Process for the preparation of a carbon aerogel / silicone rubber dual network composite modified with a silane coupling agent and the product obtained

Abstract

The application discloses a preparation method of a silane coupling agent modified carbon aerogel / silicon rubber double-network composite material and the obtained product, and adopts the silane coupling agent to modify the carbon aerogel, then fills the silicon rubber raw material solution into the obtained modified carbon aerogel through a vacuum assisted impregnation method, and then forms through vacuum solidification to obtain the silane coupling agent modified carbon aerogel / silicon rubber double-network composite material. The characteristics of high porosity, large specific surface area, high conductivity and low density of the carbon aerogel make the composite material realize excellent conductivity performance under a small amount of conductive filler, and the matching compatibility of the carbon aerogel network and the silicon rubber network is effectively improved through surface modification and optimization of the silicon rubber formula, and then the ultra-high and adjustable strain sensitivity, the ability of capturing a small strain (0.1%) and excellent resistance response stability are obtained.

Description

Technical Field

[0001] This invention relates to a method for preparing a silane coupling agent modified carbon aerogel / silicone rubber dual-network composite material, and also to a silane coupling agent modified carbon aerogel / silicone rubber dual-network composite material, belonging to the technical field of conductive silicone rubber materials. Background Technology

[0002] Conductive silicone rubber is an important conductive polymer material. It retains the excellent properties of silicone rubber, such as easy processing, high resilience, and weather resistance. Furthermore, its conductivity can be adjusted by changing the type and amount of conductive filler. Generally, fillers used in conductive silicone rubber can be divided into two main categories: metallic fillers (such as copper powder and silver powder) and carbon-based fillers (such as conductive carbon black, carbon fiber, carbon nanotubes, and graphene). Metallic fillers generally have better conductivity than carbon-based fillers, but their poor compatibility with silicone rubber and insufficient salt spray resistance lead to a decline in the overall performance of conductive silicone rubber, limiting its application range. Conversely, while carbon-based fillers have relatively weaker conductivity, they provide excellent reinforcing properties to silicone rubber, have good compatibility, and can simultaneously improve the electrical and mechanical properties of silicone rubber, meeting the more stringent requirements of high-end manufacturing fields such as aerospace and electronics. However, traditional manufacturing processes for carbon-based conductive silicone rubber require the addition of large amounts of conductive fillers to achieve good conductivity. However, the addition of large amounts of conductive fillers disrupts the original structure of the silicone rubber, and uneven dispersion of these fillers severely affects its mechanical properties, leading to an overall performance decline. These are current problems and shortcomings in the research on conductive silicone rubber. Therefore, to achieve excellent electrical and mechanical properties in silicone rubber, it is necessary to construct a continuous and matched conductive network within the silicone rubber network using a low amount of conductive filler. Thus, the process of successfully introducing a continuous conductive network into silicone rubber with mutual matching between the two networks is particularly important in the preparation of conductive silicone rubber. Currently, research in this area is limited, and researchers have not yet proposed a suitable manufacturing process for conductive silicone rubber to address this problem.

[0003] In recent years, with the deepening research on the construction of three-dimensional conductive network structures in silicone rubber, conductive carbon aerogel structures have also attracted much attention from researchers. Carbon aerogels possess characteristics such as high porosity, large specific surface area, high conductivity, good chemical inertness, and low density, making them very suitable for embedding as conductive networks into silicone rubber networks to produce dual-network conductive silicone rubbers with good overall performance. However, there are few studies on modifying carbon aerogels to suit the properties of silicone rubber. For silicone rubber systems, most research teams have used commercially available polysiloxane products without designing silicone rubber formulations that match the characteristics of carbon aerogel conductive networks. Both of these issues affect the compatibility between the carbon aerogel conductive network and the silicone rubber network, thus affecting the overall performance of the conductive silicone rubber and ultimately limiting its application in strain sensing. Therefore, this type of dual-network conductive silicone rubber still needs further optimization.

[0004] Chinese invention patent CN115010964A discloses a method for preparing conductive silicone rubber. The specific preparation method is as follows: A mixture A is obtained by uniformly mixing a conductive filler with n-heptane, wherein the conductive filler is a mixture of graphene, carbon nanotubes, and carbon fiber materials; a mixture B is obtained by uniformly mixing liquid silicone rubber with n-heptane; mixture A and mixture B are first mixed uniformly in a desired ratio, then subjected to vacuum treatment, casting, and standing until the n-heptane completely evaporates, followed by curing to obtain a conductive silicone rubber composite material. The mass ratio of mixture A to mixture B is 1:1-1.5, and the conductive silicone rubber composite material contains 4.5-5.5 wt% graphene, 1-1.25 wt% carbon nanotubes, and 6-7.5 wt% carbon fiber. The volume resistivity of the conductive silicone rubber composite material was found to be 10 Ω·cm, i.e., the conductivity was 10 S / m, as determined by the four-probe method. The patent uses a relatively large amount of conductive filler (11.5-14.25wt%) to achieve relatively excellent conductivity, which will affect the mechanical properties of silicone rubber. Furthermore, the patent does not involve research on the conductive network in the conductive silicone rubber composite material and its compatibility with the silicone rubber network. Summary of the Invention

