Surface-flexible heat-conducting silicone rubber composite material and preparation method thereof

Abstract

The invention belongs to the field of polymer composite materials, and particularly relates to a surface-flexible heat-conducting silicone rubber composite material and a preparation method thereof. The surface-flexible heat-conducting silicone rubber composite material comprises a flexible interface layer and a heat-conducting channel layer located above the flexible interface layer, the flexible interface layer is formed by enriching liquid metal particles, and the heat-conducting channel layer is formed by horizontally-oriented modified liquid metal / silicon carbide mixed filler. According to the surface-flexible heat-conducting silicone rubber composite material provided by the embodiment of the invention, an upper-lower layer structure is constructed by utilizing the size and density difference of filler particles through a natural settling rule in a solvent evaporation process, and meanwhile, the horizontal orientation arrangement of the modified liquid metal / silicon carbide mixed filler is realized under the driving of interfacial tension and capillary action. The distribution of the filler of the traditional heat-conducting composite material generally depends on random dispersion or a complex external field to realize specific orientation, and the method disclosed by the invention simplifies the processing technology, reduces the cost and avoids the limitation of external field control.

Description

Technical Field

[0001] The invention belongs to the field of polymer composite materials, and in particular relates to a surface flexible thermal conductive silicone rubber composite material and a preparation method thereof. Background Art

[0002] With the rapid development of electronic devices, the demand for thermally conductive materials continues to grow. These devices often generate a lot of heat during operation. If the heat cannot be effectively dissipated, its performance and reliability will be seriously affected. Thermally conductive materials must have both efficient heat dissipation capabilities and a certain degree of flexibility so that they can effectively fill the tolerance gaps between devices in applications, thereby achieving closer thermal contact and lower interfacial thermal resistance. In actual use, such materials not only need to conduct heat inside and outside the device, but also need to adapt to the needs of complex device structures and dynamic mechanical deformation. However, the thermally conductive fillers in traditional silicone rubber thermally conductive composite materials are usually filled in a randomly distributed manner. This structure results in a discontinuous thermal conduction path and limits the overall thermal conductivity of the composite material. In addition, in order to pursue higher thermal conductivity, the filler usually requires a high filling amount, which will significantly reduce the flexibility of the material, making it difficult to effectively fill the device gaps or adapt to deformation requirements, limiting its wide application in high-precision equipment.

[0003] To solve the above problems, in recent years, researchers have improved the arrangement of fillers in composite materials, minimized interfacial thermal resistance, formed more efficient heat conduction pathways, and thus achieved better thermal conductivity at a lower filler content. However, most of the existing orientation design technologies rely on complex external field control, such as magnetic fields, electric fields, or shear fields. Although these external field-driven methods can achieve directional arrangement of fillers, they often require expensive equipment and complex operating processes, making them difficult to promote and apply in industrial production. In addition, some studies have used high-performance but expensive special fillers (such as high-quality graphene or carbon nanotubes) as thermal conductivity enhancement materials, which perform well under laboratory conditions, but face huge challenges in cost control and large-scale production. And these strategies cannot improve the flexibility of the surface of thermally conductive materials.

[0004] Therefore, developing a composite material with simple process, controllable cost, high thermal conductivity and flexibility has become an urgent problem to be solved in current research. Summary of the invention

[0005] In order to solve the above problems, the object of the present invention is to provide a surface flexible thermal conductive silicone rubber composite material and a preparation method thereof.

[0006] In order to achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0007] According to a first aspect of an embodiment of the present invention, a surface-flexible thermally conductive silicone rubber composite material is provided, comprising a flexible interface layer and a thermally conductive channel layer located above the flexible interface layer, wherein the flexible interface layer is enriched with liquid metal particles, and the thermally conductive channel layer is formed by a horizontally oriented modified liquid metal / silicon carbide mixed filler.

[0008] Furthermore, the particle size of the liquid metal particles is 1 to 20 μm.

[0009] Furthermore, the liquid metal includes one or a combination of two or more of gallium-indium alloy and gallium-indium-tin alloy, and the liquid metal particles are modified by grinding 1-10 parts of mercaptosilane coupling agent and 90-99 parts of liquid metal together to improve the compatibility of the liquid metal with the silicone rubber matrix.

