Ultrahigh-heat-conductivity artificial graphite heat dissipation film and preparation method thereof
Through the combination technology of modified nanoboronitride and polyamic acid solution and spraying treatment of graphite dispersion, an ultra-high thermal conductivity artificial graphite heat dissipation film with high thermal conductivity and flexibility was prepared, solving the problems of poor flexibility and insufficient thermal conductivity of traditional graphite films.
Patent Information
- Application Number
- CN202510178180.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-18
- Publication Date
- 2025-05-13
AI Technical Summary
The graphite film prepared by traditional processes has poor flexibility, and its thermal conductivity is difficult to meet the needs of miniaturized electronic equipment. It is easy to electrostatic adsorption and adherence and interlayer breakage during carbonization.
The functionalized polyimide film was prepared by mixing, coating, and imidizing the modified nanoboronitride with a polyamic acid solution, and then spraying the graphite dispersion liquid on both sides of the film and carbonizing and graphitizing to produce an ultra-high thermal conductivity artificial graphite heat dissipation film.
The excellent thermal conductivity and flexibility of the graphite heat dissipation film are achieved, while avoiding the problems of electrostatic adsorption and adhesion of materials during carbonization and interlayer breakage.
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Abstract
Description
Technical Field
[0001] The invention relates to the technical field of graphite materials, in particular to an ultra-high thermal conductivity artificial graphite heat dissipation film and a preparation method thereof. Background Art
[0002] The development and innovation of science and technology have promoted the development of new materials. In recent years, electronic equipment and communication equipment have been rapidly updated and iterated, gradually moving towards miniaturization, refinement and high-density integration, and the problem of heat generation has become increasingly prominent. The increase in heat generated per unit volume not only reduces the performance of the equipment, but also reduces the service life of the equipment, and even causes serious safety problems. Graphite film with a conjugated carbon double bond planar structure and high thermal conductivity is considered to be an ideal thermal management material with great development prospects.
[0003] However, the graphite film prepared by traditional processes has poor flexibility and is not easy to bend, which limits the application of graphite film on irregular devices. With the miniaturization of electronic and communication equipment, the thermal conductivity of graphite film prepared by traditional processes is also difficult to meet the thermal conductivity requirements of these devices. During the carbonization process of graphite film, after the material softens, it is easy to adhere together through electrostatic adsorption, resulting in excessive shrinkage and resulting in the interlayer adhesion and collapse, and insufficient support strength resulting in tilted adhesion. Therefore, it is necessary to propose an ultra-high thermal conductivity artificial graphite heat dissipation film and a preparation method thereof. The graphite heat dissipation film prepared by the preparation method not only has excellent thermal conductivity and flexibility, but also overcomes the problem that the material is easy to tilt and adhere, and the interlayer adhesion and collapse during the carbonization process. Summary of the invention
[0004] The object of the present invention is to provide an ultra-high thermal conductivity artificial graphite heat dissipation film and a preparation method thereof, so as to solve the problems existing in the prior art.
[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:
[0006] An ultra-high thermal conductivity artificial graphite heat dissipation film, wherein the ultra-high thermal conductivity artificial graphite heat dissipation film is prepared by mixing modified nano boron nitride with a polyamic acid solution, coating, and imidizing to obtain a functionalized polyimide film; spraying a graphite dispersion on both sides of the functionalized polyimide film to obtain a pretreated polyimide film; and carbonizing and graphitizing the pretreated polyimide film to obtain an ultra-high thermal conductivity artificial graphite heat dissipation film;
[0007] The modified nano boron nitride is prepared by treating the nano boron nitride with isopropoxy triisostearyloxy titanate;
[0008] The polyamic acid solution is prepared by polymerizing 4,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzoxazole, 2-(4-aminophenyl)-5-aminobenzimidazole and pyromellitic acid anhydride;
[0009] The graphite dispersion is prepared by uniformly mixing graphite and deionized water.
