Adsorption of an Emulsifier at the Interface and its Role on Emulsion Stability

The four interfacial parameters viz. critical micelle concentration (CMC), interfacial tension at CMC (γCMC), surface excess concentration (Γ) and the area occupied at the interface per molecule (A) for a surfactant are largely dependent on the structure of the surfactant and its orientation at the interface. While the first two are known to have influence on the formation (i. e. efiiciency) the last two have great bearing on the stability of an emulsion containing the surfactant. In the present paper an attempt has been made to correlate the emulsification and stabilization of a water-in-oil emulsion with these four parameters by changing the hydrophobic part of two non-ionic surfactants viz 1,4 Sorbitan fatty acid esters and PEG alkyds of long chain fatty acids. Adverse effects of higher 'A' and lower Γ on emulsion stability has been clearly demonstrated.