Electromagnetic shielding composite material based on waste materials as well as preparation method and application of electromagnetic shielding composite material

Abstract

The invention discloses a waste material-based electromagnetic shielding composite material, a preparation method and application thereof, the composite material comprises the following raw materials: a waste polymer material, waste iron oxide powder, zinc oxide powder, manganese oxide powder, carbon nanotubes and a silane coupling agent; the electromagnetic shielding composite material is prepared by carrying out cleaning, crushing, grinding and step-by-step melting process treatment on the raw materials. According to the invention, high-valued cyclic utilization of the waste high polymer material and the waste iron oxide powder is realized, waste is turned into wealth, and environmental pollution is reduced. By adopting clean crushing, zirconium oxide ball dry-method nanometer grinding and a specific step-by-step melting process, introduction of impurities is effectively avoided, the problem of agglomeration of inorganic filler in an organic matrix is solved, and the interface bonding force and the magnetic loss performance of the material are remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to an electromagnetic shielding composite material, in particular to an electromagnetic shielding composite material based on waste materials, a preparation method and applications thereof. BACKGROUND

[0002] With the continuous development of the national economy and the acceleration of industrialization, the ultra-clean emission requirements of the environmental protection industry have promoted the rapid development of the core filter material industry, but a large amount of high molecular waste has accumulated in the production process, mainly the head and tail excess materials generated during the cutting of the filter material from the semi-finished product to the finished product. At the same time, the steel industry also produces a large amount of iron oxide powder (commonly known as iron scale) during the rolling of steel plates. Although these powders contain oil stains, silicon dioxide, manganese oxide and other impurities, they are essentially reusable industrial by-products. In the current era of pursuing high-quality development and building "new quality productivity", these waste materials have high recycling value. If they are properly purified and pretreated, they can be used as high-quality raw materials for preparing ferrite composite materials, realizing the recycling of resources from waste to treasure.

[0003] However, the existing treatment methods for the above-mentioned waste filter materials and iron oxide powder mainly rely on industrial garbage collection and incineration. This extensive treatment method not only consumes energy, but also produces new dust pollution, which cannot meet the requirements of green low-carbon and circular economy. On the other hand, in specific workplace or group meeting scenarios, there is a rigid demand for shielding mobile phone signals to prevent sudden noise interference and ensure the seriousness of the meeting. However, the current market mobile phone shielding box or shielding cabinet technology is mainly oriented towards high security, integrating complex functions such as ultrasonic anti-recording, wireless charging and active cooling. The high-end materials and complex process of such products result in high costs, and the functional design far exceeds the basic needs of "silence and order" in general situations, causing complex operation and resource waste, making it difficult to be widely popularized and applied in ordinary workplaces and public scenarios. SUMMARY

[0004] The technical problem to be solved by the present application is to provide an electromagnetic shielding composite material based on waste materials, a preparation method and applications thereof, which solves the problems of waste of existing high molecular material waste and steel industry waste.

[0005] The technical problem to be solved by the present application is solved by the following technical solution: The present application provides an electromagnetic shielding composite material based on waste materials, which raw materials include waste high molecular materials, waste iron oxide powder, zinc oxide powder, manganese oxide powder, carbon nanotubes and silane coupling agent. The electromagnetic shielding composite material is prepared by cleaning, crushing, grinding and step-by-step fusion and blending process of the above raw materials.

[0006] As a preferred technical scheme of the present application, the raw materials include, in parts by weight: 2-3 parts of waste high molecular material; 5-7 parts of waste iron oxide powder; 0.8-1.2 parts of zinc oxide powder; 0.4-0.6 parts of manganese oxide powder; the addition amount of the carbon nanotube is 0.2%-0.4% of the mass of the waste high molecular material; the addition amount of the silane coupling agent is 0.3%-0.7% of the total mass of the inorganic powder; and the waste high molecular material is selected from the excess high molecular polyethylene produced in the process of filtering material.

[0007] As a preferred technical scheme of the present application, the waste iron oxide powder, zinc oxide powder and manganese oxide powder are dispersed in the electromagnetic shielding composite material in a nanoscale, and the particle size range is 600-800 nm; and the waste iron oxide powder is a product obtained after purification of the iron oxide powder produced in the process of rolling steel.

[0008] As a preferred technical scheme of the present application, the thickness of the electromagnetic shielding composite material is 0.8-1.2 mm.

