Magnetic wave-absorbing honeycomb and method of making same

Abstract

The application provides a magnetic wave-absorbing honeycomb and a preparation method thereof. The preparation method comprises the following steps: S1, heating a hot melt resin to a molten state to obtain a molten resin; S2, mixing the molten resin with a magnetic wave-absorbing agent to obtain a magnetic sizing material, and preparing a wave-absorbing sizing film from the magnetic sizing material; S3, treating the wave-absorbing sizing film and aramid paper or fiber felt through impregnation to obtain a wave-absorbing impregnated felt; and S4, sequentially performing glue sticking, lamination, stretching and curing on the wave-absorbing impregnated felt to obtain the magnetic wave-absorbing honeycomb. The hot melt resin is mixed with the magnetic wave-absorbing agent to obtain the wave-absorbing sizing film, the wave-absorbing sizing film is impregnated into the aramid paper or the fiber felt to obtain the wave-absorbing impregnated felt, and then the wave-absorbing impregnated felt is subjected to the processes of glue sticking, lamination, stretching and curing to obtain the magnetic wave-absorbing honeycomb. The application does not involve the impregnation process in the honeycomb forming process, the forming process is simple, the environment is friendly, and the overall uniformity and wave-absorbing strength of the honeycomb are improved.

Description

Technical Field

[0001] This invention relates to the field of microwave absorbing materials technology, and more specifically, to a magnetic microwave absorbing honeycomb and its preparation method. Background Technology

[0002] With the rapid development of electronics and information technology, electromagnetic waves, as an important carrier of information transmission, have permeated all aspects of life. At the same time, the widespread use of electronic and electrical products in the information age has created a complex electromagnetic environment, bringing numerous negative effects, such as malfunctions caused by electromagnetic interference, information leakage, and electromagnetic radiation. To address these issues, microwave absorbing materials with wide frequency bands and high absorption have attracted increasing attention from scholars. Currently, various methods have been used to improve the absorption performance of microwave absorbing materials, such as optimizing the content of absorbing agents, doping with different absorbing agents, and using multilayer structural designs. Existing experimental results show that structural design can give materials "wide frequency band and high absorption" characteristics. Honeycomb structures have advantages such as light weight and high strength, and are widely used as the matrix for designing honeycomb-shaped microwave absorbing materials. Traditional microwave absorbing honeycombs are mostly prepared by impregnating aramid paper honeycomb with microwave absorbing slurry. Due to the special porous structure of the honeycomb, the structural design process within the honeycomb pores is relatively complex, which is not conducive to large-scale production. Summary of the Invention

[0003] The main objective of this invention is to provide a magnetic absorbing honeycomb and its preparation method, so as to solve the problems of complex molding process, large environmental pollution during molding process and poor absorption effect of magnetic absorbing honeycomb in the prior art.

[0004] To achieve the above objectives, according to one aspect of the present invention, a method for preparing a magnetic absorbing honeycomb is provided, the method comprising: step S1, heating a hot-melt resin to a molten state to obtain molten resin; step S2, mixing the molten resin with a magnetic absorbing agent to obtain a magnetic adhesive, and forming the magnetic adhesive into an absorbing film; step S3, impregnating the absorbing film with aramid paper or fiber felt to obtain an absorbing impregnated felt; and step S4, sequentially subjecting the absorbing impregnated felt to adhesive bonding, lamination, stretching, and curing to obtain a magnetic absorbing honeycomb.

[0005] Further, in step S2, the weight ratio of molten resin to magnetic absorbing agent is 20:1 to 1:2; preferably, the weight ratio of molten resin to magnetic absorbing agent is 19:1 to 1:1.

[0006] Further, step S2 includes: mixing N different proportions of molten resin with magnetic absorbing agents to obtain N magnetic adhesives, and making N absorbing films from the N magnetic adhesives. Correspondingly, during the lamination process in step S4, the N absorbing impregnation felts corresponding to the N absorbing films are arranged in order of increasing magnetic absorbing agent content, where N = 2 to 20; preferably, N = 10 to 15; preferably, after arranging the N magnetic adhesives in order of increasing magnetic absorbing agent content, the difference in magnetic absorbing agent content between two adjacent magnetic adhesives is 3 to 5 wt%.

