Crystal modifications and multiple melting behavior of poly(L-lactic acid-co-D-lactic acid)

✍ Scribed by Changyu Shen; Yaming Wang; Ming Li; Defu Hu

• Publisher: John Wiley and Sons
• Year: 2010
• Tongue: English
• Weight: 182 KB
• Volume: 49
• Category: Article
• ISSN: 0887-6266
• DOI: 10.1002/polb.22175

✦ Synopsis

Abstract

The crystal modifications and multiple melting behavior of poly(L‐lactic acid‐co‐D‐lactic acid) (98/2) as a function of crystallization temperature were studied by wide‐angle X‐ray diffraction (WAXD) and differential scanning calorimetry (DSC). It was found that the disorder (α′) and order (α) phases of poly(L‐lactic acid) (PLLA) were formed in cold‐crystallized poly(L‐lactic acid‐co‐D‐lactic acid) samples at low (<110 °C) and high (≥110 °C) temperatures, respectively. A disorder‐to‐order (α′‐to‐α) phase transition occurred during the annealing process of the α′‐crystal at elevated temperatures, which proceeded quite slowly even at the peak temperature of the exotherm P~exo~ but much more rapidly at higher temperature close to the melting region. The presence or absence of an additional endothermic peak before the exotherm in the DSC thermograph of the α′‐crystal was strongly dependent on the heating rate, indicating that a melting process involved during the α′‐to‐α phase transition. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011