The development of phase morphology and polymer chain orientation in the processing of incompatible polymer blends

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Abstract
A critical review is presented of experimental research on development of phase morphology and polymer chain orientation in disperse two phase flow of polymer melts. It is shown that, in stratified flow, phase morphology variations are primarily caused by viscosity differences between the two phases. For disperse two‐phase flow, the phase morphology is strongly influenced by the interfacial tension as well as the viscosity ratio. This appears to be through the capillarity or Taylor number. Large interfacial tensions and small shear stresses or matrix viscosities lead to coarse phase morphologies and phase growth under quiescent conditions. Interface modification additives (compatibilizers) may be interpreted in terms of reduction of interfacial tensions. Applications to polymer processing operations and interpretation of rheological properties are described. The development of orientation of individual polymers in blends is reviewed. It is shown that chain orientation develops differently for the individual components in both compatible and incompatible blend systems. In incompatible systems, an addition of a second polymer to a crystallizing melt would appear to reduce the levels of eventual crystalline orientation in the latter, if the former shows sharp viscosity rises prior to the crystallization.

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