A method for preparing a flexible and highly sensitive polyurethane-based sensing material

Abstract

The invention discloses a method for preparing a flexible high-sensitivity polyurethane-based sensing material, comprising the following steps: dissolving polyurethane in an organic solvent to obtain a polyurethane solution; dispersing dopamine hydrochloride powder, MWCNT powder, and fly ash powder in an organic deionized water solvent, placing under light shielding, so that dopamine hydrochloride undergoes self-polymerization to obtain a dispersion; electrostatic spinning is performed on the polyurethane solution, and during the electrostatic spinning process, the above-mentioned dispersion is sprayed on the preliminarily formed polyurethane film, and electrostatic spinning is continued to obtain a polyurethane film doped with MWCNTs / fly ash particles; the polyurethane film doped with MWCNTs / fly ash particles is hot pressed to obtain. The sensitivity factor of the composite material of the present invention can reach up to 166, the strain range is 0-60%, the tensile strength can reach up to 166.67MPa, and it has omnidirectional flexibility.

Description

Technical Field

[0001] The invention relates to a method for preparing a flexible sensing material, in particular to a method for preparing a flexible high-sensitivity polyurethane-based sensing material. Background Art

[0002] The rapid development of electronic skin, robotics, motion detection and similar technologies has increased the requirements for wearability, flexibility and stretchability of sensors. Traditional metal or semiconductor-based strain sensors have a narrow strain range (usually less than 5%) and high stiffness, which cannot meet the needs of future strain sensors.

[0003] Therefore, polymer-based flexible strain sensors are receiving more and more attention. In response to the growing demand, flexible strain sensor process technology with high stretchability and excellent sensitivity is urgently needed. The composite materials prepared based on the polyurethane matrix can meet the flexibility and human compatibility requirements in applications, and the raw material supply is abundant and the manufacturing process is easy to operate. However, a product with stronger sensitivity, wider strain range and higher tensile strength still needs to be developed. Summary of the invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a method for preparing a flexible high-sensitivity polyurethane-based sensing material with stronger sensitivity, wider strain range and higher tensile strength.

[0005] Technical solution: The method for preparing the flexible high-sensitivity polyurethane-based sensing material of the present invention comprises the following steps:

[0006] (1) dissolving polyurethane in an organic solvent to obtain a polyurethane solution;

[0007] (2) dispersing dopamine hydrochloride, MWCNT and fly ash in a solvent to obtain a dispersion, and shielding the dispersion from light to allow the dopamine hydrochloride to self-polymerize;

[0008] (3) electrospinning the polyurethane solution to obtain a polyurethane film. In the process of preparing the polyurethane film, spraying the dispersion obtained after the self-polymerization in step (2) onto the initially formed polyurethane film, and then continuing to electrospin to obtain a polyurethane film doped with MWCNTs / fly ash;

[0009] (4) A polyurethane film doped with MWCNTs / fly ash is hot pressed to obtain a polyurethane film.

[0010] Wherein, before step (4), PDMS is coated on the upper and lower surfaces of the polyurethane film doped with MWCNTs / fly ash particles.

[0011] Wherein, in step (3), in the polyurethane film doped with MWCNTs / fly ash, the thickness of the polyurethane film located on the upper and lower sides of the MWCNTs / fly ash is the same.

[0012] Wherein, in step (1), the mass ratio of polyurethane particles to organic solvent is 0.163 to 0.190:1. When the ratio is less than 0.163:1, the viscosity of the spinning solution is insufficient, resulting in dripping, and the raw material utilization rate is low; when the ratio is greater than 0.190:1, the spinning viscosity is too high, and the droplets agglomerate at the needle tip during the electrospinning process, and fly to the collection device under the action of the electrostatic field, resulting in uneven mass distribution of the obtained film.

[0013] The mass ratio of dopamine hydrochloride: multi-walled carbon nanotubes: fly ash: solvent is 0.001: 0.005: 0.0075-0.0125: 1. When the fly ash is less than 0.0075, the sensing performance of the obtained sample is not at the optimal value; when it is greater than 0.0125, the sensing performance will decrease; and the sample between 0.0075 and 0.0125 has a better sensing performance.

