Ultra-long acting self-powered frictional filtration ortho-composite polylactic acid nanofiber membrane and preparation method thereof

Abstract

This invention discloses a triboelectrically self-powered stereocomposite polylactic acid (PLA) nanofiber membrane for ultra-long-lasting filtration and its preparation method. Copper nanowires are prepared using reduction technology and adhered to the surface of a polylactic acid nonwoven fabric to form an electrode membrane. Subsequently, a highly oriented stereocomposite PLA nanofiber membrane is obtained through stereocomposite bonding of PLLA and PDLA and electrospinning. Finally, these are assembled into a triboelectrically self-powered stereocomposite PLA nanofiber membrane. This PLA fiber filter membrane exhibits a tensile strength of 18–21 MPa, a surface potential of 6–16 kV, a Tg temperature of 52.42–54.58 °C, a PM2.5 filtration efficiency of 98%–99.9%, a PM0.3 filtration efficiency of 95%–99.5%, and a bacterial filtration efficiency of over 99%. It possesses high mechanical properties, high surface potential, high heat resistance, antibacterial properties, and long-lasting filtration, extending the application of biodegradable materials in the field of air filtration.

Description

Technical Field

[0001] This invention relates to the field of fully degradable fiber membrane materials for high-efficiency air filtration, specifically to triboelectric self-powered stereocomposite polylactic acid nanofiber membranes for ultra-long-lasting filtration and their preparation methods. Background Technology

[0002] PM2.5 removal filters are mainly divided into two types: porous membrane filters and fiber filters. The latter is considered to have more potential due to its high surface area, light weight, low pressure drop, and ease of synthesis. However, traditional fiber filters have not been widely developed and applied due to their unavoidable drawbacks such as low filtration efficiency, poor mechanical properties, and poor thermal stability.

[0003] Dust particles have become a special route for virus transmission. Therefore, in order to protect human health and life, it is urgent to develop a highly efficient air ultrafine particulate matter filtration material in response to complex air dust and virus pollution.

[0004] Currently, methods that improve filtration efficiency and lifespan by incorporating electret materials into filter media have been widely adopted. However, most electret materials are susceptible to environmental factors such as humidity and temperature. Without proper storage, the static charge within the electret is easily lost and wasted, significantly reducing filtration efficiency. Furthermore, since most of the materials used are recalcitrant, they are difficult to effectively degrade in a green manner after use, posing a potential risk of secondary pollution. Therefore, given these factors, the research and development of green bio-based high-efficiency filter materials is particularly important.

[0005] Therefore, providing a triboelectrically self-powered stereochemical composite polylactic acid nanofiber membrane for ultra-long-lasting filtration that can provide charge to fiber filter membranes for electrostatic adsorption over a long period of time, with significant application effects, and whose preparation method is simple, efficient, and easily industrialized, is a problem worthy of further research. Summary of the Invention

[0006] The purpose of this invention is to provide a triboelectrically self-powered stereocomposite polylactic acid nanofiber membrane for ultra-long-lasting filtration that can provide charge to a fiber filter membrane for electrostatic adsorption over a long period of time, with significant application effects. Furthermore, the preparation method is simple, efficient, and easily industrialized.

[0007] The objective of this invention is achieved as follows:

[0008] The triboelectric self-powered three-dimensional composite polylactic acid nanofiber membrane for ultra-long-lasting filtration includes a highly oriented three-dimensional composite polylactic acid nanofiber membrane and electrode membranes located on both sides of the highly oriented three-dimensional composite polylactic acid nanofiber membrane. The highly oriented three-dimensional composite polylactic acid nanofiber membrane and the electrode membrane are arranged in a three-layer sandwich structure.

[0009] The high-orientation stereocomposite polylactic acid nanofiber membrane has an average diameter of 30 nm to 800 nm and a thickness of 50 μm to 300 μm.

[0010] A method for preparing a triboelectrically powered stereocomposite polylactic acid nanofiber membrane for ultra-long-lasting filtration includes the following steps:

[0011] Step S1, Preparation of spinning solution: Dissolve L-polylactic acid (PLLA) and D-polylactic acid (PDLA) separately in solvents, mix them evenly to obtain a stereocomposite polylactic acid spinning solution;

[0012] Step S2, Preparation of highly oriented stereocomposite polylactic acid nanofiber membrane: The stereocomposite polylactic acid spinning solution obtained in step S1 is used to prepare a highly oriented stereocomposite polylactic acid nanofiber membrane by electrospinning.

