PTFE microporous membrane as well as preparation method and application thereof

Abstract

The invention relates to the technical field of high-molecular compounds, in particular to a PTFE microporous membrane and a preparation method and application thereof. The composite conductive material is prepared from the following components in parts by weight: 55 to 65 parts of PTFE dispersion resin, 5 to 8 parts of graphene quantum dot / carbon nanotube and metal organic framework composite conductive phase, 6 to 9 parts of POSS-graphene hybrid modified nano silicon dioxide, 7 to 10 parts of fluorosilane grafted polyether-ether-ketone-polyimide block copolymer, 3 to 5 parts of nano hydroxyapatite-chitosan composite particles and 10 to 15 parts of composite pore-foaming agent. 1 to 3 parts of organic montmorillonite; wherein the grafting rate of the block copolymer is 25-30%, the fluorine content is 12-15 wt%, and the silicon-oxygen bond density is 0.8-1.2 mmol / g. The preparation method has the advantages of good mechanical properties and stability, multifunction synergy, pollution resistance, good biocompatibility, process optimization, improvement of consistency, meeting of multi-field requirements, and wide application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer compounds, in particular to a PTFE microporous membrane and a preparation method and application thereof. Background Art

[0002] PTFE microporous membranes, with their exceptional chemical stability, high-temperature resistance, low surface energy, and excellent air permeability, have been widely used in water treatment, energy conversion, biomedicine, and other fields. However, existing PTFE microporous membranes still have many limitations in performance and functionality, making them difficult to meet the needs of high-end applications.

[0003] Traditional PTFE microporous membranes are mostly based on pure PTFE resin and produced through simple stretching or pore-forming processes. These membranes have relatively simple mechanical properties, with insufficient tensile strength and toughness. They are prone to rupture under harsh environments such as high pressure and high-frequency vibration, resulting in a short service life. Furthermore, the single PTFE component limits the membrane's functionality, making it unable to combine various properties such as conductivity, antibacterial properties, and biocompatibility, restricting its application in high-end applications such as proton exchange membranes and medical dressings.

[0004] In terms of functional modification, existing technologies often use the direct addition of functional fillers. However, due to the highly crystalline state of PTFE molecular chains and their poor compatibility with other materials, the fillers tend to agglomerate. This not only prevents them from effectively functioning but also damages the membrane's microporous structure, reducing basic properties such as air permeability and filtration. For example, when adding carbon nanotubes to improve conductivity, uneven dispersion can cause localized excessive conductivity and overall performance fluctuations. Furthermore, aggregates can clog micropores, significantly reducing flux.

[0005] In terms of porogen selection and removal, traditional porogens are mostly single-component, resulting in limited pore-forming effects and high residual rates, which affect the purity and chemical stability of the membrane. Some porogens require extraction with organic solvents, which not only pollutes the environment but can also damage the membrane structure. Furthermore, the existing sintering and stretching process parameters are crudely controlled, leading to uneven micropore distribution, large pore size deviations, poor membrane performance consistency, and significant batch-to-batch quality fluctuations.

[0006] The rapid development of industries like new energy and biomedicine has placed higher demands on the performance of PTFE microporous membranes. These membranes must not only possess excellent basic properties but also integrate multiple functions such as conductivity, flame retardancy, biocompatibility, and pollution resistance. Existing technologies struggle to achieve the coordinated optimization of these properties. Therefore, the development of high-performance, multifunctional PTFE microporous membranes, prepared through multi-component collaborative design and innovative processes, has become an urgent need for industry development. Summary of the Invention

[0007] (1) Technical problems solved

[0008] The application provides a preparation method of a PTFE microporous membrane.

[0009] (II) Technical solutions

[0010] A PTFE microporous membrane comprises, by weight fraction, 55-65 parts of PTFE dispersion resin, 5-8 parts of graphene quantum dot / carbon nanotube@metal organic framework composite conductive phase, 6-9 parts of POSS-graphene hybrid modified nanosilica, 7-10 parts of fluorosilane grafted polyether ether ketone-polyimide block copolymer, 3-5 parts of nanohydroxyapatite-chitosan composite particles, 10-15 parts of composite pore-forming agent and 1-3 parts of organic montmorillonite; wherein the fluorosilane grafted polyether ether ketone-polyimide block copolymer has a grafting rate of 25-30%, a fluorine content of 12-15 wt% and a siloxane bond density of 0.8-1.2 mmol / g.

