“…FTIR analysis was performed on powders (Figure 2A), monolayer (Figure 2B), and bilayer films (Figure 2C) in order to identify the influence of the additives on the chemical structure of the PLA. The FT-IR spectrum of umbelliferone showed a sharp peak of OH group at 3,153 cm −1 (Ittadwar and Puranik, 2017), frequencies identified at 3,122 and 2,987 cm −1 are designated to C-H stretching vibrations, single bonded carbonyl group vibrations at 1388, 1,345, and 1,233 cm −1 , while frequencies at 1,578, 1,454, 1,446, 1,409, and 1,386 cm −1 have been designated to C-C stretching vibrations (Rexali, 2007).…”