[0007] Furthermore, the hot-melt resin is any one or more of hot-melt epoxy resin and bismaleimide resin; preferably, the viscosity of the hot-melt resin at 70°C is 7000-16000 mPa·s, more preferably 14000-16000 mPa·s.

[0008] Furthermore, the magnetic absorbing agent includes any one or more of carbonyl iron powder, iron-silicon-aluminum alloy powder, and ferrite.

[0009] Preferably, the average particle size of the iron-silicon-aluminum alloy powder is 10-13 μm.

[0010] Preferably, the carbonyl iron powder has an average particle size of 5-10 μm.

[0011] Preferably, the average particle size of the ferrite is 1–5 μm.

[0012] Furthermore, the thickness of the microwave absorbing film is 0.1–0.2 mm.

[0013] Further, step S3 includes: passing the microwave absorbing film through impregnated aramid paper or fiber felt to obtain microwave absorbing prepreg felt, and keeping the microwave absorbing prepreg felt at 80-90°C for 60-70 minutes to obtain microwave absorbing feed felt; preferably, the impregnation is single-sided impregnation.

[0014] Furthermore, the fiber felt is an aramid fiber felt.

[0015] Furthermore, the curing temperature is 80–160°C. Preferably, the curing process includes: holding at 80–85°C for 55–60 min, holding at 125–130°C for 120–125 min, and holding at 155–160°C for 60–65 min.

[0016] According to another aspect of this application, a magnetic absorbing cell is provided, which is prepared by any of the above-described preparation methods.

[0017] The technical solution of this invention involves mixing a hot-melt resin with a magnetic absorbing agent to obtain an absorbing film, and then preparing an absorbing felt by impregnating aramid paper or fiber felt with the film. Finally, magnetic absorbing honeycomb is obtained through processes such as adhesive bonding, lamination, stretching, and curing. This application does not involve an impregnation process during honeycomb molding, resulting in a simple and environmentally friendly molding process while improving the overall uniformity and absorption strength of the honeycomb. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0019] Figure 1 A schematic diagram of the fabrication process of magnetic absorbing cell according to Embodiment 1 of the present invention is shown. Detailed Implementation

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0021] As analyzed in the background section of this application, the existing technology has problems such as complex magnetic absorbing honeycomb molding process, large environmental pollution during molding process and poor wave absorption effect. In order to solve this problem, this application provides a magnetic absorbing honeycomb and its preparation method.

[0022] According to a typical embodiment of this application, a method for preparing a magnetic absorbing honeycomb is provided. The method includes: step S1, heating a hot-melt resin to a molten state to obtain molten resin; step S2, mixing the molten resin with a magnetic absorbing agent to obtain a magnetic adhesive, and forming the magnetic adhesive into an absorbing film; step S3, impregnating the absorbing film with aramid paper or fiber felt to obtain an absorbing impregnated felt; and step S4, sequentially subjecting the absorbing impregnated felt to adhesive bonding, lamination, stretching, and curing to obtain a magnetic absorbing honeycomb.

[0023] This application obtains a microwave absorbing film by mixing a hot-melt resin with a magnetic microwave absorbing agent, and then prepares a microwave absorbing impregnation felt by impregnating aramid fiber paper or vinyl felt with the microwave absorbing film. Finally, magnetic microwave absorbing honeycomb is obtained through processes such as adhesive bonding, lamination, stretching, and curing. This application does not involve an impregnation process during honeycomb molding, resulting in a simple and environmentally friendly molding process, while simultaneously improving the overall uniformity and microwave absorption strength of the honeycomb.

[0024] The ratio of hot-melt resin to magnetic absorbing agent in the microwave absorbing film of this application can be determined according to specific application requirements and is not particularly limited. In some embodiments of this application, in step S2 above, the weight ratio of molten resin to magnetic absorbing agent is 20:1 to 1:2; especially when the weight ratio of molten resin to magnetic absorbing agent is 19:1 to 1:1, the prepared honeycomb material has better uniformity and microwave absorption effect.

