Models for structure-rheology of highly concentrated emulsions

Abstract

Highly concentrated emulsions (HCE) are classified as high internal phase ratio emulsions (or simply HIPRE), and the dispersed phase droplets are ranged In a hexagonal closely packed configuration. This closely packed configuration and the profound hydrodynamic interaction between neighbouring droplets induce mechanical interference between the droplets, thus prohibiting their free movement. Hence, while the highly concentrated emulsions consist of very low viscosity and inelastic components, they show gel-like behaviour with high elasticity and non-Newtonian flow response. It has been suggested in the literature that this behaviour originated from interfacial energy in terms of Laplace pressure. Therefore, the scaling of rheological properties with Laplace pressure is expected, but several publications show a deviation from this scaling behaviour. It seems that the source of deviation from this scaling is interdroplet interaction, which can contribute to the rheological behaviour of highly concentrated emulsions. The shear modulus of highly concentrated emulsions in the presence of interdroplet interaction was developed in this work. The prediction of model was verified by the data presented in the literature. It was shown that a small source of interdroplet interaction can result in deviation from scaling of shear modulus with Laplace pressure.