Heterogeneous wave-absorbing polymethacrylimide foam material and preparation method thereof

Abstract

The invention provides a heterogeneous wave-absorbing polymethacrylimide foam material and a preparation method thereof, the raw materials of the heterogeneous wave-absorbing polymethacrylimide foam material comprise polymethacrylimide pre-foaming particles and a binder component, and the raw material of the binder component comprises expandable reinforced resin; polymethacrylimide pre-foaming particles containing self-foaming groups are obtained through pre-foaming, then the particles are immersed into the binder component to be fully impregnated, and finally secondary high-temperature foaming forming is carried out in the mold, so that the prepared heterogeneous wave-absorbing polymethacrylimide foam material has good wave-absorbing performance and also has good wave-absorbing performance. And the material also has excellent mechanical properties, and can meet the requirements of the fields of aerospace, traffic transportation and weaponry on the comprehensive performance of the radar wave-absorbing material.

Description

Technical Field

[0001] The invention belongs to the technical field of foam materials, and in particular relates to a non-homogeneous wave-absorbing polymethacrylimide foam material and a preparation method thereof. Background Art

[0002] Functional absorbing polymethacrylimide foam material has the advantages of light weight, broadband, high efficiency and compatibility. It has been widely used as radar structural absorbing material in aerospace, transportation, weapons and equipment and other fields.

[0003] At present, the relevant technical research on polymethacrylimide structured absorbing materials mainly focuses on the process of crushing the polymethacrylimide prepolymer plate containing the absorber and then foaming it in the mold. For example, CN107857843A discloses a preparation method of a homogeneous polymethacrylimide foam absorbing foam, which crushes the copolymer plate containing a high-density absorber and mixes it with methacrylic acid, methacrylonitrile and other reaction raw materials containing a light absorber through a two-step method, and then polymerizes it again, so that the absorber is dispersed more evenly; although this method improves the heat resistance and absorbing performance of the polymethacrylimide foam absorbing foam to a certain extent, the secondary copolymerization and crushing process increase the process complexity, and the mechanical properties of the foam are greatly reduced compared with the primary copolymerization. For another example, CN115651266 discloses a heterogeneous polymethacrylimide foam absorbing foam and a preparation method thereof, wherein expandable polymethacrylimide foam prepolymer particles are first prepared by pelletizing and screening, and then polymethacrylimide foam particles are prepared, and the pre-foamed foam particles and unfoamed prepolymer particles are mixed and prepared in different proportions, and then heterogeneous polymethacrylimide foam absorbing foam particles are prepared by impregnating absorbing slurry, and finally the foamed particles are placed in a mold for foaming; the heterogeneous polymethacrylimide foam absorbing foam prepared by the method has good absorbing performance and relatively improved mechanical properties, but the mechanical properties of the polymethacrylimide composite absorbing foam prepared by in-mold foaming after particle crushing are still significantly reduced compared with the complete foam, and it is difficult to balance the relationship between the foam density, the foam mechanical strength and the absorbing performance, and thus cannot meet the requirements for the comprehensive performance of radar absorbing materials in the fields of aerospace, transportation and weapon equipment.

[0004] Therefore, in view of the above technical problems, developing a non-homogeneous absorbing polymethacrylimide foam material with low density, high strength and excellent absorbing performance is still a technical problem that needs to be solved urgently in this field. Summary of the invention

[0005] In view of the deficiencies in the prior art, the object of the present invention is to provide a heterogeneous absorbing polymethacrylimide foam material and a preparation method thereof, wherein the heterogeneous absorbing polymethacrylimide foam material can have a good balance among foam density, mechanical strength and absorbing performance, and can have low density, high strength and excellent absorbing performance, thereby meeting the requirements for comprehensive performance of radar absorbing materials in the fields of aerospace, transportation and weaponry.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a non-homogeneous wave-absorbing polymethacrylimide foam material, wherein the raw materials of the non-homogeneous wave-absorbing polymethacrylimide foam material include polymethacrylimide pre-foamed particles and a binder component;

[0008] The raw materials of the polymethacrylimide pre-foamed particles include the following components in parts by weight:

[0009]

[0010] The raw materials of the binder component include the following components in parts by weight:

[0011] 10 to 50 parts by weight of expandable resin.

