Nonionic surfactant concentration effects in the HLD mapping of oil-in-water emulsion stability

It is well established that alcohol ethoxylate surfactant concentration can have a large impact on the temperature-dependent behavior of Surfactant-Oil-Water (SOW) systems, especially for molecularly-disperse commercial surfactants. Although commonly reported Hydrophilic-Lipophilic Deviation (HDL) modeling approaches generally do not account for this concentration dependency, recent efforts have attempted to capture this behavior in terms of replacing the HLD surfactant parameter with a concentration-dependent function. We have prior reported that such an approach enables successful quantitative prediction of the upper temperature boundary of oil solubilization into aqueous surfactant solution. In this presentation, we expand on our prior studies by describing efforts to map concentration-dependent behavior in the context of oil-in-water emulsion stability. In one example, quantification of macroemulsion stability at 23 ËšC with increasing surfactant concentration for SOWs comprising C10E4 (tetraethylene glycol monodecyl ether, 99+%) and n-dodecane demonstrated a maximum in stability that corresponded to the transition from Winsor I to Winsor III phase behavior; increasing surfactant concentration further into the Winsor III region resulted in strong destabilization of macroemulsion even though the calculated HLD of the SOW system was unchanged. Mapping of emulsion stability versus concentration and temperature for SOWs comprising individual component C10Ei surfactants and their mixtures, as well as for commercial alcohol ethoxylate surfactants will be reported in the context of the HLD framework.