Study On Properties Of Branched Benzoxazole Grafted PBO Fibers And Composites

The development of aerospace technology places higher demands on the heat resistance of radar radome used in aircraft structures.PBO fiber cyanate ester composites have excellent heat resistance,dielectric properties and mechanical properties and can be used to prepare high-performance aircraft radomes.However,the interfacial adhesion properties of PBO fiber composites are poor,and it is necessary to modify PBO fibers to improve the interface bonding strength of composites.In this paper,the end-amino branched benzoxazole and carboxyl branched benzoxazole were synthesized,and the correctness of the branched benzoxazole structure was characterized by FT-IR,Raman and 1HNMR.XRD and TG indicated Branched benzoxazoles have good crystallinity and heat resistance.Branched benzoxazole is poorly soluble at room temperature and can be dissolved in polyphosphoric acid at 110°C~160°C.The branched benzoxazole was grafted onto the PBO fibers by ?-ray co-irradiation and the irradiation parameters were determined.The irradiation dose was 30 k Gy,the dose rate was 2 k Gy/h,and the optimal infiltration concentration was 0.8%.The results of FT-IR,XPS,and SEM indicated that the branched benzoxazole was successfully grafted onto the PBO fiber.TG showed that the grafting rate of aralkylamine-terminated branched benzoxazole grafted PBO fibers was 1.6%,and the grafting rate of carboxyl-terminated branched benzoxazole grafted PBO fibers was 2.1%.XRD,monofilament stretching The results indicate that the crystallinity and bulk strength of the irradiated PBO fiber do not change significantly.In this paper,branched benzoxazole grafted PBO fiber cyanate unidirectional laminates were prepared by hot-pressing,and the interface properties,bending properties,heat resistance and dielectric properties of the composites were studied.influences.Infiltration tests showed that the branched benzoxazole grafted PBO fibers significantly improved the infiltration of cyanate esters,and the maximum saturation infiltration amount increased by 26.8%.The monofilament pull-out test results show that after graft modification,the interfacial properties of PBO fiber composites are significantly improved,the maximum increase is 45.65%,the maximum increase in interlayer shear strength at room temperature is 23.86%,and the high temperature interlayer shear strength The retention rate is higher,and the bending strength is increased by 13.71%.SEM results show that the surface of PBO fiber grafted with more resin,TG results show that the heat resis tance of the composite material after graft modification has been significantly improved,at room temperature to 300 °C The dielectric constant increases slightly;at 300°C,the dielectric loss becomes significantly smaller than that of unmodified composit es.Therefore,the grafted modified PBO fiber composites have good high-temperature dielectric properties.