Preparation and distinguish dielectric properties of multi-layer nanoparticles-based polyimide films

Insulation structure of inverter fed motors, mainly used in high-speed railways undergo continuous stresses of short pulses, making it difficult to maintain the insulation strength. Core–shell type of dielectric material and deposition of multilayer nanocomposite structures are being utilized in modern research to enhance the mechanical and dielectric strength of motor insulation. There is a high demand to explore electrical properties of such multilayer structure possessing thin dielectric layers of nanometric dimensions particles. The electrical performance of single-layer (polyimide/nano) and three-layer structure (nano-polyimide-nano) consisting of two different types of nano particles (Al₂O₃ and SiO₂) are investigated, and results are compared with each other as well as with single layer structure. The structural interface and physical properties of dispersion of nano additive layers on polyimide are studied by microscopic analysis and other features such as weight loss, dielectric spectroscopy, and electrical and mechanical breakdown strength are also analyzed. Results showed that the three-layer structure with SiO₂ additive have higher electrical breakdown strength compared with other types, 40% increase compared with single-layer nanofilms, 30% enhancement compared with three-layer Al₂O₃-PI-Al₂O₃ films. Besides, notable variations in results are observed at higher temperatures. The current research study on the basis of type, size and structure of sample will help manufacturers especially in the field of motor industry to select nano reinforced PI film according to industrial application. (paper)