[0010] A method for preparing an ultra-high thermal conductivity artificial graphite heat dissipation film, the method for preparing the ultra-high thermal conductivity artificial graphite heat dissipation film comprising the following preparation steps:
[0011] (1) Mix nano boron nitride and anhydrous ethanol in a mass ratio of 1:(50-60) and disperse them evenly by ultrasonic dispersion for 30-40 min. Add a coupling agent solution 20-30 times the mass of the nano boron nitride, stir at 10-30°C and 300-500 r / min for 3-4 h, filter, wash with anhydrous ethanol and deionized water for 3-5 times respectively, and dry at 50-60°C under vacuum conditions for 8-10 h to obtain modified nano boron nitride;
[0012] (2) Under nitrogen protection, 4,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzoxazole, and 2-(4-aminophenyl)-5-aminobenzimidazole were added to dimethylacetamide (20 to 30 times the mass of 4,4'-diaminodiphenyl ether) in a molar ratio of 1:(0.1 to 0.2):(0.1 to 0.2) and mixed evenly. 4,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzoxazole, and 2-(4-aminophenyl)-5-aminobenzimidazole were added dropwise at a uniform speed within 30 minutes. The polyamide acid solution is prepared by mixing the polyamide acid solution with the modified nano boron nitride in a mass ratio of 1:(0.003-0.005) and then uniformly coating the mixture on a glass sheet. The mixture is kept at 75-85°C for 2-3 hours under vacuum conditions, and kept at 120°C, 150°C, 180°C, 230°C and 300°C for 1 hour respectively. The mixture is cooled to room temperature and then peeled off from the glass sheet to obtain a functionalized polyimide film.
[0013] (3) The functionalized polyimide film is cut into a width of 133 to 257 mm, and the cut functionalized polyimide film is placed in a spraying device. The graphite dispersion is evenly sprayed on both sides of the functionalized polyimide film through the upper nozzle and the lower nozzle of the spraying device, and the spraying thickness is 5 to 10 μm. After spraying, it is immediately dried at 100 to 120° C. for 3 to 4 hours, and rolled up to obtain a pretreated polyimide film; the pretreated polyimide film is placed in a carbonization furnace, and carbonized to obtain a carbonized film; the carbonized film is placed in a graphite furnace, and after graphitization treatment, it is placed in a calender, and calendered to obtain an ultra-high thermal conductivity artificial graphite heat dissipation film.
[0014] As an optimization, the nano boron nitride in step (1) is specifically nano hexagonal boron nitride
[0015] As an optimization, the preparation method of the coupling agent solution in step (1) is: isopropoxy triisostearyl titanate, deionized water, and anhydrous ethanol are evenly mixed in a mass ratio of 1: (2-3): (20-30) to prepare a coupling agent solution.
[0016] As an optimization, the preparation method of the graphite dispersion in step (3) is: graphite and deionized water are uniformly mixed in a mass ratio of 1:(80-100), and ultrasonically dispersed for 1-2 hours to obtain a graphite dispersion.
[0017] As an optimization, the particle size of the graphite is 5 to 10 μm.
[0018] As an optimization, the process flow of the carbonization treatment in step (3) is as follows: the pretreated polyimide film is placed in a carbonization furnace, and under vacuum conditions, the temperature is increased from room temperature to 600°C at a heating rate of 20°C / min, and kept warm for 1 to 2 hours, and then the temperature is continued to be increased to 1300°C at a heating rate of 20°C / min, and kept warm for 20 to 30 minutes, and then cooled to room temperature to obtain a carbonized film.
[0019] As an optimization, the process flow of the graphitization treatment in step (3) is as follows: the carbonized film is placed in a graphite furnace, and under nitrogen protection, the temperature is increased from room temperature to 1600°C at a heating rate of 20°C / min, and kept warm for 4 to 5 hours, and then the temperature is increased to 2800°C at a heating rate of 20°C / min, and kept warm for 10 to 20 minutes, and then cooled to room temperature.
[0020] As an optimization, the calendering pressure in step (3) is 10 to 20 MPa.
[0021] Compared with the prior art, the beneficial effects achieved by the present invention are:
[0022] When preparing the ultra-high thermal conductive artificial graphite heat dissipation film, the present invention comprises the following steps: treating nano boron nitride with isopropoxy triisostearyloxy titanate to obtain modified nano boron nitride; polymerizing 4,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzoxazole, 2-(4-aminophenyl)-5-aminobenzimidazole and pyromellitic acid dianhydride to obtain a polyamic acid solution; mixing, coating and imidizing the modified nano boron nitride with the polyamic acid solution to obtain a functionalized polyimide film; spraying graphite dispersion on both sides of the functionalized polyimide film to obtain a pretreated polyimide film; and carbonizing and graphitizing the pretreated polyimide film to obtain the ultra-high thermal conductive artificial graphite heat dissipation film.
