Sustainable additive manufacturing through recycled and reinforced thermoplastic composites: state of the art

The transformation of plastic waste into valuable products remains a significant challenge for sustainable manufacturing. Fused deposition modeling (FDM), a melt extrusion-based additive manufacturing (AM) technique, has emerged as a promising solution for repurposing waste thermoplastics. However, multiple recycling cycles introduce substantial changes in material properties, limiting their mechanical performance and surface quality. Despite ongoing research efforts, FDM-printed components still lag behind conventionally manufactured parts in terms of mechanical integrity, microstructure, and overall durability. Additionally, while the use of recycled plastics in FDM has been explored, a structured literature review focusing on the development of functional and customized products from recycled waste is still lacking. To address this gap, the present study provides a comprehensive review of the utilization of recycled plastic waste in FDM-based 3D printing, emphasizing the role of reinforced materials in enhancing performance. It examines the effects of processing conditions on the properties of recycled FDM components and explores the incorporation of diverse additives to improve material quality. Furthermore, this review presents two case studies from the existing literature that demonstrate the successful integration of thermoplastic waste into FDM-based manufacturing. By identifying existing limitations and potential research directions, this study aims to contribute to the advancement of sustainable and circular manufacturing practices through FDM technology.