Preparation method of wave-absorbing porous material with flame-retardant property

Abstract

This application discloses a method for preparing a flame-retardant microwave-absorbing porous material, specifically including: preparation of an organic phase: mixing polymeric monomer materials, an initiator, and nano-conductive fillers, performing prepolymerization, and then adding a crosslinking agent and an emulsifier to obtain an organic phase; preparation of an aqueous phase: adding ammonium polyphosphate to an aqueous sodium chloride solution to obtain an aqueous phase; preparation of a polymer emulsion: adding the aqueous phase to the organic phase and stirring to obtain a polymer emulsion; polymerization of the material: heating and polymerizing the polymer emulsion to obtain the flame-retardant microwave-absorbing porous material. The flame-retardant microwave-absorbing porous material obtained by this preparation method can be applied to flame-retardant materials, electronic and electrical electromagnetic shielding materials, or aerospace fields.

Description

Technical Field

[0001] This application relates to the field of materials preparation technology, and in particular to a porous polymer material with flame retardant and microwave absorption properties, its preparation method and application. Background Technology

[0002] Porous polystyrene materials possess excellent thermal insulation, noise reduction and sound absorption properties, moisture and water resistance, chemical resistance, and are easy to process, low in cost, and low in density, leading to their widespread use in construction, packaging materials, and the automotive industry. However, due to its porous structure, polystyrene foam is more flammable than its corresponding resins. In any type of environmental flammability test, the limiting index (LOI) of polystyrene foam is only 17.8%, and it burns rapidly. Its high flammability poses a potentially huge threat to human life and property safety, thus greatly limiting its application.

[0003] Since the 1990s, the excellent absorption performance of nano-electromagnetic wave absorbing materials for electromagnetic waves, especially high-frequency electromagnetic waves, has attracted widespread attention. Electromagnetic wave absorbing materials also play an important role in human protection. With the development of technology, the use of electromagnetic wave emitters such as mobile communication devices has led to increasingly serious electromagnetic wave threats to people. Electromagnetic waves have significant impacts on the blood-brain barrier, neurobehavior, and genetics. Therefore, developing a lightweight material with a wide frequency coverage and strong electromagnetic wave absorption performance is of great significance. Summary of the Invention

[0004] To address the problems in the prior art, the purpose of this application is to provide a porous polymer material that simultaneously possesses flame retardancy and microwave absorption properties, as well as a method for preparing the same.

[0005] Specifically, this application provides a method for preparing a flame-retardant microwave-absorbing porous material, which includes:

[0006] Preparation of the organic phase: The polymer monomer material, initiator, and nano-conductive filler are mixed and prepolymerized. Then, a crosslinking agent and an emulsifier are added to obtain the organic phase.

[0007] Preparation of the aqueous phase: Ammonium polyphosphate is added to an aqueous sodium chloride solution to obtain the aqueous phase;

[0008] Preparation of polymer emulsion: The aqueous phase is added to the organic phase and stirred to obtain a polymer emulsion;

[0009] Polymerization of the material: The porous microwave absorbing material is obtained by heating and polymerizing the polymer emulsion.

[0010] Furthermore, the polymeric monomer is selected from one or more of styrene, methyl methacrylate, methyl acrylate, and ethyl acrylate.

[0011] Furthermore, the initiator is selected from azo initiators or peroxide initiators.

[0012] More preferably, the initiator is selected from one or more of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, di-tert-butyl peroxide, and cumene hydroperoxide.

[0013] Furthermore, the nano-conductive filler is selected from one or more of carbon black, carbon nanotubes, carbon fibers, metal nanomaterials, and metal nanowires.

[0014] More preferably, the nano-conductive filler is carbon black or carbon nanotubes.

[0015] Furthermore, by mass fraction, the organic phase comprises 50-90% polymeric monomer material, 0.1-5% initiator, 5-15% nano-conductive filler, 5-20% crosslinking agent, and 5-20% emulsifier.

[0016] Furthermore, the reaction temperature for the prepolymerization is 50-80℃, and the prepolymerization time is 10-20 min.

