Low-thermal-resistance low-oil-permeability anti-aging thixotropic high-thermal-conductivity silicone grease and preparation method thereof

Abstract

The invention relates to the technical field of heat conduction materials, in particular to low-heat-resistance low-oil-permeability anti-aging thixotropic high-heat-conduction silicone grease and a preparation method thereof. According to the silicone grease, dimethyl silicone oil and vinyl-terminated polydimethylsiloxane serve as matrixes, layered interface modified spherical aluminum oxide and flaky boron nitride are compounded to serve as heat conduction filler, and hydrophobic fumed silica and a fixed-point micro-crosslinking system are added. Through a process of firstly constructing a heat-conducting network and then triggering sparse crosslinking, high heat conductivity coefficient, low interface thermal resistance, good thixotropy and long-term thermal stability are realized, the problems of oil leakage, sedimentation and aging under high filling are effectively solved, and the composite material is suitable for heat dissipation of high-power electronic devices.

Description

Technical Field

[0001] This invention relates to the field of thermal conductive materials technology, and in particular to a low thermal resistance, low oil seepage, aging resistant thixotropic high thermal conductivity silicone grease and its preparation method. Background Technology

[0002] Thermal grease, as a thermal interface material, is widely used in the heat dissipation of electronic devices. Its core function is to reduce contact thermal resistance and improve heat conduction efficiency by filling the microscopic gaps between the chip and the heat sink. However, traditional thermal greases, in pursuit of high thermal conductivity, often rely on the addition of a high proportion of thermally conductive fillers. This can easily lead to a sharp increase in system viscosity, resulting in poor workability and interfacial wettability. With high filler content, insufficient interfacial compatibility between the filler and the organic matrix introduces a large amount of interfacial thermal boundary resistance, making it difficult to further reduce the overall thermal resistance. Especially in thin-layer coating scenarios, interfacial thermal resistance becomes a key bottleneck restricting heat dissipation performance.

[0003] Furthermore, free silicone oil molecules in highly filled systems are prone to migration under temperature fluctuations or mechanical stress, leading to oil seepage. Oil seepage not only contaminates surrounding components but also causes localized drying of the silicone grease layer, resulting in voids in the filler network and interruption of thermal conductivity. Existing technologies attempt to improve oil seepage resistance by adding thixotropic agents or partial crosslinking, but this often comes at the cost of sacrificing thermal conductivity: an excessively strong thixotropic network inhibits filler orientation and packing density, while premature crosslinking leads to uneven filler dispersion, preventing the formation of a continuous thermally conductive network.

[0004] Long-term stability is another significant challenge. Under thermal cycling conditions, the difference in thermal expansion coefficients between the matrix and the filler can easily lead to micro-stress concentration at the interface of thermally conductive silicone grease, causing filler sedimentation or interface desorption. Existing modification methods, such as treatment with a single silane coupling agent, can improve interfacial bonding in the short term, but lack resistance to heat and oxygen aging. Under long-term high temperatures, the modified layer is prone to degradation, resulting in a significant increase in interfacial thermal resistance over time. At the same time, the traditional process of simultaneous dispersion and crosslinking causes a sudden increase in viscosity during the mixing stage, hindering filler orientation and making it difficult to simultaneously achieve high thixotropy and low application viscosity.

[0005] Furthermore, while the combination strategy of lamellar and spherical packing can improve the continuity of the heat conduction path, it does not solve the problem of synergistic relationship between interfacial impedance and network stability. If the lamellar packing is not effectively bridged with the spherical skeleton, it is prone to agglomeration under shear, increasing local thermal resistance; while when the spherical packing is improperly graded, the packing porosity increases, which not only reduces thermal conductivity but also exacerbates the risk of oil leakage and sedimentation. Existing technologies lack an integrated design for packing interface modification, metal ion stabilization, and crosslinking sequence, resulting in overall performance that is difficult to meet the requirements of high-reliability electronic devices. Summary of the Invention

[0006] In view of this, the purpose of this invention is to propose a low thermal resistance, low oil penetration, aging resistant thixotropic high thermal conductivity silicone grease and its preparation method, so as to solve the problem that high thermal conductivity silicone grease is difficult to achieve both low thermal resistance and low oil penetration when filled with high filler, and is prone to interfacial contact deterioration and pumping loss during long-term thermal cycling, resulting in unstable thermal conduction path.

[0007] To achieve the above objectives, the present invention provides a low thermal resistance, low oil seepage, aging-resistant, thixotropic, high thermal conductivity silicone grease, comprising: The matrix component includes dimethyl silicone oil and vinyl-terminated polydimethylsiloxane; Thermally conductive filler, wherein the thermally conductive filler comprises layered interface-modified spherical alumina and plate-shaped boron nitride; Thixotropic modulating component, wherein the thixotropic modulating component includes hydrophobically treated fumed silica; A site-directed micro-crosslinking system, comprising a polysiloxane crosslinking agent containing silane-hydrogen bonds, a Karstedt-type platinum catalyst xylene solution, and a reaction inhibitor; In this embodiment, based on the total mass of the thixotropic high thermal conductivity silicone grease, the total amount of the thermally conductive filler added is 88% to 91%, and the mass ratio of the layered interface modified spherical alumina to the lamellar boron nitride is 3 to 4:1.

[0008] Preferably, the dimethyl silicone oil is a mixture of low-viscosity dimethyl silicone oil and high-viscosity dimethyl silicone oil in a mass ratio of 1.4 to 1.9:1; the low-viscosity dimethyl silicone oil has a kinematic viscosity of 800 to 1000 mmHg at 25°C. 2 The kinematic viscosity of high-viscosity dimethyl silicone oil at 25°C is 8000–12000 mm / s. 2 / s.

[0009] Preferably, the amount of vinyl-terminated polydimethylsiloxane added is 8% to 15% of the mass of dimethyl silicone oil; the amount of hydrophobic treated fumed silica added is 1% to 3% of the total mass of the matrix components; the amount of polysiloxane crosslinking agent containing silane-hydrogen bonds added in the site-directed micro-crosslinking system is 4% to 8% of the total mass of the matrix components; the amount of reaction inhibitor added in the site-directed micro-crosslinking system is 0.5% to 2% of the total mass of the matrix components; and the amount of Karstedt-type platinum catalyst xylene solution added in the site-directed micro-crosslinking system is 0.8% to 1.2% of the total mass of the matrix components.

[0010] Preferably, the spherical alumina particles are multi-size composite spherical alumina particles, and include at least coarse-sized spherical alumina, medium-sized spherical alumina, and fine-sized spherical alumina, wherein the median particle size of the coarse-sized spherical alumina is 40-60 μm, the median particle size of the medium-sized spherical alumina is 15-35 μm, and the median particle size of the fine-sized spherical alumina is 0.5-2.0 μm; and based on 100 parts by mass of the total mass of the spherical alumina particles, the medium-sized spherical alumina comprises 40-50 parts by mass, the fine-sized spherical alumina comprises 8-15 parts by mass, and the remainder is coarse-sized spherical alumina.

[0011] Preferably, the median particle size of the plate-like boron nitride is 7–12 μm.