[0009] The present application provides a preparation method of the electromagnetic shielding composite material based on waste materials. S1, preparing organic premix: cleaning, crushing and grinding and screening the waste high molecular material, and performing organic pre-fusion with the carbon nanotube and part of the silane coupling agent to obtain the organic premix; S2, preparing inorganic premix: performing purification and drying treatment on the waste iron oxide powder, and performing nano-grinding with the zinc oxide powder and the manganese oxide powder, and then adding the remaining silane coupling agent to perform inorganic pre-fusion to obtain the inorganic premix; S3, final fusion: mixing the organic premix and the inorganic premix to perform final mixing and fusion to obtain the composite powder; S4, forming: placing the composite powder in a mold to perform forming treatment; S5, obtaining the sheet.

[0010] As a preferred technical scheme of the present application, in step S1, the S12 grinding and screening is repeatedly grinding the waste high molecular material to a particle size less than 10 μm; and the S13 organic pre-fusion is mixing the treated waste high molecular material with the carbon nanotube at a rotation speed of 110-130 r / min for 10-20 minutes.

[0011] As a preferred technical scheme of the present application, in step S2: the S21 purification drying is to pass the waste oxidized iron powder through a 200-300 mesh sieve and dry at 80-120 DEG C for 2-4 hours; the S22 nanometer grinding is to use zirconium oxide balls as grinding medium for dry grinding until the powder particle size reaches 600-800 nm; the S23 inorganic pre-fusion is to first mix and disperse the inorganic powder, and then add silane coupling agent and mix for 8-12 minutes.

[0012] As a preferred technical scheme of the present application, the forming treatment in step S4 is selected from a first process or a second process: The first process is a sintering forming method, the composite powder is loaded into a mold, and sintering is carried out at a temperature of 250-260 DEG C for 1.5-2.5 hours, and the mold is opened after cooling to 45-55 DEG C; The second process is a solidification forming method, the composite powder is mixed with unsaturated polyester powder and methyl ethyl ketone peroxide initiator, loaded into a mold, and heated and solidified at a temperature of 100-150 DEG C.

[0013] The present application also provides an application of the electromagnetic shielding composite material based on waste materials, based on the aforementioned electromagnetic shielding composite material based on waste materials or the preparation method of the electromagnetic shielding composite material based on waste materials, the application is to prepare the electromagnetic shielding composite material into an electromagnetic shielding sheet or an electromagnetic shielding lining for the manufacture of a mobile phone signal shielding device.

[0014] Preferably, the electromagnetic shielding lining is arranged on the inner cavity bottom, the periphery and the inner wall of the cover of the metal shielding box in a pasting or sleeving manner, and the inner cavity bottom of the metal shielding box is further provided with a base for placing a mobile phone.

[0015] The present application has the advantages that: the present application realizes the high-value recycling of waste polymer materials and waste oxidized iron powder, turns waste into treasure, and reduces environmental pollution. By adopting clean crushing, zirconium oxide ball dry nanometer grinding and a special step-by-step fusion process, the introduction of impurities is effectively avoided, the agglomeration problem of inorganic fillers in the organic matrix is solved, and the interface bonding force and magnetic loss performance of the material are significantly improved. The electromagnetic shielding composite material prepared has excellent wave absorption performance, and the electromagnetic wave absorption rate of 5G, 6G and WiFi frequency bands is greater than 99%. In addition, the finished product of the present application has simple structure, low cost and convenient use, effectively solves the bottleneck of difficult popularization of existing shielding devices, and has significant environmental and economic benefits. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 It is a process flow diagram of the present application; Figure 2 It is a wave absorption test chart before forming of the present application; Figure 3 a chart of interference capability test data of the shielding box prepared from the sheet of the present application; Figure 4 a chart of interference capability test data of the shielding box prepared from the sheet of the present application. DETAILED DESCRIPTION

[0017] The preferred embodiments of the present application are described below in conjunction with the accompanying drawings, it should be understood that the preferred embodiments described herein are only used to illustrate and explain the present application, and are not used to limit the present application.

[0018] Embodiment 1 The present embodiment provides an electromagnetic shielding composite material based on waste materials, the raw materials of which include waste polymer materials, waste iron oxide powder, zinc oxide powder, manganese oxide powder, carbon nanotubes and silane coupling agent; the electromagnetic shielding composite material is prepared by cleaning, crushing, grinding and step-by-step fusion and compounding process of the above raw materials.

