A Modified PTFE Hydrogen Energy Electrolyzer Sealing Gasket Material and Its Preparation Method

Abstract

The present invention relates to a modified PTFE sealing gasket material for a hydrogen energy electrolytic cell, which is made from raw materials including the following weight components: 70-90 parts of polytetrafluoroethylene, 10-20 parts of surface needle-shaped modified glass fiber, 0.5-5 parts of high-temperature resistant ceramic, 0.1-2 parts of lubricant, and 0.1-1 part of carbon powder; the sealing gasket is prepared by a cold pressing and sintering method. The advantages of the modified PTFE sealing gasket material for a hydrogen energy electrolytic cell of the present invention are that by using hedgehog structure glass fiber, temperature-resistant ceramic and coarse particle size lubricant to modify the PTFE material, a dense structure is formed inside. In particular, the hedgehog structure glass fiber restricts the movement of polymer chains, so that the gasket has good compression resistance and stress relaxation resistance in a long-term high-temperature environment, thereby significantly improving its sealing performance and reliability.

Description

Technical Field

[0001] The present invention relates to the field of hydrogen energy, and specifically to a modified PTFE hydrogen energy electrolyzer sealing gasket material and a preparation method thereof. Background Art

[0002] Hydrogen truly achieves completely no carbon emissions and is also a key development direction for future hydrogen production. The main reason for the high manufacturing cost of green hydrogen is the electricity price and the key equipment for electrolytic water hydrogen production (electrolyzer): 80% of the cost of hydrogen energy is the cost of electricity, and the remaining 20% of the cost is basically the depreciation cost of the electrolytic water hydrogen production equipment. Therefore, the electrolyzer plays a crucial role in reducing the cost of hydrogen production.

[0003] The existing seals of hydrogen energy water electrolyzers require harsh working conditions of high pressure and high temperature. Currently, the market mainly uses a single material such as asbestos material. Although it has excellent properties such as stable performance, corrosion resistance, and acid and alkali resistance, it also has disadvantages such as poor high-temperature resistance, short service life, low mechanical properties, and high stress relaxation rate. The existence of these disadvantages greatly restricts the application of the seals in the market of sealing gaskets for hydrogen energy electrolyzers.

[0004] Polytetrafluoroethylene has good corrosion resistance, chemical stability, and hydrophobicity, and its high-temperature resistance, high-pressure resistance, and high and low-temperature resistance are also very remarkable, making it very suitable as a sealing material. However, its stress relaxation resistance ability is poor and its resilience is poor. Generally, fillers are needed to improve its performance. The commonly used filler is glass fiber. For example, the PTEE sealing elastic material of Asahi Kasei Corporation in Japan is obtained by blending short glass fiber and PTEE and is currently the mainstream product in the market. However, the surface of the glass fiber is very smooth, and the interfacial bonding with polytetrafluoroethylene is poor, failing to effectively restrict the movement of polymer chains. Therefore, its stress relaxation resistance ability is poor and it still cannot meet the requirements of the sealing gasket for the electrolytic hydrogen production electrolyzer.

[0005] Based on this current situation, there is an urgent need for a PTFE sealing gasket with excellent comprehensive performance, high-temperature resistance, compression resistance, low stress relaxation rate, and good sealing performance to promote the application of PTFE composite materials in the field of sealing of hydrogen energy vehicle electrolyzers. Summary of the Invention

[0006] The purpose of the present invention is to provide a modified PTFE hydrogen energy electrolyzer sealing gasket material and a preparation method thereof to solve the problems raised in the above background art.

[0007] To achieve the above purpose, the present invention provides the following technical solutions:

[0008] A modified PTFE hydrogen electrolyzer gasket material is made from raw materials including the following weight components: 70-90 parts of polytetrafluoroethylene, 10-20 parts of surface needle-shaped modified glass fiber, 0.5-5 parts of high-temperature resistant ceramic, 0.1-2 parts of lubricant, and 0.1-1 part of carbon powder.