[0005] To address the shortcomings mentioned in the prior art, this invention provides a method for preparing a silane coupling agent modified carbon aerogel / silicone rubber dual-network composite material. This method involves modifying carbon aerogel with a silane coupling agent and then combining the modified carbon aerogel with silicone rubber to ultimately obtain the silane coupling agent modified carbon aerogel / silicone rubber dual-network composite material. The composite process involves using modified carbon aerogel as a conductive filler, employing a vacuum-assisted impregnation process to fill the modified carbon aerogel with a silicone rubber raw material solution, and then using a vacuum curing molding process to obtain the silane coupling agent modified carbon aerogel / silicone rubber dual-network composite material.

[0006] Specifically, the preparation method of the silane coupling agent modified carbon aerogel / silicone rubber dual-network composite material provided by the present invention includes the following steps:

[0007] (1) Carbon aerogel was prepared using carbon materials;

[0008] (2) Surface modification of carbon aerogel using silane coupling agents;

[0009] (3) Using modified carbon aerogel as a conductive filler, a vacuum-assisted impregnation process is used to fill the modified carbon aerogel with silicone rubber raw material solution, and then a vacuum curing molding process is used to obtain a silane coupling agent modified carbon aerogel / silicone rubber dual network composite material.

[0010] Furthermore, the carbon material can be graphene oxide, carbon nanotubes, carbon fibers, cellulose, resorcinol, formaldehyde, melamine, phenol, furfural, cresol, etc., preferably graphene oxide.

[0011] Furthermore, the carbon aerogel can be prepared by methods reported in the prior art, such as the sol-gel method (Gao Q, Wang X, Shi Z, et al. Synthesis of porous NiCo2S4 aerogel for supercapacitor electrode and oxygen evolution reaction electrocatalyst[J]. Chemical engineering journal (Lausanne, Switzerland: 1996), 2018, 331: 185-193.), the hydrothermal method (Xu Y, Sheng K, Li C, et al. Self-Assembled Graphene Hydrogel via a One-Step Hydrothermal Process[J]. ACS nano, 2010, 4(7): 4324-4330.), the chemical vapor deposition method (Chen Z, Ren W, Gao L, et al. Three-dimensional flexible and conductive interconnected graphene networks grown by chemical vapor deposition[J]. Nat Mater, 2011, 10(6): 424-428.), and the bubble template method (Pang K, Song X, Xu Z, et al. Hydrodroplastic foaming of graphene aerogels and artificially intelligent tactile sensors[J]. Sci Adv, 2020, 6(46)., ice template method (Huang C, Wang Y, Cheng Y, et al. Naturally dried superelastic bioinspired graphene aerogel for pressure / stretch sensing and separation[J]. Composites science and technology, 2022, 226: 109549.), or combinations of two or more of these methods.

[0012] In a specific embodiment of the present invention, carbon aerogel is prepared by a combination of bubble template method and ice template method, specifically referring to the method reported in the prior art (Zhang X, Zhang T, Wang Z, et al. Ultralight, Superelastic, and Fatigue-Resistant Graphene Aerogel Templated by GrapheneOxide Liquid Crystal Stabilized Air Bubbles[J].ACS applied materials&interfaces,2019,11(1):1303-1310.).

[0013] Furthermore, the modified carbon aerogel is obtained by modifying carbon aerogel with a silane coupling agent. Specifically, the carbon aerogel is immersed in a mixture of silane coupling agent and organic solvent, and then dried to obtain the modified carbon aerogel. The purpose of immersion is to ensure that the silane coupling agent fully penetrates the carbon aerogel.

[0014] Furthermore, modifying the carbon aerogel with a silane coupling agent before compounding it with silicone rubber optimizes the interfacial compatibility between the aerogel and silicone rubber, thereby effectively improving the tensile strength of the composite material. The silane coupling agent can be vinyltriethoxysilane, vinyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, anilinemethyltriethoxysilane, etc., preferably vinyltriethoxysilane. The successful introduction of the silane coupling agent improves the crosslinking degree of the composite material.

[0015] Furthermore, in the mixture of silane coupling agent and organic solvent, the concentration of silane coupling agent is 3-9 wt%, for example, 3%, 4%, 5%, 6%, 7%, 8%, or 9%. The organic solvent can be an alcohol solvent, such as methanol or ethanol, which can dissolve the silane coupling agent.

[0016] Furthermore, the soaking is carried out at room temperature, and the soaking time is generally 10-12 hours.

[0017] Furthermore, after soaking, the product is dried under normal pressure at a temperature of 55-65℃, such as 55℃, 56℃, 57℃, 58℃, 59℃, 60℃, 61℃, 62℃, 63℃, 64℃, or 65℃, preferably 60℃. The drying time is generally 24-26 hours.

