.woodheadpublishing.com. Textile Institute books still in print are also available directly from the Institute’s website at: www.textileinstitutebooks.com. A list of Woodhead books on textile science and technology, most of which have been published in collaboration with The Textile Institute, can be found towards the end of the contents pages.

© Woodhead Publishing Limited, 2011

Woodhead Publishing Series in Textiles: Number 108

Textiles for hygiene and infection control Edited by Brian J. McCarthy

Oxford

Cambridge

Philadelphia

© Woodhead Publishing Limited, 2011

New Delhi

Published by Woodhead Publishing Limited in association with The Textile Institute Woodhead Publishing Limited, 80 High Street, Sawston, Cambridge CB22 3HJ, UK www.woodheadpublishing.com Woodhead Publishing, 1518 Walnut Street, Suite 1100, Philadelphia, PA 19102-3406, USA Woodhead Publishing India Private Limited, G-2, Vardaan House, 7/28 Ansari Road, Daryaganj, New Delhi – 110002, India www.woodheadpublishingindia.com First published 2011, Woodhead Publishing Limited © Woodhead Publishing Limited, 2011 The authors have asserted their moral rights. This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. Reasonable efforts have been made to publish reliable data and information, but the authors and the publisher cannot assume responsibility for the validity of all materials. Neither the authors nor the publisher, nor anyone else associated with this publication, shall be liable for any loss, damage or liability directly or indirectly caused or alleged to be caused by this book. Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming and recording, or by any information storage or retrieval system, without permission in writing from Woodhead Publishing Limited. The consent of Woodhead Publishing Limited does not extend to copying for general distribution, for promotion, for creating new works, or for resale. Specific permission must be obtained in writing from Woodhead Publishing Limited for such copying. Trademark notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation, without intent to infringe. British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library. ISBN 978-1-84569-636-8 (print) ISBN 978-0-85709-370-7 (online) ISSN 2042-0803 Woodhead Publishing Series in Textiles (print) ISSN 2042-0811 Woodhead Publishing Series in Textiles (online) The publisher’s policy is to use permanent paper from mills that operate a sustainable forestry policy, and which has been manufactured from pulp which is processed using acid-free and elemental chlorine-free practices. Furthermore, the publisher ensures that the text paper and cover board used have met acceptable environmental accreditation standards. Typeset by Ann Buchan (Typesetters), Middlesex, UK Printed by TJI Digital, Padstow, Cornwall, UK

© Woodhead Publishing Limited, 2011

Contents

Contributor contact details

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Part I Design and production techniques for hygiene textiles 1

The design of novel hygiene textile products

3

M. JASSAL, Indian Institute of Technology (IIT), India

1.1 1.2 1.3 1.4 1.5 2

Introduction: hygiene products Applications of hygiene products Key property requirements of hygiene products Types of new technology to improve the performance of hygiene products References

3 3 4 5 10

Nanotechnology and its application to medical hygiene textiles

14

F. SARTAIN, A. READER, M. FISHER, B. PARK, M. KEMP and J. JOHNSTONE, NanoKTN, UK and B. J. MCCARTHY, TechniTex Faraday Limited, UK

2.1 2.2 2.3 2.4 2.5

Introduction Healthcare and life sciences Standards and regulations for nanotechnology products The global textiles and clothing sectors References

14 15 18 19 25

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Contents

3

Use of knitted spacer fabrics for hygiene applications

27

A. M. DAVIES, De Montfort University, UK

3.1 3.2 3.3 3.4 3.5 3.6 4

Introduction: key issues in hygiene and moisture management Three-dimensional fabrics: an overview Principles of knitting spacer fabrics Application of knitted spacer fabrics in hygiene products Future trends References

27 29 31 35 44 45

Innovative and sustainable packaging strategies for hygiene products

48

S. LAM PO TANG, TechniTex Faraday Limited, UK

4.1 4.2 4.3 4.4 4.5 4.6

Introduction Key considerations and drivers for the packaging of hygiene products Growing trends and innovation strategies Future trends for the hygiene industry Sources of further information and advice References

51 56 64 66 66

5

Biodegradable hygiene products

68

5.1 5.2 5.3 5.4 5.5

48

M. BENEDETTI, W.I.P. Spa, Italy

68

Introduction A classification of sustainable materials according to their ecological footprint Criteria for the selection and implementation of sustainable alternative raw materials Alternative raw materials Conclusion

68 69 70 72 80

Part II Design and production techniques for infectioncontrol textiles 6

Micro-organisms, infection and the role of textiles

85

R. JAMES, University of Nottingham, UK

6.1 6.2

Introduction to infections Superbugs and healthcare-associated infections

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Contents

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6.3 6.4 6.5 6.6 6.7 6.8

Principles of infection prevention and control in hospitals The role of textiles in infection prevention and control Future trends A holistic approach to preventing infections Sources of further information and advice References

94 97 98 100 101 101

7

Creating barrier textiles through plasma processing

104

S. COULSON, P2i Ltd, UK

7.1 7.2 7.3

7.5 7.6 7.7 7.8

Introduction The importance of liquid repellency Current solutions for rendering barrier textiles liquid repellent Use of plasmas for imparting liquid repellency to barrier textiles Applications for plasma-processed barrier textiles Future trends Sources of further information and advice References

111 115 123 123 124

8

Disposable and reusable medical textiles

125

7.4

104 105 109

G. SUN, University of California, Davis, USA

8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8

Introduction: disposable versus reusable Life cycles of disposable and reusable textiles Costs of disposable and reusable textiles Protection provided by disposable and reusable materials Biocidal woven and nonwoven textiles Conclusions Acknowledgment References

125 126 128 130 131 133 133 133

9

Ensuring fabrics survive sterilisation

136

M. J. A. M. ABREU, Universidade do Minho, Portugal

9.1 9.2 9.3 9.4 9.5

Introduction Purpose and importance of sterilisation Quality assurance of the sterilising process Effect of sterilisation on fibres and fabrics Reprocessing sterilised products

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136 137 143 144 145

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Contents

9.6 9.7 9.8

Normalisation Conclusions References

147 148 148

Part III Product types 10

Washable textile-based absorbent products for incontinence

153

A. M. COTTENDEN, R. SANTAMARTA VILELA, M. C. MACAULAY, D. J. COTTENDEN, M. A. LANDERYOU and D. LILBURN, University College London, UK and M. J. FADER, University of Southampton, UK

10.1 10.2 10.3 10.4 10.5 10.6 10.7 10.8 10.9 11

Introduction Incontinence pad designs Functional requirements of washable, textile-based incontinence products Clinical performance of existing products Laboratory evaluation Correlation with user data Future trends Sources of further information and advice References

153 155 155 157 161 168 170 171 171

Biological containment suits used in microbiological high containment facilities and by emergency responders 173 J. T. WALKER, K. GIRI, T. POTTAGE, S. PARKS, A. DAVIES and A. M. BENNETT, HPA, UK and C. LECULIER AND H. RAOUL, Laboratoire P4 INSERM Jean Mérieux, France

11.1 11.2 11.3 11.4

Introduction Containment fabrics to protect against biological threats Conclusions References

173 174 183 183

12

Coated textiles for skin infections

186

G. SENTI, A. U. FREIBURGHAUS and T. M. KÜNDIG, Centre for Clinical Research, University Hospital of Zurich, Switzerland

12.1 12.2

Introduction: textiles, skin and infections Types of coated textiles with anti-infectious properties

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186 187

Contents

12.3 12.4 12.5 12.6 13

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Applications for coated textiles to prevent or treat cutaneous infections Future trends for coated textiles against skin infections Sources of further information and advice References

188 192 192 193

Antimicrobial treatments of textiles for hygiene and infection control applications: an industrial perspective

196

S. C. BURNETT-BOOTHROYD, Advanced Textiles Limited, UK and B. J. MCCARTHY, TechniTex Faraday Limited, UK

13.1 13.2 13.3 13.4 13.5 13.6 13.7

Introduction Processes for biocidal application for textile structures Application during yarn and fibre manufacture: natural and synthetic Antimicrobial testing procedures Future trends Conclusion Sources of further information and advice

196 198

Index

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199 204 205 208 208

Contributor contact details

(* = main contact)

Editor Brian J. McCarthy TechniTex Faraday Limited Arch 30, North Campus Incubator Sackville Street Manchester M13 9PL UK E-mail: [email protected]

Chapter 1 Dr Manjeet Jassal Department of Textile Technology Indian Institute of Technology (IIT) Delhi India E-mail: [email protected]

Chapter 2 Felicity Sartain, Alec Reader, Mike Fisher, Barry Park, Martin Kemp and James Johnstone NanoKTN PETEC Thomas Wright Way, NETPark Sedgefield TS21 3FG UK

Brian J. McCarthy* TechniTex Faraday Limited Arch 30, North Campus Incubator Sackville Street Manchester M13 9PL UK E-mail: [email protected]

Chapter 3 Dr A. M. Davies TEAM Research Group De Montfort University The Gateway Leicester LE1 9BH UK E-mail: [email protected]

Chapter 4 Sharon Lam Po Tang TechniTex Knowledge Expert TechniTex Faraday Limited Arch 30 North Campus Incubator Sackville Street Manchester M13 9PL UK E-mail: [email protected] xi

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Contributor contact details

Chapter 5

Chapter 9

Marco Benedetti W.I.P. Spa Via Palasciano 39 59100 Prato Italy

Professor Maria J. A. M. Abreu Department of Textile Engineering Universidade do Minho 4800-058 Guimarães Portugal

E-mail: [email protected]

E-mail: [email protected]

Chapter 6

Chapter 10

Professor Richard James Professor of Microbiology Director of the Centre for Healthcare Associated Infections CBS Building University of Nottingham NG7 2RD UK

Professor Alan M. Cottenden*, Ms Raquel Santamarta Vilela, Ms Margaret Macaulay, Dr D. J. Cottenden, Dr M. A. Landeryou and Mr D. Lilburn Continence & Skin Technology Group Departments of Medicine/Medical Physics and Bioengineering University College London Archway Campus, Clerkenwell Building Highgate Hill London N19 5LW UK

E-mail: richard.james@nottingham. ac.uk

Chapter 7 Dr Stephen Coulson P2i Ltd 127 North Milton Park Abingdon Oxfordshire OX14 4SA UK

E-mail: [email protected]; [email protected]

E-mail: [email protected]

Chapter 8

Professor Mandy J. Fader Continence Technology and Skin Health Group School of Health Sciences University of Southampton UK

Chapter 11

Professor Gang Sun Division of Textiles and Clothing University of California, Davis CA 95616 USA E-mail: [email protected]

Dr Jimmy T. Walker*, K. Giri, T. Pottage, S. Parks, A. Davies and A. M. Bennett HPA, Biosafety Unit Microbiological Services Division Research Department

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Chapter 13

Porton Down Salisbury SP4 0JG UK E-mail: [email protected] C. Leculier and H. Raoul Laboratoire P4 INSERM Jean Mérieux 21 Avenue Tony Garnier 69365 Lyon Cédex 07 France

Chapter 12 Dr Gabriela Senti*, Dr Andreas Freiburghaus and Dr Thomas Kündig FMH Dermatology and Allergology Clinical Trial Centre Centre for Clinical Research, University Hospital of Zurich Switzerland E-mail: [email protected]; [email protected]; [email protected]

Simon Burnett-Boothroyd* 3 Quartz Avenue Berry Hill Mansfield Nottinghamshire NG18 4XB UK E-mail: simon.burnettboothroyd@ btinternet.com; simon.burnett-boothroyd@ adv-tex.com Brian J. McCarthy TechniTex Faraday Limited Arch 30, North Campus Incubator Sackville Street Manchester M13 9PL UK E-mail: [email protected]

© Woodhead Publishing Limited, 2011

Woodhead Publishing Series in Textiles

1 Watson’s textile design and colour Seventh edition Edited by Z. Grosicki 2 Watson’s advanced textile design Edited by Z. Grosicki 3 Weaving Second edition P. R. Lord and M. H. Mohamed 4 Handbook of textile fibres Vol 1: Natural fibres J. Gordon Cook 5 Handbook of textile fibres Vol 2: Man-made fibres J. Gordon Cook 6 Recycling textile and plastic waste Edited by A. R. Horrocks 7 New fibers Second edition T. Hongu and G. O. Phillips 8 Atlas of fibre fracture and damage to textiles Second edition J. W. S. Hearle, B. Lomas and W. D. Cooke 9 Ecotextile ’98 Edited by A. R. Horrocks 10 Physical testing of textiles B. P. Saville 11 Geometric symmetry in patterns and tilings C. E. Horne 12 Handbook of technical textiles Edited by A. R. Horrocks and S. C. Anand 13 Textiles in automotive engineering W. Fung and J. M. Hardcastle 14 Handbook of textile design J. Wilson 15 High-performance fibres Edited by J. W. S. Hearle xv © Woodhead Publishing Limited, 2011

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16 Knitting technology Third edition D. J. Spencer 17 Medical textiles Edited by S. C. Anand 18 Regenerated cellulose fibres Edited by C. Woodings 19 Silk, mohair, cashmere and other luxury fibres Edited by R. R. Franck 20 Smart fibres, fabrics and clothing Edited by X. M. Tao 21 Yarn texturing technology J. W. S. Hearle, L. Hollick and D. K. Wilson 22 Encyclopedia of textile finishing H-K. Rouette 23 Coated and laminated textiles W. Fung 24 Fancy yarns R. H. Gong and R. M. Wright 25 Wool: Science and technology Edited by W. S. Simpson and G. Crawshaw 26 Dictionary of textile finishing H-K. Rouette 27 Environmental impact of textiles K. Slater 28 Handbook of yarn production P. R. Lord 29 Textile processing with enzymes Edited by A. Cavaco-Paulo and G. Gübitz 30 The China and Hong Kong denim industry Y. Li, L. Yao and K. W. Yeung 31 The World Trade Organization and international denim trading Y. Li, Y. Shen, L. Yao and E. Newton 32 Chemical finishing of textiles W. D. Schindler and P. J. Hauser 33 Clothing appearance and fit J. Fan, W. Yu and L. Hunter 34 Handbook of fibre rope technology H. A. McKenna, J. W. S. Hearle and N. O’Hear 35 Structure and mechanics of woven fabrics J. Hu 36 Synthetic fibres: nylon, polyester, acrylic, polyolefin Edited by J. E. McIntyre

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Woodhead Publishing Series in Textiles 37 Woollen and worsted woven fabric design E. G. Gilligan 38 Analytical electrochemistry in textiles P. Westbroek, G. Priniotakis and P. Kiekens 39 Bast and other plant fibres R. R. Franck 40 Chemical testing of textiles Edited by Q. Fan 41 Design and manufacture of textile composites Edited by A. C. Long 42 Effect of mechanical and physical properties on fabric hand Edited by Hassan M. Behery 43 New millennium fibers T. Hongu, M. Takigami and G. O. Phillips 44 Textiles for protection Edited by R. A. Scott 45 Textiles in sport Edited by R. Shishoo 46 Wearable electronics and photonics Edited by X. M. Tao 47 Biodegradable and sustainable fibres Edited by R. S. Blackburn 48 Medical textiles and biomaterials for healthcare Edited by S. C. Anand, M. Miraftab, S. Rajendran and J. F. Kennedy 49 Total colour management in textiles Edited by J. Xin 50 Recycling in textiles Edited by Y. Wang 51 Clothing biosensory engineering Y. Li and A. S. W. Wong 52 Biomechanical engineering of textiles and clothing Edited by Y. Li and D. X-Q. Dai 53 Digital printing of textiles Edited by H. Ujiie 54 Intelligent textiles and clothing Edited by H. R. Mattila 55 Innovation and technology of women’s intimate apparel W. Yu, J. Fan, S. C. Harlock and S. P. Ng 56 Thermal and moisture transport in fibrous materials Edited by N. Pan and P. Gibson 57 Geosynthetics in civil engineering Edited by R. W. Sarsby

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xviii

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58 Handbook of nonwovens Edited by S. Russell 59 Cotton: Science and technology Edited by S. Gordon and Y-L. Hsieh 60 Ecotextiles Edited by M. Miraftab and A. R. Horrocks 61 Composite forming technologies Edited by A. C. Long 62 Plasma technology for textiles Edited by R. Shishoo 63 Smart textiles for medicine and healthcare Edited by L. Van Langenhove 64 Sizing in clothing Edited by S. Ashdown 65 Shape memory polymers and textiles J. Hu 66 Environmental aspects of textile dyeing Edited by R. Christie 67 Nanofibers and nanotechnology in textiles Edited by P. Brown and K. Stevens 68 Physical properties of textile fibres Fourth edition W. E. Morton and J. W. S. Hearle 69 Advances in apparel production Edited by C. Fairhurst 70 Advances in fire retardant materials Edited by A. R. Horrocks and D. Price 71 Polyesters and polyamides Edited by B. L. Deopura, R. Alagirusamy, M. Joshi and B. S. Gupta 72 Advances in wool technology Edited by N. A. G. Johnson and I. Russell 73 Military textiles Edited by E. Wilusz 74 3D fibrous assemblies: Properties, applications and modelling of threedimensional textile structures J. Hu 75 Medical and healthcare textiles Edited by S. C. Anand, J. F. Kennedy, M. Miraftab and S. Rajendran 76 Fabric testing Edited by J. Hu 77 Biologically inspired textiles Edited by A. Abbott and M. Ellison 78 Friction in textile materials Edited by B. S. Gupta

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79 Textile advances in the automotive industry Edited by R. Shishoo 80 Structure and mechanics of textile fibre assemblies Edited by P. Schwartz 81 Engineering textiles: Integrating the design and manufacture of textile products Edited by Y. E. El-Mogahzy 82 Polyolefin fibres: Industrial and medical applications Edited by S. C. O. Ugbolue 83 Smart clothes and wearable technology Edited by J. McCann and D. Bryson 84 Identification of textile fibres Edited by M. Houck 85 Advanced textiles for wound care Edited by S. Rajendran 86 Fatigue failure of textile fibres Edited by M. Miraftab 87 Advances in carpet technology Edited by K. Goswami 88 Handbook of textile fibre structure Volume 1 and Volume 2 Edited by S. J. Eichhorn, J. W. S. Hearle, M. Jaffe and T. Kikutani 89 Advances in knitting technology Edited by K-F. Au 90 Smart textile coatings and laminates Edited by W. C. Smith 91 Handbook of tensile properties of textile and technical fibres Edited by A. R. Bunsell 92 Interior textiles: Design and developments Edited by T. Rowe 93 Textiles for cold weather apparel Edited by J. T. Williams 94 Modelling and predicting textile behaviour Edited by X. Chen 95 Textiles, polymers and composites for buildings Edited by G. Pohl 96 Engineering apparel fabrics and garments J. Fan and L. Hunter 97 Surface modification of textiles Edited by Q. Wei 98 Sustainable textiles Edited by R. S. Blackburn 99 Advances in yarn spinning technology Edited by C. A. Lawrence

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100 Handbook of medical textiles Edited by V. T. Bartels 101 Technical textile yarns Edited by R. Alagirusamy and A. Das 102 Applications of nonwovens in technical textiles Edited by R. A. Chapman 103 Colour measurement: Principles, advances and industrial applications Edited by M. L. Gulrajani 104 Fibrous and composite materials for civil engineering Edited by R. Fangueiro 105 New product development in textiles: innovation and production Edited by L. Home 106 Improving comfort in clothing Edited by G. Song 107 Advances in textile biotechnology Edited by V. A. Nierstrasz and A. Cavaco-Paulo 108 Textiles for hygiene and infection control Edited by B. J. McCarthy 109 Nanofunctional textiles Edited by Y. Li 110 Joining textiles: principles and applications Edited by I. Jones and G. Stylios 111 Soft computing in textile engineering Edited by A. Majumdar 112 Textile design Edited by A. Briggs-Goode and K. Townsend 113 Biotextiles as medical implants Edited by M. King and B. Gupta 114 Textile thermal bioengineering Edited by Y. Li 115 Woven textile structure B. K. Behera and P. K. Hari 116 Handbook of textile and industrial dyeing. Volume 1: principles, processes and types of dyes Edited by M. Clark 117 Handbook of textile and industrial dyeing. Volume 2: Applications of dyes Edited by M. Clark 118 Handbook of natural fibres. Volume 1: Types, properties and factors affecting breeding and cultivation Edited by R. Kozlowski

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119 Handbook of natural fibres. Volume 2: Processing and applications Edited by R. Kozlowski 120 Functional textiles for improved performance, protection and health Edited by N. Pan and G. Sun 121 Computer technology for textiles and apparel Edited by Jinlian Hu 122 Advances in military textiles and personal equipment Edited by E. Sparks 123 Specialist yarn, woven and fabric structure: Developments and applications Edited by R. H. Gong 124 Handbook of sustainable textile production M. I. Tobler-Rohr

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1 The design of novel hygiene textile products M. J A S S A L, Indian Institute of Technology (IIT), India

Abstract: Absorbent personal hygiene products, such as diapers, sanitary napkins, tampons, incontinence products, panty shields, wipes, etc., are mostly single-use items and are designed to receive, absorb and retain body fluids and solid wastes. Significant innovation has been carried out to improve the performance of these products. This chapter discusses recent advances in technologies to improve the performance of hygiene products. Key words: absorbents, adult incontinence devices, gel blocking, hydrogels, hygiene products, superabsorbent polymers.

1.1

Introduction: hygiene products

Hygiene products form an important group of medical textiles. Use of these products was once restricted to hospitals and operating theatres for the hygiene, care, and safety of patients and hospital staff. Now, with the growing global population, longer life span, and improved hygiene and healthcare standards, textile materials used in the healthcare/hygiene sector have gradually taken on more important roles. Recently, the use of these products has also penetrated into the household sector. Owing to recent advancements in the polymer, fiber and textile engineering fields, the use of textile materials in this sector has witnessed a tremendous growth. This chapter is intended to provide the key requirements of hygiene products and recent advancements in the technologies to improve their performance. Several reviews1,2 have been published in the literature and the reader is referred to these publications.

1.2

Applications of hygiene products

Hygiene products include both disposable and non-disposable items that are mainly used in hospitals, such as antimicrobial textiles, towels, diapers, sanitary napkins, tampons, panty shields, wipes, incontinence products and so on. Based on their application, these can be broadly classified into the following categories: • Wipes. Baby wipes are commonly based on a nonwoven substrate material that is coated or impregnated with a liquid lotion, packaged in such a way that the wipes are dispensed as required. The absorbency of the nonwoven substrate is important in achieving good non-linting and cleaning performance from the wipes. 3 © Woodhead Publishing Limited, 2011

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Textiles for hygiene and infection control

• Baby diapers, training pants. Baby diapers provide an effective absorbent structure to receive, absorb and retain urine and waste products from babies. The products should deliver absorption/retention functionality in such a way as to prevent irritation of the baby’s skin and contamination of the baby’s clothing, and be capable of disposal after use. Training pants represent an extension of diaper use for toddlers in helping with toilet training, in such a way as to provide a backup system of protection in case of accidents. • Feminine hygiene products. The requirement of these absorbent products is to absorb and retain menstrual fluid discharges. The products are in intimate contact with the user, hence they must be without skin irritant tendencies, and provide containment and absorption without leakage. • Adult diapers and incontinence pads. Adults who have to remain on duty for long durations (such as nonstop drivers and astronauts who cannot reach the toilet on time) and those who do not have control over their continence, find adult diapers very useful. They are worn like an under garment. These absorbent products can be durable (cloth type) or disposable. The disposable category is hygienic, comfortable and multi-layered. The interior layer is highly absorbent, has high wicking tendency and can retain fluid. The exterior layer is composed of a waterproof material. Hence, they absorb the fluid and at the same time keep the skin dry. Recent developments are hybrid reusable diapers and ultra thin diapers. Hybrid reusable diapers are made up of a material that is fully flushable and compostable to give extra care and comfort to adults as well as to babies. Ultra thin diaper manufacturing is possible due to the emergence of superabsorbent technology. These are highly functional and comfortable.

1.3

Key property requirements of hygiene products

The properties of hygiene products are dictated by typical end-use requirements, and are achieved by suitable raw material choices and design considerations. • Water and saline absorption. High absorption and absorption under load are key requirements for diapers, training pants and continence devices. Appropriate absorption, absorption under load and absorption rate are needed for the design of different products. • Barrier performance. Partial or total barrier requirements can apply to particulates, bacteria, fluids and viruses. In general, a hydrostatic head of >40 cm is required and, to date, the only products that consistently pass a required viral barrier test are fabrics reinforced with impervious film. • Mechanical properties/strength. Generally, strength requirements vary with the end-use application. High strength and good abrasion resistance are necessities because barrier performance may be affected by these properties. • Sterilization stability. Fabrics used for medical purposes are generally to be

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sterilized. This can be done using a steam autoclave which operates at 121– 132 °C, or using flash sterilization at temperatures up to 138 °C. Thus, when designing fabrics it is essential to understand the impact of sterilization procedures on performance features. • Comfort and breathability. Comfort and good barrier properties represent two opposite requirements. For a sterilization wrap, the issue is that the barrier must prevent dust and micro-organisms from penetrating the sterilized package during storage and transportation. At the same time, it must be porous enough for the sterilant to penetrate the wrapped package and completely sterilize the contents of the surgical set. Comfort is also related to the breathability of the fabric used. As the required characteristics of breathable fabrics vary widely depending on their application, it is important to understand the differences in their construction. Further evaluation of the products is necessary to realize their potential for the intended end use. Breathability properties are also affected by temperature gradients. • Disposable or reusable. Operating room garments can be broadly classified as single-use or reusable. The public image of the single-use medical garment industry is that they are less environmentally friendly, but a recent study has shown that the environmental burden for single-use textiles is slightly less than that for reusables when laundering operations are included. Also, the performance of single-use items is better than that of reusable garments. • Linting and cleanliness. For wipes and related applications, linting is not acceptable because particles from the product drape may adversely affect the user.

1.4

Types of new technology to improve the performance of hygiene products

The films, tapes, adhesives, fluff pulps, superabsorbents and other materials that comprise baby diapers, feminine hygiene items and other disposable hygiene products are constantly being researched, and manufacturers continue to be challenged with making more sophisticated and advanced products to feed consumers’ craving for better designs and performance. In recent years, improvements in diapers, in particular, have included more stretchable waistbands, improved leg cuffs, thinner and more absorbent cores, more textile-like backsheets, and environmentally responsive products. Many aspects must be considered in the design of the hygiene products (and raw materials or components of them) to improve their performance as well as aesthetics. Some of the important factors are: • • • •

breathability and comfort barrier properties/leaking wicking and wetting behaviour disposal and flushability

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Textiles for hygiene and infection control

• protection/antimicrobial properties • smartness/environmental response.

1.4.1

Superabsorbents

The storage of liquid in these products is achieved by the use of superabsorbent polymers. The first commercial hygiene product with superabsorbent polymer was a feminine napkin in Japan. In fact, personal hygiene products (diapers and incontinence products) account for the largest consumption of these polymers. Requirements of hygiene products are different for baby diapers, adult incontinence products and feminine hygiene products; therefore the swelling behaviour/ properties of the superabsorbent are required to be adjusted/tuned accordingly. Superabsorbent polymers absorb, and retain under slight mechanical pressure (1–5 kPa in diapers), about thirty times their weight in urine or physiological solution. The swollen polymer gel holds the liquid in a solid, rubbery state and thereby prevents it from leaking. The first diapers produced contained about 12% of the mass as absorbent core. To make the products thinner, recently these hygiene products have incorporated about 60% of superabsorbent polymer. The fraction of superabsorbent polymer in the product has increased as the properties of these polymers and properties of product become better understood. For the desired performance, the superabsorbent polymers are required to function in combination with the other components in the product (primarily the fluff). In the first generation products, the absorption and retention of liquid were considered as important and the absorption capacity of urine/physiological solution was maximized. Therefore, the superabsorbent polymers were lightly cross-linked hydrophilic polymers of partially neutralized acrylic acid. 3 At low cross-link density, the gel strength of the swollen superabsorbent was low and resulted in high deformability. This created a swollen gel that blocked the channels that should allow liquid to penetrate in the absorbent structure. For diapers, the superabsorbent polymers are desired to have high saline absorption as well as high absorption under load (AUL). The swelling and the elasticity of these polymers depend on the precise structure of the polymer network and primarily on the cross-link density.2 With increase in cross-link density, the free swelling in water and saline decrease, while the absorption under load increases. The techniques for synthesis of superabsorbents are all aimed at adjusting the balance of properties of these hydrogels through control of the network structure. Modification of these absorbent polymers has been carried out to enhance their superabsorbency, gel strength, and absorption rate.4–9 Homopolymers of acrylic acid show a sharp decrease in absorbency in the presence of the electrolytes usually present in physiological fluids. Novel salttolerant co-monomers such as AMPS, 3-dimethyl(methacryloyloxyethyl) ammonium propane sulphonate (DMAPS) and trimethyl methacrylamidopropyl ammonium iodide (TMMAAI) are used to improve saline absorption.10–12 This

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increase in saline absorption is due to the presence of e.g. sulphonic acid groups in the chain, which have a higher degree of ionization compared with the carboxylate groups of acrylic acid. Also, the introduction of cross-links on the surface of these hydrogels particles can be utilized to modify the cross-linked zones on the surface and in the core, independently, to obtain high saline absorption as well as high AUL. Cross-links on the surface of these hydrogels can be introduced so that the fluid does not saturate the surface (as the surface swelling is less, due to the higher crosslink density), but at the same time the final absorption remains high due to the lightly cross-linked core.13–16 Super absorbent polymers thus produced have better mechanical properties while maintaining high absorption properties, giving both high AUL and free absorption. However, the degree of surface cross-linking needs to be optimized and carefully carried out because cross-links tend to decrease the free absorption. Adult incontinence products are ideally very thin and easily disposed of. The urine volume and flow rates are larger for adults than infants and also the product must also absorb under the higher pressures exerted by adults. Faster swelling superabsorbents17–24 are desired for these applications. The various approaches used for fast swelling involve increasing the specific surface area of the superabsorbent polymer by • using porous agglomerates of smaller particles,17–22 • making wrinkled particles, and • using superabsorbent fiber.23 For feminine hygiene, the fluid is complex – a more viscous mixture of water, salts and cells. The cells are too large to diffuse into the network structure of superabsorbent polymer and generally absorb onto the surfaces of superabsorbent polymer particles. For these applications the blood dispersibility is improved by • surface coating the superabsorbent with surface active agents • neutralizing the superabsorbents with potassium or lithium salts. Jassal and co-workers24 have reported the influence of (i) AMPS co-monomer concentration (ii) and the extent and nature of cross-linking, on the absorption properties of superabsorbent polymers synthesized by an inverse suspension polymerization technique. The authors have also shown the effect of surface crosslinking with polyethylene glycol 600 (PEG600), a cheaper alternative to ethylene glycol dimethacrylate (EGDMA) or ethylene glycol diglycidyl ether (EGDGE). Polymer/clay superabsorbent composites have recently been introduced because of their relatively low cost and high water absorbency. Many investigators have proposed different kinds of clay materials. For example, Li An and Wang25 have used attapulgite for this purpose, which is a layered aluminium silicate with reactive –OH groups on the surface. The water absorbency of a poly(acrylic acid)/ attapulgite superabsorbent composite in distilled water was greatly improved as

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compared to cross-linked poly(acrylic acid), but the saline absorption increased only slightly. The latter was enhanced by using acrylamide as a monomer along with the acrylic acid. Acrylamide is a non-ionic monomer and imparts good saltresistant performance when used as a raw material in superabsorbent composite materials. So, if acrylic acid and acrylamide co-polymer is grafted onto attapulgite and a composite is fabricated consisting of polymer and attapulgite micro-powder, it gives the advantage of reduced cost as well as improved water absorbing properties (in distilled water and in 0.9% NaCl solution). Xiang et al.26 have made a new type of stimuli-responsive organic/inorganic nano-composite hydrogel by introducing fibrillar attapulgite into a co-polymer of hydroxyethyl methacrylic acid in which the nanosized attapulgite fibrils work as the cross-linker instead of the conventional cross-linker. These composite hydrogels had a much faster response rate to pH and significantly improved tensile mechanical properties. They have been reported26,27 to exhibit excellent physical, mechanical and other properties compared with those of pure superabsorbents or conventional superabsorbent composites. This may be attributed to the nano scale dispersion of the clay in the matrix, the high aspect ratio of the clay platelets and the interfacial interaction between clay and polymer. Different metals can be used to impart various properties to the superabsorbents. Condenas et al.28 made superabsorbent polymers from co-polymers of methacrylic acid with several metals such as Pd, Ag, Au, Cu, Zn, Cd, Ge, Sn, Sb, In and Bi. The metal was stabilized between the Π-system of the vinyl group and also through the carboxylate anion of the methacrylic acid. The most relevant characteristic of these polymers doped with metal clusters is the stability increase due to the presence of the metal. Apart from this, the incorporation of silver nanoparticles imparts antibacterial properties to the SAPs and results in better hygiene products. Glass-containing superabsorbent polymers with core/shell structures have been developed29 by embedding hollow glass spheres of different sizes and densities into a matrix of cross-linked sodium polyacrylate. By this approach, the absorbing capacity of the cross-linked polyacrylate could be improved because, during swelling in water, the core/shell contact is interrupted and the system is able to imbibe additional water between the embedded glass spheres and the surrounding polyacrylate shell. Highly stable and uniformly distributed silver nanoparticles have been obtained with hydrogel networks as nanoreactors via in situ reduction of silver nitrate (AgNO3) using sodium borohydride (NaBH4) as the reducing agent. The formation of silver nanoparticles has been confirmed with ultraviolet visible (UV–vis) spectroscopy, Fourier transform infrared (FT–IR) spectroscopy and X-ray diffraction (XRD) analyses. Thermogravimetric analysis (TGA) provides the amount of silver nanoparticles existing in the hydrogel network. Transmission electron microscopy (TEM) results demonstrate that acacia-employed hydrogels have regulated the silver nanoparticles size to 2–5 nm whereas CMC and starchcomposed hydrogel networks result in a heterogeneous size from 2–20 nm. These

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hydrogel–silver nanocomposites show antibacterial activity.30 Several other modified fibers31–35 with antibacterial properties have been used for improving the hygienic properties of the products. Significant advances in biodegradable superabsorbent-based products36–40 have also recently been made. However, the raw material and processing costs place these new polymers at considerable disadvantage compared with conventional superabsorbents. Furthermore, the advantages of a biodegradable superabsorbent polymer will be realized fully only in conjunction with a completely biodegradable structure, e.g. a diaper with biodegradable backsheet, tapes, adhesives and elastics. Responsive superabsorbent polymers/smart gels41 are also being researched for hygiene applications.

1.4.2

Product design

One major concern of diaper manufacturers is improvement in design to improve the overall fit of their product, and this is being achieved through stretch. The incorporation of more stretchable materials – in the leg cuffs, at the waist band and even through the overall chassis of the diaper – has been ongoing. The challenge here is adding stretch to the diaper in both the machine and cross directions. While the use of spandex fibers has contributed to improved stretch in leg cuffs and waist bands, now manufacturers are examining ways to add stretch into the entire diaper, particularly in the topsheet or backsheet, to not only make the diaper more comfortable but also to better control leakage. There have also been some developments in stretchable spunbond nonwovens but the costs of these materials have been prohibitive. The stretchable nonwoven sheets are prepared41–43 by substantially uniformly impregnating a necked nonwoven substrate with an elastomeric polymer by treatment with an elastomeric polymer solution. Thus, a wettable spunbond polypropylene nonwoven was impregnated in a 20 wt% polyurethaneurea dimethylacetamide (PUUDMAC) solution. The polyurethaneurea is derived from poly(tetramethylene ether) glycol, 1-isocyanato-4-[(4-isocyanatophenyl)methyl]benzene, and ethylenediamine. The increased stretchability continues to change the look, feel and fit of diapers and, similar to training pants, pull-on style diapers have become popular. More hybrid items that can serve the purpose of both diaper and pant are expected to gain importance. As discussed above, the absorption rate of superabsorbent polymers is affected by the maximum absorption capacity of the polymer and its particle size and shape. The placement of fast or slow absorbing polymers in the composite structure therefore has important implications for the effectiveness of the composite. Many different schemes for mixing fluff and superabsorbent polymer have been investigated in order to find optimum diaper performance. In addition, particle size, placement, and relative amounts play large roles in the optimization of absorption. In some diaper designs, fast swelling may cause the diaper to leak if the porosity and permeability of the composite is reduced. On the other hand, when the

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superabsorbent swelling is delayed in the wetting region of some diaper designs, there is more time to distribute urine through the diaper. By distributing the liquid better throughout the diaper, there is less saturation of the core in the wetting region, so further wetness may be absorbed. A separate layer of nonwoven fibers can be introduced to improve urine distribution in the diaper. This distribution layer is placed between the composite absorbent core, which consists of the cellulose fiber and superabsorbent, and the porous cover sheet. The distribution layer has lower absorbency than either the standard cellulose fluff or the superabsorbent polymer, and a lower density, which allows for a fast liquid distribution within the diaper. The layer is made from either chemically crosslinked cellulose fibers or a nonabsorbent nonwoven material such as polypropylene fiber, and it is sufficiently porous to allow liquid to pass through freely. The initial stage of liquid absorption in nonwoven fabrics (e.g. dry wipes, absorbent materials and hygiene products) is an unsteady-state fluid flow. For engineering design of these nonwoven products, there is a need to predict the unsteady-state fluid flow in both homogeneous anisotropic nonwoven structures and heterogeneous patterned nonwoven fabrics having a dual-scale porosity structure. The unsteady-state liquid wicking in homogeneous anisotropic nonwoven fabric structure has been modeled, and the relationship between unsteady-state liquid absorption in patterned nonwoven fabrics and their structural parameters has been established44 based on the fabric structural parameters. New materials or design features are introduced in marketed products only if they have been shown to be safe under the conditions of recommended or foreseeable use.45 A systematic, stepwise approach to safety assessment starts with a thorough evaluation of new design features and materials, using the principles of general risk assessment including, as appropriate, controlled trials to assess clinical endpoints or independent scientific review of safety data. In modern hygiene and healthcare for babies and the elderly, there is a need to have a diaper that somehow alerts the caretaker when it is time to change it. Several ideas of putting this extra functionality into a diaper have been reported.46–49

1.5

References

1 Rigby A J, Anand S C and Horrocks A R, ‘Textile materials for medical and healthcare applications’, J. Text. Inst., 1997, 88(3), 83–93. 2 Rajendran S and Anand S C, ‘Developments in medical textiles’, Textile, 2002, 32(4), 1– 42. 3 Buchholz F L and Peppas N A, ‘Super absorbent polymer’, Washington DC ACS Symposium Series, 1994, 573, 121–124. 4 Askari F, Nafisi S, Omidian H and Hashemi S A, ‘Synthesis and characterization of acrylic-based superabsorbents’, J. Appl. Polym. Sci., 1993, 50(10), 1851–1855. 5 Omidian H, Hashemi S A, Askari F and Nafisi S, ‘Modified acrylic-based superabsorbent polymers (dependence on particle size and salinity)’, Polymer, 1999, 40(7), 1753–1761. 6 Omidian H, Hashemi S A, Askari F and Nafisi S, ‘Modifying acrylic-based

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superabsorbents. I. Modification of crosslinker and comonomer nature’, J. Appl. Polym. Sci., 1994, 54(2), 241–249. Gotoh T, Nakatani Y and Sakohara S, ‘Novel synthesis of thermosensitive porous hydrogels’, J. Appl. Polym. Sci., 1998, 69(5), 895–906. Yan Q and Hoffman A, ‘Synthesis of macroporous hydrogels with rapid swelling and deswelling properties for delivery of macromolecules’, Polymer, 1995, 36(4), 887–889. Lind E J, ‘Enhancing absorption rates of superabsorbents by incorporating a blowing agent’ US Patent 5118719, 1992, (Nalco Chemical Company, Naperville, IL, USA). Lee W F and Wu R J, ‘Superabsorbent polymeric materials. II. Swelling behavior of crosslinked poly(sodium acrylate-co-3-dimethyl(methacryloyloxyethyl) ammonium propane sulfonate) in aqueous salt solution’, J. Appl. Polym. Sci., 1997, 64(9), 1701– 1712. Lee W F and Wu R J, ‘Superabsorbent polymeric material. V. Synthesis and swelling behavior of sodium acrylate and sodium 2-acrylamido-2-methylpropanesulfonate copolymeric gels’, J. Appl. Polym. Sci., 1998, 69(2), 229–237. Lee W F and Wu R J, ‘Superabsorbent polymeric materials. VI. Effect of sulfobetaine structure on swelling behavior of crosslinked poly(sodium acrylate-co-sulfobetaines) in aqueous salt solutions’, J. Appl. Polym. Sci., 1999, 72(9), 1221–1232. Tominaga M, JP 622659 (Fuji Raito Kogyo Kk, Japan), 1994; Chem. Abstr., 120: 227067x (1994). Gross J R and Harland R S, ‘Osmotically enhanced absorbent structures,’ US Patent 5082723, 1992 (Kimberly-Clark Corp., USA). Goldman S A, Haynes N A, Mansfied T L, Plischke M, Retzsch H L, Walker T and Young G A, ‘Absorbent members for body fluids having good wet integrity and relatively high concentrations of hydrogel-forming absorbent polymer’, US Patent 5599335, 1997 (Procter & Gamble Co., USA). Kimura K, Nagasuna K and Namba T, ‘Water absorbent resin and production process’, European Patent 349240, 1990 (Nippon Catalytic Chem. Ind., Japan). Omidian H, Rocca J G and Park K ‘Advances in superporous hydrogels’, J. Controlled Release, 2005, 102(1), 3–12. Chang C, Duan B, Cai J and Zhang L ‘Superabsorbent hydrogels based on cellulose for smart swelling and controllable delivery’, Europ. Polym. J., 2010, 46(1), 92–100. Chen Yu, Liu Yun-fei, Tang Huan-lin and Tan Hui-min ‘Study of carboxymethyl chitosan based polyampholyte superabsorbent polymer. I: Optimization of synthesis conditions and pH sensitive property study of carboxymethyl chitosan-g-poly(acrylic acid-co-dimethyldiallylammonium chloride) superabsorbent polymer’, Carbohydrate Polym., 2010, 81(2), 365–371. Kabiri K, Omidian H, Hashemi S A and Zohuriaan-Mehr M J, ‘Synthesis of fast-swelling superabsorbent hydrogels: effect of crosslinker type and concentration on porosity and absorption rate’, Europ. Polym. J., 2003, 39(7), 1341–1348. Wang W, and Wang A, ‘Nanocomposite of carboxymethyl cellulose and attapulgite as a novel pH-sensitive superabsorbent: Synthesis, characterization and properties’, Carbohydrate Polym., 2010, 82(1), 83–91. Wang W, and Wang A, ‘Synthesis and swelling properties of pH-sensitive semi-IPN superabsorbent hydrogels based on sodium alginate-g-poly(sodium acrylate) and polyvinylpyrrolidone’, Carbohydrate Polym., 2010, 80(4), 1028–1036. Cooke T F, ‘Fibers: Superabsorbent’, In Encyclopedia of Materials: Science and Technology, Elsevier Publishing, 2008, 3146–3150. Jassal M, Chattopadhyay R and Ganguly D, ‘Synthesis and characterization of sodium

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Textiles for hygiene and infection control acrylate and 2-acrylamido-2-methylpropane sulphonate copolymer gels’, Fibers and Polym., 2004, 5(2), 95–104. Li An and Wang Aiqin, ‘Synthesis and properties of clay-based superabsorbent composite’, Europ. Polym. J., 2005, 41, 1630–1637. Xiang Y, Peng Z and Chen D ‘A new polymer/clay composite hydrogel with improved response rate and tensile mechanical properties’, Europ. Polym. J., 2006, 42, 2125–2132. Liu Z, Zhou P and Yan D, ‘Preparation and properties of nylon-10:10/montmorillonite nanocomposites by melt intercalation’, J. App. Polym. Sci., 2004, 91, 1834–1841. Condenas G, Menoz C, Rodrguez M, Morales J and Soto H, ‘Synthesis and properties of poly(methacrylic acid) doped with metal clusters’, Europ. Polym. J., 1999, 35, 1017– 1021. Ruttschied A and Borchard W, ‘Synthesis and characterization of glass containing superabsorbent polymers’, Europ. Polym. J., 2005, 1927–1933. Vimala K, Samba Sivudu K, Murali Mohan Y, Sreedhar B and Mohana Raju K,‘Controlled silver nanoparticles synthesis in semi-hydrogel networks of poly(acrylamide) and carbohydrates: A rational methodology for antibacterial application’, Carbohydrate Polym., 2009, 75, 463–471. Onda K, Noguchi Y, Hirata H, Suzuki Y, Kitagawa T, Shimizu K and Kubokawa H, ‘Antibacterial deodorant fiber materials manufactured using aloe having reduced harmful effect on human body and manufacture thereof and hygienic materials and daily necessities therefrom’ (Gunma Prefecture, Japan; Hirata Noen Co., Ltd; Noguchi Senshoku Co., Ltd). Jpn. Kokai Tokkyo Koho, 2008, JP 2008231593. Corry B, Hovda R and Caswell M L, ‘Feminine anti-itch cloth’, US Pat. Appl. Publ. (2006), US 2006147504. Nishioka K, Ochi S, Sunada K and Doke T, ‘Modified polyester fiber products with improved hygienic properties manufactured by heat-treating copolyester fiber products treated with bactericides and manufacture thereof’ (Toyobo Co., Ltd, Japan), Jpn. Kokai Tokkyo Koho, 2001. Matsunaga A, Yoshida N and Nagaoka K, ‘Antibacterial nonwoven fabrics manufactured by treating nonwoven fabrics comprising lactic acid polymer fibers and hygroscopic fibers with hydrophilic surfactants’ (Unitika Ltd, Japan), Jpn. Kokai Tokkyo Koho, 2000, JP 2000248452. Nishioka K, Ochi S, Sunada K and Nitano Y, ‘Manufacture of fiber products comprising fibers of acrylonitrile-protein copolymers or blends of the copolymers with washfast hygienic properties by treating the fiber products with aqueous solutions containing bactericides and heat-treating the products’, (Toyobo Co., Ltd., Japan), Jpn. Kokai Tokkyo Koho, 2001, JP 2001064879. Matsunaga A and Yoshida N, ‘Biodegradable hygienic materials comprising nonwoven fabrics of aliphatic polyester composite fibers’, (Unitika Ltd., Japan), Jpn. Kokai Tokkyo Koho, 2008. Shanmugasundaram O L, ‘Biopolymers in healthcare and medical applications’, Syn. Fibres, 2007, 36(3), 13–17. Furno F, De Bruin, N and Schmidt H, ‘Biodegradable super-absorbent polymer compositions with good absorption and retention properties for use in hygiene articles’. PCT Int. Appl. (Kahlhofer Neumann Herzog Fiesser, Karlstrasse 76, 40210 Düsseldorf (DE), (2007), WO 2007098932. Huppe S, ‘SNAPs: A safe and natural alternative to SAPs the new generation of superabsorbents’. Conference Proceedings – International Nonwovens Technical Conference, Baltimore, MD, USA, Sept. 5–7, 2001, 597–613.

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40 Tamatani H, Nagatomo A, Ajioka M and Yamaguchi A, ‘ Superabsorbent polymers synthesized from amino acids’. Annual Technical Conference – Society of Plastics Engineers, 1995, 53rd (Vol. 2), 1510–13. 41 Martin K E, ‘Manufacture of elastic nonwoven sheets by impregnating a necked or easily extensible nonwoven substrate with an elastomeric polymer solution, and stretchable nonwoven fabrics therefrom and diapers, personal hygienic garments and undergarments therefrom’, PCT Int. Appl. 2005, 32 pp. 42 Martin K E, ‘Elastic nonwoven sheet for diapers and other hygiene articles’, US Patent (Invista North America S.a r.l., USA), Appl. Publ. (2005), US 2005239363. 43 Martin K E, ‘Elastic nonwoven sheets for diapers and personal hygiene articles’ (E. I. Du Pont de Nemours & Co., USA). PCT Int. Appl. (2003), WO 2003089713. 44 Mao N, ‘Unsteady-state liquid transport in engineered nonwoven fabrics having patterned structure’, Text. Res. J., 2009, 79(15), 1358–1363. 45 Kosemund K, Schlatter H, Ochsenhirt J L, Krause E L, Marsman D S and Erasala G N, ‘Safety evaluation of superabsorbent baby diapers’, Reg. Toxicolo. Pharmacol., 2009, 53(2), 81–89. 46 Chaterji S, Kwon I K, Park K, ‘Smart polymeric gels: Redefining the limits of biomedical devices’, Prog. in Polym. Sci., 2007, 32(8–9), 1083–1122. 47 Fujimoto T, Hashimoto T, Sakaki H, Higashi Y, Tamura T and Tsuji T, ‘Automated handling system for excretion’, Engineering in Medicine and Biology Society, 1998. Proc. Ann. Int. Conf. of the IEEE, 4, Oct–Nov, 1998, 1973 –1976. 48 Nakae T E, Takemae T, Egami E, Sugihara O and Ikeda H, ‘A sensing system for simultaneous detection of urine and its components’, IEEE APCCAS 1998, The 1998 IEEE Asia-Pacific Conference on Circuits and Systems, 221–224, Nov. 1998. 49 Siden J, Kopioung A and Gulliksson M, ‘The “smart” diaper moisture detection system’, 2004 IEEE MTT-S Digest, 2, 659–662.

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2 Nanotechnology and its application to medical hygiene textiles F. S A R T A I N, A. R E A D E R, M. F I S H E R, B. P A R K, M. K E M P and J. J O H N S T O N E, NanoKTN, UK and B. J. M c C A R T H Y,

TechniTex Faraday Limited, UK

Abstract: This chapter seeks to give an introduction to nanotechnology and its role in the emerging applications in the rapidly growing medical textile sector. Keywords: nanotechnology, medical textiles, nanosilver, biocidal, market sectors, standards, environmental issues.

2.1

Introduction

The general public may think that nanotechnologies exist only in the realms of science fiction; however, in recent years, such technologies have become a reality and are currently used in manufacturing processes and products that are bought on a daily basis. The market for nanotechnology products is predicted to reach around US$4.4 billion by 2014. A nanometre is one-billionth of a metre, or 100 000 times smaller than the diameter of a human hair. Nanoparticles exist in nature; for example, the human body relies on nano-sized protein complexes to function. Such particles have been exploited by man for thousands of years – the Lycurgus cup, made in ancient Greece, uses nanogold to change the colour of the glass (depending on whether light is transmitted through, or reflected by, the glass). In 2011, Environmental Science and Technology posted a key peer-reviewed pre-publication article entitled ‘120 Years of Nano-silver History: Implications for Policy Makers,’1 which showed that nanosilver in the form of colloidal silver had been used for more than 100 years and, according to the authors, has been registered as a biocidal material in the US since 1954. The article states that 53% of US Environmental Protection Agency (EPA)-registered biocidal silver products probably contain nanosilver, but most of the applications (silverimpregnated water filters, algicides, and antimicrobial additives) do not claim to contain nanoparticles. The authors state: ‘The implications of this analysis for policymakers regarding nanosilver is that it would be a mistake for regulators to 14 © Woodhead Publishing Limited, 2011

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ignore the accumulated knowledge of our scientific and regulatory heritage in a bid to declare nanosilver materials as new chemicals, with unknown properties and automatically harmful simply on the basis of a change in nomenclature to the term “nano”.’1 The British Standards Institution (BSI) defines nanotechnology as the: Design, characterisation, production and application of structures, devices and systems by controlling shape and size in the nanoscale, which covers the size range from approximately 1 nm to 100 nm. Nanomaterials can also be defined in terms of their functionality, as opposed to relying strictly on their size alone. Hence, nanotechnologies can be thought of as any technology which either incorporates or employs nanomaterials or involves processes performed at the nanoscale. The UK has a world-class reputation in nanotechnologies research with a nationwide network of research institutes and universities involving approximately 1500 research scientists focusing on the development of nanotechnologies covering a number of fields including Healthcare and Life Sciences, ICT and Electronics, Chemical and Consumer Products, Engineering & Energy, Environmental Sciences, and Metrology.

2.2

Healthcare and life sciences

A relatively new application of nanotechnology is in life sciences. However, it is particularly suited for this technology as most biological interactions are at the nanoscale. An ability to manipulate biological processes at this scale is enabling companies and researchers to develop products that are more specific and targeted to diseased tissues. The key areas where nanotechnology is affecting the development of healthcare products are outlined below. • Pharmaceuticals. Nanotechnology is beginning to penetrate the pharmaceutical industry in two main ways. The first is in tools for drug discovery, where nano-enabled systems allow faster analysis in high throughput screening; this also provides greater information about targets and potential drugs. The technology is becoming more pervasive as benefits are recognised. The second area is formulation. Drug delivery has recently come to dominate nanotechnology in pharmaceuticals, through improving bioavailability, reducing side effects and enabling oral availability through nanoencapsulation. • Diagnostics. The trend in healthcare diagnostics is towards developing pointof care systems that can provide the care-giver with rapid information about disease states and the condition of their patient. In order to achieve true point of care, systems must be miniaturised to make them portable, easy to use, and robust. Nanotechnology is enabling a number of application areas, from sample processing and pre-analytics to signal transduction.

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• Regenerative medicine. Nanotechnology is enabling the development of 3D scaffolds upon which cells can grow to form new tissue. These scaffolds require features at the nanoscale level that allow cells to incorporate and grow into the structures, effectively integrating the structure into the host. Examples of this technology are bone fillers and substitutes. Other applications are the nanostructuring of surfaces used in implants to again allow integration with the patient’s tissues, which increases the lifetime of the implant.

2.2.1

ICT and electronics

One of the most important areas where nanotechnology has been used by endconsumers for many years now is the field of ICT hardware, particularly in nanoelectronics and nanosystems. The use of nanotechnology in these particular markets continues to outgrow most other application areas of nanotechnology. In 2010, worldwide semiconductor sales were about $310 billion, of which around a half by value can be attributed to electronic devices containing active nanoscale components in microprocessors (nanoelectronics), Nano-Electro-Mechanical Systems (NEMS) and nanosensors. The high-end nanoprocessors (although still called ‘micro-processors’) are known by everybody today and can be found as the ‘brains’ in all sorts of electronic equipment, from computers and mobile phones through to washing machines and automobiles. These electronic devices have been sold for many years, in high volumes, and are produced by household names such as Intel, AMD and Nokia. The emerging field of NEMS and nanosensors utilises nanoscale embedded devices that are typically etched into a (substrate) material to produce tiny mechanical components with integrated electrical sensory features, which can accurately measure rotation or movement of the assembly. For example, such devices are now frequently found in the handsets of gaming machines in the home, and in tablet computers, incorporated to measure human movement or rotation of the handheld system. The market for such components is rapidly growing, with an estimated compound average annual growth of over 20%. In research laboratories worldwide, there are numerous innovative devices being investigated, too many to list here in detail, although they include such fascinating nanoscale components as quantum devices and nanophotonic systems. Due to the continued relentless development and exploitation of nanotechnology in this particular market area, new features are created for consumers on an almost daily basis. From this, it is clear that this field of ICT-hardware will continue to expand at the current very high growth rate due to the progressive incorporation of nanotechnology. In turn, this will ensure the continuing increase in importance of nanotechnology throughout the world.

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Chemical and consumer products

Within the chemical and consumer products area, there are many sectors where nanotechnology is being evaluated for the benefits that might be gained from its use, but there are two main sectors where nanotechnology is currently being applied to products. These are for coatings and for food. According to the inventory published in 2009 by the Project on Emerging Nanotechnologies at the Woodrow Wilson Centre for Scholars, 90 marketed products used nanocoatings and 39 utilised nanocoatings in the food sector (mainly packaging and neutraceuticals). The value of nanotechnology in food packaging is on an upward trend, with a worldwide market value for 2008 of $4.13 billion and a forecast to rise to $7.3 billion by 2014 as nanotechnology expands into areas such as ingredient functionality, emulsions and sensors. The current level of adoption in the European food sector is at an elementary stage, but it is expected that more and more products will be available in the EU over the coming years. Potential applications for nanotechnologies within food and related industries range from ingredients to smart packaging. Interest in nanotechnology for the food industry has been a major focus since the publication of a report Nanotechnology and Food by the UK’s House of Lords Science and Technology Committee. This report was released in January 2010 and stimulated much discussion. Publications on improvements in ingredient functionality and health benefits from using nanotechnologies followed. It is estimated that the world market for intermediates, from coatings to display components, enabled by nanomaterials, will grow from $29 billion in 2010 to $498 billion in 2015, with coatings leading the growth in intermediates and projected to reach nearly $20 billion in 2015. A further report noted that the nanocoatings market will be worth $5 billion by 2013 (www.nano.org.uk/nanotechnologyreports/8). Nano-enabled coatings have been widely championed over the past decade. Applications ranging from UV protection through abrasion resistance to selfcleaning surfaces have been promoted. However, most applications have been small scale and high added value. Although this is typical of any new technology, the time has come for the breakthrough to larger volume, mass applications. To date, nanotechnology has been included in novel formulations that may be applied across many different coatings applications, including paints, inks, wall coverings and coatings that may have UV resistance, antibacterial effects or scratch resistance.

2.2.3

Engineering and energy

Nanotechnology is providing scientists with a new tool kit of materials and approaches that can be used to solve problems posed by engineering challenges. Ceramics, polymers and paints with improved mechanical and environmental

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durability and performance have been achieved. With international interest increasing in the development of clean energy production, many new developments in solar cells, batteries, hydrogen storage, fuel cells, catalysts and more, are enabled by nanotechnology.

