Eco-friendly synthesis of a monomeric sizing agent and its effectiveness in carbon fiber reinforced poly (aryl ether ketone) composites

To simplify the preparation and application of polyimide-based (PI) high-temperature resistant sizing agents for carbon fiber (CF) and to promote environmentally friendly and efficient practices, a method for preparing PI-based water-soluble sizing agent suitable for carbon fiber reinforced poly (aryl ether ketone) composites (CF/PAEK) based on monomer in situ polymerization mechanism was proposed. The dianhydride monomer (3,3′,4,4′-benzophenone tetracarboxylic dianhydride) was alcoholized and mixed with the diamine monomer (m-phenylenediamine) to form a monomer mixture in water, resulting in a water-based sizing agent. The in situ polymerization of the monomer mixture on the CF surface was completed under high-temperature conditions during the CF/PAEK molding process, simplifying the sizing process. The thermal analysis results show that the prepared sizing agent’s 5 wt% weight loss temperature is 465°C, which meets the high temperature forming requirements of CF/PAEK. Under optimal sizing conditions, the O/C ratio of the CF surface increased by 19%, the surface energy rose by 57%, the interfacial shear strength between the CF and PAEK increased by 24%, and the interlaminar shear strength of the composites improved by 53%. The sizing agent created through this method provides several advantages, including environmental friendliness, a straightforward process, high-temperature resistance, and a significant improvement in CF/PAEK interface performance.