A sustainable process for cotton and polyester/cotton blend dyeing with nucleophilic disperse dyes through chemical modification

In this study, the dyeing of cellulose fibre with disperse dyes is attempted by chemically modifying the cellulose fibre with a previously reported bifunctional cross-linker AXL-2 at a neutral pH. The modified cellulose was then dyed with nucleophilic disperse dyes containing amino and/or hydroxyl groups. One end of the cross-linker binds with the hydroxyl groups of cellulose, while the second one binds with the disperse dye molecule containing free NH₂ or OH groups. After optimizing the parameters on 100% cellulose, the bifunctional cross-linker was applied on polyester/cotton (P/C) blended fabric. The chemical composition, morphology, and strength of the modified cellulose and P/C fibres were analyzed by ATR-FTIR, SEM-EDX, tensile strength testing, water absorbency testing, and thermogravimetric analysis (TGA). The characterization analyses verified the binding of the synthesized epoxy compound with the hydroxyl group of cellulose. The tensile strength of the modified fabric was reduced slightly compared to the unmodified one. No significant change in the absorbency and thermal stability of the fabric was noticed after chemical modification. The colour depth of the modified cotton and P/C blend, after dyeing with disperse dyes, was assessed by K/S measurements and compared to the respective unmodified fabrics. The results indicated the successful dyeing of the modified P/C blend in one-bath using disperse dyes containing amino and/or hydroxyl functionalities. The fastness properties of the dyed samples were examined by following ISO standard test procedures, and the crosslinked fabrics were found to have good overall fastness except for the light fastness.