[0023] Firstly, nano boron nitride is treated with isopropoxy triisostearyloxy titanate to obtain modified nano boron nitride; surface modification of nano boron nitride with titanate coupling agent can increase the dispersibility of nano boron nitride in matrix resin and avoid agglomeration; nano boron nitride is a typical non-oxidizing ceramic material, which has a layered structure and sublimates at high temperature and is often used as a foaming agent; in the high-temperature graphitization stage, nano boron nitride in the carbonized film sublimates into gas, and the gas escapes from the graphite layer, leaving bubble gaps, so that the graphite layer becomes a foamed graphite film, and the foamed graphite film is calendered to obtain an ultra-high thermal conductivity artificial graphite heat dissipation film; when the foamed graphite film is calendered under a certain pressure, the gaps between the graphite sheets become smaller, and the graphite film layers are easy to overlap and lock, forming a flexible graphite film with a certain bonding strength. When the graphite film is subjected to bending stress, shear slip occurs between the graphite middle layer and the ordered structural layer of graphite. The small gap formed by the sublimation of nano-boron nitride can provide sufficient adjustment space for the shear slip, and some stresses around the gap can offset each other, giving the ultra-high thermal conductivity artificial graphite heat dissipation film excellent flexibility.
[0024] Secondly, 4,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzoxazole, 2-(4-aminophenyl)-5-aminobenzimidazole and pyromellitic acid dianhydride are polymerized to obtain a polyamic acid solution; the modified nano-boron nitride is mixed with the polyamic acid solution, coated and imidized to obtain a functionalized polyimide film; 2-(4-aminophenyl)-5-aminobenzoxazole and 2-(4-aminophenyl)-5-aminobenzimidazole are involved in the polymerization reaction, and benzoxazole and benzimidazole structures are introduced into the main chain of the polyimide molecule to improve the in-plane orientation of the functionalized polyimide film, which is beneficial to the flat stacking growth of graphite flakes, increase the degree of graphitization of the graphite film, and improve the thermal conductivity of the ultra-high thermal conductivity artificial graphite heat dissipation film.
[0025] Finally, during the carbonization process, the functionalized polyimide film will soften, and the softened material will easily adhere together through electrostatic adsorption. In order to prevent this phenomenon, a graphite dispersion is sprayed on both sides of the functionalized polyimide film to form a conductive anti-adhesive layer on both sides of the functionalized polyimide film to prevent the accumulation of charges on the surface of the functionalized polyimide film and the adhesion due to electrostatic adsorption; this conductive anti-adhesive layer also plays a certain supporting role, preventing the interlayer adhesion and breakage caused by excessive shrinkage, and preventing the skewed adhesion caused by insufficient support strength. DETAILED DESCRIPTION
[0026] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0027] Example 1
[0028] A method for preparing an ultra-high thermal conductivity artificial graphite heat dissipation film, the method for preparing the ultra-high thermal conductivity artificial graphite heat dissipation film comprising the following preparation steps:
[0029] (1) isopropoxy triisostearyl titanate, deionized water and anhydrous ethanol are mixed uniformly in a mass ratio of 1:2:20 to prepare a coupling agent solution; nano boron nitride and anhydrous ethanol are mixed uniformly in a mass ratio of 1:50, ultrasonically dispersed for 30 minutes, and a coupling agent solution 20 times the mass of nano boron nitride is added, stirred at 10°C and 300 r / min for 4 hours, filtered, washed with anhydrous ethanol and deionized water for 3 times each, and dried at 50°C for 10 hours under vacuum conditions to obtain modified nano boron nitride;
[0030] (2) Under nitrogen protection, 4,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzoxazole, and 2-(4-aminophenyl)-5-aminobenzimidazole were added to dimethylacetamide (20 times the mass of 4,4'-diaminodiphenyl ether) in a molar ratio of 1:0.1:0.1 and mixed evenly. 4,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzoxazole, 2-(4-aminophenyl)-5-aminobenzimidazole were added dropwise at a uniform speed within 30 minutes. The total molar amount of imidazole is 1 times that of pyromellitic anhydride; under nitrogen protection, the mixture is stirred at 0°C and 300r / min for 24h to obtain a polyamic acid solution; the polyamic acid solution and modified nano-boron nitride are mixed evenly at a mass ratio of 1:0.003, and the mixture is evenly coated on a glass sheet; under vacuum conditions, the mixture is kept at 75°C for 3h, and kept at 120°C, 150°C, 180°C, 230°C, and 300°C for 1h respectively, and after cooling to room temperature, the mixture is peeled off from the glass sheet to obtain a functionalized polyimide film;
