High-temperature-resistant heat-conducting silica gel, preparation method and application thereof

Abstract

The application discloses a high-temperature-resistant heat-conducting silica gel and a preparation method and application thereof, relates to the technical field of heat-conducting silica gel, and comprises the following components in parts by weight: vinyl-terminated polydimethylsiloxane 80-120 parts; phenyl-modified siloxane 10-40 parts; spherical alumina 150-600 parts; flaky boron nitride 50-300 parts; nano-alumina 10-80 parts; heat-conducting filler modified by a silane coupling agent 1-10 parts; MQ resin 5-50 parts; and hydrogen-containing silicone oil crosslinking agent 1-20 parts. The application improves the thermal stability and prolongs the service life through a high-temperature-resistant matrix and a compact crosslinking structure, improves the heat-conducting efficiency and stability through a continuous heat-conducting channel constructed by multi-scale fillers, and realizes good fluidity and interface fitting capacity by optimizing the formula, so that the efficient heat dissipation performance and construction adaptability are taken into account.

Description

Technical Field

[0001] This application relates to the field of thermally conductive silicone technology, specifically to a high-temperature resistant thermally conductive silicone, its preparation method, and its application. Background Technology

[0002] Thermally conductive silicone is a type of interfacial thermally conductive functional material constructed with organosilicon materials as the continuous phase and highly thermally conductive fillers as the dispersed phase. Essentially, it belongs to the category of thermal interface materials (TIMs). Specifically, it uses polysiloxane as the matrix, introducing thermally conductive fillers such as alumina, boron nitride, magnesium oxide, or silver powder into the matrix, and combining coupling modification and cross-linking curing processes to form a composite system with continuous thermally conductive pathways. In actual operation, this material fills the microscopic gaps between electronic devices and heat dissipation components, thereby reducing interfacial contact thermal resistance and enabling efficient heat conduction from the heat source to the heat dissipation end. Compared to traditional thermal pads or thermal pastes, thermally conductive silicone exhibits superior performance in high-temperature stability, electrical insulation, flexible adhesion, and long-term reliability. It maintains relatively stable thermal conductivity and interfacial bonding under temperature cycling or long-term service conditions, thus finding wide application in power device packaging, LED heat dissipation, new energy battery thermal management, and thermal control of high-performance electronic equipment.

[0003] Existing thermally conductive silicone exhibits multi-dimensional performance degradation issues during long-term service, specifically: Under high temperature or temperature cycling, the silicone matrix undergoes low-molecular-weight volatilization and chain rearrangement, leading to gradual relaxation of the contact interface between thermally conductive fillers. This disrupts the original thermal conductivity pathways, resulting in a decrease in thermal conductivity. Simultaneously, fillers are prone to agglomeration or sedimentation under high-filling conditions, causing uneven distribution of thermal conductivity paths within the system and increasing local thermal resistance. At the interface level, due to mismatched coefficients of thermal expansion and repeated thermal shocks, interface debonding or pumping effects may occur, weakening the adhesion between the device and the heat dissipation components. In terms of rheological properties, high-filler systems often lead to a significant increase in application viscosity, making it difficult to spread evenly during coating and easily trapping air bubbles, further increasing interfacial thermal resistance. In addition, some systems may exhibit oil seepage and cross-linked network aging under long-term high temperatures, increasing material hardness and decreasing flexibility, leading to cracking or failure under continuous stress, ultimately affecting the overall heat dissipation reliability and service life.

[0004] The information disclosed in the background section is only intended to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] The purpose of this application is to provide a high-temperature resistant thermally conductive silicone, its preparation method, and its application, in order to solve the problems in the background art mentioned above.

[0006] To achieve the above objectives, this application provides the following technical solution: a high-temperature resistant thermally conductive silicone, characterized in that, by weight, it comprises the following components: 80-120 parts of vinyl-terminated polydimethylsiloxane; 10-40 parts of phenyl-modified siloxane; 150-600 parts of spherical alumina; 50-300 parts of sheet-like boron nitride; 10-80 parts of nano-alumina; 1-10 parts of thermally conductive filler modified with a silane coupling agent; 5-50 parts of MQ resin; 1-20 parts of hydrogen-containing silicone oil crosslinking agent; 0.001-0.5 parts of platinum catalyst; and 0.001-0.2 parts of inhibitor. The vinyl-terminated polydimethylsiloxane and phenyl-modified siloxane together constitute a high-temperature resistant organosilicon matrix. The spherical alumina, sheet-like boron nitride, and nano-alumina synergistically construct a continuous thermally conductive pathway. The MQ resin is used to improve the density of the crosslinking network, thereby enabling the thermally conductive silicone to maintain stable thermal conductivity and interfacial bonding performance under high temperature and thermal cycling conditions.

[0007] Preferably, the spherical alumina has a particle size of 1–50 μm, the sheet-like boron nitride has an aspect ratio of 5–100, and the nano-alumina has a particle size of 10–200 nm, in order to form a multi-scale filler composite structure.

[0008] Preferably, spherical alumina is used to fill the gaps in the system, plate-like boron nitride is used to construct surface contact heat conduction paths, and nano-alumina is used to fill microscopic voids to form a three-dimensional continuous heat conduction network structure.

