CN112316749B - Chemical-hydrophilicity-resistant reversible PTFE microporous membrane and preparation method thereof - Google Patents
Chemical-hydrophilicity-resistant reversible PTFE microporous membrane and preparation method thereof Download PDFInfo
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- CN112316749B CN112316749B CN202011125154.5A CN202011125154A CN112316749B CN 112316749 B CN112316749 B CN 112316749B CN 202011125154 A CN202011125154 A CN 202011125154A CN 112316749 B CN112316749 B CN 112316749B
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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Abstract
The invention belongs to the technical field of membrane separation, and particularly relates to and discloses a chemical-hydrophilicity-resistant reversible PTFE microporous membrane. The invention also discloses a preparation method of the PTFE microporous membrane, which comprises the following steps: 1) preparing aniline monomer emulsion; 2) carrying out in-situ polymerization reaction; 3) and (5) post-treatment. According to the chemical-resistant hydrophilic reversible polytetrafluoroethylene microporous membrane and the preparation method thereof, the nano-scale polyaniline particles are closely distributed on the surfaces of polytetrafluoroethylene fibrils, hydrophilic amino groups are arranged in molecular chains of the polyaniline particles, the polyaniline particles are hydrophilic materials, the super-hydrophilic surfaces can be obtained by combining a three-dimensional micro-nano structure, the chemical resistance of the polyaniline microporous membrane is excellent, and the polytetrafluoroethylene microporous membrane can operate under the condition of poor water quality for a long time, so that the excellent performance of the polytetrafluoroethylene is really exerted.
Description
Technical Field
The invention belongs to the technical field of membrane separation, and particularly relates to a chemical-hydrophilicity-resistant reversible PTFE microporous membrane and a preparation method thereof.
Background
The PTFE material has many excellent properties, such as chemical corrosion resistance, thermal stability, aging resistance, good lubricity, electrical insulation property and the like, has the reputation of "plastic king", and is widely applied to the fields of sealing, aerospace, automotive mechanical and electronic, biomedical, cable, textile, environmental protection and the like. However, the polytetrafluoroethylene microporous membrane has strong hydrophobicity due to high carbon-fluorine bond energy, highly symmetrical molecular structure and low surface energy of polytetrafluoroethylene molecules, so that water molecules cannot penetrate through pores of the polytetrafluoroethylene membrane under normal pressure or low pressure, and the application of the polytetrafluoroethylene membrane in aqueous solution treatment is limited. Therefore, the polytetrafluoroethylene microporous membrane is modified, the hydrophilic performance of the polytetrafluoroethylene microporous membrane is improved, and the polytetrafluoroethylene microporous membrane has important practical significance and economic value.
At present, experts and scholars at home and abroad research the hydrophilic modification of the surface of the PTFE flat sheet membrane by a series of methods such as chemistry, physics and the like and obtain certain effect. Patent CN201610490422.0 discloses a hydrophilic modification method of polytetrafluoroethylene microporous membrane, which comprises immersing polytetrafluoroethylene microporous membrane in acrylate monomer solution for sufficient replacement, and then initiating polymerization reaction by thermal initiation or ultraviolet light. Patent CN201310153056.6 discloses a method for modifying a polytetrafluoroethylene microporous membrane with a lasting hydrophilic property, which comprises impregnating the polytetrafluoroethylene microporous membrane with polyhydroxyl compounds such as diethanolamine, polyvinyl alcohol or water-soluble starch, and then cross-linking with glutaraldehyde or glyoxal. Patent CN201810633164.6 discloses a preparation method of hydrophilic polytetrafluoroethylene microporous membrane, which comprises immersing polytetrafluoroethylene microporous membrane in levodopa polymerization solution for reaction for a period of time, and heating and curing with curing solution (formaldehyde, paraformaldehyde or glutaraldehyde). The patent CN201610123764.9 discloses a method for hydrophilization modification of the surface of a polytetrafluoroethylene hollow fiber membrane, which comprises the steps of immersing the polytetrafluoroethylene hollow fiber membrane in a solution containing hydrophilic groups, then treating the polytetrafluoroethylene hollow fiber membrane by using radio frequency plasma, bombarding and etching the membrane body and hydrophilic substances on the surface of the membrane simultaneously to generate active free radicals, and then initiating and grafting the hydrophilic groups onto the polytetrafluoroethylene hollow fiber membrane to form a stable hydrophilic layer.
