Flexible insulating composite heat-conducting film and preparation method thereof

Abstract

The application discloses a flexible insulating composite heat-conducting film and a preparation method thereof. The film is composed of polyvinyl alcohol, glycerol, graphene and graphene oxide. The mass ratio of polyvinyl alcohol to glycerol is 8-10:1, the total amount of graphene and graphene oxide is 1-15 wt% of the total amount of polyvinyl alcohol and glycerol, and the amount of graphene is greater than that of graphene oxide. The synergistic effect of graphene and graphene oxide is utilized, and under the condition of low filler content, the horizontal thermal conductivity of the composite film can reach 8.27 W / (m*K), and the vertical thermal conductivity can reach 1.47 W / (m*K), which is about 20 times higher than that of pure polyvinyl alcohol film. The improvement is due to the inhibition of graphene agglomeration by graphene oxide as a surfactant, the formation of a through heat-conducting network, and the further optimization of sp2 conjugated structure through chemical reduction, which reduces the interface thermal resistance and is suitable for the thermal management of high-power electronic equipment.

Description

Technical Field

[0001] This invention belongs to the field of thermal conductive materials technology, specifically relating to a flexible insulating composite thermal conductive film and its preparation method. Background Technology

[0002] With the rapid development of cutting-edge fields such as 5G communication, artificial intelligence, new energy vehicles, and high-performance chips, the power density of electronic devices continues to rise. This not only exacerbates the accumulation of internal heat but also makes thermal management increasingly prominent, becoming a core bottleneck restricting the overall performance, stability, and long-term reliability of equipment. Against this backdrop of rapid technological evolution, the need to develop new, highly efficient thermal management materials has become increasingly urgent. These materials must not only effectively address the increasingly complex challenges of heat dissipation, such as the rapid diffusion of hot spots and heat transfer in multi-layered structures, but also fully adapt to the stringent requirements of modern electronic products for thinness, high integration, and portability, thereby ensuring that devices maintain stable operation under high loads or extreme conditions and extending their service life.

[0003] Traditional polymer-based thermally conductive materials typically have thermal conductivity below 0.5 W / (m·K), which severely limits their practical heat dissipation applications in high-power electronic devices and fails to meet the increasingly stringent standards required in the field of thermal management. To effectively overcome this fundamental limitation, a widely accepted and effective strategy is to incorporate nanofillers with ultra-high thermal conductivity, such as graphene, carbon nanotubes, and boron nitride (BN), into the polymer matrix. This precise composite method constructs a continuous, dense, and efficient thermally conductive network within the material, significantly improving the overall thermal conductivity of the polymer material and elevating its performance to a new level, better matching the thermal demands of modern electronic applications. However, achieving the ideal target thermal conductivity (greater than 5 W / (m·K)) often requires extremely high filler loadings (exceeding 50 vol%), which introduces a series of practical problems. The primary reason for this requirement lies in the significant interfacial thermal resistance between the polymer and the filler, as well as between the filler particles themselves. This thermal resistance acts as an obstacle, hindering the smooth transfer of heat energy, resulting in the actual thermal conductivity of the composite material being far lower than the theoretically expected value, sometimes even only a fraction of the expected value. Furthermore, the high specific surface energy of the filler itself and its low compatibility with the polymer matrix easily lead to filler particle agglomeration. This agglomeration not only further weakens thermal conductivity and causes breakage of heat transfer paths, but also degrades the mechanical properties of the composite material, such as reduced flexibility, decreased mechanical strength, and even embrittlement or cracking, thus affecting the overall durability and application reliability of the material. Therefore, under the premise of strictly maintaining low filler content, how to ensure the uniform and stable dispersion of fillers in the polymer matrix through optimized interface design and dispersion technology, thereby significantly improving the thermal conductivity of the composite material, remains one of the most critical challenges facing the field of materials science. Successfully solving this challenge will not only directly promote innovation and breakthroughs in thermal management technology, but also provide strong support for the expansion of applications in the electronics industry, promote a comprehensive upgrade from consumer electronics to industrial equipment, and ultimately contribute to the achievement of sustainable development goals. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects of the prior art and provide a flexible insulating composite thermally conductive film.

[0005] Another object of the present invention is to provide a method for preparing the above-mentioned flexible insulating composite thermally conductive film.

