CN110641130A - Preparation method of wave-absorbing foam for absorbing low-frequency electromagnetic waves - Google Patents
Preparation method of wave-absorbing foam for absorbing low-frequency electromagnetic waves Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B38/00—Ancillary operations in connection with laminating processes
- B32B38/08—Impregnating
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B38/00—Ancillary operations in connection with laminating processes
- B32B38/0036—Heat treatment
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B38/00—Ancillary operations in connection with laminating processes
- B32B38/16—Drying; Softening; Cleaning
- B32B38/162—Cleaning
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B38/00—Ancillary operations in connection with laminating processes
- B32B38/16—Drying; Softening; Cleaning
- B32B38/164—Drying
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/36—After-treatment
- C08J9/40—Impregnation
- C08J9/42—Impregnation with macromolecular compounds
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K9/00—Screening of apparatus or components against electric or magnetic fields
- H05K9/0073—Shielding materials
- H05K9/0081—Electromagnetic shielding materials, e.g. EMI, RFI shielding
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2250/00—Layers arrangement
- B32B2250/22—All layers being foamed
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2266/00—Composition of foam
- B32B2266/02—Organic
- B32B2266/0214—Materials belonging to B32B27/00
- B32B2266/0278—Polyurethane
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2375/00—Characterised by the use of polyureas or polyurethanes; Derivatives of such polymers
- C08J2375/04—Polyurethanes
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2475/00—Characterised by the use of polyureas or polyurethanes; Derivatives of such polymers
- C08J2475/04—Polyurethanes
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/02—Elements
- C08K3/04—Carbon
- C08K3/041—Carbon nanotubes
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/02—Elements
- C08K3/04—Carbon
- C08K3/042—Graphene or derivatives, e.g. graphene oxides
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
Abstract
The invention relates to the technical field of wave-absorbing material preparation, in particular to a method for preparing wave-absorbing foam for absorbing low-frequency electromagnetic waves, which comprises the steps of compounding polyurethane soft foam with reduced graphene oxide/carbonyl iron foam or hydroxylated carbon nano tube/carbonyl iron foam slurry through an impregnation process, further performing thermal reduction to obtain an upper-layer matched absorbing layer, compounding the polyurethane soft foam with carbon nano tube aqueous slurry or low-defect graphene through the impregnation process to obtain a lower-layer reflecting absorbing layer, attaching to form final wave-absorbing foam, and researching the influence of process parameters on the structure and the performance of the wave-absorbing foam.
Description
Technical Field
The invention relates to the technical field of wave-absorbing material preparation, in particular to a preparation method of wave-absorbing foam for absorbing low-frequency electromagnetic waves.
Background
With the continuous development of human society, people have more and more requirements on convenience, informatization and intellectualization of life, and the development of electronic communication technology, computer technology and radar technology is greatly promoted. Along with this, there are many problems such as electromagnetic safety and electromagnetic radiation pollution. Particularly in the fields of computers, radar communication and the like, the influence of external electromagnetic radiation, electromagnetic interference among equipment and interference among electronic devices in the equipment seriously influence the normal transmission of signals and the normal operation of the equipment. Therefore, eliminating clutter and improving electromagnetic compatibility of electronic devices are hot spots in current research and discussion.
The wave-absorbing material absorbs and attenuates harmful electromagnetic radiation, and is one of effective ways for protecting electronic equipment and improving the electromagnetic compatibility of the equipment. Among a plurality of wave-absorbing materials, the wave-absorbing foam material becomes a popular wave-absorbing material at present due to light weight, wide absorption frequency band and good wave-absorbing effect, and is widely used for eliminating clutter interference at microwave anechoic chambers, antenna covers, antenna supports, radar cabins and other parts. The traditional wave-absorbing foam material usually uses carbon black as an absorbent and is filled into a foam matrix by adopting an impregnation or in-situ foaming process. However, the absorbing foam prepared by singly adopting carbon black as an absorbent has poor absorption effect in a low-frequency area, and the foam thickness is often required to be increased to meet the requirement. The application of the wave-absorbing foam in narrow spaces such as electronic equipment and radar equipment is limited. In addition to carbon black, another commonly used low frequency absorber is carbonyl iron powder. The carbonyl iron powder belongs to magnetic metal particle powder, has excellent low-frequency wave-absorbing performance, but has narrow self-absorption frequency band and heavy weight, and is not beneficial to being applied to a broadband light-weight absorption material.