The modification methods can achieve that the PTFE membrane has certain hydrophilicity, and hydrophilic groups such as carbonyl, hydroxyl, amino and sulfonic groups are introduced on the surface of the membrane in the modification process. In these modification methods, radiation grafting, plasma treatment, and the like require complicated and expensive equipment, resulting in serious limitations in industrial production applications. More importantly, the introduced hydrophilic substance is not in acid, alkali and oxidation resistant environment, is easy to be eroded, degraded and lost by chemical reagents and cannot operate under severe water quality condition for a long time; after the hydrophilic modification layer is damaged, the hydrophobic membrane material has no water treatment application value although the polytetrafluoroethylene membrane skeleton is intact. The hydrophilic modified layer without drug resistance makes the super stability of the polytetrafluoroethylene useless. Thus, the hydrophilic modification of PTFE membranes has yet to be studied.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides the chemical-hydrophilicity-resistant reversible PTFE microporous membrane with the hydrophilic modified layer, which has good acid and alkali resistance and oxidation stability and can operate under the severe water quality condition for a long time, thereby really playing the excellent performance of the polytetrafluoroethylene, and the preparation method thereof.
In order to achieve the purpose, the invention adopts the following technical scheme:
a chemical-resistant hydrophilic reversible PTFE (polytetrafluoroethylene) microporous membrane comprises micrometer-scale polytetrafluoroethylene fibrils and nanometer-scale polyaniline particles, wherein the nanometer-scale polyaniline particles are tightly distributed on the surfaces of the micrometer-scale polytetrafluoroethylene fibrils in a lattice form to form a three-dimensional micro-nano structure.
Polyaniline is one of the materials which are developed rapidly and widely in recent years. The molecular chain of polyaniline has hydrophilic amino which is a hydrophilic material, and the super-hydrophilic surface can be obtained by changing the micro roughness of the surface. Meanwhile, compared with other hydrophilic high polymers, polyaniline has good environmental stability, and has a long history of being used as an anticorrosive coating. In the invention, the nano-scale polyaniline particles are closely arranged on the surface of the micrometer-scale polytetrafluoroethylene fibril in a lattice form to form a three-dimensional micro-nano structure, and the three-dimensional micro-nano structure has excellent hydrophilicity and chemical resistance.
Preferably, the hydrophilicity of the polyaniline particles generates reversible change along with the doping/de-doping bidirectional response or the oxidation/reduction bidirectional response of the polyaniline particles on the surface in the using process, and the reversible change range of the water contact angle is 10-70 degrees.
Reversible doping/de-doping and oxidation/reduction processes of the polyaniline nano structure are accompanied by reversible change of hydrophilicity, and different hydrophilic characteristics can be displayed in different environments. Under the condition of strong acid or strong alkali, the polyaniline nano structure shows super-hydrophilic property, so that the polyaniline nano structure is particularly suitable for wastewater treatment under severe conditions of strong acid, strong alkali and the like which can not be performed by common membrane materials.
Preferably, the polyaniline particles have an average diameter of 5 to 60nm, and the polytetrafluoroethylene fibrils have a diameter of 0.05 to 2.0 μm.
Preferably, the membrane is a flat membrane, a hollow fiber membrane, a homogeneous membrane or a composite membrane, and the average pore diameter is 0.02 to 10 μm.
A preparation method of a chemical-resistant hydrophilic reversible PTFE microporous membrane comprises the following steps:
1) preparing aniline monomer emulsion: dissolving a surfactant in water, dropwise adding an aniline monomer while stirring, and regulating the pH value of the aniline monomer to be 1-6 by doping acid to obtain a uniform and stable aniline monomer emulsion with the concentration of 0.01-0.5M;
2) in-situ polymerization reaction: soaking a PTFE microporous membrane in the prepared aniline monomer emulsion for 10-60 min, taking out, placing in an oxidant aqueous solution with the pH value of 1-6, reacting at 0-40 ℃ for 5 min-24 h, and adjusting the pH value of the oxidant aqueous solution by doping acid;
3) and (3) post-treatment: and taking out the PTFE microporous membrane subjected to the in-situ polymerization reaction, repeatedly rinsing with water, and airing.
The surfactant is a structure directing agent for preparing polyaniline nano particles. Because the aniline molecule is slightly soluble in water, the surfactant encapsulates the aniline after forming a gel in water, thus forming a plurality of aniline-encapsulated nanoscale particles in the aqueous solution. And after the oxidant is added, oxidizing the aniline by the oxidant through the surfactant to obtain the polyaniline nanoparticles.
