Low-density conductive foam material, its slurry and preparation method

Abstract

The present invention provides a low-density conductive foam material, its slurry and a preparation method thereof, belonging to the field of conductive foam materials and their preparation. Through creative labor, the applicant has developed a new slurry for preparing a low-density conductive foam material. The low-density conductive foam material prepared from the slurry has the advantages of light weight, excellent conductivity performance and better strength; by adding different conductive carbon nanomaterials into different base materials, the conductivity of the material is improved; at the same time, the density of the material is reduced by hollow glass microspheres.

Description

Technical Field

[0001] This application relates to the field of conductive foam materials and their preparation, and more specifically, to low-density conductive foam materials, their slurries, and preparation methods. Background Art

[0002] Lightweight rigid foam materials have been widely used in fields such as aerospace, ships, petroleum, electronic equipment, vehicles, and food. In recent years, with the continuous improvement of the requirements for material functionality, the conductivity of rigid foams has received a great deal of attention. When such foams are used in fields such as aviation, ships, and electronic equipment, on the basis of reducing the weight of the material, they also possess multiple electromagnetic functions such as reducing electromagnetic interference, avoiding static electricity accumulation, radar stealth, and conductive connection.

[0003] There are mainly two types of lightweight rigid foams. One type is prepared by polymer foaming, such as PMI foam, epoxy resin foam, polyurethane foam, etc. However, limited by the material preparation technology, it is difficult to foam such foams after adding conductive fillers. Therefore, the preparation of conductive foams is difficult and the conductivity is low. The other type is composite foams formed by filling porous materials in resins, such as hollow glass microsphere (HGM) / resin composite foams (abbreviated as HGM foams). Such foams can be made into conductive foams by blending with conductive resins or modifying HGM to be conductive.

[0004] However, the density of HGM foams prepared by existing technologies is relatively high, and it is difficult to obtain a relatively high conductivity, mainly limited by the existing preparation technologies. For example, (1) when using the conventional method of blending resin and HGM, the volume percentage content of the resin is generally higher than 40% (the mass percentage is usually ≥80%), and it is impossible to prepare foams with a density lower than 0.4 g / cm3 because less resin is difficult to fully infiltrate HGM and implement the blending process; (2) after the resin is modified with conductive fillers, the viscosity increases significantly, making it more difficult to obtain low-density HGM foams and also difficult to achieve a relatively high conductivity. In recent years, people have obtained HGM foams with relatively high conductivity through the selective microphase distribution of conductive media, selective solvent etching combined with HGM filling, and the conductivity can reach 10 -4 S / cm, but the filling amount of lightweight HGM is less than 8 wt%, and the process is complex and involves organic solvent etching, making it difficult to mass-produce (Journal of materials science, 2018, 53: 6042 - 6052).

[0005] Therefore, there is still a need to develop new preparation technologies that are simple and easy to implement to prepare HGM foams with higher conductivity and lower density. Summary of the Invention

[0006] The present invention mainly aims at the above problems and provides a low-density conductive foam material, its slurry and a preparation method, which can improve the conductivity of the foam material and simultaneously improve the mechanical properties of the foam material.

[0007] On the one hand, the present invention provides a low-density conductive foam material, which is prepared from the following raw materials, and the raw materials include:

[0008] Conductive hollow microspheres, conductive resin and reinforcing material.

[0009] Preferably, the volume content of the conductive hollow microspheres is 60%-80%, the volume content of the conductive resin is 5%-20%, and the volume content of the reinforcing material is 0.01-20%.

[0010] Preferably, the conductive hollow microspheres include conventional microspheres and / or conductive modified microspheres;

[0011] The diameter of the conductive hollow microspheres is 20-100 μm, and the density is 0.10-0.30 g / cm 3 ;

[0012] The conductive hollow microspheres are hollow microspheres coated with a first carbon nanomaterial, and 0.01-0.3 g of the first carbon nanomaterial is coated on the surface of each square meter of the hollow microspheres;

[0013] The first carbon nanomaterial includes at least one of carbon nanotubes, graphene or nanofibers.

[0014] Preferably, the conductive resin is a conductivity-modified resin; the conductivity-modified conductive resin contains a second carbon nanomaterial, and the content is 1 wt%-15 wt%;

[0015] The second carbon nanomaterial includes carbon nanotubes and / or carbon fibers.

[0016] Preferably, the reinforcing material is chopped fibers, including at least one of carbon fibers, aramid fibers, polyimide fibers or nylon fibers.

