Preparation method of hydrophobic and oleophobic PTFE membrane

Abstract

The invention relates to a preparation method of a hydrophobic and oleophobic PTFE membrane, and belongs to the technical field of PTFE membrane preparation. Aiming at the problems that an existing PTFE membrane is difficult to construct a micro-nano multi-stage coarse structure and has a synergistic effect with low chemical surface energy, the hydrophobic and oleophobic properties are insufficient and the structural stability is poor, the key points of the technical scheme provided by the invention are as follows: firstly, carrying out ethanol ultrasonic cleaning on a PTFE base membrane of 20-30 microns, and carrying out vacuum plasma treatment to form a nano coarse structure and oxygen-containing polar group active sites; then, under the protection of nitrogen, immersing into an ethanol solution containing perfluorodecyltriethoxysilane, dibutyltin dilaurate and nano cellulose whiskers, carrying out hot-pressing compounding with PET non-woven fabric, carrying out heat treatment, and finally, coating with a fluorine-containing polymer nano fiber layer through an electrostatic spinning process; the composite hydrophobic layer with the synergistic effect of a micro-nano multistage coarse structure and chemical low surface energy is formed, the water contact angle is larger than or equal to 155 degrees, and the oil contact angle is larger than or equal to 130 degrees. The PTFE film prepared by the preparation method can be used in the fields of waterproof breathable materials, self-cleaning surfaces, oil-resistant packaging and the like.

Description

Technical Field

[0001] The present invention relates to the field of PTFE membranes. More specifically, the present invention relates to a method for preparing a hydrophobic and oleophobic PTFE membrane. Background Art

[0002] In the field of materials, the demand for thin films with hydrophobic and oleophobic properties is increasing day by day, and they are widely used in many fields such as waterproof and breathable clothing, self-cleaning surfaces, and oil-proof packaging. However, traditional thin films have many deficiencies in terms of hydrophobic and oleophobic properties.

[0003] For currently common ordinary thin films, their surface energy is relatively high, and water molecules and oil molecules are easily attached and spread on their surfaces, making it difficult to achieve an ideal hydrophobic and oleophobic effect. Taking ordinary polymer thin films as an example, the water contact angle is often much lower than 150°, and the oil contact angle is lower than 120°. In practical applications, such as when used in waterproof clothing, once there is heavy rain or high environmental humidity, moisture is likely to penetrate the thin film, causing the clothing to lose its waterproof function and affecting the wearing experience; in the field of food packaging, if the thin film cannot effectively repel oil, the oil is likely to penetrate the packaging, which will not only pollute the external environment but also may accelerate the spoilage of food and shorten the food shelf life.

[0004] There are also many problems with some existing methods for improving the hydrophobic and oleophobic properties of thin films. For example, some methods reduce the surface energy through simple surface coating treatment, but the binding force between the coating and the substrate is weak. During long-term use, when subjected to external friction, stretching, etc., the coating is likely to peel off, resulting in a rapid decline in the hydrophobic and oleophobic properties. Moreover, these coatings are often difficult to construct a suitable micro-rough structure. Simply relying on the coating of low-surface-energy substances cannot fully utilize the synergistic effect of the micro-nano multi-level rough structure and the chemical low surface energy, making the hydrophobic and oleophobic effect unable to reach the best state.

[0005] There are also some methods that are complex and costly in the preparation process. For example, some methods that construct microstructures through special lithography techniques not only require high-precision equipment and complex process flows but also have extremely high technical requirements for operators, which greatly increases the production cost and limits their large-scale industrial application. At the same time, some chemical reagents used in the preparation process are toxic, causing significant pollution to the environment and not conforming to the concept of sustainable development.

[0006] In addition, traditional thin films have poor performance stability in the face of complex environmental factors. For example, in high-temperature, high-humidity, or strong ultraviolet environments, the hydrophobic and oleophobic properties of the thin film will be significantly affected. Ultraviolet irradiation may cause changes in the molecular structure on the surface of the thin film, increasing the surface energy and thus reducing the hydrophobic and oleophobic properties; the high-temperature and high-humidity environment may accelerate the aging of the thin film material and damage its internal structure, also affecting its hydrophobic and oleophobic effect.

[0007] In summary, it is of great practical significance to develop a film preparation method that can effectively improve the hydrophobic and oleophobic properties of the film while having good structural stability, simple preparation process, low cost and environmental friendliness. This is also a key issue that needs to be urgently solved in the current materials field. Summary of the invention

[0008] An object of the present invention is to solve at least the above problems and to provide at least the advantages which will be described hereinafter.

[0009] One purpose of the present invention is to solve the problem that it is difficult to simultaneously construct the synergistic effect of micro-nano multi-level rough structure and chemical low surface energy in the existing PTFE membrane preparation method, resulting in insufficient hydrophobic and oleophobic properties, and the bonding strength and structural stability between the base membrane and the modified layer and composite layer need to be improved. At the same time, the parameter control of the preparation process has a significant impact on the final performance, and the conditions of each step need to be optimized to achieve efficient and stable preparation. One purpose of the present invention is to solve the problem that when the PTFE base film is hot-pressed and composited with the PET non-woven fabric, the interface bonding force may be insufficient, resulting in easy delamination of the composite film, affecting the overall structural stability and service life, and the interface compatibility and adhesion need to be enhanced through pretreatment. One purpose of the present invention is to solve the problem that the cross-linking reaction of the silane layer on the surface of the base film may not be sufficient, and the formed network structure is not dense enough, which affects the chemical stability of the membrane surface and the durability of the hydrophobic and oleophobic properties. Post-treatment is required to promote the cross-linking reaction to enhance the structural strength. One purpose of the present invention is to solve the problem that the dispersibility and bonding force of nanocellulose whiskers with the base film may be insufficient, which affects the effect of modifying the base film surface in an ethanol solution, and the surface activity and dispersibility of nanocellulose need to be improved through pretreatment. One purpose of the present invention is to solve the problem that the composite film may age due to ultraviolet radiation during long-term use, and the surface structure and chemical composition change, thereby reducing the hydrophobic and oleophobic properties, and it is necessary to improve the weather resistance by adding ultraviolet absorbers. One purpose of the present invention is to solve the problem that the pore size and pore density are difficult to uniformly control during the preparation of the microporous structure on the surface of the composite membrane, and the microporous surface is prone to liquid penetration due to its high surface energy. It is necessary to give the micropores hydrophobic properties through modification and optimize the processing parameters. One purpose of the present invention is to solve the problem that the interface bonding between the siloxane cross-linked network and the underlying nanocellulose network may not be tight enough, and interlayer peeling is prone to occur when a gradient structure is formed. It is necessary to enhance the interface compatibility and bonding strength through plasma treatment and hydrolysis condensation reaction. One purpose of the present invention is to solve the problem that the active sites of oxygen-containing polar groups on the surface of the base film after plasma treatment may be oxidized or contaminated due to exposure to air, affecting the efficiency and effect of the subsequent grafting reaction, and the stability of the active sites needs to be maintained by inert gas protection. One object of the present invention is to solve the problem that the anchoring effect between the PTFE-based film and the PET non-woven fabric during hot pressing composite is single, relying only on the chemical bonding of the adhesive, with insufficient physical intercalation, resulting in limited composite strength. It is necessary to form a chemical-physical dual anchoring effect by adding fluorine-containing microspheres. One object of the present invention is to solve the problem that the compatibility between nano-SiO₂ and the fluorine-containing polymer is poor, and uneven dispersion easily leads to a decrease in the stability of the spinning solution, resulting in many structural defects in the formed nano-fiber layer. It is necessary to improve the surface properties of the nano-particles by pretreatment to enhance the compatibility. Another object of the present invention is to provide a preparation method of a hydrophobic and oleophobic PTFE film, which can construct a nano-rough structure and active sites through vacuum plasma treatment, combined with the graft modification of fluorinated silane and nano-cellulose, and electrospinning a fluorine-containing polymer nano-fiber layer to form the synergistic effect of micro-nano multi-level structure and low surface energy, significantly improving the water contact angle and oil contact angle.

