Surface modification of textiles
Edited by Q. Wei
Published by Woodhead Publishing Limited in association with The Textile Institute
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M. J. JOHN AND R. D. ANANDJIWALA, CSIR, South Africa
viContents
3Textile surface functionalization by physical vapor deposition (PVD)58
Q. WEI, Y. XU AND Y. WANG, Jiangnan University, China
3.1Introduction58
3.2Working principles of physical vapor deposition59
3.3Funtionalization of textiles by sputtering63
3.4Interfacial bonding79
3.5Future trends86
3.6References86
4Surface grafting of textiles91
N. ABIDI, Texas Tech University, USA
4.1Introduction91
4.2Techniques of surface grafting91
4.3Properties achieved and applications101
4.4Strengths and weaknesses of surface grafting104
4.5Future trends105
4.6Sources of further information and advice105
4.7References105
5Modification of textile surfaces using electroless deposition108
S. Q. JIANG AND R. H. GUO, The Hong Kong Polytechnic University, China
5.1Introduction108
5.2The techniques and key principles of electroless deposition109
5.3Characterisation of electroless copper- and nickel-plated polyester fabrics112
5.4Strengths and weaknesses of electroless deposition122
5.5Future trends123
5.6Sources of further information and advice123
5.7References124
Contentsvii
6Textile surface functionalisation by chemical vapourdeposition (CVD)126
J. I. B. WILSON, Heriot-Watt University, UK
6.1Introduction126
6.2Practical methods for chemical vapour deposition129
6.3Characteristics of chemical vapour deposition coatings132
6.4Applications133
6.5Current trends and potential advances in uses and techniques136
6.6Further sources of information137
6.7References137
7Enzyme surface modification of textiles139
V. A. NIERSTRASZ, Ghent University, Belgium
7.1Introduction: principles of enzyme surface modification of textile materials139
7.2Enzymes, technologies and materials (natural materials, synthetic materials, biomaterials)142
7.3Strengths and weaknesses of enzyme surface modification155
7.4Future trends156
7.5Acknowledgements157
7.6References158
8Modification of textile surfaces using nanoparticles164
N. VIGNESHWARAN, Central Institute for Research on Cotton Technology, India
8.1Introduction164
8.2Nanoparticles synthesis and characterization165
8.3Functional properties using nanoparticles169
8.4Commercialization of nanofinishing in textiles180
8.5Strengths and weaknesses of nanotechnology for surface modification182
8.6Future trends182
8.7References182
viiiContents
9Modification of textile surfaces using the sol-gel technique185
T. TEXTOR, Deutsches Textilforschungszentrum Nord-West e.V., Germany
9.1Introduction: the principles of the sol-gel technique185
9.2General aspects of textile finishing using (nano-)sols190
9.3Sol-gel-based finishing effects197
9.4Future trends209
9.5References210
10Nano-modification of textile surfaces using layer-by-layer deposition methods214 P. LU, University of California, USA; and B. DING, Donghua University, China
10.1Introduction214
10.2The LbL deposition technique218
10.3LbL deposition on textile surfaces221
10.4Conclusions and future trends232
10.5Acknowledgements233
10.6References233
11Surface modification of textiles for composite and filtration applications238
A. S. HOCKENBERGER, Uludag University, Turkey
11.1Introduction238
11.2Surface modification of textiles for composites239
11.3Surface properties of reinforcing fibers and applications246
11.4Surface modification of textiles for filtration257
11.5Applications of surface-modified fibers used for filtration260
11.6Future trends262
11.7References264
Contentsix
12Surface modification of textiles by aqueous solutions269
J. WANG, The Procter & Gamble Company, USA; and J. LIU, Zhejiang Sci-Tech University, China
12.1Introduction269
12.2Mechanisms and chemistries of textile surface modifications270
12.3Applications of surface modification of textiles by aqueous solutions280
12.4Future trends291
12.5References293
13Surface modification of textiles by plasma treatments296
R. R. MATHER, Heriot-Watt University, UK
13.1Introduction296
13.2Nature of plasmas297
13.3Plasma generation297
13.4Low-pressure versus atmospheric-pressure treatments299
13.5Strengths and limitations of plasma treatments300
13.6Characterisation of plasma-treated textile surfaces301
13.7Modifications to textile surfaces303
13.8Applications311
13.9Future trends313
13.10Sources of further information and advice314
13.11References314
14Emerging approaches to the surface modification oftextiles318
Q. WEI, Jiangnan University, China
14.1The expansion of textiles into technical applications318
14.2New techniques for surface modification319
14.3Future trends321
14.4References322
Index325
(* = main contact)
Chapter 1
Dr M. J. John and Dr R. D. Anandjiwala*
CSIR Materials Science and Manufacturing Fibres and Textiles Competence Area
P.O. Box 1124
Port Elizabeth 6000
South Africa
E-mail: ranandi@csir.co.za
Chapter 2
Dr Q. Wei,* F. Huang and Y. Cai
Key Laboratory of Eco-textiles
Ministry of Education
Jiangnan University
Wuxi 214122
People’s Republic of China
E-mail: qfwei@jiangnan.edu.cn
Chapter 3
Dr Q. Wei,* Y. Xu and Y. Wang
Key Laboratory of Eco-textiles
Ministry of Education
Jiangnan University
Wuxi 214122
People’s Republic of China
E-mail: qfwei@jiangnan.edu.cn
Contributor contact details
Chapter 4
Dr N. Abidi
Fiber and Biopolymer Research Institute
Department of Plant and Soil Science
Texas Tech University 1001 East Loop 289 Lubbock, TX 79403
USA
E-mail: n.abidi@ttu.edu
Chapter 5
Dr S. Q. Jiang* and R. H. Guo Institute of Textiles and Clothing
The Hong Kong Polytechnic University
Hung Hom, Kowloon
Hong Kong
People’s Republic of China
E-mail: tckinor@inet.polyu.edu.hk
Chapter 6
Professor J. I. B. Wilson Physics Department School of Engineering and Physical Sciences
Heriot-Watt University Riccarton
Edinburgh EH14 4AS
Scotland UK
E-mail: j.i.b.wilson@hw.ac.uk
Chapter 7
Dr ir. V. A. Nierstrasz
Department of Textiles
Ghent University
Technologiepark 907 9052 Gent/Zwijnaarde Belgium
E-mail: Vincent.Nierstrasz@UGent.be
Chapter 8
Dr N. Vigneshwaran
The Nanotechnology Research Group
Central Institute for Research on Cotton Technology
Adenwala Road, Matunga Mumbai 400019 India
E-mail: nvw75@yahoo.com
Chapter 9
Dr T. Textor
Deutsches Textilforschungszentrum
Nord-West e.V.