[0031] (3) Graphite and deionized water were mixed at a mass ratio of 1:80, and ultrasonically dispersed for 1 hour to obtain a graphite dispersion; the functionalized polyimide film was cut to a width of 133 mm, and the cut functionalized polyimide film was placed in a spraying device, and the graphite dispersion was evenly sprayed on both sides of the functionalized polyimide film through the upper nozzle and the lower nozzle of the spraying device, with a spraying thickness of 5 μm. After spraying, it was immediately dried at 100° C. for 4 hours and rolled up to obtain a pretreated polyimide film; the pretreated polyimide film was placed in a carbonization furnace and, under vacuum conditions, The temperature was increased from room temperature to 600°C at a heating rate of 20°C / min, kept warm for 1 hour, continued to be increased to 1300°C at a heating rate of 20°C / min, kept warm for 20 minutes, and cooled to room temperature to obtain a carbonized film; the carbonized film was placed in a graphite furnace, and under nitrogen protection, the temperature was increased from room temperature to 1600°C at a heating rate of 20°C / min, kept warm for 4 hours, increased to 2800°C at a heating rate of 20°C / min, kept warm for 10 minutes, cooled to room temperature, and placed in a calender, and calendered at 10MPa to obtain an ultra-high thermal conductive artificial graphite heat dissipation film.
[0032] Example 2
[0033] A method for preparing an ultra-high thermal conductivity artificial graphite heat dissipation film, the method for preparing the ultra-high thermal conductivity artificial graphite heat dissipation film comprising the following preparation steps:
[0034] (1) isopropoxy triisostearyl titanate, deionized water and anhydrous ethanol are mixed uniformly in a mass ratio of 1:2.5:25 to prepare a coupling agent solution; nano boron nitride and anhydrous ethanol are mixed uniformly in a mass ratio of 1:55, ultrasonically dispersed for 35 minutes, and a coupling agent solution 25 times the mass of nano boron nitride is added, stirred at 20°C and 400r / min for 3.5 hours, filtered, washed with anhydrous ethanol and deionized water 4 times each, and dried at 55°C under vacuum conditions for 9 hours to obtain modified nano boron nitride;
[0035] (2) Under nitrogen protection, 4,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzoxazole, and 2-(4-aminophenyl)-5-aminobenzimidazole were added to dimethylacetamide (25 times the mass of 4,4'-diaminodiphenyl ether) in a molar ratio of 1:0.15:0.15 and mixed evenly. 4,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzoxazole, 2-(4-aminophenyl)-5-aminobenzimidazole were added dropwise at a uniform speed within 30 minutes. The total molar amount of imidazole is 1 times that of pyromellitic dianhydride; under nitrogen protection, the mixture is stirred at 1°C and 400r / min for 22h to obtain a polyamic acid solution; the polyamic acid solution and modified nano-boron nitride are mixed evenly at a mass ratio of 1:0.004, and the mixture is evenly coated on a glass sheet; under vacuum conditions, the mixture is kept at 80°C for 2.5h, and kept at 120°C, 150°C, 180°C, 230°C, and 300°C for 1h respectively, and then the mixture is cooled to room temperature and peeled off from the glass sheet to obtain a functionalized polyimide film;
[0036] (3) Graphite and deionized water were mixed at a mass ratio of 1:90, and ultrasonically dispersed for 1.5 hours to obtain a graphite dispersion; the width of the functionalized polyimide film was cut to 195 mm, and the cut functionalized polyimide film was placed in a spraying device, and the graphite dispersion was evenly sprayed on both sides of the functionalized polyimide film through the upper nozzle and the lower nozzle of the spraying device, and the spraying thickness was 7.5 μm. After spraying, it was immediately dried at 110°C for 3.5 hours and rolled up to obtain a pretreated polyimide film; the pretreated polyimide film was placed in a carbonization furnace and heated under vacuum. , the temperature was increased from room temperature to 600°C at a heating rate of 20°C / min, kept warm for 1.5 hours, continued to be heated to 1300°C at a heating rate of 20°C / min, kept warm for 25 minutes, and cooled to room temperature to obtain a carbonized film; the carbonized film was placed in a graphite furnace, and under nitrogen protection, the temperature was increased from room temperature to 1600°C at a heating rate of 20°C / min, kept warm for 4.5 hours, increased to 2800°C at a heating rate of 20°C / min, kept warm for 15 minutes, cooled to room temperature, and placed in a calender, and calendered at 15MPa to obtain an ultra-high thermal conductive artificial graphite heat dissipation film.
