Water in wool

The polymer absorption model developed by Vrentas and Vrentas is applied to the wool/water isotherm. In principle, all parameters in this model can be determined independently of sorption behavior so that a genuine prediction can be made. This model emphasizes the role of the glass transition in generating the sigmoidal shape of the absorption isotherm. By applying an extended version of the model and thermodynamic data obtained from the literature to the wool/water isotherm, a reasonable fit to experimental data is achieved. Sorption behavior at higher temperatures is also reasonably well predicted. The influence of the glass transition in restricting the rate of water crystallization during cooling is used to reinterpret the results of a previous study using differential scanning calorimetry (DSC). This study concluded that three different states of water may exist in wool, cotton, and silk, i.e., free water, freezing bound water, and nonfreezing bound water. However, an alternative and more plausible interpretation for the DSC behavior recognizes the influence of the glass transition, and the appearance of freezing bound water coincides with the depression of the glass transition to just below 0 degrees C. Thus, the DSC data do not support the presence of different classes of water in wool.