Toughening and strengthening of low-temperature resistant epoxy resins by introducing high-performance thermoplastic resin with phthalazinone structure

This paper used phthalazinone-based copoly(biphenyl ether nitrile) (co-PPEN) to improve the low-temperature toughness of epoxy resin E51. The effects of co-PPEN content on the normal/low-temperature mechanical properties, thermomechanical properties, and thermal stability of epoxy resins were studied. Results showed that co-PPEN significantly improved the normal/low-temperature mechanical properties of E51. At room temperature, the impact strength, flexural strength, and tensile strength of co-PPEN/E51 blends increased by 144.0%, 12.8%, and 28.1%, respectively; at low temperature, the impact strength, flexural strength, and tensile strength of co-PPEN/E51 blends increased by 87.9%, 43.6%, and 18.5%, respectively. From the cross-sectional analysis, the crack deflection and crack bridging of co-PPEN are the main toughening mechanisms of the blends. The blend system has high thermal property, and the glass transition temperature of the co-PPEN/E51 blend increased by about 50 °C. Simultaneously, all blends exhibited better thermal stability.