High-sensitivity flexible strain sensing coating liquid, and preparation method and application thereof

Abstract

The application belongs to the technical field of preparation of photocuring materials, and particularly relates to a high-sensitivity flexible strain sensing coating liquid and a preparation method and application thereof. The preparation method of the high-sensitivity flexible strain sensing coating liquid comprises the following steps: preparing modified MXene nanosheets in a silane coupling manner; and preparing a rubber / modified MXene nanosheet high-sensitivity flexible strain sensing coating liquid, which is applied to a conductive material. The application provides the preparation method of the high-sensitivity flexible strain sensing coating liquid, which has the advantages of simple process, easily available raw materials, mild reaction conditions and high raw material utilization rate. The application also provides the flexible strain sensing coating liquid, which has the advantages of good strain, good stability, high sensitivity and good durability. The application also provides the application of the flexible strain sensing coating liquid, which is uniformly distributed and randomly stacked on the surface of different substrates by using a spraying or dipping process, has strong adhesion, forms a stable conductive path, and maximally plays the conductive performance of the conductive filler.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation of light-curing materials, and in particular relates to a highly sensitive flexible strain sensing coating liquid and a preparation method and application thereof. Background Art

[0002] Conductive coatings with strain sensing capabilities are coatings applied to non-conductive substrates to impart a certain degree of electrical current conduction and electrostatic charge dissipation. The use of two-dimensional materials to create coatings for the development of new flexible and stretchable electronic devices holds great promise for exciting applications in motion detection, medical monitoring, and human-machine interfaces, and as such, these materials are currently attracting significant attention.

[0003] Among them, the conductive coating with strain sensing function refers to a coating material with certain strain sensing function constructed by spraying or spin-coating a conductive filler (MXene, CNTs, Graphene, etc.) onto a non-conductive substrate. However, the current spraying method for spraying the conductive filler on a non-conductive substrate will cause poor adhesion due to the difference in surface properties between the substrate and the filler. In order to solve this problem, the conductive filler is usually grafted with a silane coupling agent to increase its compatibility with the substrate and further improve the adhesion between the coating and the substrate. However, the conductive material obtained by this method has not yet formed a relatively complete conductive network. At the same time, this coating also has the problem of weak adhesion, so the conductive material generates large strain during use, resulting in cracking and falling off of the coating. The low adhesion, weak robustness and weak durability of the coating will also greatly limit the application of conductive materials, and its sensitivity, stability and durability will be poor.

[0004] Therefore, in order to create a good interaction between the conductive filler and the substrate and build a complete conductive path network, patent CN108716885A uses a simple physical blend of conductive carbon black and polydimethylsiloxane to create a conductive coating, which is then applied through a multi-layer coating process to create a flexible strain sensor. However, this coating requires a long time to cure during preparation, and the multi-layer coating reduces strain sensing capabilities. Furthermore, this method is relatively complex in its preparation process.

[0005] CN116199925A discloses a method for preparing a flame-retardant, high-performance electromagnetic shielding material, comprising an active spraying liquid and a functionalized polymer substrate. The active spraying liquid is self-assembled from an aqueous solution of MXene nanosheets and epoxy cage silsesquioxane (EPOSS), and the functionalized polymer substrate is prepared by a thiol-ene click chemistry reaction of 1,2-polybutadiene. MXene is sprayed onto a pre-stretched functionalized polymer substrate and heated to form a covalent bond with the substrate to construct an electromagnetic shielding film. This process is relatively complex, and unsilanized MXene has poor compatibility with the coating, making it difficult to apply to strain sensing functions.

[0006] Two-dimensional MXene materials have attracted widespread attention in the conductive material field due to their excellent electrical conductivity. CN110117431A discloses a method for preparing a MXene-based electromagnetic shielding coating material. The method involves etching the MAX phase through direct hydrofluoric acid etching or in-situ hydrofluoric acid generation, followed by exfoliation to obtain a monolithic, low-defect MXene dispersion. The MXene is then modified with dopamine to produce a polyvinyl alcohol-coated polypyrrole sphere dispersion in a one-step process. The dopamine-modified MXene and the polypyrrole sphere dispersion are then uniformly mixed to form a MXene-based electromagnetic shielding coating material with excellent adhesion and high conductivity. However, the use of dopamine for modification and the subsequent use of polypyrrole is not only complex but also costly, making industrialization difficult.

