Preparation And Study On The Properties Of PI/AlN Hybrid Films

Polyimide (PI) is widely used in the field of nuclear energy, aerospace andmicroclectronics for its excellent performance. However, the requirements of PIproperty become increasingly with the rapid development of modern technology.Inorganic hybrid can effectively improve the performance of certain aspects of PI,therefore, it is having high practical significance to research in this fie ld.In this background, we prepared the PI/AlN nanocomposites by in-situpolymerization method in this paper. In addition to, we researched the propertiesof former composites in different doping content, which include resistivity,breakdown strength, dielectric constant (ε), dielectric loss (tan δ) and coronaaging. The link and mechanism between the macriscopic properties andmicroscopic structure of the PI/AlN were explpred through the structural testingand analys is which include small-angle scattering ray, isothermal decay currentand UV-visible spectral. The tests of dielectric properties show that, thepermittivity decrease first and then increase with the increase of components. Thepermittivity of PI/AlN reaches a minimum value at content of0.5%of inorganic.The relative permittivit ies of different composite films decrease as the frequencyincreasesing. The dielectric loss of PI/AlN increases at low frequencies with thecomposite increasing. At the content of0.1%, the resistivity of PI/AlN is uping to1.511016Ohm.m, which was improved an order of magnitude than resistivity ofthe pure PI. The insulations of the composite films have been improved atvarying degrees as components within the range of5%. The exchange breakdownfie ld strength of PI/AlN composite film increases first and then decrease with theincrease of nano-inorganic content, which higher than130kV/mm. The coronaresistant aging of the PI/AlN nano-composite films increase significantly withthe increasing of AlN. The corona resistant time of PI/AlN is57.57h when the doping amount is20%, which is13.76times than the pure PI. The results showthat, nano-AlN could improve cirona aging ability significantly and reduce thepermittivity of composite films at acertain extent, and maintain the basicdielectric properties of pure PI.The micro-structural properties and the mechanism between microstructureand macroscopic properties of composite films which have differ ent componentswere studied through the tests which include small-angle scattering, UV-spectroscopy and isothermal decay current. The results show that, the scatteringcurves of PI/AlN films do not follow Porod theorem and showing a positivedeviation; electronic density fluctuations present in the white transition zonebetween organic and inorganic; the fractal structure convert to quality andsurface pairs of fractal from quality fractal when nano-AlN more than5%; thedepth of the trap levels change little and the trap level density is increasedsignificantly with the components increasing; the introduction of the trap levelshave a certain impact to the dielectric properties of thecomposite films; UVabsorptions of PI/AlN increase.