Heat-conducting silicone grease with low thermal resistance and preparation method thereof
By optimizing the composition and preparation process of thermal grease, and using silicone oil polymers and thermally conductive fillers to form a uniform network, the problems of poor thixotropy and silicone oil precipitation in thermal grease were solved, achieving low thermal resistance and stable thermal conductivity.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-30
- Publication Date
- 2026-04-10
AI Technical Summary
Existing thermal greases have low thixotropy due to the addition of a large amount of fillers, and silicone oil is prone to precipitation during long-term hot and cold cycles, which increases the interfacial contact thermal resistance.
Using silicone oil polymer as the matrix, combined with thermally conductive fillers, methylcyclosiloxane, alkylalkoxysilane and lubricating agents, a uniform conductive network is formed by optimizing reaction conditions and mixing process, which improves thermal conductivity and reduces thermal resistance, while also improving thixotropy and workability.
The prepared thermal grease is less prone to silicone oil precipitation during long-term hot and cold cycling, maintains excellent thixotropic properties and low thermal resistance stability, and improves thermal conductivity and ease of application.
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Abstract
Description
Technical Field
[0001] This application relates to the field of thermal grease, and in particular to a low thermal resistance thermal grease and a method for preparing the same. Background Technology
[0002] Thermal grease is a paste-like composite material made from an organosilicon polymer as a matrix and filled with highly thermally conductive functional fillers. It possesses excellent thermal conductivity, good electrical insulation, a wide operating temperature range, and stable chemical inertness. It can effectively fill the microscopic air gaps between heat-generating components and heat sinks, establishing efficient heat conduction channels. Therefore, thermal grease is widely used in thermal management systems for electronic and electrical devices such as central processing units (CPUs), graphics processing units (GPUs), light-emitting diodes (LEDs), power semiconductor devices, and communication equipment.
[0003] To meet the stringent heat dissipation requirements of high-performance computing, high-power devices, and other fields, current technologies focus on developing thermal greases with high thermal conductivity and low thermal resistance. These greases typically use organosilicon compounds such as polydimethylsiloxane as a matrix and are filled with a high volume fraction of thermally conductive fillers to construct an effective thermal conductivity network. Commonly used thermally conductive fillers include metal or non-metal oxides / nitrides such as alumina, zinc oxide, aluminum nitride, and boron nitride. Among these, aluminum nitride and boron nitride have attracted considerable attention due to their significantly higher intrinsic thermal conductivity compared to traditional alumina. Furthermore, by optimizing the particle size distribution of the fillers (e.g., using a blend of micron- and nano-sized fillers) and surface modification with silane coupling agents, the filling density and dispersibility of the fillers in the matrix can be improved to a certain extent, thereby obtaining thermal greases with excellent thermal conductivity.
[0004] However, in the existing technology, the filler content is continuously increased in order to improve the thermal conductivity, which causes the viscosity of thermal grease to increase sharply, thereby deteriorating the thixotropy, making it difficult to apply and coat. In addition, silicone oil is prone to precipitation during long-term hot and cold cycle use, which increases the interfacial contact thermal resistance and reduces the long-term reliability of thermal grease. Summary of the Invention
[0005] To address the issues that existing thermal greases have low thixotropy due to the addition of large amounts of fillers, and are prone to silicone oil precipitation during long-term hot and cold cycling, resulting in increased interfacial thermal resistance, this application provides a low thermal resistance thermal grease and its preparation method.
[0006] In a first aspect, this application provides a low thermal resistance thermal grease, employing the following technical solution: A low thermal resistance thermal grease is prepared from the following raw materials in parts by weight: 100-120 parts of silicone oil polymer 135-150 parts of thermally conductive filler 4-6.5 parts of methylcyclosiloxane 2-4 parts of alkylalkoxysilane Lubricant additive: 0.2-0.4 parts; The silicone oil polymer is prepared by reacting trimethyltrivinylcyclotrisiloxane, vinyl-terminated polydiphenylsiloxane-polymethylvinylsiloxane block polydimethylsiloxane, trimethylolpropane diallyl ether, hydrogen-containing silicone oil and platinum catalyst.
