FEP
ASTM D3368 · ISO 21138 · also Fluorinated Ethylene Propylene, Teflon FEP
FEP (Teflon FEP, ASTM D3368) is a melt-processable copolymer of tetrafluoroethylene and hexafluoropropylene that keeps close to PTFE's chemical inertness, very low dielectric loss and non-stick surface while being injection mouldable, extrudable and blown into film.
FEP grades and fills
FEP is supplied in 4 conditions, soft to hard.
Compare all 4 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Injection-moulding grade, high MFI (e.g. FEP 4100-type) | Use for thin-wall or complex injection-moulded fittings, valve parts and connectors needing easy cavity fill. | 12 | 20 | 290 | 55 Shore D |
Aqueous dispersion / coating powder grade | Chosen for non-stick and anti-corrosion coatings on metal (tanks, rolls, cookware, glass-cloth impregnation) rather than for structural parts. | 12 | 20 | 250 | 54 Shore D |
Extrusion grade, low MFI / high molecular weight (e.g. FEP 140-type) | Pick for thick-wall tube, rod, liners and heavy cable jackets where stress-crack resistance and melt strength matter more than cycle time. | 14 | 25 | 340 | 57 Shore D |
20 % glass-fibre reinforced FEP compound | Use where FEP's chemical resistance is needed but creep, stiffness and dimensional stability of the unfilled resin are inadequate. | 24 | 15 | 63 Shore D |
Supply forms, finishes and certifications
Ways FEP is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
FDA-Med | FDA / USP Class VI medical & food-contact grade | Certification |
UnfilledDefault | Natural (translucent) FEP resin, general purpose | Standard supply |
What is FEP?
FEP (Teflon FEP, ASTM D3368) is a melt-processable copolymer of tetrafluoroethylene and hexafluoropropylene that keeps close to PTFE's chemical inertness, very low dielectric loss and non-stick surface while being injection mouldable, extrudable and blown into film. Typical forms are high-frequency coaxial cable insulation, corrosion-resistant tubing and linings, transparent chemical and solar films, and medical tubing, at 23 MPa tensile and 320 % elongation. Continuous service is about 200 °C against 260 °C for PTFE, stiffness and creep resistance are low, resin cost is high, and processing releases corrosive HF gas, so extraction is mandatory. PFA is the nearest higher-temperature alternative. FEP has a density of 2.15 g/cm³ (0.0777 lb/in³), heavier than 99% of polymer grades. Its glass-transition temperature is -90°C (-130 °F). FEP has a yield strength of 13 MPa (1.89 ksi) and a tensile strength of 23 MPa (3.34 ksi) — weaker than 86% of polymer grades. Elongation at break is 320% and the elastic modulus is 0.48 GPa (0.0696 Msi).
What is FEP used for?
- High-frequency coaxial cable insulation
- Corrosion-resistant tubing and pipe linings
- Transparent chemical labware
- Solar module and chemical process film
- Medical catheters and tubing
- Heat-shrink sleeving
- Release film and non-stick surfaces
Advantages
- Good corrosion resistance — 98/100, better than 99% of polymer grades
- Good UV / weathering resistance — 98/100, better than 99% of polymer grades
- Low moisture uptake — 0.01%, better than 97% of polymer grades
- High service temperature — 200°C (392 °F), better than 87% of polymer grades
- Readily welded — 80/100, better than 86% of polymer grades
Limitations
- Heavy — 2.15 g/cm³ (0.0777 lb/in³), worse than 99% of polymer grades
- High mold shrinkage — 4%, worse than 99% of polymer grades
- High embodied carbon — 12 kg CO₂/kg, worse than 91% of polymer grades
- Low strength — 13 MPa (1.89 ksi), worse than 86% of polymer grades
FEP properties
Typical room-temperature values in the Unfilled condition; bars are the position among polymer grades.
Physical7
FEP has a density of 2.15 g/cm³ (0.0777 lb/in³), heavier than 99% of polymer grades. Its glass-transition temperature is -90°C (-130 °F).
Mechanical11
FEP has a yield strength of 13 MPa (1.89 ksi) and a tensile strength of 23 MPa (3.34 ksi) — weaker than 86% of polymer grades. Elongation at break is 320% and the elastic modulus is 0.48 GPa (0.0696 Msi).
Thermal10
FEP is rated for continuous service to 200°C (392 °F). It conducts heat at 0.2 W/m·K (0.116 BTU/hr·ft·°F), worse than 56% of polymer grades. Thermal expansion is 100 µm/m·K (55.6 µin/in·°F).
Electrical7
FEP is an electrical insulator with a dielectric strength of 24 kV/mm (609.6 V/mil) and a resistivity of 1×10¹⁶ Ω·m.
Chemical & Environmental3
Corrosion resistance is excellent (98/100), better than 99% of polymer grades. UV resistance is excellent.
Sustainability4
Producing a kilogram of FEP takes about 220 MJ of energy and emits 12 kg of CO₂ — more than 90% of polymer grades. Typical recycled content is 0%.
