Thermoplastic flexible electronic skin material and preparation method thereof

Abstract

The invention provides a thermoplastic flexible electronic skin material and a preparation method thereof.The thermoplastic flexible electronic skin material is prepared from, by weight, 20-70 parts of HSBC resin, 3-5 parts of compatilizer, 1-7 parts of carbon nanotubes, 25-70 parts of PDMS rubber compound, 1-7 parts of conductive carbon black, 0.1-1.0 part of silane coupling agent and 0.5-2.0 parts of vulcanizing agent; the PDMS rubber compound is a mixture of PDMS and white carbon black, and the mass ratio of the PDMS to the white carbon black is (6-8): (2-4). By optimizing the composition of the material and adopting the step-by-step mixing and dynamic vulcanization processes, the prepared material has the advantages of good conductive uniformity, aging resistance, bending resistance, wear resistance, good formability and the like.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a thermoplastic flexible electronic skin material and its preparation method. Background Technology

[0002] In recent years, with the rapid development of AI humanoid robots, AI healthcare, and AI smart wearables, flexible electronic skin materials (e-SKIN) have played an increasingly important role as a key carrier for AI-driven intelligent upgrades. Electronic skin needs to convert physical stimuli such as pressure and temperature into electrical signals, and conductive materials can form a highly efficient conductive network to ensure the sensitivity and response speed of signal transmission. In daily life, the resistivity of human skin is typically between one thousand ohms and tens of thousands of ohms. In the field of AI humanoid robots, conductive flexible elastomers, as the core component of electronic skin, integrate multi-dimensional sensing functions such as touch and temperature, giving robots near-human interactive capabilities. Their flexibility and dynamic conductivity can adapt to the needs of joint movement, maintaining stable performance even after tens of thousands of bends, significantly improving the robot's environmental adaptability and operational precision. In the field of AI healthcare, such materials are used in smart bandages and wearable monitoring devices to collect physiological data such as heart rate and blood pressure in real time. They can also achieve seamless adhesion to the skin through flexible substrates, improving patient comfort and monitoring accuracy.

[0003] Traditional thermoplastic materials, such as conductive TPE and conductive TPU, cannot adequately meet requirements due to poor heat resistance, easy migration, and conductivity decay. Traditional thermosetting rubbers, such as conductive silicone rubber, are also severely limited in many applications due to poor tensile toughness, unstable resistivity, and moldability issues. Therefore, there is an urgent need to develop a thermoplastic flexible electronic skin material with stable conductivity, minimal conductivity decay, and good processability.

[0004] Patent application number 201711381034.X discloses a halogen-free conductive TPE cable material and its preparation method. The patent describes a halogen-free conductive TPE cable material prepared by compounding superconducting carbon black, graphene, and conductive carbon fibers. The material comprises hydrogenated styrene-butadiene-styrene, a plasticizer, polypropylene, ethylene-propylene copolymer, superconducting carbon black, graphene, conductive carbon fibers, a surfactant, a stabilizer, and a lubricant, mixed and extruded using a specific weight ratio and process flow. While the above material has high resistivity, the large amount of conductive filler and the very high Shore hardness make it unsuitable for applications requiring low-modulus flexible sensing electronic skin. Furthermore, the addition of a plasticizer significantly affects the material's conductivity attenuation.

[0005] Patent application number 2022110831468.5 discloses an anti-poisoning addition-type conductive silicone rubber composition and its preparation method. The composition comprises 100 parts of organopolysiloxane, 2-8 parts of catalyst, 2-5 parts of crosslinking agent, 0.005-0.1 parts of inhibitor, 300-500 parts of conductive filler, and 5-25 parts of flow aid. The use of a platinum catalyst with organopolysiloxane as the matrix material effectively reduces the premature vulcanization problem caused by excessively high local concentrations of platinum catalyst during mixing. Simultaneously, it results in more uniform dispersion during mixing, leading to a more uniform and dense crosslinking and conductive network in the conductive rubber, thus improving its mechanical and electrical properties. However, due to the large amount of modified conductive filler added to its formulation, although the prepared material has excellent volume resistivity, it does not solve problems such as migration, aging, and delamination of the conductive silicone rubber. Summary of the Invention

[0006] One of the technical problems to be solved by the present invention is to provide a thermoplastic flexible electronic skin material to address the shortcomings of the existing technology. The method optimizes the composition of the material, and the resulting material has advantages such as good conductivity uniformity, aging resistance, bending resistance, wear resistance, and good formability.

