A preparation method of a honeycomb foam composite wave-absorbing material based on PMI foam

Abstract

The present application relates to the field of molded composite materials, and particularly relates to a preparation method of a honeycomb foam composite wave-absorbing material based on PMI foam; the honeycomb wave-absorbing composite sandwich material obtained by laminating hard wave-absorbing foam into honeycomb material through a flat plate hot press has wide frequency and large angle strong absorption characteristics on radar waves, and has excellent mechanical properties, which can significantly broaden the engineering application field of foam wave-absorbing materials. The preparation method is simple, stable and controllable, and is suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of functional composite materials, and in particular to a method for preparing a honeycomb foam composite microwave absorbing material based on PMI foam. Background Technology

[0002] Structural absorbing materials are multifunctional composite materials that can serve as both a carrier and a wave-absorbing agent. Based on their structural form, they can be classified into laminate type, honeycomb sandwich type, and foam sandwich type.

[0003] Application No. 201510894877.4 discloses a metamaterial absorbing structure based on magnetic absorbing materials and multilayer resistive films. The structure comprises an array of multiple absorbing units, each of which is composed of alternating layers of multilayer PMI foam (1), multilayer PET dielectric substrate (2), multilayer resistive films (3(1)-3(4)), a layer of magnetic absorbing material (4), and a layer of metal ground (5). This invention combines magnetic absorbing materials and multilayer resistive films, reconciling the contradiction between thickness and low-frequency absorption characteristics in composite absorbing structures.

[0004] CN113801492A discloses a microwave-absorbing composite foam material and its preparation method. This microwave-absorbing composite foam material is prepared by mixing a mixture system A and an adhesive system B, followed by foaming. The mixture system A is composed of expandable PMI resin with an average particle size of 0.001–3 mm, a microwave-absorbing agent, and performance-modifying components. The adhesive system B is prepared by mixing an adhesive, a curing agent, and a foaming agent. Compared to traditional microwave-absorbing composite foam materials, this invention uses small-particle-size expandable PMI resin and adds a certain amount of foaming agent to the adhesive system. This allows for foaming during subsequent foaming, avoiding the problem of excessively high density in the adhesive system. Therefore, the entire system contains several foamable components, resulting in a more uniform density and preventing significant deviations.

[0005] While foam-filled radar-absorbing composite materials are lightweight and exhibit strong broadband absorption of radar waves, their low mechanical strength significantly limits their application as carriers. In contrast, simple honeycomb structure radar-absorbing foam is greatly affected by the angle of electromagnetic wave arrival; large angles of incidence reduce absorption efficiency and negatively impact absorption performance.

[0006] Honeycomb foam composite sandwich absorbing materials overcome the shortcomings of poor mechanical properties of polymer foam materials and low absorption efficiency of large-angle incident electromagnetic waves in honeycomb structures. As a uniform discontinuous absorbing structure, honeycomb foam composite sandwich absorbing materials have the characteristics of wide-band and large-angle strong absorption of radar waves and have high mechanical properties. In engineering, they can achieve "integration of structural load-bearing and wave absorption functions". Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of poor mechanical properties of polymer foam materials and low absorption efficiency of large-angle incident electromagnetic waves in honeycomb structures, and to provide a method for preparing a honeycomb foam composite microwave absorbing material based on PMI foam.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] S1: Preparation of poly(meth)acrylimide foam board

[0010] Weigh out 30-70 parts by weight of methacrylic acid, 30-70 parts by weight of methacrylonitrile, 0.1-2.2 parts by weight of initiator, 4-16 parts by weight of foaming agent, 1-5 parts by weight of crosslinking agent, 0.5-3 parts by weight of nucleating agent, and 3-18 parts by weight of microwave absorbing agent, and add them to the reactor. Stir mechanically for 2-4 hours to obtain a material mixture. Then pour the obtained material mixture into a mold, perform water bath polymerization reaction, and perform post-treatment in an oven. Heat to 180-240℃ for 2-8 hours to foam.

[0011] S2: Surface functionalization treatment of poly(methacrylimide) foam board

[0012] After the PMI foam board is foamed, it is cut into thin slices. The surface of the slices is treated with microwave absorbing material by immersing the slices in microwave absorbing adhesive multiple times.

