Lightweight epoxy resin-based electromagnetic shielding composite material and preparation method thereof

Abstract

The invention relates to a lightweight epoxy resin-based electromagnetic shielding composite material and a preparation method thereof. The preparation method comprises the following steps: preparing composite aerogel of reduced graphene and nickel nanowires from graphene oxide and nickel nanowires, and fully filling the composite aerogel with liquid epoxy resin to obtain a composite material of epoxy resin and composite aerogel; then, the composite material is subjected to microcellular foaming through a supercritical carbon dioxide microcellular foaming technology, and the light epoxy resin-based composite material is obtained; the composite material is simple in preparation method and low in production and processing cost, and has relatively low density and efficient electromagnetic shielding effectiveness, so that the composite material has the potential of being applied to the fields of civil affairs and military affairs.

Description

Technical Field

[0001] The invention relates to the field of composite materials, and in particular to a lightweight epoxy resin-based electromagnetic shielding composite material and a preparation method thereof. Background Art

[0002] With the rapid development of modern information technology, electromagnetic waves have been widely used in electronic products, data transmission, electronic communications, wireless network systems, satellite launches, modern detection technology, radar detection technology, medical diagnosis and other fields, providing great convenience for people's lives while also bringing serious electromagnetic radiation pollution problems. The problem of electromagnetic pollution should not be underestimated, and it will seriously endanger people's health. In addition, the existence of electromagnetic waves can easily cause information leakage and interfere with the normal operation of other electronic devices. Considering the diversity and inevitability of electromagnetic wave pollution sources, the use of electromagnetic shielding measures is an important and feasible way to control pollution and reduce the hazards of electromagnetic radiation. Although metal-based electromagnetic shielding materials have high shielding effectiveness, their high density and easy corrosion limit their application in aerospace, military equipment and electronic communication equipment. Polymer electromagnetic shielding materials are mainly composed of polymer matrix and conductive / magnetic nano-filling system. They have the advantages of easy processing, low cost, acid and alkali corrosion resistance, etc., but polymer-based composite materials still have the disadvantage that the electromagnetic interference shielding effectiveness (EMI SE) is worse than that of metal-based electromagnetic shielding materials. The main problem is that nanofillers are difficult to disperse in the polymer matrix, and high content of nanofillers will have an adverse effect on the fluidity and mechanical properties of the composite material. Among them, by pre-constructing a conductive network structure, such as graphene aerogel (GA), and then introducing a polymer matrix such as epoxy resin through in-situ polymerization, a highly efficient conductive structure of thermosetting polymers can be constructed to achieve efficient electromagnetic shielding performance of polymer-based electromagnetic shielding composite materials.

[0003] In the prior art, the electromagnetic shielding composite material is prepared by compounding graphene aerogel with epoxy, or the polymer matrix is ​​filled with nano-metal materials to improve its electromagnetic shielding effectiveness. However, high-density and high-content nano-fillers often increase the density of polymer-based composite materials. For example, the good properties of carbon-based nano-fillers and nano-metal fillers are combined to further improve the electromagnetic shielding effectiveness of polymer-based composite materials, while the density of low-density polymer-based composite materials is reduced, which provides a good foundation for expanding its application in the aerospace field.

[0004] Supercritical carbon dioxide microporous foaming technology is a green polymer foaming process that uses carbon dioxide as a foaming agent, and is a positive response to the country's "dual carbon" strategy. Supercritical carbon dioxide microporous foaming technology is to infiltrate carbon dioxide in a supercritical state into a polymer matrix under high pressure, rapidly expand carbon dioxide under low pressure and a certain temperature, and form a porous structure inside the polymer matrix. The use of supercritical carbon dioxide microporous foaming technology can prepare microporous materials with a pore diameter of less than 100μm in a polymer matrix. While effectively reducing the matrix density, it can achieve toughening modification of the matrix material, and the strength reduction is within a controllable range. Summary of the invention

[0005] In view of the deficiencies of the above-mentioned prior art and process, the object of the present invention is to provide an epoxy resin-based electromagnetic shielding composite material with low density, excellent electromagnetic shielding performance and simple preparation process and a preparation method thereof. The specific technical scheme is as follows:

[0006] A lightweight epoxy resin-based electromagnetic shielding composite material, characterized in that it comprises a composite aerogel of reduced graphene and nickel nanowires prepared by using graphene oxide and nickel nanowires, the composite aerogel is fully filled with epoxy resin to obtain a composite material of epoxy resin and composite aerogel; then the composite material is microporously foamed by a supercritical carbon dioxide microporous foaming process to obtain a lightweight epoxy resin-based composite material; the density of the lightweight epoxy resin-based composite material is 0.50-1.50 g / cm 3 ; When the electromagnetic wave frequency is 8~12GHz, the total electromagnetic shielding effectiveness is 30.0~70dB; the compressive strength at room temperature is 50.0~100.0MPa.