[0014] Wherein, in step (3), the spraying amount is 2.0-3.0 ml; less than the spraying amount will result in the sample not being able to form an effective sensing layer; more than the spraying amount will increase the visual thickness of the film and waste raw materials. The spraying time is preferably 1-1.5 min.

[0015] Wherein, in step (3), the thickness of the layer of MWCNTs / fly ash particles after spraying is 20 μm to 30 μm. Within this range, the sample has good sensing performance; below this range, the sensing performance is greatly reduced; above this range, the economic efficiency of the process is reduced.

[0016] Wherein, in step (1), the polyurethane is dissolved in an organic solvent using a magnetic heating stirrer and heated at a temperature of 65° C. for 8 to 12 hours.

[0017] Wherein, in step (2), the solvent is anhydrous ethanol / deionized water, and the volume ratio is 2 to 4:1. Within the range, the dopamine hydrochloride in the dispersion can achieve good self-polymerization, thereby enhancing the bonding between the spray layer and the spinning layer; when the ratio is less than 2:1, the alcohol content in the dispersion is relatively low, and it cannot evaporate quickly during spraying, which has an adverse effect on bonding; when the ratio is greater than 4:1, there is less deionized water in the dispersion, which has an adverse effect on the self-polymerization of dopamine hydrochloride, thereby affecting the bonding performance.

[0018] Wherein, in step (3), the output voltage of electrostatic spinning is set to 13-18kV, the distance between the needle and the aluminum foil is 2.5-5cm, and the propulsion rate of the syringe is 0.3-0.6ml / h. The output voltage is lower than 13kV, which is easy to cause the insufficient electric field strength to affect the formation of fiber filaments, and higher than 18kV is easy to cause overcurrent danger in the electrostatic spinning process, preferably 15kV; if the distance between the needle and the aluminum foil is less than 2.5cm, the thickness of the obtained film increases, which may cause overcurrent danger. If it is greater than 5.0cm, the thickness of the obtained film will be thinner than the product of the present invention, preferably 2.5cm; if the propulsion rate is less than 0.3ml / h, the total duration of electrostatic spinning becomes longer, and the economic efficiency of large-scale production is reduced. If it is greater than 0.6ml / h, the fiber filaments will be mixed with beads, which will affect the film quality, preferably 0.5ml / h.

[0019] Wherein, in step (4), the hot pressing temperature is 100-160° C., and the pressure is 30 MPa-100 MPa.

[0020] Beneficial effects: Compared with the prior art, the present invention achieves the following significant effects: (1) The present invention selects MWCNTs / fly ash particles and adds them to the TPU matrix, and adopts the electrospinning method to prepare them, thereby significantly improving the tensile strain sensing performance of the polyurethane-based composite material, wherein the strain range of the composite film is 0-60%, which is significantly improved compared with the 0-20% of the pure polyurethane film, and the pure polyurethane film does not have tensile sensing performance; with the addition of nanoparticles, the sensitivity factor GF of the obtained composite film is as high as 166, which gives the polyurethane matrix good resistance sensing characteristics; the tensile strength can reach up to 166.67MPa, and it has omnidirectional flexibility; (2) The introduction of fly ash particles into the film has environmental and economic effects, can partially absorb the waste fly ash stock, and the cost of the raw material is extremely low. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 1 is the SEM image of Comparative Example 1, Example 1 and Example 2 selected by the present invention;

[0022] Figure 2 is the resistance change rate-strain sensing curve of the TPU-MWCNTs composite film of comparative example 2 measured under tensile strain conditions;

[0023] Figure 3 is the resistance change rate-strain sensing curve of the TPU-MWCNTs / fly ash composite film of Example 1 measured under tensile strain conditions;

[0024] Figure 4 This is the resistance change rate-strain sensing curve of the TPU-MWCNTs / fly ash composite film of Example 2 measured under tensile strain conditions. DETAILED DESCRIPTION

[0025] The present invention is described in further detail below.

