Device for chemical aging of a plurality of polymer membrane samples

Abstract

The invention relates to a chemical aging device comprising an enclosure inside which are installed a plurality of test receptacles (16), each test receptacle containing a certain amount of aqueous solution (18) and a membrane sample (12), each test receptacle (16) being equipped with a gas and vapour evacuation duct (22) connected to its internal volume, the various evacuation ducts (22) of the various test receptacles (16) being connected to a gas and vapour extraction duct (24), this extraction duct (24) passing through a wall of the closed enclosure, this extraction duct (24) being connected to a container flask (26), situated outside the closed enclosure, and opening into a buffer solution (28) contained in this container flask, at least one check valve (32) equipping each evacuation duct, and the chemical aging device comprising an agitation device (34) for agitating the test receptacles.

Description

CHEMICAL AGING DEVICE FOR A MULTIPLE POLYMER MEMBRANE SAMPLES

[0001] The present invention relates to a device for testing the resistance to aging of different membrane samples, for example polymer.

[0002] More specifically, the invention aims to provide a device for testing the resistance to aging of samples of ion exchange membranes, or polymer electrolyte membranes, used in fuel cells for electricity production or in electrolyzers for hydrogen generation.

[0003] Indeed, when used in fuel cells or electrolyzers, polymer electrolyte membranes are in a humid environment where electrochemical reactions occur to generate electricity or hydrogen. These reactions also utilize and release various acidic or basic chemical compounds, and potentially oxidizing agents, which can chemically attack the membrane material. This chemical attack progressively degrades the membrane material, causing it to gradually lose its initial properties and performance. In some cases, this chemical attack can destroy the membranes and render them inoperable.

[0004] Also, with the aim of developing new materials for making polymer electrolyte membranes or testing new materials for making these polymer electrolyte membranes, it is useful to have a device that allows membrane samples to be subjected to the different chemical compounds that could chemically attack these membranes when used in a fuel cell or in an electrolyzer.

[0005] Document CN115201096A relates to an aging device for the gas diffusion layer of a fuel cell membrane. This aging device comprises an aging container for holding a solution containing a reactive agent capable of aging the material of the gas diffusion layer of a fuel cell membrane. The aging device also includes a sample support frame for installation within the aging container and immersion in the solution containing the aging reactive agent. This support frame allows for the complete immersion of several samples of the gas diffusion layer in the solution containing the reactive agent, ensuring that both sides of each sample are in contact with the solution. The aging container includes a lid for sealing the container tightly.This lid includes an inlet port for the injection of a gas intended to cause or amplify the chemical reaction of aging the samples, and a connection port to a condensation tube used to condense the reactive aging agent that has turned into vapor and reintroduce it in liquid form inside the aging container.

[0006] A first drawback of the solution presented in document CN115201096A is that it does not allow simultaneous testing of different samples of the same membrane in different aqueous solutions, or simultaneous testing of different samples of different membranes in different aqueous solutions.

[0007] Another drawback of the solution presented in document CN115201096A is that it does not address the risks of overpressure related to the temperature rise of gases in the aging container or to the production of gas by chemical reactions that take place in the aging container, as well as the risks related to the release of corrosive gases outside the aging container.

[0008] The present invention aims to overcome the drawbacks of prior art membrane sample aging devices.

[0009] To this end, the invention relates to a chemical aging device for different membrane samples, the chemical aging device comprising a closed chamber inside which a plurality of test containers are installed, each test container containing a certain quantity of aqueous solution and a membrane sample immersed in this aqueous solution, each test container being sealed against gases and liquids, each test container being equipped with a gas and vapor exhaust duct connected to its internal volume in a gas and liquid-tight manner, the various exhaust ducts of the different test containers being connected inside the closed chamber to a gas and vapor extraction duct, this extraction duct passing through a wall of the closed chamber,this extraction duct being connected to a guard flask located outside the closed enclosure and this extraction duct opening into a buffer solution contained in this guard flask, at least one non-return valve being fitted to each discharge duct of a test container, and the chemical aging device comprising a device for agitating the test containers inside the closed enclosure.

