Perfluoromethylvinyl ether

Fluorocarbon elastomers represent the largest group of fluoroelastomers. They have carbon-to-carbon linkages in the polymer backbone and a varied amount of fluorine in the molecule. In general, they may consist of several types of monomers poly-vinylidene fluoride (VDF), hexafluoropropylene (HFP), trifluorochloroethylene (CTFE), polytetrafluoroethylene (TFE), perfluoromethylvinyl ether (PMVE), ethylene or propylene.212 Other types may contain other comonomers, e.g., 1,2,3,3,3-pentafluropropylene instead of HFP.213 Fluorocarbon elastomers exhibit good chemical and thermal stability and good resistance to oxidation. 

The need for highly fluorinated thermoplastic polymers that, unlike PTFE, could be fabricated by conventional melt-processing methods led to the development of a group of resins that are copolymers of tetrafluoroethylene (TFE) with other perflu-orinated monomers. Commercially, the copolymer of TFE and hexafluoropropylene (HFP) is commonly known as fluorinated ethylene propylene (FEP). Copolymerization of TFE with perfluoropropylvinyl ether (PPVE) leads to PFA resins, and copolymerization of TFE with perfluoromethylvinyl ether (PMVE) produces MFA resins. 

Note HFP, hexafluoropropylene PMVE, perfluoromethylvinyl ether CTFE, chlorotrifluoroethylene P, propylene HPFP, hydropentafluoropropane VDF, vinylidene V)... 

Perfluoroelastomers—that is, elastomers based on perfluoromethylvinyl ether and TFE—exhibit a virtually unmatched resistance to a broad class of chemicals except fluorinated solvents. On the other hand, they are adversely affected by hydraulic fluid, diethyl amine, and fumed nitric acid, which cause swelling of the elastomer by 41%, 61%, and 90%, respectively [11]. 

Perfluoroelastomers (ASTM designation FFKM) such as copolymers of tetrafluoro-ethylene (TEE) and perfluoromethylvinyl ether (PMVE) can maintain their thermal stability to temperatures as high as 300°C (572°F) or even higher, with a maximum continuous service temperature of 315°C (599°F). Moreover, instead of hardening, the elastomer becomes more elastic with aging [13]. 

Copolymers of TEE with ethylene, perfluoromethylvinyl ether (PMVE),... 

Perfluoromethylvinyl ether (PMVE) A monomer used for the production of methylfluoroalkoxy (MFA). 

A pioneering work on the WAHUHA multiple-pulse sequence applied to F NMR of a fluorinated polymer was reported by Ellett et al. [116]. They obtained resolved chemical shifts for the OCF3 and CF2 peaks (separation 73 ppm) of a copolymer of 60/40 TFE and perfluoromethylvinyl ether. Good agreement between the area of the peaks and the known composition of the copolymer was obtained. The anisotropy of the chemical shift of the CF2 groups was approximately determined. 

Hyfatol 16-95, Hyfatol 16-98. See Cetyl alcohol Hyfatol 18-95, Hyfatol 18-98. See Stearyl alcohol Hyfatol CS, Hyfatol CS/EP. See Cetearyl alcohol Hyflo Super-Cel . See Diatomaceous earth Hyflon MFA 620, Hyflon MPA 640. See Tetrafluoroethylene/perfluoromethylvinyl ether copolymer... 

Acrylic elastomer Acrylonitrile-butadiene rubber, hydrogenated Polyethylene, ultrahigh m.w. high-density Polynorbornene Polyurethane elastomer, thermoplastic Styrenated diphenylamine , Styrene-ethylene/butylene-styrene block copolymer seals, chemical-resistant Chlorotrifluoroethylene polymer seals, dynamic aerospace Polyfluoroalkoxyphosphazene seals, dynamic industrial Polyfluoroalkoxyphosphazene seals, dynamic military Polyfluoroalkoxyphosphazene seals, high performance Tetrafluoroethylene/perfluoromethylvinyl ether copolymer seals, oil... 

The even more unstable difluoroketene species was generated (Figure 7.15) in an Ar matrix at 7 K by photolysis of ionized perfluoromethylvinyl ether, CFj=C(F)OCF3. The barrier for dissociation of difluoroketene into CFj and CO is 10kcal/mol. The process is exothermic by 6kcal/mol. 

Both perfluoroethylvinyl ether (PEVE) and per-fluoropropylvinyl ether (PPVE) are effective in improving the high temperature mechanical properties of TFE/ HFP polymers. Perfluoromethylvinyl ether (PMVE) does not produce such improvements due to the small size of its pendent ether group that cannot efficiently disrupt the crystallization of the polymer chain (Table 5.6). 

FFKM is usually a copolymer of TFE (tetrafluoroethylene) and perfluoromethylvinyl-ether with a cure site monomer. See Figure 4.52. 

Unfortunately, while fluorine level is increased from typically 66% to 70%, low-temperature flexibility is reduced with glass transition temperatures increasing from — 19°C to —7°C. This drop can be compensated by the substitution of HFP by PMVE (perfluoromethylvinyl ether) a more expensive monomer that improves low-temperature performance by about 15°C. 

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