Preparation method of ion exchange nanofiber membrane with high mechanical property

Abstract

The invention discloses a preparation method of an ion exchange nanofiber membrane with high mechanical property, which comprises the following steps: 1) blending perfluorosulfonic acid resin (PFSA) and polyvinylidene fluoride (PVDF) in N, N-dimethylacetamide according to a certain proportion to obtain a spinning solution; and 2) carrying out ultrasonic treatment on the prepared spinning solution to remove bubbles, and preparing a perfluorosulfonic acid ion exchange membrane by utilizing an electrostatic spinning technology to obtain the ion exchange nanofiber membrane with high mechanical property. The perfluorosulfonic acid ion exchange membrane prepared by the invention has good proton conductivity, high ion selectivity, excellent mechanical stability and chemical stability, also has excellent mechanical properties, and has wide application prospects in the fields of fuel cells, electrolyzed water, electrodialysis and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of ion exchange membranes, and in particular relates to a method for preparing an ion exchange nanofiber membrane with high mechanical properties. Background Art

[0002] Perfluorosulfonic acid ion exchange membranes have been widely used in fuel cells, water electrolysis, electrodialysis, flow batteries and other fields due to their excellent chemical stability, thermal stability, good oxidation resistance and corrosion resistance. These characteristics are mainly due to their unique perfluoro main chain structure and sulfonic acid groups (-SO3H) on the side chains. These sulfonic acid groups are the key to achieving ion exchange function. Sulfonic acid groups can attract protons (H + ) or other cations, giving the membrane good ionic conductivity.

[0003] Mechanical properties are a measure of a material's ability to resist external forces without being damaged. For ion exchange membranes, good mechanical properties mean that the structural integrity and functionality can be maintained in a variety of application environments. For perfluorosulfonic acid resin ion exchange membranes prepared by traditional solution casting, the wide molecular weight distribution of the resin and poor controllability affect the crystallization efficiency and mechanical properties of the membrane, resulting in the risk of rupture or deformation of the membrane in actual applications.

[0004] The core of ion exchange function lies in the ionic conductivity of sulfonic acid groups, while ion selectivity refers to the membrane's ability to transmit different ions. Existing perfluorosulfonic acid ion exchange membranes, such as DuPont's Nafion membrane, have excellent electrochemical performance and service life, but are deficient in ion selectivity, which limits their further industrial application in specific applications.

[0005] In order to solve these problems, researchers began to explore new preparation technologies. Electrospinning technology has attracted attention because of its ability to precisely control the diameter of the fiber and the structure of the membrane. It uses electrostatic force to make the charged polymer solution flow and deform in an electric field, and solidify through solvent evaporation or melt cooling to form a fibrous substance. This nanofiber membrane has a high surface area and high porosity, providing an effective channel for the transmission of ions, thereby improving the conductivity. The nanofiber membrane prepared by electrospinning technology can not only improve the mechanical properties of the membrane, but also optimize the ion selectivity by precisely controlling the pore structure.

[0006] In summary, the mechanical properties, ion exchange function and nanofiber membrane preparation technology of perfluorosulfonic acid ion exchange membrane are interrelated. By improving the preparation technology, the mechanical properties and ion selectivity of the membrane can be optimized, thereby improving its performance and application potential in various electrochemical devices. Electrospinning technology provides a new direction for the development of perfluorosulfonic acid ion exchange membrane, and is expected to achieve membrane materials with better performance. Summary of the invention

[0007] In view of the problems existing in the prior art, the present invention aims to provide a method for preparing an ion exchange nanofiber membrane with high mechanical properties. The method improves the electrospinning spinnability of the spinning solution by adding a specific proportion of polymer PVDF with good thermal stability and mechanical properties on the basis of perfluorosulfonic acid, and combines the selection of solvents and the regulation of processes, while greatly enhancing the mechanical properties of the membrane; in addition, the microstructure and porosity of the membrane are precisely controlled by regulating the electrospinning parameters through the introduction of electrospinning technology. During the electrospinning process, the polymer chains are arranged along the direction of the electric field, resulting in the axial arrangement of a single fiber. This orientation is conducive to the construction of an efficient transmission channel, further improving the ion conductivity and chemical stability of the membrane, while reducing the resistance of the membrane to meet the application requirements under high current density conditions. The prepared PVDF-PFSA ion exchange membrane can have good proton conductivity, high ion selectivity, excellent mechanical stability and chemical stability, and also has excellent mechanical properties. It provides basic parameters for the future application of ion exchange membrane materials, provides direction for subsequent development, and has great application prospects.

[0008] The present invention provides a method for preparing an ion exchange nanofiber membrane with high mechanical properties, comprising the following steps: 1) mixing perfluorosulfonic acid resin and polyvinylidene fluoride in a certain proportion in N,N-dimethylacetamide to obtain a spinning solution;

[0009] 2) The spinning solution is ultrasonically treated to remove bubbles in the solution, and a perfluorosulfonic acid ion exchange membrane is prepared by electrospinning.

