Swelling behaviour of cellulose by chemical and mechanical treatments.

Abstract

Chemical and mechanical pulps and pure celluloses were swollen by chemical and mechanical treatments, and these swelling mechanisms were studied. The samples were treated with SO2-diethylamine in dimethyl sulfoxide as chemical swelling treatments, and were beaten with a PFI mill as mechanical treatments. Crystallinities and water retention values were measured for the treated samples, and were compared in reference to chemical and mechanical treatments, Crystallinities were controllable from the original ones to the amorphous state for chemical pulps and pure cellulose samples by controlling the amounts of SO2-diethylamine. Simultaneously, water retention values were increased from less than 100% up to more than 400%. In these decrystallization processes, there was a range of the amounts of reagents where water retention values were increased while crystallinities were equal to those of the original samples. This phenomenon was identical to those observed for chemical pulps by beating treatments. Thus, there seems to be a mechanism of beating in which hydroxyl groups in non-crystalline regions, which are originally inaccessible to water, become accessible to water by the mechanical treatments. The increase in accessibility of hydroxyl groups in non-crystalline regions may have an influence on swelling and flexibility of pulp fibers and physical properties of papersheets greater than that of fibrillation.