WO2020155845A1 - 一种电磁屏蔽复合材料及其制备方法 - Google Patents

一种电磁屏蔽复合材料及其制备方法 Download PDF

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WO2020155845A1
WO2020155845A1 PCT/CN2019/123307 CN2019123307W WO2020155845A1 WO 2020155845 A1 WO2020155845 A1 WO 2020155845A1 CN 2019123307 W CN2019123307 W CN 2019123307W WO 2020155845 A1 WO2020155845 A1 WO 2020155845A1
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electromagnetic shielding
composite material
polyurethane sponge
solvent
polyurethane
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PCT/CN2019/123307
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English (en)
French (fr)
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肖进春
曾艳
邹超
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常德力元新材料有限责任公司
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/02—Layered products comprising a layer of synthetic resin in the form of fibres or filaments
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/12—Layered products comprising a layer of synthetic resin next to a fibrous or filamentary layer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/40—Layered products comprising a layer of synthetic resin comprising polyurethanes
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/36—After-treatment
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L75/00—Compositions of polyureas or polyurethanes; Compositions of derivatives of such polymers
    • C08L75/04—Polyurethanes

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  • the invention belongs to the technical field of electromagnetic shielding, and specifically relates to an electromagnetic shielding composite material and a preparation method thereof.
  • electromagnetic radiation has become another major pollution after air pollution, water pollution, solid waste pollution and noise pollution; electromagnetic radiation not only seriously affects people’s health, but also interferes with each other. Affect the transmission and normal operation of its own electronic signals.
  • the main method to eliminate the harm of electromagnetic waves is to use electromagnetic shielding materials to shield them. Therefore, the exploration of efficient electromagnetic shielding materials has become an urgent problem to be solved.
  • Electromagnetic shielding materials are mainly divided into: metal electromagnetic shielding materials, ferromagnetic materials, good metal conductors (a layer of good metal conductors are attached to the surface of insulators such as plastics), amorphous electromagnetic shielding materials, conductive polymer electromagnetic shielding materials, Conductive fabric, etc.
  • metal electromagnetic shielding materials ferromagnetic materials
  • good metal conductors a layer of good metal conductors are attached to the surface of insulators such as plastics
  • amorphous electromagnetic shielding materials a layer of good metal conductors are attached to the surface of insulators such as plastics
  • amorphous electromagnetic shielding materials a layer of good metal conductors are attached to the surface of insulators such as plastics
  • amorphous electromagnetic shielding materials a layer of good metal conductors are attached to the surface of insulators such as plastics
  • amorphous electromagnetic shielding materials a layer of good metal conductors are attached to the surface of insulators such as plastics
  • the molding method of conductive polyurethane foam discloses four different molding methods, including additive method, adsorption method, chemical blending method and coating method.
  • the addition method is to add the conductive material to the polyurethane foam raw material, and foam it.
  • the adsorption method is to add polyurethane foam to a solution containing conductive materials so that the conductive materials are adsorbed on the surface of the polyurethane foam.
  • the chemical blending method is obtained by pre-dipping high molecular monomer and oxidant into polyurethane foam and oxidizing and polymerizing it.
  • the coating method is to coat the conductive material on the surface of the polyurethane foam. Conductive fillers will have an impact on the mechanical properties and processing properties of the foam. It is necessary to reduce the amount of conductive fillers as much as possible and improve their dispersibility.
  • the technical problem to be solved by the present invention is to provide an electromagnetic shielding composite material and a preparation method thereof, which has a good electromagnetic shielding effect.
  • the content of the present invention is an electromagnetic shielding composite material
  • the electromagnetic shielding composite material is a sandwich structure
  • the inner layer is a polyurethane sponge with inorganic nanoparticles attached to the surface and internal ribs, and a polymer embedded with carbon nanotubes on both sides Nano-fiber membrane, the polyurethane sponge, polymer nano-fiber membrane and inorganic nano-particles are attached with a metal film layer on the surface.
  • the inorganic nano particles are one or more of graphite, carbon powder, carbon nanotubes, graphene, and ferroferric oxide, preferably carbon powder and ferroferric oxide.
  • the inorganic nanoparticles of the present invention are not only attached to the surface of the sponge, but use a certain gas pressure to atomize the non-sticky and vibrating mixed liquid, penetrate the polyurethane sponge, and make the inorganic nanoparticles not only stay on the surface of the sponge. , The internal pore structure is attached, and the distribution is relatively uniform, which effectively inhibits the agglomeration of inorganic nanoparticles.
  • the polymer is one or more of polyurethane, polylactic acid, polyvinyl alcohol, polyphthalamide, polyacrylonitrile and polyvinylidene fluoride, preferably polyurethane.
