INTERFACIAL PROPERTIES AND STABILITY OF OIL-IN-WATER EMULSIONS STABILIZED WITH BINARY-MIXTURES OF SURFACTANTS

The effect of cetyldimethylbenzylammonium chloride (CDBACl) on ζ-potential and stability of negative charged oil-in-water emulsion droplets stabilized with a nonionic surfactant (Tween 80) at two different concentrations, one above and one belo its CMC, is studied. The adsorption of CDBACl is a process characterized by neutralization of negative charge followed by charge reversal. Further adsorption results in an increase in positive ζ-potential. The flocculation rate which is calculated by counting the droplet number with time is considered the main factor of instability. A close relation in some cases is found to exist between the flocculation rate and ζ-potential values. Adsorption studies of CDBACl on the lowering of the interfacial tension of oil/water systems in the presence of Tween 80 are made and from the data obtained the amount of CDBACl adsorbed per unit area of the interface is calculated with the help of the Gibbs equation. © 1991 Academic Press, Inc. All rights reserved.