[0013] S3: Preparation of Foam Honeycomb Composite Sandwich Absorbing Material

[0014] The surface-treated PMI foam sheets are pressed layer by layer into the honeycomb foam, and the layers are pressed together to obtain a foam honeycomb composite sandwich microwave absorbing material.

[0015] As a supplement to the above scheme, the methacrylic acid and methacrylonitrile can also be replaced with acrylic acid and acrylonitrile.

[0016] As a supplement to the above scheme, the initiator includes one or more of the following: azobisisobutyronitrile (AIBN), azobisisopentanol or azobisisoheptanol, benzoyl peroxide, lauroyl peroxide, butyl percarbate, pentyl percarbate, tert-butyl perpentanoate, tert-butyl perbenzoate, and tert-butyl per-2-ethylhexanoate.

[0017] As a supplement to the above scheme, the foaming agent includes one or more of isopropanol, n-butanol, isobutanol, tert-butanol, tert-amyl alcohol, methylurea, and dimethylurea.

[0018] As a supplement to the above scheme, the crosslinking agent includes calcium oxide, magnesium oxide, acrylamide (AM), methacrylamide (MAM), allyl methacrylate, metal salt of methacrylate, metal salt of acrylate, allyl acrylate, allyl methacrylate, allyl acrylamide, allyl methacrylamide, diethylene bis(allyl carbonate), ethylene glycol diacrylate or ethylene glycol-dimethacrylate, 1,3-butanediol diacrylate or 1,3-butanediol-dimethacrylate, 1,4-butanediol diacrylate Acetic acid esters or 1,4-butanediol-dimethacrylate, neopentyl glycol diacrylate or neopentyl glycol-dimethacrylate, 1,6-hexanediol-diacrylate or 1,6-hexanediol-dimethacrylate, trimethylolpropane triacrylate or trimethylolpropane-trimethacrylate, pentaerythritol triacrylate or pentaerythritol-trimethacrylate, pentaerythritol tetraacrylate or pentaerythritol-tetramethacrylate, hyperbranched silicone resins, triallyl isocyanurate or triallyl cyanurate, rubber core-shell nanoparticles.

[0019] As a supplement to the above scheme, the nucleating agent is at least one of ultrafine calcium carbonate powder, titanium dioxide, calcium stearate, zinc stearate, and sodium benzoate.

[0020] As a supplement to the above scheme, the microwave absorbing agent is manganese dioxide or graphite.

[0021] As a supplement to the above scheme, the microwave absorbing agent is a manganese dioxide-based microwave absorbing agent.

[0022] As a supplement to the above scheme, the preparation method of the manganese dioxide-supported microwave absorbing agent is as follows:

[0023] Step 1: Mix 300-320 parts by weight of a 4-8% potassium permanganate aqueous solution and 40-46 parts by weight of SiO2 nanoparticles evenly and stir to react. After the reaction is complete, centrifuge to collect the precipitate, wash it, and add it to 3000-3500 parts by weight of a 14-22% Na2CO3 aqueous solution. Stir to react at 60-70℃. After the reaction is complete, centrifuge to collect the precipitate, wash it, and freeze-dry it to obtain hollow mesoporous MnO2 nanoparticles.

[0024] Step 2: According to the weight parts, add 7-12 parts of aminopropyltriethoxysilane to 100-120 parts of hollow mesoporous MnO2 nanoparticles and 1000-1200 parts of toluene. Use mechanical stirring and react at 60-70℃ for 30-50 minutes. Then add 6-10 parts of dicarboxyethyl germanium trioxide, 0.01-0.1 parts of ferric oleate, and 0.5-2 parts of diisopropylethylamine. React at 50-70℃ for 20-50 minutes. After the reaction is complete, filter and wash the product with deionized water. Take the floating product and vacuum dry it for 2 hours to obtain the hollow glass microsphere-supported microwave absorbing agent.

[0025] As a supplement to the above scheme, the water bath polymerization temperature is 45-65℃ and the time is 75-105h.

