Surface Modification Of PBO Fiber And Its Effects On Mechanical Properties Of The Composites

Poly(p-phenylenebenzobisoxazole)(PBO) fiber has been considered as an ideal reinforcing material for advanced polymer composites, owing to its superior tensile strength and modulus, excellent thermal stability, oxidative stability, and fire resistance. However, their performance in reinforcing a polymer matrix so far has been inadequate, which was attributed by researchers to the insufficient interfacial bonding between PBO fiber and the resin matrix. Mechanical properteis of the PBO reinforced polymer composites remained dissatisfied, and still prevented them from being applied to industries. Therefore, it is necessary to modify the surface of PBO fiber in order to increase the interfacial bonding between the fiber and polymer matrix, which results in the improvement of mechanical properties of the composites.PBO fibers were modified by acid treatment, γ-ray radiation treatment, Ar plasma treatment,coupling agent treatment, and a combined treatment of the four methods. After the treatment, surface morphologies, structures, tensile strength and the compatibility between the fiber and matrix were investigated. Based on the results, surface modification method of PBO fiber was optimized, and a combined treatment method(raw fiber-γ-ray irradiation-PPA tetching-coupling agent YDH560 coating) was established finally.Manufacturing technique of the PBO/epoxy composites was also studied. The PBO/epoxy prepregs were produced using the Drumwinder technique, and the laminateds were produced by the compression molding technique. Technical parameters for manufacture the composites were optimized, and influence of the surface modification of PBO fiber on the mechanical properteis of the composites was investigated.Tensile, interlaminlar shear and compressive properties of the PBO/epoxy composites were measured. The results indicated that the uniaxial tensile failure mode of the composites was the interfacial shear failure. Tensile strength of the surface modified PBO/epoxy composites decreased by 8 %, but the interlaminlar shear strength increased by 26 % to 43 MPa. The uniaxial compression failure mode of the composites was mainly the 45° shear failure mode. Compressive strength of the surface modified composites was improved by 17 % to 168 MPa. All the results indicated that the surface modification of PBO fiber highly improved the interfacial bonding between the fiber and matrix, and resulted in the significantly improved mechanical properties of the composites.