[0011] Preferably, the graphene quantum dot / carbon nanotube@metal organic framework composite conductive phase is prepared by mixing graphene quantum dots and multi-walled carbon nanotubes at a mass ratio of 1:4, adding 2 wt% sodium dodecylbenzenesulfonate aqueous solution, and ultrasonically dispersing for 40 min at a power of 500 W; then adding ZIF-8 metal organic framework precursor, stirring at 60 DEG C in a methanol solvent for 8 h, centrifuging and washing, and vacuum drying at 60 DEG C for 12 h to form a core-shell structure composite phase. The graphene quantum dots have a particle size of 2-4 nm, a graphene sheet thickness of 0.3-0.5 nm and a carboxyl content of 1.8-2.2 mmol / g; the multi-walled carbon nanotubes have a diameter of 5-8 nm, a length of 2-5 um and an aspect ratio of 400-600.

[0012] Preferably, the POSS-graphene hybrid modified nanosilica is prepared by adding octylamine POSS and graphene oxide at a mass ratio of 1:3 into N,N-dimethylformamide, stirring at 120 DEG C in an oil bath for 6 h, centrifuging after cooling, and vacuum drying at 100 DEG C for 8 h to obtain POSS-graphene hybrid; then adding nanosilica at a mass ratio of 1:5 into toluene, refluxing at 90 DEG C for 8 h, adding 0.5 wt% dibutyltin dilaurate as a catalyst, filtering after the reaction is completed, washing with toluene for 3 times, and vacuum drying at 80 DEG C for 10 h to obtain a grafting rate of 15-20%.

[0013] Preferably, the fluorosilane grafted polyether ether ketone-polyimide block copolymer has a number average molecular weight of 80-120 thousand, a mass ratio of polyether ether ketone segment to polyimide segment of 3:2, a polyether ether ketone segment polymerized from 4,4'-difluorobenzophenone and hydroquinone, and a polyimide segment polymerized from pyromellitic dianhydride and 4,4'-oxydianiline.

[0014] Preferably, the nano-hydroxyapatite-chitosan composite particles are prepared by adding 0.5 wt% acetic acid solution to hydroxyapatite and chitosan in a mass ratio of 5:1, stirring at a constant temperature of 55°C for 4 hours, adjusting the pH to 7.0 with 1 wt% sodium hydroxide solution after the reaction, centrifuging, and freeze-drying for 24 hours to obtain the composite particles.

[0015] Preferably, the composite porogen is polyethylene glycol 600, polyoxyethylene stearate, and sodium citrate mixed in proportion, 0.5 wt% of antioxidant 1010 is added, melt-blended at 100-120° C. for 30 min, cooled to room temperature, and then crushed through an 80-mesh sieve.

[0016] Preferably, the preparation method of the PTFE microporous membrane comprises the following steps:

[0017] S1: Preparation of composite conductive phase: Grind the prepared graphene quantum dots / carbon nanotubes@metal organic framework composite conductive phase through a 100 mesh sieve for later use;

[0018] S2: Preparation of hybrid modified SiO2, the prepared POSS-graphene hybrid modified nano-silica is vacuum dried and set aside;

[0019] S3: Mixing and plasticizing: adding PTFE dispersed resin, composite conductive phase, hybrid modified SiO2, fluorosilane grafted polyetheretherketone-polyimide block copolymer, nano-hydroxyapatite-chitosan composite particles, and organic montmorillonite into a twin-screw extruder, controlling the temperature in five stages, screw speed 200-250 rpm, vacuum degree -0.09 MPa, melt plasticizing for 5 minutes; then adding the composite porogen, continuing mixing for 8 minutes, and extruding into granules;

[0020] S4: Biaxial stretching film formation: The pellets are vacuum dried at 80°C for 4 hours and then pressed into a green film on a flat vulcanizer. The green film is heated in a stepwise manner in a sintering furnace and naturally cooled to room temperature. The film is then immersed in 85-95°C deionized water for extraction for 2.5 hours to remove the porogen. The extracted film is first stretched longitudinally and then transversely on a biaxial stretching machine and finally heat-set at 170-180°C for 4 minutes.

