Compression resistant wave-absorbing silicone rubber foam and method of making same

Abstract

The application discloses a kind of compression-resistant wave-absorbing silicone rubber foams and preparation method thereof, belong to material technical field, compression-resistant wave-absorbing silicone rubber foam includes: rubber system, 150 parts;Foaming agent, 5~10 parts;Vulcanizing agent, 1~2 parts;Wave-absorbing filler, 40 parts;The wave-absorbing filler is FeCo / Ce2Fe 17 / Fe / C contact multiple heterojunction wave-absorbing filler;The preparation method of the wave-absorbing filler is: Ce2Fe 17 7 alloy is mixed with dimethyl imidazole and dopamine, then cobalt salt and cetyltrimethylammonium bromide are added, polymerization is carried out, and a precursor is obtained by reaction;FeCo / Ce2Fe 17 / Fe / C multiple heterojunction wave-absorbing filler is obtained by calcining the precursor.The application has the advantages of excellent compression resistance, strong electromagnetic absorption capacity, etc.

Description

Technical Field

[0001] This invention belongs to the field of materials technology, and relates to a microwave absorbing material, and more particularly to a pressure-resistant microwave absorbing silicone rubber foam and its preparation method. Background Technology

[0002] With the rapid development of wireless electronic technology, people's demand for electronic products is increasing, which in turn brings electromagnetic pollution. To address this problem, scholars have intensified their research on microwave absorbing materials, especially in wearable electronic products, watches, and mobile phones. Since microwave absorbing materials can absorb electromagnetic waves and convert them into heat energy, how to attenuate electromagnetic waves to a greater extent has broad research background and value.

[0003] Microwave absorbing materials mainly consist of a matrix and absorbing fillers. The matrix primarily serves as a binder and load-bearing component, while the absorbing filler, as the main functional material, primarily attenuates electromagnetic waves entering the material. The dispersion and filler quantity within the matrix are crucial factors in determining its effectiveness. Compared to other matrices, microwave absorbing silicone rubber foam matrices possess advantages such as good elasticity, flexibility, and excellent processing performance. For example, dimethyl vinyl silicone rubber exhibits excellent processing performance, high production volume, low cost, durability, and environmental friendliness, making it widely applicable in daily life. However, while offering significant convenience, silicone rubber foam products are often used under high-pressure environments. Uneven dispersion of the added functional filler can lead to significant pore formation within the silicone rubber foam, compromising the compressive strength of subsequent silicone rubber foam products and severely impacting research and development. Therefore, achieving silicone rubber foam with excellent electromagnetic wave absorbing performance under high-pressure environments is a current research priority.

[0004] In existing technologies, traditional microwave absorbing agents are added to silicone rubber foam. These agents create a conductive network within the matrix. When charge carriers within the material migrate directionally under the influence of an electromagnetic field, overcoming the internal processes of the material significantly hinders this process, greatly reducing the skin effect. Achieving integrated microwave absorption with low filler content and good compressive deformation resistance in silicone rubber foam is currently a key research focus for scientists. Summary of the Invention

[0005] This invention provides a pressure-resistant microwave-absorbing silicone rubber foam and its preparation method to solve the problems of high filler ratio, poor compression set, and integrated microwave absorption performance in existing microwave-absorbing fillers for silicone rubber foam.

[0006] To achieve the above objectives, the present invention provides a pressure-resistant and microwave-absorbing silicone rubber foam, characterized by being prepared from the following components in parts by weight:

[0007]

[0008] The microwave absorbing filler is FeCo / Ce2Fe 17 The microwave absorbing filler is obtained by Fe / C contact and is a multi-heteromorphic interface; the preparation method of the microwave absorbing filler is as follows: Ce2Fe 17 The alloy was mixed with dimethylimidazole and dopamine, then cobalt salt and hexadecyltrimethylammonium bromide were added, and polymerization was carried out to obtain a precursor; the precursor was calcined to obtain FeCo / Ce2Fe. 17 / Fe / C multi-heterogeneous interface microwave absorbing filler.

