DYEING AND FINISHING OF SILK: TREATMENT OF SILK TO IMPROVE WRINKLE RECOVERY AND DYE RESIST BEHAVIOUR Thesis is submitted to The University of New South Wales for the degree of Master of Science by I Nyoman Supriyatna School of Fibre Science and Technology The University of New South Wales 1991 DECLARATION I certify that the work described in this thesis was performed by me in the school of Textile Technology at the University of New South Wales, and has not been submitted previously for any other university degree or award. I.N. Supriyatna. i ACKNOWLEDGEMENTS I would like to express my sincere gratitude thanks to my supervisor DR. S.K. David for her patient guidance during the course of this thesis. I also would like to thank to Associate Professor M. T. Pailthorpe for his advice and encouragement. My thanks are also due to other postgraduate students and the staff of the school of Textile Technology for their assistance in many ways. Further, I would like to thanks to my wife, N.M. Widiari, my daughter, P. Tania Sari and my parents for their encouragement. Finally, I am pleased to acknowledge to the Commonwealth Government of Australia for the provision of an AIDAB fellowship and to the Indonesian Government through Ministry of Industry for granting the necessary study leave. ii ABSTRACT This thesis is divided into two sections. The first section examines the wrinkle recovery behaviour of silk fabrics with respect to fabric structure, crosslinking treatments and surface polymer application. Changes in wrinkle recovery were measured with the Thermobench and Shirley Crease Recovery methods. It was found that the weave-type of the silk fabrics had a significant effect on their wrinkling behaviour. A crosslinking treatment utilising butane tetracarboxylic acid resulted in only marginal improvement in dry wrinkle recovery, while surface polymer application with silicone elastomers resulted in more significant improvements in dry wrinkle recovery. Both types of treatments were found to contribute to improvements in wet wrinkle recovery behaviour of the treated fabric. The second section of this thesis describes the dye resist behaviour of silk fabric treated with the reactive compounds, sulphamic acid and Sandospace R, with respect to the uptake of acid, metal complex and reactive dyestuffs. Sulphamic acid treated silk exhibited excellent dye resist behaviour toward all three classes of dyes, even at low treatment levels of this resist agent. High treatment levels of Sandospace R were required, however, for a significant resist effect to be conferred on the treated silk. The breaking strength, iii yellowness index and subjective handle of the treated fabrics were compared. iv CONTENTS page Chapter 1 The Silk Fibre 1.1 Introduction 2 1.2 Chemistry of Silk 5 1.2.1 Morphology of Silk 5 1. 2. 2 Chemical Composition of Silk 5 1.2.3 Physical Properties of Silk 7 1. 2. 4 Chemical Properties of Silk 9 Chapter 2 Introduction to Wrinkling Behaviour 11 2.1 The Phenomenon of Wrinkling/Creasing 12 2.1.1 General 12 2.1.2 Mechanism of Wrinkle Recovery 12 2.1.3 Factors Affecting Wrinkle Recovery 14 2.1.3.1 Temperature and Relative Humidity 15 2.1.3.2 Fibre, Yarn and Fabric Parameters 16 2.1.3.3 Effect of Ageing/Annealing 17 2.1.3.4 Laboratory Wrinkling Test Methods 18 2.2 Wrinkling Resist Finishing Agents 20 2.2.1 Historical Development of Wrinkle Resist Agents 20 2.2.2 Comparison of Wrinkle/Crease Resist Agents Used for Cotton, Wool, and Silk 23 2.3 Objective Measurement of Fabric Handle 29 2.4 Aim of The Present Work 30 Chapter 3 Wrinkling of Silk: Materials and Methods 32 V 3.1 Materials 33 3.1.1 Silk Fabric 33 3.1.2 Chemicals 33 3.1.2.1 Butane Tetracarboxylic Acid 33 3.1.2.2 Silicone Polymers 33 3.1.2.3 Catalyst 34 3. 2 Experimental Methods 34 3.2.1 Bleaching of Silk Fabrics 34 3.2.2 Crease Resist Finishing 34 3.2.2.1 Treatment of Silk With Butane Tetracarboxylic Acid (BTCA) 34 3.2.2.2 Treatment of Habutai Silk With Ultratex ESU and EMJ 35 3.2.3 Crease Recovery Measurements 35 3.2.3.1 Thermobench Method 35 3.2.3.2 Shirley Crease Recovery Test Method 36 3.2.3.2.1 Dry Crease Recovery 36 3.2.3.2.2 Wet Crease Recovery 37 3.2.4 Fabric Breaking Strength Measurements 37 3.2.5 Fabric Whiteness 37 3.2.6 Weight Gain 38 3.2.7 Laundering 38 Chapter 4 Wrinkling of Silk: Results and Discussion 39 4.1 Wrinkle Recovery of Silk Fabric-Various Weave Types 40 vi 4.2 Treatment of Unbleached Twill Silk Fabric With BTCA 41 4.2.1 Weight Gain 41 4.2.2 Wrinkle Recovery 42 4.3 Treatment of Various Bleached Fabrics With