A yellowing-resistant hot melt adhesive diaphragm for hydrogen fuel cells and its preparation method

Abstract

The present invention relates to a yellowing-resistant hot melt adhesive diaphragm for hydrogen fuel cells and a preparation method thereof, belonging to the technical field of hydrogen fuel cells. The diaphragm comprises, by weight percentage: 8.5-10 wt% of an organic-inorganic framework compound, 1.5-2.1 wt% of an organosilicon dispersant, 0.8-1.4 wt% of a nano filler, and 0.4-0.6 wt% of a coupling agent, with the balance being a casting solution resistant; the organic-inorganic framework compound is self-assembled by an in-situ polymerization method from a composite inorganic coordination matrix with a porous structure and pyrrole monomers to form an organic-inorganic network structure cross-linked with nitrogen-containing heterocycles, providing a large number of coordination sites as proton acceptors and having good proton conduction ability, and the casting solution resistant uses a substitution product of trifluoroethanol and vinylphenyl dichlorosilane as a modified monomer and is block copolymerized with low molecular weight polypropylene to introduce fluorine-containing groups to improve the aging resistance of the polymer.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogen fuel cells, and specifically, relates to a yellowing-resistant hot melt adhesive diaphragm for hydrogen fuel cells and a preparation method thereof. Background Art

[0002] The appearance of a fuel cell is similar to that of a storage battery, having positive / negative electrodes and an electrolyte. However, different from a traditional storage battery, a fuel cell is not an electrical energy storage device but an energy conversion device. Fuel and an oxidant are introduced into the interior of the fuel cell from the outside and directly converted into electrical energy without going through the chemical energy - thermal energy - kinetic energy conversion, with high energy utilization efficiency, and the power generation product is only non-polluting water, having broad application prospects.

[0003] A fuel cell consists of four parts: an anode, a cathode, an electrolyte, and an external circuit. Usually, the anode is the electrode where fuel is injected, and the cathode is the electrode where the oxidant is injected. There are generally catalyst coatings on the cathode and the anode. The electrolyte is between the cathode and the anode. Taking a hydrogen fuel cell as an example, hydrogen fuel is injected from the anode end, passes through the catalyst coating, and hydrogen is catalyzed into H + and electrons. H + passes through the electrolyte to reach the catalyst layer of the cathode; while the electrons are removed through the external circuit, and oxygen is injected from the cathode end. In the catalyst layer of the cathode, oxygen combines with H + and electrons to form water.

[0004] The proton exchange membrane is the core component of a hydrogen fuel cell, and its main functions are to isolate the cathode / anode of the battery to avoid direct contact between the fuel and the oxidant, and at the same time to be able to transfer protons; in the prior art, perfluorosulfonic acid-based proton exchange membranes have always occupied the market. The microphase separation structure of the hydrophilic phase and the hydrophobic phase in the membrane causes the aggregation of hydrophilic clusters, thus forming a proton transport channel, having good proton conductivity, and the perfluorinated materials have good stability; however, the price of perfluorosulfonic acid-based materials remains high and it is difficult to be mass-produced; therefore, in the prior art, fluorine-free sulfonated aromatic proton exchange membranes are developed as substitutes for perfluorosulfonic acid-based membrane materials, such as polyether ether ketone-based membrane materials, whose proton conductivity is about 0.05 S·cm -1 or so, and there is a regular benzene ring structure in the polymer chain, and the stiffness and melting point of the membrane material are relatively high, making it not easy to process. Summary of the Invention

[0005] In order to solve the technical problems mentioned in the background art, the purpose of the present invention is to provide a yellowing-resistant hot melt adhesive diaphragm for hydrogen fuel cells and a preparation method thereof.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A yellowing-resistant hot melt adhesive diaphragm for hydrogen fuel cells, comprising by weight percentage: 8.5-10 wt% of an organic-inorganic framework compound, 1.5-2.1 wt% of an organosilicon dispersant, 0.8-1.4 wt% of a nano filler, and 0.4-0.6 wt% of a coupling agent, with the balance being a casting solution resistant;

