Entangled linear polymers in fast shear: evaluation of differential tube-based modeling including flow-induced disentanglement and chain tumbling

Abstract

Flow-induced disentanglement (FID or CCR-D) and chain tumbling are two molecular mechanisms typically observed in non-equilibrium molecular dynamics simulations of entangled polymer melts under fast shear. As regards quantitative performance, classical tube models exhibit limitations at fast rates presumably due to the negligence of the aforementioned mechanisms. CCR-D or tumbling inclusion is reported in some revised tube models. For example, in Desai–Larson’s (DL) work (J Rheol 58:255–279, 2014), which focuses on uniaxial elongation, FID is coupled to the alignment and stretch status of the chains. In Costanzo et al. (Macromolecules 49:3925–3935, 2016), tumbling is accounted for via incorporation of a semi-empirical tumbling function in the stretch equation. Nevertheless, CCR-D is neglected. Here, we include tumbling in the DL differential constitutive set and we assess its performance at shear and relaxation following shear. Model predictions are compared against data on various polystyrene melts as obtained by a cone-partitioned-plate fixture.