[0010] Advantageously, but not necessarily, the invention may also provide that: - a valve is fitted to each discharge pipe of a test container, the valve being located between the test container and the non-return valve fitted to that discharge pipe, - The chemical aging device includes a temperature control device to maintain the test containers and their aqueous solution at a set temperature inside the closed chamber, - The temperature maintenance system operates by airflow, - The temperature maintenance device operates by water bath, with the test containers being partially immersed in a temperature maintenance liquid, - The chemical aging device includes a feeding device allowing the reintroduction of temperature-maintaining liquid inside the closed chamber, - The aging device includes an immersion tank for the test containers, arranged inside the closed enclosure and containing the temperature-maintaining liquid in which the test containers are immersed. - Each membrane sample to be tested is held in a flat position in a test container using a support frame, - the support frame comprises two half-frames hollowed in their center and enclosing the membrane sample by its edges.

[0011] The present invention also relates to a method for testing the aging of a plurality of membrane samples using the chemical aging device according to the invention. A first step of this testing method consists of measuring at least one mechanical, conductive, or physicochemical characteristic of each membrane sample before proceeding with the aging test. A second step consists of placing each sample in a test container of the chemical aging device, each test container containing an aqueous solution intended to induce aging of the material of a membrane sample. A third step consists of measuring again the mechanical, conductive, or physicochemical characteristic(s) of each membrane sample after aging.

[0012] This aging test procedure can also predict that: - The test containers and their aqueous solution are maintained at a set temperature between 10°C and 80°C inside the closed chamber during the second stage of the test procedure. - The membrane samples are immersed for a period ranging from a few tens of minutes to several months in the aqueous solution of their test container during the second stage of the test process. - the membranes tested are membranes formed from a polymer bearing ionic or ionizable functional groups, this polymer being able to be impregnated or assembled with a reinforcement which may be in the form of a layer of fibrillar or porous material, and this polymer being able to be mixed with formulation additives, such as antioxidant agents or catalysts for redox reactions, - aqueous solutions are aqueous solutions with a pH less than 4 containing a strong acid such as nitric, hydrochloric or sulfuric acid, or aqueous solutions with a pH greater than 12 containing a strong base such as potassium or sodium hydroxide, or aqueous solutions containing oxidizing species.

[0013] Other features and advantages of the invention will become apparent in the following description. This description, given by way of example and not limitation, refers to the attached drawings in which: - [Fig. 1] represents a first embodiment of the aging device according to the invention, with a temperature maintenance device operating by water bath, - [Fig.2] represents a second embodiment of the aging device according to the invention, with a temperature maintenance device operating by airflow, - [Fig.3] represents a membrane sample in a support frame according to the invention.

[0014] The invention relates to a device for the chemical aging of different membrane samples.

[0015] As illustrated in Figures 1 and 2, the aging device 10 according to the invention allows the aging of a plurality of membrane samples 12 to be tested simultaneously. Advantageously, the aging device according to the invention also allows the aging of different samples of the same membrane or of different membranes to be tested simultaneously in different aqueous solutions, and therefore in different aging conditions.

[0016] For this purpose, the chemical aging device 10 comprises a closed chamber 14 inside which are installed a plurality of test containers 16, each test container 16 containing a certain quantity of aqueous solution 18 and a membrane sample 12 immersed in this aqueous solution. The closed chamber 14 prevents the release of hazardous or corrosive liquids into the external environment of the aging device. A test container, for example, has a capacity of between 100 milliliters and 1 liter.

[0017] For example, the closed enclosure 14 is parallelepiped-shaped and formed by several metal walls assembled together. At least one wall of this closed enclosure includes an opening providing access to the interior volume of the enclosure, this opening being, for example, equipped with a closing door allowing the closed enclosure 14 to be closed. Advantageously, at least one wall of the closed enclosure is equipped with a window allowing visual inspection of the test containers 16 and the membrane samples 12 inside the closed enclosure. Since aqueous solutions can be acidic, basic, and possibly oxidizing, the test containers 16 are made of a material resistant to acidic, basic, and possibly oxidizing agents. The test containers 16 are, for example, made of plastic, such as high-density polyethylene or polypropylene.

