Discussion About Weight Loss And Degradation Of Chitosan Fiber During Wet Processing

Chitosan fiber is a kind of new functional textile fiber with a bright future for application. It is usually used to blend with other fibers such as cotton, viscose fiber and wool and manufacture a variety of textile products for dressing, domestic and medical purposes. Although chitosan fiber has good functionality, it suffers from many defects during wet processing, for instance, fast dyeing rate, poor leveling property, poor solid effects with other fibers, liable to degrade and lose its weight. In this work, the weight loss and degradation problems during wet processing were discussed. The weight loss and degradation of chitosan fiber during hydrogen peroxide bleaching were investigated and the factors influencing weight loss and degradation, particularly the effect of metal ions were discussed. In addition, taking into consideration the poor acid resistance of the fiber and the remarkable weight loss under acidic processing conditions, the modification of the fiber using the crosslinking agents was used to improve its acid resistance and reduce the weight loss at acidic medium. These investigations were hoped to provide theoretical data for obtaining the methods by which the degree of the degradation and weight loss of the chitosan fiber during wet processing was reduced and for improving the spinning technology of the fiber. The research results obtained were as follows:(a) The deacetylation degree, molecular weight and crystallinity of chitosan fibers produced by different enterprises were different due to their individual spinning technology and parameters as well as chitin resources, which had influence on the degradation and weight loss of the fiber during hydrogen peroxide bleaching.(b) Chitosan fiber suffered from severe degradation and weight loss problems during hydrogen peroxide bleaching. The weight loss was induced by the dissolution of chito-oligosaccharides produced during bleaching. The weight loss of the fiber with low molecular weight was higher than that of the fiber with high molecular weight. The weight loss became much higher at temperatures above 70℃. The molecular weight obviously decreased even at low concentrations of hydrogen peroxide, but the weight loss gradually increased with an increase in hydrogen peroxide concentration. Hydrogen peroxide bleaching did not change the chemical structure of the fiber and slightly decreased the crystallinity index of the fiber.(c) The different metal ions chelated by chitosan fibers had obvious different influence on the degradation and weight loss during hydrogen peroxide bleaching. Chelated Fe²⁺ and Mn²⁺ slightly increased the weight loss, but chelated Cu²⁺ significantly increased the weight loss rising with the increment in its concentration. The molecular weight of the fiber chelated by Cu²⁺ was remarkably lowered after bleaching, the initial weight loss temperature in TG curves and the degradation temperature in DSC curves obviously reduced, indicating that chelated Cu had catalytic action on the degradation reaction during bleaching.(d) The modification of the fiber using the appropriate crosslinking agents could improve its acid resistance and reduce the weight loss at acidic medium. The weakly cationic agent, Crosslinker EH, exhibited better results that the cationic agent, Crosslinker DE. As for the conditions of the modification, the concentrations of Crosslinker EH and sodium carbonate had great influence on the acid resistance of the fiber while the temperature had less effect.