An MXene-coated modified PLA nonwoven fabric and its preparation method

Abstract

This invention discloses an MXene-coated modified PLA nonwoven fabric and its preparation method. The preparation method includes the following steps: preparing an MXene solution using HCl and LiF; preparing PLA nonwoven fabric through electrospinning; etching and plasma surface treatment of the PLA nonwoven fabric to obtain the nonwoven fabric body; and spraying the MXene solution onto the surface of the nonwoven fabric body to obtain the MXene-coated modified PLA nonwoven fabric. This invention establishes a lightweight MXene-coated modified nonwoven fabric preparation technology, breaking through the technological gap in this field. The obtained nonwoven fabric material has good thermal stability, electrical conductivity, and electrothermal / photothermal conversion properties, which can integrate Joule heating and solar photothermal conversion into wearable heating systems, enabling precise body heating in various scenarios such as indoor / outdoor, day / night, sunny / cloudy conditions. Using polylactic acid as the base material is more environmentally friendly while giving the nonwoven fabric good breathability and toughness, enriching its application range.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of modified PLA non-woven fabrics, in particular, to a MXene coating modified PLA non-woven fabric. BACKGROUND

[0002] Non-woven fabric, also known as knitted cotton, is generally made of polyester fiber, polyester, polypropylene and other materials. Non-woven fabric is different from ordinary fabric, which has no warp and weft, only a network structure, which is processed by mechanical, thermal bonding and other methods. The traditional non-woven fabric has the advantages of moisture resistance, air permeability, softness, light weight and wide application, but its durability is poor, and it is mainly composed of polymers, which has low conductivity, so that the development of non-woven fabric in the electronic field is limited.

[0003] Polylactic acid (PLA) is a biobased polyester with biocompatibility and biodegradability, which is expected to replace petroleum-based polymers to produce non-woven fabrics. Electrospun PLA non-woven fabric has porosity and light weight, and its surface structure is developed, which can be used for various purposes. In order to modify the performance of electrospun PLA non-woven fabric, nano fillers or antibacterial substances can be added to the PLA solution to give it functionality, which has broad application potential in the field of intelligent wearable electronic devices.

[0004] For most wearable electronic devices based on textiles, the conductivity of the fabric is a basic requirement for designing various functional devices. MXene is widely used in EMI shielding, electrothermal applications, sensing and energy storage due to its excellent conductivity (up to 10000 S / cm), good hydrophilicity and excellent photo-thermal conversion performance, and has broad application prospects in steam power generation, clean water production, photothermal therapy, heating and warming, etc. Compared with two-dimensional conductive materials such as graphene, the rich surface groups of MXene make it easier to combine with textiles or other composite materials. Although some research reports the application progress of MXene in multifunctional electronic textiles, the potential safety hazards caused by overheating of the product limit its application, especially for elderly and child users.

[0005] Therefore, it is of great significance to develop a non-woven fabric material with good conductivity and excellent thermal stability for the development of wearable electronic devices. SUMMARY

[0006] In view of the above problems of poor conductivity and low thermal stability of traditional non-woven fabric, the present application provides a MXene coating modified PLA non-woven fabric and a preparation method thereof.

[0007] In order to achieve the above purpose, the present application provides the following technical solutions:

[0008] A method for preparing MXene-coated modified PLA nonwoven fabric includes the following steps:

[0009] (1) Acid products were obtained by etching Ti3AlC2 with HCl and LiF. The acid products were washed and centrifuged until the pH of the supernatant was ≥6. The precipitate was then dispersed in deionized water, ultrasonically treated in an ice bath, and centrifuged to obtain the supernatant, i.e. MXene solution.

