Some observations on the shrinkage of jute



Measurements have been made of the shrinkage in alkali and of the permanent contraction resulting from alkali treatment. The results supported by x-ray evidence following the changes in orientation and degree of mercerization show that the shrinkage of jute is subject to a similar restraint as swelling, and the shrinkage behavior of jute compared to ramie is as that of a yarn compared to that of its constituent fibers. Unlike swelling, the shrinkage of jute at dilute alkali is less than that of ramie and the corresponding region of the shrinkage curve is conspicuous by the smoothness of swelling curve, indicating that the shrinkage refers primarily to the structural framework of the fiber, whereas an extrastructural material may contribute to swelling. Although the crystallinity of jute is comparable to that of rayon, no appreciable permanent contraction occurs in the fiber treated in dilute alkali, and this points to a restraint in the structure of jute similar to that exercised by the crystallites in ramie. Whereas the resistance in ramie is completely neutralized in mercerizing alkali and the whole of the alkali shrinkage remains as permanent contraction, the restraint still operates in jute, and the permanent contraction is in deficit of the alkali shrinkage. The respective disorientations are also of the same order. Both permanent contraction and crystalline disorientation continually increase on repeated alkali treatments of jute and ramie; the additional effect found in jute is its complete mercerization after a number of treatments. The shrinkage as indexed by its maximum value is strongly correlated with the oriented state of the fiber, and the disorientation produced in jute on dilute alkali treatment is followed by a lower maximum shrinkage. Incomplete disorientation of mercerized jute shows up in positive shrinkage and its proportion is the same as that of unconverted cellulose I residue. In spite of a very high degree of orientation, the reoriented fiber shows a considerably low maximum shrinkage compared to the native. This is suggested to have been due to the formation of some junction points when the freely swollen plasticized fiber is mechanically strained.