Longitudinal Swelling of Permanently Set Wool Fibers

Abstract

The longitudinal swelling of permanently set wool fibers was measured by a desorption method as a function of the time the fibers were held in the extended state. It was found that, after a setting treatment involving extensions below 40%. the longitudinal swelling, following an initial rapid increase, was independent of setting time and the dimensional changes of the fiber resulting from the setting process. At a setting ex tension of 60%, a maximum in longitudinal swelling is reached, which is followed by a rapid decrease and then by a gradual decrease with increasing times of setting. The results are interpreted in terms of differences in the stabilization mechanism for the extended configuration, depending on the strain level. Elimination of free sulfhydryl groups, before the fibers are released from extension, decreases chain mobility and, therefore, decreases disordering during the subsequent recovery step.