Electrically and thermally conductive silicone rubber material and preparation method thereof

Abstract

The preparation method comprises the following steps: carrying out surface activation treatment on boron nitride nanosheets, and carrying out coupling agent modification treatment on silver-coated carbon nanotubes, so as to respectively obtain surface-activated boron nitride nanosheets and modified silver-coated carbon nanotubes; the preparation method comprises the following steps: copolymerizing a phenyl siloxane monomer and methyl vinyl siloxane to prepare a modified silicone rubber matrix; mixing the surface-activated boron nitride nanosheets and aluminum oxide nanowires according to a preset proportion, dispersing the mixture into a modified silicone rubber matrix, and performing low-speed mixing to form a heat-conducting phase composite rubber material; adding the modified silver-coated carbon nanotubes into the heat-conducting phase composite rubber material, performing high-speed mixing to obtain an electric-conducting and heat-conducting mixed rubber material, then applying a directional magnetic field to induce filler arrangement, and performing gradient curing treatment to obtain the electric-conducting and heat-conducting silicone rubber material. The compatibility of isotropic heat conduction and planar electrical conductivity of the material is realized, meanwhile, high flexibility and elasticity are kept, and the comprehensive performance requirements of a high-power electronic device on heat dissipation and electromagnetic shielding are met.

Description

Technical Field

[0001] The present invention relates to the technical field of silicone rubber materials, and in particular to a conductive and thermally conductive silicone rubber material and a preparation method thereof. Background Art

[0002] With the rapid development of 5G communications, new energy vehicles, and high-density integrated circuits, the power density of electronic devices has increased dramatically, and heat dissipation efficiency and electromagnetic interference have become increasingly prominent. Traditional heat dissipation materials (such as metals or ceramics) lack flexibility and cannot shield electromagnetic waves, making them difficult to meet the needs of flexible electronics and wearable devices. While conventional conductive silicone rubber has electromagnetic shielding capabilities, its thermal conductivity is generally less than 1 W / m·K, making it ineffective in dissipating heat. Therefore, developing silicone rubber materials with both high thermal conductivity and electrical conductivity has become a core technical direction for resolving the contradiction between thermal management and electromagnetic compatibility in high-power devices.

[0003] Currently, conductive silicone rubber mainly achieves conductivity by adding conductive fillers (such as carbon nanotubes and silver powder). However, a high filler content is required to achieve low resistivity, which results in a decrease in matrix crosslinking density, a surge in material hardness (Shore A hardness > 90), and a significant deterioration in flexibility. For example, high conductive silicone rubber uses a silver powder / carbon nanotube compound, and although the resistivity is as low as 5×10 2 Ω·cm, but the thermal conductivity is only 1.2 W / m·K and the elongation at break is insufficient, failing to simultaneously meet the requirements for heat dissipation and deformation resistance. The root cause is that excessive introduction of a single conductive filler hinders the construction of a thermal network, and the interface between the rigid filler and the flexible matrix is weak, resulting in a mutual restriction between thermal conductivity, electrical conductivity, and flexibility. This contradiction has become a key technical bottleneck restricting the reliability of high-performance electronic devices.

[0004] In view of this, it is necessary to improve the conductive silicone rubber manufacturing technology in the existing technology to solve the technical problem of insufficient comprehensive performance of a single material in high-power electronic devices. Summary of the Invention

[0005] The purpose of the present invention is to provide a high tensile strength silicone material and a preparation method thereof to solve the above technical problems.

[0006] To achieve this object, the present invention adopts the following technical solutions: A method for preparing an electrically conductive and thermally conductive silicone rubber material comprises the following steps: The boron nitride nanosheets are surface activated, and the silver-coated carbon nanotubes are modified with a coupling agent to obtain surface-activated boron nitride nanosheets and modified silver-coated carbon nanotubes, respectively. Phenylsiloxane monomer and methylvinylsiloxane are copolymerized to prepare a modified silicone rubber matrix; The surface-activated boron nitride nanosheets and aluminum oxide nanowires are mixed in a preset ratio, dispersed into the modified silicone rubber matrix, and kneaded at a low speed to form a heat-conducting phase composite rubber material; Adding the modified silver-coated carbon nanotubes to the thermally conductive composite rubber material, and mixing at high speed to obtain a conductive and thermally conductive composite rubber material; A directional magnetic field is applied to the conductive and thermally conductive mixed rubber material to induce filler arrangement, and a gradient curing process is performed to obtain a conductive and thermally conductive silicone rubber material.

[0007] Optionally, the surface activation process of the boron nitride nanosheets is specifically as follows: The boron nitride nanosheets are placed in a vacuum plasma reaction chamber and treated with a mixture of oxygen and argon for 30-40 minutes to obtain hydroxylated boron nitride nanosheets; The hydroxylated boron nitride nanosheets are dispersed in anhydrous ethanol, silane coupling agent KH-560 is added, ultrasonic stirring is performed at 60° C. for 2 hours, centrifugation is performed, and then drying is performed to obtain boron nitride nanosheets with epoxy groups grafted on the surface.

[0008] Optionally, the preparation process of the modified silver-coated carbon nanotubes is: Immersing the carbon nanotubes in a silver nitrate solution, adding ascorbic acid as a reducing agent, and reacting in a 50°C water bath for 1 hour to uniformly coat the surface of the carbon nanotubes with silver nanoparticles, thereby obtaining a primary product of silver-coated carbon nanotubes; The silver-coated carbon nanotube primary product is placed in a toluene solvent, a mercaptosilane coupling agent KH-590 is added, and the mixture is refluxed at 80° C. for 4 hours under nitrogen protection to graft the mercapto groups onto the surface of the silver layer, thereby forming a mixed solution; The mixed solution after the reaction is centrifuged and separated, and washed with acetone for multiple times to remove the unreacted coupling agent. The mixed solution is then vacuum dried to obtain thiol-functionalized modified silver-coated carbon nanotubes.

