In-mold foamed wave-absorbing rigid plastic foam and method for producing the same

Abstract

The application discloses a preparation method of a wave-absorbing type in-mold foamed hard plastic foam material, and is characterized in that: hard plastic pre-foamed particles obtained after pre-foaming of hard plastic polymer particles are mixed with a glue adhesive and a wave-absorbing agent, in-mold re-foaming is performed, and the wave-absorbing type in-mold foamed hard plastic foam material is obtained.

Description

Technical Field

[0001] This application relates to the field of materials preparation technology, and in particular to a wave-absorbing rigid plastic foam material, its preparation method, and its application. Background Technology

[0002] Rigid foam plastics are a class of foam materials with good mechanical and thermal insulation properties. They often have high compressive strength and elastic modulus, and strong compressive strength, making them suitable for applications in construction, vehicle manufacturing, and other fields requiring heavy loads. Common materials include polystyrene, polyurethane, polyethylene, and polypropylene. Among them, polymethacrylamide (PMI) foam is a cross-linked rigid closed-cell foam with outstanding structural stability and mechanical properties. It is currently the heat-resistant foam plastic with the highest strength and stiffness, and can achieve one-time co-curing of composite sandwich structures. It plays an important role and has wide applications in many high-tech fields such as aerospace, rail transportation, wind power generation, shipbuilding, and new energy vehicles.

[0003] However, most existing rigid foams are wave-transparent foams, unsuitable for specialized applications requiring electromagnetic shielding, such as electromagnetic wave absorption. The survivability and attack protection capabilities of traditional weapon systems rely on electromagnetic shielding and stealth technologies. Therefore, the development of wave-absorbing rigid plastic foam materials has become a new focus. Existing wave-absorbing rigid plastic materials suffer from drawbacks such as uneven dispersion of the absorbing material, weak absorption performance, small absorption range, low foaming rate, and the presence of voids and cracks in the foam. Therefore, developing rigid plastic foam materials that possess both excellent wave absorption performance and maintain superior mechanical properties remains a current research direction. Summary of the Invention

[0004] The purpose of this application is to provide an in-mold foamed, wave-absorbing rigid plastic foam material that maintains the excellent mechanical properties of the foam material while also having good electromagnetic wave absorption function.

[0005] Specifically, this application provides a method for preparing a microwave-absorbing in-mold foamed rigid plastic foam material, characterized in that the rigid plastic pre-foamed particles obtained by pre-foaming rigid plastic polymer particles are mixed with an adhesive and a microwave-absorbing agent, and then re-foamed in the mold to obtain the microwave-absorbing in-mold foamed rigid plastic foam material.

[0006] Furthermore, the rigid plastic polymer particles in the preparation method are obtained by granulation of rigid plastic prepolymer.

[0007] Furthermore, the rigid plastic prepolymer is one or more of PMI prepolymer, PMMA prepolymer, PET prepolymer, and PEI prepolymer.

[0008] Furthermore, the particle size of the granulation is 150-4000 micrometers.

[0009] Furthermore, in the preparation method, the rigid plastic polymer particles are subjected to a foaming treatment at a temperature of 140-250℃, a foaming time of 0.1-10h, and a foaming density of 30-200kg / m³. 3 Under certain conditions, pre-foaming treatment is performed to obtain the rigid plastic pre-foamed particles.

[0010] Furthermore, the adhesive in the preparation method is obtained by dissolving a polymer of acrylonitrile and / or methacrylonitrile, acrylic acid and / or methacrylic acid, an interface modifier, and an initiator in a solvent.

[0011] Furthermore, the interface modifier is selected from one or more of glycidyl methacrylate, silane coupling agent KH550, silane coupling agent KH560, silane coupling agent KH602, titanate coupling agent, aluminate coupling agent, BYK106, and BYK110. Preferably, the interface modifier is a titanate coupling agent.

[0012] Furthermore, the initiator is selected from one or more of tert-amyl peroxide acetate, benzoyl peroxide, tert-butyl peroxide-2-ethylhexanoate, tert-amyl peroxide, tert-butyl peroxide, azobisisobutyronitrile, and azoisobutyl cyanoformamide.