[0012] The raw materials of the heterogeneous wave-absorbing polymethacrylimide foam material provided by the present invention include polymethacrylimide pre-foamed particles and a binder component, and the raw materials of the polymethacrylimide pre-foamed particles include acrylonitrile monomer, methacrylic acid monomer, copolymerizable foaming monomer, a first wave-absorbing agent, a thickener, an initiator and a cross-linking agent, and the raw materials of the binder component include expandable reinforcing resin; firstly, the expandable copolymerizable monomer is introduced to copolymerize with acrylonitrile monomer and methacrylic acid monomer, and pre-foaming is performed to obtain polymethacrylimide prepolymer particles containing self-foaming groups; secondly, the expandable wave-absorbing functional resin is introduced as a binder of the polymethacrylimide prepolymer particles, and during the foaming process, the The expandable absorbing functional resin can be foamed and play a role of adhesive, thereby effectively avoiding the problem that traditional adhesives easily lead to an increase in the density of foam materials. While ensuring that the obtained foam material has low density and excellent absorbing performance, it can also further solidify and enhance the polymethacrylimide foam material, improve the problem of decreased mechanical properties of prepolymer particles during in-mold foaming, so that the final heterogeneous absorbing polymethacrylimide foam material can balance the deficiencies in foam density, mechanical strength and absorbing performance, and has low density, high strength and excellent absorbing performance, and can meet the requirements of the aerospace, transportation and weapon equipment fields for the comprehensive performance of radar absorbing materials.

[0013] The amount of the acrylonitrile monomer may be 40 parts by weight, 42 parts by weight, 44 parts by weight, 46 parts by weight, 48 parts by weight, 50 parts by weight, 52 parts by weight, 54 parts by weight, 56 parts by weight, 58 parts by weight or 60 parts by weight, etc.

[0014] The methacrylic acid monomer may be used in an amount of 20 parts by weight, 25 parts by weight, 30 parts by weight, 35 parts by weight, 40 parts by weight, 45 parts by weight, or 50 parts by weight.

[0015] The amount of the foamable comonomer can be 5 parts by weight, 10 parts by weight, 15 parts by weight, 20 parts by weight, 25 parts by weight, 30 parts by weight, 35 parts by weight or 40 parts by weight.

[0016] The first absorber may be used in an amount of 2 parts by weight, 3 parts by weight, 4 parts by weight, 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight or 10 parts by weight.

[0017] The thickener may be used in an amount of 1 part by weight, 1.5 parts by weight, 2 parts by weight, 2.5 parts by weight, 3 parts by weight, 3.5 parts by weight, 4 parts by weight, 4.5 parts by weight or 5 parts by weight, etc.

[0018] The amount of the initiator used can be 0.1 parts by weight, 0.12 parts by weight, 0.14 parts by weight, 0.16 parts by weight, 0.18 parts by weight, 0.2 parts by weight, 0.22 parts by weight, 0.24 parts by weight, 0.26 parts by weight, 0.28 parts by weight or 0.3 parts by weight, etc.

[0019] The amount of the cross-linking agent can be 1 part by weight, 1.5 parts by weight, 2 parts by weight, 2.5 parts by weight, 3 parts by weight, 3.5 parts by weight, 4 parts by weight, 4.5 parts by weight or 5 parts by weight.

[0020] The amount of the expandability enhancing resin can be 10 parts by weight, 15 parts by weight, 20 parts by weight, 25 parts by weight, 30 parts by weight, 35 parts by weight, 40 parts by weight, 45 parts by weight or 50 parts by weight, etc.

[0021] The schematic diagram of the foam structure of the heterogeneous wave-absorbing polymethacrylimide foam material provided by the present invention is as follows Figure 1 shown; from Figure 1 It can be seen that the polymethacrylimide foamed particles are connected by expandable reinforcing resin, and the bonding interface formed can enhance the multiple reflections and absorption losses of the incident wave. While the reinforcing resin plays a bonding role, it also helps to improve the difficulty of traditional polymethacrylimide particle foaming materials in balancing their density, mechanical properties and wave absorbing properties.

[0022] Preferably, the copolymerizable foaming monomer includes any one of tert-butyl methacrylamide, tert-butyl acrylamide, tert-butyl methacrylate, tert-butyl acrylate, tert-butoxystyrene or tert-butyl carbonate-based styrene monomers, or a combination of at least two thereof.

[0023] Preferably, the first absorber includes any one of carbon fiber, carbon nanotube, carbon black, graphite, graphene or carbon powder, or a combination of at least two of them.

[0024] Preferably, the thickener comprises any one of silicon dioxide, polyacrylate or hydroxyethyl cellulose or a combination of at least two thereof.

[0025] Preferably, the initiator includes any one of azobisisobutyronitrile, azobisisoheptanenitrile or benzoyl peroxide, or a combination of at least two thereof.

[0026] Preferably, the cross-linking agent includes any one of methyl methacrylate, ethyl methacrylate, allyl methacrylate, butyl methacrylate, acrylamide or methacrylamide, or a combination of at least two thereof.

[0027] Preferably, the expandable microwave absorbing functional resin is prepared by the following method, which comprises: reacting a dianhydride monomer and a diamine monomer in a solvent to obtain the expandable microwave absorbing functional resin.

[0028] Preferably, the molar ratio of the dianhydride monomer to the diamine monomer is (0.5-1.5):1, for example 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1 or 1.5:1.

