Wave-absorbing slurry, wave-absorbing honeycomb and preparation method thereof

Abstract

The invention relates to the technical field of wave-absorbing materials, in particular to wave-absorbing slurry, a wave-absorbing honeycomb and a preparation method of the wave-absorbing slurry. The wave-absorbing slurry comprises resin, an absorbent, a solvent, an anti-settling agent and a thickening agent; the preparation method of the wave-absorbing slurry comprises the following steps: preparing materials, preparing a component I, preparing a component II and mixing. The preparation method of the wave-absorbing honeycomb comprises the steps of preparing the wave-absorbing aramid paper and preparing the wave-absorbing honeycomb. Wave-absorbing slurry is printed on the surface of aramid paper to prepare wave-absorbing aramid paper, and then the wave-absorbing honeycomb is prepared through the procedures of gluing, overlapping, hot pressing, stretching and spraying, sizing, gum dipping, curing and the like. According to the invention, a printing process is used for replacing a soaking process, and the concentration of the wave-absorbing honeycomb is controlled by controlling the printing process; according to the wave-absorbing slurry disclosed by the invention, a wave-absorbing honeycomb can be prepared by utilizing a preparation method of a traditional aramid paper honeycomb core material, a common corrugated structure preparation process of an integrated wave-absorbing honeycomb is canceled, and the simplification of the preparation process of the wave-absorbing honeycomb is realized while excellent wave-absorbing performance is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of wave-absorbing materials, and in particular to a wave-absorbing slurry, a wave-absorbing honeycomb and a preparation method thereof. Background Art

[0002] The improvement of electronic information technology has led to excessive electromagnetic pollution, which not only poses a threat to people's health, but also causes malfunctions of communication equipment and aircraft. Absorbing materials can effectively reduce or eliminate the impact of electromagnetic waves.

[0003] Absorbing materials refer to materials that can attenuate and absorb electromagnetic waves, convert electromagnetic waves into other types of energy and dissipate them. Structural absorbing materials are prepared by impregnating and coating the inner wall of the structure with absorbing coatings and filling other types of absorbing materials in the sandwich structure. They are thin, light, wide frequency band, and strong in performance, and are widely used in aviation, aerospace and other fields.

[0004] At present, the method for preparing microwave-absorbing honeycombs is mainly to use white honeycombs to prepare microwave-absorbing honeycombs through a dipping process / flow coating process. Under this process condition, the amount of absorbent added to the coating cannot be too high, otherwise the absorbent will easily adhere to the honeycomb pore wall, causing the absorbent to fall off and the coating to crack, thereby causing problems with the appearance of the honeycomb. In addition, the dipping process / flow coating process is difficult to control and is prone to instability between batches.

[0005] In order to solve the above problems, the prior art is to obtain a wave-absorbing honeycomb by preparing a corrugated structural unit. For example, the Chinese patent with publication number CN112223772A discloses a method for preparing a polyimide film honeycomb, in which a flat polyurethane film is molded on a template to obtain a polyurethane film with a corrugated structural unit, and then the corrugated polyurethane film is stacked and cured to finally obtain a polyimide honeycomb product. Another example is the Chinese patent with publication number CN115821643A discloses a wave-absorbing honeycomb with a gradient distribution of absorbent and a preparation method, the specific operation is: prepare aramid paper doped with absorbent, prepare the aramid paper into a corrugated structural unit, and then stack and heat the corrugated units to finally prepare a wave-absorbing honeycomb. The above patents all prepare corrugated structural units, the process is relatively cumbersome, and the material loss in the honeycomb preparation process is increased.

[0006] In view of the above problems, there is an urgent need to provide an absorbing honeycomb material and a preparation method thereof that can simultaneously meet the requirements of process controllability, simple process and excellent absorbing performance. Summary of the invention

[0007] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a microwave absorbing slurry, a microwave absorbing honeycomb and a preparation method thereof.

[0008] The purpose of the present invention is achieved through the following technical solutions:

[0009] The first aspect of the present invention is to provide an absorbing slurry, comprising the following raw materials in parts by weight:

[0010]

[0011] Wherein, the resin is one or more of phenolic resin, epoxy resin, polyurethane resin or bismaleimide resin; the absorbent is one or more of carbon powder, graphene, carbon fiber, silicon nitride and ferrite.

