Journal of Thermal Analysis and Calorimetry

, Volume 111, Issue 2, pp 1507–1514 | Cite as

Calorimetric analysis of the multiple melting behavior of melt-crystallized poly(l-lactic acid) with a low optical purity

  • Ping Song
  • Guangyi Chen
  • Zhiyong Wei
  • Wanxi Zhang
  • Jicai Liang


The polymorphous crystallization and multiple melting behavior of poly(l-lactic acid) (PLLA) with an optical purity of 92 % were investigated after isothermally crystallized from the melt state by wide-angle X-ray diffraction and differential scanning calorimetry. Owing to the low optical purity, it was found that the disordered (α′) and ordered (α) crystalline phases of PLLA were formed in the samples crystallized at lower (<95 °C) and higher (≥95 °C) temperatures, respectively. The melting behavior of PLLA is different in three regions of crystallization temperature (T c) divided into Region I (T c < 95 °C), Region II (95 °C ≤ T c < 120 °C), and Region III (T c ≥ 120 °C). In Region I, an exothermic peak was observed between the low-temperature and high-temperature endothermic peaks, which results from the solid–solid phase transition of α′-form crystal to α one. In Region II, the double-melting peaks can be mainly ascribed to the melting–recrystallization–remelting of less stable α crystals. In Region III, the single endotherm shows that the α crystals formed at higher temperatures are stable enough and melt directly without the recrystallization process during heating.


Multiple melting behavior Poly(l-lactic acid) Polymorphous crystallization Phase transition 



The work was financially supported by the National Natural Science Foundation of China (No. 30870633, 31000427) and the Fundamental Research Funds for the Central Universities (No. DUT12JB09).


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Copyright information

© Akadémiai Kiadó, Budapest, Hungary 2012

Authors and Affiliations

  • Ping Song
    • 1
  • Guangyi Chen
    • 1
  • Zhiyong Wei
    • 1
  • Wanxi Zhang
    • 1
  • Jicai Liang
    • 1
  1. 1.School of Automotive EngineeringDalian University of TechnologyDalianChina

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