CHARACTERIZATION OF NAPHTHA AND CARBON-BLACK OBTAINED BY VACUUM PYROLYSIS OF POLYISOPRENE RUBBER

Pure polyisoprene and a commercial rubber sample containing 52% polyis oprene and 31% carbon black were pyrolysed at 500 degrees C and at a t otal pressure varying between 0.8 and 28.0 kPa. The yields of gas, oil and pyrolytic carbon black (CBp) changed little with the pyrolysis pr essure. However, the oil composition and the CBp characteristics depen ded considerably on the pyrolysis pressure. For example, the amount of dl-limonene, a valuable compound in the naphtha fraction, decreased w ith increasing pyrolysis pressure. The CBp and the commercial carbon b lack initially present in the rubber sample were analysed by ESCA, SIM S and SEM. With decreasing pyrolysis pressure the surface chemistry of the CBp became similar to that of the commercial carbon black initial ly present in the rubber. Therefore, rubber pyrolysis should be perfor med at low pressures in order to obtain products with a higher commerc ial value.