CN113910718A - Electromagnetic shielding composite material with multilayer gradient isolation network and preparation method thereof - Google Patents
Electromagnetic shielding composite material with multilayer gradient isolation network and preparation method thereof Download PDFInfo
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- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/30—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers
- B32B27/304—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers comprising vinyl halide (co)polymers, e.g. PVC, PVDC, PVF, PVDF
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Abstract
The invention discloses an electromagnetic shielding composite material with a multilayer gradient isolation network and a preparation method thereof, belonging to the technical field of functional composite materials, and the technical scheme is as follows: the multilayer gradient isolation network electromagnetic shielding composite material comprises a carbon-based shielding layer I, a carbon-based shielding layer II, a carbon-based shielding layer III and an incident layer, and the preparation method comprises the following steps: s1, carrying out vacuum drying on the polymer particles and the conductive carbon-based filler; s2, performing ball milling on pure polymer particles to obtain a ball-milled product I; s3, performing ball milling on the mixture of the conductive carbon-based filler and the polymer particles and dry ice; s4, respectively hot-press molding the premixes obtained from S2 and S3; s5, superposing and hot-pressing the hot-pressed forming object obtained in the step S4 from top to bottom to obtain a final product.
Description
Technical Field
The invention relates to the technical field of functional composite materials, in particular to an electromagnetic shielding composite material with a multilayer gradient isolation network and a preparation method thereof.
Background
With the rapid development of modern information technology, electromagnetic waves are applied in large scale in the fields of electronic communication, radar detection, medical diagnosis and the like, but the electromagnetic waves bring about a serious radiation pollution problem. Under the background, the development of a high-performance electromagnetic shielding material is the key for realizing electromagnetic pollution protection, wherein the conductive polymer electromagnetic shielding material filled with the carbon material has the advantages of low cost, low density, easiness in processing, controllable electromagnetic shielding performance and the like, is a novel material capable of replacing the traditional metal-based electromagnetic shielding material, and has wide application prospect.
The electromagnetic shielding mechanism is generally explained by transmission line theory, and when an incident wave reaches the surface of a material, it will be reflected. The rest will continue to propagate inwards, being attenuated during the propagation between different interfaces inside the material. Therefore, loss mechanisms of the electromagnetic shield are classified into reflection loss, absorption loss, and multiple interface reflection loss. According to the theory of electromagnetism, the impedance matching of the surface of the material and the frequency conductivity of electromagnetic waves determine the reflection loss, and the thickness of the material and the conductivity determine the absorption loss of the material. Through a large number of researches, the conductive polymer-based electromagnetic shielding material with excellent conductivity can effectively prevent the transmission of electromagnetic waves, but mainly improves the total electromagnetic shielding effect by improving the reflection efficiency, thereby causing the secondary pollution of the electromagnetic waves. Therefore, the research of the electromagnetic shielding composite material with low reflection characteristics becomes particularly important.
At present, researches are mainly carried out on conducting polymer materials to construct a perfect conducting network to realize low-reflection and high-absorption shielding effectiveness, such as constructing a homogeneous structure, a foaming structure, an isolation structure, a multilayer structure and the like, but at present, the challenges of reducing reflection loss and improving absorption loss are still faced when the high electromagnetic shielding effectiveness is realized under the condition of low filler content.
In order to solve the problems, the invention provides an electromagnetic shielding composite material with a multilayer gradient isolation network and a preparation method thereof on the basis of the prior art.
Disclosure of Invention
The invention aims to provide an electromagnetic shielding composite material with a multilayer gradient isolation network and a preparation method thereof, wherein the electromagnetic shielding performance of a polymer composite material is improved by regulating and controlling a functional filler form structure.
The technical purpose of the invention is realized by the following technical scheme:
an electromagnetic shielding composite material with a multilayer gradient isolation network comprises a carbon-based shielding layer I, a carbon-based shielding layer II coated on the surface of the carbon-based shielding layer I, a carbon-based shielding layer III coated on the surface of the carbon-based shielding layer II and an incidence layer coated on the surface of the carbon-based shielding layer III.
