CN110540729A - light high-conductivity shielding material and preparation method thereof - Google Patents

Abstract

the invention discloses a light high-conductivity shielding material and a preparation method thereof. The electric shielding foam composite material comprises a matrix with a foam porous structure, wherein the matrix is made of a high molecular polymer as a framework, conductive fillers are uniformly dispersed in the matrix, and nano silver particles grow in situ on the inner surface and the outer surface of the matrix; the matrix with the foam porous structure is prepared by a template sacrifice method, wherein the template sacrifice method is to mix a mixed organic solution of a high molecular polymer and a conductive filler with a pore-forming agent, remove the organic solvent after mixing uniformly, and then put into water to dissolve and remove the pore-forming agent to obtain the matrix with the foam porous structure. The composite material prepared by the invention has high electromagnetic shielding effectiveness of 60-90dB between 8.2GHz and 12.5GHz, and the density of the material is between 0.1 and 0.16g cm < -1 >, so that the material is light and thin, and can meet the requirements of electronic devices on electromagnetic shielding materials.

Description

light high-conductivity shielding material and preparation method thereof

Technical Field

The invention relates to the field of materials, in particular to a light high-conductivity shielding material and a preparation method and application thereof.

Background

Light and high-efficiency electromagnetic shielding materials are an important research direction in the field of electromagnetic shielding materials. The light electromagnetic shielding materials commonly used at present mainly comprise conductive foam, graphene foam, metal porous materials, carbon nanotube composite foam and the like. The conductive foam is prepared by depositing conductive metal particles on the surface of the macromolecular foam framework, has higher electromagnetic shielding performance, but the surface metal particles and the surface of the macromolecular foam framework have weak bonding force and are easy to fall off after repeated deformation. The graphene foam has the defects of complex preparation process, high cost, difficulty in practicability and the like. Most metal materials are heavy, non-corrosion resistant, difficult to process and expensive. The carbon nano tube composite foam has a series of excellent performances, such as electrical conductivity, good mechanical properties (flexibility, elasticity and the like), high porosity, low density, oleophylic and hydrophobic properties and the like.

The traditional macromolecule is a plurality of macromolecules connected by covalent bonds, each chemical bond forming the macromolecule is very stable, electrons forming the chemical bonds cannot move, no very active lone pair electrons or very active bonding electrons exist in the molecule, and the molecule is electrically neutral, so the macromolecule is always regarded as an insulating material. Generally, the resistivity value is defined as 1010 ohm cm, and the insulating polymer material is defined above this limit, and hereinafter, the insulating polymer material is collectively referred to as a conductive polymer material. The conductivity of a material is caused by the movement of charged particles present inside the material. These charged particles may be positive or negative ions, or electrons or holes, and are generally called carriers. The carriers move in the direction of the electric field under the action of the applied electric field, and thus, a current is formed. The conductivity of a material is related to the number of carriers contained in the material and the movement speed of the carriers, and the concentration and the mobility of the carriers are microscopic physical quantities for representing the conductivity of the material. The conductive polymer material can be used for a plurality of materials, thermoplastic elastomers and thermosetting elastomers are the most common, and thermoplastic elastomer SBS and polymer matrix materials with the same functions such as SIS and SEBS have outstanding application on the conductive polymer material.

Carbon black is the most common functional reinforcing filler among carbon-based fillers. The smaller the carbon black particles, i.e., the more carbon black particles per unit volume of the compound, the greater the probability of contact between carbon black particles or the smaller the inter-particle spacing, the lower the electrical resistance, and the better the conductivity. Among the carbon blacks with the same particle size, the high-structure carbon black has good conductivity, which is caused by the fact that the high-structure carbon black has more chains and thus forms more chain-branch interlaced conductive channels. Volatile matter or residual tar-like matter on the surface of the carbon black often forms an insulating film on the surface of the carbon black, thereby reducing the conductivity of the carbon black. The conductivity of such carbon black is improved by heat treatment in vacuum or inert gas to remove the surface insulating film. Carbon black having a greater surface roughness has better conductivity because the probability of contact between coarse carbon black particles is greater than between smooth carbon black particles in a compound having the same amount of carbon black. Similar conductive fillers are carbon nanofibers, carbon nanotubes, carbon fibers, graphite, graphene, and the like.

