A PTFE gasket is a flange-sealing component made from polytetrafluoroethylene, a fluoropolymer valued for near-universal chemical resistance, a −260°C to 260°C operating range and a non-contaminating surface. There are three main types: virgin PTFE (purest, most prone to cold flow), filled PTFE (glass, carbon, or graphite-reinforced for strength and creep resistance) and expanded PTFE / ePTFE (fibrillated structure that resists cold flow while keeping virgin-grade purity). The right type depends on the media, flange condition, pressure and how much bolt-load retention the application needs.
Key takeaways
- Three PTFE gasket types: virgin, filled and expanded (ePTFE) each trades off purity, strength and creep resistance differently.
- Operating range: continuous −260°C to 260°C (−436°F to 500°F), short excursions to 315°C (600°F).
- Main weakness: cold flow (creep) under sustained bolt load; filled and ePTFE grades resist it far better than virgin PTFE.
- Max pressure at 20°C: ~80 bar (virgin), ~150 bar (filled), ~120 bar (ePTFE).
- Never reuse a PTFE gasket and never apply sealant or grease to the gasket face.
- Choose by media purity needs, flange surface condition, pressure/bolt load and retorquing tolerance.
What Is PTFE?
PTFE (polytetrafluoroethylene), known by DuPont’s trade name Teflon™, is a synthetic fluoropolymer with a carbon backbone fully shielded by fluorine atoms. That molecular structure gives PTFE gaskets their defining properties:
| Property | What It Means for Sealing |
|---|---|
| Chemical inertness | Resists nearly every industrial acid, base, solvent and hydrocarbon |
| Wide temperature range | −260°C (−436°F) to 260°C (500°F) continuous; short excursions to 315°C (600°F) |
| Non-stick, non-contaminating surface | Prevents media buildup and product contamination |
| Low coefficient of friction | 0.05–0.10 — among the lowest of any solid material |
| High dielectric strength | Excellent electrical insulator |
| Physiologically inert | Safe for food, pharmaceutical and medical contact (FDA 21 CFR 177.1550, USP Class VI) |
The trade-off is cold flow (creep): under sustained bolt load, PTFE slowly deforms and loses sealing stress. Which gasket type you choose determines how big a problem that is.
Discovered accidentally by Roy Plunkett in 1938, PTFE remains the default gasket material wherever a flange has to handle aggressive chemicals, maintain product purity, or operate reliably across extreme temperatures from chemical plants and refineries to pharmaceutical and food-processing lines.
Asian Sealing Products, an ISO 9001:2015, ISO 14001:2015 and ISO 45001:2018 certified gasket manufacturer with API 6A and API 17D licenses, operating a 15,000 sq.m facility in Chennai, India, supplies PTFE and CNAF gaskets to the oil & gas, petrochemical and process industries worldwide.
How Does a PTFE Gasket Work?
A PTFE gasket seals by filling the microscopic irregularities between two flange faces when compressed during installation. Once sufficient bolt load is applied, the gasket forms a tight seal that prevents fluid or gas leakage. Unlike elastomeric gaskets, which rely mainly on elasticity, PTFE uses controlled deformation and in filled grades, strong creep resistance to hold that seal over the operating life of the joint. Correct bolt torque and gasket thickness are essential to getting this right.
Types of PTFE Gaskets
1. Virgin PTFE Gaskets
Made from 100% pure, unfilled PTFE resin (typically skived from a molded or ram-extruded billet). Virgin PTFE offers the highest chemical resistance and purity of any PTFE type, plus excellent electrical insulation, but it’s the most prone to cold flow, especially at elevated temperature and pressure and has lower mechanical strength than filled grades.
Best for: highly corrosive chemical service, pharmaceutical and food-grade applications, semiconductor manufacturing and lower-pressure duty where purity matters more than mechanical strength.
