A high-stability conductive silica gel material filled with directional metal wires and a preparation method thereof

Abstract

The application provides a high-stability conductive silica gel material filled with oriented metal wires and a preparation method, and belongs to the technical field of electromagnetic shielding materials. The conductive silica gel material is formed by compounding and solidifying metal wires and a silica gel matrix. The metal wires are spiral metal wires subjected to surface treatment. The surface treatment of the metal wires is sequentially subjected to chromium electroplating treatment and oxygen treatment. The metal wires are vertically and non-contactingly arranged in the silica gel matrix. The silica gel matrix is prepared by compounding vinyl silicone rubber, fumed silica and a vulcanizing agent. The application solves the problems of poor conductive stability, easy oxidation and corrosion, large compression permanent deformation and unstable performance of traditional conductive silica gel due to a fragile percolation network. Meanwhile, the application discards precious metal fillers, reduces the material preparation cost, and further prepares a conductive silica gel material with low impedance and high resilience, so as to meet the use requirements of electronic equipment sealing gaskets, aerospace electromagnetic protection and the like.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic shielding materials technology, and in particular to a highly stable conductive silicone material filled with oriented metal wires and its preparation method. Background Technology

[0002] Conductive silicone, as a functional material that combines electromagnetic shielding and elastic sealing properties, is widely used in many scenarios such as sealing gaskets for electronic equipment and electromagnetic protection in aerospace. It is an indispensable material in the fields of electronic information, aerospace, and national defense. Its conductivity stability, mechanical deformation resistance and manufacturing cost control have become important research directions in this field.

[0003] With the trend of miniaturization of electronic devices and high reliability of aerospace technology, various fields have increasingly higher requirements for the performance of conductive silicone and stricter control over manufacturing costs. However, the existing technology of ordinary conductive silicone and high-end silver-based conductive rubber can no longer meet the actual needs of industry development, becoming a factor that limits the further development of electromagnetic shielding materials.

[0004] Currently, most conductive silicones on the market use carbon black or metal particles as conductive fillers. The conductive network construction of this type of conductive silicone is based on percolation theory, which has many insurmountable technical problems. Not only are they prone to poor conductivity stability, oxidation and corrosion of fillers, and large permanent deformation of materials under compression in actual use, but also, because the formation of the conductive network depends on the close contact of the fillers, there are inherent limitations such as high filler requirements, the conductivity process being dominated by contact resistance, and the upper limit of the overall conductivity of the material being limited. It is difficult to adapt to the high-performance requirements of conductive silicones in high-end application scenarios.

[0005] In addition, to meet the stringent requirements of high-end fields such as national defense, pure silver or aluminum-plated silver conductive rubber is often used in related national defense products to replace conventional conductive silicone. However, the main conductive raw material is the precious metal silver, and the price of raw materials is significantly affected by market fluctuations, which directly leads to a substantial increase in the production and manufacturing costs of related national defense products, thereby adversely affecting the large-scale production and supply chain stability of enterprises.

[0006] Therefore, there is an urgent need for a conductive silicone material that achieves low impedance and high resilience through the directional arrangement of metal wires to solve the above problems. Summary of the Invention

[0007] To overcome the shortcomings of existing technologies, the purpose of this invention is to provide a highly stable conductive silicone material filled with directional metal wires and its preparation method. This invention solves the problems of poor conductivity stability, easy oxidation and corrosion, large permanent compression deformation, and unstable performance due to the fragility of the percolation network in traditional conductive silicone materials. At the same time, it eliminates the need for expensive metal fillers, reducing the material preparation cost. This results in the preparation of a conductive silicone material with low impedance and high resilience, which meets the application requirements of electronic equipment sealing gaskets, aerospace electromagnetic protection, and other scenarios.

