Hydroxylated carbon black / polyurethane composite film as well as preparation method and application thereof

Abstract

The invention discloses a hydroxylated carbon black / polyurethane composite film as well as a preparation method and application thereof, and belongs to the technical field of polyurethane-based film sensor and flexible electronic skin development, tannic acid is taken as a bridging agent, polyurethane and hydroxylated carbon black are tightly combined through hydrogen-bond interaction, and the hydroxylated carbon black / polyurethane composite film is obtained. During film forming, the composite film with the Janus structure is obtained by adopting a gravity self-settling method, so that the hydroxylated carbon black / polyurethane composite film is endowed with a bending direction recognition function, the hydroxylated carbon black / polyurethane composite film obtained by the invention has ultrahigh mechanical strength, the ultimate tensile strength reaches 35.37 Mpa, and the tensile strength reaches 36.7 Mpa. And the pressure is more than eight times of that of the traditional polyurethane-based flexible sensor (4.5 Mpa). The hydroxylated carbon black / polyurethane composite film obtained by the invention has good waterproofness, and can be used for carrying out long-time and uninterrupted signal detection on underwater movement.

Description

Technical Field

[0001] The present invention relates to the technical field of polyurethane-based thin film sensors and flexible electronic skin development, and specifically relates to a hydroxylated carbon black / polyurethane composite film, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, flexible sensors have become an important research focus, especially in the fields of wearable devices and human motion monitoring. Traditional flexible sensors usually use soft and brittle materials, so they cannot withstand high loads, thus affecting their ability to provide effective detection over a long period of time.

[0003] More importantly, most flexible sensors have a single function and are not sufficient to meet the requirements of complex application scenarios. When deployed in challenging environments, such as underwater, the mechanical properties, hydrophobicity, and interfacial stability of existing flexible electronic materials are all poor. Summary of the Invention

[0004] The present invention provides a hydroxylated carbon black / polyurethane composite film, a preparation method thereof, and an application thereof, effectively solving the technical problems of poor mechanical properties, waterproofness, and long-term underwater use stability of existing flexible electronic materials. The present invention uses tannic acid as a bridging agent to tightly bind hydroxylated carbon black and polyurethane through hydrogen bonds, improving the mechanical properties of the composite film. By using the gravity self-sedimentation technique, the composite film has a Janus structure, providing the film sensor with the ability to detect the bending direction.

[0005] The first object of the present invention is to provide a preparation method of a hydroxylated carbon black / polyurethane composite film, comprising the following steps: Prepare a hydroxylated carbon black solution.

[0006] Add tannic acid to the hydroxylated carbon black solution, and perform ultrasonic treatment to obtain tannic acid-modified hydroxylated carbon black, denoted as TA@HCB; add the tannic acid-modified hydroxylated carbon black to a polyurethane latex suspension to obtain a mixed solution, form a film, and use tannic acid as a bridging agent to bind polyurethane and hydroxylated carbon black through hydrogen bond action to obtain a hydroxylated carbon black / polyurethane composite film.

[0007] As a preferred embodiment, the mass ratio of tannic acid to hydroxylated carbon black is 1:5 to 10.

[0008] As a preferred embodiment, based on the mass of polyurethane in the polyurethane latex suspension, the mass percentage of the tannic acid-modified hydroxylated carbon black is 2% to 10%.

[0009] As a preferred embodiment, the power of the ultrasonic treatment is 200W to 300W, and the time is 0.5h to 1h.

[0010] As a preferred embodiment, during film formation, the mixed solution is injected into a mold and cured at 45°C to 50°C for 20 h to 24 h. Through the action of gravity drive, a hydroxylated carbon black / polyurethane composite film is obtained.

[0011] As a preferred embodiment, the preparation method of the hydroxylated carbon black solution includes the following steps: Dispersing carbon black in concentrated nitric acid, carrying out condensation reflux at 85°C to 95°C for 60 min to 90 min. After the reaction ends, pour it into ice-cold distilled water, let it stand to obtain a solid, wash, filter, dry to obtain hydroxylated carbon black, and add the hydroxylated carbon black to water and stir to obtain a hydroxylated carbon black solution.

[0012] As a preferred embodiment, the concentration of the concentrated nitric acid is 98%, and the dosage ratio of the carbon black to the concentrated nitric acid is 1 g to 2 g:80 mL.