[0018] Furthermore, the vacuum-assisted impregnation method is a common way to fill silicone rubber into conductive materials. The procedure is as follows: A thoroughly mixed silicone rubber raw material solution is slowly poured into a container containing modified carbon aerogel, ensuring the liquid level is approximately 2 mm above the top surface of the aerogel. The position of the modified carbon aerogel in the silicone rubber raw material solution is adjusted so that it is centered in the container. The container is then placed in a vacuum drying oven, utilizing the vacuum environment to assist in the thorough impregnation of the silicone rubber raw material solution into the aerogel. During this process, the vacuum needs to be released every 15 minutes to restore normal pressure, and then the vacuum is re-evacuated. This process is repeated several times until no more bubbles are generated in the silicone rubber raw material solution under vacuum. The vacuum level is typically 0.05-0.1 MPa. The process is complete when no more bubbles are generated in the silicone rubber raw material solution under vacuum.

[0019] Furthermore, the vacuum curing molding method is also a commonly used method in the prior art. Its operation is as follows: after completing the vacuum-assisted impregnation process, there is no need to remove the sample from the vacuum drying oven. The vacuum drying oven is directly set to a specific temperature to cure it in a vacuum environment, ultimately preparing a double-network conductive silicone rubber composite material. During vacuum curing molding, the vacuum degree is generally 0.05-0.1 MPa, and the temperature is generally 55-65℃, such as 55℃, 56℃, 57℃, 58℃, 59℃, 60℃, 61℃, 62℃, 63℃, 64℃, and 65℃, preferably 60℃. The vacuum curing time is generally 12-18 hours, such as 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, and 18 hours.

[0020] Furthermore, the weight composition of the silicone rubber raw material solution is as follows: 100 parts of vinyl-terminated polydimethylsiloxane, 0-50 parts of silica, appropriate amount of crosslinking agent, 4-6 parts of polydimethylsiloxane, 0-50 parts of vinyl-terminated methyl silicone resin, 0.2-0.4 parts of inhibitor, and 1.5-2 parts of Pt catalyst.

[0021] Further, the vinyl-terminated polydimethylsiloxane is selected from one or two of the following: vinyl-terminated polydimethylsiloxane with a viscosity of 1900-2200 mPa·s and a vinyl content of 0.0067-0.0135 mol / 100g; and vinyl-terminated polydimethylsiloxane with a viscosity of 480-520 mPa·s and a vinyl content of 0.0141-0.0173 mol / 100g, preferably a combination of both. The vinyl-terminated polydimethylsiloxane with a viscosity of 1900-2200 mPa·s accounts for 0-35 wt% of the total vinyl-terminated polydimethylsiloxane, for example, 0%, 1%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 35%, preferably 1-35%, and more preferably 10-35%.

[0022] Further amounts of silica are used in quantities of 0-50 parts, such as 0 parts, 10 parts, 20 parts, 30 parts, 40 parts, and 50 parts.

[0023] Furthermore, the viscosity of polydimethylsiloxane is 480-520 mPa·s. The amount of polydimethylsiloxane used is 4-6 parts, for example, 4 parts, 5 parts, or 6 parts.

[0024] Furthermore, the crosslinking agent is a hydrogen-containing silicone oil with a hydrogen content of 0.6-1.0 wt%. The amount of crosslinking agent added is determined according to the standard that the molar ratio of carbon-carbon double bonds in vinyl-terminated polydimethylsiloxane and vinyl-terminated methylsiloxane to silicon-hydrogen bonds in the hydrogen-containing silicone oil is 1:1.1-1.3.

[0025] Furthermore, the vinyl content of the vinyl-terminated methyl silicone resin is 0.03-0.05 mol / 100g, and the viscosity is 2300-2600 mPa·s. The amount of vinyl-terminated methyl silicone resin used is 0-50 parts, for example, 0 parts, 10 parts, 20 parts, 30 parts, 40 parts, and 50 parts.

[0026] Furthermore, the inhibitor is an acetylenecyclohexanol solution with a concentration of 4-6 wt%, and the solvent is polydimethylsiloxane with a viscosity of 480-520 mPa·s.

[0027] Furthermore, the Pt catalyst is a platinum complex of tetramethyldivinylsiloxane.

[0028] Preferably, the silicone rubber raw material solution has the following composition by weight: 100 parts vinyl-terminated polydimethylsiloxane, 10-30 parts silica, appropriate amount of crosslinking agent, 5 parts polydimethylsiloxane, 30 parts vinyl-terminated methylsilicone resin, 0.3 parts inhibitor, and 1.5-1.7 parts Pt catalyst.

[0029] In a specific embodiment of the present invention, a preferred method for preparing a vinyltriethoxysilane-modified reduced graphene oxide aerogel / silicone rubber dual-network composite material is provided, specifically including the following steps: Reduced graphene oxide is used as a raw material, and a reduced graphene oxide aerogel network structure is prepared by a combination of bubble template method and ice template method; the reduced graphene oxide aerogel is then immersed in an anhydrous ethanol solution of vinyltriethoxysilane, and then dried under normal pressure to obtain vinyltriethoxysilane-modified reduced graphene oxide aerogel. Vinyl-terminated polydimethylsiloxane, polydimethylsiloxane, silica, crosslinking agent, vinyl-terminated methylsilicone resin, inhibitor, and Pt catalyst are mixed uniformly in appropriate proportions, and then filled into the vinyltriethoxysilane-modified reduced graphene oxide aerogel using a vacuum-assisted impregnation process; finally, the vinyltriethoxysilane-modified reduced graphene oxide aerogel / silicone rubber dual-network composite material is obtained by vacuum room temperature curing.

