EFFECT OF PREEXISTING DYES AND FABRIC TYPE ON CELLULASE TREATMENT OF COTTON FABRICS

Fabric weight loss through cellulase treatment of six different cotton s depends on mercerization, yarn size, and fabric structure. Weight lo ss decreases in the order of Ne = 60 mercerized, Ne = 60 nonmercerized approximate to Ne = 40 mercerized > Ne = 40 nonmercerized knit fabric s > Ne = 20 approximate to Ne = 10 nonmercerized woven fabrics, indica ting increased enzymatic hydrolysis on mercerized cotton knits with sm aller yarn size. The effect of pre-existing dyes on cellulase activity is examined by measuring the difference in weight reduction for merce rized and nonmercerized cotton knits previously dyed with direct, reac tive, and vat dyes, All six dyes in this study inhibit the cellulase r eaction, and the degree of inhibition depends on the dye class, The co ncentration of dyes on fabric as estimated by K/S proves to be the mos t critical factor governing resulting weight losses, The planar struct ure of vat dyes with larger molecular sizes than indigo dye seems to p lay an important role in their inhibitory effect. Compared with monore active, direct, and vat dyes, the largest inhibitory effect is with bi functional dyes, implying that the crosslinking property of bifunction al 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 sl ower progress of enzymatic cleavage on crosslinked cellulose fibers.