Abstract

Perfluorinated ethylenepropylene (FEP) is a copolymer of tetrafluoroethylene (TFE) and hexafluoropropylene (HFP). It retains most of the desirable characteristics of polytetrafluoroethylene (PTFE) but with a melt viscosity low enough for conventional melt processing. The introduction of hexafluoropropylene lowers the melting point of PTFE from 327C to about 260C. The lower melt viscosity allows melt extrusion of wire insulation of longer continuous lengths than the batchwise paste extrusion of PTFE and the injection molding of intricate shaped parts. This polymer has a combination of properties that make it useful in applications that require chemical inertness, excellent dielectric properties, good weatherability, antistick properties, low coefficient of friction, and performance in temperature extremes. As a thermoplastic, it can be processed by extrusion and compression, injection, and blow molding. Films can be heat bonded and sealed, vacuum formed, and laminated to various substrates.

Aqueous and nonaqueous dispersion polymerizations are the most convenient routes to producing these copolymers. The polymerization conditions are similar to those of TFE homopolymer dispersion polymerization. The optimal composition of the copolymer requires that the mechanical properties are retained in the usable range and that the melt viscosity is low enough for easy melt processing.