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
GB/T 20042.7-2014
GB
NATIONAL STANDARD OF THE
PEOPLE’S 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 ±2µm;
- 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 ±0.1mΩ · cm;
- Low resistance tester: used to test the through-plane resistivity of sample;
the accuracy is ±0.01mΩ;
- 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 ±0.1µm;
- 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;
σ - 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 flexur...