PBO Fiber Modification And Study On Preparation And Properties Of PTFE Composites

Poly-p-phenylene benzobisoxazole fiber has excellent tensile strength and high specific modulus, compared to carbon fiber and kevlar fiber has a lower density and more stable heat resistance. As a result, PBO fibers are often used as matrix composites for resin matrix composites. However, due to its own molecular structure of PBO fiber, the interfacial adhesion between PBO fiber and the composite matrix is low, and the aging strength of PBO fiber is decreased rapidly.Whats more,the function of PBO fiber is severely degraded. Therefore, it is necessary to improve the interfacial bonding property of PBO fiber by surface modification, which can make up the aging problem of PBO fiber.In this paper we used polytetrafluoroethylene as the resin matrix of composite materials, the heating temperature, pressure and time in the process of composite materials were studied by using the control variable method;to determine the PBO/ polytetrafluoroethylene composite optimal production process. The surface morphology, surface free energy and tensile strength of PBO fiber treated with nitric acid were studied, the effects of nitric acid treatment on the structure and properties of PBO fiber were determined. Then using perfluorooctanoic acid sodium salt to deal with the modified PBO fiber surface, the effect of surfactant on the shear strength of the composite was studied, determine the best use of perfluorooctanoic acid sodium salt concentration and processing time. Finally, by the experiments of water boiling, high and low temperature alternating aging test and UV irradiation test,the aging degree of PBO fiber and composites under these conditions was studied, reference is provided for the application of composite materials in practice.After the process of pressure and high temperature sintering, PBO/ polytetrafluoroethylene composites were successfully prepared, the interfacial bonding property of PBO/ polytetrafluoroethylene composites was improved by modifying the surface of PBO fiber with nitric acid and adding perfluorooctanoic acid sodium salt. The research results show that the PBO/ polytetrafluoroethylene composite has the highest inter layer shear strength 2.4MPa after high temperature sintering of 40 min at 330℃, increasing the sintering time will decrease the shear strength between layers. After nitric acid modification, PBO fiber’s surface functional groups changed, the fiber surface roughness increased and surface free energy increased, but the tensile strength decreased; the tensile strength of PBO fibers decreased 12.5% and 9% respectively after treatment with 2 hour and 4 hour at a concentration of 10% nitric acid. After the treatment of PBO fiber surface, the surface free energy increased, SEM photos show that the polytetrafluoroethylene layer’s thickness on the PBO fiber surface increased and there is a phenomenon of bifurcation.