[0007] By adopting the above technical solution, the silicone oil polymer, as the matrix, endows the thermally conductive grease with excellent thixotropic and filling properties. The thermally conductive filler, under the synergistic effect of methylcyclosiloxane and alkylalkoxysilane, can be uniformly dispersed in the silicone oil polymer system, forming a uniform conductive network system, improving the thermal conductivity of the thermally conductive grease, reducing thermal resistance, and without affecting the thixotropic and filling properties of the thermally conductive grease. The methylcyclosiloxane and alkylalkoxysilane can be uniformly interwoven and dispersed in the silicone oil polymer system, reducing the viscosity of the thermally conductive grease system, improving thixotropy, and enhancing the dispersibility of the thermally conductive filler in the matrix, while also preventing precipitation. Lubricating agents can further improve the fluidity and application performance of the thermally conductive grease.
[0008] The silicone oil polymer is prepared by reacting trimethyltrivinylcyclotrisiloxane, vinyl-terminated polydiphenylsiloxane-polymethylvinylsiloxane block polydimethylsiloxane, trimethylolpropane diallyl ether, hydrogen-containing silicone oil, and a platinum catalyst. The resulting silicone oil polymer exhibits good micro-crosslinking chemical stability and can better disperse and synergize with other raw materials. The prepared thermal grease possesses good thixotropy, thermal conductivity, and low thermal resistance stability. It is less prone to silicone oil precipitation during long-term hot and cold cycling, thus solving the problems of low thixotropy and increased interfacial thermal resistance caused by silicone oil precipitation in existing thermal greases due to the addition of large amounts of fillers.
[0009] Preferably, the silicone oil polymer is prepared from the following raw materials in parts by weight: 45-55 parts of trimethyltrivinylcyclotrisiloxane Vinyl-terminated polydiphenylsiloxane-polymethylvinylsiloxane block polydimethylsiloxane 8-12 parts Trimethylolpropane diallyl ether 4.5-7.2 parts 0.5-1 part of hydrogen-containing silicone oil Platinum catalyst 0.05-0.15 parts.
[0010] By adopting the above technical solutions, trimethyltrivinylcyclotrisiloxane can introduce vinyl functional groups into silicone oil polymers, providing reactive centers for crosslinking and polymerization; vinyl-terminated polydiphenylsiloxane-polymethylvinylsiloxane block polydimethylsiloxane can adjust the flexibility, thermal stability and chemical resistance of silicone oil polymers; trimethylolpropane diallyl ether can further increase the branching degree and crosslinking points of the molecular chain, improving the mechanical properties and structural stability of the polymer. The three work synergistically to stably undergo micro-crosslinking reactions with hydrogen-containing silicone oil under the action of platinum catalyst, giving the thermally conductive silicone grease an excellent dispersion matrix and improving the thermal conductivity, thixotropy and thermal resistance stability of the prepared thermally conductive silicone grease.
[0011] Preferably, the silicone oil polymer is prepared by the following steps: adding trimethyltrivinylcyclotrisiloxane, vinyl-terminated polydiphenylsiloxane-polymethylvinylsiloxane block polydimethylsiloxane, trimethylolpropane diallyl ether and catalyst into a reaction apparatus, heating and reacting to obtain the silicone oil polymer.
[0012] By adopting the above technical solution, the components can react stably, thereby improving the reaction efficiency.
[0013] Preferably, the reaction is divided into two stages: the first stage has a reaction temperature of 80-90℃ and a reaction time of 1-2 hours, and the second stage has a reaction temperature of 90-100℃ and a reaction time of 30-60 minutes.
[0014] By adopting the above technical solution and optimizing the reaction temperature and time, the components can react uniformly, avoiding excessive reaction caused by excessively high initial temperature, which would result in excessively high viscosity and instability of the prepared silicone oil polymer.
[0015] Preferably, the thermally conductive filler is composed of aluminum nitride powder, boron nitride and aluminum nitride ceramic microspheres in a weight ratio of 1:(0.5-0.8):(0.1-0.2).