The conductive high polymer material has the same electromagnetic shielding performance, and has the advantages of light weight, good toughness, easy processing, easy adjustment of conductivity, low cost, easy large-area coating and convenient construction. Therefore, the electromagnetic shielding material is an ideal electromagnetic shielding material for replacing the traditional metal, and can be applied to electronic and electrical elements such as computers, mobile phones, televisions, computers, cardiac pacemakers and the like.

The preparation method of the composite conductive polymer at present mainly comprises three methods, namely a conductive filler compounding method, a conductive filler laminating compounding method and a surface conductive film forming method.

The advantages are as follows: light weight (small density), easy forming and processing, conductivity and product one-time completion, wide resistivity adjusting range, low cost and easy structure adjustment.

Challenge: the stability needs to be improved, and new application fields need to be discovered and developed.

As is known from the literature, the percolation threshold is an important parameter for filling composite conductive polymers with carbon-based materials such as carbon black and carbon nanotubes, and the lower the value, the more effective the filler is, and the required conductivity can be obtained with a smaller filling amount. Under the existing technology, it is important to control the percolation threshold of the conductive polymer.

(1) on the premise of improving the conductive polymer composite material, the consumption of the conductive filler is reduced;

(2) On the premise of increasing the using amount of the conductive filler to improve the conductive performance, the forming processing performance, the mechanical property and other properties of the conductive polymer composite material are maintained or increased;

(3) Developing new varieties of conductive polymer composite materials and developing new application fields;

(4) The conductive polymer composite material is multifunctional, and has the advantages of excellent flame retardance, barrier property, high temperature resistance, corrosion resistance, friction resistance and the like besides the conductivity.

The conductive filler compounding method is the most commonly used method for dispersing the conductive filler in the composite material at present. It uses polymer as matrix, and utilizes blending method to make conductive filler disperse in it so as to obtain the invented product with conductivity. Conductive fillers used in this process are carbon black, carbon fibers, metal fibers, metallized carbon fibers, metal foils, tapes, silver-plated glass spheres, and the like. The conductive filler is processed and formed well by a dispersion and compounding method, and the cost is low, but the problems of the conductive filler are as follows: (1) the distribution of the conductive filler in the matrix tends to be uneven, causing inconsistent conductivity throughout the finished product; (2) the adhesion between the conductive filler and the matrix is generally poor.

Disclosure of Invention

The invention adopts a material mixing method, uses cheap carbon materials as fillers, uses common polymer matrixes such as a series of thermoplastic elastomers such as SBS, SIS, SEBS and the like, has the advantages of capability of melting by heating, solidification by cooling and forming, lighter matrixes, good adhesive force between the matrixes and the fillers, capability of supporting a main body structure of foam, and uniform dispersion of the conductive fillers in polymers by using the main body structure as a framework of the foam materials. Meanwhile, the foam type porous material prepared by the experiment has the advantages of stable structure, light weight, corrosion resistance, excellent conductivity and the like.

The invention provides an electric shielding foam composite material, which comprises a matrix of a foam porous structure, wherein the matrix is made of a high molecular polymer as a framework, conductive fillers are uniformly dispersed in the matrix, and nano silver particles grow on the inner surface and the outer surface of the matrix in situ.

In the technical scheme of the invention, the high molecular polymer is selected from one or more of styrene-butadiene-styrene block copolymer (SBS), styrene-ethylene-butadiene-styrene block copolymer (SEBS), styrene-isoprene-styrene block copolymer (SIS) and hydrogenated styrene-isoprene copolymer (SEPS).

In the technical scheme of the invention, the conductive filler is selected from carbon-based fillers, preferably carbon nanotubes, carbon fibers, carbon nanofibers, graphene, graphite and carbon black.

In the solution according to the invention, the density of the matrix is 0.05-0.1g cm-1, preferably 0.05-0.08g cm-1. When the sample density was higher than 0.08g cm-1, the resilience was poor as compared with 0.08g cm-1.

