Morphology and properties of UV/ozone treated graphite nanoplatelet/epoxy nanocomposites

The nanoscopic morphologies, thermo-mechanical, mechanical and electrical properties of graphite nanoplatelet (GNP)/epoxy nanocomposites were evaluated after UV/O3 treatment of graphite. Composites containing uniformly distributed GNP reinforcements of well controlled exfoliation were prepared through the graphite intercalation compound technique, graphite surface treatment and optimized ultrasonication process with the aid of solvent. The UV/O3 treatment showed ameliorating effects on various properties of nanocomposites arising from the enhanced graphite-epoxy interfacial adhesion. The flexural moduli and strengths were higher after treatment for a given GNP content. The thermo-mechanical properties, such as glass transition temperature and storage modulus, increased with increasing exposure duration before saturation after about 30 min of exposure. The electrical resistivity of treated nanocomposites decreased with increasing GNP content much faster than those containing untreated GNPs. The percolation thresholds of both nanocomposites with and without UV/O3 treatment were similarly about 1 wt%, which is much lower than the values reported in the literature. The interparticle distances were predicted for different particle aspect ratios and volume fractions, and the comparison between the prediction and the experimental aspect ratio for a given percolation threshold indicates reasonable agreement.