Corona-resistant polyimide film and preparation method thereof

Abstract

The invention provides a corona-resistant polyimide film and a preparation method thereof. The method comprises the following steps: uniformly dispersing a first inorganic filler, a second inorganic filler and a coupling agent in a solvent to obtain nanometer slurry, adding a dehydrating agent and a catalyst, and carrying out uniform stirring and mixing to obtain a nanometer hybrid solution; dissolving diamine in a solvent under the protection of an inert atmosphere, and then adding dianhydride for condensation polymerization to obtain polyamide acid resin; and uniformly mixing the nanometer hybrid solution with the polyamide acid resin to obtain precursor resin, and carrying out tape casting, stretching and high-temperature heat setting on the precursor resin to obtain the corona-resistant polyimide film. According to the method, the first inorganic filler and the second inorganic filler with different particle sizes are introduced into the film, and a chemical imidization method is cooperatively used for allowing the inorganic fillers to form a uniform heat conduction network in the film, so the corona resistance, the heat conduction performance, the adhesive property and the mechanical property of the film are improved.

Description

technical field [0001] The invention belongs to the technical field of polymer materials, and in particular relates to a corona-resistant polyimide film and a preparation method thereof. Background technique [0002] With the rapid development of modern power electronics technology, with the advantages of energy saving, the use of variable frequency speed regulation motors is more and more widely used, but the frequency conversion motors mostly use pulse width modulation (PWM) to drive pulse speed regulation technology, which increases the motor stator winding voltage. Amplitude, and high temperature is formed locally, it is easy to generate severe partial discharge (corona) under the condition of high pressure and high temperature, which greatly reduces the life of the motor insulation system. [0003] At present, the use of nanomaterials to modify polyimide films is considered to be an effective means to improve the life of corona resistance. For example, Chinese patent C...

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Problems solved by technology

[0004] Although these methods have improved the corona resistance life of the polyimide film to a certain extent, due to the single type and size of the added inorganic fillers, the fillers are piled up It is not tight, the heat conduction channel is limited, and ultimately the improvement of the corona-resistant life of the film material is limited; moreover, most of the corona-resistant polyimide films used in the motor must be glued first and then wrapped into magnet wires However, the surface energy of the film prepared with a single small-sized filler is low and too smooth, resulting in low adhesion of the film to the substrate

At the same time, these methods all use thermal imidization technology, which simply relies on heating to cyclize polyamic acid into polyimide. During the long-term heating process, polyamic acid will inevitably be partially degraded, thereby reducing the overall thickness of the film. performance

In addition, the doping of nanomaterials in these methods generally adopts the blending method or in-situ polymerization method. The blending method is to stir the resin and nano-slurry at a high speed before forming a film. However, due to the large specific surface area of ​​the inorganic filler, it is easy to agglomerate and Settling, it is difficult to distribute evenly in the high-viscosity system, thus affecting the film performance; while the in-situ polymerization method is to first add nanomaterials to the solvent, and then add diamine and dianhydride monomers for polycondensation reaction, although in the initial stage the system The viscosity is low, and the nanomaterials are uniformly distributed, but the polycondensation of polyamic acid is an exothermic reaction, and the heat generated at the moment of the reaction will promote the secondary agglomeration of the nanomaterials, which ultimately reduces the overall performance of the film.

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