High-thermal-conductivity polytetrafluoroethylene insulating material and preparation method thereof

Abstract

The invention provides a high-thermal-conductivity polytetrafluoroethylene insulating material and a preparation method thereof, and the high-thermal-conductivity polytetrafluoroethylene insulating material comprises the following raw material components in parts by weight: 70-90 parts of fluorine-containing resin, 20-30 parts of a modified composite thermal conductive filler, 2-5 parts of a moisture-resistant modifier, 0.5-1.5 parts of a dispersant and 0.3-0.8 part of a rheology modifier, the composite heat-conducting filler comprises a mixture of hexagonal boron nitride subjected to surface modification by a silane coupling agent, fluorinated ceramic microspheres and spherical silicon carbide. Through synergistic compounding and interface modification of the composite heat-conducting filler, a continuous three-dimensional heat-conducting network is constructed, the heat conductivity of the material is improved by 5-6 times compared with that of pure polytetrafluoroethylene, the product has high heat conductivity, high insulation, low dielectric loss and excellent moisture-resistant stability, and the process is stable and controllable.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, specifically to a high thermal conductivity polytetrafluoroethylene insulating material and its preparation method. Background Technology

[0002] Polytetrafluoroethylene (PTFE), with its excellent dielectric properties (dielectric constant as low as 2.1, dielectric loss ≤0.0002), strong corrosion resistance, and chemical stability, has become a core material in the fields of high-frequency insulation and high-voltage power equipment. Pure PTFE has two major bottlenecks: first, its extremely low thermal conductivity means that the large amount of heat generated during the operation of high-voltage switches and other power equipment cannot be dissipated quickly, leading to accelerated thermal aging and dielectric property degradation, severely affecting the service life and operational reliability of the equipment; second, insufficient moisture resistance. In humid environments such as outdoors and near the sea, the interface between PTFE and fillers easily absorbs moisture, resulting in a decrease in volume resistivity and an increase in dielectric loss, limiting its long-term application under complex climatic conditions. With the rapid development of the power industry towards high voltage and high current, and the widespread application of 5G communication and outdoor power equipment, the inherent defects of existing PTFE materials are becoming increasingly prominent.

[0003] To address the aforementioned issues, existing technologies often employ a single thermally conductive filler (such as alumina or boron nitride) to fill PTFE. However, this approach has several drawbacks: First, a single filler cannot simultaneously improve thermal conductivity and interfacial compatibility. For instance, while plate-like boron nitride (h-BN) exhibits excellent thermal conductivity, its tendency to align in-plane results in low out-of-plane thermal conductivity, and its weak interfacial bonding with PTFE easily introduces interfacial voids. Second, moisture-resistant modification often relies on surface coating, and the modified layer is prone to detachment during high-temperature processing or long-term use, resulting in poor durability. Third, uneven dispersion of fillers during the preparation process can lead to agglomeration and breakage of thermal conductivity pathways, making it impossible to achieve synergistic optimization of thermal conductivity, insulation, and moisture resistance.

[0004] Therefore, developing a PTFE insulation material that combines high thermal conductivity, high insulation, moisture resistance, and stable and controllable process can not only overcome the pain points of existing technologies, but also meet the special needs of the power industry for new materials for high-voltage and high-current products. It can provide core materials with better performance for high-voltage switches, power equipment and other fields, and has important industrial application value and market prospects. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a PTFE insulation material and its preparation method that combine high thermal conductivity, high insulation, moisture resistance, and stable and controllable process. This invention addresses the pain points of existing technologies and better meets the special needs of the power industry for new materials for high-voltage and high-current products. It provides a core material with better performance for high-voltage switches, power equipment and other fields, and has significant industrial application value and market prospects.

[0006] The technical solution of the present invention: A high thermal conductivity polytetrafluoroethylene (PTFE) insulating material, wherein the raw materials of the high thermal conductivity PTFE insulating material, by weight, include the following components: 70-90 parts of fluorinated resin, 20-30 parts of modified composite thermally conductive filler, 2-5 parts of moisture-resistant modifier, 0.5-1.5 parts of dispersant, and 0.3-0.8 parts of rheology modifier; wherein the modified composite thermally conductive filler comprises a mixture of hexagonal boron nitride surface modified with silane coupling agent, fluorinated ceramic microspheres, and spherical silicon carbide.