  • the polymer nanofiber membrane inlaid with carbon nanotubes of the present invention is inconsistent with the general structure of the coated flat film layer after blending.
  • the polymer fiber of the present invention is fully coated carbon nanotubes or coated carbon nanotubes.
  • a small part of the carbon nanotubes is exposed (solvent volatilization, nanofiber shrinkage), so that the ultra-high specific surface area and unique structural advantages of nanofibers and carbon nanotubes are fully utilized, which also makes nanofibers and carbon nanotubes It can form a secondary network porous structure while enhancing the conductivity and physical mechanical properties of polymer nanofibers.
  • the metal element is one or more of nickel, copper, and tin, preferably metallic copper, more preferably metallic nickel-copper alloy.
  • a preparation method of electromagnetic shielding composite material includes the following steps. Firstly, inorganic nanoparticles and a solvent are mixed to obtain a spraying liquid, and then the spraying liquid is sprayed on a polyurethane sponge. After the solvent is volatilized, a polyurethane sponge with inorganic nanoparticles attached is obtained ; Mix carbon nanotubes, polymer and solvent to obtain a spinning solution, the solvent in the spinning solution can dissolve the polymer and polyurethane at the same time, and spray it on the polyurethane sponge with inorganic nanoparticles attached by the electrostatic spinning method After drying, the polyurethane sponge with the film attached on the surface is obtained; finally, the polyurethane sponge with the film attached on the surface is plated with metal, and the electromagnetic shielding composite material is obtained after drying.
  • the solvent in the spraying liquid is one or more of water, chloroform, dichloromethane, anhydrous ethanol, and acetone, preferably anhydrous ethanol.
  • the main function of the solvent in the spray liquid is to disperse inorganic nanoparticles.
  • the solvent in the spinning solution is one or more of water, chloroform, dichloromethane, absolute ethanol, dimethylformamide, dimethylacetamide, and acetone, preferably chloroform.
  • the main function of the solvent in the spinning solution is to dissolve some of the ribs on the surface of the electrospinning matrix polymer and polyurethane sponge, so that the nanofibers and some ribs on the surface of the polyurethane sponge are connected to each other due to the dissolution of the solvent.
  • the solvent is automatically volatilized and dried, and the matrix material no longer contains solvent components.
  • the strength of the connection between the inner layer and the two side layers is enhanced, and on the other hand, the polymer fiber is fully covered with carbon nanotubes or a small part of carbon nanotubes.
  • the other part of the carbon nanotubes is exposed, which can better utilize the advantages of the carbon nanotubes, and also enables the subsequent attached metal layer to better cooperate with the carbon nanotubes to exert an excellent electromagnetic shielding effect.
  • the process parameters of the electrospinning method are: the solution flow rate is 2-5ml/h, the voltage is 9-20kv, and the pole distance is 15-35cm.
  • the drying temperature is 30-80°C.
  • the step of metal plating is to immerse the polyurethane sponge with the film attached on the surface into an electroless plating solution containing metal elements for electroless plating, then electroplating in the plating solution containing metal elements, and dry to obtain an electromagnetic shielding composite material.
  • the carbon nanotubes are modified carbon nanotubes.
  • the step of modifying the carbon nanotubes is:
  • Oxidize the CNT first: adopt a mixed acid system (the volume ratio of concentrated sulfuric acid and concentrated nitric acid is 3:1), and reflux for 48 hours at 80°C;
  • modified carbon nanotubes whose dispersibility in organic solvents such as ethanol and methyl chloride was improved.
  • silane coupling agent It is modified with silane coupling agent, which effectively improves its dispersion performance.
  • the beneficial effect of the present invention is that the inorganic nano particles in step 1 of the present invention are sprayed and atomized by high-pressure spray and adhere to the surface of different ribs of the polyurethane sponge. From a macro point of view, the tiny mist beads containing CNTs are intercepted by different sponge ribs along with the airflow. After being dispersed, the degree of agglomeration is relieved to a great extent; from a microscopic view, the agglomeration of CNTs after the solvent in the tiny fog beads volatilizes is very small, which has little effect on the electromagnetic shielding material. Select carbon nanotubes in step 2 to improve the uniformity of their dispersion in the spinning solution. When the CNT spinning solution forms nanofibers, it volatilizes with the solvent, the nanofibers shrink and set, and CNTs are difficult to agglomerate, which solves the problem of CNTs. The reunion issue.
  • the surface of the polyurethane foam is coated with a polymer nanofiber film inlaid with carbon nanotubes, and finally metal is plated on it.
  • the dispersion performance of inorganic nanoparticles is greatly improved
  • the three-dimensional structure of the present invention can greatly improve the electromagnetic shielding effect of the material.