Institut an der Universität DuisburgEssen
Adlerstr. 1 47798 Krefeld Germany
E-mail: textor@dtnw.de
Chapter 10
Dr P. Lu*
Fiber and Polymer Science
University of California Davis, CA 95616
USA
E-mail: pplu@ucdavis.edu
Dr B. Ding
Modern Textile Institute
Donghua University
Shanghai 200051
People’s Republic of China
E-mail: binding75@yahoo.com
Chapter 11
Professor A. S. Hockenberger
Uludag University
Faculty of Engineering and Architecture
Textile Engineering Department 16059 Gorukle-Bursa
Turkey
E-mail: sengonul@uludag.edu.tr
Chapter 12
Dr Jiping Wang*
The Procter & Gamble Company 5289 Vine Street Cincinnati, OH 45217
USA
E-mail: wang.j.5@pg.com
Professor Jinqiang Liu
Zhejiang Sci-Tech University #2 Street Xiasha Higher Education Zone
Hangzhou
Zhejiang 310018
People’s Republic of China
E-mail: jqliu@zstu.edu.cn
Chapter 13
Dr Robert R. Mather
School of Engineering and Physical Sciences
Heriot-Watt University
Riccarton
Edinburgh EH14 4AS
Scotland, UK
E-mail: R.R.Mather@hw.ac.uk
Chapter 14
Dr Q. Wei
Key Laboratory of Eco-textiles
Ministry of Education
Jiangnan University
Wuxi 214122
People’s Republic of China
E-mail: qfwei@jiangnan.edu.cn
Woodhead Publishing 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
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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
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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
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13 Textiles in automotive engineering
W. Fung and J. M. Hardcastle
14 Handbook of textile design
J. Wilson
15 High-performance fibres
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16
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17 Medical textiles
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18 Regenerated cellulose fibres
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19 Silk, mohair, cashmere and other luxury fibres
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20 Smart fibres, fabrics and clothing
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21 Yarn texturing technology
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22 Encyclopedia of textile finishing
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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
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
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41 Design and manufacture of textile composites
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42 Effect of mechanical and physical properties on fabric hand
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43 New millennium fibers
T. Hongu, M. Takigami and G. O. Phillips
44 Textiles for protection
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45 Textiles in sport
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46 Wearable electronics and photonics
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47 Biodegradable and sustainable fibres
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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. 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
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. Horrocks
61 Composite forming technologies
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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. Deopora, 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 textiles 2007
Edited by J. Kennedy, A. Anand, M. Miraftab and S. Rajendran
76 Fabric testing
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77 Biologically inspired textiles
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78 Friction in textiles
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79 Textile advances in the automotive industry
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80 Structure and mechanics of textile fibre assemblies
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81 Engineering textiles: Integrating the design and manufacture of textile products
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82 Polyolefin fibres: industrial and medical applications
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83 Smart clothes and wearable technology
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84 Identification of textile fibres
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85 Advanced textiles for wound care
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86 Fatigue failure of textile fibres
Edited by M. Miraftab
87 Advances in carpet technology
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88 Handbook of textile fibre structure
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89 Advances in knitting technology
Edited by T. Dias
90 Smart textile coatings and laminates
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91 Tensile failure of fibres handbook
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92 Interior textiles: Design and developments
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93 Textiles for cold weather apparel
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94 Modelling and predicting textile behaviour
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95 Textiles for construction
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96 Engineering apparel fabrics and garments
J. Fan and L. Hunter
97 Surface modification of textiles
Edited by Q. Wei
Preface
Textile industries have been experiencing fast development with versatile productsfor a wide spectrum of applications being developed through technological innovations. In various applications, the functions of textile materials are associated with phenomena such as wetting, biocompatibility, adsorption and electrical conductivity. Wetting, friction, adhesion, biocompatibility and adsorptionall begin at the surface. In these cases, it is the surfaces, rather than the bulk compositions, that are critical to the material performance. The properties of textile surfaces depend closely on their surface chemical and physical structures, which vary according to differences in polymer composition, structures of fibers and fiber assemblies as well as treatment.
