Liquid metal-based epoxy resin porous composite material and preparation method thereof

Abstract

The invention relates to a liquid metal-based epoxy resin porous composite material and a preparation method thereof. Modified epoxy resin capable of being subjected to supercritical foaming is used as a matrix, and liquid metal is used as conductive functional filler; the porous composite material of the liquid metal filled epoxy resin is prepared through the processes of mechanical crushing and mixing, cold press molding, supercritical foaming and the like by utilizing the temperature-dependent phase change characteristic of the liquid metal. The composite material is low in production and processing cost, relatively low in density and extremely high in 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 present invention relates to the field of composite materials, and in particular to a liquid metal-based epoxy resin-based porous 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 technologies, radar detection technology, medical diagnosis, and other fields. While providing great convenience to people's lives, they have also brought serious electromagnetic radiation pollution problems. The problem of electromagnetic pollution should not be underestimated and can seriously endanger people's health. In addition, the presence of electromagnetic waves can easily cause information leakage and interfere with the normal operation of other electronic devices. Given 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 susceptibility to corrosion limit their application in aerospace, military equipment, and electronic communications equipment. Polymer electromagnetic shielding materials, mainly composed of a polymer matrix and a conductive / magnetic nanofiller system, have advantages such as easy processing, low cost, and acid and alkali corrosion resistance. However, polymer-based composites still have the disadvantage of inferior electromagnetic interference shielding effectiveness (EMISE) compared to metal-based electromagnetic shielding materials. The main problem is that nanofillers are difficult to disperse in a polymer matrix, and high nanofiller content can adversely affect 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, achieving high-efficiency electromagnetic shielding effectiveness of polymer-based electromagnetic shielding composites. Alternatively, by coating the surface of polymer particles with conductive or other functional fillers and then hot-pressing them to prepare an isolation structure, a three-dimensional conductive network structure can be constructed in the polymer matrix, effectively reducing the filler content and improving the conductivity of the polymer.

[0003] In existing technologies, carbon nanofillers are often used to modify polymer matrices, imparting them with excellent electrical conductivity or electromagnetic shielding properties. Metal nanofillers also have a positive effect on modifying the conductivity of polymer matrices. Liquid metal, a material with high plasticity at room temperature, has been shown to effectively enhance the electrical and thermal conductivity of polymer matrices through effective processing techniques.

[0004] Supercritical CO2 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 CO2 microporous foaming technology involves infiltrating supercritical CO2 into a polymer matrix under high pressure. Under low pressure and a certain temperature, the CO2 rapidly expands, forming a porous structure within the polymer matrix. Using supercritical CO2 microporous foaming technology, microporous materials with pore diameters below 100 μm can be prepared in a polymer matrix. This effectively reduces the matrix density while achieving toughening modification of the matrix material, while keeping the strength reduction within a controllable range. Summary of the Invention

[0005] In view of the shortcomings of the above-mentioned existing technologies and processes, the present invention aims to provide an epoxy resin-based porous composite material with excellent electromagnetic shielding performance and a simple preparation process, and a preparation method thereof. The specific technical solutions are as follows:

[0006] A liquid metal-based epoxy resin porous composite material and a preparation method thereof, characterized in that it comprises a modified epoxy resin capable of supercritical foaming as a matrix and liquid metal as a conductive functional filler; utilizing the temperature-dependent phase change characteristics of liquid metal, the liquid metal-filled epoxy resin porous composite material is prepared by mechanical crushing and mixing, cold pressing and supercritical foaming processes; the density of the epoxy resin porous composite material is 0.80 to 2.50 g / cm 3 ; When the electromagnetic wave frequency is 8~12GHz, the total electromagnetic shielding effectiveness is 20.0~80.0dB.

[0007] Preferably, the epoxy resin is a modified epoxy resin capable of supercritical foaming.

[0008] Preferably, the epoxy resin is a bisphenol A epoxy resin, including but not limited to E51, E44, etc., the curing agent is diethyltoluenediamine, and the modifier is polyether monoamine.

[0009] Preferably, the liquid metal includes but is not limited to gallium, gallium-indium alloy, gallium-indium-tin alloy, etc.