[0008] The organic-inorganic framework compound is prepared by the following method:

[0009] Step A1: Dissolve ferric chloride, cobalt nitrate and 2-methylimidazole in an ethanol solution, heat up to 50-60 °C, add carbon nanotubes and ultrasonically disperse, while slowly dripping a sodium hydroxide solution to adjust the pH value of the reaction system to 8.5, continue to heat up to 82-88 °C and reflux for 1-1.5 h. After the reflux ends, centrifuge to take the lower layer, dry it and then calcine it at 220-240 °C for 5-6 h, and then finely crush the calcined product to obtain an inorganic coordination matrix;

[0010] Furthermore, the dosage ratio of ferric chloride, cobalt nitrate, 2-methylimidazole and carbon nanotubes is 0.1 mol: 5-12 mmol: 35-45 mmol: 60-80 mg. 2-methylimidazole is a coordination material, interacting with iron ions and cobalt ions in a solution state. The fine carbon nanotubes serve as a nucleation aid and pore support material. Under alkaline conditions, iron ions hydrolyze to form a gel-like substance, which shrinks during calcination to form a pore structure.

[0011] Step A2: Mix pyrrole monomer, inorganic coordination matrix and ethanol solution, heat up to 32-36 °C, set the stirring rate to 120-180 rpm, keep stirring and reacting for 15-18 h, then heat up to 55-65 °C, increase the stirring rate to 840-960 rpm, add ammonium persulfate solution, and stir and react at high speed for 1.2-1.5 h. Filter to take the filter cake, wash it with ethanol and water, grind it and dry it to obtain the organic-inorganic framework compound;

[0012] Furthermore, the dosage ratio of pyrrole monomer, inorganic coordination matrix, ethanol solution and ammonium persulfate is 0.1 mol: 0.26-0.35 g: 40-55 mL: 18-23 mg. The metal elements in the inorganic coordination matrix interact with the pyrrole monomer, enrich in the inorganic coordination matrix and are preliminarily polymerized under the catalysis of trivalent iron to form clusters, and then are assembled by polymerization under the catalysis of ammonium persulfate.

[0013] The casting solution resistant is prepared by the following method:

[0014] Step B1: Mix trifluoroethanol, triethylamine and dioxane, set the stirring rate to 240-300 rpm, heat up to 65-75 °C, slowly add vinylphenyl dichlorosilane, keep stirring and reacting for 3-4 h, and rotary evaporate under reduced pressure after the reaction ends to obtain a fluorine-modified monomer;

[0015] Furthermore, the dosage ratio of vinylphenyldichlorosilane, trifluoroethanol, triethylamine and dioxane is 0.1 mol: 0.24 - 0.28 mol: 20 - 25 mL: 120 - 160 mL.

[0016] Step B2: Preheat and mix low molecular weight polypropylene and xylene, then add a fluorine-modified monomer and acrylic acid, heat up to 120 - 130 °C, set the stirring rate to 80 - 120 rpm, slowly add benzoyl peroxide, control the overall addition reaction time to be 2.5 - 3.2 h, cool to room temperature and add pine oil to adjust the viscosity to 65 s to obtain a resistant casting solution.

[0017] Furthermore, the dosage ratio of low molecular weight polypropylene, fluorine-modified monomer, acrylic acid, benzoyl peroxide and xylene is 100 g: 18 - 25 mmol: 5 - 9 mmol: 0.2 - 0.3 g: 260 - 300 mL.

[0018] A preparation method of a yellowing-resistant hydrogen fuel cell hot melt adhesive diaphragm includes the following steps:

[0019] Step S1: Dilute the coupling agent with an ethanol solution, then sequentially add an organosilicon dispersant, an organic-inorganic framework compound and a nano filler and mix them, add the resistant casting solution under stirring, heat up to 175 - 185 °C and knead for 17 - 22 min to obtain a hot melt adhesive material.

