Method for bonding graphite bipolar plate for fuel cell to sealant

Abstract

The application relates to a method for bonding a graphite bipolar plate for a fuel cell and sealant, and the method comprises the following steps: S1, coating a flash-drying adhesive on the bottom of a sealing groove of the graphite bipolar plate, allowing the flash-drying adhesive to stand and solidify, and forming a flash-drying adhesive layer; S2, coating a primer on the surface of the flash-drying adhesive layer, allowing the primer to stand and dry, and forming a primer layer; S3, applying the sealant to the surface of the primer layer through a dispensing process, and then performing solidification bonding to obtain a sealant strip. Compared with the prior art, the method can firmly bond the graphite bipolar plate and the sealant, avoids the problems of weak bonding between the graphite bipolar plate and the sealant and easy falling off of the sealant after solidification due to low surface energy, many internal pores and low mechanical strength of the graphite bipolar plate, meanwhile, the method has high production efficiency, is simple in process and is suitable for continuous production.

Description

Technical Field

[0001] This invention relates to the field of fuel cell sealing technology, and in particular to a method for bonding graphite bipolar plates and sealant for fuel cells. Background Technology

[0002] A hydrogen-oxygen fuel cell is an energy conversion device with advantages such as high energy efficiency, no harmful gas emissions, and environmental friendliness. A hydrogen fuel cell consists of core components such as bipolar plates, a proton exchange membrane, and sealant.

[0003] As a core component of hydrogen fuel cells, bipolar plates require resistance to electrochemical corrosion. Graphite materials exhibit outstanding resistance to electrochemical corrosion and are widely used in the fabrication of bipolar plates for hydrogen fuel cells. For example, patent CN112310426A discloses a method for producing bipolar plates using resin-filled expanded graphite, which offers advantages such as good airtightness and resistance to electrochemical corrosion. Another example is patent CN109786779A, which discloses a method for improving the corrosion resistance of bipolar plates by adhering a thin graphite layer to the surface of the plate.

[0004] The biggest difference between the energy conversion process of hydrogen-oxygen fuel cells and hydrogen combustion is that hydrogen and oxygen do not come into direct contact; this is mainly achieved through the sealant in the fuel cell. However, due to the low surface energy, numerous internal pores, and low mechanical strength of graphite bipolar plates, their adhesion to the sealant is weak, and the sealant easily detaches after curing. For example, patent CN114171755A discloses a method for preparing pre-pressed graphite bipolar plates, which uses resin impregnation, cleaning, and curing to prepare a thin and high-strength graphite bipolar plate. The resin impregnation process fills the internal pores of the graphite plate, improving airtightness and mechanical strength. The cleaning process removes residual resin from the surface of the graphite bipolar plate, maintaining the high electrical conductivity of the graphite material. However, the cleaning process also further exposes the difficulty in bonding sealant to the surface of the graphite bipolar plate, namely, the low surface energy, numerous internal pores, and low mechanical strength of the graphite material. For example, patent CN110783599B discloses a method for dispensing sealant onto graphite plates in hydrogen fuel cells. This method cures and bonds sealant to the graphite plate through a dispensing process, but suffers from very weak adhesion between the sealant and graphite. Consequently, the sealant is prone to detachment during subsequent fuel cell production and stack maintenance. Patent CN114784314A discloses a method for sealing bipolar plates in fuel cells, as well as the fuel cell and vehicle. This method improves adhesion by forming an adhesive layer between the bipolar plate and the sealant. However, this method uses a high-viscosity primer resin with poor penetration into the graphite surface, resulting in insufficient enhancement of adhesion. Furthermore, the coating cures slowly, requiring heating or light exposure, leading to low production efficiency.

[0005] Therefore, there is an urgent need for a method to firmly bond graphite bipolar plates to sealant in order to solve the problem of weak adhesion and easy detachment of sealant after curing. Summary of the Invention

[0006] The purpose of this invention is to overcome the defects of the prior art by providing a method for bonding graphite bipolar plates and sealant for fuel cells, thereby solving the problems of weak adhesion and easy detachment of sealant when directly applied to graphite bipolar plates.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] This invention provides a method for bonding a graphite bipolar plate for a fuel cell to a sealant. The graphite bipolar plate has a graphite bipolar plate sealing groove. The method for bonding the graphite bipolar plate for a fuel cell to the sealant includes the following steps:

[0009] S1. Apply instant adhesive to the bottom of the graphite bipolar plate sealing groove and cure the instant adhesive. Let the instant adhesive dry to form an instant adhesive layer.

