A stretchable conductive rubber based on blending process, its preparation method and application

Abstract

This invention discloses a stretchable conductive rubber material based on a blending process, its preparation method, and its application. The preparation method includes the following steps: S1, preparing EPDM rubber composite material and silicone rubber composite material; S2, blending: taking the prepared EPDM rubber composite material and silicone rubber composite material, adding a compatibilizer, mixing, and kneading to obtain a mixture; S3, vulcanization: vulcanizing in two stages, with the vulcanization temperature of the second stage being 20-30°C higher than that of the first stage. This invention prepares a stretchable conductive rubber with high sensitivity, excellent mechanical properties, and low resistance hysteresis using an efficient, pollution-free, and low-cost method, which can be applied to the preparation of strain sensors.

Description

Technical Field

[0001] This invention relates to the fields of rubber materials and strain sensing technology, specifically to a stretchable conductive rubber based on a blending process, its preparation method, and its applications. Background Technology

[0002] Stretchable strain sensors can detect the deformation of materials under external forces and convert it into electrical signals. They are widely used in health monitoring, flexible electronics, smart wearables, robotics, and structural health monitoring. With the rapid development of flexible electronics technology, stretchable strain sensors have become a research and application hotspot due to their excellent flexibility, stretchability, and high sensitivity. Their basic principle is to monitor strain by measuring the change in the resistance of a material under external force, and they are typically used to detect information such as deformation, displacement, and pressure of objects. In recent years, with the surge in demand for wearable devices, smart robots, and biomedical devices, researchers have been dedicated to developing stretchable strain sensors that can operate stably and with high sensitivity under deformation conditions such as tension and bending.

[0003] Despite the immense application potential of tensile strain sensors in many fields, they still face several technical challenges in practical use. One significant challenge is the hysteresis phenomenon in the output resistance response signal. When the sensor material deforms, the resistance value changes accordingly. However, especially under high-frequency or large-amplitude strain changes, the sensor's resistance response does not change immediately in sync with the external deformation; this delayed response phenomenon is commonly referred to as "signal hysteresis." The primary cause of this phenomenon is the viscoelasticity of the material. Many materials used in tensile strain sensors, such as conductive polymers and carbon nanotube composites, possess a certain degree of viscoelasticity. During strain loading and unloading, these materials exhibit not only elastic strain but also viscous strain. The strain hysteresis caused by the viscous component results in a hysteresis in the resistance response, especially under high-frequency strain, where this hysteresis effect is more pronounced.

[0004] The hysteresis problem in the resistance response signal severely affects the real-time performance and accuracy of tensile strain sensors, causing them to fail to accurately and promptly reflect rapid changes in the external environment. This impacts the reliability of measurement data. In smart wearable devices or health monitoring, hysteresis can lead to erroneous physiological parameter analysis, affecting users' health management decisions. In robotics or automation systems, hysteresis can cause slow responses in the control system, affecting task execution efficiency and accuracy. Furthermore, hysteresis signals can interfere with real-time data processing and feedback, increasing system errors and reducing the overall performance and application value of tensile strain sensors. Therefore, solving the problem of resistance response signal hysteresis is crucial to improving the performance of tensile strain sensors. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned problems by providing a stretchable conductive rubber based on a blending process, its preparation method, and its applications. This invention utilizes an efficient, pollution-free, and low-cost method to prepare a stretchable conductive rubber with high sensitivity, excellent mechanical properties, and low resistivity hysteresis, which can be applied to the fabrication of strain sensors.

[0006] To achieve its objective, the present invention employs the following technical solution:

[0007] The first aspect of the present invention provides a method for preparing a stretchable conductive rubber material based on a blending process, comprising the following steps:

[0008] S1. Preparation of EPDM rubber composites and silicone rubber composites:

[0009] Preparation of EPDM rubber composite material: By weight, take 30-70 parts (preferably 50-70 parts) of raw material EPDM rubber, 2-6 parts of conductive filler, 3-7 parts of zinc oxide, 0.5-2.5 parts of stearic acid, 1.5-3.5 parts of accelerator, 1-3 parts of antioxidant, and 0.5-2.5 parts of sulfur, mix them, and knead them to obtain EPDM rubber composite material;

[0010] Prepare silicone rubber composite material: Take 30-70 parts (preferably 30-50 parts) of raw material methyl vinyl silicone rubber, 2-6 parts of conductive filler, 27-33 parts of silica, 15-21 parts of hydroxyl silicone oil and 0.5-1.5 parts of vulcanizing agent by weight, mix them and knead them to obtain silicone rubber composite material.

