Preparation method of an electromagnetic shielding material and electromagnetic shielding material

Abstract

The present invention discloses a preparation method of an electromagnetic shielding material and the electromagnetic shielding material, which comprises the following steps: sequentially performing electroless nickel plating and electroless copper plating on a plant fiber fabric to obtain a fabric with double-layer coating; coating a polydimethylsiloxane solution on both the front and back sides of the fabric with double-layer coating, and drying to obtain the electromagnetic shielding material; the inner layer of the fabric with double-layer coating is a nickel coating layer, and the outer layer is a copper coating layer. The electromagnetic shielding material of the present invention can effectively reduce the electromagnetic reflection loss, enhance the electromagnetic absorption loss, is beneficial to the absorption and conversion of electromagnetic energy, and avoids the secondary pollution of electromagnetic waves.

Description

Technical Field

[0001] The present invention belongs to the field of shielding materials, and particularly relates to a preparation method of an electromagnetic shielding material and an electromagnetic shielding material. Background Art

[0002] With the gradual influx of highly integrated and intelligent electronic and electrical devices into fields such as communication, electrical appliances, and transportation, while electromagnetic technology brings great convenience to people's lives, it also brings a large amount of electromagnetic radiation, resulting in electromagnetic pollution. Therefore, it is imperative to develop materials with electromagnetic shielding performance. Electromagnetic interference shielding is to reflect and attenuate electromagnetic waves through a shielding body, so that various electronic devices have a certain electromagnetic compatibility, thereby reducing or even completely eliminating the harm of electromagnetic radiation to the human body and other electronic devices.

[0003] The ability of a shielding body to reduce electromagnetic wave signals through reflection, attenuation, etc. is called shielding effectiveness, which is an index to measure the shielding performance of an electromagnetic shielding material. The reduction of electromagnetic waves by an electromagnetic shielding material mainly includes: (1) The incident electromagnetic wave is reflected by the surface of the shielding material, causing reflection loss (SE R ); (2) The electromagnetic wave entering the shielding body is directly absorbed, causing absorption loss (SE A ); (3) The electromagnetic wave entering the shielding body undergoes multiple reflections between internal interfaces, resulting in more electromagnetic wave energy being converted into internal energy and dissipated, causing multiple reflection loss (SE M ). The total shielding effectiveness of the electromagnetic shielding material is represented by the sum of the three: SE T = SE R + SE A + SE M .

[0004] Currently, the commercially available electromagnetic protective clothing is a polyester backing coated with a layer of silver particles as an EMI shielding material, and its EMI shielding efficiency is as high as 50 - 75 dB. However, the cost of the Ag printing composite material is relatively high and precious metal resources are wasted. In addition, the reflected electromagnetic wave will cause secondary pollution to the environment. Improving the absorption loss of the material to electromagnetic waves and reducing the reflection loss can effectively avoid the secondary pollution of electromagnetic waves, which is of great significance. Summary of the Invention

[0005] Based on the above technical problems, the present invention provides a preparation method of an electromagnetic shielding material and an electromagnetic shielding material. The electromagnetic shielding material can effectively reduce the electromagnetic reflection loss, enhance the electromagnetic absorption loss, is beneficial to the absorption and conversion of electromagnetic energy, and avoids the secondary pollution of electromagnetic waves.

[0006] The specific method of the present invention is as follows:

[0007] The present invention provides a method for preparing an electromagnetic shielding material, which includes the following steps: subjecting a plant fiber fabric to electroless nickel plating and electroless copper plating in sequence to obtain a double-layer coated fabric; coating a polydimethylsiloxane solution on both the front and back sides of the double-layer coated fabric, and drying to obtain the electromagnetic shielding material; the inner layer of the double-layer coated fabric is a nickel coating layer, and the outer layer is a copper coating layer.

[0008] Preferably, it further includes calcining the double-layer coated fabric before coating the polydimethylsiloxane solution; the calcination temperature is 200-300 °C, and the calcination time is 0.5-5 h.

[0009] Preferably, the calcination temperature is 200 °C, and the calcination time is 1 h.

[0010] Calcining the double-layer coated fabric before coating PDMS to form double-layer coated carbon nanotubes. Different calcination temperatures result in different carbon nanotube structures and morphologies; calcining at 300 °C forms hollow carbon nanotubes; calcining at 200 °C results in carbon nanotubes containing carbon core rods, which is more conducive to increasing the reflection path of electromagnetic waves compared to hollow carbon nanotubes, enabling more electromagnetic waves to be absorbed.

