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GB/T 20042.7-2014 English PDF (GBT20042.7-2014)

GB/T 20042.7-2014 English PDF (GBT20042.7-2014)

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GB/T 20042.7-2014: Proton exchange membrane fuel cells -- Part 7: Test method of carbon paper properties

This Part of GB/T 20042 specifies terms and definitions, thickness uniformity test, electrical resistance test, mechanical strength test, air permeability test, porosity test, bulk density test, areal density test, roughness test and test report for test method of carbon paper properties of proton exchange membrane fuel cells.
GB/T 20042.7-2014
GB
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 27.070
K 82
Proton exchange membrane fuel cells ?€?
Part 7: Test method of carbon paper properties
ISSUED ON: DECEMBER 05, 2014
IMPLEMENTED ON: JULY 01, 2015
Issued by: General Administration of Quality Supervision, Inspection and Quarantine;
Standardization Administration of the People's Republic of
China.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Terms, definitions and symbols ... 4
4 Test preparations ... 8
5 Test instruments and apparatus ... 9
6 Thickness uniformity test ... 9
7 Resistance test ... 11
8 Mechanical strength tests ... 14
9 Gas permeability test ... 17
10 Porosity test ... 20
11 Bulk density test ... 21
12 Area density test ... 22
13 Roughness measurement ... 22
14 Test report ... 24
Annex A (informative) Test preparation ... 25
Annex B (informative) Test report ... 26
Annex C (informative) Thermal conductivity test ... 28
Annex D (informative) Test of sum of body resistance of two copper electrodes, contact resistance between carbon paper and electrode ... 32
Bibliography ... 33
Proton exchange membrane fuel cells ?€?
Part 7: Test method of carbon paper properties
1 Scope
This Part of GB/T 20042 specifies terms and definitions, thickness uniformity test, electrical resistance test, mechanical strength test, air permeability test, porosity test, bulk density test, areal density test, roughness test and test report for test method of carbon paper properties of proton exchange membrane fuel cells.
This Part is applicable to various carbon papers used for proton exchange membrane fuel cells.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 1040.3-2006, Plastics - Determination of Tensile Properties - Part 3: Test Conditions for Films and Sheets
GB/T 13465.2-2002, Test method for flexure strength of impermeable
graphite materials
GB/T 20042.1-2005, Proton exchange membrane fuel cell - Terminology
GB/T 28816-2012, Fuel cell - Terminology
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the terms and definitions defined in GB/T 20042.1-2005 and GB/T 28816-2012 as well as the followings apply.
3.1.1 through-plane resistivity
Resistivity of carbon paper in thickness direction, in milliohm centimeter 4.2.3 Unless otherwise specified, the test environment is: the temperature is 5??C~40??C and the relative humidity is 10%~90%.
5 Test instruments and apparatus
The instruments and apparatus used by the test method given in this Part as well as the accuracy requirements are as follows:
- Thickness gauge: used to measure sample thickness; accuracy is ??2??m;
- Length measuring instrument: used to test sample?€?s length and width; the accuracy is ??0.02mm;
- Precision electronic balance: used to test sample mass; the accuracy is ??0.1mg;
- Four-probe resistivity tester: used to test the in-plane resistivity of sample; the accuracy is ??0.1m?? ?? cm;
- Low resistance tester: used to test the through-plane resistivity of sample; the accuracy is ??0.01m??;
- Mechanical performance testing machine: used to test sample?€?s tensile strength and flexural strength; the force accuracy is ??0.5% of its
measuring range;
- Mechanical performance testing machine: used to test sample?€?s
compressive strength; the force accuracy is ??0.5% of its measuring range; - Density meter: used to test sample?€?s density; the accuracy is ??0.002g/cm3; - Surface roughness profiler: the accuracy is ??0.1??m;
- Micro differential pressure gauge: used to test differential pressure; the accuracy is ??2Pa;
- Micro regulating valve: used to adjust the intake air flow; the accuracy is ??1% of its full measuring range;
- Gas flow meter: used to measure gas flow; the accuracy is ??1% of its full measuring range.
6 Thickness uniformity test
6.1 Test method
(mm);
- Average sample thickness at a certain pressure, in millimeters (mm);
di - Measured thickness value of sample at a certain point and at a certain pressure, in millimeters (mm);
n - Number of measurement data points.
6.2.4 The thickness dispersion coefficient is expressed by formula (3): Where,
- Dispersion coefficient, reflecting the degree of dispersion on unit mean; ?? - Standard thickness deviation of sample at a certain pressure, in millimeters (mm);
- Average sample thickness at a certain pressure, in millimeters (mm).
