Dyeing and dye-induced changes in the physico-mechanical properties of polyacrylonitrile fibres

Polyacrylonitrile (PAN) and bicomponent PAN fibres have been dyed with three different cationic dyes, viz. C.I. Basic Blue 3, C.I. Basic Red 18 and C.I. Basic Violet 1 using different per cent of shades. The dyeing parameters have been optimized and dye-induced changes in the dyed fibres studied. It is observed that both PAN and bicomponent PAN fibres can successfully be dyed with cationic dyes under the optimized conditions (2% retarder, 5% exhausting agent and pH 4.5). Bicomponent PAN fibres show better dyeing performance. The mechanical properties of both the dyed fibres improve due to the physical hindrance offered by the dye molecules, the effect being more pronounced with higher dye concentration. Dyed PAN fibres show higher critical dissolution time due to the development of crystallinity in the fibres. Both the PAN and bicomponent PAN fibres show decrease in moisture regain on dyeing due to the blocking of water-absorption sites by the dye molecules.