Electrically conductive coated foam silicone strip and method of making same

Abstract

This invention discloses a conductive coated foamed silicone strip and its preparation method. The conductive coated foamed silicone strip includes: a foamed silicone strip core material with an overall cross-sectional dimension ≤2mm and a hardness ≤40 Shore A; and a conductive coating composited on the surface of the foamed silicone strip core material. The conductive coating comprises two-dimensional sheet-like metal conductive fillers, one-dimensional fibrous carbon-based conductive fillers, and zero-dimensional granular carbon-based conductive fillers, forming a three-dimensional interconnected synergistic conductive network of points, lines, and surfaces. Shape memory polymers can be added to the foamed silicone strip core material to actively compensate for permanent compression deformation; the resin matrix of the conductive coating can contain a polysiloxane crosslinking agent with reversible Diels-Alder covalent bonds to impart thermally reversible self-healing functionality to the coating. The conductive coated foamed silicone strip exhibits a volume resistivity ≤0.002Ω·cm and a compressive stress ≤10N at 50% compression, making it suitable for the confined installation space of micro-precision electronic devices. It also possesses long-term conductive reliability and coating self-healing functionality, with low production costs.

Description

Technical Field

[0001] This invention relates to the field of conductive elastomer materials technology, and more particularly to a conductive coated foamed silicone strip and its preparation method. Background Technology

[0002] Conductive foamed silicone strips are commonly used electromagnetic shielding and conductive connection accessories in the field of electronic equipment. With their excellent elastic deformation capability, fit, and insulating substrate properties, they are widely used in precision equipment such as 5G communication equipment, smart wearable terminals, and new energy electronic devices. They are mainly used for conductive connections in equipment gaps, electromagnetic shielding, cushioning and shock absorption, and sealing protection. As electronic devices continue to iterate towards miniaturization, thinness, and high integration, the internal assembly space of these devices is significantly reduced. This places stringent requirements on the size, flexibility, compressibility, and conductivity stability of conductive silicone strips. Small-sized, low-hardness, and highly compressible conductive silicone strips have become the mainstream trend in industry research and development and are also key components for ensuring the stable operation of precision electronic equipment.

[0003] Currently, most conductive foamed silicone strips on the market are prepared using single-filler conductive modification or conventional coating processes. The mainstream preparation methods fall into two categories: one is to directly blend carbon-based or metal-based single conductive fillers into the silicone matrix, achieving conductivity through overall matrix doping; the other is to coat the surface of the foamed silicone with a conductive coating, relying on the surface conductive layer to achieve conductivity. Among these, surface-coated products, due to the insulating properties of the substrate and the high conductivity of the surface layer, offer advantages over overall doped products, including lower material consumption, controllable cost, and a balance of insulation and conductivity, making them the preferred solution for precision electronic components at present. Existing conductive coating systems mostly use single-dimensional conductive fillers, employing sheet-like metal fillers or tubular or granular carbon-based fillers as the conductive medium alone, combined with a coating of conventional thickness to complete the coating preparation.

[0004] Current conductive coated foamed silicone strip technology still suffers from numerous unavoidable drawbacks, hindering its application in high-precision equipment. Single-dimensional conductive fillers cannot construct a complete three-dimensional conductive network; large overlap gaps between fillers make the conductive pathways prone to breakage under high compression deformation conditions, leading to a significant decrease in conductive stability. Furthermore, to ensure conductive continuity, existing coatings are generally too thick, requiring high amounts of precious metal fillers, resulting in high production costs. Thick coatings also reduce the overall flexibility of the strip, making it unsuitable for the assembly requirements of small-sized micro-devices. In addition, traditional silicone coatings lack self-healing capabilities; long-term repeated compression easily leads to micro-cracks in the coating, causing irreversible damage to the conductive network, resulting in short product lifespan and rapid performance degradation, failing to meet the long-term stable operation requirements of precision electronic equipment. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, this invention provides a conductive coated foamed silicone strip and its preparation method.