In the technical scheme of the invention, the matrix of the foam porous structure is prepared by a template sacrificial method, wherein the template sacrificial method is that a mixed organic solution of a high molecular polymer and a filler is mixed with a pore-forming agent, the organic solvent is removed after the mixture is uniform, and then the mixture is put into water to be dissolved and remove the pore-forming agent, so that the matrix of the foam porous structure is obtained; the pore-forming agent is water-soluble inorganic salt or sugar, the inorganic salt or sugar is in a dispersed particle or powder shape, preferably, the particle diameter of the inorganic salt or sugar is 100-3000 μm, preferably in the range of 100-1000 μm, more preferably 100-300 μm.

Wherein the organic solvent is removed by drying, preferably the drying temperature is lower than 100 ℃, more preferably lower than 80 ℃.

in the technical scheme of the invention, the inorganic salt is selected from one or a combination of more of sodium chloride, potassium chloride, sodium carbonate, potassium carbonate, sodium bicarbonate and potassium bicarbonate.

In the technical scheme of the invention, the nano silver is attached to the surface of the substrate by the following method: soaking a substrate containing conductive filler in a silver salt solution, adding a reducing agent for in-situ reduction, and growing in situ on the inner surface and the outer surface of the substrate to obtain a nano silver layer;

Preferably, the silver salt solution takes ethanol, propanol or butanol as a solvent;

Preferably, the silver salt is selected from silver trifluoroacetate, silver nitrate, silver acetate, silver oxide, silver sulfate, silver carbonate, silver formate, silver acetate.

Preferably, the reducing agent is selected from hydrazine hydrate, concentrated sulfuric acid, hydroiodic acid, sodium borohydride.

According to the scheme, the silver salt solution can swell the matrix polymer, silver ions permeate into the shallow surface layer and the surface of the polymer matrix, and hydrazine hydrate is used for reducing silver salt on the SBS matrix, so that a thin nano silver layer grows on the surface of the SBS matrix in situ, and nano silver particles are embedded into the shallow surface layer of the polymer matrix SBS.

in the technical scheme of the invention, the mass ratio of the conductive filler for preparing the matrix to the high molecular compound is 1: 3-9.

In the technical scheme of the invention, the mass of the silver nano-silver particles accounts for 30-50 wt% of the mass of the electric shielding foam composite material.

In the technical scheme of the invention, the density of the electric shielding foam composite material is 0.1-0.16g cm < -1 >.

In the technical scheme of the invention, the EMI SE value of the electric shielding foam composite material is 60-90 dB.

In the technical scheme of the invention, the shielding value of the foam composite material CB/SBS is 5-15 dB.

In another aspect, the present invention provides a method for preparing an electrically shielding foam composite, comprising the steps of:

1) Respectively dissolving high molecular polymer and conductive filler in organic solvent, mixing uniformly,

2) Mixing a pore-forming agent with the mixed solution obtained in the step 1),

3) Removing the solvent, removing the pore-forming agent by using water, and drying to obtain a foamed substrate containing the conductive filler;

4) Soaking the substrate containing the conductive filler in a silver salt solution, adding a reducing agent for in-situ reduction, growing in situ on the inner surface and the outer surface of the substrate to obtain a nano silver layer, and drying to obtain the electromagnetic shielding foam composite material.

Advantageous effects

1. Compared with the traditional conductive composite metal material, the composite conductive high polymer material has the following advantages: the preparation is simple and economical, the molding processing is convenient, the electrical property and the mechanical property of the material can be adjusted under certain conditions, and the sample has the characteristic of high molecular.

2. The conductive filler which can be applied to the invention has wide range, and carbon-based fillers can be applied, for example, Carbon Black (CB) is spherical filler, has isotropy, low price and low density, is the conductive filler which has the largest using amount and is most widely applied at present, can effectively improve the electromagnetic property of the composite material, and can reduce the conductive seepage threshold value of the composite material and increase the electromagnetic shielding efficiency. In addition, the conductive filler can also be common carbon-based materials, such as a series of conductive carbon fillers of carbon nanotubes, carbon fibers, carbon nanofibers, graphene, graphite, and the like.

3. The characteristics that the high molecular compound has an adsorption effect on silver salt and the specific surface area of the foamy matrix material is large are utilized, so that silver salt is reduced in situ on a pore column of SBS, nano silver particles can grow in the column, and the conductivity and shielding performance of the formed composite material are greatly improved.

