Friction and Wear Behavior of Graphene and Graphite Oxide–Reinforced Epoxy Composites

Graphene has gained prominence owing to its excellent mechanical, thermal, and electrical properties. Indeed, polymer–graphene composites have demonstrated superior mechanical properties over monoliths and are well suited for seals and bearings. The objective of this work was to gain a fundamental understanding of the friction and wear mechanics of epoxy reinforced by graphene-based fillers. Epoxy composites were prepared with three commercially available graphene/graphite fillers identified as KS6, synthetic graphite powder; xGNP, graphene platelets; and iGO, industrial graphite oxide and tribologically evaluated in a ball-on-disc configuration at sliding velocities from 0.047 to 1.61 m/s. It was found that only the epoxy +5 wt% iGO demonstrated a lower wear rate among other fillers, with 1 wt% being the best for a range of iGO content. The addition of iGO improved the friction and wear resistance due to functional groups on the surface and the resulting enhanced adhesion; it was the nature of the surface film rather than the bulk polymer that dictated the tribological response. Although further studies are warranted, there are indications that harder particles such as iGO may have limited the rate of detachment and wear by arresting crack propagation in the matrix and filler dispersion. The wrinkled morphology of iGO led to better interlocking with the matrix, thereby limiting the detachment of particles; the filler–matrix interaction between functional groups on the graphene oxide surface may also play an important role. These results have important implications for improving the manufacture of composites with superior tribological and mechanical properties.