Cloud Points of Poly(L-lactide)in HCFC-22,HFC-23,HFC-32,HFC-125,HFC-143a,HFC-152a,HFC-227ea,Dimethyl Ether(DME),and HCFC-22+CO_2 in the Supercritical State

摘要

Cloud points were measured using the high-pressure variable-volume cell apparatus for poly(L-lactide)in chlorodifluoromethane(HCFC-22),trifluoromethane(HFC-23),difluoroethane(HFC-32),pentafluo-roethane(HFC-125),1,1,1-trifluoroethane(HFC-143a),1,1-difluoroethane(HFC-152a),1,1,1,2,3,3,3-heptafluoropropane(HFC-227ea),and dimethyl ether(DME),respectively.The cloud points were characterized as functions of pressure,temperature,and polymer molecular weight.Cloud point pressures of poly(L-lactide)were studied at temperature ranging up to 413.2 K for polymer concentrations of about 3 mass %.The phase behavior of poly(L-lactide)in DME,HCFC-22,and HFC-23 exhibited LCST(lower critical solution temperature)behavior,and that of poly(L-lactide)in HFC-32 and HFC-152a exhibited UCST(upper critical solution temperature)behavior.However,poly(L-lactide)had a low solubility in HFC-125,HFC-143a,and HFC-227ea even at 413.2 K and 150 MPa.In addition,the phase behavior of poly(L-lactide)was investigated as a function of CO_2 in a HCFC-22+CO_2 mixture.