Fluorocarbons presence

HF is used as a source of fluorine for production of all the various fluorocarbon products. HF reacts in the presence of a suitable catalyst and under the appropriate temperature and pressure conditions with various organic chemicals to yield a family of products. A by-product stream of hydrochloric acid may be co-produced. 

There are over 100 minerals known to contain lanthanides but the only two of commercial importance are monazite, a mixed La, Th, Ln phosphate, and bastnaesite, an La, Ln fluorocarbonate (M C03F). Monazite is widely but sparsely distributed in many rocks but, because of its high density and inertness, it is concentrated by weathering into sands on beaches and river beds, often in the presence of other... 

Infrared spectra and F-NMR spectroscopy showed the presence of IF5 and covalently bonded fluorine. Grafoil turns white upon intercalation with IF, this is reminiscent of graphite fluoride, CFi.ij (1,6). The IF, intercalate also evolves IF5 upon heating, but at much higher temperatures than C/IF5 this has been attributed to the lowered mobility of IF5 in the fluorinated matrix, which may no longer be planar. At 450°C, considerable amounts of fluorocarbons are evolved. 

Thermal degradation studies of EB-cured terpolymeric fluorocarbon rubber [430] by nonisothermal thermogravimetry in the absence and presence of cross-link promoter TMPTA reveal that thermal stability is improved on radiation and more so in the presence of TMPTA. Initial decomposition temperature, maximum decomposition temperature and the decomposition... 

Lee and Meisel incorporated Py, at levels of 10 M or more, into 1200 EW acid form samples that were swollen with water and with ferf-butyl alcohol. It was concluded based on the /3//1 value for water swollen samples that the Py molecules were located in the water clusters and were most likely near fluorocarbon—water interfaces. It was also concluded, based on both absorption and emission spectra, that the probes had strong interactions with the SO3 groups that were exchanged with Ag+ and Pb + cations in the case of water containing samples. Likewise, the pyrene molecules were rationalized as being surrounded by terf-butanol molecules in that case. However, excimer formation (due to the presence of adjacent pyrene molecules) in the ferf-butyl alcohol system suggested the loss of cluster morphology-... 

Polymers such as polystyrene, poly(vinyl chloride), and poly(methyl methacrylate) show very poor crystallization tendencies. Loss of structural simplicity (compared to polyethylene) results in a marked decrease in the tendency toward crystallization. Fluorocarbon polymers such as poly(vinyl fluoride), poly(vinylidene fluoride), and polytetrafluoroethylene are exceptions. These polymers show considerable crystallinity since the small size of fluorine does not preclude packing into a crystal lattice. Crystallization is also aided by the high secondary attractive forces. High secondary attractive forces coupled with symmetry account for the presence of significant crystallinity in poly(vinylidene chloride). Symmetry alone without significant polarity, as in polyisobutylene, is insufficient for the development of crystallinity. (The effect of stereoregularity of polymer structure on crystallinity is postponed to Sec. 8-2a.)... 

The mechanism we believe is responsible for the large SiOj-to-Si etch-rate ratios which have been obtained in fluorine-deficient discharges is based on several experimental observations. First of all, it has been shown that there are several ways in which carbon can be deposited on surfaces exposed to CF, plasmas. One way is to subject the surface to bombardment with CF ions which are the dominant positive ionic species in a CF plasma. The extent to which this can occur is shown by the Auger spectra in Fig. 3.3. Curve (a) is the Auger spectrum of a clean silicon surface and curve (b) is the Auger spectrum of the same surface after bombardment with 500 eV CFj" ions. Note that the silicon peak at 92 eV is no longer visible after the CFj bombardment indicating the presence of at least two or three monolayers of carbon. Another way in which carbon can be deposited on surfaces is by dissociative chemisorption of CFj or other fluorocarbon radicals. 

The copolymer of vinyl ferrocene (VF) and butadiene has also been reported in the literature for use as a binder for composite propellants. It does not require any burn-rate (BR) accelerator because of the presence of iron (Fe) in vinyl ferrocene which is converted to finely divided Fe203 (a well-known BR accelerator) during combustion. A few groups of scientists have also studied fluorocarbon polymers as binders for composite propellants because of their excellent compatibility with oxidizers and fuels coupled with high density. Accordingly, Kel-F elastomer (a copolymer of vinylidene fluoride and chlorotrifluoroethylene, trade name of 3M, USA) and Viton-A (copolymer of hexafluoropropylene and vinylidene fluoride, trade name of Du Pont, USA) have also been reported for this purpose. The structures of Kel-F 800 [Structure (4.13)] and Viton-A [Structure (4.14)] are ... 

CF2Cl)2CO and CFC]2C0CF2C1 and in the electrical discharge103 of fluorocarbons. In the presence of a large excess of 02 there was no evidence for BrO radicals in contrast to analogous experiments with CCl2Br2. Furthermore, the CF2 concentration was independent of the 02 pressure. Simons and Yarwood concluded that the primary process was... 

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