Studies on the acid degradation of cellulosic fibres. I. Behaviour in hydrochloric acid-zinc chloride solutions

Abstract

This paper studies the changes which occur in the physical and supermolecular characteristics of cotton cellulose on addition of zinc chloride during mild hydrochloric acid degradation to levelling off of the degree of polymerisation (LODP). Both the rate and site of hydrolysis, as well as the supermolecular characteristics, are strongly affected. The zinc chloride enhances the decrystallisation of the cellulose and results in higher LODP. In addition, the role of zinc chloride is greatly dependent upon the acid concentration. At lower acid concentration, intercrystalline degradation predominates in the less ordered domains which are created by zinc chloride. This results in a lower rate of degradation. At higher acid concentration, on the other hand, zinc chloride results in a sharper initial degradation which is mostly due to the increase in the susceptibility of the cellulose macromolecules, and thereby creating the conditions under which severe degradation is to be expected.