A method for preparing a superhydrophobic film

Abstract

The present invention discloses a preparation method of a superhydrophobic film, comprising the following steps: Step 1: Add fluorinated carbon nanotubes into an ethanol solvent, then add a coupling agent γ-methacryloxypropyltrimethoxysilane, perform ultrasonic dispersion and then condensation reflux, filter, wash with ethanol and then vacuum dry to obtain activated fluorinated carbon nanotubes; Step 2: Add the activated fluorinated carbon nanotubes into DMF, perform ultrasonic dispersion, add styrene to obtain a mixed solution, dissolve polyvinylidene fluoride in a mixed solvent of DMF and ethyl acetate, and then add it into the mixed solution; add an initiator, stir and heat up for reaction under an inert gas atmosphere to obtain an in-situ polymerization reaction solution. The present invention improves the dispersibility of polystyrene in a polyvinylidene fluoride (PVDF) solution through in-situ polymerization, and the hydrophobicity of the in-situ polymer is further improved compared with that of polyvinylidene fluoride (PVDF).

Description

Technical Field

[0001] The present invention relates to the technical field of hydrophobic membranes, and particularly relates to a method for preparing a superhydrophobic membrane. Background Art

[0002] The unique hydrophobicity of superhydrophobic surfaces makes them have great application prospects in oil-water separation, anti-corrosion, self-cleaning, etc. The key to preparing superhydrophobic materials lies in the surface chemical composition and geometric microstructure. When the surface tension of a solid is lower than that of a liquid and the surface is relatively rough, the material surface often shows liquid repellency. Therefore, there are generally two methods to obtain a super-liquid-repellent surface: one is to construct a rough structure on the surface of a low-energy material; the other is to graft low-surface-energy groups on the surface of a rough material.

[0003] Polyvinylidene fluoride (PVDF) has good chemical stability, thermal stability, mechanical properties, and hydrophobicity, and is an excellent hydrophobic membrane material. There is still room for further improvement in the hydrophobicity of polyvinylidene fluoride (PVDF). Fluorinated carbon nanotubes contain C-F bonds. Due to the introduction of F atoms, the surface polarity is improved, and the hydrophobicity is higher. Moreover, as inorganic nanoparticles, fluorinated carbon nanotubes have rich active hydroxyl groups on the surface and can graft polymer monomers. By introducing fluorinated carbon nanotubes into polyvinylidene fluoride (PVDF) and further preparing a hydrophobic membrane, the hydrophobic performance of the polyvinylidene fluoride (PVDF) hydrophobic membrane can be further improved. Summary of the Invention

[0004] 1. Technical problems to be solved:

[0005] In view of the above technical problems, the present invention provides a method for preparing a superhydrophobic membrane.

[0006] 2. Technical solutions:

[0007] A method for preparing a superhydrophobic membrane includes the following steps:

[0008] Step 1: Add fluorinated carbon nanotubes into an ethanol solvent, then add a coupling agent γ-methacryloxypropyltrimethoxysilane, perform ultrasonic dispersion, followed by reflux condensation, filtration, washing with ethanol, and vacuum drying to obtain activated fluorinated carbon nanotubes;

[0009] Step 2: Add the activated fluorinated carbon nanotubes into DMF, perform ultrasonic dispersion, add styrene to obtain a mixed solution, dissolve polyvinylidene fluoride in a mixed solvent of DMF and ethyl acetate, and then add it to the mixed solution; add an initiator, stir and heat up the reaction under an inert gas atmosphere to obtain an in-situ polymerization reaction solution;

[0010] Step 3: Use the in-situ polymerization reaction solution obtained in Step 2 to construct a superhydrophobic surface on a support, and obtain a superhydrophobic membrane after air drying.

[0011] Further, the mass ratio of the fluorinated carbon nanotubes to the coupling agent is 1:1 - 3.

[0012] Further, the mass ratio of the styrene to the activated carbon nanotubes is 1:9 - 12.

[0013] Further, the mass ratio of the polyvinylidene fluoride to the styrene is 4 - 5:1.

[0014] Further, the volume ratio of DMF to ethyl acetate in the mixed solvent is 6:4.

[0015] Further, the initiator is AIBN.