[0006] The technical solution of the present invention is as follows:

[0007] A flexible insulating composite thermally conductive film, with a thickness of 50-80 μm, is composed of polyvinyl alcohol, glycerol, graphene, and graphene oxide.

[0008] The mass ratio of polyvinyl alcohol to glycerol is 8-10:1, and the total amount of graphene and graphene oxide is 1-15 wt% of the total amount of polyvinyl alcohol and glycerol, with the amount of graphene being greater than the amount of graphene oxide.

[0009] Graphene oxide acts as a surfactant to inhibit graphene aggregation, thereby forming a continuous thermally conductive network within the flexible insulating composite thermally conductive film. Furthermore, graphene oxide is linked to polyvinyl alcohol, which serves as the matrix, through hydrogen bonds and anchors the graphene through π-π conjugation, achieving molecular-level uniform dispersion of graphene in the flexible insulating composite thermally conductive film.

[0010] In a preferred embodiment of the present invention, the graphene oxide is reduced graphene oxide.

[0011] In a preferred embodiment of the present invention, the mass ratio of graphene to graphene oxide is 0.12-1.8: 0.08-1.2.

[0012] The preparation method of the above-mentioned flexible insulating composite thermally conductive film includes the following steps:

[0013] (1) Preparation of graphene aqueous dispersion, graphene oxide aqueous dispersion and polyvinyl alcohol aqueous solution containing glycerol;

[0014] (2) Mix the graphene aqueous dispersion obtained in step (1) with the graphene oxide aqueous dispersion evenly to obtain GO / G composite dispersion.

[0015] (3) Mix the GO / G composite dispersion obtained in step (2) with a polyvinyl alcohol aqueous solution containing glycerol to obtain a PVA / GO / G composite slurry.

[0016] (4) The PVA / GO / G composite slurry obtained in step (3) is coated and spread on the substrate and then dried to obtain the flexible insulating composite thermal conductive film.

[0017] In a preferred embodiment of the present invention, step (5) is further included: chemically reducing the flexible insulating composite thermally conductive film obtained in step (4).

[0018] More preferably, the chemical reduction treatment is: soaking and reducing with a 40 wt% HI anhydrous ethanol solution at a temperature of 70°C for 16 h.

[0019] In a preferred embodiment of the present invention, the concentration of graphene in the graphene aqueous dispersion is 0.12-1.8 wt%.

[0020] In a preferred embodiment of the present invention, the concentration of graphene oxide in the graphene oxide aqueous dispersion is 0.08-1.2 wt%.

[0021] In a preferred embodiment of the present invention, the concentration of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 12.8 wt%, and the concentration of glycerol is 1.25 wt%.

[0022] In a preferred embodiment of the present invention, the drying in (4) is vacuum drying at 70°C for 12 h.

[0023] The beneficial effects of this invention are:

[0024] 1. This invention utilizes the synergistic effect of graphene and graphene oxide to achieve a horizontal thermal conductivity of 8.27 W / (m·K) and a vertical thermal conductivity of 1.47 W / (m·K) in a composite film with low filler content, which is more than 20 times higher than that of pure polyvinyl alcohol film (0.4 W / (m·K)). This improvement is attributed to graphene oxide acting as a surfactant to inhibit graphene aggregation, forming a continuous thermally conductive network, and further optimizing the sp2 conjugated structure through chemical reduction to reduce interfacial thermal resistance, making it suitable for thermal management of high-power electronic devices.

[0025] 2. In this invention, graphene oxide is linked to the polyvinyl alcohol matrix via hydrogen bonds and anchored by π-π conjugation, achieving uniform molecular-level dispersion of the filler in the polymer. SEM observation shows that the filler sheets are horizontally arranged, avoiding agglomeration. Even at a filler content of 15%, good distribution is maintained, improving filler utilization and the overall stability of the composite material.

[0026] 3. This invention adds glycerol as a plasticizer and uses a low-temperature drying and blade coating film-forming process to obtain a film thickness of 50-80 μm. It has good flexibility, is not easy to become brittle or deteriorate, and is suitable for flexible electronic device applications. At the same time, it avoids the decline in mechanical properties caused by high filler load.

