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GB/T 20042.7-2024: Proton exchange membrane fuel cells - Part 7: Test method of carbon paper properties
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GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 27.070
CCS K 82
Replacing GB/T 20042.7-2014
Proton exchange membrane fuel cell - Part 7.Test method of
carbon paper properties
Issued on: DECEMBER 31, 2024
Implemented on: JULY 01, 2025
Issued by. Status Administration for Market Regulation;
National Standardization Administration.
Table of Contents
Foreword... 3
Introduction... 5
1 Scope... 6
2 Normative references... 6
3 Terms and definitions... 6
4 Symbols... 9
5 Sample and test preparation... 12
6 Test instruments and apparatus... 13
7 Thickness uniformity test... 14
8 Resistance test... 15
9 Mechanical strength test... 19
10 Gas permeability test... 21
11 Porosity test... 23
12 Bulk density test... 23
13 Surface density test... 24
14 Roughness test... 24
15 Through-plane thermal conductivity test... 26
16 Bending stiffness test... 28
17 Static contact angle test... 28
18 Durability test (acid oxidation method)... 28
19 Test Report... 28
Appendix A (Informative) Test Preparation... 30
Appendix B (Informative) Test report... 31
Appendix C (Informative) Test of the total resistance of the two copper electrodes and
the contact area specific resistance between the carbon paper and the electrodes... 33
Appendix D (Informative) Test for in-plane gas permeability... 34
Appendix E (Informative) Porosity test... 36
Appendix F (Informative) Surface roughness test method... 38
Appendix G (Informative) Bending stiffness test... 40
Appendix H (Informative) Static contact angle test... 42
Appendix I (Informative) Durability test (acid oxidation method)... 43
References... 45
Proton exchange membrane fuel cell - Part 7.Test method of
carbon paper properties
1 Scope
This document defines the terms and definitions of carbon paper for proton exchange
membrane fuel cells; describes the test methods for the properties of carbon paper for
proton exchange membrane fuel cells, including thickness uniformity test, resistance
test, mechanical strength test, air permeability test, porosity test, bulk density test,
surface density test, roughness test, vertical thermal conductivity test, bending stiffness
test, static contact angle test, durability test, as well as the test report.
This document is applicable to the detection of carbon paper for proton exchange
membrane fuel cells.
2 Normative references
The contents of the following documents constitute the essential terms of this document
through normative references in the text. Among them, for dated references, only the
version corresponding to that date applies to this document; for undated references, the
latest version (including all amendments) applies to this document.
GB/T 1040.3-2006 Plastics - Determination of tensile properties - Part 3.Test
conditions for films and sheets
GB/T 20042.1-2017 Proton exchange membrane fuel cell - Part 1.Terminology
GB/T 28816-2020 Fuel cell - Terminology
3 Terms and definitions
The terms and definitions defined in GB/T 20042.1-2017 and GB/T 28816-2020, as
well as the following terms and definitions, apply to this document.
3.1
Area specific resistance
Under specified pressure conditions, the ohmic resistance of carbon paper multiplied
by its effective area.
5.2.4 Unless otherwise specified, the temperature of the test environment is 23 °C ±
5 °C.
6 Test instruments and apparatus
The instruments and apparatus used in the test methods given in this document and their
accuracy requirements are as follows.
a) Thickness gauge. Used to measure the thickness of the sample, with an accuracy
of not less than 0.001 mm;
b) Length measuring instrument. Used to measure the length and width of the sample,
with an accuracy of ±0.02 mm;
c) Precision electronic balance. Used to measure the mass of the sample, with an
accuracy of ±0.1 mg;
d) Four-probe resistivity tester. Used to test the in-plane resistivity of the sample,
with an accuracy of ±0.1 mΩ·cm;
e) Low resistance tester. Used to test the vertical resistance of the sample, with an
accuracy of ±0.01 mΩ;
f) Mechanical properties testing machine. Used to test the tensile strength and
compressive strength of the sample, with a test accuracy of ±0.5% of its range;
g) Density meter. Used to measure the specific gravity of the sample, with an
accuracy of ±0.002 g/cm3;
h) Surface roughness profiler. With an accuracy of ±0.1 μm;
i) Micro differential pressure gauge. Used to test pressure difference, with an
accuracy of ±2 Pa;
j) Throttle valve. Used to adjust the intake flow;
k) Gas flow meter. Used to measure gas flow, with an accuracy of ±1% of its full
scale;
l) Stiffness meter. A device that can measure the bending force or torque specified
by the stiffness of the sample, with a bending angle of 15° ± 0.3°; the nominal
bending length is 50 mm; the instrument measurement range is at least 0.05
mN·m ~ 5 mN·m;
m) Thermal conductivity tester. Used to test the thermal conductivity of the sample;
the instrument measurement range required for the vertical thermal conductivity
test is at least 0.1 W/(m·K) ~ 10.0 W/(m·K), with an accuracy of ±0.1 W/(m·K);
10.1.2.3 Install the pressed sample/frame assembly between the flat clamps with air
inlet and outlet on both sides, to form an air chamber on both sides; test the air tightness.
