| With the restrictions and guidance provided by nonequilibrium thermodynamics in mind, we develop a thermodynamically admissible single-segment reptation model that unifies all the effects identified as relevant to the flow behavior of polymer melts on the reptation time scale. Starting from a formulation of a reptation model without independent alignment, we incorporate Marrucci's recent ideas of convective constraint release and anisotropic tube cross sections, and, in particular, we provide consistent time-evolution equations for the anisotropic tube cross section in flow. Important features, such as irreversibility in double-step shear strain experiments with flow reversal and a non-decaying shear stress at high shear rates, are appropriately seized by the proposed model. The ratio of normal-stress differences is determined in terms of the change of the mean-square curvature of the tube cross section in shear flow. A model simplification ideal for efficient computer simulations and for matching the experimentally observed linear viscoelastic behavior is proposed.
for LaTeX users @article{HC\"Ottinger2000-89,
author = {H. C. \"Ottinger},
title = {Thermodynamically admissible reptation models with anisotropic tube cross sections and convective constraint release},
journal = {J. Non-Newtonian Fluid Mech.},
volume = {89},
pages = {165-185},
year = {2000}
}
\bibitem{HC\"Ottinger2000-89} H.C. \"Ottinger,
Thermodynamically admissible reptation models with anisotropic tube cross sections and convective constraint release,
J. Non-Newtonian Fluid Mech. {\bf 89} (2000) 165-185.HC\"Ottinger2000-89
H.C. \"Ottinger
Thermodynamically admissible reptation models with anisotropic tube cross sections and convective constraint release
J. Non-Newtonian Fluid Mech.,89,2000,165-185 |
mk@mat.ethz.ch
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