A polytetrafluoroethylene composite material, its preparation method and application

Abstract

The present invention relates to a polytetrafluoroethylene composite material and a preparation method thereof; it belongs to the technical field of composite material preparation. The present invention provides a polytetrafluoroethylene composite material, which is prepared from boron nitride, silicon nitride, other fillers except boron nitride and silicon nitride, a surfactant, a thickener, deionized water, and polytetrafluoroethylene as raw materials; the obtained polytetrafluoroethylene composite material simultaneously has a high thermal conductivity coefficient, a low dielectric loss, and good adhesion performance, solves the problem of mutual restriction of thermal conductivity, low dielectric loss, and adhesion of existing PTFE composite materials, and has the potential to be applied to high-frequency copper clad laminates.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite material preparation, and particularly relates to a polytetrafluoroethylene composite material, a preparation method thereof and an application thereof. Background Art

[0002] With the rapid development of communication technology towards high-frequency bands such as 5G and 6G, digital circuits are gradually moving towards high-speed information processing and high-frequency signal transmission, and electronic devices are continuously developing towards integration, miniaturization and high power. This poses higher requirements for the dielectric properties, thermal conductivity and bonding properties of future electronic communication products to ensure the integrity and reliability of signal transmission and the safety and stability of device use. Polytetrafluoroethylene (PTFE) has become one of the indispensable materials for preparing high-performance radio frequency microwave composite materials due to its excellent insulation, dielectric properties, high heat resistance, weather resistance and other characteristics. However, PTFE itself has poor adhesion, is difficult to process, and has a low thermal conductivity, which limits its application in the copper clad laminate industry. Therefore, PTFE composite materials have emerged. PTFE composite materials for copper clad laminates can be divided into two categories: glass fiber-reinforced and non-glass fiber-reinforced composite materials. Glass fiber-reinforced PTFE composite materials are manufactured by impregnating glass fiber cloth with PTFE emulsion, but the glass fiber cloth effect has a greater impact on signal transmission and is limited in application in the field of high-end microwave products; for non-glass fiber-reinforced PTFE composite materials, most use inorganic fillers as reinforcing materials. The addition of inorganic fillers can improve the thermal conductivity of the composite material, but usually increases the dielectric loss of the composite material and affects the bonding properties of the composite material at the same time. Therefore, the key to preparing high-performance radio frequency microwave composite materials lies in solving the problem of mutual restriction between the thermal conductivity, low dielectric loss and bonding properties of PTFE composite materials.

[0003] Most of the current research in the field still uses fillers of a single size to modify PTFE, and the actual application performance of PTFE composites in copper clad laminates has not been investigated, ignoring the overall effect of PTFE composites. For example, Youhong Tan et al. modified PTFE composites with glass fiber matrix by alumina and boron nitride of a single size, and obtained PTFE composites with a thermal conductivity of 1.05 W / m K and a dielectric constant of 3.53. However, the dielectric loss of this composite is as high as 0.0022. Another example is that Mengni Ge et al. obtained a copper clad laminate with a thermal conductivity of 1 W / m K, a dielectric constant of 4.0, a dielectric loss of 0.016, and a peel strength of 1.1 N / mm by mixing silica and boron nitride of a single size. Its comprehensive performance still cannot meet the application requirements of the current high-frequency band. Yanhong Feng et al. mixed boron nitride and silicon carbide of a single size in a ratio of 3:1 and obtained PTFE composites with a thermal conductivity of 1.49 W / m K, a dielectric constant of 3.27, and a dielectric loss of 0.0058. However, the peel strength of its copper clad laminate product was not investigated, and its actual application effect is still unknown. Therefore, it is difficult to modify PTFE into a composite material that can meet the use requirements of the high-frequency band by adding fillers of a single size, and it is difficult to simultaneously achieve the properties of high thermal conductivity, low dielectric loss, and high bonding strength of PTFE composites.

