Preparation method of enhanced graphene film with high thermal conductivity

Abstract

The invention discloses a preparation method of an enhanced high-thermal-conductivity graphene film, which comprises the following steps: (1) mixing graphene with a polymer salt solution containing a benzene ring, and dispersing to obtain a graphene / polymer salt solution; (2) performing suction filtration on the graphene / polymer salt solution to form a film, dropwise adding an organic solvent in the process, and performing suction filtration to obtain a graphene embryo film; (3) drying to remove moisture to obtain a graphene film; the inherent high thermal conductivity of the graphene layer is fully maintained, meanwhile, the overall thermal conductivity of the composite film is further improved through the non-covalent effect of the polymer salt containing the benzene ring and a continuous thermal conduction network formed by winding polymer chain segments, and compared with a common graphite / polymer composite material, the composite film has higher thermal conductivity.

Description

Technical Field

[0001] The present invention relates to the technical field of graphene composite material preparation, and particularly relates to a preparation method for enhancing a highly thermally conductive graphene film. Background Art

[0002] Graphene material is a functional material with a hexagonal honeycomb lattice structure composed of sp 2 hybrid orbitals. The perfect crystal structure of graphene material endows it with good electrical, thermal, optical, mechanical and other properties, making it have broad application potential in the fields of chemical engineering, energy storage, electronic devices, biomedicine, aerospace and so on.

[0003] High thermal conductivity is one of the most widely used properties of graphene materials. Among the many methods for enhancing the high thermal conductivity of graphene, the method of compounding graphene with polymers such as organic substances and macromolecules is one of the simplest and most efficient methods. However, the graphene layers are bonded by weak binding forces, and the interfacial binding force is poor when combined with polymers. Therefore, the key to this method lies in improving the weak binding force between graphene layers and the interfacial binding force between polymers and graphene, so as to achieve the purpose of enhancing high thermal conductivity.

[0004] For example, Chinese Patent Application for Invention (Publication No. CN202011116087.0) discloses a graphene film enhanced thermally conductive composite film and its preparation method and uses, including: (1) using a punching technique to penetrate the closed bubble structure inside the low-density graphene film without calendering to form open holes; (2) coating the polymer with adjusted fluidity on the surface of the graphene film, and injecting it into the graphene film along the drilled small holes to fill the original bubble structure; (3) obtaining the graphene film enhanced thermally conductive composite film after curing the polymer structure. However, this form of graphene composite heat dissipation film does not essentially solve the problem of weak binding force between graphene layers, and this structure is prone to peeling at the interface where the graphene layer and the polymer layer are combined, thereby reducing the heat dissipation performance.

[0005] Therefore, how to solve the weak binding force between graphene layers to prepare a high-strength and highly thermally conductive composite film is an urgent problem to be solved in this field. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the main purpose of the present invention is to provide a preparation method for enhancing a highly thermally conductive graphene film, aiming to improve the weak binding force between graphene layers and enhance the interfacial binding strength between the graphene layer and the polymer salt, so as to achieve the enhancement of the high thermal conductivity of the graphene film.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for preparing a high thermal conductivity graphene film with enhanced properties, comprising the following steps:

[0009] (1) Mix graphene with a polymer salt solution containing benzene rings and disperse them to obtain a graphene / polymer salt solution;

[0010] (2) Filter the graphene / polymer salt solution into a film, and during this process, add an organic solvent dropwise. After filtration, a graphene embryo film is obtained;

[0011] (3) Dry to remove moisture to obtain a graphene film.

[0012] Preferably, for the preparation method described in claim 1, for the polymer salt solution containing benzene rings, disperse the polymer salt containing benzene rings in water, add sodium hydroxide solution or potassium hydroxide solution until the polymer salt is completely dissolved to obtain it.

[0013] Preferably, the polymer includes one of a polystyrene / N-phenylmaleimide / epoxy functional group terpolymer, a polyacrylonitrile / butadiene styrene / epoxy functional group terpolymer, and a polybutadiene / acrylonitrile / styrene / epoxy functional group quaternary copolymer.

[0014] Preferably, the polymer salt solution containing benzene rings is soluble in water and insoluble in organic solvents.

[0015] Preferably, the mass ratio of graphene to the polymer salt is 1:1 - 5:1, and the concentration of the polymer salt solution is 0.5% - 5%.

[0016] Preferably, the volume ratio of the graphene / polymer salt solution to the organic solvent is 1:1 - 1:0.2.

[0017] Preferably, the organic solvent includes any one or a combination of at least two of methanol, ethanol, isopropanol, acetone, cyclohexanone, N-methylformamide, N-methylacetamide, and dimethyl sulfoxide.

[0018] Preferably, the drying temperature is 30 - 60 °C, and the film thickness is 10 - 200 μm.

[0019] Preferably, the dispersion is ultrasonic dispersion.

