High-thermal-conductivity insulating pouring sealant material and preparation method thereof

Abstract

The preparation method comprises the following steps: carrying out prepolymerization reaction on a hydroxyl-containing elastic polymer, a liquid aryl diisocyanate prepolymer, modified epoxy-acrylic resin and a catalyst in an inert atmosphere to obtain a precursor mixture; the preparation method comprises the following steps: sequentially carrying out silane coupling treatment and boron nitride coating treatment on multi-particle-size spherical aluminum oxide to obtain surface-functionalized composite powder; mixing a reactive diluent, a plasticizer, a dispersing agent and a defoaming agent, then adding the composite powder, and carrying out shear dispersion and defoaming treatment to prepare high-solid-content filler slurry with thixotropy; the precursor mixture and the high-solid-content filler slurry are mixed according to a preset proportion, and pouring sealant slurry is obtained; the pouring sealant slurry is injected into a mold to construct a heat-conducting passage, and then is cured and shaped, so that the pouring sealant material with high heat conductivity, good electrical insulating property and stability is provided.

Description

Technical Field

[0001] This invention relates to the field of potting compound technology, and in particular to a high thermal conductivity insulating potting compound material and its preparation method. Background Technology

[0002] In the fields of building energy conservation and building-integrated photovoltaics (BIPV), building envelopes and waterproofing layers also face heat dissipation requirements. For example, solar roofs, photovoltaic roofs, and heat dissipation structures in underground projects not only require waterproofing materials to possess excellent waterproofing, weather resistance, and flexibility, but also a certain degree of thermal conductivity to accelerate heat dissipation and prevent heat accumulation that could lead to accelerated aging of the waterproofing layer, structural damage, or decreased system efficiency. Currently common building waterproofing materials, such as elastomeric modified bitumen, plastomeric modified bitumen, EPDM rubber waterproofing membranes, and thermoplastic polyolefin waterproofing membranes, while possessing good waterproofing performance and a certain degree of flexibility, generally have low thermal conductivity, failing to meet the ever-increasing demands for building heat dissipation and energy conservation.

[0003] Currently, to improve the thermal conductivity of polymer-based potting compounds, the industry generally adopts a high-proportion filling approach with thermally conductive fillers (such as alumina and boron nitride). However, this method has significant drawbacks: when the filler content reaches a level sufficient to construct an efficient thermally conductive pathway, the filler particles easily form physical contact surfaces in the matrix. This not only increases the system viscosity and deteriorates processability, but more importantly, it may form conductive or leakage pathways, leading to a decrease in the material's volume resistivity and dielectric strength, making it difficult to guarantee insulation reliability. Especially under long-term damp heat and vibration stress, the filler and matrix may undergo interfacial delamination or relative displacement, further exacerbating the risk of electrical performance degradation.

[0004] Therefore, existing high-filler potting compound technologies cannot maintain the high insulation properties of materials under harsh conditions while ensuring high thermal conductivity, and thus cannot meet the technical requirements of the aforementioned high-reliability application scenarios. Summary of the Invention

[0005] The purpose of this invention is to provide a high thermal conductivity insulating potting compound and its preparation method, thereby solving the above-mentioned technical problems.

[0006] To achieve this objective, the present invention adopts the following technical solution: A method for preparing a high thermal conductivity insulating potting compound includes the following steps: S1, a hydroxyl-containing elastic polymer, liquid aryl diisocyanate prepolymer, modified epoxy-acrylic resin and catalyst are subjected to a prepolymerization reaction under an inert atmosphere to obtain a precursor mixture. Multi-size spherical alumina is then subjected to silane coupling treatment and boron nitride coating treatment in sequence to obtain a surface-functionalized composite powder. S2, a reactive diluent, plasticizer, dispersant and defoamer are mixed and then added to the composite powder. After shearing dispersion and degassing treatment, a high solids content filler slurry with thixotropic properties is obtained. S3, the precursor mixture and the high solids content filler slurry are mixed in a preset ratio to obtain a potting slurry; after the potting slurry is injected into the mold, the filler particles are densely arranged and thermally conductive pathways are constructed through controlled centrifugation and temperature control treatment, and then ultraviolet light is irradiated to crosslink the photocurable sites in the slurry to achieve preliminary shaping.

[0007] Optionally, the hydroxyl-containing elastic polymer is hydroxy-terminated polybutadiene, and the liquid aryl diisocyanate prepolymer is a prepolymer formed by reacting one of toluene diisocyanate, diphenylmethane diisocyanate, and isophorone diisocyanate with a polyol.

[0008] Optionally, the multi-size spherical alumina includes large-size, medium-size and small-size spherical alumina, wherein the mass ratio of large-size, medium-size and small-size alumina is (40~48):(15~22):(4~10).

