Influence of air circulation on the structure and properties of melt-spun PAN precursor fibers during thermal oxidation

A new method of melt-spun process was developed to prepare PAN precursor fibers using ionic liquid as the medium of processing. Melt-spun precursor fibers exhibited a partially cyclized structure. For the different structure of melt-spun precursor fibers from solution-spun precursor fibers, it is necessary to investigate the oxidation process of the melt-spun precursors. In this paper, the influence of air circulation on the structure and properties of melt-spun precursor fibers during the oxidative process was investigated by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetry, etc. Results showed that the air circulation almost had no visible effects on the chemical structure of pre-oxidized fibers. The crystallinity and the crystal size of pre-oxidized melt-spun fibers increased with the increase of air circulation. When the air circulation was 6 L min(-1), the pre-oxidized melt-spun fibers had the maximum density and tensile strength. Meanwhile, the tensile strength of the final carbon fibers reached a maximum.