[0007] CN111171703A discloses a preparation method for an electromagnetic shielding coating based on MXene two-dimensional material. An electromagnetic shielding material (a few-layer dispersion of a Ti3C2 two-dimensional material, i.e., a single-layer MXene), a resin-based polymerization monomer (an acrylate oligomer and an acrylate monomer), a photoinitiator, a leveling agent, and a dispersant are mixed and stirred to obtain a photocurable coating based on the MXene two-dimensional material; the obtained photocurable coating based on the MXene two-dimensional material is applied to a substrate (glass, cotton fabric, polyester fiber, paper, or wood), and cured to form a film under light, thereby obtaining a photocurable coating based on the MXene two-dimensional material, but its strain effect is poor. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a method for preparing a highly sensitive flexible strain sensing coating liquid, which has a simple process, readily available raw materials, mild reaction conditions and high raw material utilization.

[0009] The present invention also provides a flexible strain sensing coating liquid with good strainability, good stability, high sensitivity and good durability.

[0010] The present invention also provides the application of flexible strain sensing coating liquid, which is evenly distributed and randomly stacked on the surfaces of different substrates using a spraying or dipping process. It has strong adhesion, forms a stable conductive path, and maximizes the conductive performance of the conductive filler.

[0011] The method for preparing the highly sensitive flexible strain sensing coating liquid of the present invention comprises the following steps:

[0012] S1, preparing modified MXene nanosheets by silane coupling;

[0013] S2. Preparation of highly sensitive flexible strain sensing coating liquid:

[0014] Polybutadiene rubber or styrene-butadiene rubber and a polar small molecule containing a thiol group are weighed and dispersed in tetrahydrofuran to obtain solution A; the modified MXene nanosheets in S1 are weighed and dispersed in tetrahydrofuran to obtain dispersion B; solution A and dispersion B are mixed, stirred and reacted in a water bath at 50-60°C for 6-8 hours, and a photoinitiator is added to the obtained polymer to obtain a highly sensitive flexible strain sensing coating liquid.

[0015] The steps of preparing modified MXene nanosheets by silane coupling are as follows: taking MXene nanosheets, ultrasonically dispersing them in ethanol, successively adding ammonia water, tetraethyl orthosilicate, and mercaptosilane compounds, stirring for 6 to 12 hours in a water bath at 50 to 70°C, filtering and cleaning, and vacuum drying to obtain modified MXene nanosheets; the mass ratio of the MXene nanosheets, ammonia water, tetraethyl orthosilicate, and mercaptosilane compounds is 1:(1.5 to 10):(0.2 to 0.5):(0.05 to 0.3); the mass ratio of the MXene nanosheets to ethanol is 1:(50 to 100), the ethanol is anhydrous ethanol, the filtration and cleaning uses a mixture of water and ethanol, and the vacuum drying is carried out in a vacuum drying oven at 90°C for 4 hours.

[0016] The mercaptosilane compound in S1 is one or more of 3-mercaptopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, and 3-mercaptopropylmethyldimethoxysilane.

[0017] The mass ratio of the polybutadiene rubber or styrene-butadiene rubber, the polar small molecule containing mercapto groups, and tetrahydrofuran in solution A in S2 is 1:(0.5-2):(10-50).

[0018] The mass ratio of modified MXene nanosheets to tetrahydrofuran in dispersion B in S2 is 1:(30-50).

[0019] The mass ratio of polybutadiene rubber or styrene butadiene rubber to modified MXene nanosheets in S2 is 1:(1~10).

[0020] The polar small molecules containing thiol groups in S2 are one or more of 3-mercaptopropionic acid, 3-mercapto-2-pentanol, 3-mercaptohexanol, 3-mercaptopropionic acid methyl ester, 3-mercaptopropionic acid ethyl ester, 2-mercaptoethanol, 1,9-nonanedithiol, and methyl methylthioglycolate.

[0021] The molecular weight of the polybutadiene rubber or styrene butadiene rubber in S2 is 1,000 to 300,000.

[0022] The photoinitiator is benzoin and its derivatives, which is one of benzoin, benzoin dimethyl ether, benzoin ethyl ether, benzoin isopropyl ether and benzoin butyl ether, and the mass ratio of the photoinitiator to the polymer is 1:(200-2000).

[0023] A highly sensitive flexible strain sensing coating liquid is prepared by the preparation method of the highly sensitive flexible strain sensing coating liquid.

[0024] Application of a highly sensitive flexible strain sensing coating liquid: The highly sensitive flexible strain sensing coating liquid is applied to a substrate via dipping or spraying, and then cured by light exposure to produce a conductive material. The light curing step involves irradiating the substrate with ultraviolet light for 20-30 minutes. Spraying is preferred for this application, with a spray gun pressure of 0.3 MPa and a distance of 30 cm between the spray gun and the substrate. The resulting material is preferably a flexible strain sensor.

[0025] The base materials are fiber products, vulcanized rubber products, and paper.