[0010] Furthermore, in step 1), the blending process is carried out under stirring at 25° C. and 700 rpm for at least 6 hours.

[0011] Furthermore, in step 1), the mass proportion of the polyvinylidene fluoride is 10%-40%, and the mass proportion of the perfluorosulfonic acid resin is 60%-90%, and more preferably, the polyvinylidene fluoride accounts for 40% and the perfluorosulfonic acid resin accounts for 60%.

[0012] Furthermore, the ion exchange capacity of the perfluorosulfonic acid resin is 1.01 to 1.05 mmol / g.

[0013] Furthermore, in step 2), the voltage of the electrospinning is 20 kV, the distance between the nozzle and the receiver is 20 cm, the propulsion speed of the spinning solution is 1 mL / h, the spinning temperature is 23° C., and the relative humidity of the spinning is 40%.

[0014] The solvent selected and the blending method adopted in the present invention have an important influence on the electrospinnability of the obtained solution. Through a large number of experiments, it is found that when other solvents or mixing methods are used, the obtained solution often cannot be electrospun smoothly, has poor spinnability, and cannot obtain a fiber membrane with both excellent mechanical properties and ion exchange function.

[0015] A high mechanical performance ion exchange nanofiber membrane is obtained by using any of the methods described.

[0016] Furthermore, the nanofiber membrane has excellent mechanical properties and ion exchange functions, with a tensile strength of 4.2-14.9 MPa, an elongation at break of 100.1%-153.4%, a water absorption rate of 5.9-15.1%, a swelling rate of 3.6-14.2%, a proton conductivity of 82.5-101.2 mS / cm, and an ion exchange capacity of 0.81-0.92 mmol / g.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The present invention uses a specific method to add polyvinylidene fluoride to perfluorosulfonic acid resin for doping and blending, thereby improving the electrospinning spinnability of the solution. The electrospinning technology is used to control its parameters to accurately regulate the microstructure and pore structure of the perfluorosulfonic acid ion exchange membrane. The optimization of this structure greatly enhances the mechanical properties of the membrane. The nanofiber membrane with high surface area and high porosity not only improves the proton conductivity of the membrane, but also significantly enhances the ion selectivity of the membrane by constructing an efficient ion transmission channel. The prepared ion exchange membrane not only achieves high mechanical properties but also satisfies high ion selectivity.

[0019] (2) The preparation method of the present invention is scientifically and rationally designed, simple and easy to implement, and is conducive to production; the prepared material can be widely used in various fields such as fuel cells, water electrolysis, electrodialysis, etc., and has important industrial application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the electrospinning principle of an embodiment of the present invention;

[0021] Figure 2 The present invention is a preparation flow chart of an embodiment of the present invention. DETAILED DESCRIPTION

[0022] The technical method of the present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0023] Example 1

[0024] A method for preparing an ion exchange nanofiber membrane with high mechanical properties specifically comprises the following steps: weighing 1.35 g of PFSA powder and dissolving it in 5 mL of N,N-dimethylacetamide. Stirring at 25° C. and 700 rpm until the perfluorosulfonic acid resin powder is completely dissolved, then adding 0.15 g of PVDF powder and continuing to stir until the PVDF is completely dissolved. A spinning solution with a PFSA:PVDF mass ratio of 9:1 is prepared. The PVDF / PFSA spinning solution is ultrasonicated at room temperature for 5 minutes to remove the bubbles remaining in the spinning solution. A 10 mL syringe is used to absorb the PVDF / PFSA spinning solution, placed in a spinning machine, and the position of the syringe is adjusted. A roller wrapped with aluminum foil is cut to receive the fiber. The spinning conditions are set as follows: voltage 20 kV, distance between the needle and the wheel axle receiver 20 cm, propulsion speed 1 mL / h, spinning temperature 23° C., and spinning relative humidity 40%. After spinning is completed, the prepared fluorosulfonic acid ion exchange membrane is removed from the roller and sealed for storage.

[0025] Example 2

[0026] A method for preparing an ion exchange nanofiber membrane with high mechanical properties specifically comprises the following steps: weighing 1.2 g of PFSA powder and dissolving it in 5 mL of N,N-dimethylacetamide. Stirring at 25° C. and 700 rpm until the perfluorosulfonic acid resin powder is completely dissolved, then adding 0.3 g of PVDF powder and continuing to stir until the PVDF is completely dissolved. A spinning solution with a PFSA:PVDF mass ratio of 4:1 is prepared. The PVDF / PFSA spinning solution is ultrasonicated at room temperature for 5 minutes to remove the bubbles remaining in the spinning solution. A 10 mL syringe is used to absorb the PVDF / PFSA spinning solution, placed in a spinning machine, and the position of the syringe is adjusted. A roller wrapped with aluminum foil is cut to receive the fiber. The spinning conditions are set as follows: voltage 20 kV, distance between the needle and the wheel axle receiver 20 cm, propulsion speed 1 mL / h, spinning temperature 23° C., and spinning relative humidity 40%. After the spinning is completed, the prepared perfluorosulfonic acid ion exchange membrane is removed from the roller and sealed for storage.