By adopting the technical scheme, the reflection loss can be effectively reduced by utilizing the incident layer, and the gradient isolation conductive network can be constructed and formed by utilizing the carbon-based shielding layer I, the carbon-based shielding layer II and the carbon-based shielding layer III, so that electromagnetic waves can generate a large amount of interface reflection through different interfaces after entering the material, and the high electromagnetic shielding effect mainly based on the absorption loss can be realized.
This scheme of adoption can effectively reduce impedance mismatch nature, guarantees that the electromagnetic wave can enter into the combined material smoothly inside, and then can reduce reflection loss to, the electromagnetic wave enters into the combined material back, and there is a large amount of interface reflection in inside isolation network, through reducing reflection loss and increasing the two combination of absorption loss, can realize using the high electromagnetic shield mechanism that absorption loss is the main, thereby can realize increasing substantially of electromagnetic shield efficiency.
The invention also provides a preparation method of the electromagnetic shielding composite material with the multilayer gradient isolation network, which comprises the following steps:
and S1, carrying out vacuum drying treatment on the polymer particles and the conductive carbon-based filler for later use.
S2, adding the pure polymer particles processed in the step S1 into a ball milling tank for ball milling to obtain a ball milling product I.
And S3, adding the mixture of the conductive carbon-based filler and the polymer particles processed in the step S1 and dry ice into a ball milling tank in proportion for ball milling to obtain a second premix, a third premix and a fourth premix.
And S4, taking the ball-milling product I, the premix II, the premix III and the premix IV out of the ball-milling tank respectively, and performing hot-press molding respectively to obtain hot-press molded products, namely the incident layer, the carbon-based shielding layer I, the carbon-based shielding layer II and the carbon-based shielding layer III.
And S5, taking out the incident layer, the first carbon-based shielding layer, the second carbon-based shielding layer and the third carbon-based shielding layer respectively, and laminating and hot-pressing from top to bottom to obtain a final product.
By adopting the technical scheme, the conductive carbon-based filler is favorably subjected to in-situ stripping and modification through ball milling, the interface action of the conductive carbon-based filler and a polymer can be enhanced, so that the coating and pre-dispersion effects of the conductive carbon-based filler on polymer particles can be realized, the construction of a gradient isolation network can be realized, and the electromagnetic shielding efficiency can be greatly improved; hot-pressing and molding the ball-milled product I, the premix II, the premix III and the premix IV respectively to obtain an incident layer, a carbon-based shielding layer I, a carbon-based shielding layer II and a carbon-based shielding layer III; the incidence layer, the carbon-based shielding layer I, the carbon-based shielding layer II and the carbon-based shielding layer III are overlapped and hot-pressed, so that a multilayer gradient isolation network can be constructed and formed, and the incidence layer is utilized to help to reduce reflection loss; the carbon-based shielding layer I, the carbon-based shielding layer II and the carbon-based shielding layer III are utilized to contribute to forming an internal isolation network together, so that a large amount of interface reflection can occur after electromagnetic waves enter the composite material, and then the high electromagnetic shielding effect mainly based on absorption loss can be realized.
Further, the conductive carbon-based filler includes any one of graphite, expanded graphite, graphite oxide, graphene oxide, carbon nanotubes, and carbon black.
Further, the polymer particles comprise one or more of polyvinylidene fluoride, polystyrene, polyurethane, polyphenylene sulfide, polyethylene, polypropylene and polyvinyl alcohol.
Further, in the step S3, the mass ratio of the conductive carbon-based filler to the polymer particles is 2.5 to 15: 100.
further, in step S3, the addition amount of the polymer particles in the ball milling tank is 10 to 70g, the addition amount of the dry ice is 50 to 100g, and the ball milling beads are controlled to be 4 to 10: 8-20: 16-40.
Further, in the step S2 and the step S3, the ball milling time is controlled to be 24-48 h; the rotating speed of the ball mill is controlled to be 300-600 rpm.
Further, in the step S4 and the step S5, the hot pressing temperature is 170-200 ℃, and the hot pressing pressure is 5-20 MPa.