[0012] The method for preparing the layered interface modified spherical alumina includes the following steps: mixing and reacting a polysiloxane crosslinking agent containing silane-hydrogen bonds, anhydrous p-xylene, vinyltriethoxysilane, and a Karstedt-type platinum catalyst xylene solution; subsequently adding a rare earth metal organometallic solution, a zirconium metal organometallic solution, and a reaction inhibitor to obtain a metal ion complex-brush layer precursor; dispersing spherical alumina particles in anhydrous p-xylene, adding the metal ion complex-brush layer precursor and mixing to construct an inner polysiloxane brush layer on the surface of the spherical alumina particles; adding anhydrous ethanol and deionized water to initiate hydrolysis condensation, followed by adding vinyltriethoxysilane and zirconium(IV) acetylacetone to form an outer vinyl / zirconium coordination fixation layer on the surface of the spherical alumina particles; filtering, washing, and drying to obtain layered interface modified spherical alumina.

[0013] Preferably, the rare earth metal ions are selected from one or more of cerium ions, lanthanum ions, and yttrium ions.

[0014] Preferably, the raw materials for preparing the metal ion complex-brush layer precursor, based on 100 parts by weight of a polysiloxane crosslinking agent containing silane-hydrogen bonds, include: 60-100 parts by weight of anhydrous p-xylene, 15-25 parts by weight of vinyltriethoxysilane, 0.5-1.5 parts by weight of a Karstedt-type platinum catalyst xylene solution, 3-7 parts by weight of a rare earth metal organometallic solution, 3-7 parts by weight of a zirconium metal organometallic solution, and 0.5-1.5 parts by weight of a reaction inhibitor.

[0015] Preferably, in the raw materials for preparing the layered interface modified spherical alumina, based on 100 parts by weight of spherical alumina particles: the total amount of anhydrous ethanol and deionized water used to initiate hydrolysis and condensation is 8 to 15 parts by weight, the amount of vinyltriethoxysilane added is 0.8 to 2.5 parts by weight, and the amount of zirconium(IV) acetylacetone added is 0.3 to 1.2 parts by weight.

[0016] A method for preparing a low thermal resistance, low oil penetration, aging-resistant thixotropic, high thermal conductivity silicone grease as described above includes the following steps: (1) Dimethyl silicone oil, vinyl-terminated polydimethylsiloxane and hydrophobic fumed silica are mixed to obtain a matrix slurry; (2) Add layered interface modified spherical alumina and flake boron nitride to the matrix slurry and disperse them to make the thermally conductive filler form a thermally conductive network; (3) Add a polysiloxane crosslinking agent containing silane-hydrogen bonds and a reaction inhibitor and mix them; (4) Add a platinum catalyst to trigger the addition reaction between the polysiloxane crosslinking agent containing silane-hydrogen bonds and the vinyl-terminated polydimethylsiloxane to form a site-directed crosslink; (5) Degas and heat to cure to obtain thixotropic high thermal conductivity silicone grease.

[0017] The beneficial effects of this invention are: This invention significantly improves the continuity and stability of the heat conduction pathway by synergistically constructing a three-dimensional thermally conductive network through layered interface-modified spherical alumina and plate-like boron nitride. The polysiloxane brush layer and metal ion gradient formed on the surface of the layered interface-modified spherical alumina effectively reduce the thermal boundary impedance between the inorganic filler and the organic matrix, enabling efficient heat transfer at the interface. At the same time, the plate-like boron nitride acts as a bridging sheet across the gaps in the spherical skeleton, reducing the void thermal resistance in the heat conduction path, thereby achieving excellent thermal conductivity even with high filler content.

[0018] By employing a pre-network-based, post-formation micro-crosslinking strategy, the system triggers sparse crosslinking only after the thermally conductive network has fully formed, avoiding the inhibition of filler orientation caused by sudden viscosity increases in traditional processes. This design enables the silicone grease to exhibit a high thixotropic index during resting, enhancing its anti-sagging and anti-settling capabilities, while its viscosity rapidly decreases under application shear, facilitating thin-layer coating. The chemical locking of the filler-matrix interface by the micro-crosslinked network further reduces the tendency of silicone oil migration and improves its morphological stability during long-term use.

[0019] The introduction of a metal ion gradient and a zirconium coordination immobilization layer enhances the thermo-oxidative aging stability of the interfacial layer. The rare earth metal ions and zirconium coordination system form a stable anchor in the polysiloxane brush layer, inhibiting the degradation and relaxation of the interfacial layer at high temperatures, thus maintaining low thermal resistance and low pump-out loss during thermal cycling. The outer vinyl groups participate in the micro-crosslinking reaction, strengthening the interfacial bonding between the filler and the matrix and reducing the risk of interfacial delamination caused by thermal expansion and contraction.

[0020] The gradation design of multi-size spherical alumina optimizes the packing density, while fine-grained packing fills the coarse-to-medium-grained pores, reducing the system's free volume and thus lowering the probability of oil seepage channel formation. The bridging effect of lamellar boron nitride, in conjunction with the spherical framework, ensures the structural integrity of the heat-conducting network under mechanical stress or temperature changes, preventing localized interruptions in heat conduction pathways. The overall solution maintains high thermal conductivity while also considering ease of construction and long-term reliability, making it suitable for thermal management applications in high-power electronic devices. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0022] 1. Overall Framework of Technical Solution This invention provides a low thermal resistance, low oil seepage, aging resistance, and thixotropic high thermal conductivity silicone grease. The grease uses dimethyl silicone oil as a base, and constructs a three-dimensional thermally conductive network by combining layered, interface-modified spherical alumina and lamellar boron nitride. Furthermore, it employs a site-specific micro-crosslinking strategy of first constructing the network and then shaping it, resulting in a silicone grease that simultaneously possesses high thermal conductivity, low interfacial thermal resistance, good thixotropy, and long-term stability.

[0023] In the silicone grease provided by this invention, the core design can be summarized into two parallel and mutually coupled technical paths: (1) Layered interface modified spherical alumina: “inner polysiloxane brush layer + metal ion gradient” is constructed on the surface of spherical alumina, and vinyl groups are further introduced on the outer layer, so that the surface of inorganic filler has both low interfacial thermal boundary impedance and reaction sites that can participate in micro-crosslinking, thereby achieving low thermal resistance and low oil permeation without sacrificing high filling capacity, and improving thermo-oxidative aging stability with the help of rare earth / zirconium coordination system.

[0024] (2) "Network first, shape later" fixed-point micro-crosslinking process: crosslinking is triggered after the formation of the thermally conductive network, avoiding the viscosity surge and filler orientation obstruction caused by the traditional "dispersion and reaction at the same time", thereby obtaining low thermal resistance and high thixotropy at the same time, and reducing oil leakage rate and long-term sedimentation risk through sparse chemical locking.

[0025] 2. Component composition and parameter optimization 2.1 Matrix Components In the silicone grease provided by the present invention, the matrix preferably includes: dimethyl silicone oil and vinyl-terminated polydimethylsiloxane; wherein, dimethyl silicone oil is used to provide basic rheology and wettability, and vinyl-terminated polydimethylsiloxane is used to provide reactive sites and participate in subsequent micro-crosslinking and shaping.

[0026] In the silicone grease provided by this invention, the dimethyl silicone oil is preferably a blend of dimethyl silicone oils of different viscosity grades to achieve "gradual control of matrix viscosity". The dimethyl silicone oil is preferably a mixture of low-viscosity dimethyl silicone oil and high-viscosity dimethyl silicone oil in a mass ratio of 1.4 to 1.9:1; the kinematic viscosity of the low-viscosity dimethyl silicone oil at 25°C is preferably 800 to 1000 mmHg. 2 The kinematic viscosity of high-viscosity dimethyl silicone oil at 25°C is preferably 8000–12000 mm / s. 2 / s.