[0009] Preferably, the silane coupling agent is one or more of aminopropyltriethoxysilane, epoxysilane, or vinylsilane, used to modify the surface of the thermally conductive filler to enhance the interfacial bonding force between the filler and the organosilicon matrix.

[0010] Preferably, the phenyl content in the phenyl-modified siloxane is 5% to 30%, which is used to improve the high temperature resistance and resistance to thermo-oxidative aging of the material.

[0011] Preferably, the hydrogen-containing silicone oil crosslinking agent and the vinyl-terminated polydimethylsiloxane form a crosslinked network structure through an addition reaction, the platinum catalyst is used to catalyze the crosslinking reaction, and the inhibitor is used to regulate the reaction rate.

[0012] Preferably, MQ resin is used to increase the crosslinking density of the system, suppress low molecular weight volatilization and oil exudation, and enhance the structural stability of the material.

[0013] A method for preparing high-temperature resistant thermally conductive silicone includes the following steps: Vinyl-terminated polydimethylsiloxane is mixed with phenyl-modified siloxane to form a matrix system; Spherical alumina, flake boron nitride, and nano alumina were added in proportion and dispersed and mixed. The thermally conductive filler was surface-modified with a silane coupling agent and then added to the system. Add MQ resin and mix well; Add hydrogen-containing silicone oil crosslinking agent, platinum catalyst and inhibitor for degassing treatment; Thermally conductive silicone is obtained by curing the silicone at a certain temperature.

[0014] Preferably, the dispersion and mixing are carried out by planetary mixing or three-roll milling, the degassing process is carried out under vacuum conditions, and the curing temperature is 80-180℃.

[0015] Preferably, thermally conductive silicone is used as a thermal interface material between electronic devices and heat dissipation components, and is applied in the fields of power device packaging, LED heat dissipation, thermal management of new energy batteries, and heat dissipation of high-performance electronic devices.

[0016] The technical effects and advantages provided by this application in the above technical solution are as follows: This application introduces phenyl-modified siloxanes to construct a high-temperature resistant matrix system and combines it with MQ resin to enhance the density of the cross-linked network. This enables the material to effectively inhibit molecular chain migration and low-molecular-weight volatilization during high-temperature environments and long-term thermal aging, thereby maintaining structural stability and interfacial integrity. Under continuous thermal stress, the material can still maintain low performance degradation, significantly improving overall service life and reliability, and is suitable for long-term stable operation under high-temperature conditions.

[0017] This application constructs a multi-scale synergistic thermal conductivity structure using spherical alumina, sheet-like boron nitride, and nano-alumina, enabling continuous heat conduction through different scale paths, effectively reducing interfacial thermal resistance and improving thermal conductivity. Simultaneously, surface modification enhances the interfacial bonding between the filler and the matrix, ensuring the stability of the thermal conductivity pathway during thermal cycling and preventing performance degradation due to a loose structure, thereby achieving stable and efficient heat dissipation performance.

[0018] This application optimizes the filler gradation and matrix ratio to achieve a system with good flowability and construction adaptability while ensuring thermal conductivity. In practical applications, it can more fully fill the microscopic gaps at the interface and reduce air bubble residue, thereby reducing contact thermal resistance and improving interface bonding quality. Uniform coating can also be achieved on complex structural surfaces, improving processing consistency and application stability, and meeting the heat dissipation requirements of various electronic devices. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings.

[0020] Figure 1 This is a flowchart illustrating the preparation process of the thermally conductive silicone material used in this application. Detailed Implementation

[0021] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, they are provided so that the description of this disclosure will be more complete and fully convey the concept of the exemplary embodiments to those skilled in the art.

[0022] This application provides a high-temperature resistant thermally conductive silicone, comprising the following components by weight: 80-120 parts of vinyl-terminated polydimethylsiloxane; 10-40 parts of phenyl-modified siloxane; 150-600 parts of spherical alumina; 50-300 parts of lamellar boron nitride; 10-80 parts of nano-alumina; 1-10 parts of thermally conductive filler modified with silane coupling agent; 5-50 parts of MQ resin; 1-20 parts of hydrogen-containing silicone oil crosslinking agent; 0.001-0.5 parts of platinum catalyst; and 0.001-0.2 parts of inhibitor. The vinyl-terminated polydimethylsiloxane and phenyl-modified siloxane together constitute a high-temperature resistant organosilicon matrix. The spherical alumina, lamellar boron nitride, and nano-alumina synergistically construct a continuous thermally conductive pathway. The MQ resin is used to improve the density of the crosslinking network, thereby enabling the thermally conductive silicone to maintain stable thermal conductivity and interfacial bonding performance under high temperature and thermal cycling conditions.

[0023] Example 1: This example provides a thermally conductive silicone composition with high-temperature resistance. This composition maintains stable thermal conductivity and excellent interfacial reliability even under long-term high-temperature service and thermal cycling conditions. The thermally conductive silicone composition comprises the following components by weight: 100 parts vinyl-terminated polydimethylsiloxane (Vinyl-PDMS), 20 parts phenyl-modified siloxane, 300 parts spherical alumina, 120 parts lamellar boron nitride, 40 parts nano-alumina, 5 parts thermally conductive filler modified with a silane coupling agent, 20 parts MQ resin, 8 parts hydrogen-containing silicone oil crosslinking agent, 0.05 parts platinum catalyst, and 0.05 parts inhibitor.