[0010] Furthermore, the preparation method of the modified liquid metal / silicon carbide hybrid filler includes adding 1-10 parts of mercaptosilane coupling agent to 90-99 parts of liquid metal and silicon carbide mixed filler by weight, and surface-modifying the liquid metal and silicon carbide mixed filler by grinding to obtain the modified liquid metal / silicon carbide hybrid filler.

[0011] Furthermore, in the modified liquid metal / silicon carbide mixed filler, the mass ratio of the modified liquid metal to silicon carbide is 1:3 to 1:10, the silicon carbide has a whisker-like structure, and the aspect ratio of the silicon carbide is 3:1 to 1000:1.

[0012] Furthermore, the mercaptosilane coupling agent includes one or a combination of two or more of mercaptosilanes such as mercaptopropyltrimethoxysilane, mercaptopropyltriethoxysilane, mercaptopropylmethyldimethoxysilane, and mercaptopropylmethyldiethoxysilane.

[0013] According to a second aspect of an embodiment of the present invention, a method for preparing a surface-flexible thermally conductive silicone rubber composite material is provided, comprising the following steps:

[0014] S1. Mixing liquid metal particles with liquid metal / silicon carbide mixed filler in a mass ratio of 1:3 to 1:5 to obtain a mixture; adding the mixture and an inhibitor to a solvent and a silicone rubber matrix to obtain a filler suspension; the silicone rubber matrix is ​​composed of vinyl siloxane-based silicone rubber and hydrogen siloxane-based silicone rubber;

[0015] According to the weight percentage, the liquid metal / silicon carbide mixed filler is 60-80 parts, the vinyl siloxane silicone rubber is 15-30 parts, the hydrogen siloxane silicone rubber is 1-10 parts, and the inhibitor is 0.01-0.5 parts;

[0016] S2, pouring the filler suspension into a mold, and after reduced pressure distillation, the filler in the filler suspension is graded and settled, and the liquid metal / silicon carbide mixed filler is horizontally oriented;

[0017] S3. After the solvent in the filler suspension is completely volatilized, the suspension is cured at a temperature of 70 to 120° C. to obtain the surface-flexible thermally conductive silicone rubber composite material.

[0018] Furthermore, the solvent is any one of toluene, dichloromethane, tetrahydrofuran, and n-hexane, or a combination of two or more thereof.

[0019] Furthermore, the inhibitor includes any one or a combination of two or more of inhibitors such as methyl butynol, acetylene cyclohexanol, tert-butyl cyclohexanol, phenyl butynol, and dimethyl acetylene alcohol.

[0020] Furthermore, the distillation temperature of the reduced pressure distillation is 30-50°C and the pressure is 0.01-0.1 kPa.

[0021] Compared with the prior art, the advantages of the embodiments of the present invention are:

[0022] (1) The embodiment of the present invention provides a surface-flexible thermally conductive silicone rubber composite material and a preparation method thereof, which utilizes the difference in filler particle size and density and the natural sedimentation law during the solvent volatilization process to construct an upper and lower layer structure. The distribution of fillers in traditional thermally conductive composite materials usually relies on random dispersion or complex external fields (such as electric fields and magnetic fields) to achieve specific orientation. The method of the present invention simplifies the processing technology, reduces costs, and avoids the limitations of external field control.

[0023] (2) The present invention forms a horizontally oriented arrangement of the modified silicon carbide and liquid metal hybrid fillers in the upper layer through the synergistic effects of interfacial tension, capillary action and sedimentation. This design significantly improves the continuity of the heat conduction path and solves the problem of discontinuous heat conduction network in traditional composite materials. Compared with randomly distributed fillers, the oriented structure of the present invention can achieve more efficient heat transfer.

[0024] (3) The liquid metal particles of the present invention are large in size, high in density, and have a fast sedimentation rate, so they are quickly enriched to form a high thermal conductivity flexible layer. This natural sedimentation method replaces the complex multi-step layering process, achieves a balance between thermal conductivity and flexibility, and utilizes the high deformation capacity of liquid metal. Compared with the traditional method of using plasticizers or adding flexible coatings, the design of the present invention is more efficient and integrated. The formation of a high thermal conductivity flexible layer enables the material to adapt to the complex shape of device surfaces and dynamic mechanical deformation, effectively fill the tolerance gaps between devices, reduce the interface thermal resistance, and ensure the stability and reliability of heat conduction.

