ABSTRACT To achieve stable thermal processing of water plasticized PVA and improve the brittleness of the final films, citric acid (CA) was introduced. By establishing a new hydrogen bonding network with PVA and water, and forming an ester crosslinking network with PVA, CA effectively inhibited the intense evaporation of water and improved the thermal processing stability of the system. The plasticization and crosslinking of CA competed with each other, reaching the optimal balance at a concentration of 20%. The obtained PVA film exhibited structural integrity and excellent oxygen barrier property (OTR of 0.90 × 10 −16 cm 3 ·cm/cm 2 ·s·Pa), surpassing the commercial EVOH/PA/PE film (OTR of 6.83 × 10 −16 cm 3 ·cm/cm 2 ·s·Pa), and achieved the elongation at break of 93%, six times higher than pure PVA film, and tensile strength of 51 MPa. CA also endowed the film with antibacterial properties, effectively delaying the spoilage process of strawberries for more than 5 days. This synergistic plasticization and crosslinking mechanism of CA on PVA would provide a reference for solving the big challenge in thermal processing of water‐plasticized PVA, and a feasible strategy for developing sustainable food packaging films that integrate barrier, toughness, and antimicrobial properties.
Zhang et al. (Fri,) studied this question.