Abstract:
Nowadays, market trends for green products and processes are being developed all around the world. Utilization of natural dyes for textile dyeing is also one of these trends due to its environmentally friendly concept. However, textiles made of natural dyeing often show light shade and low colorfastness to washing and to light. This research introduces a low molecular weight chitosan (20,000 -30,000 Dalton) treatment on hemp yarn in order to enhance the dyeability of hemp yarn as well as to improve the colorfastness of dyed yarn. In this work, grey hemp yarn was first conventionally scoured and bleached. It was then treated in a chitosan solution at room temperature (32°C); 40°C; 50°C; 60°C; and 70°C, for 30 minutes; 1 hour; and 2 hours, in 3 different ways comparing between treatment before dyeing; treatment and dyeing all together; and treatment after dyeing. The yarn was dyed in a solution containing natural dyes extracted from Garciniadulcis (Roxb.) Kerz Bark. For dye fixation process, 1-10% of alum solution was used (as a mordant) in 3 different methods, comparing between pre-mordant; meta-mordant; and post-mordant. Results indicate that the best and reasonable dye fixation process was obtained when 10% of alum solution was used at a meta-mordant condition. The best chitosan treatment was to treat the yarn before dyeing and to treat at room temperature for 30 minutes, followed by an oven dry. After dyeing, chitosan treated yarn obviously showed a higher dye adsorption (darker yellow shade or higher color strength) than the untreated yarn. In addition, chitosan treated and dyed yarn also showed better colorfastness to washing and to light than the untreated and dyed yarn. However, the chitosan treatment decreased the yarn strength by approximately 30%.