[0007] Furthermore, the weight ratio of the hexagonal boron nitride, fluorinated ceramic microspheres, and spherical silicon carbide is (2-3):(1-2):(2-3).

[0008] Furthermore, the fluorinated resin is a polytetrafluoroethylene suspension resin.

[0009] Furthermore, the hexagonal boron nitride has a plate-like structure and a particle size of 5-10 μm; the fluorinated ceramic microspheres are at least one of fluorinated alumina, fluorinated silicon dioxide, or boron nitride microspheres; and the spherical silicon carbide has a particle size of 10-20 μm.

[0010] Furthermore, the silane coupling agent is at least one of phenyltrimethoxysilane, epoxypropyltrimethoxysilane, and diphenyldimethoxysilane.

[0011] Furthermore, the moisture-resistant modifier is at least one of trifluoroethyl acrylate, octafluoropentyl methacrylate, trifluoroethyl methacrylate, and hexafluorobutyl acrylate.

[0012] Furthermore, the dispersant is at least one of BYK-9076 and BYK-190; the rheology modifier is at least one of bentonite, silicate, anti-settling wax, and polyurea.

[0013] Furthermore, the preparation method of the modified composite thermally conductive filler includes the following steps: Hexagonal boron nitride, fluorinated ceramic microspheres, and spherical silicon carbide were mixed in a weight ratio, and a mixed solution of deionized water and ethanol was added. The mixture was ultrasonically dispersed for 25-35 minutes. The pH of the solution was adjusted to 4-5, a silane coupling agent was added, and the mixture was stirred at 50-60℃ for 80-100 minutes. The mixture was then dried at 75-85℃ for 20-28 hours. After drying, the mixture was passed through a 100-120 mesh sieve to obtain the modified composite thermally conductive filler.

[0014] This invention provides a method for preparing a polytetrafluoroethylene (PTFE) insulating material with high thermal conductivity, characterized by comprising the following steps: (1) Take fluorinated resin by weight, add dispersant and rheology modifier, stir at 380-420 r / min for 55-65 min; add modified composite thermally conductive filler and moisture-resistant modifier in sequence, and mix at high speed to obtain premixed emulsion; (2) The premixed emulsion is cast into a film, dried at 75-85℃ for 4-6 min, and then heat-treated at 370-390℃ for 25-35 min to obtain a porous preform film; (3) Press the porous preform film described in step (2) into a dense preform, perform stepwise sintering under inert gas protection, and then cool down to obtain a polytetrafluoroethylene insulating material with high thermal conductivity.

[0015] Furthermore, in step (3), the stepwise sintering specifically involves heating to 320-340℃ at a rate of 20-50℃ / h and holding for 1-4 hours; then heating to 365-380℃ at a rate of 20-40℃ / h and holding for 2-8 hours. The inert gas in step (3) is nitrogen or argon, and the purity of the inert gas is ≥99.99%.

[0016] Beneficial effects: The high thermal conductivity polytetrafluoroethylene insulating material of the present invention has the following beneficial effects: 1. The modified composite thermally conductive filler adopts a special compound system. After being modified by silane coupling agent, it constructs a continuous and uniform three-dimensional thermally conductive network. The thermal conductivity of the material is 5-6 times higher than that of pure PTFE. It can quickly dissipate the concentrated heat generated during the operation of high-voltage equipment, delay the thermal aging of the material, and ensure the long-term stable operation of the equipment, which meets the heat dissipation requirements of the power industry for high-voltage and high-current products.

[0017] 2. Low dielectric loss filler and electrical-grade PTFE emulsion are selected to ensure stable dielectric constant and low dielectric loss, meeting high-voltage insulation requirements. The silane coupling agent and moisture-resistant modifier work synergistically to form double hydrophobic protection on the material surface and interface, effectively resisting moisture adsorption in humid environments, avoiding insulation performance degradation, and broadening the application scenarios of the material in complex climatic conditions such as outdoor and coastal areas.

[0018] 3. The process is controllable. The preparation method, especially the stepwise sintering process, is conducive to eliminating internal stress, promoting the fusion of phases, and ensuring the uniformity and stability of the material structure. Detailed Implementation

[0019] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope.

