Abstract Summary (Max 250 words)
Drop breakup is a vital process of producing emulsions across industries and flow regimes. The effect of turbulence on drop breakup has been extensively studied, likewise, how emulsifiers lower the interfacial tension between phases, affecting the coalescence and initial breakup in laminar flows. However, the combination of the two is less explored - how emulsifiers affect the drop breakup in turbulent flows where the drop breakage is much faster than diffusional transport. Some suggested mechanisms, beyond lowering the interfacial tension, show that under some conditions the emulsifier makes the drops more difficult to break. The mechanisms have been described as an increase in effective viscosity [1] or interfacial tension [2]. These kinds of elastic effects have also been seen in a model of a homogeniser, a highly turbulent emulsification device. In this study, we investigated the effect of emulsifiers on drop breakup by screening different emulsifiers with emulsifications experiments using a batch rotor-stator mixer and a low disperse phase volume fraction oil-in-water emulsion with different concentrations of the emulsifier. The results show that there is an effect of the emulsifier that cannot solely be explained by interfacial tension as there is a stabilising elastic effect at intermediate concentrations in some conditions. We also report on how the effect depend on the molecular properties of the emulsifier. References [1] Padron & Calabrese, 2023. Chem. Eng. Res. Des. 195, 447. [2] Janssen et al., 1994. Colloids Surf. A. 91, 141. With support from the Swedish Research Council (VR 2024-04823).
