Thermal degradation behaviour of aromatic poly(ester-imide) investigated by pyrolysis-GC/MS

The thermal degradation behaviours of a novel aromatic poly(ester-imide) (PEI) derived from pyromellitic dianhydride and 2,7-bis(4-aminobenzoyloxy)naphthalene have been investigated by thermogravimetric analysis (TGA) and by pyrolysis-gas chromatography/mass spectrometry (pyrolysis-GC/MS). The weight of PEI fell slightly in the temperature range of 350-450 degrees C in the TGA analysis, but the major weight loss occurred at 520 degrees C. Evolve gas analysis (EGA) of the PEI showed maximum release of pyrolyzates at 550 degrees C. The chemical structure of the volatile products resulted from the PEI pyrolysis at different temperatures was identified by pyrolysis-GC/MS. The cleavage of the ester linkage within the polymer chain initiated at 350 degrees C, and bond scission in the partially hydrolyzed pyromellitimide unit occurred in the temperature range of 450-500 degrees C. The bonds within the pyromellitimide unit started to cleave at 550 degrees C. The extensive decomposition of the pyromellitimide segment within the polymer backbone occurred at 600 degrees C. The possible thermal degradation pathways of this PEI are proposed on the basis of the pyrolysis products.