[0008] To achieve the above objectives, the present invention provides the following solution: On one hand, the present invention provides a highly stable conductive silicone material filled with oriented metal wires. The conductive silicone material is formed by composite curing of metal wires and silicone matrix. The metal wires are surface-treated spiral metal wires. The surface treatment of the metal wires is sequential electroplating with chromium and oxygen treatment. The metal wires are arranged in a vertical non-contact orientation in the silicone matrix. The silicone matrix is ​​composed of vinyl silicone rubber, fumed silica and vulcanizing agent.

[0009] Preferably, the metal wire is made of one or more of the following materials: nickel-copper alloy wire, iron-nickel alloy wire, copper wire, nickel wire, stainless steel wire, and aluminum wire.

[0010] Preferably, the diameter of the metal wire is 0.01~0.15mm, and the thickness of the chromium layer formed by electroplating is 0.5~1μm.

[0011] Preferably, the compounding ratio of the silicone matrix by weight is: 100 parts vinyl silicone rubber, 10-20 parts fumed silica, and 2-4 parts vulcanizing agent.

[0012] Preferably, the directional arrangement density of the spiral metal wires in the silicone matrix is ​​25~8000 wires / cm². 2 .

[0013] On the other hand, the present invention also provides a method for preparing the above-mentioned oriented metal wire-filled high-stability conductive silicone material, comprising the following steps: S1. The metal wire is subjected to electroplating chromium and oxygen treatment in sequence to obtain the surface-treated metal wire. S2. Twist water-soluble fibers with the surface-treated metal wire obtained in step S1 to form a spiral wire. Remove the water-soluble fibers by soaking in water to obtain a spiral metal wire, or directly use a multi-wire twisted wire formed by twisting multiple metal wires as a spiral metal wire. S3. Fix the spiral metal wire obtained in step S2 to the frame and assemble it to form a glue injection cavity, so that the spiral metal wire is arranged vertically and non-contactly in the cavity to obtain a shaped glue injection cavity. S4. Mix vinyl silicone rubber, fumed silica and vulcanizing agent evenly according to the specified ratio to obtain silicone matrix mixture; S5. The silicone matrix mixture obtained in step S4 is injected into the shaping injection cavity obtained in step S3, and cured through a two-stage vulcanization process to obtain the high-stability conductive silicone material filled with directional metal wires.

[0014] Preferably, in step S2, the diameter of the water-soluble fiber is 0.08~0.12mm, and the diameter of a single strand of the multi-wire stranded thread formed by twisting multiple metal wires is 0.01~0.05mm. Preferably, in step S3, a CNC winding device is used to fix the spiral metal wire to the alloy frame, and the interval between adjacent alloy frames is 0.2~2mm.

[0015] Preferably, in step S5, the two-stage vulcanization process is as follows: first, a first-stage vulcanization is carried out at 120~130℃, and then a second-stage vulcanization is carried out at 150~160℃.

[0016] Compared with the prior art, the present invention discloses at least the following technical effects: This invention improves the conductivity and environmental adaptability of conductive silicone materials. It fundamentally breaks through the inherent limitations of traditional conductive silicone based on percolation theory by constructing macroscopically continuous metallic conductive pathways, replacing the random dispersion pattern of traditional fillers. This fundamentally improves the problem of poor conductivity stability. Simultaneously, the material's resistance to oxidation and corrosion is significantly enhanced, maintaining stable conductivity in complex environments across a wide temperature range, meeting the application requirements of electronic device sealing gaskets, aerospace electromagnetic protection, and other scenarios. Furthermore, this invention uses conventional metal wires instead of precious metal fillers, minimizing the impact of raw material price fluctuations and reducing and stabilizing production costs from the source.