[0010] Preferably, the solid epoxy resin is mechanically crushed to a particle size of 50 to 1000 μm, and then mechanically blended with liquid metal, the mass fraction of the liquid metal in the blend is controlled at 20 to 80%, and then cold-pressed at a pressure of 20 to 50 MPa, and finally subjected to supercritical carbon dioxide microporous foaming to prepare a liquid metal-based epoxy resin porous composite material.

[0011] Preferably, the supercritical carbon dioxide microporous foaming process is as follows: the holding pressure is 10-30 MPa, the holding time is 20-80 h, the foaming temperature is room temperature, and the foaming time is 3-60 s.

[0012] On the other hand, the present invention also provides a method for preparing a liquid metal-based epoxy resin porous composite material, which specifically comprises the following steps:

[0013] (1) Weigh E51 or E44, etc., weigh the required mass of curing agent diethyltoluenediamine and modifier polyether monoamine, and mix them evenly with mechanical stirring. Set the required curing process (curing temperature and curing time) according to the selected epoxy resin and curing agent brand, and cure to obtain the epoxy resin capable of supercritical microcellular foaming.

[0014] (2) The supercritical microporous foamable epoxy resin in (1) is mechanically crushed, and epoxy resin particles with a particle size of 50 to 1000 μm are screened after crushing.

[0015] (3) Weigh a certain amount of epoxy resin particles in (2), weigh the liquid metal according to a mass fraction of 20 to 80%, and mix the two by mechanical stirring.

[0016] (4) The mixture of epoxy resin particles and liquid metal uniformly mixed in (3) is placed in a square mold and cold-pressed using a flat vulcanizer at a pressure of 20 to 50 MPa to prepare a block material of the mixture of epoxy resin particles and liquid metal.

[0017] (5) The solid block material in (4) is placed in a supercritical reactor, and supercritical carbon dioxide is compressed into the reactor; the holding pressure is set to 10-30 MPa, the holding time is 20-80 h, the foaming temperature is room temperature, and the foaming time is 3-60 s, and finally a liquid metal-based epoxy resin porous composite material is obtained.

[0018] Preferably, in step (1), the modifier is a copolymer of 3-glycidyloxypropyltrimethylsilane and polyetheramine, and its mass fraction is 5% to 20%.

[0019] Preferably, in step (4), the square mold is made of stainless steel and has a release cloth pasted inside.

[0020] Preferably, in step (5), the purity of the supercritical carbon dioxide is greater than 95%.

[0021] The beneficial effects of the present invention are:

[0022] 1. The present invention uses liquid metal as a functional modified filler, and after compounding it with epoxy resin, it still has good conductivity, so that the composite material has good dielectric loss to electromagnetic waves, thereby giving the composite material efficient electromagnetic shielding performance.

[0023] 2. The present invention uses supercritical carbon dioxide foaming technology to prepare porous epoxy resin-based composite materials. Carbon dioxide is used as the 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.

[0024] 3. The liquid metal-based epoxy resin porous composite material prepared by the present invention has a simple preparation method and a density of 0.80 to 2.50 g / cm 3 ; When the electromagnetic wave frequency is 8~12GHz, the total electromagnetic shielding effectiveness is 20.0~80.0dB, and the electromagnetic wave shielding effect is significant. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The following are scanning electron microscope images of a liquid metal-based epoxy resin porous composite material prepared in a certain embodiment of the present application. Among them, (a) and (e) are scanning electron microscope images of the liquid metal-based epoxy resin porous composite material at different magnifications when the liquid metal content is 5%; (b) and (f) are scanning electron microscope images of the liquid metal-based epoxy resin porous composite material at different magnifications when the liquid metal content is 10%; (c) and (g) are scanning electron microscope images of the liquid metal-based epoxy resin porous composite material at different magnifications when the liquid metal content is 15%; (d) and (h) are scanning electron microscope images of the liquid metal-based epoxy resin porous composite material at different magnifications when the liquid metal content is 20%. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. These specific features, structures or characteristics in the embodiments can be combined in one or more embodiments in any suitable manner. In the following description, specific details such as specific configurations 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 clarity and brevity, the description of known functions and structures is omitted in the embodiments.

[0027] Example 1

[0028] (1) Weigh E51 or E44, etc., weigh the required mass of curing agent diethyltoluenediamine and modifier polyether monoamine, and mix them evenly with mechanical stirring. Set the required curing process (curing temperature and curing time) according to the selected epoxy resin and curing agent brand, and cure to obtain the epoxy resin capable of supercritical microcellular foaming.