[0017] On the one hand, the present invention provides a slurry preparation method for preparing a low-density conductive foam material, and the slurry preparation method includes the following steps:

[0018] Mix the conductive resin slurry with the reinforcing material and homogenize to obtain a homogenized mixture;

[0019] Mix the homogenized mixture with the conductive hollow microspheres;

[0020] Obtain a low-density conductive foam material slurry.

[0021] Preferably, it further includes the preparation of the conductive resin slurry, which includes the following steps:

[0022] Mix the aqueous dispersion slurry of the second carbon nanomaterial with the resin emulsion and homogenize to obtain a homogeneous slurry; the concentration of the aqueous dispersion slurry of the second carbon nanomaterial is 0.5-10 wt%.

[0023] Add a curing agent and perform homogenization treatment to obtain the conductive resin slurry.

[0024] The concentration of the resin emulsion is 20-60 wt%.

[0025] The volume ratio of the homogeneous slurry mixture to the conductive hollow microspheres is 1:2.2-3.5.

[0026] Preferably, the second carbon nanomaterial is a mixture obtained by mixing carbon nanotubes and nanofibers in a mass ratio of 1:0.1-2.

[0027] The mass ratio of the homogeneous slurry to the curing agent is 1:0.01-0.15.

[0028] Preferably, the curing agent is a water-soluble curing agent or a fine particle type curing agent, and the particle size of the curing agent is less than 10 μm

[0029] Preferably, the curing agent is 4,4'-diaminodiphenyl sulfone and / or dicyandiamide

[0030] On the one hand, the present invention provides a method for preparing a low-density conductive foam material. The slurry obtained by the foregoing slurry preparation method is shaped and cured to obtain a low-density conductive foam material;

[0031] The curing temperature does not exceed 135 °C;

[0032] Preferably, the curing temperature is 105-135 °C;

[0033] The curing method includes atmospheric pressure curing or vacuum bag pressing curing.

[0034] The technical solution of the present invention has the following beneficial effects:

[0035] Through creative labor, the applicant of the present invention has developed a new slurry for preparing low-density conductive foam materials. The low-density conductive foam materials prepared from the slurry are light in weight, excellent in conductivity performance, and good in strength; by adding different conductive carbon nanomaterials to different base materials, the conductivity of the materials is improved; at the same time, the density of the materials is reduced by hollow glass microspheres. The preparation steps of the conductive foam materials are few, and the required equipment and materials are simple, bringing cost advantages; the density of the prepared conductive hollow microsphere foam is much lower than that of the existing hollow microsphere foam, the conductivity is higher than that of the existing conductive hollow microsphere foam and can be adjusted within a wide range, and the conductivity can meet the requirements of wave-absorbing materials and electrical conduction materials Description of the Drawings

[0036] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following accompanying drawings only show certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related accompanying drawings can also be obtained based on these accompanying drawings.

[0037] Figure 1 It is a schematic diagram of the wave-absorbing coating structure provided in Experimental Example 1 of this application;

[0038] Figure 2 It is a schematic diagram of the wave-absorbing performance of the wave-absorbing material provided in Experimental Example 1 of this application.

[0039] Reference numerals:

[0040] 1 - Hollow glass microspheres; 2 - Reinforcing material; 3 - Pores; 4 - Resin; 5 - Carbon nanomaterials. Specific embodiments

[0041] The implementation solutions of the present invention will be described in detail below in conjunction with the embodiments. However, those skilled in the art will understand that the following embodiments are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. For those where specific conditions are not indicated in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For reagents or instruments whose manufacturers are not indicated, they are all conventional products that can be obtained through commercial purchase. The hollow glass microspheres used are conventional products purchased commercially.

[0042] The present invention provides a low-density conductive foam material, which is prepared from the following raw materials, and the raw materials include:

[0043] Conductive hollow microspheres, conductive resin and reinforcing material.

[0044] Preferably, the volume content of the conductive hollow microspheres is 60% - 80%, the volume content of the conductive resin is 5% - 20%, and the volume content of the reinforcing material is 0 - 20%.

[0045] Preferably, the conductive hollow microspheres include conventional microspheres and / or conductive modified microspheres;

[0046] The diameter of the conductive hollow microspheres is 20 - 100 μm, and the density is 0.10 - 0.30 g / cm3;

[0047] The conductive hollow microspheres are hollow microspheres coated with a first carbon nanomaterial, and 0.01 - 0.3 g of the first carbon nanomaterial is coated on the surface of each square meter of the hollow microspheres;

[0048] The first carbon nanomaterial includes at least one of carbon nanotubes, graphene or nanofibers.

