Reduced curing kinetic energy and enhanced thermal resistance of phthalonitrile resins modified with inorganic particles

The effects of inorganic particles such as Al2O3 and B4C on the solidification kinetics and heat resistance of phthalonitrile resin were investigated. The properties of the blends and the cured products were tested by rheometer, differential scanning calorimetry, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The results revealed that B4C and Al2O3 inorganic particles could prolong the gel time of phthalonitrile resin and broaden the processing window. The curing kinetic analysis showed that the presence of the particles could significantly reduce the curing activation energy of phthalonitrile resins by 72.38 kJ/mol down to 43.03 kJ/mol. Meanwhile, the heat resistance of the phthalonitrile resin was improved. Among them, the blend system combined with 30% B4C showed prominent thermoresistance. And while the Td5% weight loss temperature was 600°C, char yield at 1000°C was higher than 86% under nitrogen atmosphere; while the Td5% weight loss temperature was 581°C, char yield at 1000°C was higher than 80% under air atmosphere. Hence, the resulting resins were good candidate matrix of high‐temperature structural composites.