[0009] Furthermore, the present invention provides a pressure-resistant, microwave-absorbing silicone rubber foam, which may also have the following characteristic: wherein the Ce2Fe 17 The alloy is prepared by mixing CeO2 and carbonyl iron thoroughly in an argon atmosphere using a three-dimensional mixer for 10–14 h, followed by decalcification with an ammonium acetate aqueous solution to obtain Ce2Fe. 17 alloy.

[0010] Furthermore, the present invention provides a pressure-resistant microwave-absorbing silicone rubber foam, which may also have the following characteristics: wherein, in the preparation method of the microwave-absorbing filler, the cobalt salt is cobalt nitrate hexahydrate; the mass ratio of carbonyl iron, CeO2, dopamine, dimethylimidazole, cobalt nitrate hexahydrate, and hexadecyltrimethylammonium bromide is 10∶2∶3∶7~18∶2~5∶0.5~2.

[0011] Furthermore, the present invention provides a pressure-resistant microwave-absorbing silicone rubber foam, which may also have the following characteristics: wherein the preparation method of the microwave-absorbing filler specifically involves: using Ce2Fe 17 The alloy was dispersed evenly in deionized water; then dimethylimidazole and dopamine were added, and the mixture was stirred for 10–14 h; cobalt salt and hexadecyltrimethylammonium bromide were then added, and the mixture was stirred for 1–3 h to obtain the precursor; the precursor was heated to 600–800 °C at a heating rate of 1–3 °C / min under an argon atmosphere and held for 1–3 h to obtain FeCo / Ce2Fe. 17 / Fe / C multi-heterogeneous interface microwave absorbing filler.

[0012] Furthermore, the present invention provides a pressure-resistant and microwave-absorbing silicone rubber foam, which may also have the following characteristics: wherein the rubber system includes methyl vinyl silicone rubber, a reinforcing agent and an additive; the mass ratio of methyl vinyl silicone rubber, a reinforcing agent and an additive is 80-90:10-30:20-30.

[0013] Furthermore, the present invention provides a pressure-resistant and microwave-absorbing silicone rubber foam, which may also have the following feature: wherein the reinforcing agent in the rubber system is silicon dioxide.

[0014] Furthermore, the present invention provides a pressure-resistant and microwave-absorbing silicone rubber foam, which may also have the following characteristics: wherein, in the rubber system, the additives include low molecular weight hydroxyl silicone oil, diphenylsilanediol and silane coupling agent, and the mass ratio of low molecular weight hydroxyl silicone oil, diphenylsilanediol and silane coupling agent is 2:5:2.

[0015] Furthermore, the present invention provides a pressure-resistant and microwave-absorbing silicone rubber foam, which may also have the following feature: wherein the foaming agent is a hydroxyl-containing hydrogen silicone oil.

[0016] Furthermore, the present invention provides a pressure-resistant and microwave-absorbing silicone rubber foam, which may also have the following feature: wherein the vulcanizing agent is a bis(2,4)vulcanizing agent.

[0017] The present invention also provides a method for preparing the above-mentioned pressure-resistant and microwave-absorbing silicone rubber foam, characterized by the following steps: Step 1, mixing the rubber system and microwave-absorbing filler in a mixer to obtain raw pressure-resistant and microwave-absorbing silicone rubber foam; Step 2, pouring the raw pressure-resistant and microwave-absorbing silicone rubber foam obtained in Step 1 into a mold, adding a foaming agent and a vulcanizing agent, and foaming at 110-130°C for 30-60 minutes to obtain the pressure-resistant and microwave-absorbing silicone rubber foam.

