High-thermal-conductivity low-modulus graphene fiber heat-conducting gasket and preparation method thereof

Abstract

The invention provides a high-thermal-conductivity low-modulus graphene fiber heat-conducting gasket and a preparation method thereof. Graphene fibers are directionally wound and impregnated to prepare a prepreg, the prepreg is laminated and bonded to form a high-orientation fiber plate, and then the high-orientation fiber plate is directionally cut in the direction perpendicular to the fibers to obtain the heat-conducting gasket composed of continuous vertical fibers and organic silicon. The fiber is of an X-shaped crossed network structure, and is combined with an elastic silica gel matrix to form a hinge-like structure which can be highly deformed under the orientation of 0.5-10 degrees and-10--0.5 degrees, so that the compression resilience and durability are remarkably improved, and meanwhile, efficient heat conduction is kept. According to the structure, the problems of buckling, fracture and stress concentration which are easily caused by traditional vertical or random arrangement are avoided. A one-way felt impregnation lamination cutting method is adopted, the processing problem caused by high filler is solved, the fiber content can reach 85.1 wt%, and the array density is 2.4-195.9 mg / cm. The gasket has high thermal conductivity, low modulus and excellent rebound resilience, and is suitable for thermal management of high-power electronic equipment such as electronic base stations, communication radars, new energy automobiles, aerospace and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of thermal management materials, and particularly relates to a high-thermal-conductivity low-modulus graphene fiber thermal conductive gasket and a preparation method thereof. BACKGROUND

[0002] Carbon fibers have extremely high axial thermal conductivity, excellent corrosion resistance and low thermal expansion coefficient, and can be used to prepare high-performance thermal conductive gaskets with high out-of-plane thermal conductivity after being induced to be oriented by field orientation and other methods. The performance of the current carbon fiber thermal conductive gasket is mainly limited by the following factors: (1) high-thermal-conductivity pitch-based carbon fibers (axial thermal conductivity 800-950 W m -1 K -1 ) have high Young's modulus (750-960 GPa), and it is difficult to balance high thermal conductivity and high compressibility at a high filler content, which hinders the improvement of the comprehensive thermal conductivity; (2) carbon fibers are mainly compounded in the form of short fibers with a flexible polymer matrix, and the heat dissipation depends on the continuous thermal conduction network formed by the mutual lapping of short fibers in the compression process, and there is an unavoidable problem of interface phonon scattering; (3) the preparation processes such as electric field, magnetic field and flow channel orientation have high requirements on the viscosity of the material, and the filler content of the carbon fiber thermal conductive gasket obtained by the traditional preparation process is usually not higher than 40 wt%, and the thermal conductivity has obvious bottlenecks. How to solve the above problems is a key problem to promote the further development and application of the carbon fiber thermal conductive gasket. SUMMARY

[0003] The application aims to provide a high-thermal-conductivity low-modulus graphene fiber thermal conductive gasket and a preparation method thereof. The graphene fiber is directionally wound and impregnated to prepare a prepreg, and then the prepreg is laminated and bonded to obtain a high-orientation graphene fiber plate, and the plate is directionally cut along a direction perpendicular to the fiber orientation direction to obtain a thermal conductive gasket composed of continuous vertical orientation graphene fibers and silicone.

[0004] To achieve the above-mentioned purpose, the application adopts the following technical scheme: a high-thermal-conductivity low-modulus graphene fiber thermal conductive gasket, comprising a polymer matrix, wherein oriented graphene fibers are penetrated in the polymer matrix, the density of the graphene fibers ranges from 1.2 to 1.5 g cm -3 , the diameter is 5-30 μm, and the axial thermal conductivity is 1000-1200 W m -1 K -1, Young's modulus 50~100 GPa. The graphene fibers constitute a first array having a first orientation and a second array having a second orientation; and the first orientation forms an angle of 0.5°~10° with the thickness direction of the thermal conductive gasket, and the second orientation forms an angle of -10~-0.5° with the thickness direction of the thermal conductive gasket; the graphene fibers in the first array and the second array are interpenetrated; wherein the graphene fiber orientation layers are oriented at angles of 0.5°~10° and -10~-0.5° respectively, and cross each other to form an "X" structure, and the layers are combined by an elastic silicone matrix, thus forming a hinge-like structure that can be highly deformed. In the compression process, the graphene fibers have a high modulus, and when the "X" structure is subjected to an external force, the compression load is mainly converted into a torque that causes the carbon fiber arms to rotate, which is easier than compressing a vertically oriented fiber array, and is manifested as a smaller modulus and hardness, and a larger strain under the same compression force; after the external force is removed, the fibers are tightened from the originally relaxed state, and a certain tensile stress is generated inside, and after the external force is removed, the fibers will return to the original state and rotate around the hinge center, and the potential energy stored in the silicone matrix is released synchronously, thus exhibiting high compression resilience. In addition, since the "X" structure compression causes less bending and twisting of the graphene fibers, it is less likely to cause compression fracture of the graphene fibers, and thus can withstand repeated compression deformation, and can still maintain high thermal conductivity after multiple compression-releasing. In contrast, when the vertically arranged graphene fibers are compressed, the load directly acts on the top end of the carbon fiber, and the fiber will undergo Euler buckling due to its slenderness ratio, which easily leads to mutual friction between the fibers, cracking of the matrix, and even fiber fracture, resulting in large energy dissipation and low resilience efficiency; randomly distributed graphene fibers deform unevenly, easily forming local stress concentration points, leading to premature fracture of some fibers or debonding with the matrix, in addition, they cannot effectively transfer heat in the vertical direction, making it difficult to meet the performance requirements.

