High-temperature-resistant bendable heat-conducting silica gel composite material and preparation method thereof

Abstract

The invention provides a high-temperature-resistant bendable heat-conducting silica gel composite material and a preparation method thereof.The preparation method comprises the steps that a polyol component, isocyanate, silicone rubber and a catalyst are sequentially added into a reaction kettle in an inert atmosphere and stirred for a synthesis reaction, and a prepolymer is obtained; adding a chain extender into the prepolymer while stirring, and carrying out a chain extension reaction to obtain a pre-colloid; stirring and adding a heat-conducting filler into the pre-colloid, uniformly mixing, transferring into curing equipment, and carrying out cross-linking reaction in the curing equipment to obtain the high-temperature-resistant bendable heat-conducting silica gel. The high-temperature-resistant bendable heat-conducting silica gel composite material synthesized by combining the components has excellent heat-conducting property and heat resistance under the condition of high flexibility and mechanical strength.

Description

Technical Field

[0001] The invention belongs to the technical field of electronic thermal conductive materials, and in particular relates to a high-temperature resistant and bendable thermal conductive silicone composite material and a preparation method thereof. Background Art

[0002] The core reason why flexible electronic components such as OLED screens and FPCs can be folded is the combination of flexible substrates, thin-film packaging and flexible electrode materials. At the same time, with advanced manufacturing processes and stress dispersion design, the high performance and long life of flexible electronic components in a bent state are achieved.

[0003] At the same time, since the thin film structure of flexible electronic components has high requirements for thermal management, long-term operation will cause the temperature to rise. Therefore, the bends and complex shapes require the thermal conductive material to be flexible and provide an effective heat dissipation channel. Although ordinary silicone thermal pads have a certain degree of flexibility, their molecular structure determines that their elasticity and flexibility are limited. The silicone substrate of the thermal pad is usually formed by high-density cross-linking to form a harder structure. This structure makes it easy to break when it is locally subjected to bending stress, thereby losing its thermal conductivity. Ordinary silicone thermal pads are often filled with a large amount of high-hardness thermal conductive fillers. The interaction between these filler particles increases the rigidity of the material and reduces the overall flexibility. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a high-temperature resistant and bendable thermally conductive silicone composite material and a preparation method thereof, aiming to solve the problem of insufficient flexibility of the thermally conductive silicone material while ensuring thermal conductivity.

[0005] In order to solve the above problems, the present invention provides a method for preparing a high temperature resistant and bendable thermally conductive silicone composite material, the steps comprising: S1. Adding a polyol component, an isocyanate, a silicone rubber and a catalyst into a reactor in an inert atmosphere in sequence, stirring for synthesis reaction, and obtaining a prepolymer, wherein the reactor has a stirring and heating function, the polyol component comprises a natural polyol and a high temperature resistant polyol, the natural polyol comprises at least one of soybean oil polyol, castor oil and coconut oil polyol, and the high temperature resistant polyol comprises at least one of polyester polyol, polycarbonate polyol, polytetrafluoroethylene polyol and polyaromatic polyether polyol; S2, adding a chain extender to the prepolymer by stirring, performing a chain extension reaction, and obtaining a pre-colloid, wherein the chain extender comprises at least one of ethylene glycol, propylene glycol, 1,4-butanediol, and 1,4-cyclohexanedimethanol; S3. Stir and add thermally conductive filler into the pre-gel, transfer the mixture to a curing device after uniform mixing, and carry out a cross-linking reaction in the curing device to obtain a high-temperature resistant and bendable thermally conductive silicone rubber, wherein the thermally conductive filler comprises an inorganic filler and a carbon-based filler, the inorganic filler comprises at least one of boron nitride, aluminum oxide, magnesium oxide, and aluminum nitride, and the carbon-based filler comprises at least one of carbon nanotubes, carbon fibers, graphite, and graphene.

[0006] In some embodiments of the present invention, the reaction temperature of the synthesis reaction in step S1 is , The reaction temperature is 70~80℃ and the reaction time is , The stirring speed is 30~60min. , is 200-400 rpm, and the reaction temperature of the cross-linking reaction in step S3 is , , The reaction temperature is 30~50℃ and the reaction time is , stirring speed is , and Both are 1.5~2.

[0007] In some embodiments of the present invention, step S1 comprises: S1.1, placing the polyol component and the silicone rubber in a reaction kettle under an inert atmosphere, stirring and mixing, and obtaining a premix; S1.2, adding isocyanate to the premix several times, stirring at a temperature of 40-50°C; S1.3, raising the stirring temperature to 60-70°C for synthesis reaction, measuring the viscosity of the premix to reach the preset viscosity, confirming that the synthesis reaction is completed, and obtaining the prepolymer.

[0008] In some embodiments of the present invention, the isocyanate includes at least one of hexamethylene diisocyanate, isophorone diisocyanate, trimethylene hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, and chlorinated diphenylmethane diisocyanate, and the catalyst includes at least one of dibutyltin dilaurate, triethylamine, zinc ethylhexanoate, and bismuth isooctanoate; In the prepolymer, calculated by mass percentage, the isocyanate accounts for 15-25%, the silicone rubber accounts for 20-30%, the catalyst accounts for 0.5-1%, the natural polyol accounts for 15-25%, and the balance is the high temperature resistant polyol.