[0010] (2) Dissolve PLA raw material in an organic solvent to obtain PLA solution, perform electrospinning to obtain wet nonwoven fabric, and perform drying and crystallization to obtain dry nonwoven fabric;

[0011] (3) The dry nonwoven fabric obtained in step (2) is etched and subjected to plasma surface treatment to obtain the nonwoven fabric body;

[0012] (4) Spray the MXene solution obtained in step (1) onto the surface of the nonwoven fabric obtained in step (3), and dry it to obtain MXene-coated modified PLA nonwoven fabric.

[0013] This invention uses PLA nonwoven fabric as the matrix and obtains a conductive network through a spray drying process, giving the PLA nonwoven fabric low resistance and exhibiting good conductivity and electromagnetic shielding properties. By measuring the highest temperature achievable under voltage and sunlight, it can be seen that the PLA nonwoven fabric has good electrothermal / photothermal conversion efficiency. Measuring its char residue at 800℃ shows that the PLA nonwoven fabric has excellent thermal stability.

[0014] Preferably, step (1) includes: adding LiF and Ti3AlC2 in a mass ratio of 1:(0.8~1.5) to HCl with a concentration of 6~9M, stirring at 35~40℃ for 20~24 hours to obtain an acid product, washing the acid product with deionized water and centrifuging at 3000~3500rpm for 30~60 seconds until the pH of the supernatant is ≥6, then dispersing the obtained precipitate in deionized water, sonicating in an ice bath for 50~60 minutes, centrifuging at 3000~3500rpm for 50~60 minutes to obtain the supernatant, i.e., the MXene solution.

[0015] After etching Ti3AlC2, as Figure 1 As shown, the (002) peak on the XRD pattern shifted from 9.6° to 6.1°, while the Ti3C2T peak... x The (104) peak disappeared at 38.8°, proving that MXene was successfully prepared.

[0016] Under acidic conditions, a large number of surface functional groups (-OH, -F, =O) are formed during the etching process, giving MXene anionic properties. Furthermore, as... Figure 2As shown, the Zeta potential of MXene solution with pH = 6 is -39.4 mV, indicating that the MXene solution has good dispersibility.

[0017] Preferably, the PLA raw material in step (2) is racemic PLA.

[0018] The mixing ratio of poly-L-lactic acid (PLLA) and poly-D-lactic acid (PDLA) in racemic PLA is 1:1, and obvious stereocomplexation occurs between PLLA and PDLA. The interaction between the chain segments in the amorphous region leads to high-density chain packing in this region, and the structure is more compact, so that the glass transition temperature can be increased.

[0019] Preferably, the PLA raw material in step (2) is dried at 95-100°C under reduced pressure.

[0020] Preferably, the concentration of the PLA solution in step (2) is 10-12 wt%.

[0021] Preferably, the organic solvent in step (2) is selected from one or more of hexafluoroisopropanol (HFIP) and dichloromethane.

[0022] Preferably, the organic solvent in step (2) is HFIP.

[0023] In the electrospinning process, the properties of the solvent such as volatility and the solubility of the solvent to the polymer will affect the electrospinning process, and then affect the morphology of the electrospun fiber, and finally affect the performance of the product. In addition to being soluble in hexafluoroisopropanol, PLA is also soluble in dichloromethane and the like. However, when dichloromethane is used as a solvent, it is too volatile in the electrospinning process, and the nozzle is always blocked during spinning, and the spun fiber is too thick. In contrast, hexafluoroisopropanol is a relatively ideal organic solvent for PLA.

[0024] Preferably, the wet non-woven fabric in step (2) is dried at 30-35°C under reduced pressure until the non-woven fabric contains 7.5-8 wt% of the organic solvent.

[0025] The organic solvent remaining in the non-woven fabric plays a crucial role in the subsequent elongation of the fiber. Too little residual solvent will cause the nascent fiber to be too brittle and produce brittle fracture; too much residual solvent will cause the nascent fiber to easily absorb moisture and hydrolyze, causing the entire non-woven fabric to shrink and bend, which seriously affects the performance. Selecting 7.5-8 wt% of the organic solvent can make the non-woven fabric surface have fewer cracks and be more smooth and flat overall.

