A fuel cell seal material life testing device and evaluation method

Abstract

The application provides a fuel cell sealing material life test device and an evaluation method, the test device comprises an upper end cover, an upper sealing cover, a lower sealing cover and a lower end cover; the lower sealing cover is provided with a groove for placing a rubber sample block, and the upper sealing cover is provided with a protrusion corresponding to the groove for compressing the rubber sample block; the evaluation method comprises the following steps: placing the test device into a relaxation tester, compressing the rubber sample block by 25%, obtaining stress relaxation rate curves of the rubber sample block under conditions of 120 DEG C, 135 DEG C and 150 DEG C respectively, then obtaining a stress relaxation rate curve of the rubber sample block under a condition of 80 DEG C, taking 50% stress relaxation rate attenuation as a critical value, and obtaining a corresponding life of the rubber sample block under the condition of 80 DEG C. The technical scheme of the application can utilize a stress relaxation device and a kinetic curve method to calculate the life of the sealing material, and complete durability evaluation of the fuel cell sealing material with stress relaxation performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fuel cell manufacturing, in particular, especially relates to a fuel cell sealing material life test device and evaluation method. BACKGROUND

[0002] The life evaluation of fuel cell sealing material is the prerequisite for material selection, which can reduce the cost of sealing structure material selection and guarantee the service life of sealing structure. The stress relaxation phenomenon occurs in the actual working environment of fuel cell sealing material, which leads to sealing failure. The stress relaxation performance of fuel cell sealing material can determine the service life of fuel cell. It is a difficult problem to construct the working environment of fuel cell, design the experimental device conforming to the working environment of fuel cell, and complete the performance test by using stress relaxation test equipment. The service life of sealing material in fuel cell is calculated by using dynamic formula, and the evaluation method of fuel cell sealing material life with stress relaxation as performance index has important significance for the design of sealing structure. SUMMARY

[0003] In order to achieve the above target demand, the present application provides a fuel cell sealing material life evaluation method with stress relaxation as performance index, and a test device, which can predict the service life of fuel cell sealing material. The fuel cell sealing material works in a certain temperature, high humidity and weak acid environment, so the sealing material must have heat resistance, humidity resistance and acid resistance. In order to simulate these three performances, an experimental device suitable for use in stress relaxation equipment is proposed, which can realize the simulation of fuel cell environment; the life curve under each high temperature condition is fitted by using dynamic formula, the life curve of sealing material under working temperature is obtained by using the life curve under each high temperature condition, the critical value of performance is determined, and the time when the performance reaches the critical value is determined by using the life curve under working temperature.

[0004] The technical means adopted by the present application is as follows:

[0005] A fuel cell sealing material life test device, comprising upper end cover, upper sealing cover, lower sealing cover and lower end cover arranged in sequence;

[0006] The upper end cover and the lower end cover are connected through a guide column, and a step structure is arranged in the middle of the guide column, which is used to limit the continuous pressing of the upper end cover;

[0007] A fluororubber ring capable of sealing is installed between the upper sealing cover and the lower sealing cover;

[0008] The lower sealing cap is provided with a groove for placing a rubber sample block, and the upper sealing cap is provided with a protrusion for pressing the rubber sample 7 at a position corresponding to the groove; the upper sealing cap and the fluororubber ring can achieve the sealing of the groove.

[0009] Furthermore, the rubber sample is a cylindrical standard sample block with dimensions of [missing information]. Thickness tolerance ±0.1mm.

[0010] Furthermore, the surface of the lower sealing cover is provided with a sealing groove for installing the fluororubber ring.

[0011] Furthermore, a plurality of guide posts are provided between the upper end cover and the lower end cover; mounting holes are provided on the edges of the upper end cover and the lower end cover respectively, and the two ends of the guide posts are fixedly installed in the mounting holes on the upper end cover and the lower end cover respectively by nuts.

[0012] Furthermore, both the upper sealing cap and the lower sealing cap are made of polytetrafluoroethylene, and both the upper end cap and the lower end cap are made of stainless steel.