Preferably, the surfactant is sodium octyl sulfonate, sodium octyl sulfate, dodecylbenzenesulfonic acid, sodium dodecylbenzenesulfonate, sodium dodecylsulfonate, sodium dodecylsulfate, sodium tetradecylsulfate, sodium hexadecylsulfate, sodium octadecyl sulfate, nonylphenol polyoxyethylene ether-9, polyethylene glycol isooctylphenol ether, stearic acid, potassium stearate, potassium oleate, potassium laurate, azobenzenesulfonate having an alkyl group, octyltrimethylammonium bromide, dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, dodecylpyridinium bromide, hexadecyltrimethylammonium chloride, 1-hexadecyl-3-methyl-imidazoline chloride, laureth oxide, tetradecyl polyoxyethylene ether, dioctyl sodium sulfosuccinate, sucrose laurate, sucrose palmitate, sodium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium dodecyltrimethylammonium bromide, 1-hexadecyl-3-methyl-imidazoline chloride, lauryl sulfate, sucrose palmitate, sodium lauryl sulfate, sodium lauryl sulfate, sodium chloride, sodium lauryl sulfate, sodium chloride, sodium lauryl sulfate, sodium lauryl sulfate, sodium chloride, sodium lauryl sulfate, sodium lauryl sulfate, sodium chloride, sodium lauryl sulfate, sodium chloride, sodium lauryl sulfate, sodium chloride, sodium, Sucrose stearate, tween, span, etc.
Preferably, the surfactant concentration is 1.0X 10 -4 0.3M to 1 to 10 times of the critical micelle concentration. The shape and stability of the micelle are related not only to the properties of the surfactant itself but also to the concentration of the surfactant, the properties of the dispersion medium, the shearing force, and the like. Surfactant micelles do not appear in a specific shape, often several shapes coexist, and the main morphology of the micelle has a large relationship with the concentration of the surfactant. When the concentration of the surfactant is not so large, the micelle is mostly spherical. When the concentration is 10 times the critical micelle concentration or more, rod-like micelles are formed, the surface of which is composed of hydrophilic groups and the core of which is composed of hydrophobic groups.
Preferably, the doping acid is one or a mixture of two of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, perchloric acid, formic acid, acetic acid, citric acid, malic acid, tartaric acid, salicylic acid, oxalic acid, lactic acid, methanesulfonic acid, p-toluenesulfonic acid, azobenzenesulfonic acid, camphorsulfonic acid, naphthalenesulfonic acid, and the like.
Preferably, the oxidizing agent is any one of hydrogen peroxide, ammonium persulfate, potassium dichromate, ferric chloride, and the like.
Preferably, the concentration of the oxidant is 0.01 to 0.5M, and the ratio of the oxidant to the amount of aniline monomer material is 1:2 to 2: 1.
The invention relates to a chemical-resistant hydrophilic reversible polytetrafluoroethylene microporous membrane and a preparation method thereof. The polyaniline molecular chain has hydrophilic amino, is a hydrophilic material, and can obtain a super-hydrophilic surface by combining a three-dimensional micro-nano structure. Meanwhile, polyaniline has excellent chemical resistance and can operate under the condition of poor water quality for a long time, so that the excellent performance of polytetrafluoroethylene is truly exerted.
Drawings
FIG. 1 is a scanning electron microscope image of a chemically resistant hydrophilic reversible PTFE microporous membrane described in example 1.
Fig. 2 is a partially enlarged view of fig. 1.
FIG. 3 is a scanning electron micrograph of PTFE microporous membrane fibrils described in example 1.
Fig. 4 is a partially enlarged view of fig. 3.
Detailed Description
The present invention will be further described with reference to FIGS. 1 to 4 and the following detailed description.
Example 1
A chemical-resistant hydrophilic reversible PTFE microporous membrane comprises micrometer-scale polytetrafluoroethylene fibrils as shown in figures 1 and 2, and nanoscale polyaniline particles which are closely distributed on the surfaces of the micrometer-scale polytetrafluoroethylene fibrils in a lattice form to form a three-dimensional micro-nano structure. Wherein: scanning electron micrographs of the PTFE microporous membrane fibrils are shown in FIGS. 3 and 4.
In the using process, the hydrophilicity of the polyaniline particles generates reversible change along with the doping/de-doping bidirectional response or the oxidation/reduction bidirectional response of the polyaniline particles on the surface, and the reversible change range of the water contact angle is 30-65 degrees.
