A method for modifying PVDF flexible membrane with nanowires

Abstract

The invention relates to a method for modifying a PVDF flexible membrane with nanowires, comprising the following steps: step 1, immersing a self-made PVDF flexible membrane in an ethanol solution, ultrasonically cleaning it for 25-35 minutes, and washing it with deionized water to remove the solvent and impurities on the surface of the self-made PVDF flexible membrane; step 2, immersing the washed PVDF flexible membrane in a dopamine hydrochloride solution for 2-4 hours, and washing it with deionized water to obtain a polydopamine flexible membrane; step 3, adding 3-aminopropyltriethoxysilane to TiO2 NWs, stirring at 85-95°C for 7-9 hours, adding the polydopamine flexible membrane prepared in step 2, and reacting in a blast drying oven at 55-65°C to obtain a titanium dioxide nanowire-modified PVDF flexible membrane; the application uses a chemical grafting process to construct a stable hydrophilic functional layer on the membrane surface while maintaining the characteristics of the PVDF flexible membrane itself, thereby improving the hydrophilicity and anti-fouling properties of the membrane.

Description

Technical Field

[0001] The invention belongs to a method for modifying a PVDF flexible membrane, and in particular relates to a method for modifying a PVDF flexible membrane with nanowires. Background Art

[0002] Polyvinylidene fluoride (PVDF) material has excellent chemical stability, thermal stability, mechanical stability, and radiation resistance because it contains CF bonds with higher bond energy, which makes CC bonds with lower bond energy surrounded by CF bonds. It is mainly used as a microfiltration and ultrafiltration membrane material and is widely used in various water treatments such as domestic sewage treatment and industrial wastewater treatment. However, the CF bonds and CH bonds on the surface of the PVDF membrane determine its weak hydrophilicity, making it difficult for PVDF to produce hydrogen bonds with water molecules, poor wettability, strong hydrophobicity, and it is difficult for water molecules to adhere to the surface of the PVDF membrane, resulting in low water flux, which cannot meet the requirements for water flux in actual production. Therefore, when PVDF is used to separate oil-water systems, due to its strong hydrophobic effect and low surface energy, oily pollutants are easily adsorbed on the membrane surface and cause blockage of the membrane pores. As the use time of the water filter membrane increases, the water flux of the membrane gradually decreases, and eventually the water filter membrane cannot be used. The strong hydrophobic effect has become an important factor limiting the flux of PVDF, limiting the further promotion and application of PVDF in actual production and life. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for modifying PVDF flexible membranes with nanowires.

[0004] The present invention adopts the following technical solution:

[0005] A method for modifying a PVDF flexible membrane with nanowires comprises the following steps:

[0006] Step 1, immersing the self-made PVDF flexible membrane in an ethanol solution, ultrasonically cleaning for 25-35 minutes, and washing with deionized water to remove the solvent and impurities on the surface of the self-made PVDF flexible membrane;

[0007] Step 2, soaking the cleaned PVDF flexible membrane in a dopamine hydrochloride solution for 2-4 hours, and washing with deionized water to obtain a polydopamine flexible membrane;

[0008] Step 3: add 3-aminopropyltriethoxysilane to TiO2 NWs, stir at 85-95°C for 7-9 h, add the polydopamine flexible membrane prepared in step 2, and react in a forced air drying oven at 55-65°C to obtain a titanium dioxide nanowire-modified PVDF flexible membrane.

[0009] Preferably, the mass concentration of the dopamine hydrochloride solution is 2-4%.

[0010] Preferably, in step three, the mass ratio of 3-aminopropyltriethoxysilane to TiO2 NWs is 1:0.5.

[0011] Preferably, the homemade PVDF flexible membrane is composed of the following raw materials in parts by weight: 50-70 parts of polyvinylidene fluoride, 10-15 parts of nano-carbon fiber scraps, 8-12 parts of polycarbonate, 1-3 parts of polymethyl acrylate, 3-5 parts of diethylene glycol, 6-8 parts of triethanolamine, 18-22 parts of polyvinyl pyrrolidone, and 2-3 parts of polyethylene wax.

[0012] Preferably, the carbon fiber scraps include 50-70 parts of 80-120nm nano-carbon fiber scraps, 15-25 parts of 40-60nm nano-carbon fiber scraps, and 15-25 parts of 20-30nm nano-carbon fiber scraps.

