Thermodynamic phase behavior of fluoropolymer mixtures with supercritical fluid solvents

Cloud-point experimental data were presented at temperatures up to 260 °C and pressures up to 2,500 bar for poly(vinylidene fluoride) (PVDF) [Mw=180,000 and 275,000] in CO2, CHF3, CHClF2, and dimethyl ether (DME). Also, phase behavior curves were shown for the PVDF [Mw= 180,000] in CO2 with 1-propanol and 1-pentanol. Poly(vinyl fluoride) does not dissolve in CO2 even at 215 °C and 2,500 bar, while poly(vinylidene fluoride) does dissolve in CO2 at 220 °C and pressures of 1,700 bar. To dissolve poly(vinylidene fluoride) in dimethyl ether, pressures in excess of 200 bar and temperatures in excess of 165 °C are needed. The cloud-point behavior between the ternary PVDF [Mw=180,000]-CO2-DME mixture shows a temperature range of 100–195 °C and pressure range of 350–1,360 bar by adding the 11, 29, and 60 wt% DME in cosolvent. The phase behavior for PVDF [Mw=180,000]-CHF3-9, 19, and 40 wt% CHClF2 system shows a temperature at below 200 °C and pressure up to 1,700 bar. The effect of CHClF2 as a cosolvent for PVDF [Mw=275,000] in CO2 decreased with the pressure increasing 10, 26, 40 and 61 wt% of cosolvent (CHClF2) contents. Also, the effect of 15 and 40 wt% DME for the PVDF [Mw=275,000]-CHF3 mixture shows temperature ranges of 120–206 °C and pressures up to 1,570 bar.