Wang Bin, Li Chenggao, Cao Weiyu
Central Research Institute of Building and Construction Co., Ltd., MCC, Beijing 100088, China.
Key Lab of Structures Dynamic Behavior and Control, Harbin Institute of Technology, Ministry of Education, Harbin 150090, China.
Materials (Basel). 2021 Jun 11;14(12):3237. doi: 10.3390/ma14123237.
The thermal stabilization process of polyacrylonitrile (PAN) precursor fiber was the key step to prepare high-performance carbon fiber. During the thermal stabilization process, the aggregation structure and the reactivity of molecular chains have significant effects on the microstructures and mechanical properties of carbon fiber. In the present paper, the effects of the orientation structure of PAN precursor fiber on the thermal stabilization reaction and the mechanical properties of carbon fiber were experimentally studied. Using multi-dimensional structural and mechanical properties tests, such as XRD, DSC, C NMR and Instron machine testing, the crystalline and skeleton structure, exothermic behavior, and tensile properties of PAN precursor fiber with different orientations in the process of thermal stabilization were characterized to reveal the relationship between microstructure evolution and tensile properties. The results showed that the orientation structure of PAN precursor fiber had an obvious effect on the thermal stabilization process and the tensile stress-strain characteristic. When the heat treatment temperature was lower than 200 °C, the crystallinity and crystallite size of PAN fibers with higher orientation degrees increased significantly. After sufficient thermal stabilization, the original PAN precursor fiber with a higher orientation degree could form more aromatic lamellar structures and showed better regularity. Furthermore, the yield strength and initial modulus of the fibers with a higher orientation degree increased due to the formation of more aromatic rings. The maximum increase in the percentages of yield strength and tensile modulus of the PAN fibers were achieved when the heat-treated temperature was 200 °C, and the percentage values were 138.4% and 158.7% compared to the precursor without heat-treatment. In addition, the elongation at break of the fibers with a higher orientation degree was also relatively larger.
聚丙烯腈（PAN）原丝纤维的热稳定化过程是制备高性能碳纤维的关键步骤。在热稳定化过程中，分子链的聚集结构和反应活性对碳纤维的微观结构和力学性能有显著影响。本文通过实验研究了PAN原丝纤维的取向结构对热稳定化反应及碳纤维力学性能的影响。利用XRD、DSC、C NMR和Instron试验机测试等多维结构和力学性能测试手段，对热稳定化过程中不同取向的PAN原丝纤维的结晶和骨架结构、放热行为及拉伸性能进行了表征，以揭示微观结构演变与拉伸性能之间的关系。结果表明，PAN原丝纤维的取向结构对热稳定化过程和拉伸应力-应变特性有明显影响。当热处理温度低于200℃时，取向度较高的PAN纤维的结晶度和微晶尺寸显著增加。经过充分的热稳定化后，取向度较高的原始PAN原丝纤维能够形成更多的芳香层状结构，且规整性更好。此外，由于形成了更多的芳香环，取向度较高的纤维的屈服强度和初始模量增加。当热处理温度为200℃时，PAN纤维的屈服强度和拉伸模量的增加百分比达到最大值，与未热处理的原丝相比，百分比值分别为138.4%和158.7%。此外，取向度较高的纤维的断裂伸长率也相对较大。
