High-thermal-conductivity insulating polyamide powder coating and preparation method thereof

Abstract

The invention discloses a high-thermal-conductivity insulating polyamide powder coating and a preparation method thereof, and belongs to the technical field of polymer modification. The preparation method comprises the following steps: dispersing a metal oxide in a resin matrix through a solvent precipitation method to obtain a modified polyamide suspension; dispersing a heat-conducting auxiliary agent in the modified polyamide suspension through a solvent mixing method; and finally, the leveling agent and other auxiliaries are mechanically stirred and mixed, so that the coating can be coated after being heated and melted after being sprayed. The three-dimensional isolation structure formed by the invention is easier to form an effective heat-conducting network after the material is formed, so that the heat conductivity coefficient of the material is greatly improved, and meanwhile, the problem that the heat-conducting filler is agglomerated in polyamide is effectively solved, so that the surface flatness of a coating film is improved. On the premise that the mechanical property of the polyamide material is not sacrificed, the powder coating has excellent heat-conducting property.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer modification, and particularly relates to a high thermal conductivity and insulation polyamide powder coating and a preparation method thereof. Background Art

[0002] Powder coatings are solvent-free coatings primarily composed of a mechanical mixture of resins, pigments, fillers, and leveling agents. Compared to traditional solvent-based coatings, powder coatings offer advantages such as zero solvent emissions, high solids content, and recyclability. Consequently, they are widely used in applications such as home appliances, automotive, and construction. High-thermal-conductivity polyamide coatings, as an emerging high-performance thermal management material, have broad application prospects in the electronics, electrical, and aerospace sectors due to their excellent wear resistance, insulation, corrosion resistance, and processability.

[0003] As the core component of the new generation of intelligent lighting systems, light-emitting diodes (LEDs) have the advantages of high integration, high brightness, and high reliability. Among them, LED matrix headlights are gradually replacing traditional halogen and xenon headlights and are widely used in automotive headlights and daytime running lights. However, LEDs generate large and concentrated heat, which makes heat dissipation a key factor restricting their luminous efficiency and service life. Metal-based heat dissipation materials such as aluminum alloys are widely used in LED radiators due to their good thermal conductivity and lightweight properties, but they have defects such as easy corrosion. Traditional electroplating or chemical plating processes are complicated, and a layer of high thermal conductivity coating is usually applied to the surface of the radiator through spraying or dipping. In order to meet the trend of automated and environmentally friendly production and improve material utilization, the current solution is to use high thermal conductivity polyamide powder coating as raw material and adopt electrostatic spraying process to achieve high-precision coating of the radiator. This solution is expected to replace the solvent-based coating process and become the mainstream solution for radiator coating of LED thermal management systems in the future.

[0004] However, this technology is still in its early stages of development and faces many challenges that need to be addressed. First, although the thermal conductivity of high thermal conductivity polyamide coatings is better than that of traditional polyamide materials, there is still a certain gap compared to metal materials, and it is difficult to meet the heat dissipation needs of electronic components. Generally, a high filling method of thermal conductive fillers is required to enhance thermal conductivity. However, excessive filling of fillers will affect the processing performance of composite materials, so it is necessary to find a balance between thermal conductivity and processability. Secondly, certain high thermal conductivity fillers such as carbon-based materials or metal powders may affect the charging efficiency of powder coatings and the insulation of materials, and electrical insulation is crucial to the safety of LED lamps. Finally, the agglomeration and uneven dispersion of fillers will reduce the flatness of the coating and affect the thermal conductivity and mechanical properties of the coating. Chinese patent CN109705725A mixes graphene, polyamide and other raw materials by mechanical blending and extrudes them into tablets, crushes and sieves them to obtain powder coatings with excellent thermal conductivity. The disadvantage is that the thermal conductive fillers have poor dispersion uniformity and poor insulation. Overall, while high-thermal-conductivity polyamide coating technology holds great promise, it still faces numerous challenges in thermal conductivity and processability, requiring continued technological innovation and process improvements to address these challenges. Therefore, the development of high-thermal-conductivity and high-insulation polyamide powder coatings for LED thermal management systems represents a significant market need. Summary of the Invention

[0005] The purpose of the present invention is to provide a high thermal conductivity insulating polyamide powder coating and a preparation method thereof. By improving the preparation process, the problem of agglomeration of thermal conductive fillers in polyamide is solved, thereby improving the surface smoothness of the coating. Without sacrificing the mechanical properties of the polyamide material, the powder coating can have excellent thermal conductivity.

