FEP Ext-LowMFI
Grade
ASTM D3368 · ISO 21138 · also Fluorinated Ethylene Propylene, Teflon FEP
Pick for thick-wall tube, rod, liners and heavy cable jackets where stress-crack resistance and melt strength matter more than cycle time.
Values for the Ext-LowMFI condition
Other FEP grades and fills
FEP is listed in 4 conditions; see the grade overview at FEP.
- IM-HighMFI
- Dispersion
- Ext-LowMFI
- GF20
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 |
Ext-LowMFIThis page 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 |
What is FEP Ext-LowMFI?
FEP Ext-LowMFI is FEP in the Ext-LowMFI grade — pick for thick-wall tube, rod, liners and heavy cable jackets where stress-crack resistance and melt strength matter more than cycle time. FEP Ext-LowMFI has a yield strength of 14 MPa (2.03 ksi) and a tensile strength of 25 MPa (3.63 ksi) — weaker than 84% of polymer grades. Elongation at break is 340% and the elastic modulus is 0.5 GPa (0.0725 Msi). FEP Ext-LowMFI 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
- Forms and bends easily — 90/100, better than 91% of polymer grades
- High service temperature — 205°C (401 °F), better than 88% of polymer grades
Limitations
- Heavy — 2.15 g/cm³ (0.0777 lb/in³), worse than 99% of polymer grades
- High mold shrinkage — 3.8%, worse than 99% of polymer grades
- High embodied carbon — 12 kg CO₂/kg, worse than 91% of polymer grades
- Low strength — 14 MPa (2.03 ksi), worse than 84% of polymer grades
FEP Ext-LowMFI properties
Typical room-temperature values for FEP Ext-LowMFI; 25 are specific to this condition. Other listed values are FEP reference data and may not represent this condition. Bars are the position among polymer grades.
Physical7
FEP Ext-LowMFI 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 Ext-LowMFI has a yield strength of 14 MPa (2.03 ksi) and a tensile strength of 25 MPa (3.63 ksi) — weaker than 84% of polymer grades. Elongation at break is 340% and the elastic modulus is 0.5 GPa (0.0725 Msi).
Thermal10
FEP Ext-LowMFI is rated for continuous service to 205°C (401 °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 Ext-LowMFI 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 Ext-LowMFI 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 Ext-LowMFI's machinability is good (55/100, worse than 64% of polymer grades); weldability very good (78/100); formability excellent (90/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with FEP Ext-LowMFI
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 Ext-LowMFI — frequently asked
What is FEP Ext-LowMFI used for?
FEP Ext-LowMFI 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 Ext-LowMFI?
FEP Ext-LowMFI has a typical yield strength of 14 MPa (2.03 ksi) and a tensile strength of 25 MPa (3.63 ksi) — weaker than 84% of polymer grades. Strength varies by condition: see the 4 listed tempers.
Is FEP Ext-LowMFI 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 Ext-LowMFI be welded?
Yes — weldability is rated very good (78/100). 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 Ext-LowMFI?
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 Ext-LowMFI 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 Ext-LowMFI?
FEP Ext-LowMFI is rated for continuous use to about 205°C (401 °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 Ext-LowMFI?
Yes — FEP Ext-LowMFI 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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.