[0026] Specifically, the highly sensitive flexible strain sensing coating liquid of the present invention is used to prepare a flexible strain sensor, comprising the following steps:

[0027] S1. Modified MXene nanosheets were prepared by silane coupling:

[0028] MXene nanosheets were ultrasonically dispersed in ethanol, and ammonia water, tetraethyl orthosilicate, and mercaptosilane compounds were added successively. The mixture was stirred in a water bath at 50-70°C for 6-12 hours, filtered and washed with a mixture of water and ethanol, and dried in a vacuum drying oven at 90°C for 4 hours to obtain modified MXene nanosheets. The mass ratio of the MXene nanosheets, ammonia water, tetraethyl orthosilicate, and mercaptosilane compounds was 1:(1.5-10):(0.2-0.5):(0.05-0.3); the mass ratio of the MXene nanosheets to ethanol was 1:(50-100).

[0029] S2. Preparation of highly sensitive flexible strain sensing coating liquid

[0030] Polybutadiene rubber (PBAR) or styrene-butadiene rubber (SBAR) with a molecular weight of 1,000 to 300,000 and a polar small molecule containing a thiol group are dispersed in tetrahydrofuran at a mass ratio of 1:(0.5-2):(10-50) to obtain solution A. The modified MXene nanosheets from S1 are dispersed in tetrahydrofuran at a mass ratio of 1:(30-50) to obtain dispersion B. Solutions A and B are mixed and reacted in a water bath at 50-60°C for 6-8 hours with stirring. A photoinitiator is then added to the resulting polymer to obtain a highly sensitive flexible strain sensing coating. The mass ratio of PBAR or SBAR to modified MXene nanosheets is 1:(1-10).

[0031] S3. The highly sensitive flexible strain sensing coating liquid is sprayed onto the substrate through a spray gun through an immersion or spraying process. The spray gun pressure is 0.3 MPa, and the distance between the spray gun and the elastic fabric is 20 cm. The flexible strain sensor is obtained by curing it through ultraviolet light irradiation for 20 to 30 minutes.

[0032] The present invention creates a good interaction force between the conductive filler and the matrix, constructs a complete conductive path network, and then uses the conductive filler and modified rubber to blend for spraying. The present invention increases the compatibility between MXene and rubber by silanization modification of MXene, and at the same time adds polar thiol small molecule compounds to the rubber to increase the adhesion between the rubber and the substrate. It is then coated on the surface of substrates such as fibers, vulcanized rubber products, and paper through simple spraying, dipping, and other processes, and then photocured by ultraviolet light to form a conductive coating with good strain sensing. After modification, MXene can produce a good chemical bond with the rubber, while forming a complete conductive path, ensuring the firmness and integrity of the conductive structure of the coating, thereby significantly improving the stability and durability of the conductive coating.

[0033] The present invention combines silanized two-dimensional conductive MXene nanosheets with butadiene rubber to create a strain-sensitive coating. After dipping or spraying, the silanized surface-treated MXene can be continuously and evenly applied to the substrate surface and gaps in a peeled state, creating a good conductive path. The modified MXene also forms a good chemical bond with the rubber, forming a complete conductive path between the conductive fillers. The addition of polar thiol small molecule compounds to the rubber enhances the adhesion between the conductive fillers and the substrate, ensuring the robustness and integrity of the coating's conductive structure, thereby significantly improving the stability and durability of the conductive coating.

[0034] The rubber used in this invention is polybutadiene rubber, which is rich in reactive sites. The use of a polar thiol compound enhances the adhesion and chemical bonding between the conductive filler and the substrate. Effective control of adhesion is achieved by using polybutadiene rubbers of varying molecular weights and carefully selecting and proportioning the mass ratio of vinyl rubber to the thiol compound. Furthermore, this method boasts readily available raw materials, mild reaction conditions, and high raw material utilization, thus offering significant potential for large-scale development compared to other current methods for preparing flexible strain sensing coatings. The photocurable flexible strain sensing coatings prepared in this invention, suitable for application to various substrates, utilize a one-step process involving liquid-phase mixing of the modified conductive filler with rubber and a small molecule modifier, followed by dipping or spraying and subsequent illumination. This differs from the traditional method of spraying the filler and adhesive onto the substrate in separate steps. The conductive coating with strain sensing function prepared by the present invention is a method of spraying silanized modified MXene and polybutadiene rubber on the surface of the substrate. More preferably, compared with the solution dipping method, the spraying method is more suitable for most substrate surfaces, and the conductive coating can be constructed at a specified position and on the surface without adhering to other parts of the material, especially the fabric material, so the scope of implementation is wider. At the same time, during the spraying process, MXene nanosheets are more easily evenly distributed and randomly stacked on the surface of the substrate, making it easy for the conductive filler to quickly form a film on the surface of the material to construct a more stable conductive path, so that the charge is stably transferred between the sheets. Therefore, this is of great significance for the application of this material in smart wearable devices.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) The flexible strain sensing coating liquid prepared by the method of the present invention has high sensitivity and can detect small deformations as low as 1% and large deformations as high as 200%, which greatly broadens the application range of the strain sensing coating. In addition, it still has excellent stability after 15,000 cycles under a strain of 200%.