[0020] Step S2: Extrude the hot melt adhesive material into a film, cool to 120 °C and perform biaxial stretching and shaping, then place it at 70 °C for heat preservation and homogenization for 30 min, and cut it after cooling to obtain a yellowing-resistant hydrogen fuel cell hot melt adhesive diaphragm.

[0021] Preferably, the organosilicon dispersant is BYK-346.

[0022] Preferably, the nano filler is fumed silica.

[0023] Preferably, the coupling agent is silane coupling agent KH550.

[0024] The beneficial effects of the present invention:

[0025] The present invention provides a method for preparing a polypropylene-based hot melt adhesive diaphragm, which has high processability compared with the existing polyaryletherketone diaphragm, a simple preparation process, and good mechanical properties, and can meet the use requirements of hydrogen fuel cells. Among them, the organic-inorganic framework compound uses 2-methylimidazole as a coordination material, adsorbs iron ions and cobalt ions by coordination through a solution method, doped with a small amount of carbon nanotubes as a nucleation aid and pore support material, and uses a hydrothermal method to prepare a composite inorganic coordination matrix with a porous structure to form a proton channel. Then, pyrrole monomers and the inorganic coordination matrix are self-assembled by in-situ polymerization to form an organic-inorganic network structure crosslinked with nitrogen-containing heterocycles. The nitrogen-containing structure can provide a large number of coordination sites as proton acceptors, has good proton conduction ability, and can also block the contact between fuel and oxidant. In addition, in the present invention, a hot melt type casting solution resistant to hydrogen fuel cells is prepared as a film-forming matrix, which uses a substitution product of trifluoroethanol and vinylphenyl dichlorosilane as a modified monomer, block copolymerizes with low molecular weight polypropylene, and introduces fluorine-containing groups to improve the aging resistance of the polymer and meet the service conditions of hydrogen fuel cells. Detailed implementation mode

[0026] The following will combine the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work belong to the protection scope of the present invention.

[0027] Example 1

[0028] In this example, a yellowing-resistant hydrogen fuel cell hot melt adhesive diaphragm is prepared, and the specific implementation process is as follows:

[0029] I. Preparation of organic-inorganic framework compound

[0030] a1. Prepare an ethanol solution with a concentration of 20%, add ferric chloride, cobalt nitrate and 2-methylimidazole and stir to dissolve, preheat to 50 °C, add a small amount of carbon nanotubes and disperse them by ultrasonic wave at 28 kHz for 30 min. At the same time, dropwise add 0.1 moL / L sodium hydroxide solution to adjust the pH value of the reaction system to 8.5, then continue to heat up to 82 °C and reflux for 1.5 h. After the reflux is completed, centrifuge to take the lower layer of flocculent precipitate and place it in a drying oven, dry it for 2 h under nitrogen protection, then place the dried product in a roasting furnace, roast it at 220 °C for 6 h, and then place the roasted product in a blade crusher and crush it at a high speed of 20000 rpm for 10 min to obtain an inorganic coordination matrix. Among them, the dosage ratio of ferric chloride, cobalt nitrate, 2-methylimidazole and carbon nanotubes is 0.1 mol: 5 mmol: 35 mmol: 60 mg.

[0031] a2. Take pyrrole monomer, inorganic coordination matrix and ethanol solution with a concentration of 80% and stir and mix them for 2 h. Then, raise the temperature to 32 °C, set the stirring rate to 120 rpm, keep the temperature and stir for reaction for 18 h. After the reaction, continue to raise the temperature to 55 °C, increase the stirring rate to 840 rpm, add ammonium persulfate solution, and stir at high speed for reaction for 1.5 h. Filter the reaction solution by suction, take the filter cake and wash it with ethanol and water in turn, then place it in a grinder and grind it cyclically until the grinding slurry passes through a 1800-mesh sieve, and spray-dry the slurry to prepare an organic-inorganic framework compound. Among them, the dosage ratio of pyrrole monomer, inorganic coordination matrix, ethanol solution and ammonium persulfate is 0.1 mol: 0.26 g: 40 mL: 18 mg.

