Phase morphology and melt viscoelastic properties in blends of ethylene/vinyl acetate copolymer and metallocene-catalysed linear polyethylene

The aim of this study was to determine the linear viscoelastic properties of a series of ethylene/vinyl acetate copolymer/metallocene-catalysed polyethylene (mPEs) blends. Newtonian viscosity showed a pronounced positive deviation from the double reptation model, which assumes miscibility or, at least, cooperative relaxation between the mixed species. Enhanced values of steady-state compliance and elastic indices with respect to those of the pure components were also noted. These features are typical of emulsion-like polymer blends and are thought to arise from additional relaxation processes associated with dispersed phase deformability. Application of the Palierne model for emulsions of two viscoelastic liquids showed good agreement with our experimental dynamic results at both ends of the phase diagram. However, the model failed at intermediate compositions. Through the application of several rheological criteria we were able to locate the phase inversion concentration at a weight fraction of w=0.60 in the mPEs. It is suspected that, in this composition range, a fully co-continuous phase develops due to the phase inversion mechanism, which has considerable effects on the viscoelastic properties of the blends.