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

We report on enhancing the mechanical and structuralcharacteristicsof polypropylene (PP) three-dimensional (3D)-printed structures fabricatedvia fused filament fabrication (FFF) by employing composite PP-basedfilament with subsequent microwave (MWV) treatment. The compositefilament contained a minute (0.9 vol %) fraction of silicon carbidewhiskers (SiCWs) and was prepared via melt blending of PP pelletswith SiCW using an extruder. The surface of the whiskers was modifiedwith trimethoxy(octadecyl) silane to improve compatibility betweenthe polar SiCW and nonpolar PP matrix. We employed SiCWs in compositefilament because of the whiskers' high thermal conductivityand ability to generate heat locally under MWV irradiation. Indeed,we were able to conduct the heating of printed parts by MWV withoutsacrificing the structural integrity and improving the overall adhesionbetween the 3D-printed polymer layers. Our modeling captures an extentof heating upon MWV irradiation observed in our experiments. In general,utilization of the composite PP/SiCW filament significantly improvedthe printed parts' mechanical characteristics and sinteringlevel compared to those made from pure PP filament. Specifically,after the MWV treatment, the adjusted (for density) storage modulusof the PP/SiCW material was just & SIM;20% lower than that for thePP sample obtained by conventional compression molding. After theMWV irradiation, Young's modulus, yield stress, and toughnessof the printed structures were increased by & SIM;65, 53, and 55%,respectively. We attribute the improvement of mechanical propertiesvia MWV treatment to enhancing the entanglement level at the weld.