[0017] Furthermore, the crosslinking agent is selected from one or more of ethylene glycol dimethacrylate, divinylbenzene, triallyl cyanurate, and pentaerythritol triacrylate.

[0018] More preferably, the crosslinking agent is divinylbenzene.

[0019] Furthermore, the emulsifier is selected from one or more of span20, span80, DDBSS, CATB and Hypermer1070.

[0020] More preferably, the emulsifier is Span20.

[0021] Furthermore, the concentration of the calcium chloride aqueous solution is 10-30 g / L.

[0022] Furthermore, the ammonium polyphosphate in the aqueous phase is 0.75-8% by mass.

[0023] Furthermore, in the preparation of the polymer emulsion, the stirring rate is 500-800 rpm.

[0024] Furthermore, in the polymerization of the material, the heating polymerization temperature is 60-100℃, and the polymerization reaction time is 12-192h.

[0025] Furthermore, the weight ratio of the organic phase to the aqueous phase in the polymer emulsion is 15-40:60-85.

[0026] Furthermore, the mass ratio of ammonium polyphosphate to the organic phase in the polymer emulsion is 5-20:100.

[0027] This application provides flame-retardant microwave-absorbing porous materials prepared by the above-described preparation method.

[0028] This application also provides the application of the porous absorbing material in the fields of flame retardant materials, electronic and electrical electromagnetic shielding materials, and aerospace.

[0029] The effects of the invention

[0030] The flame-retardant and microwave-absorbing porous material provided in this application uses ammonium polyphosphate as the flame-retardant component. Ammonium polyphosphate is a high-performance non-halogenated flame retardant, but in conventional flame-retardant foam materials, it can cause some structural damage, thus affecting the mechanical properties of the material. However, in this preparation system, because it is soluble in water but insoluble in polymer monomers, it accumulates in the aqueous phase of the water-in-oil (W / O) emulsion and does not easily diffuse into the organic phase. After the organic phase polymerization is complete and the water evaporates, the ammonium polyphosphate remains on the cell walls of the porous polystyrene foam and does not affect the structural characteristics of the foam itself. Therefore, even with a large addition amount, the flame-retardant performance can be guaranteed without affecting the mechanical properties of the polymer foam.

[0031] Because nano-conductive fillers are added to the organic phase and prepolymerization is performed to prevent the organic phase from diffusing into the aqueous phase, the polymer and nano-conductive fillers can also be composited to improve the mechanical properties of the porous foam. The resulting foam satisfies the requirements of absorbent polymer interiors and flame-retardant cell walls, expanding the application areas of polystyrene foam without affecting its mechanical properties. Detailed Implementation

[0032] 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.

[0033] It should be noted that the terms "comprising" or "including" used throughout the specification and claims are open-ended terms and should be interpreted as "comprising but not limited to". The subsequent 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.

[0034] This application relates to a method for preparing a flame-retardant microwave-absorbing porous material, comprising:

[0035] Preparation of the organic phase: The polymer monomer material, initiator, and nano-conductive filler are mixed and prepolymerized. Then, a crosslinking agent and an emulsifier are added to obtain the organic phase.

[0036] Preparation of the aqueous phase: Ammonium polyphosphate is added to an aqueous sodium chloride solution to obtain the aqueous phase;

[0037] Preparation of polymer emulsion: The aqueous phase is added to the organic phase and stirred to obtain a polymer emulsion;

[0038] Polymerization of the material: The flame-retardant microwave absorbing porous material is obtained by heating and polymerizing the polymer emulsion.

[0039] The preparation and polymerization of polymer emulsions described in this application refer to the preparation of porous polymers using an emulsion modular method. Specifically, this includes preparing water-in-oil (W / O) type polymer emulsions, using an oil-soluble monomer (polymer phase) as the continuous phase and an aqueous phase as the dispersed phase, and utilizing the droplet structure of the emulsion as a template to prepare materials with specific morphologies and structures. The polymerization reaction is carried out under certain conditions to polymerize the continuous phase. After washing and drying, a porous polymer with controllable pore size and distribution is obtained. Simultaneously, to impart flame-retardant properties to the porous material without affecting its mechanical properties, a hydrophilic flame retardant is added to the aqueous phase, which forms at the pores during polymerization, thus avoiding damage to the polymer's bulk properties.