Manufacturability8
FEP's machinability is good (55/100, worse than 64% of polymer grades); weldability very good (80/100); formability very good (75/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the polymer family
Yield strength against density for every polymer grade FabDigit runs. FEP is highlighted; hover a dot for its name, or open the interactive family chart.
Working with FEP
Is FEP easy to machine?
Machines easily but is soft and springy — use sharp positive-rake carbide tools, high speed, light feed, and support thin walls; expect elastic recovery, so cut slightly oversize and allow parts to relax before final measurement.
Can FEP be welded?
Fully melt-fusible: hot-gas, heat-sealing, impulse and butt-fusion joining all work above ~300 °C; adhesive bonding requires sodium-etch or plasma surface treatment.
Can FEP be formed, bent or molded?
Extrude/injection mould at 315–380 °C melt with corrosion-resistant (Hastelloy/nickel-alloy) screws and dies; use ~200 °C tool temperature, slow cooling to limit voids, and mandatory HF-rated ventilation.
Manufacturability
The process limits FabDigit applies to FEP. Every FEP part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Good55 / 100 |
|---|---|
| ISO material group | N.8 |
| Cutting speed (rough / finish) | 400 / 500 m/min |
| Minimum wall | 0.5 mm |
| Minimum internal radius | 1 mm |
| Drill depth limit | 10× diameter |
| Best surface (machined / polished) | Ra 0.8 / — |
| Hardenable after machining | No |
Sheet metal
| Formability | Better75 / 100 |
|---|---|
| Weldability | Fair80 / 100 |
Injection molding
| Mold shrinkage | — |
|---|---|
| Wall thickness | — – — |
| Recommended draft | — |
| Pre-drying | — |
FEP chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| tetrafluoroethylene (TFE)wt% of copolymer backbone | 85 – 95 | 88 |
| hexafluoropropylene (HFP)comonomer that lowers Tm and enables melt processing | 5 – 15 | 12 |
| perfluoro(alkyl vinyl ether) (PPVE)optional third monomer in modified FEP (e.g. FEP-100 series) for crack resistance | 0 – 1 | 0.3 |
What surface finishes work on FEP?
Cannot be painted or plated without sodium-naphthalene etch or plasma activation; normally used as-moulded with a naturally low-friction, non-stick, translucent surface.
Surface treatments FabDigit runs on polymer parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Injection Molding Coating
Organic Coating
Metallization / Functional
Equivalent designations
Standards and trade names that resolve to FEP in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- ASTM
- D3368
- ISO
- 21138
- Trade names
- Fluorinated Ethylene PropyleneTeflon FEP
- Also called
- F46
How much does FEP cost?
FEP is a specialty-cost polymer ($$$$$), pricier than about 99% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
FEP — frequently asked
What is FEP used for?
FEP is typically used for high-frequency coaxial cable insulation, corrosion-resistant tubing and pipe linings, transparent chemical labware, solar module and chemical process film, medical catheters and tubing and heat-shrink sleeving. In short: high-heat chemical resistant.
What is the yield strength of FEP?
FEP has a typical yield strength of 13 MPa (1.89 ksi) and a tensile strength of 23 MPa (3.34 ksi) — weaker than 86% of polymer grades. Strength varies by condition: see the 4 listed tempers.
Is FEP easy to machine?
Reasonably — machinability is rated good (55/100, worse than 64% of polymer grades). Machines easily but is soft and springy — use sharp positive-rake carbide tools, high speed, light feed, and support thin walls; expect elastic recovery, so cut slightly oversize and allow parts to relax before final measurement.
Can FEP be welded?
Yes — weldability is rated very good (80/100). Fully melt-fusible: hot-gas, heat-sealing, impulse and butt-fusion joining all work above ~300 °C; adhesive bonding requires sodium-etch or plasma surface treatment.
What surface finishes work on FEP?
Cannot be painted or plated without sodium-naphthalene etch or plasma activation; normally used as-moulded with a naturally low-friction, non-stick, translucent surface.
Can FEP be formed, bent or molded?
Extrude/injection mould at 315–380 °C melt with corrosion-resistant (Hastelloy/nickel-alloy) screws and dies; use ~200 °C tool temperature, slow cooling to limit voids, and mandatory HF-rated ventilation.
What is the maximum service temperature of FEP?
FEP is rated for continuous use to about 200°C (392 °F), and briefly to 230°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does FEP cost?
FEP is a specialty-cost polymer ($$$$$), pricier than about 99% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Can FabDigit make parts in FEP?
Yes — FEP is available for CNC machining, sheet metal and injection molding; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- ASTM D2116 – Standard Specification for FEP-Fluorocarbon Molding and Extrusion Materials — ASTM International (2018)
- ASTM D3159 – FEP Fluorocarbon Film (Extruded) — ASTM International (2015)
- Teflon FEP Fluoroplastic Resin – Properties Handbook — Chemours (formerly DuPont) (2019)
- Neoflon FEP Technical Information — Daikin Industries (2020)
- Dyneon FEP Product Comparison Guide — 3M / Dyneon (2018)
- Fluoroplastics Vol. 1 & 2 (Melt-Processible Fluoropolymers) — Ebnesajjad / Elsevier (2015)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.