The carbon-fluorine bond is the most stable single bond.
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The high bond dissociation energy of the C-F bond is the main reason for the thermal, oxidative and chemical stability of fluorinated polymers. Table 1 lists the typical bond dissociation energies of single bonds.
Table 1. Typical bond dissociation energies for aliphatic bonds (kJ/mol).
Homo-polytetrafluoroethylene (PTFE) contains all C-F substitution, which makes it one of the most chemically and thermally stable polymers. However, PTFE has very high crystallinity. As a result, it is a rigid thermoplastic, not an elastomer. Randomly incorporating other monomers into homopolymers breaks the regularity andforms amorphous polymers with a low glass transition temperature. Perfluoromethylvinylether(PMVE) and other perfluoro (alkoxy/alkyl) vinyl ethers are the monomers that are incorporated withTFE monomer in most commercial perfluoroelastomers. If other partially fluorinated monomers are incorporated, it forms fluoroelastomers.
So, fluorinated elastomers containeither a partially or fully fluorinated backbone. If the backbone is fully fluorinated, it is a perfluoroelastomer (FFKM); if it is partially fluorinated, it is a fluoroelastomer (FKM). The polymer backbone comprises many repeating monomerunits. Typical monomer units for these polymers are shown below.
FFKM is marked under it brand names like Kalrez® (DuPont™) Tecnoflon® PFR (Solvay), Dyneon™ PFE (3M™) DAI-EL GA (Daikin) or Chemraz® (Greene Tweed)