Composite dielectric film and preparation method and application thereof

Abstract

The invention belongs to the technical field of dielectric materials, and particularly relates to a composite dielectric film and a preparation method and application thereof. Through a nano-particle coating technology and an optimized formula, the breakdown voltage and the breakdown strength of the composite film are improved while the high dielectric constant and the low loss of the film are ensured; the interface bonding between the BT particles and the PP matrix is good, the uniform distribution of the nano filler is ensured, the performance stability of the film is improved, and the film has excellent stability and durability especially in a high electric field environment. The preparation process is simplified, a one-step film forming process is adopted, traditional multi-step operation is avoided, the production efficiency is improved, and the production cost is reduced; the technological process is simple, the controllability is high, the application requirements of electronic devices on miniaturization, high energy efficiency and high performance are met, and industrial popularization of high-performance dielectric materials is promoted; the thin film capacitor is compatible with various applications, and is suitable for high-performance thin film capacitor requirements of filtering, power electronics, new energy equipment and the like.

Description

Technical Field

[0001] This invention belongs to the field of dielectric materials technology, specifically relating to a composite dielectric thin film, its preparation method, and its application. Background Technology

[0002] Film capacitors use plastic film as the dielectric and are characterized by non-polarity, high voltage withstand, and high temperature resistance, making them widely used in filtering, AC / DC conversion, and DC power supply. With the rapid development of new energy sources, the film capacitor market is also expanding. Over the past two decades, film capacitors have been a key component in electrical equipment and electronic devices, particularly in new energy vehicles, advanced weaponry, renewable energy, and high-voltage power transmission. As electronic devices evolve towards miniaturization, high energy efficiency, and high performance, the requirements for dielectric film materials are increasing. Dielectric films are widely used in capacitors, sensors, and energy storage devices, especially in high-voltage and high-frequency environments, where high breakdown strength, high dielectric constant, and low loss are required.

[0003] Traditional dielectric materials such as polypropylene (PP) and barium titanate (BT) each have their own advantages: PP possesses good mechanical properties and thermal stability, while BT, as a classic ceramic material, exhibits high dielectric constant and good electrical properties. However, single-material dielectric films struggle to simultaneously meet the requirements of high dielectric constant and high breakdown strength. Therefore, composite materials have gradually emerged as a solution, combining organic polymers with inorganic ceramics to achieve synergistic effects and improve overall electrical performance and breakdown strength. Traditional BT / PP composite film preparation methods typically involve multiple steps, such as the sol-gel method or layer-by-layer assembly. These methods are complex, and interfacial bonding between different materials presents challenges, affecting material uniformity and performance stability. Therefore, simplifying the preparation process while obtaining dielectric films with both high breakdown strength and high dielectric constant has become a key research focus in the field of dielectric materials. Summary of the Invention

[0004] The purpose of this invention is to provide a composite dielectric thin film, its preparation method and application. The preparation method provided by this invention is simple and the resulting composite thin film has both high breakdown strength and high dielectric constant.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing a composite dielectric thin film, comprising the following steps: Barium titanate nanoparticles were coated with a silane coupling agent to obtain coated barium titanate. The coated barium titanate, polypropylene, antioxidant, nucleating agent and silicone rubber are mixed and then subjected to internal mixing, extrusion and stretching in sequence to obtain the composite dielectric film.

[0006] Preferably, the silane coupling agent is at least one selected from γ-aminopropyltriethoxysilane and vinyltriethoxysilane; The particle size of the nano-barium titanate is 5~200nm; The coating process is as follows: nano-barium titanate is dispersed in an alcohol solvent, a silane coupling agent is added to the resulting dispersion under stirring, and the coated barium titanate is obtained after drying. The mass of the silane coupling agent is 1-10% of the mass of the nano-barium titanate; The dispersion is carried out under ultrasonic conditions, wherein the ultrasonic power is 100~200W and the time is 30~180min; When adding the silane coupling agent, the temperature of the dispersion is 80~100℃; The method of addition is dropwise addition.