[0011] S2, blending:

[0012] Take the prepared EPDM rubber composite material and silicone rubber composite material, add a compatibilizer, and mix them according to the mass ratio of the starting raw materials EPDM rubber, methyl vinyl silicone rubber and compatibilizer of the composite material prepared in step S1 of 30-70:30-70:3-7 (preferably 50-70:30-50:3-7) to obtain a mixture.

[0013] S3, vulcanization:

[0014] The mixture prepared in step S2 is vulcanized in two stages. The vulcanization temperature of the second stage is 20-30°C higher than that of the first stage to obtain a stretchable conductive rubber material.

[0015] Preferably, the raw material ratio of the EPDM rubber composite material is as follows: 50-70 parts of EPDM rubber, 3-4 parts of conductive filler, 4-6 parts of zinc oxide, 1.0-2.0 parts of stearic acid, 2.0-3.0 parts of accelerator, 1-3 parts of antioxidant, and 1.0-2.0 parts of sulfur are mixed together.

[0016] The raw material ratio of the silicone rubber composite material is as follows: 30-50 parts of methyl vinyl silicone rubber, 3-4 parts of conductive filler, 29-31 parts of silica, 17-19 parts of hydroxyl silicone oil, and 0.8-1.2 parts of vulcanizing agent.

[0017] The mixing temperature in step S1 is 30-50℃, the roller gap is 0.05-1mm, the speed is 20-30rpm, and the mixing process is 40-60min.

[0018] The mixing temperature in step S2 is 40-60℃, the roller gap is 0.05-1mm, the speed is 40-60rpm, and the mixing process takes 60-80min.

[0019] Preferably, in step S3,

[0020] The vulcanization temperature for the first stage is 150–170℃, the time is 10–20 min, and the pressure is 10–20 MPa. The preferred vulcanization temperature is 160–170℃, the time is 10–15 min, and the pressure is 10–15 MPa.

[0021] The second stage of vulcanization is then carried out at a temperature of 180–200°C for 2–4 hours.

[0022] Preferably, in step S3, the first stage of vulcanization is carried out on a flat vulcanizing apparatus, and the second stage of vulcanization is carried out in an oven.

[0023] In this invention, the vulcanization of the mixture is carried out in two stages. The first stage of vulcanization is mainly to vulcanize the conductive mixture and form a cross-linked network inside. The second stage of vulcanization is mainly to increase the cross-linking density of the first stage of vulcanization, thereby improving the mechanical properties and aging resistance of the composite material.

[0024] The accelerator is selected from one or more of tetramethylthiuram disulfide, N-tert-butyl-2-benzothiazole sulfenamide, and tetrasulfide bispentamethylenethiuram;

[0025] The antioxidant is selected from one or more of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, 2-hydroxy-4-methoxybenzophenone, and 2,2,4-trimethyl-1,2-dihydroquinoline polymer.

[0026] The conductive filler is selected from multi-walled carbon nanotubes or conductive carbon black.

[0027] The vulcanizing agent is selected from one or more of dicumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, tert-butyl perbenzoate, and dibenzoyl peroxide;

[0028] The compatibilizer is selected from one or more of γ-aminopropyltriethoxysilane, vinyltris(β-methoxyethoxy)silane, and maleic anhydride graft compatibilizer.

[0029] The conductive filler has a length of 10-20 μm, a diameter of 7-9 nm, and a specific surface area of ​​100-200 m². 2 / g;

[0030] The density of the EPDM rubber is 0.85-0.9 g / cm³. 3 The molecular weight is 15×10 4 g / mol;

[0031] The methyl vinyl silicone rubber has a vinyl content of 0.16% and a molecular weight of 7.2 × 10⁻⁶. 5 g / mol;

[0032] The silica particles have a diameter of 7-40 nm and a specific surface area of ​​200 m². 2 / g;

[0033] The hydroxyl silicone oil has a hydroxyl content of 7-9% and a viscosity of 25-30 Pa·s.

