Organic semiconductor grafted polypropylene composite film and its preparation method and application

Abstract

The present invention provides an organic semiconductor grafted polypropylene composite film and its preparation method and application. In a first aspect, the present invention provides an organic semiconductor grafted polypropylene composite film, wherein organic semiconductor molecules are grafted onto at least part of the side chains of polypropylene; the electrical conductivity of the organic semiconductor molecules is 10 ‑10 The present invention grafts polypropylene with organic semiconductor small molecules, which helps to reduce the conductivity of polypropylene film under high temperature conditions, and improves its breakdown strength and energy storage density, promoting the stable operation of capacitors in a wider temperature range.

Description

Technical Field

[0001] The invention relates to an organic semiconductor grafted polypropylene composite film and a preparation method and application thereof, and relates to the technical field of dielectric energy storage materials. Background Art

[0002] Dielectric film capacitors have become fundamental components for charge storage and control in electronic devices and power systems. Biaxially oriented polypropylene (BOPP) holds the largest market share in commercial film capacitors and plays a crucial role in their operational stability. During continuous operation, capacitors are subjected to strong electrothermal fields, which not only exacerbate charge injection but also promote collision and recombination of carriers within the dielectric film, leading to a degradation of dielectric and capacitance properties. To ensure safe operation, BOPP film capacitors are typically limited to operating temperatures below ~85°C. However, due to Joule heat accumulation, internal device temperatures can reach as high as 105°C. Studies have shown that the conduction loss of BOPP film increases exponentially with increasing temperature from room temperature to 120°C, further exacerbating heat accumulation and leading to a sharp decrease in breakdown strength. The energy storage efficiency of BOPP film drops to ~65% at 120°C, severely threatening device stability and limiting the application of film capacitors under high-temperature conditions. However, in critical applications such as electric vehicles, operating temperatures can reach above 120°C, placing increasingly stringent requirements on dielectric film capacitors.

[0003] In these extreme temperature environments, auxiliary cooling systems are the traditional approach to addressing the gap between the capacitor's withstand temperature and the ambient temperature. This not only sacrifices economic efficiency but also hinders the development of lightweight and compact devices. To address this issue, various modification methods have been employed to tune the high-temperature capacitance of polymer films, with nanocomposites showing great potential. However, their effectiveness is limited by the dispersion and compatibility of nanofillers in the polymer matrix, making it difficult to achieve a comprehensive balance between breakdown strength, dielectric loss, and energy storage density. For example, the European GRIDABLE project developed PP / SiO2 nanocomposites for DC capacitors, demonstrating that SiO2 doping improves breakdown strength only in weak regions with non-ideal crystalline morphology. At room temperature and 80°C, the Weibull characteristic breakdown value of the nanocomposite film is reduced compared to that of the original PP. The agglomeration of SiO2 nanoparticles inevitably creates structural defects and localized weaknesses, leading to performance degradation under electrothermal conditions. Furthermore, inorganic fillers have limited inhibitory effects on charge transport due to the insufficient trap depth they introduce, even at the expense of localized voids and degradation. Summary of the Invention

[0004] The invention provides an organic semiconductor grafted polypropylene composite film and a preparation method thereof, which are used to improve the breakdown strength and energy storage performance of the polypropylene composite film at high temperatures.

[0005] The present invention also provides application of the polypropylene composite film in capacitors.

[0006] A first aspect of the present invention provides an organic semiconductor-grafted polypropylene composite film, wherein organic semiconductor molecules are grafted onto at least part of the side chains of the polypropylene;

[0007] The conductivity of the organic semiconductor molecule is 10 -10 ~100S / cm, molecular weight is 900~1500.