[0016] Further, the support includes a metal wire mesh, a polyester cotton cloth, and a filter paper.

[0017] 3. Beneficial effects:

[0018] In the present invention, styrene monomers are grafted onto the surface of fluorinated carbon nanotubes, and in-situ polymerization of the grafted styrene is carried out in a polyvinylidene fluoride (PVDF) solution. The in-situ polymerization improves the dispersibility of polystyrene in the polyvinylidene fluoride (PVDF) solution, and the hydrophobicity of the in-situ polymer is further improved compared to polyvinylidene fluoride (PVDF). It can be used as an oil-water separation membrane. After separating 0# diesel with a water content of 0.5%, the water content can be reduced to less than 0.03. When separating substances containing aniline and methylamine, the oil phase concentration is concentrated to more than 20 times, and the separation efficiency is as high as more than 95%. Specific embodiments

[0019] The present invention will be specifically described below.

[0020] Example 1:

[0021] A method for preparing a superhydrophobic membrane includes the following steps:

[0022] Step 1: Add 3.0 g of fluorinated carbon nanotubes to 150 ml of 95% ethanol solvent, then add 3.0 g of coupling agent γ-methacryloxypropyltrimethoxysilane (MPS). After ultrasonic dispersion for 30 min, carry out condensation reflux, filter, wash with 95% ethanol multiple times to wash away the adsorbed coupling agent, and then place it in an oven at 80°C for vacuum drying to obtain activated fluorinated carbon nanotubes, and double bonds are introduced into the activated fluorinated carbon nanotubes;

[0023] Step 2: Add 0.5 g of activated fluorinated carbon nanotubes into 10 ml of DMF, ultrasonically disperse for 30 min, add 5.0 g of styrene to obtain a mixed solution. Dissolve 22 g of polyvinylidene fluoride in a mixed solvent of 24 ml of DMF and 16 ml of ethyl acetate (6:4), and then add it to the mixed solution; add 0.03 g of initiator AIBN (azobisisobutyronitrile), stir and heat up to 50 °C under a nitrogen atmosphere and react for 6 h to obtain an in-situ polymerization reaction solution;

[0024] Step 3: Immerse the stainless steel wire mesh in the in-situ polymerization reaction solution obtained in Step 2, take it out and dry it in a blast dryer at 45 °C for 2 h to obtain a superhydrophobic membrane.

[0025] Comparative Example 1

[0026] A preparation method of a superhydrophobic membrane, comprising the following steps:

[0027] Step 1: Add 5.0 g of styrene into 10 ml of DMF, dissolve 22 g of polyvinylidene fluoride in a mixed solvent of 24 ml of DMF and 16 ml of ethyl acetate (6:4), and then add it to the above DMF solution of styrene; add 0.03 g of initiator AIBN (azobisisobutyronitrile), stir and heat up to 50 °C under a nitrogen atmosphere and react for 6 h to obtain an in-situ polymerization reaction solution;

[0028] Step 2: Immerse the stainless steel wire mesh in the in-situ polymerization reaction solution obtained in Step 2, take it out and dry it in a blast dryer at 45 °C for 2 h to obtain a superhydrophobic membrane.

[0029] Comparative Example 2

[0030] A preparation method of a superhydrophobic membrane, comprising the following steps: Dissolve 22 g of polyvinylidene fluoride in a mixed solvent of 24 ml of DMF and 16 ml of ethyl acetate (6:4), immerse the stainless steel wire mesh and take it out, and dry it in a blast dryer at 45 °C for 2 h to obtain a superhydrophobic membrane.

[0031] Performance test:

[0032] 1. Hydrophobic performance test: Use a full-automatic video contact angle tester to conduct static water contact angle analysis on the hydrophobic membranes of Example 1, Comparative Example 1 and Comparative Example 2. The amount of water tested is 3 μL, and it is tested 5 times at different positions of the same sample, and the average value is taken. The test results are shown in Table 1:

[0033]

[0034] By comparing Comparative Example 1 and Comparative Example 2, it can be seen that in-situ polymerization of styrene can slightly improve the hydrophobic performance of polyvinylidene fluoride. By comparing Example 1 and Comparative Example 1, it can be seen that adding activated carbon nanotubes fluoride during the in-situ polymerization of styrene can further improve the hydrophobic performance of polyvinylidene fluoride. It is speculated that the possible reason is that the inorganic carbon nanotubes fluoride have good hydrophobic performance themselves. In addition, after grafting of active carbon nanotubes fluoride and styrene, in-situ polymerization improves the surface roughness of the hydrophobic membrane, further improving the hydrophobic performance.