[0005] Further, the polymer matrix is formed by in-situ polymerization of vinyl silicone oil and hydrogen-containing silicone oil, and has a Shore hardness of 10~50 degrees, a tensile breaking strength of ≥100 kPa, an elongation at break of 30~100 %, and a 1100 o C thermal weight loss ≤5 %. Reasonable control of the mechanical properties of the polymer matrix can ensure the compression and tensile properties of the overall thermal conductive gasket material, so that the material can better reduce the thermal resistance under compression and build a thermal conductive channel.

[0006] Furthermore, the angle between the orientation direction of the first orientation array and the thickness direction of the thermally conductive pad is 3~10°, and the angle between the orientation direction of the second orientation array and the thickness direction of the thermally conductive pad is -10~-3°. The adjacent graphene fiber layers form an "X"-shaped structure with a certain angle between them, and the layers are bonded by an elastic silicone matrix, thus forming a highly deformable hinge-like structure. During compression, this reduces the compressive rigidity caused by the vertical alignment of the fibers, making the material easier to compress and deform. After the external force is removed, the graphene fibers can rotate rapidly, achieving deformation recovery, thus the material possesses both high compression and high resilience characteristics. Although the fibers running through the entire structure have a certain angle with the vertical direction of the interface, they can still effectively conduct heat, providing an efficient heat conduction channel. During compression, the higher compression ratio results in lower overall thermal resistance. In addition, the graphene fibers in the "X"-shaped structure experience less axial compressive force, making them less prone to brittle fracture and phase separation, resulting in better long-term stability compared to highly vertically oriented graphene fiber pads.

[0007] Furthermore, the mass fraction of the graphene fiber is between 13.1% and 85.1%. If the fiber content is too low, the number of heat conduction channels is insufficient, resulting in poor thermal conductivity; if the fiber content is too high, the overall rigidity is too large, the gasket is difficult to compress, and the interfacial thermal resistance is high.

[0008] Furthermore, the overall density is 0.62~1.24 g cm⁻¹. -3 The Shore hardness is 20-80 degrees, and the out-of-plane thermal conductivity is 90.5-502.5 W / m. -1 K -1 Tensile breaking strength ≥0.5 MPa.

[0009] This invention also provides a method for preparing the above-mentioned high thermal conductivity, low modulus graphene fiber thermal pad, comprising the following steps: (1) Graphene fibers are introduced into a fiber winding machine to wind a rectangular substrate. The fiber winding machine alternately runs a forward winding program and a reverse winding program. During the forward winding program, the graphene fibers are wound from the near end to the far end of the rectangular substrate, and the winding angle of the graphene fibers is -10° to -0.5°. During the reverse winding program, the graphene fibers are wound from the far end to the near end of the rectangular substrate, and the winding angle of the graphene fibers is 0.5° to 10°. The single-sided load of the rectangular substrate after winding is 20 to 200 mg cm⁻¹. -2 ; (2) Immerse the rectangular substrate of wound graphene fiber into an organosilicon precursor solution containing 1-5 parts vinyl silicone oil, 1 part hydrogen-containing silicone oil, 0.01-0.15 parts catalyst and 0.02-0.2 parts inhibitor. After immersion under vacuum for 10-60 min, remove the substrate, press it with rollers, and place it at 40-60°C. oC heat for 10~30 min in oven to preform, and then draw the substrate to get high orientation graphene fiber / silica gel composite material; (3) cut the high orientation graphene fiber / silica gel composite material obtained in step (2) to get thermal conductive gasket, the cutting direction is perpendicular to the orientation direction of graphene fiber, so that the graphene fiber penetrates the upper and lower surfaces of the gasket; the cutting rate is 0.1~5 mm / min, and the high thermal conductive low modulus graphene fiber thermal conductive gasket with a thickness of 0.3~5 mm is obtained.

[0010] Through the preparation method of the application, the forward winding procedure forms a graphene fiber array with a first orientation, the reverse winding procedure forms a graphene fiber array with a second orientation, the forward winding procedure and the reverse winding procedure are alternately operated, the "rows" in the first array and the second array are alternately arranged, the graphene fibers with different orientations cross each other to form an "X" structure, and the layers are combined through the elastic silica gel matrix, so that a hinge-like structure which can be highly deformed is formed.

[0011] In addition, compared with the scheme of preparing a thermal conductive gasket by using traditional pitch-based carbon fiber short fibers, the application uses high thermal conductive low modulus graphene fibers to replace traditional pitch-based carbon fibers to achieve the purpose of enhancing thermal conductivity and reducing modulus; the unidirectional felt glue impregnation lamination cutting process is used to replace the traditional field orientation processing scheme to overcome the viscosity problem caused by the increase of fiber content in the orientation processing process of carbon fiber materials, and the controllable preparation of ultra-wide carbon fiber content thermal conductive gaskets is realized; long fibers are used to replace short fibers as the thermal conductive reinforcing phase, which has continuous thermal conduction conditions in any compression state, eliminates the phonon scattering caused by the lap joint interface of short fibers, and realizes the improvement of the comprehensive thermal conduction effect.

[0012] Further, the high orientation graphene fiber / silica gel composite material obtained in step (2) is again put into the organic silicon precursor solution in step (2) for impregnation, and after extrusion by rollers, the layers are stacked, and the high thermal conductive low modulus graphene fiber thermal conductive gasket with a thickness of 0.3~5 mm is obtained after curing at 60~100 o C heat for 10~30 min in oven to preform, and then draw the substrate to get high orientation graphene fiber / silica gel composite material;

[0013] Further, the roller gap spacing in step (2) is 2~5 mm, which is used to extrude the excess organic silicon precursor solution, so that the mass ratio of graphene fiber to silica gel in the extruded prepreg is 3:1~27. The roller gap spacing is adjusted to extrude the excess organic silicon precursor solution and optimize the graphene fiber filling amount.