[0012] As a preferred technical solution, the following raw materials are included in weight:

[0013]

[0014] Furthermore, the solvent is one or more of methanol, ethanol, acetone, methyl ether, ethyl ether or industrial water.

[0015] Furthermore, the anti-settling agent is one or more of organic bentonite, sodium carboxymethyl cellulose, polyvinyl alcohol, silicon dioxide or sodium polyacrylate.

[0016] Furthermore, the thickener is one or more of polyamide, modified acrylic acid, fatty amine or propylene glycol sodium alginate.

[0017] The second aspect of the present invention is to provide a method for preparing an absorbing slurry, which comprises the following steps:

[0018] S1. Prepare materials: weigh each raw material according to the formula ratio and set aside;

[0019] S2. Preparation of component 1: The solvent is divided into two parts A and B, wherein the volume ratio of the solvent A to the solvent B is 1:8 to 12, the absorbent, the anti-settling agent and the solvent A are mixed and stirred to obtain component 1;

[0020] S3. Preparation of component II: The resin and the solvent of part B were mixed and stirred to obtain component II;

[0021] S4. Mixing: Component 1 and component 2 are mixed and stirred to obtain a mixed solution, a thickener is added to the mixed solution to adjust the viscosity to 6000-9000 mPa.s, the solution is stirred and then crushed and dispersed to obtain a radar absorbing slurry.

[0022] In the preparation method of the above-mentioned microwave absorbing slurry:

[0023] (1) First, the absorbent, anti-settling agent and part of the solvent are mixed together, which can fully wet the absorbent, reduce the agglomeration of the absorbent, and facilitate the mixing of the absorbent in the subsequent solution;

[0024] (2) Mix the resin with the remaining solvent. Because the viscosity of the resin is relatively high, the resin is diluted initially before being mixed with the soaked absorbent. This can prevent the absorbent from agglomerating in large quantities, resulting in uneven dispersion, and the resin from being too viscous to mix. After the initial mixing, a thickener is added to increase the viscosity of the absorbing slurry and improve its overall fluidity. Among them, for the anti-settling agent, since the absorbing slurry is a solid-liquid mixture, this additive is used to increase its surface tension through a chemical reaction on the surface of the material to prevent the absorbent in the absorbing slurry from settling and stratification; for the thickener, in order to increase the overall viscosity of the absorbing slurry, improve its fluidity, and reduce the sagging phenomenon of the absorbing slurry. The combined use of thickeners and anti-settling agents is, on the one hand, to improve the stability of the absorbing slurry and ensure the stability of the subsequently prepared absorbing aramid paper; on the other hand, to improve its fluidity. If the fluidity is too large, it is not conducive to the control of the subsequent printing process.

[0025] (3) Finally, the obtained slurry is crushed and dispersed. The slurry is refined through collision, friction and shearing to further improve the dispersion effect.

[0026] Furthermore, in step S2, the absorbent, anti-settling agent and part A solvent are mixed and stirred at a rate of 500 to 1500 rad / min for 60 to 120 min; in step S3, the resin and part B solvent are mixed and stirred at a rate of 1000 to 2000 rad / min for 20 to 50 min; in step S4, component one and component two are mixed and stirred at a rate of 1000 to 2000 rad / min for 20 to 50 min; and the number of rolling times is 3 to 10 times.

[0027] The third aspect of the present invention is to provide a method for preparing a microwave absorbing honeycomb, which comprises the following steps:

[0028] A. Preparation of microwave-absorbing aramid paper: Printing the microwave-absorbing slurry on both sides of the aramid paper to form a surface coating, the printing is carried out using a fully automatic screen printing machine, setting the scraper parameters: 0.3-1.2, the air pressure: 0.4-1.2 MPa, the printing speed: 1%-20%, the thickness of the surface coating is 1-100 μm, and the aramid paper with the microwave-absorbing slurry on the surface is baked to obtain the microwave-absorbing aramid paper;

[0029] B. Preparation of microwave-absorbing honeycombs: The microwave-absorbing aramid paper is processed into microwave-absorbing honeycomb blocks through an aramid honeycomb production line, and the microwave-absorbing honeycomb blocks are processed into microwave-absorbing honeycombs through resin dipping and curing.

[0030] Furthermore, the glue solution for dipping in step B is a mixed solution of resin and dipping solvent, the resin is one or more of phenolic resin, epoxy resin, polyurethane resin or bismaleimide resin, and the dipping solvent is one or more of methanol, ethanol, acetone, methyl ether, ethyl ether or industrial water.