[0009] In some embodiments of the present invention, step S2 includes: S2.1, placing the chain extender in an inert solvent, mixing and preheating, the preheating temperature being close to the temperature of the prepolymer, to obtain a dispersed chain extension solution; S2.2, adding the dispersed chain extension solution to the prepolymer, raising the temperature to 70-80°C for chain extension reaction, measuring the viscosity of the prepolymer to reach a preset viscosity, confirming that the synthesis reaction is completed, and obtaining a pre-colloid.

[0010] In some embodiments of the present invention, step S3 includes: S3.1, first adding the inorganic filler to the pre-colloid, and then adding the carbon-based filler, stirring and mixing, to obtain a pre-prepared silica gel composite material, wherein in the thermal conductive filler, in terms of mass percentage, the inorganic filler accounts for 60-80%, and the carbon-based material accounts for 20-40%; S3.2, transferring the mixed pre-prepared silica gel composite material to a curing device for cross-linking reaction to obtain a high temperature resistant, bendable, thermally conductive silica gel.

[0011] In some embodiments of the present invention, a heating device, a hot air circulation device, a temperature detection device and a curing mold with adjustable volume are provided inside the curing device; The step S3.2 comprises: Calculating the thermal expansion coefficient of the pre-prepared silica gel composite material; adjusting the volume of the curing mold according to the thermal expansion rate; Transferring the mixed pre-prepared silica gel composite material to the curing mold, Acquire a temperature distribution image when the curing device is turned on; Determining a placement area of ​​the pre-prepared silica gel composite material according to the temperature distribution image; The cross-linking reaction is carried out by heating to obtain a high temperature resistant and bendable thermally conductive silicone.

[0012] In some embodiments of the present invention, in the step of adjusting the volume of the curing mold according to the thermal expansion coefficient, the adjustment formula is: ,in, is the adjustment amount of the curing mold volume, is the initial length or width of the pre-prepared silica composite material, is the thermal expansion coefficient of the pre-prepared silica gel composite material, It is the temperature change from the lowest temperature to the highest temperature during the cross-linking reaction.

[0013] The present invention provides a high-temperature resistant, bendable, thermally conductive silicone composite material, which is prepared by the preparation method as described above. The synthetic components of the high-temperature resistant, bendable, thermally conductive silicone composite material include the natural polyol, the high-temperature resistant polyol, the isocyanate, the silicone rubber, the catalyst, the chain extender, the inorganic filler and the carbon-based filler, wherein the natural polyol is used to provide flexibility and improve the bendability of the material, the high-temperature resistant polyol is used to enhance the high-temperature resistance and mechanical strength of the material, the isocyanate reacts with the polyol to form a polyurethane chain segment, and improves the crosslinking and stability of the material, the silicone rubber is used to enhance the elasticity and flexibility of the material, the catalyst is used to accelerate the reaction between the isocyanate and the polyol, the chain extender is used to extend the length of the polyurethane chain segment, and the inorganic filler and the carbon-based material are used to improve the thermal conductivity, mechanical strength and high-temperature resistance of the material.

[0014] Compared with the prior art, the high temperature resistant bendable thermally conductive silica gel composite material and the preparation method thereof in the present invention have the following beneficial effects: Natural polyols significantly improve the elasticity and flexibility of materials by providing flexible groups, so that the composite material can still maintain stable performance under complex deformation conditions (such as folding and bending). Ensure that the material will not crack or lose thermal conductivity when bent. Silicone rubber itself has excellent flexibility and durability, and further enhances the overall elasticity in the composite material. The high thermal stability of high-temperature resistant polyols significantly improves the high-temperature resistance of the material, ensuring that the material maintains stable structure and performance in high-temperature working environments, suitable for high-temperature electronic equipment or industrial uses. The combined effect of inorganic fillers and carbon-based fillers not only improves thermal conductivity, but also enhances the heat resistance of the material. The high-temperature resistant, bendable, thermally conductive silicone composite material synthesized by combining the above components has excellent thermal conductivity and heat resistance while having high flexibility and mechanical strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic flow chart of a method for preparing a high temperature resistant, bendable, thermally conductive silicone composite material in one embodiment of the present invention. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0017] The "material" in the manual generally refers to "high-temperature resistant, bendable, thermally conductive silicone composite material". Unless otherwise specified, it is an abbreviation.

[0018] Please refer to Figure 1The present invention provides a method for preparing a high temperature resistant and bendable thermally conductive silicone composite material, the steps comprising: S1. Add a polyol component, isocyanate, silicone rubber and a catalyst into a reactor in an inert atmosphere in sequence, stir to carry out a synthesis reaction, and obtain a prepolymer, wherein the reactor has a stirring and heating function, the polyol component includes a natural polyol and a high-temperature resistant polyol, the natural polyol includes at least one of soybean oil polyol, castor oil and coconut oil polyol, and the high-temperature resistant polyol includes at least one of polyester polyol, polycarbonate polyol, polytetrafluoroethylene polyol and polyaromatic polyether polyol. The isocyanate includes at least one of hexamethylene diisocyanate, isophorone diisocyanate, trimethylene hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, and chlorinated diphenylmethane diisocyanate, and the catalyst includes at least one of dibutyltin dilaurate, triethylamine, zinc ethylhexanoate, and bismuth isooctanoate; calculated by mass percentage, the isocyanate accounts for 15-25%, for example, 15%, 20%, and 25%, the silicone rubber accounts for 20-30%, for example, 20%, 25%, and 30%, the catalyst accounts for 0.5-1%, for example, 0.5%, 0.8%, and 1%, the natural polyol accounts for 15-25%, for example, 15%, 20%, and 255, and the balance is high temperature resistant polyol.

