REVIEW OF VEGETABLE NANOLUBRICANTS FOR TRIBOLOGICAL APPLICATIONS

About 40 million tons of lubricants are used every year for various industry purposes and applications, where most of them are petroleum based oils. These oils are difficult and expensive to dispose of, have low biodegradability and are contamination risks. Recent efforts have been focused on reducing the environmental impact of petroleum based lubricants through the use of vegetable oils since they are biodegradable and have good lubricity. A drawback of vegetable oils is their poor thermal stability and oxidation, which causes them to decrease their properties at higher loads. Nanoparticle (NP) additives have been explored for improving the tribological performance of vegetable. This literature review seeks to compare and analise the impact of the different NP types, concentrations and vegetable oil type on the coefficient of friction. The vegetable oils that have shown to provide the best tribological behaviour were coconut oil, sunflower oil, palm sesame oil, canola oil, among others. The NP with the best performance were SiO₂ and CuO and the concentration with the highest improvement was between 0.01-3.0 wt.%. The results of this study provide an insight on the areas of opportunity for developing new lubricant formulations with vegetable oils and NP additives for industrial applications.