Compression yielding of polypropylenes above glass transition temperature

Yielding behaviour under compressive loading of two materials based on polypropylene, an isotactic homopolymer and an ethylene–propylene block copolymer, is studied at different strain rates and temperatures. Quasi-static tests, performed in electromechanical machines, and dynamic tests, carried out in a Hopkinson bar, were compared and simultaneously analyzed to generate a master curve representative of the material yielding, assuming the strain rate-temperature superposition principle. Experimental data were fitted to equations based on the cooperative model for semi-crystalline polymers.