[0007] Preferably, the graphene oxide is prepared by the Hummers method, with a two-dimensional size of 0.1 to 10 μm; the nickel nanowires are prepared by the sol-gel method, with a length of 10 to 100 μm.

[0008] Preferably, the composite aerogel of reduced graphene and nickel nanowires is prepared by a hydrothermal method, the hydrothermal reaction temperature is 100-150° C., and the reaction time is 2-6 hours; the mass ratio of nickel nanowires to graphene oxide is less than 50.

[0009] Preferably, the epoxy resin is a liquid epoxy resin, including but not limited to epoxy E51, E44 and the like.

[0010] Preferably, the supercritical carbon dioxide microporous foaming process is: the holding pressure is 10-50 MPa, the holding time is 5-100 h, the foaming temperature is 80-160° C., and the foaming time is 5-100 s.

[0011] On the other hand, the present invention also provides a method for preparing a lightweight epoxy resin-based electromagnetic shielding composite material, which specifically comprises the following steps:

[0012] (1) Graphene oxide is prepared by a Hummers method and nickel nanowires are prepared by a sol-gel method, and the obtained graphene oxide and nickel nanowires are dispersed in water. The concentration of the graphene oxide dispersion is adjusted to 5-20 mg / ml, and the concentration of the nickel nanowire dispersion is adjusted to 100-1000 mg / ml.

[0013] (2) Weigh 10-50 ml of graphene oxide dispersion and 10-50 ml of nickel nanowire dispersion respectively into a hydrothermal reactor, add 3-5 ml of ethylenediamine catalyst; place the reactor in an oven at 100-150° C. for reaction for 2-6 hours to obtain a composite hydrogel of reduced graphene and nickel nanowires. Freeze-dry the hydrogel to obtain a composite aerogel of reduced graphene and nickel nanowires.

[0014] (3) estimating the mass of the epoxy resin based on the volume of the composite aerogel and making it slightly excessive; taking the calculated mass of liquid epoxy resin such as E44 or E51 and the mass of curing agent required for curing, stirring and mixing the two and placing the composite aerogel of reduced graphene and nickel nanowires therein; using a vacuum-assisted process to fully adsorb the mixed solution of the epoxy resin and the curing agent into the porous structure of the composite aerogel; and then placing it in an oven, setting the oven temperature and heating time according to the curing temperature and reaction time required by the selected epoxy resin and curing agent type, and curing to obtain a solid block material of the epoxy resin and the composite aerogel.

[0015] (4) placing the solid block material in (3) in a supercritical reactor, compressing supercritical carbon dioxide into the reactor, setting the holding pressure of the reactor to 10 to 50 MPa, and the holding time to 5 to 60 h, until the solid block material is saturated with carbon dioxide.

[0016] (5) The adsorption saturated solid block material is placed in an oil bath, the oil bath temperature is set to 80-160°C, the solid block material begins to foam in the oil bath, and the foaming time is set to 5-100s. Since the strength of the epoxy resin matrix decreases at high temperature, the expansion pressure of the carbon dioxide gas is sufficient to overcome its yield strength, so a pore structure is formed in the epoxy resin. The three-dimensional porous network structure of the reduced graphene and nickel nanowire composite aerogel is constantly rebuilt by extrusion during the foaming process, so it still maintains a good three-dimensional conductive network structure, so it has good dielectric loss for electromagnetic waves. At the same time, nickel nanowires have good magnetic loss for electromagnetic waves, so the obtained lightweight epoxy resin-based composite material has good electromagnetic shielding performance.

[0017] Preferably, in step (1), the water is deionized water.

[0018] Preferably, in step (2), the catalyst is ethylenediamine.

[0019] Preferably, in step (3), the volume of the mixed solution of epoxy resin and curing agent is greater than the volume of the composite aerogel; and the curing temperature and time are set according to the grades of epoxy resin and curing agent.