[0004] Chinese invention patent CN116285296A discloses a high thermal conductivity and low dielectric composite material, its preparation method and application. After modifying hexagonal boron nitride with a silane coupling agent containing double bonds, it is uniformly mixed with thermosetting polyphenylene ether, dried, and hot pressed to obtain the high thermal conductivity and low dielectric composite material. Its thermal conductivity is: 3.8902 W / m K, the dielectric constant is 2.95928, and the dielectric loss is 0.00262. However, the bonding performance of the composite material is not disclosed.

[0005] In the existing preparation methods of copper clad laminate composites, basically none of them can meet the requirements that the dielectric properties, thermal conductivity, and bonding properties are all at a relatively high level, which greatly limits the copper clad laminates for high-power radio frequency microwaves. Therefore, it is of great significance to develop a PTFE composite material with high thermal conductivity, low dielectric loss, and good bonding performance. Summary of the Invention

[0006] Aiming at the above defects, the present invention uses boron nitride, silicon nitride, other fillers except boron nitride and silicon nitride, surfactant, thickener, deionized water, and polytetrafluoroethylene as raw materials to prepare a polytetrafluoroethylene composite material; the obtained polytetrafluoroethylene composite material simultaneously has a high thermal conductivity coefficient, low dielectric loss, and good bonding performance, solving the problem that the thermal conductivity, low dielectric loss, and bonding property of existing PTFE composites restrict each other.

[0007] Technical solution of the present invention:

[0008] The first technical problem solved by the present invention is to provide a polytetrafluoroethylene composite material, and the raw materials of the composite material include polytetrafluoroethylene, boron nitride and silicon nitride.

[0009] Furthermore, the volume ratio of the polytetrafluoroethylene, boron nitride and silicon nitride is 40-90:1-50:1-50.

[0010] Furthermore, the boron nitride selects boron nitrides with various different particle sizes.

[0011] Furthermore, the particle sizes of the boron nitride include 1-3 μm, 3-5 μm, 10-20 μm or 20-30 μm; when boron nitrides of multiple sizes exist simultaneously, the thermal conductivity of the polytetrafluoroethylene composite material is improved.

[0012] Furthermore, the raw materials of the composite material further include other fillers, surfactants and thickeners except boron nitride and silicon nitride.

[0013] Even further, the other fillers except boron nitride and silicon nitride are selected from at least one of titanium dioxide, silicon dioxide, zinc oxide, aluminum oxide, iron oxide, barium titanate or calcium titanate.

[0014] Furthermore, the volume ratio of the boron nitride, silicon nitride, fillers except boron nitride and silicon nitride, surfactants, thickeners and polytetrafluoroethylene is 1-50:1-50:0-50:1-5:1-5:40-90, and the sum of the volume ratios of each raw material is 100.

[0015] Furthermore, the surfactant is a fluorine-containing surfactant; preferably a fluorocarbon surfactant, a fluoroalkyl polyether or a fluorine-modified polymer.

[0016] Furthermore, the thickener includes carboxymethyl cellulose, polyvinyl alcohol or gelatin.

[0017] The second technical problem to be solved by the present invention is to provide a preparation method of the above-mentioned polytetrafluoroethylene composite material, and the preparation method is: first, blend each raw material (such as polytetrafluoroethylene, boron nitride and silicon nitride, etc.) to obtain a polytetrafluoroethylene mixed emulsion, then form a film of the polytetrafluoroethylene mixed emulsion, and finally obtain the polytetrafluoroethylene composite material through post-treatment.

[0018] Furthermore, the post-treatment refers to drying, sintering and cooling treatments.

[0019] Furthermore, the preparation method includes the following steps:

[0020] Step 1: Mix polytetrafluoroethylene, boron nitride, silicon nitride, other fillers except boron nitride and silicon nitride, surfactant, and deionized water for 10 - 15 min to obtain a dispersion slurry.

[0021] Step 2: Add a thickener to the dispersion slurry, mix and defoam for 10 - 15 min to obtain a PTFE mixed emulsion.

[0022] Step 3: Form a film from the PTFE mixed emulsion, and then obtain the polytetrafluoroethylene composite material through drying, sintering, and cooling.

