Self-catalytic phthalonitrile polymer with improved processing performance and long-term thermal stability

Phthalonitrile monomer with alkyl, pyrimidine, and amino is successfully prepared by nucleophilic substitution. The monomer is cured by autocatalysis of active hydrogen in the amino group, in order to obtain polymers through different temperature procedures. The low melting point (96°C) and curing kinetics of the monomer are analyzed by DSC, which manifest a processing window of 163°C. With lower energy barriers to overcome, the apparent activation energy (E _a ) is 59.6 kJ mol⁻¹ after fitting and calculating, signifying that the monomers are easier to process into polymers. This study focuses on the usefulness of the polymer, especially the long-term thermal stability by the comparison of numerous commonly used polymers. The consequence demonstrates that the polymer could be used for long periods at 300°C, keeping weight loss within 5 wt.% for 6 h. The advantage of long-term usage at high temperatures has not been proved in previous works on phthalonitrile polymer. Moreover, the thermal and thermal-mechanical stability are examined through TGA and DMA. The results indicate preferable thermal properties, that the glass transition temperature is up to 400°C.