2. Filled PTFE Gaskets
Virgin PTFE reinforced with glass fiber, carbon, graphite, bronze, or mineral fillers to cut cold flow and boost mechanical strength. The filler determines the performance profile:
| Filler | What It Improves | Typical Use |
|---|---|---|
| Glass fiber (15–25%) | Compressive strength, creep resistance, wear resistance | General chemical processing, moderate-to-high pressure, steam |
| Carbon (10–35%) | Hardness, wear resistance, thermal conductivity, antistatic behavior | High-pressure service, hot water, steam |
| Graphite (5–15%) | Chemical resistance near virgin PTFE, low friction | High-temperature service, aggressive chemicals |
| Bronze (40–60%) | Wear resistance, hardness, thermal conductivity | High-pressure hydraulic/pneumatic systems, bearing pads (less common for static gaskets) |
| Barium sulfate / silica microspheres | Creep resistance without major chemical trade-off | Caustics, hydrogen peroxide, fragile flanges |
Best for: general industrial sealing where higher pressure or reduced retorquing is needed, but purity requirements are less strict than pharma or food-grade. Trade-off: chemical resistance can drop slightly depending on filler compatibility and purity is reduced versus virgin PTFE.
3. Expanded PTFE Gaskets (ePTFE)
Made by mechanically expanding 100% virgin PTFE into a fibrillated, node-and-fibril microstructure with no fillers or binders. This gives ePTFE a rare combination: universal chemical resistance and purity like virgin PTFE, plus far better resistance to cold flow and effective sealing at much lower bolt loads on rough or damaged flange surfaces. Its lower density (0.6–1.0 g/cm³ vs. ~2.2 g/cm³ for virgin PTFE) makes it notably softer and more conformable, with biaxial (multi-directional) strength instead of the “grain” effect seen in skived virgin PTFE.
Best for: fragile or irregular flanges (glass-lined, FRP, ceramic), low bolt-load applications and services demanding both purity and creep resistance. It also carries TA-Luft (VDI 2440) certification for low fugitive emissions.
Quick Comparison: Virgin vs. Filled vs. ePTFE
| Property | Virgin PTFE | Filled PTFE | Expanded PTFE (ePTFE) |
|---|---|---|---|
| Chemical resistance | Excellent | Good–Excellent (filler dependent) | Excellent |
| Cold flow / creep | High | Low | Low–Moderate |
| Mechanical strength | Moderate | High | Low–Moderate (biaxially strong) |
| Conformability to rough flanges | Moderate | Low | Excellent |
| Purity | Highest | Reduced by filler | High (100% PTFE) |
| Continuous temperature | Up to 260°C (500°F) | Up to 260°C (500°F) | Up to 260°C (500°F) |
| Max pressure @ 20°C | ~80 bar | ~150 bar | ~120 bar |
| Required bolt/seating stress | Moderate | High | Very low |
| Flange surface tolerance (Ra) | 3.2–6.3 µm | 3.2–6.3 µm | Up to 12.5 µm |
Other formats you’ll encounter: skived PTFE (thin sheet peeled from a virgin billet, good surface finish and electrical properties, but directional grain increases creep risk) and molded PTFE (compression-molded and sintered, suited to thick sections or custom shapes like valve seats).