[0018] Each test container 16 is sealed against gases and liquids. Thus, the different membrane samples 12 present in the different test containers 16 can be tested independently in different aqueous solutions corresponding to different aging conditions. For example, each test container includes a cap A sealing plug 20 allows for a gas- and liquid-tight closure. These plugs are also made of a material resistant to acid, alkaline, and potentially oxidizing agents. For example, they are made of plastic, such as high-density polyethylene. These plugs can be fitted with a membrane or a sealing gasket.

[0019] To manage the various gas emissions from the different chemical reactions taking place in the test vessels 16, each test vessel 16 is equipped with a gas and vapor vent 22 connected to its internal volume in a gas- and liquid-tight manner. For example, each vent 22 is connected to the sealing plug 20 of a test vessel via a fitting 23, also known as a bulkhead adapter. For example, the fittings 23 are made of plastic, particularly polyethylene.

[0020] In order to manage the different gas emissions from the different chemical reactions taking place in the different test containers 16, the different exhaust ducts 22 of the different test containers are connected inside the closed enclosure 14 to an extraction duct 24 for gases and vapors which passes through a wall of the closed enclosure 14. This extraction duct 24 is connected to a guard flask 26 located outside the closed enclosure 14 and it opens into a buffer solution 28 contained in this guard flask. For example, the various exhaust ducts 22 are connected to the extraction duct 24 of gases and vapors via a manifold 30. This manifold 30 includes a plurality of inlet ports receiving the various exhaust ducts 22, an outlet port connected to the extraction duct 24, and an internal chamber allowing the inlet ports to be put in communication with the outlet port.For example, the various exhaust ducts 22, the gas and vapor extraction duct 24, and the manifold 30 are made of plastic, specifically polyethylene. The gas and vapor extraction duct 24 opens into the buffer solution contained in the guard flask in order to conduct the vapors or gases from the various test vessels directly into this buffer solution. This guard flask also includes an orifice for venting excess gases. Thus, the buffer solution in the guard flask allows the vapors or gases from the various test vessels to be washed before the excess gases are released into the atmosphere surrounding the aging device.

[0021] For example, the buffer solution in the guard flask includes species capable of carrying out acid-base reactions with the gases from the different test containers and with the aim of readjusting the pH of the corresponding vapors to a value of 7 or to values ​​close to 7. A buffer solution may, for example, consist of a mixture of sodium hydrogen phosphate and potassium dihydrogen phosphate.

[0022] Advantageously, the exhaust ducts 22, the extraction duct 24 and the guard flask 26 make it possible to manage gas overpressures related to the temperature rise of the gases in the test vessels and / or related to the production of gas by the chemical reactions which take place in the test vessels, and to avoid releasing corrosive or environmentally harmful gases outside the closed enclosure 14.

[0023] To prevent the backflow of the various gases circulating in the manifold 30 and the extraction duct 24 towards the test vessels 16, at least one non-return valve 32 is fitted to each exhaust duct 22 connected to a test vessel. For example, a non-return valve 32 comprises a body made of plastic, in particular polypropylene, and an internal membrane made of fluoroelastomer, in particular Viton®.

[0024] Advantageously, a valve 36 is fitted to each discharge conduit 22 of a test vessel 16, the valve being located between the test vessel 16 and the non-return valve 32 fitted to that discharge conduit. This valve 36 ensures that the discharge conduit 22 is closed when it is not in use or when it is disconnected from a test vessel, for example, during the installation of new membrane samples 12 in test containers 16. For example, a valve 36 is made of plastic material, in particular polypropylene.

[0025] To promote chemical aging reactions between the different membrane samples 12 and the chemical aging agents contained in the different aqueous solutions, the chemical aging device 10 includes a stirring device 34 for the test containers 16 inside the closed enclosure 14. For example, the stirring device 34 is a vibrating or rotating plate on which the test containers 16 are placed.

[0026] To further promote chemical aging reactions between the different membrane samples 12 and the chemical aging agents contained in the different aqueous solutions, the chemical aging device 10 includes a temperature maintenance device 38 to maintain the test containers and their aqueous solution at a set temperature inside the closed enclosure 14. For example, the set temperature is between 10°C and 80°C.

