05 Mar Engineered to Endure: High-Heat O-Ring Materials
Temperature range is one of the most misunderstood variables in seal selection, and it can catch experienced engineers off guard. Why? A material might rate well for high heat. But if that rating does not account for real-world spikes, sustained exposure, or repeated heating and cooling cycles, performance will eventually drop off.
At I.B. Moore Manufacturing, we work through these kinds of material decisions every day. The materials that hold up under those conditions have a few key things in common; once we explain that, this will all make sense.
Not Every O-Ring Material Can Handle the Heat
Standard O-ring compounds like Buna-N (nitrile) work well in moderate conditions, but they degrade quickly under sustained high heat. As temperatures climb, those elastomers (flexible, rubber-like materials) soften, compress permanently, or crack, leading to leaks.
The goal with high-heat O-rings is to find a gasket material that maintains its shape, flexibility, and sealing force across a wide temperature range, including repeated heating and cooling cycles. Material selection also depends on what fluids or gases the O-ring will contact, because chemical compatibility matters just as much as thermal performance.
When Situations Call for Viton™
Temperature rating is where Viton™ stands out. It typically ranges from -20°F to 400°F (-29°C to 204°C), with some specialty grades rated up to 446°F (230°C). This fluoroelastomer (a type of synthetic rubber) withstands fuels, oils, hydraulic fluids, and many chemicals, making it a strong choice for the aerospace, automotive, and chemical processing industries.
That Viton™ temperature rating is worth its higher cost compared to standard elastomers. Its longevity in high-temp conditions and exceptional resistance to oils and chemicals can make it the more economical choice over time.
PTFE Has Outstanding Thermal Stability
Polytetrafluoroethylene, more easily pronounced as PTFE, is a synthetic material made of tightly bonded carbon and fluorine atoms. It behaves differently from rubber-based O-ring compounds because it is a thermoplastic, not an elastomer.
The PTFE temperature rating spans from -328°F to 500°F (-200°C to 260°C), making it one of the most thermally stable sealing materials available. PTFE is also virtually chemically inert, so it resists nearly all industrial fluids and solvents.
Unlike rubber, PTFE does not compress and spring back, so it works best in static applications where nothing is moving and the groove dimensions can hold it in place. One thing to watch for is cold flow, which occurs when the material slowly deforms under constant pressure.
Silicone O-Rings: Flexible Across a Wide Temperature Range
Silicone is a good fit for applications that swing between hot and cold, as it stays flexible across a wide temperature range. It also handles continuous heat up to 400°F (204°C) without going brittle in the cold. Though it’s not the toughest material under pressure, it holds up better in static applications where the seal isn’t constantly moving or rubbing against another surface.
We recommend these O-rings for food processing and medical equipment because silicone doesn’t react with most substances and is available in FDA-compliant grades. However, silicone breaks down quickly in petroleum-based oils, so always check fluid compatibility first.
Perfluoroelastomer (FFKM) Are Extreme High-Heat O-Rings
Perfluoroelastomer, commonly known as FFKM and sold under trade names such as Kalrez®, is a chemically reinforced fluoroelastomer. Consider this material when conditions are truly extreme. It withstands continuous temperatures up to 572°F (300°C), with some grades rated even higher, and resists harsh solvents and reactive chemicals.
FFKM compounds can handle temperatures up to 600°F (316°C) or higher in select grades, while also resisting aggressive solvents and reactive chemicals that would degrade even Viton™. The tradeoff is price, as FFKM is the most expensive option in this category by a significant margin. The price is high, but so is the standard of performance it delivers.
How Can I Pick the Best High-Heat O-Rings?
Start by knowing your actual operating conditions, not just the ideal ones.
- What is the highest temperature the seal will face, and is that sustained or a spike?
- What fluids or chemicals will the O-ring contact?
- Is the application static or dynamic?
- What are the consequences if the seal underperforms?
Once you have those answers, the right material becomes much easier to identify. P.S.: An I.B. Moore Manufacturing materials specialist can make this process a lot faster.
Built for Heat: High-Heat O-Ring Materials From I.B. Moore Manufacturing
Our I.B. Moore Manufacturing team members identify the best high-heat O-ring solutions for demanding applications, from Viton™ and PTFE compounds to specialty FFKM grades. We’re ready to discuss your temperature requirements, chemical environment, and design constraints to deliver the sealing performance your application demands. Contact our Lexington, KY, team for nationwide service.