[0020] The polytetrafluoroethylene suspension resin was purchased from Shandong Dongyue; the ceramic microspheres were purchased from Shanghai Bihe Industry & Trade Co., Ltd., model G-600; the spherical silicon carbide was purchased from Shanghai Yingfeng Ruihuang Metal Materials Co., Ltd., with a particle size of 20μm; and the hexagonal boron nitride was purchased from Guangzhou Hongwu Materials Technology Co., Ltd., with a specification of 6µm.

[0021] Unless otherwise specified, all chemical reagents used in this invention are commercially available analytical grade reagents.

[0022] Preparation method of fluorinated ceramic microspheres: S1: Add ceramic microspheres to a 5% (w / w) dilute hydrochloric acid solution, ultrasonically clean for 30 min, then wash repeatedly with deionized water until the pH of the washing solution is 7, place the ceramic microspheres in a vacuum drying oven and dry at 120℃ for 2 h. S2: Dry fluorinated ceramic microspheres, polytetrafluoroethylene suspension resin, and aluminum trichloride were placed in a planetary ball mill jar at a mass ratio of 10:4:0.5. Anhydrous ethanol was added as a dispersion medium, with a solid-liquid mass ratio of 1:6. The ball milling speed was set to 350 r / min, and the milling time was 2.5 h to obtain a uniform ceramic microsphere-PTFE composite slurry. Then, the ceramic microsphere-PTFE composite slurry was placed in a 65℃ constant temperature water bath and stirred until the anhydrous ethanol was completely evaporated. The slurry was then passed through a 120-mesh sieve to obtain the composite powder. S3: Place the composite powder in a tube furnace, heat it to 600℃ under nitrogen protection, hold it at that temperature for 4 hours, and after the reaction is complete, cool it to room temperature under a nitrogen atmosphere. After slight grinding and dispersion, fluorinated ceramic microspheres are obtained.

[0023] Example 1 Raw material ratio (parts by weight): Polytetrafluoroethylene suspension resin (60% solid content): 80 parts; Modified composite thermally conductive filler A: 25 parts; Moisture-resistant modifier (trifluoroethyl acrylate): 3 parts; Dispersant (BYK-9076): 1 part; Rheology modifier (bentonite): 0.5 parts.

[0024] Preparation of modified composite thermally conductive filler A: Hexagonal boron nitride, fluorinated ceramic microspheres, and spherical silicon carbide (hexagonal boron nitride, fluorinated ceramic microspheres, and spherical silicon carbide in a weight ratio of 2:1:2) were mixed. A mixed solution of deionized water and ethanol (volume ratio of deionized water to ethanol 1:1) was added, which was ultrasonically dispersed for 30 min. The pH of the solution was adjusted to 4.5. 0.75 parts of silane coupling agent (Z6124) (Z6124 weight is 3% of the total weight of hexagonal boron nitride, fluorinated ceramic microspheres, and spherical silicon carbide) were added. The mixture was stirred at 55℃ for 90 min, and then dried at 80℃ for 24 h. After drying, it was passed through a 120-mesh sieve to obtain the modified composite thermally conductive filler.

[0025] A method for preparing highly thermally conductive polytetrafluoroethylene (PTFE) insulating material includes the following steps: (1) Take fluorinated resin by weight, add dispersant and rheology modifier, stir at 400 r / min for 60 min; add modified composite thermally conductive filler and moisture-resistant modifier in sequence, and mix at high speed to obtain premixed emulsion; (2) The premixed emulsion is cast into a film, dried at 80°C for 5 min, and then heat-treated at 380°C for 30 min to obtain a porous preform film; (3) Press the porous preform film described in step (2) under a pressure of 40 MPa for 5 minutes to form a preform of Φ50×5mm. Then, under nitrogen protection, the preform is sintered in stages. Under nitrogen protection, the temperature is raised to 330℃ at 30℃ / h and held for 2 hours. Then, the temperature is raised to 370℃ at 30℃ / h and held for 5 hours. Finally, the temperature is lowered to room temperature at 30℃ / h to obtain a polytetrafluoroethylene insulating material with high thermal conductivity.

