The basic limitation of biopolymers compared to the petroleum-based polymers is their weak physical and mechanical properties. In recent years, efforts have been made to properly incorporate nanoparticles into the polymer to reduce the limitation of their use in the packaging industry by partially improving the physical and mechanical properties of these films. This study aimed to incorporate zinc oxide nanoparticles into gelatin-biopolymer-based nanocomposite films, in order to improve their physical, mechanical and thermal properties.

Gelatin-based nanocomposite films were prepared by adding different amounts of zinc oxide nanoparticles (0, 0.5, 1.5 and 3%) using the so-called casting method. By performing several tests, different properties of the manufactured nanocomposite films including thickness, density, water vapor permeability, mechanical properties, degree of transparency, color properties and finally, their biodegradability were investigated.

the results showed that increasing the concentration of zinc oxide nanoparticles increased the tensile strength and decreased the elongation-at-break of this biofilm. The results of physical tests showed that increase in nanoparticles concentration reduced the permeability to water vapor from 0.76 to 0.48. Incorporating zinc oxide nanoparticles affected the transparency of the biofilms i.e. their transparency reduced by increasing nanoparticles concentration. By adding nanoparticles to gelatin-based films, thermal properties including glass transition temperature and melting temperature increased. Also, the thermal stability of the biofilms increased from 533.38°C (0.5% nanoparticles) to 559.53°C (1.5% nanoparticles). The results of biodegradability in soil and light showed that with increasing the concentration of nanoparticles, the biodegradability was reduced. This is mainly due to the addition of nanoparticles, which results in a greater bond strength between the components, and consequently the delay in biodegradation.