Quality over Quantity: How Different Dispersion Qualities of Minute Amounts of Nano-Additives Affect Material Properties in Powder Bed Fusion of Polyamide 12

Abstract

The great interest, within the fields of research and industry, in enhancing the range and functionality of polymer powders for laser powder bed fusion (LB-PBF-P) increases the need for material modifications. To exploit the full potential of the additivation method of feedstock powders with nanoparticles, the influence of nanoparticles on the LB-PBF process and the material behavior must be understood. In this study, the impact of the quantity and dispersion quality of carbon nanoparticles deposited on polyamide 12 particles is investigated using tensile and cubic specimens manufactured under the same process conditions. The nano-additives are added through dry coating and colloidal deposition. The specimens are analyzed by tensile testing, differential scanning calorimetry, polarized light and electron microscopy, X-ray diffraction, infrared spectroscopy, and micro-computed tomography. The results show that minute amounts (0.005 vol%) of highly dispersed carbon nanoparticles shift the mechanical properties to higher ductility at the expense of tensile strength. Despite changes in crystallinity due to nano-additives, the crystalline phases of polyamide 12 are retained. Layer bonding and part densities strongly depend on the quantity and dispersion quality of the nanoparticles. Nanoparticle loadings for CO2 laser-operated PBF show only minor changes in material properties, while the potential is greater at lower laser wavelengths.

Dry powder coating in additive manufacturing

“…Moreover, an improvement of mechanical properties in parts produced from composite powders of PA12-carbon nanoplateletes or from PEEK (wet) coated with fullerene-like WS 2 and graphene nanoplatelets was reported (Yazdani et al, 2018;Chen et al, 2020). Hupfeld et al (2020c), Hupfeld et al (2020d) demonstrated that the crystallization behavior of PA12 feedstocks and their microstructure (spherulites, lamellae) can be tuned by (wet) coating with carbon nanoparticles, respectively, Ag nanoparticles produced in-situ in the liquid phase by laser-induced fragmentation of precursors (Hupfeld et al, 2020a;Sommereyns et al, 2021a;Sommereyns et al, 2021b). These authors observed improved homogeneity of the nanoparticulate coating, if the functionalization was performed by wet coating from dispersion as compared to dry particle coating.…”

New Frontiers in Materials Design for Laser Additive Manufacturing

“…A lot of research focuses on semi-crystalline polyamide 12 (PA12). The authors of [ 16 ] were able to prove in their investigations that even small amounts of added carbon nanoparticles can significantly influence the mechanical properties without adversely changing the crystallization behavior. Metallic or ceramic additives in micro- or nanoscale embedded in a polymer matrix can be used to produce highly specialized parts even with new functionalities, like, e.g., magnetic characteristics [ 17 ].…”