The surfaces of textiles offer a platform for functional modifications to meet specific requirements for a variety of applications. Surface modification of textiles refers to the use of a wide range of technologies designed to modify the surface properties of textiles to create the surface structures that give the textile product the desired properties. The surface modification of textiles may be achieved by various techniques ranging from traditional solution treatments to biological approaches. Functionalization of textile surfaces has attracted a great deal of attention in recent years, with the help of new technologies such as high energy beam processes, vapor deposition and nanoparticle coatings. In textiles, the fiber is the basis for creating structural forms and functional properties, and by manipulatingthe bulk and surface structures of fibers, the resulting textiles maypossess new capabilities and functions to meet the demands for particular uses.
It has been recognized that surface analysis is an essential process in improving our understanding of surface structure and its relationship to the technical performance of textiles and the technologies used for the surface modification of textiles. New developments in surface analysis technologies allow surface characterizations to be achieved at the nano-scale level.
This book provides a detailed review of the surfaces of textiles, the surface
characterization and modification of textiles, and the applications of the modified textiles. It is believed that this book will promote understanding of surface modification and the development of surface modification strategies for various applications of textiles.
Q. Wei
Surface modification and preparation techniques for textile materials
Abstract: This chapter presents an overview of some important surface modification techniques employed for improved functional behaviour of textiles. Textile materials are used in a variety of applications where surface modification is of profound importance as it improves various properties –such as softness, dyeability, absorbance and wettability. In this chapter, the most commonly used surface modification techniques, ranging from plasma treatment to nanocoatings, for both natural and synthetic fibres have been discussed. Recent studies involving the modification and characterisation of textiles have also been highlighted.
Key words: textile, modification, preparation techniques, wet processing.
1.1Introduction
Textile technology deals with several disciplines including: the structure, propertiesand behaviour of fibres; how fibres are assembled into fibrous structuresand fabrics; surface modification of fibres; and the making, analysis, sale and end uses of fibres and fabrics. Of these disciplines, surface modification of textiles is of profound importance as it improves properties such as softness, adhesion and wettability. Functional properties can also be imparted to textile fibres. Textiles find use in a variety of applications, the most common of which are clothing, carpeting and furnishing. Textiles used for industrial purposes, and chosen for characteristics other than their appearance, are commonly referred to as technical textiles. Technical textiles include textile structures for automotive applications, medical textiles (e.g. bandages, pressure garments and implants), geotextiles (for reinforcement of embankments), agro-textiles (textiles for crop protection), protective clothing (e.g. against heat and radiation for fire-fighter clothing, against molten metals for welders, stab-proof clothing and bullet-proof vests). In all these applications, stringent performance requirements must be met. Textile fibres are classified into two main groups, i.e. natural and man-made, depending upon their origin. Natural fibres can be mainly divided into protein fibres of animal origin (wool, silk), plant fibres of cellulosic origin and mineral fibres. Man-made fibres include three main categories:
Plant origin
Animal origin
Natural Man-made (see Fig. 1.2)
Mineral origin (asbestos)
1.1 Classification of textile fibres.1
•from synthetic polymers, such as polyester, nylon and acrylic;
•from regenerated cellulose, such as viscose and lyocell;
•cellulose acetates, such as diacetate and triacetate.
A number of reports on the classification of textile fibres have been published.1–4 There are also newly synthesised fibres engineered for high-performance end uses, for example, aramid and polysulfide fibres. Figures 1.1 and 1.2 give the detailed classification of textile fibres.
1.2Natural fibres
1.2.1Plant origin
Plant fibres include bast (or stem or soft sclerenchyma) fibres, leaf or hard fibres, seed, fruit, wood, cereal straw, and other grass fibres. Plant fibres are composed of cellulose, hemicelluose and lignin. Common examples of plant fibres are flax (bast fibre), sisal (leaf fibre) and cotton and oil palm (seed). Table 1.1 presents a list of
Textile fibres
Fruit (coir)
Leaf (sisal)
Bast (flax)
Hair Silk Wool
Natural polymer
Regenerated protein (casein)
Man-made fibres
Synthetic polymer
Synthetic polymer, natural origin (PLA fibre)
Regenerated cellulose Polyesters Polyamides Polyurethanes
Cellulose esters
Polyvinyl derivatives Polymerised hydrocarbons
Polysulphides Polybenzimidazoles
1.2 Classification of man-made fibres.1 (PLA = poly-lactic acid.)
commonly used plant fibres and their origin. The use of such plant fibres in reinforced composites has increased owing to their low costs, biodegradability and the fact that they can compete well with other fibres in terms of strength per weight of material.
1.2.2Animal origin
Animal fibres include silk, wool and hair. Silk is the secretion product from silkworm. Wool is classified in the soft hair group while the coarse hair group comprises horse hair, cow hair and human hair. Animal fibres are composed mainly of proteins. Wool fibres are composed of keratin, a complex mixture of proteins characterised by the presence of a considerable amount of the amino acid cystine. The disulfide bond in this amino acid residue forms cross-linkages between different protein chains thereby making it more stable and less soluble than other proteins.5 Table 1.2 presents a list of commonly used animal fibres. Deer hair and racoon dog hair are also used, mainly for the bristles of paint brushes.