[0026] Preferably, the crystallization in step (2) is performed at 100-110°C for 25-30 minutes, and a plate is used to compact during the crystallization process.

[0027] Preferably, the plate material is an aluminum plate.

[0028] Preferably, the etching in step (3) comprises alkaline etching and enzyme etching, the alkaline etching is that the dry non-woven fabric is etched in an alkaline solution with a concentration of 0.05-0.1 mol / L at room temperature for 15-120 minutes, and the enzyme etching is that the dry non-woven fabric is etched in a solution containing 0.6-0.8 mg / mL Bacillus, 10-12.2 mg / mL trizma base and 0.3-0.4 mg / mL sodium azide at 37℃ for 30-180 minutes.

[0029] Preferably, the alkaline solution is a sodium hydroxide and / or potassium hydroxide solution.

[0030] Preferably, the solvent of the alkaline solution is a mixture of methanol and distilled water with a mass ratio of 2:3.

[0031] Methanol has high polarity and low surface tension, and can interact with PLA molecules to disperse them and improve etching ability.

[0032] After etching, the surface roughness of the non-woven fabric is significantly improved, which is beneficial to the interface bonding with the MXene coating.

[0033] Preferably, the power of the plasma surface treatment in step (3) is 600-800 W, and the time is 3-5 minutes.

[0034] Plasma surface treatment and etching treatment enable the non-woven fabric to obtain a large number of hydrophilic groups and improve wettability.

[0035] Preferably, the concentration of the MXene solution in step (4) is 1.30-1.43 mg / mL, the spraying time is 3-5 seconds, and the non-woven fabric is sprayed 16-34 times on each side.

[0036] After spraying and drying, multiple layers of MXene are formed on the surface of the non-woven fabric, and the thickness of a single layer of MXene nanosheet is about 1.95 nm.

[0037] Due to the low content of MXene and the porous structure of the PLA non-woven fabric itself, the modified non-woven fabric maintains good flexibility and air permeability.

[0038] The application also provides a MXene-coated modified PLA non-woven fabric prepared by the above method.

[0039] The surface of the non-woven fabric body is smooth and light yellow before being sprayed with MXene. As the number of MXene spraying increases, the surface of the non-woven fabric becomes rough and wrinkled, and the color gradually changes to black (as shown in Figure 4

[0040] ​By comparing the XRD spectra of the non-woven fabric before and after the MXene spraying treatment, the characteristic peak (002) of MXene can be found, indicating that MXene is successfully adhered to the surface of the non-woven fabric.

[0041] By washing the MXene coating modified PLA non-woven fabric, it is found that the MXene nanosheets do not fall off, confirming the good adhesion of MXene to the fabric.

[0042] By observing the micro-morphology of the MXene coating modified PLA non-woven fabric (such as Figure 3 As shown), it can be seen that the fibers in the non-woven fabric are arranged in disorder, forming many pores of different sizes, indicating that the non-woven fabric has a good porous structure.

[0043] Through the above technical solutions, the present application achieves the following beneficial effects:

[0044] 1、The present application establishes a light MXene coating modified non-woven fabric preparation technology, which breaks through the technical blank in this field. The non-woven fabric prepared by the method has a surface resistance of about 4.36Ω / sq, a SET of single-layer fabric in the x wave band of 35.7dB, a non-woven fabric surface temperature of 41~263℃ under a power voltage of 1~5V, a non-woven fabric surface temperature of 49~107℃ under the irradiation of 50~125mW / cm 2 of sunlight, and a carbon residue rate of 51.6% at 800℃, indicating that the non-woven fabric has good electrical conductivity, electromagnetic shielding property, electrothermal / photothermal conversion property and thermal stability.

[0045] 2、The preparation technology of the present application can integrate joule heating and solar light thermal conversion into a wearable heating system, so that the flame-retardant MXene fabric can accurately heat the body in various scenes such as indoor / outdoor, daytime / nighttime, sunny / cloudy, etc.

