Birefringence, compliance, and viscoelasticity of poly(ethylene terephthalate) fibers

Abstract

Abstract The experimental relation between birefringence and dynamic compliance has been determined for a wide range of poly(ethylene terephthalate) fibers. This relation is explained by two complementary versions of the series aggregate model. The classical series aggregate model provides a satisfactory interpretation of the data for the low‐oriented fibers. A model developed earlier for aramid fibers explains the data for the well‐oriented fibers. By monitoring the dynamic compliance during creep and stress relaxation of well‐oriented fibers it is shown that these phenomena are caused by shear relaxation, resulting in a progressive contraction of the chain orientation distribution.