The nano material, especially the carbon nano material such as graphene, carbon nano tube and the like shows a plurality of unique advantages in the field of electromagnetic protection and is a good broadband wave absorbing agent. In a carbon-based material family, graphene has high dielectric constant, low density and good chemical stability and thermal stability. Is a high-efficiency absorbent with great application prospect. The carbon nano tube has excellent conductivity and higher electrical loss tangent angle. A large number of lattice defects and surface dangling bonds formed by the carbon nano tubes with high specific surface area promote interface polarization and multiple scattering, and can effectively attenuate incident electromagnetic wave energy. In addition, the carbon nano tube is used as a one-dimensional nano material, and the particle size is far smaller than radar and infrared wavelength, so that the wave absorbing performance of the wave absorbing material is better than that of the traditional wave absorbing material. However, the electromagnetic wave loss mechanism of the graphene is relatively single and the graphene itself has high conductivity, which results in poor impedance matching with the incident space, and increases the reflection of the electromagnetic wave. The lowest value of pure graphene Reflectivity (RL) is reported to be only-7 dB. However, the preparation of the wave-absorbing foam by using a single-component carbon nano material as an absorbent still has its limitations, and the existing requirements cannot be met particularly for low-frequency absorption.
Carbonyl iron is one of the traditional magnetic wave absorbers, but has high density and narrow absorption frequency band. In addition, carbonyl iron is mostly in a micron-sized spherical structure, and is filled in a large amount of foam to block a pore channel instead, so that the attenuation of electromagnetic waves is not facilitated.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides a preparation method of wave-absorbing foam for absorbing low-frequency electromagnetic waves, which mainly solves the problem that the wave-absorbing foam is not high in absorption performance in a low-frequency area on the premise of keeping the wave-absorbing foam thin in thickness and wide-frequency absorption.
A preparation method of wave-absorbing foam for absorbing low-frequency electromagnetic waves comprises the following steps:
s1, uniformly mixing the graphene oxide powder, carbonyl iron powder and aqueous polyurethane emulsion to obtain wave-absorbing slurry A;
s2, fully dipping the first soft polyurethane foam in the wave-absorbing slurry A in S1, and then carrying out thermal reduction;
s3, after the reaction is finished, fully leaching the foam subjected to thermal reduction in S2 with deionized water, and drying to obtain matched absorbing layer wave-absorbing foam;
s4, uniformly mixing the multi-walled carbon nanotube powder, deionized water, a surfactant and a waterborne polyurethane emulsion to obtain wave-absorbing slurry B;
s5, fully soaking the second soft polyurethane foam in the wave-absorbing slurry B, and drying to obtain the wave-absorbing foam of the reflection absorption layer;
s6, tightly attaching the absorbing layer wave-absorbing foam and the reflecting absorbing layer wave-absorbing foam to prepare the wave-absorbing foam.
Further, the mass ratio of the graphene oxide to the carbonyl iron powder in the S1 is 1:1-1: 5; the dosage of the S4 surfactant is 10-50% of that of the multi-wall carbon nano-tube; the solid content of the multi-wall carbon nano-tube in the S4 is 1-10%.