[0027] This parameter affects the matrix's ability to wet and resist oil seepage of highly filled thermally conductive powders, which in turn affects the system's oil seepage rate and thixotropic recovery rate: low viscosity can easily lead to the migration of free silicone oil and increased oil seepage; high viscosity may make dispersion difficult and reduce shear workability.

[0028] In the silicone grease provided by the present invention, the mass ratio of low viscosity dimethyl silicone oil to high viscosity dimethyl silicone oil is preferably 1 to 2.2:1, specifically 1.1:1, 1.3:1, 1.6:1, 1.8:1, 2.0:1 or 2.2:1; more preferably 1.4 to 1.9:1.

[0029] In the silicone grease provided by the present invention, the amount of vinyl-terminated polydimethylsiloxane added is preferably 8% to 15% of the mass of dimethyl silicone oil.

[0030] The amount added affects the density of crosslinking points and network locking strength of subsequent micro-crosslinking, which in turn affects the thixotropic index, oil impermeability, and long-term thermal cycling stability: too little addition will lead to insufficient sizing, while too much addition may result in too many reaction sites and excessively rapid thickening of the system.

[0031] Alternative raw materials: Without affecting the technical effect of the present invention, the dimethyl silicone oil can be replaced with the same type of linear polysiloxane oil or end-capped polysiloxane oil (methyl-capped, etc.); the vinyl-terminated polydimethylsiloxane can be replaced with other vinyl-terminated polysiloxanes (different degree of polymerization), or vinyl side-chain modified polysiloxanes can be used as the reaction component.

[0032] 2.2 Thermally conductive filler composition In the silicone grease provided by the present invention, the thermally conductive filler preferably comprises: spherical alumina with layered interface modification and lamellar boron nitride; wherein the spherical alumina is used to form a high-density particle skeleton, and the lamellar boron nitride is used as a high aspect ratio "bridging sheet" to cross the particle gaps and improve the continuity of the effective thermal conductivity path.

[0033] In the silicone grease provided by this invention, the spherical alumina is preferably a multi-size composite to construct a multi-scale particle stacking framework. The spherical alumina preferably comprises at least: coarse-grained spherical alumina, medium-grained spherical alumina, and fine-grained spherical alumina; wherein: The median particle size of the coarse-grained spherical alumina is preferably 40–60 μm, specifically 40 μm, 45 μm, 46 μm, 50 μm, 55 μm or 60 μm; The median particle size of the medium-diameter spherical alumina is preferably 15–35 μm, specifically 15 μm, 20 μm, 24 μm, 25 μm, 30 μm or 35 μm; The median particle size of the fine-grained spherical alumina is preferably 0.5–2.0 μm, specifically 0.5 μm, 0.8 μm, 0.9 μm, 1.2 μm, 1.5 μm or 2.0 μm.

[0034] The particle size distribution affects the packing porosity and the number of particle-particle contact points, which in turn affects the effective contact thermal resistance of the heat-conducting network: fine particles can fill the pores created by the packing of coarse and medium-sized particles, increasing the packing density; coarse and medium-sized particles provide a framework to prevent the ineffective increase of the system viscosity.

[0035] In the silicone grease provided by the present invention, the median particle size of the sheet-like boron nitride is preferably 5 to 15 μm, specifically 5 μm, 8 μm, 8.5 μm, 10 μm, 12 μm or 15 μm; more preferably 7 to 12 μm.

[0036] This parameter affects the bridging distance and orientation behavior of the sheet-like filler, which in turn affects the cross-scale connectivity of the heat conduction pathway: if the particle size is too small, the bridging ability is insufficient, while if it is too large, it may cause dispersion difficulties and an increase in shear viscosity.

[0037] In the silicone grease provided by the present invention, the total amount of thermally conductive filler added (based on the total mass of the silicone grease) is preferably 85% to 92%, specifically 85%, 86%, 88%, 89%, 90%, 91% or 92%; more preferably 88% to 91%.

[0038] This parameter directly affects the thermal conductivity and the processability of the system: increasing the filler content is beneficial to improving the thermal conductivity, but too high a content will cause the system to be unable to be uniformly dispersed or to lose its coatability; this invention maintains low thermal resistance and thixotropic properties even with high filler content by using interface modification and a pre-network and post-sizing process.

[0039] In the silicone grease provided by the present invention, the mass ratio of layered interface modified spherical alumina to plate boron nitride is preferably 2.5:1 to 4.5:1, specifically 2.5:1, 3.0:1, 3.5:1, 4.0:1 or 4.5:1; more preferably 3.0:1 to 4.0:1.

[0040] This mass ratio affects the degree of synergy between the "particle skeleton-sheet bridging": too low a proportion of spherical alumina can easily lead to an unstable skeleton and increased thermal resistance; too low a proportion of sheet boron nitride will result in insufficient bridging and discontinuous global heat conduction pathways.

[0041] Alternative materials: Without departing from the technical effect of this invention, the sheet-like boron nitride can be replaced with other sheet-like boron nitride or high thermal conductivity sheets (such as sheet-like aluminum nitride); the spherical alumina can be replaced with other high-purity spherical alumina or surface-modifiable spherical oxide fillers. To maintain low thermal resistance and low oil permeation, it is preferable to still use spherical particles that can be modified at the layered interface as the skeleton filler.

[0042] 2.3 Thixotropic Regulator Components In the silicone grease provided by this invention, the thixotropic modulating component is preferably hydrophobically treated fumed silica. The amount of hydrophobically treated fumed silica added (based on the total mass of the matrix components) is preferably 0.5% to 5%, specifically 0.5%, 1%, 2%, 3%, 4%, or 5%; more preferably 1% to 3%.

[0043] This parameter affects the yield stress and thixotropic recovery of the system: an appropriate amount of fumed silica can form a weak network with the matrix, improving static flow resistance and inhibiting oil seepage; an excessive amount will significantly thicken the system and affect the dispersion efficiency and workability under high filling conditions.

[0044] The hydrophobic treated fumed silica can be replaced with other hydrophobic silica, surface organosilicon alkylated silica, or a compound system with a small amount of thixotropic additives (provided that the thixotropic index and low oil permeability target can still be achieved).

[0045] 2.4 Site-directed micro-crosslinking system In the silicone grease provided by the present invention, the site-directed micro-crosslinking system preferably includes: a polysiloxane crosslinking agent containing silane-hydrogen bonds, a platinum catalyst, and a reaction inhibitor; wherein, the polysiloxane crosslinking agent containing silane-hydrogen bonds undergoes an addition reaction with the polysiloxane containing vinyl end groups to achieve sparse micro-crosslinking; the reaction inhibitor is used to delay the reaction rate during the mixing and dispersion stage; and the platinum catalyst is used to trigger / accelerate crosslinking during the shaping stage.

[0046] In the silicone grease provided by the present invention, the amount of the polysiloxane crosslinking agent containing silane-hydrogen bonds added (based on the total mass of the matrix components) is preferably 2% to 10%, specifically 2%, 4%, 6%, 8% or 10%; more preferably 4% to 8%.

[0047] This parameter affects the micro-crosslinking density and network locking strength: too low a value will lead to insufficient shaping, reduced resistance to oil seepage and sedimentation; too high a value will lead to excessively rapid system curing, narrowing of the construction window, and may introduce additional elasticity, resulting in poor interfacial contact.

[0048] In the silicone grease provided by the present invention, the platinum catalyst is preferably a Karstedt-type platinum catalyst or other platinum-based catalysts capable of catalyzing hydrosilylation reactions.

