Crystallinity of celluloses after treatment with sodium hydroxide (mercerization)

Abstract The crystallinity of rayons measured with a standardized x‐ray method increases from 40 to 50% after previous treatment with 18% sodium hydroxide followed by removal of the alkali with boiling water. If the washing‐out of the alkali is carried out at room temperature, or if 4% sodium hydroxide is employed, the increase in crystallinity is smaller. Neither exclusion of oxygen during mercerization nor addition of hydrogen peroxide to the soaking lye has an influence on the final crystallinity. Native celluloses (ramie and wood pulp), after soaking in 18% sodium hydroxide and washing at the boil, yield the same figure of 50% crystallinity. A crystallinity figure of 50% is also obtained upon heterogeneous acid hydrolysis of rayon fibers at 100°C. and in cellulose precipitated from dilute viscose solution at 100°.