Optimization of ZnO/GO nanocomposite-loaded polylactic acid active films using response surface methodology

Abstract

Development of biodegradable polymer as food packaging has been emerged with the increasing awareness of achieving sustainable development goals. As a replacement of petroleum-based polymers, Polylactic acid (PLA) has been widely utilized for food packaging. However, the main disadvantage of PLA for food packaging is its brittleness and low stiffness. Therefore, this work aimed to evaluate the potential usability of Zinc oxide (ZnO) and Graphene oxide (GO) as mechanical strengthening nanocomposites and their synergistic effect towards antibacterial property. The optimum formulation of PLA/ZnO/GO nanocomposite active film was determined using RSM by defining concentration of ZnO (0–1.5 wt%), concentration of GO (0–1.5 wt%) and mixing temperature (40, 50, 60 °C) as process parameters. The synergistic effect of ZnO/GO demonstrated a significant improvement in mechanical property. Both ZnO and GO exhibited significant antibacterial activity towards E. coli and B. subtilis and their synergistic antibacterial property performed the best with 0.75 wt% ZnO and 0.75 wt% GO at 50 °C. Results also revealed that ZnO was dominated in their synergistic effect for both mechanical and antibacterial properties. The optimum formulations for PLA/ZnO/GO nanocomposite active film were determined at 1.06 wt% ZnO, 1.11 wt% GO at 60 °C and 0.99 wt% ZnO, 1.28 wt% GO at 40 °C. The regression models by RSM were validated with the experimental results based on optimal formulations. In addition, SEM and FTIR investigation on two optimal films confirmed the good compatibility between ZnO, GO and PLA matrix. Taken together, optimized formula could provide useful insights for fabricating PLA-based active film and broadening their application in food packaging industry.