Fabrication and Characterization of 3D Filament from Recycled High-Density Polyethylene (HDPE)

Khoo, Tilly Zi Li (2026) Fabrication and Characterization of 3D Filament from Recycled High-Density Polyethylene (HDPE). Final Year Project (Diploma), Tunku Abdul Rahman University of Management and Technology.

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Abstract

This study focuses on the fabrication and characterization of 3D printing filament produced from recycled high-density polyethylene (r-HDPE), sourced from injection-moulded waste such as sprues, gates and runners (i-HDPE), and blended with extrusion-grade (e-HDPE) materials. The motivation behind this work is to promote sustainable utilization of plastic waste through additive manufacturing. Different blend ratios of i-HDPE to e-HDPE (100:0, 50:50, and 40:60) were prepared and extruded into filaments. The filament quality was evaluated in terms of diameter consistency, ovality, and melt flow index (MFI), while the thermal stability of the blends was analysed using thermogravimetric analysis (TGA). Among the formulations, the 40:60 (i-HDPE:e-HDPE) blend demonstrated the most consistent filament diameter and acceptable thermal stability, making it suitable for 3D printing applications. Tensile specimens printed from this optimized filament were tested at three different infill densities (20%, 60%, and 100%) as the infill densities affect the tensile properties of 3D printed parts. The results revealed that higher infill density significantly enhanced tensile strength and elastic modulus, primarily due to improved interlayer bonding and reduced void content. Overall, this project demonstrates the feasibility of recycling HDPE waste into functional 3D printing filaments, contributing to circular economy initiatives while reducing plastic waste. Future work is recommended to explore the incorporation of reinforcement, surface treatment, and scalability of recycled filaments for wider engineering applications