Challenges and Frontiers in the Circularity of Polymer Additive Manufacturing: A Systematic Review of Recycling Pathways and Material Degradation

Additive Manufacturing (AM) is frequently framed as a sustainable production paradigm due to its material efficiency and design flexibility. However, this narrative often overlooks the complex challenges associated with the end-of-life (EoL) management of polymer components. This systematic review critically evaluates the recyclability of AM polymers by examining the intersection of material chemistry, manufacturing-induced degradation, and the inherent heterogeneity of AM waste streams. Drawing from a corpus of 175 studies (2015–2025), this work assesses both mechanical and chemical recycling pathways for thermoplastics and thermosets. The findings reveal a significant disparity between theoretical recyclability and practical circularity. Common thermoplastics, such as PLA, ABS, and PA12, exhibit rapid thermomechanical degradation, typically losing structural integrity and mechanical performance after only one to three recycling cycles. Furthermore, photopolymer resins used in high-precision AM processes present a critical barrier, as current technologies remain largely incapable of reintegrating these materials into circular value chains. The critical review identifies several AM-specific obstacles such as mechanical anisotropy, contamination from support structures, and the complexity of multi-material parts that render recycling both technically challenging and economically unviable. Furthermore, Life Cycle Assessment (LCA) data further suggests that the environmental benefits of AM recycling are frequently offset by high energy demands. The study concludes that achieving a truly circular polymer AM ecosystem requires more than isolated technical improvements. It demands systemic interventions in “Design for Recycling” (DfR), the development of more resilient polymer blends, the establishment of industry standards, and the expansion of specialized waste management infrastructure.