[0026] Example 2 This preparation example is basically the same as Example 1, except that: Raw material ratio (parts by weight): Polytetrafluoroethylene suspension resin (60% solid content): 75 parts; Modified composite thermally conductive filler B: 30 parts; Moisture-resistant modifier (trifluoroethyl methacrylate): 4 parts; Dispersant (BYK-9076): 1.2 parts; Rheology modifier (bentonite): 0.6 parts; The preparation of modified composite thermal conductive filler B is basically the same as that of modified composite thermal conductive filler A, except that the weight ratio of hexagonal boron nitride, fluorinated ceramic microspheres and spherical silicon carbide is 3:2:3, and the silane coupling agent (Z6124) is 0.75 parts (Z6124 weight is 2% of the total weight of hexagonal boron nitride, fluorinated ceramic microspheres and spherical silicon carbide).

[0027] Example 3 This preparation example is basically the same as Example 1, except that: Raw material ratio (parts by weight): Polytetrafluoroethylene suspension resin (60% solid content): 90 parts; Modified composite thermally conductive filler C: 20 parts; Moisture-resistant modifier (trifluoroethyl acrylate): 2 parts; Dispersant (BYK-9076): 0.5 parts; Rheology modifier (anti-settling wax): 0.3 parts; The preparation of modified composite thermal conductive filler C is basically the same as that of modified composite thermal conductive filler A, except that the weight ratio of hexagonal boron nitride, fluorinated ceramic microspheres and spherical silicon carbide is 2:1.5:2.5, and the silane coupling agent (Z6124) is 0.4 parts (Z6124 weight is 2% of the total weight of hexagonal boron nitride, fluorinated ceramic microspheres and spherical silicon carbide).

[0028] Example 4 This preparation example is basically the same as Example 1, except that: Raw material ratio (parts by weight): Polytetrafluoroethylene suspension resin (60% solid content): 80 parts; Modified composite thermally conductive filler D (hexagonal boron nitride, fluorinated ceramic microspheres, and spherical silicon carbide in a weight ratio of 1:3:1): 25 parts; Moisture-resistant modifier (trifluoroethyl acrylate): 3 parts; Dispersant (BYK-9076): 1 part; Rheology modifier (bentonite): 0.5 parts; Silane coupling agent (Z6124): 0.75 parts (3% of the total weight of hexagonal boron nitride, fluorinated ceramic microspheres, and spherical silicon carbide); The preparation of modified composite thermal conductive filler D is basically the same as that of modified composite thermal conductive filler A, except that the weight ratio of hexagonal boron nitride, fluorinated ceramic microspheres and spherical silicon carbide is 1:3:1, and the silane coupling agent (Z6124) is 0.75 parts (the weight of Z6124 is 3% of the total weight of hexagonal boron nitride, fluorinated ceramic microspheres and spherical silicon carbide).

[0029] Comparative Example 1 Raw material ratio (parts by weight): Polytetrafluoroethylene suspension resin (60% solid content): 80 parts; Composite thermally conductive filler E: 25 parts; Moisture-resistant modifier (trifluoroethyl acrylate): 3 parts; Dispersant (BYK-9076): 1 part; Rheology modifier (bentonite): 0.5 parts.

[0030] Preparation of composite thermally conductive filler E: Hexagonal boron nitride, fluorinated ceramic microspheres, and spherical silicon carbide (hexagonal boron nitride, fluorinated ceramic microspheres, and spherical silicon carbide in a weight ratio of 2:1:2) were mixed. A mixed solution of deionized water and ethanol (volume ratio of deionized water to ethanol 1:1) was added, which was then ultrasonically dispersed for 30 min. The pH of the solution was adjusted to 4.5, and then the mixture was dried at 80℃ for 24 h. After drying, the mixture was passed through a 120-mesh sieve to obtain the composite thermally conductive filler.

[0031] A method for preparing highly thermally conductive polytetrafluoroethylene (PTFE) insulating material includes the following steps: (1) Take fluorinated resin by weight, add dispersant and rheology modifier, stir at 400 r / min for 60 min; add composite thermally conductive filler and moisture-resistant modifier in sequence, and mix at high speed to obtain premixed emulsion; (2) The premixed emulsion is cast into a film, dried at 80°C for 5 min, and then heat-treated at 380°C for 30 min to obtain a porous preform film; (3) Press the porous preform film described in step (2) under a pressure of 40 MPa for 5 minutes to form a preform of Φ50×5mm. Then, under nitrogen protection, the preform is sintered in stages. Under nitrogen protection, the temperature is raised to 330℃ at 30℃ / h and held for 2 hours. Then, the temperature is raised to 370℃ at 30℃ / h and held for 5 hours. Finally, the temperature is lowered to room temperature at 30℃ / h to obtain a polytetrafluoroethylene insulating material with high thermal conductivity.