[0013] Furthermore, the solvent is selected from one or more of tetrahydrofuran, DMF, DMAC, NMP, ethanol, isopropanol, n-hexaneisopropanol, n-butanol, isobutanol, tert-butanol, tert-amyl alcohol, hexanol, urea, methylurea, and dimethylurea.

[0014] Furthermore, the microwave absorbing agent in the preparation method is selected from one or more of carbon nanotubes, graphene, carbon black, carbon powder, porous carbon, carbon aerogel, ferrite compounds, magnetic metal and alloy nanoparticles, magnetic nano metal oxides, and carbonyl iron.

[0015] Furthermore, in the preparation method, the adhesive and the microwave absorber are first mixed and dispersed for a certain period of time to obtain a mixed solution, which is then mixed with the rigid plastic pre-foamed particles.

[0016] Furthermore, when the adhesive and the microwave absorber are mixed, the mass ratio of the adhesive to the microwave absorber is 0.1-10:10-95.

[0017] Furthermore, when the mixed solution is further mixed with the rigid plastic pre-foamed particles, the mass ratio of the rigid plastic pre-foamed particles to the mixed solution is 50-95:5-10.

[0018] Furthermore, in the preparation method, the foaming temperature during in-mold re-foaming is 140-250℃, and the foaming time is 0.1-10h.

[0019] This application also provides a wave-absorbing in-mold rigid plastic foam material, which is prepared by the preparation method provided in this application.

[0020] This application also provides the application of the aforementioned microwave-absorbing in-mold rigid plastic foam material in the fields of aviation, aerospace, military, and electromagnetic shielding materials.

[0021] The effects of the invention

[0022] The microwave-absorbing in-mold foamed rigid plastic foam material provided in this application is prepared by mixing a special adhesive containing rigid plastic prepolymer (such as PMI) raw materials and interface modifiers with a microwave-absorbing agent, and then in-mold foaming the mixture with rigid plastic pre-foamed particles. The microwave-absorbing agent, through molecular-level bonding, is uniformly dispersed during the foaming process, is less prone to sedimentation, prevents subsequent agglomeration, and effectively improves the microwave-absorbing performance of the rigid plastic foam. Furthermore, compared with commonly used adhesives such as epoxy resins and phenolic resins, the adhesive in this application contains rigid plastic raw materials and interface modifiers, which can improve the interfacial bonding strength between pre-foamed particles and enhance mechanical properties such as tensile strength. Simultaneously, the preparation method can form a core-shell structure with pre-foamed particles as the core and the adhesive and microwave-absorbing agent as the outer shell, making the connections between pre-foamed particles and between pre-foamed particles and the microwave-absorbing agent more compact, effectively improving defects in the prior art such as curing, increased system viscosity, and foam voids caused by resin components. The in-mold foaming technology in this application can directly foam and form within the mold, reducing subsequent processing costs and increasing material utilization. Attached Figure Description

[0023] Figure 1 Test results of the microwave absorption performance of rigid plastic foam. Detailed Implementation

[0024] The present application will now be described in further detail with reference to specific embodiments. The embodiments given are intended to enable a more thorough understanding of the present application and to fully convey the scope of the present application to those skilled in the art.

[0025] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "comprising" or "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." The following descriptions in the specification are preferred embodiments for carrying out this application; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of this application. The scope of protection of this application shall be determined by the appended claims.

[0026] This application relates to a method for preparing a microwave-absorbing in-mold foamed rigid plastic foam material, characterized in that rigid plastic pre-foamed particles obtained by pre-foaming rigid plastic polymer particles are mixed with an adhesive and a microwave-absorbing agent, and then re-foamed in the mold to obtain the microwave-absorbing in-mold foamed rigid plastic foam material.

[0027] In one specific embodiment, the rigid plastic polymer particles are obtained by granulation of rigid plastic prepolymer.

[0028] The rigid plastic prepolymer in this application may be one or more of PMI prepolymer, PMMA prepolymer, PET prepolymer, and PEI prepolymer.