[0026] Reaction mechanism of this invention:

[0027] During the preparation of manganese dioxide-supported microwave absorber, under anhydrous conditions, aminopropyltriethoxysilane reacts with a large number of hydroxyl groups on the surface of hollow mesoporous MnO2 nanoparticles to undergo an alcohol condensation reaction, resulting in amino-containing hollow mesoporous MnO2 nanoparticles. Then, an amidation reaction occurs, and the nanoparticles are linked with dicarboxyethyl germanium trioxide through amidation.

[0028]

[0029] When radar waves reach the surface of a conductive medium such as metal, they induce a current and are then emitted and received by a receiver, failing to achieve the purpose of absorbing radar waves. However, when radar waves reach the surface of a rigid absorbing foam material, the electromagnetic waves enter the material and undergo multiple scattering and absorption processes, thereby achieving the purpose of dissipating radar wave energy.

[0030] Honeycomb absorbing materials have good absorption performance for vertically incident radar waves, but their absorption efficiency is poor for radar waves incident at large angles. Adding rigid absorbing foam can improve the absorption efficiency of radar waves incident at large angles. Furthermore, due to the blocking effect of the honeycomb structure on radar waves, the honeycomb absorbing composite sandwich material will not become a conductive material, thus allowing radar waves to pass through.

[0031] Due to the special mechanical structure of honeycomb materials, honeycomb absorbing composite sandwich materials obtained by pressing them into rigid absorbing foam of equal thickness using a flat hot press can increase the compressive strength, tensile strength and shear strength of the honeycomb absorbing composite sandwich materials.

[0032] Compared with the prior art, the method for preparing a honeycomb foam composite microwave absorbing material based on PMI foam of the present invention has the following significant advantages:

[0033] (1) The honeycomb absorbing composite sandwich material has the characteristics of wide-band, large-angle, and strong absorption of radar waves;

[0034] (2) It increases the mechanical properties of the material, such as compressive strength, tensile strength and shear strength;

[0035] (3) The honeycomb absorbing composite sandwich material has high absorption efficiency for radar waves. Detailed Implementation

[0036] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0037] The tensile strength was determined according to GB / T 1452-2005 Test Method for Tensile Strength of Sandwich Structures;

[0038] The compressive strength was determined according to GB / T 8813-2008, "Determination of compressive properties of rigid foamed plastics".

[0039] The reflectivity of radar absorbing materials was tested according to GJB 2038A-2011 "Test Method for Reflectivity of Radar Absorbing Materials".

[0040] Example 1

[0041] A method for preparing a honeycomb foam composite microwave absorbing material based on PMI foam, comprising the following steps:

[0042] S1: Preparation of poly(meth)acrylimide foam board

[0043] Weigh 30g of methacrylic acid, 30g of methacrylonitrile, 0.5g of initiator azobisisopentanol, 4g of foaming agent isopropanol, 1g of crosslinking agent calcium oxide, 0.5g of nucleating agent ultrafine calcium carbonate powder, and 3g of manganese dioxide immobilized microwave absorbing agent and add them to the reactor. Stir mechanically for 2 hours to obtain a material mixture. Then, pour the obtained material mixture into a mold, heat it to 45℃ in a water bath, polymerize for 105 hours, and then perform post-treatment in an oven, heating it to 180℃ for 2 hours to foam.

[0044] S2: Surface functionalization treatment of poly(methacrylimide) foam board

[0045] After the PMI foam board is foamed, it is cut into thin slices. The surface of the slices is treated with microwave absorbing material by immersing the slices in microwave absorbing adhesive multiple times.

[0046] S3: Preparation of Foam Honeycomb Composite Sandwich Absorbing Material

[0047] The surface-treated PMI foam sheets are pressed layer by layer into the honeycomb foam, and the layers are pressed together to obtain a foam honeycomb composite sandwich microwave absorbing material.

[0048] The preparation method of the manganese dioxide-supported microwave absorber is as follows:

[0049] Step 1: Mix 300g of 4% potassium permanganate aqueous solution and 40g of SiO2 nanoparticles evenly and stir to react. After the reaction is complete, centrifuge to collect the precipitate, wash it, add it to 3000g of 14% Na2CO3 aqueous solution, stir to react at 60℃, centrifuge to collect the precipitate after the reaction is complete, wash it, freeze dry it to obtain hollow mesoporous MnO2 nanoparticles.