[0027] Example 3

[0028] A method for preparing an ion exchange nanofiber membrane with high mechanical properties specifically comprises the following steps: weighing 0.9 g of PFSA powder and dissolving it in 5 mL of N,N-dimethylacetamide. Stirring at 25° C. and 700 rpm until the perfluorosulfonic acid resin powder is completely dissolved, then adding 0.6 g of PVDF powder and continuing to stir until the PVDF is completely dissolved. A spinning solution with a PFSA:PVDF mass ratio of 3:2 is prepared. The PVDF / PFSA spinning solution is ultrasonicated at room temperature for 5 minutes to remove the bubbles remaining in the spinning solution. A 10 mL syringe is used to absorb the PVDF / PFSA spinning solution, placed in a spinning machine, and the position of the syringe is adjusted. A roller wrapped with aluminum foil is cut to receive the fiber. The spinning conditions are set as follows: voltage 20 kV, distance between the needle and the wheel axle receiver 20 cm, propulsion speed 1 mL / h, spinning temperature 23° C., and spinning relative humidity 40%. After the spinning is completed, the prepared fluorosulfonic acid ion exchange membrane is removed from the roller and sealed for storage.

[0029] Results and Discussion: The performance of the electrospun perfluorosulfonic acid ion exchange membranes prepared in Examples 1 to 3 is shown in Table 1

[0030] Table 1 Properties of electrospun perfluorosulfonic acid ion exchange membrane

[0031]

[0032]

[0033] As can be seen from Table 1, the perfluorosulfonic acid ion exchange membrane prepared by the blending of perfluorosulfonic acid and polyvinylidene fluoride by the present invention through electrostatic spinning technology has good comprehensive performance. Because polyvinylidene fluoride is a material with good mechanical properties, hydrophobicity, and chemical stability, as its content increases, the tensile strength of the electrostatic spinning ion membrane is continuously improved, showing good mechanical properties. At the same time, water absorption and swelling rate are continuously reduced, showing excellent chemical stability. In addition, perfluorosulfonic acid resin is due to its unique perfluoro main chain structure, and the sulfonic acid group (-SO3H) contained on its side chain can attract protons (H+) or other cations. During the electrostatic spinning process, the polymer chain is arranged along the electric field direction, resulting in the axial arrangement of a single fiber, and this orientation is conducive to the construction of an efficient transmission channel, further improving the conductivity of protons so that the membrane has excellent ion exchange function. The present invention, by adjusting the ratio of the spinning polymer, the prepared ion exchange membrane has excellent tensile strength, water absorption swelling rate and ion exchange capacity, which means that it has a wide range of applications, and has better stability, durability and sustainability in practical applications.

[0034] The above-described embodiments are only preferred solutions of the present invention and are not intended to limit the present invention in any form. Other variations and modifications are possible without exceeding the technical solutions described in the claims.

Claims

1. A method for preparing an ion exchange nanofiber membrane with high mechanical properties, characterized in that: The following steps are involved: 1) mixing perfluorosulfonic acid resin and polyvinylidene fluoride in a certain ratio in N,N-dimethylacetamide to obtain a spinning solution; 2) The spinning solution is subjected to ultrasound to remove bubbles, and an ion exchange nanofiber membrane with high mechanical properties is prepared by electrospinning.

2. The method for preparing the high mechanical performance ion exchange nanofiber membrane according to claim 1, characterized in that: In step 1), the blending is carried out by stirring at 25° C. and 700 rpm for at least 6 hours.

3. The method for preparing a perfluorosulfonic acid ion exchange membrane according to claim 1, characterized in that: In step 1), the mass proportion of the polyvinylidene fluoride is 10%-40%, and the mass proportion of the perfluorosulfonic acid resin is 60%-90%.

4. The method for preparing the high mechanical property ion exchange nanofiber membrane according to claim 1, characterized in that: The ion exchange capacity of the perfluorosulfonic acid resin is 1.01 to 1.05 mmol / g.

5. The method for preparing the high mechanical property ion exchange nanofiber membrane according to claim 4, characterized in that: In step 2), the voltage of the electrospinning is 20 kV, the distance between the nozzle and the receiver is 20 cm, the propulsion speed of the spinning solution is 1 mL / h, the spinning temperature is 23° C., and the relative humidity of the spinning is 40%.

6. A high mechanical performance ion exchange nanofiber membrane, characterized in that: The method is obtained by any one of claims 1 to 5.

7. The high mechanical performance ion exchange nanofiber membrane according to claim 6, characterized in that: The nanofiber membrane has both high mechanical properties and ion exchange functions, with a tensile strength of 4.2-14.9 MPa, an elongation at break of 100.1%-153.4%, a water absorption rate of 5.9-15.1%, a swelling rate of 3.6-14.2%, a proton conductivity of 82.5-101.2 mS / cm, and an ion exchange capacity of 0.81-0.92 mmol / g.

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