Rheological behaviour of LDPE/EVAc blends. II. Linear viscoelasticity and extrusion properties

This study was designed to determine the linear viscoelastic and extrusion properties of a series of LDPE/ EVAc blends. Newtonian viscosity was found to show strong positive deviation from the double reptation model, which assumes miscibility or, at least, cooperative relaxation between the mixed species. The blends also showed enhanced steady-state compliance and elastic indices compared to those of the pure components. These features, typical of emulsion-like polymer blends, seem to be attributable to additional relaxation processes at low frequencies associated with dispersed phase deformability. Good agreement with experimental dynamic results was shown by the Palierne model for emulsions of two viscoelastic liquids, for values of a/R = 3.5 · 103 Pa across the whole frequency range examined. The double reptation model, usually applied to miscible blends, showed good agreement with experimental data for frequencies higher than 10)2 rad s)1. This could lead to erroneous conclusions on the miscibility of certain systems, for which a complete set of experimental data is lacking.