Method for producing a polytetrafluoroethylene composite membrane

Abstract

This invention belongs to the field of membrane separation technology, specifically relating to a method for preparing a polytetrafluoroethylene (PTFE) composite membrane. The preparation method includes: (1) dissolving a spinning aid, a barium source, a titanium source, and a manganese source in a composite solvent, and then electrospinning to obtain precursor fibers; subsequently, blending the precursor fibers with a grain refiner, and heat-treating to obtain doped ferroelectric fiber bundles; (2) further polymerizing organic acids, inorganic acids, conductive fillers, and conductive polymers with monomers and oxidants to finally obtain a conductive polyaniline composite; (3) incorporating Mxene and the conductive polyaniline composite into an aqueous PTFE emulsion, and then further incorporating the doped ferroelectric fiber bundles and stirring to obtain a suspension; the suspension is then coated, post-treated, and kept warm to obtain a PTFE composite membrane. This invention improves the long-term fouling resistance of the PTFE membrane by doping the doped ferroelectric fiber bundles, the conductive polyaniline composite, Mxene, and PTFE.

Description

Technical Field

[0001] This invention belongs to the field of membrane separation technology, and specifically relates to a method for preparing a polytetrafluoroethylene composite membrane. Background Technology

[0002] Hydrogen energy is an ideal alternative energy source due to its clean, efficient, and sustainable characteristics. However, traditional hydrogen production methods such as natural gas reforming and coal gasification rely on fossil fuels and generate large amounts of carbon dioxide. Freshwater electrolysis for hydrogen production is limited by the scarcity of freshwater resources, making large-scale application difficult. Since coastal areas are often rich in renewable energy sources such as wind and solar power, seawater electrolysis for hydrogen production is considered a feasible solution for large-scale green hydrogen production. However, direct seawater electrolysis easily leads to chlorine evolution at the anode, competing with oxygen evolution and resulting in the formation of toxic chlorine gas or hypochlorite, which corrodes the electrode. Calcium and magnesium ions in seawater easily precipitate near the cathode, clogging the electrode active sites. Due to the low ion concentration, near-neutral pH, and impurities in seawater, the reaction kinetics are slow, requiring higher overpotentials to drive the reaction, resulting in insufficient energy efficiency. Microorganisms and organic impurities can deposit in the electrolyzer, limiting the long-term safety of seawater electrolysis hydrogen production systems.

[0003] Therefore, a gas-liquid interface is constructed between seawater and the electrolyte using a membrane material. Utilizing phase transition migration and the saturated vapor pressure difference between seawater and water in the electrolyte as the mass transfer driving force, water in the seawater migrates across the membrane in gaseous form to the electrolyte. This completely isolates various impurities in the seawater, achieving direct hydrogen production from seawater without desalination, side reactions, or additional energy consumption. Currently, polytetrafluoroethylene (PTFE) is a common choice for this membrane material. However, PTFE's long-term antifouling ability is still limited; it easily adsorbs microorganisms and organic pollutants from seawater. The deposition of these pollutants on the PTFE membrane surface can lead to membrane pore blockage, reducing water vapor transfer efficiency. In severe cases, frequent shutdowns for chemical cleaning are required, increasing maintenance costs and reducing hydrogen production efficiency.

[0004] Chinese patent CN111996811A discloses a two-component waterproof and breathable PTFE membrane, comprising a modified PTFE membrane and a modified polyurethane membrane coated on its surface. The modified polyurethane membrane includes graphene oxide. The graphene oxide is prepared by sequentially adding sodium nitrate and concentrated sulfuric acid for mixing, adding potassium chlorate and heating in a water bath, adding deionized water and raising the temperature, and adding an aqueous solution of hydrogen peroxide to continue the reaction. PVA, an emulsion B containing PTFE resin, and nano-silica are mixed and calcined to remove PVA, thus obtaining the modified PTFE membrane.

