The effect of chitosan and its derivatives on the dyeability of silk

Abstract

Chitosans of different degree of deacetylation (DD) were derived directly from chitin in alkaline solution under different experimental conditions. Chitosans of the same DD with different molecular weights (MW) were prepared using ultrasonic degradation. All chitosans obtained were applied in the study of dye uptake efficiency using various acid dyes on silk under different experimental conditions. The color yield, color difference and colorfastness to washing of the dyed silk fabrics were evaluated using standard techniques. The DD of chitosans was determined using the 1H NMR method. The MW was estimated with a dilute solution viscometry method. The effect on the DD in deacetylation of chitin due to reaction time, condition, temperature, and the concentration of the alkaline solution is discussed, as is the result of ultrasonic degradation time on the MW and DD. The effect of chitosans of different MW and DD, treatment conditions, and dye structures on the dyeability of silk is also discussed. O-carboxymethyl (O-CM) chitosans with a low degree of substitution (DS) and a high degree of deacetylation (DD) were prepared by treating chitin with chloroacetic acid in alkaline solution. N/O-(2-hydroxy)propyl-3-trimethyl ammonium chitosan chloride (N/O-HTCC) with different degrees of substitution were prepared by reacting chitosan and glycidyltrimethylammonium chloride (GTMAC) in D.I. water or buffer (pH=10) solution. The obtained chitosan derivatives were characterized using NMR, FTIR, TA, and elemental analysis methods. The dye uptake efficiency of both O-CM chitosans and N/O-HTCC were investigated. Their application for dyeing silk fabrics effectively increased the dye uptake of acid dyes without lowering color fastness to washing or affecting the fabric hand feel.