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

Abstract

The invention belongs to the technical field of preparation of photocuring materials, and particularly relates to high-sensitivity flexible strain sensing coating liquid as well as a preparation method and application thereof. The preparation method of the high-sensitivity flexible strain sensing coating liquid comprises the following steps: preparing a modified MXene nanosheet in a silane coupling manner; and preparing the high-sensitivity flexible strain sensing coating liquid of the rubber / modified MXene nanosheet, and applying the high-sensitivity flexible strain sensing coating liquid of the rubber / modified MXene nanosheet to a conductive material. The preparation method of the high-sensitivity flexible strain sensing coating liquid provided by the invention has the advantages of simple process, easily available raw materials, mild reaction conditions and high raw material utilization rate. The invention further provides a flexible strain sensing coating liquid which is good in strain property, good in stability, high in sensitivity and good in durability. The invention further provides application of the flexible strain sensing coating liquid, the flexible strain sensing coating liquid is uniformly distributed and randomly piled on the surfaces of different substrates by adopting a spraying or dipping process, the adhesiveness is strong, a stable conductive path is formed, and the conductivity of the conductive filler is exerted to the maximum extent.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of photocurable 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 functional coatings applied to non-conductive substrates to give them a certain ability to conduct current and dissipate electrostatic charge. The use of two-dimensional materials to prepare coatings to develop new flexible and stretchable electronic devices is expected to open up exciting applications in motion detection, medical monitoring and human-machine interfaces, so this material is currently receiving much attention.

[0003] Among them, the conductive coating with strain sensing function refers to spraying or spin-coating conductive fillers (MXene, CNTs, Graphene, etc.) onto non-conductive substrates to construct coating materials with certain strain sensing functions. However, the current spraying method for spraying conductive fillers on non-conductive substrates 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, forming cracking and falling off of the coating. The low adhesion, weak firmness 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 generate a good interaction force between the conductive filler and the substrate and construct a perfect conductive path network, in patent CN108716885A, conductive carbon black and polydimethylsiloxane are simply physically blended to obtain a conductive coating, and a flexible strain sensor is obtained through a multi-layer coating process. However, the coating requires a long time to solidify and form during the preparation process, and the multi-layer coating causes the problem of reduced strain sensing capability. At the same time, the preparation process of this method is relatively complicated.

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

[0006] Two-dimensional MXene materials have attracted wide attention in the field of conductive materials due to their good electrical conductivity. CN110117431A discloses a method for preparing a MXene-based electromagnetic shielding coating material, wherein the MAX phase is etched by direct hydrofluoric acid etching or in-situ generation of hydrofluoric acid, followed by peeling to obtain a monolayer and low-defect MXene dispersion, and then the MXene is modified by dopamine to prepare a polyvinyl alcohol-coated polypyrrole beads dispersion by a one-step method, and then the dopamine-modified MXene is uniformly mixed with the polypyrrole beads dispersion wrapped in polyvinyl alcohol to form a MXene-based electromagnetic shielding coating material with excellent adhesion and high electrical conductivity. However, the use of dopamine for modification and then the use of polypyrrole not only has a complex modification process, but also has high costs and is difficult to promote industrially.

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

[0009] The 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 by spraying or dipping process, 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. Modified MXene nanosheets are prepared by silane coupling;

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

[0014] Weigh polybutadiene rubber or styrene-butadiene rubber and polar small molecules containing thiol groups and disperse them in tetrahydrofuran to obtain solution A; weigh the modified MXene nanosheets in S1 and disperse them in tetrahydrofuran to obtain dispersion B; mix solution A and dispersion B, stir and react in a water bath at 50-60° C. for 6-8 hours, add a photoinitiator to the obtained polymer, and 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 drying 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 the 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 by dipping or spraying, and then cured by light exposure to obtain a conductive material. The light exposure curing is performed by ultraviolet light irradiation for 20 to 30 minutes. In this application, the spraying process is preferably used, the spray gun pressure is 0.3Mpa, the distance between the spray gun and the substrate is 30cm, and the prepared 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] Take MXene nanosheets, ultrasonically disperse them in ethanol, add ammonia water, tetraethyl orthosilicate, and mercaptosilane compounds in turn, stir for 6 to 12 hours in a water bath at 50 to 70°C, filter and wash with a mixed solution of water and ethanol, and dry 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 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).

