Mechanical and tribological performance of neat epoxy,epoxy-graphene nanoplatelets,and epoxy-carbon nanotubes

Abstract

Epoxy polymer is widely used in adhesives, coatings, and composite structures due to its mechanical resistance, chemical stability, and low friction. However, high brittleness and low abrasive resistance limit its range of applications. In this work, an epoxy polymeric matrix is reinforced with carbon nanotubes (CNTs) or graphene nanoplatelets (GNPs), for an expected improvement in mechanical and tribological performance. Concentrations of 0.5% wt and 1.0% wt are investigated. Monotonic tensile tests (under three displacement rates) and tensile-tensile fatigue tests were carried out. Tensile and fatigue strength degraded due to a greater number of discontinuities demonstrated by microscopic analysis. Brinnel and instrumented indentations tests were performed, to assess hardness and compressive stress-strain behavior. They revealed that 0.5% GNP increased hardness, while 0.5% CNT and 1.0% GNP reduced compressive stiffness. Rotating sphere micro-abrasive tests were carried out for the evaluation of wear performance. 1.0% GNP and 0.5% CNT significantly reduced the wear coefficient (−47% and −41%, respectively) when compared to neat epoxy. In conclusion, voids and filler agglomerates had a negative impact on bulk mechanical properties, restricting usage in structural applications. However, the significant reduction in wear shows that GNP and CNT could be successfully employed as reinforcement in protective epoxy coatings.