High dielectric composite material and method for preparing the same

Abstract

The application discloses a high-dielectric composite material and a preparation method thereof, and belongs to the technical field of composite materials. The preparation method comprises the following steps: mixing and grinding dielectric ceramic powder and polymer particles at a temperature of-200 DEG C to-100 DEG C, so that the dielectric ceramic powder is coated on the surface of the polymer particles or dispersed between the polymer particles, and a premix is obtained; and the premix is subjected to hot-pressing treatment, and a high-dielectric composite material with an isolation structure is obtained. The polymer-based composite material with the isolation structure is obtained through the preparation steps of low-temperature grinding mixing and hot-pressing, the isolation structure makes the dielectric ceramic powder regularly and continuously enriched in the composite material matrix, the dielectric constant of the composite material can be greatly improved, the preparation method is simple in process, low in cost and pollution-free.

Description

Technical Field

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

[0002] Combining polymers with ceramic or conductive fillers possessing high dielectric constants is the most common method for preparing high dielectric constant composite materials. Current methods for preparing high dielectric constant composite materials involve melting or solution blending the functional filler with the polymer matrix. This direct mixing method results in the filler being randomly distributed throughout the polymer matrix. To obtain a satisfactory dielectric constant, a large filler content is usually required, which increases the density of the composite material, worsens its processability, and increases its cost. Summary of the Invention

[0003] Purpose of the invention: This application provides a high dielectric composite material with low ceramic filler content and high dielectric constant, and its preparation method.

[0004] Technical solution: This application provides a method for preparing a high-dielectric composite material, including the following steps:

[0005] Dielectric ceramic powder and polymer particles are mixed and ground at a temperature of -200℃ to -100℃, so that the dielectric ceramic powder coats the surface of the polymer particles or disperses between the polymer particles to obtain a premix.

[0006] The premixture was hot-pressed to obtain a high-dielectric composite material with an insulating structure.

[0007] In some embodiments, the mass ratio of the dielectric ceramic powder to the polymer particles is 3-40:60-97.

[0008] In some embodiments, the dielectric ceramic powder has a particle size of a nm, and the polymer particles have a particle size of b μm, satisfying:

[0009] 1×10 -4 ≤a / (b×1000)≤0.2.

[0010] In some embodiments, the particle size a nm of the dielectric ceramic powder satisfies: 10 nm ≤ a ≤ 200 nm; and / or

[0011] The polymer particles have a particle size of bμm that satisfies the following condition: 1μm≤b≤100μm.

[0012] In some embodiments, the dielectric ceramic powder is selected from at least one of perovskite ceramics and oxide ceramics; or

[0013] The dielectric ceramic powder is selected from at least one of barium titanate, strontium titanate, barium strontium titanate, calcium titanate, calcium copper titanate, titanium dioxide, magnesium oxide, silicon oxide, and zirconium oxide.

[0014] In some embodiments, the polymer is selected from at least one of polyvinylidene fluoride and its copolymers, polyimide, polymethyl methacrylate, polycarbonate, polypropylene, polyethylene, polyvinyl chloride, polyvinyl alcohol, polystyrene, polyethylene terephthalate, polyhexamethylene adipamide, polycaprolactam, thermoplastic polyurethane, ethylene-vinyl acetate copolymer, maleic anhydride-grafted styrene-butadiene-styrene block copolymer, maleic anhydride-grafted styrene-ethylene-butene-styrene block copolymer, and maleic anhydride-grafted polyolefin elastomer; or

[0015] The polymer has a number-average molecular weight of 10,000 to 1,000,000; or

[0016] The glass transition temperature of the polymer is -100 to 300°C; or

[0017] The polymer has a melting temperature of -100 to 300°C.

[0018] In some embodiments, prior to the step of mixing and grinding the dielectric ceramic powder and polymer particles at a temperature of -200°C to -100°C, the method further includes:

[0019] The polymer particles are surface-treated to form polar groups on the surface of the polymer particles; wherein the polar groups are selected from at least one of carbonyl, carboxyl, hydroxyl, and amino groups.

[0020] In some embodiments, the surface treatment is plasma treatment, the plasma treatment pressure is 10-20 Pa, the plasma treatment power is 5-15 W, and the plasma treatment time is 2-10 min; the gas used in the plasma treatment is at least one selected from Ar, N2, O2, NH3, CO, CO2, and SO2.