[0027] In a first embodiment of the aging device 10 according to the invention and illustrated in Figure 1, the temperature maintenance device 38 operates by means of a water bath. For this purpose, the test vessels 16 are partially immersed in a temperature maintenance liquid, such as water. The temperature maintenance liquid is maintained at the set temperature by the temperature maintenance device 38, for example, by heat exchange between a steam heating circuit and the temperature maintenance liquid. The temperature maintenance device 38 includes, for example, a temperature probe (not shown) immersed in the temperature maintenance liquid and coupled to a solenoid valve (not shown) controlling the steam circulation in the heating circuit.

[0028] If a high setpoint temperature is used for aging tests, the temperature-maintaining liquid may evaporate. This is because the closed chamber 14 is not necessarily gas-tight. Therefore, in this first embodiment, the chemical aging device 10 includes a supply device 40 for reintroducing temperature-maintaining liquid into the closed chamber.

[0029] In this first embodiment of the aging device 10 according to the invention, the aging device 10 comprises, for example, an immersion tank 42 for the test vessels arranged inside the closed enclosure 14 and containing the temperature-maintaining liquid in which the test vessels are immersed. In this case, the supply device 40 allows the temperature-maintaining liquid to be reintroduced into the immersion tank 42. For example, this immersion tank is made of stainless steel.

[0030] In a second embodiment of the aging device 10 according to the invention and illustrated in Figure 2, the temperature maintenance device 38 operates by means of an airflow. In this case, the temperature maintenance device 38 allows the temperature of the gases inside the closed enclosure to be regulated. For example, the temperature maintenance device 38 includes means for generating an airflow, such as a fan, and means for heating this airflow, such as a heating element.

[0031] In either embodiment, the closed enclosure helps maintain the test containers 16, their aqueous solutions, and the membrane samples 12 they contain at the set temperature. The closed enclosure 14, and optionally the immersion tank 42, also act as a safety receptacle in case of accidental spillage of an aqueous solution into the closed enclosure.

[0032] In addition to the stirring device 34 of the test containers, and to ensure optimal contact between the two faces of a membrane sample 12 and the aqueous solution in which it is immersed, each membrane sample 12 to be tested is held in a flat position in a test container using a support frame 42, such as the one illustrated in Figure 3. For example, this The support frame 42 comprises two half-frames 44, 46, hollow in their center, which enclose the membrane sample 12 by its edges. The two half-frames 44, 46 are, for example, hinged to each other and joined together by interlocking.

[0033] The invention also relates to a method for testing the aging of a plurality of membrane samples using the aging device 10 which has just been described.

[0034] A first step in this aging test process is to measure at least one mechanical, conductive or physicochemical characteristic of each membrane sample 12 before proceeding with the aging test.

[0035] A second step in this aging test procedure involves placing each membrane sample 12 into a test container 16 of the chemical aging device 10. Each test container 16 contains an aqueous solution designed to induce aging of the membrane sample material. For example, the membrane samples 12 are immersed for several hours to several days in the aqueous solution in their test container during this second step of the test procedure.

[0036] A third step in this aging test process involves re-measuring the mechanical, conductive or physicochemical characteristic(s) of each membrane sample after aging.

[0037] Thus, by comparing the measured characteristic(s) before and after aging, we can estimate the resistance to aging of different membrane samples under different aging conditions.

[0038] As previously stated, the invention aims to test the resistance to aging of samples of ion exchange membranes, or polymer electrolyte membranes, used in fuel cells for electricity production or in electrolyzers for hydrogen generation.

[0039] For example, the membranes tested are membranes formed from a polymer bearing ionic or ionizable functional groups. This polymer may be impregnated or bonded with a reinforcement, which can be in the form of a layer of fibrillar or porous material. This polymer may also be mixed with formulation additives, such as antioxidants or catalysts for redox reactions. The constituent polymers of the membranes are typically polymers with a hydrocarbon main chain, possibly substituted, for example, with fluorine atoms as in the case of Nation™, or polysulfones, polyarylethers, or polyketones. The main chain or backbone of these polymers bears ionic groups such as quaternary ammonium groups, sulfonates, or ionizable groups such as sulfonic acid groups (SO3H).

[0040] Aqueous solutions are typically aqueous solutions with a pH less than 4 containing a strong acid such as nitric, hydrochloric or sulfuric acid, or aqueous solutions with a pH greater than 12 containing a strong base such as potassium or sodium hydroxide, or aqueous solutions containing oxidizing species.