[0029] (2) The supercritical microporous foamable epoxy resin in (1) is mechanically crushed, and epoxy resin particles with a particle size of 50 μm are screened after crushing.

[0030] (3) Weigh 8g of the epoxy resin particles in (2) and 2g of the liquid metal. Mix the two by mechanical stirring.

[0031] (4) The mixture of epoxy resin particles and liquid metal uniformly mixed in (3) is placed in a square mold and cold-pressed using a flat vulcanizer at a pressure of 20 MPa to obtain a block material of the mixture of epoxy resin particles and liquid metal.

[0032] (5) The solid block material in (4) is placed in a supercritical reactor, and supercritical carbon dioxide is compressed into the reactor; the holding pressure is set to 10 MPa, the holding time is 20 h, the foaming temperature is room temperature, and the foaming time is 3 s, and finally a liquid metal-based epoxy resin porous composite material is obtained.

[0033] The density of the lightweight epoxy resin-based electromagnetic shielding composite material prepared in this embodiment is 0.80 g / cm 3 , in the band of 8 to 12 GHz, the total electromagnetic shielding effectiveness is 20.0 dB.

[0034] Example 2

[0035] (1) Weigh E51 or E44, etc., weigh the required mass of curing agent diethyltoluenediamine and modifier polyether monoamine, and mix them evenly with mechanical stirring. Set the required curing process (curing temperature and curing time) according to the selected epoxy resin and curing agent brand, and cure to obtain the epoxy resin capable of supercritical microcellular foaming.

[0036] (2) The supercritical microporous foamable epoxy resin in (1) is mechanically crushed, and epoxy resin particles with a particle size of 1000 μm are screened after crushing.

[0037] (3) Weigh 2 g of the epoxy resin particles in (2) and 8 g of the liquid metal. Mix the two by mechanical stirring.

[0038] (4) The mixture of epoxy resin particles and liquid metal uniformly mixed in (3) is placed in a square mold and cold-pressed using a flat vulcanizer at a pressure of 50 MPa to prepare a block material of the mixture of epoxy resin particles and liquid metal.

[0039] (5) The solid block material in (4) is placed in a supercritical reactor, and supercritical carbon dioxide is compressed into the reactor; the holding pressure is set to 30 MPa, the holding time is 80 h, the foaming temperature is room temperature, and the foaming time is 60 s, and finally a liquid metal-based epoxy resin porous composite material is obtained.

[0040] The density of the lightweight epoxy resin-based electromagnetic shielding composite material prepared in this embodiment is 2.50 g / cm 3 , in the band of 8 to 12 GHz, the total electromagnetic shielding effectiveness is 80.0 dB.

[0041] Example 3

[0042] (1) Weigh E51 or E44, etc., weigh the required mass of curing agent diethyltoluenediamine and modifier polyether monoamine, and mix them evenly with mechanical stirring. Set the required curing process (curing temperature and curing time) according to the selected epoxy resin and curing agent brand, and cure to obtain the epoxy resin capable of supercritical microcellular foaming.

[0043] (2) The supercritical microporous foamable epoxy resin in (1) is mechanically crushed, and epoxy resin particles with a particle size of 500 μm are screened after crushing.

[0044] (3) Weigh 5 g of the epoxy resin particles in (2) and 5 g of the liquid metal. Mix the two by mechanical stirring.

[0045] (4) The mixture of epoxy resin particles and liquid metal uniformly mixed in (3) is placed in a square mold and cold-pressed using a flat vulcanizer at a pressure of 30 MPa to prepare a block material of the mixture of epoxy resin particles and liquid metal.

[0046] (5) The solid block material in (4) is placed in a supercritical reactor, and supercritical carbon dioxide is compressed into the reactor; the holding pressure is set to 20 MPa, the holding time is 60 h, the foaming temperature is room temperature, and the foaming time is 30 s, and finally a liquid metal-based epoxy resin porous composite material is obtained.

[0047] The density of the lightweight epoxy resin-based electromagnetic shielding composite material prepared in this embodiment is 1.50 g / cm 3 , in the band of 8 to 12 GHz, the total electromagnetic shielding effectiveness is 50.0 dB.

