Characteristics of poly(vinyl alcohol) films crosslinked by cinnamaldehyde with improved transparency and water resistance

ABSTRACT Poly(vinyl alcohol) (PVA) films crosslinked by cinnamaldehyde (CIN) at various concentrations were prepared. Their physicochemical and antibacterial properties were compared with those of uncrosslinked films. The results suggest that the crosslinked films exhibited higher transparency, tensile strength, and elongation at break in a certain CIN concentration range. They also displayed decreased water vapor permeability and water solubility. Although the antibacterial activity of the crosslinked film‐forming solution was less slightly than that of the uncrosslinked film‐forming solution, the crosslinked film‐forming solution still demonstrated strong antibacterial activity when the concentration of CIN was 2% v/v. The aldol condensation reaction between the aldehyde group of CIN and the alcoholic hydroxyl group of PVA was determined by Fourier transform infrared spectroscopy. By the crosslinking reaction, the heat stability of the crosslinked film was enhanced compared with that of the uncrosslinked film. Meanwhile, a compact, smooth, and continuous cross‐sectional microstructure present in the crosslinked film was observed by scanning electron microscopy. The higher water resistance and transparency gave the crosslinked films priority for use in food packaging. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45324.