[0024] The vinyl-terminated polydimethylsiloxane preferably has a viscosity of 3000–8000 mPa·s (25°C) and a vinyl content of 0.05–0.2 mol%. The phenyl-modified siloxane preferably has a phenyl molar fraction of 10%–20%. Its introduction can effectively improve the high-temperature resistance and thermo-oxidative aging resistance of the material. In particular, it can inhibit the degradation of the main chain and the oxidation reaction of the side groups in long-term working environments above 150°C, thereby maintaining the structural stability of the material.

[0025] The spherical alumina is preferably high-purity α-Al₂O₃ with a particle size distribution of 5–30 μm. It has good flow and filling characteristics and can be used to fill macroscopic gaps and reduce the porosity of the system. The plate-shaped boron nitride is preferably hexagonal boron nitride (h-BN) with an aspect ratio of 10–50. It can form a surface contact heat conduction path in the system and effectively improve the heat conduction efficiency. The nano-alumina has a particle size of 20–100 nm and is used to fill microscopic gaps and enhance the contact interface between fillers, thereby constructing a multi-scale synergistic heat conduction network structure, enabling heat flow to be transferred at different scales and significantly reducing interfacial thermal resistance.

[0026] Before being added to the system, the thermally conductive filler undergoes surface modification treatment. Specifically, it is coupled with aminopropyltriethoxysilane at a dosage of 0.5%–2% of the filler mass. The modification method involves adding the filler to a mixed solution containing 95% ethanol and 5% deionized water, adjusting the pH to 4–5, adding the silane coupling agent, and stirring at room temperature for 1–2 hours to allow the coupling agent to hydrolyze and react with the hydroxyl groups on the filler surface. The mixture is then filtered and dried (at 80°C for 4 hours) to obtain the modified filler. This modification treatment significantly enhances the interfacial bonding between the filler and the organosilicon matrix, reduces interfacial thermal resistance, and inhibits filler agglomeration.

[0027] MQ resin is a silicone resin containing SiO4 / 2 (Q unit) and R3SiO1 / 2 (M unit), with an M / Q ratio preferably of 0.6 to 1.2. The introduction of MQ resin can effectively improve the crosslinking density and structural compactness of the system, while restricting the migration of low molecular weight chain segments, thereby suppressing oil exudation under high temperature conditions and improving the dimensional stability and mechanical strength of the material.

[0028] The Si-H content of the hydrogen-containing silicone oil crosslinking agent is preferably 0.5% to 1.5%. It undergoes an addition reaction (hydrosilicification reaction) with vinyl-terminated polydimethylsiloxane under the action of a platinum catalyst to form a three-dimensional crosslinked network structure. The platinum catalyst is preferably a Karstedt catalyst with a platinum content of 1000 to 3000 ppm. The inhibitor is preferably an ethynyl alcohol or maleate compound to extend the working time of the system and prevent premature curing during processing.

[0029] In the preparation process, vinyl-terminated polydimethylsiloxane and phenyl-modified siloxane were first added to a planetary stirred tank in proportion and stirred at 300 rpm for 10 minutes at 25°C to form a uniform matrix system. Then, spherical alumina, flake boron nitride and nano alumina were added in batches and dispersed for 30 minutes at a stirring speed gradually increased to 800 rpm to ensure uniform distribution of multi-scale fillers and avoid local agglomeration.

[0030] After the filler is fully dispersed, the filler modified with silane coupling agent is added to the system and stirred for 15 minutes to form a stable dispersion in the matrix; then MQ resin is added and mixed at 500 rpm for 20 minutes to ensure uniform distribution and participation in the subsequent crosslinking network construction.

[0031] The system temperature was then controlled below 40°C, and hydrogen-containing silicone oil crosslinking agent, platinum catalyst and inhibitor were added in sequence. The mixture was stirred at low speed (200 rpm) for 10 minutes to avoid introducing too many air bubbles. After mixing, the system was transferred to a vacuum degassing device and degassed at -0.095 MPa for 15 minutes to remove air entrained in the system and improve the material density.

[0032] The degassed mixture can be applied to the interface to be cooled by scraping or dispensing, and then heat-cured at 120°C for 2 hours to form a thermally conductive silicone layer with a three-dimensional cross-linked structure. The thickness of the silicone layer is preferably 50-200 μm.

[0033] Performance test results show that the thermally conductive silicone prepared in this embodiment has an initial thermal conductivity of 4.5–5.5 W / m·K. After continuous aging at 200℃ for 500 hours, the thermal conductivity retention rate can still reach more than 90%, showing excellent heat resistance stability. After 500 cycles under thermal cycling conditions from -40℃ to 200℃, the material did not show obvious interface debonding, pumping out or cracking, and the interface thermal resistance change rate was less than 15%. In addition, after being placed at 150℃ for 300 hours, no obvious oil exudation was observed, and the material surface remained dry, indicating that it has good anti-oil exudation performance.