[0025] (4) Many existing orientation design methods rely on external field control such as magnetic field and electric field, which are complex and energy-intensive. The present invention achieves structural optimization entirely through solvent volatilization and particle sedimentation rate differences, has a simple process, can be mass-produced, and has obvious economic and practical advantages.

[0026] (5) The modified liquid metal / silicon carbide hybrid filler prepared by grinding in the present invention is not only well dispersed in the polymer matrix, but also endows the hybrid filler with excellent thermal conductivity. At the same time, the construction of the thermal conductivity path of the filler in the polymer matrix can be enhanced by compounding the filler, which is beneficial to the improvement of the thermal conductivity of the composite material.

[0027] (6) The present invention can flexibly control the thermal conductivity and flexibility of the composite material by adjusting the ratio of liquid metal and modified liquid metal / silicon carbide mixed filler, particle size distribution and solvent volatilization conditions, so as to meet the diverse requirements of thermal conductivity and mechanical properties in different application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0029] Figure 1 This is a SEM image of the modified liquid metal / silicon carbide filler in Example 1 of the present invention.

[0030] Figure 2 This is a SEM image of the horizontally oriented structure of the upper modified liquid metal / silicon carbide filler in Example 1 of the present invention.

[0031] Figure 3 This is a SEM image of the cross section of the surface flexible thermally conductive silicone rubber composite material in Example 1 of the present invention. DETAILED DESCRIPTION

[0032] In view of the deficiencies in the prior art, the inventor of this case has proposed the technical solution of the present invention after long-term research and extensive practice. The technical solution, its implementation process and principle will be further explained as follows.

[0033] The present invention is further described in detail below in conjunction with specific embodiments, and the examples provided are only for illustrating the present invention, rather than for limiting the scope of the present invention. The examples provided below can be used as a guide for further improvements by those of ordinary skill in the art, and do not constitute a limitation of the present invention in any way.

[0034] The experimental methods in the following examples, unless otherwise specified, are all conventional methods, and are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. The materials, reagents, etc. used in the following examples, unless otherwise specified, can all be obtained from commercial channels.

[0035] The embodiment of the present invention provides a surface-flexible heat-conducting silicone rubber composite material, comprising a flexible interface layer and a heat-conducting channel layer located above the flexible interface layer, wherein the flexible interface layer is enriched with liquid metal particles, and the heat-conducting channel layer is formed by a horizontally oriented modified liquid metal / silicon carbide mixed filler. The composite material forms a layered structure through the graded sedimentation of fillers during solvent volatilization, wherein the liquid metal particles are enriched in the lower layer due to their large particle size and fast sedimentation rate, forming a flexible surface layer; the mixed fillers are arranged horizontally in the upper layer due to their small density and slow sedimentation rate, driven by interfacial tension and capillary action, thereby constructing a composite material with high flexibility and high thermal conductivity.

[0036] The method for preparing the surface flexible thermally conductive silicone rubber composite material provided by the present invention comprises the following steps:

[0037] S1. Mix liquid metal particles with liquid metal / silicon carbide mixed filler in a mass ratio of 1:3 to 1:5 to obtain a mixture; add the mixture and an inhibitor to a solvent and a silicone rubber matrix to obtain a filler suspension; the silicone rubber matrix is ​​composed of vinyl siloxane-based silicone rubber and hydrogen siloxane-based silicone rubber; the inhibitor includes any one of methyl butynol, acetylene cyclohexanol, tert-butyl cyclohexanol, phenyl butynol, and dimethyl acetylene alcohol, or a combination of two or more thereof, but is not limited thereto.

[0038] According to the weight percentage, the liquid metal / silicon carbide mixed filler is 60-80 parts, the vinyl siloxane silicone rubber is 15-30 parts, the hydrogen siloxane silicone rubber is 1-10 parts, and the inhibitor is 0.01-0.5 parts;

[0039] S2, pouring the filler suspension into a mold, volatilizing excess solution in a vacuum distillation device, achieving graded sedimentation of the filler through the solvent volatilization process, and the liquid metal / silicon carbide mixed filler is horizontally oriented, the lower layer of liquid metal particles are enriched to form a flexible surface layer due to their large particle size and fast sedimentation rate, and the upper layer of mixed filler is horizontally arranged due to its small density and slow sedimentation rate driven by interfacial tension and capillary action;

[0040] S3, after the solvent in the filler suspension is completely volatilized and then cured at 70-120° C., the surface flexible thermally conductive silicone rubber composite material is obtained.