[0018] The beneficial effects of this invention are as follows: This invention provides a pressure-resistant and microwave-absorbing silicone rubber foam and its preparation method. Based on existing carbonyl iron powder, rare earth Ce is doped into the carbonyl iron powder. The resulting alloy powder is coated with dopamine in an alkaline environment to form active sites, achieving in-situ growth of ZIF-67 on the surface of the alloy powder. The resulting powder is then heated to 700℃ under argon at a heating rate of 2℃ / min and held for 2 hours to generate FeCo / Ce2Fe. 17 Microwave-absorbing fillers with multiple heterogeneous interfaces obtained through Fe / C contact are composited with silicone rubber foam. The different chemical compositions and crystal structures in the heterogeneous structure induce compressive lattice strain, increasing the adsorption energy of intermediates at the sites and enhancing grain boundary strengthening. This results in silicone rubber foam that possesses excellent compressive strength as well as superior electromagnetic absorption capabilities. Enhanced interfacial polarization simultaneously achieves a synergistic effect of magneto-dielectric properties to further enhance electromagnetic wave absorption, thus producing a silicone rubber foam that integrates compressive strength and microwave absorption.

[0019] Specifically, by adjusting the pH using dimethylimidazole (one of the raw materials for synthesizing ZIF-67), dopamine can coat the metal particles. Simultaneously, the dopamine surface has a large number of negatively charged OH groups, which can adsorb a large number of positively charged Co ions, thus enabling the polymerization of ZIF-67 on dopamine. At this point, dopamine can effectively synthesize carbonyl iron and ZIF-67 together. Furthermore, the precursor forms numerous heterostructures after high-temperature annealing. The resulting FeCo alloy increases microwave absorption performance while also achieving grain boundary strengthening. It also induces compressive lattice strain, increasing the adsorption energy of the intermediate sites and thus increasing compressive strength. At the same time, C and rare earth elements significantly increase the adsorption energy for FeCo and iron, making the bond between them tighter and further enhancing compressive strength. Attached Figure Description

[0020] Figure 1 These are electromagnetic parameter diagrams of the pressure-resistant and microwave-absorbing silicone rubber foams of Examples 1-3 and Comparative Examples 1-2;

[0021] Figure 2 These are microwave absorption performance diagrams of the pressure-resistant and microwave-absorbing silicone rubber foams of Examples 1-3 and Comparative Examples 1-2. Detailed Implementation

[0022] The present invention will be further described below with reference to specific embodiments.

[0023] Example 1

[0024] This example provides a pressure-resistant and microwave-absorbing silicone rubber foam, which is composed of 90 parts of methyl vinyl silicone rubber, 30 parts of reinforcing silica, 30 parts of additives, 10 parts of hydroxyl-containing hydrogen silicone oil foaming agent, 2 parts of bis(2,4)-dichloroethylene vulcanizing agent, and 40 parts of microwave-absorbing filler.

[0025] The additives include low molecular weight hydroxyl silicone oil, diphenylsilanediol and silane coupling agent, in a mass ratio of 2:5:2.

[0026] The preparation method of the microwave absorbing filler is as follows:

[0027] Two parts of CeO2 and ten parts of carbonyl iron were thoroughly mixed in an argon atmosphere using a three-dimensional mixer for 12 hours. The mixture was then removed, crushed, and the resulting powder was decalcified with a 5% ammonium acetate aqueous solution to obtain Ce2Fe. 17 alloy powder.

[0028] First, Ce2Fe 17Alloy powder was poured into 100 parts of deionized water and sonicated for 2 hours to ensure uniform dispersion. Then, 18 parts of dimethylimidazole and 3 parts of dopamine were added, and the stirrer speed was adjusted to 50-80 rpm for mechanical stirring for 12 hours. Next, 5 parts of cobalt nitrate hexahydrate and 2 parts of hexadecyltrimethylammonium bromide were added, and the mixture was mechanically stirred for 2 hours. The resulting solution was washed several times with deionized water and ethanol, and then dried overnight in a vacuum oven at 60°C. The dried powder was heated to 700°C at a heating rate of 2°C / min under an argon atmosphere and held for 2 hours to obtain FeCo / Ce2Fe alloy. 17 Microwave absorbing filler with multiple heterogeneous interfaces of Fe / C contact.