[0034] Furthermore, scanning electron microscopy (SEM) revealed that the filler was uniformly distributed in the matrix, forming a continuous thermally conductive network structure. The fillers were in close contact with each other and there was no obvious agglomeration. Dynamic mechanical analysis (DMA) results showed that the material maintained a low storage modulus change under high temperature conditions, indicating that it has good flexibility and stress buffering capacity.

[0035] This embodiment uses phenyl-modified siloxane to construct a high-temperature resistant matrix system, combines it with multi-scale thermally conductive fillers to synergistically construct a thermally conductive network, and enhances the density of the cross-linked structure with MQ resin. At the same time, it utilizes silane coupling agents to improve interfacial bonding performance. This effectively solves the problems of thermal conductivity decay, filler agglomeration, interfacial failure, and oil seepage of thermally conductive silicone under high temperature and thermal cycling conditions in the prior art, and significantly improves the overall performance and long-term service reliability of the material.

[0036] Example 2: This example provides a high thermal conductivity silicone composition for heat dissipation applications in high-power devices. This composition ensures high thermal conductivity while also maintaining high-temperature stability and interface reliability. The silicone composition comprises the following components by weight: 90 parts vinyl-terminated polydimethylsiloxane, 25 parts phenyl-modified siloxane, 500 parts spherical alumina, 250 parts lamellar boron nitride, 60 parts nano-alumina, 8 parts epoxy-modified thermally conductive filler, 30 parts MQ resin, 12 parts hydrogen-containing silicone oil crosslinking agent, 0.1 parts platinum catalyst, and 0.08 parts inhibitor.

[0037] Among them, the vinyl-terminated polydimethylsiloxane is a linear polymer with a viscosity of 2000-5000 mPa·s, and its vinyl content is controlled within the range of 0.08-0.15 mol% to ensure appropriate reactivity and processing fluidity; the phenyl-modified siloxane preferably has a phenyl content of 15%-25%, which improves the thermal stability and oxidation resistance of the material under high temperature conditions by introducing a rigid benzene ring structure, while enhancing the interaction between molecular chains, which helps to maintain the structural integrity of the structure under high filler conditions.

[0038] In terms of the thermally conductive filler system, spherical alumina is used as the main filler phase, with its dosage significantly increased to 500 parts. The preferred particle size distribution is 3-20 μm, which can maintain a certain fluidity while ensuring high filling efficiency. The plate-shaped boron nitride adopts a hexagonal crystal structure with a radial dimension of 5-30 μm, a thickness of 0.1-1 μm, and an aspect ratio of 20-80. It preferentially forms a surface contact structure in the system, thereby reducing the interfacial thermal resistance between fillers and constructing an efficient heat conduction path. The nano-alumina has a particle size of 30-80 nm and is distributed between the spherical and plate-shaped fillers as a microscale filler component. It effectively fills the micropores and increases the contact probability between fillers, thereby forming a continuous thermally conductive network in the macroscopic and microscopic multi-scale range.

[0039] To further improve the interfacial compatibility and interfacial thermal conductivity between the filler and the organosilicon matrix, surface modification treatment was performed before the filler was added. During the modification process, epoxy-based silanes were used as coupling agents. These silane groups chemically bond with the hydroxyl groups on the filler surface, while their siloxane ends form a well-compatible interface with the matrix. Specifically, spherical alumina, flake boron nitride, and nano-alumina were added to a mixed solution of ethanol and deionized water at a volume ratio of 9:1. The pH of the system was adjusted to 4.5–5.5. The coupling agent was added, and the mixture was stirred at 50°C for 2 hours to allow for complete hydrolysis and the formation of a coating layer on the filler surface. The mixture was then filtered and dried (100°C, 3 hours) to obtain the modified filler. After this treatment, the filler surface changed from a hydrophilic structure to an organic-phase compatible structure, significantly reducing interfacial thermal resistance and the tendency for filler agglomeration.

[0040] MQ resin, used as a structural reinforcing component, is increased to 30 parts, with the M / Q ratio controlled within the range of 0.7–1.0. This allows the system to form a relatively dense three-dimensional network structure even under high filler conditions. This structure not only fixes the filler position, preventing sedimentation or migration during high-temperature or long-term use, but also inhibits the volatilization of low-molecular-weight segments, thereby reducing oil seepage and improving the overall stability of the material.

[0041] The crosslinking system is achieved through an addition reaction between hydrogen-containing silicone oil and vinyl-terminated polydimethylsiloxane. The Si-H content in the hydrogen-containing silicone oil is controlled at 1.0% to 1.3% to ensure that the crosslinking reaction proceeds fully. The platinum catalyst is a Karstedt type catalyst, with an addition amount of 0.1 parts, which allows the reaction to proceed rapidly under medium temperature conditions. The inhibitor is an acetylene alcohol compound, which delays the release of catalytic activity and maintains an appropriate operating time during the mixing and coating process.

[0042] Because the filler content in this embodiment is extremely high, the viscosity of the system increases significantly. Therefore, a three-roll milling process is used to disperse the mixture during the preparation process. The specific process is as follows: First, vinyl-terminated polydimethylsiloxane and phenyl-modified siloxane are mixed evenly and stirred at low speed at room temperature to form a matrix; then, spherical alumina, flake boron nitride and nano alumina are added in batches and premixed; the premixed system is fed into a three-roll milling machine, and the milling is repeated by gradually reducing the roller gap (from 50 μm to 5 μm) to fully disperse the filler under high shear force, break up agglomerates and improve the uniformity of filler distribution.