[0031] Furthermore, the baking temperature in step A is 120-180° C., and the baking time is 1-6 hours; the curing temperature in step B is 120-180° C., and the time is 4-8 hours.

[0032] In the preparation method of the above-mentioned wave-absorbing honeycomb:

[0033] The absorbing slurry of the prior art is attached to the surface of aramid paper or aramid paper honeycomb by spraying / dipping / painting. On the one hand, due to the stratification of the slurry itself on the surface and the spraying / dipping / painting operation mode, the same aramid paper / the same honeycomb will have uneven impregnation at different positions. The most direct manifestation is that the film thickness of the absorbing slurry on the surface of aramid paper or aramid paper honeycomb after impregnation is uncontrollable (meaning that the concentration area is uncontrollable and the impregnation range is larger) and the appearance has particles, which will affect the absorbing performance of the prepared absorbing honeycomb; on the other hand, the same raw materials and the same process conditions will cause different batches of absorbing honeycombs to be impregnated with different absorbing slurries due to changes in the viscosity of the absorbing slurry and the sedimentation of the absorbing slurry during the impregnation process, which ultimately leads to poor stability of the absorbing honeycombs between batches. The method of the present invention can accurately control the film thickness of each printing by printing, realize the control of the concentration of the absorbing honeycomb, so that the film thickness of the absorbing slurry remains basically consistent during each printing process, and the appearance is flat, without particles, gum tumors, etc. This not only solves the problems of unevenness and particle appearance during the soaking process, but also solves the problem of instability between batches.

[0034] The viscosity of the absorbing slurry used in different impregnation methods is different. The viscosity of the absorbing slurry used by spraying / impregnation / coating is lower, which will make it easier to stratify, agglomerate and settle during the use of the slurry, and will cause surface particles when preparing the absorbing aramid paper / absorbing honeycomb later. If the viscosity of the slurry is increased, it will make it difficult to soak the honeycomb surface during the spraying / impregnation / coating process, and the uniformity will be worse; at the same time, the appearance is more likely to have particles, nodules and other phenomena. Therefore, when using processes such as spraying / impregnation / coating, it is necessary to consider the instability of the slurry itself and the instability caused by the process. When using the printing process, the viscosity used is relatively high, which will improve the stability of the slurry itself; the film thickness on the surface of the aramid paper can be accurately controlled.

[0035] It should be noted that the aramid honeycomb production line is an existing technology, including gluing, lamination, hot pressing, stretching spraying, and shaping processes to prepare honeycomb blocks. Among them, the glue strip coating area is a single side of the absorbing aramid paper, and the gluing distance is related to the side length of the honeycomb grid, and the side length of the honeycomb grid is preferably 0.9-5.5 mm; when overlapping, the different layers of absorbing aramid paper need to be staggered and overlapped, so that the position of the next glue strip should be aligned with the middle position of the previous adjacent glue strip. The hot pressing temperature in the hot pressing process is 120-180°C, and the hot pressing time is 2-5h. After the gluing, lamination, and hot pressing operations are completed, the honeycomb block is stretched. After the stretching is completed, the honeycomb block needs to be sprayed to ensure that the absorbing aramid paper in different areas of the honeycomb block remains moist. The moist honeycomb block is then baked and shaped. The shaping temperature in the shaping process is 80-180°C, and the shaping time is 3-6h. After shaping, the honeycomb block is taken out.

[0036] The present invention has the following advantages: the present invention provides an absorbing slurry, an absorbing honeycomb and a preparation method thereof, wherein the absorbing slurry is prepared with resin, solvent, anti-settling agent and thickener as raw materials, and the absorbing slurry is printed on the surface of aramid paper by technical means to prepare the absorbing aramid paper; and then the absorbing honeycomb is prepared by gluing, laminating, hot pressing, stretching spraying, shaping, dipping, curing and other processes. The present invention uses a printing process to replace the dipping process, and the concentration of the absorbing honeycomb is controlled by controlling the printing process; the absorbing slurry disclosed in the present invention can be used to prepare the absorbing honeycomb using the preparation method of the traditional aramid paper honeycomb core material, and the common corrugated structure preparation process of the integrated absorbing honeycomb is eliminated, and the absorbing honeycomb preparation process is simplified while ensuring excellent absorbing performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of the preparation process of the microwave absorbing slurry of the present invention.

