Effect of pretreatment with solvents and solvent mixtures on the structure/properties and dye uniformity of textured polyester yarn

Textured polyester multifilament yam was subjected to swelling in single and mixed solvents (with varying ratio) at room temperature for different durations. The changes in the structure and properties of the yam were investigated by measuring birefringence, crystallinity, critical dissolution time, shrinkage on treatment, % change in bulk, residual shrinkage, crimp rigidity, dye uptake and dye uniformity. Among the four single solvents used, dimethyl formamide (DMF) and methylene chloride showed better balance of the above properties and dye uniformity. Use of a mixture of tetrachloroethane and DMF in the ratio of 1:3 gave dye uptake at par or slightly better than that given by the corresponding single solvent but showed more dye uniformity.