[0021] S5: Surface functionalization: Place the stretched and shaped film in a plasma treatment apparatus, introduce argon / oxygen mixed gas, power 300-400W, treatment time 5-8min, and increase the surface hydroxyl density to 3.0-3.5mmol / m².

[0022] Preferably, the screw combination of the twin-screw extruder in S3 is: conveying section, kneading section, dispersion section, and metering section; and the temperature of the five-section temperature control zone of the twin-screw extruder is 100-120°C, 130-150°C, 150-170°C, 140-160°C, and 130-150°C.

[0023] Preferably, the extraction process in S4 adopts ultrasonic assistance, power 200W, frequency 40kHz, and deionized water is replaced every 30min to ensure complete extraction of the pore former; an infrared temperature detector is used to monitor the surface temperature of the membrane material in real time during the stretching process.

[0024] Preferably, when the PTFE microporous membrane is used for high-temperature proton exchange membranes, the thickness of the membrane is controlled to be 80-120μm, and after being doped with phosphoric acid, the proton conductivity is 0.2-0.3S / cm under the condition of 80-120℃ and 100% humidity, and the performance retention rate is ≥90% after continuous operation for 1000h at 120℃; when the membrane is used for anti-pollution oil-water separation membranes, the membrane pore size is controlled to be 0.2-0.5μm, the separation efficiency for emulsified oil wastewater containing 5000mg / L of oil is ≥99%, the flux is 500-800L / m²・h, and the separation efficiency is still ≥98% after 50 cycles; when the membrane is used for degradable medical anti-adhesion membranes, the thickness of the membrane is controlled to be 50-80μm, the water absorption rate is 200-300%, the water vapor transmission rate is 1500-2000g / m²・24h, the cytotoxicity is 0 level, and the membrane is completely degraded in the body within 6 months.

[0025] (Three) Beneficial technical effects

[0026] Compared with the prior art, the beneficial effects of the present application are:

[0027] 1. By introducing POSS-graphene hybrid modified nanosilica and organic montmorillonite, a three-dimensional network reinforcing structure is formed inside the membrane material, effectively solving the problem of insufficient toughness and easy brittle fracture of traditional PTFE microporous membranes, so that the membrane material can still maintain structural integrity when subjected to large external force or frequent deformation, the service life is significantly prolonged, and it can adapt to complex working conditions such as high pressure and vibration.

[0028] 2. The innovative design of the composite conductive phase gives the membrane material good electrical conductivity while not negatively affecting its basic properties such as air permeability and filtration, meeting the demand for both electrical conductivity and air permeability of proton exchange membranes and the like; the addition of fluorosilane grafted block copolymer forms superhydrophobic properties on the surface of the membrane material, significantly improving the anti-pollution ability, and the membrane material is not easily attached by pollutants in oil-water separation and other scenes, and the filtration efficiency is stable for a long time; the introduction of nanohydroxyapatite-chitosan composite particles greatly improves the biocompatibility of the membrane material, so that it can be safely used in the biological and medical fields, such as medical anti-adhesion membranes, and has degradable properties, avoiding the trouble of secondary surgery removal.

[0029] 3. The stepped temperature sintering process avoids internal stress in the membrane caused by sudden temperature changes during high-temperature treatment, reducing defects such as cracks and micropore collapse. Gradient stretching technology ensures a more uniform micropore distribution in the membrane, controllable pore size, minimal performance fluctuations between batches, and highly stable product quality. Furthermore, the selection of a composite porogen and ultrasonic-assisted extraction process not only enhances the pore-forming effect but also reduces the residual porogen rate, ensuring the purity and chemical stability of the membrane while being more environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a flow chart of a method for preparing a PTFE microporous membrane proposed by the present invention;

[0031] Figure 2 is a line comparison chart of the tensile strength and biocompatibility scores of the examples and comparative examples;

[0032] Figure 3 is a comparative chart of elongation at break and electrical conductivity of the embodiment and the comparative example;

