PCTFE O-rings
When a sealing ring has to hold a tight barrier against gas and moisture at cryogenic temperatures and stay dimensionally stable under load, PCTFE is the fluoropolymer engineers turn to. Vanéflon machines PCTFE O-rings and near-net ring blanks to tight tolerances for demanding static sealing in cryogenic, oxygen, vacuum and high-purity service.
One point up front, because it matters for specifying correctly: PCTFE is a rigid fluoropolymer with very little elasticity, so it is chosen for static sealing where rubber and softer polymers fail, not for the flexible, repeatedly compressed seals people usually picture. You may also know it under its trade names Kel-F, Neoflon or Voltalef, all the same base polymer, which Vanéflon supplies as a ring blank, a finished O-ring or a fully machined part.
What is a PCTFE O-ring?
Unlike rubber O-rings, PCTFE (polychlorotrifluoroethylene) is a rigid fluoropolymer rather than an elastomer. A PCTFE O-ring therefore functions as a high-integrity static sealing or back-up ring: it seals under compressive load in grooves and flanges where flexibility is less important than purity, low permeation and extreme-temperature reliability. This makes PCTFE the material of choice wherever traditional EPDM, FKM or silicone O-rings fail, for example in cryogenic media, high vacuum, aggressive chemicals or ultra-clean process environments.
PCTFE was first sold as Kel-F and is produced today as Neoflon or Voltalef, but the Kel-F name is still used widely across the industry, so you will encounter all these terms describing the same polymer.
Why PCTFE for O-rings
In a sealing ring PCTFE brings a set of properties that few materials match:
- High rigidity and resistance to cold flow, so the ring keeps its shape and its seal under sustained load and pressure.
- Excellent cryogenic performance, holding mechanical integrity down to extremely low temperatures where elastomers become brittle and fail.
- Outstanding gas and moisture barrier, with the lowest water vapour transmission rate of the common fluoropolymers.
- Near-zero moisture absorption, which keeps dimensions stable in humid and vacuum conditions.
- Very low outgassing, making PCTFE suitable for vacuum and aerospace applications.
- Excellent chemical resistance to most acids, bases and oxidising agents, plus non-flammability with a high limiting oxygen index.
- Food contact compliant, meeting FDA and EU 10/2011 requirements.
Two honest points help you specify correctly. PCTFE has very little elastic recovery, so it seals through precise machining and controlled compression rather than by stretching over a gland the way an elastomer does. And while its upper temperature limit is lower than PTFE or PEEK, it is stronger and more stable in the cold, which is precisely why it is chosen for cryogenic sealing rings.
Technical specifications & key properties of PCTFE O-rings
- Material: PCTFE (polychlorotrifluoroethylene)
- Also known as: Kel-F, Neoflon, Aclon
- Temperature range: –273 °C to +170 °C — excellent cryogenic performance, retaining stability at liquid-gas temperatures
- Chemical resistance: excellent
- Moisture absorption: near-zero
- Gas permeability: very low — the lowest water-vapour transmission rate of the common fluoropolymers, for outstanding gas-barrier performance
- Hardness & stability: high hardness and rigidity, with high dimensional stability and resistance to cold flow (low creep)
- Outgassing: very low, suitable for high-vacuum and aerospace applications
- Radiation resistance: yes
- Electrical insulation: stable
- Food contact: FDA compliant – EU 10/2011
Values are indicative and depend on grade. Download the PCTFE datasheet for the full technical detail, or ask our team for the grade that suits your application.
When a PCTFE O-ring is the right choice
PCTFE O-rings earn their place where:
- Temperatures are cryogenic, in liquid oxygen, liquid nitrogen and LNG service, where elastomer O-rings go brittle and crack.
- The seal must block gas and moisture, thanks to the lowest permeability of the common fluoropolymers.
- The medium is aggressive, and elastomers or softer polymers would swell or degrade.
- The environment is vacuum or high-purity, where PCTFE’s very low outgassing and near-zero moisture absorption keep the system clean.
- The seal is static, seated in a groove or between faces rather than moving rapidly against a shaft.
Talk to our specialists about your application
Not sure PCTFE is the right fit? Share your temperature, media and sealing conditions, and we’ll help you specify the right solution.
Dimensions, tolerances and custom O-rings
Vanéflon machines PCTFE O-rings across a wide range of cross-sections and diameters, to your groove design and drawing. Standard fluoropolymer ring sizes can be produced from stock, while custom dimensions and non-standard cross-sections are made to your specification, with tight and repeatable tolerances.
Tell us the inner diameter, cross-section and groove details, along with your application and operating conditions, and we will confirm feasibility, tolerances and lead time. Where a rigid ring is not the ideal solution, we will say so and suggest the seal type that fits.
PCTFE O-rings compared to PTFE, PEEK and elastomers
Choosing a ring material is always a trade-off.
- Against elastomer O-rings (such as FKM or EPDM), PCTFE is far more chemically resistant and stable at cryogenic temperatures, but it lacks their elasticity, so it suits static rather than dynamic, repeatedly compressed seals.
- Against PTFE, PCTFE is harder, more resistant to cold flow and holds tighter tolerances under load, which makes it the stronger sealing ring at low temperature, though PTFE offers lower friction and a higher temperature ceiling.
- Against PEEK, PCTFE is the better choice for cryogenic and oxygen service, while PEEK takes over when very high pressure and high temperature dominate.
PCTFE is more expensive than PTFE, but for cryogenic, vacuum and oxygen sealing it remains indispensable. If you are weighing up materials, our specialists are happy to help you make the right call for your operating window. Get in touch and we will advise on the best fit.
Industries
PCTFE O-rings and sealing rings from Vanéflon are trusted across:
- Oil and gas, including LNG storage and transport
- Aerospace and vacuum applications
- Chemical processing
- Semiconductor manufacturing
- Cryogenic and industrial gas handling
Why choose Vanéflon for PCTFE O-rings
High-quality products
With more than 45 years of experience in liners, valve seats and sealing components, we control the full chain from powder to finished ring. Every PCTFE O-ring machined to drawing and finished to tight, repeatable tolerances.
Excellent service & support
Our team acts as your design partner in material selection, not just your supplier. Whether you need a single near-net ring blank or a fully machined PCTFE O-ring, we help you specify the right solution for your operating window.
Full traceability & certification
Thanks to in-house material production, every order is fully traceable from raw material to final part and leaves our facility certified.
Delivery reliability
We deliver as promised, with flexible VMI systems that keep your supply of sealing components seamless and reliable.
Frequently asked questions
Request a quote
Looking for a reliable partner for PCTFE O-rings and sealing rings? Vanéflon supports you from material choice through to the finishing of the most complex sealing components.
Request a quote or reach out to our team, and we will come back with the right solution, tolerances and lead time.
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