[0009] Optionally, the preparation process of the composite powder is as follows: S11, the multi-size spherical alumina is vacuum dried at 100-120°C for 1-2 hours, and then dispersed in a neutral buffer solution with a pH of 7.2-7.8 to form a uniform suspension; S12, add a silane coupling agent containing catechol functional groups to the suspension, the amount of the silane coupling agent added is 2.0-2.5% of the total mass of spherical alumina, stir continuously at 25-35°C for 2-3 hours, filter, wash and dry after the reaction to obtain intermediate powder with surface grafted silane; S13, the intermediate powder is redispersed in an alcohol-water mixed solvent, and 3-8% of the total mass of hexagonal boron nitride dispersion is added. The mixture is treated for 30-60 minutes under the combined action of ultrasound and shearing. Then, a trace amount of crosslinking promoter is added and the mixture is gently stirred at 40-60°C for 1-2 hours to anchor the boron nitride sheets to the powder surface through chemical action. The surface-functionalized composite powder is then obtained by drying.

[0010] Optionally, the preparation process of the precursor mixture is as follows: S14. Under an inert atmosphere, add a hydroxyl-containing elastic polymer to the reactor and heat it to 70-78°C. After vacuum dehydration for 30-60 minutes, slowly add liquid aryl diisocyanate prepolymer and control the NCO value of the reaction system to reach the preset range. S15, add modified epoxy-acrylic resin and catalyst to the reaction system, stir at 80-85°C for 1.5-2.5 hours to carry out prepolymerization and grafting reaction, and obtain a viscous precursor mixture after cooling.

[0011] Optionally, step S2 specifically includes: S21. Mix the reactive diluent, plasticizer and dispersant at 25-35°C and stir at 300-500 rpm for 10-20 minutes until the system is clear and uniform. Then add the defoamer and continue stirring at low speed for 5 minutes to obtain the additive premix. S22, the surface-functionalized composite powder is added to the premixed additive liquid in batches and slowly. During the addition process, the stirring speed is maintained at 400-600 rpm. After all the powder is added, the system is heated to 40-50°C and stirred at a constant speed at this temperature for 15-30 minutes to allow the additive system to fully wet the surface of the filler. S23, the system that has completed the primary dispersion is transferred to a high-speed shearing device. Under the condition of vacuum degree of -0.08 to -0.095MPa, it is first sheared at a high speed of 1500-2000rpm for 8-15 minutes, and then switched to a medium speed of 800-1200rpm for 5-10 minutes. During this process, low-boiling substances are extracted by vacuum and the state of the slurry is observed to obtain a primary mixed slurry with uniform flowability. S24, the initial mixed slurry is placed in a sealed container and kept in a high vacuum environment of 50-60°C and above -0.1MPa for 20-40 minutes. Then the vacuum is released and the slurry is allowed to stand and mature for 1-2 hours under the protection of inert gas to obtain the high solids content filler slurry with stable thixotropic properties.

[0012] Optionally, step S3 specifically includes: S31, the precursor mixture and the high solids content filler slurry are placed in a mixing tank at a mass ratio of 2.6~2.8:1, and stirred for 5-10 minutes at 40-50°C and 200-400 rpm. Then the speed is increased to 600-800 rpm and stirring is continued for 3-5 minutes to obtain a uniform and viscosity-stable potting slurry. S32, the potting compound is transferred to a vacuum filling device and kept under a vacuum of -0.08 to -0.1 MPa for 5-10 minutes to remove air bubbles entangled in the stirring, and then injected into a mold or cavity of the device to be encapsulated that has been preheated to 40-50°C. S33, the mold that has been filled is placed in a programmable temperature-controlled centrifuge device for controlled centrifugation and temperature control treatment, so that filler particles of different sizes and boron nitride thin layers on the surface are arranged in an orderly manner and in close contact along the heat flow direction, thus constructing an insulating and heat-conducting path. S34. After centrifugation, the slurry system is irradiated with ultraviolet light. First, ultraviolet light is used to irradiate the main plane of the mold vertically for 60-90 seconds to achieve the initial cross-linking of the main area. Then, the angle of the light source is adjusted or a side auxiliary light source is added to irradiate the side wall of the mold or complex structure area for 20-40 seconds to fully excite and cross-link the photocurable sites in the slurry, forming a primary cured body that can lock the spatial position of the filler network. S35, the primary cured body, together with the mold, is placed in an oven at 60-80°C and left to stand for 20-40 minutes to obtain a preform.

[0013] Optionally, the controlled centrifugation and temperature control treatment are performed under the following conditions: centrifugation at 800-1500 rpm for 5-20 minutes at 40-60°C.

[0014] Optionally, step S3 may be followed by: S4 involves subjecting the initially cured slurry to a stepped heating process, which fully crosslinks the thermosetting groups in the precursor and promotes the formation of covalent bonds between the functional layer on the filler surface and the matrix, ultimately resulting in a cured potting compound.

[0015] This invention also provides a high thermal conductivity insulating potting compound material, prepared by the method described above, wherein the high thermal conductivity insulating potting compound material comprises: A matrix polymer, consisting of 100 parts, is formed by reacting a hydroxyl-containing elastic polymer, a liquid aryl diisocyanate prepolymer, a modified epoxy-acrylic resin, and a catalyst. A combination of functional fillers dispersed in the matrix polymer, totaling 50 to 100 parts; In addition, there are 8-14 parts of reactive diluent, 5-8 parts of plasticizer, 0.3-1.0 parts of dispersant and 0.02-0.1 parts of defoamer.

