Dynamic-mechanical behavior of polyethylenes and ethene/α-olefin-copolymers: Part II. α- and β-relaxation

摘要: The temperature- and frequency-dependent dynamic-mechanical properties in the temperature regime of γ-transition were determined for a number polyethylenes ethylene/α-olefin-copolymers differing their crystallinity crystal morphology. dependence was found to obey Arrhenius law thermally activated processes. at frequency 1 Hz corresponding activation energy analyzed as function crystallinity. As an overall trend, both quantities are decrease with decreasing crystallinity, which is explained by increase free volume due incorporation short-chain branches or thermal pretreatment (e.g., quenching). Taking into account that morphology can be classified four different groups, more detailed picture appears. Within one type quantities, namely transition energy, independent α-olefin used comonomer. These findings partial orientations molecule segments interlamellar amorphous space case HDPE increased steric hindrance crankshaft motion branches. From this series studies, it concluded glass polyethylene polyethylene/α-olefin-copolymers β- not γ-transition.