Influence of thermal history on the nonisothermal crystallization of poly(L-lactide)

The effect of thermal history on the nonisothermal crystallization of poly(L-lactide) (PLA) was studied. The cold crystallization of PLA by heating from the glassy state was dominated by the heating rate. However, the temperature to which PLA was cooled before crystallization markedly affected the crystallization kinetics. The lower the temperature was to which PLA was cooled, the lower the nonisothermal crystallization peak temperature was and the larger the crystallization enthalpy was, which indicated enhanced nucleation of spherulites. Fast heating from the glassy state reduced the time available for the growth of spherulites and also suppressed the number of nuclei stable at elevated temperatures by limiting the recrystallization of nuclei formed at low temperatures and their overgrowth by thicker and more perfect crystals. (C) 2007 Wiley Periodicals, Inc.