Compression-resistant conductive foam
By combining a gradient pore structure with a chemically bonded elastic conductive matrix, the problem of insufficient compressive strength, conductivity and durability of traditional conductive foams is solved, achieving excellent compressive strength, stable conductivity and high elastic recovery performance, making it suitable for electromagnetic shielding and structural buffering applications in electronic devices.
Patent Information
- Application Number
- CN202511015953.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-23
- Publication Date
- 2025-11-14
AI Technical Summary
Traditional conductive foams have defects in structural design, interface bonding and material properties, making it difficult to balance compressive strength and conductivity. Moreover, the conductivity degrades significantly with long-term use, failing to meet the requirements of high-frequency electromagnetic shielding.
A gradient-channel conductive reinforcement layer is combined with a chemically bonded elastic conductive matrix through chemical covalent grafting and physical interpenetrating interlocking. This is combined with silica nanosphere reinforcement and a conductive polymer film to form a continuous conductive network, which is connected by chemical covalent bonds and physical interpenetrating interlocking.
It achieves excellent compressive strength, stable conductivity and high elastic recovery performance, improves the material's resistance to permanent compressive deformation and the stability of the conductive network, and adapts to the needs of dynamic working conditions.
Smart Images
Figure CN120954785A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of functional composite materials technology, and specifically relates to a pressure-resistant conductive foam. Background Technology
[0002] As a key material for electromagnetic shielding, signal transmission, and buffering protection in electronic devices, the performance of compression-resistant conductive foam directly affects the reliability and service life of the equipment. In fields such as 5G communication, smart wearable devices, and new energy vehicles, the trend of miniaturization and integration of equipment places higher demands on the compressive strength, conductivity stability, and fatigue resistance of foam.
[0003] Traditional conductive foams currently suffer from the following main drawbacks: structural design flaws, insufficient uniformity of pore distribution, and a single-pore structure that makes it difficult to balance compressive strength and porosity, leading to easy pore collapse under pressure and a significant decrease in conductivity; weak interfacial bonding, with the conductive phase and elastic matrix often bonded through physical doping, resulting in poor interfacial compatibility, and the conductive filler easily detaching or agglomerating during long-term use, causing the conductive network to break; limited material properties, with insufficient compatibility between thermoplastic polyurethane (TPU) and silicone rubber in traditional interpenetrating network structures, low crosslinking density, and an elastic recovery rate typically below 80%, and poor dispersion of the conductive phase (such as single silver nanowires or carbon nanotubes), resulting in a sheet resistivity higher than 50 Ω / sq, which cannot meet the requirements of high-frequency electromagnetic shielding; and insufficient functional durability, with the pore walls lacking reinforcing structures, leading to irreversible pore deformation after repeated pressure, significant attenuation of conductivity, and difficulty in adapting to dynamic working conditions.
[0004] Therefore, there is an urgent need to develop a new type of foam material that combines gradient structure reinforcement, interfacial chemical bonding, and a highly elastic conductive network to solve the problems of insufficient compressive strength, conductivity, and durability in existing technologies. Summary of the Invention
[0005] To address the aforementioned pain points, this invention provides a pressure-resistant conductive foam that achieves excellent compressive strength, stable conductivity, and high elastic recovery performance through chemical covalent grafting and physical interpenetration bonding between a gradient channel conductive reinforcement layer and a chemically bonded elastic conductive matrix.
[0006] The present invention is as follows: A pressure-resistant conductive foam, characterized in that it comprises a gradient-pore conductive reinforcement layer and a chemically bonded elastic conductive matrix: the gradient-pore conductive reinforcement layer consists of a surface layer, a transition layer, and a core layer, with silica nanospheres distributed in its pore walls and a conductive polymer film covering its surface; the chemically bonded elastic conductive matrix uses an interpenetrating network structure formed by thermoplastic polyurethane and vinyl silicone rubber as a continuous phase, and a conductive phase formed by surface-modified silver nanowires and carbon nanotubes is bonded in the continuous phase; the gradient-pore conductive reinforcement layer and the chemically bonded elastic conductive matrix are connected by chemical covalent grafting and physical interpenetrating interlocking composite.
