Improvement of Oxidation Stability, Hydrolytic Stability and Tribological Properties of Kaolin Particles Doped Bio-Based Green Palm Oil

Abstract

Petroleum-based lubricants used in metalworking pose environmental and health risks due to harmful byproducts from combustion and waste disposal. This highlights the need for eco-friendly bio-based lubricants, which, despite their benefits, exhibit low oxidative and hydrolytic stability. Nano-additives provide a sustainable and cost-effective solution to improve these properties. In this study, nanolubricants were prepared by doping kaolin nanoparticles subjected to surface modification with oleic acid to bio-based palm lubricants. The tribological performance of lubricants was assessed via wear tests, oxidative stability was evaluated using the hot oil oxidation test, and hydrolytic stability was determined through the Karl Fischer titration method. Palm lubricants doped with 0.75 wt% kaolin improved the coefficient of friction and wear rate by 29.5 %, and 43.9 %, respectively. Kaolin nanoparticles doped to palm lubricants were found to reduce wear damage and encourage the development of tribo-films. The oxidation and hydrolytic stability of palm lubricants doped with 0.125 wt% kaolin nanoparticles increased by 21.81 % and 29.5 %, respectively, in comparison to undoped palm lubricants.