[0019] The raw materials include, by weight fraction, 2-3 parts of waste polymer materials; 5-7 parts of waste iron oxide powder; 0.8-1.2 parts of zinc oxide powder; 0.4-0.6 parts of manganese oxide powder; the addition amount of the carbon nanotubes is 0.2%-0.4% of the mass of the waste polymer materials; the addition amount of the silane coupling agent is 0.3%-0.7% of the total mass of the inorganic powder; the waste polymer materials are selected from the excess high molecular polyethylene produced in the process of filtering materials.

[0020] The waste iron oxide powder, zinc oxide powder and manganese oxide powder are dispersed in the electromagnetic shielding composite material in nanoscale, and the particle size range is 600-800 nm; the waste iron oxide powder is the product after purification of the iron oxide powder produced by rolling steel.

[0021] The thickness of the electromagnetic shielding composite material is 0.8-1.2 mm.

[0022] Specifically, in the present embodiment, specific values within the above range are selected for proportioning: the waste polymer materials are taken as 2.5 parts, the waste iron oxide powder is taken as 6 parts, the zinc oxide powder is taken as 1 part, and the manganese oxide powder is taken as 0.5 part; the addition amount of the carbon nanotubes is 0.3% of the mass of the waste polymer materials, and the addition amount of the silane coupling agent is 0.5% of the total mass of the inorganic powder. The electromagnetic shielding composite material thus prepared is a new composite material using waste polymer and iron oxide to compound magnetic materials such as carbon nanotubes, and the thickness thereof is preferably 1 mm. The material has significant wave absorption or scattering characteristics, and can absorb more than 99% of electromagnetic waves of different frequency bands such as 5G / 6G, WiFi and automatic driving radar in cooperation with a metal shell.

[0023] Embodiment 2 As Figure 1 shown, the embodiment provides a preparation method of an electromagnetic shielding composite material based on waste materials, for preparing an electromagnetic shielding composite material based on waste materials in Embodiment 1, comprising the following steps: S1 Preparation of organic premix: S11 cleaning, crushing and S12 grinding and screening treatment are performed on the waste polymer materials, and S13 organic pre-fusion is performed with carbon nanotubes and part of the silane coupling agent to obtain an organic premix; S2 Preparation of inorganic premix: S21 purification and drying treatment is performed on the waste iron oxide powder, and S22 nano-grinding is performed with zinc oxide powder and manganese oxide powder, followed by S23 inorganic pre-fusion with the remaining silane coupling agent to obtain an inorganic premix; S3 Final fusion: the organic premix and the inorganic premix are combined for final mixing and fusion to obtain a composite powder; S4 Forming: the composite powder is placed in a mold for forming treatment; S5 Sheet obtained.

[0024] In step S1, the S12 grinding and screening is repeatedly grinding the waste polymer materials to a particle size of less than 10 μm; the S13 organic pre-fusion is mixing the treated waste polymer materials with carbon nanotubes at a speed of 110-130 r / min for 10-20 minutes.

[0025] In step S2: the S21 purification and drying is passing the waste iron oxide powder through a 200-300 mesh screen and drying at 80-120°C for 2-4 hours; the S22 nano-grinding is dry grinding using zirconia balls as grinding media until the powder particle size reaches 600-800 nm; the S23 inorganic pre-fusion is first mixing and dispersing the inorganic powder, then adding the silane coupling agent and mixing for 8-12 minutes.

[0026] The forming treatment in step S4 is selected from a first process or a second process: First process: sintering forming method, the composite powder is loaded into a mold, sintered at a temperature of 250-260°C for 1.5-2.5 hours, and cooled to 45-55°C to open the mold; Second process: curing forming method, the composite powder is mixed with unsaturated polyester powder and methyl ethyl ketone peroxide initiator, loaded into a mold, and heated and cured at a temperature of 100-150°C.