[0025] In some typical embodiments of this application, to further improve the shortcomings of narrow absorption bandwidth and low absorption intensity in absorbing honeycomb, step S2 includes: mixing N different proportions of molten resin with magnetic absorbing agents to obtain N magnetic adhesives; preparing N absorbing films from the N magnetic adhesives; impregnating these N films with aramid paper or fiber felt to obtain corresponding N absorbing impregnation felts; and in the subsequent step S4, during the lamination process, arranging the N absorbing films and corresponding N absorbing impregnation felts in order of the content of magnetic absorbing agents, where N = 2 to 20. Introducing an impedance gradient structure can effectively improve the honeycomb absorption bandwidth and absorption intensity. Preferably, N = 10 to 15, resulting in a honeycomb with even better performance.

[0026] In some preferred embodiments, after the N magnetic adhesives are arranged in ascending order of magnetic absorbing agent content, the magnetic absorbing agent content of adjacent magnetic adhesives differs by 3 to 5 wt%. More preferably, after the N magnetic adhesives are arranged in ascending order of magnetic absorbing agent content, the magnetic absorbing agent content of each adjacent magnetic adhesive is the same. That is, when the N absorbing impregnation felts are laminated, the magnetic absorbing agent content in each layer of absorbing impregnation felt increases by a value between 3 and 5 wt%. In other words, the gradient of increase is a value between 3 and 5 wt%. For example, the gradient of increase can be 3 wt%, 3.5 wt%, 3.8 wt%, 4 wt%, 4.2 wt%, 4.5 wt%, 4.8 wt%, 5 wt%, or any range between the two.

[0027] The aforementioned hot-melt resin can be selected from existing technologies, as long as it is easy to heat and melt and mix with the magnetic absorbing agent. There are no special requirements. In some embodiments of this application, the hot-melt resin is any one or more of hot-melt epoxy resin and bismaleimide resin. In particular, when using hot-melt epoxy resin, it has good encapsulation properties for the magnetic absorbing agent, a long working time, and is more convenient for process implementation. In some preferred embodiments, the viscosity of the aforementioned hot-melt resin at 70°C is 7000-16000 mPa·s, which makes it easier to knead with the magnetic absorbing agent, and the impregnation effect is better, resulting in better overall uniformity of the magnetic honeycomb. More preferably, the viscosity of the hot-melt resin at 70°C is 14,000-16,000 mPa·s. In particular, when a hot-melt epoxy resin is used, this viscosity significantly improves the overall performance of the magnetic honeycomb. For example, the viscosity of the hot-melt resin at 70°C is 8,000 mPa·s, 9,000 mPa·s, 10,000 mPa·s, 11,000 mPa·s, 12,000 mPa·s, 13,000 mPa·s, 14,000 mPa·s, 14,500 mPa·s, 15,000 mPa·s, 15,500 mPa·s, 16,000 mPa·s, or any range between the two.

[0028] In step S1 above, those skilled in the art can easily heat the hot-melt resin to a molten state according to the specific type and performance parameters of the selected hot-melt resin to obtain molten resin, which is then uniformly mixed with the magnetic absorbing agent to prepare an absorbing film. In some embodiments of this application, the viscosity of the hot-melt resin at 70°C is 14000-16000 mPa·s. When performing step S1, the resin is kept at 70-80°C for 30-35 minutes, for example, in an 80°C oven for 30 minutes.

[0029] The aforementioned magnetic absorbing agents can be selected from existing technologies. In some embodiments of this application, the magnetic absorbing agent includes any one or more of carbonyl iron powder, iron-silicon-aluminum alloy powder, and ferrite, which facilitates dispersion in the aforementioned hot-melt resin and results in better absorbing performance of the prepared absorbing honeycomb. Preferably, the average particle size of the iron-silicon-aluminum alloy powder is 10-13 μm, the average particle size of the carbonyl iron powder is 5-10 μm, and the average particle size of the ferrite is 1-5 μm, which helps to further improve the overall uniformity of the honeycomb.