Take 3 valid samples as a group. Calculate the average value as test result. 7 Resistance test
7.1 Test of in-plane resistivity
7.1.1 Test method
7.1.1.1 Use the length measuring instrument to measure sample?€?s length and width.
7.1.1.2 According to the method in Clause 6, measure the average sample thickness .
7.1.1.3 Before measurement, first calibrate the zero point of the four-probe resistivity tester.
7.1.1.4 Place the sample on the measuring table of the instrument. Gently lower the measuring head of the tester to make the probe touch the sample surface. NOTE: Rc can be calculated by using carbon paper of different material, different thickness, through formula (D.1), as shown in Annex D. This experiment uses gold electrode or gold- plated copper block. The value of Rc is small and can be neglected.
- Average sample thickness at a certain pressure, in centimeters (mm).
Take 3 samples as a group. Calculate the average value as test result.
8 Mechanical strength tests
8.1 Tensile strength test
8.1.1 Sample test
8.1.1.1 According to the provisions of GB/T 1040.3-2006, divide the sample into vertical and horizontal directions (samples with no orientation can be taken in any direction) and cut out a long sample of a certain size (70mm??10mm) at equal intervals.
8.1.1.2 Use length measuring instrument to measure the width W of each
sample.
8.1.1.3 According to the method in Clause 6, measure the average sample thickness .
8.1.1.4 Place the sample in two fixtures of the testing machine (as shown in Figure 3). The centerline of the upper and lower fixtures of the testing machine shall be parallel to the direction of the sample. And during the process of the stress, keep the sample on the same plane. During the test, the sample must not slide in the fixture and the test fixture shall not cause the sample to break at the fixture. The fixture shall be lined with an elastic material such as rubber. Take 5 samples from each batch as a group. Calculate the average value as test result.
8.2 Flexural strength test
8.2.1 Sample test
8.2.1.1 According to the test requirements, take a certain size of test material as sample.
NOTE: The sample length shall not be less than the span of the support. 8.2.1.2 According to the method in Clause 6, measure the average sample thickness.
8.2.1.3 Use length measuring instrument to measure sample?€?s width and length. 8.2.1.4 Adjust the span of the support. Put the well-prepared sample on the support and make the tester indenter and support axis perpendicular to the sample. By referring to GB/T 13465.2-2002, it shall use the three-point bending method to test the sample?€?s flexural strength.
8.2.1.5 The tester indenter applies the load at a loading speed of
0.01mm/min~10mm/min, evenly and without impact, until the sample is
fractured. Read the breaking load value.
8.2.2 Data processing
Calculate the flexural strength according to formula (7):
Where,
Tb - Flexural strength, in megapascals (MPa);
F - Bending fracture load value, in Newtons (N);
L - Span of the support, in millimeters (mm);
Wcp - Sample width, in millimeters (mm);
- Average sample thickness at a certain pressure, in millimeters (mm).
Take 3 valid samples as a group. Calculate the average value as test result. 9.2.1 According to the method in Clause 6, measure the average sample
thickness .
9.2.2 Place the sample between two hollow frames of the same size. The
middle hole size of the frame is 4cm??4cm. At a certain temperature and
pressure, it is pressed into a sample / frame assembly that is airtight at the edges. The component pressing process shall ensure that the effective part of the sample is not deformed or damaged.
9.2.3 Place the pressed sample / frame assembly between the plate fixtures with air inlet and air outlet on both sides, to make air chambers formed on both sides. Test the airtightness. Both plate fixtures shall have sealing elements. 9.2.4 Install the test cell without external leakage on the test equipment according to the schematic diagram of test equipment shown in Figure 4. NOTE: Conduct the external leakage testing by referring to GB/T 20042.5-2009. 9.2.5 Adjust micro regulating valve. Use micro differential pressure meter to control a certain pressure difference stable for at least 5min at room
temperature and a certain pressure difference. Based on the displayed value of the flow meter, calculate the velocity Vs and the displayed value of micro differential pressure meter ps.
NOTE: The recommended pressure difference is 5Pa~50Pa.
9.2.6 Press hollow frame of the same size as in 9.2.3 into a test component. Pressing conditions are the same as 9.2.3.
9.2.7 After assembling according to the method in 9.2.4, conduct the test. At the velocity Vs same with 9.2.5, read the displayed number of micro differential pressure meter of blank sample p0. Correct the test result.
9.3 Data processing
Use formula (9) to calculate the sample?€?s gas permeability.
Where,
Vpe - Sample?€?s gas permeability, in millimeters of mercury per square centimeter of hour [mL ?? mm / (cm2 ?? h ?? mmHg)];
Vs - Volume flow rate of gas through sample at differential pressure (ps-p0), in Where,
?? - Sample porosity, %;
M -Sample mass, in grams (g);
??CF - Carbon fiber density, in grams per cubic centimeter (g/cm3);
Lcp - Sample length, in centimeters (cm);
Wcp - Sample width, in centimeters (cm);
- Average sample thickness, in centimeters (cm).
