Structure/property relationships in wool and hair

STRUCTURE/PROPERTY RELATIONSHIPS IN WOOL AND HAIRFranz-J.WortmannTextiles & Paper, School of Materials, University of Manchester, UKKeratin fibres, such as wool or hair, exhibit a complex biological composite structure, which is common to all mammalian ??-keratin fibres. In view of their physical properties the dominant morphological components are the cuticle, as a protective outer sheath, and the fibre core (cortex). This consists mainly of partly ??-helical intermediate filaments (IF), which are embedded with largely axial orientation in an amorphous matrix of so-called intermediate filament associated proteins (IFAP). This filament/matrix structure leads for keratin fibres to the characteristic, marked differences between axial and lateral properties. In view of the broad spectrum of individual and synergistic performance of the morphological components only a small number of pertinent aspects, relating to their thermal transitions is elucidated. Keratin fibres show those viscoelastic transitions, which are characteristic for semi-crystalline polymers, such as a low temperature ??- and a higher temperature ??- (glass) transition. The strong humidity dependence of these transitions and differences between keratins will be discussed in relation to their protein composition. Certain aspects of the results lead to the conclusion that absorbed water is effectively homogeneously distributed over filaments and matrix. At high temperatures (240??C dry, 150??C wet) the denaturation of the helical filaments takes place. The size and the location of the denaturation peak differ between keratins. They depend on the amount of ??-helical material and on the composition of the surrounding matrix. The change of the denaturation temperature with water content is considered in view of the potential applicability of the Flory-equation.