Low-oil-permeability heat-conducting silica gel gasket as well as preparation method and application thereof

Abstract

The invention relates to the technical field of thermal interface materials, and discloses a low-oil-permeability heat-conducting silica gel gasket and a preparation method and application thereof. The low-oil-permeability heat-conducting silica gel gasket comprises the following raw material components: vinyl silicone oil, hydrogen-containing silicone oil, a modified porous filler, a heat-conducting filler, a silane coupling agent I, an inhibitor, a catalyst and a photoinitiator, wherein the modified porous filler is prepared by performing ultrasonic modification on a porous filler, a silane coupling agent II, a dispersing agent and a solvent; the components of the silane coupling agent I and the silane coupling agent II are the same; the porous filler is selected from at least one of a silicon-based porous material and a carbon-based porous material. The preparation method of the low-oil-permeability heat-conducting silica gel gasket is simple and efficient, the modified porous filler prepared through ultrasonic treatment is added in the preparation process, and the curing mode of combining heating and ultraviolet curing is adopted, so that the prepared low-oil-permeability heat-conducting silica gel gasket has good heat conductivity under the condition that the hardness and the heat conductivity coefficient are moderate, and the service life of the low-oil-permeability heat-conducting silica gel gasket is prolonged. And the unilateral oil leakage value in a compression state is less than 1mm.

Description

Technical Field

[0001] This application relates to the field of thermal interface materials technology, and in particular to a low-oil-permeability thermally conductive silicone pad, its preparation method, and its application. Background Technology

[0002] Thermally conductive silicone pads, as a thermal interface material, play a vital role in many industrial sectors such as electronics, new energy, automotive, aerospace, and communications. With their excellent thermal conductivity, flexibility, resilience, insulation, and shock absorption, they effectively fill gaps and defects in thermal interfaces and smooth out air pockets on uneven surfaces, thereby reducing thermal resistance between contact surfaces, significantly improving thermal conductivity, and ensuring the stability of various equipment operations.

[0003] However, during long-term use, thermally conductive silicone pads often experience oil seepage, leading to a gradual decline in pad performance and even contaminating equipment components, thus affecting performance. Chinese patent application CN114369369A provides a low-volatility, low-oil-seepage thermally conductive pad that achieves low oil seepage through the tiny pores created by foaming. However, this method is difficult to control in terms of the number and size of micropores, and it increases the difficulty and cost of mass production. Chinese patent application CN116335259A provides a low-oil-seepage silicone thermally conductive pad that uses coatings on both sides of the middle thermally conductive layer to prevent small silicone oil molecules inside the middle layer from migrating to the surface. However, this side-coating solution cannot fundamentally solve the oil seepage problem. Under compression, oily components will overflow from the surrounding cross-sections, and the coating material itself does not have thermal conductivity, reducing the intrinsic thermal conductivity of the thermal interface material. Chinese patent application CN109401732A controls the degree of crosslinking of the adhesive by adjusting the appropriate silicon-hydrogen ratio to obtain a thermally conductive silicone grease pad with low oil permeation. However, this patent ignores the influence of silicone oil ratio, thermal pad hardness, mixing process and type of polymethylhydrosiloxane on the oil permeation performance of the thermal pad, which has certain defects. Summary of the Invention

[0004] To at least overcome one of the problems existing in the prior art, one objective of this application is to provide a low-oil-permeability thermally conductive silicone pad. This low-oil-permeability thermally conductive silicone pad has moderate hardness and thermal conductivity, and under long-term compression, the oil permeation value (single-sided permeation distance) is <1mm, which can meet the low oil permeation requirements under compression in practical applications. A second objective of this application is to provide a method for preparing the aforementioned low-oil-permeability thermally conductive silicone pad. A third objective of this application is to provide applications of the aforementioned low-oil-permeability thermally conductive silicone pad.

[0005] Therefore, this application adopts the following technical solution: The first aspect of this application provides a low-oil-permeability thermally conductive silicone pad, wherein the raw material components of the low-oil-permeability thermally conductive silicone pad include: vinyl silicone oil, hydrogen-containing silicone oil, modified porous filler, thermally conductive filler, silane coupling agent I, inhibitor, catalyst, and photoinitiator; the modified porous filler is prepared by ultrasonic modification of porous filler, silane coupling agent II, dispersant, and solvent; the silane coupling agent I and silane coupling agent II have the same composition; the porous filler is selected from at least one of silicon-based porous materials and carbon-based porous materials.

[0006] By adopting the above technical solution, the compatibility between the raw materials is improved by using ultrasonically modified porous fillers, and a silicone gasket with low oil permeability and good thermal conductivity is prepared through a specific raw material formulation, thereby improving the overall performance of the gasket.

[0007] Preferably, the modified porous filler is prepared from the following raw material components in parts by weight: 20-300 parts of porous packing Silane coupling agent II 0.3–1.5 parts Dispersant 0.1-0.5 parts Solvent: 100-300 parts.