[0030] The present invention has the following beneficial effects:

[0031] 1. In the composite process of carbon aerogel and silicone rubber, silane coupling agents such as vinyltriethoxysilane are used to modify the surface of carbon aerogel. The successful introduction of silane coupling agents such as vinyltriethoxysilane improves the crosslinking degree of the composite material, optimizes the interfacial compatibility between carbon aerogel and silicone rubber, and improves the matching degree between the two, thereby effectively improving the tensile strength of the composite material. Secondly, vinyl-terminated methyl silicone resin (VMQ) and high-viscosity vinyl-terminated polydimethylsiloxane (1900-2200 mPa·s) are introduced. Through hydrosilylation reaction, a co-crosslinking system of vinyl-terminated polydimethylsiloxane (PDMS) and vinyl-terminated methylsiloxane (VMQ) can be obtained. Based on the unique large-size cage structure of vinyl-terminated methylsiloxane and the long molecular chain of high-viscosity vinyl-terminated PDMS, the vinyltriethoxysilane-modified carbon aerogel and the co-crosslinked organosilicon system are combined to form an interpenetrating network with "button-like" interpenetrating network crosslinking points. This can further enhance the matching compatibility between the carbon aerogel network and the silicone rubber network, so that the composite material finally obtains an ultra-high (up to 1792.78) and adjustable (range 3.29-1792.78) strain sensitivity (gauge factor), the ability to capture small strain (0.1%), and excellent electrical response stability.

[0032] 2. The silane coupling agent-modified carbon aerogel / silicone rubber dual-network composite material provided by this invention can achieve excellent conductivity with very low amounts of conductive filler. When the amount of conductive filler is 0.487 wt%, the conductivity of the composite material can reach 8.8496 S / m. With the same amount of conductive filler, the conductivity of the composite material is superior to that of carbon material conductive silicone rubber prepared by traditional blending processes. Attached Figure Description

[0033] Figure 1 This is a diagram illustrating the changes in the internal structure of the vinyltriethoxysilane-modified reduced graphene oxide aerogel / silicone rubber dual-network composite material (without the addition of 2000 mPa·s vinyl-terminated polydimethylsiloxane) in Example 1 as the tensile strength changes from 0 to the strain corresponding to the modulus transition point.

[0034] Figure 2 This is a diagram illustrating the changes in the internal structure of the vinyltriethoxysilane-modified reduced graphene oxide aerogel / silicone rubber dual-network composite material (with 2000 mPa·s vinyl-terminated polydimethylsiloxane added) in Example 2, from the tensile stress to the strain corresponding to the modulus transition point. Detailed Implementation

[0035] The principles, features, and advantages of the present invention will be described in more detail below. The embodiments given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0036] Unless otherwise specified, all raw materials and reagents used in the following examples are commercially available products. Vinyl-terminated polydimethylsiloxanes were purchased from Shandong Dayi Chemical Co., Ltd., with viscosities of approximately 500 mPa·s and 2000 mPa·s, and vinyl contents of 0.0141-0.0173 mol / 100g and 0.0067-0.0135 mol / 100g, respectively. Polydimethylsiloxane and vinyl-terminated methylsilicone resin were also purchased from Shandong Dayi Chemical Co., Ltd., with a vinyl content of 0.0404 mol / 100g and a viscosity of approximately 2500 mPa·s. The catalyst was purchased from Guangzhou Changsheng Chemical Co., Ltd.

[0037] Example 1: Effect of vinyl-terminated methyl silicone resin (VMQ) on the internal structure and properties of vinyltriethoxysilane-modified reduced graphene oxide aerogel / silicone rubber dual-network composite material

[0038] When preparing the silicone rubber raw material solution, by weight, take 100 parts of vinyl-terminated polydimethylsiloxane, an appropriate amount of crosslinking agent, 5 parts of polydimethylsiloxane, 0 or 30 parts of vinyl-terminated methyl silicone resin, 0.3 parts of inhibitor, 1.6 parts of Pt catalyst, and 10-30 parts of silica. Mix all raw materials evenly to obtain the silicone rubber raw material solution. The obtained silicone rubber raw material solution is then impregnated into vinyltriethoxysilane-modified reduced graphene oxide aerogel using a vacuum-assisted impregnation process. The results show that the silicone rubber raw material solution without vinyl-terminated methyl silicone resin can only add a maximum of 20 parts of silica; further increases in silica content prevent sufficient impregnation into the vinyltriethoxysilane-modified reduced graphene oxide aerogel. However, the double-network composite material with 30 parts of vinyl-terminated methyl silicone resin can only add a maximum of 30 parts of silica. This allows the composite material with added vinyl-terminated methyl silicone resin to effectively improve its crosslinking degree while maintaining tensile strength.

