辐照与热处理时序对预氧化聚丙烯腈纤维分子结构影响的分子动力学模拟研究

Pre-oxidation is a key step in the preparation of polyacrylonitrile-based (PAN) carbon fibres, and -irradiation is an effective means to optimize the pre-oxidation process of heat treatment. However, the effect and mechanism of -irradiation and heat treatment time-sequence on the pre-oxidation are still unclear. In this regard, this paper adopts molecular dynamics simulation methods to analyse the effects of -irradiation and heat treatment time-sequence on the structural changes of the pre-oxidation process of PAN fibres in terms of the evolution of molecular chain morphology, species changes and reaction paths. The results showed that the -irradiation followed by heating (-T) treatment makes the morphology of PAN molecular chain segments more stable and the pre-oxidation product species more concentrated, and this approach can induce the PAN molecular chain to produce more free radicals earlier, thus accelerating the reaction processes of cyclization, oxidation and cross-linking, and realizing the secondary cross-linking during the heating process, which can enhance the degree of the pre-oxidation of the PAN fibre. In contrast, the treatment method of heating and then irradiation (T-) has fewer free radicals formed in the PAN molecular chain during the heat treatment stage, resulting in relatively fewer cross-linking structures, which is easy to cause molecular chain breakage during irradiation, and the product types are complicated, resulting in a relatively poor pre-oxidation effect in the end. This study reveals the mechanism of -irradiation and heat treatment on the pre-oxidation process of PAN fibre, which provides theoretical support for the structural regulation of the pre-oxidation process of PAN fibre.