Heat-dissipation flame-retardant composite material as well as preparation method and application thereof

Abstract

The invention discloses a heat-dissipation flame-retardant composite material as well as a preparation method and application thereof, and belongs to the field of functional composite materials. The preparation method comprises the following steps: S1, mixing a ceramic filler with a phosphorus-containing modifier, and carrying out inorganic modification to obtain a first modified filler; s2, mixing the first modified filler with an organic modifier to obtain a second modified filler; s3, mixing the second modified filler with the polymer matrix to obtain the heat-dissipation flame-retardant composite material. The organic modifier is at least one of polysilazane, polysilazane and polysiloxane. The phosphorus-containing modifier and the organic modifier are adopted to modify the ceramic filler, so that the flame retardant property, the thermal stability and the high temperature resistance of the composite material are improved, the compatibility between the ceramic filler and the filler and between the filler and a polymer substrate is improved, the dispersity of the ceramic filler in the polymer substrate is improved, and the thermal resistance of the composite material is reduced; and the heat dissipation capability of the composite material is improved.

Description

Technical Field

[0001] The present invention belongs to the field of functional composite materials, and in particular relates to a heat dissipation and flame retardant composite material and a preparation method and application thereof. Background Art

[0002] With the development of miniaturization, integration and multifunctionality of electronic technology, the power density of chips, new energy batteries, communication products, energy storage systems, etc. has increased. Failure to dissipate heat in a timely manner will lead to overheating of devices, reduced performance, and even electrical fires in severe cases. Currently, the commonly used heat dissipation methods include air cooling, liquid cooling, or improving the thermal conductivity of materials by introducing high thermal conductivity fillers into plastic polymers. This polymer-based composite material is composed of a polymer matrix and a thermally conductive filler, and has the advantages of high heat dissipation efficiency, small footprint, and easy performance adjustment. In application scenarios such as thermal interface locations and battery packaging, polymer-based composite materials can improve interfacial heat transfer by filling pores and increasing the effective contact area.

[0003] However, the high power density in electronic devices can lead to local hot spots. On the one hand, polymer-based thermally conductive composite materials need to be able to dissipate heat in a timely manner at room temperature and high temperature. On the other hand, it is also necessary to improve the flame retardancy of the electronic devices themselves to avoid electrical fires. Therefore, the development of high-power density devices has put forward higher requirements on the heat dissipation performance, high temperature resistance, and even flame retardancy of thermally conductive fillers and composite materials used in electronic packaging. In addition, directly mixing thermally conductive fillers into the polymer matrix will cause uneven distribution of the filler, and there will be a large number of pores between the filler and the polymer matrix, which will reduce the heat dissipation performance of the composite material. Existing thermally conductive fillers are generally modified with silane coupling agents to improve the dispersibility of the filler. However, silane coupling agent modification has the problems of low thermal conductivity efficiency, high temperature resistance, and poor flame retardancy, and it is difficult to maintain good heat dissipation performance in high temperature environments.

[0004] CN 110591255 A discloses a substrate material comprising a fluoropolymer and a ceramic filler material, wherein the ceramic filler material is made from ceramic powder modified with a coupling agent. While this invention improves the dispersibility of the ceramic material, it does not consider the high-temperature resistance and flame retardancy of the composite material. JPH10204300A discloses a high-thermal-conductivity resin composition obtained by treating aluminum nitride powder with a phosphate compound and mixing it with an inorganic powder having lipophilic groups on its surface and a resin. This improves the dispersibility of the aluminum nitride in the resin, but does not consider the high-temperature resistance of the composite material. Summary of the Invention

[0005] In order to solve the above problems in the prior art, an object of the present invention is to provide a method for preparing a heat-dissipating flame-retardant composite material.

[0006] Another object of the present invention is to provide a heat-dissipating flame-retardant composite material.

[0007] Another object of the present invention is to provide an application of the heat dissipating and flame-retardant composite material in the preparation of electronic packaging materials.

[0008] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0009] A method for preparing a heat-dissipating flame-retardant composite material comprises the following steps:

[0010] S1. The ceramic filler is mixed with a phosphorus-containing modifier to obtain a first modified filler after inorganic modification;

[0011] S2. The first modified filler is mixed with an organic modifier to obtain a second modified filler;

[0012] S3. Mixing the second modified filler with the polymer matrix to obtain the heat-dissipating flame-retardant composite material.