[0049] In the silicone grease provided by the present invention, the reaction inhibitor is preferably an alkynyl alcohol inhibitor; the amount of the inhibitor added (based on the total mass of the matrix components) is preferably 0.2% to 3%, specifically 0.2%, 0.5%, 1%, 2% or 3%; more preferably 0.5% to 2%.

[0050] This parameter affects the timing controllability of "network construction followed by setting": too little inhibitor will cause premature reaction and sudden increase in viscosity during the mixing stage; too much will cause insufficient reaction during the setting stage.

[0051] Alternative raw materials: In addition to 3-methyl-1-pentyn-3-ol, other alkynols, alkynes, or platinum inhibitors containing coordination groups can be selected as the inhibitors, as long as they can inhibit during the dispersion stage, release inhibition after heating or encapsulation, and complete micro-crosslinking.

[0052] 3. Preparation method of layered interface modified spherical alumina This invention also provides a method for preparing layered interface-modified spherical alumina, wherein the layered interface-modified spherical alumina comprises: spherical alumina particles, and an inner polysiloxane brush layer (introducing a metal ion gradient) and an outer vinyl / zirconium coordination fixation layer sequentially formed on the surface of the spherical alumina. In this invention, by synergistically controlling the amounts of precursor, solvent, hydrolysis system, and outer layer introducer, the uniformity of the modified layer and the density of reaction sites can be improved without significantly increasing viscosity, thereby reducing the thermal boundary impedance of the inorganic / organic interface, inhibiting oil seepage, and improving aging resistance.

[0053] 3.1 Preparation of metal ion complex-brush layer precursor In the preparation of the precursor provided by this invention, the proportioning is preferably controlled based on the amount of the polysiloxane crosslinking agent containing silane-hydrogen bonds. The proportion of the polysiloxane crosslinking agent containing silane-hydrogen bonds is 100 parts by weight: The anhydrous p-xylene is preferably 60 to 100 parts by weight, and more specifically, 80 parts by weight; Vinyltriethoxysilane is preferably 15 to 25 parts by weight, and more specifically, 20 parts by weight; The xylene solution containing Karstedt platinum catalyst is preferably 0.5 to 1.5 parts by mass, and more specifically, 1 part by mass. The rare earth metal organic solution (preferably cerium(III) 2-ethylhexanoate solution) is preferably 3 to 7 parts by mass, specifically 5 parts by mass; The zirconium metal organic solution (preferably zirconium(IV)2-ethylhexanoate mineral oil solution) is preferably 3 to 7 parts by mass, specifically 5 parts by mass; The reaction inhibitor (preferably 3-methyl-1-pentyn-3-ol) is preferably 0.5 to 1.5 parts by weight, specifically 1 part by weight.

[0054] The amount of anhydrous p-xylene affects the system viscosity and mass transfer efficiency, which in turn affects the homogeneity of the precursor and the uniformity of subsequent brush layer deposition; the amount of vinyltriethoxysilane affects the density of hydrolyzable alkoxy groups, which in turn affects the number of anchor points and the coverage of the brush layer; the amount of platinum catalyst affects the reaction rate, which in turn affects the molecular weight distribution of the precursor and the consistency of subsequent film formation on the filler surface; the amount of rare earth / zirconium organic compounds affects the metal ion gradient and coordination stability, which in turn affects aging resistance and interfacial stability; the amount of inhibitor affects the controllability of the reaction sequence, which in turn affects batch stability and repeatability.

[0055] Rare earth metal organometallic compounds can be replaced by lanthanum salts or yttrium salts instead of cerium salts; zirconium metal organometallic compounds can be replaced by zirconium carboxylate salts, etc.; and the solvent can be replaced by p-xylene with toluene, ethylbenzene, or a mixture thereof.

[0056] 3.2 Construction of the inner polysiloxane brush layer In the inner layer brush construction step provided by the present invention, it is preferable to determine the amount of each substance based on the total mass of spherical alumina.

[0057] 1) Spherical alumina particle size distribution and dosage In the method provided by this invention, the spherical alumina is preferably a multi-particle-size composite. Based on a total mass of 100 parts by weight of spherical alumina: The preferred amount of medium-sized spherical alumina is 40-50 parts by weight, specifically 43-45 parts by weight; The fine-particle-size spherical alumina is preferably 8 to 15 parts by weight, and more specifically, it can be 10 to 14 parts by weight. The remainder is coarse-grained spherical alumina.

[0058] 2) Amount of dispersing solvent In the method provided by the present invention, the amount of anhydrous p-xylene (relative to the total mass of spherical alumina) is preferably 130% to 200%, and more specifically 160% to 190%.

[0059] 3) Amount of metal ion complex-brush layer precursor In the method provided by the present invention, the amount of the metal ion complex-brush layer precursor added (relative to the total mass of spherical alumina) is preferably 4% to 8%, and more specifically 5% to 7%.

[0060] The amount of solvent determines the slurry's solid content and shear dispersion efficiency, which in turn affects the uniformity of the brush layer deposition; the amount of precursor added determines the brush layer thickness and coverage: insufficient addition will lead to inadequate interface modification, while excessive addition may form a free polysiloxane phase and increase the burden of subsequent washing.

[0061] 3.3 Hydrolysis-condensation and outer vinyl / zirconium coordination fixation Amount and ratio of hydrolysis system (anhydrous ethanol / deionized water) In the method provided by the present invention, the total amount of anhydrous ethanol and deionized water added to initiate hydrolysis and condensation (relative to the total mass of spherical alumina) is preferably 8% to 15%; wherein the mass ratio of anhydrous ethanol to deionized water is preferably 2.5 to 3.5:1.

[0062] 2) Amount of outer vinyl introducing agent In the method provided by the present invention, the amount of the outer vinyl introducing agent (preferably vinyltriethoxysilane) added (relative to the total mass of the spherical alumina) is preferably 0.8% to 2.5%, specifically 1.0% to 2.0%.

[0063] 3) Amount of zirconium coordination immobilization layer (zirconium(IV) acetylacetone) and amount of dissolving solvent In the method provided by the present invention, the amount of zirconium coordination fixative (preferably zirconium(IV) acetylacetone) added (relative to the total mass of spherical alumina) is preferably 0.3% to 1.2%, specifically 0.4% to 0.8%; the amount of anhydrous ethanol used for dissolution is preferably 5 to 15 times the mass of zirconium(IV) acetylacetone.

[0064] The amount of water used determines the hydrolysis rate and the degree of condensation, which in turn affects the density of the brush layer and the fixation effect of the metal ion gradient; the amount of the outer layer vinyl introducer determines the density of reactive vinyl sites, which in turn affects the chemical locking strength of the filler-matrix interface by subsequent site-directed micro-crosslinking; the amount of zirconium coordination fixative affects the stability and aging resistance of the outer layer: too low zirconium coordination results in insufficient fixation, while too high coordination may introduce ineffective deposition and affect dispersion.

[0065] 3.4 Filtration, Washing and Drying In the method provided by this invention, it is preferable to filter while hot after the reaction is complete, and wash with anhydrous ethanol to remove free small molecules. The number of anhydrous ethanol washes is preferably 2 to 3 times, specifically 2 times.

[0066] In the method provided by the present invention, the vacuum drying temperature is preferably 100-140°C, specifically 110°C, 120°C or 130°C; the vacuum drying time is preferably 300-600 min, specifically 360 min, 480 min or 540 min.