2.2.4

Environmental sciences

Clean water and environmental remediation are areas increasingly looking to nanotechnology for filtration, water treatment, and for new methods of detoxifying industrial waste water and producing potable water.

2.2.5

Metrology

The development of instrumentation for the nanoscale world has been a longstanding strength of the UK around the world. From the development of electron microscopes over 30 years ago to the advancement of nano (ultrafine) particle sizers, successful companies have grown up over the last 25 years to provide a good steady export trade, which is so valuable to the UK. It is estimated that the world market for nanotools (analytical equipment) is around $1000 million per annum, so the UK targets this market rigorously. These tools feed into both commercial business sectors and academia. However, measurement at the nanoscale is often fraught with difficulties due to the very close relationship between physical matter and electromagnetic radiation at the nanoscale. Measurement of material properties becomes very complex, and deconvoluting these from the measurement technique itself is extremely demanding. As an example, explaining, predicting and controlling why nanoscale powders disperse or flocculate in liquids and why certain surfaces can emit light under an electric potential are all function of these interactions. The forces and fields include van der Waals, surface energy, surface atomic mobility (self assembly) and field confinement (quantum effects etc.). These can give different values for apparent particle size, depending on the technique used.

2.3

Standards and regulations for nanotechnology products

The commercialisation of new and enabling nanotechnologies will be critical to securing global growth, and solving long-standing quality-of-life and societal challenges such as human and environmental health, water, food and energy security issues, which challenge the world both today and in the future. For this to be achieved, an infrastructure of governance tools must be in place to stimulate and regulate markets. In recent years, nanotechnologies have moved from the world of discovery to the practical reality of commercialisation in products and processes, and their safe and responsible application and use will have a pivotal role in

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delivering solutions to current challenges. The exploitation and governance of nanotechnologies is therefore high on the agenda and is seen by many organisations as a key enabler of progress. There is a global race between nations and trading blocks to be the first, biggest and best producers, and competition is evermore fierce to gain the lead. Standards are crucial for the safe and responsible development of markets, and active participation in the standards-making process allows countries and organisations to help create, regulate and shape markets to their requirements. Proactive and anticipatory standards development can also contribute to social engagement through encouraging the participation of consumer groups, NGOs and members of the public. Standards also bring rational order to debates that can otherwise prove emotional, especially in areas of public concern. Standards development is an example of a supporting innovation activity and the standards resulting provide an authoritative framework on best practice, guidance and authoritative information which has been agreed, usually at the very highest levels of academia, industry and government. This ensures that the deepest and fastest exploitation can be achieved through rigorous adherence and widespread adoption. Would CDs or DVDs ever have gained such prominence if the underpinning technical standards were not developed? In the world of nanostandards, a new portfolio of documents is being developed to cover many areas of interest to governments, industry and academia.

2.4

The global textiles and clothing sectors

The global textiles and clothing sectors in 2009 were valued at some $527 billion (World Trade Organization) – a 14.8% reduction over the previous year, representing the worse fall for 20 years. The textiles sector was valued at some $211 billion and the clothing sector at some $316 billion. World fibre production was estimated at 63.9 million tonnes – with technical textiles accounting for some 14 million tonnes. Hygiene and medical textiles accounted for some 1.65 million tonnes. In the EU, medical textiles accounted for approximately 10% of all technical textiles – valued at some $7 billion. The worldwide market for specialty textiles in 2010 was about $127 billion, according to the 2010 statistics from US-based Industrial Fabrics Association International. Due to economic recession, future growth was expected to be around 2–3%. According to David Rigby Associates (DRA) of England, growth in the near future, in value terms, is expected to be 3.2%. Over the past decade, tremendous efforts have been made around the world, including China and India, to develop value-added textile products or technical textiles. It is widely recognised that the Techtextil fair organiser, MesseFrankfurt, pioneered the categorisation of technical textiles into 12 categories. These are: (1) Agrotech; (2) Mobiltech; (3) Buildtech; (4) Clothtech; (5) Geotech; (6) Hometech; (7) Indutech; (8) Medtech; (9) Oekotech; (10) Packtech; (11) Protech and (12)

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Sportstech. As is evident from the above twelve categories, technical textiles are grouped into products that find applications in different fields. Textiles are used in many different ways in medical and related areas. However, according to the way they are used, medical textiles can be classified into four categories: (i) (ii) (iii) (iv)

non-implantable materials; extra-corporeal devices; implantable materials; healthcare and hygiene products.

In recent years, niche-dedicated products have been playing an increasingly significant role in the field of medical textiles. The diverse areas of application include healthcare (hospital and community), wound care, sutures, orthopaedic implants, vascular grafts, artificial ligaments and tendons, heart valves, and even artificial skins and extra-corporeal devices. Non-implantable materials refer to those used outside the human body to assist the recovery of wounds. These include wound dressings, bandages and plasters. Advanced dressings are being developed to enable antibiotic and other drugs to be delivered directly to affected parts of the body. Easing the hassle of further medical attention once stitching has been conducted, sutures are now obtained from advanced biodegradable or bio-absorbable materials. Implantable materials are the textile structures that can be used inside the human body for various purposes, such as closure, repair and replacement. Available products are sutures, vascular grafts, artificial ligaments, artificial joints, scaffolds for tissue growth, and so on, each providing suitable properties for the end-use. For instance, trauma- or surgery-related injuries are being repaired by fibres applying nerve regeneration techniques. Open veins and arteries are being supported and kept intact by textile-based stents. Bioglass fibres are being used in tissue engineering to create new bone structures. Bioglass is a commercially available family of bioactive glasses, composed of SiO2, Na2O, CaO and P2O5 in specific proportions. Textile scaffolds are being used to bolster cell growth and build cell structures. Also, textile fibres are being used in implantable devices to release therapeutic drugs at rates and lengths of time that are controllable. Researchers elsewhere have further developed the idea of using silk films for medical applications. At the Georgia Institute of Technology, Eugenia Kharlampieva has experimented with depositing silver nanoparticles on films of silk as a way of strengthening them. Medical applications of technical textiles have resulted in one of the fastest growing segments in the global technical textiles market. Healthcare products comprise a key market sector in Asia’s emerging economies and have a large growth potential. Drivers such as increased life expectancy, better healthcare programmes and higher disposable incomes are some important factors that will create a huge market for both nonwovens and woven fabric-based products. The domestic market volume of these products is generally proportional to the popula-

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tion of a country, and this subsector of the technical textiles industry is obviously of special interest to all countries in Asia. Currently, the big market players in advanced healthcare and hygiene products in Asia are mainly some large European and US companies. However, a greater involvement in production and sales of these products by regional Asian companies is foreseen for the near future.2 Most innovations are taking place in the field of nonwovens and with the application of nanotechnologies. New products are primarily aimed at infection prevention or deodorisation of medical clothing, wound dressing and bedding. The key nanomaterials principally being used are silver and other metallic nanoparticles, and nanofibres. A recent study (2011) has identified some 1300 nanotechnology-enabled products from 30 countries (some 212 products were listed in 2006 and the projected figure for 2020 is 3400).3 Some 313 products incorporate nanosilver – i.e. 24% of the total inventory. The Hohenstein Institute of Germany has undertaken a field study of the effect of antibacterial clothing containing nanosilver on the extant skin flora and microclimate, using human volunteers. According to the Institute, natural skin flora were unaffected, even after long periods of wear. A total of 60 healthy volunteers participated in the sixweek study. Special t-shirts were made for the study, with an antibacterial treatment on one side (verum), while the other half served as a non-antibacterial placebo. Researchers found that the skin flora and microclimate of healthy skin remained unaffected by the antibacterial t-shirts that were worn next to the skin: no damage to the skin flora could be detected, i.e. no change to the total number of bacteria on the skin or variation in the range of bacteria. The researchers concluded that the antibacterial textiles could, therefore, be classified as safe. They noted that, nevertheless, the antibacterial textiles are effective against bacteria entering the fabric in perspiration, as shown by previous studies.4 Considerable research has been directed at the preparation of the polymer nanofibres. For this purpose, electro-spinning is used, in which polymer fluid (solution or melt) is charged with a high electrical voltage. When the electrical force rises high enough to overcome the surface tension of the polymer fluid, a metal spinneret or needle of 0.1–1 mm diameter ejects a fluid jet towards a grounded metal collector. Market projections for the application and take-up of nanofibres are as follows: • $80.7 million in 2009, • $443 million in 2015, • $2 billion in 2020. Bicomponent splittable or fibrillated fibres, nanotechnology and fibre modification also are used in recent developments involving filtration and barrier technologies. Splittable bicomponent fibres have been commercially produced for many years, mostly in Asia. With these types of fibres, filament deniers as low as 0.1 are routinely produced. Generally, these fibres are spun in a standard FDY or

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POY process as continuous bi-component filaments of 2 to 3 denier with 16 or 32 segments. The fibres are woven or knitted into fabric using standard techniques, after which a mild caustic solution is used to swell and split the fibres. Some type of mechanical process such as combing or brushing is then used to fully separate the tiny fibres. These same types of fibres can be spun in a staple form. Nanofibres, ranging between 25 and 400 nm, produced using melt-blown nonwoven technology, are extensively applied for medical textiles used to filter viruses and bacteria. Manufacturing processes used to make these medical nonwovens include hydro-entanglement, spun-bonding, needle-punching, melt blowing and combinations of these processes (and thermal bonding).5

2.4.1

Antimicrobial textiles

An antimicrobial agent is defined as a natural or synthetic substance that kills or inhibits the growth of micro-organisms such as bacteria, fungi and algae. A wide range of natural and synthetic agents is commercially available and new products and applications continue to be introduced. For example, Quick-Med Technologies Inc. have announced that the US Environmental Protection Agency has granted registration of the company’s patent-pending Stay Fresh antimicrobial technology for use in a wide range of textile applications including apparel, interior furnishings, automotive upholstery and carpeting. Stay Fresh is claimed to be a breakthrough antimicrobial technology. The active ingredient is hydrogen peroxide – the ingredient that provides the gentle disinfecting and bleaching action in today’s generation of colour-safe, alternative bleaches. This advance is made possible by Quick-Med’s development of the first commercially viable technology for bonding the active ingredient onto the textile. Wound dressings The application of textiles to wound healing involves products for covering minor wounds, burns, ulcers and other deep skin wounds.6 Antimicrobial wound dressings manufactured by means of a bi-layer of silver-coated, high-density polyethylene mesh on a rayon adsorptive polyester core delivers nanocrystalline silver from a non-adhering, non-abrasive surface. In vitro studies have shown that the sustained release of this ionised nanocrystalline silver maintains an effective antibacterial and fungicidal activity. In addition, nanocrystalline silver dressings have been clinically tested in a variety of patients with burn wounds, ulcers and other non-healing wounds facilitating wound care. The amount of National Health Service cash spent in the UK on total wound care products has risen in recent years from around £23 million in 2005 to around £25 million in 2006/7. The latest figure is a quarter of all the cash spent on wound dressings in that year, with silver dressings accounting for one seventh of the total number of dressings.7

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Wound dressings have also been developed combining electro-spun polyurethane membrane and silk fibroin nanofibres. These electro-spun materials, characterised by a wide range of pore size distribution, high porosity, and high surface-area-to-volume ratio, provide favourable parameters for cell attachment, growth and proliferation. Besides, the porous structure is particularly important for fluid exudation from the wound, avoiding wound desiccation, and impairing exogenous micro-organism infection. Smith & Nephew (UK) manufacture Acticoat antimicrobial barrier dressings containing Silcryst™ nanocrystals that provide efficacy including bacterial reduction over a broad antimicrobial spectrum, inhibiting a wide range of pathogens, including drug-resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enteroccocus (VRE). Other properties of Acticoat coatings are fluid management, sustained release and non-adherence. Chronic wounds can have a variety of exudate levels from low to very high.8 Acticoat dressings have different degrees of absorbency to assist in the management of exudates, while helping to maintain an optimally moist wound-healing environment. Silcryst nanocrystals release silver ions in the dressing quickly, sustain release for up to 7 days and allow for pain-free removal without disruption of the wound bed. The anti-adhesive property is obtained by coating common bandages with silica nanosol modified with long chain alkyl tri-alkoxysilanes. AQUACEL® Ag Hydrofiber® dressing is supplied by Convatec and is intended for moderate to highly exuding wounds that are infected or at risk of infection. It is the only antimicrobial dressing that incorporates Hydrofiber®Technology. This dressing: • releases ionic silver in a controlled manner as wound exudate is absorbed into the dressing, • may help protect periwound skin by helping reduce the risk of maceration, • may help minimise cross-infection during dressing removal, • is soft and conformable, • supports wound healing by providing a moist wound-healing environment, • provides rapid and sustained antimicrobial activity in vitro, and • as demonstrated in in vitro testing, provides sustained antimicrobial activity for up to 7 days. Swiss-based Tissupor provide a structured wound dressing based on a textile composite and made functional by embroidery technology. The company was founded in 2001 and was a subsidiary of Bischoff Textil AG in St Gallen, which is a specialist in manufacturing precious embroidery for export all over the world. The wound dressing system is applied for chronically non-healing wounds (e.g. ulcus cruris and pressure sores) for tissue regeneration through controlled revascularisation of the epidermal tissue. In textile implant materials, tissue formation and vascularisation depend on the size and distribution of pores and fibres. An arrangement of pores of different orders of magnitude will stimulate the tissue in

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growth and the formation of new blood vessels and capillaries. The dressing pads comprise a multi-layer nonwoven base, a spacer fabric filling, and a 3-dimensionally embroidery-structured textile architecture that combines pores for directed angiogenesis and elements for local mechanical stimulation.8 Masks and filters Another early adopter of nanosilver technology has been the market for protective face masks and respirators. Recent warnings of a swine flu (H1N1) pandemic (and related organisms) have provided an impetus to nonwoven face mask and respirator sales worldwide. Carey International Ltd is a worldwide distributor of a new, multiple-use respirator mask made with a needle-punched, four-ply fabric comprising two outer layers featuring Ag ion silver/copper zeolite compounds permanently embedded into the fibre and two inner filtration layers to prevent microbial or other particle penetration. The outer layers have been shown to kill Streptococcus pyogenes, methicillin-resistant Staphylococcus aureus (MRSA), and other bacteria; and to inactivate H1N1, H5N1, the common cold and other viruses. The filtration layers comply with National Institute of Occupational Safety and Health N959 and N9910 standards. XTI 360™ Active-Shield is based on XTI’s world-exclusive Active-Nucleus Nano-Particle bonding technology, proven with the highest possible antibacterial rate of 99.9999% (JIS-Z-2801-standard/SGS R6.08), SGS test result on XTIcoated materials (PBS-plastic/fabric/ceramic/etc.). XTI’s Active-Shield™ TiO2 Ag (titanium-dioxide-nanosilver) nanoparticles respond to UV-light creating super-oxide-ions that burn viruses and bacteria, effectively reducing surface germ-counts within their environment and wearing down air pollutants (main reason for allergies), bacteria and VOCs (volatileorganic-compounds; harmful pollutants such as formaldehyde, ammonia and other contaminants released from building materials and household cleaners). The XTI Anti-germ System: XTI 360™ Nanocoating and XTI™ Nano-Facemask (three-layer-0.3µm-filtration) is easily the most effective preventive measure and best defence against airborne germs; it protects against the common cold and flu viruses, drug-resistant microbes (NDM-1) along with other dangerous germs and bacteria (such as H1N1, H5N1, H3N2, H2N5, E-Coli, MRSA and pneumonia bacterium).11 Foss Manufacturing’s Fosshield Antimicrobial Technology is now available to the commercial market and has been selected by Nexera Medical as the antibacterial technology in its new SpectraShield 9500 Surgical N95 respirator mask. Unlike other antimicrobial agents that are applied via topical coatings or include actual metals, the patented antimicrobial technology in Fosshield uses a silver and copper ion fibre system to deliver effective and permanent protection from microbes without risk to humans or impact on the environment.

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Medical textiles: protective surgical products

Surgical gowns, caps and shoe-covers comprise the normal protective gear for medical professionals. Factors affecting their properties and expected in-use barrier performance will influence fabric selection. In North America alone, disposable nonwoven medical apparel products represent a market totalling nearly $1.46 billion (according to INDA) and the market is growing by approximately 2% annually. Globally, the medical nonwoven disposables market is estimated at $12 billion. Revenues for suppliers of clean-room hardware and consumables will exceed $10.3 billion in 2011. Consumables revenues are steadily increasing. Gloves are the single biggest consumable purchase; wipes are the second. Reusable and disposable garments are equal in revenues but not in unit sales.

2.4.3

Knitted fabrics with medical applications

Knitted fabrics with non-apparel/non-commodity applications can be classified as technical knits. Knitted fabrics that have value-added applications belong to the emerging class of textiles known as technical textiles. One of the important applications of knits in the medtech area is the spacer fabric. The University of Bolton in the UK and The South Indian Textile Research Association (SITRA) in Coimbatore, India have been working actively in this technology. These fabrics are predominantly warp-knitted using mainly synthetic materials. As a principle, the spacer material, which is normally a pile-like structure, is laid between the top and bottom layers and provides good wicking and breathability characteristics. A recent research project at SITRA focuses on spacer fabrics in orthopaedic shoes, particularly used for diabetic patients. These spacer fabrics can also be functionalised with antibacterial treatments. Another important day-to-day application where knitted fabrics are used to enhance quality of life is in compressional socks, which are used to alleviate suffering due to deep vein thrombosis (DVT) and blood clots.

2.5

References

1 Nowack B., Krug H. F. and Height M., ‘120 years of nanosilver history: implications for policy makers’, Environ. Sci. Technol., 2011, 45(4), 1177–1183. 2 Shishoo R., ‘Strong market potential in Asia – High-performance textiles and nonwovens are targeted for growth’, Specialty Fabrics Rev., March 2011 (http://specialtyfabrics review.com/articles/0311_wv_asia_potential.html). 3 http://www.sify.com/news/over-1-300-nanotech-related-items-in-marts-worldwidenews-international-ldlr4obfeba.html. 4 http://www.hohenstein.cn/ximages/1416101_hohhautflo.pdf. 5 http://www.neumag.oerlikontextile.com/Portaldata/1/Resources/neumag/downloads/ avr_0309_Linz.pdf. 6 Silver dressings – do they work? Drug and Therapeutic Bulletin 2010; 48, 38– 42, doi:10.1136/dtb.2010.02.0014.

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7 Rajendran S. (ed.), ‘Advanced Textiles for Wound Care’, Woodhead Publishing Series in Textiles No. 85 (2010), Woodhead Publishing, Cambridge, UK. 8 http://global.smith-nephew.com/master/ACTICOAT_27517.htm. 9 http://www.cdc.gov/niosh/npptl/topics/respirators/disp_part/RespSource3.html#e. 10 http://www.cdc.gov/niosh/npptl/topics/respirators/disp_part/n99list1.html. 11 http://www.xti.tm/tech/technologyeng.htm.

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3 Use of knitted spacer fabrics for hygiene applications A. M. D A V I E S, De Montfort University, UK

Abstract: The healthcare sector is under constant financial pressure due to the ageing population. Medical textiles have been identified as a growth area, with the incontinence market predicted to see substantial growth. The incidence of incontinence is a growing burden on the healthcare sector, so improved forms of intervention are required. Knitted spacer fabrics have created much interest in the textile industry, offering unique properties and being ideal for use next to the skin. Being washable and thus reusable, spacer fabrics are viable alternatives to disposable products in the medical sector, at a time when there is great emphasis on sustainability and the environmental impact of textile products. Focusing on incontinence products requiring bulk liquid absorption, the use of weft-knitted spacer fabrics is discussed. To understand how liquid moves through a spacer fabric, a new test method is presented offering scope as a tool to aid the design and development of functional spacer fabrics for hygiene applications. Key words: spacer fabric, incontinence, liquid absorbency, three dimensional.

3.1

Introduction: key issues in hygiene and moisture management

Textiles are playing an increasingly important role in the healthcare and hygiene sector. Constant innovations in structures and fibre developments are leading to increased interest in the capabilities of textile materials. The global healthcare market is one of the world’s largest industries with a value estimated at over US$3.5–4 trillion a year (Fisher, 2006). Medical textiles have been identified as a growth area due to the ageing and increasingly affluent population, with the incontinence market projected to see the greatest growth (David Rigby Associates, 2005). Because consumers and healthcare providers are demanding improved, hygienic and comfortable products with enhanced properties, the market for textiles within the sector is increasing. Textiles can be found within a number of medical applications, from those that absorb natural bodily waste (nappies, incontinence pads and feminine hygiene products) to specialist wound dressings, orthopaedic braces and implantable devices. Many healthcare products demand that fluids be absorbed, distributed or 27 © Woodhead Publishing Limited, 2011

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retained within a textile substrate. The control of liquids and moisture requires careful management in order to ensure that the product, such as an incontinence pad or nappy, performs effectively, absorbing liquids without causing leakage. Many medical textile products in direct contact with the skin are required to be non-toxic, non-allergenic, and non-carcinogenic; and if reusable, should withstand sterilisation at high temperatures. With healthcare-associated infections (HAIs) currently one of the most pressing issues facing the Health Services, controlling hygiene (bacteria and odour) through the effective use of textile materials is becoming increasingly important.

3.1.1

The ageing population

In less than 20 years, half of the UK adult population will be over 50, and one in four children born today will live beyond 100, with a similar picture existing across the developed countries. This creates an ever-increasing need for society to adapt to new challenges and opportunities (Jeavans, 2004; Govnet, 2009). Medical advances are one of the key contributors to this longevity; however, it follows that these advances and technologies should also keep people healthier for longer, allowing them to live more independent lives and even work for a longer period. An ageing population means increased healthcare spending (European Generic Medicines Association, 2004). People in the UK today are living longer than ever; however, latest figures show that, on average, older men and women will live 6.8 and 9.1 years respectively of their lives with a limiting long-term illness. It is estimated that 50% of people over 75 currently suffer with long-term infirmity (Office for National Statistics, 2006). Increased numbers of infirm people having limited mobility or being completely bed-bound mean that the incidence of incontinence, pressure sores, and other skin-related conditions is an increasing burden on the health sector, requiring enhanced products and new forms of intervention (Office for National Statistics, 2006; Help the Aged, 2009). Many of the elderly suffering from an infirmity also suffer from some form of incontinence, which can increase the risk of skin conditions, as wet skin is more susceptible to damage. The health of skin is dependent on age, and for older people the process of damage is exacerbated by lower resistance to shear forces, and a much slower healing process than for younger skin. It is therefore of paramount importance that hygiene products designed for the elderly and bed-bound patients should minimise skin damage to prevent further health deterioration. With increasing pressure on the healthcare and hygiene industry to provide for the ageing population, the provision of textile materials with enhanced properties over conventional materials will have an important role to play. Three-dimensional spacer structures (primarily knitted spacer fabrics) have created much interest in the textile industry, offering unique properties and extensive opportunities for modification to suit a growing number of end-uses. Within the medical industry, it is becoming more apparent that such structures provide optimum

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properties, and economic and ecological characteristics as an alternative to traditional woven fabrics, nonwovens or composite materials. They are appropriate to be worn next to the skin due to their favourable surface design, which can be engineered to suit specific end-use requirements. The three-dimensional nature of a spacer fabric allows for heat and moisture to be circulated within the structure, keeping the fabric cool and dry next to the skin. With the correct selection of fibres, a spacer fabric can absorb liquids and moisture, and transport these through the material away from the skin, where either evaporation can take place or liquid can be stored. To date, spacer fabrics have proved useful for compression bandages, supports for beds, wheelchairs, and in the operating theatre to ensure pressure control, and they have been employed in bio surgery as carriers of living maggots used for wound debridement and stimulation of healing. Knitted spacer fabrics can be cost-effective and more environmentally friendly than other fabric structures, as they are produced using a one-step process. These materials are washable without degradation and thus reusable, making them viable alternatives to disposable products in the hygiene sector, particularly for the incontinence market, at a time when there is great emphasis on sustainability and the environmental impact of textile products.

3.2

Three-dimensional fabrics: an overview

Conventional knitted, woven and nonwoven fabrics can be described as twodimensional structures (although technically all fabrics could be considered as three-dimensional). Conventional materials can meet the requirements of many end-uses from clothing to upholstery. However, many technical applications require structures that provide a thick, lightweight fabric in combination with good mechanical properties, which three-dimensional materials are clearly able to deliver. Roye and Gries (2007) defined a three-dimensional textile as one that has three directions in yarn architecture and/or textile architecture, regardless of whether the material is made in a one-step process or a multi-step process. A clearer definition provided by Hearle (2008) described three-dimensional fabrics as thick planar sheets or shaped solid forms with multiple layers of yarns, hollow structures, or thin three-dimensional shells. The production and application of three-dimensional fabrics has become of significant importance with many recent developments. These textile structures have great potential for new fabrics and applications, with such structures being widely used in the aerospace, automobile, geotechnical and marine industries, primarily as the reinforcing medium for composites. Three-dimensional fabrics can be categorised into distinct types. • Layers of two-dimensional materials joined together to create a three-dimensional structure in a multi-step process (multilayer).

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• A three-dimensional structure produced in a one-step process – dense structures (example: a multi-axial warp knit); – structures comprising a hollow core produced using yarns to set a controlled distance between the outer layers, commonly referred to as spacer or distance fabrics.

3.2.1

Spacer (distance) fabrics

Spacer fabrics can be described as three-dimensional orthogonal structures with yarns in the x, y and z directions (Fig. 3.1). Numerous definitions of a spacer fabric exist. Roye and Gries (2007) describe such materials as comprising a threedimensional yarn architecture and a three-dimensional textile architecture, produced by the weaving process (woven spacer fabrics), by circular knitting machines (weft-knitted spacer fabrics), or by double needle bar warp knitting processes (warp-knitted spacer fabrics). A number of researchers (Denton and Daniels, 2002; Bruer, 2005; Badawi, 2007; Yip and Ng, 2008) describe spacer fabrics as materials that consist of two ground fabrics, simultaneously woven or knitted, and connected together to form a structure in three directions. Fabrics consist of upper and lower layers, interconnected by a resilient yarn in the z direction that represents the thickness of the spacer fabric. Some researchers (Denton and Daniels, 2002; Yip and Ng, 2008) focus on spacer fabrics being knitted structures, whereas Badawi (2007) examines the role of woven spacer fabrics, while Russell et al. (2005) and Le Roy (1995) introduce nonwoven spacer structures. Nonwoven spacer materials are relatively new and are not as widely established as woven and knitted spacer fabrics. Russell et al. (2005) presented nonwoven spacer fabrics as those comprising at least two separate but interconnected layers, with the incorporation of discrete voids or cells within the cross-section of the structure. Spacer structures have created considerable interest in the textile industry, offering unique properties and opportunities for modification to suit a growing number of end-uses. Knitted spacer fabrics are the most advanced of the aforementioned spacer structures, attracting the greatest market interest.

Courses (x) Wales (y) y

Thickness x

z

3.1 Schematic of a knitted three-dimensional spacer fabric.

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Knitted spacer fabrics

The concept of knitted spacer fabrics is simple and well established. Verpoest et al. (1993) developed a specialised group of three-dimensional knitted fabrics in the 1990s, now referred to commonly as spacer fabrics. These materials were initially designed as reinforcement for polymer composites, due to their high resistance to peeling and delamination. Knitted spacer fabrics have since been developed to meet the needs of a number of end-uses, combining the advantages of the woven sandwich structures (integral structures, low-cost production) with the deformability and handleability of knitted preforms (Composites Materials Group, 2006). Spacer fabrics are a stable knit construction comprising two surface fabrics (which, for simplicity, will be referred to as layers), connected together by spacer yarns, commonly used to separate the surfaces (Fig. 3.2). The two outer layers can consist of differing fibre compositions, as they are separately produced layers joined together in one process. These layers can feature different structures (open or closed), colours, pattern or surface textures. Additionally, the fabric can be engineered to have specific characteristics such as the direction of stretch, depending on the yarns used (Melliand Textilberichte, 2003). The spacer-free zones, i.e. the spaces or pockets between the monofilaments in the centre of the fabric, can be utilised to incorporate stiffening bones, foam padding or other moisture transporting, shape retaining, or functional elements.

3.3

Principles of knitting spacer fabrics

Knitted spacer fabrics can be either warp- or weft-knitted, with the warp variety being the furthest-developed of all textile spacer structures, and the most popular choice. Weft-knitted versions have been slow to develop, with initial stimulation for the development of jacquard patterned weft-knitted spacer fabrics coming from the automotive industry in the early 1990s. Since the start of this century, economic and technical environmental pressure has increased, leading to renewed and greater interest in weft-knitted spacer fabrics to meet design requirements, which can be achieved through jacquard patterning (Choi and Powell, 2005). Weftknitted spacer fabrics are now currently competing for many of the same applications as warp-knitted types due to extensive development work.

Face (cylinder) Spacer yarns Back (dial)

3.2 Schematic of a weft-knitted spacer fabric.

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Warp-knitted spacer fabrics

Warp-knitted spacer fabrics are normally manufactured on double needle bar Raschel machines (with gauges between 22 and 32 needles per inch) by knitting the face and back layers simultaneously on each needle bed, with guide bars passing between the needles of both beds as they oscillate from the front to the back of the machine. The setup involves guide bars 1 and 2 knitting the front fabric layer on the front needle bar only, and guide bars 5 and 6 knitting the back layer on the back needle bar only. Guide bars 3 and 4 carry the spacer yarns and knit on both needle bars in succession (Mouritz et al., 1999; Anand, 2003). The thickness of the spacer fabric depends on the distance between the two needle bars by use of an adjustable trick plate, and can be adjusted between 1 and 30 mm depending on the required end-use. Some machines are capable of producing spacer fabrics up to 65 mm in thickness through the use of amplified drives, enabling their use in applications ranging from textile-reinforced concrete buildings to wheelchair cushions (Knitting International, 2004).

3.3.2

Weft-knitted spacer fabrics

Weft-knitted spacer fabrics can be manufactured using cylinder and dial machines (circular double jersey) or V-bed machines (electronically controlled flat knitting machines). Fabrics can be produced on both machines where two sets of needles have the ability to create two individual layers of fabric that are held together by tucks. As the spacer stitches are of the tuck variety, the spacer yarn is generally hidden on the technical back of the two plain surface layers. This has the advantage of preventing a rough or harsh feel to the material (Anand, 2003; Bremner, 2004). What sets the circular machines apart is that they have needles set radially or in parallel, in one or more circular beds. Flat knitting machines employ straight needle beds carrying independently operated needles. Compared to flat knitting machines, circular machines have higher production speeds and thus rapid productivity. Material produced on both types of machine benefits from patterning possibilities using the jacquard technique, but are limited in fabric thickness, which at present even using modified cams can only reach approximately 10 mm.

3.3.3

Fabric comparisons and mechanical alterations

Warp- and weft-knitted spacer fabrics are in direct competition with each other for similar applications across different industries. However, thick products, such as mattresses, cannot currently be made using weft-knit machinery. The main advantages of weft-knitted spacer fabrics are their inherent stretch, easy incorporation of spun yarns, and lower yarn costs (as heavier yarn counts can be used) (Millington, 2002; Knitting International, 2003). The structure and appearance of both warp- and weft-knitted spacer fabrics can

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be modified to suit specific end-uses. In warp-knitted structures, varying the threading of one or more guide bars and latch needle manipulation allow open-hole structures to be created on both of the surface layers. A perforated or mesh construction on one or both layers of the fabric offers a number of design possibilities, and provides a product with functional characteristics such as enhanced breathability. At present, a perforated structure can be achieved only on one layer of a weft-knitted spacer fabric, since this structure is achieved through jacquard patterning on the cylinder (face) of the fabric. Although warp-knitted spacer fabrics can allow diverse patterns and surface constructions, weft-knitted versions have always been at the forefront in terms of surface patterning. Much of this can be achieved with electronic needle selection, which translates into a wide selection of surface designs, including coloured patterns and surface effects that, on a weft-knitting machine, can be set up quickly, enabling designs to be modified and changed easily. This flexibility cannot be achieved with warp knitting, giving weft knitting a distinct advantage in production time and costs. One key advantage that weft-knitting machinery has over warp machinery, is the ease of the incorporation of inlay yarn into the centre of the fabric through weft insertion. Inlaid yarns can be thicker than normal knitting yarns, assuming a relatively straight configuration, and are fed through carriers or feeder guides. Weft insertion can be used to insert inlay yarn into the centre of a weft-knitted spacer fabric, with many manufacturers utilising this method in the production of mattress ticking fabrics, often inserting standard inexpensive yarns such as polyester or cotton to create bulk, warmth and fabric stability. Although an inlay yarn can be inserted into weft-knitted spacer structures, the process used to feed thick yarns into the void space within warp-knitted spacer fabrics is more complex due to machinery restrictions (Wood, personal communication, 2009). Both layers of a spacer fabric and the separating yarns are produced at the same time; however, the construction of each layer can be optimised separately, providing fabrics with unique properties. Monofilaments, which are used as the spacer yarns in spacer fabrics, play a vital role in the fabric’s construction and the way it will behave. The yarn count and method of insertion of the monofilament is important to create a stable structure. Thicker spacer yarns have a stable structure with enhanced compression resistance. However they can produce a rougher and harder fabric, whereas thinner yarns will provide a softer surface suitable for use next to the skin. The overall thickness and compressibility of the fabric is dependent on the thickness and lay of the spacer yarns during the production process. The hollow space between the two outer layers is maintained by monofilament yarns, usually of either polyester or polypropylene, with yarn diameters of 0.03 mm to 0.12 mm often used. However, yarns as thick as 1.1 mm are utilised for some applications, to provide a hard but stable structure. Polyester yarns of thicknesses between 0.03 mm and 0.1 mm are the most suitable spacer yarns for use next to the skin, ensuring that the required gap between the layers is maintained, and that the

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surface in contact with skin is soft. The thicker the spacer yarn used, the more abrasive the fabric surface will feel, with spacer yarns thicker than 0.1 mm potentially causing irritation, as they can protrude from the surface and come into contact with skin. The type of monofilament yarn used must therefore be selected to suit the intended end-use. The method of inserting the monofilaments into the centre of the fabric during production has an impact on the material stability. In warp-knitted structures, the yarns are inserted in an intercrossed arrangement promoting stability in the spacer fabric, and a structure with good compression resistance, ideal for withstanding high loads in applications such as pressure mattresses. In weft-knitted structures, monofilaments are inserted in one direction without as much crossing of threads, thereby potentially causing problems in terms of buckling under high levels of loading. However, the insertion of inlay yarns into the centre of a weft-knitted spacer fabric can enhance the fabric’s compression resistance and reduce the likelihood of buckling. The stability of a spacer fabric is partly determined by the laying angle of the spacer yarns, which should be able to withstand displacement by a laterally applied load, and should also be able to counteract shear forces during the end-use, such as in bed sore prevention. The laying angle of the spacer yarns can be adapted to suit the end-use and the desired width of the space between the two layers, therefore influencing the compression resistance. In warp- and weft-knitted fabrics, an angle of 45° is the most widely used laying angle, although angles can vary depending on the type and versatility of the knitting machine.

3.3.4

Knitted spacer fabric manufacturing and use

The structure of the spacer fabric is vital when aiming to meet the needs of a particular end-use. Different fibres used for the layers of the fabric, the thickness of fabric, design, surface construction, and monofilament selection can be modified to produce a fabric with specific desirable characteristics. The end-uses of warp- and weft-knitted spacer fabrics are similar, and can be categorised into distinct areas. Table 3.1 shows the current main areas of application. Knitted spacer fabric usage within the medical industry is becoming more widespread as the structures can provide an alternative to traditional woven fabrics, nonwovens or composite materials by offering enhanced breathability, compression resistance and comfort. The benefits of using knitted spacer fabrics over woven or nonwoven spacer fabrics include the fabrics’ ability to stretch and deform, moulding to body shape, allowing movement that could not be achieved to the same level with a rigid or non-pliable structure. The various characteristics of knitted spacer fabrics make them versatile materials, finding uses as substitutes for foam, and also as an excellent alternative to Neoprene (Bartels, 2002). Many medical applications, including hospital mattresses for infants or the

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Table 3.1 Warp- and weft-knitted spacer fabric end-uses Medical

Transport

Sport/leisure

Apparel

Mattresses Mattress underlays Neck supports Wheelchair cushions Medical aids

Upholstery Containers Car headrest liners Seat covers

Backpack linings Diving underwear Rucksack straps Helmet inners

Seat pockets

Shoe inserts

Surgery curtains

Dashboard covers

Trainers (top and lining fabrics)

Heel protectors Bra cups Corsetry Firefighter jackets Ballistic vest linings Outdoor weather gear

Knee orthoses Bio surgery Bandages

Car boot liners Lorry rain guards Car roof liners

infirm, demand better bioclimatic and hygienic properties in addition to other characteristics such as pressure resistance, a key area in which spacer fabrics can provide an important contribution. Due to these beneficial properties, spacer fabrics have been used in the construction of proof-of-concept prototypes for wearable active orthoses for the suppression of upper limb tremor, where a comfortable, durable and breathable material is required (Davies and Williams, 2005c). The application of spacer fabrics for the prevention of chronic wounds is relatively new; they have been utilised in the prevention of plantar ulcers in patients with Diabetic Foot Syndrome and as bandages for the treatment of oedema in cases of chronic venous or lymphatic insufficiency. Additionally, there has been considerable interest in the use of these fabrics in bio surgery and tissue engineering, areas in which spacer fabrics can contribute to future medical advances (Wollina et al., 2002; Wollina, 2003).

3.4

Application of knitted spacer fabrics in hygiene products

Many claims have been made over recent years for the ability of spacer fabrics to move heat and moisture away from a source such as the skin, while leaving the user comfortable (Heide, 1998; Wollina et al., 2002). These properties are desirable for many applications, including medical uses where comfort, pressure, bacteria control and moisture/liquid management are all critical, and where there is scope for spacer fabrics to offer enhanced properties over conventional fabrics. One of the primary reasons why spacer fabrics are beneficial in the healthcare sector is due to their moisture transporting and absorbing properties. Space between the two fabric layers allows air and heat to circulate through the material, while the incorporation of moisture-conducting yarn can enhance moisture trans-

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port. Moisture can be conducted through the fabric away from the side facing the skin; therefore the skin-facing layer of the fabric must have a low water absorption capacity, yet have high water vapour permeability. Using the right yarn combinations, spacer fabrics can be produced to enhance absorption, wicking and liquid movement properties, which would allow these materials to offer an ideal alternative to, and in many respects superiority over, conventional fabrics for medical end-uses requiring bulk liquid movement, such as bladder weakness (urinary incontinence). Pressure-sore prevention on beds in the operating theatre and in wheelchairs are primary applications for spacer fabrics in the medical sector. These fabrics can be used separately or to complement existing prevention systems such as foam mattresses and variable-pressure mattresses. Due to the three-dimensional nature of the spacer fabric, it is able to create a microclimate (a local atmospheric zone in which the climate differs from the surrounding area) between the body of the patient and the cover, preventing moisture and heat build-up, and allowing ventilation. The fabric’s compression resistance properties reduce the pressure exerted by the body, thus helping in the prevention of bedsores in bed-bound patients.

3.4.1

Incontinence

More than 200 million people worldwide suffer from a significant level of urinary incontinence (UI) (Abrams et al., 2002). In the UK, over 3 million people suffer from some form of incontinence, with this figure predicted to rise dramatically to over 4 million by 2025 (Help the Aged, 2009). It is estimated that incontinence in adults (both urinary and faecal) accounts for 2% of the total annual healthcare budget of the UK (£500m per year), with urinary incontinence accounting for a significant cost (over £233m per year to treat women alone), although the full cost of incontinence is difficult to quantify (Continence Foundation, 2000; NICE, 2004, 2006). Retail sales of adult incontinence products will be worth US$5 billion globally in 2010 and annual growth is projected at 6% by 2014, higher than in any other tissue and hygiene sector (Walker, 2010). The total value of the incontinence market is £63.9m (Kantar Worldpanel, 2010). Although incontinence is not lifethreatening, it does present high costs to health services. Incontinence is a common problem affecting both sexes and all age groups, but at all ages UI is more common in females. Prevalence increases with advancing age, and with a growing older population there is an increase in occurrence with over 60% of elderly in nursing homes experiencing bladder problems. There are numerous ways of dealing with voided urine, ranging from catheterisation to pads based on nonwoven absorbent fibres or super-absorbent polymer powders. The majority of these products are cheap and disposable, but increasing concerns over sustainability and environmental impact are driving a move back to reusable products. Whereas terry towelling was the fabric of choice in the 1970s,

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new developments in fibres and fabrics have led to other possibilities, including the use of three-dimensional spacer fabrics. With the average person urinating 750–2000 ml per day, and, on average urinating 6–7 times a day with an average urine volume of 200–300 ml per addition, incontinence products are required to rapidly absorb and retain large volumes of liquid (Race and White, 1979). Bacteria feed and grow on warm fresh urine when it is expelled from the body and absorbed by incontinence products; therefore pads should be designed to restrict further bacteria growth and unnecessary odour. Incontinence products predominantly for the older population are a growing area of application for knitted spacer fabrics. Although the market has advanced over recent years, there is still room for further improvements, with products often failing to meet customers’ increasing demands. One of the key areas of concern is that of wetback, wherein the fluid continues to wet the body with which it is in contact, from the textile. The medical profession (Cottenden, personal communication, 2005) requires improved products that perform by rapidly removing urine from the source to a controlled area of storage. There are two main types of products used within the sector: body-worn pads and bed pads, in both disposable and reusable form (Figs 3.3 and 3.4). Body-worn pads are used in a similar way to nappies, and are contoured to fit around the body. Spacer fabrics could offer enhanced properties to this section of the incontinence market. However, to compete with conventional materials for body-worn pads, spacer fabrics would need to take into account liquid movement through the fabric layers, while being contoured to fit around and in contact with the body. Due to their flat nature and cushioning properties, knitted spacer fabrics have much to offer the incontinence bed pad market. Similarly to body-worn pads, bed pads can be either disposable or reusable, and are used in hospitals, nursing homes or in patients’ homes. Pads are sometimes used as the only incontinence protection when a patient, unclothed beneath the waist, sleeps; however, they are more often used as a backup system on the patient’s bed to absorb bulk liquid. Reusable products are attracting renewed interest at a time when environmental impact is becoming increasingly important. However, two main issues prevent their increased use: in general, their weight and lengthy drying time after laundering make them difficult to manage by healthcare providers. Spacer fabrics may provide a solution, offering faster drying, stability when laundered, and light weight due to their bulky yet open form. Risk of infection is one of the main issues that have, in the past, prevented uptake of reusable products. Disposable bed pads are often used by healthcare professionals instead of reusables, as they are perceived to possess greater infection control than laundered bed pads (Penn, personal communication, 2003). However, studies carried out by Cottenden et al. (1999) disproved this misconception, demonstrating that with the correct standard foul wash procedure, the pads can be effectively cleaned and made safe to reuse, with the additional benefit that skin problems, such as soreness and irritation, are less likely

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3.3 Disposable body-worn pads.

3.4 Reusable bed pad.

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than with disposables (Haeker, 1985; NHS Executive, 1995). Successful patient-friendly incontinence products have been available only since the start of the twenty-first century (Cottenden, personal communication, 2005). During the 1980s, producers failed to consider the effect of wetness on the skin (Penn, personal communication, 2003). Products for use as bed pads should prevent both wetback to the patient and also the pooling of liquid around the abdominal area, which, when a patient is lying down, can move toward the shoulders and head area caused by the upper body exerting a greater force on the bed than the legs (Cottenden, personal communication, 2005). There are many bed pads on the European market, both disposable and reusable, that aim to keep the skin dry but do not necessarily take into account the tracking of liquid up the body under pressure. Incontinence pads should not only be absorbent and move liquid quickly into the pad, but should consider other factors such as skin dryness and comfort, to prevent incontinence-associated conditions, namely skin degradation and potential pressure sores. Incontinence and other conditions such as pressure ulcers often co-exist, particularly in bed-bound patients. Usually, two separate types of intervention are employed; a pressure mattress and a disposable bed pad. Spacer fabrics have the potential to offer a solution which addresses both. Due to their flexible nature, open structure, and compression-resisting properties, spacer fabrics can be used for weight dissipation in mattresses to reduce pressure-sore development and allow the skin to breathe. The area of incontinence and spacer fabrics is relatively new and only a small amount of work has been carried out in this area, with few products available on the market to date. A number of products have been patented; however, these are primarily for warp-knitted spacer fabrics (Rock and Lohmueller, 1998; Miskie, 2006a,b). Pernick (1998) patented a method of producing a weft-knitted spacer fabric for use as an incontinence product, but the patent does not focus on the inclusion of inlay yarns or roving within the fabric core, which could be utilised to provide enhanced absorbency. Controlling liquid uptake within a spacer fabric allows for more effective products to be developed for applications, such as incontinence products, that require fast removal and distribution of fluid from source to provide comfort for the consumer. The ability of weft-knitted spacer fabrics to manage bulk liquids has been studied to cater for more challenging applications within the medical sector, where large volumes of liquid need to be managed. Design options for a reusable bed pad, produced using weft-knitted spacer fabrics have been presented by Davies and Williams (2005b), with different concepts for transport and storage of liquid being considered. The bed pad could act in one of two ways; the pad could consist of a spacer fabric which draws urine into the pad to be absorbed and retained, or the pad could act as a filter via a series of channels, by drawing the urine in but moving the liquid into a separate storage area for disposal. An impermeable fabric, such as a waterproof breathable one, could act as a barrier to the liquid leaking onto the bed. This method would allow liquid to be moved away

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from the skin and held for a period of time within the layers below until the pad is removed and washed.

3.4.2

Controlling liquid within spacer fabrics

Research has shown that spacer fabrics exhibit good moisture control and excellent comfort properties (Glawe et al., 1999). The liquid absorption of a 100% polyester knitted spacer fabric is relatively low, but the inclusion of a moistureconducting yarn in the middle of the fabric can allow a moisture absorbent capacity of 200–300% to be achieved. Using multifilament yarns as the spacer yarns instead of monofilament, can facilitate liquid absorption and moisture transport (Yip and Ng, 2008). Figure 3.5 shows a cross-section of a moisture-managing warp-knitted spacer fabric, containing polyester multifilament yarns instead of monofilament yarns used to absorb liquid. Fibre selection has an important impact on the flow of liquid through the fabric layers, with differential fibre densities used in the two outer layers assisting moisture transport. The use of multifilament as the spacer yarns instead of monofilament spacer yarns can have an impact on both the absorption and compressive properties of the fabric (Yip and Ng, 2008). Compression resistance and recovery are generally greater in materials comprised of monofilament as the

300 µm

3.5 Moisture management warp-knitted spacer.

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3.6 Cross-section of absorbent spacer fabric.

spacer yarn rather than those using multifilament yarn, although the use of multifilament can encourage liquid absorption and moisture transport. The ability of both warp- and weft-knitted spacer fabrics to control large and small quantities of liquid has been analysed by assessing comfort properties using conventional test procedures and microclimate sensors (Davies and Williams, 2005a,b). Preliminary results suggested that with an open-mesh structure that could be in contact with the skin, and with the correct selection of fibres, a spacer fabric could control larger volumes of liquid, keeping the skin relatively dry. An incontinence pad should not cause undue pressure, and should prevent the wetback of urine when a pressure of up to 10–15 kPa is applied to the pad (Cottenden, personal communication, 2005). Experimental testing has been carried out, comparing the compression resistance of a range of warp- and weft-knitted spacer fabrics, showing that the majority of the spacer fabrics assessed performed well under loads of up to 49 kPa with little collapse and distortion of the spacer yarns (Davies and Williams, 2005a). When assessed for absorption of liquid under a small specified pressure, results showed that spacer fabrics are able to utilise the void spaces between the spacer yarns to hold the liquid under pressure, without lowering the absorption capacity. The results suggested that spacer fabrics, in general, can be designed to withstand the pressure of a body, with potential to retain bulk liquid under small amounts of loading. Weft-knitted spacer structures offer patterning possibilities to aid liquid dispersal and can be engineered to contain a highly absorbent medium to offer bulk liquid absorption, movement and retention. Weft-knitting machinery allows for the easy incorporation of fibrous material into the internal space to increase liquid absorp-

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tion. Inlay yarn and roving can be fed into the centre of a spacer fabric to act as an absorbent medium to meet the needs of an incontinence product. Focusing on incontinence pads requiring bulk liquid absorption, a range of three-dimensional weft-knitted spacer fabrics have been designed, produced and evaluated for desirable properties such as high absorbency and liquid retention using standard test methods (a commercially available Absorbency Testing System (ATS), and video imaging). The surfaces of the fabrics were engineered to provide rapid liquid transfer, and they incorporated various absorbent non-standard yarns and roving into the fabric core. A number of the fabrics exhibited fast liquid movement, with good absorbency and retention. One fabric, in particular, which contained roving in the centre of the structure offered the absorbency requirements of a bed pad, and in addition demonstrated potential for a solution to the current bed pad limitation of liquid moving toward the upper body during use, causing discomfort to the user (Fig. 3.6). This material showed great potential to compete as an alternative to pads currently on the market (Davies and Williams, 2009; Davies, 2009).

3.4.3

Mapping liquid movement within spacer fabrics

The level of liquid spreading on the surface of a spacer fabric can be measured using conventional test methods, but these tests are unable to monitor liquid movement within the centre, an important characteristic of a material designed to control the movement and storage of bulk liquid. To understand how the liquid spreads at different points through the thickness of the fabric, a new test method was designed. This used sets of conductive sensors whose tips could be positioned using spacer plates, to detect liquid presence at controlled points through the thickness of the spacer fabric, depending on the area that needed to be assessed. The test was designed to map the spreading of liquid at set points over a 200 cm2 area, and differed from other liquid spreading tests in that the spreading could be mapped and repeated at a given point through the thickness of the fabric, using minimal sensors and electronics (Davies, 2009). To map the actual distance of spreading across and through a fabric at specific times rather than using times taken to reach a given distance, statistical formulae can be used on the raw data. Two methods of mapping were used to enable spreading through the thickness of a spacer fabric to be displayed with ease and meaning, for direct comparison between fabrics. The first method displayed spreading every 5 seconds (5–50 s) through the fabric in horizontal and vertical directions. The second method displayed spreading at set times (snap shots) through the fabric (mapping top, middle and bottom of fabric) through 360°. The two methods, when compared together, showed strong correlation, suggesting that either method could be used to measure the distance and direction of spreading through a fabric, depending on preference. The method was used to assess a number of absorbent spacer fabrics and proved successful and repeatable (Davies, 2009). Since some of the materials tested

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Top

Middle

Bottom

–1

0

–8

–6

–4

–2

0

cm W ale s

2

4 6

–6

8 10

0 –1

–4

–2

–8

4

2

0

6

8

10

cm es s ur Co

0

0

mm 2

2 mm

4

4

–1

10

0

–8

–6

–4

–2

0

cm W ale s

2

0

4

6 8

10

0 –1

–8

–6

–4

–2

2

4

6

8

cm es s ur Co

3.7 Liquid spreading through absorbent spacer fabric.

exhibited significantly different behaviour between each other and through the thickness of the individual fabrics, the method has identified the need for a test that measures liquid movement in the core of the spacer fabric. Such a prototype test offers scope for further development to assist in the design and development of functional spacer fabrics or multi-layer structures for hygiene applications where the control liquid movement is crucial. One fabric (discussed in Section 3.4.2) which contained absorbent roving, offered scope for an incontinence bed pad. The fabric, which contained the largest quantity of absorbent media, was able to retain liquid within a controlled area. Figure 3.7 shows the liquid spreading through the absorbent spacer fabric over a set time, using the prototype test method. The illustrations show that the liquid was

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drawn quickly into the fabric, and spread predominantly across the fabric, with only limited spreading down the length of the material, and most spreading taking place within the core of the fabric, away from the skin. The spreading behaviour demonstrated that the fabric offered scope for a material that has the ability to direct and retain liquid into a controlled area. The fabric had properties suitable for use as an incontinence bed pad with potential as a solution to the problem identified by Cottenden (2005), of tracking of liquid moving up the body of an incontinent patient.

3.5

Future trends

The capabilities of warp- and weft-knitting machines are allowing for more sophisticated fabrics to be produced to meet the growing demands of the healthcare and hygiene industry. To date, spacer fabrics produced on weft-knitting machines generally possess a thickness of less than 10 mm. Developments within the industry have progressed to enable machine manufacturers to modify certain existing machines to produce thicker fabrics, whereby the dial diameter is reduced to open up the gap between cylinder and dial. This development is of interest to the mattress ticking sector, where an increased fabric thickness is desirable. For the incontinence sector, weft-knitted spacer structures of increased thickness would enable a larger distance between the face and the back of the spacer fabric, which could be filled with increased amounts of absorbent media. Constructions of increased thickness and enhanced absorbency could be investigated to achieve an improved bed pad material over that already developed, if further development testing identified such a requirement. Within weft knitting, the spacer fabric face can be a perforated surface, produced using jacquard patterning. New developments within the industry have taken place; using jacquard patterning, larger perforations have now been achieved on the surface of a weft-knitted structure by incorporating monofilament yarn into the cylinder (used to produce the face yarn) to achieve a fully formed hole. This development may allow for more rapid dispersal of liquid from the face surface into the material core if required. Within the warp-knitting sector, manufacturer Karl Mayer have developed a machine with two additional guide bars, enabling convex and concave shapes to be produced by varying the tension of the spacer yarns. This development enables complex structures of varying thicknesses to be achieved, which could produce contoured spacer structures to fit around the body for use as body-worn pads, or for shaped structures engineered for use as bed pads/pressure-relieving mattresses to move liquid to a specified location, or to offer enhanced body distribution in the prevention of pressure sores. Further developments in spacer fabrics for the healthcare market include the recent development of novel elastomeric spacer structures for use as orthopaedic knee braces, wherein a predicted level of compression can be applied to the brace

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in accordance with the patient’s requirements. The product currently being commercialised includes enhanced comfort properties, and the incorporation of yarns that are inherently antibacterial to reduce infection (Knitting Industry, 2009).

3.6

References

Abrams, P., Cardozo, L., Khoury, S. and Wein, A. (eds) (2002) Incontinence Report of the Second International Consultation on Incontinence, Health Publications Ltd, Plymbridge Distributors Ltd, Plymouth, UK. Anand, S. (2003) Spacers at the technical frontier, Knitting Internat. (July), pp. 38–41. Badawi, S. (2007) Development of the Weaving Machine and 3D Woven Spacer Fabric Structures for Lightweight Composites Materials, (PhD thesis), Technische Universität Dresden. Bartels, V. T. (2002) Warp-knitted spacer fabrics versus Neoprene, Kettenwirk-Praxis, 35(1), pp. 20–22. Bremner, N. (2004) Spacers about to take-off?, Knitting Internat. (June), pp. 40–41. Bruer, S. M. (2005) Three dimensional knit spacer fabrics – A review of production techniques and applications, JTATM, 4(4), pp. 1–31. Choi, W and Powell, N. B (2005) Three dimensional seamless garment knitting on v-bed flat knitting machines, JTATM, 4(3), pp. 1–33. Composites Materials Group (2006) Textile sandwich material development. Available from: http://www.mtm.kuleuven.ac.be/Research/C2/poly/research/sandwich_textile/ sandwich_textile.html (accessed 12/01/09). Continence Foundation (2000) Making a Case for Investment in Continence Services, Continence Foundation, London, UK. Cottenden, A. M., Moore, K. N., Fader, M. J. and Cremer, A. W. (1999) Is there a risk of crossinfection from laundered reusable bedpads?, Brit. J. Nursing, 8(17), pp. 1161–1163. David Rigby Associates (2005) Technical Textiles and Nonwovens: World Market Forecasts to 2010, David Rigby Associates, Manchester, UK. Davies, A. M. (2009) The Behaviour of Liquid Movement in Three Dimensional Weft Knitted Spacer Fabrics, (PhD thesis), De Montfort University, Leicester, UK. Davies, A. M. and Williams, J. T. (2009) The use of spacer fabrics for absorbent medical applications, J. Fiber Bioeng. and Informatics, 1(4), pp. 321–329. Davies, A. M. and Williams, J. T. (2005a) Moisture management of spacer fabrics for medical applications. In: Proc. of 84th World Textile Institute Conference, Raleigh, USA, March 2005, World Textile Institute, USA. Davies, A. M. and Williams, J. T. (2005b) Spacer fabrics for incontinence. In: Proc. of Incontinence: The Engineering Challenge, London, November 2005. The Instn Mech. Eng., London, UK. Davies, A. M. and Williams, J. T. (2005c) Part 4, Bandaging and pressure garments: Assessment of fabrics worn on the upper limbs. In: Anand, S., Miraftab, M. and Rajendran, S. (eds), Medical Textiles and Biomaterials for Healthcare, Woodhead Publishing, Cambridge, UK. Denton, M. J. and Daniels, P. N. (2002) Textile Terms and Definitions, Textile Institute, Manchester, UK. European Generic Medicines Association (2004) Healthcare Economics, EGA, Available from: http://www.egagenerics.com/gen-economics.htm (accessed 2/07/10).