[0049] Preferably, the conductive resin is a resin modified with conductivity; the conductive resin modified with conductivity contains a second carbon nanomaterial, and the content is 1 wt% - 15 wt%;

[0050] The second carbon nanomaterial includes carbon nanotubes and / or carbon fibers.

[0051] Preferably, the reinforcing material is chopped fibers, including at least one of carbon fibers, aramid fibers, polyimide fibers or nylon fibers.

[0052] In order to achieve the purpose of the present invention, by using common hollow microspheres, such as hollow glass microspheres, as the base material, by using the microsphere material, the specific surface area is increased, the performance after conductive modification of the hollow microspheres is improved, and the conductivity of the reinforcing material is enhanced. The resin material, as a bonding material, connects the conductive hollow microspheres and the reinforcing material. And the strength and conductivity of the foam material are enhanced through the reinforcing material.

[0053] The conductive hollow microspheres are selected from conventional microspheres, preferably conductive modified microspheres. A conductive carbon nanomaterial such as carbon nanotubes, graphene or a mixture of two or more of nanofibers is coated on the surface of the hollow microspheres. By virtue of the large specific surface area of the hollow microspheres, the conductive carbon nanomaterial is coated to obtain modified conductive hollow microspheres; thereby playing a role in improving the conductivity of the entire foam material.

[0054] By using conductive hollow microspheres instead of blank microspheres, the conductivity of the conductive foam can be increased by 2 to 10 times. As a preference, the conductive hollow glass microspheres are hollow glass beads coated with a carbon nanomaterial, and the coating amount of the carbon nanomaterial on the surface of each square meter of microspheres is 0.01 - 0.3 g. The carbon nanomaterial is one of carbon nanotubes, graphene, carbon black, nanofibers or a mixture thereof. When such conductive hollow glass microspheres are blended with conventional epoxy resins, the carbon nanomaterial attached to the surface will become debonded during the mixing process, resulting in the failure of conductivity. However, this special system of the present invention will not cause the debonding of the carbon nanomaterial on the surface of the conductive hollow microspheres, bringing a significant improvement in conductivity.

[0055] The diameter of the conductive hollow microspheres is appropriate, and the density is shown, which helps to improve the properties of the foam material, and while ensuring the material strength, the conductivity of the material is improved.

[0056] And an appropriate amount of the carbon nanomaterial can not only ensure that the conductivity of the foam material is improved by the carbon nanomaterial, but also avoid the problems of insufficient or excessive amount of the carbon nanomaterial.

[0057] Adding reinforcing fillers can further improve the mechanical properties of the foam. However, the dosage should not exceed 20% of the mass of the conductive resin. We found that when the dosage is higher than this value, the bonding between HGMs becomes poor, which instead leads to a decrease in mechanical properties.

[0058] The conductive resin is modified by carbon nanotubes and / or carbon fibers to obtain a conductivity-modified conductive resin. The base resin can have various choices, such as ordinary epoxy resin, polyimide resin, etc. In this embodiment, epoxy resin is selected as the base resin material.

[0059] The conductive resin actually plays the roles of cross-linking the conductive hollow microspheres and the reinforcing material and conducting electricity at the same time; both the conductive resin and the conductive hollow microspheres can conduct electricity, forming a conductive path and improving the conductivity of the foam material.

[0060] Reinforcing materials are added to the material, mainly adding some chopped fibers, increasing at least one of carbon fiber, aramid fiber, polyimide fiber or nylon fiber, and the strength of the foam material is improved by the chopped fibers. The reinforcing material can form a network structure to improve the strength of the foam material.

[0061] Especially, the addition of materials such as carbon fiber with a small dosage and high strength can better improve the strength of the foam material.

[0062] On the one hand, the present invention provides a slurry preparation method for preparing a low-density conductive foam material. The slurry preparation method includes the following steps:

[0063] Mix and homogenize the conductive resin slurry with the reinforcing material to obtain a homogenized mixture;

[0064] Mix the homogenized mixture with the conductive hollow microspheres;

[0065] Obtain a low-density conductive foam material slurry.

[0066] Preferably, it further includes the preparation of the conductive resin slurry, including the following steps:

[0067] Mix and homogenize the aqueous dispersion slurry of the second carbon nanomaterial with the resin emulsion to obtain a homogenized slurry; the concentration of the aqueous dispersion slurry of the second carbon nanomaterial is 0.5 - 10 wt%;

[0068] Add a curing agent and perform homogenization treatment to obtain the conductive resin slurry.