[0008] In a specific embodiment, the organic semiconductor molecule is selected from one or more compounds represented by Formula 1 to Formula 3:

[0009]

[0010] A second aspect of the present invention provides a method for preparing any of the above-mentioned polypropylene composite films, comprising the following steps:

[0011] Performing surface amination treatment on the organic semiconductor to obtain amino-modified organic semiconductor particles;

[0012] mixing the amino-modified organic semiconductor particles with anhydride-modified polypropylene particles and reacting them to obtain organic semiconductor-grafted polypropylene particles;

[0013] The organic semiconductor grafted polypropylene particles and polypropylene matrix particles are dispersed in a solvent and stirred evenly to form a dispersion liquid. The dispersion liquid is dropped onto a glass sheet. After removing the solvent, the formed film is peeled off from the glass sheet to obtain a polypropylene composite film.

[0014] In a specific embodiment, the amination treatment includes: adding an organic semiconductor and a diamine to an organic solvent, carrying out an amination reaction at 100-200° C. for 1-4 hours under an inert gas atmosphere, collecting the precipitate after the reaction, and washing the precipitate to obtain amino-modified organic semiconductor particles.

[0015] In a specific embodiment, the diamine is selected from one or more of ethylenediamine, m-phenylenediamine, p-phenylenediamine, and 3,4'-diaminodiphenyl ether.

[0016] In one embodiment, the amino-modified organic semiconductor particles are mixed with anhydride-modified polypropylene particles and reacted to obtain organic semiconductor-grafted polypropylene particles, specifically comprising:

[0017] The anhydride-modified polypropylene particles are dissolved in an organic solvent, and the amino-modified organic semiconductor particles are added. The mixed system is controlled to react at 100-130° C. for 2-6 hours. After the reaction is completed, the solvent is removed to obtain organic semiconductor-grafted polypropylene particles.

[0018] In a specific embodiment, the molar ratio of the anhydride groups in the anhydride-modified polypropylene particles to the amino groups in the amino-modified organic semiconductor particles is 1:1.

[0019] In a specific embodiment, the mass ratio of the organic semiconductor grafted polypropylene particles to the polypropylene matrix particles is (5-20): (9995-9980).

[0020] In a specific embodiment, the formed film is peeled off from the glass sheet and then dried at 50-100° C. for 4-24 hours to obtain a polypropylene composite film.

[0021] A third aspect of the present invention provides use of any of the above-mentioned polypropylene composite films in capacitors.

[0022] The present invention grafts polypropylene with organic semiconductor small molecules, thereby avoiding the problems of poor dispersibility, agglomeration, poor binding, easy dissociation, and low trap depth that are inherent in nanoparticle addition and modification. On the one hand, the organic semiconductor small molecules can introduce deep traps of 1 to 5 eV into the polypropylene matrix, thereby limiting carrier migration within the polypropylene film. On the other hand, the grafting of the organic semiconductor small molecules can enhance the internal interaction of the polypropylene film, improve the crystallization morphology of the polypropylene film, and increase the breakdown strength and energy storage density of the polypropylene film under high temperature conditions, thereby facilitating the stable operation of the capacitor within a wider temperature range. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic structural diagram of an organic semiconductor small molecule grafted polypropylene provided in Example 1 of the present invention;

[0024] Figure 2 Infrared spectra of the organic semiconductor small molecule PCBM and the organic semiconductor small molecule grafted polypropylene composite film PP-g-PCBM provided in Example 1 of the present invention;

[0025] Figure 3 A comparison chart of the test results of the electrical conductivity of the films provided in Example 1 of the present invention and Comparative Examples 1-2 at 120°C;

[0026] Figure 4 A comparison chart of the breakdown strength test results of the films provided in Example 1 of the present invention and Comparative Examples 1-2 at 120°C;

[0027] Figure 5A comparison chart of the test results of the charge-discharge efficiency and discharge energy density of the films provided in Example 1 of the present invention and Comparative Examples 1-2 at 120° C.;

[0028] Figure 6 A comparison chart of the test results of the charge-discharge efficiency and discharge energy density of the films provided in Example 2 of the present invention and Comparative Example 1 at 120° C.

[0029] Figure 7 This is a comparison chart of the test results of the charge and discharge efficiency and discharge energy density of the films provided in Example 3 of the present invention and Comparative Example 1 at 120°C. DETAILED DESCRIPTION

[0030] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are 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 efforts shall fall within the scope of protection of the present invention.

