Perfluorinated monomer

Modified PTFE — Copolymer of TFE and a small amount (less than 1%) of other perfluorinated monomer (e.g., perfluoroalkoxy monomer) exhibiting considerably improved physical properties, moldability, and much lower microporosity. 

TFE — Tetrafluoroethylene, a perfluorinated monomer used as a feedstock for the production of PTFE and as a comonomer for the production of a variety of other fluoropolymers. 

Perfluoroelastomers (ASTM designation FFKM) are essentially copolymers of two perfluorinated monomers, TFE and PMVE with a CSM, which is essential for cross-linking. Perfluoroelastomers can be cured by ionizing radiation without any additives. The advantage of radiation cured FFKM is the absence of any additives, so that the product is very pure. The disadvantage is the relatively low upper-use temperature of the cured material, typically 150°C, which limits the material to special sealing applications only [32]. 

Kharitonov et al. [59] have shown that direct fluorination of the polyimide Matrimid is possible, hence the resulting membrane should have a nice potential for use in harsh environment. Perfluorinated materials were also studied by Hagg [60] for chlorine gas purification, and were shown to be exceptionally stable in these harsh environments. The selectivity was however too low. In a later publication on chlorine purification [31] it was suggested to use perfluorinated monomers as surface-modifying compounds for pore tailoring of glass membranes for chlorine gas separation. 

Nafion-perfluorinated membranes are manufactured from copolymers of tetrafluoroethylene and perfluorinated monomers and contain sulfonic groups on one side and carboxylic acid groups on the other. The membranes, originally designed for use in... 

This monomer is fairly simple to manufacture compared with the perfluorinated monomers.F f The commercial process for the synthesis of CTFE (CF2=CC1F, 79-38-9) begins with 1,1,2-trichloro-l,2,2-trifluoroethane (TCTFE). It is dechlori-nated by pyrolysis at 500-600°C in vapor phase. An alternative method for the preparation of TCTFE is catalytic dechlorination ... 

XPS-analysis of surface exposed to the perfluorinated monomers showed the presence of all possible species regardless of monomer structure. Fig. 1 shows the deconvoluted carbon Is XPS spectrum of a poly(ethylene) surface after exposure of hexafluoropropylene in a glow discharge. A 1 1 1 ratio of the CF3, CF2 and CF groups was found suggesting the structure of a normal addition polymer. 

Polytetrafluoroethylene for these applications is known as modified, which refers to the presence of a small amount of a second perfluorinated monomer, known as a modifier, in its structure. The modifier molecule always contains a pendent group. 

Chemical in Japan where membrane cells are now dominant. Because of their Teflon -like chemical composition, perfluorinated membranes resist chemical and thermal degradation better than any of the hydrocarbon ion-exchange membranes that preceded them. For most of them the starting materials are perfluorinated monomers such as tetrafluoroethylene (TFE) CF2=CF2 and hexa-fluoropropylene oxide (FIFPO)... 

The preparation of perfluorinated membranes from these monomers is rather complex, and several research groups developed different routes to similar end points. Typically they utihzed the monomers TFE and HFPO and a variety of other reagents to synthesize a complex perfluorinated monomer (PFM) containing ether linkages. The general stracture of PFM is... 

I.K. Shundrina, TA. Vaganova, S.Z. Kusov, V.I. Rodionov, E.V. Karpova, E.V. Malykhin, Synthesis and properties of organosoluble polyimides based on novel perfluorinated monomer hexafluoro-2,4-toluenedi amine, J. Ruorine Chem. 132 (3) (2011) 207-215. 

Perfluoropolymers The manufacturing of TFE/HFP monomers consumes large amounts of energy (>10,000 kWh/ton TFE). In the past, there were many efforts to recover perfluorinated monomers from scrap materials. All of the approaches were based on the findings that perfluorinated polymers can be pyrolyzed under high temperature conditions into TFE/HFP [90-95] (Scheme 21.13). The pyrolysis back to monomers of perfluorinated polymers is a rare property in the materials industry there are only a few other polymer classes [e.g.. Polystyrene, Poly(methylmethacrylate)] which can be converted into monomers upon heating. 

Dobreva-Veleva, A. N., Kaler, E. W., Schubert, K.-V., Feiring, A. E. and Farnham, W. B., Phase behaviour and microemulsion formation in compressible perfluorinated monomer oil and water mixtures, Langmuir, 15, 4480 (1999). 

However, compared to the large number of radically polymerizable hydrocarbon monomers, only a few classes of perfluorinated monomers can homopolymerize under normal conditions via a free-radical mechanism. The most typical example is tetrafluoroethylene (TFE), developed by DuPont in 1938. As is well known, poly(tetrafluoroethylene) is opaque white, despite the... 

FFKM is a perfluorinated polymethylene rubber with fluoro, perfluoroalkyl, and/or perfluoroalkoxy groups on the polymer chain, likely with a small fraction of perfluorinated monomer units containing functionality to enable vulcanization. 

A terpolymer of tetrafluoroethylene (60 mole %), perfluoro(methyl vinyl ether) (VII) and a perfluorinated monomer with a reactive site is also commercially available. The material may be cross-linked to give an elastomer which has very low volume swell in a wide range of solvents and which withstands air oxidation up to 315°C. 

To the best of our knowledge, aromatic fluorinated macromolecules for PEMFCs may be prepared by direct radical (co)polymerization from two groups of functionalized aromatic perfluorinated monomers (i) a,, -trifluorostyrene (TFS) and... 

Table 1.2 Properties of perfluorinated monomer membranes (e.g. Nation, Fiemion, Acipiex, Dow)...

A third perfluorinated monomer (perhaps 1-hydropentafluoropropylene) provides a cross-linking site. The random copolymer has a molar ratio of 3 2 for the two major monomers, C2F4 and C3pgO, respectively, and a 7 of -12°C. The rubbery material and its cross-linked derivative are quite stable for months at 288°C. Two other monomers that have been used with C2F4 are a vinyl propyl ether and an ionic ether ... 

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