[0041] In order to better understand the technical solution of the present invention, it is described in detail below in conjunction with specific embodiments.

[0042] Embodiment 1:

[0043] Preparation process of liquid metal particles: According to weight, 2 parts of mercaptopropyl trimethoxysilane, 98 parts of gallium-indium alloy, and modifier are added to a mortar containing gallium-indium alloy and silicon carbide and ground until liquid metal particles are obtained. Liquid metal particles with a particle size of 10 to 20 μm are screened through a sieve.

[0044] Preparation process of modified liquid metal / silicon carbide hybrid filler: The modified liquid metal / silicon carbide hybrid filler comprises 10 parts of mercaptopropyltrimethoxysilane, 20 parts of gallium-indium alloy, and 70 parts of silicon carbide with an aspect ratio of 100:1 according to weight. The modifier is added into a mortar containing gallium-indium alloy and silicon carbide and ground until a powdered modified liquid metal / silicon carbide hybrid filler is obtained.

[0045] Preparation process of thermally conductive silicone rubber composite material with flexible surface:

[0046] (1) mixing liquid metal particles and liquid metal / silicon carbide hybrid filler in a mass ratio of 1:3, adding the mixture to n-hexane solvent, methyl butynol and silicone rubber matrix to prepare a filler suspension in a weight ratio of: 80 parts of filler, 18 parts of vinyl siloxane-based silicone rubber, 2 parts of hydrogen siloxane-based silicone rubber and 0.05 parts of methyl butynol;

[0047] (2) pouring the suspension into a mold, volatilizing the excess solution in a vacuum distillation device at 40° C. and 0.01 kPa, and achieving graded sedimentation of the filler through the solvent volatilization process. The lower layer of liquid metal particles are enriched to form a flexible surface layer due to their large particle size and fast sedimentation rate, and the upper layer of mixed fillers are arranged horizontally due to their small density and slow sedimentation rate driven by interfacial tension and capillary action;

[0048] (3) After the solvent evaporates completely, the composite material is cured at 70°C to form a layered structure.

[0049] Embodiment 2:

[0050] Preparation process of liquid metal particles: According to weight, 5 parts of mercaptopropyl triethoxysilane and 95 parts of gallium indium tin alloy are added. The modifier is added into a mortar containing gallium indium tin alloy and ground until the surface of the liquid metal particles is uniformly modified. Liquid metal particles with a particle size of 5 to 15 μm are screened through a sieve.

[0051] Preparation process of modified liquid metal / silicon carbide hybrid filler: The modified liquid metal / silicon carbide hybrid filler comprises 8 parts of mercaptopropylmethyldiethoxysilane, 15 parts of gallium indium tin alloy, and 77 parts of silicon carbide with an aspect ratio of 100:1. The modifier is added to the gallium indium tin alloy and silicon carbide and ground until a powdered modified liquid metal / silicon carbide hybrid filler is obtained.

[0052] Preparation process of thermally conductive silicone rubber composite material with flexible surface:

[0053] (1) mixing liquid metal particles and liquid metal / silicon carbide hybrid filler in a mass ratio of 1:4, adding tetrahydrofuran solvent, acetylene cyclohexanol and silicone rubber matrix to prepare a filler suspension, the weight ratio of which is: 70 parts of filler, 25 parts of vinyl siloxane silicone rubber, 5 parts of hydrogen siloxane silicone rubber, and 0.1 parts of acetylene cyclohexanol;

[0054] (2) pouring the suspension into a mold and volatilizing the solvent in a vacuum distillation device at 30° C. and 0.05 kPa;

[0055] (3) After the solvent is completely volatilized, the mixture is cured at 100°C to obtain a layered structure composite material.

[0056] Embodiment 3:

[0057] Preparation process of liquid metal particles: According to weight, 3 parts of mercaptopropylmethyldimethoxysilane, 90 parts of gallium, and 10 parts of indium. The modifier is added to the gallium-indium alloy, ground and screened to obtain liquid metal particles with a particle size of 10 to 20 μm.

[0058] Preparation process of modified liquid metal / silicon carbide hybrid filler: The hybrid filler is composed of 6 parts of mercaptopropylmethyldimethoxysilane, 20 parts of gallium-indium alloy, and 74 parts of silicon carbide with an aspect ratio of 100:1. After modification, a powder filler is obtained.