[0029] PMI (polymethacrylimide) is currently the strongest and stiffest heat-resistant foam plastic, exhibiting outstanding structural stability and mechanical properties. However, most ordinary PMI materials are wave-transparent foams, limiting their application in fields requiring electromagnetic shielding. The PMI material provided in this application incorporates a wave-absorbing agent and uses a specific adhesive to improve its properties, enabling the material to achieve excellent electromagnetic wave absorption while maintaining superior mechanical properties.

[0030] PMMA (polymethyl methacrylate) is a long-chain polymer with high mechanical strength. It has high tensile and impact resistance. Treated PMMA can be used as bulletproof glass or canopy for military aircraft.

[0031] PET (poly(terephthalic acid)) is a polyester thermoplastic resin with good creep resistance, fatigue resistance, abrasion resistance and dimensional stability. It has low wear and high hardness, and has the greatest toughness among thermoplastics.

[0032] PEI (polyetherimide) is a super engineering plastic made of amorphous polyetherimide. It has the best high temperature resistance and dimensional stability. It has high strength, high rigidity, wear resistance and dimensional stability at high temperatures. It can be widely used in high temperature terminals, aircraft internal parts, medical equipment and other fields.

[0033] In a preferred embodiment, the rigid plastic prepolymer may be a PMI prepolymer.

[0034] In one specific embodiment, the PMI prepolymer is obtained by polymerizing acrylonitrile and / or methacrylonitrile, acrylic acid and / or methacrylic acid, initiator, foaming agent, and nucleating agent after uniform mixing.

[0035] In a preferred embodiment, the mass ratio of acrylonitrile and / or methacrylonitrile, acrylic acid and / or methacrylic acid, initiator, foaming agent and nucleating agent during polymerization is 20-45:20-50:1-5:1-10:0.5-1; the polymerization temperature is 45-80℃ and the polymerization time is 60-240h.

[0036] Preferably, the initiator is selected from one or more of tert-amyl acetate peroxide, benzoyl peroxide, tert-butyl peroxy-2-ethylhexanoate, tert-amyl benzoate peroxide, tert-butyl peroxybenzoate, azobisisobutyronitrile, and azoisobutylcyanoformamide; the foaming agent is selected from one or more of ethanol, propanol, isopropanol, water, tert-butanol, and pentanol; and the nucleating agent is selected from one or more of silicon dioxide, titanium dioxide, aluminum oxide, benzoic acid, adipic acid, sodium benzoate, sodium acetate, and boron nitride.

[0037] In one specific embodiment, the particle size of the rigid plastic prepolymer granulated is 150-4000 micrometers, for example, it can be 150, 200, 300, 500, 8000, 1000, 1500, 2000, 2500, 3000, 3500, 4000 micrometers, etc.

[0038] In one specific embodiment, the rigid plastic polymer particles are foamed at a temperature of 140-250°C, for example, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, or 250°C, for a foaming time of 0.1-10 hours, for example, 0.1, 0.2, 0.5, 1.0, 2.0, 3.0, 5.0, 8.0, or 10.0 hours, with a foaming density of 30-200 kg / m³. 3， For example, 30, 40, 50, 80, 100, 120, 150, 180, 200 kg / m³ 3 The rigid plastic pre-foamed particles are obtained by performing a foaming process.

[0039] In one specific embodiment, the adhesive of this application is obtained by dissolving a polymer of acrylonitrile and / or methacrylonitrile, acrylic acid and / or methacrylic acid, an interface modifier and an initiator in a solvent.

[0040] In one specific embodiment, the interface modifier is selected from one or more of glycidyl methacrylate, silane coupling agent KH550, silane coupling agent KH560, silane coupling agent KH602, titanate coupling agent, aluminate coupling agent, BYK106, and BYK110. In a preferred embodiment, it is a titanate coupling agent.

[0041] In one specific embodiment, the initiator is selected from one or more of tert-amyl peroxide, benzoyl peroxide, tert-butyl peroxide, tert-amyl peroxide, tert-butyl peroxide, azobisisobutyronitrile, and azoisobutyl cyanoformamide.

