Bulk and interfacial rheology of emulsions stabilized with clay particles

Abstract

This contribution aims to investigate the stabilizing effect of clay particles on oil-in-water emulsions using bulk and interfacial rheological measurements. Depending on the surface properties of clay particles, the emulsion showed different rheological responses as a result of different stabilization behavior. Hydrophilic clays (natural montmorillonite (NMt)) stabilized the emulsion via an interfacial layer with distinguished interfacial modulus (G*(interface)), while hydrophobic clays (organically modified montmorillonite (OMt)) stabilized the emulsion by increasing the bulk modulus of the oil phase (G*(oil)) In composite systems, when NMt is present together with cationic surfactant or OMt, complex formation at the oil-water interface significantly influenced the rheological response and emulsion stability. The high interfacial modulus (G*(interface)) of the composite interface stabilized the flocculated droplets more than the repulsive interaction between droplets. As a consequence, the bulk modulus of the emulsion (G*(emulsion)) also increases. Finally it could be shown that with increasing interfacial area (oil-to-water ratio), microscopic and macroscopic stabilization of emulsions could be improved. Rheological study provided structural information of the complex interface and defined the role of clay particles for the stabilization. (C) 2016 Elsevier B.V. All rights reserved.