[0046] 3、The present application selects polylactic acid as the base material, which is a new biodegradable material that can be degraded into CO2 and H2O by microorganisms, light, etc., causing little environmental pollution, and the polylactic acid composite material has good air permeability and toughness, enriching its application range.

[0047] 4、In a preferred technical solution of the present application, a new enzyme etching system of bacillus-trizma alkali-sodium azide is used, which has higher etching efficiency and better hydrophilic property of the etched non-woven fabric than the traditional lipase system. DETAILED DESCRIPTION

[0048] Figure 1 is the XRD pattern of Ti3AlC2 and Ti3C2T x in the present application;

[0049] Figure 2 is the Zeta potential diagram of the MXene solution in the present application;

[0050] Figure 3 is the micro-morphology of the MXene coating modified PLA non-woven fabric in the present application;

[0051] Figure 4 is the preparation flowchart of the embodiment of the present application. DETAILED DESCRIPTION

[0052] The specific embodiments of the present application are described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only for illustration and explanation of the present application, and are not intended to limit the present application.

[0053] Example 1:

[0054] As shown in the preparation method of the MXene coating modified PLA non-woven fabric, comprising the following steps: Figure 4

[0055] (1) 3g LiF was added to 60mL 6M HCl, stirred for 5 minutes, then 2.4g Ti3AlC2 powder was slowly added, stirred at 35℃ for 20 hours to obtain an acid product. The acid product was washed with deionized water and centrifuged at 3000rpm for 30 seconds until the supernatant pH≥6. The obtained precipitate was dispersed in deionized water, ice-bath ultrasonic treatment for 50 minutes, then centrifuged at 3000rpm for 50 minutes, and the supernatant was obtained by removing the precipitate, which was the MXene solution.

[0056] (2) PLA raw material was dried at 95℃ under reduced pressure, and the dried raw material was dissolved in 99% pure HFIP to obtain a 10wt% PLA solution. Electrospinning was performed using the solution, and the obtained wet non-woven fabric was dried at 30℃ under reduced pressure until the non-woven fabric contained 7.5wt% HFIP. The dried non-woven fabric was placed in a 100℃ muffle furnace for 25 minutes, and in order to prevent the non-woven fabric from deforming and shrinking during crystallization, an aluminum plate was used to press it tightly, and the dry non-woven fabric was obtained.

[0057] (3) Alkaline etching was carried out in a 0.05mol / L sodium hydroxide solution at room temperature for 120 minutes, and the solvent of the solution was a mixture of methanol and distilled water with a mass ratio of 2:3. The etching solution for enzyme etching contained 0.6mg / mL Bacillus, 10mg / mL trizma base and 0.3mg / mL sodium azide, and the etching was carried out at 37℃ for 180 minutes. In order to facilitate the penetration of the etching solution between the fibers, the non-woven fabric immersed in the etching solution was ultrasonicated in an ultrasonic bath for 5 minutes. After etching, the non-woven fabric was washed in a distilled water ultrasonic bath for 5 minutes and dried. The dried non-woven fabric was subjected to plasma surface treatment, 600W for 3 minutes, to obtain the non-woven fabric body.​

[0058] (4) such as Figure 2 As shown, MXene solution (1.30 mg / mL) was evenly sprayed onto the surface of the nonwoven fabric using a small sprayer for 3 seconds each time, and then dried with a hair dryer. The spraying was repeated 16 times on each side to obtain an MXene-coated modified PLA nonwoven fabric with an MXene coating content of 7.97 wt%, named MNF-1.

[0059] Example 2:

[0060] The preparation method of MXene-coated modified PLA nonwoven fabric includes the following steps:

[0061] (1) Add 3g LiF to 60mL 9M HCl and stir for 5 minutes. Then slowly add 4.5g Ti3AlC2 powder and stir at 38℃ for 22 hours to obtain an acid product. Wash the acid product with deionized water and centrifuge at 3300rpm for 45 seconds until the pH of the supernatant is ≥6. Disperse the obtained precipitate in deionized water, sonicate in an ice bath for 55 minutes, and then centrifuge at 3300rpm for 55 minutes to remove the precipitate and obtain the supernatant, which is the MXene solution.