4. in the experiment, soluble fillers are used as pore-forming agents to prepare the polymer foam with adjustable pore diameter and pore appearance, the selection range of the fillers is wide, and the fillers are non-toxic and harmless, are dissolved in water and have no influence on the environment.

5. the electromagnetic shielding effect of the conductive composite material sample is mainly absorption, the overall shielding performance of the foam composite material is improved through the combined action of the absorption effect of the carbon material on electromagnetic waves and the reflection effect of the metal silver on the electromagnetic waves, and the combined action of the absorption effect of the carbon material on the electromagnetic waves and the reflection effect of the metal silver on the electromagnetic waves supplement each other, so that the EMI value of the conductive foam composite material reaches a higher value.

compared with the existing experimental scheme:

the present invention solves the two problems described above: (1) the distribution of the conductive filler in the matrix tends to be uneven, causing inconsistent conductivity throughout the finished product; (2) the adhesion between the conductive filler and the matrix is generally poor.

the invention adopts a very simple experimental method, the conductive filler is uniformly dispersed in the matrix by manufacturing the foam type porous material, the appearance of the sample prepared by the experiment is regular, the conductive filler is uniformly distributed in the matrix, a resistance instrument is adopted to carry out resistance test on the upper part and the lower part of the surface of the sample, and the resistance values of the sample are approximately equal. The conductivity of the solid sample is basically equal everywhere, the conductive filler and the matrix are firmly bonded, and the solid sample cannot be separated even after being subjected to ultrasonic treatment for more than 24 hours in an ultrasonic machine through experimental verification. Meanwhile, a layer of silver is uniformly adsorbed on the surface and the inside of the macromolecular composite foam by a chemical method, so that the conductivity is greatly improved, and the electromagnetic wave shielding material with good magnetic field shielding property and excellent molding processability of a high-frequency electromagnetic field of 8.2-12.5GHz is prepared. Meanwhile, the method has the characteristics of low cost of raw materials, light sample mass (the density is 0.1-0.16g cm < -1 >), excellent conductivity (the conductivity is 400-700s m < -1 >), and good anti-electromagnetic wave radiation effect (the SE value is 60-90 dB).

In the present invention, SBS is a styrene-butadiene-styrene block copolymer, and CB is carbon black.

Drawings

FIG. 1 is the results of an experiment demonstrating the use of a squaraine as a pore former.

Fig. 2 is a flow chart illustrating the preparation of the electromagnetic shielding foam composite according to the present invention. Wherein, (a) is the preparation flow chart illustration, (b) is the picture of SBS/CB and SBS/CB/Ag on the stamen, and (c) is the state before and after the SBS/CB/Ag sample is compressed for a plurality of times.

FIG. 3 shows the results of the compression cycle test of the present invention, wherein (a) is SBS/Ag sample and (b) is SBS/CB/Ag.

FIG. 4 is a SEM image of a CB/SBS composite material, wherein a, b, c are foams prepared using sodium bicarbonate with the smallest particle size as a pore former (example 1), d, e, f are foams prepared using sodium chloride with the medium particle size as a pore former (example 2), and g, h, i are foams prepared using sugar with the largest particle size as a pore former (example 3).

FIG. 5 is an SEM photograph of the CB/SBS/Ag composite material prepared in example 6, wherein a, b, c and d are SBS/CB/Ag composite materials obtained by silver reduction of foams (example 1) prepared by using sodium bicarbonate with the smallest particle size as a pore-forming agent, e, f, g and h are SBS/CB/Ag composite materials obtained by silver reduction of foams (example 2) prepared by using sodium chloride with the medium particle size as a pore-forming agent, and i, j, k and l are SBS/CB/Ag composite materials obtained by silver reduction of foams (example 3) prepared by using sugar with the largest particle size as a pore-forming agent.

FIG. 6 is a photograph of SBS/Ag composite material prepared by literature method, i.e. directly adsorbing silver on SBS surface, wherein a is sample photograph, b and c are scanning electron microscope photographs of foam sample, d and e are scanning electron microscope photographs of/Ag composite material.

FIG. 7 shows the electromagnetic shielding values of the CB/SBS/Ag sample. The EMI SE value of SBS/CB/Ag formed by silver salt reduction of SBS/CB at different thickness, (b) the EMI SE value of SBS/Ag and SBS/CB/Ag formed by silver salt reduction of SBS and SBS/CB at the same thickness, (c) the EMI SE value of SBS/CB/Ag under multiple reduction, (d) the SEAbs and SEref values of SBS/CB/Ag.

