Thermoset fracture toughness improvements at extremely low loadings using graphene and functionalized graphene oxide fillers

Filler materials with nanoscale dimensions have the potential to substantially improve different properties in polymer composites. For reinforced thermoset polymers, one property of special interest is the ability of the matrix to adsorb energy and resist fracture. Many materials used to toughen thermosets require a high weight percent to be added to the resin before beneficial effects can be observed. Previously, we showed that fracture toughness can be increased in epoxy-based systems as very low loadings of functionalized graphene oxide were added. With the addition of functionalized graphene oxide (GO) to an unsaturated polyester (UP) resin, we have been able to achieve a significant improvement in fracture energy (G_1C) at substantially lower weight concentrations (<0.1 wt%). G_1C can be increased two times the neat UP resin with only 0.04 wt% of vinyl-modified GO. These improvements are due to the modifier being covalently bonded to the surface of GO, allowing for improved adhesion to the matrix. Depending on the synthesis condition used, dispersability into the matrix can also be increased alongside a 2.2 times improvement over the neat UP resin in G_1C.