[0032] Comparative Example 2 This preparation example is basically the same as Example 1, except that: Raw material ratio (parts by weight): Polytetrafluoroethylene suspension resin (60% solid content): 80 parts; Modified composite thermally conductive filler A: 25 parts; Dispersant (BYK-9076): 1 part; Rheology modifier (bentonite): 0.5 parts;

[0033] A method for preparing highly thermally conductive polytetrafluoroethylene (PTFE) insulating material includes the following steps: (1) Take fluorinated resin by weight, add dispersant and rheology modifier, stir at 400 r / min for 60 min; add modified composite thermally conductive filler in sequence, and mix at high speed to obtain premixed emulsion; (2) The premixed emulsion is cast into a film, dried at 80°C for 5 min, and then heat-treated at 380°C for 30 min to obtain a porous preform film; (3) Press the porous preform film described in step (2) under a pressure of 40 MPa for 5 minutes to form a preform of Φ50×5mm. Then, under nitrogen protection, the preform is sintered in stages. Under nitrogen protection, the temperature is raised to 330℃ at 30℃ / h and held for 2 hours. Then, the temperature is raised to 370℃ at 30℃ / h and held for 5 hours. Finally, the temperature is lowered to room temperature at 30℃ / h to obtain a polytetrafluoroethylene insulating material with high thermal conductivity.

[0034] Comparative Example 3 This preparation example is basically the same as Example 1, except that: Raw material ratio (parts by weight): Polytetrafluoroethylene suspension resin (60% solid content): 80 parts; Modified composite thermally conductive filler A: 40 parts; Moisture-resistant modifier (trifluoroethyl acrylate): 3 parts; Dispersant (BYK-9076): 1 part; Rheology modifier (bentonite): 0.5 parts.

[0035] The following performance tests were performed on the materials obtained in Examples 1-4 and Comparative Examples 1-3: 1. Thermal Conductivity: According to the standard "Determination of Thermal Conductivity and Thermal Diffusion Coefficient of Plastics - Laser Flash Method" (GB / T 22588-2008), a laser thermal conductivity meter was used. A circular sample with a diameter of 25.4 mm × 0.6 mm was cut. At room temperature (25℃), both sides of the sample were coated with gold to ensure uniform heat absorption. The gold coating thickness was typically 100 nm. The sample was placed on the instrument's sample stage, and a laser pulse was used to vertically irradiate the upper surface of the sample. The surface temperature change curve over time was recorded. The thermal diffusion coefficient was calculated using the instrument's built-in software. Combined with the sample density and specific heat capacity (calculated according to the mixing principle), the thermal conductivity was derived. Three samples were measured in parallel, and the arithmetic mean was taken as the final result, with an allowable error of ≤5%.

[0036] 2. Dielectric constant and dielectric loss (10GHz): Referring to the "Stripline Method for Testing Dielectric Properties of Microwave Dielectric Materials" (GB / T 16938-2008), a vector network analyzer was used with a stripline test fixture. A rectangular sample of 30mm × 50mm × 1mm was cut, and the surface copper foil was etched away. The sample was then washed with deionized water and dried at 80℃ for 2 hours. The sample was tightly fitted to the middle of the stripline fixture, and constant pressure was applied to ensure good contact. The test frequency range was 1~15GHz. The dielectric constant and dielectric loss tangent at 10GHz were extracted. Three samples were measured in parallel, and the arithmetic mean was taken as the final result. The allowable error for the dielectric constant was ≤0.05, and the allowable error for the dielectric loss was ≤0.0002.

[0037] 3. Volume Resistivity: According to the "Test Methods for Volume Resistivity and Surface Resistivity of Solid Insulating Materials" (GB / T1410-2006), a high-resistivity meter was used. A square sample of 100mm × 100mm × 3mm was cut and placed in a standard environment of 23℃ and 50% relative humidity for 24 hours. The sample was placed between the electrodes of the instrument, a 500V DC voltage was applied, and the resistance value was read after 1 minute. The volume resistivity was calculated based on the sample thickness and electrode area. Three samples were measured in parallel, and the arithmetic mean was taken as the final result, with an allowable error ≤10%.