[0069] Preferably, the concentration of the resin emulsion is 20 - 60 wt%;

[0070] The volume ratio of the homogenized mixture to the conductive hollow microspheres is 1:2.2 - 3.5;

[0071] Preferably, the second carbon nanomaterial is a mixture of carbon nanotubes and nanocarbon fibers in a mass ratio of 1:0.1-2;

[0072] The mass ratio of the slurry to the curing agent is 0.01-0.15.

[0073] Preferably, the curing agent is a water-soluble curing agent or a fine particle curing agent, and the particle size of the curing agent is less than 10 μm.

[0074] Preferably, the curing agent is 4,4'-diaminodiphenyl sulfone and / or dicyandiamide.

[0075] In the embodiment, the conductive resin slurry and the reinforcing material are first mixed to obtain a homogenous slurry mixture, which is dispersed when the resin content is low, and does not cause shear damage to the hollow microspheres.

[0076] The conductive second nanomaterial is made into an aqueous dispersion slurry, and then mixed with the resin emulsion and emulsified to obtain a uniform slurry; the second carbon nanomaterial and the resin emulsion are ensured to be mixed, and a curing agent is added to accelerate the hardening of the material.

[0077] Selecting a curing agent with the appropriate particle size can avoid increasing the shear force of the material and help improve the stability and strength of the material.

[0078] During the preparation of low-density conductive foam material slurry, gelation is more likely to occur, resulting in difficulty in foam preparation. When the volume ratio of aqueous slurry to hollow glass microspheres is lower than 1:2.2, it is impossible to obtain foam with uniform conductivity and resin distribution; when the volume ratio is higher than 1:3.5, it is difficult to obtain foam with uniform conductivity and resin distribution, and the mechanical properties are significantly reduced.

[0079] We found that when the carbon nanomaterial contained in the conductive resin is carbon nanotubes, or carbon nanotubes and nanocarbon fibers, the mechanical properties and conductivity of the foam are better than those of the graphene modified system. Therefore, this system is preferred. The mass ratio of carbon nanotubes and nanocarbon fibers is preferably 1:0 to 1:2. After further increasing the amount of nanocarbon fibers, the strength of the foam decreases. The principle is that the interface adhesion deteriorates.

[0080] In one aspect, the present invention provides a wave-absorbing honeycomb, characterized in that the wave-absorbing honeycomb is obtained by absorbing the wave-absorbing material onto a common honeycomb; and the coating thickness of the wave-absorbing material is 0.05-1 mm.

[0081] On one hand, the present invention provides a method for preparing a low-density conductive foam material, wherein the slurry obtained by the above-mentioned slurry preparation method is shaped and solidified to obtain a low-density conductive foam material;

[0082] The curing temperature does not exceed 135°C;

[0083] Preferably, the curing temperature is 105 - 135 °C;

[0084] The curing method includes atmospheric pressure curing or vacuum bag pressure curing.

[0085] In the embodiments of the present invention, according to the required shape, etc., or by selecting a suitable mold, etc., the slurry prepared previously is subjected to steps such as shaping, curing, drying, etc. to obtain a low-density conductive foam.

[0086] The low-density conductive foam material formed by pre-shaping, then in-situ drying and curing has more excellent mechanical properties compared to first drying the mixture and then shaping and curing it into a foam. Scanning electron microscopy analysis shows that this is because during the in-situ drying process, the resin gradually aggregates into the tiny gaps between the hollow glass microspheres under capillary action, forming resin columns that connect and support the microspheres, thereby achieving the effect of good mechanical connection with a small amount of resin bonding. If the mixture is first dried and then shaped and cured into a foam, the resin is randomly distributed in the large gaps between the hollow glass microspheres (HGM) in the form of particles, and cannot play the role of bonding different HGMs, and it is impossible to form a foam body with a complete structure and acceptable mechanical properties at a very low resin content or a high HGM mass fraction.

[0087] The following will be described in detail with specific examples.