[0040] In a specific embodiment, the polymeric monomer is one or more of styrene, methyl methacrylate, methyl acrylate, and ethyl acrylate.

[0041] In a preferred embodiment, the polymeric monomer is styrene.

[0042] The preparation method described in this application is applicable to various types of porous materials, such as polymethyl methacrylate-based porous materials, organosilicon polystyrene porous materials, and polyethersulfone porous materials. In specific embodiments, the appropriate polymer monomer can be selected according to the specific material.

[0043] In a specific embodiment, the initiator is selected from azo initiators or peroxide initiators.

[0044] In some preferred embodiments, the initiator is selected from one or more of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, di-tert-butyl peroxide, and cumene hydroperoxide.

[0045] In a specific embodiment, the nano-conductive filler is selected from one or more of carbon black, carbon nanotubes, carbon fibers, metal nanomaterials, and metal nanowires.

[0046] In some preferred embodiments, the nano-conductive filler is carbon black or carbon nanotubes, and more preferably carbon black.

[0047] In a specific embodiment, the polymerizable monomer material, initiator, and nano-conductive filler are mixed in a mass ratio of 50-90:0.1-5:5-15. For example, the mass ratio of the polymerizable monomer material, initiator, and nano-conductive filler is 50 or 55 or 60 or 65 or 70 or 75 or 80:0.1 or 0.5 or 1 or 1.5 or 2 or 2.5 or 3 or 3.5 or 4 or 4.5 or 5:5 or 6 or 7 or 8 or 9 or 10 or 11 or 12 or 13 or 14 or 15. The prepolymerization reaction is carried out at a temperature of 50-80℃, for example, 50, 55, 60, 65, 70, 75, or 80℃, and the prepolymerization reaction time is 10-20 min, for example, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 min.

[0048] In a specific embodiment, after the prepolymerization is completed, a crosslinking agent and an emulsifier are further added to the mixture obtained by the prepolymerization to prepare an organic phase.

[0049] In some specific embodiments, after adding the crosslinking agent and emulsifier, the mixture is stirred at 300-1000 rpm for 5-30 min to obtain the organic phase.

[0050] In a specific implementation, the added crosslinking agent is divinylbenzene.

[0051] In a specific implementation, the added emulsifier is selected from one or more of span20, span80, DDBSS, CATB and Hypermer1070.

[0052] In some preferred embodiments, the emulsifier is Span20.

[0053] In a specific embodiment, by mass parts, the formed organic phase contains 50-90% polymeric monomer material, 0.1-5% initiator, 5-15% nano-conductive filler, 5-20% crosslinking agent, and 5-20% emulsifier.

[0054] In one specific embodiment, the organic phase comprises the following components:

[0055] 50-90wt% Styrene

[0056] 5-20wt% divinylbenzene

[0057] 0.1-5wt% initiator

[0058] 5-15wt% Nano-conductive filler

[0059] 5-20wt% emulsifier

[0060] In a specific embodiment, the concentration of the calcium chloride aqueous solution is 10-30 g / L, for example, 10, 15, 20, 25, or 30 g / L.

[0061] In a specific embodiment, the ammonium polyphosphate in the aqueous phase is 0.75-8% by mass. For example, the mass percentage of ammonium polyphosphate in the aqueous phase is 0.75%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, or 8%.

[0062] Ammonium polyphosphate is a flame retardant component that is readily soluble in water but insoluble in organic phases. When added to an aqueous phase and polymerized via an emulsion module method, it can be uniformly dispersed and cover the pores of the formed polymer, greatly improving the overall flame retardant performance of the material.

[0063] In a specific embodiment, an aqueous phase is added to an organic phase to obtain a polymer emulsion.

[0064] In some preferred embodiments, the aqueous phase is slowly added to the organic phase at a constant rate.

[0065] In some specific implementations, stirring is performed simultaneously with or after the addition of the aqueous phase to the organic phase.

