Solid state C-NMR spectroscopy and XRD studies of commercial and pyrolytic carbon blacks

Abstract

The bulk chemistry of commercial carbon blacks and carbon blacks obtained by vacuum pyrolysis (CB ) of used tires was P 13 investigated by C-NMR spectroscopy with and without magic angle spinning of the sample. Two different kinds of carbon atoms can be distinguished: Graphite like carbon atoms in poly-condensed aromatic rings and carbon atoms in a less ordered environment. Commercial carbon blacks and CB obtained under different pyrolysis conditions have practically the same P concentrations of the different types of carbon atoms in the bulk, whereas earlier ESCA and SIMS investigations have shown that the surface chemistry of CB is different from commercial carbon blacks and depends strongly on the pyrolysis P conditions. Thus, during the pyrolysis only the carbon black surface chemistry is changed. The carbon black bulk structure was also studied by X-ray diffraction. The XRD results, including the radial distribution function (RDF) indicated, in agreement with the NMR results, that the bulk structure of commercial carbon blacks and of CB are similar.