[0006] The objective of this invention can be achieved through the following technical solutions: A conductive coated foamed silicone strip, comprising: The core material of the foamed silicone strip has an overall cross-sectional dimension ≤2mm and a hardness ≤40 Shore A. The conductive coating is composited on the surface of the foamed silicone strip core material. The conductive coating includes two-dimensional sheet-like metal conductive filler, one-dimensional fibrous carbon conductive filler and zero-dimensional particulate carbon conductive filler. The three types of conductive fillers interweave and overlap in the conductive coating to form a three-dimensional interconnected synergistic conductive network of points, lines and surfaces.

[0007] The conductive coating constructs a unique three-dimensional conductive network connecting points, lines, and surfaces by synergistically combining three different types of conductive fillers. Two-dimensional sheet-like metallic conductive fillers serve as the conductive framework, providing a large conductive contact surface and constructing planar conductive pathways. One-dimensional fibrous carbon-based conductive fillers act as conductive bridges, connecting adjacent two-dimensional sheet-like metallic conductive fillers and filling the conductive gaps between the sheet-like fillers to form long-range conductive pathways. Zero-dimensional granular carbon-based conductive fillers act as conductive nodes, filling the micro-voids between the two-dimensional and one-dimensional fillers, perfecting the local conductive connectivity structure, and forming a dense conductive network. These three different types of conductive fillers interweave and overlap within the coating, synergistically constructing multi-point conductive channels from macroscopic to microscopic levels. This structure can adaptively adjust to the deformation of the matrix when the foamed silicone strip undergoes high compression deformation, maintaining the integrity of the conductive network and thus maintaining excellent conductivity and stability even under high compression ratios.

[0008] Preferably, the thickness of the conductive coating is 30μm-80μm. This thickness is much thinner than the conventional coating thickness of 100-200μm, which can significantly reduce the amount of precious metals used while ensuring sufficient conductivity, and effectively control production costs.

[0009] Preferably, the two-dimensional sheet-like metallic conductive filler is sheet-like silver powder or sheet-like silver-coated aluminum powder. Sheet-like silver powder has excellent conductivity, while sheet-like silver-coated aluminum powder has both good conductivity and lower cost advantages. Both have a high aspect ratio, which is beneficial for forming a large-area conductive contact surface.

[0010] Preferably, the one-dimensional fibrous carbon-based conductive filler is a carbon nanotube. Carbon nanotubes have a high aspect ratio, excellent electrical conductivity, and mechanical flexibility, which can effectively bridge adjacent sheet-like metal fillers and form long-range conductive channels in the coating.

[0011] Preferably, the zero-dimensional particulate carbon-based conductive filler is conductive carbon black. Conductive carbon black has a small particle size and a large specific surface area, which can effectively fill the micro-voids inside the coating and improve the local connectivity of the conductive network.

[0012] Preferably, the weight ratio of the two-dimensional sheet-like metallic conductive filler, the one-dimensional fibrous carbon-based conductive filler, and the zero-dimensional granular carbon-based conductive filler is (100-200):(1-10):(1-5). Within this ratio range, the three fillers can form an optimal synergistic conductive network structure, balancing conductivity, coating mechanical properties, and production cost. If the amount of the two-dimensional sheet-like metallic conductive filler is too low, the conductive pathways will be insufficient; if the amount is too high, the cost will increase and the coating processability will deteriorate. If the amount of the one-dimensional carbon nanotube is too low, the bridging effect will be insufficient; if the amount is too high, dispersion will be difficult. If the amount of the zero-dimensional conductive carbon black is too low, the conductive network micro-areas will not be fully filled; if the amount is too high, the viscosity of the coating liquid will be too high, and the coating uniformity will decrease.

[0013] Preferably, the conductive coated foamed silicone strip has a volume resistivity ≤0.002Ω·cm and a compressive stress ≤10N at a 50% compression rate.

[0014] Preferably, the foamed silicone strip core material contains a shape memory polymer, which is trans-1,4-polyisoprene. Trans-1,4-polyisoprene has a suitable shape memory transition temperature, which matches well with the operating temperature rise range of electronic devices, and has good compatibility with silicone rubber blending / copolymerization processes.