[0023] Furthermore, the boron nitride is boron nitrides with multiple different particle sizes.

[0024] Furthermore, the particle sizes of the boron nitride are 1 - 3 μm, 3 - 5 μm, 10 - 20 μm, and 20 - 30 μm; when boron nitrides of multiple sizes coexist, the thermal conductivity of the polytetrafluoroethylene composite material is improved.

[0025] Furthermore, the other fillers except boron nitride and silicon nitride are selected from one or more of titanium dioxide, silicon dioxide, zinc oxide, aluminum oxide, iron oxide, barium titanate, or calcium titanate.

[0026] Furthermore, the surfactant is a fluorine-containing surfactant; preferably a fluorocarbon surfactant, a fluoroalkyl polyether, or a fluorine-modified polymer.

[0027] Furthermore, the thickener includes carboxymethyl cellulose, polyvinyl alcohol, or gelatin.

[0028] Furthermore, the volume ratio of the boron nitride, silicon nitride, fillers except boron nitride and silicon nitride, surfactant, thickener, and polytetrafluoroethylene is 1 - 50:1 - 50:0 - 50:1 - 5:1 - 5:40 - 90, and the sum of the volume ratios of each raw material is 100.

[0029] Furthermore, the drying temperature is 60 - 65 °C, and the drying time is 15 - 20 min.

[0030] Furthermore, the sintering temperature is 360 - 365 °C, and the sintering time is 20 - 30 min.

[0031] The third technical problem solved by the present invention is to point out the application of the above-mentioned polytetrafluoroethylene composite material in high-frequency copper clad laminates.

[0032] The fourth technical problem solved by the present invention is to provide a method for improving the peel strength of polytetrafluoroethylene. The method is to introduce boron nitride and silicon nitride during the preparation of the polytetrafluoroethylene composite material, wherein the volume ratio of polytetrafluoroethylene, boron nitride, and silicon nitride is 40 - 90:1 - 50:1 - 50.

[0033] Further, the method for improving the peel strength of polytetrafluoroethylene is as follows: First, blend various raw materials (such as polytetrafluoroethylene, boron nitride, and silicon nitride, etc.) to obtain a polytetrafluoroethylene mixed emulsion, then form a film from the polytetrafluoroethylene mixed emulsion, and finally perform post-treatment to obtain a polytetrafluoroethylene composite material.

[0034] The fifth technical problem solved by the present invention is to provide a method for improving the thermal conductivity of polytetrafluoroethylene. The method is to introduce silicon nitride and boron nitride when preparing the polytetrafluoroethylene composite material, and use boron nitride with multiple different particle sizes. Among them, the volume ratio of polytetrafluoroethylene, boron nitride, and silicon nitride is 40-90:1-50:1-50.

[0035] Further, the method for simultaneously improving the thermal conductivity, peel strength, and dielectric properties of polytetrafluoroethylene is as follows: First, blend various raw materials (such as polytetrafluoroethylene, boron nitride, and silicon nitride, etc.) to obtain a polytetrafluoroethylene mixed emulsion, then form a film from the polytetrafluoroethylene mixed emulsion, and finally perform post-treatment to obtain a polytetrafluoroethylene composite material.

[0036] Further, the particle sizes of the boron nitride with different particle sizes include 1-3 μm, 3-5 μm, 10-20 μm, or 20-30 μm.

[0037] Further, the post-treatment refers to drying, sintering, and cooling treatments.

[0038] Advantages of the present invention:

[0039] 1. The polytetrafluoroethylene composite material obtained by the present invention has excellent high-frequency dielectric properties. Its dielectric constant (at 10 GHz) is up to 3.35 at most, the dielectric loss (at 10 GHz) can be as low as 0.0007, the thermal conductivity coefficient can reach 1.21 W / m K, and the peel strength with copper foil can reach 2.13 N / mm. The performance is significantly higher than the industry level and can be widely applied in many fields such as microwave communication, radar systems, aerospace, satellite communication, etc.

