Rheologica Acta

, Volume 38, Issue 5, pp 393–403

Creep recovery behavior of metallocene linear low-density polyethylenes

  • Claus Gabriel
  • Helmut Münstedt

DOI: 10.1007/s003970050190

Cite this article as:
Gabriel, C. & Münstedt, H. Rheol. Acta (1999) 38: 393. doi:10.1007/s003970050190


The rheological behavior of two metallocene linear low-density polyethylenes (mLLDPE) is investigated in shear creep recovery measurements using a magnetic bearing torsional creep apparatus of high accuracy. The two mLLDPE used are homogeneous with respect to the comonomer distribution. The most interesting feature of the two mLLDPE is that their molecular mass distributions are alike. Therefore, as one of the mLLDPE contains long-chain branches, the influence of long-chain branching on the elastic properties of polyethylene melts could be investigated. It was found that long-chain branches increase the elasticity of the melt characterized by the steady-state recoverable compliance. The long-chain branched mLLDPE has a flow activation energy of 45 kJ/mol which is distinctly higher than that of the other mLLDPE. The shear thinning behavior is much more pronounced for the long-chain branched mLLDPE. A discrepancy between the weight average molecular mass Mw calculated from size exclusion chromatography measurements by the universal calibration method and the zero shear viscosities of the two mLLDPE was observed. These observations are discussed with reference to the molecular architecture of the long-chain branched mLLDPE. The rheological properties of the long-chain branched mLLDPE are compared with those of a classical long-chain branched LDPE. It is surprisingly found that the rheological behavior is very much the same for these two products although their molecular mass distributions and presumedly the branching structures differ largely.

Key words Metallocene linear low-density polyethyleneCreep recoveryShort- and long-chain branchingChemical composition distributionFlow activation energy

Copyright information

© Springer-Verlag Berlin Heidelberg 1999

Authors and Affiliations

  • Claus Gabriel
    • 1
  • Helmut Münstedt
    • 1
  1. 1.Institute of Polymer Materials Department of Materials Science University Erlangen-Nürnberg Martensstrasse 7 D-91058 Erlangen, GermanyDE