Rheological studies of water-in-oil-in-water double emulsions

Abstract

In this study the rheological behaviour of water-in-oil-in-water (W₁/O/W₂) multiple emulsions was investigated. Different emulsions varying in volumetric ratio of the components were prepared and characterised using small-amplitude oscillatory rheological measurements. The microstructure of the multiple emulsions was examined using laser diffraction. The results indicate that the microstructure of the multiple emulsions plays a dominant role in its rheological behaviour. W₁/O/W₂ multiple emulsions are found to be more viscoelastic than simple W₁/O emulsions of comparable total volumetric composition. The rheological response of W₁/O/W₂ emulsions depends highly on the amount of internal phase (W₁/O) but also on the amount of the internal water, W₁. An attempt was made to fit the results into the Krieger-Dougherty and Palierne models, taking into account the contributions of the individual components. It seems, however, that the amount of internal interfacial area is the determining factor for the rheology of stabilised multiple emulsions.