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在惰性气氛条件下,将PAN原丝在180-280℃进行恒温热处理。通过傅里叶变换红外1、3C固体核磁共振方法研究了PAN纤维在热稳定化过程中的结构演变规律,并对PAN纤维的热稳定化反应进程进行了探索。结果表明:随着热处理温度升高,共聚单体中的羧基首先引发环化交联反应;在220℃左右开始发生剧烈的环化交联反应;当热处理温度高于240℃时,环化交联反应趋于平缓,脱氢反应逐渐占据主导地位。通过差式扫描量热仪、热重-质谱联立分析仪和元素分析仪分别研究了不同热稳定化阶段PAN纤维的剩余焓变量、H2的逸出量及纤维中剩余H元素的含量。结果进一步佐证了提出的热稳定化反应进程。牵伸实验表明,张力越大,PAN纤维初期的热稳定化进程越缓慢。
The PAN strands were heat-treated at a constant temperature of 180-280 ° C under inert atmosphere. The structure evolution of PAN fibers during thermal stabilization was investigated by Fourier transform infrared spectroscopy (IR) and 1, 3-C solid-state resonance spectroscopy. The thermal stabilization of PAN fibers was also investigated. The results showed that the carboxyl group in the comonomer firstly initiated the cyclization and crosslinking reaction with the increase of the heat treatment temperature. The severe cyclization and crosslinking reaction began at about 220 ℃. When the heat treatment temperature was higher than 240 ℃, the cyclization United reaction tends to be gentle, dehydrogenation gradually occupy a dominant position. The residual enthalpy variable, the evolution of H2 and the content of remaining H in the fiber were investigated by differential scanning calorimetry, TG-MS and elemental analyzer respectively. The results further corroborate the proposed thermostabilization process. Drawing experiments showed that the larger the tension, the slower the initial thermal stabilization of PAN fibers.