[0010] To achieve these and other advantages in accordance with the present invention, a preparation method of a hydrophobic and oleophobic PTFE film is provided, comprising the following steps: 1) Use a PTFE-based film with a thickness of 20 - 30 μm, and ultrasonically clean it with ethanol to remove impurities; 2) Perform vacuum plasma treatment on the PTFE-based film: Introduce argon (20 ± 2 sccm) and oxygen (8 ± 1 sccm), and treat it at a vacuum degree of 12 ± 1 Pa and a power of 250 ± 10 W for 50 ± 5 seconds to form a nano-rough structure with Ra of 80 - 120 nm. The nano-structure includes nano-protrusions formed by etching the PTFE surface and active sites of oxygen-containing polar groups (C-O, C=O); 3) Immerse the PTFE-based film after vacuum plasma treatment in an ethanol solution containing 0.5 - 1.5 wt% perfluorodecyltriethoxysilane, 0.2 wt% dibutyltin dilaurate, and 0.05 - 0.1 wt% nano-cellulose whiskers within 30 minutes under nitrogen protection. The diameter of the nano-cellulose whiskers is 10 - 20 nm and the aspect ratio > 50, and ultrasonically oscillate at 28 ± 2 °C and 40 kHz for 20 ± 2 minutes; 4) Thermally press and composite the grafted base film with a 5 - 8 μm PET non-woven fabric at a temperature of 190 ± 5 °C and a pressure of 0.4 ± 0.05 MPa, and pre-place a fluorinated acrylate adhesive (coating amount 0.8 - 1.2 g / m²) at the hot pressing interface to form a PTFE / PET composite film; 5) Place the PTFE / PET composite film in an oven at 130 ± 5 °C for heat treatment for 1.5 ± 0.2 hours to crosslink and cure the grafted layer; 6) The surface of the PTFE / PET composite film is coated with a fluoropolymer nanofiber layer by electrospinning. The fluoropolymer is polyvinylidene fluoride - hexafluoropropylene copolymer. 0.5 - 1.0 wt% of nano - SiO₂ (15 - 25 nm) pre - modified by γ - aminopropyltriethoxysilane is added to the spinning solution. The spinning voltage is 19 - 21 kV, the receiving distance is 15 - 20 cm, the fiber layer thickness is 1.0 ± 0.1 μm and the fiber diameter is 200 - 400 nm, forming a composite hydrophobic layer with the synergistic effect of micro - nano multi - level rough structure and chemical low surface energy. The water contact angle of the composite hydrophobic layer is ≥155°, and the oil contact angle is ≥130°. Preferably, before the hot - press lamination in step 4), the composite surface of the PTFE base film is corona - treated with a voltage of 18 ± 1 kV and a time of 12 ± 1 s. Within 5 minutes after the treatment, a 2.5 wt% ethanol solution of silane coupling agent KH - 550 is coated with a coating thickness of 2 ± 0.5 μm, and dried at 90 ± 5 °C for 6 ± 1 minute. Preferably, the present invention further includes: step 7) placing the PTFE film with micro - nano multi - level structure in an environment of glutaraldehyde vapor at a temperature of 100 - 120 °C for 20 - 30 minutes to cause the aldehyde group in the glutaraldehyde molecule to undergo an aldol condensation reaction with the hydroxyl group in the silane layer, forming a silicone cross - linked network on the film surface. After the treatment, the composite film is placed in a vacuum drying oven and dried at 40 - 50 °C and a vacuum degree of ≤10 Pa for 1 - 2 hours; the glutaraldehyde vapor is generated by evaporating a 25 - 35 wt% aqueous glutaraldehyde solution in a 50 - 60 °C constant - temperature water bath. Preferably, in step 3) of the present invention, the nanocellulose is dispersed in a dilute sulfuric acid solution with pH = 3 - 4, hydrolyzed at 45 °C for 2 hours, centrifuged and washed to neutrality and then freeze - dried. After the pretreatment, it is impregnated with a 0.5 - 1.0 wt% ethanol solution of silane coupling agent KH - 550 for 10 minutes and dried and cured at 80 °C. Preferably, after the heat treatment in step 5), step 5a) is added. The heat - treated composite film is immersed in an ultraviolet absorber solution with a concentration of 0.3 - 0.8 wt%. The ultraviolet absorber is a compound system of benzophenone - type compound and hindered amine light stabilizer with a mass ratio of 3:1, immersed at 50 - 60 °C for 10 - 15 minutes, and then dried in an oven at 120 - 140 °C for 5 - 8 minutes. Preferably, step 5b) is added after step 5a) of the present invention. The laser micropore processing technology is used to prepare a uniformly distributed micropore structure on the surface of the composite membrane: the laser parameters are a wavelength of 1064 nm, a pulse frequency of 20 - 30 kHz, a scanning speed of 100 - 200 mm / s, a single pulse energy of 50 - 80 μJ. After processing, the average pore diameter of the micropores is 3 - 8 μm, and the pore density is 100 - 200 pores / cm². Then, it is impregnated with a 0.1 - 0.3 wt% perfluorooctyltriethoxysilane ethanol solution for 3 - 5 minutes to form a hydrophobic modification layer. Preferably, step 5c) is added after step 5b) of the present invention. The composite membrane is placed in a plasma processing device, and a mixed gas of argon (30 - 50 sccm) and vinyltriethoxysilane vapor is introduced. The total pressure is controlled at 5 - 10 Pa, and a radio frequency power of 100 - 150 W is applied for 5 - 10 minutes. Subsequently, it is hydrolyzed and condensed in an environment of 90 - 110 °C for 2 - 3 hours to enable the generated silicone cross - linked network to form a gradient interface bonding structure with the underlying nanocellulose network. Preferably, after the plasma treatment in step 2) of the present invention, the PTFE - based membrane is immediately transferred to a sealed container filled with nitrogen and left standing for 10 - 15 minutes to generate active sites with oxygen - containing polar groups (C - O, C = O) on the surface, and then step 3 is carried out. Preferably, during the hot - pressing lamination in step 4) of the present invention, fluorinated microspheres with a particle size of 10 - 20 μm are evenly spread between the PTFE - based membrane and the PET non - woven fabric so that during the hot - pressing process, part of them is embedded in the surface nanostructure of the PTFE - based membrane, forming a chemical - physical double anchoring effect with the fluorinated acrylate adhesive. The addition amount of the fluorinated microspheres is 0.3 - 8 g per square meter of the composite membrane area, and the surface of the hot - pressing mold is coated with a 3 - 5 μm thick polytetrafluoroethylene coating. Preferably, the pretreatment method of nano - SiO₂ in step 6) of the present invention is as follows: nano - SiO₂ is dispersed in a 2 wt% γ - aminopropyltriethoxysilane ethanol solution, stirred at 70 ± 5 °C for 2.5 hours, centrifuged and dried, and then blended with a fluorinated polymer. It is ultrasonically dispersed at 50 kHz for 20 minutes. 5 wt% deionized water is added to the γ - aminopropyltriethoxysilane ethanol solution to promote the hydrolysis of the silane so that a uniform silane coating layer is formed on the surface of nano - SiO₂, forming a covalent bond with the fluorinated polymer. The present invention has at least the following beneficial effects: 1. By constructing a nano - rough structure and active sites through vacuum plasma treatment, combining the graft modification of fluorosilane and nanocellulose, and electrospinning a fluorinated polymer nanofiber layer, the synergistic effect of the micro - nano multi - level structure and low surface energy is formed, significantly improving the water contact angle and oil contact angle. At the same time, hot - pressing lamination and heat treatment ensure the tight combination between layers, and the precise control of process parameters realizes stable and efficient preparation. 2. Corona treatment and silane coupling agent coating can increase the surface energy and active groups of the composite surface of the PTFE-based membrane, promote the interfacial bonding with PET non-woven fabric and adhesives, reduce delamination, and enhance the structural stability and mechanical properties of the composite membrane. 3. Glutaraldehyde vapor treatment promotes the condensation reaction between hydroxyl groups and aldehyde groups in the silane layer to form a dense siloxane cross-linked network, enhancing the chemical stability and mechanical strength of the membrane surface, delaying the attenuation of hydrophobic and oleophobic properties, and improving the long-term use reliability. 4. Acid hydrolysis and silane modification of nanocellulose improve its dispersibility and surface activity, making it more evenly distributed in the ethanol solution, enhancing the binding force with the PTFE-based membrane, and improving the uniformity and modification effect of the grafted layer. 5. Impregnation treatment with ultraviolet absorber solution can effectively absorb ultraviolet energy, inhibit the material aging process, protect the chemical structure and micro-nano morphology of the membrane surface, extend the retention time of hydrophobic and oleophobic properties, and improve weather resistance. 6. Laser micro-hole processing technology precisely controls the pore size and density of the micro-holes. Combined with perfluorosilane modification, it endows the micro-hole surface with hydrophobic properties, prevents liquid penetration while maintaining the gas permeability of the membrane, and expands its applications in fields such as filtration and separation. 7. Plasma treatment and hydrolysis condensation reaction promote the formation of a gradient interface between the siloxane cross-linked network and the nanocellulose network, enhancing the interlayer compatibility and binding force, reducing interface defects, and improving the overall structural strength and durability of the composite membrane. 8. Standing the base membrane under nitrogen protection can avoid the contamination or oxidation of surface active sites, ensure the effective binding of reagents such as perfluorodecyltriethoxysilane in subsequent grafting reactions, and improve the modification efficiency and utilization rate of surface active sites. 9. Fluorinated microspheres are embedded in the nano-structure of the base membrane during the hot pressing process, forming a chemical-physical dual anchoring with the adhesive, significantly improving the composite strength of the PTFE-based membrane and PET non-woven fabric, reducing interface peeling, and enhancing the overall mechanical properties of the membrane material. 10. The silane pretreatment of nano-SiO2 forms a uniform coating layer on its surface, improves the compatibility and dispersibility with fluorinated polymers, enhances the stability of the spinning solution, and the formed nano-fiber layer has a dense structure and few defects, enhancing the mechanical properties and hydrophobic-oleophobic synergistic effect of the composite hydrophobic layer.

[0011] Other advantages, objectives and features of the present invention will be partially reflected by the following description and partially understood by those skilled in the art through the research and practice of the present invention. Detailed Embodiments

[0012] The following further elaborates on the present invention in detail so that those skilled in the art can implement it according to the description in the specification.

[0013] It should be understood that terms such as "having", "comprising", and "including" used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0014] It should be noted that, unless otherwise specified, the experimental methods described in the following embodiments are all conventional methods, and the reagents and materials, unless otherwise specified, can all be obtained commercially.