[0062] (2) The PLA raw material was dried under reduced pressure at 98°C. The dried raw material was dissolved in 99% HFIP to obtain an 11wt% PLA solution. Electrospinning was performed using this solution. The resulting wet nonwoven fabric was dried under reduced pressure at 38°C until the nonwoven fabric contained 7.8wt% HFIP. The dried nonwoven fabric was placed in a muffle furnace at 105°C and kept for 28 minutes. To prevent the nonwoven fabric from deforming and shrinking during crystallization, it was pressed with an aluminum plate to obtain a dry nonwoven fabric.

[0063] (3) Alkaline etching was performed in a 0.08 mol / L potassium hydroxide solution at room temperature for 60 minutes, wherein the solvent of the solution was a mixture of methanol and distilled water in a mass ratio of 2:3. Enzymatic etching was performed in an etching solution containing 0.7 mg / mL Bacillus subtilis, 11 mg / mL Trizma base, and 0.35 mg / mL sodium azide, and was performed at 37°C for 90 minutes. To facilitate the penetration of the etching solution between the fibers, the nonwoven fabric soaked in the etching solution was ultrasonicated in an ultrasonic bath for 5 minutes. After etching, the nonwoven fabric was washed in a distilled water ultrasonic bath for 5 minutes and then dried. The dried nonwoven fabric was subjected to plasma surface treatment at 700W for 4 minutes to obtain the nonwoven fabric body.

[0064] (4) The MXene solution (1.38 mg / mL) was uniformly sprayed on the surface of the non-woven fabric body by a small sprayer, each time for 4 seconds, and dried with a hair dryer. The spraying was repeated 26 times on each side to obtain a MXene coating modified PLA non-woven fabric with a MXene coating content of 10.14 wt%, which was named MNF-2.

[0065] Example 3:

[0066] The preparation method of the MXene coating modified PLA non-woven fabric comprises the following steps:

[0067] (1) 3 g of LiF was added to 60 mL of 7M HCl and stirred for 5 minutes, then 3 g of Ti3AlC2 powder was slowly added and stirred at 40°C for 24 hours to obtain an acid product. The acid product was washed with deionized water and centrifuged at 3500 rpm for 60 seconds until the supernatant pH≥6. The obtained precipitate was dispersed in deionized water, ice bath ultrasonic treatment for 60 minutes, and then centrifuged at 3500 rpm for 60 minutes to remove the precipitate to obtain the supernatant, which was the MXene solution.

[0068] (2) The PLA raw material was dried at 100°C under reduced pressure, and the dried raw material was dissolved in HFIP with a purity of 99% to obtain a 12 wt% PLA solution. Electrospinning was performed using the solution, and the obtained wet non-woven fabric was dried at 35°C under reduced pressure until the non-woven fabric contained 8 wt% HFIP. The dried non-woven fabric was placed in a muffle furnace at 110°C for 30 minutes. In order to prevent the non-woven fabric from shrinking and deforming during the crystallization process, an aluminum plate was used to press it tightly, and a dry non-woven fabric was obtained.

[0069] (3) Alkaline etching was carried out in a 0.1 mol / L potassium hydroxide solution at room temperature for 15 minutes, and the solvent of the solution was a mixture of methanol and distilled water with a mass ratio of 2:3. The etching solution for enzyme etching contained 0.8 mg / mL Bacillus, 12.2 mg / mL trizma base and 0.4 mg / mL sodium azide, and etching was carried out at 37°C for 30 minutes. In order to facilitate the penetration of the etching solution between the fibers, the non-woven fabric immersed in the etching solution was ultrasonicated in an ultrasonic bath for 5 minutes. After etching, the non-woven fabric was washed in a distilled water ultrasonic bath for 5 minutes and dried. The dried non-woven fabric was subjected to plasma surface treatment, and the working power was 800W for 5 minutes to obtain a non-woven fabric body.

