Fluorine Containing Polymers

Bernal and co-workers [29] characterised fluorine terminated hyper-branched polyarylenes ether phosphine oxides by GC-MS, also NMR and elemental analysis. 

In this investigation GC - matrix assisted laser desorption ionisation (MALDI)-MS was used to check on the completeness of oxidation to phosphine oxides during the synthesis of these polymers. 

1 (b)) by Plunkett in 1938 which gave an impetus to the study of fluorine-containing polymers. 

The fluororubbers also form an important class of speciality elastomers and although the market is dominated by the vinylidene fluoride-hexafluoro-propylene copolymers a wide range of materials has been produced over the past 40 years. 

World-wide capacity for fluoropolymers in the late 1990s has been estimated at 90 000 t.p.a. divided roughly equally between Western Europe, North America and the rest of the world. This total is dominated by PTFE although this has decreased from about 80% of the total in 1980 to about 60% in the late 1990s. 

The perfluorohydrocarbon polymers are among the most thermally resistant organic polymers. Polytetrafluoroethylene (PTFE), polytrifluoroethylene and various copolymers of fluorine-containing monomers are the most important among them. 

Fluoropolymers are arranged in the following order to their thermal stability  

PTFE has the highest thermal stability of this group, its thermal degradation under vacuum proceeding over the temperature range 473-533 °C [20]. The half-life temperature for PTFE is 409 °C [21]. 

The incomplete substitution of hydrogen atoms, as exemplified by polyvinylidene fluoride (T = 445 °C) as well as the presence of chlorine atoms as in polytrifluorochloroethylene (T = 413 °C) reduces their thermal stability Polyvinyl fluoride (T = 389 °C) proves to be the least thermally stable [21], even less so than polyethylene. 

Where Wg is the initial mass of the sample, w is the mass of volatiles liberated over the period of time t, is the effective rate constant for the destruction of the 

A combination of gas chromatography and either electron-impact or chemical ionization mass spectrometry has been used to analyse the products of thermal degradation of poly(vinyl fluoride) and of a number of other polymers [poly(vinyl chloride), aromatic polyimides, polyurethane]. The degradation of poly(vinyl-idene fluoride) has been related to its crystalline form. It is claimed that dehydrofluorination may take place preferentially in crystalline segments containing trans sequences. Thermo-oxidative breakdown is modified if vinylidene fluoride is copolymerized with tetrafluoroethylene or hexafluoroacetone. Dehydrofluorination occurred in both copolymers, but in the latter it was preceded by cleavage of the H from the CHj group in the alpha position to the ether bond followed by scission of the C-0 bond.  

Kazama, K. Ikeda, Y. Takekawa, and Y. Sekine, fVaseda Datgaku Rikogaku Kenkyusho Hokoku, 1979,84,42 (Chem. Abstr., 1979,91,57 909). 

Jaroszynska, T. Kleps, and D. Gdowska-Tutak,/. Thermal. Anal., 1980, 19,69. 

Thermal decomposition of a y-irradiated poly( vinyl fluoride) occurred in two main steps firstly, elimination of hydrogen fluoride and secondly, main chain scission to yield unsaturated hydrocarbons. Polytetrafluoroethylene and the copolymer of tetrafluoroethylene and hexafluoropropene were degraded in various atmospheres and the decomposition products analysed. - For an inert atmosphere over twenty different fluorinated products were identified. For air the major products were COF, CF , and COj with minor amounts of fluorocarbons. The gaseous and solid decomposition products have also been analysed from the thermal degradation of poly(carbon monofluorides) containing different proportions of fluorine. Kinetic data were also obtained. 

---

PTFE Polyietrafluoroethene. See also fluorine-containing polymers. 

Polytetrafluoroethylene contains only C—C and C—F bonds. These are both very stable and the polymer is exceptionally inert. A number of other fluorine-containing polymers cU e available which may contain in addition C—H and C—Cl bonds. These are somewhat more reactive and those containing C—H bonds may be cross-linked by peroxides and certain diamines and di-isocyanates. 

The high thermal stability of the carbon-fluorine bond has led to considerable interest in fluorine-containing polymers as heat-resistant plastics and rubbers. The first patents, taken out by IG Farben in 1934, related to polychlorotri-fluoroethylene (PCTFE) (Figure 13.1 (a)), these materials being subsequently manufactured in Germany and the United States. PCTFE has been of limited application and it was the discovery of polytetrafluoroethylene (PTFE) (Figure... 

Fluorine-containing Polymers 13.6 POLY(VINYL FLUORIDE) (PVF)... 

The polymer, like many fluorine-containing polymers has very good weathering resistance and may also be used continuously up to 150°C. Outside of the electrical field it finds use in fluid handling, in hot water piping systems, in packaging and in chemical plant. A widely used specific application for PVDF is in ultra-pure water systems for the semiconductor industry. 

Many fluorine containing polymers are being evaluated for possible use as permeable selective membranes. The fluorine containing polymers have been shown to increase permeation rates without decreasing in the selec-... 

Postelnek,W., Colemann, L. E., and Lovelace, A. M. Fluorine-Containing Polymers. I. Fluorinated Vinyl Polymers with Functional Groups, Condensation Polymers, and Styrene Polymers. Vol. 1, pp. 75— 113. 

Postelnek, W., Coleman, L. E., and Lovelace, A. M. Fluorine-Containing Polymers. 

C21-0025. Write the stmctural formula for an example of each of the following (a) Lewis acid-base adduct (b) polyphosphate (c) fluorine-containing polymer and (d) alkyllithium reagent. 

Fluorinated phenols, 3- and 4-fiuorophenols, and 2,6-difluorophenol, were subjected to peroxidase-catalyzed polymerization in an aqueous organic solvent, yielding fluorine-containing polymers. Elimination of fluorine atom partly took place during the polymerization to give polymers with complicated structures. 

Fluorine-containing polymers such as teflon are chemically and thermally particularly resistant. These surfaces also exhibit good nonstick properties, making them ideal materiab in many areas in home and industry. 

---