[0059] Preparation process of thermally conductive silicone rubber composite material with flexible surface:

[0060] (1) Liquid metal particles and mixed fillers are mixed in a mass ratio of 1:5, and toluene solvent is added 、 A suspension is prepared in methyl butynol and silicone rubber matrix, with a weight ratio of 60 parts of filler, 30 parts of vinyl siloxane silicone rubber, 9.5 parts of hydrogen siloxane silicone rubber, and 0.5 parts of methyl butynol;

[0061] (2) casting in a mold and distilling the volatile solvent under reduced pressure at 50°C and 0.1 kPa;

[0062] (3) After volatilization, it is cured at 120°C to form a layered structure composite material.

[0063] Embodiment 4:

[0064] The preparation process of liquid metal particles: according to the weight parts, 4 parts of mercaptopropylmethyldiethoxysilane and 96 parts of gallium indium tin alloy are ground and screened to obtain liquid metal particles with a particle size of 1 to 10 μm.

[0065] Preparation process of modified liquid metal / silicon carbide hybrid filler: The hybrid filler is composed of 5 parts of mercaptopropyl trimethoxysilane, 10 parts of gallium-indium alloy, and 85 parts of silicon carbide with an aspect ratio of 100: 1. After modification and grinding, a uniform hybrid filler is obtained.

[0066] Preparation process of thermally conductive silicone rubber composite material with flexible surface:

[0067] (1) Liquid metal particles and mixed fillers are mixed in a mass ratio of 1:3, and added to dichloromethane solvent, tert-butyl cyclohexanol and silicone rubber matrix to prepare a suspension, and the weight ratio is: 80 parts of filler, 15 parts of vinyl siloxane silicone rubber, 5 parts of hydrogen siloxane silicone rubber, and 0.01 parts of tert-butyl cyclohexanol;

[0068] (2) distilling the volatile solvent under reduced pressure at 40° C. and 0.02 kPa;

[0069] (3) Finally, the composite material is cured at 70°C to form a layered structure.

[0070] Embodiment 5:

[0071] Preparation process of liquid metal particles: According to weight, 1 part of mercaptopropyl triethoxysilane and 99 parts of gallium-indium alloy are ground and screened to obtain liquid metal particles with a particle size of 5 to 15 μm.

[0072] Preparation process of modified liquid metal / silicon carbide hybrid filler: The hybrid filler components are 6 parts of mercaptopropylmethyldimethoxysilane, 15 parts of gallium-indium alloy, and 79 parts of silicon carbide with an aspect ratio of 100:1, to obtain a modified filler.

[0073] Preparation process of thermally conductive silicone rubber composite material with flexible surface:

[0074] (1) Liquid metal particles and mixed fillers are mixed in a mass ratio of 1:5, and n-hexane solvent, phenyl butynol and silicone rubber matrix are added to prepare a suspension, and the weight ratio is: filler 75 parts, vinyl siloxane silicone rubber 19 parts, hydrogen siloxane silicone rubber 6 parts, phenyl butynol 0.5 parts;

[0075] (2) distilling the volatile solvent under reduced pressure at 35°C and 0.03 kPa;

[0076] (3) The curing temperature is controlled at 90°C.

[0077] Embodiment 6:

[0078] The preparation process of liquid metal particles: according to the weight parts, 8 parts of mercaptopropylmethyldiethoxysilane and 92 parts of gallium-indium alloy are ground and screened to obtain particles with a particle size of 15 to 20 μm.

[0079] Preparation process of modified liquid metal / silicon carbide hybrid filler: The hybrid filler consists of 7 parts of mercaptopropyltrimethoxysilane, 18 parts of gallium indium tin alloy, and 75 parts of silicon carbide with an aspect ratio of 100:1 to obtain a modified filler.

[0080] Preparation process of thermally conductive silicone rubber composite material with flexible surface

[0081] (1) Liquid metal particles and mixed fillers are mixed in a mass ratio of 1:3, and tetrahydrofuran solvent, dimethyl acetylene alcohol and silicone rubber matrix are added to prepare a suspension, and the weight ratio is: 65 parts of filler, 25 parts of vinyl siloxane silicone rubber, 10 parts of hydrogen siloxane silicone rubber, and 0.3 parts of dimethyl acetylene alcohol;

[0082] (2) vacuum distillation at 30°C and 0.01 kPa;

[0083] (3) Finally, the mixture was cured at 120°C.

