Partial Coalescence in Emulsions Comprising Partially Crystallized Droplets

Partial Coalescence in Emulsions Comprising Partially Crystallized Droplets 

The experimental studies described in this chapter certainly led to a better understanding of the coalescence phenomena in concentrated emulsions. Despite the complexity and variety of the destruction scenarios, different methods for measuring the coalescence frequency, ty, have been proposed. It should be within the reach of future work to measure ty for a large variety of systems in order to establish a comparative stability scale. This is a necessary step to determine the microscopic parameters that control the activation energy Ea and the attempt frequency coo. 

It is probable that numerous interfacial parameters are involved (surface tension, spontaneous curvature, Gibbs elasticity, surface forces) and differ from one system to the other, according the nature of the surfactants and of the dispersed phase. Only systematic measurements of will allow going beyond empirics. Besides the numerous fundamental questions, it is also necessary to measure u for an evident practical reason, which is predicting the emulsion lifetime. This remains a serious challenge for anyone working in the field of emulsions because of the polydisperse and complex evolution of the droplet size distribution. Finally, it is clear that the mean-field approaches adopted to measure are acceptable as long as the droplet polydispersity remains quite low (P 50%) and that more elaborate models are required for very polydisperse systems to account for the spatial fiuctuations in the droplet distribution. 

Taylor Ostwald Ripening in Emnlsions. CoUoids Surfaces 99, 175 (1995). 

Herrmatm, and D.J. McClements Ostwald Ripening of Hydrocarbon Emulsion Droplets in Surfactant Solutions. Langmuir 15, 6652 (1999). 

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