Effect of curing behaviors on performances of phthalonitrile resins: A deep molecular dynamics exploration with experiment

Abstract

The curing process and mechanism of high-performance phthalonitrile (PN) thermosetting resin are crucial for its excellent mechanical and thermal-oxidation properties. The complicated polymerization reactions of PN resins were effectively controlled to obtain three types of major cured products (triazine, polyindoline and phthalocyanine). The corresponding cross-linking evolution processes and atomistic microstructural models were dynamically constructed and visualized through a creatively self-compiled procedure. Molecular dynamics simulations combined with experiment were properly conducted on two typical PN resins to illustrate the relationship between cross-linked microstructures and performance. The cross-linking degree and types of final products are positively correlated with the mechanical strength of PN resin. The hydrogen bonds present in the cross-linked structure mainly consolidate the cured networks of PN resin and the unique phenolic hydroxyl groups in PN75 enhance the hydrogen bonding contribution. The dominant pyrolysis gases were experimentally detected and distinguished as H2O, NH3, HCN, CH4, CO2 and CO during the thermal pyrolysis process of PN resin as the temperature rose. This work provides a new approach to probe the curing process and generated species, and further tailor the mechanical behavior and thermal-oxidation properties of resins or composites.