PRIMARY THERMAL-DEGRADATION PROCESSES OF POLY(ETHER-SULFONE) AND POLY(PHENYLENE OXIDE) INVESTIGATED BY DIRECT PYROLYSIS MASS-SPECTROMETRY

The thermal degradation processes which occur in poly(ether-sulfone) ( PES) and poly(phenylene oxide) (PPO) have been studied by Direct Pyrol ysis-Mass Spectrometry (DPMS). The pyrolysis mass spectra of PES and P PO contain molecular ions up to m/z 700, corresponding to pyrolysis co mpounds of sufficient size to allow the characterization of the primar y processes which occur in the thermal cleavage of these polymers. The results obtained indicate that the thermal degradation of PES and PPO proceeds by thermal cleavage of the groups located at the bridges. In the case of PPO the bridges are all homogeneous, and therefore both a n intramolecular thermal rearrangement or a radical cleavage process c an account for the formation of the primary pyrolysis products. Format ion of dibenzofuran units along the PPO chain is a parallel thermal pr ocess. In the case PES the simultaneous thermal cleavage of two differ ent bridged units, diphenyl sulfone and diphenyl ether, occurs. Extrus ion of SO2, with consequent formation of compounds containing biphenyl units, is observed in the thermal degradation of PES. This process is accompanied by formation of dibenzofuran units along the polymer chai n, as expected from the thermal cleavage of diphenyl ether units, and by another rearrangement of the polymer backbone, yielding structures containing more oxygen atoms with respect to that of PES.