[0043] During the grinding process, the system temperature must be strictly controlled to not exceed 60℃ to avoid premature reaction of the platinum catalyst system or unnecessary thermal rearrangement of siloxane segments. After grinding, the modified filler and MQ resin are added to the system for secondary mixing to further homogenize the structure. Then, hydrogen-containing silicone oil crosslinking agent, platinum catalyst and inhibitor are added and stirred evenly under low speed conditions.

[0044] After mixing, the system is placed in a vacuum environment (-0.095MPa) for 20 minutes to degas, in order to remove the tiny air bubbles introduced during the high shear process and prevent the air bubbles from becoming sources of thermal resistance. After degassing, the material is applied to the interface to be cooled by scraping or screen printing and cured at 150°C for 1.5 hours to form an interface layer with high thermal conductivity.

[0045] Performance test results show that the thermal conductivity of the material in this embodiment can stably reach 6-8 W / m·K, which is a significant improvement compared to conventional thermally conductive silicone (approximately 2-4 W / m·K). Interfacial thermal resistance tests show that under the same contact pressure conditions, its interfacial thermal resistance is reduced by approximately 30%-50%. After aging at 200℃ for 300 hours, the thermal conductivity retention rate is still higher than 88%, demonstrating excellent heat resistance. After thermal cycling tests (-40℃ to 200℃, 300 cycles), no obvious interfacial debonding or pumping phenomenon was observed, indicating good structural stability.

[0046] From a microstructural perspective, scanning electron microscopy reveals that the sheet-like boron nitride exhibits an oriented arrangement within the system, forming a continuous surface-contact heat conduction path. Spherical alumina fills the spaces between these structures, creating a supporting framework. Nano-alumina fills the microscopic gaps, making the overall heat conduction network more compact and thus enabling efficient heat transfer at different scales.

[0047] It should be noted that, due to the high filler content in this embodiment, the viscosity of the system increases significantly, exhibiting high thixotropy and high structural strength in a static state. Under shearing action, the viscosity decreases, which is beneficial for construction. However, compared to filler systems, it has higher requirements for equipment and process conditions. For example, high-torque dispensing equipment or pressure coating methods are required to ensure that the material can be spread evenly and fully fill the micro gaps at the interface.

[0048] This embodiment constructs a continuous thermally conductive network at both the macroscopic and microscopic levels by increasing the content of multi-scale thermally conductive fillers and optimizing the filler morphology combination and interface modification methods. At the same time, it combines MQ resin to enhance structural stability, thereby achieving comprehensive performance of high thermal conductivity, low thermal resistance and good reliability in high-temperature and high-power-density application environments. It is particularly suitable for application scenarios with extremely high heat dissipation requirements, such as IGBT modules, CPU / GPU chips and new energy vehicle power systems.

[0049] Example 3: This example provides a highly reliable thermally conductive silicone composition suitable for extreme temperature cycling environments. This material maintains stable thermal conductivity and interfacial bonding under repeated thermal shock and long-term high-temperature service conditions. The thermally conductive silicone comprises the following components by weight: 110 parts vinyl-terminated polydimethylsiloxane, 35 parts phenyl-modified siloxane, 250 parts spherical alumina, 100 parts lamellar boron nitride, 30 parts nano-alumina, 6 parts vinylsilane-modified thermally conductive filler, 40 parts MQ resin, 15 parts hydrogen-containing silicone oil crosslinking agent, 0.08 parts platinum catalyst, and 0.1 parts inhibitor.

[0050] The design of this system focuses on enhancing high-temperature stability and resistance to thermal cycling failure. Vinyl-terminated polydimethylsiloxane is selected with a medium-to-high molecular weight structure, and its viscosity is controlled within the range of 5000–10000 mPa·s, ensuring good flexibility and stress buffering capacity after curing. The content of phenyl-modified siloxane is increased to 35 parts, with the phenyl molar fraction controlled within the range of 20%–30%. The introduction of a rigid benzene ring structure significantly improves the thermal stability of the molecular chain and enhances intermolecular interactions, making the material less prone to chain segment rearrangement and thermo-oxidative degradation under high-temperature conditions, thus maintaining structural integrity even in environments above 200°C.

[0051] The filler system employs a moderate filler content design to avoid increased brittleness caused by excessive filler content. Spherical alumina particles with a size distribution of 5–25 μm are used to construct the main thermally conductive framework and provide good flowability. Flaky boron nitride particles are controlled to a size of 10–20 μm with an aspect ratio of approximately 15–40, enabling them to form oriented surface contact structures within the system, which helps establish low thermal resistance channels at the interface. Nano-alumina particles with a size of 20–60 nm are distributed in the filler gaps, increasing the contact density between fillers and reducing microscopic voids, thereby ensuring that the thermally conductive network is not easily damaged during thermal cycling.

