The influence of thermal treatment conditions on features of the chemical structure in the imidization of polyamic acids and on the thermal stability of the polyimide products

• Published in: Polymer science USSR 1983, Vol.25 (3), p.663-671
• Main Authors: Novikova, S.V., Oprits, Z.G., Smirnova, A.I., Sorokin, V.Ye, Khudoshev, I.F., Popik, N.I., Shabligin, M.V., Kudryavtsev, G.I.
• Format: Article
• Language: English
• ISSN: 0032-3950; 1878-268X
• DOI: 10.1016/0032-3950(83)90249-6

The chemical structural transformations occurring in poly-( p, p′-diphenylene oxide) pyromellitamic acid during cyclisation in fibres, over a wide temperature range, in the presence of o-phosphoric acid (arimide T) and without it (arimide PM) have been studied comparatively, using IR-spectroscopy, X-ray diffraction, free torsional vibration and thermomechanical methods. It was shown that the thermal treatment conditions significantly affect the physical structure and relaxation viscoelastic properties of the polyimides. One of the reasons for the higher thermal stability of arimide T fibres is linked with the catalytic effect of o-phosphoric acid on cyclisation of the polyamic acid, permitting attainment of higher degrees of conversion. For the same degree of cyclisation, the thermal stability of the polyimides depends essentially on the structural prehistory and the related relaxation behaviour of the samples.