Ultra-low gas permeability and efficient reinforcement of cellulose nanocomposite films by well-aligned graphene oxide nanosheets

Cellulose is often considered to be an ideal candidate for biodegradable packaging films, but its main weakness is its poor gas barrier performance. We used a simple, efficient, low cost, recyclable, non-toxic and environmentally friendly processing solvent (an aqueous solution of NaOH/urea) to fabricate graphene oxide nanosheet (GONS)/regenerated cellulose (RC) nanocomposite films with an ultra-low O-2 permeability and high mechanical performance. Transmission electron microscopy and two-dimensional wide-angle X-ray diffraction measurements showed that the GONSs were fully exfoliated, homogeneously dispersed and highly aligned along the surface of the cellulose nanocomposite films. Rheological and Fourier transform infrared spectroscopy measurements demonstrated the existence of strong H-bonding interactions between the GONSs and the cellulose matrix. A significant improvement in the barrier properties of the regenerated cellulose nanocomposite films was achieved. The O-2 permeability coefficient was reduced by about 1000 times relative to the pure regenerated cellulose film at a low GONS loading of 1.64 vol%. The tensile strength and Young's modulus of the regenerated cellulose nanocomposite films were enhanced by about 67 and 68%, respectively, compared with the RC film. The theoretical simulation results of the Cussler and Halpin-Tsai models consistently confirmed that the GONSs tended to align parallel to the film surface; this was probably induced by gravitational forces and further consolidated by hot pressing. The work presented here indicates that this simple and environmentally friendly method is an effective strategy to design highly aligned nanofillers in polymer nanocomposite films. The cellulose nanocomposite films obtained have excellent potential as packaging materials for protecting perishable goods susceptible to O-2 degradation.