ISOTHERMAL CRYSTALLIZATION AND CHAIN MOBILITY OF POLY(L-LACTIDE)

Isothermal melt crystallization of poly(L-lactide) (PLLA) has been stu died in the temperature range of 90 to 135 degrees C. A maximum in cry stallization kinetic was observed around 105 degrees C. A transition f rom regime II to regime III is present around 115 degrees C. The cryst al morphology is a function of the degree of undercooling. At crystall ization temperatures (T-c) below 105 degrees C, further crystallizatio n occurs upon heating; this behavior is not detected for T-c above 110 degrees C. The analysis of the heat capacity increment at glass trans ition temperature (T-g) and of dielectric properties of PLLA indicates the presence of a fraction of the amorphous phase which does not rela x at the T-g, and the amount of this so-called rigid amorphous phase i s a function of T-c. (C) 1997 John Wiley & Sons, Inc.