Silicon rubber-conductive silver paste with core-shell structure for surface coating and preparation method of silicon rubber-conductive silver paste
By designing a core-shell structure with a continuous silver shell layer on the surface of silicone rubber microspheres and combining it with a coupling agent to improve interfacial compatibility, the conductivity failure problem of traditional conductive silver paste during repeated bending is solved, achieving a synergy of high flexibility and high conductivity, which is suitable for flexible electronics and electromagnetic shielding.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-23
- Publication Date
- 2026-03-13
AI Technical Summary
Traditional conductive silver paste is prone to cracking after repeated bending, resulting in the breakage of the conductive network. The poor compatibility between silver particles and the substrate leads to easy peeling of the coating, making it impossible to achieve a balance between flexibility and conductivity.
A core-shell structure design is adopted, with a composite filler consisting of a silicone rubber core and a conductive silver shell. By forming a continuous silver shell on the surface of silicone rubber microspheres and combining it with a coupling agent to improve interfacial compatibility, a continuous conductive network is constructed.
It achieves a synergy of high flexibility and high conductivity, improves the adhesion and bending stability of the coating, and solves the problem of conductivity failure of traditional silver paste under repeated deformation. It is suitable for flexible electronics and electromagnetic shielding.
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Figure CN121662478A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of conductive silver paste technology, and in particular to a core-shell structured silicone rubber-conductive silver paste for surface coating and its preparation method. Background Technology
[0002] With the development of flexible electronics technology, higher requirements have been placed on the comprehensive performance of surface coating materials. Traditional conductive silver pastes are mostly based on epoxy resin, acrylic resin, etc. Although they have good conductivity, the polymer matrix is rigid and is prone to cracking after repeated bending, which leads to the breakage of the conductive network. At the same time, the silver particles have poor compatibility with the matrix, the coating is easy to fall off, and the matrix is prone to aging at high temperatures, affecting long-term reliability.
[0003] Silicone rubber is considered an ideal functional matrix due to its good molecular chain flexibility, resistance to high and low temperatures, and strong weather resistance. However, pure silicone rubber has extremely poor conductivity and cannot be directly used as a conductive paste. In the prior art, composite conductive materials are prepared by adding silver powder to silicone rubber. However, directly dispersing silver powder in the silicone rubber matrix can easily lead to agglomeration, resulting in an uneven conductive network and large sheet resistance fluctuations. At the same time, the interfacial bonding force between silver powder and silicone rubber is weak, and slippage is prone to occur under stress, reducing conductivity stability. Moreover, the hybrid structure cannot achieve a balance between flexibility and conductivity. Therefore, this invention proposes a core-shell structure silicone rubber-conductive silver paste for surface coating and its preparation method to solve the problems existing in the prior art. Summary of the Invention
[0004] To address the aforementioned problems, the present invention aims to provide a core-shell structured silicone rubber-conductive silver paste for surface coating and its preparation method. This core-shell structured silicone rubber-conductive silver paste and its preparation method, through a core-shell structure design of a silicone rubber core and a conductive silver shell, enables the paste to achieve both high tensile strength and stable conductivity. It achieves efficient synergy between the flexibility of the silicone rubber core and the conductivity of the silver shell layer. The silicone rubber core provides rubber-like high flexibility, while the silver shell layer constructs a continuous conductive network. This solves the problem of traditional silver pastes being rigid, prone to cracking under repeated deformation, and leading to conductive failure. The silicone rubber core is compatible with the substrate material, and the coupling agent modifies the surface of the silver shell layer, significantly improving coating adhesion and bending stability.
[0005] To achieve the objectives of this invention, the invention is implemented through the following technical solution: a core-shell structured silicone rubber-conductive silver paste for surface coating, comprising a core-shell structured filler, a silicone rubber matrix, a coupling agent, a crosslinking agent, a catalyst, and a diluent mixed in a mass percentage of 60%-85%:10%-25%:0.5%-3%:1%-5%:0.1%-1%:3.4%-6%, wherein the core-shell structured filler is a composite filler formed by using silicone rubber microspheres as the core and a continuous silver shell layer coated on the surface.
[0006] A further improvement is that the silicone rubber microspheres account for 30%-50% of the mass of the core-shell structure filler, the silver shell layer accounts for 50%-70% of the mass of the core-shell structure filler, the particle size of the silicone rubber microspheres is 0.5μm-5μm, and the thickness of the silver shell layer is 50nm-300nm.