[0070] (4) The MXene solution (1.43 mg / mL) was uniformly sprayed on the surface of the non-woven fabric body by a small sprayer, each time for 5 seconds, and dried with a hair dryer. The spraying was repeated 34 times on each side to obtain a MXene coating modified PLA non-woven fabric with a MXene coating content of 18.87 wt%, which was named MNF-3.

[0071] Comparative Example 1:

[0072] Other conditions are the same as example 3, except that the enzyme etching in step (3) is omitted.

[0073] The obtained MXene coating modified PLA nonwoven fabric is named as PNF-1.

[0074] Comparative example 2:

[0075] Other conditions are the same as example 3, except that the alkali etching in step (3) is omitted.

[0076] The obtained MXene coating modified PLA nonwoven fabric is named as PNF-2.

[0077] Comparative example 3:

[0078] Other conditions are the same as example 3, except that step (3) is:

[0079] (3) The alkali etching is carried out in a 0.1 mol / L potassium hydroxide solution at room temperature for 15 minutes, wherein the solvent of the solution is a mixture of methanol and distilled water with a mass ratio of 2:3. The etching solution for enzyme etching contains 2 mg / mL lipase, and the etching is carried out at 45°C for 480 minutes. In order to facilitate the penetration of the etching solution between the fibers, the nonwoven fabric immersed in the etching solution is ultrasonically treated in an ultrasonic bath for 5 minutes. After the etching is completed, the nonwoven fabric is washed in a distilled water ultrasonic bath for 5 minutes and dried. The dried nonwoven fabric is subjected to plasma surface treatment at 800 W for 5 minutes to obtain a nonwoven fabric body.

[0080] The obtained MXene coating modified PLA nonwoven fabric is named as PNF-3.

[0081] Comparative example 4:

[0082] Other conditions are the same as example 3, except that the plasma surface treatment in step (3) is omitted.

[0083] The obtained MXene coating modified PLA nonwoven fabric is named as PNF-4.

[0084] Comparative example 5:

[0085] Other conditions are the same as example 3, except that the alkali etching and enzyme etching in step (3) are omitted.

[0086] The obtained MXene coating modified PLA nonwoven fabric is named as PNF-5.

[0087] Comparative example 6:

[0088] Other conditions are the same as example 3, except that the alkali etching, enzyme etching and plasma surface treatment in step (3) are omitted.

[0089] The obtained MXene coating modified PLA nonwoven fabric is named as PNF-6.

[0090] Performance test:

[0091] The resistivity, EMI shielding efficiency, maximum temperature under different conditions and carbon residue rate at 800 ℃ of the different PLA nonwoven fabrics obtained in the examples and comparative examples were determined respectively, and the determination methods were as follows:

[0092] Resistivity: four-probe tester (Ningbo Ruikai Micro Intelligence Technology Co., Ltd.);

[0093] EMI shielding efficiency: Agilent E5071C network analyzer, EMI shielding efficiency was calculated according to EN55022 test standard;

[0094] Maximum temperature under different conditions: xenon light source system (CEL-PF300-T9, Beijing Zhongjiaojinyuan Technology Co., Ltd.) and outdoor sunlight were used to evaluate the photo-thermal conversion performance of the fabric. Infrared thermal imaging (FLIR E60) was used to record the temperature change of the fabric surface in real time.

[0095] Carbon residue rate at 800 ℃: thermogravimetric analyzer (PerkinElmer TGA4000), under nitrogen environment, the heating rate was 10 °C / min, and the temperature range was 25 ℃-800 ℃.

