Excellent thermal resistance and mechanical properties polyimide resin with dual crosslinking network structure for thermal oxidation aging

The development of polyimide (PI) resins with excellent heat resistance is of great significance in promoting equipment that meets the application requirements of harsh environments. Here, thermosetting PI resins with dual cross-linked networks were successfully fabricated using a vacuum hot press molding process. The dual cross-linked relied on hydrogen bonds derived from 3, 5-diaminobenzoic acid (DABA) and chemical bonds originated from acetylene in 4-phenylethynyl phthalic anhydride (4-PEPA) during heating. PI-3 (DABA: m-PDA = 2:2) possessed excellent heat resistance and mechanical properties, with a glass transition temperature (T g ) of 407°C, an initial thermal decomposition temperature of 535.6°C in N 2 , a compressive strength of 82.4 MPa, and a compressive modulus of 1107.8 MPa. Furthermore, PI-3 exhibited excellent resistance to thermal and oxidative aging, its compressive strength and compressive modulus remained at 76.4 MPa and 1213.0 MPa after being treated at 250 °C for 12 h. In all, the PI resins owned excellent mechanical strength and heat resistance, and were expected to be used as high-temperature-resistant structural material in fields such as aerospace and nuclear technology.