[0013] The second object of the present invention is to provide a hydroxylated carbon black / polyurethane composite film, which is prepared by using the preparation method described in any one of the above. The hydroxylated carbon black / polyurethane composite film has a Janus structure. The Janus structure will cause the TA@HCB nanoparticles in the polyurethane matrix to be distributed in a gradient manner. The sensing performance of the film is mainly determined by the conductive network composed of high-concentration HCB nanoparticles in the TA@HCB layer, resulting in different signal response values for the Janus film in different bending directions, thereby achieving the ability to identify different bending directions.

[0014] The third object of the present invention is to provide an application of the above-mentioned hydroxylated carbon black / polyurethane composite film in the preparation of flexible sensors.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention provides a preparation method of a hydroxylated carbon black / polyurethane composite film. Using tannic acid as a bridging agent, polyurethane and hydroxylated carbon black are tightly combined through hydrogen bond action to obtain a hydroxylated carbon black / polyurethane composite film. During film formation, the composite film with a Janus structure of the present invention is obtained by the gravity self-sedimentation method. Through gravity drive, tannic acid-modified hydroxylated carbon black is gradiently dispersed in the polyurethane network, thereby endowing the hydroxylated carbon black / polyurethane composite film with the function of identifying bending directions. The hydroxylated carbon black / polyurethane composite film obtained by the present invention has ultra-high mechanical strength, and its ultimate tensile strength reaches 35.37 Mpa, which is more than eight times that of traditional polyurethane-based flexible sensors (4.5 Mpa). The hydroxylated carbon black / polyurethane composite film obtained by the present invention has good waterproof performance and can perform long-term and uninterrupted signal detection on underwater movements.

[0016] The hydroxylated carbon black / polyurethane composite film prepared by the present invention has good self-healing and recyclable functions, and can also selectively respond to directional bending and stretching, which can be reused to save costs. The flexible sensor made of the hydroxylated carbon black / polyurethane composite film prepared by the present invention can be used for detecting human motion signals, writing boards and Morse code recognition, and has high stability sensing performance underwater. The present invention provides a new idea for the multifunctional application of flexible sensors.

[0017] The gravity-driven method adopted by the present invention is simple, easy to implement, has a simple process, low cost and strong universality, is convenient for popularization, and realizes large-scale industrial production. Brief Description of the Drawings

[0018] Figure 1 It is the SEM image of the polyurethane surface in the hydroxylated carbon black / polyurethane composite film of Example 1 of the present invention.

[0019] Figure 2 It is the SEM image of the tannic acid-modified hydroxylated carbon black surface of the hydroxylated carbon black / polyurethane composite film of Example 1 of the present invention.

[0020] Figure 3 It is the SEM image of the polyurethane surface of the carbon black / polyurethane composite film of Comparative Example 1 of the present invention.

[0021] Figure 4 It is the SEM image of the carbon black surface of the carbon black / polyurethane composite film of Comparative Example 1 of the present invention.

[0022] Figure 5 It is the FI-TR diagram of the hydroxylated carbon black / polyurethane composite film of Example 1 of the present invention.

[0023] Figure 6 It is the comparison diagram of the tensile properties of the hydroxylated carbon black / polyurethane composite films prepared in Examples 1, 4, 5, 6, 7 of the present invention and the polyurethane film prepared in Comparative Example 3.

[0024] Figure 7 It is the anti-fatigue performance diagram of the hydroxylated carbon black / polyurethane composite film of Example 1 of the present invention under different strains.

[0025] Figure 8 It is the DMA diagram of the hydroxylated carbon black / polyurethane composite film of Example 1 of the present invention.

[0026] Figure 9 It is the diagram of lifting heavy objects of the hydroxylated carbon black / polyurethane composite film of Example 1 of the present invention.

[0027] Figure 10 It is the self-healing tensile property diagram of the hydroxylated carbon black / polyurethane composite film of Example 1 of the present invention.

[0028] Figure 11 The recyclable tensile property diagram of the hydroxylated carbon black / polyurethane composite film of Embodiment 1 of the present invention.

[0029] Figure 12 The sensing property diagram of the hydroxylated carbon black / polyurethane composite film of Embodiment 1 of the present invention under small strain conditions.

[0030] Figure 13 The sensing property diagram of the hydroxylated carbon black / polyurethane composite film of Embodiment 1 of the present invention under large strain conditions.

