16—the Application of Sorption and Calorimetric Measurements to the Study of Fibre Structure

The sorption isotherms of several fibres, of different types and structures, have been determined by a gravinietric method. The experiniental results obtained can be used in the confirmation of the equations of Hailwood and Horrobin, which were obtained by considering fibre–water systems as solutions of water in the disordered regions of the polymer, the ordered regions being regarded as inert elements dispersed throughout the polymer. A study of the variation in moisture regain as a function of time has been made over very long periods for cellulosic, polyamide, and polyester fibres. This has allowed a determination to be made of the accuracy that one can attribute to the parameters of the equation when account is taken of supplementary information from a knowledge of the hysteresis. On the other hand, measurements of the heat of wetting of fibres previously conditioned at different relative humidities have shown that the heats depend only on the actual value of the moisture content and not on the route by which the moisture content has been reached: this confirms results obtained by other authors. This consideration of collected results suggests that there exists a considerable internal pressure in the fibre that may be described in terms of entropy.