Electron Beam-Mediated Cross-Linking of Blown Film-Extruded Biodegradable PGA/PBAT Blends toward High Toughness and Low Oxygen Permeation

Abstract

Due to its high crystallinity, tailored compostability, and superior barrier performance, poly(glycolic acid) (PGA) has great potential as a substitute for current single-use plastics used in food packaging applications and with a lower carbon footprint. However, its susceptibility to hydrolysis and mechanical brittleness hinders its direct suitability in packaging. In this work, we circumvent this limitation by first blending PGA with a thermoplastic polyester, poly(butylene adipate-co-terephthalate) (PBAT), and a glycidyl cross-linker via industrial-scale twin-screw extrusion and then converting to a film by blown film extrusion. The surface of the films was then chemically cross-linked using electron beam treatment (EBT) to impart excellent barrier properties. Here, the electron beam plays a dual role. Firstly, it cross-links the surface of the films and improves the oxygen and moisture barrier performance, both improved due to blending with PBAT. Second, it does not compromise the toughness or extension at break of the polymer blend, both desirable for flexible packaging applications. A dosage of 250 kGy EBT resulted in the film having an oxygen barrier permeation of 57.0–59.8 cm³ mm m⁻² 24 h⁻¹ atm⁻¹ and a water vapor permeation of 26.8 g m⁻² 24 h⁻¹ while maintaining a high toughness of 75 MPa. At dosages higher than 300 kGy, inhomogeneities formed on the surface of the films and some degradation in the mechanical properties of the films is observed. This work highlights the possibility of deriving superior biopolymer barrier performance while retaining the mechanical properties required for food packaging using a combination of blending and electron beam treatment, both scalable processes.