Preparation method of polyimide film
By using boron nitride and nanosilicon dioxide as thermal conductivity fillers in the polyimide film to form a composite structure of sheet layer + particles, the problems of low thermal conductivity and poor mechanical performance of the polyimide film are solved, and efficient thermal conductivity and mechanical performance improvement are achieved.
Patent Information
- Application Number
- CN202510184513.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-19
- Publication Date
- 2025-06-03
AI Technical Summary
The thermal conductivity of polyimide films is low, and the mechanical properties are poor after adding thermal fillers, so it is necessary to improve its thermal conductivity and mechanical properties.
Boron nitride and nanosilicon dioxide are used as thermal fillers, and ultrasonic dispersion and silane coupling agent modification treatment are used to form a composite structure of sheet layer + particles to improve the dispersion effect of thermal fillers and the thermal conductivity of polyimide films.
The thermal conductivity and mechanical properties of the polyimide film are significantly improved, the dielectric constant is reduced, and a stable water resistance effect is formed.
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Figure BDA0005278111320000121
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of polyimide films, and more specifically, to a method for preparing a polyimide film. Background Art
[0002] Polyimide is a kind of rigid chain polymer with highly regular chemical structure containing imide rings on the main chain of the polymer. Its special imide ring structure gives it excellent thermal stability, mechanical, dielectric, mechanical, radiation resistance, flame retardant and solvent resistance. Due to its excellent thermal stability, chemical stability, mechanical properties and electrical insulation properties, it is widely used in the packaging substrate material of integrated circuits in the microelectronics industry.
[0003] Due to the high regularity of the polyimide molecular chain, the internal intermolecular interaction is strong, resulting in a slow heat conduction rate, so it is necessary to find a suitable method to improve the thermal conductivity. At present, it is usually used to add thermal conductive fillers to polyimide films to improve their thermal conductivity, but the dispersion of thermal conductive fillers in polyimide is poor, resulting in poor mechanical properties of polyimide films. Therefore, further improvements to polyimide films are still needed. Summary of the invention
[0004] In order to improve the thermal conductivity and mechanical properties of a polyimide film, the present application provides a method for preparing a polyimide film.
[0005] The present application provides a method for preparing a polyimide film, which adopts the following technical solution:
[0006] A method for preparing a polyimide film comprises the following steps:
[0007] S1. Filler dispersion: pre-disperse the thermal conductive filler in the DMAc solution, and ultrasonically disperse the solution to obtain a dispersion;
[0008] S2, preparation of polyimide solution: adding dianhydride and diamine to the dispersion in sequence, and continuously stirring to obtain a mixed colloid;
[0009] S3. Film preparation: vacuum the mixed colloid to remove bubbles, apply a knife, perform thermal imidization, and demould to obtain a polyimide film.
[0010] By adopting the above technical solution, the thermal conductive filler is dispersed in the solvent in advance, which can further improve the dispersion uniformity of the thermal conductive filler in the polyimide film, so that the polyimide film can obtain a uniform thermal conductive effect and better mechanical strength.
[0011] Optionally, the polyimide film includes the following raw materials in parts by weight:
[0012] 50-100 parts of 4,4-diaminodiphenyl ether;
[0013] 2 - 10 parts of dianhydride;
[0014] 2 - 15 parts of diamine;
[0015] 10 - 25 parts of thermal conductive filler;
[0016] The thermal conductive filler includes boron nitride and nano - silica, and the nano - silica has a hollow structure.
[0017] By adopting the above - mentioned technical solution, preferably, boron nitride and nano - silica are used in combination as the thermal conductive filler. Boron nitride has a graphene - like two - dimensional layered structure, so that boron nitride can obtain better thermal conductivity. The combination of nano - silica and boron nitride can obtain a composite structure of lamella + particles, which can effectively reduce the agglomeration between boron nitride lamellae, effectively improve the dispersion effect of boron nitride in the polyimide substrate, and the loading of nano - silica on boron nitride can further improve the bonding effect between boron nitride and the polyimide substrate, that is, the thermal conductive filler can synergistically improve the thermal conductivity and mechanical properties of the polyimide film.