Physical & Mechanical Properties
| Property | Typical Value |
|---|---|
| Material | Polytetrafluoroethylene (PTFE) |
| Color | White (virgin), varies (filled grades) |
| Density | 2.14–2.30 g/cm³ (virgin/filled); 0.6–1.0 g/cm³ (ePTFE) |
| Operating temperature | −260°C to 260°C (short excursions to 315°C) |
| Melting point | ~327°C |
| Water absorption | Less than 0.01% |
| Coefficient of friction | 0.05–0.10 |
| Tensile strength | 15–40 MPa (virgin/filled); 10–20 MPa (ePTFE) |
| Elongation at break | Up to 400% (virgin), lower for filled and ePTFE |
| Chemical, UV and electrical resistance | Excellent across all PTFE types |
Temperature vs. Maximum Pressure
| PTFE Type | Max Pressure @ 20°C | Max Pressure @ 100°C | Max Pressure @ 200°C | Max Pressure @ 250°C |
|---|---|---|---|---|
| Virgin PTFE | 80 bar (1,160 psi) | 30 bar (435 psi) | 10 bar (145 psi) | 5 bar (75 psi) |
| Filled PTFE (25% glass) | 150 bar (2,175 psi) | 80 bar (1,160 psi) | 40 bar (580 psi) | 20 bar (290 psi) |
| Expanded PTFE (ePTFE) | 120 bar (1,740 psi) | 60 bar (870 psi) | 30 bar (435 psi) | 15 bar (220 psi) |
All three types share a 260°C continuous temperature ceiling, with ePTFE and some grades tolerating short excursions to 315°C.
Chemical Compatibility
General guidance only — always confirm with a manufacturer’s chemical resistance chart and test for critical applications, since concentration, temperature and pressure all affect compatibility.
| Chemical Class | Examples | Virgin PTFE | Filled PTFE | ePTFE |
|---|---|---|---|---|
| Strong acids | Hydrochloric, sulfuric, nitric | Excellent | Excellent | Excellent |
| Strong bases | Sodium hydroxide, potassium hydroxide | Excellent | Excellent | Excellent |
| Organic solvents | Acetone, toluene, benzene, MEK | Excellent | Excellent | Excellent |
| Hydrocarbons | Oils, gasoline, kerosene | Excellent | Excellent | Excellent |
| Halogens | Chlorine, bromine, fluorine | Excellent | Good | Excellent |
| Oxidizing agents | Hydrogen peroxide, bleach, ozone | Excellent | Good | Excellent |
| Steam | Saturated / superheated | Good | Excellent | Good |
| Molten alkali metals | Sodium, potassium | Not recommended | Not recommended | Not recommended |
| Elemental fluorine (high temp/pressure) | — | Not recommended | Not recommended | Not recommended |
Molten alkali metals and elemental fluorine under extreme conditions are essentially the only chemicals that attack PTFE — filled grades are the exception where a specific filler is incompatible with the media.
PTFE Gasket vs. Rubber Gasket
A PTFE gasket handles a far wider temperature range and broader chemical resistance than a rubber gasket, but it costs more, requires higher installation precision and is prone to cold flow. Rubber gaskets are cheaper, more elastic and easier to install, but degrade quickly with aggressive chemicals or high heat. Rubber (elastomeric) gaskets rely on elasticity to seal and recover their shape after compression, so they tolerate minor bolt-load variation well. PTFE gaskets seal through controlled deformation, not elastic recovery, which is why torque accuracy and retorquing matter so much more.
| Factor | PTFE Gasket | Rubber Gasket |
|---|---|---|
| Chemical resistance | Excellent; resists nearly all acids, bases and solvents | Limited, varies widely by rubber compound (EPDM, NBR, Viton, etc.) |
| Temperature range | −260°C to 260°C (short excursions to 315°C) | Typically −40°C to 150°C, compound-dependent |
| Elastic recovery | Low — relies on cold flow and confinement, not elasticity | High — recovers shape after compression |
| Cold flow / creep | Significant risk (especially virgin PTFE) | Minimal |
| Installation tolerance | Requires precise, calibrated torque | More forgiving of torque variation |
| Typical cost | Higher | Lower |
| Best for | Aggressive chemicals, high purity, high/low temperature extremes | General-purpose, water, air, mild chemicals, vibration-prone joints |
Choose PTFE when the media, temperature, or purity requirement would degrade rubber. Choose rubber for lower-cost, general-purpose service where its chemical and temperature range are sufficient.
How to Choose the Right PTFE Gasket ?
Selecting the right PTFE gasket comes down to four questions:
- What’s the media? Strong acids, caustics, halogens and solvents are all handled well by any PTFE type. For food, pharma, or semiconductor purity requirements, choose virgin PTFE or ePTFE fillers can compromise purity.
