Enhancement of Polypropylene 3D-Printed Structures via the Addition of SiC Whiskers and Microwave Irradiation

We report on enhancing the mechanical and structural characteristics of polypropylene (PP) three-dimensional (3D)-printed structures fabricated via fused filament fabrication (FFF) by employing composite PP-based filament with subsequent microwave (MWV) treatment. The composite filament contained a minute (0.9 vol %) fraction of silicon carbide whiskers (SiCWs) and was prepared via melt blending of PP pellets with SiCW using an extruder. The surface of the whiskers was modified with trimethoxy(octadecyl) silane to improve compatibility between the polar SiCW and nonpolar PP matrix. We employed SiCWs in composite filament because of the whiskers' high thermal conductivity and ability to generate heat locally under MWV irradiation. Indeed, we were able to conduct the heating of printed parts by MWV without sacrificing the structural integrity and improving the overall adhesion between the 3D-printed polymer layers. Our modeling captures an extent of heating upon MWV irradiation observed in our experiments. In general, utilization of the composite PP/SiCW filament significantly improved the printed parts' mechanical characteristics and sintering level compared to those made from pure PP filament. Specifically, after the MWV treatment, the adjusted (for density) storage modulus of the PP/SiCW material was just ∼20% lower than that for the PP sample obtained by conventional compression molding. After the MWV irradiation, Young's modulus, yield stress, and toughness of the printed structures were increased by ∼65, 53, and 55%, respectively. We attribute the improvement of mechanical properties via MWV treatment to enhancing the entanglement level at the weld.