Influence of molecular structure on rheological properties of polyethylenes
作者： H. Münstedt , Stefan Kurzbeck , Lothar Egersdörfer
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摘要: Elastic properties of melts a long-chain branched low density polyethylene (LDPE) with broad molecular mass distribution and short-chain linear low-density (LLDPE) more narrow were investigated by creep recovery measurements in shear. The results obtained means magnetic bearing torsional apparatus the linear-viscoelastic region, showed that steady state recoverable compliance LLDPE is greater factor two than LDPE. In short-time region up to 1000 s, however, time-dependent LDPE higher LLDPE. retardation times for are considerably longer For temperature dependence entanglement transition consistent terminal zone compliance. activation energy 58 kJ/mole lies typical range polyethylenes. case compliances can be shifted give mastercurve an 34 kJ/mole, whereas do not follow time-temperature superposition principle. characterization using TREF has bimodal branching structure. addition component, percentage constituent high was found. It postulated this component forms dispersed phase matrix constituent. resulting interfacial tension could reason long times, fact principle fulfilled investigated.
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