title: Droplet-based characterization of surfactant efficacy in colloidal stabilization of carbon black in nonpolar solvents.
abstract: Development of an electrostatic stabilization mechanism for colloidal suspensions in nonpolar fluids requires an improved understanding of the interactions between the inverse micelles and particles as well as the roles that steric and electrostatic effects play. A droplet-based millifluidic device is designed and used to investigate the stabilization effects of surfactants on colloidal suspensions. A system containing carbon black and the surfactant OLOA 11000 suspended in dodecane is chosen as a well-characterized system to study sedimentation quantitatively. This device takes advantage of sub-millimeter optical path lengths to characterize sedimentation at concentrations at which sedimentation is not observable in the bulk and to achieve higher resolution in composition. A simple image analysis algorithm has been developed and applied to quantify sedimentation. Conductivity measurements using electrochemical impedance spectroscopy (EIS) are coupled with the sedimentation experiments to identify the concentration ranges in which steric and electrostatic effects are dominant. A more gradual transition is observed than previously reported.
authors.affiliation: Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, United States. Electronic address: bbleier@andrew.cmu.edu.
authors.forename: Blake J
authors.initials: BJ
authors.lastname: Bleier
authors.affiliation: Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, United States. Electronic address: byezer@andrew.cmu.edu.
authors.forename: Benjamin A
authors.initials: BA
authors.lastname: Yezer
authors.affiliation: The Dow Chemical Company, Core Research and Development, Solids Processing, United States. Electronic address: BJFreireich@dow.com.
authors.forename: Ben J
authors.initials: BJ
authors.lastname: Freireich
authors.affiliation: Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, United States. Electronic address: sanna@andrew.cmu.edu.
authors.forename: Shelley L
authors.initials: SL
authors.lastname: Anna
authors.affiliation: Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, United States. Electronic address: lwalker@andrew.cmu.edu.
authors.forename: Lynn M
authors.initials: LM
authors.lastname: Walker
keywords: Aggregation; Carbon black; Colloidal stability; Conductivity; Dispersant; Droplets; Electrostatics; Millifluidic; Nonpolar fluids; Particle; Sedimentation