[0009] Further, the surface needle-shaped modified glass fiber is obtained by a preparation method including the following steps:

[0010] (S1) The chopped glass fiber treated by alkali etching is immersed in a mixed aqueous solution containing cobalt ions, nickel ions and urea, subjected to hydrothermal reaction, the glass fiber is taken out, washed and dried, and then immersed in an aqueous solution of thiourea, subjected to hydrothermal reaction, taken out, washed and dried to obtain glass fiber with a nickel cobalt sulfide needle-like structure;

[0011] (S2) The glass fiber with a nickel cobalt sulfide needle-like structure obtained in step (S1) is added to a Tris-HCl buffer solution dissolving dopamine hydrochloride, fully reacted, washed and dried to obtain surface needle-shaped modified glass fiber.

[0012] Further, in step (S1), in the mixed aqueous solution containing cobalt ions, nickel ions and urea, the Co ion concentration is 1-50 mmol / L, the Ni ion concentration is 1-50 mmol / L, and the urea concentration is 1-50 mmol / L; the concentration of the thiourea aqueous solution is 1-200 mmol / L.

[0013] Further, in step (S1), the hydrothermal reaction is carried out at 90-120 °C for 2-20 h.

[0014] Further, in step (S2), the pH of the Tris-HCl buffer solution is 8-9, such as 8.5; the concentration of dopamine hydrochloride is 1-5 g / L, such as 2 g / L, 3 g / L, 4 g / L; the mass ratio of the glass fiber with a nickel cobalt sulfide needle-like structure to dopamine hydrochloride is 1:0.1-0.5, such as 1:0.2-0.3; the full reaction is carried out at room temperature for 12-24 h.

[0015] In the present invention, the surface of the glass fiber is modified with a nickel cobalt sulfide needle-like structure, and then polydopamine is coated on the nickel cobalt sulfide needle-like structure. The nickel cobalt sulfide needle-like structure and polydopamine cooperate with each other and act synergistically, greatly improving the bonding at the interface between the glass fiber and tetrafluoroethylene. There is both mechanical interlocking of the needle-like structure and the effect after polydopamine coating. The two jointly contribute to the excellent comprehensive performance of the modified PTFE hydrogen electrolyzer gasket material of the present invention.

[0016] Even further, the surface needle-shaped modified glass fiber is obtained by a preparation method including the following steps:

[0017] 1) Etching the desized glass fiber with alkali solution for 0.5 to 2 hours, and then drying;

[0018] 2) dissolving a water-soluble cobalt source, a water-soluble nickel source, and urea in deionized water to obtain a mixed solution;

[0019] 3) transferring the mixed solution obtained in step 2) to a reaction kettle provided with a polytetrafluoroethylene liner, and then immersing the glass fiber treated in step 1) in the mixed solution obtained in step 2), reacting at 90-120° C. for 2-20 hours, and then naturally cooling the reaction kettle to room temperature;

[0020] 4) taking out the glass fiber obtained in step 3), and then rinsing and drying;

[0021] 5) immersing the glass fiber obtained in step 4) in a thiourea aqueous solution and reacting at 80-180° C. for 2-20 hours, and then naturally cooling the reactor to room temperature;

[0022] 6) taking out the glass fiber from step 5), washing and drying it to obtain the glass fiber modified with nickel cobalt sulfide of needle-like structure;

[0023] 7) preparing a Tris-HCl buffer solution with a pH of 8-9 and a concentration of 1-5 g / L dopamine hydrochloride;

[0024] 8) adding the glass fiber modified with needle-like structure nickel cobalt sulfide in step 6) to the buffer solution in step 7) to fully react to obtain surface needle-like modified glass fiber.

[0025] Preferably, the alkali solution in step (1) is a 10-30wt% NaOH and / or KOH solution; the water-soluble cobalt source is selected from the group consisting of cobalt chloride, cobalt nitrate, and hydrates thereof; and the water-soluble nickel source is selected from the group consisting of nickel chloride, nickel nitrate, and hydrates thereof.