[0007] Preferably, the antioxidant includes at least one of hindered phenolic antioxidant 1010, hindered phenolic antioxidant 1076, trinonylphenyl phosphite, dialkyl thiophosphate, antioxidant 300, antioxidant 900 and antioxidant 1790.

[0008] Preferably, the nucleating agent includes at least one of aluminum tetrahydrophenyldicarboxylate, rare earth β-nucleating agents, calcium salt nucleating agents, dibenzoamide nucleating agents, and organophosphate nucleating agents.

[0009] Preferably, the silicone rubber includes at least one of vinyl silicone rubber, phenyl silicone rubber, liquid silicone rubber, and room temperature vulcanizing silicone rubber.

[0010] Preferably, the mixture obtained by mixing comprises the following components in mass percentage: 0.2-5% coated barium titanate, 90-99% polypropylene, 0.1-0.5% antioxidant, 0.05-0.3% nucleating agent, and 0.5-3% silicone rubber.

[0011] Preferably, the mixing method is centrifugal stirring. The internal mixing extrusion is carried out using a twin-screw internal mixing extruder; The conditions and parameters for the internal mixing and extrusion include: homogenization zone temperature of 200~250℃, melt extrusion zone temperature of 210~240℃, mixing time of 3~10min, stirring rate of 70~120rpm, and maximum torque of 10~40N·m.

[0012] Preferably, the stretching method is uniaxial stretching; the stretching conditions include: the speed of the differential roller is 300~700mm / min, the torque of the traction roller is 40~60N·m, and the stretching ratio is 1.5~3 times.

[0013] The present invention also provides a composite dielectric film prepared by the preparation method described above, wherein the composite dielectric film comprises a polypropylene matrix and barium titanate filled in the polypropylene matrix.

[0014] The present invention also provides the application of the composite dielectric film described in the above technical solution in film capacitors.

[0015] This invention provides a method for preparing a composite dielectric film, comprising the following steps: coating nano-barium titanate with a silane coupling agent to obtain coated barium titanate; mixing the coated barium titanate, polypropylene, antioxidant, nucleating agent and silicone rubber, and then sequentially performing internal mixing, extrusion and stretching to obtain the composite dielectric film.

[0016] The advantages of this invention over the prior art are: (1) This invention uses nanoparticle coating technology and optimized formulation to ensure that the film has high dielectric constant and low loss, while improving the breakdown voltage and breakdown strength of the composite film; the interface between BT particles and PP matrix is ​​well bonded, ensuring uniform distribution of nanofillers and improving the performance stability of the film, especially with excellent stability and durability under high electric field environment.

[0017] (2) The present invention simplifies the preparation process by adopting a one-step film formation process, avoiding traditional multi-step operations, improving production efficiency and reducing production costs; the process flow is simple and highly controllable, so as to support the application requirements of electronic devices towards miniaturization, high energy efficiency and high performance, and promote the industrialization of high-performance dielectric materials; it is compatible with a variety of applications and is suitable for the demand of high-performance thin film capacitors such as filters, power electronics and new energy equipment. Attached Figure Description

[0018] Figure 1 A schematic diagram of the apparatus structure for the preparation method provided by the present invention; Figure 2 The cross-sectional SEM image (a) and cross-sectional EDS energy spectrum (b) of the composite dielectric thin film obtained in Example 2 are shown. Figure 3 The frequency dependence of the dielectric constant and dielectric loss of the composite dielectric films obtained in the examples and comparative examples; Figure 4 The breakdown strength of the composite dielectric films obtained in the examples and comparative examples is based on the Weibull distribution. Figure 5 The discharge energy density and discharge efficiency of the composite dielectric thin films obtained in the examples and comparative examples are shown. Detailed Implementation

[0019] This invention provides a method for preparing a composite dielectric thin film, comprising the following steps: Barium titanate nanoparticles were coated with a silane coupling agent to obtain coated barium titanate. The coated barium titanate, polypropylene, antioxidant, nucleating agent and silicone rubber are mixed and then subjected to internal mixing, extrusion and stretching in sequence to obtain the composite dielectric film.

