Influences of Commercial Dispersants on the Dyeing Performance and Dye–Fiber Interaction of Disperse Dyes in D5 Nonaqueous Medium Dyeing Systems

Abstract

In the decamethylcyclopentasiloxane (D5) nonaqueous medium dyeing system, the uptake of dye can be improved by the accelerant. However, traditional dispersants used in disperse dye formulations can lead to the dissolution of disperse dyes in the dye-promoting phase, which negatively influences the uniformity of the dyeing process. This study focuses on three commonly used dispersants found in commercial disperse dyes, studying their effects on the dyeing performance of these dyes in the D5 nonaqueous medium dyeing systems. In the D5 nonaqueous medium dyeing system, the leveling property of the dyed polyester fabric became worse, and more and more spotted occurred on the fabric surface with the amount of dispersant increased from 0.2% to 2.0%. Compared with no accelerant, more disperse dyes would be dispersed in the dyeing accelerant phase under the action of the dispersant when dyes, dispersants, and accelerants were employed in the nonaqueous medium dyeing system. In comparison to the absence of dispersants and dye accelerants, the adsorption rate of the dye on polyester fibers increased by 22%, while the final equilibrium adsorption capacity improved by 30% if accelerants were employed in the dyeing system. However, the simultaneous addition of both dye accelerants and dispersants resulted in a slight decrease in the equilibrium dye uptake of dispersed dyes on polyester. Compared with pure D5 dyeing, the dye accelerant significantly enhances the affinity between disperse dye and polyester fibers. However, when both the dye accelerant and dispersant are added simultaneously, the affinity between the dye and fibers would be decreased. For the composition of the fabric surface stains, the content of dispersant was the most (more than 96%), while the proportion of disperse dyes was only about 1%, and the impurities in disperse dyes were less than 1% when only the dispersant was used during dyeing. However, the content of the dispersant was increased by 3–6 times after adding the dyeing accelerant. These results have demonstrated that the use of a dyeing accelerator during the dyeing process significantly increases the concentration of the dispersant on the fabric surface, leading to the aggregation of certain disperse dyes on the fiber surface. An analysis of the chemical environment on the fabric surface before and after dyeing reveals that the use of a traditional water-soluble dispersant in the dyeing system results in an increased presence of C–C or C–H bonds on the fabric surface. Therefore, the intermolecular forces between polyester fibers, disperse dyes, and dispersants influence the dyeing performance, resulting in dispersants unsuitable for nonaqueous medium dyeing systems.