[0007] The second technical problem to be solved by this invention is to provide a method for preparing a thermoplastic flexible electronic skin material. This method uses a step-by-step dynamic vulcanization technology to give the material a unique two-phase structure, which improves the problems of easy migration, easy aging, easy oxidation and peeling, and rapid decay of electrical conductivity of single-phase materials. The resulting material also has excellent molding properties.

[0008] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0009] A thermoplastic flexible electronic skin material, by weight, comprises the following components: 20-70 parts HSBC resin, 3-5 parts compatibilizer, 1-7 parts carbon nanotubes, 25-70 parts PDMS compound, 1-7 parts conductive carbon black, 0.1-1.0 parts silane coupling agent, and 0.5-2.0 parts vulcanizing agent; the PDMS compound is a mixture of PDMS and silica, wherein the mass ratio of PDMS to silica is (6-8):(2-4).

[0010] Preferably, the HSBC resin is one or more selected from hydrogenated styrene-butadiene-styrene block copolymer, hydrogenated styrene-isoprene-styrene block copolymer, and styrene-isobutylene-styrene triblock copolymer; the styrene content of the HSBC resin is <30%. More preferably, the styrene content of the HSBC resin is <20%. Preferably, the compatibilizer is a reactive maleic anhydride graft; the reactive maleic anhydride graft is selected from one or more selected from PP-g-MAH, PE-g-MAH, POE-g-MAH, or EVA-g-MAH. More preferably, the maleic anhydride grafting rate of the reactive maleic anhydride graft is >1.0%.

[0011] Preferably, the carbon nanotube is a single-layer or multi-layer coaxial carbon nanotube; the peak value of the G line wavenumber / the peak value of the D line wavenumber of the carbon nanotube is >100.

[0012] Preferably, the vinyl molar mass of the PDMS is 0.05-2.5%. More preferably, the vinyl molar mass of the PDMS is 0.1-1.0%.

[0013] Preferably, the silica is fumed silica or precipitated silica.

[0014] Preferably, the conductive carbon black is nano-conductive carbon black; the BET value of the conductive carbon black is ≥800m. 2 / g.

[0015] Preferably, the general structural formula of the silane coupling agent is Y. n SiX (4-n) , where n is an integer from 0 to 3; where the X group is methoxy or ethoxy, and the Y group is one of vinyl, ethoxy, amino, epoxy, methacryloyloxy, and mercapto.

[0016] Preferably, the vulcanizing agent is an organic peroxide or a silane crosslinking agent; the vulcanizing agent includes a chloroplatinic acid catalyst, and also includes one of odorless DCP and hydrogen-containing silicone oil.

[0017] A method for preparing a thermoplastic flexible electronic skin material includes the following steps:

[0018] (1) PDMS compound, conductive carbon black and silane coupling agent are added to the kneader in sequence and kneaded at 145-155℃ for 20-30 minutes, vacuum devoured for 20-30 minutes, cooled and then granulated at room temperature through a single screw extruder to obtain mixture one.

[0019] (2) HSBC resin, compatibilizer and carbon nanotubes are melt-granulated in sequence through a twin-screw extruder at a granulation temperature of 180-200℃ to obtain mixture two.

[0020] (3) Mix the first mixture and the second mixture with the vulcanizing machine and add them to the high torque twin screw extruder for reactive extrusion granulation. The screw speed is 500 rpm and the reaction temperature is 200-250℃ to obtain thermoplastic flexible electronic skin material.

[0021] Due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0022] 1. This invention provides a thermoplastic flexible electronic skin material, comprising HSBC resin, compatibilizer, carbon nanotubes, PDMS compound, conductive carbon black, silane coupling agent, and vulcanizing agent. The PDMS compound is a mixture of PDMS and silica. By optimizing the dosage of each component, the resulting material has advantages such as good conductivity uniformity, aging resistance, bending resistance, wear resistance, and good formability.