[0029] The preparation method of pressure-resistant microwave-absorbing silicone rubber foam is as follows: Methyl vinyl silicone rubber, silica, low-molecular-weight hydroxyl silicone oil, diphenylsilanediol, silane coupling agent, and the prepared microwave-absorbing filler are mixed to obtain pressure-resistant microwave-absorbing silicone rubber foam raw material. The pressure-resistant microwave-absorbing silicone rubber foam raw material is poured into a mold, a foaming agent and a vulcanizing agent are added, and the program is set to 110–130℃ for a foaming time of 30–60 minutes to obtain the pressure-resistant microwave-absorbing silicone rubber foam.

[0030] The pressure-resistant and microwave-absorbing silicone rubber foam prepared in Example 1 was used to stamp a ring with an inner diameter of 3.05 mm and an outer diameter of 7 mm using a custom mold. The electromagnetic parameters of the ring-shaped sample were tested using the coaxial method, and the results are shown below. Figure 1 Electromagnetic absorption performance is shown in Figure 2 Take a small, flat sample as required, and measure its compressive strength using a pressure testing machine. The results are shown in Table 1-1.

[0031] Table 1-1 Mechanical property data of pressure-resistant and microwave-absorbing silicone rubber foam in Example 1

[0032] <![CDATA[Sample density g / cm 3 > Tensile strength / MPa Elongation at break / % Tear strength / KN / m <![CDATA[Compressive strength / kg / m 2 > 0.7792 1.02 205 4.02 2.1

[0033] Example 2

[0034] This embodiment provides a pressure-resistant microwave-absorbing silicone rubber foam and its preparation method, which is basically the same as that in Example 1, except that in the preparation method of the microwave-absorbing filler, dimethylimidazole is 11 parts, cobalt nitrate hexahydrate is 3 parts, and hexadecyltrimethylammonium bromide is 1 part.

[0035] The pressure-resistant and microwave-absorbing silicone rubber foam prepared in Example 2 was used to stamp a ring with an inner diameter of 3.05 mm and an outer diameter of 7 mm using a custom mold. The electromagnetic parameters of the ring sample were tested using the coaxial method, and the results are shown in [Figure 1]. Figure 1 Electromagnetic absorption performance is shown in Figure 2 Take a small, flat sample as required, and measure its compressive strength using a pressure testing machine. The results are shown in Table 1-2.

[0036] Table 1-2 Mechanical property data of pressure-resistant and microwave-absorbing silicone rubber foam in Example 2

[0037] <![CDATA[Sample density g / cm 3 > Tensile strength / MPa Elongation at break / % Tear strength / KN / m <![CDATA[Compressive strength / kg / m 2 > 0.7762 1.05 215 4.08 2.3

[0038] Example 3

[0039] This embodiment provides a pressure-resistant microwave-absorbing silicone rubber foam and its preparation method, which is basically the same as that in Example 1, except that in the preparation method of the microwave-absorbing filler, dimethylimidazole is 7 parts, cobalt nitrate hexahydrate is 2 parts, and hexadecyltrimethylammonium bromide is 0.5 parts.

[0040] The pressure-resistant and microwave-absorbing silicone rubber foam prepared in Example 3 was used to stamp a ring with an inner diameter of 3.05 mm and an outer diameter of 7 mm using a custom mold. The electromagnetic parameters of the ring-shaped sample were tested using the coaxial method, and the results are shown in [Figure 1]. Figure 1 Electromagnetic absorption performance is shown in Figure 2 Take a small, flat sample as required, and measure its compressive strength using a pressure testing machine. The results are shown in Table 1-3.

[0041] Table 1-3 Mechanical property data of pressure-resistant and microwave-absorbing silicone rubber foam in Example 3

[0042] <![CDATA[Sample density g / cm 3 > Tensile strength / MPa Elongation at break / % Tear strength / KN / m <![CDATA[Compressive strength / kg / m 2 > 0.7798 1.10 246 4.16 2.5

[0043] Comparative Example 1

[0044] This comparative example provides a silicone rubber foam and its preparation method, which is basically the same as Example 2, except that no microwave absorbing filler is added.

