Processable polyimide resins and their composites for long-term application at 300 ℃

Abstract

A series of processable and high-temperature resistant polyimide resins terminated with 4-phenylethynyl phthalic anhydride were synthesized by PMR (for in situ polymerization of monomer reactants) using isopropyl alcohol as esterifying agent. The resin solution stored at room temperature for sixteen weeks has no solid precipitation, and the viscosity of the solution does not change significantly, which shows good storage stability at room temperature. The minimum melt viscosity of the imide oligomers is less than 300 Pa·s, which is suitable for compression moulding or autoclaved process. The cured polyimides exhibit extremely high glass transition temperatures (Tg) up to 462℃. The flexural strength and modulus of T300/PMR-PE-2 carbon fiber composite are 963 MPa and 53 GPa, respectively. The inter-laminar shear strength of the composite is 56 MPa. Moreover, the composite can maintain no lower than 66% of their room temperature mechanical properties at 300℃. After isothermal aging in air atmosphere for 500 h at 300℃, the mass loss of the composite is only 0.96%, meanwhile, the composite retention rate maintains 72% of its room temperature flexural strength and 98% of its room temperature inter-laminar shear strength, which demonstrates its excellent thermal-oxidative aging resistance.

Keywords

• processable
• high temperature resistance
• polyimide resin
• carbon fiber composite
• isothermal aging