Further, a preparation method of the wave-absorbing foam for absorbing low-frequency electromagnetic waves comprises the following steps:
s1, uniformly mixing the carbonylation carbon nanotube powder, a surfactant, carbonyl iron powder and an aqueous polyurethane emulsion to obtain wave-absorbing slurry A;
s2, fully dipping the first soft polyurethane foam in the wave-absorbing slurry A in S1, and then carrying out thermal reduction;
s3, after the reaction is finished, fully leaching the foam subjected to thermal reduction in S2 with deionized water, and drying to obtain matched absorbing layer wave-absorbing foam;
s4, uniformly mixing the low-defect graphene powder, deionized water and the waterborne polyurethane emulsion to obtain wave-absorbing slurry B;
s5, fully soaking the second soft polyurethane foam in the wave-absorbing slurry B, and drying to obtain the wave-absorbing foam of the reflection absorption layer;
s6, tightly attaching the absorbing layer wave-absorbing foam and the reflecting absorbing layer wave-absorbing foam to prepare the wave-absorbing foam.
Further, the solid content of the aqueous polyurethane emulsion in the S1 is 30%, and the solid content of the aqueous polyurethane emulsion in the S4 is 25% -45%.
Further, the thermal reduction in S2 is carried out in a Teflon reaction kettle, the thermal reduction temperature is 85-95 ℃, and the thermal reduction time is 12-15 h.
Further, the surfactant in S4 is one or more of sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, and a carbon nanotube water dispersant.
Further, the wave-absorbing slurry A in the S2 completely soaks the first flexible polyester foam, and the wave-absorbing slurry B in the S5 completely soaks the second flexible polyurethane foam.
Further, the first flexible polyurethane foam in S2 is the same specification as the second flexible polyurethane foam in S5.
Furthermore, the wave absorbing foam in the S6 is composed of two layers of foam, wherein the upper layer is absorbing layer foam, and the lower layer is reflecting absorbing layer foam.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides a preparation method of wave-absorbing foam aiming at low-frequency electromagnetic wave absorption, which utilizes the broadband high-efficiency absorption characteristics of graphene and carbon nano tubes, combines the flexibility and the porous characteristics of polyurethane soft foam, takes the polyurethane soft foam as a matrix, fills carbon nano materials on the walls and the pore passages of the foam, and provides loss mechanisms mainly based on dielectric loss by using a carbon nano material wave-absorbing agent, wherein the loss mechanisms comprise resistance loss, polarization relaxation, multiple scattering and the like; the carbonyl iron provides an additional magnetic loss mechanism such as eddy current loss, and compared with the prior art, the broadband absorption characteristic of the wave-absorbing foam is ensured on the premise of reducing the thickness of the foam, and the absorption performance in a low-frequency area is improved; the carbon nano absorbent is combined with the carbonyl iron powder absorbent, a multi-layer wave-absorbing foam impedance matching design is carried out, and components and contents of each layer are respectively designed, compared with the prior art, the prepared wave-absorbing foam has excellent wave-absorbing performance in a low-frequency region (1-4 GHz) on the premise of ensuring broadband absorption, deep absorption lower than-20 dB occurs, and compared with single carbonyl iron, the density is reduced, and the lightness is realized; the raw materials are graphene oxide, multi-wall carbon nano tubes and carbonyl iron powder, are industrial raw materials, are relatively low in price and are easy to amplify to realize product production.
According to the invention, after the graphene is modified by functional groups and defects are introduced, the impedance matching degree is improved, and the wave-absorbing performance is improved. Compounding a modified carbon nano material (reduced graphene oxide or functionalized carbon nano tube) and carbonyl iron to serve as a matching absorption layer wave absorber, further introducing a magnetic loss mechanism on the basis of an original dielectric loss mechanism, expanding the loss path of the material to electromagnetic waves, enabling an absorption peak to move to low frequency, and realizing efficient absorption of the electromagnetic waves; meanwhile, the density of the absorbent is reduced, and the weight is reduced. The high-solid-content high-conductivity carbon nanomaterial (low-defect graphene or multi-walled carbon nanotube) is used as a wave absorbing agent of the reflection absorption layer, electromagnetic radiation penetrating through the absorption layer is absorbed again, and the rest electromagnetic waves are reflected into the absorption layer again, so that incident electromagnetic waves are fully attenuated, and particularly the high-efficiency absorption of the electromagnetic radiation in a low-frequency region is realized.