[0030] In step S2 above, there are no particular requirements for the method of mixing the magnetic absorbing agent and the molten resin to obtain the magnetic adhesive and the method of preparing the magnetic adhesive into an absorbing film. Existing mixing and film preparation methods can be referenced. For example, the molten resin can be introduced into a kneader, the kneader turned on, the magnetic absorber added and mixed evenly, and the evenly mixed adhesive can be poured into a film-making machine to prepare the absorbing film. In some embodiments of this application, the thickness of the absorbing film is 0.1–0.2 mm, which facilitates the preparation of the film and the implementation of subsequent processes.

[0031] In step S3 above, the microwave-absorbing adhesive film is bonded to aramid paper or fiber felt through impregnation. During this process, the microwave-absorbing adhesive film can penetrate the surface and penetrate into the interior of the aramid paper or fiber felt. Combined with subsequent bonding, curing, and other processing steps, a broadband, high-absorption honeycomb material can be obtained without impregnation. Specific implementation methods for impregnation can refer to existing technologies. In some embodiments of this application, the heating temperature during impregnation is 80–82°C, and the pressure is 3–4 MPa, which can efficiently obtain the microwave-absorbing impregnated felt.

[0032] In some preferred embodiments of this application, step S3 includes: impregnating the microwave-absorbing film with aramid paper or fiber felt to obtain a microwave-absorbing prepreg felt; keeping the microwave-absorbing prepreg felt at 80-90°C for 60-70 minutes until it does not stick together at room temperature to obtain a microwave-absorbing impregnated felt; by heating and keeping the impregnated microwave-absorbing prepreg felt at a certain temperature, the microwave-absorbing feed felt can be initially cured, which is beneficial to further improve the overall uniformity and microwave absorption performance of the magnetic honeycomb, and also facilitates subsequent processing. Depending on the actual application requirements, double-sided impregnation or single-sided impregnation can be performed. In some embodiments of this application, in order to improve the preparation efficiency, the above impregnation is single-sided impregnation, that is, during the impregnation process, the microwave-absorbing film is placed on one surface of the aramid paper or fiber felt for impregnation.

[0033] The aramid paper and fiber mat used for impregnation can be selected from existing technologies. In some embodiments of this application, the fiber mat is aramid fiber mat, also known as aramid fiber needle-punched mat, which produces a magnetic absorbing honeycomb with better performance. Preferably, the thickness of the aramid fiber mat is 0.1-0.2 mm.

[0034] After processing the above-mentioned microwave absorbing feed felt through adhesive bonding, lamination, stretching, and curing, a magnetic microwave absorbing honeycomb with excellent microwave absorption performance can be obtained. The specific processes of adhesive bonding, lamination, stretching, and curing can be referred to existing technologies and are not particularly required. Those skilled in the art can easily implement them, and they will not be described in detail here. In some embodiments of this application, the curing temperature is 80-160℃, resulting in magnetic honeycomb material with good microwave absorption performance and high strength. A programmed temperature increase method can also be used during curing. Preferably, the temperature is 80-85℃ for 55-60 minutes, 125-130℃ for 120-125 minutes, and 160-165℃ for 60-65 minutes, which helps to further improve the overall performance of the microwave absorbing honeycomb.

[0035] According to another typical embodiment of this application, a magnetic absorbing honeycomb is provided, which is prepared by any of the above-described preparation methods. This magnetic absorbing honeycomb does not involve an impregnation process during honeycomb molding, resulting in a simple and environmentally friendly molding process, while simultaneously improving the overall uniformity and absorption strength of the honeycomb.

[0036] The beneficial effects that this application can achieve will be further illustrated below with reference to embodiments and comparative examples.