[0016] Compared with existing technologies, this invention has the following advantages: This method constructs a silane chemically bonded layer and an insulating boron nitride coating layer on the surface of multi-size spherical alumina. While improving the interfacial bonding between the filler and the matrix and reducing the interfacial thermal resistance, the interlayer insulation properties of boron nitride effectively block leakage paths that may form under high filling conditions, thereby constructing a highly efficient and insulating thermally conductive network inside the material. Combined with controlled centrifugal arrangement and rapid primary curing under ultraviolet light, it not only achieves control and locking of the spatial distribution of the filler and the thermal channel structure, preventing sedimentation and structural relaxation, but also ensures sufficient thermal curing. This allows the final material to simultaneously achieve high thermal conductivity, high volume resistivity, and excellent long-term environmental stability, providing a potting compound material with high thermal conductivity, good electrical insulation, and stability, suitable for long-term use in high-power-density equipment. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] The structures, proportions, sizes, etc., shown in the accompanying drawings of this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0019] Figure 1 This is a schematic flowchart illustrating the preparation method of the high thermal conductivity insulating potting compound material in this embodiment. Detailed Implementation

[0020] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0021] In the description of this invention, it should be understood that the terms "upper," "lower," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be a component positioned centrally in the connection.

[0022] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0023] Example 1: Combination Figure 1 As shown, this embodiment of the invention provides a method for preparing a high thermal conductivity insulating potting compound, comprising the following steps: S1, a hydroxyl-containing elastic polymer, a liquid aryl diisocyanate prepolymer, a modified epoxy-acrylic resin, and a catalyst are subjected to a prepolymerization reaction under an inert atmosphere to obtain a precursor mixture. Multi-sized spherical alumina is then subjected to silane coupling treatment and boron nitride coating treatment in sequence to obtain a surface-functionalized composite powder.

[0024] S2 involves mixing reactive diluents, plasticizers, dispersants, and defoamers, then adding composite powder, followed by shear dispersion and degassing treatment to obtain a thixotropic high-solids-content filler slurry.

[0025] S3. The precursor mixture and high solids content filler slurry are mixed in a preset ratio to obtain potting slurry. After the potting slurry is injected into the mold, the filler particles are densely arranged and thermally conductive pathways are constructed through controlled centrifugation and temperature control. Then, ultraviolet light is applied to cross-link the photocuring sites in the slurry to achieve preliminary shaping.

[0026] S4 involves subjecting the initially cured slurry to a stepped heating process, which fully crosslinks the thermosetting groups in the precursor and promotes the formation of covalent bonds between the functional layer on the filler surface and the matrix, ultimately resulting in a cured potting compound.

[0027] The working principle of this invention is as follows: This method constructs a silane chemically bonded layer and an insulating boron nitride coating layer on the surface of multi-sized spherical alumina. While improving the interfacial bonding between the filler and the matrix and reducing the interfacial thermal resistance, the interlayer insulation properties of boron nitride effectively block leakage paths that may form under high filling conditions, thereby constructing a highly efficient and insulating thermally conductive network inside the material. Combined with controlled centrifugal arrangement and rapid primary curing under ultraviolet light, it not only achieves control and locking of the spatial distribution of the filler and the thermal channel structure, preventing sedimentation and structural relaxation, but also ensures sufficient thermal curing. This allows the final material to simultaneously achieve high thermal conductivity, high volume resistivity, and excellent long-term environmental stability, providing a potting compound material with high thermal conductivity, good electrical insulation, and stability, suitable for long-term use in high-power-density equipment.

[0028] It should be noted that the high thermal conductivity insulating potting compound material provided by this invention is not only suitable for potting and protecting high power density electronic devices, but also applicable to the field of building waterproofing and heat dissipation, providing a high-performance solution for applications requiring heat dissipation and sealing, such as photovoltaic roofs, building joints, and solar collectors. For example, it can be used for sealing and thermally conductive filling of joints in photovoltaic roof panels, helping to improve the heat dissipation efficiency of photovoltaic modules; it can also be used for thermally conductive and waterproof sealing of building expansion joints and pipe penetrations, improving local heat accumulation problems while ensuring waterproof performance. Its construction method is similar to that of conventional potting compounds, and it can be applied to the area to be sealed by injection, scraping, etc., and then formed into a dense, thermally conductive, and insulating sealant through the controlled centrifugation, ultraviolet light curing, and thermal curing processes.

[0029] In this embodiment, the hydroxyl-containing elastic polymer is hydroxy-terminated polybutadiene, and the liquid aryl diisocyanate prepolymer is a prepolymer formed by reacting one of toluene diisocyanate, diphenylmethane diisocyanate, and isophorone diisocyanate with a polyol.

[0030] It should be noted that the hydroxyl-containing elastic polymer specifically selected is hydroxyl-terminated polybutadiene, whose main chain has a compliant carbon-carbon single and double bond structure, which can contribute excellent flexibility, fatigue resistance and low moisture absorption to this system, making it a preferred material for constructing potting compound with damping and crack resistance properties.

[0031] The liquid aryl diisocyanate prepolymer is specifically selected from the reaction of toluene diisocyanate, diphenylmethane diisocyanate or isophorone diisocyanate with a polyol to form a prepolymer; compared with the direct use of small molecule diisocyanates, this prepolymer form can effectively reduce toxicity, control reactivity and adjust the viscosity of the system.

