The Forces and Kinetics of Supercontraction of Keratin Fibers in 9 M LiCl

The supercontraction in 9 M LiCl of human hair, kid mohair, a non-crimp coarse wool, and a fine, high-crimp wool was studied as a function of time. The fibers were held under constant length, and the forces generated were measured. The kinetics of the process was studied at three different temperatures, and activation energies were evaluated using the Arrhenius law. The maximum stresses of supercontraction were recorded and compared with the breaking stresses of these fibers at 70° F and 65% RH. It was observed that kid mohair and the coarse wool were quite similar in showing high reaction rate constants, low activation energies, and high supercontraction forces. Human hair was the slowest of the four fiber types and required the highest activation energy. The fine, high-crimp wool was intermediate in most parameters.