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Chemical characterization of postindustrial recycled polyethylene terephthalate obtained from multilayer PET/PE sheets: a baseline study on safety aspects
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Advisor(s)
Abstract(s)
Trays made from thermoformed plastic sheets represent the second major application of PET packaging after beverage bottles. PET recycling is promoted in the European Union, where ambitious targets for recycling rates and recycled content in packaging have already been established. However, PET trays, contrary to most beverage bottles, pose recycling challenges due to multilayer structures with polyethylene (PE) tie-layers and barrier materials. In this study, a delamination process using a hot alkaline solution was applied to postindustrial multilayer PET/PE thermoforming waste to recover PET flakes and produce sheets containing varying rPET contents. The process showed > 95% PE removal. Sheets incorporating rPET exhibited increased yellowness, haze and decreased intrinsic viscosity but maintained suitable thermal properties for thermoforming applications. Among thermal properties, only the cold crystallization temperature was notably affected. Results from FTIR and GC–MS analyses, combined with principal component analysis, were used to differentiate the samples containing rPET and confirmed chemical similarity between recycled and virgin PET, although residual tie-layer compounds and delamination process residues were detected. Overall migration tests yielded values below regulatory limits, while untargeted GC–MS screening revealed the presence of degradation products, surfactant residues and oligomers. As expected, sheet production led to a decrease in the concentration of volatile and semivolatile migrants. However, higher concentrations of oligomers, particularly 1st series cyclic trimers, were quantified by LC–MS in the sheets compared to the flakes, indicating thermal stress effects during extrusion. Several PET degradation compounds were also identified in the sheets, highlighting the need for further migration studies to assess safety. These findings demonstrate that alkaline delamination is an effective strategy for recovering PET from multilayer tray waste although safety assessment of oligomers and specific migrants remains essential for food-contact applications.
Description
Keywords
Multilayer trays Oligomers from PET PE layer separation PET degradation compounds Tie-layer adhesive removal
Pedagogical Context
Citation
Daras, I. F. A., Singh, S., Vieira, T., & Pereira, J. et al. (in press). Chemical characterization of postindustrial recycled polyethylene terephthalate obtained from multilayer pet/pe sheets: a baseline study on safety aspects. Packaging Technology and Science, 1-14. https://doi.org/10.1002/pts.70034