[0027] 4. While improving thermal conductivity, this invention retains the insulating properties of polyvinyl alcohol. Tests show that it is an insulator, avoiding the conductive risks that may be introduced by highly conductive fillers (such as pure graphene). It is suitable for thermal management scenarios that require electrical isolation, such as chip heat dissipation films.

[0028] 5. The preparation method of the present invention only requires three steps: physical mixing, coating and film formation, and chemical reduction. There is no organic solvent residue, the processing is carried out at low temperature, the energy consumption is low, it is easy to carry out continuous production, the manufacturing cost is reduced, the environmental friendliness is improved, and the application scope of graphene-based polymer materials in the field of thermal management is expanded.

[0029] 6. Compared with single graphene or graphene oxide composites, the multi-level interactions (hydrogen bonds, π-π stacking) of the graphene-graphene oxide-polyvinyl alcohol ternary system significantly enhance the performance, improving it by 883% even with a low filler content of 1%, demonstrating the potential of the filler complementary mechanism and providing new ideas for the design of similar composite materials. Attached Figure Description

[0030] Figure 1 This is a process flow diagram of a method for preparing a flexible insulating composite thermally conductive film according to the present invention.

[0031] Figure 2 The images shown are cross-sectional SEM images of the composite films obtained in Comparative Example 1 and Examples 1 to 6 of this invention.

[0032] Figure 3 The images shown are cross-sectional SEM images of the composite films obtained after reduction in Comparative Examples 2 to 3 and Example 5 of this invention.

[0033] Figure 4 The graph shows the thermal conductivity of the composite films obtained in Comparative Example 1 and Examples 1 to 6 of this invention.

[0034] Figure 5 The graphs show the thermal conductivity of the composite films obtained before and after reduction in Comparative Examples 2 to 3 and Example 5 of this invention.

[0035] Figure 6 The diagram shows the electrical insulation properties of the composite films obtained in Examples 1 to 6 of this invention.

[0036] Figure 7 The diagram shows the electrical insulation properties of the composite films obtained before and after reduction in Comparative Examples 2 to 3 and Example 5 of this invention. Detailed Implementation

[0037] The technical solution of the present invention will be further explained and described below with reference to specific embodiments and accompanying drawings.

[0038] The preparation principle of the following embodiments is as follows: Figure 1 As shown.

[0039] In the following examples and comparative examples:

[0040] The polyvinyl alcohol aqueous solution was prepared by fully dissolving polyvinyl alcohol and glycerol in deionized water to obtain a polyvinyl alcohol aqueous solution, wherein the concentration of polyvinyl alcohol was 12.8 wt% and the concentration of glycerol was 1.25 wt%.

[0041] The graphene aqueous dispersion was prepared by dispersing graphene in deionized water by ultrasound to obtain a graphene aqueous dispersion, wherein the concentration of graphene was 0.12-1.8 wt%.

[0042] The graphene oxide aqueous dispersion was prepared by dispersing graphene oxide in deionized water by ultrasound to obtain the graphene oxide aqueous dispersion, wherein the concentration of graphene oxide was 0.08-1.2 wt%.

[0043] Example 1

[0044] (1) Mix equal volumes of a graphene aqueous dispersion with a concentration of 0.12 wt% and a graphene oxide aqueous dispersion with a concentration of 0.08 wt% thoroughly to obtain a GO / G composite dispersion.

[0045] (2) Mix the GO / G composite dispersion obtained in step (1) with the above polyvinyl alcohol aqueous solution to obtain PVA / GO / G composite slurry.

[0046] (3) The PVA / GO / G composite slurry obtained in step (2) is spread on a stainless steel mirror panel and then placed in a vacuum drying oven and dried at 70°C for 12 h to obtain a composite thermally conductive film PVA / GO / G-1wt% with a thickness of 54 μm (meaning that the total mass of graphene oxide and graphene is 1 wt% of the total mass of polyvinyl alcohol and glycerol).

[0047] Example 2

[0048] (1) Mix equal volumes of a graphene aqueous dispersion with a concentration of 0.36 wt% and a graphene oxide aqueous dispersion with a concentration of 0.24 wt% thoroughly to obtain a GO / G composite dispersion.

[0049] (2) Mix the GO / G composite dispersion obtained in step (1) with the above polyvinyl alcohol aqueous solution to obtain PVA / GO / G composite slurry.