[0033] Figure 4 It is a radar comparison chart made by unifying the dimensions of the performance comparison data of the embodiment and the comparative example. DETAILED DESCRIPTION

[0034] according to Figures 1 to 4 , the specific implementation of the present invention is as follows:

[0035] Example 1

[0036] Raw material preparation: 55 parts of PTFE dispersion resin (number average molecular weight 600,000, particle size 250 μm, standard specific gravity 0.46 g / cm³), 5 parts of graphene quantum dots / carbon nanotubes@ZIF-8 composite conductive phase (graphene quantum dots particle size 2 nm, carbon nanotube diameter 5 nm), 6 parts of POSS-graphene hybrid modified nano-SiO2 (SiO2 particle size 15 nm), 7 parts of fluorosilane grafted polyetheretherketone-polyimide block copolymer (grafting rate 25%, fluorine content 12 wt%), 3 parts of nano-hydroxyapatite-chitosan composite particles (hydroxyapatite particle size 30 nm), 10 parts of composite porogen (40% polyethylene glycol 600, 35% polyoxyethylene stearate, 25% sodium citrate), and 1 part of organic montmorillonite (interlayer spacing 3.0 nm).

[0037] Preparation of composite conductive phase: Graphene quantum dots and multi-walled carbon nanotubes were mixed in a ratio of 1:4, and a 2wt% aqueous solution of sodium dodecylbenzenesulfonate (solid-to-liquid ratio of 1:20) was added. Ultrasonic dispersion was performed at 500W power for 40 minutes (temperature 50°C). ZIF-8 precursor (zinc nitrate and 2-methylimidazole molar ratio of 1:4, concentration 0.2 mol / L) was added. The mixture was stirred in methanol at 60°C for 8 hours, centrifuged at 8000 rpm for 10 minutes, vacuum dried at 60°C for 12 hours, and ground through a 100-mesh sieve.

[0038] Preparation of hybrid modified SiO2: octaamino POSS and graphene oxide (1:3) were added to N,N-dimethylformamide (solid-liquid ratio 1:30), stirred in an oil bath at 120℃ for 6h (500rpm), centrifuged at 6000rpm for 15min, and vacuum dried at 100℃ for 8h to obtain a hybrid; toluene was added to nano-SiO2 at a ratio of 1:5 (solid-liquid ratio 1:40), refluxed at 90℃ for 8h (added with 0.5wt% dibutyltin dilaurate), filtered, washed with toluene 3 times, and vacuum dried at 80℃ for 10h.

[0039] Mixing and plasticizing: Add PTFE dispersed resin, composite conductive phase, hybrid modified SiO2, block copolymer, composite particles, and organic montmorillonite into a twin-screw extruder (length-to-diameter ratio 40:1), control the temperature in five sections (zone 1 100°C, zone 2 130°C, zone 3 150°C, zone 4 140°C, zone 5 130°C), screw speed 200rpm, vacuum degree -0.09MPa, melt plasticization for 5min; add composite porogen and continue mixing for 8min, and extrude into granules (granule diameter 2-3mm, length 3-5mm).

[0040] Biaxial stretching film forming: the pellets were vacuum dried at 80°C for 4 h (-0.08 MPa), and calendered at 120°C and 5 MPa for 5 min to form a 0.3 mm green film; the sintering furnace was heated in steps (room temperature → 200°C, 5°C / min, hold for 5 min; 200 → 300°C, 3°C / min, hold for 5 min; 300 → 380°C, 2°C / min, hold for 8 min), and naturally cooled; the pellets were extracted with deionized water at 85°C for 2.5 h (bath ratio 1:50, 200W ultrasonic assistance, water change every 30 min); the pellets were longitudinally stretched in a biaxial stretching machine (60°C × 1.5 times → 80°C × 1.5 times → 100°C × 1.5 times, chuck speed 80 mm / min), and transversely stretched (110°C × 2 times → 130°C × 2 times → 150°C × 1.5 times, chuck speed 120 mm / min), and heat-set at 170°C for 4 min (tension 8 N).

[0041] Surface functionalization: The membrane was placed in a plasma treatment apparatus and introduced with argon / oxygen (3:1, flow rate 20 sccm) at 300 W power for 5 min.

