Barium Crosslinking in Bio‐Based Sodium Alginate Films: Improved Barrier and Thermal Performance Toward Biodegradable Packaging Applications

Abstract

Growing environmental concerns associated with petroleum‐based plastics have intensified the demand for sustainable, biodegradable materials for packaging applications. Sodium alginate is a natural polysaccharide with excellent biodegradability, biocompatibility, and film‐forming ability; however, its high moisture sensitivity and moderate thermal stability limit its application. In this study, sodium alginate films were produced by solvent casting and ionically cross‐linked with BaCl 2 solutions at concentrations of 1%, 2%, and 5% (w/v) to evaluate the influence of Ba 2+ on their structural, barrier, and thermal properties. The films were characterized by SEM/EDS, FTIR‐ATR, TGA, and measurements of water vapor absorption, swelling, and mass loss. Cross‐linking promoted denser polymer networks, reducing water vapor absorption from 20% ± 0.55% to 10.5% ± 0.56% at 75% relative humidity, while swelling decreased from 40% ± 2.5% to 29% ± 0.9% after 400 min. TGA indicated improved thermal stability, and mass loss after 24 h in water ranged from 11% to 13%. SEM revealed a more compact morphology with crystalline deposits, while FTIR confirmed ionic interactions between alginate carboxylate groups and Ba 2+ ions. Overall, Ba 2+ cross‐linking significantly improved the physicochemical, barrier, and thermal properties of sodium alginate films, highlighting their potential as biodegradable packaging materials.