Production and characterization of biodegradable bi-layer films from poly(lactic) acid and zein

Recently, packaging industry has turned to biodegradable packaging, and poly(lactic acid) has become the most remarkable polymer. However, the high oxygen permeability of PLA films significantly limits their use. Therefore, this study, it was aimed to improve the oxygen barrier properties of PLA films without adversely affecting the mechanical and water vapor barrier properties. Biodegradable PLA-Zein bi-layer films were produced by changing PLA and zein thickness. Transparent and UV barrier bi-layer films were obtained. Mechanical properties of PLA films were improved by the production of bi-layer films. Water vapor permeability of bi-layer films increased whereas the permeance decreased with zein coating of PLA. Multi-criteria decision hierarchy was used to select the best bi-layer films based on mechanical, permeance, and opacity results. Oxygen barrier properties of PLA film significantly improved by zein coating, and hydrophobicity of PLA film was not affected by zein coating. The crystallization and melting temperatures of films decreased when compared to PLA films, supporting the mechanical results. Homogeneous, non-porous, and smooth film surface was obtained and zein layer was in good compatibility with PLA layer. These results suggest that zein coatings could be used to decrease oxygen permeability of PLA films without negatively affecting other properties.