[0045] The silicone rubber foam prepared in Comparative Example 1 was used to stamp a ring with an inner diameter of 3.05 mm and an outer diameter of 7 mm using a custom mold. The electromagnetic parameters of the ring-shaped sample were tested using the coaxial method, and the results are shown below. Figure 1 Electromagnetic absorption performance is shown in Figure 2 Take a small, flat sample as required, and measure its compressive strength using a pressure testing machine. The results are shown in Table 2-1.

[0046] Table 2-1 Mechanical property data of silicone rubber foam in Comparative Example 1

[0047] <![CDATA[Sample density g / cm 3 > Tensile strength / MPa Elongation at break / % Tear strength / KN / m <![CDATA[Compressive strength / kg / m 2 > 0.5823 0.54 165 3.56 1.42

[0048] Comparative Example 2

[0049] This comparative example provides a silicone rubber foam and its preparation method, which is basically the same as Example 2, except that cobalt nitrate hexahydrate was not added in the preparation of the microwave absorbing filler.

[0050] The silicone rubber foam prepared in Comparative Example 2 was used to stamp a ring with an inner diameter of 3.05 mm and an outer diameter of 7 mm using a custom mold. The electromagnetic parameters of the ring-shaped sample were tested using the coaxial method, and the results are shown below. Figure 1 Electromagnetic absorption performance is shown in Figure 2 Take a small, flat sample as required, and measure its compressive strength using a pressure testing machine. The results are shown in Table 2-2.

[0051] Table 2-1 Mechanical property data of silicone rubber foam in Comparative Example 1

[0052] Sample density (g / cm3) Tensile strength / MPa Elongation at break / % Tear strength / KN / m <![CDATA[Compressive strength / kg / m 2 > 0.7767 0.58 168 3.68 1.44

[0053] Comparing Examples 1-3, it was found that with the increase of the amount of synthesized ZIF-67, the real and imaginary parts of the dielectric and the real and imaginary parts of the magnetic permeability of the samples all increased. Calculated microwave absorption performance showed that the sample in Example 2 had the best absorption performance. In Example 3, the high dielectric constant caused a large amount of electromagnetic waves to be reflected from the sample surface, resulting in poor absorption. Further comparison with Comparative Examples 1-2 revealed that the microwave absorption bandwidth of the silicone rubber foam with added microwave-absorbing filler was significantly greater than that without it. Comparing Example 2 and Comparative Example 2, it was found that the compressive strength of the silicone rubber foam was improved to some extent after adding cobalt nitrate hexahydrate. This indicates that different chemical compositions and crystal structures in heterogeneous structures can induce compressive lattice strain, increase the adsorption energy of intermediates at sites, increase grain boundary strengthening, and enhance the compressive strength of the silicone rubber foam.

[0054] This invention provides a pressure-resistant, microwave-absorbing silicone rubber foam and its preparation method. First, a microwave-absorbing filler with magnetoelectric coupling is prepared and then introduced into silicone rubber to obtain a pressure-resistant, microwave-absorbing silicone rubber foam composite microwave-absorbing material with excellent microwave absorption performance. The pressure-resistant, microwave-absorbing silicone rubber foam prepared by this invention is tested using a vector network analyzer with coaxial transmission method. The results show that the real parts of the electrical conductivity and magnetic permeability of the silicone rubber without the microwave-absorbing filler are significantly smaller than those of the silicone rubber foam with the filler. This indicates that the introduction of the microwave-absorbing filler increases the electromagnetic wave absorption capacity of the silicone rubber. Simultaneously, the compressive strength of the silicone rubber foam without cobalt nitrate hexahydrate is significantly lower than that with cobalt nitrate hexahydrate. This demonstrates that introducing heterojunctions can increase the lattice strain caused by the different chemical compositions and crystal structures in the heterostructure, increase the adsorption energy of intermediates at the sites, increase grain boundary strengthening, and increase the compressive strength of the silicone rubber foam. This fully meets the current demand for integrated functional microwave-absorbing materials and will have a profound impact on the future development of microwave-absorbing materials.

[0055] In this invention, unless otherwise stated, scientific and technical terms used herein have the meanings commonly understood by those skilled in the art. Furthermore, the reagents, materials, and procedures used herein are all widely used in the relevant fields.