The polyaniline particles have an average diameter of 5 to 10 nm.
The polytetrafluoroethylene fibrils have diameters of 0.05-0.5 μm.
The chemical-resistant hydrophilic reversible PTFE microporous membrane is a hollow fiber composite membrane, and the average pore diameter of the composite membrane is 0.02 mu m.
A preparation method of a chemical-resistant hydrophilic reversible PTFE microporous membrane comprises the following steps:
1) preparing aniline monomer emulsion: dissolving sodium octyl sulfonate in water, dropwise adding an aniline monomer while stirring, and regulating the pH value to be 1 by doping acid to obtain a uniform and stable aniline monomer emulsion with the concentration of the sodium octyl sulfonate being 0.3M and the concentration of the aniline monomer being 0.5M;
2) in-situ polymerization reaction: soaking a PTFE microporous membrane in the prepared aniline monomer emulsion for 60min, taking out, placing in a hydrogen peroxide aqueous solution with the pH value of 1, reacting for 24h at 0-40 ℃, adjusting the pH value of an oxidant aqueous solution by sulfuric acid, wherein the concentration of the hydrogen peroxide is 0.5M, and the amount ratio of the hydrogen peroxide to the aniline monomer is 1: 1;
3) and (3) post-treatment: and taking out the PTFE microporous membrane subjected to the in-situ polymerization reaction, repeatedly rinsing with water, and airing.
The polytetrafluoroethylene microporous membrane in the step 2) is a hollow fiber composite membrane, and the average pore diameter is 0.1 mu m.
Example 2
A PTFE microporous membrane with reversible resistance to chemical hydrophilicity, the structure of which is the same as example 1 except that:
the reversible change range of the water contact angle is 30-70 degrees.
The average diameter of the polyaniline particles is 5-10 nm.
The polytetrafluoroethylene fibrils have diameters of 0.05-0.5 μm.
The chemical-resistant hydrophilic reversible PTFE microporous membrane is a hollow fiber composite membrane, and the average pore diameter is 0.03 mu m.
A preparation method of a chemical-resistant hydrophilic reversible polytetrafluoroethylene microporous membrane comprises the following steps:
1) preparing aniline monomer emulsion: dissolving sodium octyl sulfate in water, dropwise adding an aniline monomer while stirring, and regulating the pH value to be 2 by hydrochloric acid to obtain a uniform and stable aniline monomer emulsion with the sodium octyl sulfate concentration of 0.14M and the aniline monomer concentration of 0.3M;
2) in-situ polymerization reaction: soaking a polytetrafluoroethylene microporous membrane in the prepared aniline monomer emulsion for 60min, taking out, placing in an ammonium persulfate aqueous solution with the pH value of 2 (regulated by hydrochloric acid) (the concentration is 0.18M, and the mass ratio of ammonium persulfate to aniline monomer substances is 3: 5), and reacting for 24h at the temperature of 0 ℃;
3) and (3) post-treatment: and taking out the polytetrafluoroethylene microporous membrane subjected to the in-situ polymerization reaction, repeatedly rinsing with water, and airing.
The polytetrafluoroethylene microporous membrane in the step 2) is a hollow fiber composite membrane, and the average pore diameter is 0.1 mu m.
Example 3
A PTFE microporous membrane with reversible resistance to chemical hydrophilicity, the structure of which is the same as example 1 except that:
the reversible change range of the water contact angle is 30-70 degrees.
The average diameter of the polyaniline particles is 10-20 nm.
The polytetrafluoroethylene fibrils have diameters of 0.05-0.5 μm.
The chemical-resistant hydrophilic reversible PTFE microporous membrane is a hollow fiber composite membrane. The average pore diameter was 0.05. mu.m.
A preparation method of a chemical-resistant hydrophilic reversible polytetrafluoroethylene microporous membrane is characterized by comprising the following steps:
1) preparing aniline monomer emulsion: dissolving dodecyl trimethyl ammonium bromide in water, dropwise adding an aniline monomer while stirring, and regulating the pH value to 3 by nitric acid to obtain a uniform and stable aniline monomer emulsion with the concentration of the dodecyl trimethyl ammonium bromide of 0.032M and the concentration of the aniline monomer of 0.2M;
2) in-situ polymerization reaction: soaking a polytetrafluoroethylene microporous membrane in the prepared aniline monomer emulsion for 60min, taking out, placing in a potassium persulfate aqueous solution with the pH value of 3 (adjusted by nitric acid) (the concentration is 0.16M, and the weight ratio of potassium persulfate to aniline monomer substances is 4: 5), and reacting for 24h at the temperature of 0 ℃;
3) and (3) post-treatment: and taking out the polytetrafluoroethylene microporous membrane subjected to the in-situ polymerization reaction, repeatedly rinsing with water, and airing.