[0007] A further improvement is that: the silicone rubber matrix is an addition-type liquid silicone rubber; the coupling agent is one of γ-glycidoxypropyltrimethoxysilane and γ-methacryloyloxypropyltrimethoxysilane; the crosslinking agent is a hydrogen-containing silicone oil with a hydrogen content of 0.1wt%-1.0wt%; the catalyst is a platinum catalyst; and the diluent is one of dimethyl silicone oil and white oil.
[0008] A method for preparing a core-shell structured silicone rubber-conductive silver paste for surface coating includes the following steps:
[0009] Step 1: Preparation of silicone rubber microspheres. Hydroxyl-terminated polydimethylsiloxane and hydrogen-containing silicone oil are mixed in a certain proportion, a catalyst is added for prepolymerization reaction, an emulsifier is added for emulsification, and after ultrasonic dispersion, centrifugation, washing and vacuum drying, silicone rubber microspheres with a particle size of 0.5μm-5μm are obtained.
[0010] Step 2: Preparation of core-shell structured filler. Silicone rubber microspheres are dispersed in an ethanol-water mixed solvent, silver nitrate solution and ascorbic acid are added, and reduction deposition is carried out at 40℃-60℃ for 1-2 hours to form a continuous silver shell layer on the surface of the silicone rubber microspheres. After centrifugation, washing and vacuum drying, the core-shell structured filler is obtained.
[0011] Step 3: Slurry preparation. The core-shell structure filler, silicone rubber matrix, coupling agent, and crosslinking agent are added to a planetary mixer. After vacuum low-speed stirring to remove bubbles, the mixture is dispersed at high speed. Then, a catalyst and diluent are added to adjust the viscosity to 5000 mPa·s-20000 mPa·s, thus obtaining the conductive silver paste.
[0012] The further improvement is as follows: in step one, the mass ratio of terminal hydroxyl polydimethylsiloxane to hydrogen-containing silicone oil is 10:1; the prepolymerization reaction conditions are stirring at 80℃-100℃ for 2-4 hours; the catalyst is chloroplatinic acid, with an amount of 0.01wt% based on the mass of terminal hydroxyl polydimethylsiloxane; and the emulsifier is sodium dodecylbenzenesulfonate, with an amount of 1wt% based on the total mass of the system.
[0013] Further improvements are made in the following aspects: the ultrasonic dispersion conditions in step one are: ultrasonication at a power of 300W-500W for 10-20 minutes; centrifugation conditions are: centrifugation at a speed of 3000rpm-5000rpm for 10-15 minutes; and vacuum drying conditions are: drying at a temperature of 60℃ for 24 hours.
[0014] The further improvement is that: in step two, the volume ratio of ethanol to water in the mixed solvent is 1:1; the concentration of the silver nitrate solution used is 0.1mol / L-0.5mol / L, and the molar ratio of silver nitrate to ascorbic acid is 1:2; the vacuum drying conditions are drying at 60℃ for 24 hours.
[0015] The further improvement is that: in step three, the stirring conditions are a vacuum pressure ≤ -0.08MPa and low-speed stirring at 50rpm-100rpm for 30min; the high-speed dispersion conditions are high-speed stirring at 1000rpm-2000rpm for 60min-120min.
[0016] Further improvements are made in the following aspects: the viscosity of the slurry after dilution and adjustment in step three is 8000mPa·s-15000mPa·s, the sheet resistance of the slurry is ≤0.1Ω / □, and after the slurry is coated and cured into a film, the elongation at break is >200%, and the cross-cut adhesion is ≥5B.
[0017] The beneficial effects of this invention are as follows: This invention achieves efficient synergy between the flexibility of the silicone rubber core and the conductivity of the silver shell layer through the core-shell structure design. The silicone rubber core provides rubber-like high flexibility, and the silver shell layer constructs a continuous conductive network, which solves the problem of traditional silver paste being rigid and prone to cracking due to repeated deformation, leading to conductive failure.
[0018] Meanwhile, the silicone rubber core is compatible with the matrix material, and the coupling agent modifies the surface of the silver shell layer, which effectively improves the interfacial bonding force between the filler and the matrix, and significantly improves the coating adhesion and bending stability.