[0037] Example 3
[0038] A method for preparing an ultra-high thermal conductivity artificial graphite heat dissipation film, the method for preparing the ultra-high thermal conductivity artificial graphite heat dissipation film comprising the following preparation steps:
[0039] (1) isopropoxy triisostearyl titanate, deionized water and anhydrous ethanol are mixed uniformly in a mass ratio of 1:3:30 to prepare a coupling agent solution; nano boron nitride and anhydrous ethanol are mixed uniformly in a mass ratio of 1:60, ultrasonically dispersed for 40 minutes, and a coupling agent solution 30 times the mass of nano boron nitride is added, stirred at 30°C and 500r / min for 3 hours, filtered, washed with anhydrous ethanol and deionized water for 5 times each, and dried at 60°C under vacuum conditions for 8 hours to obtain modified nano boron nitride;
[0040] (2) Under nitrogen protection, 4,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzoxazole, and 2-(4-aminophenyl)-5-aminobenzimidazole were added to dimethylacetamide (30 times the mass of 4,4'-diaminodiphenyl ether) in a molar ratio of 1:0.2:0.2 and mixed evenly. 4,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzoxazole, 2-(4-aminophenyl)-5-aminobenzimidazole were added dropwise at a uniform speed over 30 minutes. The total molar amount of imidazole is 1 times that of pyromellitic anhydride; under nitrogen protection, the mixture is stirred at 2°C and 500r / min for 20h to obtain a polyamic acid solution; the polyamic acid solution and modified nano-boron nitride are mixed evenly at a mass ratio of 1:0.005, and the mixture is evenly coated on a glass sheet; under vacuum conditions, the mixture is kept at 85°C for 2h, and kept at 120°C, 150°C, 180°C, 230°C, and 300°C for 1h respectively, and after cooling to room temperature, the mixture is peeled off from the glass sheet to obtain a functionalized polyimide film;
[0041] (3) Graphite and deionized water were mixed at a mass ratio of 1:100, and ultrasonically dispersed for 2 hours to obtain a graphite dispersion; the width of the functionalized polyimide film was cut to 257 mm, and the cut functionalized polyimide film was placed in a spraying device, and the graphite dispersion was evenly sprayed on both sides of the functionalized polyimide film through the upper nozzle and the lower nozzle of the spraying device, and the spraying thickness was 10 μm. After spraying, it was immediately dried at 120°C for 3 hours and rolled up to obtain a pretreated polyimide film; the pretreated polyimide film was placed in a carbonization furnace and heated under vacuum. , the temperature was increased from room temperature to 600°C at a heating rate of 20°C / min, kept warm for 2 hours, continued to be heated to 1300°C at a heating rate of 20°C / min, kept warm for 30 minutes, and cooled to room temperature to obtain a carbonized film; the carbonized film was placed in a graphite furnace, and under nitrogen protection, the temperature was increased from room temperature to 1600°C at a heating rate of 20°C / min, kept warm for 5 hours, increased to 2800°C at a heating rate of 20°C / min, kept warm for 20 minutes, cooled to room temperature, and placed in a calender, and calendered at 20MPa to obtain an ultra-high thermal conductive artificial graphite heat dissipation film.
