Evaluation of Recycled Polypropylene (PP) Made from Plastic Cups as Filaments for Additive Manufacturing

Abstract

Plastic waste is one of the most problematic wastes produced daily. A potential solution to this problem is to recycle and convert them into filaments for 3D printing. This study aims to prepare recycled polypropylene (rPP) from plastic cups and convert them into filaments for 3D printing using an extrusion process. It also aims to produce a quality printout and compare its mechanical properties with a commercial filament, polylactic acid (PLA). In this study, rPP cups were collected and treated to undergo an extrusion process. A temperature calibration tower was then fabricated to determine the ideal temperature settings for printing. Lastly a total of 24 tensile and flexural specimens were printed utilizing both rPP and PLA, facilitating a comparative evaluation of their mechanical properties. Results showed that the best extruder heater settings were 240°C, 235°C, 210°C, and 180°C from heat zone 1 to 4. The ideal printing temperature for rPP material was established at 230°C. The application of polypropylene packaging tapes, hairspray, and incorporation of a brim around the model proved effective in mitigating warpage during the printing process. Mechanical testing indicated an average tensile strength and flexural strength of 24.5 MPa and 45 MPa, respectively. In contrast the average tensile strength and flexural strength for PLA was measured at 43 MPa and 80 MPa respectively. It is clear that PLA demonstrated higher outcomes, but it lacks durability and flexibility exhibited by rPP.