  • the invention and innovation points of the present invention (1) Sandwich structure, superposition of multi-layer shielding theory (macro-sandwich structure, three-layer electromagnetic shielding effect; micro-layer of metal film coating polymer double-layer electromagnetic shielding effect ).
  • Sandwich structure superposition of multi-layer shielding theory (macro-sandwich structure, three-layer electromagnetic shielding effect; micro-layer of metal film coating polymer double-layer electromagnetic shielding effect ).
  • On both sides is a secondary mesh membrane structure composed of thin electrospun nanofibers and carbon nanotubes, and the inner layer is a microporous polyurethane foam structure, and the metal film layer that does not change its overall structure is coated on the outside, which gives full play to its
  • the advantages of light weight, sandwich model and hole structure in the field of electromagnetic shielding materials enable the electromagnetic wave energy to be greatly and hierarchically weakened, attenuated to absorption.
  • the present invention introduces inorganic nano particles such as carbon nanotubes on the polyurethane sponge ribs, which can greatly enhance its conductive and magnetic effect, and the carbon nanotubes are mixed into the polymer fibers to form a combination of carbon nanotubes and polymer nanofibers when the solvent evaporates.
  • the secondary dense network structure is fused with polyurethane sponge (a small amount of solvent in the polymer nanofibers after spinning has a certain dissolving effect on the polyurethane sponge) to form a sandwich structure that is not easy to layer, eliminating the need for heat pressure to the structure Destruction. Then, the good metal conductor is wrapped, and a sandwich carbon nanotube reinforced polymer fiber/polyurethane sponge metal shielding material is obtained. The shielding effect of this shielding material is excellent.
  • the multi-layer network structure composed of metal cored fibers on the surface of the present invention reduces the reflectivity of electromagnetic waves.
  • the electromagnetic waves with reduced transmission and absorption reach the middle foam metal, the multiple reflection absorption of the pore structure and the interception and absorption of the surface layer make this This kind of sandwich structure material becomes a high-loss electromagnetic shielding material.
  • the resistivity of the polyurethane sponge is 10 11 ⁇ 10 13 ⁇ /m
  • the resistivity of the conductive carbon black polyurethane sponge prepared by the free foaming method is 10 6 ⁇ 10 8 ⁇ /m
  • the resistivity of the conductive polyurethane sponge prepared by the immersion adsorption method The rate is 10 3 to 10 6 ⁇ /m
  • the resistivity of the present invention is 10 2 to 10 3 ⁇ /m.
  • Increasing the conductivity of the polyurethane sponge is conducive to the increase of the electromagnetic shielding effectiveness SE of the composite material.
  • the electromagnetic shielding effectiveness SE of the ordinary coating film is less than 60dB, and the electromagnetic shielding effectiveness SE value of this application is 70-100dB.
  • the material coated with the metal foil layer has excellent conductivity, it has no structural advantage, limited application scenarios, and high cost.
  • the coating sandwich electromagnetic shielding material SE of the present invention is more than 10dB higher than the ordinary coating layer.
  • the reason is that the multi-layer electromagnetic shielding theory is used to optimize the structure layering.
  • this application combines the structural advantages of each of steps 1, 2, and 3.
  • the resulting sandwich structure has a much higher SE than the electromagnetic shielding effectiveness of 1, 2, and 3.
  • the reason is that the sandwich structure completely preserves the network structure composed of polyurethane sponge, nanofibers and carbon nanotubes to achieve structural optimization. After step 3, the complete conductive network system is completed. The wave loss effect is also greatly enhanced.
  • Fig. 1 is a schematic diagram of the structure of the present invention without metal elements attached.
  • 1 is a polyurethane sponge with inorganic nanoparticles attached
  • 2 is a polymer single-layer nanofiber membrane inlaid with carbon nanotubes.
  • the present invention includes the following steps:
  • the electrical conductivity measurement method is to place two electrodes on opposite ends of two opposite surfaces of a certain size sample to measure the resistance between the two electrodes, and then calculate the resistivity value according to the size (length and cross-sectional area).
  • the electromagnetic shielding effectiveness test standard is GJB6190-2008.
  • the present invention includes the following steps:
  • the present invention includes the following steps:
  • the resistivity is about 10 3 ⁇ m
  • the electromagnetic shielding effectiveness SE value is 70dB.
  • step (3) is: put the sandwich carbon nanotube-reinforced polymer fiber/polyurethane sponge composite material into a nickel sulfate electroless plating solution for electroless plating reaction, and then in the chlorine Conduct low-current electroplating and drying in the copper plating solution, and finally a sandwich carbon nanotube reinforced polymer fiber/polyurethane sponge metal shielding material is obtained.