[0013] Step S3, Preparation of copper nanowires: Dissolve the copper source in a solvent, add a reducing agent, and obtain uniformly dispersed copper nanowires by microwave-assisted synthesis.

[0014] Step S4, Electrode film preparation: The copper nanowires obtained in step S3 are uniformly adhered to polylactic acid nonwoven fabric, and the electrode film is obtained after drying.

[0015] Step S5: Assembly of triboelectric self-powered stereocomposite polylactic acid nanofiber membrane: Assemble the electrode membrane obtained in step S4 and the highly oriented stereocomposite polylactic acid nanofiber membrane obtained in step S2 into a triboelectric self-powered stereocomposite polylactic acid nanofiber membrane.

[0016] The solvent in step S1 is at least one of N,N-dimethylformamide, dichloromethane, chloroform, and hexafluoroisopropanol. The mass ratio of L-polylactic acid (PLLA) to D-polylactic acid (PDLA) in the stereocomposite polylactic acid spinning solution is 1:50 to 50:1. The mass fraction of PLLA and D-polylactic acid (PDLA) in the spinning solution is 5 wt% to 30 wt%, with the remainder being solvent. The dissolution temperature is 10 to 50°C.

[0017] In step S2, the output voltage of electrospinning is 25~50 kV, the solution consumption rate is 0.3~2.5 mL / h, the spinning winding speed is 2000~5000 rpm, the spinning temperature is 10~40℃, and the humidity is 30%~60%.

[0018] In step S3, the copper source is at least one of copper chloride, copper hydroxide, and copper oxide; the solvent is at least one of water, methanol, ethanol, ethylene glycol, glycerol, and isopropanol; the mass fraction of the copper source is 0.1wt% to 3wt%; the reducing agent is at least one of glucose, tetradecylamine, hexadecylamine, octadecylamine, and vitamin C; the mass ratio of the reducing agent to the copper source is 1:5 to 1:1; and the remainder is solvent.

[0019] In step S3, the output power of microwave-assisted synthesis is 100~1000W, the reaction temperature is 120~250℃, and the reaction time is 0.1h~1.5h; the diameter of the copper nanowires is 5~40 nm and the length is 20~70 μm.

[0020] In step S4, the average fiber diameter of the polylactic acid nonwoven fabric is 10~50 μm, and the basis weight of the polylactic acid nonwoven fabric is 10~100 g / m².

[0021] The adhesion process in step S4 includes at least one of ultrasonic vibration, stirring, spraying, filtration, drop coating, eccentric spin coating, and impregnation.

[0022] The beneficial effects of this invention are as follows: Copper nanowires are prepared by reduction technology and then adhered to the surface of polylactic acid (PLA) nonwoven fabric to form an electrode film. Subsequently, a highly oriented stereocomposite PLA nanofiber membrane is obtained through stereocomposite composite of PLLA and PDLA and electrospinning. Finally, these membranes are assembled into a triboelectric self-powered stereocomposite PLA nanofiber membrane. This PLA fiber filter membrane exhibits a tensile strength of 18–21 MPa, a surface potential of 6–16 kV, a Tg temperature of 52.42–54.58 °C, a PM2.5 filtration efficiency of 98%–99.9%, a PM0.3 filtration efficiency of 95%–99.5%, and a bacterial filtration efficiency of over 99%. It possesses significant characteristics such as high mechanical properties, high surface potential, high heat resistance, antibacterial properties, and long-lasting filtration, effectively extending the application of biodegradable materials in the field of air filtration. Attached Figure Description

[0023] Figure 1 This is a flowchart of the present invention;

[0024] Figure 2 The copper nanowires adhered to the surface of the electrode film in Example 1 were observed using a scanning electron microscope (SEM) according to the present invention.

[0025] Figure 3 This is a SEM image of the highly oriented stereocomposite polylactic acid nanofiber membrane at 2000 rpm in Example 1 of the present invention;

[0026] Figure 4This is a SEM image of the highly oriented stereocomposite polylactic acid nanofiber membrane at 3000 rpm in Example 2 of the present invention. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] Example 1

[0029] A method for preparing a triboelectrically powered stereocomposite polylactic acid nanofiber membrane for ultra-long-lasting filtration includes the following steps:

[0030] Step S1: Preparation of spinning solution: At 50℃, 0.1g of PLLA was completely dissolved in 5ml of NN dimethylformamide to obtain solution 11, and 0.5g of PDLA was completely dissolved in 5ml of hexafluoroisopropanol to obtain solution 2. Then, solution 11 and solution 12 were mixed and stirred evenly to obtain the stereocomposite polylactic acid spinning solution.