[0056] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A pressure-resistant and microwave-absorbing silicone rubber foam, characterized in that: It is prepared from the following components in parts by weight: The microwave absorbing filler is FeCo / Ce2Fe 17 Multi-heteromeric interface microwave absorbing filler obtained by Fe / C contact; The method for preparing the microwave absorbing filler is as follows: Ce2Fe 17 The alloy was mixed with dimethylimidazole and dopamine, then cobalt salt and hexadecyltrimethylammonium bromide were added, and polymerization was carried out to obtain a precursor; the precursor was calcined to obtain FeCo / Ce2Fe. 17 / Fe / C multi-heterogeneous interface microwave absorbing filler.

2. The pressure-resistant and microwave-absorbing silicone rubber foam according to claim 1, characterized in that: in, The Ce2Fe 17 The alloy is prepared by mixing CeO2 and carbonyl iron thoroughly in an argon atmosphere using a three-dimensional mixer for 10–14 h, followed by decalcification with an ammonium acetate aqueous solution to obtain Ce2Fe. 17 alloy.

3. The pressure-resistant and microwave-absorbing silicone rubber foam according to claim 2, characterized in that: in, In the preparation method of the microwave absorbing filler, the cobalt salt is cobalt nitrate hexahydrate; The mass ratio of carbonyl iron, CeO2, dopamine, dimethylimidazole, cobalt nitrate hexahydrate, and cetyltrimethylammonium bromide is 10:2:3:7-18:2-5:0.5-2.

4. The pressure-resistant and microwave-absorbing silicone rubber foam according to claim 1, characterized in that: in, The specific preparation method of the microwave absorbing filler is as follows: Ce2Fe 17 The alloy was dispersed evenly in deionized water; then dimethylimidazole and dopamine were added, and the mixture was stirred for 10–14 h; cobalt salt and hexadecyltrimethylammonium bromide were then added, and the mixture was stirred for 1–3 h to obtain the precursor; the precursor was heated to 600–800 °C at a heating rate of 1–3 °C / min under an argon atmosphere and held for 1–3 h to obtain FeCo / Ce2Fe. 17 / Fe / C multi-heterogeneous interface microwave absorbing filler.

5. The pressure-resistant and microwave-absorbing silicone rubber foam according to claim 1, characterized in that: in, The rubber system includes methyl vinyl silicone rubber, reinforcing agents, and additives; The mass ratio of methyl vinyl silicone rubber, reinforcing agent, and additives is 80–90:10–30:20–30.

6. The pressure-resistant and microwave-absorbing silicone rubber foam according to claim 5, characterized in that: in, In the rubber system, the reinforcing agent is silicon dioxide.

7. The pressure-resistant and microwave-absorbing silicone rubber foam according to claim 5, characterized in that: in, In the rubber system, the additives include low molecular weight hydroxyl silicone oil, diphenylsilanediol and silane coupling agent, and the mass ratio of low molecular weight hydroxyl silicone oil, diphenylsilanediol and silane coupling agent is 2:5:

2.

8. The pressure-resistant and microwave-absorbing silicone rubber foam according to claim 1, characterized in that: in, The foaming agent is hydroxyl-containing hydrogen silicone oil.

9. The pressure-resistant and microwave-absorbing silicone rubber foam according to claim 1, characterized in that: in, The vulcanizing agent is a bis(2,4)24 vulcanizing agent.

10. The method for preparing the pressure-resistant and microwave-absorbing silicone rubber foam according to any one of claims 1-9, characterized in that: Includes the following steps: Step 1: Mix the rubber system and microwave-absorbing filler in an internal mixer to obtain raw, pressure-resistant, microwave-absorbing silicone rubber foam. Step 2: Pour the pressure-resistant and microwave-absorbing silicone rubber foam raw material obtained in Step 1 into a mold, add foaming agent and vulcanizing agent, and foam at 110-130℃ for 30-60 minutes to obtain the pressure-resistant and microwave-absorbing silicone rubber foam.

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