[0008] Porous fillers are the foundational material for low-oil-permeability thermally conductive silicone gaskets, and their properties directly affect the final gasket's hardness, thermal conductivity, and oil-permeability resistance. Silane coupling agent II improves the compatibility between the porous filler and the silicone matrix interface, enhances the dispersibility of the porous filler in the adhesive, reduces the adhesive viscosity, and increases the adsorption of free siloxane molecules by the pores of the porous filler, thereby reducing oil permeation at its source and stabilizing the thermal conductivity network. Dispersants inhibit the aggregation of porous materials, promoting uniform dispersion. Therefore, modified porous fillers prepared using specific weight proportions of porous filler, silane coupling agent II, dispersant, and solvent can be used to prepare low-oil-permeability thermally conductive silicone gaskets, resulting in gaskets with low oil permeability and excellent thermal conductivity.

[0009] Preferably, the silicon-based porous material is porous silica. More preferably, the D50 (average particle size) of the porous silica is 4~9 μm.

[0010] Preferably, the carbon-based porous material is at least one of nanoporous carbon powder and porous activated carbon powder. More preferably, the carbon-based porous material is at least one of nanoporous carbon powder and porous activated carbon powder with a pore size range of 10~36nm.

[0011] The porous structure of porous fillers such as porous silica, nanoporous carbon powder, and porous activated carbon powder is used to adsorb free siloxane small molecules, reducing oil seepage. Nanoporous carbon powder and porous activated carbon powder have high specific surface area and abundant pore structure, which can increase the contact area with other raw materials, enhance thermal conductivity, and porous activated carbon powder can also improve the adsorption performance of the gasket, further reducing oil seepage.

[0012] Preferably, the vinyl silicone oil is a vinyl-terminated silicone oil.

[0013] Preferably, the vinyl group in the vinyl-terminated silicone oil has a vinyl content of 0.6-0.9% by weight and a viscosity of 500-1000 mPa·s. More preferably, the vinyl group in the vinyl-terminated silicone oil has a vinyl content of 0.6-0.8% by weight and a viscosity of 500-900 mPa·s. Even more preferably, the vinyl group in the vinyl-terminated silicone oil has a vinyl content of 0.7-0.8% by weight and a viscosity of 650-900 mPa·s.

[0014] Vinyl groups are the active sites in the crosslinking reaction of silicone. In vinyl-terminated silicone oil, vinyl groups are located only at both ends of the molecular chain, allowing for more precise control of the crosslinking reaction and optimization of product performance. The vinyl content directly determines the crosslinking density, affecting the product's mechanical properties, oil resistance, and stability. If the vinyl content is too low, there are insufficient crosslinking sites; if the content is too high, the crosslinking density is too high. The viscosity of vinyl-terminated silicone oil reflects its flowability and molecular weight characteristics, directly affecting the dispersion of thermally conductive fillers and the processability and oil resistance of the product. If the viscosity is too low, the system has excessive flowability, and the thermally conductive filler is prone to sedimentation and stratification during mixing. If the viscosity is too high, the system has poor flowability, and the filler is prone to agglomeration during mixing. Using vinyl-terminated silicone oil as the vinyl silicone oil, controlling the vinyl weight percentage to 0.6-0.9% and the viscosity to 500-1000 mPa·s helps to prepare thermally conductive silicone gaskets with superior performance and low oil resistance.

[0015] Preferably, the hydrogen-containing silicone oil is selected from at least one of side-containing hydrogen-containing silicone oil and end-containing hydrogen-containing silicone oil, and the weight percentage of active hydrogen in the hydrogen-containing silicone oil is 0.1-0.4%. More preferably, the hydrogen-containing silicone oil is a side-containing hydrogen-containing silicone oil, and the weight percentage of active hydrogen in the hydrogen-containing silicone oil is 0.1-0.4%. Even more preferably, the hydrogen-containing silicone oil is a side-containing hydrogen-containing silicone oil, and the weight percentage of active hydrogen in the hydrogen-containing silicone oil is 0.1-0.3%.

[0016] Hydrogen-containing silicone oil primarily functions as a crosslinking agent in the raw materials. Through the active hydrogen (Si-H bond) in its molecule, it undergoes a hydrosilylation reaction with the vinyl groups in the vinyl silicone oil. The Si-H bonds on the side chains or ends of the hydrogen-containing silicone oil can react with the vinyl silicone oil at multiple positions on the main chain, forming a "multi-point crosslinked" three-dimensional network. This inhibits the leakage of small-molecule oil and helps stabilize the crosslinked structure, resulting in more stable mechanical properties of the gasket. The active hydrogen content in the hydrogen-containing silicone oil is 0.2-0.4% by weight, which helps control the crosslinking density, inhibits oil leakage, and also avoids structural defects caused by excessive crosslinking.