[0031] Figure 14 The Morse code sensing signal diagram of the hydroxylated carbon black / polyurethane composite film of Embodiment 1 of the present invention.

[0032] Figure 15 The finger bending detection diagram of the hydroxylated carbon black / polyurethane composite film of Embodiment 1 of the present invention underwater.

[0033] Figure 16 The electrical signal change of the hydroxylated carbon black / polyurethane composite film of Embodiment 1 of the present invention under 1000 cycles.

[0034] Figure 17 The shark swimming detection diagram of the hydroxylated carbon black / polyurethane composite film of Embodiment 1 of the present invention underwater.

[0035] Figure 18 The different direction bending detection diagram of the shooting wrist of the hydroxylated carbon black / polyurethane composite film of Embodiment 1 of the present invention. Detailed implementation manners

[0036] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention will be further described below in conjunction with specific embodiments, but the exemplified embodiments shall not be construed as limiting the present invention. The following test methods and detection methods are all conventional methods unless otherwise specified; the reagents and raw materials are all commercially available unless otherwise specified.

[0037] Aiming at the technical problems of poor mechanical properties, waterproofness and long-term underwater use stability of existing flexible electronic materials. The present invention provides a hydroxylated carbon black / polyurethane composite film and its preparation method and application.

[0038] The technical solution of the present invention will be described in detail below.

[0039] The present invention provides a preparation method of a hydroxylated carbon black / polyurethane composite film, including the following steps: Prepare a hydroxylated carbon black solution.

[0040] Tannic acid was added to the hydroxylated carbon black solution and ultrasonicated to obtain tannic acid-modified hydroxylated carbon black; the tannic acid-modified hydroxylated carbon black was added to the polyurethane latex suspension to obtain a mixed solution, and a film was formed. Using tannic acid as a bridging agent, polyurethane was combined with hydroxylated carbon black through hydrogen bonding to obtain a hydroxylated carbon black / polyurethane composite film.

[0041] In the above technical solution, using tannic acid as a bridging agent, polyurethane was tightly combined with hydroxylated carbon black through hydrogen bonding to obtain a hydroxylated carbon black / polyurethane composite film. During film formation, gradient dispersion of tannic acid-modified hydroxylated carbon black in the polyurethane network was achieved by gravity drive. The sensing performance of the composite film was mainly determined by the conductive network composed of high-concentration HCB nanoparticles in the TA@HCB layer. This conductive network could enable the composite film to generate different signal response values in different bending directions, thereby achieving the ability to identify different bending directions and endowing the hydroxylated carbon black / polyurethane composite film with the function of identifying bending directions. Moreover, the obtained hydroxylated carbon black / polyurethane composite film had extremely high mechanical strength and good waterproofness.

[0042] To achieve the composite of hydroxylated carbon black and polyurethane, the present invention used tannic acid as a bridging agent and limited the mass ratio of tannic acid to hydroxylated carbon black to 1:5 - 10. If the dosage of hydroxylated carbon black was less than 5 defined here, that is, tannic acid was used in excess, it would lead to uneven stress distribution and increased stress concentration, thus reducing the strength of the composite film. If the dosage of hydroxylated carbon black was greater than 10 defined here, that is, the dosage of tannic acid was insufficient, it would lead to a reduction in the bonding connection between hydroxylated carbon black and polyurethane, and the interaction forces between substances in the system were weak, thus resulting in a reduction in the strength of the composite film and a decrease in toughness.

[0043] To further improve the strength of the hydroxylated carbon black / polyurethane composite film, based on the mass of polyurethane in the polyurethane latex suspension, the mass percentage of the tannic acid-modified hydroxylated carbon black was 2% - 10%. If it was less than 2%, that is, the dosage of tannic acid-modified hydroxylated carbon black was reduced, it would lead to the inability of tannic acid-modified hydroxylated carbon black to form a support network in the composite film, thus causing abnormal strength. If it was greater than 10%, that is, the dosage of tannic acid-modified hydroxylated carbon black in the composite film was increased, it would lead to an increase in the rigid component in the flexible matrix, and excessive tannic acid-modified hydroxylated carbon black would cause cracks in the composite film and be prone to rupture, thus reducing the mechanical properties of the composite film.

[0044] To achieve effective modification of hydroxylated carbon black by tannic acid, the power of the ultrasonic treatment was 200W - 300W, and the time was 0.5h - 1h.