[0050] Step 2: Add 7g of aminopropyltriethoxysilane to 100g of hollow mesoporous MnO2 nanoparticles and 1000g of toluene. Stir mechanically and react at 60℃ for 30 minutes. Then add 6g of dicarboxyethyl germanium trioxide, 0.01g of ferric oleate, and 0.5g of diisopropylethylamine. React at 50℃ for 20 minutes. After the reaction is complete, filter the mixture. Wash the product with deionized water. Take the floating product and vacuum dry it for 2 hours to obtain the hollow glass microsphere-supported microwave absorbing agent.

[0051] Example 2

[0052] A method for preparing a honeycomb foam composite microwave absorbing material based on PMI foam, comprising the following steps:

[0053] S1: Preparation of poly(meth)acrylimide foam board

[0054] Weigh 35g acrylic acid, 35g acrylonitrile, 0.6g initiator lauroyl peroxide, 6g foaming agent n-butanol, 2g crosslinking agent acrylamide (AM), 0.8g nucleating agent ultrafine calcium carbonate powder, and 5g manganese dioxide immobilized microwave absorbing agent and add them to the reactor. Stir mechanically for 2 hours to obtain a material mixture. Then, pour the obtained material mixture into a mold, heat it to 50°C in a water bath, polymerize for 100 hours, and then perform post-treatment in an oven, heating it to 185°C for 2 hours to foam.

[0055] S2: Surface functionalization treatment of poly(methacrylimide) foam board

[0056] After the PMI foam board is foamed, it is cut into thin slices. The surface of the slices is treated with microwave absorbing material by immersing the slices in microwave absorbing adhesive multiple times.

[0057] S3: Preparation of Foam Honeycomb Composite Sandwich Absorbing Material

[0058] The surface-treated PMI foam sheets are pressed layer by layer into the honeycomb foam, and the layers are pressed together to obtain a foam honeycomb composite sandwich microwave absorbing material.

[0059] The preparation method of the manganese dioxide-supported microwave absorbing agent is completely consistent with that in Example 1.

[0060] Example 3

[0061] A method for preparing a honeycomb foam composite microwave absorbing material based on PMI foam, comprising the following steps:

[0062] S1: Preparation of poly(meth)acrylimide foam board

[0063] Weigh out 40g of methacrylic acid, 40g of methacrylonitrile, 0.9g of initiator tert-butyl per-2-ethylhexanoate, 8g of foaming agent isobutanol, 2g of crosslinking agent neopentyl glycol diacrylate, 1.2g of nucleating agent titanium dioxide, and 7g of manganese dioxide immobilized microwave absorbing agent and add them to the reactor. Stir mechanically for 2 hours to obtain a material mixture. Then, pour the obtained material mixture into a mold, heat it to 55℃ in a water bath, polymerize for 95 hours, and then perform post-treatment in an oven, heating it to 190℃ for 3 hours to foam.

[0064] S2: Surface functionalization treatment of poly(methacrylimide) foam board

[0065] After the PMI foam board is foamed, it is cut into thin slices. The surface of the slices is treated with microwave absorbing material by immersing the slices in microwave absorbing adhesive multiple times.

[0066] S3: Preparation of Foam Honeycomb Composite Sandwich Absorbing Material

[0067] The surface-treated PMI foam sheets are pressed layer by layer into the honeycomb foam, and the layers are pressed together to obtain a foam honeycomb composite sandwich microwave absorbing material.

[0068] The preparation method of the manganese dioxide-supported microwave absorber is as follows:

[0069] Step 1: Mix 310g of 6% potassium permanganate aqueous solution and 43g of SiO2 nanoparticles evenly and stir to react. After the reaction is complete, centrifuge to collect the precipitate, wash it, add it to 3200g of 17% Na2CO3 aqueous solution, stir to react at 65℃, centrifuge to collect the precipitate after the reaction is complete, wash it, freeze dry it to obtain hollow mesoporous MnO2 nanoparticles.