[0013] The organic modifier is at least one of polysilazane, polycarbosilane, and polysiloxane.

[0014] The present invention adopts phosphorus-containing modifier and organic modifier to modify ceramic filler, the surface reaction of phosphorus-containing modifier and ceramic filler generates flame retardant layer (phosphorus-containing compound), improves the flame retardant performance of composite material, and then improves the thermal stability and high temperature resistance of composite material, and promotes ceramic filler surface to generate more hydroxyl groups, is conducive to being connected with organic modifier.Phosphorus-containing modifier and organic modifier composite use improve the compatibility between ceramic filler and filler, between filler and polymer substrate, improve the dispersibility of ceramic filler in polymer substrate, thus can improve the filling amount of ceramic filler in composite material, be conducive to building the heat conduction network of Unicom in polymer interior, reduce the interface pore between ceramic filler and polymer substrate.Due to polymer insulator is the energy transfer (i.e. phonon heat conduction) produced by lattice vibration, less interface pore can reduce phonon scattering, and stronger interface bonding force is conducive to energy transfer simultaneously, thus improves phonon transmission performance, reduces thermal resistance, improves heat dissipation capacity.

[0015] For easily hydrolyzed ceramic fillers, such as aluminum nitride, since hydrolysis of this type of ceramic filler will greatly reduce thermal conductivity and dispersibility, phosphoric acid can react with it to form an aluminum dihydrogen phosphate layer, which plays a role in inhibiting hydrolysis; organic modifiers can make ceramic fillers hydrophobic, further improving the hydrolysis resistance of easily hydrolyzed ceramic fillers.

[0016] In specific implementation, the present invention selects a variety of ceramic fillers for compound use, which plays the role of particle size grading. The combination of ceramic fillers of different dimensions increases the filling rate of high thermal conductivity ceramics, enables the composite material to have more thermal conduction channels, and improves the thermal conductivity and heat dissipation performance of the material.

[0017] Specifically, the phosphorus-containing modifier is at least one of phosphoric acid, ammonium polyphosphate, ammonium phosphate salt, phosphate, polyphosphate, phosphate ester, phosphonate, phosphaphenanthrene, and phosphazene.

[0018] Specifically, the polysilazane is at least one of methylpolysilazane, vinylpolysilazane, polycarbosilazane, polyborosilazane, phenylpolysilazane, polyureasilazane, hydrogenvinylpolysilazane, and methylvinylpolysilazane.

[0019] Specifically, the polycarbosilane is at least one of liquid polycarbosilane, polycarbomethylsilane, and polyzirconium carbosilane.

[0020] Specifically, the siloxane is at least one of hydroxy-terminated polydimethylsiloxane, polymethylsiloxane, and vinyl polydimethylsiloxane.

[0021] Specifically, the ceramic filler is at least one of aluminum nitride, boron nitride, silicon nitride, aluminum oxide, magnesium oxide, zinc oxide, titanium oxide, silicon oxide, silicon carbide, silicon carbonitride, and diamond.

[0022] Specifically, the mass ratio of the phosphorus-containing modifier to the ceramic filler is (0.1-10):100.

[0023] Specifically, the mass ratio of the organic modifier to the ceramic filler is (0.1-5):100.

[0024] Specifically, the modification method includes dry modification and / or wet modification.

[0025] More specifically, the modification method is wet modification.

[0026] More specifically, the wet modification includes dispersing the ceramic filler in an organic solvent, and then sequentially adding a phosphorus-containing modifier and an organic modifier.

[0027] More specifically, the organic solvent is at least one of methanol, ethanol, isopropanol, acetone, dichloromethane, ether, ethyl acetate, chloroform, benzene, and toluene.

[0028] Specifically, the modification time in step S1 or step S2 is 0.5 to 6 hours.

[0029] Specifically, in step S2, the step further includes heat treatment after mixing with the organic modifier or mixing with the organic modifier again after heat treatment.

[0030] After heat treatment, the organic modifier decomposes and forms a ceramic coating on the surface of the ceramic filler, thereby improving the thermal stability of the modified filler. Mixing with the organic modifier again after heat treatment can further improve the compatibility of the modified filler with the polymer.

[0031] More specifically, the heat treatment temperature is 100-1600° C., and the heat treatment time is 0.5-24 hours.