[0037] (2) The flexible strain sensing coating liquid prepared by the present invention is sprayed on the substrate, covering the surface of the substrate and the gaps to construct a good conductive path, with strong viscosity, thereby achieving a significant improvement in the stability and durability of the coating liquid.

[0038] (3) The method of the present invention has readily available raw materials, mild reaction conditions, high raw material utilization rate, and has the potential for large-scale development.

[0039] (4) The method of the present invention greatly reduces the waste of conductive filler-modified MXene during the production process, simplifies the operation steps, maximizes the conductive properties of the conductive filler, and conforms to the concept of green economic production. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a scanning electron microscope (SEM) image of the modified MXene nanosheets prepared in Example 1.

[0041] Figure 2 This is a scanning electron microscope (SEM) image of the highly sensitive flexible strain sensing coating liquid prepared in Comparative Example 1.

[0042] Figure 3 This is a graph showing the resistance change of the flexible strain sensor prepared in Example 1 as the strain increases.

[0043] Figure 4 This is a graph showing the strain-resistance change of the flexible strain sensor prepared in Example 1 after 2000 repetitions.

[0044] Figure 5 This is a resistance change diagram of the flexible strain sensors prepared in Example 1, Comparative Example 1, and Comparative Example 2 under 1% strain.

[0045] Figure 6 This is a scanning electron microscope (SEM) image of the highly sensitive flexible strain sensing coating liquid of Example 2. DETAILED DESCRIPTION

[0046] The preferred embodiments of the present invention will be described in detail below with reference to the examples. It should be understood that the following examples are provided for illustrative purposes only and are not intended to limit the scope of the present invention. Those skilled in the art may make various modifications and substitutions to the present invention without departing from the purpose and spirit of the present invention.

[0047] Example 1

[0048] The highly sensitive flexible strain sensing coating liquid is used to prepare a flexible strain sensor, which includes the following steps:

[0049] S1. Modified MXene nanosheets were prepared by silane coupling:

[0050] Take 1 g of MXene nanosheets, ultrasonically disperse it in 50 g of ethanol, and add 1.5 g of ammonia water, 0.2 g of tetraethyl orthosilicate, and 0.05 g of 3-mercaptopropyltriethoxysilane successively. Stir for 6 h in a 70 ° C water bath, and use a mixture of water and ethanol to filter and wash to remove impurities and unreacted compounds. Dry it in a vacuum drying oven at 90 ° C for 4 h to obtain modified MXene nanosheets.

[0051] S2. Preparation of highly sensitive flexible strain sensing coating liquid

[0052] 1 g of liquid polybutadiene rubber with a molecular weight of 1000 and 0.5 g of 3-mercaptopropionic acid were dispersed in 10 g of tetrahydrofuran to obtain solution A; 1 g of modified MXene nanosheets in S1 were dispersed in 30 g of tetrahydrofuran to obtain dispersion B; solution A and dispersion B were mixed, stirred and reacted in a 60°C water bath for 6 hours, and 0.0005 g of benzoin was added to the obtained polymer to obtain a highly sensitive flexible strain sensing coating liquid.

[0053] S3. The highly sensitive flexible strain sensing coating liquid is sprayed onto the surface of a 3cm×5cm spandex stretch fabric using a spray gun. The spray gun pressure is 0.3 MPa and the distance between the spray gun and the stretch fabric is 20 cm. The flexible strain sensor is obtained by curing the coating liquid through ultraviolet light exposure for 25 minutes.

[0054] Example 2

[0055] The highly sensitive flexible strain sensing coating liquid is used to prepare a flexible strain sensor, which includes the following steps:

[0056] S1. Modified MXene nanosheets were prepared by silane coupling:

[0057] Take 1 g of MXene nanosheets, ultrasonically disperse it in 80 g of ethanol, and add 4.5 g of ammonia water, 0.3 g of tetraethyl orthosilicate, and 0.2 g of 3-mercaptopropyltriethoxysilane successively. Stir for 6 h in a 70 ° C water bath, and use a mixture of water and ethanol to filter and wash to remove impurities and unreacted compounds. Dry it in a vacuum drying oven at 90 ° C for 4 h to obtain modified MXene nanosheets.