[0021] In some embodiments, the hot pressing process is carried out at a temperature of 100–305°C, for a time of 5–30 min, and at a pressure of 10–20 MPa.

[0022] In some embodiments, this application also provides a high dielectric composite material prepared by the preparation method described above, comprising, by mass percentage: 3 wt% to 40 wt% dielectric ceramic powder and 60 wt% to 97 wt% polymer; wherein, a portion of the dielectric ceramic powder aggregates to separate the polymer and form an isolation structure.

[0023] Beneficial Effects: Compared with existing technologies, the preparation method of a high-dielectric composite material of this application includes the following steps: mixing and grinding dielectric ceramic powder and polymer particles at a temperature of -200℃ to -100℃, so that the dielectric ceramic powder coats the surface of the polymer particles or disperses between the polymer particles to obtain a premix; and hot-pressing the premix to obtain a high-dielectric composite material with an insulating structure. This application obtains a polymer-based composite material with an insulating structure through a combination of low-temperature grinding and mixing with hot pressing. The preparation method is simple, low-cost, and pollution-free, making it a promising method for producing polymer-based high-dielectric composite materials.

[0024] This application discloses a high-dielectric composite material, comprising, by mass percentage: 3 wt% to 40 wt% dielectric ceramic powder and 60 wt% to 97 wt% polymer; wherein the dielectric ceramic powder partially aggregates to separate the polymer and form an insulating structure. In this high-dielectric composite material, the insulating structure allows for the regular and continuous enrichment of the dielectric ceramic powder within the composite matrix, significantly improving the dielectric constant of the composite material. Under the same formulation, the dielectric constant of the composite material prepared by this method is increased by up to 60% compared to traditional melt blending and solution blending methods. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 PVDF particles with surface-coated barium titanate nanoparticles provided in the embodiments of this application;

[0027] Figure 2 for Figure 1 A magnified view of a portion of the image;

[0028] Figure 3 SEM image of the brittle fracture surface of a high-dielectric composite material isolation structure;

[0029] Figure 4 This is a schematic diagram of an insulating dielectric composite material structure. Detailed Implementation

[0030] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0031] In the description of this application, it should be understood that the terms "upper," "lower," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In the description of this application, "a plurality of" means two or more, and "at least one" can mean one, two, or more, unless otherwise expressly specified.

[0032] The applicant discovered that polymer-based composite materials with high dielectric constants can not only store more electrical energy but also integrate the advantages of polymers, such as light weight, flexibility, and ease of processing. In passive devices, the application of high dielectric constant composite materials in capacitors has attracted significant attention. In the field of microelectronics, high dielectric constant composite materials can enable decoupling capacitors to achieve higher capacitance values ​​and shorter operating distances in the devices they serve. Beyond the electronics industry, high dielectric constant composite materials are widely used in civilian and military applications, including active vibration control, aerospace, underwater navigation and surveillance, biomedical imaging, and non-destructive testing. Therefore, high dielectric constant polymer-based composite materials are a very active research direction in the field of functional materials and have become one of the key foundational materials for the development of cutting-edge fields such as electronic information, power energy, biomedicine, and aerospace.

[0033] Combining polymers with ceramic fillers or conductive fillers with high dielectric constants is the most common method for preparing high dielectric constant composite materials. The polymers involved include polyvinylidene fluoride (PVDF) and its copolymers, epoxy resin (ER), polycarbonate (PC), polyimide (PI), polypropylene (PP), polymethyl methacrylate (PMMA), etc. The high dielectric ceramic particles used mainly include barium titanate, strontium titanate, barium strontium titanate, calcium copper titanate, etc. The conductive fillers mainly include silver, carbon nanotubes, graphene, polypyrrole, etc.

[0034] Current methods for preparing high dielectric constant composites involve melting or solution blending functional fillers with a polymer matrix. This direct mixing method results in random distribution of the filler throughout the polymer matrix. To achieve a satisfactory dielectric constant, a large filler content is typically required, leading to increased composite density, poorer processability, and higher costs. To improve this situation, controlling the distribution of fillers within the polymer matrix could potentially allow the composite to maintain excellent dielectric properties even with a lower addition amount of functional filler compared to conventional blending methods. Conductive fillers can be used as functional fillers. While using conductive fillers as dielectric fillers significantly improves the dielectric constant of dielectric composites, it often leads to a substantial increase in dielectric loss, resulting in severe heat generation during practical applications.

