Vinylidene fluoride free radical polymerization

Solution polymerization. Solution polymerization involves polymerization of a monomer in a solvent in which both the monomer (reactant) and polymer (product) are soluble. Monomers are polymerized in a solution that can be homogeneous or heterogeneous. Many free radical polymerizations are conducted in solution. Ionic polymerizations are almost exclusively solution processes along with many Ziegler-Natta polymerizations. Important water-soluble polymers that can be prepared in aqueous solution include poly(acrylic acid), polyacrylamide, poly(vinyl alcohol), and poly(iV-vinylpyrrolidinone). Poly(methyl methacrylate), polystyrene, polybutadiene, poly(vinyl chloride), and poly(vinylidene fluoride) can be polymerized in organic solvents. 

Polyvinylidene fluoride (PVDF) is produced by free radical polymerization of vinylidene fluoride (CH2=CF2). The demand for PVDF has been growing remarkably because of its outstanding properties such as ... 

The proportion of head-to-head structures can be considerable in some cases. For example, in free-radical-polymerized poly(vinylidene fluoride), -fOH2—CF2 fi, there are about 10-12% of such links according to nuclear magnetic resonance measurements ( H and F). The proportion is as high as 6-10% in poly(vinyl fluoride). Admittedly, these physical methods... 

Vinylidene fluoride (b.p. — 84°C) is free-radically polymerized in suspension or emulsion at 10-300 bar and 10-150°C. Suspension-polymerized material contains less branching and consequently a narrower molecular-weight distribution than the emulsion-polymerized material. For this reason, the suspension-polymerized material has higher crystallinity, greater mechanical strength, and better chemical stability. Materials from both polymerization methods contain a considerable proportion of head-to-head linkages. 

POLVINYLIDENE FLUORIDE. This product is made by the free-radical chain polymerization of vinylidene fluoride (H2C=CF2). This odorless gas which has a boiling point of —82°C is produced by the thermal dehydrochlorination of 1,1,1-chlorodifluoroethane or by the dechlorination of 1,2-dichloro-l.l-difluoro-ethane. As shown by the following equations, 1,1,1-chlorodifluoroethane may be obtained by the bydroflnorination and... 

There are essentially two methods used for the production of commercial FTPEs. The first is referred to as iodine transfer polymerization, which is similar to the living anionic polymerization used to make block copolymers such as styrene-butadiene-styrene (e.g., Kraton ). The difference is that this living polymerization is based on a free radical mechanism. The products consist of soft segments based on copolymers of vinylidene fluoride (VDF) with hexafluoropropylene (HFP) and... 

Four perfluorodiacylperoxide free radical initiators were prepared by condensing perfluoroacyl chloride derivatives with hydrogen peroxide and sodium hydroxide. When the product bis(2-fluoro-2-trifluoromethyl-perfluoropropionyl) peroxide was used to polymerize vinylidene fluoride, a 90% conversion was observed. 

The first reported polymerization of fluoroolefins in carbon dioxide was by Fukui and coworkers [39,40]. Tetrafluoroethylene, chlorotrifluoroethylene,and other fluoroolefins were polymerized in the presence of CO2 using ionizing radiation [39, 40] and free-radical initiators [40]. DeSimone and coworkers reported the homogeneous telomerization of tetrafluoroethylene [41] and vinylidene fluoride [42] in CO2 using AIBN as an initiator. The kinetics of AIBN decomposition in CO2 is well understood [4]. However, peroxide initiators are preferred over azo initiators for producing stable endgroups in fluoroolefins... 

Commercial process for the production of PCTFE is essentially polymerization initiated by free radicals at moderate temperatures and pressures in an aqueous system at low temperatures and moderate pressures. It is reported that it is possible to polymerize CTEE in bulk, solution, suspension, and emulsion. According to some reports the emulsion system produces the most stable polymer [65]. The tendency of PCTFE to become brittle during use can be reduced by incorporating a small amount (less than 5%) of vinylidene fluoride (VDF) during the polymerization process [67]. 

Tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, vinyl fluoride, vinylidene fluoride, perfluoroalkyl vinyl ether Free-radical-initiated chain polymerization Coatings for chemical process equipment, cable insulation, electrical components, nonsticking surfaces for cookware... 

PVDF is correctly named poly(l,l-difluoroethylene) and represented by (-CF2CH2-)n- It is a hard, tough thermoplastic fluoropolymer. PVDF is prepared by free-radical initiated polymerization, either in suspension or (usually) in emulsion systems. The basic raw material for PVDF is vinylidene fluoride (CH2=CF2), a preferred synthesis of which is dehydrochlorination of chlorodifluoroethane. 

Vinylidene fluoride (1,1-difluoroethylene) n, H2C=CF2. a colorless, nearly odorless gas prepared by the dehydrohalogenation of 1-chlorol,l-difluoroethane, or by the dehalo-genation of l,2-dichloro-l,l-difluorethane. It polymerizes readily in the presence of free-radical initiators to produce the homopolymer polyvinylidene fluoride, and is also co-polymerized with olefins and other fluorocarbon monomers to make fluorocarbon elastomers. (See image). 

Vinylidene fluoride (VF2) as well as vinyl fluoride (VF) resemble more ethylene than other vinyl monomers in regard to the properties and can also be polymerized in a manner analogous to that of ethylene. The first successful polymerization of vinylidene fluoride was reported by Du Pont in 1948 [517]. Poly(vinylidene fluoride) (PVF2 or PVDF) is commercially available from various companies (Kureha Chemical Co., Pennalt Chemicals Corp., Solvay Co., Siiddeutsche Kalkstickstoff-Werke AG now Degussa, Diamond Shamrock, Du Pont) since 1965 under the trade names KF, Kynar, Foraflon, Vidar, and Dalvor, respectively. VF2 can be polymerized by free-radical initiators to give high-molar-mass, crystalline polymers. 

While partially fluorinated alkenes such as vinyl fluoride and vinylidene fluoride polymerize with the same facility as tetrafluoroethylene, the latter is unique in the class of the perfluoroalkenes with the respect to the ease of polymerization as will be described later. Perfluoroalkenes such as hexafluoropropylene (HFP) and hexafluorobutadiene polymerize only with great difficulty as the result of the steric inhibition in the propagation step [598]. HFP can be converted to high-molar-mass polymer only at pressures above 1000 atm. The polymerizations are carried out most conveniently in a perfluorinated solvent using perfluorinated free-radical initiators [599]. For the polymerization of hexafluorobutadiene, similar conditions are reported [600]. Due to these very drastic polymerization conditions, these oligomers/polymers are not yet commercially applied. 

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]. 

Poly(vinylidene fluoride) n Poly(l,l-difluoroethylene) Poly(vinylidene fluoride) is made by free radical vinyl polymerization of the monomer vinylidene fluoride Poly(vinylidene fluoride) of PVDF has a has very high electrical resistance, PVDF resists ultraviolet and is often blended with poly(methyl methacrylate) (PMMA) to make it more resistant to UV light. It is a piezoelectric material and when placed in an electric field wiU change its shape. 

Reaction temperature ranges between 10 and 150°C at pressure of 1 MPa or higher. Similar to TFE, emulsion polymerization of vinylidene fluoride requires a stable fluorinated surfactant and an initiator such as peroxide or persulfate. Suspension polymerization is conducted in an aqueous medium, sometimes in the presence of a colloidal dispersant like hydroxy cellulose. Solution polymerization of VDF in solvents uses free radical initiators. PVDF is commercially produced by aqueous emulsion or suspension processes [72]. 

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