Enhancement of processability, thermal stability, and mechanical properties of phthalonitrile resins via 3-aminophenylacetylene modification

Abstract

Phthalonitrile resins are widely recognized for their outstanding heat resistance, dielectric properties, and mechanical properties. However, the excessively high melting temperature and narrow processing window constrain their applications in fields such as thermal protection. This study successfully prepared BPL-P resins with enhanced processing, thermal, and mechanical properties by modifying laboratory-synthesized silicone-containing phthalonitrile (BPL) resins with 3-aminophenylacetylene (APA). The alkyne group in APA can self-polymerize to form polyene and trisubstituted benzene structures, and the amino group in APA encourages the conversion of cyano groups into triazine and phthalocyanine. These modifications confer exceptional thermal and thermo-oxidative stability to the resins, with the T_d5 of BPL-P2 resin (containing 20 wt% APA) reaching 563.2 °C and 522.2 °C, respectively. Additionally, the strong solubility and relatively low viscosity of APA significantly enhance the processing performance of the resin. The softening point of BPL-P2 resin decreases from 161 °C to 94 °C, and its processing window expands from 32 °C to 59 °C under a viscosity of 1 Pa·s. Moreover, the mechanical properties of the quartz fiber-reinforced composite QF/BPL-P2 were substantially enhanced, with flexural strength increasing from 673.6 MPa to 731.9 MPa at room temperature, and from 115.1 MPa to 358.4 MPa after heat treatment at 400 °C for 16 h. These findings broaden the potential applications of phthalonitrile resins in high-end industrial sectors.