Low-viscosity silica gel and preparation method thereof
Low-viscosity silicone was prepared by wet grinding and controlled feeding sequence, which solved the problem of balancing viscosity and performance in silicone-based shielding materials. This method achieved uniform dispersion and improved mechanical properties of low-viscosity silicone, making it suitable for injection molding.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BEIJING RADIATION APPL RES CENT
- Filing Date
- 2026-01-28
- Publication Date
- 2026-04-10
AI Technical Summary
Existing technologies struggle to effectively control low viscosity and ensure physical properties when preparing silicone-based shielding materials, especially when adding shielding additives such as iron powder, tungsten powder, and lead powder, as it is difficult to balance particle size selection and curing rate.
Low-viscosity silica gel is prepared by using wet grinding and controlled feeding sequence, mixing fumed silica, aluminum hydroxide, atomized iron powder and boron carbide to form a graded mixed additive, and partially coating it, combined with volatile organic solvents and dry grinding.
It achieves uniform dispersion and performance improvement of low-viscosity silicone, making it suitable for injection molding, reducing agglomeration, and improving the mechanical properties and flowability of silicone products.
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Figure CN121825253A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of shielding materials technology. Specifically, it relates to a low-viscosity silicone rubber and its preparation method. Background Technology
[0002] When preparing silicone products from liquid silicone, injection molding is typically used. Therefore, the viscosity of the liquid silicone is one of the key parameters affecting the molding effect, mainly reflected in:
[0003] 1. Flowability and filling properties: High viscosity silicone has high flow resistance, which may lead to incomplete filling of thin walls or complex structures, but it can reduce overflow; low viscosity silicone flows more easily and is suitable for fine textures or deep cavity molds, but injection pressure needs to be controlled to avoid flash.
[0004] 2. Bubble removal: High-viscosity silicone is difficult to degas, requiring the use of vacuum equipment or extended degassing time; low-viscosity silicone bubbles escape easily, resulting in fewer internal defects in the finished product.
[0005] 3. Curing and performance: Viscosity is related to the crosslinking rate. High viscosity silicone may cure faster, but excessive thickening will reduce tensile strength; low viscosity silicone cures uniformly, but the catalyst ratio may need to be adjusted to ensure mechanical properties.
[0006] When preparing silicone-based shielding materials using liquid silicone, a large amount of shielding additives, such as iron powder, tungsten powder, and lead powder, need to be added. In order to obtain low-viscosity silicone, it is necessary to avoid using shielding additives with small particle size. However, in order to ensure the physical properties of silicone-based shielding materials, the particle size of the selected shielding additives cannot be too small. At the same time, shielding additives with small particle size will affect the curing rate of silicone. Summary of the Invention
[0007] Therefore, the technical problem to be solved by the present invention is to provide a low-viscosity silicone and its preparation method. By using wet grinding and controlling the feeding sequence, fumed silica, aluminum hydroxide, atomized iron powder and boron carbide are mixed in a graded manner. At the same time, aluminum hydroxide partially coats boron carbide, which effectively controls the viscosity of silicone and provides convenience for subsequent injection molding.
[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution:
[0009] A low-viscosity silicone rubber comprises the following components: 100 parts by weight of vinyl silicone oil, 1-3 parts by weight of platinum catalyst, 5-15 parts by weight of hydrogen-containing silicone oil, 1-5 parts by weight of fumed silica, 15-25 parts by weight of aluminum hydroxide, 500-600 parts by weight of atomized iron powder, 20-30 parts by weight of boron carbide, 0-3 parts by weight of silane coupling agent, and 0.1-0.5 parts by weight of inhibitor; wherein the vinyl content of the vinyl silicone oil is 0.3%, and the hydrogen-containing silicone oil has a hydrogen content of 0.35%; the low-viscosity silicone rubber is prepared by the following steps to prepare the mixed additives:
[0010] S11) Aluminum hydroxide and boron carbide are placed in a volatile organic solvent and stirred at a stirring speed greater than or equal to 300 r / min for 5 to 10 min. Then, they are wet-milled for 15 to 20 min to obtain the first mixture.
[0011] S12) Add fumed silica to the first mixture, then stir for 5 to 10 minutes at a stirring speed greater than or equal to 300 r / min, and then wet grind for 15 to 20 minutes to obtain the second mixture;
[0012] S13) Add atomized iron powder to the second mixture, then stir for 5 to 10 minutes at a stirring speed of 300 r / min or higher, and then wet grind for 15 to 20 minutes to obtain the third mixture;
[0013] S14) The third mixture is vacuum dried and then dry-ground for 20-30 minutes to obtain the mixed additive.