Drawings
FIG. 1 is a preparation method of a wave-absorbing foam for low-frequency electromagnetic wave absorption provided by the invention;
FIG. 2 is an SEM image of the wave-absorbing slurry A;
FIG. 3 is an SEM image of the wave-absorbing slurry B;
FIG. 4 is a sample diagram of a microwave absorbing foam for low frequency electromagnetic wave absorption according to the present invention;
FIG. 5 is a reflectivity curve of the wave-absorbing foam for low-frequency electromagnetic wave absorption in the L-band according to the present invention;
fig. 6 is a reflectivity curve of the wave-absorbing foam for low-frequency electromagnetic wave absorption in the S-band provided by the invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1, a method for preparing a microwave absorbing foam for absorbing low-frequency electromagnetic waves includes the following steps:
s1, uniformly mixing the graphene oxide powder, carbonyl iron powder and the aqueous polyurethane emulsion to obtain wave-absorbing slurry A, wherein an SEM image of the wave-absorbing slurry A is shown in FIG. 2;
s2, fully soaking the first soft polyurethane foam in the wave-absorbing slurry A in the S1, and then carrying out thermal reduction in a Teflon reaction kettle, wherein the thermal reduction temperature is 85-95 ℃, and the thermal reduction time is 12-15 h;
s3, after the reaction is finished, fully leaching the foam subjected to thermal reduction in S2 with deionized water, and drying to obtain matched absorbing layer wave-absorbing foam;
s4, uniformly mixing the multi-wall carbon nano tube powder, deionized water, a surfactant and a waterborne polyurethane emulsion to obtain wave-absorbing slurry B, wherein an SEM image of the wave-absorbing slurry B is shown in FIG. 3;
s5, fully soaking the second soft polyurethane foam in the wave-absorbing slurry B, and drying to obtain the wave-absorbing foam of the reflection absorption layer;
s6, tightly attaching the absorbing layer wave-absorbing foam and the reflecting absorbing layer wave-absorbing foam to prepare the wave-absorbing foam.
In this embodiment, the mass ratio of the graphene oxide to the carbonyl iron powder in S1 is 1:1-1:5, and the solid content of the aqueous polyurethane emulsion is 30%. The dosage of the surfactant in the S4 is 10-50% of that of the multi-walled carbon nanotube, and the solid content of the multi-walled carbon nanotube is 1-10%.
In this embodiment, the surfactant is one or more of sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, and TNWDIS.
In this embodiment, the wave-absorbing slurry a in S2 completely soaks the first flexible polyester foam, and the wave-absorbing slurry B in S5 completely soaks the second flexible polyurethane foam. The first flexible polyurethane foam in S2 is the same specification as the second flexible polyurethane foam in S5.
The wave-absorbing foam prepared in the embodiment is composed of two layers of foam, wherein the upper layer is absorbing layer foam, the lower layer is reflecting absorbing layer foam, the prepared wave-absorbing foam is shown in figure 4, and the reflectivity curve of the prepared wave-absorbing foam in the L wave band (1-2 GHz) is shown in figure 5. The wave-absorbing foam provided by the invention has good wave-absorbing performance in other wave bands, for example, the reflectivity curve of the wave-absorbing foam in the S wave band (2-4 GH) is shown in figure 6. The carbon nano material and the polyurethane foam are compounded, the effective attenuation of electromagnetic waves in a wide frequency range can be realized by means of the porous structure of the foam, and the deep absorption of the wave-absorbing foam which is lower than-20 dB in a low frequency region (1-4 GHz) can be realized by combining the porous structure of the base material and the impedance matching design of a multilayer structure.