[0029] Preferably, the dianhydride monomer includes any one of pyromellitic anhydride, 3,3',4,4'-biphenyltetracarboxylic anhydride, 2,3',3,4'-biphenyltetracarboxylic anhydride, 3,3',4,4'-benzophenonetetracarboxylic anhydride, 3,3',4,4'-diphenyl ether tetracarboxylic anhydride, 2,3,3',4'-diphenyl ether tetracarboxylic anhydride, hexafluoro dianhydride or 3,3,4,4-diphenyl sulfone tetracarboxylic anhydride, or a combination of at least two thereof.

[0030] Preferably, the diamine monomer includes 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, p-phenylenediamine, 4,4'-bis(3-aminophenoxy)-biphenyl, 4,4'-bis(4-aminophenoxy)-biphenyl, 4,4'-bis(3-aminophenoxy)diphenyl sulfone, 4,4'-bis(4-aminophenoxy)diphenyl sulfone, 2,2'-bis(trifluoromethyl)-(1,1'-diphenyl )-4,4'-diamine, 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis(4-aminophenyl)hexafluoropropane, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 2-(4-aminophenyl)-5-aminobenzimidazole or 3,4'-diaminodiphenyl ether, or a combination of at least two thereof.

[0031] Preferably, the solvent includes any one of methanol, ethanol, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone or dimethyl sulfoxide, or a combination of at least two thereof.

[0032] Preferably, the amount of the solvent is 30-50% (e.g., 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48% or 50%) based on the solid content of the diamine monomer and the dianhydride monomer in the reaction solution. Preferably, the temperature of the esterification reaction is 60-80°C, such as 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 76°C, 78°C or 80°C.

[0033] Preferably, the esterification reaction time is 1 to 5 h, for example, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h or 5 h.

[0034] Preferably, after the reaction is completed, the step of adding a second absorber for mixing is further included.

[0035] Preferably, the mass percentage of the second wave absorbing agent in the expandable wave absorbing functional resin is 1-10%, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%.

[0036] Preferably, the second absorber includes any one of carbon fiber, carbon nanotube, carbon black, graphite, graphene or carbon powder, or a combination of at least two of them.

[0037] In a second aspect, the present invention provides a method for preparing the heterogeneous wave-absorbing polymethacrylimide foam material as described in the first aspect, the preparation method comprising the following steps:

[0038] (1) mixing acrylonitrile monomer, methacrylic acid monomer, foamable comonomer, a first absorber, a thickener, an initiator and a crosslinking agent, and then pouring the obtained mixture into a glass mold, and then performing a polymerization reaction to obtain a polymethacrylimide expandable prepolymer plate;

[0039] (2) sequentially dehydrating, pre-foaming and cutting the polymethacrylimide expandable pre-polymerized sheet obtained in step (1) to obtain polymethacrylimide pre-foamed particles;

[0040] (3) The polymethacrylimide pre-foamed particles obtained in step (2) are fully immersed in the binder component, taken out and dried, and then placed in a mold, and then preheated, foamed and post-treated in sequence to obtain the heterogeneous absorbing polymethacrylimide foam material.

[0041] The invention provides a method for preparing a heterogeneous wave-absorbing polymethacrylimide foam material. First, polymethacrylimide pre-foamed particles containing self-foaming groups are obtained by pre-foaming, and then the obtained polymethacrylimide pre-foamed particles are fully impregnated in an expandable wave-absorbing functional resin (binder component) containing a wave-absorbing agent, so that the expandable wave-absorbing functional resin can be coated on the surface of the polymethacrylimide pre-foamed particles and serve as a binder for the pre-foamed particles. In the subsequent foaming process, the expandable wave-absorbing functional resin containing the wave-absorbing agent can be foamed and formed and play a bonding role, thereby avoiding the problem that the traditional binder easily leads to an increase in density. While ensuring that the foam material can have excellent wave-absorbing performance, the mechanical properties of the heterogeneous wave-absorbing polymethacrylimide foam material obtained by secondary in-mold foaming of the pre-foamed particles are greatly improved, so that the preparation method provided by the invention can prepare a heterogeneous wave-absorbing polymethacrylimide foam material with low density, high strength and excellent wave-absorbing performance.

[0042] Preferably, the mixing in step (1) comprises: first mechanically stirring at 40-70°C (for example, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C or 70°C, etc.) for 1-4h (for example, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h or 4h, etc.), and then ultrasonically dispersing at 40-70°C (for example, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C or 70°C, etc.) for 10-50min (for example, 10min, 15min, 20min, 25min, 30min, 35min, 40min, 45min or 50min, etc.) to complete the mixing.

[0043] Preferably, the polymerization reaction in step (1) is carried out at a temperature of 40 to 70°C (for example, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C or 70°C, etc.), and the reaction time is 24 to 96h (for example, 24h, 28h, 32h, 36h, 40h, 44h, 48h, 52h, 56h, 60h, 64h, 68h, 72h, 76h, 80h, 84h, 88h, 92h or 96h, etc.).

