A thermodynamically admissible reptation model for fast flows of entangled polymers.: 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 molecular-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 approximation. Here, no use is made of the ingredient of anisotropic tube cross sections of the previously proposed model. Simulation results reveal that the model at a highly simplified level with few structural variables, i.e., four degrees of freedom, is able to capture qualitatively all features of the available experimental observations and is highly competitive with recently proposed models in describing nonlinear rheological properties of linear entangled polymers. (C) 2000 The Society of Rheology. [S0148-6055(00)00406-5].