[0009] Optionally, the phenylsiloxane monomer is any one of diphenyldimethoxysilane, methylphenyldiethoxysilane, phenyltrimethoxysilane, and tetraphenylcyclotetrasiloxane; The methylvinylsiloxane is any one of methylvinyldimethoxysilane, methylvinyldiethoxysilane, and vinyltrimethoxysilane; Wherein, the mass ratio of the phenylsiloxane monomer to the methylvinylsiloxane is 1:1.5 to 1:4.

[0010] Optionally, the copolymerization of phenylsiloxane monomer and methylvinylsiloxane to prepare a modified silicone rubber matrix specifically includes: Phenylsiloxane monomer and methylvinylsiloxane monomer were mixed in a molar ratio of 1:4, a catalyst was added, and the mixture was dehydrated under vacuum conditions for 30 minutes to obtain a preactivated mixed monomer; The preactivated mixed monomers were placed in a reaction kettle, heated to 80° C. under nitrogen protection, and stirred for reaction for 2 hours to generate an oligomer prepolymer; Adding a hydrogenated silicone oil crosslinker and an inhibitor, methyl butynol, to the oligomer prepolymer, controlling the molar ratio of hydrogenated groups to vinyl groups to be 1.2:1, and stirring at a low speed at 60° C. for 1 hour to form a uniform colloid; The colloid was injected into a vacuum degassing machine and degassed at -0.1 MPa and 50° C. for 40 minutes to obtain a modified silicone rubber matrix without bubbles.

[0011] Optionally, the surface-activated boron nitride nanosheets and aluminum oxide nanowires are mixed in a preset ratio, dispersed into the modified silicone rubber matrix, and kneaded at a low speed to form a thermally conductive composite rubber material, specifically comprising: The surface-activated boron nitride nanosheets and aluminum oxide nanowires were pre-mixed in a mass ratio of 3:1, anhydrous ethanol was added, and ultrasonic treatment was performed for 20 minutes to form a uniform pre-dispersed slurry of thermal conductive filler; The thermal conductive filler pre-dispersed slurry was mixed with the modified silicone rubber matrix in a volume ratio of 1:5, and stirred at a low speed of 100 rpm at 40° C. for 30 minutes to allow the filler to initially infiltrate the matrix; The impregnated mixture was transferred to a mixer, and the temperature of the first stage was controlled at 60°C and the temperature of the second stage was controlled at 80°C. The mixture was mixed in sections at a preset speed. The material was first conveyed through a wide-pitch screw, and then switched to a narrow-pitch screw to apply shear dispersion.

[0012] Optionally, the step of mixing at a preset speed includes first conveying the material through a wide-pitch screw and then switching to a narrow-pitch screw to apply shear dispersion, and then further includes: Inject xylene solvent into the mixer, adjust the solid content to 40 wt%, and use an ultrasonic probe to intermittently assist dispersion, ultrasonicating for 5 minutes each time with a 2-minute interval, and repeat for 3 or more times; Monitor the viscosity of the rubber compound at the mixer outlet in real time. When the viscosity reaches the preset value, stop mixing and transfer the rubber compound to a sealed container and let it stand for defoaming for 1 hour. The defoamed rubber material is passed through a vacuum devolatilization device to remove the residual solvent, and is rolled into a sheet with a thickness of 2 mm by a calender to obtain a heat-conducting phase composite rubber material.

[0013] Optionally, the modified silver-coated carbon nanotubes are added to the thermally conductive composite rubber material, and mixed at high speed to obtain a conductive and thermally conductive composite rubber material, specifically comprising: The heat-conducting phase composite rubber material is preheated to 50° C. and added to an internal mixer, and stirred at a preset speed under nitrogen protection to form a rubber carrier with enhanced fluidity; The modified silver-coated carbon nanotubes were added to the sizing agent carrier in equal amounts three times, and after each addition, the mixture was switched to a high-speed shear mode of 200 rpm for mixing for 8 minutes, while acetone solvent was injected to assist in dispersion, so that the conductive filler was exfoliated from the agglomerates and embedded in the gaps of the thermal conductive network; After the mixing is completed, the rubber material is transferred to a vacuum degassing tank and degassed at -0.06 MPa and 60°C for 20 minutes to obtain a bubble-free conductive and thermally conductive mixed rubber material.

[0014] Optionally, applying a directional magnetic field to the conductive and thermally conductive mixed rubber material to induce filler alignment, and performing a gradient curing process to obtain a conductive and thermally conductive silicone rubber material, specifically comprising: The conductive and thermal conductive mixed rubber material is injected into a metal mold with an electromagnetic coil, the mold is preheated to 60° C., and a horizontal static magnetic field of a preset strength is applied for 10 minutes to align the silver-coated carbon nanotubes along the XY plane to form a pre-oriented rubber material; The pre-oriented rubber compound and the mold were transferred to a hot press and pre-cured at 0.5 MPa pressure and 80°C for 1 hour, and a 0.8 T pulsed magnetic field was simultaneously applied to further enhance the filler orientation stability; The hot press is released and the temperature is raised to 120° C., then raised to 150° C. at a rate of 2° C. / min, and maintained for 2 hours to fully crosslink the phenylsiloxane side chains to form a primary cured product; The primary solidified body is placed in a vacuum annealing furnace and annealed at 180° C. for 30 minutes under a nitrogen atmosphere to eliminate internal stress and enhance filler-matrix interface bonding; After cooling to room temperature, the mold is demoulded, edge overflow is removed by cutting, and the surface is cleaned to obtain a silicone rubber material with anisotropic electrical and thermal conductivity.

[0015] The present invention also provides a conductive and thermally conductive silicone rubber material, which is prepared by the above-mentioned method for preparing the conductive and thermally conductive silicone rubber material. The conductive and thermally conductive silicone rubber material specifically comprises: The matrix component is a modified silicone rubber matrix formed by copolymerization of phenylsiloxane monomer and methylvinylsiloxane; Thermally conductive filler, a three-dimensional thermal conductive network constructed of surface-activated boron nitride nanosheets and aluminum oxide nanowires in a 3:1 mass ratio; The conductive filler, mercapto-functionalized silver-coated carbon nanotubes, is oriented along the XY plane to form a continuous conductive path.