[0035] Based on this, this embodiment provides a high-dielectric composite material and its preparation method. Using nanoscale dielectric ceramic powder and micron-sized polymer particles treated with low-temperature plasma as raw materials, the materials are ground in liquid nitrogen to coat the surface of the polymer particles with the nanoscale dielectric ceramic powder. The uniformly ground powder is then directly hot-pressed to obtain a high-dielectric composite material with an insulating structure. The dielectric constant of the composite material prepared by this method is significantly improved compared to composite materials prepared by traditional melt blending and solution blending methods, with a maximum improvement of up to 60% under the same formulation. This method is simple, low-cost, and pollution-free, making it a promising method for producing polymer-based dielectric composite materials.

[0036] In some embodiments, a method for preparing a high-dielectric composite material according to this application includes the following steps:

[0037] Dielectric ceramic powder and polymer particles are mixed and ground at a temperature of -200℃ to -100℃, so that the dielectric ceramic powder coats the surface of the polymer particles or disperses between the polymer particles to obtain a premix.

[0038] The premixture was hot-pressed to obtain a high-dielectric composite material with an insulating structure.

[0039] It is understood that the method of this application mixes and grinds dielectric ceramic powder and polymer particles at a temperature of -200℃ to -100℃. Grinding at this temperature can avoid the influence of temperature rise caused by grinding on polymer particles. Therefore, the dielectric ceramic powder and polymer particles can be fully mixed after low-temperature grinding. After full mixing, a polymer-based dielectric composite material with an isolation structure can be obtained by hot pressing. This structure allows the dielectric ceramic powder to be continuously enriched in the composite matrix in a regular manner, which is beneficial to the adjustment of polarization direction in the electric field, enhances the local electric field, obtains a high dipole moment, and thus can significantly improve the dielectric constant of the composite material.

[0040] Furthermore, the mixing and grinding temperature can be any one of -100℃, -110℃, -120℃, -130℃, -140℃, -150℃, -160℃, -170℃, -180℃, -190℃, -200℃ or a range between any two of these values.

[0041] In some embodiments, the temperature generated during grinding may exceed the glass transition temperature or melting temperature of the polymer particles. In order to avoid melting or decomposition of the polymer particles, it is necessary to control the ambient temperature during grinding to be less than or equal to the glass transition temperature or melting temperature of the polymer particles.

[0042] In some embodiments, the mass ratio of dielectric ceramic powder to polymer particles is 3–40:60–97. For example, the mass ratio of dielectric ceramic powder to polymer particles can be any one of 5:95, 10:90, 15:85, 20:80, 25:75, 30:70, or 35:65. Therefore, the amount of dielectric ceramic powder added is less than that of conventional melt blending or solution blending, but a balanced dielectric constant can be achieved.

[0043] In some embodiments, the particle size of the dielectric ceramic powder is a nm, and the particle size of the polymer particles is b μm, satisfying: 1 × 10⁻⁶. -4 ≤a / (b×1000)≤0.2.

[0044] It is understandable that when the above relationship range is met, the dielectric ceramic powder can be guaranteed to be in the nanometer scale and the polymer particles in the micrometer scale. In this case, when the two are ground and mixed, the nanometer-sized dielectric ceramic powder is more likely to coat the surface of the micrometer-sized polymer particles, thereby improving the mixing uniformity. Excess dielectric ceramic powder can also be dispersed between the polymer particles. Here, a / (b×1000) can be in the range of 1×10⁻⁶. -4 2×10 -4 5×10 -4 8×10 -4 1×10 -3 2×10 -3 5×10 -3 8×10 -3 The range of any one or any two values ​​from 0.01, 0.02, 0.05, 0.08, 0.1, 0.12, 0.15, 0.18, and 0.2. Further, if a / (b×1000) is less than 1×10... -4If a / (b×1000) is greater than 0.2, it means that the size of the dielectric ceramic powder is too small compared to the size of the polymer particles, and it is impossible to ensure that the dielectric ceramic powder is uniformly coated on the polymer particles. If a / (b×1000) is greater than 0.2, it means that the size of the dielectric ceramic powder is not significantly different from the size of the polymer particles, and it is difficult to ensure that the dielectric ceramic powder is coated on the polymer particles.

