Thermal characteristics of high-strength and thermostable aromatic fibres

The thermal characteristics of para-aramid, polyoxadiazole, and polyimide fibres were comparatively investigated by dynamic thermogravimetric analysis, differential scanning calorimetry, and thermomechanical analysis. It was shown that thermooxidative degradation of these types of fibres began at 400–450 °C and intensified at higher temperatures. The fibres investigated are characterized by size stability up to the initial temperature of thermooxidative processes (400–450 °C). With respect to thermal stability, these fibres are in the following order: polyimide > polyoxadiazole, and carbocyclic para-aramid fibres. The correlation of the “hydrogen index” I_H and “aromaticity index” I_Ar for thermostable fibres with their thermal stability was demonstrated. Translated from Khimicheskie Volokna, No. 3, pp. 72–74, May–June, 2008.