FEP Polymer: Properties, Uses & Cost Guide
Tensile data verified against MatWeb.com database & manufacturer datasheets · Last updated July 2026
Published: 2026-05-30
Fluorinated ethylene propylene (FEP) is a fully fluorinated melt-processable fluoropolymer—a copolymer of tetrafluoroethylene (TFE) and hexafluoropropylene (HFP). The HFP comonomer introduces -CF₃ side groups that disrupt the PTFE crystal...
Fluorinated ethylene propylene (FEP) is a fully fluorinated melt-processable fluoropolymer—a copolymer of tetrafluoroethylene (TFE) and hexafluoropropylene (HFP). The HFP comonomer introduces -CF₃ side groups that disrupt the PTFE crystal lattice, reducing crystallinity from PTFE's ~90% to FEP's ~50-70% and enabling conventional melt processing while maintaining the fully fluorinated chemistry that provides near-universal chemical resistance. In effect, FEP is the melt-processable version of PTFE—it offers PTFE-level chemical inertness in a form that can be injection molded, extruded, and thermoformed.
FEP is naturally transparent (the reduced crystallinity allows visible light transmission), which is a distinguishing feature among fluoropolymers—PTFE and PFA are opaque white. This transparency makes FEP the material of choice for chemical process sight glasses, laboratory tubing where fluid visibility is required, and molded components for analytical instruments. FEP processes at melt temperatures of 330-370°C with mold temperatures of 150-200°C. Its continuous service temperature of 200°C is lower than PTFE/PFA (260°C) due to the reduced crystallinity, but this is sufficient for most chemical processing and laboratory applications. FEP's main limitation is low mechanical strength (23 MPa tensile, the lowest among engineering fluoropolymers) and susceptibility to stress cracking at elevated temperature under sustained load.
Recommended Applications
FEP Fluorinated Ethylene Propylene is commonly specified for:
⚠ Not Recommended For
FEP Fluorinated Ethylene Propylene is not recommended for:
- High-pressure sealing applications (FEP creeps more than PTFE — lower melt viscosity means more cold flow)
- Structural applications (tensile strength only 20-30 MPa; use PEEK or PEI instead)
- Applications requiring stiffness (FEP is significantly less stiff than PTFE or PFA)
Selection & Application Guide
FEP (fluorinated ethylene propylene) is the transparent, melt-processable fluoropolymer that bridges the gap between PTFE and commodity plastics. Choose FEP when you need PTFE-like chemical resistance and non-stick properties in a melt-processable, transparent form. FEP's 200°C service temperature is lower than PTFE's 260°C, but its processability and transparency open applications that PTFE cannot serve.
Real-World Applications
FEP's transparency for fluid visibility, chemical inertness, and non-stick surface make it standard for laboratory transfer tubing and peristaltic pump applications.
FEP provides excellent dielectric properties and flame resistance for plenum-rated communications cable and high-frequency coaxial cable insulation.
FEP's non-stick surface and chemical resistance suit it for roller coverings in fusing, laminating, and processing equipment where material must not adhere.
FEP's ultra-high purity grades and chemical resistance to etching acids make it suitable for wafer processing baskets and carriers.
Processing & Cost Considerations
Manufacturing Tips
- FEP processes at 340-380°C melt temperature — achievable on standard high-temperature equipment. It has good melt flow for a fluoropolymer, enabling injection molding and extrusion of complex shapes that PTFE cannot achieve.
- FEP has low melt strength — it tends to sag during extrusion. Use lower take-up speeds and proper cooling for consistent tubing and profile dimensions. Die design must account for significant die swell.
- FEP adheres poorly to most substrates. Surface treatment (sodium etching or plasma) is required for bonding or coating applications. Mechanical interlocking is preferred for non-adhesive applications.
FEP costs $40-80/kg — more than ETFE ($30-60/kg) but less than PFA ($50-100/kg). FEP offers PTFE-like properties at a lower total processing cost due to melt processability. For applications requiring transparency plus chemical resistance below 200°C, FEP is typically the most economical fluoropolymer choice.
Technical Properties
| Density | 2.15 g/cm³ |
|---|---|
| Tensile Strength | 23 MPa |
| Melting Point | 260 °C |
| Shrinkage Rate | 3.0-5.0% |
| Flexural Modulus | 0.5 GPa |
| Hdt | 55 °C at 1.82 MPa |
| Continuous Service Temp | 200 °C |
Engineering Tool: Shrinkage & Cost Estimator
Calculate part weight, mold cavity dimensions accounting for shrinkage, and material cost — all locally in your browser.
Equivalents & Cross-References
| Equivalent / Alternate | Action |
|---|---|
| Chemours Teflon FEP | |
| Dyneon FEP | |
| Daikin Neoflon FEP |
Frequently Asked Questions
When should I specify FEP over PFA for a fluoropolymer application?
FEP is preferred over PFA when (1) optical transparency is required—FEP is naturally clear, PFA is opaque white; (2) the application temperature is below 200°C, making PFA's 260°C rating unnecessary; (3) cost is a significant factor—FEP is typically 20-30% less expensive than PFA. PFA is preferred when (1) the application requires the full 260°C continuous service temperature; (2) higher mechanical strength at temperature is needed (PFA retains ~15% higher tensile at 200°C than FEP); (3) flex life is critical—FEP has a lower flexural modulus but is more prone to flex cracking over repeated cycling; (4) the application involves permeation-sensitive environments—PFA's lower gas permeability (~50% less than FEP) is critical for ultra-high-purity semiconductor chemical delivery.
How does FEP compare to PFA?
Both are melt-processable fluoropolymers with similar chemical resistance. PFA offers higher service temperature (260°C vs 200°C for FEP) and better mechanical properties at elevated temperature. FEP is less expensive, more transparent, and easier to process. Choose FEP when temperatures stay below 200°C; PFA for higher temperatures.
Is FEP safe for food contact?
Yes. FEP complies with FDA 21 CFR 177.1550 for repeated food contact. It is also USP Class VI certified for medical device applications. FEP's non-porous surface and chemical inertness prevent contamination and allow easy cleaning.
Can FEP be used for high-frequency applications?
Yes. FEP has a very low dielectric constant (2.1) and dissipation factor (0.0002) that remain stable across frequencies from 1 kHz to 10 GHz. This makes FEP standard insulation for coaxial cables, microwave transmission lines, and high-frequency test equipment.
What colors are available for FEP?
Natural FEP is water-clear transparent. It can be pigmented in various colors for wire identification, but colorants may slightly reduce chemical resistance and purity. For semiconductor and pharmaceutical applications, natural (unpigmented) FEP is standard.
How does FEP handle cryogenic temperatures?
FEP remains flexible and retains its mechanical properties down to -200°C, making it suitable for cryogenic fluid transfer lines and liquid nitrogen handling equipment. Unlike many polymers, FEP does not become brittle at cryogenic temperatures.
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References & Industry Standards
- ASTM International. Standard Specifications for Engineering Plastics & Thermoplastics. astm.org
- UL Prospector. Plastics & Elastomers Material Database. ulprospector.com
- MatWeb. Material Property Data for Engineering Thermoplastics. matweb.com
- ISO 1043. Plastics — Symbols and Abbreviated Terms. iso.org