LAUSR

Abstract Film stretch was incorporated in the enthalpy relaxation experiment in order to examine physical ageing response of polystyrene subjected to large deformation. It was stretched in the midst of ageing step, where ageing temperature was located slightly higher than the onset of the glass transition shoulder to minimise the stretching effect on the enthalpy decay, and then heat capacity, cp(T), versus temperature curve was acquired by DSC (differential scanning calorimetry) as functions of the ageing time and stretch ratio. Pre-hold and post-hold stretches are both carried out, those are stretching-and-ageing and ageing-and-stretching, respectively. As a result, the stretching effect appeared as the shift of glass transition shoulder in cp(T) curve; its onset temperature increased with the increase in the stretch ratio. A remarkable discrepancy for the shift of glass transition shoulder was observed between the samples of pre-hold and post-hold stretches. The experimental cp(T) was reproduced by the modelling data calculated on the basis of Tool-Narayanaswamy-Moynihan framework to derive the data of fictive temperature (Tf). It was revealed that Tf isothermally increases with stretching. The amount of Tf increase depends on both the ageing time and stretch ratio. The discrepancy of the shift amount appeared between pre-hold and post-hold stretches was interpreted in terms of the increase in Tf.