Polylactic acid has the potential to be an alternative to petroleum-based materials in the food packaging industry. In this study, the effect of zinc oxide nanoparticles, polyethylene glycol 400, and Tween 80 as plasticizers on the properties of polylactic acid films was investigated. In order to study the mechanical properties more accurately, the tests were repeated for four months. An experimental design method was used to investigate the effects of additives on the measurement factors and finally to choose the optimal combination with the help of the TOPSIS technique. The results showed that the addition of different materials increased the opacity, most of which being related to P400/ZnO (6.82 ± 0.07 mm−1). The presence of plasticizers increases the hydrophilicity of the film and the water vapor permeability. The highest contact angle (85.33° ± 4.00) and the lowest water vapor permeability (0.074 ± 0.002 g mm/kPa h m2) were related to neat PLA film. The lowest modulus of elasticity, the highest tensile strength and elongation at break were related to P400/T80/ZnO (1.18 ± 0.17 GPa, first month), PLA/ZnO (96.28 ± 3.17 MPa, fourth month), and P400/ZnO (76.82 ± 27.22 %, first month), respectively. The effect of plasticizers was significant in most of the measurement factors, but the effect of nanoparticles was significant in some cases such as opacity and contact angle. The results of an ANOVA analysis showed that the effect of film type on the mechanical properties was significant, and the effect of storage time was only significant on the elongation at break. According to the results obtained from the TOPSIS technique, P400/ZnO was chosen as the combination with the best features among the produced films.

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