Tribological performances of palm oil derived-oleic acid biolubricant incorporated with antioxidant and viscosity improver

A tribological study on oleic acid (OA) as a base stock, with added antioxidants and a viscosity improver, was conducted to determine the coefficient of friction (COF) and wear scar diameter (WSD) values. This study aims to identify the most effective antioxidant for achieving high-performance lubrication. Antioxidants such as tertbutylhydroquinone (TBHQ), butylated hydroxytoluene (BHT), and 3-tert-butyl-4-hydroxyanisole (BHA) were used in the four-ball test, performed under varying operating conditions in accordance with ASTM D4172 standards, with a load of 392 N, and speeds ranging from 1200 to 2400rpm at 75 degrees C. The antioxidant concentration was maintained at 0.5wt.% while the viscosity improver, ethylene vinyl acetate (EVA), was used at 1.2 wt.%. The combination of TBHQ and EVA was observed to result in a maximum COF reduction of approximately 22% compared to BHA and BHT. Scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) analyses were conducted to examine the morphology and thermal behavior of the biolubricants, respectively. TBHQ produced the best results for COF and WSD, followed by BHT, and then BHA.