PHA and PLA Dispersions as Biodegradable Sealing Lacquers for Paper-based Barrier Packaging

The shortage of biodegradable options for sealing lacquers for paper-based packaging has led to research on biopolyesters like PLA and PHA, though both pose challenges due to their high crystallinity and melting temperatures, complicating film formation at lower coating temperatures. In our research, we addressed these challenges by using low crystalline polymer grades in an emulsification/solvent evaporation process, resulting in dispersions characterised by small particle sizes in the range of 220-510 nm and effective film formation at reduced temperatures of maximum 150 °C. Coated papers showed strong barrier performance, with WVTR and oxygen permeance values below 20 g/m²·d and 1 cm³/m²·d·bar, respectively. While PLA-based coatings achieved acceptable seal strengths, PHA coatings require further optimization. The potential for use in food packaging applications was confirmed by overall migration below regulatory limits and sensory tests on chocolate showing no differences to the conventional packaging over the given shelf-life.