[0014] The aforementioned low-viscosity silica gel and atomized iron powder include atomized iron powder with a particle size of 300-500 mesh and atomized iron powder with a particle size of 800-1000 mesh.
[0015] The aforementioned low-viscosity silica gel and atomized iron powder are made by mixing atomized iron powder with a particle size of 300-500 mesh and atomized iron powder with a particle size of 800-1000 mesh in a weight ratio of 3:2 to 5:3.
[0016] The aforementioned low-viscosity silica gel has boron carbide particles with a diameter of 30–45 μm and aluminum hydroxide particles with a diameter of 3–10 μm.
[0017] The aforementioned low-viscosity silica gel has a fumed silica particle size of 10–30 nm.
[0018] The aforementioned low-viscosity silica gel uses alkynyl alcohol inhibitors as its inhibitors.
[0019] The volatile organic solvents of the aforementioned low-viscosity silica gel are one or more of anhydrous methanol, anhydrous ethanol, anhydrous acetone, or tetrahydrofuran.
[0020] The above-mentioned method for preparing low-viscosity silica gel includes the following steps:
[0021] Step 1) Prepare materials according to the following ratio: 100 parts by weight of vinyl silicone oil, 1-3 parts by weight of platinum catalyst, 5-15 parts by weight of hydrogen-containing silicone oil, 1-5 parts by weight of fumed silica, 15-25 parts by weight of aluminum hydroxide, 500-600 parts by weight of atomized iron powder, 20-30 parts by weight of boron carbide, 0-3 parts by weight of silane coupling agent and 0.1-0.5 parts by weight of inhibitor;
[0022] Step 2) Preparation of the mixed additives, the specific steps are as follows:
[0023] 2-1) Aluminum hydroxide and boron carbide are placed in a volatile organic solvent and stirred at a speed greater than or equal to 300 r / min for 5 to 10 min. Then, they are wet-milled for 15 to 20 min to obtain the first mixture.
[0024] 2-2) Add fumed silica to the first mixture, then stir for 5-10 minutes at a stirring speed of 300 r / min or higher, and then wet grind for 15-20 minutes to obtain the second mixture;
[0025] 2-3) Add the atomized iron powder to the second mixture, then stir for 5-10 minutes at a stirring speed of 300 r / min or higher, and then wet grind for 15-20 minutes to obtain the third mixture;
[0026] 2-4) The third mixture is vacuum dried, and then dry-ground for 20-30 minutes to obtain the mixed additive;
[0027] Step 3) Mix the mixed additives obtained in Step 2) with silane coupling agent, vinyl silicone oil and platinum catalyst until homogeneous to obtain the first mixture;
[0028] Step 4) Stir and mix the hydrogen-containing silicone oil and the inhibitor evenly to obtain the second mixture;
[0029] Step 5) Mix the first mixture and the second mixture evenly, pour into the mold, and cure for 6 to 24 hours at a temperature of 20 to 100°C.
[0030] In the above preparation method, during the stirring and mixing in steps 2-1), 2-2), and 2-3), the stirring and mixing are carried out under the condition of heating and reflux.
[0031] In the above preparation method, dry grinding is performed under a nitrogen atmosphere in steps 2-4). The technical solution of this invention achieves the following beneficial technical effects:
[0032] 1. This invention uses a high-speed stirring and mixing followed by wet grinding to achieve graded mixing of fumed silica, aluminum hydroxide, atomized iron powder, and boron carbide. This facilitates the uniform dispersion of the mixture of these four components in vinyl silicone oil, effectively overcoming the problem of agglomeration. At the same time, the use of liquid solvent to remove air from the surface of the particles promotes the adhesion of smaller particles to the surface of larger particles, thereby reducing the agglomeration of smaller particles and facilitating the dispersion of smaller particles in vinyl silicone oil.
