Thermal Degradation of Polyimides, Polyoxidiazoles, and Polyquinoxalines

The technique mentioned in the previous section of pyrolysis and radiochemical gas chromatography was also applied in a study to thermal degradation of aromatic polyimides [512]. Aromatic polyimides are more stable thermally than previously discussed polymers and require higher temperature for decomposition. Based on the experimental results, the following mechanism was proposed [512]. Initially, hydrogen radicals form. They come from various places of the polymer backbone during the pyrolytic decomposition. Also, decomposition of amic acid may yield water (see Chap. 6). 

The thermal degradation ofpolyoxidiazoles was shown to proceed mainly through the heterocyclic rings that are apparently the weak spots [514, 515]  

The process by which aromatic polyquinoxalines decompose is random. At 500-600°C, it involves the opening of the heterocyclic ring with loss of fragment [516]  

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