[0066] In some specific embodiments, the stirring rate is 500-800 rpm, for example, 500, 520, 550, 580, 600, 620, 650, 680, 700, 750 or 800 rpm.

[0067] In some specific embodiments, the stirring continues for 5-10 minutes after the aqueous solution has been added.

[0068] In a specific embodiment, the weight ratio of the organic phase to the aqueous phase in the polymer emulsion is 15-40:60-85, for example, 15:85, 18:82, 20:80, 22:78, 25:75, 28:72, 30:70, 35:65 or 40:60.

[0069] In a specific embodiment, the mass ratio of ammonium polyphosphate to the organic phase in the polymer emulsion is 5-20:100, for example, 5:100, 10:100, 12:100, 15:100, 18:100 or 20:100.

[0070] In a specific embodiment, the polymer emulsion is heated and polymerized to obtain the flame-retardant microwave-absorbing porous material.

[0071] In some specific embodiments, the polymerization reaction temperature is 60-100℃, for example, 60, 70, 80, 90 or ℃, and the polymerization reaction time is 12-192h, for example, 20, 30, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190h, etc.

[0072] In some specific embodiments, the preparation method further dries the obtained material after polymerization is completed.

[0073] This application also relates to a flame-retardant porous material for absorbing microwaves prepared by the above-described preparation method, and the application of the material in the fields of flame-retardant materials, electronic and electrical electromagnetic shielding materials, or aerospace.

[0074] Example

[0075] 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. All reagents or instruments used, unless otherwise specified, are commercially available conventional reagent products or conventional laboratory instruments.

[0076] Example 1: Preparation of Flame-Retardant Porous Materials

[0077] (1) Add 75g of polymer monomer (styrene), 1.5g of initiator (azobisisobutyronitrile), and 8g of nano-conductive filler (carbon black) to the reactor and carry out a prepolymerization reaction at 68℃ for 17min.

[0078] (2) Add 13g of crosslinking agent (divinylbenzene) and 10g of emulsifier (span20) to the prepolymer obtained in the above steps, and stir at 450rpm to obtain an organic phase;

[0079] (3) Prepare 250g of calcium chloride aqueous solution with a concentration of 22g / L, add 15g of ammonium polyphosphate to it, and after dissolving and clarifying, obtain the aqueous phase;

[0080] (4) The above aqueous phase is slowly added to the above organic phase at 400 rpm, and stirred at 570 rpm for 5-10 minutes to obtain a polymer emulsion.

[0081] (5) The polymer emulsion from the previous step is heated at 87°C for 145 hours and then dried to obtain a flame-retardant, microwave-absorbing porous material.

[0082] Example 2: Preparation of Flame-Retardant and Microwave-Absorbing Porous Materials

[0083] (1) Add 75g of polymer monomer (styrene), 1.5g of initiator (azobisisobutyronitrile), and 8g of nano-conductive filler (carbon black) to the reactor and carry out a prepolymerization reaction at 68℃ for 17min.

[0084] (2) Add 13g of crosslinking agent (divinylbenzene) and 10g of emulsifier (span20) to the prepolymer obtained in the above steps, and stir at 450rpm to obtain an organic phase;

[0085] (3) Prepare 430g of calcium chloride aqueous solution with a concentration of 22g / L, add 15g of ammonium polyphosphate to it, and after dissolving and clarifying, obtain the aqueous phase;

[0086] (4) The above aqueous phase is slowly added to the above organic phase at 400 rpm, and stirred at 570 rpm for 5-10 minutes to obtain a polymer emulsion.

[0087] (5) The polymer emulsion from the previous step is heated at 87°C for 145 hours and then dried to obtain a flame-retardant, microwave-absorbing porous material.

[0088] Example 3: Preparation of Flame-Retardant and Microwave-Absorbing Porous Materials

[0089] (1) Add 75g of polymer monomer (styrene), 1.5g of initiator (azobisisobutyronitrile), and 5g of nano-conductive filler (carbon black) to the reactor and carry out a prepolymerization reaction at 68℃ for 17min.

