Enhanced Coalescence and Tailored Properties in Polymeric Powder Bed Fusion by Molecular Design of Feedstocks

Coalescence is a crucial step in 3D printing that directly impacts the strength, quality, and properties of printed parts. In this presentation, we will discuss our recent work that utilizes a processing protocol based on liquid-liquid phase separation to controllably create polypropylene (PP) powders from 12k, 250k, and 340k PP molecular weight (Mw) along with their blends, which tunes their coalescence dynamics, impacting powder bed fusion. Monitoring the particle coalescence of these powders shows that the addition of 12k PP significantly increases the coalescence rate of high Mw PP, consequently reducing the void space and increasing the mechanical strength of the resultant printed parts. The coalescence of these multi-components powders follows the Hopper model, offering insight into the underlying mechanisms governing particle consolidation. A holistic interpretation of the data shows that the 12k PP does not surface segregate in the powder but is homogeneously distributed, improving the coalescence process by lowering the extensional viscosity of the polymer melt. These findings provide a straightforward mechanism to molecularly design powder coalescence properties and offer avenues to broaden the feedstocks available for powder bed fusion.