[0013] Furthermore, the rubber sample is pressed between the upper and lower sealing caps by the protrusion on the upper sealing cap. When the upper cap is pressed down to the stepped structure, the rubber sample can achieve 25% compression deformation.

[0014] This invention also provides a method for evaluating the lifespan of fuel cell sealing materials, using the aforementioned testing apparatus, specifically including the following steps:

[0015] S1. Prepare an acidic mixed solution using sulfuric acid with a pH of 2 and hydrofluoric acid at 5 ppm.

[0016] S2. Assemble the testing device, place the rubber sample block into the groove, and use a dropper to drip the prepared acidic mixed solution into the groove;

[0017] S3. Place the testing device into the relaxation testing machine, adjust the rotating handle of the relaxation testing machine to control the downward pressing distance of the pressure head of the relaxation testing machine, so that the upper end cover is pressed down to the stepped structure, thereby achieving a 25% compression deformation of the rubber sample block:

[0018] S4. Set the test temperature of the relaxation tester to 120℃ and observe the force F exerted by the indenter of the relaxation tester on the rubber sample under 25% compression deformation. n With time t n The changes are recorded as F. n (t n A sequence of records, where n represents the column number of the sequence;

[0019] The force F exerted by the upper sealing cover on the rubber sample block is calculated according to the following formula. s (t n ):

[0020] F s (t n ) = F n (t n )-F p -F c

[0021] Among them, F p F represents the saturated vapor pressure exerted on the upper sealing cover at 120°C. c This indicates the support reaction force generated when the fluororubber ring is compressed at 120°C.

[0022] The rubber sample block is subjected to a force F. s (t n The stress σ generated n (t n The following formula is used to obtain:

[0023] σ n (t n ) = F s (t n ) / 660.185

[0024] The stress relaxation rate of the rubber sample is calculated using the following formula:

[0025] P = σ n (t n ) / σ max

[0026] Where, σ max The maximum stress before aging, i.e., σ n (t n The maximum stress in the sequence;

[0027] Fitting stress relaxation rates P and σ n (t n The stress relaxation rate curve of the rubber sample at 120℃ was obtained by analyzing the series of data.

[0028] P = Aexp(-kt) a )

[0029] Where P is the stress relaxation rate of the rubber sample, and A and a are constants;

[0030] S5. Set the test temperature of the relaxation tester to 135℃ and 150℃ respectively, and repeat step S4 to obtain the stress relaxation rate curves of the rubber sample under the conditions of 135℃ and 150℃ respectively.

[0031] S6, the working temperature of the fuel cell is 80 DEG C, the stress relaxation rate curves under the conditions of 120 DEG C, 135 DEG C and 150 DEG C are fitted by using the following formula, and the k value of the stress relaxation rate curve of the rubber sample under the condition of 80 DEG C is obtained by combining the stress relaxation rates of the rubber sample under the compression deformation of 25% after 1h, 72h and 168h under the condition of 80 DEG C, and then the stress relaxation rate curve of the rubber sample under the condition of 80 DEG C is obtained:

[0032]

[0033] Wherein, a120, a135, a150 respectively represent the a value obtained by using the kinetic curve fitting under the conditions of 120 DEG C, 135 DEG C and 150 DEG C; A120, A135, A150 respectively represent the A value obtained by using the kinetic curve fitting under the conditions of 120 DEG C, 135 DEG C and 150 DEG C;

[0034] S7, taking the stress relaxation rate attenuation of 50% as a critical value, the corresponding life of the rubber sample under 80 DEG C is obtained by using the stress relaxation rate curve of the rubber sample under 80 DEG C obtained in step S6.

[0035] Further, in step S3, the down pressure distance of the relaxation testing machine pressure head is h0=h2-(h1-12.5)-3.125, wherein h0 is the height difference between the upper end cover 1 and the step structure when no pressure is applied, h1 is the height difference between the groove and the step structure, and h2 is the thickness of the position of the convex on the upper sealing cover.