[0058] S2. Preparation of highly sensitive flexible strain sensing coating liquid

[0059] 1 g of liquid polybutadiene rubber with a molecular weight of 5000 and 0.5 g of 1,9-nonanedithiol were dispersed in 25 g of tetrahydrofuran to obtain solution A; 1 g of modified MXene nanosheets in S1 were dispersed in 35 g of tetrahydrofuran to obtain dispersion B; solution A and dispersion B were mixed, stirred and reacted in a 60°C water bath for 6 hours, and 0.0007 g of benzoin was added to the obtained polymer to obtain a highly sensitive flexible strain sensing coating liquid.

[0060] S3. The highly sensitive flexible strain sensing coating liquid is sprayed onto the surface of a 3cm×5cm spandex stretch fabric using a spray gun. The spray gun pressure is 0.3 MPa and the distance between the spray gun and the stretch fabric is 20 cm. The flexible strain sensor is obtained by curing the coating liquid through ultraviolet light exposure for 25 minutes.

[0061] Example 3

[0062] The high-sensitivity flexible strain sensing coating liquid is used for preparation of a flexible strain sensor, including the following steps:

[0063] S1, a modified MXene nanosheet is prepared in a silane coupling manner:

[0064] Take 1g of MXene nanosheet, ultrasonic dispersion in 100g of ethanol, add 10g of ammonia water, 0.5g of tetraethyl orthosilicate, 0.3g of 3-mercaptopropyl trimethoxysilane, in a 70℃ water bath, stirring for 6h, using water and ethanol mixture to filter and clean, remove impurities and unreacted compounds, dry in a vacuum drying oven at 90℃ for 4h, to obtain modified MXene nanosheet.

[0065] S2, preparation of high-sensitivity flexible strain sensing coating liquid

[0066] Take 1g of molecular weight 30000 polybutadiene rubber and 2g of 3-mercapto-2-pentanol, disperse in 50g of tetrahydrofuran to obtain solution A; take 1g of modified MXene nanosheet in S1, disperse in 50g of tetrahydrofuran to obtain dispersion B; mix solution A and dispersion B, stir and react at 50℃ water bath for 6h, add 0.005g of benzo pinacol to the obtained polymer to obtain high-sensitivity flexible strain sensing coating liquid.

[0067] S3, the high-sensitivity flexible strain sensing coating liquid is sprayed onto a 3cm*5cm spandex elastic cloth by spraying process, the spraying gun pressure is 0.3Mpa, the distance between the spraying gun and the elastic cloth is 20cm, and the flexible strain sensor is obtained after curing under ultraviolet light for 25min.

[0068] Example 4

[0069] The high-sensitivity flexible strain sensing coating liquid is used for preparation of a flexible strain sensor, including the following steps:

[0070] S1, a modified MXene nanosheet is prepared in a silane coupling manner:

[0071] Take 8g of MXene nanosheet, ultrasonic dispersion in 640g of ethanol, add 56g of ammonia water, 2g of tetraethyl orthosilicate, 0.96g of 3-mercaptopropyl methyl dimethoxysilane, in a 70℃ water bath, stirring for 6h, using water and ethanol mixture to filter and clean, remove impurities and unreacted compounds, dry in a vacuum drying oven at 90℃ for 4h, to obtain modified MXene nanosheet.

[0072] S2, preparation of high-sensitivity flexible strain sensing coating liquid

[0073] 1 g of polybutadiene rubber with a molecular weight of 150,000 and 2 g of methyl 3-mercaptopropionate were weighed and dispersed in 30 g of tetrahydrofuran to obtain solution A; 8 g of modified MXene nanosheets in S1 were weighed and dispersed in 300 g of tetrahydrofuran to obtain dispersion B; solution A and dispersion B were mixed, stirred and reacted in a 60°C water bath for 8 hours, and 0.005 g of benzoin ethyl ether was added to the obtained polymer to obtain a highly sensitive flexible strain sensing coating liquid.

[0074] S3. The highly sensitive flexible strain sensing coating liquid is sprayed onto a 3cm×5cm spandex stretch fabric using a spray gun. The spray gun pressure is 0.3 MPa and the distance between the spray gun and the stretch fabric is 20 cm. The coating is cured by ultraviolet light for 30 minutes to obtain a flexible strain sensor.

