Circular Economy Insights on the Suitability of New Tri-Layer Compostable Packaging Films after Degradation in Storage Conditions

The environmental degradation of the films used in packaging is a key factor in their commercial use. Industrial and academic research is aimed at obtaining materials that have degradation features that ensure their eco-sustainability but, at the same time, preserve their use properties during storage and distribution periods. This study analyzes the degradability behavior over time of commercial packaging that meets the requirements of the UNE 13432 standard and the prEN 17427 (2020) home composting certification requirements under standard storage conditions. The study attempts to provide insight into the durability of the films under standard storage conditions, verifying that this type of packaging has a useful life of more than 12 months and that after this storage period it still retains the usability properties for which it was conceived. The analyzed sample has been manufactured using a three-layer technology under some commercial formulations based on PBAT + STARCH + PLA and has been analyzed monthly for 12 consecutive months. The macroscopic monitoring of the degradation of the sample has been carried out through the evolution of the mechanical properties and the quantification of the color changes (very important in films) via colorimetry. The nature of the observed variations has been justified at the microstructural level from the data obtained in calorimetric analysis (DSC) and from the characterization using FTIR. The results indicate a loss of properties in the tensile, elongation and impact tests and a behavior of stability or improvement in the tear properties of the film. Analyzing the microstructural changes, it is observed that the degradation of a hydrolytic and thermo-oxidative type occurs in the amorphous part of the film. The conclusion of this study is that the proposed packaging, focused on domestic composting and stored under standard conditions, has a useful life of more than 12 months. This period should be sufficient to cover the stages of production, storage and final use.