Rheology of polypropylene in the solid state

摘要: The tensile behaviour of a commercial grade isotactic polypropylene was tested in temperature range between 20 and 150 °C with video-controlled testing system which is capable imposing constant true strain-rate within the neck automatically. results are displayed form effective stress-strain curves modelled by constitutive equation multiplicative form. It thus shown that, for each temperature, plastic response can be described up to very large strains (ɛ ≃ 2.0) set four parameters. assumptions introduced this modelling critically discussed order check validity simplifying hypotheses (strain homogeneity, isochoric deformation, etc.). obtained utilized finite difference code predict development stretching instabilities polypropylene. simulation gives access engineering stretched test piece detailed kinetics incipient neck. found that severity less at room than near melting point because decrease strain-hardening sensitivity temperature.