[0016] By employing the above technical solutions, aluminum nitride powder possesses a high thermal conductivity, providing the primary heat conduction pathway; the hexagonal crystal structure of boron nitride helps supplement heat conduction paths at the microscopic level; and the spherical structure of aluminum nitride ceramic microspheres allows them to be dispersed within the aluminum nitride powder and boron nitride, reducing microscopic air gaps, while the ceramic material on their surface enhances the stability of heat transfer. These three fillers work synergistically to optimize the thermal conductivity network, effectively improving the thermal conductivity of thermal grease and reducing thermal resistance.
[0017] Preferably, the methylcyclosiloxane is decamethylcyclopentasiloxane and / or dodecylcyclohexasiloxane.
[0018] By adopting the above technical solution, using decamethylcyclopentasiloxane and / or dodecylcyclohexasiloxane as methylcyclosiloxanes, a stable interwoven and dispersed system can be formed with silicone oil polymers. This gives the thermal grease good fluidity and low volatility, while also helping to reduce the viscosity of the system and improve the thixotropic properties of the thermal grease. At the same time, it is less likely to cause silicone oil precipitation during long-term hot and cold cycling, further ensuring the stable performance of the thermal grease with low thermal resistance.
[0019] Preferably, the alkylalkoxysilane is at least one selected from isobutyltrimethoxysilane, isobutyltriethoxysilane, isooctyltrimethoxysilane, and isooctyltriethoxysilane.
[0020] By adopting the above technical solution, medium- and long-chain alkylsilanes are selected, which have better dispersion and spreading properties. This can improve the dispersion uniformity of thermally conductive fillers in thermally conductive silicone grease while minimizing precipitation problems. Experiments revealed that if the chain segments of alkylalkoxysilanes are too short, precipitation is likely to occur; conversely, if the chain segments are too long, the rheological properties of the prepared thermally conductive silicone grease are reduced, and long-term thermal resistance stability is decreased.
[0021] Preferably, the lubricant is one or a combination of stearic acid, calcium stearate, zinc stearate, and stearate ester.
[0022] By adopting the above technical solutions, the lubricant can further improve the thixotropy and fluidity of the thermal grease system and enhance the filling stability.
[0023] Secondly, this application provides a method for preparing a low thermal resistance thermal grease, which adopts the following technical solution: A method for preparing a low thermal resistance thermal grease includes the following steps: A low-thermal-resistance thermal grease is prepared by uniformly mixing and grinding silicone oil polymer, thermally conductive filler, methylcyclosiloxane, alkylalkoxysilane and lubricant.
[0024] By adopting the above technical solution, and grinding the mixture after it is evenly mixed, the uniformity of the thermal grease system can be improved.
[0025] Preferably, the mixing temperature is 80-120℃.
[0026] By adopting the above technical solution, the optimal mixing temperature can enable the silicone oil polymer, thermally conductive filler, methylcyclosiloxane, alkylalkoxysilane and lubricant to be mixed more thoroughly and evenly.
[0027] In summary, this application includes at least one of the following beneficial technical effects: 1. The low thermal resistance thermal grease of this application is prepared from silicone oil polymer, thermally conductive filler, methylcyclosiloxane, alkylalkoxysilane and lubricating agent. The silicone oil polymer is prepared by reacting trimethyltrivinylcyclotrisiloxane, vinyl-terminated polydiphenylsiloxane-polymethylvinylsiloxane block polydimethylsiloxane, trimethylolpropane diallyl ether, hydrogen-containing silicone oil and platinum catalyst. The prepared thermal grease has good thixotropic properties, thermal conductivity and low thermal resistance stability, and is not prone to silicone oil precipitation during long-term hot and cold cycle use.
[0028] 2. By using decamethylcyclopentasiloxane and / or dodecylcyclohexasiloxane as methylcyclosiloxanes, and at least one of isobutyltrimethoxysilane, isobutyltriethoxysilane, isooctyltrimethoxysilane, and isooctyltriethoxysilane as alkylalkoxysilanes, and working synergistically with thermally conductive fillers composed of aluminum nitride powder, boron nitride, and aluminum nitride ceramic microspheres, the prepared thermally conductive silicone grease exhibits good thermal conductivity and low thermal resistance stability, can establish efficient heat conduction channels, and while improving thermal conductivity and reducing thermal resistance, is less prone to silicone oil precipitation.
