Containing Vinylidene Fluoride

Of these materials the most widely used and most studied are the vinylidene fluoride/hexafluoropropylene copolymers and the terpoly-mers which also contain tetrafluoroethylene. They are generally superior in heat and fluid resistance to the other types. The copolymer of vinylidene fluoride and chlorotrifluoroethylene has superior resistance of oxidizing acids such as fuming nitric acid. The copolymer containing 70 mole% vinylidene fluoride (Kel F 3700) has good low temperature flexibility. 

Hexafluoropropylene, in common with the perfluoro derivatives of other alkenes such as 1-butene, 2-butene, isobutene, 1-pentene and 1-nonene, does not homopolymerize but readily copolymerizes with other alkenes (Adams and Bovey, 1952). 

The commercial elastomers are commonly prepared by aqueous emulsion polymerization at elevated temperatures and pressures using a redox initiating system such as a bisulphite-persulphate mixture. Ammonium perfluorooctoate or some other highly fluorinated surfactant is used as a dispersing agent since it is important that any surfactant used does not become involved in transfer reactions. 

NMR spectroscopy (Ferguson, 1960) of vinylidene fluoride/ hexofluoropropylene (VDF/HFP) copolymers containing 60-85 mole% of VDF has indicated that, as might be expected with a monomer that does not homopolymerize, the HFP residues do not occur adjacent to one another and that where there are adjacent VDF residues these almost always join in a head-to-tail fashion. The linking of HFP to VDF occurs about 13 times more frequently in mode A than in mode B. 

The elastomers based on vinylidene fluoride are saturated and cannot be vulcanized with sulphur. As with other saturated rubbers cross-linking can be brought about by irradiation and by the use of peroxides but the only agents of commercial importance until the 1970s were diamines and certain of their derivatives. Of particular importance have been the amine carbamates which are somewhat less reactive and less likely to scorch (premature vulcanization) during processing. Typical materials of this class are ethylene diamine carbamate (IX), hexamethylene diamine carbamate (X) and N,N -dicinnamylidene-1,6-hexane diamine (XI)  

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L. D. Albia and M. M. Lynn, Chemistry of Elastomers Containing Vinylidene Fluoride, at the MCA Meeting of the Energy Rubber Group, Rubber Division, Educational Symposium, Arlington, Tex, Sept. 23, 1985, American Chemical Society, Washiagton, D.C. 

Starting in 1969, D.E. Rice used this method to prepare dicarboxylic oligomers which contained vinylidene fluoride and perfluoropropene. He used the way these fluorinated monomers fit the reaction of chain-termination by recombination but the basic difficulty lay in the preparation of the difunctional initiator [80-83] ... 

Also, FEPM is a class of fluoroelastomers prepared from monomeric units containing one or more alkyl, perfluoroalkyl, or perfluoroalkoxy groups, with a reactive pendant group. This class of fluoroelastomers does not contain vinylidene fluoride monomer units. 

The inability to process PTFE by conventional thermoplastics techniques has nevertheless led to an extensive search for a melt-processable polymer but with similar chemical, electrical, non-stick and low-friction properties. This has resulted in several useful materials being marketed, including tetrafluoro-ethylene-hexafluoropropylene copolymer, poly(vinylidene fluoride) (Figure 13.1(d)), and, most promisingly, the copolymer of tetrafluoroethylene and perfluoropropyl vinyl ether. Other fluorine-containing plastics include poly(vinyl fluoride) and polymers and copolymers based on CTFE. 

Silastic LS 420, possessing approximately Q.6%-0.9% pendant vinyl groups, was blended with Kynar 7201, a vinylidene fluoride copolymer with tetrafluoroethylene (Atochem), in the presence of triallylisocyanurate (TAIC) and DAP containing a small amount of benzoyl peroxide in the DAP fraction. 

Taguet, A., Ameduri, B. and Boutevin, B. Crosslinking of Vinylidene Fluoride-Containing Fluoropolymers. Vol. 184, pp. 127-211. 

Beside SILP experiments with silica as support material, reports have also been made on the use of membranes coated with ionic liquid catalyst solution for the hydrogenation reaction of propene and ethene. The membranes were obtained by supporting various ionic liquids, each containing 16 to 23 mmol Rh(I) complex Rh(nbd)(PPh3)2 (nbd=norbornadiene), in the pores of poly(vinylidene fluoride) filter membranes [118]. 

