Fluoroolefins peroxides

Bromine- and iodine-containing fluoroolefins have been copolymerized with the above monomers in order to allow peroxide cure (14—21). The peroxide cure system does not requite dehydrofluorination of the polymer backbone, resulting in an elastomer that shows improved properties after heat and fluid aging. 

Photooxidation reactions of fluoroolefins in the presence of oxygen is one commercial method used in the production of PFPEs, generally employing either TFE or HFP. Fluorolefin concentration, oxygen level, light intensity, and temperature are all variables that have substantial impact on reaction rates, product distributions, polymer microstructure, peroxide content, and molecular weight. While HFP photooxidations are often carried out in bulk at low temperatures, TFE photooxidation must be carried out in an inert solvent, historically chlorofluor-ocarbons. 

Ideal conditions for polymerization of a fluoroolefin are those where little, or better yet, no chain-transfer occurs. Thus perfluoroalkyl iodides are not used to initiate polymerizations. Instead, non-chain-transfer agents, particularly peroxide initiators, including perfluorodiacyl peroxides and ammonium persulfate, are used effectively for this purpose [67]. 

A large variety of telogens has been used in telomerisation of traditional fluoroolefins and numerous studies have been performed on the telomerisation of VDF, TFE, CTFE. Yet, less investigations were carried out on trifluoroethylene and hexafluoropropene. According to the telomers searched, more adequate ways of initiation have to be chosen. For instance, the peroxide induced telomerisation of VDF with CC14 leads to higher molecular weight-telomers than that catalysed by copper salts which appears more selective [92]. 

Using this methodology for systems with fluorine atoms considerably enriches our knowledge of the properties of olefinic systems. The reagent also plays an important role. Thus calcium hypochlorite is occasionally ineffective in epoxidations of fluoroolefins, whereas lithium tert-butyl peroxide is extremely effective (95JCS(CC)629, 96RCI703). 

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... 

The peroxy initiators bis(perfluoro-2-Ar-propoxypropionyl) peroxide (BPPP) and diethyl peroxydicarbonate (DEPDC) have had the greatest application in the heterogeneous polymerization of fluoroolefins in CO2. 

Uses. There are about forty to fifty organic peroxides commercially available in more than seventy formulations designed for specific applications which include (1) initiators for vinyl monomer polymerizations, and copolymerizations of monomers such as vinyl chloride, ethylene, styrene, vinyl acetate, acrylics, fluoroolefins and buta-dienestyrene (2) curing agents for thermoset polyesters, styrenated alkyds and oils, silicone rubbers and poly allyl diglycol carbonates ... 

A fluorinated monomer susceptible to copolymerizing or terpolymerizing vinylidene fluoride is needed to undergo free-radical attack to render peroxide curable elastomeric co- or terpolymers of VDF [35]. So, this monomer must be functionalized or halogenated to ensure a free-radical crosslinking. The monomers mainly used are bromine-containing fluoroolefins such as [42,43] ... 

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