[0019] The preparation method uses an in-situ reduction method to deposit a silver shell layer on the surface of silicone rubber microspheres. The process is simple and controllable, and can be mass-produced without complex equipment. It is both practical and economical, and provides a high-performance surface coating material solution for fields such as flexible electronics and electromagnetic shielding. Attached Figure Description
[0020] Figure 1 This is a flowchart of the preparation method of the present invention. Detailed Implementation
[0021] To enhance understanding of the present invention, the present invention will be further described in detail below with reference to embodiments. These embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.
[0022] Example 1
[0023] according to Figure 1As shown, this embodiment provides a core-shell structured silicone rubber-conductive silver paste for surface coating, comprising a core-shell structured filler, a silicone rubber matrix, a coupling agent, a crosslinking agent, a catalyst, and a diluent mixed in a mass percentage of 80%:10%:2%:1%:1%:6%. The core-shell structured filler is a composite filler formed by using silicone rubber microspheres as the core and coating the surface with a continuous silver shell layer. The coverage of the silver shell layer on the surface of the silicone rubber microspheres is ≥90%.
[0024] Silicone rubber microspheres account for 45% of the mass of the core-shell structure filler, and the silver shell layer accounts for 55% of the mass of the core-shell structure filler. The particle size of the silicone rubber microspheres is 1μm-3μm, and the thickness of the silver shell layer is 100nm-200nm.
[0025] The silicone rubber matrix is an addition-type liquid silicone rubber, such as vinyl silicone rubber, with a viscosity of 35000 mPa·s at 25°C. The coupling agent is γ-methacryloyloxypropyltrimethoxysilane, the crosslinking agent is hydrogen-containing silicone oil with a hydrogen content of 0.7 wt%, the catalyst is chloroplatinic acid-isopropanol solution with a platinum content of 0.1 wt%-1.0 wt%, and the diluent is one of dimethyl silicone oil (viscosity 10 mPa·s-100 mPa·s) and white oil.
[0026] A method for preparing a core-shell structured silicone rubber-conductive silver paste for surface coating includes the following steps:
[0027] Step 1: Preparation of silicone rubber microspheres. Hydroxyl-terminated polydimethylsiloxane with a molecular weight of 8000-15000 is mixed with hydrogen-containing silicone oil at a mass ratio of 10:1. A catalyst is added and the mixture is stirred at 90°C for 2 hours to carry out a prepolymerization reaction. Then, an emulsifier is added for emulsification. After ultrasonic dispersion, centrifugation, washing, and vacuum drying, silicone rubber microspheres with a particle size of 0.5μm-5μm are obtained.
[0028] The catalyst was chloroplatinic acid, used at a rate of 0.01 wt% based on the mass of hydroxyl-terminated polydimethylsiloxane; the emulsifier was sodium dodecylbenzenesulfonate, used at a rate of 1 wt% based on the total mass of the system.
[0029] The ultrasonic dispersion conditions were: ultrasonication at 500W power for 10 minutes; centrifugation conditions were: centrifugation at 4500rpm for 15 minutes; and vacuum drying conditions were: drying at 60℃ for 24 hours.
[0030] Step 2: Preparation of core-shell structured filler. Silicone rubber microspheres were dispersed in an ethanol-water mixed solvent with a volume ratio of ethanol to water of 1:1. A 0.35 mol / L silver nitrate solution (silver source) and ascorbic acid (as a reducing agent) were added with a molar ratio of silver nitrate to ascorbic acid of 1:2. The mixture was reduced and deposited at 60°C for 1 hour to form a continuous silver shell layer on the surface of the silicone rubber microspheres. After centrifugation, washing, and vacuum drying, the core-shell structured filler was obtained.
[0031] The vacuum drying conditions were 60℃ for 24 hours.
[0032] Step 3: Slurry preparation. The core-shell structure filler, silicone rubber matrix, coupling agent, and crosslinking agent are added to a planetary mixer. After vacuum low-speed stirring to remove bubbles, the mixture is dispersed at high speed. Then, a catalyst and diluent are added to adjust the viscosity to 8000 mPa·s-15000 mPa·s, thus obtaining the conductive silver paste.
[0033] The stirring conditions were: vacuum pressure ≤ -0.08MPa, low speed stirring at 100rpm for 30min; and high speed dispersion conditions were: high speed stirring at 2000rpm for 80min.