[0019] Silicone rubber includes at least one of polydimethylsiloxane, polymethylchlorosilane silicone, fluorosilicone rubber, and hydrogenated silicone rubber. Silicone rubber has chemical and thermal stability and can maintain its mechanical properties under high temperature conditions. The silicon-oxygen chain structure in silicone rubber is highly stable and not easily oxidized, thermally degraded, or chemically degraded, so it can still maintain good physical properties at higher temperatures.

[0020] High temperature resistant polyols react with isocyanates to form polyurethane chains. The structure of these polymers gives the material strong thermal stability. The ester and carbonate groups in the polyester and polycarbonate structures are not easy to decompose at higher temperatures, which can significantly enhance the thermal stability of the material.

[0021] By combining silicone rubber with high temperature resistant polyols, the composite material can not only maintain the elasticity and high temperature resistance of silicone rubber, but also improve the thermal stability of the material with the help of high temperature resistant polyols. This combination enables the final material to continue to work in high temperature environments without performance degradation.

[0022] Natural polyols are composed of molecules with long-chain fatty acid structures. Their molecular structures are relatively flexible and can effectively increase the flexibility of materials. By selecting appropriate natural polyols, they can make composite materials have good flexibility at both room temperature and high temperature.

[0023] Although high-temperature resistant polyols are relatively rigid in structure, the synergistic effect with natural polyols can provide the required strength to the material without reducing flexibility, ensuring that the material can deform without cracking when subjected to external forces.

[0024] The flexibility and elasticity of polyurethane materials come from their linear chain structure and the adjustability of cross-linking density. Through reasonable formulation design, polyurethane with low cross-linking density can maintain good elasticity and bendability. At high temperatures, the elasticity of silicone rubber and the flexibility of polyurethane combine to give the composite material good bending properties.

[0025] Specifically, step S1 includes: S1.1. Place the polyol component and silicone rubber in a reaction kettle under an inert atmosphere, stir and mix to obtain a premix.

[0026] Mix the polyol component with the silicone rubber to ensure that the two are evenly dispersed in the reactor, providing a consistent reaction basis for subsequent reactions. This step ensures good compatibility between silicone rubber and polyols, which helps to improve the overall performance of the composite material.

[0027] Use an inert atmosphere (such as nitrogen or argon) to prevent unwanted oxidation reactions between oxygen and reactants. An inert atmosphere helps improve the selectivity and stability of the reaction, ensuring that the reaction proceeds as expected.

[0028] Premixing the raw materials and distributing them evenly under stirring can ensure that the components can fully react when the isocyanate is subsequently added, thereby improving product consistency and reaction efficiency.

[0029] S1.2, adding isocyanate to the premix in multiple portions, with the stirring temperature being 40-50°C, for example, 40°C, 45°C, 50°C.

[0030] Isocyanate is a key component in polyurethane synthesis, which reacts with polyols to form polyurethane chains. If too much is added at one time, it may cause a too fast reaction or local overheating, affecting the uniformity of the product. Therefore, adding it in multiple times can ensure the smoothness and uniformity of the reaction.

[0031] Adding isocyanate at a lower temperature of 40~50°C helps control the reaction rate and avoid overreaction in the early stage of the reaction, which can maintain the controllability of the reaction and ensure that a prepolymer with good properties is obtained.

[0032] By adding isocyanate in batches, it is ensured that the amount added each time can fully contact the reaction mixture, thereby improving the interaction between the reactants and obtaining an intermediate product with better consistency, which also helps the subsequent synthesis reaction to proceed smoothly.

[0033] S1.3, raising the stirring temperature to 60-70°C (for example, 60°C, 65°C, 70°C) to carry out the synthesis reaction, measuring the viscosity of the premix to reach the preset viscosity, confirming that the synthesis reaction is completed, and obtaining the prepolymer.

[0034] Increasing the temperature to 60-70°C helps accelerate the synthesis reaction and promote the reaction between isocyanate and polyol. The increase in temperature provides sufficient activation energy, thereby accelerating the reaction rate and making the polymerization process more efficient.

[0035] By measuring the viscosity, the progress and molecular weight of the polymerization reaction can be directly reflected. Reaching the preset viscosity is a sign of the completion of the reaction, indicating that the reactants have been successfully converted into prepolymers, and the molecular weight and degree of reaction have reached the expected goals. The equipment for measuring viscosity can be a torsional rheometer, a cylindrical viscometer, a rotational viscometer, a capillary viscometer, etc. The specific use and structure of the equipment are known to those skilled in the art and will not be repeated here. By controlling the temperature and viscosity, the molecular structure and properties of the composite material can be accurately regulated to ensure the quality consistency and high performance of the final product.

