Copolymers of fluoroolefins

Mary different copolymers of fluoroolefins are possible and were reported in the literature. Commercial use of fluoroolefln copolymers, however, is restricted mainly to elastomers. Such materials offer superior solvent resistance and good thermal stability. 

Copolymers of vinylidine fluoride with hexafluoropropylene are prepared in aqueous dispersions using persulfate initiators. Hexafluoropropylene does not homopolymerize but it does copolymerize. This means that its content in the copolymer cannot exceed 50%. Preferred compositions appear to contain about 80% of vinylidine fluoride. The cross-linking reactions with diamines are not completely understood. It is believed that the reaction takes place in two steps [285, 286]. In the first one, a dehydrofluorination occurs  

The above elimination is catalyzed by basic materials. These may be in the form of MgO, which is often included in the reaction medium. In the second step the amine groups add across the double bonds  

Free diamines, used for cross-linking, are too reactive and can cause premature gelation. It is common practice, therefore, to add these diamine compounds in the form of carbamates, like ethylenediamine carbamate or hexamethylene diamine carbamate. The above fluoro elastomers exhibit good resistance to chemicals and maintain useful properties from —50 to -i-300°C. 

Copolymers of tetrafluoroethylene with hexafluoropropylene are truly thermoplastic polyperfluor-oolefins that can be fabricated by common techniques. Such copolymers soften at about 285°C and have a continuous use temperature of —260 to -i-205°C. Their properties are similar to, though somewhat inferior to, poly tetrafluoroethylene. 

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What conunon copolymers of fluoroolefins are used commercially ... 

The problem of the aging of raw rubbers and cured rubbers based on them, which manifest ability to work at high temperatures (200-400°C) has attracted the attention of many scientists in recent years [26-33]. Among the large number of thermally stable polymers synthesized in laboratories, copolymers of fluoroolefins and silicone rubbers have received the greatest industrial use abroad. 

The alternating copolymer of fluoroolefin and hydrocarbon vinyl ether provides an amorphous, solvent-soluble and ambient cure type paint resin with the excellent weather resistance. Lumiflon is rapidly expanding the market of protective coating in the field of roofs, siding walls of buildings, out door constructions and vehicles. 

A fluoroolefin - vinyl ether terpolymer (Lumiflon) has recently been developed [2.14]. This polymer is an amorphous, alternating copolymer of a fluoroolefin with several vinyl monomers (Fig. 2.2). The alternating sequence is responsible for the high performance of the resultant finish. The combination of vinyl monomers provides the polymer with various properties necessary for a coating material. 

As previously mentioned, another class of fluoropolymers known to be readily soluble in CO2 are perfluoropolyethers (PFPEs) [1]. A unique class of fluoropolymers, PFPE polymers and copolymers have been established as high performance materials, exhibiting low surface energies and low moduli, as well as excellent thermal and chemical stabilities. PFPEs are primarily found in high-performance lubricant applications, e.g., for magnetic data storage media and as heat exchanger fluids. One of the main industrial processes for the production of PFPEs is photooxidation of fluoroolefins [41]. Currently, only TFE and HFP are used commercially in this process. Typically, HFP is photooxidized in bulk because of its very low reactivity, while TFE requires an inert diluent in order to prevent homopolymerization of the olefin. 

One of the miscellaneous fluoroolefin polymers is a copolymer of trifluoronitrosomethane and tetrafluoroethylene [287], an elastomer ... 

The copolymerization of fluoroolefin and vinyl ester has also been studied, one example is CTFE and vinyl pyvalate, which afford a random copolymer, as expected from these monomer reactivities shown in Fig. 5. The copolymer is featured by ultra thin film formation by casting and the resultant film shows a relatively high oxygen permeability. One practical application of thie ultra thin film supported by a porous sheet is an oxygen enricher for medical use, supplying the air with 40 wt% oxygen concentration (7). 

Since PTFE was first synthesized more than 50 years ago, fluoropolymers have been produced by radical polymerization and copolymerizaton processes, but without any functional groups, for several reasons. First, the synthesis of functional vinyl compounds suitable for radical polymerization is much more complicated and expensive in comparison with common fluoroolefins. In radical polymerization of one of the simplest possible candidates—perfluorovinyl sulfonic acid (or sulfonyl fluoride—there was not enough reactivity to provide high-molecular-weight polymers or even perfluorinated copolymers with considerable functional comonomer content. Several methods for the synthesis of the other simplest monomer—trifluoroacrylic acid or its esters—were reported,1 but convenient improved synthesis of these compounds as well as radical copolymerization with TFE induced by y-irradiation were not described until 1980.2... 

Fig. 4 Structural Features of Lumiflon Polymer Fluoroolefin-Vinyl Ester Copolymer...

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