[0034] The sheet resistance of the prepared slurry is ≤0.1Ω / □. After the slurry is coated and cured into a film, the elongation at break is >200%, the tensile rate is 50mm / min, the cross-cut adhesion is ≥5B, and the sheet resistance change is <10% after 10,000 180° bends.
[0035] Example 2
[0036] according to Figure 1 As shown, this embodiment provides a core-shell structured silicone rubber-conductive silver paste for surface coating, comprising a core-shell structured filler, a silicone rubber matrix, a coupling agent, a crosslinking agent, a catalyst, and a diluent mixed in a mass percentage of 75%:15%:1.5%:3%:0.5%:5%. The core-shell structured filler comprises a 40% silicone rubber core and a 60% silver shell. The silicone rubber matrix is a vinyl silicone rubber matrix with a viscosity of 3000 mPa·s. The coupling agent is γ-glycidyl etheroxypropyltrimethoxysilane. The crosslinking agent is a hydrogen-containing silicone oil with a hydrogen content of 0.5 wt%. The catalyst is a chloroplatinic acid-isopropanol solution with a platinum content of 0.5 wt%. The diluent is dimethyl silicone oil.
[0037] The preparation method is as follows:
[0038] 1. Preparation of silicone rubber microspheres: Hydroxyl-terminated polydimethylsiloxane with a molecular weight of 10,000 was mixed with hydrogen-containing silicone oil with a hydrogen content of 0.5 wt% at a ratio of 10:1. 0.01 wt% chloroplatinic acid was added, and the mixture was stirred at 80℃ for 3 h to obtain a prepolymer emulsion. 1 wt% sodium dodecylbenzenesulfonate was added for emulsification, and the mixture was ultrasonically dispersed at 400 W for 15 min. Then, it was centrifuged at 4000 rpm for 10 min, washed with water 3 times, and vacuum dried at 60℃ for 24 h to obtain silicone rubber microspheres with a particle size of 1-3 μm.
[0039] 2. Preparation of core-shell filler: Silicone rubber microspheres were dispersed in a 1:1 mixture of ethanol and water, and 0.2 mol / L AgNO3 and ascorbic acid were added. The molar ratio of AgNO3 to ascorbic acid was 1:2. The mixture was stirred at 50℃ for 1.5 h, centrifuged and washed, and then dried at 60℃ for 24 h to obtain silicone rubber@silver with a silver shell thickness of 150 nm.
[0040] 3. Slurry preparation: Add the core-shell filler, vinyl silicone rubber, KH-560, and hydrogen-containing silicone oil to a planetary mixer and stir at low speed for 30 min under vacuum conditions of ≤-0.08 MPa. Then disperse at high speed of 1500 rpm for 90 min. Add the catalyst and diluent and adjust the viscosity to 10000 mPa·s to obtain the slurry.
[0041] Performance testing:
[0042] The sheet resistance was measured to be 0.08 Ω / □ using the four-probe method. After the slurry was coated and cured into a film, the elongation at break was measured to be 230% using a tensile testing machine. The adhesion was measured to be 5B using the cross-cut test. The sheet resistance change was 7.8% after 10,000 bends.
[0043] Example 3
[0044] according to Figure 1 As shown, this embodiment provides a core-shell structured silicone rubber-conductive silver paste for surface coating, comprising a core-shell structured filler, a silicone rubber matrix, a coupling agent, a crosslinking agent, a catalyst, and a diluent mixed in a mass percentage ratio of 75%:15%:1.5%:3%:0.5%:5%. The core-shell structured filler comprises a 35% silicone rubber core and a 65% silver shell. The silicone rubber matrix is a vinyl silicone rubber matrix with a viscosity of 3000 mPa·s. The coupling agent is γ-glycidyl etheroxypropyltrimethoxysilane. The crosslinking agent is a hydrogen-containing silicone oil with a hydrogen content of 0.5 wt%. The catalyst is a chloroplatinic acid-isopropanol solution with a platinum content of 0.5 wt%. The diluent is dimethyl silicone oil.