[0032] Among them, toluene diisocyanate prepolymer is cost-effective and has a fast reaction rate; diphenylmethane diisocyanate prepolymer imparts higher mechanical strength and hardness to the product; while isophorone diisocyanate prepolymer provides excellent weather resistance and hydrolytic stability. All of them react with the hydroxyl groups of hydroxy-terminated polybutadiene through the reaction of their terminal isocyanate groups to form polyurethane (or polyurethane-urea) segments that serve as the matrix backbone. These segments then synergistically work with modified epoxy-acrylic resins to construct interpenetrating or semi-interpenetrating polymers that combine toughness and rigidity. This is crucial for achieving long-term durability of materials under vibration.

[0033] In this embodiment, the multi-size spherical alumina includes large-size, medium-size and small-size spherical alumina, wherein the mass ratio of large-size, medium-size and small-size alumina is (40~48):(15~22):(4~10).

[0034] It should be noted that this gradient ratio design follows the theory of close packing of particles, and its purpose is to achieve the optimal space occupation of the filler in the matrix, thereby maximizing the formation efficiency of the heat conduction path.

[0035] Specifically, the dominant large-diameter particles (40-48 parts) first construct the supporting main framework structure; medium-diameter particles (15-22 parts) effectively fill the gaps between the large particles; and a small amount of small-diameter particles (4-10 parts) further fills the remaining tiny voids, playing a role in lubrication and densification. Through this precisely controlled particle size combination and ratio, the volumetric loading of functional fillers can be maximized while ensuring that the potting compound still has good fluidity and processability, thereby constructing an extremely high-density and low-thermal-resistance thermally conductive network inside the cured composite material.

[0036] In this embodiment, the preparation process of the composite powder is specifically described as follows: S11 involves vacuum drying multi-sized spherical alumina at 100-120°C for 1-2 hours, followed by dispersion in a neutral buffer solution with a pH of 7.2-7.8 to form a uniform suspension.

[0037] First, the multi-sized spherical alumina particles are vacuum dried at 100-120°C for 1-2 hours to remove adsorbed moisture from the filler surface and prevent moisture from interfering with the subsequent hydrolysis and condensation reactions of the silane coupling agent. Then, the dried filler is dispersed in a neutral buffer solution (such as phosphate) with a pH of 7.2-7.8. Excessively acidic or alkaline conditions may cause protonation or deprotonation of the aluminum hydroxyl groups on the alumina surface, altering its surface charge and reactivity; while a neutral buffer system can maintain the optimal reaction state of the surface hydroxyl groups and prevent unnecessary aggregation or dissolution of the filler during dispersion.

[0038] S12, add a silane coupling agent containing catechol functional groups to the suspension. The amount of silane coupling agent added is 2.0-2.5% of the total mass of spherical alumina. Stir and react continuously at 25-35°C for 2-3 hours. After the reaction is completed, filter, wash and dry to obtain an intermediate powder with surface grafted silane. It should be noted that when a silane coupling agent containing a catechol functional group (2.0-2.5% of the mass of alumina) is added to the suspension and reacted gently at 25-35°C for 2-3 hours, one end of the silane coupling agent molecule is a hydrolyzable alkoxysilane, which can be slowly hydrolyzed into silanol in a neutral aqueous solution, and then undergoes dehydration condensation with the aluminum hydroxyl groups on the surface of alumina to form a strong Si-O-Al covalent bond; the other end of the molecule introduces a biomimetic catechol functional group, whose catechol structure endows it with strong adhesive properties similar to marine mussel adhesive proteins, and can form strong hydrogen bonds, coordination bonds and even subsequent oxidizable cross-linking points with various organic functional groups, significantly enhancing the adhesion strength and durability of the interface.

[0039] S13: The intermediate powder is redispersed in an alcohol-water mixed solvent, and 3-8% of the total mass of hexagonal boron nitride dispersion is added. The mixture is treated for 30-60 minutes under the combined action of ultrasound and shearing. Then, a trace amount of crosslinking promoter is added and the mixture is gently stirred at 40-60°C for 1-2 hours to anchor the boron nitride sheets to the powder surface through chemical action. After drying, the surface-functionalized composite powder is obtained.

[0040] It should be noted that the intermediate powder is redispersed, and 3-8% (by weight) of hexagonal boron nitride dispersion is added. Hexagonal boron nitride is an ideal insulating and thermally conductive material. Under the synergistic effect of ultrasound and shearing, the hexagonal boron nitride sheets are fully exfoliated and dispersed, and initially adhere to the alumina spheres through physical adsorption and chemical interaction. Then, a trace amount of crosslinking promoter (such as a specific metal salt or organic base) is added, and the mixture is gently stirred at 40-60°C for 1-2 hours. This gentle heat treatment promotes deeper physicochemical crosslinking and anchoring between the hexagonal boron nitride sheets and the catechol groups of the underlying silane layer, forming a stable and uniformly coated thin layer. This thin layer can build microscopic thermal bridges between adjacent alumina particles, significantly reducing interfacial thermal resistance. Simultaneously, its sheet structure effectively blocks current pathways. The final dried surface-functionalized composite powder achieves a synergistic effect of high thermal conductivity and high insulation.