[0090] (2) Add 13g of crosslinking agent (divinylbenzene) and 10g of emulsifier (span20) to the prepolymer obtained in the above steps, and stir at 450rpm to obtain an organic phase;

[0091] (3) Prepare 250g of calcium chloride aqueous solution with a concentration of 22g / L, add 15g of ammonium polyphosphate to it, and after dissolving and clarifying, obtain the aqueous phase;

[0092] (4) The above aqueous phase is slowly added to the above organic phase at 400 rpm, and stirred at 570 rpm for 5-10 minutes to obtain a polymer emulsion.

[0093] (5) The polymer emulsion from the previous step is heated at 87°C for 145 hours and then dried to obtain a flame-retardant, microwave-absorbing porous material.

[0094] Example 4: Preparation of Flame-Retardant and Microwave-Absorbing Porous Materials

[0095] (1) Add 75g of polymer monomer (styrene), 1.5g of initiator (azobisisobutyronitrile), and 8g of nano-conductive filler (carbon black) to the reactor and carry out a prepolymerization reaction at 68℃ for 17min.

[0096] (2) Add 13g of crosslinking agent (divinylbenzene) and 10g of emulsifier (span20) to the prepolymer obtained in the above steps, and stir at 450rpm to obtain an organic phase;

[0097] (3) Prepare 250g of calcium chloride aqueous solution with a concentration of 22g / L, add 3g of ammonium polyphosphate to it, and after dissolving and clarifying, obtain the aqueous phase;

[0098] (4) The above aqueous phase is slowly added to the above organic phase at 400 rpm, and stirred at 570 rpm for 5-10 minutes to obtain a polymer emulsion.

[0099] (5) The polymer emulsion from the previous step is heated at 87°C for 145 hours and then dried to obtain a flame-retardant, microwave-absorbing porous material.

[0100] Example 5: Preparation of Flame-Retardant and Microwave-Absorbing Porous Materials

[0101] (1) Add 80g of polymer monomer (styrene), 0.5g of initiator (azobisisobutyronitrile), and 10g of nano-conductive filler (carbon black) to the reactor and carry out a prepolymerization reaction at 68℃ for 17min.

[0102] (2) Add 15g of crosslinking agent (divinylbenzene) and 13g of emulsifier (span20) to the prepolymer obtained in the above steps, and stir at 450rpm to obtain an organic phase;

[0103] (3) Prepare 300g of calcium chloride aqueous solution with a concentration of 22g / L, add 15g of ammonium polyphosphate to it, and after dissolving and clarifying, obtain the aqueous phase;

[0104] (4) The above aqueous phase is slowly added to the above organic phase at 400 rpm, and stirred at 570 rpm for 5-10 minutes to obtain a polymer emulsion.

[0105] (5) The polymer emulsion from the previous step is heated at 87°C for 145 hours and then dried to obtain a flame-retardant, microwave-absorbing porous material.

[0106] Example 6: Preparation of Flame-Retardant and Microwave-Absorbing Porous Materials

[0107] (1) Add 75g of polymer monomer (styrene), 1.5g of initiator (azobisisobutyronitrile), and 8g of nano-conductive filler (carbon black) to the reactor and carry out a prepolymerization reaction at 68℃ for 17min.

[0108] (2) Add 13g of crosslinking agent (divinylbenzene) and 10g of emulsifier (span20) to the prepolymer obtained in the above steps, and stir at 450rpm to obtain an organic phase;

[0109] (3) Prepare 250g of calcium chloride aqueous solution with a concentration of 22g / L, add 15g of ammonium polyphosphate to it, and after dissolving and clarifying, obtain the aqueous phase;

[0110] (4) The above aqueous phase is slowly added to the above organic phase at 400 rpm, and stirred at 570 rpm for 5-10 minutes to obtain a polymer emulsion.

[0111] (5) The polymer emulsion from the previous step is heated at 90°C for 180 hours and then dried to obtain a flame-retardant, microwave-absorbing porous material.