[0096] Table 1. Electro-thermal / photo-thermal performance of MXene coating modified PLA nonwoven fabric obtained in different examples

[0097]

[0098] As can be seen from Table 1, with the increase of the content of MXene coating, the resistivity of the MXene coating modified PLA nonwoven fabric continuously decreases, while the EMI shielding efficiency increases, showing good electrical conductivity and electromagnetic shielding property. Under the voltage of 4V or 5V, the higher the content of MXene coating, the higher the maximum temperature that the nonwoven fabric can reach, which can reach up to 263℃, proving that the electro-thermal conversion rate and thermal stability performance of the nonwoven fabric are high; under the voltage of 5V, MNF-2 can melt 4.5 cm 3 of ice in 32 min, and the temperature of the ice-water mixture can be raised from 1.2 ℃ to 12.1 ℃; MNF-3 is sewn together with ordinary cotton fabric, and under the condition of applying 2V voltage, the surface temperature of the cotton fabric can be raised to 60 ℃ within 60s. Under sunlight, MNF-3 can convert light energy into heat energy, and the temperature can be raised to 76.8℃, proving that the photo-thermal conversion property of the nonwoven fabric is also very outstanding.

[0099] Comparing the performance data of PNF-1, PNF-2 and PNF-5 with MNF-3, it can be concluded that etching has a very large impact on the resistivity of the PLA non-woven fabric, and the resistivity can be as high as 45.78 Ω / sq without etching, which is very unfavorable for its application in wearable electronic devices. Comparing PNF-3 and MNF-3, although the impact of lipase enzyme etching on resistivity, EMI shielding efficiency and maximum temperature under different conditions is not as great as that of PNF-1, PNF-2 and PNF-5, the time required for lipase to complete saturated etching is at least 8 hours, while the time required for Bacillus-trizma-sodium azide system to complete saturated etching is only 30 minutes, which is much less efficient than the method provided by the present application. Comparing PNF-4 and MNF-3, the impact of no plasma surface treatment on the maximum temperature under different conditions is not great, but the resistivity and EMI shielding efficiency are still reduced. PNF-6 is far inferior to MNF-3 in various performance aspects and cannot be applied in wearable electronic devices at all.

[0100] In summary, the present application first uses polylactic acid as the matrix and prepares a crystalline polylactic acid non-woven fabric by the electrospinning method. In order to improve the surface roughness, an alkali treatment and enzyme treatment method are used. The Bacillus solution system used in the present application has a higher treatment efficiency than the existing technology lipase system. After treatment, the water contact angle of the polylactic acid non-woven fabric is reduced, the surface hydrophilic property is enhanced, and the treatment efficiency is higher. Then, a conductive network is obtained by using a spray drying process, and by adjusting the drying cycle number, a MXene coating modified fabric with a MXene content of 18.87 wt% and a sheet resistance of 4.36 Ω / sq is obtained. Due to the low MXene content in the modified fabric and the porous structure of the fabric, the modified fabric maintains good flexibility and air permeability. The low resistance of the MXene modified fabric makes it have excellent electro-thermal conversion performance. Under an external voltage of 5 V, the surface temperature of MNF-3 can reach 263 ℃. Due to the reflection and absorption of electromagnetic waves on the surface of the fabric, the shielding efficiency of a single layer of fabric is as high as 35.7 dB, and the shielding efficiency of a double layer of fabric is as high as 62.9 dB. Moreover, the thermal stability of the non-woven fabric is very excellent, and the carbon residue rate at 800 ℃ is as high as 51.6%, the amount of flammable gas generated during thermal degradation is low, and the flame retardancy is excellent. In addition, polylactic acid is a high molecular polymer polymerized from lactic acid monomers produced by microbial fermentation. Polylactic acid can be decomposed without pollution in nature through the action of soil, water or microorganisms. The introduction of polylactic acid into the field of non-woven fabrics actively responds to the call for sustainable green development. Therefore, the present application provides a new method for the development of multifunctional wearable textiles, which has a wide application prospect in the fields of intelligent wearable devices, flexible electric heaters, shielding clothing, multifunctional textiles and the like.