[0005] According to the patent, the graphene oxide surface in the polyurethane coating contains abundant oxygen-containing functional groups; the modified PTFE membrane has a hollow structure, and the nano-silica further increases the surface roughness and porosity of the modified PTFE membrane. These factors will affect the hydrophobic properties of the PTFE matrix, which is not conducive to isolating impurities such as chloride ions in seawater, and will also increase the risk of microbial attachment in seawater, affecting the antifouling performance of the modified PTFE membrane. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a polytetrafluoroethylene (PTFE) composite membrane to improve the anti-fouling performance of the PTFE membrane during long-term use.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] The method for preparing the polytetrafluoroethylene composite film of the present invention includes the following steps:

[0009] (1) The spinning aid, barium source, titanium source and manganese source are dissolved in a composite solvent and electrospinned to obtain precursor fibers; then the precursor fibers are mixed with a grain refiner and heat-treated to obtain doped ferroelectric fiber bundles.

[0010] (2) Dissolve organic acid, inorganic acid, conductive filler and conductive polymer in water to obtain solution A; dissolve monomer in organic solvent to obtain solution B; dissolve oxidant in water to obtain solution C; add solution B and solution C to solution A to carry out polymerization reaction, and after post-treatment, obtain conductive polyaniline composite;

[0011] (3) Mxene, conductive polyaniline composite, polytetrafluoroethylene aqueous emulsion, surfactant and deionized water are stirred, and doped ferroelectric fiber bundles are added and stirred to obtain a suspension; the suspension is coated, post-treated and kept warm to obtain a polytetrafluoroethylene composite film.

[0012] in:

[0013] The spinning aid is one of polyvinylpyrrolidone, sodium polyacrylate or polycaprolactone, the barium source is barium acetate, the titanium source is titanium tetraisopropoxide or titanium acetylacetonate, the manganese source is manganese acetate, and the composite solvent is prepared by mixing acetic acid and ethanol in a mass ratio of (0.7~1):1.

[0014] The mass ratio of the spinning aid, barium source, titanium source, manganese source and composite solvent is (100~120):(170~200):150:(150~180):(900~1100); during electrospinning, the spinning voltage is 15~20kV, the spinning nozzle flow rate is 25.5~40.5mL / h, and the collection distance of the precursor fiber is 10~15cm.

[0015] In step (1), the grain refiner is nano-zirconia; the mass ratio of precursor fiber to grain refiner is 300:(10~25).

[0016] In step (1), the heat treatment includes preheating and calcination in an atmosphere. The preheating temperature is 300~400℃ and the preheating time is 10~20min. The atmosphere is a mixture of oxygen and nitrogen, wherein the volume fraction of oxygen is 3.2~3.5%. The calcination temperature is 820~860℃ and the calcination time is 1.5~2h.

[0017] In step (2), the organic acid is dodecylbenzene sulfonic acid, the inorganic acid is boric acid, the conductive filler is sulfonated graphene, and the conductive polymer is conductive polyaniline; the mass ratio of organic acid, inorganic acid, conductive filler, conductive polymer, and water is (75~90):25:(9~12):(65~85):(400~600). The conductive polyaniline is doped with polystyrene sulfonic acid (PSSA), which is a water-soluble conductive polymer.

[0018] In step (2), the monomer is aniline, and the organic solvent is one of ethanol, acetone or ethylene glycol monomethyl ether; the ratio of monomer to organic solvent is (180~260):(650~950), where the monomer is in g and the organic solvent is in mL; the oxidant is one of ammonium persulfate, sodium persulfate or potassium persulfate, and the mass ratio of oxidant to water is (80~120):(400~800).

[0019] In step (2), solution A is based on the mass of inorganic acid, solution B is based on the mass of monomer, and solution C is based on the mass of oxidant. The mass ratio of solution A, solution B and solution C is 25:(180~260):(80~120).

[0020] In step (2), the polymerization reaction temperature is 0~6℃ and the polymerization reaction time is 2~3h; during the polymerization reaction, solution A is stirred and the stirring speed is 70~90rpm; the post-treatment includes adding acetone and water to wash until the water phase washed out is clear and colorless, and the washing is completed.

[0021] In step (3), the mass ratio of Mxene, conductive polyaniline composite, polytetrafluoroethylene aqueous emulsion, surfactant, doped ferroelectric fiber bundle and deionized water is 13:(120~140):(900~1100):(36~70):(20~30):(300~500), wherein the solid content of polytetrafluoroethylene aqueous emulsion is 55~65%, and the surfactant is one of Tritonx-100, Tween-80 or Span-80.