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

[0030] Weigh polybutadiene rubber or styrene butadiene rubber with a molecular weight of 1000 to 300000 and polar small molecules containing mercapto groups and disperse them in tetrahydrofuran at a mass ratio of 1:(0.5 to 2):(10 to 50) to obtain solution A; weigh the modified MXene nanosheets in S1 and disperse them in tetrahydrofuran at a mass ratio of 1:(30 to 50) to obtain dispersion B; mix solution A and dispersion B, stir and react for 6 to 8 hours in a water bath at 50 to 60° C., add a photoinitiator to the obtained polymer, and obtain a highly sensitive flexible strain sensing coating liquid. The mass ratio of polybutadiene rubber or styrene butadiene rubber to the modified MXene nanosheets is 1:(1 to 10).

[0031] S3. The highly sensitive flexible strain sensing coating liquid is sprayed onto the substrate by 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 by ultraviolet light irradiation for 20 to 30 minutes.

[0032] The present invention generates 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, and is applied to the surface of substrates such as fibers, vulcanized rubber products, and paper through simple spraying, dipping and other processes, and then forms a conductive coating with good strain sensing after photocuring through ultraviolet light. After modification, MXene can produce a good chemical bonding reaction with the rubber, while forming a complete conductive path, ensuring the firmness and integrity of the conductive structure of the coating, thereby achieving a significant improvement in the stability and durability of the conductive coating.

[0033] The present invention uses silanized modified two-dimensional conductive MXene nanosheets and butadiene rubber together to realize the preparation of a good strain sensing coating. After the silanized surface treatment, the MXene can be continuously and evenly covered on the substrate surface and the gaps in a peeled state after the dipping or spraying process to build a good conductive path. At the same time, the modified MXene can produce a good chemical bonding effect with the rubber, so that a perfect conductive path is formed between the conductive fillers. At the same time, the polar mercapto small molecule compound added to the rubber increases the adhesion between the conductive filler and the substrate. Ensure the firmness and integrity of the conductive structure of the coating, thereby significantly improving the stability and durability of the conductive coating.

[0034] The rubber used in the present invention is polybutadiene rubber containing abundant reaction sites. The use of polar thiol compounds increases the adhesion performance and chemical bonding between the conductive filler and the substrate. The adhesion performance is effectively controlled by using polybutadiene rubber of different molecular weights and selecting and matching the mass ratio between vinyl rubber and thiol compounds. At the same time, the scheme has easy-to-obtain raw materials, mild reaction conditions, and high raw material utilization. Therefore, compared with other current methods for preparing flexible strain sensing coatings, this method has large-scale development potential. The photocurable flexible strain sensing coating suitable for the surface of different substrates prepared by the present invention adopts a one-step method to mix the modified conductive filler with rubber and a small molecule modifier in liquid phase, then immerse or spray and then illuminate to prepare the strain sensing coating, which is different from the traditional method of spraying the filler and the glue solution on the substrate in steps. The conductive coating with strain sensing function prepared by the present invention is to spray the silanized modified MXene and polybutadiene rubber on the surface of the substrate. The spraying method is more suitable for most substrate surfaces than the solution dipping method, 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 implementation scope is wider. At the same time, during the spraying process, MXene nanosheets are easier to achieve uniform distribution and random stacking on the surface of the substrate, so that the conductive filler is easy to quickly form a film on the surface of the material to construct a more stable conductive path, so that the charge is stably transmitted 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 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, covers the surface of the substrate and the gaps to construct a good conductive path, has strong viscosity, and achieves 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 in the production process, simplifies the operation steps, and maximizes the conductive properties of the conductive filler, which is in line with 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 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 of strain-resistance variation 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 sensor 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 in conjunction with examples. It should be understood that the following examples are provided only for the purpose of illustration 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, comprising 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, 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, filter and wash with a mixed solution of water and ethanol to remove impurities and unreacted compounds, and dry 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 water bath at 60°C 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. Use a spraying process to spray the highly sensitive flexible strain sensing coating liquid onto the surface of 3cm×5cm spandex stretch fabric using a spray gun. The spray gun pressure is 0.3Mpa, and the distance between the spray gun and the stretch fabric is 20cm. Curing is carried out by ultraviolet light irradiation for 25 minutes to obtain a flexible strain sensor.

[0054] Example 2

[0055] The highly sensitive flexible strain sensing coating liquid is used to prepare a flexible strain sensor, comprising 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, 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, use a mixed solution of water and ethanol to filter and wash to remove impurities and unreacted compounds, and dry 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 water bath at 60°C for 6 h, and 0.0007 g of benzoin was added to the obtained polymer to obtain a highly sensitive flexible strain sensing coating liquid.