[0041] In this embodiment, the preparation process of the precursor mixture is specifically described as follows: S14. Under an inert atmosphere, add a hydroxyl-containing elastic polymer to the reactor and heat it to 70-78°C. After vacuum dehydration for 30-60 minutes, slowly add liquid aryl diisocyanate prepolymer and control the NCO value of the reaction system to reach the preset range. It should be noted that operation under an inert atmosphere (such as nitrogen) is primarily aimed at isolating the air from moisture and oxygen, preventing the isocyanate groups (-NCO) from reacting with water to produce carbon dioxide and generate bubbles, or causing unnecessary side reactions. First, the hydroxyl-containing elastic polymer (such as hydroxyl-terminated polybutadiene) is heated to 70-78°C and subjected to vacuum dehydration at this temperature for 30-60 minutes to thoroughly remove trace amounts of moisture from the raw material. This is a necessary prerequisite for ensuring the normal progress of the polyurethane reaction and avoiding bubble defects. Afterward, liquid aryl diisocyanate prepolymer is slowly added dropwise, and the exothermic reaction and viscosity increase of the system are managed by controlling the dropping rate. The core control indicator is to ensure that the NCO value of the reaction system reaches the preset range (e.g., the residual NCO content is 48-52% of the initial value). This means that not all isocyanate groups have completely reacted with the hydroxyl groups, but rather a prepolymer of a certain molecular weight has been formed, and sufficient -NCO has been retained for subsequent reaction with modified epoxy-acrylic resin and bonding with functional groups on the filler surface, thus reserving sufficient reaction sites for the formation of the entire cured network.

[0042] S15, add modified epoxy-acrylic resin and catalyst to the reaction system, stir at 80-85°C for 1.5-2.5 hours to carry out prepolymerization and grafting reaction, and obtain a viscous precursor mixture after cooling.

[0043] It should be noted that modified epoxy-acrylic resin and catalyst are added to the prepolymer system. The modified resin molecules here contain both epoxy groups and photocurable groups such as (meth)acryloyloxy groups. At a reaction temperature of 80-85°C, the catalyst (such as organotin or amine catalysts) begins to function, promoting the reaction between the residual isocyanate groups (-NCO) and the hydroxyl groups on the epoxy resin chain. Simultaneously, the epoxy groups may also undergo partial ring-opening under the action of the catalyst. This process is a prepolymerization and grafting reaction, lasting 1.5-2.5 hours. Its purpose is to graft photocurable acrylate segments onto the already formed polyurethane prepolymer backbone through chemical bonds, rather than a simple mixing. After the reaction is complete and cooled, a viscous precursor mixture is obtained. This product is a chemical intermediate: it contains both unreacted -NCO and epoxy groups (for subsequent thermosetting) and acrylate double bonds (for UV curing), realizing the material design of a "photothermal dual-curing" system.

[0044] In this embodiment, step S2 specifically includes: S21. Mix the reactive diluent, plasticizer and dispersant at 25-35°C and stir at 300-500 rpm for 10-20 minutes until the system is clear and uniform. Then add the defoamer and continue stirring at low speed for 5 minutes to obtain the additive premix. It should be noted that, at a mild temperature of 25-35°C, the reactive diluent, plasticizer, and dispersant are first stirred at 300-500 rpm for 10-20 minutes. This temperature and shear condition are designed to ensure that the liquid components are fully miscible, the dispersant is completely dissolved, and the steric hindrance effect is utilized to form a clear and homogeneous system. Only then is the defoamer added and stirring continues at a low speed. This sequence prevents the defoamer from being prematurely encapsulated and ineffective under high-speed shear, ensuring that it remains intact to act on newly generated bubbles during the subsequent dispersion process.

[0045] S22, add the surface-functionalized composite powder in batches and slowly to the premixed additive solution. During the addition process, keep the stirring speed at 400-600 rpm. After all the powder has been added, heat the system to 40-50°C and stir at a constant speed at this temperature for 15-30 minutes to allow the additive system to fully wet the surface of the filler.

[0046] The method of adding filler in batches and slowly, while maintaining a moderate stirring speed of 400-600 rpm during the addition process, is to control the solid phase introduction rate so that each batch of filler can be fully and timely coated by the liquid medium, preventing the formation of hard agglomerates that are difficult to disperse due to local over-drying.

[0047] S23. The system that has completed the primary dispersion is transferred to a high-speed shearing device. Under the condition of vacuum degree of -0.08 to -0.095 MPa, it is first sheared at a high speed of 1500-2000 rpm for 8-15 minutes, and then switched to a medium speed of 800-1200 rpm for 5-10 minutes. During this process, low-boiling substances are extracted by vacuum and the state of the slurry is observed to obtain a primary mixed slurry with uniform flowability.

