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Water vapor permeability of poly(lactide)s: Effects of molecular characteristics and crystallinity

Authors

  • Hideto Tsuji,

    Corresponding author
    1. Department of Ecological Engineering, Faculty of Engineering, Toyohashi University of Technology, Tempaku-cho, Toyohashi, Aichi 441-8580, Japan
    • Department of Ecological Engineering, Faculty of Engineering, Toyohashi University of Technology, Tempaku-cho, Toyohashi, Aichi 441-8580, Japan
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  • Rumiko Okino,

    1. Department of Ecological Engineering, Faculty of Engineering, Toyohashi University of Technology, Tempaku-cho, Toyohashi, Aichi 441-8580, Japan
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  • Hiroyuki Daimon,

    1. Department of Ecological Engineering, Faculty of Engineering, Toyohashi University of Technology, Tempaku-cho, Toyohashi, Aichi 441-8580, Japan
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  • Koichi Fujie

    1. Department of Ecological Engineering, Faculty of Engineering, Toyohashi University of Technology, Tempaku-cho, Toyohashi, Aichi 441-8580, Japan
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Abstract

Amorphous-made poly(L-lactide) [i.e., poly(L-lactic acid) (PLLA)], poly(L-lactide-co-D-lactide)[P(LLA-DLA)](77/23), and P(LLA-DLA)(50/50) films and PLLA films with different crystallinity (Xc) values were prepared, and the effects of molecular weight, D-lactide unit content (tacticity and optical purity), and crystallinity of poly(lactide) [i.e., poly(lactic acid) (PLA)] on the water vapor permeability was investigated. The changes in number-average molecular weight (Mn) of PLLA films in the range of 9 × 104–5 × 105 g mol−1 and D-lactide unit content of PLA films in the range of 0–50% have insignificant effects on their water vapor transmission rate (WVTR). In contrast, the WVTR of PLLA films decreased monotonically with increasing Xc from 0 to 20%, while leveled off for Xc exceeding 30%. This is probably due to the higher resistance of “restricted” amorphous regions to water vapor permeation compared with that of the “free” amorphous regions. The free and restricted amorphous regions are major amorphous components of PLLA films for Xc ranges of 0–20% and exceeding 30%, respectively, resulting in the aforementioned dependence of WVTR on Xc. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006

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