Microscopic Pyrolytic and Electric Decomposition Mechanism of Insulating Polyimide/Boron Nitride Nanosheet Composites based on ReaxFF

Abstract

High thermal conductivity insulating materials with excellent comprehensive properties can be obtained by doping boron nitride nanosheets (BNNSs) into polyimide (PI). To study the microscopic mechanism of composite material decomposition in an actual working environment and the inhibitory effect of BNNS doping on the decomposition process, molecular dynamics simulations were carried out at high temperatures, in intense electric fields, and with various reactive species in plasma based on the reactive force field (ReaxFF). The results showed that the decomposition was mainly caused by hydrogen capture and adsorption, which broke the benzene ring and C-N bond on the PI chains and led to serious damage to the PI structure. The BNNS filling was shown to inhibit the decomposition of the PI matrix at high temperatures and in intense electric fields. Moreover, the BNNS filling also inhibited the material decomposition caused by ·OH and ·NO. The erosive effect of the positive corona on the PI composites was more obvious than that of the negative corona. In this paper, the microscopic dynamic reaction paths of material pyrolysis in various environments were revealed at the atomic level, and it was concluded that BNNS doping could effectively inhibit the decomposition of PI in various environments.

Investigation of Polymer Aging Mechanisms Using Molecular Simulations: A Review

“…The study of Wang et al [120] also confirmed the weakening effect of the electric field on the van der Waals forces of the polymer system. They also investigated the electric decomposition mechanism of composites [121]; compared with a high concentration of BNNSs, they found that the doping of a low concentration of BNNSs into PI could improve the breakdown strength of the material, and prevent electric distortion caused by excessive ion aggregation. The main aging mechanisms under an electric field obtained from the above works are summarized in Figure 8.…”

“…The design principles of degradable polymer materials can be obtained by studying the influence of internal and external factors on material degradation [118]. At present, there are several simulations that set their research objective as promoting the degradation of materials [119][120][121], which is contrary to the anti-aging research mentioned in this paper. However, the simulation methods adopted by these studies are similar, and both of these research areas are aimed at achieving sustainable development.…”

Microscopic Mechanism of Electrical Aging of PVDF Cable Insulation Material

“…The theory of quantum mechanics means that molecular simulation technology is not only limited to the study of chemistry, but also extended to electrical, physical, biological and material science and other disciplines, promoting the development of interdisciplinary research and providing a new means for people to understand the material world, in addition to experimental methods and theoretical methods [15]. Many scholars have applied molecular simulation methods to the field of high-voltage insulation, such as the synergistic effect of electric fields and temperature on insulating oil [16,17], the microscopic mechanism of the overheating of insulating oil [18,19], the aging and degradation of insulating materials [20,21], and the diffusion of gas molecules in oil paper insulation systems [22,23]. Meanwhile, molecular simulation has been successfully used in the study of PVDF, the static and dynamical mechanical properties of PVDF [24], elastic properties of PVDF crystals [25], and the effect of the addition of ionic liquids to PVDF [26].…”