FIG. 8 is a foam object diagram.

Fig. 9 is a schematic diagram of material shielding theory.

Figure 10 is a schematic of sodium bicarbonate, sodium chloride, and sugar in an example.

Detailed Description

Example 1 foam sample preparation experiment

before the experiment, the needed polymer SBS is dried and then is placed in an oven to be dried for about 2 hours at the temperature of 50-60 ℃ for use. Ethyl acetate is used as a solvent of SBS in the experiment, 20 wt% of mixed solution of SBS/ethyl acetate is prepared for standby, meanwhile, conductive filler particle Carbon Black (CB) is used as carbon-series filler, the CB is dispersed in the ethyl acetate solution by an ultrasonic dispersion method, the proportion is 5 wt%, concentration is controlled in the experiment process, and the solution is excessively viscous and colloidal due to overhigh concentration. Secondly, mixing 20 wt% SBS/ethyl acetate and 5 wt% CB/ethyl acetate solution in a fixed ratio to prepare a mixed solution of CB and SBS in ethyl acetate, wherein the ratio of CB to SBS is 1: and 4, stirring the mixed solution by magnetic force for more than 24 hours, uniformly stirring the mixed solution to mix the materials, stirring and mixing the mixed solution and a crystalline solid of sodium bicarbonate which is used as a pore-forming agent and is soluble in water by a mixer, transferring the mixed solution into a glass dish, and putting the glass dish into an oven at 75 ℃ for 24 hours to remove the ethyl acetate solvent in the glass dish. And after the solvent is completely volatilized, taking out the sample, placing the sample in deionized water for a period of time to remove the soluble pore-forming agent in the sample, and drying to form the SBS/CB polymer composite foam.

Example 2 foam sample preparation experiment

The experimental process is similar to that of example 1, and the pore-forming agent is replaced by sodium chloride to carry out the experiment, so that the ratio of the pore diameter of the SBS/CB obtained polymer composite foam is larger than 1.

Example 3 foam sample preparation experiment

The experimental procedure was similar to that of example 1, and the pore-forming agent was replaced with only crude sugar to carry out the experiment, and the SBS/CB polymer syntactic foam was obtained in the same manner with a slightly larger pore-size ratio of 2.

Example 4 foam sample preparation experiment

The experimental procedure was similar to that of example 1, and an experiment was carried out by replacing only the polymer matrix with SIS, and a polymer composite foam of SIS/CB was also obtained.

Example 5 foam sample preparation experiment

The experimental procedure was similar to that of example 1, and an experiment was carried out by replacing the polymer matrix with SEBS, and a polymer syntactic foam of SEBS/CB was obtained in the same manner.

Example 6 composite sample preparation experiment

Examples 1-3 are experimental procedures for the preparation of SBS/CB composites. Following the adsorption of the nanosilver particles, the SBS/CB samples of examples 1-3 were trimmed to form a syntactic foam 20mm by 11mm with a thickness of 5 mm. Preparing 10 wt% ethanol solution of silver trifluoroacetate, soaking the cut foam for 30min, taking out the foam, naturally drying the foam for 3h, preparing 50 wt% hydrazine hydrate ethanol aqueous solution, and reducing the foam, wherein the sample is called SBS/CB/Ag composite material. The reaction formula of hydrazine hydrate for reducing silver ions is as follows: 2Ag + + N2H4+2H2O ═ 2Ag +2NH3OH +. Through the reduction of hydrazine hydrate, the surface and the inner part of the foam porous material are covered with a uniform silver layer. Calculating the nano-silver loading capacity to be 30-40 wt% of the mass of the SBS/CB/Ag composite material through the mass difference of the SBS/CB material and the SBS/CB/Ag composite material before reaction

The concentration of the ethanol solution of silver trifluoroacetate is reduced to 5 wt%, and the loading amount of nano silver is increased through the secondary soaking, and as can be seen from fig. 7(c), the electromagnetic shielding performance of the sample is enhanced.

