The Effect Of Inorganic Nano-Particles On The Properties Of Polyimide Hybrid Films

Polyimide(PI) represent an important class of high-performance polymers that exhibit a very high glass transition temperature,ductility,thermal oxidative stability,and solvent resisitance coupled with relatively low permittivity and dielectric losses up to very high temperature.For this reason these materials find applications as insulating materials in high voltage frequency conversion machines,microelectronic devices.However,there are some disadvantages of PI films such as absorbability and high expansile constant,and with the development of industry more demands put forward because of the miniaturization,frequency conversion timing and high voltage of electric machines and motor.So,future improvement in the properties of PI films is need to meet these requirements.Inorganic materials have usually lower absorbility quality and expansile constant,especially the inorgainic nano-particles possess some particular effects such as small gauge effect,interface effect,quantum dimension effect and quantum tunnel effect which can produce some new properties that are different from common solid particles.In recent years,more and more attention has been paid to the polyimide/inorganic nano-particles hybrid materials,and it has owned the properties of both organic and inorganic materials.The hybrid films will be more and more important in our lives and they will have a good development in the future.In this paper,PI/inorganic nano-particles hybrid films were prepared by sol-gel method.Silica and alumina sol were added in poly (amic acid)solution according to proper proportion, and the mixture was stirred mechanically.After complete imidization PI/inorganic nano-particles hybrid films were obtained.We charactered the structure and properties of the hybrid films.The results displayed that there were structures such as Si-O-Si,Al-O-Al and Si-O-Al existed in the hybrid films.And there were some linkings between polyimide and nano-pariticles.The diameter of the inorganic particles in the hybrid films was nano-meter scale,and the doping of coupling agent DB550 was beneficial for the particles distributed in the film.When the inorganic weight content of PI/ SiO₂ -Al₂O₃ hybrid films doped some coupling agent DB550 was 4wt% in the weight ratio of SiO₂/Al₂O₃ at 4 ,the properties of the hybrid films was the best. Comparing with pure PI film,the decomposed temperature of the hybrid film was increased about 18℃and the hybrid film's electrical breakdown stength was increased about 20%.The corona resisitance time of the hybrid film was improved about sixteen times than pure PI film.