Environmental protection and thermostability modified sizing agent based on fluorenyl poly(aryl ether ketone) for carbon fiber/poly(ether ether ketone) composite interfacial enhancement

Abstract Carbon fiber reinforced poly(ether ketone) (CF/PEEK) composite has been widely studied due to excellent mechanical properties, chemical inertness, and thermal stability, etc. The interfacial strengthening sizing agent for large‐scale industrial production has a crucial requirement for thermostability and environmental protection. In this study, fluorenyl poly(aryl ether ketone) (W‐nPAEK) was successfully prepared, and a new water‐based sizing agent was prepared by emulsion/solvent evaporation. Meanwhile, W‐nPAEK was grafted onto carboxylated carbon nanotubes (CNT‐gPAEK) and anchored to CF using the silane coupling agent KH560. The CNT‐gPAEK anchored carbon fiber is then starched using the sizing agent. As a result, our sizing agent possesses temperature resistance (500°C) suitable for resin processing, long‐term storage stability, and the tensile strength of monofilament and interfacial shear strength (IFSS) are enhanced accordingly. The IFSS increased to a notable 90.82 MPa when compared with untreated carbon fiber, which increased the upper limit of the interface strengthening by the water‐based sizing agent. The improvement of interfacial bonding performance is mainly ascribed to the excellent compatibility between the sizing agent and the resin matrix. More importantly, the π‐π interaction between the benzene rings of each component and the hydrogen bonding effect between CF and the sizing agent also further improves the interfacial bonding between the composites. The sizing agent in this work not only shows the characteristics of safety and environmental protection but also breaks through the interface strengthening threshold of the water‐based sizing agent. Highlights Excellent dispersion stability of fluorenyl poly(aryl ether ketone) in water over three months. Preparing eco‐friendly water‐based fluorenyl poly(aryl ether ketone) sizing agent. Enhancing the interface between CF and PEEK by fluorenyl poly(aryl ether ketone) sizing. Enhancing the surface roughness of CF and the π‐π interaction between the sizing agent and CF by grafting fluorenyl poly(aryl ether ketone) on CNT‐COOH.