[0052] To enhance the interfacial bonding stability between the filler and the matrix, vinyl silane was introduced to modify the filler surface. During the modification process, the filler was first dispersed in an ethanol-water solution system, the pH was adjusted to a weakly acidic condition, vinyl silane was added, and the reaction was carried out at 50°C for 1.5–2 hours. This caused the silane molecules to hydrolyze and form a covalently bonded organic layer on the filler surface. One end of this organic layer is bonded to the filler surface, while the other end contains a vinyl structure, which can participate in network construction during subsequent crosslinking reactions. This creates a "chemical bridging structure" between the filler and the matrix, significantly improving the interfacial bonding strength and reducing the interfacial thermal resistance.

[0053] The increase of MQ resin content to 40 parts is one of the key features of this embodiment. MQ resin has a highly branched structure, and its introduction can significantly improve the crosslinking density and spatial network stability of the system. During thermal cycling, this structure can effectively restrict the migration and relaxation of molecular chain segments, prevent structural fatigue caused by repeated expansion and contraction, and reduce the precipitation of low-molecular-weight substances, thereby suppressing oil seepage and maintaining interfacial stability. In addition, the higher content of MQ resin can also enhance the creep resistance of the material, making it less prone to deformation and flow under long-term pressure conditions, which helps to reduce the risk of pump-out.

[0054] The crosslinking system utilizes an addition reaction between hydrogen-containing silicone oil and vinylsiloxane to construct a three-dimensional network structure. The Si-H content in the hydrogen-containing silicone oil is controlled at 1.2%–1.5% to ensure sufficient crosslinking points; 0.08 parts of platinum catalyst are used to ensure uniform reaction under moderate temperature conditions; and 0.1 parts of inhibitor are added to extend the system's operating time and control the reaction rate.

[0055] During the preparation process, a stepwise crosslinking strategy was adopted to improve network uniformity and reduce internal stress concentration. The specific process is as follows: First, vinyl-terminated polydimethylsiloxane and phenyl-modified siloxane were mixed uniformly at room temperature to form a basic organosilicon system; then, spherical alumina, flake boron nitride, and nano-alumina were added and dispersed in a planetary mixer at a speed controlled between 400 and 800 rpm for about 30 minutes to ensure uniform distribution of the fillers.

[0056] After the filler is dispersed, the vinylsilane-modified filler is added to the system and stirred to ensure it is fully mixed with the matrix and forms a stable interface. Then, MQ resin is added and mixed for 20 minutes under medium-speed stirring to ensure it is uniformly dispersed in the system.

[0057] In the crosslinking system addition stage, approximately 70% of the hydrogen-containing silicone oil crosslinking agent is first added and premixed, allowing some crosslinking reactions to proceed gradually under low-speed conditions, forming a primary network structure. Subsequently, the remaining crosslinking agent, platinum catalyst, and inhibitor are added, enabling the system to form a more uniform three-dimensional network structure during the subsequent curing process. This stepwise addition method effectively avoids excessively rapid local crosslinking reactions that could lead to network unevenness, thereby reducing internal stress concentration points and improving the overall structural stability of the material.

[0058] After mixing, the system is placed in a vacuum environment (-0.095MPa) for 20-25 minutes to degas and remove residual bubbles. The degassed material is then uniformly applied to the interface area by a scraping method, with the thickness controlled in the range of 80-150μm. Subsequently, it is cured at 130℃ for 3 hours to allow the crosslinking reaction to proceed fully and form a dense and stable structure.

[0059] Performance test results show that after 1000 thermal cycles in the range of -40℃ to 200℃, no obvious interface debonding, pumping out or structural cracking was observed, and the interface integrity remained good; the thermal conductivity decreased only from the initial value of about 4.0 to 4.8 W / m·K to 3.6 to 4.3 W / m·K, with a decrease of less than 10%; after continuous aging at 200℃ for 500 hours, the material still maintains low compressive deformation and stable mechanical properties.

[0060] Interfacial shear strength tests show that the material's shear strength changes by less than 12% before and after thermal cycling, indicating stable interfacial bonding performance. Dynamic thermomechanical analysis shows that the storage modulus changes gradually under high-temperature conditions, and the material maintains good flexibility and stress buffering capacity, thus effectively absorbing the stress caused by thermal expansion mismatch.

[0061] Microstructural observations revealed that the filler was uniformly distributed within the matrix, with no significant sedimentation or agglomeration. Lamellar boron nitride formed an overlapping structure, with spherical alumina filling the spaces to create a supporting network. Nano-alumina filled the microscopic voids, ensuring the continuity of the thermally conductive network across multiple scales. Even with slight structural adjustments during thermal cycling, the network maintained effective contact, thus guaranteeing stable thermal conductivity.

[0062] This embodiment enhances high-temperature stability by increasing the content of phenyl-modified siloxane, improves network density and creep resistance by increasing the content of MQ resin, and enhances interfacial bonding and structural uniformity through vinyl silane modification and stepwise crosslinking strategy. As a result, it significantly reduces the risk of interfacial failure in environments with repeated high and low temperature cycles, effectively solving the problems of pump-out, debonding and thermal conductivity decay that are prone to occur in traditional thermal conductive silicone under thermal cycling conditions. It is particularly suitable for application scenarios with extremely high reliability requirements, such as new energy vehicle battery modules, power electronic modules and aerospace electronic equipment.

