CN110757677B

CN110757677B - Shielding material containing hard conductive sponge structure and manufacturing method thereof

Info

Publication number: CN110757677B
Application number: CN201911088088.6A
Authority: CN
Inventors: 魏飞鸣; 谢兵; 许勇刚; 高伟
Original assignee: Shanghai Radio Equipment Research Institute
Current assignee: Shanghai Radio Equipment Research Institute
Priority date: 2019-11-08
Filing date: 2019-11-08
Publication date: 2021-07-20
Anticipated expiration: 2039-11-08
Also published as: CN110757677A

Abstract

The invention discloses a shielding material containing a hard conductive sponge structure and a manufacturing method thereof, wherein the shielding material comprises the following components: step 1, preparing a hard conductive sponge as an intermediate layer of a shielding material, specifically comprising: step 1.1, blending the conductive particles and the plastic particles through a screw extruder to obtain a blend, and adding the blend into a wire drawing machine for wire drawing forming to obtain a wire rod required by three-dimensional forming; step 1.2, carrying out three-dimensional forming on the wire rod after fused deposition to obtain a sample plate; step 1.3, sintering the sample plate at high temperature to obtain a conductive sponge; step 1.4, filling the conductive sponge with resin to obtain hard conductive sponge; step 2, attaching conductive glass fiber mesh cloth to the upper surface and the lower surface of the hard conductive sponge, and attaching a carbon fiber film to the outer side of the conductive glass fiber mesh cloth to obtain a prefabricated body; and 3, pouring and pouring glue into the prefabricated body to integrally form the prefabricated body. The material of the invention has high shielding performance and high tensile strength.

Description

Shielding material containing hard conductive sponge structure and manufacturing method thereof

Technical Field

The invention relates to the technical field of electromagnetic shielding materials, in particular to a shielding material containing a hard conductive sponge structure and a manufacturing method thereof.

Background

The electromagnetic environment of modern complex battlefield makes weapons and equipment systems face huge electromagnetic threat and serious interference influence, especially the requirement on low density of electromagnetic protection materials is more and more strict, the requirement on the performance of the adverse environment is more and more high, and the power of various electromagnetic radiation body radiation sources such as military radars, communication, navigation and the like in the modern battlefield is more and more large, the number is multiplied, the frequency is more and more wide, and in addition, the electromagnetic pulse bomb and the ultra wide band and strong electromagnetic radiation interference machine appear, especially the appearance of high-performance microwave electromagnetic pulse weapons, so that the electromagnetic environment of the battlefield is more and more complex, and the requirement on the electromagnetic protection design and the reinforcement technology level is more and more high. The electromagnetic protection technology under the complex electromagnetic environment is a necessary means for guaranteeing modern weaponry, and the electromagnetic protection material research is a foundation of the electromagnetic shielding technology, so that the research on the electromagnetic protection materials of equipment and fighters is developed, and the electromagnetic protection material has very important practical significance and profound strategic significance for improving the battlefield viability of active weaponry and fully exerting the operational effectiveness of weaponry and staff. Secondly, information security in countries, enterprises, individuals, etc. is compromised by information leakage and information crime generated by modern electronic information devices. Most of the information systems of computers process and transmit low-voltage and high-current digital signals, which easily generate abundant radiation spectrums and harmonic waves, and if the useful information carried in the radiation spectrums is intercepted, amplified, interpreted and recovered by interested persons, the information systems cause great economic, political and military losses. Therefore, the electromagnetic wave shielding technology plays an important role in the aspects of electromagnetic information interference prevention, secret leakage prevention and the like, the technology of applying the electromagnetic wave shielding material to protect the information equipment and the environment where the information equipment is located is very important, and the research and development of novel equipment and the electromagnetic wave shielding composite material for commercial information safety are particularly necessary.

Currently, research on shielding materials has been mainly focused on two aspects, i.e., a surface conductivity type, a filling type, and a structural type. Common methods for preparing the surface conductive shielding material include surface metallization (vacuum gold plating, cathode sputtering, chemical plating, electroplating, etc.), surface metal foil pasting, etc.; the filling type shielding material is mainly obtained by adding conductive liquid such as metal (Cu, Ag, Fe, Ni, etc.), carbon (carbon black, graphite, fiber, etc.), etc. into synthetic polymer with good flexibility, and drying and molding. The structural shielding material refers to a shielding material with certain bearing capacity and the characteristic of a multilayer regular structure as a whole, such as a conductive carbon fiber composite material and a conductive sponge composite material. The surface layer type shielding material is easy to damage in actual work due to the fact that the surface layer material is easy to damage, the shielding performance of the filling type shielding material is affected, the shielding performance of the filling type shielding material mainly depends on conductive particles inside the filling, the material is usually in a film form and poor in bearing capacity, the structural type shielding material has typical structural characteristics and is usually used for bearing, the interlayer properties of the structural type shielding material are more and more diversified along with the improvement of the performance of each layer of material, and meanwhile, the thickness of the structural type shielding material is also smaller and smaller due to the space constraint of the working environment.

