Enhancing the mechanical and barrier properties of starch-based green packaging films via acetalization reaction and hydrogen bond dual crosslinking.

As an abundant, eco-friendly bio-material, starch has great potential to address pollution from petroleum-based plastic films, but starch-based films still need improved mechanical and barrier properties for practical use. Therefore, this study proposes an oxidation-dual crosslinking strategy. Native cassava starch (CS) was initially oxidized using NaIO4 to produce dialdehyde starch (DAS). Subsequently, polyvinyl alcohol (PVA) and cellulose nanofibrils (CNF) were incorporated into the DAS matrix, forming a compact-structured DAS composite film, through a dual crosslinking network involving acetalization reactions and intermolecular hydrogen bonding. Compared with the CS film, the optimized DAS-6c-12p composite film (with 6 % CNF and 12 % PVA based on the dry weight of DAS) demonstrated significant improvements in mechanical and barrier properties: tensile strength increased from 15.28 ± 1.11 MPa to 65.67 ± 2.50 MPa, tensile strain rose from 4.67 ± 0.68 % to 6.21 ± 0.13 %, water vapor permeability coefficient decreased from 11.50 ± 0.60 to 3.04 ± 0.19 g·mm/(m2·d), oxygen permeability coefficient reduced from 10.322 ± 0.303 to 0.097 ± 0.003 cm3·mm/(m2·d·0.1 MPa), and edible oil permeability coefficient declined from 4.80 ± 0.14 to 0.50 ± 0.02 g·mm/(m2·d). Notably, compared to the polyethylene packaging film, this composite film exhibited superior fruit preservation capability and biodegradability. This work provides a novel strategy for developing biobased high strength barrier film.