Development of Stiff, Tough and Conductive Composites by the Addition of Graphene Nanoplatelets to Polyethersulfone/Epoxy Composites.

In this study, polyethersulfone (PES) was blended into epoxy resins to improve the fracture toughness of the epoxy resin without loss of mechanical properties, and then two grades of pristine graphene nanoplatelets (GnPs) were separately introduced into the PES/epoxy system to fabricate thermally conductive GnPs/PES/epoxy composites with high toughness as well as high stiffness. It was observed that the addition of GnPs obviously affected the final phase morphology by suppressing the phase separation process of the PES modified epoxy due to the increased viscosity and cure-reaction rate of PES/epoxy. The GnPs with a larger lateral dimension revealed a greater reinforcing effect, and the inclusion of 3 wt % GnPs (~5 μm in diameter) endowed the PES/epoxy matrix with a good thermal conductivity and improved the tensile, flexural, and storage modulus by 27.1%, 17.5%, and 15.6% (at 30 °С), respectively. Meanwhile, the fracture toughness was further enhanced by about 29.5% relative to the PES modified epoxy at the same GnPs concentration. The positive results suggest that the modification of epoxy resins using the PES and GnPs is an attractive approach for fabricating tougher and stiffer epoxy-based nanocomposites with multifunctional properties, which could widen the industrial applications of the epoxy resins.