In conclusion, the invention has the following beneficial effects:
1. the gradient structure is constructed by controlling the filler content of the incident layer and the carbon-based shielding layer, so that the impedance mismatching can be effectively reduced, the electromagnetic waves can smoothly enter the composite material, and the reflection loss can be reduced.
2. After the electromagnetic waves enter the composite material, a large amount of interface reflection exists in the internal isolation network, and by combining the reduction of reflection loss and the increase of absorption loss, a high electromagnetic shielding mechanism mainly based on absorption loss can be realized, so that the electromagnetic shielding efficiency can be greatly improved.
3. The method for preparing the electromagnetic shielding composite material of the multilayer gradient isolation network has the advantages of low cost, simple process, convenient operation, high production efficiency and good industrial application prospect, and can be widely applied to preparation of electromagnetic shielding polymer-based composite materials.
Drawings
FIG. 1 is an electron microscope image of the multi-layered gradient isolated network electromagnetic shielding composite prepared in example 2;
FIG. 2 is a diagram illustrating the mechanism of shielding electromagnetic waves incident thereon;
FIG. 3 is a flow chart of composite material preparation;
FIG. 4 is a graph comparing total shielding effectiveness;
FIG. 5 is a graph of shielding performance/reflective performance in comparison.
Detailed Description
The invention is described in further detail below with reference to the following figures and embodiments:
example 1: a preparation method of an electromagnetic shielding composite material with a multilayer gradient isolation network comprises the following steps:
s1, selecting raw materials: polyvinylidene fluoride (PVDF, Suwei 6010, USA), melt index of 8g/10min (190 ℃, 2.16Kg), density of 1.75g/cm3Melting point 165 ℃; graphite (Qingdao Xingdong graphite Co., Ltd.) with a density of 2.21g/cm3(ii) a Dry ice (chengdu conogong chemical limited).
And (3) putting the polyvinylidene fluoride and the graphite into a vacuum oven, and carrying out vacuum drying for 12h at the temperature of 60 ℃.
S2, adding the pure polyvinylidene fluoride processed in the step S1 into a stainless steel vacuum ball milling tank, and carrying out ball milling by using a planetary ball mill, wherein the ball milling speed is 500rpm, and the ball milling time is 36 hours, so that a ball milling product I is obtained.
And S3, adding the polyvinylidene fluoride, the graphite and the dry ice processed in the step S1 into a planetary ball mill for ball milling, wherein the ratio of the mass of the graphite to the total mass of the polyvinylidene fluoride and the graphite is 5%, 10% and 15%, the mass of the dry ice is 75g, the ball milling speed is 500rpm, and the ball milling time is 36h, so that a second premix, a third premix and a fourth premix are obtained.
And S4, respectively taking the ball-milling product I, the premix II, the premix III and the premix IV out of the ball-milling tank, respectively carrying out hot-press molding at 190 ℃ under 10MPa for 5min to obtain a pure PVDF incident layer with the thickness of 500 micrometers, a polyvinylidene fluoride/graphite shielding layer with the graphite mass ratio of 5%, a polyvinylidene fluoride/graphite shielding layer with the graphite mass ratio of 10% and a polyvinylidene fluoride/graphite shielding layer with the graphite mass ratio of 15%.
S5, laminating and hot-pressing a pure PVDF incident layer, a polyvinylidene fluoride/graphite shielding layer with graphite mass ratio of 5%, a polyvinylidene fluoride/graphite shielding layer with graphite mass ratio of 10% and a polyvinylidene fluoride/graphite shielding layer with graphite mass ratio of 15% from top to bottom under the conditions that the hot-pressing temperature is 180 ℃, the hot-pressing pressure is 5MPa, and the pressure is maintained for 5min to obtain a final product with the total thickness of 2 mm.
Example 2: a method for preparing an electromagnetic shielding composite material with a multilayer gradient isolation network, as shown in fig. 1, comprises the following steps:
s1, selecting raw materials: polyvinylidene fluoride (PVDF, Suwei 6010, USA), melt index of 8g/10min (190 ℃, 2.16Kg), density of 1.75g/cm3Melting point 165 ℃; carbon nanotubes (NC7000, Belgium, average diameter 9.5 nm); dry ice (chengdu conogong chemical limited).