[0070] Step 2: Add 9g of aminopropyltriethoxysilane to 110g of hollow mesoporous MnO2 nanoparticles and 1100g of toluene. Stir mechanically and react at 65℃ for 40 minutes. Then add 8g of dicarboxyethyl germanium trioxide, 0.06g of ferric oleate, and 1.0g of diisopropylethylamine. React at 60℃ for 35 minutes. After the reaction is complete, filter the mixture. Wash the product with deionized water. Take the floating product and vacuum dry it for 2 hours to obtain the hollow glass microsphere-supported microwave absorbing agent.

[0071] Example 4

[0072] A method for preparing a honeycomb foam composite microwave absorbing material based on PMI foam, comprising the following steps:

[0073] S1: Preparation of poly(meth)acrylimide foam board

[0074] Weigh out 45g of methacrylic acid, 45g of methacrylonitrile, 1.4g of initiator tert-butyl perbenzoate, 12g of foaming agent tert-butanol, 3g of crosslinking agent allyl methacrylamide, 1.8g of nucleating agent calcium stearate, and 11g of manganese dioxide immobilized microwave absorbing agent and add them to the reactor. Stir mechanically for 3 hours to obtain a material mixture. Then, pour the obtained material mixture into a mold, heat it to 60℃ in a water bath, polymerize for 90 hours, and then perform post-treatment in an oven, heating it to 200℃ for 4 hours to foam.

[0075] S2: Surface functionalization treatment of poly(methacrylimide) foam board

[0076] After the PMI foam board is foamed, it is cut into thin slices. The surface of the slices is treated with microwave absorbing material by immersing the slices in microwave absorbing adhesive multiple times.

[0077] S3: Preparation of Foam Honeycomb Composite Sandwich Absorbing Material

[0078] The surface-treated PMI foam sheets are pressed layer by layer into the honeycomb foam, and the layers are pressed together to obtain a foam honeycomb composite sandwich microwave absorbing material.

[0079] The preparation method of the manganese dioxide-supported microwave absorber is completely consistent with that in Example 3.

[0080] Example 5

[0081] A method for preparing a honeycomb foam composite microwave absorbing material based on PMI foam, comprising the following steps:

[0082] S1: Preparation of poly(meth)acrylimide foam board

[0083] Weigh out 60g of acrylic acid, 60g of acrylonitrile, 1.8g of initiator pentyl perdicarbonate, 14g of foaming agent tert-amyl alcohol, 4g of crosslinking agent rubber core-shell nanoparticles, 2.4g of nucleating agent zinc stearate, and 15g of manganese dioxide immobilized microwave absorbing agent and add them to the reactor. Stir mechanically for 4 hours to obtain a material mixture. Then, pour the obtained material mixture into a mold, heat it to 60℃ in a water bath, polymerize for 80 hours, and then perform post-treatment in an oven, heating it to 220℃ for foaming for 6 hours.

[0084] S2: Surface functionalization treatment of poly(methacrylimide) foam board

[0085] After the PMI foam board is foamed, it is cut into thin slices. The surface of the slices is treated with microwave absorbing material by immersing the slices in microwave absorbing adhesive multiple times.

[0086] S3: Preparation of Foam Honeycomb Composite Sandwich Absorbing Material

[0087] The surface-treated PMI foam sheets are pressed layer by layer into the honeycomb foam, and the layers are pressed together to obtain a foam honeycomb composite sandwich microwave absorbing material.

[0088] The preparation method of the manganese dioxide-supported microwave absorber is as follows:

[0089] Step 1: Mix 320g of 8% potassium permanganate aqueous solution and 46g of SiO2 nanoparticles evenly and stir to react. After the reaction is complete, centrifuge to collect the precipitate, wash it, add it to 3500g of 2% Na2CO3 aqueous solution, stir to react at 70℃, centrifuge to collect the precipitate after the reaction is complete, wash it, freeze dry it to obtain hollow mesoporous MnO2 nanoparticles.

[0090] Step 2: Add 12g of aminopropyltriethoxysilane to 120g of hollow mesoporous MnO2 nanoparticles and 1200g of toluene. Stir mechanically and react at 70℃ for 50 minutes. Then add 10g of dicarboxyethyl germanium trioxide, 0.1g of ferric oleate, and 2g of diisopropylethylamine. React at 70℃ for 50 minutes. After the reaction is complete, filter the mixture. Wash the product with deionized water. Take the floating product and vacuum dry it for 2 hours to obtain the hollow glass microsphere-supported microwave absorbing agent.

