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采用红外、13 C核磁共振确定了聚丙烯腈预氧化纤维中氮的存在特征,采用X射线光电子能谱(XPS)测试了纤维中不同结合态氮的相对含量。通过对聚丙烯腈纤维进行不同温度、时间热处理,研究了纤维中不同结合态氮相对含量随温度时间的变化规律。结果表明:较低温度下(<210℃)纤维中氮以未反应氰基(—C≡N)、共轭亚胺(—CC—CN—)及烯胺(C—NH—)形式存在,当温度高于210℃,烯胺结构中的氮转变为含氧吡啶环中的氮;延长预氧化时间有利于烯胺含量的累积,纤维结构中烯胺结构有利于氧原子与纤维环结构的结合。
The presence of nitrogen in polyacrylonitrile pre-oxidized fibers was confirmed by infrared and 13 C nuclear magnetic resonance. The relative contents of different bound nitrogen in fibers were measured by X-ray photoelectron spectroscopy (XPS). By changing the temperature and time of polyacrylonitrile fiber, the changing law of the relative content of different bound nitrogen in the fiber with temperature and time was studied. The results showed that the nitrogen content in the fiber at lower temperature (<210 ℃) was higher than that of unreacted cyano (-C≡N), conjugated imine (-CC-CN-) and enamine (C-NH -). When the temperature is higher than 210 ℃, the nitrogen in the enamine structure is converted into nitrogen in the oxygen-containing pyridine ring. Prolonged pre-oxidation time is conducive to the accumulation of enamine content. The enamine structure in the fiber structure is favorable for oxygen atoms Binding to the annulus structure.