THE EFFECTS OF MOLECULAR WEIGHT ON THE PRESSURE-DEPENDENT MECHANICAL PROPERTIES OF POLYPROPYLENE

摘要

Tensile tests and compression tests of polypropylene (PP) samples with different molecular weights have been carried out at various high pressures. Three different molecular weights were studied up to pressures of 6 kbars. At a given pressure, the effect of increasing molecular weight was to decrease the modulus and the strength. Observations could be explained by a pressure-induced shift of the beta-transition to room temperature. The elongation to fracture and the mode of fracture were found to depend on the molecular weight. The influence of the pressure medium on the observed tensile behavior was also studied. The pressure medium was observed to influence the deformation behavior only for the case of the lower molecular weight samples.