[0091] Example 6

[0092] A method for preparing a honeycomb foam composite microwave absorbing material based on PMI foam, comprising the following steps:

[0093] S1: Preparation of poly(meth)acrylimide foam board

[0094] Weigh out 70g of methacrylic acid, 70g of methacrylonitrile, 2.2g of initiator azobisisoheptanol, 16g of foaming agent methylurea, 5g of crosslinking agent hyperbranched silicone resin, 3g of nucleating agent sodium benzoate, and 18g of manganese dioxide supported microwave absorbing agent and add them to the reactor. Stir mechanically for 4 hours to obtain a material mixture. Then pour the obtained material mixture into a mold, heat it to 65℃ in a water bath, polymerize for 75 hours, and then perform post-treatment in an oven, heating it to 240℃ for 6 hours to foam.

[0095] S2: Surface functionalization treatment of poly(methacrylimide) foam board

[0096] After the PMI foam board is foamed, it is cut into thin slices. The surface of the slices is treated with microwave absorbing material by immersing the slices in microwave absorbing adhesive multiple times.

[0097] S3: Preparation of Foam Honeycomb Composite Sandwich Absorbing Material

[0098] The surface-treated PMI foam sheets are pressed layer by layer into the honeycomb foam, and the layers are pressed together to obtain a foam honeycomb composite sandwich microwave absorbing material.

[0099] The preparation method of the manganese dioxide-supported microwave absorber is completely consistent with that of Example 5.

[0100] Comparative Example 1

[0101] A method for preparing a honeycomb foam composite microwave absorbing material based on PMI foam, comprising the following steps:

[0102] S1: Preparation of poly(meth)acrylimide foam board

[0103] Weigh 30g of methacrylic acid, 30g of methacrylonitrile, 0.5g of initiator azobisisopentanol, 4g of foaming agent isopropanol, 1g of crosslinking agent calcium oxide, 0.5g of nucleating agent ultrafine calcium carbonate powder, and 3g of graphite microwave absorber and add them to the reaction vessel. Stir mechanically for 2 hours to obtain a material mixture. Then, pour the obtained material mixture into a mold, heat it to 45℃ in a water bath, polymerize for 105 hours, and then perform post-treatment in an oven, heating it to 180℃ for 2 hours to foam.

[0104] S2: Surface functionalization treatment of poly(methacrylimide) foam board

[0105] After the PMI foam board is foamed, it is cut into thin slices. The surface of the slices is treated with microwave absorbing material by immersing the slices in microwave absorbing adhesive multiple times.

[0106] S3: Preparation of Foam Honeycomb Composite Sandwich Absorbing Material

[0107] The surface-treated PMI foam sheets are pressed layer by layer into the honeycomb foam, and the layers are pressed together to obtain a foam honeycomb composite sandwich microwave absorbing material.

[0108] Comparative Example 2

[0109] A method for preparing a honeycomb foam composite microwave absorbing material based on PMI foam, comprising the following steps:

[0110] S1: Preparation of poly(meth)acrylimide foam board

[0111] Weigh 30g of methacrylic acid, 30g of methacrylonitrile, 0.5g of initiator azobisisopentanol, 4g of foaming agent isopropanol, 1g of crosslinking agent calcium oxide, 0.5g of nucleating agent ultrafine calcium carbonate powder, and 3g of manganese dioxide microwave absorber and add them to the reaction vessel. Stir mechanically for 2 hours to obtain a material mixture. Then, pour the obtained material mixture into a mold, heat it to 45℃ in a water bath, polymerize for 105 hours, and then perform post-treatment in an oven, heating it to 180℃ for 2 hours to foam.

[0112] S2: Surface functionalization treatment of poly(methacrylimide) foam board

[0113] After the PMI foam board is foamed, it is cut into thin slices. The surface of the slices is treated with microwave absorbing material by immersing the slices in microwave absorbing adhesive multiple times.

