Wevo-Chemie materials advance sealing for hydrogen-based fuel cells

STUTTGART, Germany—When it comes to hydrogen-based fuel cells, the need for reliable sealing is a no-brainer. But according to Wevo-Chemie GmbH, today's technology has fallen short.

Until now.

Wevo—a Stuttgart-based chemical manufacturer in the field of casting and potting solutions as well as bonding and sealing compounds—has developed chemically resistant, two-component materials for use in proton exchange membrane (PEM) fuel cells, based on polyurethane and silicone.

"Since hydrogen is the smallest of all molecules, the adhesives and sealants used for fuel cells must ensure a very tight seal in order to prevent diffusion," the company said in a March 7 press release.

Preformed inlay gaskets or addition-curing liquid silicone gaskets have been used for this purpose, but both have their drawbacks, Wevo said.

Due to inlay gaskets' need to be inserted manually on both sides of a bipolar plate, "they are not suitable for automated production of high volumes."

And addition-curing liquid silicone gaskets have high gas permeability and "poor adhesion to the majority of substrates."

Wevo's materials, applied as liquid and formed in place, can be used both for fuel cells and the surrounding system, and they "have further advantages for the manufacture and operation of fuel cell components," the manufacturer said, noting the materials are an asset to the automated production of high volumes.

The materials have "unusually low gas permeability," as confirmed by ZBT, the Duisburg hydrogen and fuel cell center.

One of the silicone-based products, the company said, exhibited a "very low" hydrogen permeation coefficient of about 130 E-8 cm² per second after a measurement time of 16 hours.

"Moreover, adhesion to metal surfaces was optimized by Wevo and compression set reduced," it added.

In addition, Wevo's polyurethane sealants, which the company says have similar thermomechanical properties to silicones, have "even lower" hydrogen permeability depending on the Shore hardness, with permeation coefficients varying between 30 and 70 E-8 cm² per second—also after a 16-hour measurement period.

According to Wevo, the products adhere "significantly better than silicones to the different substrates of bipolar plats," preventing the seal from detaching throughout the manufacturing process or during stacking.

The company also boasts faster curing compared to silicones, "a major asset when it comes to automated production of high volumes."

Additionally, the polyurethane-based products can be used as adhesives for other applications in the fuel cell stack due to their "good adhesion properties," Wevo said, like bonding an entire stack together.

Wevo claims this is due to the material's high ion purity and low levels of volatile component.

The composition of the adhesives also offers high hydrolysis resistance at temperatures up to 100°C, the company added.

Wevo is an international, independent, family-run company that uses polyurethanes, epoxy and silicone. The company supplies to more than 1,250 customers in the automotive, home, engineering and energy sectors across more than 50 countries.