[0088] Example 1

[0089] The implementation process of the technical solution of this example is as follows:

[0090] (1-1) A water-based dispersion slurry of carbon nanotubes with a concentration of 2.5 wt% and an epoxy resin emulsion with a concentration of 30% are uniformly mixed at a volume ratio of 1:1. Subsequently, the curing agent 4,4'-diaminodiphenyl sulfone (DDS) is added to the above co-dispersion slurry according to the epoxy resin equivalent, and stirred thoroughly to obtain a carbon nanomaterial / epoxy resin co-dispersion water-based slurry; the carbon nanotube slurry is purchased online from Taobao, Suzhou Carbon Feng Graphene, and diluted to 2.5% with deionized water for use; the epoxy resin emulsion and the curing agent are both conventional raw materials, purchased from domestic manufacturers;

[0091] (1-2) The uniformly mixed water-based slurry and hollow glass microspheres are mixed at a volume ratio of 1:2.5, and stirred thoroughly to obtain a slurry-like mixture. The hollow glass microspheres are of the brand K1, produced by 3M Company, with an average diameter of 55 μm and a density of 0.125 g / cm 3 ;

[0092] (1-3) The slurry-like mixture is shaped into a rectangular flat plate shape, and then the shaped mixture is dried, and the drying temperature does not exceed 135 °C;

[0093] (1-4) The dried plastic mixture is further cured at 185 °C for 2 h. During the curing process, the atmospheric pressure curing method is adopted. After cooling, a low-density conductive foam rectangular flat plate is obtained by taking it out.

[0094] Example 2

[0095] The implementation process of the technical solution of this example is as follows:

[0096] (2-1) An aqueous slurry of 2 wt% carbon nanotubes, an aqueous dispersion slurry of 4 wt% nanofibers, and an epoxy resin emulsion of 40 wt% are uniformly mixed at a volume ratio of 1:1:2. Subsequently, the curing agent DDS is added to the above co-dispersion slurry according to the epoxy resin equivalent, and stirred evenly to obtain a carbon nanomaterial / epoxy resin co-dispersion aqueous slurry. Subsequently, T700 short carbon fibers are added to the slurry, and the dosage of the short carbon fibers is 15% of the mass of the conductive resin; the carbon nanotube slurry is purchased from Jiangsu Tiannai Technology Co., Ltd. and diluted to 2% with deionized water for use. The nanofiber slurry is purchased from Suzhou First Element Nanotechnology Co., Ltd. and diluted to 4 wt% with deionized water for use;

[0097] (2-2) The above-mentioned uniformly mixed slurry is placed for 4 hours until the slurry becomes mud-like. Subsequently, the mud-like aqueous slurry and hollow glass microspheres are mixed at a volume ratio of 1:2.8, and stirred evenly to obtain a mud-like mixture. The hollow glass microspheres are of the brand K1, produced by 3M Company, with an average diameter of 55 μm and a density of 0.125 g / cm3;

[0098] (2-3) The mud-like mixture is shaped into a cube, and then the shaped mixture is dried at a drying temperature of 120 °C;

[0099] (2-4) The dried plastic mixture is further cured at 185 °C for 2 hours. During the curing process, the vacuum bag pressing curing method is adopted. After cooling and demolding, a low-density block-shaped conductive foam is obtained.

[0100] Example 3

[0101] The implementation process of the technical solution of this example is as follows:

[0102] (3-1) Aqueous slurry of 2 wt% carbon nanotubes, aqueous dispersion slurry of 4 wt% nanofiber and 40 wt% epoxy resin emulsion were uniformly mixed at a volume ratio of 1:1:2. Subsequently, curing agent DDS was added to the above co-dispersion slurry according to the epoxy equivalent, and stirred evenly to obtain a carbon nanomaterial / epoxy resin co-dispersion aqueous slurry. Then, short-cut T700 carbon fiber was added to the slurry, and the dosage of short-cut carbon fiber was 15% of the mass of the conductive resin. The carbon nanotube slurry was purchased from Jiangsu Tiannai Technology Co., Ltd. and diluted to 2% with deionized water before use. The nanofiber slurry was purchased from Suzhou First Element Nanotechnology Co., Ltd. and diluted to 4 wt% with deionized water before use;

[0103] (3-2) The above uniformly mixed slurry was left for 4 hours until it became a mud-like state. Subsequently, the mud-like aqueous slurry and conductive modified hollow glass microspheres were mixed at a volume ratio of 1:2.8 and stirred evenly to obtain a mud-like mixture. The hollow glass microspheres were of the brand K1, produced by 3M Company, with an average diameter of 55 μm and a density of 0.125 g / cm3. The hollow glass microspheres were surface-coated and conductively modified with carbon nanotubes. After modification, the density became 0.135 g / cm3, and the coating amount was about 0.1 g / m2. The subsequent steps were the same, and the conductivity of the obtained conductive foam was increased by 7 times, while the density increased very little. The coating amounts of 0.15 g / m2 and 0.25 g / m2 could also be used.

[0104] (3-3) The mud-like mixture was shaped into a cube, and then the shaped mixture was dried at a drying temperature of 120 °C;

[0105] (3-4) The dried plastic mixture was further cured at 185 °C for 2 hours. During the curing process, the vacuum bag pressing curing method was adopted. After cooling and demolding, a low-density square conductive foam was obtained.