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Fisher, G. (2006) Medical and Hygiene Textiles: Initiatives for Growth, International Newsletters Ltd, UK. Glawe, A., Gimpel, S. and Heide, M. (1999) Comparative measurements of thermophysiological properties of textile fabrics, MelliandTextilberichte–English, 80(5), pp. E114–E116. GOVNET (2009) Strategies of an ageing population, Govnet publications. Available from: http://www.govnet.co.uk/ageing/ (accessed 2/01/09). Haeker, S. (1985) Disposable vs reusable incontinence products, Geriatric Nursing, (Nov/ Dec), pp. 345–7. Hearle, J. W. S. (2008) Innovation for 3D fabrics, In Proceedings of 1st World Conference on 3D Fabrics, Manchester, 10th–11th April 2008, Manchester, TexEng Software Ltd, Manchester, UK. Heide, M. (1998) Spacer fabrics for medical applications, Kettenwirk Praxis, 32(4), pp. E15– E19. Help the Aged (2009) Help the Aged warns that age-related long term illness is the single greatest health issue facing the UK, Help the Aged. Available from: http:// press.helptheaged.org.uk/_press/Releases/_items/_Help+The+Aged+Warns+That+AgeRelated+Long+Term+Illness+Is+The+Single+Greatest+Health+Issue.htm (accessed 04/ 01/09). Jeavans, C. (2004) Welcome to the ageing future. BBC News. Available from: http:// news.bbc.co.uk/1/hi/uk/4012797.stm (accessed 12/12/04). Kantar Worldpanel (2010) Category focus: Incontinence, Chemist and Druggist. Available from: http://www.chemistanddruggist.co.uk/main-content/-/article_display_list/4206932/ 4206928. Knitting Industry (2009) Baltex extends XD spacer fabric range. Knitting Industry. Available from: http://www.knittingindustry.com/articles/596.php (accessed 12/08/10). Knitting International (2004) Ultra thick fabric finishing, Knitting Internat., 111(1317), p. 40. Knitting International (2003) Technical circular knits, Knitting Internat., 110(1306), pp. 39. Le Roy, G. (1995) Method and device for producing composite laps and composites thereby obtained, US Patent 5,475,904. Melliand Textilberichte (2003) New spacer knit product for medical bandages, Melliand English, 84(6), pp. E87–E88. Millington, J. (2002) Do we have lift off?, Knitting Internat., 109(1297), pp. 31–34. Miskie, M. (2006a) Multi-layer moisture management fabric composite, US Patent 0100597. Miskie, M. (2006b) Invertible multi-layer moisture management fabric pad, US Patent 0189955. Mouritz, A. P. et al. (1999) Review of applications for advanced three-dimensional fibre textile composites, Composites: Part A, 30, pp. 1445–1461. NHS Executive (1995) Hospital laundry arrangements for used and infected linen, Health Service Guidelines (HSG), (95) 18, NHS Executive, London. NICE (2006) Costing report – urinary incontinence in women, NICE, London, UK, October. NICE (2004) The management of faecal incontinence in adults, NICE, London, UK. Office for National Statistics (2006) General Household Survey 2006 – General Health and Use of Health Services, ONS, London, SN:5804. Pernick, B. M. (1998) Weft knit wicking fabric and method of producing the same, US Patent 5,735,145. Race, G. J and White, M. G. (1979) Basic Urinalysis, Harper and Row, Maryland, USA. Rock, M. and Lohmueller, K. (1998) Three dimensional knit spacer fabric for bedpads, US Patent 5,817,391.

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Roye, A. and Gries, T. (2007) 3-D Textiles for Advanced Cement Based Matrix Reinforcement, J. Indust. Textiles, 37(2), pp. 163–173. Russell, S. J., Pourmohammadi, A., Mao, N., Ahmed, I. A. and Rathod, M. K. (2005) Nonwoven spacer fabric, European Patent Application EP1644564, World Intellectual Property Organisation Patent WO/2005/007962. Verpoest, I., Ivens, J., Van Vivure, A. W. and Efstratiou, V. (1993) Research in textile composites at K.U. Leuven. In: Proc. Fiber-Tex 1992, NASA Conference, 6th Conference on Advanced Engineering Fibers and Textile Structures for Composites, 27th–29th October 1992. Philadelphia, Pennsylvania, USA, pp. 49–77. Walker, R. (2010) Incontinence products are a growth opportunity for hygiene companies, Euromonitor Global Market Research, London, UK. Available from http:// blog.euromonitor.com/2010/05/incontinence-is-a-hygiene-opportunity-goingbegging.html. Wollina, U. (2003) Functional textiles in prevention of chronic wounds, wound healing and tissue engineering, Textiles and the Skin, Karger, Basel, 31, pp. 82–97. Wollina, U., Heide, M. and Swerev, M. (2002) Spacer fabrics – a potential tool in the prevention of chronic wounds, Exogenous Dermatol., 1, pp. 276–278. Yip, J. and Ng, S. P. (2008) Study of three-dimensional spacer fabrics: physical and mechanical properties, J. Mat. Proc. Technol., 206(1–3), pp. 359–364.

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4 Innovative and sustainable packaging strategies for hygiene products S. L A M P O T A N G, TechniTex Faraday Limited, UK

Abstract: Packaging serves several purposes and can consist of several layers, with different functions, depending on the product. The hygiene packaging industry is characterised by the specific requirements of the products and business, the need to keep costs low, a dependency on the supply chain, particularly packaging suppliers, and the need to manage the inevitable waste. These key characteristics of the industry positively drive the innovation strategies in this sector, leading to strong sustainability strategies, strategies and tactics to drive down costs, and consideration for design differentiation, and the use of new technology, and alternative and smart materials. Key words: packaging, sustainability, innovation, hygiene products, personal care.

4.1

Introduction

The primary function of packaging is to prevent wastage of products by providing protection from damage and/or contamination. This function is required continuously throughout the manufacturing and selling cycles, for raw materials, intermediate products and finished products equally. It has an even greater importance nowadays as transport and storage requirements increase due to the spread of industrialisation, globalisation and geographical coverage of the supply chain, distribution networks and selling points – factors that all contribute to the size of the market. Globally, over 267 million tonnes of containers and packaging were used in 2009; this volume is expected to grow to over 310 million tonnes in 2014 (Datamonitor, 2009a). Value-wise, this corresponds to an estimated US$425 billion in 2009 – with a breakdown illustrated in Fig. 4.1 – and an expectation to grow by 17.4% to US$498.8 billion in 2014. Growth in the basic packaging types is driven by demands from developing countries in Asia, Latin America and Eastern Europe, with China now already the second largest market for flexible packaging (Kalkowski, 2009). The profile of the industry is summarised in Fig. 4.1. Paper has the largest global market segment. This popularity is also observed in Europe, where paper accounts for 31.5% of the total value of packaging used 48 © Woodhead Publishing Limited, 2011

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4.1 Global packaging market breakdown. (a) Global market segments by value; (b) breakdown of packaging type by value (source: Datamonitor).

(Datamonitor, 2009b). The plastic sector, consisting of flexible and rigid varieties, takes the second largest share of the industry. The flexible plastic sector is particularly healthy, due to its reported convenience, quality, functionality, versatility and value (Kalkowski, 2009). For some products, the solution may be a combination of various types of material, as exemplified by Figs. 4.2a, b. For most products, packaging is likely to be a combination of primary, secondary and/or tertiary layers, which may or may not be of the same material. The primary component (Fig. 4.2b–d) is in direct contact with the product, and therefore has the critical protective function until the point of use. Other functions, for example, that of portion control or of maintaining freshness/sterility of the remaining products in the pack, are also often supplied by the primary packaging. The secondary layer

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(a)

(b)

(c)

(d)

4.2 Examples of packaging in the hygiene industry. (a) Flexible plastic primary packaging with paper secondary packaging; (b) rigid and flexible components of primary packaging; (c) paper primary packaging; (d) flexible plastic primary packaging.

generally combines individually wrapped or packaged products in a manageable number, to facilitate handling, storage, or display. Tertiary packaging materials are typically cartons or films, with the main role of facilitating the bulk handling and protection of larger quantities of products during transit and storage. Tertiary packaging tends to have a more physically functional role, as opposed to an aesthetic role such as making a visual impact via the design, colour, texture and branding; this is done with the primary and secondary packaging in order to provide more shelf visibility and help to attract the shopper. Over the years, the traditional protective function of packaging has been supplemented with equally important tasks, such as that of providing information to the user (for example, safety, regulatory, recycling, instructions for use, and shelf-life) or preventing misuse of the product, particularly in the pharmaceutical sector. Packaging is also used as part of the product solution, e.g. a dispenser improving the ease with which the product can be extracted (Fig. 4.2b). Additionally, it can be used as a prominent feature to increase brand visibility and recognition. How packaging evolves depends a lot on the industry it is serving. Higher premium products can afford to increase their cost of packaging, and are

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therefore likely to evolve in a different way to products from the other end of the spectrum. The leading single end-market for packaging, and due to its volume and range (from value to premium), one of the key drivers of the industry, is the food and beverage market. To a large extent, the lead market can be compared to the hygiene packaging sector. Both are high volume consumables, with the predominant products being used only once and where there is potential for a large amount of daily packaging waste. The food and beverage industry has a larger proportion of premium products, which is unmatched in the hygiene industry. However, the market drivers are likely to be comparable, with the hygiene industry taking more of a follower’s role. This chapter explores how innovation in the hygiene packaging industry might be influenced by these main drivers, starting in Section 4.2 with developing an understanding of the key requirements of this industry, moving on to the current trends in innovation strategies in Section 4.3 and ending with the likely future trends in Section 4.4.

4.2

Key considerations and drivers for the packaging of hygiene products

The packaging industry is one that spans the whole breadth of commercial and non-commercial products. Overall, the same issues are relevant across the range of industry sectors, but the depth or impact of the issues may differ between sectors and geographical markets. In this section, some specific considerations for the hygiene industry packaging aspects are outlined. They provide the basis that drives the innovation strategies in this field.

4.2.1

Product and business needs

In selecting and designing packaging that is fit for purpose, consideration must be given to a range of factors (Griffin et al., 1993), such as the product properties, the legal and the marketing requirements, and how these dictate certain technical aspects of the packaging. Likewise, development costs, evaluation costs and the profit margins must also be taken into account. Table 4.1 illustrates non-exhaustively how specific features of the design of hygiene products require specific packaging needs; it is also a framework that could either provide opportunities for resolving challenges, or limitations to the scope of innovation. In addition to the items in Table 4.1, consideration should be made to the transporting and warehousing requirements, logistics and the reliability of the supply chain. The choice of material type, process, design and so on, is therefore affected firstly by the product design and functional requirements, the process requirements, and subsequently by the legal, regulatory and pricing requirements. A vast range of paper and plastics material is available for packaging (Griffin et al., 1993; Brooks, 2000), but to date, the types most used for hygiene products are

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Table 4.1 Typical features of hygiene textile products and their packaging requirements Needs

Product design

Packaging requirement

Consumer-led Affordable as a daily disposable product Ease of opening of packaging Sustainable (packaging and product) Disposable (packaging and product) Maintains functional attributes (e.g. absorbent, antimicrobial, moisturising) of product until the point of use Hygienic

Material cost and availability Material tear or peel strength Packaging design to facilitate opening under conditions of use Recyclable material Sustainable material Not harmful to the environment when disposed of in high volumes Minimise the effects of ageing Protection of product from external factors that may affect the performance Protection of product from contamination

Product-led

Protection of product from moisture Sealable packaging material Protection of product from physical deformation (e.g. compression, bending) during display, transit and storage Protection from contaminants (dust, microbial, chemical, etc.) Sealable packaging material

Absorbent product material Soft and easily deformable Contacts the body

Marketing-led Visually distinctive from Visually distinctive artwork competitor products and design Innovative edge on competitors Can be printed or labelled using other technologies Technologically innovative packaging design Value-added packaging design

flexible plastics (primarily low density polyethylene) and lightweight cartons, with a small amount of other thermoplastics such as polypropylene and rigid plastics. These materials are characterised by their low cost, ease of processing, widespread availability, well accepted aesthetics, and recyclability, which make them most suited for the purpose. They are also able to meet most of the requirements of Table 4.1, with the exception of long-term sustainability. The innovation challenge of the future is to improve on these ‘gold standards’, without compromising on the cost.

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4.3 Sales price and volume matrix.

4.2.2

Cost of goods

The cost of goods is important for the hygiene business because few customers will be willing to pay premium rates for a daily disposable product, particularly if these rates are driven by expensive packaging. The industry is, for the most part, a large volume/low-cost one, with a tendency for increased interest in low-cost packaging (Fig. 4.3). Price competition is now higher due to an increasing presence of supermarket own-brands (private labels), which compete with the few leading brands and contribute to keeping prices low. An additional characteristic of the hygiene industry structure is that the majority of manufacturers purchase the packaging material and, in some cases, sub-contract the actual packaging processes from third parties. The potential for premium packaging is therefore limited if the final selling price or the profit margin is likely to be detrimentally affected. As an illustration of the importance of cost, a TerraChoice (2009) market research revealed that purchasers (71% of whom were involved in packaging purchases) rated pricing as the second most important factor after performance, and 75% of those surveyed believed that better pricing will encourage more ‘green’ purchasing. In other words, only if the cost is right, will the proposition be assessed more favourably. Although limited to North America, these findings are likely to be similar elsewhere in the world and more so, where and when there is less disposable cash. This cost consciousness plays a key part in steering the innovation and sustainability strategies of the hygiene sector.

4.2.3

Supply chain dependency

Despite the fact that the brand owners are responsible for the product and the packaging, their capability to deliver improved packaging is constrained to what the packaging suppliers are able to offer. As briefly mentioned in Section 4.2.2,

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packaging materials and components are generally sourced from packaging suppliers in the form of rollstock of flexible plastics, pre-sealed pouches or cartons. The major global players are large companies such as International Paper Company, Amcor Ltd, Owens-Illinois Inc., Rexam Plc, Alcan Ltd, and Ball Corp. Aside from the biggest players, the packaging market is fragmented with thousands of smaller suppliers; the market leaders (International Paper Company) only capture around 3.4% of the global share (Datamonitor, 2009a). This wide range of suppliers encourages differentiation by innovative solutions, or by reduced prices; therefore, opportunities are present to implement different packaging strategies. However, to be able to compete on a bigger or global scale, large investments in specialist equipment are required, which limits the reach of the smaller players, and hence the choice of the purchaser. The hygiene industry, being mostly volumedriven, does not therefore always have the option of smaller-scale premium suppliers that, for example, may be able to provide a broader range of innovative solutions to smaller sized markets.

4.2.4

Waste

Packaging starts out preventing product waste by protecting it, but eventually ends up as waste itself when the product is used. In the UK, each household generates about 4 kg of packaging waste per week, compared to an average of 23 kg of general waste (ACP, 2008). According to the same report, the total packaging waste sent to landfills consists of less than 3% of the total weight or volume of waste. Despite this apparent low number, there are still public concerns over the environmental impact of packaging, some of which have been quantified by market research. In a study in 2008, 51% of respondents stated that they are personally concerned about the amount of packaging, and 82% agreed to the statement that ‘packaging is a major environmental problem’ (Ipsos MORI, 2008). Conversely, according to the same report, only 10% of consumers always look for labelling information on recycling and only 9% avoid products with too much packaging. The main concern is therefore not felt at the point of purchase, but arises with disposal of packaging at home, and this is compounded with confusion over the recyclability and labelling of plastics, which is still the dominant material for the hygiene textile packaging industry. With the exception of re-usable nappies, which account for approximately 5% of nappies used (Aumônier and Collins, 2005), most hygiene textile materials and their packaging are disposed of after use. Consumption is regular, throughout the year, and by a large proportion of the population, thereby contributing consistently to the annual household waste. The options for waste disposal are restricted – landfilling (with limited capacity), recycling (with confusion from consumers), incineration and composting. Considering the predominant types of materials used for packaging in the hygiene industry, the most sensible route is recycling. Both low density polyethylene and

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high density polyethylene, which are the main polymers used, are high on the recyclability list (Boylston, 2009). In the UK, 60% of packaging is recovered and recycled (ACP, 2008). This number could potentially be higher for hygiene products, considering the recyclability of the materials used. To help improve the global management of packaging waste, various policies and directives have been implemented. The Packaging and Packaging Waste Directive was first adopted in Europe in 1994 (94/62/EC), and subsequently amended in 2004 (2004/12/EC). The objectives were to harmonise national measures to prevent or reduce the impact of packaging and its waste on the environment, with provisions on prevention, re-use, recovery and recycling. Out of this came a number of regulations from various member states. In the UK, for instance, the key ones are the Producer Responsibility Obligations (Packaging Waste) Regulation, 2008 (SI 2008 No. 413) and the Packaging (Essential Requirements) Regulations, 2003 (SI 2003 No. 1941), last amended in 2006 (SI 2006 No. 1492). Globally, the ISO 14000 series for environmental management provide guidelines for life-cycle assessment, designing for the environment, labelling and declaration as well as communication (Boylston, 2009). More recently, in December 2009, work started on the development of an international standard for packaging and the environment involving the EU countries, the US, China, Japan and Korea, to aim for a globally harmonised approach to reducing environmental impact (EUROPEN, 2009). With the implementation of regulation and with the likelihood of further standards and regulations being set up, trends in the packaging industry – including the hygiene one – are likely to be externally affected by the regulatory landscape.

4.2.5

Demographics and global economy

Two elements into which the industry has minimal input, but which are intimately linked to the amount of waste generated, are the world demographics and the state of the global economy. A recession has a different effect on packaging innovation, and emphasises the cost-cutting aspect; a boom in the economy increases consumer expenditure and retail competition. Both of these are outside of the control of the packaging industry, but it has to respond accordingly with different innovation strategies. Likewise, due to the increase in population, the need for protecting goods increases, and by default, the total volume of packaging required is also increasing, despite various strategies to minimise waste. Although packaging regulations and general waste awareness ensures that industry has an element of responsibility for the amount of waste that packaging generates, the effect of demographic changes is also beyond the influence of the industry. Some of the main demographic drivers for hygiene industry packaging are the ageing population, increasing wealth in developing countries, increasing numbers of working mothers and increasing numbers of smaller households. These drivers influence not only the amount of packaging required, but also other aspects of its design,

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such as ease of opening by the elderly or by the busy mum, or the size of packages and labelling.

4.3

– D

Growing trends and innovation strategies

In this section, the most significant trends in the packaging industry are highlighted. Innovation is considered in its broader term, i.e. not only regarding ‘new’ packaging, but also new solutions to old problems. The need for innovation is driven and influenced by the issues raised in the items described in Section 4.2. The hygiene sector has actively participated in most of the trends identified and some examples are given as illustration; however, it lags behind significantly with regard to alternative and smart materials.

4.3.1

Sustainability

The main topic of interest across the packaging industry is sustainability, i.e. how to ensure that the process can be carried out so that, in the long term, there is no depletion of resources and damage to the environment. Two priorities are highlighted here; firstly, reliance on non-renewable sources must reduce, and secondly, the rate of landfilling must be controlled. Public concerns and various regulations contribute to make this a priority for every industry, but more so for those that deal with large packaging volumes. The general trend is for brand owners and retailers to minimise negative impacts on the environment, and, in parallel, to be joined in their efforts by users and suppliers alike. This often starts with sustainability awareness and a sustainability policy or strategy. The concept of having a sustainability policy is gaining ground. In the US and Canada, a survey of purchasers revealed that 56.5% had a formal or informal sustainability policy (TerraChoice, 2009). Most key players in the hygiene product industry – such as Kimberly-Clark, Procter & Gamble, and all major supermarkets – have a sustainability policy or plan. In the TerraChoice (2009) survey, the motivating factors for having a sustainability policy were quoted to be mostly interest from senior management and employees, compliance with regulations, and enhancement of brand image. Table 4.2 summarises the various aspects that may need to be investigated within a generic sustainability strategy. Innovations arise within these various routes for achieving a sustainability target. Simply categorised, they are either about minimising waste, switching to renewable resources or minimising energy and toxic residues. One aspect to point out in the area of minimising waste or increasing recycling is that, despite improvements in labelling, a remaining challenge for the industry and society as a whole is the clarity of the labelling for recycling, particularly as more polymers become integrated into the packaging portfolio. It is important to note also that a holistic approach must be taken, in order to prevent actions in one aspect causing unnecessary damage to another aspect of

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Re-design of smaller packaging Reduce weight (downgauging) of material Switch to naturally lighter material

Minimise packaging

Re-design of packaging for re-use

Increase use of recyclable materials Increase use of recycled material Improve labelling for packaging recycle Improve recycling facilities Improve education and opportunities in recycling Re-design packaging with recycling in mind

Increase use of Minimise compostable additives in material packaging Improve bioImprove waste degradability of disposal for existing material toxic residues Increase use of non-toxic inks

Increase re-use of Increase recycling Increase Minimise toxic packaging biodegradability/ release compostability

Minimising damage to the environment

Table 4.2 Sustainability strategy areas of interest

Increase use of renewable alternatives Support development of renewable alternatives Increase recycling

Reduce dependence on non-renewables

Improve logistics efficiency Use alternative energy sources during packaging Minimise energy use during packaging

Minimise nonrenewable energy use

Minimising depletion of non-renewable resources

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the chain. For example, a narrow focus on minimising the weight of primary packaging may lead to an increase in product waste, an increase in overall packaging weight if secondary and tertiary packaging must be increased, or a disincentive to use heavier materials such as recycled paper or some plastics when they might otherwise have been a better fit for the intended purpose (Envirowise, 2008). The waste of resources arising from product wastage caused by underpackaging is normally much higher than the resources required for over-packaging. One area that has been explored on a broader scale is increasing the biodegradability of packaging. Two routes have been investigated with reasonable success. One of them is the improvement of the biodegradability of polyethylene-based plastics. This is typically done by adding degradation-inducing, metal-based additives, which speed up the degradation of the polymer to between 18 months and 4 years (Bretton, 2006). The resultant polymer is not compostable, and neither is it a solution for minimising the use of non-renewable resources. Still, this is an incremental improvement towards environmental protection as large supermarket chains have adopted this technology for their carrier bags. With regard to a firmer move towards the use of renewable resources for plastics, the second route is the replacement of plastics with paper packaging. One example is the IntegraGuardTM bag (Bemis Co. Inc), which demonstrates how the plastic liner in multi-walled paper bags can be removed and replaced with a coated paper one, thus making the whole packaging fully biodegradable within 180 days. Elsewhere, plastic packaging has been fully substituted with paper. Some examples of paper packaging in the hygiene industry, which is predominantly plastics-based in the UK, can be seen, as exemplified by Fig. 4.2c. Much work has been carried out and trialled, to a large extent by the food industry, to explore other renewable resources for plastics. Section 4.4 provides some examples. Focusing more specifically upon hygiene, on average, this industry has been lean in its approach to packaging. In the last few decades, significant innovative approaches have been taken in the area of minimisation of packaging. Part of this move would have been to comply with the Packaging Minimum Requirements Regulations; but the cost and sustainability benefits would have been significant drivers too. For example, two leading players, Kimberly-Clark and Procter & Gamble, both detail on their websites (2010) successes in packaging minimisation. Kimberly-Clark’s Huggies® and Pull-ups® packaging film weights were reduced by 16% and some pack sizes were changed, saving over 902 tons of polymer yearly. Huggies® also now use less corrugated packaging, leading to a saving of 550 tons. Procter & Gamble’s Pampers® nappies packaging has been reduced by two-thirds in the last 20 years, and the average packaging weight of their wipes has decreased by 56% in North America in the last 10 years, with the introduction of wipe refill packages. Reductions in energy use (which is covered in the next section on cost reduction) and improvement in labelling (as exemplified by Fig. 4.4) have also taken place across the board. Generally these changes were implemented to also bring along

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(b)

(c)

4.4 Examples of labelling on hygiene product packaging.

either cost savings, or compliance with regulation. Further opportunities may exist from the list of Table 4.2; however, the barriers to penetration will undoubtedly be financially related.

4.3.2

Driving down costs

For most manufacturers, cost-cutting exercises may be conducted across their range of processes, including packaging, to improve productivity and maintain the competitiveness of the brand. The identification of short and long term possibilities for driving down costs may lead to the examples of tactics given in Table 4.3, and several of these options are clearly aligned with the sustainability strategies of Section 4.3.1. Thus, the minimisation of packaging has already been discussed and illustrated with examples from the hygiene industry, and if done correctly, this exercise naturally leads to cost savings. On the equipment and processing side, a good example from Procter & Gamble is the 80% reduction in material warehousing space, 25% reduction in material, and reduced energy usage in transportation for their Always® feminine products packaging, following a packaging and machinery re-design (Dupont, 2010). The process swapped from wicketed polyethylene bags to continuous flow wrapping

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Table 4.3 Example strategies and tactics for driving down costs Design

Material cost

Equipment

Process and overheads

Minimise expensive components and print Design with recycled material Minimise packaging material

Film overwrapping when possible Use re-usable transit packaging material Develop cheaper alternatives

Invest in equipment to reduce waste Machine vision for better quality control Higher automation of manual processes Robotic equipment to minimise error Equipment re-design to minimise waste

Optimisation of work processes Removal of nonvalue steps Minimise energy use during processing Optimising of volumes for work orders Lean principles

technology. This example illustrates how a leaner process can be created through a re-evaluation of the existing processes, which can easily be outdated, obsolete, or simply maladapted. Of the total energy in the food chain, from production to cooking and storing, 10.8% is used to make the packaging (Monkhouse et al., 2004). By comparison, for clothing and personal care, which presumably includes hygiene products, packaging production accounts for only 3.5% of the energy requirements. The area of minimisation of energy during the packaging process has been investigated by several equipment manufacturers, in the form of process and design optimisation. This is driven principally by the food industry, which utilises the most energy for packaging, compared with other products. The technology available is now able to monitor energy parameters to help quantify and characterise energy use, to go into hibernation mode to save energy when the equipment is not needed for a defined period of time, and to capture energy generated during the process (such as braking) and re-use it (PMMI, 2009). A number of the options in Table 4.3 rely on recent technological advances and capital investment. This may be a barrier for smaller volume industries, but for the supply chain in the hygiene industry, the quantities involved may rationalise the use of advanced systems, such as machine vision quality control, higher automation and robotisation to minimise product waste due to production defects.

4.3.3

Design differentiation and re-design

This is one innovation strategy that may go against the efforts to drive down cost, but if it is well balanced, it may lead to a competitive advantage. The need for design differentiation and packaging uniqueness is fuelled partly by the pressures of private labels. Combined with attractive pricing, shelf visibility is one of the

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most important criteria for hygiene products. The differentiation of the packaging design – whether by shape, colour, logo, texture, etc., is necessary to grab the attention of the consumer. The ‘First moment of truth’, i.e. the instantaneous interaction of the brand with the shopper, should not be compromised by poor design and/or a poor understanding of the consumer insights. The packaging – particularly for the hygiene industry and less so for the food industry – is often the only visual differentiating parameter and does influence the shopper. A premiumlooking packaging is likely to give the impression that the product is of better quality, despite the fact that the performance may not necessarily be better. A visually striking packaging may attract attention more easily. A packaging that emotionally links to the shopper at the right level may trigger a sale on this basis only. Kimberly-Clark recently unveiled a radical new look for their Huggies® brand, focusing on the emotional values of the brand (Packaging Europe, 2010). Amongst the various improvements are: an evolution of the logo, aiming at making the packaging and brand stand out, inclusion of the nappy size on the pack to guide the customer, and pictures of babies of the right age for each product size. The redesign was carried out by a strategic design agency, and is an example of how packaging design differentiation is shaping the market. Another case of product redesign is one by Procter & Gamble for their Alldays® and Always® feminine care products (Reynolds, 2010). The shelf-ready packaging was re-designed to improve its appearance on the shelf, and resulted in reduced cost, less use of inks and packaging material, and simplified handling by store staff. Table 4.4 provides some additional examples and supporting technologies for design differentiation. Typically, the hygiene market is characterised by being mostly basic in style, materials and processes – likely due to a need to minimise cost. Although innovative to some extent within their circles, the examples cited are still constrained by the industry’s other pressures. Few hygiene products have additional built-in function in the packaging, such as dispensing functions, special sealing functions, and so on. Elsewhere, for example in the food industry and the Table 4.4 Examples of strategies and support for design differentiation Innovation through: Focus

Technology enablers

Supporting technologies

Print design/ colour/logo Texture and other sensorial attributes New material New packaging design Consumer insight

Flexible/versatile packaging equipment Advances in packaging print Digital printing Computer aided manufacturing

Design agencies Computer aided design for development Computer aided visualisation Finite element analysis Rapid prototyping

Shelf visibility and impact Emotional link to brand and packaging Brand visibility Speed to market Value addition in packaging

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cosmetic industry, the innovativeness of packaging designers shines through the various approaches taken to provide a more interesting and interactive packaging for the user. Likewise, there are significantly more examples of design for better recyclability and/or for re-use of the packaging. The hygiene industry is limited in this respect due to pricing constraints, but if the cost of design drops, or can be justified by a corresponding increase in market share, the evolution of the hygiene packaging industry will take a more creative route. The support chain for packaging design is now well established to assist the hygiene industry – market research, insight analysis, design agencies, finite element analysis, computer aided design and visualisation, and rapid prototyping, are no longer in their infancy and are powerful tools for rapid responses in packaging change (Giles and Bain, 2000). Finite element analysis (FEA) enables the designers and developers to predict how the packaging will perform under certain conditions such as loading or compression during transportation or storage. Computer aided design and visualisation enables the designers to simulate how the packaging will look at various angles, without any sample being available. Rapid prototyping enables the team to obtain prototypes for customer evaluation and feedback without having to disrupt the manufacturing line. Advances in technology provide new opportunities and challenges for designers, and the incorporation of smart or responsive materials for visual impact is feasible.

4.3.4

Alternative and smart packaging

Alternative materials, smart materials and electronics in packaging are gaining much interest, but have, so far, been driven mostly by food, pharmaceutical and electronic applications. In some instances, this area is still in an exploratory phase with a number of successful trials. Packaging from renewable sources The most progressed area in the alternative materials category is the production of plastics from renewable resources, which aims to address the sustainability challenges. Packaging derived from corn starch (polylactide, PLA) has been trialled in large companies such as Wal-Mart, Nestlé and Cadburys (Bretton, 2006). PLA is a biodegradable thermoplastic polymer produced by breaking down starches into sugars, which are fermented to produce lactic acid, which in turn is converted into lactide molecules and subsequently polymerised. Corn-based PLA has actually been around since the 1960s, but only in the 90s was the process made commercially viable (Retka Schill, 2007). Since then, several companies have exploited the opportunities for PLA, and packaging materials such as NatureWorksTM PLA and Plantic® have been truly successful. Vegetable oil and other plant starches, such as potato starches, have also been processed successfully (Mater-Bi®), as have wood-pulp-based films for general packaging and twist

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wrapping (NatureFlexTM) (Bretton, 2006). Interestingly, Innovia Film, the manufacturers of NatureFlexTM, have a feminine hygiene range suitable for tampons. Plantic is working on flushable film applications suitable for personal care. It is clear that from the supplier side, work is ongoing to create new opportunities for the hygiene industry. However, there may be some concerns over the barrier properties and mechanical strength of biopolymers (de Azeredo, 2009), and to date, the leaders of the hygiene industry have not yet committed to these new materials. Nevertheless, if the properties are fit for purpose, the benefits of bioplastics are quite attractive, not the least for reducing the packaging industry’s dependency on non-renewable resources, but also to improve the biodegradability of waste packaging. Bioplastic packaging materials are fully biodegradable, and a number of them may pass the criteria for compostability, as defined by BS EN 13432. For those that do not, the solution remains recycling or biodegrading treatment under accelerated conditions. It is interesting to note that the quality of PLA does not decline during recycling; however, adding it to the recycling infrastructure may lead to initial complications given that PLA looks very similar to polyethylene terephthalate (PET), but is incompatible with its current recycling route (Good, 2010). A smaller contribution to the reduction of our dependency on non-renewable resources is the field of recyclable blended plastics – those containing a percentage of material produced from renewable sources. Coca Cola’s PlantBottleTM packaging is an example, and is made of up to 30% sugarcane-based plastics that can be recycled along with conventional polyesters (DuPont, 2010). Antibacterial packaging The food industry also leads the way in the development of antibacterial packaging, mainly to find solutions to maintain freshness of products. Various types of active coatings for packaging films have been investigated in the past, including, for example, silver, organic acids and their salts, enzymes, essential oils, chitosan, bacteriocins and nanocomposites (Quintavalla and Vicini, 2002; Rodriguez et al., 2007; Fernandez-Saiz, 2008; Iseppi et al., 2008; de Azeredo, 2009). The antimicrobial agent is typically applied in the polymeric film, or as a coating onto the film or paper substrate. Smart packaging A smart packaging is one that is able to sense and respond to a stimulus for a specific functional purpose. The term ‘functional purpose’ is key here, and responses that are purely aimed to be a visual effect – such as the use of thermochromic inks for visual impact only – are not considered to be within the remit of this section. They are however notable for providing design differentiation, as mentioned in Section 4.3.3.

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Despite advances in smart materials, such as shape memory polymers and phase change materials, the packaging material itself, typically the plastic or paper, is generally not the smart component but carries a smart feature or technology. This may be about to change with research currently being funded on intelligent plastics that are able to change colour with changes in the state of the product (University of Strathclyde, 2011). Smart packaging has only recently gained ground, starting with high value industries such as the pharmaceutical or cosmetic industry, but spreading steadily. To date, a large number of innovative smart solutions have been devised for medical compliance or for anti-counterfeit purposes (LeGood and Coulson, 2007). Some examples are bottle caps and blisters that help to record when the packaging was opened through various mechanisms such as mechanical indices, server alert, Radio Frequency Identification (RFID), micro electronics and conductive inks. In the anti-counterfeit area, current solutions include various materials such as chemically reactive paper, magnetic coated fibres, colour shift pigments, taggants, tracers and printing methods such as pantograph, watermarks, microdot encryption as well as micro chips, magnetic strips, RFID and RFID enabled stretch film. Smart design, with the incorporation of additional technology from the electronics or telecommunication industries, has thus been created when there is a need to monitor and/or remind users about an event or identity. The most widespread technology is RFID, which is used mostly for identification and tracking down, using radio waves. The RFID component is usually attached to the base packaging material, and consists of an integrated circuit, and an antenna for receiving and transmitting signals. Advances in this area, combined with reduction in prices, are contributing to making it more widely used, particularly in the supply chain logistics around transfer and storage. Tesco, Sainsburys and Marks & Spencers have all used RFID in their supply chain to improve stock control (LeGood and Clarke, 2006; LeGood and Coulson, 2007). In one step further, RFID has been combined with other technologies, such as sensors for temperature, principally in the pharmaceutical industry where a price premium is possible and the criticality of temperature requires monitoring. Examples are ThermAssureRFTM (Log-ic®) and VarioSens® for permanent monitoring of temperature-sensitive goods combined with supply-chain tracking. Although this particular combination is unlikely to be required for the hygiene industry, it illustrates the direction in which smart labelling is moving and may inspire different features for the hygiene industry.

4.4

Future trends for the hygiene industry

Amongst the major current trends outlined in this section for the packaging industry in general, the one that is set to affect the hygiene sector the most is the sustainability of the materials and processes. The priority in this area is further reinforced by current legislation, compliance with various directives globally, and

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public pressures. At the same time, the degree of realism is increasing in this area and there is now a better understanding of what are reasonable targets. Sustainability will, however, not be considered in isolation and the cost of change will be a driver with an equally powerful influence. For example, it is unlikely that new materials or breakthrough design will be widely used unless there can be a proven advantage in the cost versus benefit analysis. Conversely, should the price of a technology or material drop significantly to make it competitive to the ‘gold standard’ of polyethylene, it is easy to foresee rapid adoption. For the shorter term, until the cost of new materials drops sufficiently, the main focus is likely to continue to be on the waste minimisation and recycling aspect of hygiene products packaging, and on the minimisation of energy during the processing. In general, the industry has been good at the former, and large advances are being made on the equipment front to address the latter. The sustainability of packaging materials and processes is indeed moving beyond the responsibility of brand owner, and efforts from across the whole chain are clearly resulting in positive outcomes and will continue to do so. On one side of the spectrum, equipment manufacturers are rapidly developing equipment with sustainability in mind. On the other side, most governments are providing support for recycling facilities, and education of the public. There is a better understanding of the relationship and dependency between supplier and manufacturer in the whole value chain and although brand owners and retailers are only believed to have direct control over as little as 5% of the environmental impacts of packaging (O’Dea, 2010), more efforts are being directed at addressing issues at various points along the value chain, from raw material to recycling, through national or regional policies, standards and regulations. One example is the Green Dot concept, where manufacturers or brand owners contribute to the cost of recovery and recycling by paying a licence fee, which takes into account the cost of collection, sorting and recycling of the materials. The concept of design for sustainability is also gaining ground. Re-design of hygiene packaging is not to be underestimated in parallel as a marketing tool, and it may be defined as an investment with an expected return. It can be considered as a powerful tool for differentiation from competitors. With regards to the most technologically advanced innovation in packaging, adoption by the hygiene industry will occur only at the right price; hence, in most cases, not in the short term. Some of these advances do not align with the sustainability road map; for example, mixing newly developed polymers or coatings with different functionalities to current ones makes it more difficult to separate and recover the materials for recycling. As recycling is still likely to remain a key priority, it may become a barrier for innovation until acceptable solutions are available. Overall, the hygiene industry will follow the packaging leaders in the long term, if waste can be managed properly, and if the costbenefit balance is right for the business.

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Sources of further information and advice

• www.incpen.org. • www.wrap.org.uk.

4.6

References

Advisory Committee on Packaging ACP (2008), Packaging in Perspective, London, UK. Aumônier S and Collins M (2005), Life cycle assessment of disposable and reusable nappies in the UK, Environmental Agency, Science Report Pl-481 (SC010018), Bristol, UK, May 2005. Bretton T (2006), ‘Breaking down’, Resource Magazine, 30(Jul–Aug), available from http:/ /www.resourcepublishing.co.uk/eresource/eresourcearticle.html (accessed 27 June 2010). Boylston S (2009), Designing Sustainable Packaging, Laurence King Publishing, London, UK. Datamonitor (2009a), Global containers and packaging: industry profile, reference code 0199-2036, Datamonitor, December 2009. Datamonitor (2009b), Containers and packaging in Europe: Industry profile, reference code 0201-2036, Datamonitor, December 2009. de Azeredo H M C (2009), ‘Nanocomposites for food packaging applications’, Food Research International, 42(9), 1240–1253, November 2009. DuPont (2010), Consumer driven innovations named as winners in 22nd DuPont awards for packaging innovation, 25 May 2010, available from http://www2.dupont.com/ Packaging_Resins/en_US/whats_new/article20100525.html (accessed 27 June 2010). Envirowise (2008), Packguide – A guide to packaging eco-design, GG 908, Envirowise, Didcot, August 2008. European Parliament and Council Directive 94/62/EC of 20 Dec 1994 on Packaging and Packaging Waste. European Parliament and Council Directive 2004/12/EC of 11 Feb 2004 on Packaging and Packaging Waste. EUROPEN (2009), Press Release, 08 Dec 2009: Work to begin on international packaging and environment standards, EUROPEN Publications, Belgium. Fernandez-Saiz P, Lagaron J M, Hernandez-Muñoz P and Ocio M J (2008), ‘Characterization of antimicrobial properties on the growth of S. aureus of novel renewable blends of gliadins and chitosan of interest in food packaging and coating applications’, International Journal of Food Microbiology, 124(1), 13–20. Giles G A and Bain D R (2000), Materials and Development of Plastic Packaging for the Consumer Market, Sheffield Academic Press, Sheffield, UK. Good, M (2010), ‘The challenge of recycling’, Climate Action, 30 April 2010, available from http://www.climateactionprogramme.org/news/the_challenge_of_recycling/ (accessed 27 June 2010). Griffin, R C, Sacharow S and Brody A L (1993), Principles of Package Development, 2nd Edition, Krieger Publishing Co., Florida, USA. Ipsos MORI (2008), Public Attitudes to Packaging – 2008, Ipsos MORI, London. Iseppi R, Pilati R, Marini M, Toselli M, de Niederhäusern S, Guerrieri E, Messi P, Sabia C, Manicardi G, Anacarso I and Bondi M (2008), ‘Anti-listerial activity of a polymeric film coated with hybrid coatings doped with Enterocin 416K1 for use as bioactive food packaging’, International Journal of Food Microbiology, 123(3), 281–287.

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Kalkowski J (2009), ‘Flexible packaging tightens its wrap on the market’, Packaging Digest, 46(11) (November), 10, Chicago, USA. Kimberly-Clark, Packaging – Performance 2009, available from http://www.kimberlyclark.com/aboutus/sus_2010/sustainability_pg26.aspx (accessed 26 June 2010). LeGood P and Clarke A (2006) Smart and active packaging to reduce food waste, Smart Materials, 7 November 2006. Available from: https://ktn.innovateuk.org/c/document_ library/get_file?p_l_id=72904&folderId=121313&name=DLFE-1016.pdf. LeGood P and Coulson W (2007) Consumer packaging opportunities for smart technologies, Smart Materials, February 2007. Available from: https://ktn.innovateuk.org/c/document _library/get_file?p_l_id=72904&folderId=121313&name=DLFE-1015.pdf. Monkhouse C, Bowyer C and Farmer A (2004) Packaging for sustainability: Packaging in the context of the product, supply chain and consumer needs, 27 September 2004, Institute for European Environmental Policy, for INCPEN, Reading, UK. Available from: http:// www.ieep.eu/assets/179/packingforsustainability.pdf. O’Dea K (2010), ‘Supply-chain collaboration does matter’, Packaging Digest, 47(3) (March), 21, Chicago, USA. Packaging Europe (2010), ‘Kimberly-Clark invests in a new look for Huggies®’, Packaging Europe 03 Mar 2010, available from http://www.packagingeurope.com/ NewsDetails.aspx?nNewsID=34755 (accessed 26 June 2010). PMMI (2009), ‘Packaging trends 2010: Brand building, improving efficiency and reducing costs are driving forces heading into 2010’, Packaging Intelligence Brief, 19 November 2009, PMMI, Arlington, VA, USA. Procter & Gamble, Frequently asked questions: packaging, available from: http://www. pampers.com/en_US/frequently-asked-questions (accessed 26 June 2010). Quintavalla S and Vicini L (2002), ‘Antimicrobial food packaging in meat industry’, Meat Science, 62(3), 373–380. Retka Schill S (2007), ‘Building better bioplastics’, Biomass Magazine, June 2007. Available from http://www.biomassmagazine.com/article-print.jsp?article_id=1158 (accessed 27 June 2010). Reynolds P (2010), ‘P&G optimizes shelf-ready packaging’, Healthcare Packaging, 30 Apr 2010. Available from http://www.healthcarepackaging.com/archives/2010/04pg_ optimizes_shelf-ready_packa.php (accessed 26 June 2010). Rodríguez A, Batlle R and Nerín C (2007), ‘The use of natural essential oils as antimicrobial solutions in paper packaging. Part II’, Progress in Organic Coatings, 60(1), 33–38. Statutory Instruments (2003), The packaging (Essential requirements), SI 2003 No. 1941, The Stationery Office, Norwich, UK. Statutory Instruments (2006), The packaging (Essential requirements) (Amendment), SI 2006 No. 1492, The Stationery Office, Norwich, UK. Statutory Instruments (2008), The producer responsibility obligations (Packaging waste) regulations (Amendment), SI 2008 No. 413, The Stationery Office, Norwich, UK. TerraChoice (2009), Ecomarkets 2009 Summary Report, TerraChoice Environmental Marketing Inc., Ottawa, Canada, September 2009. University of Strathclyde (2011), ‘Packaging that knows when food is going off’, January 2011 News, 11 January 2011. Available from http://www.chem.strath.ac.uk/news/archive/january_2011 (accessed 20 January 2011).

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5 Biodegradable hygiene products M. B E N E D E T T I, W.I.P. Spa, Italy

Abstract: This chapter aims to provide an overview of possible alternatives to the materials that are currently used today in the manufacture of disposable products for personal care, with an emphasis on environmental issues and conservation. The alternative materials take into account the sustainability of natural resources such as: crude oil (the basis for most plastics); starches, which are the starting point for all biopolymers; and natural fibres such as cotton. Key words: sustainability, ethical view, biopolymer, biodegradable, compostable.

5.1

Introduction

Nowadays, words such as ‘ecological’, ‘organic’, ‘biodegradable’ and ‘compostable’ are applied to a wide variety of items or even processes. They can be found almost everywhere on supermarket shelves across the globe, and are a constant presence in media campaigns; these terms are often used incorrectly, playing on the fact that they are largely unregulated, until eventually their meaning becomes obscured and discredited, with consumers viewing them with irritation and scepticism. Thus everything is reduced to the same level, based on marketing trends which are in turn driven by the recurring cycles of fashion. In order to better understand what will be covered in this chapter, it is necessary to refer to the more or less accepted and internationally shared definition of ‘sustainable development’. This term also covers those terms mentioned above, and consequently is not only connected to the protection of the environment but is also inseparable from health concerns. The concept of an ‘ecological foot print’ is based on the definition of ‘sustainable development’. The following definitions were found on the web: • ‘Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs’ (World Commission on Environment and Development). • ‘Sustainable development is a dynamic process which enables all people to realise their potential and to improve their quality of life in ways which simultaneously protect and enhance the Earth’s life support systems’ (Forum for the Future). 68 © Woodhead Publishing Limited, 2011

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In any case, it seems fair to state that any raw material collected from natural resources in a certain quantity, and employed in or processed by industry, can never be re-incorporated into the environment, whether as compost or liquid or gaseous materials, in a way that would allow it to be completely re-used to sustain future populations. In other words, the correct use of products – disposable products in particular – must be approached with a more critical eye in order to limit the damage caused by over-exploitation of finite natural resources. The use of such products should be based on the awareness that we are all biologically predisposed to guaranteeing the propagation of the species, and that for the foreseeable future and in daily life, we are also consumers who cannot escape the mechanisms of a global economy. Therefore, the choice of more sustainable materials cannot be reduced to mere commercial exploitation, which is usually simply a temporary attempt to recover profitability; the continued lack of regulation in this area serves only to allow a distorted and selfish use of something that could benefit everyone.

5.2

A classification of sustainable materials according to their ecological footprint

The materials that will be discussed and those that represent practical alternatives can be identified in the two definitions provided above. In the field of disposable hygienic products, the materials used can be broadly subdivided in two categories: • Cellulosic materials derived from plants, such as cellulose pulp, cotton or viscose fibres. • Materials generally recognized as plastics, i.e. derived from hydrocarbons. The cellulosic materials normally used can, in fact, be contrasted with cellulosic materials obtained through the implementation of more natural, socially and ethically responsible environmental management techniques that are more compatible with the maintenance of future resources, thus protecting human health and the environment. Examples of this are cellulose pulp obtained only from cultivated (and not primary) forests, organic cotton fibre, and Lyocell fibre to replace the traditional viscose. Synthetic materials, such as polypropylene or polyester fibres, along with superabsorbent gels, can be contrasted with natural raw materials of vegetable origin, which are technically or artificially modified by purely industrial processes, such as starches extracted from grains, potatoes and any other plants rich in polysaccharides, and then transformed into substances known as ‘biopolymers’. The ‘opposition’ principle does not a priori exclude other principles such as ‘alternative to’, ‘integration’ or ‘co-existence’ since all materials, regardless of any environmental considerations, have the following elements in common.

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• Health protection: they are classified as hygienic products, in other words products that come into direct or indirect contact with the skin, which is the part of the human body acting as the first defence against external agents and perspiration, and is, in general, a sensory organ. • Effectiveness: in other words the ability to offer a specific performance. For hygienic products this is generally understood to be a means of drying or absorbing fluids (tissues, hygienic pads, tampons, nappies, cloths, etc.) or containing and releasing fluids of different densities (hand wipes, make-up removing wipes, etc.) or at least of providing protection against the possible passage of fluids or gaseous materials (napkins, tablecloths, but also work coats, etc.)

5.3

Criteria for the selection and implementation of sustainable alternative raw materials

The performance of a product, especially of a single-use product, is determined by a variety of factors, including the assembly techniques of the various materials, the manufacturing techniques required for semi-finished products, and the choice of raw materials. In many cases, and again especially in the case of single-use products, chemical processes are used to optimize the performance of the raw materials. When more sustainable materials are used, additional considerations can and should apply in their research and application. • Essentiality. Anything that can be considered ‘useless but beautiful’ should be eliminated. This means any elements that have an impact on the purchase choice (especially those which play on psychological factors and on a lack of knowledge amongst consumers) and that are purely a marketing tool. In this case the purpose is twofold: to avoid misleading the consumer and to reduce the quantity of materials, which are on average more expensive. An example is the textile back sheet of nappies, which technically has no other use but to give a more ‘textile’ and less ‘plastic’ feel to the product, or else to limit the use of the film (usually made of polyethylene and used in the second layer) to the necessary external protection areas. • Concreteness. The reduction and, whenever technically possible, the complete elimination of all devices (especially those which rely on chemical processes) that are used in the industry to unnaturally increase product performance (sometimes with no regard for health considerations). In this case, possible partial reductions in individual product performance under the same conditions (weight, dimensions, etc.) must be taken into account, and this performance must then be communicated to the client. In certain cases a parallel campaign may then need to be carried out in order to educate consumers on product use. As an example – the use of soothing anti-irritation creams on nappy filters with the aim of covering up a possible defect without removing its cause.

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• Price. In this case, the commercial lever used to encourage the public to accept a benefit that is on average more expensive and/or in certain cases offers a lower level of performance becomes exclusively a question of ‘transparency in communication’ and, in extreme cases, adherence to an ethical code made public through direct contact with the critical consumer and initially, through the company website, e.g. printing the list of materials used to manufacture hygienic pads or nappies. This is mandatory for cosmetics and food products, but not for hygiene products, or for those that are in any way related to consumer health. • Warranty certification. The practice of certification covers both safeguard and warranty of technical choices and transparency. Certification is sometimes a safeguard solely of the process (environmental impact and social protection) but not of the raw materials and their origin, as in the case of the ECOLABEL. At present there are no procedures issued by the EU standard (ECOLABEL) related to disposable products for personal care. Below are some of the most popular standards currently used in the hygiene sector: – GOTS (global organic textile standard) (www.gots-standard.org). This is ‘the worldwide textile processing standard for organic fibres, including ecological and social criteria, backed up by independent certification of the entire textile supply chain’. The standard is applied from harvesting to labelling. – Fairtrade (www.fairtrade.org). ‘The Fairtrade standards go further in seeking to support the development of disadvantaged and marginalized small-scale farmers and plantation workers. Fairtrade standards relate to three areas of sustainable development: social development, economic development and environmental development’. In other terms, it is a means of protecting the social value of manufacture and processing promoted by organizations that encourage and support an equal and fair treatment of workers. Equality should be understood in terms of salaries and added value, while fairness relates to the treatment of employees at all levels. These Fairtrade certifications are generally tied to international cooperation projects supporting the balanced and sustainable development of developing rural or suburban areas worldwide, and especially in those developing countries where exploitation is a large-scale problem, such as in many southern hemisphere countries. – NORDIC ECOLABEL (www.nordic-ecolabel.org). This is ‘the official Ecolabel of the Nordic (European) countries and it was established in 1989 by the Nordic Council of Ministers. The purpose of the Nordic Ecolabel is to contribute to sustainable manufacturing and consumption’. The label ‘evaluates a product’s impact on the environment throughout the whole lifecycle’. It ‘guarantees that climate requirements are taken into account and that emissions of CO2 (and other harmful gases) are limited’. This standard is currently unique in Europe in having procedures designed for the measure-

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Textiles for hygiene and infection control ment of the environmental impact of products from the hygiene sector (disposable goods for personal care). – LCA (www.epa.gov/nrmrl/lcaccess/). ‘LCA is a technique to assess the environmental aspects and potential impacts associated with a product, process, or service by: compiling an inventory of relevant energy and material inputs and environmental releases; evaluating the potential environmental impacts associated with identified inputs and releases; interpreting the results to help you make a more informed decision’. The LCA will become one of the most important instruments of evaluation of the sustainability of a manufacturer and of its products. It must become the main instrument for consumers to compare competitors and products, and finally to help them to make a conscious choice. It is based on procedures defined from the norm: ISO 14040.

5.4

Alternative raw materials

As mentioned above, the selection of alternative raw materials does not automatically mean that they can be used to replace others without carrying out appropriate modifications to the processing lines. In particular, adopting artificial raw materials such as fibres and films from biopolymers requires the following upstream factors to be taken into account: • the technical qualities of the polymer (e.g. melting degree and curve, potential mechanic wear and tear index, causes – if known – that could, for example, impact upon the biodegradation principle, such as resistance to environmental conditions such as humidity and temperature). • the specific application of the polymer (e.g. as a barrier against the passage of fluids or the speed of passage of fluids). In other words, the main mistake made by those considering alternative materials is the expectation that, in production terms, they will be technically just like the materials that they are substituting. This inaccurate and unrealistic belief is the main reason behind the failure of many attempts to adopt alternative materials. In reality, adjustments to the processing lines can often be made with no need for structural changes. However, similar considerations apply when natural fibres are substituted with more ecological versions, such as the use of Lyocell instead of viscose, or other organic versions such as organic cotton in lieu of the industrial cotton, because these fibres have different organoleptic qualities and features. In many cases, the qualities and features of these alternative fibres are better, such that an overall analysis, including analysis of technical parameters and costs, is required only after all the processing has taken place. Considering these additional conditions, an overview of the materials that are considered the most natural alternative to those used for hygienic and single-use

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products is given below. The subheadings list materials currently used and sustainable alternatives where available.

5.4.1

Absorbent fibres

This category includes mainly ‘natural’ and artificial fibres made of cellulose. Examples are described in more detail below. Viscose fibre – sustainable alternative: Lyocell® fibre and Tencel® fibre Lyocell (trademark of the Lenzing Group) is the proper name of the fibre and it is the only ecological alternative fibre to viscose. Processing of Lyocell is more sustainable because it requires less power consumption and creates less pollution than the older more traditional process of the transformation of cellulose (from tree or farm waste) into viscose fibre. Lyocell, and above all its UK version developed in the 1990s and called Tencel (trademark of the Lenzing Group), offers a higher mechanical strength and therefore a lower fibre fragmentation and tearing risk under traction, and also produces less powder both during processing (i.e. during its transformation from fibre to non-woven) and in the finished product. The ability to absorb fluids is practically unchanged, as is its ability to biodegrade moulds and bacteria. However, Tencel fibre, particularly thanks to its specific manufacturing process (which is different from that of Lyocell) offers a higher mechanical strength than viscose when used with fluids. With the exception of specific variations, the price of Lyocell/Tencel follows the price trends of viscose and is lower than the cost of cotton fibre. Lyocell/Tencel is particularly suitable for the production of handkerchiefs and serviettes, or as a cotton substitute in make-up remover wipes, hygienic pads, hospital sheets, filters (Tencel fibre in particular). Bamboo and Crabyon® fibre An alternative to ‘simpler’ artificial fibres, these are still made of artificial cellulosic fibres, but thanks to technology and research they have properties that can offer advantages, particularly in terms of direct skin contact (e.g. softness) or healthcare (e.g. bacteriostaticity). These fibres are mostly made using Lyocell technology. During the manufacturing process, natural or artificial substances are added to the cellulose. The main factor that limits their application is their price, which is significantly higher (in certain cases excessively so) than that of other alternatives. Bamboo fibres were first used in hygienic products; they are made of cellulose extracted from the bamboo plant, which, thanks to its particular molecular structure, provides an excellent softness to the artificial fibre. In addition, bamboo contains a natural chemical that makes the cellulose less susceptible to the decomposing action of

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bacteria (in nature, bamboo degrades very slowly), and this is also injected into the fibre. A particular fibre that should be mentioned is Crabyon. This is manufactured by Omikenshi in Japan and consists of Lyocell, to which chitosan, a polysaccharide extracted from shrimp and crab shells, is added. Thanks to the active principle of bamboo, this fibre is particularly suited for hygienic products that come into contact with the skin, as well as when the skin is particularly sensitive or subject to significant stress, as with children’s skin, or in cases of dermatitis or diabetes. Fibres containing chitosan are also used in the manufacture of sticking plasters since their active principle stimulates skin regeneration. Since the material is incorporated into the fibre, the benefits of chitosan are generally long lasting and the fibre’s biodegradation ability is unaffected. Cotton fibre – sustainable alternative: organic cotton fibre Organic cotton is now grown wherever traditional cotton is grown. Its market availability is also growing, although it still constitutes less than 5% of global cotton production. It is particularly suitable for the manufacture of hygienic products, in particular when the product must be guaranteed to be allergen-free. On the technical side, there are no particular processing differences in the workability, absorption capacity, or mechanical performance in comparison with cotton produced through intensive farming, with the only differences being the intrinsic peculiarities of the type of seeds used, the microclimate, and the general environmental conditions of the place of production, just like in any other type of cultivation. However, even if the organic fibre is no better than that obtained from traditional or genetically modified (GMO) seeds, it is certainly not worse, particularly when it is grown in a non-intensive manner and when the natural pattern of soil rotation is respected. In this case, the natural organic composition of the soil cannot be replaced by the forced introduction of fertilizers, which are much more demanding in terms of their consumption of natural resources such as water. The increasing salinity not only destroys the bacteria in the soil but also requires an increasing quantity of water in order to reduce the mineral concentration in the soil; furthermore, these minerals pollute the aquifer. Organic cotton is essentially like hair that is not damaged by the continuous use of dyes and de-colouring agents, but is instead continuously enriched by natural substances, treated as a precious resource and not only as a product to be quickly consumed. Today, two methods are employed for cotton production: through sustainable but industrialized techniques (mostly connected to the demands of the market) and through sustainable and fair techniques. In the latter case, cotton farming is managed by international cooperative projects set up to ensure sustenance for rural populations and the reclamation of areas impoverished by speculative intensive farming. Generally, organic cotton cultivation is less expensive for farmers, especially when it is grown as part of a fair project (which is generally small to medium scale).

