Hydrogen Energy
Plastic materials for hydrogen energy production, transportation, and storage
Hydrogen is an increasingly important source of clean energy. In order to be economically stored and transported, hydrogen must either be compressed or cooled and liquified to reduce its volume. Hydrogen is a small molecule that can be difficult to seal due to its high permeability through many plastics and elastomers. It is also extremely flammable under certain circumstances.
Due to these engineering challenges, the production, transportation, and storage of hydrogen are complex processes that often require the use of specialized engineering plastics and composites.
Plastics and composites are well suited to hydrogen applications since they do not exhibit hydrogen embrittlement in the same way as metals.
Hydrogen Energy Equipment Manufacturers Rely on Plastics and Composites for:
- Low hydrogen permeability for sealing performance
- Low friction and a low wear rate to minimize actuation torque for actuated valves
- Resistance to degradation from process chemicals including potassium hydroxide, which is often used in alkaline electrolyzers
- Strong, lightweight structures for portable processing machinery
- Machinability to complex shapes
- The ability to function throughout a broad operating temperature range from cryogenic temperatures to elevated temperatures
- Resistance to creep and stress relaxation for long-term performance
PLASTIC MATERIALS FOR HYDROGEN ENERGY PRODUCTION, TRANSPORTATION, AND STORAGE
Plastic Applications for Hydrogen Energy Production, Transportation, and Storage
- Electrolyzer frames, insulation plates, and end plates
- Valve seals and seats
- Gaskets
- Fuel cell spacers, frames, and end plates
- Storage tanks
- Pipe and fittings
- Electrical insulators
- Thermal insulators
- Mechanical fasteners made from threaded thermoset composites
- Piston rings
- Bearings
- Compressor seals
- Cages for roller bearings
Plastics for Electrolyzers

There are a number of different technologies used for hydrogen electrolysis including PEM (proton exchange membrane), AE (alkaline electrolysis), and AEM (Anion Exchange Membrane). All of these designs use lightweight, chemically resistant plastics and composites for applications including mechanical fasteners, separator plates, end plates, and seals.
Durostone® composite threaded rods, bolts, and nuts are often used for assembling electrolysis equipment.
The alkaline electrolysis process uses 20% to 40% KOH (potassium hydroxide) at temperatures ranging from 70 to 120 ºC. This requires plastics that resist degradation in these environments. Depending on the concentration of KOH and the operating temperature, polysulfone, FEP, PPS, PEEK, Noryl® PPO, and certain thermoset composites may be suitable for KOH applications.
Plastics for use at Cryogenic Temperatures
Hydrogen becomes liquid at -253 °C. The plastic used for devices that produce, transport, and store liquid hydrogen need to maintain ductility and also be resistant to the effects of thermal cycling. Some applications require low rates of thermal expansion and low thermal conductivity.
PEEK, glass-filled PEEK, and DuPont™ Vespel® are often specified for applications that require performance at cryogenic temperatures. Mitsubishi’s Ketron™ CR-S (for static seals) and Ketron™ CR-D (for dynamic seals) have good ductility at cryogenic temperatures. Both Vespel® SP-21 and Ketron™ CR-D are used for dynamic seals when low actuation torque is required at cryogenic temperatures.
Norplex-Micarta’s CryoLAM™ glass/epoxy composite materials including NP500CR sheet and RT521M tube are also widely used for cryogenic applications. CryoLAM™ materials have enhanced resistance to fatigue failures due to thermal cycling.
Plastics with Low Hydrogen Gas Permeability
PEEK, PCTFE, Vespel®, and certain types of polyamide have relatively low permeability to hydrogen. Some grades of Rochling’s Durostone® composites also have low hydrogen permeability.
Hydrogen permeability values for various engineering plastics at room temperature are shown below.
Kynar® PVDF: 0.18 x 109 (mol H2)·(m·s·MPa)-1
PCTFE: 0.31 x 109 (mol H2)·(m·s·MPa)-1
PEEK (31% crystallinity): 0.61 x 109 (mol H2)·(m·s·MPa)-1
HDPE (density 0.9605): 1.00 x 109 (mol H2)·(m·s·MPa)-1
Acrylic: 1.24 x 109 (mol H2)·(m·s·MPa)-1
Polypropylene: 3.10 x 109 (mol H2)·(m·s·MPa)-1
Sources: Sandia National Laboratories Reports SAND2012-7321 and SAND2013-8904
It is important to note that for semicrystalline polymers, higher crystallinity grades tend to have lower hydrogen permeation rates. For example, the hydrogen permeability values for PEEK processed to various levels of crystallinity are shown below.
PEEK, extruded, 15% crystallinity: 1.20 x 109 (mol H2)·(m·s·MPa)-1
PEEK, injection molded, 27% crystallinity: 0.67 x 109 (mol H2)·(m·s·MPa)-1
PEEK, extruded, 31% crystallinity: 0.61 x 109 (mol H2)·(m·s·MPa)-1
PEEK, compression molded, 38% crystallinity: 0.39 x 109 (mol H2)·(m·s·MPa)-1
Source: Sandia National Laboratories Report SAND2013-8904
Vespel® SCP-5000 is a premium grade of Vespel® that has extremely low hydrogen permeability. It is often specified for critical-service hydrogen applications where exceptional sealing performance is required.
Plastics for use in Compressors at Elevated Temperatures
The compressors used for hydrogen service may operate at temperatures up to 200 ºC. There are a number of variables that need to be considered when selecting plastics for high temperature compressor applications including:
- The strength and modulus of the plastic at the required temperature
- The creep and stress relaxation behavior of the material at the high end of the operating temperature range
- Thermal expansion rates
- Resistance to the degradation of mechanical properties over long periods of time at the high end of the operating temperature range
Plastic materials including Vespel®, PEEK, glass-filled PEEK, and Torlon® PAI are often used for elevated temperature compressor applications.