[0026] Example 1

[0027] A 15wt.% TPU doped with 1.50wt.% MWCNTs / fly ash TPU-based composite film without PDMS dip coating, the specific preparation steps of which are as follows:

[0028] (1) Weigh 1.00 g of TPU particles using an analytical balance, add 6 ml of DMF solvent dropwise, and place on a magnetic heating stirrer set at 65° C. to dissolve for 8 h to obtain a polyurethane solution;

[0029] (2) Weigh 200 ml of anhydrous ethanol and 50 ml of deionized water, mix and place on a magnetic stirrer set at room temperature, weigh 0.021 g of dopamine hydrochloride powder, 1.05 g of carbon nanotube powder, and 2.10 g of fly ash powder using an analytical balance, and then place the weighed powders in the mixed solution and stir overnight for 24 hours to make the solution evenly dispersed;

[0030] (3) The mixed solution in step (1) is placed in a plastic syringe with a capacity of 12 ml and equipped with a stainless steel needle with an outer diameter of 0.9 mm. During the electrospinning process, the positive electrode of the high-voltage DC power supply is connected to the needle, the output voltage is 15.0 kV, and the total injection volume is 5 ml. The negative electrode is connected to a high-speed coaxial roller as the receiving end, the surface of which is covered with a layer of aluminum foil, and the speed of the roller is set at 800 r / min. The syringe is pushed forward under the operation of the injection pump, the pushing rate is 0.5 ml / h, and the operation process reaches 50%;

[0031] (4) adjusting the drum speed to 200 r / min, filling the mixed solution in step (2) into the spray gun, and spraying evenly for 1 min until the surface of the film layer is completely black. The final spraying amount is 2.5 ml; the thickness of the MWCNTs / fly ash particle layer after spraying is 25 μm;

[0032] (5) Adjust the drum speed to 800r / min and run the process to 100%. After spinning, a polyurethane-based composite film will be left on the aluminum foil.

[0033] (6) The film in step (5) was removed and placed in an oven at 80° C. for 3 h to remove residual DMF solvent.

[0034] (7) removing the film from step (6) and placing it in a hot press, with the temperature set at 160° C., the pressure set at 60 MPa, and the hot press time set at 30 min;

[0035] (8) Cut the film prepared in step (7) into strips of 10 mm × 50 mm and paste 10 mm × 10 mm copper tapes on both ends as electrodes.

[0036] After testing, the composite film has a sensitivity factor GF of up to 135 and a strain of up to 60%, which indicates it has excellent strain sensing capability.

[0037] Example 2

[0038] A TPU-based composite film with 15wt.% TPU doped with 1.50wt.% MWCNTs / fly ash dipped in PDMS, wherein the specific preparation steps are as follows:

[0039] (1) Weigh 1.00 g of TPU particles using an analytical balance, add 6 ml of DMF solvent dropwise, and place on a magnetic heating stirrer set at 65° C. to dissolve for 8 h to obtain a polyurethane solution;

[0040] (2) Weigh 200 ml of anhydrous ethanol and 50 ml of deionized water, mix and place on a magnetic stirrer set at room temperature, weigh 0.021 g of dopamine hydrochloride powder, 1.05 g of carbon nanotube powder, and 2.10 g of fly ash powder using an analytical balance, and then place the weighed powders in the mixed solution and stir overnight for 24 hours to make the solution evenly dispersed;

[0041] (3) The mixed solution in step (1) is placed in a plastic syringe with a capacity of 12 ml and equipped with a stainless steel needle with an outer diameter of 0.9 mm. During the electrospinning process, the positive electrode of the high-voltage DC power supply is connected to the needle, the output voltage is 15.0 kV, and the total injection volume is 5 ml. The negative electrode is connected to a high-speed coaxial roller as the receiving end, the surface of which is covered with a layer of aluminum foil, and the speed of the roller is set at 800 r / min. The syringe is pushed forward under the operation of the injection pump, the pushing rate is 0.5 ml / h, and the operation process reaches 50%;

[0042] (4) Adjust the drum speed to 200 r / min, fill the mixed solution in step (2) into the spray gun, and spray evenly for 1 min until the surface of the film layer turns completely black;

[0043] (5) Adjust the drum speed to 800r / min and run the process to 100%. After spinning, a polyurethane-based composite film will be left on the aluminum foil.