[0006] In order to achieve the above object, the present invention provides a method for preparing a high thermal conductive insulating polyamide powder coating, which specifically includes three implementation steps: solvent precipitation, solvent mixing and mechanical mixing:

[0007] S1. Solvent precipitation: polyamide resin, metal oxide nanoparticles and solvent are placed in a sealed autoclave, and the temperature and pressure are increased under a protective atmosphere while stirring; when the temperature is between 140°C and 220°C, the temperature is maintained for 2 hours to allow the resin to fully dissolve in the solvent; then the pressure of the autoclave is uniformly released to normal pressure within 2 hours, the temperature is maintained for 1 hour, and the mixture is slowly cooled to room temperature under low-speed stirring to obtain a modified polyamide suspension; preferably, the solvent is anhydrous ethanol; and the protective atmosphere is an inert gas atmosphere or a nitrogen atmosphere;

[0008] S2. Solvent mixing: The suspension is transferred to a glass reactor, and a first type thermal conductive additive and a second type thermal conductive additive are added, followed by dispersion under mechanical stirring and ultrasonic-assisted treatment for 2 hours. The solvent is then recovered by vacuum distillation, and the remaining product is vacuum dried, ball-milled, and sieved to obtain a polyamide-based powder material.

[0009] S3. Mechanical mixing: 100 parts of polyamide-based powder material, 0.1-0.2 parts of leveling agent, 0-0.2 parts of color powder and 0-0.2 parts of antioxidant are put into a high-speed mixer and mechanically mixed to obtain a high thermal conductive insulating polyamide powder coating.

[0010] Preferably, the polyamide resin in step S1 is at least one of a condensation polymer of an aliphatic or aromatic dicarboxylic acid and an aliphatic diamine, a condensation polymer of an aliphatic dicarboxylic acid and an aromatic diamine, and a copolymer having a polyamide condensation polymer as a copolymer component. More preferably, the polyamide resin is at least one of PA6, PA56, PA66, MXD6, PA510, PA513, PA610, PA612, PA1010, PA1012, PA11, PA12, and PA1212.

[0011] Preferably, the metal oxide nanoparticles in step S1 are metal oxide nanoparticles with high thermal conductivity. More preferably, the metal oxide nanoparticles are at least one of silicon oxide (SiO2), aluminum oxide (Al2O3), titanium oxide (TiO2), zinc oxide (ZnO), magnesium oxide (MgO), zirconium oxide (ZrO), molybdenum oxide (MoO2 or MoO3), cerium oxide (CeO2), and beryllium oxide (BeO).

[0012] Preferably, the amount of the metal oxide nanoparticles used in step S1 is 0.1-2% of the amount of the polyamide used, by mass;

[0013] Preferably, the amount of anhydrous ethanol used in step S1 is 5-15 times the amount of polyamide used, based on mass;

[0014] Preferably, in step S1, the heating rate is 10-20°C / min, and the stirring rate is 50-150 rpm;

[0015] Preferably, in step S1, the cooling rate is 2-5°C / min, and the stirring rate is 10-30 rpm;

[0016] Preferably, the thermal conductive additive in step S2 is a nitride or a carbide. More preferably, the nitride or carbide is at least one of boron nitride (BN), aluminum nitride (AlN), silicon nitride (Si3N4), and silicon carbide (SiC);

[0017] Preferably, the amount of the thermal conductive additive in step S2 is 10-30% by mass of the polyamide in step S1;

