Authors: Julia A Resch Joachim Kaschta Friedrich Wolff Helmut Münstedt
Publish Date: 2010/11/16
Volume: 50, Issue: 1, Pages: 53-63
Abstract
The stress dependencies of the steadystate viscosity η and particularly that of the steadystate elastic compliance J e of various linear isotactic polypropylenes PP and one longchain branched PP are investigated using creeprecovery tests The creep stresses applied range from 2 to 10000 Pa In order to discuss the stressdependent viscosity η and elastic compliance J e with respect to the influence of the weight average molar mass M w and the polydispersity factor M w/M n the PP are characterized by SEC–MALLS For the linear PP linear steadystate elastic compliances J rm e0 in the range of 10 − 5–10 − 3 Pa − 1 are obtained depending on the molar mass distribution J rm e0 of the LCBPP is distinctly higher and comes to lie at around 10 − 2 Pa − 1 J rm e0 is found to be independent of M w but strongly dependent on polydispersity η and J e decrease with increasing stress For the linear PP J e as a function of the stress τ is temperature independent The higher M w/M n the stronger is the shear thinning of η and the more pronounced is the stress dependence of J e For the LCBPP the strongest stress dependence of η and J e is observed Furthermore for all PP J e reacts more sensitively to an increasing stress than η A qualitative explanation for the stronger stress dependence of J e compared to η is given by analyzing the contribution of long relaxation times to the viscosity and elasticityThe authors would like to thank the German Research Foundation DFG for the financial support of this work The contributions of Mrs Inge Herzer Mrs Marika Sturm and Mrs Michelle Malter regarding the SEC–MALLS the IRspectroscopy and the DSC measurements are gratefully acknowledged Prof Dr Florian Stadler School of Semiconductor and Chemical Engineering Chonbuk National University deserves acknowledgement for the calculation of the relaxation spectrum and its evaluation concerning η 0 and J rm e0
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