ON THE FORMATION AND STABILITY OF CONCENTRATED WATER-IN-OIL EMULSIONS, APHRONS

The stability of concentrated w/o emulsions is discussed on the basis of stability measurements of systems containing water, dodecane (or hexadecane) and a nonionic surfactant, viz., polyoxyethylene dodecyl ether. In these emulsions the ratio of the dispersed aqueous phase to the organic phase is so high that the aqueous domains are polyhedral, so-called aphrons, so that the maximum available space is filled. The stability is dependent on: (i) the structure of the surfactant, which determines the preferential solvency of the surfactant in the organic or the aqueous phase; and (ii) the presence of salts in the aqueous phase, which influences the stability by stopping the Ostwald ripening and/or decreasing the attractive force across the oil lamellae between the aqueous droplets. © 1990.