[0014] Further, the winding angle in step (1) is 3~10°. The winding angle is adjusted to construct the included angle structure between the orientation layers of graphene fibers. If the winding angle is lower than 3°, the high orientation graphene fiber structure is close, the thermal conduction channel is the shortest, but the rigidity is greater; if the winding angle is higher than 10°, the thermal conductivity in the direction perpendicular to the interface will be reduced.

[0015] The obtained high-thermal-conductivity low-modulus graphene fiber thermal conductive gasket has a thickness range of 0.3-5 mm, and an applicable temperature range of-45-150 o C, and a bulk thermal conductivity range of 130.3-502.5 W m -1 K -1 , a compression range of 11-32 % under a pressure of 10 psi, a compression range of 20-65 % under a pressure of 50 psi, and an equivalent thermal conductivity range of 36.1-184.7 W m -1 K -1 , a thermal impedance range of 0.017-0.221 K cm 2 W -1 .

[0016] The present application has the following beneficial effects: The graphene-based carbon fiber is used to replace the traditional pitch-based carbon fiber as a thermal conductive filler, and is cross-formed into an "X" structure, which has a hinge-like effect, effectively reduces the compression rigidity of the gasket, and simultaneously realizes a rapid rebound effect. The fibers running through the upper and lower parts can provide an efficient thermal conductive channel, and with the help of a higher compression rate, a lower overall thermal resistance is realized. In addition, the graphene fibers in the "X" structure are subjected to smaller axial compression forces and are less likely to break and separate, and thus have better long-term use stability than the graphene fiber gasket with a high vertical orientation.

[0017] The unidirectional felt impregnation lamination cutting process is used to replace the traditional carbon fiber short fiber slurry process, which greatly improves the orientation and continuity, avoids the high viscosity problem in the slurry process of the carbon fiber short fiber, is easy to operate, and is easy to mass produce. In addition, if the graphene fiber short fiber is used to prepare the slurry, the addition amount is difficult to increase, and the thermal conductive advantage of the graphene fiber cannot be fully utilized. In comparison, the present method can realize controllable preparation of a super-wide carbon fiber content thermal conductive gasket.

[0018] The graphene-based carbon fiber has a higher axial thermal conductivity (1000-1200 W m -1 K -1 ) and a lower Young's modulus (50-100 GPa), effectively improves the problem that the high thermal conductivity and excellent thixotropic performance of the carbon fiber thermal conductive gasket are difficult to be balanced, significantly reduces the modulus and thermal resistance of the thermal conductive gasket under the same filler content, significantly increases the carbon fiber content that can be filled under the same compression modulus, and breaks through the performance bottleneck of the pitch-based carbon fiber thermal conductive gasket. In addition, the rigidity of the pitch-based carbon fiber is too large, and if it is pre-oriented and wound according to the present scheme, serious fracture will occur, and subsequent processing steps cannot be performed.

[0019] Using carbon fiber filaments instead of carbon fiber powder (chopped fibers) as the thermally conductive reinforcing phase allows for the formation of continuous thermally conductive pathways within the material without requiring high filler content and high compressibility. This results in greater tolerance to pressure and compressibility during the encapsulation process, while also eliminating phonon scattering caused by the overlapping interfaces of chopped fibers, thus improving the overall thermal conductivity.

[0020] This invention provides a thermally conductive pad prepared by impregnating, laminating, and cutting high thermal conductivity, low modulus graphene fiber unidirectional felt, which has the advantages of higher thermal conductivity, better thixotropy, and more flexible usage conditions. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the graphene fiber structure in a thermal pad; Figure 2 This is a flowchart of the winding process of the present invention; Figure 3 This is an optical photograph of highly oriented graphene fibers wound on a substrate, as shown in Example 1.

[0022] Figure 4 The images show the tensile fracture curve (left) and compressive stress-strain curve (right) of the graphene fiber thermal conductive pad in Example 1.

[0023] Figure 5 Photographs of the graphene fiber thermal pad of Example 1 (left), and scanning electron microscope images of its cross section (middle) and surface (right) (middle and right).

[0024] Figure 6 Scanning electron microscope images of the cross section (left) and surface (right) of the graphene fiber thermal pad of Example 2.

[0025] Figure 7 The thermogravimetric curve is shown for the graphene fiber thermal pad in Example 4. Detailed Implementation

[0026] The present invention will be specifically described below through embodiments. These embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential changes and adjustments made by those skilled in the art based on the above-described invention shall fall within the scope of protection of the present invention.

[0027] like Figure 1This is a schematic diagram of the graphene fiber structure in the thermally conductive pad of the present invention. The graphene fibers form a first array (solid line) with a first orientation and a second array (dashed line) with a second orientation, bonded together by an elastic silicone matrix to form a hinge-like structure that can be highly deformed at orientation angles of 0.5°~10° and -10~-0.5°. This design allows the pad to effectively convert external force into rotational torque during compression, reducing the bending and torsion of the graphene fibers, thereby improving compression recovery performance and durability, while maintaining high thermal conductivity, making it particularly suitable for the heat dissipation requirements of high-power-density electronic devices. Compared to vertically arranged or randomly distributed graphene fibers, this structure significantly improves the material's stability and thermal conductivity efficiency.

