In alkaline electrolysis systems, the hot potassium hydroxide solution (30–35% aqueous KOH solution at a temperature of 80–90°C) used as the electrolyte creates challenging ambient conditions. The newly developed Wevo materials, based on modified polyurethanes, epoxy resins and silicones, enable innovative solutions for sealing, stack design, and automated production for this technology. These materials are also increasingly being used for AEM electrolysers, where the requirements are high, despite the much lower concentration of KOH solution in comparison.
Materials for alkaline and AEM electrolysers
As sealing materials for bipolar plates, individual stack cells, and the entire stack, the new Wevo epoxy resin systems offer especially high chemical resistance. This has been confirmed by immersing test specimens in a 35% aqueous potassium hydroxide solution at 90°C for several weeks. The subsequent examination showed a very low weight loss of <0.8% and only a very slight change in Shore hardness of ±0.2 units. In addition, no visual changes to the surface of the test specimen could be detected, as verified by laser confocal microscopy. Furthermore, the materials have very low gas permeability and also provide very good adhesion to various metal substrates used as electrodes and membranes, such as stainless steel or nickel, as well as to various plastics.
Due to its low viscosity, WEVOPOX 30010 is also suitable as a potting compound in the production of flow frames. This opens up completely new and customizable options for the design of the individual cells and the complete stack. Cell components such as electrode or membrane foils can be connected to the frame seamlessly and tightly, without the need for additional gaskets or adhesives.
Materials for PEM electrolysers
In the field of PEM electrolysers, Wevo’s developers have utilized the knowledge gained in recent years in the development of sealants for PEM fuel cells.
For sealing the components of the electrolyser stack, addition-curing silicones or modified polyurethanes have been developed. Thixotropic silicone systems offering very high resistance levels are available for acidic conditions. The elasticity and elongation of these materials can also 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. Wevo’s portfolio already offers various solutions for the Shore A 30–40 range, including a soft and elastic and a thixotropic version – WEVOSIL 28002 and 28102, respectively. Due to their special chemical composition, these two sealing materials are characterized by a very low level of hydrogen permeability for silicones.
Furthermore, the silicone products mentioned and the modified polyurethanes are free from per- and polyfluoroalkyl substances (PFAS) and therefore represent an alternative to the FKM (Fluorine Kautschuk Materials) frequently used as inlay gaskets to date. By switching over early, it is possible to avoid the impact of any future ban on PFAS.
Application by dispensing or screen-printing
During automated production, the materials are applied as a liquid using a dispensing or screen-printing process and hardened as a CIPG (cured-in-place gasket) or FIPG (formed-in-place gasket) prior to the stacking process, depending on customer requirements.
To enable Wevo’s silicone materials to be used with the faster of these two processes, screen-printing, their pot life has been modified (WEVOSIL 18001, 18002, 18102, and 18001 T): it is at least 24 hours at room temperature, meaning 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 between 100°C and 140°C or using near-infrared radiators. The two curing methods can also be combined.
Thanks to its long pot life, a soft and elastic isocyanate-free and therefore label-free polyurethane sealant can also be applied using the screen-printing process. Wevo’s developers are also currently working on a more reactive version, with a shorter pot life and curing time, that can be used with the dispensing process.