Table 1.1 List of important plant fibres
Fibre sourceSpeciesOrigin
Abaca
Musa textilis Leaf
Bagasse – Grass
Bamboo(>1250 species)Grass
Banana
Broom root
Cantala
Caroa
China jute
Coir
Cotton
Curaua
Date palm
Flax
Hemp
Henequen
Musa indica Leaf
Muhlenbergia macroura Root
Agave cantala Leaf
Neoglaziovia variegate Leaf
Abutilon theophrasti Stem
Cocos nucifera Fruit
Gossypium sp.Seed
Ananas erectifolius Leaf
Phoenix dactylifera Leaf
Linum usitatissimum Stem
Cannabis sativa Stem
Agave fourcroydes Leaf
Isora Helicteres isora Stem
Istle
Jute
Kapok
Kenaf
Kudzu
Mauritius hemp
Nettle
Oil palm
Phormium
Piassava
Pineapple
Roselle
Ramie
Sansevieria
Samuela carnerosana Leaf
Corchorus capsularis Stem
Ceiba pentranda Fruit
Hibiscus cannabinus Stem
Pueraria thunbergiana Stem
Furcraea gigantea Leaf
Urtica dioica Stem
Elaeis guineensis Fruit
Phormium tenas Leaf
Attalea funifera Leaf
Ananus comosus Leaf
Hibiscus sabdariffa Stem
Boehmeria nivea Stem
Sansevieria Leaf (Bowstring hemp)
Sisal
Sponge gourd
Agave sisilana Leaf
Luffa cylinderica Fruit
Straw (cereal) – Stalk
Sun hemp
Cadillo/urena
Crorolaria juncea Stem
Urena lobata Stem
Wood(>10000 species)Stem
1.3Synthetic fibres
Synthetic fibres form an important part of the textile industry, with the production of polyester alone surpassing that of cotton. There are many different kinds of synthetic fibres but among them polyamide is widely used, for example nylon. The fibres of polyvinyl alcohol and polypropylene (PP) are also important. Given this importance, research into effective production of these fibres and improving fibre
Surface modification and preparation techniques5
Table 1.2 List of important animal fibres
Animal fibreOrigin
Silk (domestic silk, wild silk)Silkworm
WoolSheep
Cashmere woolGoat reared in Himalayan region
Camel woolCamel
MohairAngora goat
Alpaca woolGoat reared in Andes mountains in Peru
Rabbit hairAngora rabbit
Cow hairCow
From reference 6. properties is warranted. A great disadvantage of some synthetic fibres is their low hydrophilicity. This affects the processing of the fibres especially during wet treatments. The surfaces are not easily wetted, thus impeding the application of finishing compounds and colouring agents. In addition, a hydrophobic material hinders water from penetrating into the pores of fabric.
Nonwoven fabrics are formed by extrusion processes and may be manufactured inexpensively so that they can be used in disposable products that are discarded after only one or a few uses. For example, polypropylene (PP) and polyester nonwoven fabrics are used in disposable absorbent articles, such as diapers, feminine care products and wipes. Moreover, they are also widely used as filtration media, battery separators and geotextiles. In all these applications, the PP and polyester nonwoven fabrics need to be wettable by water or aqueous liquids, which is not an inherent characteristic of the material.
Surface modification of textiles is performed to improve various properties such as softness, dyeability, absorbance and wettability. Recent advances in textile chemistry have resulted in imparting various functional properties such as antimicrobial activity, decreased skin irritation properties and also enhanced fragrance to textiles.
1.4Surface preparation techniques for textile materials
Surface preparation techniques are mainly used for the removal of foreign materialsto improve uniformity, hydrophilic nature and affinity for dyestuffs and other treatments and relaxation of residual tensions in synthetic fibres. The surface preparation technique usually depends on the type of fibre (natural or synthetic) and the form of the fibrous structure (i.e. spun yarn, woven or knitted fabric). Some of the common preparation techniques are outlined below.
1.4.1Singeing
Singeing is usually carried out on woven cotton fabrics and yarns to burn protruding fibres which affect subsequent processing, such as dyeing and finishing.The fabric is passed over a row of gas flames and then immediately dipped into a quench bath to extinguish the sparks and cool the fabric. The quench bath often contains a desizing solution, in which case the final step in singeing becomes a combined singeing and desizing operation.
1.4.2Desizing
Desizing is used for removing previously applied sizing compounds from woven fabric and is usually the first wet finishing operation performed on woven fabric. Different desizing techniques are employed depending upon the kind of sizing agent to be removed. Sizing agents are commonly based on natural polysaccharides (starch, protein and cellulosic derivatives) and synthetic polymers (polyvinyl alcohol (PVA), polyacrylates, polyesters and polyvinyl acetates). Depending on the sizing agent used, sizes can be removed using hot water, enzymes or hydrogen peroxide.
Currently applied techniques can be categorised as follows: (a)removal of starch-based sizing agents (water-insoluble sizes); (b)removal of water-soluble sizes (PVA and polyacrylates).
1.4.3Scouring
The purpose of scouring is to extract impurities present in the raw fibre or picked up at a later stage – such as pectins, fat and waxes, proteins, inorganic substances (e.g. alkali metal salts), calcium and magnesium phosphates, aluminium and iron oxides, sizes (when scouring is carried out on woven fabric as part of desizing), residual sizes and sizing degradation products (when scouring is carried out on woven fabric after desizing).
Scouring can be carried out as a separate step of the process or in combination with other treatments (usually bleaching or desizing) on all kind of substrates: woven fabric (sized or desized), knitted fabric and yarn. The action of scouring is performed by an alkali (sodium hydroxide or sodium carbonate) together with auxiliaries that include non-ionic (alcohol ethoxylates, alkyl phenol ethoxylates) and anionic (alkyl sulfonates, phosphates, carboxylates) additives.
