Fraunhofer project targets elastomer seals for H2 applications

Darmstadt, Germany – The transport and containment of hydrogen for new-energy and new-mobility applications place severe demands on sealing materials, particularly as any leakage could cause critical safety issues.

These challenges form the background for a recently launched two-year joint project, led by the Fraunhofer Institute for Structural Durability and System Reliability in Germany.

Until now, only a few reliable findings exist on the use of elastomers in combination with hydrogen, said Fraunhofer , explaining the project being carried out with industrial partners.

The main aim of the HydroTransSeal project is, therefore, to provide a fundamental understanding of the behaviour of elastomer seals when used under hydrogen.

This includes understanding interaction mechanisms of H2 with elastomers and how to make the materials more robust to permeation, adsorption and swelling.

The research will also seek to evaluate the suitability of elastomer seals used in existing pipeline systems for hydrogen transport.

A focus of the study will be on the use of existing gas infrastructure pipeline systems for hydrogen transport, and the special challenges this poses for the sealing elements used.

System pressure in initial series applications of hydrogen tank systems is 350bar, with future developments aiming at applications with 700bar nominal pressure or beyond, noted Fraunhofer .

In addition to the enormous stresses placed on the seals by the pressure, there are also temperature ranges of -40°C to 85°C that can occur during refuelling operations, it noted.

Due to the small molecular size of hydrogen, potential migration of hydrogen into and through the sealing elements must also be addressed.

This can cause swelling of the sealing elements, which must be considered for component design, according to Fraunhofer.

Meanwhile, H2 absorption by the material can lead to abrupt volume expansion in the event of a sharp drop in pressure – possibly damaging the component and leading to a rapid escape of gas.

As well as the high demands placed on the nominal properties of seals, elastomer materials also experience aging effects over their service life, noted Fraunhofer.

By developing a model, "it will be possible to estimate the service life of elastomer materials based on their aging behaviour,” it explained.

In the long-term, this will make it possible to optimise sealing compounds for hydrogen applications, according to the Darmstadt-based research body.

The project, it added, “should also be an incentive for raw material suppliers to [develop] innovative elastomer formulations in the promising field of hydrogen transport.”