FEP · grade · default condition
FEP Unfilled
Properties of the Unfilled condition, compared with the other FEP grades.
Default choice for wire insulation, tubing, film and lined parts where full chemical inertness and clarity are wanted.
What is FEP Unfilled?
FEP Unfilled is FEP in the Unfilled grade — default choice for wire insulation, tubing, film and lined parts where full chemical inertness and clarity are wanted. FEP Unfilled has a yield strength of 13 MPa (1.89 ksi) and a tensile strength of 23 MPa (3.34 ksi) — weaker than 91% of polymer grades. Elongation at break is 320% and the elastic modulus is 0.48 GPa (0.0696 Msi). FEP Unfilled 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).
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 84% 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
- Low strength — 13 MPa (1.89 ksi), worse than 91% of polymer grades
- High embodied carbon — 12 kg CO₂/kg, worse than 91% of polymer grades
FEP Unfilled properties
Typical room-temperature values for FEP Unfilled — 7 properties are specific to this condition; the rest are grade-level values shared by every FEP grade. Each bar shows where the value sits among the polymer grades in FabDigit's library — further right is higher.
Physical7
FEP Unfilled 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 Unfilled has a yield strength of 13 MPa (1.89 ksi) and a tensile strength of 23 MPa (3.34 ksi) — weaker than 91% of polymer grades. Elongation at break is 320% and the elastic modulus is 0.48 GPa (0.0696 Msi).
Thermal10
FEP Unfilled 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 Unfilled 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 Unfilled 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 Unfilled's machinability is good (55/100, worse than 63% 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.
Other FEP grades and fills
FEP is also supplied in 5 other conditions. The full side-by-side table is on the FEP overview.
- UnfilledDefaultDefault choice for wire insulation, tubing, film and lined parts where full chemical inertness and clarity are wanted.23 MPa tensile
- GF20Use where FEP's chemical resistance is needed but creep, stiffness and dimensional stability of the unfilled resin are inadequate.24 MPa tensile
Working with FEP Unfilled
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.
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.
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 |
FEP Unfilled — frequently asked
What is FEP Unfilled used for?
FEP Unfilled 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 Unfilled?
FEP Unfilled has a typical yield strength of 13 MPa (1.89 ksi) and a tensile strength of 23 MPa (3.34 ksi) — weaker than 91% of polymer grades. Strength varies by condition: see the 6 listed tempers.
Is FEP Unfilled easy to machine?
Reasonably — machinability is rated good (55/100, worse than 63% 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 Unfilled 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 Unfilled?
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 Unfilled 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 Unfilled?
FEP Unfilled 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.
Can FabDigit make parts in FEP Unfilled?
Yes — FEP Unfilled is available for CNC machining, sheet metal and injection molding with instant online pricing. 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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.