[0018] Preferably, nano - silica with a hollow structure is used as the thermal conductive filler. It can not only improve the dispersion effect of boron nitride, but also bring an air phase due to its own hollow structure, making the polyimide film generate electronic polarization, orientation polarization and space - charge polarization under an external electric field, thereby effectively reducing the dielectric constant of the polyimide film. In addition, the nano - silica with a hollow structure can also form a good interface effect in the polyimide film and act as rigid particles to transfer load, absorb and disperse impact energy, further improving the mechanical properties of the polyimide film.
[0019] Optionally, the preparation of nano - silica is as follows: Ammonia water, ethanol solution and CTAB are placed in a container and stirred to obtain solution A; TEOS is added to solution A and continuously stirred to obtain a solution of silica hollow spheres, centrifuged, washed and dried to obtain silica with a hollow structure.
[0020] By adopting the above - mentioned technical solution, in this application, the soft template method is preferably used to prepare nano - silica with a hollow structure, and nano - silica with uniform wall thickness, uniform size and uniform hollow structure can be obtained.
[0021] Optionally, the nano - silica is nano - silica modified by a silane coupling agent.
[0022] By adopting the above technical solution, the nano-silica is modified by a silane coupling agent. Through the hydroxyl condensation reaction, long carbon chain groups can be grafted onto the surface of the nano-silica, effectively improving the dispersibility of the nano-silica, reducing the possibility of nano-silica agglomeration, enabling the nano-silica to be fully dispersed, hindering the agglomeration of boron nitride, and enhancing the strength of the polyimide film. At the same time, the introduction of long carbon chains can also improve the hydrophobic effect of the nano-silica, compensate for the hydrophilic effect brought by the hollow structure, and endow the polyimide film with a stable water resistance effect.
[0023] Optionally, the boron nitride is boron nitride modified by polydopamine.
[0024] By adopting the above technical solution, the boron nitride modified by polydopamine can form uniform flakes, and each layer is evenly exfoliated, reducing the agglomeration between the boron nitride layers and improving the dispersion uniformity of the boron nitride in the polyimide film. At the same time, after being modified by polydopamine, the surface of the boron nitride layer is relatively rough, which is beneficial to the loading of nano-silica, forming a composite structure of layers + particles in the thermal conductive filler.
[0025] Optionally, the filler further includes silicon carbide fibers.
[0026] By adopting the above technical solution, silicon carbide fibers have high mechanical strength, hardness, wear resistance, high thermal conductivity, excellent thermal stability, and good thermal shock resistance. Therefore, when added to the polyimide film, they can further improve the thermal conductivity of the polyimide film. And due to the one-dimensional linear structure of the silicon carbide fibers, an intertwined fiber network can be formed in the polyimide film, thereby improving the mechanical strength of the polyimide film. In addition, the silicon carbide fibers can be connected to the layer structure in the thermal conductive filler, forming a multi-dimensional composite structure of particles + fibers + layers. The silicon carbide fibers can connect adjacent layer structures to form conductive and heat-conductive channels, further improving the thermal conductivity effect of the polyimide film.
[0027] Optionally, carbon nanotubes are loaded on the silicon carbide fibers.
[0028] By adopting the above technical solution, carbon nanotubes have a high thermal conductivity effect. After being loaded on the silicon carbide fibers, a uniformly distributed carbon nanotube array can be formed on the silicon carbide fibers, which can further increase the roughness of the silicon carbide fibers and improve the bonding effect between the silicon carbide fibers and the polyimide. At the same time, the addition of carbon nanotubes can increase the connection paths between the thermal conductive fillers, forming a uniformly structured thermal conductive network in the polyimide film, not only improving the thermal conductivity effect of the polyimide film, but also further enhancing the mechanical strength of the polyimide film.
[0029] Optionally, the silicon carbide fibers are silicon carbide fibers modified by magnetization.
