The Mechanical Properties of Wool Fibers in Water at Temperatures Above 100° C

Abstract

The mechanical properties of normal and of chemically modified wool fibers in water were examined for temperatures up to 140°C. Marked changes in the mechanical properties of normal wool fibers occurs at temperatures around 130°C. At this tempera ture the Hookean modulus of the load-extension curve approaches zero, the x-ray diffraction pattern shows that the organized α-keratin structure of the wool is replaced by a randomized β-structure, unstrained fibers supercontract and the longitudinal swelling from dry to wet increases. Chemical modification of the fibers can alter the temperature at which these physical property changes occur. The set, dry-wet longi tudinal swelling and load-extension curves in water at 20°C of fibers held extended in water at temperatures up to 140°C were also examined. It is concluded that the α-helices stabilize the structure of the wool fibers longitudi nally by opposing both extension and swelling. The disappearance of the α-keratin structure for normal fibers at around 130°C results in a loss of this longitudinal stability. During setting of normal fibers, for temperatures less than 130°C, the modification only occurs in the unfolded structural components. The maximum modification (the best setting condition) occurred at 120°C, which was the highest temperature used below the "melting" temperature of 130°C.