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Séminaire de Catherine Whitby

Rheology of Particle-Stabilised Emulsions

In this seminar I will give an overview of my research into how the interactions between particles and drops can be manipulated to control drop stability. Hydrophobic particles form strongly attached layers on oil drop surfaces that inhibit liquid drainage and are a steric barrier to closely approaching drops. Additional stabilisation is generated by particle aggregation in the aqueous phase of emulsions.
The drop surfaces can be regarded as compact networks of solid particles with strong lateral attractive interactions. The susceptibility of drops to orthokinetic coalescence is controlled by the extent of particle flocculation. Concentrated emulsions have a very high elasticity due to deformation of the surfaces and hence the attached particle layer. Particle aggregation determines the interfacial shear elasticity.

The viscosity of aggregated particle dispersions can vary with time. Aggregate structures in emulsions which are disrupted by shear may recover once at rest. Thus there is a complex interplay between the effects of drops on structure breakdown and recovery in emulsions showing time-dependent rheology.