[0018] Preferably, the second type of thermal conductive additive in step S2 is a long rod-shaped or thin-sheet carbon-based filler. More preferably, the second type of thermal conductive additive is at least one of carbon fiber, carbon nanotube, graphite, graphene, graphene oxide, and diamond;

[0019] Preferably, the amount of the second type of thermal conductive additive used in step S2 is 2-5% of the amount of polyamide used in step S1, by mass;

[0020] Preferably, in step S2, the stirring rate is 50-1000 rpm, and the ultrasonic treatment temperature is 60-80° C.;

[0021] Preferably, the average particle size (D50) of the polyamide-based powder material in step S2 is 40 to 80 μm;

[0022] Preferably, the leveling agent in step S3 is at least one of silicone, acrylate, and fluorocarbon leveling agents; and / or, the color powder in step S3 is at least one of titanium dioxide, zinc sulfide, zinc titanium yellow, barium sulfate, calcium carbonate, talc, cobalt oxide, ultramarine, and other colored inorganic pigments; and / or, the antioxidant in step S3 is at least one of hindered phenol antioxidants, hindered amine antioxidants, and phosphite antioxidants;

[0023] Preferably, in step S3, the mechanical mixing rate is 600-1200 rpm, and the mixing time is 3-10 min;

[0024] Compared with the prior art, the preparation method provided by the present invention disperses thermally conductive metal oxide nanoparticles in a polyamide resin matrix by a solvent precipitation method to obtain a modified polyamide suspension; disperses a first type of thermal conductive additive such as nitride / carbide and a second type of thermal conductive additive such as a long rod-shaped or thin-sheet carbon-based filler in the suspension by a solvent mixing method; and finally, mixes other additives such as a leveling agent by mechanical stirring. After spraying, the additives are heated and melted to form a coating, and a high thermal conductivity coefficient and coating film flatness are maintained. The method has the following beneficial effects:

[0025] (1) In the solvent precipitation, ethanol is used as the solvent, accompanied by high-speed stirring, and the polyamide in the reactor is fully dissolved at high temperature and high pressure, and the metal oxide nanoparticles are also uniformly dispersed in the solvent; during the cooling process, the appropriate metal oxide nanoparticles provide the crystal nuclei required for the polyamide crystallization, and the polyamide changes from the original homogeneous nucleation to heterogeneous nucleation, the crystallization speed is accelerated, the polyamide continues to grow around the core and precipitates in the form of crystals, and the particle size distribution becomes more uniform. At the same time, the metal oxide nanoparticles are uniformly dispersed in the polyamide particles. The present invention limits the amount of metal oxide nanoparticles to 0.1-2% of the amount of polyamide. When the metal oxide nanoparticles are excessive, on the one hand, the nanoparticles themselves are easy to agglomerate, affecting the sphericity. On the other hand, if the amount is too high, it will lead to the formation of more crystal nuclei, thereby producing more polyamide particles, smaller particle size, and wider particle size distribution.

[0026] (2) Ethanol is used as a dispersant in the solvent mixture, and the interface compatibility between the thermal conductive additive and the polyamide is improved by heating, high-speed stirring and ultrasonic treatment, so that the nitride / carbide and carbon-based material are selectively dispersed on the surface of the polyamide particles, forming an isolation structure and enhancing the heat conduction efficiency. As a one-dimensional or two-dimensional filler, the long rod-shaped or thin-sheet carbon-based material has a high intrinsic thermal conductivity and synergizes with the metal oxide and nitride / carbide. At the same time, its intrinsic electrical conductivity is also very high, so the present invention limits its dosage to 2-5% of the polyamide dosage. In application, after being formed by spraying or dipping processes, the metal oxide, nitride / carbide and the long rod-shaped or thin-sheet carbon-based material uniformly dispersed in the polyamide matrix are more likely to overlap with each other, thereby forming an effective three-dimensional heat conduction network, greatly improving the thermal conductivity coefficient of the material. Finally, the present invention effectively solves the problem of agglomeration of thermal conductive fillers in the polymer, thereby improving the surface smoothness of the coating film, and can achieve excellent thermal conductivity of the powder coating without sacrificing the mechanical properties of the polyamide material.

