Synthesis and characterization of Nano-ZnO incorporated polyurethane-chitosan composite films

This study developed novel polyurethane-chitosan/zinc oxide (PU/CS/ZnO) nanocomposite films for food packaging applications. ZnO nanoparticles were synthesized via a green approach using Mentha pulegium leaf extract and incorporated into PU/CS blends at various concentrations. The PU/CS/ZnO-5% nanocomposite exhibited optimal performance across multiple properties. XRD and FTIR analyses confirmed the successful incorporation of ZnO nanoparticles (average crystallite size 28 nm) and their interaction with the polymer matrix. SEM and TEM imaging revealed uniform dispersion of ZnO nanoparticles throughout the film. The results of mechanical testing indicated a significant improvement in both tensile strength and Young's modulus, with a 51% increase in the former and a 68% increase in the latter when compared to the pure PU/CS blend. UV-vis spectroscopy demonstrated excellent UV-blocking ability, with a UV protection factor of 42.7 for the PU/CS/ZnO-5% film. The nanocomposite films exhibited enhanced antioxidant activity, with a 110% increase in DPPH radical scavenging activity for the PU/CS/ZnO-5% sample. Biodegradability studies showed 58.1% weight loss after 12 weeks of soil burial. Shelf-life extension studies on strawberries revealed that the PU/CS/ZnO-5% film significantly outperformed commercial LDPE packaging, with only 4.2% weight loss and 78.5% firmness retention after 14 days of storage. The nanocomposite films also demonstrated antimicrobial properties, with reduced microbial growth on packaged strawberries. These results highlight the potential of PU/CS/ZnO nanocomposite films as multifunctional, biodegradable packaging materials for perishable foods.