[0028] The present invention also provides a method for preparing the thermally conductive pad of the above-mentioned dual-outflow thermally conductive network, specifically using a winding machine preparation method that can be industrially produced. Figure 2 The winding process diagram is shown, alternating between forward and reverse winding programs. During the forward winding program, the graphene fiber is wound from the near end to the far end of the rectangular substrate, with a winding angle of -10° to -0.5°. During the reverse winding program, the graphene fiber is wound from the far end to the near end of the rectangular substrate, with a winding angle of 0.5° to 10°. After winding, the single-sided load of the rectangular substrate is 20–200 mg cm⁻¹. -2 Those skilled in the art will foresee that the back side of the rectangular substrate also constitutes this layered cross structure.

[0029] This invention forms an array of graphene fibers with alternating forward and reverse winding processes, which are arranged in opposite directions. The fibers intersect to form an "X" shape and are bonded to an elastic silicone matrix to form a highly deformable hinge-like structure.

[0030] The following examples are provided to further illustrate the present invention and are intended to explain the invention, not to limit its scope. Unless otherwise specified, all figures are expressed in parts by weight and weight percentages.

[0031] Unless otherwise specified, the raw materials used in this invention are all conventional commercially available products; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0032] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0033] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise expressly defined.

[0034] Furthermore, the "vertical" mentioned in this invention refers to approximately 90 degrees, specifically an intersection angle between 80 and 100 degrees.

[0035] Example 1: Use a fiber winding machine to wind fibers with a density of 1.2 g / cm³. -3 15 μm in diameter, 1000 W / m axial thermal conductivity -1 K -1 Graphene fibers with a Young's modulus of 50 GPa are alternately wound onto a 1 mm thick substrate to form a unidirectional felt. Figure 3 ), control the single-sided load of the unidirectional felt to 150 mg cm -2 The fiber winding machine alternates between forward winding and reverse winding programs. During the forward winding program, the graphene fiber is wound from the near end to the far end of the rectangular substrate, with a winding angle of 0.5°. During the reverse winding program, the graphene fiber is wound from the far end to the near end of the rectangular substrate, with a winding angle of 0.5°.

[0036] (2) Immerse the unidirectional felt in an organosilicon precursor solution composed of vinyl silicone oil, hydrogen-containing silicone oil, catalyst and inhibitor in a mass ratio of 1:1:0.01:0.02, place it in a vacuum environment for 10 min, then remove the rollers and place them in a 40°C environment. oThe pre-formed graphene fiber / silicone composite material was heated in an oven at 2°C for 20 minutes. The substrate was then removed to obtain the composite material. The roller gap during the rolling process was 2 mm, and the mass ratio of graphene fiber to silicone in the resulting prepreg was 2:1. The high-orientation graphene fiber / silicone composite material was cut into fixed-size sheets using a die-cutting machine. These sheets were then immersed again in the aforementioned silicone precursor solution and held for 10 minutes before being transferred through a 2 mm gap roller to a hot press mold for layer-by-layer lamination. During the lamination process, the fiber orientation was kept consistent. Excess silicone solution was extruded from the mold during lamination. The maximum pressure was controlled at 15 MPa, the lamination rate at 10 mm / min, and the hot pressing temperature at 60°C. o C, hot pressing time 2 h, after demolding, a highly oriented graphene fiber / silicone composite block is obtained.

[0037] (3) Cut the highly oriented graphene fiber / silicone composite block obtained in step (2) at a 90° angle to the orientation direction of the graphene fiber. o The cutting rate is 0.2 mm / min and the cutting spacing is 1.2 mm.

[0038] The obtained graphene fiber thermal pad has a thickness of 1.2 mm, with graphene fibers running through both the top and bottom surfaces of the pad at an angle of -0.5 to 0.5° to the thickness direction. The graphene fiber mass fraction is 61.3 wt%, and the fiber array density is 73.6 mg / cm². -2 The density of the thermal pad is 0.92 g / cm³. -3 Shore hardness 52, tensile strength at break 0.057 MPa Figure 4 (Left), the stress-strain curve during the compression-springback process is as follows: Figure 4 As shown on the right, the rebound rate is over 90%. (Through...) Figure 5 Optical and SEM microscopic images reveal that the graphene fibers are highly oriented along the thickness direction, with a continuous fiber ratio >85% (breakage rate <15%). They are densely and uniformly distributed within the organosilicon matrix, with smooth cut surfaces and no obvious fiber pull-out. The out-of-plane thermal conductivity, measured using transient laser scintillation, is 397.3 W / m². -1 K -1 The compressibility at 10 psi was measured to be 18% using the steady-state method, and the equivalent thermal conductivity was 92.4 W / m². -1 K -1 The thermal resistance is 0.106 K cm. 2 W -1 At 50 psi, the compression ratio is 38%, and the equivalent thermal conductivity is 139.2 W / m². -1 K -1 The thermal resistance is 0.053 K cm.2 W -1 -45~150 o The rate of change in thermal resistance after 1000 hours of high and low temperature thermal shock is <5%.

[0039] Example 2: Use a fiber winding machine to wind fibers with a density of 1.2 g / cm³. -3 20 μm in diameter, 1000 W / m axial thermal conductivity -1 K -1 Graphene fibers with a Young's modulus of 50 GPa were directionally wound onto a 1 mm thick substrate to form a unidirectional felt, and the unidirectional felt was controlled to have a single-sided load of 20 mg / cm². -2 The fiber winding machine alternates between forward winding and reverse winding programs. During the forward winding program, the graphene fiber is wound from the near end to the far end of the rectangular substrate, with a winding angle of 1°. During the reverse winding program, the graphene fiber is wound from the far end to the near end of the rectangular substrate, with a winding angle of 1°.