[0017] Furthermore, the metal wire provided by this invention adopts a spiral structure, which makes the material compression deformation more uniform and significantly improves the resilience, thus improving the problem of large permanent deformation under compression of traditional materials. The surface treatment process of the metal wire enhances its interfacial bonding force with the silicone matrix, fundamentally avoiding the detachment of metal fillers and further improving the electrical and mechanical properties of the material. At the same time, the CNC directional wire laying process significantly improves production efficiency compared with the traditional manual process, and further improves the product qualification rate. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A flowchart of a method for preparing a highly stable conductive silicone material filled with oriented metal wires is provided by the present invention. Figure 2 This is a schematic diagram of a spiral metal wire structure provided in an embodiment of the present invention; Figure 3 The resistance-compressive strain curve of the conductive silicone material provided in the embodiments of the present invention; Figure 4 A comparison diagram of stress-strain curves of conductive silicone material and ordinary 45A silicone provided in the embodiments of the present invention; Figure 5 The curve of the life test of the conductive silicone material under multiple compression cycles provided in the embodiments of the present invention; wherein... Figure 5 (a) in the figure is a graph showing the change in resistance after 10,000 compression cycles. Figure 5 (b) in the figure is a trend curve of the rate of change of resistance relative to the initial value. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] like Figure 1 As shown, this invention provides a method for preparing a highly stable conductive silicone material filled with oriented metal wires, comprising the following steps: S1. The metal wire is subjected to electroplating chromium and oxygen treatment in sequence to obtain the surface-treated metal wire.

[0023] Specifically, the metal wires selected include Monel alloy wire, 1J85 iron-nickel soft magnetic alloy wire, copper wire, nickel wire, stainless steel wire, aluminum wire, and other metal wires with special functions, and the diameter of the metal wires is controlled to be 0.01~0.15mm; the metal wires are electroplated with chromium, and the plating thickness is controlled to be 0.5~1μm; then the electroplated metal wires are subjected to oxygen treatment, so that chromium trioxide (Cr2O3) is generated on the surface of the metal wires. Cr2O3 can chemically react with silicon and oxygen elements in the silicone matrix or form a tight interaction, which significantly enhances the bonding force of the metal-silicone interface and prevents the metal wires from falling off during use.

[0024] S2. Twist the water-soluble fiber with the surface-treated metal wire obtained in step S1 to form a spiral wire. Remove the water-soluble fiber by soaking in water to obtain a spiral metal wire, or directly use a multi-wire twisted wire formed by twisting multiple metal wires as a spiral metal wire.

[0025] Specifically, water-soluble fibers with a diameter of 0.08~0.12mm are twisted in the same direction with surface-treated metal wires to form a continuous spiral. Before adhesive injection, the spiral is soaked in deionized water until the water-soluble fibers are completely dissolved and removed, resulting in independent spiral metal wires. Alternatively, multiple metal wires can be directly twisted together to form a twisted spiral. Figure 2 As shown, the spiral structure allows the metal wire to deform uniformly during compression, thereby effectively improving the compressibility and resilience of the material.

[0026] S3. Fix the spiral metal wire obtained in step S2 to the frame and assemble it to form a glue injection cavity, so that the spiral metal wire is arranged vertically and non-contactly in the cavity to obtain a shaped glue injection cavity.

[0027] Specifically, the twisted spirals are wound using a CNC winding machine at a rate of 25-8000 strands / cm. 2 The density of the wires is fixed on the titanium alloy frame, and the spacing between adjacent frames is controlled at 0.2~2mm, assembling to form a sealed injection cavity. This wire arrangement method ensures that the metal wires are arranged vertically within the cavity and do not contact each other, while also supporting the mixed assembly of different functional metal wires to broaden and improve the shielding effectiveness of the product.

[0028] S4. Mix vinyl silicone rubber, fumed silica and vulcanizing agent evenly according to the specified ratio to obtain silicone matrix mixture.

[0029] Specifically, by mass, the composition of the silicone matrix mixture is as follows: 100 parts vinyl silicone rubber, 15 parts fumed silica, and 3 parts 2,5-dimethyl-2,5-di-tert-butylperoxide (commonly known as "double 25") as the vulcanizing agent; the above raw materials are added to a two-roll mill and mixed evenly using conventional mixing processes to obtain a silicone matrix mixture with good flowability.

[0030] S5. The silicone matrix mixture obtained in step S4 is injected into the shaping injection cavity obtained in step S3, and cured through a two-stage vulcanization process to obtain the high-stability conductive silicone material filled with directional metal wires.