[0034] A second aspect of the present invention provides a stretchable conductive rubber material, which is prepared by any of the preparation methods described above.

[0035] A third aspect of the present invention provides the application of the above-described stretchable conductive rubber material in the fabrication of flexible strain sensors.

[0036] The beneficial effects of this invention are:

[0037] 1. Improved response speed: The blending of EPDM rubber and methyl vinyl silicone rubber can effectively improve the elasticity of the material, enabling the sensor to respond more quickly to external deformation changes, reducing the hysteresis of the resistance signal, and improving the real-time and dynamic performance of the tensile strain sensor.

[0038] 2. Enhanced flexibility and durability: The conductive rubber material prepared by blending has excellent tensile strength and wear resistance, and can maintain stable performance in working environments with repeated stretching and bending, reducing the hysteresis of resistance signals caused by material fatigue, thereby improving the long-term reliability of the stretchable strain sensor.

[0039] 3. Improved resistance stability: The blending of EPDM rubber and methyl vinyl silicone rubber optimizes the volume conductivity change characteristics of the material, making the resistance signal more stable during strain changes when the conductive rubber material of the present invention is used as a tensile strain sensor. This reduces the influence of external environmental factors such as temperature and humidity, and improves measurement accuracy.

[0040] 4. Expanded Application Range: Due to its excellent weather resistance, oxidation resistance, and chemical stability, this blended conductive rubber material can be widely used in various harsh environments. It can also be applied to wearable devices, smart healthcare, robot control, and other fields, expanding the application scenarios of tensile strain sensors.

[0041] The lightweight, highly elastic, stretchable conductive rubber material prepared by the method of this invention possesses advantages such as good volumetric conductivity, excellent mechanical properties, high sensitivity, and low resistance hysteresis. It can be applied as a strain sensor, suitable for damage monitoring in human physiology and large structural components; thus promoting the development of intelligent sensing technology. Attached Figure Description

[0042] Figure 1 This is a flowchart of the preparation method of the conductive rubber material of the present invention.

[0043] Figure 2 This is a physical image of the conductive rubber material prepared in Example 4.

[0044] Figure 3 The images show the SEM microstructure of the flexible strain sensors in Comparative Example 2 and Example 4.

[0045] Figure 4 This is a comparison chart of the output monitoring signals of the conductive rubber materials prepared in Example 4 and Comparative Example 2. Detailed Implementation

[0046] The present invention will be further described below with reference to embodiments, but these embodiments are not intended to limit the scope of the invention.

[0047] Unless otherwise specified, the experimental methods described in the following examples are conventional methods.

[0048] The raw materials are: ethylene propylene diene monomer (EPDM) rubber and methyl vinyl silicone rubber (VMQ) as the matrix; multi-walled carbon nanotubes (MWCNT) as the conductive filler; zinc oxide, stearic acid, accelerator tetramethylthiuram disulfide (accelerator TMTD, CAS No. 137-26-8), antioxidant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (antioxidant 6PPD, CAS No. 793-24-8), and sulfur (S) as fillers for EPDM rubber. Nano-silica, hydroxyl silicone oil (PDMS), and dicumyl peroxide (vulcanizing agent DCP) are used as fillers for methyl vinyl silicone rubber. γ-aminopropyltriethoxysilane (silane coupling agent KH-550, CAS No. 919-30-2) is used as a compatibilizer for EPDM rubber and methyl vinyl silicone rubber.

[0049] Among them, multi-walled carbon nanotubes have a length of 10-20 μm, a diameter of 7-9 nm, and a specific surface area of ​​100-200 m². 2 / g;

[0050] The density of ethylene propylene diene monomer (EPDM) rubber is 0.85-0.9 g / cm³. 3 The molecular weight is 15×10 4 g / mol;

[0051] Zinc oxide, stearic acid, antioxidants, accelerators, and sulfur were all of analytical grade.