  • the resistivity is about 1.5*10 2 ⁇ m
  • the electromagnetic shielding effectiveness SE value is 95dB.
  • this comparative example 1 differs in that the carbon nanotubes in step 2 are changed to graphene, and the other steps are the same.
  • the carbon nanotubes in step 2 are changed to graphene, that is, there is no secondary network structure composed of nanofibers and carbon nanotubes in the electrospun nanofiber membrane.
  • the presence of graphene sheets only increases the conductivity of the spinning fibers, and No structural advantage.
  • the resistivity is about 5*10 2 ⁇ m
  • the electromagnetic shielding effectiveness SE value is 72dB.
  • this comparative example 2 differs in that step 1 is omitted, and the polyurethane sponge with inorganic nanoparticles in step 2 is modified into a polyurethane sponge.
  • the polyurethane sponge has no preliminary electrical conductivity treatment, nor has it possessed the characteristics of inorganic nanoparticles.
  • step 3 is modified as follows: pre-treat the sandwich carbon nanotube-reinforced polymer fiber/polyurethane sponge substrate, and then put it in a nickel sulfate plating solution for low-current electroplating and baking Dry, the final sandwich carbon nanotube reinforced polymer fiber/polyurethane sponge metal shielding material.
  • the resistivity is about 6*10 2 ⁇ m
  • the electromagnetic shielding effectiveness SE value is 68dB.

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  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
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Abstract

一种电磁屏蔽复合材料及其制备方法，具体是涉及到电磁屏蔽技术领域，电磁屏蔽复合材料为夹层结构，内层为表面和内部筋丝附着有无机纳米颗粒的聚氨酯海绵（1），两侧为镶嵌有碳纳米管的聚合物纳米纤维膜（2），聚氨酯海绵、聚合物纳米纤维膜和无机纳米颗粒表面附着有金属膜层，该材料电磁屏蔽效果好，是一种高损耗型电磁屏蔽材料。