[0031] In order to improve the high-temperature capacitance of polypropylene film, nano-inorganic particles are used to modify polypropylene in this field. For example, K.Lahti, I.Rytluoto, M.Niittymki, E.Saarimki, M.Paajanen, From Laboratory to Industrial Scale: Comparison of Short-and Long-Term Dielectric Performance of Silica-Polypropylene Capacitor Films, in proceedings of IEEE ICD (2020) 661-664. discloses a silica-polypropylene (PP) nanocomposite BOPP film material with the characteristics of improving trap distribution, reducing electrical conductivity and improving dielectric loss. However, it has been found that the doping of SiO2 only has the effect of improving the breakdown strength of weak areas with non-ideal crystalline morphology. At room temperature and 80°C, the Weibull characteristic breakdown value of the silica-polypropylene (PP) nanocomposite BOPP film material is reduced, even lower than that of the unmodified pure PP film.

[0032] For example, Hiziroglu, H., & Shkolnik, I.. (2018). Electrical characteristics of polypropylene mixed with natural nanoclay. Polymers, 10(9), 942., or Zhang, C., Shi, W., Wang, Q., Si, Z., & Hiziroglu, HR. (2020). Effect of nano-clay filler on the thermal breakdown mechanism and lifespan of polypropylene film under acfields. IEEE Access, PP (99), 1-1. both use natural nanoclay to fill polypropylene materials. Compared with unfilled isotactic PP, the breakdown strength of PP loaded with 2wt% and 6wt% natural nanoclay is improved, mainly due to the reduction of the net electric polarization enhancement rate in PP and its composite materials with nanoclay. Studies have shown that polypropylene filled with 2 wt% natural nanoclay exhibits a shorter lifespan than unfilled isotactic polypropylene under a thermoelectric field. This is primarily due to the enhanced thermal motion of all molecules in the PP film as the temperature increases, disrupting the diffuse ion barrier between the clay flakes and the polymer matrix. Consequently, numerous clay flakes detach from the polymer matrix. Consequently, the natural nanoclay and polypropylene can no longer be handled as a single entity. These clay fragments detach from the matrix and accumulate, colliding with polymer molecules. The acceleration of these fragments by the AC electric field imparts additional energy to these fragments, exacerbating structural damage. This ultimately destroys the original molecular structure of the nanoclay-loaded PP film.

[0033] Although nanomaterials have great potential in polypropylene modification, their effectiveness is limited by their dispersibility and compatibility in the polymer matrix, resulting in limited breakdown strength and energy storage density of current polypropylene films under high temperature conditions.

[0034] Based on the above technical problems, the first aspect of the present invention provides an organic semiconductor-grafted polypropylene composite film, wherein organic semiconductor molecules are grafted onto at least part of the side chains of the polypropylene;

[0035] The conductivity of the organic semiconductor molecule is 10 -10 ~100S / cm, molecular weight is 900~1500.

[0036] In the present invention, organic semiconductor refers to an organic material with semiconductor properties, that is, an electrical conductivity between that of metals and insulators, with thermally activated conductivity and a conductivity of 10-10 Organic matter with a molecular weight of 100 to 100 S / cm. Organic semiconductor materials can be divided into polymer macromolecular materials and polymer small molecule materials. The organic semiconductor used in the present invention is an organic semiconductor small molecule material with a molecular weight between 900 and 1500.

[0037] Grafting means that at least part of the carbon atoms of polypropylene are connected to the organic small molecule semiconductor through chemical bonds. Through the grafting reaction, the bonding between the organic semiconductor small molecules and the polypropylene matrix can be effectively improved, preventing the destruction of the polypropylene film structure.