[0011] Regarding the calcination temperature, in addition to affecting the structure and morphology of the formed carbon nanotubes, it also affects the mechanical properties of the copper coating layer and the shielding material. Calcining at 300 °C forms a layer of cuprous oxide on the surface of the copper coating layer. Excessive cuprous oxide to a certain extent leads to a decrease in the reflection ability and the overall shielding performance; in addition, the mechanical properties of the shielding material obtained by calcining at 300 °C are weakened, and cracks are likely to form during subsequent processing.

[0012] Preferably, the electroless nickel plating method includes: placing the plant fiber fabric in a palladium chloride activation solution at 60-70 °C and soaking for 0.5-1 h; taking it out, drying it, and then placing it in an electroless nickel plating solution at 60-80 °C for plating for 0.5-1 h.

[0013] Preferably, the electroless copper plating method includes: placing the plant fiber fabric after electroless nickel plating in an electroless copper plating solution at 20-30 °C and soaking for 8-12 h.

[0014] Preferably, the palladium chloride activation solution includes: palladium chloride 0.05-0.6 g / L, boric acid 5-30 g / L, and the pH is 1-3.

[0015] Preferably, the electroless nickel plating solution includes: nickel sulfate 10-20 g / L, trisodium citrate 5-15 g / L, ammonium chloride 16-22 g / L, sodium hypophosphite 10-18 g / L, and the pH is 9-12.

[0016] Preferably, the electroless copper plating solution comprises: 11 - 58 g / L of copper sulfate, 12 - 18 g / L of disodium ethylenediaminetetraacetate, 12 - 18 g / L of potassium sodium tartrate, 10 - 18 ml / L of formaldehyde, 0.1 - 0.8 g / L of potassium ferrocyanide, 0.01 - 0.05 g / L of 2,2'-bipyridine, 1 - 2 g / L of polyethylene glycol, and 12 - 18 g / L of sodium hydroxide.

[0017] Preferably, the polydimethylsiloxane solution comprises: polydimethylsiloxane and a curing agent; the mass ratio of polydimethylsiloxane to the curing agent is 8 - 15:1.

[0018] The present invention also provides an electromagnetic shielding material prepared by any one of the above methods.

[0019] The beneficial effects of the present invention are as follows:

[0020] Through two - step electroless plating treatment of the plant fiber fabric, a double - layer coated fabric is obtained. Then, the polydimethylsiloxane solution is coated on both the front and back sides and dried to obtain an electromagnetic shielding material. Compared with the existing electromagnetic shielding materials, it has a higher electromagnetic shielding efficiency, can effectively reduce the electromagnetic reflection loss, enhance the electromagnetic absorption loss, and reduce the secondary pollution of electromagnetic waves. Description of the Drawings

[0021] Figure 1 It is a flowchart of the preparation method of Example 2;

[0022] Figure 2 It is the structural analysis of the cotton fabric of the Ni@Cu coated tube obtained after calcination in Example 2, where (I) is the SEM image of the sample; (II) is the EDS image of the sample; (III) is the SEM image of a single fiber; (IV) is the mapping analysis image of the sample;

[0023] Figure 3 It is the XRD pattern of the uncalcined double - layer coated fabric and the cotton fabric of the Ni@Cu coated tube calcined at 200 °C and 300 °C. Detailed Embodiments

[0024] Next, the technical solutions of the present invention will be described in detail through specific examples. It should be clearly stated that these examples are for illustrative purposes only and are not to be construed as limiting the scope of the present invention.

[0025] Example 1

[0026] An electromagnetic shielding material, the preparation method of which comprises:

[0027] (1) Electroless nickel plating: Wash the white cloth in clean water and dry it to ensure that there is no dirt such as oil stains on the surface; then soak it completely in a palladium chloride activation solution at 60 °C for 30 min for activation; after taking it out, rinse it once with deionized water, put it in an oven at 100 °C to dry, and take it out; put it into an electroless nickel plating solution at 60 °C for electroless nickel plating for 1 h, take it out, clean the surface of the broken nickel and the excess nickel with deionized water, flatten it and put it in an oven at 100 °C to dry to obtain a fabric with nickel deposited on the surface;

[0028] Among them, the palladium chloride activation solution includes: palladium chloride 0.1 g / L, boric acid 10 g / L; adjust the pH to 2 with HCl solution; the electroless nickel plating solution includes: nickel sulfate 15 g / L, trisodium citrate 8 g / L, ammonium chloride 18 g / L, sodium hypophosphite 15 g / L; adjust the pH to 10 with NaOH solution;

