Composite electromagnetic wave-absorbing material preparation method, composite electromagnetic wave-absorbing material, and rail vehicle
By using a composite material made of polypropylene, flame retardant, antioxidant, superconducting carbon nanotubes, and nickel-plated calcium silicate, the environmental pollution and performance degradation problems of traditional microwave absorbing materials have been solved, and the preparation of a high-efficiency and environmentally friendly composite microwave absorbing material has been achieved, which is suitable for partition materials in buildings and rail vehicles.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- CRRC TANGSHAN CO LTD
- Filing Date
- 2025-10-11
- Publication Date
- 2026-05-21
Smart Images
Figure CN2025127005_21052026_PF_FP_ABST
Abstract
Description
Preparation method of composite absorbing material, composite absorbing material and rail vehicle Technical Field
[0001] This application relates to microwave absorbing material technology, and more particularly to a method for preparing a composite microwave absorbing material, the composite microwave absorbing material, and a rail vehicle. Background Technology
[0002] Currently, the majority of anechoic chambers in China use two main types of absorbing materials: flexible polyurethane foam and non-woven fabric absorbing materials. Flexible polyurethane foam is a traditional absorbing material for anechoic chambers. Its preparation process includes cutting, molding, impregnation, and drying. Its advantages include simple processing, low cost, low equipment requirements, high production efficiency, and strong absorption capacity. However, this polyurethane foam also has several drawbacks. First, during the preparation process, flame retardants and absorbing agents are adsorbed into the pores of the polyurethane foam through impregnation. With increasing service life, these can easily detach and cause environmental pollution. Second, polyurethane foam has open pores, making it prone to moisture absorption, which can lead to a decline in absorption performance. Third, in EMC anechoic chambers, to obtain good low-frequency performance, polyurethane foam is often made into long wedges. However, after a period of use, due to its own weight, the pointed ends of the material pyramids may bend, resulting in drooping, which degrades the aesthetics of the anechoic chamber and reduces its overall performance.
[0003] The preparation process of non-woven microwave absorbing materials generally includes coating, embossing, folding and assembly. The advantages of this microwave absorbing material are its strong flame retardancy and better power resistance than polyurethane foam. However, its preparation process is more complex and requires more labor, resulting in lower production efficiency and higher cost compared to polyurethane foam. Secondly, due to the large number of manual processes, product consistency is difficult to guarantee, and long-term use can easily cause the microwave absorbing agent and flame retardant to fall off, polluting the environment and reducing microwave absorbing performance.
[0004] In addition, there is a type of microwave-absorbing polyurethane foam / rigid foam composite material. This uses microwave-absorbing polyurethane foam as the matrix, filling the polyurethane foam cells with rigid foam foaming material, which cures to form rigid microwave-absorbing foam. The microwave-absorbing polyurethane foam is obtained by repeatedly impregnating non-microwave-absorbing polyurethane foam sheets with an absorbent slurry and then drying them. The rigid foam filling the polyurethane foam cells can be either microwave-absorbing or non-microwave-absorbing. In the preparation process of this material, the drying temperature is extremely critical. Too high a temperature can deform the polyurethane foam sheet, while too low a temperature will prevent the resin from curing properly and providing adhesion. Re-impregnation can easily cause the resin to bleed away, resulting in a poor yield. Furthermore, the curing temperature for rigid foam is 80℃~120℃, and the time is 2h~4h. The long curing time of rigid foam leads to a long production cycle and high costs. The foaming material of rigid foam contains isocyanates, which pose a threat to human health and safety, and its inability to be recycled causes environmental damage. Furthermore, rigid foam is made of brittle materials, which are prone to aging, crumbling, and difficult to handle. Summary of the Invention
[0005] This application provides a method for preparing a composite absorbing material, the composite absorbing material itself, and a rail vehicle.
[0006] According to a first aspect of the embodiments of this application, a method for preparing a composite microwave absorbing material is provided, comprising:
[0007] Mix 50%-80% polypropylene, 20%-30% flame retardant, 5%-10% antioxidant, 1%-5% powdered superconducting carbon nanotubes, and 1%-10% nickel-plated calcium silicate by weight.
[0008] The mixed materials are melted and plasticized into granules using a twin-screw extruder;
[0009] The granular material is foamed to obtain foamed granules;
[0010] The foamed particles are pre-compressed and then dried to obtain the microwave absorbing material.
