Mechanical Densification of Precipitated Biobased Polyamide 1012 Powders for Laser Additive Manufacturing

Nowadays, polymer powders for laser powder bed fusion (PBF-LB/P) additive manufacturing are primarily prepared through the dissolution–precipitation method. These powders usually possess a porous structure, which results in low powder bed densities and deteriorated part performance. Herein, a simple mechanical densification strategy was employed to optimize the microstructure, PBF-LB/P processing behavior, and part performance of precipitated biobased polyamide 1012 (PA1012) powders. It was found that roller milling densified the PA1012 particles, greatly reduced their specific surface area, and improved the high-temperature flowability of the powders. Parts based on milled powders exhibited largely improved appearance and mechanical properties. After 90 min of powder milling, the tensile modulus, strength, and elongation-at-break of the parts increased by 37%, 51%, and 150%, respectively. The substantial upgrade in part performance was attributed to the increase in the bulk density and powder bed density of milled powders, the reduction of internal void defects in the parts, and the suppression of degradation during processing. These positive effects were considered to outweigh the adverse impact of reduced laser absorptance caused by powder densification. Furthermore, the milled powder demonstrated a slower postcondensation rate and better recyclability due to the large reduction in the surface area of the powder. Therefore, mechanical densification represents a simple strategy to improve the PBF-LB/P processability and part mechanical performance of precipitated polymer powders.