A coaxial wet spinning multifunctional fiber, its preparation method and application

Abstract

The present invention discloses a coaxial wet spinning multifunctional fiber, its preparation method and application. The core layer of the multifunctional fiber is two-dimensional titanium carbide / polyvinyl alcohol, and the skin layer is aramid nanofibers. The preparation method includes the following steps: (1) preparing an aramid nanofiber spinning solution; (2) preparing a core layer spinning solution; (3) preparing a nascent fiber of two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofibers; (4) coagulation bath; (5) freeze-drying. The preparation method of the present invention can mass-produce fibers. The obtained fibers are materials with good air permeability, flexibility and easy-to-control morphology, and can be used in fields such as pressure sensors, humidity sensors, wearable electronic devices, etc., and have broad application prospects.

Description

Technical Field

[0001] The present invention belongs to the field of intelligent fibers, and particularly relates to a coaxial wet-spun multifunctional fiber, a preparation method thereof, and an application thereof. Background Art

[0002] Flexible sensors have the advantages of being portable and reliable, having high integration potential, good flexibility, and convenient operation, and have broad potential application prospects in the fields of electronic skin, human-machine interface, flexible touch screen, intelligent robotics, real-time personal health monitoring, etc. Since the vast majority of flexible sensors are composed of flexible or elastic polymer substrates with poor air permeability, it is difficult to firmly and comfortably wear these sensors on the human body. The fabric sensors prepared from fiber sensors provide an effective way to prepare flexible highly conductive fibers for wearable electronic devices.

[0003] The emergence of two-dimensional nanomaterials has brought a new breakthrough to flexible sensing. Two-dimensional titanium carbide is the most studied two-dimensional transition metal carbide in the field of flexible sensing. It has good mechanical properties, electrical properties, excellent hydrophilicity, and extensive modifiability. Two-dimensional titanium carbide improves the performance of the sensitive layer and electrode layer of flexible sensors, and can further expand the application field of flexible sensing. However, the small stress-strain, poor compression resilience, and insufficient oxidation tendency of two-dimensional titanium carbide limit its application. Summary of the Invention

[0004] The problem to be solved by the present invention is to provide a coaxial wet-spun multifunctional fiber, a preparation method thereof, and an application thereof. The multifunctional fiber uses aramid nanofibers as a flexible matrix and two-dimensional titanium carbide / polyvinyl alcohol as a sensing material to prepare a two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber aerogel fiber with a core-shell structure. The multifunctional fiber prepared by the present invention has excellent pressure sensing performance and humidity sensing performance. The preparation method of the present invention can mass-produce fibers, and the obtained fibers have good air permeability, flexibility, and materials with easily controllable morphology, and can be used in the fields of pressure sensors, humidity sensors, wearable electronic devices, etc.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A coaxial wet-spun multifunctional fiber according to the present invention has a core layer of two-dimensional titanium carbide / polyvinyl alcohol and a cortical structure of aramid nanofibers.

[0007] The core layer of the two-dimensional titanium carbide / polyvinyl alcohol is prepared by mixing a two-dimensional titanium carbide solution and a polyvinyl alcohol solution. The two-dimensional titanium carbide solution is prepared by combining hydrochloric acid etching of aluminum titanium carbide and ultrasonic peeling with manual shaking.

[0008] The preparation method of the coaxial wet-spun multifunctional fiber includes the following steps:

[0009] (1) Preparation of aramid nanofiber spinning solution: Add DuPont Kevlar fiber into a solvent for dissolution to obtain an aramid nanofiber spinning solution;

[0010] (2) Preparation of core layer spinning solution: Obtain a single-layer two-dimensional titanium carbide solution by etching aluminum titanium carbide with hydrochloric acid and ultrasonic exfoliation, and prepare a polyvinyl alcohol solution by dissolving polyvinyl alcohol particles at high temperature. Uniformly mix the two-dimensional titanium carbide solution and the polyvinyl alcohol solution by magnetic stirring to obtain a core layer spinning solution;

[0011] (3) Preparation of two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber nascent fiber: Prepare a core-shell structured fiber from the cortical aramid nanofiber spinning stock solution and the core layer two-dimensional titanium carbide / polyvinyl alcohol spinning stock solution through a coaxial wet spinning process;

[0012] (4) Coagulation bath: Immerse the fiber in a coagulation bath at room temperature to obtain a nascent fiber;

[0013] (5) Freeze-drying: The nascent fiber after passing through the coagulation bath is soaked in deionized water, then frozen, and then freeze-dried to obtain a two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber aerogel fiber.

