OIL EXCHANGE BETWEEN OIL-IN-WATER EMULSION DROPLETS STABILIZED WITH A NONIONIC SURFACTANT

Differential scanning calorimetry has been used to monitor crystallization and melting of hydrocarbons in oil-in-water emulsions containing a mixture of pure n-hexadecane droplets (10 wt%) and pure octadecane droplets (10 wt%) stabilized by a non-ionic surfactant, (2 wt% polyoxyethylene sorbiton monolaurate). The crystallization and melting behavior of the emulsions changed with time in a manner consistent with exchange of oil between the n-hexadecane and octadecane droplets. Complete mixing of the oils in the droplets took over 7 days. The rate of exchange increased when additional surfactant was added to the aqueous phase of the emulsion. The droplet size of the emulsions did not change during the course of the experiment. The probable mechanism for oil exchange between the droplets involved the solubilisation of the oil in the aqueous phase by surfactant micelles.