[0020] Idea description: First, graphene is ultrasonically dispersed in a polymer salt solution containing benzene rings at a certain concentration. The polymer salt is soluble in water but insoluble in organic solvents, thus obtaining a uniform graphene / polymer salt dispersion. Subsequently, the dispersion is filtered by vacuum-assisted self-assembly, and graphene membranes are prepared using the layer-by-layer self-assembly characteristics of graphene. During the filtration process, organic solvents are introduced into the dispersion system to promote the phase transition of the polymer salt component at the graphene interface, forming a uniformly distributed composite interface structure. This phase transition process enables the polymer salt component to have a synergistic interaction with the graphene layers, effectively filling the nano-pores between the graphene layers and constructing a continuous and dense heat conduction network. This unique structure not only fully retains the inherent high thermal conductivity of the graphene layers but also significantly improves the mechanical strength, interfacial bonding performance, and structural stability of the composite membrane through the interfacial enhancement effect and staggered filling effect between the polymer salt and graphene.

[0021] The specific mechanism is as follows:

[0022] 1. Graphene dispersion and self-assembly: Graphene is ultrasonically dispersed in a polymer salt solution containing benzene rings to form a uniform and stable dispersion. Subsequently, through vacuum-assisted self-assembly, using the layer-by-layer self-assembly characteristics of graphene, graphene membranes are obtained.

[0023] 2. Precipitation and filling of polymer salt: During the filtration process, organic solvents are introduced to induce phase separation of the polymer salt, causing it to be uniformly distributed at the graphene interface. This process promotes the formation of a tight bond between the polymer salt component and the graphene layers and effectively fills the pores between the graphene layers through synergistic effects, optimizing the interlayer structure.

[0024] 3. Heat conduction network and interfacial enhancement: The polymer salt forms a continuous and dense heat conduction path between the graphene layers. At the same time, the interfacial interaction enhances the bonding force between graphene and the polymer salt, thereby improving the thermal conductivity, mechanical strength, and structural stability of the composite membrane.

[0025] Due to the adoption of the above technical solutions in the present invention, the following beneficial effects are achieved:

[0026] 1. The preparation method of the present invention fully retains the inherent high thermal conductivity of the graphene layers. At the same time, the continuous heat conduction network formed by the non-covalent interaction of the polymer salt containing benzene rings further improves the overall thermal conductivity of the composite membrane, having a higher thermal conductivity than ordinary graphite / polymer composites;

[0027] 2. The interfacial interaction between the polymer salt and graphene and its uniform distribution between the layers significantly improve the mechanical strength and structural stability of the composite membrane. This unique filling method optimizes the interlayer stress transfer and avoids the brittleness problem of traditional graphene membranes.

[0028] 3. The uniform distribution of polymer salts between graphene layers and their strong interaction with graphene effectively enhance the interfacial bonding strength, solving the problems of easy interlayer peeling of traditional graphene membranes and poor compatibility between graphene and polymers.

[0029] 4. The process of the present invention is simple, the conditions are easy to control, and it is convenient for large-scale automated production. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Process flow chart of the process for enhancing the high thermal conductivity graphene film of the present invention.

[0031] Figure 2 SEM image of Example 1 of the present invention.

[0032] Figure 3 SEM image of Comparative Example 1 of the present invention.

[0033] Figure 4 SEM image of Comparative Example 2 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0034] The technical solutions in the embodiments of the present invention will be described in detail below in conjunction with several embodiments and the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0035] Example 1

[0036] 1) Disperse 1 g of a ternary copolymer of polystyrene / N-phenylmaleimide / epoxy functional groups into 150 ml of water, add 5 g of a 4 mol / L sodium hydroxide solution, and stir at 80 °C until dissolved to obtain a polymer salt solution;

[0037] 2) Disperse 2 g of graphene into the above polymer salt solution, and ultrasonically stir for 2 h to obtain a graphene / polymer salt solution;

[0038] 3) Filter the graphene / polymer salt solution by suction filtration. During the suction filtration process, add 30 ml of methanol, and obtain a green film after the suction filtration is completed;

[0039] 4) Dry at 45 °C to obtain a graphene film with a thickness of 150 μm.

[0040] The in-plane thermal conductivity of the prepared graphene film is 650 W / mK, the peel strength is 230 KPa, the tensile strength is 89 MPa, its deformation reaches 40% under a compressive pressure of 400 KPa, and its deformation reaches 30% under a tensile strength of 50 MPa.

[0041] Example 2

[0042] 1) Disperse 1 g of polyacrylonitrile / butadiene / styrene / epoxy functional group terpolymer into 100 ml of water, add 5 g of 4 mol / L sodium hydroxide solution, and stir until dissolved at 80 °C to obtain a polymer salt solution;

[0043] 2) Disperse 1 g of graphene into the above polymer salt solution, and stir while ultrasonically treating for 3 h to obtain a graphene / polymer salt solution;

[0044] 3) Perform suction filtration on the graphene / polymer salt solution. During the suction filtration process, add 30 ml of acetone, and obtain a green film after the suction filtration ends;

[0045] 4) Dry at 60 °C to obtain a graphene film with a thickness of 110 μm.