[0011] The microwave absorbing material and polyurethane are placed into a mold to form a shape;
[0012] The molding material is immersed in absorbent slurry and then dried to obtain composite microwave absorbing material.
[0013] According to a second aspect of the embodiments of this application, a composite absorbing material is provided, which is prepared by the method described above.
[0014] According to a third aspect of the embodiments of this application, a partition wall is provided, comprising: a core material and a skin disposed on the outside of the core material, wherein the core material is a composite microwave absorbing material as described above.
[0015] According to a fourth aspect of the embodiments of this application, a rail vehicle is provided, including: the partition wall as described above.
[0016] The technical solution provided in this application involves mixing 50%-80% polypropylene, 20%-30% flame retardant, 5%-10% antioxidant, 1%-5% powdered superconducting carbon nanotubes, and 1%-10% nickel-plated calcium silicate by weight. The mixed material is then melted and plasticized into granules using a twin-screw extruder. The granules are foamed to obtain foamed granules. These foamed granules are pre-pressed and then dried to obtain a microwave absorbing material. The microwave absorbing material and polyurethane are placed in a mold to form a composite microwave absorbing material. The formed material is then impregnated in an absorbent slurry and dried to obtain a composite microwave absorbing material. This composite microwave absorbing material has a wide operating frequency band, good toughness, is not prone to aging during long-term operation, and is easy to handle. It is also non-toxic, harmless, flame-retardant, and contains no heavy metals, resulting in superior environmental performance. Furthermore, the preparation method provided in this embodiment has a short cycle time, reduces material molding conditions, and improves production efficiency while lowering manufacturing costs. Attached Figure Description
[0017] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:
[0018] Figure 1 is a flowchart of the preparation method of the composite microwave absorbing material provided in the embodiment of this application;
[0019] Figure 2 is a process flow diagram of the preparation method of the composite absorbing material provided in the embodiment of this application. Detailed Implementation
[0020] To make the technical solutions and advantages of the embodiments of this application clearer, the exemplary embodiments of this application will be described in further detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not an exhaustive list of all embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.
[0021] This embodiment provides a method for preparing a composite microwave absorbing material. This material can be used to manufacture partition panels, possessing a certain strength and strong microwave absorption capacity, good vibration reduction and noise reduction effects, and is environmentally friendly and does not pollute the environment. Such partition panels can be used in various buildings, such as factory workshops and simple houses; they can also be used in rail vehicles as partitions for toilets, electrical cabinets, and luggage storage racks.
[0022] As shown in Figures 1 and 2, the method for preparing the composite absorbing material provided in this embodiment includes:
[0023] Step 101: Mix 50%-80% polypropylene, 20%-30% flame retardant, 5%-10% antioxidant, 1%-5% powdered superconducting carbon nanotubes, and 1%-10% nickel-plated calcium silicate by weight.
[0024] Step 102: The mixed materials are melted and plasticized into granules using a twin-screw extruder.
[0025] Step 103: Foam the granular material to obtain foamed granules.
[0026] Step 104: Pre-press the foamed particles into shape, and then dry them to obtain the microwave absorbing material.
[0027] Step 105: Place the microwave absorbing material and polyurethane into the mold to form a shape.
[0028] Step 106: Immerse the molding material in the absorbent slurry and dry it to obtain the composite microwave absorbing material.
[0029] The above solution uses microwave absorbing material as the matrix, fills it with polyurethane, and after curing, forms a composite microwave absorbing material with good toughness, environmental friendliness, and a wider operating frequency band.
[0030] This embodiment provides a specific implementation method:
[0031] Step 101 above can be performed in the following manner:
[0032] First, place the granular superconducting carbon nanotubes into a grinder and grind them into powder particles of a preset diameter. The preset diameter can be around 30 nanometers.
[0033] Then, nickel sulfate, sodium hypophosphite, and sodium citrate dihydrate are dissolved in distilled water, and the activated calcium silicate is added to the solution to obtain nickel-plated calcium silicate.
[0034] Next, preheat the mixer to approximately 120°C. Add 50%-80% polypropylene, 20%-30% flame retardant, 5%-10% antioxidant, 1%-5% powdered superconducting carbon nanotubes, and 1%-10% nickel-plated calcium silicate by weight to the mixer and stir at high speed for about 30 minutes until homogeneous. Conductive color masterbatch can also be added during this process.
