Unveiling the Multiplicity of Silica Nanoparticles in Improving the Laser Powder Bed Fusion Processability of Polypropylene Copolymer

Polypropylene (PP) copolymer powder usually displays low laser absorbance and inferior laser powder bed fusion (PBF-LB) additive manufacturing processability. Herein, hydrophobic silica nanoparticles (NPs), which are generally used as flow aids to coat powders, were in-particle compounded into PP particles and were found to cause an unexpected upgrade in the PBF-LB processability of PP powder. PP powders with minute amounts (∼0.3 wt %) of in-particle compounded silica NPs exhibited a largely reduced zero-shear viscosity (∼45%), a broadened sintering window, and stronger laser heating behavior. As a result, the PP powder was fabricated successfully into parts with fewer defects, better shape accuracy, and higher mechanical performance. The new phenomena observed were interpreted in terms of better fusion due to abnormal rheological behavior and improved laser absorbance in the presence of trace silica NPs. Therefore, this study unleashed the multiplicity and enormous potential of silica NPs in developing new feedstocks for PBF-LB.