[0052] The vinyl content of methyl vinyl silicone rubber is 0.16%, and its molecular weight is 7.2 × 10⁻⁶. 5 g / mol;

[0053] Silica particles have a diameter of 7-40 nm and a specific surface area of ​​200 m². 2 / g;

[0054] Hydroxysilicone oil contains 7-9% hydroxyl groups and has a viscosity of 25-30 Pa·s.

[0055] Dicumyl peroxide was of analytical grade, and γ-aminopropyltriethoxysilane was of reagent grade.

[0056] All of the above raw materials are commercially available regular products.

[0057] The preparation method of the stretchable conductive rubber material of the present invention is as follows (process flow diagram is shown below). Figure 1 As shown):

[0058] S1. Preparation of EPDM rubber composites and silicone rubber composites:

[0059] EPDM rubber, multi-walled carbon nanotubes, zinc oxide, stearic acid, accelerator, antioxidant, and sulfur were sequentially placed into a two-roll mill and mixed evenly. The mixing temperature was 50℃, the roll gap was 1mm, the speed was 30rpm, and the mixing process lasted for 40min. EPDM rubber composite material was thus prepared.

[0060] Methyl vinyl silicone rubber, multi-walled carbon nanotubes, silica, hydroxyl silicone oil, and dicumyl peroxide were sequentially placed into a two-roll mill and mixed evenly. The mixing temperature was 50℃, the roll gap was 1mm, the speed was 30rpm, and the mixing process lasted for 40min. A silicone rubber composite material was prepared.

[0061] S2, blending:

[0062] The prepared EPDM rubber composite material and silicone rubber composite material were mixed on a two-roll mill, and 5 parts of silane coupling agent KH-5505 were added. The mixing temperature was 60℃, the roll gap was 1mm, the speed was 40rpm, and the mixing process lasted for 60min; the resulting mixture was obtained.

[0063] In this process, conducted in a two-roll mill, two rolls rotate relative to each other at different speeds. Internal and external friction, as well as shear forces between the rolls, cause the material to deform and flow. Under this shear force, the matrix and filler disperse, break down, and recombine. This shearing action allows the filler to be effectively dispersed within the matrix, forming a three-dimensional tunneling conductive network structure that enables it to acquire response signals.

[0064] S3, vulcanization:

[0065] The mixture prepared in step S2 is subjected to the first stage of vulcanization on a flat vulcanizing apparatus at a temperature of 170℃ for 15 minutes and a pressure of 15 MPa. Subsequently, it is placed in a forced-air drying oven (or vacuum oven) for the second stage of vulcanization at a temperature of 200℃ for 2 hours. This yields a stretchable conductive rubber material. Figure 2 This is a physical image of the conductive rubber material prepared in Example 4.

[0066] The first stage of vulcanization initiates a cross-linking reaction between EPDM rubber and methyl vinyl silicone rubber. The peroxide (diisopropylbenzene peroxide) decomposes to produce free radicals, which react with double bonds in the rubber molecules to form a cross-linked structure. This stage of cross-linking is primarily initiated by the vulcanizing agent; sulfur reacts with unsaturated groups in the rubber to form cross-linking points, transforming the rubber from a linear structure to a three-dimensional network structure. The vulcanization reaction promotes the initial cross-linking of the rubber material. Although the degree of cross-linking is incomplete, the material's elasticity and plasticity are improved to some extent, and its mechanical properties and heat resistance are initially enhanced.

[0067] The second stage of vulcanization takes place in a forced-air drying oven. High-temperature treatment further enhances the degree of cross-linking, promoting the continued reaction between sulfur and the double bonds in the rubber molecules. Increased cross-linking density makes the molecular structure of the material more stable, thereby improving its thermal stability, physical properties, and aging resistance. Further completion of the cross-linking reaction makes the material structure even more stable, ultimately achieving ideal mechanical properties and durability.

[0068] The conductive rubber material products of Examples 1-4 in Table 1 were prepared according to the above method. The raw material ratios used in each example are shown in Table 1 (the values ​​in Table 1 are the weight parts of the components).

[0069] Table 1

[0070]

[0071] The methyl vinyl silicone rubber composite material or ethylene propylene diene monomer (EPDM) rubber composite material prepared in Examples 1 and 2 are directly subjected to two-stage vulcanization in step S3 without step S2 to obtain conductive rubber material.