1.4.4Bleaching
Bleaching is used to remove colour impurities in natural and some man-made fibres to produce a whiter substrate. This is usually accomplished by oxidising the natural pigments of the fibre using an oxidising agent, for example, hydrogen
Surface modification and preparation techniques7
peroxide. Cotton is usually bleached using hydrogen peroxide under alkaline conditions,with the addition of sodium silicate and magnesium sulfate to stabilise the process and reduce fibre damage. Metal ions, such as iron and copper, can catalyse the decomposition of the hydrogen peroxide resulting in the formation of oxycellulose and localised damage to the fibres. Bleaching of cotton fabrics can be undertaken as continuous or pad batch processes. Newer research in this field is directed towards non-peroxide bleaching to reduce the adverse effects on the environment caused by effluent discharge. Non-peroxide bleaching agents like sodium hypochlorite and sodium chlorite are widely used but have lost favour because of environmental issues.
1.4.5Mercerisation
Mercerisation is another technique and is used for cellulosic and cotton fibres in particular.7 The process involves the treatment of fabrics with sodium hydroxide and is named after John Mercer. It has been observed that compared with untreated cotton mercerised cotton has greater strength and lustre, is more absorbent and has a greater capacity to absorb dye. When natural fibres are treated with sodium hydroxide, it results in dissolution of hemicellulose and rearrangement of microfibrils in a more compact manner.
Surface preparation techniques for man-made composites would involve techniqueslike solvent cleaning with solvents such as isopropyl alcohol, surface abrasion, and conditioning and neutralisation with suitable chemical agents.
1.5Surface modification techniques for textile materials
There are several surface modification techniques that have been developed to improve wetting, adhesion and other properties of textile surfaces by introducing a variety of reactive groups. Some of the common techniques are described below.
1.5.1Wet chemical processing
In wet chemical surface modification, the textile surface is treated with liquid reagents to generate reactive functional groups on the surface. This technique results in the penetration of the textile substrate by the chemical agent. The commonly used chemical processing agents are chromic acid and potassium permanganate which introduce oxygen-containing moeties to PP and polyethylene fibres. The degree of surface functionalisation is therefore not repeatable between polymers of different molecular weight and crystallinity. This type of treatment can also lead to the generation of hazardous chemical waste and can result in surface etching.
1.5.2Ionised gas treatments
Plasma treatment
Plasma is a high-energy state of matter in which a gas is partially ionised into charged particles, electrons and neutral molecules. Gas plasmas were introduced in the 1960s but it is only recently that it has been possible to treat textiles on a commercial scale. Plasma is essentially a dry process providing modification of the top nanometre surface without using solvents or generating chemical waste. The type of functionalisation imparted can be varied by the plasma gas selected (e.g. Ar, He, N2, O2, H2O, CO2 and NH3) and operating parameters (e.g. pressure, power, time and gas flow rate). Oxygen plasma is used to impart oxygencontaining functional groups to polymer surfaces. Carbon dioxide plasma has been used to introduce carboxyl groups. Inert gases are used to introduce radical sites on the polymer surface for subsequent graft polymerisation.
Exposure to plasma results in the cleaning of the surface of materials and modification of surface energies. Active species from the plasma bombard or react with monolayers on the surface of materials and change the properties either temporarily or permanently. The advantages of plasma technology are its potential environmental friendliness and energy conservation benefits in developing highperformance materials.
The properties of natural and synthetic fibres are modified by processes such as polymerisation, grafting and cross-linking. As adhesion is a surface-dependent property, plasma technology can achieve modification of the near-surface region effectively without affecting the bulk properties of the materials of interest. The common benefits of plasma surface modifications on textile materials are enhancements in wettability8, 9, printability10, 11, adhesion 12, 13 and sterilisation.14
Plasma can also be used as a precursor to other surface modification techniques; for example, plasma activation followed by ultraviolet (UV) graft polymerisation or plasma activation followed by silane treatment.
Dielectric barrier discharges (DBDs) or ‘silent’ discharges are widely used for the plasma treatment of polymer films and textiles.15, 16 These discharges demonstrate great flexibility with respect to their geometric shape, working gas composition and operational parameters (input power, frequency of the applied voltage, pressure, gas flow, substrate exposure time, etc.). A DBD is obtained between two electrodes, at least one of which is covered with a dielectric, when a high-voltage alternating current is applied between the electrodes. The most interesting property of DBDs is that in most gases the breakdown starts at many points, followed by the development of independent current filaments (termed ‘micro-discharges’). These micro-discharges are of nanosecond duration and are uniformly distributed over the dielectric surface.
A disadvantage of plasma treatment is that plasma generation requires a vacuum to empty the chamber of latent gases; this is complicated for continuous operation
Surface modification and preparation techniques9
in a large-scale industrial setting. In addition, there are several processing parametersto optimise – including time, temperature, power and distance of substrate from plasma source – which can affect the reproducibility of results. Morent et al . 17 have presented an interesting overview of the literature on the treatment of textiles with non-thermal plasmas.
Corona discharge
Corona discharge is a low-cost, simple process in which an electrically induced stream of ionised air bombards the polymer surface. It is usually used to promote adhesion in inert polymers. A disadvantage of the process is contamination of the polymer surface since vacuum conditions are not required.