[0036] Compared with the prior art, the present application has the following advantages:

[0037] The fuel cell sealing material life test device and evaluation method provided by the present application can use a stress relaxation device and a kinetic curve method to calculate the life of the sealing material, and complete the durability evaluation of the fuel cell sealing material with stress relaxation performance.

[0038] Based on the above reasons, the present application can be widely popularized in the field of fuel cells. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0040] Figure 1The schematic diagram of the test device structure according to the present application.

[0041] Figure 2 The Figure 1 The enlarged view of A part in the middle.

[0042] Figure 3 The schematic diagram of the test device according to the present application in the installation state on the relaxation testing machine.

[0043] Figure 4 The schematic diagram of the gas acting area of the upper sealing end cover.

[0044] In the figure: 1, upper end cover; 2, lower end cover; 3, upper sealing cover; 4, lower sealing cover; 5, guide column; 6, fluororubber ring; 7, rubber sample block; 100, relaxation testing machine. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. The description of the at least one exemplary embodiment is actually only illustrative, but not as any limitation to the present application and its application or use. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0046] It should be noted that the terms used herein are only for describing the specific embodiments, but not intended to limit the exemplary embodiments according to the present application. As used herein, the singular form is intended to include the plural form, unless the context clearly indicates otherwise, and it should also be understood that, when the terms "comprise" and / or "include" are used in the specification, there is a feature, step, operation, device, component and / or combination thereof.

[0047] The foregoing description, for purposes of clarity, describes the present application in terms of its components, processes and operations. Such descriptions and related comments are not intended to be limiting. Although the present application has been described in detail with reference to certain illustrative embodiments, variations and modifications exist within the scope and spirit of the application as described and defined in the following claims. The foregoing description discloses preferred embodiments only and does not limit the scope of the application. The scope of the present application is limited only by the claims.

[0048] In the description of the present application, it is to be understood that the orientation terms such as "front", "back", "up", "down", "left", "right", "transverse", "vertical", "horizontal", "top", "bottom", and the like are generally made with reference to the orientation of the device or element as shown in the drawings and are merely used for convenience in describing the present application and simplifying the description, and do not indicate or imply that the device or element must have a particular orientation or be constructed and operated in a particular orientation, and therefore should not be construed as limiting the scope of the present application. The orientation terms "inner", "outer" refer to the inner and outer relative to the outline of the component itself.

[0049] For the convenience of description, spatial relative terms such as "over", "above", "upper surface", "upper", and the like can be used herein to describe the spatial positional relationship of one device or feature with respect to other devices or features as shown in the drawings. It should be understood that the spatial relative terms are intended to include different orientations in use or operation in addition to the orientation of the device as described in the drawings. For example, if the device in the drawings is inverted, the device described as "above" or "over" other devices or structures will be positioned "below" or "under" the other devices or structures. Thus, the exemplary term "above" can include both "above" and "below" orientations. The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein are interpreted accordingly.

[0050] In addition, it should be noted that the use of "first", "second", and the like words to qualify parts of components is merely for the convenience of distinguishing the corresponding parts of components, and the above words have no special meaning unless otherwise stated, and therefore should not be construed as limiting the scope of the present application.

[0051] Example 1

[0052] As Figure 1 shown, the application provides a kind of fuel cell sealing material life test device, suitable for use in stress relaxation equipment and can realize the simulation of fuel cell working environment, such as heat aging resistance, acid resistance, water vapor resistance of fuel cell sealing material environment simulation;

[0053] The test device includes upper end cover 1, upper sealing cover 3, lower sealing cover 4 and lower end cover 2 arranged in sequence;

[0054] The upper end cover 1 and the lower end cover 2 are connected by guide column 5, and the middle part of the guide column 5 is provided with a step structure for limiting the upper end cover 1 to continue to press down;

[0055] The upper sealing cover 3 and the lower sealing cover 4 are provided with fluororubber ring 6 which can play a sealing role;

[0056] The lower sealing cover 4 is provided with a groove for placing rubber sample block 7, and the upper sealing cover 3 is provided with a protrusion corresponding to the groove for pressing the rubber sample block 7;The upper sealing cover 3 and the fluororubber ring 6 can realize the sealing of the groove.