[0016] Compared with the prior art, the present invention has the following beneficial effects: first, surface activation treatment of boron nitride nanosheets and coupling agent-modified silver-coated carbon nanotubes is performed to enhance the interface compatibility of the filler; then, phenylsiloxane monomer and methylvinylsiloxane are copolymerized to form a high-temperature resistant modified silicone rubber matrix; then, the activated boron nitride nanosheets and alumina nanowires are dispersed in proportion into the matrix and mixed at a low speed to construct a three-dimensional heat-conducting network; then, the modified silver-coated carbon nanotubes are introduced and mixed at a high speed to achieve uniform distribution of the conductive phase; finally, a directional magnetic field is used to induce the plane of the conductive filler Directed arrangement, combined with a gradient curing process to optimize the matrix cross-linking density, thereby producing a silicone rubber material with high thermal conductivity, electrical conductivity and flexibility; this method improves the interfacial bonding strength between the filler and the matrix through surface activation and coupling agent modification, avoids agglomeration and enhances the continuity of the thermal / electrical conductive channels; a staged mixing strategy and magnetic field-induced directional arrangement, combined with a gradient curing process to regulate the matrix cross-linking density, achieves the compatibility of isotropic thermal conductivity and planar electrical conductivity of the material, while maintaining high flexibility, meeting the comprehensive performance requirements of high-power electronic devices for heat dissipation and electromagnetic shielding. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] The structures, proportions, sizes, etc. depicted in the drawings of this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with this technology. They are not intended to limit the conditions under which the present invention can be implemented and therefore have no substantive technical significance. Any structural modifications, changes in proportional relationships, or adjustments in size should still fall within the scope of the technical contents disclosed in the present invention without affecting the effects and objectives that can be achieved by the present invention.

[0019] Figure 1 This is a schematic diagram of a process for preparing the conductive and thermally conductive silicone rubber material of the first embodiment; Figure 2 This is the second flow chart of the method for preparing the conductive and thermally conductive silicone rubber material of the first embodiment. DETAILED DESCRIPTION

[0020] In order to make the purpose, features, and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0021] In the description of the present invention, it should be understood that the terms "upper," "lower," "top," "bottom," "inner," "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of the present invention and simplify the description. They are not intended to indicate or imply that the devices or elements referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. It should be noted that when a component is considered to be "connected" to another component, it may be directly connected to the other component or there may be a centrally located component.

[0022] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0023] Example 1: Combine Figure 1 and Figure 2 As shown, the present invention provides a method for preparing an electrically conductive and thermally conductive silicone rubber material, comprising the following steps: S1, performing surface activation treatment on boron nitride nanosheets and modifying silver-coated carbon nanotubes with a coupling agent to obtain surface-activated boron nitride nanosheets and modified silver-coated carbon nanotubes, respectively; Surface activation treatment of boron nitride nanosheets (such as plasma oxidation or hydroxylation modification) can enhance their surface polarity, improve the interfacial bonding strength with the silicone rubber matrix, and prevent the agglomeration of thermal conductive fillers; coupling agent modification of silver-coated carbon nanotubes (such as silane coupling agent grafting) can improve the compatibility of conductive fillers and the matrix through chemical bonding, ensuring stable dispersion of the conductive network.

[0024] S2, copolymerizing phenylsiloxane monomer and methylvinylsiloxane to prepare a modified silicone rubber matrix; By copolymerizing phenylsiloxane monomer with methylvinylsiloxane and introducing phenyl side chains, the high temperature resistance and mechanical strength of the matrix can be improved, while retaining the flexibility of the methylvinyl chain segment, forming a modified silicone rubber matrix with both rigidity and elasticity, providing a stable carrier for subsequent filler dispersion.

[0025] S3, mixing the surface-activated boron nitride nanosheets and aluminum oxide nanowires in a preset ratio, dispersing them into the modified silicone rubber matrix, and kneading at a low speed to form a thermally conductive composite rubber material; Surface-activated boron nitride nanosheets and alumina nanowires are mixed in proportion and dispersed into the matrix. Alumina nanowires act as "bridging fibers" and are interspersed in the gaps between boron nitride sheets. Through low-speed mixing, a three-dimensional continuous thermal conductive network is formed, thereby improving the overall thermal conductivity of the material.

[0026] S4, adding the modified silver-coated carbon nanotubes to the thermal conductive phase composite rubber material, and mixing at high speed to obtain a conductive and thermal conductive composite rubber material; Modified silver-coated carbon nanotubes are added to the thermal conductive phase composite rubber, and the conductive filler agglomerates are peeled off through high-speed shear mixing, so that they are evenly embedded in the gaps of the thermal conductive network to form a penetrating conductive path, thereby achieving a synergistic improvement in the electrical and thermal conductivity of the material.

[0027] S5, applying a directional magnetic field to the conductive and thermally conductive mixed rubber material to induce filler alignment, and performing a gradient curing treatment to obtain a conductive and thermally conductive silicone rubber material.

[0028] Applying a directional magnetic field induces the conductive fillers to arrange in a specific direction (such as planar distribution), thereby enhancing the continuity of the conductive path; gradient curing controls the cross-linking density by increasing the temperature in stages, avoiding matrix shrinkage that causes disordered filler arrangement, and ultimately obtaining a silicone rubber material with both anisotropic electrical and thermal conductivity and high flexibility.

[0029] The working principle of the invention is as follows: first, surface activation treatment of boron nitride nanosheets and coupling agent-modified silver-coated carbon nanotubes is performed to enhance the interfacial compatibility of the filler; then, phenylsiloxane monomer and methylvinylsiloxane are copolymerized to form a high-temperature resistant modified silicone rubber matrix; then, the activated boron nitride nanosheets and alumina nanowires are dispersed in proportion into the matrix and mixed at a low speed to construct a three-dimensional heat-conducting network; then, the modified silver-coated carbon nanotubes are introduced and mixed at a high speed to achieve uniform distribution of the conductive phase; finally, a directional magnetic field is used to induce the planar oriented arrangement of the conductive filler. The gradient curing process is combined with the optimization of the matrix cross-linking density to produce a silicone rubber material with high thermal conductivity, electrical conductivity and flexibility. This method improves the interfacial bonding strength between the filler and the matrix through surface activation and coupling agent modification, avoids agglomeration and enhances the continuity of the thermal / electrical conductive channels. The phased mixing strategy and magnetic field-induced directional arrangement are combined with the gradient curing process to regulate the matrix cross-linking density, achieving the compatibility of isotropic thermal conductivity and planar electrical conductivity of the material while maintaining high flexibility to meet the multiple application requirements of high-power electronic devices for heat dissipation and electromagnetic shielding.

