Spontaneous emulsification of oils containing hydrocarbon, nonionic surfactant, and oleyl alcohol

Phase behavior and videomicroscopy experiments were used to investigate spontaneous emulsification of n-hexadecane/oleyl alcohol/C12E6 mixtures in water at 30 degrees C. It was found that complete emulsification of a drop of the oil phase to form small oil droplets having diameters of about 1 mu m occurred only when diffusion of water into the initial oil drop first converted it completely into the lamellar liquid crystalline phase and/or a microemulsion and then caused this phase (or these phases) to become supersaturated in oil so that many oil droplets nucleated. This behavior occurred when the hydrocarbon/alcohol ratio of the initial oil drop was near that of the excess oil phase for a balanced system at this temperature, i.e,, at the phase inversion temperature (PIT), and when surfactant content was sufficiently high. The stability of these emulsions was investigated by means of turbidity measurements. The most stable emulsion appeared to occur under conditions where the drops were coated by a layer of the lamellar phase. (C) 1999 Academic Press.