Tough and Biodegradable Gelatin-Based Film via the Synergistic Effect of Multi-Cross-Linking

Large amounts of petroleum-derived packaging film waste cause environmental problems and threaten human health. In this study, a multi-cross-linked biodegradable film containing gelatin, dialdehyde oligo-chitosan (DOC), and polyvinyl alcohol (PVA), with excellent mechanical properties, was fabricated via a facile process. The DOC simultaneously acted as an antioxidative and antimicrobial component and a crosslinker to covalently crosslink the gelatin matrix to form the first gelatin network. PVA cross-linked via its crystalline domains acted as the second network, interpenetrating the first gelatin network. The film with such a structure contained multi-cross-linking of hydrogen bonds, covalent bonds, and crystalline domains that all could act as sacrificial bonds to dissipate energy. Therefore, the fabricated film exhibited high mechanical strength and toughness. Additionally, it also demonstrated good light transmittance, improved moisture resistance, and biodegradability in natural soil, and its food preservation efficiency was comparable to that of commercial polyethylene materials. The fabrication process is facile and harmful solvent-free; all these properties make the film a promising alternative to conventional non-biodegradable petroleum-derived packaging films for food preservation.