Research Of Enhancing Uv-resistance Of PBO Fibers Through Surface Modification

Polyparaphenylene benzobisoxazole(PBO) fiber is a kind of high-performance organic fiber, which includes excellent mechanical property, thermal property, and so on. In addition, it has been widely applied in military defense, spaceflight, aviation, sports equipment, buildingmaterials, protective clothing and other areas. However, all aspects of PBO fiber’s performance decreased rapidly after UV irradiation for some time. At the same time, the surface of PBO fiber is extremely inert, it results in the combination with anti-ultraviolet finishing agent becoming poor. So the key to improving the light stability of PBO fiber are finding the specific wavelengths which PBO fiber is sensitive and improving the combination with anti-ultraviolet finishing agent according to the surface modification to PBO fiber.Irradiating the PBO fiber respectively by three wavelength ultraviolet(UVA, UVB and UVC), then taking out the sample at different time. According to the investigation of breaking strength, scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FT-IR), X-ray diffraction(XRD),simultaneous thermal analysis(TG/DSC), Limiting oxygen index(LOI)etc, we have find that when the fiber Irradiated the same time by three wavelength ultraviolet, the decrease of PBO fiber’s performance is the most serious at UVC. Declining rate of breaking strength is large.The damage on the surface of the fiber is serious. The crystallinity of the fiber decreased significantly. When the fiber was irradiated for 6 days, the stability of oxazole ring from UVA began to decrease, oxazole ring from UVB started to open, oxazole ring from UVC already had been opened. When the fiber was irradiated for 13 days, the macromolecules of three wavelength ultraviolet were all destroyed. However the limiting oxygen index changed little, and then keeping a good flame retardant performance finally. So the PBO fiber is the sensitive to UVC, and then UVB, UVA is the last.On the premise of keep ing fiber original good qualities,low temperature plasma technology has been adopted to modify the surface properties of PBO fiber. The effects of air plasma discharging, power, treatment and pressure time on the PBO fiber strength and the friction coefficient have been analyzed through a single factor experiment. The results indicate the greater the discharge power is, the longer the treatment is, the lower the discharge pressure is and more intensity the PBO fiber treatment is. Meanwhile, process optimization parameters are determined through the orthogonal experiment: discharge power is 200 W, the treatment time is 240 s and the discharge pressure is 20 Pa. According to the investigation of scanning electron microscopy(SEM), Fourier transform infrared spectroscopy(FT-IR), X-ray diffraction(XRD),simultaneous thermal analysis(TG/DSC), etc, we have find that the surface of PBO fiber appeared obvious grooves and bumps and the surface roughness has increased. At the same time, the surface activity of the fiber was increased according to the introduction of the reactive group, such as –O H,-CH3. Lattice structure remains the same but the crystallinity was decreased slightly.Two kinds of anti- ultraviolet finishing agent which mainly absorb UVB,UVC and named DM3090 and UV SUN CEL was cho se. Two methods called padding and cold pad-batch was chose to optimize the dosage of finishing agent, curing temperature and curing or cold time. The results indicate that the optimal process of DM3090 for padding is 70 g/L,120℃,90 s, the optimal process of UV SUN CEL for padding is 40 g/L,130℃,120 s, the optimal process of UV SUN CEL for cold pad-batch is 35 g/L、8h. Meanwhile, the finished fiber after irradiating by UV was used to test mechanical property. The results indicate that after irradiating the same time by different wavelength UV, the strengthretention of finished PBO fiber was higher than the unfinished.