[0038] Figure 2 The figure is a schematic diagram of the preparation process of the microwave-absorbing aramid paper of the present invention.

[0039] Figure 3 The figure is a schematic diagram of the preparation process of the wave-absorbing honeycomb of the present invention.

[0040] Figure 4 It is a schematic diagram of the gluing and laminating steps of the wave-absorbing aramid paper of the present invention. DETAILED DESCRIPTION

[0041] The present invention is further described below in conjunction with the accompanying drawings and embodiments. The protection scope of the present invention is not limited to the following: Embodiment 1: A microwave absorbing slurry comprises the following raw materials in parts by weight:

[0042]

[0043] Wherein, the resin is phenolic resin; the absorbent is carbon powder; the solvent is methanol; the anti-settling agent is organic bentonite; and the thickener is polyamide.

[0044] Embodiment 2: A microwave absorbing slurry, comprising the following raw materials in parts by weight:

[0045]

[0046] Among them, the resin is a mixture of epoxy resin and polyurethane resin, and the weight ratio is 1:1; the absorbent is a mixture of graphene and carbon fiber, and the weight ratio is 2:1; the solvent is a mixture of ethanol and acetone, and the volume ratio is 1:1; the anti-settling agent is a mixture of sodium carboxymethyl cellulose and polyvinyl alcohol, and the weight ratio is 3:1; the thickener is a mixture of modified acrylic acid and fatty amine, and the weight ratio is 1:1.

[0047] Embodiment 3: A microwave absorbing slurry comprising the following raw materials in parts by weight:

[0048]

[0049] Among them, the resin is a mixture of phenolic resin, polyurethane resin and bismaleimide resin, and the weight ratio is 1:1:1; the absorbent is a mixture of carbon powder, graphene, carbon fiber, silicon nitride and ferrite, and the weight ratio is 3:0.5:1:1:1; the solvent is a mixture of methyl ether, ethyl ether and industrial water, and the volume ratio is 2:1:1; the anti-settling agent is a mixture of sodium carboxymethyl cellulose, polyvinyl alcohol and silicon dioxide, and the weight ratio is 1:2:2; the thickener is a mixture of polyamide, modified acrylic acid, fatty amine and propylene glycol sodium alginate, and the weight ratio is 3:1:0.5:0.1.

[0050] Embodiment 4: A microwave absorbing slurry comprising the following raw materials in parts by weight:

[0051]

[0052]

[0053] The resin is a mixture of phenolic resin, epoxy resin, polyurethane resin and bismaleimide resin, and the weight ratio thereof is 1:3:1:0.5; the absorbent is a mixture of carbon powder, carbon fiber and silicon nitride, and the weight ratio thereof is 0.3:1:0.7; the solvent is a mixture of methanol, ethanol, acetone and industrial water, and the volume ratio thereof is 0.5:0.5:2:2; the anti-settling agent is a mixture of organic bentonite, sodium carboxymethyl cellulose, polyvinyl alcohol and sodium polyacrylate, and the weight ratio thereof is 3:2:1:1; the thickener is propylene glycol sodium alginate.

[0054] Embodiment 5: A microwave absorbing slurry comprising the following raw materials in parts by weight:

[0055]

[0056] The resin is bismaleimide resin; the absorbent is a mixture of graphene, carbon fiber, silicon nitride and ferrite, and the weight ratio is 0.1:1:0.5:2; the solvent is industrial water; the anti-settling agent is a mixture of organic bentonite, sodium carboxymethyl cellulose, polyvinyl alcohol, silica and sodium polyacrylate, and the weight ratio is 2:1:1:1:2; the thickener is a mixture of modified acrylic acid, fatty amine and propylene glycol sodium alginate, and the weight ratio is 2:2:1.

[0057] Example 6: Figure 1 As shown, a method for preparing a microwave absorbing slurry comprises the following steps:

[0058] S1. Preparation: Weigh the raw materials according to the formula ratio of Example 1 and set aside;

[0059] S2. Preparation of component 1: The solvent was divided into two parts, A and B, wherein the volume ratio of the solvent A to the solvent B was 1:8, the absorbent, anti-settling agent and the solvent A were mixed and stirred uniformly at a stirring rate of 500 rad / min for 120 min to obtain component 1;

[0060] S3. Preparation of component II: The resin and the solvent of part B were mixed and stirred uniformly at a stirring rate of 1000rad / min for 50min to obtain component II;

[0061] S4. Mixing: Component 1 and component 2 are mixed and stirred to obtain a mixed solution at a stirring rate of 1000 rad / min for 50 min. A thickener is added to the mixed solution to adjust the viscosity to 7000 mPa.s. The solution is stirred and then crushed and dispersed for 3 times to obtain a microwave absorbing slurry.