[0044] Preferably, the temperature of the dehydration treatment in step (2) is 70-120°C (for example, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C or 120°C, etc.), and the time is 0.5-2h (for example, 0.5h, 0.7h, 0.9h, 1.1h, 1.3h, 1.5h, 1.7h, 1.9h or 2h, etc.).

[0045] Preferably, the pre-foaming temperature in step (2) is 160-210°C (for example, 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, 190°C, 200°C or 210°C, etc.), and the pre-foaming time is 10-30min (for example, 10min, 12min, 14min, 16min, 18min, 20min, 22min, 24min, 26min, 28min or 30min, etc.).

[0046] Preferably, the immersion time in step (3) is 1 to 4 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours or 4 hours.

[0047] Preferably, the temperature of the preheat treatment in step (3) is 160-210°C (for example, 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, 190°C, 200°C or 210°C, etc.), and the time is 0.5-2h (for example, 0.5h, 0.7h, 0.9h, 1.1h, 1.3h, 1.5h, 1.7h, 1.9h or 2h, etc.).

[0048] Preferably, the temperature of the foaming treatment in step (3) is 170-240°C (for example, 170°C, 175°C, 180°C, 185°C, 190°C, 200°C, 210°C, 220°C, 230°C or 240°C, etc.), and the time is 0.5-2h (for example, 0.5h, 0.7h, 0.9h, 1.1h, 1.3h, 1.5h, 1.7h, 1.9h or 2h, etc.).

[0049] Preferably, the post-treatment temperature in step (3) is 160-230°C (e.g., 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, 190°C, 200°C, 210°C, 220°C or 230°C, etc.), and the time is 3-5h (e.g., 3h, 3.5h, 4h, 4.5h or 5h, etc.).

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] The raw materials of the heterogeneous absorbing polymethacrylimide foam material provided by the present invention include polymethacrylimide pre-foamed particles and a binder component, and the raw materials of the binder component include expandability enhancing resin. First, polymethacrylimide pre-foamed particles containing self-foaming groups are obtained by pre-foaming, and then the pre-foamed particles are immersed in the binder component and dried, and then secondary high-temperature foaming molding is performed in a mold, so that the finally obtained heterogeneous absorbing polymethacrylimide foam material can have low density, high strength and excellent absorbing performance, and can meet the requirements of the fields of aerospace, transportation and weapon equipment for the comprehensive performance of radar absorbing materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 This is a schematic diagram of the foam structure of the inhomogeneous wave-absorbing polymethacrylimide foam material provided by the present invention. DETAILED DESCRIPTION

[0053] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0054] Unless otherwise specified, the raw materials involved in the following specific embodiments are all conventional materials in the art and can be purchased from commercial products.

[0055] Preparation Example 1

[0056] A expandable wave-absorbing functional resin, the preparation method of which comprises: dissolving 21.8g (0.1mol) of pyromellitic anhydride in 98g of methanol, carrying out esterification reaction at 70°C for 3.5h, subsequently adding 20g (0.1mol) of 4,4'-diaminodiphenyl ether and continuing stirring and reacting for 2h to obtain a polyester ammonium salt solution with a solid content of 30%, and then adding 0.5g of carbon fiber and 0.5g of graphite and continuing stirring for 2h to obtain the expandable wave-absorbing functional resin.

[0057] Example 1

[0058] A non-homogeneous wave-absorbing polymethacrylimide foam material, the raw materials of which include polymethacrylimide pre-foamed particles and a binder component;

[0059] The raw materials of the polymethacrylimide pre-foamed particles include the following components in parts by weight:

[0060]

[0061] The raw materials of the binder component include the following components in parts by weight:

[0062] 40 parts by weight of expandable reinforcing resin;

[0063] Wherein, the expandable microwave absorbing functional resin is from Preparation Example 1;

[0064] The preparation method of the heterogeneous wave-absorbing polymethacrylimide foam material provided in this embodiment comprises the following steps:

[0065] (1) First, acrylonitrile monomer, methacrylic acid monomer and tert-butyl methacrylate are added to a 100 mL reaction bottle and mixed evenly, and then carbon fiber, graphite, silicon dioxide, azobisisobutyronitrile and methyl methacrylate are added, and mechanical stirring is performed at 50° C. for 2 hours, and then ultrasonic dispersion is performed at 50° C. for 20 minutes, and then the obtained mixture is poured into an assembled glass mold, and then the glass mold is placed in a constant temperature water bath at 50° C. for polymerization reaction for 48 hours to obtain a polymethacrylimide expandable prepolymer plate;