[0029] (2) Electroless copper plating: Immerse the fabric with nickel deposited on the surface in an electroless copper plating solution at 20 °C for 8 h, take it out, and rinse it once with deionized water to remove the easily peeled copper on the surface to obtain a double-layer coated fabric;

[0030] Among them: the electroless copper plating solution includes: copper sulfate 15 g / L, disodium ethylenediaminetetraacetate 14 g / L, potassium sodium tartrate 14 g / L, formaldehyde 15 ml / L, potassium ferrocyanide 0.1 g / L, 2,2'-bipyridine 0.02 g / L, polyethylene glycol 1 g / L, sodium hydroxide 14 g / L;

[0031] (3) Coating with PDMS: Evenly apply PDMS solution (including PDMS and curing agent, the mass ratio of PDMS to curing agent is 10:1) on both the front and back sides of the double-layer coated fabric, avoid wrinkles and protrusions, and put it in an oven at 100 °C to dry to obtain an electromagnetic shielding material, denoted as Cup-cotton.

[0032] Example 2

[0033] An electromagnetic shielding material, the preparation method thereof includes:

[0034] (1) Electroless nickel plating: The same as in Example 1;

[0035] (2) Electroless copper plating: The same as in Example 1;

[0036] (3) Calcination: Put the double-layer coated fabric obtained in step (2) in an oven at 100 °C to dry, take it out, and place it in a muffle furnace for calcination at 200 °C for 1 h;

[0037] (4) Coating with PDMS: After the calcination is completed, take it out, and evenly apply PDMS solution (including PDMS and curing agent, the mass ratio of PDMS to curing agent is 10:1) on both the front and back sides, avoid wrinkles and protrusions, and put it in an oven at 100 °C to dry to obtain an electromagnetic shielding material, denoted as CupL-cotton.

[0038] The flow chart of the preparation method of this embodiment is as Figure 1 shown;

[0039] The structural analysis diagram of the cotton cloth of the Ni@Cu coated tube obtained after calcination in this embodiment is as Figure 2 shown, where (I) is the SEM image of the sample; (II) is the EDS image of the sample; (III) is the SEM image of a single fiber; (IV) is the mapping analysis image of the sample.

[0040] Example 3

[0041] A preparation method of an electromagnetic shielding material, compared with Example 2, only adjusts the calcination temperature from "200 °C" to "300 °C", and the calcination time remains unchanged; others are the same as in Example 2.

[0042] The electromagnetic shielding material obtained in this embodiment is denoted as CupH-cotton.

[0043] The XRD diagrams of the uncalcined double-layer coated fabric in Example 1 above and the cotton cloth of the Ni@Cu coated tube obtained by calcination at 200 °C and 300 °C in Examples 2 and 3 respectively are as Figure 3 shown. It can be seen that calcination at 300 °C will generate cuprous oxide on the copper coating layer on the fabric surface, and excessive cuprous oxide on the surface of the copper coating layer will cause a weakening of the reflection ability and the total shielding performance to a certain extent.

[0044] Comparative Example 1

[0045] An electromagnetic shielding material, the preparation method of which includes:

[0046] (1) Electroless nickel plating: The same as in Example 1, to obtain a fabric with nickel deposited on the surface;

[0047] (2) Calcination: Place the fabric with nickel deposited on the surface obtained in step (1) in a muffle furnace and calcine at 300 °C for 1 h;

[0048] (3) Electroless copper plating: Perform electroless copper plating on the material after calcination in step (2), and the method and parameters are the same as in Example 1;

[0049] (4) Coating PDMS: Uniformly apply PDMS solution (including PDMS and curing agent, the mass ratio of PDMS to curing agent is 10:1) on both the front and back sides of the material obtained in step (3), and dry it in an oven at 100 °C to obtain an electromagnetic shielding material, denoted as NipA-cotton.

[0050] In this comparative example, calcination is carried out before electroless copper plating, and the material after calcination is fragile in the copper plating solution and it is not easy to prepare large-size samples.

[0051] Comparative Example 2

[0052] An electromagnetic shielding material, and its preparation method includes:

[0053] (1) Electroless nickel plating: The same as in Example 1, to obtain a fabric with nickel deposited on the surface;

[0054] (2) Coating with PDMS: Coat the fabric with nickel deposited on the surface evenly on both the front and back sides with a PDMS solution (including PDMS and a curing agent, and the mass ratio of PDMS to the curing agent is 10:1), and place it in an oven at 100 °C for drying to obtain the electromagnetic shielding material, denoted as Nip-cotton.

