Keywords: Biolubricant; corn oil fatty acids; trimethylolpropane; polyol ester

Abstract

Mineral oils are widely used in the manufacture of biolubricant. However, mineral oils are toxic, non-biodegradable and limited in supply. Therefore, there is a need to find another alternative source to replace mineral oils. Plant oils have been identified as an alternative source to replace mineral oils because they are renewable and environmentally friendly due to their biodegradable and non-toxic properties. However, plant oils also have several drawbacks which cannot be directly used due to the presence of β-hydrogen in the glycerol backbone of the triacylglycerol structure which makes plant oils unstable at higher temperatures and tend to be easily damaged. This limitation can be overcome by chemical modification through the esterification of corn oil fatty acids with trimethylolpropane to produce corn oil trimethylolpropane (COTMP) ester. The esterification was carried out in a mole ratio of 3.5:1 (COFAs: TMP), 2.9% sulfuric acid as a catalyst at 128 °C for 3.9 hours. The characterization of COTMP ester has been done using Fourier Transform Infrared Spectroscopy (FTIR) and Nuclear Magnetic Resonance (1H NMR and 13C NMR) spectroscopy. Next, the evaluation test of COTMP ester has been carried out to evaluate the physicochemical properties of COTMP ester. The result showed that COTMP ester was successfully synthesized with a 97.93% yield. The existence of the ester functional group is evidenced by FTIR at 1743 cm-1, the chemical shift of 1H NMR at 2.29 – 2.37 ppm and 13C NMR at 173.44 ppm. The physicochemical properties analysis showed that COTMP ester has a pour point value of -20 °C, a flash point value of 300 °C, viscosity at 40 °C (48.92 cSt) and viscosity at 100 °C (9.60 cSt), which made COTMP ester suitable to be used as biolubricant base stock.