[0062] Example 7: Figure 1 As shown, a method for preparing a microwave absorbing slurry comprises the following steps:

[0063] S1. Preparation: Weigh the raw materials according to the formula ratio of Example 4 and set aside;

[0064] S2. Preparation of component 1: The solvent was divided into two parts, A and B, wherein the volume ratio of the solvent A to the solvent B was 1:12, the absorbent, anti-settling agent and the solvent A were mixed and stirred uniformly at a stirring rate of 1500rad / min for 60min to obtain component 1;

[0065] S3. Preparation of component II: The resin and the solvent of part B were mixed and stirred uniformly at a stirring rate of 2000rad / min for 20min to obtain component II;

[0066] S4. Mixing: Component 1 and component 2 are mixed and stirred to obtain a mixed solution at a rate of 2000 rad / min for 20 min. A thickener is added to the mixed solution to adjust the viscosity to 6000 mPa.s. The solution is stirred and then crushed and dispersed for 10 times to obtain a microwave absorbing slurry.

[0067] Example 8: Figure 1 As shown, a method for preparing a microwave absorbing slurry comprises the following steps:

[0068] S1. Preparation: Weigh the raw materials according to the formula ratio of Example 5 and set aside;

[0069] S2. Preparation of component 1: The solvent was divided into two parts, A and B, wherein the volume ratio of the solvent A to the solvent B was 1:10, the absorbent, the anti-settling agent and the solvent A were mixed and stirred uniformly at a stirring rate of 1000 rad / min for 80 min to obtain component 1;

[0070] S3. Preparation of component II: The resin and the solvent of part B were mixed and stirred uniformly at a stirring rate of 1500rad / min for 35min to obtain component II;

[0071] S4. Mixing: Component 1 and component 2 are mixed and stirred to obtain a mixed solution at a stirring rate of 1600 rad / min for 40 min. A thickener is added to the mixed solution to adjust the viscosity to 9000 mPa.s. The solution is stirred and then crushed and dispersed for 6 times to obtain a microwave absorbing slurry.

[0072] Example 9: Figure 3 As shown, a method for preparing a wave-absorbing honeycomb comprises the following steps:

[0073] A. Preparation of microwave-absorbing aramid paper: Figure 2 As shown, the absorbing slurry of Example 6 is printed on the front and back sides of the aramid paper to form a surface coating, the printing is carried out using a fully automatic screen printing machine, the scraper parameters are set to 0.3, the air pressure is 0.4MPa, the printing speed is 20%, the thickness of the surface coating is 1μm, and the aramid paper with the absorbing slurry on the surface is baked, the baking temperature is 120°C, and the baking time is 6h; the curing temperature in step B is 120°C, the time is 8h, and the absorbing aramid paper is obtained after baking;

[0074] B. Preparation of microwave-absorbing honeycombs: microwave-absorbing aramid paper is processed into microwave-absorbing honeycomb blocks through an aramid honeycomb production line, and the microwave-absorbing honeycomb blocks are processed into microwave-absorbing honeycombs through dipping and curing, wherein the dipping glue is a mixed solution of resin and dipping solvent, the resin is a mixture of epoxy resin and bismaleimide resin, the weight ratio of epoxy resin to bismaleimide resin is 1:1, and the dipping solvent is a mixture of methanol and ethanol, the volume ratio is 2:1.

