Rheologica Acta

, Volume 50, Issue 1, pp 53–63 | Cite as

Influence of molecular parameters on the stress dependence of viscous and elastic properties of polypropylene melts in shear

  • Julia A. Resch
  • Joachim Kaschta
  • Friedrich Wolff
  • Helmut Münstedt
Original Contribution

Abstract

The stress dependencies of the steady-state viscosity η and, particularly, that of the steady-state elastic compliance Je of various linear isotactic polypropylenes (PP) and one long-chain branched PP are investigated using creep-recovery tests. The creep stresses applied range from 2 to 10,000 Pa. In order to discuss the stress-dependent viscosity η and elastic compliance Je with respect to the influence of the weight average molar mass Mw and the polydispersity factor Mw/Mn the PP are characterized by SEC–MALLS. For the linear PP, linear steady-state elastic compliances \(J_{\rm e}^0 \) in the range of 10 − 5–10 − 3 Pa − 1 are obtained depending on the molar mass distribution. \(J_{\rm e}^0 \) of the LCB-PP is distinctly higher and comes to lie at around 10 − 2 Pa − 1. \(J_{\rm e}^0 \) is found to be independent of Mw but strongly dependent on polydispersity. η and Je decrease with increasing stress. For the linear PP, Je as a function of the stress τ is temperature independent. The higher Mw/Mn the stronger is the shear thinning of η and the more pronounced is the stress dependence of Je. For the LCB-PP, the strongest stress dependence of η and Je is observed. Furthermore, for all PP Je reacts more sensitively to an increasing stress than η. A qualitative explanation for the stronger stress dependence of Je compared to η is given by analyzing the contribution of long relaxation times to the viscosity and elasticity.

Keywords

Polypropylene Viscosity Steady-state elastic compliance Stress dependence Molecular structure 

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Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  • Julia A. Resch
    • 1
  • Joachim Kaschta
    • 1
  • Friedrich Wolff
    • 1
  • Helmut Münstedt
    • 1
  1. 1.Institute of Polymer MaterialsFriedrich-Alexander-University Erlangen-NürnbergErlangenGermany

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