[0057] Further, the rubber sample 7 adopts cylindrical standard sample block, and the size is The thickness tolerance is ±0.1mm.

[0058] Further, the surface of the lower sealing cover 4 is provided with a sealing groove for mounting the fluororubber ring 6.

[0059] Further, a plurality of guide columns are arranged between the upper end cover 1 and the lower end cover 2, the more guide columns 5, the more accurate positioning;The edge of the upper end cover 1 and the lower end cover 2 is respectively provided with mounting hole, and the both ends of the guide column 5 are respectively fixedly installed in the mounting hole on the upper end cover 1 and the lower end cover 2 through nut;When the upper end cover 1 is pressed down by a specified distance as required, the position of the upper end cover 1 on the guide column 5 can be fixed by nut, so that the rubber sample block 7 in the test device keeps the current compression deformation state.

[0060] Further, 3-5 guide columns 5 are arranged between the upper end cover 1 and the lower end cover 2.

[0061] Further, the upper sealing cover 3 and the lower sealing cover 4 are made of polytetrafluoroethylene material, so that the whole test device has the characteristics of acid corrosion resistance, and the test device can be repeatedly used.

[0062] Further, the upper end cover 1 and the lower end cover 2 are made of stainless steel material, which can increase the rigidity of the test device.

[0063] Furthermore, the rubber sample 7 is pressed between the upper sealing cover 3 and the lower sealing cover 4 by the protrusion on the upper sealing cover 3. When the upper end cover 1 is pressed down to the stepped structure, the rubber sample 7 can achieve 25% compression deformation.

[0064] This invention also provides a method for evaluating the lifespan of fuel cell sealing materials. Using the aforementioned testing apparatus and a kinetic curve experiment, the lifespan of the sealing material under fuel cell operating conditions can be evaluated. Specifically, the method includes the following steps:

[0065] S1. Prepare an acidic mixed solution using sulfuric acid with a pH of 2 and hydrofluoric acid at 5 ppm.

[0066] S2. Assemble the testing device, place the rubber sample 7 into the groove, and use a dropper to drip the prepared acidic mixed solution into the groove for about 2 to 3 millimeters;

[0067] S3, such as Figure 3 As shown, the testing device is placed in the relaxation testing machine, and the rotating handle of the relaxation testing machine is adjusted to control the downward pressing distance of the pressure head of the relaxation testing machine, so that the upper end cover 1 is pressed down to the stepped structure, thereby achieving a 25% compression deformation of the rubber sample block 7.

[0068] S4. Set the test temperature of the relaxation tester to 120℃ and observe the force F exerted by the indenter of the relaxation tester on the rubber sample 7 under 25% compression deformation. n With time t n The changes are recorded as F. n (t n The following table shows a sequence of numbers, where n represents the column number of the sequence.

[0069] n 1 2 3 … n t n ]]> [t1] [t2] [ t3 ] … <![CDATA[t n ]]> F n ]]> [F1] F2 F3 … F n ]]>

[0070] The force F exerted by the upper sealing cap 3 on the rubber sample 7 is calculated according to the following formula. s (t n ):

[0071] F s (t n ) = F n (t n )-F p -F c

[0072] Among them, F p F represents the saturated vapor pressure experienced by the upper sealing cover 3 at 120°C. crepresents the reaction force of the fluororubber ring 6 after compression at 120℃; F p and F c can be calculated according to an empirical formula;

[0073] The stress σ s (t n ) of the rubber sample 7 under the action of the force F n (t n ) is obtained by the following formula:

[0074] σ n (t n ) = F s (t n ) / 660.185

[0075] The stress relaxation rate of the rubber sample 7 is calculated by the following formula:

[0076] P = σ n (t n ) / σ max

[0077] wherein σ max is the maximum stress before aging, i.e. the maximum stress in the σ n (t n ) sequence;