[0015] A method for preparing a hydrophobic and oleophobic PTFE membrane, comprising the following steps: 1) Using a PTFE base film with a thickness of 20 - 30 μm, and ultrasonically cleaning it with ethanol to remove impurities; 2) Performing vacuum plasma treatment on the PTFE base film: introducing argon (20 ± 2 sccm) and oxygen (8 ± 1 sccm), and treating it at a vacuum degree of 12 ± 1 Pa and a power of 250 ± 10 W for 50 ± 5 seconds to form a nano-rough structure with Ra of 80 - 120 nm. The nano-structure includes nano-protrusions formed by etching the PTFE surface and active sites of oxygen-containing polar groups (C - O, C = O); 3) Immersing the PTFE base film after vacuum plasma treatment in an ethanol solution containing 0.5 - 1.5 wt% perfluorodecyltriethoxysilane, 0.2 wt% dibutyltin dilaurate, and 0.05 - 0.1 wt% nanocrystalline cellulose whiskers under nitrogen protection within 30 minutes. The diameter of the nanocrystalline cellulose whiskers is 10 - 20 nm and the aspect ratio is > 50, and ultrasonically oscillating at 28 ± 2 °C and 40 kHz for 20 ± 2 minutes; 4) Thermally pressing and laminating the grafted base film with a 5 - 8 μm PET non-woven fabric at a temperature of 190 ± 5 °C and a pressure of 0.4 ± 0.05 MPa, and pre-setting a fluorinated acrylate adhesive (coating amount 0.8 - 1.2 g / m²) at the thermocompression interface to form a PTFE / PET composite membrane; 5) Placing the PTFE / PET composite membrane in an oven at 130 ± 5 °C for heat treatment for 1.5 ± 0.2 hours to crosslink and cure the grafted layer; 6) Coating a fluoropolymer nanofiber layer on the surface of the PTFE / PET composite membrane by electrospinning. The fluoropolymer is a polyvinylidene fluoride - hexafluoropropylene copolymer, adding 0.5 - 1.0 wt% of nano - SiO₂ (15 - 25 nm) pre - modified by γ - aminopropyltriethoxysilane to the spinning solution, with a spinning voltage of 19 - 21 kV, a receiving distance of 15 - 20 cm, a fiber layer thickness of 1.0 ± 0.1 μm and a fiber diameter of 200 - 400 nm, to form a composite hydrophobic layer with the synergistic effect of a micro - nano multi - level rough structure and a chemically low surface energy. The water contact angle of the composite hydrophobic layer is ≥ 155 °, and the oil contact angle is ≥ 130 °.

[0016] In pre-treatment and surface modification, a PTFE-based membrane with a thickness of 20-30 μm is used. Specific values can be selected as 20 μm, 25 μm, or 30 μm. The base membrane can be a polytetrafluoroethylene microporous membrane produced by Zhejiang Juhua Group. In the ethanol ultrasonic cleaning step, ethanol is an analytical reagent. The ultrasonic cleaning equipment can be the KQ-500DE type ultrasonic cleaner produced by Kunshan Shumei Company. During cleaning, the base membrane is placed on the grid in the cleaning tank, and sufficient ethanol is added to cover the base membrane. The ultrasonic frequency is set at 40 kHz, and the cleaning time is 15-20 minutes to remove surface impurities. During vacuum plasma treatment, the argon gas flow rate can be selected as 18 sccm, 20 sccm, or 22 sccm, the oxygen gas flow rate can be selected as 7 sccm, 8 sccm, or 9 sccm, the vacuum degree is controlled at 11 Pa, 12 Pa, or 13 Pa, the power is set at 240 W, 250 W, or 260 W, and the treatment time is 45 seconds, 50 seconds, or 55 seconds. The plasma treatment equipment can be the SSP-100 type vacuum plasma treatment system produced by Shenyang Ke Yi Company. The base membrane is placed on the sample stage in the equipment cavity. The gas flow rate and vacuum degree are controlled by adjusting the intake valve and vacuum pump. During the treatment process, the high-frequency power source excites the gas to generate plasma, etching the surface of the base membrane to form a nano-rough structure with Ra of 80-120 nm, and at the same time introducing active sites of oxygen-containing polar groups. In the compounding and curing section, during the grafting treatment, the concentration of perfluorodecyltriethoxysilane can be selected as 0.5wt%, 1.0wt% or 1.5wt%, and the addition amount of nanocellulose whiskers can be selected as 0.05wt%, 0.075wt% or 0.1wt%. Its diameter is 10 - 20nm and the aspect ratio is >50. Products from Nanjing Jicang Nanotechnology Co., Ltd. can be purchased. When preparing the ethanol solution, first add dibutyltin dilaurate at a ratio of 0.2wt% to anhydrous ethanol, then add a certain amount of nanocellulose whiskers, and disperse them by ultrasonic oscillation at 40kHz in an environment of 28°C. The oscillation time can be selected as 18 minutes, 20 minutes or 22 minutes. The ultrasonic device can be the FS-600N type ultrasonic cell disruptor from Shanghai Shengxi Instruments Co., Ltd. In the hot pressing and compounding step, the thickness of the PET non-woven fabric can be selected as 5μm, 6.5μm or 8μm. Polyester non-woven fabric products from Jiangsu Sanfangxiang Group can be purchased. The coating amount of the fluorinated acrylate adhesive is controlled at 0.8g / m², 1.0g / m² or 1.2g / m². The hot pressing temperature is set at 185°C, 190°C or 195°C, and the pressure is controlled at 0.35MPa, 0.4MPa or 0.45MPa. The hot pressing device can be the TY-300 type hot pressing compounding machine from Nantong Tongda Machinery Co., Ltd. Stack the grafted base film and the PET non-woven fabric between the upper and lower molds of the device. The adhesive is pre-coated on the compounding surface of the base film, and compounding is achieved by heating and pressurizing the mold. During the heat treatment, the oven temperature is controlled at 125°C, 130°C or 135°C, and the time is 1.3 hours, 1.5 hours or 1.7 hours. The device can be the DHG-9140A type electrothermal blast drying oven from Shanghai Yiheng Scientific Instruments Co., Ltd. Place the compound film flat on the grid in the oven, and keep it at a constant temperature through the temperature control system to crosslink and cure the grafted layer. The hydrophobic layer is constructed by electrospinning process, and the fluorinated polymer is polyvinylidene fluoride-hexafluoropropylene copolymer, and Teflon FEP resin of 3M Company in the United States can be selected. The particle size of nano-SiO2 is 15-25nm, and it is pre-modified by γ-aminopropyl triethoxysilane. The modification agent can be KH-550 silane coupling agent of Nanjing Daoning Chemical Co., Ltd. The addition amount of nano-SiO2 in the spinning solution is 0.5wt%, 0.75wt% or 1.0wt%, the spinning voltage is set to 19kV, 20kV or 21kV, the receiving distance is 15cm, 17.5cm or 20cm, the fiber layer thickness is controlled at 0.9μm, 1.0μm or 1.1μm, and the fiber diameter is 200nm, 300nm or 400nm. The electrospinning equipment can be the XTC-01 electrospinning machine of Suzhou Xuanteng Instrument Equipment Co., Ltd. The spinning solution is loaded into the syringe, and the voltage is applied by the high-voltage power supply to form an electric field between the needle and the receiving device. The solution is stretched into nanofibers and deposited on the surface of the composite membrane to form a composite hydrophobic layer with a micro-nano multi-level rough structure. During the entire process, the parameters of each step are precisely adjusted by the control system of the equipment itself. The raw materials are all commercially available conventional chemical products. The composite interface of the base membrane and the non-woven fabric is tightly combined by adhesives and hot pressing. The nanofiber layer and the bottom layer are enhanced by chemical group interactions. The adhesion, ultimately achieving hydrophobic and oleophobic properties with a water contact angle of ≥155° and an oil contact angle of ≥130°, and at the same time, the selection of each layer of materials and the matching of process parameters ensure the stability of the membrane structure and the repeatability of the preparation process. In another technical solution, before step 4) hot pressing and laminating, the composite surface of the PTFE base film is subjected to corona treatment at a voltage of 18±1 kV for 12±1 seconds, and a 2.5wt% silane coupling agent KH-550 ethanol solution is coated within 5 minutes after the treatment, with a coating thickness of 2±0.5 μm, and dried at 90±5°C for 6±1 minutes.