[0017] Preferably, the thermally conductive filler is selected from at least one of alumina, aluminum nitride, boron nitride, aluminum powder, and silicon dioxide. More preferably, the thermally conductive filler is selected from at least one of alumina, aluminum nitride, boron nitride, and aluminum powder. Even more preferably, the thermally conductive filler is selected from at least one of alumina and aluminum nitride.

[0018] Preferably, both silane coupling agent I and silane coupling agent II are selected from at least one of alkylsilanes, aminosilanes, and epoxysilanes. More preferably, both silane coupling agent I and silane coupling agent II are selected from at least one of alkylsilanes and aminosilanes. Even more preferably, both silane coupling agent I and silane coupling agent II are selected from at least one of N-decyltrimethoxysilane, dodecyltrimethoxysilane, and hexadecyltrimethoxysilane.

[0019] Preferably, the dispersant is selected from at least one of polyether-modified polydimethylsiloxane, hydroxyl polydimethylsiloxane, and copolymer solutions containing acidic groups. More preferably, the dispersant is selected from at least one of polyether-modified polydimethylsiloxane and hydroxyl polydimethylsiloxane. Even more preferably, the dispersant is polyether-modified polydimethylsiloxane.

[0020] Preferably, the inhibitor is an alkynyl alcohol inhibitor. More preferably, the inhibitor is selected from at least one of acetylenol and methylbutynol.

[0021] Preferably, the catalyst is a platinum catalyst. More preferably, the catalyst is a platinum organocatalyst.

[0022] Preferably, the photoinitiator is selected from at least one of benzophenone, 2-isopropylthioxanthraphenone, and 2,4,6-trimethylbenzoyldiphenylphosphine oxide. More preferably, the photoinitiator is selected from at least one of 2-isopropylthioxanthraphenone and 2,4,6-trimethylbenzoyldiphenylphosphine oxide. Even more preferably, the photoinitiator is 2-isopropylthioxanthraphenone.

[0023] Preferably, the solvent is an alcohol solvent. More preferably, the solvent is selected from methanol or ethanol.

[0024] Preferably, in the raw materials of the low-oil-permeability thermally conductive silicone pad, the weight ratio of vinyl silicone oil, hydrogen-containing silicone oil, and modified porous filler is 100:(2-12):(20-300).

[0025] Preferably, in the raw materials of the low-oil permeability thermally conductive silicone pad, the weight ratio of vinyl silicone oil, hydrogen-containing silicone oil, modified porous filler, and thermally conductive filler is 100:(2-12):(20-300):(500-1400).

[0026] Preferably, in the raw materials of the low-oil permeability thermally conductive silicone pad, the weight ratio of vinyl silicone oil, hydrogen-containing silicone oil, modified porous filler, thermally conductive filler, and silane coupling agent I is 100:(2-12):(20-300):(500-1400):(0.6-2.5).

[0027] Preferably, in the raw materials of the low-oil permeability thermally conductive silicone pad, the weight ratio of vinyl silicone oil, hydrogen-containing silicone oil, modified porous filler, thermally conductive filler, silane coupling agent I, and inhibitor is 100:(2-12):(20-300):(500-1400):(0.6-2.5):(0.02-0.8).

[0028] Preferably, in the raw materials of the low-oil permeability thermally conductive silicone pad, the weight ratio of vinyl silicone oil, hydrogen-containing silicone oil, modified porous filler, thermally conductive filler, silane coupling agent I, inhibitor, and catalyst is 100:(2-12):(20-300):(500-1400):(0.6-2.5):(0.02-0.8):(0.1-0.9).

[0029] Preferably, in the raw materials of the low-oil permeability thermally conductive silicone pad, the weight ratio of vinyl silicone oil, hydrogen-containing silicone oil, modified porous filler, thermally conductive filler, silane coupling agent I, inhibitor, catalyst, and photoinitiator is 100:(2-12):(20-300):(500-1400):(0.6-2.5):(0.02-0.8):(0.1-0.9):(0.5-3).

[0030] By adopting the above technical solution, using specific weight proportions of vinyl silicone oil, hydrogen-containing silicone oil, modified porous filler, thermally conductive filler, silane coupling agent I, inhibitor, catalyst, and photoinitiator, and precisely adjusting the raw material ratio, and using specific types of materials, the prepared low-oil-permeability thermally conductive silicone gasket has good thermal conductivity and low oil permeability. Furthermore, the use of modified porous filler can make the internal structure of the gasket more conducive to heat conduction and inhibit oil permeation.

[0031] The second aspect of this application provides a method for preparing a low-oil-permeability thermally conductive silicone pad according to the first aspect of this application, comprising the following steps: S1: Mix vinyl silicone oil, hydrogen-containing silicone oil, silane coupling agent I, inhibitor, catalyst and photoinitiator, and stir under vacuum to obtain mixed silicone oil; S2: Mix thermally conductive filler, modified porous filler and mixed silicone oil, and stir under vacuum to obtain adhesive; S3: The adhesive material is calendered into a sheet, then baked and cured with ultraviolet light to obtain the low oil permeability thermally conductive silicone pad; Preferably, the preparation method of the modified porous filler includes the following steps: The silane coupling agent II, dispersant, and solvent are mixed and stirred. The porous filler is then added and stirred again. Finally, the mixture is ultrasonicated, filtered, and baked to obtain the modified porous filler.