[0045] The preparation method is as follows:
[0046] 1. Preparation of silicone rubber microspheres: Hydroxyl-terminated polydimethylsiloxane with a molecular weight of 10,000 was mixed with hydrogen-containing silicone oil with a hydrogen content of 0.5 wt% at a ratio of 10:1. 0.01 wt% chloroplatinic acid was added, and the mixture was stirred at 80℃ for 3 h to obtain a prepolymer emulsion. 1 wt% sodium dodecylbenzenesulfonate was added for emulsification, and the mixture was ultrasonically dispersed at 400 W for 15 min. Then, it was centrifuged at 4000 rpm for 10 min, washed with water 3 times, and vacuum dried at 60℃ for 24 h to obtain silicone rubber microspheres with a particle size of 1-3 μm.
[0047] 2. Preparation of core-shell filler: Silicone rubber microspheres were dispersed in a 1:1 mixture of ethanol and water, and 0.2 mol / L AgNO3 and ascorbic acid were added. The molar ratio of AgNO3 to ascorbic acid was 1:2. The mixture was stirred at 50℃ for 1.5 h, centrifuged and washed, and then dried at 60℃ for 24 h to obtain silicone rubber@silver with a silver shell thickness of 150 nm.
[0048] 3. Slurry preparation: Add the core-shell filler, vinyl silicone rubber, KH-560, and hydrogen-containing silicone oil to a planetary mixer and stir at low speed for 30 min under vacuum conditions of ≤-0.08 MPa. Then disperse at high speed of 1500 rpm for 90 min. Add the catalyst and diluent and adjust the viscosity to 10000 mPa·s to obtain the slurry.
[0049] Performance testing:
[0050] The sheet resistance was measured to be 0.07 Ω / □ using the four-probe method. After the slurry was coated and cured into a film, the elongation at break was measured to be 220% using a tensile testing machine. The adhesion was measured to be 5B using the cross-cut test. The sheet resistance change was 7.5% after 10,000 bends.
[0051] Example 4
[0052] according to Figure 1 As shown, this embodiment provides a core-shell structured silicone rubber-conductive silver paste for surface coating, comprising a core-shell structured filler, a silicone rubber matrix, a coupling agent, a crosslinking agent, a catalyst, and a diluent mixed in a mass percentage of 60%:25%:3%:5%:1%:6%. The core-shell structured filler comprises a 30% silicone rubber core and a 70% silver shell. The silicone rubber matrix is a vinyl silicone rubber matrix with a viscosity of 3000 mPa·s. The coupling agent is γ-glycidyl etheroxypropyltrimethoxysilane. The crosslinking agent is a hydrogen-containing silicone oil with a hydrogen content of 0.5 wt%. The catalyst is a chloroplatinic acid-isopropanol solution with a platinum content of 0.5 wt%. The diluent is dimethyl silicone oil.
[0053] The preparation method is as follows:
[0054] 1. Preparation of silicone rubber microspheres: Hydroxyl-terminated polydimethylsiloxane with a molecular weight of 10,000 was mixed with hydrogen-containing silicone oil with a hydrogen content of 0.5 wt% at a ratio of 10:1. 0.01 wt% chloroplatinic acid was added, and the mixture was stirred at 80℃ for 3 h to obtain a prepolymer emulsion. 1 wt% sodium dodecylbenzenesulfonate was added for emulsification, and the mixture was ultrasonically dispersed at 400 W for 15 min. Then, it was centrifuged at 4000 rpm for 10 min, washed with water 3 times, and vacuum dried at 60℃ for 24 h to obtain silicone rubber microspheres with a particle size of 1-3 μm.
[0055] 2. Preparation of core-shell filler: Silicone rubber microspheres were dispersed in a 1:1 mixture of ethanol and water, and 0.2 mol / L AgNO3 and ascorbic acid were added. The molar ratio of AgNO3 to ascorbic acid was 1:2. The mixture was stirred at 50℃ for 1.5 h, centrifuged and washed, and then dried at 60℃ for 24 h to obtain silicone rubber@silver with a silver shell thickness of 150 nm.
[0056] 3. Slurry preparation: Add the core-shell filler, vinyl silicone rubber, KH-560, and hydrogen-containing silicone oil to a planetary mixer and stir at low speed for 30 min under vacuum conditions of ≤-0.08 MPa. Then disperse at high speed of 1500 rpm for 90 min. Add the catalyst and diluent and adjust the viscosity to 10000 mPa·s to obtain the slurry.