[0010] S2. After the instant adhesive has cured, a primer is applied to the surface of the instant adhesive layer, and the primer is allowed to dry to form a primer layer.

[0011] S3. Apply the sealant to the surface of the primer layer using a dispensing process and then cure and bond it to obtain a sealant strip.

[0012] Preferably, the viscosity of the instant adhesive in step S1 is 1-1000 mPa·s.

[0013] More preferably, the viscosity of the instant adhesive in step S1 is 1-100 mPa·s.

[0014] Furthermore, the components of the instant adhesive described in step S1 include a reactive resin and a polymerization inhibitor.

[0015] More preferably, the reactive resin is mainly composed of cyanoacrylate.

[0016] More preferably, the cyanoacrylate is ethyl α-cyanoacrylate.

[0017] Furthermore, the method of applying the instant adhesive in step S1 is selected from brushing, screen printing, or air spraying.

[0018] Further, the amount of instant adhesive applied in step S1 is 0.01–1 g / cm³. 2 .

[0019] More preferably, the amount of instant adhesive applied in step S1 is 0.01–0.2 g / cm³.2 .

[0020] Furthermore, the curing time of the instant adhesive in step S1 is 0.1-60 minutes.

[0021] More preferably, the curing time of the instant adhesive in step S1 is 0.1-10 minutes.

[0022] Preferably, the components of the primer in step S2 include an active resin and a diluent.

[0023] Furthermore, the active resin is selected from one or more of siloxane resins or epoxy resins.

[0024] Furthermore, the diluent is selected from one or more of toluene, xylene, ethanol, acetone or isopropanol.

[0025] Furthermore, the method of applying the primer in step S2 includes one of brushing, screen printing, and air spraying.

[0026] Further, the amount of primer applied in step S2 is 0.01–1 g / cm³. 2 .

[0027] More preferably, the amount of primer applied in step S2 is 0.01–0.2 g / cm³. 2 .

[0028] More preferably, the method of allowing the primer to dry in step S2 is to allow it to dry at room temperature for a period of 0.1-60 minutes.

[0029] Preferably, the sealant in step S3 is a liquid or semi-solid sealant before curing and has rubber elasticity after curing.

[0030] Furthermore, the sealant is a high thixotropic silicone sealant, which can be cured by heat curing or ultraviolet light irradiation.

[0031] Preferably, the curing temperature of the bonding process in step S3 is 60-150℃, and the curing time is 1-300 minutes.

[0032] More preferably, the curing temperature of the curing bonding in step S3 is 120°C and the curing time is 120 minutes.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The present invention provides a method for bonding graphite bipolar plates and sealant for fuel cells. The method first uses a low-viscosity instant adhesive to penetrate and mechanically reinforce the graphite on the surface of the graphite bipolar plate. Then, a primer is applied to the surface to enhance the adhesion between the graphite bipolar plate surface and the sealant, resulting in a significantly enhanced bonding effect. This avoids the problem of sealant falling off during the actual production and stack maintenance of fuel cells.

[0035] 2. The present invention provides a method for bonding graphite bipolar plates for fuel cells with sealant. The instant adhesive has the advantage of rapid curing and can cure without additional heating or light exposure, resulting in high production efficiency and meeting the requirements of continuous industrial production. The low-viscosity instant adhesive partially penetrates into the pores of the surface graphite, playing a role in filling, agglomerating, and improving the mechanical strength of the surface graphite material. At the same time, it does not significantly increase the thickness of the coating area of ​​the graphite bipolar plate. A small amount of instant adhesive coating can achieve the purpose of mechanical reinforcement. The production efficiency is high, the instant adhesive cures quickly, and it does not require heating or light exposure, making it suitable for continuous industrial production.

[0036] 3. The present invention provides a method for bonding graphite bipolar plates for fuel cells to sealant, wherein the primer can increase the surface energy of the bonded materials and bridge the graphite surface layer reinforced by the instant adhesive and the sealant. Detailed Implementation

[0037] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These modifications and improvements are all protected by the present invention.

