Some Phenomenological Relations for Strain-Induced Birefringence of Amorphous Polymers

Abstract

The strain-induced birefringence of amorphous polymers can be described with the stress-optical rule in the rubbery plateau and the terminal flow zones. This is not the case in the glassy and the glass-to-rubber transition zones. When the stress or the strain is sufficiently small, the birefringence may be described in terms of the linear response theory similar to the linear viscoelasticity theory. In this paper, we present some new relations among the response functions such as the time-dependent stressoptical coefficient and strain-optical coefficient. The birefringence in the following processes were considered: the stress relaxation at constant strain, the creep, the oscillatory deformation, the strain of constant rate, and the subsequent elastic recoil.