The polytetrafluoroethylene microporous membrane in the step 2) is a hollow fiber composite membrane, and the average pore diameter is 0.1 mu m.
Example 4
A PTFE microporous membrane with reversible chemical resistance and hydrophilicity, the structure of which is the same as example 1 except that:
the reversible change range of the water contact angle is 20-60 degrees.
The average diameter of the polyaniline particles is 10-20 nm.
The polytetrafluoroethylene fibrils have diameters of 0.1-1 μm.
The chemical-resistant hydrophilic reversible PTFE microporous membrane is a flat composite membrane, and the average pore diameter is 0.1 mu m.
A preparation method of a chemical-resistant hydrophilic reversible polytetrafluoroethylene microporous membrane is characterized by comprising the following steps:
1) preparing aniline monomer emulsion: dissolving dodecyl pyridine bromide in water, dropwise adding an aniline monomer while stirring, and regulating the pH value to be 4 by perchloric acid to obtain a uniform and stable aniline monomer emulsion with the dodecyl pyridine bromide concentration of 0.025M and the aniline monomer concentration of 0.15M;
2) in-situ polymerization: soaking a polytetrafluoroethylene microporous membrane in the prepared aniline monomer emulsion for 10min, taking out, placing in a potassium dichromate aqueous solution with the pH value of 4 (regulated by perchloric acid) (the concentration of the potassium dichromate is 0.15M, and the weight ratio of the potassium dichromate to the aniline monomer substances is 1: 1), and reacting for 60min at the temperature of 20 ℃;
3) and (3) post-treatment: and taking out the polytetrafluoroethylene microporous membrane subjected to the in-situ polymerization reaction, repeatedly rinsing with water, and airing.
And 2) the polytetrafluoroethylene microporous membrane is a flat composite membrane, and the average pore diameter is 0.2 mu m.
Example 5
A PTFE microporous membrane with reversible resistance to chemical hydrophilicity, the structure of which is the same as example 1 except that:
the reversible change range of the water contact angle is 10-50 degrees.
The average diameter of the polyaniline particles is 10-20 nm.
The polytetrafluoroethylene fibril has a diameter of 0.1 to 1 μm.
The chemical-resistant hydrophilic reversible PTFE microporous membrane is a hollow fiber composite membrane, and the average pore diameter is 0.15 mu m.
A preparation method of a chemical-resistant hydrophilic reversible polytetrafluoroethylene microporous membrane is characterized by comprising the following steps:
1) preparing aniline monomer emulsion: dissolving sodium dodecyl sulfate in water, dropwise adding aniline monomer while stirring, and regulating the pH value to 5 by tartaric acid to obtain a uniform and stable aniline monomer emulsion with the sodium dodecyl sulfate concentration of 0.025M and the aniline monomer concentration of 0.1M;
2) in-situ polymerization reaction: soaking a polytetrafluoroethylene microporous membrane in the prepared aniline monomer emulsion for 60min, taking out, placing in an iron chloride aqueous solution with the pH value of 5 (adjusted by tartaric acid) (the concentration of the iron chloride is 0.12M, and the quantity ratio of the iron chloride to the aniline monomer is 6: 5), and reacting at 20 ℃ for 45 min;
3) and (3) post-treatment: and taking out the polytetrafluoroethylene microporous membrane subjected to the in-situ polymerization reaction, repeatedly rinsing with water, and airing.
The polytetrafluoroethylene microporous membrane in the step 2) is a hollow fiber composite membrane, and the average pore diameter is 0.2 mu m.
Example 6
A PTFE microporous membrane with reversible resistance to chemical hydrophilicity, the structure of which is the same as example 1 except that:
the reversible change range of the water contact angle is 20-60 degrees.
The average diameter of the polyaniline particles is 10-20 nm.
The polytetrafluoroethylene fibrils have diameters of 0.1-1 μm.
The chemical-resistant hydrophilic reversible PTFE microporous membrane is a hollow fiber composite membrane, and the average pore diameter is 0.1 mu m.