[0029] 3. The thermally conductive silicone grease prepared by uniformly mixing and grinding silicone oil polymer, thermally conductive filler, methylcyclosiloxane, alkylalkoxysilane and lubricating agent has good system uniformity and thixotropic properties. Detailed Implementation
[0030] The present application will be further described in detail below with reference to the embodiments.
[0031] The following are some of the sources and specifications of the raw materials used in this application. The raw materials used in the preparation examples and embodiments of this application can all be obtained commercially, including but not limited to the following models and manufacturers of raw materials. Raw materials with equivalent performance can also be used: 1. Vinyl-terminated polydiphenylsiloxane-polymethylvinylsiloxane block polydimethylsiloxane: SiSiB® VF6872; 2. Hydrogen-containing silicone oil: Hydrogen-containing silicone oil with a hydrogen content of 0.4-0.6%; 3. Platinum catalyst: Platinum content 10000-2000ppm; 4. Aluminum nitride powder: Hexagonal aluminum nitride, particle size 100-200nm, specific surface area 28-29m² 2 / g; 5. Boron nitride: Hexagonal boron nitride, particle size 50-100nm; 6. Aluminum nitride ceramic microspheres: particle size 1-3µm.
[0032] Preparation examples of silicone oil polymers Preparation Example 1 Preparation Example 1 discloses a silicone oil polymer, which is prepared by the following steps: 4.5 kg of trimethyltrivinylcyclotrisiloxane, 0.8 kg of vinyl-terminated polydiphenylsiloxane-polymethylvinylsiloxane block polydimethylsiloxane, 0.45 kg of trimethylolpropane diallyl ether, 0.05 kg of hydrogen-containing silicone oil with a hydrogen content of 0.4%, and 0.005 kg of platinum catalyst with a platinum content of 10000 ppm were added to a reactor and heated to a certain temperature. The reaction was divided into two stages: the first stage reaction temperature was 80℃ and the reaction time was 2 h; the second stage reaction temperature was 90℃ and the reaction time was 60 min, thus obtaining the silicone oil polymer.
[0033] Preparation Examples 2-3 The difference between Preparation Example 2-3 and Preparation Example 1 lies in the amount of raw materials used and the preparation conditions, as detailed in Table 1 below.
[0034] Table 1. Parameters for Preparation Examples 1-3
[0035] Preparation of Comparative Example 1 The difference between Comparative Example 1 and Preparation Example 1 is that trimethyltrivinylcyclotrisiloxane was replaced in equal amounts with vinyl-terminated polydiphenylsiloxane-polymethylvinylsiloxane block polydimethylsiloxane, otherwise it was the same as Preparation Example 1.
[0036] Preparation of Comparative Example 2 The difference between Comparative Example 2 and Preparation Example 1 is that vinyl-terminated polydiphenylsiloxane-polymethylvinylsiloxane block polydimethylsiloxane was replaced with vinyl-terminated polydiphenylsiloxane in equal amounts, with a vinyl content of 0.2%, while the rest was the same as Preparation Example 1.
[0037] Preparation of Comparative Example 3 The difference between Comparative Example 3 and Preparation Example 1 is that trimethylolpropane diallyl ether was replaced with an equal amount of trimethyltrivinylcyclotrisiloxane, otherwise it was the same as Preparation Example 1. Example Example 1
[0038] Example 1 discloses a low thermal resistance thermal grease, which is prepared by the following steps: 10 kg of the silicone oil polymer prepared in Example 1, 13.5 kg of thermally conductive filler, 0.4 kg of methylcyclosiloxane, 0.2 kg of alkylalkoxysilane and 0.02 kg of lubricant were mixed evenly at a temperature of 80°C and then ground twice with a three-roll mill for 10 min each time to obtain a low thermal resistance thermally conductive silicone grease. The thermally conductive filler is composed of aluminum nitride powder, boron nitride, and aluminum nitride ceramic microspheres in a weight ratio of 1:0.5:0.1, with aluminum nitride powder having a particle size of 100 nm, boron nitride having a particle size of 50 nm, and aluminum nitride ceramic microspheres having a particle size of 1 µm; the methylcyclosiloxane is decamethylcyclopentasiloxane; the alkylalkoxysilane is composed of isobutyltrimethoxysilane and isooctyltrimethoxysilane in a weight ratio of 1:1; and the lubricant is stearic acid.