[0032] Preferably, in step S1, the stirring speed is 30–80 r / min, and the stirring time is 5–15 min. More preferably, in step S1, the stirring speed is 40–80 r / min, and the stirring time is 5–12 min. Even more preferably, in step S1, the stirring speed is 50–70 r / min, and the stirring time is 5–10 min.

[0033] Preferably, in step S1, the stirring can be carried out under vacuum conditions, wherein the vacuum degree is -0.09 MPa to -0.1 MPa.

[0034] Preferably, in step S2, the vacuum degree is -0.09 MPa to -0.1 MPa, the stirring speed is 50 to 150 r / min, and the stirring time is 30 to 50 min. More preferably, in step S2, the vacuum degree is -0.09 MPa to -0.1 MPa, the stirring speed is 50 to 120 r / min, and the stirring time is 35 to 50 min. Even more preferably, in step S2, the vacuum degree is -0.09 MPa to -0.1 MPa, the stirring speed is 60 to 110 r / min, and the stirring time is 40 to 50 min.

[0035] Preferably, in step S3, the baking temperature is 100–140°C, the baking time is 15–30 min, and the UV curing time is 0.2–3 min. More preferably, in step S3, the baking temperature is 100–130°C, the baking time is 20–30 min, and the UV curing time is 1–3 min. Even more preferably, in step S3, the baking temperature is 110–130°C, the baking time is 25–30 min, and the UV curing time is 2–3 min.

[0036] In the preparation method of the low-oil-permeability thermally conductive silicone pad of this application, step S1 involves mixing vinyl silicone oil, hydrogen-containing silicone oil, silane coupling agent I, inhibitor, catalyst and photoinitiator. Although there is a catalyst in this step, the presence of the inhibitor prevents the reaction from proceeding. This step involves stirring under vacuum conditions to ensure that the components are evenly dispersed, thereby obtaining a mixed silicone oil.

[0037] Step S2 involves mixing the thermally conductive filler, modified porous filler, and mixed silicone oil under vacuum to obtain a rubber compound. The siloxane group (-Si-OR) generated by the hydrolysis of the silane coupling agent I in the mixed silicone oil undergoes an interfacial condensation reaction with the thermally conductive filler and modified porous filler, reducing the interfacial gap between the filler and the matrix. This results in stronger bonding between the filler and the matrix, and more uniform dispersion of the filler, laying a good structural foundation for the preparation of low-oil-permeability thermally conductive silicone gaskets. Vacuum stirring helps to expel gas, reduce porosity, and further improve the performance of the silicone gasket.

[0038] In step S3, the adhesive is calendered into a sheet, then baked and cured with ultraviolet light. Under the baking temperature of 100-140℃, the catalyst promotes the hydrosilylation reaction between the active hydrogen (Si-H bond) in the hydrogen-containing silicone oil and the vinyl group in the vinyl silicone oil, forming a three-dimensional network cross-linked structure. The ultraviolet curing process further forms a high cross-linking density network, which allows the adhesive to fully cure and form, locks the structure and reduces free oil, and finally achieves low oil permeation, high thermal conductivity and stable mechanical properties of the silicone pad.

[0039] Preferably, in the method for preparing the modified porous packing, the ultrasonic frequency is 40–80 kHz, the ultrasonic duration is 25–35 min, the baking temperature is 100–120 °C, and the baking time is 3–6 h. More preferably, in the method for preparing the modified porous packing, the ultrasonic frequency is 50–80 kHz, the ultrasonic duration is 30–35 min, the baking temperature is 100–115 °C, and the baking time is 4–6 h. Even more preferably, in the method for preparing the modified porous packing, the ultrasonic frequency is 55–80 kHz, the ultrasonic duration is 30–32 min, the baking temperature is 100–110 °C, and the baking time is 5–6 h.

[0040] Porous packings have abundant pore structures and large specific surface areas. During ultrasonic modification, the high-frequency vibration of ultrasound generates strong mechanical stirring and cavitation effects. Mechanical stirring can reduce the aggregation of silane coupling agent II on the surface of porous packings; while the cavitation effect causes the formed microbubbles to burst instantly, releasing huge energy that impacts the surface of porous packings, making it easier for silane coupling agent II to penetrate into the pores of porous packings. Therefore, the modified porous packings obtained by ultrasonic modification have excellent dispersibility and compatibility with other raw materials, thereby further improving the performance of low-oil-permeability thermally conductive silicone gaskets.

[0041] A third aspect of this application provides the application of a low-oil-permeability thermally conductive silicone pad in thermal interface materials, wherein the low-oil-permeability thermally conductive silicone pad is the aforementioned low-oil-permeability thermally conductive silicone pad, or is prepared by the aforementioned preparation method.

