Biodegradable Anti-Ultraviolet Film from Modified Gallic Acid Cross-linked Gelatin

The use of leather production waste to prepare degradable films is a sustainable production concept that can improve resource utilization and reduce the environmental pollution caused by traditional packaging waste. In this study, a biodegradable anti-ultraviolet film was prepared using gelatin obtained from tanning waste as the raw material and modified gallic acid as a cross-linking agent. The aldehyde group in the modified gallic acid reacts with the amino group in the gelatin molecule to form a stable covalent bond, which increases the cross-linking degree of the gelatin film. Compared with the conventional gelatin film, the modified gallic acid cross-linked gelatin film exhibited stronger tensile strength (6.357 MPa) and higher elongation at break (155.11%). The anti-ultraviolet capability of the film significantly increased as the conjugation system was enhanced owing to the formation of a Schiff base structure between the modified gallic acid and gelatin molecule, with strong UV absorption (T < 1%) in the range of 200–458 nm. The modified gallic acid cross-linked gelatin films also showed good antioxidant and antibacterial properties and excellent biodegradability, indicating its application potential in the packaging field.