[0022] In step (3), the thickness of the polytetrafluoroethylene composite film is 15~20µm, and the post-treatment includes drying at a temperature of 70~85℃; heat preservation at a temperature of 330~340℃ and a heat preservation time of 8~12min.

[0023] ZrO2 nanoparticles can hinder grain growth in doped ferroelectric fiber bundles, improve the mechanical strength and thermal stability of doped ferroelectric fiber bundles, prevent local phase transformation at high temperatures, and affect electrical conductivity; Mn doping is beneficial to the enhancement of anisotropy and phase stability of ferroelectric fiber bundle lattices.

[0024] The beneficial effects of this invention are as follows:

[0025] (1) Due to the phase change mass transfer effect on the seawater side, a large amount of water vapor enters the electrolyte side through the micropores on the PTFE composite membrane. The pressure difference and other effects in this process will induce the doped ferroelectric fiber bundle to generate an internal electric field, forming charge carriers (free electrons and holes). The charge carriers can further interact with dissolved oxygen to form reactive oxygen species (ROS), promoting the degradation of organic matter.

[0026] (2) In this invention, the doped ferroelectric fiber bundle is combined with Mxene, conductive polyaniline composite and polytetrafluoroethylene. Mxene, as a two-dimensional conductive layered material, has metallic conductivity, high specific surface area and abundant surface functional groups, which makes it easy to form interfacial polarization with metal oxides such as doped ferroelectric fiber bundles and construct continuous electron channels. In addition, Mxene has a certain degree of flexibility, which can help the doped ferroelectric fiber bundle maintain conductivity continuity when deformed.

[0027] As a conductive polymer, the conductive polyaniline composite possesses a fluidity unmatched by Mxene and doped ferroelectric fiber bundles. During the fabrication of PTFE composite films, it can encapsulate doped ferroelectric fiber bundles, filling voids between Mxene layers and reducing contact resistance between layers and between layers and doped ferroelectric fiber bundles. Mxene and the conductive polyaniline composite together form a three-dimensional conductive network, effectively contacting and covering surface defects in the ferroelectric material, reducing carrier recombination centers. Furthermore, the conjugated backbone of the conductive polyaniline composite allows holes to migrate between polymer chains, while free electrons can migrate along the two-dimensional conductive channels of Mxene. This combined effect reduces the risk of recombination between free electrons and holes, ensuring that the charge carriers generated by the doped ferroelectric fiber bundles are effectively used for catalytic degradation of organic matter.

[0028] PTFE, as a film-forming matrix, can regulate the distribution, porosity, and hydrophilicity-hydrophobic balance of MXene, conductive polyaniline composites, and doped ferroelectric fiber bundles, promoting the formation of heterogeneous interfaces between MXene, conductive polyaniline composites, and doped ferroelectric fiber bundles. These interfaces can promote electronic coupling between different materials, optimize the electronic energy level structure at the interface, and thus reduce the energy barrier of the catalytic reaction. PTFE's high chemical stability and good mechanical strength provide a robust support and protective layer for the ferroelectric fiber bundles, preventing the loss of active components. In addition, the uniform hydrophobic porous structure on the PTFE surface provides an environment for the polarization of the doped ferroelectric fiber bundles, ensuring the uniform and stable formation of charge carriers on the PTFE composite film surface and in the porous structure.

[0029] (3) Sulfonated graphene itself has high electronic conductivity and specific surface area, which enables aniline monomers to be uniformly dispersed and polymerized in situ on the surface of sulfonated graphene, thereby forming a continuous conductive network of sulfonated graphene / polyaniline, significantly reducing the resistance of polyaniline and improving the overall conductivity. When polystyrene sulfonate is added to aniline monomers, conductive polymers such as polyaniline can be pre-composite with aniline monomers and sulfonated graphene through π-π conjugation and other interactions, promoting the in-situ polymerization reaction of aniline monomers. At the same time, the conductive polyaniline has good flexibility and stretchability, which can enhance the interfacial compatibility between inorganic materials such as sulfonated graphene and organic matrices such as PTFE, and prevent phase separation or cracks from occurring during subsequent high-temperature treatment.

