Recycling post-consumer expanded polystyrene waste into 3D printing filament for fuse filament fabrication

Expanded polystyrene (EPS) is a widely used packaging, but it has very low recycling rate, and improper disposal contributes significantly to environmental pollution. Recycling this EPS waste into 3D-printable materials offers a promising and sustainable solution. Nevertheless, recycled EPS (rEPS) is inherently brittle and unsuitable for use as filament in Fused Filament Fabrication (FFF) 3D printing. In this study, filaments were produced from rEPS with the addition of 1–5 wt% Styrene-Ethylene-Butylene-Styrene (SEBS). The resulting filaments were successfully produced as standard filaments with an average diameter of 1.75 mm. All formulated filaments were printed into test specimens and evaluated for their tensile properties. The results showed that the highest tensile and impact strength values were obtained for printed specimens containing 3 wt% SEBS. However, the tensile modulus and elongation at break of the printed specimens gradually decreased with increasing SEBS content compared to specimens printed with neat rEPS. The printed specimens produced using the formulated rEPS filament with 3 wt% SEBS content demonstrated over 153% higher tensile strength but approximately 22% lower impact strength compared to those printed with commercial high-impact polystyrene (HIPS) filament. These improved mechanical properties are attributed to the developed formulation, which enhances the ductility of rEPS without compromising interlayer adhesion during printing.