CN-121270989-B - Method for modifying polypropylene energy storage medium film through melt blending and application

Abstract

A method for modifying a polypropylene energy storage medium film by melt blending and application thereof belong to the field of manufacturing of medium materials for electric element components. The invention aims to solve the problem of insulation failure caused by embrittlement cracking and mechanical property degradation of the existing polypropylene film in a low-temperature environment. The invention uses homopolymerized polypropylene and ternary copolymerized polypropylene resin as raw materials, and is prepared by combining melt blending extrusion and unidirectional stretching rolling process. Due to the introduction of ethylene and butene in the ternary polymerization polypropylene, the regular arrangement of polypropylene chain segments is inhibited, the flexibility of molecular chains is enhanced, and the glass transition temperature is reduced. On the other hand, the increased proportion of amorphous regions also provides sufficient free volume for the methyl orientation polarization of the weak polar groups of the polypropylene molecular main chain, and the orientation polarization effect is enhanced. Compared with a pure polypropylene energy storage medium film, the blended polypropylene energy storage medium film prepared by the invention has the advantages that the elongation at break can be increased by 43.6%, and the blended polypropylene energy storage medium film has application prospect under extreme working conditions.

Inventors

• ZHANG TIANDONG
• SUN HAI
• LU YUMENG
• YIN CHAO
• ZHANG CHANGHAI
• CHI QINGGUO

Assignees

• 哈尔滨理工大学

Dates

Publication Date

20260512

Application Date

20251209

Claims (6)

1. 1. The method for modifying the polypropylene energy storage medium film by melt blending is characterized by comprising the following steps: 1. uniformly mixing the dried homo-polypropylene resin and the dried ternary polymerization polypropylene resin to obtain a raw material; The mass fraction of the ternary polymerization polypropylene resin in the raw materials in the first step is 5-10 wt%; The ternary polymerization polypropylene resin in the first step is a polypropylene material prepared by copolymerizing three monomers of propylene, ethylene and 1-butene; 2. setting the heating zone temperature, the head extrusion temperature and the screw rotation speed of a double-screw extruder, and feeding raw materials into a hopper of the extruder; 3. drawing the melted resin onto the surface of a chilled roller for cooling, and then carrying out unidirectional stretching; the temperature of the chilling roller in the third step is 130-150 ℃; 4. And rolling the stretched film to obtain the blended modified polypropylene energy storage medium film.
2. 2. The method for modifying a polypropylene energy storage medium film by melt blending according to claim 1, wherein the heating zone temperature in the second step is 190 ℃ to 210 ℃.
3. 3. The method of claim 1, wherein the extrusion temperature of the die in the second step is 210 ℃.
4. 4. The method for modifying a polypropylene energy storage medium film by melt blending according to claim 1, wherein the screw rotation speed in the second step is 80r/min.
5. 5. The method for modifying the polypropylene energy storage medium film by melt blending according to claim 1, wherein the rotational speed of a roller in the winding process in the step four is 90 r/min-100 r/min, and the tension of the roller is 40N-50N.
6. 6. The application of the blended modified polypropylene energy storage medium film prepared by the method according to any one of claims 1-5, which is characterized in that the blended modified polypropylene energy storage medium film is applied to a capacitor.

Description

Method for modifying polypropylene energy storage medium film through melt blending and application Technical Field The invention belongs to the field of manufacturing of dielectric materials for electric element components, and particularly relates to a method for modifying a polypropylene energy storage dielectric film by melt blending and application thereof. Background The capacitor is used as a basic electric element of an electronic circuit and is widely applied to the fields of high-voltage direct-current transmission converter stations, electromagnetic energy weaponry, new energy automobile electric control systems and the like. Among them, the polymer film capacitor has excellent power density, ultra-high cycle life and excellent self-healing characteristics, and becomes an indispensable element of modern electric power equipment. Currently biaxially oriented polypropylene (BOPP) is the main stream energy storage dielectric material for commercial thin film capacitors by virtue of high insulating properties, low dielectric loss and good processability. However, researches on the reduction of the service life of the polypropylene film caused by the deterioration of mechanical properties under the low-temperature working condition are fresh. The lowest temperature in winter in the cold region of China can reach-40 to-50 ℃, at this time, polypropylene can undergo the transformation from a high-elastic state to a glassy state, and the problem of insulation failure caused by the deterioration of mechanical properties in a low-temperature environment is to be solved. While improving the low-temperature mechanical property, the industrial production flow of the good compatible film capacitor element reel-to-reel is of great importance, so that the development of a dielectric film for a capacitor with excellent mechanical property and processing compatibility is of great importance. Disclosure of Invention The invention aims to solve the problem of insulation failure caused by embrittlement cracking and mechanical property degradation of the existing polypropylene film in a low-temperature environment, and provides a method for modifying a polypropylene energy storage medium film by melt blending and application thereof. The method for modifying the polypropylene energy storage medium film by melt blending is specifically completed by the following steps: 1. uniformly mixing the dried homo-polypropylene resin and the dried ternary polymerization polypropylene resin to obtain a raw material; 2. setting the heating zone temperature, the head extrusion temperature and the screw rotation speed of a double-screw extruder, and feeding raw materials into a hopper of the extruder; 3. drawing the melted resin onto the surface of a chilled roller for cooling, and then carrying out unidirectional stretching; 4. And rolling the stretched film to obtain the blended modified polypropylene energy storage medium film. The blended modified polypropylene energy storage medium film is applied to a capacitor. The invention provides a preparation method and application of a polypropylene energy storage medium film capable of realizing large-scale preparation by combining a melt blending extrusion technology with a unidirectional stretching winding process, wherein the prepared blending modified polypropylene energy storage medium film contains ethylene and butylene chain segments, so that the regular arrangement of polypropylene molecular chain segments can be effectively reduced, the modification of the film from rigidity to flexibility is realized, the elongation at break of the prepared blending modified polypropylene energy storage medium film is up to 950.24%, compared with an unblended modified polypropylene film, the free volume of the prepared blending modified polypropylene energy storage medium film is increased, and meanwhile, the free volume is increased, and sufficient free volume is provided for the oriented polarization of a weak polar group methyl on a polypropylene molecular main chain, and meanwhile, the discharge energy density and the charge-discharge efficiency of the blending modified polypropylene energy storage medium film are respectively 1.65J/cm 3 and 88.3%, the high-temperature energy storage performance is excellent, and the excellent cycling stability is shown in a five-thousand charge-discharge test process. Compared with the prior art, the invention has the remarkable effects that: 1. The invention is different from laboratory-level small-scale modification, can realize the industrial production flow of 'roll-to-roll', has simple and environment-friendly preparation process, and can carry out macro preparation of the thickness-uniform blending modified polypropylene energy storage medium film; 2. The invention realizes the large-scale preparation of the modified film by the melt blending extrusion mode of the homo-polypropylene and ternary polymerization polypropylene resin (the ternary polymeri