[0042] Comparative Example 1
[0043] The difference between the preparation method of the ultra-high thermal conductive artificial graphite heat dissipation film of Comparative Example 1 and Example 2 is that step (1) is not performed, and step (2) is modified as follows: under nitrogen protection, 4,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzoxazole, and 2-(4-aminophenyl)-5-aminobenzimidazole are added in a molar ratio of 1:0.15:0.15 to dimethylacetamide (25 times the mass of 4,4'-diaminodiphenyl ether) and mixed evenly; 4,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzoxazole, and 2-(4-aminophenyl)-5-aminobenzimidazole are added at a molar ratio of 1:0.15:0.15 to 4,4'-diaminodiphenyl ether The mass of dimethylacetamide is 25 times that of the mass of the ether, and 4,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzoxazole are added dropwise at a uniform speed within 30 minutes. 5-aminobenzoxazole, 2-(4-aminophenyl)-5-aminobenzimidazole total molar amount of 1 times of pyromellitic dianhydride; under nitrogen protection, 1 ° C, 400r / min stirring reaction for 22h to obtain a polyamic acid solution; the polyamic acid solution and nano boron nitride are mixed at a mass ratio of 1:0.004, uniformly coated on a glass sheet, and kept at 80 ° C for 2.5h under vacuum conditions, and kept at 120 ° C, 150 ° C, 180 ° C, 230 ° C, and 300 ° C for 1h each, and then cooled to room temperature and peeled off from the glass sheet to obtain a functionalized polyimide film. The remaining steps are the same as in Example 2.
[0044] Comparative Example 2
[0045] The difference between the preparation method of the ultra-high thermal conductive artificial graphite heat dissipation film of Comparative Example 2 and Example 2 is that step (1) is not performed, and step (2) is modified as follows: under nitrogen protection, 4,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzoxazole, and 2-(4-aminophenyl)-5-aminobenzimidazole are added in a molar ratio of 1:0.15:0.15 to dimethylacetamide (25 times the mass of 4,4'-diaminodiphenyl ether) and mixed evenly; 4,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzoxazole, and 2-(4-aminophenyl)-5-aminobenzimidazole are added in a molar ratio of 1:0.15:0.15 to 4,4'-diaminodiphenyl ether The mass of dimethylacetamide is uniformly added within 30 minutes. 2-(4-aminophenyl)-5-aminobenzoxazole, 2-(4-aminophenyl)-5-aminobenzimidazole total molar amount of 1 times pyromellitic dianhydride; under nitrogen protection, 1 ° C, 400r / min stirring reaction for 22h to obtain a polyamic acid solution; the polyamic acid solution is evenly coated on a glass sheet, under vacuum conditions, 80 ° C for 2.5h, 120 ° C, 150 ° C, 180 ° C, 230 ° C, 300 ° C for 1h each, and after cooling to room temperature, it is peeled off from the glass sheet to obtain a functionalized polyimide film. The remaining steps are the same as in Example 2.
[0046] Comparative Example 3
[0047] The difference between the preparation method of the ultra-high thermal conductive artificial graphite heat dissipation film of Comparative Example 3 and that of Example 2 lies in the difference in step (2), and step (2) is modified as follows: under nitrogen protection, 4,4'-diaminodiphenyl ether is added to dimethylacetamide with a mass of 25 times that of 4,4'-diaminodiphenyl ether and mixed evenly, and 1 times the molar mass of 4,4'-diaminodiphenyl ether is added dropwise at a uniform speed within 30 minutes; under nitrogen protection, 1°C, 400r / min stirring reaction is carried out for 22 hours to obtain a polyamic acid solution; the polyamic acid solution and modified nano-boron nitride are mixed evenly at a mass ratio of 1:0.004, and evenly coated on a glass sheet, and under vacuum conditions, 80°C is kept warm for 2.5 hours, and 120°C, 150°C, 180°C, 230°C, and 300°C are kept warm for 1 hour each, and after cooling to room temperature, it is peeled off from the glass sheet to obtain a functionalized polyimide film. The remaining steps are the same as those of Example 2.
[0048] Test Example 1
[0049] Flexibility test
[0050] Test method: The ultra-high thermal conductivity artificial graphite heat dissipation film prepared in the embodiment and the comparative example was folded to test the number of folds (folded first, then released, if the ultra-high thermal conductivity artificial graphite heat dissipation film does not break, it is considered that the folding is effective), 20 samples were tested in each group, and the folding number interval of each group of samples was counted. If the folding number exceeds 1000 times, it is expressed as >1000 times. The results are shown in Table 1.
[0051] Table 1
[0052] Foldable times (times) Foldable times (times) Example 1 >1000 Comparative Example 1 <200 Example 2 >1000 Comparative Example 2 300～500 Example 3 >1000 Comparative Example 3 >1000
[0053] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 3 in Table 1, it can be found that the ultra-high thermal conductive artificial graphite heat dissipation film prepared by the present invention has good flexibility.
