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. 2021 Oct 19;807:151084. doi: 10.1016/j.scitotenv.2021.151084

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© 2021 Published by Elsevier B.V.

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Fig. 3 — (a) Integration ratio (CH₃/CH) with respect to soak duration for polylactic acid (PLA) mask layer samples. (b) Fourier transform infrared spectroscopy (FTIR) peak height ratio for the respective characteristic stretching vibration bands of PLA in the middle layer.