[0032] Specifically, the polymer matrix is ​​at least one of silicone grease, silicone rubber, epoxy resin, polytetrafluoroethylene, polyimide, polyester, phenolic resin, polypropylene, polycarbonate, nylon, polyetheretherketone, and polyethersulfone.

[0033] Specifically, the mixing temperature in step S1 or step S2 is 25-100°C.

[0034] The present invention also protects the heat dissipation and flame retardant composite material prepared by the above preparation method.

[0035] The present invention also protects the use of the heat dissipation and flame retardant composite material in the preparation of electronic packaging materials.

[0036] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0037] The present invention uses a phosphorus-containing modifier and an organic modifier to modify a ceramic filler. The phosphorus-containing modifier reacts with the surface of the ceramic filler to form a flame retardant layer (phosphorus-containing compound), thereby improving the flame retardancy of the composite material, thereby improving the thermal stability and high-temperature resistance of the composite material. The phosphorus-containing modifier and the organic modifier are used in combination to improve the compatibility between the ceramic filler and the filler, and between the filler and the polymer substrate, improve the dispersibility of the ceramic filler in the polymer substrate, and improve the bonding strength of the above interfaces, thereby increasing the filling amount of the ceramic filler in the composite material, facilitating the construction of a connected heat conduction network within the polymer, reducing the interface pores between the ceramic filler and the polymer substrate, thereby improving phonon transmission performance, reducing thermal resistance, and improving heat dissipation capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of the modification method of the ceramic filler according to the present invention.

[0039] Figure 2 Cross-sectional morphology of the modified aluminum nitride-polytetrafluoroethylene heat dissipation film (80FAlN-PTFE) in Example 1. DETAILED DESCRIPTION

[0040] The present invention is further described below with reference to the examples. These examples are intended to illustrate the present invention only and are not intended to limit the scope of the present invention. Experimental methods in the following examples where specific conditions are not specified are generally performed in accordance with conventional conditions in the art or the conditions recommended by the manufacturer; the raw materials and reagents used, unless otherwise specified, are all commercially available from conventional markets. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention fall within the scope of protection claimed in the present invention.

[0041] Methyl polycarbosilane: Manufacturer: Huada Nanomaterial Technology.

[0042] Liquid polysilazane: Manufacturer: Guangzhou Honghai Chemical Technology Co., Ltd.

[0043] Polydimethylsiloxane: Manufacturer: Dow Corning; Brand: PMX-200.

[0044] Example 1

[0045] This embodiment provides a heat dissipation flame retardant composite material, the preparation method of which includes the following steps:

[0046] S1. Aluminum nitride (AlN) powder was dispersed in dichloromethane (the mass ratio of AlN to dichloromethane was 1:5), ultrasonically dispersed, and stirred. Phosphoric acid (the mass ratio of AlN to phosphoric acid was 100:3) was added and stirred at 30°C for 1 hour to obtain a first modified AlN dispersion.

[0047] S2. Add methyl polysilazane (the mass ratio of methyl polysilazane to aluminum nitride is 1:100) to the above solution and continue stirring at 30°C for 1 hour to obtain an inorganic-organic composite modified aluminum nitride dispersion. The above inorganic-organic composite modified aluminum nitride dispersion is filtered, washed, vacuum dried, and ground to obtain a second modified aluminum nitride powder.

[0048] S3. Mix a polytetrafluoroethylene (PTFE) dispersion, modified aluminum nitride, and ethanol, where the mass ratio of the polytetrafluoroethylene dispersion to the ethanol is 80:20. The modified aluminum nitride filling mass is adjustable within a range of 0.1 to 80 wt.% of the total mass. Stir thoroughly to mix thoroughly. After removing the mixture, pass it through a roller press to obtain a modified aluminum nitride-polytetrafluoroethylene heat dissipation and flame-retardant film material with adjustable thickness. Samples with an aluminum nitride addition of x% are designated as x FAlN-PTFE, where x can be set to 20, 40, 60, 80, or any other value within this range.

[0049] Example 2

[0050] This embodiment provides a heat dissipation flame retardant composite material, the preparation method of which includes the following steps:

[0051] S1. Disperse aluminum nitride and aluminum oxide in diethyl ether (the mass ratio of aluminum nitride, aluminum oxide to diethyl ether is 7:3:20), disperse by ultrasonication, and stir. Add phosphoric acid (the mass ratio of aluminum nitride to phosphoric acid is 100:1), and stir at 30°C for 2 hours to obtain a first modified aluminum nitride-alumina dispersion.

