From intermediate anisotropic to isotropic friction at large strain rates to account for viscosity thickening in polymer solutions.
- Stephanou PS Department of Mathematics and Statistics, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus.
- Kröger M Department of Materials, Polymer Physics, ETH Zürich, CH-8093 Zürich, Switzerland.
- 2018-05-17
Published in:
- The Journal of chemical physics. - 2018
English
The steady-state extensional viscosity of dense polymeric liquids in elongational flows is known to be peculiar in the sense that for entangled polymer melts it monotonically decreases-whereas for concentrated polymer solutions it increases-with increasing strain rate beyond the inverse Rouse time. To shed light on this issue, we solve the kinetic theory model for concentrated polymer solutions and entangled melts proposed by Curtiss and Bird, also known as the tumbling-snake model, supplemented by a variable link tension coefficient that we relate to the uniaxial nematic order parameter of the polymer. As a result, the friction tensor is increasingly becoming isotropic at large strain rates as the polymer concentration decreases, and the model is seen to capture the experimentally observed behavior. Additional refinements may supplement the present model to capture very strong flows. We furthermore derive analytic expressions for small rates and the linear viscoelastic behavior. This work builds upon our earlier work on the use of the tumbling-snake model under shear and demonstrates its capacity to improve our microscopic understanding of the rheology of entangled polymer melts and concentrated polymer solutions.
- Language
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- English
- Open access status
- green
- Identifiers
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- DOI 10.1063/1.5019337
- PMID 29764144
- Persistent URL
- https://sonar.ch/global/documents/140144
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