PTFE O-Rings for Chemical Processing
Virtually universal chemical resistance for static seals in reactors, pumps, valves and transfer lines — when no elastomer survives the media.
PTFE (polytetrafluoroethylene / Teflon) is not an elastomer — it is a semi-crystalline fluoropolymer with near-universal chemical inertness and service from -200°C to +260°C. PTFE O-rings are specified in chemical processing when aggressive acids, bases, solvents or oxidizers destroy FKM, EPDM and FFKM within hours.
Where PTFE seals chemical equipment
- Reactor vessel and manway covers — static seals on glass-lined and stainless reactors
- Pump and valve bonnets — face seals on chemical transfer pumps (static service only)
- Sample ports and instrumentation — small static seals in analytical and dosing skids
- Pharmaceutical and biotech CIP/SIP — where elastomer extractables are unacceptable (often FEP encapsulated instead)
Important limitation: PTFE has no elastic recovery. It cold-flows under compression and is unsuitable for reciprocating or rotary dynamic service without spring-energized designs. For dynamic chemical sealing, see spring-energized PTFE seals or FEP encapsulated O-rings.
When temperature exceeds +260°C or ketones attack PTFE at high concentration, FFKM may be required — but PTFE remains the most cost-effective option for static seals in harsh chemical service below +260°C.
Related: chemical-resistant O-rings guide, pharmaceutical CIP/SIP, semiconductor processing. Full material data: PTFE product page.
Why PTFE for This Application
Universal chemical inertness
Resists strong acids (including hydrofluoric), bases, ketones, esters and oxidizers that destroy elastomer O-rings.
Extreme temperature span
Cryogenic to +260°C continuous — covers liquid nitrogen transfer through high-temperature chemical reactors.
FDA & USP compliance
Virgin PTFE meets FDA 21 CFR §177.1550 and USP Class VI for pharmaceutical and food contact static seals.
Static sealing focus
Best for flange, cap and bonnet static joints — pair with spring-energized designs for dynamic chemical duty.
Common Sizes
| Size | Typical Use |
|---|---|
| AS568 standard sizes | Machined PTFE o-rings in standard groove dimensions — verify groove fill (PTFE does not compress like rubber) |
| Metric lathe-cut | Custom ID × CS from PTFE rod stock — typical for non-standard reactor manways |
| Large diameter (>300 mm) | Segmented or lathe-cut from PTFE billet — quote ID, CS and flatness tolerance |
| Filled PTFE (glass/carbon) | Improved creep resistance for high-pressure static — specify filler type with application pressure |
| Enveloped PTFE | FEP/PFA jacket over elastomer core when elasticity and chemical resistance both required |
Related Application Guides
FAQ
PTFE or FKM for sulfuric acid?
PTFE for concentrated sulfuric acid above ambient temperature. FKM handles dilute acids but fails in concentrated H2SO4 above +80°C. Always confirm concentration and temperature.
Can PTFE O-rings be used in dynamic pumps?
No for standard PTFE o-rings — they lack elastic recovery and will leak in reciprocating or rotary service. Use spring-energized PTFE seals for dynamic chemical duty.
Why do PTFE seals leak after installation?
PTFE cold-flows: initial compression creates a seal, but the material creeps out of the groove over days to weeks. Re-torque flanged joints after 24 hours or specify filled PTFE for better creep resistance.
Virgin or filled PTFE for chemical reactors?
Virgin PTFE for maximum chemical purity and FDA compliance. Glass- or carbon-filled PTFE for high-pressure static joints where creep resistance matters more than extractables.
PTFE vs FFKM for chemical processing?
PTFE is lower cost and handles more aggressive chemicals at static conditions. FFKM is required when elastic recovery, dynamic motion, or temperatures above +260°C are involved.
Do you machine custom PTFE O-rings?
Yes. Lathe-cut PTFE O-rings from virgin or filled rod stock in any ID × CS. MOQ 1 piece; typical lead time 5–10 days depending on diameter.
Quote PTFE chemical processing seals
Send chemical name, concentration, temperature and pressure. We confirm PTFE suitability or recommend FFKM, FEP encapsulated or spring-energized alternatives.