[0048] The embodiments described above only express several implementation methods of the present invention, which are convenient for understanding the technical solutions of the present invention in a specific and detailed manner, 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, without departing from the concept of the present invention, several variations and improvements can be made, which all fall within the scope of protection 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 scope of protection of the claims attached to the present invention. Therefore, the scope of protection of the patent of the present invention shall be based on the content of the attached claims, and the description and drawings can be used to interpret the content of the claims.

Claims

1. A liquid metal-based epoxy resin porous composite material, characterized in that: The invention relates to a porous composite material of epoxy resin filled with liquid metal, which is prepared by using a modified epoxy resin capable of supercritical foaming as a matrix and liquid metal as a conductive functional filler; the temperature-dependent phase change characteristics of the liquid metal are utilized to prepare the porous composite material of epoxy resin filled with liquid metal through mechanical crushing and mixing, cold pressing and supercritical foaming processes; the density of the porous composite material of epoxy resin is 0.80 to 2.50 g / cm 3 ; When the electromagnetic wave frequency is 8~12GHz, the total electromagnetic shielding effectiveness is 20.0~80.0dB.

2. The liquid metal-based epoxy resin porous composite material and the preparation method thereof according to claim (1), characterized in that: The epoxy resin is a modified epoxy resin capable of supercritical foaming.

3. The supercritically foamable modified epoxy resin according to claim (2), characterized in that: The epoxy resin is a bisphenol A type epoxy resin, including but not limited to E51, E44, etc., the curing agent is diethyltoluenediamine, and the modifier is polyether monoamine.

4. The liquid metal-based epoxy resin porous composite material and the preparation method thereof according to claim (1), characterized in that: The liquid metal includes, but is not limited to, gallium, gallium-indium alloy and gallium-indium-tin alloy.

5. The liquid metal-based epoxy resin porous composite material and the preparation method thereof according to claim (1), characterized in that: The solid epoxy resin is mechanically crushed to a particle size of 50 to 1000 μm, and then mechanically blended with liquid metal, the mass fraction of the liquid metal blend is controlled to be 20 to 80%, and then cold-pressed at a pressure of 20 to 50 MPa. Finally, the liquid metal-based epoxy resin porous composite material is prepared by supercritical carbon dioxide microporous foaming.

6. The supercritical carbon dioxide microcellular foaming according to claim (5), characterized in that: The supercritical carbon dioxide microporous foaming process is as follows: the holding pressure is 10-30MPa, the holding time is 20-80h, the foaming temperature is room temperature, and the foaming time is 3-60s.

7. A method for preparing a liquid metal-based epoxy resin porous composite material, characterized in that: The specific steps include: (1) Weighing E51 or E44, etc., weighing the required mass of curing agent diethyltoluenediamine and modifier, mechanically stirring and mixing them evenly, setting the required curing process (curing temperature and curing time) according to the selected epoxy resin and curing agent brand, and curing to obtain the epoxy resin capable of supercritical microcellular foaming; (2) mechanically crushing the epoxy resin capable of supercritical microporous foaming in step (1), and selecting epoxy resin particles with a particle size of 50 to 1000 μm after crushing; (3) Weighing a certain mass of the epoxy resin particles in step (2), weighing the liquid metal according to a mass fraction of 20 to 80%, and mixing the two uniformly by mechanical stirring; (4) placing the mixture of epoxy resin particles and liquid metal uniformly mixed in step (3) in a square mold, and cold pressing the mixture using a flat vulcanizer at a pressure of 20 to 50 MPa to obtain a block material of the mixture of epoxy resin particles and liquid metal; (5) placing the solid block material in step (4) in a supercritical reactor, compressing supercritical carbon dioxide into the reactor; setting the holding pressure to 10-30 MPa, the holding time to 20-80 h, the foaming temperature to room temperature, and the foaming time to 3-60 s, to finally obtain a liquid metal-based epoxy resin porous composite material.

8. The method for preparing the liquid metal-based epoxy resin porous composite material according to claim 7, characterized in that: In step (1), the modifier is a copolymer of 3-glycidyloxypropyltrimethylsilane and polyetheramine, and its mass fraction is 5% to 20%.

9. The method for preparing the liquid metal-based epoxy resin porous composite material according to claim 7, characterized in that: In step (4), the square mold is made of stainless steel and has a release cloth pasted inside.

10. The method for preparing the liquid metal-based epoxy resin porous composite material according to claim 7, characterized in that: In step (5), the purity of the supercritical carbon dioxide is greater than 95%.

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