[0040] The unidirectional felt was immersed in an organosilicon precursor solution composed of vinyl silicone oil, hydrogen-containing silicone oil, catalyst, and inhibitor in a mass ratio of 5:1:0.15:0.2. After being placed in a vacuum environment for 30 minutes, the rollers were removed and placed in a 60°C environment. o The pre-formed graphene fiber / silicone composite material was heated in an oven at C for 30 minutes. The substrate was then removed to obtain the composite material. The roller gap during the rolling process was 2 mm, and the graphene fiber to silicone mass ratio in the resulting prepreg was 1:9. The high-orientation graphene fiber / silicone composite material was cut into fixed-size sheets using a die-cutting machine. These sheets were then immersed again in the aforementioned silicone precursor solution and held for 10 minutes before being transferred through a 2 mm gap roller to a hot press mold for layer-by-layer lamination. During lamination, the fiber orientation was kept consistent. Excess silicone solution was extruded from the mold during lamination. The maximum pressure was controlled at 5 MPa, the lamination rate at 5 mm / min, and the hot pressing temperature at 80°C. o C, hot pressing time 1 h, after demolding, a highly oriented graphene fiber / silicone composite block is obtained.

[0041] (3) Cut the highly oriented graphene fiber / silicone composite block obtained in step (2) at a 90° angle to the orientation direction of the graphene fiber. o The cutting rate is 5 mm / min and the cutting spacing is 0.3 mm.

[0042] The obtained graphene fiber thermal pad has a thickness of 0.3 mm, with graphene fibers running through both the top and bottom surfaces of the pad at an angle of -1 to 1° to the thickness direction. The graphene fiber mass fraction is 29.1 wt%, and the fiber array density is 6.5 mg / cm².-2 The density of the thermal pad is 0.75 g / cm³. -3 It has a Shore hardness of 20 and a tensile breaking strength of 0.065 MPa. Its microstructure is as follows: Figure 6 As shown, continuous graphene fibers are highly oriented along the thickness direction. Both the surface and cross-section of the pad contain a significant amount of organosilicon, and no obvious fiber pull-out is observed in the cut surface. The out-of-plane thermal conductivity, measured using transient laser scintillation, is 130.3 W / m². -1 K -1 The compressibility at 10 psi was measured to be 32% using the steady-state method, and the equivalent thermal conductivity was 45.1 W / m². -1 K -1 The thermal resistance is 0.047 K cm. 2 W -1 At 50 psi, the compression ratio is 65%, and the equivalent thermal conductivity is 62.9 W / m². -1 K -1 The thermal resistance is 0.017 K cm. 2 W -1 .

[0043] Example 3: Use a fiber winding machine to wind fibers with a density of 1.2 g / cm³. -3 30 μm in diameter, axial thermal conductivity 1000 W / m -1 K -1 Graphene fibers with a Young's modulus of 50 GPa were directionally wound onto a 1 mm thick substrate to form a unidirectional felt, and the unidirectional felt was controlled to have a single-sided load of 100 mg cm⁻¹. -2 The fiber winding machine alternates between forward winding and reverse winding programs. During the forward winding program, the graphene fiber is wound from the near end to the far end of the rectangular substrate, with a winding angle of 3°. During the reverse winding program, the graphene fiber is wound from the far end to the near end of the rectangular substrate, with a winding angle of 3°.

[0044] (2) Immerse the unidirectional felt in an organosilicon precursor solution composed of vinyl silicone oil, hydrogen-containing silicone oil, catalyst and inhibitor in a mass ratio of 1:1:0.01:0.02, place it in a vacuum environment for 60 min, then remove the rollers and place them in a vacuum environment for 60 min. oThe pre-formed graphene fiber / silicone composite material was heated in an oven at 1°C for 10 minutes. The substrate was then removed to obtain the composite material. The roller gap during the rolling process was 5 mm, and the mass ratio of graphene fiber to silicone in the resulting prepreg was 1:2. The high-orientation graphene fiber / silicone composite material was cut into fixed-size sheets using a die-cutting machine. These sheets were then immersed again in the aforementioned silicone precursor solution and held for 10 minutes before being transferred through a 5 mm roller gap to a hot press mold for layer-by-layer lamination. During the lamination process, the fiber orientation was kept consistent. Excess silicone solution was extruded from the mold during lamination. The maximum pressure was controlled at 10 MPa, the lamination rate at 1 mm / min, and the hot pressing temperature at 90°C. o C, hot pressing time 0.5 h, after demolding, a highly oriented graphene fiber / silicone composite block is obtained.

[0045] (3) Cut the highly oriented graphene fiber / silicone composite block obtained in step (2) at a 90° angle to the orientation direction of the graphene fiber. o The cutting rate is 5 mm / min and the cutting spacing is 5 mm.

[0046] The obtained graphene fiber thermal pad has a thickness of 5 mm, with graphene fibers running through both the top and bottom surfaces of the pad at an angle of -3 to 3° to the thickness direction. The graphene fiber mass fraction is 47.2 wt%, and the fiber array density is 195.9 mg / cm². -2 The density of the thermal pad is 0.83 g / cm³. -3 It has a Shore hardness of 35 and a tensile breaking strength of 0.062 MPa. The out-of-plane thermal conductivity, measured using transient laser scintillation, is 228.3 W / m². -1 K -1 The compressibility at 10 psi was measured using the steady-state method to be 24%, and the equivalent thermal conductivity was 73.4 W / m². -1 K -1 The thermal resistance is 0.518 K cm. 2 W -1 At 50 psi, the compression ratio is 47.7%, and the equivalent thermal conductivity is 118.5 W / m². -1 K -1 The thermal resistance is 0.221 K cm. 2 W -1 .

