Poly(butylene adipate-co-terephthalate)/synthetic hectorite clay nanocomposite coated paper-based sustainable barrier materials for packaging application

Environmental concerns over petroleum-based packaging have driven the search for sustainable paper-based alternatives, but poor barrier and mechanical properties of paper limit its use in food packaging. This work introduces a novel, eco-friendly strategy to enhance paper-based packaging by poly (butylene adipate-co-terephthalate) (PBAT) and synthetic hectorite clay nanocomposite coating. Utilizing tetrahydrofuran (THF), a less toxic, non-chlorinated solvent for the first time, PBAT was dissolved and nanoclay dispersed, enabling safer and scalable coatings. Four hectorite clay grades were evaluated for compatibility and dispersibility in THF, with Sumecton-SEN (SEN) and Sumecton-STN (STN) selected based on NMR solvent relaxation, morphology, and dispersion analyses. Multilayer coatings with varying nanoclay content (3–7 wt%) and coating-grammage were applied to kraft paper, and the resulting materials were systematically characterized for mechanical properties, water and oil resistance, and gas barrier properties. Both PBAT-STN and PBAT-SEN nanocomposite papers outperformed neat PBAT coatings, with PBAT-STN delivering superior performance, with optimal results at 5 wt% clay loading. The well-dispersed hectorite nanoclay in the PBAT matrix significantly improved barrier performance by increasing the tortuosity of diffusion pathways, leading to substantial reductions in oxygen and water vapor transmission rates (up to 58.3 % and 48.5 %, respectively compared to neat PBAT coated paper). The optimized PBAT-clay nanocomposite-coatings also demonstrated excellent water resistance (lowest Cobb 60 value 0.3 g.m⁻²), high grease resistance (Kit number-12), and no oil penetration for extended periods, even at elevated temperatures. These results establish PBAT/hectorite nanocomposite-coated paper as a promising, sustainable solution for advanced food packaging, combining biodegradability, mechanical robustness, and superior protective functionality.