[0027] (3) Additives known to those skilled in the art, such as antioxidants and color powders, are added to the system by mechanical mixing after the precipitation stage in order to ensure isothermal conditions in both the nucleation and precipitation stages in the solvent precipitation process and to avoid thermal heterogeneity in the reactor, which would result in a decrease in particle sphericity and a wider particle size distribution. DETAILED DESCRIPTION

[0028] To facilitate understanding of the present invention, the present invention will be described more fully below in conjunction with specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to provide a more thorough and comprehensive understanding of the disclosure of the present invention.

[0029] Unless otherwise defined, technical and scientific terms used in the following examples have the same meanings as commonly understood by those skilled in the art to which this invention pertains. The experimental reagents used in the following examples, unless otherwise specified, are conventional biochemical reagents; and the experimental methods described, unless otherwise specified, are conventional methods.

[0030] The technical solution of the present invention is described in detail below through specific embodiments.

[0031] The specific information of the raw materials used in the following examples and comparative examples is as follows:

[0032] The polyamide resin is PA1012 or PA612 resin, and the melt index is 20g / 10min at 230℃ / 2.16kg.

[0033] Metal oxide nanoparticles 1: titanium dioxide, R103, DuPont, USA;

[0034] Metal oxide nanoparticles 2: aluminum oxide, Alu C, Evonik, Germany;

[0035] Class I thermal conductive additive 1: Boron nitride, GBN-100, Ya'an Baitu High-tech Materials Co., Ltd.

[0036] Class I thermal conductive additive 2: aluminum nitride, TA-F2, Ya'an Baitu High-tech Materials Co., Ltd.

[0037] Type II thermal conductive additive 1: multi-walled carbon nanotubes, CP1002M, LG Chem, South Korea;

[0038] Type II thermal conductive additive 2: graphene, XF022, Xianfeng Nanomaterial Technology Co., Ltd.

[0039] Leveling agent: polyacrylate, BYK-180, BYK Chemicals, Germany;

[0040] Color powder: Cobalt blue, K6310 PB28, BASF, Germany;

[0041] Antioxidant: Phosphite antioxidant, Irganox 168, BASF, Germany.

[0042] Example 1

[0043] A high thermal conductivity insulating polyamide powder coating, the preparation method of which comprises the following steps:

[0044] S1. Solvent precipitation. Place 100 parts of PA1012 resin, 1 part of TiO2, and 800 parts of anhydrous ethanol into a sealed autoclave. Raise the temperature and pressure at 10°C / min while stirring at 60 rpm under a nitrogen atmosphere. Maintain the temperature at 160°C for 2 hours. Then, evenly release the pressure in the autoclave to atmospheric pressure over 2 hours, maintain the pressure for 1 hour, and cool to room temperature at 5°C / min while stirring slowly to obtain a modified PA1012 ethanol suspension.

[0045] S2. Solvent mixing. The suspension was transferred to a glass reactor, and 15 parts of boron nitride and 3 parts of carbon nanotubes were added. The mixture was then ultrasonically dispersed at 70°C for 2 hours under mechanical stirring at 600 rpm. The solvent was then recovered by vacuum distillation. The remaining product was vacuum dried, ball-milled, and sieved to obtain a polyamide-based powder material with an average particle size (D50) of 50 μm.

[0046] S3. Mechanical mixing: 100 parts of polyamide-based powder material, 0.1 parts of leveling agent, 0.1 parts of color powder, and 0.1 parts of antioxidant are placed in a high-speed mixer and stirred continuously at 1000 rpm for 3 minutes to obtain a polyamide powder coating.

[0047] Example 2

[0048] This embodiment provides a highly thermally conductive and insulating polyamide powder coating, the preparation method of which is the same as that of Example 1, except that: in this embodiment, step S1 is as follows: 100 parts of PA612 resin, 1 part of Al2O3, and 700 parts of anhydrous ethanol are placed in a sealed autoclave, and the temperature and pressure are increased at 10°C / min under a nitrogen atmosphere while stirring at 60 rpm. When the temperature reaches 180°C, the temperature is maintained for 2 hours; then, the pressure of the autoclave is uniformly released to atmospheric pressure over 2 hours, the temperature is maintained for 1 hour, and the modified PA612 ethanol suspension is cooled to room temperature at 5°C / min while stirring at a low speed, to obtain a suspension.