[0039] The preparation of vinyltriethoxysilane-modified reduced graphene oxide aerogel / silicone rubber dual-network composite material includes the following steps:

[0040] 1. Preparation of reduced graphene oxide aerogel

[0041] 1.1 Preparation of dispersion:

[0042] 12 ml of graphene oxide (GO) aqueous dispersion, 1.5 ml of sodium dodecyl sulfate (SDS) aqueous solution (concentration: 50 mg / ml), and 264 mg of L-ascorbic acid were mixed evenly to obtain a mixed solution; wherein the graphene oxide has a sheet diameter of 10-20 μm, a sheet thickness of about 1 nm, a number of layers of 1-5, a carbon content of less than 46%, an oxygen content of more than 46%, and a concentration of 11 mg / ml for the graphene oxide aqueous dispersion.

[0043] 1.2 In-situ foaming:

[0044] The mixed solution was magnetically stirred to induce foaming. The stirring speed of the magnetic stirrer was 2100 r / min, and the stirring time was 5 min.

[0045] 1.3 Two-step hydrothermal reduction, freeze-thaw cycle, water washing, solvent replacement, room temperature and pressure drying, and post-treatment:

[0046] The foamed sample was kept at 75℃ for 1 hour for partial hydrothermal reduction. Then, the sample was placed in a freezer and frozen at -18℃ for 2 hours. After freezing, it was thawed at room temperature. After thawing, it was kept at 90℃ for 6 hours for complete hydrothermal reduction. The resulting sample was then washed with 830 times its mass of deionized water. The sample was then replaced with 830 times its mass of anhydrous ethanol for 1 hour. After filtering to remove the ethanol, the same replacement process was repeated 4 times. The replaced sample was placed in a forced-air drying oven and dried at 60℃ for 24 hours. The dried sample was then placed in a tube furnace and heated to 400℃ under a nitrogen atmosphere. It was then calcined at this temperature for 2 hours to obtain reduced graphene oxide aerogel.

[0047] The cross-section and longitudinal section of the obtained reduced graphene oxide aerogel were imaged using a scanning electron microscope. The cross-section showed a dense distribution of pores, including large pores with diameters of approximately 50-300 μm and ultra-large pores of approximately 800 μm. The longitudinal section also showed pores with diameters comparable to the cross-section (large pores: 50-300 μm, ultra-large pores: 500-1200 μm).

[0048] The density of the obtained reduced graphene oxide aerogel was tested and found to be 0.006 g / cm³. 3 .

[0049] 2. Modification of reduced graphene oxide aerogel

[0050] Vinyltriethoxysilane was prepared into a 5 wt% solution with anhydrous ethanol. The reduced graphene oxide aerogel prepared in step 1 was then completely immersed in the solution for 11 h. After immersion, the aerogel was removed and dried in a forced-air drying oven at 60 °C for 24 h to obtain vinyltriethoxysilane modified reduced graphene oxide aerogel.

[0051] 3. Composite of vinyltriethoxysilane-modified reduced graphene oxide aerogel with silicone rubber

[0052] 3.1 Preparation of silicone rubber raw material solution:

[0053] By weight, take 100 parts of vinyl-terminated polydimethylsiloxane, 20 parts of silica, an appropriate amount of crosslinking agent, 5 parts of polydimethylsiloxane, 0 parts of vinyl-terminated methylsilicone resin, 0.3 parts of inhibitor, and 1.6 parts of Pt catalyst, mix all raw materials evenly to obtain silicone rubber raw material solution 1.

[0054] By weight, take 100 parts of vinyl-terminated polydimethylsiloxane, 30 parts of silica, an appropriate amount of crosslinking agent, 5 parts of polydimethylsiloxane, 30 parts of vinyl-terminated methylsilicone resin, 0.3 parts of inhibitor, and 1.6 parts of Pt catalyst, mix all raw materials evenly to obtain silicone rubber raw material solution 2.

[0055] In silicone rubber raw material solutions 1 and 2, the viscosity of vinyl-terminated polydimethylsiloxane is 500 mPa·s, and the vinyl content is 0.0141-0.0173 mol / 100g; the viscosity of polydimethylsiloxane is 500 mPa·s; the vinyl content of vinyl-terminated methyl silicone resin is 0.0404 mol / 100g, and the viscosity is approximately 2500 mPa·s; the inhibitor is a 5 wt% acetylenecyclohexanol solution, and the solvent is polydimethylsiloxane with a viscosity of 500 mPa·s; the Pt catalyst is a platinum complex of tetramethyldivinylsiloxane; the crosslinking agent is hydrogen-containing silicone oil with a hydrogen content of 0.8 wt%, added according to the standard that the molar ratio of carbon-carbon double bonds in vinyl-terminated polydimethylsiloxane and vinyl-terminated methyl silicone resin to silicon-hydrogen bonds in hydrogen-containing silicone oil is 1:1.2.

