TORSIONAL PROPERTIES OF NORMAL AND SULFUR-ENRICHED WOOL FIBERS .2. MODULUS OF RIGIDITY AND TORSIONAL RELAXATION OF FIBERS IN WATER AT TEMPERATURES BETWEEN 20 DEGREES C AND 85 DEGREES C

The effects of temperature on the mechanical properties in torsion of wet fibers of normal and sulfur-enriched wool have been determined at 20–85°C. In addition, the behavior of the fibers in aqueous solutions of HCl of pH 2.9 and 1.85 at 20°C and of pH 0.84 at 20, 40, and 70°C has been observed. The modulus of rigidity and the torsional relaxation at each condition were measured. The moduli of rigidity of wet fibers of both wools were found to be similar in magnitude and decreased approximately linearly with increasing temperature at 20–85°C. The fractional relaxation of torque in fibers held at constant twist was least in wet fibers of the sulfur-enriched wool. The difference in behavior between the normal and sulfur-enriched wools appeared to be related to the difference in aspartic acid content in the two types of wool and not to the difference in sulfur content. The process of disulfide-sulfhydryl interchange appears to be of little significance for wet fibers of wool in torsion at temperatures below 50°C, but is of increasing significance at temperatures above 50°C and at least up to 85°C. In general, the torsional properties of wool fibers in distilled water at temperatures below 50°C are dependent upon polar and disulfide bonds, the most important polar bonds being salt links. The presence of other linkage systems such as entanglements or apolar groups were not detectable in these tests. At higher temperatures, disulfide-sulfhydryl interchange affects the torsional relaxation behavior. The transition in behavior is distinctly evident at approximately 50°C. © 1969, SAGE Publications. All rights reserved.