Initiators vinylidene fluoride

Poly vinylidene fluoride is polymerized under pressure at 25-150°C in an emulsion using a fluorinated surfactant to minimize chain transfer with the emulsifying agent. Ammonium persulfate is used as the initiator. The homopolymer is highly crystalline and melts at 170°C. It can be injection molded to produce articles with a tensile strength of 7000 psi (48 MPal. a modulus of elasticity in tension of 1.2 x 105 psi and a heat deflection of 3003F (149°C). 

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. 

The telomerisation of vinylidene fluoride (1,1-difluoroethylene) has been investigated by many authors. Almost all kinds of transfer agents have been used, as mentioned below, requiring various ways of initiation thermal, photochemical or from systems involving redox catalysts or radical initiators (Tables 3 and 4) and also hypofluorites as mentioned in Sect. 2.3.1. 

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] ... 

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. 

TABLE 1. Selected perfluoroalkyl peroxides and their effectiveness in initiating the polymerization of vinylidene fluoride. 

Polymerization of vinylidene fluoride by emulsion or suspension polymerization in water is conducted at conditions of 10-130 °C and 10-200 bar. In the emulsion polymerization, either water-soluble peroxides or monomer-soluble peroxy or organic peroxides are used as initiators [ 17]. Fluorinated surfactants, such as ammonium perfluorooctanoate, are used as dispersing agents. Chain transfer agents, such as acetone, chloroform, or trichlorofluoromethane, may be... 

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]. 

Vinylidene fluoride (VDF), also known as refrigerant 1132a, 1,1-difluoroethylene, 1,1-difluoroethene, vinylidene difluoride, etc., is a colorless, nearly odorless gas. Unlike the other fluoromonomers, VDF has long shelf life stability and does not self-initiate unwanted polymerization. Therefore, VDF can be stored, and shipped pure or with polymerization inhibitors. Its properties are summarized in Table 1. ... 

The use of reverse ATRP enlarges the scope of substrate polymers for controlled polymerizations even further because the required radical initiators can in many cases be provided more easily than ATRP initiators on surfaces of inert polymers. For example, poly(vinylidene fluoride) microfiltration membranes were irradiated with UV light and then exposed to air to create hydro(peroxide) species [11]. These were then used to initiate the reverse ATRP of methyl methacrylate in the presence of copper(I) chloride, 2,2 -bipyridine, and benzoylperoxide (Figure 3.5). Similar reaction schemes are applicable to (hydro)perox-ide patterns created directly on polymer surfaces using the lithographic methods discussed in Chapter 2. 

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 (CH2=CF2), Free-radical-initiated chain Aerospace industry (20%),... 

Fluoroelastomers are fluorine-containing hydrocarbon polymers with a saturated structure obtained by polymerizing fluorinated monomers such as vinylidene fluoride, hexafluoropropene, and tetrafluoroethylene. The result is a high-performance s)mthetic rubber with exceptional resistance to oils and chemicals at elevated temperatures. Initially, this material was used to produce O-rings for use in severe conditions. Although this remains a major area of application, these compoimds have found wide use in other applications because of their chemical resistance at high temperatures and other desirable properties. 

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