Development of multilayer films based on PLA/PBAT and sodium alginate for active packaging

In this study, polylactic acid (PLA) and polyadipic acid/butylene terephthalate (PBAT) blend polymer were used as matrix to prepare PLA/PBAT substrate film by twin-screw extruder. A series of multilayer films were prepared by starch-based adhesive by loading 1% chitosan (CS), 1% zinc oxide nanoparticles (ZnONPs) or 1% silver nanoparticles (AgNPs) with sodium alginate (SA) as three different coatings. Compared with PLA/PBAT, the combination of adhesive and SA-based antibacterial coating significantly improved the water vapor barrier, oxygen barrier and mechanical properties of the film, regardless of the type of antibacterial agent. The water vapor transmission of SA-based AgNPs coating film decreased from the original 5.77 × 10⁻¹⁴ to 3.41 × 10⁻¹⁴ g·cm·cm⁻²·Pa⁻¹·s⁻¹. The oxygen permeability of SA-based chitosan coating decreased from the original 74.35 × 10⁻¹⁴ to 6.40 × 10⁻¹⁴ cm³·cm·cm⁻²·Pa⁻¹·s⁻¹. The tensile strength of the SA-based AgNPs coating film increased from the original 264.79 to 286.22 MPa. The film is yellow and has good ultraviolet absorption capacity. Membranes doped with CS, ZnONPs or AgNPs inhibited the growth of Escherichia coli and Staphylococcus aureus. Among them, chitosan doped membrane has weak antibacterial activity, AgNPs doped membrane has the best antibacterial activity against E. coli and S. aureus, and has potential application prospects in active packaging.