A method for preparing a sandwich-structured electromagnetic shielding composite material

Abstract

A method for preparing a sandwich-structured electromagnetic shielding composite material includes the following steps: Step 1, preparing raw materials including carbon cloth, carbon paper, copper wire, N,N-dimethylformamide, 4,4'-diaminodiphenyl ether, bisphenol A type diether dianhydride, and Ketjen black; Step 2, sewing the sandwich-structured fabric; Step 3, preparing a polyetheramic acid / Ketjen black composite sol; Step 4, coating the sandwich-structured fabric with the polyetheramic acid / Ketjen black composite sol; Step 5, performing drying and thermal imidization treatment; Step 6, hot pressing using a hot press; Through copper wire sewing and adhesive coating, the components of the composite material are more tightly bonded, and the composite material has a high electromagnetic shielding efficiency, up to 70.14 dB, exhibiting excellent electromagnetic shielding effect.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic shielding materials technology, and specifically relates to a method for preparing a sandwich-structured electromagnetic shielding composite material. Background Technology

[0002] In recent years, with the widespread application of electronic technology and equipment across various industries, electromagnetic waves, as an important carrier of information transmission, have become ubiquitous in all aspects of life. However, as wireless electronic devices develop towards intelligence, high frequency, and multifunctionality, these devices inevitably generate electromagnetic radiation of different frequencies during operation, leading to a series of serious social and environmental problems. Electromagnetic interference (EMI) pollution from both natural and artificial electronic devices has attracted worldwide attention, as this pollution not only causes malfunctions in sensitive electronic equipment but also adversely affects human health. Strong electromagnetic radiation can disrupt the central nervous system, causing dizziness, insomnia, and memory decline. More seriously, those working in environments with prolonged exposure to high-energy radiation, such as those repairing and maintaining high-voltage electronic equipment, may experience problems with their blood, lymphatic system, and brain nerves, and may even develop cancer.

[0003] To eliminate these negative effects, researchers have dedicated decades to developing high-performance EMI shielding materials. Metals and their composites, due to their excellent conductivity, are widely used in electromagnetic protection. For certain specialized applications, metals can generate an electric field under the influence of high-frequency electromagnetic fields, thereby attenuating the electromagnetic wave energy generated by electronic devices and achieving electromagnetic shielding. However, with the increasing demands for lightweight, intelligent, flexible, and miniaturized smart devices, the poor corrosion resistance, high density, poor mechanical flexibility, and poor processability of metals lead to a decline in material structural integrity and a loss of electromagnetic shielding performance, limiting their further application. Furthermore, the high conductivity of metals causes electromagnetic waves to be reflected multiple times on the metal surface, severely causing secondary electromagnetic pollution, which no longer meets the growing demands for electromagnetic protection. Fabrics, due to their good flexibility and ease of processing, are one option for electromagnetic shielding materials. Using fabric as a base, applying highly conductive materials to the fabric surface through impregnation, coating, or other methods can impart good electromagnetic shielding performance to the material. However, the electromagnetic shielding function of the above materials still needs to be further improved. Furthermore, the lack of effective bonding between the conductive material and the fabric makes it easy for the conductive material to detach from the fabric surface during use, thereby reducing the electromagnetic shielding effectiveness of the material. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention aims to provide a method for preparing a sandwich structure electromagnetic shielding composite material with high electromagnetic shielding effectiveness.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a sandwich-structured electromagnetic shielding composite material includes the following steps:

[0007] Step 1, prepare the following raw materials: including carbon cloth, carbon paper, copper wire, N,N-dimethylformamide, 4,4'-diaminodiphenyl ether, bisphenol A type diether dianhydride, and Ketjen Black;

[0008] Step 2, sewing the sandwich-structured fabric;

[0009] Step 3: Prepare polyetheramic acid / Ketjen black composite sol;

[0010] Step 4: Coat the sandwich structure fabric with polyetheramic acid / Ketjen black composite sol;

[0011] Step 5: Drying and thermal imidization;

[0012] Step 6: Perform hot pressing using a hot press.

[0013] In step 2, the sandwich structure fabric is sewn by stitching two layers of carbon cloth and a layer of carbon paper sandwiched between the carbon cloths with copper wire to form a sandwich structure.

