Potential perspectives of CMC-PET/ZnO bilayer nanocomposite films for food packaging applications: physical, mechanical and antimicrobial properties

In this study, CMC-PET bilayer nanocomposites films containing different levels of zinc oxide nanoparticles (ZnO NPs; 0%, 1%, 2%, 3%, 4%) were prepared and characterized. The water vapor permeability, color, mechanical, microbial and structural properties of the films were analyzed. The FESEM images indicated some fragmental and smooth surfaces on the pure CMC-PET films, while a rough fragment surface was seen for the ZnO NPs/CMC-PET nanocomposite films. Along with increasing the ZnO NPs percentage, the water vapor permeability of CMC-PET films decreased compared to the pure film. Increasing the nanoparticles percentage had a positive impact on the tensile strength and increased this factor from 123.77 to 466.80 MPa, while the elongation at break decreased from 48.38 to 10.59% and the nanocomposite films were revealed more resistant compared to the pure CMC-PET film, which facilitates the transport and storing of the foodstuffs. In addition, the incorporation of zinc oxide NPs decreased a* and b* values, whereas it increased L* and ∆E. The presence of ZnO NPs in CMC-PET films exhibited antimicrobial activity against Escherichia coli and Staphylococcus aureus compared to the film samples without any NPs. In general, this research verifies improvement in physical, mechanical and microbial characteristics of CMC-PET nanocomposite films along with the ZnO NPs increase from 1 to 4% of matrices. Moreover, these films exhibit a high versatility in food packaging as well as having antimicrobial properties, and can extend the shelf-life of packaged foods as active packaging.