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Crystallinity development in cellular poly(lactic acid) in the presence of supercritical carbon dioxide
Author(s) -
Mihai Mihaela,
Huneault Michel A.,
Favis Basil D.
Publication year - 2009
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.30338
Subject(s) - crystallinity , supercritical carbon dioxide , supercritical fluid , materials science , lactic acid , chemical engineering , differential scanning calorimetry , scanning electron microscope , microstructure , crystallite , extrusion , polymer chemistry , composite material , chemistry , organic chemistry , physics , biology , bacteria , metallurgy , genetics , engineering , thermodynamics
This 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 (CO 2 ) 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 CO 2 concentration, polymer flow rate, and die diameter. Cellular PLA, with densities as low as 30 kg/m 3 , 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 CO 2 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. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009