The conductive sponge is used as a typical shielding material, has a large hollowing proportion and low density, and is widely applied to shielding materials. Patent document CN109180997A provides a high-elasticity conductive sponge for solving the problems of the conductive sponge in the prior art, such as difficult preparation, environmental pollution and hard brittleness. The preparation raw materials comprise the following substances in parts by weight: the composite sponge comprises a composite sponge matrix, conductive modification liquid, an additive A, an additive B, zinc oxide, sodium fluosilicate, an accelerator A and an accelerator B. The sponge body is subjected to conductive treatment in the preparation stage by adding the conductive modification liquid into the raw materials, and the sponge body has the characteristics of high elasticity, high flexibility and the like while generating good conductive performance. On the basis, the unit provides a preparation method of the high-elasticity conductive sponge in patent document CN 109280211A. It includes: (S1) batching; (S2) preparing a mixed solution for immersion modification; (S3) modifying the composite sponge matrix; (S4) adding the additive components and vulcanizing to prepare the high-elasticity conductive sponge. In the method, the sponge is made of elastic material and has limited conductivity. Patent document CN108998778A discloses a preparation method of a conductive sponge, which comprises the following steps: firstly, selecting sponge; then, carrying out hole-finishing oil removal, pre-dipping treatment and activation treatment by using an ionic palladium activation solution on the sponge, then carrying out peptization treatment by using a 3% sulfuric acid aqueous solution, then carrying out chemical copper deposition, copper sulfate electroplating, nickel sulfate electroplating, carrying out four-stage water washing, blowing off moisture by using an air knife, drying by using an overheated air circulation oven, and then rolling to finish the preparation of the conductive sponge, wherein the prepared sponge is still elastic. Patent document CN107828080A provides a method for preparing a copper nanowire composite latex conductive sponge, which comprises preparing a copper nanowire conductive adhesive, soaking the latex sponge with a surface treatment in the copper nanowire conductive adhesive, and finally performing vacuum drying treatment. The conductive path is completed by conductive adhesive, and the sponge is only used as a supporting template, so that the conductivity is limited. Patent document CN106965509A discloses a composite conductive sponge and a preparation method thereof, which comprises a bare sponge and a bare cloth, wherein the bare sponge and the bare cloth are adhered to form an integral sponge cloth by glue compounding or fire pasting compounding, a nickel layer or a copper layer is plated on the sponge cloth, the surface of a sponge cloth substrate plated with the nickel layer or the copper layer is directly plated with a nickel layer or a copper layer and then with a nickel layer, and the composite conductive sponge is obtained by washing and drying. The conductive sponge is made of elastic material, and the interior of the sponge is not electrically continuous. Patent document CN107452433A discloses an omnibearing conductive sponge and a preparation method thereof, comprising a substrate, conductive latex, a pre-plating layer and an electroplated layer, wherein the substrate is three-dimensional porous polyurethane or PE, the substrate is soaked with a layer of conductive latex on the surface layer after pretreatment, the pre-plating layer is plated by secondary chemical plating, and the surface layer of the pre-plating layer is plated with a nickel layer or a copper-nickel layer. The conductive sponge relies on the surfaces of the sponge to achieve electrical continuity, and is not internally conductive. Patent document CN105504338A discloses a preparation method of a novel conductive sponge, which comprises the following steps: 1) oxidation-reduction reaction, 2) preparing conductive adhesive, 3) soaking, and 4) drying. The method is simple and feasible, and the prepared conductive sponge has low impedance and excellent grounding performance. The sponge is still an elastic material. Patent document CN103215590A discloses a method for preparing a conductive sponge, which uses a coiled material or a sheet of polyester sponge or polyether sponge with a thickness of not more than 10 mm as a substrate, and comprises the steps of chemical pretreatment, coating a carbon conductive layer on the chemically pretreated substrate, then carrying out vapor physical deposition of metallic nickel or metallic copper, electroplating nickel on the substrate on which the vapor physical deposition of nickel or copper is carried out, and obtaining the conductive sponge after washing and drying; or electroplating copper on the base material of the gas-phase physical deposition nickel or copper, then electroplating nickel, and obtaining the conductive sponge after water washing and drying. The invention overcomes the problem that the base material is not plated through the limitation of thickness, but the material is elastic material. Patent document CN103172900B discloses a method for preparing a conductive sponge, which comprises compressing and stirring in a conductive solution and a glue solution respectively by adopting different compression and stirring methods during the preparation process of the conductive sponge, so that the prepared conductive sponge better adsorbs conductive particles, the glue better adheres the conductive particles and the sponge, the surface resistance of the conductive sponge is smaller, the volume resistance distribution is more uniform, and the hardness change of the treated sponge is smaller. Patent document CN101481467A discloses a method for preparing a conductive sponge and a conductive emulsion solution. The preparation method of the conductive sponge comprises the following steps: firstly, soaking polyurethane sponge into a conductive latex solution for 17-23 minutes; secondly, spin-drying treatment; thirdly, drying; fourthly, placing the dried polyurethane sponge in a room-temperature ventilation environment for 48 hours. The preparation method of the conductive latex solution comprises the following steps: prefabricating a 25% polyurethane resin latex solution; secondly, grinding the conductive carbon black into carbon slurry; and finally, adding the carbon slurry into 25% of polyurethane resin latex solution, adding a water-based wetting dispersant, and stirring at a high speed, so that the good resilience of the sponge is kept, and scraps are not dropped.

