PTFE / Teflon Plastic: Properties, Grades & Uses
Polytetrafluoroethylene (PTFE), sold commercially as Teflon, is a fully fluorinated thermoplastic fluoropolymer that outperforms virtually every other plastic in chemical resistance, temperature range, and surface friction. Continuous service reaches 500°F (260°C), the coefficient of friction sits between 0.05 and 0.10 — the lowest of any unfilled engineering plastic — and the material remains inert to nearly every acid, solvent, and oxidizer at concentrations and temperatures that destroy nylon, acetal, and most other polymers. Those properties make PTFE the default specification for chemical seals, high-temperature insulators, non-stick liners, and precision bearings in aggressive environments.
At a Glance
- Continuous use temperature: 500°F (260°C); intermittent to 550°F (288°C)
- Coefficient of friction: 0.05–0.10 (unfilled virgin grade)
- Chemical resistance: inert to virtually all acids, bases, solvents, and fuels
- FDA compliant: virgin PTFE meets 21 CFR 177.1550 for direct food contact
- Dielectric strength: 480 V/mil — excellent electrical insulator
- Density: 2.15 g/cc — heaviest common fluoropolymer
- Key limitation: significant cold flow (creep) under sustained compressive load
What Is PTFE?
PTFE is a linear, high-molecular-weight polymer of tetrafluoroethylene (CF₂=CF₂). The carbon–fluorine bond (C–F) is one of the strongest in organic chemistry at roughly 116 kcal/mol, which explains why PTFE resists chemical attack at concentrations and temperatures that dissolve or swell competing materials. The fluorine atoms form a continuous helical sheath around the carbon backbone, preventing reagents from accessing the polymer chain.
PTFE cannot be melt-processed using conventional injection molding or extrusion — the melt viscosity at processing temperatures exceeds 10¹⁰ Pa·s. Instead, manufacturers use compression molding followed by sintering, ram extrusion, or paste extrusion. That processing constraint shapes the available stock forms: sheet, rod, tube, and skived film are standard; complex net-shape moldings are less common and more expensive than with thermoplastics like nylon or acetal.
Physical Appearance
Virgin PTFE is opaque white with a waxy, slightly soft surface feel. Filled grades take on the color of their filler: glass-filled appears off-white or translucent beige, carbon-filled is black, bronze-filled is golden-brown. The material is noticeably denser than other white engineering plastics — at 2.15 g/cc it is heavier than PVDF (1.78 g/cc) and roughly twice the density of UHMW (0.93 g/cc).
Why "Teflon"?
Teflon is a registered trademark of Chemours (formerly DuPont), who discovered PTFE in 1938. The name has become a genericized reference to the material class, but not all PTFE is Teflon-branded. For engineering and procurement purposes, the ASTM designation D1457 (for resin) and the finished-form standards D3293 / D3295 / D3308 govern product qualification regardless of brand.
Grades of PTFE
Virgin PTFE delivers peak chemical resistance and electrical insulation but creeps under load. Fillers address mechanical shortfalls without significantly degrading chemical resistance.
Virgin PTFE
The baseline grade: no fillers, maximum chemical purity, FDA-compliant, lowest friction, lowest compressive strength. Best for corrosive chemical service, electrical insulation, and food-contact applications.
Glass-Filled PTFE (15% and 25%)
Glass fiber dramatically reduces creep and increases compressive strength. A 25% glass-filled grade roughly doubles the deformation resistance of virgin material. Chemical resistance is slightly reduced because glass fibers can be attacked by hydrofluoric acid and strong caustics.
Carbon-Filled PTFE
Carbon (10–25%) improves compressive creep resistance, thermal conductivity, and wear life. It is the preferred filler for dynamic seals and rotary applications where virgin PTFE would deform or develop excessive wear tracks. The material is electrically conductive, which disqualifies it from electrical insulation applications.
Bronze-Filled PTFE
Bronze (40–60%) provides the highest compressive strength and best dimensional stability of the standard filled grades. Thermal conductivity is markedly higher, which helps dissipate frictional heat in bearings and thrust washers. Not suitable for oxidizing chemical environments — bronze corrodes.
MoS₂-Filled PTFE
Molybdenum disulfide additions at 2–5% reduce the coefficient of friction slightly further and improve wear performance in dry sliding applications. Less common than carbon or glass fills; used in precision bearing pads and slide plates.
Key Properties
PTFE's defining properties span thermal, mechanical, chemical, and electrical domains. The table below summarizes the most specifiable values for virgin grade material.
For a complete datasheet including filled-grade comparisons, see the PTFE properties guide.
Chemical Resistance
PTFE is resistant to essentially every industrial chemical — including concentrated sulfuric acid, hydrofluoric acid, aqua regia, chlorine gas, and all common solvents. The practical exceptions are elemental fluorine under pressure, chlorine trifluoride, and alkali metals (liquid sodium, potassium) at elevated temperature. These are extreme laboratory or industrial conditions encountered by almost no general-engineering application.
