Nucleation and crystallization kinetics of poly(lactic acid)

A commercial grade PLA was characterized using differential scanning calorimetry under both isothermal and non-isothermal conditions, and the experimental data were analyzed evaluating the crystallization kinetics constants for melt and cold isothermal crystallization at some temperatures. Furthermore, a peculiar experimental protocol was adopted, varying each time the minimum cooling temperature before the isothermal step, performed monitoring nucleation and growth rate in an adequate range of temperatures. Morphological characterizations were modeled using the classical Lauritzen–Hoffman theory, which assumes that the free energy barrier associated with nucleation has an energetic origin, estimating the dependence on temperature using physical parameters derived from the linear Hoffman–Weeks plot. Crystallization kinetics was evaluated using the Avrami model, through nucleation and growth rate, describing both the melt and cold crystallization experimental results. Detailed comprehensive description of the crystallization kinetics of PLA is provided, predicting the final crystallinity and the morphology with tailored thermal history.