[0030] Conductive polyaniline is polystyrene sulfonate-doped polyaniline. Dodecylbenzenesulfonic acid and boric acid can further optimize its doping level, preventing dedoping during polymerization and maintaining its high conductivity. Besides acting as an organic acid dopant, dodecylbenzenesulfonic acid has an amphiphilic structure, allowing it to adsorb onto the surface of sulfonated graphene, enhancing its dispersibility in solution, preventing the stacking of sulfonated graphene sheets, and providing more active sites for subsequent polymerization. The benzene ring structure of dodecylbenzenesulfonic acid can form π-π stacks with the aromatic ring structure in polyaniline, enhancing electronic coupling between molecular chains and promoting hole migration in the polymer network. Boric acid, in addition to acting as an inorganic acid dopant, can also provide a mild acidic environment with ammonium persulfate, controlling the oxidative polymerization rate of aniline and preventing excessively rapid polymerization leading to structural inhomogeneity. Furthermore, the long-chain structure of dodecylbenzenesulfonic acid can effectively encapsulate the conductive polyaniline composite, while boric acid forms a stable dopant with dodecylbenzenesulfonic acid through hydrogen bonding, enhancing the stability of the conductive polyaniline composite. Attached Figure Description

[0031] Figure 1 The image shows a scanning electron microscope image of the PTFE composite membrane prepared in Example 1. Detailed Implementation

[0032] The present invention will now be described and illustrated in detail with reference to the embodiments.

[0033] The raw materials used in the following examples and comparative examples are all commercially available products. Mxene was provided by Beijing Beike Nanotechnology Co., Ltd.; nano-zirconia was provided by Shandong Guoci Functional Materials Co., Ltd.; sulfonated graphene was provided by Suzhou Carbon-rich Graphene Technology Co., Ltd.; and conductive polyaniline, with polystyrene sulfonic acid (PSSA) as the dopant, a water-soluble conductive polymer, was provided by Nanjing Bermuda Biotechnology Co., Ltd.

[0034] Example 1

[0035] Acetic acid and ethanol were mixed in a mass ratio of 0.85:1 to form a composite solvent. 120g of polyvinylpyrrolidone, 180g of barium acetate, 150g of titanium acetylacetonate, and 150g of manganese acetate were added to 1000g of the composite solvent and mixed well. The mixture was then passed into an electrospinning device. Under the conditions of 15kV voltage, nozzle flow rate of 40.5mL / h, and collection distance of 15cm, the mixture was spun onto aluminum foil to obtain precursor fibers. 300g of precursor fibers were mixed with 25g of nano-zirconia and placed in a muffle furnace. The mixture was preheated at 350℃ for 15min, then heated to 860℃ and calcined in an oxygen / nitrogen mixed atmosphere of 3.2% (vol%) for 1.8h to obtain doped ferroelectric fiber bundles.

[0036] Dissolve 80g of dodecylbenzenesulfonic acid, 25g of boric acid, 10g of sulfonated graphene, and 70g of conductive polyaniline in 400g of deionized water and stir until no obvious particles are visible to obtain solution A. Add 220g of aniline to 800mL of ethanol and mix well to obtain solution B. Add 120g of ammonium persulfate to 400g of deionized water and mix well to obtain solution C. Turn on the mechanical stirring and ice-water bath of solution A, and add solutions B and C to solution A at 0℃ and 70rpm, and continue stirring for 3h to carry out the polymerization reaction. Add acetone and deionized water to the system after the polymerization reaction is completed to wash, and obtain organic phase and aqueous phase. Continue until the aqueous phase washed with deionized water is clear and colorless to obtain conductive polyaniline composite.

[0037] 13g Mxene, 140g conductive polyaniline composite, 1100g PTFE aqueous emulsion with 60% solid content, 58g Tween-80, and 500g deionized water were mixed. 30g doped ferroelectric fiber bundles were then added and mixed thoroughly to obtain a suspension. The suspension was evenly coated onto a substrate using a spin-coating method. A sample with a standard size of 1020×100mm was taken and placed in an oven to dry at 80℃ to constant weight, obtaining a dry film. The dry film was then kept at 330℃ for 12 minutes in an inert atmosphere. After removal and natural cooling, a PTFE composite film was obtained. The scanning electron microscope image of the film surface is shown below. Figure 1 As shown, the film thickness is 20µm.

