Temperature- and Humidity-Induced Transitions in Alpha-Keratinous Materials

Abstract

Despite their complex morphology, alpha-keratinous fibres are essentially fibrous, semi-crystalline protein composites. The material exhibits all the expected thermal transitions, such as the beta-, glass and melting or rather denaturation transition. These processes and their pronounced dependence on water content are the central topic of this review. For the viscoelastic transitions the effects of water are well described by the Fox-equation, indicating an effectively homogeneous distribution of water throughout the keratin structure. The humidity dependence of the denaturation transition of the alpha-helical material follows the Flory-equation, though in a rather ambiguous manner. The consequences of these observations for our understanding of the interaction of the various morphological components of alpha-keratinous materials with water are discussed.