Polypropylene composite material as well as preparation method and application thereof

Abstract

The invention discloses a polypropylene composite material as well as a preparation method and application thereof, and belongs to the technical field of polymer insulation. The material is prepared from the following components in parts by weight: 75 to 99.5 parts of polypropylene and 0.5 to 25 parts of imidazole monomers. According to the material, the imidazole monomer is introduced into the polypropylene by a simple and practical technology, so that the batch production of the modified PP is realized; due to the introduction of the imidazole monomer, a charge trap can be constructed in a polypropylene matrix, the mechanical property of the polypropylene matrix is improved, and the high-voltage resistance of PP in a high-temperature environment is improved; the introduction of the polar monomer improves the polarity of the PP, enhances the dielectric property of the PP, and can well inhibit the loss so as to greatly improve the energy storage density. And putting the modified polypropylene particles into a melt extrusion casting film machine to prepare the modified polypropylene film for subsequent performance detection. The power capacitor film provided by the invention has excellent electrical properties, and has high-density deep charge trap, high direct current breakdown field strength, high energy storage density and low energy loss in a high-temperature environment.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer insulation, and in particular to a polypropylene composite material and a preparation method and application thereof. Background Art

[0002] Metallized film capacitors are widely used in modern electronic devices as energy storage devices. With the rapid development of automotive electronics, power systems, and aerospace, metallized film capacitors need to operate reliably under extreme conditions, which poses a huge challenge to their high voltage resistance, high temperature resistance, and high energy storage performance. Polypropylene has become the most advanced and widely used metallized dielectric film due to its excellent high voltage resistance, extremely low dielectric loss, excellent flexibility, good self-healing properties, and outstanding cost-effectiveness. However, polypropylene will accelerate chemical degradation processes such as thermal oxidation and molecular chain breakage under high temperature conditions, which will form more conductive paths or defects. This will cause the capacitor to fail prematurely in a high temperature environment, reducing its operating life and reliability in critical applications. These fatal weaknesses highlight the necessity of polypropylene modification.

[0003] In order to solve the problem of insufficient voltage resistance and energy storage performance of polypropylene under high temperature environment, relevant researchers at home and abroad have conducted a lot of research; through the formula U e =1 / 2(ε0ε r E b 2 ) It can be seen that to improve the energy storage performance of polypropylene in high temperature environment, it is necessary to improve its dielectric properties and high voltage resistance in high temperature environment; however, compared with improving the dielectric properties of polypropylene, improving its high voltage resistance in high temperature environment is a faster and more effective method; chemical modification grafting is one of the modification methods that has been studied more frequently; researchers have introduced cross-linking structures on the polypropylene molecular chain to suppress the sharp increase in leakage loss of polypropylene under high temperature and high electric field, thereby improving its high voltage resistance in high temperature environment; however, factors such as the complex chemical grafting process, high research cost, and unstable performance have forced researchers to seek more economical and efficient modification methods; physical blending is currently one of the simplest, lowest cost, and most effective modification methods; introducing wide-bandgap high-dielectric inorganic nanomaterials into the polypropylene matrix by blending can significantly improve the dielectric properties and high voltage resistance of polypropylene, thereby improving its energy storage performance; however, there are serious compatibility and dispersibility shortcomings between inorganic nanofillers and the polypropylene matrix. A large number of interface defects will cause a rapid accumulation of charge at the interface, which will cause the high voltage resistance and energy storage performance of the composite polypropylene film to be significantly reduced in high temperature environment, seriously restricting the application of polypropylene film capacitors. Summary of the Invention

[0004] The present invention provides a polypropylene composite material and a preparation method and application thereof, aiming to improve the interface defects, structural stability and mechanical properties of the composite material and solve the problem that polypropylene is prone to breakdown at high temperatures.

[0005] A first aspect of the present invention provides a polypropylene composite material comprising the following components in parts by weight: 75-99.5 parts of polypropylene and 0.5-25 parts of imidazole monomers.

[0006] In some embodiments of the first aspect, the imidazole monomer includes at least one of 2-(3-amino-4-oxophenyl)benzimidazole and 2-phenylbenzimidazole.

[0007] In some embodiments of the first aspect, the particle size of the imidazole monomer is 1-5 μm.