[0042] Compared with the prior art, this application has at least the following beneficial effects: 1) This application utilizes ultrasonic cavitation effect to modify the pore surface of porous packing, improving the dispersibility of the porous packing and enhancing its compatibility with other raw materials, while shortening the modification time. The modified porous packing obtained through ultrasonic modification makes the internal structure of the thermally conductive silicone gasket more conducive to heat conduction and inhibits oil seepage.

[0043] 2) This application adopts a segmented curing molding process. First, a mixed silicone oil is prepared by physical mixing, and then a rubber compound is prepared. The compound is then heated and cured to form a silicone crosslinking network structure through a hydrosilylation reaction. Then, under ultraviolet light irradiation, a photoinitiator is used to condense the uncrosslinked vinyl silicone oil free molecules to form a super molecular chain. The super molecular chain forms an entanglement effect with the silicone crosslinking network, or grafts onto the free molecular chain ends of the silicone crosslinking network during condensation, eliminating free siloxane molecules and achieving a low oil permeation effect for the thermally conductive silicone pad.

[0044] 3) This application obtains a low-oil-permeability thermally conductive silicone pad by adjusting the proportion of raw materials such as porous filler, hydrogen-containing silicone oil, and thermally conductive filler, and by using the specific preparation method of this application. Under moderate hardness and thermal conductivity (approximately 3.0 W / mK), the single-sided oil permeability value is <1 mm under compression. Attached Figure Description

[0045] Figure 1 This is a schematic cross-sectional view of the fixture used to test the oil leakage value on one side of a silicone gasket.

[0046] Figure 2 This is a top view of the fixture used to test the oil leakage value on one side of a silicone gasket.

[0047] Figure 3 This is an exploded view of the fixture used to test the oil leakage value on one side of a silicone gasket.

[0048] Explanation of reference numerals in the attached diagram: 1. Thermal pad; 2. Circular stainless steel sheet; 3. Filter paper; 4. Glass plate; 5. Screw; 6. Nut; 7. Through hole. Detailed Implementation

[0049] The following detailed description of the contents of this application is provided through specific embodiments, comparative examples, and tables, but is not limited to all the arguments and data.

[0050] In the raw material for the low-oil permeability thermally conductive silicone gasket, the vinyl content of the vinyl-terminated polydimethylsiloxane is 0.7-0.8% by weight, and the viscosity is 650-900 mPa·s. The active hydrogen content of the side-containing hydrogen silicone oil is 0.1-0.3% by weight. The D50 of the porous silica is 4-9 μm. The modified porous filler is prepared according to the formulation and preparation method of this application.

[0051] Example of preparation of modified porous packing: Preparation Example 1: The preparation method of a modified porous filler has the following steps: 150g of ethanol, 1g of N-decyltrimethoxysilane, and 0.3g of polyether-modified polydimethylsiloxane were added to a container, mixed, and stirred until homogeneous. Then, 50g of porous silica was added, and the mixture was stirred again until homogeneous. The mixture was then ultrasonically dispersed at a frequency of 55kHz for 30 minutes. After filtration, the solid obtained from the filtration was baked at a temperature of 110℃ for 5 hours to obtain the modified porous filler.

[0052] Preparation Example 2: The preparation method of a modified porous filler has the following steps: 200g of ethanol, 1.2g of N-decyltrimethoxysilane, and 0.4g of polyether-modified polydimethylsiloxane were added to a container, mixed, and stirred until homogeneous. Then, 150g of nanoporous carbon powder was added, and the mixture was stirred again until homogeneous. The mixture was then ultrasonically dispersed at a frequency of 70kHz for 30 minutes. After filtration, the solid obtained was baked at a temperature of 115℃ for 5 hours to obtain the modified porous filler.

[0053] Preparation Example 3: The preparation method of a modified porous filler has the following steps: 250g of ethanol, 1.5g of N-decyltrimethoxysilane, and 0.5g of polyether-modified polydimethylsiloxane were added to a container, mixed, and stirred until homogeneous. Then, 200g of porous activated carbon powder was added, and the mixture was stirred again until homogeneous. The mixture was then ultrasonically dispersed at a frequency of 75kHz for 35 minutes. After filtration, the solid obtained was baked at a temperature of 120℃ for 5.5 hours to obtain the modified porous filler.

[0054] It is particularly important to emphasize that, unless otherwise specified, the raw materials, reagents or devices used in this application can be obtained from conventional commercial sources.

[0055]

[0056] Example 1

[0057] A low-oil-permeability thermally conductive silicone pad is prepared by the following steps: S1: Add 100g vinyl silicone oil, 3g hydrogen-containing silicone oil, 2g silane coupling agent I, 0.2g inhibitor, 0.6g catalyst, and 1.5g photoinitiator to a mixing tank, mix, set the stirring speed to 60r / min, and the stirring time to 10min to obtain mixed silicone oil.

