Rheological and Interfacial Properties of Silicone Oil Emulsions Stabilized by Silica Particles

Abstract

Emulsions stabilized by colloidal particles, namely Pickering emulsions were prepared by mixing silicone oil with silica particles dispersed in the continuous water phase as functions of silica concentration and silicone oil viscosity. Characteristics of the resulting oil dispersed in water (O/W) emulsions were determined by the measurements of adsorbed amounts of the silica particles, oil droplet size, and some rheological responses, such as hysteresis loop, stress-strain sweep curve, and dynamic viscoelastic moduli. Oil droplets were found to be stabilized by the formation of a fractal structure of the silica particles dispersed in the continuous water phase surrounding the oil droplets. The oil droplet size decreased with an increase in the silica concentration, whereas it increased with increasing the viscosity of the silicone oil. The resulting emulsions showed an ideal elastic matter at the smaller deformation since their stress-strain sweep curves were satisfied with Hooke's law. On the other hand, at the larger deformation the emulsions showed thixotropic behavior and such thixotropy much more pronounced with an increase in the silica concentration, due to partially breaking the fractal structure of the silica particles.

Keywords:

• Emulsions
• fractal structure
• hydrophobicity
• pickering emulsions