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However, the end-user sees a much higher price. This is mainly due to an attempt to make a profit during the various processing stages of the fibre, especially when third party companies are involved. Farmers are assured a purchase price that is on average 10 to 20% higher than the market price of traditional cotton. In many cases, non-profit cooperative projects also offer technical and economic support and specialized certification, which in turns leads to an increase in the sale price to the processing plant. Organic cotton fibre can be used wherever traditional cotton fibre would be used. Other natural cellulosic fibres – sustainable alternative: bamboo, hemp fibre These natural fibres often in a sense constitute an alternative to themselves, since the farming techniques employed traditionally respect the eco-system. In the field of hygienic products, these fibres are not currently used or, when they are used, they are underestimated, because they are considered expensive from the start. In fact, their applications in the manufacture of hygienic products have never been subject to an in-depth study based on an analysis of their properties. Certified organic versions of these fibres also exist. Possible applications of these fibres would be appropriate wherever the following properties are desired: reduction of overheating by contact, transpirability, high resistance to degradation by immersion, mechanical strength, and filtering capacity. They are suitable for direct skin contact in fabrics intended to have a scrubbing-like effect, because they are resistant to rubbing and ageing.

5.4.2

Non-absorbent fibres

Nearly all petroleum-based fibres are non-absorbent fibres. They are particularly suitable for drainage, substrate strengthening and protection, and also constitute a cost-effective alternative to more ‘noble’ fibres, in which case they are enhanced by the use of chemical or mechanical devices. Biopolymers, generally obtained from starch, the most common vegetable material found in nature, are included in this category. Starch constitutes the energy reservoir of the Earth and is particularly rich in polysaccharides, complex sugars that have natural characteristics that have always stimulated the imagination of both nutritionists and chefs. An idea of the plastic properties of sugar can be gathered simply by looking at the recipes of many cultures worldwide. Sugar is often melted, spun, stretched, and mixed to constitute an aggregating substance; in other words, it is the very first natural plastic material ever handled by mankind. Polypropylene and polyester (PET) – sustainable alternative: PLA (poly-lactic acid) fibre or similar PLA fibre is obtained by extruding a biopolymer through the production lines

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normally used for the manufacture of polyester. The biopolymer manufacturing process starts from dextrose, a polysaccharide extracted from grain seeds (particularly from starch-bearing corn) through fermentation with enzymes, which digest it and transform it first into lactic acid and then into poly-lactic acid. The fibre obtained from the biopolymer is particularly soft to the touch; it does not absorb fluids, but is a natural medium for moisture management. Unlike synthetic fibres it does not seem to accumulate heat; thus, it is particularly suitable for use in contact with the body (which produces heat). In terms of environmental impact, PLA is completely biodegradable and does not produce toxic fumes and dioxins when it burns. In general, the grains used are not those intended for food purposes, but are second tier products, and the biopolymer manufacturing process shows a significant reduction (up to 6–8 times) in CO2 production compared to synthetic polymers. However, the fibre has a crystalline structure and a slippery surface that requires attention during the mixing and carding phases; it is also less resilient than synthetic fibres of equal dimension, and can experience accelerated degradation, which is probably influenced by a combination of external agents such as temperature and humidity. It degrades only in the presence of moulds and bacteria that cause decomposition and can be processed into compost, but only under the optimal conditions that can generally be found in industrial plants. PLA is, on average, two or three times more expensive than petroleum-based fibres; on the other hand it is not subject to the price fluctuations caused by changing oil prices. PLA can be used in filtering fabrics, handkerchiefs and serviettes when mixed with other fibres. If used with due care, it can usually replace polypropylene fibres and partially even polyester fibres when there is no requirement for the products to be able to withstand high mechanical traction. Low-melting-point fibres for thermo-bonding processes – sustainable alternative: PLA/PLA bi-component fibre The bi-component fibre ‘dip la’ is made of two different grades of PLA that have different softening points. The PLA biopolymer (outer layer) has a lower melting point than the inner core and its toughness is not comparable to that of the outer layer used for a normal, non-biogradable polyester bi-component fibre. The low melting (140 °C) PLA polymer employed in the production of fibres actually reduces the application field of the PLA bi-component fibre; moreover, the polymer production process does not currently allow the same range of solutions that can be used with synthetic polymers. In addition, mixing different polymers with the PLA polymer to expand supply would probably prove difficult, especially if the same level of degradability is to be maintained At this point, it should be noted that bi-component fibres with a PLA core and an external shield of a synthetic fibre which is neither sustainable nor biodegradable have been recently introduced onto the market. This seems incompatible with

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the need for compostable, or at least biodegradable, finished products, and singleuse products in particular, since the PLA portion inserted into a synthetic fibre shell will not degrade and will prevent the product from being certified as ecosustainable. Therefore, this cancels out the advantages offered by PLA, both in terms of its naturally hydrophilic nature and its ability to avoid the accumulation of irradiated heat at body temperatures. This type of bi-component fibre seems to be motivated more by marketing needs than by true sustainability considerations. The price of PLA bi-component fibre is two or three times the price of standard bi-component fibre. Applications: PLA can be used in products and textile substrates where there is no need for significant mechanical strength, and is particularly suitable for laminated products with derivatives of biopolymers of the same type.

5.4.3

Barrier and protective films

This category includes all substrates and films that are manufactured to create barriers to fluids, or partial barriers to gases, in order to contain or isolate them or to protect them from contact with other elements. Polyethylene and polyurethane – sustainable alternative: eco-film or bio-film obtained from biopolymers A variety of alternative biopolymers currently exists on the market. Although they have been inspired by a common denominator (starches or flours), they have nevertheless followed different paths in order to create a range of options from which films are obtained through fusion. Moreover, the technology used for film melting and lamination leads to differences in what these films are able to offer. Not all bio-films are interchangeable in the manufacturing process. On the contrary, the variants obtained can carve out their own privileged niche market, based on their individual characteristics and performances. For example, a film obtained using a PLA biopolymer is fully crystalline and transparent, but is not very elastic and, in fact, is quite rigid, making it unsuitable for the production of films offering the barrier characteristics required by hygienic pads or nappies; the most frequently used films for single-use hygienic products are, therefore, those that require greater traction flexibility and high porosity (transpirability). It is not necessarily the case, however, that this type of film contains only biopolymers: it is likely to be a mix of synthetic polymers, or of other polymers of natural origin, which are in any case biodegradable or degradable in the presence of environmental agents. Of these polymers, both Mater-bi® polymer (Novamont Spa) and Bioplast® polymer (Biotec GmbH) are particularly important. Technology and research have led to the development of an interesting range of grades and variations for these films, with special and diversified applications. Biofilms are three to five times the prices of synthetic films. They can be used

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as barrier films, lining films, insulating films, and single or three dimensional perforated film supports in fluid filtering. Bi-laminated and similar films – sustainable alternative: biopolymers in combination with synthetic polymers In response to technical requirements and the possibility of adapting the products with the final goal of, for example, reducing skin irritation caused by rubbing, technological compromises are acceptable, in particular when a limit is set by the type and configuration of the production machinery, as in the case of extrusion or coupling. Here the use of biopolymers should be preferred for those layers that are in direct contact with the skin, in order to take advantage of the natural effect and capability of the biopolymer derivatives to be tolerated when in contact with the skin. Many laminated or coupled products are still in the development or setting-up stage. Due to the complexity of the adjustment and tuning of the existing processes, prices are expected to be quite high. With due precautions and limitations (also considering the insufficiency of experiences and statistical data), biopolymer/synthetic polymer combinations can substitute their petroleum-based equivalents for most applications.

5.4.4

Superabsorbent powder and fibre

Superabsorbent powders and fibres are used as high-efficiency supports, or as alternatives to cellulose, whose absorbance:weight ratio is approximately 10:1 g/g. In this case the efficiency can be more than doubled, assuming the weight remains the same. Superabsorbent polymer (SAP) (synthetic poly-acrylate) – sustainable alternative: polysaccharide-based polymer Polysaccharide-based polymers such as Lysorb® (ADM Ltd) are already used with good results in the production of sanitary towels, but are not fit for the absorption of more fluid liquids, such as urine. Therefore, when used in the production of children’s or incontinence nappies, this polymer can be used only in combination with traditional superabsorbent polymers. However, growing market pressure, especially from highly industrialized and economically more mature countries (especially tied to the disposal of nappies, but also to the expected turnover) is pushing the international industry to investigate various alternatives. More sustainable solutions to synthetic polymers are claimed to have been developed from many sources. The common objective is to make them biodegradable (rather than sustainable). The use of affordable superabsorbent polymers could also lead to further evolution of bulkier hygienic products, which have a high

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impact on the environment, such as children’s nappies, but above all incontinence pads for adults, which are the true business of the future. In fact, some alternatives to poly-acrylate of synthetic origin can be already found on the market; these alternatives may not have been studied for these specific applications, and may already be in use in the food industry, as is the case with synthetic polymers derived from cellulose (such as carboxymethyl cellulose), but their cost is still very high, discouraging their use and research for applications. The area with the greatest potential in R&D terms may well be polysaccharides, since they are widely available on the market and are perhaps easier to find and to exploit industrially. In this scenario, high volumes would be required by the market, which could lead to changes in land use, with farmland used for nonalimentary farming, and to the use of genetic biotechnologies, which are not always well accepted by society. Due to the ambiguities that remain in the marketplace, and the lack of precise definitions, the greatest interest in marketing terms remains the appeal that such innovations have for the consumer. A product’s ability to apparently disappear, at least from the consumer’s sight, is the most fitting example in this respect. This was the case with ‘flushable’ hygienic pads, which could be flushed down the toilet, giving the consumer the impression of having reduced her impact on the environment or having simplified her life (in fact, no material truly disappears, but in this case is simply transferred to the septic tank – perhaps that of the apartment block). Along the same lines, superabsorbent polymers of mineral origin are also claimed to be ‘degradable’ (but not bio-degradable, i.e. not broken down and transformed into compost by decomposition bacteria), with degradation occurring through weathering or other natural factors, such as ultraviolet rays, ultimately leading to them becoming inert powders (such as sand in a field). In other cases, polymers are mixed with materials that are negatively affected by humidity, which in turn allows bacteria to attack these elements (thanks to humidity and temperature) and, therefore, to break the synthetic parts. This then aids the process of disintegration (but not transformation into useful environmental material, such as compost). When this type of polymer is burned by waste-to-energy plants (since industrial plants for transforming material to compost are not particularly common in Europe), dioxins are produced; these polymers are therefore neither ecologically compatible nor more sustainable. Superabsorbent fibre (SAF) (synthetic poly-acrylate) – no alternatives yet discovered or developed

5.4.5

Packaging

Polyethylene flexible film – sustainable alternative: polysaccharide derived film The most commonly used alternative materials for polyethylene film are the bio-

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polymers Mater-bi® (Novamont Spa) and Biotech® (Biotec GmbH). In both cases, these polymers are obtained through a sometimes complex extraction and processing of polysaccharides (starch) from tubers (such as potatoes) or seeds (such as corn). In order to transform the biopolymer grains into packaging film, these materials are enriched by combining them with other polymers such as PLA (poly-lactic acid) or synthetic materials, with the amounts involved still ensuring that the film is completely biodegradable. The films that are obtained, unlike those obtained from petroleum-based polymers, are much more porous, and more sensitive to humidity and temperature. In some applications this is a desirable property, such as in the case of protective barriers used in the production of nappies and hygienic pads. However, they can have limitations if employed for packaging materials. These films are generally extremely elastic and delicate to the touch, but they are not transparent, unlike polyethylene synthetic film or PLA biopolymer, the latter being very crystalline and therefore less flexible and elastic. A general problem here is that film packaging manufacturers often have little or no experience in the usage of these materials; this problem ultimately also impacts on the final cost. Generally, biodegradable films for packaging are produced in lots, since adjustments to the production plant are usually required, particularly with respect to the speed and temperature of production, as well as greater attention to the storage of both the grains and the films. A lack of attention can lead to a rapid decline in the performance of the packaging, increasing waste and consequently also cost. Laminated polyethylene/polyester film – sustainable alternative: laminated film paper/PE or paper/biopolymers (PLA or similar) This film is normally used in the production of hand wipes. The (laminated) double layer offers an absolute barrier to the perspiration of fluids caused by the pressure and temperature that the packages undergo during packaging and storage. The sustainable alternatives consist mainly of polyethylene (in contact with the fluids) coupled with paper, with the aim of reducing the use of film parts deriving from petroleum, which are not biodegradable. The lack of supply, high price, and lower mechanical strength have limited both experimentation with this film and its application. A new line of non-transparent packaging products could consist of a range of fully biodegradable films, laminated with biopolymers as their internal barrier, and non-wovens or paper.

5.5

Conclusion

The use of natural biopolymers and raw materials from organic agriculture in the hygiene market is not an ‘eco-friendly’ alternative simply because they are biodegradable or because they are an immediate low-cost solution to the daily problem of city-waste (green waste-cycle) or even because they are a naive dream

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of a researcher. The fact is that they are more sustainable for the environment (the planet) than the current massive use of synthetic oil-derived materials for the production of disposable hygiene products. Therefore, the key point in hygiene products can not be reduced to just a question of the cost of the raw materials, as seems to be the main cause of concern of the major global players; it has to be part of a long-term political strategy of governments in order to assure the future of all our children.

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6 Micro-organisms, infection and the role of textiles R. J A M E S, University of Nottingham, UK

Abstract: This chapter discusses the importance of Clostridium difficile and methicillin-resistant Staphylococcus aureus (MRSA) in healthcare-associated infections (HAIs). The chapter reviews the significance of HAI and the principles of infection prevention and control that are used to try to reduce the scale of the problem. The chapter then considers the role of textiles in preventing infection and considers future challenges such as emerging infections that are a threat to healthcare systems worldwide. Key words: Clostridium difficile, healthcare-associated infections (HAIs), infection prevention and control, methicillin-resistant Staphylococcus aureus (MRSA), superbugs. Note: This chapter is adapted from Chapter 13 ‘Infection prevention and control and the role of medical textiles’ by R. James, also published in Handbook of Medical Textiles, ed. V. T. Bartels, Woodhead Publishing Limited. Published 2011, ISBN: 978-1-84569-691-7.

6.1

Introduction to infections

Infections are caused by pathogenic micro-organisms that are capable of invading the body of a human, where they then replicate and cause tissue damage. The human body is colonised (in which case the micro-organisms are not causing tissue damage) on the skin and mucosal surfaces by micro-organisms that constitute the ‘normal flora’ of the body. It is estimated that the 1013 human cells that make up a human body coexist to form a complex ecosystem with the 1014 microbial cells that colonise our skin, mouth and throat, bowel and urino-genital tract. These microbial cells can provide benefit to the human host by, for example, producing antimicrobial com-pounds that inhibit the growth of pathogens, or by denying an ecological niche in the body to pathogens. Humans have a number of additional defences against microbial infection whose main aim is to prevent access to the normally sterile, deeper tissues that lie below the skin and mucous membranes. These can be divided into consti-tutive defences, which are always activated (innate immunity), and inducible defences, which are switched on by the presence of an invading microbe (adaptive immunity). In this chapter we will investigate how infections are spread in hospitals, the principles of infection prevention and control in hospitals, and the role that textiles may have in reducing infections. 85 © Woodhead Publishing Limited, 2011

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6.1.1

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Historical examples of serious infections

Plague is an infectious disease, caused by the bacteria Yersinia pestis, which has a high fatality rate without treatment. Plague infections have occurred in three pandemics since the 6th century, the first of which was the ‘plague of Justinian’, named after the Roman Emperor. It started around 532 in Africa and then spread, reaching Constantinople in 541 and then Italy, France and Germany. The outbreak in Constantinople is described in detail by Procopius of Caesarea in records that have survived to this day (Zietz and Dunkelberg, 2004). At that time, the medical explanation for epidemics such as plague was contributed by Hippocrates and Galen, and was based on the theory of miasmatic fouling of the air by putrid exhalations from swamps or the victims of plague. We now know that bubonic plague presents in humans in several distinct ways, with the primary pneumonic plague form being the most important (WHO, 2002). Bubonic plague is characterised by the swelling of lymph nodes (buboes), and results from the transfer of Yersinia pestis by a flea bite or direct contact of a skin lesion with infected material. Primary pneumonic plague is the form with the highest mortality rate and is spread by person-to-person transmission. This occurs by direct inhalation of droplets containing the pathogen which are spread by coughing and requires being in close proximity to an infected patient (Perry and Fetherston, 1997). The second plague pandemic started around 1332 and rapidly spread around the world; it became known as the Black Death. It is estimated that this plague pandemic killed between 15 and 23.5 million Europeans, or 25% to 33% of the entire population. Many cities introduced quarantine measures, based upon the forty-day restriction on travel imposed in Marseille in 1384. The second plague pandemic continued sporadically until the early 18th century, with major outbreaks occurring regularly. The most famous in the UK started in London in 1665 and the London Bill of that year records 68 596 out of a total of 97 306 deaths were caused by plague: this amounts to between 15% and 20% of the population of the city. Interestingly, some towns such as Bristol which acted promptly to prevent anyone from London from entering, had only a few cases. In 1674, the development of a higher magnification microscope by Antoni van Leeuwenhoek resulted in the first observation of bacteria. It was over a hundred years later that Louis Pasteur demonstrated that the contamination of beer is due to airborne micro-organisms, and in the same year Robert Koch identified Bacillus anthracis as the causative agent of anthrax. The causative agent of plague was identified during the third pandemic, which originated in China around 1855 and reached Hong Kong in 1894, from where it spread to all continents. France sent the bacteriologist Alexandre Yersin to Hong Kong where, in 1894, he succeeded in identifying the causative organism (which, after several name changes, was called Yersinia pestis in 1970). Several researchers have questioned whether Yersinia pestis was actually the causative organism of the Black Death. This question has

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been unambiguously resolved by using the polymerase chain reaction method to amplify Yersinia pestis DNA from the dental pulp of teeth extracted from the skeletons of three Black Death victims, who were excavated from the same grave in Montpellier, France (Raoult et al., 2000). The rapid discovery of this and many other pathogenic micro-organisms in the following years resulted in a firm foundation for the new science of medical bacteriology and an increased understanding of the nature of infection.

6.1.2

Man fights back: antibiotics

In the 17th century it was known that natural products were effective in minimising the symptoms of certain protozoal diseases. The bark of the cinchona tree, which contains quinine, was effective against malaria, whilst emetine, obtained from the ipecacuanha root, was effective against amoebic dysentery. There were, however, very few options for the treatment of bacterial infections, although mercury had been used to treat syphilis since the 16th century (thus explaining the warning to men ‘One night with Venus, a lifetime with Mercury’). Similarly, chaulmoogra oil has been used for centuries in India for the treatment of leprosy. Once the agents of infectious disease were identified by Pasteur, Koch and Yersin then, began the search for specific antimicrobial drugs, which was led by Paul Ehrlich. Ehrlich realised that, since the protozoa that cause malaria or African sleeping sickness could be distinguished from the host tissues of infected patients by staining with dyes, there might be compounds that exhibited high affinity for the parasite that could be the basis for selective toxicity. Ehrlich began by studying methylene blue and trypan red, without any success, and then switched his attention to arsenicals, after research in the Liverpool School of Tropical Medicine revealed that atoxyl, an arsenical, protected mice from trypanosomal infection. Ehrlich and his chemist Bertheim began trying to synthesise less toxic arsenical derivatives and in 1909, showed that their compound number 606 cured rabbits infected with the spirochaete that causes syphilis. This compound, marketed as Salvarsan, was the first effective antibacterial agent with an acceptable level of toxicity, although it had a limited spectrum of activity. A more soluble derivative, Neosalvarsan, was discovered by Ehrlich in 1912. The German dyestuff industry started to take an interest in antimicrobial compounds and a derivative of trypan blue was developed by Bayer and marketed in 1924 for the treatment of parasitic diseases. This success spurred research into antimicrobials that resulted in the discovery of the first broad-spectrum antibacterial agents, the sulphonamides, at Bayer in 1932 by Gerhard Domagk, for which he won the Nobel Prize in 1939 and became the subject of a Hollywood movie called ‘Dr Ehrlich’s Magic Bullet’ (made in 1940). The discovery came from work with Prontosil Rubrum, a compound in which a sulphonamide group was linked to a red dye to aid binding to bacterial cells. Unfortunately for Bayer, the active ingredient in Prontosil Rubrum was

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sulphanilamide, a compound which was already in the public domain so that they were unable to patent it and obtain exclusive rights to its marketing. As a result, many other companies began to manufacture and market sulphanilamide. The S.E. Massengill Company in Tennessee developed a liquid form by dissolving sulphanilamide in diethylene glycol. At that time it was not necessary to carry out toxicity testing on new drugs in the USA which, had it been carried out, would have discovered that diethylene glycol is a poison (Wax, 1995). The death of more than 100 people after being prescribed ‘Elixir Sulphanilamide’ in 1937 led to the enactment of the Federal Food, Drug, and Cosmetic Act, which remains the basis for the US Food and Drug Administration regulation of these products today and undoubtedly saved the USA from the thalidomide tragedy of the early 1960s (Ballentine, 1981). On a more positive note for medicine, the patent position of sulphanilamide was the driver behind the intensive research for derivatives that could be patented, of which May and Baker 693 was the most potent and broad spectrum. It was revealed later that this drug had saved the life of Winston Churchill during the Second World War when he contracted pneumonia. The discovery of penicillin by Sir Alexander Fleming in London in 1928 has been suggested to be one of the most important events in medicine. Fleming began his medical studies at St Mary’s Hospital Medical School in 1901. He was offered a position in the Inoculation Department at St Mary’s in 1906 where the research group led by Almroth Wright aimed to develop vaccines against bacterial infections. During the next eight years, Fleming was introduced to bacteriology and vaccine preparation and was involved in the clinical trials of Salvarsan, before Wright and his research group were sent to France to study methods to treat infections in wounds. The high mortality rate in soldiers caused by bacterial infections influenced the research interests of Fleming when he returned to St Mary’s at the end of the war. His discovery that nasal mucous and tears contained lysozyme, an antibacterial agent that was effective against some pathogenic strains of streptococci and staphylococci, undoubtedly prepared him for the serendipitous discovery of penicillin in 1928. Several researchers have tried to duplicate the events of that summer when, on his return from holiday, Fleming observed that an agar plate that he had inoculated with a pathogenic strain of staphylococcus and then left on the laboratory bench had become contaminated with a penicillium mould that inhibited the growth of the bacterial colonies (Hare, 1982; Bentley, 2005). Further experiments quickly determined the best temperature to grow the mould and how to obtain a ‘mould juice’ extract that contained the antibiotic agent, which he termed penicillin. It was to be 10 years later that work by Howard Florey and Ernst Chain in Oxford would solve the problem of obtaining sufficient quantities of the new drug to allow the successful testing in 1940 of its antibacterial properties in mice infected with a lethal dose of streptococci. Production was scaled up in Oxford to obtain the even larger amounts of penicillin needed for a clinical trial in patients, although perhaps surprisingly by this time a decision

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had been taken not to patent this new drug, as desired by Chain, who was informed by the Medical Research Council that ‘the patenting of drugs was unethical and contrary to the traditions of medical research in Britain’ (Bentley, 2009). Florey travelled to the USA to enlist their help with increasing the availability of penicillin. Improvements in fermentation technology soon resulted. After the citizens of Peoria were encouraged to send in mouldy food for analysis, the isolation of a high yielding strain from a cantaloupe further enhanced the yield of penicillin (Scoutaris, 1996). Entry into the war after the Japanese attack at Pearl Harbour led to the deployment of enormous resources of money and manpower in the USA to further increase production in order to be able to treat wounded soldiers at the battle front. This enabled them to survive their wounds and fight again, thus gaining a military advantage for America. In the UK in 1942, Florey donated enough penicillin to enable Fleming to save the life of a family friend with meningitis. As a result, Fleming persuaded the UK Government to scale up the production of penicillin in this country with the help of the pharmaceutical companies. It was fitting in 1945 that Fleming, Florey and Chain were jointly awarded the Nobel Prize for the discovery of penicillin. It can be argued that Norman Heatley, a biochemist in Oxford who made outstanding contributions to solving the problem of purifying penicillin from crude extracts also deserved recognition. The structure of the penicillin molecule was solved in 1945 and revealed the presence of an unusual four-membered beta-lactam ring which subsequently gave rise to the name of the family of antibiotics that included penicillin, the betalactams. The identification of a critical building block in the synthesis of penicillin that could be modified by chemical synthesis resulted in the development of a large number of ‘semi-synthetic penicillins’ in the 1960s. The discovery in Oxford of the same beta-lactam ring structure in cephalosporin C, an antibiotic first discovered in Italy in 1945 by Brotzu (Hamilton-Miller, 2000), this time resulted in UK patents that generated millions of pounds of licence income from the subsequent development of semi-synthetic cephalosporin derivatives. That beta-lactam antibiotics still constitute one of our most important weapons against bacterial infections is a testament to the importance of the discovery of penicillin. The discovery of sulphonamide and the widespread clinical use of penicillin during World War II marked the beginning of the ‘golden age of antibiotic discovery’ which lasted until the 1960s. Selman Waksman at Rutgers University carried out an extensive investigation of the ability of micro-organisms in soil to inhibit pathogenic bacteria, which resulted in the discovery of streptomycin in 1943. This was the first antibiotic with activity against Mycobacterium tuberculosis, the causative agent of TB, which affects about one third of the world’s population. Rifampicin was also found to be produced by a soil micro-organism. During this period, many of the major classes of antibiotic that are still in use today were discovered.

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6.1.3

Bacteria fight back: antibiotic resistance mechanisms

Fleming observed in his early laboratory experiments that he could isolate resistant colonies of bacteria that had been treated with penicillin. He sounded a very prescient note of warning in his Nobel Lecture on the potential risk of underdosing when treating a streptococcal infection and how this could ‘educate them to resist penicillin’ (Fleming, 1945). However, the rate of discovery of a large number of antibiotics that were effective in treating infections caused by bacterial pathogens seems to have generated a misplaced complacency such that, in 1967, the US Surgeon General William H. Stewart told a group of health officers in the White House that it was time to close the book on infectious diseases and shift all national attention (and dollars) to what he termed the New Dimensions of health: chronic diseases. It is now apparent that neither Fleming, nor Stewart, appreciated the ingenuity and sheer variety of the ways in which bacterial pathogens would become resistant to antibiotics. In many ways, exposure of growing bacterial cells to an antibiotic is an extreme example of Charles Darwin’s ‘survival of the fittest’ theory of natural selection, as only the bacterial cells that have in some way developed resistance will survive to reproduce and thus pass on their resistance to future generations. There are four major antibiotic resistance mechanisms: • • • •

antibiotic inactivation; altered antibiotic target or overproduction of antibiotic target; reduced antibiotic accumulation; bypass antibiotic-sensitive step.

Resistance against a class of antibiotics, such as the beta-lactams, can result from more than one of these four mechanisms (Table 6.1). There are two types of antibiotic resistance in clinical isolates; intrinsic resistance, which is an intrinsic property of a bacterial species that makes them resistant to an antibiotic, and acquired resistance, where a population of bacteria that were initially sensitive to an antibiotic become resistant. Acquired resistance can be due to the acquisition of mutations in the gene that encodes the cellular target of the antibiotic that, for example, reduces antibiotic binding, or by the acquisition of a plasmid that encodes a resistance gene. Intrinsic resistance, since it is predictable, is by far the easiest to overcome; however, acquired resistance is a serious threat to the continued existence of many antibiotic treatments. Plasmids are extra-chromosomal genetic elements that replicate independently of the bacterial circular genome and can be transferred from cell to cell by the process of bacterial conjugation. Plasmids frequently carry several different antibiotic resistance genes that are transferred en bloc during plasmid transfer, with the result that the recipient bacterial cell that acquires the plasmid becomes resistant to several classes of antibiotic simultaneously. It is obvious that the

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Table 6.1 Antibiotic resistance mechanisms Inactivation

Altered target

Reduced accumulation

Aminoglycosides Beta-lactams Chloramphenicol

Beta-lactams Chloramphenicol Quinolones Rifampicin Streptomycin

Aminoglycosides Beta-lactams Chloramphenicol Quinolones Tetracyclines

Bypass target Trimethoprim Sulphonamides

transfer of these resistance-encoding plasmids, or R-plasmids, to bacterial pathogens will significantly reduce the available therapeutic options to treat an infected patient. The mobilisation of antibiotic resistance genes between plasmids and/or the bacterial genome is mediated by ‘transposons’, which are mobile DNA sequences that are often termed ‘jumping genes’; these can transpose from one DNA molecule to another in a replicative process that results in the transposon being present in both DNA molecules. Since the central region of a transposon often carries antibiotic resistance gene(s), it is easy to appreciate how a newly developed resistance gene can be rapidly spread between different R-plasmids and thus be mobilised into a wide variety of bacterial pathogens. This has led to the concept of the ‘antibacterial resistome’, which effectively is made up of the whole microbial world together with its complement of R-plasmids and transposons. A resistance gene that has been developed in any micro-organism can be mobilised to any bacterial pathogen which is exposed to the formidable selective pressure of antibiotic therapy. It is perhaps amazing that some antibiotic resistance mechanisms are inducible and are switched on in the host bacterial cell only in the presence of the antibiotic, with the effect that they save energy for the cell by producing the resistance gene products only when they are required.

6.2

Superbugs and healthcare-associated infections

With the realisation that hospitals are populated both by ‘sick patients’, with underlying medical conditions that may make them more susceptible to infection, and by ‘fit bacteria’ that are capable of causing serious infections and often carry antibiotic resistance genes, it is easy to see why the UK is confronted with a serious problem of healthcare-associated infections (HAIs) caused by ‘superbugs’. This term appeared in newspapers in the UK in 1985 in the context of stories about the agricultural use of antibiotics leading to the evolution of antibiotic-resistant pathogenic bacteria. From about 1997, the term began to be used widely, both in broadsheet newspapers and by politicians, in stories concerning methicillinresistant Staphylococcus aureus (MRSA). The use of the term superbugs implies that there are ordinary ‘bugs’ which, although capable of causing infections, are not a threat, and then there are superbugs, such as Clostridium difficile (C. difficile)

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and MRSA, that are ubiquitous in healthcare settings such as hospitals, threatening and unconquerable (Washer and Joffe, 2006; Nerlich, 2009). The accepted definition of an HAI today is ‘An infection that occurs more than 48 hours after admission to hospital; or an infection that occurs within 10 days of discharge from hospital (within 30 days for a surgical wound infection); or an infection that occurs within 72 hours of an out-patient procedure’. Prior to the introduction of antibiotics, the mortality rate of individuals with a Staphylococcus aureus (S. aureus) infection was 80%. In 1942, two years after the introduction of penicillin, the first penicillin-resistant S. aureus isolate was observed in a hospital patient. The first MRSA strain was reported in the UK in 1961 after the introduction of methicillin in 1959 to counter the emergence of the penicillin-resistant S. aureus strains (Barber, 1961). The strain was observed to spread rapidly and caused outbreaks of infections, especially amongst children, and a small number of deaths (Stewart and Holt, 1963). MRSA strains were subsequently isolated in a number of countries and the first serious outbreaks were observed in eastern Australia in the 1970s. A dramatic increase in the number of MRSA bacteraemias began in the UK in the early 1990s. MRSA strains result from the acquisition by methicillin-sensitive S. aureus (MSSA) strains of the mecA gene that encodes a modified penicillin-bindingprotein that confers resistance to all beta-lactam antibiotics. The mecA gene is found in all MRSA strains as part of a staphylococcal cassette chromosome (SCCmec) element that inserts into the S. aureus genome at the same specific site. SCCmec elements can be grouped into one of eight types (SCCmec type I to SCCmec type VIII), based upon their genetic composition. This is indicative that the evolution of MRSA strains from MSSA has happened independently a number of times. Several of the SCCmec types carry resistance genes against other classes of antibiotics in addition to the beta-lactams. This has significant implications in reducing the therapeutic options available to clinicians and explains the widespread use of vancomycin to treat patients diagnosed with an MRSA infection. The identification of nine MRSA isolates in the USA that exhibit resistance to high concentrations of vancomycin, together with the general increase in the vancomycin concentration required to kill many MRSA isolates, are worrying developments for the continued effectiveness of this antibiotic. S. aureus colonises many sites on the human body without causing an infection. Some 30% of the population have been found to carry S. aureus at any one time, principally in the nose. 20% of the population always seem to be colonised whilst 10% are only transiently colonised. A significant percentage of the population are thus never colonised with S. aureus, but the reasons for this are not entirely clear (Wertheim et al., 2005). The MRSA colonisation rate is significantly lower, at between 1 and 10%, depending on patient age and degree of previous exposure to healthcare settings, but again some individuals seem always to be colonised. C. difficile is found in the gastrointestinal tract of 2–3% of healthy adults without causing any clinical symptoms. C. difficile, unlike S. aureus, can exist as either

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vegetative, growing bacterial cells or as dormant, heat-resistant spores. The latter are an important route of transmission from one patient to another. Antibiotic therapy, particularly of elderly patients in hospitals, allows the C. difficile to proliferate in the GI tract and cause an infection that can range from mild diarrhoea to life-threatening pseudomembranous colitis. Patients with a C. difficile infection (CDI) are treated with one of two antibiotics, metronidazole or vancomycin. In a significant percentage of treated patients the CDI recurs, often several times, and results in significant mortality.

6.2.1

The scale of the healthcare-associated infections problem

The number of MRSA bacteraemia reports in England, together with the number of death certificates that either mention MRSA, or list MRSA as the cause of death, are shown for 2001–2008 in Table 6.2. The number of CDI cases dramatically increased in England between 1990 and 2004. Nearly 50 000 cases were reported in 2007, with 20% of them being in younger age groups previously not considered Table 6.2 Number of MRSA bacteraemia cases and deaths in England Year

2001 2002 2003 2004 2005 2006 2007 2008

Bacteraemia

7291 7426 7700 7233 7096 6383 4451 2935

Death certificate Mentions MRSA

MRSA listed as cause of death

731 794 968 1069 1536 1556 1517 1137

258 246 322 334 432 580 439 200

Table 6.3 Number of C. difficile infections and deaths in England Year

2004 2005 2006 2007 2008

CDI

Death certificate

44 314 51 767 55 681 49 785 37 134

Mentions CDI

CDI listed as cause of death

2238 3757 6480 8324 5931

1229 2063 3490 4056 2502

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to be high risk. The number of CDI cases in England, together with the number of death certificates that either mention C. difficile, or list C. difficile as the cause of death, are shown for 2004–2008 in Table 6.3. An important factor in the increase of CDI cases was the appearance of a more virulent strain, C. difficile 027, which produces more toxins and is associated with more severe disease, increased risk of relapse and higher mortality. This strain was involved in two big outbreaks in England at Stoke Mandeville in 2003–05 (Caldwell, 2006) and at Maidstone and Tunbridge Wells NHS Trust in 2005–06 that led to a large number of deaths. The latter outbreak was investigated in a BBC TV Panorama programme with which I was pleased to be significantly involved. The annual cost of HAIs to the NHS in the UK was estimated to be £1 billion by the National Audit Office (Bourn, 2000). In the US, 1.7 million people per year develop an HAI, resulting in 100 000 deaths (Klevens et al., 2007), at an annual cost to the healthcare system of between $28.4 to $45 billion (in 2007 dollars) (Scott, 2009). Assuming that 20% of US HAIs are preventable, the annual benefits of prevention range from $5.7 to $6.8 billion; whilst if we assume that 70% of HAIs are preventable, the annual benefits of prevention are between $25 and $31.5 billion.

6.3

Principles of infection prevention and control in hospitals

Ignaz Semmelweis in Vienna was the first to show that infections can be transmitted to susceptible patients within hospitals. Semmelweis carried out a detailed investigation to find out why the two maternity clinics at his hospital had significantly different mortality rates due to puerperal fever. A major difference between the two clinics was that the first clinic (with significantly higher death rates) was used for the training of medical students, whilst the second clinic (with lower death rates) was used for the training of midwives. Following the death in 1847 of a colleague who had received a cut from a student’s scalpel during a post-mortem, Semmelweis carried out the autopsy of his friend and noticed similarities in the pathology to that of the mothers who had died of puerperal fever. He proposed that medical students carried ‘cadaverous particles’ on their hands from the autopsy room to the mothers that they examined in the first clinic. This explained why the midwives, who were not involved in post-mortem examinations, had much lower death rates in the second clinic. As a result, Semmelweis introduced a policy of hand washing in chlorinated lime that resulted in a drastic reduction in death rates in the first clinic. However his work was ridiculed by the medical profession as he could not explain his findings and, by implication, his work implied that doctors were the cause of the puerperal fever and subsequent death of the mothers. This was perhaps the reason why he was eventually committed to an asylum in 1865 and died 14 days later of septicaemia. It was some 20 years later, when Louis Pasteur developed the germ theory of disease, that Semmelweis was vindicated.

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Infection prevention and control, as a discipline, now uses epidemiological principles and statistical analysis in order to prevent the transmission of infections from one patient to another. The key concepts in preventing infections involve the three links in the chain of infection: • potential sources of infection; • the routes of transmission of infection; • the role of host factors (i.e. the patient). The aim is to utilise this information to break the chain of transmission of infection by targeting any or all of the links of the chain.

6.3.1

Sources of infection

Possible sources of infection are patients who are carriers of an infectious organism, such as MRSA in the nose or C. difficile in the gastrointestinal tract; or patients who are infected. There are also potential environmental sources such as surfaces in a hospital ward, door handles, or toilets in communal areas used by patients that are contaminated with body fluids; however, there is little evidence to enable a judgement to be made on the relative significance of the hospital environment as a source of infection (Dancer, 2008). Whilst it is possible to show that pathogenic bacteria such as MRSA can be recovered by sampling the hospital environment, it is much more difficult to conclusively demonstrate that these organisms are the source of infections in patients who are in contact with this environment.

6.3.2

Routes of transmission of infection

The routes of transmission by which pathogens can be transferred from the source of infection to the host can be either airborne; by contact; or percutaneous. Airborne transmission involves the spread of infections such as influenza and TB via water droplets. Contact transmission can involve direct person-to-person transmission from the source to a susceptible host (as with MRSA), or can involve contact with body fluids such as faecal material (C. difficile), equipment such as endoscopes, or food. Percutaneous transmission can occur via insect vectors (malaria); intravascular lines (MRSA); or as a result of sharps injuries (hepatitis B, HIV).

6.3.3

The role of host factors

The host is the third link in the chain of infection. Patients in hospital may have a serious underlying medical condition that reduces their normal defences against infection; for example, if they are being treated with immunosuppressive drugs to avoid organ rejection after a transplant. A pathogen such as MRSA may enter the

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Textiles for hygiene and infection control Exposure of at-risk patients

Dissemination of spores

Symptomatic infection (diarrhoea)

6.1 The chain of infection for C. difficile. At-risk patients are exposed to C. difficile spores after contact with faecal matter contaminating surfaces, door handles, etc. in hospital wards. In those patients where a symptomatic infection results in diarrhoea, more faecal material containing C. difficile spores can contaminate the ward again. Preventing infection requires the chain to be broken by, for example, isolating infected patients and enhanced cleaning of the ward.

host through breaks in the skin such as a surgical site; via a medical device such as an intravenous catheter; or via the lungs. C. difficile is acquired via contact of the host with faecal material containing cells or spores and subsequent entry via the gastrointestinal tract. Patients in intensive care, or having a history of recurrent admissions or prolonged hospital stays, have a higher incidence of HAIs.

6.3.4

Breaking the chain of infection

The chain of infection is vulnerable at each of the three links in the chain. Sources of infection can be minimised by a high standard of cleaning (Dancer, 2008); cleaning and sterilising all surgical equipment; and controlling the standard of food given to patients. The introduction in April 2009 of MRSA screening of all patients admitted to hospitals in England for elective surgery has the potential to identify MRSA carriers on admission to hospital and allow the opportunity for decolonisation treatments. If successful, this policy would be expected to result in a considerable reduction in the potential sources of MRSA infection in English hospitals. Transmission of infections can be blocked by the provision of suitable protective clothing (including medical textiles) for both healthcare workers and patients; observance of the requirements for handwashing, especially by healthcare workers; and the isolation of MRSA carriers, and of C. difficile or MRSA infected patients. Improved host resistance to infection can be achieved by good nutrition; immunisation; minimising the use of invasive medical devices; the appropriate use of antibiotics; and education of both healthcare workers and patients. The chain of infection for C. difficile is shown in Fig. 6.1. Under considerable political pressure to reduce the incidence of HAIs, many

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hospitals in England introduced a large number of improvements in their infection control measures from 2004 onwards. Since 2005/6 there has been a considerable reduction in the number of reported CDIs and MRSA bacteraemias but it is difficult to determine what contribution any individual infection control measure has made to this reduction. It would be very expensive and time consuming to set up a randomised clinical trial to obtain this information.

6.4

The role of textiles in infection prevention and control

The traditional uses for textiles in infection prevention and control are in areas such as bedding, bed curtains, drapes, dressings and uniforms; these are highlighted in other chapters in this book. There is now considerable interest in the application of nanotechnology in medical textiles. The accepted definition of nanotechnology is ‘the application of scientific knowledge to control and utilise matter at the nanoscale (size range 1–100 nm) where size-related properties and phenomena can emerge’.

6.4.1

Antimicrobial wound dressings

Silver nanoparticles are widely used in antimicrobial wound dressings because of their recognised antibacterial activity (Madhumathi et al., 2010). Wound dressings are manufactured by means of a bi-layer of silver-coated, high-density polyethylene mesh with an adsorptive rayon/polyester core that delivers nanocrystalline silver to maintain an effective antimicrobial activity. Nanocrystalline silver dressings have been clinically tested in patients with burns, ulcers and other non-healing wounds and have been very successful in facilitating wound care. Wound dressings have also been developed which combine an electrospun polyurethane nanofibrous membrane and silk fibroin nanofibres. These electrospun materials are characterised by a wide range of pore size distribution, high porosity, and high surface-area-to-volume ratio that is important for fluid exudation from the wound, avoiding wound desiccation, and preventing infections by exogenous microorganisms.

6.4.2

Anti-adhesive wound dressings

Textile wound dressings such as plasters or bandages are used to cover wounds until the healing process can protect the wound. However, traditional wound dressings generally adhere to the healing wound, causing a new injury on removal, and thereby interrupt the healing process. Innovative wound dressings with antiadhesive properties to the healing wound have been obtained by coating the common viscose bandages with a silica nanosol modified with long-chain alkyltrialkoxysilanes. An additional, valuable feature of these innovative wound

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dressings is their excellent absorption properties of wound exudates, which facilitates the healing process especially in bedridden patients with chronic wounds.

6.5

Future trends

The data indicate that it took some 15 years for UK hospitals to start to get to grips with the problems caused by CDI and MRSA infections. It should be borne in mind that whilst the number of reported MRSA bacteraemias has fallen from a quarterly average of 1925 in 2003/4 to 482 between January and March 2010, bacteraemias caused by other bacteria such as Escherichia coli and Klebsiella pneumoniae have increased over the same time period. This implies that the infection control measures that have been successful against MRSA are less effective against other pathogens, which raises clear concerns as healthcare systems face the threat from a range of emerging infections such as Acinetobacter baumannii and ESBLs (extended spectrum beta-lactamases). In addition, infections with C. difficile and MRSA are increasingly being found in the community in patients who have had limited exposure to hospitals.

6.5.1

Emerging infections in hospitals: Acinetobacter baumannii

Acinetobacter baumannii (A. baumannii) is an example of an opportunistic pathogen that is generally harmless to healthy individuals but can cause serious infections such as ventilator-associated pneumonia, wound infections and bacteraemias in critically ill hospital patients. Wound infections caused by A. baumannii have been identified in a significant number of soldiers injured in Iraq after repatriation to the UK or USA (Davis et al., 2005). Its resistance to desiccation and disinfectants make it difficult to eliminate A. baumannii from the hospital environment. Epidemics of A. baumannii in hospital are most commonly triggered by the introduction of a patient who is colonised, followed by spread to other patients (Dijkshoorn et al., 2007). There is evidence of the spread of epidemic strains of A. baumannii between hospitals, presumably due to the transfer of patients. Epidemics in hospitals are usually ended by cleaning and disinfecting wards, which implies that the environment is an important source of A. baumannii infection. The bacteria can spread short distances through the air in water droplets or on scales of skin, but the most common route of transmission appears to be person-to-person, via the hands of healthcare workers. The treatment of A. baumannii infections can be complicated by both its intrinsic resistance to many widely used antibiotics, and the acquisition of resistance to many other classes of antibiotic, resulting in multidrug resistant (MDR) strains. Resistance to the carbapenems, such as imipenem, is particularly significant as these antibiotics have been widely used to treat MDR-A. baumannii infections. The recent reports of acquired resistance to colistin and

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tigecycline imply that the potential of A. baumannii strains to develop resistance against all the currently available antibiotics has now been achieved. It is fortunate that such strains are still only opportunistic pathogens as A. baumannii is perfectly adapted to maximise its transmission to susceptible patients whilst being able to resist the antibiotics and disinfectants that are used to try to control it (Perez et al., 2008).

6.5.2

Emerging infections in hospitals: extended spectrum beta-lactamases (ESBLs)

One reason for the importance of beta-lactam antibiotics has been the success in developing second- and third-generation antibiotics of this class in response to the widespread appearance of resistance to earlier generations of beta-lactams encoded by beta-lactamase enzymes that cleave the beta-lactam ring and inactivate the antibiotic. The first beta-lactamase enzyme produced by a strain of Klebsiella pneumonia that was able to inactivate such ‘extended spectrum beta-lactam antibiotics’ was described in Germany in 1983 and this was soon followed by others. These enzymes were described as extended spectrum beta-lactamases (ESBLs) in 1989 (Philippon et al., 1989) and were increasingly isolated during the 1990s in many countries. A new family of ESBLs, the CTX-M enzymes, were first detected in patients in Germany and Argentina but have now become the most prevalent ESBLs worldwide (Canton and Coque, 2006). A large number of CTXM beta-lactamases have now been identified, with the common gastrointestinal tract organism Escherichia coli being identified as the most common producing strain. Bacteria such as Klebsiella pneumonia and Escherichia coli can cause urinary tract infections, pneumonia, bacteraemia and meningitis (Schwaber and Carmeli, 2008). Based on amino-acid sequence homology, chromosomal beta-lactamase genes in Kluyvera species have been identified as the potential source of many of the CTX-M enzymes. These genes have migrated onto plasmids that can readily be transferred between different bacterial species, hence explaining the rapid spread of the ESBLs. CTX-M-producing isolates are also now being identified increasingly in infections in the community, as well as in hospital settings. Some studies have suggested that it is these community strains that have been the source of the large increase in CTX-M infections in hospitals. ESBL-producing isolates typically display resistance to other classes of antibiotics as well as beta-lactams, due to the acquisition of additional antibiotic-resistance genes by these isolates. This reduces the options for treating hospital patients infected with CTX-M isolates to the carbapenems, which have been termed the ‘antibiotics of last resort’. The recent appearance of bacteria producing carbapenemases (beta-lactamases that can inactivate carbapenems) means that there is no reliable antibiotic left to treat these infections, with potentially devastating consequences for healthcare systems worldwide (Schwaber and Carmeli, 2008).

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6.5.3

Textiles for hygiene and infection control

Community infections: community-associated MRSA (CA-MRSA)

Since the isolation of the first MRSA strain in 1961, various hospital-associated MRSA (HA-MRSA) clones have spread worldwide and have been the cause of the majority of hospital-acquired infections (Deurenberg and Stobberingh, 2008). The first report of community-associated MRSA (CA-MRSA) infections was in 1993, in Aboriginal patients living in remote communities in Western Australia with no contact with hospitals; this caused skin and soft tissue infections. Since then a number of CA-MRSA clones have spread worldwide and have been largely responsible for the increased incidence of MRSA infections, even in countries such as Denmark and Norway, which had previously been very successful in preventing the large increase in HA-MRSA infections. The Centre for Disease Control and Prevention in the USA defines CA-MRSA as MRSA strains isolated in an outpatient setting, or isolated from patients within 48 hours of hospital admission. Most CA-MRSA strains can also be distinguished by production of Panton–Valentine leucocidin (PVL), a toxin that may have a role in their pathogenicity. The UK Health Protection Agency report a significant increase in the number of PVL-positive strains of S. aureus in the UK but suggest that the incidence of CA-MRSA or CA-MSSA is still low compared with many other countries. CA-MRSA has had a dramatic effect on the treatment of suspected staphylococcal infections in geographical regions where CA-MRSA is prevalent, as it is likely that most beta-lactam antibiotics will be ineffective (Chambers and Deleo, 2009). The acquisition by CA-MRSA strains of resistance to other classes of antibiotic will further reduce the therapeutic options for treating these infections. CA-MRSA strains have started to replace HA-MRSA strains in hospitals, especially in the USA and Taiwan. There is evidence that CA-MRSA strains are more virulent and more transmissible by person-to-person contact. The improved infection control policies that have resulted in a significant reduction in MRSA bacteraemias in hospital patients in the UK may be threatened, both by the expected increase in CA-MRSA infections and by the wider range of types of infections that they have been observed to cause. At the extreme, CA-MRSA can cause necrotising pneumonia with a mortality rate of >50% in less than 72 hours.

6.6

A holistic approach to preventing infections

The increasing incidence of CA-MRSA, CDI and ESBLs in patients in the community suggests that we will have to change our perception of the problem of infection. Serious infections are no longer concentrated in hospitals where facilities for their diagnosis and expertise to advise on their treatment are more readily available. This will have significant implications for the effective delivery of healthcare in the 21st century. We will have to develop improved

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diagnostic tests that can be used closer to the point of care rather than just in hospital microbiology laboratories, so that we have more rapid information on the causative organism to aid treatment. We also need new antibiotics to give more treatment options, especially against infections caused by MDR organisms such as A. baumannii, ESBLs and MRSA. Unfortunately, the pace of discovery of new antibiotics has declined dramatically since the 1980s. The reasons for this are complex and involve the difficulty (and hence higher cost) of developing new antibiotics compared with most other types of therapeutic agents; profits will be higher for drugs to treat chronic conditions that have to be taken every day for life, rather than for antibiotics that are only taken for 7 days when the patient has an infection; and antibiotics and anticancer agents are the only drugs that have built-in obsolescence due to the development of resistance against their activity. Some interesting ideas to promote the development of new antibiotics are now starting to appear (Vagsholm and Hojgard), but it would make sense in this connected world in which we live if these could be coordinated by bodies such as the WHO, rather than being left to individual nations or pharmaceutical companies. Infection control measures must be more available in the community, along with better education of the public, in order to prevent the acquisition and prevention of infections. This will open up opportunities for innovative products such as medical textiles for use in the community. Dressings that can detect a wound infection in an elderly person living alone in their own home and then send a wireless signal to a community infection control team may be an example of what will become common in the next decade. This will allow rapid point-of-care diagnostic tests to be carried out, both to identify the pathogen and detect any antibiotic resistance properties, allowing treatment of the infection to be commenced during a single home visit.

6.7

Sources of further information and advice

Brown K (2004), Penicillin Man: Alexander Fleming and the antibiotic revolution, Stroud: Sutton Publishing Limited. Friedman M and Friedland G W (1998), Medicine’s 10 greatest discoveries, Yale: Yale University Press, pp. 37–64 and pp. 168–191. Lax E (2004), The mould in Dr Florey’s coat, London: Little, Brown. Mann J (1999), The Elusive Magic Bullet, Oxford: Oxford University Press, 1–76. Walsh C (2003), Antibiotics: Actions, origins, resistance, Washington, DC: ASM Press.

6.8

References

Ballentine C (1981), Sulphanilamide Disaster, U.S. Food and Drug Administration. Available from: http://www.fda.gov/AboutFDA/WhatWeDo/history/ProductRegulation/ Sulfanilamide (accessed 16 June 2010). Barber M (1961), Methicillin-resistant staphylococci, J Clin Pathol, 14, 385–393.

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Bentley R (2005), The development of penicillin: Genesis of a famous antibiotic, Perspect Biol Med, 48, 444–452. Bentley R (2009), Different roads to discovery; Prontosil (hence sulfa drugs) and penicillin (hence beta-lactams), J Ind Microbiol Biotechnol, 36, 775–786. Caldwell S (2006), HSE investigation into outbreaks of Clostridium difficile at Stoke Mandeville Hospital, Buckinghamshire Hospitals NHS Trust. Health and Safety Executive, UK. Available from: http:// www.hse.gov.uk/healthservices/hospitalinfect/stoke mandeville.htm (accessed 16 June 2010). Canton R and Coque T M (2006), The CTX-M beta-lactamase pandemic, Curr Opin Microbiol 9, 466–475. Chambers H F and Deleo F R (2009), Waves of resistance: Staphylococcus aureus in the antibiotic era, Nat Rev Microbiol 7, 629–641. Dancer S J (2008), Importance of the environment in methicillin-resistant Staphylococcus aureus acquisition: The case for hospital cleaning, Lancet Infect Dis, 8, 101–113. Davis K A, Moran K A, McAllister C K and Gray P J (2005), Multidrug-resistant Acinetobacter extremity infections in soldiers, Emerg Infect Dis, 11, 1218–1224. Deurenberg R H and Stobberingh E E (2008), The evolution of Staphylococcus aureus, Infect Genet Evol, 8, 747–763. Dijkshoorn L, Nemec A and Seifert H (2007), An increasing threat in hospitals: Multidrugresistant Acinetobacter baumannii, Nat Rev Microbiol, 5, 939–951. Hamilton-Miller J M (2000), Sir Edward Abraham’s contribution to the development of the cephalosporins: a reassessment, Int J Antimicrob Agents, 15, 179–184. Hare R (1982), New light on the history of penicillin, Medical History, 26, 1–24. Klevens R M, Edwards J R, Richards C L, Horan T C, Gaynes R P, Pollock D A and Cardo D M (2007), Estimating healthcare-associated infections and deaths in U.S. hospitals, 2002. Public Health Rep, 122, 160–166. Madhumathi K, Kumar P T S, Abhilash S, Sreeja V, Tamura H, Manzoor K, Nair S V and Jayakumar R (2010), Development of novel chitin/nanosilver composite scaffolds for wound dressing applications, J Mater Sci, Mater Med, 21, 807–813. Nerlich B (2009), ‘The post-antibiotic apocalypse’ and the ‘war on superbugs’: Catastrophe discourse in microbiology, its rhetorical form and political function, Public Underst Sci, 18, 574–588; discussion 588–590. Perez F, Endimiani A and Bonomo R A (2008), Why are we afraid of Acinetobacter baumannii? Expert Rev Anti Infect Ther, 6, 269–271. Perry R D and Fetherston J D (1997), Yersinia pestis – etiologic agent of plague, Clin Microbiol Rev, 10, 35–66. Philippon A, Labia R and Jacoby G (1989), Extended-spectrum beta-lactamases, Antimicrob Agents Chemother, 33, 1131–1136. Raoult D, Aboudharam G, Crubezy E, Larrouy G, Ludes B and Drancourt M (2000), Molecular identification by ‘suicide PCR’ of Yersinia pestis as the agent of medieval black death, Proc Natl Acad Sci USA, 97, 12800–12803. Schwaber M J and Carmeli Y (2008), Carbapenem-resistant Enterobacteriaceae: A potential threat, JAMA, 300, 2911–2913. Scoutaris M (1996), ‘Moldy Mary’ and the Illinois Fruit and Vegetable Company, Pharm Hist, 38, 175–177. Stewart G T and Holt R J (1963), Evolution of natural resistance to the newer penicillins, Br Med J, 1, 308–311. Vagsholm I and Hojgard S (2010), Antimicrobial sensitivity – A natural resource to be protected by a Pigouvian tax? Prev Vet Med, 96, 9–18.

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Washer P and Joffe H (2006), The ‘hospital superbug’: Social representations of MRSA, Soc Sci Med, 63, 2141–2152. Wax P M (1995), Elixirs, diluents, and the passage of the 1938 Federal Food, Drug and Cosmetic Act, Ann Intern Med, 122, 456–461. Wertheim H F, Melles D C, Vos M C, van Leeuwen W, van Belkum A, Verbrugh H A and Nouwen J L (2005), The role of nasal carriage in Staphylococcus aureus infections, Lancet Infect Dis, 5, 751–762. Zietz B P and Dunkelberg H (2004), The history of the plague and the research on the causative agent Yersinia pestis, Int J Hyg Environ Health, 207, 165–178.

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7 Creating barrier textiles through plasma processing S. C O U L S O N, P2i Ltd, UK

Abstract: This chapter discusses how plasma processing of textiles has the potential to offer a robust alternative to traditional wet finishing methods for imparting functional barrier properties. The chapter first reviews the theory and testing of water and oil repellency before considering the various textile treatments available. It then discusses the markets for plasma processing, where there is no room for a compromise between performance, comfort and cost. The chapter concludes by looking at ongoing work to develop additional performance enhancements through plasma processing, from antimicrobial and hydrophilic, to bio-static effects. Key words: liquid repellent, oil repellent, hydrophobic, oleophobic, lowpressure plasma processing, plasma treatment, P2i, barrier textiles.

