Effect of polymer-clay interaction on solvent transport behavior of fluoroelastomer-clay nanocomposites and prediction of aspect ratio of nanoclay

Diffusion and sorption of methyl ethyl ketone and tetrahydrofuran through fluoroelastomer-clay nanocomposites were investigated in the temperature range of 30-60 degrees C by swelling experiments. Slightly non-Fickian transport behavior was found for these nanocomposites, having variation of type of nanoclay and loading. Different transport parameters depend on the size and shape of the penetrant molecules. The results were used to study the effect of nanoclay on the solvent transport-properties of nanocomposites and their interactions with solvents. The diffusion coefficient of methyl ethyl ketone at 30 degrees C for neat rubber was 1.43 x 10(-8) cm(2) s(-1), while those of the unmodified and the modified clay filled samples at 4 phr loading were 0.24 x 10(-8) and 0.50 X 10(-8) cm(2) s(-1), respectively. At 8 and 16 phr loading of the unmodified clay, it was found to be 0.44 x 10(-8) and 0.64 x 10(-8) cm(2) s(-1), respectively. The samples were also reswelled after deswelling. Surprisingly, transport behavior became Fickian on reswelling. Interestingly, ratio of diffusion coefficients of the filled system to the neat system was found to be almost same for the first time swelling and reswelling experiments. The results showed that better polymer-clay interaction in the case of the unmodified-clay filled nanocomposites is responsible for enhanced solvent-resistance property. From the permeation data, for the first time, aspect ratio of nanoclays in different composites was calculated and found to have good correlation with the morphology data obtained from transmission electron microscopy. (c) 2007 Wiley Periodicals, Inc.