The Oxidation and Alkaline Degradation of Mercerized Cotton: A Morphological Study

Abstract

The morphological changes introduced during slack mercerization of cotton fibers, as detected after oxidation with sodium hypochlorite at pH 7 and after subsequent hot alkaline degradation with sodium bicarbonate, are described. X-ray diffraction and electron microscopy techniques were used. Slack mercerization produces, besides the recognized phase transition from Cell. I to Cell. II, a decrease in order inside the crystallites themselves rather than in the low- ordered regions (LOR). The hypochlorite oxidation of the mercerized cotton induces morphological changes which can be understood as the result of a duality in behavior, i.e., as an oxidant, and as a poor intracrystalline swelling agent. The alkaline degradation results in an extraction of the anhydrous glucose units and an increase in crystallinity and morphologi cal order. However, crystallite lateral size is clearly reduced from that of the original Deltapine cotton but increased from that of the mercerized-oxidized sample. A model for the peeling off mechanism is visualized which involves not only those LOR regions associated in series with the crystalline regions, but those associated laterally to their fringes and also those limiting the macrofibrils. Advantage of extraction with a particular alkaline medium over others is explained by the critical swelling effect neces sary for transporting the anhydrous glucose units outside the remaining fibril morphology.