Preparing water-based phosphorylated PEEK sizing agent for CF/PEEK interface enhancement

The weak interfacial bonding between fiber and matrix needs to be improved for obtaining good mechanical properties of carbon fiber/polyetheretherketone (CF/PEEK) composites due to the inert nature of both components. Organic sizing is a typical interface improvement method, but it is harmful to both the human and local environment. Here, a two-step process is proposed to modify PEEK for preparing an environmentally friendly water-based sizing agent, involving taking the ketone reduction via NaBH₄ and then an esterification reaction with phosphoric acid. This PEEK derivative has good thermal stability, and its dispersion in water is stable for one month. It improves the interface between CF and PEEK by increasing the wettability and surface roughness of CFs, ultimately enhancing the mechanical properties of composites. The two-step process of fabricating the PEEK derivative may have potentials in the industrial application of the polyaryletherketone family.