[0032] II. Preparation of the tolerance casting solution

[0033] b1. Take trifluoroethanol, triethylamine and dioxane and stir and mix them. Set the stirring rate to 240 rpm, raise the temperature to 65 °C, and then slowly add vinylphenyl dichlorosilane within 30 min. Then, continue to keep the temperature and stir for reaction for 4 h. After the reaction, remove the excessive trifluoroethanol, triethylamine and solvent dioxane by rotary evaporation under reduced pressure to obtain a fluorine-modified monomer. Among them, the dosage ratio of vinylphenyl dichlorosilane, trifluoroethanol, triethylamine and dioxane is 0.1 mol: 0.24 mol: 20 mL: 120 mL.

[0034] b2. Take low molecular weight polypropylene (average molecular weight is 2000, the same raw materials are used hereinafter) and xylene, preheat and stir and mix them. Then, add the fluorine-modified monomer and acrylic acid at 80 °C. Then, continue to raise the temperature to 120 °C, set the stirring rate to 80 rpm, slowly add benzoyl peroxide within 1.5 h, and continue to keep the temperature and stir for reaction after adding. Control the total addition reaction time to be 3.2 h, cool to room temperature and add pine perfume to adjust the viscosity to 65 s to obtain a tolerance casting solution. Among them, the dosage ratio of low molecular weight polypropylene, fluorine-modified monomer, acrylic acid, benzoyl peroxide and xylene is 100 g: 18 mmol: 9 mmol: 0.2 g: 260 mL.

[0035] III. Preparation of the hot melt adhesive diaphragm

[0036] s1. Take materials for preparing 5 kg of diaphragm masterbatch. Respectively take 8.5 wt% of the organic-inorganic framework compound, 2.1 wt% of the organosilicon dispersant (selected from BYK-346, the same raw materials are used hereinafter), 1.4 wt% of the nano filler (selected from fumed silica, the same raw materials are used hereinafter) and 0.6 wt% of the coupling agent (selected from silane coupling agent KH550, the same raw materials are used hereinafter), and the balance is the tolerance casting solution. Additionally, take an ethanol solution with a concentration of 60% which is 1.8 times the concentration of the organic-inorganic framework compound.

[0037] s2. Stir and dilute the coupling agent with an ethanol solution, then sequentially add an organosilicon dispersant, an organic-inorganic framework compound, and nano-fillers, stir and mix at 360 rpm for 30 min. Then, keep the stirring rate at 120 rpm, slowly add the resistant casting solution within 10 min, and keep stirring and heating up to 175 °C for kneading for 22 min to obtain a hot-melt adhesive material;

[0038] s3. Transfer the hot-melt adhesive material into an extruder to extrude into a film. Cool the extruded film to 120 °C for biaxial stretching, then place the stretched film at 70 °C for heat preservation and homogenization for 30 min, and cut it after cooling to obtain a yellowing-resistant hydrogen fuel cell hot-melt adhesive separator.

[0039] Example 2

[0040] In this example, a yellowing-resistant hydrogen fuel cell hot-melt adhesive separator is prepared, and the specific implementation process is as follows:

[0041] I. Preparation of the organic-inorganic framework compound

[0042] a1. Prepare an ethanol solution with a concentration of 20%, add ferric chloride, cobalt nitrate, and 2-methylimidazole and stir to dissolve. Preheat to 60 °C, add a small amount of carbon nanotubes and ultrasonically disperse at 33 kHz for 20 min. At the same time, dropwise add 0.1 moL / L sodium hydroxide solution to adjust the pH value of the reaction system to 8.5. Then continue to heat up to 88 °C for reflux for 1 h. After the reflux ends, centrifuge to take the lower-layer flocculent precipitate and place it in a drying oven, dry it for 2 h under nitrogen protection. Then place the dried product in a roasting furnace, roast it at 240 °C for 5 h. Then place the roasted product in a blade-type pulverizer and pulverize it at a high speed of 20000 rpm for 10 min to prepare an inorganic coordination matrix. Among them, the dosage ratio of ferric chloride, cobalt nitrate, 2-methylimidazole, and carbon nanotubes is 0.1 mol: 12 mmol: 45 mmol: 80 mg.

