Comparison of dumbell-based theory and experiment for a dilute polymer solution in a corotating two-roll mill

Abstract

The Chilcott–Rallison FENE dumbbell model is used to solve for the polymer and flowfield response in transient startup flow of a dilute solution in a corotating two-roll mill. These predictions are then compared to experimental results obtained in an identical geometry using a high molecular weight dilute (c/c*∼0.1) polystyrene solution. As predicted by the dumbbell model, the experiments indicate a substantial coupling between the polymer deformation and changes to the Newtonian flowfield. As the polymer stretches, the experimentally measured shear rate decreases, as does the flow-type parameter. However, dumbbell model parameters based upon an isolated chain do not result in FENE model predictions quantitatively similar to the experimental results. Based upon steady-state birefringence values for the same dilute solution in an extension dominated flow at large strain rates, it appears that chain–chain interactions restrict the maximum attainable polymer deformation. Further calculations incorporating th...