[0045] In some embodiments, the particle size 'a' nm of the dielectric ceramic powder satisfies: 10 nm ≤ a ≤ 200 nm. For example, the particle size 'a' nm of the dielectric ceramic powder can be any one or any two values ​​from 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, and 200 nm. It is understood that when the particle size of the dielectric ceramic powder is within the above range, it can be ensured that it is within a reasonable range to achieve better coating and improve the dielectric constant of the composite material.

[0046] In some embodiments, to obtain a suitable particle size, the preparation methods of dielectric ceramic powder include, but are not limited to, hydrothermal synthesis, sol-gel method, precipitation method, microemulsion method, ball milling method, etc.

[0047] In some embodiments, the particle size of the polymer particles is b μm, satisfying: 1 μm ≤ b ≤ 100 μm. For example, the polymer particle size b μm can be any one or any two values ​​from 1 μm, 2 μm, 5 μm, 8 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, and 100 μm. It is understood that when the polymer particle size is within the above range, it is more conducive to providing adhesion points for the dielectric ceramic powder, so as to ensure the formation of an isolation structure within the composite material, thereby further enhancing the local electric field and obtaining a high dipole moment.

[0048] In some embodiments, to obtain a suitable particle size, the methods for preparing polymer particles include, but are not limited to, pulverization, non-solvent methods, vapor-induced phase separation methods, suspension polymerization methods, etc.

[0049] In some embodiments, the dielectric ceramic powder is selected from at least one of perovskite ceramics and oxide ceramics.

[0050] In some embodiments, the dielectric ceramic powder is preferably selected from at least one of barium titanate, strontium titanate, barium strontium titanate, calcium titanate, calcium copper titanate, titanium dioxide, magnesium oxide, silicon oxide, and zirconium oxide.

[0051] In some embodiments, the polymer is selected from at least one of polyvinylidene fluoride and its copolymers, polyimide, polymethyl methacrylate, polycarbonate, polypropylene, polyethylene, polyvinyl chloride, polyvinyl alcohol, polystyrene, polyethylene terephthalate, polyhexamethylene adipamide, polycaprolactam, thermoplastic polyurethane, ethylene-vinyl acetate copolymer, maleic anhydride-grafted styrene-butadiene-styrene block copolymer, maleic anhydride-grafted styrene-ethylene-butene-styrene block copolymer, and maleic anhydride-grafted polyolefin elastomer. The polyvinylidene fluoride copolymer is selected from at least one of poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)), poly(vinylidene fluoride-tetrafluoroethylene) (P(VDF-TFE)), poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)), poly(vinylidene fluoride-trifluorochloroethylene) (P(VDF-CTFE)), poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)), poly(vinylidene fluoride-trifluoroethylene-difluorochloroethylene) (P(VDF-TrFE-CDFE)), poly(vinylidene fluoride-trifluoroethylene-trifluorochloroethylene) (P(VDF-TrFE-CTFE)), and poly(vinylidene fluoride-trifluoroethylene-hexafluoropropylene) (P(VDF-TrFE-HFP)).

[0052] In some embodiments, the number-average molecular weight of the polymer is between 10,000 and 1,000,000. For example, it can be any one or any two of the following values: 10,000, 20,000, 50,000, 80,000, 100,000, 200,000, 300,000, 400,000, 500,000, 600,000, 700,000, 800,000, 900,000, and 1,000,000. When the number-average molecular weight of the polymer meets the above range, it can ensure that it has good melt viscosity and mechanical strength, ensuring the integrity of the isolation structure and the mechanical properties of the composite material during hot pressing.

