Recycled Polylefin and Polymeric Waste for Industrial Applications: A Comprehensive Review

Abstract

Polyolefin-rich plastics dominate global demand, yet post-consumer waste streams often consist of mixed and multilayer recyclates, where contamination (e.g., polypropylene (PP) in polyethylene (PE), polyethylene terephthalate (PET) in polyolefins, or trace Poly(vinyl chloride) (PVC)) disrupts material properties, morphology, and long-term performance. This review presents an interphase-engineering framework that links waste-stream variability with compatibilization and technology selection. A comprehensive literature review (2000–2025) was conducted using major databases, synthesizing data on composition, processing routes, compatibilizer architecture, morphology, degradation indicators, and mechanical property retention. The review critically evaluates non-reactive and reactive compatibilization methods (including grafting during extrusion), filler-assisted interphase reinforcement, and feedstock management practices (sorting, decontamination, and purification) in case studies such as PP/PE blends, PP contamination in recycled PE, PET-polyolefin mixtures, and multilayer packaging residues. The analysis reveals that toughness recovery is primarily driven by dispersed-phase refinement and interfacial adhesion, with contaminants—especially PVC—imposing significant processing and corrosion challenges. Additionally, the review proposes metrics and reporting strategies to enhance cross-study comparability and industrial relevance. Finally, a portfolio strategy is recommended that prioritizes mechanical recycling for cleaner streams, utilizes purification/compatibilization to avoid downcycling, and reserves chemical/catalytic processes for residues unsuitable for closed-loop recycling, with testable hypotheses for scale-up.