The conductive sponge materials developed so far are mostly formed by filling high-conductivity electromagnetic shielding fillers in a polymer matrix through composite processing, or are formed by depositing metal on the surface of sponge in a chemical or electroplating mode and the like through composite processing, are not suitable for being used as structural supports, and only utilize the characteristic of large specific surface area of the sponge template materials.

Disclosure of Invention

The invention aims to provide a shielding material containing a hard conductive sponge structure with high shielding performance and high tensile strength and a manufacturing method thereof.

In order to achieve the above object, the present invention provides a method for manufacturing a shielding material containing a hard conductive sponge structure, comprising the following steps:

step 1, preparing a hard conductive sponge as an intermediate layer of the shielding material, specifically comprising:

step 1.1, blending conductive particles and plastic particles through a screw extruder to obtain a blend, and adding the blend into a wire drawing machine for wire drawing forming to obtain a wire required by three-dimensional forming;

step 1.2, carrying out three-dimensional forming on the wire after fused deposition to obtain a composite material sample plate;

step 1.3, sintering the composite material plate at high temperature to enable conductive particles to be mutually bonded to form conductive sponge;

step 1.4, filling the conductive sponge with resin to obtain the hard conductive sponge;

step 2, attaching conductive glass fiber mesh cloth to the upper surface and the lower surface of the hard conductive sponge, and attaching a carbon fiber film to the outer side of the conductive glass fiber mesh cloth to obtain a prefabricated body;

and 3, pouring and pouring glue into the prefabricated body to integrally form the prefabricated body.

Preferably, the conductive particles are any one or a combination of more than two of aluminum powder, copper powder or silver powder.

Preferably, the weight ratio of the conductive particles to the plastic particles ranges from 5% to 400%.

Preferably, in step 1.1, the blend is crushed by a crusher and then added into a wire drawing machine.

Preferably, the diameter of the wire is 1.75 mm-3 mm.

Preferably, the space ratio of the composite sample plate is 40%.

Preferably, the resin is epoxy resin.

Preferably, the conductive glass fiber mesh cloth is silver-plated glass fiber mesh cloth.

The invention also provides a shielding material containing the hard conductive sponge structure, which comprises the hard conductive sponge; the hard conductive sponge is obtained by filling resin into conductive sponge; the conductive sponge is a sponge structure made of conductive materials.

Preferably, the hard conductive sponge is used as an intermediate layer of the shielding material; the shielding material further comprises: the conductive glass fiber layer is conductive glass fiber gridding cloth which is pasted on the upper surface and the lower surface of the hard conductive sponge; and the carbon fiber reinforced layer is a carbon fiber film which is pasted on the outer side of the conductive glass fiber layer.

Has the advantages that:

(1) according to the invention, the conductive sponge is used as a matrix and is filled with resin, so that a hollow conductive sponge composite material structure is realized, the conductivity of the conductive material can be ensured, and the strength and low density characteristics can be considered;

(2) the invention utilizes the structure of the multilayer composite material of the hollow hard conductive sponge and the surface resin-based conductive fiber, can ensure the shielding performance requirement of the material, and has higher tensile strength, bending strength and lower elongation.

