Ageing and thermal conductivity of Porous Transport Layers used for PEM Fuel Cells

The through-plane thermal conductivity of dry PTLs is known to decrease with increasing PTFE content, which was also seen in this study. The chosen ageing procedure is known to wash PTFE from the PTL, and this verified using NMR. Water-PTL contact angle measurements also demonstrate that the PTL becomes less hydrophobic with ageing. This coincides with the increase in the through-plane thermal conductivity. Because the dry PTL retains its thermal conductivity while the PTFE content decreases we suggest that the PTFE remains in the fibre to fibre contact region and is removed predominantly elsewhere.