Perfluoropolyether concentration

Here again, we might argue that the 5000 MW PFPE-functional material exhibits the best balance between C02-phihcty and anchoring to the polymer parti-de (hydrophilicity). Interestingly, the behavior of the 2500 PFPE surfactant varied as the amount of monomer in the system varies. At an initial concentration of 7% NVF, the behavior of the 2500 MW perfluoropolyether surfactant is as shown in Table 7.1 however when the monomer concentration is increased to 17 wt%, the behavior changes, such that the rate varies as [S] - it is not clear why this behavior occurs. 

Table 9.4 Peroxide content in the perfluoropolyethers synthesized under varied HFP concentrations in HFP, CO2, and PCB.

The water-supercritical CO2 system has been used to synthesize nanoparticles of copper [227]. Copper nitrate in water was used as the aqueous phase and a mixture of (1 2 concentration ratio) AOT and a perfluoropolyether phosphate as surfactant the w value (with only AOT) was 12. The reverse micelle water/C02 was prepared under stirring at 38"C and 200 atm in a high pressure cell. A high pressure fiber optic system under the same (P, T) conditions monitored the reactions. After stirring for 1 h, a reducing agent (a) NaBHjCN, sodium cyanoborohydride in ethanol solution or (b) TMPD, N,N,N ,N -tetramethyl-p-phenylenediamine without ethanol was added at 250 atm. Transmission electron microscopy showed the copper particles to have a size range of 5-15 nm. 

The use of water-in-C02 microemulsions in particle synthesis has been extended recently to palladium [425]. An aqueous solution of PdCl2 was dispersed in supercritical CO2, and the surfactants NaAOT and (about twice its concentration of) perfluoropolyether phosphate (PFPE-PO4) were used for microemulsion stabilization. As in other similar cases, the formation of microemulsion and particle synthesis took place within a high pressure cell (at 200 atm). Reduction of palladium was caused by hydrogen gas (unlike in other similar investigations) because of its... 

Perfluoropolyether oils were used in thermoplastic urethane, TPU, polyether-block-amide, PEBA, low density polyethylene, LDPE, styrene ethylene butylene styrene block copolymer, SEES in small concentrations (0.1 and 0.5 wt%). The tensile strength of TPU, PEBA, and LDPE was not changed and that of SEES was doubled with any of the two levels of addition. The elongation of all these polymers was slightly increased (SEES elongation was tripled). 

Perfluoropolyether oils are added in small concentrations (0.1 to 0.5%) to thermoplastic pol5mrethanes to improve their mar and abrasion resistance." ... 

Perfluoropolyethers [185-193] are thermally and chemically stable materials of great commercial importance. Perfluoropolyethers CF3[CF(CF3)CF20) CF2CF3, where n = 27 average, being chemically inert, form stable films on concentrated acids (e.g., sulfuric acid, nitric acid, and phosphoric acid) [194]. The fluorinated polyether is insoluble in the acids and lowers their surface tension. Steady-state spreading pressures, calculated from the nearly constant surface tension values, correlate with the Hammett acidity of the acid. This relationship suggests that the... 

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