Preparation of Poly(Ether Ketone Ketone) Powders for Powder Bed Fusion via Cryogenic Milling and Thermally Induced Phase Separation

Poly(ether ketone ketone) (PEKK) is a high-performance thermoplastic with significant potential for laser-based powder bed fusion (L-PBF), but the preparation of powders with suitable morphology, flowability, and thermal stability remains challenging. In this study, cryogenic milling and thermally induced phase separation (TIPS) were compared as two routes for producing PEKK powders for L-PBF applications. Cryogenic milling effectively preserved the chemical and thermal integrity of PEKK and reduced the median particle size to 23.3–36.4 μm. However, the resulting powders showed irregular particle morphology, broad size distribution, and a high proportion of fine particles, which may restrict powder spreading and layer uniformity. By contrast, TIPS provided improved control over powder morphology. Under optimized conditions, particularly 7 wt.% PEKK and holding temperatures of 225°C–250°C, near-spherical particles with smooth surfaces were obtained. The TIPS-derived powders exhibited Dv(50) values of 15.3–26.0 μm, suggesting potential for fine-feature L-PBF, although further optimization is required to reduce fine-particle content and improve flowability. Post-processing by sieving and adding 1 wt.% hydrophobic fumed silica increased bulk density and reduced the angle of repose to 35.97°. DSC and FTIR results confirmed that both methods retained the intrinsic melting behavior and chemical structure of PEKK. Overall, TIPS is demonstrated as a promising and tunable route for preparing PEKK powders for advanced polymer powder bed fusion.