[0007] Preferably, the total thickness of the gradient channel conductive reinforcement layer is 1.0 to 3.0 mm, and the sum of the thickness percentages of all layers is 100%, wherein: The surface layer has a thickness of 5% to 15% of the total thickness, a pore size of 40 to 60 micrometers, and a porosity of 40% to 60%. The core layer has a thickness of 60% to 70% of the total thickness, a pore size of 180 to 220 micrometers, and a porosity of not less than 80%. The thickness of the transition layer accounts for 15% to 30% of the total thickness, and its pore size and porosity increase linearly from the surface layer to the core layer.
[0008] Preferably, the diameter of the silica nanospheres is 50 to 200 nanometers, and their surface contains silanol groups (Si-OH). The amount added is 3% to 8% of the mass of the gradient pore conductive reinforcement layer material. The conductive polymer film is polypyrrole or poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS).
[0009] Preferably, the interpenetrating network structure contains a silane-modified TPU compatibilizer, the amount of which is 1%-5% of the total weight of the continuous phase, the content of the vinyl silicone rubber accounts for 15% to 25% of the total weight of the continuous phase, and the thermoplastic polyurethane molecular chain contains isocyanate groups (-NCO).
[0010] Preferably, the isocyanate groups (-NCO) on the thermoplastic polyurethane molecular chain and the silanol groups (Si-OH) on the vinyl silicone rubber molecular chain form -Si-OC(O)-NH- crosslinking bonds through a condensation reaction, and these crosslinking bonds are interconnected in three-dimensional space, so that the molecular chains form a continuous network structure.
[0011] Preferably, the weight ratio of the silver nanowires to the carbon nanotubes is 1:2 to 1:4, the amount of the conductive phase added to the continuous phase is 5% to 15%, and after surface modification with a silane coupling agent, the amino groups on its surface form urea bonds (-NH-CO-) covalent bonds with the isocyanate groups in the continuous phase.
[0012] Preferably, the thermoplastic polyurethane has a Shore hardness of A60-A70, and the vinyl silicone rubber has an elastic recovery rate of not less than 85%.
[0013] Preferably, a conductive polymer transition layer with a thickness of 50 to 200 nanometers is provided between the gradient channel conductive reinforcement layer and the chemically bonded elastic conductive substrate. The conductive polymer film extends from the pore wall of the reinforcement layer to the surface of the elastic substrate to form a continuous conductive path, and the sheet resistance of the transition layer is ≤10Ω / sq.
[0014] Preferably, the dispersion density of the conductive phase formed by the composite of silver nanowires and carbon nanotubes in the conductive polymer transition layer is (10-15)×10. 4 The number of nanowires per mm² is ≥5000, and the aspect ratio of the silver nanowires is ≥5000.
[0015] Preferably, in the interface region between the gradient channel conductive reinforcement layer and the chemically bonded elastic conductive matrix, the concentration of the silane-modified TPU compatibilizer is gradient-distributed, with a concentration of 3% to 5% of the total weight of the continuous phase near the reinforcement layer side, decreasing to less than 1% towards the matrix side, and the interface region forms a continuous cross-linked network through chemical covalent bonds and physical interpenetration.
[0016] Compared with the prior art, the advantages of the present invention are as follows: (1) In this invention, the unique gradient channel structure effectively disperses compressive stress. Combined with the interpenetrating network elastic matrix of TPU / silicone rubber chemical crosslinking, it gives the foam excellent resistance to permanent compression deformation. After repeated high compression, it can quickly and fully rebound, maintaining a stable shape and contact pressure.
[0017] (2) In this invention, the gradient pore walls are covered with a conductive polymer film and silica nanospheres are introduced to enhance the bonding. The chemically bonded silver nanowires and carbon nanotubes in the matrix form a conductive phase to form an efficient pathway. In particular, the low-resistance (≤10Ω / sq) conductive polymer transition layer specially designed at the interface of the two together constructs a three-dimensional continuous and stable conductive network that runs through the entire foam. This makes the network less prone to damage during compression cycles, with small resistance changes and conductivity stability far exceeding that of traditional physical mixing or coating foam.
[0018] (3) In this invention, from the bonding between the conductive phase and the matrix to the interface between the gradient layer and the matrix, the bonding is mainly through chemical covalent bonds, supplemented by physical interpenetrating interlocking and interface compatibilizer gradient design, which greatly enhances the rigidity and toughness of the overall structure, effectively prevents interlayer peeling, filler shedding and conductive network breakage, and significantly improves the long-term service reliability of foam in complex mechanical stress environments such as impact, vibration and bending. Attached Figure Description
[0019] Figure 1 This is a schematic diagram of the structure of a pressure-resistant conductive foam. Detailed Implementation
[0020] The technical solutions of the embodiments of the present invention will be explained and described below. However, the following embodiments are only preferred embodiments of the present invention and not all of them. Based on the embodiments described in the embodiments, other embodiments obtained by those skilled in the art without creative effort are all within the protection scope of the present invention. It should be particularly noted that the preparation process described in the embodiments is only one of the feasible solutions to achieve the structure of the claims. Any equivalent preparation method based on the gradient pore structure and chemically bonded matrix defined in the claims is within the protection scope of the present invention.