[0038] Any preparation methods, materials, structures, or composition ratios not explicitly described in this technical solution are considered common technical features disclosed in the prior art.

[0039] Based on the problems mentioned in the background art, this invention, in its conceptualization process, achieves the mechanical reinforcement of the graphite material surface by coating the surface of the sealing groove area of ​​a graphite bipolar plate with a low-viscosity instant adhesive, and then improves the adhesion between the adhesive and the sealant by applying a primer. The low-viscosity instant adhesive partially penetrates into the pores of the surface graphite and cures without the need for heating or light exposure, thus filling, agglomerating, and enhancing the mechanical strength of the surface graphite material. It also has the following advantages: 1. It does not significantly increase the thickness of the coating area of ​​the graphite bipolar plate; a small amount of instant adhesive is sufficient to achieve mechanical reinforcement; 2. It has high production efficiency, the instant adhesive cures quickly, and it does not require heating or light exposure, making it suitable for continuous industrial production. The primer increases the surface energy of the bonded materials and bridges the graphite surface reinforced by the instant adhesive with the sealant.

[0040] In all embodiments and comparative examples provided by this invention, the preparation of the sealing strip and the tensile peel force test are carried out according to the following method: the sealant is evenly applied to the surface of the test sample using a dispensing machine. The outline of the applied sealant is semi-circular, with a diameter of 2 mm, a height of 1 mm, and a length of 15 cm. Then, it is cured under the corresponding conditions to obtain the sealing strip. After curing, it is left to stand at room temperature for 24 hours. Then, a tensile peel test is performed at 180°C on a tensile testing machine, and the tensile peel force value is recorded.

[0041] In all the embodiments and comparative examples provided by this invention, the high thixotropic silicone sealant used is the DB9682L sealant from Huizhou Duko New Materials Co., Ltd.

[0042] Example 1

[0043] This embodiment provides a method for bonding a graphite bipolar plate for a fuel cell to a sealant. The graphite bipolar plate has a graphite bipolar plate sealing groove. The method for bonding the graphite bipolar plate for a fuel cell to the sealant includes the following steps:

[0044] S1. Loctite 401 acrylate instant adhesive from Henkel was selected as the instant adhesive. This instant adhesive has a viscosity of 80 mPa·s and a surface drying time of 1-3 minutes. The adhesive content is 0.1 g / cm³. 2 The amount and brushing method are specified. Apply instant adhesive to the bottom of the graphite bipolar plate sealing groove and let it stand to cure for 5 minutes to form an instant adhesive layer.

[0045] S2. Select IMB3050 siloxane primer from Lord Company, at a concentration of 0.1 g / cm³. 2 Apply the primer to the surface of the instant adhesive layer by brushing, and let it dry for 5 minutes to form the primer layer.

[0046] S3. Apply the high thixotropic silicone sealant to the surface of the primer layer using a dispensing process. The sealant dispensing width is 2mm and the height is 1mm. Then, place it in a 120℃ oven to cure for 2 hours to obtain a sealant strip.

[0047] After the above-mentioned sealing strip was left to stand at room temperature for 24 hours, a tensile peel force test was conducted, and the tensile peel force of the above-mentioned sealing strip was found to be 0.36N.

[0048] Example 2

[0049] This embodiment provides a method for bonding a graphite bipolar plate for a fuel cell to a sealant. The graphite bipolar plate has a graphite bipolar plate sealing groove. The method for bonding the graphite bipolar plate for a fuel cell to the sealant includes the following steps:

[0050] S1. Use Deli's 502 acrylate-based super glue as the instant adhesive. This instant adhesive has a viscosity of 60 mPa·s and a surface drying time of 10-60 seconds, with a viscosity of 0.08 g / cm³. 2 The amount and brushing method are specified. Apply instant adhesive to the bottom of the graphite bipolar plate sealing groove and let it stand to cure for 5 minutes to form an instant adhesive layer.

[0051] S2. Select IMB3050 siloxane primer from Lord Company, at a concentration of 0.1 g / cm³. 2 The amount and brushing method are specified. Apply the primer to the surface of the instant adhesive layer and let it dry for 5 minutes to form the primer layer.

