Influence of physical interaction between organoclay and poly(ethylene-co-vinyl acetate) matrix and effect of clay content on rheological melt state

In this study nanocomposites of poly(ethylene-vinyl acetate) (EVA) and organophilic montmorillonite clay (OMMT) (0, 2, 5 and 10 phr) were prepared. The nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), parallel plate rheometry and mechanical analysis. Oscillatory rheometry provided relaxation and retardation spectra, and the stress relaxation modulus and the creep compliance curves were obtained using the nonlinear regularization (NLREG) program. The results showed that 2 phr of OMMT were not sufficient to promote dispersion and exfoliation of the clay, although in the form of clay tactoids it had a catalytic effect on the degradation of EVA. The OMMT content had a strong influence on the thermal stability of chain segments containing vinyl acetate (VAc). The rheological study showed that at 5 phr there were substantial changes in the viscosity and energy dissipation of the sample, suggesting that at above 2 phr the nanocomposites become more stable leading to changes in the creep and viscoelastic properties of the material. The addition of OMMT promoted significant gains in terms of the mechanical properties, and thus a study on the clay content and flow behavior was carried out.