[0030] In this embodiment, it is specifically described that the surface activation process of the boron nitride nanosheets is as follows: S11, placing the boron nitride nanosheets in a vacuum plasma reaction chamber, and introducing a mixed gas of oxygen and argon for 30-40 minutes to obtain hydroxylated boron nitride nanosheets; Boron nitride nanosheets are treated in a vacuum plasma reaction chamber using a mixture of oxygen and argon (1:1 by volume). Oxygen introduces hydroxyl groups on the surface of the nanosheets through chemical oxidation, while argon removes impurities and increases surface roughness through physical bombardment. The synergistic effect of the two significantly improves the hydroxylation efficiency. The design of 200-250W power and 30-40 minutes of treatment time can not only fully activate the surface, but also avoid excessive bombardment that may cause the boron nitride layered structure to peel off, ensuring the subsequent chemical bonding strength with the substrate.

[0031] S12, dispersing hydroxylated boron nitride nanosheets in anhydrous ethanol, adding silane coupling agent KH-560, stirring ultrasonically at 60° C. for 2 hours, washing by centrifugation and drying to obtain boron nitride nanosheets with epoxy groups grafted on the surface.

[0032] Hydroxylated boron nitride nanosheets were dispersed in anhydrous ethanol, a solvent with moderate polarity that prevented nanosheet aggregation and promoted the hydrolysis and condensation of the silane coupling agent KH-560. Ultrasonic stirring at 60°C for two hours drove the KH-560 molecules to penetrate the interlayers of the boron nitride and graft epoxy groups, achieving a grafting rate exceeding 75%, significantly enhancing the compatibility of the filler with the phenylsiloxane matrix. Three centrifugal washes, followed by vacuum drying at 60°C, completely removed the free coupling agent, preventing any residue from interfering with subsequent mixing and dispersion, ensuring uniform distribution of the thermally conductive filler within the matrix.

[0033] In this embodiment, it is further explained that the preparation process of modified silver-coated carbon nanotubes is: S13, immersing the carbon nanotubes in a silver nitrate solution, adding a reducing agent ascorbic acid, and reacting in a 50° C. water bath for 1 hour to uniformly coat the surface of the carbon nanotubes with silver nanoparticles, thereby obtaining a primary product of silver-coated carbon nanotubes; A 0.1M silver nitrate solution and ascorbic acid (molar ratio 1:1.5) are reacted in a 50°C water bath for one hour. This mildly reducing environment allows for uniform coating of silver nanoparticles on the carbon nanotube surface, resulting in a dense, pore-free silver layer. The appropriate excess amount of ascorbic acid ensures complete reduction of the Ag⁺, preventing the risk of electrochemical corrosion from residual unreacted ions. A controlled temperature of 50°C inhibits excessive growth of silver particles and prevents conductive path disruption caused by uneven particle size. This process improves the conductivity of the silver-coated carbon nanotubes while retaining the carbon nanotubes' inherent high thermal conductivity.

[0034] S14, placing the primary product of silver-coated carbon nanotubes in a toluene solvent, adding a mercaptosilane coupling agent KH-590, and refluxing at 80° C. for 4 hours under nitrogen protection to graft the mercapto groups onto the surface of the silver layer, thereby forming a mixed solution; Toluene was used as the solvent for dispersing the silver-coated carbon nanotubes. Its non-polar properties provide excellent compatibility with KH-590, promoting the directional adsorption of mercaptosilane molecules on the silver surface. Refluxing at 80°C for 4 hours under nitrogen accelerated the hydrolysis and condensation reaction of KH-590 through thermal activation, covalently grafting the mercapto groups (-SH) onto the silver surface while preventing conductivity degradation caused by silver oxidation. This step imparts a strong interfacial bond between the conductive filler and the silicone rubber matrix, preventing delamination of the silver layer during mixing or molding, and ensuring the long-term stability of the conductive network.

[0035] S15, centrifuging the reaction mixture, washing it with acetone for multiple times to remove the unreacted coupling agent, and vacuum drying it to obtain thiol-functionalized modified silver-coated carbon nanotubes.

[0036] High-speed centrifugation at 10,000 rpm for 15 minutes efficiently separated the functionalized filler from the reaction byproducts. Three acetone washes (10 minutes each) leveraged its strong polarity to dissolve unreacted KH-590, ensuring the filler surface was chemically pure (free coupling agent residue <0.5 wt%). Vacuum drying at 60°C for 12 hours thoroughly removed the solvent without melting the silver layer, maintaining the structural integrity of the carbon nanotubes and the continuity of the silver coating.

[0037] In this embodiment, the phenylsiloxane monomer is any one of diphenyldimethoxysilane, methylphenyldiethoxysilane, phenyltrimethoxysilane, and tetraphenylcyclotetrasiloxane; the methylvinylsiloxane is any one of methylvinyldimethoxysilane, methylvinyldiethoxysilane, and vinyltrimethoxysilane.

[0038] Among them, the mass ratio of phenylsiloxane monomer to methylvinylsiloxane is 1:1.5 to 1:4. By adjusting the ratio of phenyl and vinyl chain segments, the rigidity and flexibility of the matrix are balanced. When the mass ratio is lower than 1:1.5, excessive phenyl can easily lead to brittleness of the matrix, and when it is higher than 1:4, excessive vinyl will result in insufficient high temperature resistance.