[0112] Comparative Example 1

[0113] (1) 75g of polymer monomer (styrene), 1.5g of initiator (azobisisobutyronitrile), 8g of nano-conductive filler (carbon black), 13g of crosslinking agent (divinylbenzene), 10g of emulsifier (span20), and 15g of hexaphenoxycyclotriphosphazene were added to the reactor and stirred at 450 rpm to obtain the organic phase.

[0114] (2) Prepare 250g of calcium chloride aqueous solution with a concentration of 22g / L to obtain the aqueous phase;

[0115] (3) The above aqueous phase is slowly added to the above organic phase at 400 rpm, and stirred at 570 rpm for 5-10 minutes to obtain a polymer emulsion;

[0116] (4) The polymer emulsion from the previous step is heated at 87°C for 145 hours and then dried to obtain a flame-retardant, microwave-absorbing porous material.

[0117] Comparative Example 2

[0118] (2) Add 75g of polymer monomer (styrene), 1.5g of initiator (azobisisobutyronitrile), 8g of nano-conductive filler (carbon black), 13g of crosslinking agent (divinylbenzene), and 10g of emulsifier (span20) to the reactor and stir at 450rpm to obtain the organic phase;

[0119] (2) Prepare 250g of calcium chloride aqueous solution with a concentration of 22g / L, add 15g of ammonium polyphosphate to it, and after dissolving and clarifying, obtain the aqueous phase;

[0120] (3) The above aqueous phase is slowly added to the above organic phase at 400 rpm, and stirred at 570 rpm for 5-10 minutes to obtain a polymer emulsion;

[0121] (4) The polymer emulsion from the previous step is heated at 87°C for 145 hours and then dried to obtain a flame-retardant, microwave-absorbing porous material.

[0122] Comparative Example 3

[0123] (1) Add 75g of polymer monomer (styrene), 1.5g of initiator (azobisisobutyronitrile), and 8g of nano-conductive filler (carbon black) to the reactor and carry out a prepolymerization reaction at 68℃ for 17min.

[0124] (2) Add 13g of crosslinking agent (divinylbenzene) and 10g of emulsifier (span20) to the prepolymer obtained in the above steps, and stir at 450rpm to obtain an organic phase;

[0125] (3) Prepare 250g of calcium chloride aqueous solution with a concentration of 22g / L, add 3g of ammonium polyphosphate to it, and after dissolving and clarifying, obtain the aqueous phase;

[0126] (4) The above aqueous phase is slowly added to the above organic phase at 400 rpm, and stirred at 570 rpm for 5-10 minutes to obtain a polymer emulsion.

[0127] (5) The polymer emulsion from the previous step is heated at 87°C for 145 hours and then dried to obtain a flame-retardant, microwave-absorbing porous material.

[0128] Comparative Example 4

[0129] (1) Add 75g of polymer monomer (styrene), 1.5g of initiator (azobisisobutyronitrile), and 1g of nano-conductive filler (carbon black) to the reactor and carry out a prepolymerization reaction at 68℃ for 17min.

[0130] (2) Add 13g of crosslinking agent (divinylbenzene) and 10g of emulsifier (span20) to the prepolymer obtained in the above steps, and stir at 450rpm to obtain an organic phase;

[0131] (3) Prepare 250g of calcium chloride aqueous solution with a concentration of 22g / L, add 15g of ammonium polyphosphate to it, and after dissolving and clarifying, obtain the aqueous phase;

[0132] (4) The above aqueous phase is slowly added to the above organic phase at 400 rpm, and stirred at 570 rpm for 5-10 minutes to obtain a polymer emulsion.

[0133] (5) The polymer emulsion from the previous step is heated at 87°C for 145 hours and then dried to obtain a flame-retardant, microwave-absorbing porous material.

[0134] The specific composition and reaction conditions of each of the above embodiments and comparative examples are summarized in Table 1.

[0135] Table 1. Components and reaction conditions of the examples and comparative examples

[0136]

[0137]

[0138] Experimental Example 1

[0139] The mechanical properties, microwave absorption properties, and flame retardant properties of the flame-retardant porous materials obtained in the above embodiments and comparative examples were tested. The results are shown in Table 2.

