Perfluoroalkoxy comonomers

Perfluoroalkoxy resin (PFA) is a copolymer of TFE and perflnoropropy-1 vinyl ether (PPVE) in a mole ratio of approximately 100 1. Even snch a small amonnt of comonomer is snflicient to prodnce a copolymer with a greatly rednced crystallinity. The relatively long side chains also markedly rednce the cold flow. Methylflnoroalkoxy resin (MFA), a copolymer of TFE and perfln-oromethylvinyl ether (PMVE), has similar properties with a somewhat lower melting point. 

Making a more dramatic change in the side group than that done in making FEP, chemists put a perfluoroalkoxy (PFA) group on the polymer chain. This group is signified as —O—Rf, where Rf can be any number of totally fluorinated carbons. The most common comonomer is perfluoropropyl (—O—CF2—CF2—CF3). However, other comonomers are shown in Table 9.3. 

Melt processing is achieved by reducing the crystallinity (PTFE 95% crystalline) through incorporation of a small concentration of a fluoro comonomer, e.g. hexafluoropropene or perfluoroalkoxy compounds. 

PFA polymers are fully fluorinated and melt processible. They have chemical resistance and thermal stability comparable to polytetrafluoroethylene (PTFE). Melt viscosity of PFA is over one million times lower than PTFE. Perfluoroalkoxy resins are in general copolymers of tetrafiuoroethylene with one or more of perfluoroalkyl vinyl ether comonomers. Commercial examples of the latter include perfluoromethyl vinyl ether (PMVE), perfluoroethyl vinyl ether (PEVE), and perfluoropropyl vinyl ether (PPVE). PFA resins are specified by ASTM Method D3307, which also provides procedures or references to other ASTM methods for the measurement of resin properties. Commercial PFA resins offered by major manufacturers have been listed in Tables 6.1 through 6.7. 

EKM Polymethylene fluoro rubber from vinylidene fluoride and a comonomer fluoro, alkyl, perfluoroalkyl, or perfluoroalkoxy substituent groups with... 

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