[0106] Example 4

[0107] The implementation process of the technical solution of this example is as follows:

[0108] (4-1) Aqueous slurry of 5 wt% carbon nanotubes and 40 wt% epoxy resin emulsion were uniformly mixed at a volume ratio of 1:3. Subsequently, ultrafine DDS with an average diameter of 2.5 μm was added to the above co-dispersion slurry according to the epoxy equivalent, and stirred evenly to obtain a carbon nanotube / epoxy resin co-dispersion aqueous slurry. Then, short-cut aramid fiber was added to the slurry, and the dosage of short-cut aramid fiber was 10% of the mass of the conductive resin. The short-cut aramid fiber was Kevlar fiber, a product of DuPont Company, and the carbon nanotube aqueous slurry was a product of Jiangsu Tiannai Company, with the brand LB217-54;

[0109] (4-2) Mix the above-mentioned well-mixed aqueous slurry and hollow glass microspheres in a volume ratio of 1:3.1, and fully stir to obtain a slurry-like mixture. The hollow glass microspheres are of grade A16, produced by 3M Company, with an average diameter of 50 μm and a density of 0.13 g / cm 3 ;

[0110] (4-3) Shape the slurry-like mixture into a cylinder, and then dry the shaped mixture at a drying temperature of 130 °C;

[0111] (4-4) Further cure the dried shaped mixture at 180 °C for 2 hours. During the curing process, use the vacuum bag curing method. After cooling and demolding, a cylindrical low-density conductive foam is obtained.

[0112] Example 5

[0113] The implementation process of the technical solution in this example is as follows:

[0114] (5-1) Uniformly mix an aqueous slurry of 3 wt% carbon nanotubes, an aqueous slurry of 3 wt% graphene, and 25 wt% epoxy resin emulsion in a volume ratio of 2:0.5:2. Then add ultrafine dicyandiamide with an average diameter of 5.5 μm to the above-mentioned co-dispersed slurry according to the epoxy resin equivalent, and fully stir to obtain a carbon nanotube / epoxy resin co-dispersed aqueous slurry. Then add aramid pulp to the slurry, and the dosage of aramid pulp is 25% of the mass of the conductive resin. Mix well. The carbon nanotube slurry and graphene slurry are purchased from Jiangsu Tianneng Technology and diluted to 3% with deionized water for use. The aramid pulp is purchased from DuPont Company;

[0115] (5-2) Mix the above-mentioned well-mixed aqueous slurry and hollow glass microspheres in a volume ratio of 1:2.2, and fully stir to obtain a slurry-like mixture. The hollow glass microspheres are of grade A20, produced by 3M Company, with an average diameter of 50 μm and a density of 0.2 g / cm3;

[0116] (5-3) Shape the slurry-like mixture into a saddle shape, and then dry the shaped mixture at a drying temperature of 125 °C;

[0117] (5-4) Further cure the dried plastic mixture at 180 °C for 2 hours. During the curing process, use the autoclave curing method. After cooling and demolding, a saddle-shaped low-density conductive foam is obtained;

[0118] Example 6

[0119] The implementation process of the technical solution in this example is as follows:

[0120] (6-1) Aqueous slurries of 3 wt% carbon nanotubes, aqueous slurries of 3 wt% graphene, and 25 wt% epoxy resin emulsion were uniformly mixed at a volume ratio of 2:0.5:2. Subsequently, ultrafine dicyandiamide with an average diameter of 5.5 μm was added to the above co-dispersed slurry according to the epoxy resin equivalent, and stirred evenly to obtain a carbon nanotube / epoxy resin co-dispersed aqueous slurry. Subsequently, aramid pulp was added to the slurry, and the dosage of aramid pulp was 25% of the mass of the conductive resin. After thorough mixing, the carbon nanotube slurry and graphene slurry were purchased from Jiangsu Tiannai Technology Co., Ltd. and diluted to 3% with deionized water before use. The aramid pulp was purchased from DuPont Company;

[0121] (6-2) Hollow glass microspheres were surface-conductively modified by silver plating. After modification, the density became 0.375 g / cm3 and the coating amount was about 1.5 g / m2. The subsequent steps were the same, and the conductivity of the obtained conductive foam could reach 0.271 S / cm, but the density increased significantly. The above-mentioned uniformly mixed aqueous slurry and modified hollow glass microspheres were mixed at a volume ratio of 1:2.2, and stirred evenly to obtain a slurry-like mixture;

[0122] (6-3) The slurry-like mixture was shaped into a saddle shape, and then the shaped mixture was dried at a drying temperature of 125 °C;

[0123] (6-4) The dried plastic mixture was further cured at 180 °C for 2 hours. During the curing process, the autoclave curing method was adopted. After cooling and demolding, a saddle-shaped low-density conductive foam was obtained.