[0017] In this technical solution, in the corona treatment process, the voltage is set to 18±1kV, and the specific value can be selected as 17kV, 18kV or 19kV. The treatment time is 12±1 seconds, and 11 seconds, 12 seconds or 13 seconds can be selected. The corona treatment equipment can be the MN-500 corona treatment machine of Dongguan Mingen Electronic Technology Co., Ltd., and the composite surface of the PTFE base film is placed on the conveyor belt of the equipment with the composite surface facing up, and the distance between the electrode and the surface of the base film is adjusted to 2-3mm. The output voltage is set by the voltage adjustment knob of the equipment, and the treatment time is set by the timer. After starting the equipment, the high-voltage electrode generates corona discharge, so that active groups are generated on the surface of the base film, and the surface energy is increased. After the treatment is completed, the base film must enter the next process within 5 minutes to avoid the surface activity from decreasing due to excessive exposure time. In the silane coupling agent coating step, a 2.5 wt% KH-550 ethanol solution is used. The silane coupling agent KH-550 can be a product of Nanjing Daoning Chemical Co., Ltd. The ethanol is analytical pure anhydrous ethanol. KH-550 is dissolved in ethanol according to the mass ratio, and after stirring evenly, it is reserved for use. The coating thickness is controlled at 2 ± 0.5 μm. The coating equipment can be the K112 wire bar coater of RK Print Coat Instruments Co., Ltd. The treated base film is placed flat on the coating table. After dipping the coater into the solution, it is moved uniformly along the composite surface of the base film to ensure that the solution covers evenly. The coating process needs to be carried out in an environment with a constant temperature of 25 ± 2 °C to avoid the too fast volatilization rate of the solvent affecting the coating effect. During the drying treatment, the coated base film is put into an oven, and the temperature is set at 90 ± 5 °C. Specifically, 85 °C, 90 °C or 95 °C can be selected. The drying time is 6 ± 1 minute, that is, 5 minutes, 6 minutes or 7 minutes. The oven can be the DHG-9070A electric blast drying oven of Shanghai Yiheng Scientific Instruments Co., Ltd. The base film is placed on the metal wire rack in the oven to ensure good ventilation up and down. The temperature is precisely adjusted through the temperature control system of the oven, and the drying time is controlled by a timer to make the ethanol solvent volatilize fully, and the silane coupling agent forms a uniform active coating on the surface of the base film. The technical principle of this process is that the corona treatment bombards the surface of the base film with high-energy particles, introducing polar groups, improving the surface roughness and activity. Subsequently, the coated silane coupling agent reacts with the active sites on the surface of the base film through hydroxyl groups to form chemical bonding, enhancing the interfacial bonding force between the base film and the subsequent PET non-woven fabric and adhesive. During the whole process, the time and parameters of each step are strictly connected to avoid the inactivation of the active sites due to exposure or contamination. Finally, the surface energy of the composite surface of the base film is significantly improved. When hot-pressing and compounding with the PET non-woven fabric, the adhesive can adhere more firmly, reducing the interfacial delamination phenomenon and improving the structural stability and durability of the composite film. In another technical solution, the present invention further includes: Step 7) placing the PTFE film with a micro-nano multi-level structure in a glutaraldehyde vapor environment at a temperature of 100 - 120 °C for 20 - 30 minutes to make the aldehyde group in the glutaraldehyde molecule undergo an aldol condensation reaction with the hydroxyl group in the silane layer, forming a silicone cross-linked network on the film surface. After the treatment, the composite film is placed in a vacuum drying oven and dried at 40 - 50 °C and a vacuum degree ≤ 10 Pa for 1 - 2 hours; the glutaraldehyde vapor is generated by evaporating a 25 - 35 wt% glutaraldehyde aqueous solution in a 50 - 60 °C constant temperature water bath.

[0018] In this technical solution, in the glutaraldehyde vapor preparation stage, an aqueous glutaraldehyde solution with a concentration of 25 - 35 wt% is used. The specific concentration can be selected as 25 wt%, 30 wt% or 35 wt%. The aqueous glutaraldehyde solution can be an analytical reagent produced by Sinopharm Chemical Reagent Co., Ltd. Pour the solution into a 500 mL glass beaker, and place the beaker in a constant temperature water bath. The water bath temperature is controlled at 50 - 60 °C, and specifically, it can be selected as 50 °C, 55 °C or 60 °C. The constant temperature water bath can be the DK-S22 type produced by Shanghai Jinghong Experimental Equipment Co., Ltd. Evaporate the solution through water bath heating to generate glutaraldehyde vapor, and the vapor is introduced into the steam treatment box above through a conduit. The connection position of the conduit is at the bottom of the steam treatment box to ensure uniform diffusion of the steam. During steam cross-linking treatment, place the micro-nano multi-level structure PTFE membrane that has completed the previous steps horizontally on the stainless steel wire rack in the steam treatment box. The wire rack is about 10 - 15 cm away from the steam inlet at the bottom of the box. The temperature of the steam treatment box is set at 100 - 120 °C, and specifically, it can be selected as 100 °C, 110 °C or 120 °C. The treatment time is 20 - 30 minutes, that is, 20 minutes, 25 minutes or 30 minutes. The steam treatment box can be the YQX-II type steam aging box produced by Nanjing Experimental Instrument Factory. Maintain a constant temperature through the temperature control system in the box. The aldehyde group in the glutaraldehyde vapor reacts with the hydroxyl group in the silane layer on the PTFE membrane surface through aldol condensation reaction to gradually form a dense siloxane cross-linking network. Keep the box door sealed during the treatment process to avoid steam leakage affecting the reaction efficiency. During vacuum drying treatment, transfer the reacted composite membrane to a vacuum drying oven and place it on the ceramic tray in the oven. The temperature of the vacuum drying oven is set at 40 - 50 °C, and specifically, it can be selected as 40 °C, 45 °C or 50 °C. The vacuum degree is adjusted to ≤10 Pa through a vacuum pump, and the drying time is 1 - 2 hours, that is, 1 hour, 1.5 hours or 2 hours. The vacuum drying oven can be the DZF-6050 type produced by Shanghai Yiheng Scientific Instrument Co., Ltd. Monitor the vacuum degree in real time through the vacuum gauge in the box, and start timing after reaching the set value. The technical principle of this process is that the aldehyde group in the glutaraldehyde vapor forms covalent bonds with the hydroxyl group in the silane layer through condensation reaction, promoting cross-linking between silane molecules and constructing a three-dimensional network structure to enhance the chemical stability and mechanical strength of the membrane surface. The vacuum drying stage accelerates the removal of residual moisture and volatile substances by reducing the air pressure to avoid affecting the formation of the cross-linking network. During the whole process, the glutaraldehyde concentration, water bath temperature, steam treatment time and vacuum drying parameters cooperate with each other to ensure that the cross-linking reaction is sufficient and the membrane structure is not damaged. Finally, the siloxane network on the surface of the composite membrane becomes denser, enhancing the durability and structural stability of the hydrophobic and oleophobic properties and reducing the shedding or failure of the surface modification layer during long-term use. In another technical solution, in step 3) of the present invention, the nanocellulose is dispersed in a dilute sulfuric acid solution with pH = 3 - 4, hydrolyzed at 45°C for 2 hours, centrifuged and washed until neutral, then freeze-dried, and impregnated with a 0.5 - 1.0 wt% ethanol solution of silane coupling agent KH-550 for 10 minutes after pretreatment, and dried and cured at 80°C.

[0019] In this technical solution, in the acid hydrolysis treatment step, the nanocellulose whiskers are dispersed in a dilute sulfuric acid solution with pH = 3 - 4. The specific pH value can be 3, 3.5 or 4. The dilute sulfuric acid is prepared from analytical pure sulfuric acid (such as the product of Shanghai National Pharmaceutical Group) and deionized water. The hydrolysis reaction is carried out in a 45°C constant temperature water bath for 2 hours. The water bath equipment can be the DK-S22 type constant temperature water bath of Shanghai Jinghong Experimental Equipment Co., Ltd. Place the beaker containing nanocellulose and dilute sulfuric acid in the water bath, and stir evenly with a magnetic stirrer (rotation speed about 200 rpm) to ensure uniform reaction. The nanocellulose can be the softwood pulp-based nanocellulose whiskers produced by the Industrial Technology Research Institute of Nanjing Forestry University, with an initial diameter of about 10 - 20 nm and an aspect ratio > 50. During the washing and drying process, the hydrolyzed mixture is poured into a centrifuge (such as the TGL-16C type centrifuge of Changsha Pingfan Instrument Co., Ltd.), centrifuged at 8000 rpm for 10 minutes, the supernatant is removed, and deionized water is added to redisperse, and the centrifugation and washing are repeated 3 - 5 times until the solution pH value is close to neutral (pH = 6.5 - 7.5). The washed nanocellulose is dried by a freeze dryer (such as the Pilot10-15 type freeze dryer of Beijing Boyikang Experimental Instrument Co., Ltd.). The pre-freezing temperature is -50°C, the vacuum degree < 10 Pa, and the drying time is 24 hours to obtain fluffy nanocellulose powder, which is stored in a desiccator for later use. During the silane modification treatment, the dried nanocellulose is impregnated in a 0.5 - 1.0 wt% ethanol solution of silane coupling agent KH-550. The solution is prepared from KH-550 and anhydrous ethanol (analytical grade) of Nanjing Daoning Chemical Co., Ltd. The impregnation time is 10 minutes, and gentle stirring is carried out during this period to avoid agglomeration. After impregnation, the nanocellulose is taken out and laid flat in an enamel tray, and then placed in an oven at 80 °C (such as the DHG-9070A type electrothermal blast drying oven of Shanghai Yiheng Scientific Instruments Co., Ltd.) for drying and curing for 2 hours. The oven temperature is precisely controlled by a temperature controller with an error of ±2 °C. The technical principle of this process is that acid hydrolysis removes the amorphous regions and impurities on the surface of the nanocellulose, exposing more hydroxyl groups and improving the surface activity; the silane coupling agent undergoes a condensation reaction with the hydroxyl groups on the surface of the nanocellulose through hydroxyl groups, forming a silicone oxide coating layer, reducing the surface energy and introducing alkoxy active sites, making it more easily dispersed in the subsequent ethanol solution and binding more tightly with the oxygen-containing polar groups on the surface of the PTFE-based membrane. Through strict control of the hydrolysis conditions and modification parameters during the entire pretreatment process, overdegradation or agglomeration of the nanocellulose is avoided, ensuring its uniform distribution in the grafting reaction in step 3, enhancing the synergistic effect with perfluorodecyltriethoxysilane, improving the uniformity and adhesion of the surface modification layer of the base membrane, and further optimizing the hydrophobic and oleophobic properties and structural stability of the composite membrane. In another technical solution, after the heat treatment in step 5), step 5a) is added. The heat-treated composite membrane is immersed in an ultraviolet absorber solution with a concentration of 0.3 - 0.8 wt%. The ultraviolet absorber is a compounding system of benzophenone compounds and hindered amine light stabilizers with a mass ratio of 3:1. It is impregnated at 50 - 60 °C for 10 - 15 minutes, and then dried in an oven at 120 - 140 °C for 5 - 8 minutes.