[0020] This invention utilizes a silane coupling agent to coat nano-barium titanate to obtain coated barium titanate.

[0021] In this invention, the silane coupling agent preferably includes at least one of γ-aminopropyltriethoxysilane and vinyltriethoxysilane; the particle size of the nano barium titanate is preferably 5~200 nm.

[0022] In this invention, the coating process is preferably as follows: Barium titanate nanoparticles are dispersed in an alcohol solvent; a silane coupling agent is added to the resulting dispersion under stirring; and the mixture is dried to obtain the coated barium titanate. The alcohol solvent preferably includes isopropanol or ethanol. The mass of the silane coupling agent is preferably 1-10% of the mass of the barium titanate nanoparticles, specifically 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%. This invention does not have a specific limitation on the amount of alcohol solvent used, as long as the barium titanate nanoparticles are uniformly dispersed. In this invention, the dispersion is preferably carried out under ultrasonic conditions, with the ultrasonic power preferably being 100-200W; the time is preferably 30-180 min, specifically 30 min, 60 min, 90 min, 120 min, 150 min, or 180 min. In this invention, the addition method is preferably dropwise; when adding the silane coupling agent, the temperature of the dispersion is preferably 80-100℃, specifically 80℃, 90℃, or 100℃. In this invention, the drying temperature is preferably 80~100℃, and the drying time is preferably 4~6h.

[0023] After obtaining the coated barium titanate, the present invention mixes the coated barium titanate, polypropylene, antioxidant, nucleating agent and silicone rubber, and then performs internal mixing, extrusion and stretching in sequence to obtain the composite dielectric film.

[0024] In this invention, the antioxidant preferably includes at least one of hindered phenolic antioxidant 1010, hindered phenolic antioxidant 1076, trinonylphenyl phosphite (TNPP), dialkyl thiophosphate (DSTP), antioxidant 300, antioxidant 900 and antioxidant 1790 (N-tert-butyl-α-phenylnitrone).

[0025] In this invention, the nucleating agent preferably includes at least one of aluminum tetrahydrophenyldicarboxylate (TMB-5), rare earth β-nucleating agents, calcium salt nucleating agents, dibenzoamide nucleating agents, and organophosphate nucleating agents; the rare earth β-nucleating agent is specifically the β-nucleating agent WBG-Ⅱ.

[0026] In this invention, the silicone rubber includes at least one of vinyl silicone rubber (VMQ), phenyl silicone rubber (PMQ), liquid silicone rubber (LSR), and room temperature vulcanizing silicone rubber (RTV); the room temperature vulcanizing silicone rubber is preferably silicone rubber 107.

[0027] In this invention, the mixture obtained by mixing preferably includes the following components in mass percentage: 0.2-5% coated barium titanate, 90-99% polypropylene, 0.1-0.5% antioxidant, 0.05-0.3% nucleating agent, and 0.5-3% silicone rubber.

[0028] In this invention, the mixing method is preferably centrifugal stirring, which preferably includes sequentially performing a first stirring and a second stirring. The rotation speed of the first stirring is preferably 300~1000 rpm, specifically 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm, or 1000 rpm; the time is preferably 0.5~5 min, specifically 0.5 min, 1 min, 2 min, 3 min, 4 min, or 5 min; the rotation speed of the second stirring is preferably... The speed is selected to be 1300~2300 rpm, specifically 1300 rpm, 1400 rpm, 1500 rpm, 1600 rpm, 1700 rpm, 1800 rpm, 1900 rpm, 2000 rpm, 2100 rpm, 2200 rpm, and 2300 rpm; the time is preferably 1~10 min, specifically 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, and 10 min; the centrifugal mixing is preferably carried out in a planetary mixer.