[0067] 4. Preparation method and key process parameters of silicone grease The present invention also provides a method for preparing the silicone grease described in the above technical solution, preferably comprising: matrix premixing and degassing, segmented addition of thermally conductive filler to form a network, addition of a micro-crosslinking system and point-triggered shaping, vacuum degassing and encapsulation curing.

[0068] In the preparation method provided by the present invention, the matrix premixing temperature is preferably 20-60°C, specifically 20°C, 30°C, 40°C, 50°C or 60°C; more preferably 30-45°C.

[0069] This parameter affects the viscosity of the matrix and the wetting rate: a moderate increase in temperature can reduce viscosity and facilitate the uniform dispersion of fumed silica and vinyl polysiloxane; excessive temperature may cause the inhibitor to volatilize or cause abnormal reaction rates.

[0070] In the preparation method provided by the present invention, the preferred order of adding the thermally conductive filler is "spherical skeleton filler first, followed by sheet-like bridging filler", or "spherical filler and sheet-like filler are added alternately in segments"; more preferably, layered interface modified spherical alumina is added first, followed by sheet-like boron nitride.

[0071] This order affects the efficiency of network formation and the orientation of sheet fillers: first the skeleton and then the bridging is conducive to the formation of stable three-dimensional channels and reduces sheet agglomeration and ineffective adhesion.

[0072] In the preparation method provided by the present invention, the vacuum degassing pressure is preferably 5 to 20 kPa (absolute pressure), specifically 5 kPa, 8 kPa, 10 kPa, 15 kPa or 20 kPa; the degassing time is preferably 10 to 60 min, specifically 10 min, 20 min, 30 min, 40 min, 50 min or 60 min.

[0073] This parameter affects the residual bubbles and the interfacial contact thermal resistance: residual bubbles can significantly increase thermal resistance and reduce reliability, so it is preferable to set a debubbling step before and after mesh formation.

[0074] In the preparation method provided by the present invention, the shaping and curing temperature is preferably 60-100℃, specifically 60℃, 70℃, 80℃, 90℃ or 100℃; the curing time is preferably 30-240min, specifically 30min, 60min, 90min, 120min, 180min or 240min; more preferably 75-90℃ or 90-150min.

[0075] This parameter affects the degree of micro-crosslinking completion and thixotropic recovery: insufficient curing will lead to weak network locking and increased risk of oil seepage; excessive curing may cause the system to be too hard and affect interface wetting.

[0076] In the preparation method provided by this invention, the key control point of "first constructing the network and then shaping" is: after the thermally conductive filler is dispersed and constructed, a platinum catalyst is added to trigger crosslinking, or an inhibitor is used to delay the reaction before adding the platinum catalyst, so as to avoid a sudden increase in viscosity and obstruction of filler orientation during the mixing stage, thereby taking into account both low thermal resistance and high thixotropy, and reducing the risk of oil seepage and sedimentation.

[0077] 5. Summary of Mechanism and Effects In the silicone grease provided by this invention: By constructing a high-packed framework using multi-sized spherical alumina and bridging the gaps between the frameworks with plate-like boron nitride, a continuous three-dimensional thermally conductive network can be formed, which improves the thermal conductivity and reduces the bulk thermal resistance of the system.

[0078] By modifying the interface layer (inner polysiloxane brush layer + metal ion gradient, outer vinyl layer), the thermal boundary impedance of the inorganic / organic interface can be reduced, thereby reducing the interface thermal resistance; at the same time, the rare earth / zirconium coordination system improves the stability of thermo-oxidative aging and reduces the tendency of oil seepage.

[0079] By using a "network-first, shape-later" method of point-based micro-crosslinking, sparse chemical locking is triggered after the network is formed, avoiding a sudden increase in viscosity and obstruction of filler orientation during the dispersion process. This achieves both low thermal resistance and high thixotropy, and reduces the risk of oil seepage and long-term sedimentation at 85°C.

[0080] The technical solution will be clearly and completely described below through embodiments; obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0081] Example 1: In this example, the dimethyl silicone oil used is Wacker Chemicals polydimethylsiloxane WACKER AK1000 (kinematic viscosity at 25°C approximately 1000 mmHg). 2 / s) and WACKER AK10000 (kinematic viscosity at 25°C approximately 10000 mm) 2 / s) was used as the matrix viscosity step-adjusting component. Spherical alumina was selected from the DENKA SPHERICAL ALUMINA series by Denka Company Limited, including DAW-45 (d50 approx. 46.1 μm), DAW-20 (d50 approx. 23.8 μm), and ASFP-07S (d50 approx. 0.9 μm), used to construct a multi-scale spherical particle stacked thermally conductive framework. Plate-like boron nitride was selected from Saint-Gobain Boron Nitride's Standard Platelet SP8 (d50 approx. 8.5 μm) as the high aspect ratio thermally conductive bridging sheet. The thixotropic auxiliary component was selected from Evonik Operations GmbH's hydrophobic fumed silica AEROSIL R972 (DDS post-treated fumed silica). The rare earth and zirconium metal organometallic compounds used were cerium (III) 2-ethylhexanoate solution (49% solution, Ce content 12%) from Thermo Scientific Chemicals, and zirconium (IV) 2-ethylhexanoate mineral oil solution (approximately 6% Zr concentration, product number 768634) and zirconium (IV) acetylacetone (product number 338001) from Sigma-Aldrich. The Karstedt-type platinum catalyst xylene solution used was Karstedt-type platinum catalyst (approximately 2% Pt xylene solution, product number 479519) from Sigma-Aldrich. The vinyl-terminated polydimethylsiloxane and the silanol-containing polysiloxane crosslinking agent used were vinyl-terminated polydimethylsiloxane DMS-V31 and methylhydrosiloxane-dimethylsiloxane copolymer HMS-301 from Gelest, respectively.

[0082] Step 1: Under dry and nitrogen-protected conditions, 100g of a polysiloxane crosslinking agent containing silane bonds and 80g of anhydrous p-xylene were added to a mechanically stirred reactor. The mixture was heated to 80°C and stirred at 600 rpm for 30 min to form a homogeneous solution. Then, 20g of vinyltriethoxysilane was added and the temperature was raised to 90°C. 1g of a Karstedt-type platinum catalyst xylene solution was added, and the mixture was stirred at 90°C for 180 min to obtain a polysiloxane precursor carrying triethoxysilane groups. After the reaction was completed, the temperature was lowered to 40°C, and 5g of cerium(III) 2-ethylhexanoate solution and 5g of zirconium(IV) 2-ethylhexanoate mineral oil solution were added sequentially. Then, 1g of 3-methyl-1-pentyn-3-ol was added as an inhibitor for subsequent processes and the mixture was stirred at 40°C for 30 min to obtain a metal ion complex-brush layer precursor. Step 2: Under dry and nitrogen-protected conditions, add 300g of spherical alumina DAW-45, 300g of spherical alumina DAW-20, and 90g of spherical alumina ASFP-07S to the reactor, along with 1200g of anhydrous p-xylene. Disperse at 800rpm for 60min at 90°C, then add 40g of the metal ion complex-brush layer precursor and continue stirring at 90°C for 120min. Subsequently, premix 60g of anhydrous ethanol with 20g of deionized water and add dropwise at 90°C over 60min intervals. After the addition was completed, the mixture was kept at a constant temperature and stirred for 120 min to form the inner layer of the polysiloxane brush layer. Then, the temperature was lowered to 60°C, and 10 g of vinyltriethoxysilane was added and stirred for 30 min. Then, 4 g of zirconium(IV) acetylacetone was dissolved in 40 g of anhydrous ethanol and added at once and stirred for 20 min. The mixture was stirred at 60°C for 180 min. After the reaction was completed, the mixture was filtered while hot and washed twice with anhydrous ethanol to remove free small molecules. Then, it was vacuum dried at 120°C for 480 min to obtain the layered interface modified spherical alumina. Step 3: Add 55g of WACKER AK1000 dimethyl silicone oil, 34g of WACKER AK10000 dimethyl silicone oil, 10g of vinyl-terminated polydimethylsiloxane, and 2g of hydrophobic fumed silica to a planetary vacuum stirred tank. Premix at 600rpm for 30min at 40°C, then vacuum to 8kPa for degassing for 20min to obtain a uniform matrix slurry. Subsequently, add 700g of layered interface-modified spherical alumina and 200g of flake boron nitride powder sequentially at 40°C, disperse at 800rpm for 20min, then add 6g of polysiloxane crosslinking agent containing silane-hydrogen bonds and 1g of 3-methyl-1-pentyn-3-ol and stir for 10min. Finally, add 1g of... After stirring the Karstedt type platinum catalyst xylene solution for 5 minutes, the vacuum was drawn to 8 kPa for degassing for 30 minutes and then filled into a sealed aluminum tube. After filling, the aluminum tube was placed in an 80°C constant temperature oven for 120 minutes and then cooled to 25°C to obtain a low thermal resistance, low oil seepage, aging resistant thixotropic high thermal conductivity silicone grease.