[0058] S2: Add 1050g of thermally conductive filler and 50g of the modified porous filler from Preparation Example 1 to a mixing tank, and stir them together with the mixed silicone oil under vacuum. During the stirring process, the vacuum degree is -0.09Mpa to -0.1MPa, the stirring speed is 80r / min, and the stirring time is 50min to obtain the adhesive.

[0059] S3: Calender the rubber compound into a 2mm thick sheet, bake it at 125℃ for 30 minutes, and then cure it under ultraviolet light for 2 minutes to obtain a low-oil-permeability thermally conductive silicone pad. Example 2

[0060] A low-oil-permeability thermally conductive silicone pad is prepared by the following steps: S1: Add 100g vinyl silicone oil, 5g hydrogen-containing silicone oil, 1.8g silane coupling agent I, 0.3g inhibitor, 0.5g catalyst, and 2.2g photoinitiator to a mixing tank, mix, set the stirring speed to 30r / min, and the stirring time to 15min to obtain mixed silicone oil.

[0061] S2: 1100g of thermally conductive filler and 150g of modified porous filler from Preparation Example 2 were added to a mixing tank and stirred under vacuum with mixed silicone oil. During the stirring process, the vacuum degree was -0.09Mpa to -0.1MPa, the stirring speed was 50r / min, and the stirring time was 40min to obtain the adhesive.

[0062] S3: Calender the rubber compound into a 2mm thick sheet, bake it at 100℃ for 25 minutes, and then cure it under ultraviolet light for 3 minutes to obtain a low-oil-permeability thermally conductive silicone pad. Example 3

[0063] A low-oil-permeability thermally conductive silicone pad is prepared by the following steps: S1: Add 100g vinyl silicone oil, 12g hydrogen-containing silicone oil, 2.5g silane coupling agent I, 0.8g inhibitor, 0.9g catalyst, and 3g photoinitiator to a mixing tank, mix, set the stirring speed to 80r / min, and the stirring time to 5min to obtain mixed silicone oil.

[0064] S2: 1300g of thermally conductive filler and 280g of the modified porous filler from Preparation Example 3 were added to a mixing tank and stirred under vacuum together with mixed silicone oil. During the stirring process, the vacuum degree was -0.09Mpa to -0.1MPa, the stirring speed was 150r / min, and the stirring time was 30min to obtain the adhesive.

[0065] S3: Calender the rubber compound into a 2mm thick sheet, bake it at 140℃ for 15 minutes, and then cure it under ultraviolet light for 0.2 minutes to obtain a low-oil-permeability thermally conductive silicone pad. Example 4

[0066] The preparation method of a low-oil-permeability thermally conductive silicone pad is the same as in Example 1, except that the quality of each raw material is added according to that in Example 4. Example 5

[0067] The preparation method of a low-oil-permeability thermally conductive silicone pad is the same as in Example 1, except that the quality of each raw material is added according to that in Example 5. Example 6

[0068] The preparation method of a low-oil-permeability thermally conductive silicone pad is the same as in Example 1, except that the quality of each raw material is added according to that in Example 6. Example 7

[0069] The preparation method of a low-oil-permeability thermally conductive silicone pad is the same as in Example 1, except that the quality of each raw material is added according to that in Example 7.

[0070] Comparative Example 1: A thermally conductive silicone pad is prepared by the following steps: S1: Add 100g vinyl silicone oil, 3g hydrogen-containing silicone oil, 3g silane coupling agent I, 0.3g dispersant, 0.2g inhibitor, 0.6g catalyst, and 1.5g photoinitiator to a mixing tank, mix, set the stirring speed to 60r / min, and the stirring time to 10min to obtain mixed silicone oil.

[0071] S2: Add 1050g of thermally conductive filler and 50g of porous filler to a mixing tank and mix them with the mixed silicone oil under vacuum. During the mixing process, the vacuum degree is -0.09Mpa to -0.1MPa, the mixing speed is 80r / min, and the mixing time is 50min to obtain the adhesive.

[0072] S3: Calender the rubber compound into a 2mm thick sheet, bake it at 125℃ for 30 minutes, and then cure it under ultraviolet light for 2 minutes to obtain a thermally conductive silicone pad.

[0073] Comparative Example 2: A method for preparing a thermally conductive silicone pad is the same as that for Comparative Example 1, except that the mass of each raw material is added according to that for Comparative Example 2, and UV curing for 2 min is not performed in step S3 of Comparative Example 2.

[0074] Comparative Example 3: A method for preparing a thermally conductive silicone pad is the same as that for Comparative Example 1, except that the mass of each raw material is added according to that for Comparative Example 3, and no porous filler is added in step S2 of Comparative Example 3.

[0075] Comparative Example 4: A method for preparing a thermally conductive silicone pad is the same as that for Comparative Example 1, except that the mass of each raw material is added according to that of Comparative Example 4, and no porous filler is added in step S2 of Comparative Example 4, and no ultraviolet curing for 2 min is performed in step S3.