[0037] Example 1

[0038] The fabrication process of the magnetic absorbing cell in this embodiment is as follows: Figure 1As shown. Step 1: Place 300g of epoxy resin (brand name YPH160, viscosity at 70℃ is 14000mP.s) in an oven at 80℃ for 30min until it melts. Step 2: Pour the melted resin into a kneader, turn on the kneader, add 15g of carbonyl iron powder (purchased from Jiangsu Tianyi Ultrafine Metal Powder Co., Ltd., average particle size 5μm), which is 5% of the weight of the epoxy resin, and mix evenly to obtain the microwave absorbing adhesive. Step 3: Pour the evenly mixed microwave absorbing adhesive into a film-making machine to make a microwave absorbing film of 0.1-0.12mm for later use, labeled P05. Repeat steps 2 and 3, increasing the microwave absorbing agent content in a gradient of 5% of the weight of epoxy resin to prepare microwave absorbing films with different magnetic microwave absorbing agent contents, labeled P05, P10, P15, P20, P25, P30, P35, P40, P45 and P50 respectively. Step 4: Place the prepared adhesive film and aramid fiber felt (purchased from Wuxi Wenqi Industry and Trade Co., Ltd.) into an impregnation machine for single-sided impregnation. Set the impregnation machine heating temperature to 80℃ and the pressure to 3MPa to prepare microwave absorbing prepreg felts numbered P05-P50. The numbering of the microwave absorbing prepreg felts is the same as that of the microwave absorbing adhesive film it impregnates, and the same numbering will be used in subsequent processing. Step 5: Place the prepared microwave absorbing prepreg felts numbered P05-P50 into an oven and keep them at 80℃ for 60 minutes until the microwave absorbing prepreg felts no longer stick together at room temperature. Step Six: Adhere the core strip adhesive to the P05-P50 microwave absorbing impregnation felts with a core strip adhesive spacing of 1.8mm. Then, stack the microwave absorbing impregnation felts in descending order of their numbers and place them at room temperature for 24 hours to allow the adhesive strips to cure. Then, stretch them to obtain a magnetic microwave absorbing honeycomb intermediate with a honeycomb structure. Then, heat the intermediate at 80℃ for 60min, 130℃ for 120min, and 160℃ for 60min to cure it and obtain a magnetic microwave absorbing honeycomb with a thickness of about 30mm and a gradient impedance structure.

[0039] Example 2

[0040] The only difference from Example 1 is that carbonyl iron powder was replaced with iron-silicon-aluminum (Qinghe County Fengye Metal Materials Co., Ltd.) with an average particle size of 10 μm.

[0041] Example 3

[0042] The only difference from Example 1 is that carbonyl iron powder is replaced with ferrite (Qinghe County Benyu Metal Materials Co., Ltd.) with an average particle size of 5 μm.

[0043] Example 4

[0044] The only difference from Example 1 is that carbonyl iron powder is replaced with ferrite (Qinghe County Benyu Metal Materials Co., Ltd.) with an average particle size of 5 μm and iron-silicon-aluminum (Qinghe County Fengye Metal Materials Co., Ltd.) with an average particle size of 10 μm, wherein the weight ratio of iron-silicon-aluminum to ferrite is 2:1.

[0045] Example 5

[0046] Step 1: Place 300g of epoxy resin (same as in Example 1) in an oven at 80℃ for 30 minutes until it melts. Step 2: Pour the melted resin into a kneader, open the kneader, and add 150g of carbonyl iron powder (purchased from Jiangsu Tianyi Ultrafine Metal Powder Co., Ltd., average particle size 5μm), which is 50% of the epoxy resin weight, and mix thoroughly. Step 3: Pour the thoroughly mixed microwave-absorbing adhesive into a film-making machine to form a 0.1-0.12mm microwave-absorbing film for later use. Step 4: Place the prepared film and aramid fiber felt (same as in Example 1) separately in an impregnation machine for single-sided impregnation. Set the impregnation machine heating temperature to 80℃ and the pressure to 3MPa to prepare microwave-absorbing prepreg felt. Step 5: Place the prepared microwave-absorbing prepreg felt in an oven at 80℃ for 60 minutes until the microwave-absorbing prepreg felts no longer stick together at room temperature. Step Six: Adhere the core strip adhesive to the microwave absorbing impregnation felt, with a core strip spacing of 1.8mm. Then, stack the microwave absorbing impregnation felt and let it sit at room temperature for 24 hours to allow the adhesive strips to cure. Then, stretch it to obtain a magnetic microwave absorbing honeycomb intermediate with a honeycomb structure. Then, keep it at 80℃ for 60min, 130℃ for 120min, and 160℃ for 60min to cure it and obtain a magnetic microwave absorbing honeycomb with a thickness of about 30mm.

[0047] Example 6

[0048] The only difference from Example 1 is that the epoxy resin is YPH200T (viscosity at 70°C is 15000 mP.s).