And (3) putting the polyvinylidene fluoride and the carbon nano tube into a vacuum oven, and carrying out vacuum drying for 12h at the temperature of 60 ℃.
S2, adding the pure polyvinylidene fluoride processed in the step S1 into a stainless steel vacuum ball milling tank, and carrying out ball milling through a planetary ball mill, wherein the ball milling speed is 500rpm, and the ball milling time is 36 hours, so that a ball milling product I is obtained.
And S3, adding the polyvinylidene fluoride, the carbon nano tubes and the dry ice processed in the step S1 into a planetary ball mill for ball milling, wherein the mass ratio of the carbon nano tubes to the total mass of the polyvinylidene fluoride and the graphite is 5%, 10% and 15%, the mass ratio of the dry ice is 75g, the ball milling speed is 500rpm, and the ball milling time is 36h, so that a second premix, a third premix and a fourth premix are obtained.
And S4, respectively taking the ball-milling product I, the premix II, the premix III and the premix IV out of the ball-milling tank, respectively carrying out hot-press molding, wherein the hot-press temperature is 190 ℃, the hot-press pressure is 10MPa, and the pressure is maintained for 5min to obtain a pure PVDF incident layer with the thickness of 500 mu m, a polyvinylidene fluoride/carbon nanotube shielding layer with the carbon nanotube mass ratio of 5%, a polyvinylidene fluoride/carbon nanotube shielding layer with the carbon nanotube mass ratio of 10% and a polyvinylidene fluoride/carbon nanotube shielding layer with the carbon nanotube mass ratio of 15%.
S5, laminating and hot-pressing a pure PVDF incident layer, a polyvinylidene fluoride/carbon nano tube shielding layer with 5% of carbon nano tube mass ratio, a polyvinylidene fluoride/carbon nano tube shielding layer with 10% of carbon nano tube mass ratio and a polyvinylidene fluoride/carbon nano tube shielding layer with 15% of carbon nano tube mass ratio from top to bottom under the conditions that the hot-pressing temperature is 180 ℃, the hot-pressing pressure is 5MPa, and the pressure is maintained for 5min to obtain a final product with the total thickness of 2 mm.
Example 3: a preparation method of an electromagnetic shielding composite material with a multilayer gradient isolation network comprises the following steps:
s1, selecting raw materials: polystyrene (Taiwan Chimei), melt index 8g/10min (190 deg.C, 2.16Kg), density 1.15g/cm3Melting point 173 ℃; graphite oxide (Qingdao Xingdong graphite Co., Ltd.) with a density of 2.21g/cm3(ii) a Dry ice (chengdu conogong chemical limited).
Placing the polystyrene and the graphite oxide in a vacuum oven, and drying for 12 hours in vacuum at the temperature of 60 ℃.
S2, adding the pure polystyrene processed in the step S1 into a stainless steel vacuum ball milling tank, and carrying out ball milling by a planetary ball mill, wherein the ball milling rotation speed is 500rpm, and the ball milling time is 36h, so that a ball milling product I is obtained.
And S3, adding the polystyrene, the graphite oxide and the dry ice processed in the step S1 into a planetary ball mill for ball milling, wherein the mass ratio of the graphite oxide to the total mass of the polystyrene and the graphite oxide is 5%, 10% and 15%, the mass ratio of the dry ice is 75g, the ball milling speed is 500rpm, and the ball milling time is 36h, so that a second premix, a third premix and a fourth premix are obtained.
S4, taking the ball-milling product I, the premix II, the premix III and the premix IV out of the ball-milling tank respectively, and performing hot-press molding respectively at 190 ℃ under 10MPa for 5min to obtain a pure polystyrene incident layer, a polystyrene/graphite oxide shielding layer and a polystyrene/graphite oxide shielding layer, wherein the pure polystyrene incident layer, the polystyrene/graphite oxide shielding layer and the graphite oxide shielding layer are 500 microns in thickness, the polystyrene/graphite oxide shielding layer and the graphite oxide shielding layer are 5% in mass, 10% in mass and 15% in mass respectively.
