THE EFFECT OF COLLOIDAL PARTICLES ON FLUID-FLUID INTERFACIAL PROPERTIES AND EMULSION STABILITY

This paper reviews the relevant work done on the effects of colloidal particles on the theological properties of fluid-fluid interfaces and on emulsion stability. Results are presented to show that colloidal particles stabilize emulsions primarily by providing steric hindrance to drop-drop coalescence and by modifying the theological properties of the interfacial region. The effectiveness of colloidal particles in stabilizing emulsions depends largely on the formation of a sufficiently 'dense layer' of particles at the oil-water interface. The rheological properties of the interfacial region also change as the concentration of particles at the interface increases and complete surface coverage is achieved. It is shown that at sufficiently high concentrations of particles, colloid-laden interfaces exhibit viscoelastic behavior. Viscoelastic interfaces enhance emulsion stability by increasing the magnitude of steric hindrance and by retarding the rate of liquid drainage between coalescing emulsion droplets.