A Comparative Study of Fused Filament Fabrication Using Recycled Polystyrene and Commercial High-Impact Polystyrene

Discarded expanded polystyrene (EPS) poses significant environmental challenges due to its accumulation in landfills and resistance to degradation. Upcycling EPS into 3D-printable recycled polystyrene (rPS) filament for use in fused filament fabrication (FFF) shows a promising sustainable solution. This study explores the mechanical recycling of EPS into rPS resin, which is then extruded into 3D-printable filament using a 3DEVO filament maker. A key focus is on studying the filament’s properties and the properties of its printed specimen. Filament diameter was monitored in real-time during extrusion using DevoVision software. The results showed that the rPS filament achieved an average diameter of 1.75 mm with a standard deviation of ±0.03 mm when extruded at 200 °C. Extrusion at temperatures above 200 °C resulted in filament diameters exceeding 1.75 mm. Specimens printed with rPS filament exhibited higher tensile strength, tensile modulus, and elongation at break, but lower impact strength compared to those printed with commercial high-impact polystyrene (HIPS) filament. Micrographs show that HIPS is a more ductile material, which contributes to its better impact strength. However, due to poor layer adhesion during printing, it exhibited lower tensile properties. The onset and maximum decomposition temperature of rPS did not show a significant change during the recycling process from EPS to filament. The onset decomposition temperature was above printing temperature, thus it did not limit the use of rPS for FFF printing applications. Despite HIPS displaying greater thermal stability, rPS still demonstrates strong potential as a sustainable printing material, and its applications include printing prototypes and serving as a support material in 3D printing, since it can be dissolved in acetone.