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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 NaBH 4 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. [Display omitted] • Proposing a novel and facile two-step modification route on PEEK. • Preparing eco-friendly water-based phosphorylated PEEK sizing agent. • Excellent dispersion stability of phosphorylated PEEK in water over one month. • Enhancing interface between CF and PEEK by phosphorylated PEEK sizing. [ABSTRACT FROM AUTHOR]

The weak interfacial adhesion caused by the low wettability of carbon fiber (CF) and inert polyetheretherketone (PEEK) hinders the great application potential of CF/PEEK composites. In this study, the interface between CF and PEEK was modified by coating hydroxylated PEEK grafted onto multi-walled carbon nanotubes (M-HPEEK). Modified CFs by M-HPEEK sizing had rougher surfaces with more polar groups, showing decreased contact angle and increased surface energy. The wettability of these CFs was enhanced, beneficial to PEEK infiltration and physical adhesion improvement. As a result, the interlaminar shear strength, flexural strength, and flexural modulus of modified CF/PEEK composites were increased by 73.0% (84.7 MPa), 163.2% (906.2 MPa), and 84.8% (58.4 GPa), respectively. An improved interface with stress transferring was proved by the interface debonding failure changed to fiber crack and resin yield. M-HPEEK sizing is considered as a promising modification method to optimize the interface performance of composites. [Display omitted] [ABSTRACT FROM AUTHOR]

The weak interfacial adhesion between carbon fiber (CF) and polyetheretherketone (PEEK) is a longstanding problem that hinders the applications of CF/PEEK composites. To solve this problem, a mixture sizing agent containing hydroxylated boron nitride (BNO) and polyetherimide (PEI) is synthesized to coat CF. In this study, BNO is synthesized via the liquid exfoliation method. The interfacial adhesion between CF and PEEK is improved using a mixture sizing layer of BNO and PEI on CF. The synergistic effects of hydrogen bonding, π-π interaction and good compatibility are evaluated to remarkably increase the miscibility and mechanical interlocking, ultimately enhancing the thermal conductivity, mechanical and tribological properties. Therefore, the PEI-BNO sizing layer on CF has proven to have great potential for high-performance CF/PEEK composites. [Display omitted] [ABSTRACT FROM AUTHOR]