Drawings

Fig. 1 is a schematic structural diagram of a shielding material containing a hard conductive sponge structure according to the present invention.

FIG. 2 is a flow chart of a composite sample plate prepared by mixing conductive particles and plastics.

Fig. 3 is a schematic structural diagram of a three-dimensionally formed composite sample plate.

Detailed Description

The technical solution of the present invention is further described below with reference to the accompanying drawings and examples.

According to the invention, based on the distribution characteristic of conductive particles in a three-dimensional forming sample, high-temperature thermal decomposition operation is carried out on a polymer, so that a conductive sponge template is formed, then epoxy resin is adopted to fill the sponge, a hollow hard structure of conductive liquid is realized in a heating and curing mode after vacuumizing, and high-strength reinforcing layers are constructed on the upper surface and the lower surface of the hard conductive sponge, so that the high shielding performance, the high tensile strength and the micro elongation of the material are ensured.

As shown in fig. 1, the shielding material containing the hard conductive sponge structure of the present invention is divided into 5 layers, which are symmetrically arranged from top to bottom, wherein the 1 st layer and the 5 th layer are carbon fiber reinforced layers 3, the 2 nd layer and the 4 th layer are conductive glass fiber layers 2 (for example, silver-plated glass fibers are selected as materials), and the middle layer is a conductive sponge filled resin layer 1 (the material is a conductive sponge filled with resin).

Example 1

A method for manufacturing a shielding material based on a conductive sponge structure mainly comprises the following steps:

(1) blending conductive particles with plastic particles (see FIG. 2)

The conductive particles are selected from aluminum powder, copper powder, silver powder and the like, the particle size is 20-200 mu m, the shape can be spherical or flake, and the plastic particles are hot-melt plastics. The hot-melt plastic comprises PLA (polylactic acid), PETG (non-crystalline copolyester), PE (polyethylene), nylon and the like, the particle size is 2-8 mm, and the shape can be spherical, cylindrical, square and the like. The hot melt plastic can be used as a carrier of conductive particles after being heated and melted, and the conductive particles are distributed in the hot melt plastic.

The mixing of the conductive particles with the hot-melt plastic is performed using a screw extruder, and the extrusion type is a single screw series (step S1). Axial grooves are formed in the inner surface of the feeding section of the machine barrel of the single-screw extruder, and after the grooves are formed in the feeding section of the extruder, the friction coefficient between plastic particles and the inner wall surface of the machine barrel is improved, the plastic particles are prevented from sliding in the circumferential direction, so that the solid conveying efficiency is improved, and finally the yield is greatly improved.

Mixing according to the corresponding weight ratio, wherein the weight ratio of the conductive particles to the plastic is 5-400%. Because the hot melt plastic belongs to a solid state at normal temperature, the hot melt plastic gradually softens when the heating temperature reaches more than 100 ℃, then becomes a viscous state, and is finished by gradually adding powder and gradually stirring uniformly in the process of mixing the plastic and the powder, the melting temperature is set to be different according to different selected hot melt plastics, generally the melting temperature is 180-250 ℃, particles are gradually added into an extruder, and the mixing of the raw materials can be finished by mixing.

Since the proportion of the conductive particles added to the mixture is related to the real-time state of the feeding, the uniformity of the proportion of the conductive particles added to the extruded mixture is difficult to ensure. Therefore, in order to ensure the uniformity of filling the conductive particles with the printing wire material, the processed preliminary mixture (conductive plastic-based mixture) is pulverized by a pulverizer to obtain more refined mixed particles (step S2). Although the single particles may have different addition ratios, the overall distribution of the mixture may be considered uniform after the particles pulverized by the pulverizer are uniformly mixed, and the mixture is then fed into a subsequent wire drawing machine for wire rod preparation, and the filled particles may also be considered uniform.

And finally, adding the crushed mixture powder (conductive plastic-based particles) into a wire drawing machine for wire drawing forming (step S3), setting different heating temperature values for different plastic base materials, such as setting the temperature of a PLA material to be 200-210 ℃, and cooling wires extruded by the wire drawing machine to form wires (conductive plastic-based wires) required by three-dimensional forming, wherein the diameter of the wires can be 1.75mm or 3 mm.