[0045] In order to endow the hydroxylated carbon black / polyurethane composite film with the ability to identify different bending directions, during film formation, the mixed solution is injected into a mold and cured at 45 °C to 50 °C for 20 h to 24 h. Through the action of gravity drive, tannic acid-modified hydroxylated carbon black is gradiently dispersed in the polyurethane network. The sensing performance of the composite film is mainly determined by the conductive network composed of high-concentration HCB nanoparticles in the TA@HCB layer. This conductive network can enable the composite film to generate different signal response values under different bending directions, thereby achieving the ability to identify different bending directions, endowing the hydroxylated carbon black / polyurethane composite film with the bending direction identification function, and obtaining the hydroxylated carbon black / polyurethane composite film.

[0046] To prepare hydroxylated carbon black, the preparation method of the hydroxylated carbon black solution in the present invention includes the following steps: According to the dosage ratio of 1 g to 2 g: 80 mL, carbon black is dispersed in concentrated nitric acid with a mass concentration of 98%, and condensed and refluxed at 85 °C to 95 °C for 60 min to 90 min. After the reaction ends, it is poured into ice-cold distilled water, allowed to stand, and the solid is obtained. After washing, filtering, and drying, hydroxylated carbon black is obtained. The hydroxylated carbon black is added to water and stirred to obtain a hydroxylated carbon black solution.

[0047] The following specifically illustrates the content of the present invention through the following examples and comparative examples.

[0048] Example 1 A preparation method of a hydroxylated carbon black / polyurethane composite film includes the following steps: S1, 1.5 g of raw carbon black is dispersed in 80 mL of concentrated nitric acid, and condensed and refluxed at 95 °C for 90 min. After the reflux ends, the sample is poured into distilled water at 0 °C. After standing for 1 h, the supernatant is poured out to obtain the remaining solid. The remaining solid is washed, filtered, and dried to obtain hydroxylated carbon black, denoted as HCB. The hydroxylated carbon black is added to water and stirred for 1 h to obtain a hydroxylated carbon black solution.

[0049] S2, according to a mass ratio of 1:5, tannic acid (TA) is added to the hydroxylated carbon black solution, and ultrasonicated in a 300 W ultrasonic machine for 1 h to obtain tannic acid-modified hydroxylated carbon black, denoted as TA@HCB.

[0050] S3, 3 mL of TA@HCB accounting for 6% of the mass of polyurethane is added to a polyurethane latex suspension with a concentration of 38 wt%, and stirred on a stirring table at 500 rpm for 12 h. Then the obtained uniformly mixed solution is injected into a mold and cured in a drying oven at 5 °C for 20 h. Through the principle of gravity drive, nanoparticles of TA@HCB form a concentration gradient in the polyurethane latex suspension to obtain a hydroxylated carbon black / polyurethane composite film with a Janus structure.

[0051] Example 2 A preparation method of a hydroxylated carbon black / polyurethane composite film, comprising the following steps: S1, Disperse 1.5 g of raw carbon black in 80 mL of concentrated nitric acid, carry out condensation reflux at 95 °C for 90 min. After the reflux ends, pour the sample into distilled water at 0 °C, let it stand for 1 h, then pour out the supernatant to obtain the remaining solid. Wash, filter, and dry the remaining solid to obtain hydroxylated carbon black, denoted as HCB. Add the hydroxylated carbon black to water and stir for 1 h to obtain a hydroxylated carbon black solution.

[0052] S2, Add tannic acid (TA) to the hydroxylated carbon black solution according to a mass ratio of 1:5, and ultrasonicate in a 300 W ultrasonic machine for 1 h to obtain tannic acid-modified hydroxylated carbon black, denoted as TA@HCB.

[0053] S3, Add 3 mL of TA@HCB, which is 2% of the mass of the polyurethane, to a polyurethane latex suspension with a concentration of 38 wt%, and stir on a stirring table at 500 rpm for 12 h. Then inject the obtained uniformly mixed solution into a mold and cure it in a drying oven at 5 °C for 20 h. Through the principle of gravity drive, the nanoparticles of TA@HCB form a concentration gradient in the polyurethane latex suspension to obtain a hydroxylated carbon black / polyurethane composite film with a Janus structure.