[0013] Preferably, the preparation process of the homemade PVDF flexible membrane specifically comprises the following steps:

[0014] Step 1, weighing polyvinylidene fluoride, polycarbonate, polyvinyl pyrrolidone, and polyethylene wax according to the required weights and sequentially putting them into a twin-screw extruder for melting, and then mixing the melted raw material solutions evenly to obtain a mixed solution;

[0015] Step 2, then adding polymethyl acrylate, diethylene glycol, and triethanolamine in required weight parts in sequence for mixed melting, and then adding nano-carbon fiber scraps and mixing and stirring evenly to obtain a membrane-making solution;

[0016] Step 3, evenly pouring the prepared film-making solution on a glass plate to form a film monomer, then putting the film monomer into an oven to completely solidify the film monomer, and then peeling it off from the glass plate to obtain the self-made PVDF flexible film.

[0017] Preferably, the drying temperature of the oven is 150-160°C.

[0018] Preferably, in step 2, the temperature of the nano-carbon fiber scraps during mixing is 120° C., the mixing time is 45 min, and the mixing speed is 800 r / min.

[0019] Preferably, in step 1, the melting temperature is 160° C., the rotation speed during mixing is 600 r / min, and the mixing time is 60 min.

[0020] Preferably, in step 2, the smelting temperature is 130°C.

[0021] From the above description of the present invention, it can be seen that compared with the prior art, the beneficial effects of the present invention are as follows: the present application uses a self-made PVDF flexible membrane as a substrate, TiO2 NWs as a functional modifier, and polydopamine as a cross-linking agent, and uses a chemical grafting process to construct a stable hydrophilic functional layer on the membrane surface while maintaining the characteristics of the PVDF flexible membrane itself, thereby improving the hydrophilicity and anti-fouling properties of the membrane and preventing the nanomaterial from falling off during the operation of the membrane; in addition, the present application specifically defines the raw material composition of the self-made PVDF flexible membrane, adds nano-carbon fiber scraps as a reinforcing agent, and uses polymethyl acrylate and polyethylene wax to mix the added carbon fiber scraps with the raw materials uniformly, so that the prepared PVDF flexible membrane has good strength to ensure the stability of the PVDF flexible membrane during the modification process;

[0022] A method for preparing a homemade PVDF flexible membrane is specifically defined. First, the raw materials except nano-carbon fiber scraps are melted and mixed through a twin-screw extruder, and then the nano-carbon fiber scraps are added to make the nano-carbon fiber scraps with different particle size compositions mixed and distributed in the membrane-making liquid horizontally and vertically, so that the prepared PVDF flexible membrane has good strength. Among them, the particle size composition of the nano-carbon fiber scraps is specifically defined to effectively recycle the carbon fiber scraps. DETAILED DESCRIPTION

[0023] The present invention is further described below through specific implementation modes.

[0024] A method for modifying a PVDF flexible membrane with nanowires comprises the following steps:

[0025] Step 1, immersing the self-made PVDF flexible membrane in an ethanol solution, ultrasonically cleaning for 25-35 minutes, and washing with deionized water to remove the solvent and impurities on the surface of the self-made PVDF flexible membrane;

[0026] Step 2, soaking the cleaned PVDF flexible membrane in a dopamine hydrochloride solution with a mass concentration of 2-4% for 2-4 hours, and washing with deionized water to obtain a polydopamine flexible membrane;

[0027] Step 3: add 3-aminopropyltriethoxysilane to TiO2 NWs, stir at 85-95°C for 7-9 h, add the polydopamine flexible membrane prepared in step 2, and react in a forced air drying oven at 55-65°C to obtain a titanium dioxide nanowire-modified PVDF flexible membrane.

[0028] Among them, the mass ratio of 3-aminopropyltriethoxysilane to TiO2 NWs is 1:0.5.

[0029] The homemade PVDF flexible membrane is composed of the following raw materials in parts by weight: 50-70 parts of polyvinylidene fluoride, 10-15 parts of nano-carbon fiber scraps, 8-12 parts of polycarbonate, 1-3 parts of polymethyl acrylate, 3-5 parts of diethylene glycol, 6-8 parts of triethanolamine, 18-22 parts of polyvinyl pyrrolidone, and 2-3 parts of polyethylene wax; specifically, the carbon fiber scraps include 50-70 parts of 80-120nm nano-carbon fiber scraps, 15-25 parts of 40-60nm nano-carbon fiber scraps, and 15-25 parts of 20-30nm nano-carbon fiber scraps.