[0026] Preferably, in step (1), the glass fiber is chopped glass fiber with an aspect ratio of 3-10 and a diameter of 5-15 μm.

[0027] Preferably, the polytetrafluoroethylene is one of suspended PTFE and dispersed PTFE or a mixture of the two, and the average particle size is between 300-600 meshes.

[0028] Preferably, the temperature-resistant ceramic is one or both of barium sulfate and aluminum oxide.

[0029] Preferably, the lubricant is a metal sulfide with a median particle size (D50) of not less than 40 μm; for example, at least one of molybdenum disulfide, tin disulfide, and tungsten disulfide with a D50 of ≥40 μm.

[0030] The present invention also provides a preparation method of the modified PTFE sealing gasket material for a hydrogen energy electrolyzer, comprising the following steps:

[0031] T1. Mixing and stirring: Pour tetrafluoroethylene, surface needle-shaped modified glass fiber, high-temperature resistant ceramic, lubricant, and carbon powder into a mixer and stir evenly;

[0032] T2. Compression molding: Add the mixed material obtained in step S1 into the mold cavity of a mold, and perform a pre-forming process under the forming conditions of a temperature of 23 - 28 °C;

[0033] T3. Sintering: Put the pre-formed blank into a sintering furnace for heating, and make the polytetrafluoroethylene composite material self-coagulate into a finished product of a certain shape through heat conduction.

[0034] T4. Machining: Machine the sintered finished product according to the required specifications and dimensions to obtain the required gasket.

[0035] Preferably, the number of stirring times in step T1 is 3 - 5 times, the stirring speed is 1000 - 2000 revolutions per minute, and the number of sieving times is 1 - 4 times.

[0036] Preferably, the molding press used in step T2 is hydraulically powered, the molding pressure is between 30 - 70 MPa, and the molding pressure holding time is 1 - 5 minutes.

[0037] Preferably, the sintering environment in step T3 is air, the sintering heat preservation temperature is between 330 - 380 °C, the sintering time is 5 - 20 hours, and the heating and cooling rates are generally controlled between 1 - 10 °C / min, such as 5 °C / min.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows: The sealing gasket of the PTFE hydrogen energy electrolyzer provided by the present invention has better sealing performance compared with the traditional sealing gaskets of hydrogen energy electrolyzers on the market. Especially the application of the surface needle-shaped modified glass fiber. On the one hand, its hedgehog structure glass fiber restricts the movement of polymer chains, enabling the gasket to have good compression resistance and stress relaxation resistance in a long-term high-temperature environment, thus significantly improving its sealing performance and reliability; on the other hand, the surface of the glass fiber is very smooth, and the interface combination with polytetrafluoroethylene is poor. After modifying the micro-needle structure, it can form a mechanical interlock with polytetrafluoroethylene at the interface. Combining the role of polydopamine, it improves the interface bonding strength, and at the same time restricts the movement of polymer chains, increasing the stress relaxation resistance rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is the SEM photograph of the hedgehog structure glass fiber adopted by the present invention.

[0040] Figure 2It is a schematic cross-sectional view of the hedgehog structure glass fiber.

[0041] Figure 3 It is an SEM photograph of the unmodified glass fiber. Specific embodiments

[0042] The present invention is further described below in conjunction with specific embodiments:

[0043] Preparation Example 1

[0044] 1) The desized chopped glass fiber (the glass fiber has an aspect ratio > 3 and a diameter of about 10 μm) was etched with a 10 wt% aqueous NaOH solution for 2 h, and then dried.

[0045] 2) CoCl2·6H2O, NiCl2·6H2O and urea were dissolved in deionized water to obtain a mixed solution, wherein the concentration of CoCl2·6H2O was 5 mmol / L, the concentration of NiCl2·6H2O was 5 mmol / L, and the concentration of urea was 10 mmol / L.

