Applications of Thermodynamics to the Stretching of Cellulose Fibers

Abstract

Mechanical deformations of cellulose are recognized to take place primarily in the amorphous regions whose nature has not been well defined. Since these regions do not have a regular type of order, attention has been turned to entropy of stretching as a sta tistical measure of the changes in structure on stretching. Data are presented giving the.retractive force, coefficient of thermal expansion, and modulus under a wide variety of conditions. Thermodynamic treatment of the data shows that moisture content and temperature control the bonding between chains in the amorphous regions. These cross links to a large extent determine the mechanical prop erties, which vary from an elastic glass in the dry state to those of a partially rubbery material in the wet state at high temperatures. At low temperatures in the wet state, the amorphous parts of the chains "precipitate" out of the swelling water and thereby form cross links between chains, which makes the modulus tend to approach infinity at the cellulose-water eutectic point. This work provides a better understanding of the relationship between molecular and fiber properties.