[0036] The formation of prepolymer is an intermediate product of the entire polymerization reaction. It needs to be generated at a suitable temperature to ensure that it has good stability and is suitable for subsequent chain extension or cross-linking reactions. Temperature control between 60~70℃ helps to obtain prepolymers with appropriate chain length and reaction degree. Through the synthesis reaction, the prepolymer formed usually has high mechanical strength and heat resistance, which provides a solid foundation for subsequent material curing, cross-linking and application.

[0037] S2. Adding a chain extender to the prepolymer with stirring to carry out a chain extension reaction to obtain a pre-colloid, wherein the chain extender includes at least one of ethylene glycol, propylene glycol, 1,4-butanediol, and 1,4-cyclohexanedimethanol.

[0038] Chain extenders react with isocyanate groups in prepolymers to extend polymer chains, thereby increasing the molecular weight of the polymer. Chain extension not only increases the length of the polymer chain, but also increases the cross-linking density, making the material structure stronger and more durable. Chain extension increases the length of the polymer chain, thereby improving the mechanical strength, hardness and wear resistance of the material. For example, long-chain polymers perform better than short-chain polymers in mechanical properties such as stretching and bending.

[0039] By choosing different chain extenders, the chain extension reaction can precisely control the flexibility and elasticity of the composite material. For example, using a shorter chain extender (such as ethylene glycol) can increase the flexibility of the material, while using a longer chain extender (such as 1,4-cyclohexanedimethanol) may increase the rigidity of the material.

[0040] Specifically, step S2 includes: S2.1. Place the chain extender in an inert solvent, mix well and then preheat. The preheating temperature is close to the temperature of the prepolymer to obtain a dispersed chain extension solution.

[0041] Dissolving the chain extender in an inert solvent can effectively reduce the viscosity of the chain extender, making it easier to evenly disperse in the prepolymer. Inert solvents (such as toluene, xylene, chloroform, etc.) can reduce the reactivity of the chain extender, improve its fluidity in the solution, and prevent the chain extender from agglomerating or agglomerating. Ensure that the chain extender can be evenly distributed when added to the prepolymer, improve the uniformity of the reaction, and avoid incomplete or uneven local reactions.

[0042] Before heating the chain extender solution, the temperature of the solution is close to that of the prepolymer, which can reduce the temperature difference and avoid drastic changes in the reaction rate due to excessive temperature difference. The temperature balance helps the reaction between the chain extender and the prepolymer to proceed gradually, ensuring the stability and controllability of the reaction process. Provide a mild reaction environment, control the reaction rate, and avoid local overheating or uneven heating of the material.

[0043] Using an inert solvent to dissolve the chain extender and stirring it at an appropriate preheating temperature can ensure that the chain extender does not have too many side reactions during the reaction, thereby avoiding unnecessary polymer chain breakage or other adverse effects. It improves the selectivity of the chain extension reaction, reduces the generation of by-products, and ensures that the reaction of the prepolymer is more efficient and accurate.

[0044] S2.2, add the dispersed chain extension solution to the prepolymer, raise the temperature to 70-80°C for chain extension reaction, measure the viscosity of the prepolymer to reach the preset viscosity, confirm that the synthesis reaction is completed, and obtain the pre-colloid.

[0045] Adding the preheated dispersed chain extension solution to the prepolymer and heating it to 70-80°C can significantly accelerate the rate of the chain extension reaction. This temperature range can accelerate the reaction between isocyanate and chain extender, effectively promoting the extension of the polymer chain. Heating to an appropriate reaction temperature allows the chain extension reaction to proceed smoothly, and the generated polymer chain length and molecular weight increase.

[0046] By measuring the viscosity, the progress of the chain extension reaction can be monitored in real time. As the reaction proceeds, the growth of the polymer chain will cause the viscosity to gradually increase, and reaching the preset viscosity value marks the completion of the reaction. By accurately controlling the reaction time and temperature, the molecular weight and viscosity of the polymer can be precisely adjusted. Ensure the completeness of the reaction and control the viscosity to the preset value to ensure the quality and performance of the obtained pre-gelatin. Viscosity is a sign of the completion of the reaction, ensuring that the material has suitable fluidity and good subsequent processing performance.

[0047] Chain extension reaction increases the length of polymer chains, thereby improving the mechanical properties (such as strength, toughness, wear resistance) and high temperature resistance of composite materials. Through chain extension, the thermal stability and anti-aging properties of the material are enhanced, providing strong support for subsequent curing, cross-linking or use. Through chain extension reaction, the high temperature resistance, elasticity and mechanical strength of the composite material are enhanced, allowing the composite material to withstand higher mechanical loads and high temperature environments.

[0048] During the chain extension reaction, the rheological properties of the material can be optimized by controlling the increase in viscosity. Appropriate viscosity makes the material neither too dense (affecting processing) nor too thin (affecting strength), ensuring that subsequent processing (such as injection molding, molding) proceeds smoothly. It improves the processability of the composite material and ensures that the material can flow evenly during the molding process, avoiding bubbles, defects or uneven physical properties.