[0046] 3) The mixed solution obtained in step 2) was transferred to a reaction kettle with a polytetrafluoroethylene lining, and then the glass fiber treated in step 1) was immersed in the mixed solution obtained in step 2). Then, the reaction was carried out at 110 °C for 6 h, and then the reaction kettle was naturally cooled to room temperature.

[0047] 4) The glass fiber obtained in step 3) was taken out, rinsed and dried.

[0048] 5) The glass fiber obtained in step 4) was immersed in an aqueous thiourea solution with a concentration of 5 mmol / L, and the reaction was carried out at 140 °C for 4 h. Then, the reaction kettle was naturally cooled to room temperature.

[0049] 6) The glass fiber obtained in step 5) was taken out, rinsed and dried to obtain the glass fiber modified with needle-like nickel cobalt sulfide.

[0050] 7) A Tris-HCl buffer solution with a concentration of 2 g / L and a pH value of 9.0 was prepared. Then, a dopamine solution with a concentration of 2 g / L was prepared with hydrochloric acid dopamine as the solute and Tris-HCl buffer solution as the solvent, and the pH was adjusted to 8.5.

[0051] 8) 1 g of the glass fiber modified with needle-like nickel cobalt sulfide obtained in step 6) was added to 100 ml of the buffer solution obtained in step 7). Under room temperature conditions, the glass fiber obtained after stirring and reacting for 24 h was rinsed with deionized water and dried to obtain the surface needle-like modified glass fiber.

[0052] Figure 1 It is an SEM photograph of the hedgehog structure glass fiber adopted by the present invention. Figure 2It is a schematic cross-sectional view of the hedgehog structure glass fiber. Figure 3 It is an SEM photograph of untreated glass fiber. It can be clearly seen that the surface of the glass fiber treated by the method of the present invention is covered with needle-like structures, which are needle-like nickel cobalt sulfide coated with polydopamine.

[0053] Comparative Preparation Example 1

[0054] 1) The desized chopped glass fiber (the glass fiber has an aspect ratio > 3 and a diameter of about 10 μm) is etched with a 10 wt% aqueous NaOH solution for 2 h, and then dried.

[0055] 2) Prepare a Tris-HCl buffer solution with a concentration of 2 g / L and a pH value of 9.0. Then, using dopamine hydrochloride as the solute and the Tris-HCl buffer solution as the solvent, prepare a 2 g / L dopamine solution and adjust the pH to 8.5.

[0056] 3) Put the dried glass fiber into 100 ml of the buffer solution obtained in step 2, and under room temperature conditions, stir and react for 24 h. The obtained glass fiber is rinsed with deionized water and dried to obtain polydopamine-modified glass fiber.

[0057] Example 1

[0058] A preparation method of a modified PTFE hydrogen energy electrolytic cell gasket material, comprising the following steps:

[0059] S1. Put 79 parts by mass of suspension-type PTFE with an average particle size of 600 mesh (its density is 2.2 g / cm 3 ), 15 parts of the glass fiber of needle-like nickel cobalt sulfide prepared in Preparation Example 1, 3 parts of barium sulfate, 2 parts of molybdenum disulfide with a coarse particle size of D50 of 40 μm, and 1 part of carbon powder into a mixer for uniform stirring at a stirring speed of 1500 rpm, and then perform sieving treatment, with the number of sieving times being 4 times;

[0060] S2. Take the raw material mixture obtained in step S1 for molding, with a molding pressure of 40 MPa and a molding pressure holding time of 2 min, and sinter in an air atmosphere in a sintering furnace. The sintering holding temperature is 365 °C and the sintering time is 15 hours to obtain the modified PTFE hydrogen energy electrolytic cell gasket.

[0061] Example 2

[0062] Other conditions are the same as those in Example 1, except that the amount of suspension-type PTFE used is 84 parts by mass, and the amount of the glass fiber of needle-like nickel cobalt sulfide prepared in Preparation Example 1 used is 10 parts.

