GB/T 20042.7-2024Proton exchange membrane fuel cells - Part 7: Test methods for carbon paper characteristics (English PDF)

1 Scope

GB/T 20042.7-2024 specifies the test methods for the carbon paper used as the gas diffusion layer in a proton exchange membrane fuel cell. The carbon paper has to do several contradictory things at once: conduct electrons and heat, let reactant gas through to the catalyst, get liquid water out of the way, and hold its structure under compression for thousands of hours. Which is why it is characterised on a long list of properties, and why until now those properties were measured differently by every supplier. This document fixes the methods: the measurement of thickness and areal weight, the through-plane and in-plane electrical resistivity, the compressive behaviour and the thickness under load, the gas permeability, the thermal conductivity, the contact angle and the hydrophobicity after PTFE treatment, the porosity and pore size distribution, the surface morphology and the mechanical strength, together with the sample preparation and the conditions each measurement requires. For a carbon paper producer, an MEA maker or a buyer qualifying a supply in China, this is the basis of comparison.

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 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.

Note. The unit of area specific resistance is milliohm square centimeter (mOmega·cm2).

3.2 Through-plane resistivity The resistivity in the direction perpendicular to the surface of carbon paper.

Note. The unit of through-plane resistivity is milliohm centimeters (mOmega·cm).

3.3 In-plane resistivity The resistivity in the direction parallel to the surface of carbon paper.

Note. The unit of in-plane resistivity is milliohm centimeters (mOmega·cm).

3.4 Through-plane gas permeability The permeability in the direction perpendicular to the surface of carbon paper.

Note. The unit of through-plane gas permeability is milliliter millimeters per square centimeter hour Pa [mL·mm/(cm2·h·Pa)].

3.5 In-plane gas permeability The permeability in the direction parallel to the surface of carbon paper.

Note. The unit of in-plane gas permeability is milliliter millimeters per square centimeter hour Pa [mL·mm/(cm2·h·Pa)].

3.6 Porosity The percentage of pore volume of carbon paper to its total volume.

4 Symbols

The following symbols apply to this document.

Note. The symbols, meanings, units used in this document are shown in Table 1, including appropriate units of measurement.

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: