Emulsification: Mechanistic understanding

This paper reviews current work from our group on the mechanism of droplet break-up and coalescence. In order to do this a reflectance technique was used to measure the rate of coalescence for different emulsifier types and concentrations. It was shown that droplet coalescence in flow cannot be stopped by emulsifiers and the coalescence rate was unaffected by emulsifier type or concentration. However, addition of a high concentration of Pickering particles suppressed coalescence in flow, which can be explained by the associated high adsorption energy. If the interface is only partially covered by particles, this can result in phase inversion. These results were compared for several emulsification techniques: high pressure valve homogenisation, microfluidization and membrane emulsification. In contrast to previous studies it has been shown that membranes produce droplets smaller than the pore size, and this is only possible if the emulsifier has a fast adsorption rate.