Calorimetric analysis of the multiple melting behavior of poly(L-lactic acid)

This article contains a detailed calorimetric analysis of the multiple melting behavior of poly(L-lactic acid) (PLLA) in dependence of crystallization conditions. PLLA crystals formed upon primary crystallization have a greater tendency to reorganize into more stable structures during the heating scan that leads to fusion. Depending on crystallization temperature, one or multiple melting endotherms and/or reorganization exotherms can be evidenced. This complex melting behavior arises from the fusion of a certain amount of the original crystals (already partially perfected during the heating scan), followed by recrystallization and final melting of more perfect crystals, partly grown during primary crystallization, and partly formed through the reorganization processes occurring during the heating scan. A detailed map of the melting behavior of PLLA is described in this contribution.