[0072] Meanwhile, comparative examples 1-2 were prepared:

[0073] Comparative Example 1 (using the same raw materials as the present invention, but with a different process)

[0074] Using the raw materials and dosages of Example 4, all raw materials—methyl vinyl silicone rubber, ethylene propylene diene monomer (EPDM) rubber, multi-walled carbon nanotubes, zinc oxide, stearic acid, accelerator, antioxidant, sulfur, silica, and diisopropylbenzene peroxide—were simultaneously and directly fed into an open mill for mixing. The temperature was set at 50°C, the speed at 70 rpm, the roll gap at 1 mm, and the time at 50 min. Subsequently, the mixture was placed in a flat vulcanizing apparatus for the first stage of vulcanization molding at a pressure of 10 MPa, a temperature of 170°C, and a time of 10 min, yielding the final product.

[0075] Comparative Example 2 (using different raw materials but the same process as the present invention)

[0076] The raw materials used in Comparative Example 2 differ from those of the present invention. Specifically, the fillers in Comparative Example 2 include EPDM rubber, methyl vinyl silicone rubber, conductive carbon black, silica, naphthenic oil, and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (vulcanizing agent bis-25). Conductive rubber materials were prepared using the preparation process of the present invention.

[0077] Specifically, the preparation process is as follows: 70 parts of EPDM rubber, 20 parts of conductive carbon black, and 2 parts of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane are mixed evenly in a two-roll mill at a mixing temperature of 50℃, a roll gap of 1mm, a speed of 30rpm, and a mixing time of 40min. This yields an EPDM rubber composite material. 30 parts of methyl vinyl rubber, 20 parts of conductive carbon black, 40 parts of silica, 24 parts of naphthenic oil, and 2 parts of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane are mixed evenly in a two-roll mill at a mixing temperature of 50℃, a roll gap of 1mm, a speed of 30rpm, and a mixing time of 40min. This yields a methyl vinyl silicone rubber composite material. Finally, the EPDM rubber composite material and the silicone rubber composite material are mixed in a two-roll mill at a mixing temperature of 60℃, a roll gap of 1mm, a speed of 40rpm, and a mixing time of 60min. The material was then subjected to the first stage of vulcanization on a flat vulcanizing apparatus at a temperature of 170℃ for 15 minutes and a pressure of 15 MPa. A second stage of vulcanization was then performed in a forced-air drying oven at 200℃ for 2 hours. This yielded a stretchable conductive rubber material.

[0078] Performance testing

[0079] The properties of the prepared flexible conductive rubber material were tested.

[0080] (1) Volumetric conductivity: The volumetric conductivity of the conductive nano-rubber material was tested according to the GT / T1692-2008 standard. First, the sample was cut into standard specimens with dimensions of 40mm × 10mm × 1mm (surface cleaned with anhydrous ethanol). The resistance value of the specimen under strain-free conditions was measured using a Keysight 34465A digital multimeter. The average resistance value within 1 second was collected from the digital multimeter. Three specimens were tested in each group, and the average value was taken. The volumetric conductivity formula is defined as:

[0081]

[0082] In equation (1), σ is the volume conductivity (S / m), ρ is the volume resistivity of the material (Ω·m), R is the volume resistance (Ω), L is the length of the sample (m), and S is the cross-sectional area (m²). 2 ).

[0083] (2) Sensitivity test: Clamp both ends of the conductive nano-rubber material on the electronic universal testing machine, take a wire, connect one end of the wire to the conductive nano-rubber material, and connect the other end of the wire to a digital multimeter. Set the strain through the universal testing machine. After a single stretching cycle, the maximum resistance value is transmitted to the computer through the digital multimeter. Then, calculate the sensitivity based on the resistance and strain according to formula (2).

[0084] Sensitivity calculation method: The sensitivity of the composite material is evaluated using equation (2):

[0085] GF=(ΔR / R0) / ε Equation (2)

[0086] In equation (2), ε is the strain. ΔR / R0, ΔR=R-R0, where R0 is the initial resistance and R is the test resistance.