7.1

Introduction

Barrier textiles – materials that have been engineered to provide enhanced protection against contamination by liquids and airborne pathogens – are well established in some industries (Brewer, 2011). In occupations where people are at high risk of contamination by infectious or toxic material, such as those in the medical, chemical, biological and military sectors, barrier textiles are widely used for clothing, dressings and equipment to resist penetration by hazardous liquids or particles. In hospital operating theatres, for example, barrier textiles form a significant part of the hygienic regime of surgical procedures, preventing the spread of infectious pathogens to both patients and staff. The protective function of barrier textiles is traditionally obtained using wet finishing methods on the fabrics or by applying laminates to the material, effectively shielding the wearer from contamination. However, a serious limitation of these approaches is that the resulting garments lack airflow and true breathability, impacting comfort – an important requirement in strenuous or life-critical occupations. Plasma technology, when developed at a commercially viable level, has the potential to offer a strong alternative method for imparting barrier functionalities to textiles. Allowing the surface property of a material to be optimised to repel hazardous liquids without affecting its bulk properties, plasma processing does not force a compromise between performance, comfort and cost. Furthermore, work is ongoing to develop additional performance enhancements through plasma process104 © Woodhead Publishing Limited, 2011

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ing, from antimicrobial and hydrophilic, to bio-static effects, opening up entirely new markets altogether for barrier textiles. This chapter considers the requirements for barrier textiles, with a core focus on water- and oil-based liquid repellency. The theory and testing of liquid repellency is explained in Section 7.2, with current techniques for rendering barrier textiles liquid repellent covered in Section 7.3. The use of plasmas for imparting liquid repellency is addressed in Section 7.4, while applications of the technology for delivering liquid repellent, as well as antimicrobial, effects to textiles are discussed in Section 7.5. Finally, Section 7.6 looks at the broad commercial opportunities being opened up by plasma technologies in the textile sector. A list of useful references where further information can be sought, in addition to the details of where much of the information has been sourced, is presented in Section 7.7.

7.2

The importance of liquid repellency

Many everyday products use materials that are selected either for their bulk physical properties or ease of industrial processing. However, their resulting surface properties can be far from ideal for their intended use. Therefore, modifying the surface of a material is a very effective way of generating considerable value by delivering additional functionality; for example, passivation of a metal surface to inhibit corrosion. Liquid repellency – against water, oil and alcohol-based substances – is one of the most sought-after technical effects for barrier textiles. Added value is provided by protecting the textile from interacting with liquids, enabling them to roll off or be easily removed, leaving the underlying textile clean and unchanged. There are many different methods for making textiles liquid repellent; however, this section explains the theory and testing of water and oil repellency, before considering the various solutions available in Sections 7.3 and 7.4.

7.2.1

Surface energy and surface tension

Generally speaking, liquid repellency relies on three main aspects: • surface energy of the coated material; • surface roughness; • surface tension of the liquid in contact with the material. Repellency in itself is a confusing term, as it is often perceived as forcing something away, in the way that magnetic poles repel each other. The majority of liquid repellents do not ‘force’ the liquid away, but merely present an inert surface where fewer interactions can then take place. All solid surfaces have surface energy, which is a function of surface area and the types of chemical groups present at that surface. In addition, all liquids have a surface tension, which is a measure of the interaction energies between the

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molecules that make up that liquid when at the gas/liquid interface. The most common units used to measure surface energy and surface tension are dynes/cm and mN/m, i.e. force per unit length, which is analogous to energy per unit area. Liquids such as water have a high surface tension due to the strong interactions between the polar water molecules. At the air/water interface, this interaction energy is exhibited by the surface molecules displaying a ‘skin’ like effect. Oils have lower surface tensions due to the weaker interactions between the apolar molecules. All liquids, as is common with many things in nature, wish to attain the minimum energy state possible and are mobile enough to do that. They will move to minimise the interfacial tension between themselves and the environment they are in. What this means in practice is that for a pure liquid suspended in mid-air, providing there are no external forces, the shape adopted to minimise the interfacial tension is that of a sphere, i.e. the geometric shape where the maximum amount of molecules are in contact with each other. When the liquid is in contact with a surface, the shape will adjust to minimise the new interfacial energy. Water has one of the highest surface tensions of common liquids around us, with a value of ~72 mN/m at 20°C. It should be noted here that surface tension and surface energy are a function of temperature – both will increase as temperature increases. Generally speaking, high surface tension liquids will sit with high contact angles on a low surface energy material; for example, a droplet of water on a freshly waxed car. Conversely, low surface tension liquids will sit with low contact angles on high surface energy materials; for example olive oil in a metal frying pan. In reality, few surfaces are truly flat, and especially so in the textile world. It is important to understand how the surface roughness affects the interactions between the liquid and the material and this will help explain why textiles are adversely affected by liquids.

7.1 Super hydrophobicity resulting from surface roughening of a hydrophobic surface.

7.2 Effect of surface roughening of a hydrophilic surface.

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Surface roughness

Surface roughness will enhance the repellency effects seen on a flat surface of the same chemical composition. Generally speaking, and taking water as an example, if a droplet of water is in contact with a flat material and has a contact angle greater than 90°, if the surface is roughened, the contact angle will increase, displaying super hydrophobicity (Wenzel, 1936). The material is said to be inherently hydrophobic and less energy is required to move the droplet across the surface (Fig. 7.1) (Cassie and Baxter, 1994). Conversely, if the droplet of water sits at less than 90° on a surface, then the material is inherently hydrophilic, and roughening the surface will result in a lower contact angle, as greater interaction energy results (Fig. 7.2).

7.2.3

Achieving liquid repellency

As described earlier, many materials do not display the surface properties required for a particular product to function. There is a need to change these properties to give the product a much wider scope of use. Very few textiles are inherently water or oil repellent. Therefore, an additional process must be added to impart these properties. This process can be any one of a number of techniques, which will be discussed in greater detail in Sections 7.3 and 7.4. All the techniques apply lower surface energy chemical groups to the surface in order to reduce the interaction energies. The main three chemical types used are hydrocarbons, silicones and fluorocarbons, which can be used alone or in combination. Hydrocarbon and silicone-based repellents repel only high surface tension liquids, i.e. water. So, if oil repellency is required where the surface tension of the liquid is below 30 mN/m, fluorocarbons have to be used to some degree. Fluorocarbons are far more expensive than hydrocarbons, especially when used in large quantities, which is why they are often co-applied. Finding techniques for reducing the amount of fluorocarbon used, whilst still retaining the high levels of repellency, are much sought after. Fluorocarbons have the potential to reduce the surface energy to the lowest values possible, where the long fluorinated chains of the chemical attach at ninety degrees to the surface of the substrate. The repellency of the resultant finish depends on several factors, such as the fluorinated and nonfluorinated segments used in the polymer coating, their orientation, the distribution of the fluorocarbon groups on the fibres, and the surface topography and geometry of the fabric.

7.2.4

Testing water and oil repellency

Not surprisingly there are numerous ways of measuring liquid repellency – many of which have been developed by companies in order to deliver the specific product requirements of their customers. Depending on the product and application,

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Table 7.1 Commonly used water repellency tests for treated textiles Name

Test

Comments

Spray test

AATCC 22-1996 Developed by DuPont Co. and can be carried out without destroying the article. Difficult to differentiate fabrics with good water repellency

Sutter apparatus

AATCC 21-1998 The lowest hydrostatic head needed to cause penetration is recorded. Normally used for fabrics coated with an impermeable film

Dynamic absorption AATCC 70-1997 Measure weight increase as a percent of water absorbed Table 7.2 Test liquids for oil repellency ratings Oil repellency rating

Test liquid

Surface tension (mN/m)*

1 2 3 4 5 6 7 8

Nujol oil 65/35 Nujol/n-hexadecane n-Hexadecane n-Tetradecane n-Dodecane n-Decane n-Octane n-Heptane

31.2 28.7 27.1 26.1 25.1 23.5 21.3 19.7

*Data supplied in personal communication from R. H. Dettre.

several testing methodologies may need to be applied to demonstrate that the right performance characteristics are delivered. Table 7.1 lists some of the more popular water repellency tests that are available. These fall into three main categories: (i) spray tests, (ii) hydrostatic pressure tests and (iii) sorption of water tests. Many requirements for fabric treatments state that air permeability properties need to be retained in addition to ‘handle’ and ‘drape’ qualities. In these instances, tests such as air permeability and water vapour permeability (ASTM D 737-96; DIN 53 887) are also required. The main oil and water repellency tests for semi-quantitative measurements of surface energy involve placing three small droplets of the test liquid onto the fabric surface, usually for 30 s for oil-based, and 10 s for aqueous-based liquids. The droplets are removed using an absorptive tissue. If no wetting is observed on the fabric from two out of the three droplets, the next test liquid is used, and so on until wetting is observed. The highest test liquid used where no wetting is observed is the value given to the textile. The example shown in Table 7.2 is for the AATCC 118-1997 test method, where the oil series of liquids ranges form Oil 1 (O1) – Oil 8 (O8), where O1 has the

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highest surface tension and O8 has the lowest, i.e. the easiest to repel and the hardest to repel respectively. The range of polar test liquids are from W0 (100% water) to W10 (100% isopropyl alcohol), where W6 is composed of 60% isopropyl alcohol and 40% water. If the test sample fails the lowest water or oil repellency tests, a value of WF and OF can be recorded, respectively.

7.3

Current solutions for rendering barrier textiles liquid repellent

The main issues providing fit-for-purpose liquid protection for barrier textiles have traditionally come down to a compromise between the level of protection provided and the physiological burden imposed. It is very easy to provide complete liquid protection to a person; however, the solution would involve dressing the wearer head-to-toe in a rubber suit, which is totally impractical in most situations. By providing just enough protection, greater comfort can be achieved for the wearer of the garment. Therefore, it is necessary to fully segment a market and its varying demands to deliver the right level of protection for each application. The earliest treatments for rendering textiles water repellent involved using hydrophobic substances such as paraffin wax. Mixtures of wax or paraffin emulsions containing aluminium acetate have also been used, in addition to hydrocarbons and silicones. However, as explained earlier, in order to achieve both water and oil repellency, it is necessary to use fluorocarbon moieties. There are numerous methods on the market for rendering textiles water and oil repellent, with both advantages and disadvantages for manufacturers. The majority of processes come under the general category of wet finishing – dip coating and spray coating – the resulting products often being referred to as DWRs (durable water repellents).

7.3.1

Dip processing

The vast majority of treatments for creating liquid repellent barrier textiles are applied using a dip-pad-dry-cure process (Fig. 7.3). Such treatments typically include silicone or perfluorinated compounds that are added to the material during manufacture, or afterwards to a finished article, and have several factors in common: Dry and cure Dip/pad Product construction

Fabrics

7.3 Traditional process for wet finishing of textiles

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• The process is applied to the textiles in roll format before construction of the garment or end product. • Vats of complex chemical formulations are used, which not only contain the chemicals required on the textile to give the repellent effect, but also contain other adjuvants that are required to deliver the polymer coating to the textile. The vats used are of a particular formulation to attach specific chemical groups onto the specific textile, so other formulations are required to attach to different types of materials. • High temperatures are required to effect fixation, secure the groups on the surface, and drive off the water/solvent required to apply the technical effect. There are many different companies that provide their own trademarked formulations to achieve this effect and there are specific advantages and disadvantages of these forms of processing. Advantages: • high throughputs available; • cost-effective when processing in large quantities; • high levels of liquid repellency possible. Disadvantages: • not applied to the end product, therefore complete protection of the constructed product is not possible; • expensive/impracticable for small batches; • can not be applied to 3D formats and limited to textiles of specific chemical make-up (e.g. natural materials such as cotton and canvas); • significant environmental impact, due to the large quantities of chemicals and energy required, as well as the need to dispose of chemical waste at the end of the processes; • can not be used as a re-coating process for the end product due to unfavourable solution energetics and incompatibility of product form.

7.3.2

Spray coatings

A wide variety of spray-applied products is also available, providing a range of both water and oil repellency. The general form of application is through an aerosol can and, while good levels of protection can be provided, the main issues surround the durability of the treatment along with how much coverage has occurred and the amount of chemical that is lost into the environment. There are many applications where solution-based dip or spray application are the most appropriate method of providing both water and oil repellency. However, as with any technique, there are inherent economic drawbacks, market demands and environmental concerns that are leading manufacturers of barrier textiles to look for alternative technologies.

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111

Use of plasmas for imparting liquid repellency to barrier textiles

While there are some advantages in using wet finishing techniques to render items liquid repellent, a move away from solution-based processing is also very attractive. Low-pressure plasma processing achieves nano-scale polymerisation of monomers on materials, offering an alternative approach to providing barrier effects for textiles and is proving commercially successful across many market sectors. The plasma coatings are conformal due to the gaseous nature of the process, enabling coating of individual fibres with nano-scale thickness.

7.4.1

Background

The majority of low pressure plasma processing systems are batch processes. There are a number of examples where continuous roll-to-roll processing is carried out within a batch process, i.e. there is down-time when changing between rolls as the whole roll is pumped down to low pressure, and a few examples where fully continuous processing is possible through ‘whistling leaks’, where differentially pumped systems allow the constant transport of material. Batch processing is also possible on a continuous basis or on an in-line system, where samples can be loaded whilst pump down and processing occurs in other sections. Nevertheless, compared with continuous treatment with atmospheric plasma processing, the line speeds and initial capital costs appear unattractive. However, experience has shown that there are numerous technical benefits of operating at low pressure, where even relatively modest throughputs can provide a cost effective solution (providing the technical effect adds sufficient value). The main features of processing at low pressure are: • ability to treat complex shapes including finished products and off-the-shelf items; • items can be re-treated if necessary; • process can be sited anywhere and can be easily integrated into a production line at any point along the value chain; • can process a wide range of different materials in one process; • greater control of the degree of ionisation and hence fragmentation of the starting material, when compared to higher pressure plasma systems, which allows desired chemical functional groups to be preserved and attached to the product; • low amounts of starting raw chemicals are required; not only does this lead to cheaper processing costs but also to negligible waste and environmental impact; • depending on the items to be treated, fast throughputs are possible by simply optimising the system for a particular product; • circumvents the entrapment of toxic oligomers often associated with atmospheric plasma processing.

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Although nobody would expect one process to be optimal for every application and volume demand, it is because of the features presented above that it is possible that low pressure plasma processing can deliver considerable value to barrier textiles for numerous market applications.

7.4.2

Process development

Conventionally, low pressure plasmas have been used as a means of fragmenting the process gases in order to achieve novel surface functionalisation and display a new range of features. More recently, people have used the vapours from liquids in an attempt to maximise the retention of desirable functional groups, which could be used to subsequently react with other chemicals to obtain a specific technical effect. In order to achieve attachment of the long fluorinated chains to the surface, critical for the levels of liquid repellency required, it is necessary to both select a chemical that displays the appropriate functional group, and to apply this under plasma conditions that initiate polymerisation of the monomer but minimise fragmentation. Modulating the power through a pulse cycle is one way to achieve the power required to initiate the plasma and create reactive intermediates – allowing conventional polymerisation to occur in order to retain the structure as much as possible. Through careful choice of starting chemical and optimisation of the plasma parameters to maximise the CF2:CF3 ratio (this determines the length of the chain where longer chains can achieve lower surface energies), a pulsed plasma polymerisation process has been developed to provide high levels of both water and oil repellency, achieving repellency to both isopropyl alcohol and heptane on cotton samples. In fact, if very rough materials are used, repellency to hexane can also be achieved. The key is to generate the active species whilst allowing conventional free radical polymerisation to occur.

7.4.3

Results

Synthetic and natural fibres do not show any inherent repellency to oils. Some, particularly the natural fibres, may show a residual degree of hydrophobicity due to the natural oils within the product. However, as the surface tension of the test liquids begins to decrease, wetting will soon occur and will usually happen at around 10–20% isopropyl alcohol content (W1–W2) for the polar series of test liquids. Several companies report that they can apply oleophobic properties to textiles through post treatment, either through the use of plasma processing or by a solution based approach; however, the level of oleophobicity is not widely reported. Table 7.3 lists the levels of both water and oil repellency obtained using the P2i low pressure plasma process on textiles and can be used for comparison when other results using different techniques are known. The results illustrate the universal

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Table 7.3 List of water and oil repellency values obtained on a variety of textiles. WF and OF represent failure at lowest level Textile

Untreated

100% Cotton interlock 65% Polyester 35% cotton 65% Polyester 35% cotton interlock Spun viscose woven 50% Cotton 50% polyester Cotton sheeting 100% Cotton poplin Polyester cross tuck 100% Nylon 66 cross tuck Wool

Plasma processed

Water

Oil

Water

Oil

W1 WF W1 WF WF WF WF W0 WF W1

OF OF OF OF OF OF OF OF OF OF

W10 W10 W10 W10 W10 W10 W10 W10 W10 W10

O8 O8 O8 O8 O8 O8 O8 O8 O8 O8

attachment of the chemical groups to a variety of different materials, displaying the highest levels of repellency, all of which were processed in the same chamber run. Another value that is also reported is the surface energy, where two factors are particularly important: (i) the sample should be flat as surface roughness plays a major role in enhancing contact angles, and (ii) the probe liquids selected need to assess the end-use functionality desired. This latter point means that if one seeks to determine the level of oil repellency, it is necessary that oils are used to probe the surface. Methylene iodide has been widely used in the past to calculate the surface energy and determine the degree of oleophobicity; however, the surface tension of methylene iodide is significantly higher than a typical hydrocarbon oil. Methylene iodide should therefore be used only to benchmark different surfaces reported in the literature, whereas a homologous series of hydrocarbons would be used to probe the level of oleophobicity.

7.4.4

Scale-up challenges

The author’s original work in obtaining a high level of both water and oil repellency was carried out in a 470 cm3 (~ 0.5 litre) quartz reactor. The next steps were to scale up the process to provide a cost-effective, value-added industrial process. The chamber volume was subsequently increased to 3 litres and then 40 litres, the biggest challenge being the development of a commercially viable process. Of particular concern for textiles is that as the textile volume increases, the amount of water that needs to be removed to reach an adequate base pressure increases and the pumping conductance needs to be taken into consideration. The first major scale-up step was to a plasma chamber with an internal processing volume of around 300 litres. The major technical differentiators were: • a stainless steel chamber with internal capacitively coupled electrodes;

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• a large vacuum pump capacity for evacuating the chamber as quickly as possible; • an alternative monomer inlet system to ensure the required processing pressure and precision delivery. By increasing the conductance of the pipe work between the pump stack and the chamber, shorter pump-down times could be obtained. However, with a full loading of textiles, pump-down times could still be lengthy due to removal of water absorbed by hydroscopic materials (e.g. cotton). What needs to be determined is the base pressure to processing pressure to product out-gassing relationship, in order to ensure the polymer deposits effectively. The last is important because processing while a significant out-gassing rate remains can result in hydrophilic species (predominantly water) perturbing the plasma environment or being incorporated into the deposited polymer, both of which can result in an inferior technical effect. Although the increase to 300 litres represents just over a seven-fold scale-up on the previous chamber, using the process to treat textile products is cost effective only for very high value-added items, where performance reigns over cost. A further scale-up was required in order to cope with the demands of the garment and accessories industries where numerous items could be processed at once. The next processing volume was 2000 litres, to prove that the process could be applied to

7.4 P2i’s 2000 litre plasma chamber.

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fully constructed items. It was then possible to treat a wide range of items in sufficient quantities to be able to carry out market trials to benchmark the technology (Fig. 7.4). The chamber has shown many similarities to the 300 litre system and has demonstrated a high degree of homogeneity with regards to the levels of liquid repellency on cellulose substrates and textiles such as polyester.

7.4.5

Commercialisation

Processing costs can be competitive, despite the equipment costs. To maximise return on investment, the systems need to operate throughout the day. When analysing the throughput, there are seven main time-related tasks that cumulatively give the total processing time: (i) (ii) (iii) (iv) (v) (vi) (vii)

loading of samples; pumping down to base pressure; introduction of gases and vapours; ignition of plasma and processing; turning off plasma power and gases; evacuating chamber back to base pressure; venting up to atmosphere and unloading.

Tasks (ii) and (iv) are the most time-consuming and need to be reduced as much as possible while still achieving the technical requirements. Today in manufacturing, two pairs of shoes can be processed in as little as 3 minutes.

7.4.6

Durability

Durability often provides an interesting discussion, since different products have different durability requirements. When durability is mentioned in connection with barrier textiles, people are often referring to laundry-wash durability, dry cleaning or abrasion resistance. However, the number of cycles required varies vastly across the industry. Laundry-wash durability is more challenging than durability to dry cleaning cycles, where independent tests on the latter have shown that the pulsed plasma process developed by P2i could achieve, at its first attempt, the same level of repellency as a leading benchmark for solution-based applications. Further improvements are believed possible once optimised. Mechanical durability has also shown very good comparisons with industry standards where, although some drop off is noticed, very good oil and water repellency are still provided.

7.5

Applications for plasma-processed barrier textiles

Plasma processing of barrier textiles has enormous potential across many industry sectors.

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7.5.1

Textiles for hygiene and infection control

Hospital applications

Medical textiles are a major growth area with a wide range of applications, including wound care, hospital and operating theatre gowns, ward curtains, gloves and other disposables. Due to their regular use in environments with hazardous liquids, and the requirement to provide both protection and breathability to the end product (including seams and fastenings, not just the components), hospital garments especially benefit from plasma processing. Here, barrier performance should be equally effective against airborne particles as well as those that are mechanically transported – in particular, hospital ‘superbugs’, which are increasingly prevalent with the advent of micro-organisms that can resist antibiotic action, e.g. methicillin-resistant Staphylococcus aureus (MRSA) and C. difficile. Much work, therefore, has been carried out to engineer antimicrobial methods and materials in recent years. Since propensity for infection is directly related to bacterial colonisation on surfaces, antimicrobial properties can be greatly influenced by methods that prevent surface contamination, e.g. hydrophobicity. Due to the benefits of plasma processing already outlined, Poulter (2010) proposed that thin films containing an organometallic element could be deposited to create antimicrobial films on a range of substrates. Several novel antimicrobial monomer systems were synthesised and characterised based on silver, copper and zinc as the active constituent, with phosphines, phosphites, maleimide and a novel Schiff base among the ligand systems. In addition, Schofield and Badyal (2009) have reported that existing methods for imparting antibacterial performance (such as metal-based systems) can rely upon leaching modes of action that cause ecological damage. They propose an alternative approach by functionalisation, using poly(4-vinyl pyridine) followed by activation with bromobutane to yield bactericidal activity that can be easily regenerated by rinsing with water.

7.5.2

Military applications

Tactical clothing is another area where plasma processing is being used to provide high performance protection against oil and contamination by hazardous liquids. Designed to withstand the most challenging conditions, clothing and footwear designed for the military requires maximum levels of barrier performance against toxic liquids and vapours, including chemical and biological warfare agents, which typically have low surface tension. Protecting the human body against toxic liquids and vapours is relatively straightforward using impermeable, gas-tight suits and self-contained breathing apparatus. However, such equipment would be completely unsuitable for most military operations owing to its weight, limited wear time and high physiological burden. For this reason, chemical and biological military protective clothing is generally constructed from air-permeable materials treated with a liquid-repellent

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Table 7.4 Filtration measurement results obtained using a Europlasma CERTITEST 8130 for different types of uncoated and plasma-coated filter media (five layers) Filter medium

Conditioning

Initial penetration (%)

Penetration (%) after (x) minutes

Supplier 1–28 g/m2 Supplier 1–28 g/m2 Supplier 1–22 g/m2 Supplier 1–22 g/m2 Supplier 2–25 g/m2 Supplier 2–25 g/m2

Uncoated Plasma coated Uncoated Plasma coated Uncoated Plasma coated

1.20 0.48 1.25 0.40 n/a 0.02

6.4 (30) 1.08 (30) 3.90 (10) 0.75 (10) n/a 0.03 (10)

plasma treatment in order to achieve an acceptable balance between protection and comfort. Plasma-processed barrier textiles allow low surface tension liquids to roll effortlessly off contaminated clothing, greatly improving protection and aiding decontamination procedures, while reducing contact hazards, since the liquid agent does not adhere to the clothing in the first place.

7.5.3

Filtration applications

Plasma processing is also being used on an industrial scale to provide hydrophobic and oleophobic properties to gas filter media, such as that used for respirator masks. The coating deployed increases oil and water repellency without affecting the material’s bulk properties or pore size distribution and therefore airflow. With plasma processing techniques, it is possible to enhance alternative, more sustainable filtration media – such as cellulose or nylon – to a level that matches, or exceeds, the repellency performance of traditional, more expensive materials – such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) – that are more difficult to work with. In addition to enhancing filtration media, plasma processing is equally effective at treating the often complex structures they are formed into. For example, filter media are generally manufactured in 2D form, though are rarely used in this format. The sections required are cut into the desired shapes and configured into elements contained in housings by direct placement or pleating. Liquid repellent coatings result throughout because the gas plasma permeates every exposed surface of the finished filter structures, meaning that the membrane may be treated while sealed in a permanent housing. It also means that the same chemistry can be imparted to a wider range of media, including surface and depth filter media, woven (PET, cotton) and nonwoven (PTFE) textiles, membranes and media combinations created to form a filter medium, element or system format. Table 7.4 gives an overview of filtration efficiency as measured with Europlasma’s CERTITEST 8130 equipment using DOP (dioctyl phthalate aerosol

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Parallel plate, capacitively coupled PECVD (plasma-enhanced chemical vapour deposition) system made up of a cylindrical stainless steel vacuum chamber. The powered electrode is connected to a 13.56 MHz supply, coupled with an automatic impedance matching. The deposition (at 80 °C) was performed at a constant plasma pressure of 3–5 Pa.

Moisture barrier

Cremona, A., Vassallo, E., Merlo, A., Srikantha Phani, A., Lagueardi, L., Deposition of silicon-like hybrid films by PECVD on carbon-fibre reinforced polymers for high precision engineering applications. Journal of Physics: Conference Series, 2008, 100, 062005.

Nimmanpipug, P., Lee, V. S., Janhom, S., Suanput, P., Boonyawan, D., Tashiro, K., Molecular functionalisation of cold-plasma-treated Bombyx mori silk. Macromolecular Symposia, 2008, 264, 107.

Inductively coupled 13.56 MHz RF plasma system at powers 50–100 W using SF6 at 2.5 Pa.

Water repellency

Barnes, J. J., Process for forming a durable low emissivity moisture vapour permeable metallized sheet including a protective metal oxide layer. US Patent 20070166528, 19th July, 2007. Wong, Y. W. H., Yuen, C. W. M., Leung, M. Y. S., Ku, S. K. A., Lam, H. L. I., Selected applications of nanotechnology in textiles. AUTEX Research Journal, 2006, 6, 1.

Fabrics and textiles which had undergone metallisation with aluminium were exposed to oxygen plasma at 1 kW power using an RF power supply with a frequency set at 340 kHz.

Water/air repellency

Reference

Water repellency, Plasma coatings by various methods. UV-protection, antibacteria, antistatic, wrinkle resistance

Plasma treatment type

Barrier type

Table 7.5 Barrier textiles prepared by plasma treatment

118 Textiles for hygiene and infection control

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Dielectric barrier discharge with plane-parallel electrodes for operation at atmospheric pressure.

Biocidal barrier

Kostik, M., Radic, N., Obradovic, B. M., Dimitrjevic, S., Kuraica, M. M., Skundric, P., Silver-loaded cotton/polyester fabric, modified by dielectric barrier discharge treatment. Plasma Processes and Polymers, 2009, 6, 58.

Liu, D., Yin, Y., Niu, J., Feng, Z., Surface modification of materials by dielectric barrier discharge deposition of fluorocarbon films. Thin Solid Films, 2009, 517, 3656.

Atmospheric plasma, generated at 5 kHz audiofrequency using helium, providing surface activation for grafting for GMA (glycidal methacrylate). Quaternary ammonium chitosan is attached to GMA to provide finish. Atmospheric plasma, generated at 5 kHz audiofrequency using helium, providing surface activation for grafting for GMA. Quaternary ammonium chitosan is attached to GMA to provide finish.

Biocidal barrier

Biocidal barrier

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Continued

Gawish, S. M., Matthews, S. R.,Wafa, D. M., Breidt, F., Bouham, M. A., Atmospheric plasmaaided biocidal finishes for non-woven PP fabrics. I Synthesis and characterization. Journal of Applied Polymer Science, 2007, 103, 1900.

Wafa, D. M., Breidt, F., Gawish, S. M., Matthews, S. R., Donohue, K. V., Roe, R. M., Bouham, M. A., Atmospheric plasma-aided biocidal finishes for non-woven PP fabrics. II Functionality of synthesized fabrics. Journal of Applied Polymer Science, 2007, 103, 1911.

Biocidal and leaching barrier Dielectric barrier discharge reactor at atmospheric Paulussen, S., Vangeneugden, D., Vartianen, J., pressure. Two parallel plates covered with Ratto, M., Hurme, E., Antimicrobial material with dielectric material. Nitrogen gas used as inert reduced oxygen permeability. European Patent carrier. Butylamine was active species using an 1857498, 21st November, 2007. AC field with a frequency of 1.5 kHz, generated by a 1 kW AC power supply with a power density of 0.5W/cm2.

Chamber consists of stainless steel ground electrode and a parallel 3.5 mm thick glass dielectric barrier plate. The AC power supply source is capable of supplying bipolar sine wave output with 0–24 kV peak voltage and AC frequency range of 1–15 kHz. Deposition of CH2F2 or CF4 is at 25–1000 Pa pressure.

Moisture barrier

Creating barrier textiles through plasma processing 119

Oxygen plasma at 0.2 torr, 120 W on PET fabric followed chitosan grafting.

Plasma treatment and corona treatment are considered for polypropylene cloths.

The microwave flowing post-discharge reactor is composed of a Pyrex cylinder of 15 cm internal diameter and 20 cm height separated 30 cm from the plasma source by a 5 mm (i.d.) quartz tube. The discharge is generated by a 2.45 GHz microwave source. The discharge tube is sealed to a bent quartz tube of 15 mm (i.d.) which is connected to the post-discharge reactor. CF4 treatment of wool, cotton and polyamide 6 at 667 Pa pressure.

Wound infection resistance

Wound infection resistance

Oxygen plasma of fabrics in an RF-plasma cavity (Harrick Corp., 13.56 MHz, 100 W) at 0.8 torr.

Biocidal barrier

Wound infection resistance

Plasma treatment type

Barrier type

Table 7.5 Continued

Canal, C., Gaboriau, F., Villeger, S., Cvelbar, U., Ricard, A., Studies on antibacterial dressings obtained by fluorinated post-discharge plasma. International Journal of Pharmaceutics, 2009, 367, 155.

Donovan, M. G., Keogh, J. R., Holmblad, C. M., Adsorptive wound dressing for wound healing promotion. US Patent 5695777, 9th December, 1997.

Huh, M. W., Kyu, I., Lee, D. H., Kim, W. S., Lee, D. H., Park, L. S., Min, K. E., Seo, K. H., Surface characterization and antibacterial activity of chitosan-grafted poly(ethylene terephthalate) prepared by plasma glow discharge. Journal of Applied Polymer Science, 2001, 81, 2769.

Yuranova, T., Rincon, A. G., Bozzi, A., Parra, S., Pulgarin, C., Albers, P., Kiwi, J., Antibacterial textiles prepared by RF-plasma and vacuum-UV mediated deposition of silver. Journal of Photochemistry and Photobiology A: Chemistry, 2003, 161, 27.

Reference

120 Textiles for hygiene and infection control

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Oxygen plasma treatment of wool.

Microwave generator (2.46 GHz) with a tunable Tsafack, M. J., Levalois-Grutzmacher, J., Plasmapower ranging from 0 to 600 W with a vacuum induced graft-polymerization of flame retardant chamber (27 litres). Argon plasma at 40 Pa monomer onto PAN fabrics. Surface and Coatings pressure, 100 W followed by grafting of monomers. Technology, 2006, 200, 3503. Microwave generator (2.46 GHz) with a tunable Tsafack, M. J., Levalois-Grutzmacher, J., Flame power ranging from 0 to 600 W with a vacuum retardancy of cotton textiles by plasma-induced chamber (27 litres). Argon plasma 0.66 mbar graft-polymerization. Surface and Coatings pressure, 100 W followed by grafting of monomers. Technology, 2006, 201, 2599. A review of different plasma uses to graft monomers and polymers to fibre surface.

Shrink resistance

Flame retardant

Flame retardant

Flame retardant

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Zhang, S., Horrocks, A. R., A review of flame retardant polypropylene fibres. Progress in Polymer Science, 2003, 28, 1517. Continued

Hocker, H., Plasma treatment of textile fibers. Pure and Applied Chemistry, 2002, 74, 423.

Simor, M., Fiala, A., Kovacik, D., Hlidek, P., Wykema, A., Kuipers, R., Corrosion protection of a thin aluminium layer deposited on polyester. Surface and Coatings Technology, 2007, 201, 7802.

Hexamethyl disiloxane deposition at atmospheric pressure with a mixture of carrier gas and gasified precursor. A sinusoidal high voltage of 4 kV with a frequency of 13 kHz was used to generate plasma. The voltage between the discharge and the induction electrode was measured with a Tektronix P6015a capacitive resistive HV divider, with a high bandwidth of 75 MHz. The power was kept constant at 70 W.

Corrosion resistance

Yahiaoui, A., Spencer, A. S., Anti-static, breathable, nonwoven laminate having improved barrier properties. International Patent WO2009077889, 25th June, 2009.

Plasma deposition of fluorinated monomers via several known methods such as RF plasma discharge and corona discharge treatment.

Antistatic and alcohol resistance

Creating barrier textiles through plasma processing 121

Microwave generator (2.46 GHz) with a tunable power ranging from 0 to 600 W with a vacuum chamber (27 litres). Pasting of 1,1,2,2, tetrahydroperfluorodecyl acrylate onto samples followed by Argon plasma 0.66 mbar pressure.

Oil repellency

Application of a cold plasma process for polymerization and copolymerization of fluorinated and hydrogenated (meth)acrylates. Polymer, 2000, 41, 3159.

Capacitively coupled flow system with two parallel Vohrer, U., Muller, M., Oehr, C., Glow-discharge electrodes supplied by a 13.56 MHz power source. treatment for the modification of textiles. Surface Plasma of methane–argon at low pressure (0.2 and Coatings Technology, 1998, 98, 1128. mbar).

Oil repellency

Brewer, S. A., Willis, C. R., Structure and oilrepellency textiles with liquid repellecy to hexane. Applied Surface Science, 2008, 254, 6450.

Hochart, F., De Jaegar, R., Levalois-Grutzmacher, J., Graft-polymerization of a hydrophobic monomer onto PAN textile by low-pressure plasma treatments. Surface and Coatings Technology, 2003, 165, 201.

PFAC8 deposition at low pressure.

Microwave generator (2.46 GHz) with a tunable power ranging from 0 to 600 W with a vacuum chamber (27 litres). Argon plasma 0.66 mbar pressure, 100 W followed by grafting of 1,1,2,2, tetrahydroperfluorodecyl acrylate.

Oil repellency

Reference

Oil repellency

Plasma treatment type

Barrier type

Table 7.5 Continued

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particles). During measurement, the filter (consisting of five layers of single ply nonwoven PP) is loaded with 200mg of DOP particles. Penetration tests have been carried out on electrostatic charged filters. The results clearly illustrate that a thin oleophobic plasma coating increases both initial and final filtration efficiency. In this sense, it can convert, for instance, an R95 filter into an R99 filter.

7.6

Future trends

Plasma treatment of textiles for high-performance water and oil repellency is gaining widespread appeal in markets where enhanced barrier functionality is not only required, but imperative. With added processing and environmental advantages over traditional wet processing techniques, plasma treatment of barrier textiles is also gaining commercial traction – generating the associated costefficiencies. Indeed, in recent years the technology has been deployed in mass manufacturing with compact batch-processing machines constructed exclusively for industrial operations. The machines can be operated at the touch of a single button and integrate seamlessly and effortlessly with existing assembly lines. Furthermore, the platform technology has almost limitless potential, meaning that in addition to water and oil repellency, the low-pressure plasma process can be tailored to deliver a wide range of invisible functional benefits. These range from fire retardant and insect repellent, to antimicrobial and anti-static properties. In particular, barrier textiles utilising plasma technologies are opening up a new array of commercial opportunities (Table 7.5). Continued demand for barrier textiles with enhanced performance characteristics, coupled with the outstanding potential for finishing material surfaces without alteration of their bulk properties, will continue to drive development of plasmabased techniques. As an example, plasma functionalised smart textiles where colour changes or other responses indicate contamination may lead us into the future.

7.7

Sources of further information and advice

3M, Water Repellency Test II, Water/alcohol Drop Test, 3M Test Methods (Oct 1988). 3M, Oil Repellency Test I, 3M Test Methods (Oct 1988). Biederman H (2004), Plasma Polymer Films, London, Imperial College Press. Coulson S R, Brewer S A, Willis C R and Badyal J P S (1997), Patent: WO 98/ 58117. Coulson S R, Woodward I S, Badyal J P S, Brewer S A and Willis C R (2000), ‘Plasmachemical Functionalization of Solid Surfaces with Low Surface Energy Perfluorocarbon Chains’, Langmuir, 16, 6287–6293. Coulson S R, Woodward I S, Badyal J P S, Brewer S A and Willis C R (2000) ‘Super-Repellent Composite Fluoropolymer Surfaces’, J. Phys. Chem. B, 104, 8836–8840.

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Coulson S R, Woodward I S, Badyal J P S, Brewer S A and Willis C R (2000) ‘Ultralow Surface Energy Plasma Polymer Films’. Chem. Mater., 104, 2031– 2038. Grill A (1994), Cold Plasma Materials Fabrication: From Fundamentals to Applications, Piscataway, New Jersey, IEEE Press. Kissa E (1984) ‘Functional Finishes’ Part B, in Lewin M, and Sello, S B (eds), Handbook of Fibre Science Vol. II, New York, Marcel Dekker. Kissa E (2001), Fluorinated Surfactants and Repellents, New York, Marcel Dekker. Legein F (2009), ‘Innovative low pressure plasma coatings for gas and liquid filter media’, The Filtration Soc. Conf., Chester, UK.

7.8

References

Brewer S A (2011), ‘Recent Advances in Breathable Barrier Membranes for Individual Protective Equipment’, Recent Patents on Mat. Sci., 4, 1–14. Cassie A B D and Baxter S (1994), ‘Wettability of Porous Surfaces’, Trans. Farad. Soc., 40, 546. Poulter N (2010), ‘Novel antimicrobial plasma deposited films’, PhD thesis, The University of Bath, UK. Schofield W C E and Badyal J P S (2009), ‘A Substrate-independent Approach for Bactericidal Surfaces’, ACS Appl. Mat. Interfaces, 1(12), 2763–2767. Wenzel R N (1936), ‘Resistance of Solid Surfaces to Wetting by Water’, Ind. Eng. Chem., 28, 988.

© Woodhead Publishing Limited, 2011

8 Disposable and reusable medical textiles G. S U N, University of California, Davis, USA

Abstract: As infectious diseases circle the globe, medical costs skyrocket and the waste stream continues to grow, it is imperative to look for medical textiles with improved protective performance, low costs, and minimized environmental impacts. Medical textiles include surgical gowns, gloves, drapes, facemasks, dresses, and linens, which could be disposable or reusable based on uses. The selection of reusable and disposable textiles is determined by many factors, such as cost, protective and comfort properties of the textiles, government regulations, and possibly social and psychological perceptions of both types of textile. This chapter intends to provide a broad view on both disposable and reusable textiles, as well as suggestions on improved protection against transmission of infectious diseases by textile materials. Key words: medical textiles, biocidal functions, disposable, reusable.

8.1

Introduction: disposable versus reusable

Disposable and reusable textiles are two popular but competing types of products employed in healthcare and other fields requiring protection against biological and chemical hazards. All healthcare workers must wear or use protective textiles such as gowns, gloves, drapes, and facemasks when in contact with patients to reduce or prevent disease transmission (NIOSH, 1988). Whereas disposable textiles are often perceived to have protective advantages over reusable textiles, they must be immediately discarded as bio-hazardous materials. In contrast, reusable protective textiles can be sterilized and laundered for reuse, with a lifetime of more than 50 cycles; however, reusable textiles may be perceived as less protective and more time-consuming to maintain. The repeated laundering of reusable medical textiles may consume more energy and generate more waste water to the environment. Currently, the political dispute between disposable and reusable health protective textiles is very intense, with proponents of each claiming to have economic or protective advantages over the other (Zins, 2006). The current divide on disposable/reusable medical textiles pertains to a larger dilemma of how to protect individuals from biological and chemical agents. Surgeons and their assistants, for example, have worn protective clothing since the nineteenth century (Laufman et al., 2000). Gowns and drapes, initially made of cotton, over time were constructed into more tightly woven fabrics, which were eventually treated with fluid-repellent chemicals. During the Second World War, 125 © Woodhead Publishing Limited, 2011

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the US Army developed very densely woven materials treated with fluorocarbon and pyridinium compounds. After the war, hospitals quickly adopted these applications (Belkin, 1975). Until the 1960s, hospitals used reusable woven fabrics almost exclusively for surgical gowns and drapes (Bernard and Beck, 1975); new woven materials with improved protective performance and durability were used in healthcare facilities by the 1970s (Laufman et al., 1975). Simultaneously, since the 1950s, nonwoven materials have been produced with enhanced physical and liquid-resistance properties; manufacturers have aggressively promoted these materials to the surgical community. As a result, disposable nonwoven textiles have gained a significant market share in healthcare and other institutional contexts. This trend is continuing: the North American market is predicted to have a 7% annual increase in the next five years (INDA). Disposable textiles have become the most popular materials for surgical gowns, chemicalprotective clothing and other institutional textiles in the US, and they are gaining more market share in developing countries such as China. In contrast, reusable textiles are retaining market share in Europe due to increasing concerns about the environmental pollution caused by the disposal of used disposable textiles (Schmidt, 2000). Hence, from a global perspective, the selection of protective textiles becomes a varied and complicated process affected not only by material functionality, but also by cultural, economic, and environmental factors.

8.2

Life cycles of disposable and reusable textiles

Both disposable and reusable medical use textiles are made of polymeric fibers, but they have different fabric structures. Disposables, usually nonwoven fabrics, are produced by closely entangling fibers into a web and then layering the resulting material into sheets. The fibers employed in making nonwoven fabrics for medical use are predominately polyethylene, polypropylene and polyester, and their blends; in general, they are synthetic polymers derived from fossil oil. Many disposable textiles also contain wood pulp fibers as a major component. Disposable textiles generally serve only as single-use products in healthcare facilities and many other institutional protective clothing applications. After usage, these have to be immediately discarded as hazardous materials. Such a use pattern provides perceptions of sanitation and proper protection for users, but creates an overwhelming amount of wastes. In particular, products made from non-renewable energy resources from the earth have become problematic. The disposal of biologically contaminated nonwoven materials has been traditionally done by incineration. When burned, hospital waste and medical/infectious waste emit various air pollutants, including hydrochloric acid, dioxin/furan, and toxic metals such as lead, cadmium, and mercury. In the US, medical waste incinerators are a major source of mercury and dioxin air emissions, in particular (EPA, 2009). In 1997, the EPA issued the first federal rule to protect public health by significantly reducing the harmful air pollution from medical waste incinerators (EPA, 2009). Under this rule, emissions

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Garment production

Wood pulp Energy, water consumption

Environmental pollution

Incineration or landfill

Large amount of medical waste

Medical uses

8.1 Life cycle of disposable medical textiles (emissions also occur from each box – hydrochloric acid, dioxin/furan, and toxic metals including lead, cadmium, and mercury).

at medical waste incinerators must be reduced by 74 percent for mercury and 95 percent for dioxin and other toxins in five years from the baselines given in the document. Another way of medical waste disposal is to use landfill, which is very costly. A complete life cycle for disposable medical textiles is shown in Fig. 8.1. The energy consumption in the cycle is shown by arrows indicating how one product is converted to another. In contrast, reusable textiles, which were traditionally made of cotton fiber and currently are made of polyester, can be repeatedly used in healthcare facilities. After each usage, the textiles should be professionally laundered following the CDC’s guidelines (CDC, 1997, 2001). When laundered, the used textiles are not only cleaned but also disinfected with bleaching agents such as diluted sodium hypochlorite solution or concentrated hydrogen peroxide solution. Thus, laundering is a very necessary process in the life cycle of reusable textiles. This process consumes large amounts of water and consequently produces the same amount of wastewater. And, even if the resulting wastewater is fully treated and recycled to reduce deleterious effects to the environment, there is still the problem of energy consumption during the laundry operation. From a material life cycle perspective, however, reusable textiles (woven or knitted fabrics) have the advantage of a longer lifetime, capable of surviving more than 50 commercial laundry cycles and thereby offering an additional saving to users and the environment. The final products are biologically degradable if cotton or biodegradable polyester fibers such as polylactic acid (PLA) are the major component. If incineration is used, the emissions are thus about 1/50 (2%) of those for disposable textiles. A brief life cycle of reusable textiles is illustrated in Fig. 8.2. Comparing the above two systems, it seems that reusable textiles may have advantages over disposable materials in terms of natural resource use and sustainability. The latter consumes non-renewable fossil oil as the basic material and generates large amounts of wastes in the life cycle. Moreover, disposable

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Production of cotton fiber

Production of polyester fiber

Yarns and fabrics

Garment production

Medical uses

Energy, water consumption

Mostly biodegradable

Medical wastes

Sterilization and laundry

8.2 Life cycle of reusable medical textiles (emissions also occur from each box).

materials release more toxic compounds such as dioxins and mercury into the environment during the disposal process. However, reusable textiles are not perfect. The laundering of reusable textiles consumes more energy and water, and adds more wastewater to the environment. Cotton fiber, for example, is a naturally renewable material that is often perceived by consumers to render excellent comfort and performance. But it is almost all replaced by polyester due to durability and cost concerns. The superior durability of reusable textiles made of polyester fibers means more repeated uses and, hence, significant environmental advantages over disposable materials in the amount of waste produced. However, other concerns, such as the cost and protective performance of the two clothing materials, are also of great importance to healthcare systems. Unfortunately, existing comparisons between disposable and reusable textiles tend to be anecdotal rather than comprehensive, and political or economic interests often intervene in these analyses.

8.3

Costs of disposable and reusable textiles

The selection of reusable or disposable textiles involves a very complicated decision-making process. At least eight social, economic, and behavioral factors are affecting this process, including costs, marketing efforts of manufacturers, user perceptions, comfort, and performance of materials, industry or government standards, and government regulations. The costs and impact of the medical textiles on the environment have had increasing influence on the decision-making process in recent years. The following sections highlight some of the issues revealed in a study that was financially sponsored by the US National Science Foundation. Nonwoven fabrics for medical use have a market size of 5.5 billion square yards per year worldwide, and represent $7 billion in end product sales (Lickfield, 2002). Most nonwoven products are marketed by large companies, although there are

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many smaller companies as well. Nonwoven fabrics for disposable surgical gowns usually are made of meltblown and spunbond polypropylene and polyethylene fibers with dense fiber entanglement. In order to increase waterproofing functions, spunbond/meltblown composite nonwoven fabrics and nonwoven laminated with thin plastic films are popular fabric structures. Nonwoven fabrics can prevent almost all possible strike-through of blood and body fluid – a common risk to surgeons in operations. However, excellent barrier properties to liquids make the fabrics non-permeable to air and moisture, and thus uncomfortable to wear, particularly for lengthy operations. The energy consumption and overall cost of manufacturing nonwoven fabrics are lower than those of woven fabrics, in general, because nonwovens are made directly from fibrous webs, similar to paper production, without manufacturing yarns and going through weaving and other processes. When disposable textiles were first introduced to the healthcare market, they were characterized as more protective, more cost-effective, more convenient, and more comfortable for wearers. In the 1970s and 1980s, many hospitals and healthcare facilities began using disposable materials in their surgical gowns and drapes. But later on, hospitals and healthcare facilities realized that the surgical gown materials might have substantial impact on increased healthcare costs, and they became more cautious in selecting non-renewable materials (Wong et al., 1994). The cost components of both disposable and reusable textiles can be divided into: (a) direct purchasing costs, (b) setup and changing costs, (c) handling and laundry costs, (d) storage and inventory costs, and (e) disposal costs. Using this framework, the unit purchasing cost of a disposable surgical gown is lower than that of a reusable one. However, as the reusable materials can be laundered and reused, the overall cost of using them becomes significantly lower based on some calculation (Zins, 2006). Independent studies have revealed that the use of disposable clothing can be 4–10 times more costly than that of reusable materials, on a per-use-cost basis (Badner at al., 1973a,b). Another comparative study between two similarly sized hospitals demonstrated that the hospital using reusable materials could save $100 000 more than the hospital using disposables only (DiGiacomo, 1992). A recent review of single-use and reusable gowns and drapes in healthcare facilities, however, found no clear superiority for either materials in terms of costs (Rutala and Weber, 2001). In a recent survey of healthcare administrators and infection control professionals in over 200 hospitals across the USA, about one third of the surveyed hospitals still use reusable surgical gowns and drapes (Sun et al., 2004), but many are considering changing to disposables. The hospital administrators weigh barrier properties as the most important factor, and antimicrobial function as third and environmental impact fifth important factors, in making their decisions. The survey also suggests that the intent to change to disposables is linked to their virgin-clean image as well as economic and protective values. A similar perception is being fostered in many developing countries, such as in China, where the government prefers disposable textiles as a symbol of modern

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science. However, the European Union countries hold a different view – one that views progress in relation to environmental protection. The European Union has banned the construction of incinerators for the use of medical waste disposal, and reusable medical textiles are gaining in market share as environmental concerns and increasing disposal costs have led to their revival. The same principle applies to the use of disposable/reusable diapers in the EU.

8.4

Protection provided by disposable and reusable materials

Disposables have a cleaner image than reusables, because disposables have never been used by anyone else. This image is psychologically important to both healthcare workers and patients. However, clinical investigations of the protective value of surgical gowns and drapes against surgical related infections have never provided convincing results to support this perception. Garibaldi used a randomized method to study the surgical infection rates or wound contamination with either disposable or reusable gowns and drapes, and found the rates were almost the same – 2.2% for both single-use and reusable (Garibaldi et al., 1986). This has been confirmed by other researchers, with infection rates of 5.25% for single-use and 5.08% for reusable materials being found by Bellchambers et al. (1999). Belkin (1998) reported a prospective and crossover clinical investigation in which the surgical site infection rates were 5.0% for single-use and 6.0% for reusable textiles. On the other hand, some researchers have found significant differences between the two textile materials. One study reported that the infection rate using single-use textiles was only one third that of reusables – 2.27% versus 6.41% (Moylan and Kennedy, 1987). Another study revealed a similar result, i.e. that disposables could reduce the infection rate to one third (Baldwin et al., 1981). Textile researchers have conducted many lab-scale tests to evaluate barrier properties and protective values of nonwoven and woven fabrics, and their results have indicated that laminated nonwoven fabrics perform better than reusable woven fabrics in blocking the penetration of Staphylococcus aureus and liquids (Leonas and Jinkins, 1997; Granzow et al., 1998). Both disposable and reusable textiles can be designed to provide a defensive barrier to liquids and particles. However, the greater the barrier, the lower the air and moisture permeability the fabric possesses (Bernard, 1999). Furthermore, barrier textiles cannot completely protect healthcare workers and patients from infections, because bacteria can survive on textiles for days or even months (Neely et al., 2000a,b, 2001). The outbreaks of severe acute respiratory syndrome among healthcare workers directly indicated the insufficient protection provided by the barrier protective clothing materials (Scales et al., 2003; Lau et al., 2004). The only solution to reduce material-related infections while maintaining comfort properties is to develop and employ biocidal textiles that can completely inactivate any micro-organisms upon surface contact. Theoretical risk assessment study has shown that the use of biocidal textiles can reduce risk of transmission of infectious

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diseases in hospitals (Nicas and Sun, 2006). For protective purposes, biocidal functions – especially the rapid and efficient inactivation of a broad spectrum of micro-organisms – are required. Technologies for producing biocidal textiles are available nowadays (Sun and Worley, 2006; Kenway et al., 2007; Badrossamay and Sun, 2009a,b), thanks to vigorous research efforts in recent years. These textiles can kill micro-organisms rapidly and completely, while regular antimicrobial functions can only inhibit growth of micro-organisms (biostatic effect). More importantly, the halamine biocidal functions are durable and refreshable in laundry.

8.5

Biocidal woven and nonwoven textiles

Biocidal functions can be incorporated into nonwoven, woven, or other fabric structures for optimal use in medical textiles (Badrossamay and Sun, 2009b). Careful studies of biocidal mechanisms have revealed the promising nature of halamine compounds – the structures, for example, that are widely used in swimming pools (Worley et al., 1988, 1996; Sun and Worley, 2006). These structures are similar to, but are safer than, free chlorine. Halamine structures are not likely to produce carcinogens (HCCl3) in water when used as water disinfectants. Halamines inactivate micro-organisms mainly by oxidation mechanisms rather than biological functions; thus, wide usage of them does not result in biological resistance from micro-organisms, a significant environmental concern. When halamine moieties are covalently connected to polymers, a reversible redox reaction can then be introduced on the solid materials according to Equations 8.1 and 8.2. Covalent bonding between polymers and agents provides a permanent connection between biocidal sites and the fabric. Furthermore, the antimicrobial function can be easily regenerated by a chlorine bleaching process. The design of modified cellulosic and synthetic fabrics, the activation or regeneration of halamine structures, and the inactivation of micro-organisms have been successfully demonstrated so far (Sun and Worley, 2006). Rapid and rechargeable antibacterial functions were found on both woven and nonwoven textile materials that have been incorporated with halamine moieties (Tables 8.1 and 8.2) (Sun and Sun, 2002; Badrossamay and Sun, 2009a). Table 8.1 provides results on woven fabrics incorporated with halamines, while Table 8.2 shows the results of polypropylene fibers that can be used in nonwoven fabrics. Both are rechargeable with diluted chlorine bleach solutions. N Cl + H2O

N H + Cl+ + OH–

[8.1]

Kill bacteria

N Cl

Bleach

N H

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Table 8.1 Percentage reduction of E. coli on ADMH-grafted fabrics (E. coli concentration: 105~106 CFU/mL) (Sun and Sun, 2002) Fabric

ADMH graft (%)

Nylon PET PP Acrylic Cotton PET/cotton

Percentage reduction of E. coli at different contact times (%)

4.8 5.3 3.9 5.4 3.3 4.9

5 min

10 min

20 min

30 min

99.9 UD UD 90 99.999 99.99

99.999 99 90 99.9 99.999 99.999

99.999 99.9 99.9 99.999 99.999 99.999

99.999 99.999 99.999 99.999 99.999 99.999

ADMH, 3-allyl-5,5-dimethylhydatoin. UD, undetectable.

Table 8.2 Influence of monomer type and contact time on the antimicrobial activity of grafted polypropylene fibers against E. coli (Badrossamay and Sun, 2009a). Values given are percentage bacteria reduction

1h PP-g-ADMH PP-g-NTBA PP-g-AM PP-g-MAM PP-g-NDAM PP-g-VBDMH

Average of diameter = 6 µm

Average of diameter = 0.6 µm

Contact time

Contact time

2h

4h

8h

16 h 1 h

2h

4h

8h

16 h

5% 25% 20% 30% 45% 30% 40% 45% 68% 80% 85% 99% 100% 100% 100% 90% 100% 100% 100% 100% 5% 35% 30% 60% 70% 40% 42% 40% 70% 80% 20% 55% 80% 98% 100% 40% 80% 100% 100% 100% 100% 100% 100% 100% 100% 100% 100% 100% 100% 100% 30% 58% 50% 80% 90% 25% 50% 80% 82% 99%

PP-g-ADMH: PP = polypropylene; ADMH = 3-allyl-5,5-dimethylhydantoin. PP-g-NTBA: NTBA = N-t-butyl-acrylamide. PP-g-AM: AM = acrylamide. PP-g-MAM: MAM = methacrylamide. PP-g-NDAM: NDAM = 2, 4-diamino-6-diallylamino-1, 3, 5-triazine. PP-g-VBDMH: VBDMH = 3-(4’-vinylbenzyl)-5, 5-dimethylhydantoin.

Since biocidal functions consume active biocides on fabrics, a rechargeable or refreshable function is desirable for repeated uses. If rechargeable properties are considered in the selection of biocidal agents, only oxidative biocidal agents fit closely to the requirements: redox reactions are reversible or regenerable. Bleaching chemicals such as chlorine and oxygen bleaches are commonly used in institutional laundry as recommended by CDC (CDC, 1997). A primary requirement for surgical gown and drape materials is liquid barrier properties. According to the classification of barrier performance of surgical

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gowns and drapes by the Association for the Advancement of Medical Instrumentation (AAMI) (AAMI PB70), a high barrier property obviously lowers comfort performance of the materials, while a lower barrier property could lead to penetration of micro-organisms, particularly wet penetration of pathogens. In fact, experimental results have shown that bacteria could wet penetrate AAMI PB 70 level 3 materials in a short contact time (Zhang, 2010), which further justifies the incorporation of biocidal functions on medical textiles. Based on the understanding of the need of biological protection in medical areas, ideal surgical gowns and drapes could be made of either woven or nonwoven structures but should have the following properties: (a) waterproofing to block strike-through of blood or body liquid; (b) comfort during wear, so as to avoid heat stress to wearers; (c) rapid inactivation of a broad spectrum of micro-organisms; (d) non-toxicity and a minimized environmental impact; (e) durability to a specified number of washes; (f) possession of a biocidal function that can be easily recharged or refreshed, and (g) ability to be eventually disposed of with minimum environmental impact.

8.6

Conclusions

Both disposable and reusable medical textiles are widely used in hospitals now, with designed barrier properties against infectious diseases. Increased biological protective functions on medical textiles create extremely low air permeability and complete liquid blockage, which reduces comfort and increases heat stress to healthcare workers. Incorporation of biocidal functions onto both textiles is necessary since such functions can improve the protection of wearers without sacrificing comfort properties. In addition, to reduce the environmental impact caused by the use of medical textiles, making nonwoven textile reusable is quite attractive, while reduction of water and energy use in laundering and transportation of textiles is also necessary.