[0052] S2. Liquid polycarbosilane (the mass ratio of liquid polycarbosilane to aluminum nitride is 3:100) is added to the above solution and stirred at 30°C for 2 hours to obtain an inorganic-organic composite modified aluminum nitride dispersion. The above aluminum nitride-alumina dispersion is filtered, washed, and vacuum dried. It is then calcined at 800°C for 2 hours under an argon atmosphere and ground to obtain a second modified aluminum nitride-alumina powder.

[0053] S3. Take 10 parts of polyimide resin dispersion and 10 parts of modified aluminum nitride-alumina powder, stir and mix them thoroughly, take them out and vacuum degas, cast the suspension into a film with a thickness of about 100 μm, and then obtain the aluminum nitride-alumina-polyimide film material through the solvent removal and heat curing process. The specific curing procedure is: first cure at 80°C for 1 hour; then cure at 120°C for 1 hour; then cure at 200°C for 1 hour; and finally cure at 300°C for 2 hours to obtain the heat dissipating and flame-retardant composite material.

[0054] Example 3

[0055] This embodiment provides a heat dissipation flame retardant composite material, the preparation method of which includes the following steps:

[0056] S1. Phosphoric acid and ethanol (mass ratio of phosphoric acid to ethanol is 1:20) were added to a beaker. After uniform dispersion, hexagonal boron nitride and diamond powder (mass ratio of hexagonal boron nitride, diamond powder to ethanol is 9:1:20) were added. The mixture was stirred at 60°C for 6 hours to obtain a first modified hexagonal boron nitride-diamond dispersion.

[0057] S2. Add hydroxyl-terminated polydimethylsiloxane (the mass ratio of hydroxyl-terminated polydimethylsiloxane to boron nitride is 1:20) dropwise to the above solution and continue stirring at 60°C for 2 hours. Filter the above suspension, rinse several times with anhydrous ethanol, dry under vacuum at 110°C overnight, and grind to obtain a second modified boron nitride-diamond composite powder.

[0058] S3. Take 10 parts of bisphenol A epoxy resin (E-51) and 8 parts of methyltetrahydrophthalic anhydride (MeTHPA), stir at 60°C for 1 hour, then add 3 parts of modified boron nitride-diamond composite material and continue stirring for 1 hour. Transfer the above resin slurry to a mold coated with a release agent, degas under vacuum for 1 hour, and then heat cure. The specific curing procedure is as follows: first cure at 100°C for 2 hours, then cure at 150°C for 2 hours, and finally cure at 200°C for 4 hours to obtain the heat-dissipating flame-retardant composite material.

[0059] Example 4

[0060] This embodiment provides a heat dissipation flame retardant composite material, the preparation method of which includes the following steps:

[0061] S1. Add phosphate and dichloromethane (the mass ratio of phosphate to dichloromethane is 1:20) to a beaker, disperse them evenly, then add alumina (the mass ratio of alumina to dichloromethane is 1:5), stir for 2 hours, and obtain the first modified alumina powder.

[0062] S2. Add polyborosilazane (polyborosilazane to alumina mass ratio of 1:20) dropwise to the above solution and continue stirring for 2 hours. Filter the above suspension, wash several times, dry under vacuum at 50°C overnight, and grind to obtain modified alumina.

[0063] S3. Take 10 parts of thermoplastic polyimide micropowder, 5 parts of modified alumina, and 10 parts of acetone, mix and stir evenly, degas, cast the slurry onto the surface of a clean glass plate, dry it at 50°C, transfer it to a hot pressing amination furnace, and heat cure it at 400°C for 2 hours to obtain a polyimide-based composite heat-dissipating flame-retardant film.

[0064] Example 5

[0065] This embodiment provides a heat dissipation flame retardant composite material, the preparation method of which includes the following steps:

[0066] S1. Add phosphoric acid and ethanol (the mass ratio of phosphoric acid to ethanol is 1:50) to a beaker, disperse them evenly, then add aluminum nitride (the mass ratio of aluminum nitride to ethanol is 1:10). Stir at 60°C for 2 hours, filter, and vacuum dry at 60°C overnight. Grind and collect to obtain the first modified aluminum nitride.