[0049] Example 7

[0050] The only difference from Example 1 is that the epoxy resin is replaced with liquid bismaleimide resin (purchased from Wuhan Huaxiang Kejie Biotechnology Co., Ltd., with a viscosity of 8000 mP.s at 25°C).

[0051] Example 8

[0052] The only difference from Example 1 is that the average particle size of the carbonyl iron powder is 10 μm.

[0053] Example 9

[0054] The only difference from Example 1 is that the aramid fiber felt in Example 1 is replaced with para-aramid fiber felt produced by Shandong Xuzheng Textile Co., Ltd.

[0055] Example 10

[0056] The only difference from Example 1 is that the aramid fiber felt in Example 1 is replaced with aramid paper (YT822A type meta-aramid paper).

[0057] Example 11

[0058] The only difference from Example 1 is that steps two and three are repeated, with the content of the microwave absorber being increased sequentially in a gradient of 7% of the weight of the epoxy resin.

[0059] Example 12

[0060] The only difference from Example 1 is that steps two and three are repeated, with the content of the microwave absorber being increased sequentially in a gradient of 3% of the weight of the epoxy resin.

[0061] Example 13

[0062] Step 1: Place 300g of epoxy resin (same as in Example 1) in an oven at 80℃ for 30 minutes until it melts. Step 2: Pour the melted resin into a kneader, turn on the kneader, add 15g of carbonyl iron powder (purchased from Jiangsu Tianyi Ultrafine Metal Powder Co., Ltd.), which is 5% of the epoxy resin weight, and mix thoroughly to obtain the microwave absorbing adhesive. Step 3: Pour the thoroughly mixed microwave absorbing adhesive into a film-making machine to prepare microwave absorbing films with a thickness of 0.1-0.12mm, labeled P05. Repeat steps 2 and 3, increasing the microwave absorbing agent content in increments of 2% of the epoxy resin weight to prepare microwave absorbing films with different magnetic microwave absorbing agent contents, labeled P1, P2, P3…P20. Step 4: Place the prepared adhesive film and aramid fiber felt (purchased from Wuxi Wenqi Industry and Trade Co., Ltd.) into an impregnation machine for single-sided impregnation. Set the impregnation machine heating temperature to 80℃ and the pressure to 3MPa to prepare microwave absorbing prepreg felts numbered P1-P20. The numbering of the microwave absorbing prepreg felts is the same as that of the microwave absorbing adhesive film they impregnate, and the same numbering will be used in subsequent processing. Step 5: Place the prepared microwave absorbing prepreg felts numbered P1-P20 into an oven and keep them at 80℃ for 60 minutes until the microwave absorbing prepreg felts no longer stick together at room temperature. Step Six: Apply adhesive to the core strips of the microwave absorbing impregnation felt from P1 to P20, then stack the microwave absorbing impregnation felts in descending order of number. Let the strips cure at room temperature for 24 hours. Then, stretch them to obtain a magnetic microwave absorbing honeycomb intermediate with a honeycomb structure. Then, heat the intermediate at 80℃ for 60 minutes, 130℃ for 120 minutes, and 160℃ for 60 minutes to cure it and obtain a magnetic microwave absorbing honeycomb with a thickness of about 60 mm and a gradient impedance structure.

[0063] Example 14

[0064] The only difference from Example 1 is that the thickness of the microwave absorbing film is 0.2 mm, and correspondingly, the thickness of the cured magnetic microwave absorbing honeycomb is about 30 mm.

[0065] Example 15

[0066] The only difference from Example 1 is that in step one, the amount of carbonyl iron powder added is 100% of the weight of epoxy resin (i.e., 300g). When repeating steps two and three, the amount is increased in a 5% gradient. All other conditions are the same as in Example 1.