[0044] (6) The film in step (5) was removed and placed in an oven at 80° C. for 3 h to remove residual DMF solvent.

[0045] (7) Place the film in step (6) on a flat glass plate, dip PDMS to evenly cover the upper and lower surfaces, fully penetrate the interior of the film, keep it for 5 minutes, then clean the surface residue and let it stand at room temperature for 24 hours.

[0046] (8) removing the film from step (7) and placing it in a hot press, with the temperature set at 160° C., the pressure set at 60 MPa, and the hot press time set at 30 min;

[0047] (9) Cut the film prepared in step (8) into strips of 10 mm × 50 mm and paste 10 mm × 10 mm copper tapes on both ends as electrodes.

[0048] After testing, the composite film has a sensitivity factor GF of up to 166, and a maximum strain of 55%, which shows excellent strain sensing capability. At the same time, it can promote the disposal of industrial fly ash and has green environmental protection value.

[0049] Example 3

[0050] A 13wt.% TPU doped with 1.25wt.% MWCNTs / fly ash TPU-based composite film without PDMS dip coating, the specific preparation steps of which are as follows:

[0051] (1) Weigh 0.847 g of TPU particles using an analytical balance, add 6 ml of DMF solvent dropwise, and place on a magnetic heating stirrer set at 65° C. to dissolve for 8 h to obtain a polyurethane solution;

[0052] (2) Weigh 200 ml of anhydrous ethanol and 50 ml of deionized water, mix and place on a magnetic stirrer set at room temperature, use an analytical balance to weigh 0.021 g of dopamine hydrochloride powder, 1.05 g of carbon nanotube powder, and 1.575 g of fly ash powder, then place the weighed powder in the mixed solution and stir overnight for 24 hours to make the solution evenly dispersed;

[0053] (3) The mixed solution in step (1) is placed in a plastic syringe with a capacity of 12 ml and equipped with a stainless steel needle with an outer diameter of 0.9 mm. During the electrospinning process, the positive electrode of the high-voltage DC power supply is connected to the needle, the output voltage is 13.0 kV, and the total injection volume is 5 ml. The negative electrode is connected to a high-speed coaxial roller as the receiving end, the surface of which is covered with a layer of aluminum foil, and the speed of the roller is set at 800 r / min. The syringe is pushed forward under the operation of the injection pump, the pushing rate is 0.3 ml / h, and the operation process reaches 50%;

[0054] (4) adjusting the drum speed to 200 r / min, filling the mixed solution in step (2) into the spray gun, and spraying evenly for 1 min until the surface of the film layer is completely black. The final spraying amount is 2 ml; the thickness of the MWCNTs / fly ash particle layer after spraying is 20 μm;

[0055] (5) Adjust the drum speed to 800r / min and run the process to 100%. After spinning, a polyurethane-based composite film will be left on the aluminum foil.

[0056] (6) The film in step (5) was removed and placed in an oven at 80° C. for 3 h to remove residual DMF solvent.

[0057] (7) removing the film from step (6) and placing it in a hot press, with the temperature set at 100° C., the pressure set at 30 MPa, and the hot press time set at 30 min;

[0058] (8) Cut the film prepared in step (7) into strips of 10 mm × 50 mm and paste 10 mm × 10 mm copper tapes on both ends as electrodes.

