A thermodynamically admissible reptation model for fast flows of entangledpolymers. II. Model predictions for shear and extensional flows

Numerical predictions of a previously proposed thermodynamically consistent reptation model for linear entangled polymers are presented for shear and extensional flows. Comparisons with experimental data and two alternative m olecular-based models are given in detail. The model studied in this paper incorporates the essence of double reptation, convective constraint release , and chain stretching, and it avoids the independent alignment approximati on. Here, no use is made of the ingredient of anisotropic tube cross sectio ns of the previously proposed model. Simulation results reveal that the mod el at a highly simplified level with few structural variables, i.e., four d egrees of freedom, is able to capture qualitatively all features of the ava ilable experimental observations and is highly competitive with recently pr oposed models in describing nonlinear rheological properties of linear enta ngled polymers. (C) 2000 The Society of Rheology. [S0148-6055(00)00406-5].