[0124] Example 7

[0125] The implementation process of the technical solution of this example is as follows:

[0126] (7-1) Aqueous slurries of 2.5 wt% carbon nanotubes, aqueous slurries of 2.5 wt% nanofibers, and 50 wt% epoxy resin emulsion were uniformly mixed at a volume ratio of 2:1:3. Subsequently, the curing agent dicyandiamide was added to the above co-dispersed slurry according to the epoxy resin equivalent, and stirred evenly to obtain a carbon nanotube / epoxy resin co-dispersed aqueous slurry. The carbon nanotube aqueous slurry was a product of Suzhou Carbon Feng Graphene Co., Ltd. and was diluted to 2.5 wt% before use. The nanofibers were products of Jiangsu First Element Technology Co., Ltd., and the slurry was self-dispersed;

[0127] (7-2) The diluted aqueous slurry and hollow glass microspheres were mixed at a volume ratio of 1:3.5, and stirred evenly to obtain a slurry-like mixture. The hollow glass microspheres were of grade K1, produced by 3M Company, with an average diameter of 55 μm and a density of 0.125 g / cm3;

[0128] (7-3) Shape the slurry-like mixture into a dumbbell shape, and then dry the shaped mixture at a drying temperature not exceeding 125 °C;

[0129] (7-4) Further cure the dried plastic mixture at 185 °C for 2 hours. During the curing process, use the method of atmospheric pressure curing. After cooling and removing the mold, a dumbbell-shaped conductive foam is obtained.

[0130] Example 8

[0131] The implementation process of the technical solution of this example is as follows:

[0132] (7-1) Uniformly mix an aqueous slurry of 2.5 wt% carbon nanotubes, an aqueous slurry of 2.5 wt% nanofibers, and 50 wt% epoxy resin emulsion in a volume ratio of 2:1:3. Then add dicyandiamide as a curing agent according to the epoxy resin equivalent to the above co-dispersed slurry, and stir well to obtain a carbon nanotube / epoxy resin co-dispersed aqueous slurry. The carbon nanotube aqueous slurry is a product of Suzhou Carbon Feng Graphene, diluted to 2.5 wt% for use. The nanofibers are products of Jiangsu First Element Technology Co., Ltd., and the slurry is self-dispersed;

[0133] (7-2) Mix the diluted aqueous slurry and hollow glass microspheres in a volume ratio of 1:3.5, and stir well to obtain a slurry-like mixture. The hollow glass microspheres are of the brand K25, produced by 3M Company, with an average diameter of 55 μm and a density of 0.25 g / cm3;

[0134] (7-3) Shape the slurry-like mixture into a dumbbell shape, and then dry the shaped mixture at a drying temperature not exceeding 125 °C;

[0135] (7-4) Further cure the dried plastic mixture at 185 °C for 2 hours. During the curing process, use the method of atmospheric pressure curing. After cooling and removing the mold, a dumbbell-shaped conductive foam is obtained.

[0136] Comparative Example 1

[0137] The process method of Comparative Example 1 is basically the same as that of Example 1, except that the aqueous slurry and hollow glass microspheres are mixed in a volume ratio of 1:1.5, and the others remain unchanged.

[0138] Comparative Example 2

[0139] The process method of Comparative Example 2 is basically the same as that of Example 1, except that the aqueous slurry and hollow glass microspheres are mixed in a volume ratio of 1:1.2, and the others remain unchanged.

[0140] Comparative Example 3

[0141] The process method of Comparative Example 3 is basically the same as that of Example 1, except that the aqueous slurry and hollow glass microspheres are mixed in a volume ratio of 1:4.0, and the others remain unchanged.

[0142] Comparative Example 4

[0143] The process method of Comparative Example 4 is basically the same as that of Example 1, except that the aqueous slurry and hollow glass microspheres are mixed in a volume ratio of 1:4.5, and the others remain unchanged.

[0144] Comparative Example 5

[0145] The process method of Comparative Example 5 is basically the same as that of Example 3, except that the amount of carbon nanotubes used is 0.2 wt%.

[0146] Comparative Example 6

[0147] The process method of Comparative Example 6 is basically the same as that of Example 3, except that the amount of carbon nanotubes used is 0.7 wt%.