- What’s the flange condition? Smooth, standard-finish flanges (Ra 3.2–6.3 µm) work well with virgin or filled PTFE. Rough, corroded, glass-lined, or plastic flanges need ePTFE’s conformability (up to Ra 12.5 µm).
- What’s the pressure and bolt load? High-pressure service favors filled PTFE. Limited bolt-load capacity (fragile equipment) favors ePTFE.
- How much retorquing can the application tolerate? Virgin PTFE typically needs a retorque after the first thermal cycle. Filled and ePTFE gaskets hold load significantly better over time.
Still unsure? Contact our engineering team with your pressure, temperature, chemical and flange details and we’ll recommend the right grade including our range of PTFE and CNAF gaskets.
Installation Best Practices
- Never use sealant or grease on the gasket face. PTFE seals by conforming to the flange; lubricants create a slip plane and accelerate cold flow.
- Use a controlled, star-pattern tightening sequence in at least three passes (30%, 60%, 100% of final torque), with a calibrated torque wrench.
- Lubricate bolt threads and nut faces only, so applied torque translates accurately into clamping force.
- Plan for a retorque on virgin and some filled PTFE gaskets after the first thermal cycle. ePTFE typically needs little to none.
- Use the thinnest practical thickness — 1.5 mm or 3.0 mm are standard; thinner gaskets creep and extrude less than thicker ones.
- Prefer recessed (ring) gasket designs on raised-face flanges over full-face designs — confinement significantly reduces extrusion risk.
Recommended Flange Surface Finish
| Gasket Material | Recommended Ra (µm) | Notes |
|---|---|---|
| Virgin PTFE | 3.2–6.3 | Spiral serrated finish is advantageous |
| Filled PTFE | 3.2–6.3 | Spiral serrated finish is advantageous |
| Expanded PTFE (ePTFE) | Up to 12.5 | Ideal for irregular, damaged, or fragile flanges |
Common Causes of PTFE Gasket Failure (and Fixes)
| Failure Mode | Typical Cause | Fix |
|---|---|---|
| Leakage | Under-torquing, cold flow/relaxation, damaged flange face, wrong gasket type for the application | Verify and re-torque to spec, retorque after the first thermal cycle, inspect and re-machine flanges if needed, switch to filled or ePTFE where creep resistance is required |
| Extrusion | Over-torquing, insufficient confinement, gasket too thick, low flange rigidity | Use recessed (ring) designs, thinnest practical gasket, correct torque, verify flange rigidity |
| Premature failure | Wrong PTFE grade for the pressure/temperature/chemical, filler incompatible with media, mechanical damage in storage or handling | Re-verify application parameters (pressure, temperature, chemical), check filler compatibility, follow storage guidelines, never reuse a compressed gasket |
Standards and Certifications to Look For
- ASTM F104, F36, F37, F38, F152 — gasket classification, compressibility, sealability, creep and tensile testing
- ISO 13000 — PTFE molding and extrusion materials
- FDA 21 CFR 177.1550 — food-contact compliance
- USP Class VI — biocompatibility for pharmaceutical use
- TA-Luft (VDI 2440) — low fugitive-emissions certification (up to 230°C)
Always request a Certificate of Conformance for critical applications. Asian Sealing Products’ PTFE and CNAF gaskets are manufactured under our ISO 9001:2015-certified quality system, with material traceability and test documentation available on request — see our full certifications.