[0021] Example 1 1. Material Composition 1-1. Gradient pore conductive reinforcement layer: The surface layer accounts for 10% of the total thickness, with a total thickness of 2.0 mm, a pore size of 50 μm, and a porosity of 50%; the core layer accounts for 65% of the total thickness, with a pore size of 200 μm and a porosity of 85%; the transition layer accounts for 25% of the total thickness, and the pore size increases linearly from the surface layer to the core layer; 5% by mass of silica nanospheres with a diameter of 100 nm are added to the pore walls, and the surface is covered with a polypyrrole conductive polymer film.
[0022] 1-2. Chemically bonded elastic conductive matrix: thermoplastic polyurethane with a Shore hardness of A65, vinyl silicone rubber content accounting for 25% of the total weight of the continuous phase, and silane-modified TPU compatibilizer accounting for 3% of the total weight of the continuous phase; the conductive phase is a 1:3 mixture of silver nanowires and carbon nanotubes, accounting for 10% of the weight of the continuous phase, which forms urea covalent bonds with the matrix after modification with silane coupling agent.
[0023] 1-3. Interface transition layer: 100 nm thick PEDOT:PSS conductive polymer layer, sheet resistance 8 Ω / sq.
[0024] 2. Preparation method 2-1. A gradient pore reinforcement layer was prepared by template method. The pore size gradient of the surface layer-transition layer-core layer was formed by adjusting the concentration of pore-forming agent. After introducing silica nanospheres, a polypyrrole film was coated. 2-2. Thermoplastic polyurethane and vinyl silicone rubber are blended, a compatibilizer and a modified silver nanowire-carbon nanotube composite are added, and an interpenetrating network matrix is formed by internal mixing. 2-3. The reinforcing layer and the substrate are reacted at 130°C for 2 hours by hot pressing to form a chemical covalent bond and a physical interpenetrating interlocking structure, while a conductive polymer transition layer is prepared.
[0025] 3. Performance parameters Compressive strength: 15MPa; Sheet resistivity: 7.5Ω / sq; Elastic recovery rate: 90%; Compression set: 12%; Electromagnetic shielding effectiveness (1-10GHz): 62dB; Conductivity retention after 1000 cycles at 80% compression: 92%.
[0026] Example 2 1. Material Composition 1-1. Gradient channel conductive reinforcement layer: the surface layer has a thickness of 15%, a total thickness of 2.0 mm, a pore size of 60 μm, and a porosity of 60%; the core layer has a thickness of 60%, a pore size of 220 μm, and a porosity of 82%; the transition layer has a thickness of 25%, with a linear increase in pore size; 8% by mass of silica nanospheres with a diameter of 100 nm are added to the pore walls, and the surface is covered with a polypyrrole film.
[0027] 1-2. The parameters of the matrix and interface layer are the same as in Example 1: 20% vinyl silicone rubber content, 2% compatibilizer, 10% conductive phase 1:3 compound, and 100 nm transition layer PEDOT:PSS.
[0028] 2. Preparation method The only difference from Example 1 is that when preparing the reinforcing layer by template method, the concentration gradient of the pore-forming agent is adjusted so that the thickness ratio of the surface layer / transition layer / core layer is 15% / 25% / 60%, and the rest of the steps are the same.
[0029] 3. Performance parameters Compressive strength: 14MPa; Sheet resistivity: 8.2Ω / sq; Elastic recovery rate: 88%; Compression set: 13%; Electromagnetic shielding effectiveness: 61dB; Conductivity retention after cycling: 91%.
[0030] Example 3 1. Material Composition 1-1. Gradient pore reinforcement layer: The layer thickness ratio is the same as in Example 1, the pore size parameters are the same as in Example 1, and silica nanospheres with a mass fraction of 5% and a diameter of 200 nm are added to the pore walls, and the surface is covered with a polypyrrole film.
