Effect of sepiolite on the quiescent and non-quiescent crystallization behaviour of the biodegradable poly(lactic acid) prepared via casting and melting

• Main Authors: S. A. Cruz, L. A. Onoue, C. M. Paranhos, E. Longo
• Format: Article
• Language: English
• Published: Budapest University of Technology 2019-09-01
• Series: eXPRESS Polymer Letters
• Subjects: Nanocomposites; Poly(lactic acid); Sepiolite; Crystallization
• Online Access: http://www.expresspolymlett.com/letolt.php?file=EPL-0009934&mi=cd

Poly(lactic acid) (PLA) is one of the most extensively investigated and used aliphatic polyesters due to some aspects such as biodegradability and biocompatibility. However, PLA has some disadvantages that restrict its applicability for instance its limited thermal resistance and low crystallization kinetics. In this work, nanoclay mineral sepiolite (Sep) was used to enhance the crystallization of PLA. The samples were prepared by casting and melting to evaluate the influence of the processing type on the PLA crystallization. For this purpose, the crystallization kinetics as a function of (i) Sep content and (ii) different types of processing was evaluated by polarized optical microscopy, flow-induced crystallization and differential scanning calorimetry under isothermal condition and glassy crystallization (Avrami model), X-ray diffraction and small angle X-ray scattering. The results of quiescent crystallization show that the presence of Sep enhanced the nucleation density leading to faster spherulites growing and lower crystallization half-time compared with pure PLA. The Sep also affects the flow-induced crystallization in different way. Altogether, the relevance of the present study lies in the fact that it sheds some light on how the Sep content, processing and molar mass of the initial precursor can affect the crystallization of PLA.