Heat-treatment of carbon blacks obtained by pyrolysis of used tires. Effect on the surface chemistry, porosity and electrical conductivity

Truck tire particles were pyrolysed at 490 degreesC at atmospheric pressure and under vacuum, respectively. The recovered pyrolytic carbon black (CBp) was heated in a post-pyrolysis process at temperatures ranging from 670 to 860 degreesC. The CB, were studied in comparison to a commercial tire carbon black by low-pressure nitrogen adsorption and surface spectroscopic methods (ESCA and SIMS). Furthermore, the CB, properties were correlated to their electrical conductivities. During tire pyrolysis, carbonaceous deposits are formed on the CBp surface and between the carbon black particles. These deposits have a lower polyaromatic character as compared with the surface of the commercial carbon black. Therefore, the electrical conductivity of CB, is lower as compared with commercial blacks. Fewer deposits are formed during vacuum pyrolysis as compared with atmospheric pyrolysis. Upon heating, a portion of the deposits is desorbed and the polyaromatic character of the CBp surface increases. The CB, conductivity increases as well, in the case of vacuum pyrolysis CBp, to values higher than commercial blacks. (C) 2002 Elsevier Science B.V. All rights reserved.