Investigation of the Effects of Mold Temperature, Test Temperature and Strain Rate on Mechanical Behaviour of Polypropylene

This paper investigates the time and temperature dependence of a ductile polymer, polypropylene, from the mechanical point of view. As the polymeric specimens have been manufactured by the injection molding process, the influence of mold temperature has been also subjected to the study. Compression tests have been performed both in quasi static and dynamic range (10(-3)/10(3) s(-1)), at different test temperatures (-20/40 degrees C), and the results have been analysed in terms of yield stress and failure behaviour. The strength of the polymer is strongly influenced from all the input parameters. Mold temperature has a relevant effect only at room and high temperature. Polypropylene reveals a ductile to brittle transition when it is loaded at high rates, except when test temperature is high. The relation between test temperature, strain rate and yield stress is found to be well described by the Ree-Eyring model, adapted to the two relaxation mechanisms involved.