The processability of fluorine-containing polymers is improved by replacement of one or more of the fluorine atoms. Replacing one of the eight fluorine atoms with a trifluoromethyl group gives a product called FEP or Viton, actually a copolymer of tetrafluoroethylene and hexafluoropropylene (Equation 6.53). Polytrifluoromonochloroethylene (PCTFE, Kel F) (Equation 6.54), in which one fluorine atom has been replaced by a chlorine atom, has a less regular structure and is thus more easily processed. Poly(vinylidene fluoride) (PVDF, Kynar) (Equation 6.55) is also more easily processable but less resistant to solvents and corrosives. 

Many other crosslinking reactions are used in commercial applications. A variety of halogen-containing elastomers are crosslinked by heating with a basic oxide (e.g., MgO or ZnO) and a primary diamine [Labana, 1986 Schmiegel, 1979]. This includes poly(epichlorohydrin) (Sec. 7-2b-6) various co- and terpolymers of fluorinated monomers such as vinylidene fluoride, hexafluoropropene, perfluoro(methyl vinyl ether), and tetrafluoroethylene (Sec. 6-8e) and terpolymers of alkyl acrylate, acrylonitrile, and 2-chloroethyl vinyl ether (Sec. 6-8e). 

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. 

PDD as well as other dioxoles have been copolymerized with monomers such as vinyl fluoride, vinylidene fluoride, tiifluoroediylene, perfluoroalkylethylenes, chlorotrifluoroethylene, hexafluoropropylene, and perfluorovinyl ethers, some of which contain functional groups. 

Materials. For holographic information storage, materials are required which alter their index of refraction locally by spotwise illumination with light. Suitable are photorefractive inorganic crystals, eg, LiNb03, BaTi03, LiTa03, and Bi SiO. Also suitable are photorefractive ferroelectric polymers like poly(vinylidene fluoride-co- trifluorethylene) (PVDF/TFE). Preferably transparent polymers are used which contain approximately 10% of monomeric material (so-called photopolymers, photothermoplasts). These polymers additionally contain different initiators, photoinitiators, and photosensitizers. 

Using the same method Akutin (7) was able to produce block and graft copolymers from several systems containing methyl methacrylate monomer and polydimethyl siloxane, polytrifluoroethylene or a copolymer tetrafluoroethylene-vinylidene fluoride. 

Table 11 shows very little variation in the orientation of the addition of trihalogenomethyl radicals to vinyl fluoride, but for vinylidene fluoride there is a 4.5-fold increase in the orientation ratio (kjkj across the table. This change in orientation does not follow polarity and suggests that steric effects may be having some effect. The rates relative to ethylene for the three fluorine-containing radicals are very similar. 

Commercial grades of vinylidene fluoride may contain an inhibitor such as the monomethyl ether of hydroquinone (MEHQ). This inhibitor can be removed by distillation or by washing with 25% by weight aqueous caustic under an inert atmosphere at low temperatures. 

The inclusion of the relatively large chlorine into the polymeric chain reduces the tendency to crystallize. Commercially available grades include a homopolymer, which is mainly used for special applications, and copolymers with small amounts (less than 5%) of vinylidene fluoride.84 The products are supplied as powder, pellets, pellets containing 15% glass liber, and dispersions. Low-molecular-weight polymer is available as oil or grease. The oil is used to plasticize PCTFE.85... 

Solutions of Biomer were obtained from Ethicon Inc. Biomer is poly (ether polyurethane) which contains urea linkage in the hard segment according to our IR analysis (19). Films of Biomer were cast on clean glass plates by diluting the polymer solution in dimethyl acetyl-amide. The films were dried in a vacuum oven at 50°C for 24 hr. The final film thickness was around 125/a. GPC analysis showed that the content of oligomers in Biomer was also negligible. Kel-F82, which is a copolymer composed of chlorotrifluoroethylene (97%) and vinylidene fluoride (3% ), was obtained from the 3M Company. 

Blends Containing Poly(Vinylidene Fluoride), Part IV, unpublished data. 

Blends Containing Poly (vinylidene Fluoride), Part I, Polym. Eng. Sci. 

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