Controlling the Rheology of Montmorillonite Stabilised Oil-in-Water Emulsions

The rheology of hexadecane-in-water emulsions stabilised by montmorillonite platelets was investigated. In these systems excess particles form a network in the continuous phase which strongly dictates their rheological behaviour. The emulsions were modified by the addition of NaCl and Na₄P₂O₇ to the continuous phase at varying concentrations. Remarkably, changes of up to three orders of magnitude in elastic modulus and yield stress of the emulsions were achieved. The droplets retained long term coalescence stability after the addition of NaCl or Na₄P₂O₇ and even after the removal of the continuous phase network. The latter finding shows that the droplets are primarily stabilised by the formation of a solid barrier at the interface. These emulsions are therefore highly versatile formulation materials with an exceptional degree of stability and tunability.