[0039] In this embodiment, it is specifically described that step S2 specifically includes: S21, mixing a phenylsiloxane monomer and a methylvinylsiloxane monomer in a molar ratio of 1:4, adding a catalyst, and dehydrating the mixture under vacuum conditions for 30 minutes to obtain a preactivated mixed monomer; Phenylsiloxane monomers are mixed with methylvinylsiloxane monomers in a 1:4 molar ratio. The rigid structure of the phenyl side chains and the flexible elasticity of the methylvinyl segments are synergistically designed to form a rigid and flexible molecular framework within the matrix, providing a highly compatible carrier for subsequent filler dispersion. A 30-minute vacuum dehydration treatment effectively removes moisture and low-boiling impurities from the monomers, preventing the formation of byproducts during the polycondensation reaction. The addition of a catalyst (such as a platinum catalyst) precisely controls the reaction activity, ensuring the stability of the preactivated mixed monomers and laying the foundation for a controlled reaction for subsequent polymerization.

[0040] S22, placing the preactivated mixed monomer in a reaction kettle, heating to 80° C. under nitrogen protection and stirring for reaction for 2 hours to generate an oligomer prepolymer; Under nitrogen, the temperature was raised to 80°C and stirred for 2 hours. The nitrogen atmosphere isolated oxygen, preventing oxidation of the vinyl groups and the resulting decrease in crosslinking activity. The mild temperature of 80°C also avoided high-temperature decomposition of the phenyl side chains, ensuring a smooth polycondensation reaction. The stirring effect promoted uniform contact between the monomers, resulting in a low-molecular-weight oligomer prepolymer. Its moderate molecular weight distribution (PDI ≈ 1.5) retained active sites for subsequent crosslinking while avoiding processing difficulties caused by premature crosslinking, providing an ideal intermediate for controlled crosslinking.

[0041] S23, adding a hydrogenated silicone oil crosslinker and an inhibitor, methyl butynol, to the oligomer prepolymer, controlling the molar ratio of hydrogenated groups to vinyl groups to be 1.2:1, and stirring at a low speed at 60° C. for 1 hour to form a uniform colloid; A hydrogenated silicone oil crosslinker and vinyl group were added in a 1.2:1 molar ratio. The slightly excessive hydrogenated groups ensured a sufficient crosslinking reaction while suppressing matrix embrittlement caused by excessive crosslinking density. The addition of methylbutynol, an inhibitor, precisely inhibited the activity of the platinum catalyst, preventing premature crosslinking during mixing. Low-speed stirring at 60°C for one hour balanced crosslinking rate and dispersion uniformity, resulting in a colloid with rheological properties (viscosity approximately 2000 Pa·s) that was well-suited for subsequent degassing and filler dispersion processes, preventing air bubbles or filler sedimentation.

[0042] S24, injecting the colloid into a vacuum degassing machine, and degassing for 40 minutes at -0.1 MPa and 50° C. to obtain a modified silicone rubber matrix without bubbles.

[0043] Vacuum degassing was performed at -0.1 MPa and 50°C for 40 minutes. This low-pressure environment effectively removed microbubbles and residual solvent from the colloid. Controlling the temperature at 50°C maintained colloid fluidity, promoting bubble escape while also preventing pre-crosslinking reactions induced by high temperatures. The degassing significantly reduced the matrix porosity (<0.3%), improving surface finish and mechanical uniformity. This provided a defect-free carrier for the subsequent uniform dispersion of thermally and electrically conductive fillers, ensuring the stability of the final material's performance.

[0044] In this embodiment, it is specifically explained that step S3 specifically includes: S31, premixing surface-activated boron nitride nanosheets and aluminum oxide nanowires in a mass ratio of 3:1, adding anhydrous ethanol, and ultrasonically treating for 20 minutes to form a uniform thermal conductive filler pre-dispersed slurry; Vacuum degassing was performed at -0.1 MPa and 50°C for 40 minutes. This low-pressure environment effectively removed microbubbles and residual solvent from the colloid. Controlling the temperature at 50°C maintained colloid fluidity, promoting bubble escape while also preventing pre-crosslinking reactions induced by high temperatures. The degassing significantly reduced the matrix porosity (<0.3%), improving surface finish and mechanical uniformity. This provided a defect-free carrier for the subsequent uniform dispersion of thermally and electrically conductive fillers, ensuring the stability of the final material's performance.

[0045] S32, mixing the thermal conductive filler pre-dispersed slurry with the modified silicone rubber matrix in a volume ratio of 1:5, and stirring at a low speed of 100 rpm at 40° C. for 30 minutes to allow the filler to initially infiltrate the matrix; A pre-dispersed slurry of thermally conductive filler is mixed with the modified silicone rubber matrix in a 1:5 volume ratio. Low-proportion addition of the slurry avoids local overloading of the filler and ensures adequate coverage of the filler by the matrix. A low temperature of 40°C reduces the matrix viscosity, while low-speed stirring at 100 rpm for 30 minutes allows the filler to gradually penetrate the matrix and reduces shear damage to the nanostructure. This initially forms a "matrix-filler" interface, providing a stable material foundation for subsequent high-intensity mixing.

[0046] S33, the impregnated mixture is transferred to a mixer, the temperature of the first stage is controlled to be 60°C and the temperature of the second stage is controlled to be 80°C, and the mixture is mixed in stages at a preset speed. The material is first conveyed by a wide-pitch screw, and then switched to a narrow-pitch screw to apply shear dispersion.

[0047] Staged temperature control (60°C in Zone 1 and 80°C in Zone 2) matches the rheological properties required at different mixing stages. In the low-temperature zone (60°C), a wide-pitch screw gently conveys the material, preventing filler agglomeration due to shear overheating. In the high-temperature zone (80°C), a narrow-pitch screw applies high shear forces, exploiting the window of reduced matrix viscosity to achieve deep dispersion of the filler. This design balances dispersion efficiency with structural protection, preventing thermal conductivity loss caused by nanowire breakage or flake delamination.

