Entropy Changes Accompanying the Stretching of Cellulose Fibers in Water

Abstract

Thermodynamic equations for elasticity are used to relate the force-temperature behavior of cellulosic fibers in water to the entropy of stretching. Water-fiber inter actions may have an appreciable influence on the observed behavior, but this cannot be decided without further experimental data on the swelling and sorption behavior of cellulose in water. A transition in the elasticity of textile viscose rayon occurs in water at about 45°C, with a negative entropy of stretching (rubberlike elasticity) being found above the transition temperature. Alkali swelling of viscose rayon causes an increase in rubberlike elasticity and a lowering of the transition temperature. The elasticity of cotton is primarily due to energy forces, and no marked change after mer cerization is found over the temperature range from 5° to 80°C. Comparison of highly oriented cellulose acetate experimental samples before and after saponification shows that the acetate side groups cause a lower temperature of transition to rubberlike elasticity, due to a reduction in intermolecular attractions. Commercial-type cellulose acetate fibers show effects of extension on elastic behavior which indicate complex structural changes in the fiber as it is being stretched.