Improving the interfacial properties of carbon fiber-reinforced epoxy composites by grafting of branched polyethyleneimine on carbon fiber surface in supercritical methanol

We report on a new application of branched polyethyleneimine as a coupling agent to functionalize carbon fibers in conventional and supercritical methods. The microstructure and mechanical properties of carbon fibers before and after modification were investigated. Polyethyleneimine could increase the polarity, wettability and roughness of the carbon fiber surface, and supercritical methanol was also able to improve the reaction efficiency. The interfacial shear strength and impact toughness improved significantly when using the two methods, especially in supercritical methanol. Reinforcing and toughening mechanisms have also been discussed. Functionalization does not decrease fiber tensile strength.