Exfoliated graphite sheets, or graphene, are currently being studied for their electrical, mechanical, and thermal properties. This material also has great potential for mass transfer barrier properties when dispersed in polymer to form polymer nanocomposites (PNCs), and these graphene-based PNCs (GPNCs) should yield better properties as compared to PNCs made using other nanofillers, including nano-layered silicates. In this work, commercially-available graphene was surface treated with silanes to impart hydrophobic character to the graphene surface allowing for better dispersion in a matrix of polyvinyl acetate (PVAc). This was verified using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Moisture diffusion through PVAc samples containing up to 1.5 wt.% treated and untreated graphene with platelets of two different aspect ratios was studied at room temperature which showed that the initial moisture diffusivity decreased with increasing filler content. The diffusion coefficient was found to reduce by as much as two orders of magnitude from that of the neat polymer. These results are superior to those obtained by us in the past using organoclay as the filler, where the observed reduction was about 20%. Clearly, graphene platelets form an excellent barrier against water diffusion.
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