A Second Order Transition Temperature in Wool Fibers in the Post-Yield Region

Abstract

A second order transition temperature exists for stretched wool fibers in water for the temperature range 60-70° C. This transition is indicated by the transformation in certain physical properties of the fibers such as birefringence and the ability to set per manently. Below the transition temperature a fiber under constant rate of loading passes from the yield to post-yield regions at a value of extension of about 30%, which is independent of the temperature. Above the transition temperature the value of the extension increases with increase of temperature. This variation of the extension at the turnover from the yield to post-yield region with change of temperature above a transition temperature and the constancy of the extension below were shown to hold for chemically and physically modified fibers.