[0048] The system is transferred to a high-speed shearing device and a vacuum of -0.08 to -0.095 MPa is applied. Shearing under vacuum is a crucial design feature of this process. First, shearing is performed at a high speed of 1500-2000 rpm for 8-15 minutes. The purpose is to use the strong shearing force to thoroughly break down agglomerates (especially soft agglomerates) between filler particles, achieving a uniform distribution of primary particles or micro-agglomerates in the base liquid. Then, the speed is switched to medium-speed shearing at 800-1200 rpm for 5-10 minutes. During this stage, while maintaining the dispersion, the main function is to remove air entrained during stirring and any trace amounts of low-boiling substances under vacuum assistance, allowing the slurry system to become homogeneous and obtaining a uniformly flowing initial mixture.

[0049] S24. Place the initial mixed slurry in a sealed container and maintain it in a high vacuum environment of 50-60°C and above -0.1MPa for 20-40 minutes. Then release the vacuum and let it stand and mature for 1-2 hours under inert gas protection to obtain a high solids content filler slurry with stable thixotropic properties.

[0050] It should be noted that placing the initial mixed slurry in a high vacuum environment of 50-60°C and above -0.1 MPa for 20-40 minutes aims to thoroughly remove residual gases dissolved inside the slurry or attached to the micropores of the filler, thus preventing pinhole defects after curing. The curing process is not simply static; it allows the tense molecular chains of additives (especially dispersants) after shearing to undergo sufficient adsorption and rearrangement on the filler surface, achieving a more stable thermodynamic equilibrium. At the same time, the internal stress generated by high-speed shearing inside the slurry is relaxed.

[0051] In this embodiment, step S3 specifically includes: S31, the precursor mixture and the high solids content filler slurry are placed in a mixing tank at a mass ratio of 2.6~2.8:1, and stirred at 40-50°C and 200-400 rpm for 5-10 minutes. Then the speed is increased to 600-800 rpm and stirring is continued for 3-5 minutes to obtain a uniform and viscosity-stable potting slurry. The precursor mixture and high-solids-content filler slurry are mixed at a preset ratio of 2.6~2.8:1 by mass. This ratio is an optimized equilibrium point that ensures the matrix resin fully encapsulates the high-solids-content filler while maintaining good slurry flowability and final mechanical properties. The mixing process is carried out at 40-50°C, which appropriately reduces the viscosity of the precursor mixture and promotes compatibility between the two. A two-stage stirring strategy is adopted: first, stirring is carried out at a lower speed of 200-400 rpm for 5-10 minutes to initially fuse the two viscous materials and avoid excessive heating or excessive air entrainment due to violent shearing; then, the speed is increased to 600-800 rpm and stirring is continued for 3-5 minutes to apply sufficient shear force to break up any possible local agglomerates and ensure that the filler is evenly distributed in the overall slurry.

[0052] S32, transfer the potting compound to a vacuum filling device and maintain it under a vacuum of -0.08 to -0.1 MPa for 5-10 minutes to remove air bubbles entangled in the agitation, and then inject it into a mold or cavity of the device to be encapsulated that has been preheated to 40-50°C. First, the potting compound is transferred to a vacuum filling machine and maintained at a vacuum level of -0.08 to -0.1 MPa for 5-10 minutes. This deep degassing treatment effectively removes tiny air bubbles that are inevitably drawn into the compound during the S31 mixing process, a key measure to prevent fatal defects such as voids and pinholes inside the cured encapsulated body. After degassing, the compound is injected into a mold or device cavity preheated to 40-50°C. Preheating the mold has several benefits: firstly, it prevents a sudden increase in the viscosity of the compound in contact with the low-temperature mold surface, which would affect its flow and filling, especially for complex and narrow cavities; secondly, it ensures that the compound maintains relatively uniform and suitable flowability within the cavity, ensuring complete filling and helping to reduce internal stress concentration caused by temperature differences.

[0053] S33 involves placing the filled mold in a programmable temperature-controlled centrifuge for controlled centrifugation and temperature control, which causes filler particles of different sizes and the boron nitride thin layer on the surface to be arranged in an orderly manner and in close contact along the heat flow direction, thus constructing an insulating and heat-conducting path.

[0054] The filled mold is placed in a programmable temperature-controlled centrifuge. Through the synergistic effect of precisely controlled centrifugal force and temperature fields, the filler is oriented and densified. Under centrifugal force, filler particles with a density higher than the resin matrix migrate and settle along the direction of centrifugal force. Simultaneously, the applied temperature control reduces the instantaneous local viscosity of the resin matrix, significantly reducing the resistance to filler movement. This synergistic effect of physical fields forces spherical alumina particles of different sizes to achieve the closest possible packing according to their size gradient, while also causing the boron nitride thin layer attached to its surface to adjust its orientation accordingly. The filler particles achieve close point-to-surface or surface-to-surface contact through the thin layer, forming a large number of continuous microscopic thermal bridges within the material. However, due to the insulating properties of the boron nitride thin layer itself, these bridges are non-conductive, thus creating highly efficient insulating and thermally conductive pathways.