Description

一种电磁屏蔽复合材料及其制备方法 技术领域
本发明属于电磁屏蔽技术领域，具体是涉及到一种电磁屏蔽复合材料及其制备方法。
背景技术
随着电子电器和无线电通讯的大众化使用，电磁辐射己成为继大气污染、水污染、固体废物污染及噪声污染之后的又一大污染；电磁辐射不仅严重影响人们的身体健康，同时存在相互干扰而影响自身电子信号的传递与正常运行。目前消除电磁波危害的主要方法是采用电磁屏蔽材料对其进行屏蔽，因此，探索高效的电磁屏蔽材料已经成为迫切需要解决的问题。
电磁屏蔽材料主要分为：金属电磁屏蔽材料、铁磁材料、金属良导体(在塑料等绝缘体的表面附着一层金属良导体导电层)、非晶型电磁屏蔽材料、导电聚合物电磁屏蔽材料、导电织物等。根据电磁屏蔽材料的分类，可得知其主要结构为块体型及表面型。前者代表物是导电塑料，这类材料屏蔽效能低、成本高，不宜广泛采用。后者包括采用化学镀金、真空喷镀、喷涂等制备的金属箔层，导电聚合物涂覆层等，但基本上只能达到中等电磁屏蔽效能。单一种类、单一结构的屏蔽材料对电磁波的屏蔽效果是有限的。为此，在schelkkunoff多层电磁屏蔽理论的基础上，人们提出三明治模型并导出其屏蔽效能增量函数关系，但这种三明治结构因厚度和制备方法仅限导电涂料及金属箔层之间，这严重限制了其在微孔泡沫结构屏蔽材料上的制备和应用。
导电聚氨酯泡沫塑料的成型方法，材料导报，2008年5月第22卷第5期，公开了四种不同的成型方法，包括添加法、吸附法、化学共混法和涂覆法。添加法为将导电材料加入到聚氨酯泡沫原料中，发泡处理。吸附法为将聚氨酯泡沫加入到含有导电材料溶液中，使导电材料吸附在聚氨酯泡沫表面。化学共混法为将高分子单体、氧化剂预浸到聚氨酯泡沫中，氧化聚合得到。涂覆法为将导电材料涂覆在聚氨酯泡沫表面。导电填料会对泡沫的力学性能和加工性能产生影响，需要尽可能降低导电填料的量，提高其分散性。
发明内容
本发明要解决的技术问题是提供一种电磁屏蔽复合材料及其制备方法，其电磁屏蔽效果好。
本发明的内容为一种电磁屏蔽复合材料，所述电磁屏蔽复合材料为夹层结构，内层为表面和内部筋丝附着有无机纳米颗粒的聚氨酯海绵，两侧为镶嵌有碳纳米管的聚合物纳米纤维膜，所述聚氨酯海绵、聚合物纳米纤维膜和无机纳米颗粒表面附着有金属膜层。
所述无机纳米颗粒为石墨、碳粉、碳纳米管、石墨烯、四氧化三铁中的一种或多种，优选为碳粉和四氧化三铁。本发明的无机纳米颗粒不仅仅附着在海绵的表层，而是利用一定气 体压力使得并不粘稠且时刻振动的混合液雾化，穿透聚氨酯海绵，使得无机纳米颗粒不仅仅是停留在海绵表面，其内部孔洞结构中都附有，且分布较均匀，有效抑制了无机纳米颗粒的团聚。
聚合物为聚氨酯、聚乳酸、聚乙烯醇、聚酞胺、聚丙烯睛和聚偏氟乙烯中的一种或多种，优选为聚氨酯。本发明的镶嵌有碳纳米管的聚合物纳米纤维膜，其与一般的共混后涂覆的平面膜层结构不一致，本发明的聚合物纤维是全包覆碳纳米管或包覆碳纳米管的一小部分，露出碳纳米管另一部分(溶剂挥发，纳米纤维收缩)，从而将纳米纤维及碳纳米管超高的比表面积和独特的结构优势发挥的淋漓尽致，也使得纳米纤维及碳纳米管能够组成的二次网络多孔结构，同时增强聚合物纳米纤维的导电性和物理机械性能。
金属元素为镍、铜、锡中的一种或多种，优选为金属铜，更优选为金属镍铜合金。
一种电磁屏蔽复合材料的制备方法，包括如下步骤，首先将无机纳米颗粒和溶剂混合，得到喷涂液，然后将喷涂液喷涂在聚氨酯海绵上，溶剂挥发后，得到附着有无机纳米颗粒的聚氨酯海绵；将碳纳米管、聚合物和溶剂混合，得到纺丝溶液，所述纺丝溶液中的溶剂能同时溶解聚合物和聚氨酯，采用静电纺丝方法将其喷射在附着有无机纳米颗粒的聚氨酯海绵上，干燥后得到表面附着薄膜的聚氨酯海绵；最后将表面附着薄膜的聚氨酯海绵镀上金属，干燥后得到电磁屏蔽复合材料。
喷涂液中的溶剂为水、三氯甲烷、二氯甲烷、无水乙醇、丙酮的一种或多种，优选为无水乙醇。喷涂液中的溶剂的主要作用为分散无机纳米颗粒。