[0029] In this invention, the internal mixing extrusion is preferably carried out using a twin-screw extruder; the preferred conditions and parameters for the internal mixing extrusion include: a homogenization section temperature of 200~250℃, specifically 200℃, 210℃, 220℃, 230℃, 240℃, or 250℃; a melt extrusion section temperature of 210~240℃, specifically 210℃, 220℃, 230℃, or 240℃; a mixing time of 3~10min, specifically 3min, 4min, 5min, 6min, 7min, 8min, 9min, or 10min; a stirring rate of 70~120rpm, specifically 70rpm, 80rpm, 90rpm, 100rpm, 110rpm, or 120rpm; and a maximum torque of 10~40N·m, specifically 10N·m, 20N·m, 30N·m, or 40N·m.

[0030] In this invention, the mixing and extrusion process preferably includes cooling, and the cooling method is preferably air knife cooling.

[0031] In this invention, the stretching method is preferably uniaxial stretching; the stretching conditions preferably include: the speed of the differential roller is 300~700mm / min, specifically 300mm / min, 400mm / min, 500mm / min, 600mm / min, or 700mm / min; the torque of the traction roller is 40~60N·m, specifically 40N·m, 50N·m, or 60N·m; and the stretching ratio is 1.5~3 times, specifically 1.5 times, 2 times, 2.5 times, or 3 times.

[0032] In this invention, the film thickness is adjusted to the desired thickness under the control of the speed and tension of the differential roller and traction roller. The film is then further stretched by the traction roller, and the stretching ratio is controlled to improve the film's orientation and density. The film is then wound into a roll, ensuring uniform winding tension and preventing air bubbles or wrinkles. This invention achieves efficient film processing by rationally adjusting process parameters (such as temperature, extrusion speed, mixing time, and stretching ratio). The prepared film has uniform thickness and stable quality, and the process exhibits continuity and high repeatability.

[0033] A schematic diagram of the apparatus structure for the preparation method provided by this invention is shown below. Figure 1 As shown.

[0034] The present invention also provides a composite dielectric film prepared by the preparation method described above, wherein the composite dielectric film comprises a polypropylene matrix and barium titanate filled in the polypropylene matrix. In the present invention, the mass ratio of barium titanate to polypropylene matrix is ​​preferably 0.002~0.05:1; the thickness of the composite dielectric film is preferably 5~20 μm.

[0035] The present invention also provides the application of the composite dielectric film described in the above technical solution in film capacitors.

[0036] Unless otherwise specified, the materials and equipment used in this invention are all commercially available products in the field.

[0037] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0038] Example 1 10g of 5nm barium titanate nanoparticles were ultrasonically dispersed in 200mL of isopropanol at a power of 100W for 120min. The uniformly dispersed barium titanate suspension was transferred to an oil bath at 85℃. 0.2g of γ-aminoethylaminopropyltrimethoxysilane (KH792) was added dropwise as a silane coupling agent while stirring. The amount of coupling agent added was 2% of the mass of barium titanate. The product was placed in a vacuum drying oven and dried at 95℃ for 5h to obtain coated barium titanate. 10g of PP powder, 0.01g of antioxidant 1010, 0.015g of β-nucleating agent WBG-Ⅱ, 0.3g of silicone rubber 107 and 0.05g of the above-obtained coated barium titanate were added to a planetary mixer for centrifugal stirring and premixing. The mixture was stirred at a low speed of 500 rpm for 2 minutes and then stirred at a high speed of 1500 rpm for 5 minutes to obtain a mixture. Add the mixture into the hopper of the twin-screw extruder, set the homogenization section temperature to 210℃, the melt extrusion section temperature to 220℃, the screw extruder stirring speed to 100rpm, the maximum torque to 25N·m, and the mixing time to 8min. The extruded material is cooled by an air knife and then subjected to uniaxial stretching. The speed of the differential roller is 500 mm / min, the torque of the traction roller is 50 N·m, and the stretching ratio is controlled at 2.5 times. Finally, a composite dielectric film with a thickness of 10 μm ± 200 nm is obtained, in which the mass percentage of barium titanate is 0.5%.