Take 3 valid samples as a group. Calculate the average value as test result. 11 Bulk density test
11.1 Test method
11.1.1 Use precision electronic balance to weigh sample mass M.
11.1.2 According to the method in Clause 6, measure the average sample
thickness .
11.1.3 Use length measuring instrument to measure sample length (Lcp) and width (Wcp).
11.2 Data processing
Calculate the sample density according to formula (11):
Where,
??0 - Sample density, in grams per cubic centimeter (g/cm3);
M - Sample mass, in grams (g);
Lcp - Apparent length of sample, in centimeters (cm);
Wcp - Apparent width of sample, in centimeters (cm);
Annex A
(informative)
Test preparation
A.1 Overview
This Annex describes typical items that shall be considered before testing. For each test, it shall select high-precision testing instruments and equipment, so as to minimize the equipment error. It shall prepare a written test plan. The following information shall be listed in the test plan:
a) Purpose;
b) Test specification;
c) Test personnel qualification. The test personnel shall be trained in operation, have experience in operating instruments, and be familiar with safe operating procedures;
d) Quality assurance standards (in accordance with ISO 9000 and related standards);
e) Uncertainty of results (guidelines for expressing uncertainty of test values in accordance with IEC/ISO);
f) Requirements for measuring instruments and equipment;
g) Estimation of test parameter range;
h) Data acquisition plan.
A.2 Data acquisition and recording
In order to meet the target error requirements, the data acquisition system and data recording equipment shall meet the requirements of acquisition frequency and acquisition speed. Its performance shall be better than performance test equipment.
- Date and time of test;
- Test application organization.
B.2.2 Content directory
Each type of report shall provide a directory.
B.3 Report type
B.3.1 Summary type report
The summary type report shall contain the following data:
- Test purpose;
- Test type, instrument and equipment;
- Results of all tests;
- Uncertainty and certainty factors of each test result;
- Summary conclusion.
B.3.2 Detailed type report
In addition to the contents of summary type report, the detailed type report shall also contain the following data:
- Test operation mode and test flow chart;
- Description of arrangement, layout and operation conditions of instrument and equipment;
- Calibration of instrument and equipment;
- Test result explained in diagrams or tables;
- Discussion and analysis of test result.
B.3.3 Complete type report
In addition to the detailed contents, the complete type report shall also include the copy of original data as well as the following information:
- Test time;
- Accuracy of testing equipment for test.
C.3.2 Cut a certain size of carbon paper as sample. Sample shape and size shall be the same as those of the heating and cooling plates.
C.3.3 The number of samples is 5 (3 valid values are guaranteed). There shall be no wrinkles, scratches and breaks.
C.3.4 Sample shall be taken from reproducible uniform batches or from different batches.
C.3.5 Use thermal insulation material to seal the sample edges, so that reduce the edge heat loss to an acceptable level.
C.4 Test method
C.4.1 Through-plane thermal conductivity
C.4.1.1 Use length measuring instrument to test the size of sample to be tested. Calculate the area A of sample.
C.4.1.2 Use thickness gauge to measure sample thickness d.
C.4.1.3 Use length measuring instrument and thickness gauge to measure
diameter and thickness of instrument heat sink.
C.4.1.4 After n samples are overlapped, place them in the thermal conductivity tester. The surface of the sample shall be in close contact with the heat sink of the instrument.
NOTE: The number of samples n shall be determined by the requirements of the instrument.
C.4.1.5 Operate the instrument to form a temperature gradient in the sample thickness direction.
C.4.1.6 Measure the temperature T2, T1, heat and time of heating and cooling plates.
C.4.1.7 Data processing
Calculate thermal conductivity according to formula (C.1):
Where,
- Thermal conductivity, in Watts per metre Kelvin [W/(m ?? K)];
Annex D
(informative)
Test of sum of body resistance of two copper electrodes, contact
resistance between carbon paper and electrode
The sum of body resistance of two copper electrodes, contact resistance between sample and two electrodes can be calculated according to formula (D.1):
Where,
Rc - Sum of body resistance of two copper electrodes, contact resistance between sample and two electrodes, in milliohm square centimeter (m?? ?? cm2); Rm1 - Measured resistance value of instrument when thickness is , that is, sum of the vertical resistance of sample, the contact resistance between two samples and electrode, and the resistance of two gold-plated electrodes, in milliohms (m??);
- Average thickness of sample 1, in centimeters (cm);
Rm2 - Measured resistance value of instrument when thickness is , that is, sum of the vertical resistance of sample, the contact resistance between two samples and electrode, and the resistance of two gold-plated electrodes, in milliohms (m??);
- Average thickness of sample 2, in centimeters (cm);
S - Contact area between sample and two electrodes, in square centimeters (cm2).
NOTE: Take at least 4 samples of different thicknesses for testing.

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