[0114] S3: Preparation of Foam Honeycomb Composite Sandwich Absorbing Material

[0115] The surface-treated PMI foam sheets are pressed layer by layer into the honeycomb foam, and the layers are pressed together to obtain a foam honeycomb composite sandwich microwave absorbing material.

[0116] Comparative Example 3

[0117] A method for preparing a honeycomb foam composite microwave absorbing material based on PMI foam, comprising the following steps:

[0118] S1: Preparation of poly(meth)acrylimide foam board

[0119] Weigh 30g of methacrylic acid, 30g of methacrylonitrile, 0.5g of initiator azobisisopentanol, 4g of foaming agent isopropanol, 1g of crosslinking agent calcium oxide and 0.5g of nucleating agent ultrafine calcium carbonate powder and add them to the reaction vessel. Stir mechanically for 2 hours to obtain a material mixture. Then pour the obtained material mixture into a mold, heat it to 45℃ in a water bath, polymerize for 105 hours, and then perform post-treatment in an oven, heating it to 180℃ for 2 hours to foam.

[0120] S2: Surface functionalization treatment of poly(methacrylimide) foam board

[0121] After the PMI foam board is foamed, it is cut into thin slices. The surface of the slices is treated with microwave absorbing material by immersing the slices in microwave absorbing adhesive multiple times.

[0122] S3: Preparation of Foam Honeycomb Composite Sandwich Absorbing Material

[0123] The surface-treated PMI foam sheets are pressed layer by layer into the honeycomb foam, and the layers are pressed together to obtain a foam honeycomb composite sandwich microwave absorbing material.

[0124] The mechanical property test results of the above embodiments and comparative examples are shown in the table below:

[0125] Test Project Compressive strength / MPa Tensile strength / MPa Shear strength / MPa Example 1 3.5 2.7 0.9 Example 2 3.6 2.8 1.2 Example 3 4.0 2.9 1.1 Example 4 3.8 3.1 1.1 Example 5 3.9 3.0 0.8 Example 6 3.9 2.9 0.9 Comparative Example 1 3.3 2.2 0.6 Comparative Example 2 3.0 1.9 0.6 Comparative Example 3 3.1 2.4 0.5 PMI bubble 1.9 1.7 0.6 honeycomb foam 2.5 1.3 0.4

[0126] The reflectivity test results of the radar absorbing materials in the above embodiments and comparative examples are shown in the table below:

[0127]

[0128] Although the present invention has been described herein with reference to illustrative embodiments, the above embodiments are merely preferred embodiments of the present invention, and the implementation of the present invention is not limited to the above embodiments. It should be understood that those skilled in the art can devise many other modifications and implementations, which will fall within the scope and spirit of the principles disclosed in this application.

Claims

1. A method for preparing a honeycomb foam composite microwave absorbing material based on PMI foam, the preparation method comprising: S1: Preparation of poly(meth)acrylimide foam board Weigh out 30-70 parts by weight of methacrylic acid, 30-70 parts by weight of methacrylonitrile, 0.1-2.2 parts by weight of initiator, 4-16 parts by weight of foaming agent, 1-5 parts by weight of crosslinking agent, 0.5-3 parts by weight of nucleating agent, and 3-18 parts by weight of microwave absorbing agent, and add them to the reactor. Stir mechanically for 2-4 hours to obtain a material mixture. Then pour the obtained material mixture into a mold, perform water bath polymerization reaction, and perform post-treatment in an oven. Heat to 180-240℃ for 2-8 hours to foam. S2: Surface functionalization treatment of poly(methacrylimide) foam board After the PMI foam board is foamed, it is cut into thin slices. The surface of the slices is treated with microwave absorbing material by immersing the slices in microwave absorbing adhesive multiple times. S3: Preparation of Foam Honeycomb Composite Sandwich Absorbing Material The surface-treated PMI foam sheets are pressed layer by layer into the honeycomb foam, and the layers are pressed together to obtain a foam honeycomb composite sandwich microwave absorbing material.

2. The method for preparing a honeycomb foam composite microwave absorbing material based on PMI foam according to claim 1, characterized in that: The methacrylic acid and methacrylonitrile can also be replaced by acrylic acid and acrylonitrile.