(2) Carrying out three-dimensional forming on the wire rod after fused deposition (step S4) to obtain a composite material sample plate

The preparation of the filled plastic-based composite sample plate is the basis for the subsequent formation of the conductive sponge, and the distribution of the filled conductive particles in the composite sample plate determines the structural characteristics of the conductive sponge forming. The three-dimensional forming principle of the filling type plastic-based composite material is fused deposition, the working principle is that filamentous thermoplastic materials (ABS, PLA and the like) or composite materials thereof are fed into a heating pipeline which is continuously heated through a wire feeding mechanism, the materials reach a high-temperature nozzle to be molten under the pushing of a friction wheel, a 3D printing control system controls the movement track of a spray head according to a planned path, the molten materials are extruded to a specified position on a flat plate by matching with the wire feeding and the back pumping of the wire feeding mechanism, and the layers are gradually stacked and formed layer by layer through adhesive force.

Firstly, a three-dimensional model is designed in Computer Aided Design (CAD) software, then the model is stored as a general STL file, and further the model is imported into slicing software, and after a path program is generated, a composite material can be printed on a three-dimensional forming machine. The temperature of the printing platform is 45-55 ℃, the strength of the adhesive is kept, the temperature of the printing head is 195-220 ℃, and the moving speed of the printing head in an XOY plane is 30-80 mm/s. After current one deck plane printing, beat printer head and remove a bed thickness 0.05 ~ 0.3mm in Z axle direction to the combined material that the successive layer printed out the design comes, and final preparation has the sample plate piece (combined material sample panel) of space dispersion conductive particle, and it is different with spatial structure according to the duty ratio of electrically conductive sponge, uses different filling proportions in three-dimensional forming, thereby forms different spatial structure, also can directly design different spatial structure in the model design stage.

(3) Forming of conductive sponge structure under high-temperature sintering

And (2) placing the prepared composite material sample plate filled with the conductive particles into a high-temperature sintering furnace for sintering, wherein the sintering temperature is set differently according to different filled conductive particles, the set temperature is kept close to the melting point of the metal particles, the temperature value is higher than the melting point of the metal particles, and the heat preservation time is independently set according to the material of each metal particle. The temperature and time are selected to ensure that the metal particles are not completely melted, and the metal particles with melted surfaces are mutually bonded, so that a conductive sponge structure formed by mutually bonding the conductive particles is obtained.

The high-temperature sintering furnace that adopts is laboratory muffle furnace, leads to nitrogen gas or helium earlier before the heating and gets rid of the air in the muffle furnace, prevents the oxidation of conductive particle among the heating process, then continuously heats, when the heating temperature reaches the settlement temperature, the plastics basement will be decomposed completely among the hollow composite who adds, closes the heating afterwards, continues to let in nitrogen gas or helium, stops to let in gas after the sample piece cools off, takes out the sample piece, can acquire the conductive sponge.

(4) Filling resin into the conductive sponge to obtain the hard conductive sponge

The conductive sponge is hardened by filling epoxy resin in the conductive sponge, and performing surface high-strength resin curing treatment on the conductive sponge by adopting an extrusion adsorption method and a vacuum pumping method to finish the manufacture of the hollow hard conductive sponge.

a. Firstly, processing the conductive sponge into a flat sample, putting the processed conductive sponge into absolute ethyl alcohol, heating and boiling for 30min, and completely removing impurities remained in gaps in the processing process.

b. And taking out the conductive sponge test piece, and drying in an oven.

c. Then, a certain amount of epoxy resin and a certain amount of curing agent are respectively contained in two plastic cups, and the two plastic cups are put into a numerical control constant temperature water bath kettle to be heated for a period of time so as to reduce the viscosity of the plastic cups.

d. In order to fully permeate the epoxy resin into the conductive sponge, a plasticizer and a defoaming agent are respectively added into the epoxy resin, then the mixture is stirred for about 30min, when bubbles in the epoxy resin are fully discharged and the epoxy resin becomes clear liquid with good fluidity, a curing agent which is heated and has the same amount as the epoxy resin is poured into the mixture, and the mixture is rapidly stirred.

e. Pouring the uniformly-stirred mixed liquid into a mold, slowly pushing the processed conductive sponge into the mold to enable the solution to completely permeate into the conductive sponge, curing at room temperature for 24 hours, then opening the mold, taking out the test piece, removing the redundant epoxy resin at the two ends of the test piece, and polishing the two ends of the test piece on sand paper to be smooth.

Step 2, obtaining the integrally formed shielding material containing the hard conductive sponge structure:

(1) preparation of conductive silver-plated glass fiber woven cloth

The method comprises the steps of adopting continuous glass fibers, carrying out three-dimensional weaving treatment on the continuous glass fibers to prepare fiber mesh cloth, then carrying out chemical plating and Ag film electroplating processes on the surface of the fiber mesh cloth to realize the conductive property of the fiber mesh cloth, and finally carrying out prepreg treatment on the prepared conductive glass fiber mesh cloth.

