Biodegradable starch-polyvinyl alcohol composite films by the incorporation of lignin for packaging applications

In this work, firstly, the optimal performance ratio of potato starch and polyvinyl alcohol (PVA) was selected, and then the sustainable high-grade food packaging film was developed by adding different amounts (0, 5, 10, 15, 20, and 25 wt% based on the starch mass) of functional additive lignin into the starch - PVA film matrix. Starch - PVA based films with different amounts of lignin were studied from the aspects of morphology, physical and chemical properties, barrier properties, mechanical properties and antioxidant properties. Mechanical tests showed that lignin significantly improved the tensile strength (TS) of the film and effectively blocked the passage of water vapor. Lignin, starch and PVA were linked by hydrogen bond to form polymer network structure, which improved the interfacial compatibility between polymers. The interaction between polymer molecules and the distribution of lignin particles were confirmed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The high content of phenolic hydroxyl in lignin undergoes proton coupled electron transfer mechanism, which endows the composite film with high antioxidant activity, which is proved by DPPH radical scavenging activity experiment. At the same time, it also gives the film excellent UV barrier and antibacterial properties. The introduction of lignin in this study provides a valuable way for the preparation of multifunctional composite films using biomass as raw materials, and has a potential application prospect in food packaging.