Polyamide acid dispersion liquid and preparation method thereof as well as polyimide film

Abstract

The invention provides a preparation method of a polyamide acid dispersion liquid. The preparation method comprises the following steps: dispersing metal oxide nanoparticles with the surfaces modified by a coupling agent into an organic solvent, thereby obtaining a nanoparticle dispersion liquid; and mixing the obtained nanoparticle dispersion liquid with dianhydride and diamine and reacting, thereby obtaining the polyamide acid dispersion liquid. According to the preparation method, the surfaces of the metal oxide nanoparticles are modified firstly; and then the nanoparticles are dispersed into the organic solvent with the low viscosity, so that the nanoparticles are dispersed evenly and stably, and therefore, the defect that the nanoparticles are not dispersed evenly because the polyamide acid solution is high in viscosity is overcome. Finally, the polyamide acid dispersion liquid is obtained by performing a polymerization reaction. A polyimide film prepared by the polyamide acid dispersion liquid is good in corona-resistant performance and mechanical performance.

Description

technical field [0001] The invention relates to the technical field of nanometer materials, in particular to a polyamic acid dispersion liquid, a preparation method thereof and a polyimide film. Background technique [0002] Polyimide film is a new type of high-temperature-resistant organic polymer film. It is the best film insulating material in the world. Since it was first introduced to the market in 1966, it has been known for its excellent electrical properties, flame High temperature resistance and radiation resistance, as a high-performance insulating material, it is used in various fields such as aerospace industry, electronic and electrical industry, and information industry. [0003] However, the corona resistance effect of polyimide is poor. When it is applied to the variable frequency motor, because the variable frequency motor adopts the pulse width modulation driving pulse speed regulation technology, it will cause partial discharge phenomenon, that is, the gen...

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Problems solved by technology

[0003] However, the corona resistance effect of polyimide is poor. When it is applied to the variable frequency motor, because the variable frequency motor adopts the pulse width modulation driving pulse speed regulation technology, it will cause partial discharge phenomenon, that is, the generation of corona, and the polyimide used Imide film insulation materials have poor corona resistance, which will cause local high-temperature oxidation in the motor insulation materials, resulting in decomposition of insulation materials, embrittlement of molecular chains, and fractures, eventually causing insulation breakdown, making the insulation system of the motor The service life is greatly reduced, and may even cause the motor to be damaged during the trial run. Therefore, to prolong the service life of the motor, it is necessary to improve the corona resistance of its insulating material, that is, the polyimide film

[0004] At present, the method of adding corona-resistant nanoparticles in polyimide films is often used to improve the corona resistance of polyimide films. The prior art discloses the use of sol-gel methods to prepare nano-metal oxide dispersions, and then make However, this method is complicated and not suitable for large-scale industrial production, and during the gel drying process, the volatilization of solvents and small molecules may cause shrinkage stress inside the material, affecting the mechanical and mechanical properties of the material; There is also the technology of directly dispersing nanoparticles in polyamic acid solution to prepare polyimide film with corona resistance, but due to the large specific surface area and surface energy of nanoparticles, there is a strong interaction between the particles , easy to agglomerate, and the polyamic acid solution itself has a high viscosity, it is difficult to achieve the ideal nanoscale composite of nanoparticles and polyamic acid, and finally the mechanical properties of the prepared polyimide film are poor.

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