纺丝溶液中的溶剂为水、三氯甲烷、二氯甲烷、无水乙醇、二甲基甲酞胺、二甲基乙酞胺、丙酮中的一种或多种，优选为三氯甲烷。纺丝溶液中的溶剂主要作用是溶解静电纺丝基体高分子聚合物及聚氨酯海绵两表面的部分筋丝，使得纳米纤维与聚氨酯海绵两表面的部分筋丝因溶剂的溶解而相互连接，随着溶剂的自动挥发及干燥，基体材料中不再含有溶剂的成分。一方面增强了内层和两侧层之间的联系强度，另一方面使得聚合物纤维全包覆碳纳米管或包覆碳纳米管的一小部分。且露出碳纳米管另一部分，能更好的发挥碳纳米管的优势，也使得后续贴附的金属层能更好的和碳纳米管协同，发挥出优异电磁屏蔽效果。
静电纺丝方法的的工艺参数为：溶液流速2-5ml/h，电压9-20kv，极距15—35cm。
优选的，干燥温度为30-80℃。
优选的，镀上金属的步骤为，将表面附着薄膜的聚氨酯海绵浸入含金属元素的化学镀液中进行化学镀，然后在含金属元素的镀液中电镀，干燥后得到电磁屏蔽复合材料。
优选的，所述的碳纳米管优选为改性后的碳纳米管。
所述碳纳米管改性的步骤为：
先对CNT进行氧化处理：采用混酸体系(浓硫酸与浓硝酸体积比为3:1)，80℃条件下冷 凝回流48h；
再用偶联剂对氧化碳纳米管进行表面改性：将20g硅烷偶联剂(KH-304、KH-550、KH-570、Si69等)溶于DCC或甲苯中油浴110℃条件下，机械搅拌冷凝回流10h；
然后丙酮清洗，80℃真空干燥，得改性后的碳纳米管，其在乙醇、氯甲烷的等有机溶剂中的分散性得到了提高。
采用硅烷偶联剂对其进行改性，有效提高了其分散性能。
本发明的有益效果是，本发明的步骤1中的无机纳米颗粒高压喷涂雾化后附着在聚氨酯海绵不同的筋丝表面，从宏观看，包含CNT的微小雾珠随气流被不同海绵筋丝拦截分散开来，在很大程度上缓解了其团聚程度；从微观看，微小雾珠中的溶剂挥发后CNT的团聚现象非常少，对本电磁屏蔽材料影响不大。步骤2中选择碳纳米管，改善其在纺丝溶液中的分散均匀性，当CNT纺丝液形成纳米纤维后，随溶剂挥发，纳米纤维收缩定型，CNT再难团聚，很好的解决了CNT的团聚问题。
本发明将无机纳米颗粒喷涂到聚氨酯泡沫后，再在聚氨酯泡沫表面涂覆镶嵌有碳纳米管的聚合物纳米纤维膜，最后再在其上镀上金属，一方面无机纳米颗粒的分散性能大大提高，另一方面，提高了金属和聚氨酯泡沫的连接强度，不易脱落，抗静电效果较好。本发明的立体结构能极大提高材料的电磁屏蔽效果。
本发明的发明点及创新点：(1)夹心式结构，多层屏蔽理论的叠加(宏观—夹心式结构，三层电磁屏蔽效果；微观—金属膜层包覆聚合物的双层电磁屏蔽效果)。两侧为较薄的静电纺纳米纤维与碳纳米管组成的二次网状膜结构，内层则是微孔聚氨酯泡沫结构，且外镀不改变其整体结构的金属膜层，这充分发挥其轻质、三明治模型及孔洞结构在电磁屏蔽材料领域的优势，使得电磁波能量大幅度的、有层次的削弱，衰减至吸收。(2)两侧的静电纺聚合物纳米纤维与碳纳米管的二次网状结构，利于其致密纳米纤维网状结构的建立，充分发挥出纳米纤维及碳纳米管超高的比表面积和独特的结构优势，提升其屏蔽效果。(3)屏蔽材料的两侧采用传统静电纺丝制备，膜厚度及纤维直径可控，且利用纺丝液中的聚合物与聚氨酯在选定溶剂中相似相溶的原理，免除热压对其夹心结构的破坏。
本发明在聚氨酯海绵筋丝上引入碳纳米管等无机纳米颗粒，能大大增强其导电导磁效果，且聚合物纤维里混入碳纳米管，在溶剂挥发时形成碳纳米管与聚合物纳米纤维的二次致密网络结构，且与聚氨酯海绵(纺丝后聚合物纳米纤维中未挥发的少量溶剂对聚氨酯海绵有一定溶解作用)相融合，形成不易分层的夹心式结构，免除了热压对结构的破坏。然后再外包金属良导体，得夹心式碳纳米管增强聚合物纤维/聚氨酯海绵金属屏蔽材料。此屏蔽材料的屏蔽效果优异，这不仅是金属材料、导电聚合物及纳米颗粒的叠加屏蔽效果，更是得益于其夹心式的泡沫纤维二次网状结构。其表面致密的网状纤维再加上内层较大的孔洞结构使得电磁波 能量大幅度的、有层次的削弱，衰减至吸收。
本发明表面由金属包芯纤维组成的多层网络结构使电磁波的反射率减少，透射和吸收减弱的电磁波达到中间的泡沫金属时，由于孔洞结构的多重反射吸收及对表层的拦截吸收，使这种夹心式结构材料成为高损耗型电磁屏蔽材料。