[0014] In step 3, the polyetheramic acid / Ketjen black composite sol is prepared by in-situ polymerization. The specific steps are as follows:

[0015] 1.5 g of 4,4'-diaminodiphenyl ether was dissolved in 10-15.5 mL of N,N-dimethylformamide to obtain a 4,4'-diaminodiphenyl ether dispersion. Ketjen black was dissolved in 9-11 mL of N,N-dimethylformamide and magnetically stirred for 12 h to obtain a Ketjen black / N,N-dimethylformamide solution. The obtained Ketjen black / N,N-dimethylformamide solution was added to the 4,4'-diaminodiphenyl ether dispersion and sonicated until fully dissolved to obtain a composite solution. Then, 4.02 g of bisphenol A type diether dianhydride was added to the solution and mechanically stirred for 2-3 h to finally obtain a polyetheramic acid / Ketjen black composite sol.

[0016] The Ketjen black comprises 5-10 wt% of the total solids content.

[0017] The solid content of the polyetheramic acid / Kejtien black composite sol is 18-23 wt%.

[0018] The Ketjen black is to be acid-treated at 90°C for 12 hours using a hydrothermal method, then filtered until neutral and dried.

[0019] The bisphenol A type diether dianhydride was prepared by dividing it into four equal parts, adding each part slowly at 30-minute intervals.

[0020] Step 5, drying, refers to transferring the glued sandwich structure fabric to a precision high-temperature drying oven for drying at 80°C for 5 hours.

[0021] Step 5, thermal imidization, specifically involves further treating the dried sandwich structure fabric at 150℃, 200℃, 250℃, and 300℃ for 1 hour each.

[0022] In step 6, the hot pressing conditions are as follows: hot pressing temperature is 180-200℃, pressure is 15-18 MPa, and time is 25-35 min.

[0023] The beneficial effects of this invention are:

[0024] Compared with existing technologies, this invention constructs a sandwich structure by stitching conductive carbon cloth and carbon paper together with conductive copper wires, thus possessing characteristics such as a conductive three-dimensional network, multiple reflections, and interface loss. Simultaneously, by coating the material surface with a conductive composite sol and performing thermal imidization and hot pressing treatments, the conductive loss of the composite material is further enhanced, and the adhesion between the components of the composite material is also improved, solving the problem of easy detachment of layered materials. Through the above treatments, the sandwich structure electromagnetic shielding composite material finally obtained by this invention maintains a uniform and compact structure while possessing high electromagnetic shielding effectiveness. A significant portion of the electromagnetic shielding effectiveness in the 8.2-12.4 GHz frequency range is above 50 dB, with a maximum reaching 70.14 dB, demonstrating excellent electromagnetic shielding performance and applicability in various practical applications. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating the preparation process of the sandwich-structured electromagnetic shielding composite material of the present invention.

[0026] Figure 2 This is a physical image of the sandwich structure electromagnetic shielding composite material obtained in Embodiment 1 of the present invention.

[0027] Figure 3 This is a cross-sectional scanning electron microscope image of the sandwich-structured electromagnetic shielding composite material obtained in Example 1 of the present invention.

[0028] Figure 4 This is a graph showing the electromagnetic shielding effectiveness of the sandwich-structured electromagnetic shielding composite material obtained in Example 1 of the present invention as a function of frequency. Detailed Implementation

[0029] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Example

[0030] A method for preparing a sandwich-structured electromagnetic shielding composite material includes the following steps:

[0031] Step 1, prepare the following raw materials: including carbon cloth, carbon paper, copper wire, N,N-dimethylformamide, 4,4'-diaminodiphenyl ether, bisphenol A type diether dianhydride, and Ketjen Black;

[0032] Step 2: Sew two layers of carbon cloth and a layer of carbon paper sandwiched between the carbon cloths together with copper wire to obtain a sandwich structure fabric.

[0033] Step 3: Dissolve 1.5g of 4,4'-diaminodiphenyl ether in 14.55mL of N,N-dimethylformamide to obtain a 4,4'-diaminodiphenyl ether dispersion;

[0034] Weigh 0.61g of Ketjenblack powder, which accounts for 10wt% of the total solid content. To prepare the polyetheramic acid / Ketjenblack composite sol, the solid content should be 20wt%.

[0035] Ketjen black powder was subjected to acid treatment at 90°C for 12 hours by hydrothermal method, then filtered until neutral and dried. The dried powder was then dissolved in 10 mL of N,N-dimethylformamide and magnetically stirred for 12 hours to obtain a Ketjen black / N,N-dimethylformamide solution.

