Fundamental studies on the interaction between moisture and textiles. Part X. Moisture sorption properties of wool and hair fibers.

Abstract

The moisture sorption isotherm was determined primarily at 30°C for fifteen kinds of wool and hair fibers from sheep, goat, camel, and rabbit families. The isotherm was analyzed in terms of Brunauer, Emmett and Teller (B. E. T.)'s parameters: C (adsorptive energy factor), vm (maximum volume of adsorbed water in monolayer per gram of dry material), and nmax (maximum number of layers in multilayer adsorption), in order to discuss the moisture sorption properties in relation to structural feature of the materials.Despite of wide variety of the wool and hair fibers, the values of the parameters were found to be almost equal to each other; i.e., C ranging from 9.40 to 11.7, vm from 0.0574 to 0.0718 and nmax from 5 to 6. The X-ray crystallinity, Xx, was estimated by Ruland method as ranging from 24.2 to 30.9% in association with the value of lattice imperfection of around 5. The plots of vm against the degree of noncrystallinity, (1-Xx), exhibited roughly a linear relation passing through origin with a slope of 0.0927 for a series of wool specimens, but deviated from the linear relation toward larger vm side for particular specimens having the medulla structure.The moisture sorption process was also investigated by thermodynamic means as a function of moisture regain of the specimen from dryness up to saturation. Namely, the differential heat of moisture sorption, QL (enthalpy difference of the sorbed water in reference to liquid water), and the excess energy, TΔS (entropy difference of the sorbed water also in reference to liquid water), were determined to conclude that the sorbed water is in highly ordered state at dryness and is still in a little more ordered state than in liquid state at saturation.