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Phthalonitrile resin is a potential high-performance composite matrix, its brittleness and weak interaction with fiber are the main obstacles to its wide application. High-performance thermoplastic poly(phthalazinone ether nitrile)s (PPEN) and poly(phthalazinone ether nitrile ketone)s (PPENK) have been used to toughen basalt fiber (BF) reinforced 4,4′-bis(3,4-dicyanophenoxy)biphenyl (BPh) composite. The curing kinetics for the BPh/PPEN and BPh/PPENK blends have been investigated using DSC. The structures and thermal properties of the cured BPh blends have been studied in detail. The effects of PPEN and PPENK on the mechanical properties of the modified BF/BPh composite have been assessed. The non-notched impact strength of BF/BPh/PPENK laminate can be up to 107.7 kJ/m2, which is 64.2% higher than that of the BF/BPh laminate. And the interlaminar shear strength of BF/BPh/PPEN laminate can reach 42.5 MPa, 134.8% higher than that of the BF/BPh laminate. Simultaneously, the fracture surface of the laminate showed that the thermoplastic PPEN and PPENK can significantly inhibit the delamination between the layers and the fiber pullout and debonding. [Display omitted] • The mechanical properties of BF/BPh were significantly improved by the introduction of PPEN(K) with pendant cyano groups. • The properties of modified BF/BPh composites can be tuned by the pendant cyano content on thermoplastic resin. • The introducing of high-performance thermoplastic PPEN(K) remains the excellent thermal properties of BF/BPh composites. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • High-performance thermoplastic co-PPEN engineering plastic toughened epoxy resin. • Modified co-PPEN/E51 composites have good low-temperature properties (−183 °C). • Modified co-PPEN/E51 composites have good thermal properties. [ABSTRACT FROM AUTHOR]