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Int. J. Mol. Sci. 2009, 10(12), 5381-5397; doi:10.3390/ijms10125381

A Study of the Crystallization, Melting, and Foaming Behaviors of Polylactic Acid in Compressed CO2

Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario, M5S 3G8, Canada
* Author to whom correspondence should be addressed.
Received: 27 October 2009 / Revised: 26 November 2009 / Accepted: 14 December 2009 / Published: 16 December 2009
(This article belongs to the Special Issue Supercritical Carbon Dioxide)
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The crystallization and melting behaviors of linear polylactic acid (PLA) treated by compressed CO2 was investigated. The isothermal crystallization test indicated that while PLA exhibited very low crystallization kinetics under atmospheric pressure, CO2 exposure significantly increased PLA’s crystallization rate; a high crystallinity of 16.5% was achieved after CO2 treatment for only 1 min at 100 °C and 6.89 MPa. One melting peak could be found in the DSC curve, and this exhibited a slight dependency on treatment times, temperatures, and pressures. PLA samples tended to foam during the gas release process, and a foaming window as a function of time and temperature was established. Based on the foaming window, crystallinity, and cell morphology, it was found that foaming clearly reduced the needed time for PLA’s crystallization equilibrium.
Keywords: crystallization; polylactic acid; compressed CO2 crystallization; polylactic acid; compressed CO2
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Zhai, W.; Ko, Y.; Zhu, W.; Wong, A.; Park, C.B. A Study of the Crystallization, Melting, and Foaming Behaviors of Polylactic Acid in Compressed CO2. Int. J. Mol. Sci. 2009, 10, 5381-5397.

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