8.7

Acknowledgment

The author is grateful for the financial support of the study of disposable and reusable medical textiles from the US National Science Foundation (CTS 0424716).

8.8

References

Badner B., Zelner L., Merchant R. and Laufman H. (1973a). Costs of Linen vs. Disposable OR Packs: Results of Analysis of Recycling and Storage Costs in 24 Hospitals by Various Sizes and Types, Hospitals, 47, 10–13. Badner B., Zelner L., Merchant R. and Laufman H. (1973b). A Fresh Look at Cost of Hospital Laundry vs. Disposables, Inst. Laundry, 17, 8–13. Badrossamay M.R. and Sun G. (2009a). Durable and Rechargeable Biocidal Polypropylene Polymers and Fibers Prepared by Using Reactive Extrusion, J. Biomed. Mat. Res.: Part B – Appl. Biomat. V, 89B, 93–101. Badrossamay M.R. and Sun G. (2009b). ‘Enhancing Hygiene/Antimicrobial Properties of

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Polyolefins’, Chapter 8, Polyolefin Fibres, Ed. S.C.O. Ugbolue, Woodhead Publishing Ltd, Cambridge, UK. Pages 262–285. Baldwin B.C., Fox I.L. and Russ C. (1981). Affect of Disposable Draping on Wound Infection Rate, Va. Med., 108, 477. Belkin N.L. (1975). The Rationale for Reusables: The Other Side of the Drape. Hospital Topics, 53, 45–51. Belkin N.L. (1998). Are ‘Barrier’ Drapes Cost Effective? Today’s Surg. Nurse, 20, 18–23. Bellchambers J., Harris J.M., Cullinan P., Gaya H. and Pepper J.R. (1999). A Prospective Study of Wound Infection in Coronary Artery Surgery, Eur. J. Cardiothoratic Surg., 15, 45–50. Bernard, H.R., Beck, W.C. (1975). Operating Room Barriers: Idealism, Practically and the Future. Bull. Am. Coll. Surg., 60, 16. Bernard T.E. (1999). Heat Stress and Protective Clothing: An Emerging Approach from the United States. Ann. Occupational Hygiene, 43(5), 321–327. CDC (1997). Guidelines for Laundry in Health Care Facilities, Centers for Disease Control and Prevention, Atlanta, USA. CDC (2001). Draft Guidelines for Environmental Infection Control in Healthcare Facilities, Centers for Disease Control and Prevention, Atlanta, USA. DiGiacomo J.C., Odom J.W., Ritota P.C. and Swan K.G. (1992). Cost Containment in the Operating Room: Use of Reusable versus Disposable Clothing, Am. Surg., 58, 654–656. EPA (2011). http://www.epa.gov/ttnatw01/129/hmiwi/fr91597.pdf, visited on April 10, 2011. Garibaldi R.A., Maglio S., Lerer T., Becker D. and Lyons, R. (1986). Comparison of Nonwoven and Woven Gown and Drape Fabric to Prevent Intraoperative Wound Contamination and Postoperative Infection, Am. J. Surg., 122, 152–157. Granzow J.W., Smith J.W., Nicholes R.L., Waterman R.S. and Muzik A.C. (1998). Evaluation of the Protective Value of Hospital Gowns Against Blood Strike-through and Methicillinresistant Staphylococcus aureas Penetration. Am. J. Infect. Control, 26, 85–93. INDA, Association of Nonwoven Fabrics Industry, Cary NC, USA. http://www.inda.org. Kenway E., Worley S.D. and Broughton R. (2007). The Chemistry and Applications of Antimicrobial Polymers: A State-of-the-Art, Biomacromolecules, 8(5), 1359–1384. Lau J.T.F., Fung K.S., Wong T.W., Kim J.H., Wong E., Chung S., Ho De., Chan L.Y., Lui S.F., Cheng A. (2004). SARS Transmission among Hospital Workers in Hong Kong, Emerging Infectious Diseases, 10(2), 280–286. Laufman H., Eudy W.W., Vandermoot A.M., Harris C.A. and Liu D. (1975). Strike-through of Moist Contamination by Woven and Nonwoven Surgical Materials, Ann. Surg., 181, 857–862. Laufman H., Belkin N.L. and Meyer K.K. (2000). A Critical Review of a Century’s Progress in Surgical Apparel: How Far Have We Come? J. Am. Coll. Surg., 191, 554–568. Leonas K.K. and Jinkins R.S. (1997). The Relationship of Selected Fabric Characteristics and the Barrier Effectiveness of Surgical Gown Fabrics, Am. J. Infect. Control, 25, 16–23. Lickfield D.K. (2002). Nonwoven Technology in Medical Applications, Indus. Fabric Prod. Rev., January, 46–52. Moylan J.A. and Kennedy B.V. (1980). The Importance of Gown and Drape Barriers in the Prevention of Wound Infection, Surg. Gynecol. Obstet., 151, 465–470. Neely A.N. and Maley M.P. (2000a). Survival of Enterococci and Staphylococci on Hospital Fabrics and Plastics. J Clin Microb., 38, 724–726. Neely A.N. (2000b). A Survey of Gram-negative Bacteria Survival on Hospital Fabrics and Plastics. J Burn Care Rehabil., 21, 523–527.

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Neely A.N. and Orloff M.M. (2001). Survival of Some Medically Important Fungi on Hospital Fabrics and Plastics. J Clin Microb., 39, 3360–3361. Nicas M. and Sun G. (2002). An Integrated Model of Infection Risk in a Health-Care Environment, Risk Analysis, 26, 1085–1096. NIOSH (1988). Guidelines for Protecting the Safety and Health of Healthcare Workers, National Institute of Occupational Safety and Health, Washington DC, USA. Rutala W.A. and Weber D.J. (2001). A Review of Single-use and Reusable Gowns and Drapes in Health Care, Infect. Control and Hosp. Epidemiol., 22, 248–257. Scales D. C., Green K., Chan A.K., Poutanen S.M., Foster D., Nowak K., Raboud J.M., Saskin, R., Lapinsky, S.E. and Stewart T.E. (2003). Illness in Intensive Care Staff after Brief Exposure to Severe Acute Respiratory Syndrome, Emerging Infect. Diseases, 9(10), 1205–1210. Schmidt A. (2000). Simplified Life Cycle Assessment of Surgical Gowns – Second Draft, European Textile Service Association, Brussels, Belgium. Sun G. and Worley S.D. (1997). Oxidation of Secondary Alcohols and Sulfides by Halamine Polymers, Chemical Oxidation: Technology for the Nineties, Eckenfelder W., Bowers A.R. and Roth (eds), Technomic Publishing Co. Inc., Lancaster, USA, V6, 134–144. Sun Y.Y. and Sun G. (2002). Durable and Regenerable Antimicrobial Textile Materials Prepared by a Continuous Grafting Process, JAPS, 84(8), 1592–1599. Sun G., Kaiser S.B, Rucker M.H., Chandler J., Sun Y.Y. and Lu Y. (2004). Disposable and Reusable Textile Materials in Healthcare Facilities, Proc. of 2004 DMII Grantees’ Conference, Dallas, TX. Sun G. and Worley S.D. (2006). ‘Halamine Chemistry and its Applications in Biocidal Textiles and Polymers’, Chapter 6, Modified Fibers with Medical and Specialty Applications, Edwards J.V., Goheen S. and Buschle-Diller G. (eds), Springer, Netherlands, 2006, 81–89. Wong K.F.V., Narasimhan R., Kashyap R. and Fu J. (1994). Medical Waste Characterization, J. Env. Health, 57, 19–25. Worley S.D. and Williams D.E. (1988). Halamine Water Disinfectants, CRC Critical Reviews in Environmental Control, 18, p.133. Worley S.D. and Sun, G. (1996). Biocidal Polymers. Trends in Polym. Sci., 11, 364–370. Zhang J. and Sun G. (2010). http://nsf-muses.ucdavis.edu/pdf/STAMPconference/STAMPpenetration.pdf, Biological Protective Performance of Medical Textiles. Zins H.M. (2006). Environmental, Cost and Product Issues Related to Reusable Healthcare Textiles, Res. J. Text. and Apparels, 10(4), 73.

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9 Ensuring fabrics survive sterilisation M. J. A. M. A B R E U, Universidade do Minho, Portugal

Abstract: This chapter will examine the importance of sterilisation as an instrument to control the spread of infection and guarantee the hygiene of textiles, more precisely the surgical textiles used in operating theatres and hospital wards for hygiene, care and safety of staff and patients. The main goal is to ensure that the manufacturing industry and the end-users can select the most suitable sterilisation process for each product, avoiding damage of the product through sterilisation and at the same time preventing nosocomial infections through micro-organisms. Key words: sterilisation methods, sterilisation requirements, surgical fabrics, ageing effect, reprocessing.

9.1

Introduction

This chapter will examine the importance of sterilisation as an instrument to control the spread of infection and guarantee the hygiene of textiles; more precisely, the textiles used in operating theatres and hospital wards for hygiene, and the care and safety of staff and patients. The effects of sterilisation on the properties of textile fabrics can influence the substrate, positively or negatively affecting the performance of these products. It is important to know what kind of sterilisation method is therefore suitable for each type of material and/or finished product, ensuring that fabrics survive through sterilisation and at the same time are capable of preventing hygiene or infection problems. Due to recent advances in medical procedures and textile engineering (Abreu et al., 2006a), the use of new and advanced materials in the healthcare industry is growing and they have taken more important roles. As more research has been completed, textiles have found their way into a variety of medical applications. In the past, the main reason for using textiles in the operating theatre has been to protect the patient from the medical staff. Today, this situation is reversed, because of the spread of the Aids virus, Hepatitis B infection and other infectious diseases. The need to protect healthcare workers from the patient and vice versa has become a major concern, which demands the development of more effective protective textiles that survive through the sterilisation process, but at the same time allows inactivation of all bacteria and virus particles. Various single-use and reusable textiles have been proposed for operating-room garments and drapes, with the objective of reducing microbial contamination of 136 © Woodhead Publishing Limited, 2011

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the surgical incision site and of protecting the operating theatre staff from infection. In the interest of patient and medical personnel protection, identical requirements must be applied to single-use and to reusable surgical materials. This chapter is intended to help to ensure that the manufacturing industry and the end-users are able to select the most suitable sterilisation process for each product, avoiding damage of the product through sterilisation and at the same time, preventing nosocomial infections.

9.2

Purpose and importance of sterilisation

It was Louis Pasteur and then Robert Koch who first postulated the link between micro-organisms and infection. Ever since this link was established, man has developed many procedures to reduce the risk of disease caused by microorganisms, including topical, systemic antimicrobial chemicals, physical barriers and sterilisation of clinical materials (Walker, 1997). Accordingly, Massey (1994) stated that the primary purpose of sterilising an item is to render it safe for use by destroying all living microscopic organisms. Transmissible agents (such as spores, bacteria and viruses) can be eliminated through sterilisation. This is different from disinfection, where only organisms that can cause disease are removed (Eurotherm, 2011). Abreu et al. (2004a) has pointed out that because bacteria multiply very quickly, the sterilisation process must be absolute. Even a few organisms invading the patient’s body during a surgical procedure can reproduce rapidly and contribute to post-operative complications. So, an object can never be ‘almost’, ‘partially’ or ‘practically’ sterilised – it is either sterilised or not sterilised. The European Norm 556-1 2001: Sterilisation of Medical Devices – Requirements for Medical Devices to be Designated Sterile – Part 1, defines sterility as the state of being free from viable micro-organisms (≤1 × 10–6) and defines sterilisation as the process used to inactivate microbiological contaminants and thereby transform the non-sterile items into sterile ones. This definition is, however, very simplistic, because the probability of survival is determined by the number and resistance of the micro-organisms and by the environment in which the organisms exist during treatment, the bioburden of raw materials, the subsequent storage and the control of the environment in which the product is manufactured, assembled and packaged.

9.2.1

Sterilising requirements for single-use and reusable textile fabrics

The products are either used once (sterilised single-use fabrics) or are laundered and afterwards sterilised again and used multiple times (life cycle is a maximum of 50 uses). In the USA, single-use dominates the market, with 90% of drapes and gowns being single-use. In Europe, the situation is very different, with single-use

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accounting for less than 50%. These numbers differ significantly throughout Europe. In southern Europe and the UK, the penetration of single-use is much lower than in the Scandinavian countries, where the single-use penetration is over 80% (Abreu et al., 2006a). A product (single-use or reusable) that is designed successfully, could, after a sterilisation process, be transformed into an unrecognisable piece of material. This sterilisation process can induce some positive changes in the product, such as improved strength and tear resistance while some sterilisation procedures could restrict the product’s use for defined applications, causing brittleness for example (Abreu et al., 2004a). To achieve sterilisation by any available method, Walker (1997) has indicated a number of required key parameters: (i)

achieve intimate contact between the individual micro-organism and the sterilising agent used; (ii) deliver the required quantity of sterilising agent to each individual microorganism; (iii) maintain the required quantity for the required time period to achieve inactivation of the micro-organism; (iv) remove sterilising agent residues from the product to a pre-determined acceptable level. Specifically, textile fabrics contain interstices that can entrap gases and liquids used for sterilisation. This entrapment of gases and liquids can shelter microorganisms on the surface and in the interior of the fabric, which will restrain the intimate contact between the sterilising agent and each individual micro-organism and the entrapment of sterilisation residues will increase the difficulties in achieve the removal of sterilising agent residues from the product to a pre-determined acceptable level.

9.2.2

Common types of sterilisation methods

Four common types of sterilisation are in use today: gas, irradiation, steam autoclave and dry heat. The first two types of sterilisation are also called lowtemperature sterilisation methods, applied mostly to single-use products. The latter two types are also called high-temperature sterilisation methods, and are applied to reusable products. Many sterilisers, such as those used in hospitals, use saturated steam and dry heat, but these methods are not practical for some plastics and other synthetic materials because high temperatures damage them. These materials require lowtemperature sterilisation (Abreu, 2004). New procedures such as those using plasma and X-rays are also increasingly used for a variety of applications. Table 9.1 summarises the advantages and disadvantages of the most common sterilisation methods.

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Table 9.1 Advantages and disadvantages of the most common sterilisation methods Sterilisation method Advantages

Disadvantages

Steam autoclave

Highly effective, safe and inexpensive

Unsuitable for heat- and moisture-sensitive objects Inefficient compared to autoclaves

Ethylene oxide (EtO)

Suitable for heat- and moisture-sensitive items. Reliable

Leaves toxic residue on sterilised items. Long cycles

Gamma rays

Penetrate a much greater distance than E-beam rays. Fast, reliable and cost competitive

The radiation can change the properties of some materials e.g. PVC, PTFE and acetal. Adverse effects on glues and adhesives

E-beam rays

Cost competitive

Limited by the density/ thickness of the object

X-rays

Faster and environmentfriendly compared with gamma rays. Machine source can be turned on and off

Only competitive for largevolume sterilisation

Gas plasma

Fills the gap between steam sterilisation and EtO sterilisation

Damages polyamide-based materials and is very expensive

Dry heat

Gamma and electron beam irradiation Irradiation is an effective sterilisation method, but it is limited to commercial use only. Radiation sterilisation can be accomplished using one of two forms of radiation, either gamma radiation (electromagnetic radiation) from 60Co or 137Cs, or electron beam radiation from accelerated electrons (particle radiation). These high-energy particles or electromagnetic radiation exert their sterilising effect by inducing ionising events in the materials. The released energetic electrons collide with neighbouring atoms and create a shower of secondary electrons. These energetic electrons bombard DNA molecules in the harmful micro-organisms and induce irreversible damage to inactivate them. On the other hand, the same energetic electron shower can also induce severe damage to the material and cause mechanical or biocompatibility failures. Table 9.2 compares the two ionising energy sources (Woo and Purohit, 2002). Gamma radiation. Gamma radiation is the result of transition of an atomic nucleus from an excited state to a ground state, as in certain radioactive

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Textiles for hygiene and infection control Table 9.2 Properties of ionising energy sources

Charge Rest mass Energy Velocity

Electron

Gamma (60Co)

–1 9e–28 gm 0.1–15 Mev 0.3–0.99c

0 0 1.2 Mev c

Source: Woo and Purohit (2002). c = speed of light.

materials. It involves the bombardment of photons and has considerable penetrating power emitted from a 60Co source. It is characterised by deep penetration and low dose rates (Massey, 2005). Gamma rays thus are electromagnetic waves. They have the capability of penetrating to a much greater distance than electron beam rays before losing their energy from collision. Because they travel at the speed of light, they must pass through a thickness measuring several feet before making sufficient collisions to lose all of their energy. 60Co is the most common source of irradiation used for sterilisation. The product must be exposed to radiation for 10 to 20 hours, depending on the strength of the source (URMC, 2010). Electron beam radiation. Electron beam radiation consists of electrons with a single negative charge and a low mass, generated from a linear accelerator. In this method, sterilisation is quick, but with limited penetration. Electrons normally cannot penetrate materials deeply, but when produced in man-made machines they can be accelerated to high energies with a subsequent improvement in penetrating ability (Block, 2001). Recent advances in electron beam technology have made it a worthy competitor to traditional gamma sterilisation. Increased power, compact design, improved reliability and a power source that does not deplete with time, in addition to security issues, are contributing to E-beam technology’s gains for medical device sterilisation (Woo and Purohit, 2002). Ethylene oxide Ethylene oxide (EtO) gas sterilisation was introduced in the 1950s, and is an effective, low-temperature chemical sterilisation method. It takes longer than steam sterilisation, typically 16–18 hours for a complete cycle. Temperatures reached during sterilisation are usually in the 50–60 °C range (Patel, 2003). EtO is a colourless gas; it is an eye and skin irritant, and a suspected human carcinogen (Massey, 2005). Due to EtO being highly flammable and explosive in air, it must be used in an explosion-proof sterilising chamber in a controlled environment.

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EtO sterilisation is used mainly to sterilise medical products that cannot support conventional high-temperature steam sterilisation – such as devices that incorporate electronic components, plastic packaging or plastic containers. EtO gas infiltrates packages, as well as products themselves, to kill micro-organisms that are left during production or packaging processes. Most EtO sterilisation lines involve three stages. These different stages depend on the size or number of devices to be treated. The stages are as follows: (i) pre-conditioning (ii) sterilising (iii) aeration (Eurotherm, 2011). During the second stage, sterilisation depends on four parameters: (i) (ii) (iii) (iv)

EtO gas concentration temperature humidity exposure time.

Each parameter may be varied. Consequently, EtO sterilisation is a complex multiparameter process, where each parameter affects the other dependent parameters (URMC, 2010). EtO is still a dominant sterilisation technique, but general use is declining for the following reasons: (i) (ii) (iii) (iv) (v)

changes in the physical properties of the polymers due to the reactivity of the gas; length of degassing time, product aeration and elimination of gas toxic residues; absorption and adsorption of the gas, leaving residues and damaging the optical properties of the polymer; the Environmental Protection Agency has found EtO to be mutagenic and has initiated steps to restrict its use; operator safety (because of toxic gas residues).

Nevertheless, EtO is the least aggressive form of sterilisation for many materials. In addition, the replacement of the most common EtO carrier gas (CFC-12, Freon) with non-ozone-depleting alternatives, such as carbon dioxide and chloraltetrafluoroethane, will ensure EtO remains a viable choice for many users of sterilisation services (Abreu et al., 2003). Saturated steam Steam autoclaving is the oldest, safest and most cost-effective method of sterilisation. The definition given by Massey (2005) is ‘sterilisation by steam under pressure in an autoclave’. In the steam autoclaving process, micro-organisms are

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killed by heat and this is accelerated by the addition of moisture. Steam, by itself, is not sufficient for sterilisation. To be effective against spore-forming bacteria and viruses, autoclaves need to: (i)

have steam in direct contact with the material being sterilised (i.e. loading of items is very important); (ii) create vacuum in order to displace all the air initially present in the autoclave and replace it with steam; (iii) implement a well-designed control scheme for steam evacuation and cooling so that the load does not perish. The efficiency of the sterilisation process depends on two major factors. One of them is the thermal death time, i.e. the time for which microbes must be exposed at a particular temperature before they are all dead. The second factor is the thermal death point or temperature at which all microbes in a sample are killed. Any living thing will be killed when exposed to saturated steam at 120° longer than 15 minutes. As temperature is increased, time may be decreased (Eurotherm, 2011). Heat by itself can, of course, also readily kill bacteria, but because saturated steam can circulate and penetrate porous items in the steriliser chamber, it substantially reduces the time required for sterilisation. Like all gases, saturated steam cannot undergo a reduction in temperature without a reduction in pressure. Conversely, it cannot undergo a reduction in pressure unless the temperature is proportionately lowered. An excellent demonstration of this phenomenon is seen in locations that are subject to unusual levels of atmospheric pressure. In those areas, changes in steam pressure are required to achieve the minimum temperatures required for sterilisation. Dry heat Death of microbial life by dry heat is a physical oxidation or slow-burning process of coagulating the protein in the cells. In the absence of moisture, higher temperatures are required than when moisture is present, because micro-organisms are destroyed through a very slow process of heat absorption by conduction (URMC, 2010). The disadvantages of dry heat sterilisation are given below. (i)

Heating is slow. Diffusion and penetration of heat are slow because the heat transfer medium is poor and there is a distinct lack of available heat compared with steam in particular. (ii) It requires long sterilising periods. Long exposure times are required because the killing rate by dry heat is slow, as is heat absorption. (iii) It requires high temperatures. These temperatures may be harmful to materials. (iv) Materials are damaged. Deterioration of materials occurs with oxidation. Killing by dry heat is an oxidation process and the medium that facilitates this killing action also augments its harmful effects. (Block, 2001).

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Other sterilisation methods Plasma. Low-temperature plasma sterilisation was introduced to fill the gap between autoclave: high-temperature steam sterilisation (safest, fastest and least expensive) and EtO gas sterilisation, which leaves toxic residuals. It is a lowtemperature, non-toxic, but fairly expensive sterilisation method. Plasma is ionised gas made up of ions and electrons, and it is distinguishable from solid, liquid or gas phases. Plasma is often referred to as the fourth state of matter. The Sterrad system is a hydrogen peroxide gas plasma sterilisation system with an operating temperature range of 45–50 °C. Operating cycle times range from 45 to 70 minutes, depending on the size of system. This sterilisation system uses a combination of hydrogen peroxide and low-temperature gas plasma to quickly sterilise, for example, most medical instruments and materials without leaving any toxic residues. Hydrogen peroxide is a known antimicrobial agent that is capable of inactivating resistant bacterial spores. Sterilisation by this method occurs in a low-moisture environment (Patel, 2003). This sterilisation method can be produced through the action of either a strong electric or magnetic field, somewhat like a neon light. The cloud of plasma created consists of ions, electrons and neutral atomic particles that produce a visible glow. Free radicals of the hydrogen peroxide in the cloud interact with the cell membranes, enzymes or nucleic acids to disrupt life functions of micro-organisms (URMC, 2010). X-ray sterilisation. This is a new, developing process that is based on obtaining Xrays through conversion of electron beams. The X-rays produced have the same penetrating properties as the rays produced by Cobalt-60, but this treatment is faster, more flexible, and more environmentally friendly. X-rays offer excellent product penetration in sterilisation, thoroughly treating the surface and interior of a product (Patel, 2003).

9.3

Quality assurance of the sterilising process

To ensure that products submitted to sterilisation are sterile, monitoring the sterilisation process is crucial. Mechanical, chemical or biological indicators can be used.

9.3.1

Mechanical indicators

Sterilisers have gauges, thermometers, timers, recorders and/or other devices that monitor their functions. Some have alarm systems that are activated if the steriliser fails. Records are maintained and reviewed for each cycle. Test packs are run at least daily to monitor functions of each steriliser, as appropriate. These can identify process errors in packing or loading.

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Chemical indicators

A chemical indicator on a package verifies exposure to a sterilisation process. An indicator should be clearly visible on the outside of every on-site sterilised package. This helps differentiate sterilised from unsterilised items. More importantly, it helps monitor physical conditions within the steriliser to alert personnel if the process has been inadequate. An indicator may be placed inside a package in a position most likely to be difficult for the sterile agent to penetrate. A chemical indicator can detect steriliser malfunction or human error in packaging or loading the steriliser. If a chemical reaction on the indicator does not show the expected results, the item should not be used.

9.3.3

Biological indicators

Positive assurance that sterilisation conditions have been achieved can be obtained only through a biologic control test. The biologic indicator detects non-sterilising conditions in the steriliser. A biologic indicator is a preparation of living spores resistant to the sterilising agent. These may be supplied in a self-contained system, in dry spore strips or discs in envelopes, or sealed vials or ampoules of spores to be sterilised and a control that is not sterilised. Some incorporate a chemical indicator also. The sterilised units and the control are incubated for 24 hours for Bacillus stearothermophilis at 55 to 66 °C to test steam under pressure, and for 48 hours for Bacillus subtilis at 35 to 37 °C to test ethylene oxide (URMC, 2010).

9.4

Effect of sterilisation on fibres and fabrics

The range of fibre types used is large and goes from natural fibres, such as cotton, to man-made fibres including regenerated fibres (e.g. Viscose) and synthetic fibres such as polyester, polypropylene and polyethylene. The textile manufacture and production systems of the fabric are mostly woven, nonwoven and knitted systems (Abreu et al., 2006b). There is a wide range of fibres that cannot be sterilised using certain sterilisation methods. Table 9.3 indicates the limitations for several fibres of some sterilisation methods. Table 9.3 Limitations of fibres for some sterilisation methods Fibre

Limitation

Cellulosic-based fibres Not suitable for sterilisation by some new methods due (natural or artificial) to reaction with sterilants (e.g. plasma) Polyethylene

Not suitable for steam as the melting point is lower than 134 ºC

Polypropylene

Not suitable for irradiation as there can be polymer degradation

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Ageing effect

Abreu (2004) has pointed out that the medical device industry has long been interested in techniques for predicting the shelf-life of polymer-based devices. Since 14 June 1998, the European Union has banned the sale of sterile or degradable medical devices that have no expiry dates. Hence, according to the ISO 11137-1 – Sterilization of Health Care Products – Requirements for Validation and Routine Control – Radiation Sterilization (ANSI, 2006a) – and the United States Food and Drug Administration regulations, medical devices must be given an expiry date, which indicates how long they may be stored prior to use. Real-time ageing is the best way to determine expiration periods, but no organisation can afford to delay its product’s launch, waiting for the results of realtime ageing tests. A method of accelerated ageing is required that realistically recreates what a product may experience during storage. Since most medical devices have to be guaranteed for 5 years storage prior to use, Abreu and co-workers (2006b) compared the results obtained for material that had been stored for a period of 5 years real-time ageing with those for a material that had undergone an artificial ageing. It was simulated through artificial ageing of non-active medical devices, specifically surgical gowns, that had been stored for 5 years. In a previous study, Abreu et al. (2004b) made the comparison considering just 1 year of ageing based on hospital enquiries that confirm that this type of product is stored for a maximum of 7 years. Therefore the artificial ageing simulated 7 years of storage. Testing included specific properties essential for the intended function of the product, and the minimum radiation dose level was 25 kGy (this is the radiation dose usually used for this kind of product and as described in ISO 11137-2 (ANSI, 2006b)). Ageing trial Accelerated ageing can be defined as a procedure that seeks to determine the response of a device or material under normal-usage conditions over a relatively long time, by subjecting the product for a much shorter time to stresses that are more severe or more frequently applied than normal environmental or operational stresses (Hemmerich, 1998). If accelerated ageing is achieved by storing the product at an elevated temperature, clearly, there is a limit to the temperature that can be applied to a medical product or package that is made of a plastic material. Accelerated ageing must be carried out below the glass transition temperature of any components of the product. It is generally accepted that 60 ºC is the maximum temperature that is suitable for most products (ASTM F1980) and the most indicated equipment is a climatic chamber (Abreu et al., 2006b).

9.5

Reprocessing sterilised products

A commentary titled ‘A Call to Go Green in Healthcare by Reprocessing Medical

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Equipment,’ published in the March 2010 issue of Academic Medicine, argues that the reprocessing of medical equipment, including single-use devices (SUDs), should be encouraged. ‘Healthcare can contribute to creating a livable planet by reducing the amount of medical waste it produces’. Eucomed, the voice of the medical technology industry in Europe tells a different story. It cites several ways in which refurbishing them elevates risk for the user. (i)

Potential cross infection. The refurbishment process may be unable to completely remove viable micro-organisms from devices designed for single-use because of narrow lumens or the type of material used. A study conducted at the University of Tübingen in Germany found that none of the refurbished instruments they tested were adequately cleaned, disinfected or sterilised. (ii) Possible leaching of disinfectants. Some materials used to manufacture devices can absorb or adsorb chemicals, which may leach over time. (iii) Material alteration. Reprocessed plastics may soften, crack or become brittle after having been exposed to elevated temperatures or pressure, for example. (iv) Potential mechanical failure. Reusable devices have been designed to withstand stress that occurs each time the device is used. This is not the case for single-use devices, which may be subject to unpredictable fatigue-induced failure and fracturing following refurbishment (Sparrow, 2010). However, unlike Europe, in the United States, the Food and Drug Administration (FDA) regulates the reprocessing of so called ‘single-use’ medical devices and has determined that ‘reprocessed SUDs that meet FDA’s regulatory requirements are as safe and effective as a new device’. On the other hand, Directive 93/42/EEC concerning medical devices specifies that a label must be attached to devices indicating ‘for single use’ when they have been designed, manufactured and certified for single use. These devices are not accompanied by instructions for appropriate reprocessing as is required for devices declared by the manufacturer to be reusable. The manufacturer of a singleuse device may lawfully expect that: • The device be discarded after its first use. • The manufacturer will not be responsible or liable for any subsequent processes performed or later reuse. Therefore, when the device is not discarded after its first use, all information provided by the original manufacturer such as labelling, instructions for use, declaration of conformity and markings are no longer valid and those affixed to the device will be eliminated before any possible further processing. Single-use devices, which must always be labelled as such, are, by definition, for single use only. So, medical devices marked as single-use devices are not intended to be reused. Only reusable medical devices, that are provided with instructions on the processes required for reuse, may be used more than once.

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Provided the information given by the manufacturers on how to reprocess the device is followed, the device should be suitable for reuse. The Medical Devices Directive does not cover the reprocessing and the reuse of devices labelled ‘for single use’ (Eucomed, 2009).

9.6

Normalisation

The first European standards for sterilisation were published in 1994 and the first international standards in 1994 and 1995. The European standards are harmonised and give a presumption of conformity with the European Medical Device Directives. The international standards have been adopted as a United States (US) standard and are recognised by the Food and Drug Administration. The 1994 and 1995 European and international standards are technically equivalent and entirely compatible, but they are editorially different. This has meant added complexity for manufacturers and sterilisation contractors who need to meet US and European requirements to market medical devices in both jurisdictions. Under the normal practice of standards organisations, standards are reviewed after five years. It was agreed in 1999 that a joint revision should be prepared under the leadership of the International Organisation for Standardisation (ISO) – ISO11137, Sterilisation of Health Care Products, Radiation. This standard is divided into three parts: Part 1: Requirements for development, validation and routine control of a sterilisation process for medical devices. This part is normative and contains an annex, which is informative and provides guidance on the application of each clause in Part 1, where guidance is available. Part 2: Establishing the sterilisation dose. If a decision is made to follow the methods detailed in Part 2, then the methods must be followed in their entirety. Part 3: Guidance on dosimetric aspects. This part is informative and contains guidance on the application of dosimetry to the validation and routine control of sterilisation of healthcare products using radiation. The new standard was published in April 2006. However, Part 2 had to be republished to correct errors introduced by the ISO editors. It has been published as a European standard. These revised standards represent a significant step forward in consolidating previously separate international and European standards into single, globally applicable documents. This will benefit manufacturers of medical devices, particularly those who supply products internationally. There is a recognition of advances in validation and routine control since the original standards were published in 1994. In particular, the increased recognition of parametric release in EtO sterilisation and the expansion of methods of

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establishing the sterilisation dose in radiation sterilisation represent improvements over the previous editions (Hoxey et al., 2007).

9.7

Conclusions

Medical devices are developed using engineering principles and process qualification techniques to ensure that they perform as intended. Product engineering has realised that, to accomplish the task of sterilisation process validation, the materials involved must be developed in tandem with the final product development. The new ISO standard provides designers and manufacturers of medical devices with a framework of laboratory tests and evaluations that can be used to qualify the overall performance of the sterilisation, and there are several means within this framework to achieve the end result. Because of the many sterilisation methods available on the market, it is critical to know that different sterilisation methods are more suited to different material types. Many of the emerging sterilisation methods are low-temperature based. It is known that steam autoclaving is the most widely used, inexpensive and effective sterilisation method that is currently available. Also, historically, many hospitals have relied on EtO-based sterilisation systems, but due to time, environmental and safety concerns, they have been investigating alternatives. Thus, we can also consider the two common, low-temperature sterilisation alternatives to EtO gas sterilisation: the Steris System and the Sterrad system.

9.8

References

Abreu M J (2004) Contribution to the Study of Textiles used in the Healthcare Sector: The Influence of Sterilisation over the Mechanical and Physical Properties. PhD thesis, Universidade do Minho (P)/Université de Haute Alsace (F). Abreu M J, Cabeço Silva M E, Schacher L and Adolphe D (2003) Designing Surgical Clothing and Drapes According to the New Technical Standards. International Journal of Clothing Science and Technology, 15(1), 69–74. Abreu M J, Cabeço Silva M E, Schacher L and Adolphe D (2004a) Microscopical Examination: The Impact of Different Ionising Radiation Doses over Protective Clothing Used in the Operating Theatre. Journal Materials Science Forum, 455/456, 792–796. Abreu M J, Cabeço Silva M E, Schacher L and Adolphe D (2004b) The Influence of Ageing over the Properties of Nonwoven-based Surgical Gowns. The Textile Institute 83rd World Conference, Shanghai. Abreu M J, Schacher L, Cabeço Silva M E and Adolphe D (2006a) ‘Recycling Textiles in the Operating Theatre’. In Recycling in Textiles, Woodhead Publishing, Cambridge, UK. Abreu M J, Cabeço Silva M E and Ribeiro M (2006b) Artificial Ageing versus Real Time Ageing of Non active Medical Devices, FiberMed Conference, Finland. ANSI/AAMI/ISO 11137-1 (2006a) Sterilization of Health Care Products – Radiation – Part 1: Requirements for Development, Validation, and Routine Control of a Sterilization Process for Medical Devices. ANSI/AAMI/ISO 11137-2 (2006b) Sterilization of Health Care Products – Radiation – Part 2: Establishing the Sterilization Dose.

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Block S (2001) Disinfection, Sterilisation and Preservation, Lippincott Williams and Wilkins, USA. Eucomed (2009) Eucomed White Paper on the Reuse of Single Use Devices, Report, Brussels. Eurotherm (2011) Ethylene Oxide (EtO) Sterilization Process. Available from http:// www.eurotherm-lifesciences.com (accessed 15 January 2011) Hemmerich, K (1998) General Ageing Theory and Simplified Protocol for Accelerated Ageing of Medical Device Category, Medical Plastics and Biomaterials Magazine, July. Hoxey S, Strain P, Harries J and Kirk B (2007) Revised Standards for Sterilisation: The Changes. European Medical Device Technology, March–April, 18(2). Massey L (2005) The Effect of Sterilization Methods on Plastics and Elastomers, Plastics Design Library, USA. Patel M (2003) Medical Sterilization Methods, Lemo, USA. Sparrow N (2010) An Inconvenient Truth about Reprocessing Single Use Devices. European Medical Device Technology, April, 1(4). URMC, University of Rochester Medical Centre. Basics on Processing & Sterilisation. Available from http://www.urmc.rochester.edu/sterile/basics (accessed 10 September 2010). Walker I V (1997) Textiles and Sterilization Assurance. In Medical Textiles 96, (ed. Shubash Anand), Woodhead Publishing, UK. Woo L and Purohit K (2002) Advancements and Opportunities in Sterilisation. Medical Device Technology, March, 12–17.

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10 Washable textile-based absorbent products for incontinence A. M. C O T T E N D E N, R. S A N T A M A R T A V I L E L A, M. C. M A C A U L A Y, D. J. C O T T E N D E N, M. A. L A N D E R Y O U and D. L I L B U R N,

University College London, UK and M. J. F A D E R, University of Southampton, UK

Abstract: This chapter focuses on the current place of washable, textilebased absorbent products in the management of urinary incontinence. It opens by describing the principal categories of products available, summarises the functional requirements of users, and reviews the clinical literature to establish how well existing products meet current needs. It then reviews the very limited work that has been published to characterise the fluidhandling properties of such products in the laboratory and relates the results to clinical data. It concludes by focusing on future trends, suggesting where improved products are needed. Key words: incontinence, pads, washable/reusable products, absorbency, laboratory/user data correlations.

10.1

Introduction

Urinary incontinence is a common and debilitating condition that erodes the quality of life of millions. It affects about 5% of women under 60 in the Western world; 9% of those over 65; 17% of the over 85s; and 55% of those in nursing homes. Figures for men are around half those for women (Hunskaar et al., 2005). The severity of urinary incontinence varies enormously between sufferers but even light incontinence can be highly disruptive, causing a devastating loss of confidence and severely restricting home, social and work-life activities (Ashworth and Hagan, 1993). The economic costs of incontinence are high too; for example, in 2000 the UK Health Service was estimated to spend some £423m per annum on diagnosing, treating and managing it (Continence Foundation, 2000). Much incontinence can be cured by addressing the underlying cause using drugs, surgery or physiotherapy. However, complete cure is not always possible and even those who are successfully treated may have to live with incontinence while they wait for treatment to yield its benefits. Still others may not be candidates for treatment or may choose management over attempted cure. For all such people, the challenge is to minimise the impact of incontinence on their quality of life, and 153 © Woodhead Publishing Limited, 2011

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Female

Male

(a) Waterproof (fabric-covered) gusset

Integral washable pad

(b)

(c) (d)

(e) (f)

10.1 The principle designs of washable, textile-based absorbent products for managing urinary incontinence: (a) diaper-style garment; (b) pants with integral pad; (c) stand-alone pad for light incontinence; (d) stand-alone pad for heavy incontinence; (e) male pouch; (f) underpad for use on a bed.

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this usually involves using some kind of continence product – most commonly absorbent pads.

10.2

Incontinence pad designs

Most incontinence pads are disposable, exploiting technology first developed for the much more lucrative baby diaper and sanitary protection markets, but a number of reusable designs are available that can be used, laundered and reused many times. Such washable, textile-based products (Fig. 10.1) – the focus of this chapter – can, like disposable products, be divided into two broad groups: first, those that are worn by the user (body-worn products); and second, those that are placed between user and bed (bed pads) or chair (chair pads), collectively called underpads. Regarding body-worn products, traditional cotton towelling squares of the kind widely used for babies (until the advent of disposable diapers) are still available and they can be bought in adult sizes for use with separate waterproof pants. The same towelling can be fashioned into a diaper-style garment, often with integral waterproof backing, and secured with Velcro or press-stud fastenings (Fig. 10.1a). The towelling may be replaced by a needlefelt (usually a blend of polyester and rayon fibres) faced with a water-permeable top sheet (usually a knitted cotton or polyester fabric) for contact with the skin. These products are intended to deal with quite substantial urine losses. Other designs are available for lighter incontinence. Pants with a pad sewn into the crotch are available in designs for men and women (Fig. 10.1b). Stand-alone washable body-worn pads are also available in a variety of sizes/absorbency levels (Fig. 10.1c and d) and they are worn with close-fitting normal underwear to keep them in place. Finally, there are male pouches which are worn over the penis – and often the scrotum too (Fig. 10.1e) – and held in place by close-fitting underwear. Like washable diapers, all of these designs most commonly have an absorbent needlefelt core sandwiched between a waterproof backing and a water-permeable fabric top sheet. Underpads (Fig. 10.1f) are rectangular and usually comprise the same threelayer composite structure as body-worn products, although some are supplied with a separate waterproof backing.

10.3

Functional requirements of washable, textilebased incontinence products

There has been a considerable number of published clinical trials of incontinence pads (Cottenden et al., 2009) from which the functional requirements sought by their users can be gleaned. Recently, however, Fader et al. (2008) published an extensive evaluation of disposable and washable body-worn products that included an initial phase in which lightly incontinent women and moderate/heavily incontinent men and women living in the community were asked to list and prioritise their requirements. The findings, which are consistent with earlier work

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Table 10.1 Pad characteristics ranked in the top five by women with light incontinence (Fader et al., 2008, p.117) Characteristic (day)

% Women (n = 99)

Hold urine Contain smell Stay in place Be discreet Be comfortable when wet

83.8 75.8 54.5 41.4 40.4

Characteristic (night) Hold urine Stay in place Contain smell Be comfortable when wet Keep the skin dry

% Women (n = 81) 93.8 77.8 54.3 54.3 48.1

Table 10.2 Pad characteristics ranked in the top five by men and women with moderate/heavy incontinence (Fader et al., 2008, p.117) Characteristic (day)

% Men and women (n = 67)

Hold urine Contain smell Stay in place Be discreet Fit well Be comfortable when wet

92.5 56.7 50.1 46.3 43.3 35.8

Characteristic (night)

Hold urine Stay in place Be comfortable when wet Fit well Keep the skin dry Contain smell

% Men and women (n = 67) 95.5 68.7 53.7 43.3 37.3 34.3

(as reviewed by Cottenden et al., 2009), are summarised in Tables 10.1 and 10.2. The similarities between the two tables are striking. There has been no formal investigation of the functional requirements of bodyworn pads for lightly incontinent men but the findings of the most comprehensive clinical evaluation of such products (Fader et al., 2005) suggest that they are not very different from those listed in Tables 10.1 and 10.2. Similarly, the functional requirements of underpads have not been studied formally but a review of the literature (Cottenden et al., 2009) suggests that they will be similar to those shown in Tables 10.1 and 10.2. The data in Tables 10.1 and 10.2 relate to pads generally – that is, both disposable and washable designs – but there are additional requirements for washables, that concern ease of laundering (washing and drying) at home, and especially when away. In particular, washing bed pads, which may hold several litres of water during laundering, can be heavy work for frail users. An inconvenience of changing body-worn products when out is the need to carry the used item around until returning home. For pads incorporated into a pant design, there is the additional inconvenience when changing of having to remove trousers or tights and, for men, the resulting need for a cubicle when a urinal might otherwise be sufficient. Concern for the environment (and also for controlling costs) has led to an

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increase in the number of washable products available on the market in recent years. An important consideration in the comparison of washable and disposable designs is the relative environmental costs, particularly the disposal (landfill) costs of disposable designs and the energy costs associated with laundering the washables. A recent report on baby diapers concluded that there was no significant difference in environmental impact between three diaper systems (disposables, and washables that were laundered at home or commercially) although the types of impacts did vary (Aumônier and Collins, 2005).

10.4

Clinical performance of existing products

Clinical evaluations of all products for managing incontinence have been reviewed recently (Cottenden et al., 2009) and the notes below summarise the findings for washable absorbent products.

10.4.1 Body-worn products for lightly incontinent women Two major clinical evaluations of washable body-worn products for lightly incontinent women have been published. Most recently, Fader et al. (2008) compared washable pants with an integral pad, washable inserts, disposable inserts and disposable menstrual pads. Eighty-five women (mean age 60) completed the study. The disposable insert was significantly better than the other designs on most variables except for discreetness. For leakage prevention, overall acceptability and preference, disposable inserts were found to be significantly better than menstrual pads, which were better than washable pants with integral pad, which were better than washable inserts. There was no clear benefit for skin health using either washable or disposable designs. Most women preferred the disposable insert pad but some preferred the other cheaper designs (6/85 preferred menstrual pads; 13/ 85 preferred washable pants), both of which were >50% cheaper to use than disposable inserts. Washable inserts were significantly worse than the other designs (72/85 found them unacceptable). Overall, there were generally more practical problems with washables, particularly when away from the home. In an earlier study, Clarke-O’Neill et al. (2002) compared all ten washable pants with integral pad for lightly incontinent women, on the UK market in 1999. Seventy-two community-based women who usually used absorbent products for light incontinence tested each product, scoring the various aspects of product performance using questionnaires. They were also asked to weigh used products when they changed them (so that the mass of urine in them could be estimated by subtracting the product dry weight) and to record the severity of any leakage from the product on a three point scale: none, a little or a lot. These pad weighing/ leakage data were then used to produce plots showing the probability of a product leaking as a function of urine mass. The key findings for six of the products – the six that were subsequently

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Table 10.3 Key results from the clinical evaluation of six pants with integral pads for lightly incontinent women (Clarke-O’Neill et al., 2002) Product code 1

3

5

6

7

10

Estimated product leakage performance from pad weighing % of pads not leaking at all for: 10 g urine 53 55 20 g urine 28 27

67 50

69 44

47 18

67 46

% of pads not leaking a lot for: 10 g urine 90 89 20 g urine 75 75

92 83

96 88

80 58

87 77

Questionnaire: Ability to hold urine without leaking? (% of subjects) Good OK Poor

31 33 36

40 31 29

27 34 39

47 31 22

34 26 40

28 45 28

Questionnaire: How well did the pad keep the skin dry? (% of subjects) Good OK Poor

40 25 35

39 41 20

26 35 40

36 39 25

33 35 32

26 38 36

subjected to laboratory study (See Section 10.5) – are summarised in Table 10.3. Their leakage performance was found to be disappointing, with the best performing product not leaking 69% of the time at a loading of 10 g of urine, compared to 47% for the least successful product. Subjects’ ‘overall opinion’ scores showed wide differences between products, with the best scoring 85% Good or OK (as opposed to Poor) compared with 34% for the least successful product.

10.4.2 Body-worn products for lightly incontinent men Only one evaluation of absorbent products for men with light urinary incontinence has been published (Fader et al., 2005). It compared the four main absorbent designs of products: disposable insert pads, pouches, leafs (a variant on the pouch which is positioned over the penis and scrotum) and washable pants with integral pad. All six leaf products (five disposable and one washable) and all six pouches (all disposable) on the UK market in 2003 were evaluated, together with a selected disposable insert pad and a selected washable pant with integral pouch (chosen to represent their respective designs). Seventy men with light urinary incontinence evaluated the products. The pouch design performed significantly worse than the leaf and the insert design. The most common problems with the pouch were staying in place and difficulties re-inserting the penis in the pouch once the pouch was wet. The leaf designs had the best leakage scores. The disposable insert was also effective for leakage prevention and was substantially cheaper than the leaf designs. The washable leaf was the least successful of the leaf designs. The

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washable pants with integral pad received polarised overall opinion scores (loved or hated) and scored well for staying in place but poorly for leakage. Those who favoured them were generally very light wetters who were mobile and active.

10.4.3 Body-worn products for moderately/heavily incontinent men and women There have been two recent studies of washable absorbent pads for heavily incontinent men and women. Most recently, Fader et al. (2008) conducted a trial with 85 moderate/heavily incontinent adults living in their own homes (49 men and 36 women). Each evaluated three products from each of five design categories (total of 14 test products): disposable inserts (with mesh pants); disposable diapers; disposable pull-ups; disposable T-shape diapers; and washable diapers. All products were provided in a daytime and a (mostly more absorbent) nighttime variant. Just the results relating to the three washable products are reported here. They gave diverse results. Two of the products were made from cotton towelling (one a simple square, folded and pinned in a diaper shape; the other a shaped diaper-like design, both worn with plastic pants) while the third product had a needlefelt absorbent core, with an integral plastic backing and was fixed by poppers. This third product performed significantly worse for leakage than the other two washables. The cotton towelling washables were less likely to leak at night than all the disposable designs, but they were less popular overall for daytime use. Three quarters of the women (27/36) found them unacceptable, but nearly two thirds of men (31/49) found them highly acceptable at night. Testers highlighted many practical problems dealing with washable products, particularly when out of the house, but judged them to be more acceptable for use at home. In earlier work, Macaulay et al. (2004) carried out a pilot study of 19 washable products with 14 community dwelling subjects. The products included a mixture of washable insert and brief designs and two disposable body-worn products. Product performances varied widely: the most popular was rated as good (for overall performance) by 78% of testers, while the least popular scored 22%. Although most of the washable products performed poorly for leakage, one washable product made of cotton towelling (used with plastic pants), scored better than all the other products (washable and disposable) in the trial. Eight older trials have compared disposable with washable body-worn products for moderate–heavy incontinence (Beber, 1980; Grant, 1982; Haeker, 1986; Dolman, 1988; Merret et al., 1988; Hu et al., 1990; Harper et al., 1995). The trials varied in size and design from a large controlled trial with 276 subjects (Beber, 1980) to a small trial of eleven subjects (Dolman, 1988). In addition, some trials have compared disposable and washable bedpads and body-worns. Brown (1994a,b) undertook a large trial of this kind. The fact that no systematic method of product selection was used for these studies limits the utility of the results since

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particularly good or poor products may have been selected to represent the disposable or washable groups. Skin condition was used as an outcome measure in five of the above trials. However, only three used experimental design and statistical methods of analysis. Beber (1980) and Grant (1982) both reported that they did not find statistically significant differences between their washable and disposable products in terms of an adverse change in skin condition. But Hu et al. (1990) reported a statistically significant improvement in the skin condition of their disposable product users as compared to their users of washable products. Other parameters frequently investigated in these studies were staff preference, product leakage and laundry. Overall, the disposables in the studies were considered to have performed better than the washable products in terms of preventing leakage (often measured by quantity of laundry) and staff preference. Four studies attempted to measure costs (Grant, 1982; Haeker, 1986; Hu et al., 1988; Merret et al., 1988; Brown, 1994b). Of these, three used statistical methods of analysis. Hu et al. (1988) and Brown (1994b) reported that although there were no statistically significant differences in terms of per-day product costs for washable and disposable products, the laundry costs associated with the disposable product (i.e. for laundering soiled bed linen and clothes) were significantly lower than those associated with the washable product (i.e. for laundering the products as well as soiled bed linen and clothes). Brown (1994b) found no significant differences between daily costs of the washable and disposable products. However, statistically significant differences were found between the groups in terms of incontinence-related laundry, with the disposable group producing less laundry than the washable group. Grant (1982) reported that the cost of washable products was significantly lower than that of disposables, but laundry costs were not taken into account.

10.4.4 Underpads There is no published work on washable chair pads but there have been a number of studies of washable bed pads (Cottenden et al., 2009). Some evaluations have found significant differences between products relating, for example, to leakage performance and impact on skin health. However, the compared products always differed from one another in many respects, making it impossible to draw reliable generic conclusions relating to particular product features or materials. It appears that choice of top sheet material and the presence/absence of design features such as tuck-in flaps and integral/separate waterproof backing are, primarily, matters of personal preference. In institutional settings, washable bed pads are commonly used by multiple patients and questions are often asked about the risk of cross-infection. Cottenden et al. (1999) assessed the risk by determining the microbial content of 145 bed pads of five different designs after a night’s use by incontinent adults, followed by

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laundering using a standard foul wash procedure which included heat disinfection at 71 °C for three minutes. Laundering destroyed all known pathogenic organisms, although some commensal flora were isolated in small numbers. It was concluded that foul wash laundry had left bed pads safe for multiple patient reuse with no demonstrable risk of cross-infection.

10.4.5 Summary of clinical work In summary, washable, textile-based absorbent incontinence products are currently much less commonly used than disposables and are, generally, less effective. However, they can be considerably cheaper on a per-use basis and are commonly perceived to be more environmentally friendly than disposables, even though published environmental audits suggest there is little difference. Body-worn products for heavy incontinence, based on cotton towelling, are impressively absorbent – outperforming disposable products – and are tolerable for men for use at night. However, their bulk and poor aesthetics make them unpopular with men for daytime use and unacceptable to most women at any time. The leakage performance and aesthetics of body-worn products for heavy incontinence, based on needlefelts, are generally very poor and there is currently little demand for them. The leakage performance of disposable body-worn products for lightly incontinent men and women is generally better than that of washable alternatives. However, the normal appearance of pants with an integral pad is attractive to some users who may prefer them over disposables – especially if their incontinence is very light: the difference in leakage performance between disposable and washable products narrows for small urine weights. Stand-alone washable pads for light incontinence are generally ineffective and unpopular. Washable underpads are now used primarily as a backup to body-worn products, to protect bedding and soft furnishings. Cross-infection between users is not a serious threat if products are subjected to standard foul-wash laundry cycles.

10.5

Laboratory evaluation

Many laboratory methods described in international, European and various national and industry standards could be used to measure properties such as the absorption speed, absorption capacity and wicking behaviour of whole washable incontinence products, composite samples cut from them, or their constituent materials. But, although some companies use (variants on) such tests in support of their product development and quality assurance, virtually no work is published. Only Landeryou et al. (2003) have reported on a comprehensive laboratory study of a set of products, including a comparison of their results with data from clinical studies on the same products. Their work forms the backbone of the sections that follow.

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10.5.1 Whole product testing Landeryou et al. (2003) conducted a laboratory investigation of a sample of six of the ten washable pants with integral pad for lightly incontinent women that had been evaluated clinically by Clarke-O’Neill et al. (2002). The pads (that is, the absorbent cores and their associated top sheets) were removed from the pants and waterproof backing so that their liquid handling properties could be studied more easily. Pad shapes are shown in Fig. 10.2. The cores were all made from rayon/PET blend needlefelts, while the top sheets were knitted fabrics. In all experiments, the top sheet and absorbent core from each product were tested as a single entity. In three of the products (coded 1, 5 and 7 in Table 10.3) the top sheets were stitched (quilted) to the cores while in the other three they were separate (once removed from the pants). In five of the products the absorbent core was made from a single layer of fabric while in Product 6, a second layer of felt was added beneath the central region (Fig. 10.2). All products were preconditioned prior to testing by washing twice at 40 °C and tumble drying. A range of laboratory experiments were run on these cores and top sheets to characterise their fluid handling properties. First, to test them in a laboratory 40 cm

40 cm

40 cm

0

0

0

Product 5

40 cm

0

Product 10

40 cm

Product 7

0

Product 3

40 cm

Product 1

0

Product 6

10.2 Shapes and sizes of the absorbent cores from pads used in the laboratory study of Landeryou et al. (2003). Dimensions of the absorbent areas are shown, and where pads included quilting this is indicated. The darker region of Product 6 indicates the area over which a second felt layer extended on the underside.

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Video camera

Perspex sheet (marked in a 20 mm × 10 mm grid)

Fluid introduced from a mechanical bladder

Adjustments for height and position Core of pad

Video camera Angled mirror

10.3 Curved former used by Landeryou et al. (2003) to support an absorbent core from a pad in a geometry designed to reproduce an anatomical cross-section. The placement of video cameras used to record liquid spreading from above and below (using an angled mirror) is shown. Liquid was introduced at the point illustrated, using a computer-controlled pump.

simulation that imitated real use, a simple anatomical model was constructed. A single axis curve found from an average through the midline of three female volunteers was used as the most important geometrical factor governing liquid movement. The lower portion was approximated closely by a half cylinder of radius 110 mm. An apparatus to hold absorbent cores in this geometry was built (Fig. 10.3). A curved transparent plastic sheet supported the sample and angled mirrors were used so that liquid spreading in the pad could be observed from both above and below. Each absorbent core/top sheet sample was positioned on the curved former in the same position as it would have been held by the pant on a wearer, using the vertical seam lines on the core and the grid on the curved former to ensure correct orientation. A computer-controlled piston pump was used to deliver an aliquot of

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Table 10.4 Extent of fluid spread forward and backward of the lowest point in the rig (Fig 10.3) at the end of fluid introduction and at one hour (Landeryou et al., 2003). The product codes (1–10) from the original evaluation (Clarke-O’Neill et al., 2002) are retained here for consistency. Time

Direction

Distance from lowest point in rig (mm) Product

After fluid introduction After 1 h

Forward Back Forward Back

1

3

5

6

7

10

73 39 98 53

85 13 90 45

80 25 83 45

83 15 104 61

75 43 77 53

98 56 135 127

50 mL of liquid at 2 mL/s onto the top sheet, on the longitudinal centre line at a point 55 mm (measured along the curved surface) forward of the lowest point. The liquid was room temperature water, coloured with a red dye (known not to have any significant effect on the absorbent properties of water) to facilitate visual observation of liquid spreading. Spreading was recorded using a mirror and a pair of video cameras, recording continuously from the beginning of liquid introduction for 20 minutes, and then briefly at regular intervals until one hour had elapsed. The volume of liquid used was much larger than that associated with the median 10 g loss found in the clinical study; this was to ensure that the products would be studied towards the upper range of their absorption capability, allowing leakage mechanisms to be identified. The extent of fluid spread forward and backward of the lowest point in the rig (measured along the curved surface) at the end of fluid introduction and at one hour are given in Table 10.4. This imitative testing highlighted three primary phases of liquid handling: (i) fluid penetration; (ii) initial distribution and retention when gravity assisted flow and forced low are important; and (iii) subsequent redistribution dominated by capillary action but limited by desaturation and gravity. Opportunities for leakage could be identified for each of these phases, as follows: Phase 1: Inadequate absorption speed. With three of the products (5, 7 and 10), once liquid had penetrated the top sheet and core it rapidly ran downhill (inside the core) to the lowest point. Not only did this result in a large portion of the pad being unused for absorption, but also the lowest region rapidly became fully saturated, and lateral leakage followed. In addition, in one of the products, some fluid failed to penetrate the top sheet and ran downwards over the top surface. Phase 2: Lack of temporary storage volume. Having been initially absorbed into the product, liquid infiltrated downwards towards the lowest point of the curve. The pad then became increasingly saturated around the lowest

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point and in three of the products (1, 7 and 10) this led to early leakage from the sides of the pad. Phase 3: Insufficient redistribution of liquid by capillary action. Once liquid is absorbed by a product, capillary action acts to redistribute it; but this occurs over a longer time scale than the preceding phase of infiltration (which is dominated by gravity). By comparing images of fluid distribution one hour after starting the experiment with images taken at the end of liquid introduction, the increase in wetted area due to capillary spreading could be seen. Redistribution is important in preventing leakage in that it can move liquid away from areas where liquid escape might be expected, making more efficient use of the available storage volume. Additionally, by reducing saturation levels in high saturation regions, the risk of leakage brought about by deformation of the absorbent or contact with other materials is likely to be greatly reduced. Recognition of these different elements of fluid fabric interaction provoked further work using a range of methods designed to focus on some limited properties, as detailed in the following sections.