[0015] Preferably, the resin matrix of the conductive coating comprises a polysiloxane crosslinking agent containing reversible Diels-Alder covalent bonds. This crosslinking agent is a double-terminated siloxane monomer (DA-Si monomer) formed by a Diels-Alder cycloaddition reaction between a furan-containing siloxane and a maleimide-containing siloxane. The DA-Si monomer has hydrolyzable siloxane groups at both ends, which can participate in the crosslinking reaction of silicone rubber during curing, thereby introducing reversible Diels-Alder covalent bonds into the silicone rubber crosslinking network. When microcracks or localized breaks in the conductive pathways appear in the coating during long-term use, the Diels-Alder bonds undergo reversible breakage and recombination using the heat from the equipment itself or external heating. This causes chain segment movement and interfacial fusion in the coating matrix, leading to the re-reassembly of the conductive filler network, thus achieving self-repair of the conductive function.

[0016] In addition, the present invention also provides a method for preparing a conductive coated foamed silicone strip, comprising the following steps: (1) The foamed silicone strip core material is subjected to plasma treatment or corona treatment to obtain surface activated foamed silicone strip core material; (2) Two-dimensional sheet-like metal conductive filler, one-dimensional fibrous carbon conductive filler, zero-dimensional granular carbon conductive filler and polysiloxane crosslinking agent containing Diels-Alder reversible covalent bonds are added to liquid silicone rubber matrix, stirred and dispersed evenly, and the viscosity is adjusted to 4000-8000 mPa·s to obtain coating liquid. (3) The coating liquid obtained in step (2) is applied to the surface of the surface-activated foamed silicone strip core material obtained in step (1) by dip coating, curtain coating or micro piezoelectric spraying to form a wet film. (4) The foamed silicone strip coated with wet film is cured by gradient heating to cure the coating and bond it with the surface of the foamed silicone strip core material.

[0017] Step (4) employs a gradient temperature curing method, allowing the solvent in the coating to gradually evaporate and the liquid silicone rubber to gradually crosslink and cure, which is beneficial for forming a dense and strongly adhesive conductive coating. Preferably, in step (4), the gradient temperature curing procedure is as follows: first, cure at 110-130℃ for 4-6 minutes, and then cure at 170-190℃ for 4-6 minutes. The first stage of curing at a lower temperature allows volatile components such as diluents in the coating to slowly escape, and the coating is initially shaped; the second stage of curing at a higher temperature allows the liquid silicone rubber to fully crosslink, forming the final conductive coating. The two-stage gradient curing can produce a coating with a dense structure, stable conductivity, and excellent adhesion. Furthermore, this gradient curing procedure is naturally matched with the thermodynamic characteristics of the reversible covalent bonds of Diels-Alder: the first stage curing temperature is in the dynamic equilibrium region of the DA bonds, which is beneficial for coating leveling and stress release; at the second stage curing temperature, the DA bonds dissociate, the silicone rubber backbone is fully crosslinked, and after cooling, the DA bonds rebuild a complete network.

[0018] The beneficial effects of this invention are as follows: (1) This invention constructs a three-dimensional interconnected conductive network of points, lines, and surfaces, which significantly improves the conductivity stability under high compression conditions. This invention uses a three-dimensional composite system with two-dimensional sheet-like metal fillers as conductive skeletons, one-dimensional carbon nanotubes as conductive bridges, and zero-dimensional conductive carbon black as conductive nodes. This system compensates for the defects of insufficient overlap and excessive gaps in single-dimensional conductive fillers, forming a dense conductive channel from macroscopic to microscopic. This three-dimensional network can adaptively adjust with the compression deformation of the foamed silicone matrix, effectively avoiding the problem of conductive path breakage under high compression. This allows the product to maintain an ultra-low volume resistivity of ≤0.002Ω·cm under a high compression ratio of 50%, while the compressive stress is ≤10N. It takes into account both excellent conductivity and flexible fit, and is suitable for the assembly and deformation requirements of precision microelectronic devices.

