Phthalocyanine sizing modification: An excellent strategy in establishing high-temperature-resistant and high-strength interface of CF/PPESK composites based on conjugated structure

Carbon fiber-reinforced high-performance thermoplastic composites have been widely used in military science, aerospace, and new energy fields. However, the inert surface of carbon fibers leads to poor interfacial strength, necessitating surface modification. In this study, Pc was introduced onto the CF surface via a solution impregnation–coating method to enhance the interface interactions of CF/PPESK composites. The effects of Pc structure on the interfacial bonding and high-temperature performance of the composites were investigated. When CF was impregnated in a 5 mg/mL Pc solution and dried at 150 °C, its surface energy reached 36.9 mN/m, representing a 41.37% increase compared with untreated CF. Meanwhile, the CF/PPESK composites modified with 5 mg/mL Pc exhibited 18%, 67%, 14%, and 36% increases in interlaminar shear strength, interfacial shear strength, tensile strength, and flexural strength, respectively, compared with those based on desized fibers. At 150 ℃, 200 ℃, and 250 ℃, the composites retained 93%, 85%, and 75% of their flexural strength, respectively, outperforming the unmodified counterparts. These improvements are attributed to π – π conjugation between Pc, CF, and PPESK, which enhances interfacial bonding, as well as the increased surface roughness and polarity of CF after Pc modification. Moreover, the excellent thermal stability of Pc ensures the maintenance of interfacial performance at elevated temperatures. This work provides a new approach for developing high-temperature-resistant sizing agents for high-performance thermoplastic resin composites.