[0014] In step (2), the concentration of the polyvinyl alcohol solution is 5 wt%, and the concentration of the two-dimensional titanium carbide solution is 40 mg / ml.

[0015] The single-layer two-dimensional titanium carbide solution is prepared by the following method: Weigh 3.2 g of lithium fluoride and add it to a reaction kettle. At the same time, add 40 ml of 9 mol / L hydrochloric acid to the reaction kettle, and stir at a temperature of 40 °C for 48 hours; Pour the reaction product into a centrifuge tube; Place the centrifuge tube in a centrifuge and adjust the rotation speed to 3500 rpm, and centrifuge for one minute; Take out the centrifuge tube, pour out the supernatant, add the prepared 2 mol / L dilute hydrochloric acid to the precipitate, and then put it into the centrifuge again, centrifuge at 3500 rpm for one minute, and wash with dilute hydrochloric acid 2 - 3 times; Next, perform water washing and centrifugation on the precipitate: Add deionized water to the centrifuge tube, centrifuge at 3500 rpm for 1 h until the upper layer solution is washed with deionized water until it turns black, and collect the concentrated single-layer two-dimensional titanium carbide colloidal dispersion.

[0016] The concentration of aramid nanofibers in the aramid nanofiber spinning solution is 1 - 3 wt%.

[0017] The aramid nanofiber spinning solution is prepared by the following method: 0.5 - 1.5 g of DuPont Kevlar fiber and 0.5 - 1.5 g of potassium tert-butoxide are added to 100 mL of dimethyl sulfoxide, and stirred rapidly. Then, 0.05 - 0.15 g of anhydrous methanol is added in three batches within 1 hour, and magnetically stirred for 3 - 8 hours. The prepared aramid nanofiber solution is centrifuged to remove a small amount of undissolved DuPont Kevlar fiber in the solution.

[0018] The coagulating liquid in the coagulation bath contains 0.06 wt% boric acid and 25 wt% tert-butanol.

[0019] The freeze-drying conditions are -80 °C for 48 h.

[0020] Application of the coaxial wet spinning multifunctional fiber in pressure or humidity sensing.

[0021] Compared with the existing multifunctional fibers, the present invention has the following technical advantages:

[0022] (1) The spinnability of pure two-dimensional titanium carbide fiber is poor, and the production process cost is high. There are many influencing factors for single forming. The present invention improves the spinnability of single-layer two-dimensional titanium carbide by adding polyvinyl alcohol to the core layer solution, which also plays a role in regulating its multifunctional application, while reducing costs and achieving high-value effects.

[0023] (2) The current passes through the two-dimensional titanium carbide / polyvinyl alcohol in the fiber core layer and is insulated by the aramid nanofiber in the skin layer, without contacting the human skin. Therefore, the two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber aerogel fiber of the present invention is a safer fiber.

[0024] (3) Using aramid nanofiber in the skin layer can effectively slow down the oxidation of the core layer. At the same time, the aerogel structure provides a flexible matrix, enabling the fiber to have functions such as pressure and humidity sensing performance.

[0025] (4) The prepared two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber aerogel fiber-shaped sensor device is more suitable for the human wearable field than traditional bulk or film-shaped sensor devices, broadening the application field of the two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber aerogel multifunctional fiber sensor.

[0026] The core layer of the present invention is mainly composed of two-dimensional titanium carbide and polyvinyl alcohol, and the skin layer is aramid nanofibers. The two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber multifunctional fiber with a skin-core structure prepared by the present invention is a safer conductive fiber. The current passes through the titanium carbide / polyvinyl alcohol in the fiber core layer and is isolated by the aramid nanofibers in the skin layer, without contacting the human skin. In addition, by improving the traditional method of natural drying of fibers, the present invention uses freeze-drying to prepare two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber aerogel fibers, improving the disadvantage of structural collapse during natural drying, and providing a structural guarantee for subsequent multifunctional applications such as flexible sensor devices. The present invention proposes an effective scheme for compounding two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber aerogel fibers, which can produce two-dimensional titanium carbide fibers on a large scale, continuously, and efficiently. At the same time, a fiber structure is introduced to prepare a sensing device. The fiber substrate can effectively adapt to severe and complex deformations, and has high stability, flexibility, light weight, and recoverability, expanding the application fields and environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic diagram of the two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber aerogel multifunctional fiber in the present invention;