Example 1
1) Uniformly mixing 8.2 g of Graphene Oxide (GO) powder, 16.4 g of carbonyl iron powder and 250 mL of aqueous polyurethane emulsion with the solid content of 30% to obtain wave-absorbing slurry A;
2) fully soaking the soft polyurethane foam with the size of 180 mm multiplied by 10 mm in the wave-absorbing slurry A, transferring the soaked foam to a Teflon reaction kettle, and thermally reducing the foam for 12 hours at the temperature of 95 ℃;
3) after the reaction is finished, taking the foam out of the Teflon reaction kettle, fully leaching the foam with deionized water, and drying the foam to obtain matched absorbing layer wave-absorbing foam;
4) uniformly mixing 12.5 g of multi-walled carbon nanotube, 400 mL of deionized water, 3.8 g of sodium dodecyl sulfate and 100 mL of aqueous polyurethane emulsion with the solid content of 30% to obtain wave-absorbing slurry B;
5) fully soaking the soft polyurethane foam with the size of 180 mm multiplied by 10 mm in the wave-absorbing slurry B, and drying to obtain the wave-absorbing foam of the reflection absorption layer;
6) and taking the matched absorbing layer wave-absorbing foam as a first layer and the reflecting absorbing layer wave-absorbing foam as a second layer, and tightly attaching to prepare the target product.
Example 2
1) Uniformly mixing 8.2 g of Graphene Oxide (GO) powder, 8.2 g of carbonyl iron powder and 250 mL of aqueous polyurethane emulsion with the solid content of 30% to obtain wave-absorbing slurry A;
2) fully soaking soft polyurethane foam with the size of 300 mm multiplied by 10 mm in the wave-absorbing slurry A, transferring the soaked foam to a Teflon reaction kettle, and thermally reducing the foam for 15 hours at 85 ℃;
3) after the reaction is finished, taking the foam out of the Teflon reaction kettle, fully leaching the foam with deionized water, and drying the foam to obtain matched absorbing layer wave-absorbing foam;
4) uniformly mixing 12.5 g of multi-wall carbon nano tube, 400 mL of deionized water, 4 g of carbon nano tube aqueous dispersant (TNWDIS) and 50 mL of aqueous polyurethane emulsion with the solid content of 30% to obtain wave-absorbing slurry B;
5) fully soaking soft polyurethane foam with the size of 300 mm multiplied by 10 mm in the wave-absorbing slurry B, and drying to obtain the wave-absorbing foam of the reflection absorption layer;
6) and taking the matched absorbing layer wave-absorbing foam as a first layer and the reflecting absorbing layer wave-absorbing foam as a second layer, and tightly attaching to prepare the target product.
Example 3
1) Uniformly mixing 8.2 g of Graphene Oxide (GO) powder, 16.4 g of carbonyl iron powder and 250 mL of aqueous polyurethane emulsion with the solid content of 30% to obtain wave-absorbing slurry A;
2) fully soaking soft polyurethane foam with the size of 300 mm multiplied by 8 mm in the wave-absorbing slurry A, transferring the soaked foam to a Teflon reaction kettle, and thermally reducing the foam for 12 hours at the temperature of 95 ℃;
3) after the reaction is finished, taking the foam out of the Teflon reaction kettle, fully leaching the foam with deionized water, and drying the foam to obtain matched absorbing layer wave-absorbing foam;
4) uniformly mixing 12.5 g of multi-wall carbon nano tube, 400 mL of deionized water, 4 g of carbon nano tube aqueous dispersant (TNWDIS) and 80 mL of aqueous polyurethane emulsion with the solid content of 40% to obtain wave-absorbing slurry B;
5) fully soaking soft polyurethane foam with the size of 300 mm multiplied by 8 mm in the wave-absorbing slurry B, and drying to obtain the wave-absorbing foam of the reflection absorption layer;
6) and taking the matched absorbing layer wave-absorbing foam as a first layer and the reflecting absorbing layer wave-absorbing foam as a second layer, and tightly attaching to prepare the target product.