聚氨酯海绵的电阻率为10 11～10 13Ω/m，采用自由发泡方法制备的导电炭黑聚氨酯海绵的电阻率为10 6～10 8Ω/m；浸渍吸附法制备的导电聚氨酯海绵的电阻率为10 3～10 6Ω/m，本发明的电阻率为10 2～10 3Ω/m。增加聚氨酯海绵的导电性利于复合材料电磁屏蔽效能SE的增加，普通涂覆膜电磁屏蔽效能SE<60dB，本申请的电磁屏蔽效能SE值在70-100dB。采用金属箔层涂覆的材料，虽然导电性优秀，但没有结构优势，应用场景受限，且成本高昂。
本发明的涂料三明治型电磁屏蔽材料SE比普通涂料层高10dB以上，原因在于运用多层电磁屏蔽理论使得结构分层优化，同理，本申请在将步骤1、2、3各自的结构优势组合起来得到的夹心式结构，其SE也要比1、2、3各自的电磁屏蔽效能要高得多。原因是夹心结构完整地保存了聚氨酯海绵、纳米纤维及碳纳米管组成的网络结构，实现结构优化，经过步骤3后，完整的导电网络体系完成，并利用孔洞结构及材料的纳米优势，对入射波的损耗效应也大大增强。
附图说明
图1为未附着金属元素的本发明的结构示意图。
在图中，1为附着有无机纳米颗粒的聚氨酯海绵，2为镶嵌有碳纳米管的聚合物单层纳米纤维膜。
具体实施方式
实施例1
本发明包括如下步骤：
(1)将配置好的由无机纳米颗粒：碳粉和溶剂无水乙醇配制成的喷涂液(5mg/l)加入到喷涂装置中，然后将喷涂装置的喷口分别对准聚氨酯海绵的两面，启动喷涂装置喷涂，喷涂完毕后，溶剂挥发，碳粉附着在聚氨酯海绵筋丝上。
(2)配制含一定量碳纳米管(重量浓度为5％)的高分子聚合物纺丝溶液(纺丝溶液之中聚合物浓度为0.1g/ml；聚合物种类为聚氨酯)，溶剂为三氯甲烷，并采用传统静电纺丝方法(溶液流速3ml/h，电压10kv，极距20cm，时间20min)在(1)中得到的附有无机纳米颗粒的聚氨酯海绵两面均制备出致密碳纳米管增强聚合物单层纳米纤维膜，并加温干燥(45℃，6h)，从而得夹心式碳纳米管增强聚合物纤维/聚氨酯海绵复合材料。
(3)将夹心式碳纳米管增强聚合物纤维/聚氨酯海绵复合材料放入硫酸镍化学镀液中进行化学镀反应，再在硫酸镍镀液中进行小电流电镀并烘干，最终得夹心式碳纳米管增强聚合 物纤维/聚氨酯海绵金属屏蔽材料。
测定上述材料的性能，其电阻率为约2.8*10 2Ω·m，电磁屏蔽效能SE值为78dB。
所述电导率测量方法为在一定尺寸试样的相对两表面两端上放置两电极测得两电极之间的电阻，然后根据尺寸(长度和横截面积)计算出电阻率值。电磁屏蔽效能检测标准为GJB6190-2008。
实施例2
本发明包括如下步骤：
(1)将配置好的由无机纳米颗粒石墨烯和溶剂丙酮配制成的喷涂液(0.2mg/l)加入到喷涂装置中，然后将喷涂装置的喷口分别对准聚氨酯海绵的两面，启动喷涂装置喷涂，喷涂完毕后，溶剂挥发，无机纳米颗粒附着在聚氨酯海绵筋丝上。
(2)配制含一定量碳纳米管(重量浓度为0.05％)的高分子聚合物纺丝溶液(纺丝溶液之中聚合物浓度为0.2g/ml；聚合物种类为聚乙烯醇，溶剂为水，并采用传统静电纺丝方法(溶液流速2ml/h，电压15kv，极距30cm，时间30min)在(1)中得到的附有无机纳米颗粒的聚氨酯海绵两面均制备出致密碳纳米管增强聚合物单层纳米纤维膜，并加温干燥(50℃，6h)，从而得夹心式碳纳米管增强聚合物纤维/聚氨酯海绵复合材料。
(3)将夹心式碳纳米管增强聚合物纤维/聚氨酯海绵复合材料放入氯化铜的化学镀液中进行化学镀反应，再在氯化铜镀液中进行小电流电镀并烘干，最终得夹心式碳纳米管增强聚合物纤维/聚氨酯海绵金属屏蔽材料。
测定上述材料的性能，其电阻率为2*10 2Ω·m，电磁屏蔽效能SE值为87dB。
实施例3
本发明包括如下步骤：
(1)将配置好的由无机纳米颗粒四氧化三铁和溶剂盐酸配制成的喷涂液15mg/l)加入到喷涂装置中，然后将喷涂装置的喷口分别对准聚氨酯海绵的两面，启动喷涂装置喷涂，喷涂完毕后，溶剂挥发，无机纳米颗粒附着在聚氨酯海绵筋丝上。
(2)配制含一定量碳纳米管(重量浓度为8％)的高分子聚合物纺丝溶液(纺丝溶液之中聚合物浓度为0.05g/ml；聚合物种类为聚丙烯睛)，溶剂为二甲基乙酞胺，采用传统静电纺丝方法(溶液流速5ml/h，电压20kv，极距15cm，时间25min)在(1)中得到的附有无机纳米颗粒的聚氨酯海绵两面均制备出致密碳纳米管增强聚合物单层纳米纤维膜，并加温干燥(80℃，5h)，从而得夹心式碳纳米管增强聚合物纤维/聚氨酯海绵复合材料。
