Transition from approximately linear to marked nonlinear viscoelasticity in antiplasticized PVC

Abstract

Tensile creep tests have been carried out on poly(vinyl chloride) with small amounts of dioctyl phthalate (DOP) and dioctyl adipate (DOA) at room temperature. Creep compliance, the stress limit of approximately linear viscoelasticity, and stress dilatation are reported as functions of additive content in the time range from 10 to 1000 sec and up to 13% of additive. For both PVC-DOP and PVC-DOA, a maximum antiplasticization effect was observed at 5% additive. In the linear viscoelastic range, there were only minor differences in the degree and character of antiplasticization between the two types of blends, as visualized from dynamic mechanical data and linear viscoelastic creep compliance. The stress levels of transition from approximately linear to marked nonlinear viscoelasticity were increased during antiplasticization more than proportional to the decrease in linear viscoelastic creep compliance. This new aspect on antiplasticization showed that DOA caused stronger intermolecular interaction with the polymer compared to DOP, though less compatibility. The stress dilatation of the blends showing maximum antiplasticization was slightly lower than that of pure PVC. Nonlinear stress dilatational behavior occurred at approximately the same stress levels as the transition from linear to nonlinear viscoelasticity for both pure PVC and the blends.