[0050] (3) The PVA / GO / G composite slurry obtained in step (2) is spread on a stainless steel mirror panel and then placed in a vacuum drying oven and dried at 70°C for 12 h to obtain a composite thermally conductive film PVA / GO / G-3wt% with a thickness of 73 μm (meaning that the total mass of graphene oxide and graphene is 3wt% of the total mass of polyvinyl alcohol and glycerol).

[0051] Example 3

[0052] (1) Mix equal volumes of a graphene aqueous dispersion with a concentration of 0.6 wt% and a graphene oxide aqueous dispersion with a concentration of 0.4 wt% thoroughly to obtain a GO / G composite dispersion.

[0053] (2) Mix the GO / G composite dispersion obtained in step (1) with the above polyvinyl alcohol aqueous solution to obtain PVA / GO / G composite slurry.

[0054] (3) The PVA / GO / G composite slurry obtained in step (2) is spread on a stainless steel mirror panel and then placed in a vacuum drying oven and dried at 70°C for 12 h to obtain a composite thermally conductive film PVA / GO / G-5wt% with a thickness of 67 μm (meaning that the total mass of graphene oxide and graphene is 5 wt% of the total mass of polyvinyl alcohol and glycerol).

[0055] Example 4

[0056] (1) Mix equal volumes of a graphene aqueous dispersion with a concentration of 0.84 wt% and a graphene oxide aqueous dispersion with a concentration of 0.56 wt% thoroughly to obtain a GO / G composite dispersion.

[0057] (2) Mix the GO / G composite dispersion obtained in step (1) with the above polyvinyl alcohol aqueous solution to obtain PVA / GO / G composite slurry.

[0058] (3) The PVA / GO / G composite slurry obtained in step (2) is spread on a stainless steel mirror panel and then placed in a vacuum drying oven and dried at 70°C for 12 h to obtain a composite thermally conductive film PVA / GO / G-7wt% with a thickness of 72 μm (meaning that the total mass of graphene oxide and graphene is 7 wt% of the total mass of polyvinyl alcohol and glycerol).

[0059] Example 5

[0060] (1) Mix equal volumes of a 1.2 wt% graphene aqueous dispersion and a 0.8 wt% graphene oxide aqueous dispersion thoroughly to obtain a GO / G composite dispersion.

[0061] (2) Mix the GO / G composite dispersion obtained in step (1) with the above polyvinyl alcohol aqueous solution to obtain PVA / GO / G composite slurry.

[0062] (3) The PVA / GO / G composite slurry obtained in step (2) is spread on a stainless steel mirror panel and then placed in a vacuum drying oven and dried at 70°C for 12 h to obtain a composite thermally conductive film PVA / GO / G-10wt% with a thickness of 75 μm (meaning that the total mass of graphene oxide and graphene is 10 wt% of the total mass of polyvinyl alcohol and glycerol).

[0063] (4) Place the composite thermally conductive film PVA / GO / G-10 wt% obtained in step (3) into an anhydrous ethanol solution of HI (55 wt%) with a concentration of 40 wt% and reduce it at 70°C for 16 h to obtain the composite thermally conductive film PVA / rGO / G-10wt%.

[0064] Example 6

[0065] (1) Mix equal volumes of a 1.2 wt% graphene aqueous dispersion and a 1.8 wt% graphene oxide aqueous dispersion to obtain a GO / G composite dispersion.

[0066] (2) Mix the GO / G composite dispersion obtained in step (1) with the above polyvinyl alcohol aqueous solution to obtain PVA / GO / G composite slurry.

[0067] (3) The PVA / GO / G composite slurry obtained in step (2) is spread on a stainless steel mirror panel and then placed in a vacuum drying oven and dried at 70°C for 12 h to obtain a composite thermally conductive film PVA / GO / G-15wt% with a thickness of 76 μm (meaning that the total mass of graphene oxide and graphene is 15 wt% of the total mass of polyvinyl alcohol and glycerol).

[0068] Comparative Example 1

[0069] This comparative example provides a pure polyvinyl alcohol film, the preparation method of which includes the following steps:

[0070] The above-mentioned polyvinyl alcohol aqueous solution was spread onto a stainless steel mirror panel and then placed in a vacuum drying oven and dried at 70°C for 12 h to obtain a pure polyvinyl alcohol film PVA with a thickness of 66 μm.