Flame treatment
Flame treatment is a non-specific surface functionalisation technique that bombardsthe polymer surface with ionised air generating large amounts of surface oxidation products. The reactive oxygen is generated by burning an oxygen-rich gas mixture. Flame treatment has been shown to impart hydroxyl, aldehyde and carboxylic acid functionalities to polyethylene and is utilised to enhance printability, wettability and adhesion. One drawback of flame treatment is that it can reduce the optical clarity of polymers; in addition, there are many parameters (including flame temperature, contact time and composition) that must be accurately controlled to maintain consistent treatment and to avoid burning.
Ultraviolet irradiation
When polymer surfaces are exposed to UV light, polymer surfaces generate reactive sites which can become functional groups upon exposure. The difference between ionised gas treatments and UV irradiation is the ability to tailor the depth of surface reactivity by varying wavelength and absorption coefficient.
1.6Recent studies on the modification of textiles
Strnad et al. 18 investigated the effect of chitosan treatment on sorption and mechanical properties of cotton fibres. Cotton fibres initially underwent different pre-treatments (alkali treatment, bleaching, demineralisation) and were then oxidisedusing differing procedures containing KIO4 solutions and then treated with chitosan. The authors observed that all the oxidation procedures, even under very mild conditions, had a significant influence on the worsening of mechanical properties. The treatment of oxidised cotton with chitosan had no influence on breaking force and elongation, but increased the Young’s modulus of fibres. This was attributed to the fact that chitosan bound itself to raw cotton through inter-
4µm 9.3KV 02 172 S (a) (b)
1.3 Surface structure of polyester fibre (a) untreated (b) under high fluence (5pulses at 100mJ/cm2) laser irradiation.19
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"It was more than any fellow could stand," he said, gnawing his yellow mustache, and looking down at his mother with those handsome, idle gray eyes of his, which were the most convincing of arguments, before which all her excellent reasons for attending church—such as "what people would say," and "how would it look," and "what a bad example it would set," if he did not go—crumbled to ashes. She found John more amenable; but I do not on this account credit John with any great superiority to Humphrey only that he had greater powers of endurance, and was not so sure as Humphrey that the very surest way to please his mother was to please himself. Then, too, Sunday mornings at Brooklands were apt to hang heavy on his hands, for he had not the resources of Humphrey. He could not spend an hour or two in contented contemplation of a family of fox-terrier puppies; he found that "the points" of the very cleverest little mare in creation palled after five minutes' serious consideration, and that the conversation of grooms and stablemen still left a good deal to be desired in the way of entertainment; in fact, he had none of the elevated and refined tastes of an English country gentleman; so John Rossitter went to church with his mother, and endured, with equal stoicism, sermons from Mr. Peters, Mr. Glover, or Mr. Malone. He did not yawn in the undisguised manner of Dr. Gardener Jones opposite, who let every one see what a fine set of teeth he had, and healthy red tongue, at short intervals; he did not go to sleep and snore like old Mrs. Robbins, and one or two more; but when the regulation half hour was over, his eyebrows would rise and the calm inattention of his face became ruffled, and his hand move quietly to his waistcoat pocket and his watch appear, an action which Mr. Glover felt acutely in every fibre, though his back was turned to John Rossitter, and he would grow red to the very finger-tips, and his "finally," "lastly," and "in conclusion" would get sadly muddled in his nervous efforts to make short cuts to the end. So strong had this habit of inattention become, that it would have required something much more striking than our missionary Bishop to startle him out of it; and it was only the sight of Miss Toosey's face that brought back his thoughts from their wanderings, to Martel church and its sleepy congregation, and the Bishop's voice from the high pulpit. He could see her through a vista of heads between Mr. Cooper's bald head and Miss Purts's feathers and pink rosebuds; now and then the view was cut off by Mrs. Robbins giving a convulsive nod, or one of the little Miss Coopers fidgeting up a broad-brimmed hat.
(Church-goers)
"Was the sermon so eloquent?" John Rossitter wondered. Certainly that listening, rapt face was—quite a common, little, wizen, old-maidish face, with nothing intellectual or noble about it, and yet transfigured into something like beauty with the brightness of a reflected light. Don't you know how sometimes a scrap of broken glass on a dust heap will catch the sunlight and shine with quite dazzling brilliancy, and how a little smutty raindrop in a London court will hold the sun and a gleaming changing rainbow in its little mirror?
CHAPTER
III.
"Where does Miss Toosey live?" said John Rossitter on Monday morning. "I think I may as well go and call on her, as I have nothing else to do."
I do not know what impelled him to go. It is impossible to define motives accurately, even our own. We cannot say sometimes why we do a thing; every reason may be against it—common sense, habit, inclination, experience, duty, all may be pulling the other way, and yet we tear ourselves loose, and do the thing, urged by some invisible motive of whose existence we are hardly conscious. And if it is so in ourselves, how much more difficult to dissect other people's motives! and it is generally safer to leave the cause alone altogether, and only regard the effects produced. So it is enough to say that, on that Monday morning, Miss Toosey heard the rattle of wheels along North Street, and, looking out, saw the Rossitters' dog-cart and high-stepping chestnut mare, which, to her extreme surprise, stopped in front of her door.
"Something wrong with the harness," she concluded, as the little groom flew out and stood at the horse's head, with his arms crossed.
"Bless the child!" Miss Toosey said, "as if the creature could not have swallowed him at a mouthful, top-boots and all!"
But her observation of the groom from the bedroom window was interrupted by a loud knock at the door, and before she had time to tie her cap-strings, or put a pin in the back of her collar, Betty came rushing up, out of breath and red-faced, with a card held in the corner of her apron, bearing the name, "Mr. John Rossitter."
