Last updated: April 2026
A PTFE gasket is a soft-faced flange gasket cut from polytetrafluoroethylene (Teflon™) sheet. It is the default choice for aggressive chemical service — acids, alkalis, solvents, and high-purity media — because PTFE is chemically inert across virtually the entire pH range and remains stable from −200 °C up to +260 °C.
GritGasket supplies virgin PTFE, expanded PTFE (ePTFE), and filled PTFE (glass, carbon, graphite) gaskets cut to ASME B16.21, AS 2129, or any custom pattern in our Sydney workshop. FDA-compliant grades stocked for food, pharma, and potable water. Shipped anywhere in Australia or New Zealand.
What Is a PTFE Gasket?
PTFE (polytetrafluoroethylene) is a fluoropolymer best known by DuPont's trade name Teflon™. A PTFE gasket is a flat or full-face sealing element cut from PTFE sheet and used on bolted flange joints. Three forms dominate industrial service:
- Virgin PTFE — 100% pure, chemically inert, FDA-approved. Creeps under load, so best on Class 150 flat-face flanges.
- Expanded PTFE (ePTFE) — multi-directionally expanded to reduce cold flow; handles higher pressures and conforms to irregular flanges. Often the right choice for glass-lined, FRP, or damaged flange faces.
- Filled PTFE — PTFE blended with glass fibre, carbon, graphite, or barium sulphate to improve creep resistance and raise the working pressure.
PTFE Chemical Compatibility
PTFE is resistant to almost every industrial chemical at all concentrations, including strong acids (sulphuric, hydrochloric, nitric, hydrofluoric), strong alkalis (NaOH, KOH), and all common solvents. The handful of exceptions are molten alkali metals, elemental fluorine at elevated temperature, and some fluorinated solvents at pressure.
This chemical neutrality is why PTFE gaskets dominate chemical processing and pharmaceutical flange duties where graphite contamination or elastomer attack would be disqualifying.
Pressure and Temperature Limits
| PTFE form | Max continuous temp | Typical flange class | Key attribute |
|---|---|---|---|
| Virgin PTFE | 260 °C | Class 150 flat-face | Highest purity, FDA |
| Expanded PTFE (ePTFE) | 315 °C (short) | Class 150 – 900 | Creep-resistant, conformable |
| Glass-filled PTFE | 260 °C | Class 150 – 300 | Strong, low cold flow |
| Graphite-filled PTFE | 260 °C | Class 150 – 300 | Good conductivity, anti-static |
For service above 260 °C or on Class 600+ raised-face flanges, step up to a PTFE-filled spiral wound gasket or a kammprofile gasket with PTFE facing.
Where Are PTFE Gaskets Used?
- Chemical processing — acid/alkali transfer lines, reactor manways.
- Food & pharmaceutical — sanitary flanges, CIP/SIP systems, FDA-compliant plant.
- Semiconductor & high-purity water — ultra-pure PTFE grades with low extractables.
- Glass-lined reactors — expanded PTFE conforms to brittle glass flange faces.
- Potable water — WRAS/AS 4020 compliant grades on ductile-iron and uPVC flanges.
PTFE Gasket vs Rubber vs Spiral Wound
| Requirement | Choose PTFE | Choose Rubber | Choose Spiral Wound |
|---|---|---|---|
| Strong acids / alkalis | ✓ | — | ✓ (PTFE filler) |
| Potable water / HVAC | ✓ (FDA PTFE) | ✓ (EPDM) | — (overkill) |
| Temperature > 260 °C | — | — | ✓ |
| Pressure > Class 300 | — (use ePTFE/filled) | — | ✓ |
| Food / pharma hygiene | ✓ | ✓ (FDA EPDM) | — (metal contamination) |
Installation Notes
PTFE cold-flows under sustained bolt load, so target assembly stress and retorque practice matter. A typical seating stress for virgin PTFE is 14 MPa, for ePTFE 20–25 MPa. Follow ASME PCC-1 four-pass cross-pattern bolt-up and retorque after 24 hours to compensate for cold flow. Our bolt torque calculator handles the conversion from gasket stress to bolt torque for your bolt size and lubricant.
Stocked PTFE Gaskets
PTFE-VIR-FF
PTFE-EXP-STRIP
Frequently Asked Questions
A PTFE gasket is a flange gasket cut from polytetrafluoroethylene (Teflon™) sheet. It seals bolted flange joints against almost any chemical — acids, alkalis, solvents, hydrocarbons — across pH 0 to 14 and temperatures from −200 °C to +260 °C. Virgin, expanded (ePTFE) and filled PTFE grades cover different pressure and creep requirements.
Virgin PTFE is 100% pure polymer — chemically inert and FDA-compliant, but it cold-flows under sustained bolt load. Expanded PTFE (ePTFE) is mechanically expanded so its fibril structure resists creep while retaining full chemical inertness. ePTFE conforms to irregular or damaged flange faces, handles higher pressures, and is the right choice for glass-lined reactors and FRP flanges.
Yes — virgin PTFE meets FDA 21 CFR 177.1550 and EU 10/2011 for repeated food contact. Our food-grade PTFE gaskets are suitable for dairy, beverage, confectionery, and pharmaceutical CIP/SIP flange service. WRAS and AS/NZS 4020 approved grades are available for potable-water duties.
The usual cause is cold flow — virgin PTFE relaxes under bolt load, so bolts lose preload over hours to days. Two fixes: (1) specify expanded or filled PTFE, which resists creep, or (2) retorque the flange 24 hours after initial bolt-up using the same cross-pattern sequence. For Class 300+ duties consider stepping up to a spiral wound or kammprofile gasket with PTFE filler/facing.
The continuous service limit for all PTFE grades is about 260 °C. PTFE remains stable to around 315 °C for short excursions, but begins to degrade and release hazardous fumes above 400 °C. For flange service above 260 °C, use a PTFE-filled spiral wound gasket (with the PTFE protected inside a metallic winding) or switch to a flexible graphite gasket.
Related Products
- Spiral wound gaskets — PTFE-filled for higher pressure/temperature service
- Kammprofile gaskets — PTFE-faced for severe chemical service
- Gasket sheet — PTFE and CNAF sheet for cut-to-pattern gaskets
- Custom gasket cutting — PTFE cut to any flange pattern
Learn More
Sources
- ASME B16.21 — Nonmetallic Flat Gaskets for Pipe Flanges
- ASME PCC-1 — Guidelines for Pressure Boundary Bolted Flange Joint Assembly
- FDA 21 CFR 177.1550 — Perfluorocarbon resins (PTFE food-contact compliance)
- AS/NZS 4020 — Testing of products for use in contact with drinking water