[0031] Specifically, the silicone matrix mixture is injected into the molding cavity at -0.08~-0.1MPa and 25℃ to ensure that the cavity is filled with material. Then, a two-stage vulcanization process is used for curing: the first stage vulcanization temperature is 120~130℃ and the holding temperature is 10~15min; the second stage vulcanization temperature is 150~160℃ and the holding temperature is 2~3h. After curing, it is naturally cooled to room temperature and demolded to obtain a highly stable conductive silicone material filled with oriented metal wires.

[0032] The conductive silicone material prepared according to the above method is specifically formed by the composite curing of metal wires and silicone matrix, wherein the metal wires are surface-treated spiral metal wires, and the metal wires are arranged in a vertical non-contact orientation in the silicone matrix.

[0033] Furthermore, the performance of the obtained conductive silicone material was verified: like Figure 3 As shown, the resistance-compressive strain curve indicates that the initial vertical resistivity of the material is ≤10 mΩ / cm. 2 @1mm, the resistance drops rapidly from an initial high resistance to about 7mΩ in the 0~5% compressive strain range, and the resistance is stably maintained at 6.5~7mΩ in the 5~30% compressive strain range with a fluctuation range of <2%, exhibiting excellent conductivity and outstanding stability.

[0034] like Figure 4 As shown in the stress-strain curve comparison diagram, the conductive silicone material with a Shore A specification of 45 maintains a low level of compressive stress in the 0~5% compressive strain range, and the compressive stress increases steadily with increasing strain in the 5~30% compressive strain range. The compressive stress under different compressive strains is compared between ordinary 45A silicone and the conductive silicone of this invention, and the results are shown in Table 1.

[0035] Table 1 Comparison of compressive stress under different compressive strains

[0036] From Table 1 and Figure 4 It can be seen that the 45 Shore A conductive silicone of the present invention has a higher stress value than ordinary 45A silicone of the same specification in all compression strain ranges. While maintaining the same excellent compression resilience as ordinary 45A silicone, the mechanical load-bearing capacity is improved, and it can be adapted to higher intensity repeated compression application scenarios.

[0037] like Figure 5 As shown, the 10,000 compression cycle life test curve indicates that the material's initial resistivity is 7.005 mΩ, and the resistance fluctuates smoothly throughout the entire cycle test without drastic jumps, remaining consistently within the range of 7.005~7.15 mΩ; Figure 5As shown in (a) and (b), the resistance is 7.126 mΩ after 10,000 compression cycles, and the resistance change rate is only 1.73%, which fully demonstrates the excellent long-term durability and conductivity stability. Meanwhile, tests showed that the material's conductivity fluctuated by less than 8% within a temperature range of -55℃ to 200℃, and it showed no rust after 500 hours of salt spray testing, demonstrating strong environmental adaptability. The CNC wire laying process improved efficiency by 50 times compared to manual wire laying, and the finished product qualification rate was >98%, making it suitable for large-scale production.

[0038] The above content will be further described below through specific implementation methods. The provided embodiments are only some embodiments of the present invention.

[0039] Example 1 A Monel alloy wire with a diameter of 0.1 mm was selected and electroplated with chromium, with the thickness of the chromium plating layer controlled to be 0.5~1 μm. Subsequently, the metal wire was subjected to an aerobic oxidation treatment. The surface-treated metal wires are fixed to the titanium alloy frame using a CNC winding machine, with the wire density controlled at 160 wires / cm². 2 Assemble a 10-layer frame to form a sealed injection molding cavity; Inject silicone matrix mixture into injection mold cavity and cure it using a two-stage vulcanization process. First, keep it at 120℃ for 30 minutes to complete the first stage of vulcanization, and then keep it at 160℃ for 4 hours to complete the second stage of vulcanization. The cured product is vertically cut into conductive silicone pads with a thickness of not less than 1 mm to obtain the high-stability conductive silicone material filled with oriented metal wires as described in this embodiment.