[0046] The in-plane thermal conductivity of the prepared graphene film is 550 W / mK, the peel strength is 250 KPa, the tensile strength is 100 MPa, its deformation reaches 10% under a compressive pressure of 400 KPa, and its deformation reaches 15% under a tensile strength of 50 MPa.

[0047] Example 3

[0048] 1) Disperse 0.2 g of polybutadiene / acrylonitrile / styrene / epoxy functional group quaternary copolymer into 50 ml of water, add 5 g of 4 mol / L sodium hydroxide solution, and stir until dissolved at 80 °C to obtain a polymer salt solution;

[0049] 2) Disperse 1 g of graphene into the above polymer salt solution, and stir while ultrasonically treating for 6 h to obtain a graphene / polymer salt solution;

[0050] 3) Perform suction filtration on the graphene / polymer salt solution. During the suction filtration process, add 20 ml of N-methylformamide, and obtain a green film after the suction filtration ends;

[0051] 4) Dry at 30 °C to obtain a graphene film with a thickness of 105 μm.

[0052] The in-plane thermal conductivity of the prepared graphene film-reinforced thermally conductive epoxy composite film is 500 W / mK, the peel strength is 300 KPa, the tensile strength is 60 MPa, its deformation reaches 40% under a compressive pressure of 400 KPa, and its deformation reaches 40% under a tensile strength of 50 MPa.

[0053] Comparative Example 1: Compared with Example 1, change the polystyrene / N-phenylmaleimide / epoxy functional group terpolymer to polyacrylic acid, and other conditions are similar.

[0054] Comparative Example 2: Compared with Example 1, no organic solvent was added during the suction filtration process, and it was dried after suction filtration was completed.

[0055]

[0056] It can be seen from the experimental results that under the condition of an appropriate ratio of polymer salt to graphene, the polymer salt containing benzene rings has better thermal conductivity performance. Further, from the comparison between Figure 1 and Figure 2 , it can be seen that the polymer salt containing benzene rings can not only form strong interfacial coupling with graphene through hydrogen bonding, but also enhance their interaction through π-π conjugation; in contrast, the polymer salt without benzene rings only relies on hydrogen bonding, and the binding with graphene is weak, resulting in larger pores between graphene layers, which is not conducive to the improvement of heat conduction. In addition, from the comparison between Figure 1 and Figure 3 , it can be known that during the suction filtration process, the polymer salt containing benzene rings did not undergo phase transformation, resulting in uneven distribution on the surface of graphene, and there are still large pores between graphene layers, thus further restricting the improvement of thermal conductivity.

Claims

1. A preparation method of an enhanced high - thermal - conductivity graphene film, characterized in that, It includes the following steps: (1) Mix graphene with a polymer salt solution containing benzene rings and disperse them to obtain a graphene / polymer salt solution; (2) Filter the graphene / polymer salt solution to form a membrane, and add an organic solvent during this process. After filtration, a graphene embryo membrane is obtained; (3) Dry to remove moisture to obtain a graphene membrane.

2. The preparation method according to claim 1, characterized in that, The polymer salt solution containing benzene rings is obtained by dispersing the polymer salt containing benzene rings in water and adding sodium hydroxide solution or potassium hydroxide solution until the polymer salt is completely dissolved.

3. The preparation method according to claim 2, characterized in that, The polymer includes one of a polystyrene / N-phenylmaleimide / epoxy functional group terpolymer, a polyacrylonitrile / butadiene styrene rubber / epoxy functional group terpolymer, and a polybutadiene / acrylonitrile / styrene / epoxy functional group quaternary copolymer.

4. The preparation method according to claim 1 or 2, characterized in that The polymer salt solution containing benzene rings is soluble in water and insoluble in organic solvents.

5. The preparation method according to claim 1, characterized in that, The mass ratio of the graphene to the polymer salt is 1:1 - 5:1, and the concentration of the polymer salt solution is 0.5% - 5%.

6. The preparation method according to claim 1, characterized in that, The volume ratio of the graphene / polymer salt solution to the organic solvent is 1:1 - 1:0.

2.

7. The preparation method according to claim 1, characterized in that, The organic solvent includes any one or a combination of at least two of methanol, ethanol, isopropanol, acetone, cyclohexanone, N-methylformamide, N-methylacetamide, and dimethyl sulfoxide.

8. The preparation method according to claim 1, characterized in that, The drying temperature is 30 - 60 °C, and the membrane thickness is 10 - 200 μm.

9. The preparation method according to claim 1, wherein, The dispersion is ultrasonic dispersion.

Images