[0063] Example 4: This example provides a low-viscosity thermally conductive silicone composition that balances thermal conductivity and workability. This material is particularly suitable for thermal management applications involving complex interface structures or precision electronic devices. It significantly reduces system viscosity while maintaining a certain level of thermal conductivity, improving coating uniformity and interfacial adhesion. The thermally conductive silicone comprises the following components by weight: 120 parts vinyl-terminated polydimethylsiloxane, 15 parts phenyl-modified siloxane, 200 parts spherical alumina, 80 parts lamellar boron nitride, 20 parts nano-alumina, 3 parts thermally conductive filler modified with aminopropyltriethoxysilane, 10 parts MQ resin, 5 parts hydrogen-containing silicone oil crosslinking agent, 0.02 parts platinum catalyst, and 0.02 parts inhibitor.

[0064] The system design focuses on "reducing system viscosity and improving construction adaptability." By reducing the overall filler content and optimizing the multi-scale particle size distribution, the filler reduces interparticle interactions while ensuring the continuity of the heat conduction path, thereby significantly reducing the frictional resistance within the system. Vinyl-terminated polydimethylsiloxane is selected from products with low to medium viscosity, controlled between 1500 and 4000 mPa·s, ensuring good flowability of the matrix. The content of phenyl-modified siloxane is reduced to 15 parts, and the phenyl molar fraction is controlled within the range of 10% to 15%, to balance certain temperature resistance performance with avoiding an increase in system viscosity due to excessive rigidity.

[0065] In terms of the filler system, a strategy of "low filling + optimized gradation" is adopted. The spherical alumina particle size is controlled in the range of 10-40 μm. As the main filler phase, its regular spherical structure helps to reduce the friction coefficient between particles, so that the system exhibits lower resistance under shear conditions. The content of plate-shaped boron nitride is controlled at 80 parts, and its aspect ratio is 10-30. It can still form local surface contact heat conduction paths in the system, but will not significantly increase the viscosity of the system due to excessive stacking. The nano-alumina particle size is controlled in the range of 30-100 nm, and its amount is reduced to 20 parts. It is only used to fill micro-voids, thereby avoiding the increase in specific surface area and the sharp increase in viscosity caused by excessive nanoparticles.

[0066] Before being added to the system, the filler undergoes surface modification treatment using aminopropyltriethoxysilane as a coupling agent. During the modification process, the filler is dispersed in an ethanol-water solution system. Under weakly acidic conditions, the coupling agent is added and stirred to allow the silane molecules to hydrolyze and form chemical bonds with the filler surface, simultaneously forming an organic-phase compatible layer on the filler surface. This modification treatment reduces the surface energy of the filler, decreasing the tendency for particle aggregation; it also improves the wettability of the filler in the organosilicon matrix, making it easier for the filler to be coated by the matrix, thus ensuring effective connection of the thermal conductivity path while reducing viscosity.

[0067] Reducing the amount of MQ resin to 10 parts moderately decreases the crosslinking density of the system, thereby maintaining the material's high flexibility and compressibility after curing, which is beneficial for achieving full adhesion during interfacial contact. At the same time, an appropriate amount of MQ resin can still provide the necessary structural stability, preventing significant flow or precipitation of the material during use.

[0068] The crosslinking system utilizes an addition reaction between hydrogen-containing silicone oil and vinylsiloxane to construct a network structure. The amount of hydrogen-containing silicone oil is 5 parts, with the Si-H content controlled within the range of 0.8%–1.2% to ensure a moderate crosslinking density. The amount of platinum catalyst added is 0.02 parts, resulting in a relatively mild reaction rate. The amount of inhibitor is 0.02 parts, used to extend the system's workability time and facilitate coating and adjustment during application.

[0069] In terms of the preparation process, to further reduce bubble entrainment and improve dispersion uniformity, a planetary stirring method combined with low-speed shear dispersion is used. The specific steps are as follows: First, vinyl-terminated polydimethylsiloxane and phenyl-modified siloxane are added to a stirring container and stirred at 200-300 rpm for 10 minutes at room temperature to ensure thorough mixing of the matrix; then, spherical alumina, plate-like boron nitride, and nano-alumina are added in batches and dispersed and mixed within the range of 300-600 rpm to avoid introducing too much air due to high-speed shear.

[0070] During the filler dispersion process, the stirring speed and time are controlled to gradually form a uniform slurry, while avoiding excessive local shear that could lead to temperature rise. Subsequently, the modified filler and MQ resin are added, and mixing continues under low-speed conditions to stabilize the system structure. Throughout the mixing process, the temperature is controlled below 50°C to prevent premature crosslinking reactions.

[0071] After adding the hydrogen-containing silicone oil crosslinking agent, platinum catalyst, and inhibitor, the mixture is thoroughly mixed using low-speed stirring, followed immediately by vacuum degassing. The degassing conditions are a vacuum of -0.09 to -0.095 MPa, with the time controlled at 15 to 20 minutes. The vacuum is released slowly to avoid the material expanding violently and introducing new bubbles.

[0072] After degassing, the material exhibits low viscosity and good flowability, allowing for application via dispensing, scraping, or screen printing. In practical applications, this material can automatically spread and fill the microscopic unevenness of the interface under low pressure, forming a continuous and uniform thermally conductive layer. It is then cured at 100°C for 2 hours to ensure sufficient cross-linking and the formation of a stable structure.