[0056] 3.2 Preparation of Vinyltriethoxysilane-modified reduced graphene oxide aerogel / silicone rubber dual-network composite material: Silicone rubber raw material solutions 1 and 2, after thorough mixing, were slowly poured into a beaker containing vinyltriethoxysilane-modified reduced graphene oxide aerogel, ensuring the liquid level was approximately 2 mm above the upper surface of the aerogel. The position of the aerogel in the silicone rubber raw material solution was adjusted using a glass rod to ensure it was centered in the beaker. The beaker was then placed in a vacuum drying oven, and a vacuum environment (0.1 MPa) was used to assist in the complete immersion of the silicone rubber raw material solution into the aerogel. During this process, the vacuum was deactivated every 15 minutes to restore atmospheric pressure, and then re-vacuumed. This process was repeated several times until no more bubbles were generated in the silicone rubber raw material solution under vacuum (0.1 MPa). After completing the above operations, without removing the beaker, directly set the temperature of the vacuum drying oven to 60℃ and cure it in a vacuum environment (vacuum degree 0.1Mpa) for 12 hours. Finally, two vinyltriethoxysilane modified reduced graphene oxide aerogel / silicone rubber dual network composite materials were prepared, one with vinyl-terminated methyl silicone resin and the other without vinyl-terminated methyl silicone resin.

[0057] Tensile tests were conducted on the two vinyltriethoxysilane-modified reduced graphene oxide aerogel / silicone rubber dual-network composites prepared above using an electronic universal testing machine. It was found that the stress-strain curve of the composite with 30 parts of vinyl-terminated methyl silicone resin showed a significant Young's modulus transition point (43%) compared to the composite without vinyl-terminated methyl silicone resin. This indicates the formation of an interpenetrating network with "button-like" interpenetrating network crosslinking points within the composite material. A schematic diagram of the interpenetrating network with "button-like" interpenetrating network crosslinking points is shown below. Figure 1 As shown.

[0058] The conductivity of the two vinyltriethoxysilane-modified reduced graphene oxide aerogel / silicone rubber dual-network composites prepared above was tested using a four-probe resistance meter. The conductivity of the composite with 30 parts of vinyl-terminated methyl silicone resin was 8.85 S / m, while the conductivity of the composite without vinyl-terminated methyl silicone resin was 8.83 S / m. The conductivity did not change significantly, indicating that the introduction of vinyl-terminated methyl silicone resin does not destroy the original conductive network of the reduced graphene oxide aerogel.

[0059] Calculations showed that in the composite material with 30 parts of vinyl-terminated methyl silicone resin, the proportion of vinyltriethoxysilane-modified reduced graphene oxide aerogel was only 0.487 wt%. This indicates that the composite material of the present invention achieves superior conductivity with only a small amount of conductive filler. At the same amount of conductive filler, the conductivity of the composite material of the present invention is superior to that of conductive silicone rubber made from carbon materials prepared by traditional blending processes. Example 2: Effect of high-viscosity polydimethylsiloxane (2000 mPa·s PDMS) on the internal structure and properties of vinyltriethoxysilane-modified reduced graphene oxide aerogel / silicone rubber dual-network composite material.

[0060] The preparation of vinyltriethoxysilane-modified dual-template reduced graphene oxide aerogel / silicone rubber composite material includes the following steps:

[0061] 1. Preparation of reduced graphene oxide aerogel

[0062] Reduced graphene oxide aerogel was prepared by following the procedure in step 1 of Example 1.

[0063] 2. Modification of reduced graphene oxide aerogel

[0064] Following the procedure in step 2 of Example 1, vinyltriethoxysilane-modified reduced graphene oxide aerogel was prepared.

[0065] 3. Composite of vinyltriethoxysilane-modified reduced graphene oxide aerogel with silicone rubber

[0066] 3.1 Preparation of silicone rubber raw material solution: By weight, take 100 parts of vinyl-terminated polydimethylsiloxane, 30 parts of silica, appropriate amount of crosslinking agent, 5 parts of polydimethylsiloxane, 30 parts of vinyl-terminated methylsilicone resin, 0.3 parts of inhibitor, and 1.6 parts of Pt catalyst, mix all raw materials evenly to obtain silicone rubber raw material solution.

[0067] The vinyl-terminated polydimethylsiloxane contains two components with different viscosities: 2000 mPa·s and 500 mPa·s. The mass ratios of the 2000 mPa·s and 500 mPa·s products are 0 (meaning the product does not contain 2000 mPa·s), 1:5, and 1:2, respectively. The vinyl content of the 500 mPa·s vinyl-terminated polydimethylsiloxane is 0.0141-0.0173 mol / 100g, and the vinyl content of the 2000 mPa·s vinyl-terminated polydimethylsiloxane is 0.0067-0.0135 mol / 100g. The viscosity of the polydimethylsiloxane is 500 mPa·s. The vinyl content of the vinyl-terminated methylsilicone resin is 0.0404 mol / 100g, and its viscosity is approximately 2500 mPa·s. The inhibitor was a 5 wt% acetylenecyclohexanol solution, and the solvent was polydimethylsiloxane with a viscosity of 500 mPa·s. The Pt catalyst was a platinum complex of tetramethyldivinylsiloxane. The crosslinking agent was hydrogen-containing silicone oil with a hydrogen content of 0.8 wt%, added according to a standard molar ratio of 1:1.2 between the carbon-carbon double bonds in vinyl-terminated polydimethylsiloxane and vinyl-terminated methylsiloxane and the silicon-hydrogen bonds in the hydrogen-containing silicone oil.