[0031] Step S2: Preparation of highly oriented stereocomposite polylactic acid nanofiber membrane: Take 2 ml of the stereocomposite polylactic acid spinning solution obtained in step S1 into a syringe, and spin it into a highly oriented stereocomposite polylactic acid nanofiber membrane under the following conditions: output voltage of 40 kV, solution propulsion speed of 2.5 ml / h, fiber winding speed of 2000 rpm, spinning temperature of 40℃, and humidity of 50%. The resulting highly oriented stereocomposite polylactic acid nanofiber membrane has an average diameter of 800 nm and a thickness of 300 μm.

[0032] Step S3: Preparation of copper nanowires: 0.1 g of copper chloride and 0.1 g of octadecylamine were uniformly mixed in 100 ml of aqueous solution. The mixture was then transferred to a microwave-assisted synthesizer and reacted at 100 W output power and 120 °C for 1 h to obtain a copper nanowire dispersion. The obtained copper nanowires had a diameter of 10–40 nm and a length of 40–70 μm.

[0033] Step S4: Electrode film preparation: Polylactic acid nonwoven fabric with a fiber diameter of 50 μm and a basis weight of 100 g / ㎡ is used as the substrate material. Copper nanowire dispersion is uniformly sprayed onto the surface of polylactic acid nonwoven fabric by spraying. After it is completely dried, the electrode film is obtained.

[0034] Step S5: Assembly of triboelectric self-powered stereocomposite polylactic acid nanofiber membrane: The electrode membrane obtained in step S3 and the highly oriented stereocomposite polylactic acid nanofiber membrane obtained in step S2 are assembled into a triboelectric self-powered stereocomposite polylactic acid nanofiber membrane according to the structure of "electrode membrane - highly oriented stereocomposite polylactic acid nanofiber membrane - electrode membrane".

[0035] Example 2

[0036] A method for preparing a triboelectrically powered stereocomposite polylactic acid nanofiber membrane for ultra-long-lasting filtration includes the following steps:

[0037] Step S1: Preparation of spinning solution: At 10℃, 0.2g of PLLA was completely dissolved in 5ml of chloroform to obtain solution 21, and 0.3g of PDLA was completely dissolved in 5ml of dichloromethane to obtain solution 22. Then, solution 21 and solution 22 were mixed and stirred evenly to obtain the stereocomposite polylactic acid spinning solution.

[0038] Step S2: Preparation of highly oriented stereocomposite polylactic acid nanofiber membrane: Take 2 ml of the stereocomposite polylactic acid spinning solution obtained in Step S1 into a syringe, and spin it into a highly oriented stereocomposite polylactic acid nanofiber membrane under the following conditions: output voltage of 30 kV, solution propulsion speed of 1.5 ml / h, fiber winding speed of 3000 rpm, spinning temperature of 10℃, and humidity of 30%. The resulting highly oriented stereocomposite polylactic acid nanofiber membrane has an average fiber diameter of 600 nm and a membrane thickness of 150 μm.

[0039] Step S3: Preparation of copper nanowires: 1g of copper oxide and 2g of glucose were uniformly mixed in 100ml of aqueous alcohol solution (water:ethanol=1:1), and then the mixed solution was transferred to a microwave-assisted synthesizer and reacted at 400W output power and 150℃ for 0.5h to obtain a copper nanowire dispersion; the diameter of the obtained copper nanowires was 10~30 nm and the length was 40~60 μm.

[0040] Step S4: Electrode film preparation: Polylactic acid nonwoven fabric with a fiber diameter of 80 μm and a basis weight of 50 g / m2 is used as the substrate material. Copper nanowire dispersion is uniformly adhered to the surface of polylactic acid nonwoven fabric by ultrasonic vibration. After it is completely dried, the electrode film is obtained.

[0041] Step S5: Assembly of triboelectric self-powered stereocomposite polylactic acid nanofiber membrane: The electrode membrane obtained in step S3 and the highly oriented stereocomposite polylactic acid nanofiber membrane obtained in step S2 are assembled into a triboelectric self-powered stereocomposite polylactic acid nanofiber membrane according to the structure of "electrode membrane - highly oriented stereocomposite polylactic acid nanofiber membrane - electrode membrane".