[0042] In one specific embodiment, the solvent is selected from one or more of tetrahydrofuran, DMF, DMAC, NMP, ethanol, isopropanol, n-hexaneisopropanol, n-butanol, isobutanol, tert-butanol, tert-amyl alcohol, hexanol, urea, methylurea, and dimethylurea.

[0043] In one specific embodiment, the microwave absorbing agent in this application is selected from one or more of carbon nanotubes, graphene, carbon black, carbon powder, porous carbon, carbon aerogel, ferrite compounds, magnetic metal and alloy nanoparticles, magnetic nano metal oxides, and carbonyl iron.

[0044] In one specific embodiment, the adhesive and the microwave absorber are first mixed and dispersed for a certain period of time to obtain a mixed solution, which is then mixed with the rigid plastic pre-foamed particles.

[0045] In a preferred embodiment, the mass ratio of the adhesive to the microwave absorber is 0.1-10:10-95.

[0046] In a preferred embodiment, the adhesive and the microwave absorber are mixed and then ultrasonically dispersed, preferably for 2 hours, to obtain the mixed solution.

[0047] In one specific embodiment, when the rigid plastic pre-foamed particles are mixed with the adhesive and microwave absorbing agent mixture, the mass ratio of the rigid plastic pre-foamed particles to the mixture is 50-95:5-10.

[0048] In one specific embodiment of this application, during the in-mold re-foaming, the foaming temperature is 160-250℃ and the foaming time is 0.1-10h.

[0049] The method for preparing microwave-absorbing in-mold rigid plastic foam provided in this application involves the free-basic polymerization reaction between the raw material components in a rigid plastic prepolymer to obtain the rigid plastic prepolymer. Simultaneously, an adhesive is prepared by adding interface modifiers such as titanate interface modifiers, silane interface modifiers KH550 or KH560 to raw materials such as acrylonitrile and acrylic acid, replacing commonly used adhesives such as epoxy resin and phenolic resin. A microwave-absorbing agent is then added and mixed with the pre-foamed particles, allowing the microwave-absorbing agent to be uniformly dispersed during the foaming process through molecular-level bonding, reducing sedimentation and effectively improving the microwave absorption performance of the rigid foam. Furthermore, the adhesive can also improve the interfacial bonding strength between the pre-foamed particles, enhance mechanical properties, and reduce problems such as voids and cracks caused by using traditional thermosetting resins as adhesives.

[0050] This application also relates to a microwave-absorbing in-mold rigid plastic foam material, which is prepared by the preparation method provided in this application. In this microwave-absorbing foam material, the addition of an adhesive containing an interface modifier makes the connections between pre-foamed particles and between the pre-foamed particles and the microwave-absorbing agent more compact, thus maintaining good mechanical properties of the microwave-absorbing foam material.

[0051] This application also relates to the application of the aforementioned microwave-absorbing in-mold rigid plastic foam material in the fields of aviation, aerospace, military, and electromagnetic shielding materials.

[0052] Example

[0053] This application provides a general and / or specific description of the materials and test methods used in the experiments. In the following examples, unless otherwise specified, % represents wt%, i.e., weight percentage. Among the reagents used, the PMI prepolymer was prepared in-house, the PMMA prepolymer was purchased from Shanghai Miaoxin Plastics Co., Ltd., the PET prepolymer was purchased from Jiangyin Nopde Technology Co., Ltd., methacrylonitrile and acrylonitrile were purchased from Ningbo Jinfei Chemical Technology Co., Ltd., and methacrylic acid and acrylic acid were purchased from Ningbo Huajia Chemical Co., Ltd. Other reagents or instruments whose manufacturers are not specified were all commercially available conventional reagents or conventional laboratory instruments.