[0055] S34. After centrifugation, the slurry system is irradiated with ultraviolet light. First, ultraviolet light is used to irradiate the main plane of the mold vertically for 60-90 seconds to achieve the initial cross-linking of the main area. Then, the angle of the light source is adjusted or a side auxiliary light source is added to irradiate the side wall of the mold or complex structure area for 20-40 seconds to fully excite and cross-link the photocurable sites in the slurry, forming a primary cured body that can lock the spatial position of the filler network. First, ultraviolet light with an intensity of 30-50 mW / cm² is vertically irradiated from the main plane of the mold for 60-90 seconds. This fully excites the photocuring sites (originating from acrylate groups in the precursor) in the main area of ​​the slurry (usually the thickest and hottest region), causing a rapid photo-initiated free radical polymerization reaction and forming a cross-linked network, achieving initial cross-linking of the main area. Subsequently, the light source angle is adjusted or a side auxiliary light source is added to supplement the irradiation of the mold sidewalls, corners, or areas with complex structures for 20-40 seconds. This selective curing strategy of main irradiation plus supplementary irradiation ensures that ultraviolet light covers all areas, avoiding localized insufficient curing due to shading effects. Through this comprehensive and rapid photocuring process, the newly constructed, unstable filler thermally conductive network is quickly locked in the newly generated three-dimensional polymer skeleton, forming a primary cured body with sufficient mechanical strength to maintain its shape and microstructure.

[0056] S35, the primary cured body, along with the mold, is placed in an oven at 60-80°C and left to stand for 20-40 minutes to obtain a preform. This eliminates the internal stress generated during the rapid photocuring process and promotes the initial cross-linking of unreacted thermosetting groups, thereby enhancing the integrity and dimensional stability of the primary cured body and obtaining a preform that can be transported or fully cured.

[0057] In this embodiment, the controlled centrifugation and temperature control treatment are performed under the following conditions: centrifugation at 800-1500 rpm for 5-20 minutes at 40-60°C.

[0058] Example 2: This invention also provides a high thermal conductivity insulating potting compound material, prepared using the method described in Example 1. The high thermal conductivity insulating potting compound material comprises: A matrix polymer, consisting of 100 parts, is formed by reacting a hydroxyl-containing elastic polymer, a liquid aryl diisocyanate prepolymer, a modified epoxy-acrylic resin, and a catalyst. A functional filler assembly dispersed in a matrix polymer, totaling 50 to 100 parts; wherein the functional filler assembly includes: Spherical alumina powder composed of large, medium, and small particle sizes in a mass ratio of (40~48): (15~22): (4~10); A silane coupling agent layer containing catechol functional groups, comprising 2.0-2.5% of the total mass of spherical alumina powder, bonded to its surface; A hexagonal boron nitride coating layer, comprising 3-8% of the total mass of spherical alumina powder, is chemically anchored to the silane coupling agent layer. In addition, there are 8-14 parts of reactive diluent, 5-8 parts of plasticizer, 0.3-1.0 parts of dispersant and 0.02-0.1 parts of defoamer.

[0059] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a high thermal conductivity insulating potting compound, characterized in that, Includes the following steps: S1, a hydroxyl-containing elastic polymer, liquid aryl diisocyanate prepolymer, modified epoxy-acrylic resin and catalyst are subjected to a prepolymerization reaction under an inert atmosphere to obtain a precursor mixture. Multi-size spherical alumina is then subjected to silane coupling treatment and boron nitride coating treatment in sequence to obtain a surface-functionalized composite powder. S2, a reactive diluent, plasticizer, dispersant and defoamer are mixed and then added to the composite powder. After shearing dispersion and degassing treatment, a high solids content filler slurry with thixotropic properties is obtained. S3, the precursor mixture and the high solids content filler slurry are mixed in a preset ratio to obtain a potting slurry; after the potting slurry is injected into the mold, the filler particles are densely arranged and thermally conductive pathways are constructed through controlled centrifugation and temperature control treatment, and then ultraviolet light is irradiated to crosslink the photocurable sites in the slurry to achieve preliminary shaping.

2. The method for preparing the high thermal conductivity insulating potting compound material according to claim 1, characterized in that, The hydroxyl-containing elastic polymer is hydroxy-terminated polybutadiene, and the liquid aryl diisocyanate prepolymer is a prepolymer formed by reacting one of toluene diisocyanate, diphenylmethane diisocyanate, and isophorone diisocyanate with a polyol.

3. The preparation method of the high thermal conductivity insulating potting compound material according to claim 1, characterized in that, The multi-size spherical alumina includes large-size, medium-size and small-size spherical alumina, wherein the mass ratio of large-size, medium-size and small-size alumina is (40~48):(15~22):(4~10).

4. The method for preparing the high thermal conductivity insulating potting compound material according to claim 1, characterized in that, The preparation process of the composite powder is as follows: S11, the multi-sized spherical alumina is vacuum dried at 100-120°C for 1-2 hours, and then dispersed in a neutral buffer solution with a pH of 7.2-7.8 to form a uniform suspension; S12, add a silane coupling agent containing catechol functional groups to the suspension, the amount of the silane coupling agent added is 2.0-2.5% of the total mass of spherical alumina, stir continuously at 25-35°C for 2-3 hours, filter, wash and dry after the reaction to obtain intermediate powder with surface grafted silane; S13, the intermediate powder is redispersed in an alcohol-water mixed solvent, and 3-8% of the total mass of hexagonal boron nitride dispersion is added. The mixture is treated for 30-60 minutes under the combined action of ultrasound and shearing. Then, a trace amount of crosslinking promoter is added and the mixture is gently stirred at 40-60°C for 1-2 hours to anchor the boron nitride sheets to the powder surface through chemical action. The surface-functionalized composite powder is then obtained by drying.

