A foam carbon wave-absorbing material, its preparation method and application

Abstract

The present invention relates to a foam carbon wave-absorbing material, which comprises foaming component A and foaming component B, and the ratio of the foaming component A to the foaming component B is 150-160:100; the foaming component A comprises a polyurethane foaming ingredient A, ammonium polyphosphate, expanded graphite powder, and molybdenum trioxide; the foaming component B comprises a polyurethane foaming ingredient B. In the preparation of foam carbon in the prior art, the foaming and carbonization steps are carried out simultaneously at a high temperature, so the yield is low and the reaction process is difficult to control; however, in the preparation process of the present application, the polyurethane foam is first generated from the foaming material at room temperature and then carbonized at a high temperature, so the process route in the present application is easier to control the finished product quality and has a lower cost, and the requirements for equipment are not high.

Description

Technical Field

[0001] The invention relates to a new material, in particular to a foamed carbon wave-absorbing material and a preparation method and application thereof. Background Art

[0002] Foam carbon refers to a foamy porous carbon material. Foam carbon is a lightweight porous material with a three-dimensional network structure composed of pores and interconnected pore walls. In addition to the conventional properties of carbon materials, foam carbon also has the characteristics of low density, high strength, thermal shock resistance, easy processing, and good physical and chemical properties such as electrical conductivity, thermal conductivity, and wave absorption. By compounding with metals or non-metals, high-performance structural materials can be obtained.

[0003] These excellent properties make carbon foam have great application potential in many technical fields such as chemical industry, aerospace, electronics, etc. The research content of carbon foam materials involves the selection and adjustment of new raw materials, the development and optimization of preparation process technology, the microstructure of products, the mechanical properties of materials, the revelation and regulation of thermal properties, and the expansion of the best application path.

[0004] The most popular industrial method for preparing carbon foam is to use inert gas to protect and isolate the air and heat it to 600℃-1000℃; however, this preparation method has high requirements on equipment and high manufacturing cost. Moreover, this process is foaming at high temperature, so it is difficult to control the reaction process, which leads to low yield. Summary of the invention

[0005] The purpose of the present invention is to provide a foamed carbon absorbing material.

[0006] The above technical purpose of the present invention is achieved through the following technical scheme: a foamed carbon absorbing material, comprising a foaming component A and a foaming component B, wherein the ratio of the foaming component A to the foaming component B is 150-160:100; the foaming component A comprises a polyurethane foaming ingredient A, ammonium polyphosphate, expanded graphite powder, and molybdenum trioxide; and the foaming component B comprises a polyurethane foaming ingredient B.

[0007] Preferably, the foaming component A also includes an organosilicon foaming aid.

[0008] Preferably, the contents of the various material components are as follows:

[0009] Foaming component A

[0010]

[0011] Foaming component B

[0012] Polyurethane foaming ingredient B 100 parts.

[0013] Preferably, the ammonium polyphosphate used is a product with a polymerization degree greater than 1000, and the expanded graphite powder used is a product with a mesh size of 325 and an expansion ratio greater than 200 times.

[0014] The purpose of the present invention is to provide a preparation method of a foam carbon wave-absorbing material.

[0015] The above technical purpose of the present invention is achieved through the following technical solutions: A method for preparing the above foam carbon wave-absorbing material includes the following preparation steps:

[0016] Step 1: Weigh the foaming component A and the foaming component B according to the amount, put the weighed foaming component A and foaming component B into a foaming container, stir evenly, and then foam.

[0017] Step 2: Cut the polyurethane foam successfully foamed in Step 1 into the required size, then place it in a refractory crucible, cover the lid, and then put it into a muffle furnace with an accurate temperature control function together with the refractory crucible, quickly heat up to 300 °C, and maintain for at least 120 minutes.

[0018] Step 3: After cooling the reactant in Step 2 to room temperature, take it out to obtain a black foam carbon primary product.

