Mechanical enhancement of graphite nanoplatelet composites: Effect of matrix material on the atmospheric plasma-treated GnP reinforcement

Graphite nanoplatelets (GnPs) are currently employed to manufacture a new class of carbon nanomaterial composites with unique electrical and thermal as well as mechanical properties. However, due to their unreactive graphitic structure, surface activation of GnPs is critical to promote bonding to the matrix material. In a previous study, the effect of atmospheric plasma treatment (APT) on the mechanical performance of GnP epoxy composites was evaluated where the GnP surface activation resulted in a significant increase in composite strength. The current investigation evaluates the effect of GnP plasma activation when using a polycyanurate (PCN) resin as the matrix material. GnPs (5, 25 microns in particle size) were surface treated as a function of plasma exposure durations and then used to manufacture composites. Flexural strengths of these plasma-treated PCN composites increased by 25%, for both the 0.5 wt.% loaded M25 and M5 composite systems. The higher loaded systems (1.0 wt.%) exhibited smaller increases in strength (11%) with APT, due to increased particle-to-particle interactions. The glass transition temperature (Tg) of surface-treated GnP PCN composites exhibited little variation with APT, which was in sharp contrast to APT-treated GnP epoxy composites that exhibited Tg increase up to 20℃. This suggests that the oxygen functional groups formed on the surface of GnPs are less chemically reactive toward the PCN than epoxy resins, translating to relatively limited composite strength improvements when utilizing oxygen APT-treated GnPs in PCN matrices.