A preparation method of a chemical-resistant hydrophilic reversible polytetrafluoroethylene microporous membrane is characterized by comprising the following steps:
1) preparing aniline monomer emulsion: dissolving sodium dodecyl sulfate in water, dropwise adding an aniline monomer while stirring, and adjusting the pH value to 6 by acetic acid to obtain a uniform and stable aniline monomer emulsion with the sodium dodecyl sulfate concentration of 0.036M and the aniline monomer concentration of 0.15M;
2) in-situ polymerization reaction: soaking a polytetrafluoroethylene microporous membrane in the prepared aniline monomer emulsion for 60min, taking out, placing in a hydrogen peroxide aqueous solution with the pH value of 6 (adjusted by acetic acid) (the concentration of the hydrogen peroxide is 0.21M, and the quantity ratio of the hydrogen peroxide to the aniline monomer is 7: 5), and reacting at 20 ℃ for 30 min;
3) and (3) post-treatment: and taking out the polytetrafluoroethylene microporous membrane subjected to the in-situ polymerization reaction, repeatedly rinsing with water, and airing.
The polytetrafluoroethylene microporous membrane in the step 2) is a hollow fiber composite membrane, and the average pore diameter is 0.2 mu m.
Example 7
A PTFE microporous membrane with reversible resistance to chemical hydrophilicity, the structure of which is the same as example 1 except that:
the reversible change range of the water contact angle is 20-60 degrees.
The average diameter of the polyaniline particles is 20-30 nm.
The polytetrafluoroethylene fibril has a diameter of 0.1 to 1 μm.
The chemical-resistant hydrophilic reversible PTFE microporous membrane is a flat composite membrane, and the average pore diameter is 0.4 mu m.
A preparation method of a chemical-resistant hydrophilic reversible polytetrafluoroethylene microporous membrane is characterized by comprising the following steps:
1) preparing aniline monomer emulsion: dissolving sodium tetradecyl sulfate in water, dropwise adding aniline monomer while stirring, and regulating pH to 2 with p-toluenesulfonic acid to obtain uniform and stable aniline monomer emulsion with sodium tetradecyl sulfate concentration of 0.012M and aniline monomer concentration of 0.08M;
2) in-situ polymerization: soaking a polytetrafluoroethylene microporous membrane in the prepared aniline monomer emulsion for 40min, taking out, placing in an ammonium persulfate aqueous solution with the pH value of 2 (adjusted by p-toluenesulfonic acid) (the concentration of the ammonium persulfate is 0.12M, and the mass ratio of the ammonium persulfate to the aniline monomer is 3: 2), and reacting for 20min at 30 ℃;
3) and (3) post-treatment: and taking out the polytetrafluoroethylene microporous membrane subjected to the in-situ polymerization reaction, repeatedly rinsing with water, and airing.
The polytetrafluoroethylene microporous membrane in the step 2) is a flat composite membrane, and the average pore size is 0.5 mu m.
Example 8
A PTFE microporous membrane with reversible resistance to chemical hydrophilicity, the structure of which is the same as example 1 except that:
the reversible change range of the water contact angle is 20-60 degrees.
The average diameter of the polyaniline particles is 30-40 nm.
The polytetrafluoroethylene fibrils have diameters of 0.1-1 μm.
The chemical-resistant hydrophilic reversible PTFE microporous membrane is a hollow fiber homogeneous membrane, and the average pore diameter is 0.45 mu m.
A preparation method of a chemical-resistant hydrophilic reversible polytetrafluoroethylene microporous membrane is characterized by comprising the following steps:
1) preparing aniline monomer emulsion: dissolving sodium hexadecyl sulfate in water, dropwise adding an aniline monomer while stirring, and adjusting the pH value to be 3 by using camphorsulfonic acid to obtain a uniform and stable aniline monomer emulsion with the concentration of the sodium hexadecyl sulfate of 0.046M and the concentration of the aniline monomer of 0.05M;
2) in-situ polymerization reaction: soaking a polytetrafluoroethylene microporous membrane in the prepared aniline monomer emulsion for 40min, taking out, placing in a potassium persulfate aqueous solution with the pH value of 3 (regulated by camphorsulfonic acid) (the concentration of the potassium persulfate is 0.08M, and the weight ratio of the potassium persulfate to the aniline monomer substances is 8: 5), and reacting for 20min at the temperature of 30 ℃;
3) and (3) post-treatment: and taking out the polytetrafluoroethylene microporous membrane subjected to the in-situ polymerization reaction, repeatedly rinsing with water, and airing.
And 2) the polytetrafluoroethylene microporous membrane is a hollow fiber homogeneous membrane, and the average pore diameter is 0.5 mu m.
