STRUCTURAL SEPARATION OF MULTILAYER PACKAGING FOR MECHANICAL RECYCLING

Multilayer packaging (MLP) is widely used because it delivers barrier performance, strength, and product protection that single-material systems cannot match. Worldwide, flexible MLP contributes a substantial portion of production, amounting to 100 million tons each year. Its complex structure, involving various materials, makes traditional recycling very challenging. As a result, MLP recycling rates remain very low, and most of this waste is currently sent to landfills or incinerated. Therefore, developing technologies capable of separating MLP into clean, reusable material streams is critically important. This study investigates a mild aqueous formulation approach for the structural separation of multilayer systems, including PE/Al, PET/Al/PE, and PP/Al/PP. Formulations composed of organic acid (30-50 vol%), surfactant (0-10 vol%), and water were designed to weaken interfacial adhesion while maintaining the chemical and physical properties of the primary polymer layers. The design of experiments was employed to evaluate the influence of temperature (50-90 °C), acid concentration, and surfactant loading on delamination kinetics. Separation performance was assessed by measuring delamination time, material recovery efficiency, and preservation of polymer properties using FTIR, DSC, and TGA analyses. Two recycling pathways for aluminum were observed: delamination, which preserves intact foil layers, and leaching, which recovers ultrathin, vapor-deposited metallized aluminum to recover polymer substrates. Both methods achieved recovery efficiencies exceeding 95 wt%. Results reveal that adding a surfactant alongside the acid shortens the separation time. The results demonstrate that mild aqueous formulations can effectively reduce interfacial adhesion in multilayer systems without compromising bulk polymer integrity. The strong temperature dependence indicates kinetically controlled separation, while the surfactant contribution suggests enhanced interfacial wetting and improved penetration of the acidic medium into adhesive domains. This dual effect enables rapid and controlled structural separation under moderate processing conditions. Compared to aggressive chemical or thermal treatments, the proposed approach operates under milder conditions, preserves material quality, and achieves high recovery yields. These characteristics make the method promising for scalable integration into mechanical recycling workflows.