[0040] Furthermore, specific performance tests were conducted on the conductive silicone material obtained in this embodiment, and the results are as follows: The vertical resistance is 0.007 Ω / cm 2 @1mm, (equivalent to 7mΩ / cm) 2 (@1mm) Initial vertical resistance ≤10mΩ / cm 2 @1mm; Mechanical properties: Compression set rate is 4.2%, springback rate is 96%; Stability performance: The resistance change rate after 10,000 compression cycles is 1.5%; Environmental adaptability: The conductivity fluctuates by 6% within a temperature range of -55℃ to 200℃, and the resistance change rate is 1.2% after 500 hours of salt spray testing; The finished product qualification rate of CNC fabrication process is 98.5%.

[0041] Example 2 Select 1J85 iron-nickel soft magnetic alloy wire with a diameter of 0.08mm, electroplat chromium on it, control the thickness of the chromium plating layer to be 0.5~1μm, and then perform aerobic oxidation treatment on the metal wire. The surface-treated metal wires are fixed to the titanium alloy frame using a CNC winding machine, with the wire density controlled at 160 wires / cm². 2 Assemble an 8-layer frame to form a sealed injection molding cavity; Inject silicone matrix mixture into injection mold cavity and cure it using a two-stage vulcanization process. First, keep it at 120℃ for 30 minutes to complete the first stage of vulcanization, and then keep it at 160℃ for 4 hours to complete the second stage of vulcanization. The cured product is vertically cut into conductive silicone pads with a thickness of not less than 1 mm to obtain the high-stability conductive silicone material filled with oriented metal wires as described in this embodiment.

[0042] Furthermore, specific performance tests were conducted on the conductive silicone material obtained in this embodiment, and the results are as follows: The vertical resistance is 0.009 Ω / cm 2 @1mm, (equivalent to 9mΩ / cm) 2 (@1mm) Initial vertical resistance ≤10mΩ / cm 2 @1mm; Mechanical properties: Compression set rate is 4.5%, springback rate is 95%; Stability performance: The resistance change rate after 10,000 compression cycles is 1.8%; Environmental adaptability: The conductivity fluctuates by 7% within a temperature range of -55℃ to 200℃, and the resistance change rate is 1.6% after 500 hours of salt spray testing; The finished product qualification rate of CNC fabrication process was 98.2%.

[0043] Example 3 Select copper wire with a diameter of 0.12 mm, electroplat it with chromium, control the thickness of the chromium plating layer to be 0.5~1 μm, and then perform aerobic oxidation treatment on the metal wire; The surface-treated metal wires are fixed to the titanium alloy frame using a CNC winding machine, with the wire density controlled at 180 wires / cm². 2 Assemble a 10-layer frame to form a sealed injection molding cavity; Inject silicone matrix mixture into the injection mold cavity and cure it using a two-stage vulcanization process. First, the first stage of vulcanization is completed by holding at 120℃ for 35 minutes, and then the second stage of vulcanization is completed by holding at 160℃ for 3.5 hours. The cured product is vertically cut into conductive silicone pads with a thickness of not less than 1 mm to obtain the high-stability conductive silicone material filled with oriented metal wires as described in this embodiment.

[0044] Furthermore, specific performance tests were conducted on the conductive silicone material obtained in this embodiment, and the results are as follows: The vertical resistance is 0.003 Ω / cm 2 @1mm (equivalent to 3mΩ / cm) 2 @1mm), initial vertical resistance ≤10mΩ / cm 2 @1mm; Mechanical properties: Compression set rate is 4.0%, and springback rate is 95.5%; Stability performance: The resistance change rate after 10,000 compression cycles is 1.3%; Environmental adaptability: The conductivity fluctuates by 5.5% within a temperature range of -55℃ to 200℃, and the resistance change rate is 0.9% after 500 hours of salt spray testing; The finished product qualification rate of CNC fabrication process is 98.8%.

[0045] Comparative Example 1 This comparative example uses conventional silver-aluminum conductive rubber as the control sample, and the control sample is prepared according to conventional preparation process.