[0067] Comparative Example 1

[0068] 1500g of YPH-160 epoxy resin and 2500g of methyl ethyl ketone were dissolved. 750g of carbonyl iron powder with an average particle size of 5μm (purchased from Jiangsu Tianyi Ultrafine Metal Powder Co., Ltd., average particle size 5μm) was added while stirring at 600 rpm. The mixture was stirred for 30 minutes until homogeneous. The mixture was poured into an impregnation tank. Aramid honeycomb (ACT2-3.2-48-30) was immersed in the impregnation tank and then removed and dried. After most of the solvent evaporated, it was placed in an oven and kept at 80℃ for 60 minutes, 130℃ for 120 minutes, and 160℃ for 60 minutes to obtain magnetic absorbing honeycomb.

[0069] The materials prepared in the examples and comparative examples were used respectively, and the reflectivity of the honeycomb was tested in the range of 2GHz to 18GHz using the arc field test according to GJB2038A-2011. The test results are shown in Table 1.

[0070] Table 1

[0071]

[0072]

[0073] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects: a microwave absorbing film is obtained by mixing a hot-melt resin with a magnetic microwave absorbing agent; a microwave absorbing impregnating felt is made by impregnating aramid paper or fiber felt with the microwave absorbing film; and then a magnetic microwave absorbing honeycomb is obtained through processes such as adhesive bonding, lamination, stretching, and curing. This application does not involve an impregnation process during the honeycomb molding process, resulting in a simple molding process that is environmentally friendly, while simultaneously improving the overall uniformity and microwave absorption strength of the honeycomb.

[0074] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a magnetic absorbing honeycomb, characterized in that, include: Step S1: Heat the hot-melt resin to a molten state to obtain molten resin; the hot-melt resin is any one or more of hot-melt epoxy resin and bismaleimide resin, and the viscosity of the hot-melt resin at 70°C is 14000-16000 mPa·s. Step S2: Mix the molten resin with the magnetic absorbing agent to obtain a magnetic adhesive, and then form the magnetic adhesive into an absorbing film; the weight ratio of the molten resin to the magnetic absorbing agent is 20:1 to 1:1; the magnetic absorbing agent includes any one or more of carbonyl iron powder, iron-silicon-aluminum alloy powder, and ferrite. Step S3: The microwave absorbing film is impregnated with aramid paper or fiber felt to obtain microwave absorbing impregnation felt; Step S4: The microwave absorbing impregnation felt is sequentially subjected to adhesive bonding, lamination, stretching and curing to obtain a magnetic microwave absorbing honeycomb. Step S2 includes: mixing N different proportions of the molten resin with the magnetic microwave absorbing agent to obtain N magnetic adhesives, and making N microwave absorbing films from the N magnetic adhesives. Correspondingly, when performing the lamination in step S4, the N microwave absorbing felts corresponding to the N microwave absorbing films are arranged in order of increasing magnetic microwave absorbing agent content, where N = 10~15. After the N types of magnetic adhesives are arranged in ascending order of magnetic absorbing agent content, the magnetic absorbing agent content changes in the two adjacent magnetic adhesives in the same way. When the N types of microwave absorbing impregnation felts are laminated, the magnetic absorbing agent content in each layer of microwave absorbing impregnation felt increases by any value between 3.5% and 5 wt%.

2. The preparation method according to claim 1, characterized in that, The average particle size of the iron-silicon-aluminum alloy powder is 10-13 μm. And / or, the average particle size of the carbonyl iron powder is 5-10 μm. And / or, the average particle size of the ferrite is 1~5μm.

3. The preparation method according to claim 1, characterized in that, The thickness of the microwave absorbing film is 0.1~0.2mm.

4. The preparation method according to claim 1, characterized in that, Step S3 includes: passing the microwave absorbing film through impregnated aramid paper or fiber felt to obtain microwave absorbing prepreg felt, and keeping the microwave absorbing prepreg felt at 80~90℃ for 60~70min to obtain microwave absorbing impregnated felt.

5. The preparation method according to claim 4, characterized in that, The impregnation is a one-sided impregnation.

6. The preparation method according to claim 1, characterized in that, The fiber felt is an aramid fiber felt.

7. The preparation method according to claim 1, characterized in that, The curing temperature is 80~160℃.

8. The preparation method according to claim 7, characterized in that, The curing process includes: holding at 80~85℃ for 55~60 min, holding at 125~130℃ for 120~125 min, and holding at 155~160℃ for 60~65 min.

9. A magnetic absorbing honeycomb, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 8.

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