[0008] In some embodiments of the first aspect, the polypropylene is ultra-low ash polypropylene.

[0009] In some embodiments of the first aspect, the weight ratio of the polypropylene component is 85-95 parts, and the weight ratio of the imidazole monomer component is 5-15 parts.

[0010] In some embodiments of the first aspect, the polypropylene composite material further comprises the following components in parts by weight: 0.2-2 parts of an auxiliary agent, wherein the auxiliary agent is one or more of a plasticizer, an antioxidant, and a light stabilizer.

[0011] The second aspect of the present invention provides a method for preparing the polypropylene composite material according to the first aspect, comprising the following steps: melt blending the components in proportion, and then melt-extruding and granulating to obtain the polypropylene composite material.

[0012] The third aspect of the present invention provides a power capacitor film, which is made of the polypropylene composite material described in the first aspect.

[0013] In some embodiments of the third aspect, the power capacitor film has a thickness of 2-20 μm.

[0014] The fourth aspect of the present invention provides an application of the polypropylene composite material described in the first aspect or the power capacitor film described in the third aspect in a power capacitor, wherein the power capacitor includes any one of a high-energy storage pulse capacitor, an automotive capacitor, a power system capacitor, and an aerospace capacitor.

[0015] It can be seen from the above technical solutions that the present invention has the following advantages:

[0016] This embodiment provides a polypropylene composite material. By introducing imidazole monomers into polypropylene, the polar groups of the imidazole monomers are introduced into the polypropylene to enhance its dielectric properties. After the monomers are introduced, the weak chemical interactions between the polypropylene molecular chains are enhanced, that is, charge traps are constructed in the polypropylene matrix to enhance the mechanical properties, significantly improving the breakdown voltage and energy storage density of the composite material, making it suitable for energy storage application scenarios requiring high electric fields and high energy density. At the same time, due to the introduction of the imidazole monomers, the imidazole monomers are fully organic monomers and have good compatibility with polypropylene, which can effectively avoid interfacial defects and prevent the formation of major carrier transmission channels in the high-temperature stage. In addition, the thermal decomposition temperature of the composite material is significantly increased, extending the service life of the material in a high-temperature environment, and effectively promoting the use of the polypropylene composite material in a high-temperature environment. Therefore, the polypropylene composite material of this embodiment has the characteristics of high-temperature resistance and high-voltage resistance, and effectively solves the problem of the prior art that polypropylene is prone to breakdown at high temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 A process diagram for preparing a power capacitor film according to an embodiment of the present invention;

[0019] Figure 2 A breakdown strength diagram provided by an embodiment of the present invention;

[0020] Figure 3 A graph showing dielectric constant and dielectric loss in accordance with an embodiment of the present invention;

[0021] Figure 4 This is an energy density curve provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0022] The embodiments of the present invention provide a polypropylene composite material, a preparation method thereof, and an application thereof, aiming to improve the interface defects, structural stability, and mechanical properties of the composite material and solve the problem that polypropylene is prone to breakdown at high temperatures.

[0023] In order to make the purpose, features, and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0024] In a first aspect, the present embodiment provides a polypropylene composite material. The polypropylene composite material includes the following components in parts by weight: 75-99.5 parts of polypropylene and 0.5-25 parts of imidazole monomer.

[0025] In this embodiment, polypropylene is used as the matrix material and imidazole monomers are used as the reinforcing components. They are a class of organic compounds containing an imidazole ring structure. The imidazole monomers are introduced into polypropylene. The benzimidazole ring in the polar molecular structure of the imidazole monomers can enhance the interaction between polypropylene segments, and the polar structure can act as a charge trap to inhibit the migration of carriers, thereby significantly improving the high-voltage resistance. At the same time, the introduction of imidazole monomers can improve the energy storage density of the composite material. Moreover, due to the introduction of imidazole monomers, the imidazole monomers are all-organic monomers and have good compatibility with polypropylene, which can effectively avoid interface defects and prevent the formation of major carrier transmission channels in the high-temperature stage, effectively promoting the use of polypropylene composite materials in high-temperature environments and significantly improving the high-temperature resistance.