[0054] By comparison, the folding times of Examples 1 to 3 are greater than the folding times of Comparative Examples 1 to 2, indicating that modified nano boron nitride is prepared by treating nano boron nitride with isopropoxy triisostearyloxy titanate; surface modification of nano boron nitride with a titanate coupling agent can increase the dispersibility of nano boron nitride in the matrix resin and avoid agglomeration; nano boron nitride is a typical non-oxidizing ceramic material, which has a layered structure, sublimates at high temperatures, and is often used as a foaming agent; in the high-temperature graphitization stage, the nano boron nitride in the carbonized film sublimates into gas, and the gas escapes from the graphite layer, leaving bubble gaps, so that the graphite layer becomes a foamed graphite film, and the foamed graphite film is calendered to obtain an ultra-high thermal conductivity artificial graphite heat dissipation film; when the foamed graphite film is calendered under a certain pressure, the gaps between the graphite sheets become smaller, and the graphite film layers are easily overlapped and locked to form a flexible graphite film with a certain bonding strength. When the graphite film is subjected to bending stress, shear slip occurs between the graphite middle layer and the ordered structural layer of graphite. The small gap formed by the sublimation of nano-boron nitride can provide sufficient adjustment space for the shear slip, and some stresses around the gap can offset each other, giving the ultra-high thermal conductivity artificial graphite heat dissipation film excellent flexibility.
[0055] Test Example 2
[0056] Thermal conductivity test
[0057] Test method: The thermal conductivity of the embodiment and the comparative example was analyzed using the LFA467HT laser thermal conductivity measuring instrument of NETZSCH, Germany. The thermal diffusion coefficient was tested at room temperature according to ASTM E1461 (laser flash method) and the thermal conductivity was calculated. The sample size was a disc with a diameter of 12.5 mm and a sample thickness of 0.038 mm. The results are shown in Table 2.
[0058] Table 2
[0059]
[0060] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 3 in Table 2, it can be found that the ultra-high thermal conductive artificial graphite heat dissipation film prepared by the present invention has good thermal conductivity.
[0061] By comparison, the thermal conductivity of Examples 1 to 3 is greater than that of Comparative Example 3, indicating that 4,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzoxazole, 2-(4-aminophenyl)-5-aminobenzimidazole and pyromellitic acid dianhydride are polymerized to obtain a polyamic acid solution; modified nano-boron nitride is mixed with the polyamic acid solution, coated, and imidized to obtain a functionalized polyimide film; 2-(4-aminophenyl)-5-aminobenzoxazole and 2-(4-aminophenyl)-5-aminobenzimidazole are involved in the polymerization reaction, and benzoxazole and benzimidazole structures are introduced into the main chain of the polyimide molecule to improve the in-plane orientation of the functionalized polyimide film, which is beneficial to the smooth stacking growth of graphite flakes, increases the degree of graphitization of the graphite film, and improves the thermal conductivity of the ultra-high thermal conductivity artificial graphite heat dissipation film.
[0062] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.
Claims
1. An ultra-high thermal conductivity artificial graphite heat dissipation film, characterized in that: The ultra-high thermal conductivity artificial graphite heat dissipation film is prepared by mixing modified nano boron nitride with a polyamic acid solution, coating, and imidizing to obtain a functionalized polyimide film; spraying a graphite dispersion on both sides of the functionalized polyimide film to obtain a pretreated polyimide film; and carbonizing and graphitizing the pretreated polyimide film to obtain an ultra-high thermal conductivity artificial graphite heat dissipation film. The modified nano boron nitride is prepared by treating the nano boron nitride with isopropoxy triisostearyloxy titanate; The polyamic acid solution is prepared by polymerizing 4,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzoxazole, 2-(4-aminophenyl)-5-aminobenzimidazole and pyromellitic acid anhydride; The graphite dispersion is prepared by uniformly mixing graphite and deionized water.
