Morphology and transport characteristics of poly (ethylene-co-vinyl acetate)/clay nanocomposites

Poly(ethylene-co-vinyl acetate)/clay nanocomposite membranes were prepared with different clay loadings. The morphology of the nanocomposites was investigated using X-ray diffraction technique and transmission electron microscopy. The dispersion of layered silicates decreased with increasing filler loading. Samples with low filler content showed excellent dispersion of layered silicates resulting in a partially exfoliated structure. The transport characteristics of aromatic hydrocarbons through the nanocomposite membranes were studied by the simple sorption gravimetric analysis in the temperature range 28 - 70 degrees C and the results were compared with unfilled membranes. The solvent uptake nature of the nanoclay filled polymer samples was found to be much reduced. The solvent uptake was minimum for composites with 3 wt% of filler and increased with increasing filler content, which is presumably due to aggregation of clay filler at higher loading. The influence of free volume on the transport properties of the membranes was studied using positron annihilation lifetime spectroscopy. The transport phenomenon was found to follow an anomalous mode. Activation parameters were estimated and the molar mass between crosslinks was calculated using Flory - Rehner Theory. The experimental data were compared with theoretical predictions. (c) 2008 Elsevier B.V. All rights reserved.