[0076] Material performance testing: The low-oil-permeability thermally conductive silicone pads obtained in Examples 1-7 and the thermally conductive silicone pads obtained in Comparative Examples 1-4 were subjected to various performance tests. The test methods are as follows: Hardness: Prepare a 100mm×100mm×2mm silicone pad, stack it into 3 layers, gently place the hardness tester on the test sample, and read the hardness value after 3 seconds.

[0077] Thermal conductivity: tested according to ASTM D5470.

[0078] Unilateral oil seepage value: such as Figures 1-3 As shown, the silicone pad is cut into a sample of 25.4mm × 25.4mm. A filter paper is placed on each of the top and bottom sides of the sample. The sample with the filter paper is placed between two square glass plates with through holes at the four corners. The filter paper should cover the holes on the glass plates and have through holes at the corresponding positions. There is a circular stainless steel sheet with a diameter of 30mm and a thickness of 1.5mm at each of the four through holes between the two filter papers. The stainless steel sheet has a through hole in the middle. Screws are passed through the holes of the top and bottom glass plates, the two filter papers, and the stainless steel sheet, and nuts are locked to lock the glass plates, filter papers, and stainless steel sheets around the perimeter, thereby compressing and fixing the test sample. The entire fixture is placed in a 125℃ oven and baked for 168 hours. It is then left to cool at room temperature for 3 hours. After cooling, the fixture is disassembled, and the single-sided oil seepage value from the edge of the silicone pad to the edge of the oil halo is measured with vernier calipers.

[0079] The test performance of the low-oil-permeability thermally conductive silicone pads of Examples 1-7 and Comparative Examples 1-4 is shown in Table 3 below:

[0080] The low-oil permeability thermally conductive silicone pads in Examples 1-7 were prepared by adding modified porous fillers obtained by ultrasonication, and by using a curing method combining heating and ultraviolet light curing in step S3. This resulted in low-oil permeability thermally conductive silicone pads with moderate hardness and thermal conductivity (approximately 3.0 W / m·K) and a single-sided oil permeation value of <1 mm under compression.

[0081] Compared with Example 1, the porous filler in Comparative Example 1 was not modified. The results showed that the hardness of the thermally conductive silicone pads in Comparative Example 1 and Example 1 was 50 Shore 00 and 31 Shore 00, respectively, and their thermal conductivity was similar. The single-sided oil leakage values ​​were 2.36 mm and 0.64 mm, respectively. The single-sided oil leakage value of the thermally conductive silicone pad in Comparative Example 1 was 3.69 times that of Example 1. Therefore, the modified porous filler prepared by ultrasound effectively improves the adsorption effect of the porous filler, thereby further improving the oil leakage phenomenon of the thermally conductive silicone pad.

[0082] Compared to Example 1, Comparative Example 2's porous filler was not modified, and only heat curing was used in step S3, without UV curing. Conversely, compared to Comparative Example 1, Comparative Example 2 only used heat curing in step S3. The results showed that the hardness of the thermally conductive silicone pads in Comparative Example 2 and Example 1 were 45 Shore 00 and 31 Shore 00, respectively, with comparable thermal conductivity. The single-sided oil seepage value of the thermally conductive silicone pad in Comparative Example 2 was as high as 3.54 mm, significantly higher than that of the thermally conductive silicone pad in Example 1, and also much higher than that of the silicone pad in Comparative Example 1. This indicates that the UV curing process greatly eliminates free siloxane molecules, reducing the oil seepage phenomenon of the thermally conductive silicone pad.

[0083] Compared to Comparative Example 1, Comparative Example 3 did not include porous filler in step S2. The results showed that the hardness and thermal conductivity of the thermally conductive silicone pads in Comparative Example 3 and Comparative Example 1 were comparable. However, the single-sided oil leakage value of the thermally conductive silicone pad in Comparative Example 3 was 3.87 mm, which was higher than that of the thermally conductive silicone pad in Comparative Example 1. Therefore, the addition of porous filler helps reduce oil leakage in thermally conductive silicone pads, and the modified porous filler treated with ultrasound in this application has a more significant effect on reducing oil leakage in thermally conductive silicone pads.

[0084] Compared to Comparative Example 3, Comparative Example 4 did not undergo UV curing in step S3. The results showed that the hardness of the thermally conductive silicone pads in Comparative Example 4 and Comparative Example 3 were 28 Shore OO and 40 Shore OO, respectively, with comparable thermal conductivity. However, the single-sided oil seepage value of the thermally conductive silicone pad in Comparative Example 4 was as high as 6.42 mm, which is 1.66 times that of the thermally conductive silicone pad in Comparative Example 3. This demonstrates that UV curing is highly effective in reducing oil seepage in thermally conductive silicone pads.

[0085] Obviously, the above embodiments of this application are merely examples for clearly illustrating this application, and are not intended to limit the implementation of this application. For those skilled in the art, other variations or modifications can be made based on the above description. Any obvious variations or modifications derived from the technical solutions of this application are still within the protection scope of this application.