[0028] Figure 2 is a schematic diagram of the wet spinning device of the two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber aerogel fiber in the present invention;

[0029] Figure 3 is a scanning electron microscope image of the two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber - 70% aerogel fiber in Example 4 of the present invention. Among them, Figure 3 a is the fiber surface, Figure 3 b and 3c are cross-sections of the fiber at different magnifications.

[0030] In the figure, the core layer is 1, the skin layer is 2, the injection pump is 3, the coagulation bath is 4, the washing bath is 5, and the collecting roller is 6. DETAILED DESCRIPTION OF THE INVENTION

[0031] The following will further elaborate on the present invention in combination with specific embodiments. In addition, it should be understood that these embodiments are only used to illustrate the present invention.

[0032] A coaxial wet spinning multifunctional fiber described in the present invention has a core layer of two-dimensional titanium carbide / polyvinyl alcohol and a skin layer structure of aramid nanofibers. The core layer of the two-dimensional titanium carbide / polyvinyl alcohol is prepared by using a two-dimensional titanium carbide solution and a polyvinyl alcohol solution. The two-dimensional titanium carbide solution is prepared by combining hydrochloric acid etching of titanium aluminum carbide and ultrasonic peeling with manual shaking. The aramid nanofiber spinning solution is prepared by a deprotonation method.

[0033] The described coaxial wet spinning multifunctional fiber is prepared by the following method: A single-layer two-dimensional titanium carbide solution obtained by combining hydrochloric acid etching of aluminum titanium carbide and ultrasonic peeling with manual shaking and a polyvinyl alcohol solution prepared by dissolving polyvinyl alcohol particles at high temperature are used as the core layer spinning solution. The cortical aramid nanofiber spinning solution is prepared by a deprotonation method. The primary fiber with a core-shell structure is prepared by coaxial wet spinning of the cortical aramid nanofiber spinning stock solution and the core layer two-dimensional titanium carbide / polyvinyl alcohol spinning stock solution; the primary fiber is soaked in a coagulation bath and then soaked in deionized water; finally, it is freeze-dried to obtain a two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber aerogel fiber with a core-shell structure. The specific preparation method is as follows:

[0034] 1), Preparation of aramid nanofiber spinning solution:

[0035] Add 0.5 - 1.5 g of DuPont Kevlar fiber and 0.5 - 1.5 g of potassium tert-butoxide to 100 mL of dimethyl sulfoxide, stir rapidly, and then add 0.05 - 0.15 g of anhydrous methanol in three batches within 1 hour, and stir magnetically for 3 - 8 hours. Centrifuge the prepared aramid nanofiber solution to remove a small amount of undissolved DuPont Kevlar fiber in the solution. The concentration of the solvent for the cortical aramid nanofiber spinning is 1 - 3 wt%.

[0036] 2), Preparation of core layer spinning solution:

[0037] A single-layer two-dimensional titanium carbide solution obtained by combining hydrochloric acid etching of aluminum titanium carbide and ultrasonic peeling and a polyvinyl alcohol solution prepared by dissolving polyvinyl alcohol particles at high temperature are used. The two-dimensional titanium carbide and the polyvinyl alcohol solution are uniformly mixed by magnetic stirring to obtain the core layer spinning solution. In the mixed solution, the concentration of the polyvinyl alcohol solution is 5 wt%.

[0038] The method for preparing two-dimensional titanium carbide is as follows: Weigh 3.2 g of lithium fluoride and add it to the reaction kettle. At the same time, add 40 ml of 9 mol / L hydrochloric acid to the reaction kettle and stir at a temperature of 40 °C for 48 hours; pour the reaction product into a centrifuge tube; adjust the centrifuge to a speed of 3500 rpm and centrifuge for one minute; take out the centrifuge tube, pour out the supernatant, add the prepared 2 mol / L dilute hydrochloric acid to the precipitate, and then put it into the centrifuge again and centrifuge at 3500 rpm for one minute, and wash with dilute hydrochloric acid 2 - 3 times; Next, perform water washing and centrifugation on the precipitate: Add deionized water to the centrifuge tube and centrifuge at 3500 rpm for one hour until the supernatant of the deionized water washing shows black, and collect the concentrated single-layer two-dimensional titanium carbide colloidal dispersion.