3. The method for preparing a honeycomb foam composite microwave absorbing material based on PMI foam according to claim 1, characterized in that: The initiator includes one or more of the following: azobisisobutyronitrile (AIBN), azobisisopentanol or azobisisoheptane, benzoyl peroxide, lauroyl peroxide, butyl percarbate, pentyl percarbate, tert-butyl perpentanoate, tert-butyl perbenzoate, and tert-butyl per-2-ethylhexanoate.

4. The method for preparing a honeycomb foam composite microwave absorbing material based on PMI foam according to claim 1, characterized in that: The foaming agent includes one or more of isopropanol, n-butanol, isobutanol, tert-butanol, tert-amyl alcohol, methylurea, and dimethylurea.

5. The method for preparing a honeycomb foam composite microwave absorbing material based on PMI foam according to claim 1, characterized in that: The crosslinking agent includes calcium oxide, magnesium oxide, acrylamide (AM), methacrylamide (MAM), allyl methacrylate, metal methacrylate, metal acrylate, allyl acrylate, allyl methacrylate, allyl acrylamide, allyl methacrylamide, diethylene bis(allyl carbonate), ethylene glycol diacrylate or ethylene glycol-dimethacrylate, 1,3-butanediol diacrylate or 1,3-butanediol-dimethacrylate, 1,4-butanediol diacrylate or 1, 4-Butanediol-dimethacrylate, neopentyl glycol diacrylate or neopentyl glycol-dimethacrylate, 1,6-hexanediol-diacrylate or 1,6-hexanediol-dimethacrylate, trimethylolpropane triacrylate or trimethylolpropane-trimethacrylate, pentaerythritol triacrylate or pentaerythritol-trimethacrylate, pentaerythritol tetraacrylate or pentaerythritol-tetramethacrylate, hyperbranched silicone resin, triallyl isocyanurate or triallyl cyanurate, rubber core-shell nanoparticles.

6. The method for preparing a honeycomb foam composite microwave absorbing material based on PMI foam according to claim 1, characterized in that: The nucleating agent is at least one of ultrafine calcium carbonate powder, titanium dioxide, calcium stearate, zinc stearate, and sodium benzoate.

7. The method for preparing a honeycomb foam composite microwave absorbing material based on PMI foam according to claim 1, characterized in that: The microwave absorbing agent is manganese dioxide or graphite.

8. The method for preparing a honeycomb foam composite microwave absorbing material based on PMI foam according to claim 1, characterized in that: The microwave absorbing agent is a manganese dioxide-based microwave absorbing agent.

9. The method for preparing a honeycomb foam composite microwave absorbing material based on PMI foam according to claim 8, characterized in that: The preparation method of the manganese dioxide-supported microwave absorber is as follows: Step 1: Mix 300-320 parts by weight of a 4-8% potassium permanganate aqueous solution and 40-46 parts by weight of SiO2 nanoparticles evenly and stir to react. After the reaction is complete, centrifuge to collect the precipitate, wash it, and add it to 3000-3500 parts by weight of a 14-22% Na2CO3 aqueous solution. Stir to react at 60-70℃. After the reaction is complete, centrifuge to collect the precipitate, wash it, and freeze-dry it to obtain hollow mesoporous MnO2 nanoparticles. Step 2: According to the weight parts, add 7-12 parts of aminopropyltriethoxysilane to 100-120 parts of hollow mesoporous MnO2 nanoparticles and 1000-1200 parts of toluene. Use mechanical stirring and react at 60-70℃ for 30-50 minutes. Then add 6-10 parts of dicarboxyethyl germanium trioxide, 0.01-0.1 parts of ferric oleate, and 0.5-2 parts of diisopropylethylamine. React at 50-70℃ for 20-50 minutes. After the reaction is complete, filter and wash the product with deionized water. Take the floating product and vacuum dry it for 2 hours to obtain manganese dioxide immobilized microwave absorbing agent.

10. The method for preparing a PMI-based honeycomb foam composite microwave absorbing material according to claim 1, characterized in that: The water bath polymerization temperature is 45-65℃, and the time is 75-105h.

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