[0084] Embodiment 7-11

[0085] On the basis of Example 1, the aspect ratios of silicon carbide in this example are 3:1, 50:1, 300:1, 500:1, and 1000:1 respectively; the rest are the same.

[0086] Examples 12-14

[0087] On the basis of Example 1, in the preparation process of liquid metal particles in this example, the amounts of mercaptopropyltrimethoxysilane and gallium-indium alloy used are: 10 parts, 90 parts, 5 parts, 95 parts and 1 part, 99 parts respectively; the rest are the same.

[0088] Examples 15-16

[0089] On the basis of Example 1, the modified liquid metal / silicon carbide mixed filler components in this example are calculated by weight, and the amounts of mercaptopropyltrimethoxysilane, gallium-indium alloy and silicon carbide are: 1 part, 9 parts, 90 parts, 8 parts, 23 parts, 69 parts respectively; the rest are the same.

[0090] Examples 18-19

[0091] On the basis of Example 1, in the preparation process of the thermally conductive silicone rubber composite material with flexible surface in this embodiment, the mass ratios of liquid metal particles and liquid metal / silicon carbide mixed filler are 1:4 and 1:5; the rest are the same.

[0092] Embodiment 20

[0093] On the basis of Example 1, the amounts of the components in this example are: 60 parts of filler, 30 parts of vinyl siloxane-based silicone rubber, 10 parts of hydrogen siloxane-based silicone rubber, and 0.01 parts of inhibitor; the rest are the same.

[0094] Comparative Example 1

[0095] The preparation process of liquid metal particles and the preparation process of modified liquid metal / silicon carbide mixed filler are the same as those in Example 1. The amounts of filler, vinyl siloxane-based silicone rubber, hydrogen siloxane-based silicone rubber, and inhibitor in the thermally conductive silicone rubber composite material are also the same as those in Example 1, except that the preparation process directly adopts a mechanical mixing method for blending the components, and then directly cures them at 70°C.

[0096] Comparative Example 2

[0097] Most of the steps are the same as Example 1, except that only the modified liquid metal / silicon carbide hybrid filler is added, and no liquid metal particles are added.

[0098] Comparative Example 3

[0099] Most of the steps are the same as those in Example 1, except that only liquid metal particles are added and no modified liquid metal / silicon carbide hybrid filler is added.

[0100] Comparative Example 4

[0101] Most of the steps are the same as Example 1, except that the modified liquid metal / silicon carbide mixed filler is replaced by a modified silicon carbide filler, and no liquid metal particles are added.

[0102] evaluate

[0103] The thermal conductivity and surface hardness of the thermally conductive silicone rubbers prepared in the above-mentioned Examples 1-6 and Comparative Examples 1-4 of the present invention are tested below. The results are shown in Table 1.

[0104] Table 1 Thermal conductivity and surface hardness of thermal conductive silicone rubber

[0105] Example Total amount of filler (parts) Thermal conductivity (W / mk) Shore A hardness 1 80 6.2 25 2 70 5.7 24 3 60 4.8 27 4 80 6.3 23 5 75 5.9 25 6 65 5.2 21 Comparative Example 1 80 2.6 34 Comparative Example 2 80 6.3 39 Comparative Example 3 80 1.8 20 Comparative Example 4 80 3.2 63

[0106] In the embodiment of the present invention, the amount of filler added is moderate, and the surface hardness is effectively reduced while maintaining high thermal conductivity through the synergistic effect of liquid metal particles and liquid metal / silicon carbide hybrid fillers. This balance enables the material to have both high thermal conductivity and flexibility. The layered structure design of the present invention forms a flexible liquid metal layer in the lower layer, and at the same time utilizes the high deformation ability of the liquid metal to reduce the surface hardness, especially the surface hardness of Examples 1-6 is up to 27 Shore A. In contrast, the hardness of Comparative Example 1 reaches 34, and the thermal conductivity is only 2.6W / (m·K), which verifies that it is difficult to achieve high flexibility and high thermal conductivity without stratification and orientation design. Compared with Example 1, Comparative Example 2 proves the role of the liquid metal layer in reducing the hardness of the system, and Comparative Example 3 proves the role of the horizontally oriented modified liquid metal / silicon carbide hybrid filler in improving the thermal conductivity. Compared with Comparative Example 2, Comparative Example 4 proves the role of liquid metal in reducing the hardness of the system and improving the thermal conductivity of the material, because the liquid metal particles can bridge silicon carbide and promote the formation of thermal conductive paths.

