Investigation and Monitoring of Rheological Behavior of Mg(OH)2 Nanoparticles at the Water / Oil Interface

Objectives of this study focused is understanding the mechanisms involved in the stabilization of water / oil interfaces by solid nanoparticles (NPs). Magnesium hydroxide of different sizes and in different electrolyte concentrations were studied and compared, at a model water / cyclohexane interface, in a drop tensiometer. Gradual interfacial adsorption of NPs, initially dispersed in water, were followed by tensiometry and the interfacial behavior of NPs layers were characterized by two-dimensional rheology. Owing to the direct relationship between emulsion stability and the interfacial properties of these layers, different nanoparticulate systems were compared, magnesium hydroxide (Mg(OH)2) NPs, with different size. In addition, the concentration of electrolytes (NaCl) in the bulk phase was shown to induce a partial NPs aggregation (so-called NPs flocs), with an important incidence on the interfacial layer stability. Theoretical phase shift was calculated from Winter and Chambon models corresponding to a two-dimensional gel behavior at the gel-point. This interfacial gelation results in strengthening the interfacial layer, and is actually a considerable advantage in the stabilization of Pickering emulsions.