This part of GB/T 20042 specifies the terms and definitions for the test method of carbon paper properties for the proton exchange membrane fuel cells, thickness uniformity test, resistance test, mechanical strength test, gas permeability, porosity test, bulk density test, area density test, roughness test and test report.
This part is applicable to all types of 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 given in GB/T 20042.1-2005 and GB/T 28816-2012 as well as the following ones apply.
3.1.1
through-plane resistivity
resistivity of carbon paper in the thickness direction, expressed in milliohm centimeters (mΩ?cm)
3.1.2
in-plane resistivity
resistivity of carbon paper in the flat surface direction, expressed in milliohm centimeters (mΩ?cm)
3.1.3
gas permeability
volume of gas permeating sample of unit thickness and unit area at unit pressure difference within unit time, expressed in millimeter milliliter per square centimeter hour millimeter mercury [mL?mm/(cm2?h?mmHg)]
3.1.4
porosity
percentage of pore volume of carbon paper to its total volume
3.1.5
area density
ratio of the mass of the carbon paper to its apparent area, expressed in gram per square centimeter (g/cm2)
Note: The apparent area of carbon paper is the product of its apparent length and width.
3.1.6
bulk density
ratio of the mass of the carbon paper to its apparent volume, expressed in gram per cubic centimeter (g/cm3)
Note: The apparent volume of carbon paper is the product of its average thickness and apparent area.
3.1.7
surface roughness
micro unevenness of micro peaks and valleys on the surface of carbon paper, which is generally expressed by the arithmetic mean of the absolute value from each point on the profile to the midline X of the profile within a sampling length L (arithmetic mean deviation of the profile, Ra) or by the sum of the maximum profile peak height and the maximum profile valley depth (maximum height of the profile, Rz), expressed in micron (μm)
Note: The midline of the profile (see X in Figure 1) includes the arithmetic mean midline of the profile and the least square midline of the profile. The arithmetic mean midline 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 square midline of the profile is a line which minimizes the sum of squares of distances from each point on the profile to it within the sampling length.
