Thermal properties of non-crystallizable oil-in-water highly concentrated emulsions

In this work, a differential-scanning-calorimetry (DSC) technique is applied to studying the thermal properties of highly concentrated oil-in-water (O/W) emulsions of two immiscible liquids (castor oil and water) with high viscosity ratios (3400/1 for O/W), similar densities (0.974/1 for O/W) and stabilized by a non-ionic surfactant. A low-energy mixing process was used to produce highly concentrated emulsions (typically more than 90% O/W) with different mean droplet sizes, dependent on the emulsification time. The oil is non-crystallizable, thus only very thin water-surfactant films and water-surfactant solutions at the Plateau border and node regions between the compressed oil droplets crystallize under freezing. We show that the DSC technique is able to reveal the influence of interfacial energy phenomena (i.e., surface-to-volume effects) on the supercooling degree and on the apparent specific heat capacities of the concentrated emulsions. (C) 2010 Elsevier B.V. All rights reserved.