"And he said he hoped as how you'd excuse his calling so early—and a flower in his button-hole beautiful," added Betty in a snorting whisper, distinctly audible in the parlor below.
Then followed some hasty opening and shutting of drawers, and hurried footsteps; and then Miss Toosey descended, rather fluttered and nervous, with her Sunday cap on, and a clean pocket handkerchief.
"I must introduce myself, Miss Toosey," John said, "for I dare say you have quite forgotten me."
"Forgotten you, Mr. John? Why I knew you long before you were born, or thought of. Oh, dear!" said Miss Toosey, "I don't mean that, of course; but I knew your mamma before she was born"—
"I ought to apologize," John struck in, anxious to save Miss Toosey from any further floundering in the bogs of memory, "for coming so early; but the fact is, that I am going up to London this evening; and my mother tells me that Dr. Toosey had a very capital cure for toothache, and she thought you would very likely have kept it, and would let me have it."
Impostor that he was! looking at her with such serious, earnest eyes, when he had composed this ridiculous and barefaced excuse for calling as he came along.
Miss Toosey racked her brain to remember this renowned remedy, and could only recall an occasion when she had toothache, and her father dragged out a double tooth, with great exertion and bad language on his part, and great pain and many tears on hers.
"I cannot quite remember the remedy your mamma means; but I have a book full of very valuable prescriptions, which I will find at once."
"Pray don't trouble, Miss Toosey; I have no toothache at present; but if you would let my mother have it some time at your leisure, I should be greatly obliged."
And then they talked for five minutes about toothache; and John, smiling, showed such white, even teeth that you would have fancied that he had not had much trouble with them; and you would have fancied right.
"What a curious book you have here," John Rossitter said, looking at a book lying open on the table. It was an old book called "Voyages and Adventures;" and it was open at an awful picture of a cannibal feast, with a man being roasted in front of a fire, and a group of savages dancing ferociously around, in all the horrors of war-paint and feathers, and in a
simple but effective costume of a necklace, a fringe round the waist, a ring in the nose, and a penny in the under lip.
Miss Toosey blushed; she was not used to fashionable picture galleries where Eves and Venuses, in unadorned beauty, are admired and criticised by the sensible young people of the present day.
"Though to be sure," she said afterwards, "it's not so bad, as the poor things are black, so they don't look quite so naked; and I always think a white pig is a more indecent looking creature than a black one."
So she turned his attention with great tact to the atlas that was also lying open on the table. It was the atlas that was in use fifty years ago, and which had been bought for Miss Toosey when she went to Miss Singer's "Academy for Young Ladies" to be finished. At this abode of learning, she had been taught to make wax flowers and do crochet, to speak a few words of what was supposed to be French, and to play a tune or two laboriously on the piano, an education which was considered very elegant and elaborate at that time, but would hardly, I am afraid, qualify her for one of the Oxford and Cambridge local examinations, or even for a very high standard at a national school. She had also learnt a little geography and the use of the globes, but not enough to survive for fifty years; and she felt quite at sea this morning, when she reached down the long-unused atlas to find the position of the diocese of Nawaub, and, after long study, had arrived at the conclusion that it must be on the celestial globe, which had always been a puzzle to her.
It was no wonder that she had not been able to find Nawaub, for where the towns and rivers and mountains and plains stood, which the Bishop had described, there was only marked on the map "Undiscovered territory," a vague-looking spot altogether, gradually shading off into the sea without any distinct red or blue line to mark the extent of terra firma, as in other parts of the world.
John Rossitter showed her where he imagined Nawaub to be, and then inquired if she were interested in Missions.
"Well, Mr. John," Miss Toosey said, "I don't mind telling you, though I have not told any one else, except Betty; but I've made up my mind to go out
to Nawaub as soon as I can arrange everything."
"As a missionary, Miss Toosey?"
"Yes, Mr. John, as a missionary."
She spoke quite quietly, as if she were not sixty-five, with a tendency to asthma, and more than a tendency to rheumatism,—a nervous, fidgety old maid, to whom a journey to Bristol was an event to flutter the nerves, and cause sleepless nights, and take away the appetite for some time beforehand. I think the very magnitude of her resolution took away her attention from the terrible details, just as we lose sight of the precipices, chasms, and rocks that lie between, when we are looking to the mountain top. The way to Bristol was beset with dangers, such as losing the train, getting wrong change when you take your ticket, the draughtiness of the waiting-room, the incivility of the porters, the trains starting from unexpected platforms, the difficulty of opening doors and shutting windows, the constant tendency to get into smoking carriages by mistake, not to speak of railway accidents, and murderers and thieves for traveling companions; but these were lost sight of in the prospect of a journey to the other end of the world, full of real, substantial dangers of which she was ignorant. This ignorance was no doubt a great help to her in some ways; she could not form the slightest idea of what a missionary's life really is; nor can you, reader, nor can I, though we may have read missionary books by the dozen, which Miss Toosey had not. But this same ignorance, while it covered up many real difficulties, also painted grotesque horrors before Miss Toosey's mind, which might well have frightened any old maiden lady of sixty-five. She mixed up "Greenland's icy mountains" and "Afric's coral strands" with great impartiality in her ideas of Nawaub, forming such a frightful combination of sandy deserts and icebergs, lions and white bears, naked black savages and snow drifts, that the stoutest heart might have quailed at the prospect; and yet, when Miss Toosey came down to breakfast that morning, with her mind firmly made up to the venture, her little maid, Betty, did not notice anything remarkable about her, except that her cap was put on wrong side in front,—which was not a very unusual occurrence—and that she stirred up her tea with her spectacles once. Her interview with Betty had been rather upsetting. Betty was not quick at taking in new ideas; and she had got it so firmly into her head that Miss Toosey was wishing to administer a reproof to her about the handle of a
certain vegetable dish, "which come to pieces in my hand as was that cracked," that it was some time before she could be led to think differently; but when at last a ray of the truth penetrated her mental fog, her feelings can only be described by her own ejaculation, "Lor, now!" which I fear may offend ears polite. She had not been at church the evening before, having stepped round to see her mother, who was "doing nicely, thank you, with her fourteenth, a fine boy, as kep' on with fits constant, till Mr. Glover half christened him, which James Joseph is his name, and better ever since."