[0078] The stress relaxation rate P and the σ n (t n ) sequence are fitted to obtain the stress relaxation rate curve of the rubber sample 7 at 120℃:

[0079] P = Aexp(-kt a )

[0080] wherein P is the stress relaxation rate of the rubber sample 7, and A and a are constants;

[0081] S5, the test temperature of the relaxation tester is set to 135℃ and 150℃ respectively, and step S4 is repeated to obtain the stress relaxation rate curves of the rubber sample 7 at 135℃ and 150℃ respectively;

[0082] S6, the working temperature of the fuel cell is 80℃, the stress relaxation rate curves at 120℃, 135℃ and 150℃ are fitted by the following formula, and the k value of the stress relaxation rate curve of the rubber sample 7 at 80℃ is obtained by combining the stress relaxation rates of the rubber sample 7 at 25% compression deformation for 1h, 72h and 168h at 80℃, and then the stress relaxation rate curve of the rubber sample 7 at 80℃ is obtained:

[0083]

[0084] wherein a120, a135, a150 represent the a values obtained by fitting the kinetic curves at 120℃, 135℃, 150℃, respectively; A120, A135, A150 represent the A values obtained by fitting the kinetic curves at 120℃, 135℃, 150℃, respectively;

[0085] S7, taking the stress relaxation rate attenuation of 50% as the critical value, using the stress relaxation rate curve of the rubber sample 7 at 80℃ obtained in step S6, the corresponding life of the rubber sample 7 at 80℃ is obtained, that is, the time corresponding to the stress relaxation rate of 50%.

[0086] Further, in step S3, the pressing distance of the relaxation tester head is controlled to be h0 = h2-(h1-12.5)-3.125, wherein, as shown in Figure 2 , h0 is the height difference between the upper end cover 1 and the step structure when no pressure is applied, h1 is the height difference between the groove and the step structure, and h2 is the thickness of the position where the protrusion on the upper sealing cover 3 is located.

[0087] Further, according to the empirical formula, the saturated vapor gas pressure F p experienced by the upper sealing cover 3 at 120℃ can be calculated according to the corresponding relationship between temperature and saturated vapor pressure P in the following table p , F Figure 4 = P*A, wherein P is the saturated vapor pressure and A is the gas acting area of the upper sealing cover 3, as shown in , the gas acting area of the upper sealing cover 3 is the area of the projection of the upper sealing cover 3 surface on the horizontal plane between the outer edge of the rubber sample 7 and the position corresponding to the center line of the fluororubber ring 6 to the surface of the upper sealing cover 3;

[0088] Temperature 120℃ 135℃ 150 degrees Celsius Saturation vapor pressure P 198 kPa 313 kPa 476 kPa

[0089] According to the following empirical formula, the reaction force F c generated by the fluororubber ring 6 after being compressed at 120℃ can be calculated

[0090]

[0091] wherein Δ represents the deformation amount of the fluororubber ring 6; E represents the apparent elastic modulus; a represents the circumference of the center line of the fluororubber ring 6; b represents the width of the rectangular compression surface after the fluororubber ring 6 is compressed; h represents the outer diameter of the fluororubber ring 6; the deformation amount of the fluororubber ring 6 is usually 15% to 25%, and assuming that the outer diameter of the fluororubber ring 6 is 2mm, the deformation amount of the fluororubber ring 6 is about 0.4mm.

[0092] Further, in step S6, the stress relaxation rate of the rubber sample 7 at 80°C after 1 h, 72 h, 168 h of 25% compression deformation is calculated by the method in step S4, and any one of the time-stress relaxation rate data is substituted into the formula in step S6, so as to obtain the k value of the stress relaxation rate curve of the rubber sample 7 at 80°C, and further obtain the stress relaxation rate curve of the rubber sample 7 at 80°C.

