CN-121975234-A - Polypropylene dielectric film based on fluorinated polypropylene particles, preparation method and application

CN121975234ACN 121975234 ACN121975234 ACN 121975234ACN-121975234-A

Abstract

The invention relates to the technical field of dielectric films and discloses a polypropylene dielectric film based on fluorinated polypropylene particles, a preparation method and application thereof, wherein the preparation method comprises the following steps of 1, mixing polypropylene and surface fluorinated polypropylene to form a mixture; 70-95 parts of polypropylene and 5-30 parts of surface fluorinated polypropylene in the mixture; the method comprises the steps of mixing a mixture with 100 parts in total, carrying out melt blending and hot press molding on the mixture obtained in the step 1 to obtain a sheet to be stretched, carrying out bidirectional synchronous biaxial stretching on the sheet to be stretched to obtain a required dielectric film, mixing fluorinated polypropylene particles with a polypropylene matrix, and effectively avoiding phase boundary or agglomeration, wherein after a fluorine group is introduced, the fluorine group can induce stronger oriented polarization under the action of an alternating electric field due to high dipole moment of the fluorine group, and electron traps are formed on the surface and inside of the film, so that the dielectric constant of the film is effectively improved and conduction loss is inhibited.

Inventors

HAN RUI
ZHAO CAN
NIE MIN
WU QI
WAN WEICAI
LI GUANGZHAO
YANG CHANGHUA

Assignees

西华大学
成都十米云帆科技有限公司

Dates

Publication Date: 20260505
Application Date: 20260407

Claims (10)

1. A method for preparing a polypropylene dielectric film based on fluorinated polypropylene particles, comprising the steps of: Step 1, mixing polypropylene and surface fluorinated polypropylene to form a mixture, wherein 70-95 parts of polypropylene and 5-30 parts of surface fluorinated polypropylene in the mixture are mixed, and the total weight of the mixture is 100 parts; step 2, the mixture obtained in the step 1 is subjected to melt blending and hot press molding to obtain a sheet to be stretched; And 3, carrying out bidirectional synchronous biaxial stretching on the sheet to be stretched to obtain the required dielectric film.
2. The method for preparing a polypropylene dielectric film based on fluorinated polypropylene particles according to claim 1, wherein the surface fluorinated polypropylene is prepared by the following steps: and (3) carrying out fluorination treatment for 1.5-2.5 hours under the conditions of 50 ℃ and 500 mbar by adopting mixed gas consisting of fluorine and nitrogen.
3. The preparation method of the polypropylene dielectric film based on the fluorinated polypropylene particles, which is characterized in that the stretching rate of the bi-directional synchronous biaxial stretching process is 20-40%/s, and the stretching rate is 450% -600% ×600%.
4. A method of producing a polypropylene dielectric film based on fluorinated polypropylene particles according to claim 3, further comprising the steps of: Preheating the sheet to be stretched, wherein the preheating temperature is 158-165 ℃, the preheating time is 30-90 s, and performing biaxial synchronous biaxial stretching under the preheating temperature condition.
5. The method for producing a polypropylene dielectric film based on fluorinated polypropylene particles according to claim 1, wherein the melt blending is performed by a twin screw extruder at a melting temperature of 190 ℃.
6. The method for producing a polypropylene dielectric film based on fluorinated polypropylene particles according to claim 5, wherein the twin-screw extruder has a screw speed of 50 rpm.
7. The method for producing a polypropylene dielectric film based on fluorinated polypropylene particles according to claim 1, wherein the hot press molding is performed first with hot press and then with cold press.
8. The method for preparing a polypropylene dielectric film based on fluorinated polypropylene particles according to claim 7, wherein the hot pressing is carried out at 185-195 ℃ under a pressure of 5MPa for 5-8 min; The cold pressing temperature was 30 ℃, the pressure was 5 MPa, and the time was 5 min.
9. The polypropylene dielectric film based on fluorinated polypropylene particles obtained by the preparation method according to any one of claims 1 to 8, wherein the dielectric film is obtained by uniformly dispersing fluorinated polypropylene in a polypropylene matrix and molding.
10. Use of a polypropylene dielectric film based on fluorinated polypropylene particles according to claim 9 for the preparation of polymer film capacitors.