Example 9
A PTFE microporous membrane with reversible resistance to chemical hydrophilicity, the structure of which is the same as example 1 except that:
the reversible change range of the water contact angle is 10-50 degrees.
The average diameter of the polyaniline particles is 40-50 nm.
The polytetrafluoroethylene fibrils have diameters of 0.2-2 μm.
The chemical-resistant hydrophilic reversible PTFE microporous membrane can be a hollow fiber membrane homogeneous membrane, and the average pore diameter is 1 mu m.
A preparation method of a chemical-resistant hydrophilic reversible polytetrafluoroethylene microporous membrane is characterized by comprising the following steps:
1) preparing aniline monomer emulsion: dissolving sodium octadecyl sulfate in water, dropwise adding aniline monomer while stirring, and regulating the pH value to 4 by oxalic acid to obtain a uniform and stable aniline monomer emulsion with the concentration of the sodium octadecyl sulfate of 0.0017M and the aniline monomer of 0.02M;
2) in-situ polymerization reaction: soaking a polytetrafluoroethylene microporous membrane in the prepared aniline monomer emulsion for 20min, taking out, placing in a potassium dichromate aqueous solution with the pH value of 4 (adjusted by oxalic acid) (the concentration of the potassium dichromate is 0.01M, and the weight ratio of the potassium dichromate to the monomer substances is 1: 2), and reacting for 60min at the temperature of 30 ℃;
3) and (3) post-treatment: and taking out the polytetrafluoroethylene microporous membrane subjected to the in-situ polymerization reaction, repeatedly rinsing with water, and airing.
And 2) the polytetrafluoroethylene microporous membrane is a hollow fiber homogeneous membrane, and the average pore diameter is 1 mu m.
Example 10
A PTFE microporous membrane with reversible chemical resistance and hydrophilicity, the structure of which is the same as example 1 except that:
the reversible change range of the water contact angle is 10-50 degrees.
The average diameter of the polyaniline particles is 50-60 nm.
The polytetrafluoroethylene fibrils have diameters of 0.2-2 μm.
The chemical-resistant hydrophilic reversible PTFE microporous membrane can be a hollow fiber homogeneous membrane, and the average pore diameter is 10 mu m.
A preparation method of a chemical-resistant hydrophilic reversible polytetrafluoroethylene microporous membrane is characterized by comprising the following steps:
1) preparing aniline monomer emulsion: dissolving tetradecanol polyoxyethylene ether in water, dropwise adding an aniline monomer while stirring, and regulating the pH value to 5 by citric acid to obtain a uniform and stable aniline monomer emulsion with the concentration of the tetradecanol polyoxyethylene ether of 0.0001M and the concentration of the aniline monomer of 0.01M;
2) in-situ polymerization: soaking a polytetrafluoroethylene microporous membrane in the prepared aniline monomer emulsion for 10min, taking out, placing in an ammonium persulfate aqueous solution with the pH value of 5 (regulated by citric acid) (the concentration of ammonium persulfate is 0.02M, and the mass ratio of the ammonium persulfate to the aniline monomer is 2: 1), and reacting for 5min at 40 ℃;
3) and (3) post-treatment: and taking out the polytetrafluoroethylene microporous membrane subjected to the in-situ polymerization reaction, repeatedly rinsing with water, and airing.
And 2) the polytetrafluoroethylene microporous membrane is a hollow fiber homogeneous membrane, and the average pore diameter is 10 mu m.
The chemical-resistant hydrophilic reversible polytetrafluoroethylene microporous films obtained in the above examples were subjected to performance test evaluation by the following test methods, and the test results are shown in table 1. It can be seen that the water contact angle of the sample remains substantially unchanged before and after the chemical resistance test, indicating that the resulting chemically resistant hydrophilic reversible polytetrafluoroethylene microporous membrane has excellent chemical resistance.
1. Water contact angle
And respectively soaking the samples in water with the pH values of 1, 7 and 12 for 2 hours, taking out and airing. The static contact angle of the sample surface was measured by the sitting drop method. During testing, 2 mu L of ultrapure water is dripped on the surface of the film, the curved surface of the liquid drop is rapidly shot by a camera, and fitting calculation is carried out by a computer in a Conic mode to obtain the static contact angle of the sample.
2. Chemical resistance test
The sample was immersed in a mixed solution of 4wt% sodium hydroxide and 0.3wt% sodium hypochlorite for 10 days, and then in a 3wt% sulfuric acid solution for 3 days. The sample was removed and tested for neutral water contact angle.
