Introduction: Packaging is one of the effective ways to increase the storage life and quality of the food products. Nowadays, most of the materials used in packaging are fossil origin and usually non-degradable and hardly dissoluble. Also biodegradable films, due to their fragility and poor resistant to gas exchange are in limited use. It is possible that by employing nanotechnology, some particles on nano scale may be added to these polymer composites to improve the mechanical properties and permeability of the biodegradable packing films. Silver nanoparticles and zinc oxide have been incorporated in polymers individually by researchers. The objective of this study is to compare the effect of incorporating the mixture of silver and zinc oxide nanoparticles with the case of adding them separately into poly vinyl alcohol matrix, on some relevant mechanical and physical properties of the outcome Nono-composite films.
Materials and methods: To make polymer films polyvinyl alcohol, solvent (deionized water) and glycerol (as softener) were used. Then, zinc oxide and silver nanoparticles at 3% by weight, were added to the polymer solution in two different ways, separately and in combination. To specify the pattern of nano-particles size distribution, transmission electron microscope (TEM) test was performed. To determine the characteristics of the films’ surface scanning electron microscope (SEM) was employed. To investigate the bondings between the components of nono-composite films, FTIR was employed.For identification of matrix structure and formation of nano-composite, the XRD was performed. To measure the infiltration of water vapor, the approved E96 ASTM method was used. Also, for measuring the color and transparency of films, the HunterLab test and for mechanical properties of the films, Instron Universal Testing Machine (H5 KS, England) were used (considering the ASTM standard for tensile tests - D88201). For statistical analysis and comparison of means, variance analysis and Dunkan test were performed, using SPSS software.
Results & discussion: SEM, XRD and FTIR tests showed that nanoparticles were distributed uniformly within the polymer matrix, and react well with the polymer chains. Besides, the effect of adding silver and zinc oxide nanoparticles on the relevant properties of the films was significant. By individual adding of these nanoparticles on polyvinyl alcohol matrix, the tensile strength and the elongation of films increased. On the other hand, their transparency and water vapor permeability decreased. The results also showed that the combined incorporation of silver and zinc oxide nanoparticles into the packing films can significantly affect their mechanical properties and permeability. Hence, due to the high prices of silver nanoparticles than zinc oxide nanoparticle, the combined incorporation of these two nano-particles is recommended, while maintaining the properties of the nano-composite films in a reasonable level. It can be implied that the combined use of silver and zinc oxide nanoparticles in the polymer provides a more affordable Nano-film with good enough quality. It may also reduce their mutual side effects.