Effect of the Nucleation Mechanism on Complex Poly(L-lactide) Nonisothermal Crystallization Process. Part 1: Thermal and Structural Characterization

The effect of the holding temperature and time in the melt state of poly(L-lactide) (PLLA) samples on the nonisothermal melt crystallization process and on the structure have been investigated by means of DSC, polarized optical microscopy and wide angle X-ray scattering. As standard starting material, single crystals grown from dilute solution were used. In the mild melting condition, the survived athermal nuclei favor high temperature polymer crystallization, while the more severe treatment leads the PLLA to crystallize at higher supercooling with a sporadic nucleation. At the intermediate melting temperature a distinct double nucleation mechanism was observed while at the lower nuclei concentration, a double crystallization rate was also found. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 3368-3376, 2011