[0075] Example 10: Figure 3 As shown, a method for preparing a wave-absorbing honeycomb comprises the following steps:

[0076] A. Preparation of microwave-absorbing aramid paper: Figure 2 As shown, the absorbing slurry of Example 7 is printed on the front and back sides of the aramid paper to form a surface coating, the printing is carried out using a fully automatic screen printing machine, the scraper parameters are set to 1.2, the air pressure is 1.2MPa, the printing speed is 1%, the thickness of the surface coating is 100μm, and the aramid paper with the absorbing slurry on the surface is baked, the baking temperature is 180°C, and the baking time is 1h; the curing temperature in step B is 180°C, the time is 4h, and the absorbing aramid paper is obtained after baking;

[0077] B. Preparation of microwave-absorbing honeycombs: microwave-absorbing aramid paper is processed into microwave-absorbing honeycomb blocks through an aramid honeycomb production line, and the microwave-absorbing honeycomb blocks are processed into microwave-absorbing honeycombs through dipping and curing, wherein the dipping glue is a mixed solution of resin and dipping solvent, the resin is a mixture of phenolic resin, polyurethane resin and bismaleimide resin in a weight ratio of 3:1:1, and the dipping solvent is a mixture of acetone, methyl ether and ethyl ether in a volume ratio of 1:2:1.

[0078] Example 11: Figure 3 As shown, a method for preparing a microwave absorbing honeycomb comprises the following steps:

[0079] A. Preparation of microwave-absorbing aramid paper: Figure 2 As shown, the absorbing slurry of Example 8 is printed on the front and back sides of the aramid paper to form a surface coating, the printing is carried out using a fully automatic screen printing machine, the scraper parameters are set to 0.8, the air pressure is 1.0 MPa, the printing speed is 12%, the thickness of the surface coating is 30 μm, and the aramid paper with the absorbing slurry on the surface is baked, the baking temperature is 140° C., and the baking time is 3 hours; the curing temperature in step B is 150° C., and the time is 5 hours. After baking, the absorbing aramid paper is obtained;

[0080] B. Preparation of microwave-absorbing honeycombs: microwave-absorbing aramid paper is processed into microwave-absorbing honeycomb blocks through an aramid honeycomb production line, and the microwave-absorbing honeycomb blocks are processed into microwave-absorbing honeycombs through dipping and curing, wherein the dipping glue is a mixed solution of resin and dipping solvent, the resin is a mixture of phenolic resin, epoxy resin, polyurethane resin and bismaleimide resin in a weight ratio of 2:2:2:1, and the dipping solvent is a mixture of methanol, ethanol, acetone and industrial water in a volume ratio of 1:1:1:3.

[0081] The beneficial effects of the present invention are described below by experiments:

[0082] Experimental Example 1: Figure 3 As shown, a method for preparing a wave-absorbing honeycomb comprises the following steps:

[0083] A. Preparation of microwave-absorbing aramid paper: Figure 2 As shown, the absorbing slurry prepared in Example 6 is printed on the front and back sides of the aramid paper to form a surface coating, the printing is carried out using a fully automatic screen printing machine, the scraper parameters are set to 1.0, the air pressure is 0.6MPa, the printing speed is 5.0%, and the aramid paper with the absorbing slurry on the surface is baked to obtain the absorbing aramid paper; the baking temperature is 120°C, and the baking time is 3h; the thickness of the surface coating is 15μm, and the surface resistance of the absorbing aramid paper is 4.16KΩ / □;

[0084] B. Preparation of microwave-absorbing honeycombs: The microwave-absorbing aramid paper is prepared into microwave-absorbing honeycomb blocks through an aramid honeycomb production line (gluing, laminating, hot pressing, stretching, spraying, and shaping operations); the microwave-absorbing honeycomb blocks are prepared into microwave-absorbing honeycombs through gluing and curing operations.

[0085] The surface of the absorbing aramid paper is smooth and wrinkle-free, the pattern of the absorbing coating area is complete and there is no missing or unclear area of ​​the absorbing coating. Figure 4 As shown, when applying glue, the spacing between the glue strips is 9.4mm, and the side length of the prepared honeycomb grid is 2.75mm; when stacking, different layers of absorbing aramid paper need to be stacked in an offset manner; the temperature during hot pressing is 150℃, and the time is 2h. After the hot pressing is completed, the honeycomb block is stretched. In the stretched state, the honeycomb block is sprayed to ensure that the absorbing aramid paper in different areas of the honeycomb block remains moist. Then the moist honeycomb is shaped at a temperature of 150℃ for 3h. The shaped honeycomb block is dipped in glue. If the increase in wet weight is higher than the theoretical weight gain, the excess glue on the surface of the honeycomb material grid is blown away. If the increase in wet weight is lower than the theoretical weight gain, the honeycomb structure material is dipped multiple times, and the honeycomb structure material reaches the theoretical weight gain and then enters the curing operation; the curing temperature is 150℃, and the time is 4h. After the curing is completed, the honeycomb is sliced ​​and cleaned to obtain an absorbing honeycomb.