[0039] Example 2-3 The difference between Examples 2-3 and Example 1 lies in the different amounts of raw materials and preparation conditions, as detailed in Table 2 below.
[0040] Table 2 Parameter Table for Examples 1-3
[0041] Example 4
[0042] The difference between Example 4 and Example 1 is that the alkylalkoxysilane is dodecyltrimethoxysilane, otherwise it is the same as Example 1.
[0043] Example 5
[0044] The difference between Example 5 and Example 1 is that the alkylalkoxysilane is methyltrimethoxysilane, otherwise it is the same as Example 1.
[0045] Comparative Example Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the silicone oil polymer was derived from the preparation of Comparative Example 1, while the rest is the same as Example 1.
[0046] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the silicone oil polymer was derived from the preparation of Comparative Example 2, while the rest is the same as Example 1.
[0047] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that the silicone oil polymer was derived from the preparation of Comparative Example 3, while the rest is the same as Example 1.
[0048] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that decamethylcyclopentasiloxane was replaced with an equal amount of silicone oil polymer, while the rest was the same as Example 1.
[0049] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that alkylalkoxysilane is replaced with vinyltrimethoxysilane in equal amounts, while the rest is the same as Example 1.
[0050] Performance testing The performance of the thermal greases prepared in Examples 1-5 and Comparative Examples 1-5 was tested below: 1. Thermal resistance test According to the test method in ASTM D5470, the thermal grease coating thickness is 25µm, the test closing pressure is 10psi, the thermal resistance of the thermal grease is tested (unit: °C·cm² / W), and the test results are recorded. 2. Thixotropic test According to the test method in ASTM D2196, test the thixotropic index of the thermal grease, and record the test results; 3. Damp heat test The thermal grease was placed in a constant temperature and humidity environment of 85℃ and 85% for 2000 hours. The rate of change of thermal resistance (in %) was tested according to the test method in ASTM D5470, and the test results were recorded. 4. Precipitation test The thermal grease was placed in a constant temperature and humidity environment of 85℃ and 85% for 24 hours. The silicone oil precipitation of the thermal grease was observed and the test results were recorded. The following are the performance test data of the thermal greases prepared in Examples 1-5 and Comparative Examples 1-5, as detailed in Table 3 below.
[0051] Table 3 Performance data of thermal greases prepared in Examples 1-5 and Comparative Examples 1-5
[0052] Based on Examples 1-3 and Comparative Examples 1-3, and in conjunction with Table 3, it can be concluded that the thermal grease prepared using the specific components of the silicone oil polymer of this application exhibits good thermal conductivity and thermal resistance stability, as well as a good thixotropic index, and is less prone to silicone oil precipitation after long-term damp heat testing. In Comparative Examples 1-3, the type of silicone oil polymer was changed, resulting in a higher thermal resistance and a larger rate of change in thermal resistance after damp heat testing, along with slight silicone oil precipitation. This may be due to a reduction in the polymerization efficiency of the silicone oil polymer, which in turn reduces the synergistic effect between the silicone oil polymer, the thermally conductive filler, and the silane. The slight increase in the thixotropic index of the thermal grease in Comparative Example 2 may be due to the excessive phenyl groups in the vinyl-terminated polydiphenylsiloxane-polymethylvinylsiloxane block polydimethylsiloxane, which reduced the fluidity of the thermal grease, after an equal amount of vinyl-terminated polydiphenylsiloxane-polymethylvinylsiloxane-block polydimethylsiloxane was replaced with vinyl-terminated polydiphenylsiloxane.