Example 4
1) Uniformly mixing 8.2 g of hydroxylated carbon nanotube powder, 16.4 g of carbonyl iron powder, 2.8 g of carbon nanotube aqueous dispersant (TNWDIS) and 250 mL of aqueous polyurethane emulsion with the solid content of 30% to obtain wave-absorbing slurry A;
2) fully soaking soft polyurethane foam with the size of 300 mm multiplied by 12 mm in the wave-absorbing slurry A, and drying to obtain matched absorbing layer wave-absorbing foam;
3) uniformly mixing 12.5 g of low-defect graphene powder, 400 mL of deionized water and 80 mL of aqueous polyurethane emulsion with the solid content of 40% to obtain wave-absorbing slurry B;
5) fully soaking soft polyurethane foam with the size of 300 mm multiplied by 12 mm in the wave-absorbing slurry B, and drying to obtain the wave-absorbing foam of the reflection absorption layer;
6) and taking the matched absorbing layer wave-absorbing foam as a first layer and the reflecting absorbing layer wave-absorbing foam as a second layer, and tightly attaching to prepare the target product.
Example 5
1) Uniformly mixing 8.2 g of Graphene Oxide (GO) powder, 41 g of carbonyl iron powder and 250 mL of aqueous polyurethane emulsion with the solid content of 30% to obtain wave-absorbing slurry A;
2) fully soaking soft polyurethane foam with the size of 300 mm multiplied by 8 mm in the wave-absorbing slurry A, transferring the soaked foam to a Teflon reaction kettle, and thermally reducing the foam for 13 hours at the temperature of 90 ℃;
3) after the reaction is finished, taking the foam out of the Teflon reaction kettle, fully leaching the foam with deionized water, and drying the foam to obtain matched absorbing layer wave-absorbing foam;
4) uniformly mixing 12.5 g of multi-walled carbon nanotubes, 400 mL of deionized water, 1.25 g of sodium dodecyl benzene sulfonate and 50 mL of aqueous polyurethane emulsion with the solid content of 20% to obtain wave-absorbing slurry B;
5) fully soaking soft polyurethane foam with the size of 300 mm multiplied by 8 mm in the wave-absorbing slurry B, and drying to obtain the wave-absorbing foam of the reflection absorption layer;
6) and taking the matched absorbing layer wave-absorbing foam as a first layer and the reflecting absorbing layer wave-absorbing foam as a second layer, and tightly attaching to prepare the target product.
Example 6
1) Uniformly mixing 8.2 g of Graphene Oxide (GO) powder, 32.8 g of carbonyl iron powder and 250 mL of aqueous polyurethane emulsion with the solid content of 30% to obtain wave-absorbing slurry A;
2) fully soaking soft polyurethane foam with the size of 300 mm multiplied by 8 mm in the wave-absorbing slurry A, transferring the soaked foam to a Teflon reaction kettle, and thermally reducing the foam for 12 hours at the temperature of 95 ℃;
3) after the reaction is finished, taking the foam out of the Teflon reaction kettle, fully leaching the foam with deionized water, and drying the foam to obtain matched absorbing layer wave-absorbing foam;
4) uniformly mixing 12.5 g of multi-walled carbon nanotubes, 400 mL of deionized water, 6.25 g of sodium dodecyl benzene sulfonate and 80 mL of aqueous polyurethane emulsion with the solid content of 45% to obtain wave-absorbing slurry B;
5) fully soaking soft polyurethane foam with the size of 300 mm multiplied by 8 mm in the wave-absorbing slurry B, and drying to obtain the wave-absorbing foam of the reflection absorption layer;
6) and taking the matched absorbing layer wave-absorbing foam as a first layer and the reflecting absorbing layer wave-absorbing foam as a second layer, and tightly attaching to prepare the target product.
Although only the preferred embodiments of the present invention have been described in detail, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the knowledge of those skilled in the art, and all changes are encompassed in the scope of the present invention.
