Birefringence of Wool

Abstract

The birefringence of wool fibers from three different breeds of sheep, Lincoln, Chokla, and Merino, was measured at various relative humidities. Assuming that the α-helical phase in the crystalline regions is the only anisotropic component contributing to birefringence, the reduction in birefringence with increasing moisture content can be predicted reasonably satisfactorily if the intrinsic crystalline birefringence is taken to be 0.043 for all three wools. The contribution of form birefringence has also been estimated and comes out to between 8 to 13% of the total birefringence. In set fibers, humidity has an effect similar to native fibers. With increased temperature, there is a reduction of birefringence in set fibers, particularly around the melting point. The dependence of birefringence on structure and morphological features of wool is dis cussed.