[0038] 4. Tensile Strength: According to GB / T 1040.1-2018, "Determination of Tensile Properties of Plastics Part 1: General Rules", an electronic universal testing machine was used. The specimens were processed into standard dumbbell shape (Type I), with a gauge length of 25 mm, a width of 4 mm, and a thickness of 3 mm. A tensile force was applied at a tensile rate of 2 mm / min at 23℃. The maximum load at fracture was recorded, and the tensile strength was calculated based on the specimen's cross-sectional area. Three specimens were tested in parallel, and the arithmetic mean was taken as the final result, with an allowable error ≤3%.

[0039] 5. Moisture Resistance Stability (Change in Dielectric Loss after Damp Heat Aging): Referring to "Environmental Testing for Electrical and Electronic Products Part 2: Test Methods Test Db: Alternating Damp Heat (12h+12h Cycle)" (GB / T 2423.4-2008), cut a 30mm×50mm×1mm dielectric performance test specimen. First, measure the initial dielectric loss (10GHz). Place the specimen in a damp heat test chamber, set the temperature to 85℃ and the relative humidity to 85%, and continue aging for 1000h. After aging, allow the specimen to recover under standard conditions for 24h, and measure the dielectric loss again. Calculate the difference between the dielectric loss after aging and before aging, as the evaluation index for moisture resistance stability. Perform parallel testing on 3 specimens, and take the arithmetic mean as the final result, with an allowable error ≤0.0003.

[0040] Table 1: Performance Test Results

[0041] As shown in Table 1, the high thermal conductivity polytetrafluoroethylene (PTFE) insulating materials prepared in Examples 1-3 of this invention exhibit excellent performance in terms of high thermal conductivity, high insulation, moisture resistance, and mechanical stability. Specific analysis is as follows: Comparing Example 4 with Example 1, it can be seen that when the proportion of the composite thermally conductive filler deviates, the material's thermal conductivity decreases, dielectric loss increases, volume resistivity decreases, and tensile strength decreases. This demonstrates that a reasonable compounding ratio of hexagonal boron nitride, fluorinated ceramic microspheres, and spherical silicon carbide is key to constructing a continuous three-dimensional thermally conductive network and optimizing interfacial bonding. Excessive fluorinated ceramic microspheres disrupt the continuity of the thermal conductivity pathway and introduce more interfacial voids, leading to a simultaneous decline in insulation and mechanical properties. Comparing Comparative Example 1 with Example 1, it can be seen that without modification of the composite thermally conductive filler with a silane coupling agent, the material's thermal conductivity decreases, dielectric loss increases, volume resistivity decreases, and tensile strength decreases. This indicates that the silane coupling agent can effectively reduce the interfacial thermal resistance between the filler and the PTFE matrix and promote uniform dispersion of the filler. The lack of this modification step leads to filler agglomeration, weak interfacial bonding, and inability to form a complete thermally conductive network. The addition of a moisture-resistant modifier creates an effective thermal conductivity path, but also disrupts the insulation continuity and structural integrity of the material. Comparing Comparative Example 2 with Example 1, it is evident that without the moisture-resistant modifier, the material's moisture resistance stability deteriorates significantly, and dielectric loss increases after humid heat aging. Although the thermal conductivity is similar to Example 1, the performance degradation rate in humid environments is significantly accelerated. This indicates that the synergistic effect of the moisture-resistant modifier and the silane coupling agent can form a double hydrophobic protection on the material surface and interface, effectively inhibiting moisture adsorption. The lack of this component will prevent the material from meeting the long-term use requirements of humid environments such as outdoors and near the sea. Comparing Comparative Example 3 with Example 1, it is evident that when the amount of modified composite thermally conductive filler exceeds the range, the tensile strength of the material decreases, dielectric loss increases, and volume resistivity decreases. This is because excessive filler disrupts the continuity of the PTFE matrix, leading to increased internal porosity. Simultaneously, filler agglomeration intensifies, weakening the mechanical support and introducing interfacial polarization centers, thus affecting both insulation performance and thermal conductivity. This demonstrates that the filler amount needs to be controlled within a reasonable range to balance various performance indicators.

