Cosolvent effect of water in supercritical carbon dioxide facilitating induced crystallization of polycarbonate
writer：翟文濤, 余堅*, 馬偉明, 何嘉松.
keywords：polycarbonate，crystallization，supercritical CO2，cosolvent
source：期刊
specific source：Polymer Engineering Science, 2007, 47(9): 1338-1343.
Issue time：2007年
Water-induced crystallization of polycarbonate (PC) was investigated in water-saturated supercritical CO2 (scCO2) in the range of 80–1608C and 12–20 MPa, with the help of differential scanning calorimetry and wide angle X-ray diffraction. Compared with pure scCO2, the enhanced plasticizing effect of water-saturated scCO2 reduced the energy-barrier for the motion of polymer chains, hence increased the crystallization rate of PC, and reduced the pressure threshold for crystallization from 14 to 12 MPa. On the other hand, the presence of water did not affect the thermodynamics of PC crystallization in scCO2. A 3D-diagram was established to show the relationship between crystallization and solubility
parameter of mixed supercritical fluid at different temperatures and pressures. The results show clearly that the PC has a wider range of crystallization temperature
and pressure in water-saturated scCO2 than in pure scCO2, mostly because the addition of water increased significantly the solubility parameter of mixed supercritical fluid, and decreased the difference in solubility parameter between PC and water-saturated scCO2.