[0049] S3. Add thermally conductive filler into the pre-colloid by stirring, transfer to a curing device after mixing evenly, and carry out a cross-linking reaction in the curing device to obtain a high-temperature resistant and bendable thermally conductive silicone rubber, wherein the thermally conductive filler includes an inorganic filler and a carbon-based filler, the inorganic filler includes at least one of boron nitride, aluminum oxide, magnesium oxide, and aluminum nitride, and the carbon-based filler includes at least one of carbon nanotubes, carbon fibers, graphite, and graphene.

[0050] Inorganic fillers and carbon-based fillers form heat conduction channels to improve the thermal conductivity of composite materials. The addition of fillers can enhance the thermal stability and high temperature resistance of materials. Fillers can improve the compressive strength, wear resistance and rigidity of materials. Reasonable selection of fillers can ensure the flexibility and bendability of composite materials. Fillers promote cross-linking reactions and improve the structural stability of materials. Reasonable configuration of fillers can improve the fluidity and processability of materials.

[0051] Specifically, step S3 includes: S3.1. First add an inorganic filler to the pre-colloid, and then add a carbon-based filler, stir and mix, and obtain a pre-prepared silica gel composite material, wherein, in the thermal conductive filler, according to mass percentage, the inorganic filler accounts for 60-80%, for example, 60%, 70%, 80%, and the carbon-based material accounts for 20-40%, for example, 20%, 30%, 40%.

[0052] Inorganic fillers and carbon-based fillers have different thermal conductivity properties. Inorganic fillers usually provide stronger thermal conduction channels, while carbon-based fillers can provide extremely high thermal conductivity. By properly configuring these two fillers, the thermal conductivity of the material can be optimized while ensuring the strength of the material. The design of the mass percentage ensures the uniform distribution of the thermal conduction channel, while avoiding the problem of excessive hardness or brittleness that may be caused by excessive carbon-based fillers, ensuring that the material maintains appropriate flexibility while providing excellent thermal conductivity. Through the ratio of inorganic fillers and carbon-based fillers, the thermal conduction efficiency of the composite material can be significantly improved, heat accumulation at high temperatures can be avoided, and the heat dissipation performance can be improved. Ensure the uniform dispersion of the filler, so that the thermal conduction path is coherent, and the overall thermal conductivity effect is improved.

[0053] Inorganic fillers, such as alumina and aluminum nitride, can significantly increase the hardness and rigidity of composite materials, improving their compressive strength and wear resistance. Carbon-based fillers, such as carbon nanotubes and graphene, in addition to providing thermal conductivity, can also enhance the tensile strength, bending resistance and toughness of the material. Inorganic fillers enhance the compressive resistance of composite materials, allowing them to maintain good mechanical properties in high temperature environments. Carbon-based fillers such as graphite and carbon nanotubes can improve the anti-friction ability of composite materials, making them suitable for high-wear environments.

[0054] The flexibility and elasticity of silicone rubber itself provide good bendability for the composite material. Through the proper proportion of fillers, it is possible to increase strength and hardness while maintaining appropriate flexibility, ensuring that the composite material does not become brittle during application. By optimizing the ratio of inorganic fillers and carbon-based fillers, the material can be prevented from being too rigid, thereby ensuring its fluidity and flexibility during molding and subsequent processing. The proportion of fillers ensures that the composite material has good bendability, and even after adding fillers, the material can still maintain its shape in high temperature or mechanical stress environments.

[0055] S3.2. Transfer the mixed pre-prepared silicone composite material to a curing device for cross-linking reaction to obtain a high temperature resistant, bendable, thermally conductive silicone.

[0056] Cross-linking is the process of forming a network structure between polymer chains through chemical bonds. Through the cross-linking reaction in the curing equipment, a three-dimensional network structure is formed between the silicone rubber and polyurethane segments, which improves the thermal and chemical stability of the material. The cross-linking reaction makes the composite material have higher temperature resistance, corrosion resistance and mechanical strength, ensuring that the material can withstand high temperature environments and mechanical stress for a long time.

[0057] Enhanced thermal and chemical stability: The cross-linked material has higher heat resistance and aging resistance, and can maintain performance for a long time in high temperature environment. The cross-linked three-dimensional structure improves the overall rigidity and fatigue resistance of the material, allowing the composite material to remain stable under repeated bending, compression and stretching.

[0058] During the cross-linking process, the thermal stability and bending properties of the material are significantly improved. Silicone rubber itself has good high temperature resistance, and the combination of fillers and cross-linked networks further improves the shape stability and mechanical properties of the material at high temperatures. The addition of carbon-based fillers and inorganic fillers not only optimizes thermal conductivity, but also enables the composite material to maintain higher strength and toughness at high temperatures through the cross-linked network.

[0059] The cross-linking reaction makes the composite material more resistant to high temperatures and maintains elasticity and strength even at higher temperatures. The cross-linked material still has high flexibility and can withstand a certain amount of bending, stretching or compression force, and is not prone to brittle fracture or cracking. Through the cross-linking reaction during the curing process, the distribution of thermal conductive fillers in the material is more uniform and the thermal conductive channels are more coherent. The thermal conductivity of the cross-linked material is more stable at high temperatures, which helps to quickly dissipate heat. The cross-linking reaction ensures the uniform distribution of thermal conductive fillers and stable thermal conductive channels, thereby improving the thermal conductivity of the composite material, which is widely used in electronic heat dissipation, thermal management and other fields.