[0066] (2) placing the polymethacrylimide expandable prepolymerized sheet obtained in step (1) in a high-temperature oven and maintaining a constant temperature of 100° C. for dehydration treatment for 1 hour, and then continuing to raise the temperature to 200° C. for prefoaming for 10 minutes to obtain a prefoamed sheet, and cutting the obtained prefoamed sheet into small pieces to obtain polymethacrylimide prefoamed particles with a side length of more than 8 mm;

[0067] (3) After fully immersing the polymethacrylimide pre-foamed particles obtained in step (2) in the binder component for 1 hour, the particles are taken out and dried at 80° C., and then 35 g of the dried pre-foamed particles coated with the expandable absorbing resin are placed in a closed stainless steel mold with a side length of 50 mm and a height of 40 mm, and preheated at 200° C. in a high-temperature oven for 1 hour, then foamed at 230° C. for 1 hour, and finally post-treated at 210° C. for 3 hours to obtain the heterogeneous absorbing polymethacrylimide foam material.

[0068] Example 2

[0069] A non-homogeneous wave-absorbing polymethacrylimide foam material, the raw materials of which include polymethacrylimide pre-foamed particles and a binder component;

[0070] The raw materials of the polymethacrylimide pre-foamed particles include the following components in parts by weight:

[0071]

[0072] The raw materials of the binder component include the following components in parts by weight:

[0073] 35 parts by weight of expandable reinforcing resin;

[0074] Wherein, the expandable microwave absorbing functional resin is from Preparation Example 1;

[0075] The preparation method of the heterogeneous wave-absorbing polymethacrylimide foam material provided in this embodiment comprises the following steps:

[0076] (1) First, acrylonitrile monomer, methacrylic acid monomer and tert-butyl methacrylate were added to a 100 mL reaction bottle and mixed evenly, and then carbon fiber, graphite, hydroxyethyl cellulose, azobisisobutyronitrile and methyl methacrylate were added, and mechanical stirring was performed at 55° C. for 1 hour, and then ultrasonic dispersion was performed at 55° C. for 20 minutes, and then the obtained mixture was poured into an assembled glass mold, and then the glass mold was placed in a constant temperature water bath at 55° C. for polymerization reaction for 48 hours to obtain a polymethacrylimide expandable prepolymer plate;

[0077] (2) placing the polymethacrylimide expandable prepolymerized sheet obtained in step (1) in a high temperature oven and maintaining a constant temperature of 80° C. for dehydration treatment for 2 h, and then continuing to raise the temperature to 190° C. for prefoaming for 10 min to obtain a prefoamed sheet, and cutting the obtained prefoamed sheet into small pieces to obtain polymethacrylimide prefoamed particles with a side length of 7 mm or more;

[0078] (3) After fully immersing the polymethacrylimide pre-foamed particles obtained in step (2) in the binder component for 1 hour, taking them out and drying them at 80° C., then putting 30 g of the dried pre-foamed particles coated with the expandable absorbing resin into a closed stainless steel mold with a side length of 50 mm and a height of 40 mm, preheating them at 190° C. in a high-temperature oven for 1 hour, continuing to rise to 220° C. for foaming treatment for 1 hour, and finally post-treating them at 200° C. for 3 hours to obtain the heterogeneous absorbing polymethacrylimide foam material.

[0079] Example 3

[0080] A non-homogeneous wave-absorbing polymethacrylimide foam material, the raw materials of which include polymethacrylimide pre-foamed particles and a binder component;

[0081] The raw materials of the polymethacrylimide pre-foamed particles include the following components in parts by weight:

[0082]

[0083] The raw materials of the binder component include the following components in parts by weight:

[0084] 25 parts by weight of expandable reinforcing resin;

[0085] Wherein, the expandable microwave absorbing functional resin is from Preparation Example 1;

[0086] The preparation method of the heterogeneous wave-absorbing polymethacrylimide foam material provided in this embodiment comprises the following steps:

[0087] (1) First, acrylonitrile monomer, methacrylic acid monomer and tert-butyl methacrylate were added to a 100 mL reaction bottle and mixed evenly, and then carbon fiber, graphite, conductive carbon black, hydroxyethyl cellulose, azobisisobutyronitrile and methyl methacrylate were added, and mechanical stirring was performed at 50° C. for 2 h, and then ultrasonic dispersion was performed at 50° C. for 20 min, and then the obtained mixture was poured into an assembled glass mold, and then the glass mold was placed in a constant temperature water bath at 50° C. for polymerization reaction for 24 h, and then reacted in a constant temperature water bath at 55° C. for 12 h to obtain a polymethacrylimide expandable prepolymer plate;

[0088] (2) placing the polymethacrylimide expandable prepolymerized sheet obtained in step (1) in a high-temperature oven and maintaining a constant temperature of 100° C. for dehydration treatment for 1 hour, and then continuing to raise the temperature to 180° C. for prefoaming for 10 minutes to obtain a prefoamed sheet, and cutting the obtained prefoamed sheet into small pieces to obtain polymethacrylimide prefoamed particles with a side length of more than 6 mm;

