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在氮气气氛下,对PAN纤维分别在210～260℃进行热处理,得到不同环构化结构的PAN纤维,并在空气气氛中进行热稳定化处理。借助红外吸收光谱(FT-IR)、固体核磁(13C-NMR)、差示扫描量热分析(DSC)、元素分析(EA)和热重分析(TG)等测试手段,研究氮气中形成的PAN纤维环构化结构特点,及对后续热环化氧化反应的影响。结果表明:在氮气气氛中,随热处理温度从210℃升至260℃,PAN纤维的环化程度提高,不同热处理温度导致了不同PAN纤维环构化结构的形成:其中210～240℃区间内脱氢反应逐渐剧烈,-C=C-C=N-结构逐步增多;230～260℃区间,其易于捕获氧的官能团-CH2-C=C-NH-逐渐增多;随前期热处理温度的升高,前期形成的环构化结构使得后期环化和初步氧化反应可在更低的温度下进行,反应更加缓和,环化更加彻底,有利于生成更加完善的耐热网状梯形结构。
Under nitrogen atmosphere, the PAN fibers were heat-treated at 210-260 ℃ respectively to obtain PAN fibers with different cyclical structure and thermally stabilized in air atmosphere. The formation of PAN in nitrogen was studied by means of FT-IR, 13C-NMR, DSC, EA and TG. Structural characteristics of fiber ring structure, and the subsequent thermal cyclization oxidation. The results showed that the degree of cyclization of PAN fibers increased with the increase of the heat treatment temperature from 210 ℃ to 260 ℃ under nitrogen atmosphere. Different heat treatment temperatures led to the formation of cyclic structures of PAN fibers: in 210 ~ 240 ℃ The reaction of hydrogen becomes more and more intense and the structure of -C = CC = N gradually increases; the functional group -CH2-C = C-NH- which is easy to capture oxygen increases gradually from 230 ℃ to 260 ℃. With the increase of pre-heat treatment temperature, The cyclization structure makes the late cyclization and preliminary oxidation reaction can be carried out at lower temperatures, the reaction more moderate, more complete cyclization, help to generate a more perfect heat-resistant network of trapezoidal structure.