S5, laminating and hot-pressing the pure polystyrene incident layer, the polystyrene/graphite oxide shielding layer with graphite oxide mass ratio of 5%, the polystyrene/graphite oxide shielding layer with graphite oxide mass ratio of 10% and the polystyrene/graphite oxide shielding layer with graphite oxide mass ratio of 15% from top to bottom under the conditions that the hot-pressing temperature is 180 ℃, the hot-pressing pressure is 5MPa, and the pressure is maintained for 5min to obtain the final product with the total thickness of 2 mm.
Comparative example 1: the difference from example 1 is that: in step S3, the ratio of the graphite mass to the total mass of the polyvinylidene fluoride and the graphite is respectively 2.5%, 5% and 7.5%; the hot pressing temperature in the step S4 is 108 ℃, the hot pressing pressure is 10MPa, and the pressure is maintained for 5 min; in step S5, the hot pressing temperature is 170 ℃, the hot pressing pressure is 5MPa, and the pressure is maintained for 5 min.
Comparative example 2: the difference from example 2 is that: in step S3, the ratio of the mass of the carbon nanotubes to the total mass of the polyvinylidene fluoride and the carbon nanotubes is 2.5%, 5%, and 7.5%, respectively.
Comparative example 3: the difference from example 2 is that: step S2 is not included, 4 layers in step S3 are all carbon-based shielding layers, the mass ratio of the carbon nano tubes to the total mass of the polyvinylidene fluoride and the carbon nano tubes is 7.5%, and in step S4, the polyvinylidene fluoride/carbon nano tube shielding layers with the mass ratio of the 4 layers of the carbon nano tubes being 7.5% are overlapped and hot-pressed to obtain a final product with the total thickness of 2mm
Comparative example 4: the difference from example 2 is that: in step S3, the thickness of the pure PVDF incident layer obtained by hot press molding, the polyvinylidene fluoride/carbon nanotube shielding layer with the carbon nanotube mass ratio of 5%, the polyvinylidene fluoride/carbon nanotube shielding layer with the carbon nanotube mass ratio of 10%, and the polyvinylidene fluoride/carbon nanotube shielding layer with the carbon nanotube mass ratio of 15% are all 375 μm; in step S5, the final product obtained by the superposition heat pressing has a total thickness of 1.5 mm.
Comparative example 5: the difference from example 2 is that: in step S3, the thickness of the pure PVDF incident layer obtained by hot press molding, the polyvinylidene fluoride/carbon nanotube shielding layer with the carbon nanotube mass ratio of 5%, the polyvinylidene fluoride/carbon nanotube shielding layer with the carbon nanotube mass ratio of 10%, and the polyvinylidene fluoride/carbon nanotube shielding layer with the carbon nanotube mass ratio of 15% are 250 μm; in step S5, the final product obtained by the superposition heat pressing has a total thickness of 1 mm.
TABLE 1 electromagnetic shielding effectiveness values of examples and comparative examples
As shown in table 1, in example 1, polyvinylidene fluoride is used as a polymer raw material, graphite is used as a carbon-based conductive filler, graphite is firstly peeled off by ball milling to coat the graphite on the surface of polyvinylidene fluoride particles, a conductive isolation network is formed by hot pressing, and then a shielding layer including an incident layer and a carbon-based filler with the content increasing from top to bottom is laminated in four layers to finally obtain a multilayer gradient isolation network. The result shows that compared with pure polyvinylidene fluoride, the gradient isolation conductive network greatly improves the shielding effectiveness of the composite material, the electromagnetic shielding effectiveness reaches 52dB, the electromagnetic shielding reflection effectiveness is only 1.2dB, and the shielding mechanism of the gradient isolation conductive network is mainly absorption.
In embodiment 2, polyvinylidene fluoride is used as a polymer raw material, carbon nanotubes are used as carbon-based conductive fillers, the carbon nanotubes are dispersed by ball milling to be coated on the surfaces of polyvinylidene fluoride particles, a conductive isolation network is formed by hot pressing, and then a shielding layer with an incident layer and carbon-based filler content increasing from top to bottom is laminated in four layers to finally obtain a multilayer gradient isolation network. The results show that the gradient isolated conductive network greatly improves the shielding effectiveness of the composite material compared with pure polyvinylidene fluoride, and the electromagnetic shielding effectiveness is further improved by 66dB compared with example 1, because the carbon nanotubes are easier to lap to form a conductive path, and the electromagnetic shielding reflection effectiveness is only 0.5 dB.