[0043] a2. Take pyrrole monomer, inorganic coordination matrix, and an ethanol solution with a concentration of 80% and stir and mix for 2.5 h. Then heat up to 36 °C, set the stirring rate to 180 rpm, keep stirring and reacting for 15 h. After the reaction, continue to heat up to 65 °C, increase the stirring rate to 960 rpm, add ammonium persulfate solution, and stir and react at a high speed for 1.2 h. Filter the reaction solution, take the filter cake and wash it with ethanol and water in turn, then place it in a grinder for cyclic grinding until the grinding slurry passes through a 1800-mesh sieve, and spray-dry the slurry to prepare an organic-inorganic framework compound. Among them, the dosage ratio of pyrrole monomer, inorganic coordination matrix, ethanol solution, and ammonium persulfate is 0.1 mol: 0.35 g: 55 mL: 23 mg.

[0044] II. Preparation of the resistant casting solution

[0045] b1. Take trifluoroethanol, triethylamine, and dioxane, stir and mix them, set the stirring rate to 300 rpm, heat up to 75 °C, then slowly add vinylphenyldichlorosilane within 30 min. After that, continue to stir and react at a constant temperature for 3 h. After the reaction is completed, remove the excessive trifluoroethanol, triethylamine, and the solvent dioxane by rotary evaporation under reduced pressure to obtain a fluorine-modified monomer. Among them, the dosage ratio of vinylphenyldichlorosilane, trifluoroethanol, triethylamine, and dioxane is 0.1 mol: 0.28 mol: 25 mL: 160 mL.

[0046] b2. Take low molecular weight polypropylene and xylene, preheat and stir and mix them, then add the fluorine-modified monomer and acrylic acid at 80 °C. After that, continue to heat up to 130 °C, set the stirring rate to 120 rpm, slowly add benzoyl peroxide within 1 h. After adding, continue to stir and react at a constant temperature, control the overall addition reaction time to be 2.5 h, cool to room temperature, and add pine oil to adjust the viscosity to 65 s to obtain a tolerance casting solution. Among them, the dosage ratio of low molecular weight polypropylene, fluorine-modified monomer, acrylic acid, benzoyl peroxide, and xylene is 100 g: 25 mmol: 5 mmol: 0.3 g: 300 mL.

[0047] III. Preparation of the hot melt adhesive diaphragm

[0048] s1. For preparing 5 kg of diaphragm masterbatch, take 10 wt% of the organic-inorganic framework compound, 1.5 wt% of the organosilicon dispersant, 0.8 wt% of the nano filler, and 0.4 wt% of the coupling agent respectively, and the balance is the tolerance casting solution. Additionally, take an ethanol solution with a concentration 1.5 times that of the organic-inorganic framework compound and a concentration of 60%.

[0049] s2. Stir and dilute the coupling agent with the ethanol solution, then successively add the organosilicon dispersant, the organic-inorganic framework compound, and the nano filler, stir and mix at 360 rpm for 30 min. After that, keep the stirring rate at 120 rpm, slowly add the tolerance casting solution within 10 min, keep stirring and heat up to 185 °C, and knead for 17 min to obtain a hot melt adhesive material.

[0050] s3. Transfer the hot melt adhesive material into an extruder to extrude into a film. Cool the extruded film to 120 °C for biaxial stretching, then place the stretched film at 70 °C for heat preservation and homogenization for 30 min, and cut it after cooling to obtain a yellowing-resistant hydrogen fuel cell hot melt adhesive diaphragm.