[0019] Step 4: Take lithium silicate, ethylene-vinyl acetate emulsion, alkaline auxiliary agent, surface wetting agent and defoaming agent and mix them to obtain the impregnating solution A liquid; place the foam carbon primary product prepared in Step 3 into the impregnating solution A liquid, soak it thoroughly, and then take it out and drain the excess impregnating solution A liquid.

[0020] Step 5: Prepare a 60% aluminum dihydrogen phosphate solution with aluminum dihydrogen phosphate to obtain the impregnating solution B liquid; then place the reactant in Step 4 into the impregnating solution B liquid for 25 - 40 minutes, take it out and drain it to obtain a foam carbon finished product with a mixture of insoluble silicate and phosphate formed in the voids of the foam carbon primary product.

[0021] Preferably, the content of each substance component in the impregnating solution A liquid is as follows:

[0022]

[0023] Preferably, the impregnating solution A liquid includes the following preparation steps:

[0024] Stp1: Under the stirring state of 500 - 700 revolutions per minute, slowly drop the alkaline auxiliary agent into the ethylene-vinyl acetate emulsion.

[0025] Stp2: After reducing the rotation speed to 300 - 400 revolutions per minute, slowly drop lithium silicate, and then stir for 9 - 11 minutes at a constant speed.

[0026] Stp3: After adding a surface wetting agent and an antifoaming agent dropwise to the mixture in Stp3 and continuously stirring until uniform, an impregnating solution A liquid is obtained.

[0027] The purpose of the present invention is to provide an application of a foam carbon wave-absorbing material.

[0028] The above technical object of the present invention is achieved through the following technical solution: An application of a foam carbon wave-absorbing material in an electromagnetic and optical composite stealth material.

[0029] In summary, the present invention has the following beneficial effects:

[0030] 1. In the preparation of foam carbon in the prior art, foaming and carbonization are carried out simultaneously at a high temperature state, so the yield is low, and the reaction process is difficult to control; however, in the preparation process of the present application, first, a foaming material generates polyurethane foam at room temperature, and then it is put into a high temperature for carbonization. Therefore, the process route in the present application is easier to control the finished product quality, has a lower cost, and has low requirements for equipment;

[0031] 2. When electromagnetic waves are perpendicularly incident on the surface of the prepared wave-absorbing material, part of the electromagnetic waves are reflected back; the rest enter the material interior and convert electromagnetic energy into heat energy dissipation or attenuate the electromagnetic waves due to interference through mechanisms such as conduction current loss, dielectric loss, and magnetic loss during the propagation of the electromagnetic waves; part of the electromagnetic waves that are not dissipated or attenuated are reflected between the free space and the interfaces of the wave-absorbing coating surface and the coating bottom surface and the metal plate. During the back-and-forth reflection process, part of the electromagnetic waves are absorbed and attenuated by the wave-absorbing coating, and the part that is not attenuated passes through the upper surface of the coating and returns to the free space again.

[0032] 3. The foam carbon primary product after high-temperature carbonization is successively immersed in the impregnating solution A liquid and the impregnating solution B liquid. After two immersions, a mixed structure of insoluble silicate and phosphate is formed in the pore part of the foam carbon, thereby improving the structural strength of the overall structure, such as the compressive capacity, etc., and polyethylene-vinyl acetate can improve the toughness of the overall structure;

[0033] 4. During the foaming process of polyurethane, molybdenum trioxide is added as a catalyst component, and a graphite-like structure can be formed during the carbonization process. A similar structure can make the expanded graphite powder more closely connected in the microstructure and have a higher structural strength; while the silicone foam stabilizer can make the size of the bubbles more uniform and dense; ammonium polyphosphate will release gas during the reaction. Because the component of the ammonium root (NH4 + ) is nitrogen and hydrogen, it can decompose into nitrogen and ammonia after being heated. These gases overflowing outwards can protect the reaction, which is why no additional protective gas needs to be added in the preparation process claimed in the present application;