[0033] 2. This invention utilizes volatile organic solvents as a dispersion and mixing system for solid particles and as a grinding dispersant, which can effectively reduce the amount of water molecules adsorbed by the solid particle additives and reduce the impact of water on the curing of low-viscosity silicone. Attached Figure Description
[0034] Figure 1 This is a scanning electron microscope image of the mixed additives prepared in Example 1. Detailed Implementation
[0035] Example 1
[0036] In this embodiment, the low-viscosity silicone is made from the following components: 100g vinyl silicone oil, 1g platinum catalyst, 5g hydrogen-containing silicone oil, 1g fumed silica with a particle size of 10-30nm, 15g aluminum hydroxide with a particle size of 3-10μm, 500g atomized iron powder with a particle size of 400-800 mesh, 20g boron carbide with a particle size of 30-45μm, 1g silane coupling agent A172, and 0.1g inhibitor; wherein, the vinyl content in the vinyl silicone oil is 0.3%, the hydrogen-containing silicone oil is hydrogen-containing silicone oil with a hydrogen content of 0.35%, and the inhibitor is 1-ethynyl-1-cyclohexanol.
[0037] The low-viscosity silicone in this embodiment is prepared by the following steps:
[0038] Step 1) Prepare the materials according to the above proportions;
[0039] Step 2) Preparation of the mixed additives, the specific steps are as follows:
[0040] 2-1) Aluminum hydroxide and boron carbide were placed in anhydrous ethanol and stirred at a speed of 300 r / min for 8 min. Then, they were wet-milled for 15 min to obtain the first mixture.
[0041] 2-2) Add fumed silica to the first mixture, then stir for 5 minutes at a stirring speed of 300 r / min, and then wet grind for 20 minutes to obtain the second mixture;
[0042] 2-3) Add the atomized iron powder to the second mixture, then stir for 10 minutes at a stirring speed of 300 r / min, and then wet grind for 18 minutes to obtain the third mixture;
[0043] 2-4) The third mixture was dried under vacuum and then dry-milled for 25 minutes under a nitrogen atmosphere to obtain the mixed additive;
[0044] Step 3) Mix the mixed additives obtained in Step 2) with silane coupling agent, vinyl silicone oil and platinum catalyst until homogeneous to obtain the first mixture;
[0045] Step 4) Stir and mix the hydrogen-containing silicone oil and the inhibitor evenly to obtain the second mixture;
[0046] Step 5) Mix the first and second mixtures evenly, pour the mixture into the mold, and cure at 25°C.
[0047] Electron micrographs of the mixed additives prepared in this embodiment are as follows: Figure 1 As shown in the figure, the larger particles are atomized iron powder particles or boron carbide particles, while the smaller particles are silicon dioxide or aluminum hydroxide. Figure 1 As can be seen, small particles adhere to the surface of large particles. Specifically, through the preparation steps of the mixed additives in this embodiment, silica can be attached to aluminum hydroxide particles. At the same time, aluminum hydroxide particles and silica can also be attached to atomized iron powder or boron carbide particles. This improves the dispersion uniformity of silica and aluminum hydroxide in vinyl silicone oil when small-diameter silica and aluminum hydroxide are dispersed in vinyl silicone oil, thereby improving the performance of silicone products.
[0048] Example 2
[0049] In this embodiment, the low-viscosity silicone is made from the following components: 100g vinyl silicone oil, 2g platinum catalyst, 10g hydrogen-containing silicone oil, 3g fumed silica with a particle size of 10-30nm, 20g aluminum hydroxide with a particle size of 3-10μm, 550g atomized iron powder with a particle size of 400-600 mesh, 25g boron carbide with a particle size of 30-45μm, 2g silane coupling agent A172, and 0.3g inhibitor; wherein, the vinyl content in the vinyl silicone oil is 0.3%, the hydrogen-containing silicone oil is hydrogen-containing silicone oil with a hydrogen content of 0.35%, and the inhibitor is 1-ethynyl-1-cyclohexanol.
[0050] The difference between the low-viscosity silica preparation method in this embodiment and the low-viscosity silica preparation method in Example 1 is that in steps 2-1), 2-2), and 2-3), the stirring and mixing are carried out under the condition of heating and reflux.
[0051] Example 3
[0052] In this embodiment, the low-viscosity silicone is made from the following components: 100g vinyl silicone oil, 3g platinum catalyst, 15g hydrogen-containing silicone oil, 5g fumed silica with a particle size of 10-30nm, 25g aluminum hydroxide with a particle size of 3-10μm, 600g atomized iron powder with a particle size of 300-800 mesh, 30g boron carbide with a particle size of 30-45μm, 3g silane coupling agent A172, and 0.5g inhibitor; wherein, the vinyl content in the vinyl silicone oil is 0.3%, the hydrogen-containing silicone oil is hydrogen-containing silicone oil with a hydrogen content of 0.35%, and the inhibitor is 1-ethynyl-1-cyclohexanol.
[0053] The method for preparing low-viscosity silica gel in this embodiment is the same as that in Example 2.