[0063] Example 3

[0064] Other conditions are the same as those in Example 1, except that the amount of suspension PTFE is 77 parts by mass, and the amount of glass fiber of needle-like nickel cobalt sulfide prepared in Preparation Example 1 is 17 parts.

[0065] Example 4

[0066] Other conditions are the same as those in Example 1, except that the amount of suspension PTFE is 74 parts by mass, and the amount of glass fiber of needle-like nickel cobalt sulfide prepared in Preparation Example 1 is 25 parts.

[0067] Comparative Example 1

[0068] Other conditions are the same as those in Example 1, except that the glass fiber used in the raw materials is ordinary glass fiber instead of the surface needle-like modified glass fiber prepared in Preparation Example 1.

[0069] Comparative Example 2

[0070] Other conditions are the same as those in Example 1, except that the glass fiber used in the raw materials is the glass fiber with needle-like nickel cobalt sulfide modified on the surface obtained in step 6) of Preparation Example 1.

[0071] Comparative Example 3

[0072] Other conditions are the same as those in Example 1, except that the glass fiber used in the raw materials is the polydopamine-modified glass fiber prepared in Comparative Preparation Example 1.

[0073] Take the modified PTFE hydrogen energy electrolyzer gasket materials prepared in the examples and comparative examples, and test their tensile strength, elongation at break, compressive strength, stress relaxation rate and leakage rate respectively. Among them, the tensile strength is tested by the ASTM-D4894 test method; the compression rate is tested by the ASTM-D695 test method, the stress relaxation rate is tested by the GB / T12621A standard, and the leakage rate is tested by the GB / T12385A standard. The test results are shown in Table 1:

[0074] Table 1 Performance test of electrolyzer gasket materials

[0075]

[0076] As can be seen from Table 1 above, the modified PTFE hydrogen energy electrolyzer gasket material of the present invention has excellent tensile properties, pressure resistance, stress relaxation resistance and sealing properties.

Claims

1. A modified PTFE sealing gasket material for hydrogen energy electrolytic cells, characterized in that, Made from raw materials including the following weight components: 70-90 parts of polytetrafluoroethylene, 10-20 parts of surface acicular modified glass fiber, 0.5-5 parts of high-temperature resistant ceramic, 0.1-2 parts of lubricant, 0.1-1 part of carbon powder; the surface acicular modified glass fiber is obtained by a preparation method including the following steps: (S1) The short-cut glass fiber treated by alkali etching is immersed in a mixed aqueous solution containing cobalt ions, nickel ions and urea, subjected to hydrothermal reaction, taken out, washed and dried, and then immersed in an aqueous thiourea solution, subjected to hydrothermal reaction, taken out, washed and dried to obtain glass fiber with a nickel cobalt sulfide acicular structure; (S2) The glass fiber with a nickel cobalt sulfide acicular structure obtained in step (S1) is added to a Tris-HCl buffer solution containing hydrochloric acid dopamine, fully reacted, washed and dried to obtain surface acicular modified glass fiber; the concentration of hydrochloric acid dopamine is 1-5 g / L, and the mass ratio of the glass fiber with a nickel cobalt sulfide acicular structure to hydrochloric acid dopamine is 1:0.1-0.5; the full reaction is carried out at room temperature for 12-24 h.

2. The modified PTFE hydrogen electrolyzer gasket material according to claim 1, wherein In step (S1), in the mixed aqueous solution containing cobalt ions, nickel ions and urea, the Co ion concentration is 1-50 mmol / L, the Ni ion concentration is 1-50 mmol / L, and the urea concentration is 1-50 mmol / L; the concentration of the aqueous thiourea solution is 1-200 mmol / L; the hydrothermal reaction is carried out at 90-120 °C for 2-20 h.

3. The modified PTFE hydrogen energy electrolytic cell gasket material according to claim 2, characterized in that, In step (S2), the pH of the Tris-HCl buffer solution is 8-9.

4. The modified PTFE hydrogen electrolyzer gasket material according to claim 3, wherein, The pH of the Tris-HCl buffer solution is 8.

5.