In example 3, polystyrene is used as a polymer raw material, graphite oxide is used as a carbon-based conductive filler, the graphite oxide is firstly peeled off by ball milling and coated on the surface of polyvinylidene fluoride particles, a conductive isolation network is formed by hot pressing, and then a shielding layer including an incident layer and a carbon-based filler with the content increasing from top to bottom is laminated in four layers to finally obtain a multilayer gradient isolation network. The result shows that compared with pure polystyrene, the gradient isolation conductive network greatly improves the shielding effectiveness of the composite material, the electromagnetic shielding effectiveness reaches 48dB, and the electromagnetic shielding reflection effectiveness is only 1.5 dB.
In comparative example 1, polyvinylidene fluoride is used as a polymer raw material, graphite is used as a carbon-based conductive filler, the polyvinylidene fluoride is firstly subjected to ball milling, graphite stripping and modification, the polyvinylidene fluoride is coated on the surface of polyvinylidene fluoride particles, a conductive isolation network is formed through hot pressing, and then a shielding layer (the mass ratio of graphite to the incident layer is respectively 2.5%, 5% and 7.5%) with the content of the carbon-based filler increased from top to bottom is laminated for four layers, so that the multilayer gradient isolation network composite material is finally obtained, wherein the electromagnetic shielding efficiency reaches 45dB, and the electromagnetic shielding reflection efficiency is only 0.9 dB.
In comparative example 2, polyvinylidene fluoride is used as a polymer raw material, carbon nanotubes are used as carbon-based conductive filler, the carbon nanotubes are dispersed by ball milling to be coated on the surfaces of polyvinylidene fluoride particles, a conductive isolation network is formed by hot pressing, and then a shielding layer (the mass ratio of the carbon nanotubes is respectively 2.5%, 5% and 7.5%) which comprises an incident layer and the carbon-based filler is increased from top to bottom is laminated by four layers, so that the electromagnetic shielding efficiency of the multilayer gradient isolation network composite material is 54dB, and the reflection efficiency value is only 0.3 dB.
In comparative example 3, polyvinylidene fluoride is used as a polymer raw material, carbon nanotubes are used as a carbon-based conductive filler, the carbon nanotubes are dispersed by ball milling to be coated on the surfaces of polyvinylidene fluoride particles, a conductive isolation network (the mass ratio of the carbon nanotubes is 7.5%) is formed by hot pressing, and four layers are laminated, compared with example 2, the electromagnetic shielding efficiency of the common isolation network composite material reaches 40dB, the reflection efficiency value is 29dB, and the reason that the reflection efficiency is higher is that the electromagnetic shielding mechanism of the isolation network is mainly reflection.
In comparative example 4, polyvinylidene fluoride is used as a polymer raw material, carbon nanotubes are used as carbon-based conductive fillers, the polyvinylidene fluoride is coated on the surfaces of polyvinylidene fluoride particles through ball milling dispersion carbon nanotube modification, a conductive isolation network is formed through hot pressing, and then a shielding layer (the mass ratio of graphite is respectively 5%, 10% and 15%) which comprises an incident layer and the carbon-based fillers is increased from top to bottom is laminated for four layers, so that the electromagnetic shielding efficiency of the multilayer gradient isolation network composite material (the total thickness is 1.5mm) is finally obtained and reaches 46 dB.
In comparative example 5, polyvinylidene fluoride is used as a polymer raw material, carbon nanotubes are used as carbon-based conductive filler, the carbon nanotubes are dispersed by ball milling to be modified and coated on the surface of polyvinylidene fluoride particles, a conductive isolation network is formed by hot pressing, the mass ratios of graphite of a shielding layer, which comprises an incident layer and the carbon-based filler, are respectively (5%, 10% and 15%), four layers are laminated, and finally the multilayer gradient isolation network composite material (the total thickness is 1mm) is obtained, and the electromagnetic shielding efficiency reaches 35 dB.
