Rheologica Acta

, Volume 45, Issue 5, pp 717–727 | Cite as

Rheological properties of branched polystyrenes: nonlinear shear and extensional behavior

Original contribution

Abstract

Nonlinear shear and uniaxial extensional measurements on a series of graft-polystyrenes with varying average numbers and molar masses of grafted side chains are presented. Step-strain measurements are performed to evaluate the damping functions of the melts in shear. The damping functions show a decreasing dependence on strain with an increase in mass fraction of grafted side chains. Extensional viscosities of the melts of graft-polystyrenes exhibit a growing strain hardening with increasing average number of grafted side chains as long as the side branches have a sufficient molar mass to be entangled. Graft-polystyrenes with side arms below the critical molar mass Mc for entanglements of linear polystyrene but above the entanglement molar mass Me of linear polystyrene (Me < Mw,br < Mc) still show a distinct strain hardening. With decreasing molar mass of the grafted side chains (Mw,br < Me) the nonlinear-viscoelastic properties of the graft-polystyrene melts approach the behavior for a linear polystyrene with comparable polydispersity.

Keywords

Graft-polystyrenes Long-chain branching Shear and elongational viscosity Damping function in shear and elongation Elongational viscosity Strain hardening Entanglements 

Notes

Acknowledgements

Financial support from the German Research Foundation (DFG) (grant numbers Mu 1336/2-1 and Mu 1336/2-3) is gratefully acknowledged. J.H. wants to thank Prof. Dr. M. H. Wagner for the source code of the program for the damping function calculations.

Supplementary material

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Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  1. 1.Institute of Polymer MaterialsUniversity Erlangen-NürnbergErlangenGermany
  2. 2.Bayer Technology Services GmbHLeverkusenGermany

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