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.

Recycled polyethylene terephthalate (rPET) is widely considered a sustainable alternative to virgin polyethylene terephthalate (PET). Nevertheless, its application in value‐added processes is frequently restricted due to property degradation occurring during recycling. This study investigates the use of slate dust (SD) as a reinforcing filler and its effects on the structural, thermal, and thermomechanical properties of rPET. Twin‐screw extrusion and injection molding were used to prepare composites with up to 20 wt% of SD. Gel permeation chromatography, Fourier transform infrared spectroscopy, and x‐ray diffraction confirmed that SD maintains chemical inertness during processing, with no detectable molecular degradation due to the filler. With a 20 wt% SD content, the thermal conductivity of rPET increased by approximately 41%, from 0.267 to 0.377 W/mK. Additionally, the crystallization temperature increased by 5°C, indicating the filler's nucleating effect. Dynamic mechanical analysis (DMA) indicates a ~39% increase in storage modulus at room temperature. To further explore the filler‐matrix interaction, Cole‐Cole plots and C‐factor, reinforcement efficiency, degree of entanglement, and adhesion‐related factors (A and B factors) were calculated from the DMA results. This study promotes waste valorization strategies by using slate waste as a filler and enhancing rPET to develop recycled polymer composites aligned with circular economy principles.