In the embodiment of the invention, the gradient structure is constructed by controlling the filler contents of the incident layer and the carbon-based shielding layer, so that the impedance mismatching can be effectively reduced, the electromagnetic waves can be ensured to smoothly enter the composite material, and the reflection loss can be further reduced; meanwhile, after the electromagnetic waves enter the composite material, a large amount of interface reflection exists in the internal isolation network, and by combining the reduction of reflection loss and the increase of absorption loss, a high electromagnetic shielding mechanism mainly based on absorption loss can be realized, so that the electromagnetic shielding efficiency can be greatly improved; in addition, the method for preparing the electromagnetic shielding composite material of the multilayer gradient isolation network, provided by the invention, has the advantages of low cost, simple process, convenience in operation, high production efficiency and good industrial application prospect, and can be widely applied to preparation of electromagnetic shielding polymer-based composite materials.
The present embodiment is only for explaining the present invention, and it is not limited to the present invention, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present invention.
Claims (8)
1. An electromagnetic shielding composite material with a multilayer gradient isolation network is characterized in that: the light-emitting diode comprises a carbon-based shielding layer I, a carbon-based shielding layer II covering the surface of the carbon-based shielding layer I, a carbon-based shielding layer III covering the surface of the carbon-based shielding layer II and an incidence layer covering the surface of the carbon-based shielding layer III.
2. A preparation method of an electromagnetic shielding composite material with a multilayer gradient isolation network is characterized by comprising the following steps:
s1, carrying out vacuum drying treatment on the polymer particles and the conductive carbon-based filler for later use;
s2, adding the pure polymer particles processed in the step S1 into a ball milling tank for ball milling to obtain a ball milling product I;
s3, adding the mixture of the conductive carbon-based filler and the polymer particles processed in the step S1 and dry ice into a ball milling tank in proportion for ball milling to obtain a second premix, a third premix and a fourth premix;
s4, taking the ball-milling product I, the premix II, the premix III and the premix IV out of the ball-milling tank respectively, and performing hot-press molding respectively to obtain hot-press molded products, namely an incident layer, a carbon-based shielding layer I, a carbon-based shielding layer II and a carbon-based shielding layer III;
and S5, taking out the incident layer, the first carbon-based shielding layer, the second carbon-based shielding layer and the third carbon-based shielding layer respectively, and laminating and hot-pressing from top to bottom to obtain a final product.
3. The method for preparing the electromagnetic shielding composite material with the multilayer gradient isolation network as claimed in claim 2, is characterized in that: the conductive carbon-based filler comprises any one of graphite, expanded graphite, graphite oxide, graphene oxide, carbon nanotubes and carbon black.
4. The method for preparing the electromagnetic shielding composite material with the multilayer gradient isolation network as claimed in claim 2, is characterized in that: the polymer particles comprise one or more of polyvinylidene fluoride, polystyrene, polyurethane, polyphenylene sulfide, polyethylene, polypropylene and polyvinyl alcohol.
5. The method for preparing the electromagnetic shielding composite material with the multilayer gradient isolation network as claimed in claim 2, is characterized in that: in the step S3, the mass ratio of the conductive carbon-based filler to the polymer particles is 2.5-15: 100.
6. the method for preparing the electromagnetic shielding composite material with the multilayer gradient isolation network as claimed in claim 2, is characterized in that: in the step S3, the addition amount of polymer particles in the ball milling tank is 10-70 g, the addition amount of dry ice is 50-100 g, and the ball milling beads are controlled to be 4-10: 8-20: 16-40.
7. The method for preparing the electromagnetic shielding composite material with the multilayer gradient isolation network as claimed in claim 2, is characterized in that: in the step S2 and the step S3, the ball milling time is controlled to be 24-48 h; the rotating speed of the ball mill is controlled to be 300-600 rpm.
8. The method for preparing the electromagnetic shielding composite material with the multilayer gradient isolation network as claimed in claim 2, is characterized in that: in the step S4 and the step S5, the hot pressing temperature is 170-200 ℃, and the hot pressing pressure is 5-20 MPa.
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