Electrical conductivity of carbon black pigments

The properties of carbon black surfaces which might affect their influence on the conductivity of dispersions in polar and non-polar media were analysed. Low-structured furnace black, high-structured gas black and extremely high-structured extra-conductive carbon black were studied. The size distribution of aggregates was measured. Raman spectroscopy provides relative amounts of disordered, graphitic and amorphous phases, and the lateral size of crystallites. X-ray photoelectron spectroscopy gives the oxygen content and the nature of functional groups on particle surfaces. The chemical nature of surface functional groups was analysed with infrared spectroscopy. All samples are disordered carbon blacks with different amounts of oxygen on their surfaces. The carbonyl-based surface groups were obtained on the acidic sample and other oxygen groups on the alkaline ones. A negligible amount of oxygen combined with a high amount of the graphitic phase and alkaline nature gives high conductivity of carbon black in polar and non-polar solvents. The conductivity of dispersion also increases with a higher structure, i.e. larger aggregates with a wide size distribution.

► Disordered phase highly prevails over the graphitic and amorphous ones.
► Branching of primary particles gives larger aggregates and wider size distribution.
► Highly graphitic and alkaline particles without oxygen give conductive dispersions.
► The structure and particle size distribution of aggregates promotes conductivity.