[0052] S3. Apply the high thixotropic silicone sealant to the surface of the primer layer using a dispensing process. The sealant dispensing width is 2mm and the height is 1mm. Then, place it in a 120℃ oven to cure for 2 hours to obtain a sealant strip.

[0053] After the above-mentioned sealing strip was left to stand at room temperature for 24 hours, a tensile peel force test was conducted, and the tensile peel force of the above-mentioned sealing strip was found to be 0.40N.

[0054] Example 3

[0055] This embodiment provides a method for bonding a graphite bipolar plate for a fuel cell to a sealant. The graphite bipolar plate has a graphite bipolar plate sealing groove. The method for bonding the graphite bipolar plate for a fuel cell to the sealant includes the following steps:

[0056] S1. Loctite 401 acrylate instant adhesive from Henkel was selected as the instant adhesive. This instant adhesive has a viscosity of 80 mPa·s and a surface drying time of 1-3 minutes. The adhesive content is 0.1 g / cm³. 2 The amount and brushing method are specified. Apply instant adhesive to the bottom of the graphite bipolar plate sealing groove and let it stand to cure for 5 minutes to form an instant adhesive layer.

[0057] S2. Select KJ-770-50X9-60C primer produced by Shenzhen Kejia Adhesive Materials Co., Ltd., at a concentration of 0.12 g / cm³. 2 The amount and brushing method are specified. Apply the primer to the surface of the instant adhesive layer and let it dry for 5 minutes to form the primer layer.

[0058] S3. Apply the high thixotropic silicone sealant to the surface of the primer layer using a dispensing process. The sealant dispensing width is 2mm and the height is 1mm. Then, place it in a 120℃ oven to cure for 2 hours to obtain a sealant strip.

[0059] After the above-mentioned sealing strip was left to stand at room temperature for 24 hours, a tensile peel force test was conducted, and the tensile peel force of the above-mentioned sealing strip was found to be 0.33N.

[0060] Comparative Example 1

[0061] This comparative example provides a method for bonding a graphite bipolar plate for a fuel cell to a sealant. The graphite bipolar plate and sealant are directly bonded together. The graphite bipolar plate has a sealing groove. The method for bonding the graphite bipolar plate to the sealant includes the following steps:

[0062] High thixotropic silicone sealant was applied to the bottom of the graphite bipolar plate sealing groove using a dispensing process. The sealant was dispensed with a width of 2 mm and a height of 1 mm. The sealant was then placed in a 120°C oven for 2 hours to cure, resulting in a sealing strip.

[0063] After the above-mentioned sealing strip was left to stand at room temperature for 24 hours, a tensile peel force test was conducted, and the tensile peel force of the above-mentioned sealing strip was found to be 0.03N.

[0064] Comparative Example 2

[0065] This comparative example provides a method for bonding a graphite bipolar plate for a fuel cell to a sealant. The method involves applying an instant adhesive and then bonding it to the sealant. The graphite bipolar plate has a graphite bipolar plate sealing groove. The bonding method for the graphite bipolar plate for a fuel cell to the sealant includes the following steps:

[0066] S1. Loctite 401 acrylate instant adhesive from Henkel is selected. This instant adhesive has a viscosity of 80 mPa·s and a surface drying time of 1-3 minutes. The adhesive is produced at a concentration of 0.1 g / cm³. 2 The amount and brushing method are specified. Apply instant adhesive to the bottom of the graphite bipolar plate sealing groove and let it stand to cure for 5 minutes to form an instant adhesive layer.

[0067] S2. Apply the high thixotropic silicone sealant to the surface of the instant adhesive layer using a dispensing process. The sealant dispensing width is 2mm and the height is 1mm. Then, place it in a 120℃ oven to cure for 2 hours to obtain a sealant strip.

[0068] After the above-mentioned sealing strip was left to stand at room temperature for 24 hours, a tensile peel force test was conducted, and the tensile peel force of the above-mentioned sealing strip was found to be 0.02N.

