Abstract: The PBO fiber is currently one of the high-performance organic fibers with the best comprehensive performance, featuring high strength, modulus, flame retardancy, and heat resistance. It is dubbed the "super fiber of the twenty-first century." The strength of PBO fibers reaches 5.8 GPa, and their modulus can reach 280 GPa. Their limiting oxygen index (LOI) is 68, and the thermal decomposition temperature is 650 °C. Due to these excellent properties, PBO fibers can be applied in aerospace, weaponary and naval vessels, building reinforcement, high-temperature filtration, special protection and other fields.
However, PBO fibers have performance shortcomings such as poor UV-aging resistance and weak interfacial adhesion, which limit its further application and development. They can not meet the stringent criteria of aerospace, weaponary, and other fields. Therefore, it is urgent to modify PBO fibers to improve their performance. This paper summarized the research progress of copolymerization modification technology of PBO fibers at home and abroad in recent years. It can be divided into four aspects based on the modification objectives: improving tensile mechanical properties, enhancing compressive strength, improving interfacial adhesion performance, and improving UV-aging resistance. The mechanical characteristics of PBO fibers can be further enhanced by copolymerizing PBO molecular chains with functionalized carbon nanotubes or graphene; although PBO fibers have a high tensile strength and modulus, they have a weak transverse compressive strength. By introducing chemical cross-links into the PBO macromolecular chain, their compressive strength can be significantly improved. However, PBO fibers have a smooth surface and do not contain polar groups, resulting in a weaker ability to bond with resin matrices. Adding carboxyl or hydroxyl groups to PBO molecular chains can effectively enhance the composite ability of PBO fibers with resins; the anti-UV aging performance of PBO fibers is relatively weak. Introducing intermolecular hydrogen bonds or fused ring structures into PBO molecular chains can help improve the anti-UV aging performance of PBO fibers.
In summary, PBO fibers possess excellent physicochemical properties but also have certain performance defects. The in-situ copolymerization modification technique, designed from the perspective of chemical structural, can fundamentally address the performance defects of PBO fibers and has high practical value. Nonetheless, the preparation process of PBO fibers involves liquid crystals spinning. If the addition of a third monomer disrupts the liquid crystal behavior of the spinning solution, the spinnability may be diminished. Co-polymerization modification may also break the structural symmetry and sequence consistency of PBO macromolecules, which could change the regularity of the PBO fibers' ultimate condensed state structure and lessen their mechanical qualities. Therefore, copolymerization modified PBO fibers should completely evaluate the impact of the third monomer on spinning performance and fiber condensed structure. However, it can not be denied that PBO fibers remain one of the organic fibers with the best comprehensive properties at the moment. Introducing new monomer structures into PBO fibers and developing new benzoxazole-based high-performance fibers would allow them to broaden their application value and play a larger role in military and civilian industries.

Key words: PBO fiber, copolymerization modification, mechanical properties, interfacial bonding performance, UV-aging resistance

摘要： 聚对苯撑苯并二噁唑(PBO)纤维是目前综合性能最好的高性能有机纤维之一，但PBO纤维存在抗紫外光老化性能差、压缩强度低和界面粘结性能差等缺陷，无法满足航天、兵器等领域的严苛需求，因此需对其进行改性以提高性能。文章根据改性目的，从提升拉伸力学性能、提升压缩强度、改善界面粘接性能和提升抗紫外老化性能四个方面综述了近年来国内外PBO纤维共聚改性技术的研究进展，提出共聚改性应充分考虑化学结构、凝聚态结构和纺丝工艺对最终纤维性能的综合影响，并对未来PBO纤维的共聚改性技术进行了展望。

关键词: PBO纤维, 共聚改性, 力学性能, 界面粘结性能, 耐紫外光老化性能