10.5.2 Absorption/acquisition time Landeryou et al. (2003) used the apparatus shown in Fig. 10.4 to measure the absorption time of 75 mm squares of composite core and top sheet cut from their

Automatic solenoid valve Electrodes to clock Weight

Perspex block Sample

10.4 Apparatus used by Landeryou et al. (2003) for measuring the absorption time for core/top sheet samples.

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Table 10.5 A summary of results (with standard deviations in parentheses) from all the technical tests carried out on pant cores by Landeryou et al. (2003). The product codes (1–10) from the original evaluation by Clarke-O’Neill et al. (2002) are retained here for consistency.* Wicking test pieces for Product 6 had a single layer of the core fabric while test pieces for all other experiments were cut from the central region of the core and had two layers (Fig. 10.2) Test

Product 1 Product 3 Product 5 Product 6* Product 7 Product 10

Absorption 1.57 (0.31) 1.23 (0.06) time (s) Absorption capacity (g/m2) @ 1 kPa 4500 (200) 5400 (100) @ 2 kPa 4100 (100) 4900 (200) @ 4 kPa 3700 (100) 4600 (100) Max. wicked 69.3 55.3 height (mm) Max. wicked 5.44 4.15 mass (g)

2.23 (0.15) 0.90 (0.17) 2.17 (0.15) 5.33 (0.32)

4900 (500) 4300 (200) 3900 (100) 83.3

9100 (100) 3500 (200) 2400 (0) 8400 (400) 3200 (300) 2400 (100) 7600 (100) 2900 (100) 2200 (0) 74.5 29.8 77.5

5.80

4.29

2.06

2.83

six test products. The test rig was based on the apparatus described by INDA and EDANA, intended primarily for measuring nonwoven coverstock liquid strikethrough time (Method WSP 70.3) (WSP, 2005), but the cavity was completely open to the sample at the lower surface instead of having a floor with a series of holes in it. This modification was used because the resistance to liquid flow of the holes in the WSP apparatus was often found to be greater than that of the sample being evaluated. Samples were placed under a weight to compress the sample lightly (2.8 kPa) and, using an automatic valve, 10 mL of water was released into the cavity (25 mm diameter at the sample interface) in the 75 mm diameter weighted Perspex block. An electronic timer and pair of conductance sensors in the cavity measured the elapsed time between the arrival of liquid and it being fully absorbed into the pad. This was recorded as the absorption time. Three runs were made per product. Absorption times for the six products varied between 0.9 and 5.3 s (Table 10.5).

10.5.3 Absorption capacity under pressure Landeryou et al. (2003) measured the absorption capacity under pressure of 75 mm squares of composite core and top sheet cut from their six test products, using the apparatus shown in Fig. 10.5. Each sample was placed on top of a 75 mm plain square block and under a second containing a 25 mm diameter cylindrical cavity used to deliver test fluid. A weight was then applied to achieve a pressure of 1, 2 or 4 kPa, pressures chosen to reflect those measured by Allen et al. (1993) beneath the sacrum and buttocks of supine volunteers on a foam mattress. Water was then run through the sample for three minutes (by keeping the cavity topped up) to ensure full saturation, after which the dry sample weight was subtracted

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Distilled water

Weight

Perspex blocks

Sample

10.5 Apparatus used by Landeryou et al. (2003) for measuring the absorption capacity of core/top sheet samples.

from the wet, to determine the absorption capacity of the material under a given pressure. Three repeat runs were taken per product. Under a pressure of 1 kPa, absorption capacities for the six products varied between 2400 and 9100 g/m2, falling to 2200–7600 g/m2 at 4 kPa (Table 10.5).

10.5.4 Wicking In the study of Landeryou et al. (2003), a vertical wicking test was used to find the equilibrium wicking height and mass for each product core and top sheet combination. The bottom 10 mm of a 25 mm wide strip cut from the core and top sheet of each pant was introduced into a large diameter (big enough for the fluid level not to drop significantly during wicking tests) reservoir of water (using the same red dye as used for imitative tests) and the reservoir was placed on an electronic balance to record the mass loss due to wicking. The samples were left for one hour, after which time the mass loss recorded by the balance and the height of the wetted region of the sample were measured. Two runs were taken for each product. Equilibrium wicked heights for the six products varied between 30 and 83 mm while equilibrium wicked masses fell in the range 2.1–5.4 g (Table 10.5).

10.5.5 Laundry and durability The durability of washable products is a key factor in their per-use cost, as it determines the number of uses over which product purchase price is defrayed.

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Accordingly, it is common for suppliers to quote the number of various standard wash cycles their products can be expected to withstand without serious loss of function or appearance. It is common to quote 100 washes, sometimes 200 and occasionally up to 400. Clarke-O’Neill et al. (2002) and Landeryou et al. (2003) did not determine the durability of the pants with integral pad for lightly incontinent women that they investigated.

10.6

Correlation with user data

Although many laboratory tests have been devised to characterise the various fluid-handling properties of materials used in washable incontinence pads, none of them has been clinically validated; that is, none has been demonstrated to provide data which correlates reliably with pad performance in real use. However, Landeryou et al. (2003) used observations of leakage mechanisms in their imitative laboratory testing of pants with integral pad for lightly incontinent women to interpret the results from clinical evaluation (Table 10.3) and laboratory tests (Tables 10.4 and 10.5) on the same products.

10.6.1 Initial insult absorption During imitative testing, three of the six test products (5, 7 and 10) showed signs of difficulties in coping with the liquid insult during the early stages of absorption. In one case (Product 10) a portion of the liquid was seen to run over the surface of the top sheet and then to leak from the edges of the pad at the lowest point, without having entered the absorbent core. Absorption time testing showed that this product had a significantly longer absorption time than the other products (Table 10.4), taking more than twice as long to absorb 10mL of fluid as the next worst material, a trait which may lead to liquid persisting on the pad surface long enough to run downwards before being absorbed. In the clinical questionnaire, the same product was rated as Poor at keeping the skin dry by 36% of subjects, the second worst of the six products in this respect (Table 10.3). Conversely, the two products that performed best in terms of absorption time (3 and 6) were rated as Poor for skin dryness by 20% and 25% of subjects respectively, making them the most acceptable of these six products.

10.6.2 Temporary absorption capacity Two products (7 and 10) suffered from low absorption capacities (most likely as a result of the small thickness of their absorbent cores). In imitative testing, these products were observed to lose liquid through leakage from the sides of the absorbent core around the lowest point. The leakage seen in Product 1 (less severe than in Products 7 and 10) is not so readily understood by referring to the laboratory measurements as the absorption time and capacity for Product 1 were

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comparable to those for products that did not exhibit any leakage in imitative testing.

10.6.3 Equilibrium distribution of the absorbed volume For all the products, apart from Product 7, the wetted region increased substantially in length between the end of fluid application and the end of testing one hour later (Table 10.4). However, the increase in the forward direction was at most 38% (for Product 10) while increases were generally rather greater in the backward direction – some 300% in the case of Product 6. Furthermore, the forward liquid front was invariably higher than the backward. This suggests that the mechanism of distribution was different in forward and backward directions, yet since the rig was roughly symmetric, the only geometric asymmetry was in the shape of Product 1. However, liquid was introduced 55 mm forward of the lowest point, leading to an initial asymmetry in distribution, which was made more pronounced by observed uphill flow from the point of application during fluid inflow. This suggests that, although wicking contributed to the equilibrium liquid distribution, the retention of liquid distributed by forced flow during the initial introduction phase was also important. Further, the finite volume of liquid introduced into the products appears to limit the extent of capillary redistribution to be significantly smaller than suggested by equilibrium wicking tests, which took place from a large reservoir.

10.6.4 Relation to clinical leakage record There were some differences between the pad weighing/leakage data and questionnaire responses (Table 10.3), which serve to highlight some of the problems of survey-based evaluations. The correlation coefficients between Good or OK (as opposed to Poor) leakage performance, based on questionnaire results and the probability of a lot of leakage (based on pad weighing/leakage data) at 10 g and 20 g, were 0.13 and 0.54, respectively. Clearly, users consider a range of factors when evaluating a product for leakage performance. For example, for some users, infrequent, though severe or distressing, incidents may have a disproportionately large impact on their questionnaire response. It is important to note that in the imitative testing a large volume of liquid (by the standards of the clinical tests) was used in order to reveal the failure mechanisms outlined. The results from the technical tests show that under ideal conditions, all the pads are capable of holding ~40 mL (at least) of fluid below the height at which it is introduced (approximately 20 mm vertically), a volume exceeded in only around 10% of saved pads in the clinical study. It is not possible to similarly relate the absorption times to clinical data since much less is known about the flow rates associated with incontinence events from lightly incontinent women. It is therefore impossible to say whether the slowest absorption speed of 1.9 mL/s is sufficient for idealised cases of this

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type. As these results show, it is difficult to devise simple laboratory tests that relate directly to clinical performance: for these products the simple requirements for absorption capacity and redistribution appear to be fulfilled, given the situations encountered clinically. In both the pad weighing/leakage data and the questionnaire responses, Product 6 was rated as good and Product 7 as poor for leakage performance. There was less agreement for other products, and differences in leakage performance did not achieve statistical significance. Product 7 was also the poorest performing product in laboratory testing, and failed to contain liquid in both of the absorption phases described – with liquid initially running down the pad, followed by leaking from the sides and poor redistribution. The best performing Product (6) showed no evidence of leakage from the imitative testing, and it had the highest absorption capacity and fastest absorption speed. Of the remaining products, results from laboratory testing indicated that Product 10 should, according to the understanding gained in the course of this study, have leaked (having a significantly long absorption time, and low absorption capacity). However, pad weighing/leakage data indicated it to be in the better performing half of the products, and few users rated its leakage performance as poor. By assuming uniform saturation over the wetted area, an estimate of the average saturation at equilibrium was made. In this case the lowest saturation was exhibited by Product 6 (42%), and the highest by Product 7 (110%). This correlates reasonably well with the clinical rankings for dryness; that is, low saturation corresponds to low leakage. It seems therefore that low equilibrium saturation is an important factor in reducing subsequent leakage. It may be that low saturations help prevent leakage under more demanding conditions such as applied pressure, deformation of the product, or changes in orientation.

10.7

Future trends

Although washable, textile-based incontinence pads are currently much less commonly used than their disposable counterparts, they continue to attract attention because of their (usually) lower per-use cost and perceived ‘green’ credentials. The market for washable underpads is probably decreasing since the leakage performance of disposable body-worn pads – for which they are commonly used as backup – continues to improve. Washable pants with integral pad are popular among men and women with very light incontinence because of their normal appearance and low-bulk comfort, but their leakage performance is not as good as that of disposable inserts. Products with improved leakage performance are likely to extend their appeal to users with heavier (although still relatively light) incontinence. Neat solutions to the problem of carrying around used products, having changed them when away from home, would also be likely to extend their appeal. With the exception of men using towelling products at night, current washable

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body-worn products for heavy incontinence, especially those with a needlefelt absorbent core, are generally ineffective and unpopular. There is scope for designing ergonomically and aesthetically improved products for men for night use (and possibly day use) capitalising on the proven properties of existing towelling fabrics. Finally, the fabrics used in existing washable products are simple and homogenous, and product designs are basic. The potential for improvement based on more sophisticated fabrics and structures would seem to be considerable.

10.8

Sources of further information and advice

Details of existing washable textile-based (and other) products on the UK market are given in the directory of the Bladder and Bowel Foundation on their web site (Bladder and Bowel Foundation, 2010). Cottenden et al. (2009) have published a critical review of the clinical literature relating to washable textile-based (and other) products, including suggestions on research priorities. Mao et al. (2007) have provided a useful tabulation of the principal international, European, national and industry standard test methods that could be used to measure properties such as the absorption speed, absorption capacity and wicking behaviour of washable incontinence products or their constituent materials.

10.9

References

Allen V, Ryan D W and Murray A (1993), Repeatability of subject/bed interface pressure measurements, Journal of Biomedical Engineering, 15, 329–332. Ashworth P D and Hagan M T (1993), The meaning of incontinence: a qualitative study of non-geriatric urinary incontinence sufferers, Journal of Advanced Nursing, 18, 1415– 1423. Aumônier S and Collins M (2005), Life cycle assessment of disposable and reusable nappies in the UK, London: Environmental Agency. Beber C R (1980), Freedom for the incontinent, American Journal of Nursing, 80(3), 482– 4. Bladder and Bowel Foundation (2010), Directory of Incontinence Products, at http:// www.continence-foundation.org.uk/directory/index.php. Brown D S (1994a), Diapers and underpads, Part 1: Skin integrity outcomes, Ostomy Wound Management, 40(9), 20–6, 28. Brown D S (1994b), Diapers and underpads, Part 2: Cost outcomes, Ostomy Wound Management, 40(9), 34–6, 38, 40. Clarke-O’Neill S, Pettersson L, Fader M, Dean G, Brooks R and Cottenden A (2002), A multicentre comparative evaluation: pants with integral pad for light incontinence, Journal of Clinical Nursing, 11, 79–89. Continence Foundation (2000), Making the Case for Investment in an Integrated Continence Service, p. 16. Published by the Continence Foundation (now the Bladder & Bowel Foundation), SATRA Innovation Park, Rockingham Rd, Kettering, NN16 9JH, UK. Cottenden A M, Moore K N, Fader M J and Cremer A W (1999), Is there a risk of crossinfection from laundered reusable bedpads?, British Journal of Nursing, 8(17), 1161–3.

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Cottenden A, Bliss B, Buckley B, Fader M, Getliffe K, Paterson J, Pieters R and Wilde M (2009), Management with Continence Products, pp. 1519–1642 in Incontinence, Fourth edition (eds Abrams P, Cardozo L, Khoury S and Wein A), Health Publications Ltd, Plymouth, UK. Dolman M (1988), Continence. The cost of incontinence, Nursing Times, 84(31), 67–9. Fader M, Macaulay M, Pettersson L, Brooks R and Cottenden A (2005), A multi-centre evaluation of absorbent products for men with light urinary incontinence. Neurology and Urodynamics, 24(5&6), 475–477. Fader M, Cottenden A, Getliffe A, Gage H, Clarke-O’Neill S, Jamieson K, Green N, Williams P, Brooks R and Malone-Lee J (2008), Absorbent products for urinary/faecal incontinence: a comparative evaluation of key product designs, Health Technology Assessment, 12(29) (www.hta.ac.uk/1303). Grant R (1982), Washable pads or disposable diapers?, Geriatric Nursing, 3(4), 248–251. Haeker S (1986), What’s best – reusable or disposable incontinence products?, Textile Rental, 69(9), 86–91. Harper D W, O’Hara P A, Lareau J, Cass J, Black E K and Stewart S (1995), Reusable versus disposable incontinent briefs: a multiperspective crossover clinical trial, Journal of Applied Gerontology, 14(4), 391–407. Hu T W, Kaltreider D L and Igou J F (1988), Disposable versus reusable incontinent products: a controlled cost-effectiveness experiment, Ostomy Wound Management, 21, 46–53. Hu T W, Kaltreider D L and Igou J (1990), The cost-effectiveness of disposable versus reusable diapers. A controlled experiment in a nursing home, Journal of Gerontological Nursing, 16(2), 19–24. Hunskaar S, Burgio K, Clark A, Lapitan M C, Nelson R, Sillen U and Thom D (2005), ‘Epidemiology of urinary and faecal incontinence and pelvic organ prolapse’, p. 265 and following, and p. 281 and following, in Incontinence. Third edition (eds Abrams P, Cardozo L, Khoury S and Wein A), Health Publications Ltd, Plymouth UK. Landeryou M, Lilburn D, Cottenden D and Cottenden A (2003), Liquid distribution in small reusable body-worn incontinence pads, Proceedings of Incontinence: The Engineering Challenge, Institution of Mechanical Engineers, London, October 2003. Macaulay M, Clarke-O’Neill S, Fader M, Pettersson L and Cottenden A (2004), A pilot study to evaluate reusable absorbent body-worn products for adults with moderate/heavy urinary incontinence, Journal of Wound Ostomy and Continence Nursing, 31(6), 357– 366. Mao N, Russell S J and Pourdeyhimi B (2007), ‘Characterisation, testing and modelling of nonwoven fabrics’, pp. 415–423 in Handbook of Nonwovens (ed.) Russell S J, Textile Institute/CRC Press/Woodhead Publishing, Cambridge, UK. Merrett S, Adams L and Jordan J (1988), Incontinence research provides some answers, Australian Nurses Journal, 18(2), 17–18. WSP (2005), Standard test methods for the nonwovens industry, Worldwide Strategic Partners (INDA and EDANA).

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11 Biological containment suits used in microbiological high containment facilities and by emergency responders J. T. W A L K E R, K. G I RI, T. P O T T A G E, S. P A R K S, A. D A V I E S and A. M. B E N N E T T, HPA, UK and C. L E C U L I E R and H. R A O U L, Laboratoire

P4 INSERM Jean Mérieux, France

Abstract: A range of suits are available to provide operator protection against biological and chemical agents. These suits are composed of various impervious, non-absorbent materials that are used to reduce the attachment or retention of chemical or biological agents. The properties of the suits and their composite materials have both advantages and disadvantages that have to be considered when selecting appropriate protective wear for any circumstance involving highly pathogenic micro-organisms. This chapter describes the suits available for different purposes and locations when dealing with either biological or chemical agents, and the decontamination procedures that should be carried out following their use. Key words: microbiological containment, positive pressure air-fed suits, hazardous and rapid response teams, biological containment suits, Biological Safety Level 4 facilities (BSL4).

11.1

Introduction

Over the last decade there has been an increase in the number of incidents involving hazardous substances, whether naturally occurring or deliberately released (Bennett, 2006; North et al., 2005; Alexander, 2003; Bree and Stevenson, 2002; Blendon et al., 2002). Protecting those who respond to and prepare for such events is of paramount importance (Grugle and Kleiner, 2007; Stephens, 2009; Hick et al., 2003). A level of protection that is sufficient to prevent operator exposure to hazardous substances or organisms while enabling the operator to perform their work safely and with as little restriction on their freedom of movement as possible is essential. For those who work with hazardous substances in the laboratory, this may be a structural barrier, such as a fume cabinet for chemicals, microbiological safety cabinets (MSC) for biological pathogens, or safety shielding items for nuclear laboratory equipment (Clark et al., 1988; Barbeito and Taylor, 1968; Klein and Weilandics, 1996; Klemola, 2008; Kubale et al., 2008; Lepoire et al., 2008). However, often containment cabinets are not suitable or appropriate for the work that needs to be carried out. A number of high 173 © Woodhead Publishing Limited, 2011

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containment laboratories and emergency services use positive pressure air-fed suits, the properties, design and associated requirements of which vary according to the type of hazard: chemical, biological, radiological, nuclear or explosive. This chapter reviews the different types and material characteristics of suits used to protect workers from exposure to a biological hazard that is present either as a result of an accident or deliberate release (bioterrorism).

11.2

Containment fabrics to protect against biological threats

The level of protection and containment that is required to protect operators from exposure to micro-organisms varies according to a defined microbial hazard group (Table 11.1), as classified by the World Health Organization (WHO) Laboratory Biosafety Manual, 2004 (http://www.who.int/csr/resources/publications/biosafety/ Biosafety7.pdf). The level of personal protective equipment (PPE) required is balanced against the hazard group of the organism, ranging from 1 to 4: the higher the hazard group, the higher the level of containment and PPE required. A biological agent that is classified as Risk Group 1 is unlikely to cause a human disease. Risk Group 2 micro-organisms can cause human disease, but rarely in Table 11.1 Definition of the WHO Risk Group hazard categories (courtesy of WHO) WHO Risk Group

Definition of hazard

Example micro-organisms

1

Unlikely to cause human disease

Bacillus atrophaeus, Staphylococcus epidermidis

2

Can cause human disease and may be a hazard to employees. Unlikely to spread to the community and there is usually a treatment available

Pseudomonas aeruginosa Campylobacter jejuni Escherichia coli (except nonpathogenic strains) Staphylococcus aureus

3

Can cause severe human disease E. coli O157 and may be a serious hazard to Bacillus anthracis employees. It may spread to the Mycobacterium tuberculosis community, but there is usually effective prophylaxis or treatment available

4

Causes severe human disease and is a serious hazard to employees. It is likely to spread to the community and there is usually no effective prophylaxis or treatment available

Ebola virus Marburg virus Crimean-Congo haemorrhagic fever virus Variola (smallpox) and monkey pox virus

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healthy individuals, and it is unlikely these micro-organisms will spread to the community. Effective treatments are available to treat infected people and limit the spread of infection. These organisms can be handled safely within a Containment Level 2 (CL2) or Biological Safety Level 2 (BSL2) laboratory using good laboratory practice. However, there are a number of criteria where Risk Group 2 agents need to be handled within a BSL3 laboratory, such as when large culture volumes are being grown or there is the risk of aerosolisation (Buswell et al., 2001; Rogers et al., 1994; Bacon and Hatch, 2009; Bacon et al., 2010). Risk Group 3 micro-organisms can cause severe human disease, presenting a serious hazard to personnel, but there is usually an effective treatment available. These micro-organisms must be handled within a BSL3 laboratory, where the pathogens must be contained within a microbiological safety cabinet (MSC) to protect the worker. Currently in the UK, Risk Group 4 organisms must be handled inside Class III MSCs that are joined together to form a continuous sealed cabinet line. These Class III MSCs contain all the equipment that is required to work with Risk Group 4 micro-organisms, such as incubators and centrifuges. The pathogenic sample (in three layers of packaging) enters one end of the cabinet line through a decontamination dunk tank (containing an appropriately validated chemical agent). The sample is then passed down the central spine of the cabinet line where work can be carried out. When the work has been completed, the sample is triple contained and passed through a dunk tank containing an approved and validated disinfectant, and is removed into the laboratory. Finally the sample is placed in an integral autoclave so that any remaining sample or waste from the procedures is destroyed prior to safe disposal. Whilst MSCs provide the primary protection for the worker, there are certain circumstances, such as work with animals, which preclude the use of a rigid safety cabinet. While Risk Group 3 micro-organisms would usually be contained in a microbiological safety cabinet, the welfare of the animals prior to and during infection needs to be maintained (Clark et al., 2008; Sharpe et al., 2010; Williams et al., 2009; HSC Advisory Committee on Dangerous Pathogens, 1997). There are guidelines that limit the amount of air changes and restrict the temperature range to which the animals may be subjected that can restrict the use of normal MSCs. Instead the animals can be housed within large containment rooms where laboratory operators wear appropriate personal protective equipment to provide a barrier against the micro-organism.

11.2.1 Positive pressure laboratory containment suits Fixed cabinet lines can present inherent ergonomic issues, due to their inflexibility as well as physical and space limitations, and are not generally used for animal husbandry. As a consequence of these drawbacks, a number of institutes across the world that handle Risk Group 4 micro-organisms use positive pressure

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11.1 An ILC Dover Chemturion suit with umbilical air line.

11.2 A Delta Mururoa suit being used in a simulated decontamination shower.

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containment suits, e.g. in Winnipeg (Canada) and Lyon (France). Air-fed positive pressure suits enable operators to work with micro-organisms on the bench, in an open fronted Class II MSC within the laboratory, or carry out animal husbandry duties, according to the activities they are performing. The positive pressure suits give a range of freedom to the worker that is not available to those using cabinet lines. Medical grade breathing air is supplied to the operators from a compressor (or auxiliary gas bottles) through a set of filters to remove any contaminants via compressed gas air lines. This airflow also raises the pressure within the suit relative to the surrounding environment causing the suit to ‘inflate’ so that if the suit becomes torn or a hole develops the positive pressure will force the air out of the suit and prevent any ingress of a pathogenic aerosol. The suits used at BSL4 come in a variety of designs, the use of which must be considered in conjunction with the design of the BSL4 laboratory. Full body biological containment suits are constructed as all-in-one suits with a zip to allow entry and exit of the operator. The zips often have to be greased to aid opening and closing and to lengthen their life span. Biological suits that use an allin-one design are intended to be reusable; for example, ILC Dover’s Chemturion BSL4 suit (Fig. 11.1) and Delta Mururoa suit (http://www.sperianprotection.eu) (Fig. 11.2). The ILC Dover Chemturion suits cost approximately €3300 (in 2010) and are constructed from a base polymer of durable blue waterproof chlorinated polyethylene (Cloropel™) with a large visor, made from a base polymer of polyvinyl chloride (PVC), to enable a good field of vision. Chlorinated polyethylene was chosen by the manufacturer as the base polymer because of its overall high rating when tested for resistance to many industrially used chemicals. The ILC Dover Chemturion suits have been tested in accordance with the NFPA 1991 Standard on Vapour-Protective Ensembles for Hazardous Materials Emergencies, 2000 edition, Section 6–8 Overall Ensemble Inward Leakage Test. The results demonstrated that the suit model tested (3525) exceeded the industry standards for preventing inward leakage and operator protection factor (OPF). The Delta suits are made from a polyester fabric with a PVC coating (450 g/m²), sealed with high frequency welding. The suits weigh approximately 1.6 kg, are resistant to decontamination shower viricides, and cost in the region of €4000 (in 2010). Each suit undergoes a rigorous visual inspection before each use by the wearer/ operator and is regularly subjected to a series of pressure hold tests to demonstrate its continued protection functions. In use, compressed air is supplied to the suit via an umbilical cord and is directed into a Scott NIOSH approved pass-through valve incorporating a high efficiency particulate absorption (HEPA) filter. Air then exits through four exhaust valves, two located in the legs and two in the upper back. Each valve is protected by an integral splash cover. The volume of air leaving the suit (through one way magnetic valves) is initially less than the volume of air entering the suit, creating

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a positive pressure to ‘inflate’ the suit. Once this pressure difference has been achieved, the air volumes into and out of the suit equilibrate, resulting in a constant positive pressure within the suit. The airflow to the ILC Dover suit is a minimum of 142–255 L/min and the Delta suit requires 470–950 L/min. A gas and airtight pressure sealing zipper in the front of the Delta and Dover suits allows entrance to the suit. Moulded wrist cuffs with mating rubber wrist rings for attachment of protective gloves are incorporated into the suits. Gloves can be removed and selected depending on the tasks to be carried out but are generally disposable butyl, PVC and/or neoprene. The gloves are also inspected prior to the suit being worn but are not subjected to pressure testing. The suit legs of the ILC Dover consist of an integrated bootie of the same material with a large overhanging gauntlet. The integrated booties are worn inside hardwearing boots, such as Wellington boots, with gauntlet tabs pulled down over the outside of the Wellington boots to prevent spillage into the outer boots (Fig. 11.1). The Delta suit has integrated boots (Fig. 11.2). These suits are not without their problems. Bending over can change pressure differentials causing the suit to collapse, they are difficult to get in and out of, and some people find them claustrophobic. Working in positive pressure suits can also be very uncomfortable: the air temperature inside the suits can rapidly rise to > 30 ºC at which point wearing the suit even for moderate working can cause significant physiological stress (Cortili et al., 1996; Hussey, 2005) and overheating. However, this can be overcome by conditioning the supply air. Some laboratories issue noise reduction hearing protectors to their workers as well as supplying compressed air that has passed through a noise reduction venturi.

11.2.2 Containment suits outside the laboratory Positive pressure suits are not solely used within the laboratory environment. Different situations require different suit applications, some of which require reusable suits and others single-use suits. Containment suits may be employed for use in a number of situations, such as in emergency response (fire brigade, ambulance and police) by first responders, and for those specialist personnel carrying out environmental sampling. Different suit designs will be needed depending on the requirements of the scenario. For example, to protect against a chemical or biological hazard requires different filters to be used. The presence of a biological agent warrants the use of a HEPA filter, to remove the organisms from the breathing air, while an activated carbon filter is required for chemical agents. Often both filters will be used in case the hazard is not immediately identified. Alternatively, a compressed air line or a self-contained breathing apparatus can be used to provide uncontaminated air to the suit user, negating the need for filters and a source of possible breach by the hazard. The choice of suit is also affected by the environment in which the suit is to be used. A suited high containment laboratory must be designed to incorporate the use

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11.3 A Martindale half suit with air filters and battery pack (round waist), gloves are taped onto the ends of the arms.

of reusable positive pressure suits. Since the suits are fed with air from compressors or gas cylinders through a compressed air line, the length of the air line feeding the suit restricts the distance from the air supply that the suit can be used. For work that needs to be undertaken outside of the laboratory, such as environmental sampling of pathogenic micro-organisms, a fixed air supply via an umbilical cord is clearly unsuitable. A half-suit such as the Martindale suit (Fig. 11.3) that is not connected to an umbilical air line provides sufficient freedom of movement to complete the task whilst affording suitable protection and is more appropriate. Suits that use either a battery-operated fan unit in combination with filters or a selfcontained breathing apparatus are ideally suited to these environments. Battery packs provide a mobile clean air supply, allowing the user to move freely to complete their operation. However, the time spent within suits with an independent air supply is limited by the battery life of the units. Batteries need to be maintained to ensure guaranteed battery life for the whole operation and need to be designed either to be decontaminated or to be single-use only.

11.2.3 Single piece suits for first responders Hazardous Area Response Team (HART) is the generic term applied to specially recruited and trained personnel who provide the ambulance response to major incidents. These incidents may involve chemical, biological, radiological, nuclear (CBRN), explosive (E) or other hazardous materials, or could involve other

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complex scenarios such as train crashes, large-scale motorway accidents, building collapses or significant fires (Grugle and Kleiner, 2007). These scenarios could be the result of an accident or caused deliberately. HART works alongside fire and rescue services within an ‘inner cordon’ (or ‘hot zone’) of a major incident. Their job is to triage and treat casualties and to save lives in very difficult circumstances. The team also has a role in looking after other emergency service personnel who may become injured whilst attending incidents. HART may also be involved in providing decontamination facilities for ‘Bioresponse Teams’ during a biological incident. While responding to these incidents, HART, in the UK, wear disposable Respirex PRPS suits (Respirex International Ltd), designed to be worn by emergency response personnel following a CBRN incident. These are lime yellow one-piece gas-tight chemical protective suits manufactured from DuPont Tychem TK, a high performance multi-layer, non-woven fabric sandwiched between proprietary non-halogenated barrier films that act as a chemical barrier. The suit has a dual glove system comprising neoprene outer gloves bonded to inner Silver Shield® (North®, USA) laminate gloves. Sizes of glove vary according to suit size, with a gas-tight locking cuff mechanism. A pair of cotton gloves is also supplied to ensure maximum comfort for the wearer. Footwear comprises highly chemically resistant HAZMAX safety boots with a steel toecap that are permanently attached to the suit. The respiratory system comprises an air filter unit (AFU) fitted with a visual display unit mounted inside the suit at the base of the visor.

11.2.4 Biological half suits The biological half suit is another approach to positive pressure suit protection. The suit is designed to be used with waterproof salopettes worn over Wellington boots sealed with waterproof tape to create an airtight seal. The suit itself consists of a PVC blouse, which incorporates a head section with a clear PVC visor allowing 360 degree visibility. The blouse section of the suit stops at the cuffs: separate butyl protective gloves are worn overlapping the suit cuffs and are taped to the suit with watertight tape to create an airtight seal. A Tyvek suit is worn under the salopettes and half suit, to provide a secondary barrier, additional comfort for the wearer and a modesty garment when removing the suit. Clean air is fed in from an external battery-powered fan and filter unit attached to a plastic belt, which is used to create a seal around the base of the blouse. The filtered air is carried via an external reinforced PVC tube, which enters the suit at the base of the rear of the hood section. The air is then diverted up over the head and pushed over the face of the user and down towards the chest of the suit. The air either leaves the suit from a valve at the rear of the hood or from underneath the blouse around the waist of the wearer. The use of a half suit with a battery-powered fan unit allows the user a greater

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level of freedom since they are not restricted by the distance that they can travel from a compressor by the length of the umbilical cord. The suits can be and are used for environmental sampling, decontamination work, and within high containment facilities for animal husbandry. However, certain environmental conditions can preclude the use of the half suit. Cold temperatures, for example, can make the suit very stiff and difficult to move in and the consequent decrease in dexterity may increase the risk of a suit failure in the event of an accident.

11.2.5 Passive respirator chemical, biological, radiological and nuclear (CBRN) suits The Armed Forces also use biological safety suits to protect their personnel. They are designated chemical, biological, radiological and nuclear (CBRN) suits and come in two pieces for rapid attire. These suits are not positive pressure; instead, air is breathed in through a negative pressure respirator. The respirator is worn with a seal made around it, using the hood of the upper part of the suit. Overshoes are worn in addition to the normal footwear already worn. A number of nations’ suits (e.g. USA, Canada and Russia) are made of impervious material that effectively prevents a biological agent from contacting the body. By contrast, the British suit is designed with a layer of activated charcoal between the fabric weave to absorb the microbiological agent. This suit gives more comfort to the wearer but also has a shorter lifespan because, as the charcoal absorbs moisture, its protection factor decreases.

11.2.6 Compressed air line or battery filter fan unit? Compressed air suits limit the freedom of the wearer because of the constraints associated with attachment to a fixed compressor pump. The powerful compressors needed to generate the high flow rates essential for a safe working environment within the suit require a particular electricity source (e.g. three-phase) stationed in close proximity. The ILC Dover Chemturion suit requires 142–255 L/min and the Delta biological suit requires 470–950 L/min of air for safe operation. Within a high containment laboratory there are numerous connectors suspended from the laboratory ceiling that allow connections and reconnections to be made as the personnel move through the laboratory. As a contingency in an emergency situation where there may be a failure in the power supply to the compressors, tanks of air must also be provided, although these air tanks may have a limited supply time and may provide only enough air to make safe and exit from the laboratory. The compressor sizes required effectively limits the use of these suits to an indoor laboratory environment and the space to incorporate the hardwiring of the air system must be designed and integrated into the construction of new high biological containment facilities. The length of the umbilical cord also limits the range that the suits can be operated away from the compressor.

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By comparison, biological containment suits with air supplied from a batterypowered filtration fan unit are more mobile and offer a greater level of freedom to the worker, allowing the worker to move independently through more complex areas. These suits are appropriate for work outside a laboratory such as environmental sampling for a biological agent (Anaraki et al., 2008; Riley, 2007). The main drawback for these systems is that the time within the suit is dependent on the capacity of the battery. It should also be noted that the length of time that the batteries can be used is reduced in cold weather. The filters must also be periodically changed.

11.2.7 Suit decontamination Positive pressure respiratory suits must be decontaminated on exit from the laboratory or from a hot zone. This can be carried out individually, or in pairs, i.e. with a laboratory buddy in a designated decontamination room. A decontamination room is generally designed to accommodate two (or more) laboratory partners who can assist each other in the cleaning process to ensure that all areas of the suits have been treated during the cleaning process. The length of decontamination and disinfectant used varies between facilities. For example, at the BSL4 facility in Lyon, suits are decontaminated for 4 minutes with a quaternary ammonium product (3% Sanytex, Roche) followed by a 2 minute rinse (30 L). In Winnipeg (Canada), the BSL4 facility uses MicroChem Plus (5%) for a 2 minute chemical wash (64 L) followed by a 3 minute rinse (159 L). In the event that the automatic shower fails there is a fail-safe manual system that can be used by the operators. Volumes of up to 260 L can be used in a single decontamination run. In BSL4 facilities, the waste water is stored and heated to sterilise the contents before being released into the domestic drain. Only three cycles of decontamination would therefore require storage for up to 1000 L. The decontamination approach for suits that are used outside of the laboratory environment, such as the Martindale half suit, follows the same method as for suits that are used within a laboratory. Following environmental sampling, the suit is initially rinsed with a suitable chemical disinfectant. This can be performed using, for example, sprayer bottles containing a 10 000 ppm sodium hypochlorite solution. However, the sodium hypochlorite solution must be in contact with the suit for the recommended time sufficient to kill the organism present, i.e. 10 minutes for Bacillus anthracis spores. While being sprayed, the suited worker must stand in a receptacle to collect any waste disinfectant that runs off the suit. The personnel in suits can then be further decontaminated by passing through an emergency disposable HAZMAT decontamination shower rig where the suit wearers are showered using detergents/disinfectants and are also scrubbed by other suited (nonexposed) personnel. The collected waste is either treated with a disinfectant to inactivate any biological hazards present prior to discharge to a drain, or transported to a safe location and treated using an alternative method such as heat treatment.

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Conclusions

Whilst cabinet lines have traditionally provided a high level of operator protection within the microbiological laboratory, the majority of high level containment microbiology centres across the world have designed their laboratories to operate with air-fed positive pressure respiratory suits. The suits used at BSL4 provide a level of flexibility for the operator and increases the range of duties, e.g. animal husbandry that can be undertaken whilst in the suit, in comparison with Class III microbiological safety cabinet lines. The most commonly used suits include the ILC Dover Chemturion BSL4 suit and the white Delta Mururoa suit. Positive pressure suits are also worn by Hazardous Area Response Teams and first responders to emergencies and incidents. The yellow suits worn in such circumstances have been produced to cope with either a chemical or biological attack. These suits are single-use and are disposed of once they have been worn. Other Government Agencies have also employed a biological half suit known as the ‘Martindale suit’. For military purposes a range of suits are available but are used with a negative pressure respirator that is worn under the suit. Reusable and singleuse suits are both decontaminated following any possible exposure. This is generally carried out in a shower using a range of water flows, volumes and chemical agents according to local HSE and occupational exposure limits. In conclusion a range of suits are available to provide operator protection against chemical and biological hazards and are composed of a range of impervious, nonabsorbent materials including PVC, and chlorinated polyethylenes that are used to reduce the attachment or retention of chemical or biological agents.

11.4

References

Alexander, D. A. (2003) Bioterrorism: Preparing for the unthinkable. J R Army Med Corps, 149, 125–30. Anaraki, S., Addiman, S., Nixon, G., Krahe, D., Ghosh, R., Brooks, T., Lloyd, G., Spencer, R., Walsh, A., McCloskey, B. and Lightfoot, N. (2008) Investigations and control measures following a case of inhalation anthrax in East London in a drum maker and drummer, October 2008. Euro Surveill, 13. Bacon, J. and Hatch, K. A. (2009) Continuous culture of mycobacteria. Methods Mol Biol, 465, 153–71. Bacon, J., Hatch, K. A. and Allnutt, J. (2010) Application of continuous culture for measuring the effect of environmental stress on mutation frequency in Mycobacterium tuberculosis. Methods Mol Biol, 642, 123–40. Barbeito, M. S. and Taylor, L. A. (1968) Containment of microbial aerosols in a microbiological safety cabinet. Applied Microbiol., 16, 1225–9. Bennett, R. L. (2006) Chemical or biological terrorist attacks: an analysis of the preparedness of hospitals for managing victims affected by chemical or biological weapons of mass destruction. Int J Environ Res Public Health, 3, 67–75. Blendon, R. J., Benson, J. M., Desroches, C. M., Pollard, W. E., Parvanta, C. and Herrmann, M. J. (2002) The impact of anthrax attacks on the American public. Med Gen Med, 4, 1.

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Bree, M. and Stevenson, J. (2002) Response to bioterrorism. US anthrax incidents led to scares in Scotland. Brit Med J, 324, 363. Buswell, C. M., Nicholl, H. S. and Walker, J. T. (2001) Use of continuous culture bioreactors for the study of pathogens such as Campylobacter jejuni and Escherichia coli O157 in biofilms. Meth Enzymol, 337, 70–8. Clark, R. P., Rueda-pedraza, M. E., Teel, L. D., Salkin, I. F. and Mahoney, W. (1988) Microbiological safety cabinets and laboratory acquired infection. Lancet, 2, 844–5. Clark, S., Cross, M. L., Smith, A., Court, P., Vipond, J., Nadian, A., Hewinson, R. G., Batchelor, H. K., Perrie, Y., Williams, A., Aldwell, F. E. and Chambers, M. A. (2008) Assessment of different formulations of oral Mycobacterium bovis Bacille CalmetteGuerin (BCG) vaccine in rodent models for immunogenicity and protection against aerosol challenge with M. bovis. Vaccine, 26, 5791–7. Cortili, G., Mognoni, P. and Saibene, F. (1996) Work tolerance and physiological responses to thermal environment wearing protective NBC clothing. Ergonomics, 39, 620–33. Grugle, N. L. and Kleiner, B. M. (2007) Effects of chemical protective equipment on team process performance in small unit rescue operations. Appl Ergon, 38, 591–600. Hick, J. L., Penn, P., Hanfling, D., Lappe, M. A., O’laughlin, D. and Burstein, J. L. (2003) Establishing and training health care facility decontamination teams. Ann Emerg Med, 42, 381–90. HSC Advisory Committee on Dangerous Pathogens (1997) Working Safely with Research Animals: Management of Infection Risks, HSE Books, Sudbury. Hussey, D. (2005) Evaluation of Cooling Technologies: Delta Mururoa Suit and AVAcore. Electric Power Research Institute, California, USA. Klein, R. C. and Weilandics, C. (1996) Potential health hazards from lead shielding. Am Ind Hyg Assoc J, 57, 1124–6. Klemola, S. K. (2008) Inter-laboratory comparisons of short-lived gamma-emitting radionuclides in nuclear reactor water. Appl Radiat Isot, 66, 760–3. Kubale, T., Hiratzka, S., Henn, S., Markey, A., Daniels, R., Utterback, D., Waters, K., Silver, S., Robinson, C., Macievic, G. and Lodwick, J. (2008) A cohort mortality study of chemical laboratory workers at Department of Energy nuclear plants. Am J Ind Med, 51, 656–67. Lepoire, D., Richmond, P., Cheng, J. J., Kamboj, S., Arnish, J., Chen, S. Y., Barr, C. and Mckenney, C. (2008) Web-based training course for evaluating radiological dose assessment in NRC’s license termination process. Health Phys, 95 Suppl 2, S137–42. North, C. S., Pollio, D. E., Pfefferbaum, B., Megivern, D., Vythilingam, M., Westerhaus, E. T., Martin, G. J. and Hong, B. A. (2005) Concerns of Capitol Hill staff workers after bioterrorism: focus group discussions of authorities’ response. J Nerv Ment Dis, 193, 523–7. Riley, A. (2007) Report on the management of an anthrax incident in the Scottish borders. http://www.nhsborders.org.uk/__data/assets/pdf_file/0019/6580/anthrax_report_ 131207.pdf. Rogers, J., Dowsett, A. B., Dennis, P. J., Lee, J. V. and Keevil, C. W. (1994) Influence of temperature and plumbing material selection on biofilm formation and growth of Legionella pneumophila in a model potable water system containing complex microbial flora. App Environ Microbiol, 60, 1585–92. Sharpe, S. A., McShane, H., Dennis, M. J., Basaraba, R. J., Gleeson, F., Hall, G., McIntyre, A., Gooch, K., Clark, S., Beveridge, N. E., Nuth, E., White, A., Marriott, A., Dowall, S., Hill, A. V., Williams, A. and Marsh, P. D. (2010) Establishment of an aerosol challenge model of tuberculosis in rhesus macaques, and an evaluation of endpoints for vaccine testing. Clin Vaccine Immunol, 17(8), 1170–82.

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Stephens, S. J. (2009) Case study on industrial hazmat response teams. J Bus Contin Emer Plan, 4, 22–32. Williams, A., Hall, Y. and Orme, I. M. (2009) Evaluation of new vaccines for tuberculosis in the guinea pig model. Tuberculosis (Edin), 89, 389–97.

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12 Coated textiles for skin infections G. S E N T I, A. U. F R E I B U R G H A U S and T. M. K Ü N D I G, Centre for Clinical Research, University Hospital of Zurich, Switzerland

Abstract: This chapter gives an overview of the current developments in anti-infectious textiles used for patients prone to skin infections. Clinical data are available for the common condition of atopic dermatitis (eczema), which predominantly affects children and young adults. The clinical picture of atopic dermatitis is dominated by pruritus (itching) and ensuing skin damage from excessive scratching. The self-inflicted cutaneous wounds and a genetic predisposition towards an impaired barrier function of the skin promote infections with ubiquitous germs, such as Staphylococcus aureus. Clothes in contact with eczematous skin may promote microbial growth. Clothes made from fibres coated with anti-infectious compounds appear to reduce microbial colonization and improve symptoms in atopic dermatitis. Various types of fibres and coatings are described. The rather scant clinical evidence for their effectiveness is reviewed. Commercially available anti-infectious garments are made from fibres coated with immobilized or adsorbed silver or a quaternary ammonium base. Another clinical use of anti-infectious textiles on skin are wound dressings. No clinical trials have been published for antimicrobial textile wound dressings, but in vitro tests provide evidence of diminished microbial growth in wounds covered with such pads. Key words: antimicrobial garments, atopic dermatitis, quaternary ammonium base, silver coating, skin infection.

12.1

Introduction: textiles, skin and infections

Since the phylogenetic loss of fur (Rantala, 2007), Homo sapiens has needed to protect his skin with acquired animal skin or some form of fabric in all but a few climatic zones. Very late in evolution, the technical skills of man reached a level that allowed the production of textiles for many more purposes than just avoiding loss of heat or mechanical injury. While the use of textiles on human skin is overwhelmingly beneficial to the wearer (Elsner, 2003), there are situations when the intimate contact of fabrics (or animal skins) with injured or irritated skin may be harmful (Fenske and Lober, 1990; Bolognia, 1995; Fisher et al., 2002; Romagnani, 2004). Mechanical or chemical properties of textiles may lead to skin affections, e.g. chafe, toxicity or allergy. Fabrics may also contribute to skin infection, especially where skin is already injured or stressed. Tightly woven fabrics may favour bacterial or fungal growth by maintaining a moist and warm environment, and fabrics may themselves harbour bacteria (e.g. Teufel et al., 186 © Woodhead Publishing Limited, 2011

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2010). Indeed, the three-dimensional structure of textiles with a high proportion of ‘empty’ and capillary spaces, and the hydrophilic or lipophilic surfaces of the fibres have a tendency to absorb aqueous or fatty liquids or emulsions, as well as particulate dirt. These same properties of textiles can be a blessing or a curse. On the one hand, textiles soaked in medicinal compounds, for example, are helpful in wound care. On the other hand, fabrics soaked in sweat or exudates offer an ideal substrate and nutrients for pathogenic bacteria or fungi. The combination of mechanical irritation, susceptible skin, and ‘infectious’ textiles is a particularly unfavourable trio. In order to shift the balance towards bless, the fibre surface can be modified in ways that make it one or all of less absorptive, drug eluting, or even germicidal. Such textiles have become commercially available in the last decade. The marketing efforts raise great hopes in those parts of the population who suffer from ‘stinking socks’ and, of special interest here, who suffer from dermatological conditions such as atopic dermatitis or eczema with bacterial or fungal super infections. Moderately priced functional textiles that can, at the same time, stop and/or prevent infections, add to the quality of life, and reduce the need for medication, are a very attractive prospective for the individual and the healthcare system. Unfortunately, the marketing efforts seem to be disproportionately high compared with the current extent of systematic clinical evidence for the benefit of anti-infectious textiles.

12.2

Types of coated textiles with anti-infectious properties

Currently available textiles with anti-infectious properties are woven or knitted fibres fashioned into various garments and underwear, e.g. T-shirts, pants, leggings, socks, shoe linings, inlay soles, as well as wound dressings (Table 1 in Heide et al., 2006). Frequently used fibres for commercial anti-infectious textiles are made of proteinacious native silk or denuded silk devoid of the allergenic component sericin (DermaSilk®, Al.Pre.Tec. S.r.l., Verona, Italy) (Koller et al., 2007). Other common natural fibres are cellulose as in natural cotton or, more recently, seaweed-derived cellulose fibres (SeaCell® Active, Smartfiber AG, D07407 Rudolstadt) (Zikeli, 2006). Artificial fibres, e.g. polyamides (PA 6.6 a.k.a. nylon) are also used for garments (SkinProtect®, Julius Zorn GmbH, Aiersbach, Germany) and medical (wound) dressings (Adams et al., 1999). The germicidal properties of silver, though not known as such, have been exploited for centuries (Silvestry-Rodriguez et al., 2007). Its earliest systematic use in modern medicine was introduced by Credé in the second half of the 19th century to prevent gonorrhoeic ophthalmia in newborns (Oriel, 1991). Numerous ways of ‘coating’ fibres with silver are known to convey antimicrobial properties (Djokic, 2008). Ionized silver has broad spectrum antibacterial properties (Lansdown, 2002b), hardly ever causes drug resistance, and is well tolerated

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(Lansdown, 2002a). Anti-infectious textiles expose silver in a non-metallic, oxidized form at the surface of the component fibres, even in the case of pure silver coated filaments (X-Static®, Noble Fiber Technologies Inc., Scranton PA, USA, and Padycare®, Tex-A-Med GmbH, Gefrees, Germany). Similarly to silver, copper has been used since early times for fighting microbes, and it is also reported to have antiviral properties (Borkow and Gabbay, 2005). Various methods have been established for attaching copper to textile fibres (Borkow and Gabbay, 2004). Quaternary ammonium bases in solution are widely used as disinfectants, and a derivative tertiary ammonium base (3-trimethylsilylpropyl-dimethyloctadecyl ammonium chloride, AEGIS AEM 5772/5) immobilized to silk fibres (Gettings and Triplett, 1978) has found commercial application in anti-infectious textiles (DermaSilk®, Al.Pre.Tec. S.r.l., Verona, Italy). Aqueous solutions of the said compounds have proven their anti-infectious power in many biological and medical situations in vitro and in vivo. To control the toxicity for human cells and tissues, appropriate concentrations of the substances must not be exceeded. Using textiles soaked in anti-infectious solutions is a traditional way to treat/prevent skin infections, but may be flawed by undesired systemic absorption of the active compounds through the skin. To avoid potential toxicity and to assure a prolonged antimicrobial effect over many washing cycles, manufacturing processes are required that sufficiently immobilize the reactive groups on the fibres. The immobilization may be permanent with virtually no detectable release of active chemicals. Alternatively, fibres can be engineered to release active molecules very slowly. Commercial anti-infectious wearable textiles for which clinical data are available are made from fibres with permanently immobilized germicidal agents.

12.3

Applications for coated textiles to prevent or treat cutaneous infections

The literature is aware of two general applications of anti-infectious textiles, namely garments and wound dressings. Garments are available as sleeves, underwear, T-shirts and pyjamas, as well as sheets, pillowcases and under pads. Wound dressings are sold as sterile pads in various dimensions.

12.3.1 Garments Disease Atopic eczema (according to the recommendation of the World Allergy Organization 2003 Nomenclature Task Force (Johansson et al., 2004)) or atopic dermatitis (AD, the more popular term in the literature), is the only clinical entity for which garments made of coated textiles have been systematically tested in patients.

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Atopic eczema is an inflammatory, chronically relapsing, non-contagious and extremely itching skin disease that is also named ‘neurodermatitis’ or ‘endogenous eczema’, etc. It is one of the most common dermatoses, with an overall prevalence of two to five per cent, and even ten per cent in children and young adults. Patients have a genetic predisposition for the disease, but environmental factors modulate the intensity and the development of allergies (Ring et al., 2006, Ring and Darsow, 2008). Skin infections are frequently seen in patients with eczema. The infections may occur as secondary superinfections, but may also be a contributing factor. Staphylococcus aureus is a common germ found in skin infections and patients with eczema appear to have an enhanced susceptibility for this bacterium (Bunikowski et al., 2000). Non-clinical evidence Fibres coated with non-migrating known antimicrobial compounds (e.g. silver, copper, quaternary ammonium bases) have been shown to have an inhibitory effect on the growth and survival of a number of pathogenic germs commonly found on (diseased) skin. As the anti-infectious effect can be exerted only when the germs are in contact with the fibres, a key issue in using anti-infectious garments is the close contact of the textiles with the skin or its exudates. Therefore, factors such as fabric type, fabric density, tailoring, sizing and wearing compliance are of importance for the clinical application. Clinical evidence Nine publications in peer reviewed journals report on clinical applications of garments made of three different types of fibres and two germicidal compounds (silver and a quaternary ammonium base). Five clinical trials (Ricci et al., 2004; Senti et al., 2006; Ricci et al., 2006; Koller et al., 2007; Stinco et al., 2008) used DermaSilk® textiles made of sericin-free silk coated with the quaternary ammonium base AEGIS AEM 5772/5. Three trials used Padycare® garments (Gauger et al., 2003, 2006) made of 82% silver coated polyamide and 18% polyurethane– polyurea copolymer (elastane a.k.a. spandex) or SkinProtect® garments (Juenger et al., 2006) made of 67% polyamide, 15% polyurethane–polyurea copolymer and 18% X-Static® silver filaments. One recent trial tested SeaCell® Active T-shirts made of silver-ion loaded cellulose fibres derived from seaweed (Fluhr et al., 2010). Eight reports concluded that the tested anti-infectious garments improved the symptoms compared with a control and one report found no difference (Ricci et al., 2006). The reports involved a total of 271 patients (12; 15; 15; 22; 26; 30; 37; 46; 68) of which 203 were exposed to anti-infectious fibres. At least 162 patients were children younger than 17 years. Some 129 patients were their own control (side-byside or sequential-periods comparisons). All but one study monitored subjective

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criteria such as pruritus scores (Schmitt et al., 2007) (seven times SCORAD, once EASI) and/or visual analogue or step scales (skin appearance, quality of life, wearing comfort, etc.) as primary outcome parameters. Objective criteria were used to monitor clinical efficacy in one study testing bacterial colonization and skin physiology parameters only (Fluhr et al., 2010), and two studies used S. aureus skin colonization as a second parameter (Gauger et al., 2003; Ricci et al., 2006). Observation periods were one week (Ricci et al., 2004, 2006), two weeks (Gauger et al., 2003, 2006; Juenger et al., 2006), three weeks (Senti et al., 2006), four weeks (Stinco et al., 2008), and 12 weeks (Koller et al., 2007; Fluhr et al., 2010). Four of the studies were single-blinded (Ricci et al., 2004; Juenger et al., 2006; Koller et al., 2007; Fluhr et al., 2010), two double-blinded (Gauger et al., 2006, Stinco et al., 2008) and three were not explicitly blinded (Gauger et al., 2003; Senti et al., 2006; Ricci et al., 2006). Patient numbers were small, observation periods short, and most of the assessed parameters were of a subjective nature (pruritus, overall improvement, clinical assessment, visual appearance, etc.). Compliance in this type of study tends to be compromised, particularly in paediatric patients. In two studies the control fabric was untreated cotton, while the verum was coated sericin-free silk. Silk is reported to be better tolerated than cotton, due to lower mechanical irritation (Diepgen et al., 1990; Arcangeli et al., 2002). Although the scientific evidence of the individual studies is not overwhelmingly strong, all but one study concluded that the tested antimicrobially coated textiles were superior to the non-coated control fabrics. Two studies non-enthusiastically concluded that ‘special silk clothes may be useful in the management of AD in children’ (Ricci et al., 2004) or ‘showed potential to become an effective treatment of AD’ (Senti et al., 2006). Two studies testing bacterial colonization of the skin found lower counts under silver-containing textiles than in the control area after two weeks (Gauger et al., 2003) and 12 weeks (Fluhr et al., 2010), while one study with twelve children found no difference after seven days (Ricci et al., 2006). No adverse effects were noted that could have been caused by the coated textiles. Overall, the clinical studies suggest that at least three commercial brands of antiinfectious textiles may be beneficial for paediatric and adult patients with eczema, and that they are well tolerated and well accepted by patients. Evidence that the antimicrobial function of the textiles is at least partially responsible for the observed effects is insufficient, but plausible. No cost-effectiveness data have been published for anti-infectious garments. Considering the potential saving of (anti-infectious or anti-pruritic) ointments and, particularly, steroid treatments, the higher price of these textiles may be justified.