Example 7 Effect test

The samples of the examples are analyzed by a scanning electron microscope, and the comparison of the results of the scanning electron microscope shows that the foam samples of the examples 1-3 have larger pore diameters and smaller densities as the particle size of the pore-forming agent increases, the minimum density is the sample of the pore-forming agent which adopts crude sugar with the particle size of 1000-3000 microns, the density can reach 0.05g cm < -1 >, and the density of the sample of sodium bicarbonate with the particle size of 50-200 microns is the maximum and is 0.1g cm < -1 >. However, the too large pore diameter can lead to the sample not being easily compressed and the poor resilience. The experimental result proves that the pore-forming agent of the sodium chloride has good pore-forming performance and resilience performance because the pore-forming agent of the sample prepared by the sodium chloride has moderate size and the aperture is about 100-300 microns.

Through comparison of example 1, example 4 and example 5, it is found that composite foams can be prepared in all three experiments, but the SBS/CB composite material has the best conductive performance under the same conditions, and the compression performance of the sample is more excellent through verification of a compression test.

And (3) testing the electromagnetic shielding performance of the sample by using a vector analyzer, and recording data.

in example 6, it can be known from the shielding performance experiment that the EMI SE value of the SBS/Ag foam is much lower than the SE value of the SBS/CB/Ag foam under the same conditions as shown in the upper right diagram of fig. 7, which proves that the EMI SE value of the sample is greatly improved by testing the EMI SE value of the sample with a vector analyzer after the sample is added with CB.

the compression experiment is carried out on the sample, then the resistance of the sample to the compression treatment and the change of the electrical property are analyzed, as can be seen from fig. 3, when the foam sample is compressed, the a picture is the sample of SBS/Ag, the b picture is the sample of SBS/CB/Ag, the electrical property of the sample of SBS/Ag changes after a plurality of times of compression, firstly, when the number of cycles is increased, the sample a has larger fluctuation, the resistance always shows the increasing trend, after the CB is added, a certain conductive network is formed in the sample, and then, after the Ag is added, the conductive property of the sample of SBS/CB/Ag is stronger, so that the change of the resistance of the sample after a plurality of times of compression is quite stable, and the electrical property is excellent.

Meanwhile, as can be seen from the upper left graph of fig. 7, the thickness of the foam sample using the sodium chloride pore-forming agent has an influence on the shielding performance of the sample under the condition that the time for adsorbing silver is the same, and when the thickness of the foam sample is 6mm, the EMI SE of the sample can reach a peak value of about 70 dB. Meanwhile, as can be seen from the upper right diagram of fig. 7, the addition of CB greatly improves the electromagnetic shielding performance of the sample. When samples of two kinds of CB/SBS and pure SBS with the same thickness and the same adsorption time adsorb Ag, the sample of the composite material with CB has more excellent electromagnetic shielding performance. Fig. 7(c) shows that if the concentration of silver salt is decreased to perform adsorption a plurality of times, the amount of nano-silver of the sample increases as the number of times increases, and the sample has better shielding performance, thereby illustrating that the amount of nano-silver has a greater influence on the performance of electromagnetic shielding.

The foam porous material prepared by the method has the advantages of large specific surface area, good hole dispersibility, uniform hole diameter distribution and correlation, and meanwhile, the CB particles with high conductivity are adopted, the particle size is small, the CB particles can be uniformly distributed in high polymer materials such as SBS and the like during magnetic stirring, after the foam is prepared, a conductive network mainly comprising the conductive material is formed in the polymer, and the sample has good conductivity and certain EMI performance. If a layer of nano silver particles is further reduced on the surface of the sample, the conductivity of the sample is further improved. The electromagnetic shielding value of the sample at high frequency of 8.2GHz-12.5GHz is very high, the maximum electromagnetic shielding value can reach about 90dB, generally about 60-80dB, and as can be seen from figure 7(d), the SEAbs of the sample is higher than that of SEref, and most of the shielding performance of the foam composite material is absorption loss.

and (3) performing resistance tests on the upper and lower surfaces of the sample by using a resistance instrument, wherein the resistance values of the sample are approximately equal. The conductivity of the solid sample is basically equal everywhere, which proves that the conductive filler is distributed in the matrix more uniformly.

And (3) carrying out ultrasonic treatment on the foam sample for 24 hours by adopting an ultrasonic machine, and testing the resistance value of the sample before and after ultrasonic treatment by using a resistance instrument without change, so that the connection relation between the conductive filler and the matrix is proved to be tight and not easy to fall off.