Both flat clamps shall have sealing elements.
10.1.2.4 Install the test cell on the test device as shown in Figure 4; ensure that the test
cell has no leakage.
Note. The method for detecting external leakage is to put the sample into the test cell; block the
outlet of the differential pressure gauge and the outlet of the flow meter; open the throttle valve;
introduce a certain pressure difference of gas; close the throttle valve; observe the indication of
the differential pressure gauge. If there is no obvious change within 2 minutes, the device has
good air tightness.
10.1.2.5 Adjust the throttle valve; use the differential pressure gauge to control a certain
differential pressure. Keep it stable for at least 5 minutes at room temperature and a
certain differential pressure. Calculate the flow rate Vs and the differential pressure
indication Ps according to the flow meter reading.
Note. The differential pressure is selected to be 2 Pa ~ 300 Pa.
10.1.2.6 Press the hollow frame of the same size as in 10.1.2.3 into a test assembly. The
pressing conditions are the same as in 10.1.2.2.
10.1.2.7 Assemble and test according to the method in 10.1.2.4.At the same flow rate
Vs as in 10.1.2.5, read the indication P0 of the differential pressure gauge of the blank
sample and calibrate the test results.
Note. Indicate the gas medium used in the report. Dry air is preferred.
10.1.3 Data processing
Calculate the through-plane gas permeability of the sample according to formula (9).
Where.
Vpe - Through-plane gas permeability of the sample, in milliliters per square
centimeter per hour Pa [mL • mm/(cm2 • h • Pa)];
Vs - Volume flow rate of gas passing through the sample under pressure difference
(Ps - P0), in milliliters per minute (mL/min);
- Average thickness of the sample, in micrometers (μm);
S1 - Effective area of the sample, i.e. the size of the middle hole of the frame (cm2);
Ps - Pressure difference indication number when testing the sample, in Pascals (Pa);
P0 - Pressure difference indication number of the blank sample, in Pascals (Pa).
Take 3 valid samples as a group; calculate the average value as the test result.
10.2 In-plane gas permeability test
In-plane gas permeability test method is as shown in Appendix D.
11 Porosity test
Porosity test method is as shown in Appendix E.
12 Bulk density test
12.1 Test method
12.1.1 Use a precision electronic balance to weigh the mass m of the sample.
12.1.2 Measure the average thickness of the sample, according to the method in
Chapter 7.
12.1.3 Use a length measuring instrument, to measure the length Lcp and width Wcp of
the sample.
12.2 Data processing
Calculate the bulk density of the sample according to formula (10).
Where.
ρ0 - Bulk density of the sample, in grams per cubic centimeter (g/cm3);
m - Mass of the sample, in grams (g);
Lcp - Length of the sample, in centimeters (cm);
Wcp - Width of the sample, in centimeters (cm);
- Thickness of the sample at 25 kPa, in micrometers (μm).
Take 3 valid samples as a group; calculate the average value as the test result.
Appendix B
(Informative)
Test report
B.1 General
Based on the test conducted, the test report should provide sufficient, correct, clear,
objective data for analysis and reference. The report shall include all the data in each
chapter. There are three forms of reports. summary, detailed, complete. Each type of
report shall include a title page and a table of contents.
B.2 Report contents
B.2.1 Title page
The title page should include the following information.
- National standard number;
- Sample name, material composition, specifications;
- Sample state conditioning and test standard environment;
- Test machine model;
- Results of each test and the average value of the results;
- Test date and personnel.
The title page should include the following content.
- Report number (optional);
- Report type (summary, detailed, complete);
- Report author;
- Test location;
- Test name;
- Test applicant.
B.2.2 Table of contents
Each type of report should provide a table of contents.
B.3 Report type
B.3.1 Summary report
The summary report should include the following data.
- Purpose of the test;
- Type of test, instrument, equipment;
- All test results;
- Uncertainties and certainties of each test result;
- Summary conclusions.
B.3.2 Detailed report
In addition to the content of the summary report, the detailed report should include the
following data.
