Surface Modification of PBO Fibers by Low Temperature Plasma

Two methods including coupling agents after argon plasma and coupling agents before argon plasma were employed to modify the poly[1,4-phenylene-cis-benzobisoxazole] (PBO) fiber surface. The surface properties of PBO fibers were comparing treated by two methods of Coupling Agents before Argon Plasma and Coupling Agents after Argon Plasma. The interfacial shearing strength (IFSS) of PBO fibers/epoxy resin was measured by the single fiber pull-out test, The surface morphology and the wettability of PBO fibers were determined by scanning electron microscopy and Washburn method. The results showed that the wettability of the treated fibers were improved. Under the same concentration of the coupling agents and the same parameter of argon plasma, the IFSS of PBO fibers treated by coupling agents before argon plasma (PBO-A-187-Ar) was always larger than that of PBO fibers treated by coupling agents after argon plasma (PBO-Ar-A-187). The IFSS of the untreated fibers was 5.88MPa, while at a 2% concentration of coupling agents (A-187), the highest IFSS of PBO-A-187-Ar and PBO-Ar-A-187 were 10.44MPa and 9.30MPa, respectively. Poly(1,4-phenylene-cis-benzobisoxazole)(PBO), as one kind of aromatic heterocyclic rigid-rod polymeric fiber, exhibits several outstanding properties, such as excellent mechanical property, high flame resistance, high thermal stability and good resistance to creep, chemicals and abrasion ([1-3]). So PBO fibers show a bring vision of future application as reinforcement fibers in advanced composites ([4,5]). However, the poor interfacial adhesion of PBO fibers/resins confines their applications due to the inertia and smoothness of their surface. The adhesion between the fiber and the resin in the composite system is a primary factor for the stress transfer from resin to fiber. Therefore, it is essential to enhance the adhesion between the fiber and the resin. Several studies have shown the modification effects on the surface performance of PBO fibers of argon plasma and adding coupling agents before argon plasma ([6,7]). In this paper, in order to study the effects of the different orders of argon plasma combined with coupling agents on the surface performance of PBO fibers, the coupling agents before argon plasma and coupling agents after argon plasma have been used to modify PBO fiber surface. Under the same concentration of the coupling agents and the same parameter of argon plasma, the effects of the orders of argon plasma and coupling agents on the surface performance of PBO fibers have been investigated. The single fiber pull-out test was used to measure the IFSS of PBO fibers/resin. The scanning electron microscopy was used to study the morphology of the fibers respectively. The single fiber tensile strength and the wettability of the fibers were also investigated.