[0019] (2) This invention achieves ultra-thin coating molding, significantly reducing production costs while ensuring conductivity. Compared to the conventional conductive coating thickness of 100-200μm in the prior art, this invention controls the coating thickness to an ultra-thin range of 30μm-80μm, and overcomes the technical limitation that coating thickness determines conductivity by relying on the three-dimensional filler synergistic conductivity mechanism. The ultra-thin coating structure greatly reduces the amount of precious metal sheet filler used, effectively compressing raw material costs while ensuring conductivity continuity and stability. At the same time, it avoids the problems of increased overall hardness and decreased flexibility of the adhesive strip caused by thick coatings, making it suitable for the use scenarios of small-sized, narrow-gap microelectronic devices.

[0020] (3) This invention introduces a Diels-Alder reversible covalent crosslinking system, endowing the product with conductive self-healing function and effectively extending its service life. This invention introduces a polysiloxane crosslinking agent containing reversible DA covalent bonds into the coating resin matrix, enabling the coating to have thermally triggered self-healing characteristics. When the product is repeatedly compressed for a long time, resulting in microcracks in the coating or local breakage of the conductive network, the DA bonds can be reversibly broken and recombined by relying on the temperature rise of the equipment itself, driving the conductive filler network to re-overlap and repair, solving the defects of irreversible damage and rapid performance decay of traditional conductive coatings. In addition, the foamed silicone core material is enriched with trans-1,4-polyisoprene shape memory polymer, which is temperature-suitable for the working range of electronic devices and has excellent deformation recovery, further improving the compressibility of the adhesive strip; a two-stage gradient temperature curing process is adopted to match the thermodynamic characteristics of DA bonds, achieving slow solvent evaporation, full crosslinking of the coating, and effective stress release, resulting in a conductive coating with a dense structure, strong adhesion, and good uniformity. Detailed Implementation

[0021] To further illustrate the technical means and effects of the present invention in achieving the intended purpose, the following detailed description of the specific implementation methods, structures, features and effects of the present invention, in conjunction with preferred embodiments, is provided below.

[0022] Example 1 Core material preparation: The core material is made of foamed silicone rubber with a cross-sectional dimension of 0.5×0.5mm and a hardness of 20 Shore A. This core material is produced by foaming, extruding, and vulcanizing liquid silicone rubber, and has a closed-cell or semi-closed-cell foam structure with a density of approximately 0.45g / cm³. 3 .

[0023] Preparation of coating solution (parts by weight): Liquid silicone rubber matrix (vinyl silicone oil, viscosity 2000 mPa·s): 100 parts Hydrogen-containing silicone oil crosslinking agent (0.3% hydrogen content): 5 parts Flaky silver-coated aluminum powder (average particle size 15μm, aspect ratio ≥20): 150 parts Carbon nanotubes (multi-walled carbon nanotubes, diameter 10-20 nm, length 5-15 μm): 5 parts Conductive carbon black (specific surface area approximately 250m²) 2 / g, DBP absorption value ≥180mL / 100g): 3 portions Xylene diluent: 50 parts Alkyne alcohol inhibitor (1-ethynyl-1-cyclohexanol): 0.02 parts Platinum catalyst (vinyl silicone oil solution with a platinum content of 3000 ppm): 0.1 parts Preparation process: (1) Surface activation treatment: Place the foamed silicone strip core material in a plasma treatment device with a treatment power of 1000W and a treatment time of 120s. The surface activated foamed silicone strip core material is then obtained.

[0024] (2) Preparation of coating solution: After mixing the liquid silicone rubber matrix, diluent and inhibitor evenly, add flake silver-coated aluminum powder, carbon nanotubes and conductive carbon black in sequence. Grind and disperse the mixture with a three-roll mill until the fineness is ≤15μm. Then add hydrogen-containing silicone oil crosslinking agent and platinum catalyst and stir evenly. Adjust the viscosity to 4500±500mPa·s and degas under vacuum for 10min to obtain the coating solution.

