Characterization of naphtha and carbon black obtained by vacuum pyrolysis of polyisoprene rubber

Pure polyisoprene and a commercial rubber sample containing 52% polyisoprene and 31% carbon black were pyrolysed at 500°C and at a total pressure varying between 0.8 and 28.0 kPa. The yields of gas, oil and pyrolytic carbon black (CB_P) changed little with the pyrolysis pressure. However, the oil composition and the CB_P characteristics depended considerably on the pyrolysis pressure. For example, the amount of dl-limonene, a valuable compound in the naphtha fraction, decreased with increasing pyrolysis pressure. The CB_P and the commercial carbon black initially present in the rubber sample were analysed by ESCA, SIMS and SEM. With decreasing pyrolysis pressure the surface chemistry of the CB_P became similar to that of the commercial carbon black initially present in the rubber. Therefore, rubber pyrolysis should be performed at low pressures in order to obtain products with a higher commercial value.