Understanding the circular economy and mechanical performance of additively manufactured recycled PET for sustainable process optimization

Purpose This study aims to evaluate the mechanical and microstructural attributes of 3D-printed recycled polyethylene terephthalate (rPET) produced through fused deposition modeling (FDM). Given the environmental concerns surrounding plastic waste, this research focuses on optimizing the reuse of polymeric materials to produce consumable products and provide these materials with a second life. By examining the effects of various FDM parameters, this study seeks to identify the optimal settings to enhance the mechanical properties and surface quality of rPET. Design/methodology/approach This research involves recycling polyethylene terephthalate (PET) through an element extrusion process to create filaments suitable for additive manufacturing via FDM. This study systematically investigates the influence of five FDM parameters – build orientation, layer height (Lh), printing orientation (Op), infill pattern (Ip) and printing speed (Sp) – on the mechanical properties [tensile strength (TS), impact strength (IS), hardness (H) and surface roughness (Ra)] of the rPET. Microstructural analyses are performed using optical and scanning electron microscopy to correlate mechanical properties with microstructural features. The significance of these parameters is further examined using analysis of variance and multivariate analysis of variance. Findings This study concludes that optimal parameter settings significantly enhance the mechanical properties of 3D-printed rPET. Specifically, a maximum TS of 29 MPa and IS of 0.27 J are achieved with Lh of 0.10–0.15 mm, Sp of 70–100 mm/sec and Op of 80°–90°. Maximum hardness (68 HV) is observed at layer heights of 0.25–0.30 mm, printing speeds of 90–100 mm/sec, and orientations of 80°–90°. Microstructural analysis reveals that high-strength samples exhibit ductile fracture with prominent elongation (3.91%), whereas low-strength samples display brittle fracture with less elongation (3.08%). Originality/value This study provides valuable insights into the recycling of PET for additive manufacturing, demonstrating the potential of rPET in producing high-quality 3D-printed parts. By optimizing FDM parameters, the research highlights the feasibility of transforming waste materials into valuable products, contributing to environmental sustainability and waste management. The findings offer a practical guide for industries and researchers seeking to enhance the mechanical performance and surface quality of 3D-printed recycled materials.