[0069] Comparative Example 3

[0070] This comparative example provides a method for bonding a graphite bipolar plate for a fuel cell to a sealant. The method involves applying a primer followed by sealant bonding. The graphite bipolar plate has a sealing groove. The bonding method for the graphite bipolar plate for a fuel cell to the sealant includes the following steps:

[0071] S1. Select IMB3050 siloxane primer from Lord Company, at a concentration of 0.1 g / cm³. 2 The amount and brushing method are specified. Apply the primer to the bottom of the graphite bipolar plate sealing groove and let it stand and dry for 5 minutes to form a primer layer.

[0072] S2. Apply the high thixotropic silicone sealant to the surface of the primer layer using a dispensing process. The sealant dispensing width is 2mm and the height is 1mm. Then, place it in a 120℃ oven to cure for 2 hours to obtain a sealant strip.

[0073] After the above-mentioned sealing strip was left to stand at room temperature for 24 hours, a tensile peel force test was conducted, and the tensile peel force of the above-mentioned sealing strip was found to be 0.09N.

[0074] Analysis and comparison of Examples 1-3 and Comparative Examples 1-3 show that the bonding effect of Comparative Example 1, which directly bonded the graphite bipolar plate to the sealant, Comparative Example 2, which bonded the plate to the sealant after applying an instant adhesive, and Comparative Example 3, which bonded the plate to the sealant after applying a primer, was not ideal. The tensile peel force of the sealant strips was less than 0.1N. However, Examples 1-3, which were carried out according to the method described in this technical solution, showed a significant improvement in the tensile peel force of the sealant strips compared to Comparative Examples 1-3. In particular, the tensile peel force of the sealant strips obtained in Comparative Example 1 was more than ten times higher.

[0075] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for bonding a graphite bipolar plate to a sealant for a fuel cell, wherein the graphite bipolar plate has a graphite bipolar plate sealing groove, characterized in that... The method for bonding the graphite bipolar plate for fuel cells to the sealant includes the following steps: S1. Apply instant adhesive to the bottom of the graphite bipolar plate sealing groove, and allow it to cure to form an instant adhesive layer. S2. Apply a primer to the surface of the instant adhesive layer and allow it to dry to form a primer layer. S3. After applying the sealant to the surface of the primer layer using a dispensing process, the sealant is cured and bonded to obtain a sealant strip. The graphite bipolar plate is first penetrated and mechanically reinforced by a low-viscosity instant adhesive, and then the adhesion between the graphite bipolar plate surface and the sealant is strengthened by applying a primer to the surface. The viscosity mentioned in step S1 is 1-100 mPa•s; The components of the instant adhesive include reactive resin and polymerization inhibitor; The reactive resin is mainly composed of cyanoacrylate; The components of the primer in step S2 include an active resin and a diluent; The active resin is selected from one or more of siloxane resins or epoxy resins; The diluent is selected from one or more of toluene, xylene, ethanol, acetone or isopropanol; The sealant mentioned in step S3 is a liquid or semi-solid sealant before curing and has rubber elasticity after curing.

2. The method for bonding a graphite bipolar plate to a sealant for a fuel cell according to claim 1, characterized in that, The curing time of the instant adhesive in step S1 is 0.1-60 minutes.

3. The method for bonding a graphite bipolar plate to a sealant for a fuel cell according to claim 2, characterized in that, The curing time of the instant adhesive in step S1 is 0.1-10 minutes.

4. The method for bonding a graphite bipolar plate to a sealant for a fuel cell according to claim 1, characterized in that, The method of applying instant adhesive in step S1 is selected from one of brushing, screen printing, or air spraying; The amount of instant adhesive applied in step S1 is 0.01~1 g / cm³. 2 .

5. The method for bonding a graphite bipolar plate to a sealant for a fuel cell according to claim 1, characterized in that, The method of applying the primer in step S2 includes one of brushing, screen printing, and air spraying; The amount of primer applied in step S2 is 0.01~1 g / cm³. 2 .

6. The method for bonding a graphite bipolar plate to a sealant for a fuel cell according to claim 1, characterized in that, The sealant is a highly thixotropic silicone sealant.

7. The method for bonding a graphite bipolar plate to a sealant for a fuel cell according to claim 1, characterized in that, The curing temperature for the bonding process described in step S3 is 60-150℃, and the curing time is 1-300 minutes.