[0075] Example 5

[0076] The highly sensitive flexible strain sensing coating liquid is used to prepare a flexible strain sensor, which includes the following steps:

[0077] S1. Modified MXene nanosheets were prepared by silane coupling:

[0078] Take 10g of MXene nanosheets, ultrasonically disperse them in 600g of ethanol, and add 26g of ammonia water, 3.6g of tetraethyl orthosilicate, and 2.8g of 3-mercaptopropylmethyldimethoxysilane successively. Stir for 6h in a 70℃ water bath, and use a mixture of water and ethanol to filter and wash to remove impurities and unreacted compounds. Dry in a vacuum drying oven at 90℃ for 4h to obtain modified MXene nanosheets.

[0079] S2. Preparation of highly sensitive flexible strain sensing coating liquid

[0080] 1 g of polybutadiene rubber with a molecular weight of 150,000 and 1.5 g of 2-mercaptoethanol were dispersed in 42 g of tetrahydrofuran to obtain solution A; 10 g of modified MXene nanosheets in S1 were dispersed in 300 g of tetrahydrofuran to obtain dispersion B; solution A and dispersion B were mixed, stirred and reacted in a 60°C water bath for 6 hours, and 0.003 g of benzoin isopropyl ether was added to the obtained polymer to obtain a highly sensitive flexible strain sensing coating liquid.

[0081] S3. The highly sensitive flexible strain sensing coating liquid is sprayed onto a 3cm×5cm spandex stretch fabric using a spray gun. The spray gun pressure is 0.3 MPa and the distance between the spray gun and the stretch fabric is 20 cm. The coating is cured by ultraviolet light for 20 minutes to obtain a flexible strain sensor.

[0082] Example 6

[0083] The highly sensitive flexible strain sensing coating liquid is used to prepare a flexible strain sensor, which includes the following steps:

[0084] S1. Modified MXene nanosheets were prepared by silane coupling:

[0085] Take 10g of MXene nanosheets, ultrasonically disperse them in 600g of ethanol, and successively add 26g of ammonia water, 3.6g of tetraethyl orthosilicate, and a mixture of 2.8g of 3-mercaptopropylmethyldimethoxysilane and 2-mercaptoethanol (mass ratio of 1:1). Stir for 6h in a 70℃ water bath, and use a mixture of water and ethanol to filter and wash to remove impurities and unreacted compounds. Dry in a vacuum drying oven at 90℃ for 4h to obtain modified MXene nanosheets.

[0086] S2. Preparation of highly sensitive flexible strain sensing coating liquid

[0087] 1 g of polybutadiene rubber with a molecular weight of 150,000 and 1.5 g of 2-mercaptoethanol were dispersed in 42 g of tetrahydrofuran to obtain solution A; 10 g of modified MXene nanosheets in S1 were dispersed in 300 g of tetrahydrofuran to obtain dispersion B; solution A and dispersion B were mixed, stirred and reacted in a 60°C water bath for 6 hours, and 0.003 g of benzoin isopropyl ether was added to the obtained polymer to obtain a highly sensitive flexible strain sensing coating liquid.

[0088] S3. The highly sensitive flexible strain sensing coating liquid is immersed in a 3 cm × 5 cm vulcanized rubber sheet, immersed back and forth three times, and cured by ultraviolet light for 20 minutes to obtain a flexible strain sensor.

[0089] Example 7

[0090] The highly sensitive flexible strain sensing coating liquid is used to prepare a flexible strain sensor, which includes the following steps:

[0091] S1 is the same as step S1 in embodiment 1.

[0092] S2. Preparation of highly sensitive flexible strain sensing coating liquid

[0093] The process is the same as step S2 in Example 1, except that the rubber used is styrene-butadiene rubber with a molecular weight of 2000, and the photoinitiator used is a blend of benzoin isopropyl ether and benzoin ethyl ether (mass ratio is 1:1).

[0094] S3 is the same as step S3 in Example 1.

[0095] Example 8

[0096] The highly sensitive flexible strain sensing coating liquid is used to prepare a flexible strain sensor, which includes the following steps:

[0097] S1 is the same as step S1 in embodiment 1.

[0098] S2. Preparation of highly sensitive flexible strain sensing coating liquid

[0099] The process is the same as step S2 in Example 1, except that the rubber used is polybutadiene rubber with a molecular weight of 10,000.

[0100] S3 is the same as step S3 in Example 1.

[0101] Example 9

[0102] The highly sensitive flexible strain sensing coating liquid is used to prepare a flexible strain sensor, which includes the following steps:

[0103] S1 is the same as step S1 in embodiment 1.

[0104] S2. Preparation of highly sensitive flexible strain sensing coating liquid

[0105] The process is the same as step S2 in Example 1, except that the rubber used is styrene-butadiene rubber with a molecular weight of 300,000.

[0106] S3 is the same as step S3 in Example 1.

