The influence of emulsifier concentration on the rheological properties of an oil-in-water emulsion stabilized by an anionic soap

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Abstract
The rheological properties of liquid paraffin emulsions stabilized by potassium laurate have been found to be markedly dependent on emulsifier concentration. Reversible aggregation of the emulsion began at 1.0% soap and the more highly aggregated systems demonstrated pseudoplastic flow. A maximum relative viscosity was found at 5.0% soap concentration. The viscosity was dependent on particle size but correction for particle size differences did not alter the viscosity concentration relation. The addition of electrolytes to the emulsion demonstrated the difference between surfactant aggregation and electrolyte aggregation. The latter was explained by the Derjaguin-Verwey-Overbeek theory of colloid stability, whilst the former was only satisfactorily explained by the theory advanced by Cockbain in 1952 involving polymolecular adsorption at the oil-water interface and hydrophobic bonding.