The pyrolysis of polyimide and epoxy resin by the ReaxFF molecular dynamics simulation

YZ Du and J Li and N Wen and Z Zhang and D Song, JOURNAL OF MOLECULAR MODELING, 31, 279 (2025).

DOI: 10.1007/s00894-025-06492-8

ContextPolyimide (PI) and epoxy resin will age by hot corrosion and long-term high temperature, losing the heat insulting property and forming tremendous potential dangers. In order to evaluate the thermal properties accurately and detect the potential damage of them, the pyrolysis processes of them were studied. The results show that the main products of PI are CO2 and CN at high temperature, and their formation are both associated with the break of C-N bond in the imide rings. With the increase of the temperature, the number of CN increases, but the number of CO2 decrease. Among several reaction path of the PI productions, the p1 is the lowest activation energy and can form CO2. The bond dissociation energies of C-N bond in p3 and p4 are higher than p1. We also investigated the pyrolysis process of the epoxy resin. The results show that the main products of epoxy resin are H2, CH2O, H2O, and CH4 at 1300 K, and the H2 is generated by the collision of the hydrogen atoms (p1 path), the CH2O is generated by the partial decomposition of the C2 or C3, which can form the epoxy groups on the ends of the epoxy resin.MethodsReactive force field (ReaxFF) molecular dynamics simulations were used to study the pyrolysis of PI and epoxy resin. The initial structures of PI and epoxy resin were constructed using Material Studio software, followed by geometry optimization to achieve the most stable configuration. Pyrolysis simulations were performed using the large-scale atomic/molecular massively parallel simulator (LAMMPS). The simulation employed NPT ensemble (0.1 MPa, 298 K) to adjust the system density to 1.0 g/cm3, and NVT ensemble for pyrolysis Calculations with a time step of 1 fs and total simulation time of 1 ns. Temperature was controlled using the Bersenden method, with key simulation temperatures including 1300 K (epoxy resin) and 2800-3800 K (PI).

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