[0042] Example 3

[0043] A method for preparing a triboelectrically powered stereocomposite polylactic acid nanofiber membrane for ultra-long-lasting filtration includes the following steps:

[0044] Step S1: Preparation of spinning solution: At 30℃, 0.5g of PLLA was completely dissolved in 5ml of NN dimethylformamide to obtain solution 31, and 0.1g of PDLA was completely dissolved in 5ml of dichloromethane to obtain solution 32. Then, solution 31 and solution 32 were mixed and stirred evenly to obtain the spinning solution.

[0045] Step S2: Preparation of highly oriented stereocomposite polylactic acid nanofiber membrane: Take 2 ml of the stereocomposite polylactic acid spinning solution obtained in step S1 into a syringe, and spin it into a highly oriented stereocomposite polylactic acid nanofiber membrane under the following conditions: output voltage of 50 kV, solution propulsion speed of 2 ml / h, fiber winding speed of 4000 rpm, spinning temperature of 30℃, and humidity of 40%. The resulting highly oriented stereocomposite polylactic acid nanofiber membrane has an average fiber diameter of 100 nm and a membrane thickness of 80 μm.

[0046] Step S3: Preparation of copper nanowires: 1 g of copper oxide and 5 g of hexadecylamine were uniformly mixed in 100 ml of alcohol / glycerol solution (ethanol:glycerol = 1:1). The mixed solution was then transferred to a microwave-assisted synthesizer and reacted at 1000 W output power and 250 °C for 0.1 h to obtain a copper nanowire dispersion. The diameter of the obtained copper nanowires was 5~30 nm and the length was 30~60 μm.

[0047] Step S4: Electrode film preparation: Polylactic acid nonwoven fabric with a fiber diameter of 30 μm and a basis weight of 40 g / m2 is used as the substrate material. Copper nanowire dispersion is uniformly adhered to the surface of polylactic acid nonwoven fabric by drop coating. After it is completely dried, the electrode film is obtained.

[0048] Step S5: Assembly of triboelectric self-powered stereocomposite polylactic acid nanofiber membrane: The electrode membrane obtained in step S3 and the highly oriented stereocomposite polylactic acid nanofiber membrane obtained in step S2 are assembled into a triboelectric self-powered stereocomposite polylactic acid nanofiber membrane according to the structure of "electrode membrane - highly oriented stereocomposite polylactic acid nanofiber membrane - electrode membrane".

[0049] Example 4

[0050] A method for preparing a triboelectrically powered stereocomposite polylactic acid nanofiber membrane for ultra-long-lasting filtration includes the following steps:

[0051] Step S1: Preparation of spinning solution: At 35°C, 1.5g of PLLA was completely dissolved in 5ml of NN dimethylformamide to obtain solution 41, and 1.5g of PDLA was completely dissolved in 5ml of chloroform to obtain solution 42. Then, solution 41 and solution 42 were mixed and stirred evenly to obtain the stereocomposite polylactic acid spinning solution.

[0052] Step S2: Preparation of highly oriented stereocomposite polylactic acid nanofiber membrane: Take 2 ml of the stereocomposite polylactic acid spinning solution obtained in step S1 into a syringe, and spin it into a highly oriented stereocomposite polylactic acid nanofiber membrane under the following conditions: output voltage of 40 kV, solution propulsion speed of 0.3 ml / h, fiber winding speed of 5000 rpm, spinning temperature of 25℃, and humidity of 60%. The resulting highly oriented stereocomposite polylactic acid nanofiber membrane has an average fiber diameter of 30 nm and a membrane thickness of 50 μm.

[0053] Step S3: Preparation of copper nanowires: 3g of copper hydroxide and 6g of vitamin C were uniformly mixed in 100ml of aqueous solution. The mixed solution was then transferred to a microwave-assisted synthesizer and reacted at 800W output power and 200℃ for 0.3h to obtain a copper nanowire dispersion. The diameter of the obtained copper nanowires was 5~25 nm and the length was 20~55 μm.

[0054] Step S4: Electrode film preparation: Polylactic acid nonwoven fabric with a fiber diameter of 10 μm and a basis weight of 10 g / m2 is used as the substrate material. Copper nanowire dispersion is uniformly adhered to the surface of polylactic acid nonwoven fabric by impregnation. After it is completely dried, the electrode film is obtained.

[0055] Step S5: Assembly of triboelectric self-powered stereocomposite polylactic acid nanofiber membrane: The electrode membrane obtained in step S3 and the highly oriented stereocomposite polylactic acid nanofiber membrane obtained in step S2 are assembled into a triboelectric self-powered stereocomposite polylactic acid nanofiber membrane according to the structure of "electrode membrane - highly oriented stereocomposite polylactic acid nanofiber membrane - electrode membrane".

