Solid state C-13-NMR spectroscopy and XRD studies of commercial and pyrolytic carbon blacks

The bulk chemistry of commercial carbon blacks and carbon blacks obtained b y vacuum pyrolysis (CBp) of used tires was investigated by C-13-NMR spectro scopy with and without magic angle spinning of the sample. Two different ki nds of carbon atoms can be distinguished: Graphite like carbon atoms in pol y-condensed aromatic rings and carbon atoms in a less ordered environment. Commercial carbon blacks and CBp obtained under different pyrolysis conditi ons have practically the same concentrations of the different types of carb on atoms in the bulk, whereas earlier ESCA and SIMS investigations have sho wn that the surface chemistry of CBp is different from commercial carbon bl acks and depends strongly on the pyrolysis conditions. Thus, during the pyr olysis only the carbon black surface chemistry is changed. The carbon black bulk structure was also studied by X-ray diffraction. The XRD results, inc luding the radial distribution function (RDF) indicated, in agreement with the NMR results, that the bulk structure of commercial carbon blacks and of CBp are similar. (C) 2000 Elsevier Science Ltd. All rights reserved.