Rheological Properties of Particle-Stabilized Emulsions

Abstract

We have studied the rheological properties of fumed silica particle-stabilized emulsions. Two particles of different polarity were considered, the first more hydrophilic “Aerosil R7200,” the second more hydrophobic “Aerosil R972.” These particles flocculate and probably form a network at the investigated concentration. The flow curves of emulsions stabilized by a single type of particles exhibit yield stress, shear-thinning behavior and thixotropy. Moreover they display rheological features typical of gels. These features are attributed to strengthening of the particle network by droplets. Moreover the rheological properties of w/o emulsions stabilized by hydrophobic are similar to the ones of o/w emulsions stabilized by hydrophilic particles. The rheological properties of o/w emulsions stabilized by mixtures of hydrophilic and hydrophobic particles have then been studied by keeping the total particle concentration constant and varying the mass ratio between particles. The results show that when the hydrophobic particle concentration increases, the viscosity and stability of emulsions decrease establishing evidence that the network is weakened due to preferential orientation of hydrophobic particles towards the oil phase.

Keywords:

• Fumed silica
• particle-stabilized emulsions
• pickering emulsions
• rheology

Acknowledgments

The authors are grateful for the financial contributions from the members of the Joint Industrial Project on “Particle-Stabilized Emulsions/Heavy Crude Oils,” including Statoil ASA, Vetco Aibel AS, Shell Global Solutions, Aker Kvaerner, BP, Champion Technologies, Chevron Texaco, Norsk Hydro, Petrobras, Total, ENI Technology, and Maersk Oil & Gas.