Influence of Thermal Temperature on the Structure and Sealed Micropores of Stabilized Polyacrylonitrile Fibers

Thermal stabilization is an important process in carbon fibers’ production, during which the polyacrylonitrile fibers are heated from 180 °C to 280 °C in air. In this study, the samples were characterized by X-ray diffraction, Fourier infrared spectroscopy, differential scanning calorimetry, small angle X-ray Scattering(SAXS) and mechanical tensile tests. A new rule was suggested by the results of structural characterization for the cyclization, dehydrogenation and oxidation reactions that were observed to be drastic from 200 °C to 220 °C, from 220 °C to 250 °C, and in the later period of the thermal stabilization reactions, respectively. The sizes, shapes and distributions of the sealed micropores were obtained from the SAXS data. The breaking elongation was significantly affected by the drastic cyclization and dehydrogenation reactions. The breaking force was affected considerably by the bigger micropores, especially from 220 °C to 250 °C, owing to the drastic dehydrogenation reactions.