[0025] (3) Precision coating: Using dip coating, under tension control (tension 0.02-0.05N), the core material treated in step (1) is passed through the coating liquid tank at a speed of 4mm / s, and the wet film thickness is controlled to be about 100μm.

[0026] (4) Gradient curing: The foamed silicone strip coated with wet film is fed into the drying tunnel and passed through the first 120℃ drying zone (stay for 5 min) and the second 180℃ drying zone (stay for 5 min) in sequence. After cooling to room temperature, the conductive coated foamed silicone strip is obtained. The dry film thickness is 50±5μm.

[0027] Example 2 The core material is made of foamed silicone strips with a cross-sectional dimension of 0.3×1.5mm and a hardness of 30 Shore A. Coating solution preparation (parts by weight): 200 parts flake silver-coated aluminum powder, 5 parts carbon nanotubes, 3 parts conductive carbon black, 100 parts liquid silicone rubber matrix, 5 parts hydrogen-containing silicone oil crosslinking agent, 50 parts diluent, 0.02 parts alkynyl alcohol inhibitor, 0.1 parts platinum catalyst (3000 ppm). Preparation process: Step (2) Adjust the viscosity to 6000±500mPa·s; Step (3) Use spraying method, speed 6mm / s, control the wet film thickness to about 80μm; the rest is the same as in Example 1.

[0028] Example 3 Core material preparation: 100 parts of raw silicone rubber, 5 parts of trans-1,4-polyisoprene (TPI), 3 parts of foaming agent (azodicarbonamide), and 1.2 parts of vulcanizing agent (dicumyl peroxide) were mixed evenly on an open mill, extruded and molded, and then foamed and vulcanized at 170°C for 15 minutes to obtain a foamed silicone strip core material containing shape memory polymer. The cross-sectional dimensions are 0.3 × 1.5 mm, and the hardness is 30 Shore A.

[0029] Coating solution formulation and preparation process: exactly the same as in Example 1.

[0030] Example 4 Synthesis of DA-Si monomers: ① 9.8 g (0.1 mol) of furfuryl alcohol was dissolved in 50 mL of anhydrous tetrahydrofuran. 0.1 g of dibutyltin dilaurate was added as a catalyst. Under nitrogen protection, 24.7 g (0.1 mol) of 3-isocyanate-propyltriethoxysilane was added dropwise. The mixture was stirred at 60 °C for 4 h. The solvent was removed by rotary evaporation to obtain the synthesized furan-containing siloxane (F-Si). FTIR (thin film method): 3345 cm⁻¹ -1 (NH stretching vibration), 2974 cm -1 (CH), 1718 cm -1 (C=O, carbamate), 1532 cm -1 (NH bending vibration), 1102 cm -1 (Si-OC), 956 cm -1 (Si-OEt); Characteristic peak of NCO in raw material (2270 cm⁻¹) -1 )disappear.

[0031] ② Dissolve 9.8 g (0.1 mol) of maleic anhydride in 50 mL of acetone, add 22.1 g (0.1 mol) of γ-aminopropyltriethoxysilane dropwise, stir at room temperature for 2 h, then add 20.4 g of acetic anhydride, 10.1 g of triethylamine, and 0.5 g of sodium acetate, stir at 60 °C for 3 h, cool, filter, and remove the solvent by rotary evaporation to obtain a siloxane containing maleimide groups (M-Si). FTIR (thin film method): 2975 cm⁻¹ -1 (CH), 1773 cm -1 and 1705 cm -1 (C=O, characteristic double peak of maleimide five-membered ring), 1392 cm⁻¹ -1 (CNC), 1105 cm -1 (Si-OC), 958 cm -1 (Si-OEt); Characteristic double peaks of the raw material acid anhydride (1845 cm⁻¹) -1 / 1775 cm -1 )disappear.