- Test operation method and test flow chart;
- Description of the arrangement, layout, operating conditions of instruments and
equipment;
- Calibration of instruments and equipment;
- Description of test results in the form of graphs or tables;
- Discussion and analysis of test results.
B.3.3 Complete report
In addition to the detailed content, the complete report should have a copy of the
original data and the following items.
- Test time;
- Accuracy of the measuring equipment used for testing.
Appendix E
(Informative)
Porosity test
E.1 Test method 1 (mercury intrusion method)
Perform porosity test according to the method specified in GB/T 21650.1-2008.
E.2 Test method 2 (solution method)
E.2.1 Prepare the sample according to 5.1.
E.2.2 Measure the average thickness of the sample according to the method in
Chapter 7; measure the length (Lcp) and width (Wcp) of the sample using a length
measuring instrument; weigh the mass m of the sample using a precision electronic
balance.
E.2.3 Prepare a mixture of n-heptane and dibromoethane in a certain volume ratio;
inject it into a stoppered measuring cylinder.
E.2.4 Cut the sample fiber into pieces; crush it with an agate mortar to a length of less
than 2 mm; put it into the mixed solution in the stoppered measuring cylinder; stir it
with a glass rod to disperse the fiber in the mixed solution; cover it with a ground
stopper; put it into a constant temperature water bath at 25 °C ± 1 °C. The stopper and
neck of the stoppered measuring cylinder shall be exposed to the water surface.
E.2.5 Observe the mixed solution. If the fiber floats or sinks in the mixed solution, n-
heptane or dibromoethane needs to be added accordingly to adjust the density of the
mixed solution, until the fiber is evenly suspended in the mixed solution.
E.2.6 After the mixed solution is left to stand for 4 hours, if the fiber is still evenly
distributed in the mixed solution, use a hydrometer to measure the density of the mixed
solution at this temperature, which is the density value of the fiber (ρCF).
E.3 Data processing
Calculate the porosity of the sample according to formula (E.1).
Where.
ε - Porosity of the sample;
m - Mass of the sample, in grams (g);
Appendix F
(Informative)
Surface roughness test method
F.1 Test instrument
A 3D surface profiler or any surface roughness tester that meets the requirements can
be used.
F.2 Test method
F.2.1 Prepare the sample according to 5.1.
F.2.2 Debug the test instrument and prepare for the test.
F.2.3 Place the sample on the test bench; select a suitable lens (magnification) until the
fiber is clearly visible; scan it. The instrument observation software samples are 2 cm
× 3 cm; the subsequent analysis software sets the reference plane. Surface roughness
tests of different areas and line roughness tests can be performed within the sampling
area.
F.2.4 Move the test bench; change the test area; repeat the operation; obtain data from
3 ~ 5 test areas.
F.3 Data processing
F.3.1 The surface average height deviation is calculated according to formula (F.1).
Where.
Sa - Surface average height deviation, in micrometers (μm);
M, N - Number of sampling points in two mutually perpendicular directions in the
evaluation area;
Z - Distance from a point on the contour of the object surface area to the reference
plane.
F.3.2 Average surface average height deviation is calculated according to formula (F.2).
Appendix I
(Informative)
Durability test (acid oxidation method)
I.1 Sample preparation
The sample is a square carbon paper of not less than 100 cm2 (10 cm × 10 cm), at least
5 sets.
Note. Use repeatable batches of samples.
I.2 Test method
I.2.1 Select 2 ~ 3 samples and test the thickness, area specific resistance, compression
characteristics, etc. of the samples according to the test method specified in this
document, as the initial value.
I.2.2 Place the remaining samples in a mixed solution of 15%H2O2 + 1 mol/L H2SO4
with a solution volume ratio of 1.1; treat it in a constant temperature water bath (80 °C).
During the process, the container containing the solution needs to be sealed with plastic
film. The amount of reagents needs to be observed in the middle. If the reagent stock is
insufficient, it needs to be adjusted and added in time.
Note. The purity level of the chemical reagents used is analytical grade.
I.2.3 After 20 days of treatment, the sample is taken out, rinsed repeatedly with
deionized water, placed in an oven at 120 °C for 2 hours.
I.2.4 Then test the thickness, area specific resistance, compression characteristics, etc.
of the sample again according to the test method specified in this document.
I.3 Data processing
Analyze the durability of carbon paper according to formula (I.1).
Record the change rate of the thickness, area specific resistance, compression
characteristics, etc. of the carbon paper sample as ηi.
Where.
ηi - The change rate of the thickness, area specific resistance, compression
characteristics, etc. of the sample;
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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