Influence of modification with H2O2 on chemical structure of polyacrylonitrile precursor
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摘要: 为节省预氧化进程的能耗和时间并优化聚丙烯腈（PAN）预氧纤维的性能，用H2O2改性PAN原丝，使其提前环化。采用FTIR、XPS等方法表征不同处理温度获得的未改性和改性PAN原丝。结果表明：H2O2水溶液在60℃改性PAN原丝时，H2O2可引发氰基环化，末端环发生亚胺、烯胺互变异构，由此出现亚氰基、类芳香伯胺；改性温度越高，改性PAN原丝的亚氰基含量、共轭程度越大。在模拟稳定化过程中，改性PAN原丝的类芳香伯胺可在较低温度下引发相邻氰基环化。使用氨水（NH3H2O）作为助剂获得改性PAN原丝，与未改性PAN原丝经历相同的预氧化进程，改性后的PAN原丝能在较短时间内达到适合的预氧化程度，且PAN预氧纤维径向结构的均匀性被改善，由此获得热稳定性更高的PAN预氧纤维。Abstract: In order to save energy consumption and time of the pre-oxidation process and optimize the performance of polyacrylonitrile(PAN) pre-oxidized fiber, PAN precursor could cyclize in advance with modification with H2O2. The unmodified and modified PAN precursor treated at different temperatures was analyzed by FTIR and XPS, et al. The results show that the modification with H2O2 aqueous solution at 60℃ induces nitrile of the PAN precursor to cyclize and terminal ring structure tautomerizes, hence it brings about imine and quasi-aromatic primary amine. With the increase of the modification temperature, the content and conjugation degree of the imine of modified PAN precursor is promoted. In the process of the simulated stabilization, quasi-aromatic primary amine of the modified PAN precursor could induce adjacent nitrile to cyclize at lower temperature. The modified PAN precursor with NH3H2O as additives experiences the same pre-oxidation process as the unmodified PAN precursor. The former can reach suited pre-oxidation degree within a short time and the radial structure of PAN pre-oxidized fiber becomes more uniform, so that the PAN pre-oxidized fiber which has higher thermostability can be obtained.
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Keywords:
- polyacrylonitrile precursor /
- H2O2 /
- modification /
- nitrogen structure /
- cyclization /
- radial structure
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