Preparation And Properties Researching Of Poly-P-Phenylene-Benzobisoxazole/Poly-Pyridobisimidazole Composite Fibers

Poly-p-phenylene-benzobisoxazole(PBO) fiber as the "King of organic fibers," has high strength, high modulus, excellent thermo-oxidative stability and other properties, it has broad application prospects in military defense, aerospace and civilian high-tech fields. But as reinforcement of fiber-reinforced resin matrix composites, the poor binding property between the PBO fibers and resin has limited the application of PBO fibers. In this paper, in order to improve the binding properties between the PBO fibers and resin, [2,5-dihydroxy-1,4-phenylene pyridodiimidazole](PIPD) polymer is added into the PBO polymerization system to prepare PBO/PIPD composite fibers, which have better adhesion performance betwee n the fibers and resin than PBO fibers.In this paper, by adding PIPD polymer into the PBO polymeriazation system, the composite fibers were obtianed. By studying the molecular changes in the polymerization process, the mechanical properties of the composite fibers abtained by adding PIPD at different blending temperature, and fiber diameters of different spin rates, the composite fiber spinning process and optimum synthesis parameters were determined. Using X-ray diffraction, X-ray photoelectron spectroscopy, thermal gravimetric analysis and invasive testing, the crystallite size, surface element content and heat resistance of PBO/PIPD composite fibers were characterized. Finally, using the method of monofilament pulling out, the interfacial shear strength between PBO/PIPD composite fibers and the epoxy resin were tested.Through the data analysis, the optimum temperature for blending is 160℃. To make PIPD polymer dispersed in the PBO system uniformly, PIPD polymer needs to be stirring 2 h in a solution of polyphosphoric acid under ultrasonic, after that the PIPD is added to the polymerization system. The optimum spinning rate is 90 m/min. The content of N element of PBO/PIPD composite fibers is higher than that of the PBO fiber. The surface morphology of the composite fibers is firmer than PBO fiber, compared with PBO fiber, the morphology of composite fiber section after pulling off has less microfibers and hierarchical situation. With the PIPD amount increases, the tensile strength of fibers decreases, it has agreement with crystal size. With PIPD content increases, the contact angle between the composite fibers and deionized water/ethylene glycol becomes smaller and smaller, and the surface energy of composite fibers increases. The interfacial shear strength between the composite fibers and epoxy resin has greatly improved and when PIPD content is 10 mass%, the interfacial shear strength between the epoxy and the fiber is increased by 63.8% compared to PBO fibers. The interface performance of composite fibers has been greatly improved compared with PBO fibers.Through the above research, composite fibers can be obtianed with the above process parameters employed. The intensity of composite fibers prepared decrease slightly compared to PBO fiber, but its interfacial properties of reinforcing resin matrix has improved greatly. The comprehensive performance of composites prepared with the composite fibers will be enhanced and the scope of PBO fiber application can be expanded.