Volume 1 | Issue 1 ©2015 IJIRCT | ISSN: 2454-5988 IJIRCT1201020 International Journal of Innovative Research and Creative Technology www.ijirct.org 76 Modified acid colour dyeing of silk for energy preservation Dr. Bipin J. Agrawal (Associate Professor) Department of Textile Chemistry, Faculty of Technology & Engineering The Maharaja Sayajirao University of Baroda Vadodara, India Abstract—Textile wet processing, particularly dyeing, consumes considerable amounts of water and thermal energy. In the recent times, both water and thermal energy are rapidly becoming more and more expensive and therefore there is a need to conserve them for better tomorrow. Various modifications in the dyeing system have been adopted to make the energy conservation feasible. Performing the dyeing process at lower dyeing temperature and for short duration can lead to the conservation of energy. This can be done by the utilization of an appropriate solvent for physical modification of the substrate and subsequently dyeing it at lower temperatures and for shorter duration in order to conserve energy. The solvent used for the pretreatment of silk substrate is acetophenone. Commercial anionic acid dyes have been applied on the solvent pretreated silk substrates at different dyeing temperatures, ranging from room temperature to 70 o C and the results compared with conventionally dyed samples, in terms of colour strength values and fastness properties of the dyed samples. The solvent treatment not only aids in reducing the dyeing time and temperature but also retains the aesthetic values associated with silk fibre Keywords— solvent, silk, acid dyes, fastness characteristics, energy conservation I. INTRODUCTION The dyeing process is regarded as one of the most important parts of textile wet processing, which utilizes very large amounts of energy. In general, dyeing involves adsorption of dye molecules/ions on the fibre surface from the solution phase (i.e. dyebath), followed by the diffusion of the adsorbed species into the fibre substance, and finally interaction of these species into the fibre substance. These processes are influenced by controlled conditions of pH, temperature, dye concentration, presence of dyeing assistants (viz. leveling or exhausting agents), liquor ratio, etc. Temperature plays a very key role in the economics of the dyeing process [1 – 3]. Hence, one of the main objectives of a successful dyer is to lower the temperature of dyeing in order to conserve energy. This can be achieved by various methods, viz. graft polymerization, redox system, solvent dyeing etc. [4 – 13]. Since time immemorial, man has been marveled by the beauty of silk owing to its scientific, technological and aesthetic values. . It is a non-keratin type of protein filament fibre. The cocoon of a silkworm contains about 360 to 1200 meters of continuous twin filament [14], joined together by silk gum sericin. Silk has always been regarded as the “Queen of textile fibres”; the luster, handle and the draping qualities of silk are superior to those of many other textile fibres. The natural luster and smoothness, possessed by silk fibre, is something unique, which is usually not observed in any natural textile fibre [15]. The conventional dyeing of silk by exhaust dyeing method, with commercial acid, basic, reactive and other dyes, is usually performed at near boiling temperature, which substantially damages the silk fibre, loses its magnificent luster and deteriorates its qualities [16, 17]. Therefore, low- temperature dyeing is an attractive approach in order to decrease this potential damage. In this work, an effort has been made to dye Tasar silk fabric with commercial metal-complex acid dyes at lower dyeing temperatures in order to preserve its luster and other qualities, which give an aesthetic appeal to silk. The silk substrate was pretreated with acetophenone solvent and subsequently dyed with metal-complex acid dyes at different temperatures for varying lengths of time. The physic- mechanical changes in the fibre were evaluated by various testing and analysis methods, viz. tensile strength, shrinkage behavior and weight analysis. The colour strengths (in terms of K/S values) of such dyed samples were measured spectrophotometrically and the results were compared with those of conventionally exhaust dyed samples. Fastness characteristics of various dyed samples were also evaluated and compared with each other. II. MATERIALS & EXPERIMENTAL METHODS A. Materials (1) Fabric : Plain weave Tasar silk fabric (65 gm/sq. m.) having 80 ends/inch and 60 picks/inch was used for the present investigation. The grey fabric was procured from the Khadi Gram Udhyog, Vadodara. For experimental work, silk fabric was cut in a square dimension, which exactly weighed 1 gram on electronic balance. Before dyeing, the fabric was first degummed (scoured) to remove the natural gum sericin and other natural impurities so as to ensure uniform application of the colour. The degumming bath was prepared with 5 gpl Soap solution 0.5 gpl Soda ash using liquor ratio of 50:1. The treatment was given in the above bath at 90° - 95° C for 1 hour. The fabric was then thoroughly washed with hot and cold water and air-dried.