Characterization of the thermomechanical behaviour of polymers: non-isothermal creep deflection processes

A non-isothermal creep process of a thermorheologically simple polymer is considered. For such a material, if the results of isothermal creep experiments are known, the creep compliance can be calculated as a function of time for any given thermal history by a suitable method. The results of creep deflection measurements on a sample of commercial polystyrene are reported. The data isothermally obtained at different temperatures are determined so as to obtain the master curve of the compliance as a function of time and the shift factor as a function of temperature. As an example, the above method is applied to predict the course of a laboratory test which is commonly used to determine the heat deflection temperature of thermoplastic polymers. The experimental results agree satisfactorily with the predicted values