[0067] S2. Add the first modified aluminum nitride and dichloromethane (the mass ratio of the first modified aluminum nitride to dichloromethane is 1:20) into a beaker, stir evenly, add methylpolysilazane (the mass ratio of methylpolysilazane to the first modified aluminum nitride is 1:50), stir at room temperature for 2 hours, filter the above suspension, wash several times, vacuum dry at 50°C overnight, grind and collect, and heat treat at 600°C for 2 hours to obtain the second modified aluminum nitride.

[0068] S3. Add the second modified aluminum nitride and dichloromethane (the mass ratio of the second modified aluminum nitride to dichloromethane is 1:20) into a beaker, stir evenly, then add liquid polysilicon carboxylate (the mass ratio of liquid polysilicon carboxylate to the second modified aluminum nitride is 3:100), stir at room temperature for 2 hours, filter the above suspension, wash several times, vacuum dry at 110°C overnight, grind and collect to obtain the modified aluminum nitride material.

[0069] S4. Take 10 parts of bisphenol A epoxy resin (E-51) and 8 parts of methyltetrahydrophthalic anhydride (MeTHPA), stir at 60°C for 1 hour, then add 3 parts of modified aluminum nitride material and continue stirring for 1 hour. Transfer the above resin slurry to a mold coated with a release agent, degas under vacuum for 1 hour, and then heat cure. The specific curing procedure is as follows: first cure at 100°C for 2 hours, then cure at 150°C for 2 hours, and finally cure at 200°C for 4 hours to obtain the heat-dissipating flame-retardant composite material.

[0070] Comparative Example 1

[0071] This comparative example provides a method for preparing a composite material, comprising the following steps:

[0072] Aluminum nitride was directly mixed with a polytetrafluoroethylene dispersion and ethanol (the mass ratio of polytetrafluoroethylene to ethanol was 80:20, and the mass ratio of aluminum nitride to polytetrafluoroethylene was 80:20). The mixture was thoroughly stirred and evenly mixed. After removal, the mixed material was passed through a roller press to obtain an aluminum nitride-polytetrafluoroethylene heat dissipation film material with adjustable thickness, which is the sample of Comparative Example 1. The filling mass of aluminum nitride was 80 wt.% of the total mass.

[0073] Comparative Example 2

[0074] This comparative example provides a method for preparing a composite material, comprising the following steps:

[0075] S1. Disperse aluminum nitride powder in dichloromethane (the mass ratio of aluminum nitride to dichloromethane is 1:5), disperse by ultrasonication, and stir. Add phosphoric acid (the mass ratio of aluminum nitride to phosphoric acid is 100:3), and stir at 30°C for 1 hour to obtain an inorganic modified aluminum nitride dispersion.

[0076] S2. The aluminum nitride dispersion is filtered, washed, vacuum-dried, and ground to obtain inorganic modified aluminum nitride powder.

[0077] S3. The inorganic modified aluminum nitride was directly mixed with a polytetrafluoroethylene dispersion and ethanol (wherein the mass ratio of polytetrafluoroethylene to ethanol was 80:20, and the mass ratio of aluminum nitride to polytetrafluoroethylene was 80:20). The mixture was thoroughly stirred and evenly mixed. After removal, the mixed material was passed through a roller press to obtain an aluminum nitride-polytetrafluoroethylene heat dissipation film material with adjustable thickness, which is the sample of Comparative Example 2. The filling mass of the inorganic modified aluminum nitride was 80 wt.% of the total mass.

[0078] Comparative Example 3

[0079] This comparative example provides a method for preparing a composite material, comprising the following steps:

[0080] S1. Disperse aluminum nitride powder in dichloromethane (the mass ratio of aluminum nitride to dichloromethane is 1:5), disperse by ultrasonication, and stir. Add methylpolysilazane (the mass ratio of methylpolysilazane to aluminum nitride is 1:100), and stir at 30°C for 1 hour to obtain an inorganic modified aluminum nitride dispersion.

[0081] S2. The aluminum nitride dispersion is filtered, washed, vacuum-dried, and ground to obtain organically modified aluminum nitride powder.

[0082] S3. Aluminum nitride was directly mixed with a polytetrafluoroethylene dispersion and ethanol (the mass ratio of polytetrafluoroethylene to ethanol was 80:20, and the mass ratio of aluminum nitride to polytetrafluoroethylene was 80:20). The mixture was thoroughly stirred and evenly mixed. After removal, the mixed material was passed through a roller press to obtain an aluminum nitride-polytetrafluoroethylene heat dissipation film material with adjustable thickness, which is the sample of Comparative Example 3. The filling mass of the organically modified aluminum nitride was 80 wt.% of the total mass.

