PAN纤维环构化结构形成对温度的依赖性研究

摘要

The chemical structure of PAN fibers heat treated at 100-260℃ in nitrogen atmosphere was explored by infrared absorption spectrometry and solid-state 13C nuclear magnetic resonance imaging (13C-NMR). It can be concluded that the C≡N bond in PAN molecules has a low activity energy prior to cyclize, and then transforms into a C=N bond at 150℃. Above 170℃, the C=N bond reacts with a C=C group resulted from CH2/CH-functionalgroup dehydrogenation. This reaction may contribute to the conjugate structure, -C=N-C=C-, which subsequently isomerizates to the more stable -C-C=C-N-structure at temperatures above 260℃.%在氮气气氛、100～260℃条件下对PAN纤维进行热处理,通过红外吸收光谱(FTIR)和固体核磁(13C-NMR)研究PAN分子在热处理过程中化学结构的转化,推测其发生的化学反应.研究表明,PAN大分子中腈基(C≡N)反应活化能较低,C≡N可以在较低温度下优先发生环化反应,150℃时首先生成C=N官能团;温度高于170℃,CH2/CH上发生脱氢反应,生成C=C官能团,同时,此C=C结构与已生成的C=N转化为六元环上的-C=N-C=C-共轭结构;温度高于260℃,六元杂环中的共轭-C=C-C=N-结构不稳定,它在分子内发生了异构化反应,转化成更稳定的-C-C=C-N-结构.