[0093] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not limited thereto; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions described in the foregoing examples can still be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for evaluating the lifespan of fuel cell sealing materials, characterized in that, The device used includes an upper end cover, an upper sealing cover, a lower sealing cover, and a lower end cover arranged in sequence; The upper and lower end caps are connected by a guide post, and the guide post has a stepped structure in the middle, which restricts the upper end cap from being pressed down further. A fluororubber ring for sealing is installed between the upper and lower sealing covers; The lower sealing cover has a groove for placing a rubber sample block, and the upper sealing cover has a protrusion for pressing the rubber sample at a position corresponding to the groove; the upper sealing cover and the fluororubber ring achieve groove sealing; The methods include: S1. Prepare a mixed solution using sulfuric acid with a pH of 2 and hydrofluoric acid at 5 ppm; S2. Assemble the device by placing the rubber sample block into the groove and using a dropper to drip the mixed solution into the groove. S3. Place the device into the relaxation testing machine, adjust the rotating handle to control the downward pressing distance of the indenter, and press the upper end cap down to the stepped structure to achieve 25% compression deformation of the rubber sample: S4. Set the temperature to 120℃ and observe the force exerted by the indenter on the rubber sample under 25% compression deformation. Over time The changes are recorded as A sequence, where n is the sequence number; Calculate the force exerted on the sample block by the upper sealing cap. : , The saturated vapor pressure experienced by the sealing cap at 120℃; The support reaction force generated when the fluororubber ring is compressed at 120℃; The sample block is subjected to force Stress generated for: ； Stress relaxation rate of the sample: , This represents the maximum stress before aging. Fitting P and The stress relaxation rate curve at 120℃ was obtained: P is the stress relaxation rate, and A and a are constants; S5. Set the test temperatures to 135℃ and 150℃ respectively, and repeat S4 to obtain the stress relaxation rate curves of the rubber sample at 135℃ and 150℃. S6. The battery operating temperature is 80℃. The stress relaxation rate curves at 120℃, 135℃, and 150℃ are fitted using the following formula. Combined with the stress relaxation rate of the rubber sample at 80℃ after 1h, 72h, and 168h under 25% compression deformation, the k value of the stress relaxation rate curve at 80℃ is obtained, and thus the stress relaxation rate curve at 80℃ is obtained: a120, a135, and a150 are the a values ​​obtained by fitting the kinetic curve at 120℃, 135℃, and 150℃, respectively; A120, A135, and A150 are the A values ​​obtained by fitting the kinetic curve at 120℃, 135℃, and 150℃, respectively. S7. Using 50% stress relaxation rate reduction as the critical value, the life of the rubber sample at 80℃ is obtained using the stress relaxation rate curve at 80℃ obtained in S6.

2. The fuel cell sealing material life assessment method according to claim 1, characterized in that, The rubber sample is a cylindrical standard sample block with dimensions of φ29mm x12.5mm and a thickness tolerance of ±0.1mm.

3. The method for evaluating the lifespan of fuel cell sealing materials according to claim 1, characterized in that, A plurality of guide posts are provided between the upper end cover and the lower end cover; mounting holes are provided on the edges of the upper end cover and the lower end cover respectively, and the two ends of the guide posts are fixedly installed in the mounting holes on the upper end cover and the lower end cover respectively by nuts.

4. The method for evaluating the lifespan of fuel cell sealing materials according to claim 1, characterized in that, Both the upper and lower sealing caps are made of polytetrafluoroethylene, while both the upper and lower end caps are made of stainless steel.

5. The method for evaluating the lifespan of fuel cell sealing materials according to claim 1, characterized in that, The rubber sample is pressed between the upper and lower sealing caps by the protrusion on the upper sealing cap. When the upper cap is pressed down to the stepped structure, the rubber sample can achieve 25% compression deformation.

6. The method for evaluating the lifespan of fuel cell sealing materials according to claim 1, characterized in that, In step S3, the downward pressure distance of the relaxation test machine head is controlled as h0=h2-(h1-12.5)-3.125, where h0 is the height difference between the upper cover and the step structure when no pressure is applied, h1 is the height difference between the groove and the step structure, and h2 is the thickness of the protrusion on the upper sealing cover.

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