LAUSR

Abstract Preparation of epoxidized tung oil ethyl ester (ETOEE) was explored in this work via a two-step approach to produce bio-lubricant with enhanced thermal-oxidative stability. Transesterification of tung oil with ethanol was first carried out with KOH as the catalyst at 60 °C and a molar ratio of tung oil to ethanol of 1:20 for 2 h. The obtained tung oil ethyl ester (TOEE) was subjected to epoxidation in the presence of hydrogen peroxide and formic acid (FA). The highest conversion (93.6%, based on reduction of iodine value) was achieved by reacting 10 g of TOEE with 14.5 g of hydrogen peroxide and 5.86 g of FA at 50 °C for 3 h. Under these conditions, the resulting ETOEE has an oxirane number or epoxy value of 5.1%, and the presence of epoxy groups was confirmed by Fourier transform infrared spectroscopic analysis. The resulting ETOEE was further analyzed of its thermal stability under both oxidative and non-oxidative atmospheres. The viscosity index was determined and improvements in both thermal stability and lubricity were observed with the aid of a modular compact rheometer and a thermos-gravimetric analyzer, respectively. The ETOEE produced may be suitable for use as lubricating oil in gear boxes and engines. Graphic Abstract