[0027] Specifically, in this embodiment, specific process parameters within the above range are selected for preparation: In step S1, the mixing speed of the organic pre-fusion in S13 is selected as 120 r / min, and the mixing time is selected as 15 minutes. In step S2, the mixing time after adding the silane coupling agent in the inorganic pre-fusion in S23 is selected as 10 minutes. In step S3, the final mixing and melting time is selected as 20 minutes. In step S4, if the first process (sintering molding method) is used, the sintering temperature is precisely controlled at 252 ℃, the isothermal sintering time is 2 hours, and the mold is opened when cooled to 50 ℃ after being taken out of the furnace; if the second process (curing molding method) is used, it is preferable to heat and cure at a temperature of 120 ℃.

[0028] The preparation method in this embodiment employs a unique "dual-path parallel pretreatment + step-by-step fusion" process logic. This involves parallel processing of the clean grinding of waste polymer materials and the purification and nano-sizing of waste iron oxide powder, followed by "organic pre-fusion" and "inorganic pre-fusion" respectively, before final merging and shaping. The core advantage of this process lies in effectively solving the problems of easy agglomeration of inorganic fillers and poor interfacial bonding when mixing multi-component waste materials. This is because, on the one hand, dry nano-grinding using zirconia balls avoids the introduction of impurities and ensures that the magnetic powder particle size is controlled within 600-800 nm; on the other hand, by adding silane coupling agents step-by-step, their inorganic ends first bind with the hydroxyl groups on the surface of iron oxide and zinc oxide to improve dispersibility, and then their organic ends entangle with the polymer chains to enhance interfacial adhesion. Figure 2 As shown, the material treated with this process exhibits significant wave absorption performance (continuously decreasing reflectivity) in the 26.5-40GHz high-frequency band even before molding (in sheet form); for example... Figure 3 As shown, the material after molding and curing also maintains stable electromagnetic loss characteristics in the 6-18GHz frequency band, proving that the process successfully endows the waste material with excellent and wide-band electromagnetic shielding performance while retaining the characteristics of the waste material.

[0029] Example 3 This embodiment provides an application of an electromagnetic shielding composite material based on waste materials. Based on one of the electromagnetic shielding composite materials based on waste materials in Embodiment 1 or 2, the application involves preparing the electromagnetic shielding composite material into an electromagnetic shielding sheet or an electromagnetic shielding liner for use in the manufacture of mobile phone signal shielding equipment.

[0030] The electromagnetic shielding liner is attached to the bottom, sides, and inner wall of the lid of the metal shielding box by pasting or fitting. The bottom of the metal shielding box is also provided with a base for placing mobile phones.

[0031] Specifically, the mobile phone shielding device can be assembled using one of the following two methods: Method one is the adhesive method, where the electromagnetic shielding composite material sheet is cut to the dimensions of the inner cavity of the metal shielding box, evenly coated with adhesive, and then flatly attached to the inner wall of the box cover and the perimeter and bottom of the box cavity. After drying, the base is installed. Method two is the kitting method, where the pre-made electromagnetic shielding liner is directly kitted and fixed to the metal shielding box and box cover using dotted adhesive application. In use, simply place the mobile phone on the base and close the box cover to shield the signal. Figure 4 As shown, the interference protection effectiveness of the mobile phone shielding box manufactured using the above process was tested according to the DB45 / T 2588—2022 standard. The results show the measured value of the difference in field strength before and after interference. It is 13.5 dB, which is better than the Class 1 standard requirement. The rating is Level 1 (safe). This indicates that the shielding box can effectively block signal transmission between mobile phones and base stations, meeting the needs of meeting confidentiality and order maintenance.

[0032] This application provides an innovative technical solution that is not merely a simple material mixing process, but a rigorous closed-loop process system based on microstructure control. This system uses the component combination described in Example 1 as its material basis, the "dual-path step-by-step pre-fusion" process described in Example 2 as its core technology, and ultimately achieves excellent electromagnetic shielding applications through the specific assembly method described in Example 3.