[0030] The preparation process of the homemade PVDF flexible membrane specifically includes the following steps:

[0031] Step 1, weighing polyvinylidene fluoride, polycarbonate, polyvinyl pyrrolidone, and polyethylene wax according to the required weights and sequentially putting them into a twin-screw extruder for melting, and then mixing the melted raw material solutions evenly to obtain a mixed solution;

[0032] Step 2, then adding polymethyl acrylate, diethylene glycol, and triethanolamine in required weight parts in sequence for mixed melting, and then adding nano-carbon fiber scraps and mixing and stirring evenly to obtain a membrane-making solution;

[0033] Step 3, evenly pouring the prepared film-making liquid on a glass plate to form a film monomer, then putting the film monomer into an oven, completely curing the film monomer at a temperature of 150-160° C., and then peeling it off from the glass plate to obtain the self-made PVDF flexible film.

[0034] Wherein, in step 1, the melting temperature is 160° C., the rotation speed during mixing is 600 r / min, and the mixing time is 60 min.

[0035] In step 2, the melting temperature is 130°C; the temperature of the nano-carbon fiber scraps during mixing is 120°C, the mixing time is 45 minutes, and the mixing speed is 800 r / min. Example 1

[0036] A method for modifying a PVDF flexible membrane with nanowires comprises the following steps:

[0037] Step 1: soak the self-made PVDF flexible membrane in an ethanol solution, perform ultrasonic cleaning for 25 minutes, and then rinse with deionized water to remove the solvent and impurities on the surface of the self-made PVDF flexible membrane;

[0038] Step 2, soaking the cleaned PVDF flexible membrane in a 2% dopamine hydrochloride solution for 4 hours, and washing with deionized water to obtain a polydopamine flexible membrane;

[0039] Step three, add 3-aminopropyltriethoxysilane to TiO2 NWs, stir at 85°C for 9 h, add the polydopamine flexible membrane prepared in step two, and react in a forced air drying oven at 55°C to obtain a titanium dioxide nanowire-modified PVDF flexible membrane.

[0040] Among them, the homemade PVDF flexible membrane is composed of the following raw materials in parts by weight: 50 parts of polyvinylidene fluoride, 10 parts of nano-carbon fiber scraps, 12 parts of polycarbonate, 1 part of polymethyl acrylate, 5 parts of diethylene glycol, 6 parts of triethanolamine, 18 parts of polyvinyl pyrrolidone, and 3 parts of polyethylene wax; specifically, the carbon fiber scraps include 50 parts of 80-120nm nano-carbon fiber scraps, 25 parts of 40-60nm nano-carbon fiber scraps, and 25 parts of 20-30nm nano-carbon fiber scraps.

[0041] The preparation process of the homemade PVDF flexible membrane specifically includes the following steps:

[0042] Step 1, weighing polyvinylidene fluoride, polycarbonate, polyvinyl pyrrolidone, and polyethylene wax according to the required weights and sequentially putting them into a twin-screw extruder for melting, and then mixing the melted raw material solutions evenly to obtain a mixed solution;

[0043] Step 2, then adding polymethyl acrylate, diethylene glycol, and triethanolamine in required weight parts in sequence for mixed melting, and then adding nano-carbon fiber scraps and mixing and stirring evenly to obtain a membrane-making solution;

[0044] Step 3, evenly pouring the prepared film-making liquid on a glass plate to form a film monomer, then putting the film monomer into an oven, completely curing the film monomer at a temperature of 150° C., and then peeling it off from the glass plate to obtain the self-made PVDF flexible film. Example 2

[0045] A method for modifying a PVDF flexible membrane with nanowires comprises the following steps:

[0046] Step 1: immerse the self-made PVDF flexible membrane in an ethanol solution, perform ultrasonic cleaning for 35 minutes, and then rinse with deionized water to remove the solvent and impurities on the surface of the self-made PVDF flexible membrane;

[0047] Step 2, soaking the cleaned PVDF flexible membrane in a 4% dopamine hydrochloride solution for 2 hours, and washing with deionized water to obtain a polydopamine flexible membrane;

[0048] Step three, add 3-aminopropyltriethoxysilane to TiO2 NWs, stir at 95°C for 7 h, add the polydopamine flexible membrane prepared in step two, and react in a forced air drying oven at 65°C to obtain a titanium dioxide nanowire-modified PVDF flexible membrane.

