A constitutive model for entangled polydisperse linear flexible polymers with entanglement dynamics and a configuration dependent friction coefficient. Part II. Modeling “shear modification” following cessation of fast shear flows

The polydisperse Mead–Park (MP) “toy” molecular constitutive model developed in Paper I [Mead et al., J. Rheol. 62, 121–134 (2017)] as well as our previously published work [e.g., J. Rheol. 59, 335–363 (2015)] is used in the “forward” direction to study model polydisperse melts of entangled linear flexible polymers in severe, fast shear flows. The properties of our new model are elucidated by way of numerical simulation of a representative model polydisperse polymer melt in step shear rate and interrupted shear flow. In particular, we demonstrate how the MP model simulates the individual molecular weight distribution (MWD) component dynamics as well as the bulk material properties. Additionally, we demonstrate that the polydisperse MP model predicts the phenomenon of “shear modification” for model MWD's with a long, high molecular weight tail. Specifically, the terminal dynamic moduli following cessation of severe, disentangling deformation, are shown to slowly heal/recover on the orientational relaxation...