[0039] 3), Preparation of two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber aerogel fiber:

[0040] The cortical aramid nanofiber spinning dope and the core layer two-dimensional titanium carbide / polyvinyl alcohol spinning dope are used to obtain fibers through coaxial wet spinning.

[0041] 4) Coagulation bath for two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber aerogel fiber

[0042] The bath solution of the coagulation bath is formed by uniformly mixing boric acid, tert-butanol, and water. The mass concentrations of boric acid and tert-butanol are 0.06 wt% and 25 wt% respectively, the temperature of the coagulation bath is room temperature, the treatment time of the coagulation bath is 15 min, and the nascent fiber is obtained after passing through the coagulation bath.

[0043] 5) Preparation of two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber aerogel fiber:

[0044] After passing through the coagulation bath, it is soaked in deionized water and then freeze-dried to obtain two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber aerogel fiber. The specific operation is as follows:

[0045] The obtained nascent fiber is soaked in deionized water for 5 min, then placed in an ultra-low temperature refrigerator at -80 °C and frozen for 24 h, and then freeze-dried for 48 h to obtain two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber aerogel fiber.

[0046] Example 1

[0047] This example is an example of preparing the coaxial wet-spun multifunctional fiber by the method of the present invention. The specific steps are as follows:

[0048] 1) Preparation of aramid nanofiber spinning solution:

[0049] 1 g of DuPont Kevlar fiber and 1 g of potassium tert-butoxide are added to 100 mL of dimethyl sulfoxide (DMSO), and rapidly stirred for 10 minutes. Then, 1 g of anhydrous methanol is added in three batches within 1 hour, and then magnetically stirred for 6 hours until the sample is uniform. The aramid nanofiber solution prepared is centrifuged to remove a small amount of undissolved DuPont Kevlar fiber in the solution. The concentration of aramid nanofibers in the obtained aramid nanofiber spinning solution is 2 wt%;

[0050] 2) Preparation of core layer spinning solution:

[0051] 5 g of polyvinyl alcohol particles are added to 95 g of deionized water and dissolved at 95 °C for 8 hours until the polyvinyl alcohol particles are completely dissolved and uniformly dispersed. The concentration of the obtained polyvinyl alcohol solution is 5 wt%.

[0052] The preparation method of two-dimensional titanium carbide is as follows: Weigh 3.2 g of lithium fluoride and add it to the reaction kettle. At the same time, add 40 ml of 9 mol / L hydrochloric acid to the reaction kettle, and stir at 40 °C for 48 hours. Pour the reaction product into a centrifuge tube. Place the centrifuge tube in a centrifuge and adjust the rotation speed to 3500 rpm for 1 minute. Take out the centrifuge tube, pour out the supernatant, add the prepared 2 mol / L dilute hydrochloric acid to the precipitate, then put it into the centrifuge again, centrifuge at 3500 rpm for 1 minute, and wash with dilute hydrochloric acid 2 - 3 times. Next, perform water washing and centrifugation on the precipitate: Add deionized water to the centrifuge tube, centrifuge at 3500 rpm for 1 hour until the supernatant of the deionized water washing shows black, and collect the concentrated monolayer two-dimensional titanium carbide colloidal dispersion.

[0053] 3) Preparation of two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber aerogel fiber:

[0054] The concentration of the aramid nanofiber spinning solution in the skin layer is 2 wt%, the concentration of the two-dimensional titanium carbide / solution in the core layer is 40 mg / mL, and the polyvinyl alcohol solution is 5 wt%. Mix 1 g of two-dimensional titanium carbide and 9 g of polyvinyl alcohol in the core layer evenly. Place the spinning solutions of the skin layer and the core layer into the outer needle and the inner needle of a coaxial needle 19 / 15G respectively, and the extrusion speeds of the outer layer and the inner layer are 180 uL / min and 150 uL / min respectively. The spinning device of the present invention is as Figure 2 shown.