[0056] Comparative Example 1 (low fiber winding speed selected)

[0057] The triboelectrically powered stereocomposite polylactic acid fiber nanofiber membrane was prepared using the method described in Example 1. The difference was that the fiber winding speed during electrospinning was 100 rpm in this example. Specifically, S11: Preparation of spinning solution: At 50℃, 0.1g of PLLA was completely dissolved in 5ml of N,N-dimethylformamide to prepare solution 11, and 0.5g of PDLA was completely dissolved in 5ml of hexafluoroisopropanol to prepare solution 12. Then, solution 11 and solution 12 were mixed and stirred evenly to prepare a stereocomposite polylactic acid spinning solution; 2ml of the prepared stereocomposite polylactic acid spinning solution was placed in a syringe, and under the conditions of a set output voltage of 40 kV, a solution propulsion speed of 2.5 ml / h, a fiber winding speed of 100 rpm, a spinning temperature of 40℃, and a humidity of 50%, a highly oriented polylactic acid fiber membrane was spun to obtain a stereocomposite polylactic acid fiber membrane with an average fiber diameter of 2 μm and a membrane thickness of 300 μm; 0.1g of copper chloride and 0.1g of... Octadecylamine was uniformly mixed in 100 ml of aqueous solution, and then the mixture was transferred to a microwave-assisted synthesizer and reacted at 120 °C for 1 h at an output power of 100 W to obtain a copper nanowire dispersion. The diameter of the obtained copper nanowires was 10-40 nm and the length was 40-70 μm. Subsequently, polylactic acid nonwoven fabric with a fiber diameter of 100 μm and a basis weight of 100 g / m2 was used as the substrate material, and the copper nanowire dispersion was uniformly sprayed onto the surface of the polylactic acid nonwoven fabric by spraying. After it was completely dried, an electrode film was obtained. The obtained electrode film and the obtained stereocomposite polylactic acid fiber film were assembled into a triboelectric self-powered stereocomposite polylactic acid nanofiber film according to the structure of "electrode film-stereocomposite polylactic acid fiber film-electrode film".

[0058] Comparative Example 2 (without using triboelectrically powered polyemulsion nanofiber membrane)

[0059] The triboelectric self-powered stereocomposite polylactic acid (PLA) nanofiber membrane was prepared using the method described in Example 2. The difference is that this example does not use a stereocomposite PLA nanofiber membrane. Specifically, 1 g of copper oxide and 2 g of glucose were uniformly mixed in 100 ml of a water-ethanol solution (water:ethanol = 1:1). The mixture was then transferred to a microwave-assisted synthesizer and reacted at 400 W output power and 150 °C for 0.5 h to obtain a copper nanowire dispersion. The obtained copper nanowires had a diameter of 10–30 nm and a length of 40–60 μm. PLA nonwoven fabric with a fiber diameter of 80 μm and a basis weight of 50 g / m² was used as the substrate material. The copper nanowire dispersion was uniformly adhered to the surface of the PLA nonwoven fabric by ultrasonic vibration. After complete drying, the electrode membrane was obtained. The obtained electrode membrane was then assembled with polylactic acid nonwoven fabric (average fiber diameter of 80 μm and basis weight of 50 g / m2) according to the structure of "electrode membrane - polylactic acid nonwoven fabric - electrode membrane" to form a triboelectric self-powered three-dimensional composite polylactic acid nanofiber membrane.

[0060] Comparative Example 3 (without electrode film)

[0061] The method of Example 3 was basically adopted to prepare a triboelectric self-powered stereocomposite polylactic acid (PLLA) nanofiber membrane, except that no electrode membrane was added in this example. Specifically, at 30°C, 0.5 g of PLLA was completely dissolved in 5 ml of N,N-dimethylformamide to obtain solution 31, and 0.1 g of PDLA was completely dissolved in 5 ml of dichloromethane to obtain solution 32. Then, solutions 31 and 32 were mixed and stirred evenly to obtain a stereocomposite polylactic acid spinning solution. 2 ml of the prepared stereocomposite polylactic acid spinning solution was placed in a syringe, and under the conditions of a set output voltage of 50 kV, a solution feed rate of 2 ml / h, a fiber winding rate of 4000 rpm, and a spinning temperature of 30°C, a highly oriented stereocomposite polylactic acid nanofiber membrane was spun to obtain a highly oriented stereocomposite polylactic acid nanofiber membrane with an average fiber diameter of 100 nm and a membrane thickness of 80 μm. The highly oriented stereocomposite polylactic acid nanofiber membrane was used as the triboelectric self-powered stereocomposite polylactic acid nanofiber membrane.

