Polybenzoxazole (PBO) fiber with extraordinary high strength

modulus

excellent heat stability and flame resistance has received great attention as one of competitive candidates applied in the field of national defense and aerospace. In this article

the preparation of PBO polymer with high molecular weight

the technique to spin high performance PBO fiber were studied; and the property improvement of PBO fiber

including the interface strength

ultraviolet stability and compressive strength were investigated. The development history of PBO fiber was also shortly reviewed. We found that only under the optimization of monomers

processing and equipments could PBO polymer with high molecular weight be obtained; high performance PBO fiber could be spun by crystalline spinning through twin screw extruder which is also the polymerization reactor at the same time. It was also found that the chemically incorporation of the third monomer containing ionic groups or dihydroxy groups into PBO chains could greatly improve the interfacial shear strength with epoxy resin; and the compressive strength of PBO fiber could also be raised owing to the hydrogen bonds between PBO macromoleculars occurred between dihydroxy groups and nitrogens in benzobisoxazole rings of PBO chains; moreover the third monomer containing dihydroxy groups possesses the ability to absorb ultraviolet light

which makes modified PBO fiber more resistance to ultraviolet exposure. In addition

the loading of some ultraviolet absorbents during polymerization and the coating of soluble polyimides on PBO fiber surface are also effective mothods to improve the ultraviolet stability.