Effects of Waste-Plastic-Derived Carbon Nano-Onions as Additive on Rheological and Tribological Performance of Oil Lubricant

Abstract The development of sustainable, high-performance lubricant additives is crucial for advancing energy efficiency and prolonging the operational lifespan of mechanical systems. In this study, carbon nano-onions (CNOs) synthesized from plastic waste were evaluated as multifunctional additives in two distinct base oils: mineral oil (MO) and synthetic oil (SO). Rheological measurements revealed that CNOs increased the viscosity of MO, while slightly reducing that of SO, highlighting base oil-dependent interactions. Tribological tests of steel-on-steel demonstrated substantial reductions in friction and wear with CNOs. addition. In MO, the coefficient of friction decreased by up to 46%, and wear-rates dropped by 35% at higher concentrations. In SO, friction was reduced by 31% and wear by up to 53% under lower loads. These results position CNOs as an environmentally friendly and effective additive for diverse lubrication systems.