[0041] To obtain faster aging results, aqueous solutions are more concentrated in the chemical species that cause the aging of the material of membrane samples than is the humid environment in which these membranes will be used, for example, in fuel cells or electrolyzers.

[0042] For example, the test vessels and their aqueous solution are maintained at a set temperature between 10°C and 80°C inside the closed enclosure 14 during the second stage of the test process.

Claims

DEMANDS 1. Chemical aging device (10) for different membrane samples (12), the chemical aging device comprising a closed chamber (14) inside which are installed a plurality of test containers (16), each test container containing a certain quantity of aqueous solution (18) and a membrane sample (12) immersed in this aqueous solution, each test container (16) being sealed against gases and liquids, each test container (16) being equipped with a gas and vapor exhaust duct (22) connected to its internal volume in a gas and liquid-tight manner, the different exhaust ducts (22) of the different test containers (16) being connected inside the closed chamber to a gas and vapor extraction duct (24), this extraction duct (24) passing through a wall of the closed chamber,this extraction conduit (24) being connected to a guard flask (26) located outside the closed enclosure and this extraction conduit opening into a buffer solution (28) contained in this guard flask, at least one non-return valve (32) being fitted to each discharge conduit of a test container, and the chemical aging device comprising a device for stirring (34) the test containers inside the closed enclosure.

2. Chemical aging device (10) according to claim 1, in which a valve (36) is fitted to each discharge conduit of a test vessel (16), the valve being located between the test vessel (16) and the check valve (32) fitted to this discharge conduit.

3. Chemical aging device according to any one of the preceding claims, which chemical aging device (10) comprises a temperature maintenance device for maintaining the test vessels and their aqueous solution at a set temperature inside the closed enclosure.

4. Chemical aging device (10) according to claim 3, wherein the temperature maintenance device operates by airflow.

5. Chemical aging device (10) according to claim 3, wherein the temperature maintenance device operates by water bath, the test vessels being partially immersed in a temperature maintenance liquid.

6. Chemical aging device (10) according to claim 5, which chemical aging device includes a supply device (40) for reintroducing temperature-maintaining liquid inside the closed enclosure (14).

7. Chemical aging device (10) according to claim 5 or 6, which chemical aging device (10) comprises an immersion tank (42) for the test containers disposed inside the closed enclosure (14) and containing the temperature-maintaining liquid in which the test containers are immersed.

8. Chemical aging device (10) according to any one of the preceding claims, wherein each membrane sample (12) to be tested is held in a flat shape in a test container using a support frame (42).

9. Chemical aging device (10) according to claim 8, in which the support frame (42) comprises two half-frames (44,46) hollowed in their center and enclosing the membrane sample (12) by its edges.

10. A method for testing the aging of a plurality of membrane samples (12) using the chemical aging device (10) according to any one of claims 1 to 9 and comprising the following steps: - measurement of at least one mechanical, conductive or physicochemical characteristic(s) of each membrane sample (12) before proceeding with the aging test, - disposition of each membrane sample (12) in a test container (16) of the chemical aging device (10), each test container (16) containing an aqueous solution intended to cause aging of the material of a membrane sample, - new measurement of the mechanical, conductive or physicochemical characteristic(s) of each membrane sample after aging.

11. Aging test method according to claim 10, wherein the test containers and their aqueous solution are maintained at a set temperature between 10°C and 80°C inside the closed enclosure (14) during the second step of the test method.

12. Aging test method according to claim 10 or 11, wherein the membrane samples (12) are immersed for several hours to several days in the aqueous solution of their test container during the second step of the test method.

13. Aging test method according to any one of claims 10 to 12, wherein the membranes tested are membranes formed from a polymer bearing ionic or ionizable functional groups, this polymer being able to be impregnated or assembled with a reinforcement which may be in the form of a layer of fibrous or porous material, and this polymer being able to be mixed with formulation additives, such as antioxidant agents or catalysts for redox reactions.

14. Aging test method according to any one of claims 10 to 13, wherein the aqueous solutions are aqueous solutions of pH less than 4 containing a strong acid such as nitric, hydrochloric or sulfuric acid, or aqueous solutions having a pH greater than 12 containing a strong base such as potassium or sodium hydroxide, or aqueous solutions containing oxidizing species.

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