[0089] (3) After fully immersing the polymethacrylimide pre-foamed particles obtained in step (2) in the binder component for 1 hour, taking them out and drying them at 80° C., then putting 25 g of the dried pre-foamed particles coated with the expandable absorbing resin into a closed stainless steel mold with a side length of 50 mm and a height of 40 mm, preheating them at 180° C. in a high-temperature oven for 1 hour, continuing to rise to 210° C. for foaming treatment for 1 hour, and finally post-treating them at 190° C. for 4 hours to obtain the heterogeneous absorbing polymethacrylimide foam material.

[0090] Example 4

[0091] A non-homogeneous wave-absorbing polymethacrylimide foam material, the raw materials of which include polymethacrylimide pre-foamed particles and a binder component;

[0092] The raw materials of the polymethacrylimide pre-foamed particles include the following components in parts by weight:

[0093]

[0094]

[0095] The raw materials of the binder component include the following components in parts by weight:

[0096] 20 parts by weight of expandable reinforcing resin;

[0097] Wherein, the expandable microwave absorbing functional resin is from Preparation Example 1;

[0098] The preparation method of the heterogeneous wave-absorbing polymethacrylimide foam material provided in this embodiment comprises the following steps:

[0099] (1) First, acrylonitrile monomer, methacrylic acid monomer and tert-butyl methacrylate were added to a 100 mL reaction bottle and mixed evenly, and then carbon fiber, carbon nanotubes, conductive carbon black, hydroxyethyl cellulose, azobisisobutyronitrile and methyl methacrylate were added, and mechanical stirring was performed at 55° C. for 2 h, and then ultrasonic dispersion was performed at 55° C. for 20 min, and then the obtained mixture was poured into an assembled glass mold, and then the glass mold was placed in a constant temperature water bath at 55° C. for polymerization reaction for 24 h, and then reacted in a constant temperature water bath at 60° C. for 12 h to obtain a polymethacrylimide expandable prepolymer plate;

[0100] (2) placing the polymethacrylimide expandable prepolymerized sheet obtained in step (1) in a high-temperature oven and maintaining a constant temperature of 100° C. for dehydration treatment for 1 hour, and then continuing to raise the temperature to 170° C. for pre-foaming for 20 minutes to obtain a pre-foamed sheet, and cutting the obtained pre-foamed sheet into small pieces to obtain polymethacrylimide pre-foamed particles with a side length of 5 mm or more;

[0101] (3) After fully immersing the polymethacrylimide pre-foamed particles obtained in step (2) in the binder component for 1 hour, taking them out and drying them at 80° C., then putting 20 g of the dried pre-foamed particles coated with the expandable absorbing resin into a closed stainless steel mold with a side length of 50 mm and a height of 40 mm, preheating them at 170° C. in a high-temperature oven for 1 hour, continuing to rise to 200° C. for foaming treatment for 1 hour, and finally post-treating them at 180° C. for 4 hours to obtain the heterogeneous absorbing polymethacrylimide foam material.

[0102] Example 5

[0103] A non-homogeneous wave-absorbing polymethacrylimide foam material, the raw materials of which include polymethacrylimide pre-foamed particles and a binder component;

[0104] The raw materials of the polymethacrylimide pre-foamed particles include the following components in parts by weight:

[0105]

[0106] The raw materials of the binder component include the following components in parts by weight:

[0107] 15 parts by weight of expandable resin;

[0108] Wherein, the expandable microwave absorbing functional resin is from Preparation Example 1;

[0109] The preparation method of the heterogeneous wave-absorbing polymethacrylimide foam material provided in this embodiment comprises the following steps:

[0110] (1) First, acrylonitrile monomer, methacrylic acid monomer and tert-butyl methacrylate were added to a 100 mL reaction bottle and mixed evenly, and then carbon fiber, conductive carbon black, hydroxyethyl cellulose, azobisisobutyronitrile and methyl methacrylate were added, and mechanical stirring was performed at 55° C. for 1 hour, and then ultrasonic dispersion was performed at 55° C. for 20 minutes, and then the obtained mixture was poured into an assembled glass mold, and then the glass mold was placed in a constant temperature water bath at 55° C. for polymerization reaction for 12 hours, and then reacted in a constant temperature water bath at 60° C. for 24 hours to obtain a polymethacrylimide expandable prepolymer plate;

[0111] (2) placing the polymethacrylimide expandable prepolymerized sheet obtained in step (1) in a high-temperature oven and maintaining a constant temperature of 100° C. for dehydration treatment for 1 hour, and then continuing to raise the temperature to 160° C. for prefoaming for 10 minutes to obtain a prefoamed sheet, and cutting the obtained prefoamed sheet into small pieces to obtain polymethacrylimide prefoamed particles with a side length of more than 4 mm;

[0112] (3) After fully immersing the polymethacrylimide pre-foamed particles obtained in step (2) in the binder component for 1 hour, taking them out and drying them at 80° C., then putting 15 g of the dried pre-foamed particles coated with the expandable absorbing resin into a closed stainless steel mold with a side length of 50 mm and a height of 40 mm, preheating them at 160° C. in a high-temperature oven for 1 hour, continuing to rise to 190° C. for foaming treatment for 1 hour, and finally post-treating them at 170° C. for 4 hours to obtain the heterogeneous absorbing polymethacrylimide foam material.

