LAUSR

Abstract An increasing concern on environmental and health problems caused by petroleum-based oil leads to the development of environmentally benign metalworking fluids from crude jatropha oil (CJO). Commonly, CJO is commercially utilized in food industry but in this current work, is selected to be used as a base stock due to its renewability and biodegradability. CJO was modified through transesterification processes and mixing with solid lubricant nanoparticle additive, hexagonal boron nitride (hBN) in order to improve the lubrication properties. The lubrication properties of modified jatropha oils (MJOs) as base oil, in comparison with synthetic ester (SE) and CJO were explored. Two types of tribological tests, comprising Four Ball test and tapping torque test were performed. The samples labelled as MJO1, MJO3 and MJO5 were formulated at various molar ratios of jatropha methyl ester (JME) and trimethylolpropane (TMP). These MJOs were blended with various concentrations of hBN particles, ranging from 0.05 to 0.5 wt%. The results obtained indicated that MJO5-base mixed with 0.5 wt% of hBN nanoparticle provided the best physicochemical properties due to lowest thermal expansion coefficient of hBN nanoparticles. High formation of TMP triester in MJO5 formed a strong lubrication film which significantly affected the lubrication and tribological behaviour. MJO5 sample exhibited better friction and wear behaviour by 75% and 20% reduction, respectively, especially when compared to SE. An addition of 0.05 wt% of hBN nanoparticles in MJO5 (MJO5a) was found to reduce the friction and wear up to 76% and 24%, respectively. MJO5a also recorded the highest tapping torque efficiency of 118%. Conclusively, the performance of MJO5a sample has the potential impact on the lubricant market place in regard to the environmental concern and energy saving.