Linear viscoelastic behaviour of sterically stabilized oil–water emulsions

Abstract

Shear moduli of several soya oil–water emulsions stabilized by xanthan and of comparable xanthan solutions have been studied. Comparison of the xanthan values and the emulsion values indicates the presence of strong interactions between the xanthan microgel and emulsion droplets in the emulsions. Analysis of the data suggests that most of the contribution to the shear modulus arises from the repulsive forces between the emulsifier molecules, the contribution from attractive forces being negligible. The rheological behaviour of the emulsions is similar to that of highly concentrated emulsions with deformable droplets, even at relatively low disperse phase concentrations of 20%. The results are interpreted with a model that treats the emulsions droplets as an assembly of soft spheres. The form of the interaction is found to be consistent with a system where the principal forces between the droplets arise from undulating membranes rather than rigid bodies.