Light matters: Quantifiable optical interaction between near-infrared laser radiation and nano-additivated polymers in all states of matter present in laser powder bed fusion

Comprehending the interaction between light and material is crucial to the success of various laser-based processes, including laser powder bed fusion of polymers. The use of the promising near-infrared laser wavelength in laser powder bed fusion of polymers is limited by the necessity for absorption-enhancing (nano-) additives and insufficient knowledge of the (nano-) particulate impact on the material and process behavior. The present study lays the groundwork for an improved understanding of the laser-material interaction at different states of matter in laser powder bed fusion by means of thermo-optical measurements with a double integrating sphere setup. Analyses and experiments were based on polyamide 12 and its nanocomposite powder surface-coated with carbon black nanoparticles by two distinct additivation methods. The attenuation coefficient and penetration depth of each material were calculated from the measured transmittance and reflectance in all relevant states of matter. The effects of the feedstock particle size, the nano-additivation method, and the nanoparticle quantity were evaluated. The optical results of resolidified samples were validated using a commercially available spectrophotometer. Finally, the thermo-optical results were qualitatively correlated with the depth of fusion of specimens processed by powder bed fusion using an 808 nm diode laser. [Display omitted] •Simultaneous NIR measurement of reflection and transmission in polymer powders.•Thermo-optical analysis close to material conditions in powder bed fusion.•Influence of nanoparticle quantity and quality on optical material properties.•Optical attenuation coefficient as quantifiable and comparable variable.•Good correlation between penetration depth and thickness of 3D printed specimens.