(349e) Design of Emulsified Products: Effects of Disperse Phase Rheology

Emulsions are ubiquitous in personal care products, foods, cosmetics, and pharmaceutical formulations. In many of these products, additives give rise to non-Newtonian behavior in either the continuous or disperse phase. However, currently available models for emulsification processes assume Newtonian behavior of both phases. In this talk we discuss our recent efforts to account for droplet rheology in models for conceptual design. We consider laminar emulsification of a dilute emulsion in a colloid mill. For a given set of processing conditions and equipment, we compare predicted drop sizes for two model fluids, shear-thinning droplets and viscoelastic droplets, with Newtonian droplets. We find that that increasing shear-thinning of the dispersed phase yields finer emulsions than the corresponding Newtonian case. Droplet viscoelasticity was found to have a significant impact on droplet break-up when the relaxation time of the droplets is on the same order as the droplet break-up time. Increasing the droplet Deborah number produces a coarser emulsion and delays droplet break-up. We also examined the robustness of several configurations of colloid mill, where the concept of robustness captures both the sensitivity of the systems and their capability to accommodate different product targets. The method of the Attainable Region was used to generate design alternatives and a new graphical framework was developed to overcome some of the limitations encountered in applying the Attainable Region approach. We utilized this technique to quantify the ability of different process configurations to accommodate specifications when the rheology of the emulsion droplets is uncertain.