[0054] Example 4
[0055] In this embodiment, the low-viscosity silicone is made from the following components: 100g vinyl silicone oil, 1.5g platinum catalyst, 8g hydrogen-containing silicone oil, 4g fumed silica with a particle size of 10-30nm, 22g aluminum hydroxide with a particle size of 3-5μm, 520g atomized iron powder, 26g boron carbide with a particle size of 40-45μm, 1.8g silane coupling agent A172, and 0.2g inhibitor; wherein, the vinyl content of the vinyl silicone oil is 0.3%, the hydrogen-containing silicone oil is hydrogen-containing silicone oil with a hydrogen content of 0.35%, the inhibitor is 1-ethynyl-1-cyclohexanol, and the atomized iron powder is a mixture of atomized iron powder with a particle size of 300-500 mesh and atomized iron powder with a particle size of 800-1000 mesh in a weight ratio of 3:2.
[0056] The method for preparing low-viscosity silica gel in this embodiment is the same as that in Example 2.
[0057] Example 5
[0058] In this embodiment, the low-viscosity silicone is made from the following components: 100g vinyl silicone oil, 2.4g platinum catalyst, 13g hydrogen-containing silicone oil, 4g fumed silica with a particle size of 10-30nm, 18g aluminum hydroxide with a particle size of 6-10μm, 540g atomized iron powder, 22g boron carbide with a particle size of 30-45μm, 1.8g silane coupling agent A172, and 0.1g inhibitor; wherein, the vinyl content of the vinyl silicone oil is 0.3%, the hydrogen-containing silicone oil is hydrogen-containing silicone oil with a hydrogen content of 0.35%, the inhibitor is 1-ethynyl-1-cyclohexanol, and the atomized iron powder is a mixture of atomized iron powder with a particle size of 300-500 mesh and atomized iron powder with a particle size of 800-1000 mesh in a weight ratio of 8:5.
[0059] The method for preparing low-viscosity silica gel in this embodiment is the same as that in Example 2.
[0060] Example 6
[0061] In this embodiment, the low-viscosity silicone is made from the following components: 100g vinyl silicone oil, 1.2g platinum catalyst, 12g hydrogen-containing silicone oil, 5g fumed silica with a particle size of 10-30nm, 18g aluminum hydroxide with a particle size of 5-8μm, 570g atomized iron powder, 26g boron carbide with a particle size of 30-45μm, 2.4g silane coupling agent A172, and 0.3g inhibitor; wherein, the vinyl content of the vinyl silicone oil is 0.3%, the hydrogen-containing silicone oil is hydrogen-containing silicone oil with a hydrogen content of 0.35%, the inhibitor is 1-ethynyl-1-cyclohexanol, and the atomized iron powder is a mixture of atomized iron powder with a particle size of 300-500 mesh and atomized iron powder with a particle size of 800-1000 mesh in a weight ratio of 31:20.
[0062] The method for preparing low-viscosity silica gel in this embodiment is the same as that in Example 2.
[0063] Example 7
[0064] In this embodiment, the low-viscosity silicone is made from the following components: 100g vinyl silicone oil, 2.7g platinum catalyst, 14g hydrogen-containing silicone oil, 3g fumed silica with a particle size of 10-30nm, 20g aluminum hydroxide with a particle size of 8-10μm, 580g atomized iron powder, 27g boron carbide with a particle size of 30-45μm, 2.1g silane coupling agent A172, and 0.1g inhibitor; wherein, the vinyl content of the vinyl silicone oil is 0.3%, the hydrogen-containing silicone oil is hydrogen-containing silicone oil with a hydrogen content of 0.35%, the inhibitor is 1-ethynyl-1-cyclohexanol, and the atomized iron powder is a mixture of atomized iron powder with a particle size of 300-500 mesh and atomized iron powder with a particle size of 800-1000 mesh in a weight ratio of 33:20.
[0065] The method for preparing low-viscosity silica gel in this embodiment is the same as that in Example 2.
[0066] Example 8
[0067] In this embodiment, the low-viscosity silicone is made from the following components: 100g vinyl silicone oil, 2.4g platinum catalyst, 15g hydrogen-containing silicone oil, 3g fumed silica with a particle size of 10-30nm, 24g aluminum hydroxide with a particle size of 3-5μm, 540g atomized iron powder, 30g boron carbide with a particle size of 30-45μm, 1.2g silane coupling agent A172, and 0.5g inhibitor; wherein, the vinyl content of the vinyl silicone oil is 0.3%, the hydrogen-containing silicone oil is hydrogen-containing silicone oil with a hydrogen content of 0.35%, the inhibitor is 1-ethynyl-1-cyclohexanol, and the atomized iron powder is a mixture of atomized iron powder with a particle size of 300-500 mesh and atomized iron powder with a particle size of 800-1000 mesh in a weight ratio of 5:3.