[0036] The obtained Ketjen black / N,N-dimethylformamide solution was added to a 4,4'-diaminodiphenyl ether dispersion and sonicated until fully dissolved to obtain a composite solution. Then, 4.02 g of bisphenol A type diether dianhydride was weighed and added to the composite solution in four equal portions in four slow additions, with an interval of 30 min between each addition and mechanical stirring for 2.5 h, finally obtaining polyetheramic acid / Ketjen black composite sol.

[0037] Step 4: Coat the sandwich structure fabric with polyetheramic acid / Ketjen black composite sol;

[0038] Step 5: Transfer the coated sandwich structure fabric to a precision high-temperature drying oven for drying at 80°C for 5 hours.

[0039] The dried sandwich structure fabric was further treated at 150℃, 200℃, 250℃, and 300℃ for 1 hour each to perform thermal imidization.

[0040] Step 6: Use a hot press to hot press the hot imidized sandwich structure fabric at a temperature of 200℃, a pressure of 18 MPa, and a time of 30 min.

[0041] Figure 2 This is a physical image of the sandwich-structured electromagnetic shielding composite material obtained in Embodiment 1 of the present invention. As can be seen from the image, the components of the composite material are combined to form a whole, with a uniform and compact structure.

[0042] Figure 3 This is a cross-sectional scanning electron microscope (SEM) image of the sandwich-structured electromagnetic shielding composite material obtained in Embodiment 1 of the present invention. It can be seen that the cross-section of the sandwich-structured electromagnetic shielding composite material exhibits a three-layer structure, and copper wires can be seen connecting the three layers in series.

[0043] Figure 4 This is a graph showing the electromagnetic shielding effectiveness of the sandwich-structured electromagnetic shielding composite material obtained in Embodiment 1 of the present invention as a function of frequency. As can be seen from the graph, the electromagnetic shielding effectiveness of the sandwich-structured electromagnetic shielding composite material is above 50dB in a considerable portion of the X-band (8.2-12.4GHz), reaching a maximum of 70.14dB, demonstrating excellent electromagnetic shielding performance. Example

[0044] A method for preparing a sandwich-structured electromagnetic shielding composite material includes the following steps:

[0045] Step 1, prepare the following raw materials: including carbon cloth, carbon paper, copper wire, N,N-dimethylformamide, 4,4'-diaminodiphenyl ether, bisphenol A type diether dianhydride, and Ketjen Black;

[0046] Step 2: Sew two layers of carbon cloth and a layer of carbon paper sandwiched between the carbon cloths together with copper wire to obtain a sandwich structure fabric.

[0047] Step 3: Dissolve 1.5g of 4,4'-diaminodiphenyl ether in 15.5mL of N,N-dimethylformamide to obtain a 4,4'-diaminodiphenyl ether dispersion;

[0048] Weigh 0.29g of Ketjenblack powder, which accounts for 5wt% of the total solid content. To prepare the polyetheramic acid / Ketjenblack composite sol, the solid content should be 18wt%.

[0049] Ketjen black powder was subjected to acid treatment at 90°C for 12 hours by hydrothermal method, then filtered until neutral and dried. The dried powder was then dissolved in 11 mL of N,N-dimethylformamide and magnetically stirred for 12 hours to obtain a Ketjen black / N,N-dimethylformamide solution.

[0050] The obtained Ketjen black / N,N-dimethylformamide solution was added to a 4,4'-diaminodiphenyl ether dispersion and sonicated until fully dissolved to obtain a composite solution. Then, 4.02 g of bisphenol A type diether dianhydride was weighed and added to the composite solution in four equal portions in four slow additions, with an interval of 30 min between each addition and mechanical stirring for 2 h, to finally obtain polyetheramic acid / Ketjen black composite sol.

[0051] Step 4: Coat the sandwich structure fabric with polyetheramic acid / Ketjen black composite sol;

[0052] Step 5: Transfer the coated sandwich structure fabric to a precision high-temperature drying oven for drying at 80°C for 5 hours.

[0053] The dried sandwich structure fabric was further treated at 150℃, 200℃, 250℃, and 300℃ for 1 hour each to perform thermal imidization.

