(541f) Influence of Surfactant-Nanoparticle Interactions on the Stability and Rheology of Emulsions
AIChE Annual Meeting
2019 AIChE Annual Meeting
Engineering Sciences and Fundamentals
Particulate and Multiphase Flows: Emulsions and Droplets
Wednesday, November 13, 2019 - 1:45pm to 2:00pm
Our results showed that the addition of a non-ionic surfactant to emulsions stabilized by hydrophobic nanoparticles decreased the droplet size of emulsions unlike emulsions stabilized by partially hydrophobic nanoparticles. Even under negligible shear conditions, the addition of a non-ionic surfactant displaced the hydrophobic nanoparticles from the oil-water interface unlike partially hydrophobic nanoparticles. Our results suggested that the displacement of hydrophobic nanoparticles by the addition of a non-ionic surfactant was not due to the change in nanoparticle wettability by surfactant adsorption onto the surface of nanoparticles. The viscosity of emulsions stabilized by partially hydrophobic nanoparticles decreased upon the addition of a non-ionic surfactant. In contrast, the viscosity of emulsions stabilized by hydrophobic nanoparticles increased upon the addition of a non-ionic surfactant. Depending on the nanoparticle wettability, the addition of a non-ionic surfactant influenced the elastic and viscous properties of Pickering emulsions.
Our results further showed that simultaneous emulsification using hydrophobic nanoparticles and a surfactant (either Span 80 or Triton X-100) resulted in a single-step formation of multiple oil-in-oil-in-oil (O/O/O) emulsions. Regardless of the initial phase to which the surfactant was added, simultaneous emulsification using surfactants and hydrophobic nanoparticles led to the formation of multiple emulsions. The addition of Span 80 to a vegetable oil-in-PDMS oil (VO/PDMS) emulsion stabilized by only hydrophobic nanoparticles did not have a significant influence on the droplet size. However, the addition of Triton X-100 to a VO/PDMS emulsion stabilized by only hydrophobic nanoparticles resulted in the formation of a multiple PDMS/VO/PDMS emulsion. Multiple O/O/O emulsions had lower viscosity compared to simple O/O emulsions. Simple O/O emulsions had a lower degree of shear thinning behavior compared to multiple O/O/O emulsions.