[0060] Specifically, a heating device, a hot air circulation device, a temperature detection device and a curing mold with adjustable volume are provided inside the curing equipment. The volume of the curing mold can be adjusted by a movable telescopic plate, or when manufacturing high-temperature resistant, bendable thermally conductive silicone rubber of different formulations, a curing mold with a volume that meets the expansion requirements of the pre-prepared silicone composite material is manufactured in advance. The specific manufacturing method and the manufacturing materials used are known to those skilled in the art and will not be repeated here.

[0061] Step S3.2 includes: Step 321: Calculate the thermal expansion coefficient of the pre-prepared silica gel composite material.

[0062] By calculating the thermal expansion rate, we can predict the volume change of the material at different temperatures and understand the thermal expansion characteristics of the material in advance. This step ensures that the material will not cause mold deformation or unstable product quality due to excessive expansion or contraction during the curing process.

[0063] The thermal expansion coefficient of the pre-prepared silicone composite material can be calculated as follows: (1) Calculate the thermal expansion coefficient in a linear manner and conduct multiple preliminary experiments. In each experiment, measure the initial length or width of the pre-prepared silicone composite material and place it in a curing mold of the same specifications. The size of the curing mold should be larger than the initial volume of the pre-prepared silicone composite material used in the experiment. , and then measure the real-time volume of the pre-prepared silica composite after the cross-linking reaction is completed ,pass To calculate the thermal expansion coefficient ,in, It is the temperature change from the lowest temperature to the highest temperature during the cross-linking reaction. The thermal expansion coefficients calculated from multiple experiments are averaged to obtain the final thermal expansion coefficient.

[0064] (2) Thermal expansion coefficient that changes with temperature. The same calculation method is used as above. A base temperature is selected. The base temperature can be 100°C or 120°C. The thermal expansion coefficient at the base temperature and at the changing temperature in multiple experiments is calculated to obtain a curve of the thermal expansion coefficient that changes with the maximum temperature of the cross-linking reaction. The curve is fitted to obtain a constant that describes the temperature dependence of the thermal expansion coefficient. ,in, is the thermal expansion coefficient when the maximum temperature is T, is the thermal expansion coefficient at the reference temperature. In one embodiment, β may be 0.001-0.005.

[0065] Step 322, adjusting the volume of the curing mold according to the thermal expansion coefficient; In the step of adjusting the spacing of the curing mold according to the thermal expansion coefficient, the adjustment formula is: ,in, is the adjustment amount of the curing mold volume, To prepare the initial long volume of silica composite material, is the thermal expansion coefficient of the pre-prepared silicone composite material, It is the temperature change from the lowest temperature to the highest temperature during the cross-linking reaction.

[0066] Adjusting the volume of the curing mold according to the thermal expansion rate can compensate for the expansion of the material during heating and ensure that the size of the cured product meets the expected requirements. If the thermal expansion rate is too high, increasing the mold volume appropriately can avoid excessive force on the mold or deformation of the material due to material expansion during curing, thereby maintaining the shape stability of the final product.

[0067] Step 323: transfer the mixed pre-prepared silicone composite material to a curing mold.

[0068] Step 324: Acquire a temperature distribution image when the curing device is turned on.

[0069] Step 325 : determining a placement area for the pre-prepared silica gel composite material according to the temperature distribution image.

[0070] During the curing process, the hot air circulation device in the curing equipment continuously circulates the hot air, so that the hot air in the equipment can be transferred to the material surface faster and transfer heat more effectively, which can shorten the heating time and improve production efficiency.

[0071] However, when hot air flows through the curing mold, the temperature of the air will change as it contacts the mold. Due to the thermal conductivity of the curing mold, the hot air will quickly transfer heat to the curing mold after contacting the surface of the curing mold, and the heat of the curing mold will in turn affect the temperature of the surrounding air, forming a convection loop in which hot air rises and cold air sinks. This convection phenomenon causes uneven temperature distribution on the surface of the curing mold and the surrounding area. Especially during the curing process, the temperature distribution of the material is crucial to the performance of the final product. A large temperature difference between the mold and the air will cause the temperature in some areas to be too high or too low, thus affecting the uniformity of the cross-linking reaction.

[0072] A temperature detection device, such as an infrared sensor, is used to detect the area with relatively uniform temperature inside the curing device, and then the curing mold is placed in an area where the temperature display is accurate, meets the curing requirements and is uniform, thereby eliminating the influence of convection and improving the uniformity of curing. In some embodiments, the temperature distribution image detected by the temperature detector may be annular, that is, due to the influence of convection, the temperature in the middle is lower and the temperature in the outer area is higher.

[0073] Step 326: heating to carry out a cross-linking reaction to obtain a high temperature resistant and bendable thermally conductive silicone.