[0038] Example 2

[0039] Acetic acid and ethanol were mixed in a 1:1 mass ratio to form a composite solvent. 100g of polycaprolactone, 200g of barium acetate, 150g of tetraisopropoxide, and 180g of manganese acetate were added to 900g of the composite solvent and mixed well. The mixture was then passed into an electrospinning device. Under the conditions of 20kV voltage, nozzle flow rate of 25.5mL / h, and collection distance of 10cm, the mixture was spun onto aluminum foil to obtain precursor fibers. 300g of precursor fibers were mixed with 10g of nano-zirconia and placed in a muffle furnace. The mixture was preheated at 300℃ for 20min, then heated to 820℃ and calcined for 2h in an oxygen / nitrogen mixed atmosphere with 3.5% (vol%) oxygen to obtain doped ferroelectric fiber bundles.

[0040] 90g of dodecylbenzenesulfonic acid, 25g of boric acid, 12g of sulfonated graphene, and 65g of conductive polyaniline were dissolved in 600g of deionized water and stirred until no obvious particles were observed, yielding solution A. 260g of aniline was added to 650mL of acetone and mixed well, yielding solution B. 95g of sodium persulfate was added to 600g of deionized water and mixed well, yielding solution C. Mechanical stirring and an ice-water bath were started for solution A. Under conditions of 6℃ and 80rpm, solutions B and C were added to solution A, and stirring was continued for 2.5h to carry out the polymerization reaction. Acetone and deionized water were added sequentially to the system after the polymerization reaction was completed to wash, yielding an organic phase and an aqueous phase. The aqueous phase washed with deionized water became clear and colorless, yielding the conductive polyaniline composite.

[0041] 13g Mxene, 130g conductive polyaniline composite, 1000g PTFE aqueous emulsion with 65% solid content, 70g Span-80, and 400g deionized water were mixed. 26g doped ferroelectric fiber bundles were then added and mixed thoroughly to obtain a suspension. The suspension was evenly coated onto a substrate using a spin-coating method. A sample with a standard size of 1020×100mm was taken and placed in an oven to dry at 70℃ to constant weight, obtaining a dry film. The dry film was then kept at 340℃ for 8 minutes in an inert atmosphere. After removal and natural cooling, a PTFE composite film with a thickness of 18µm was obtained.

[0042] Example 3

[0043] Acetic acid and ethanol were mixed in a mass ratio of 0.7:1 to form a composite solvent. 115g of sodium polyacrylate, 170g of barium acetate, 150g of titanium acetylacetonate, and 170g of manganese acetate were added to 1100g of the composite solvent and mixed well. The mixture was then passed into an electrospinning device. Under the conditions of 18kV voltage, nozzle flow rate of 30.5mL / h, and collection distance of 12cm, the mixture was spun onto aluminum foil to obtain precursor fibers. 300g of precursor fibers were mixed with 18.5g of nano-zirconia and placed in a muffle furnace. The mixture was preheated at 400℃ for 10min, then heated to 850℃ and calcined for 1.5h in an oxygen / nitrogen mixed atmosphere of 3.3% (vol%) to obtain doped ferroelectric fiber bundles.

[0044] 75g of dodecylbenzenesulfonic acid, 25g of boric acid, 9g of sulfonated graphene, and 85g of conductive polyaniline were dissolved in 500g of deionized water and stirred until no obvious particles were observed, yielding solution A. 180g of aniline was added to 950mL of ethylene glycol monomethyl ether and mixed well, yielding solution B. 80g of potassium persulfate was added to 800g of deionized water and mixed well, yielding solution C. Mechanical stirring and an ice-water bath were started for solution A. Under conditions of 3℃ and 90rpm, solutions B and C were added to solution A, and stirring was continued for 2 hours to carry out the polymerization reaction. Acetone and deionized water were added sequentially to the system after the polymerization reaction was completed to wash, yielding an organic phase and an aqueous phase. The conductive polyaniline composite was obtained after the aqueous phase washed with deionized water became clear and colorless.