[0107] Comparative Example 1

[0108] A method for preparing a flexible strain sensor comprises the following steps:

[0109] 4 g of pure MXene nanosheets were ultrasonically dispersed in 50 g of tetrahydrofuran to obtain dispersion A; 2 g of polybutadiene rubber with a molecular weight of 10,000 and 2 g of 3-mercaptopropionic acid were dissolved in 25 g of tetrahydrofuran to obtain solution B; dispersion A and solution B were stirred and reacted in a 60°C water bath for 6 h, and then 0.005 g of benzoin ethyl ether was added to obtain a photocurable flexible strain sensing coating solution, which was sprayed onto a 3 cm × 5 cm spandex stretch fabric using a spray gun with a spray gun pressure of 0.3 MPa and a distance of 20 cm between the spray gun and the stretch fabric. The solution was then cured under ultraviolet light for 25 min to obtain a flexible strain sensor.

[0110] Comparative Example 2

[0111] A method for preparing a flexible strain sensor comprises the following steps:

[0112] Take 4g pure MXene nanosheet ultrasonic dispersion in 50g tetrahydrofuran, get dispersion liquid A; 2g of molecular weight 10000 polybutadiene rubber is dissolved in 25g tetrahydrofuran, get solution B; The dispersion liquid A and solution B are stirred at 60℃ water bath condition for 6h, then add 0.005g benzoin ethyl ether, get light curing flexible strain sensing coating solution, through spray gun spraying to 3cm×5cm spandex elastic cloth, spray gun pressure is 0.3Mpa, the distance between spray gun and elastic cloth is 20cm, then irradiation under UV light for 25min for curing, get flexible strain sensor.

[0113] Comparative example 3

[0114] A preparation method of a flexible strain sensor, comprising the following steps:

[0115] S1, the modified MXene nanosheet is prepared by silane coupling method:

[0116] Take 1g MXene nanosheet, ultrasonic dispersion in 50g ethanol, add 1.5g ammonia water, 0.2g tetraethyl orthosilicate, in 70℃ water bath, stirring for 6h, using water and ethanol mixture to filter cleaning, remove impurities and unreacted compounds, in 90℃ vacuum drying box drying for 4h, get modified MXene nanosheet.

[0117] S2, preparation of flexible strain sensing coating liquid

[0118] Take 1g of liquid polybutadiene rubber with molecular weight of 1000 and 0.5g of 3-mercaptopropionic acid dispersion in 10g tetrahydrofuran, get solution A; Take 1g of modified MXene nanosheet in S1 dispersion in 30g tetrahydrofuran, get dispersion liquid B; The solution A and dispersion liquid B are mixed, and the mixture is stirred at 60℃ water bath for 6h, then 0.0005g benzoin is added to the obtained polymer, and the obtained flexible strain sensing coating liquid is obtained.

[0119] S3, the flexible strain sensing coating liquid is sprayed on the surface of 3cm×5cm spandex elastic cloth by spray gun, the spray gun pressure is 0.3Mpa, the distance between spray gun and elastic cloth is 20cm, and the flexible strain sensor is obtained by irradiation under UV light for 25min.

[0120] Comparative example 4

[0121] A preparation method of a flexible strain sensor, comprising the following steps:

[0122] Take 1g of MXene nanosheets, 1.5g of ammonia water, 0.2g of tetraethyl orthosilicate, 1g of liquid polybutadiene rubber with a molecular weight of 1000 and 0.5g of 3-mercaptopropionic acid, disperse them in 20g of tetrahydrofuran, stir them in a 60℃ water bath for 6h, then add 0.0005g of benzoin, and spray them onto 3cm×5cm spandex stretch fabric with a spray gun. The spray gun pressure is 0.3Mpa, and the distance between the spray gun and the stretch fabric is 20cm. Then, irradiate under ultraviolet light for 25min for curing to obtain a flexible strain sensor.

[0123] Comparative Example 5

[0124] A method for preparing a flexible strain sensor comprises the following steps:

[0125] S1. Modified MXene nanosheets were prepared by silane coupling:

[0126] Take 1 g of MXene nanosheets, ultrasonically disperse it in 50 g of ethanol, add 1.5 g of ammonia water and 0.2 g of tetraethyl orthosilicate successively, stir it in a 70 ° C water bath for 6 hours, filter and wash it with a mixture of water and ethanol to remove impurities and unreacted compounds, and dry it in a vacuum drying oven at 90 ° C for 4 hours to obtain modified MXene nanosheets.

[0127] S2. Preparation of flexible strain sensing coating liquid

[0128] 0.5 g of 3-mercaptopropionic acid was dispersed in 10 g of tetrahydrofuran to obtain solution A. 1 g of the modified MXene nanosheets in S1 was dispersed in 30 g of tetrahydrofuran to obtain dispersion B. Solution A and dispersion B were mixed and stirred in a 60°C water bath for 6 h. 0.0005 g of benzoin was added to the obtained polymer to obtain a strain sensing coating liquid.