Description

Polypropylene dielectric film based on fluorinated polypropylene particles, preparation method and application Technical Field The invention relates to the technical field of dielectric films, in particular to a polypropylene dielectric film based on fluorinated polypropylene particles, a preparation method and application thereof. Background The film capacitor becomes a core device in the modern energy fields of hybrid electric vehicles, power grid frequency adjustment, high-voltage transmission systems and the like by virtue of the rapid charge and discharge capacity, high voltage resistance and excellent power density. As the current polymer dielectric marker post material, biaxially oriented polypropylene BOPP is always the preferred material of the film capacitor by virtue of low conductive loss, easy processing property and high resistance property. In recent years, the demands for extremely high temperature environmental applications have proliferated, but BOPP has a lower intrinsic glass transition temperature, resulting in significant deterioration of its dielectric properties at high temperatures (> 80 ℃). Under the high-temperature and high-electric-field environment, the amorphous region chain segment is highly activated, so that not only is the conductive loss increased, but also the charge and discharge efficiency (eta) of the film capacitor is suddenly reduced. In addition, the generation of large amounts of joule heat may cause thermal runaway. Therefore, suppressing the conduction loss at high temperature is critical to improving the high temperature energy storage performance of BOPP. The conduction loss of a polymer dielectric increases exponentially at high temperatures, mainly due to thermally activated carriers in the bulk of the polymer and the charge injected by the metal electrode. The formation of a local deep trap by doping a narrow bandgap inorganic material into a polymer is a well-established high-efficiency strategy in the industry, which can capture carriers and inhibit conduction loss at high temperature. Due to the fermi level difference, the potential well formed at the interface of the polymer matrix and the inorganic material can trap electrons and holes, preventing them from escaping. However, the compatibility problem and aggregation phenomena of nanofillers in polymers remain a difficult point of investigation. The high surface energy tends to cause spontaneous aggregation of the inorganic material, which reduces interface contact area, and makes trap depth shallow or even vanish. On the other hand, under the condition of high temperature and high electric field, carriers generated by the electrode can easily break through the electrode/dielectric energy barrier and migrate to the polymer matrix to trigger Schottky emission. To enhance the energy barrier height and disperse the electrode carriers, a wide bandgap inorganic barrier layer is typically coated on the surface of the polymer dielectric. However, the construction of the layer-by-layer structure requires precise equipment such as magnetron sputtering, plasma activation and the like. In addition, the inorganic layer and the polymer layer often have poor adhesion and even delamination due to excessively large young's modulus differences. The direct gas fluorination technique is capable of replacing hydrogen atoms on the surface of the polymer film with fluorine atoms of high electronegativity. Research shows that introducing fluorine atoms on the surface of the dielectric film can enhance electron affinity, form deep level traps and inhibit electron transport. More importantly, such chemical bond substitution is effective in avoiding compatibility problems between the inorganic layer/filler and the polymer matrix. However, direct gas fluorination reactions still present several difficult problems that remain the major bottleneck in achieving stable high temperature capacitance enhancement and industrial applications. First, most fluorination equipment has severe limitations on the thickness of the sample, making it difficult to directly fluorinate the film. It is therefore often necessary to carry out the fluorination on a thicker pre-stretched sheet, but during biaxial stretching the fluorinated regions will be stretched into isolated islands, resulting in a large area of the polymer film being exposed to the electrode surface, thereby increasing the conduction losses. Second, the fluorinated surface layer inhibits schottky emissions while carriers within the polymer body can still be thermally activated under high temperature and high electric field conditions. Disclosure of Invention Aiming at the problems existing in the prior art, the invention provides a polypropylene dielectric film based on fluorinated polypropylene particles, a preparation method and application thereof. The technical scheme adopted by the invention is that the preparation method of the polypropylene dielectric film based on the fluorin