[0049] Among them, the homemade PVDF flexible membrane is composed of the following raw materials in parts by weight: 70 parts of polyvinylidene fluoride, 15 parts of nano-carbon fiber scraps, 8 parts of polycarbonate, 3 parts of polymethyl acrylate, 3 parts of diethylene glycol, 8 parts of triethanolamine, 22 parts of polyvinyl pyrrolidone, and 2 parts of polyethylene wax; specifically, the carbon fiber scraps include 70 parts of 80-120nm nano-carbon fiber scraps, 15 parts of 40-60nm nano-carbon fiber scraps, and 15 parts of 20-30nm nano-carbon fiber scraps.

[0050] The preparation process of the homemade PVDF flexible membrane specifically includes the following steps:

[0051] Step 1, weighing polyvinylidene fluoride, polycarbonate, polyvinyl pyrrolidone, and polyethylene wax according to the required weights and sequentially putting them into a twin-screw extruder for melting, and then mixing the melted raw material solutions evenly to obtain a mixed solution;

[0052] Step 2, then adding polymethyl acrylate, diethylene glycol, and triethanolamine in required weight parts in sequence for mixed melting, and then adding nano-carbon fiber scraps and mixing and stirring evenly to obtain a membrane-making solution;

[0053] Step 3, evenly pouring the prepared film-making liquid on a glass plate to form a film monomer, then putting the film monomer into an oven, completely curing the film monomer at a temperature of 160° C., and then peeling it off from the glass plate to obtain the self-made PVDF flexible film. Example 3

[0054] A method for modifying a PVDF flexible membrane with nanowires comprises the following steps:

[0055] Step 1: soak the self-made PVDF flexible membrane in an ethanol solution, perform ultrasonic cleaning for 30 minutes, and then rinse with deionized water to remove the solvent and impurities on the surface of the self-made PVDF flexible membrane;

[0056] Step 2, soaking the cleaned PVDF flexible membrane in a 3% dopamine hydrochloride solution for 3 hours, and washing with deionized water to obtain a polydopamine flexible membrane;

[0057] Step 3: add 3-aminopropyltriethoxysilane to TiO2 NWs, stir at 90°C for 8h, add the polydopamine flexible membrane prepared in step 2, and react in a forced air drying oven at 60°C to obtain a titanium dioxide nanowire-modified PVDF flexible membrane.

[0058] Among them, the homemade PVDF flexible membrane is composed of the following raw materials in parts by weight: 60 parts of polyvinylidene fluoride, 12 parts of nano-carbon fiber scraps, 10 parts of polycarbonate, 2 parts of polymethyl acrylate, 4 parts of diethylene glycol, 7 parts of triethanolamine, 20 parts of polyvinyl pyrrolidone, and 2.5 parts of polyethylene wax; specifically, the carbon fiber scraps include 60 parts of 80-120nm nano-carbon fiber scraps, 20 parts of 40-60nm nano-carbon fiber scraps, and 20 parts of 20-30nm nano-carbon fiber scraps.

[0059] The preparation process of the homemade PVDF flexible membrane specifically includes the following steps:

[0060] Step 1, weighing polyvinylidene fluoride, polycarbonate, polyvinyl pyrrolidone, and polyethylene wax according to the required weights and sequentially putting them into a twin-screw extruder for melting, and then mixing the melted raw material solutions evenly to obtain a mixed solution;

[0061] Step 2, then adding polymethyl acrylate, diethylene glycol, and triethanolamine in required weight parts in sequence for mixed melting, and then adding nano-carbon fiber scraps and mixing and stirring evenly to obtain a membrane-making solution;

[0062] Step 3, evenly pouring the prepared film-making liquid on a glass plate to form a film monomer, then putting the film monomer into an oven, completely curing the film monomer at a temperature of 155° C., and then peeling it off from the glass plate to obtain the self-made PVDF flexible film.

