A Kinetic Network Model for Nonlinear Viscoelastic Flow Properties of Entangled Monodisperse Polymers.

摘要

In this work, we shall propose a kinetic network model which appears to predict the observed nonlinear viscoelastic flow properties of entangled polymer systems. The basic molecular mechanism of this model attributes the rate-dependence of viscosity and normal stress difference to the decrease in entanglement density with increasing shear rate. In a flow field, entanglements are being formed and disengaged constantly. The entanglement loss process is caused primarily by the imposed shear and is assumed to be proportional to the shear rate to a power a; where a(<1) accounts for the elastic nature of the polymer. The entanglement creation process, driven by thermal diffusion, is assumed to be independent of shear rate.