Table 1 results of the performance test of the chemically resistant hydrophilic reversible microporous polytetrafluoroethylene membranes of the different examples:
TABLE 1
In summary, the present invention is only a preferred embodiment, and is not intended to limit the scope of the invention, and all equivalent variations and modifications made according to the content of the claims should be regarded as the technical scope of the invention.
Claims (7)
1. A chemically resistant hydrophilic reversible PTFE microporous membrane comprising microscale polytetrafluoroethylene fibrils, characterized by: the chemical-resistant hydrophilic reversible PTFE microporous membrane further comprises nano-scale polyaniline particles, wherein the nano-scale polyaniline particles are closely distributed on the surface of the micro-scale polytetrafluoroethylene fibrils in a lattice form to form a three-dimensional micro-nano structure, and the preparation method of the chemical-resistant hydrophilic reversible PTFE microporous membrane comprises the following steps:
1) preparing aniline monomer emulsion: dissolving a surfactant in water, dropwise adding an aniline monomer while stirring, and adjusting the pH value to 1-6 by doping acid to obtain a uniform and stable aniline monomer emulsion with the concentration of 0.01-0.5M;
2) in-situ polymerization reaction: soaking the PTFE microporous membrane in the prepared aniline monomer emulsion for 10-60 min, taking out, placing in an oxidant aqueous solution with the pH value of 1-6, reacting at 0-40 ℃ for 5 min-24 h, and adjusting the pH value of the oxidant aqueous solution by doping acid;
3) and (3) post-treatment: taking out the PTFE microporous membrane subjected to the in-situ polymerization reaction, repeatedly rinsing with water, and airing;
the concentration of the surfactant is 1.0 x 10 -4 0.3M to 1 to 10 times of the critical micelle concentration;
the concentration of the oxidant is 0.01-0.5M, and the amount ratio of the oxidant to the aniline monomer is 1: 2-2: 1.
2. The PTFE microporous membrane of claim 1, wherein: in the using process, the hydrophilicity of the polyaniline particles generates reversible change along with the doping/de-doping bidirectional response or the oxidation/reduction bidirectional response of the polyaniline particles on the surface, and the reversible change range of the water contact angle is 10-70 degrees.
3. The PTFE microporous membrane of claim 1, wherein: the polyaniline particles have an average diameter of 5-60 nm, and the polytetrafluoroethylene fibrils have a diameter of 0.05-2.0 μm.
4. The microporous chemical hydrophilicity resistant reversible PTFE membrane of claim 1, wherein: the membrane is a flat membrane, a hollow fiber membrane, a homogeneous membrane or a composite membrane, and the average pore diameter of the membrane is 0.02-10 mu m.
5. The PTFE microporous membrane of claim 1, wherein: the surfactant is sodium octyl sulfonate, sodium octyl sulfate, dodecylbenzene sulfonic acid, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, sodium tetradecyl sulfate, sodium hexadecyl sulfate, sodium octadecyl sulfate, nonylphenol polyoxyethylene ether-9, polyethylene glycol isooctylphenol ether, stearic acid, potassium stearate, potassium oleate, potassium laurate, azobenzene sulfonate with alkyl, octyl trimethyl ammonium bromide, dodecyl trimethyl ammonium bromide, hexadecyl trimethyl ammonium bromide, dodecyl pyridinium bromide, hexadecyl trimethyl ammonium chloride, 1-hexadecyl-3-methyl imidazoline chloride, lauryl polyoxyethylene ether, tetradecyl polyoxyethylene ether, dioctyl sodium sulfonate succinate, sucrose laurate, sucrose palmitate, sucrose stearate, sodium dodecyl benzene sulfonate, sodium sulfate, sodium dodecyl benzene sulfonate, sodium dodecyl benzene sulfonate, dodecyl, Tween and span or their mixture.
6. The PTFE microporous membrane of claim 1, wherein: the doping acid is any one or a mixture of two of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, perchloric acid, formic acid, acetic acid, citric acid, malic acid, tartaric acid, salicylic acid, oxalic acid, lactic acid, methanesulfonic acid, p-toluenesulfonic acid, azobenzenesulfonic acid, camphorsulfonic acid and naphthalenesulfonic acid.
7. The PTFE microporous membrane of claim 1, wherein: the oxidant is any one of hydrogen peroxide, ammonium persulfate, potassium dichromate and ferric chloride.
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