[0039] Example 2 The composite dielectric film was prepared according to the method of Example 1, except that the content of barium titanate in the obtained composite dielectric film was 1%.

[0040] Example 3 The composite dielectric film was prepared according to the method of Example 1, except that the content of barium titanate in the obtained composite dielectric film was 1.5%.

[0041] Example 4 The composite dielectric film was prepared according to the method of Example 2, except that the rotation speed of the differential roller was 300 mm / min, and the thickness of the resulting composite dielectric film was 20 μm ± 200 nm.

[0042] Example 5 The composite dielectric film was prepared according to the method of Example 2, except that the homogenization temperature was 210°C and the melt extrusion temperature was 210°C.

[0043] Example 6 The composite dielectric film was prepared according to the method of Example 2, except that the mixing time was 3 minutes.

[0044] Comparative Example 1 The composite dielectric film was prepared according to the method of Example 1, except that silicone rubber 107 and barium titanate coating were not added.

[0045] Comparative Example 2 The composite dielectric film was prepared according to the method of Example 1, except that barium titanate was not added and the dopant of silicone rubber 107 was 3%.

[0046] Comparative Example 3 The composite dielectric film was prepared according to the method of Example 1, except that barium titanate was not coated.

[0047] Performance testing Test Example 1 The cross-sectional morphology of the composite dielectric film prepared in Example 2 was characterized by scanning electron microscopy (SEM) at room temperature. The test results are as follows: Figure 2 As shown. From Figure 2 It can be seen that the stretched composite dielectric film has a dense structure, no obvious pores, and uniform thickness, which is maintained within the range of 10μm±20nm.

[0048] Test Example 2 The composite dielectric films prepared in the examples and comparative examples were deposited with gold in a small ion sputtering instrument, and their dielectric properties were tested using a Novocontrol broadband dielectric spectrometer (Germany). The dielectric constant and dielectric loss at different frequencies were analyzed at room temperature.

[0049] The dielectric constant and dielectric loss of the films prepared in the examples at 1 kHz are shown in Table 1. The results show that with increasing barium titanate (BT) doping, the dielectric constant of the composite dielectric film gradually increases, while the dielectric loss factor remains at a low level, exhibiting excellent dielectric properties. Comparison with Comparative Examples 1 and 2 shows that the dielectric properties of the films prepared in this invention are significantly better than those of the comparative sample.

[0050] Furthermore, for Examples 1-2 and Comparative Examples 1-2, the values ​​were 1-10. 4 The dielectric constant and dielectric loss were tested in the Hz frequency range, and the results are as follows: Figure 3 As shown. By Figure 3 As can be seen, the dielectric constant of the thin film prepared in Example 2 remains stable at 3.27 within this frequency range, and the dielectric loss is less than 10. -3 It exhibits excellent dielectric properties.

[0051] Test Example 3 The composite dielectric films prepared in Examples 1 and 2 were gold-plated in a small ion sputtering apparatus, and their breakdown strength was tested using a High Voltage Withstand Tester. The samples were placed in silicone oil, and a DC voltage was applied at a boost rate of 500 V / s. Breakdown was determined when the leakage current reached 50 mA. The test results were characterized using a Weibull distribution, as shown in Table 1.

[0052] The results show that, compared with Comparative Examples 1 and 3, the breakdown strength of the films prepared in the examples is significantly improved, indicating that the insulation performance of the composite dielectric films is significantly enhanced. Further comparison of the Weibull distributions of the breakdown strengths of Examples 1, 2, and Comparative Examples 1 and 2 (e.g., ...) Figure 4 As shown in the figure, it can be seen that the breakdown performance of the example sample is significantly better than that of the comparative sample, exhibiting excellent insulation performance.