[0060] S3. Use a spraying process to spray the highly sensitive flexible strain sensing coating liquid onto the surface of 3cm×5cm spandex stretch fabric using a spray gun. The spray gun pressure is 0.3Mpa, and the distance between the spray gun and the stretch fabric is 20cm. Curing is carried out by ultraviolet light irradiation for 25 minutes to obtain a flexible strain sensor.

[0061] Example 3

[0062] The highly sensitive flexible strain sensing coating liquid is used to prepare a flexible strain sensor, comprising the following steps:

[0063] S1. Modified MXene nanosheets were prepared by silane coupling:

[0064] Take 1 g of MXene nanosheets, ultrasonically disperse it in 100 g of ethanol, add 10 g of ammonia water, 0.5 g of tetraethyl orthosilicate, and 0.3 g of 3-mercaptopropyltrimethoxysilane successively, stir for 6 h in a 70 ° C water bath, filter and wash with a mixed solution of water and ethanol to remove impurities and unreacted compounds, and dry in a vacuum drying oven at 90 ° C for 4 h to obtain modified MXene nanosheets.

[0065] S2. Preparation of highly sensitive flexible strain sensing coating liquid

[0066] 1 g of polybutadiene rubber with a molecular weight of 30,000 and 2 g of 3-mercapto-2-pentanol were dispersed in 50 g of tetrahydrofuran to obtain solution A; 1 g of modified MXene nanosheets in S1 were dispersed in 50 g of tetrahydrofuran to obtain dispersion B; solution A and dispersion B were mixed, stirred and reacted in a water bath at 50°C for 6 h, and 0.005 g of benzoin dimethyl ether was added to the obtained polymer to obtain a highly sensitive flexible strain sensing coating liquid.

[0067] S3. Use a spraying process to spray the highly sensitive flexible strain sensing coating liquid onto a 3cm×5cm spandex stretch fabric using a spray gun. The spray gun pressure is 0.3Mpa, and the distance between the spray gun and the stretch fabric is 20cm. Curing is performed by ultraviolet light irradiation for 25 minutes to obtain a flexible strain sensor.

[0068] Example 4

[0069] The highly sensitive flexible strain sensing coating liquid is used to prepare a flexible strain sensor, comprising the following steps:

[0070] S1. Modified MXene nanosheets were prepared by silane coupling:

[0071] Take 8 g of MXene nanosheets, ultrasonically disperse them in 640 g of ethanol, add 56 g of ammonia water, 2 g of tetraethyl orthosilicate, and 0.96 g of 3-mercaptopropylmethyldimethoxysilane successively, stir for 6 h in a 70 ° C water bath, use a mixed solution of water and ethanol to filter and wash to remove impurities and unreacted compounds, and dry in a vacuum drying oven at 90 ° C for 4 h to obtain modified MXene nanosheets.

[0072] S2. Preparation of highly sensitive 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 dispersed in 30 g of tetrahydrofuran to obtain solution A; 8 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 water bath at 60°C for 8 h, 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. Use a spraying process to spray the highly sensitive flexible strain sensing coating liquid onto a 3cm×5cm spandex stretch fabric using a spray gun. The spray gun pressure is 0.3Mpa, and the distance between the spray gun and the stretch fabric is 20cm. Curing is performed by ultraviolet light irradiation 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, comprising 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, 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, filter and wash with a mixed solution of water and ethanol to remove impurities and unreacted compounds, and 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 water bath at 60°C for 6 h, 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. Use a spraying process to spray the highly sensitive flexible strain sensing coating liquid onto a 3cm×5cm spandex stretch fabric using a spray gun. The spray gun pressure is 0.3Mpa, and the distance between the spray gun and the stretch fabric is 20cm. After curing by ultraviolet light for 20 minutes, a flexible strain sensor is obtained.

[0082] Example 6

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

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

[0085] Take 10 g of MXene nanosheets, ultrasonically disperse them in 600 g of ethanol, and successively add 26 g of ammonia water, 3.6 g of tetraethyl orthosilicate, and 2.8 g of a mixture of 3-mercaptopropylmethyldimethoxysilane and 2-mercaptoethanol (mass ratio of 1:1), stir for 6 h in a 70 ° C water bath, filter and wash with a mixed solution of water and ethanol to remove impurities and unreacted compounds, and dry in a vacuum drying oven at 90 ° C for 4 h 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 water bath at 60°C for 6 h, 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 3cm×5cm vulcanized rubber sheet for 3 times, and then 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, comprising the following steps:

[0091] S1. Same as step S1 in Example 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. The same as step S3 of embodiment 1.