[0054] Step 6: Use a hot press to hot press the hot imidized sandwich structure fabric at a temperature of 180°C, a pressure of 15 MPa, and a time of 25 min. Example

[0055] A method for preparing a sandwich-structured electromagnetic shielding composite material includes the following steps:

[0056] Step 1, prepare the following raw materials: including carbon cloth, carbon paper, copper wire, N,N-dimethylformamide, 4,4'-diaminodiphenyl ether, bisphenol A type diether dianhydride, and Ketjen Black;

[0057] Step 2: Sew two layers of carbon cloth and a layer of carbon paper sandwiched between the carbon cloths together with copper wire to obtain a sandwich structure fabric.

[0058] Step 3: Dissolve 1.5g of 4,4'-diaminodiphenyl ether in 13.6mL of N,N-dimethylformamide to obtain a 4,4'-diaminodiphenyl ether dispersion;

[0059] Weigh 0.48g of Ketjen black powder, which accounts for 8wt% of the total solid content. To prepare the polyetheramic acid / Ketjen black composite sol, the solid content should be 21wt%.

[0060] Ketjen black powder was subjected to acid treatment at 90°C for 12 hours by hydrothermal method, then filtered until neutral and dried. The dried powder was then dissolved in 9 mL of N,N-dimethylformamide and magnetically stirred for 12 hours to obtain a Ketjen black / N,N-dimethylformamide solution.

[0061] The obtained Ketjen black / N,N-dimethylformamide solution was added to a 4,4'-diaminodiphenyl ether dispersion and sonicated until fully dissolved to obtain a composite solution. Then, 4.02 g of bisphenol A type diether dianhydride was weighed and added to the composite solution in four equal portions in four slow additions, with an interval of 30 min between each addition and mechanical stirring for 2.5 h, finally obtaining polyetheramic acid / Ketjen black composite sol.

[0062] Step 4: Coat the sandwich structure fabric with polyetheramic acid / Ketjen black composite sol;

[0063] Step 5: Transfer the coated sandwich structure fabric to a precision high-temperature drying oven for drying at 80°C for 5 hours.

[0064] The dried sandwich structure fabric was further treated at 150℃, 200℃, 250℃, and 300℃ for 1 hour each to perform thermal imidization.

[0065] Step 6: Use a hot press to hot press the hot imidized sandwich structure fabric at a temperature of 190°C, a pressure of 17 MPa, and a time of 30 min. Example

[0066] A method for preparing a sandwich-structured electromagnetic shielding composite material includes the following steps:

[0067] Step 1, prepare the following raw materials: including carbon cloth, carbon paper, copper wire, N,N-dimethylformamide, 4,4'-diaminodiphenyl ether, bisphenol A type diether dianhydride, and Ketjen Black;

[0068] Step 2: Sew two layers of carbon cloth and a layer of carbon paper sandwiched between the carbon cloths together with copper wire to obtain a sandwich structure fabric.

[0069] Step 3: Dissolve 1.5g of 4,4'-diaminodiphenyl ether in 10mL of N,N-dimethylformamide to obtain a 4,4'-diaminodiphenyl ether dispersion;

[0070] Weigh 0.61g of Ketjenblack powder, which accounts for 10wt% of the total solid content. To prepare the polyetheramic acid / Ketjenblack composite sol, the solid content should be 23wt%.

[0071] Ketjen black powder was subjected to acid treatment at 90°C for 12 hours via hydrothermal method, then filtered until neutral and dried. The dried powder was then dissolved in 10.55 mL of N,N-dimethylformamide and magnetically stirred for 12 hours to obtain a Ketjen black / N,N-dimethylformamide solution.

[0072] The obtained Ketjen black / N,N-dimethylformamide solution was added to the 4,4'-diaminodiphenyl ether dispersion and sonicated until fully dissolved to obtain a composite solution. Then, 4.02g of bisphenol A type diether dianhydride was weighed and added to the composite solution in four equal portions in four slow additions, with an interval of 30min between each addition and mechanical stirring for 3h, finally obtaining polyetheramic acid / Ketjen black composite sol.

[0073] Step 4: Coat the sandwich structure fabric with polyetheramic acid / Ketjen black composite sol;

[0074] Step 5: Transfer the coated sandwich structure fabric to a precision high-temperature drying oven for drying at 80°C for 5 hours.

[0075] The dried sandwich structure fabric was further treated at 150℃, 200℃, 250℃, and 300℃ for 1 hour each to perform thermal imidization.

[0076] Step 6: Use a hot press to hot press the hot imidized sandwich structure fabric at a temperature of 200℃, a pressure of 18 MPa, and a time of 35 min.