Comparative example 1

the method adopts the cube sugar used in the prior art as a pore-forming agent, and experiments are carried out according to documents, as shown in figure 1, and the experiments prove that the polymer SBS (a, b) and the composite material CB/SBS (b, c, e, f) are difficult to enter the cube sugar, most of the polymer SBS and the composite material CB/SBS (b, c, e, f) stay on the surface part, and the pore diameter range is limited. The invention adopts the pore-forming agent which is commonly used in laboratories and can be dissolved in water, such as sodium chloride, potassium chloride, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sugar and baking soda which are commonly used in life, and the pore-forming agent is in a dispersion state and can be better dispersed in a matrix material to form communicated and uniform pores.

Claims (10)

1. An electric shielding foam composite material comprises a matrix with a foam porous structure, wherein the matrix is made of a high molecular polymer as a framework, conductive fillers are uniformly dispersed in the matrix, and nano silver particles grow in situ on the inner surface and the outer surface of the matrix;

Preferably, the matrix of the foam porous structure is prepared by a template sacrificial method, wherein the template sacrificial method is to mix a mixed organic solution of a high molecular polymer and a conductive filler with a pore-forming agent, remove the organic solvent after mixing uniformly, and then put into water to dissolve and remove the pore-forming agent to obtain the matrix of the foam porous structure;

More preferably, the pore-forming agent is water-soluble inorganic salt or sugar, and the inorganic salt or sugar is in the form of dispersed particles or powder;

most preferably, the particle size of the inorganic salt or sugar is 100-3000 μm.

2. In the technical scheme of the invention, the inorganic salt is selected from one or a combination of more of sodium chloride, potassium chloride, sodium carbonate, potassium carbonate, sodium bicarbonate and potassium bicarbonate.

3. The electrically shielding foam composite of claim 1, the high molecular weight polymer being selected from the group consisting of one or more combinations of styrene-butadiene-styrene block copolymers, styrene-ethylene-butadiene-styrene block copolymers, styrene-isoprene-styrene block copolymers, hydrogenated styrene-isoprene copolymers.

4. The electrically shielding foam composite of claim 1, wherein the electrically conductive filler is selected from carbon-based fillers, preferably carbon nanotubes, carbon fibers, carbon nanofibers, graphene, graphite, carbon black.

5. The electrically shielding foam composite of claim 1, having a density of 0.1-0.16g cm "1.

6. The electrically shielding foam composite of claim 1, having an EMI SE value of 60dB or greater, preferably 60-90 dB.

7. The electrically shielding foam composite of claim 1, wherein the nanosilver is embedded on the surface of the substrate by: soaking a substrate containing conductive filler in a silver salt solution, adding a reducing agent for in-situ reduction, and growing in situ on the inner surface and the outer surface of the substrate to obtain a nano silver layer;

Preferably, the silver salt solution takes ethanol, propanol or butanol as a solvent;

preferably, the silver salt is selected from silver trifluoroacetate, silver nitrate, silver acetate, silver oxide, silver sulfate, silver carbonate, silver formate, silver acetate;

Preferably, the reducing agent is selected from hydrazine hydrate, concentrated sulfuric acid, hydroiodic acid, sodium borohydride.

8. The electrically shielding foam composite of claim 1, wherein the mass ratio of the conductive filler to the polymeric compound of the matrix is 1: 3-9.

9. The electrically shielding foam composite of claim 1, the silver nano-silver particles being present in an amount of 30-50 wt% based on the mass of the electrically shielding foam composite.

10. A method of making the electrically shielding foam composite of claims 1-9, comprising the steps of:

1) Respectively dissolving high molecular polymer and conductive filler in organic solvent, mixing uniformly,

2) mixing a pore-forming agent with the mixed solution obtained in the step 1),

3) Removing the solvent, removing the pore-forming agent by using water, and drying to obtain a foamed substrate containing the conductive filler;

4) Soaking the substrate containing the conductive filler in a silver salt solution, adding a reducing agent for in-situ reduction, growing in situ on the inner surface and the outer surface of the substrate to obtain a nano silver layer, and drying to obtain the electromagnetic shielding foam composite material.