Correlation between the morphology and dynamic mechanical properties of ethylene vinyl acetate/linear low‐density polyethylene blends: Effects of the blend ratio and compatibilization

Abstract

AbstractThe effects of the blend composition and compatibilization on the morphology of linear low‐density polyethylene (LLDPE)/ethylene vinyl acetate (EVA) blends were studied. The blends showed dispersed/matrix and cocontinuous phase morphologies that depended on the composition. The blends had a cocontinuous morphology at an EVA concentration of 40–60%. The addition of the compatibilizer first decreased the domain size of the dispersed phase, which then leveled off. Two types of compatibilizers were added to the polymer/polymer interface: linear low‐density polyethylene‐g‐maleic anhydride and LLDPE‐g phenolic resin. Noolandi's theory was in agreement with the experimental data. The conformation of the compatibilizer at the blend interface could be predicted by the calculation of the area occupied by the compatibilizer molecule at the interface. The effects of the blend ratio and compatibilization on the dynamic mechanical properties of the blends were analyzed from −60°C to +35°C. The experiments were performed over a series of frequencies. The area under the curve of the loss modulus versus the temperature was higher than the values obtained by group contribution analysis. The loss tangent curve showed a peak corresponding to the glass transition of EVA, indicating the incompatibility of the blend system. The damping characteristics of the blends increased with increasing EVA content because of the decrease in the crystalline volume of the system. Attempts were made to correlate the observed viscoelastic properties of the blends with the morphology. Various composite models were used to model the dynamic mechanical data. Compatibilization increased the storage modulus of the system because of the fine dispersion of EVA domains in the LLDPE matrix, which provided increased interfacial interaction. Better compatibilization was effected at a 0.5–1% loading of the compatibilizer. This was in full agreement with the dynamic mechanical spectroscopy data. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4526–4538, 2006