(3)将夹心式碳纳米管增强聚合物纤维/聚氨酯海绵基底复合材料放入四氯化锡化学镀液中进行化学镀反应，再在四氯化锡镀液中进行小电流电镀并烘干，最终得夹心式碳纳米管增强聚合物纤维/聚氨酯海绵金属屏蔽材料。
测定上述材料的性能，其电阻率约10 3Ω·m，电磁屏蔽效能SE值为70dB。
实施例4
实施例4和实施例1相比，区别在于，步骤(3)为：将夹心式碳纳米管增强聚合物纤维/聚氨酯海绵复合材料放入硫酸镍化学镀液中进行化学镀反应，再在氯化铜镀液中进行小电流电镀并烘干，最终得夹心式碳纳米管增强聚合物纤维/聚氨酯海绵金属屏蔽材料。
测定上述材料的性能，其电阻率为约1.5*10 2Ω·m，电磁屏蔽效能SE值为95dB。
对比例1
本对比例1和实施例1相比，区别在于步骤2中的碳纳米管改为石墨烯，其他步骤相同。
步骤2中的碳纳米管改为石墨烯，即静电纺丝纳米纤维膜中无纳米纤维与碳纳米管组成的二次网络结构，石墨烯片的存在只是增加了纺丝纤维的导电性，并无结构优势。
测定上述材料的性能，其电阻率为约5*10 2Ω·m，电磁屏蔽效能SE值为72dB。
对比例2
本对比例2和实施例1相比，区别在于省略掉步骤1，将步骤2中的附有无机纳米颗粒的聚氨酯海绵，修改为聚氨酯海绵。
即聚氨酯海绵无初步导电化处理，也无发拥有无机纳米颗粒的特性。
测定上述材料的性能，其电阻率为约4*10 2Ω·m，电磁屏蔽效能SE值为73dB。
对比例3
本对比例3和实施例1相比，区别在于步骤3修改为：将夹心式碳纳米管增强聚合物纤维/聚氨酯海绵基底进行前处理，然后放入硫酸镍镀液中进行小电流电镀并烘干，最终得夹心式碳纳米管增强聚合物纤维/聚氨酯海绵金属屏蔽材料。
测定上述材料的性能，其电阻率为约6*10 2Ω·m，电磁屏蔽效能SE值为68dB。

Claims (10)

  1. 一种电磁屏蔽复合材料，其特征是，所述电磁屏蔽复合材料为夹层结构，内层为表面和内部筋丝附着有无机纳米颗粒的聚氨酯海绵，两侧为镶嵌有碳纳米管的聚合物纳米纤维膜，所述聚氨酯海绵、聚合物纳米纤维膜和无机纳米颗粒表面附着有金属膜层。
  2. 如权利要求1所述的电磁屏蔽复合材料，其特征是，所述无机纳米颗粒为石墨、碳粉、碳纳米管、石墨烯、四氧化三铁中的一种或多种。
  3. 如权利要求1或2所述的电磁屏蔽复合材料，其特征是，聚合物为聚氨酯、聚乳酸、聚乙烯醇、聚酞胺、聚丙烯睛和聚偏氟乙烯中的一种或多种。
  4. 如权利要求1或2所述的电磁屏蔽复合材料，其特征是，金属元素为镍、铜、锡中的一种或多种。
  5. 一种如权利要求1-4任一项所述的电磁屏蔽复合材料的制备方法，其特征是，包括如下步骤，首先将无机纳米颗粒和溶剂混合，得到喷涂液，然后将喷涂液喷涂在聚氨酯海绵上，溶剂挥发后，得到附着有无机纳米颗粒的聚氨酯海绵；将碳纳米管、聚合物和溶剂混合，得到纺丝溶液，所述纺丝溶液中的溶剂能同时溶解聚合物和聚氨酯，采用静电纺丝方法将其喷射在附着有无机纳米颗粒的聚氨酯海绵上，干燥后得到表面附着薄膜的聚氨酯海绵；最后将表面附着薄膜的聚氨酯海绵镀上金属，干燥后得到电磁屏蔽复合材料。
  6. 如权利要求5所述的制备方法，其特征是，喷涂液中的溶剂为水、三氯甲烷、二氯甲烷、无水乙醇、丙酮的一种或多种。
  7. 如权利要求5所述的制备方法，其特征是，纺丝溶液中的溶剂为水、三氯甲烷、二氯甲烷、无水乙醇、二甲基甲酞胺、二甲基乙酞胺、丙酮中的一种或多种。
  8. 如权利要求5-7任一项所述的制备方法，其特征是，静电纺丝方法的的工艺参数为：溶液流速2-5ml/h，电压9-20kv，极距15—35cm。
  9. 如权利要求5-7任一项所述的制备方法，其特征是，干燥温度为30-80℃。
  10. 如权利要求5-7任一项所述的制备方法，其特征是，镀上金属的步骤为，将表面附着薄膜的聚氨酯海绵浸入含金属元素的化学镀液中进行化学镀，然后在含金属元素的镀液中电镀，干燥后得到电磁屏蔽复合材料。
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