The effects of clay content and sonication time on water uptake in epoxy-organoclay nanocomposites

The effects of clay loading and the extent of sonication time on water uptake in epoxyorganoclay based nanocomposites have been investigated as a function of exposure time in 3.5% NaCl at room temperature. Three clay loadings (2%, 4%, and 5wt.%) were dispersed in the epoxy resin by 10 and 60 minute sonication. The weight gains in the neat epoxy and the nanocomposites with 2 wt.% and 4 wt.% clay loadings showed a common asymptotic saturation value of 0.72 wt.% after 1000 hours of exposure. The saturation value was independent of sonication time. Nanocomposite with 5% clay loading and 60 minutes sonication exhibited a unique behavior and did not show saturation after 1000 hours of exposure. Scanning electron microscopy of tensile fractured nanocomposite specimens revealed the presence of organoclay aggregates, the size and number of which increased with an increase in clay loading. The Glass transition temperatures (T _g) for the nanocomposites decreased by approximately 20-25C° after 1000 hours of exposure in 3.5% NaCl solution.