[0053] Test Example 4 The discharge energy density and charge / discharge efficiency of the examples and comparative examples were determined using a Radiant ferroelectric testing instrument (USA). During testing, the samples were placed in silicone oil, and the test electric field strength was 450 kV / mm. The results are shown in Table 1.

[0054] Test results show that the thin films prepared in the examples have stable energy storage performance, with charge and discharge efficiencies all exceeding 90%. Compared with Comparative Examples 1 and 2, the thin films prepared in Examples 1 and 2 exhibit higher discharge energy densities, meeting the practical requirements of energy storage applications.

[0055] Table 1 Performance test results of the composite dielectric thin films obtained in the examples and comparative examples

[0056] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a composite dielectric thin film, characterized in that, Includes the following steps: Barium titanate nanoparticles were coated with a silane coupling agent to obtain coated barium titanate. The coated barium titanate, polypropylene, antioxidant, nucleating agent and silicone rubber are mixed and then subjected to internal mixing, extrusion and stretching in sequence to obtain the composite dielectric film.

2. The preparation method according to claim 1, characterized in that, The silane coupling agent is at least one of γ-aminopropyltriethoxysilane and vinyltriethoxysilane; The particle size of the nano-barium titanate is 5~200nm; The coating process is as follows: barium titanate nanoparticles are dispersed in an alcohol solvent, a silane coupling agent is added to the resulting dispersion under stirring, and the coated barium titanate is obtained after drying. The mass of the silane coupling agent is 1-10% of the mass of the nano-barium titanate; The dispersion is carried out under ultrasonic conditions, wherein the ultrasonic power is 100~200W and the time is 30~180min; When adding the silane coupling agent, the temperature of the dispersion is 80~100℃; The method of addition is dropwise addition.

3. The preparation method according to claim 1, characterized in that, The antioxidants include at least one of hindered phenolic antioxidant 1010, hindered phenolic antioxidant 1076, trinonylphenyl phosphite, dialkyl thiophosphate, antioxidant 300, antioxidant 900 and antioxidant 1790.

4. The preparation method according to claim 1, characterized in that, The nucleating agent includes at least one of aluminum tetrahydrophenyldicarboxylate, rare earth β-nucleating agents, calcium salt nucleating agents, dibenzoamide nucleating agents, and organophosphate nucleating agents.

5. The preparation method according to claim 1, characterized in that, The silicone rubber includes at least one of vinyl silicone rubber, phenyl silicone rubber, liquid silicone rubber, and room temperature vulcanizing silicone rubber.

6. The preparation method according to claim 1, characterized in that, The mixture obtained by mixing includes the following components in mass percentage: 0.2-5% coated barium titanate, 90-99% polypropylene, 0.1-0.5% antioxidant, 0.05-0.3% nucleating agent, and 0.5-3% silicone rubber.

7. The preparation method according to claim 1, characterized in that, The mixing method is centrifugal stirring; The internal mixing extrusion is carried out using a twin-screw internal mixing extruder; The conditions and parameters for the internal mixing and extrusion include: homogenization zone temperature of 200~250℃, melt extrusion zone temperature of 210~240℃, mixing time of 3~10min, stirring rate of 70~120rpm, and maximum torque of 10~40N·m.

8. The preparation method according to claim 1, characterized in that, The stretching method is uniaxial stretching; the stretching conditions include: the speed of the differential roller is 300~700mm / min, the torque of the traction roller is 40~60N·m, and the stretching ratio is 1.5~3 times.

9. The composite dielectric thin film prepared by the preparation method according to any one of claims 1 to 8, characterized in that, The composite dielectric film comprises a polypropylene matrix and barium titanate filled in the polypropylene matrix.

10. The application of the composite dielectric film according to claim 9 in a film capacitor.

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