[0047] Example 4: Use a fiber winding machine to wind fibers with a density of 1.2 g / cm³. -3 5 μm in diameter, 1000 W / m axial thermal conductivity -1 K -1Graphene fibers with a Young's modulus of 50 GPa were directionally wound onto a 1 mm thick substrate to form a unidirectional felt, and the unidirectional felt was controlled to have a single-sided load of 150 mg cm⁻¹. -2 The fiber winding machine alternates between forward winding and reverse winding programs. During the forward winding program, the graphene fiber is wound from the near end to the far end of the rectangular substrate, with a winding angle of 1°. During the reverse winding program, the graphene fiber is wound from the far end to the near end of the rectangular substrate, with a winding angle of 1°.

[0048] The unidirectional felt was immersed in an organosilicon precursor solution composed of vinyl silicone oil, hydrogen-containing silicone oil, catalyst, and inhibitor in a mass ratio of 1:1:0.01:0.02. After being placed in a vacuum environment for 10 minutes, the rollers were removed and placed in a 50°C environment. o The pre-formed graphene fiber / silicone composite material was heated in an oven at C for 20 minutes, and then the substrate was removed to obtain the highly oriented graphene fiber / silicone composite material. The roller gap during the rolling process was 2 mm, and the mass ratio of graphene fiber to silicone in the obtained prepreg was 2:1. The highly oriented graphene fiber / silicone composite material was cut into fixed-size sheets using a die-cutting machine, and then immersed again in the aforementioned silicone precursor solution. After holding for 10 minutes, it was transferred through a 2 mm roller gap to a hot press mold for layer-by-layer pressing. During the lamination process, the fiber orientation was kept consistent. Excess silicone solution was extruded from the mold during pressing. The maximum pressure was controlled at 20 MPa, the pressing rate at 5 mm / min, and the hot pressing temperature at 100°C. o C, hot pressing time 1.5 h, after demolding, a highly oriented graphene fiber / silicone composite block is obtained.

[0049] (3) Cut the highly oriented graphene fiber / silicone composite block obtained in step (2) at a 90° angle to the orientation direction of the graphene fiber. o The cutting rate is 0.1 mm / min and the cutting spacing is 0.5 mm.

[0050] The obtained graphene fiber thermal pad has a thickness of 0.5 mm, with graphene fibers running through both the top and bottom surfaces of the pad at an angle of -1 to 1° to the thickness direction. The graphene fiber mass fraction is 85.1 wt%, and the fiber array density is 52.7 mg / cm². -2 The density of the thermal pad is 1.24 g / cm³. -3 It has a Shore hardness of 80 and a tensile breaking strength of 0.058 MPa. Its thermogravimetric curve is as follows. Figure 7 As shown. The out-of-plane thermal conductivity, measured using the transient laser scintillation method, is 502.5 W / m. - 1 K -1The compressibility at 10 psi was measured to be 11% using the steady-state method, and the equivalent thermal conductivity was 135.2 W / m². -1 K -1 The thermal resistance is 0.033 K cm. 2 W -1 At 50 psi, the compression ratio is 20%, and the equivalent thermal conductivity is 184.7 W / m². -1 K -1 The thermal resistance is 0.022 Kcm. 2 W -1 .

[0051] Example 5: (1) Use a fiber winding machine to wind 1.5 g cm -3 15 μm in diameter, 1200 W / m axial thermal conductivity -1 K -1 Graphene fibers with a Young's modulus of 100 GPa were directionally wound onto a 1 mm thick substrate to form a unidirectional felt, and the unidirectional felt was controlled to have a single-sided load of 150 mg cm⁻¹. -2 The fiber winding machine alternates between forward winding and reverse winding programs. During the forward winding program, the graphene fiber is wound from the near end to the far end of the rectangular substrate, with a winding angle of 5°. During the reverse winding program, the graphene fiber is wound from the far end to the near end of the rectangular substrate, with a winding angle of -5°.

[0052] (2) Immerse the unidirectional felt in an organosilicon precursor solution composed of vinyl silicone oil, hydrogen-containing silicone oil, catalyst and inhibitor in a mass ratio of 5:1:0.15:0.2, place it in a vacuum environment for 30 min, then remove the rollers and place them in a 60°C environment. o The pre-formed graphene fiber / silicone composite material was heated in an oven at C for 30 minutes. The substrate was then removed to obtain the composite material. The roller gap during the rolling process was 2 mm, and the graphene fiber to silicone mass ratio in the resulting prepreg was 1:7. The high-oriented graphene fiber / silicone composite material was cut into fixed-size sheets using a die-cutting machine. These sheets were then immersed again in the aforementioned silicone precursor solution and held for 10 minutes before being transferred through a 2 mm roller gap to a hot press mold for layer-by-layer lamination. During the lamination process, the fiber orientation was kept consistent. Excess silicone solution was extruded from the mold during lamination. The maximum pressure was controlled at 5 MPa, the lamination rate at 5 mm / min, and the hot pressing temperature at 80°C. o C, hot pressing time 1 h, after demolding, a highly oriented graphene fiber / silicone composite block is obtained.

[0053] (3) Cut the highly oriented graphene fiber / silicone composite block obtained in step (2) at a 90° angle to the orientation direction of the graphene fiber. oThe cutting rate is 5 mm / min and the cutting spacing is 0.3 mm.

