The simultaneous sorption of carbon dioxide and vinylidene fluoride (VDF) in poly(vinylidenefluoride) from their supercritical (sc) mixtures was studied using an experimental method, already described ina previous publication, based on the gas-chromatographic determination of the equilibrium composition of thefluid phase in contact with the polymer. Argon was added to the system as a nonabsorbable molecular probe inthe polymer to take into account the effect of the volume swelling on the measurement. Sorption behavior has been studied at 50 °C by changing the composition and the density of the supercritical phase. We have found thatVDF dissolves in its polymer with concentrations much lower than carbon dioxide at similar total and partialpressures. The mixed fluid CO2/VDF behaves as a worse solvent toward PVDF with respect to pure CO2, leading to a reduction of the cumulative sorption. This effect becomes progressively more significant when thefluoromonomer concentration increases. Experimental data obtained from binary systems were fitted using theSanchez-Lacombe equation of state, and this model was used to estimate the drift in the composition of the polymer phase during the polymerization of VDF in scCO2. This estimate shows that the concentration of themonomer dissolved in the polymer remains low during the whole polymerization.
|Stato di pubblicazione||Published - 2008|
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