Effect of Supercritical CO2 and Olive Leaf Extract on the Structural, Thermal and Mechanical Properties of an Impregnated Food Packaging Film

Abstract

Poly(ethylene terephthalate)/polypropylene (PET/PP) films containing olive leaf extract (OLE) were obtained by supercritical solvent impregnation (SSI) in batch (BM) and semi-continuous (SM) modes. The study focused on the impact of pressure, temperature, CO2 flow and OLE on the properties of the impregnated films. Thermal analysis of non-impregnated samples revealed a decrease in the crystallinity of PP layer treated at 35 °C and an increase in the Tg of PET treated at 55 °C due to CO2 sorption. In impregnated samples, high pressures caused a decrease in the crystallinity of PP layer, whereas PET layer remained unaffected. Higher pressures favour impregnation in BM, whereas different trends were found for SM impregnations. Although the film properties were not compromised after impregnation, the CO2 stream used in SM slightly weakened the impregnated films. Overall, conditions of 400 bar and 35 °C in BM were favorable for producing highly antioxidant films with minor structural modifications.