[0059] Example 4

[0060] A TPU-based composite film of 18wt.% TPU doped with 1.75wt.% MWCNTs / fly ash without PDMS dip coating, wherein the specific preparation steps are as follows:

[0061] (1) Weigh 1.245 g of TPU particles using an analytical balance, add 6 ml of DMF solvent dropwise, and place on a magnetic heating stirrer set at 65° C. to dissolve for 12 h to obtain a polyurethane solution;

[0062] (2) Weigh 200 ml of anhydrous ethanol and 100 ml of deionized water, mix them and place them on a magnetic stirrer set at room temperature, use an analytical balance to weigh 0.021 g of dopamine hydrochloride powder, 1.05 g of carbon nanotube powder, and 2.625 g of fly ash powder, then place the weighed powders in the mixed solution and stir overnight for 24 hours to make the solution evenly dispersed;

[0063] (3) The mixed solution in step (1) is placed in a plastic syringe with a capacity of 12 ml and equipped with a stainless steel needle with an outer diameter of 0.9 mm. During the electrospinning process, the positive electrode of the high-voltage DC power supply is connected to the needle, the output voltage is 18.0 kV, and the total injection volume is 5 ml. The negative electrode is connected to a high-speed coaxial roller as the receiving end, the surface of which is covered with a layer of aluminum foil, and the speed of the roller is set at 800 r / min. The syringe is pushed forward under the operation of the injection pump, the pushing rate is 0.6 ml / h, and the operation process reaches 50%;

[0064] (4) adjusting the drum speed to 200 r / min, filling the mixed solution in step (2) into the spray gun, and spraying evenly for 1 min until the surface of the film layer is completely black. The final spraying amount is 3 ml; the thickness of the MWCNTs / fly ash particle layer after spraying is 30 μm;

[0065] (5) Adjust the drum speed to 800r / min and run the process to 100%. After spinning, a polyurethane-based composite film will be left on the aluminum foil.

[0066] (6) The film in step (5) was removed and placed in an oven at 80° C. for 3 h to remove residual DMF solvent.

[0067] (7) removing the film from step (6) and placing it in a hot press, with the temperature set at 160° C., the pressure set at 100 MPa, and the hot press time set at 30 min;

[0068] (8) Cut the film prepared in step (7) into strips of 10 mm × 50 mm and paste 10 mm × 10 mm copper tapes on both ends as electrodes.

[0069] Comparative Example 1

[0070] A 15wt.% pure TPU film, the specific preparation steps are as follows:

[0071] (1) Weigh 1.00 g of TPU particles using an analytical balance, add 6 ml of DMF solvent dropwise, and place on a magnetic heating stirrer set at 65° C. to dissolve for 8 h to obtain a polyurethane solution;

[0072] (2) The mixed solution in step (1) is placed in a plastic syringe with a capacity of 12 ml and equipped with a stainless steel needle with an outer diameter of 0.9 mm. During the electrospinning process, the positive electrode of the high-voltage DC power supply is connected to the needle, and the output voltage is 15.0 kV. The negative electrode is connected to a high-speed coaxial roller as the receiving end, and its surface is covered with a layer of aluminum foil. The speed of the roller is set at 800 r / min. During the spinning process, DMF, which serves as a solvent, evaporates under the action of the electrostatic field, leaving the TPU spinning fibers attached to the surface of the aluminum foil to form a thin film;

[0073] (3) The film in step (2) was removed and placed in an oven at 80° C. for 3 h to remove residual DMF solvent.

[0074] (4) Cut the film prepared in step (3) into strips of 10 mm × 50 mm and paste 10 mm × 10 mm copper tapes on both ends as electrodes.