[0048] S34, injecting xylene solvent into the mixer, adjusting the solid content to 40 wt%, and using an ultrasonic probe to intermittently assist in dispersion, sonicating for 5 minutes each time with a 2-minute interval, for 3 or more cycles; Xylene solvent was injected to adjust the solids content to 40wt%. The solvent's plasticizing effect reduced the system viscosity, improving filler mobility and dispersion uniformity during mixing. Intermittent ultrasonic assistance (5 minutes of ultrasound followed by 2 minutes of interval, three cycles) superimposed cavitation energy on mechanical shear, breaking through the energy barrier that prevents secondary filler aggregation. This, in particular, targeted the weakly bonded areas at the edges of the boron nitride flakes, significantly improving the continuity of the thermal conductivity network. The synergistic effect of the solvent and ultrasound maintained a tensile strength of >6MPa at a filler volume fraction of 35%.

[0049] S35, real-time monitoring of the viscosity of the rubber compound at the mixer outlet, stopping mixing when the viscosity reaches a preset viscosity value, and transferring the rubber compound to a sealed container for defoaming for 1 hour; Real-time monitoring of the compound viscosity (threshold set at 4000 ± 200 Pa·s) was used as an indirect indicator of dispersion uniformity, and mixing was dynamically terminated to prevent matrix molecular chain breakage caused by excessive shear. The compound was allowed to stand for one hour to defoam, utilizing its inherent leveling properties to expel microbubbles, reducing internal defects after curing (porosity <0.5%) and ensuring that filler arrangement during the subsequent magnetic field orientation process was not disturbed by bubbles.

[0050] S36, removing the residual solvent from the defoamed rubber material through a vacuum devolatilization device, and rolling it into a sheet with a thickness of 2 mm through a calender to obtain a heat-conducting phase composite rubber material.

[0051] The vacuum devolatilization device (-0.08MPa, 70℃) efficiently removes residual xylene solvent, avoiding matrix plasticization or interface weakening caused by solvent residue; when the calender rolls it into a 2mm sheet, the precise control of the roller gap and temperature (60℃) gives the material consistent thickness and surface flatness (roughness Ra <1μm), providing geometric constraints for the subsequent directional arrangement of conductive fillers, while adapting to the standardized requirements of electronic device packaging for material morphology.

[0052] In this embodiment, it is specifically explained that step S4 specifically includes: S41, preheating the heat-conducting phase composite rubber material to 50° C. and adding the composite rubber material to an internal mixer, stirring the composite rubber material at a preset speed under nitrogen protection to form a rubber material carrier with enhanced fluidity; The thermal conductive phase composite rubber is preheated to 50°C. By moderately increasing the temperature, the matrix viscosity is reduced, the fluidity of the rubber is improved, and ideal rheological conditions are created for the uniform dispersion of the conductive filler. Under nitrogen protection, the mixture is stirred at a preset speed (such as 100 rpm) to isolate oxygen and prevent surface oxidation of the silver-coated carbon nanotubes. At the same time, gentle stirring is used to avoid damage to the constructed thermal conductive network structure, forming a rubber carrier with both fluidity and stability, laying the foundation for the subsequent efficient introduction of the conductive phase.

[0053] S42, adding the modified silver-coated carbon nanotubes to the rubber carrier in equal amounts three times, switching to a high-speed shear mode of 200 rpm for mixing for 8 minutes after each addition, and injecting acetone solvent to assist dispersion, so that the conductive filler is exfoliated from the agglomerates and embedded in the gaps of the thermal conductive network; Modified silver-coated carbon nanotubes were added in equal portions three times, using a gradient loading strategy to mitigate the risk of localized agglomeration caused by high filler loadings. After each addition, mixing was switched to high-speed shear mode at 200 rpm for 8 minutes, utilizing the strong shear force to exfoliate conductive filler aggregates. Acetone solvent was simultaneously injected to reduce the system viscosity and facilitate the precise embedding of the conductive filler into the gaps of the thermal network. The volatility of acetone (boiling point 56°C) ensured easy removal after mixing, preventing residual solvent from interfering with interfacial bonding. Ultimately, an interpenetrating structure of conductive pathways and thermal networks was achieved, synergistically improving the overall performance of the material.

[0054] S43, after the mixing is completed, the rubber material is transferred to a vacuum degassing tank and degassed at -0.06 MPa and 60° C. for 20 minutes to obtain a bubble-free conductive and thermally conductive mixed rubber material.

[0055] Vacuum degassing is performed at -0.06 MPa and 60°C for 20 minutes. The low-pressure environment accelerates bubble expansion and escape, while the temperature is controlled at 60°C to maintain moderate fluidity in the rubber compound, promoting bubble migration while preventing high temperatures from initiating pre-crosslinking reactions. This degassing treatment eliminates microbubbles (porosity <0.3%) introduced by high-speed shearing during mixing, ensuring that filler alignment in the subsequent magnetic field orientation process is unaffected by bubbles, safeguarding the uniformity of the material's internal structure and the reliability of its interfacial bonding, and providing a defect-free intermediate product for the precise control of anisotropic properties.

[0056] In this embodiment, it is specifically explained that step S5 specifically includes: S51, injecting the conductive and thermal conductive mixed rubber material into a metal mold with an electromagnetic coil, preheating the mold to 60° C. and applying a horizontal static magnetic field of a preset strength for 10 minutes to orient the silver-coated carbon nanotubes along the XY plane to form a pre-oriented rubber material; Preheating the mold to 60°C reduces the viscosity of the rubber compound and enhances its fluidity, facilitating the directional migration of the conductive filler. A horizontal static magnetic field (e.g., 1.2T) is applied to induce the silver-coated carbon nanotubes to align along the XY plane through magnetic moments. A 10-minute hold ensures full filler orientation while preventing premature curing of the rubber compound, which could lead to orientation relaxation. The mold's metal material enhances magnetic field uniformity and reduces edge effects, providing a foundation for the precise construction of anisotropic conductive and thermally conductive structures.

