Fluorinated Ethylene Propylene
Fluorinated ethylene propylene or FEP is a copolymer of hexafluoropropylene and tetrafluoroethylene. It differs from the PTFE (polytetrafluoroethylene) resins in that it is melt-processible using conventional injection molding and screw extrusion techniques.
Fluorinated ethylene propylene was invented by DuPont and is sold under the brandname Teflon FEP. Other brandnames are Neoflon FEP from Daikin or Dyneon FEP from Dyneon/3M.
FEP is very similar in composition to the fluoropolymers PTFE (polytetrafluoroethylene) and PFA (perfluoroalkoxy polymer resin). FEP and PFA both share PTFE's useful properties of low friction and non-reactivity, but are more easily formable. FEP is softer than PTFE and melts at 260 °C; it is highly transparent and resistant to sunlight.
Density 2150 kg/m3
Flexural modulus(E) 586 MPa
Tensile strength(t) 23 MPa
Elongation @ break 325%
Folding endurance Varies
Notch test Melting point 260 °C
Maximum operating temperature 204 °C
Water absorption (ASTM) <0.01 % after 24 hours
Dielectric constant (Dk) at 1MHz 2.1
Dissipation factor at 1MHz 0.0007
Arc resistance < 300 seconds
Resistivity at 50% R.H. > 1016Ω m
Properties Useful comparison tables of PTFE against FEP, PFA and ETFE can be found on DuPonts website, listing the mechanical, thermal, chemical, electrical and vapour properties of each, side by side.
In terms of corrosion resistance, FEP is the only other readily available fluoropolymer that can match PTFE's own resistance to caustic agents, as it is a pure carbon-fluorine structure and fully fluorinated
Thermally, FEP stands out from PTFE and PFA by having a melting point of 260 °C (500 °F), around forty degrees lower than PFA and lower again than PTFE.
Electrically, PTFE, FEP and PFA have identical dielectric constants, but FEP's dielectric strength is only surpassed by PFA. However, while PFA has a similar dissipation factor to PTFE, FEP's dissipation is around six times that of PFA and EFTE (making it a more non-linear conductor of electrostatic fields)
Mechanically, FEP is slightly more flexible than PTFE. Perhaps surprisingly, it does not withstand repetitive folding as well as PTFE. It also features a poorer co-efficient of dynamic friction, is softer and has a slightly lower tensile strength than PTFE and FAP A noteworthy property of FEP is that it is vastly superior to PTFE in some coating applications involving exposure to detergents
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