[0054] Example 3 A preparation method of a hydroxylated carbon black / polyurethane composite film, comprising the following steps: S1, Disperse 1.5 g of raw carbon black in 80 mL of concentrated nitric acid, carry out condensation reflux at 95 °C for 90 min. After the reflux ends, pour the sample into distilled water at 0 °C, let it stand for 1 h, then pour out the supernatant to obtain the remaining solid. Wash, filter, and dry the remaining solid to obtain hydroxylated carbon black, denoted as HCB. Add the hydroxylated carbon black to water and stir for 1 h to obtain a hydroxylated carbon black solution.

[0055] S2, Add tannic acid (TA) to the hydroxylated carbon black solution according to a mass ratio of 1:5, and ultrasonicate in a 300 W ultrasonic machine for 1 h to obtain tannic acid-modified hydroxylated carbon black, denoted as TA@HCB.

[0056] S3, Add 3 mL of TA@HCB, which is 4% of the mass of the polyurethane, to a polyurethane latex suspension with a concentration of 38 wt%, and stir on a stirring table at 500 rpm for 12 h. Then inject the obtained uniformly mixed solution into a mold and cure it in a drying oven at 5 °C for 20 h. Through the principle of gravity drive, the nanoparticles of TA@HCB form a concentration gradient in the polyurethane latex suspension to obtain a hydroxylated carbon black / polyurethane composite film with a Janus structure.

[0057] Example 4 A preparation method of a hydroxylated carbon black / polyurethane composite film, comprising the following steps: S1, Disperse 1.5 g of raw carbon black in 80 mL of concentrated nitric acid, carry out condensation reflux at 95 °C for 90 min. After the reflux ends, pour the sample into distilled water at 0 °C, let it stand for 1 h, then pour out the supernatant to obtain the remaining solid. Wash, filter, and dry the remaining solid to obtain hydroxylated carbon black, denoted as HCB. Add the hydroxylated carbon black to water and stir for 1 h to obtain a hydroxylated carbon black solution.

[0058] S2, Add tannic acid (TA) to the hydroxylated carbon black solution according to a mass ratio of 1:5, and ultrasonicate in a 300 W ultrasonic machine for 1 h to obtain tannic acid-modified hydroxylated carbon black, denoted as TA@HCB.

[0059] S3, Add 3 mL of TA@HCB, which is 8% of the mass of the polyurethane, to a 38 wt% polyurethane latex suspension, and stir on a stirring table at 500 rpm for 12 h. Then inject the obtained uniformly mixed solution into a mold and cure it in a drying oven at 5 °C for 20 h. Through the principle of gravity drive, the nanoparticles of TA@HCB form a concentration gradient in the polyurethane latex suspension to obtain a hydroxylated carbon black / polyurethane composite film with a Janus structure.

[0060] Example 5 A preparation method of a hydroxylated carbon black / polyurethane composite film, comprising the following steps: S1, Disperse 1.5 g of raw carbon black in 80 mL of concentrated nitric acid, carry out condensation reflux at 95 °C for 90 min. After the reflux ends, pour the sample into distilled water at 0 °C, let it stand for 1 h, then pour out the supernatant to obtain the remaining solid. Wash, filter, and dry the remaining solid to obtain hydroxylated carbon black, denoted as HCB. Add the hydroxylated carbon black to water and stir for 1 h to obtain a hydroxylated carbon black solution.

[0061] S2, Add tannic acid (TA) to the hydroxylated carbon black solution according to a mass ratio of 1:5, and ultrasonicate in a 300 W ultrasonic machine for 1 h to obtain tannic acid-modified hydroxylated carbon black, denoted as TA@HCB.

[0062] S3, Add 3 mL of TA@HCB, which is 10% of the mass of the polyurethane, to a 38 wt% polyurethane latex suspension, and stir on a stirring table at 500 rpm for 12 h. Then inject the obtained uniformly mixed solution into a mold and cure it in a drying oven at 5 °C for 20 h. Through the principle of gravity drive, the nanoparticles of TA@HCB form a concentration gradient in the polyurethane latex suspension to obtain a hydroxylated carbon black / polyurethane composite film with a Janus structure.

[0063] Example 6 A preparation method of a hydroxylated carbon black / polyurethane composite film, comprising the following steps: S1, Disperse 1.5 g of raw carbon black in 80 mL of concentrated nitric acid, carry out condensation reflux at 95 °C for 90 min. After the reflux ends, pour the sample into distilled water at 0 °C, let it stand for 1 h, then pour out the supernatant to obtain the remaining solid. Wash, filter, and dry the remaining solid to obtain hydroxylated carbon black, denoted as HCB. Add the hydroxylated carbon black to water and stir for 1 h to obtain a hydroxylated carbon black solution.