BTCA 44 4.4 Changes in Wet and Dry Wrinkle Recovery of Bleached Habutai Silk Treated With a Variety of Finishing Agents 45 4.5 Low Stress Mechanical Properties of Silk Fabric Treated With BTCA, ESU and EMJ Finishing Treatments 49 4.5.1 General 49 4.5.2 Bending Properties 49 4.5.3 Shear Properties 51 4.5.4 Compression and Surface Characteristics 52 4.5.5 Tensile Properties 54 4.5.6 Handle Evaluation 54 4.6 Conclusions 55 Chapter 5 Introduction to Dye Resist Effects 60 5.1 General 61 5.2 Dyeing of Silk 63 5.2.1 Acid Dyes 63 5.2.2 Metal Complex Dyes 65 5.2.3 Reactive Dyes 66 5.3 Reactive Dye Resist Agents 67 5.3.1 General 67 5.3.2 Sulphamic Acid 68 vii 5.3.3 Sandospace R 70 5.4 Aim of The Present Work 71 Chapter 6 Dye Resist Behaviour of Silk: Materials and Method 73 6.1 Materials 74 6.1.1 Fabric 74 6.1.2 Chemicals 74 6.2 Methods 74 6.2.1 Treatment With Sulphamic Acid 75 6.2.1.1 Determination of Free Acid 75 6.2.1.2 Determination of Bound Acid 75 6.2.2 Treatment With Sando space R 76 6.2.3 Dyeing 76 6.2.3.1 Acid Dyeing 77 6.2.3.2 2:1 Metal Complex Dyeing 77 6.2.3.3 Reactive Dyeing 77 6.2.4 Resist Effect Evaluation 78 6.2.5 Test Methods 6.2.5.1 Weight Gain 79 6.2.5.2 Yellowness Index 79 6.2.5.3 Breaking Strength Retention 79 Chapter 7 Dye Resist Behaviour of Silk: Results and Discussion 81 7.1 Treatment of Silk With Sulphamic Acid 82 7.1.1 Weight Gain, Yellowness Index and Strength Loss 82 viii 7.1.2 Free and Bound Acid on Sulphamic Acid Treated Silk 82 7.1.3 Dye Resist Effects of Sulphamic Acid Treated Silk 84 7.2 Treatment of Silk With Sandospace R 86 7.2.1 Weight Gain, Yellowness Index and Strength Loss 86 7.2.2 Dye Resist Effects of Sandospace R Treated Silk 87 7.3 Conclusion 88 Chapter 8 Conclusions 90 Bibliography 93 ix CHAPTER ONE THE SILK FIBRE 1.1 INTRODUCTION Silk is considered to be a luxury fibre owing to its fine, soft handle, drape and comfortable next-to-skin qualities during wear. Silk fabric can also be very easily dyed or printed with a range of dyestuffs and thus lends itself well to fashion demands. One major limitation of this unique fibre, however, relates to the very poor fastness properties of bright coloured dyestuffs used in the dyeing and printing of silk fabrics. Another entirely different drawback associated with fabric usage arises from the tendency of silk fabrics to develop unsightly wrinkles during wear. As silk articles have generally been regarded as delicate and exclusive in quality, little attention has been given to these limitations associated with silk fabric usage. A vast amount of research has been carried out in order to develop wrinkle resistant finishes for cotton, and more recently wool, whereas, relatively little work has been done on silk. Traditionally, formaldehyde utilising chemical treatments have been successful on silk, however, as a result of the rapid growth of prohibitive legislation concerning formaldehyde usage, non-formaldehyde treatments are now being explored for all fibre types. 2 In the first part of this thesis, chemical treatments that have been shown to be successful on cotton or wool, with respect to improving the wrinkle resistance of these fibre types, were applied onto silk fabric. The potential for both crosslinking treatments and surface polymer applications were separately investigated with respect to the wrinkle recovery behaviour imparted to the treated silk fabrics. Multicolour effects that are often necessitated by fashion demands are generally achieved by fabric printing rather than dyeing; consequently, a large proportion of silk fabric is printed, either by direct or discharge methods. The most commonly used dyestuffs are acid and metal complex dyes although the bright shades within these two ranges generally exhibit poor fastness properties. Moreover, very little published information is available on the printing or dyeing of silk, which remains very much a trade secret of printers and dyers specialising in this exclusive fibre. An alternative to discharge or direct printing is offered through resist printing (or dyeing). This procedure requires the resist agent, which serves to retard the uptake of dyestuff, to be initially printed onto the fabric surface. The fabric may then be subsequently printed or 3 dyed in order to achieve tone-on-tone effects. Resist methods are well established in the printing of cellulosic and wool textile fabrics, and offer an attractive alternative permitting the use of a wider range of dyestuffs than those applicable to discharge styles, and with better fastness properties.