[0033] Firstly, regarding the selection of raw materials and the synergistic mechanism (based on Example 1), this application breaks through the limitation of traditional electromagnetic shielding materials relying on high-purity and expensive raw materials, and innovatively proposes a resource utilization strategy of "turning waste into treasure". The waste polymer material we selected is not ordinary plastic, but specifically ultra-high molecular weight polyethylene (UHMWPE) residues generated from the processing of filter materials. This material itself has an extremely high molecular weight, which endows the matrix with excellent impact resistance and wear resistance, providing a solid mechanical skeleton for the composite material. As for the selection of magnetic fillers, we utilize waste iron oxide powder (iron scale) generated during the rolling process in the steel industry. Although these powders are often regarded as waste in industry, they are essentially iron oxide and have natural magnetic loss potential. In order to compensate for the shortcomings of single iron oxide in frequency response, this application cleverly introduces zinc oxide powder and manganese oxide powder. In the subsequent micro-dispersion, these three metal oxides (Fe-Zn-Mn system) essentially construct a composite system similar to soft magnetic ferrite, which can absorb electromagnetic waves through the resonance of magnetic domain walls and hysteresis loss. More importantly, to address the electromagnetic wave reflection problem caused by the insulation of the polymer matrix, this application introduces carbon nanotubes (CNTs). Carbon nanotubes not only have an extremely high aspect ratio, enabling them to build a highly efficient conductive network in the matrix and generate dielectric loss, but they can also form a dual absorption mechanism of "magnetic loss + dielectric loss" with the aforementioned magnetic oxides, thereby greatly broadening the absorption bandwidth of the material.

[0034] Secondly, to fully realize the potential of the aforementioned materials, this application has made profound technological innovations in the construction and pretreatment process of the micro-interface (based on stages S1 and S2 of Example 2). It is well known that waste materials often involve numerous impurities and wide particle size distributions, and direct mixing inevitably leads to poor performance. Therefore, this application introduces a rigorous cleaning, crushing, purification, and drying process. Specifically for inorganic powders, we employ a dry nano-grinding process using zirconia balls as the grinding medium. The ingenuity of this process design lies in: first, the zirconia balls possess extremely high hardness and wear resistance, avoiding the iron filings and impurities that may result from traditional steel ball grinding, ensuring the purity of the material; second, dry grinding avoids the complex drying and agglomeration problems associated with wet grinding; and third, through precise grinding control, the particle size of waste iron oxide, zinc oxide, and manganese oxide is forcibly unified within the 600-800 nm nanometer range. The nano-sized powder exhibits a dramatically increased specific surface area and enhanced surface atomic activity, which not only facilitates the scattering and absorption of electromagnetic waves at the micro-interface but also provides abundant reaction sites for subsequent coupling agent modification.

[0035] Furthermore, the core technical advantage of this application lies in its unique **"dual-path parallel pretreatment + step-by-step fusion" process logic (based on stages S13 and S23 of Example 2)**. Traditional composite material preparation often adopts a "one-pot" approach, that is, directly mixing all fillers and the matrix. This approach ignores the natural interfacial repulsion ("oleophobic and hydrophilic" properties) between organic materials (polymers, CNTs) and inorganic materials (oxides), which easily leads to the aggregation of inorganic fillers in the matrix, forming defect points and severely weakening the shielding performance. To solve this problem, this application designs two non-contradictory pre-fusion paths: First, organic pre-fusion (S13): We first mix the treated waste polymer powder with carbon nanotubes and a portion of silane coupling agent. In this process, the shear force generated by high-speed mixing (110-130 r / min) is used to pre-disperse carbon nanotubes on the surface of polymer particles, building a preliminary conductive framework and preventing the aggregation of extremely fine carbon nanotubes. Secondly, inorganic pre-fusion (S23): This is a crucial step. We separately mix the nano-sized inorganic oxide powder (Fe / Zn / Mn) with the remaining silane coupling agent. Here, the silane coupling agent acts as a "molecular bridge." Its inorganic affinity ends (such as hydrolyzed hydroxyl groups) are directionally adsorbed and bonded to the hydroxyl groups on the surfaces of iron oxide and zinc oxide, thereby modifying the surface properties of the inorganic powder from "hydrophilic" to "lipophilic." This targeted surface modification, if carried out in a large mixture, would easily be interfered with by other impurities, while separate pre-fusion ensures high efficiency and high coverage of the modification. When these two pretreated materials converge in the final fusion (S3) step, a remarkable chemical and physical synergy occurs: the organic functional groups of the coupling agent on the surface of the inorganic powder become physically entangled or chemically bonded to the polymer matrix segments, greatly enhancing the interfacial bonding force. This enhanced interfacial bonding directly eliminates microscopic voids, allowing electromagnetic waves to be transmitted more smoothly between the matrix and filler and converted into heat energy when they enter the material, rather than being simply reflected at the interface.