[0038] The present invention uses organic semiconductor small molecules to graft-modify polypropylene, which can avoid the problems of poor dispersibility, agglomeration, poor binding, easy dissociation, and low trap depth that are encountered in nanoparticle addition and modification. On the one hand, the organic semiconductor small molecules can introduce deep traps of 1 to 5 eV into the polypropylene matrix (the trap depth introduced by conventional nanoparticles is less than 1.0 eV), thereby limiting carrier migration within the polypropylene film. On the other hand, the grafting of the organic semiconductor small molecules can enhance the internal interaction of the polypropylene film, improve the crystal morphology of the polypropylene film, and increase the breakdown strength and energy storage density of the polypropylene film under high temperature conditions, thereby helping to promote the stable operation of the capacitor over a wider temperature range.

[0039] In a specific embodiment, the organic semiconductor molecule is specifically selected from one or more compounds represented by Formula 1 to Formula 3:

[0040]

[0041] The electron affinities of the organic semiconductor small molecules represented by Formulas 1 to 3 are 3.9, 4.2, and 4.0 eV, respectively. The organic semiconductor small molecule represented by Formula 2 has the highest electron affinity and can introduce the greatest trap depth. Therefore, in a preferred embodiment, the organic semiconductor molecule has the structure represented by Formula 2.

[0042] In one embodiment, the grafting reaction of the organic semiconductor small molecule is achieved by connecting the diamine compound and the anhydride group to the carbon atoms on the polypropylene. The reaction formula involved is as follows:

[0043]

[0044] A second aspect of the present invention provides a method for preparing any of the above-mentioned polypropylene composite films, comprising the following steps:

[0045] performing amination treatment on the organic semiconductor to obtain amino-modified organic semiconductor particles;

[0046] mixing the amino-modified organic semiconductor particles with anhydride-modified polypropylene particles and reacting them to obtain organic semiconductor-grafted polypropylene particles;

[0047] The organic semiconductor grafted polypropylene particles and polypropylene matrix particles are dispersed in a solvent and stirred evenly to form a dispersion liquid. The dispersion liquid is dropped onto a glass sheet. After removing the solvent, the formed film is peeled off from the glass sheet to obtain a polypropylene composite film.

[0048] In one embodiment, the method for preparing the polypropylene film comprises the following steps:

[0049] Step 1: Perform surface amination treatment on the organic semiconductor to obtain amino-modified organic semiconductor particles.

[0050] First, the diamine compound used in the present invention is used to aminate the organic semiconductor. The diamine compound refers to a compound having at least two amino groups, wherein one amino group reacts with the organic semiconductor molecule and the other amino group reacts with the anhydride group in the polypropylene grafted maleic anhydride, thereby grafting the organic molecular semiconductor onto the polypropylene molecular chain; the diamine compound can be a conventional compound in the art, for example, the diamine is selected from one or more of ethylenediamine, m-phenylenediamine, p-phenylenediamine, and 3,4'-diaminodiphenyl ether.

[0051] Secondly, during the reaction process, the organic semiconductor and diamine are added to an organic solvent, and the amination reaction is carried out at 100-200°C for 1-4 hours under an inert gas atmosphere. After the reaction is completed, the precipitate is collected and washed to obtain amino-modified organic semiconductor particles.

[0052] Furthermore, the molar ratio of the organic semiconductor to the diamine compound is 1:1.

[0053] Furthermore, the organic solvent is a reagent that can dissolve the organic semiconductor and the diamine compound, for example, it can be 1-methyl-2-pyrrolidone (NMP).

[0054] In addition, a catalyst needs to be added during the amination reaction, and the catalyst can be dibutyltin oxide.

[0055] Finally, after the amination reaction is completed, the reaction system is centrifuged, and after the precipitate is collected, the precipitate is ultrasonically cleaned with ethanol to obtain aminated organic semiconductor particles.

[0056] Step 2: mixing the amino-modified organic semiconductor particles and the anhydride-modified polypropylene particles and reacting them to obtain organic semiconductor-grafted polypropylene particles.

