Nonlinear Viscoelasticity of Amorphous Polymers in the Vicinity of the Glass Transition Temperature (FUNDAMENTAL MATERIAL PROPERTIES-Molecular Rheology)

Abstract

Nonlinear viscoelasticity of atactic polystyrene around the glass transition was studied by means of constant rate elongation. The strain-induced birefringence and the stress were simultaneously measured and then the stress was separated into two components (Rubbery and Glassy components) by using the modified stress-optical rule. Behavior of the R component, having the molecular origin of chain orientation, was essentially linearly viscoelastic. On the other hand, the G component, originated by rotational orientation of chain units, showed remarkable thinning phenomena, which is commonly observed for glassy materials. Thus, the separation of stress for polymeric material simplifies phenomenological interpretation of nonlinear viscoelasticity of polymers near the glass transition zone.