[0071] Comparative Example 2

[0072] (1) A 0.8 wt% graphene oxide aqueous dispersion was mixed with the above polyvinyl alcohol aqueous solution to obtain a PVA / GO composite slurry.

[0073] (2) The PVA / GO composite slurry obtained in step (1) is spread on a stainless steel mirror panel and then placed in a vacuum drying oven and dried at 70°C for 12 h to obtain a composite thermally conductive film PVA / GO-10 wt% with a thickness of 69 μm (meaning that the total mass of graphene oxide is 10 wt% of the total mass of polyvinyl alcohol and glycerol).

[0074] Comparative Example 3

[0075] (1) A graphene aqueous dispersion with a concentration of 1.2 wt% was mixed with the above polyvinyl alcohol aqueous solution to obtain a PVA / G composite slurry;

[0076] (2) The PVA / G composite slurry obtained in step (1) is spread on a stainless steel mirror panel and then placed in a vacuum drying oven and dried at 70°C for 12 h to obtain a composite thermally conductive film PVA / G-10 wt% with a thickness of 76 μm (meaning that the total mass of graphene is 10 wt% of the total mass of polyvinyl alcohol and glycerol).

[0077] Structural characterization:

[0078] The cross-sectional microstructure of the composite thermally conductive films PVA / GO / G-1~15 wt% in Examples 1 to 6 are shown in the figures below. Figure 2 As shown, by Figure 2 It can be observed that with the increase of the total mass fraction of graphene and graphene oxide, the number of graphene sheets inside gradually increases, and most of them are arranged horizontally. This will help to form a continuous thermally conductive network inside the matrix and significantly improve the thermal conductivity of the composite material. When the total amount of graphene and graphene oxide is 10 wt% (PVA + glycerol), the graphene sheet distribution is the most uniform, while when the total amount of graphene and graphene oxide is 15 wt% (PVA + glycerol), some graphene sheets agglomerate inside the matrix.

[0079] The cross-sectional microstructures of the pure PVA film, the composite thermally conductive film PVA / GO-10 wt%, the composite thermally conductive film PVA / G-10 wt%, and the composite thermally conductive film PVA / rGO / G-10 wt% in Example 5 are shown in the figures below. Figure 3 As shown in the figure, the cross-section of the pure PVA matrix is ​​very smooth. After PVA is combined with graphene oxide, its cross-section exhibits a uniform and rough texture. This is because the oxygen-containing functional groups on the surface of graphene oxide are cross-linked with polyvinyl alcohol through hydrogen bonds. However, when the same mass of graphene is combined with polyvinyl alcohol, due to the poor compatibility between graphene and polyvinyl alcohol, graphene agglomeration occurs, and its cross-section exhibits a micromorphology of locally smooth and locally agglomerated graphene.

[0080] Combination Figure 2 and Figure 3 By comparing the cross-sectional microstructures of the composite thermally conductive films PVA / GO / G-10 wt% and PVA / rGO / G-10 wt% before and after reduction in Example 5, it can be seen that after reduction, the graphene sheets of PVA / GO / G-10 wt% are uniformly distributed in the matrix and the number is greatly increased compared with that before reduction. This is because the oxygen-containing functional groups on the surface of graphene oxide lose their cross-linking ability with polyvinyl alcohol after in-situ reduction and are exposed.

[0081] Performance testing:

[0082] The thermal conductivity of the films obtained in Examples 1 to 6 and Comparative Examples 1 to 3 was tested. The thermal conductivity of the composite films obtained in Examples 1 to 6 and Comparative Examples 1 to 3 is as follows: Figure 4 and Figure 5 As shown.

[0083] By Figure 4 It can be seen that at an extremely low filler ratio, i.e., when the total mass of graphene and graphene oxide is 1 wt% (PVA + glycerol), the thermal conductivity is significantly improved (883%) compared to pure PVA film (0.4 W / (m·K)), demonstrating the great potential of graphene and graphene oxide composite fillers in the field of thermally conductive fillers. At a total mass of 10 wt% (PVA + glycerol), the composite film achieves horizontal and vertical thermal conductivity as high as 5.77 W / (m·K) and 1.09 W / (m·K), respectively, representing a 1343% improvement compared to pure polyvinyl alcohol film, while the vertical thermal conductivity is improved by a staggering 2928%.