[0034] 5. During the impregnation process, lithium silicate and aluminum dihydrogen phosphate form lithium phosphate crystals with high structural strength, which can enhance the overall structural strength. A part of the lithium remains in a soluble lithium salt state. When applied to green camouflage, this part of the lithium salt absorbs moisture from the air by deliquescence. When infrared light passes through the leaves, there are two absorption peaks at 1400 μm and 1900 μm. After passing through this foam carbon material containing lithium salt, two absorption peaks also form near 1400 μm and 1900 μm. Therefore, it can achieve a better stealth interference effect. Specific embodiments

[0035] This specific embodiment is only an explanation of the present invention and does not limit the present invention. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as it is within the scope of the claims of the present invention, it is protected by the patent law.

[0036] Example:

[0037] A foam carbon wave-absorbing material and its preparation method, including foaming component A and foaming component B, and the ratio of the foaming component A to the foaming component B is 150 - 160:100; the foaming component A includes polyurethane foaming ingredient A, ammonium polyphosphate, expanded graphite powder, and molybdenum trioxide; the foaming component B includes polyurethane foaming ingredient B.

[0038] Polyurethane foaming ingredient A and polyurethane foaming ingredient B can be common materials on the market and any one of them can form polyurethane foam, also known as polyurethane foaming black and white materials; such as polyurethane rigid foam composite polyether and polymeric MDI, or polyurethane foaming ingredient B uses isocyanate and polyurethane foaming ingredient A uses an organic compound containing amino groups.

[0039] The ammonium polyphosphate uses a product with a polymerization degree greater than 1000, and the expanded graphite powder uses a product with a mesh size of 300 - 400 and an expansion ratio greater than 200 times, and 325 mesh is the best.

[0040] The preparation method of the foam carbon absorbing material includes the following preparation steps:

[0041] Step 1: Weigh the foaming component A and the foaming component B according to the amount, put the weighed foaming component A and foaming component B into a foaming container, stir evenly, and then carry out foaming;

[0042] Step 2: Cut the polyurethane foam successfully foamed in Step 1 into the required size, then place it in a refractory crucible, cover the lid, and then put it into a muffle furnace with precise temperature control function together with the refractory crucible, quickly heat it to 300 °C, and maintain it for at least 120 minutes;

[0043] Step 3: After cooling the reactants in Step 2 to room temperature, take them out to obtain a preliminary product of black foamed carbon;

[0044] Step 4: Take lithium silicate, polyvinyl acetate - vinyl acetate emulsion, alkaline auxiliary agent, surface wetting agent and defoaming agent and mix them to obtain dipping solution A; Place the preliminary product of foamed carbon prepared in Step 3 into dipping solution A, soak it thoroughly and then take it out, draining off the excess dipping solution A;

[0045] Step 5: Then place the reactants in Step 4 into dipping solution B for 25 - 40 minutes, take them out and drain, to obtain a finished product of foamed carbon with a mixture of insoluble silicate and phosphate formed in the voids of the preliminary product of foamed carbon.

[0046] Among them, dipping solution B is a 60% aluminum dihydrogen phosphate solution.

[0047] The preparation steps of dipping solution A are as follows:

[0048] Stp1: Under the stirring state of 500 - 700 revolutions per minute, slowly drop the alkaline auxiliary agent into the polyvinyl acetate - vinyl acetate emulsion;

[0049] Stp2: After reducing the rotation speed to 300 - 400 revolutions per minute, slowly drop lithium silicate and then stir for 9 - 11 minutes;

[0050] Stp3: Drop the surface wetting agent and defoaming agent into the mixture in Stp2, and continue to stir until it is uniform to obtain dipping solution A.

[0051] After surface cleaning and drying for standby, the prepared finished product of foamed carbon has good wave - absorbing performance and good compressive strength. Therefore, after spraying a solvent - based camouflage coating on the surface, it can be used as a material for electromagnetic and optical composite stealth.

[0052] Example 1:

[0053] In this example, the ratio of foaming component A to foaming component B is 150:100.