[0031] 1-2. Chemically bonded elastic conductive matrix: 22% vinyl silicone rubber, 4% silane-modified TPU compatibilizer, and 10% conductive phase in a 1:4 mixture.
[0032] 2. Preparation method 2-1. The only difference from Example 1 is that when preparing the reinforcing layer, the silica nanospheres are replaced with a product with a diameter of 200 nanometers; the rest of the steps are the same.
[0033] 3. Performance parameters Compressive strength: 13MPa; Sheet resistivity: 7.8Ω / sq; Elastic recovery rate: 89%; Compression set: 14%; Electromagnetic shielding effectiveness: 60dB; Conductivity retention after cycling: 90%.
[0034] Example 4 1. Material Composition 1-1. The parameters of the gradient pore reinforcement layer are the same as in Example 1.
[0035] 1-2. Chemically bonded elastic conductive matrix: Silver nanowires and carbon nanotubes are compounded in a 1:2 ratio, and the amount added accounts for 10% of the weight of the continuous phase. The other parameters are the same as in Example 1: vinyl silicone rubber content is 18%, and compatibilizer is 5%.
[0036] 1-3. The interface transition layer is the same as in Example 1.
[0037] 2. Preparation method The only difference from Example 1 is that the ratio of silver nanowires to carbon nanotubes was adjusted to 1:2 when preparing the matrix; the other steps are the same.
[0038] 3. Performance parameters Compressive strength: 15MPa; Sheet resistivity: 6.8Ω / sq; Elastic recovery rate: 91%; Compression set: 12%; Electromagnetic shielding effectiveness: 63dB; Conductivity retention after cycling: 93%.
[0039] Example 5 1. Material Composition 1-1. The parameters of the gradient pore reinforcement layer are the same as in Example 1.
[0040] 1-2. Chemically bonded elastic conductive matrix: vinyl silicone rubber content accounts for 15% of the total weight of the continuous phase, compatibilizer 3%, conductive phase 1:3 compound 10%, and other parameters are the same as in Example 1.
[0041] 1-3. The interface transition layer is the same as in Example 1.
[0042] 2. Preparation method 2-1. The difference from Example 1 is that the amount of vinyl silicone rubber added is adjusted to 15% when blending the matrix; the hot pressing time is extended to 3 hours, and the other steps are the same.
[0043] 3. Performance parameters Compressive strength: 16MPa; Sheet resistivity: 7.6Ω / sq; Elastic recovery rate: 87%; Compression set: 13%; Electromagnetic shielding effectiveness: 62dB; Conductivity retention after cycling: 92%.
[0044] Example 6 1. Material Composition 1-1. Gradient pore reinforcement layer: 5% by mass and 50 nm in diameter of silica nanospheres are added to the pore walls, and the other parameters are the same as in Example 1.
[0045] 1-2. Chemically bonded elastic conductive matrix: The amount of silane-modified TPU compatibilizer added accounts for 1% of the total weight of the continuous phase, the content of vinyl silicone rubber is 20%, the conductive phase is 10% compounded in a 1:3 ratio, and the other parameters are the same as in Example 1.
[0046] 1-3. The interface transition layer is the same as in Example 1.
[0047] 2. Preparation method The only difference from Example 1 is that the amount of compatibilizer added is adjusted to 1% when blending the matrix; the other steps are the same.
[0048] 3. Performance parameters Compressive strength: 14MPa; Sheet resistivity: 8.5Ω / sq; Elastic recovery rate: 86%; Compression set: 15%; Electromagnetic shielding effectiveness: 60dB; Conductivity retention after cycling: 90%.
[0049] Example 7 1. Material Composition 1-1. The parameters of the gradient pore reinforcement layer are the same as in Example 1.
[0050] 1-2. The parameters of the chemically bonded elastic conductive matrix are the same as in Example 1.
[0051] 1-3. Interface transition layer: 50 nm thick PEDOT:PSS, sheet resistance 9 Ω / sq.
[0052] 2. Preparation method The only difference from Example 1 is that when preparing the interface transition layer, the thickness is adjusted to 50 nanometers by controlling the coating amount; the other steps are the same.
[0053] 3. Performance parameters Compressive strength: 15MPa; Sheet resistivity: 8.0Ω / sq; Elastic recovery rate: 87%; Compression set: 12%; Electromagnetic shielding effectiveness: 61dB; Conductivity retention after cycling: 92%.