[0068] The method for preparing low-viscosity silica gel in this embodiment is the same as that in Example 2.
[0069] Example 9
[0070] In this embodiment, the low-viscosity silicone is made from the following components: 100g vinyl silicone oil, 2.5g platinum catalyst, 12g hydrogen-containing silicone oil, 4g fumed silica with a particle size of 10-30nm, 25g aluminum hydroxide with a particle size of 3-5μm, 600g atomized iron powder, 30g boron carbide with a particle size of 30-45μm, 2.5g silane coupling agent A172, and 0.3g inhibitor; wherein, the vinyl content of the vinyl silicone oil is 0.3%, the hydrogen-containing silicone oil is hydrogen-containing silicone oil with a hydrogen content of 0.35%, the inhibitor is 1-ethynyl-1-cyclohexanol, and the atomized iron powder is a mixture of atomized iron powder with a particle size of 300-500 mesh and atomized iron powder with a particle size of 800-1000 mesh in a weight ratio of 34:21.
[0071] The method for preparing low-viscosity silica gel in this embodiment is the same as that in Example 2.
[0072] Comparative Example 1
[0073] The components used in the low-viscosity silica gel in this embodiment are the same as those used in the low-viscosity silica gel in Example 9, the difference being the preparation method. The low-viscosity silica gel in this embodiment is prepared through the following steps:
[0074] Step 1) Prepare the materials according to the above proportions;
[0075] Step 2) Mix vinyl silicone oil, platinum catalyst, fumed silica, aluminum hydroxide, atomized iron powder and boron carbide evenly to obtain the first mixture;
[0076] Step 3) Stir and mix the hydrogen-containing silicone oil and the inhibitor evenly to obtain the second mixture;
[0077] Step 4) Mix the first and second mixtures evenly, pour the mixture into the mold, and cure for 6 to 24 hours at a temperature of 20 to 100°C.
[0078] The performance of the low-viscosity silicone prepared in Examples 1-9 and Comparative Example 1 was tested respectively, and the test results are shown in Table 1.
[0079] Table 1. Test results of low viscosity silicone.
[0080]
[0081] As can be seen from the data recorded in Table 1, under the same formulation, Example 9 and Comparative Example 1, with different treatments of aluminum hydroxide, fumed silica, atomized iron powder and boron carbide and without chemical modification of the above four components, can effectively reduce the viscosity of silicone using the above four components by mixing them with the treatment method described in this invention, which is convenient for processing silicone products by injection molding. The components used in the low-viscosity silicone in Examples 1 and 6, as well as the data recorded in Table 1, show that the amount of platinum catalyst used in the low-viscosity silicone in Examples 1 and 6 is similar, but the curing time differs by 7.5 hours. This is because aluminum hydroxide, fumed silica, atomized iron powder, and boron carbide will adsorb some water molecules on their surface. Simply using volatile organic solvents as the dispersion system for the physical mixing of the above four components and as the dispersant for wet grinding is insufficient to remove the water molecules adsorbed on the particles of the above four components as much as possible. Therefore, stirring and mixing under the condition of heating and refluxing the volatile organic solvent in steps 2-1), 2-2), and 2-3) not only helps to remove the gas and water molecules adsorbed on the surface of the particles of the above four components, but also helps smaller particles to adsorb on the surface of larger particles during wet grinding. This is beneficial to the dispersion of the mixture of the above four components in vinyl silicone oil, and thus helps to reduce the viscosity of the silicone.
[0082] Research has shown that for solid particles, direct mixing requires a good particle size distribution to achieve a low viscosity while maintaining the mechanical properties of silicone. Dry grinding can expand the particle size range, but it is still affected by other impurities adhering to the particle surface. However, using wet mixing, wet grinding, and heating the mixture during mixing can effectively reduce the influence of impurities such as water molecules that are detrimental to silicone curing.
[0083] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of the claims of this patent application.