[0075] Comparative Example 2

[0076] A TPU-based composite film of 15wt.% TPU doped with 0.5wt.% MWCNTs without PDMS dip coating, wherein the specific preparation steps are as follows:

[0077] (1) Weigh 1.00 g of TPU particles using an analytical balance, add 6 ml of DMF solvent dropwise, and place on a magnetic heating stirrer set at 65° C. to dissolve for 8 h to obtain a polyurethane solution;

[0078] (2) Weigh 200 ml of anhydrous ethanol and 50 ml of deionized water, mix and place on a magnetic stirrer set at room temperature, weigh 0.021 g of dopamine hydrochloride powder and 1.05 g of carbon nanotube powder using an analytical balance, and then place the weighed powder in the mixed solution and stir overnight for 24 hours to make the solution evenly dispersed;

[0079] (3) The mixed solution in step (1) is placed in a plastic syringe with a capacity of 12 ml and equipped with a stainless steel needle with an outer diameter of 0.9 mm. During the electrospinning process, the positive electrode of the high-voltage DC power supply is connected to the needle, the output voltage is 15.0 kV, and the total injection volume is 5 ml. The negative electrode is connected to a high-speed coaxial roller as the receiving end, the surface of which is covered with a layer of aluminum foil, and the speed of the roller is set at 800 r / min. The syringe is pushed forward under the operation of the injection pump, the pushing rate is 0.5 ml / h, and the operation process reaches 50%;

[0080] (4) Adjust the drum speed to 200 r / min, fill the mixed solution in step (2) into the spray gun, and spray evenly for 1 min until the surface of the film layer turns completely black;

[0081] (5) Adjust the drum speed to 800r / min and run the process to 100%. After spinning, a polyurethane-based composite film will be left on the aluminum foil.

[0082] (6) The film in step (5) was removed and placed in an oven at 80° C. for 3 h to remove residual DMF solvent.

[0083] (7) Place the film in step (6) on a flat glass plate, dip PDMS to evenly cover the upper and lower surfaces, fully penetrate the interior of the film, keep it for 5 minutes, then clean the surface residue and let it stand at room temperature for 24 hours.

[0084] (8) removing the film from step (7) and placing it in a hot press, with the temperature set at 160° C., the pressure set at 60 MPa, and the hot press time set at 30 min;

[0085] (9) Cut the film prepared in step (8) into 10 mm × 50 mm strips and paste 10 mm × 10 mm copper tapes on both ends as electrodes.

[0086] Figure 1From left to right, the SEM images of the 15wt.% pure TPU film plan view and cross-section view of the comparative example, the cross-section view of TPU-MWCNTs / fly ash without PDMS dipping of Example 1, and the cross-section view of TPU-MWCNTs / fly ash with PDMS dipping of Example 2 are shown. Comparative Example 1 shows a uniform and continuous distribution of polyurethane fibers, while Example 1 shows that randomly distributed fly ash is tightly surrounded by the CNTs fiber network, which proves that MWCNTs and fly ash particles can coexist stably for a long time and participate in the fiber network to provide a conductive channel in a physical contact manner; Example 2 shows that the fiber network is wrapped by PDMS as a whole, proving that the PDMS is filled on the fiber surface and gaps during the dipping process, and the introduction of PDMS improves the sensitivity of the conductive network, and the sensitivity factor GF is increased by 23% to 233% in different strain ranges compared with Example 1.

[0087] Figure 2 , 3 4 respectively give the resistance-strain sensing curves of the samples prepared in Comparative Example 2, Example 1 and Example 2. In Comparative Example 2, fly ash was not added, and the highest sensitivity factor was 6.49, and the maximum strain was 0.4; the highest sensitivity factor of Example 1 was 133, and the maximum strain was 60%, which was greatly improved compared with Comparative Example 2. This is because the addition of fly ash improves the conductivity of the MWCNTs network. During the stretching process, the easy mobility of fly ash will cause the MWCNTs fiber network to undergo severe deformation, which is reflected in the material resistance being more sensitive to strain; the high sensitivity factor of Example 2 is 166, and the maximum strain is 55%, but the sensitivity factor is greatly improved in the small strain range of 0-30%. This is because under the coating of PDMS, the gaps in the wire network are filled with PDMS. Under the tensile strain, not only some conductive paths are lost, but PDMS also hinders the formation of new conductive paths, reflecting a more superior sensing performance. Comparative Example 1 is a pure TPU film with no sensing characteristics, and the maximum strain under no hot pressing conditions is only about 20%.

