The Physical Properties of Wool Fibers at Various Regains

Abstract

Each water molecule in the keratin-water system is considered to have four asso ciations, each of which may be either an association directly with the keratin structure or an association with another water molecule. By assuming, as a first approximation, that the energy of binding of a water-keratin association is a fixed value above that of a water-water association, and using available data on the differential heats of wetting of keratin, the change in the proportion of keratin-water and water-water associations with change of regain may be calculated. From this, the proportion of water molecules with four, three; two, one, or no associations with keratin at any regain may be estimated. If the water not associated at all with' the keratin structure is considered "free" or "liquid" water, and the associated water "bound" or "localized" water, then reasonable agreement is found with the corresponding water fractions estimated by Cassie. Experi mental data are presented which appear to indicate that these two fractions have a definite physical Significance Nuclear magnetic resonance results are also discussed, to show where disagreement exists with the earlier concept of water sorption. The model presented is shown to be compatible with. these results and with other evidence from experiments on the drying of wool from saturation and from intermediate relative humidities.