Comparison study on the physicochemical properties of phosphate esters from epoxidised palm kernel oil and soybean oil

Abstract

A series of phosphate esters from soybean oil and palm kernel oil has been synthesised by reacting each epoxidised soybean oil and epoxidised palm kernel oil with o-phosphoric acid in the presence of t-butyl alcohol as the solvent. The amount of o-phosphoric acid was varied at 0, 2.5, 5.0 and 7.5 wt-%. The hydrolysis was conducted at a temperature range of 80-90°C. The physiochemical properties of the phosphate esters were determined, that were, acid value, hydroxyl value, oxirane and moisture contents. The Fourier transform infrared spectroscopy analysis was carried out to confirm the formation of the phosphate ester (P-O-C). The oxirane content after hydrolysis was below 0.2%. Higher addition of phosphoric acid (7.5 wt-%) increased the moisture content and the acid value of the phosphate esters. These results were applicable for both soybean oil-based phosphate ester (SOPE) and the palm kernel oil-based phosphate ester (PKOPE). However, SOPE and PKOPE with 2.5 wt-% of phosphoric acid showed higher hydroxyl value.