[0040] 2. The present invention selects boron nitride and silicon nitride as the main fillers. Both of their energy gaps and thermal conductivity coefficients are at a relatively high level, which has a positive effect on the control of the dielectric properties and the improvement of the thermal conductivity of the PTFE composite material.

[0041] 3. The present invention adds boron nitride with different sizes and different proportions. The large-sized boron nitride and the small-sized boron nitride are uniformly dispersed in the composite material with each other. The small-sized boron nitride is beneficial to the formation of the heat conduction path, and the large-sized boron nitride is beneficial to reducing the interfacial thermal resistance between the filler and the polymer matrix. The two work together to improve the thermal conductivity of the composite material.

[0042] 4. In the present invention, boron nitride and silicon nitride with different sizes and proportions are added and cooperate with each other. Under the restriction of silicon nitride, boron nitride has more out-of-plane orientation in the composite material, which can effectively improve the out-of-plane thermal conductivity of the PTFE composite material.

[0043] 5. The present invention adds specific fillers, which have a certain regulating effect on the dielectric constant and thermal expansion coefficient of the PTFE composite material, so that the PTFE composite material meets the application requirements.

[0044] 6. The PTFE composite material prepared by the present invention can adjust its thickness by changing the coating process, or can be formed after hot pressing and melting of multiple layers of materials, which has high operability and process performance, and the prepared PTFE composite material has excellent uniformity. Description of the Drawings

[0045] Figure 1 is the SEM image of the PTFE composite material obtained in Example 1 of the present invention.

[0046] Figure 2 is the SEM image of the PTFE composite material obtained in Comparative Example 1 of the present invention. Specific Embodiment Method

[0047] The present invention uses boron nitride, silicon nitride, other fillers except boron nitride and silicon nitride, surfactant, thickener and polytetrafluoroethylene as raw materials to prepare a polytetrafluoroethylene composite material with high thermal conductivity, low dielectric loss and good bonding performance, solving the problem of mutual restriction of thermal conductivity, low dielectric loss and bonding property of the current PTFE composite material.

[0048] The present invention will be described in detail below through specific embodiments. However, these embodiments are only illustrative and not restrictive.

[0049] In the examples and comparative examples of the present invention, the polytetrafluoroethylene raw material used is a PTFE mixed emulsion with a solid content of 45-60 vol%.

[0050] Example 1

[0051] This example provides a preparation method of a PTFE composite material, and the preparation steps include:

[0052] (1) Mix boron nitride, silicon nitride, silicon dioxide, titanium dioxide, fluorocarbon alkyl polyethylene glycol ether, and polytetrafluoroethylene in proportion, and use a high-speed mixer to stir them evenly to obtain a dispersion slurry. The mass of polytetrafluoroethylene is 34.7 g, the mass of deionized water is 22.4 g, the mass of silicon nitride is 17.2 g, the mass of 20 - 30 μm boron nitride is 2.2 g, the mass of 3 - 5 μm boron nitride is 0.5 g, the mass of silicon dioxide is 3.5 g, the mass of titanium dioxide is 2 g, and the mass of the surfactant is 0.6 g; the volume ratio of each raw material is: polytetrafluoroethylene: silicon nitride: 20 - 30 μm boron nitride: 3 - 5 μm boron nitride: silicon dioxide: titanium dioxide = 50:36:3.2:0.8:5:5;

[0053] (2) Add carboxymethyl cellulose to the mixed emulsion, and use a high-speed mixer to stir it evenly and defoam to obtain a PTFE mixed emulsion. The mass of carboxymethyl cellulose is 2.2 g;

[0054] (3) Coat the PTFE mixed emulsion into a composite film with a film thickness of 250 μm;

[0055] (4) Put the PTFE composite film into an oven for drying, set the drying temperature at 60 - 65 °C, and set the drying time at 15 - 20 min;

[0056] (5) Put the dried PTFE composite film into a high-temperature oven for sintering treatment to obtain a PTFE composite material. Set the sintering temperature at 360 - 365 °C and the sintering time at 20 - 30 min.

