PAN预氧化纤维结构与热处理温度的关系

Relationship between preoxidized PAN fiber structure and heat treatment temperature

在空气气氛中不同温度下对聚丙烯腈（PAN）原丝热处理8h，制得PAN预氧化纤维。借助差示扫描量热分析、红外吸收光谱、X射线衍射、固体核磁等测试手段，表征了不同温度处理的PAN纤维的预氧化程度，研究了PAN预氧化纤维的结构特点。结果表明：不同温度下PAN纤维的预氧化程度不同，随着温度的提高而提高；PAN纤维预氧化程度不同，缘于不同温度下预氧化反应差异造成的预氧化结构的不同；预氧化温度越高，未环化的C≡N结构中共轭的C≡N结构相对含量越多，不利于进一步环化；环化反应在190-220℃较剧烈，在220℃以后反应趋于缓和；脱氢反应在190-210℃比较缓慢，在温度高于220℃开始剧烈进行；190℃以上发生氧化反应。

Preoxidized polyacrylonitrile （PAN） fibers were prepared from PAN precursor subjected to heat treatment for 8 h in air atmosphere at different temperatures. The preoxidation degree of PAN fibers was characterized and the structure characteristics of preoxidized PAN fiber was studied by differential scanning calorimetry, infared absorption spectroscopy, X-ray diffraction anal- ysis and solid-state nuclear magnetic resonance spectroscopy. The results showed that the preoxidation degree of PAN fibers was raised while elevating the temperature ; the different preoxidization degree of PAN fibers resulted from the different preoxidization structure caused by the preoxidation reaction difference at different temperatures. The higher the preoxidization temperature was, the higher the relative content of the conjugated C≡N structure in uncyclized C≡N structure was, which was not beneficial to the further eyclization. The cyclization reaction proceeded violently at 190 - 220℃ and moderated above 220℃. The dehydrogenation reaction proceeded moderately at 190 -220℃ and became violent above 220℃. The oxidation reaction started at above 190℃.