[0054] Foaming component A includes 100 parts of polyurethane foaming ingredient A, 30 parts of ammonium polyphosphate, 10 parts of expanded graphite powder, 1 part of molybdenum trioxide, and 1 part of silicone foam stabilizer.

[0055] Example 2:

[0056] In this example, the ratio of foaming component A to foaming component B is 150:100.

[0057] Foaming component A includes 100 parts of polyurethane foaming ingredient A, 40 parts of ammonium polyphosphate, 20 parts of expanded graphite powder, 2 parts of molybdenum trioxide, and 3 parts of silicone foam stabilizer.

[0058] Example 3:

[0059] In this example, the ratio of Foaming Component A to Foaming Component B is 150:100.

[0060] Foaming Component A includes 100 parts of polyurethane foaming ingredient A, 35 parts of ammonium polyphosphate, 15 parts of expanded graphite powder, 1 part of molybdenum trioxide, and 2 parts of silicone foam stabilizer.

[0061] Example 4:

[0062] In this example, the ratio of Foaming Component A to Foaming Component B is 160:100.

[0063] Foaming Component A includes 100 parts of polyurethane foaming ingredient A, 30 parts of ammonium polyphosphate, 10 parts of expanded graphite powder, 1 part of molybdenum trioxide, and 1 part of silicone foam stabilizer.

[0064] Example 5:

[0065] In this example, the ratio of Foaming Component A to Foaming Component B is 160:100.

[0066] Foaming Component A includes 100 parts of polyurethane foaming ingredient A, 40 parts of ammonium polyphosphate, 20 parts of expanded graphite powder, 2 parts of molybdenum trioxide, and 3 parts of silicone foam stabilizer.

[0067] Example 6:

[0068] In this example, the ratio of Foaming Component A to Foaming Component B is 160:100.

[0069] Foaming Component A includes 100 parts of polyurethane foaming ingredient A, 35 parts of ammonium polyphosphate, 15 parts of expanded graphite powder, 1 part of molybdenum trioxide, and 2 parts of silicone foam stabilizer.

[0070] In Examples 1 - 6, the content of the substance components in Immersion Liquid A is the same, including 20 parts of lithium silicate, 65 parts of ethylene - vinyl acetate emulsion (VAE), 2 parts of alkaline auxiliary agent, 0.5 part of surface wetting agent, and 0.5 part of defoaming agent.

[0071] In Examples 7 - 9, the ratio of Foaming Component A to Foaming Component B is 158:100.

[0072] The content of each substance in Foaming Component A is as follows: 100 parts of polyurethane foaming ingredient A, 40 parts of ammonium polyphosphate, 20 parts of expanded graphite powder, 2 parts of molybdenum trioxide, and 3 parts of silicone foam stabilizer.

[0073] Example 7:

[0074] The impregnating solution A contains 15 parts of lithium silicate, 45 parts of ethylene-vinyl acetate emulsion (VAE), 1 part of alkaline auxiliary agent, 0.3 part of surface wetting agent, and 0.2 part of defoaming agent.

[0075] Example 8:

[0076] The impregnating solution A contains 15-25% of lithium silicate, 45-65 parts of ethylene-vinyl acetate emulsion (VAE), 1-3 parts of alkaline auxiliary agent, 0.3-1.0 part of surface wetting agent, and 0.2-0.6 part of defoaming agent.

[0077] Example 9:

[0078] The impregnating solution A contains 25 parts of lithium silicate, 65 parts of ethylene-vinyl acetate emulsion (VAE), 3 parts of alkaline auxiliary agent, 1.0 part of surface wetting agent, and 0.6 part of defoaming agent.

[0079] The prepared foam carbon product can be tested according to the national standards. The national standards relied on are GJB2038-94 Test Method for Reflectivity of Radar Absorbing Materials and GJB5239-2004 Test for Absorbing Performance of Radio Frequency Absorbing Materials.