[0083] Example 2: The difference from Example 1 is that in step 3, the amounts of dimethyl silicone oil WACKER AK1000 and dimethyl silicone oil WACKER AK10000 are adjusted to 50g and 39g respectively; the other conditions are the same as in Example 1. Example

[0084] The difference from Example 1 is that: in step 1, the cerium(III) 2-ethylhexanoate solution is replaced with the lanthanum(III) 2-ethylhexanoate solution, and the amount added is still 5g; in step 1, the zircon(IV) 2-ethylhexanoate mineral oil solution is replaced with the zircon(IV) neodecanoate mineral oil solution, and the amount added is still 5g; the other conditions are the same as in Example 1. Example

[0085] The difference from Example 1 is that the amount of layered interface modified spherical alumina and flake boron nitride powder added in step 3 is adjusted to 740g and 160g respectively; the other conditions are the same as in Example 1. Example

[0086] The difference from Example 1 is that the amount of 3-methyl-1-pentyn-3-ol added in step 1 is adjusted to 0.5g; the other conditions are the same as in Example 1. Example

[0087] The difference from Example 1 is that the amount of 3-methyl-1-pentyn-3-ol added in step 1 is adjusted to 1.5g; the other conditions are the same as in Example 1.

[0088] Comparative Example 1: The difference from Example 1 is that: in step 2, the spherical alumina is not subjected to layered interface modification treatment, and unmodified spherical alumina is directly obtained and used in step 3 to replace the layered interface modified spherical alumina; the other conditions are the same as in Example 1.

[0089] Comparative Example 2: The difference from Example 1 is that: in step 1, cerium(III) 2-ethylhexanoate solution is not added, and the mixture is made up with an equal mass of anhydrous p-xylene; the other conditions are the same as in Example 1.

[0090] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that: in step 1, zirconium(IV)2-ethylhexanoate mineral oil solution is not added, and an equal mass of anhydrous p-xylene is used to make up the difference; the other conditions are the same as in Example 1.

[0091] Comparative Example 4: The difference from Example 1 is that zirconium(IV) acetylacetone is not added in step 2, and 40g of anhydrous ethanol originally used to dissolve zirconium(IV) acetylacetone is added separately at once to keep the solvent conditions consistent; the other conditions are the same as in Example 1.

[0092] Comparative Example 5: The difference from Example 1 is that the outer vinyltriethoxysilane is not added in step 2 and is replaced by an equal mass of anhydrous p-xylene; the other conditions are the same as in Example 1.

[0093] Comparative Example 6: The difference from Example 1 is that in step 3, the timing of adding the Karstedt-type platinum catalyst xylene solution was changed from adding it after the thermally conductive filler dispersion and network formation was completed to adding it during the matrix premixing stage, thus failing to meet the key control point for post-network formation and shaping; that is, adding 55g of dimethyl silicone oil WACKER AK1000, 34g of dimethyl silicone oil WACKER AK10000, 10g of vinyl-terminated polydimethylsiloxane DMS-V31 and 2g of hydrophobic fumed silica AEROSIL to a planetary vacuum stirred tank. R972 was premixed at 40°C and 600 rpm for 20 min, followed by the addition of 1 g of Karstedt-type platinum catalyst xylene solution and stirring for 10 min. The mixture was then degassed under vacuum to 8 kPa for 20 min to obtain a uniform matrix slurry. Subsequently, 700 g of layered interface modified spherical alumina and 200 g of flake boron nitride powder were added sequentially at 40°C and dispersed at 800 rpm for 20 min. Then, 6 g of methylhydrosiloxane-dimethylsiloxane copolymer HMS-301 and 1 g of 3-methyl-1-pentyn-3-ol were added and stirred for 10 min. The remaining conditions were the same as in Example 1.

[0094] Comparative Example 7: The difference from Example 1 is that: in step 2, spherical alumina DAW-45 and spherical alumina ASFP-07S are not added, and the amount of spherical alumina DAW-20 added is adjusted to 690g; the other conditions are the same as in Example 1.

[0095] Performance testing: Thermal conductivity test: The transient planar heat source method was used to test the thermal conductivity according to GB / T 32064-2015. Each sample was placed in a cylindrical sample cup with an inner diameter of 50 mm and a depth of 15 mm. After loading the sample, obvious voids were removed and the surface was smoothed with a scraper. A planar heat source probe with a diameter of 12.8 mm was clamped between the same sample in two cups to form a symmetrical structure. The contact pressure was set to 0.20 MPa, the test temperature was 25℃, the heating power was 0.20 W, and the test time was 20 s. Each sample was tested three times and the arithmetic mean was taken to obtain the thermal conductivity.

[0096] Area thermal resistance test: Referring to GB / T 43611-2023 regarding the classification of thermal interface materials using thermal conductivity and thermal resistance as indicators, the steady-state one-dimensional heat flow interface method was used to test the thermal resistance. Two copper hot blocks (effective contact area 25mm × 25mm) were selected. The contact surfaces were sequentially sanded to a surface roughness Ra = 0.8μm and then cleaned and dried with anhydrous ethanol. A 50μm thick silicone grease layer was prepared on the surface of the lower hot block using a scraping method and limited by a metal gasket. After loading the upper hot block, a clamping pressure of 0.40MPa was applied. The hot end temperature was set to 60℃ and the cold end temperature to 20℃. After the heat flow and temperature stabilized for 30 minutes, the steady-state heat flow density and the temperature difference between the upper and lower hot blocks' temperature measuring holes were recorded. The area thermal resistance R was then measured. A = (ΔT / q) × 10 4 The area thermal resistance is then calculated.

[0097] Apparent viscosity and thixotropic index test: Apparent viscosity was determined according to GB / T 2794-2022 single-cylinder rotational viscometer method, and the thixotropic index was given: After the sample was kept at 25℃ for 24 hours, it was placed into a standard rotor sample cup, the temperature was set at 25℃, and a shear rate of 0.5s was applied first. -1 Shearing for 60 seconds to record viscosity η 0.5 Then, at a shear rate of 50s -1 Shearing for 60 seconds to record viscosity η 50 Define the thixotropic index TI = η 0.5 / η 50 Each sample was repeated 3 times and the average value was taken.

