Plastic waste to 3D printing filaments preparation, mechanical and surface characterization for sustainable application to complex non-functional geometries

In recent years, plastic dependency has become a significant issue, where almost 90% of all households contain plastic products. Plastic waste accumulates because of its non-biodegradable nature, posing a threat to the ecosystem. This article investigates the indigenous process of converting polyethylene terephthalate (PET) bottle waste into filament using a 1.75 mm nozzle extruder for 3D printing. PET bottles were collected, heated, cleaned, cut into strips, and fed into a custom-made extrusion machine to form a filament while maintaining a constant diameter at the end of the extruder. The study also evaluates the process parameters of fused deposition modeling (FDM), including extrusion speed, nozzle temperature, and plastic waste preparation. Mechanical performance of the recycled PET filament was thoroughly assessed via tensile and compression tests, hardness measurements, surface roughness analysis, and scanning electron microscopy (SEM) examination of fractured and as-printed samples. Results indicate the recycled PET filament exhibited approximately half the tensile strength compared to commercial or virgin PET filament, highlighting its inherent brittleness and limitations in interlayer adhesion. Conversely, the compressive strength was superior by approximately 30 MPa, and hardness values also exceeded those of recycled PET filament. SEM analysis of 3D-printed PET under tensile testing reveals brittle fracture characteristics, weak interlayer adhesion, void coalescence, and microcracks, indicating inhomogeneities and incomplete layer fusion as primary failure contributors. This approach aims to reduce plastic waste by recycling it into functional products and providing a sustainable solution.