Effect of Pre-Existing Dyes and Fabric Type on Cellulase Treatment of Cotton Fabrics

Abstract

Fabric weight loss through cellulase treatment of six different cottons depends on mercerization, yarn size, and fabric structure. Weight loss decreases in the order of Ne = 60 mercerized > Ne = 60 nonmercerized ≈ Ne = 40 mercerized > Ne = 40 nonmercerized knit fabrics > Ne = 20 ≈ Ne = 10 nonmercerized woven fabrics, indicating increased enzymatic hydrolysis on mercerized cotton knits with smaller yarn size. The effect of pre-existing dyes on cellulase activity is examined by measuring the difference in weight reduction for mercerized and nonmercerized cotton knits previously dyed with direct, reactive, and vat dyes. All six dyes in this study inhibit the cellulase reaction, and the degree of inhibition depends on the dye class. The concentration of dyes on fabric as estimated by K/S proves to be the most critical factor governing resulting weight losses. The planar structure of vat dyes with larger molecular sizes than indigo dye seems to play an important role in their inhibitory effect. Compared with monoreactive, direct, and vat dyes, the largest inhibitory effect is with bifunctional dyes, implying that the crosslinking property of bifunctional dyes is related to cellulase hydrolysis. This suggestion is further supported by the small reduction in weight after cellulase treatment of DMDHEU-treated cotton fabric. A model is proposed to explain the slower progress of enzymatic cleavage on crosslinked cellulose fibers.