[0063] This application uses a homemade PVDF flexible membrane as a substrate, TiO2 NWs as a functional modifier, and polydopamine as a cross-linking agent. While maintaining the characteristics of the PVDF flexible membrane itself, a stable hydrophilic functional layer is constructed on the membrane surface through a chemical grafting process, thereby improving the hydrophilicity and anti-fouling properties of the membrane and preventing the nanomaterial from falling off during membrane operation. In addition, this application specifically defines the raw material composition of the homemade PVDF flexible membrane, adds nano-carbon fiber scraps as a reinforcing agent, and combines polymethyl acrylate and polyethylene wax to evenly mix the added carbon fiber scraps with the raw materials, so that the prepared PVDF flexible membrane has good strength to ensure the stability of the PVDF flexible membrane during the modification process.

[0064] The above description is only a preferred embodiment of the present invention, and therefore cannot be used to limit the scope of implementation of the present invention. That is, equivalent changes and modifications made according to the scope of the patent application of the present invention and the contents of the specification should still fall within the scope covered by the patent of the present invention.

Claims

1. A method for modifying a PVDF flexible membrane using nanowires, characterized in that: The specific steps include: Step 1, immersing the self-made PVDF flexible membrane in an ethanol solution, ultrasonically cleaning for 25-35 minutes, and washing with deionized water to remove the solvent and impurities on the surface of the self-made PVDF flexible membrane; Step 2, soaking the cleaned PVDF flexible membrane in a dopamine hydrochloride solution for 2-4 hours, and washing with deionized water to obtain a polydopamine flexible membrane; Step 3, adding 3-aminopropyltriethoxysilane to TiO2 NWs, stirring at 85-95°C for 7-9 h, adding the polydopamine flexible membrane prepared in step 2, and reacting in a forced air drying oven at 55-65°C to obtain a titanium dioxide nanowire-modified PVDF flexible membrane; In step 3, the mass ratio of 3-aminopropyltriethoxysilane to TiO2 NWs is 1:0.5; The self-made PVDF flexible membrane is composed of the following raw materials in parts by weight: 50-70 parts of polyvinylidene fluoride, 10-15 parts of nano-carbon fiber scraps, 8-12 parts of polycarbonate, 1-3 parts of polymethyl acrylate, 3-5 parts of diethylene glycol, 6-8 parts of triethanolamine, 18-22 parts of polyvinyl pyrrolidone, and 2-3 parts of polyethylene wax; The carbon fiber scraps include 50-70 parts of 80-120nm nano carbon fiber scraps, 15-25 parts of 40-60nm nano carbon fiber scraps, and 15-25 parts of 20-30nm nano carbon fiber scraps; The preparation process of the self-made PVDF flexible membrane specifically comprises the following steps: Step 1, weighing polyvinylidene fluoride, polycarbonate, polyvinyl pyrrolidone, and polyethylene wax according to the required weights and sequentially putting them into a twin-screw extruder for melting, and then mixing the melted raw material solutions evenly to obtain a mixed solution; Step 2, then adding polymethyl acrylate, diethylene glycol, and triethanolamine in required weight parts in sequence for mixed melting, and then adding nano-carbon fiber scraps and mixing and stirring evenly to obtain a membrane-making solution; Step 3, evenly pouring the prepared film-making solution on a glass plate to form a film monomer, then putting the film monomer into an oven to completely solidify the film monomer, and then peeling it off from the glass plate to obtain the self-made PVDF flexible film.

2. The method for modifying a PVDF flexible membrane with nanowires according to claim 1, characterized in that: The mass concentration of the dopamine hydrochloride solution is 2-4%.

3. The method for modifying a PVDF flexible membrane with nanowires according to claim 1, characterized in that: The drying temperature of the oven is 150-160°C.

4. The method for modifying a PVDF flexible membrane with nanowires according to claim 1, characterized in that: In step 2, the temperature of the nano-carbon fiber scraps during mixing is 120° C., the mixing time is 45 min, and the mixing speed is 800 r / min.

5. The method for modifying a PVDF flexible membrane with nanowires according to claim 1, characterized in that: In step 1, the melting temperature is 160° C., the rotation speed during mixing is 600 r / min, and the mixing time is 60 min.

6. The method for modifying a PVDF flexible membrane with nanowires according to claim 1, characterized in that: In step 2, the melting temperature is 130°C.