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Abstract
The dependence of stress-strain relationships upon structural phases in wool keratin is briefly discussed. It is concluded that the Hooke's law and yield regions of the stress-strain curve are due to transformation of the microfibrils alone, while the post-yield region is also associated with deformation of the matrix. Relationships are given which enable estimates to be made of the relative proportions of different phases present in wool keratin at various extensions. It is shown that an entropy-of-mixing function leads to good agreement, at low extensions, between the observed and predicted entropy contribution to stress. Analysis of quantitative data from X-ray diffraction investigations of the α-β transformation further supports the contention that the matrix does not become sufficiently ordered to contribute to the crystalline-β diffraction pattern.