[0042] In summary, this invention achieves synergistic optimization of the material's thermal conductivity, insulation, moisture resistance, and mechanical properties through precise compounding of composite thermally conductive fillers, interfacial modification of silane coupling agents, and the synergistic effect of moisture-resistant modifiers. All key indicators meet the stringent requirements of applications such as high-voltage switches and 5G communication base stations. Any deviation from the components or proportions defined in the claims will lead to significant performance degradation.

[0043] The present invention can also be implemented in various other ways. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A high thermal conductivity polytetrafluoroethylene insulating material, characterized in that, The raw materials of the high thermal conductivity polytetrafluoroethylene insulating material, by weight, include the following components: 70-90 parts of fluorinated resin, 20-30 parts of modified composite thermally conductive filler, 2-5 parts of moisture-resistant modifier, 0.5-1.5 parts of dispersant, and 0.3-0.8 parts of rheology modifier; the modified composite thermally conductive filler comprises a mixture of hexagonal boron nitride, fluorinated ceramic microspheres, and spherical silicon carbide surface modified with silane coupling agent.

2. The high thermal conductivity polytetrafluoroethylene insulating material according to claim 1, characterized in that, The weight ratio of the hexagonal boron nitride, fluorinated ceramic microspheres, and spherical silicon carbide is (2-3):(1-2):(2-3).

3. The high thermal conductivity polytetrafluoroethylene insulating material according to claim 1, characterized in that, The fluorinated resin is a polytetrafluoroethylene suspension resin.

4. The high thermal conductivity polytetrafluoroethylene insulating material according to claim 1, characterized in that, The hexagonal boron nitride has a plate-like structure and a particle size of 5-10 μm; the fluorinated ceramic microspheres are at least one of fluorinated alumina, fluorinated silicon dioxide, or boron nitride microspheres; the spherical silicon carbide has a particle size of 10-20 μm.

5. The high thermal conductivity polytetrafluoroethylene insulating material according to claim 1, characterized in that, The silane coupling agent is at least one of phenyltrimethoxysilane, epoxypropoxypropyltrimethoxysilane, and diphenyldimethoxysilane.

6. The high thermal conductivity polytetrafluoroethylene insulating material according to claim 1, characterized in that, The moisture-resistant modifier is at least one of trifluoroethyl acrylate, octafluoropentyl methacrylate, and hexafluorobutyl acrylate.

7. The high thermal conductivity polytetrafluoroethylene insulating material according to claim 1, characterized in that, The dispersant is at least one of BYK-9076 and BYK-190; the rheology modifier is at least one of bentonite, silicate, anti-settling wax, and polyurea.

8. The high thermal conductivity polytetrafluoroethylene insulating material according to claim 1, characterized in that, The preparation method of the modified composite thermally conductive filler includes the following steps: Hexagonal boron nitride, fluorinated ceramic microspheres, and spherical silicon carbide were mixed in a weight ratio, and a mixed solution of deionized water and ethanol was added. The mixture was ultrasonically dispersed for 25-35 minutes. The pH of the solution was adjusted to 4-5, a silane coupling agent was added, and the mixture was stirred at 50-60℃ for 80-100 minutes. The mixture was then dried at 75-85℃ for 20-28 hours. After drying, the mixture was passed through a 100-120 mesh sieve to obtain the modified composite thermally conductive filler.

9. The method for preparing the high thermal conductivity polytetrafluoroethylene insulating material according to any one of claims 1-8, characterized in that, Includes the following steps: (1) Take fluorinated resin by weight, add dispersant and rheology modifier, stir at 380-420 r / min for 55-65 min; add modified composite thermally conductive filler and moisture-resistant modifier in sequence, and mix at high speed to obtain premixed emulsion; (2) The premixed emulsion is cast into a film, dried at 75-85℃ for 4-6 min, and then heat-treated at 370-390℃ for 25-35 min to obtain a porous preform film; (3) Press the porous preform film described in step (2) into a dense preform, perform stepwise sintering under inert gas protection, and then cool down to obtain a polytetrafluoroethylene insulating material with high thermal conductivity.

10. The method for preparing the high thermal conductivity polytetrafluoroethylene insulating material according to claim 9, characterized in that, In step (3), the stepwise sintering specifically involves heating to 320-340℃ at a rate of 20-50℃ / h and holding for 1-4 hours; then heating to 365-380℃ at a rate of 20-40℃ / h and holding for 2-8 hours. The inert gas in step (3) is nitrogen or argon, and the purity of the inert gas is ≥99.99%.

Images