[0020] In this technical solution, in the solution preparation process, the ultraviolet absorber uses a compounding system of benzophenone compounds and hindered amine light stabilizers with a mass ratio of 3:1. Among them, the benzophenone compound can be selected as commercially available 2-hydroxy-4-methoxybenzophenone (such as the product of Shanghai Aladdin Biochemical Technology Co., Ltd.), and the hindered amine light stabilizer can be selected as bis(1,2,2,6,6-pentamethylpiperidinyl) sebacate (such as the product of Nanjing Dermech Innovation Chemical Co., Ltd.). The two reagents are added to ethanol in proportion to prepare a solution with a concentration of 0.3 - 0.8 wt%. The specific concentration can be selected as 0.3 wt%, 0.5 wt% or 0.8 wt%. During the dissolution process, it is stirred at room temperature for 30 minutes by a magnetic stirrer (such as the 85-2 type of Shanghai Meiyingpu Instrument Co., Ltd.) to ensure uniform mixing. During the impregnation treatment, the heat-treated PTFE / PET composite film is placed flat on the stainless-steel wire mesh in a constant-temperature water bath. The water bath temperature is controlled at 50 - 60 °C, specifically, 50 °C, 55 °C or 60 °C can be selected. The constant-temperature water bath can be the DK-S22 type produced by Shanghai Jinghong Experimental Equipment Co., Ltd. The composite film is completely immersed in the ultraviolet absorber solution, and the impregnation time is 10 - 15 minutes, that is, 10 minutes, 12 minutes or 15 minutes. During this period, the water bath temperature is kept stable to avoid the influence of solution temperature fluctuation on the penetration effect of the absorber. The wire mesh is placed in the middle of the water bath to ensure full contact between the composite film and the solution, while avoiding direct contact with the inner wall of the water bath. During the drying treatment, the impregnated composite film is taken out, gently drained of the surface solution, and laid flat on the ceramic tray in the oven. The oven temperature is set at 120 - 140 °C, specifically, 120 °C, 130 °C or 140 °C can be selected. The drying time is 5 - 8 minutes, that is, 5 minutes, 6 minutes or 8 minutes. The oven can be the DHG-9140A type electric heating forced-air drying oven produced by Shanghai Yiheng Scientific Instruments Co., Ltd. The temperature is precisely adjusted through the temperature control system of the oven to quickly volatilize the ethanol solvent, while the ultraviolet absorber molecules firmly adhere to the surface and internal structure of the composite film. The technical principle of this process is that benzophenone compounds can absorb ultraviolet energy in the range of 280 - 360 nm and convert it into harmless heat energy, and hindered amine light stabilizers inhibit oxidation reactions by capturing free radicals. The two are compounded to form a synergistic effect, effectively delaying the material aging and surface structure damage of the composite film caused by ultraviolet irradiation. Throughout the process, the reasonable selection of solution concentration, impregnation temperature and drying parameters ensures the uniform distribution of the ultraviolet absorber and its tight combination with the film material, improves the weather resistance of the composite film, extends the effective retention time of the hydrophobic and oleophobic properties, and at the same time avoids damage to the film structure due to improper treatment process. In another technical solution, after step 5a) of the present invention, step 5b) is added. A uniformly distributed microporous structure is prepared on the surface of the composite film by laser micropore processing technology: the laser parameters are wavelength 1064 nm, pulse frequency 20 - 30 kHz, scanning speed 100 - 200 mm / s, single pulse energy 50 - 80 μJ. After processing, the average pore diameter of the micropores is 3 - 8 μm, and the pore density is 100 - 200 pores / cm², and it is impregnated with 0.1 - 0.3 wt% perfluorooctyltriethoxysilane ethanol solution for 3 - 5 minutes to form a hydrophobic modification layer.

[0021] In this technical solution, in the laser micro-hole processing step, a solid-state laser with a wavelength of 1064 nm is used. The pulse frequency can be selected as 20 kHz, 25 kHz or 30 kHz, the scanning speed is set at 100 mm / s, 150 mm / s or 200 mm / s, and the single-pulse energy is controlled at 50 μJ, 65 μJ or 80 μJ. The laser processing equipment can be the GH-T series laser micro-hole processing machine of Wuhan Huagong Laser Engineering Co., Ltd. The heat-treated composite film is flatly fixed on the equipment workbench, and the laser head is vertically aligned with the film surface, with a distance of 10 - 15 cm maintained. The processing parameters are set through the equipment control software, and the laser beam scans along the preset path. Using the high-energy pulse energy, the film material is locally vaporized to form a uniform micro-hole structure with an average pore diameter of 3 μm, 5 μm or 8 μm and a pore density of 100 pores / cm², 150 pores / cm² or 200 pores / cm². During the processing, the workbench moves at a constant speed to ensure the neat distribution of the micro-holes. During the hydrophobic modification treatment, a perfluorooctyltriethoxysilane ethanol solution with a concentration of 0.1 wt%, 0.2 wt% or 0.3 wt% is prepared. The perfluorooctyltriethoxysilane can be a product of Dow Corning Corporation of the United States, and the ethanol is analytical pure anhydrous ethanol. The processed composite film is completely immersed in the solution for an immersion time of 3 minutes, 4 minutes or 5 minutes. During this period, it is stirred at a low speed of 50 rpm by a magnetic stirrer (such as the 85-2 type of Shanghai Meiyingpu Instrument Co., Ltd.) to ensure that the solution uniformly contacts the film surface. The immersion equipment can be a glass immersion tank with a constant temperature function, which is placed on a normal-temperature clean workbench to avoid impurity contamination of the solution.

[0022] The technical principle of this process is that laser micro-hole processing forms a regular micro-hole structure on the surface of the composite film by precisely controlling the energy and scanning parameters, improving the gas permeability and surface roughness of the film. Subsequently, the perfluorooctyltriethoxysilane molecules undergo a condensation reaction with the surface material of the film through hydroxyl groups to form a low-surface-energy hydrophobic layer on the inner wall of the micro-holes, making it difficult for liquids to penetrate the micro-holes and maintaining the surface hydrophobic property. During the whole process, the parameters of the laser equipment are precisely adjusted through the built-in control system, and the concentration and time of the immersion solution are matched according to the size of the micro-hole diameter to ensure uniform adhesion of the modified layer. Finally, while maintaining the gas permeability of the micro-hole structure on the surface of the composite film, the hydrophobic modification effectively prevents the penetration of liquids such as water and oil, improving the reliability and durability of the film material in applications such as filtration and separation, and avoiding micro-hole blockage or performance degradation caused by liquid retention. In another technical solution, the present invention adds step 5c after step 5b), places the composite membrane in a plasma treatment device, introduces a mixed gas of argon (30-50sccm) and vinyltriethoxysilane vapor, controls the total pressure to be 5-10Pa, applies a radio frequency power of 100-150W for treatment for 5-10 minutes, and then hydrolyzes and condenses in an environment of 90-110°C for 2-3 hours so that the generated siloxane cross-linked network forms a gradient interface bonding structure with the underlying nanocellulose network. In this technical solution, in the plasma treatment link, the argon flow rate can be selected to be 30sccm, 40sccm or 50sccm, and the vinyl triethoxysilane vapor is generated by heating the liquid reagent. The equipment can use the SSP-100 vacuum plasma treatment system of Shenyang Keyi Co., Ltd. The composite film treated in step 5b is placed horizontally on the sample stage of the equipment cavity, and the sample stage is about 5-8cm away from the air inlet to ensure uniform distribution of the gas. The argon flow rate is adjusted by the mass flow controller, and vinyl triethoxysilane (the product of Nanjing Daoning Chemical Co., Ltd. can be selected) is poured into the evaporator of the equipment, and evaporated at 40-50°C to generate steam. After mixing with argon, the total pressure is controlled at 5Pa, 7.5Pa or 10Pa, and the applied RF power is set to 100W, 125W or 150W. The treatment time is 5 minutes, 7.5 minutes or 10 minutes. During this period, the pressure is maintained stable by the vacuum system of the equipment. The high-energy particles in the plasma promote the generation of active sites on the surface of the composite film and introduce silane groups. During the hydrolysis and condensation treatment, the composite membrane after plasma treatment is transferred to an oven, and the oven temperature is set to 90°C, 100°C or 110°C, and the time is controlled at 2 hours, 2.5 hours or 3 hours. The equipment can be the DHG-9140A electric heating blast drying oven of Shanghai Yiheng Scientific Instrument Co., Ltd. The composite membrane is laid flat on the metal grid in the oven, and the grid is about 10 cm away from the heating tube to ensure uniform temperature. During the heating process, the ethoxy group in the vinyl triethoxysilane molecule reacts with water (from the ambient humidity and the residue on the surface of the membrane) to hydrolyze to generate silanol groups, which then condense to form siloxane covalent bonds, and at the same time bond with the hydroxyl groups in the underlying nanocellulose network, gradually constructing a siloxane cross-linked network and forming a gradient interface with the underlying structure. The technical principle of this process lies in that plasma treatment bombards the surface of the composite membrane with high-energy particles, activates surface molecules and introduces vinylsilyl groups, providing active sites for subsequent hydrolysis and condensation reactions. By controlling specific gas composition, pressure and power, the silyl groups can be evenly distributed on the membrane surface and in the microporous structure. During the hydrolysis and condensation process, the formation of the silicone cross-linked network not only enhances the chemical stability of the membrane surface, but also combines with the underlying nanocellulose network through covalent bonds to form a gradient interface structure from the surface layer to the inner layer, reducing the physical gaps and chemical differences between layers. Throughout the process, the plasma treatment parameters cooperate with the hydrolysis temperature and time to ensure that the cross-linking reaction is sufficient and does not damage the micro-nano structure of the membrane. Eventually, the interfacial bonding force between the silicone layer and the nanocellulose layer of the composite membrane is significantly improved, effectively reducing the interlayer peeling phenomenon caused by stress or environmental changes during long-term use, enhancing the overall structural stability and durability of the membrane material, and further optimizing the persistence of hydrophobic and oleophobic properties.

