A comparative study on the lubricant properties of chemically modified Calophyllum inophyllum oils for bio-lubricant applications

The trend of using non-edible vegetable oils as a potential base stock for industrial lubricants is increasing due to environmental issues and fossil fuel depletion. Calophyllum inophyllum oil (CIO) is a non-edible tree seed oil available in various parts of the world. The major disadvantage of CIO is the high acid and peroxide value, which leads to poor oxidation stability. This study focused on the chemical modification of CIO by epoxidation and transesterification processes to improve its oxidation stability. The fatty acid profile of CIO used in the study was obtained using Gas chromatography - Mass spectroscopy technique and the functional groups present in CIO and chemical modified CIO were identified using Fourier transform infrared spectroscopy. The lubricant properties such as tribological, rheological, physicochemical, thermal properties, and oxidative stability of pure CIO, epoxidized CIO (ECIO), and transesterified CIO (TCIO) have been evaluated and compared in this study. The experimental results indicated that there is a significant improvement in the chemical properties and oxidative stability of CIO after the transesterification and epoxidation process. The viscosity and wear scar diameter of ECIO was observed to be better than that of CIO by 42.81% and 7.97%, respectively. TCIO has shown the least viscosity increment ie., 25.45% after 120 h of heating which shows better oxidative stability. The modified CIO can be considered as a potential base-stock for bio-lubricant formulation.