Enhanced interaction of dye molecules and fibers via bio-based acids for greener coloration of silk/polyamide fabric

Multi-component fabrics combined with natural silk fibers and man-made polyamide fibers are good choices for high-quality textile owing to the remarkable comfort and excellent resistance. The silk/polyamide fabric colored with reactive dyes generally shows good fastness, but the problems still remain that large dye effluent discharge, high chemical consumption, and long-time dyeing process. To counter these issues, herein we report a greener coloration method without any salt or alkali added for the coloration of silk/polyamide fabrics. Three bio-based acids like acetic acid, citric acid, and tannic acid were introduced into the dye solution to improve the interaction of dye molecules and fibers. Much of the focus has been given to understand the mechanism between the dye molecules, bio-based acids and fibers, which was determined through dynamic surface tension and UV–visible absorption spectrum measurement. Through this, it was found that the citric acid due to its maximum number of carboxyl groups than acetic acid and tannic acid promoted the disaggregation of dyes and enhanced the dye diffusion to fiber surface. As a result, the dye fixation and color strength of silk and polyamide fibers were all significantly improved when using citric acid at pH 6 with the steaming for 5 min. From the SEM analysis, it was seen that the surface morphology of silk/polyamide fibers was not so much affected. Compared with the traditional dyeing method, this method exhibited enhanced color performance with a shorter dyeing process, lower chemical consumption and nice fastness property. This work presented a potential and practical application of natural additives in the dyeing of multi-component fabrics to achieve eco-friendly and high-quality textile products.