Upcycling of PET Waste: From One Polymer to Another Polymer

Abstract

Polyethylene terephthalate (PET), a dominant polymer in global plastic production, faces critical recycling challenges due to its persistence in ecosystems and limitations of conventional mechanical/thermal recycling. Upcycling PET waste into valueadded polymers represents a transformative approach toward a circular plastics economy. This review systematically examines innovative strategies for chemically converting post-consumer PET into novel polymeric materials, thereby bypassing the performance degradation typically associated with traditional recycling. Key pathways include (1) depolymerization into monomers (terephthalic acid, ethylene glycol) for repolymerization into high-purity PET or advanced polyesters (e.g., biodegradable or bio-based variants), (2) transformation into functional polymers such as polyurethanes, epoxy resins, and ion-exchange membranes via tailored catalytic processes, and (3) copolymerization/blending with biopolymers to enhance material properties. Breakthroughs in catalysts (enzymes, ionic liquids), solvent-free systems, and energy-efficient reactors are highlighted for improving reaction selectivity and scalability. Despite progress, challenges persist in managing mixed plastic wastes, removing contaminants, and achieving cost parity with virgin polymers. Emerging trends, including enzymatic engineering and AI-guided monomer-to-polymer design, are proposed to address these barriers.By bridging molecular innovation with industrial feasibility, PET upcycling offers a dual environmental and economic incentive to close the plastic lifecycle loop.