Industrial & Engineering Chemistry Research, Vol.48, No.6, 2913-2919, 2009
Emulsion Catastrophic Inversion from Abnormal to Normal Morphology. 8. Effect of Formulation on the Inversion Produced by Continuous Stirring
This paper deals with the influence of the global formulation of a water-oil-surfactant system, expressed by the hydrophilic-lipophilic difference (HLD), on the emulsion inversion produced just by the continuous stirring of an abnormal system, without any internal phase addition or any composition change. Evidence confirms that, under stirring, a w/O/W multiple emulsion is formed by the continuous inclusion of the external water phase inside the dispersed drops, which results in an increase of the effective dispersed phase volume until a critical value at which the inversion is triggered. Results suggest that the stability of the most internal emulsion determines the kinetics of inclusion and the-stirring time required to induce inversion. However, it is the stability of both internal (w/O) and external (O/W) emulsions which determines the dispersed phase fraction at which the inversion is triggered. When different water fractions are used, the change of the critical dispersed phase fraction reveals that this process is affected by the partitioning of the surfactant mixture species between phases and results confirm that the critical. dispersed phase fraction is a property related to the interfacial formulation of the system.