Advances in Structural Separation Technologies for Multilayer Packaging Recycling

Multilayer materials have become an essential part of modern packaging design. They are engineered to merge different materials into a single, lightweight structure. However, their recycling is challenging because the layers are strongly bonded and chemically heterogeneous. As a result, multilayer packages (MLPs) often bypass recycling streams, causing environmental pollution and resource depletion. A potential long-term solution is represented by disassembly processes that separate layers and direct them into single-polymer streams. This review examines studies on separation technologies and categorizes them by their dominant mechanism of action. Delamination techniques chemically remove or deactivate bonding layers, whereas selective dissolution-precipitation (SDP) uses polymer-solvent thermodynamic windows to dissolve and recover polymer layers sequentially. For solvent selection, we consolidated Hansen Solubility Parameters to produce polymer solvent compatibility and distance maps for common polymers. Additionally, a detailed comparison is made of recovery outcomes, technology readiness levels, and their impacts on recyclate purity and food-contact safety. Structural separation offers a feasible approach to reintroducing post-consumer MLPs into mechanical recycling, provided solvent management, contamination control, and regulatory compliance are properly managed. We recommend prioritized research into closed-loop solvent management, energy reduction, and scale-up validation of promising delamination and SDP methods.