Sodium Lignosulfonate Synergistically Modified LDHs Achieve Toughening and Enhanced Barrier Properties in PVA-Based Nanocomposite Films

Polyvinyl alcohol (PVA) has been widely used in the packaging field due to its biodegradability and excellent film-forming properties, making it an ideal candidate to replace petroleum-based plastics. However, the intrinsic brittleness and limited barrier performance of PVA films severely limit their further applications. Conventional reinforcement strategies relying on inorganic fillers often fail to balance strength and toughness, mainly due to their static interfacial interactions and inadequate energy dissipation capacity. To solve this problem, this study draws inspiration from the interfacial regulation mechanism of bone tissue and proposes an innovative biomimetic interface design strategy. Surface-modified TA-Fe(III)@LDHs or intercalated SA-LDHs are incorporated into the PVA matrix, while sodium lignosulfonate (LS) is introduced as a dynamic interfacial molecule. This synergistic design constructs reversible sacrificial bonds and energy dissipation pathways within the composite system, thereby realizing the simultaneous enhancement of strength and toughness. Among all the prepared composite films, the surface-modified system (P1L5S) exhibits the most balanced overall performance. It reaches a tensile strength of 61 MPa, an elongation at break of 228%, and a toughness of 131 MJ/m3, outperforming most reported PVA-based composite films. Meanwhile, the intercalation-modified system (P1A5S) shows superior gas barrier properties. Its relative water vapor permeability and oxygen permeability are reduced to 57% and 14%, respectively. The PVA/modified LDHs/LS ternary nanocomposite film developed in this research integrates high strength, excellent toughness, and outstanding barrier performance. This study provides a novel biomimetic method and a sustainable solution for developing eco-friendly and biodegradable food packaging materials.