Effect of Water and Crystallinity on Gas Barrier Properties of Poly(butylene 2,5-furandicarboxylate) and Its Copolymers

Gas barrier properties are essential for food packaging materials, ensuring the preservation of goods [1]. Poly(butylene 2,5-furandicarboxylate) (PBF), a fully biobased polyester, shows excellent gas barrier performance, making it a sustainable alternative to petrochemical plastics for single-material flexible packaging [2]. However, understanding how crystallinity and water exposure affect PBF’s barrier properties is key to evaluating its potential for real-world applications. In this study, PBF was synthesized, characterized, and its gas barrier properties were investigated in dry and 85% RH atmosphere. For comparison, poly(butylene isophthalate) (PBI), a petrochemical analog with a benzene ring instead of the furan ring, and random PBF-PBI copolymers were synthesized and analyzed under identical conditions. Gas permeability measurements revealed that, unlike PBI, amorphous PBF maintains its barrier performance in moist environments, while PBI exhibited a tenfold increase in permeability. Additionally, amorphous PBF-rich copolymers showed permeability reductions of up to -95% when transitioning from dry to wet conditions. This behavior was investigated using water-bath DMA, showing that water interacted uniquely with PBF, altering its relaxation behavior, hence mediating its barrier performance, while PBI exhibited a pure plasticization effect. The impact of crystallinity was also evaluated under both dry and moist conditions. Crystallinity caused a slight deterioration in barrier performance under dry conditions for both PBF and PBI, whereas it significantly increased the permeability of PBI under wet conditions. These findings underscore how PBF’s furan structure governs its interactions with water, offering the potential for high-barrier performance even in moist conditions. References 1. González-López, M.E.; Calva-Estrada, S. de J.; Gradilla-Hernández, M.S.; Barajas-Álvarez, P. Current Trends in Biopolymers for Food Packaging: A Review. Front. Sustain. Food Syst. 2023, 7, doi:10.3389/fsufs.2023.1225371. 2. Guidotti, G.; Soccio, M.; García-Gutiérrez, M.C.; Ezquerra, T.; Siracusa, V.; Gutiérrez-Fernández, E.; Munari, A.; Lotti, N. Fully Biobased Superpolymers of 2,5-Furandicarboxylic Acid with Different Functional Properties: From Rigid to Flexible, High Performant Packaging Materials. ACS Sustainable Chem. Eng. 2020, 8, 9558–9568, doi:10.1021/acssuschemeng.0c02840.