[0055] 4) Coagulation bath of two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber aerogel fiber:

[0056] In a coagulation bath with the mass concentrations of boric acid and tert-butanol being 0.06 wt% and 25 wt% respectively, the temperature of the coagulation bath is at room temperature, and the treatment time of the coagulation bath is 15 min. The as-spun fiber is obtained after passing through the coagulation bath.

[0057] 5) Preparation of two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber aerogel fiber:

[0058] After the as-spun fiber passes through the coagulation bath, soak it in deionized water for 5 minutes, then place it in an ultra-low temperature refrigerator at -80 °C and freeze it for 24 h, and then freeze-dry it at -80 °C for 48 h to obtain two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber - 10% aerogel fiber.

[0059] Example 2

[0060] This example is another example of preparing the coaxial wet spinning multifunctional fiber by the method of the present invention. The specific steps are as follows:

[0061] Steps 1, 2, and 4 of this Example 2 are the same as those of Example 1.

[0062] 3) Preparation of two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber aerogel fiber:

[0063] The spinning solution concentration of aramid nanofibers in the skin layer is 2 wt%, the concentration of the two-dimensional titanium carbide solution in the core layer is 40 mg / mL, and the polyvinyl alcohol solution is 5 wt%; 3 g of two-dimensional titanium carbide and 7 g of polyvinyl alcohol in the core layer are mixed evenly. The spinning solutions of the skin layer and the core layer are respectively placed in the outer needle and the inner needle of a coaxial needle 19 / 15G, and the extrusion speeds of the outer layer and the inner layer are 180 uL / min and 150 uL / min respectively.

[0064] 5) Preparation of two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber aerogel fiber:

[0065] After being immersed in deionized water for 5 minutes after passing through the coagulation bath, it is placed in an ultra-low temperature refrigerator at -80 °C and frozen for 24 h, and then freeze-dried at -80 °C for 48 h to obtain two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber-30% aerogel fiber.

[0066] Example 3

[0067] This example is another example of preparing the coaxial wet spinning multifunctional fiber by the method of the present invention, and the specific steps are as follows:

[0068] Steps 1, 2, and 4 of this Example 3 are the same as those of Example 1.

[0069] 3) Preparation of two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber aerogel fiber:

[0070] The spinning solution concentration of aramid nanofibers in the skin layer is 2 wt%, the concentration of the two-dimensional titanium carbide solution in the core layer is 40 mg / mL, and the polyvinyl alcohol solution is 5 wt%; 5 g of the two-dimensional titanium carbide solution and 5 g of the polyvinyl alcohol solution in the core layer are mixed evenly. The spinning solutions of the skin layer and the core layer are respectively placed in the outer needle and the inner needle of a coaxial needle 19 / 15G, and the extrusion speeds of the outer layer and the inner layer are 180 ul / min and 150 ul / min respectively. 5) Preparation of two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber aerogel fiber:

[0071] After being immersed in deionized water for 5 minutes after passing through the coagulation bath, it is placed in an ultra-low temperature refrigerator at -80 °C and frozen for 24 h, and then freeze-dried at -80 °C for 48 h to obtain two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber-50% fiber.

[0072] Example 4

[0073] This example is another example of preparing the coaxial wet spinning multifunctional fiber by the method of the present invention, and the specific steps are as follows:

[0074] The first, second, and fourth steps of this Example 4 are the same as those of Example 1.

[0075] 3) Preparation of two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber aerogel fiber:

[0076] The spinning solution concentration of aramid nanofibers in the skin layer is 2 wt%, the concentration of the two-dimensional titanium carbide solution in the core layer is 40 mg / mL, and the polyvinyl alcohol solution is 5 wt%; 7 g of two-dimensional titanium carbide and 3 g of polyvinyl alcohol in the core layer are mixed evenly. The spinning solutions of the skin layer and the core layer are respectively placed in the outer needle and the inner needle of a coaxial needle 19 / 15G, and the extrusion speeds of the outer layer and the inner layer are 180 uL / min and 150 uL / min respectively.

