57 Fuel cell adhesives | Deep insight Institute of RWTH Aachen University. The subsequent examination showed a very low weight loss of <0.8% and only a very slight change in the Shore hardness of ±0.2 units. In addition, no visual change to the surface of the test specimen could be detected, which was also verified by laser confocal microscopy. Furthermore, the materials have very low gas permeability: the hydrogen permeation coefficient measured at the hydrogen and fuel cell centre ZBT in Duisburg is just 0.3 10E-8 cm²/s for the WEVOPOX VP 414 epoxy resin. The adhesives and sealing materials also provide very good adhesion to the various metal substrates that are used as electrodes and membranes, such as stainless steel or nickel, as well as to various plastics. Other low-viscosity epoxy resin systems are also suitable as potting compounds in this area thanks to their high chemical resistance and viscosity properties, opening up new customisable options for the design of individual cells and the entire stack. Cell components such as electrode or membrane foils can be connected to the frame seamlessly and completely tightly without there being any need for additional gaskets or adhesives. Wevo is also currently working on special hydrolysis-resistant polyurethane resins as potential sealing materials for alkaline and AEM electrolysers. In initial ageing tests in KOH solution, the WEVOPUR materials demonstrated good resistance properties, said Arlt. “We are collaborating with various research institutes and industrial partners with a view to offering more solutions in this area in the future,” he confirmed. Electrolyser materials The expertise from fuel cells has also been used for PEM electrolysers to seal the components of the electrolyser stack. Addition-curing silicones or modified polyurethanes have been developed for this with thixotropic silicone systems offering very high chemical resistance levels in the highly acidic conditions. The elasticity and elongation of these materials can be adjusted over a wide range, allowing individual adaptation to the structure and operating pressure of the respective electrolyser. Elastomer materials with a Shore A hardness in the range of 60–70 include the soft and elastic silicone sealant WEVOSIL 28001 and the thixotropic version WEVOSIL 18001 T. The special chemical composition of the silicones allows a very low level of hydrogen permeability. The hydrogen permeation coefficients measured at ZBT are approximately 130 10E-8 cm²/s for WEVOSIL 28002 and around 220 10E-8 cm²/s for WEVOSIL 28102. Addition-curing silicones are typically in the range of around 500 to over 1000 10E-8 cm²/s. The silicone products and the modified polyurethanes are an alternative to the flurorubber materials frequently used for inlay gaskets. These flurorubber materials include per- and polyfluoroalkyl substances that are being phased out and so the material will eventually be replaced. During automated production, the materials are applied as a liquid using a dispensing or screen-printing process and hardened as a CIPG (cured-inplace gasket) or FIPG (formed-in-place gasket) prior to the stacking process, depending on customer requirements. To enable the silicone materials to be used with the faster of these two processes (screen-printing), the pot life has been modified to at least 24 hours at room temperature, which means that the materials can be used on the screen and screen-printing machine without the need for intermediate cleaning. Fast curing is then carried out either in a convection oven at temperatures of 100–140 C or using near-infrared radiators. The two curing methods can also be combined. The long pot life allows the soft and elastic isocyanate-free polyurethane sealant to be applied using the screenprinting process. Wevo is developing a more reactive version, with a shorter pot life and curing time, that can be used with the dispensing process. Conclusion Adhesives and sealing materials are a key challenge for hydrogen-based fuel cells and electrolysers. The same dispensing techniques that are used for adhesives can be used with curable liquid materials for gaskets, simplifying the supply chain and production line. The latest inkjet technology can also provide more accuracy in dispensing and flexibility in the choice of materials, as well as the ability to handle variations in batches, which is a key consideration on the production line. E-Mobility Engineering | January/February 2026 A PEM electrolyser for hydrogen production (Image: Wevo Chemie)
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