Microstructure and thermal properties of ethylene-(vinyl acetate) copolymer/rectorite nanocomposites

Ethylene-(vinyl acetate) copolymer (EVA)/rectorite nanocomposites were prepared by direct melt extrusion of EVA and organo-rectorite. The microstructures and thermal properties of EVA nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), solid-state nuclear magnetic spectroscopy, positron annihilation spectroscopy, thermal gravimetric analysis (TGA) and dynamic mechanical analysis techniques. XRD pattern and SEM images show that the intercalated structure is formed and rectorite is finely dispersed in EVA matrix. When organoclay content of the hybrid increases to 7.5 wt%, or pristine rectorite was used instead of organoclay, the crystallization behavior of EVA nanocomposite changes greatly and the ratio of the monoclinic to orthorhombic crystal increases significantly. The relative fractional free volume of the nanocomposite decreases with the increasing organo-rectorite content, and the values of damping factor (tan delta) for all nanocomposites are lower than that of pure EVA. These facts illuminate that intercalated structure restricts the segment motion and mobilization of polymer chain. TGA results of EVA nanocomposites in air indicate that deacylation of EVA is accelerated because of the catalytic effect and the thermal degradation of the main chain is delayed owing to the barrier effect of silicate layers. (C) 2005 Society of Chemical Industry.