[0054] Comparative Example 1 1. Material Composition 1-1. Pore reinforcement layer: The entire layer has a pore size of 200 micrometers and a porosity of 85%, with no gradient stratification. The pore walls are filled with silica nanospheres with a mass fraction of 5% and a diameter of 100 nanometers, and the surface is covered with a polypyrrole film.
[0055] 1-2. The parameters of the substrate and interface layer are the same as in Example 1.
[0056] 2. Preparation method 2-1. A pore reinforcement layer was prepared using a single concentration of pore-inducing agent without controlling the pore size gradient, forming a structure with a full-layer pore size of 200 micrometers; 2-2. After introducing silica nanospheres, a polypyrrole film is coated on them; 2-3. The preparation steps of the substrate and interface layer are the same as in Example 1, and the substrate and interface layer are physically integrated by hot pressing.
[0057] 3. Performance parameters Compressive strength: 8MPa; Sheet resistivity: 7.5Ω / sq; Elastic recovery rate: 87%; Compression set: 25%; Electromagnetic shielding effectiveness: 62dB; Conductivity retention after 1000 cycles at 80% compression: 75%.
[0058] Comparative Example 2 1. Material Composition 1-1. Gradient pore reinforcement layer: The layer thickness ratio is the same as in Example 1, the pore size parameters are the same as in Example 1, no silica nanospheres are added to the pore walls, and the surface is covered with a polypyrrole film.
[0059] 1-2. The parameters of the substrate and interface layer are the same as in Example 1.
[0060] 2. Preparation method 2-1. A gradient pore reinforcement layer was prepared using the template method, following the same steps as in Example 1, but without introducing silica nanospheres; 2-2. After coating with polypyrrole film, it is connected to the substrate by hot pressing. The remaining steps are the same as in Example 1.
[0061] 3. Performance parameters Compressive strength: 10MPa; Sheet resistivity: 7.8Ω / sq; Elastic recovery rate: 86%; Compression set: 20%; Electromagnetic shielding effectiveness: 61dB; Conductivity retention after cycling: 80%.
[0062] Comparative Example 3 1. Material Composition 1-1. The parameters of the gradient pore reinforcement layer are the same as in Example 1.
[0063] 1-2. Chemically bonded elastic conductive matrix: Only silver nanowires are used as the conductive phase, and the amount added accounts for 10% of the weight of the continuous phase. The other parameters are the same as in Example 1.
[0064] 1-3. The interface transition layer is the same as in Example 1.
[0065] 2. Preparation method 2-1. When preparing the matrix, no carbon nanotubes were added, only silane-modified silver nanowires were added, and the remaining blending steps were the same as in Example 1; 2-2. The hot pressing molding process for the reinforcing layer is the same as in Example 1.
[0066] 3. Performance parameters Compressive strength: 15MPa; Sheet resistivity: 12Ω / sq; Elastic recovery rate: 87%; Compression set: 12%; Electromagnetic shielding effectiveness: 55dB; Conductivity retention after cycling: 85%.
[0067] Comparative Example 4 1. Material Composition 1-1. The parameters of the gradient pore reinforcement layer are the same as in Example 1.
[0068] 1-2. Chemically bonded elastic conductive matrix: Silver nanowires and carbon nanotubes are compounded in a 1:3 ratio, without silane modification, and added to the matrix through physical mixing. There are no urea bonds or covalent bonds. The other parameters are the same as in Example 1.
[0069] 1-3. The interface transition layer is the same as in Example 1.
[0070] 2. Preparation method 3-1. When preparing the matrix, the conductive phase is not modified with silane, but is directly physically blended with thermoplastic polyurethane and vinyl silicone rubber; 3-2. When hot-pressing with the reinforcing layer, the connection is only through physical interlocking, without the formation of chemical covalent bonds. The remaining steps are the same as in Example 1.
[0071] 3. Performance parameters Compressive strength: 15MPa; Sheet resistivity: 15Ω / sq; Elastic recovery rate: 87%; Compression set: 12%; Electromagnetic shielding effectiveness: 58dB; Conductivity retention after cycling: 70%.
[0072] Comparative Example 5 1. Material Composition 1-1. The parameters of the gradient pore reinforcement layer are the same as in Example 1.
[0073] 1-2. The parameters of the chemically bonded elastic conductive matrix are the same as in Example 1.
[0074] 1-3. No conductive polymer transition layer is provided; the reinforcement layer and the substrate are only physically interlocked.
