Physical evolution mechanism of polyimide/fluorinated graphene composite insulating materials under extreme conditions

Polyimide (PI) has been widely utilized as an insulating coating material in electrical and electronic packaging applications. Doping fluorinated graphene (FG) into PI can result in a composite insulating coating that combines a high thermal conductivity with a low dielectric constant. To explore the mechanism of the physical property evolution under extreme conditions such as high temperatures, intense electric fields, oxygen-rich, and highhumidity environments, PI neat and PI/FG composite systems were constructed, and molecular dynamics simulations were conducted under the reactive force field (ReaxFF). The results demonstrated that compared with the PI neat system, doping FG into the PI/FG composite significantly increased the thermal conductivity and free volume fraction by 164.7 % and 18.4 %, respectively. Furthermore, FG effectively mitigated the degradation of PI molecules under high temperatures and intense electric fields, reducing the generation of small-molecule degradation products such as CO, CO2, H2O, and H3N. Additionally, FG doping reduced the binding energy with O2 and H2O onto PI molecules, thereby preventing erosion of PI by these species. Finally, a comparative analysis with other studies revealed excellent agreement between the experiments and simulations. This study provides valuable theoretical insights for designing insulating coating materials with enhanced durability and reliability.