39—the Swelling Behaviour of Jute in Water and Alkali Solution

The results of measurement of transverse and longitudinal swelling of jute in water and those of absorption of water and alkali from caustic soda solutions are described. The very low value of the longitudinal swelling of jute is taken to indicate a restrained swelling for the structural elements of the fibre. Both delignification and treatment with mild alkali encourage swelling to a certain extent; but while the former affects uniformly the longitudinal and the transverse swelling, the effect of the latter is preferential in the longitudinal direction on account of the accompanying disorientation. Compared with cotton, jute is characterized by high values of absorption and swelling in dilute alkali, low values in strong alkali, and the attainment of the maximum swelling at a lower concentration. This can be explained by picturing jute as a cellulosic framework with small and/or imperfect crystals, associated with hemicelluloses and lignin which may form crosslinkages also with cellulose. The results further suggest that the incomplete mercerization of jute has its precursor in the subdued swelling.