Fluorinated ethylene-propylene resin properties

Fluorinated ethylene-propylene resin (FEP, PFEP) n. This member of the fluorocarbon family is a copolymer of tetrafluoroethy-lene and hexafluoropropylene, possessing most of the desirable properties of PTFE, yet truly meltable and, therefore, process-able in conventional extrusion and injection-molding equipment. It is available in pellet form for those operations and as dispersions for spraying and dipping. 

These materials were first introduced by Du Pont in 1956 and are now known as Teflon FEP resins. (FEP = fluorinated ethylene-propylene.) Subsequently other commercial grades have become available (Neoflon by Daikin Kogyo and Teflex by Niitechim, USSR). These copolymers may be regarded as the first commercial attempt to provide a material with the general properties of PTFE and the melt processability of the more conventional thermoplastics. 

Copolymers of tetrafluoroethylene were developed in attempts to provide materials with the general properties of PTFE and the melt process-ability of the more conventional thermoplastics. Two such copolymers are tetrafluoroethylene-hexafluoropropylene (TFE-HFP) copolymers (Teflon FEP resins by Du Pont FEP stands for fluorinated ethylene propylene) with a melting point of 290°C and tetrafluoroethylene-ethylene (ETFE) copolymers (Tefzel by Du Pont) with a melting point of 270°C. These products are melt processable. A number of other fluorine containing melt processable polymers have been introduced. 

It can be seen in Table 4.3 that electrical properties cover a wide range and thus the volume resistivity of various polymers is between 2 ohm.cm for epoxy resins to 10 ohm.cm for fluorinated ethylene-propylene copolymer. Similarly, dielectric strength is in the range from 12 mV/m for urea-formaldehyde resins to 55 mV/m for fluorinated ethylene-propylene copolymer and 60 mV/m for PA 12. 

Fluorinated ethylene propylene (FEP) is an effective alternative to PTFE Teflon. Sharing many of the properties of PTFE, e.g. can be heat-shaped, but being less permeable to gases and also more transparent. In fact, FEP is the most transparent of all resins in the Teflon family. 

Figure 6-61. Heat-resistance properties of resins retaining 50 percent of properties obtainable at room temperature with resin exposure and testing at elevated temperature. Zone 1 Acrylics, cellulose esters, LDPE, PS, PVC, SAN, SBR, UF, etc. Zone 2 Acetals, ABS, chlorinated polyether, ethyl cellulose, EVA, ionomer, PA, PC, HDPE, PET, PP, PVC, PUR, etc. Zone 3 PCTFE, PVDF, etc. Zone 4 Alkyds, fluorinated ethylene-propylene, MF, polysulfone, etc. Zone 5 TS acrylic, DAP, epoxy, PF, TS polyester, PTFE, etc. Zone 6 Parylene, polybenzimidazole, silicone, etc. Zone 7 PAI, PI, etc. Zone 8 Plastics in R D etc. Since plastics compounding is rather extensive, certain basic resins can be modified to meet different heat-resistance properties.

The materials examined were high and low density polyethylene, silvered fluorinated ethylene propylene teflon blanket material, polysulphone matrix resin/graphite fibre reinforced composites, poly(methyl methacrylate) and silicones [326, 450,1326, 2314]. Long term exposed polymeric samples show loss of surface integrity and surface erosion. The radiation combines with atomic oxygen to initiate chain scission and crosslinking, both of which greatly affect the polymers structural properties. 

Potentially, this direct fluorination process is a new approach to the synthesis of fluorocarbon polymers. Polyethylene, polypropylene, polystyrene, polyacrylonitrile, polyacrylamide, resor phenol formaldehyde resin, and ethylene propylene copolymer have been fluorinated to produce perf1uorocarbon polymers which are structurally similar to the hydrocarbon starting materials and have physical properties similar to known structurally related fluorocarbon polymers obtained by polymerization of fluorocarbon monomers. High yield of fluorocarbon polymers approaching 100 have been obtained. This direct technique used for fluorination of hydrocarbons and polymers is called the LaMar process and has been previously described in connection with the direct fluorination of Lt ver molecular weight species ". ... 

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