MS Final Examination Seminar
An investigation of droplet growth and phase separation in an oil and water emulsion under controlled shear and temperature conditions
Hannan Nadeem
https://iastate.zoom.us/j/94867501561?pwd=ZUsxUDhrNEZ5SzdYSjVweHZaOWsyUT09
Abstract
Many researchers in the food and pharmaceutical industry have emphasized the importance of emulsion stability, and the need for stability tests. However, the emulsion stability tests can take a long time before meaningful results can be obtained. Therefore, there is a need for accelerated emulsion stability tests, and there aren’t many research studies for it. For this research, an oil in water type emulsion’s stability is studied primarily using optical methods. The effects of shear strain and temperature on phase separation, droplet growth, and emulsion’s physical characteristics are reported. The Taylor Couette flow reactor is used to detect the onset of phase separation. Optical microscopy is used to confirm that the droplet growth is due to coalescence, which leads to complete phase separation. Laboratory equipment and apparatus are used to measure and record emulsion’s physical characteristics like viscosity, interfacial tension, and density. To detect the onset of phase separation as a function of time, the emulsion is tested at a temperature range of 25 °C to 35 °C and a shear strain range of 10.5 s-1 to 62.8 s-1. At some experimental conditions, there was no phase separation detected, labeled as stable cases. Cases where phase separation is detected, are labeled as separated cases. A boundary is fitted to segregate the experimental conditions that lead to stable cases from the conditions leading to separated cases with the help of dimensionless parameters, Eotvos, and Galilei numbers. The boundary line decreases linearly as the shear strain rate increases from 10.5 s-1 to 47.1 s-1. For shear strain rates, higher than 47.1 s-1, the boundary line decreases exponentially as there is a drastic drop in viscosity of the emulsion. Through viscosity measurements, it is confirmed that the emulsion is Non-Newtonian fluid, and the interfacial tension also decreases with increasing temperature. The research presented is valid for the investigation of emulsion stability characteristics. The results will help Pfizer Inc. to understand this emulsion’s stability and help them with the manufacturing process design.