[0057] The anhydride-modified polypropylene particles used in the present invention can be conventional maleic anhydride-grafted polypropylene in the art. During the preparation process, first, the maleic anhydride-grafted polypropylene is dissolved in a solvent, stirred evenly, and then the amino-modified organic semiconductor particles prepared in step 1 are added.

[0058] Furthermore, the molar ratio of the anhydride groups in the anhydride-modified polypropylene particles to the amino groups in the amino-modified organic semiconductor particles is 1:1.

[0059] Furthermore, the solvent for dissolving maleic anhydride polypropylene can be a conventional organic solvent such as xylene.

[0060] Secondly, the mixed system is controlled to react at 100-130° C. to allow the amino groups in the organic semiconductor particles to react completely with the anhydride groups in the maleic anhydride grafted polypropylene. Generally, the reaction time is controlled to be 2-6 hours.

[0061] Finally, after the reaction is completed, the reaction system is dried to remove the solvent to obtain organic semiconductor grafted polypropylene particles.

[0062] Furthermore, the drying temperature is 50-100° C., and the drying time is 4-24 hours.

[0063] Step 3: Disperse the organic semiconductor grafted polypropylene particles and polypropylene matrix particles in a solvent, stir evenly to form a dispersion, drop the dispersion on a glass sheet, remove the solvent, and peel off the formed film from the glass sheet to obtain a polypropylene film.

[0064] First, the organic semiconductor grafted polypropylene particles prepared in step 2 are mixed with a polypropylene matrix in a certain ratio, wherein the polypropylene matrix particles refer to particles whose chemical composition only includes polypropylene, and the polypropylene is not modified or doped.

[0065] Taking into account the influence of the proportion of organic semiconductor grafted polypropylene particles in the polypropylene film on the performance of the polypropylene film, the mass ratio of the organic semiconductor grafted polypropylene particles to the polypropylene matrix particles can be controlled to be (5-20): (9995-9980). Otherwise, the proportion of organic semiconductor grafted polypropylene is too low and cannot achieve the desired effect. The electrical conductivity of the organic small molecule semiconductor itself is relatively high. If its content is too high, it may cause increased loss of the polypropylene composite film, which is not conducive to improving the charge and discharge efficiency.

[0066] Furthermore, the mass ratio of the organic semiconductor grafted polypropylene particles to the polypropylene matrix particles can be controlled to be (5-10):(9995-9990).

[0067] Furthermore, the solvent for dissolving and dispersing the organic semiconductor grafted polypropylene particles and the polypropylene matrix particles can be a conventional organic solvent such as xylene.

[0068] Furthermore, the mixing time is controlled within 4 to 24 hours to form a dispersion having a concentration of 5 mg / ml to 15 mg / ml.

[0069] Secondly, the dispersion is dropped onto a clean glass sheet and dried at 50-100°C for 4-24 hours to remove the solvent. The formed film sample is then peeled off from the glass sheet and placed in a vacuum oven for drying. The temperature of the vacuum oven is controlled at 50-100°C and the drying time is 4-24 hours to obtain a polypropylene composite film.

[0070] The polypropylene composite film prepared by the preparation method provided by the present invention has good dispersibility and bonding of organic semiconductor molecules in polypropylene, and the organic semiconductor molecules can be introduced into a higher trap depth. The prepared polypropylene composite film can effectively suppress the electrical conductivity of the film at high temperatures and improve the breakdown strength and energy storage performance of the film.

[0071] A third aspect of the present invention provides use of the polypropylene film in capacitors.

[0072] Based on the characteristics of the polypropylene film provided by the first aspect of the present invention, the operating temperature of a capacitor including the polypropylene film can reach 120°C.

[0073] The polypropylene film provided by the present invention is described in detail below with reference to specific embodiments:

[0074] The purity of [6,6]-phenyl C61 butyric acid methyl ester (PCBM, structure shown in Formula 2) used in the following examples is >99%.

