Vinyl-ester nanocomposites based on a binary-solvent system for well-exfoliated graphene and enhanced performance

This paper introduces a green approach for preparing well-dispersed graphene nanoplates (GNPs) in vinyl-ester (VE) resin. The GNPs were exfoliated in a novel binary-solvent system comprised of a water and ethanol mixture (S nanocomposites). Water and ethanol were considered poor solvents for graphene, but a combination of them could be an ideal solvent mixture. TEM images of the S nanocomposites revealed well-exfoliated graphene sheets with a few wrinkles. Hence, the effective surface areas of the GNPs considerably increased, playing a vital role in enhancing the performance of the nanocomposites. With the incorporation of just 0.4 wt% of exfoliated GNPs (S2 nanocomposite) in the VE, the tensile strength, and toughness enhanced by 51%, and 63%, respectively. Fractography analysis indicated smooth fracture surfaces of pure resin changed to very rough surface structures for the S2 nanocomposite. The viscoelastic properties of the specimens indicated that directly loading GNPs into the resin decreased the glass transition temperature (Tg) of the VE resin. In contrast, the samples prepared by liquid-phase exfoliation enhanced the Tg of the VE. Lastly, the barrier properties of the S2 nanocomposite revealed that its water absorption decreased by 26% compared to the pure resin.