Overcoming technical barriers in mechanical recycling of plastic waste: The role of engineered additives

Mechanical recycling of plastic waste has gained significant attention over other recycling approaches due to its practicality and cost-effectiveness. Life cycle assessments (LCA) also highlight its environmental advantages, including lower emissions, energy savings, and reduced waste generation. However, mechanical recycling faces substantial challenges, particularly due to the diverse range of plastic products and additives, as well as the complexity of multilayer film packaging. During mechanical recycling, polymer degradation, radical formation, immiscible polymer phases, gelation, and contamination are major barriers that lead to a decline in the quality of recycled plastics, making it difficult to produce high-performance recyclates. Upcycling plastic waste through additives presents a transformative solution to these challenges by significantly enhancing recyclate properties . This approach involves the strategic incorporation of compatibilizers, plasticizers, antioxidants, UV stabilizers, and fillers to optimize the mechanical, thermal, and aesthetic characteristics of recycled materials. This review critically examines the key technical barriers in mechanical recycling and explores additive strategies to address them. Additionally, it evaluates the potential for replacing petroleum-based additives with sustainable, bio-derived alternatives to improve recyclate performance while minimizing environmental and health risks. The discussion emphasizes the importance of selecting and formulating appropriate additives tailored to specific recycling challenges, ultimately contributing to more efficient and sustainable plastic waste management.