[0087] (3) Test method for resistance hysteresis: The conductive nano-rubber material was cut into strips of 40mm×40mm×1mm. The samples were fixed on an electronic universal testing machine for cyclic loading-unloading tests, and the changes in resistance hysteresis were recorded using a digital multimeter (see results). Figure 4 ).

[0088] (4) Mechanical property testing methods: According to GB / T528-2009, the mechanical properties of dumbbell-shaped standard conductive nano-rubber material samples were measured using an electronic universal testing machine (DDL10) at a tensile rate of 200 mm / min. -1 The average value of the three sets of experimental data was taken.

[0089] The performance test results are shown in Table 2.

[0090] Table 2: Performance Results of Conductive Rubber Materials

[0091]

[0092] As can be seen from the various embodiments and comparative examples, the volumetric conductivity of each embodiment of the present invention is significantly reduced compared with Comparative Example 1 or Comparative Example 2. In particular, for Example 4, which uses the same filler, the reduction in volumetric conductivity is more significant compared with Comparative Example 1, indicating that the blending process of the present invention can greatly reduce volumetric conductivity.

[0093] All embodiments achieved good sensitivity. Compared with Comparative Example 1 or Comparative Example 2, which used different raw materials or preparation methods than the present invention, the sensitivity of each embodiment was improved to varying degrees.

[0094] After the two rubbers are mixed, the cross-linking structure can be optimized through appropriate processing and vulcanization conditions to form a more uniform and stronger three-dimensional cross-linked network. This structure helps to enhance the overall mechanical properties of the material, especially in terms of tensile strength and elongation at break. Compared with Comparative Example 1 or Comparative Example 2, the tensile strength and elongation at break of each embodiment are improved. In particular, the tensile strength and elongation at break of Example 4, which uses the filler ratio and blending process of the present invention, are significantly improved.

[0095] The SEM microstructure images of Comparative Example 2 and Example 4 ( Figure 3 As can be seen, the conductive carbon black in Comparative Example 2 exhibits severe agglomeration in the rubber matrix, hindering the continuity of the conductive filler within the rubber matrix. In contrast, the self-assembled conductive filler in Example 4 demonstrates good dispersion in the rubber matrix, which is a crucial factor in obtaining a low volumetric conductivity, high sensitivity, good mechanical properties, and stable resistance / strain response signal.

[0096] Resistance / strain response signal diagrams of Comparative Example 2 and Example 4 ( Figure 4 As can be seen, in Comparative Example 2, the resistance only stabilizes with increasing cycle count. In contrast, the resistance / strain response signal in Example 4 remains stable, without the initial increase followed by a decrease; the resistance / strain response signal remains consistently stable. This is because EPDM rubber typically possesses good elastic properties, allowing for rapid recovery under stress; while methyl vinyl silicone rubber exhibits low internal friction, preventing excessive energy loss during repeated deformation. The composite material formed by blending these two materials exhibits a synergistic effect during deformation, mitigating the material's resistive hysteresis effect.

[0097] By employing the method of this invention, and combining a specific mass ratio of EPDM rubber to methyl vinyl silicone rubber with a specific vulcanization system and multi-walled carbon nanotubes, a stretchable strain sensor with low volume conductivity, high sensitivity, good mechanical properties, and low resistive hysteresis can be produced. Furthermore, the innovative raw material ratio of this invention reduces the resistive hysteresis in the monitoring signal, resulting in a stable monitoring signal. This conductive nano-rubber material can be fabricated into a flexible strain sensor for real-time strain monitoring of seismic isolation bearings and human physiological monitoring. Simultaneously, this stretchable conductive rubber material overcomes the shortcomings of traditional strain sensors, such as brittleness, low sensitivity, and narrow monitoring range. During monitoring, the output monitoring signal perfectly coordinates with the deformation of the measured structure, making real-time monitoring of the object more advantageous. This invention can promote the development of intelligent sensing technology.

