Flow-Induced Phase Inversion in Immiscible Polymer Blends

The morphology of immiscible polymer blends is one of the major factors controlling their final properties. For two-phase immiscible polymer blends, several parameters are important in determining the final morphology: composition of the blend, shear rate, viscosity and elasticity of the both phases, interfacial tension and time of mixing. Paul and Barlow (1980) have proposed an empirical equation to predict the point of dual phase continuity: $$\frac{{\Phi _A \eta _B }} {{\Phi _B \eta _A }} = 1$$ (1) where ФAand ФB are the volume fractions of phases A and B, and ŋA and ŋB their viscosities. If the ratio in equation (1) is lower than 1, phase A should form the dispersed phase in a continuous matrix of B, whereas B should be dispersed in A for values higher than 1. It has been suggested by Miles and Zurek (1988) that the viscosities should be taken at the shear rate of the actual flow. But it does not always describe satisfactory the inversion for various systems, especially for viscosity ratios diverging from unity. Luciani et al. (1993) formulated another expression for the prediction of dual-phase continuity based on the equilibrium of a bi-fibrillar structure.