O-ring material
PTFE O-Rings
PTFE is the fluoropolymer sold as Teflon® and under other names, and a PTFE O-ring is a different animal from a rubber one: it does not stretch back, it creeps under load, and it shrugs off chemistry that no elastomer survives. Four constructions put PTFE in a groove: a solid ring, an encapsulated ring with a rubber core, a spring-energized seal and the backup ring beside an elastomer O-ring, and the print rarely says which. Conquest supplies all four in AS568 and metric sizes as a distributor; no maker sheet on file states a service range for a solid PTFE ring as a finished part, and the product sheet governs.
- Family
- PTFE (polytetrafluoroethylene); Teflon is The Chemours Company's brand for its fluoropolymer resins
- Standard range
- No maker range on file for a solid PTFE O-ring; the product sheet governs
- Jacket resins on file
- FEP to 200 C upper service temperature and PFA to 260 C continuous use, from the resin maker's sheets; an encapsulated ring is the lower of the jacket and core figures
- Durometers
- Not applicable to solid PTFE; encapsulated rings take the core's rubber hardness; spring-energized seals are rated by spring load
- Standards
- SAE AS8791 (formerly MIL-R-8791) for PTFE backup rings; FDA-listed virgin resins on specific products, per the product sheet
- Product
- Solid, encapsulated and spring-energized PTFE seals and PTFE backup rings in AS568 and ISO 3601 sizes, quoted in the construction the print names
No family range is on file for this material; the compound datasheet and your application govern the final choice.
Why a PTFE O-ring is not a rubber O-ring
An elastomer seals by being squeezed and pushing back; PTFE has almost no push-back. Squeeze a solid PTFE ring and it takes a set, and under a steady load it creeps, so the seal that was tight at assembly loosens over months. What PTFE offers instead is chemical inertness across nearly every medium, very low friction, a wide temperature span on the resin sheets, and no aging in storage. The four constructions below exist to keep those virtues and lend the ring some elasticity from somewhere else.
The four constructions
| Construction | Where the sealing force comes from | Belongs in | Watch for |
|---|---|---|---|
| Solid PTFE O-ring, virgin | Groove fill and a tight gland; the ring itself barely recovers | Static face and flange seals in aggressive chemistry; food and pharmaceutical lines on FDA-listed resin | Cold flow and creep; no reuse after disassembly; a groove designed for rubber leaks |
| Solid PTFE O-ring, filled | As virgin, with a filler that resists creep and wear | Static seals under higher load; slow-moving service | Fillers reduce chemical inertness; glass fillers abrade soft mating metals |
| Encapsulated O-ring | A silicone or FKM core inside a thin FEP or PFA jacket | Static and slow-moving seals that need PTFE chemistry with rubber recovery; process flanges, couplings, sanitary fittings | Stiffer than rubber, so the groove and the mating finish matter; the jacket sets the top temperature |
| Spring-energized seal | A metal spring inside a U-shaped PTFE jacket | Rod, piston, face and rotary seals in cryogenic, vacuum, high-pressure and chemical service | Made to the hardware, not to an AS568 size; the spring alloy must suit the medium |
| Backup ring | None; it is a hard PTFE ring that closes the extrusion gap beside a rubber O-ring | Any elastomer O-ring gland at pressure | It is not a seal on its own |
Virgin and filled PTFE
Virgin PTFE is the unfilled resin: the cleanest, the most inert and the lowest in friction, and the one the FDA-listed products are made from. Fillers trade some of that inertness for mechanical strength. Glass adds creep resistance and dimensional stability; carbon and graphite add wear resistance and conduct heat; bronze adds strength and creep resistance at the cost of chemical resistance; molybdenum disulfide lowers friction further; stainless steel fills the highest-load grades. A print that says PTFE without a filler is asking for virgin resin, and a filler is named on the print when one is wanted.
