Improved barrier properties of poly(lactic acid) with randomly dispersed graphene oxide nanosheets

Poly(lactic acid) (PLA) is undoubtedly the most suitable for the environmentally friendly biodegradable packaging film due to its excellent integrated performances, but the insufficient gas barrier performance is its weakness. In the present work, graphene oxide nanosheets (GONSs) were fully exfoliated and randomly dispersed in the PLA matrix. A large decline in gas permeability coefficients of PLA films was obtained, where both O2 and CO2 permeability coefficients were respectively decreased by about 45% and 68% at a low GONS loading of 1.37 vol%. The enhanced gas barrier performance was ascribed to the outstanding impermeable property of GONSs as well as the strong interfacial adhesion between GONSs and PLA matrix, rather than the changes in crystallinity and crystalline structure of PLA matrix as demonstrated by the scanning electron microscopy, two-dimensional wide angle X-ray diffraction, and differential scanning calorimetry results. Meanwhile, the incorporation of GONSs could effectively block the transmission of UV light in the nanocomposite films and endow PLA matrix with an excellent thermal stability. These results suggest the potential application of GONS/PLA films as packaging materials for protecting perishable goods vulnerable to degradation from O2 or high-energy light. And the new insight into the contribution of randomly dispersed GONSs to gas barrier properties of the semicrystalline polymer provides a significant guidance for fabricating high barrier films on a large scale in the packaging industry.