Recycling PET Waste into Functional 3D Printing Material: Effect of Printing Temperature on Physio-mechanical Properties of PET Parts

This study examined the reuse of recycled polyethylene terephthalate (RPET) from different PET sources as feedstock material for 3D printing. The filament for 3D printing was made using virgin PET pellets (VPET-P), RPET pellets (RPET-P), and commercially available RPET flakes (RPET-CF). The effect of different printing temperatures (250 degrees C, 260 degrees C, and 270 degrees C) on the physio-mechanical properties of 3D-printed samples was studied, and the properties were compared with those of 3D-printed VPET-P samples. The density analysis showed that VPET-P had optimal values at 260 degrees C (1.12 g/cm3). RPET-P and RPET-CF showed higher densities at 270 degrees C, which improved compaction. Higher temperatures reduced shrinkage in RPET samples, with warpage decreasing to 0.347 mm for RPET-P and 0.559 mm for RPET-CF at 270 degrees C. Surface roughness improved with increasing printing temperature, with the best results for RPET samples at 260 degrees C. Mechanical testing showed that RPET-CF performed best, especially at 270 degrees C, with the highest Young's modulus of 1354 MPa, yield stress of 27.9 MPa, and tensile strength of 47.3 MPa. This was attributed to increased crystallinity and molecular orientation. RPET-CF also showed the highest hardness of 79 SHD and strong flexural properties, making it suitable for rigid applications. Microscopy showed fewer layer delamination and voids in RPET-CF compared to the brittle fractures observed in VPET-P and RPET-P. RPET-CF proved to be a promising material for structural 3D printing applications. Higher temperatures enhance its interlayer bonding, rigidity, and durability, making it suitable for load-bearing uses in additive manufacturing.