[0057] Performance testing:
[0058] The sheet resistance was measured to be 0.06 Ω / □ using the four-probe method. After the slurry was coated and cured into a film, the elongation at break was measured to be 240% using a tensile testing machine. The adhesion was measured to be 5B using the cross-cut test. The sheet resistance change was 6.5% after 10,000 bends.
[0059] Example 5
[0060] according to Figure 1 As shown, this embodiment provides a core-shell structured silicone rubber-conductive silver paste for surface coating, comprising a core-shell structured filler, a silicone rubber matrix, a coupling agent, a crosslinking agent, a catalyst, and a diluent mixed in a mass percentage ratio of 85%:10%:0.5%:1%:0.1%:3.4%. The core-shell structured filler comprises a 50% silicone rubber core and a 50% silver shell. The silicone rubber matrix is a vinyl silicone rubber matrix with a viscosity of 3000 mPa·s. The coupling agent is γ-glycidyl etheroxypropyltrimethoxysilane. The crosslinking agent is a hydrogen-containing silicone oil with a hydrogen content of 0.5 wt%. The catalyst is a chloroplatinic acid-isopropanol solution with a platinum content of 0.5 wt%. The diluent is dimethyl silicone oil.
[0061] The preparation method is as follows:
[0062] 1. Preparation of silicone rubber microspheres: Hydroxyl-terminated polydimethylsiloxane with a molecular weight of 10,000 was mixed with hydrogen-containing silicone oil with a hydrogen content of 0.5 wt% at a ratio of 10:1. 0.01 wt% chloroplatinic acid was added, and the mixture was stirred at 80℃ for 3 h to obtain a prepolymer emulsion. 1 wt% sodium dodecylbenzenesulfonate was added for emulsification, and the mixture was ultrasonically dispersed at 400 W for 15 min. Then, it was centrifuged at 4000 rpm for 10 min, washed with water 3 times, and vacuum dried at 60℃ for 24 h to obtain silicone rubber microspheres with a particle size of 1-3 μm.
[0063] 2. Preparation of core-shell filler: Silicone rubber microspheres were dispersed in a 1:1 mixture of ethanol and water, and 0.2 mol / L AgNO3 and ascorbic acid were added. The molar ratio of AgNO3 to ascorbic acid was 1:2. The mixture was stirred at 50℃ for 1.5 h, centrifuged and washed, and then dried at 60℃ for 24 h to obtain silicone rubber@silver with a silver shell thickness of 150 nm.
[0064] 3. Slurry preparation: Add the core-shell filler, vinyl silicone rubber, KH-560, and hydrogen-containing silicone oil to a planetary mixer and stir at low speed for 30 min under vacuum conditions of ≤-0.08 MPa. Then disperse at high speed of 1500 rpm for 90 min. Add the catalyst and diluent and adjust the viscosity to 10000 mPa·s to obtain the slurry.
[0065] Performance testing:
[0066] The sheet resistance was measured to be 0.08 Ω / □ using the four-probe method. After the slurry was coated and cured into a film, the elongation at break was measured to be 220% using a tensile testing machine. The adhesion was measured to be 5B using the cross-cut test. The sheet resistance was measured to be 7% after 10,000 bends.
[0067] Comparative Example
[0068] Conductive silver paste was prepared using 75% silver powder with a particle size of 1 μm, 15% vinyl silicone rubber, 1.5% γ-glycidyl etheroxypropyltrimethoxysilane, 3% hydrogen-containing silicone oil, 0.5% catalyst, and 5% diluent. Performance testing showed a sheet resistance of 0.05 Ω / □. However, after the paste was coated and cured into a film, the elongation at break was only 80%, and the sheet resistance increased to 0.5 Ω / □ after 10,000 bends. Silver powder agglomeration and interfacial slippage were observed, indicating that the performance was significantly lower than that of the pastes prepared in Examples 1-5.
[0069] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.
Claims
1. A core-shell structured silicone rubber-conductive silver paste for surface coating, characterized in that: The product is made by mixing core-shell structured filler, silicone rubber matrix, coupling agent, crosslinking agent, catalyst and diluent in a mass percentage of 60%-85%:10%-25%:0.5%-3%:1%-5%:0.1%-1%:3.4%-6%. The core-shell structured filler is a composite filler with silicone rubber microspheres as the core and a continuous silver shell layer on the surface.