For chemical-resistant liner service, PTFE outperforms PVDF / Kynar — which has excellent but not universal chemical resistance — and vastly outperforms polyethylene or polypropylene liners. Where cost is a constraint and the service environment falls within PVDF's resistance envelope, PVDF may be substituted; see the PVDF vs PTFE comparison for a side-by-side breakdown.
Applications
Seals and Gaskets
PTFE is the standard material for chemical plant seals, valve stem packing, and flange gaskets. Its chemical inertness prevents contamination of the process stream and degradation of the seal itself. Skived-film tape and cut-from-sheet gaskets are both common forms. For dynamic sealing with higher pressure, filled grades (glass or carbon) are preferred to resist extrusion.
Bearings and Bushings
The ultralow coefficient of friction allows PTFE to run without lubrication in many applications. Bronze-filled and carbon-filled grades are specified for bushing stock where dimensional stability under load matters. Virgin PTFE creeps significantly under sustained compressive stress — if you are designing a bearing for continuous load, a filled grade or a fabric-reinforced composite is required.
Electrical Insulation
The dielectric constant of 2.1 is among the lowest of any solid insulator, and dielectric strength at 480 V/mil exceeds most plastics. PTFE tape, tubing, and film are used in high-frequency coaxial cable insulation, printed circuit boards, and aerospace wire harnesses.
Chemical Process Equipment
PTFE-lined pipe, valves, fittings, and reactor vessels isolate aggressive reagents from carbon steel or stainless steel substrates. Skived film applied as a liner is more cost-effective than solid PTFE for large-diameter pipe. In pharmaceutical and semiconductor manufacturing, the combination of chemical purity and smooth surface (low bacterial adhesion) justifies the material premium.
Non-Stick Cookware and Industrial Release
The high-temperature stability and non-stick surface translate directly to industrial roll covers, mold-release sheets, and conveyor belts for high-temperature processing. Cookware coatings are a thinner application, but the same C–F chemistry governs both uses.
For a deep dive into each market, see the PTFE applications guide.
Available Forms and Sizes
PTFE is available as:
- Sheet: typically 12 × 12 in. to 48 × 48 in., thicknesses from 1/16 in. to 4 in.
- Rod: diameters from 1/4 in. to 12 in., lengths to 24 in. (compression-molded) or longer (ram-extruded)
- Tube: OD from 1/4 in. to 6 in., wall thicknesses from 1/16 in.
- Skived film: 0.001 in. to 0.060 in. thick, rolls up to 48 in. wide
Virgin white and filled variants (glass, carbon, bronze, MoS₂) are stocked in the most common sizes; specialty grades and tight-tolerance blanks may require lead time. See PTFE specifications for standard ASTM size ranges and tolerances.
Machining PTFE
PTFE machines cleanly with standard carbide tooling — it does not require coolant in most operations — but its softness and tendency to cold-flow demand specific technique. Feeds and speeds that work for aluminum or nylon produce gummy, smeared surfaces on PTFE if clearance angles are inadequate. Critical points:
- Use sharp tooling with 10–15° positive rake angles
- Support thin sections — the material deflects under cutter pressure
- Tolerances tighter than ±0.005 in. require accounting for thermal expansion (10× higher than steel)
- Filled grades (glass, carbon) are more dimensionally stable and hold tighter tolerances than virgin
The PTFE machining guide covers speeds, feeds, tolerances, and fixturing in detail.
Comparison with Competing Fluoropolymers and Polymers
PTFE does not exist in isolation. Engineers frequently evaluate it against PVDF, UHMW, PEEK, and PFA for cost, machinability, or mechanical performance.
- PVDF vs PTFE: PVDF is stiffer, easier to machine, and much less expensive, but its temperature and chemical resistance ceilings are lower. See the PVDF vs PTFE comparison.
- UHMW vs PTFE: UHMW is far cheaper and has excellent impact resistance, but the temperature limit is ~200°F and chemical resistance is limited. See the UHMW vs PTFE comparison.
- PEEK vs PTFE: PEEK is dramatically stiffer and stronger with lower creep, but costs 3–5× more per pound and has limited chemical resistance against some acids. See the PEEK vs PTFE comparison.
- PFA vs PTFE: PFA is melt-processable and has equivalent chemical resistance, making it the choice for complex molded shapes; PTFE remains the standard for stock shapes and precision machined parts.
For a structured comparison index, visit PTFE comparisons.
FDA and Food-Grade Status
Virgin PTFE is listed in FDA 21 CFR 177.1550 for repeated use in contact with food. This makes it a standard choice for seals, bearings, and conveyor components in food processing and pharmaceutical equipment. Filled grades (glass, carbon, bronze) require review on a case-by-case basis — not all fillers maintain FDA status. See PTFE FDA food-grade compliance for details on applicable grades and NSF/3-A certification.
Procurement and Sourcing
PTFE stock shapes are available cut-to-order in virgin and filled grades from distribution. Lead times for standard sizes are typically one to three days from stock; custom-pressed blanks, large-diameter rods, or precision-ground billets may require one to three weeks.
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