[0051] Example 3

[0052] In this example, a yellowing-resistant hydrogen fuel cell hot melt adhesive diaphragm is prepared, and the specific implementation process is as follows:

[0053] I. Preparation of the organic-inorganic framework compound

[0054] a1. Prepare an ethanol solution with a concentration of 20%. Add ferric chloride, cobalt nitrate, and 2-methylimidazole and stir to dissolve. Preheat to 55 °C, add a small amount of carbon nanotubes, and ultrasonically disperse them at 33 kHz for 25 min. At the same time, dropwise add a 0.1 moL / L sodium hydroxide solution to adjust the pH value of the reaction system to 8.5. Then continue to heat up to 85 °C and reflux for 1.2 h. After the reflux ends, centrifuge to obtain the lower-layer flocculent precipitate, place it in a drying oven, dry it for 2 h under nitrogen protection. Then place the dried product in a roasting furnace and roast it at 240 °C for 5.5 h. Then place the roasted product in a blade-type crusher and crush it at a high speed of 20,000 rpm for 10 min to prepare an inorganic coordination matrix. Among them, the dosage ratio of ferric chloride, cobalt nitrate, 2-methylimidazole, and carbon nanotubes is 0.1 mol: 10 mmol: 42 mmol: 75 mg.

[0055] a2. Take pyrrole monomer, inorganic coordination matrix, and an ethanol solution with a concentration of 80% and stir and mix them for 2.2 h. Then heat up to 35 °C, set the stirring rate to 180 rpm, and keep stirring and reacting for 16 h. After the reaction, continue to heat up to 60 °C, increase the stirring rate to 960 rpm, add ammonium persulfate solution, and stir and react at a high speed for 1.3 h. Filter the reaction solution, take the filter cake, wash it successively with ethanol and water, and then place it in a grinder for cyclic grinding until the grinding slurry passes through a 1800-mesh sieve. Spray-dry the slurry to prepare an organic-inorganic framework compound. Among them, the dosage ratio of pyrrole monomer, inorganic coordination matrix, ethanol solution, and ammonium persulfate is 0.1 mol: 0.32 g: 50 mL: 20 mg.

[0056] II. Preparation of the casting solution resistant

[0057] b1. Take trifluoroethanol, triethylamine, and dioxane and stir and mix them. Set the stirring rate to 300 rpm and heat up to 70 °C. Then slowly add vinylphenyl dichlorosilane within 30 min. Then continue to keep stirring and reacting for 3.5 h. After the reaction ends, carry out rotary evaporation under reduced pressure to remove the excessive trifluoroethanol, triethylamine, and the solvent dioxane to obtain a fluorine-modified monomer. Among them, the dosage ratio of vinylphenyl dichlorosilane, trifluoroethanol, triethylamine, and dioxane is 0.1 mol: 0.26 mol: 22 mL: 150 mL.

[0058] b2. Preheat and stir to mix low molecular weight polypropylene and xylene, then add fluorine-modified monomer and acrylic acid at 80°C. After that, continue to heat up to 125°C, set the stirring rate to 120 rpm, slowly add benzoyl peroxide within 1.3 h, and keep stirring and reacting at the same temperature after adding. Control the overall addition and reaction time to be 2.8 h, cool to room temperature, and add mineral spirits to adjust the viscosity to 65 s to obtain a resistant casting solution. Among them, the dosage ratio of low molecular weight polypropylene, fluorine-modified monomer, acrylic acid, benzoyl peroxide, and xylene is 100 g: 20 mmol: 7 mmol: 0.26 g: 300 mL.

[0059] III. Preparation of hot melt adhesive diaphragm

[0060] s1. For preparing 5 kg of diaphragm masterbatch, take 9.2 wt% of organic-inorganic framework compound, 1.8 wt% of organosilicon dispersant, 1.2 wt% of nano-filler, and 0.55 wt% of coupling agent respectively, and the balance is the resistant casting solution. Additionally, take an ethanol solution with a concentration 1.7 times that of the organic-inorganic framework compound and a concentration of 60%.

[0061] s2. Stir and dilute the coupling agent with the ethanol solution, then successively add the organosilicon dispersant, organic-inorganic framework compound, and nano-filler, stir and mix at 360 rpm for 30 min. After that, keep the stirring rate at 120 rpm, slowly add the resistant casting solution within 10 min, and keep stirring and heating up to 180°C for kneading for 20 min to obtain a hot melt adhesive material.