[0035] Specifically, step 102 involves placing the mixed material from step 101 into a twin-screw extruder to fully disperse and plasticize the mixed material at a preset temperature, which can be around 190°C.
[0036] The mixed material is extruded through a die to a diameter of approximately 1 mm. It is then cut into uniform granules, each about 1 mm long, using a high-precision cutter. Finally, a vibrating screen filters out any granules that are too short, yielding high-polymer polypropylene (PP) particles.
[0037] Step 103 above specifically involves: placing the granular material (i.e., PP particles) obtained in step 102 into a reactor, controlling the temperature inside the reactor at approximately 140°C, introducing carbon dioxide into the reactor, and foaming under a preset pressure, followed by instantaneous depressurization to the atmosphere to obtain foamed particles. The preset pressure can be 4.5 MPa, and the foaming ratio is 15 times.
[0038] Step 104 above specifically involves: placing the material foamed in the reactor in step 103 into a pre-compression tank for pre-compression, and forming it into a microwave absorbing frame using high-pressure steam at a pressure of 4 MPa for 12 hours. Then, the pre-compressed microwave absorbing material is placed in an oven for drying at approximately 80°C for 2 hours to obtain a dry microwave absorbing material.
[0039] Nickel-plated calcium silicate can withstand high temperatures of 1540℃, which can enhance the toughness of foamed products, improve tensile strength, and make the products less prone to aging. Nickel-plated calcium silicate itself is conductive, and when combined with conductive masterbatch and superconducting carbon nanotubes, it can form a material with better conductivity, which plays a positive role in improving the material's wave absorption and broadening the operating frequency band of the wave absorbing material.
[0040] In addition, carbon dioxide foaming is used without adding any foaming agent, thus avoiding the use of toxic foaming agents. Generally, foaming agents can also weaken the flame retardant effect, so this implementation method is more environmentally friendly.
[0041] Specifically, step 105 involves placing the pre-formed microwave absorbing material obtained in step 104 into a microwave absorbing structure mold and applying a release agent. Then, polyurethane is poured into the microwave absorbing structure mold for foaming at a temperature of approximately 25°C, resulting in a microwave absorbing foamed polypropylene (EPP) / polyurethane composite microwave absorbing material.
[0042] Before or after step 105, a step of preparing the absorbent slurry is also included, specifically: weighing a certain mass of conductive carbon black, carbon nanotube powder, and modified epoxy resin, and pouring them into plasma water and stirring thoroughly to obtain the absorbent slurry. The mass ratio of the total mass of conductive carbon black, carbon nanotube powder, and modified epoxy resin to the mass of plasma water is 5:1. For example, the total mass of conductive carbon black, carbon nanotube powder, and modified epoxy resin is 1 kg, and the plasma water is 5 kg.
[0043] Step 106 above specifically involves: immersing the molding material (i.e., the microwave-absorbing EPP / polyurethane composite material) in the absorbent slurry, then drying it at 100℃-120℃, repeating this process three times to solidify the absorbent slurry, ultimately obtaining the composite microwave-absorbing material. The composite material improves the operating frequency range of the microwave-absorbing material, and due to the presence of EPP, the overall material exhibits superior toughness, is less prone to aging, and is easier to install or transport.
[0044] The conventional performance test results of the composite absorbing material obtained by the above steps are shown in the table below:
[0045] The test data shows that the microwave absorbing EPP / polyurethane composite material obtained in this embodiment is lightweight, temperature resistant, anti-aging, tough, environmentally friendly, and has a wider operating frequency band. It can be installed in areas with large displacement, such as shielding doors and movable test probes.
[0046] The technical solution provided in this embodiment involves mixing 50%-80% polypropylene, 20%-30% flame retardant, 5%-10% antioxidant, 1%-5% powdered superconducting carbon nanotubes, and 1%-10% nickel-plated calcium silicate by weight. The mixed material is then melted and plasticized into granules using a twin-screw extruder. The granules are foamed to obtain foamed granules. These foamed granules are pre-pressed and then dried to obtain a microwave absorbing material. The microwave absorbing material and polyurethane are placed in a mold to form a composite microwave absorbing material. The formed material is then impregnated in an absorbent slurry and dried to obtain a composite microwave absorbing material. This composite microwave absorbing material has a wide operating frequency band, good toughness, is not prone to aging during long-term operation, and is easy to handle. It is also non-toxic, harmless, flame-retardant, and contains no heavy metals, resulting in superior environmental performance. Furthermore, the preparation method provided in this embodiment has a short cycle time, reduces material molding conditions, and improves production efficiency while lowering manufacturing costs.