[0064] S2, Add tannic acid (TA) to the hydroxylated carbon black solution according to a mass ratio of 1:10, and ultrasonicate in a 300 W ultrasonic machine for 1 h to obtain tannic acid-modified hydroxylated carbon black, denoted as TA@HCB.

[0065] S3, Add 3 mL of TA@HCB, which is 6% of the mass of the polyurethane, to a 38 wt% polyurethane latex suspension, and stir on a stirring table at 500 rpm for 12 h. Then inject the obtained uniformly mixed solution into a mold and cure it in a drying oven at 5 °C for 20 h. Through the principle of gravity drive, the nanoparticles of TA@HCB form a concentration gradient in the polyurethane latex suspension to obtain a hydroxylated carbon black / polyurethane composite film with a Janus structure.

[0066] Example 7 A preparation method of a hydroxylated carbon black / polyurethane composite film, comprising the following steps: S1, Disperse 1.5 g of raw carbon black in 80 mL of concentrated nitric acid, carry out condensation reflux at 95 °C for 90 min. After the reflux ends, pour the sample into distilled water at 0 °C, let it stand for 1 h, then pour out the supernatant to obtain the remaining solid. Wash, filter, and dry the remaining solid to obtain hydroxylated carbon black, denoted as HCB. Add the hydroxylated carbon black to water and stir for 1 h to obtain a hydroxylated carbon black solution.

[0067] S2, Add tannic acid (TA) to the hydroxylated carbon black solution according to a mass ratio of 1:7, and ultrasonicate in a 300 W ultrasonic machine for 1 h to obtain tannic acid-modified hydroxylated carbon black, denoted as TA@HCB.

[0068] S3, Add 3 mL of TA@HCB, which is 6% of the mass of the polyurethane, to a 38 wt% polyurethane latex suspension, and stir on a stirring table at 500 rpm for 12 h. Then inject the obtained uniformly mixed solution into a mold and cure it in a drying oven at 5 °C for 20 h. Through the principle of gravity drive, the nanoparticles of TA@HCB form a concentration gradient in the polyurethane latex suspension to obtain a hydroxylated carbon black / polyurethane composite film with a Janus structure.

[0069] To further illustrate the effects of the present invention, the present invention also sets up comparative examples as follows: Comparative Example 1 Compared with Example 1, the difference is that the carbon black is not hydroxylated and modified.

[0070] A method for preparing a carbon black / polyurethane composite film includes the following steps: S1. Add 1.5 g of raw carbon black to water and stir for 1 h to obtain a carbon black solution.

[0071] S2. Add tannic acid (TA) to the carbon black solution according to a mass ratio of 1:5, and ultrasonicate in a 300 W ultrasonic machine for 1 h to obtain tannic acid-modified carbon black, denoted as TA@CB.

[0072] S3. Add 3 mL of TA@CB, which is 6% of the mass of the polyurethane, to a polyurethane latex suspension with a concentration of 38 wt%, and stir on a stirring table at 500 rpm for 12 h. Then inject the obtained uniformly mixed solution into a mold and cure it in a drying oven at 5°C for 20 h. Through the principle of gravity drive, the nanoparticles of TA@CB form a concentration gradient in the polyurethane latex suspension to obtain a carbon black / polyurethane composite film with a Janus structure.

[0073] Comparative Example 2 Compared with Example 6, the difference is that the carbon black is not hydroxylated and modified.

[0074] A method for preparing a carbon black / polyurethane composite film includes the following steps: S1. Add 1.5 g of raw carbon black to water and stir for 1 h to obtain a carbon black solution.

[0075] S2. Add tannic acid (TA) to the carbon black solution according to a mass ratio of 1:10, and ultrasonicate in a 300 W ultrasonic machine for 1 h to obtain tannic acid-modified carbon black, denoted as TA@CB.

[0076] S3. Add 3 mL of TA@CB, which is 6% of the mass of the polyurethane, to a polyurethane latex suspension with a concentration of 38 wt%, and stir on a stirring table at 500 rpm for 12 h. Then inject the obtained uniformly mixed solution into a mold and cure it in a drying oven at 5°C for 20 h. Through the principle of gravity drive, the nanoparticles of TA@CB form a concentration gradient in the polyurethane latex suspension to obtain a carbon black / polyurethane composite film with a Janus structure.

