HLD mapping of emulsion characteristics: Water-in-oil emulsions with alcohol ethoxylate

Abstract: Hydrophilic-Lipophilic Deviation (HLD) modeling provides a useful framework for mapping the effects of parameters such as temperature, salinity, and oil hydrophobicity on the macroemulsion stability of surfactant-oil-water (SOW) systems. We have prior reported the detailed mapping of oil-in-water (O/W) macroemulsion characteristics for some alcohol ethoxylates in combination with linear hydrocarbon, using the HLD framework in combination with Fish Diagrams to assess how system distance from the HLD = 0 condition and surfactant concentration both strongly influence emulsion stability. In this presentation, we expand on these prior studies by describing the surfactant concentration-dependent behavior of water-in-oil (W/O) macroemulsions. In one study, W/O macroemulsions comprising C10E3 (triethylene glycol monodecyl ether, 99+%) and n-tetradecane were found to exhibit both lower and upper temperature boundaries within which modest, short-temp emulsion stability was maintained. Lower temperature boundary was found to be essentially independent of surfactant concentration and corresponded to the SOW approaching the system HLD = 0 condition, as expected. The unanticipated existence of an upper temperature boundary as the system moved away from the HLD = 0 condition, similarly characterized by rapid droplet coalescence, was found to be highly dependent on surfactant concentration. This destabilization behavior may be associated with a reduction in surfactant interfacial activity with increasing temperature, a factor that becomes meaningful to emulsion stability for systems in which surfactant partitioning into the oil phase is relatively high. Detailed mapping of W/O emulsion stability for this system, as well as for a system comprising commercial alcohol ethoxylate will be presented. These results shed light on the similarities and differences between O/W and W/O macroemulsion stability within the HLD framework.