Recycling post-consumer polypropylene utensils into 3D printing filaments for fused filament fabrication

Abstract This study focuses on the development of three-dimensional (3D) printer filament made from post-consumer polypropylene utensils (PCP). A blend of injection-grade and extrusion-grade PCP was used to fabricate filament through extrusion process. The filament was then characterized based on diameter consistency, ovality, melt flow rate (MFR) and thermal properties followed by tensile testing of 3D printed specimens. The results showed that blending extrusion-grade PCP improved filament uniformity and reduced MFR, enhancing its suitability for fused filament fabrication (FFF). Among the prepared filament with injection-grade to extrusion-grade ratios of 100:0; 50:50 and 40:60, the 40:60 ratio was identified the starting ratio for producing filament with uniform diameter. Therefore, the 40:60 ratio was chosen for 3D printing tensile specimens for tensile testing. The tensile testing revealed that the tensile properties were influenced by printing layer height, with the 0.4 mm and 0.6 mm layers performing better than 0.8 mm due to better interlayer bonding. Comparative analysis with commercial poly(lactic acid) (PLA) filament at 0.6 mm layer height, while PLA outperformed PCP in tensile strength and elastic modulus, the PCP filament still demonstrated acceptable performance for non-structural 3D printed applications. Furthermore, the printing temperature used for this PCP blend was appropriate, as it did not exceed the onset thermal degradation temperature determined from thermal analysis. This project highlights the potential of upcycling the post-consumer polypropylene utensils in additive manufacturing.