[0095] Example 8

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

[0097] S1. Same as step S1 in Example 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. The same as step S3 of embodiment 1.

[0101] Example 9

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

[0103] S1. Same as step S1 in Example 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. The same as step S3 of embodiment 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 with a spray gun. The spray gun pressure was 0.3 MPa and the distance between the spray gun and the stretch fabric was 20 cm. The solution was then irradiated under ultraviolet light for 25 min for curing to obtain a flexible strain sensor.

[0110] Comparative Example 2

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

[0112] 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 was 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 with a spray gun. The spray gun pressure was 0.3 MPa and the distance between the spray gun and the stretch fabric was 20 cm. The solution was then irradiated under ultraviolet light for 25 min for curing to obtain a flexible strain sensor.

[0113] Comparative Example 3

[0114] A method for preparing a flexible strain sensor comprises the following steps:

[0115] S1. Modified MXene nanosheets were prepared by silane coupling:

[0116] 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 for 6 h in a 70 ° C water bath, filter and wash with a mixed solution of water and ethanol to remove impurities and unreacted compounds, and dry in a vacuum drying oven at 90 ° C for 4 h to obtain modified MXene nanosheets.

[0117] S2. Preparation of flexible strain sensing coating liquid

[0118] 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 water bath at 60°C for 6 hours, and 0.0005 g of benzoin was added to the obtained polymer to obtain a flexible strain sensing coating liquid.

[0119] S3. The flexible 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, and the distance between the spray gun and the stretch fabric is 20cm. The flexible strain sensor is obtained by curing the coating liquid by ultraviolet light for 25 minutes.

[0120] Comparative Example 4

[0121] A method for preparing a flexible strain sensor comprises 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, spray it onto 3cm×5cm spandex stretch fabric with a spray gun, the spray gun pressure is 0.3Mpa, the distance between the spray gun and the stretch fabric is 20cm, and 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 for 6 h in a 70 ° C water bath, filter and wash with a mixed solution of water and ethanol to remove impurities and unreacted compounds, and dry in a vacuum drying oven at 90 ° C for 4 h 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 modified MXene nanosheets in S1 was dispersed in 30 g of tetrahydrofuran to obtain dispersion B; solution A and dispersion B were mixed, stirred and reacted in a water bath at 60°C for 6 h, and 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 elastic fabric by a spray gun through a spraying process, the spray gun pressure is 0.3Mpa, the distance between the spray gun and the elastic fabric is 20cm, and the strain sensor is obtained by curing it by ultraviolet light for 25min.

[0130] The flexible strain sensors prepared in the above embodiments and comparative examples were tested for performance 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] From the above table, it can be seen that the high-sensitivity flexible strain sensing coating liquid prepared by the present invention is applied to the flexible strain sensor, 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, which is not only conducive to the construction of a complete conductive path, but also achieves a significant improvement in 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 cannot be considered to limit the scope of the embodiments of the present invention. The present invention is not limited to the above examples, and equal changes and improvements made by ordinary technicians in the technical field within the essential scope of the present invention should all fall within the scope of the patent coverage of the present invention.

Claims

1. A method for preparing a highly sensitive flexible strain sensing coating liquid, characterized in that: The following steps are involved: S1. Modified MXene nanosheets are prepared by silane coupling; S2. Preparation of highly sensitive flexible strain sensing coating liquid: Weigh polybutadiene rubber or styrene-butadiene rubber and polar small molecules containing thiol groups and disperse them in tetrahydrofuran to obtain solution A; weigh the modified MXene nanosheets in S1 and disperse them in tetrahydrofuran to obtain dispersion B; mix solution A and dispersion B, stir and react at 50-60° C. for 6-8 hours, add a photoinitiator to the obtained polymer, and obtain a highly sensitive flexible strain sensing coating liquid.

2. The method for preparing the highly sensitive flexible strain sensing coating liquid according to claim 1, characterized in that: 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).

3. The method for preparing the highly sensitive flexible strain sensing coating liquid according to claim 2, characterized in that: The mercaptosilane compound in S1 is one or more of 3-mercaptopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, and 3-mercaptopropylmethyldimethoxysilane.

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

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

6. The method for preparing the highly sensitive flexible strain sensing coating liquid according to claim 1, characterized in that: 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.

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

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

9. An application of the highly sensitive flexible strain sensing coating liquid according to claim 8, 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.

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

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