[0030] By adopting the above technical solution, the silicon carbide fiber is magnetically modified, so that the silicon carbide fiber can deflect under the induction of a magnetic field, thereby forming a regular network structure in the polyimide film, reducing the phenomenon of agglomeration of the silicon carbide fiber, and enabling the polyimide film to obtain a uniform heat conduction effect and a better mechanical structure.
[0031] Optionally, the diamine is selected from one or more of N,N-dimethylacetamide, 2,6-dimethyl-p-phenylenediamine, 4,4-diaminodiphenyl ether 2, 2,3,5-trimethyl-p-phenylenediamine, 2,5-di-tert-butyl-p-phenylenediamine; the dianhydride is selected from one or more of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride.
[0032] Optionally, in step S3, after the mixed colloid is scrape-coated, a vertical external magnetic field is introduced, and the magnetic field strength is 5-15 mT.
[0033] By adopting the above technical solution, by using a vertical external magnetic field, magnetic fibers can be oriented and arranged in the vertical direction, so that not only a horizontal cross-linked heat conduction network exists in the polyimide film, but also a cross-linked heat conduction network exists in the vertical direction, which can further improve the heat conduction effect of the polyimide film. And because the magnetic fibers also participate in the construction of the heat conduction network in the horizontal direction, under the action of the external magnetic field and driven by the magnetic fibers, the heat conduction network can be stretched in the vertical direction to form a three-dimensional network structure that is staggered in both the horizontal and vertical directions, effectively improving the heat conduction effect and mechanical properties of the polyimide film. And because the magnetic fibers are still within the horizontal cross-linked network, the end structures of the fibers are not easy to protrude from the surface of the polyimide film or form protruding points on the surface of the polyimide film, enabling the heat conduction network to stably exist and conduct heat in the film.
[0034] In summary, the present application has the following beneficial effects:
[0035] 1. Since the present application preferably uses boron nitride and nano-silica in combination as heat conduction fillers, the above two can obtain a composite structure of flakes + particles, which can effectively reduce the agglomeration between boron nitride flakes, effectively improve the dispersion effect of boron nitride in the polyimide substrate, and the loading of nano-silica on boron nitride can further improve the bonding effect between boron nitride and the polyimide substrate, that is, the heat conduction fillers can synergistically improve the heat conduction effect and mechanical properties of the polyimide film.
[0036] It is preferred to use hollow-structured nano-silica as the thermal conductive filler, which can not only improve the dispersion effect of boron nitride, but also utilize its own hollow structure to introduce an air phase, enabling the polyimide film to generate electronic polarization, orientation polarization, and space charge polarization under an external electric field, thereby effectively reducing the dielectric constant of the polyimide film. In addition, the hollow-structured nano-silica can also form a good interfacial effect in the polyimide film and act as a rigid particle to transfer load, absorb and disperse impact energy, further improving the mechanical properties of the polyimide film.
[0037] 2. In this application, it is preferred to use silicon carbide fibers as the thermal conductive filler. Silicon carbide fibers have high mechanical strength, hardness, wear resistance, high thermal conductivity, excellent thermal stability, and good thermal shock resistance. Therefore, when added to the polyimide film, they can further improve the thermal conductivity of the polyimide film. And due to the one-dimensional linear structure of the silicon carbide fibers, an intertwined fiber network can be formed in the polyimide film, thereby improving the mechanical strength of the polyimide film. In addition, the silicon carbide fibers can be connected to the lamellar structure in the thermal conductive filler to form a multi-dimensional composite structure of particles + fibers + lamellae. The silicon carbide fibers can connect adjacent lamellar structures to form conductive and thermal conductive channels, further improving the thermal conductivity of the polyimide film.