[0148] Comparative Example 7

[0149] The process method of Comparative Example 7 is basically the same as that of Example 3, except that the amount of carbon nanotubes used is 18 wt%.

[0150] Comparative Example 8

[0151] The process method of Comparative Example 7 is basically the same as that of Example 3, except that the amount of carbon nanotubes used is 20 wt%.

[0152] The densities of the absorbing coatings of the absorbing honeycombs obtained in each example and comparative example were measured respectively, and the results are shown below.

[0153] Table 1 Densities of the absorbing coatings in each example and comparative example

[0154]

[0155]

[0156]

[0157] From the process of the present invention, it can be known that the density of the HGM foam prepared by the prior art is generally higher than 0.4 g / cm 3 , when less resin is used, it is impossible to infiltrate and mix to form a bonding structure, while the density of the HGM foam prepared in the present invention can be lower than 0.25 g / cm 3 , compared with the prior art, the weight reduction effect brought by the present invention is relatively obvious.

[0158] In addition, the foam obtained by the existing preparation technology has poor conductivity and is difficult to mix when the nano content is high. The low-density conductive foam prepared by the present invention has good conductivity, and a foam with a high content of conductive nanoparticles can be obtained. The surface resistance can be lower than 100 Ω / sq, and the single conductivity can reach 0.007 S / cm.

[0159] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. Low-density conductive foam material, Characterized in that, The low-density conductive foam material is prepared from the following raw materials, and the raw materials include: Conductive hollow glass microspheres, conductive resin and reinforcing material; The conductive resin is a resin modified with conductivity; the second carbon nanomaterial is included in the conductive resin modified with conductivity, and the second carbon nanomaterial includes carbon nanotubes and carbon fibers, and the mass ratio of carbon nanotubes to nanofibers is 1:0 to 1:2; The slurry method for preparing the low-density conductive foam material includes the following steps: mixing and homogenizing the conductive resin slurry with the reinforcing material to obtain a homogenized mixture; mixing the homogenized mixture with the conductive hollow glass microspheres; The preparation of the conductive resin slurry includes the following steps: mixing and homogenizing the aqueous dispersion slurry of the second carbon nanomaterial with the resin emulsion to obtain a homogenized slurry; adding a curing agent and homogenizing to obtain the conductive resin slurry; The volume ratio of the homogenized mixture to the conductive hollow glass microspheres is 1:2.2 - 2.

5.

2. The low-density conductive foam material according to claim 1, Characterized in that, The volume content of the conductive hollow glass microspheres is 60% - 80%, the volume content of the conductive resin is 5% - 20%, and the volume content of the reinforcing material is 0.01 - 20%.

3. The low-density conductive foam material according to claim 2, Characterized in that, The diameter of the conductive hollow glass microspheres is 20-100 μm, and the density is 0.10-0.30 g / cm 3 ; The conductive hollow glass microspheres are hollow glass microspheres coated with the first carbon nanomaterial, and 0.01 - 0.3 g of the first carbon nanomaterial is coated on the surface of each square meter of the hollow glass microspheres; The first carbon nanomaterial includes at least one of carbon nanotubes, graphene or nanofibers.

4. The low-density conductive foam material according to claim 2, Characterized in that, The content of the second carbon nanomaterial is 1 wt% - 15 wt%.

5. The low-density conductive foam material according to claim 2, Characterized in that, The reinforcing material is chopped fiber, including at least one of carbon fiber, aramid fiber, polyimide fiber or nylon fiber.

6. The low-density conductive foam material according to claim 1, Characterized in that, The concentration of the aqueous dispersion slurry of the second carbon nanomaterial is 0.5 - 10 wt%.

7. The low-density conductive foam material according to claim 1, Characterized in that, The concentration of the resin emulsion is 20 - 60 wt%; The mass ratio of the homogenized mixture to the curing agent is 1:0.01 - 0.

15.

8. The low-density conductive foam material according to claim 1, Characterized in that, The curing agent is a water-soluble curing agent or a fine particle type curing agent, and the particle size of the curing agent is less than 10 μm; The curing agent is 4,4'-diaminodiphenyl sulfone and / or dicyandiamide.

9. The preparation method of the low-density conductive foam material, Characterized in that, The slurry of the low-density conductive foam material according to any one of claims 1 - 8 is shaped and cured to obtain a low-density conductive foam material; The curing temperature does not exceed 135 °C; The curing method includes atmospheric pressure curing or vacuum bag pressing curing.

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