Surface modification of Poly-p-phenylene benzobisoxazole fiber by dielectric barrier discharge for magnet reinforcement

At present, Poly-p-phenylene benzobisoxazole (PBO) fiber is one of the most preferred reinforcement materials for magnet. However, the poor interface performance between the PBO fiber and resin matrix has become the bottleneck of the pulse magnetic field intensity improvement. Surface modification of the PBO fiber may be an effective way to solve this problem. In this paper, PBO fibers were treated by atmospheric dielectric barrier discharge (DBD) in air under different treatment time. It is found that when the discharge power density remained unchanged at 8.49W/cm2, the optimal treatment time is 60s. In this case, the shear strength of PBO fiber-resin interface increases up to 52.77% compared with the untreated, while the tensile strength of fiber monofilament only decreases 4.73%. The plasma treatment results in a large number of deep pits and protrusions on the surface of PBO fibers and a significant increase in roughness. The relative content of C element on the surface of PBO fiber decreases significantly, the content of O element increases obviously, and the content of N element increases slightly. Polar groups -O-C=N- and -C=O- are introduced through grafting copolymerization reaction, which enhances the chemical activity and wettability of the fiber surface. All of these contribute to the interfacial shear strength increase between the PBO fiber and the resin.