[0075] 2. Preparation method 2-1. The steps for preparing the reinforcing layer and the substrate are the same as in Example 1, but the conductive polymer transition layer is not prepared; 2-2. The two are physically interlocked by hot pressing, with no conductive polymer filling the interface gaps. The remaining steps are the same as in Example 1.
[0076] 3. Performance parameters Compressive strength: 12MPa; Sheet resistivity: 9Ω / sq; Elastic recovery rate: 85%; Compression set: 18%; Electromagnetic shielding effectiveness: 60dB; Conductivity retention after cycling: 82%.
[0077] Performance test comparison I. Specific Testing Standards and Methods 1. Compressive strength: According to GB / T 1041-2022, a universal testing machine was used to apply a compressive load to the sample at a rate of 10 mm / min, and the stress value when the sample was compressed to 50% of its original thickness was recorded.
[0078] 2. Sheet resistance: According to GB / T 24522-2009, the sheet resistance of the conductive path on the sample surface is tested using a four-probe tester at 25℃ and 50% relative humidity.
[0079] 3. Elastic recovery rate: Referring to GB / T 1683-2009, the sample is compressed to 50% of its original thickness and kept for 24 hours. After unloading, it is left to stand for 30 minutes, and the sample thickness recovery rate is calculated.
[0080] 4. Compression set: According to GB / T 7759.1-2015, the sample was compressed by 25% at 70℃ and held for 22 hours. After unloading, the permanent deformation of the sample was measured.
[0081] 5. Electromagnetic shielding effectiveness: In accordance with GB / T 30148-2013, the shielding ability of the sample against electromagnetic radiation was tested in the frequency range of 1-10 GHz using the flange coaxial method.
[0082] 6. Conductivity retention rate after compression cycling: The sample was subjected to 80% compression cycling test: the compression-unloading cycle was 30 seconds, and after 1000 cycles, the surface resistance was measured using a four-probe tester, and the ratio of the surface resistance to the initial surface resistance was calculated as the conductivity retention rate.
[0083] II. Performance Test Comparison Table III. Relevant Summary 1. Summary of the embodiments: Each embodiment achieved multiple performance standards by using a composite design of gradient channel structure and chemically bonded elastic matrix, indicating that the design of gradient channel pore size distribution, silica nanosphere reinforcement, and conductive phase chemical bonding can effectively improve the compressive strength, conductivity and durability of the material. Among them, Example 4 has the best comprehensive performance, with a compressive strength of 15MPa, a sheet resistance of 6.8Ω / sq, an elastic recovery rate of 91%, and electromagnetic shielding effectiveness and conductivity retention rate of 63dB and 93% respectively, which verifies the optimization effect of the silver nanowire to carbon nanotube composite ratio (1:2) and the interface transition layer design.
[0084] 2. Summary of proportions: Comparative Example 1: The non-gradient pore structure has a compressive strength of only 8MPa and a compression permanent deformation rate of 25%. Due to the single pore diameter, stress concentration occurs and the pore is prone to collapse. Comparative Example 2: Without the reinforcement of silica nanospheres, the compression set reached 20%, and the pore walls lacked a supporting structure, resulting in significant plastic deformation after repeated compression. Comparative Example 3: Single conductive phase, surface resistance 12Ω / sq, electromagnetic shielding effectiveness 55dB, insufficient continuity of conductive network, and reduced high-frequency shielding capability. Comparative Example 4: Physical doping has no chemical bonding, sheet resistance is 15Ω / sq, conductivity retention is 70%, conductive phase is easy to agglomerate and detach, and network stability is poor. Comparative Example 5, without an interface transition layer, has a compression permanent deformation rate of 18% and a conductivity retention rate of 82%. The weak interface bonding leads to insufficient structural toughness. 3. Key Design Summary: The gradient pore structure can disperse compressive stress, improve compressive strength and elastic recovery rate; silica nanospheres enhance the pore wall structure and reduce permanent compression deformation; the conductive phase constructs a continuous conductive network through chemical bonding and compounding design, ensuring surface resistance and electromagnetic shielding effectiveness; the interface transition layer and compatibilizer gradient design enhance interlayer bonding force and improve conductivity retention.
[0085] This invention solves the problems of insufficient pressure resistance, conductivity and durability of traditional conductive foam through multi-dimensional collaborative design, and is suitable for electromagnetic shielding and structural buffering scenarios of electronic devices.
