CaO‐catalyzed simplified synthesis of fully bio‐based self‐cross‐linkable MB‐polyether ether ketone toward waterborne carbon fiber sizing agent to enhance the interfacial properties and solvent‐resistance of carbon fiber/polyether ether ketone composites

Abstract Sizing treatment stands out as an indispensable part of actual carbon fiber reinforced polyether ether ketone (CF/PEEK) production for its simple operation and distinct enhancement effects, and the recently reported novel waterborne self‐cross‐linkable PEEK derivative sizing agents have achieved tremendous attentions for bolstering interfacial bonding for CF/PEEK. Nevertheless, the key polymer‐precursors utilized in the related waterborne self‐cross‐linkable PEEK researches to date are majority rely on petroleum‐based reagents and prepared through cumbersome and toxic catalytic systems, which have become a bottleneck of its future developments. In this research, a simple and sustainable‐minded approach was performed utilizing fully biogenic‐sourced materials. Specifically, magnolol and 2,5‐furandicarboxylic‐acid derived 2,5‐bis(4‐fluorobenzoyl)‐furan were utilized to elaborate a self‐cross‐linkable MB‐PEEK. Notably, the incorporation of CaO as catalyst, possessing excellent water absorption properties, allowed for eliminating the highly toxic azeotropic solvent, thereby achieving a simple and green synthetic process. The fastidiously designed full‐bio‐based self‐cross‐linkable MB‐PEEK sizing agent conspicuously boosted the interfacial performances of CF/PEEK. Noteworthy, the inherent mechanism during the processing stage of CF‐(MB‐PEEK)/PEEK encompass a self‐crosslinking of allyl groups of magnolol toward stable crosslinked structures with an unparalleled resistance to solvents and unorthodox robustness to interphase. Among them, the interfacial and interlaminar shear strength of sized‐CF/PEEK were improved by 65.71% and 55.09%. Notably, even after enduring 3 days of solvent aging, the mechanical integrity preserved at approximately 93%. Our study presents a straightforward and green approach for production of sustainable waterborne sizing agent with outstanding properties that show excellent enhancement effect in interfacial performance and solvent‐resistance in CF/PEEK. Highlights A full‐bio‐based cross‐linkable MB‐PEEK sizing agents for CF/PEEK were prepared. Magnolol and 2,5‐furandicarboxylic acid were employed to substituted the petroleum‐based reagent. The green catalyst CaO was used to replace the poisonous catalyst systems. The ILSS, IFSS, and bending strength were significantly increased by 55.09%, 65.71%, and 34.14%. Treated composites remained over 93% of properties after a week solvent corrosion.