[0020] The beneficial effects of the present invention are:

[0021] 1. The present invention uses a composite aerogel of reduced graphene and nickel nanowires as a prefabricated three-dimensional conductive and magnetic network, and after compounding it with epoxy resin, it still has good conductivity and magnetism, so that the composite material has both dielectric loss and magnetic loss to electromagnetic waves, thereby giving the composite material efficient electromagnetic shielding performance.

[0022] 2. The present invention uses supercritical carbon dioxide foaming technology to prepare porous epoxy resin-based composite materials. Carbon dioxide is used as a foaming agent, which is green and environmentally friendly. At the same time, the high strength and heat resistance of epoxy resin give the composite material good mechanical properties and thermal stability. The porous structure greatly reduces the density of the composite material, providing a good foundation for its application in aviation, aerospace and other fields with high requirements for weight reduction.

[0023] 3. The epoxy resin-based electromagnetic shielding composite material prepared by the present invention has a simple preparation method and a density of 0.50 to 1.50 g / cm 3 The obtained electromagnetic shielding composite material has a total electromagnetic shielding effectiveness of 30.0-70dB in the medium frequency band of 8-12GHz, and has a significant electromagnetic wave shielding effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a scanning electron microscope image of a lightweight epoxy resin-based electromagnetic shielding composite material prepared in an embodiment of the present application and obtained at different foaming times. DETAILED DESCRIPTION

[0025] To make the purpose, technical scheme and advantages of the embodiment of the present application clearer, the technical scheme in the embodiment of the present application will be clearly and completely described below. Obviously, the described embodiment is a part of the embodiment of the present application, rather than all the embodiments. These specific features, structures or characteristics in the embodiment can be combined in one or more embodiments in any suitable manner. In the following description, specific details such as specific configuration and components are provided only to help fully understand the embodiments of the present application. Therefore, it should be clear to those skilled in the art that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present application. In addition, for the sake of clarity and brevity, the description of known functions and structures is omitted in the embodiment.

[0026] Example 1

[0027] (1) Graphene oxide was prepared by Hummers method and nickel nanowires were prepared by sol-gel method, and the obtained graphene oxide and nickel nanowires were dispersed in water. The concentration of graphene oxide dispersion was adjusted to 5 mg / ml, and the concentration of nickel nanowire dispersion was adjusted to 100 mg / ml.

[0028] (2) Weigh 10 ml of graphene oxide dispersion and 10 ml of nickel nanowire dispersion respectively into a hydrothermal reactor, add 3 ml of ethylenediamine catalyst; place the reactor in an oven at 100° C. for 2 h to obtain a composite hydrogel of reduced graphene and nickel nanowires. The hydrogel is freeze-dried to obtain a composite aerogel of reduced graphene and nickel nanowires.

[0029] (3) estimating the mass of the epoxy resin based on the volume of the composite aerogel and making it slightly excessive; taking the calculated mass of liquid epoxy resin such as E44 or E51 and the mass of curing agent required for curing, stirring and mixing the two and placing the composite aerogel of reduced graphene and nickel nanowires therein; using a vacuum-assisted process to fully adsorb the mixed solution of the epoxy resin and the curing agent into the porous structure of the composite aerogel; and then placing it in an oven, setting the oven temperature and heating time according to the curing temperature and reaction time required by the selected epoxy resin and curing agent type, and curing to obtain a solid block material of the epoxy resin and the composite aerogel.

[0030] (4) The solid block material in (3) is placed in a supercritical reactor, and supercritical carbon dioxide is compressed into the reactor. The holding pressure of the reactor is set to 10 MPa and the holding time is 5 h, until the solid block material is saturated with carbon dioxide.

[0031] (5) The adsorption saturated solid block material is placed in an oil bath, the oil bath temperature is set to 80° C., the solid block material begins to foam in the oil bath, and the foaming time is set to 5 s, thereby obtaining a lightweight porous epoxy resin-based electromagnetic shielding composite material.

[0032] The density of the lightweight epoxy resin-based electromagnetic shielding composite material prepared in this embodiment is 0.50 g / cm 3 The compressive strength is 50.0MPa, and the total electromagnetic shielding effectiveness is 30.0dB in the band of 8-12GHz.

[0033] Example 2

[0034] (1) Graphene oxide was prepared by Hummers method and nickel nanowires were prepared by sol-gel method, and the obtained graphene oxide and nickel nanowires were dispersed in water. The concentration of graphene oxide dispersion was adjusted to 20 mg / ml, and the concentration of nickel nanowire dispersion was adjusted to 1000 mg / ml.

