PHASE INVERSION IN NONIONIC SURFACTANT OIL-WATER SYSTEMS .1. THE EFFECT OF TRANSITIONAL INVERSION ON EMULSION DROP SIZES

A study has been made of the dynamics of transitional-phase inversion in agitated liquid-liquid dispersions of hydrocarbon (''oil'') and water stabilised by non-ionic surfactants. Transitional-phase inversions are caused by changes in the phase behaviour of a non-ionic surfactant-oil-water system and are induced by altering the surfactant's affinity for the oil and water phases. Drop sizes were found to decrease and emulsification rates to increase as the transitional inversion point was approached. Agitation conditions have no effect on drop sizes of three-phase emulsions present at the transitional inversion point and spontaneous emulsification was observed. Drop sizes of emulsions produced by transitional inversion are dependent on surfactant type, surfactant concentration and the emulsion's start condition. A quantitative analysis of the drop sizes of Winsor type 3 emulsions showed that the drop sizes are controlled by the area of interfacial surfactant coverage. The viscosity of the oil phase can affect drop sizes produced by transitional inversion. A comparison of transitional inversion and direct emulsification shows that much finer emulsions, with much less energy input, can be produced by transitional inversion processes.