[0026] Compared with the prior art, the prior art has disclosed a crystalline material with a three-dimensional pore structure formed by connecting organic molecules with nano-zeolite imidazole ester skeleton materials and metal atoms as the center; the present solution has the following advantages compared with the prior art: first, the dielectric properties are good, because the imidazole monomers used in the present solution are all-organic small molecules as the blended fillers, the dielectric properties of polypropylene can be improved by the chemical properties of the monomers; second, the interface defects can be avoided, because the imidazole monomers are all-organic monomers, the interface problems can be effectively avoided, that is, they have good compatibility with polypropylene, avoiding the inevitable generation of more interface defects in the prior art, which will become the main transmission channel for carriers at high temperature, inhibiting The problem of using polypropylene film dielectrics in high temperature environments; third, the distribution is more uniform. The molecular structure of imidazole monomers is relatively simple and the size is small. During the blending process, they can diffuse and move more freely in the gaps between the molecular chains of polypropylene, and more easily enter the internal microstructure of polypropylene, so there is a better chance of achieving a more uniform distribution and avoiding the problem of uneven mixing in the existing technology; fourth, the breakdown risk is small. This solution can regulate the molecular chain structure and its crystallization state, improve interface defects, structural stability and mechanical properties, and thus significantly inhibit the mechanical breakdown, thermal breakdown and electrical breakdown that may occur in polypropylene at high temperatures, thereby achieving the effect of significantly improving the high temperature resistance and high voltage resistance of polypropylene film capacitors.

[0027] In a specific embodiment, a feasible method for polypropylene is further provided, wherein the polypropylene is ultra-low ash polypropylene, wherein ultra-low ash polypropylene refers to an ash content of tens of ppm or even lower. In specific implementation, the use of polypropylene with ultra-low ash content can reduce impurities in the polypropylene composite material, thereby improving the structural stability and mechanical properties of the polypropylene composite material.

[0028] In one embodiment, polypropylene is used as the matrix material, and homopolymer polypropylene or block copolymer polypropylene can be selected. The selected polypropylene can have a narrow molecular weight distribution and a moderate melt flow rate, so that it has good processability in subsequent blending and processing.

[0029] In a specific embodiment, a feasible method for implementing the imidazole monomer is further provided, wherein the imidazole monomer is at least one of 2-(3-amino-4-oxophenyl)benzimidazole and 2-phenylbenzimidazole.

[0030] In one embodiment, the particle size of the imidazole monomer is 1-5 μm, ensuring that the particle size of the imidazole monomer is uniform and within the range of 1-5 μm, so that the imidazole monomer can be fully mixed in the polypropylene, avoiding the degradation of the performance of the polypropylene composite material due to uneven dispersion during the blending process.

[0031] In a specific embodiment, a ratio of polypropylene and imidazole monomers is further provided, wherein the weight parts of polypropylene are 85-95 parts and the weight parts of the imidazole monomers are 5-15 parts. For example, 85 parts of polypropylene and 15 parts of imidazole monomers form a polypropylene composite material, or 90 parts of polypropylene and 10 parts of imidazole monomers form a polypropylene composite material, or 95 parts of polypropylene and 5 parts of imidazole monomers form a polypropylene composite material. After adopting this ratio, the DC breakdown field strength of polypropylene can be increased to more than 800 MV / m at room temperature, and can still reach more than 650 MV / m in a high temperature environment of 100-120°C, which highlights the high pressure resistance and high temperature resistance advantages of the ratio adopted in this embodiment.

[0032] In a specific embodiment, an addible component of a polypropylene composite material is further provided. In addition to the above-mentioned imidazole monomer and polypropylene, the polypropylene composite material also includes 0.2-2 parts of an auxiliary agent, wherein the auxiliary agent is one or more of a plasticizer, an antioxidant, and a light stabilizer. After specific implementation, the addition of the auxiliary agent can improve the processing performance and service life of the composite material.

[0033] In one embodiment, the auxiliary agent is a plasticizer, and the plasticizer is a low-volatile phthalate plasticizer, and the addition amount is 0.5-2 wt % to improve the flexibility and processing fluidity of the polypropylene composite material.

[0034] In one embodiment, the antioxidant is a hindered amine antioxidant or a hindered phenol antioxidant. The hindered phenol antioxidant may be antioxidant 1010 or antioxidant 1076. The added amount is 0.2-1 wt % to improve the antioxidant capacity of the polypropylene composite material.