[0053] Based on Examples 1 and Comparative Examples 4-5, and referring to Table 2, it can be concluded that the silicone oil polymer, methylcyclosiloxane, and alkylalkoxysilane of this application have a good synergistic effect. The resulting thermal grease exhibits both good thermal conductivity and good thixotropy. In Comparative Example 4, without the addition of methylcyclosiloxane, the thixotropy of the resulting thermal grease was significantly improved, as was its thermal resistance. In Comparative Example 5, where an equal amount of alkylalkoxysilane was replaced with vinyltrimethoxysilane, the rate of change in thermal resistance of the resulting thermal grease significantly increased after damp heat testing, and significant precipitation problems were observed.
[0054] Combining Examples 1 and 4-5 with Table 3, it can be concluded that using the preferred chain segment of the alkylalkoxysilane of this application can improve the thermal conductivity of the prepared thermal grease while also improving thixotropy and reducing the likelihood of silicone oil precipitation. In Example 4, the use of a longer chain segment of dodecyltrimethoxysilane resulted in an increased thermal resistance of the prepared thermal grease; while in Example 5, the use of a shorter chain segment of methyltrimethoxysilane led to significant precipitation of the thermal grease and a decrease in the thixotropic index.
[0055] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.
Claims
1. A low thermal resistance thermal grease, characterized in that, It is prepared from the following raw materials in parts by weight: 100-120 parts of silicone oil polymer 135-150 parts of thermally conductive filler 4-6.5 parts of methylcyclosiloxane 2-4 parts of alkylalkoxysilane Lubricant additive: 0.2-0.4 parts; The silicone oil polymer is prepared by reacting trimethyltrivinylcyclotrisiloxane, vinyl-terminated polydiphenylsiloxane-polymethylvinylsiloxane block polydimethylsiloxane, trimethylolpropane diallyl ether, hydrogen-containing silicone oil and platinum catalyst.
2. The low thermal resistance thermal grease according to claim 1, characterized in that, The silicone oil polymer is prepared from the following raw materials in parts by weight: 45-55 parts of trimethyltrivinylcyclotrisiloxane Vinyl-terminated polydiphenylsiloxane-polymethylvinylsiloxane block polydimethylsiloxane 8-12 parts Trimethylolpropane diallyl ether 4.5-7.2 parts 0.5-1 part of hydrogen-containing silicone oil Platinum catalyst 0.05-0.15 parts.
3. The low thermal resistance thermal grease according to claim 1 or 2, characterized in that, The silicone oil polymer is prepared by the following steps: adding trimethyltrivinylcyclotrisiloxane, vinyl-terminated polydiphenylsiloxane-polymethylvinylsiloxane block polydimethylsiloxane, trimethylolpropane diallyl ether, hydrogen-containing silicone oil and platinum catalyst into a reaction apparatus, heating and reacting to obtain the silicone oil polymer.
4. The low thermal resistance thermal grease according to claim 3, characterized in that, The reaction is divided into two stages. The first stage has a reaction temperature of 80-90℃ and a reaction time of 1-2 hours. The second stage has a reaction temperature of 90-100℃ and a reaction time of 30-60 minutes.
5. The low thermal resistance thermal grease according to claim 1, characterized in that, The thermally conductive filler is composed of aluminum nitride powder, boron nitride, and aluminum nitride ceramic microspheres in a weight ratio of 1:(0.5-0.8):(0.1-0.2).
6. The low thermal resistance thermal grease according to claim 1, characterized in that, The methylcyclosiloxane is decamethylcyclopentasiloxane and / or dodecylcyclohexasiloxane.
7. The low thermal resistance thermal grease according to claim 1, characterized in that, The alkylalkoxysilane is at least one of isobutyltrimethoxysilane, isobutyltriethoxysilane, isooctyltrimethoxysilane, and isooctyltriethoxysilane.
8. The low thermal resistance thermal grease according to claim 1, characterized in that, The lubricating agent is one or a combination of stearic acid, calcium stearate, zinc stearate, and stearate ester.
9. A method for preparing a low thermal resistance thermal grease as described in any one of claims 1-8, characterized in that, Includes the following steps: A low-thermal-resistance thermal grease is prepared by uniformly mixing and grinding silicone oil polymer, thermally conductive filler, methylcyclosiloxane, alkylalkoxysilane and lubricant.
10. A method for preparing a low thermal resistance thermal grease according to claim 9, characterized in that, The mixing temperature is 80-120℃.