[0062] s3. Transfer the hot melt adhesive material into an extruder to extrude into a film. Cool the extruded film to 120°C for biaxial stretching, then place the stretched film at 70°C for heat preservation and homogenization for 30 min, and cut it after cooling to obtain a yellowing-resistant hydrogen fuel cell hot melt adhesive diaphragm.

[0063] Take samples of the diaphragms prepared in Examples 1 - 3, and use an electronic tensile machine to conduct mechanical property tests on the samples at a rate of 1 mm / min.

[0064] Dry the samples at 60°C for 5 h, measure the weight of the diaphragm, then place it in deionized water, soak it at 40°C for 24 h, take it out and drain for 30 min, and measure the weight of the diaphragm again to calculate the change rate to characterize the water absorption rate of the diaphragm.

[0065] Make the diaphragm into samples of 40×10 mm, and use a Philips impedance / gain-phase analyzer (1260) to conduct proton conductivity tests at a test temperature of 80°C.

[0066] The specific test data are shown in Table 1:

[0067] Table 1

[0068] 1. 2. Example 1 3. Example 2 4. Example 3 5. Tensile strength / MPa 6. 32.18 7. 36.42 8. 31.55 9. Elongation at break / % 10. 86.7 11. 78.6 12. 84.9 13. Water absorption / % 14. 9.73 15. 9.16 16. 9.32 <![CDATA[17. Proton conductivity / S·cm -1 > 18. 0.103 19. 0.124 20. 0.116

[0069] As can be seen from the data in Table 1, the separator prepared by the present invention has good strength and toughness, good mechanical properties, is suitable for battery separators, has a moderate water absorption rate of the separator, and the proton conductivity reaches 0.1 S·cm -1 or above, showing good proton conduction ability.

[0070] To verify the influence of aging yellowing on the performance of the separator, the above samples were soaked in the oxidation solution to accelerate aging. The oxidation solution was composed of 1% hydrogen peroxide solution and 2 ppm ferrous sulfate, the soaking temperature was 80 °C, the soaking time was 48 h, and after soaking, they were washed alternately with ethanol and deionized water twice, and then tested again according to the above method. The specific test data are shown in Table 2:

[0071] Table 2

[0072] 21. 22. Example 1 23. Example 2 24. Example 3 25. Tensile strength / MPa 26. 28.65 27. 34.92 28. 30.46 29. Elongation at break / % 30. 82.3 31. 77.1 32. 83.7 33. Water absorption / % 34. 10.14 35. 9.42 36. 9.85 <![CDATA[37. Proton Conductivity / S·cm -1 > 38. 0.097 39. 0.119 40. 0.112

[0073] As can be seen from the data in Table 2, the performance of the separator prepared by the present invention has no obvious change after strong oxidation aging treatment, showing excellent aging resistance.

[0074] In the description of the specification, the descriptions referring to the terms "one embodiment", "example", "specific example", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0075] The above content is only an example and illustration of the present invention. Those skilled in the art of this technology can make various modifications or supplements to the specific embodiments described or use similar methods to replace them. As long as they do not deviate from the invention or exceed the scope defined by this claim book, they should all belong to the protection scope of the present invention.

