Key Physicochemical Properties and Service Characteristics of Low Dielectric Polyimide-based Nanocomposites

Abstract

In high-frequency electrical energy systems, polyimide (PI) composite insulation materials need to possess a low dielectric constant, sufficient thermal conductivity, and robust interfacial adhesion to ensure reliable performance under elevated temperatures and pressures. These aspects are crucial for preventing local overheating and electrical breakdown, thereby ensuring reliable equipment operation. Traditional PI insulation materials often exhibit high dielectric constants and pronounced dielectric losses, compromising their insulation efficiency. In this study, molecular dynamics simulations were employed to incorporate polyhedral oligomeric silsesquioxanes (POSS) into PI through physical blending and chemical bonding to enhance dielectric properties. Key parameters of the PI/POSS composite system, including dielectric constant, thermal conductivity, glass transition temperature, Young’s modulus, Poisson’s ratio, and interfacial adhesion energy, were systematically evaluated for both doping methods. The degradation behavior of the PI composites under high-temperature and electric field conditions was also simulated to elucidate degradation pathways and product distributions, providing insights for designing low-dielectric insulation materials. Doping with POSS significantly reduces the dielectric constant of PI, thereby improving insulation performance, thermal stability, mechanical strength, and interfacial adhesion. At an optimal POSS doping ratio, the thermal conductivity of PI is enhanced. Compared with the physical blending system, the chemical bonding system yields more substantial improvements across all evaluated properties. Under high-temperature and strong electric field conditions, POSS doping enhances interfacial adhesion and thermal stability, effectively suppressing the cleavage of key chemical bonds, reducing CO emissions, and increasing the formation of oxygen-containing intermediates and water molecules, which contributes to improved environmental sustainability.