The Post-Yield Region and the Structure of Keratin

The load-extension curve of wool fibers under a variety of conditions and treatments shows little change in mechanical extensibility in the post-yield region (extension greater than ∼30%). This taken together with x-ray and water swelling data already published suggests that the cross-links and entanglements present in the matrix component of the keratin structure are concentrated rather than spread throughout the matrix. The above favors the series-zone model, which has been proposed to explain the mechanical properties of wool and hair fibers.