Reduced salt usage in dyeing of 100% cotton fabric

This study primarily focuses on the reduction of salts during the dyeing of cotton. Cotton fabrics were pretreated with Chitosan and Cibafix ECO respectively, and then dyed with reactive and direct dyes with various amount of salt in a dye bath, to determine the optimum pre-treatment conditions of a reduced salt concentration. Cotton fabric was dyed with two different classes of reactive dyes and a direct dye with 100%, 75%, 50% and 0% of the recommended amount of salt. Various methods of pre-treatment application were trialed to determine the most effective and efficient method, as well as to determine the optimum conditions of the pre-treatments. Exhaustion levels of the dye bath as well as Total Dissolved Solids (TDS) levels were measured. Colour strength measurements were also studied along with colourfastness properties. It was found that cotton fabric pre-treated with Cibafix ECO and dyed with 25% less salt was more effective than fabric pre-treated with Chitosan and dyed with 25% less salt. Any greater reduction in salt has detrimental effects on the levelness of dyeing. When using only 75% of the recommended amount of salt, the pre-treated fabrics showed higher extents of exhaustion compared with samples dyed without the pre-treatment. At optimum pre-treatment conditions a saving of 25% salt usage was observed for cotton dyed with direct and reactive dyes. In addition these samples also showed moderate to very high fastness properties.