|Flexural modulus(E)||586 MPa|
|Tensile strength(t)||23 MPa|
|Elongation @ break||325%|
|Melting point||260 °C|
|Water absorption (ASTM)||<0.01 % after 24 hours|
|Dielectric constant (Dk)|
|Arc resistance||< 300 seconds|
|Resistivity at 50% R.H.||> 1016 Ω m|
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® 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.
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, whilst 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 n
ETFE, in many ways, can be thought of as belonging to a different group, as it is essentially a high strength engineering version of the others featuring what are likely to be considered slightly diminished properties in the other fields when compared with PTFE, FEP and PFA.
Due to its flexibility, extreme resistance to chemical attack and optical transparency, this material, along with PFA is routinely used for plastic labware and tubing that involves critical or highly corrosive processes. Brand GmbH, Finemech, Savillex and Nalgene are well known laboratory suppliers that makes extensive use of the two materials.
Another application are sheet linings for chemical equipment where fabric backed PFA sheets (SYMALIT® PFA). The use of a PFA liner allows to replace expensive metals and alloys like Inconel or Hastelloy with lined carbon steel or lined FRP. Examples are SYMALIT® PFA lined columns, scrubbers, reactors and pipes which stand harsh environments like concentrated HF and HCl and halogens. Another application is for Co-axial cables like RG-316 In manufacturing high-quality composite parts, such as in the aerospace industry, FEP film can be used to protect molds during the curing process. In such applications, the film is called "release film" and is intended to prevent the curing adhesive polymer (e.g. the epoxy in a carbon fibre/epoxy composite laminate) from bonding to the metal tooling. One example is the A-5000 FEP release film by Richmond Aircraft Products (see link).