[0068] 3.2 Preparation of vinyltriethoxysilane-modified reduced graphene oxide aerogel / silicone rubber dual-network composite materials: Following the operation in step 3.2 of Example 1, three vinyltriethoxysilane-modified reduced graphene oxide aerogel / silicone rubber dual-network composite materials were finally prepared.

[0069] Tensile tests were conducted on three composite materials using an electronic universal testing machine. The results showed that as the proportion of vinyl-terminated polydimethylsiloxane with a viscosity of 2000 mPa·s increased, the strain value corresponding to the Young's modulus transition point decreased. The test results are shown in Table 1.

[0070] Table 1

[0071]

[0072] The crosslinking densities of three types of silicone rubber, three types of composite materials, and the crosslinking density ratios of the three composite materials to their corresponding silicone rubbers were measured using a low-field nuclear magnetic resonance spectrometer. The XLD2 fitting method was selected for the tests, the test temperature was 35℃, the sample density was set to 1 g / ml, and the tests were repeated four times, with the average value taken. The test results are shown in Table 2.

[0073] Table 2

[0074]

[0075] As shown in the table, with the increase of the proportion of 2000 mPa·s vinyl-terminated polydimethylsiloxane, the crosslinking density of the composite material first increases and then decreases. Among them, the crosslinking density of the composite material is the highest when the mass ratio is 1:5. As can be seen from Table 1, the composite material with this ratio has the highest tensile strength and elongation at break. However, when the mass ratio is 1:2, the crosslinking density of the composite material decreases to a certain extent, and its tensile strength and elongation at break also decrease. This is because the vinyl content of 2000 mPa·s vinyl-terminated polydimethylsiloxane (0.0091 mol / 100 g) is lower than that of 500 mPa·s vinyl-terminated polydimethylsiloxane (0.0153 mol / 100 g). Therefore, as the proportion of 2000 mPa·s vinyl-terminated polydimethylsiloxane continues to increase, the crosslinking density of the composite material begins to decrease, which also affects the mechanical properties of the composite material. As shown in Table 2, the crosslinking density ratios of the three composite materials and their corresponding silicone rubbers indicate that as the proportion of 2000 mPa·s vinyl-terminated polydimethylsiloxane increases, the crosslinking density ratio of the composite material to its corresponding silicone rubber increases and gradually approaches 1. This means that the degree of crosslinking of the composite material gradually approaches the degree of crosslinking of its corresponding silicone rubber. This demonstrates that increasing the proportion of 2000 mPa·s vinyl-terminated polydimethylsiloxane effectively improves the compatibility between the reduced graphene oxide aerogel network and the silicone rubber network, making the crosslinking degree of the interpenetrating network composed of two networks with significantly different scales essentially approach the crosslinking degree of a single silicone rubber polymer network. A schematic diagram of the internal structure of this composite material is shown below. Figure 2 .

[0076] The electrical conductivity of the three composite materials was tested using a four-probe resistance meter. The electrical conductivity values ​​were 8.8512 S / m, 8.8496 S / m, and 8.7984 S / m, respectively. It can be seen that the electrical conductivity values ​​of the three composite materials are basically the same, indicating that increasing the proportion of 2000 mPa·s vinyl-terminated polydimethylsiloxane will not affect the electrical conductivity of the composite material. That is, the addition of 2000 mPa·s vinyl-terminated polydimethylsiloxane will not affect the structural integrity of the internal conductive network of the composite material.

[0077] The tensile resistance response properties of three composite materials were tested using an electronic universal testing machine and a digital multimeter. The strain sensitivity (gauge factor, GF) can be expressed as the ratio of the relative change in resistance R to the mechanical strain ε: GF·ε= (R i -R0) / R0, where R0 and Ri These represent the resistance of the sample before and after the load is applied, respectively (R i -R0) / R0 represents the rate of change of resistance, and ε represents the strain of the sample. The rate of change of resistance-strain curves of the three composite materials were fitted with an exponential function, and the strain sensitivity of the three composite materials was obtained through differential calculation. The calculation results are shown in Table 3. It can be seen that with the increase of the proportion of 2000 mPa·s vinyl-terminated polydimethylsiloxane, the strain sensitivity of the composite material increases sharply, further demonstrating that increasing the proportion of 2000 mPa·s vinyl-terminated polydimethylsiloxane can effectively improve the matching compatibility between the reduced graphene oxide aerogel network and the silicone rubber network.

[0078] Table 3

[0079]

[0080] The resistivity response of a composite material with a mass ratio of 1:5 of vinyl-terminated polydimethylsiloxane (2000 mPa·s viscosity) and vinyl-terminated polydimethylsiloxane (500 mPa·s viscosity) under small strain (0.1%) was tested using an electronic universal testing machine and a digital multimeter. The results showed that even with a strain of 0.1%, the composite material still exhibited a certain degree of resistivity response, with a resistance change rate of approximately 1.5%.