[0113] Comparative Example 1

[0114] A polymethacrylimide foam material, the raw materials of which include the following components in parts by weight:

[0115]

[0116] The preparation method of the heterogeneous wave-absorbing polymethacrylimide foam material provided in this embodiment comprises the following steps:

[0117] (1) First, acrylonitrile monomer, methacrylic acid monomer and tert-butyl methacrylate were added to a 100 mL reaction bottle and mixed evenly, and then carbon fiber, graphite, conductive carbon black, hydroxyethyl cellulose, azobisisobutyronitrile and methyl methacrylate were added, and mechanical stirring was performed at 50° C. for 2 h, and then ultrasonic dispersion was performed at 50° C. for 20 min, and then the obtained mixture was poured into an assembled glass mold, and then the glass mold was placed in a constant temperature water bath at 50° C. for polymerization reaction for 24 h, and then reacted in a constant temperature water bath at 55° C. for 12 h to obtain a polymethacrylimide expandable prepolymer plate;

[0118] (2) placing the polymethacrylimide expandable prepolymerized sheet obtained in step (1) in a high-temperature oven and maintaining a constant temperature of 100° C. for dehydration treatment for 1 hour, and then continuing to raise the temperature to 180° C. for prefoaming for 10 minutes to obtain a prefoamed sheet, and cutting the obtained prefoamed sheet into small pieces to obtain polymethacrylimide prefoamed particles with a side length of more than 6 mm;

[0119] (3) 25 g of the polymethacrylimide pre-foamed particles obtained in step (2) were placed in a closed stainless steel mold with a side length of 50 mm and a height of 40 mm, preheated at 180° C. in a high-temperature oven for 1 h, then foamed at 210° C. for 1 h, and finally post-treated at 190° C. for 4 h to obtain the heterogeneous absorbing polymethacrylimide foam material.

[0120] Performance Test:

[0121] The heterogeneous wave-absorbing polymethacrylimide foam materials provided in Examples 1 to 5 and Comparative Example 1 were tested, and the test results are shown in Table 1:

[0122] Table 1

[0123]

[0124]

[0125] From the data in Table 1, we can see that:

[0126] (1) By comparing the data of Example 3 with that of Comparative Example 1, it can be seen that, at the same density, the use of expandable resin to strengthen the interface of the pre-foamed particles can improve the mechanical properties of the obtained heterogeneous absorbing polymethacrylimide composite foam material. At the same time, the expandable resin interface can enhance the interface multiple internal reflection, which can improve the absorbing performance of the obtained heterogeneous absorbing polymethacrylimide composite foam material.

[0127] (2) By observing the data of Examples 1 to 5 again, it can be seen that by adjusting the content of the foaming agent and coating the surface of the pre-foamed particles with different pore sizes with different contents of expandability reinforcing resin, a heterogeneous absorbing polymethacrylimide composite foam material with different densities and absorbing properties can be obtained.

[0128] The applicant declares that the present invention illustrates a non-homogeneous wave-absorbing polymethacrylimide foam material and a preparation method thereof through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned embodiments, that is, it does not mean that the present invention must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A non-homogeneous wave-absorbing polymethacrylimide composite foam material, characterized in that: The raw materials of the heterogeneous wave-absorbing polymethacrylimide composite foam material include polymethacrylimide pre-foamed particles and a binder component; The raw materials of the polymethacrylimide pre-foamed particles include the following components in parts by weight: The raw materials of the binder component include the following components in parts by weight: 10 to 50 parts by weight of expandable resin.

2. The heterogeneous wave-absorbing polymethacrylimide foam material according to claim 1, characterized in that: The copolymerizable foaming monomer includes any one of tert-butyl methacrylamide, tert-butyl acrylamide, tert-butyl methacrylate, tert-butyl acrylate, tert-butoxy styrene or tert-butyl carbonate-based styrene monomers or a combination of at least two thereof.

3. The heterogeneous wave-absorbing polymethacrylimide foam material according to claim 1 or 2, characterized in that: The first wave absorbing agent comprises any one of carbon fiber, carbon nanotube, carbon black, graphite, graphene or carbon powder or a combination of at least two thereof; Preferably, the thickener comprises any one of silicon dioxide, polyacrylate or hydroxyethyl cellulose or a combination of at least two thereof.