[0140] The following test methods were used: apparent density was determined according to GB / T 6343-2009 Determination of apparent density of foamed plastics and rubber; tensile strength was determined according to ASTM-D638-2010 Tensile strength of plastics; compressive strength was determined according to GB / T 8813-2008 Determination of compressive properties of rigid foamed plastics; shear strength was tested according to ASTM-C273-2020 Shear properties of core materials for sandwich structures; porosity was determined according to GB / T 10799-2008 Determination of open and closed cell volume percentage of rigid foamed plastics; vertical burning length was determined according to HB5469 Test method for combustion of non-metallic materials inside civil aircraft cabins; and the absorption bandwidth and absorptivity were determined according to GJB 2038A-2011 Test method for reflectivity of radar absorbing materials.

[0141] Table 2 Material Performance Test Results

[0142]

[0143] The experimental results show that by pretreating the microwave absorber to fix it in the oil phase and using a water-soluble flame retardant to fix it in the aqueous phase, the flame retardant and microwave absorber do not coexist within the polymer, thus optimizing the flame retardant and microwave absorption properties of the porous material. If the flame retardant and microwave absorber coexist within the polymer during the polymerization reaction, the polymer's additive content accounts for 50%-60% of the monomer content, leading to polymer structure destruction, a significant reduction in mechanical properties, and a weakening of both flame retardant and microwave absorption effects.

[0144] 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 flame-retardant microwave-absorbing porous material, comprising: Preparation of the organic phase: The polymer monomer material, initiator, and nano-conductive filler are mixed and prepolymerized. Then, a crosslinking agent and an emulsifier are added to obtain the organic phase. Preparation of the aqueous phase: Ammonium polyphosphate is added to an aqueous sodium chloride solution to obtain the aqueous phase; Preparation of polymer emulsion: The aqueous phase is added to the organic phase and stirred to obtain a polymer emulsion; Polymerization of the material: The flame-retardant microwave absorbing porous material is obtained by heating and polymerizing the polymer emulsion.

2. The preparation method according to claim 1, wherein, The polymer monomer is selected from one or more of styrene, methyl methacrylate, methyl acrylate, and ethyl acrylate, and / or the initiator is selected from azo initiators or peroxide initiators, preferably one or more of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, di-tert-butyl peroxide, and cumene hydroperoxide, and / or the nano-conductive filler is selected from one or more of carbon black, carbon nanotubes, carbon fibers, metal nanomaterials, and metal nanowires, preferably carbon black or carbon nanotubes.

3. The preparation method according to claim 1, wherein, By mass percentage, the organic phase contains 50-90% polymeric monomer material, 0.1-5% initiator, 5-15% nano-conductive filler, 5-20% crosslinking agent, and 5-20% emulsifier.

4. The preparation method according to claim 1, wherein, The temperature of the prepolymerization reaction is 50-80℃, and the prepolymerization time is 10-20 min.

5. The preparation method according to claim 1, wherein, The crosslinking agent is selected from one or more of ethylene glycol dimethacrylate, divinylbenzene, triallyl cyanurate and pentaerythritol triacrylate, preferably divinylbenzene, and / or the emulsifier is selected from one or more of span20, span80, DDBSS, CATB and Hypermer 1070, preferably span20.

6. The preparation method according to claim 1, wherein, The concentration of the calcium chloride aqueous solution is 10-30 g / L.

7. The preparation method according to claim 1, wherein, The ammonium polyphosphate in the aqueous phase is 0.75-8% by mass.

8. The preparation method according to claim 1, wherein, The stirring speed is 500-800 rpm.

9. The preparation method according to claim 1, wherein, The heating polymerization temperature is 60-100℃, and the polymerization reaction time is 12-192h.

10. The preparation method according to claim 1, wherein, The weight ratio of the organic phase to the aqueous phase in the polymer emulsion is 15-40:60-85.

11. The preparation method according to claim 1, wherein, The mass ratio of ammonium polyphosphate to organic phase in the polymer emulsion is 5-20:

100.

12. The flame-retardant microwave-absorbing porous material prepared by the preparation method according to any one of claims 1-11.

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