[0038] 3. The method of this application can use a vertically applied magnetic field to align the magnetic fibers in the vertical direction, so that there is not only a horizontal cross-linked thermal conductive network in the polyimide film, but also a cross-linked thermal conductive network in the vertical direction, which can further improve the thermal conductivity of the polyimide film. And because the magnetic fibers also participate in the construction of the thermal conductive network in the horizontal direction, under the action of the external magnetic field and being pulled by the magnetic fibers, the thermal conductive network can be stretched in the vertical direction to form a three-dimensional network structure that is staggered in both the horizontal and vertical directions, effectively improving the thermal conductivity and mechanical properties of the polyimide film. And because the magnetic fibers are still within the horizontal cross-linked network, the end structures of the fibers are not likely to protrude from the surface of the polyimide film or form protruding points on the surface of the polyimide film, enabling the thermal conductive network to exist stably in the film and conduct heat. Detailed implementation manners
[0039] The following further elaborates on this application with reference to the embodiments.
[0040] Preparation examples
[0041] Preparation example of hollow nano-silica
[0042] Preparation example 1
[0043] Place 1 mL of ammonia water, 120 mL of ethanol solution (volume ratio of ethanol to water is 0.5), and 0.4 g of CTAB in a container and stir to obtain solution A; add 2 g of TEOS to solution A, continuously stir for 1 h to obtain a silica hollow sphere solution, followed by centrifugal washing and heat treatment at 500 °C for 5 h to obtain silica with a hollow structure.
[0044] Preparation Example 2
[0045] Mix the hollow silica prepared in Preparation Example 1 with a silane coupling agent (HDTMS: KH550 = 1:1) at a mass ratio of 1:2, stir and mix, filter, retain the solid, and dry to obtain modified nano-silica.
[0046] Boron Nitride Preparation Example
[0047] Preparation Example 3
[0048] Add 0.726 g of tris(hydroxymethyl)aminomethane (Tris) to 600 mL of distilled water and acidify with 1 mol / L dilute hydrochloric acid to make the solution pH weakly alkaline; secondly, add 1.2 g of dopamine hydrochloride (DA) to the solution, stir well, and after DA dissolves, add 3 g of nano hBN sheets, ultrasonically treat for 3 h, and the solution gradually changes from white to gray-black; again, place the obtained solution at 60 °C and let it stand for 24 h, pour the upper layer liquid formed after precipitation and stratification into a vacuum filter, use negative pressure to separate the solute and solvent, rinse the solid matter with distilled water and filter; finally, place the black product in a 60 °C vacuum and dry for 24 h to obtain nano-boron nitride treated with dopamine hydrochloride.
[0049] Silicon Carbide Fiber Preparation Example
[0050] Preparation Example 4
[0051] Take 1 L of isopropanol solution, and successively add 0.5 g of silicon carbide nanowires, 0.5 g of aluminum nitrate nonahydrate, and 0.75 g of phenolic resin; then ultrasonically treat the above solution in an ultrasonic instrument for 3 h to obtain degummed silicon carbide fibers.
[0052] Immerse the degummed silicon carbide fibers in a xylene solution (containing 0.2 g / mL of ferrocene) for 1 h, take them out after soaking and fix them in a chemical vapor deposition container, heat up to 700 °C, spray in a catalyst solution (xylene solution containing 0.5 g / mL of ferrocene) and introduce acetylene, stop spraying the catalyst and acetylene after 2 min, and cool to room temperature to obtain silicon carbide fibers loaded with carbon nanotubes.
[0053] Among them, the silicon carbide nanowires are 20 - 150 μm silicon carbide nanowires from Changsha Saitai New Materials Co., Ltd.
[0054] Preparation Example 5
[0055] Take 1L of isopropanol solution, add 0.5g of silicon carbide nanowires, 0.5g of aluminum nitrate nonahydrate and 0.75g of phenolic resin in sequence; then ultrasonicate the above solution in an ultrasonicator for 3h to obtain degummed silicon carbide fibers.
[0056] The degummed silicon carbide fiber was immersed in a xylene solution (containing 0.2 g / mL ferrocene) for 1 hour, taken out after soaking and fixed in a vapor deposition container, heated to 700°C, sprayed with a catalyst solution (xylene solution containing 0.5 g / mL ferrocene) and acetylene, and the spraying of the catalyst and acetylene was stopped after 2 minutes, and cooled to room temperature to obtain silicon carbide fibers loaded with carbon nanotubes.