[0077] Comparative Example 3 Compared with Example 1, the difference is that hydroxylated carbon black modified with tannic acid is not added, and only polyurethane is used to form a film.

[0078] A method for preparing a polyurethane film includes the following steps: In 3 mL of a polyurethane latex suspension with a concentration of 38 wt%, stir on a magnetic stirrer at 500 rpm for 12 h. Then, inject the resulting well-mixed solution into a mold and cure it in a drying oven at 5 °C for 20 h to obtain a polyurethane film.

[0079] The properties of the hydroxylated carbon black / polyurethane composite films provided in Examples 1 to 7, the carbon black / polyurethane composite films provided in Comparative Examples 1 to 2, and the polyurethane film provided in Comparative Example 3 were tested, and the results are as follows.

[0080] Figures 1 - 2 SEM images of the polyurethane side and the tannic acid-modified hydroxylated carbon black side of the hydroxylated carbon black / polyurethane composite film of Example 1 of the present invention, respectively. Figures 3 - 4 SEM images of the polyurethane side and the carbon black side of the carbon black / polyurethane composite film of Comparative Example 1 of the present invention, respectively. It can be Figures 1 - 4 seen that the tannic acid-modified hydroxylated carbon black is uniformly dispersed in the solvent, while the carbon black without hydroxylation treatment is not uniformly dispersed in the solvent, and the tannic acid-modified hydroxylated carbon black shows a gradient distribution in the film.

[0081] Figure 5 FT-IR spectrum of the hydroxylated carbon black / polyurethane composite film of Example 1 of the present invention. It can be Figure 5 seen that the hydroxyl content in the tannic acid-modified hydroxylated carbon black is higher than that in the unmodified carbon black.

[0082] Figure 6 Tensile property comparison chart of the hydroxylated carbon black / polyurethane composite films prepared in Examples 1, 4, 5, 6, 7 of the present invention and the polyurethane film of Comparative Example 3. It can be Figure 6 seen that when the mass of TA@HCB is 6% of the mass of polyurethane, the hydroxylated carbon black / polyurethane composite film exhibits the best mechanical properties.

[0083] Figure 7 Anti-fatigue property diagram of the hydroxylated carbon black / polyurethane composite film of Example 1 of the present invention under different strains. It can be Figure 7 seen that the hydroxylated carbon black / polyurethane composite film maintains good recoverability under different strains.

[0084] Figure 8 DMA spectrum of the hydroxylated carbon black / polyurethane composite film of Example 1 of the present invention. It can be Figure 8 seen that when the mass of TA@HCB is 6% of polyurethane, the storage modulus of the hydroxylated carbon black / polyurethane composite film is the best.

[0085] Figure 9 Diagram of lifting a heavy object of the hydroxylated carbon black / polyurethane composite film of Example 1 of the present invention. It can be Figure 9It can be seen that the hydroxylated carbon black / polyurethane composite film can easily lift a heavy object of 3.5 kg, proving that the hydroxylated carbon black / polyurethane composite film has strong mechanical properties.

[0086] Figure 10 This is the self-healing tensile property diagram of the hydroxylated carbon black / polyurethane composite film of Example 1 of the present invention. From Figure 10 It can be seen that the mechanical properties of the hydroxylated carbon black / polyurethane composite film can reach 60% of the original value after self-healing for 12 h.

[0087] Figure 11 This is the recyclable tensile property diagram of the hydroxylated carbon black / polyurethane composite film of Example 1 of the present invention. From Figure 11 It can be seen that the hydroxylated carbon black / polyurethane composite film can still maintain good mechanical properties under multiple cycles of decomposition and re-filming.

[0088] Figures 12 - 13 These are the sensing property diagrams of the hydroxylated carbon black / polyurethane composite film of Example 1 of the present invention under small strain and large strain conditions respectively. From Figures 12 - 13 It can be seen that the hydroxylated carbon black / polyurethane composite film can not only identify small strains with good sensitivity, but also detect large strain signals.

[0089] Figure 14 This is the Morse code sensing signal diagram of the hydroxylated carbon black / polyurethane composite film of Example 1 of the present invention. From Figure 14 It can be seen that the hydroxylated carbon black / polyurethane composite film can accurately identify Morse code and convert it into electrical signals.

