27—THE KINETICS OF WATER-VAPOUR SORPTION IN WOOL: PART II: RESULTS OBTAINED WITH AN IMPROVED SORPTION VIBROSCOPE

Abstract

This paper reports the results of a study of water-vapour-sorption kinetics and the accompanying length changes observed in single wool fibres with the improved sorption vibroscope described in Part I of this series. Among the more interesting observations, it is shown that: after a step change in relative humidity, desorption, other than to zero regain, continued for very long times (in excess of eight days) with no sign of termination, whereas absorption reached completion relatively quickly; the position of the desorption limb of the regain versus r.h. isotherm is both time- and size-of-step-dependent; the length versus r.h. isotherm in these experiments exhibited a maximum at about 80% r.h.; length values on desorption were shorter than the corresponding absorption values over most of the r.h. range, i.e., hysteresis effects were exhibited in length-swelling; the width of the hysteresis loop appeared to be stress-dependent; and length-swelling kinetics for small sorption steps are complex and usually consist of two or more stages, the first stage being rapid and coinciding closely with the first stage of water uptake.