[0057] S52, transferring the pre-oriented rubber compound together with the mold to a hot press, pre-curing it at 0.5 MPa pressure and 80°C for 1 hour, and simultaneously applying a 0.8 T pulsed magnetic field to further enhance the filler orientation stability; A 0.5MPa pressure combined with an 80°C pre-curing condition works synergistically: the pressure forces the compound to tightly fill the mold cavity and eliminate any remaining bubbles, while the 80°C temperature activates the matrix's initial crosslinking, fixing the filler's orientation. Simultaneously, a 0.8T pulsed magnetic field (5Hz frequency) suppresses filler springback through periodic magnetic perturbations, enhancing orientation stability. This combined pulsed and static magnetic field overcomes the limitations of a single magnetic field, increasing the conductive filler's in-plane orientation to >85%, ensuring the continuity of the in-plane conductive pathway.

[0058] S53, releasing the pressure from the hot press and raising the temperature to 120°C, then increasing the temperature to 150°C at a rate of 2°C / min, and maintaining the temperature for 2 hours to fully crosslink the phenylsiloxane side chains to form a primary cured product; A gradient heating process (2°C / min to 150°C) matches the crosslinking dynamics of the phenylsiloxane side chains. The slow heating prevents stress cracking within the matrix caused by sudden temperature changes. Maintaining the temperature at 150°C for 2 hours ensures that the phenyl side chains are fully crosslinked, forming a high-density three-dimensional network structure. During this stage, the matrix's rigidity is enhanced, providing a stable skeletal support for subsequent annealing processes, while retaining a moderate degree of flexibility to accommodate the dynamic deformation requirements of electronic devices.

[0059] S54, placing the primary solidified body in a vacuum annealing furnace and annealing it at 180° C. for 30 minutes under a nitrogen atmosphere to eliminate internal stress and enhance filler-matrix interface bonding.

[0060] S55, after cooling to room temperature, demoulding, cutting to remove edge overflow and performing surface cleaning to obtain a silicone rubber material with anisotropic electrical and thermal conductivity.

[0061] Cool naturally to room temperature to avoid uneven shrinkage of the substrate caused by sudden cooling and maintain the geometric stability of the material; cut to remove overflow and plasma clean the surface to eliminate edge burrs and contaminants, improve the surface flatness of the material and its fit with electronic devices.

[0062] Example 2: The present invention further provides a conductive and thermally conductive silicone rubber material, which is prepared using the method for preparing the conductive and thermally conductive silicone rubber material of Example 1. The conductive and thermally conductive silicone rubber material specifically comprises: The matrix component is a modified silicone rubber matrix formed by copolymerization of phenylsiloxane monomer and methylvinylsiloxane.

[0063] Thermal conductive filler, a three-dimensional thermal conductive network constructed by surface-activated boron nitride nanosheets and aluminum oxide nanowires in a 3:1 mass ratio.

[0064] The conductive filler, mercapto-functionalized silver-coated carbon nanotubes, is oriented along the XY plane to form a continuous conductive path.

[0065] Among them, it also has a microstructure, which is composed of aluminum oxide nanowires interspersed in the gaps between boron nitride layers, silver-coated carbon nanotubes are distributed in a planar orientation induced by a magnetic field, and phenyl side chains form a chemical bonding interface with the coupling agent on the filler surface.

[0066] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features thereof can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an electrically conductive and thermally conductive silicone rubber material, characterized in that: The following steps are involved: The boron nitride nanosheets are surface activated, and the silver-coated carbon nanotubes are modified with a coupling agent to obtain surface-activated boron nitride nanosheets and modified silver-coated carbon nanotubes, respectively. Phenylsiloxane monomer and methylvinylsiloxane are copolymerized to prepare a modified silicone rubber matrix; The surface-activated boron nitride nanosheets and aluminum oxide nanowires are mixed in a preset ratio, dispersed into the modified silicone rubber matrix, and kneaded at a low speed to form a heat-conducting phase composite rubber material; Adding the modified silver-coated carbon nanotubes to the thermally conductive composite rubber material, and mixing at high speed to obtain a conductive and thermally conductive composite rubber material; A directional magnetic field is applied to the conductive and thermally conductive mixed rubber material to induce filler arrangement, and a gradient curing process is performed to obtain a conductive and thermally conductive silicone rubber material.

2. The method for preparing the conductive and thermally conductive silicone rubber material according to claim 1, wherein: The surface activation process of the boron nitride nanosheets is specifically as follows: The boron nitride nanosheets are placed in a vacuum plasma reaction chamber and treated with a mixture of oxygen and argon for 30-40 minutes to obtain hydroxylated boron nitride nanosheets; The hydroxylated boron nitride nanosheets are dispersed in anhydrous ethanol, silane coupling agent KH-560 is added, ultrasonic stirring is performed at 60° C. for 2 hours, centrifugation is performed, and then drying is performed to obtain boron nitride nanosheets with epoxy groups grafted on the surface.

3. The method for preparing the conductive and thermally conductive silicone rubber material according to claim 1, wherein: The preparation process of the modified silver-coated carbon nanotubes is as follows: Immersing the carbon nanotubes in a silver nitrate solution, adding ascorbic acid as a reducing agent, and reacting in a 50°C water bath for 1 hour to uniformly coat the surface of the carbon nanotubes with silver nanoparticles, thereby obtaining a primary product of silver-coated carbon nanotubes; The silver-coated carbon nanotube primary product is placed in a toluene solvent, a mercaptosilane coupling agent KH-590 is added, and the mixture is refluxed at 80° C. for 4 hours under nitrogen protection to graft the mercapto groups onto the surface of the silver layer, thereby forming a mixed solution; The mixed solution after the reaction is centrifuged and separated, and washed with acetone for multiple times to remove the unreacted coupling agent. The mixed solution is then vacuum dried to obtain thiol-functionalized modified silver-coated carbon nanotubes.

4. The method for preparing the conductive and thermally conductive silicone rubber material according to claim 1, wherein: The phenylsiloxane monomer is any one of diphenyldimethoxysilane, methylphenyldiethoxysilane, phenyltrimethoxysilane, and tetraphenylcyclotetrasiloxane; The methylvinylsiloxane is any one of methylvinyldimethoxysilane, methylvinyldiethoxysilane, and vinyltrimethoxysilane; Wherein, the mass ratio of the phenylsiloxane monomer to the methylvinylsiloxane is 1:1.5 to 1:

4.

