Virgin PTFE (Teflon®) – polytetrafluoroethylene
Fluoropolymer with minimal friction and near-total chemical inertness, from −200 to 260 °C
PTFE is the plastic with the lowest friction and the highest chemical resistance available: only molten alkali metals and fluorine attack it. It works from about −200 to 260 °C and does not absorb water. On the other hand, it is soft, has high cold flow (creep) and wears quickly under load; for this reason, parts that slide under load use filled PTFE (bronze, carbon, glass). Teflon® is the Chemours trademark that became the popular name for the material.
Designations and equivalents
| System | Designation |
|---|---|
| Abbreviation (ISO 1043) | PTFE |
| Trade names | TECAFLON PTFE (Ensinger); Fibracon PTFE virgin (Roechling); Teflon PTFE (Chemours, resin); POLYFLON PTFE (Daikin, resin) |
Standards by product form
| Form | Standard |
|---|---|
| Granular resin (raw material) | ASTM D4894 |
| Rod and extruded shapes | ASTM D1710* |
| Sheet and molded shapes | ASTM D3293 / ASTM D3294* |
| Food contact | FDA 21 CFR 177.1550; EU 10/2011 (depending on grade and lot) |
| Machined part to drawing | ISO 2768 tolerance or as per drawing |
Composition and filler
Pure polymer, unfilled (virgin grade)
| Component | Content |
|---|---|
| PTFE (polytetrafluoroethylene) | 100% |
| Filler | none (virgin) |
Mechanical properties
Typical values from the stock-shape manufacturer's catalog, 23 °C; ISO/ASTM methods as per the source
| Property | Value |
|---|---|
| Tensile strength | 22 MPa |
| Elongation at break | 220% |
| Compressive strength | 5 MPa |
| Hardness | Shore D 55 |
| Notched impact | 160 J/m |
Typical physical and thermal properties
| Property | Value |
|---|---|
| Density | 2.15 g/cm³ |
| Maximum continuous service temperature | 260 °C |
| Maximum short-term temperature | 260 °C |
| Minimum service temperature | -200 °C |
| HDT (1.8 MPa) | 45 °C |
| Melting point or glass transition | 327 °C |
| Linear thermal expansion | 130 µm/m·K |
| Thermal conductivity | 0.2 W/m·K |
| Water absorption (24 h) | <0.01% |
| Dielectric strength | 24 kV/mm |
| Flammability (UL 94) | V-0 |
Calculate the weight of Virgin PTFE (Teflon®) – polytetrafluoroethylene bar, plate or pipe →
Friction, wear and PV limit
| Property | Value |
|---|---|
| Dynamic coefficient of friction against steel | 0.1 (dynamic at 10 ft/min (0.05 m/s), PV 8,000-10,000 psi·ft/min) |
| PV limit (pressure × velocity) | 0.042 MPa·m/s (at 0.05 m/s (10 ft/min), unlubricated, 21-27 °C; original 1,200 psi·ft/min); 0.063 MPa·m/s (at 0.5 m/s (100 ft/min); original 1,800 psi·ft/min); 0.088 MPa·m/s (at 5 m/s (1,000 ft/min); original 2,500 psi·ft/min); 0.04 MPa·m/s (at 0.05 m/s); 0.07 MPa·m/s (at 0.5 m/s); 0.095 MPa·m/s (at 5 m/s) |
| Deformation under load (creep) | 10% (deformation under 14 MPa load, 24 h, 23 °C (ASTM D621)) |
| Deformation under load (creep) | 14.5% (total deformation under 14 MPa, 24 h (ASTM D621)) |
PV and friction depend on the test method, the mating surface (steel, stainless, roughness), lubrication and each manufacturer's safety factor: compare values from the same source and confirm by testing in critical applications.
Chemical resistance
| Medium | Resistance |
|---|---|
| Acids | Excellent |
| Bases (alkalis) | Excellent |
| Solvents | Excellent (practically inert) |
| Hydrocarbons and oils | Excellent |
| Steam and hot water | Excellent (limit 260 °C) |
| Caution | Molten alkali metals (sodium, potassium), fluorine gas and some fluorinated compounds (ClF₃, OF₂) |
Stock forms and sizes
- Rod (round bar)
- Sheet (plate)
- Tube and bushing
- Skived film/tape
- Raw material: rod (round bar), sheet (plate) and tube, cut to size
- Machined part to drawing or sample, in the same order as the metal parts
- Lot certificate of conformity; FDA/EU 10/2011 declaration when the grade allows
Service temperature, machining and assembly
| Item | Usual practice |
|---|---|
| Service temperature | Continuous service up to 260 °C; minimum -200 °C (unloaded; under load, limited by HDT and creep). |
| Annealing (stress relief) | Stress-relief annealing before finish machining of tight-tolerance parts; PTFE does not harden by heat treatment. |
| Bonding and welding | Cannot be welded or bonded without preparation: the surface needs chemical etching (sodium naphthalene) to accept adhesive. In sealing, it is fitted by interference or pressed in. |
| Machining | Machines easily with a sharp tool and positive rake; its high thermal expansion (ten times that of steel) requires measuring the part at room temperature and allowing clearance. |
Typical applications
- Gaskets, packings and chemical seals
- Valve seats
- Electrical and high-frequency insulators
- Sliding bearing plates for bridges and structures
- Cryogenic components
- Low-load, low-speed bearings
- Pipe and tank linings
Alternatives: PTFE with bronze, carbon or glass when there is load or wear; PVDF when more stiffness with good chemical resistance is needed; PEEK for high load and temperature.
Frequently asked questions
Which standards cover Virgin PTFE (Teflon®)?
Granular resin (raw material): ASTM D4894. Rod and extruded shapes: ASTM D1710*. Sheet and molded shapes: ASTM D3293 / ASTM D3294*. Food contact: FDA 21 CFR 177.1550; EU 10/2011 (depending on grade and lot). Machined part to drawing: ISO 2768 tolerance or as per drawing.
Up to what temperature can Virgin PTFE (Teflon®) be used?
Continuous service up to 260 °C; minimum -200 °C (unloaded; under load, limited by HDT and creep).
Which materials can replace Virgin PTFE (Teflon®)?
PTFE with bronze, carbon or glass when there is load or wear; PVDF when more stiffness with good chemical resistance is needed; PEEK for high load and temperature.
Are Teflon and PTFE the same thing?
Yes. PTFE (polytetrafluoroethylene) is the polymer; Teflon® is the Chemours registered trademark that became the popular name. A Teflon rod is a PTFE rod.
Why does virgin PTFE deform over time?
Because of cold flow (creep): under constant load the part deforms slowly, even at room temperature. For loaded seals and rings, use filled PTFE (bronze, carbon or glass), which deforms much less.
Can PTFE be used in contact with food?
The virgin grade can, under FDA 21 CFR 177.1550 and EU 10/2011. Ask for the lot declaration of conformity with your order.
