Polyvinylidene chloride copolymers (PVDC)/polyethylene (PE) immiscible blends offer improved extrusion processing over PVDC alone while retaining the excellent oxygen and water barrier properties. The transport of permeants through these com posites is related to the geometry of the dispersed phase PE. A lamella or striated type PE phase is desired as this results in a better barrier than a more spherical geometry. This morphology can originate most easily from extensional flow. Other possible mechanisms to consider are the relationship of normal and surface tension stresses, and the breakup and coalescence equilibrium of the dispersed phase.
