Structuring of polymer blends in simple shear flow

Abstract

AbstractA simplified model for the formation of steady state structure of discrete domains in polymer blends is established for simple shear flow. It is assumed that the domain size distribution, which results from an equilibrium between breakup processes and coalescence processes, may be divided in small and stable spherical domains and large and unstable ellipsoidal domains. Based on simplified rate balances and an expression for domain deformation rate the volume fraction of large domains and the large and small semiaxes of the ellipsoids are expressed as functions of volume fraction and shear rate/shear stress. The ability of the model to simulate actual behaviour is tested against quantitative data for polystyrene/poly(methyl methacrylate) blends. It is concluded that the Taylor type behaviour is approached at low volume fraction and low shear stress. The aspect ratio, P, shows a maximum in a plot against shear stress with volume fraction as discrete variable. For certain concentrations P seems to approach infinity thus forming infinitely long fibers.