Claims

1. A low-oil-permeability thermally conductive silicone pad, characterized in that, The raw material components include: vinyl silicone oil, hydrogen-containing silicone oil, modified porous filler, thermally conductive filler, silane coupling agent I, inhibitor, catalyst, and photoinitiator; The modified porous filler is prepared by ultrasonic modification of porous filler, silane coupling agent II, dispersant and solvent; The components of silane coupling agent I and silane coupling agent II are the same; The porous filler is selected from at least one of silicon-based porous materials and carbon-based porous materials.

2. The low-oil-permeability thermally conductive silicone pad according to claim 1, characterized in that, The modified porous filler is prepared from the following raw material components in parts by weight: 20-300 parts of porous packing Silane coupling agent II 0.3–1.5 parts Dispersant 0.1-0.5 parts Solvent: 100-300 parts.

3. The low-oil-permeability thermally conductive silicone pad according to claim 1, characterized in that, The silicon-based porous material is porous silicon dioxide; And / or, the carbon-based porous material is at least one of nanoporous carbon powder and porous activated carbon powder.

4. The low-oil-permeability thermally conductive silicone pad according to claim 1, characterized in that, The vinyl silicone oil is a vinyl-terminated silicone oil, wherein the vinyl content in the vinyl-terminated silicone oil is 0.6-0.9% by weight, and the viscosity of the vinyl-terminated silicone oil is 500-1000 mPa·s.

5. The low-oil-permeability thermally conductive silicone pad according to claim 1, characterized in that, The hydrogen-containing silicone oil is selected from at least one of side-containing hydrogen-containing silicone oil and end-containing hydrogen-containing silicone oil, and the weight percentage of active hydrogen in the hydrogen-containing silicone oil is 0.2% to 0.4%. And / or, the thermally conductive filler is selected from at least one of alumina, aluminum nitride, boron nitride, aluminum powder, and silicon dioxide.

6. The low-oil-permeability thermally conductive silicone pad according to claim 1, characterized in that, Both the silane coupling agent I and the silane coupling agent II can be selected from at least one of alkylsilanes, aminosilanes, and epoxysilanes; And / or, the dispersant is selected from at least one of polyether-modified polydimethylsiloxane, hydroxyl polydimethylsiloxane, and copolymer solutions containing acidic groups; And / or, the inhibitor is an alkynyl alcohol inhibitor; And / or, the catalyst is a platinum catalyst; And / or, the photoinitiator is selected from at least one of benzophenone, 2-isopropylthioxanthone, and 2,4,6-trimethylbenzoyldiphenylphosphine oxide; And / or, the solvent is an alcohol solvent.

7. The low-oil-permeability thermally conductive silicone pad according to any one of claims 1 to 6, characterized in that, Its raw materials include the following components in parts by weight: 100 parts vinyl silicone oil 2-12 parts of hydrogen-containing silicone oil 20-300 parts of modified porous packing 500-1400 parts of thermally conductive filler Silane coupling agent I: 0.6–2.5 parts Inhibitor 0.02–0.8 parts Catalyst 0.1–0.9 parts Photoinitiator 0.5 to 3 parts.

8. A method for preparing a low-oil-permeability thermally conductive silicone pad as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1: Mix vinyl silicone oil, hydrogen-containing silicone oil, silane coupling agent I, inhibitor, catalyst and photoinitiator, and stir to obtain mixed silicone oil; S2: Mix thermally conductive filler, modified porous filler and mixed silicone oil, and stir under vacuum to obtain adhesive; S3: The adhesive material is calendered into a sheet, then baked and cured with ultraviolet light to obtain the low oil permeability thermally conductive silicone pad; Preferably, the preparation method of the modified porous filler includes the following steps: The silane coupling agent II, dispersant, and solvent are mixed and stirred. The porous filler is then added and stirred again. Finally, the mixture is ultrasonicated, filtered, and baked to obtain the modified porous filler.

9. The method for preparing a low-oil-permeability thermally conductive silicone pad according to claim 8, characterized in that, In step S1, the vacuum degree is -0.09 MPa to -0.1 MPa, the stirring speed is 30 to 80 r / min, and the stirring time is 5 to 15 min. In step S2, the vacuum degree is -0.09 MPa to -0.1 MPa, the stirring speed is 50 to 150 r / min, and the stirring time is 30 to 50 min; In step S3, the baking temperature is 100-140℃, the baking time is 15-30 min, and the UV curing time is 0.2-3 min. Preferably, in the preparation method of the modified porous filler, the frequency of the ultrasound is 40-80 kHz, the duration of the ultrasound is 25-35 min, the baking temperature is 100-120 °C, and the baking time is 3-6 h.

10. The application of a low-oil-permeability thermally conductive silicone pad as described in any one of claims 1 to 7, or a low-oil-permeability thermally conductive silicone pad prepared by the preparation method as described in any one of claims 8 to 9, in thermal interface materials.

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