[0057] The silicon carbide fiber loaded with carbon nanotubes was placed in a magnetron sputtering instrument and the vacuum degree was adjusted to 10 -4 Then, argon gas was introduced, and FeNi was used as the sputtering target. The sputtering was performed at a power of 800 W for 15 minutes. After one side was completed, it was taken out and the above operation was repeated to obtain magnetized modified silicon carbide fibers.
[0058] The silicon carbide nanowires are 20-150 μm silicon carbide nanowires produced by Changsha Saitai New Materials Co., Ltd.
[0059] Example
[0060] Examples 1-3
[0061] On the one hand, the present application provides a polyimide film comprising 4,4-diaminodiphenyl ether, dianhydride, diamine and thermal conductive filler, and the specific mass is shown in the table below.
[0062] Among them, the dianhydride is selected from the pyromellitic dianhydride produced by Sinopharm Chemical Reagent Co., Ltd., the diamine is selected from the 4,4-diaminodiphenyl ether produced by Wuhan Qiaofeng Chemical Technology Co., Ltd., and the thermal conductive filler includes hexagonal lamellar boron nitride produced by Shanghai Yuhua Industrial Co., Ltd. in a mass ratio of 2:1 and the nano-silicon dioxide prepared in Preparation Example 1.
[0063] On the other hand, the present application provides a method for preparing a high-density phosphate-type positive electrode material, comprising the following steps:
[0064] S1. Filler dispersion: Pre-disperse the thermal conductive filler in the DMAc solution and perform ultrasonic dispersion for 3 h to obtain a dispersion;
[0065] S2, preparation of polyimide solution: adding dianhydride and diamine to the dispersion in sequence, and continuously stirring to obtain a mixed colloid;
[0066] S3. Film preparation: vacuum the mixed colloid to remove bubbles, apply the coating, perform thermal imidization, and demould to obtain a polyimide film.
[0067] Optionally, the thickness of the coating film can be 100 μm, 125 μm, 150 μm, 175 μm, 200 μm or 250 μm. In this embodiment, the thickness of the coating film is 100 μm.
[0068] Table 1 Composition of Examples 1 - 3
[0069] Weight / kg Example 1 Example 2 Example 3 4,4-Diaminodiphenyl ether 50 75 100 Dianhydride 2 6 10 Diamine 3 10 15 Thermal conductive filler 10 18 25
[0070] Example 4
[0071] The difference from Example 3 is that the thermal conductive filler includes boron nitride and nano - silica prepared in Preparation Example 2 with a mass ratio of 2:1.
[0072] Example 5
[0073] The difference from Example 3 is that the thermal conductive filler includes boron nitride prepared in Preparation Example 3 and nano - silica prepared in Preparation Example 2 with a mass ratio of 2:1.
[0074] Example 6
[0075] The difference from Example 3 is that the thermal conductive filler includes boron nitride prepared in Preparation Example 3, nano - silica prepared in Preparation Example 2 and silicon carbide fibers with a mass ratio of 2:1:1.
[0076] Example 7
[0077] The difference from Example 3 is that the thermal conductive filler includes boron nitride prepared in Preparation Example 3, nano - silica prepared in Preparation Example 2 and silicon carbide fibers prepared in Preparation Example 4 with a mass ratio of 2:1:1.
[0078] Example 8
[0079] On the one hand, the present application provides a polyimide film, comprising 100 kg of 4,4 - diaminodiphenyl ether, 10 kg of dianhydride, 15 kg of diamine and 25 kg of thermal conductive filler.
[0080] Among them, the thermal conductive filler includes boron nitride prepared in Preparation Example 3, nano - silica prepared in Preparation Example 2 and silicon carbide fibers prepared in Preparation Example 5 with a mass ratio of 2:1:1.