[0083] Comparative Example 4

[0084] This comparative example provides a method for preparing a composite material, comprising the following steps:

[0085] S1. Disperse aluminum nitride powder in ethanol (the mass ratio of aluminum nitride to ethanol is 1:9), ultrasonically disperse and stir, add pre-hydrolyzed silane coupling agent KH-550 (the mass ratio of silane coupling agent to aluminum nitride is 3:100), and stir at 30°C for 1 hour to obtain a silane-modified aluminum nitride dispersion.

[0086] S2. The aluminum nitride dispersion is filtered, washed, vacuum-dried, and ground to obtain silane-modified aluminum nitride powder.

[0087] S3. Aluminum nitride was directly mixed with a polytetrafluoroethylene dispersion and ethanol (the mass ratio of polytetrafluoroethylene to ethanol was 80:20, and the mass ratio of aluminum nitride to polytetrafluoroethylene was 80:20). The mixture was thoroughly stirred and evenly mixed. After removal, the mixed material was passed through a roller press to obtain an aluminum nitride-polytetrafluoroethylene heat dissipation film material with adjustable thickness, which is the sample of Comparative Example 3. The filling mass of the organically modified aluminum nitride was 80 wt.% of the total mass.

[0088] Performance Testing

[0089] (1) Powder performance test:

[0090] The modified aluminum nitride powders obtained after steps S1 and S2 in Example 1 and Comparative Examples 1-4 were tested for powder properties according to the following standards:

[0091] Contact angle: GB / T 42694; Aging test: GB / T 2423.50.

[0092] The test results are as follows:

[0093] Table 1 Powder performance test results

[0094]

[0095] Table 1 shows the performance of the aluminum nitride powders before and after modification in Example 1 and Comparative Examples 1-4. It can be seen that the modified aluminum nitride powders exhibit hydrophobic and oleophilic properties, thanks to the successful grafting of methylpolysilazane onto the powder surface. This facilitates the powder's dispersibility and compatibility within the polymer matrix. At the same addition level, the composite material exhibits lower viscosity and improved processability. Furthermore, 1000-hour aging tests (temperature: 85°C; relative humidity: 85%) demonstrate that the modified aluminum nitride powders exhibit superior hydrolysis resistance. This is due to the phosphoric acid modification creating an anti-hydrolysis layer on their surface, while the organic modifier also hinders the reaction of water molecules with the aluminum nitride raw material by increasing hydrophobicity.

[0096] (2) Composite material performance test

[0097] The modified aluminum nitride-polytetrafluoroethylene heat dissipation film material sample with an aluminum nitride addition of 80% in Example 1 and the modified aluminum nitride-polytetrafluoroethylene heat dissipation film material samples in Comparative Examples 1-4 were taken and their performance was tested according to the following standards:

[0098] Dispersion uniformity: GB / T 41316; Thermal conductivity: ASTM D 5470; Contact thermal resistance: ASTM D 5470; Flame retardancy: UL94.

[0099] The test results are as follows:

[0100] Table 2 Composite material performance test results

[0101]

[0102] Table 2 shows the test results for the 80FAlN-PTFE heat dissipation composite materials of Example 1 and the modified aluminum nitride-polytetrafluoroethylene (PTFE) heat dissipation composite materials of Comparative Examples 1-4. Visual inspection revealed good dispersibility of the modified aluminum nitride powder in the PTFE dispersion, demonstrating that the thermally conductive composite filler obtained by the present invention is easily dispersed in the polymer matrix. This is because the organic modification layer improves the compatibility and dispersibility of the powder particles in the polymer matrix.

[0103] It can be seen from the thermal conductivity test results that compared with the comparative example, the composite material prepared by the present invention exhibits good heat dissipation capacity. On the one hand, this is because the ceramic fillers are interconnected and a thermal conductive network is constructed inside the composite material; on the other hand, good surface treatment makes the filler powder-filler powder and filler powder-polymer matrix compatible, thereby realizing efficient heat transfer.

