Osfildern-Kemnat, Germany – The low gas permeability of PU adhesives and sealants from Wevo Chemie has been confirmed by the Duisburg-based hydrogen and fuel cell centre ZBT. This means the adhesives and sealants are suitable for use in hydrogen-based fuel cells.
These fuel cells produce no harmful emissions, because the reaction between hydrogen and oxygen that takes place in them creates only energy and water. They therefore have great potential for powering electric vehicles. However, it is critical that the adhesives and sealants used to manufacture the fuel cells and in the surrounding system give extremely tight seals to prevent the hydrogen diffusing out.
These materials must also be resistant to challenging conditions, such as continuous high temperatures of up to 120°C, and high acidity. Previously, pre-formed inlay gaskets were used when constructing the fuel cells, but as they need to be manually inserted on both sides of each bipolar plate within the fuel cell, they are not appropriate for automated production in high volumes, as is common in the automotive sector. There is also the risk that they may detach while the bipolar plates are being stacked.
These requirements led to Wevo creating novel chemically resistant two-component materials based on PU and silicon for use in proton exchange membrane (PEM) fuel cells. They are applied as a liquid formed-in-place gasket.
ZBT found that while the silicone materials had a very low hydrogen permeation coefficient, of about 130 E-8 cm2/s, it was even lower for the PU sealants, at 30–70 E-8 cm2/s. The PU products adhered significantly better to the different substrates in the bipolar plates, preventing the seal from detaching in manufacture and in use. They cure more quickly than the silicones, too, a further advantage in automated production.
These PU products can also be used as adhesives in other applications in the fuel cell stack.