Thermal Transitions in Keratin

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Abstract
A method is described for measuring lateral load-deformation relations of fibers. The results of tests on Lincoln wool fibers are given, for aqueous test liquids at pH 2.1, 6, and 9.1, and for fibers treated with formaldehyde, with an anionic detergent, and with mercuric acetate. In water at 20° C the shear modulus (for loading times of several seconds) is near to 2 X 108 dynes/cm2 and does not vary greatly with the chemical treatment or the acidity of the test liquid. As the temperature increases, the shear modulus slowly decreases. At a certain temperature, approximately 80° C for this Lincoln wool in water, the modulus starts to decrease much more rapidly with temperature. This transition is accentuated and dis placed to lower temperatures at pH 9.1 or by the treatment with mercuric acetate. Measurements of viscous flow under constant load were also obtained. Between 70° and 100° C the native wool fibers show a viscosity of the order of 1011-1012 poise, with an activation energy of about 26 kcl/mole. Some structural implications of these phenomena are discussed.