[0077] 5) Preparation of two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber aerogel fiber:

[0078] After passing through the coagulation bath and soaking in deionized water for 5 minutes, it is placed in an ultra-low temperature refrigerator at -80 °C and frozen for 24 h, and then freeze-dried at -80 °C for 48 h to obtain two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber-70% aerogel fiber.

[0079] The scanning electron microscope image of the two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber-70% aerogel fiber of this example is as Figure 3 shown. Among them, Figure 3 a is the fiber surface, Figure 3 b and 3c are cross-sections of the fiber at different magnifications.

[0080] Example 5

[0081] This example is another example of preparing the coaxial wet spinning multifunctional fiber by using the method of the present invention, and the specific steps are as follows:

[0082] The first, second, and fourth steps of this Example 4 are the same as those of Example 1.

[0083] 3) Preparation of two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber aerogel fiber:

[0084] The spinning solution concentration of aramid nanofibers in the skin layer is 2 wt%, the concentration of the two-dimensional titanium carbide solution in the core layer is 40 mg / mL, and the polyvinyl alcohol solution is 5 wt%; 9 g of two-dimensional titanium carbide and 1 g of polyvinyl alcohol in the core layer are mixed evenly. The spinning solutions of the skin layer and the core layer are respectively placed in the outer needle and the inner needle of a coaxial needle 19 / 15G, and the extrusion speeds of the outer layer and the inner layer are 180 uL / min and 150 uL / min respectively.

[0085] 5) Preparation of two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber aerogel fiber:

[0086] After soaking in deionized water for 5 minutes after passing through the coagulation bath, it was placed in an ultra-low temperature refrigerator at -80 °C and frozen for 24 h, and then freeze-dried at -80 °C for 48 h to obtain two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber-90% aerogel fiber.

[0087] Next, the LCR instrument IM3536 was used to measure the sensing performance of Examples 1 to 5 under different pressures when the working power supply was 1 V, and the obtained results are as described in Table 1 below.

[0088] Table 1 gives the current values of two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber-10%, two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber-30%, two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber-50%, two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber-70%, and two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber-90% aerogel fiber under different pressures. It can be seen from Table 1 that the prepared two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber aerogel fiber has good pressure sensing performance. As the applied pressure increases, the current gradually increases. At the same time, as the content of two-dimensional titanium carbide in the core layer increases, the initial current of the fiber increases from 3.8 μA to 9.1 μA. Among two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber-10%, two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber-30%, two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber-50%, two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber-70%, and two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber-90% aerogel fiber, the current change in two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber-70% aerogel fiber with pressure change is the largest. The reason is that when the core layer structure of two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber-70% aerogel fiber is stressed, the distance between the two-dimensional titanium carbide lamellae in the core layer becomes smaller, the conductive network increases, and the appropriate ratio of two-dimensional titanium carbide and polyvinyl alcohol makes the resilience of the fiber relatively good.

[0089] Secondly, the current changes in two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber-10%, two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber-30%, two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber-50%, and two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber-90% aerogel fiber with pressure change all gradually increase.

[0090] Table 1

[0091]

[0092] By controlling the environmental humidity and using an LCR instrument, the IM3536 instrument, with a working power supply of 1V, the sensing performance of Examples 1 to 5 under different humidities was measured. The results obtained are as described in Table 2 below. It can be seen from Table 2 that the prepared two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber aerogel fibers have good humidity sensing performance. As the humidity increases, the resistance change rates of the two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber-10%, two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber-30%, two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber-50%, and two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber-90% fibers gradually increase. As the content of the core layer of polyvinyl alcohol decreases, the moisture removal rate of the fibers becomes faster. However, when the mass ratio of two-dimensional titanium carbide to polyvinyl alcohol is 7:3, the network inside the core layer has the most suitable moisture removal property, and the resistance change of the fiber is the largest. Since when the mass ratio of two-dimensional titanium carbide to polyvinyl alcohol is 9:1, most of the network inside the core layer is composed of two-dimensional titanium carbide sheets. When the humidity increases, the two-dimensional titanium carbide sheets in the core layer overlap, and the moisture removal rate becomes slower. Therefore, the humidity sensing performance of the two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber-90% fiber is inferior to that of the two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber-70% fiber.