Claims (9)
1. A preparation method of wave-absorbing foam for absorbing low-frequency electromagnetic waves is characterized by comprising the following steps:
s1, uniformly mixing the graphene oxide powder, carbonyl iron powder and aqueous polyurethane emulsion to obtain wave-absorbing slurry A;
s2, fully dipping the first soft polyurethane foam in the wave-absorbing slurry A in S1, and then carrying out thermal reduction;
s3, after the reaction is finished, fully leaching the foam subjected to thermal reduction in S2 with deionized water, and drying to obtain matched absorbing layer wave-absorbing foam;
s4, uniformly mixing the multi-walled carbon nanotube powder, deionized water, a surfactant and a waterborne polyurethane emulsion to obtain wave-absorbing slurry B;
s5, fully soaking the second soft polyurethane foam in the wave-absorbing slurry B, and drying to obtain the wave-absorbing foam of the reflection absorption layer;
s6, tightly attaching the absorbing layer wave-absorbing foam and the reflecting absorbing layer wave-absorbing foam to prepare the wave-absorbing foam.
2. The method for preparing the wave-absorbing foam for absorbing the low-frequency electromagnetic waves according to claim 1, which is characterized by comprising the following steps: the mass ratio of the graphene oxide to the carbonyl iron powder in the S1 is 1:1-1: 5; the dosage of the S4 surfactant is 10-50% of that of the multi-wall carbon nano-tube; the solid content of the multi-wall carbon nano-tube in the S4 is 1-10%.
3. The preparation method of the wave-absorbing foam for low-frequency electromagnetic wave absorption according to claim 1, comprising the following steps:
s1, uniformly mixing the carbonylation carbon nanotube powder, a surfactant, carbonyl iron powder and an aqueous polyurethane emulsion to obtain wave-absorbing slurry A;
s2, fully dipping the first soft polyurethane foam in the wave-absorbing slurry A in S1, and then carrying out thermal reduction;
s3, after the reaction is finished, fully leaching the foam subjected to thermal reduction in S2 with deionized water, and drying to obtain matched absorbing layer wave-absorbing foam;
s4, uniformly mixing the low-defect graphene powder, deionized water and the waterborne polyurethane emulsion to obtain wave-absorbing slurry B;
s5, fully soaking the second soft polyurethane foam in the wave-absorbing slurry B, and drying to obtain the wave-absorbing foam of the reflection absorption layer;
s6, tightly attaching the absorbing layer wave-absorbing foam and the reflecting absorbing layer wave-absorbing foam to prepare the wave-absorbing foam.
4. A method for preparing a wave-absorbing foam for low-frequency electromagnetic wave absorption according to claim 1 or 3, wherein the method comprises the following steps: the solid content of the aqueous polyurethane emulsion in the S1 is 30%, and the solid content of the aqueous polyurethane emulsion in the S4 is 25% -45%.
5. A method for preparing a wave-absorbing foam for low-frequency electromagnetic wave absorption according to claim 1 or 3, wherein the method comprises the following steps: and the thermal reduction in the S2 is carried out in a Teflon reaction kettle, the thermal reduction temperature is 85-95 ℃, and the thermal reduction time is 12-15 h.
6. A method for preparing a wave-absorbing foam for low-frequency electromagnetic wave absorption according to claim 1 or 3, wherein the method comprises the following steps: and the surfactant in the S4 is one or more of sodium dodecyl sulfate, sodium dodecyl benzene sulfonate and carbon nano tube water dispersant.
7. A method for preparing a wave-absorbing foam for low-frequency electromagnetic wave absorption according to claim 1 or 3, wherein the method comprises the following steps: the wave-absorbing slurry A in the S2 completely soaks the first soft polyester foam, and the wave-absorbing slurry B in the S5 completely soaks the second soft polyurethane foam.
8. A method for preparing a wave-absorbing foam for low-frequency electromagnetic wave absorption according to claim 1 or 3, wherein the method comprises the following steps: the first flexible polyurethane foam in S2 is the same specification as the second flexible polyurethane foam in S5.
9. A method for preparing a wave-absorbing foam for low-frequency electromagnetic wave absorption according to claim 1 or 3, wherein the method comprises the following steps: the wave absorbing foam in the S6 is composed of two layers of foam, wherein the upper layer is absorbing layer foam, and the lower layer is reflecting absorbing layer foam.
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