[0075] Example 1

[0076] The method for preparing the polypropylene film provided in this embodiment comprises the following steps:

[0077] 1. Dissolve [6,6]-phenyl C61 butyric acid methyl ester (PCBM) (0.25 g, 0.274 mmol) in 1-methyl-2-pyrrolidone (NMP) (12 mL) in an argon-heated flask. Add dibutyltin oxide (0.068 g, 0.274 mmol) and ethylenediamine (0.2 mL) and heat to 180°C for 2 hours. The brown precipitate is sonicated with ethanol several times and then centrifuged to obtain amino-modified PCBM.

[0078] 2. Polypropylene grafted maleic anhydride (PP-g-MAH) particles were dissolved in xylene in a three-necked flask at 120 °C for 2 h, and PCBM-NH2 was added at a molar ratio of 1:1 to allow the amino groups in PCBM-NH2 to react completely with the anhydride groups in PP-g-MAH for 6 h.

[0079] The reaction product was dried at 80° C. for 12 h, and the solvent was evaporated to obtain PP-g-PCBM particles.

[0080] 3. Dissolve PP particles in xylene at 120°C, add 0.5 wt.‰ PP-g-PCBM particles, and stir for 6 hours to form a solution with a concentration of 10 mg / ml. The solution is dropped onto a clean glass slide and placed in an oven at 60°C for 8 hours to remove any remaining solvent. After slowly cooling to room temperature in deionized water, the sample is peeled from the glass substrate and the resulting film sample is dried in a vacuum oven at 80°C for another 12 hours to obtain a PP film approximately 12 microns thick.

[0081] The structural diagram of the PP-g-PCBM prepared in this example is shown in FIG. Figure 1 shown.

[0082] The PCBM and PP-g-PCBM involved in the preparation process of this embodiment were subjected to infrared testing, and the test results were compared and analyzed. The analysis results are as follows: Figure 2 As shown, it can be seen that the method provided in this embodiment indeed synthesized PP-g-PCBM.

[0083] Example 2

[0084] The preparation method of the polypropylene composite film provided in this embodiment can refer to Example 1, except that, in step 3, 0.2 wt.‰ PP-g-PCBM particles are added to the PP particles, that is, the mass ratio of the organic semiconductor grafted polypropylene particles to the polypropylene matrix particles is 2:9998.

[0085] Example 3

[0086] The preparation method of the polypropylene composite film provided in this embodiment can refer to Example 1, except that, in step 3, 1 wt.‰ PP-g-PCBM particles are added to the PP particles, that is, the mass ratio of the organic semiconductor grafted polypropylene particles to the polypropylene matrix particles is 10:9990.

[0087] Comparative Example 1

[0088] The polypropylene film provided in this comparative example is an unmodified polypropylene film.

[0089] Comparative Example 2

[0090] In this comparative example, organic semiconductor molecules are directly mixed with polypropylene matrix particles to prepare a polypropylene film, which is denoted as PP+0.5.

[0091] The electrical conductivity, breakdown strength, discharge energy density, and charge-discharge efficiency of the polypropylene films provided in Example 1 and Comparative Examples 1-2 were tested at 120°C. Leakage current and DC conductivity were measured using a Keithley 2410 electrometer and a Keithley 2290-10 high-voltage source. A DC breakdown test was conducted on a Trek610C high-voltage amplifier using an electrostatic pull-down method at a 500 V / s ramp-up rate. The DE circuit was tested at high electric field and temperature using a modified Sawyer tower circuit at a frequency of 10 Hz.

[0092] The test results are as follows Figures 3-5 ,according to Figure 3 It can be seen that compared with Comparative Examples 1 and 2, the polypropylene composite film provided in Example 1 has lower conductivity at 120°C and different voltages, which helps to reduce the leakage loss of the polypropylene composite film and improve the charge and discharge efficiency; Figure 4 It can be seen that at room temperature and 120°C, the breakdown strength of the polypropylene composite film provided by Example 1 is significantly better than that of Comparative Examples 1 and 2, and is increased by 29.6% compared with Comparative Example 1; Figure 5 It can be seen that when the charge and discharge efficiency of the polypropylene composite film provided in Example 1 is above 90%, the discharge energy density can reach 1.59 J / cm 3 , equivalent to 683.6% of conventional PP film, illustrating the potential of organic semiconductors in promoting the stable operation of capacitors over a wider temperature range.