[0036] Regarding the selection of molding processes (based on stage S4 of Example 2), this application provides two flexible paths: sintering molding and curing molding, to adapt to different production conditions and cost requirements. The first process (sintering molding) utilizes the thermoplastic properties of ultra-high molecular weight polyethylene. By sintering at a constant temperature of 250-260°C, the surface of the polymer particles melts and bonds, tightly encapsulating the nano-magnetic filler between the crystal lattice. This physical sintering method does not introduce additional chemical crosslinking agents, maximizing the preservation of the dielectric properties of the raw materials, and producing sheets with good density and high mechanical strength. The second process (curing molding) introduces unsaturated polyester and an initiator (methyl ethyl ketone peroxide), utilizing chemical crosslinking curing at a low temperature (100-150°C). This method has the advantages of low energy consumption and fast molding speed, making it suitable for large-scale continuous production. Regardless of the molding method used, due to the perfect micro-dispersion in the preceding steps, the resulting sheets with a thickness of 0.8-1.2 mm exhibit excellent uniformity. Figure 2 The test data directly demonstrates this: in pre-molding tests, the material's reflectivity continuously decreased in the high-frequency band of 26.5-40GHz, exhibiting extremely strong wave absorption potential. Figure 3 This demonstrates that the material, after molding, forms a stable electromagnetic loss waveform in the 6-18GHz frequency band due to the increased density. This wide-band absorption capability (greater than 99%) is due to the synergistic effect of resistive loss, dielectric loss and magnetic loss in the multiphase composite material.

[0037] Finally, regarding specific application scenarios and performance verification (based on Example 3), this application goes beyond material preparation and proposes a complete manufacturing solution for mobile phone shielding equipment. We use the prepared electromagnetic shielding composite material as a liner, which is then tightly bonded to the inner cavity of the metal shielding box via adhesive or fitting.

[0038] This "metal outer shell + absorbing inner liner" structural design has profound physical significance: the metal outer shell acts as a reflective layer, blocking most external signals from entering; while the inner absorbing liner acts as an "electromagnetic wave black hole." Without this liner, the minute signals entering the box or the signals emitted by the phone itself would undergo multiple reflections and oscillations (i.e., cavity resonance) inside the metal box, leading to a decrease in shielding effectiveness or even failure. The composite material liner of this application can effectively absorb these residual electromagnetic waves, converting them into micro-heat dissipation.

[0039] Figure 4The test results strongly confirm the effectiveness of this design: Actual test data based on the DB45 / T 2588—2022 standard shows that the difference in field strength before and after interference with the shielding box reached 13.5 dB. This value not only exceeds the standard passing line of 12 dB but also reaches the Level 1 (safety) rating standard. This means that in practical use, regardless of whether it's 5G, WiFi, or other communication frequency bands, once placed in this shielding box, signal transmission will be effectively cut off, perfectly meeting the needs of meeting confidentiality and order maintenance. In summary, this application, through scientific material ratio (waste polymer + Fe / Zn / Mn oxide + CNT), precise micro-processing (zirconia nano-grinding), innovative process route (dual-path step-by-step pre-fusion), and reasonable structural design (metal + absorbing liner), successfully transforms industrial waste into a high-performance electromagnetic shielding product. This not only solves the environmental pollution problem of waste materials but also overcomes the pain point of the difficulty in promoting existing shielding equipment with a low-cost and simple solution, achieving a high degree of unity between environmental, economic, and social benefits.

[0040] This invention achieves high-value recycling of waste polymer materials and waste iron oxide powder, turning waste into treasure and reducing environmental pollution. By employing clean crushing, dry nano-grinding with zirconia balls, and a unique stepwise blending process, the introduction of impurities is effectively avoided, solving the problem of inorganic filler agglomeration in an organic matrix, and significantly improving the interfacial bonding strength and magnetic loss performance of the material. The resulting electromagnetic shielding composite material exhibits excellent wave absorption performance, with an absorption rate of over 99% for electromagnetic waves in the 5G, 6G, and WiFi frequency bands. Furthermore, the finished product of this invention has a simple structure, low cost, and is easy to use, effectively solving the bottleneck of the difficulty in promoting existing shielding equipment, and possessing significant environmental and economic benefits.

