Effect of the Nucleation Mechanism on Complex Poly(L-lactide) non-isothermal Crystallization Process. Part 2: Crystallization Kinetics Analysis

In the first part of this article, we reported the crystalline memory effect on the nonisothermal crystallization of poly(L-lactide). The experiments were carried out by using polymer single crystals growth from dilute solution as standard starting material. In this article (Part II), we have analyzed in detail the effect of the melting condition on the overall crystallization kinetics by applying the Nakamura-Avrami model to DSC results. The absence or the low concentration of foreign infusible heterogeneous nuclei in our system allowed us to exalt the self-nuclei role in polymer crystallization, to follow their concentration decrease during the melting process and to find the limiting melting temperature for their disappearance. Below such a temperature, a stable equilibrium number of self-nuclei was observed, probably deriving from ordered structures, persisting in the melt, and originated from the single crystals thickening process during the polymer dynamic melting in the DSC.