[0074] Further, the reaction temperature of the synthesis reaction in step S1 is 60-70°C, for example, 60°C, 65°C, 70°C, the reaction time is 60-120min, for example, 60min, 80min, 120min, and the stirring speed is 200-300rpm, for example, 200rpm, 250rpm, 300rpm. The reaction temperature of the chain extension reaction in step S2 is , The reaction temperature is 70-80°C, for example, 70°C, 75°C, 80°C, and the reaction time is , The stirring speed is 30 to 60 minutes, for example, 30 minutes, 40 minutes, or 60 minutes. , is 200-400 rpm, 200 rpm, 300 rpm, 400 rpm, and the reaction temperature of the cross-linking reaction in step S3 is , , The reaction temperature is 30~50℃ and the reaction time is , stirring speed is , and All are 1.5~2, for example, they can be 1.5, 1.8, and 2.

[0075] The reaction conditions of chain extension reaction and cross-linking reaction have a quantitative relationship, mainly due to the continuity of chemical reaction, optimization of process control and guarantee of final material performance. This quantitative relationship ensures a smooth transition and coordination between the reaction steps, and helps to form the desired molecular structure and material properties.

[0076] Chain extension reaction and cross-linking reaction are based on the gradual growth of prepolymers. The chemical basis determines the relevance of reaction conditions. Chain extension reaction is the reaction of chain extenders (such as diols and diamines) with residual isocyanate (-NCO) in prepolymers to form longer linear molecular chains. Cross-linking reaction is based on the chain-extended prepolymer, through further reaction of trifunctional or multifunctional cross-linking agents to construct a three-dimensional cross-linked network.

[0077] The chain extension reaction requires a lower temperature to avoid excessive cross-linking, while the cross-linking reaction requires a higher temperature to promote the complete reaction. The chain extension reaction is usually shorter, and the cross-linking reaction time is longer to complete the formation of the three-dimensional network.

[0078] To ensure the uniformity and performance of the material, it is necessary to set a reasonable quantitative relationship in the two stages of chain extension and cross-linking. The rate of chain extension reaction is relatively fast. If it directly enters the high-temperature cross-linking stage, it may cause uneven cross-linking or local transition reaction. Through the design of quantitative relationship, the connection of reaction rate can be optimized. After the chain extension reaction, the viscosity of the system increases; before entering the cross-linking stage, the stirring speed and temperature need to be adjusted to adapt to the viscosity change to ensure uniform dispersion of the filler.

[0079] The chain extension stage mainly regulates the length and flexibility of the molecular chain, which has a significant impact on the mechanical properties of the material (such as bendability). The cross-linking stage mainly forms a three-dimensional cross-linked network, providing the material with thermal stability and high temperature resistance.

[0080] Through appropriate temperature, the cross-linking reaction can achieve a higher degree of cross-linking, further enhancing the mechanical strength, heat resistance and aging resistance of the composite material. The value of can be used to optimize the crosslinking time according to the specific reaction system and the required properties, thereby balancing the reaction efficiency and product performance. The value ensures the full mixing of the reactants during the cross-linking process, ultimately improving the quality of the product.

[0081] The present invention provides a high-temperature resistant, bendable, thermally conductive silicone composite material, which is prepared by the above-mentioned preparation method. The synthetic components of the high-temperature resistant, bendable, thermally conductive silicone composite material include natural polyols, high-temperature resistant polyols, isocyanates, silicone rubber, catalysts, chain extenders, inorganic fillers and carbon-based fillers, wherein the natural polyols are used to provide flexibility and improve the bendability of the material, the high-temperature resistant polyols are used to enhance the high-temperature resistance and mechanical strength of the material, the isocyanates react with the polyols to form polyurethane chain segments, and improve the crosslinking and stability of the material, the silicone rubber is used to enhance the elasticity and flexibility of the material, the catalyst is used to accelerate the reaction between the isocyanate and the polyols, the chain extender is used to extend the length of the polyurethane chain segments, and the inorganic fillers and carbon-based materials are used to improve the thermal conductivity, mechanical strength and high-temperature resistance of the material.

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a high temperature resistant and bendable thermally conductive silicone composite material, characterized in that the steps include: S1. Adding a polyol component, an isocyanate, a silicone rubber and a catalyst into a reactor in an inert atmosphere in sequence, stirring for synthesis reaction, and obtaining a prepolymer, wherein the reactor has a stirring and heating function, the polyol component comprises a natural polyol and a high temperature resistant polyol, the natural polyol comprises at least one of soybean oil polyol, castor oil and coconut oil polyol, and the high temperature resistant polyol comprises at least one of polyester polyol, polycarbonate polyol, polytetrafluoroethylene polyol and polyaromatic polyether polyol; S2, adding a chain extender to the prepolymer by stirring, performing a chain extension reaction, and obtaining a pre-colloid, wherein the chain extender comprises at least one of ethylene glycol, propylene glycol, 1,4-butanediol, and 1,4-cyclohexanedimethanol; S3. Stir and add thermally conductive filler into the pre-gel, transfer the mixture to a curing device after uniform mixing, and carry out a cross-linking reaction in the curing device to obtain a high-temperature resistant and bendable thermally conductive silicone rubber, wherein the thermally conductive filler comprises an inorganic filler and a carbon-based filler, the inorganic filler comprises at least one of boron nitride, aluminum oxide, magnesium oxide, and aluminum nitride, and the carbon-based filler comprises at least one of carbon nanotubes, carbon fibers, graphite, and graphene.

