The Effects of Iron, Silicon, Chromium, and Aluminum Additions on the Physical and Mechanical Properties of Recycled 3D Printing Filaments

With the increasing use of 3D printers especially the fused filament fabrication type in the industries and general public, there is indeed a need to consider the after-use treatment for the products. The use of recycled filaments as the feedstock for 3D printers is a feasible alternative, but its application is limited to rather poor product quality. This study, thus, evaluates the effects of adding iron (Fe), silicon (Si), chromium (Cr), and aluminum (Al) nano-crystalline powders into the recycled polypropylene/high-density polyethylene plastics feedstock for filament extrusion. Physical and mechanical analysis tests revealed that the addition of 1% Fe–Si–Cr or Fe–Si–Al resulted in better thermal stability, and up to 37% and 17% improvement, respectively, in yield strength and Young modulus compared with the original recycled filaments, possibly due to the enhancement of interfacial adhesion between the nano-metal powders and the polymer, leading to reduced crack formation.