[0053] In some embodiments, the glass transition temperature of the polymer is -100 to 300°C. For example, it can be any one or any two values ​​from -100°C, -90°C, -80°C, -70°C, -60°C, -50°C, -40°C, -30°C, -20°C, -10°C, 0°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 150°C, 200°C, 250°C, and 300°C. The glass transition temperature of a polymer refers to the temperature at which the polymer transitions from a glassy state to a highly elastic state where the polymer chain segments can move freely during heating. When the above range is met, on the one hand, it exhibits brittleness at low temperatures, making it easier to mix evenly with dielectric ceramic powder; on the other hand, it can also broaden the service temperature range of the composite material.

[0054] In some embodiments, the melting temperature of the polymer is -100 to 300°C. For example, it can be any one or a range between any two of the following values: -100°C, -90°C, -80°C, -70°C, -60°C, -50°C, -40°C, -30°C, -20°C, -10°C, 0°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 150°C, 200°C, 250°C, and 300°C. The melting temperature of the polymer refers to the temperature at which the polymer changes from a solid to a liquid state during heating. Meeting the above range ensures that the polymer particles will not melt due to temperature increases during the grinding and mixing process.

[0055] In some embodiments, prior to the step of mixing and grinding the dielectric ceramic powder and polymer particles at a temperature of -200°C to -100°C, the method further includes:

[0056] The polymer particles are surface-treated to form polar groups on the surface of the polymer particles; wherein the polar groups are selected from at least one of carbonyl, carboxyl, hydroxyl, and amino groups.

[0057] It is understandable that polar groups can ensure better coating of dielectric ceramic powder onto the surface of polymer particles. This is because the surface of dielectric ceramic powder usually has a certain degree of polarity, such as hydroxyl groups (-OH) on the surface of oxides. Introducing polymer particles with polar groups can lead to polar interactions such as hydrogen bonding and electrostatic interactions with the surface of dielectric ceramic powder, increasing the adsorption and adhesion between the two. In addition, polar groups can also react chemically with the surface of dielectric ceramic powder to form chemical bonds or covalent bonds, thereby achieving a more robust powder coating. For example, carboxyl groups (-COOH) can form coordination bonds or esterification reactions with metal ions on the surface of oxides. Methods for introducing polar groups include: using surface modifiers with polar groups, such as carboxylic acids, amines, and alcohols, to introduce polar groups onto the surface of polymer particles through solution treatment or physical adsorption; or introducing polar groups onto the surface of polymer particles through chemical reactions; or introducing polar groups onto the surface of polymer particles through surface treatments such as plasma or ozone treatment.

[0058] In some embodiments, the surface treatment is plasma treatment, with a plasma treatment pressure of 10–20 Pa, a plasma treatment power of 5–15 W, and a plasma treatment time of 2–10 min; the gas used in the plasma treatment is at least one selected from Ar, N2, O2, NH3, CO, CO2, and SO2. It is understood that plasma treatment can be completed in a short time and is a highly efficient surface treatment method. Plasma treatment can achieve uniform treatment of the entire polymer particle surface, thereby resulting in a uniform distribution of introduced polar groups. By selecting different plasmas and treatment conditions, plasma treatment can introduce different polar groups onto the surface of different types of polymer particles, making it highly flexible and applicable.

[0059] In some embodiments, the hot pressing process is carried out at a temperature of 100–305°C, for a time of 5–30 min, and at a pressure of 10–20 MPa.

[0060] It is understandable that hot pressing includes vacuum oven forming or flat vulcanizing machine forming.

[0061] In some embodiments, the vacuum oven forming method includes the following steps:

[0062] (1) Adjust the oven to a suitable temperature, which is the melting temperature of the polymer, depending on the specific polymer;

[0063] (2) Place the mold containing the uniform premix into the oven and evacuate it. Form under vacuum for 30 minutes, then turn off the heating and let it cool naturally to room temperature to obtain a high dielectric composite material with an isolation structure.

[0064] In some embodiments, the flat vulcanizing machine forming method includes the following steps:

[0065] (1) Place the mold containing the premixed mixture into a cold-pressed flat vulcanizing machine, pressurize it to 10-15 MPa, and hold it for 30 minutes;

[0066] (2) Transfer the mold from step (1) to another hot press flat vulcanizing machine. The temperature set on the flat vulcanizing machine should be the melting temperature of the polymer. Pressurize to 10-15 MPa and hold for 10 min.

