The relationship between the effect of thermal pre-treatment and the viscoelastic behaviour of polycarbonate in the glassy state

Abstract

The viscoelastic behaviour of three different samples of polycarbonate, with differing pre-treatment, is described here by a generalized non-linear Maxwell system, proposed previously. This model gives the variation of the tensile yield stress related to each sample as a function of temperature and strain rate. The response is checked over a large range of strain rates, at temperatures from 20 to 80° C. The model allows the determination of the damping peak arising from the molecular movements which it expresses. A correspondence is found with the intermediate loss peak location, which occurs for each sample just below the α transition. Results obtained from dynamic mechanical tests and differential scanning calorimetry show that the structure of the samples changes in the range of temperatures where the intermediate loss peak arises at 1 Hz.