[0062] Structural characterization and performance testing

[0063] Scanning electron microscopy observation: The microstructure of the membrane electrode and the highly oriented polylactic acid fiber membrane was observed using a field emission scanning electron microscope (model JSM-7900F, NEC). Figure 2 , 3 and 4).

[0064] Dielectric constant test: The dielectric constant of the highly oriented stereocomposite polylactic acid nanofiber film was tested using a dielectric constant tester (model WK-6500B, Wayne Kerr, UK).

[0065] DSC test: The Tg value of the highly oriented stereocomposite polylactic acid nanofiber membrane was tested using a differential scanning calorimeter.

[0066] Tensile property testing: The obtained highly oriented stereocomposite polylactic acid nanofiber membrane was cut into tensile test strips. The tensile properties of the fiber membrane were tested using a universal tensile testing machine (model 4403, sensor 100 N) from Instron, USA, according to the ASTM D638-2003 standard for testing the tensile properties of plastics. At least three parallel test samples were required for each group, and the average value was taken as the result.

[0067] Surface potential test: The surface potential of the triboelectric self-powered stereocomposite polylactic acid nanofiber membrane was tested using a non-contact electrostatic meter (VM54XQS, Quatek, USA). The test height was 2 cm, and the temperature and humidity were kept constant at 25 ℃ and 45%. Twenty data points were randomly collected for each sample and the average value was taken.

[0068] Filtration performance testing: The air filtration performance and pressure drop parameters of triboelectric self-powered three-dimensional composite polylactic acid nanofiber membranes with the same area (113.04 cm2) were tested using an LZC-K type automatic filter media tester (Suzhou Huada Instrument Equipment Co., Ltd.). The gas flow rate was set to 85 L / min, and the particle size range of NaCl atomized particles generated by the aerosol generator was 0.3~2.5 μm. At least 3 different locations were tested for each group of fiber membranes, and the average value of the results was taken.

[0069] Antimicrobial activity test: The microbial indicators specified in GB19083-2010 "Medical Protective Masks" are used for testing. The standards are: Staphylococcus aureus, coliform bacteria, Pseudomonas aeruginosa, hemolytic streptococci and fungal colonies must not be detected, and the total bacterial count must not exceed 20 CFU / g; the bacterial filtration efficiency of YY 0469~2011 "Technical Requirements for Medical Surgical Masks" must not be less than 95%.

[0070] Experimental results: such as Figure 2 As shown, the copper nanowires adhered to the electrode film in Example 1 exhibit relatively uniform adhesion to the nonwoven fibers, with good conductivity and the ability to conduct electrostatic charges. Figure 3 and 4 The SEM images show that the polylactic acid fibers obtained at high winding speeds are finer in diameter, more uniform in fiber distribution, and have a denser and more uniform pore distribution, which is more conducive to the capture and adsorption of micro-particulate matter in the air.

[0071] Table 1 compares the dielectric constant test results of triboelectric self-powered stereocomposite polylactic acid nanofiber membranes. It can be found that the dielectric constant of the highly oriented stereocomposite polylactic acid nanofiber membrane increases continuously with the increase of fiber winding speed. This indicates that at high winding speed, the strong tensile force enables the molecular structure of the fiber to be arranged in an orderly manner, and the stereocomposite effect between PLLA and PDLA is more compact, resulting in increased fiber crystallinity and dielectric constant. The low dielectric constant in Comparative Example 1 is mainly due to the inability to polarize the dipoles in the fiber at low winding speed. The stereocomposite effect between PLLA and PDLA alone can only slightly increase the dielectric constant of the fiber membrane.

[0072] Table 1 also compares the test results of Tg values, mechanical properties, and surface potential of the triboelectric self-powered stereocomposite polylactic acid nanofiber membranes obtained in the examples and comparative examples. It can be found that the Tg value of the highly oriented stereocomposite polylactic acid nanofiber membrane continuously increases with the increase of fiber winding speed. In Examples 1-4 and Comparative Example 1, the integrity of the spinning structure and the doping and adhesion of copper nanowires significantly improve the mechanical properties of the triboelectric self-powered stereocomposite polylactic acid nanofiber membrane system, fully meeting the mechanical performance requirements of fiber filter membranes in the air filtration field. The weaker mechanical properties of Comparative Example 2 are mainly due to the relatively weak mechanical properties of the selected polylactic acid nonwoven fabric. The weak mechanical properties of Comparative Example 3 are due to the lack of copper nanowire doping and adhesion, resulting in a decrease in the mechanical properties of the fiber membrane.