[0067] (3) Transfer the mold from step (2) to a cold press plate vulcanizing machine, pressurize it to 10-15 MPa, and cool it for 10 minutes to obtain a high dielectric composite material with an isolation structure.

[0068] Among them, the flat vulcanizing machine molding method has better temperature control and higher pressure, thus producing better preparation results.

[0069] In some embodiments, the preparation method of the high dielectric composite material specifically includes: using nano-scale dielectric ceramic powder and micron-scale polymer particles treated with surface plasma as raw materials, grinding them in liquid nitrogen so that the nano-ceramic powder is coated on the surface of the polymer particles or dispersed in the gaps between the polymer particles; and directly hot-pressing the uniformly ground powder to obtain a high dielectric composite material with an isolation structure.

[0070] In some embodiments, this application also provides a high dielectric composite material comprising, by weight percentage: 3 wt% to 40 wt% dielectric ceramic powder and 60 wt% to 97 wt% polymer; wherein the dielectric ceramic powder is partially aggregated to separate the polymer and form an insulating structure.

[0071] In some embodiments, preferably, this application also provides a high dielectric composite material, comprising, by weight percentage: 5 wt% to 25 wt% dielectric ceramic powder and 75 wt% to 95 wt% polymer.

[0072] In some embodiments, preferably, this application also provides a high dielectric composite material, comprising, by weight percentage: 10wt% to 20wt% dielectric ceramic powder and 80wt% to 90wt% polymer.

[0073] In some embodiments, preferably, this application also provides a high dielectric composite material, comprising, by weight percentage: 10wt% to 15wt% dielectric ceramic powder and 85wt% to 90wt% polymer.

[0074] In some embodiments, this embodiment provides a polymer-based dielectric composite material with an isolation structure. This structure allows for the regular and continuous enrichment of dielectric ceramic powder in the composite matrix, which is beneficial for adjusting the polarization direction in the electric field, enhancing the local electric field, and obtaining a high dipole moment. Under the same formulation, the dielectric constant of the composite material prepared in this embodiment is increased by up to 60% compared with that of traditional melt blending and solution blending methods.

[0075] Example 1

[0076] (1) Raw materials and formula

[0077] Raw materials: PVDF microspheres: First, PVDF resin was dissolved in N,N-dimethylacetamide to a solid content of 20 wt%. The solution was magnetically stirred at 500 rpm for 8 hours at 70°C to obtain a homogeneous PVDF solution. The homogeneous PVDF solution was then poured into a clean petri dish and placed in an environment of 30°C and 100% humidity for 12 hours. After 12 hours, the sample was removed, washed with deionized water, filtered, and dried at 60°C for 48 hours to obtain PVDF microspheres with a particle size of 2-3 μm and a molecular weight of 50,000.

[0078] Barium titanate nanoparticles: obtained by hydrothermal synthesis, with a particle size of 100 nm.

[0079] Formula: The mass ratio of PVDF to barium titanate is 75:25.

[0080] (2) Coating of fillers on polymer surfaces

[0081] PVDF microspheres were subjected to low-temperature plasma treatment under the following conditions: argon atmosphere, treatment power 100 W, treatment pressure 10 Pa, and treatment time 10 min. The treated microspheres were then mixed with nano-barium titanate in liquid nitrogen (-196℃) and ground to obtain a premix. See [link to relevant documentation] Figure 1 and Figure 2 It can be clearly seen that the barium titanate nanoparticles are coated on the surface of the PVDF microspheres.

[0082] (3) Preparation of isolation structure

[0083] Place the mold containing the homogeneous premix into a cold-press flat vulcanizing machine, pressurize it to 10 MPa, and hold for 30 minutes. Then transfer the mold to another hot-press flat vulcanizing machine at 200°C, pressurize it to 10 MPa, and hold for 15 minutes. Finally, transfer the mold to a cold-press flat vulcanizing machine, pressurize it to 10 MPa, and cool it for 10 minutes. See [link to relevant documentation]. Figure 3 The high-dielectric composite material with an isolation structure is obtained by mold opening.

[0084] See Figure 4 The figure shows a schematic diagram of the structure of the dielectric composite material. As can be seen from the figure, the dielectric ceramic powder is isolated by the polymer and is continuously distributed in the polymer to form a three-dimensional network structure.