[0081] On the other hand, the present application provides a preparation method of a high - compact phosphate - type cathode material, comprising the following steps:
[0082] S1. Filler dispersion: The thermal conductive filler is pre - dispersed in a DMAc solution and ultrasonically dispersed for 3 h to obtain a dispersion liquid;
[0083] S2. Preparation of polyimide solution: Add dianhydride and diamine to the dispersion liquid in sequence, and continuously stir to obtain a mixed colloid;
[0084] S3. Film preparation: Evacuate the mixed colloid to remove air bubbles, scrape and coat the film, introduce a vertical external magnetic field with a magnetic field strength of 10 mT, after magnetization treatment for 2 min, perform thermal imidization, and demold to obtain a polyimide film.
[0085] Comparative example
[0086] Comparative example 1
[0087] The difference between this comparative example and Example 3 is that in this comparative example, the thermal conductive filler only includes boron nitride.
[0088] Comparative example 2
[0089] The difference between this comparative example and Example 3 is that in this comparative example, the thermal conductive filler includes boron nitride and nano-silica (solid structure) with a mass ratio of 2:1.
[0090] Performance detection test
[0091] (1) Tensile strength test: Test the tensile properties of the polyimide film according to ASTM D882.
[0092] (2) Thermal conductivity detection: Use a flash method thermal conductivity meter to test the horizontal and vertical thermal conductivity coefficients of the film.
[0093] (3) Dielectric property detection: Use an Agilent 4294ALCR measuring instrument to measure the dielectric properties of the polyimide film at room temperature.
[0094] Table 2 Performance detection
[0095]
[0096] It can be found by comparing the performance detections in Table 2:
[0097] 1. By comparing Examples 1 - 3 with Comparative Examples 1 - 2, it can be found that the tensile strength and thermal conductivity of the polyimide films prepared in Examples 1 - 3 have both increased, while the dielectric properties have decreased. This indicates that in this application, the combination of nano - silica and boron nitride can obtain a composite structure of lamella + particle, which can further improve the binding effect between the thermal - conductive filler and the polyimide substrate, that is, the thermal - conductive filler can synergistically improve the thermal conductivity and mechanical properties of the polyimide film. The nano - silica with a hollow structure, as a thermal - conductive filler, can bring an air phase by virtue of its own hollow structure, causing electronic polarization, orientation polarization, and space - charge polarization in the polyimide film under an external electric field, thereby effectively reducing the dielectric constant of the polyimide film. And as rigid particles, it can play the role of transferring load, absorbing, and dispersing impact energy, further improving the mechanical properties of the polyimide film.
[0098] 2. By comparing Example 4 with Example 3, it can be found that the tensile strength and thermal conductivity of the polyimide film prepared in Example 4 have both increased. This indicates that in this application, after the nano - silica is modified by a silane coupling agent, long - carbon - chain groups are grafted on the surface of the nano - silica, effectively improving the dispersibility of the nano - silica and reducing the possibility of nano - silica agglomeration, enabling the nano - silica to be fully dispersed, preventing the agglomeration of boron nitride, and improving the strength of the polyimide film. In this example, it is preferably to use HDTMS and KH550 in combination to modify the nano - silica, which can not only achieve the combination between nano - silica and boron nitride but also enable the combination between nano - silica and silicon carbide fibers, so that an intertwined three - dimensional structure of lamella + particle + fiber can be formed in the thermal - conductive filler, effectively improving the mechanical properties and thermal conductivity of the film.
[0099] 3. By comparing Example 5 with Example 3, it can be found that the tensile strength and thermal conductivity of the polyimide film prepared in Example 5 have both increased. This indicates that in this application, after being modified by polydopamine, the surface of the boron nitride lamella is relatively rough, which is conducive to the loading of nano - silica, forming a composite structure of lamella + particle in the thermal - conductive filler.
[0100] 4. By comparing Example 6 with Example 3, it can be found that the tensile strength and thermal conductivity of the polyimide film prepared in Example 6 have both increased. This indicates that in this application, due to the one - dimensional linear structure of the silicon carbide fibers, an intertwined fiber network can be formed in the polyimide film, thereby improving the mechanical strength of the polyimide film. In addition, the silicon carbide fibers can be connected to the lamellar structure in the thermal - conductive filler, forming a multi - dimensional composite structure of particle + fiber + lamella. The silicon carbide fibers can connect adjacent lamellar structures to form conductive and heat - conductive channels, further improving the thermal conductivity of the polyimide film.
