Thermo-Optical Analysis of Surface- and Volume-Additivated Polymer Powders for Near-Infrared Laser Powder Bed Fusion

Near-infrared laser sources have the potential to change the process dynamics in laser powder bed fusion of polymers. To take full advantage of the shorter processing laser wavelength, the addition of absorbing additives, such as carbon black nanoparticles, becomes inevitable. Many nanoparticle characteristics can influence the laser-material interaction, such as quantity, dispersion, and position relative to the polymer matrix, but have not been investigated under processing conditions. Therefore, this study improves the understanding of the optical material properties present in laser powder bed fusion by quantifying the thermo-optical properties of PA11 powder, melt and solid, additivated with minute amounts of carbon black nanoparticles on the surface and throughout the volume of the particles. Surface-additivation results in the highest increase in laser attenuation overall and creates a segregated network that acts as a barrier to laser penetration in the molten and solid state. By contrast, the random distribution of agglomerated nanoparticles throughout the particle volume allows most of the laser radiation to pass through. Other nanoparticle effects, such as thermal stabilization and crystal formation, affect the volume-additivated particles the most. The thermo-optical results are complemented by analysis of process-relevant powder, thermal, structural, and compositional material properties.