Effect of Dyeing Process Variables on Colour Yield and Colour Fastness Properties for Cotton Khadi Fabric Dyed with De-Oiled Red Sandal Wood Waste

Effects of dyeing process variables on colour yield and colour fastness properties for dyeing cotton khadi fabric with Red Sandal wood (Pterocarpus Santalinius) waste (RSWW) as natural dye was studied in this work. Bleached cotton khadi fabric was subjected to pre-mordanting by initial treatment with harda(myrobolan) as mordanting assistant cum fixer followed by pre-mordanting with alum or other metallic mordants. Such dual pre-mordanted fabric was subsequently dyed with aqueous extract of de-oiled red sandal wood waste (RSWW). Effects of pre-mordanting with two different agents like harda and alum applied in sequence render better anchoring to make it more suitable for higher colour yield and better colour fastness properties. After finalizing the said dual pre-mordanting, all the dyeing process variables i.e. mordant conc., dye conc., dyeing time, temperature, MLR, pH, salt conc., for dyeing with RSWW extract were optimized. Colour fastness to washing, rubbing, light, perspiration against use of different combination of harda and other metallic mordants along with different dyeing process variables were also evaluated. It is observed that overall application of 15% of [Harda + KAl2 (SO4)3 in 50:50 ratio] in sequence (one after another) is found to be most suitable. MLR—1:40, pH-10, temperature 80°C and time 30 min were found as optimum for extraction of RSWW for maximum colour yield. Considering dyeing uniformity, colour fastness and economy, the optimized dyeing concentration is selected as 20% dye concentration (on the basis of dry weight of solid RSWW source). Other dyeing parameters are optimized as 80 °C dyeing temperature, 30 min dyeing time, 11.0 dyeing pH, 1:20 material-to-liquor ratio and 15 gpl common salt concentration. Interpretation from colour difference index (CDI) values clearly reveals that mordant concentration, dye concentration and pH of dye bath are the three most critical dyeing process variables, amongst all other parameters of dyeing process variables in this study.