Synergistic Enhancement of Barrier Performance in Silanized Modified Hemicellulose/PVA Composite Films through Oxalic Acid Crosslinking

Polyvinyl alcohol (PVA)-based materials are widely acknowledged for their commendable mechanical properties, biodegradability, and environmental friendliness. However, their limitations in water resistance, as well as water vapor/oxygen/ultraviolet (UV) barrier properties, hinder their application in the packaging industry. In this study, hemicellulose (HC) extracted from poplar wood was subjected to silane coupling agent modification, resulting in silylated modified hemicellulose (KHC) with enhanced hydrophobicity. Acting as a reinforcing filler for PVA, KHC demonstrated synergistic interactions with cost-effective green crosslinking agents, particularly oxalic acid (OA), during the preparation of a KHC/PVA/OA composite membrane using a solution casting method. SEM analysis revealed a compact and uniform network structure, accompanied by moderate tensile strength, good flexibility, and maximum elongation at a break of 132%. Compared to PVA film, the water resistance (swelling degree: 69.2%, contact angle: 85.0 degrees, solubility: 9.8%) of the composite film was significantly improved. At 10% OA content, the KHC/PVA/OA film demonstrated a 43.01% improvement in the water vapor barrier and a 36.83% enhancement in the oxygen barrier compared to the PVA film. In addition, the film with 10% OA content exhibited outstanding ultraviolet shielding performance. The improved compatibility among film components results from the enhanced synergistic effect of sulfhydryl groups introduced into the film and hydrogen bonds and ester bonds between the components. Hence, the developed KHC/PVA/OA composite membrane holds significant promise for diverse applications in the packaging industry, highlighting improved barrier performance and mechanical properties.