[0104] The contact thermal resistance reflects the contact condition of the composite material between the heat source and heat sink (i.e., the heating end and the heat dissipation end), which affects the material's actual heat dissipation performance. During testing, under a certain external pressure (40 psi), the modified thermally conductive powder in the composite material will move slightly, better conforming to the rough surfaces of the heat source and heat sink, and achieving a larger actual contact area. The test results show that the comparative example has a larger contact thermal resistance, while the composite material prepared by the present invention has a lower contact thermal resistance, indicating that the composite material has good spatial adaptability and excellent heat dissipation performance.

[0105] The flame retardant test results show that the composite material has excellent flame retardant properties. Figure 2 This is a cross-sectional morphology of the modified aluminum nitride-polytetrafluoroethylene heat dissipation film (80FAlN-PTFE) in Example 1. As can be seen from the figure, the ceramic fillers are relatively evenly distributed in the polymer matrix and the ceramic fillers are in contact with each other, which helps to form a heat conduction network.

[0106] (3) Composite material aging performance test

[0107] To characterize the high-temperature resistance of the material system, the composite materials with 80 wt.% aluminum nitride added in Example 1 and Comparative Example 4 were placed in a 200°C oven and aged for 1000 h. The performance was then tested using the following method:

[0108] Thermal conductivity: ASTM D 5470; contact thermal resistance: ASTM D 5470. The test results are as follows:

[0109] Table 3 Composite material aging performance test results

[0110]

[0111] As shown in Table 3, the 80FAlN-PTFE in Example 1 maintains good thermal conductivity and contact thermal resistance after aging at 200°C for 1000 hours, demonstrating that the composite material of the present invention has excellent high-temperature resistance. In contrast, the composite material in Comparative Example 4, with the same additive amount, exhibits a significant decrease in thermal conductivity and an increase in contact thermal resistance after aging at 200°C for 1000 hours. This is because modification with a silane coupling agent alone is insufficient to impart hydrolysis resistance to the aluminum nitride filler. Furthermore, silane coupling agents have poor heat resistance and are unstable in prolonged high-temperature environments, resulting in poor compatibility between the filler and the polymer.

[0112] The performance test results of the composite materials obtained in Examples 2 to 5 are basically similar to those in Example 1, and will not be further described here.

[0113] In summary, the composite thermally conductive filler and the polymer-based composite material based on the composite thermally conductive filler proposed in the present invention are promising for use in the packaging field to solve problems such as poor filler dispersion, insufficient heat dissipation performance, and poor high-temperature stability.

[0114] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a heat dissipating flame retardant composite material, characterized in that: The following steps are involved: S1. mixing a ceramic filler with a phosphorus-containing modifier, and obtaining a first modified filler after inorganic modification; S2. mixing the first modified filler with an organic modifier to obtain a second modified filler; S3. Mixing the second modified filler with the polymer matrix to obtain the heat dissipating flame retardant composite material; The organic modifier is at least one of polysilazane, polycarbosilane and polysiloxane.

2. The preparation method according to claim 1, characterized in that: The phosphorus-containing modifier is at least one of phosphoric acid, ammonium polyphosphate, ammonium phosphate salt, phosphate, polyphosphate, phosphate ester, phosphonate, phosphaphenanthrene and phosphazene.

3. The preparation method according to claim 1, characterized in that: The polysilazane is at least one of methyl polysilazane, vinyl polysilazane, polycarbosilazane, polyborosilazane, phenyl polysilazane, polyurea silazane, hydrogen vinyl polysilazane and methyl vinyl polysilazane.

4. The preparation method according to claim 1, characterized in that: The polycarbosilane is at least one of liquid polycarbosilane, polycarbomethylsilane and polyzirconocarbosilane.

5. The preparation method according to claim 1, characterized in that: The siloxane is at least one of hydroxy-terminated polydimethylsiloxane, polymethylsiloxane and vinyl polydimethylsiloxane.

6. The preparation method according to claim 1, characterized in that: The mass ratio of the phosphorus-containing modifier to the ceramic filler is (0.1-10):

100.

7. The preparation method according to claim 1, characterized in that: The mass ratio of the organic modifier to the ceramic filler is (0.1-5):

100.

8. The preparation method according to claim 1, characterized in that: In the step S2, the step of mixing with the organic modifier further includes heat treatment or mixing with the organic modifier again after the heat treatment.

9. The heat dissipating and flame-retardant composite material prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the heat dissipating and flame retardant composite material as claimed in claim 9 in preparing electronic packaging materials.

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