[0049] Example 3

[0050] This embodiment provides a highly thermally conductive and insulating polyamide powder coating, the preparation method of which is the same as that of Example 1, except that: in this embodiment, step S1 is as follows: 100 parts of PA1012 resin, 0.1 parts of TiO2, and 500 parts of anhydrous ethanol are placed in a sealed autoclave, and the temperature and pressure are increased at 10°C / min under a nitrogen atmosphere while stirring at 60 rpm. When the temperature reaches 190°C, the temperature is maintained for 2 hours; then, the pressure of the autoclave is uniformly released to atmospheric pressure over 2 hours, the temperature is maintained for 1 hour, and the modified PA1012 ethanol suspension is cooled to room temperature at 5°C / min under low-speed stirring to obtain a suspension.

[0051] Example 4

[0052] This embodiment provides a highly thermally conductive and insulating polyamide powder coating, the preparation method of which is the same as that of Example 1, except that: in this embodiment, step S1 is as follows: 100 parts of PA1012 resin, 2 parts of Al2O3, and 1500 parts of anhydrous ethanol are placed in a sealed autoclave, and the temperature and pressure are increased at 10°C / min under a nitrogen atmosphere while stirring at 60 rpm. When the temperature reaches 170°C, the temperature is maintained for 2 hours; then, the pressure in the autoclave is uniformly released to atmospheric pressure over 2 hours, the temperature is maintained for 1 hour, and the modified PA1012 ethanol suspension is cooled to room temperature at 5°C / min while stirring at a low speed, to obtain a suspension.

[0053] Example 5

[0054] This embodiment provides a highly thermally conductive and insulating polyamide powder coating, the preparation method of which is the same as that of Example 1, except that: in this embodiment, step S2 is: transferring the suspension to a glass reactor, adding 10 parts of boron nitride and 2 parts of graphene, and then ultrasonically dispersing the mixture at 70°C for 2 hours under mechanical stirring at 600 rpm, followed by vacuum distillation to recover the solvent, and vacuum drying, ball milling, and sieving the remaining product to obtain a polyamide-based powder material with an average particle size (D50) of 50 μm;

[0055] Example 6

[0056] This embodiment provides a highly thermally conductive and insulating polyamide powder coating, the preparation method of which is the same as that of Example 1, except that: in this embodiment, step S2 is: transferring the suspension to a glass reactor, adding 30 parts of aluminum nitride and 5 parts of carbon nanotubes, and then ultrasonically dispersing at 70° C. for 2 hours under mechanical stirring at 600 rpm, followed by vacuum distillation to recover the solvent, and vacuum drying, ball milling, and sieving the remaining product to obtain a polyamide-based powder material with an average particle size (D50) of 50 μm;

[0057] Example 7

[0058] This embodiment provides a highly thermally conductive and insulating polyamide powder coating, the preparation method of which is the same as that of Example 2, except that: in this embodiment, step S2 is: transferring the suspension to a glass reactor, adding 15 parts of aluminum nitride and 3 parts of graphene, and then ultrasonically dispersing the mixture at 70° C. for 2 hours under mechanical stirring at 600 rpm, followed by vacuum distillation to recover the solvent, and vacuum drying, ball milling, and sieving the remaining product to obtain a polyamide-based powder material with an average particle size (D50) of 50 μm;

[0059] Comparative Example 1

[0060] This comparative example proposes a polyamide powder coating, the preparation method of which is as follows:

[0061] 100 parts of PA1012 resin, 1 part of TiO2, 15 parts of boron nitride and 3 parts of carbon nanotubes were mixed evenly in a high-speed mixer, and then melt-extruded and granulated at 230°C using a screw extruder. The mixture was then cooled to below -100°C with liquid nitrogen, crushed with a crusher and sieved to obtain a polyamide-based powder material with an average particle size (D50) of 50 μm; 100 parts of the polyamide-based powder material, 0.1 parts of a leveling agent, 0.1 parts of a color powder and 0.1 parts of an antioxidant were weighed and put into a high-speed mixer, and stirred continuously at 1000 rpm for 3 minutes to obtain a polyamide powder coating.