[0042] Example 2

[0043] Raw material preparation: 60 parts of PTFE dispersion resin (number average molecular weight 750,000, particle size 320 μm, standard specific gravity 0.48 g / cm³), 6.5 parts of graphene quantum dots / carbon nanotubes@ZIF-8 composite conductive phase (graphene quantum dots particle size 3 nm, carbon nanotube diameter 6.5 nm), 7.5 parts of POSS-graphene hybrid modified nano-SiO2 (SiO2 particle size 20 nm), 8.5 parts of fluorosilane grafted polyetheretherketone-polyimide block copolymer (grafting rate 27%, fluorine content 13.5 wt%), 4 parts of nano-hydroxyapatite-chitosan composite particles (hydroxyapatite particle size 40 nm), 12.5 parts of composite porogen (45% polyethylene glycol 600, 32% polyoxyethylene stearate, 23% sodium citrate), and 2 parts of organic montmorillonite (interlayer spacing 3.5 nm).

[0044] Preparation of composite conductive phase: Graphene quantum dots and multi-walled carbon nanotubes were mixed in a ratio of 1:4, and a 2wt% aqueous solution of sodium dodecylbenzenesulfonate (solid-to-liquid ratio of 1:20) was added. Ultrasonic dispersion was performed at 500W power for 40 minutes (temperature 50°C). ZIF-8 precursor (zinc nitrate and 2-methylimidazole molar ratio of 1:4, concentration 0.2 mol / L) was added. The mixture was stirred in methanol at 60°C for 8 hours, centrifuged at 8000 rpm for 10 minutes, vacuum dried at 60°C for 12 hours, and ground through a 100-mesh sieve.

[0045] Preparation of hybrid modified SiO2: octaamino POSS and graphene oxide (1:3) were added to N,N-dimethylformamide (solid-liquid ratio 1:30), stirred in an oil bath at 120℃ for 6h (500rpm), centrifuged at 6000rpm for 15min, and vacuum dried at 100℃ for 8h to obtain a hybrid; toluene was added to nano-SiO2 at a ratio of 1:5 (solid-liquid ratio 1:40), refluxed at 90℃ for 8h (added with 0.5wt% dibutyltin dilaurate), filtered, washed with toluene 3 times, and vacuum dried at 80℃ for 10h.

[0046] Mixing and plasticizing: Add PTFE dispersed resin, composite conductive phase, hybrid modified SiO2, block copolymer, composite particles, and organic montmorillonite into a twin-screw extruder (length-to-diameter ratio 40:1), control the temperature in five sections (zone 1 110°C, zone 2 140°C, zone 3 160°C, zone 4 150°C, zone 5 140°C), screw speed 225rpm, vacuum degree -0.09MPa, melt plasticization for 5min; add composite porogen and continue mixing for 8min, and extrude into granules (granule diameter 2-3mm, length 3-5mm).

[0047] Biaxial stretching film formation: the pellets were vacuum dried at 80°C for 4 h (-0.08 MPa), and calendered at 120°C and 5 MPa for 5 min to form a 0.4 mm green film; the sintering furnace was heated in steps (room temperature → 200°C, 5°C / min, hold for 5 min; 200 → 300°C, 3°C / min, hold for 5 min; 300 → 380°C, 2°C / min, hold for 8 min), and naturally cooled; the pellets were extracted with deionized water at 90°C for 2.5 h (bath ratio 1:50, 200W ultrasonic assistance, water change every 30 min); the pellets were longitudinally stretched (60°C × 1.5 times → 80°C × 1.5 times → 100°C × 1.5 times, chuck speed 80 mm / min) and transversely stretched (110°C × 2 times → 130°C × 2 times → 150°C × 1.5 times, chuck speed 120 mm / min), and heat-set at 175°C for 4 min (tension 8 N).

[0048] Surface functionalization: The membrane was placed in a plasma treatment apparatus and treated with argon / oxygen (3:1, flow rate 20 sccm) at 350 W power for 6.5 min.

