Keywords: Pseudo-ternary phase; microemulsion; palm-based insecticides; palm methyl ester

Abstract

This research aimed to characterize microemulsion system of palm methyl ester (PME) and water/ mixed surfactants (Tween® 80 and Dehydol® LS 2)/ 1-propanol via a pseudo-ternary phase behaviour study. The microemulsion system with a hydrophilic-lyphophilic balance value of 12.33 was prepared using the constant composition method. The phases included an emulsion, a gel/viscous phase and a transparent microemulsion which were tested at different temperatures to examine their stabilities. Microemulsion samples were evaluated to obtain their colloid characteristics, such as particle size, viscosity, pH and conductivity. The optimum formulation of palm-based insecticide consisted of 48% water, with 20% PME, 20% mixed surfactants and 12% 1-propanol. The particle size of the microemulsion was 84.20 nm. The pH value was 6.6, the conductivity was 0.00951 µS/cm, and the viscosity was 20.44 cP. The results indicated that different amounts of surfactants and co-surfactant in the emulsion exhibited different phase behaviour in the pseudo-ternary phase diagram. Palm-based microemulsion potentially could be an alternative to replacing petroleum-based solvents in insecticides.