[0085] Example 2

[0086] The specific preparation method is the same as in Example 1, except that the raw materials for Example 2 are PVDF microspheres and barium titanate, with a mass ratio of 80:20; and the particle size of the raw materials is different from that in Example 1.

[0087] Example 3

[0088] The specific preparation method is the same as in Example 1, except that the raw materials for Example 3 are PVDF and strontium titanate, with a mass ratio of 90:10, and the particle size of the raw materials is different from that in Example 1.

[0089] Example 4

[0090] The specific preparation method is the same as in Example 1, except that the raw materials for Example 4 are polymethyl methacrylate (PMMA) and strontium titanate, with a mass ratio of 69:31, and the particle size of the raw materials is different from that in Example 1.

[0091] Example 5

[0092] The specific preparation method is the same as in Example 1, except that the raw materials for Example 5 are polyvinyl chloride (PVC) and barium titanate, with a mass ratio of 90:10, and the particle size of the raw materials is different from that in Example 1.

[0093] Example 6

[0094] The specific preparation method is the same as in Example 1, except that the raw materials for Example 6 are polyvinyl chloride (PVC) and barium strontium titanate, with a mass ratio of 83:17, and the particle size of the raw materials is different from that in Example 1.

[0095] Example 7

[0096] The specific preparation method is the same as in Example 1, except that the raw materials for Example 7 are polystyrene (PS) and barium titanate, with a mass ratio of 68:32, and the particle size of the raw materials is different from that in Example 1, and the grinding temperature is different.

[0097] Example 8

[0098] The specific preparation method is the same as in Example 1, except that the raw materials for Example 8 are PS and calcium copper titanate, with a mass ratio of 70:30, and the particle size of the raw materials is different from that in Example 1, and the grinding temperature is different.

[0099] Comparative Example 1

[0100] The raw materials used are the same as in Example 1, except that the mass ratio of PVDF to barium titanate is 99:1.

[0101] Comparative Example 2

[0102] The raw materials used are the same as in Example 1, except that the mass ratio of PVDF to barium titanate is 50:50.

[0103] Comparative Example 3

[0104] The raw materials used were the same as in Example 1, except that PVDF microspheres were mixed and ground with barium titanate nanoparticles at room temperature (25°C) to obtain a premix.

[0105] Comparative Example 4-5

[0106] The raw materials used are the same as in Example 1, except that the particle size a nm of the dielectric ceramic powder and the particle size b μm of the polymer particles do not meet the 1×10⁻⁶ requirement. -4 The range of ≤a / (b×1000)≤0.2.

[0107] Comparative Example 6

[0108] The raw materials used were the same as in Example 1, except that PVDF with a particle size of 2-3 μm and barium titanate with a particle size of 100 nm were directly mixed at a mass ratio of 75:25 on a two-roll mill at 200°C without grinding. The mixed PVDF / barium titanate composite material was placed in a mold and placed on a hot-press vulcanizing machine at 200°C, pressurized to 10 MPa, and held for 15 min. Subsequently, the mold was transferred to a cold-press vulcanizing machine, pressurized to 10 MPa, cooled for 10 min, and the mold was opened to obtain the sample.

[0109] The raw materials, particle size, and process parameters used in Examples 1-8 and Comparative Examples 1-6 are shown in Table 1. The characterization properties of the obtained high-dielectric composite materials are shown in Table 2.

[0110] The performance characteristics include dielectric constant and dielectric loss, which are obtained using a precision impedance analyzer.

[0111] The grinding process is carried out at -196℃ in a liquid nitrogen environment; other temperatures, such as -130℃ and -150℃, can be achieved using an ultra-low temperature freezer or other low-temperature grinding equipment.

[0112] Table 1

[0113]

[0114]

[0115] Table 2

[0116]

[0117] In Table 2: * indicates that the sample cannot be hot-pressed, therefore there is no data for dielectric constant and dielectric loss.