[0088] In summary, the present invention selects MWCNTs / fly ash particles and adds them to the TPU matrix, adopts the electrospinning method to prepare the spinning membrane, and prepares a flexible and highly sensitive TPU-based composite film by a hot pressing process. The film preparation process is simple, low-cost, and highly operable. The prepared film has excellent sensing performance and is environmentally friendly. With the introduction of MWCNTs / fly ash particles, the maximum sensitivity coefficient of the composite film is 166 and 133 respectively, depending on whether PDMS is dip-coated, and the small strain sensitivity coefficient is 26 and 8 respectively. It is worth noting that the sensitivity factor GF of the composite film prepared by the present invention can reach up to 166, which gives the polyurethane matrix excellent sensing properties and has broad application prospects in the field of flexible sensing; at the same time, the use of industrial solid waste fly ash as doping particles can continuously absorb the stockpile and promote the overall improvement of the comprehensive utilization rate of solid waste.

Claims

1. A method for preparing a flexible and highly sensitive polyurethane-based sensing material. It is characterized in that The steps include: (1) dissolving polyurethane in an organic solvent to obtain a polyurethane solution; (2) dispersing dopamine hydrochloride, MWCNTs and fly ash in a solvent to obtain a dispersion, and shielding the dispersion from light to allow the dopamine hydrochloride to self-polymerize; (3) electrospinning the polyurethane solution to obtain a polyurethane film. In the process of preparing the polyurethane film, spraying the dispersion obtained after the self-polymerization in step (2) onto the initially formed polyurethane film, and then continuing to electrospin to obtain a polyurethane film doped with MWCNTs / fly ash; (4) The polyurethane film doped with MWCNTs / fly ash is hot pressed to obtain a polyurethane film.

2. The method for preparing the flexible high-sensitivity polyurethane-based sensing material according to claim 1, It is characterized in that Prior to step (4), PDMS was coated on the upper and lower surfaces of the polyurethane film doped with MWCNTs / fly ash particles.

3. The method for preparing the flexible high-sensitivity polyurethane-based sensing material according to claim 1, It is characterized in that In step (3), in the polyurethane film doped with MWCNTs / fly ash, the polyurethane films located on the upper and lower sides of the MWCNTs / fly ash have the same thickness.

4. The method for preparing the flexible high-sensitivity polyurethane-based sensing material according to claim 1, It is characterized in that In step (1), the mass ratio of the polyurethane to the organic solvent is 0.163-0.190:

1.

5. The method for preparing the flexible high-sensitivity polyurethane-based sensing material according to claim 1, It is characterized in that The mass ratio of dopamine hydrochloride:MWCNTs:fly ash:solvent is 0.001:0.005:0.0075-0.0125:

1.

6. The method for preparing the flexible high-sensitivity polyurethane-based sensing material according to claim 1, It is characterized in that In step (3), the spraying amount is 2.0 to 3.0 ml.

7. The method for preparing the flexible high-sensitivity polyurethane-based sensing material according to claim 1, It is characterized in that In step (3), the thickness of the layer of MWCNTs / fly ash particles after spraying is 20 μm to 30 μm.

8. The method for preparing the flexible high-sensitivity polyurethane-based sensing material according to claim 1, It is characterized in that In step (2), the solvent is anhydrous ethanol and deionized water in a volume ratio of 2 to 4:

1.

9. The method for preparing the flexible high-sensitivity polyurethane-based sensing material according to claim 1, It is characterized in that In step (3), the output voltage of electrospinning is set to 13-18 kV, the distance between the needle and the aluminum foil is 2.5-5.0 cm, and the propulsion rate of the syringe is 0.3-0.6 ml / h.

10. The method for preparing the flexible high-sensitivity polyurethane-based sensing material according to claim 1, It is characterized in that In step (4), the hot pressing temperature is 100-160°C and the pressure is 30 MPa-100 MPa.

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