Crystallinity development in cellular poly(lactic acid) in the presence of supercritical carbon dioxide

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DOIResolve DOI: http://doi.org/10.1002/app.30338
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TypeArticle
Journal titleJournal of Applied Polymer Science
Volume113
Issue5
Pages29202932; # of pages: 13
Subjectpoly(lactic acid); crystallization; carbon dioxide; foam extrusion
AbstractThis article investigates the crystallinity development in cellular poly(lactic acid) (PLA) and the effect of the achieved crystalline content on its properties and microstructure. Carbon dioxide (CO₂) in its supercritical state was used as the expansion agent for three different grades of PLA that differed in terms of L-lactic acid content. Cellular PLA was produced on a twin-screw extrusion line using capillary dies of various diameters. The obtained crystalline contents were measured by differential scanning calorimetry and X-ray diffraction techniques. The morphology of the cellular structures was examined using scanning electron microscopy. The crystallinity developed on expansion depended on L-lactic acid content, on supercritical CO₂ concentration, polymer flow rate, and die diameter. Cellular PLA, with densities as low as 30 kg/m³, was obtained under the most favorable conditions. It was shown that the crystallinity development in PLA enhances its cellular structure formation and enables the fabrication of quality cellular materials at lower CO₂ concentration. The presence of PLA crystallites within expanded cell walls leads to a peculiar 2D-cavitation phenomena observed only in the cell walls of semicrystalline foams.
Publication date
LanguageEnglish
AffiliationNational Research Council Canada (NRC-CNRC); NRC Industrial Materials Institute
Peer reviewedYes
NRC number52512
NPARC number15661971
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Record identifier8a7dc3b4-f6e6-4312-a01d-5055f204ec1a
Record created2010-06-29
Record modified2016-05-09
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