Dual grafting strategy via Schiff base cross-linking for durable antibacterial and uvioresistant starch-based degradable packaging film.

In the face of the environmental crisis stemming from petrochemical plastics, there is an urgent need to search biodegradable packaging film. Starch emerges as an ideal alternative owing to eco-friendliness and renewability. Based on time, temperature, pH and molar ratio, salicylaldehyde starch (SCS) and aminated poly (vinyl alcohol) (APVA) with optimal grafting rates are successfully synthesized. Subsequently, starch-based films (SCSP) are fabricated via controllable dual-grafting strategy and Schiff base cross-linking. Because of the presence of modified APVA, the SCSP film has high tensile strength (≥ 20.5 MPa) and elongation at break (≥ 38.3 %). The incorporation of Schiff base group endows films with exceptional UV resistance (≥ 99 %) and sustained sterilization for up to 30 days. Meanwhile, excellent compatibility and gas barrier properties of films prevent bananas from browning for 120 h under ultraviolet irradiation, and extend the shelf life of strawberries by up to 7 days. In particular, the film is virtually biodegradable in soil after 35 days and exhibits high biosafety with cell viability of over 83.2 %, which presents a controllable and simplified modification strategy for starch, and opens up the possibility of alleviating the pollution caused by petrochemical plastics.