Thermal degradation of polymers with phenylene units in the chain. IV. Aromatic polyamides and polyimides

Abstract

The breakdown mechanism of an aromatic polyamide and four polyimides has been studied under vacuum in the temperature range of 375–620°C, by using techniques described earlier, involving collection and analysis of volatile products as well as analyses of residues at different temperatures. The decomposition of the polyamide up to 375°C yielded predominantly carbon dioxide, while between 375 and 450°C about equal amounts of carbon dioxide and carbon monoxide formed. Hydrogen is the major product between 450 and 550°C, along with hydrogen cyanide, methane, and carbon monoxide. The major reaction at the lower temperatures seems to be the cleavage of the linkage between the carbonyl group and the ring, with subsequent formation of a carbodiimide linkage via isocyanate intermediates, and liberation of carbon dioxide. Alternatively, cleavage between the carboxyl and the NH‐group leads to the formation of carbon monoxide. Carbon dioxide and carbon monoxide are also the major volatile decomposition products of the polyimides at the lower temperatures. The primary cleavage reaction is believed to be the rupture of the imide ring between a carbonyl and nitrogen, with subsequent formation of isocyanate groups. The latter react with each other to form carbodiimide linkages and carbon dioxide, while the remaining benzoyl radical is the source for carbon monoxide.

Laser Application of Polymers

“…An exhaustive investigation and discussion of the band assignments can be found in the literature [290][291][292][293][294][295][309][310][311][312][313][314][315].…”

“…For the analysis of the laser-induced decomposition mechanism of Kapton, several relevant vibrational frequencies are chosen which are important for the decomposition mechanism. A detailed assignment of all bands can be found in the literature [290][291][292][293][294][295]. The assignment of the polyimide bands is mainly based on model compounds; see, e.g., the thorough study by Ishida et al [291] which could also be used for many products identified in this study.…”

Structure–performance characterization for carbon molecular sieve membranes using molecular scale gas probes

“…The carbonization process is complex, and several reactions may take place at the same time such as cleavage, condensation, dehydrogenation etc. [36][37][38]. The early stages of carbonization presumably involve cleavage of bonds within the macromolecular system to give free radicals.…”

Pyrolysis and hydrolysis behaviors during steam pyrolysis of polyimide

“…Significant changes were not observed until 120 min; however, the peak sharpness decreased, since the IR transmission was blocked by the black carbonized film. A peak related to the weak isocyanato N C O vibration was observed at 2280 cm −1 (I) as the reaction progressed, suggesting that the cleavage of the imide ring had occurred via a radical reaction, as reported by Hatori et al [7] and Ehlers et al [27,28]. The FT-IR spectra did not contain any specific peaks at 240 min, implying that the carbonization of the film was almost complete by 240 min.…”