[0062] Comparative Example 2

[0063] This comparative example proposes a polyamide powder coating. The difference between this comparative example and Example 1 is that: Step S2 is: transferring the above-mentioned suspension to a glass reactor, then performing reduced pressure distillation to recover the solvent, vacuum drying, ball milling and sieving the remaining product, and putting it into a high-speed mixer, and then adding 15 parts of boron nitride and 3 parts of carbon nanotubes, and mixing at high speed for 3 minutes under mechanical stirring at 1000 rpm to obtain a polyamide-based powder material with an average particle size (D50) of 50 μm; the other processes are the same as Example 1.

[0064] Comparative Example 3

[0065] This comparative example proposes a polyamide powder coating. The difference between this comparative example and Example 1 is that: Step S2 is: transferring the above suspension to a glass reactor, continuing to add 18 parts of boron nitride and ultrasonically dispersing it at 70°C under mechanical stirring at 600 rpm for 2 hours, then performing reduced pressure distillation to recover the solvent, and vacuum drying, ball milling and sieving the remaining product to obtain a polyamide-based powder material with an average particle size (D50) of 50 μm; the other processes are the same as in Example 1.

[0066] Comparative Example 4

[0067] This comparative example proposes a polyamide powder coating. The difference between this comparative example and Example 1 is that: Step S2 is: transferring the above suspension to a glass reactor, continuing to add 18 parts of carbon nanotubes and ultrasonically dispersing them at 70°C under mechanical stirring at 600 rpm for 2 hours, then performing reduced pressure distillation to recover the solvent, and vacuum drying, ball milling and sieving the remaining product to obtain a polyamide-based powder material with an average particle size (D50) of 50 μm; the other processes are the same as in Example 1.

[0068] Comparative Example 5

[0069] This comparative example proposes a polyamide powder coating. The difference between this comparative example and Example 1 is that: Step S2 is: transferring the above suspension to a glass reactor, continuing to add 40 parts of boron nitride and 3 parts of carbon nanotubes, and then ultrasonically dispersing at 70°C for 2 hours under mechanical stirring at 600 rpm, and then performing reduced pressure distillation to recover the solvent. The remaining product is vacuum dried, ball milled and sieved to obtain a polyamide-based powder material with an average particle size (D50) of 50 μm; the other processes are the same as Example 1.

[0070] Comparative Example 6

[0071] This comparative example provides a polyamide powder coating. This comparative example differs from Example 1 in that step S2 involves transferring the suspension to a glass reactor, adding 15 parts boron nitride and 10 parts carbon nanotubes, and then ultrasonically dispersing the mixture at 70°C for 2 hours under mechanical stirring at 600 rpm. The solvent is then recovered by vacuum distillation. The remaining product is vacuum dried, ball-milled, and sieved to obtain a polyamide-based powder material with an average particle size (D50) of 50 μm. All other processes are identical to those in Example 1.

[0072] Test Case

[0073] The nylon powder materials of Examples 1-7 and Comparative Examples 1-6 were sprayed onto stainless steel plates by electrostatic spraying, baked at 250°C for 10 minutes to fully melt the resin particles, and cooled to obtain a coating film with a thickness of 80 μm. According to the standard GB / T 3505-2009, the surface roughness Ra value of the metal sheet surface of each formula was measured using a surface roughness meter. Separately, the nylon powder materials of Examples 1-7 and Comparative Examples 1-2 were used to prepare circular discs with a diameter of 10 mm and a thickness of 2 mm and standard flat plate specimens with a length and width of 100 mm and a thickness of 2 mm using a flat vulcanizer. The specimens were dried in an oven at 50°C for 24 hours and then cooled to room temperature of 23°C in a desiccator. According to the standard GB / T 42919.4-2023, the thermal conductivity of the circular flat plate specimens was tested using a laser flash method thermal conductivity meter. At the same time, according to the standard GB / T31838.2-2019, the volume resistivity of the square flat plate specimens was tested using a high resistance meter. The test results are shown in Table 1.