5. The method for preparing the conductive and thermally conductive silicone rubber material according to claim 1, wherein: The method of copolymerizing phenylsiloxane monomer and methylvinylsiloxane to prepare a modified silicone rubber matrix specifically includes: Phenylsiloxane monomer and methylvinylsiloxane monomer were mixed in a molar ratio of 1:4, a catalyst was added, and the mixture was dehydrated under vacuum conditions for 30 minutes to obtain a preactivated mixed monomer; The preactivated mixed monomers were placed in a reaction kettle, heated to 80° C. under nitrogen protection, and stirred for reaction for 2 hours to generate an oligomer prepolymer; Adding a hydrogenated silicone oil crosslinker and an inhibitor, methyl butynol, to the oligomer prepolymer, controlling the molar ratio of hydrogenated groups to vinyl groups to be 1.2:1, and stirring at a low speed at 60° C. for 1 hour to form a uniform colloid; The colloid was injected into a vacuum degassing machine and degassed at -0.1 MPa and 50° C. for 40 minutes to obtain a modified silicone rubber matrix without bubbles.

6. The method for preparing the conductive and thermally conductive silicone rubber material according to claim 1, wherein: The surface-activated boron nitride nanosheets and aluminum oxide nanowires are mixed in a preset ratio, dispersed into the modified silicone rubber matrix, and kneaded at a low speed to form a thermally conductive composite rubber material, specifically comprising: The surface-activated boron nitride nanosheets and aluminum oxide nanowires were pre-mixed in a mass ratio of 3:1, anhydrous ethanol was added, and ultrasonic treatment was performed for 20 minutes to form a uniform pre-dispersed slurry of thermal conductive filler; The thermal conductive filler pre-dispersed slurry was mixed with the modified silicone rubber matrix in a volume ratio of 1:5, and stirred at a low speed of 100 rpm at 40° C. for 30 minutes to allow the filler to initially infiltrate the matrix; The impregnated mixture was transferred to a mixer, and the temperature of the first stage was controlled at 60°C and the temperature of the second stage was controlled at 80°C. The mixture was mixed in sections at a preset speed. The material was first conveyed through a wide-pitch screw, and then switched to a narrow-pitch screw to apply shear dispersion.

7. The method for preparing the conductive and thermally conductive silicone rubber material according to claim 6, wherein: The stepwise mixing at a preset speed first conveys the material through a wide pitch screw, then switches to a narrow pitch screw to apply shear dispersion, and then further includes: Inject xylene solvent into the mixer, adjust the solid content to 40 wt%, and use an ultrasonic probe to intermittently assist dispersion, ultrasonicating for 5 minutes each time with a 2-minute interval, and repeat for 3 or more times; Monitor the viscosity of the rubber compound at the mixer outlet in real time. When the viscosity reaches the preset value, stop mixing and transfer the rubber compound to a sealed container and let it stand for defoaming for 1 hour. The defoamed rubber material is passed through a vacuum devolatilization device to remove the residual solvent, and is rolled into a sheet with a thickness of 2 mm by a calender to obtain a heat-conducting phase composite rubber material.

8. The method for preparing the conductive and thermally conductive silicone rubber material according to claim 1, wherein: The modified silver-coated carbon nanotubes are added to the thermally conductive composite rubber material, and mixed at high speed to obtain a conductive and thermally conductive composite rubber material, which specifically includes: The heat-conducting phase composite rubber material is preheated to 50° C. and added to an internal mixer, and stirred at a preset speed under nitrogen protection to form a rubber carrier with enhanced fluidity; The modified silver-coated carbon nanotubes were added to the sizing agent carrier in equal amounts three times, and after each addition, the mixture was switched to a high-speed shear mode of 200 rpm for mixing for 8 minutes, while acetone solvent was injected to assist in dispersion, so that the conductive filler was exfoliated from the agglomerates and embedded in the gaps of the thermal conductive network; After the mixing is completed, the rubber material is transferred to a vacuum degassing tank and degassed at -0.06 MPa and 60°C for 20 minutes to obtain a bubble-free conductive and thermally conductive mixed rubber material.

9. The method for preparing the conductive and thermally conductive silicone rubber material according to claim 1, wherein: Applying a directional magnetic field to the conductive and thermally conductive mixed rubber material to induce filler arrangement, and performing a gradient curing process to obtain a conductive and thermally conductive silicone rubber material, specifically comprising: The conductive and thermal conductive mixed rubber material is injected into a metal mold with an electromagnetic coil, the mold is preheated to 60° C., and a horizontal static magnetic field of a preset strength is applied for 10 minutes to align the silver-coated carbon nanotubes along the XY plane to form a pre-oriented rubber material; The pre-oriented rubber compound and the mold were transferred to a hot press and pre-cured at 0.5 MPa pressure and 80°C for 1 hour, and a 0.8 T pulsed magnetic field was simultaneously applied to further enhance the filler orientation stability; The hot press is released and the temperature is raised to 120° C., then raised to 150° C. at a rate of 2° C. / min, and maintained for 2 hours to fully crosslink the phenylsiloxane side chains to form a primary cured product; The primary solidified body is placed in a vacuum annealing furnace and annealed at 180° C. for 30 minutes under a nitrogen atmosphere to eliminate internal stress and enhance filler-matrix interface bonding; After cooling to room temperature, the mold is demoulded, edge overflow is removed by cutting, and the surface is cleaned to obtain a silicone rubber material with anisotropic electrical and thermal conductivity.

10. A conductive and thermally conductive silicone rubber material, characterized in that: The conductive and thermally conductive silicone rubber material is prepared by the preparation method of any one of claims 1 to 9, wherein the conductive and thermally conductive silicone rubber material specifically comprises: The matrix component is a modified silicone rubber matrix formed by copolymerization of phenylsiloxane monomer and methylvinylsiloxane; Thermally conductive filler, a three-dimensional thermal conductive network constructed of surface-activated boron nitride nanosheets and aluminum oxide nanowires in a 3:1 mass ratio; The conductive filler, mercapto-functionalized silver-coated carbon nanotubes, is oriented along the XY plane to form a continuous conductive path.

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