Stability of oil-in-water nano-emulsions prepared using the phase inversion composition method

The stability of isopropylmyristate-in-water nano-emulsions stabilized by PEG-60 hydrogenated caster oil varied ethanol concentrations using phase composition inversion method at room temperature was investigated. Nano-emulsions with droplet sizes below 200 nm were formed above the critical micelle concentration of surfactant. In order to investigate the effect of ethanol on nano-emulsions, time dependence of the droplet distribution was monitored at room temperature using light scattering. The main destabilization mechanism of the systems was found to be Ostwald ripening. To consider the size effect, we prepared the nano-emulsions by adding ethanol either before or after homogenization. Regardless of when we added the ethanol, the Ostwald ripening rate increased as did the concentration of ethanol of the systems. Pertaining to the long-term conditions, there was no flocculation of the nano-emulsions which showed negative zeta potential. (C) 2009 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.