[0023] In another technical solution, after the plasma treatment in step 2) of the present invention is completed, the PTFE-based membrane is immediately transferred to a sealed container filled with nitrogen and left to stand for 10 - 15 minutes to generate active sites with oxygen-containing polar groups (C-O, C=O) on the surface, and then step 3 is carried out.

[0024] In this technical solution, during the rapid transfer link after plasma treatment, when the vacuum plasma treatment in step 2 is completed, the PTFE-based membrane needs to be taken out of the plasma treatment equipment within 30 seconds, and the base film should be prevented from contacting the air for a long time during the transfer process. The plasma treatment equipment can be the SSP-100 type vacuum plasma treatment system of Shenyang KeYi Company. The base film is initially placed on the sample stage in the center of the equipment cavity and taken out through the rapid opening and closing device of the equipment after the treatment, and directly put into a pre-prepared nitrogen-sealed container. When standing under nitrogen protection, the sealed container can be a stainless steel sealed tank with a silica gel sealing ring (such as the product of Shanghai Shenbo Instrument Co., Ltd.). High-purity nitrogen (purity ≥ 99.99%, which can be the product of Shanghai Pujiang Special Gas Co., Ltd.) is pre-introduced into the tank to displace the air for 30 seconds to ensure that the oxygen content in the container is < 1%. The base film is horizontally placed on the polytetrafluoroethylene support in the sealed tank, and the support is about 5 cm away from the bottom of the tank to avoid contacting the tank wall. The standing time is set to 10 minutes, 12.5 minutes or 15 minutes, and the pressure is monitored through the pressure gauge on the tank during this period to maintain the normal pressure state. This process isolates external water vapor and oxygen through the nitrogen environment to prevent the active sites of the newly formed oxygen-containing polar groups (C-O, C=O) on the surface of the base film from being oxidized or adsorbing impurities. The technical principle of this process is that vacuum plasma treatment etches the surface of the base film through the plasma of argon and oxygen to form nano-protrusions and introduce oxygen-containing polar groups. These active sites are prone to react with water vapor and carbon dioxide in the air and become ineffective. Therefore, it is necessary to immediately place it in a nitrogen protection environment after treatment. As an inert gas, nitrogen can effectively inhibit the oxidation and pollution of active sites, enabling them to maintain high reactivity in the subsequent grafting reaction in step 3, ensuring that reagents such as perfluorodecyltriethoxysilane can fully bind to the active sites. During the whole process, the control of the transfer speed and the standing time is crucial. Being too fast or too slow may affect the retention efficiency of the active sites. Through this technical feature, the active sites on the surface of the base film are completely preserved, significantly improving the uniformity and sufficiency of the grafting reaction in step 3, thereby enhancing the bonding force between the modified layer and the base film and optimizing the stability of the chemical activity and hydrophobic and oleophobic properties of the composite film surface. In another technical solution, during the hot pressing and laminating in step 4), fluorine-containing microspheres with a particle size of 10 - 20 μm are evenly spread between the PTFE base film and the PET non-woven fabric so that they are partially embedded in the nano-structure on the surface of the PTFE base film during the hot pressing process, forming a chemical-physical dual anchoring effect. The addition amount of the fluorine-containing microspheres is 0.3 - 8 g per square meter of the composite film area, and the surface of the hot pressing mold is coated with a 3 - 5 μm thick polytetrafluoroethylene coating.

[0025] In this technical solution, during the spreading of the fluorine-containing microspheres, fluorine-containing microspheres with a particle size of 10 - 20 μm are selected. The specific particle size can be 10 μm, 15 μm or 20 μm. The fluorine-containing microspheres can be the fluororesin microsphere products produced by 3M Company in the United States. The addition amount is controlled at 0.3 g, 4 g or 8 g per square meter of the composite film area, and is evenly sprayed between the composite interface of the PTFE base film and the PET non-woven fabric through a powder spreader (such as the YY-1 type produced by Shanghai Rongya Instrument Co., Ltd.) to ensure uniform distribution of the microspheres and avoid local accumulation. During the hot pressing and laminating treatment, the hot pressing equipment in Claim 1 is used, such as the TY-300 type hot pressing and laminating machine produced by Nantong Tongda Machinery Co., Ltd. The temperature is set at 185 °C, 190 °C or 195 °C, and the pressure is controlled at 0.35 MPa, 0.4 MPa or 0.45 MPa. The base film with the spread fluorine-containing microspheres and the non-woven fabric are stacked between the upper and lower molds of the equipment. The fluorine-containing acrylate adhesive is pre-coated on the composite surface of the base film. During the hot pressing process, the fluorine-containing microspheres are partially embedded in the nano-rough structure on the surface of the base film under the action of pressure, forming a physical interlocking. At the same time, the fluorine groups on the surface of the microspheres chemically combine with the fluorine groups in the adhesive to achieve a dual anchoring effect. During the die coating treatment, a polytetrafluoroethylene coating with a thickness of 3 - 5 μm is applied to the surface of the hot press die. The coating material can be the polytetrafluoroethylene spraying liquid of Shanghai Shijian Industry Co., Ltd., and it is evenly sprayed on the die surface through a spraying device (such as the JM - 500 type of Suzhou Jimei Electronics Co., Ltd.), and then cured at 280 °C for 2 hours to form a dense coating. This coating can prevent the composite film from adhering to the die during the hot pressing process and at the same time does not affect the embedding effect of the fluorinated microspheres. The technical principle lies in the synergistic effect of the physical embedding of the fluorinated microspheres and the chemical bonding of the adhesive, forming a multi - point anchoring structure at the interface between the base film and the non - woven fabric, and the polytetrafluoroethylene coating ensures the stability of the hot pressing process. The entire process controls the particle size, addition amount of the microspheres and the thickness of the die coating, significantly improving the bonding force at the composite interface, reducing the delamination phenomenon caused by external forces during long - term use, enhancing the structural durability and mechanical properties of the PTFE / PET composite film, and providing a basic guarantee for the stable performance of the subsequent hydrophobic and oleophobic functional layers. In another technical solution, the pretreatment method of the nano - SiO2 in step 6) of the present invention is as follows: Disperse the nano - SiO2 in a 2wt% γ - aminopropyltriethoxysilane ethanol solution, stir at 70 ± 5 °C for 2.5 hours, after centrifugal drying, blend it with the fluoropolymer, and perform ultrasonic dispersion treatment at 50 kHz for 20 minutes. 5wt% deionized water is added to the γ - aminopropyltriethoxysilane ethanol solution to promote the hydrolysis of the silane so that a uniform silane coating layer is formed on the surface of the nano - SiO2, forming a covalent bond with the fluoropolymer. In this technical solution, in the link of preparing the silane solution, a 2wt% γ - aminopropyltriethoxysilane ethanol solution is used. The silane coupling agent can be the KH - 550 product of Nanjing Daoning Chemical Co., Ltd., and the ethanol is analytical - grade anhydrous ethanol. The silane coupling agent is dissolved in ethanol according to the mass ratio, and at the same time, 5wt% deionized water is added to promote the hydrolysis of the silane. The deionized water can be self - made in the laboratory or a commercially available product. During the dispersion stirring treatment, nano-SiO₂ with a size of 15 - 25 nm (products from Hangzhou Wanjing New Materials Co., Ltd. can be selected) is added to the above solution at a ratio of 0.5 - 1.0 wt%. A magnetic stirrer (Model 85 - 2 from Shanghai Meiyingpu Instrumentation Co., Ltd.) is used to stir at 70 ± 5 °C for 2.5 hours. The specific temperature can be selected as 65 °C, 70 °C, or 75 °C, and the stirring speed is set at 300 rpm to ensure the uniform dispersion of nano-particles. During the stirring process, the silane coupling agent hydrolyzes to generate silanol groups, which react with the hydroxyl groups on the surface of nano-SiO₂ to form a siloxane coating layer. After the stirring ends, the mixed solution is poured into a centrifuge (Model TGL - 16C from Changsha Pingfan Instrument Co., Ltd.) and centrifuged at 10,000 rpm for 15 minutes to separate the modified nano-SiO₂. After removing the supernatant, it is placed in an oven at 60 °C (Model DHG - 9070A from Shanghai Yiheng Scientific Instrument Co., Ltd.) and dried to a constant weight to obtain nano-particles with a uniformly coated silane on the surface. During the blending and ultrasonic treatment, the dried nano-SiO₂ is blended with polyvinylidene fluoride - hexafluoropropylene copolymer (Teflon FEP resin from 3M Company, USA can be selected) in proportion, and N,N-dimethylformamide is added as a solvent (analytical pure, products from Shanghai National Pharmaceutical Group). An ultrasonic disperser (Model FS - 600N from Shanghai Shengxi Instrument Co., Ltd.) is used to treat at a frequency of 50 kHz for 20 minutes, and the ultrasonic power is set at 400 W to make the nano-particles uniformly disperse in the fluoropolymer solution. The technical principle of this process is that the silane coupling agent forms an organic coating layer on the surface of nano-SiO₂ through hydrolysis and condensation reactions, and its amino groups form covalent bond combinations with the fluorine groups of the fluoropolymer, significantly improving the compatibility and dispersibility of the nano-particles and the polymer. Throughout the process, the precise control of the concentration of the silane solution, the stirring temperature, the centrifugation speed, and the ultrasonic parameters ensures the formation of a uniform silane coating layer on the surface of nano-SiO₂, avoiding agglomeration and uneven dispersion. Finally, the pretreated nano-SiO₂ forms a stable blend system with the fluoropolymer during the electrospinning process, improving the stability of the spinning solution, forming a nano-fiber layer with a dense structure and few defects, enhancing the uniformity of the micro-nano multi-level structure in the composite hydrophobic layer, making the nano-fibers bind more tightly to the bottom substrate film, and effectively improving the hydrophobic and oleophobic synergistic effect and mechanical properties of the composite membrane surface.