[0049] Example 3

[0050] Raw material preparation: 65 parts of PTFE dispersion resin (number average molecular weight 900,000, particle size 400μm, standard specific gravity 0.50g / cm³), 8 parts of graphene quantum dots / carbon nanotubes@ZIF-8 composite conductive phase (graphene quantum dots particle size 4nm, carbon nanotube diameter 8nm), 9 parts of POSS-graphene hybrid modified nano-SiO2 (SiO2 particle size 25nm), 10 parts of fluorosilane grafted polyetheretherketone-polyimide block copolymer (grafting rate 30%, fluorine content 15wt%), 5 parts of nano-hydroxyapatite-chitosan composite particles (hydroxyapatite particle size 50nm), 15 parts of composite porogen (50% polyethylene glycol 600, 30% polyoxyethylene stearate, 20% sodium citrate), and 3 parts of organic montmorillonite (interlayer spacing 4.0nm).

[0051] Preparation of composite conductive phase: Graphene quantum dots and multi-walled carbon nanotubes were mixed in a ratio of 1:4, and a 2wt% aqueous solution of sodium dodecylbenzenesulfonate (solid-to-liquid ratio of 1:20) was added. Ultrasonic dispersion was performed at 500W power for 40 minutes (temperature 50°C). ZIF-8 precursor (zinc nitrate and 2-methylimidazole molar ratio of 1:4, concentration 0.2 mol / L) was added. The mixture was stirred in methanol at 60°C for 8 hours, centrifuged at 8000 rpm for 10 minutes, vacuum dried at 60°C for 12 hours, and ground through a 100-mesh sieve.

[0052] Preparation of hybrid modified SiO2: octaamino POSS and graphene oxide (1:3) were added to N,N-dimethylformamide (solid-liquid ratio 1:30), stirred in an oil bath at 120℃ for 6h (500rpm), centrifuged at 6000rpm for 15min, and vacuum dried at 100℃ for 8h to obtain a hybrid; toluene was added to nano-SiO2 at a ratio of 1:5 (solid-liquid ratio 1:40), refluxed at 90℃ for 8h (added with 0.5wt% dibutyltin dilaurate), filtered, washed with toluene 3 times, and vacuum dried at 80℃ for 10h.

[0053] Mixing and plasticizing: Add PTFE dispersed resin, composite conductive phase, hybrid modified SiO2, block copolymer, composite particles, and organic montmorillonite into a twin-screw extruder (length-to-diameter ratio 40:1), control the temperature in five sections (zone 1 120°C, zone 2 150°C, zone 3 170°C, zone 4 160°C, zone 5 150°C), screw speed 250rpm, vacuum degree -0.09MPa, melt plasticization for 5min; add composite porogen and continue mixing for 8min, and extrude into granules (granule diameter 2-3mm, length 3-5mm).

[0054] Biaxial stretching film formation: the pellets were vacuum dried at 80°C for 4 h (-0.08 MPa), and calendered at 120°C and 5 MPa for 5 min to form a 0.5 mm green film; the sintering furnace was heated in steps (room temperature → 200°C, 5°C / min, hold for 5 min; 200 → 300°C, 3°C / min, hold for 5 min; 300 → 380°C, 2°C / min, hold for 8 min), and naturally cooled; the pellets were extracted with deionized water at 95°C for 2.5 h (bath ratio 1:50, 200W ultrasonic assistance, water change every 30 min); the pellets were longitudinally stretched (60°C × 1.5 times → 80°C × 1.5 times → 100°C × 1.5 times, chuck speed 80 mm / min) and transversely stretched (110°C × 2 times → 130°C × 2 times → 150°C × 1.5 times, chuck speed 120 mm / min), and heat-set at 180°C for 4 min (tension 8 N).

[0055] Surface functionalization: The membrane was placed in a plasma treatment apparatus and treated with argon / oxygen (3:1, flow rate 20 sccm) at 400 W power for 8 min.

[0056] Comparative Example

[0057] Raw material preparation: 70 parts of PTFE dispersion resin (number average molecular weight 600,000, particle size 300μm), 3 parts of carbon nanotubes (diameter 8nm), 5 parts of ordinary nano-SiO2 (particle size 20nm), 6 parts of polyetheretherketone, and 15 parts of porogen (single polyethylene glycol 600).

