In this study, the feasibility of co-grinding and the subsequent thermal rounding to produce spherical polymer blend particles for selective laser sintering (SLS) is demonstrated for polybutylene terephthalate (PBT) and polycarbonate (PC). The polymers are jointly comminuted in a planetary ball mill, and the obtained product particles are rounded in a heated downer reactor. The size distribution of PBT–PC composite particles is characterized with laser diffraction particle sizing, while the shape and morphology are investigated via scanning electron microscopy (SEM). A thorough investigation and characterization of the polymer intermixing in single particles is achieved via staining techniques and Raman microscopy. Furthermore, polarized light microscopy on thin film cuts enables the visualization of polymer mixing inside the particles. Trans-esterification between PBT and PC during the process steps is investigated via vibrational spectroscopy and differential scanning calorimetry (DSC). In this way, a new process route for the production of novel polymer blend particle systems for SLS is developed and carefully analyzed.

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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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