[0073] Meanwhile, Tables 1 and 2 also tested the surface potential retention and filtration efficiency of the triboelectric self-powered stereocomposite polylactic acid nanofiber membrane for ultrafine particles. The data in the tables show that the highly oriented stereocomposite polylactic acid nanofiber membrane prepared by electrospinning retains its surface charge well. After 15 days, the loss of charge on the fiber surface is minimal, indicating the membrane's long-lasting electrostatic adsorption capacity. Furthermore, under an airflow of 85 L / min, the surface potential of the triboelectric self-powered stereocomposite polylactic acid nanofiber membrane actually increased. This indicates that under high-speed wind vibration, the membrane undergoes shear changes due to the mechanical force exerted by the wind, leading to an ordered arrangement of dipoles within the membrane and generating dipole polarization. This induces dipole charges on the fiber surface, which are then retained on the copper nanowires due to their conductivity, creating a potential difference. The electrostatic adsorption of the fiber membrane was further improved, which greatly enhanced the long-term filtration efficiency for ultrafine particles (the filtration efficiency of PM0.3 and PM2.5 in Example 4 reached 99.5% and 99.9%, respectively). In contrast, in Comparative Examples 1, 2 and 3, the low winding speed had little effect on fiber orientation, and the disorder of polylactic acid nonwoven fibers and the absence of copper nanowire retention greatly reduced the ability of the fiber membrane to generate and retain charges, resulting in a smaller adsorption effect on ultrafine particles (the filtration efficiency of PM0.3 and PM2.5 was <85%).

[0074] Table 3 tests the antimicrobial activity of the triboelectric self-powered stereocomposite polylactic acid nanofiber membrane. The data in the table show that the bacterial filtration efficiency of the examples is all above 99%, while the antimicrobial activity of Comparative Examples 1 and 2, although slightly lower, is still >95%. This indicates that the highly oriented stereocomposite polylactic acid nanofiber membrane can effectively inactivate microorganisms. This is mainly because copper nanowires have good antimicrobial activity, which can inactivate microorganisms. Secondly, the good triboelectric self-powered performance of the highly oriented stereocomposite polylactic acid nanofiber membrane ensures that the surface of the fiber membrane has a high surface charge, which also plays a bactericidal role. Therefore, the combination of these two factors achieves comprehensive inactivation of bacteria and strong antimicrobial activity. The high bacterial filtration efficiency of Comparative Examples 1 and 2 is mainly achieved through the antimicrobial activity of copper nanowires, while the bacterial filtration of Comparative Example 3 mainly relies on the antibacterial activity achieved through the surface charge of the fiber membrane.

[0075] By comparing the data in the embodiments and comparative examples, it can be found that the electrode membrane provided in this invention can effectively retain charge, greatly improve the conductivity of nonwoven fabrics, and has excellent antibacterial properties. Furthermore, the preparation of the highly oriented stereocomposite polylactic acid nanofiber membrane, due to the improved crystallinity of the polylactic acid fiber membrane caused by the stereocomposite structure and the improved orientation of the fiber membrane caused by the high winding speed, significantly improves the characteristics of the polylactic acid fiber membrane, such as low dielectric constant and weak shear piezoelectric properties. This greatly improves the performance of generating charge changes under low mechanical force, enabling the triboelectric effect to be achieved even at low flow rates during breathing, causing the fiber membrane to generate dipole charges, thereby improving the ability to efficiently capture and adsorb microparticles. Since the generation of dipole charges is caused by dipole changes, the triboelectrically self-powered stereocomposite polylactic acid nanofiber membrane can continuously generate dipole charges, ensuring that there is always charge on the fiber membrane and guaranteeing its long-term filtration performance. Therefore, the preparation of triboelectric self-powered stereocomposite polylactic acid nanofiber membranes can meet the requirements of efficient filtration of ultrafine particles in the air, and the action time is long, which greatly expands the application prospects of bio-based degradable materials in the field of air filtration.

