Physico-chemical and tribological properties of commercial oil – bio-lubricant mixtures dispersed with graphene nanoplatelets

Abstract

This study focuses on the physicochemical and tribological properties of bio-lubricants and commercial lubricant blends dispersed with graphene nanoplatelets. In the processing of the bio lubricant, special care was taken to ensure that the physicochemical properties do not deteriorate too much when the bio lubricant is blended with commercial oil. Calophyllum inophyllum (Tamanu tree) seed oil was used to prepare a penta-erythritol (PE) ester. The PE ester was mixed with commercial SN motor oil at 10, 20, 30 & 40% v/v concentrations. The oil samples are tested on a four-ball wear tester to see how well they perform under wear, friction, and extreme pressure conditions. The optimum blend of PE ester – commercial SN motor oil for the best performance is found in the first phase. Later the optimum blend of commercial oil and bio-lubricant is dispersed with graphene nanoplatelets in 0.025%, 0.05%, 0.1%, 0.25%, 0.5% and 1% weight fractions. A blend ratio of 30% bio-lubricant in commercial oil dispersed with 0.05% graphene nanoplatelets dramatically reduces friction and wear. During the extreme pressure test, commercial oil, and bio-lubricant blends performed better in load-carrying capacity and welding force, indicating an improved load-wear index. These improved properties due to the dispersion of graphene nanoplatelets could facilitate the use of a higher blend percentage of bio lubricant. Analysis of the worn surfaces after the EP test showed that bio lubricant, additives, and graphene worked together in the blend of bio lubricant and commercial oil.