The knitting process of the three-dimensional knitted composite material is mainly a longitudinal and transverse knitting method, and comprises a four-step method, a two-step method, a multi-layer connection method, a multi-step method and the like, wherein the four-step method and the two-step method are the most commonly used and researched methods at present. The four-step three-dimensional weaving is the most representative weaving method in the technical field of three-dimensional weaving, and the basic four-step three-dimensional weaving only has one yarn system. The knitting yarns are arranged along the forming direction of the fabric, and each yarn moves according to a certain rule in the knitting process, so that the yarns are mutually interwoven to form a non-layered three-dimensional integral structure. The 3D integral structure prepared by the three-dimensional braided composite material is an integral fiber component with multidirectional orientation formed by continuously, orderly, uniformly, finely and interlacedly connecting high-performance fibers in a three-dimensional space according to the set structure, shape and size, and prevents subsequent processing from damaging the fibers and the structure, thereby improving the damage tolerance of the component and reducing the manufacturing cost. The integral structure reinforced fiber composite material improves the tensile strength and the interlaminar shear strength along the thickness direction, overcomes the fatal defect of fragility between laminated material layers, obviously improves the damage tolerance and the thermal stress mismatch, and has good integrity, interlaminar performance, shock resistance and the like.

Before the glass fiber mesh cloth is used as a template, the glass fiber mesh cloth needs to be pretreated. Because the glass fiber cloth has a large specific surface area and a smooth outer surface structure, the glass fiber can not be effectively activated by using a conventional chemical plating pretreatment method, so that the deposition and plating of a plating layer can not be realized during plating. In order to achieve an efficient activation of the glass fibers, a coupling treatment is introduced before their activation. Secondly, before the non-metal matrix is electroplated, the surface of the non-metal matrix needs to be metalized, namely a layer of conductive metal film is plated on the surface of the non-metal matrix under the condition of no power supply, so that the non-metal matrix has certain conductive capability. And 4, plating a conductive metal layer on the glass fiber particles by using a chemical plating method, wherein the plating layer is made of Cu. And then, the electroplating device is used for depositing the conductive material on the glass fiber particles. In the electroplating process, the coating quality of the glass fiber surface coating is mainly controlled by adjusting the parameters of the electroplating process. The mechanical stirring intensity is based on the stirring speed of the glass fiber particles in the electroplating solution for fully suspending. After the electroplating process is finished, the coated glass fiber mesh cloth is cleaned by absolute ethyl alcohol and is dried in vacuum, and finally the obtained conductive glass fiber mesh cloth is subjected to prepreg treatment, namely the glass fiber mesh cloth is placed in a resin solution and then is taken out and dried in the air, and the prepreg treatment can ensure that the surface of the conductive glass fiber can be adhered with a layer of resin material, so that the subsequent composite material and other composite materials can be more fully adhered and molded.

(2) After the upper surface and the lower surface of the hard conductive sponge are pasted with conductive glass fiber gridding cloth, a carbon fiber film is pasted on the outer side of the conductive glass fiber gridding cloth, the carbon fiber film is a carbon fiber composite material of prepreg, and the thickness of the carbon fiber film is between 0.1mm and 0.5 mm.

(3) Integrated molding manufacture of multilayer composite material

The method adopts a vacuum mould pressing technology (vacuum RTM technology) to realize the integrated forming of the conductive glass fiber mesh cloth and the hard conductive sponge, and comprises an upper conductive glass fiber mesh cloth layer, a lower conductive glass fiber mesh cloth layer, an upper carbon fiber film layer, a lower carbon fiber film layer and a hard sponge layer. After the preparation of the conductive glass fiber composite material prefabricated body is finished, firstly, the prepared conductive glass fiber gridding cloth layers are attached to the upper side and the lower side of the conductive sponge, and then, the mature carbon fiber composite material prefabricated body is respectively attached to the surfaces of the upper conductive glass fiber gridding cloth layer and the lower conductive glass fiber gridding cloth layer. And then, pouring and pouring glue by adopting vacuum RTM (resin transfer molding), so as to ensure that the prefabricated body and resin are fully impregnated.

The vacuum RTM process is one common composite material forming process, and has the main principle of spreading pre-formed reinforcing material in mold cavity designed based on the performance and structure requirement, injecting special resin system into the mold cavity with injection apparatus, and the mold has peripheral sealing, fastening, injecting and exhausting system to ensure smooth resin flow, exhaust all gas and soaked fiber, heating system, pressure maintaining system and heating curing to form composite material member. Compared with other processes, the method is a forming method which does not adopt prepreg and autoclave. Therefore, the method has the advantages of high efficiency, investment, green and the like, and has the greatest advantages that the manufacturing of the fiber reinforced material and the permeation process of the resin are mutually separated, the selection and the designability of the reinforcement body and the matrix are strong, and the production environment is friendly.