So it required all Miss Toosey's eloquence to put her scheme before Betty's plain common sense, so as to appear anything but a very crazy notion after all; and it was not till after half an hour's severe talking, and more than one tear falling on the two and a half pounds of neck of mutton that Betty gave in, which she did by throwing her apron over her head, and declaring, with a sob, that if Miss Toosey "would go for to do such a thing, she (Betty) would take and go too, that she would;" and Miss Toosey had to entreat her to remember her poor mother before making up her mind to such a step.
But to come back to John Rossitter. He was a barrister, you must know, and used to examine witnesses and to turn their heads inside out to pick out the grains of truth concealed there; and then, too, he had a great talent for listening, which is a rarer and more valuable gift even than that of fluent speech, which he also had at command on occasion. He had, too, a sympathetic, attentive interest in his face, if it was assumed, would have made a great actor of him, and that opened the people's hearts to him, as the sun does the flowers. And so Miss Toosey found herself laying her mittened hand on his coat sleeve, and looking up into his eyes for sympathy, and calling him "my dear," "just for all the world," she said, "as if he had been an old woman too."
(John Rossitter and Miss Toosey)
And what did he think of it all? Was he laughing at her? Certainly now and then there was a little twitch at the corner of his mouth, and a sparkle in his eye, and once he laughed aloud in uncoupled amusement; but I like John Rossitter too well to believe that he was doing what Dr. Gardener Jones called "getting a rise out of the old lady." It was so very easy to make fun of Miss Toosey, and draw her out and show up her absurdities,—even Mr. Glover, who was not a wit, could be exquisitely funny at her expense. But John Rossitter was too much of a sportsman to aim with his small-bore rifle at a little sparrow in a hedgerow; he left that sort of game for the catapults and pop-guns of the yokels.
And so Miss Toosey confided to him all the difficulties that had already come crowding into her head as she sat over her work that morning, any one of which would have occupied her mind for days at any other time,—the giving notice to leave her house, the disposal of the furniture,—"and you know, Mr. John, I have some really valuable pictures and things;" and she could not trust herself to glance at the portrait of old Toosey over the fireplace, in a black satin waistcoat and bunch of seals, a frilled shirt, a high complexion, and shiny black hair, with Corinthian pillars behind him, lest her eyes, already brimful, should overflow. She even consulted him as to whether it would be worth while to order in more coal, and lamented that she should have taken her sitting in church for another whole year only last Saturday. And then, without quite knowing how, she found herself discussing that all-important subject, dress, with John Rossitter.
"Though
to be sure, Mr. John, how should you know about such things?"
"Indeed, Miss Toosey, I'm not so ignorant as you think; and I quite agree with you that nothing looks so nice as a black silk on Sunday."
And Miss Toosey at once resolved to put a new braid round the bottom of the skirt as a good beginning of her preparations.
"I've got upstairs," Miss Toosey said reflectively, "a muslin dress that I wore when Rosina Smith was married. You remember Rosina Smith, Mr. John? No, of course not! She must have married before you were born. Sweet girl, Mr. John, very sweet! That dress has been rough dried for thirty years, and it's not quite in the fashion that ladies wear now; in fact, the skirt
has only three breadths, which is scanty, you know, as dresses go; but I thought," and there Miss Toosey glanced timidly at the picture of the cannibals, which still lay open, "that perhaps it would not matter out there."
"No, indeed, Miss Toosey," John answered, "I should think that three breadths would appear liberal and ample allowance among people whose skirts"—he was going to say, "are conspicuous from their absence," but from Miss Toosey's heightened color he changed it to "are not court trains."
The next question was whether she had better have it got up before leaving Martel.
"It might get crumpled in packing; but then, how can one guess what sort of laundresses one may find at the other side of the world,—not used, most likely, to getting up fine things."
"I have heard," said John very seriously, "that in some parts missionaries try as much as possible to become like the nations they are wishing to convert, and that the Roman Catholic priests in China shave their heads and wear pigtails."
"Yes, Mr. John, I have heard that," Miss Toosey said; "and their wives" (you see she did not rightly understand the arrangements of our sister Church as to the celibacy of the clergy) "cripple their feet in small shoes, blacken their teeth, and let their finger-nails grow."
"I suppose," says John, drawing "Voyages and Adventures" nearer, and looking at the pictures reflectively, "that the Nawaub missionaries don't go in for that sort of thing."
Miss Toosey grew red to the very finger-tips, and her back stiffened with horror.
"No, Mr. John, there is a point beyond which I cannot go!"
"To be sure! to be sure!" said John consolingly, "and you see there were no signs of anything of the kind about the Bishop."
