Studies of formation of W/O nano-emulsions

In this work, formation of water-in-oil nano-emulsions in water/mixed nonionic surfactant/oil system has been studied by a condensation method. Several mixtures of Span 20, Span 80, Tween 20 and Tween 80 were studied. It has been proved that mixtures of surfactants can provide better performance than pure surfactants. The appropriate ratio between two surfactants was studied. The existence of microemulsion, nanoemulsion and emulsion regions was investigated studying samples stability by evolution of backscattering with time multiple light scattering technique. These studies allowed to determine zones where nano-emulsions can be formed. Droplet sizes were measured by dynamic light scattering (DLS). Mean sizes between 30 and 120nm were obtained; the higher the water concentration, the higher the size. On the other hand, nano-emulsions stability was studied by dynamic light scattering. The results showed the evolution with time of the average radius droplet. For low water concentration, nano-emulsions breakdown could be attributed to Ostwald ripening; and for high water concentration, nano-emulsions breakdown could be attributed to coalescence. (C) 2004 Elsevier B.V. All rights reserved.