Improvement of tribological properties of epoxy resin by addition of oxidized nanocarbons

Graphene oxide (GO) and oxidized wood-derived nanocarbon (oWNC) were dispersed in an epoxy resin to improve the mechanical and tribological properties of an epoxy resin. Mechanical properties of the GO/epoxy (GO/EP) and oWNC/epoxy composites (oWNC/EP) were investigated by tensile tests and nano-indentation. Under dry, water, and oil lubrication conditions, friction coefficients and wear volumes of these composites were measured. GO has single-layered structure. oWNC has chain-like nanostructures, and the nanochains are aggregated. GO and oWNCs have same surface chemical composition due to the same oxidation treatment. Thus, in this study, the structure and morphology dependences of the nanocarbons in mechanical and tribological properties will be appeared when the nanocarbons were used as the additives in the resin. The tensile strength, tensile modulus, and hardness increased by 20%, 63%, and 35% in maximum by the addition of GO and oWNC to the epoxy resin, respectively. Moreover, the wear resistance of GO/EP and oWNC/EP was enhanced compared to that of a neat epoxy. The reduction rates of the wear volume for 5.0 mass% GO/EP and 1.0 mass% oWNC/EP achieved to 91% and 67%, respectively. Comparing GO and oWNC, oWNC effectively reduced the friction coefficient and wear at a lower concentration. The improvement of tribological properties after the addition of the oxidized nanocarbons can be attributed to the increase in the hardness and lubricity of the composites.