[0054] Example 1: Preparation of Wave-Absorbing In-Mold Foamed Rigid Plastic Foam Material

[0055] (1) Mix 45g of methacrylonitrile, 55g of methacrylic acid, 3g of azobisisobutyronitrile, 6g of isopropanol, and 1g of benzoic acid evenly, and polymerize at 45℃ for 150h to obtain PMI prepolymer. Crush the prepolymer using a 30kw crusher and sieve to obtain 325-micron PMI polymer particles;

[0056] (2) The PMI polymer particles obtained in the previous step are subjected to pre-foaming treatment. The pre-foaming temperature is 200℃, the pre-foaming time is 3h, and the pre-foaming density is 130kg / m³. 3 PMI pre-foamed particles were obtained;

[0057] (3) Mix 45g methacrylonitrile, 55g methacrylic acid, 2g titanate interface modifier, 3g azobisisobutyronitrile, 6g isopropanol and 1g benzoic acid, and polymerize at 45℃ for 150h to form a polymer. Add the polymer to DMF and mix. After dissolution, an adhesive is obtained.

[0058] (4) Mix 0.5g of the adhesive obtained in the previous step with 9.5g of carbon nanotubes to obtain a mixed solution;

[0059] (5) Add 92g of PMI pre-foamed particles obtained in step (2) to 8g of mixed solution, mix evenly, and perform in-mold foaming at a temperature of 230℃ for 5h to obtain the microwave-absorbing in-mold foamed rigid plastic foam material.

[0060] Example 2: Preparation of Wave-Absorbing In-Mold Foamed Rigid Plastic Foam Material

[0061] (1) The PMMA prepolymer was crushed by a 30kw PMMA prepolymer crusher and sieved to obtain 325-micron PMMA polymer particles.

[0062] (2) The PMMA polymer particles obtained in the previous step were subjected to pre-foaming treatment. The pre-foaming temperature was 200℃, the pre-foaming time was 3h, and the pre-foaming density was 130kg / m³. 3 PMMA pre-foamed particles were obtained;

[0063] (3) Mix 45g methacrylonitrile, 50g methacrylic acid, 1g titanate interface modifier, 1.5g azobisisobutyronitrile, 3g isopropanol and 0.5g benzoic acid, and polymerize at 45℃ for 150h to form a polymer. Add the polymer to DMF for mixing and dissolution to obtain an adhesive.

[0064] (4) Mix 1g of adhesive obtained in the previous step with 9g of carbon nanotubes to obtain a mixed solution;

[0065] (5) Add 92g of PMMA pre-foamed particles obtained in step (2) to 8g of mixed solution, mix evenly, and perform in-mold foaming at a temperature of 230℃ for 5h to obtain the microwave-absorbing in-mold foamed rigid plastic foam material.

[0066] Example 3: Preparation of Wave-Absorbing In-Mold Foamed Rigid Plastic Foam Material

[0067] (1) Mix 45g of methacrylonitrile, 55g of methacrylic acid, 3g of azobisisobutyronitrile, 6g of isopropanol, and 1g of benzoic acid evenly, and polymerize at 45℃ for 150h to obtain PMI prepolymer. Crush the prepolymer using a 20kw crusher and sieve to obtain 270-micron PMI polymer particles;

[0068] (2) The PMI polymer particles obtained in the previous step were subjected to pre-foaming treatment. The pre-foaming temperature was 190℃, the pre-foaming time was 5h, and the pre-foaming density was 130kg / m³. 3 PMI pre-foamed particles were obtained;

[0069] (3) Mix 45g methacrylonitrile, 55g methacrylic acid, 2g titanate interface modifier, 3g azobisisobutyronitrile, 6g isopropanol and 1g benzoic acid, and polymerize at 70℃ for 180h to form a polymer. Add the polymer to DMF and mix. After dissolution, an adhesive is obtained.

[0070] (4) Mix 1g of adhesive obtained in the previous step with 9g of carbon nanotubes to obtain a mixed solution;

[0071] (5) Add 92g of PMI pre-foamed particles obtained in step (2) to 8g of mixed solution, mix evenly, and perform in-mold foaming at a temperature of 220℃ for 4h to obtain the microwave-absorbing in-mold foamed rigid plastic foam material.

