Thermophysical and Tribological Analysis of Non-edible Coconut Oil with CuO Nanoparticles

The study investigates the thermophysical and tribological behavior of non-edible coconut oil when used as a base fluid with copper oxide (CuO) nanoparticles. The measured thermophysical properties include kinematic and dynamic viscosities, acid value, flash point, fire point, and transesterification characteristics. Tribological performance was evaluated using a pin-on-disc tribometer (ASTM G99) to determine the coefficient of friction and wear rate. Results show that the addition of CuO nanoparticles increases viscosity and improves load-carrying capacity. The underlying mechanisms are discussed, and guidance on the optimal concentrations of vegetable oil-based nano-lubricants is provided. The results indicate that the optimal concentration of CuO nanoparticle-based nano-lubricant is around 0.38 wt.%, at which the coefficient of friction and wear rate are minimized. The addition of nanoparticles can improve the overall lubricating properties of the oil, making it suitable for lubrication applications. The addition of CuO nanoparticles to the base oil increases the viscosity by 30–32%, while the decrease in viscosity at elevated temperatures becomes less pronounced with increasing nanoparticle concentration. The average wear rate is reduced by approximately 65–70% compared with that of the base oil alone. At the optimum CuO nanoparticle concentration of 0.38 wt.%, the wear rate is reduced by 72% compared with that of the base oil.