[0057] Example 2

[0058] This example provides a method for preparing a PTFE composite material, and the preparation steps include:

[0059] (1) Mix boron nitride, silicon nitride, silicon dioxide, titanium dioxide, an active agent, and polytetrafluoroethylene in proportion, and use a high-speed mixer to stir them evenly. The mass of polytetrafluoroethylene is 31.6 g, the mass of deionized water is 24.5 g, the mass of silicon nitride is 17.4 g, the mass of 20 - 30 μm boron nitride is 2.8 g, the mass of silicon dioxide is 5.3 g, the mass of titanium dioxide is 3 g, and the mass of the active agent is 0.6 g; the volume ratio of each raw material is: polytetrafluoroethylene: silicon nitride: 20 - 30 μm boron nitride: silicon dioxide: titanium dioxide = 50:36:4:5:5;

[0060] (2) Add a thickening agent to the mixed emulsion, and use a high-speed mixer to stir it evenly and defoam to obtain a PTFE mixed emulsion. The mass of the thickening agent is 2.2 g;

[0061] (3) Coat the PTFE mixed emulsion into a film with a film thickness of 250 μm;

[0062] (4) Place the PTFE composite film in an oven for drying. Set the drying temperature at 60 - 65 °C and the drying time at 15 - 20 min;

[0063] (5) Place the dried composite material in a high - temperature oven for sintering. Set the sintering temperature at 360 - 365 °C and the sintering time at 20 - 30 min.

[0064] Comparative Example 1

[0065] This example provides a preparation method of a PTFE composite material. The preparation steps include:

[0066] (1) Mix boron nitride, silicon dioxide, titanium dioxide, an active agent, and polytetrafluoroethylene in proportion with different sizes. Use a high - speed mixer to stir them evenly. The mass of polytetrafluoroethylene is 28.2 g, the mass of 3 - 5 μm boron nitride is 4.9 g, the mass of 20 - 30 μm boron nitride is 19.6 g, the mass of silicon dioxide is 4.7 g, the mass of titanium dioxide is 2.7 g, and the mass of the active agent is 0.73 g; The volume ratio of each raw material is: polytetrafluoroethylene: 20 - 30 μm boron nitride: 3 - 5 μm boron nitride: silicon dioxide: titanium dioxide = 50:32:8:5:5;

[0067] (2) Add a thickening agent to the mixed emulsion. Use a high - speed mixer to stir it evenly and defoam to obtain a PTFE mixed emulsion. The mass of the thickening agent is 2.2 g;

[0068] (3) Coat the PTFE mixed emulsion into a film with a film thickness of 250 μm;

[0069] (4) Place the PTFE composite film in an oven for drying. Set the drying temperature at 60 - 65 °C and the drying time at 15 - 20 min;

[0070] (5) Place the dried composite material in a high - temperature oven for sintering. Set the sintering temperature at 360 - 365 °C and the sintering time at 20 - 30 min.

[0071] Comparative Example 2

[0072] This example provides a preparation method of a PTFE composite material. The preparation steps include:

[0073] (1) Mix silicon nitride, silicon dioxide, titanium dioxide, active agent, and polytetrafluoroethylene (PTFE) of different sizes proportionally, and use a high-speed mixer to stir them evenly. The mass of PTFE is 21.5 g, the mass of silicon nitride with a size of 1 - 3 μm is 5 g, the mass of silicon nitride with a size of 10 - 15 μm is 20 g, the mass of silicon dioxide is 2.2 g, the mass of titanium dioxide is 3.75 g, and the mass of the active agent is 0.81 g; the volume ratio of each raw material is: PTFE: silicon nitride with a size of 10 - 15 μm: silicon nitride with a size of 1 - 3 μm: silicon dioxide: titanium dioxide = 50:32:8:5:5;

[0074] (2) Add a thickening agent to the mixed emulsion, and use a high-speed mixer to stir it evenly and defoam to obtain a PTFE mixed emulsion. The mass of the thickening agent is 2.2 g;

[0075] (3) Coat the PTFE mixed emulsion into a film with a thickness of 250 μm;

[0076] (4) Put the PTFE composite film into an oven for drying, set the drying temperature at 60 - 65 °C, and set the drying time at 15 - 20 min;

[0077] (5) Put the dried composite material into a high-temperature oven for sintering, set the sintering temperature at 360 - 365 °C, and set the sintering time at 20 - 30 min.