[0086] 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 preferred examples and are not intended to limit 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 pressure-resistant conductive foam, characterized in that, The system comprises a gradient-pore conductive reinforcement layer and a chemically bonded elastic conductive matrix. The gradient-pore conductive reinforcement layer consists of a surface layer, a transition layer, and a core layer. Silica nanospheres are distributed within the pore walls, and the surface is covered with a conductive polymer film. The chemically bonded elastic conductive matrix uses an interpenetrating network structure formed by thermoplastic polyurethane and vinyl silicone rubber as the continuous phase. A conductive phase formed by surface-modified silver nanowires and carbon nanotubes is bonded within this continuous phase. The gradient-pore conductive reinforcement layer and the chemically bonded elastic conductive matrix are connected by chemical covalent grafting and physical interpenetrating interlocking composite bonding.
2. The pressure-resistant conductive foam according to claim 1, characterized in that, The total thickness of the gradient channel conductive reinforcement layer is 1.0 to 3.0 mm, and the sum of the thickness percentages of each layer is 100%, wherein: The surface layer has a thickness of 5% to 15% of the total thickness, a pore size of 40 to 60 micrometers, and a porosity of 40% to 60%. The core layer has a thickness of 60% to 70% of the total thickness, a pore size of 180 to 220 micrometers, and a porosity of not less than 80%. The thickness of the transition layer accounts for 15% to 30% of the total thickness, and its pore size and porosity increase linearly from the surface layer to the core layer.
3. The pressure-resistant conductive foam according to claim 1, characterized in that, The silica nanospheres have a diameter of 50 to 200 nanometers and their surface contains silanol groups (Si-OH). The amount added is 3% to 8% of the mass of the gradient pore conductive reinforcement layer material. The conductive polymer film is polypyrrole or poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS).
4. The pressure-resistant conductive foam according to claim 1, characterized in that, The interpenetrating network structure contains a silane-modified TPU compatibilizer, the amount of which is 1% to 5% of the total weight of the continuous phase, the content of the vinyl silicone rubber is 15% to 25% of the total weight of the continuous phase, and the thermoplastic polyurethane molecular chain contains isocyanate groups (-NCO).
5. The pressure-resistant conductive foam according to claim 4, characterized in that, The isocyanate groups (-NCO) on the thermoplastic polyurethane molecular chain and the silanol groups (Si-OH) on the vinyl silicone rubber molecular chain form -Si-OC(O)-NH- crosslinking bonds through a condensation reaction. These crosslinking bonds are interconnected in three-dimensional space, so that the molecular chains form a continuous network structure.
6. The pressure-resistant conductive foam according to claim 1, characterized in that, The weight ratio of the silver nanowires to carbon nanotubes is 1:2 to 1:4, and the amount of the conductive phase added to the continuous phase is 5%-15%. After surface modification with a silane coupling agent, the amino groups on its surface form urea bonds (-NH-CO-) covalent bonds with the isocyanate groups in the continuous phase.
7. The pressure-resistant conductive foam according to claim 1, characterized in that, The thermoplastic polyurethane has a Shore hardness of A60 to A70, and the vinyl silicone rubber has an elastic recovery rate of not less than 85%.
8. The pressure-resistant conductive foam according to claim 1, characterized in that, A conductive polymer transition layer with a thickness of 50 to 200 nanometers is provided between the gradient channel conductive reinforcement layer and the chemically bonded elastic conductive substrate. The conductive polymer film extends from the pore wall of the reinforcement layer to the surface of the elastic substrate to form a continuous conductive path. The sheet resistance of the transition layer is ≤10Ω / sq.
9. The pressure-resistant conductive foam according to claim 1, characterized in that, The dispersion density of the conductive phase formed by the composite of silver nanowires and carbon nanotubes in the conductive polymer transition layer is (10-15)×10. 4 The number of nanowires per mm² is ≥5000, and the aspect ratio of the silver nanowires is ≥5000.
10. The pressure-resistant conductive foam according to claim 1, characterized in that, In the interface region between the gradient-channel conductive reinforcement layer and the chemically bonded elastic conductive matrix, the concentration of the silane-modified TPU compatibilizer is distributed in a gradient manner. The concentration is 3%-5% of the total weight of the continuous phase near the reinforcement layer side and decreases to less than 1% towards the matrix side. Furthermore, the interface region forms a continuous cross-linked network through chemical covalent bonds and physical interpenetrating interlocking.