Full Paper

Extrusion Foaming of Semi-Crystalline PLA and PLA/Thermoplastic Starch Blends

  1. Mihaela Mihai1,
  2. Michel A. Huneault2,*,
  3. Basil D. Favis1,
  4. Hongbo Li2

Article first published online: 28 JUN 2007

DOI: 10.1002/mabi.200700080

Issue

Macromolecular Bioscience

Macromolecular Bioscience

Volume 7, Issue 7, pages 907–920, July 9, 2007

Additional Information

How to Cite

Mihai, M., Huneault, M. A., Favis, B. D. and Li, H. (2007), Extrusion Foaming of Semi-Crystalline PLA and PLA/Thermoplastic Starch Blends. Macromolecular Bioscience, 7: 907–920. doi: 10.1002/mabi.200700080

Author Information

  1. 1

    CREPEC, Chemical Engineering Department, École Polytechnique de Montréal, P.O. Box 6079, Station Centre-Ville, Montréal, Québec, Canada, H3C 3A7

  2. 2

    Industrial Materials Institute, National Research Council of Canada, 75 de Mortagne, Boucherville, Québec, Canada, J4B 6Y4

*Industrial Materials Institute, National Research Council of Canada, 75 de Mortagne, Boucherville, Québec, Canada, J4B 6Y4. Fax: 1 450 641 5105

Publication History

  1. Issue published online: 9 JUL 2007
  2. Article first published online: 28 JUN 2007
  3. Manuscript Accepted: 4 MAY 2007
  4. Manuscript Revised: 2 MAY 2007
  5. Manuscript Received: 20 MAR 2007

Funded by

  • Canada's Natural Science and Engineering Research Council
  • Canadian Biomass Innovation Network

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Keywords:

  • foam extrusion;
  • polylactic acid;
  • polymer blends;
  • thermoplastic starch

Abstract

Low density open-cell foams were obtained from polylactic acid (PLA) and from blends of PLA with thermoplastic starch (TPS) using CO2 as a blowing agent. Two unexpected features were found. First, a 2D cavitation process in the fractured cell walls was unveiled. Elliptical cavities with dimensions in the 100–300 nm range were aligned perpendicular to large cell cracks clearly exhibiting 2D crazing prior to macroscopic cell rupture. Secondly, a significant crystallization rate increase associated with the CO2 foaming of PLA was discovered. While the PLA used in this study crystallized very slowly in isothermal crystallization, the PLA foams exhibited up to 15% crystallinity, providing evidence that CO2 plasticization and the biaxial stretching upon foam expansion provided conditions that could increase the crystallization rate by several orders of magnitude.

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