Coalescence-induced phase separation of an oil in water emulsion under controlled shear and temperature conditions

Phase separation behavior was investigated in an oil-in-water type emulsion. A Couette flow cell was utilized for the phase separation experiments. The emulsion was tested for a range of shear strain rates of 10.5 s(-1) to 62.8 s(-1) and a temperature range of 25-35 degrees C, both of which are much milder than the corresponding conditions used to manufacture the emulsion (similar to 1000 s(-1) and 51 degrees C), to identify the onset of phase separation due to droplet coagulation. The onset of phase separation is dependent on the shear strain rate and the temperature, such that the onset of phase separation is detected at earlier times as either shear strain rate or temperature increase. Some experimental conditions resulted in no phase separation during the observation period. The results of these experiments can be organized by using two dimensionless parameters, namely the Eotvos and Galilei numbers. Specifically, a phase separation regime map was constructed using these dimensionless parameters, and this map features a linear boundary that demarcates a region for which emulsion remains stable and a region in which an emulsion can be ex-pected to undergo phase separation. These results can potentially be used to characterize the stability of similar emulsions and to aid design, manufacture, packaging, and storage of similar products that have phase separation risk. (C) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.

Automated summary

Phase separation behavior in an oil-in-water emulsion was investigated. The onset of phase separation was found to be dependent on shear strain rate and temperature, with earlier onset observed at higher shear strain rates or temperatures.