[0101] The preferred embodiments of the present application are described in detail above in combination with the embodiments, but the present application is not limited to the specific details in the above-described embodiments, and various simple modifications can be made to the technical solutions of the present application within the technical concept of the present application, and these simple modifications all belong to the protection scope of the present application.

[0102] In addition, it should be noted that each specific technical feature described in the above specific embodiments can be combined in any appropriate manner without contradiction, and in order to avoid unnecessary repetition, various possible combinations are not described again by the present application.

[0103] In addition, various different embodiments of the present application can also be combined in any manner, as long as it does not deviate from the idea of the present application, and it should also be considered as disclosed by the present application.

Claims

1. A method for preparing a PLA nonwoven fabric modified with an MXene coating layer, characterized by, The preparation method comprises the following steps: (1) etching Ti3AlC2 with HCl and LiF to obtain an acid product, washing the acid product and centrifuging until the supernatant pH is greater than or equal to 6, and then dispersing the obtained precipitate into deionized water, ice-bath ultrasonic treatment, and centrifuging to obtain the supernatant, i.e. a MXene solution; (2) dissolving PLA raw materials in an organic solvent to obtain a PLA solution, electrospinning to obtain a wet non-woven fabric, drying and crystallizing to obtain a dry non-woven fabric; (3) etching and plasma surface treatment of the dry non-woven fabric obtained in step (2) to obtain a non-woven fabric body, wherein the etching comprises alkali etching and enzyme etching, the alkali etching is etching the dry non-woven fabric in an alkali solution with a concentration of 0.05-0.1 mol / L at room temperature for 15-120 minutes, the enzyme etching is etching the dry non-woven fabric in a solution containing 0.6-0.8 mg / mL Bacillus, 10-12.2 mg / mL trizma base and 0.3-0.4 mg / mL sodium azide at 37°C for 30-180 minutes, and the power of the plasma surface treatment is 600-800 W and the time is 3-5 minutes; (4) spraying the MXene solution obtained in step (1) on the surface of the non-woven fabric body obtained in step (3), the concentration of the MXene solution is 1.30-1.43 mg / mL, the spraying time is 3-5 seconds, and each side is sprayed 16-34 times, and a MXene-coated modified PLA non-woven fabric is obtained after drying.

2. The production method according to claim 1, characterized by, Step (1) comprises: adding LiF and Ti3AlC2 with a mass ratio of 1:(0.8-1.5) into HCl with a concentration of 6-9 M, stirring at 35-40°C for 20-24 hours to obtain an acid product, washing the acid product with deionized water and centrifuging at 3000-3500 rpm for 30-60 seconds until the supernatant pH is greater than or equal to 6, dispersing the obtained precipitate into deionized water, ice-bath ultrasonic treatment for 50-60 minutes, and centrifuging at 3000-3500 rpm for 50-60 minutes to obtain the supernatant, i.e. a MXene solution.

3. The preparation method according to claim 1, characterized in that, In step (2), the PLA raw material is racemic PLA; and / or The concentration of the PLA solution is 10-12 wt%.

4. The method of claim 1, wherein, In step (2), the organic solvent is selected from one or more of hexafluoroisopropanol and dichloromethane.

5. The production method according to any one of claims 1 to 4, characterized by, In step (2), the PLA raw material is dried at 95-100°C under reduced pressure; and / or The wet non-woven fabric is dried at 30-35°C under reduced pressure until the non-woven fabric contains 7.5-8 wt% of the organic solvent; and / or The crystallization is performed by pressing with a plate at 100-110°C for 25-30 minutes.

6. The method of claim 1, wherein, The alkali solution is a sodium hydroxide and / or potassium hydroxide solution.

7. A MXene-coated modified PLA non-woven fabric prepared by the preparation method of any one of claims 1-6.

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