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Commercially available materials for selective laser sintering (SLS) include mainly semicrystalline polymers and only a few composites like polyamide 12 filled with glass beads or aluminum. Powder composites can be used for setting tailored properties. Exemplarily, mechanical properties as well as thermal or electrical conductivity can be improved. Thermally conductive SLS parts filled with copper particles have not been under investigation before. This study contains the characterization of polyamide 12 filled with copper acting as a metal filler with a high thermal conductivity. Two composites differing in the filler shapes are investigated concerning powder properties and the resulting processability. The thermal conductivity in dependence on the filler content and anisotropy is of major interest. Isotropic, spherically shaped copper fillers are compared with strongly anisotropic flakes leading to the result that a much lower content of anisotropic filler is needed to reach an increased thermal conductivity. However, the powder flowability and processability is also highly influenced by the filler shape and content. Fillers with a similar shape like the matrix powder lead to a better flowability allowing higher filler contents. POLYM. COMPOS., 40:1801–1809, 2019. © 2018 The Authors Polymer Composites published by Wiley Periodicals, Inc. on behalf of Society of Plastics Engineers

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Powder Bed Fusion of Polymers (PBF-LB/P) is a layer-wise additive manufacturing process that predominantly relies on the quasi-isothermal processing of semi-crystalline polymers, inherently limiting the spectrum of polymers suitable for quasi-isothermal PBF. Within the present paper, a novel approach for extending the isothermal processing window towards significantly lower temperatures by applying the quasi-simultaneous laser-based exposure of fractal scan paths is proposed. The proposed approach is based on the temporal and spatial discretization of the melting and subsequent crystallization of semi-crystalline thermoplastics, hence allowing for the mesoscale compensation of crystallization shrinkage of distinct segments. Using thermographic monitoring, a homogenous temperature increase of discrete exposed sub-segments, limited thermal interference of distinct segments, and the resulting avoidance of curling and warping can be observed. Manufactured parts exhibit a dense and lamellar part morphology with a nano-scale semi-crystalline structure. The presented approach represents a novel methodology that allows for significantly reducing energy consumption, process preparation times and temperature-induced material aging in PBF-LB/P while representing the foundation for the processing of novel, thermo-sensitive material systems in PBF-LB/P.