Kinetic, thermodynamic and synergistic effects of pyrolysis of natural rubber, styrene-butadiene rubber and butadiene rubber

Pyrolysis is being used more and more to treat waste rubber. Natural rubber (NR), styrene-butadiene rubber (SBR) and butadiene rubber (BR) are the three most widely used rubbers. The pyrolysis of these three types of rubbers is different from that of waste tires, and thus has received little attention. In this paper, kinetic, thermodynamics and synergistic effect of rubber were studied by thermogravimetric analyzer (209F3 Tarsus, NETZSCH, Germany). The methods used were iso- conversional method, model fitting method and thermodynamic modeling. The results of kinetic calculations showed that the activation energy of mixed rubber was not the sum of single rubbers. The theoretical activation energies of NR/BR, NR/SBR, BR/SBR, and NR/BR/SBR were lower than the actual activation energies by 94.3, 45.5, 142.8, and -45.8 kJ/mol, respectively. It suggested that positive synergistic effect occurred in the pyrolysis process of NR/BR/SBR. The synergistic effect in the pyrolysis process of other mixed rubber was dominated by negative synergy. The model fitting method was used to determine the number of pyrolysis mechanism functions followed in the process of rubber pyrolysis, which was consistent with the slope method of fitting curve. The number of significant weight loss peaks in the test samples was consistent with the number of pyrolysis mechanism functions. The thermodynamic parameters indicated that the endothermic reaction occurred during rubber pyrolysis and that the pyrolysis process could not proceed spontaneously. The combined application of kinetics and thermodynamics could characterize the pyrolysis reaction process of different types of rubber and provided a theoretical basis for the recycling of waste rubber.