[0076] Table 1. Test results of dielectric constant, Tg value, tensile properties and surface potential of triboelectric self-powered stereocomposite polylactic acid nanofiber film

[0077]

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[0079]

Claims

1. A method for preparing a triboelectrically self-powered stereocomposite polylactic acid nanofiber membrane for ultra-long-lasting filtration, characterized in that: Includes the following steps: Step S1, Preparation of spinning solution: Dissolve L-polylactic acid and D-polylactic acid separately in a solvent, mix them evenly to obtain a stereocomposite polylactic acid spinning solution; the mass ratio of L-polylactic acid to D-polylactic acid in the stereocomposite polylactic acid spinning solution is 1:50~50:1, the mass fraction of L-polylactic acid and D-polylactic acid in the spinning solution is 5wt%~30wt%, the remainder is solvent, and the dissolution temperature is 10~50℃; Step S2, Preparation of highly oriented stereocomposite polylactic acid nanofiber membrane: The stereocomposite polylactic acid spinning solution obtained in step S1 is used to prepare a highly oriented stereocomposite polylactic acid nanofiber membrane by electrospinning. Step S3, Preparation of copper nanowires: Dissolve the copper source in a solvent, add a reducing agent, and obtain uniformly dispersed copper nanowires by microwave-assisted synthesis. Step S4, Electrode film preparation: The copper nanowires obtained in step S3 are uniformly adhered to polylactic acid nonwoven fabric, and the electrode film is obtained after drying. Step S5: Assembly of triboelectric self-powered stereocomposite polylactic acid nanofiber membrane: Assemble the electrode membrane obtained in step S4 and the highly oriented stereocomposite polylactic acid nanofiber membrane obtained in step S2 into a triboelectric self-powered stereocomposite polylactic acid nanofiber membrane; the electrode membrane is located on both sides of the highly oriented stereocomposite polylactic acid nanofiber membrane, and the highly oriented stereocomposite polylactic acid nanofiber membrane and the electrode membrane are arranged in a three-layer sandwich structure.

2. The method of claim 1, wherein the method of preparing the ultra-long acting friction self-powered filtration standing composite polylactic acid nanofiber membrane is characterized by: The solvent in step S1 is at least one of N,N-dimethylformamide, dichloromethane, trichloromethane, and hexafluoroisopropanol.

3. The method for preparing the triboelectric self-powered stereochemical composite polylactic acid nanofiber membrane for ultra-long-lasting filtration according to claim 1, characterized in that: In step S2, the output voltage of electrospinning is 25~50 kV, the solution consumption rate is 0.3~2.5 mL / h, the spinning winding speed is 2000~5000 rpm, the spinning temperature is 10~40℃, and the humidity is 30%~60%.

4. The method of claim 1, wherein the method of preparing the ultra-long acting friction self-powered ortho-composite polylactic acid nanofiber membrane for filtration is characterized by: In step S3, the copper source is at least one of copper chloride, copper hydroxide, and copper oxide; the solvent is at least one of water, methanol, ethanol, ethylene glycol, glycerol, and isopropanol; the mass fraction of the copper source is 0.1wt% to 3wt%; the reducing agent is at least one of glucose, tetradecylamine, hexadecylamine, octadecylamine, and vitamin C; the mass ratio of the reducing agent to the copper source is 1:5 to 1:1; and the remainder is solvent.

5. The method of claim 1, wherein the method of preparing the ultra-long acting friction self-powered ortho-composite polylactic acid nanofiber membrane for filtration is characterized by: In step S3, the output power of microwave-assisted synthesis is 100~1000W, the reaction temperature is 120~250℃, and the reaction time is 0.1h~1.5h; the diameter of the copper nanowires is 5~40 nm and the length is 20~70 μm.

6. The method for preparing the triboelectric self-powered stereocomposite polylactic acid nanofiber membrane for ultra-long-lasting filtration according to claim 1, characterized in that: In step S4, the average fiber diameter of the polylactic acid nonwoven fabric is 10~50 μm, and the basis weight of the polylactic acid nonwoven fabric is 10~100 g / ㎡.

7. The method for preparing the triboelectric self-powered stereocomposite polylactic acid nanofiber membrane for ultra-long-lasting filtration according to claim 1, characterized in that: The adhesion process in step S4 includes at least one of ultrasonic vibration, stirring, spraying, filtration, drop coating, eccentric spin coating, and impregnation.

8. A triboelectrically self-powered three-dimensional composite polylactic acid nanofiber membrane for ultra-long-lasting filtration, characterized in that: The membrane was prepared using the method described in any one of claims 1-7 for ultra-long-lasting filtration with triboelectric self-powered stereocomposite polylactic acid nanofibers.

9. The triboelectric self-powered three-dimensional composite polylactic acid nanofiber membrane for ultra-long-lasting filtration according to claim 8, characterized in that: The high-orientation stereocomposite polylactic acid nanofiber membrane has an average diameter of 30 nm to 800 nm and a thickness of 50 μm to 300 μm.

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