Perfluorocarbons viscosity

Polymer Solvent. Sulfolane is a solvent for a variety of polymers, including polyacrylonitrile (PAN), poly(vinyhdene cyanide), poly(vinyl chloride) (PVC), poly(vinyl fluoride), and polysulfones (124—129). Sulfolane solutions of PAN, poly(vinyhdene cyanide), and PVC have been patented for fiber-spinning processes, in which the relatively low solution viscosity, good thermal stabiUty, and comparatively low solvent toxicity of sulfolane are advantageous. Powdered perfluorocarbon copolymers bearing sulfo or carboxy groups have been prepared by precipitation from sulfolane solution with toluene at temperatures below 300°C. Particle sizes of 0.5—100 p.m result. 

Fluorinated compounds such as hydrofluoroethers and perfluorocarbon ethers have certain unique properties that made these fluids compete in the low-temperature HTF market. First, these fluids are nonflammable and nontoxic. Some fluorinated compounds have zero ozone depleting potential and other environmental properties. Second, some of these fluids have a very low freezing point and low viscosity at low temperatures. However, these fluids are much more expensive compared to their counterparts. Also,... 

One theoretical possibility, of course, is to break up crystallinity just enough to permit chain entanglements to substitute for interchain forces as the mechanism for generating adequate toughness This substitution should then permit reduction both in molecular weight and in melt viscosity to levels which would allow conventional melt processing In the late 1940 s the only olefin known that could be introduced into the PTFE structure to disrupt crystallinity without loss of the perfluorocarbon composition was hexafluoropropylene (HFP). 

A variety of studies using RF EMRI have been carried out on living mice. These include (i) oximetry in tumour tissues and the response to perfluorocarbons for their potential use in radiotherapy, (ii) the detection of hydroxyl radicals (by spin trapping) in y-irradiated tumours, (iii) the distribution of nitroxyl radicals with distinct pharmacological abdominal compartment affinities and (iv) quantitative measurement of the viscosity of a non-vascular compartment. 

Similar results were obtained with hydroxyethylcellulose (HEC) modified with perfluorocarbon chains attached to the HEC backbone through oligoethyleneoxide spacers. Only the HEC derivatives containing two ethyleneoxide spacer units were effective viscosifiers. Again, a sharp maximum in Brookfield viscosity as a function of modifier content is observed, in accordance with earlier results of Landoll in the corresponding HEC alkyl derivatives. 

The above results, at least qualitatively, confirm similar behavior for hydro-phobically modified HEC and polyacrylamides. As in the case of the polyacrylamide copolymers, the perfluorocarbon containing HEC polymers are generally more strongly viscosifying compared to the hydrocarbon analogs. In the case of HEC derivative 14, there is clearly a viscosity maximum with regard to perfluorocarbon content. Similar observations were made by Landoll for alkyl derivatives of HEC [4]. As in the case of the polyacrylamide copolymers, the solutions of perfluorocarbon modified HEC were found to be highly pseudoplastic. 

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