[0107] The embodiments described above are only for illustrating the preferred implementation of the present invention. It should be pointed out that, for ordinary technicians in this field, several improvements can be made without departing from the scope of protection of this patent, and these improvements should also be regarded as within the scope of protection of this patent.

Claims

1. A surface-flexible thermally conductive silicone rubber composite material, characterized in that: It comprises a flexible interface layer and a heat conduction channel layer located above the flexible interface layer, wherein the flexible interface layer is formed by enrichment of liquid metal particles, and the heat conduction channel layer is formed by horizontally oriented modified liquid metal / silicon carbide mixed filler.

2. The surface-flexible thermally conductive silicone rubber composite material according to claim 1, characterized in that: The particle size of the liquid metal particles is 1 to 20 μm.

3. The surface-flexible thermally conductive silicone rubber composite material according to claim 1, characterized in that: The liquid metal comprises one or a combination of two or more of gallium-indium alloy and gallium-indium-tin alloy. The liquid metal particles are modified by grinding 1-10 parts of mercaptosilane coupling agent and 90-99 parts of liquid metal together to improve the compatibility of the liquid metal with the silicone rubber matrix.

4. The surface-flexible thermally conductive silicone rubber composite material according to claim 1, characterized in that: The preparation method of the modified liquid metal / silicon carbide hybrid filler comprises the following steps: adding 1-10 parts of a mercaptosilane coupling agent to 90-99 parts of a liquid metal and silicon carbide mixed filler by weight, and performing surface modification on the liquid metal and silicon carbide mixed filler by grinding to obtain the modified liquid metal / silicon carbide hybrid filler.

5. The surface-flexible thermally conductive silicone rubber composite material according to claim 4, characterized in that: The mass ratio of the modified liquid metal to silicon carbide in the modified liquid metal / silicon carbide mixed filler is 1:3 to 1:10, the silicon carbide adopts a whisker-like structure, and the aspect ratio of the silicon carbide is 3:1 to 1000:

1.

6. The surface-flexible thermally conductive silicone rubber composite material according to claim 4, characterized in that: The mercaptosilane coupling agent includes one or a combination of two or more mercaptosilanes such as mercaptopropyltrimethoxysilane, mercaptopropyltriethoxysilane, mercaptopropylmethyldimethoxysilane, and mercaptopropylmethyldiethoxysilane.

7. A method for preparing the surface flexible thermally conductive silicone rubber composite material according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1. Mixing liquid metal particles with liquid metal / silicon carbide mixed filler in a mass ratio of 1:3 to 1:5 to obtain a mixture; adding the mixture and an inhibitor to a solvent and a silicone rubber matrix to obtain a filler suspension; the silicone rubber matrix is ​​composed of vinyl siloxane-based silicone rubber and hydrogen siloxane-based silicone rubber; According to the weight percentage, the liquid metal / silicon carbide mixed filler is 60-80 parts, the vinyl siloxane silicone rubber is 15-30 parts, the hydrogen siloxane silicone rubber is 1-10 parts, and the inhibitor is 0.01-0.5 parts; S2, pouring the filler suspension into a mold, and after reduced pressure distillation, the filler in the filler suspension is graded and settled, and the liquid metal / silicon carbide mixed filler is horizontally oriented; S3. After the solvent in the filler suspension is completely volatilized, the suspension is cured at a temperature of 70 to 120° C. to obtain the surface-flexible thermally conductive silicone rubber composite material.

8. The preparation method according to claim 7, characterized in that: The solvent is any one of toluene, dichloromethane, tetrahydrofuran and n-hexane, or a combination of two or more thereof.

9. The preparation method according to claim 7, characterized in that: The inhibitor includes any one or a combination of two or more of inhibitors such as methyl butynol, acetylene cyclohexanol, tert-butyl cyclohexanol, phenyl butynol, and dimethyl acetylene alcohol.

10. The preparation method according to claim 7, characterized in that: The distillation temperature of the reduced pressure distillation is 30-50° C. and the pressure is 0.01-0.1 kPa.

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