Example 2

(1) Blending of conductive particles with plastic particles

The selected conductive particles are copper powder, the particles are spherical structures, the average diameter is 100 mu m, the PLA particles are selected from the hot melt plastic, the shapes are also spherical, and the average size of the particles is 5 mm. The mixing of the conductive particles and the hot-melt plastic is accomplished by a screw extruder, which is a single screw series. The weight ratio of the conductive particles to the plastic is 1: 1, gradually adding the powder and stirring uniformly in the process of mixing the plastic and the powder, wherein the melting temperature is 200 ℃, gradually adding particles into an extruder, and mixing the raw materials. Subsequently, the prepared mixture particles were put in a pulverizer to be pulverized, and the pulverized particles were collected. And finally, adding the crushed mixture powder into a wire drawing machine for wire drawing forming, setting the heating temperature of the wire drawing machine to be 200 ℃ for the PLA material, and cooling the wire extruded by the wire drawing machine to form the wire required by three-dimensional forming, wherein the diameter of the wire is 1.75 mm.

(2) Three-dimensional forming of filling type plastic-based composite material plate

Designing a three-dimensional model in CAD software, saving the model as a general STL file, importing the model into slicing software, generating a path program, and printing the composite material on a three-dimensional forming machine. Wherein the temperature of the printing platform is 50 ℃ and the strength of the adhesive is kept, the temperature of the printing head is 210 ℃, and the moving speed of the printing head in an XOY plane is 60 mm/s. After the printing of the current layer of plane is finished, the printing head moves one layer thickness of 0.2mm in the Z-axis direction, so that the designed composite material is printed layer by layer, the length of the composite material is 140mm, the width of the composite material is set to be 70mm, the height of the composite material is set to be 3mm, a sample plate block with spatially dispersed conductive particles is finally prepared, the duty ratio of the composite material is selected to be 40%, and the spatial structure is arranged as shown in fig. 3. The area a of the sample plate 4 is enlarged and shown as structure 41 in a grid structure.

(3) Forming of conductive sponge structure under high-temperature sintering

Placing a composite material sample plate filled with the prepared conductive particles in a high-temperature sintering furnace for sintering, wherein the adopted high-temperature sintering furnace is a laboratory muffle furnace, introducing nitrogen to remove air in the muffle furnace before heating, preventing conductive particles from being oxidized in the heating process, continuously heating, selecting the heating temperature of 1090 ℃ according to the melting point of copper powder of about 1085 ℃, completely decomposing a plastic substrate in the added hollow composite material before the heating temperature reaches a set temperature, keeping the temperature for a proper time to ensure that the particles are not completely melted, bonding the powder with melted surfaces, closing the heating, continuously introducing nitrogen, stopping introducing gas after the sample piece is cooled, taking out the sample piece, and obtaining the conductive sponge structure.

(4) Resin filled conductive sponge composite material

Firstly, processing the conductive sponge into a flat plate type sample piece with the length of 100mm and the width of 50mm, putting the processed conductive sponge into absolute ethyl alcohol, heating and boiling for 30min, taking out the conductive sponge sample piece, and drying in an oven. Then, a certain amount of epoxy resin and a certain amount of curing agent are respectively contained in two plastic cups, and the two plastic cups are put into a numerical control constant temperature water bath kettle to be heated for a period of time so as to reduce the viscosity of the plastic cups. In order to fully permeate the epoxy resin into the conductive sponge, a plasticizer and a defoaming agent are respectively added into the epoxy resin, then the mixture is stirred for about 30min, when bubbles in the epoxy resin are fully discharged and the epoxy resin becomes clear liquid with good fluidity, a curing agent which is heated and has the same amount as the epoxy resin is poured into the mixture, and the mixture is rapidly stirred. Pouring the uniformly-stirred mixed liquid into a mold, slowly pushing the processed conductive sponge into the mold to enable the solution to completely permeate into the conductive sponge, curing at room temperature for 24 hours, then opening the mold, taking out the test piece, removing the redundant epoxy resin at the two ends of the test piece, and polishing the two ends of the test piece on sand paper to be smooth.