[0086] The absorbing honeycomb cells are hexagonal, and the tolerance of the side length of the honeycomb cells is within the range of ±1.5mm; the absorbing honeycomb cells are complete, without cell closure, and the cells are evenly distributed. The reflectivity of the 2-18GHz is tested perpendicular to the direction of the honeycomb cells, and the reflectivity results are shown in Table 1.

[0087] Table 1 Test results of vertical reflectivity of the absorbing honeycomb prepared in Experimental Example 1

[0088] Polarization direction 2~4GHz 4~8GHz 8~12GHz 12~18GHz T-direction horizontal polarization, dB -13.31 -14.45 -16.13 -19.79

[0089] Experimental Example 2: Figure 3 As shown, a method for preparing a microwave absorbing honeycomb comprises the following steps:

[0090] A. Preparation of microwave-absorbing aramid paper: Figure 2 As shown, the absorbing slurry of Example 8 is printed on the front and back sides of the aramid paper to form a surface coating, the printing is carried out using a fully automatic screen printing machine, the scraper parameters are set to 0.8, the air pressure is 1.0 MPa, the printing speed is 5.0%, and the aramid paper with the absorbing slurry on the surface is baked to obtain the absorbing aramid paper; the baking temperature is 120° C., and the baking time is 3 hours; the thickness of the surface coating is 10 μm, and the surface square resistance of the absorbing aramid paper is 3.88 KΩ / □;

[0091] B. Preparation of microwave-absorbing honeycombs: The microwave-absorbing aramid paper is prepared into microwave-absorbing honeycomb blocks through an aramid honeycomb production line (gluing, laminating, hot pressing, stretching, spraying, and shaping operations); the microwave-absorbing honeycomb blocks are prepared into microwave-absorbing honeycombs through gluing and curing operations.

[0092] The surface of the absorbing aramid paper is smooth and wrinkle-free, the pattern of the absorbing coating area is complete and there is no missing or unclear area of ​​the absorbing coating. Figure 4 As shown, when applying glue, the spacing between the glue strips is 9.4mm, and the side length of the prepared honeycomb grid is 2.75mm; when stacking, different layers of absorbing aramid paper need to be stacked in an offset manner; the temperature during hot pressing is 150℃, and the time is 2h. After the hot pressing is completed, the honeycomb block is stretched. In the stretched state, the honeycomb block is sprayed to ensure that the absorbing aramid paper in different areas of the honeycomb block remains moist. Then the moist honeycomb is shaped at a temperature of 150℃ for 3h. The shaped honeycomb block is dipped in glue. If the increase in wet weight is higher than the theoretical weight gain, the excess glue on the surface of the honeycomb material grid is blown away. If the increase in wet weight is lower than the theoretical weight gain, the honeycomb structure material is dipped multiple times, and the honeycomb structure material reaches the theoretical weight gain and then enters the curing operation; the curing temperature is 150℃, and the time is 4h. After the curing is completed, the honeycomb is sliced ​​and cleaned to obtain an absorbing honeycomb.

[0093] The absorbing honeycomb cells are hexagonal, and the side length tolerance of the honeycomb cells is within the range of ±1.5mm; the absorbing honeycomb cells are complete, without cell closure, and the cells are evenly distributed. The reflectivity of 2-18GHz is tested perpendicular to the direction of the honeycomb cells, and the reflectivity results are shown in Table 2.

[0094] Table 2 Test results of vertical reflectivity of the absorbing honeycomb prepared in Experimental Example 2

[0095] Polarization direction 2~4GHz 4~8GHz 8~12GHz 12~18GHz T-direction horizontal polarization, dB -12.52 -14.41 -16.36 -19.11

[0096] Comparison of Experimental Example 1 and Experimental Example 2: The absorbing honeycomb cells prepared by the method of the present invention are hexagonal, and the tolerance of the honeycomb cell side length is within the range of ±1.5mm. The absorbing honeycomb cells are complete, there is no cell closed-cell phenomenon, and the cells are evenly distributed. The surface square resistance of the absorbing aramid paper prepared in Experimental Example 1 is 4.16KΩ / □, and the surface square resistance of the absorbing aramid paper prepared in Experimental Example 2 is 3.88KΩ / □. The absorbing honeycombs prepared by the two methods have excellent absorption performance in the range of 2-18GHz, and the test results of vertical reflectivity of different segments are within the range of ±2dB, indicating that the process is controllable.