[0035] 2. Test on the oil-water separation performance of light diesel:

[0036] The superhydrophobic membranes of Example 1, Comparative Example 1 and Comparative Example 2 were respectively used to conduct oil-water separation tests on 0# diesel with a water content of 0.5%. The detection of the water content in the separated oil phase was carried out using the test method recorded in GB / T 260-77. The test results are as follows;

[0037]

[0038] When separating through the superhydrophobic membrane of Example 1, the water content decreased significantly, reaching the "water-free" standard. Note: The explanation of "water-free" in GB 252-2011 "Light Diesel Oil" is that the water content of the separated oil product is <0.03%.

[0039] 3. Test on the oil-water separation performance of substances containing aniline and methylamine:

[0040] Characteristics of substances such as aniline and methylamine: 1) Substances of aniline type are highly toxic and have relatively large volatility. 2) The specific gravity of oil substances is very close to that of water (aniline 1.0217 g / cm 3 , toluidine 0.9889 g / cm 3 ), 3) The oil content in the oil substances containing aniline type is high (normally >20%), 4) The oil substances contain hydrophilic -NH2 groups.

[0041] The superhydrophobic membranes of Example 1, Comparative Example 1 and Comparative Example 2 were used to conduct oil-water separation tests on three samples containing aniline and methylamine substances, and the contents of aniline and toluidine in the separated oil phase (unit: ppm) were analyzed. The test results are as follows;

[0042]

[0043] When separating substances containing aniline and methylamine through the superhydrophobic membrane of Example 1, the oil phase concentration was concentrated to more than 20 times, and the separation efficiency was as high as more than 95%. And compared with Comparative Example 1 and Comparative Example 2, the separation effect is more significant.

[0044] Although the present invention has been disclosed above in its preferred embodiments, they are not intended to limit the present invention. Any person skilled in this art can make various changes or modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be defined by the protection scope of the claims of this application.

Claims

1. A method for preparing a superhydrophobic membrane, characterized in that, It includes the following steps: Step 1: Add fluorinated carbon nanotubes into an ethanol solvent, then add coupling agent γ-methacryloxypropyltrimethoxysilane. After ultrasonic dispersion, carry out condensation reflux, filter, wash with ethanol and then dry in vacuum to obtain activated fluorinated carbon nanotubes; Step 2: Add the activated fluorinated carbon nanotubes into DMF, carry out ultrasonic dispersion, add styrene to obtain a mixed solution. Dissolve polyvinylidene fluoride in a mixed solvent of DMF and ethyl acetate, and then add it into the mixed solution; add an initiator, stir and heat up for reaction under an inert gas atmosphere to obtain an in-situ polymerization reaction solution; Step 3: Use the in-situ polymerization reaction solution obtained in Step 2 to construct a superhydrophobic surface on a support, and obtain a superhydrophobic membrane after air drying.

2. The preparation method of a superhydrophobic film according to claim 1, characterized in that, The mass ratio of the fluorinated carbon nanotubes to the coupling agent is 1:1 - 3.

3. The preparation method of a superhydrophobic film according to claim 1, characterized in that, The mass ratio of the styrene to the activated carbon nanotubes is 1:9 - 12.

4. The preparation method of a superhydrophobic film according to claim 1, characterized in that, The mass ratio of the polyvinylidene fluoride to the styrene is 4 - 5:

1.

5. A method for preparing a superhydrophobic film according to any one of claims 2-4, characterized in that, The volume ratio of DMF to ethyl acetate in the mixed solvent is 6:

4.

6. The preparation method of a superhydrophobic film according to claim 5, characterized in that, The initiator is AIBN.

7. The preparation method of a superhydrophobic film according to claim 6, characterized in that, The support includes a metal wire mesh, a polyester cotton cloth and a filter paper.

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