Laponite-graphene oxide hybrid particulate filler enhances mechanical properties of cross-linked epoxy

A new hybrid of Laponite and graphene oxide (LGO), prepared in aqueous media by ultrasonication followed by solvent evaporation was used to reinforce epoxy matrix. The hybrid system was dispersed in liquid epoxy using a two-step solvent-assisted process. The suspensions showed negligible enhancements in processing barrier as revealed by rheology. A combinatorial analysis of small-angle x-ray scattering (SAXS) and microscopy suggested uniform dispersion of nanofillers in the matrix. The fillers showed fractal dimensions in polymer matrix as inferred from SAXS studies. Below 0.5 wt% LGO, the structure showed surface fractal and above 0.5 wt% the composites showed mass fractal, indicating a transformation from well-dispersed to agglomerated composites as the filler content increases. The composites exhibited substantial improvements in various mechanical properties. Notably, the flexural strength and modulus increased by similar to 23% and similar to 29%, respectively, with only 0.5 wt% LGO and the fracture toughness showed an increment of similar to 23% with 0.3 wt% LGO in epoxy matrix. A bimodal distribution of glass transition temperature (T-g) with improved Tg was obtained for the composites. The simultaneous strengthening and toughening effects of nanofillers are explained by means of fractography.