[0055] Comparative Example 3

[0056] An electromagnetic shielding material, and its preparation method includes:

[0057] (1) Electroless nickel plating: The same as in Example 1, to obtain a fabric with nickel deposited on the surface;

[0058] (2) Calcination: Put the fabric with nickel deposited on the surface obtained in step (1) into an oven at 100 °C for drying, take it out, and place it in a muffle furnace for calcination at 100 °C for 1 h;

[0059] (3) Coating with PDMS: After the calcination is completed, take it out, and coat it evenly on both the front and back sides with a PDMS solution (including PDMS and a curing agent, and the mass ratio of PDMS to the curing agent is 10:1), and place it in an oven at 100 °C for drying to obtain the electromagnetic shielding material, denoted as NipL-cotton.

[0060] Comparative Example 4

[0061] An electromagnetic shielding material, and its preparation method includes:

[0062] (1) Electroless nickel plating: The same as in Example 1, to obtain a fabric with nickel deposited on the surface;

[0063] (2) Calcination: Put the fabric with nickel deposited on the surface obtained in step (1) into an oven at 100 °C for drying, take it out, and place it in a muffle furnace for calcination at 300 °C for 1 h;

[0064] (3) Coating with PDMS: After the calcination is completed, take it out, and coat it evenly on both the front and back sides with a PDMS solution (including PDMS and a curing agent, and the mass ratio of PDMS to the curing agent is 10:1), and place it in an oven at 100 °C for drying to obtain the electromagnetic shielding material, denoted as NipH-cotton.

[0065] Test the shielding performance of the electromagnetic shielding materials in the above examples and comparative examples: Use an Agilent N5230A vector network analyzer to test the samples in the X-band (8 - 12 GHz); The test results are shown in Table 1 below:

[0066] Table 1. Performance of the shielding materials described in Examples 1-3 and Comparative Examples 1-4

[0067]

[0068]

[0069] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes, shall be covered by the protection scope of the present invention.

Claims

1. A preparation method of an electromagnetic shielding material, characterized in that, it comprises the following steps: successively performing electroless nickel plating and electroless copper plating on a plant fiber fabric to obtain a double-layer coated fabric; coating a polydimethylsiloxane solution on both the front and back sides of the double-layer coated fabric, and drying to obtain the electromagnetic shielding material; the inner layer of the double-layer coated fabric is a nickel coating layer, and the outer layer is a copper coating layer; further comprising, performing a calcination treatment on the double-layer coated fabric before coating the polydimethylsiloxane solution; the calcination temperature is 200-300 °C, and the calcination time is 0.5-5 h.

2. The preparation method of the electromagnetic shielding material according to claim 1, characterized in that, the calcination temperature is 200 °C, and the calcination time is 1 h.

3. The preparation method of the electromagnetic shielding material according to claim 1 or 2, characterized in that, the electroless nickel plating method comprises: placing the plant fiber fabric in a palladium chloride activation solution at 60-70 °C, soaking for 0.5-1 h; taking out, drying and then placing it in an electroless nickel plating solution at 60-80 °C for plating for 0.5-1 h.

4. The preparation method of the electromagnetic shielding material according to claim 1 or 2, characterized in that, the electroless copper plating method comprises: placing the plant fiber fabric after electroless nickel plating in an electroless copper plating solution at 20-30 °C and soaking for 8-12 h.

5. The preparation method of the electromagnetic shielding material according to claim 3, characterized in that, the palladium chloride activation solution comprises: palladium chloride 0.05-0.6 g / L, boric acid 5-30 g / L, and the pH is 1-3.

6. The preparation method of the electromagnetic shielding material according to claim 3, characterized in that, the electroless nickel plating solution comprises: nickel sulfate 10-20 g / L, trisodium citrate 5-15 g / L, ammonium chloride 16-22 g / L, sodium hypophosphite 10-18 g / L, and the pH is 9-12.

7. The preparation method of the electromagnetic shielding material according to claim 4, characterized in that, the electroless copper plating solution comprises: copper sulfate 11-58 g / L, disodium ethylenediaminetetraacetate 12-18 g / L, potassium sodium tartrate 12-18 g / L, formaldehyde 10-18 ml / L, potassium ferrocyanide 0.1-0.8 g / L, 2,2'-bipyridine 0.01-0.05 g / L, polyethylene glycol 1-2 g / L, sodium hydroxide 12-18 g / L.

8. The preparation method of the electromagnetic shielding material according to claim 1 or 2, characterized in that, the polydimethylsiloxane solution comprises: polydimethylsiloxane and a curing agent; the mass ratio of polydimethylsiloxane to the curing agent is 8-15:

1.

9. An electromagnetic shielding material, characterized in that, it is prepared by using the method according to any one of claims 1-8.

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