[0098] Cone penetration test: Cone penetration was determined according to GB / T 269-2023. The sample was placed in a 25℃ constant temperature oven for 24 hours, then loaded into a standard cone penetration cup and leveled. The working cone penetration was measured after 60 cycles of work (60 tamping blows), and then the same sample was subjected to 10,000 cycles of work before the cone penetration was measured. The change in cone penetration ΔP = P was calculated. 10000 -P 60 To characterize mechanical shear stability.

[0099] Oil seepage rate test: The pressure separation rate was determined according to the principle of the pressure oil separator in GB / T 392-1977, and the same device was set to 85℃. 10.00g of each sample was weighed and placed above the screen of the pressure oil separator, covered with filter paper, and loaded with a 1000g weight. The device was placed in an 85℃ constant temperature chamber for 24 hours. After the test, the separated silicone oil was collected and its mass m was measured. The oil seepage rate was calculated as oil seepage rate = m / 10.00 × 100%. Three parallel tests were performed for each sample, and the average value was taken.

[0100] Thermal cycling stability test: Thermal cycling was conducted according to GB / T 2423.22-2012 temperature change test. The thermal resistance test fixture (including a 50μm thick silicone grease layer) assembled according to the sample preparation instructions was placed in a temperature change chamber. One cycle consisted of holding at -40℃ for 30 min and then raising the temperature to 125℃ and holding for 30 min. The number of cycles was set to 500. After the cycle, the sample was placed at 25℃ for 2 h, and the area thermal resistance was remeasured. The rate of change of area thermal resistance after thermal cycling, ΔR, was calculated as follows: ΔR = (R... A (After loop) -R A (before the loop) / R A (Before cycling) × 100%, and simultaneously weigh the difference in silicone grease quality before and after fixture assembly as an indicator of pumped mass loss. The test results are shown in Table 1.

[0101] Table 1 Performance Test Results

[0102] Data Analysis: As can be seen from the data in Table 1 of the embodiments, the high thermal conductivity silicone grease prepared by the present invention maintains a high level of thermal conductivity and a low interfacial thermal resistance in terms of thermal conductivity and area thermal resistance. Simultaneously, it exhibits good stability in terms of thermal resistance changes and pump-out losses after thermal cycling, indicating that it can maintain a continuous thermal conduction path and stable interfacial coverage during long-term service at metal interfaces such as chips and heat sinks. Meanwhile, the embodiments show a significant difference between low-shear viscosity and high-shear viscosity, with a high thixotropic index, reflecting that the system has good anti-sagging and anti-settling capabilities under static or low-shear conditions, and can achieve smooth spreading and thin-film formation under application shear conditions such as dispensing and scraping. The possible reason is that the layered interface modified spherical alumina and plate boron nitride construct a composite thermally conductive network of "dense packing of spherical fillers + bridging of plate fillers", and the hydrophobic fumed silica further forms a three-dimensional thixotropic framework. On this basis, vinyl-terminated polydimethylsiloxane and methylhydrosiloxane-dimethylsiloxane copolymer containing silane-hydrogen bonds achieve network construction and then shaping under the regulation of Karstedt-type platinum catalyst and 3-methyl-1-pentyn-3-ol, so that the thermally conductive network is moderately fixed after forming, thus taking into account thermal conductivity, thixotropy and thermal cycling stability.

[0103] As can be seen from the data in Example 1 and Comparative Example 1 in Table 1, when the spherical alumina was not modified at the layered interface, the thermal conductivity decreased while the area thermal resistance increased, and the oil seepage rate, the change in thermal resistance after thermal cycling, and the pumping loss all deteriorated. The main reason for this may be the insufficient interfacial compatibility between the unmodified spherical alumina and the dimethyl silicone oil system. Microscopic defects and insufficiently wetted areas easily form at the filler-matrix interface, making it difficult for the particle contact in the thermal conductivity pathway to maintain stability. Simultaneously, the weakened interfacial binding promotes the migration of low-molecular-weight components under loading and temperature fluctuations, leading to increased oil seepage and pumping losses. Therefore, layered interface modification of spherical alumina not only improves the effective connection of the thermal conductivity network but also makes a contribution to interfacial stability that is difficult to replace by a single filler gradation.

[0104] As can be seen from the data in Table 1 for Example 1 and Comparative Examples 2, 3, and 4, when components such as cerium(III) 2-ethylhexanoate, zirconium(IV)2-ethylhexanoate, or zirconium(IV)acetylacetone are reduced or omitted, the initial thermal conductivity can still be maintained at a high level, but the thermal cycling-related indicators and oil seepage rate show an overall deterioration trend. This may be because the metal ion gradient / coordination fixation layer formed by these metal compounds on the layered interface-modified spherical alumina surface helps improve the anchoring strength and thermal aging stability of the polysiloxane brush layer. When the gradient construction is incomplete, the interface layer is more prone to relaxation or local desorption under temperature alternation and shear loading, leading to microscopic rearrangement of the thermal conductivity pathway and local void growth, manifested as increased thermal resistance and intensified pumping. This result indicates that the metal ion gradient is not simply an additional anti-aging component, but a synergistic factor that, together with interface modification, determines thermal cycling stability.

[0105] As can be seen from the data in Table 1 for Example 1 and Comparative Example 5, when vinyltriethoxysilane is not introduced to construct the outer reactive fixing layer, the area thermal resistance, oil penetration rate, and changes in thermal resistance and pumping loss after thermal cycling all show unfavorable changes. The main reason may be that the outer vinyl sites provided by vinyltriethoxysilane can form a synergistic fixation of "filler surface-polysiloxane network" through the addition reaction with vinyl-terminated polydimethylsiloxane / methylhydrosiloxane-dimethylsiloxane copolymer containing silanium bonds during the pre-network construction and post-fixation process. This makes the thermally conductive filler network less prone to migration at the thin-layer interface driven by thermal expansion and contraction. Without this fixing layer, even if a thixotropic skeleton exists, it is more likely to experience slow flow and edge depletion under cycling conditions, resulting in increased fluctuations in pumping and thermal resistance, demonstrating the 1+1 greater than 2 effect of "interfacial reactive fixing layer + micro-crosslinking fixing".

[0106] As can be seen from the data in Example 1 and Comparative Example 6 in Table 1, when the Karstedt-type platinum catalyst is added in advance during the premixing stage of the base material, although the system may exhibit a higher thixotropic index or higher viscosity, the thermal conductivity and thermal cycling reliability indicators deteriorate. This may be because the premature addition reaction causes the vinyl-terminated polydimethylsiloxane and the methylhydrosiloxane-dimethylsiloxane copolymer containing silane-hydrogen bonds to thicken prematurely, thereby inhibiting the sufficient wetting, orientation, and dense packing of the layered interface-modified spherical alumina and plate-like boron nitride. The thermally conductive network is prematurely locked before the optimal interconnected structure is formed, resulting in insufficient continuity of the initial thermal conductive pathway. Simultaneously, it is more prone to structural stress concentration and interface defect evolution under thermal cycling. This phenomenon indicates that the timing control of network formation followed by shaping has a significant effect, and its effect is not simply equivalent to "earlier / more crosslinking."