[0045] 13g Mxene, 120g conductive polyaniline composite, 900g PTFE aqueous emulsion with 55% solid content, 36g Tritonx-100 and 300g deionized water were mixed; 20g doped ferroelectric fiber bundles were added and mixed well to obtain a suspension; the suspension was evenly spread on a substrate by spin coating, and a sample with a standard size of 1020×100mm was taken and placed in an oven to dry to constant weight at 85℃ to obtain a dry film; then the dry film was kept in an inert atmosphere at 335℃ for 10min; it was taken out and cooled naturally to obtain a PTFE composite film with a thickness of 15µm.

[0046] Comparative Example 1

[0047] Without adding doped ferroelectric fiber bundles, the remaining operation process and raw materials used are the same as in Example 1.

[0048] Comparative Example 2

[0049] Without adding Mxene, the rest of the operation process and raw materials used are the same as in Example 1.

[0050] Comparative Example 3

[0051] Without adding conductive polyaniline composite, the remaining operation process and raw materials used are the same as in Example 1.

[0052] Comparative Example 4

[0053] Without adding sulfonated graphene, the rest of the operation process and raw materials used are the same as in Example 1.

[0054] Comparative Example 5

[0055] The conductive polyaniline was not added, and the rest of the operation process and raw materials used were the same as in Example 1.

[0056] Comparative Example 6

[0057] Without adding nano-zirconia, the remaining operation process and raw materials used are the same as in Example 1.

[0058] Comparative Example 7

[0059] Without adding dodecylbenzenesulfonic acid and boric acid, the remaining procedures and raw materials used were the same as in Example 1, and polyaniline was prepared. The measured conductivity of the polyaniline was as low as 10. -9 ~10 -10 The conductivity is on the order of S / cm, which is in a low conductivity state and cannot meet the experimental requirements. When dodecylbenzenesulfonic acid or boric acid is not added, the polyaniline is prepared, and the measured conductivity of the polyaniline is only about 1 / 70 of the conductivity of the conductive polyaniline composite in Example 1, which also cannot meet the experimental requirements.

[0060] Implementation effect evaluation

[0061] Prepare the test solution, in which the amount of NaCl is 32.5 g·L⁻¹. -1 The concentration of MgCl2·6H2O is 1.6 g·L. -1 The concentration of CaCl2·2H2O is 0.65 g·L. -1 The concentration of Na2SO4 is 0.3 g·L⁻¹. -1 Adjust the pH to 8.0, then add humic acid, lysine, and bentonite and mix well, with humic acid at 100.5 mg / L. -1 Lysine 25.0 mg·L -1 22.5 mg·L of bentonite -1 .

[0062] Multiple PTFE composite membranes were installed between the two tanks, maintaining the pressure in the test liquid tank at least 12 kPa higher than that in the electrolyte tank. Heating was turned on, with the temperature in the test liquid tank at 70°C and the temperature in the electrolyte tank at 58°C. A current of 0.3 A·cm was applied. -2 After 10 minutes, the hydrogen flow meter was turned on, and the hydrogen volume flow rate (L / h) was recorded every 12 hours thereafter. During this period, raw materials such as humic acid could be added at any time to maintain the stable concentrations of humic acid, lysine, and bentonite. The experiment was stopped after 120 hours. Specific test data are shown in Table 1.

[0063] Table 1 Hydrogen flow rate test data

[0064]

[0065] As can be seen from Table 1, the hydrogen volumetric flow rate in Examples 1-3 can be stably maintained at a high level during the 120-hour test period, and the hydrogen production efficiency and stability are both excellent, indicating that the PTFE composite membrane of the present invention has a good effect in pollution resistance in high-concentration organic pollutant environments.