[0081] Cyclic tensile resistance response stability tests were conducted on a composite material with a mass ratio of 1:5 of vinyl-terminated polydimethylsiloxane with a viscosity of 2000 mPa·s and vinyl-terminated polydimethylsiloxane with a viscosity of 500 mPa·s using an electronic universal testing machine and a digital multimeter (strain 30%, number of cycles 500). The results showed that the composite material could maintain its resistance change rate basically unchanged during cyclic tensile testing, indicating that the composite material has excellent resistance response stability and repeatability.

Claims

1. A method for preparing a silane coupling agent-modified carbon aerogel / silicone rubber dual network composite material, characterized by Includes the following steps: (1) Carbon aerogels were prepared using carbon materials; (2) Surface modification of carbon aerogel using silane coupling agents; (3) Using modified carbon aerogel as conductive filler, the silicone rubber raw material solution is filled into the modified carbon aerogel by vacuum-assisted impregnation process, and then the silane coupling agent modified carbon aerogel / silicone rubber dual network composite material is obtained by vacuum curing molding process. The silicone rubber raw material solution has the following weight composition: 100 parts vinyl-terminated polydimethylsiloxane, 0-50 parts silica, 4-6 parts polydimethylsiloxane, 10-50 parts vinyl-terminated methyl silicone resin, 0.2-0.4 parts inhibitor, 1.5-2 parts Pt catalyst, and crosslinking agent. The crosslinking agent is hydrogen-containing silicone oil. The amount of crosslinking agent added is determined according to the standard that the molar ratio of carbon-carbon double bonds in vinyl-terminated polydimethylsiloxane and vinyl-terminated methyl silicone resin to silicon-hydrogen bonds in hydrogen-containing silicone oil is 1:1.1-1.

3. The vinyl-terminated polydimethylsiloxane is selected from at least one of the following: vinyl-terminated polydimethylsiloxane with a viscosity of 1900-2200 mPa·s and a vinyl content of 0.0067-0.0135 mol / 100g; and vinyl-terminated polydimethylsiloxane with a viscosity of 480-520 mPa·s and a vinyl content of 0.0141-0.0173 mol / 100g.

2. The method of claim 1, wherein: The carbon materials used to prepare carbon aerogels include graphene oxide, carbon nanotubes, or carbon fibers.

3. The method of claim 1 wherein: The carbon material is graphene oxide.

4. The method of claim 1 or 2, wherein: The method used to prepare carbon aerogels is selected from the sol-gel method, hydrothermal method, chemical vapor deposition method, bubble template method, ice template method, or a combination of two or more of these methods.

5. The method of claim 1 or 2, wherein: The method used to prepare carbon aerogels is a combination of the bubble template method and the ice template method.

6. The method of any one of claims 1-3, wherein: The method of surface modification of carbon aerogel using silane coupling agent is as follows: the carbon aerogel is immersed in a mixture of silane coupling agent and organic solvent, and then dried to obtain silane coupling agent modified carbon aerogel.

7. The method of claim 6 wherein: Includes at least one of the following conditions: Condition 1: The silane coupling agent includes vinyltriethoxysilane, vinyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane or anilinemethyltriethoxysilane; Condition 2: In the mixture of silane coupling agent and organic solvent, the concentration of silane coupling agent is 3-9 wt%; Condition 3: Soaking should be carried out at room temperature for 10-12 hours; Condition 4: Drying is carried out at 55-65℃ for 24-26 hours.

8. The method of claim 7, wherein: The silane coupling agent is vinyltriethoxysilane.

9. The method of claim 1 wherein: During vacuum-assisted impregnation, the vacuum level is 0.05-0.1 MPa; during vacuum curing, the vacuum level is 0.05-0.1 MPa and the temperature is 55-65℃.

10. The method of claim 1 wherein: Vinyl-terminated polydimethylsiloxanes with a viscosity of 1900-2200 mPa·s account for 0-35% of the total vinyl-terminated polydimethylsiloxanes.

11. The method of claim 10, wherein: Vinyl-terminated polydimethylsiloxanes with a viscosity of 1900-2200 mPa·s account for 10-35% of the total vinyl-terminated polydimethylsiloxanes.

12. The method of claim 1, 10 or 11, wherein: Includes at least one of the following conditions: Condition 1: The viscosity of polydimethylsiloxane is 480-520 mPa·s; Condition 2: The vinyl content of the vinyl-terminated methyl silicone resin is 0.03-0.05 mol / 100g, and the viscosity is 2300-2600 mPa·s; Condition 3: The hydrogen content of the hydrogen-containing silicone oil is 0.8 wt%; Condition 4: The inhibitor is a 4-6 wt% acetylenecyclohexanol solution, and the solvent is polydimethylsiloxane with a viscosity of 480-520 mPa·s; Condition 5: The Pt catalyst is a platinum complex of tetramethyldivinylsiloxane.

13. The product obtained by the preparation method of the silane coupling agent modified carbon aerogel / silicone rubber dual network composite material according to any one of claims 1-12.

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