High-efficiency dispersant-free polyester dyeing using D5 non-aqueous medium

Conventional polyester dyeing with disperse dyes consumes a large amount of freshwater resource and requires a great deal of dispersant, which poses a major challenge to the dyeing and finishing industry. To meet the requirements of clean production and sustainable development, a modified decamethyl-cyclopentasiloxane (D5) non-aqueous medium dyeing system containing a little water was proposed in this study, and the effect and mechanism of a little water on the polyester dyeing were investigated. Both D5 and liquid paraffin non-aqueous medium dyeing systems containing approximately 50% (on weight of fabric, owf) water are observed to significantly improve the dye uptake of disperse dyes and the color strength of dyed fabric with excellent levelness and high colorfastness. The confocal laser scanning microscopy (CLSM) with fluorescent labeling technique confirms the accessibility of water in the surface layer of polyester fiber, and the dynamic thermomechanical analysis (DTMA) reveals the diffusion of water into the polyester fiber, thereby reducing the glass transition temperature (Tg) of polyester fibers by plasticization effect, promoting the movement of fiber molecular chain segments, and enabling the fixation stage of dyeing to be performed at a lower temperature. The dyeing principle of the modified D5 medium dyeing of polyester has enriched the theoretical system of nonaqueous medium dyeing, being conducive to facilitate the development of the sustainable dispersant-free and water saving polyester dyeing technology.