Rheo‐optical studies of polyurethane block polymers

Abstract

Abstract Stress and birefringence relaxation have been measured for two polyurethane block polymers at several temperatures to 140°C. Superposition of the stress curves is possible, but the existence of multiple relaxation mechanisms makes such a process of questionable validity. Simple superposition of the birefringence relaxation was not possible. The time and temperature dependence of the stress‐optical coefficient implies different mechanisms for mechanical and optical relaxation process. Analysis of the birefringence data requires consideration of nonorientational sources of birefringence.