Study Of Inorganic Nano-Particles/Polyimide Hybrid Film

Polyimides are well known for their outstanding stability, excellent chemical resistivity, and favorable mechanical strength as an engineering material. They have widely been used in aerospace and electric industries. Along with the rapid development of generator industry, high frequency generator and high voltage generator have appeared. In this case, the demand of insulation materials in the generator has reached a new level. Not only mechanical strength, modulus and thermal stability but also the electrical capacity has been an very important factor. Though the different properties of polyimide are good. It's not far enough. Obviously, inorganic materials such as metal oxide have some excellent performance, but they have many insuperable problems in the practice. Polyimide is also limited with regard to additional improvements because of the limitation inherent in all organic materials. This suggests the combinations of inorganic and organic components with a nanoscale size will improve properties of polymer. In this thesis, the organic-inorganic nanocomposites based on the polyimides as polymer matrix were prepared. The structure, morphology and properties of these nanocomposites were investigated, meantime, we will present the polymer structure-property relationship.In this article, we obtained the solution of poly (amic acid) (PAA) in N,N-dimethylacetamide (DMAc) by the reaction of the materials of Pyromellictic dianhydride(PMDA) and 4,4 ' -oxydianiline (ODA) in the solvent N,N-dimethylacetamide (DMAc). And silica and alumina sol were prepared with tetraethoxysilicane and aluminum isopropylate by the sol-gel. Then silica and alumina sol were added in poly (amic acid)solution according to proper proportion, and the mixture was stirred mechanically .After complete imidization polyimide / inorganic nano-particles hybrid films were obtained. The films were characterized by Fourier transform infrared spectra (FTIR), Atomic forcemicroscope (AFM), thermogravimetric analysis (TGA) and breakdown experiment. The results proved that there were mutual effects between polyimide matrix and nano-particles and it formed Si-O-Al structure. After adding silica and alumina nano-particles, the thermo-decomposed temperature of the hybrid films was improved markedly and the breakdown field fell. When the nano-particles' weight content was 8%, the drop of breakdown strength reach smallest value and the thermo-decomposed temperature reach the highest value.