Effect of Cellulase Enzymes and Swelling Agents on Colour Strength and Colourfastness of Handloom Cotton Fabric Dyed with Butea Frondosa

Abstract

Cellulases and swelling agents are known to be effective in improving the colour strength of cotton. Nowadays, handloom fabrics, such as khadi cotton, are much more preferred due to the development of innovative designs with their use and their comfort in wearing. Also, due to increased environmental awareness, the use of natural dyes are much more preferred in the dyeing of handloom fabrics. However, khadi cotton has some major shortcomings, such as less dyeability. The present study is carried out by keeping in mind that the pretreatment of khadi cotton with cellulases, swelling agents and a combination of cellulases and swelling agents before dyeing improves the colour strength properties. Khadi cotton samples are treated with optimized conditions of the enzymes and swelling agents. The optimum pH, concentration, treatment time and temperature selected for treatment of the samples with acid cellulase enzymes are 5.5, 1.5% (owf), 45 minutes and 50°C, respectively, whereas in the case of neutral cellulase enzymes, 7.5, 2.0% (owf), 70 minutes and 70°C, respectively. The optimum concentration, treatment time and temperature selected for the treatment of the samples with sodium hydroxide, ethylenediamine and zinc chloride are 20% w/v, 60 minutes and 60°C; 80% w/v, 60 minutes and 70°C, and 80% w/v, 60 minutes and 70°C respectively. Butea frondosa dye (5 g) extracted for 75 minutes provides the best results on khadi cotton when dyeing is carried out for 90 minutes. It is observed that out of the various concentrations of mordants used with the Butea frondosa dye, the best shades of colour are obtained by using 0.04 g of alum, 0.01 g of copper sulphate, and 5 g of Babool bark. In terms of optimizing the mordanting, the best results are obtained with Butea frondosa dye when the samples are simultaneously mordanted and dyed with alum, Babool bark and alum. Pre-mordanting is selected for the copper sulphate. It is found that for all the enzyme treated (acid and neutral cellulase) as well as swelling agent treated (sodium hydroxide, ethylenediamine and zinc chloride) samples, the colour strength and colourfastness increase in comparison to the untreated samples.