Effect of Recycled Waste Cooking Oil on the Tensile Properties of rPET Filaments for FDM Applications

Abstract

Recycling polyethylene terephthalate (PET) waste into 3D-printing filament offers a sustainable opportunity to reduce plastic pollution and support circular-economy initiatives. However, recycled PET (rPET) filaments often exhibit brittleness, limited ductility, and poor extrusion behaviour. This study investigates the use of recycled waste cooking oil (rWCO) as a bio-based plasticiser to enhance the mechanical performance and printability of rPET filament for Fused Deposition Modelling (FDM). rPET was blended with 5%, 7.5%, and 10% rWCO by weight and extruded into 1.75 mm filament. Tensile properties were evaluated using ASTM D638 Type IV specimens and compared with a commercial PET-G filament as a control. The results show that the addition of rWCO reduces tensile strength from 14.11 MPa (0% rWCO) to between 10.45 and 11.52 MPa, while improving elongation at break from 21.21% to up to 31.39%. The 7.5% formulation demonstrated the most balanced performance, combining improved ductility with moderate strength retention. These findings demonstrate the feasibility of rWCO as a low-cost, sustainable plasticiser for enhancing rPET filaments, offering promising implications for environmentally conscious additive-manufacturing applications.