Research On Strengthening And Toughening Of PVA-based Double Network Coating On The Interface Of PBO Fiber And Its Composite

Poly-p-phenylene benzodioxazole(PBO)fiber has the characteristics of high strength,high temperature resistance,and is not easy to break.It is a very excellent high-performance organic fiber.However,the surface of PBO fiber is inert,has poor compatibility with the resin matrix,and weak interface performance,which greatly limits the application of PBO fiber in the field of composite materials.Based on this,this dissertation proposes a PBO fiber surface modification method that simultaneously increases the fiber filament strength and its interface strength.The in-situ cross-linking swelling method is used to coat the surface of PBO fiber with polyvinyl alcohol(PVA)/epoxy cross-linking coating,which establishes a mild surface modification method for PBO fiber.Using infrared spectroscopy(FT-IR),Energy dispersive X-ray spectrometer(EDS),thermal weight loss analysis(TGA),X-ray diffraction(XRD)and other methods to analyze the PBO-PVA/epoxy modified fiber,the results show that PVA/ The epoxy cross-linked coating was successfully applied.After the modification,the oxygen content on the surface of the fiber increased,and the thermal stability was improved,and the modification method would not affect the crystal structure.At the same time,the stability of the coating was explored,and the results showed that the PVA/epoxy coating exists on the surface of the PBO fiber with a stable cross-linked structure.The surface roughness and surface energy of PBO-PVA/epoxy modified fiber were tested by atomic force microscope(AFM)and dynamic contact angle test.The results showed that the surface roughness increased from 6.70 nm of the original fiber to 26.18 nm,and the surface energy was increased from the original fiber.The increase of 15.33 mN/m of fiber to 33.56 mN/m is beneficial to the compatibility of PBO fiber and resin matrix.At the same time,the influence of PVA solution concentration and PVA solution soaking time on the mechanical strength of PBO-PVA/epoxy fiber is discussed.The tensile strength of monofilament was increased by 12.5%,and the reason why the PVA cross-linked coating improved the mechanical strength of PBO fiber was analyzed;the PVA concentration,PVA soaking time,epoxy/acetone solution concentration,The influence of factors such as epoxy/acetone solution immersion time on the interfacial shear strength of PVA/epoxy coating modified PBO fibers,and the optimal preparation conditions were determined;the interfacial shear test results showed that PBO-PVA/epoxy modified The IFSS value of the fiber epoxy resin composite material is increased by51.3% at the maximum compared with the modification before.In general,the method is simple,low-cost and beneficial to continuous production.