[0107] As can be seen from the data in Example 1 and Comparative Example 7 in Table 1, when the thermally conductive filler is simplified from a multi-size spherical alumina system to a single-size spherical alumina, the thermal conductivity decreases and the area thermal resistance increases, accompanied by increased oil leakage and pumping. This may be because multi-size gradation can improve the interparticle filling efficiency, reduce porosity, and increase the number of particle contact points, thereby reducing the pore thermal resistance and interface defects in the thermally conductive network; while a single particle size leads to increased packing gaps, making it easier for localized material shortages to appear at the thin-layer interface. During thermal cycling, under the drive of thermal expansion and contraction and shear loading, migration channels are more likely to be generated, resulting in increased pumping and thermal resistance fluctuations. This result further demonstrates that layered interface modification, metal ion gradient fixation, an outer reactive fixation layer, and particle size gradation need to be synergistically matched to simultaneously achieve the comprehensive performance gains of low thermal resistance and low oil leakage.

[0108] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A low thermal resistance, low oil seepage, aging-resistant, thixotropic, high thermal conductivity silicone grease, characterized in that, include: The matrix component includes dimethyl silicone oil and vinyl-terminated polydimethylsiloxane; Thermally conductive filler, wherein the thermally conductive filler comprises layered interface-modified spherical alumina and plate-shaped boron nitride; Thixotropic modulating component, wherein the thixotropic modulating component includes hydrophobically treated fumed silica; A site-directed micro-crosslinking system, comprising a polysiloxane crosslinking agent containing silane-hydrogen bonds, a Karstedt-type platinum catalyst xylene solution, and a reaction inhibitor; In this case, based on the total mass of the thixotropic high thermal conductivity silicone grease, the total amount of the thermally conductive filler added is 88% to 91%, and the mass ratio of the layered interface modified spherical alumina to the lamellar boron nitride is 3 to 4:

1. The preparation method of the layered interface modified spherical alumina includes the following steps: mixing and reacting a polysiloxane crosslinking agent containing silane-hydrogen bonds, anhydrous p-xylene, vinyltriethoxysilane, and a Karstedt-type platinum catalyst xylene solution; subsequently adding a rare earth metal organometallic solution, a zirconium metal organometallic solution, and a reaction inhibitor to obtain a metal ion complex-brush layer precursor; dispersing spherical alumina particles in anhydrous p-xylene, adding the metal ion complex-brush layer precursor and mixing to construct an inner polysiloxane brush layer on the surface of the spherical alumina particles; adding anhydrous ethanol and deionized water to initiate hydrolysis condensation, followed by adding vinyltriethoxysilane and zirconium(IV) acetylacetone to form an outer vinyl / zirconium coordination fixation layer on the surface of the spherical alumina particles; filtering, washing, and drying to obtain layered interface modified spherical alumina.

2. The low thermal resistance, low oil seepage, aging-resistant thixotropic, high thermal conductivity silicone grease according to claim 1, characterized in that, The dimethyl silicone oil is a mixture of low-viscosity dimethyl silicone oil and high-viscosity dimethyl silicone oil in a mass ratio of 1.4 to 1.9:1; the low-viscosity dimethyl silicone oil has a kinematic viscosity of 800 to 1000 mmHg at 25°C. 2 The kinematic viscosity of high-viscosity dimethyl silicone oil at 25°C is 8000–12000 mm / s. 2 / s.

3. The low thermal resistance, low oil seepage, aging-resistant thixotropic, high thermal conductivity silicone grease according to claim 1, characterized in that, The amount of vinyl-terminated polydimethylsiloxane added is 8% to 15% of the mass of dimethyl silicone oil; the amount of hydrophobic treated fumed silica added is 1% to 3% of the total mass of the matrix components; the amount of polysiloxane crosslinking agent containing silane-hydrogen bonds added in the site-directed micro-crosslinking system is 4% to 8% of the total mass of the matrix components; the amount of reaction inhibitor added in the site-directed micro-crosslinking system is 0.5% to 2% of the total mass of the matrix components; and the amount of Karstedt-type platinum catalyst xylene solution added in the site-directed micro-crosslinking system is 0.8% to 1.2% of the total mass of the matrix components.

4. The low thermal resistance, low oil seepage, aging-resistant thixotropic, high thermal conductivity silicone grease according to claim 1, characterized in that, The spherical alumina particles are a multi-size composite of spherical alumina particles, including at least coarse-sized spherical alumina, medium-sized spherical alumina, and fine-sized spherical alumina. The median particle size of the coarse-sized spherical alumina is 40–60 μm, the median particle size of the medium-sized spherical alumina is 15–35 μm, and the median particle size of the fine-sized spherical alumina is 0.5–2.0 μm. Based on 100 parts by mass of the total spherical alumina particles, the medium-sized spherical alumina comprises 40–50 parts by mass, the fine-sized spherical alumina comprises 8–15 parts by mass, and the remainder is coarse-sized spherical alumina.

5. The low thermal resistance, low oil seepage, aging-resistant thixotropic, high thermal conductivity silicone grease according to claim 1, characterized in that, The median particle size of the plate-like boron nitride is 7–12 μm.

6. The low thermal resistance, low oil seepage, aging-resistant thixotropic, high thermal conductivity silicone grease according to claim 1, characterized in that, The rare earth metal ions are selected from one or more of cerium ions, lanthanum ions, and yttrium ions.

7. The low thermal resistance, low oil seepage, aging-resistant thixotropic, high thermal conductivity silicone grease according to claim 1, characterized in that, The raw materials for preparing the metal ion complex-brush layer precursor, based on 100 parts by mass of a polysiloxane crosslinking agent containing silane-hydrogen bonds, consist of: 60-100 parts by mass of anhydrous p-xylene, 15-25 parts by mass of vinyltriethoxysilane, 0.5-1.5 parts by mass of a Karstedt-type platinum catalyst xylene solution, 3-7 parts by mass of a rare earth metal organometallic solution, 3-7 parts by mass of a zirconium metal organometallic solution, and 0.5-1.5 parts by mass of a reaction inhibitor.

8. The low thermal resistance, low oil seepage, aging-resistant thixotropic, high thermal conductivity silicone grease according to claim 1, characterized in that, In the preparation of the layered interface modified spherical alumina, based on 100 parts by mass of spherical alumina particles: the total amount of anhydrous ethanol and deionized water used to initiate hydrolysis and condensation is 8 to 15 parts by mass, the amount of vinyltriethoxysilane added is 0.8 to 2.5 parts by mass, and the amount of zirconium(IV) acetylacetone added is 0.3 to 1.2 parts by mass.

9. A method for preparing a low thermal resistance, low oil penetration, aging-resistant thixotropic, high thermal conductivity silicone grease according to any one of claims 1-8, characterized in that, Includes the following steps: (1) Dimethyl silicone oil, vinyl-terminated polydimethylsiloxane and hydrophobic fumed silica are mixed to obtain a matrix slurry; (2) Add layered interface modified spherical alumina and flake boron nitride to the matrix slurry and disperse them to make the thermally conductive filler form a thermally conductive network; (3) Add a polysiloxane crosslinking agent containing silane-hydrogen bonds and a reaction inhibitor and mix them; (4) Add a platinum catalyst to trigger the addition reaction between the polysiloxane crosslinking agent containing silane-hydrogen bonds and the vinyl-terminated polydimethylsiloxane to form a site-directed crosslink; (5) Degas and heat to cure to obtain thixotropic high thermal conductivity silicone grease.

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