Comparative Tribological Investigation of Mahua Oil and its Chemically Modified Derivatives

For the last decade, the lubricant industry has been trying to formulate biodegradable lubricants with technical characteristics superior to those based on petroleum. A renewable resource, mahua oil, is good alternative to mineral oil because of its environmentally friendly, non toxic and readily biodegradable nature. The triacylglycerol structure of mahua oil is amphiphilic in character that makes it an excellent candidate as lubricant and functional fluid. It is also very attractive for industrial applications that have potential for environmental contact through accidental leakage, dripping or generates large quantities of after-use waste materials requiring costly disposal. Vegetable oil in its natural form has limited use as industrial fluids due to poor thermo-oxidation stability, low temperature behavior and other tribochemical degrading processes. Therefore, in the present paper epoxidation and trans-esterification were employed to overcome the mentioned drawbacks of vegetable oil and explore the possibility of modified mahua oil as lubricant because double bonds present in triacylglycerol structure offer sites for additional functionalization This paper compares the lubricating property and mechanical stability of four samples of epoxidized mahua oil, trans-esterified mahua oil, refined mahua oil and a mineral oil based lubricant. The epoxidation of mahua oil followed by oxirane ring opening, by acidic catalyzed reaction with glacial acetic acid and hydrogen peroxide, provides interesting polyfunctional compounds useful as biolubricant with improved low temperature pour properties. The double bonds were epoxidized to improve low temperature and oxidative stability properties of mahua oil. Moreover, another sample of fatty acid methyl ester mahua oil was prepared by two step transesterification process. The four samples-mahua oil, transesterified mahua oil, epoxidized mahua oil and mineral oil based lubricant were tested for their viscosity index, density variation, coefficient of friction and wear tests using four-ball tester. Comparative tests concluded that epoxidized mahua oil and transesterified mahua oil have superior lubricant characteristics with respect to oil and conventional lubricant.