[0046] The performance of Embodiment 1 of the present invention and Comparative Example 1 were compared and tested. The test results are shown in Table 2 below.

[0047] Table 2 Performance Test Results

[0048] As can be seen from the comparative data provided in Table 2, the conductive silicone material of the present invention is significantly superior to the existing conventional silver-aluminum conductive rubber in terms of resistance stability, resilience, and salt spray corrosion resistance.

[0049] Therefore, the above-mentioned high-stability conductive silicone material and preparation method filled with directional metal wire solves the problems of poor conductivity stability, easy oxidation and corrosion, large permanent compression deformation, and unstable performance due to the fragility of the percolation network in traditional conductive silicone. At the same time, it eliminates the need for expensive metal fillers, reduces the material preparation cost, and thus prepares a conductive silicone material with low impedance and high resilience, which meets the application requirements of electronic equipment sealing gaskets, aerospace electromagnetic protection and other scenarios.

[0050] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0051] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A highly stable conductive silicone material filled with oriented metal wires, characterized in that, The conductive silicone material is formed by the composite curing of metal wires and silicone matrix. The metal wires are surface-treated spiral metal wires. The surface treatment of the metal wires is sequential electroplating with chromium and oxygen treatment. The metal wires are arranged in a vertical non-contact orientation in the silicone matrix. The silicone matrix is ​​composed of vinyl silicone rubber, fumed silica and vulcanizing agent.

2. The highly stable conductive silicone material filled with oriented metal wires according to claim 1, characterized in that, The metal wire is made of one or more of the following materials: nickel-copper alloy wire, iron-nickel alloy wire, copper wire, nickel wire, stainless steel wire, and aluminum wire.

3. The highly stable conductive silicone material filled with oriented metal wires according to claim 1, characterized in that, The diameter of the metal wire is 0.01~0.15mm, and the thickness of the chromium layer formed by electroplating is 0.5~1μm.

4. The highly stable conductive silicone material filled with oriented metal wires according to claim 1, characterized in that, The compounding ratio of the silicone matrix by weight is: 100 parts vinyl silicone rubber, 10-20 parts fumed silica, and 2-4 parts vulcanizing agent.

5. The highly stable conductive silicone material filled with oriented metal wires according to claim 1, characterized in that, The directional arrangement density of the spiral metal wires in the silicone matrix is ​​25~8000 wires / cm². 2 .

6. A method for preparing a highly stable conductive silicone material filled with oriented metal wires as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1. The metal wire is subjected to electroplating chromium and oxygen treatment in sequence to obtain the surface-treated metal wire. S2. Twist water-soluble fibers with the surface-treated metal wire obtained in step S1 to form a spiral wire. Remove the water-soluble fibers by soaking in water to obtain a spiral metal wire, or directly use a multi-wire twisted wire formed by twisting multiple metal wires as a spiral metal wire. S3. Fix the spiral metal wire obtained in step S2 to the frame and assemble it to form a glue injection cavity, so that the spiral metal wire is arranged vertically and non-contactly in the cavity to obtain a shaped glue injection cavity. S4. Mix vinyl silicone rubber, fumed silica and vulcanizing agent evenly according to the specified ratio to obtain silicone matrix mixture; S5. The silicone matrix mixture obtained in step S4 is injected into the shaping injection cavity obtained in step S3, and cured through a two-stage vulcanization process to obtain the high-stability conductive silicone material filled with directional metal wires.

7. The method according to claim 6, characterized in that, In step S2, the diameter of the water-soluble fiber is 0.08~0.12mm, and the diameter of a single strand of the multi-wire twisted thread formed by twisting multiple metal wires is 0.01~0.05mm.

8. The method according to claim 6, characterized in that, In step S3, a CNC winding device is used to fix the spiral metal wire to the alloy frame, with a spacing of 0.2~2mm between adjacent alloy frames.

9. The method according to claim 6, characterized in that, In step S5, the two-stage vulcanization process is as follows: first, a first-stage vulcanization is carried out at 120~130℃, and then a second-stage vulcanization is carried out at 150~160℃.

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