[0023] 2. In the material of this invention, the PDMS compound composed of PDMS and silica provides elasticity and flexibility. Its inherent high resilience and low modulus enable the material to well mimic the mechanical properties of human skin and adapt to various deformations. HSBC resin itself is also a flexible material. The two work synergistically to ensure the overall softness and tensile strength of the material.

[0024] 3. Both carbon nanotubes and conductive carbon black nanoparticles serve as conductive fillers. Carbon nanotubes with a G / D peak ratio >100 exhibit fewer structural defects, higher purity, and excellent conductivity. Conductive carbon black nanoparticles, with their large specific surface area, also possess excellent conductivity. Within the matrix, carbon nanotubes form a one-dimensional conductive fiber network, acting as a bridging agent, while conductive carbon black forms dense conductive nodes. The combination of these two forms a stable conductive network within the matrix, ensuring that the conductive pathways are not easily disrupted even during significant material deformation, thus guaranteeing resistivity stability. This is crucial for the signal stability of electronic skin under stretching and bending conditions.

[0025] 4. This invention improves the compatibility of the components by adding reactive maleic anhydride graft compatibilizers and silane coupling agents. This avoids delamination and improves the mechanical strength and durability of the material.

[0026] 5. This invention provides a method for preparing a thermoplastic flexible electronic skin material. First, conductive carbon black, silane coupling agent, and viscous PDMS compound are thoroughly mixed under certain conditions to obtain mixture one. Then, HSBC resin, compatibilizer, and carbon nanotubes are granulated using a twin-screw extruder to obtain mixture two. Finally, mixture one, mixture two, and a vulcanizing agent are vulcanized to give the material a unique two-phase structure. The continuous phase formed by the flexible coating of high-strength HSBC resin and carbon nanotubes makes the conductive pathway less susceptible to bending or stretching damage. The dispersed phase formed by highly resilient three-dimensional network PDMS conductive microspheres avoids problems such as oxidation, peeling, and migration of conductive carbon black, and also acts as an elastic conductive "relay station" to prevent signal interruption. The two phases are connected by the "bridging effect" of conductive carbon nanotubes to form an all-around high-speed conductive pathway, making the conductivity more stable and ensuring the sensitivity and response speed of signal transmission. Furthermore, the material of this invention exhibits excellent aging resistance, minimal conductivity decay in complex environments, and good molding performance. Detailed Implementation

[0027] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0028] Many specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the invention, and not all embodiments.

[0029] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0030] Unless otherwise specified, all raw materials used in the following examples were purchased commercially.

[0031] The preparation methods of the thermoplastic flexible electronic skin materials in Examples 1-7 and Comparative Examples 1-3 are as follows:

[0032] A method for preparing a thermoplastic flexible electronic skin material includes the following steps:

[0033] (1) PDMS compound, conductive carbon black and silane coupling agent are added to the kneader in sequence and kneaded at 150°C for 30 minutes, vacuum devoured for 30 minutes, cooled and then granulated at room temperature through a single screw extruder to obtain mixture one.

[0034] (2) HSBC resin, compatibilizer and carbon nanotubes are melt-granulated in sequence through a twin-screw extruder at a granulation temperature of 190℃ to obtain mixture two.

[0035] (3) After mixing mixture one and mixture two with vulcanizing agent evenly, reactive extrusion granulation is carried out in a high torque twin-screw extruder with a screw speed of 500 rpm and a reaction temperature of 230℃ to obtain thermoplastic flexible electronic skin material.

[0036] The formulations of the following examples and comparative examples are shown in Table 1.

[0037] Table 1

[0038]

[0039] Comparative Example 4

[0040] The difference between this comparative example and Example 2 is that the preparation method of the material in Comparative Example 2 includes the following steps:

[0041] (1) PDMS compound, conductive carbon black, silane coupling agent, HSBC resin, compatibilizer and carbon nanotubes are melt-granulated by twin-screw extruder at a granulation temperature of 190℃ to obtain a mixture.

[0042] (2) After the mixture is evenly mixed with the vulcanizing agent, it is subjected to reactive extrusion granulation in a high-torque twin-screw extruder with a screw speed of 500 rpm and a reaction temperature of 230°C to obtain thermoplastic flexible electronic skin material.

[0043] The properties of the materials prepared in the above embodiments and comparative examples are shown in Table 2.