[0093] Table 2

[0094]

[0095] The principle of the present invention is to select aramid nanofibers with excellent mechanical properties and an entangled aramid nanofiber network as the skeleton material and antioxidant protection layer to make up for the deficiencies of two-dimensional titanium carbide, such as small stress and strain, poor compression resilience, and oxidation tendency. Polyvinyl alcohol is a hydrophilic polymer material. The hydroxyl groups of polyvinyl alcohol and the hydroxyl groups of two-dimensional titanium carbide are combined through hydrogen bonds, which improves the bonding force and mechanical strength of the fiber core layer.

Claims

1. Application of a coaxial wet-spun multifunctional fiber in pressure or humidity sensing, characterized in that, The coaxial wet spinning multifunctional fiber is prepared by the following method: (1) Prepare the aramid nanofiber spinning solution: Add DuPont Kevlar fiber to a solvent for dissolution to obtain the aramid nanofiber spinning solution; (2) Prepare the core layer spinning solution: Obtain a single-layer two-dimensional titanium carbide solution by hydrochloric acid etching aluminum titanium carbide and ultrasonic exfoliation and prepare a polyvinyl alcohol solution by dissolving polyvinyl alcohol particles at high temperature. Magnetically stir to uniformly mix the two-dimensional titanium carbide solution and the polyvinyl alcohol solution to obtain the core layer spinning solution; (3) Preparation of two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber nascent fiber: Prepare a fiber with a skin-core structure from the cortical aramid nanofiber spinning dope and the core layer two-dimensional titanium carbide / polyvinyl alcohol spinning dope through a coaxial wet spinning process; (4) Coagulation bath: Immerse the fiber in the coagulation bath at room temperature to obtain the nascent fiber; (5) Freeze-drying: Immerse the nascent fiber after passing through the coagulation bath in deionized water, then freeze it, and then freeze-dry it to obtain the two-dimensional titanium carbide / polyvinyl alcohol@aramid nanofiber aerogel fiber; The coagulating liquid in the coagulation bath contains 0.06 wt% boric acid and 25 wt% tert-butanol; In step (2), the concentration of the polyvinyl alcohol solution is 5 wt%, and the concentration of the two-dimensional titanium carbide solution is 40 mg / ml.

2. Application of the coaxial wet spinning multifunctional fiber according to claim 1 in pressure or humidity sensing, characterized in that, The single-layer two-dimensional titanium carbide solution is prepared by the following method: Add 3.2 g of lithium fluoride weighed to a reaction kettle, and at the same time add 40 ml of 9 mol / L hydrochloric acid to the reaction kettle, and stir at a temperature of 40 °C for 48 hours; Pour the reaction product into a centrifuge tube; Place the centrifuge tube in a centrifuge and adjust the rotation speed to 3500 rpm, and centrifuge for one minute; Take out the centrifuge tube, pour off the supernatant, add the prepared 2 mol / L dilute hydrochloric acid to the precipitate, and then put it into the centrifuge and centrifuge at 3500 rpm for one minute, and wash it with dilute hydrochloric acid 2-3 times; Next, perform water washing and centrifugation on the precipitate: Add deionized water to the centrifuge tube, and centrifuge at 3500 rpm for 1 h until the deionized water is washed until the upper layer solution shows black, and collect the concentrated single-layer two-dimensional titanium carbide colloidal dispersion.

3. Use of the coaxial wet spinning multifunctional fiber according to claim 1 in pressure or humidity sensing, characterized in that, The concentration of aramid nanofibers in the aramid nanofiber spinning solution is 1-3 wt%.

4. Use of the coaxial wet spinning multifunctional fiber according to claim 1 in pressure or humidity sensing, characterized in that, The aramid nanofiber spinning solution is prepared by the following method: Add 0.5-1.5 g of DuPont Kevlar fiber and 0.5-1.5 g of potassium tert-butoxide to 100 mL of dimethyl sulfoxide, stir rapidly, and then add 0.05-0.15 g of anhydrous methanol in three batches within 1 hour, magnetically stir for 3-8 hours, and centrifuge the prepared aramid nanofiber solution to remove a small amount of undissolved DuPont Kevlar fiber in the solution.

5. Use of the coaxial wet spinning multifunctional fiber according to claim 1 in pressure or humidity sensing, characterized in that, The freeze-drying conditions are -80 °C for 48 h.

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