2. The core-shell structured silicone rubber-conductive silver paste for surface coating according to claim 1, characterized in that: The silicone rubber microspheres account for 30%-50% of the mass of the core-shell structure filler, the silver shell layer accounts for 50%-70% of the mass of the core-shell structure filler, the particle size of the silicone rubber microspheres is 0.5μm-5μm, and the thickness of the silver shell layer is 50nm-300nm.
3. The core-shell structured silicone rubber-conductive silver paste for surface coating according to claim 1, characterized in that: The silicone rubber matrix is an addition-type liquid silicone rubber, the coupling agent is one of γ-glycidoxypropyltrimethoxysilane and γ-methacryloyloxypropyltrimethoxysilane, the crosslinking agent is a hydrogen-containing silicone oil with a hydrogen content of 0.1wt%-1.0wt%, the catalyst is a platinum catalyst, and the diluent is one of dimethyl silicone oil and white oil.
4. A method for preparing a core-shell structured silicone rubber-conductive silver paste for surface coating according to any one of claims 1-3, characterized in that, Includes the following steps: Step 1: Preparation of silicone rubber microspheres. Hydroxyl-terminated polydimethylsiloxane and hydrogen-containing silicone oil are mixed in a certain proportion, a catalyst is added for prepolymerization reaction, an emulsifier is added for emulsification, and after ultrasonic dispersion, centrifugation, washing and vacuum drying, silicone rubber microspheres with a particle size of 0.5μm-5μm are obtained. Step 2: Preparation of core-shell structured filler. Silicone rubber microspheres are dispersed in an ethanol-water mixed solvent, silver nitrate solution and ascorbic acid are added, and reduction deposition is carried out at 40℃-60℃ for 1-2 hours to form a continuous silver shell layer on the surface of the silicone rubber microspheres. After centrifugation, washing and vacuum drying, the core-shell structured filler is obtained. Step 3: Slurry preparation. The core-shell structure filler, silicone rubber matrix, coupling agent, and crosslinking agent are added to a planetary mixer. After vacuum low-speed stirring to remove bubbles, the mixture is dispersed at high speed. Then, a catalyst and diluent are added to adjust the viscosity to 5000 mPa·s-20000 mPa·s, thus obtaining the conductive silver paste.
5. The method for preparing a core-shell structured silicone rubber-conductive silver paste for surface coating according to claim 4, characterized in that: In step one, the mass ratio of hydroxyl-terminated polydimethylsiloxane to hydrogen-containing silicone oil is 10:
1. The prepolymerization reaction conditions are stirring at 80℃-100℃ for 2-4 hours. The catalyst is chloroplatinic acid, with a dosage of 0.01wt% based on the mass of hydroxyl-terminated polydimethylsiloxane. The emulsifier is sodium dodecylbenzenesulfonate, with a dosage of 1wt% based on the total mass of the system.
6. The method for preparing a core-shell structured silicone rubber-conductive silver paste for surface coating according to claim 4, characterized in that: In step one, the ultrasonic dispersion conditions are: ultrasonication at a power of 300W-500W for 10-20 minutes; centrifugation conditions are: centrifugation at a speed of 3000rpm-5000rpm for 10-15 minutes; and vacuum drying conditions are: drying at a temperature of 60℃ for 24 hours.
7. The method for preparing a core-shell structured silicone rubber-conductive silver paste for surface coating according to claim 4, characterized in that: In step two, the volume ratio of ethanol to water in the mixed solvent is 1:1; the concentration of the silver nitrate solution used is 0.1mol / L-0.5mol / L, and the molar ratio of silver nitrate to ascorbic acid is 1:2; the vacuum drying conditions are drying at 60℃ for 24 hours.
8. The method for preparing a core-shell structured silicone rubber-conductive silver paste for surface coating according to claim 4, characterized in that: In step three, the stirring conditions are: vacuum pressure ≤ -0.08MPa, low-speed stirring at 50rpm-100rpm for 30min; and high-speed dispersion conditions are: high-speed stirring at 1000rpm-2000rpm for 60min-120min.
9. The method for preparing a core-shell structured silicone rubber-conductive silver paste for surface coating according to claim 4, characterized in that: In step three, the viscosity of the diluted slurry is 8000 mPa·s-15000 mPa·s, the sheet resistance of the slurry is ≤0.1Ω / □, and after the slurry is coated and cured into a film, the elongation at break is >200% and the cross-cut adhesion is ≥5B.