Claims

1. A method for producing a sandwich-structured electromagnetic shielding composite material, characterized by, The method comprises the following steps: Step 1, preparing raw materials, including carbon cloth, carbon paper, copper wire, N,N-dimethylformamide, 4,4'-diamino diphenyl ether, bisphenol A diether dianhydride, and Ketjen black; Step 2, sandwich structure fabric sewing; The step 2, sandwich structure fabric sewing is to sew two layers of carbon cloth and one layer of carbon paper sandwiched in the carbon cloth to form a sandwich structure through copper wire; Step 3, preparing a polyether amide acid / Ketjen black composite sol; The step 3, polyether amide acid / Ketjen black composite sol is prepared by an in-situ polymerization method, and the specific steps are as follows: 1.5g of 4,4'-diamino diphenyl ether is dissolved in 10-15.5ml of N,N-dimethylformamide to obtain a 4,4'-diamino diphenyl ether dispersion liquid, and Ketjen black is dissolved in 9-11ml of N,N-dimethylformamide and magnetically stirred for 12h to obtain a Ketjen black / N,N-dimethylformamide solution; the obtained Ketjen black / N,N-dimethylformamide solution is added to the 4,4'-diamino diphenyl ether dispersion liquid, and ultrasonic is applied until it is fully dissolved to obtain a composite solution, and then 4.02g of bisphenol A diether dianhydride is added while external mechanical stirring is applied for 2-3h to finally obtain a polyether amide acid / Ketjen black composite sol; Step 4, polyether amide acid / Ketjen black composite sol coating sandwich structure fabric; Step 5, drying and thermal imidization; Step 6, hot pressing treatment with a hot press.

2. The method of claim 1, wherein the sandwich structure electromagnetic shielding composite material is prepared by the following steps: (1) preparing a first layer of the sandwich structure electromagnetic shielding composite material; (2) preparing a second layer of the sandwich structure electromagnetic shielding composite material; and (3) preparing a third layer of the sandwich structure electromagnetic shielding composite material. The Ketjen black accounts for 5-10wt% of the total solid content.

3. The method of claim 1, wherein the sandwich structure electromagnetic shielding composite material is prepared by the following steps: (1) preparing a first layer of the sandwich structure electromagnetic shielding composite material; (2) preparing a second layer of the sandwich structure electromagnetic shielding composite material; and (3) preparing a third layer of the sandwich structure electromagnetic shielding composite material. The solid content of the polyether amide acid / Ketjen black composite sol is 18-23wt%.

4. The method of claim 1, wherein the sandwich structure electromagnetic shielding composite material is prepared by the following steps: (1) preparing a first layer of the sandwich structure electromagnetic shielding composite material; (2) preparing a second layer of the sandwich structure electromagnetic shielding composite material; and (3) preparing a third layer of the sandwich structure electromagnetic shielding composite material. The Ketjen black is subjected to acid treatment at 90℃ for 12h by a hydrothermal method, and then is filtered to neutral and dried.

5. The method of claim 1, wherein the sandwich structure electromagnetic shielding composite material is prepared by the following steps: (1) preparing a first layer of the sandwich structure electromagnetic shielding composite material; (2) preparing a second layer of the sandwich structure electromagnetic shielding composite material; and (3) preparing a third layer of the sandwich structure electromagnetic shielding composite material. The bisphenol A diether dianhydride is divided into four equal parts, and each part is added slowly with an interval of 30min.

6. The method of claim 1, wherein the sandwich structure electromagnetic shielding composite material is prepared by the following steps: (1) preparing a first layer of the sandwich structure electromagnetic shielding composite material; (2) preparing a second layer of the sandwich structure electromagnetic shielding composite material; and (3) preparing a third layer of the sandwich structure electromagnetic shielding composite material. The step 5, drying refers to transferring the sandwich structure fabric after coating to a precision high-temperature drying box for drying at 80℃ for 5h.

7. The method for preparing a sandwich-structured electromagnetic shielding composite material according to claim 1, characterized in that, The step 5, thermal imidization specifically refers to continuing to treat the sandwich structure fabric after drying at 150℃, 200℃, 250℃, and 300℃ for 1h respectively.

8. The method for preparing a sandwich-structured electromagnetic shielding composite material according to claim 1, characterized in that, The step 6, hot pressing treatment is performed at a hot pressing temperature of 180-200℃, a pressure of 15-18Mpa, and a time of 25-35min.

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