Pyrolysis mechanisms benzenethiol

FIGURE 8.26 The proposed sulfur migration mechanisms during benzenethiol pyrolysis. 

The formation curve of hydrogen sulfide started to evolve after 550 "C and reached a maximum around 750 °C, indicating the contribution of main chain random scission of the sulfur groups as the major path in the pyrolysis process. The monomer benzenethiol was the next abundant species. It started to form at 550 "C, reached a maximum between 700 °C and 750 C and then drastically reduced after 850 °C, indicating that depolymerisation was also one of the major pyrolysis paths. The formation of carbon disulfide indicated the contribution of the scission of the incompletely carbonised solid residue after 850 °C. This implied that the chain transfer of carbonisation increased gradually to become the dominating mechanism in the transition from lower to higher pyrolysis temperature. 

Perng [21] and Perng and co-workers [22] studied the thermal decomposition behaviour of polyphenylene sulfide (PPS) by stepwise Py-GC-MS and TGA-MS techniques. The mechanism and kinetic model of the pyrolytic behaviour of PPS was investigated by TG-MS from room temperature to 900 °C. The mechanism indicated apparently one-stage pyrolysis, principally by depolymerisation, main chain random scission and carbonisation. The initial scission of PPS was depolymerisation and main chain random scission to evolve benzenethiol and hydrogen sulfide, respectively, as major products. Depolymerisation dominated in the lower temperature pyrolysis and main chain random scission dominated in the higher temperature pyrolysis. The chain transfer of carbonisation also produced an initial pyrolysis and gradually dominated... 

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