[0072] Example 4: Preparation of Wave-Absorbing In-Mold Foamed Rigid Plastic Foam Material

[0073] (1) The PET prepolymer was crushed by a 20kw PET prepolymer crusher and sieved to obtain 270-micron PET polymer particles;

[0074] (2) The PET polymer particles obtained in the previous step are subjected to pre-foaming treatment. The pre-foaming temperature is 190℃, the pre-foaming time is 5h, and the pre-foaming density is 130kg / m³. 3 PET pre-foamed particles were obtained;

[0075] (3) Mix 45g acrylonitrile, 55g acrylic acid, 2g silane interface modifier KH550, 3g benzoyl peroxide, 6g propanol and 1g sodium benzoate, and polymerize at 70℃ for 180h to form a polymer. Add the polymer to DMAC and mix. After dissolution, an adhesive is obtained.

[0076] (4) Mix 2g of adhesive obtained in the previous step with 8g of carbon black to obtain a mixed solution;

[0077] (5) Add 92g of the PET pre-foamed particles obtained in step (2) to 8g of the mixed solution, mix evenly, and perform in-mold foaming at a temperature of 220℃ for 4h to obtain the microwave-absorbing in-mold foamed rigid plastic foam material.

[0078] Example 5: Preparation of Wave-Absorbing In-Mold Foamed Rigid Plastic Foam Material

[0079] (1) The PMMA prepolymer was crushed by a 20kw crusher and sieved to obtain 270-micron polymethacrylamide polymer particles.

[0080] (2) The PMMA polymer particles obtained in the previous step were subjected to pre-foaming treatment. The pre-foaming temperature was 190℃, the pre-foaming time was 5h, and the pre-foaming density was 130kg / m³. 3 PMMA pre-foamed particles were obtained;

[0081] (3) Mix 45g acrylonitrile, 55g acrylic acid, 2g silane interface modifier KH550, 3g benzoyl peroxide, 6g propanol and 1g sodium benzoate, and polymerize at 70℃ for 180h to form a polymer. Add the polymer to DMAC and mix. After dissolution, an adhesive is obtained.

[0082] (4) Mix 2g of adhesive obtained in the previous step with 8g of carbon nanotubes to obtain a mixed solution;

[0083] (5) Add 95g of PMMA pre-foamed particles obtained in step (2) to 5g of mixed solution, mix evenly, and perform in-mold foaming at a temperature of 220℃ for 4h to obtain the microwave-absorbing in-mold foamed rigid plastic foam material.

[0084] Example 6: Preparation of Wave-Absorbing In-Mold Foamed Rigid Plastic Foam Material

[0085] (1) The PET prepolymer was crushed by a 20kw PET prepolymer crusher and sieved to obtain 270-micron PET polymer particles;

[0086] (2) The PET polymer particles obtained in the previous step are subjected to pre-foaming treatment. The pre-foaming temperature is 190℃, the pre-foaming time is 5h, and the pre-foaming density is 130kg / m³. 3 PET pre-foamed particles were obtained;

[0087] (3) Mix 45g acrylonitrile, 50g acrylic acid, 1g silane interface modifier KH550, 1.5g benzoyl peroxide, 3g propanol and 0.5g sodium benzoate, and polymerize at 70℃ for 180h to form a polymer. Add the polymer to DMAC and mix. After dissolution, an adhesive is obtained.

[0088] (4) Mix 2g of adhesive obtained in the previous step with 8g of carbon black to obtain a mixed solution;

[0089] (5) Add 95g of the PET pre-foamed particles obtained in step 2) to 5g of the mixed solution, mix evenly, and perform in-mold foaming at a temperature of 220℃ for 4h to obtain the microwave-absorbing in-mold foamed rigid plastic foam material.

[0090] Comparative Example 1

[0091] (1) The PET prepolymer was crushed by a 30kw PET prepolymer crusher and sieved to obtain 325-micron PET polymer particles;

[0092] (2) The PET polymer particles obtained in the previous step are subjected to pre-foaming treatment. The pre-foaming temperature is 200℃, the pre-foaming time is 3h, and the pre-foaming density is 130kg / m³. 3 PET pre-foamed particles were obtained;

[0093] (3) Mix 0.5g of epoxy resin adhesive with 9.5g of carbon nanotubes to obtain a mixed solution;

[0094] (4) Add 92g of the PET pre-foamed particles obtained in step (2) to 8g of the mixed solution, mix evenly, and foam in the mold for 5h at a temperature of 230℃ to obtain the microwave-absorbing PET foam material.