[0058] Preparation process: All raw materials were directly added to a twin-screw extruder, mixed at 150°C and 200 rpm for 10 minutes, and extruded into granules; the granules were dried at 80°C for 4 hours and calendered into 0.4 mm green films at 120°C; sintered at 380°C for 5 minutes and extracted with deionized water at 80°C for 2 hours (without ultrasound); and stretched longitudinally 5 times using a unidirectional stretching machine (100°C, rate 100 mm / min) without surface treatment.

[0059] The performance comparison of the embodiment and the comparative example is shown in the following table:

[0060] Table 1

[0061] project Example 1 Example 2 Example 3 Comparative Example Tensile strength (MPa) 32 35 38 18 Elongation at break (%) 155 165 175 85 Conductivity (S / m) 205 250 295 65 Water contact angle (°) 160 162 165 110 Biocompatibility score 95 96 97 70 Residual rate of porogen (%) 0.3 0.25 0.2 1.2

[0062] The examples address the filler agglomeration and monotonous performance issues encountered in the comparative examples by utilizing a core-shell structure design for the composite conductive phase, a three-dimensional reinforced network of hybrid SiO2, and gradient process control. Graft modification of block copolymers enhances interfacial compatibility, while step sintering and biaxial stretching ensure uniform micropores. Surface treatment enhances functional compatibility, resulting in comprehensive performance that meets the demands of high-end applications.

[0063] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A PTFE microporous membrane, characterized in that The invention comprises, by weight, 55-65 parts of PTFE dispersed resin, 5-8 parts of graphene quantum dots / carbon nanotubes@metal organic framework composite conductive phase, 6-9 parts of POSS-graphene hybrid modified nano-silica, 7-10 parts of fluorosilane grafted polyetheretherketone-polyimide block copolymer, 3-5 parts of nano-hydroxyapatite-chitosan composite particles, 10-15 parts of composite porogen, and 1-3 parts of organic montmorillonite; wherein the grafting rate of the fluorosilane grafted polyetheretherketone-polyimide block copolymer is 25-30%, the fluorine content is 12-15wt%, and the silicon-oxygen bond density is 0.8-1.2mmol / g.

2. The PTFE microporous membrane according to claim 1, wherein The graphene quantum dot / carbon nanotube@metal organic framework composite conductive phase is prepared by mixing graphene quantum dots and multi-walled carbon nanotubes in a mass ratio of 1:4, adding a 2wt% sodium dodecylbenzenesulfonate aqueous solution, and ultrasonically dispersing at a power of 500W for 40 minutes; then adding a ZIF-8 metal organic framework precursor, reacting at a constant temperature of 60°C in a methanol solvent with stirring for 8 hours, centrifuging and washing, and vacuum drying at 60°C for 12 hours to form a core-shell structure composite phase; the graphene quantum dots have a particle size of 2-4nm, a graphene sheet thickness of 0.3-0.5nm, and a carboxyl content of 1.8-2.2mmol / g; the multi-walled carbon nanotubes have a diameter of 5-8nm, a length of 2-5μm, and an aspect ratio of 400-600.

3. The PTFE microporous membrane according to claim 2, wherein The preparation of the POSS-graphene hybrid modified nano-silica comprises the following steps: adding octaamino POSS and graphene oxide in a mass ratio of 1:3 to N,N-dimethylformamide, reacting in an oil bath at 120° C. with stirring for 6 hours, cooling and centrifuging, and vacuum drying at 100° C. for 8 hours to obtain a POSS-graphene hybrid; then adding toluene with nano-SiO2 in a mass ratio of 1:5, reacting under reflux at 90° C. for 8 hours, adding 0.5wt% dibutyltin dilaurate as a catalyst, filtering after the reaction, washing with toluene three times, and vacuum drying at 80° C. for 10 hours, with a grafting rate of 15-20%.

4. The PTFE microporous membrane according to claim 3, wherein The number average molecular weight of the fluorosilane grafted polyetheretherketone-polyimide block copolymer is 80,000-120,000, wherein the mass ratio of the polyetheretherketone segment to the polyimide segment is 3:2, the polyetheretherketone segment is polymerized by 4,4'-difluorobenzophenone and hydroquinone, and the polyimide segment is polymerized by pyromellitic dianhydride and 4,4'-diaminodiphenyl ether.