[0035] (2) Weigh 50 ml of graphene oxide dispersion and 50 ml of nickel nanowire dispersion respectively into a hydrothermal reactor, add 5 ml of ethylenediamine catalyst; place the reactor in an oven at 150° C. for 6 h to obtain a composite hydrogel of reduced graphene and nickel nanowires. The hydrogel is freeze-dried to obtain a composite aerogel of reduced graphene and nickel nanowires.

[0036] (3) estimating the mass of the epoxy resin based on the volume of the composite aerogel and making it slightly excessive; taking the calculated mass of liquid epoxy resin such as E44 or E51 and the mass of curing agent required for curing, stirring and mixing the two and placing the composite aerogel of reduced graphene and nickel nanowires therein; using a vacuum-assisted process to fully adsorb the mixed solution of the epoxy resin and the curing agent into the porous structure of the composite aerogel; and then placing it in an oven, setting the oven temperature and heating time according to the curing temperature and reaction time required by the selected epoxy resin and curing agent type, and curing to obtain a solid block material of the epoxy resin and the composite aerogel.

[0037] (4) The solid block material in (3) is placed in a supercritical reactor, and supercritical carbon dioxide is compressed into the reactor. The holding pressure of the reactor is set to 50 MPa and the holding time is 60 h, until the solid block material is saturated with carbon dioxide.

[0038] (5) The adsorption saturated solid block material is placed in an oil bath, the oil bath temperature is set to 160° C., the solid block material begins to foam in the oil bath, and the foaming time is set to 100 s, thereby obtaining a lightweight porous epoxy resin-based electromagnetic shielding composite material.

[0039] The density of the lightweight epoxy resin-based electromagnetic shielding composite material prepared in this embodiment is 1.50 g / cm 3 The compressive strength is 100.0MPa, and the total electromagnetic shielding effectiveness is 70.0dB in the band of 8-12GHz.

[0040] Example 3

[0041] (1) Graphene oxide was prepared by Hummers method and nickel nanowires were prepared by sol-gel method, and the obtained graphene oxide and nickel nanowires were dispersed in water. The concentration of graphene oxide dispersion was adjusted to 10 mg / ml, and the concentration of nickel nanowire dispersion was adjusted to 500 mg / ml.

[0042] (2) Weigh 30 ml of graphene oxide dispersion and 30 ml of nickel nanowire dispersion respectively into a hydrothermal reactor, add 4 ml of ethylenediamine catalyst; place the reactor in an oven at 125° C. for 4 h to obtain a composite hydrogel of reduced graphene and nickel nanowires. The hydrogel is freeze-dried to obtain a composite aerogel of reduced graphene and nickel nanowires.

[0043] (3) estimating the mass of the epoxy resin based on the volume of the composite aerogel and making it slightly excessive; taking the calculated mass of liquid epoxy resin such as E44 or E51 and the mass of curing agent required for curing, stirring and mixing the two and placing the composite aerogel of reduced graphene and nickel nanowires therein; using a vacuum-assisted process to fully adsorb the mixed solution of the epoxy resin and the curing agent into the porous structure of the composite aerogel; and then placing it in an oven, setting the oven temperature and heating time according to the curing temperature and reaction time required by the selected epoxy resin and curing agent type, and curing to obtain a solid block material of the epoxy resin and the composite aerogel.

[0044] (4) The solid block material in (3) is placed in a supercritical reactor, and supercritical carbon dioxide is compressed into the reactor. The holding pressure of the reactor is set to 30 MPa and the holding time is 40 h, until the solid block material is saturated with carbon dioxide.

[0045] (5) The adsorption saturated solid block material is placed in an oil bath, the oil bath temperature is set to 120° C., the solid block material begins to foam in the oil bath, and the foaming time is set to 60 s, thereby obtaining a lightweight porous epoxy resin-based electromagnetic shielding composite material.

[0046] The density of the lightweight epoxy resin-based electromagnetic shielding composite material prepared in this embodiment is 1.10 g / cm 3 The compressive strength is 8.0MPa, and the total electromagnetic shielding effectiveness is 50.0dB in the band of 8-12GHz.

