Interfacial engineering of epoxy/carbon nanotubes using reactive glue for effective reinforcement of the composite

We describe a novel strategy for reinforcing an epoxy resin using carbon nanotubes (CNTs), in which polybenzimidazole (PBI) was used as the glue to enable effective adhesion between the epoxy matrix and the CNT surface. Because PBI strongly interacts with the surfaces of the CNTs and reacts with epoxy matrices to form covalent bonds, the PBI-wrapped CNTs are a promising novel epoxy-CNT hybrid. The PBI-wrapped CNTs (CNT/PBI) exhibited an effective reinforcement of the epoxy resin hybrid, resulting in a higher tensile strength and Young's modulus (that is, +28.1% and +8.8%, respectively) compared with those of the hybrid using oxidized CNTs in place of PBI-wrapped CNTs (+18.6% and -4.8% reinforcement for tensile strength and Young's modulus, respectively). Scanning electron microscopy measurements of the fracture surfaces of the CNT/PBI-epoxy hybrid revealed that only very short CNTs were observed for the CNT/PBI-epoxy hybrid due to effective load transfer resulting from the formation of covalent bonds between the PBI on the CNTs and the epoxy resin, which is in contrast to that observed for oxidized CNT-epoxy, which exhibited long CNTs in the fracture surfaces owing to slippage at the interfaces.