[0054] The obtained graphene fiber thermal pad has a thickness of 0.3 mm and a graphene fiber mass fraction of 32.4 wt%. The graphene fibers penetrate both the top and bottom surfaces of the thermal pad, forming an angle of -5 to 5° with the thickness direction of the thermal pad. The fiber array density is 7.6 mg / cm². -2 The density of the thermal pad is 0.78 g / cm³. -3 It has a Shore hardness of 42 and a tensile breaking strength of 0.076 MPa. The out-of-plane thermal conductivity, measured using the transient laser scintillation method, is 150.3 W / m². -1 K -1 The compressibility at 10 psi was measured to be 21% using the steady-state method, and the equivalent thermal conductivity was 36.1 W / m². -1 K -1 The thermal resistance is 0.066 K cm. 2 W -1 At 50 psi, the compression ratio is 46%, and the equivalent thermal conductivity is 51.2 W / m². -1 K -1 The thermal resistance is 0.032 K cm. 2 W -1 .

[0055] Example 6: (1) Use a fiber winding machine to wind fibers with a density of 1.2 g / cm³. -3 20 μm in diameter, axial thermal conductivity 1200 W / m -1 K -1 Graphene fibers with a Young's modulus of 50 GPa were directionally wound onto a 1 mm thick substrate to form a unidirectional felt, and the unidirectional felt was controlled to have a single-sided load of 20 mg cm⁻¹. -2 The fiber winding machine alternates between forward winding and reverse winding programs. During the forward winding program, the graphene fiber is wound from the near end to the far end of the rectangular substrate, with a winding angle of 10°. During the reverse winding program, the graphene fiber is wound from the far end to the near end of the rectangular substrate, with a winding angle of 10°.

[0056] (2) Immerse the unidirectional felt in an organosilicon precursor solution composed of vinyl silicone oil, hydrogen-containing silicone oil, catalyst and inhibitor in a mass ratio of 5:1:0.15:0.2, place it in a vacuum environment for 30 min, then remove the rollers and place them in a 60°C environment. oThe pre-formed graphene fiber / silicone composite material was heated in an oven at C for 30 minutes. The substrate was then removed to obtain the composite material. The roller gap during the rolling process was 2 mm, and the graphene fiber to silicone mass ratio in the resulting prepreg was 1:9. The high-orientation graphene fiber / silicone composite material was cut into fixed-size sheets using a die-cutting machine. These sheets were then immersed again in the aforementioned silicone precursor solution and held for 10 minutes before being transferred through a 2 mm roller gap to a hot press mold for layer-by-layer lamination. During the lamination process, the fiber orientation was kept consistent. Excess silicone solution was extruded from the mold during lamination. The maximum pressure was controlled at 2 MPa, the lamination rate at 5 mm / min, and the hot pressing temperature at 80°C. o C, hot pressing time 1 h, after demolding, a highly oriented graphene fiber / silicone composite block is obtained.

[0057] (3) Cut the highly oriented graphene fiber / silicone composite block obtained in step (2) at a 90° angle to the orientation direction of the graphene fiber. o The cutting rate is 5 mm / min and the cutting spacing is 0.3 mm.

[0058] The obtained graphene fiber thermal pad has a thickness of 0.3 mm and a graphene fiber mass fraction of 13.1 wt%. The graphene fibers penetrate both the top and bottom surfaces of the thermal pad. The orientation directions of adjacent graphene fiber alignment layers form angles of 5° and -5° with the thickness direction of the thermal pad, respectively. The fiber array density is 2.4 mg / cm². -2 The density of the thermal pad is 0.62 g / cm³. -3 It has a Shore hardness of 20 and a tensile breaking strength of 0.065 MPa. The out-of-plane thermal conductivity, measured using the transient laser scintillation method, is 90.5 W / m². -1 K -1 The compressibility at 10 psi was measured to be 40% using the steady-state method, and the equivalent thermal conductivity was 26.9 W / m². -1 K -1 The thermal resistance is 0.067 K cm. 2 W -1 At 50 psi, the compression ratio is 69%, and the equivalent thermal conductivity is 31.3 W / m². -1 K -1 The thermal resistance is 0.033 Kcm. 2 W -1 .

[0059] Comparative Example 1 (1) The density is 1.2 g cm -3 15 μm in diameter, 1000 W / m axial thermal conductivity -1 K -1Graphene fibers with a Young's modulus of 50 GPa are introduced into a fiber winding machine to wind a rectangular substrate. The fiber winding machine operates a parallel winding program, ensuring that all graphene fibers on both sides of the substrate are arranged in parallel, with a winding angle of 1°. After winding, the single-sided load of the rectangular substrate is 150 mg cm⁻¹. -2 .

[0060] (2) The rectangular substrate of the wound graphene fiber was immersed in an organosilicon precursor solution composed of vinyl silicone oil, hydrogen-containing silicone oil, catalyst and inhibitor in a mass ratio of 1:1:0.01:0.02. After being placed in a vacuum environment for 10 min, the rollers were removed and placed in a 40°C environment. o The pre-formed graphene fiber / silicone composite material was heated in an oven at 2°C for 20 minutes. The substrate was then removed to obtain the composite material. During the rolling process, the roller gap was 2 mm, and the mass ratio of graphene fiber to silicone in the resulting prepreg was 2:1. The high-orientation graphene fiber / silicone composite material was cut into fixed-size sheets using a die-cutting machine. These sheets were then immersed again in the aforementioned silicone precursor solution and held for 10 minutes before being transferred through a 2 mm roller gap to a hot press mold for layer-by-layer lamination. During the lamination process, the fiber orientation was kept consistent. Excess silicone solution was extruded from the mold during lamination. The maximum pressure was controlled at 15 MPa, the lamination rate at 10 mm / min, and the hot pressing temperature at 60°C. o C, hot pressing time 2 h, after demolding, a highly oriented graphene fiber / silicone composite block is obtained.

