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

acetal-sheet-rod-tube-bw

Acetal

High strength, stiff, low friction engineering plastic with good wear properties.

vespel-plaque-rod

DuPont™ Vespel® Polyimide

Extremely high temperature creep resistant plastic with excellent friction and wear characteristics.

ectfe-halar-rod

ECTFE

Fluoropolymer with outstanding mechanical properties and dimensional stability.

FR4-G10-Glass-Filled

G10/FR-4 Glass Epoxy

Glass/epoxy composite material with outstanding electrical properties.

hdpe-sheet-bw

HDPE

Durable, versatile, low cost, abrasion and chemically resistant plastic material.

noryl-sheet-black

Noryl®

Engineering plastic with outstanding strength, stiffness, and electrical insulating properties.

nylon-group-castnylon

Nylon

Strong, stiff engineering plastic often used to replace metal bearings and bushings.

pctfe-group-white

PCTFE

Fluoropolymer with outstanding dimensional stability, mechanical properties, and temperature range.

peek-sheet-rod

PEEK

Strong, stiff plastic with outstanding chemical resistance; performs over a wide range of temperatures.

two stacked sheets of white polypropylene

Polypropylene

Low cost, chemical resistant plastic with excellent aesthetic qualities.

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PPS

Plastic material with excellent chemical and corrosion resistance at elevated temperatures.

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PPSU

High temperature thermoplastic material with outstanding impact resistance that is autoclavable.

polysulphone-sheet

PSU

High temperature, semi-transparent plastic material with good mechanical properties.

ptfe-group-white

PTFE

Low friction engineering plastic with outstanding chemical, high temperature, and weathering resistance.

exp-pvc-sheets-gray

PVC

Strong, stiff, versatile low cost plastic material that is easy to fabricate, bond, and weld.

pvdf-sheet-natural

PVDF

High purity engineering plastic with excellent chemical, abrasion, and flame resistance.

uhmw-sheets-multicolor

UHMW

Extremely tough abrasion resistant, low cost plastic, used for a wide range of wear applications.

ultem-group-multi

Ultem®

High strength plastic with outstanding electrical and high service temperature properties.

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

Assembly hardware; Durostone® EPR S6 frp threaded rods, nuts, and bolts
Röchling Industrial Durostone® EPR S6 composite sheet, threaded rods, and nuts

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.

Hydrogen energy storage application

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.

FAQS

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