Highly enhancing the interfacial strength of CF/PEEK composites by introducing PAIK onto diazonium functionalized carbon fibers

The weak interfacial adhesion between carbon fibers (CFs) and poly(ether ether ketone) (PEEK) strongly hinders the true potential of composites in high performance applications. Herein, a novel heterocyclic derivative of PEEK was utilized as a linkage between CFs surface and PEEK matrix by a facile and high effective two-step method. CFs were firstly grafted with sodium sulfonate groups via aryl diazonium treatment, and then modified by the sizing agent poly(aryl indole ketone) (PAIK). This promising method takes advantages of strong cation-pi interaction between PAIK and activated CFs, increased surface roughness of CFs, as well as good compatibility between PAIK and PEEK. As a result, the tensile strength and interlaminar shear strength (ILSS) of CF/PEEK composites were both improved after aryl diazonium treatment and PAIK sizing. The highest ILSS obtained for the 1 wt% PAIK modified CF/PEEK composites, which was 62.97% higher than that of untreated CFs based composites. Finally, the interfacial reinforcing mechanism in modified composites was proposed by analyzing the interfacial microstructure. This research provided a promising approach to produce high performance CF reinforced thermoplastic polymeric composites.