5. The PTFE microporous membrane according to claim 4, characterized in that Nano-hydroxyapatite-chitosan composite particles were prepared by adding 0.5 wt% acetic acid solution to hydroxyapatite and chitosan in a mass ratio of 5:1, stirring at a constant temperature of 55°C for 4 h, adjusting the pH to 7.0 with 1 wt% sodium hydroxide solution after the reaction, centrifuging, and freeze-drying for 24 h to obtain the composite particles.

6. The PTFE microporous membrane according to claim 5, characterized in that The composite porogen is prepared by mixing polyethylene glycol 600, polyoxyethylene stearate and sodium citrate in proportion, adding 0.5 wt % of antioxidant 1010, melting and blending at 100-120° C. for 30 min, cooling to room temperature and then crushing through an 80-mesh sieve.

7. A method for preparing a PTFE microporous membrane as claimed in claim 6, characterized in that: The following steps are involved: S1: Preparation of composite conductive phase: Grind the prepared graphene quantum dots / carbon nanotubes@metal organic framework composite conductive phase through a 100 mesh sieve for later use; S2: Preparation of hybrid modified SiO2, the prepared POSS-graphene hybrid modified nano-silica is vacuum dried and set aside; S3: Mixing and plasticizing: adding PTFE dispersed resin, composite conductive phase, hybrid modified SiO2, fluorosilane grafted polyetheretherketone-polyimide block copolymer, nano-hydroxyapatite-chitosan composite particles, and organic montmorillonite into a twin-screw extruder, controlling the temperature in five stages, screw speed 200-250 rpm, vacuum degree -0.09 MPa, melt plasticizing for 5 minutes; then adding the composite porogen, continuing mixing for 8 minutes, and extruding into granules; S4: Biaxial stretching film formation: The pellets are vacuum dried at 80°C for 4 hours and then pressed into a green film on a flat vulcanizer. The green film is heated in a stepwise manner in a sintering furnace and naturally cooled to room temperature. The film is then immersed in 85-95°C deionized water for extraction for 2.5 hours to remove the porogen. The extracted film is first stretched longitudinally and then transversely on a biaxial stretching machine and finally heat-set at 170-180°C for 4 minutes. S5: Surface functionalization: Place the stretched and shaped film in a plasma treatment apparatus, introduce argon / oxygen mixed gas, power 300-400W, treatment time 5-8min, and increase the surface hydroxyl density to 3.0-3.5mmol / m².

8. The method for preparing a PTFE microporous membrane according to claim 7, wherein The screw combination of the twin-screw extruder in S3 is: conveying section, kneading section, dispersion section, and metering section; and the temperature of the five-section twin-screw extruder is controlled in zone one at 100-120°C, zone two at 130-150°C, zone three at 150-170°C, zone four at 140-160°C, and zone five at 130-150°C.

9. The method for preparing a PTFE microporous membrane according to claim 7, wherein The extraction process in S4 was ultrasonically assisted with a power of 200W and a frequency of 40kHz. Deionized water was replaced every 30 minutes to ensure complete extraction of the porogen. An infrared thermometer was used to monitor the surface temperature of the membrane in real time during the stretching process.

10. An application of the PTFE microporous membrane according to claim 1, characterized in that: When used as a high-temperature proton exchange membrane, the membrane thickness is controlled at 80-120μm. After phosphoric acid doping, the proton conductivity is 0.2-0.3S / cm at 80-120℃ and 100% humidity. After 1000h of continuous operation at 120℃, the performance retention rate is ≥90%. When used as an anti-pollution oil-water separation membrane, the membrane pore size is controlled at 0.2-0.5μm. The separation efficiency for emulsified oil wastewater with an oil content of 5000mg / L is ≥99%, and the flux is 500-800L / m²・h. After 50 cycles, the separation efficiency is still ≥98%. When used in degradable medical anti-adhesion membranes, the membrane thickness is controlled at 50-80μm, the water absorption rate is 200-300%, the water vapor permeability is 1500-2000g / m²・24h, the cytotoxicity is level 0, and it is completely degraded in the body within 6 months.

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