共聚组分对聚丙烯腈(PAN)纤维预氧化程度的影响及其与碳纤维结构和性能的关联

利用自制碳纤维连续化试验线对两类聚丙烯腈（PAN）原丝进行了不同条件的梯度升温预氧化处理，并最终得到碳纤维。采用差示扫描量热分析（DSC）、红外光谱（FT-IR）、广角X射线衍射（WAXD）等表征手段分析了共聚组分对PAN分子链规整度的影响以及分子链规整度对预氧化、炭化过程中纤维结构转变的影响。结果表明，相对于三元共聚PAN纤维，二元共聚PAN纤维由于分子链规整度的提高，与环化反应有关的放热反应相对滞后发生；在相同的预氧化条件下，二元共聚PAN纤维能得到环化度较高的预氧化纤维，所得碳纤维的类石墨晶粒尺寸Lc也较大。结合碳纤维的拉伸强度和拉伸模量数据发现，二元共聚纤维适宜预氧化的温度要高于三元共聚纤维适宜预氧化的温度。

Effects of copolymerization components on the degree of pre-oxidation of polyacrylonitrile fibers and their relevance to the structure and properties of carbon fibers

Two types of polyacrylonitrile (PAN) copolymers with different co precursors have been pre oxidized under different gradient heating conditions, and the resulting stabilized PAN fibers and carbon fibers examined on a homemade continuous test line. The samples were characterized by differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR) spectroscopy, and wide angle X-ray diffraction (WAXD) in order to analyze the effects of copolymer composition on the regularity of the molecular chain of PAN and on the structure transitions during the preoxidation and carbonization stages. The results showed that, due to the greater degree of regularity of the binary copolymer of acrylonitrile (AN) and itaconic acid (IA) ［P(AN/IA)］, the exothermic reaction related to the cyclization reaction occurs at a higher temperature than that for the terpolymer of AN, IA and methyl acrylate (MA) ［P(AN/IA/MA)］. Furthermore, compared with the terpolymer ［P(AN/IA/MA)］, the binary copolymer［P(AN/IA)］had a higher relative cyclization index (RCI) for the preoxidized fibers and a larger crystallite size (Lc) for the final carbon fibers when they were treated under identical preoxidation conditions. In addition, on the basis of the mechanical properties of the carbon fibers it was found that the optimum pre oxidization temperature of the binary copolymer ［P(AN/IA)］was higher than that of the terpolymer ［P(AN/IA/MA)］.