Free radical copolymerization reactions of vinylidene fluoride (VDF) and hexafluoropropylene(HFP) were carried out in supercritical carbon dioxide at T=50 °C. When ammonium carboxylateperfluoropolyether surfactants were used, the formation of polymer particles was observed provided that HFP mole fraction in the feed was not larger than 0.30. Under these conditions, the effect of the total interphase area of the polymer phase, Ap, on the product propertieswas investigated by comparing experiments with largely differentamounts of stabilizer, i.e., ranging from precipitation (smaller Ap) to dispersion (larger Ap) polymerization systems.We found that the copolymer molecular weight distribution (MWD) is heavily affected by Ap. This experimental evidence strongly supports the presence of two reaction sites, the CO2-rich and the polymer-rich phase: the contribution of both is important in the examined range of operating conditions.
|Numero di pagine||10|
|Stato di pubblicazione||Published - 2010|
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