[0118] As shown in Tables 1 and 2, the dielectric constant of the high-dielectric composite material with the isolation structure is significantly improved compared to the polymer. Comparative Example 1 had too low a ceramic powder content, failing to form an isolation structure; Comparative Example 2 had too high a ceramic powder content, resulting in significant stratification after premixing and making hot pressing impossible; Comparative Example 3 was not ground below the polymer's glass transition temperature, leading to ineffective dispersion of the ceramic powder; Comparative Examples 4 and 5 had ceramic powder particles that were either too large or too small, failing to effectively coat the polymer microspheres and thus hindering the formation of an isolation structure. Comparative Example 6 involved direct melt blending, resulting in random dispersion of the ceramic powder and the failure to form an isolation structure. Compared to Comparative Examples 1-6, the high-dielectric composite materials prepared in Examples 1-8 with the isolation structure exhibit a significantly improved dielectric constant.

[0119] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0120] The above provides a detailed description of a high-dielectric composite material and its preparation method provided in the embodiments of this application, and uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the technical solutions and core ideas of this application. Those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method of preparing a high dielectric composite material, characterized by, The method comprises the following steps: surface treatment is performed on the polymer particles to form polar groups on the surface of the polymer particles; wherein the polar groups are selected from at least one of a carbonyl group, a carboxyl group, a hydroxyl group, and an amino group; mixing and grinding the dielectric ceramic powder and the polymer particles at a temperature of -200 ℃ to -100 ℃ to allow the dielectric ceramic powder to coat the surface of the polymer particles or disperse between the polymer particles, to obtain a premix; heat pressing the premix to obtain a high-dielectric composite material with an isolation structure; wherein part of the dielectric ceramic powder is aggregated to separate the polymer and form the isolation structure; the mass ratio of the dielectric ceramic powder to the polymer particles is 3-40:60-97; The particle size of the dielectric ceramic powder is a nm, and the particle size of the polymer particles is b μm, satisfying: 1 x 10 -4 ≤ a / (b x 1000) ≤ 0.

2.

2. The method for preparing a high-dielectric composite material according to claim 1, characterized in that, the particle size a nm of the dielectric ceramic powder satisfies 10 nm≤a≤200 nm; and / or the particle size b μm of the polymer particles satisfies 1 μm≤b≤100 μm.

3. The method for preparing a high-dielectric composite material according to claim 1, characterized in that, The dielectric ceramic powder is selected from at least one of a perovskite ceramic and an oxide ceramic.

4. The method for preparing a high-dielectric composite material according to claim 1, characterized in that, The dielectric ceramic powder is selected from at least one of barium titanate, strontium titanate, barium strontium titanate, calcium titanate, calcium copper titanate, titanium dioxide, magnesium oxide, silicon oxide, and zirconium oxide.

5. A method for preparing a high-dielectric composite material according to claim 1, characterized in that, The polymer is selected from at least one of polyvinylidene fluoride and a copolymer thereof, polyimide, polymethyl methacrylate, polycarbonate, polypropylene, polyethylene, polyvinyl chloride, polyvinyl alcohol, polystyrene, polyethylene terephthalate, polyhexamethylene adipate, polycaprolactam, thermoplastic polyurethane, ethylene-vinyl acetate copolymer, maleic anhydride grafted styrene-butadiene-styrene block copolymer, maleic anhydride grafted styrene-ethylene-butylene-styrene block copolymer, and maleic anhydride grafted polyolefin elastomer. The number average molecular weight of the polymer is 10,000-1,000,000; or The glass transition temperature of the polymer is -100-300 ℃; or The melting temperature of the polymer is -100-300 ℃.

6. A method for preparing a high-dielectric composite material according to claim 1, characterized in that, The surface treatment is plasma treatment, the pressure of the plasma treatment is 10-20 Pa, the power of the plasma treatment is 5-15 W, and the time of the plasma treatment is 2-10 min; the gas used in the plasma treatment is at least one selected from Ar, N2, O2, NH3, CO, CO2, and SO2.

7. A method for preparing a high-dielectric composite material according to claim 1, characterized in that, In the heat pressing treatment, the treatment temperature is 100-305 ℃, the treatment time is 5-30 min, and the treatment pressure is 10-20 MPa.

8. A high dielectric composite material prepared by the method of any one of claims 1 to 7, characterized in that, In mass percentage, 3wt%-40wt% of the dielectric ceramic powder and 60wt%-97wt% of the polymer are included; wherein part of the dielectric ceramic powder is aggregated to separate the polymer and form the isolation structure.

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