[0026] <Example> A method for preparing a hydrophobic and oleophobic PTFE membrane includes the following steps: 1) Use a PTFE substrate film with a thickness of 20 - 30 μm, and ultrasonically clean it with ethanol to remove impurities; 2) Vacuum plasma treatment of the PTFE base film: Argon and oxygen are introduced, and the treatment is carried out at a vacuum degree of 12 ± 1 Pa and a power of 250 ± 10 W for 50 ± 5 seconds to form a nano-rough structure with Ra of 80 - 120 nm. The nano-structure includes nano-protrusions formed by etching the PTFE surface and active sites of oxygen-containing polar groups; Among them, after the plasma treatment, the PTFE base film is immediately transferred to a sealed container filled with nitrogen and left to stand for 10 - 15 minutes to generate active sites of oxygen-containing polar groups (C - O, C = O) on the surface; 3) Immerse the PTFE base film after vacuum plasma treatment in an ethanol solution containing 1.0 wt% perfluorodecyltriethoxysilane, 0.2 wt% dibutyltin dilaurate, and 0.07 wt% nanocellulose whiskers within 30 minutes under nitrogen protection. The diameter of the nanocellulose whiskers is 10 - 20 nm, and the aspect ratio > 50. Ultrasonic oscillation is carried out at 28 ± 2 °C and 40 kHz for 20 ± 2 minutes; Among them, the nanocellulose is dispersed in a dilute sulfuric acid solution with pH = 3 - 4, and hydrolyzed at 45 °C for 2 hours. After centrifugal washing to neutrality, it is freeze-dried, and then impregnated in a 0.5 - 1.0 wt% ethanol solution of silane coupling agent KH-550 for 10 minutes, and dried and cured at 80 °C to obtain nanocellulose whiskers; 4) Corona treatment of the composite surface of the PTFE base film, with a voltage of 18 ± 1 kV and a time of 12 ± 1 second. Within 5 minutes after treatment, a 2.5 wt% ethanol solution of silane coupling agent KH-550 is coated, with a coating thickness of 2 ± 0.5 μm, and dried at 90 ± 5 °C for 6 ± 1 minute. Then, the corona-treated base film is thermally pressed and compounded with 5 - 8 μm PET non-woven fabric at a temperature of 190 ± 5 °C and a pressure of 0.4 ± 0.05 MPa, and a fluorinated acrylate adhesive is preset at the hot-pressing interface to form a PTFE / PET composite film; Among them, during hot-pressing and compounding, fluorinated microspheres with a particle size of 10 - 20 μm are evenly spread between the PTFE base film and the PET non-woven fabric so that part of them is embedded in the nano-structure on the surface of the PTFE base film during the hot-pressing process, forming a chemical-physical double anchoring effect with the fluorinated acrylate adhesive. The addition amount of the fluorinated microspheres is 0.3 - 8 g per square meter of the composite film area, and the surface of the hot-pressing mold is coated with a 3 - 5 μm thick polytetrafluoroethylene coating; 5) Place the PTFE / PET composite film in an oven at 130 ± 5 °C for heat treatment for 1.5 ± 0.2 hours to crosslink and cure the grafted layer; 5a) Immerse the heat-treated composite film in an ultraviolet absorber solution with a concentration of 0.3 - 0.8 wt%, where the ultraviolet absorber is a compound system of benzophenone compounds and hindered amine light stabilizers with a mass ratio of 3:1. Immerse it at 55 °C for 12 minutes, and then dry it in an oven at 130 °C for 6 minutes; 5b) Use laser micro-hole processing technology to prepare a uniformly distributed micro-hole structure on the surface of the composite film: The laser parameters are wavelength 1064 nm, pulse frequency 25 kHz, scanning speed 150 mm / s, single pulse energy 60 μJ. After processing, the average pore diameter of the micro-holes is 3 - 8 μm, and the pore density is 100 - 200 holes / cm². Then immerse it in a 0.2 wt% perfluorooctyltriethoxysilane ethanol solution for 3 - 5 minutes to form a hydrophobic modification layer; 5c) Place the composite film in a plasma processing device, introduce a mixed gas of argon (40 sccm) and vinyltriethoxysilane vapor, control the total pressure at 7 Pa, apply a radio frequency power of 130 W for 7 minutes, and then hydrolyze and condense at 100 °C for 2.5 hours to enable the generated silicone cross-linked network to form a gradient interface bonding structure with the underlying nanocellulose network; 6) Use the electrospinning process to coat a fluoropolymer nanofiber layer on the surface of the PTFE / PET composite film. The fluoropolymer is a polyvinylidene fluoride - hexafluoropropylene copolymer. Add 0.7 wt% of nano - SiO₂ pre - modified with γ - aminopropyltriethoxysilane to the spinning solution. The spinning voltage is 20 kV, the receiving distance is 17 cm, the thickness of the fiber layer is 1.0 ± 0.1 μm, and the fiber diameter is 200 - 400 nm, forming a composite hydrophobic layer with the synergistic effect of micro - nano multi - level rough structure and chemical low surface energy. The water contact angle of the composite hydrophobic layer is ≥155°, and the oil contact angle is ≥130°; Among them, the pretreatment method of nano - SiO₂ is: Disperse nano - SiO₂ in a 2 wt% γ - aminopropyltriethoxysilane ethanol solution, stir at 70 ± 5 °C for 2.5 hours, centrifuge and dry it, then blend it with the fluoropolymer, and perform ultrasonic dispersion treatment at 50 kHz for 20 minutes. Add 5 wt% deionized water to the γ - aminopropyltriethoxysilane ethanol solution to promote the hydrolysis of the silane so that a uniform silane coating layer is formed on the surface of nano - SiO₂, forming a covalent bond with the fluoropolymer; 7) Place the PTFE film with micro - nano multi - level structure in a glutaraldehyde vapor environment at a temperature of 110 °C for 25 minutes to enable the aldehyde group in the glutaraldehyde molecule to undergo an aldol condensation reaction with the hydroxyl group in the silane layer, forming a silicone cross - linked network on the film surface. After treatment, place the composite film in a vacuum drying oven and dry it at 45 °C and a vacuum degree of ≤10 Pa for 1.5 hours; The glutaraldehyde vapor is generated by evaporating a 30 wt% glutaraldehyde aqueous solution in a 55 °C constant temperature water bath.

[0027] <Effect Test> Comparative Example 1: The method provided in the <Example> was adopted, except that the corona treatment and silane coating were omitted, and hot pressing and compounding were directly carried out (the remaining steps were the same as those in the test group).

[0028] Comparative Example 2: The method provided in the <Example> was adopted, except that after the plasma treatment, it was left standing in the air for 15 minutes (without nitrogen protection).

[0029] Comparative Example 3: Untreated nano-SiO2 was used and directly blended with the fluoropolymer (the remaining steps were the same as those in the test group).

[0030] Oil film performance test methods and results of the Example and Comparative Examples 1 - 3 I. Test Methods (I) Measurement of oil contact angle Equipment: Contact angle measuring instrument (Dataphysics OCA 20, Germany) Method: At room temperature (25 ± 2°C), 5 μL of olive oil (analytical pure, commercially available) was dropped on the film surface. The liquid droplet image was taken by the instrument, and the initial oil contact angle was calculated by the sessile drop method. Five different positions of each sample were tested, and the average value was taken. Standard: The larger the oil contact angle, the better the oil repellency performance.

[0031] (II) Test of oil film adhesion Standard: ASTM D3359 - 02 (Cross - hatch test rating standard) Operation: A cross - hatch knife with a 1 - mm spacing was used to cut a 10×10 grid on the film surface to the depth of the substrate. After pasting a 3M tape, it was quickly peeled off, and the oil film detachment in the grid area was observed. Rating: Grade 0 (no detachment) to Grade 5 (detachment area > 65%). The average value of 3 tests was taken.