[0047] Based on the above solutions, this embodiment also provides a composite absorbing material, which is prepared by any of the above methods and has the same technical effect as the above solutions.
[0048] The aforementioned composite wave-absorbing material can be used in partition panels, which include a core material and a skin disposed on the outside of the core material. The core material is made of the aforementioned composite wave-absorbing material. The partition panels can be used as partitions in buildings or vehicles, and have the same technical effects as the aforementioned composite wave-absorbing material.
[0049] This embodiment also provides a rail vehicle, including the aforementioned partition panel. The partition panel is installed inside the car to divide areas such as toilets, electrical cabinets, and luggage racks, and has the same technical effect as the aforementioned composite wave-absorbing material.
[0050] In the description of this application, it should be understood that the terms "front", "rear", "head", "tail", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.
[0051] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.
[0052] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," etc., should be interpreted broadly; taking connection as an example, it can be a direct connection or an indirect connection through an intermediate medium, and can be the internal connection of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.
[0053] Although some optional embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make further changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including some optional embodiments as well as all changes and modifications falling within the scope of this application.
[0054] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.
Claims
1. A method for preparing a composite wave-absorbing material, characterized in that, include: Mix 50%-80% polypropylene, 20%-30% flame retardant, 5%-10% antioxidant, 1%-5% powdered superconducting carbon nanotubes, and 1%-10% nickel-plated calcium silicate by weight. The mixed materials are melted and plasticized into granules using a twin-screw extruder; The granular material is foamed to obtain foamed granules; The foamed particles are pre-compressed and then dried to obtain the microwave absorbing material. The microwave absorbing material and polyurethane are placed into a mold to form a shape; The molding material is immersed in absorbent slurry and then dried to obtain composite microwave absorbing material.
2. The production method according to claim 1, characterized by, A mixture is prepared by mixing 50%-80% polypropylene, 20%-30% flame retardant, 5%-10% antioxidant, 1%-5% powdered superconducting carbon nanotubes, and 1%-10% nickel-plated calcium silicate by weight, comprising: The granular superconducting carbon nanotubes are placed in a grinder and ground into powder particles of a preset diameter. Nickel-plated calcium silicate is prepared by dissolving nickel sulfate, sodium hypophosphite, and sodium citrate dihydrate in distilled water, and then adding activated calcium silicate into the solution. Preheat the mixer, then add 50%-80% polypropylene, 20%-30% flame retardant, 5%-10% antioxidant, 1%-5% powdered superconducting carbon nanotubes, and 1%-10% nickel-plated calcium silicate by weight to the mixer and stir until the mixture is homogeneous.
3. The preparation method according to claim 2, characterized in that, The mixed materials are melted and plasticized into granules using a twin-screw extruder, including: The mixed materials are fed into a twin-screw extruder, where they are dispersed and plasticized at a preset temperature. The mixed material is extruded and cut into granules.
4. The production method according to claim 3, characterized by, Foaming granular materials yields foamed particles, including: Place the granular material into the reaction vessel; Carbon dioxide is introduced into the reactor and foamed under a preset pressure to obtain foamed particles.
5. The preparation method according to claim 4, characterized in that, The foaming ratio in the reactor is 15 times.
6. The production method according to claim 1, characterized by, Also includes: The preparation of the absorbent slurry includes: Conductive carbon black, carbon nanotube powder, and modified epoxy resin are poured into plasma water and stirred to obtain an absorbent slurry. The total mass ratio of conductive carbon black, carbon nanotube powder, and modified epoxy resin to plasma water is 5:
1.
7. The production method according to claim 6, characterized by, The molding material is immersed in an absorbent slurry and then dried, including: The molding material is immersed in the absorbent slurry; Dry at 100℃-120℃ for three times to solidify the absorbent slurry.
8. A composite wave-absorbing material, characterized in that, It is prepared by the method described in any one of claims 1-7.
9. A partition panel, characterized by include: The core material and the skin disposed on the outside of the core material, wherein the core material is the composite microwave absorbing material as described in claim 8.
10. A rail vehicle, characterized by include: The partition wall as described in claim 9.