2. The method for preparing a high temperature resistant and bendable thermally conductive silicone composite material according to claim 1, characterized in that: The reaction temperature of the synthesis reaction in step S1 is 60-70°C, the reaction time is 60-120 min, the stirring speed is 200-300 rpm, and the reaction temperature of the chain extension reaction in step S2 is , The reaction temperature is 70~80℃ and the reaction time is , The stirring speed is 30~60min. , is 200-400 rpm, and the reaction temperature of the cross-linking reaction in step S3 is , , The reaction temperature is 30~50℃ and the reaction time is , stirring speed is , and Both are 1.5~2.

3. The method for preparing a high temperature resistant and bendable thermally conductive silicone composite material according to claim 1, characterized in that: The step S1 comprises: S1.1, placing the polyol component and the silicone rubber in a reaction kettle under an inert atmosphere, stirring and mixing, and obtaining a premix; S1.2, adding isocyanate to the premix several times, stirring at a temperature of 40-50°C; S1.3, raising the stirring temperature to 60-70°C for synthesis reaction, measuring the viscosity of the premix to reach the preset viscosity, confirming that the synthesis reaction is completed, and obtaining the prepolymer.

4. The method for preparing a high temperature resistant and bendable thermally conductive silicone composite material according to claim 3, characterized in that: The isocyanate includes at least one of hexamethylene diisocyanate, isophorone diisocyanate, trimethylene hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, and chlorinated diphenylmethane diisocyanate; and the catalyst includes at least one of dibutyltin dilaurate, triethylamine, zinc ethylhexanoate, and bismuth isooctanoate; In the prepolymer, calculated by mass percentage, the isocyanate accounts for 15-25%, the silicone rubber accounts for 20-30%, the catalyst accounts for 0.5-1%, the natural polyol accounts for 15-25%, and the balance is the high temperature resistant polyol.

5. The method for preparing a high temperature resistant and bendable thermally conductive silicone composite material according to claim 1, characterized in that: The step S2 comprises: S2.1, placing the chain extender in an inert solvent, mixing and preheating, the preheating temperature being close to the temperature of the prepolymer, to obtain a dispersed chain extension solution; S2.2, adding the dispersed chain extension solution to the prepolymer, raising the temperature to 70-80°C for chain extension reaction, measuring the viscosity of the prepolymer to reach a preset viscosity, confirming that the synthesis reaction is completed, and obtaining a pre-colloid.

6. The method for preparing a high temperature resistant and bendable thermally conductive silicone composite material according to claim 1, characterized in that: The step S3 comprises: S3.1, first adding the inorganic filler to the pre-colloid, and then adding the carbon-based filler, stirring and mixing, to obtain a pre-prepared silica gel composite material, wherein in the thermal conductive filler, in terms of mass percentage, the inorganic filler accounts for 60-80%, and the carbon-based material accounts for 20-40%; S3.2, transferring the mixed pre-prepared silica gel composite material to a curing device for cross-linking reaction to obtain a high temperature resistant, bendable, thermally conductive silica gel.

7. The method for preparing a high temperature resistant and bendable thermally conductive silicone composite material according to claim 6, characterized in that: The curing equipment is provided with a heating device, a hot air circulation device, a temperature detection device and a curing mold with adjustable volume; The step S3.2 comprises: Calculating the thermal expansion coefficient of the pre-prepared silica gel composite material; adjusting the volume of the curing mold according to the thermal expansion rate; Transferring the mixed pre-prepared silica gel composite material to the curing mold, Acquire a temperature distribution image when the curing device is turned on; Determining a placement area of ​​the pre-prepared silica gel composite material according to the temperature distribution image; The cross-linking reaction is carried out by heating to obtain a high temperature resistant and bendable thermally conductive silicone.

8. The method for preparing a high temperature resistant and bendable thermally conductive silicone composite material according to claim 7, characterized in that: In the step of adjusting the volume of the curing mold according to the thermal expansion coefficient, the adjustment formula is: ,in, is the adjustment amount of the curing mold volume, is the initial length or width of the pre-prepared silica composite material, is the thermal expansion coefficient of the pre-prepared silica gel composite material, It is the temperature change from the lowest temperature to the highest temperature during the cross-linking reaction.

9. A high temperature resistant and bendable thermally conductive silicone composite material, characterized in that: The high-temperature resistant, bendable, thermally conductive silicone composite material is prepared by the preparation method according to any one of claims 1 to 8, and the synthetic components include the natural polyol, the high-temperature resistant polyol, the isocyanate, the silicone rubber, the catalyst, the chain extender, the inorganic filler and the carbon-based filler, wherein the natural polyol is used to provide flexibility and improve the bendability of the material, the high-temperature resistant polyol is used to enhance the high-temperature resistance and mechanical strength of the material, the isocyanate reacts with the polyol to form a polyurethane chain segment, and improves the cross-linking and stability of the material, the silicone rubber is used to enhance the elasticity and flexibility of the material, the catalyst is used to accelerate the reaction between isocyanate and polyol, the chain extender is used to extend the length of the polyurethane chain segment, and the inorganic filler and the carbon-based material are used to improve the thermal conductivity, mechanical strength and high-temperature resistance of the material.

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