[0074] Table 1 Performance test results

[0075]

[0076] From the results in Table 1 we can see that:

[0077] (1) Comparison of Example 1 and Comparative Examples 1-2 shows that: compared with the conventional melt blending-cryogenic crushing method and the solvent precipitation-mechanical blending method, Example 1 adopts the solvent precipitation-solvent blending method to disperse the thermal conductive additive and prepare the powder coating, which improves the interface compatibility between the filler and the polymer. After the material is formed, the fillers are more easily overlapped to form an effective thermal conductive network chain. The thermal conductivity coefficient of the composite material is high, and at the same time, the surface flatness of the coating film is high;

[0078] (2) By comparing Example 1 with Comparative Examples 3-6, it can be seen that: when only one type of thermal conductive additive or only one type of thermal conductive additive is added, the thermal conductivity coefficient of the composite material is low; when the content of the one type of thermal conductive additive or the second type of thermal conductive additive is too high, the surface flatness of the coating film is low; at the same time, when the content of the second type of thermal conductive additive is too high, due to the high electrical conductivity of the carbon-based filler, the volume resistivity of the material is low, and the electrical insulation performance of the product is poor.

[0079] Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

Claims

1. A method for preparing a high thermal conductive insulating polyamide powder coating, characterized in that: The following steps are involved: Adding polyamide resin, metal oxide nanoparticles and solvent into a sealed autoclave, heating and stirring under a protective atmosphere to dissolve the polyamide resin in the solvent; then releasing the pressure in the autoclave to normal pressure and cooling to room temperature to obtain a modified polyamide suspension; Adding a first type thermal conductive additive and a second type thermal conductive additive to a modified polyamide suspension and mixing them uniformly, removing the solvent to obtain a solid, and drying, ball milling and sieving to obtain a polyamide-based powder material; 100 parts of polyamide-based powder material, 0.1-0.2 parts of leveling agent, 0-0.2 parts of color powder and 0-0.2 parts of antioxidant are uniformly mixed to obtain a high thermal conductive insulating polyamide powder coating.

2. The preparation method according to claim 1, characterized in that The polyamide resin is at least one of a condensation product of an aliphatic or aromatic dicarboxylic acid and an aliphatic diamine, a condensation product of an aliphatic dicarboxylic acid and an aromatic diamine, and a copolymer with a polyamide condensation product as a copolymer component.

3. The preparation method according to claim 1, characterized in that The metal oxide nanoparticles are at least one of silicon oxide, aluminum oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, molybdenum oxide, cerium oxide, and beryllium oxide.

4. The preparation method according to claim 3, characterized in that The amount of the metal oxide nanoparticles used is 0.1-2% of the mass of the polyamide.

5. The preparation method according to claim 1, characterized in that The solvent is anhydrous ethanol; the amount of the solvent is 5-15 times the mass of the polyamide.

6. The preparation method according to claim 1, characterized in that The thermal conductive additive is at least one of nitride and carbide; the nitride is boron nitride, aluminum nitride or silicon nitride; and the carbide is silicon carbide.

7. The preparation method according to claim 6, characterized in that The amount of the thermal conductive additive is 10-30% of the mass of the polyamide.

8. The preparation method according to claim 1, characterized in that The second type of thermal conductive additive is a long rod-shaped or thin-sheet carbon-based filler.

9. The preparation method according to claim 8, characterized in that The usage of the second type of thermal conductive additive is 2-5% of the mass of the polyamide.

10. A method for preparing a high thermal conductivity insulating polyamide powder coating, characterized in that: The invention relates to a novel crystalline silicon nitrate-containing ...

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