2. A method for preparing an ultra-high thermal conductive artificial graphite heat dissipation film, characterized in that: The method for preparing the ultra-high thermal conductive artificial graphite heat dissipation film comprises the following preparation steps: (1) Mix nano boron nitride and anhydrous ethanol in a mass ratio of 1:(50-60) and disperse them evenly by ultrasonic dispersion for 30-40 min. Add a coupling agent solution 20-30 times the mass of the nano boron nitride, stir at 10-30°C and 300-500 r / min for 3-4 h, filter, wash with anhydrous ethanol and deionized water for 3-5 times respectively, and dry at 50-60°C under vacuum conditions for 8-10 h to obtain modified nano boron nitride; (2) Under nitrogen protection, 4,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzoxazole, and 2-(4-aminophenyl)-5-aminobenzimidazole were added to dimethylacetamide (20 to 30 times the mass of 4,4'-diaminodiphenyl ether) in a molar ratio of 1:(0.1 to 0.2):(0.1 to 0.2) and mixed evenly. 4,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzoxazole, and 2-(4-aminophenyl)-5-aminobenzimidazole were added dropwise at a uniform speed within 30 minutes. The polyamide acid solution is prepared by mixing the polyamide acid solution with the modified nano boron nitride in a mass ratio of 1:(0.003-0.005) and then uniformly coating the mixture on a glass sheet. The mixture is kept at 75-85°C for 2-3 hours under vacuum conditions, and kept at 120°C, 150°C, 180°C, 230°C and 300°C for 1 hour respectively. The mixture is cooled to room temperature and then peeled off from the glass sheet to obtain a functionalized polyimide film. (3) The functionalized polyimide film is cut into a width of 133 to 257 mm, and the cut functionalized polyimide film is placed in a spraying device. The graphite dispersion is evenly sprayed on both sides of the functionalized polyimide film through the upper nozzle and the lower nozzle of the spraying device, and the spraying thickness is 5 to 10 μm. After spraying, it is immediately dried at 100 to 120° C. for 3 to 4 hours, and rolled up to obtain a pretreated polyimide film; the pretreated polyimide film is placed in a carbonization furnace, and carbonized to obtain a carbonized film; the carbonized film is placed in a graphite furnace, and after graphitization treatment, it is placed in a calender, and calendered to obtain an ultra-high thermal conductivity artificial graphite heat dissipation film.
3. The method for preparing an ultra-high thermal conductive artificial graphite heat dissipation film according to claim 2, characterized in that: The nano boron nitride in step (1) is specifically nano hexagonal boron nitride.
4. The method for preparing an ultra-high thermal conductive artificial graphite heat dissipation film according to claim 2, characterized in that: The preparation method of the coupling agent solution in step (1) is as follows: isopropoxy triisostearyl titanate, deionized water and anhydrous ethanol are uniformly mixed in a mass ratio of 1:(2-3):(20-30) to prepare a coupling agent solution.
5. The method for preparing an ultra-high thermal conductive artificial graphite heat dissipation film according to claim 2, characterized in that: The preparation method of the graphite dispersion in step (3) is as follows: graphite and deionized water are uniformly mixed in a mass ratio of 1:(80-100), and ultrasonically dispersed for 1-2 hours to obtain a graphite dispersion.
6. The method for preparing an ultra-high thermal conductive artificial graphite heat dissipation film according to claim 5, characterized in that: The particle size of the graphite is 5 to 10 μm.
7. The method for preparing an ultra-high thermal conductive artificial graphite heat dissipation film according to claim 2, characterized in that: The process flow of the carbonization treatment in step (3) is as follows: placing the pretreated polyimide film in a carbonization furnace, heating it from room temperature to 600°C at a heating rate of 20°C / min under vacuum conditions, keeping it warm for 1 to 2 hours, continuing to heat it to 1300°C at a heating rate of 20°C / min, keeping it warm for 20 to 30 minutes, and cooling it to room temperature to obtain a carbonized film.
8. The method for preparing an ultra-high thermal conductive artificial graphite heat dissipation film according to claim 2, characterized in that: The process flow of the graphitization treatment in step (3) is as follows: placing the carbonized film in a graphite furnace, under nitrogen protection, heating from room temperature to 1600°C at a heating rate of 20°C / min, keeping warm for 4 to 5 hours, heating to 2800°C at a heating rate of 20°C / min, keeping warm for 10 to 20 minutes, and cooling to room temperature.
9. The method for preparing an ultra-high thermal conductive artificial graphite heat dissipation film according to claim 2, characterized in that: The pressure of the calendering molding in step (3) is 10 to 20 MPa.