[0095] Comparative Example 2

[0096] (1) Mix 45g of methacrylonitrile, 55g of methacrylic acid, 3g of azobisisobutyronitrile, 6g of isopropanol, and 1g of benzoic acid evenly, and polymerize at 45℃ for 150h to obtain PMI prepolymer. Crush the prepolymer using a 50kw crusher and sieve to obtain 325-micron PMI polymer particles;

[0097] (2) The PMI polymer particles obtained in the previous step are subjected to pre-foaming treatment. The pre-foaming temperature is 150℃, the pre-foaming time is 15h, and the pre-foaming density is 130kg / m³. 3 PMI pre-foamed particles were obtained;

[0098] (3) Mix 45g methacrylonitrile, 55g methacrylic acid, 2g titanate interface modifier, 3g azobisisobutyronitrile, 6g isopropanol and 1g benzoic acid, and polymerize at 100℃ for 50h to form a polymer. Add the polymer to DMF and mix. After dissolution, an adhesive is obtained.

[0099] (4) Mix 1g of adhesive obtained in the previous step with 9g of carbon powder to obtain a mixed solution;

[0100] (5) Add 95g of the PMI pre-foamed particles obtained in step (2) to 5g of the mixed solution, mix evenly, and foam in the mold for 3h at a temperature of 260℃ to obtain the microwave-absorbing PMI foam material.

[0101] Comparative Example 3

[0102] (1) The PMMA prepolymer was crushed by a 30kw PMMA prepolymer crusher and sieved to obtain 325-micron PMMA polymer particles.

[0103] (2) The PMMA polymer particles obtained in the previous step were subjected to pre-foaming treatment. The pre-foaming temperature was 200℃, the pre-foaming time was 3h, and the pre-foaming density was 130kg / m³. 3 PMMA pre-foamed particles were obtained;

[0104] (3) Mix 20g acrylonitrile, 50g acrylic acid, 0.5g silane interface modifier KH550, 1g benzoyl peroxide, 3g propanol and 0.5g sodium benzoate, and polymerize at 45℃ for 150h to form a polymer. Add the polymer to DMF and mix. After dissolution, an adhesive is obtained.

[0105] (4) Mix 1g of adhesive obtained in the previous step with 9g of carbon powder to obtain a mixed solution;

[0106] (5) Add 95g of the pre-foamed PMMA particles obtained in step (2) to 5g of the mixed solution, mix evenly, and foam in the mold for 5h at a temperature of 230℃ to obtain the microwave-absorbing PMMA foam material.

[0107] Comparative Example 4

[0108] (1) Mix 45g of methacrylonitrile, 55g of methacrylic acid, 3g of azobisisobutyronitrile, 6g of isopropanol, and 1g of benzoic acid evenly, and polymerize at 45℃ for 150h to obtain PMI prepolymer. Crush the prepolymer using a 30kw crusher and sieve to obtain 325-micron PMI polymer particles;

[0109] (2) The PMI polymer particles obtained in the previous step were subjected to pre-foaming treatment. The pre-foaming temperature was 200℃, the pre-foaming time was 3h, and the pre-foaming density was 130kg / m³. 3 PMI pre-foamed particles were obtained;

[0110] (3) Mix 20g acrylonitrile, 50g acrylic acid, 0.5g silane interface modifier KH550, 1g benzoyl peroxide, 3g propanol and 0.5g sodium benzoate, and polymerize at 45℃ for 150h to form a polymer. Add the polymer to DMF and mix. After dissolution, an adhesive is obtained.

[0111] (4) Mix 9g of adhesive obtained in the previous step with 1g of microwave absorber to obtain a mixed solution;

[0112] (5) Add 98g of PMI pre-foamed particles obtained in step (2) to 2g of mixed solution, mix evenly, and foam in the mold for 5h at a temperature of 230℃ to obtain microwave-absorbing PMI foam material.

[0113] Experimental Example 1: Determination of Mechanical Properties of Wave-Absorbing Rigid Plastic Foam Materials

[0114] The mechanical properties of the microwave-absorbing foam materials obtained in the above embodiments and comparative examples were measured, and the results are shown in Table 1.

