Evaluating the Rheo-electric Performance of Aqueous Suspensions of Oxidized Carbon Black

Hypothesis: The macroscopic properties of carbon black suspensions are primarily determined by the agglomerate microstructure built of primary aggregates. Conferring colloidal stability in aqueous carbon black suspensions should thus have a drastic impact on their viscosity and conductivity. Experiments: Carbon black was treated with strong acids following a wet oxidation procedure. An anal-ysis of the resulting particle surface chemistry and electrophoretic mobility was performed in evaluating colloidal stability. Changes in suspension microstructure due to oxidation were observed using small -angle X-ray scattering. Utilizing rheo-electric measurements, the evolution of the viscosity and conduc-tivity of the carbon black suspensions as a function of shear rate and carbon content was thoroughly stud-ied. Findings: The carboxyl groups installed on the carbon black surface through oxidation increased the sur-face charge density and enhanced repulsive interactions. Electrostatic stability inhibited the formation of the large-scale agglomerates in favor of the stable primary aggregates in suspension. While shear thin-ning, suspension conductivities were found to be weakly dependent on the shear intensity regardless of the carbon content. Most importantly, aqueous carbon black suspensions formulated from electrostat-ically repulsive primary aggregates displayed a smaller rise in conductivity with carbon content com-pared to those formulated from attractive agglomerates. (c) 2022 Elsevier Inc. All rights reserved.