[0073] Performance test results show that the apparent viscosity of this material at 25℃ is approximately 5×10³~1×10³. 4 mPa·s, significantly lower than that of high-filler thermally conductive silicone (typically >5×10). 4 The viscosity of the system (mPa·s) exhibits good fluidity; as the shear rate increases, the viscosity of the system decreases significantly, exhibiting typical shear-thinning behavior, which is beneficial for coating and spreading during the construction process.

[0074] In terms of thermal conductivity, the thermal conductivity of this material is about 3 to 4 W / m·K. Although it is lower than that of the high thermal conductivity embodiment, it can still meet the heat dissipation requirements in medium power devices. The interface thermal resistance test shows that due to its excellent bonding performance and low porosity, the actual heat dissipation effect is significantly narrowed compared with that of the high thermal conductivity material.

[0075] Interfacial observation reveals that the material forms a uniform and continuous interfacial layer after curing, with almost no obvious bubbles or voids; it can also achieve full filling in complex surface structures, thereby significantly reducing contact thermal resistance.

[0076] In reliability testing, the material did not show obvious oil seepage after aging at 150℃ for 300 hours, and its structure remained stable. After 300 cycles of thermal cycling from -20℃ to 150℃, no obvious interface cracking or debonding was observed, indicating that it has good thermal cycling resistance.

[0077] This embodiment reduces the filler content and optimizes the particle size distribution structure, while combining surface modification and a mild crosslinking system. This allows the material to significantly reduce viscosity while maintaining a certain thermal conductivity, thereby improving its workability and interfacial adhesion. This effectively solves the problems of construction difficulties, air bubble entrainment, and uneven interface that exist in traditional high-filler thermally conductive silicone in practical applications. It is particularly suitable for electronic packaging, flexible circuits, and heat dissipation scenarios for precision devices where high construction accuracy is required.

[0078] The foregoing has only described certain exemplary embodiments of this application by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of this application. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of this application.

Claims

1. A high-temperature resistant thermally conductive silicone, characterized in that, By weight, it comprises the following components: 80-120 parts of vinyl-terminated polydimethylsiloxane; 10-40 parts of phenyl-modified siloxane; 150-600 parts of spherical alumina; 50-300 parts of flake boron nitride; 10-80 parts of nano-alumina; 1-10 parts of thermally conductive filler modified with silane coupling agent; 5-50 parts of MQ resin; 1-20 parts of hydrogen-containing silicone oil crosslinking agent; 0.001-0.5 parts of platinum catalyst; and 0.001-0.2 parts of inhibitor.

2. The thermally conductive silicone rubber with high temperature resistance according to claim 1, characterized in that, The spherical alumina has a particle size of 1–50 μm, the plate-shaped boron nitride has an aspect ratio of 5–100, and the nano-alumina has a particle size of 10–200 nm, in order to form a multi-scale filler composite structure.

3. The thermally conductive silicone rubber with high temperature resistance according to claim 2, characterized in that, Spherical alumina is used to fill the gaps in the system, plate-like boron nitride is used to construct surface contact heat conduction paths, and nano-alumina is used to fill microscopic voids to form a three-dimensional continuous heat conduction network structure.

4. The thermally conductive silicone rubber with high temperature resistance according to claim 3, characterized in that, The silane coupling agent is one or more of aminopropyltriethoxysilane, epoxysilane, or vinylsilane, and is used to modify the surface of thermally conductive fillers.

5. The thermally conductive silicone rubber with high temperature resistance according to claim 1, characterized in that, The phenyl content in phenyl-modified siloxanes is 5% to 30%.

6. The thermally conductive silicone rubber with high temperature resistance according to claim 1, characterized in that, Hydrogen-containing silicone oil crosslinking agent and vinyl-terminated polydimethylsiloxane form a crosslinked network structure through an addition reaction. Platinum catalyst is used to catalyze the crosslinking reaction, and inhibitor is used to regulate the reaction rate.

7. The thermally conductive silicone rubber with high temperature resistance according to claim 1, characterized in that, MQ resin is used to increase the crosslinking density of the system and suppress low molecular weight volatilization and oil exudation.

8. A method for preparing high-temperature resistant thermally conductive silicone, characterized in that, Includes the following steps: Vinyl-terminated polydimethylsiloxane is mixed with phenyl-modified siloxane to form a matrix system; Spherical alumina, flake boron nitride, and nano alumina were added in proportion and dispersed and mixed. The thermally conductive filler was surface-modified with a silane coupling agent and then added to the system. Add MQ resin and mix evenly; add hydrogen-containing silicone oil crosslinking agent, platinum catalyst and inhibitor, and perform degassing treatment; carry out curing reaction at a certain temperature to obtain thermally conductive silicone.

9. The method for preparing a high-temperature resistant thermally conductive silicone according to claim 8, characterized in that, Dispersion and mixing are carried out by planetary mixing or three-roll milling, the degassing process is carried out under vacuum conditions, and the curing temperature is 80-180℃.

10. Application of high-temperature resistant thermally conductive silicone, characterized in that, Thermally conductive silicone is used as a thermal interface material between electronic devices and heat dissipation components, and is applied in power device packaging, LED heat dissipation, thermal management of new energy batteries, and heat dissipation of high-performance electronic equipment.

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