[0032] ③ Mix equal molar amounts of F-Si and M-Si and stir at room temperature for 12 h. The furan group and the maleimide group undergo a Diels-Alder cycloaddition reaction to obtain the DA-Si monomer. 1 ¹H NMR (400MHz, CDCl₃): The proton peaks of F-Si furan cycloolefins and M-Si maleimide olefins at chemical shifts δ 6.4–6.7 ppm essentially disappeared; a new set of multiplets appeared at δ 3.2–5.3 ppm, which are attributed to the skeletal protons of the DA cycloaddition product. Integral calculations showed a reaction conversion rate >95%.

[0033] Preparation of coating solution (parts by weight): Liquid silicone rubber matrix: 100 parts Hydrogen-containing silicone oil crosslinking agent: 2 parts DA-Si monomer: 3 parts Flake silver powder (average particle size 10μm, aspect ratio ≥25): 150 parts Carbon nanotubes: 5 parts Conductive carbon black: 3 parts Xylene diluent: 50 parts Alkyne alcohol inhibitors: 0.02 parts Platinum catalyst: 0.1 parts Preparation process: In step (2), the DA-Si monomer and the hydrogen-containing silicone oil crosslinking agent are added together. The remaining steps are exactly the same as in Example 1.

[0034] Example 5 Core material: Shape memory foamed silicone strip containing 5wt% TPI prepared according to Example 2, with a cross-sectional size of 0.5×0.5mm and a hardness of 25 Shore A.

[0035] Coating solution: Prepared according to the formulation of Example 3, containing three-dimensional conductive filler (150 parts of flake silver powder, 5 parts of carbon nanotubes, 3 parts of conductive carbon black) and 3 parts of DA-Si monomer.

[0036] Preparation process: (2) Preparation of coating solution: Same as in Example 3, except the viscosity is adjusted to 5000±500mPa·s; other steps are the same as in Example 1.

[0037] Comparative Example 1 The only difference from Example 1 is that only 158 parts of flake silver-coated aluminum powder were used in the coating solution, and no carbon nanotubes or conductive carbon black were added. The rest of the formulation and process are the same as in Example 1.

[0038] Comparative Example 2 The only difference from Example 1 is that only 150 parts of flake silver-coated aluminum powder and 8 parts of carbon nanotubes were used in the coating solution, and conductive carbon black was not added. The rest of the formulation and process are the same as in Example 1.

[0039] Comparative Example 3 The only difference from Example 1 is that only 150 parts of flake silver-coated aluminum powder and 8 parts of conductive carbon black were used in the coating solution, and no carbon nanotubes were added. The rest of the formulation and process are the same as in Example 1.

[0040] Comparative Example 4 The only difference from Example 1 is that the dip-coating speed is reduced to 2 mm / s and the viscosity of the coating solution is increased to 10000 mPa·s, resulting in an increased wet film thickness. After gradient curing, the dry film thickness is approximately 120 μm. Everything else is the same.

[0041] Comparative Example 5 The only difference from Example 3 is that the curing process in step (4) is constant temperature curing at 180°C for 10 minutes, without gradient temperature increase. The rest are the same.

[0042] Comparative Example 6 Differences from Example 1: The core material is a solid silicone strip (non-foamed structure) with a cross-sectional size of 0.5×0.5mm, but the hardness is 55 Shore A; the coating liquid formulation and preparation process are exactly the same as in Example 1.

[0043] Comparative Example 7 The difference from Example 1 is that the amount of flake silver-coated aluminum powder in the coating solution is reduced to 80 parts (below the lower limit of 100 parts), while the amounts of carbon nanotubes and conductive carbon black remain unchanged. Everything else is exactly the same as in Example 1.

[0044] Comparative Example 8 The difference from Example 1 is that the amount of carbon nanotubes in the coating solution is increased to 15 parts (higher than the upper limit of 10 parts), while the amounts of flake silver-coated aluminum powder and conductive carbon black remain unchanged. Everything else is exactly the same as in Example 1.