[0078] Comparative Example 3

[0079] The preparation process of Comparative Example 3 is mostly the same as that of Example 1, except that the components of boron nitride are replaced by silicon nitride of the same volume.

[0080] Comparative Example 4

[0081] The preparation process of Comparative Example 4 is mostly the same as that of Comparative Example 1, except that the particle size of boron nitride is 20 - 30 μm.

[0082] Table 1 Properties of PTFE composite materials obtained in the examples and comparative examples of the present invention

[0083]

[0084] As can be seen from Table 1, Example 1 has excellent dielectric properties, thermal conductivity, and bonding properties. The addition of silicon nitride can effectively improve the peel strength between the PTFE composite material and the copper foil. Comparing Example 2 with Comparative Example 3 shows that the compounding of boron nitride and silicon nitride significantly improves the thermal conductivity of the PTFE composite material; comparing Example 1 with Example 2 and Comparative Example 1 with Comparative Example 4 both show that the size compounding of boron nitride also significantly promotes the thermal conductivity of the PTFE composite material.

[0085] Figure 1 andFigure 2 It is the SEM cross-section diagram of the PTFE composite materials in Example 1 and Comparative Example 1, and it can be seen that: restricted by non-flaky fillers, boron nitride is arranged in the out-of-plane direction of the film, and it is not significantly oriented in the in-plane direction due to the scraping preparation method, so there is still a relatively high increase in the thermal conductivity in the out-of-plane direction. Figure 1 Large-sized boron nitride forms a thermal conduction network, and silicon nitride and small-sized boron nitride further improve the thermal conduction network; Figure 2 Large-sized boron nitride forms a thermal conduction network, and small-sized boron nitride further improves the thermal conduction network. The more perfect the thermal conduction network is, the higher the thermal conductivity of the material is.

[0086] Obviously, the above-mentioned embodiments of the present invention are only examples clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

[0087] The preparation conditions of the present invention are easy to achieve, the production cost is relatively low, it is easy to be mass-produced and scaled up, and it has a good industrial production foundation and broad application prospects.

Claims

1. A polytetrafluoroethylene composite material, characterized in that, the raw materials of the composite material include polytetrafluoroethylene, boron nitride and silicon nitride; the volume ratio of polytetrafluoroethylene, boron nitride and silicon nitride is 40-90: 1-50: 1-50; the boron nitride selects boron nitrides with a variety of different particle sizes; the particle sizes of the boron nitride include 1-3 μm, 3-5 μm, 10-20 μm or 20-30 μm; and, the large-size boron nitride and the small-size boron nitride are uniformly dispersed in the composite material with each other.

2. The polytetrafluoroethylene composite material according to claim 1, characterized in that, the raw materials of the composite material further include other fillers, surfactants and thickeners in addition to boron nitride and silicon nitride.

3. The polytetrafluoroethylene composite material according to claim 2, characterized in that, the other fillers are selected from one or more of titanium dioxide, silicon dioxide, zinc oxide, aluminum oxide, iron oxide, barium titanate or calcium titanate.

4. The polytetrafluoroethylene composite material according to claim 3, characterized in that, the volume ratio of boron nitride, silicon nitride, other fillers, surfactants, thickeners and polytetrafluoroethylene is 1-50: 1-50: 0-50: 1-5: 1-5: 40-90; the surfactant is a fluorine-containing surfactant; the thickener includes carboxymethyl cellulose, polyvinyl alcohol or gelatin.

5. The preparation method of the polytetrafluoroethylene composite material according to any one of claims 1-4, characterized in that, the preparation method is: first, blend the raw materials to obtain a polytetrafluoroethylene mixed emulsion, then make the polytetrafluoroethylene mixed emulsion into a film, and finally obtain the polytetrafluoroethylene composite material through post-treatment.

