Investigation into the high-frequency dielectric and insulating properties of KH550-modified silicon nitride (Si3N4) /polyimide composite film: Based on Experiments and Molecular Dynamics

KH550 modification improves Si3N4 dispersion and interfacial compatibility in PI. • KH550-modified PI/Si3N4 films exhibit low dielectric loss under high-frequency stress. • Corona aging lifetime reaches 31.5 min, 150% higher than that of pure PI. • MD reveals reduced free volume and enhanced interfacial charge trapping. Polyimide (PI), used as an insulation material for high frequency power transformers, tends to age as insulation due to partial discharge (PD). This study incorporates KH550 modified nanoscale silicon nitride (Si 3 N 4 ) into polyimide and prepares composite films via in situ polymerization. By combining experiments with molecular dynamics (MD) simulations, we study the dielectric performance and high frequency insulation properties of the modified films. First, FTIR and SEM analysis of the modified Si 3 N 4 particles and the composite films (before and after modification) shows that KH550 modification improves particle dispersion and interfacial compatibility in the matrix. Subsequently, the effects of KH550 modification and particle loading on film properties are examined. The results show that the dielectric constant and the dielectric loss of the modified films are lower than those of the unmodified films. In experiments, the high frequency dielectric loss of the modified films remains below 0.01. The introduction of modified Si 3 N 4 reduces local discharge activity in the film and effectively improves corona resistance lifetime, with the improvement increasing as the loading increases, reaching up to a 137% enhancement compared with the unmodified sample. Finally, MD simulations are used to explain the mechanism by which KH550 modification enhances PI performance. The results indicate that KH550 modification creates regions of low electrostatic potential on the Si 3 N 4 surface, enhancing the trapping of charge carriers and reducing interfacial polarization, while at the same time promoting aggregation of PI chains around the particles, reducing free volume and reducing potential breakdown pathways. Download: Download high-res image (609KB) Download: Download full-size image