[0061] (3) Cut the highly oriented graphene fiber / silicone composite block obtained in step (2) at a 90° angle to the orientation direction of the graphene fiber. o The cutting rate is 0.2 mm / min and the cutting spacing is 1.2 mm.

[0062] The obtained graphene fiber thermal pad has a thickness of 1.2 mm. The graphene fibers are arranged in parallel and run through both the top and bottom surfaces of the thermal pad, with an angle of 1° to the thickness direction of the pad. The graphene fiber mass fraction is 61.3 wt%, and the fiber array density is 73.6 mg / cm². -2 The density of the thermal pad is 0.92 g / cm³. -3 The Shore hardness is 93. The out-of-plane thermal conductivity, measured using transient laser scintillation, is 402.5 W / m². -1 K -1 The compressibility at 10 psi was measured to be 2% using the steady-state method, and the equivalent thermal conductivity was 71.1 W / m². -1 K -1 The thermal resistance is 0.165 K cm. 2 W -1At 50 psi, the compression ratio is 11%, and the equivalent thermal conductivity is 89.4 W / m². -1 K -1 The thermal resistance is 0.119 K cm. 2 W -1 -45~150 o The rate of change in thermal resistance after 1000 hours of high and low temperature thermal shock is <5%.

[0063] It can be observed that, compared to Example 1, Comparative Example 1 adopted an orientation method in which the fibers are arranged in the same direction, resulting in an increase in the hardness of the final gasket and a significant decrease in the compressibility under the same pressure, exhibiting high rigidity. Consequently, the thermal resistance under the same pressure increases significantly, and the interfacial thermal conductivity is greatly reduced.

Claims

1. A high thermal conductivity, low modulus graphene fiber thermal pad, characterized in that, The device includes a polymer matrix in which oriented graphene fibers are threaded through it. The graphene fibers form a first array with a first orientation and a second array with a second orientation. The angle between the first orientation and the thickness direction of the thermal pad is 0.5° to 10°, and the angle between the second orientation and the thickness direction of the thermal pad is -10° to -0.5°. The graphene fibers in the first and second arrays are interwoven. The density of graphene fibers ranges from 1.2 to 1.5 g / cm³. -3 Diameter 5~30 μm, axial thermal conductivity 1000~1200 W / m -1 K -1 Young's modulus 50~100 GPa.

2. The thermally conductive pad according to claim 1, characterized in that, The polymer matrix is ​​formed by in-situ polymerization of vinyl silicone oil and hydrogen-containing silicone oil, with a Shore hardness of 10-50, tensile strength at break ≥100 kPa, elongation at break of 30-100%, and an inert gas atmosphere of 1100 kPa. o C. Thermal weight loss ≤5%.

3. The thermally conductive pad according to claim 1, characterized in that, The angle between the orientation direction of the first orientation array and the thickness direction of the thermal pad is 3~10°, and the angle between the orientation direction of the second orientation array and the thickness direction of the thermal pad is -10~-3°.

4. The thermally conductive pad according to claim 1, characterized in that, The mass fraction of graphene fibers ranges from 13.1% to 85.1%.

5. The thermally conductive pad according to claim 1, characterized in that, The overall density is 0.62~1.24 g / cm³. -3 The Shore hardness is 20-80 degrees, and the out-of-plane thermal conductivity is 90.5-502.5 W / m. -1 K -1 Tensile breaking strength ≥0.5 MPa.

6. A method for preparing a high thermal conductivity, low modulus graphene fiber thermal pad as described in claim 1, characterized in that, Includes the following steps: (1) Graphene fibers are introduced into a fiber winding machine to alternately wind a rectangular substrate. The fiber winding machine alternately runs a forward winding program and a reverse winding program. During the forward winding program, the graphene fibers are wound from the near end to the far end of the rectangular substrate, and the winding angle of the graphene fibers is -10° to -0.5°. During the reverse winding program, the graphene fibers are wound from the far end to the near end of the rectangular substrate, and the winding angle of the graphene fibers is 0.5° to 10°. The single-sided load of the rectangular substrate after winding is 20 to 200 mg cm⁻¹. -2 ; (2) Immerse a rectangular substrate wound with graphene fibers in an organosilicon precursor solution containing 1-5 parts vinyl silicone oil, 1 part hydrogen-containing silicone oil, 0.01-0.15 parts catalyst and 0.02-0.2 parts inhibitor. After immersion under vacuum for 10-60 min, remove the substrate, press it with rollers, and place it at 40-60°C. o Heat in an oven at C for 10-30 minutes to pre-shape, then remove the substrate to obtain a highly oriented graphene fiber / silicone composite material; (3) Cut the highly oriented graphene fiber / silicone composite material obtained in step (2) to obtain a thermally conductive pad. The cutting direction is perpendicular to the orientation direction of the graphene fiber, so that the graphene fiber penetrates the upper and lower surfaces of the pad. The cutting rate is 0.1~5 mm / min, resulting in high thermal conductivity and low modulus graphene fiber thermal pads with a thickness of 0.3~5 mm.

7. The preparation method according to claim 6, characterized in that, The highly oriented graphene fiber / silicone composite material obtained in multiple steps (2) is immersed again in the organosilicon precursor solution described in step (2), and then stacked layer by layer after being extruded by rollers at 60~100. o After hot pressing at C for 0.5~2 hours to cure, it can be cut.

8. The preparation method according to claim 6, characterized in that, The gap between the rollers in step (2) is 2-5 mm, which is used to extrude excess organosilicon precursor solution so that the mass ratio of graphene fiber to silicone in the extruded prepreg is 3:1-27.

9. The preparation method according to claim 6, characterized in that, The directional winding angle described in step (1) is 3~10°.

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