[0035] In one embodiment, the light stabilizer is a benzophenone, benzotriazole, or salicylate compound, which is an additive used to inhibit or slow down the photodegradation and photooxidation reaction of the polypropylene composite material under the action of light, thereby extending the service life of the polypropylene composite material.

[0036] Please refer to Figure 1 A second aspect of this embodiment provides a method for preparing a polypropylene composite material, comprising the following steps:

[0037] S1, material pretreatment, pretreating the imidazole monomer and polypropylene to obtain pretreated imidazole monomer and pretreated polypropylene;

[0038] S2, melt blending, melt blending the pretreated imidazole monomer and the pretreated polypropylene according to a proportion;

[0039] S3, extruding and granulating to obtain the polypropylene composite material.

[0040] In this embodiment, the prepared polypropylene composite material has a 30-50% higher breakdown strength and a 20-40% higher energy storage density than traditional pure polypropylene materials. Moreover, after adopting the melt blending method, the process for preparing the polypropylene composite material is simple, suitable for industrial large-scale production, and does not require complicated post-processing steps.

[0041] In a specific embodiment, an implementable method in step S1 is further provided, specifically: the imidazole monomer powder is ball-milled or ultrasonically treated to ensure that its particle size is uniform and within the range of 1-5 microns, thereby obtaining a pretreated imidazole monomer; at the same time, the polypropylene is preheated to 30-120° C. to remove adsorbed moisture, and an antioxidant is added for pretreatment to obtain the pretreated polypropylene.

[0042] In a specific embodiment, an implementable method in step S2 is further provided, specifically:

[0043] S20, physically blending the pretreated polypropylene and the imidazole monomer according to a designed ratio (weight components: 75-99.5 parts of polypropylene, 0.5-25 parts of imidazole monomer), so that the imidazole monomer and the polypropylene are uniformly mixed.

[0044] S21, placing the imidazole monomer and polypropylene mixture into a twin-screw extruder for melt blending.

[0045] In one embodiment, the blending temperature is set to 160-250° C., the screw speed is 70-150 r / min, the blending time is 1-15 minutes, and the processing temperature is controlled within the melting temperature range of polypropylene to ensure that the imidazole monomer is evenly dispersed in the matrix material.

[0046] In a specific embodiment, an implementable method of step S3 is further provided, wherein the blended composite material is extruded through a twin-screw extruder and cooled and granulated to form uniform composite material particles.

[0047] In one embodiment, the extrusion temperature is set to 150-260° C., and the cooling rate is controlled to avoid excessive crystallization of the material resulting in microstructural defects.

[0048] Please refer to Figure 1 The third aspect of this embodiment provides a power capacitor film, which is prepared from a polypropylene composite material as a raw material, and specifically includes the following steps:

[0049] The granular polypropylene composite material is put into a melt extrusion cast film machine to prepare a high-energy storage, high-temperature resistant power capacitor film.

[0050] In this embodiment, the prepared power capacitor film has the characteristics of high temperature resistance and high voltage resistance, and can be widely used in various modern electronic devices.

[0051] In one embodiment, the temperature of the cast film machine is 110° C.-260° C., and the film winding speed is 1-20 r / min.

[0052] In one embodiment, the thickness of the power capacitor film is 2-20 μm.

[0053] The fourth aspect of this embodiment provides an application of a polypropylene composite material. The polypropylene composite material can be used in the field of preparing power capacitors. The power capacitor equipment that introduces the polypropylene composite material has significantly improved dielectric properties, mechanical properties and energy storage density, and is suitable for applications in scenarios requiring high electric fields and high energy density.

[0054] In one application scenario, polypropylene composites can be used as preparation materials for metallized power capacitors. Polypropylene composite materials can increase the high-voltage and high-temperature resistance of metallized power capacitors. Metallized power capacitors are widely used as energy storage devices in various modern electronic devices, including but not limited to high-energy storage pulse capacitors, electric / hybrid vehicle electronic equipment, power system equipment and aerospace equipment, that is, power capacitors include any one of high-energy storage pulse capacitors, automotive capacitors, power system capacitors, and aerospace capacitors.