Claims
1. A low-viscosity silicone, characterized in that, The low-viscosity silicone oil is composed of the following components: 100 parts by weight of vinyl silicone oil, 1-3 parts by weight of platinum catalyst, 5-15 parts by weight of hydrogen-containing silicone oil, 1-5 parts by weight of fumed silica, 15-25 parts by weight of aluminum hydroxide, 500-600 parts by weight of atomized iron powder, 20-30 parts by weight of boron carbide, 0-3 parts by weight of silane coupling agent, and 0.1-0.5 parts by weight of inhibitor; wherein the vinyl content of the vinyl silicone oil is 0.3%, and the hydrogen-containing silicone oil has a hydrogen content of 0.35%; the mixed additives are prepared by the following steps when preparing the low-viscosity silicone oil: S11) Aluminum hydroxide and boron carbide are placed in a volatile organic solvent and stirred at a stirring speed greater than or equal to 300 r / min for 5 to 10 min. Then, they are wet-milled for 15 to 20 min to obtain the first mixture. S12) Add fumed silica to the first mixture, then stir for 5 to 10 minutes at a stirring speed greater than or equal to 300 r / min, and then wet grind for 15 to 20 minutes to obtain the second mixture; S13) Add atomized iron powder to the second mixture, then stir for 5 to 10 minutes at a stirring speed of 300 r / min or higher, and then wet grind for 15 to 20 minutes to obtain the third mixture; S14) The third mixture is vacuum dried and then dry-ground for 20-30 minutes to obtain the mixed additive.
2. The low-viscosity silicone according to claim 1, characterized in that, Atomized iron powder includes atomized iron powder with a particle size of 300-500 mesh and atomized iron powder with a particle size of 800-1000 mesh.
3. The low-viscosity silicone according to claim 1, characterized in that, Atomized iron powder is made by mixing atomized iron powder with a particle size of 300-500 mesh and atomized iron powder with a particle size of 800-1000 mesh in a weight ratio of 3:2 to 5:
3.
4. The low-viscosity silicone according to claim 1, characterized in that, The particle size of boron carbide is 30–45 μm, and the particle size of aluminum hydroxide is 3–10 μm.
5. The low-viscosity silicone according to claim 1, characterized in that, The particle size of fumed silica is 10–30 nm.
6. The low-viscosity silicone according to claim 1, characterized in that, The inhibitor is an alkynyl alcohol inhibitor.
7. The low-viscosity silicone according to claim 1, characterized in that, The volatile organic solvent is one or more of anhydrous methanol, anhydrous ethanol, anhydrous acetone, or tetrahydrofuran.
8. The method for preparing low-viscosity silica gel according to claim 1, characterized in that, Includes the following steps: Step 1) Prepare materials according to the following ratio: 100 parts by weight of vinyl silicone oil, 1-3 parts by weight of platinum catalyst, 5-15 parts by weight of hydrogen-containing silicone oil, 1-5 parts by weight of fumed silica, 15-25 parts by weight of aluminum hydroxide, 500-600 parts by weight of atomized iron powder, 20-30 parts by weight of boron carbide, 0-3 parts by weight of silane coupling agent and 0.1-0.5 parts by weight of inhibitor; Step 2) Preparation of the mixed additives, the specific steps are as follows: 2-1) Aluminum hydroxide and boron carbide are placed in a volatile organic solvent and stirred at a speed greater than or equal to 300 r / min for 5 to 10 min. Then, they are wet-milled for 15 to 20 min to obtain the first mixture. 2-2) Add fumed silica to the first mixture, then stir for 5-10 minutes at a stirring speed of 300 r / min or higher, and then wet grind for 15-20 minutes to obtain the second mixture; 2-3) Add the atomized iron powder to the second mixture, then stir for 5-10 minutes at a stirring speed of 300 r / min or higher, and then wet grind for 15-20 minutes to obtain the third mixture; 2-4) The third mixture is vacuum dried, and then dry-ground for 20-30 minutes to obtain the mixed additive; Step 3) Mix the mixed additives obtained in Step 2) with silane coupling agent, vinyl silicone oil and platinum catalyst until homogeneous to obtain the first mixture; Step 4) Stir and mix the hydrogen-containing silicone oil and the inhibitor evenly to obtain the second mixture; Step 5) Mix the first mixture and the second mixture evenly, pour into the mold, and cure for 6 to 24 hours at a temperature of 20 to 100°C.
9. The preparation method according to claim 8, characterized in that, In steps 2-1), 2-2), and 2-3), the mixing is carried out under reflux conditions.
10. The preparation method according to claim 8, characterized in that, In steps 2-4), dry grinding is performed under a nitrogen atmosphere.