[0080] The absorbing data after testing is as follows:

[0081] Absorbing intensity: 10 db

[0082] Frequency bandwidth: 500 MHz to 12 GHz

[0083] Among them:

[0084] The thickness of the foam carbon is 15 mm

[0085] Specific gravity: 1.2-1.4 g / cm 3 。

Claims

1. A foam carbon microwave absorbing material, characterized in that: It includes foaming component A and foaming component B, and the ratio of the foaming component A to the foaming component B is 150 - 160:100; the foaming component A includes polyurethane foaming ingredient A, ammonium polyphosphate, expanded graphite powder, and molybdenum trioxide; the foaming component B includes polyurethane foaming ingredient B. The foam carbon wave-absorbing material is prepared by the following preparation steps: Step 1: Weigh the foaming component A and the foaming component B according to the amount, put the weighed foaming component A and foaming component B into a foaming container, stir evenly, and then carry out foaming. Step 2: Cut the polyurethane foam successfully foamed in Step 1 into the required size, then place it in a refractory crucible, cover the lid, and then put it into a muffle furnace with an accurate temperature control function together with the refractory crucible, quickly heat up to 300 °C, and maintain it for at least 120 minutes. Step 3: Take out the reactant in Step 2 after cooling it to room temperature to obtain a black foam carbon preliminary product. Step 4: Mix lithium silicate, polyethylene-vinyl acetate emulsion, alkaline auxiliary agent, surface wetting agent, and defoaming agent to obtain impregnating liquid A; place the foam carbon preliminary product prepared in Step 3 into the impregnating liquid A, soak it thoroughly, and then take it out and drain off the excess impregnating liquid A. Step 5: Prepare a 60% solution of aluminum dihydrogen phosphate with aluminum dihydrogen phosphate to obtain impregnating liquid B. Then place the foam carbon preliminary product with the excess impregnating liquid A drained off in Step 4 into the impregnating liquid B for 25 - 40 minutes, take it out and drain it, to obtain a foam carbon finished product with insoluble silicate and phosphate mixed in the void part of the foam carbon preliminary product.

2. The foam carbon absorbing material according to claim 1, wherein: The foaming component A further includes an organosilicon foam stabilizer.

3. The foam carbon absorbing material according to claim 2, wherein The content of each substance component is as follows: Foaming component A Polyurethane foaming ingredient A 100 parts Ammonium polyphosphate 30 - 40 parts Expanded graphite powder 10 - 20 parts Molybdenum trioxide 1 - 2 parts Organosilicon foam stabilizer 1 - 3 parts Foaming component B Polyurethane foaming ingredient B 100 parts.

4. The foam carbon absorbing material according to claim 1, wherein: The ammonium polyphosphate uses a product with a polymerization degree greater than 1000, and the expanded graphite powder uses a product with a mesh size of 300 - 400 and an expansion ratio greater than 200 times.

5. The foam carbon absorbing material according to claim 1, wherein The content of each substance component in the impregnating liquid A is as follows: Lithium silicate 15 - 25 parts Polyethylene-vinyl acetate emulsion 45 - 65 parts Alkaline auxiliary agent 1 - 3 parts Surface wetting agent 0.3 - 1.0 part Defoaming agent 0.2 - 0.6 part.

6. The foam carbon absorbing material according to claim 5, characterized in that, The impregnating liquid A is prepared by the following preparation steps: Stp1: Under the stirring state of 500 - 700 revolutions, slowly drop the alkaline auxiliary agent into the polyethylene-vinyl acetate emulsion. Stp2: After reducing the rotation speed to 300 - 400 revolutions, slowly drop lithium silicate, and then continuously stir for 9 - 11 minutes. Stp3: Drop the surface wetting agent and the defoaming agent into the mixture in Stp2, and continuously stir until it is uniform to obtain the impregnating liquid A.

7. Application of a foam carbon wave-absorbing material in an electromagnetic and optical composite stealth material, characterized in that: This foam carbon wave-absorbing material applied to electromagnetic wave and optical composite stealth materials is made of the foam carbon wave-absorbing material described in any one of Claims 1 - 6.

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