[0093] The same method was used to test the energy storage performance of the polypropylene composite film provided in Examples 2 and 3, and the results were plotted. Figures 6-7 As shown in the accompanying drawings, Figures 6-7 As can be seen, compared with Comparative Example 1, the performance of the polypropylene composite films provided by Examples 2 to 3 at 120°C is superior to that of Comparative Example 1. However, compared with Example 1, the content of organic semiconductor molecule-grafted polypropylene particles in Example 3 is higher, resulting in a decrease in the charge and discharge efficiency of the polypropylene composite film. Therefore, the present invention preferably contains 0.5 wt‰ of organic semiconductor-grafted polypropylene particles.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An organic semiconductor grafted polypropylene composite film, characterized in that: Organic semiconductor molecules are grafted onto at least some of the side chains of the polypropylene; The organic semiconductor molecule is selected from the compound shown in Formula 2: Formula 2; The preparation method of the polypropylene composite film comprises the following steps: Performing surface amination treatment on the organic semiconductor to obtain amino-modified organic semiconductor particles; mixing the amino-modified organic semiconductor particles with anhydride-modified polypropylene particles and reacting them to obtain organic semiconductor-grafted polypropylene particles; The organic semiconductor grafted polypropylene particles and polypropylene matrix particles are dispersed in a solvent and stirred evenly to form a dispersion liquid. The dispersion liquid is dropped onto a glass sheet. After removing the solvent, the formed film is peeled off from the glass sheet to obtain a polypropylene composite film.

2. A method for preparing the polypropylene composite film according to claim 1, characterized in that: The steps include: Performing surface amination treatment on the organic semiconductor to obtain amino-modified organic semiconductor particles; mixing the amino-modified organic semiconductor particles with anhydride-modified polypropylene particles and reacting them to obtain organic semiconductor-grafted polypropylene particles; The organic semiconductor grafted polypropylene particles and polypropylene matrix particles are dispersed in a solvent and stirred evenly to form a dispersion liquid. The dispersion liquid is dropped onto a glass sheet. After removing the solvent, the formed film is peeled off from the glass sheet to obtain a polypropylene composite film.

3. The preparation method according to claim 2, characterized in that The amination treatment includes: adding an organic semiconductor and a diamine to an organic solvent, performing an amination reaction at 100-200° C. for 1-4 hours under an inert gas atmosphere, collecting and washing the precipitate after the reaction, and obtaining amino-modified organic semiconductor particles.

4. The preparation method according to claim 3, characterized in that The diamine is selected from one or more of ethylenediamine, m-phenylenediamine, p-phenylenediamine, and 3,4'-diaminodiphenyl ether.

5. The preparation method according to claim 2, characterized in that The amino-modified organic semiconductor particles are mixed with anhydride-modified polypropylene particles and reacted to obtain organic semiconductor-grafted polypropylene particles, specifically comprising: The anhydride-modified polypropylene particles are dissolved in an organic solvent, and the amino-modified organic semiconductor particles are added. The mixed system is controlled to react at 100-130°C for 2-6 hours. After the reaction is completed, the solvent is removed to obtain organic semiconductor-grafted polypropylene particles.

6. The preparation method according to claim 5, characterized in that The molar ratio of the anhydride groups in the anhydride-modified polypropylene particles to the amino groups in the amino-modified organic semiconductor particles is 1:

1.

7. The preparation method according to claim 2, characterized in that The mass ratio of the organic semiconductor grafted polypropylene particles to the polypropylene matrix particles is (5-20): (9995-9980).

8. The preparation method according to claim 2, characterized in that The formed film was peeled off from the glass sheet and dried at 50-100°C for 4-24 h to obtain a polypropylene composite film.

9. Use of the polypropylene composite film according to claim 1 in capacitors.

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