(5) Preparation of conductive silver-plated glass fiber woven cloth

Before the glass fiber mesh cloth is used as a template, the glass fiber mesh cloth needs to be pretreated. Because the glass fiber cloth has a large specific surface area and a smooth outer surface structure, the glass fiber can not be effectively activated by using a conventional chemical plating pretreatment method, so that the deposition and plating of a plating layer can not be realized during plating. In order to achieve an efficient activation of the glass fibers, a coupling treatment is introduced before their activation. Secondly, before the non-metal matrix is electroplated, the surface of the non-metal matrix needs to be metalized, namely a layer of conductive metal film is plated on the surface of the non-metal matrix under the condition of no power supply, so that the non-metal matrix has certain conductive capability. And 4, plating a conductive metal layer on the glass fiber particles by using a chemical plating method, wherein the plating layer is made of Cu. And then, coating the glass fiber particles with a conductive Ag material by using an electroplating device. In the electroplating process, the coating quality of the glass fiber surface coating is mainly controlled by adjusting the parameters of the electroplating process. The mechanical stirring intensity is based on the stirring speed of the glass fiber particles in the electroplating solution for fully suspending. And after the electroplating process is finished, cleaning the coated glass fiber mesh fabric by using absolute ethyl alcohol, drying in vacuum, and finally performing prepreg treatment on the obtained conductive mesh fabric.

(6) Integrated molding manufacture of multilayer composite material

The vacuum mould pressing technology is adopted to realize the integrated forming of the conductive glass fiber mesh cloth and the hard conductive sponge, and comprises an upper conductive glass fiber mesh cloth layer, a lower conductive glass fiber mesh cloth layer, an upper carbon fiber film layer, a lower carbon fiber film layer and a hard sponge layer. After the preparation of the conductive glass fiber composite material prefabricated body is finished, firstly, the prepared conductive glass fiber gridding cloth layers are attached to the upper side and the lower side of the conductive sponge, and then, the mature carbon fiber composite material prefabricated body is respectively attached to the surfaces of the upper conductive glass fiber gridding cloth layer and the lower conductive glass fiber gridding cloth layer. And then, pouring and pouring glue by adopting vacuum RTM (resin transfer molding), so as to ensure that the prefabricated body and resin are fully impregnated. The vacuum RTM process is a commonly used forming process for forming composite materials, and compared with other processes, the vacuum RTM process has the greatest advantages that the manufacturing of fiber reinforced materials and the permeation process of resin are mutually separated, the selection and designability of a reinforcement body and a matrix are strong, and the production environment is friendly.

In summary, the hard conductive sponge material of the present invention is different from other conventional shielding materials in that a conductive resin enhancer is filled on the basis of the conductive sponge, and a resin-based conductive fiber composite material is laid on the surface. Not only can realize high conductivity of the material, but also can give consideration to high tensile strength and limited elongation of the material

While the present invention has been described in detail with reference to the preferred embodiments, it should be understood that the above description should not be taken as limiting the invention. Various modifications and alterations to this invention will become apparent to those skilled in the art upon reading the foregoing description. Accordingly, the scope of the invention should be determined from the following claims.

Claims

1. The method for manufacturing the shielding material containing the hard conductive sponge structure is characterized by comprising the following steps of:

2. The method for manufacturing the shielding material with the hard conductive sponge structure as claimed in claim 1, wherein the conductive particles are any one or a combination of two or more of aluminum powder, copper powder and silver powder.

3. The method as claimed in claim 1, wherein the weight ratio of the conductive particles to the plastic particles is in the range of 5-400%.

4. The method for manufacturing the shielding material containing the hard conductive sponge structure as claimed in claim 1, wherein in step 1.1, the blend is crushed by a crusher and then added into a wire drawing machine.

5. The method for manufacturing a shielding material with a hard conductive sponge structure according to claim 1, wherein the diameter of the wire is 1.75mm to 3 mm.

6. The method as claimed in claim 1, wherein the resin is epoxy resin.

7. The method for manufacturing the shielding material with the hard conductive sponge structure as claimed in claim 1, wherein the conductive glass fiber mesh cloth is silver-plated glass fiber mesh cloth.

8. The shielding material containing the hard conductive sponge structure is characterized in that: the shielding material comprises a hard conductive sponge; the hard conductive sponge is obtained by filling resin into conductive sponge; the conductive sponge is a sponge structure made of conductive materials; the hard conductive sponge is used as the middle layer of the shielding material; the shielding material further comprises: the conductive glass fiber layer is conductive glass fiber gridding cloth which is pasted on the upper surface and the lower surface of the hard conductive sponge; and the carbon fiber reinforced layer is a carbon fiber film which is pasted on the outer side of the conductive glass fiber layer.