5. The modified PTFE hydrogen electrolyzer sealing gasket material according to claim 1, characterized in that, The surface acicular modified glass fiber is obtained by a preparation method including the following steps: 1) Etch the desized glass fiber with alkali solution for 0.5-2 h, and then dry it; 2) Dissolve the water-soluble cobalt source, water-soluble nickel source and urea in deionized water to obtain a mixed solution; 3) Transfer the mixed solution obtained in step 2) to a reaction kettle with a polytetrafluoroethylene inner liner, and then immerse the glass fiber treated in step 1) in the mixed solution obtained in step 2), react at 90-120 °C for 2-20 h, and then let the reaction kettle cool naturally to room temperature; 4) Take out the glass fiber after step 3), and then rinse and dry it; 5) Immerse the glass fiber obtained in step 4) in an aqueous thiourea solution, and react at 80-180 °C for 2-20 h, and then let the reaction kettle cool naturally to room temperature; 6) Take out the glass fiber in step 5), rinse and dry it to obtain glass fiber modified with a nickel cobalt sulfide acicular structure; 7) Prepare a Tris-HCl buffer solution with a pH of 8-9 and a concentration of 1-5 g / L of hydrochloric acid dopamine; 8) Add the glass fiber modified with a nickel cobalt sulfide acicular structure in step 6) to the buffer solution in step 7), and fully react to obtain surface acicular modified glass fiber.

6. The modified PTFE hydrogen energy electrolytic cell gasket material according to claim 5, wherein, In step 1), the alkali solution is a 10-30 wt% NaOH and / or KOH solution; the water-soluble cobalt source is selected from the group consisting of cobalt chloride, cobalt nitrate, and their hydrates; the water-soluble nickel source is selected from the group consisting of nickel chloride, nickel nitrate, and their hydrates.

7. The modified PTFE hydrogen electrolyzer gasket material according to claim 5, characterized in that, In step 1), the glass fiber is chopped glass fiber with an aspect ratio of 3 - 10 and a diameter of 5 - 15 μm.

8. The modified PTFE hydrogen energy electrolyzer gasket material according to claim 1, wherein The polytetrafluoroethylene is one of suspension-type PTFE and dispersion-type PTFE or a mixture of the two, and the average particle size is between 300 and 600 mesh; the high-temperature resistant ceramic is one or two of barium sulfate and aluminum oxide; the lubricant is a metal sulfide with a median particle size of not less than 40 microns.

9. The modified PTFE hydrogen electrolyzer gasket material according to claim 8, wherein, The lubricant is at least one of molybdenum disulfide, tin disulfide, and tungsten disulfide with D50 ≥ 40 μm.

10. The preparation method of the modified PTFE hydrogen energy electrolyzer gasket material according to any one of claims 1-9, characterized in that, It includes the following steps: T1. Mixing and stirring: Pour tetrafluoroethylene, surface needle-like modified glass fiber, high-temperature resistant ceramic, lubricant, and carbon powder into a mixer for uniform stirring. T2. Compression molding: Add the mixed material obtained in step S1 into the cavity of the mold and perform a pre-forming process under the forming condition of a temperature of 23 - 28°C. T3. Sintering: Put the pre-formed blank into a sintering furnace for heating, and make the polytetrafluoroethylene composite material self-condense into a finished product with a certain shape through heat conduction. T4. Machining: Machine the sintered finished product according to the required specifications and dimensions to obtain the required gasket.

11. According to the preparation method of claim 10, characterized in that, In step T1, the number of stirring times is 3 - 5 times, the stirring speed is 1000 - 2000 revolutions per minute, and the sieving times are 1 - 4 times. In step T2, the used molding press is hydraulically powered, the molding pressure is between 30 - 70 MPa, and the molding holding pressure time is 1 - 5 minutes. In step T3, the sintering environment is air, the sintering holding temperature is between 330 - 380°C, the sintering time is 5 - 20 hours, and the heating and cooling rate is controlled between 1 - 10°C / min.

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