[0055] Example 1

[0056] Example 1 of the present invention provides a power capacitor film, which includes 4.99 wt% of 2-(3-amino-4-oxophenyl)benzimidazole, 95 wt% of ultra-low ash polypropylene and an antioxidant (all samples are added with 0.01 wt% of 1076 antioxidant to maintain anti-degradation ability in a high temperature environment). The thickness of the power capacitor film is 10 μm.

[0057] The preparation of the power capacitor film of this embodiment includes the following steps:

[0058] Step 1: pretreating 5 wt% of 2-(3-amino-4-oxophenyl)benzimidazole and 95 wt% of ultra-low ash polypropylene to obtain pretreated powder or granules, wherein 2-(3-amino-4-oxophenyl)benzimidazole is ball-milled or ultrasonically treated to obtain a powder with a uniform particle size in the range of 1-5 μm, and the polypropylene is preheated to 90°C to remove adsorbed moisture, and an antioxidant is added for pretreatment.

[0059] Step 2: Place the pretreated powder or granules into a twin-screw extruder for melt blending, wherein the blending temperature is set to 200° C., the screw speed is 140 rpm, and the blending time is 7 minutes.

[0060] Step 3: extrude the blended composite material through a twin-screw extruder and cool and granulate to form uniform polypropylene composite material particles, wherein the extrusion temperature is set to 220°C.

[0061] Step 4: Put the polypropylene composite material particles into a melt extrusion cast film machine to prepare a power capacitor film, wherein the temperature of the cast film machine feeding zone is 190°C, the temperature of the front area of the screw is 220°C, the temperature of the middle area of the screw is 220°C, the temperature of the rear area of the screw is 220°C, the temperature of the extrusion die head area is 220°C, and the film winding speed is 1-20 r / min.

[0062] Example 2

[0063] Example 2 of the present invention provides a power capacitor film, which has a structure and preparation method basically the same as those in Example 1, except that the composition ratio of the power capacitor film is different, that is, it is not 5 wt% of 2-(3-amino-4-oxophenyl)benzimidazole, 95 wt% of ultra-low ash polypropylene and an oxidant (all samples are added with 0.01 wt% of 1076 antioxidant to maintain anti-degradation ability under high temperature environment), but 9.99 wt% of 2-(3-amino-4-oxophenyl)benzimidazole, 90 wt% of ultra-low ash polypropylene and an oxidant (all samples are added with 0.01 wt% of 1076 antioxidant to maintain anti-degradation ability under high temperature environment).

[0064] Example 3

[0065] Example 3 of the present invention provides a power capacitor film, which has a structure and preparation method that are basically the same as those in Example 1, except that the composition ratio of the power capacitor film is different, that is, it is not 4.99 wt% of 2-(3-amino-4-oxophenyl)benzimidazole, 95 wt% of ultra-low ash polypropylene and an oxidant (all samples are added with 0.01 wt% of 1076 antioxidant to maintain anti-degradation ability under high temperature environment), but 15 wt% of 2-(3-amino-4-oxophenyl)benzimidazole, 85 wt% of ultra-low ash polypropylene and an oxidant (all samples are added with 0.01 wt% of 1076 antioxidant to maintain anti-degradation ability under high temperature environment).

[0066] Comparative Example 1

[0067] The comparative example of the present invention provides a pure polypropylene film, which has the same process conditions as Example 1.

[0068] It can be seen from Examples 1 to 3 that Examples 1 to 3 are all power capacitor films with imidazole monomers. The difference between the three lies in the different ratios. The power capacitor film prepared in Example 1 is referred to as C2-1, the power capacitor film prepared in Example 2 is referred to as C2-2, the power capacitor film prepared in Example 3 is referred to as C2-3, and the pure polypropylene film prepared in Comparative Example 1 is referred to as PP.

[0069] Next, performance characterization tests were carried out on Examples 1 to 3 and Comparative Example 1, including breakdown strength test, energy storage performance test and thermal stability test. The breakdown strength test used a standard electrical breakdown test instrument to perform a breakdown strength test on the composite material. The energy storage performance test measured the energy storage density of the composite material by a capacitor charge and discharge test. The thermal stability test used a thermogravimetric analyzer to characterize the thermal stability of the composite material. The test results are shown in FIG. Figures 2 to 4 shown.