6. The preparation method of the polytetrafluoroethylene composite material according to claim 5, characterized in that, the post-treatment refers to drying, sintering and cooling treatments.

7. The preparation method of the polytetrafluoroethylene composite material according to claim 6, characterized in that, the preparation method includes the following steps: Step 1: Mix polytetrafluoroethylene, boron nitride, silicon nitride, other fillers except boron nitride and silicon nitride, surfactant and deionized water for 10-15 min to obtain a dispersed slurry; Step 2: Add a thickener to the dispersed slurry, mix and defoam for 10-15 min to obtain a PTFE mixed emulsion; Step 3: Make the PTFE mixed emulsion into a film, and then obtain the polytetrafluoroethylene composite material through drying, sintering and cooling.

8. The preparation method of the polytetrafluoroethylene composite material according to claim 7, characterized in that, the boron nitride selects boron nitrides with a variety of different particle sizes; the particle sizes of the boron nitride include 1-3 μm, 3-5 μm, 10-20 μm or 20-30 μm.

9. The preparation method of the polytetrafluoroethylene composite material according to claim 7, characterized in that, the other fillers are selected from one or more of titanium dioxide, silicon dioxide, zinc oxide, aluminum oxide, iron oxide, barium titanate or calcium titanate; the surfactant is a fluorine-containing surfactant; The thickener includes carboxymethyl cellulose, polyvinyl alcohol or gelatin; The volume ratio of the boron nitride, silicon nitride, fillers other than boron nitride and silicon nitride, surfactant, thickener and polytetrafluoroethylene is 1~50 : 1~50 : 0~50 : 1~5 : 1~5 : 40~90.

10. The method for preparing the polytetrafluoroethylene composite material according to claim 7, characterized in that, the drying temperature is 60~65 °C and the drying time is 15~20 min; the sintering temperature is 360~365 °C and the sintering time is 20~30 min.

11. The application of the polytetrafluoroethylene composite material in high-frequency copper clad laminates, characterized in that, the polytetrafluoroethylene composite material is the polytetrafluoroethylene composite material according to any one of claims 1~4 or the polytetrafluoroethylene composite material prepared by the method according to any one of claims 5~10.

12. A method for improving the peel strength of polytetrafluoroethylene, characterized in that, the method is to introduce boron nitride and silicon nitride during the preparation of the polytetrafluoroethylene composite material, wherein the volume ratio of polytetrafluoroethylene, boron nitride and silicon nitride is 40~90 : 1~50 : 1~50.

13. The method for improving the peel strength of polytetrafluoroethylene according to claim 12, characterized in that, the method for improving the peel strength of polytetrafluoroethylene is: first, blend the raw materials to obtain a polytetrafluoroethylene mixed emulsion, then form a film from the polytetrafluoroethylene mixed emulsion, and finally perform post-treatment to obtain the polytetrafluoroethylene composite material.

14. The method for improving the peel strength of polytetrafluoroethylene according to claim 13, characterized in that, the post-treatment refers to drying, sintering and cooling treatments.

15. A method for improving the thermal conductivity of polytetrafluoroethylene, characterized in that, the method is to introduce silicon nitride and boron nitride during the preparation of the polytetrafluoroethylene composite material, and use boron nitride with a variety of different particle sizes, wherein the volume ratio of polytetrafluoroethylene, boron nitride and silicon nitride is 40~90 : 1~50 : 1~50; the particle sizes of the different boron nitrides are 1~3 μm, 3~5 μm, 10~20 μm or 20~30 μm; the large-sized boron nitride and the small-sized boron nitride are uniformly dispersed in the composite material with each other.

16. The method for improving the thermal conductivity of polytetrafluoroethylene according to claim 15, characterized in that, the method is: first, blend the raw materials to obtain a polytetrafluoroethylene mixed emulsion, then form a film from the polytetrafluoroethylene mixed emulsion, and finally perform post-treatment to obtain the polytetrafluoroethylene composite material.

17. The method for improving the thermal conductivity of polytetrafluoroethylene according to claim 16, characterized in that, the post-treatment refers to drying, sintering and cooling treatments.

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