[0097] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which are all covered by the protection scope of the present invention.

Claims

1. A microwave absorbing slurry, characterized in that: The invention comprises the following raw materials in parts by weight: Resin: 100~300, Solvent: 50~400, Absorbent: 18~60, Anti-settling agent: 0.3~10, Thickener: 0.3~5, Wherein, the resin is one or more of phenolic resin, epoxy resin, polyurethane resin or bismaleimide resin; the absorbent is one or more of carbon powder, graphene, carbon fiber, silicon nitride and ferrite.

2. The microwave absorbing slurry according to claim 1, characterized in that: The invention comprises the following raw materials in parts by weight: Resin: 220, Solvent: 100, Absorbent: 30, Anti-settling agent: 1, Thickener:

1.

3. The microwave absorbing slurry according to claim 1, characterized in that: The solvent is one or more of methanol, ethanol, acetone, methyl ether, ethyl ether or industrial water.

4. The microwave absorbing slurry according to claim 1, characterized in that: The anti-settling agent is one or more of organic bentonite, sodium carboxymethyl cellulose, polyvinyl alcohol, silicon dioxide or sodium polyacrylate.

5. The microwave absorbing slurry according to claim 1, characterized in that: The thickener is one or more of polyamide, modified acrylic acid, fatty amine or propylene glycol sodium alginate.

6. The method for preparing a microwave absorbing slurry according to claim 1 or 2, characterized in that: It includes the following steps: S1. Prepare materials: weigh each raw material according to the formula ratio and set aside; S2. Preparation of component 1: The solvent is divided into two parts A and B, wherein the volume ratio of the solvent A to the solvent B is 1:8 to 12, the absorbent, the anti-settling agent and the solvent A are mixed and stirred to obtain component 1; S3. Preparation of component II: The resin and the solvent of part B were mixed and stirred to obtain component II; S4. Mixing: Component 1 and component 2 are mixed and stirred to obtain a mixed solution, a thickener is added to the mixed solution to adjust the viscosity to 6000-9000 mPa.s, the solution is stirred and then crushed and dispersed to obtain a radar absorbing slurry.

7. The method for preparing a microwave absorbing slurry according to claim 6, characterized in that: In step S2, the absorbent, anti-settling agent and A part solvent are mixed and stirred at a rate of 500-1500 rad / min for 60-120 min; in step S3, the resin and B part solvent are mixed and stirred at a rate of 1000-2000 rad / min for 20-50 min; in step S4, component one and component two are mixed and stirred at a rate of 1000-2000 rad / min for 20-50 min; the number of rolling times is 3-10 times.

8. A method for preparing a microwave absorbing honeycomb, characterized in that: It includes the following steps: A. Preparation of microwave-absorbing aramid paper: Printing the microwave-absorbing slurry described in claim 1 or 2 on both sides of the aramid paper to form a surface coating, wherein the printing is performed using a fully automatic screen printing machine, and the scraper parameters are set to 0.3-1.2, the air pressure is set to 0.4-1.2 MPa, the printing speed is set to 1%-20%, and the thickness of the surface coating is set to 1-100 μm. The aramid paper with the microwave-absorbing slurry on the surface is baked, and the microwave-absorbing aramid paper is obtained after baking; B. Preparation of microwave-absorbing honeycombs: The microwave-absorbing aramid paper is processed into microwave-absorbing honeycomb blocks through an aramid honeycomb production line, and the microwave-absorbing honeycomb blocks are processed into microwave-absorbing honeycombs through resin dipping and curing.

9. The method for preparing a microwave absorbing honeycomb according to claim 8, characterized in that: The glue solution for dipping in step B is a mixed solution of resin and dipping solvent, the resin is one or more of phenolic resin, epoxy resin, polyurethane resin or bismaleimide resin, and the dipping solvent is one or more of methanol, ethanol, acetone, methyl ether, ethyl ether or industrial water.

10. The method for preparing a microwave absorbing honeycomb according to claim 8, characterized in that: The baking temperature in step A is 120-180° C., and the baking time is 1-6 hours; the curing temperature in step B is 120-180° C., and the time is 4-8 hours.

Images