[0084] from Figure 5 It can be seen that, under the same mass ratio, the composite films obtained by combining individual fillers (graphene or graphene oxide) with polyvinyl alcohol have significantly lower thermal conductivity (PVA / GO-10 wt%, 3.95 W / (m·K); PVA / G-10 wt%, 4.83 W / (m·K)) than the thermally conductive films prepared by the composite filler of graphene and graphene oxide, demonstrating the synergistic advantage of the graphene and graphene oxide composite filler. The thermal conductivity of the composite film obtained in Example 5 after reduction was also significantly improved, with horizontal and vertical thermal conductivity reaching 8.27 W / (m·K) and 1.47 W / (m·K), respectively, greatly expanding the application range of graphene and graphene oxide-based polymer thermally conductive materials in the field of thermal management.

[0085] The electrical insulation properties of the films obtained in Examples 1 to 6 and Comparative Examples 1 to 3 are as follows: Figure 6 and Figure 7 As shown, all the prepared films are insulating.

[0086] The above description is merely a preferred embodiment of the present invention, and therefore should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A flexible insulating composite thermally conductive film, characterized in that: With a thickness of 50-80 μm, it is composed of polyvinyl alcohol, glycerol, graphene, and graphene oxide. The mass ratio of polyvinyl alcohol to glycerol is 8-10:1, and the total amount of graphene and graphene oxide is 1-15 wt% of the total amount of polyvinyl alcohol and glycerol, with the amount of graphene being greater than the amount of graphene oxide. Graphene oxide acts as a surfactant to inhibit graphene aggregation, thereby forming a continuous thermally conductive network within the flexible insulating composite thermally conductive film. Furthermore, graphene oxide is linked to polyvinyl alcohol, which serves as the matrix, through hydrogen bonds and anchors the graphene through π-π conjugation, achieving molecular-level uniform dispersion of graphene in the flexible insulating composite thermally conductive film.

2. The flexible insulating composite thermally conductive film as described in claim 1, characterized in that: The graphene oxide is reduced graphene oxide.

3. A flexible insulating composite thermally conductive film as described in claim 1 or 2, characterized in that: The mass ratio of graphene to graphene oxide is 0.12-1.8: 0.08-1.

2.

4. The method for preparing the flexible insulating composite thermally conductive film according to any one of claims 1 to 3, characterized in that: Includes the following steps: (1) Preparation of graphene aqueous dispersion, graphene oxide aqueous dispersion and polyvinyl alcohol aqueous solution containing glycerol; (2) Mix the graphene aqueous dispersion obtained in step (1) with the graphene oxide aqueous dispersion evenly to obtain GO / G composite dispersion. (3) Mix the GO / G composite dispersion obtained in step (2) with a polyvinyl alcohol aqueous solution containing glycerol to obtain a PVA / GO / G composite slurry. (4) The PVA / GO / G composite slurry obtained in step (3) is coated and spread on the substrate and then dried to obtain the flexible insulating composite thermal conductive film.

5. The preparation method according to claim 4, characterized in that: It also includes step (5): chemically reducing the flexible insulating composite thermally conductive film obtained in step (4).

6. The preparation method according to claim 5, characterized in that: The chemical reduction treatment is as follows: soaking and reduction with a 40 wt% HI anhydrous ethanol solution at a temperature of 70°C for 16 h.

7. The preparation method according to any one of claims 4 to 6, characterized in that: The concentration of graphene in the graphene aqueous dispersion is 0.12-1.8 wt%.

8. The preparation method according to any one of claims 4 to 6, characterized in that: The concentration of graphene oxide in the graphene oxide aqueous dispersion is 0.08-1.2 wt%.

9. The preparation method according to any one of claims 4 to 6, characterized in that: The polyvinyl alcohol aqueous solution contained 12.8 wt% polyvinyl alcohol and 1.25 wt% glycerol.

10. The preparation method according to any one of claims 4 to 6, characterized in that: The drying in (4) is vacuum drying at 70°C for 12 h.

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