Vinylidene fluoride aqueous copolymerization

PDD readily copolymerizes with tetrafluoroethylene and other monomers containing fluorine, such as vinylidene fluoride (VDF), chlorotrifluoroethylene (CTFE), vinyl fluoride (VF), and propylvinyl ether (PVE) via free radical copolymerization, which can be carried out in either aqueous or nonaqueous media. It also forms an amorphous homopolymer with a Tg of 335°C (635°F) [2]. 

Apart from the fluoro monomers vinyl fluoride (VF), vinylidene fluoride (VF2), and tetrafluoroethylene (TFE), only chlorofluoroethylene has found commercial use as homopolymer. It is applied as thermoplastic resin based on its vapor-barrier properties, superior thermal stability (Tdec > 350 °C), and resistance to strong oxidizing agents [601]. Chlorofluoroethylene is homo- and copolymerized by free-radical-initiated polymerization in bulk [602], suspension, or aqueous emulsion using organic and water-soluble initiators [603,604] or ionizing radiation [605], and in solution [606]. For bulk polymerization, trichloroacetyl peroxide [607] and other fluorochloro peroxides [608,609] have been used as initiators. Redox initiator systems are described for the aqueous suspension polymerization [603,604]. The emulsion polymerization needs fluorocarbon and chlorofluorocarbon emulsifiers [610]. 

Chlorotrifluoroethylene (CTFE) can also be homo-and copolymerized by suspension and dispersion methods in aqueous andnonaqueous media. The copolymer of ethylene and CTFE is ECTFE, a melt processible polymer and a counterpart of ETFE. CTFE is also copolymerized with vinylidene fluoride (VDF). Higher VDF contents generate elastomeric polymers. Methods similar to those for PTFE are used to recover the polymer in various forms. Both powder and dispersion products are available. PCTFE can be processed by both non-melt techniques such as compression molding, and melt techniques such as injection molding and extrusion. Thicker parts are usually made by non-melt methods. 

Copolymerization of vinylidene fluoride and hexafluoropropylene (HFP) in an aqueous medium was reported in 1965.t l HFP content of the copolymer ranged from 1-13 mole%, depending on the composition of the reaction mixture and the polymerization conditions. The copolymers obtained at HFP content above 15 mole% were essentially amorphous and had low torsional modulus and high retention of rubbery properties over a wide temperature range without embrittlement. 

---