[0047] The above-described embodiments only express several implementation methods of the present invention, which are convenient for understanding the technical solutions of the present invention in detail, but they cannot be understood as limiting the scope of protection of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. It should be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning or limited experiments on the basis of the technical solutions provided by the present invention are all within the protection scope of the claims attached to the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the contents of the attached claims, and the description and drawings can be used to explain the contents of the claims.

Claims

1. A lightweight epoxy resin-based electromagnetic shielding composite material, characterized in that: The invention comprises preparing a composite aerogel of reduced graphene and nickel nanowires by using graphene oxide and nickel nanowires, fully filling the composite aerogel with a mixture of epoxy resin and a curing agent, and obtaining a composite material of epoxy resin and composite aerogel after curing; then microporously foaming the composite material by a supercritical carbon dioxide microporous foaming process to obtain a lightweight epoxy resin-based composite material; the density of the lightweight epoxy resin-based composite material is 0.50-1.50 g / cm 3 ; When the electromagnetic wave frequency is 8~12GHz, the total electromagnetic shielding effectiveness is 30.0~70dB; the compressive strength at room temperature is 50.0~100.0MPa.

2. The lightweight epoxy resin-based electromagnetic shielding composite material according to claim 1, characterized in that: The graphene oxide is prepared by the Hummers method, with a two-dimensional size of 0.1 to 10 μm; the nickel nanowire is prepared by the sol-gel method, with a length of 10 to 100 μm.

3. The lightweight epoxy resin-based electromagnetic shielding composite material according to claim 1, characterized in that: The reduced graphene and nickel nanowire composite aerogel is prepared by a hydrothermal method, the hydrothermal reaction temperature is 100-150° C., and the reaction time is 2-6 hours; the mass ratio of the nickel nanowire to the graphene oxide is less than 50.

4. The lightweight epoxy resin-based electromagnetic shielding composite material according to claim 1, characterized in that: The epoxy resin is a liquid epoxy resin, including but not limited to epoxy E51, E44 and the like.

5. The lightweight epoxy resin-based electromagnetic shielding composite material according to claim 1, characterized in that: The supercritical carbon dioxide microporous foaming process is as follows: the holding pressure is 10-50 MPa, the holding time is 5-100 hours, the foaming temperature is 80-160° C., and the foaming time is 5-100 seconds.

6. A method for preparing a lightweight epoxy resin-based electromagnetic shielding composite material, characterized in that: The specific steps include: (1) preparing graphene oxide by Hummers method and preparing nickel nanowires by sol-gel method, respectively, dispersing the obtained graphene oxide and nickel nanowires in water, and measuring the concentrations of the two in water; (2) weighing the quantitative graphene oxide and nickel nanowire dispersion in step (1) respectively into a hydrothermal reactor, adding a certain amount of catalyst; placing the reactor in an oven at a set temperature for a set time to obtain a composite hydrogel of reduced graphene and nickel nanowires, and freeze-drying the hydrogel to obtain a composite aerogel of reduced graphene and nickel nanowires; (3) placing the composite aerogel of reduced graphene and nickel nanowires in step (2) in a mixed solution of a quantitative epoxy resin and a curing agent, using a vacuum-assisted process to fully fill the composite aerogel with the mixed solution of the epoxy resin and the curing agent, and then placing it in an oven to react at a certain temperature for a specified time to solidify to obtain a solid block material of the epoxy resin and the composite aerogel; (4) placing the solid block material in step (3) in a supercritical reactor, compressing supercritical carbon dioxide into the reactor, setting the pressure holding pressure and pressure holding time of the reactor, and obtaining a solid block material after pressure holding treatment until the pressure holding is completed; (5) placing the solid block material subjected to the pressure-maintaining treatment in step (4) in an oil bath at a set temperature for foaming, and obtaining a lightweight epoxy resin-based electromagnetic shielding composite material after a specified foaming time.

7. The lightweight epoxy resin-based electromagnetic shielding composite material and the preparation method thereof according to claim 6, characterized in that: In step (1), the water is deionized water.

8. The lightweight epoxy resin-based electromagnetic shielding composite material and the preparation method thereof according to claim 6, characterized in that: In step (2), the catalyst is ethylenediamine.

9. The lightweight epoxy resin-based electromagnetic shielding composite material and the preparation method thereof according to claim 6, characterized in that: In step (3), the volume of the mixed solution of epoxy resin and curing agent is greater than the volume of the composite aerogel; and the curing temperature and time are set according to the grades of epoxy resin and curing agent.

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