4. The heterogeneous wave-absorbing polymethacrylimide foam material according to any one of claims 1 to 3, characterized in that: The initiator includes any one of azobisisobutyronitrile, azobisisoheptanenitrile or benzoyl peroxide or a combination of at least two thereof; Preferably, the cross-linking agent includes any one of methyl methacrylate, ethyl methacrylate, allyl methacrylate, butyl methacrylate, acrylamide or methacrylamide, or a combination of at least two thereof.

5. The heterogeneous wave-absorbing polymethacrylimide foam material according to any one of claims 1 to 4, characterized in that: The expandable microwave absorbing functional resin is prepared by the following method, which comprises: reacting a dianhydride monomer and a diamine monomer in a solvent to obtain the expandable microwave absorbing functional resin; Preferably, the molar ratio of the dianhydride monomer to the diamine monomer is (0.5-1.5):1; Preferably, the dianhydride monomer includes any one of pyromellitic anhydride, 3,3',4,4'-biphenyltetracarboxylic anhydride, 2,3',3,4'-biphenyltetracarboxylic anhydride, 3,3',4,4'-benzophenone tetracarboxylic anhydride, 3,3',4,4'-diphenyl ether tetracarboxylic anhydride, 2,3,3',4'-diphenyl ether tetracarboxylic anhydride, hexafluoro dianhydride or 3,3,4,4-diphenyl sulfone tetracarboxylic anhydride, or a combination of at least two thereof; Preferably, the diamine monomer includes 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, p-phenylenediamine, 4,4'-bis(3-aminophenoxy)-biphenyl, 4,4'-bis(4-aminophenoxy)-biphenyl, 4,4'-bis(3-aminophenoxy)diphenyl sulfone, 4,4'-bis(4-aminophenoxy)diphenyl sulfone, 2,2'-bis(trifluoromethyl)-(1,1'-diphenyl Any one or a combination of at least two of )-4,4'-diamine, 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis(4-aminophenyl)hexafluoropropane, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 2-(4-aminophenyl)-5-aminobenzimidazole or 3,4'-diaminodiphenyl ether; Preferably, the solvent comprises any one of methanol, ethanol, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone or dimethyl sulfoxide, or a combination of at least two thereof; Preferably, the reaction temperature is 60-80°C and the reaction time is 1-5h; Preferably, after the reaction is completed, the step of adding a second absorber for mixing is further included; Preferably, the mass percentage of the second wave absorbing agent in the expandable wave absorbing functional resin is 1 to 10%; Preferably, the second absorber includes any one of carbon fiber, carbon nanotube, carbon black, graphite, graphene or carbon powder, or a combination of at least two of them.

6. A method for preparing the heterogeneous wave-absorbing polymethacrylimide foam material according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: (1) mixing acrylonitrile monomer, methacrylic acid monomer, foamable comonomer, a first absorber, a thickener, an initiator and a crosslinking agent, and then pouring the obtained mixture into a glass mold, and then performing a polymerization reaction to obtain a polymethacrylimide expandable prepolymer plate; (2) sequentially dehydrating, pre-foaming and cutting the polymethacrylimide expandable pre-polymerized sheet obtained in step (1) to obtain polymethacrylimide pre-foamed particles; (3) The polymethacrylimide pre-foamed particles obtained in step (2) are fully immersed in the binder component, taken out and dried, and then placed in a mold, and then preheated, foamed and post-treated in sequence to obtain the heterogeneous absorbing polymethacrylimide foam material.

7. The preparation method according to claim 6, characterized in that: The mixing in step (1) comprises: firstly mechanically stirring at 40 to 70° C. for 1 to 4 hours, and then ultrasonically dispersing at 40 to 70° C. for 10 to 50 minutes to complete the mixing; Preferably, the polymerization reaction temperature in step (1) is 40 to 70° C. and the reaction time is 24 to 96 hours.

8. The preparation method according to claim 6 or 7, characterized in that: The temperature of the dehydration treatment in step (2) is 70 to 120° C. and the time is 0.5 to 2 h; Preferably, the pre-foaming temperature in step (2) is 160-210° C. and the pre-foaming time is 10-30 min.

9. The preparation method according to any one of claims 6 to 8, characterized in that: The soaking time in step (3) is 1 to 4 hours; Preferably, the preheating treatment in step (3) is carried out at a temperature of 160 to 210° C. and for a time of 0.5 to 2 h.

10. The preparation method according to any one of claims 6 to 9, characterized in that: The temperature of the foaming treatment in step (3) is 170-240° C. and the time is 0.5-2 h; Preferably, the post-treatment in step (3) is carried out at a temperature of 160 to 230° C. and for a time of 3 to 5 hours.

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