Claims

1. A method for preparing a polytetrafluoroethylene composite film, characterized in that, Includes the following steps: (1) The spinning aid, barium source, titanium source and manganese source are dissolved in a composite solvent and electrospinned to obtain precursor fibers; then the precursor fibers are mixed with a grain refiner and heat-treated to obtain doped ferroelectric fiber bundles. The composite solvent is prepared by mixing acetic acid and ethanol in a mass ratio of (0.7~1):

1. (2) Dissolve organic acid, inorganic acid, conductive filler and conductive polymer in water to obtain solution A; dissolve monomer in organic solvent to obtain solution B; dissolve oxidant in water to obtain solution C; add solution B and solution C to solution A to carry out polymerization reaction, and after post-treatment, obtain conductive polyaniline composite; The conductive filler is sulfonated graphene, the conductive polymer is conductive polyaniline, and the monomer is aniline. (3) Mxene, conductive polyaniline composite, polytetrafluoroethylene aqueous emulsion, surfactant and deionized water are stirred, and doped ferroelectric fiber bundles are added and stirred to obtain a suspension; the suspension is coated, post-treated and kept warm to obtain a polytetrafluoroethylene composite film.

2. The method for preparing the polytetrafluoroethylene composite film according to claim 1, characterized in that, The spinning aid is one of polyvinylpyrrolidone, sodium polyacrylate or polycaprolactone, the barium source is barium acetate, the titanium source is titanium tetraisopropoxide or titanium acetylacetone, and the manganese source is manganese acetate.

3. The method for preparing the polytetrafluoroethylene composite film according to claim 1, characterized in that, The mass ratio of spinning aid, barium source, titanium source, manganese source and composite solvent is (100~120):(170~200):150:(150~180):(900~1100); during electrospinning, the spinning voltage is 15~20kV, the spinning nozzle flow rate is 25.5~40.5mL / h, and the collection distance of precursor fibers is 10~15cm.

4. The method for preparing the polytetrafluoroethylene composite film according to claim 1, characterized in that, In step (1), the grain refiner is nano-zirconia; the mass ratio of precursor fiber to grain refiner is 300:(10~25).

5. The method for preparing the polytetrafluoroethylene composite film according to claim 1, characterized in that, In step (1), the heat treatment includes preheating and calcination in an atmosphere. The preheating temperature is 300~400℃ and the preheating time is 10~20min. The atmosphere is a mixture of oxygen and nitrogen, wherein the volume fraction of oxygen is 3.2~3.5%. The calcination temperature is 820~860℃ and the calcination time is 1.5~2h.

6. The method for preparing the polytetrafluoroethylene composite film according to claim 1, characterized in that, In step (2), the organic acid is dodecylbenzenesulfonic acid and the inorganic acid is boric acid; the mass ratio of organic acid, inorganic acid, conductive filler, conductive polymer and water is (75~90):25:(9~12):(65~85):(400~600).

7. The method for preparing the polytetrafluoroethylene composite membrane according to claim 1, characterized in that, In step (2), the organic solvent is one of ethanol, acetone or ethylene glycol monomethyl ether; the ratio of monomer to organic solvent is (180~260):(650~950), where the monomer is in g and the organic solvent is in mL; the oxidant is one of ammonium persulfate, sodium persulfate or potassium persulfate, and the mass ratio of oxidant to water is (80~120):(400~800); solution A is based on the mass of inorganic acid, solution B is based on the mass of monomer, and solution C is based on the mass of oxidant, and the mass ratio of solution A, solution B and solution C is 25:(180~260):(80~120).

8. The method for preparing the polytetrafluoroethylene composite membrane according to claim 1, characterized in that, In step (2), the polymerization reaction temperature is 0~6℃ and the polymerization reaction time is 2~3h; during the polymerization reaction, solution A is stirred and the stirring speed is 70~90rpm.

9. The method for preparing the polytetrafluoroethylene composite membrane according to claim 1, characterized in that, In step (3), the mass ratio of Mxene, conductive polyaniline composite, polytetrafluoroethylene aqueous emulsion, surfactant, doped ferroelectric fiber bundle and deionized water is 13:(120~140):(900~1100):(36~70):(20~30):(300~500), wherein the solid content of polytetrafluoroethylene aqueous emulsion is 55~65%, and the surfactant is one of Tritonx-100, Tween-80 or Span-80.

10. The method for preparing the polytetrafluoroethylene composite film according to claim 1, characterized in that, In step (3), the thickness of the polytetrafluoroethylene composite film is 15~20µm; the heat preservation temperature is 330~340℃ and the heat preservation time is 8~12min.

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