Achieving high heat resistance for phthalonitrile/boron blends through formation of protective phases derived from boron powder

Phthalonitrile resins or its blends with high heat resistance are urgently demanded for spacecrafts that usually operate in extreme environment. Here, the heat resistance of phthalonitrile was significantly improved by introducing boron powders. The boron powders not only played a role in physically insulating oxygen from the matrix but also forming the boron oxide phase, which both retarded the thermal decomposition process of phthalonitrile resin at elevated temperatures. The results show that the as-prepared phthalonitrile/boron blend with 20.0 wt% boron exhibited high Td5% of 549 degrees C and 552 degrees C in air and N2 atmosphere, respectively. For the carbon fiber fabric reinforced phthalonitrile/boron composites, the flexural modulus and flexural strength were improved from 82.6 GPa to 778 MPa for phthalonitrile resin composite to 134.2 GPa and 978 MPa at 450 degrees C, respectively. This work demonstrates an efficient way to prepare phthalonitrile composites with excellent thermal stability and good mechanical performance.