[0032] (III)Oil resistance test Reagent: n - hexadecane (analytical pure, commercially available) Method: The sample was immersed in n - hexadecane, taken out after soaking at room temperature for 24 hours, and the surface liquid was blotted dry with filter paper. Whether swelling, delamination or a significant decrease in oil repellency performance (a decrease in oil contact angle > 10° was regarded as failure) occurred on the film surface was observed. (IV)Long - term weather resistance test Equipment: Ultraviolet aging chamber (such as Q - Lab QUV / SE, USA) Conditions: Wavelength 340 nm, irradiance 0.89 W / m², temperature 60°C, cycle period: ultraviolet irradiation for 8 hours + condensation water for 2 hours, lasting for 72 hours. Detection: Measure the oil contact angle before and after aging, and calculate the contact angle retention rate (contact angle after aging / contact angle before aging × 100%). II. Test Results (I) Comparison of Oil Contact Angles (II) Rating of Oil Film Adhesion Example: Grade 1 (only very slight peeling at the edge, peeling area < 5%) Comparative Example 1: Grade 3 (peeling area in the grid region is 15% - 35%). Due to the omission of corona treatment and silane coating, the interfacial bonding force between the base film and the oil film is insufficient. Comparative Example 2: Grade 2 (peeling area is 5% - 15%). The lack of nitrogen protection leads to a reduction in active sites and insufficient grafting reaction. Comparative Example 3: Grade 4 (peeling area is 35% - 65%). The untreated nano - SiO₂ agglomerates severely, and the oil film structure is loose. (III) Analysis of Oil Resistance and Weather Resistance Example: Thanks to corona treatment and nitrogen protection, the active groups on the surface of the base film are dense and stable. The double - anchoring structure formed by fluorinated microspheres and silane coupling agents enables the oil film to maintain high oleophobic performance after immersion and aging. The pretreatment of nano - SiO₂ improves the stability of the spinning solution, and the formed nanofiber layer is dense, effectively blocking the penetration of oil molecules. Comparative Example 1: Due to the lack of interfacial pretreatment, the bonding between the oil film and the base film only depends on the adhesive. After immersion, it is easy to cause interfacial separation due to swelling, and the contact angle decreases significantly after aging. Comparative Example 2: Some of the active sites on the surface of the unprotected base film after plasma treatment are invalid, and the grafted silane layer is uneven. The adhesion and weather resistance of the oil film are lower than those of the example. Comparative Example 3: The unmodified nano - SiO₂ agglomerates in the spinning solution, and there are a large number of defects in the formed oil film. Oil molecules are easy to penetrate into the interior of the film, resulting in rapid performance decay. The example significantly improves the oleophobic performance, adhesion and weather resistance of the oil film through the coordination of multiple technologies such as corona treatment, nitrogen protection, and nanoparticle pretreatment. Compared with each comparative example, it has obvious stability advantages in complex environments. The performance differences of the comparative examples directly reflect the influence of each key step in the claims on the performance of the oil film, verifying the technical effect of improving the hydrophobic and oleophobic performance of the present invention through multi - step optimization.

[0033] Although the embodiments of the present invention have been disclosed as above, it is not limited to the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily made. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to specific details.

Claims

1. A preparation method of a hydrophobic and oleophobic PTFE membrane, characterized in that, It includes the following steps: 1) Use a PTFE base film with a thickness of 20 - 30μm, and ultrasonically clean it with ethanol to remove impurities; 2) Conduct vacuum plasma treatment on the PTFE base film: introduce argon and oxygen, and treat it for 50 ± 5 seconds under a vacuum degree of 12 ± 1Pa and a power of 250 ± 10W to form a nano-rough structure with Ra of 80 - 120nm. The nano-structure includes nano-protrusions formed by etching the PTFE surface and active sites of oxygen-containing polar groups; 3) Immerse the PTFE base film after vacuum plasma treatment in an ethanol solution containing 0.5 - 1.5wt% perfluorodecyltriethoxysilane, 0.2wt% dibutyltin dilaurate, and 0.05 - 0.1wt% nano-crystalline cellulose whiskers within 30 minutes under nitrogen protection. The diameter of the nano-crystalline cellulose whiskers is 10 - 20nm and the aspect ratio > 50, and ultrasonically oscillate at 28 ± 2℃ and 40kHz for 20 ± 2 minutes; 4) Thermally press and laminate the grafted base film with a 5 - 8μm PET non-woven fabric at a temperature of 190 ± 5℃ and a pressure of 0.4 ± 0.05MPa, and preset a fluorinated acrylate adhesive at the thermocompression interface to form a PTFE / PET composite film; 5) Place the PTFE / PET composite film in an oven at 130 ± 5℃ for heat treatment for 1.5 ± 0.2 hours to crosslink and cure the grafted layer; 6) Use the electrospinning process to coat a fluoropolymer nanofiber layer on the surface of the PTFE / PET composite film. The fluoropolymer is a polyvinylidene fluoride - hexafluoropropylene copolymer. Add 0.5 - 1.0wt% of nano-SiO2 pre-modified by γ-aminopropyltriethoxysilane to the spinning solution. The spinning voltage is 19 - 21kV, the receiving distance is 15 - 20cm, the thickness of the fiber layer is 1.0 ± 0.1μm, and the fiber diameter is 200 - 400nm to form a composite hydrophobic layer with the synergistic effect of micro-nano multi-level rough structure and chemical low surface energy. The water contact angle of the composite hydrophobic layer is ≥155°, and the oil contact angle is ≥130°.

2. The preparation method of the hydrophobic and oleophobic PTFE membrane according to claim 1, characterized in that, Before the thermocompression lamination in step 4), corona treat the composite surface of the PTFE base film at a voltage of 18 ± 1kV for 12 ± 1 seconds. Coat a 2.5wt% ethanol solution of silane coupling agent KH-550 within 5 minutes after treatment, with a coating thickness of 2 ± 0.5μm, and dry it at 90 ± 5℃ for 6 ± 1 minutes.

3. The preparation method of the hydrophobic and oleophobic PTFE membrane according to claim 1, characterized in that, It also includes: Step 7) Place the PTFE film with micro-nano multi-level structure in an environment of glutaraldehyde vapor at a temperature of 100 - 120℃ for 20 - 30 minutes to cause the aldehyde group in the glutaraldehyde molecule to undergo an aldol condensation reaction with the hydroxyl group in the silane layer, forming a siloxane cross-linked network on the film surface. After treatment, place the composite film in a vacuum drying oven and dry it at 40 - 50℃ and a vacuum degree ≤10Pa for 1 - 2 hours; the glutaraldehyde vapor is generated by evaporating a 25 - 35wt% aqueous glutaraldehyde solution in a 50 - 60℃ constant temperature water bath.

4. The preparation method of the hydrophobic and oleophobic PTFE membrane according to claim 1, characterized in that, In step 3), the nanocellulose is dispersed in a dilute sulfuric acid solution with pH = 3 - 4, and undergoes hydrolysis reaction at 45 °C for 2 hours. After centrifuging, washing until neutral, and then freeze-drying, it is impregnated with 0.5 - 1.0 wt% silane coupling agent KH-550 ethanol solution for 10 minutes, and dried and cured at 80 °C.

5. The preparation method of the hydrophobic and oleophobic PTFE membrane according to claim 1, characterized in that, After step 5) heat treatment, add step 5a): Immerse the heat-treated composite film into an ultraviolet absorber solution with a concentration of 0.3 - 0.8 wt%. The ultraviolet absorber is a compound system of benzophenone compounds and hindered amine light stabilizers with a mass ratio of 3:

1. Immerse it at 50 - 60 °C for 10 - 15 minutes, and then dry it in an oven at 120 - 140 °C for 5 - 8 minutes.

6. The preparation method of the hydrophobic and oleophobic PTFE membrane according to claim 5, wherein, After step 5a), add step 5b): Use laser micro-hole processing technology to prepare a uniformly distributed micro-hole structure on the surface of the composite film. The laser parameters are wavelength 1064 nm, pulse frequency 20 - 30 kHz, scanning speed 100 - 200 mm / s, single pulse energy 50 - 80 μJ. After processing, the average pore diameter of the micro-holes is 3 - 8 μm, and the pore density is 100 - 200 holes / cm². Then immerse it in 0.1 - 0.3 wt% perfluorooctyltriethoxysilane ethanol solution for 3 - 5 minutes to form a hydrophobic modification layer.

7. The preparation method of the hydrophobic and oleophobic PTFE membrane according to claim 6, characterized in that, After step 5b), add step 5c): Place the composite film in a plasma processing device, introduce a mixed gas of argon (30 - 50 sccm) and vinyltriethoxysilane vapor, control the total pressure at 5 - 10 Pa, apply a radio frequency power of 100 - 150 W and process for 5 - 10 minutes. Then, hydrolyze and condense in an environment of 90 - 110 °C for 2 - 3 hours to enable the formed silicone cross-linked network to form a gradient interface bonding structure with the underlying nanocellulose network.

8. The preparation method of the hydrophobic and oleophobic PTFE membrane according to claim 1, characterized in that, After the plasma treatment in step 2) ends, immediately transfer the PTFE-based film to a sealed container filled with nitrogen and let it stand for 10 - 15 minutes to generate active sites with oxygen-containing polar groups (C-O, C=O) on the surface, and then perform step 3.

9. The preparation method of the hydrophobic and oleophobic PTFE membrane according to claim 1, characterized in that, During the hot pressing and compounding in step 4), uniformly sprinkle fluorine-containing microspheres with a particle size of 10 - 20 μm between the PTFE-based film and the PET non-woven fabric so that during the hot pressing process, part of them is embedded in the nanostructure on the surface of the PTFE-based film, forming a chemical - physical double anchoring effect with the fluorinated acrylate adhesive. The addition amount of the fluorine-containing microspheres is 0.3 - 8 g per square meter of the composite film area, and the surface of the hot pressing mold is coated with a 3 - 5 μm thick polytetrafluoroethylene coating.

10. The preparation method of the hydrophobic and oleophobic PTFE membrane according to claim 1, characterized in that, The pretreatment method of the nano-SiO₂ in step 6) is as follows: Disperse the nano-SiO₂ in a 2 wt% γ-aminopropyltriethoxysilane ethanol solution, stir at 70 ± 5 °C for 2.5 hours, after centrifuging and drying, blend it with a fluorine-containing polymer, and perform ultrasonic dispersion treatment at 50 kHz for 20 minutes. 5 wt% deionized water is added to the γ-aminopropyltriethoxysilane ethanol solution to promote the hydrolysis of the silane so that a uniform silane coating layer is formed on the surface of the nano-SiO₂, forming a covalent bond with the fluorine-containing polymer.

Images