There is growing interest to replace petroleum-based ingredients in products with natural-based materials such as palm oil and its derivatives.One of the potential uses of these natural materials is in microemulsion formulations.This paper describes the solubilization and ternary phase behaviour of palm oil and its derivatives with a non-ionic surfactant – coco alcohol (C_12-14) ethoxylate with 6.9 moles of ethylene oxides (6.9EO) (also called Imbentin coco 6.9EO).

The capacity of solubilization by Imbentin coco 6.9EO for palm oil methyl esters (POME) ≈ tetradecane > palm kernel oil-medium chain triglycerides (PKO-MCT) and palm olein. The phase inversion temperatures (PIT) for POME, PKO-MCT and palm olein were 59°C, 70°C and 71°C at 2:1, 1:1 and 0.5:1 ratios of oil to surfactant. The PIT for tetradecane, a petroleum-based oil, was 56°C at 1:1 oil to surfactant ratio, but ~73°C at a 2:1 ratio.

The capacities for solubilization and formation of a larger microemulsion region with POME were higher than those with PKO-MCT and palm olein in Imbentin coco 6.9EO systems.The maximum solubilities of POME and PKO-MCT were 2:1 and 1:1 oil to surfactant, both at 60°C, and palm olein 0.5:1 oil to surfactant at 70°C. We indicate that the POME molecules penetrate the liquid crystalline (LC) phase into the palisade layer.They then expand the LC (L_α) region and move to the water-rich axis.However,the micellar solution and/or O/W microemulsion can exist at up to 45% (w/w) surfactant at the lower concentrations of PKO-MCT and palm olein in the ternary systems