Date of Award
Master of Science
Michael G. Olsen
The stability of a topical ointment primarily consisting of an emulsion of propylene glycol droplets dispersed in a continuous white petrolatum medium was studied using optical methods to monitor droplet size growth and phase separation when the ointment undergoes heating or fluid shear. To investigate the effects of shear, ointment at 32C was sheared using a transparent narrow-gap temperature-controlled Couette flow apparatus operated under laminar flow conditions and that provided approximately uniform shear rates. Optical microscopy was used to obtain time-dependent in-situ propylene glycol droplet size distributions, while simultaneously a wide-field lens and camera were used to detect gross phase separation as the ointment was sheared. Microscopy was also used to observe and quantify ointment stability via analysis of droplet size evolution in the absence of fluid shear for a range of elevated temperatures. For quiescent ointment, it was observed that the dispersed propylene glycol droplets do not exhibit any appreciable growth over a period of two months and temperatures as high as 45C. In contrast, fluid shear imposed at 32C was observed to cause rapid growth of dispersed phase droplets and the onset of large phase separated regions on time scales ranging between a few minutes to approximately half an hour for fluid strain rates ranging between 50 s-1 and 5 s-1, respectively. Also in order to use the CFD technique to simulate ointment behavior in a different situation a rheological model is suggested due to non-Newtonian behavior of the ointment. Furthermore, a novel experimental method is used using a wide gap Couette reactor to predict the values of the properties of the mentioned model.
Arya Ketabchi Haghighat
Ketabchi Haghighat, Arya, "Droplet coalescence in an emulsion to support process scale-up of a topical ointment" (2019). Graduate Theses and Dissertations. 17229.