[0101] 5. By comparing Example 7 and Example 2, it can be found that the tensile strength and thermal conductivity of the polyimide film prepared in Example 7 are both improved. This shows that after loading carbon nanotubes on silicon carbide fibers in this application, the roughness of the silicon carbide fibers can be further increased, the connection paths between the thermal conductive fillers can be increased, a uniformly structured thermal conductive network can be formed in the polyimide film, and the mechanical strength and thermal conductivity of the polyimide film can be improved.
[0102] 6. By comparing Example 12 - 13 and Example 2, it can be found that the tensile strength and thermal conductivity of the polyimide film prepared in Example 8 are both improved. This shows that in this application, under the action of an external magnetic field and driven by magnetic fibers, the thermal conductive network can be stretched in the vertical direction to form a three-dimensional network structure with intersections in both the horizontal and vertical directions, effectively improving the thermal conductivity and mechanical properties of the polyimide film. And because the magnetic fibers are still within the horizontal cross-linked network, the end structures of the fibers are not likely to protrude from the surface of the polyimide film or form protruding points on the surface of the polyimide film, enabling the thermal conductive network to stably exist and conduct heat in the film.
[0103] This specific embodiment is only an interpretation of this application and does not limit this application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as they are within the scope of the claims of this application, they are protected by the patent law.
Claims
1. A method for preparing a polyimide film, characterized in that: The following steps are involved: S1. Filler dispersion: Preliminarily disperse the thermal conductive filler in the DMAc solution and perform ultrasonic dispersion to obtain a dispersion; S2. Preparation of polyimide solution: adding dianhydride and diamine to the dispersion in sequence, and continuously stirring to obtain a mixed colloid; S3. Film preparation: vacuum the mixed colloid to remove bubbles, apply a knife, perform thermal imidization, and demould to obtain a polyimide film.
2. The method for preparing a polyimide film according to claim 1, characterized in that: The polyimide film comprises the following raw materials in parts by weight: 50-100 parts of 4,4-diaminodiphenyl ether; 2-10 parts of dianhydride; 2-15 parts of diamine; Thermal conductive filler 10-25 parts; The thermal conductive filler comprises boron nitride and nano silicon dioxide, and the nano silicon dioxide is a hollow structure.
3. The method for preparing a polyimide film according to claim 2, wherein: The preparation of nano-silica is as follows: ammonia water, ethanol solution and CTAB are placed in a container and stirred to obtain solution A; TEOS is added to solution A, and stirring is continued to obtain a hollow silica sphere solution, and the solution is centrifuged, washed and dried to obtain silica with a hollow structure.
4. The method for preparing a polyimide film according to claim 3, characterized in that: The nano silicon dioxide is nano silicon dioxide modified by a silane coupling agent.
5. The method for preparing a polyimide film according to claim 3, characterized in that: The boron nitride is boron nitride modified by polydopamine.
6. The method for preparing a polyimide film according to claim 5, characterized in that: The filler also includes silicon carbide fibers.
7. The method for preparing a polyimide film according to claim 6, wherein: The silicon carbide fibers are loaded with carbon nanotubes.
8. The method for preparing a polyimide film according to claim 7, characterized in that: The silicon carbide fiber is magnetized silicon carbide fiber.
9. The method for preparing a polyimide film according to claim 2, wherein: The diamine is selected from one or more mixtures of N,N-dimethylacetamide, 2,6-dimethyl-p-phenylenediamine, 4,4-diaminodiphenyl ether, 2,3,5-trimethyl-p-phenylenediamine, and 2,5-di-tert-butyl-p-phenylenediamine; the dianhydride is selected from one or more mixtures of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, and 2,2',3,3'-biphenyltetracarboxylic dianhydride.
10. The method for preparing a polyimide film according to claim 1, characterized in that: In step S3, after the mixed colloid is scraped, a vertical external magnetic field is introduced with a magnetic field strength of 5-15 mT.