Properties of poly (vinyl alcohol) films with embedded zeolitic imidazolate framework (ZIF-8) nanoparticles for food packaging applications.

This study evaluated the physical, mechanical, barrier properties, and transition temperatures of poly (vinyl alcohol) (PVA) films with embedded zeolitic imidazolate framework-8 (ZIF-8) nanoparticles carrying a natural antimicrobial, trans-cinnamaldehyde (TC). The ZIF-8 nanoparticles were synthesized using a sonochemical method and incorporated into polymeric matrices at mass ratio concentrations of 0% (control film) to 5% weight of ZIF-8@TC to PVA. Solutions were mixed, cast onto Petri dishes and dried for 12 h at 37°C in a ventilated oven. The film samples were stored in airtight containers at room temperature and used within 1 week. The engineering properties of the PVA/ZIF-8@TC films were compared with those of low-density polyethylene (LDPE) film commonly used for packaging of spinach leaves. The glass transition, melting, and crystallization temperatures of PVA compositive films all increased (p < 0.05) with ZIF-8@TC concentration. When exposed to high relative humidity environments, the PVA/ZIF-8@TC films had lower equilibrium moisture content (p < 0.05) than the LDPE film. Although the composite films have different tensile properties from the LDPE film, embedding ZIF-8@TC into PVA films improved the tensile strength by 17%, making the PVA/ZIF-8@TC films suitable for low load-bearing applications such as food packaging. The gas barrier properties of PVA-based films differed only slightly with added ZIF-8@TC (p < 0.05). PRACTICAL APPLICATION: PVA/ZIF-8@TC films are appropriate environment-friendly alternatives to polymeric food packaging in terms of their functional properties.