Synergistic enhancement of gas barrier and aging resistance for biodegradable films with aligned graphene nanosheets

There is currently great interest in biodegradable alternatives for packaging and agricultural applications. The most viable biodegradable alternative, poly (butylene adipate-co-terephthalate) (PBAT), has poor resistance to water vapor and oxygen permeation and tends to degrade rapidly under solar exposure. Herein, we report a preparation of PBAT nanocomposite films with aligned graphene nanosheets both in and on the films by combining two techniques, biaxial orientation and rod scarping. The composite films with a graphene content of 0.48 vol% exhibited 80% decrease of water vapor permeability and over 99% decrease of oxygen permeability, approaching values of 1.0 × 10⁻¹¹ g m m⁻²·Pa⁻¹ s⁻¹ and 6.2 × 10⁻¹⁶ cm³ cm cm⁻²·Pa⁻¹ s⁻¹. These values are respectively comparable to and even lower than the reported 9.9 × 10⁻¹² g m m⁻²·Pa⁻¹ s⁻¹ and 8.0 × 10⁻¹⁵ cm³ cm cm⁻²·Pa⁻¹ s⁻¹ for polyethylene films. After a 200 h aging, the composite films still possessed a fracture strength of 47.3 MPa and an elongation at break of 167%, in contrast to a complete fragmentation of pure PBAT. We believe that the controlled incorporation of aligned graphene nanosheets to biodegradable polymers could become an important strategy to develop sustainable packaging and agricultural films.