[0045] Performance testing: Volume resistivity: The test was conducted using a four-probe resistivity tester in accordance with GB / T 2439-2001 standard, combined with the actual operating conditions of the product (50% compression state): A conductive coated foamed silicone strip sample with a length of about 50 mm was taken; the sample was placed in the compression fixture, and the fixture spacing was adjusted to 50% of the original height of the sample, so that the sample was in a 50% compression state; the volume resistivity of the sample under compression state was measured using the four-probe method, with a probe spacing of 10 mm. Calculate the volume resistivity: ρ = R × A / L; where: ρ—volume resistivity (Ω·cm); R—measured resistance (Ω); A—effective conductive cross-sectional area of ​​the coating (cm²) 2L—Probe spacing (cm).

[0046] Compression performance: Referring to GB / T 7757-2009 standard, a 30mm conductive coated foamed silicone strip sample was placed between the upper and lower pressure plates of the compression fixture and compressed at a speed of 5mm / min. When the compression ratio reached 50%, the compression load F (N) was recorded. The compressive stress was calculated using the following formula: σ = F / S; where: σ—compressive stress (N / cm²) 2 F—Load at 50% compression (N); S—Contact area between the specimen and the pressure plate (cm²) 2 ).

[0047] Aging resistance: The conductive coated foamed silicone strip sample was placed in a constant temperature and humidity test chamber, with the temperature set at 85℃ and the relative humidity at 85%RH. After aging for 1000 hours, the sample was taken out and placed at room temperature for 2 hours. The volume resistivity at 50% compression ratio after aging was then tested according to the above method, and the resistance change rate was calculated.

[0048] Compression recovery rate: The conductive coated foamed silicone strip sample was placed in a compression fixture and compressed to 50% of its original height. It was then placed in an oven at 65°C and kept for 1000 hours. After being removed and unloaded at room temperature and allowed to recover freely for 2 hours, the height recovery rate was tested.

[0049] Repair performance: Take a conductive coated foamed silicone strip sample and measure its volume resistivity R0 at the initial 50% compression ratio; artificially create micro-scratches on the coating surface (scratch depth about 20-30μm, scratch direction perpendicular to the current direction) to simulate micro-crack damage generated during coating use; measure the volume resistivity R1 of the scratched sample; then heat the scratched sample at 80℃ for 30 minutes, cool it to room temperature and measure the volume resistivity R2; repair rate (%) = (R1-R2) / (R1-R0).

[0050]

[0051] The test results show that Example 1, as the basic scheme, uses a three-dimensional filler synergistic compound and a foamed core material, achieving a volume resistivity of 0.0018 Ω·cm and a compressive stress of only 8 N. This demonstrates that the combination of a point-line-surface three-dimensional conductive network and a low-hardness foamed core material can achieve excellent conductivity while maintaining extremely low compressive stress. Example 2 uses a spraying process and increases the silver content, further reducing the resistivity to 0.0016 Ω·cm. Example 3, after introducing a shape memory core material, achieves a height recovery rate of 95% and a aging resistance change rate of only 11.8%, demonstrating the active compensation effect of shape memory polymers on compression set. Example 4, after introducing a DA self-healing crosslinking agent, achieves a self-healing efficiency of up to 92.5% and a aging resistance change rate of only 7.1%, proving that the reversible covalent bonds of DA endow the coating with excellent thermally triggered self-healing function. Example 5 integrates all innovative features, achieving optimal performance in all aspects—resistivity of only 0.0012 Ω·cm, compressive stress of 7 N, aging change rate of 8.3%, height recovery rate of 96%, and self-healing efficiency of 94.5%. Comparative Examples 1-3, retaining only two-dimensional fillers, lacking zero-dimensional conductive carbon black, and lacking one-dimensional carbon nanotubes respectively, showed resistivity increases to 0.0085, 0.0042, and 0.0068 Ω·cm, respectively, with aging resistance changes as high as 106%-126%, far inferior to Example 1. This demonstrates that all three dimensions of fillers are indispensable, and the three-dimensional point-line-surface synergistic network is key to achieving stable conductivity under high compression. Comparative Example 4, with a coating thickness increased to 120 μm, although the resistivity decreased to 0.0010 Ω·cm, the compressive stress increased to 13 N, exceeding the ≤10 N performance boundary of this invention. Furthermore, the amount of precious metal used was more than twice that of Example 1, demonstrating the comprehensive advantages of ultra-thin coatings in cost reduction and low compressive stress. Comparative Example 5, using isothermal curing, showed a self-healing efficiency of only 65%, and microbubbles appeared in the coating. Comparative Example 6, using a solid high-hardness core material, showed a compressive stress as high as 18 N, far exceeding the ≤10 N requirement. When the metal filler in Comparative Example 7 was reduced to 80 parts, the resistivity soared to 0.012 Ω·cm; when the carbon nanotubes in Comparative Example 8 were increased to 15 parts, the viscosity of the coating solution increased to 12000 mPa·s, agglomeration defects appeared in the coating, and the resistivity increased to 0.0055 Ω·cm. Both examples demonstrate that the filler ratio range (100-200):(1-10):(1-5) defined in this invention has a clear critical significance, and exceeding this range will lead to a sharp deterioration in performance.

