GB/T 20042.7-2024 Proton exchange membrane fuel cells - Part 7: Test method of carbon paper properties
1 Scope
This document defines the terms and definitions related to carbon papers for proton exchange membrane fuel cells (PEMFCs), and describes the test methods for the properties of carbon papers used in PEMFCs, specifically including thickness uniformity test, resistance test, mechanical strength test, gas permeability test, porosity test, bulk density test, area density test, roughness test, through-plane thermal conductivity test, bending stiffness test, static contact angle test and durability test, together with the test report.
This document is applicable to the testing of carbon papers for PEMFCs.
2 Normative references
The following documents contain provisions which, through reference in this text, constitute provisions 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
For the purposes of this document, the terms and definitions given in GB/T 20042.1-2017 and GB/T 28816-2020 as well as the following apply.
3.1
area specific resistance
product of the ohmic resistance of a carbon paper and its effective area under specified pressure conditions
Note: The unit of area specific resistance is milliohm square centimeter (mΩ·cm2).
3.2
through-plane resistivity
resistivity in the direction perpendicular to the surface of a carbon paper
Note: The unit of through-plane resistivity is milliohm centimeter (mΩ·cm).
3.3
in-plane resistivity
resistivity in the direction parallel to the surface of a carbon paper
Note: The unit of in-plane resistivity is milliohm centimeter (mΩ·cm).
3.4
through-plane gas permeability
gas permeability in the direction perpendicular to the surface of a carbon paper
Note: The unit of through-plane gas permeability is milliliter millimeter per square centimeter hour pascal [mL·mm/(cm2·h·Pa)].
3.5
in-plane gas permeability
gas permeability in the direction parallel to the surface of a carbon paper
Note: The unit of in-plane gas permeability is milliliter millimeter per square centimeter hour pascal [mL·mm/(cm2·h·Pa)].
3.6
porosity
percentage of the pore volume to the total volume of a carbon paper
3.7
bulk density
ratio of the mass of a carbon paper to its apparent volume
Note 1: The apparent volume of a carbon paper is the product of its average thickness and apparent area.
Note 2: The unit of bulk density is gram per cubic centimeter (g/cm3).
3.8
area density
ratio of the mass of a carbon paper to its apparent area
Note 1: The apparent area of a carbon paper is the product of its apparent length and width;
Note 2: The unit of area density is gram per square meter (g/m2).
3.9
roughness
microscopic irregularity of the tiny peaks and valleys on the surface of a carbon paper
Note 1: It is usually represented by the arithmetic mean value of the absolute values of the deviations of each point on the profile from the profile mean line X within a sampling length L (i.e., arithmetic mean deviation of the profile, Ra), or by the sum of the maximum profile peak height and the maximum profile valley depth (i.e., maximum height of the profile, Rz), expressed in micrometers (μm).
Note 2: There are two kinds of profile mean lines (see X in Figure 1), i.e., the arithmetic-mean mean line of the profile and the least-squares mean line of the profile. The arithmetic-mean mean line of the profile is a straight line that divides the actual profile into upper and lower parts within the sampling length range and makes the upper and lower areas equal. The least-squares mean line of the profile is a line within the sampling length that minimizes the sum of the squares of the distances from each point on the profile to this line.
Note 3: For related terms and definitions of surface roughness, see GB/T 3505-2009.
Foreword II Introduction IV 1 Scope 2 Normative references 3 Terms and definitions 4 Symbols 5 Sample and test preparation 6 Test instruments and apparatus 7 Thickness uniformity test 8 Resistance tests 9 Mechanical strength tests 10 Gas permeability tests 11 Porosity test 13 Area density test 14 Roughness tests 15 Through-plane thermal conductivity test 16 Bending stiffness test 17 Static contact angle test 18 Durability test (by acid oxidation method) 19 Test report Annex A (Informative) Test preparation Annex B (Informative) Test report Annex C (Informative) Test on the sum of bulk resistance of two copper electrodes and contact resistance between carbon paper and electrodes Annex D (Informative) In-plane gas permeability test Annex E (Informative) Porosity test Annex F (Informative) Surface roughness test method Annex G (Informative) Bending stiffness test Annex H (Informative) Static contact angle test Annex I (Informative) Durability test (by acid oxidation method) Bibliography
