Performance Limits of Low-Cost Extrusion for rPET Upcycling: A Study on Filament Quality, Strain-Rate Sensitivity, and Energy Absorption in 3D Printing

The exponential growth in global plastic consumption has intensified the demand for effective waste management solutions, particularly for polyethylene terephthalate (PET) bottles. Converting post-consumer plastic waste into 3D printing feedstock offers a promising circular manufacturing pathway. However, adoption is constrained by the high cost of commercial filament extrusion systems. This study addresses this gap by presenting the design and fabrication of a low-cost filament extrusion system below RM 200, approximately USD 45, for recycling post-consumer PET (rPET) into 3D printing filament. Using off-the-shelf components, the system produced filament with diameters between 1.8 and 2.0 mm at an optimal extrusion temperature of 180°C. Mechanical testing showed that rPET achieved a tensile strength of 27 MPa compared to 35 MPa for PETG, with a Young’s modulus of 0.215 GPa, indicating higher stiffness due to increased crystallinity. However, rPET exhibited reduced ductility below 9 percent and brittle failure at higher strain rates. These results indicate that rPET is suitable for static, non-structural applications. The novelty of this work lies in overcoming the cost barrier in rPET filament production through an affordable and easily replicable system that enables decentralized recycling and supports circular economy objectives under SDG 12.