Industries That Rely on PTFE Gaskets
- Chemical & petrochemical processing — pipelines, reactors, distillation columns, valves handling acids, caustics and solvents
- Oil & gas (upstream & downstream) — wellheads, pipelines, refineries, especially sour gas and corrosive hydrocarbon service
- Pharmaceutical & biotechnology — sanitary connections, bioreactors, API production
- Food & beverage — processing and packaging lines requiring FDA-compliant, non-contaminating seals
- Semiconductor manufacturing — ultra-high-purity gas and liquid delivery systems
- Power generation & water treatment — steam lines, cooling systems and purification equipment
Why Source PTFE Gaskets from Asian Sealing Products
- ISO 9001:2015, ISO 14001:2015 and ISO 45001:2018 certified manufacturing across our Chennai facility
- API 6A and API 17D licensed, with EIL approval for oil & gas and process applications
- 15,000 sq.m production facility with in-house testing and quality control
- Global reach — supplying the UAE, Saudi Arabia, the USA and Southeast Asia, with a dedicated USA & Mexico distribution hub
- Recognized as a top-ranked gasket manufacturer by TradeIndia and Hindustan Times
Request a quote or explore our PTFE and CNAF gasket range for engineering support on your application.
FAQs
PTFE gaskets seal flange connections in applications with aggressive chemicals, extreme temperatures, or strict purity requirements common in chemical processing, oil & gas, pharmaceutical, food and semiconductor industries.
Virgin PTFE (pure, highest chemical resistance, most prone to cold flow), filled PTFE (reinforced with glass, carbon, or graphite for strength and creep resistance) and expanded PTFE / ePTFE (fibrillated structure that resists cold flow while keeping virgin-grade purity).
PTFE gaskets operate continuously from −260°C to 260°C (−436°F to 500°F), with short excursions up to 315°C (600°F).
Cold flow (creep) is the gradual deformation of PTFE under sustained bolt load. It’s minimized by choosing filled or ePTFE gaskets, using correct torque values, confined (recessed) gasket designs and retorquing after the first thermal cycle.
No. Once compressed, a PTFE gasket takes a permanent set and won’t reseal reliably. Always fit a new gasket at every maintenance interval.
Yes, virgin PTFE and ePTFE are physiologically inert and typically comply with FDA 21 CFR 177.1550 and USP Class VI.
No. Never apply sealant or grease to a PTFE gasket face; it interferes with the sealing mechanism. Only lubricate bolt threads and nuts.
Expanded PTFE (ePTFE) — its soft, conformable structure seals effectively on flange surfaces up to Ra 12.5 µm, including glass-lined, FRP and corroded flanges.
Filled PTFE has glass, carbon, graphite, or mineral fillers added to virgin PTFE resin, which increases mechanical strength and creep resistance at the cost of some purity and, depending on the filler, slightly reduced chemical resistance.
At 20°C, maximum pressure is roughly 80 bar for virgin PTFE, 150 bar for filled PTFE (25% glass) and 120 bar for ePTFE; all figures drop significantly as temperature rises.
Yes. Teflon™ is DuPont’s trade name for PTFE (polytetrafluoroethylene); “PTFE gasket” and “Teflon gasket” refer to the same material.
There’s no fixed lifespan; it depends on temperature, pressure, chemical exposure and installation quality. Properly selected and installed PTFE gaskets can last for years, but they should always be inspected and replaced at every maintenance interval, not reused.
CNAF (compressed non-asbestos fiber) gaskets use fiber and rubber-binder sheet material rather than fluoropolymer, giving them lower cost and good general chemical resistance for water, steam and mild chemicals. PTFE gaskets cost more but handle far more aggressive chemicals, wider temperatures and higher-purity requirements. See our PTFE and CNAF gasket range for both.
Because PTFE creeps (cold-flows) under sustained bolt load, especially virgin PTFE after its first thermal cycle. Retorquing restores the clamping force lost to that creep. Filled and ePTFE gaskets creep less and typically need little or no retorquing.
Use the thinnest practical thickness for the application; 1.5 mm or 3.0 mm are standard. Thinner gaskets creep and extrude less than thicker ones under the same bolt load.
Yes. PTFE’s low permeability and chemical inertness make it suitable for vacuum applications; ePTFE in particular is rated from vacuum up to high pressure, depending on grade.
