The effect of shear flow on phase separation in entangled polymer blends

Abstract

We model the effects of shear flow on small concentration fluctuations in well entangled polymer blends subjected to steady state shear flow. We predict that shear can result in the growth (shear induced de-mixing) and the suppression (shear induced mixing) of concentration fluctuations in the quiescent one phase region, in both the velocity gradient and vorticity directions. The controlling parameters are the relative relaxation times and the relative plateau moduli of the two components. We show that increasing the shear rate, so that the effects of shear thinning become important, can result in the behaviour changing from shear induced mixing to shear induced de-mixing and viceversa. Finally, we present quantitative predictions for the changes in the phase boundary that should occur in a high molecular weight polybutadiene/deuterated-polybutadiene blend subjected to shear.