[0090] Figure 15 This is the finger bending detection diagram of the hydroxylated carbon black / polyurethane composite film of Example 1 of the present invention underwater. From Figure 15 It can be seen that the hydroxylated carbon black / polyurethane composite film can detect human motion signals underwater, proving that the hydroxylated carbon black / polyurethane composite film can still perform sensing detection underwater.

[0091] Figure 16 This is the change in electrical signals of the hydroxylated carbon black / polyurethane composite film of Example 1 of the present invention under 1000 cycles. From Figure 16 It can be seen that the hydroxylated carbon black / polyurethane composite film still maintains good electrical stability under multiple cycles.

[0092] Figure 17 This is the underwater shark swimming detection diagram of the hydroxylated carbon black / polyurethane composite film of Example 1 of the present invention. From Figure 17 It can be seen that the hydroxylated carbon black / polyurethane composite film can detect the motion state of biomimetic organisms underwater.

[0093] Figure 18 This is the detection diagram of the hydroxylated carbon black / polyurethane composite film of Embodiment 1 of the present invention when the shooting wrist is bent in different directions. From Figure 18 it can be seen that the hydroxylated carbon black / polyurethane composite film can identify different bending directions of human joints.

[0094] In summary, the present invention uses tannic acid as a bridging agent to tightly combine polyurethane and hydroxylated carbon black through hydrogen bonding to obtain a hydroxylated carbon black / polyurethane composite film. When forming the film, the gravity self-sedimentation method is used to obtain the composite film with a Janus structure of the present invention, thereby endowing the hydroxylated carbon black / polyurethane composite film with the function of identifying the bending direction. The hydroxylated carbon black / polyurethane composite film obtained by the present invention has extremely high mechanical strength, and its ultimate tensile strength reaches 35.37 Mpa, which is more than eight times that of traditional polyurethane-based flexible sensors (4.5 Mpa). The hydroxylated carbon black / polyurethane composite film obtained by the present invention has good waterproofness and can detect signals continuously for a long time during underwater movement.

[0095] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and its equivalent technologies, the present invention also intends to include these changes and modifications.

Claims

1. A preparation method of a hydroxylated carbon black / polyurethane composite film, characterized in that It includes the following steps: Prepare a hydroxylated carbon black solution; Add tannic acid to the hydroxylated carbon black solution and ultrasonicate to obtain tannic acid-modified hydroxylated carbon black; add the tannic acid-modified hydroxylated carbon black to a polyurethane latex suspension to obtain a mixed solution, form a film, use tannic acid as a bridging agent, and combine polyurethane and hydroxylated carbon black through hydrogen bonding to obtain a hydroxylated carbon black / polyurethane composite film.

2. The preparation method according to claim 1, wherein The mass ratio of tannic acid to hydroxylated carbon black is 1:5 to 10.

3. The preparation method according to claim 1, characterized in that, Based on the mass of polyurethane in the polyurethane latex suspension, the mass percentage of the tannic acid-modified hydroxylated carbon black is 2% to 10%.

4. The preparation method according to claim 1, characterized in that, The power of the ultrasonication is 200 to 300 W, and the time is 0.5 h to 1 h.

5. The preparation method according to claim 1, characterized in that, When forming the film, inject the mixed solution into a mold, cure at 45°C to 50°C for 20 h to 24 h, and obtain a hydroxylated carbon black / polyurethane composite film through gravity driving.

6. The preparation method according to claim 1, characterized in that The preparation method of the hydroxylated carbon black solution includes the following steps: Disperse carbon black in concentrated nitric acid, carry out condensation reflux at 85°C to 95°C, pour it into ice-cold distilled water after the reaction ends, let it stand to obtain a solid, wash, filter, dry to obtain hydroxylated carbon black, and add the hydroxylated carbon black to water and stir to obtain a hydroxylated carbon black solution.

7. The preparation method according to claim 6, characterized in that, The concentration of the concentrated nitric acid is 98%, and the dosage ratio of carbon black to concentrated nitric acid is 1 to 2 g:80 mL.

8. A hydroxylated carbon black / polyurethane composite film, characterized in that, Prepared by using the preparation method described in any one of claims 1 to 8, the hydroxylated carbon black / polyurethane composite film has a Janus structure.

9. Use of the hydroxylated carbon black / polyurethane composite film described in claim 8 in the preparation of a flexible sensor.

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