[0115] The apparent density was determined according to GB / T 6343-2009 Determination of apparent density of foamed plastics and rubber; the tensile strength was determined according to ASTM-D638-2010 Tensile strength of plastics; and the compressive strength was determined according to GB / T8813-2008 Determination of compressive properties of rigid foamed plastics.

[0116] Experiment Example 2: Determination of the wave absorption performance of rigid plastic foam materials with wave absorption properties

[0117] The microwave absorption performance of the microwave-absorbing foam materials obtained in the above examples and comparative examples was measured. The measurement method was in accordance with GJB2038A-2011 "Test Method for Reflectivity of Radar Microwave Absorbing Materials".

[0118] The results are shown in Table 1 and Figure 1 As shown.

[0119] Table 1. Test results of mechanical properties of in-mold rigid plastic foam materials with microwave absorption properties.

[0120] Example 1 112.6 3.17 3.02 2.24 Example 2 112.2 2.89 2.71 2.06 Example 3 113.4 2.83 2.76 2.04 Example 4 117.4 2.54 2.34 1.77 Example 5 115.6 2.48 2.27 1.83 Example 6 116.2 2.23 2.02 1.64 Comparative Example 1 113.6 2.01 1.68 1.45 Comparative Example 2 116 1.85 1.52 1.35 Comparative Example 3 111.4 1.91 1.48 1.38 Comparative Example 4 115 1.84 1.56 1.28

[0121] The experimental results show that the microwave-absorbing in-mold rigid plastic foam material provided in this application has a certain electromagnetic wave absorption function in the range of 0.6-40GHz, which can meet the requirements for use in special microwave absorption fields such as electromagnetic shielding. At the same time, it has excellent mechanical properties, with high compressive strength and tensile strength, high density, and few defects between foam particles, which can meet more diverse application environments and has a wider range of application prospects.

[0122] The above description is merely a preferred embodiment of this application and is not intended to limit the application in any other way. Any person skilled in the art may make changes or modifications to the disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the protection scope of this application.

Claims

1. A method for preparing a wave-absorbing in-mold rigid plastic foam material, characterized in that, Rigid plastic prepolymer is granulated to obtain rigid plastic polymer particles; the rigid plastic polymer particles are foamed at a foaming temperature of 140-250℃, a foaming time of 0.1-10h, and a foaming density of 30-200kg / m3 to obtain rigid plastic pre-foamed particles; an adhesive and a microwave absorbing agent are first mixed and dispersed for a certain time to obtain a mixed solution, which is then mixed with the rigid plastic pre-foamed particles and in-mold foaming is performed to obtain the microwave absorbing in-mold foamed rigid plastic foam material; The rigid plastic prepolymer is one or more of PMI prepolymer, PMMA prepolymer, PET prepolymer, and PEI prepolymer; The adhesive is obtained by mixing 45g of methacrylonitrile, 55g of methacrylic acid, 2g of titanate interface modifier, 3g of azobisisobutyronitrile, 6g of isopropanol, and 1g of benzoic acid, polymerizing them at 45°C for 150h to form a polymer, adding the polymer to DMF for mixing, and dissolving the polymer to obtain the final product. The microwave absorbing agent is selected from one or more of carbon nanotubes, graphene, carbon black, carbon aerogel, magnetic metal and alloy nanoparticles, and magnetic nano metal oxides. When adhesives and microwave absorbers are mixed, the mass ratio of adhesive to microwave absorber is 0.1-10:10-95; The mass ratio of the rigid plastic pre-foamed particles to the mixed solution is 50-95:5-10.

2. The preparation method according to claim 1, wherein, The particle size of the granulation is 150-4000 micrometers.

3. The preparation method according to claim 1, wherein, The in-mold re-foaming temperature is 140-250℃, and the foaming time is 0.1-10h.

4. A wave-absorbing rigid plastic foam material, which is prepared by the preparation method according to any one of claims 1 to 3.

5. The application of the wave-absorbing rigid plastic foam material according to claim 4 in the military field.

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