[0041] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention, all of which fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. An electromagnetic shielding composite material based on waste materials, characterized in that, Its raw materials include waste polymer materials, waste iron oxide powder, zinc oxide powder, manganese oxide powder, carbon nanotubes, and silane coupling agents; the electromagnetic shielding composite material is obtained by processing the above raw materials through cleaning, crushing, grinding, and step-by-step melting processes.

2. The electromagnetic shielding composite material based on waste materials according to claim 1, characterized in that, The raw materials, by weight, include: 2-3 parts of waste polymer material; 5-7 parts of waste iron oxide powder; 0.8-1.2 parts of zinc oxide powder; 0.4-0.6 parts of manganese oxide powder; the amount of carbon nanotubes added is 0.2%-0.4% of the mass of the waste polymer material; the amount of silane coupling agent added is 0.3%-0.7% of the total mass of the inorganic powder; the waste polymer material is selected from ultra-high molecular weight polyethylene residues generated from the processing of filter materials.

3. The electromagnetic shielding composite material based on waste materials according to claim 1, characterized in that, The waste iron oxide powder, zinc oxide powder, and manganese oxide powder are dispersed in the electromagnetic shielding composite material at the nanoscale, with a particle size range of 600-800 nm; the waste iron oxide powder is a product of purified iron oxide powder produced by steel rolling.

4. The electromagnetic shielding composite material based on waste materials according to claim 1, characterized in that, The thickness of the electromagnetic shielding composite material is 0.8-1.2 mm.

5. A method for preparing an electromagnetic shielding composite material based on waste materials, used to prepare an electromagnetic shielding composite material based on waste materials as described in any one of claims 1-4, characterized in that, Includes the following steps: S1 Preparation of Organic Premix: Waste polymer materials are cleaned, crushed, ground and sieved using S11 and S12 respectively, and then organically pre-fused with carbon nanotubes and some silane coupling agents using S13 to obtain organic premix. S2 Preparation of Inorganic Premix: Waste iron oxide powder is purified and dried by S21, and then nano-grinded with zinc oxide powder and manganese oxide powder by S22. Subsequently, the remaining silane coupling agent is added for S23 inorganic pre-fusion to obtain inorganic premix. S3 Final Fusion: The organic premix and the inorganic premix are combined and finally mixed to obtain composite powder; S4 Molding: The composite powder is placed in a mold for molding process; S5 sheet material was obtained.

6. The method for preparing an electromagnetic shielding composite material based on waste materials according to claim 5, characterized in that, In step S1, S12 grinding and sieving involves repeatedly grinding the waste polymer material until the particle size is less than 10 μm; S13 organic pre-fusion involves mixing the treated waste polymer material with carbon nanotubes at a speed of 110-130 r / min for 10-20 minutes.

7. The method for preparing an electromagnetic shielding composite material based on waste materials according to claim 5, characterized in that, In step S2: S21 purification and drying involves passing the waste iron oxide powder through a 200-300 mesh sieve and drying it at 80-120℃ for 2-4 hours; S22 nano-grinding involves dry grinding using zirconia balls as the grinding medium until the powder particle size reaches 600-800nm; S23 inorganic pre-fusion involves first mixing and dispersing the inorganic powder, and then adding a silane coupling agent and mixing for 8-12 minutes.

8. The method for preparing an electromagnetic shielding composite material based on waste materials according to claim 5, characterized in that, The molding process described in step S4 is selected from either the first process or the second process: First process: sintering molding method, the composite powder is loaded into a mold and sintered at a constant temperature of 250-260℃ for 1.5-2.5 hours, and then cooled to 45-55℃ to open the mold; The second process is the curing and molding method, in which the composite powder is mixed with unsaturated polyester powder and methyl ethyl ketone peroxide initiator, loaded into a mold, and heated and cured at a temperature of 100-150°C.

9. An application of an electromagnetic shielding composite material based on waste materials, based on an electromagnetic shielding composite material based on waste materials as described in any one of claims 1 to 8 or a method for preparing the same, characterized in that, The application involves preparing the electromagnetic shielding composite material into electromagnetic shielding sheets or electromagnetic shielding liners for use in the manufacture of mobile phone signal shielding equipment.

10. The application of an electromagnetic shielding composite material based on waste materials according to claim 9, characterized in that, The electromagnetic shielding liner is attached to the bottom, sides, and inner wall of the metal shielding box by pasting or fitting. The bottom of the metal shielding box is also provided with a base for placing a mobile phone.

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