The temperature figures, and why solid PTFE carries none here
Every figure on this site traces to a published source, and no sheet on file states a service range for a solid PTFE O-ring as a finished part, so this page publishes none: the product sheet for the ring you order governs. The jacket resins of encapsulated rings are different, because the resin makers publish them. The Chemours sheet for Teflon FEP states an upper service temperature of 200 C, and the Teflon PFA properties handbook states a continuous use temperature of 260 C. An encapsulated ring runs at the lower of its jacket figure and its core's family figure, and the silicone and FKM pages carry the core figures.
When PTFE is the wrong part
A dynamic seal that must recover after every stroke wants a rubber O-ring or a spring-energized seal, not a solid PTFE ring. A groove cut for a rubber O-ring will not hold a solid PTFE ring tight; the gland needs redesign or an encapsulated ring. Chemistry that only FKM fails on, such as ketones, amines or hot steam, is usually an FFKM job rather than a PTFE one, because FFKM keeps the elasticity. Where the medium beats FFKM too, or where the budget will not carry FFKM, PTFE in one of its four constructions is the usual fit.
What to send
The AS568 dash number or the inside diameter and cross-section, the construction the print names (solid, filled and which filler, encapsulated and which jacket and core, spring-energized with the hardware print), the medium, the temperature and whether the seal moves. Send the groove dimensions for a solid ring, because the groove decides whether it seals. The quote names the resin or the maker for the construction your print names and sends the product sheet.
Sizes and forms we supply
Solid and encapsulated PTFE O-rings in AS568 and ISO 3601 sizes; PTFE backup rings in the MS28774, MS28782 and MS27595 families to SAE AS8791 and in commercial spiral, split and solid styles; spring-energized seals made to the hardware. The AS568 chart and the metric chart carry the dimensions.
Sources: Teflon FEP 100-J product information, The Chemours Company, 2019 (upper service temperature), read 2026-09-14; Teflon PFA properties handbook, DuPont era (continuous use temperature), read 2026-09-14; Parker® O-Ring Handbook ORD 5700 (read 2026-09-14) for the silicone and FKM core figures; SAE AS8791 and the MS28774, MS28782 and MS27595 families (documents named, not reproduced); No maker sheet for a finished solid PTFE O-ring is on file, so no range is published.
Parker is a trademark of Parker Hannifin Corporation. Teflon is a trademark of The Chemours Company; no affiliation or endorsement is implied.
Reviewed by Grant Midstokke, Conquest Seal Corporation. Last updated September 2026. Material ranges are the published references named beside them; the compound datasheet and your application govern the final choice.
Frequently asked
Can a PTFE O-ring replace a rubber O-ring in the same groove?
Usually not. A solid PTFE ring does not recover the way rubber does, and a groove cut for rubber leaves it loose; an encapsulated ring or a redesigned gland is the fix. Send the groove dimensions with the request.
What temperature is PTFE good for?
No maker sheet on file states a range for a solid PTFE O-ring, so this page states none and the product sheet governs. For encapsulated rings the resin maker's sheets put the FEP jacket at 200 C and the PFA jacket at 260 C, and the core's family figure applies below that.
What is the difference between FEP and PFA encapsulation?
Both are melt-processable fluoropolymers from the same maker family. PFA carries the higher continuous-use figure on its sheet, 260 C against 200 C for FEP, and costs more; FEP is the usual jacket where the temperature allows.
Is Teflon the same as PTFE?
Teflon is The Chemours Company's brand for a family of fluoropolymer resins that includes PTFE, FEP and PFA. PTFE is the material name; a part described as Teflon may be any of the three unless the sheet says which.
What do the fillers do?
As the fillers are usually described, glass resists creep under load, carbon or graphite wear in slow motion, bronze high load, and molybdenum disulfide friction. Name the filler your print specifies and the quote sends that grade's sheet.
What are MS27595 and MS28774?
PTFE backup ring families made to SAE AS8791, the successor to MIL-R-8791, that sit beside an elastomer O-ring to close the extrusion gap. The backup ring page covers the families and when a gland needs one.
Related guides
Send the part number and the quantity for PTFE
The AS568 dash number or the inside diameter and cross-section, the durometer, the quantity, the medium and temperature, and any specification the print names. A Conquest representative replies.
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