Claims

1. A yellowing-resistant hot melt adhesive diaphragm for hydrogen fuel cells, characterized in that, Comprising by weight percentage: 8.5 - 10 wt% of organic-inorganic framework compound, 1.5 - 2.1 wt% of organosilicon dispersant, 0.8 - 1.4 wt% of nano filler, and 0.4 - 0.6 wt% of coupling agent, with the balance being the casting solution resistant; The preparation method of the organic-inorganic framework compound is as follows: Step A1: Dissolve ferric chloride, cobalt nitrate, and 2-methylimidazole in an ethanol solution, heat up to 50 - 60 °C, add carbon nanotubes and ultrasonically disperse, while slowly dropwise adding sodium hydroxide solution to adjust the pH value of the reaction system to 8.5, continue to heat up to 82 - 88 °C and reflux for 1 - 1.5 h. After refluxing, centrifuge to take the lower layer, dry it, and then calcine it at 220 - 240 °C for 5 - 6 h. Then crush the calcined product to obtain an inorganic coordination matrix; Step A2: Mix pyrrole monomer, inorganic coordination matrix, and ethanol solution, heat up to 32 - 36 °C, keep warm and stir for reaction for 15 - 18 h, then heat up to 55 - 65 °C, add ammonium persulfate solution, and stir at high speed for reaction for 1.2 - 1.5 h. Filter by suction, take the filter cake, wash it with ethanol and water, grind it, and dry it to obtain the organic-inorganic framework compound; The preparation method of the casting solution resistant is as follows: Step B1: Mix trifluoroethanol, triethylamine, and dioxane, stir and heat up to 65 - 75 °C, slowly add vinylphenyl dichlorosilane, keep warm and stir for reaction for 3 - 4 h. After the reaction, carry out rotary evaporation under reduced pressure to obtain a fluorine-modified monomer; Step B2: Pre-heat and mix low molecular weight polypropylene and xylene, then add the fluorine-modified monomer and acrylic acid, heat up to 120 - 130 °C, slowly add benzoyl peroxide under stirring, control the overall addition reaction time to be 2.5 - 3.2 h, cool to room temperature, and add pine oil to adjust the viscosity to 65 s to obtain the casting solution resistant; 2. The yellowing-resistant hot melt adhesive diaphragm for hydrogen fuel cells according to claim 1, characterized in that, The dosage ratio of ferric chloride, cobalt nitrate, 2-methylimidazole, and carbon nanotubes is 0.1 mol : 5 - 12 mmol : 35 - 45 mmol : 60 - 80 mg.

3. The yellowing-resistant hot melt adhesive diaphragm for hydrogen fuel cells according to claim 2, characterized in that, The dosage ratio of pyrrole monomer, inorganic coordination matrix, ethanol solution, and ammonium persulfate is 0.1 mol : 0.26 - 0.35 g : 40 - 55 mL : 18 - 23 mg.

4. A yellowing-resistant hot melt adhesive diaphragm for a hydrogen fuel cell according to claim 1, characterized in that, The dosage ratio of vinylphenyl dichlorosilane, trifluoroethanol, triethylamine, and dioxane is 0.1 mol : 0.24 - 0.28 mol : 20 - 25 mL : 120 - 160 mL.

5. A yellowing-resistant hot melt adhesive diaphragm for a hydrogen fuel cell according to claim 4, characterized in that, The dosage ratio of low molecular weight polypropylene, fluorine-modified monomer, acrylic acid, benzoyl peroxide, and xylene is 100 g : 18 - 25 mmol : 5 - 9 mmol : 0.2 - 0.3 g : 260 - 300 mL, and the average molecular weight of low molecular weight polypropylene is 2000.

6. The yellowing-resistant hot melt adhesive diaphragm for hydrogen fuel cells according to claim 1, wherein The nano filler is fumed silica, the organosilicon dispersant is BYK-346, and the coupling agent is silane coupling agent KH550.

7. The preparation method of a yellowing-resistant hot melt adhesive diaphragm for a hydrogen fuel cell according to claim 6, characterized in that, Including the following steps: Step S1: Dilute the coupling agent with an ethanol solution, then sequentially add the organosilicon dispersant, organic-inorganic framework compound, and nano filler and mix, add the casting solution resistant under stirring and mix, heat up to 175 - 185 °C and knead for 17 - 22 min to obtain a hot melt adhesive; Step S2: Extrude the hot melt adhesive into a film, cool it to 120°C for biaxial stretching and shaping, then place it at 70°C for heat preservation and homogenization for 30 minutes, and cut it after cooling to obtain a yellowing-resistant hydrogen fuel cell hot melt adhesive diaphragm.