Claims

1. A method for preparing a stretchable conductive rubber material based on a blending process, characterized in that, Includes the following steps: S1. Preparation of EPDM rubber composites and silicone rubber composites: Preparation of EPDM rubber composite material: 50-70 parts by weight of raw EPDM rubber, 2-6 parts by weight of conductive filler, 3-7 parts by weight of zinc oxide, 0.5-2.5 parts by weight of stearic acid, 1.5-3.5 parts by weight of accelerator, 1-3 parts by weight of antioxidant, and 0.5-2.5 parts by weight of sulfur are mixed and kneaded to obtain the EPDM rubber composite material; the accelerator is tetramethylthiuram disulfide. Silicone rubber composite material was prepared by mixing 30-50 parts of raw material methyl vinyl silicone rubber, 2-6 parts of conductive filler, 27-33 parts of silica, 15-21 parts of hydroxyl silicone oil and 0.5-1.5 parts of vulcanizing agent by weight, and then kneading to obtain silicone rubber composite material. The conductive filler is selected from multi-walled carbon nanotubes, which have a length of 10-20 μm, a diameter of 7-9 nm, and a specific surface area of ​​100-200 m². 2 / g; S2, blending: Take the prepared EPDM rubber composite material and silicone rubber composite material, add a compatibilizer, and mix them according to the mass ratio of the starting raw materials EPDM rubber, methyl vinyl silicone rubber and compatibilizer of the composite material prepared in step S1 of 30-70:30-70:3-7, and knead them to obtain a mixture; the compatibilizer is γ-aminopropyltriethoxysilane. S3, vulcanization: The mixture prepared in step S2 is vulcanized in two stages. The vulcanization temperature of the first stage is 150-170℃, and the vulcanization temperature of the second stage is 20-30℃ higher than that of the first stage, so as to obtain a stretchable conductive rubber material.

2. The preparation method according to claim 1, characterized in that: The raw material ratio of the EPDM rubber composite material is as follows: 50-70 parts of EPDM rubber, 3-4 parts of conductive filler, 4-6 parts of zinc oxide, 1.0-2.0 parts of stearic acid, 2.0-3.0 parts of accelerator, 1-3 parts of antioxidant, and 1.0-2.0 parts of sulfur are mixed together. The raw material ratio of the silicone rubber composite material is as follows: 30-50 parts of methyl vinyl silicone rubber, 3-4 parts of conductive filler, 29-31 parts of silica, 17-19 parts of hydroxyl silicone oil, and 0.8-1.2 parts of vulcanizing agent.

3. The preparation method according to claim 1, characterized in that: The mixing temperature in step S1 is 30-50℃, the roller gap is 0.05-1mm, the speed is 20-30rpm, and the mixing process is 40-60min. The mixing temperature in step S2 is 40-60℃, the roller gap is 0.05-1mm, the speed is 40-60rpm, and the mixing process takes 60-80min.

4. The preparation method according to claim 1, characterized in that: In step S3, The vulcanization temperature for the first stage of vulcanization is 160–170℃, the time is 10–20 min, and the pressure is 10–20 MPa. The second stage of vulcanization is then carried out at a temperature of 180–200°C for 2–4 hours.

5. The preparation method according to claim 4, characterized in that: In step S3, the first stage of vulcanization is carried out on a flat vulcanizer, and the second stage of vulcanization is carried out in an oven.

6. The preparation method according to claim 1, characterized in that: The antioxidant is selected from one or more of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, 2-hydroxy-4-methoxybenzophenone, and 2,2,4-trimethyl-1,2-dihydroquinoline polymer.

7. The preparation method according to claim 1, characterized in that: The vulcanizing agent is selected from one or more of dicumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, tert-butyl perbenzoate, and dibenzoyl peroxide.

8. The preparation method according to claim 7, characterized in that: The density of the EPDM rubber is 0.85-0.9 g / cm³. 3 The molecular weight is 15×10 4 g / mol; The methyl vinyl silicone rubber has a vinyl content of 0.16% and a molecular weight of 7.2 × 10⁻⁶. 5 g / mol; The silica particles have a diameter of 7-40 nm and a specific surface area of ​​200 m². 2 / g; The hydroxyl silicone oil has a hydroxyl content of 7-9% and a viscosity of 25-30 Pa·s.

9. A stretchable conductive rubber material, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the stretchable conductive rubber material according to claim 9 in the preparation of flexible strain sensors.

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