Hydrogen is expected to play a major role in the transition to low-carbon energy systems, creating new demands for sealing technologies used in production, storage, transportation, and end-use equipment. While polymers have long been used to seal conventional gases and fluids, hydrogen presents unique challenges due to its small molecular size, high diffusivity, wide operating pressure range, and the demanding environments of hydrogen infrastructure. Selecting the appropriate polymer sealing material is therefore critical to ensuring safety, reliability, and long service life.
Why Hydrogen is Challenging for Seals
Hydrogen, being the smallest molecule in nature, means it easily permeates through many materials more readily than other industry gases. This results in gradual leaking, increased permeation rates, and long-term degradation of sealing performance.
Rapid Gas Decompression (RGD) is a major concern in high-pressure hydrogen applications. When pressure is released quickly, dissolved hydrogen within an elastomer can expand rapidly, creating internal cracks, blisters, or complete seal failure. Materials selected for hydrogen service must therefore balance low gas permeability with excellent resistance to explosive decompression.
Polymers that Mitigate these Issues and Support Rubber Materials
Polytetrafluoroethylene (PTFE) is frequently selected where extremely low friction, excellent chemical resistance, and wide temperature capability are required. Although PTFE exhibits low permeability compared with many elastomers, its lack of elasticity often requires energised seal designs or spring-assisted configurations.
PTFE is commonly found in these applications:
- Valve seats – The sealing surface inside valves that stops hydrogen flowing when the valve is closed.
- Backup rings – Support rings placed next to softer elastomer seals to prevent them from being squeezed into gaps under high pressure (a problem known as extrusion).
- Spring-energised seals – High-performance seals used where extremely low leakage and low friction are required.
- Cryogenic hydrogen systems – Equipment handling liquid hydrogen at temperatures around −253°C, where many rubber materials become brittle, but PTFE remains stable.
Polyether Ether Ketone (PEEK) is generally used as a high-performance engineering thermoplastic rather than as an elastomeric seal. Its outstanding mechanical strength, chemical resistance, and dimensional stability make it ideal for anti-extrusion rings, seal carriers, and structural sealing components operating under high pressure.
PEEK is commonly found in these applications:
- Backup rings – These sit next to softer rubber seals (such as O-rings) and stop them from being squeezed into small gaps under high pressure, preventing damage and leaks.
- Bearing components – PEEK bearings help moving parts slide smoothly while resisting wear, often without needing lubrication.
- Compressor wear rings – These protect compressors from metal-to-metal contact, reducing wear and extending equipment life
- High-pressure support elements – PEEK provides structural support for seals and other components in equipment operating at very high pressures.
Final Thoughts
As hydrogen infrastructure expands globally, demand is increasing for polymer materials that combine lower permeability with greater durability under increasingly demanding operating conditions. Engineered thermoplastics such as PEEK and PTFE continue to improve the performance of backup rings and high-pressure sealing systems.
Polymer sealing solutions are essential to the safe and efficient operation of hydrogen infrastructure. From electrolysers and compressors to storage vessels, pipelines, and fuel cell systems, seals must perform reliably in environments characterised by high pressures, rapid cycling, and the unique permeation behaviour of hydrogen. By selecting materials with appropriate mechanical properties, low permeability, and proven resistance to rapid gas decompression, engineers can improve system reliability, reduce maintenance costs, and support the continued growth of the global hydrogen economy.