EFFECT OF THE NATURE OF THE HYDROPHOBIC OIL PHASE AND SURFACTANT IN THE FORMATION OF CONCENTRATED EMULSIONS

There exists a maximum amount of dispersed phase which can be incorporated into a concentrated emulsion. The experiments have been carried out with a large number of organic molecules as either the dispersed or the continuous phase and with water as the other phase, using several surfactants as dispersants. The maximum volume ratio between the dispersed and continuous phases ranged from 10 to 420, depending upon the natures of the organic molecule and surfactant. Generally, it was found, for both O W and W O systems, that the maximum volume ratio increases as the interfacial free energy, γwo, between the organic compound and water in the absence of surfactant increases. The aromatic and halogenated molecules exhibited deviations from this rule, when nonionic surfactants with polyoxyethylene head groups were employed, because of their interactions with the head groups of the surfactants. For ionic surfactants in O W systems, it was found that the curve of maximum volume ratio against γwo passes through a maximum at relatively large values of γwo. A possible explanation is suggested for this observation. For O W concentrated emulsions and two surfactants, one ionic and the other nonionic, experiments have been performed regarding the dependence of the maximum volume ratio upon the concentration of the surfactant. For the ionic surfactant, the curve exhibits saturation, while for the nonionic surfactant, it presents a maximum. © 1991.