Isothermal melting behavior of poly(L-lactic acid)

Abstract

The isothermal melting behavior of poly(L-lactic acid) spherulites has been studied in order to understand the mechanism of melting using hot-stage microscopy. When the periphery of the spherulite melts or shrinks, the central portion undergoes thickening as a result of which the melting or shrinking rate is not linear. Annealing studies at 448 K reveal that there is an increase in melting temperature and heat of fusion with annealing time, suggesting an increase in lamellar thickness. The high activation energy (828 kJ/mol) obtained in this investigation suggests the highly complex nature of the melting process wherein both melting and thickening occur.