12.3.2 Dressings Lansdown (2002a) has reviewed the toxicity of silver in mammals and how its products aid wound repair. Dowsett (2004) has reviewed a number of commer-

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cially available silver-based dressings. Among them only Acticoat® (a polyethylene mesh coated with nanocrystalline silver, with a rayon–polyester core, Smith and Nephew, UK) and Urgotul SSD® (a textile polyester net coated with silver sulphadiazine, URGO Medical, France) are of a textile nature. Both dressings release ionic silver. Petrulyte (2008) recently outlined and reviewed the latest developments and advances in medical textiles and biopolymers for wound management, providing an overview with generalized scope about novelties in products and properties. Disease Skin wounds are prone to infection with resident germs (e.g. S. aureus) and with microbes from non-sterile objects or fluids in contact with the mutilated skin. The germs may be brought in during the process causing the wound, or later on by way of contamination from the skin adjacent to the defect or from non-sterile matter in contact with the wound. An open wound presents ideal conditions for the growth of microbes (unlimited organic nutrients, moisture, and temperature). Natural defence mechanisms (bleeding, humoral responses, inflammation, leukocyte invasion, etc.) may suffice to combat excessive microbial growth, but anti-infectious measures are often needed, e.g. application of topical or systemic antibiotics. The latter carry a risk of adverse effects and bacterial resistance. Wound dressings with anti-infectious properties immobilized on fibres can be an additional measure to impede microbial growth without these risks. Non-clinical evidence Already in 1987 it was recognized that available wound dressings were not able to control wound infections in burn patients. Deitch et al. (1987) provided evidence that silver-leaching nylon wound dressings had a germicidal effect on three common strains of skin resident bacteria (S. aureus, P. aeruginosa, and C. albicans) as long as the dressings were in contact with the wound. Adams et al. (1999) evaluated in vitro a silver chloride-coated nylon wound dressing for veterinary use for its antimicrobial activity against five common equine wound pathogens. As silver ions were released by the dressing, the antibacterial effect was confirmed, when compared with a silver chloride solution in a germicidal concentration. Lee et al. (2007) tested the product of a novel procedure for producing nanosized stable silver particles on cotton fabrics. The antibacterial effect of the silver-nanocoated fabrics on various bacteria was evaluated by growth inhibition tests. The authors also performed skin irritation tests on guinea pigs and observed no side effects. Canal et al. (2009) published recent studies on antibacterial dressings obtained by fluorination in a Ar-CF4 post-discharge plasma. Fluorinated surfaces of wool

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and polyamide 6, but not cotton, become hydrophobic and showed antibacterial properties. Clinical evidence No reports of clinical trials with wound dressings made of anti-infectious fabrics appear to have been published in peer-reviewed, English or Western European language journals.

12.4

Future trends for coated textiles against skin infections

The future in anti-infectious textiles for medical purposes will be dominated by developments in coating technologies. Immobilization of novel or hitherto unexploited conventional germicidal compounds to a wider diversity of fibres may be envisaged. Controlled elution of biocidal drugs from fabrics may be a desirable development. In the development of commercially successful anti-infectious clothes non-chemical aspects will require due attention, namely fashion and wearability. More clinical evidence will be needed for the efficacy and tolerability of antiinfectious textiles. Long-term clinical trials will be particularly important in obtaining conclusive evidence.

12.5

Sources of further information and advice

12.5.1 Reviews Atopic dermatitis • Ring, R., Przybilla, B. and Ruzicka, T. (eds), Handbook of Atopic Eczema, 2006, Berlin, Springer-Verlag. • Ricci, G., Dondi, A. and Patrizi, A. ‘Useful Tools for the Management of Atopic Dermatitis’. American Journal of Clinical Dermatology, 2009, 10, 287–300. Coating process • Djokic, S. ‘Treatment of Various Surfaces with Silver and its Compounds for Topical Wound Dressings, Catheter and Other Biomedical Applications’. ECS Transactions, 2008, 11, 1–12. Hygiene and risk • Kramer, A., Guggenbichler, P., Heldt, P., Junger, M., Ladwig, A., Thierbach, H., Weber, U. and Daeschlein, G. ‘Hygienic Relevance and Risk Assessment of Antimicrobial Impregnated Textiles’. Current Problems in Dermatology, 2006, 33, 78–109. Overview • Hipler, U.-C. and Elsner, P. (eds), Biofunctional Textiles and the Skin, 2006, Basel, Karger.

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• Petrulyte, S. ‘Advanced Textile Materials and Biopolymers in Wound Management’. Danish Medical Bulletin, 2008, 55, 72–77.

12.5.2 Websites (accessed 20 May 2011) Allergy, atopic eczema (Ring and Darsow, 2008): http://www.worldallergy.org/ professional/allergic_diseases_center/atopiceczema/. Acticoat®: http://wound.smith-nephew.com/de/Product.asp?NodeId=2627. AM/P2 antimicrobial polypropylene: http://www.covilleinc.com/products.html. DermaSilk®: http://www.alpretec.com/. Padycare®: http://www.texamed.de/. SeaCell® Active: http://www.smartfiber.de/index.php. SkinProtect® Silver: http://www.juzo.com/de/produkte/silberwaesche. Trevira® fibres: http://www.trevira.com/en/textiles-made-from-trevira/antimicrobial-textiles.html. Urgotul SSD®: http://www.urgomedical.com/70-urgotul-ssd-sag. X-Static® http://noblebiomaterials.com/.

12.6

References

Adams, A. P., Santschi, E. M. and Mellencamp, M. A. 1999. Antibacterial properties of a silver chloride-coated nylon wound dressing. Veterinary Surgery, 28, 219–25. Arcangeli, F., Feliciangeli, M., Pierleoni, M. and Morri, M. 2002. Silk tubular clothes in pediatric atopic dermatitis. 7th Congress of the European Society of Pediatric Dermatology. Madrid. Bolognia, J. L. 1995. Aging skin. The American Journal of Medicine, 98, 99S–103S. Borkow, G. and Gabbay, J. 2004. Putting copper into action: copper-impregnated products with potent biocidal activities. FASEB Journal, 18, 1728–30. Borkow, G. and Gabbay, J. 2005. Copper as a biocidal tool. Current Medicinal Chemistry, 12, 2163–75. Bunikowski, R., Mielke, M. E., Skarabis, H., Worm, M., Anagnostopoulos, I., Kolde, G., Wahn, U. and Renz, H. 2000. Evidence for a disease-promoting effect of Staphylococcus aureus-derived exotoxins in atopic dermatitis. Journal of Allergy and Clinical Immunology, 105, 814–9. Canal, C., Gaboriau, F., Villeger, S., Cvelbar, U. and Ricard, A. 2009. Studies on antibacterial dressings obtained by fluorinated post-discharge plasma. International Journal of Pharmaceutics, 367, 155–61. Deitch, E. A., Marino, A. A., Malakanok, V. and Albright, J. A. 1987. Silver nylon cloth: in vitro and in vivo evaluation of antimicrobial activity. Journal of Trauma, 27, 301–4. Diepgen, T. L., Stabler, A. and Hornstein, O. P. 1990. Textile intolerance in atopic eczema – a controlled clinical study. Zeitschrift fur Hautkrankheiten, 65, 907–10. Djokic, S. 2008. Treatment of various surfaces with silver and its compounds for topical wound dressings, catheter and other biomedical applications. ECS Transactions, 11, 1– 12. Dowsett, C. 2004. The use of silver-based dressings in wound care. Nursing Standard (Royal College of Nursing, Great Britain), 19, 56–60.

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Elsner, P. 2003. What textile engineers should know about the human skin. Current Problems in Dermatology, 31, 24–34. Fenske, N. A. and Lober, C. W. 1990. Skin changes of aging: pathological implications. Geriatrics, 45, 27–35. Fisher, G. J., Kang, S., Varani, J., Bata-csorgo, Z., Wan, Y., Datta, S. and Voorhees, J. J. 2002. Mechanisms of photoaging and chronological skin aging. Archives of Dermatology, 138, 1462–70. Fluhr, J. W., Breternitz, M., Kowatzki, D., Bauer, A., Bossert, J., Elsner, P. and Hipler, U. C. 2010. Silver-loaded seaweed-based cellulosic fiber improves epidermal skin physiology in atopic dermatitis: safety assessment, mode of action and controlled, randomized single-blinded exploratory in vivo study. Experimental Dermatology, 19(8), 9–15. Gauger, A., Fischer, S., Mempel, M., Schaefer, T., Foelster-holst, R., Abeck, D. and Ring, J. 2006. Efficacy and functionality of silver-coated textiles in patients with atopic eczema. Journal of the European Academy of Dermatology and Venereology, 20, 534–41. Gauger, A., Mempel, M., Schekatz, A., Schafer, T., Ring, J. and Abeck, D. 2003. Silvercoated textiles reduce Staphylococcus aureus colonization in patients with atopic eczema. Dermatology, 207, 15–21. Gettings, R. L. and Triplett, B. L. 1978. A new durable antimicrobial finish for textiles. AATCC National Technical Conference Book. Anaheim, CA, USA: AATCC. Heide, M., Mohring, U., Hansel, R., Stoll, M., Wollina, U. and Heinig, B. 2006. Antimicrobial-finished textile three-dimensional structures. Current Problems in Dermatology, 33, 179–99. Hipler, U.-C. and Elsner, P. (eds) 2006. Biofunctional Textiles and the Skin, Basel: Karger. Johansson, S. G., Bieber, T., Dahl, R., Friedmann, P. S., Lanier, B. Q., Lockey, R. F., Motala, C., Ortega Martell, J. A., Platts-mills, T. A., Ring, J., Thien, F., Van Cauwenberge, P. and Williams, H. C. 2004. Revised nomenclature for allergy for global use: Report of the Nomenclature Review Committee of the World Allergy Organization, October 2003. Journal of Allergy and Clinical Immunology, 113, 832–6. Juenger, M., Ladwig, A., Staecker, S., Arnold, A., Kramer, A., Daeschlein, G., Panzig, E., Haase, H. and Heising, S. 2006. Efficacy and safety of silver textile in the treatment of atopic dermatitis (AD). Current Medical Research and Opinion, 22, 739–50. Koller, D. Y., Halmerbauer, G., Bock, A. and Engstler, G. 2007. Action of a silk fabric treated with AEGIS in children with atopic dermatitis: a 3-month trial. Pediatric Allergy and Immunology, 18, 335–8. Kramer, A., Guggenbichler, P., Heldt, P., Junger, M., Ladwig, A., Thierbach, H., Weber, U. and Daeschlein, G. 2006. Hygienic relevance and risk assessment of antimicrobialimpregnated textiles. Current Problems in Dermatology, 33, 78–109. Lansdown, A. B. 2002a. Silver. 2: Toxicity in mammals and how its products aid wound repair. Journal of Wound Care, 11, 173–7. Lansdown, A. B. 2002b. Silver. I: Its antibacterial properties and mechanism of action. Journal of Wound Care, 11, 125–30. Lee, H. Y., Park, H. K., Lee, Y. M., Kim, K. and Park, S. B. 2007. A practical procedure for producing silver nanocoated fabric and its antibacterial evaluation for biomedical applications. Chemical Communications, 2959–61. Oriel, J. D. 1991. Eminent venereologists 5: Carl Crede. Genitourinary medicine, 67, 67–9. Petrulyte, S. 2008. Advanced textile materials and biopolymers in wound management. Danish Medical Bulletin, 55, 72–7. Rantala, M. J. 2007. Evolution of nakedness in Homo sapiens. Journal of Zoology, 273, 1–7.

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Ricci, G., Dondi, A. and Patrizi, A. 2009. Useful tools for the management of atopic dermatitis. American Journal of Clinical Dermatology, 10, 287–300. Ricci, G., Patrizi, A., Bendandi, B., Menna, G., Varotti, E. and Masi, M. 2004. Clinical effectiveness of a silk fabric in the treatment of atopic dermatitis. British Journal of Dermatology, 150, 127–31. Ricci, G., Patrizi, A., Mandrioli, P., Specchia, F., Medri, M., Menna, G. and Masi, M. 2006. Evaluation of the antibacterial activity of a special silk textile in the treatment of atopic dermatitis. Dermatology, 213, 224–7. Ring, J, Przybilla, B. and Ruzicka, T. (eds) 2006. Handbook of Atopic Eczema, 2nd edition. Berlin, Springer. Ring, J. and Darsow, U. 2008. Eczema (E), Atopic Eczema (AE) and Atopic Dermatitis (AD), WAO (World Allergy Organization). Available: http://www.worldallergy.org/professional/allergic_diseases_center/atopiceczema/ (accessed 20 May 2011). Romagnani, S. 2004. The increased prevalence of allergy and the hygiene hypothesis: missing immune deviation, reduced immune suppression, or both? Immunology, 112, 352–63. Schmitt, J., Langan, S. and Williams, H. C. 2007. What are the best outcome measurements for atopic eczema? A systematic review. Journal of Allergy and Clinical Immunology, 120, 1389–98. Senti, G., Steinmann, L. S., Fischer, B., Kurmann, R., Storni, T., Johansen, P., Schmidgrendelmeier, P., Wuthrich, B. and Kundig, T. M. 2006. Antimicrobial silk clothing in the treatment of atopic dermatitis proves comparable to topical corticosteroid treatment. Dermatology, 213, 228–33. Silvestry-Rodriguez, N., Sicairos-Ruelas, E. E., Gerba, C. P. and Bright, K. R. 2007. Silver as a disinfectant. Reviews of Environmental Contamination and Toxicology, 191, 23–45. Stinco, G., Piccirillo, F. and Valent, F. 2008. A randomized double-blind study to investigate the clinical efficacy of adding a non-migrating antimicrobial to a special silk fabric in the treatment of atopic dermatitis. Dermatology, 217, 191–5. Teufel, L., Pipal, A., Schuster, K. C., Staudinger, T. and Redl, B. 2010. Material-dependent growth of human skin bacteria on textiles investigated using challenge tests and DNA genotyping. Journal of Applied Microbiology, 108(2), 450–61. Zikeli, S. 2006. Production process of a new cellulosic fiber with antimicrobial properties. Current Problems in Dermatology, 33, 110–26.

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13 Antimicrobial treatments of textiles for hygiene and infection control applications: an industrial perspective S. C. B U R N E T T - B O O T H R O Y D, Advanced Textiles Limited, UK and B. J. M c C A R T H Y, TechniTex Faraday Limited, UK

Abstract: This chapter investigates the use of antimicrobial treatments applied to textiles for final hygiene and infection control products used in the healthcare sector. An antimicrobial agent is defined as a natural or synthetic substance that kills or inhibits the growth of micro-organisms such as bacteria, fungi and algae. The different chemical types (both organic and inorganic) are presented and their versatility in various antimicrobial applications is described. Historically and more recently, textiles have been worn as garments, and used as a system for the dermal (skin) application of medicines and as structural scaffolding for medical devices. Antimicrobial treatments have been utilised to enhance the properties of the garment or textile in order to either prolong the life of the textile product or for the delivery of a medicinal treatment. This chapter discusses products, applications and systems that are currently available and projects forward to look at some possible future opportunities. It also covers current legal directives put in place to protect the manufacturer, retailer and consumer from potential hazards. Key words: antimicrobial treatment, textiles, hygiene control product, infection control product, biocide, textile application methods.

13.1

Introduction

Natural and synthetic antimicrobial treatments have been used, developed and applied to textile products by mankind for centuries. An antimicrobial agent is defined as a natural or synthetic substance that kills or inhibits the growth of microorganisms such as bacteria, fungi and algae. Examples of treated textiles include: • impregnated tissues with ‘antibacterial’ properties (if not regarded as medicinal products, e.g. for certain applications in hospitals); • antibacterial textiles where the active substance is released during use; • socks treated with a biocidal active substance intended to have a biocidal action on the foot; • treated gowns or hospital drapes. 196 © Woodhead Publishing Limited, 2011

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In the current marketplace there are hundreds of products that lay claim to antimicrobial properties for many hygiene applications, such as wipes, cloths, gowns, pyjamas and the like, focusing on broad general areas such as anti-odour to the more extreme, biocidal properties of cleaning devices made with the sole aim of reducing the risk of infection in high risk areas. Antimicrobial treatments for textiles materials are necessary for the following reasons: • • • •

to avoid cross-contamination by pathogenic micro-organisms; to control infestation by micro-organisms; to arrest metabolism in bacteria in order to reduce the formation of odour; to safeguard a textile product from quality deterioration.

In certain end-uses, antimicrobial applications are applied to impart product integrity such as product protection from the effects of biodeterioration which, over time, can cause the product to fall apart. This is due, in some part, to the increased degradative activity of the viable bioburden, and the effect it has on the textile structural performance. So historically, applications using hygiene related additives have been used as a way of extending a product’s life cycle. In specialised applications, the textile can be used as a carrier or scaffolding matrix for applying or releasing an active agent onto an infected wound site; this can be either immediately released or delivered to the site over a prolonged period of time. Because of their inherent characteristics, some textiles have hydrophilic properties – they are able to attract, absorb and then capture moisture to assist in cleaning up a wound site for example. Such hydrophilic properties are found in evidence on textile products from wound dressings to incontinence products. In summary, final hygiene products can be thought of as a way of preventing, reducing or inhibiting infections by means of reducing the bioburden by a killing action (cidal) or inhibition action (static). ‘Antimicrobial agents’ is a general term for drugs, chemicals or other substances that either kill or slow the growth of microbes. Among the antimicrobial agents are antibacterial drugs, antiviral agents, antifungal agents and anti-parasitic drugs. Another definition related to the textile field suggests that an antimicrobial agent can be defined as a natural or synthetic substance that kills or inhibits the growth of micro-organisms such as bacteria, fungi and algae on a textile. When applied to a final hygiene product and having a claim for efficacy, it falls within the EU Biocidal Directive’s scope. For example, if a bathroom towel carries a claim to ‘prevent microbial growth and maintain hygiene of the towel’, this is taken as an external claim and therefore the towel is a biocidal product. Consequently, a dossier must then be developed, and authorisation for placing the product on the market sought under the European Union Biocidal Directive, based on the claims made by the manufacturers of the product. The EU Biocidal Product Directive is a policy document directive from the European Union in order to control the types of agents (chemical or others) that can be used in the European Union without infringement of safety to the person(s) or

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the environment. Over 1500 identified active biocidal products are covered by the directive. If an antimicrobial agent is added to a textile purely to preserve it (i.e. an internal effect) and there is no antimicrobial claim made, then it falls outside the scope of the BPD and is not classed as a biocidal product. However, if the product is claiming an effect such as ‘kills 99.9% of germs’ then it must follow and comply with the Directive. Taking a combination of an article and an active substance, if the active substance is placed on the market as an inseparable ingredient of the article, it has to comply with the requirements of the Directive. If it is intended that the biocidal active substance is released from the treated article to control harmful organisms outside the treated article (external effect) or if it is intended to control only organisms that are not harmful to the treated article itself, in such cases the article has the function of a delivery system and shall be considered as a biocidal product that must be authorised.

13.2

Processes for biocidal application for textile structures

One true benefit of using textiles for hygiene applications relates to their versatility in terms of the range of application options for adding an active agent. The active agent can be applied at different stages in the product’s manufacturing process – the decision as to where and when the application of the active compound should take place will depend upon the specification of the end product. The application process for antimicrobial application – i.e. how the active agent is applied and fixed to the textile – will affect the durability, efficacy and hygienic functionality of the textile. For example, a surgical dressing is a sterile textile (with no need for any active agent to be applied to it), due to the sterility of the environment within a modern hospital setting where it is used. However, it is still a sterile product and it can be assessed as a hygienic product – so that when it is placed onto an open wound (even without an active compound) it can be called a ‘passive’ hygienic product. However, if a wound ‘post surgery’ becomes highly infected, then an additional intervention of an ‘active’ wound dressing with a strong biocide is used to assist in cleaning the wound from infection and this is deemed as an acceptable intervention by clinicians. It is always an additional factor to engineer cost into the product or consider the benefit(s) the product will have over the resultant price to market. For example, if an innovative product is more expensive than the current product, then a case has to be built which always includes a cost model versus clinical impact and outcome. The price the market will pay does have an effect on product specification including the raw materials, manufacturing process route and product shelf life. For textiles there are three main application areas that are used to classify where and when the active agent is added. These application areas are:

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• into the initial polymer solution or chemical chain prior to fibre extrusion; • via chemical bonding to the natural or synthetic fibre surface; • during textile finishing – in most cases resulting in non-durable finishes.

13.3

Application during yarn and fibre manufacture: natural and synthetic

Textile fibres are derived from both natural sources (e.g. wool, cotton, flax, bamboo) and synthetic routes (e.g. polyester, nylon, aramid). Natural fibres are inherently susceptible to biodeterioration as part of the normal natural cycles of nature and will require protection from microbial attack; for example, if the commodity is stored in adverse conditions (e.g. high moisture). Synthetic polymers tend to be inherently resistant to microbial attack, but certain surface textile finishes or textile auxiliaries may serve as nutrient sources to stimulate microbial growth on the surface of fibres with associated staining and odour production.

13.3.1 Biocide applications Melt spinning (continuous synthetic filament). In this process polymer chips are melted in a container and either gravity or pressure induced through a small aperture(s) to form a long, continuous rod-like filament that is cooled and stretched under tension to achieve a specific length per weight ratio. This is measured either in Denier (weight in grams/9000 yards) or Decitex (weight in grams/ten thousand metres). This form of manufacturing was derived by copying the silk worm’s ability to extrude from its body a continuous filament to make its cocoon (the Chinese producers would then boil this cocoon to soften the gluey material holding the filament, to be able to unwind the continuous silk filament into a hank or bobbin for further processing). Melt spinning uses heat to melt the polymer to a viscosity suitable for extrusion. This type of spinning is used for polymers that are not decomposed or degraded by the temperatures necessary for extrusion. Polymer chips may be initially melted by a number of methods. The trend is toward melting and immediate extrusion of the polymer chips in an electrically heated screw extruder. Alternatively, the molten polymer is processed in an inert gas atmosphere, usually nitrogen, and is metered through a precisely machined gear pump to a filter assembly consisting of a series of metal gauges interspersed in layers of graded sand. The molten polymer is extruded at high pressure and constant rate through a spinnerette into a relatively cooler air stream that solidifies the filaments. Lubricants and finishing oils are applied to the fibres in the spin cell. At the base of the spin cell, a thread guide converges the individual filaments to produce a continuous filament yarn, or a spun yarn, that typically is composed of between 15 and 100 filaments. Once formed, the filament yarn either is immediately wound onto bobbins or is further treated for certain desired characteristics or end-uses.

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Textiles for hygiene and infection control Chitosanase

CH2OH

Chitosanase

CH2OH

O O

OH

CH2OH

O

O O

OH

OH

OH

HO NH2

NH2

NH2 n

13.1 Chitosan. Polymer of β-(1-4)-D-glucosamine units.

Wet spinning. This technology is readily available for the manufacture of continuous filaments from wood or cellulosic pulp by the addition of a wet chemical catalyst to change the chemical structure. It may also be used for the production of chitin. Chitosan (Fig. 13.1) is an effective natural antimicrobial agent derived from chitin, a major component of crustacean shells. Combined with the healing effect of kelp (seaweed) on wound tissue formation, it greatly increases the likelihood that the wound will heal more rapidly with a reduced risk of infection.

13.3.2 Fibre/yarn coated applications A metallised coating onto the surface of the fibre or yarn, or within a bi component yarn (Fig. 13.2) has an antimicrobial effect. Complexing compounds, based on metals such as silver, copper or mercury cause inhibition of the active enzyme in the pathogen, effecting the bacteria’s metabolic rate, thus rendering it unable to replicate or function. The most popular coated yarns use silver or copper. These remain flexible and usable in the textile structure and are generally noted as having permanent functionality.

13.2 Yarns with S and Z twist.

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13.3.3 Woven, knitted or non-woven technology Woven products It is necessary to weave the yarns containing the active agent in a manner that delivers the correct effect by interlacing the yarns in a way that makes either one surface or the other more or less hygienic in order to achieve the optimum performance necessary (Fig. 13.3). Surgical drapes, gowns, uniforms, bedding, ward curtains are examples of woven technology. Knitted products Due to the physical properties of the structure, knitted items can be used close to the wound site or body. The characteristic open structure, accompanied with compression, lends itself to the application of wound pressure and therefore Warp yarn

Weft yarn

13.3 Woven yarns showing warp and weft.

13.4 Knitting.

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dressings for venous ulcers, hydrotropic burns and open wounds are some of the main examples. Knitting is a method by which thread or yarn may be turned into cloth. Knitting consists of loops called stitches, pulled through each other (Fig. 13.4). The active stitches are held on a needle until another loop can be passed through them. Comparison of weaving and knitting Like weaving, knitting is a technique for producing a two-dimensional fabric from a one-dimensional yarn or thread. In weaving, threads are always straight, running parallel either lengthwise (‘warp threads’) or crosswise (‘weft threads’) (Fig. 13.3). By contrast, the yarn in a knitted fabric follows a meandering path (a ‘course’), forming symmetric loops (also called ‘bights’ or ‘stitches’) symmetrically above and below the mean path of the yarn (Fig. 13.4). These meandering loops can be stretched easily in different directions, which gives knitting much more elasticity than woven fabrics: depending on the yarn and knitting pattern, knitted garments can stretch as much as 500%. Knitting was initially developed for garments that must be elastic or stretch in response to the wearer’s movements, such as socks and hosiery. For comparison, woven garments stretch mainly along one direction (the ‘bias’) and not very much, unless they are woven from stretchable material such as spandex. Knitted garments are often more form-fitting than woven garments, since their elasticity allows them to follow the body’s curvature closely. By contrast, curvature is introduced into most woven garments only with sewn darts, flares, gussets and gores, the seams of which lower the elasticity of the woven fabric still further. Thread used in weaving is usually much finer than the yarn used in knitting, which can give the knitted fabric more bulk and less drape than a woven fabric. Types of end-use are compression hosiery, DVT socks for lymphatic complications (using variable compression) and more complex liner compression products needed for tissue regeneration in burns (on bespoke garments that aid in the healing process). Non-woven products These are utilised for disposable, one-use only devices that tend to be deployed in products such as surgical drapes and surgical dressings, in combination with knitted structures. Non-wovens are made of layered irregular fibres, generally cellulosic or synthetic, that are blown onto a surface and, through mechanical agitation or glues, are stuck into random layered sheets that can then be placed together (multi-layered) to achieve the performance needed for specific end-uses, e.g. air filtration systems, where a volume of air can pass through the structure but the foreign particles within the air are captured by the irregular fibres within the structure.

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13.3.4 Padding applications onto fabric surfaces (finishing) The antimicrobial agent can be applied to the textile substrate by padding/dry-cure, coating, spray and foam techniques, and also by exhuast application via a dyebath. The method usually applied on most textile substrates (but especially on woven and knitted systems) is where a solution containing the active agent is padded onto the surface of the fabric structure and then baked or cured onto the surface. This is generally the least expensive way of application (and some would dispute the longevity of efficacy or performance after laundering). Usually silver solutions, as well as chemically active agents such as triclosan, are applied in this manner. These surface treatments of textile fibres and fabrics significantly increase their performances for specific biomedical applications. Nowadays, silver is the most used antibacterial agent, with a number of advantages. Among them is a high degree of biocompatibility, an excellent resistance to sterilisation conditions (usually temperatures in excess of 82 °C), and antibacterial properties with respect to different bacteria associated with a long-term of efficiency. Silver ions are highly toxic to bacteria at low concentrations (ng per litre). The long-term effects of silver ion release into the environment is currently under investigation (http://go.nature.com/ GBFn5k).

13.3.5 Types of treatment One of the most durable type of antimicrobial ‘active’ agents is based on a diphenyl ether (bis-phenyl) derivative, known as 2,4,4-trichloro-2-hydroxyl diphenyl ether or 5-chloro-2(2,4-dichlorophenoxyl) phenol, or triclosan (Fig. 13.5). Historically, this compound has been used in many applications over the last 25 years, in hospitals and in personal hygiene products from toothpaste to soap. Triclosan inhibits the growth of micro-organisms by using an electrochemical mode of action to penetrate the cell walls and disrupt the internal function. In fabric preparation processes, only the first application of chemicals is usually to dry fabric, i.e. wet-on-dry. Generally fabrics are not dried between the subsequent stages of production and chemicals are applied wet-on-wet. The saturator should therefore have adequate volume to provide sufficient contact time between fabric and saturator liquor. This allows wetting out of non-absorbent grey fabrics during wet-on-dry application and liquor interchange in wet-on-wet systems. In contrast, finishing chemicals are usually applied to dry prepared fabrics and good OH

Cl O

Cl

Cl

13.5 Triclosan.

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chemical application can be obtained by passing the fabric through a small pad trough prior to the mange bowls.

13.3.6 Laminated products and coating applications Laminating is the application of a performance coating of PTFE or a PU membrane, usually carrying an active agent within its structure, by bonding it onto a twolayered or three-layered fabric substrate. It is generally used in mattress covers for the prevention of pressure sores for the long-term bed patient or for high-risk surgical barrier panels for operations to prevent body fluids from being absorbed into the fabric structure of the surgical gown or drape. The barrier is waterproof, with some breathability or vapour transfer functionality, for comfort and reduction in pressure sore manifestation. When used for mattress covers and seat covers in the hospital environment, these are easier to clean and disinfect after use. Laminated products are also used as total barrier fabrics for bio-suits for emergency services (CBRN) to stop any bioburden and virus absorption through skin surface contact (see Chapter 11).

13.4

Antimicrobial testing procedures

The lack of information on this topic leads to much misunderstanding between the industry supplying hygiene products to the marketplace and the medical profession. Basically, today, industry has only one way to prove efficacy at a cost that is borne by the industry – by standard test methods. These test methods are many and varied but revolve around the use of isolates in suspension to observe, in a subjective way, the resultant change in Petri dish activity: this method is called in vitro testing. The tests are either qualitative or quantitative methods for determining the survival, growth or inhibition of the isolate. Generally, testing involves using a gram negative bacteria such as S. aureus or K. pneumoniae, as these are common isolates, easily replicated for testing cultures. The usual test methods for testing the antimicrobial efficacy of textiles are JIS 1907 and AATCC 100.

13.4.1 Efficacy for test methods AATCC 147 (Parallel streak method) This is a quick and easy quantitative method to determine antibacterial activity. The method involves the inoculation of a nutrient agar growth surface with streaks of bacteria. Non-sterile samples of fabric are cut into 25 × 50 mm rectangles. The antimicrobial fabric samples are also cut into 25 × 50 mm rectangles and then placed directly on top of the inoculated agar plate and incubated at 37 ± 2 °C for 24 hours. The incubated plates are examined for interruption of growth beneath the

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specimen, and for a clear zone of inhibition beyond its edge. Where no bacterial colonies occur under the specimen, it is considered to have acceptable antimicrobial activity and is reported as NZI (no zone of inhibition). If the active agent diffuses over the surface of the plate, the size of the zone of inhibition around the sample is also reported, by measuring all sides and calculating an average. This test cannot be considered to be qualitative, but can be used for comparison against nonantibacterial samples, and samples known antibacterial activity. ISO20645:2004 (Agar diffusion plate test) In many respects, this is similar to AATCC 147. It is a simple qualitative test to check for the presence of active agents. The 25 mm diameter circular specimens of the material to be tested are placed on two-layer agar plates. The lower layer consists of a cultured medium, free from bacteria, and an upper layer is inoculated with a selected bacteria. The textiles are tested on both sides. Samples are incubated for between 18 and 24 hours at 37 °C and the level of antibacterial activity is assessed by examining the extent of bacterial growth in the contact zone between the agar and the specimen and, if present, the extent of the inhibition zone around the specimen. The results are then graded as: ‘good effect’ – where there must be no growth under the specimen; ‘limit of efficacy’ – where there is no inhibition zone and growth is almost completely suppressed under the specimen; and finally ‘insufficient effect’ – where there is a moderate or heavy growth of bacteria in the agar under the specimen. Quantitative test AATCC 100 Circular cuttings approximately 4.9 cm in diameter are cut. These are then inoculated with the test organisms, by allowing the cuttings to absorb 1 mL of a bacterial broth culture. Enough cuttings are used to allow the complete absorption of the liquid. In the case of hydrophobic fabrics (such as fabrics with a waterrepellent finish), a surfactant is added to enhance the wetting. If any liquid is left adhering to the jar, this gives an erroneous result. Several of these jars are prepared. Sterilised distilled water is then added to one jar. This is vigorously shaken for 1 minute. A sample of the liquid is then placed on a nutrient agar plate. This represents ‘zero time’. The other jars are similarly treated and then incubated at 37 ± 2 °C for 24 hours (but other time periods can be used to provide information on antibacterial activity). In vitro testing methods can never be used as anything more than an indication of efficacy or as a means to a proof of principles.

13.5

Future trends

Textiles have a very exciting role to play within the field of hygiene and a major future market driver will be cost reduction in the face of ever spiralling costs of

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‘Unified Method’; not published but used by Hohenstein Institute

Hydrophilic/absorbent textiles, foams

All; high volume to sample ratio

‘Shake Flask’ Method (BISFA) – quantitative

Germany

Hydrophobic textiles, plastics

Draft Method of IBRG Plastics Group

Europe

K. pneumoniae ATTC 4352 and S. aureus ATCC 6538

E. coli ATCC 10536, P. aeruginosa ATCC 15442 and S. aureus ATCC 6538 K. pneumoniae ATTC 4352

K. pneumoniae ATTC 4352 and S. aureus ATCC 6538

All; targeted for textiles

XPG-39010

K. pneumoniae ATTC 4352 and S. aureus TCC 6538P E. coli ATTC 8739 and S. aureus ATCC 6538P

France

Hydrophilic/absorbent textiles, foams Hydrophobic textiles, plastics

K. pneumoniae ATTC 4352 and S. aureus ATCC 6538

K. pneumoniae ATTC 4352 and S. aureus ATCC 6538 K. pneumoniae ATTC 4352 and S. aureus ATCC 6538 K. pneumoniae ATTC 4352 and S. aureus ATCC 6538 K. pneumoniae ATTC 4352

Test organisms

Not finalized; 23 ºC

0.1% Tryptone in saline; 37 ºC

?

5% Nutrient broth in saline; 37 ºC 0.2% Nutrient broth in distilled H2O; 35 ºC

Nutrient broth, saline or other; 37 ºC Nutrient broth, saline or other; 37 ºC Nutrient broth, saline or other; 37 ºC 0.3 mM Phosphate buffer or other; 25 ºC 0.3% Agar slurry in saline; 37 ºC

Exposure solution, temperature

24 hrs

5% Nutrient broth in saline; 37 ºC

1, 6 and 0.3 mM Phosphate 24 hrs buffer or other; 25 ºC

24 hrs

18– 24 hrs

24 hrs?

24 hrs

18 hrs

1 and 24 hrs 24 hrs

24 hrs

24 hrs

24 hrs

Contact time

Test parameters

Most matrices, depends K. pneumoniae ATTC 4352 on migration of biocide? and S. aureus ATCC 6538

JISZ 2801

JISL 1902 – quantitative

Draft Method of AATCC (based on NYS-63) ASTM Method E2149-01 (Shake Flask) ASTM Method E2180-01 (Sloppy Agar)

Hydrophilic/absorbent textiles, foams Hydrophilic/absorbent textiles, foams Hydrophobic textiles, plastics All; high volume to sample ratio Hydrophobic textiles, plastics

Use site (optimal matrices)

Switzerland SNV 195124

Japan

AATCC Method 174-Part II

USA

AATCC Method 100

Test reference

Country

Table 13.1 Antimicrobial efficacy testing methods

206 Textiles for hygiene and infection control

Antimicrobial treatments of textiles

207

13.6 Consumption of hygiene textiles in various geographical locations.

medical intervention. Textiles can use their ability of intimacy to human interaction (close to the skin) to be either a barrier or protector, using numerous technologies (such as dye stuffs that change colour when a certain protein is secreted from a hostile pathogen or to change colour when the fabric product is contaminated as indicators). Further efforts will focus on the deployment of nonlinting fabrics that reduce the number of particles released from the textile into the environment – which could potentially contaminate a more vulnerable human through dust or skin particles from the air. World consumption of textile hygiene products has to be noted as key factors can be drawn from data regarding the rise of the new economies and their internal consumption of textiles adding strain to the textile supply chain. It is estimated that some 10% of technical textiles produced in developing economies relate to medical applications. The bar chart of Fig. 13.6 shows a steady increase in interest and consumption of hygiene textiles in all sectors and geographical locations, demonstrating an increase in global deployment and usage – a growth in consumption from 3 154 000

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Textiles for hygiene and infection control

tons in 1999 to 9 050 000 tons in 2005. Coincidentally, a greater increase in market share has been driven in the Asia Pacific regions, by a factor of three, which is still far behind the consumption of North America. It seems that Western Europe has shown a fall in the world rankings of consumption and technical demand.

13.6

Conclusion

Antimicrobial treatments for final hygiene products are many and varied, especially when dealing with textile applications. A multitude of factors affect the type of application, from the ‘active’ selection which, as explained, has to comply with the Biocidal Products Directive to ensure an agent has no effect on the environment, or person using it, or to the substrate performance on which the active agent is attached. Cost and functionality will drive the type of application to be either a locked-into-the-fibres molecular structure or to an atopic solution, cured onto the surface (for a cheaper option with less durability). The overall selection of testing methods from qualitative to quantitative data to prove ‘proof of principles’ can be a costly procedure with no real commercial result from the findings, so choosing the right test method or methods is critical. The future holds the task of driving innovation into selective hygiene products with a more intelligent deployment of ‘actives’ in the textile field. A more focused approach is needed to maintain a symbiotic relationship with the environment and a more considered view of understanding when hygiene products should be used and how.

13.7

Sources of further information and advice

Anon. (1998) 98/8/EC: Directive of the European Parliament and Council of 162-98 concerning the placing of biocidal products on the market. Official Journal of the European Communities, L123, 24-04-98. Anon. (1999) Council directive 1999/13/EC of 11 March 1999 on the limitation of emissions of volatile organic compounds due to the use of organic solvents in certain activities and installations. Anon. (2006) Regulation (EC) No 1907/2006 of the European Parliament and of the Council of 18 December 2006 concerning the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH). Anon. (2007) Commission regulation (EC) No 1451/2007 of 4 December 2007 on the second phase of the 10-year work programme referred to in Article 16(2) of Directive 98/8/EC of the European Parliament and of the Council concerning the placing of biocidal products on the market. Home I (2002). ‘Antimicrobials Impart Durable Finishes’, International Dyer, December, pp 9–11. Knight DJ, Cooke M (2002). Regulatory control of biocides in Europe. In: Knight DJ, Cooke M (eds.): The Biocide Business. John Wiley, Weinheim, 45–74

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209

Menezes E. (2002). ‘Antimicrobial Finishing of Textiles.’ The Textile Industry and Trade Journal, January–February, pp 35–38. Mucha H, Hoter D and Swerev M (2002). ‘Antimicrobial Finishes and Modifications’. Melliand International, May, Vol 8, pp 148–151. Wierzbowska T and Stachowiak M (2000). ‘Non-woven Fabrics of Bacterial and Fungicidal Qualities from Biocide-modified Fibres’, Asian Textile Journal, Vol 9, pp 95–98.

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Index

AAMI PB70, 132–3 AATCC 100, 205 AATCC 147, 204–5 AATCC 118-1997 test method, 108 Absorbency Testing System, 42 absorbent fibres, 73–5 bamboo and Crabyon fibre, 73–4 organic cotton fibre, 74–5 other natural cellulosic fibres, 75 viscose fibre, 73 absorption under load, 6 Acinetobacter baumannii, 98–9 acquired resistance, 90 Acticoat, 191 Active-Shield TiO2Ag, 24 adult diapers, 4 AEGIS AEM 5772/5, 188 agar diffusion plate test, 205 ageing effect, 145–6 ageing trial, 145 air filter unit, 180 Alldays, 61 Always, 59, 61 anti-adhesive wound dressings, 97–8 antibacterial packaging, 63 antibacterial resistome, 91 antimicrobial textiles, 22–4 antimicrobial wound dressings, 97 AQUACEL Ag Hydrofiber, 23 ASTM D 737-96, 108 ASTM F1980, 146 atopic eczema, 188–9 atoxyl, 87 baby diapers, 4 baby wipes, 3 bamboo fibre, 73–4 barrier textiles, 104 applications, 115–17, 123

filtration applications, 117, 123 filtration measurement results from Europlasma CERTITEST 8130, 117 hospital applications, 116 military applications, 116–17 current solutions for rendering liquid repellency, 109–10 dip processing, 109–10 spray coatings, 110 traditional process for wet finishing of textiles, 109 future trends, 123 importance of liquid repellency, 105–9 achieving liquid repellency, 107 super hydrophobicity from surface roughening of hydrophobic surface, 106 surface energy and surface tension, 105–6 surface roughening effect on hydrophilic surface, 106 surface roughness, 107 test liquids for oil repellency ratings, 108 testing water and oil repellency, 107–9 water repellency tests for treated textiles, 108 plasma processing, 104–23 prepared by plasma treatment, 118–22 use of plasmas for imparting liquid repellency, 111–15 commercialisation, 115 P2i’s 2000 litre plasma chamber, 114 process development, 112 results, 112–13 scale-up challenges, 113–15

210 © Woodhead Publishing Limited, 2010

Index water and oil repellency values, 113 beta-lactams, 89 biocidal textiles, 131–3 antimicrobial activity of grafted polypropylene fibres against E. coli, 132 percentage reduction of E. coli on ADMH grafted fabrics, 132 biodegradable hygiene products, 68–81 absorbent fibres, 73–5 bamboo and Crabyon fibre, 73–4 organic cotton fibre, 74–5 other natural cellulosic fibres, 75 viscose fibre, 73 alternative raw materials, 72–80 barrier and protective films, 77–8 bi-laminated and similar films, 78 polyethylene and polyurethane, 77–8 criteria for selection and implementation of alternative raw materials, 70–2 non-absorbent fibres, 75–7 low-melting-point fibres for thermobonding processes, 76–7 polypropylene and polyester, 75–6 packaging, 79–80 laminated polyethylene/polyester film, 80 polyethylene flexible film, 79–80 superabsorbent powder and fibre, 78–9 superabsorbent fibre, 79 superabsorbent polymer, 78–9 sustainable materials classification according to their ecological footprint, 69–70 bioglass, 20 biological containment suits containment fabrics to protect against biological threats, 174–82 biological half suits, 180–1 compressed air line or battery filter fan unit, 181–2 design and production techniques, 174 passive respirator chemical, biological, radiological and nuclear suits, 181 single piece suits for first responders, 179–80 suit decontamination, 182 containment suits outside the laboratory, 178–9

211

Martindale half suit, 179 positive pressure laboratory containment suits, 175–8 Delta Mururoa suit, 176 ILC Dover Chemturion suit with umbilical air line, 176 used in microbiological high containment facilities and by emergency responders, 173–83 Bioplast polymer, 77 biopolymers, 69, 75 Biotech, 80 Black Death, 86 BS EN 13432, 63 bubonic plague, 86 CA-MRSA see community-associated MRSA CBRN see chemical, biological, radiological, nuclear cellulosic materials, 69 cephalosporin C, 89 Chain, Ernst, 88–9 chemical, biological, radiological, nuclear, 179, 181 chitosan, 200 chlorinated polyethylene, 177 Cloropel, 177 Clostridium difficile, 91–2, 92–3 coated textiles applications to prevent or treat cutaneous infections, 188–92 dressings, 190–2 clinical evidence, 192 disease, 191 non-clinical evidence, 191–2 future trends, 192 garments, 188–90 clinical evidence, 189–90 disease, 188–9 non-clinical evidence, 189 skin infections, 186–92 types with anti-infectious properties, 187–8 community-associated MRSA, 100 copper, 200 Crabyon fibre, 73–4 CTX-M enzymes, 99

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212

Index

Delta Mururoa suit, 176, 177–8, 181 DermaSilk, 187, 188, 189 dextrose, 76 diagnostics, 15–16 DIN 53 887, 108 dioxins, 78 dip processing, 109–10 Directive 93/42/EEC, 146 disposable medical textiles, 125–33 biocidal woven and nonwoven textiles, 131–3 antimicrobial activity of grafted polypropylene fibres against E. coli, 132 percentage reduction of E. coli on ADMH grafted fabrics, 132 costs, 128–30 life cycle, 126–8 schematic diagram, 127 protection, 130–1 vs reusable medical textiles, 125–6 Domagk, G., 87 Dover Chemturion suit, 176, 177–8, 181 dressings, 190–2 clinical evidence, 192 disease, 191 non-clinical evidence, 191–2 dry heat sterilisation, 142 durable water repellents, 109 ECOLABEL, 71 Ehrlich, Paul, 87 electron beam radiation, 140 Elixir Sulphanilamide, 88 endogenous eczema see atopic eczema environmental sciences, 18 ethylene oxide sterilisation, 140–1 European Norm 556-1 2001, 137 extended spectrum beta-lactamases, 99 fabrics sterilisation, 136–48 effect on fibres and fabrics, 144–6 normalisation, 147–8 purpose and importance, 137–43 quality assurance, 143–4 reprocessing sterilised products, 146–7 Fairtrade, 71

feminine hygiene products, 4 Fleming, Alexander, 88 Florey, Howard, 88–9 fluorocarbons, 107 gamma radiation, 139–40 ionising energy sources, 140 garments, 188–90 clinical evidence, 189–90 disease, 188–9 non-clinical evidence, 189 global organic textile standard, 71 HAI see healthcare-associated infections HART see Hazardous Area Response Team Hazardous Area Response Team, 179–80 HAZMAX, 180, 182 healthcare-associated infections, 91–4 high efficiency particulate absorption, 177 Huggies, 58, 61 hybrid reusable diapers, 4 hydrocarbons, 107 hygiene products innovative and sustainable packaging strategies, 48–65 examples of packaging, 50 future trends for hygiene industry, 64–5 global packaging market breakdown, 49 key considerations, 51–6 trends and strategies, 56–64 knitted spacer fabrics, 35–44 incontinence, 36–40 mapping liquid movement, 42–4 moisture control, 40–2 textiles antimicrobial treatments, 196–208 antimicrobial testing procedures, 204–5, 206 application during yarn and fibre manufacture: natural and synthetic, 199–204 biocidal application for textile structures, 198–9 future trends, 205, 207–8 hygiene textile products key property requirements, 4–5 barrier performance, 4

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Index comfort and breathability, 5 lining and cleanliness, 5 mechanical properties/strength, 4 sterilisation stability, 4–5 water and saline absorption, 4 novel design, 3–10 applications, 3–4 types of new technology, 5–10 incontinence pads, 4 incontinence products body-worn products lightly incontinent men, 158–9 lightly incontinent women, 157–8 moderately/heavily incontinent men and women, 159–60 clinical performance, 157–61 clinical work summary, 161 six pants with integral pads, 158 underpads, 160–1 correlation with user data, 168–70 equilibrium distribution of the absorbed volume, 169 initial insult absorption, 168 relation to clinical leakage record, 169–70 temporary absorption capacity, 168–9 functional requirements, 155–7 men and women with moderate/heavy incontinence, 156 women with light incontinence, 156 laboratory evaluation, 161–8 absorbent cores from pads, 162 absorption/acquisition time, 165–6 absorption capacity under pressure, 166–7 apparatus used for measuring absorption capacity, 167 apparatus used for measuring absorption time, 165 curved former to support an absorbent core, 163 extent of fluid spread, 164 laundry and durability, 167–8 results from technical tests carried out on pant cores, 166 whole product testing, 162–5 wicking, 167 pad designs, 154, 155

213

principal designs, 154 washable textile-based, 153–71 future trends, 170–1 infection future trends, 98–101 Acinetobacter baumannii, 98–9 community-associated MRSA, 100 extended spectrum beta-lactamases, 99 holistic approach to preventing infections, 100–1 prevention and control and the role of textiles, 85–101 antibiotic resistance mechanisms, 90–1 antibiotics, 87–9 historical examples of serious infections, 86–7 principles and practice of prevention and control in hospitals, 94–7 breaking the chain of infection, 96–7 chain of infection for C. difficile, 96 host factors, 95–6 routes of transmission, 95 sources of infection, 95 role of textiles in prevention and control, 97–8 anti-adhesive wound dressings, 97–8 antimicrobial wound dressings, 97 superbugs and healthcare-associated infections, 91–4 number of C. difficile infections and deaths in England, 93 number of MRSA bacteraemia cases and deaths in England, 93 scale of HAI problem, 93–4 infection control product textiles antimicrobial treatments, 196–208 antimicrobial testing procedures, 204–5, 206 application during yarn and fibre manufacture: natural and synthetic, 199–204 biocidal application for textile structures, 198–9 future trends, 205, 207–8 IntegraGuard, 58 intrinsic resistance, 90

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214

Index

ISO 20645:2004, 205 ISO 11137, 147 ISO 14040, 72 ISO 11137-1, 145 ISO 11137-2, 145 jumping genes, 91 knitted fabrics medical applications, 25 knitted spacer fabrics, 31 application in hygiene products, 35–44 incontinence, 36–40 mapping liquid movement, 42–4 moisture control, 40–2 3D fabrics, 29–31 spacer fabrics, 30 hygiene applications, 27–45 3D fabrics, 29–31 future trends, 44–5 issues in hygiene and moisture management, 27–9 ageing population, 28–9 knitting principles, 31–5 fabric comparisons and mechanical alterations, 32–4 manufacture and use, 34–5 warp- and weft-knitted spacer fabric end-uses, 35 warp-knitted spacer fabrics, 32 weft-knitted spacer fabrics, 32 weft-knitted spacer fabric, 31 knitting, 202 laminated polyethylene/polyester film, 80 LCA, 72 liquid repellency, 105 current solutions for rendering liquid repellency, 109–10 dip processing, 109–10 spray coatings, 110 traditional process for wet finishing of textiles, 109 importance, 105–9 achieving liquid repellency, 107 commonly used water repellency tests for treated textiles, 108 effect of surface roughening of hydrophilic surface, 106

super hydrophobicity from surface roughening of hydrophobic surface, 106 surface energy and surface tension, 105–6 surface roughness, 107 test liquids for oil repellency ratings, 108 testing water and oil repellency, 107–9 use of plasmas, 111–15 commercialisation, 115 P2i’s 2000 litre plasma chamber, 114 process development, 112 results, 112–13 scale-up challenges, 113–15 water and oil repellency values, 113 liquid spreading, 42–4 absorbent spacer fabric, 43 Logic, 64 Lyocell fibre, 73 Lysorb, 78 lysozyme, 88 Martindale half suit, 179, 182 Mater-Bi, 62, 80 polymer, 77 mecA gene, 92 medical hygiene textiles nanotechnology application, 14–25 global textiles and clothing sectors, 19–25 healthcare and life science, 15–18 standard and regulations, 18–19 medical textiles disposable and reusable, 125–33 biocidal woven and nonwoven textiles, 131–3 comparison, 125–6 costs, 128–30 life cycles, 126–8 protection, 130–1 melt spinning, 199 methicillin-resistant Staphylococcus aureus (MRSA), 91–2 methicillin-sensitive Staphylococcus aureus (MSSA), 92 metrology, 18 microbiological containment

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Index biological containment suits used by emergency responders, 173–83 containment fabrics, 174–82 microbiological safety cabinet, 175 MicroChem Plus, 182 MSC see microbiological safety cabinet nano-enabled coatings, 17 nanocrystalline silver dressings, 97 nanotechnology, 97 global textiles and clothing sectors, 19–25 antimicrobial textiles, 22–4 knitted fabrics with medical applications, 25 protective surgical products, 25 healthcare and life science, 15–18 chemical and consumer products, 17 engineering and energy, 17–18 environmental sciences, 18 ICT and electronics, 16 metrology, 18 medical hygiene textiles, 14–25 standard and regulations, 18–19 natural cellulosic fibres, 75 NatureFlex, 63 NatureWorks, 62 Neosalvarsan, 87 neurodermatitis see atopic eczema non-absorbent fibres, 75–7 low-melting fibres for thermo-bonding processes, 76–7 polypropylene and polyester, 75–6 NORDIC ECOLABEL, 71–2 operator protection factor, 177 organic cotton fibre, 74–5 packaging, 79–80 laminated polyethylene/polyester film, 80 polyethylene flexible film, 79–80 Packaging and Packaging Waste Directive, 55 Packaging (Essential Requirements) Regulations, 55 packaging strategies innovative and sustainable, for hygiene products, 48–65

215

examples of packaging, 50 future trends for hygiene industry, 64–5 global packaging market breakdown, 49 key considerations, 51–6 cost of goods, 53 demographics and global economy, 55–6 product and business needs, 51–2 requirements of hygiene textile products, 52 sales price and volume matrix, 53 supply chain dependency, 53–4 waste, 54–5 trends and innovation strategies, 56–64 alternative and smart packaging, 62–4 design differentiation and re-design, 60–2 driving down costs, 59–60 labelling on hygiene product packaging, 59 strategies and support for design differentiation, 61 sustainability, 56–9 sustainability strategy, 57 tactics for driving down costs, 60 Padycare, 188, 189 Pampers, 58 Panton–Valentine leucocidin, 100 parallel streak method, 204–5 Pasteur, Louis, 94 penicillin, 88, 89 personal protective equipment, 174 pharmaceutical industry, 15 plague, 86 PlantBottle, 63 Plantic, 62–3 plasma processing barrier textiles creation, 104–23 plasma sterilisation, 143 plasma technology, 104 plasmids, 90 polyethylene flexible film, 79–80 polyethylene glycol 600, 7 polylactic acid fibre, 75–6 polylactide, 62–3 polymer/clay superabsorbent composites, 7

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216

Index

polytetrafluoroethylene, 117 polyurethaneurea dimethylacetamide, 9 polyvinylidene fluoride, 117 primary pneumonic plague, 86 Producer Responsibility Obligations Regulation (2008), 55 product design, 9–10 Prontosil Rubrum, 87–8 Pull-up, 58 quality assurance, 143–4 biological indicators, 144 chemical indicators, 144 mechanical indicators, 143–4 quantitative test, 205 regenerative medicine, 15–16 resistance-encoding plasmids, 91 Respirex PRPS suits, 180 reusable medical textiles, 125–33 biocidal woven and nonwoven textiles, 131–3 antimicrobial activity of grafted polypropylene fibres against E. coli, 132 percentage reduction of E. coli on ADMH grafted fabrics, 132 costs, 128–30 life cycle, 126–8 schematic diagram, 128 protection, 130–1 vs disposable medical textiles, 125–6 rifampicin, 89 Salvarsan, 87 Sanytex, 182 saturated steam, 141–2 SeaCell Active, 187, 189 Semmelweis, Ignaz, 94 silicones, 107 silver, 200 Silver Shield, 180 skin infections coated textiles, 186–92 applications to prevent or treat cutaneous infections, 188–92 future trends, 192 types with anti-infectious properties, 187–8

SkinProtect, 187, 189 smart packaging, 63–4 South Indian Textile Research Association, 25 spacer fabrics, 30 mapping liquid movement, 42–4 SpectraShield 9500 Surgical N95, 24 spray coatings, 110 staphylococcal cassette chromosome (SCCmec), 92 Staphylococcus aureus, 92 Stay Fresh, 22 steam autoclaving, 141–2 sterilisation effect on fibres and fabrics, 144–6 ageing effect, 145–6 limitations of fibres, 145 fabric survival, 136–48 normalisation, 147–8 reprocessing sterilised products, 146–7 methods, 138–43 advantages and disadvantages, 139 dry heat, 142 ethylene oxide, 140–1 gamma and electron beam irradiation, 139–40 ionising energy sources properties, 140 plasma sterilisation, 143 saturated steam, 141–2 x-ray sterilisation, 143 purpose and importance, 137–43 requirements for single-use and reusable textile fabrics, 137–8 quality assurance, 143–4 biological indicators, 144 chemical indicators, 144 mechanical indicators, 143–4 Steris, 148 Sterrad, 143 streptomycin, 89 suits biological containment, 173–83 containment fabrics to protect against biological threats, 174–82 sulphanilamide, 88 sulphonamides, 87 superabsorbent film, 79

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Index superabsorbent polymer, 78–9 superabsorbents, 6–9 superbugs, 91–4 surface energy, 105–6 surface roughness, 107 surface tension, 105–6 sustainable development, 68 synthetic materials, 69 Tencel fibre, 73 textiles see also coated textiles antimicrobial testing procedures, 204–5, 206 antimicrobial efficacy testing methods, 206 antimicrobial treatments for hygiene and infection control applications, 196–208 processes for biocidal application for textile structures, 198–9 application during yarn and fibre manufacture: natural and synthetic, 199–204 laminated products and coating applications, 204 padding applications onto fabric surfaces (finishing), 203 atopic treatment types, 203–4 triclosan, 203 biocide applications, 199–200 chitosan, 200 efficacy for test methods, 204–5 AATCC 147 (Parallel streak method), 204–5 ISO20645:2004 (Agar diffusion plate test), 205 quantitative test AATCC 100, 205 fibre/yarn coated applications yarns with S and Z twist, 200 future trends, 205, 207–8 hygiene textiles consumption in various geographical locations, 207 infection prevention and control, 85–101 antibiotic resistance mechanisms, 90–1 antibiotics, 87–9 future trends, 98–101

217

historical examples of serious infections, 86–7 holistic approach to preventing infections, 100–1 principles of infection prevention and control in hospitals, 94–7 role of textiles, 97–8 superbugs and healthcare-associated infections, 91–4 woven, knitted or non-woven technology, 201–2 knitted products, 201–2 knitting, 201 non-woven products, 202 weaving vs knitting, 202 woven products, 201 woven yarns showing warp and weft, 201 ThermAssureRF, 64 training pants, 4 transposons, 91 triclosan, 203 Tychem TK, 180 ultra thin diaper, 4 Urgotul SSD, 191 urinary incontinence, 36–40, 153 disposable body-worn pads, 38 reusable bed pad, 38 vancomycin, 92 VarioSens, 64 Waksman, Seman, 89 warp-knitted spacer fabrics, 32 moisture management, 40 washable textile-based absorbent products incontinence, 153–71 (see also incontinence products) clinical performance of existing products, 157–61 correlation with user data, 168–70 functional requirements, 155–7 future trends, 170–1 laboratory evaluation, 161–8 pad designs, 155 weaving, 202 weft-knitted spacer fabrics, 32

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218

Index

cross-section, 41 wet spinning, 200 wicking, 167 World Health Organization (WHO), 174 wound dressings, 22–4, 190–2 X-ray sterilisation, 143

X-Static, 188, 189 XTI 360 Active-Shield, 24 XTI 360 Nanocoating, 24 XTI Nano-Facemask, 24 Yersin, Alexandre, 86 Yersinia pestis, 86–7

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