[0052] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A conductive coated foamed silicone strip, characterized in that, include: The core material of the foamed silicone strip has an overall cross-sectional dimension ≤2mm and a hardness ≤40 Shore A. The conductive coating is composited on the surface of the foamed silicone strip core material. The conductive coating includes two-dimensional sheet-like metal conductive filler, one-dimensional fibrous carbon conductive filler and zero-dimensional particulate carbon conductive filler. The three types of conductive fillers interweave and overlap in the conductive coating to form a three-dimensional interconnected synergistic conductive network of points, lines and surfaces.

2. The conductive coated foamed silicone strip according to claim 1, characterized in that, The thickness of the conductive coating is 30μm-80μm.

3. The conductive coated foamed silicone strip according to claim 1, characterized in that, The two-dimensional sheet-like metallic conductive filler is sheet-like silver powder or sheet-like silver-coated aluminum powder; the one-dimensional fibrous carbon-based conductive filler is carbon nanotubes; and the zero-dimensional particulate carbon-based conductive filler is conductive carbon black.

4. The conductive coated foamed silicone strip according to any one of claims 1-3, characterized in that, The weight ratio of the two-dimensional sheet-like metallic conductive filler, the one-dimensional fibrous carbon-based conductive filler, and the zero-dimensional granular carbon-based conductive filler is (100-200):(1-10):(1-5).

5. The conductive coated foamed silicone strip according to any one of claims 1-4, characterized in that, The conductive coated foamed silicone strip has a volume resistivity ≤0.002Ω·cm and a compressive stress ≤10N at a 50% compression rate.

6. The conductive coated foamed silicone strip according to any one of claims 1-5, characterized in that, The foamed silicone strip core material contains a shape memory polymer, which is trans-1,4-polyisoprene.

7. The conductive coated foamed silicone strip according to any one of claims 1-5, characterized in that, The resin matrix of the conductive coating contains a polysiloxane crosslinking agent with reversible Diels-Alder covalent bonds.

8. A method for preparing a conductive coated foamed silicone strip according to any one of claims 1-7, characterized in that, Includes the following steps: (1) The foamed silicone strip core material is subjected to plasma treatment or corona treatment to obtain surface activated foamed silicone strip core material; (2) Two-dimensional sheet-like metal conductive powder, one-dimensional fibrous carbon conductive filler, zero-dimensional granular carbon conductive filler and polysiloxane crosslinking agent containing Diels-Alder reversible covalent bonds are added to liquid silicone rubber matrix, stirred and dispersed evenly, and the viscosity is adjusted to 4000-8000 mPa·s to obtain coating liquid. (3) Apply the coating liquid obtained in step (2) to the surface of the surface-activated foamed silicone strip core material obtained in step (1) by dip coating, curtain coating or micro piezoelectric spraying to form a wet film; (4) The foamed silicone strip coated with wet film is cured by gradient heating to cure the coating and bond it with the surface of the foamed silicone strip core material.

9. The preparation method according to claim 8, characterized in that, In step (4), the gradient temperature curing procedure is as follows: first cure at 110-130℃ for 4-6 minutes, and then cure at 170-190℃ for 4-6 minutes.

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