[0044] The testing method is as follows:

[0045] 1. Conductivity uniformity:

[0046] Use a test piece the size of an A4 sheet of paper to evenly distribute and test the surface resistance at 25 points, and calculate the average standard deviation (standard deviation σ / mean value M).

[0047] 2. Resistivity retention (dual 85 aging):

[0048] The surface resistivity retention rate was tested after aging for 14 days under conditions of 85℃ temperature and 85%RH.

[0049] 3. Resistivity retention rate (bending test):

[0050] The surface resistivity retention rate was tested after the sample was bent at 90° 10,000 times.

[0051] 4. Resistivity retention rate (friction test):

[0052] The surface resistivity retention rate was tested after 2000 dry grinding cycles with a vertical pressure of 9N and a stroke of 100mm.

[0053] Table 2

[0054]

[0055]

[0056] As can be seen from the above test results, through the examples and comparative examples, it can be found that Examples 1-7 not only have excellent conductivity uniformity and anti-aging properties, but also have a high conductivity retention rate after bending or friction tests.

[0057] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are merely to aid in understanding the method and core ideas of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A thermoplastic flexible electronic skin material, characterized in that, The product comprises the following components by weight: 20-70 parts HSBC resin, 3-5 parts compatibilizer, 1-7 parts carbon nanotubes, 25-70 parts PDMS compound, 1-7 parts conductive carbon black, 0.1-1.0 parts silane coupling agent, and 0.5-2.0 parts vulcanizing agent; the PDMS compound is a mixture of PDMS and silica, wherein the mass ratio of PDMS to silica is (6-8):(2-4).

2. The thermoplastic flexible electronic skin material according to claim 1, characterized in that: The HSBC resin is one or more of hydrogenated styrene-butadiene-styrene block copolymer, hydrogenated styrene-isoprene-styrene block copolymer, and styrene-isobutylene-styrene triblock copolymer; the styrene content of the HSBC resin is <30%.

3. The thermoplastic flexible electronic skin material according to claim 1, characterized in that: The compatibilizer is a reactive maleic anhydride graft; the reactive maleic anhydride graft is selected from one or more of pp-g, pe-g, poe-g or eva-g.

4. The thermoplastic flexible electronic skin material according to claim 1, characterized in that: The carbon nanotubes are single-layer or multi-layer coaxial carbon nanotubes; the peak G-line wavenumber / peak D-line wavenumber of the carbon nanotubes is >100.

5. The thermoplastic flexible electronic skin material according to claim 1, characterized in that: The vinyl molar mass of the PDMS is 0.05-2.5%.

6. The thermoplastic flexible electronic skin material according to claim 1, characterized in that: The silica is either fumed silica or precipitated silica.

7. The thermoplastic flexible electronic skin material according to claim 1, characterized in that: The conductive carbon black is nano-conductive carbon black; the BET value of the conductive carbon black is ≥800m. 2 / g.

8. The thermoplastic flexible electronic skin material according to claim 1, characterized in that: The general structural formula of the silane coupling agent is Y. n SiX (4-n) , where n is an integer from 0 to 3; where X group is methoxy or ethoxy, and Y group is one of vinyl, ethoxy, amino, epoxy, methacryloyloxy, and mercapto.

9. The thermoplastic flexible electronic skin material according to claim 1, characterized in that: The vulcanizing agent is an organic peroxide or a silane crosslinking agent; the vulcanizing agent includes a chloroplatinic acid catalyst, and also includes one of odorless DCP and hydrogen-containing silicone oil.

10. A method for preparing a thermoplastic flexible electronic skin material according to any one of claims 1-9, characterized in that, Includes the following steps: (1) PDMS compound, conductive carbon black and silane coupling agent are added to the kneader in sequence and kneaded at 145-155℃ for 20-30 minutes, vacuum devoured for 20-30 minutes, cooled and then granulated at room temperature through a single screw extruder to obtain mixture one. (2) HSBC resin, compatibilizer and carbon nanotubes are melt-granulated in sequence through a twin-screw extruder at a granulation temperature of 180-200℃ to obtain mixture two. (3) Mix the first mixture and the second mixture with the vulcanizing machine and add them to the high torque twin screw extruder for reactive extrusion granulation. The screw speed is 500 rpm and the reaction temperature is 200-250℃ to obtain thermoplastic flexible electronic skin material.

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