Melt-recrystallization of poly (L-lactic acid) initially containing α′-crystals

The kinetics of melt-recrystallization and the stability of crystal self-nuclei of poly (L-lactic acid) initially containing disordered alpha'-crystals with a melting temperature of around 150 degrees C has been analyzed using specifically designed fast scanning chip calorimetry experiments (FSC). In general, the rate of recrystallization of the melt after complete melting of alpha'-crystals decreases with increasing melt-temperature mainly due to the lowering of the self-nuclei concentration. Self-nuclei of highest stability survive up to about 170 degrees C. The concentration of self-nuclei/alpha'-crystal remnants at a specific melt-temperature between 150 and 170 degrees C is independent on time, that is, only the temperature of the melt controls the self-nuclei content. Combining fast scanning calorimetry with polarized-light optical microscopy and with atomic force microscopy allows studying the semicrystalline morphology of samples of different self-nucleation history, providing direct information about the self-nuclei concentration in the various melts.