Application of plasma surface treatment to produce CMC-PET/ZnO bilayer nanocomposite film as a novel food packaging

In this study, PET-CMC bilayer nanocomposites films containing different levels of zinc oxide nanoparticles (ZnO NPs; 0%, 1%, 2%, 3%, 4%) were prepared and characterized. For better attachment of CMC on Polyethylene terephthalate (PET), atmospheric plasma pretreatment was used. The water vapor permeability, moisture, mechanical and microbial properties of the films were analyzed. Also, in order to investigate the effect of plasma treatment on improving the properties of bilayer films, a comparison was made between plasma treated and untreated bilayer films using FTIR test.  Results showed the formation of polar groups such as C=O and OH on the PET surface following the plasma treatment which improved the adhesion of the two layers of polymer to each other. The water vapor permeability of PET-CMC films containing ZnO NPs decreased compared to the pure film with increasing the ZnO NPs percentage. 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 PET-CMC film, which facilitates the transport and storing of the foodstuffs. In addition, the presence of ZnO NPs in PET-CMC films exhibited antimicrobial activity against Escherichia coli and Staphylococcus aureus. In general, this research verifies improvement in physical, mechanical, and microbial characteristics of PET-CMC nanocomposite films along with the increasing of ZnO NPs. Our findings suggest that plasma-treated PET/CMC films have the potential for application in food antimicrobial packaging and can extend the shelf-life of packaged food as active packaging.