[0129] S3, the strain sensing coating liquid is sprayed onto the surface of 3cm×5cm spandex stretch fabric using a spray gun, the spray gun pressure is 0.3Mpa, the distance between the spray gun and the stretch fabric is 20cm, and the strain sensor is cured by ultraviolet light for 25min.

[0130] The flexible strain sensors prepared in the above examples and comparative examples were subjected to performance tests according to GBT18806-2002 and GB / T7760-2003 standards. The test results are shown in Table 1.

[0131] Table 1 Test results

[0132]

[0133]

[0134] As can be seen from the above table, the highly sensitive flexible strain sensing coating liquid prepared by the present invention is applied to flexible strain sensors, which significantly improves the compatibility and adhesion performance between the conductive filler and the substrate, and constructs a three-dimensional conductive network during the spraying process. This is not only conducive to the construction of a complete conductive path, but also significantly improves the stability and durability of the conductive coating while ensuring the firmness and integrity of the conductive structure of the coating.

[0135] Of course, the above contents are only preferred embodiments of the present invention and should not be considered as limiting the scope of the embodiments of the present invention. The present invention is not limited to the above examples. Equivalent changes and improvements made by ordinary technicians in this technical field within the essential scope of the present invention should all fall within the scope of the patent of the present invention.

Claims

1. A method for preparing a highly sensitive flexible strain sensing coating liquid, characterized by: The following steps are involved: S1. Prepare modified MXene nanosheets by silane coupling: take MXene nanosheets, ultrasonically disperse them in ethanol, add ammonia water, tetraethyl orthosilicate, and mercaptosilane compounds in sequence, stir for 6 to 12 hours in a water bath at 50 to 70°C, filter and wash, and vacuum dry to obtain modified MXene nanosheets; the mercaptosilane compound is one or more of 3-mercaptopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, and 3-mercaptopropylmethyldimethoxysilane; S2. Preparation of highly sensitive flexible strain sensing coating liquid: Polybutadiene rubber or styrene-butadiene rubber and a polar small molecule containing a thiol group are weighed and dispersed in tetrahydrofuran to obtain solution A; the modified MXene nanosheets in S1 are weighed and dispersed in tetrahydrofuran to obtain dispersion B; solution A and dispersion B are mixed, stirred and reacted at 50-60°C for 6-8 hours, and a photoinitiator is added to the obtained polymer to obtain a highly sensitive flexible strain sensing coating liquid.

2. The method for preparing a highly sensitive flexible strain sensing coating liquid according to claim 1, wherein: The mass ratio of the MXene nanosheets, ammonia water, tetraethyl orthosilicate, and mercaptosilane compound is 1:(1.5-10):(0.2-0.5):(0.05-0.3).

3. The method for preparing a highly sensitive flexible strain sensing coating liquid according to claim 1, wherein: The mass ratio of the polybutadiene rubber or styrene-butadiene rubber and the polar small molecule containing mercapto group in solution A in S2 is 1:(0.5-2).

4. The method for preparing a highly sensitive flexible strain sensing coating liquid according to claim 1, wherein: The mass ratio of polybutadiene rubber or styrene butadiene rubber to modified MXene nanosheets in S2 is 1: (1 to 10).

5. The method for preparing a highly sensitive flexible strain sensing coating liquid according to claim 1, wherein: The polar small molecules containing thiol groups in S2 are one or more of 3-mercaptopropionic acid, 3-mercapto-2-pentanol, 3-mercaptohexanol, 3-mercaptopropionic acid methyl ester, 3-mercaptopropionic acid ethyl ester, 2-mercaptoethanol, 1,9-nonanedithiol, and methyl methylthioglycolate.

6. The method for preparing a highly sensitive flexible strain sensing coating liquid according to claim 1, wherein: The molecular weight of the polybutadiene rubber or styrene butadiene rubber in S2 is 1,000 to 300,000.

7. A highly sensitive flexible strain sensing coating liquid, characterized by: The flexible strain sensing coating liquid is prepared by the preparation method of the highly sensitive flexible strain sensing coating liquid according to any one of claims 1 to 6.

8. An application of the highly sensitive flexible strain sensing coating liquid according to claim 7, characterized in that: The highly sensitive flexible strain sensing coating liquid is coated on the substrate through a dipping or spraying process, and then cured by light to obtain a conductive material.

9. The use of the highly sensitive flexible strain sensing coating liquid according to claim 8, characterized in that: The base materials are fiber products and vulcanized rubber products.

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