[0070] Figure 2 The breakdown strength diagram shows that at room temperature, the breakdown field strength α values of C2-1, C2-2 and C2-3 can reach 768MV / m, 813MV / m and 802 MV / m; Under the conditions of 676MV / m, 679MV / m and 677MV / m, the breakdown field strength is Under the conditions of 100V / m, 100V / m and 100V / m, the breakdown field strengths are 636MV / m, 628MV / m and 675MV / m; under the conditions of 100V / m, 100V / m and 100V / m, the breakdown field strengths are 636MV / m, 628MV / m and 675MV / m. The breakdown strength of PP is only 651MV / m at room temperature. The lower one is only 563MV / m, The lower one is only 437MV / m, The lower one is only 343MV / m.

[0071] Depend on Figure 2 The test results show that the introduction of imidazole monomers effectively improves the breakdown voltage of polypropylene. The breakdown strength of the composite material is 30-50% higher than that of pure polypropylene, and it can withstand higher electric field strengths. The results also show that the introduction of imidazole monomers significantly increases the thermal decomposition temperature of the composite material, which is 15-30°C higher than that of pure polypropylene. It has good high-temperature thermal stability and is suitable for use in high-temperature environments.

[0072] Figure 3 is the dielectric constant and dielectric loss curve, Figure 3 (a) is the dielectric constant curve, Figure 3 (b) is the dielectric loss curve. Figure 3As shown in (a), at different Hz, the dielectric constants of C2-1, C2-2, and C2-3 are better than that of PP. The dielectric constant shows a trend of first increasing and then decreasing with the increase of AOBPH content. Among them, the dielectric constant of C2-2 reaches 2.7. And it maintains the excellent dielectric stability of PP. In addition, the dielectric loss of C2-1, C2-2, and C2-3 is basically consistent with the dielectric constant loss of PP, maintaining at 10 -3 to 10 -2 Within the range, it has very good loss performance.

[0073] Figure 4 The energy density curve shows the dielectric and energy storage properties of C2-1, C2-2 and C2-3 prepared in this embodiment. Under the electric field of 500 MV / m at room temperature, the energy storage density of C2-2 reaches the highest Ue=6.23 J / cm3, and the release efficiency is .

[0074] Depend on Figure 4 The test results show that the energy storage density of the composite material is 20-40% higher than that of pure polypropylene, and it still maintains excellent capacitance effect under higher electric field strength.

[0075] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

[0076] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations.

Claims

1. A polypropylene composite material, characterized in that The invention comprises the following components in parts by weight: 75-99.5 parts of polypropylene and 0.5-25 parts of imidazole monomer.

2. The polypropylene composite material according to claim 1, characterized in that The imidazole monomer includes at least one of 2-(3-amino-4-oxophenyl)benzimidazole and 2-phenylbenzimidazole.

3. The polypropylene composite material according to claim 1, characterized in that The particle size of the imidazole monomer is 1-5 μm.

4. The polypropylene composite material according to claim 1, characterized in that The polypropylene is ultra-low ash polypropylene.

5. The polypropylene composite material according to any one of claims 1 to 4, characterized in that: The weight portion of the polypropylene is 85-95 parts, and the weight portion of the imidazole monomer is 5-15 parts.

6. The polypropylene composite material according to claim 1, characterized in that The polypropylene composite material further comprises the following components in parts by weight: 0.2-2 parts of an auxiliary agent, wherein the auxiliary agent is one or more of a plasticizer, an antioxidant, and a light stabilizer.

7. A method for preparing a polypropylene composite material according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: melt-blending the components in proportion, and then melt-extruding and granulating to obtain the polypropylene composite material.

8. A power capacitor film, characterized in that: The polypropylene composite material is prepared by using the polypropylene composite material according to any one of claims 1 to 6. 9 . The power capacitor film according to claim 8 , wherein the thickness of the power capacitor film is 2-20 μm.

10. Use of the polypropylene composite material according to any one of claims 1 to 6 or the power capacitor film according to any one of claims 8 to 9 in a power capacitor, characterized in that: The power capacitor includes any one of a high energy storage pulse capacitor, an automotive capacitor, a power system capacitor, and an aerospace capacitor.

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