5. The method for preparing the high thermal conductivity insulating potting compound material according to claim 4, characterized in that, The preparation process of the precursor mixture is as follows: S14. Under an inert atmosphere, add a hydroxyl-containing elastic polymer to the reactor and heat it to 70-78°C. After vacuum dehydration for 30-60 minutes, slowly add liquid aryl diisocyanate prepolymer and control the NCO value of the reaction system to reach the preset range. S15, add modified epoxy-acrylic resin and catalyst to the reaction system, stir at 80-85°C for 1.5-2.5 hours to carry out prepolymerization and grafting reaction, and obtain a viscous precursor mixture after cooling.

6. The method for preparing the high thermal conductivity insulating potting compound material according to claim 1, characterized in that, Step S2 specifically includes: S21. Mix the reactive diluent, plasticizer and dispersant at 25-35°C and stir at 300-500 rpm for 10-20 minutes until the system is clear and uniform. Then add the defoamer and continue stirring at low speed for 5 minutes to obtain the additive premix. S22, the surface-functionalized composite powder is added to the premixed additive liquid in batches and slowly. During the addition process, the stirring speed is maintained at 400-600 rpm. After all the powder is added, the system is heated to 40-50°C and stirred at a constant speed at this temperature for 15-30 minutes to allow the additive system to fully wet the surface of the filler. S23, the system that has completed the primary dispersion is transferred to a high-speed shearing device. Under the condition of vacuum degree of -0.08 to -0.095MPa, it is first sheared at a high speed of 1500-2000rpm for 8-15 minutes, and then switched to a medium speed of 800-1200rpm for 5-10 minutes. During this process, low-boiling substances are extracted by vacuum and the state of the slurry is observed to obtain a primary mixed slurry with uniform flowability. S24, the initial mixed slurry is placed in a sealed container and kept in a high vacuum environment of 50-60°C and above -0.1MPa for 20-40 minutes. Then the vacuum is released and the slurry is allowed to stand and mature for 1-2 hours under the protection of inert gas to obtain the high solids content filler slurry with stable thixotropic properties.

7. The method for preparing the high thermal conductivity insulating potting compound material according to claim 1, characterized in that, Step S3 specifically includes: S31, the precursor mixture and the high solids content filler slurry are placed in a mixing tank at a mass ratio of 2.6~2.8:1, and stirred for 5-10 minutes at 40-50°C and 200-400 rpm. Then the speed is increased to 600-800 rpm and stirring is continued for 3-5 minutes to obtain a uniform and viscosity-stable potting slurry. S32, the potting compound is transferred to a vacuum filling device and kept under a vacuum of -0.08 to -0.1 MPa for 5-10 minutes to remove air bubbles entangled in the stirring, and then injected into a mold or cavity of the device to be encapsulated that has been preheated to 40-50°C. S33, the mold that has been filled is placed in a programmable temperature-controlled centrifuge device for controlled centrifugation and temperature control treatment, so that filler particles of different sizes and boron nitride thin layers on the surface are arranged in an orderly manner and in close contact along the heat flow direction, thus constructing an insulating and heat-conducting path. S34. After centrifugation, the slurry system is irradiated with ultraviolet light. First, ultraviolet light is used to irradiate the main plane of the mold vertically for 60-90 seconds to achieve the initial cross-linking of the main area. Then, the angle of the light source is adjusted or a side auxiliary light source is added to irradiate the side wall of the mold or complex structure area for 20-40 seconds to fully excite and cross-link the photocurable sites in the slurry, forming a primary cured body that can lock the spatial position of the filler network. S35, the primary cured body, together with the mold, is placed in an oven at 60-80°C and left to stand for 20-40 minutes to obtain a preform.

8. The method for preparing the high thermal conductivity insulating potting compound material according to claim 7, characterized in that, The controlled centrifugation and temperature control treatment are performed under the following conditions: centrifugation at 800-1500 rpm for 5-20 minutes at 40-60°C.

9. The method for preparing the high thermal conductivity insulating potting compound material according to claim 1, characterized in that, Following step S3, the following is also included: S4 involves subjecting the initially cured slurry to a stepped heating process, which fully crosslinks the thermosetting groups in the precursor and promotes the formation of covalent bonds between the functional layer on the filler surface and the matrix, ultimately resulting in a cured potting compound.

10. A high thermal conductivity insulating potting compound, characterized in that, The high thermal conductivity insulating potting compound is prepared by the preparation method of any one of claims 1-9, wherein the high thermal conductivity insulating potting compound comprises: A matrix polymer, consisting of 100 parts, is formed by reacting a hydroxyl-containing elastic polymer, a liquid aryl diisocyanate prepolymer, a modified epoxy-acrylic resin, and a catalyst. A combination of functional fillers dispersed in the matrix polymer, totaling 50 to 100 parts; In addition, there are 8-14 parts of reactive diluent, 5-8 parts of plasticizer, 0.3-1.0 parts of dispersant and 0.02-0.1 parts of defoamer.

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