Biobased alginate– <scp>PBAT</scp> blend films for sustainable packaging: overcoming the performance trade‐offs of ionic crosslinking

Abstract In the pursuit of sustainable packaging to combat plastic pollution, sodium alginate, a renewable biopolymer, holds promise but demands enhancements for brittleness and moisture sensitivity. This study compares ionic crosslinking and polymer blending to develop high‐performance films from a tensile strength‐optimized formulation. Ionic crosslinking with CaCl 2 boosts tensile strength to 41 MPa but induces brittleness (&lt;2% elongation), reduced thermal stability and barrier trade‐offs. On the contrary, compatibilizer‐free blending with 30 wt% poly[(butylene adipate)‐ co ‐terephthalate] (PBAT) yields better films with 47 MPa tensile strength, 852 g m −2 day −1 water vapor transmission rate and improved thermal stability, driven by hydrogen bonding and ‘sea–island’ morphology. Based on published literature on PBAT compostability and reported degradation behavior of PBAT/alginate‐type systems, the blend films are expected to be compatible with industrial composting end‐of‐life routes; however, biodegradation was not measured in this study. Polymer blending emerges as a superior strategy, decoupling trade‐offs for multifunctional, ecofriendly packaging films. © 2026 Society of Chemical Industry.