@inproceedings{46764,
  abstract     = {{Polymer composites represent the industry standard in injection molding for the production 
of plastic components with increased requirements in terms of heat resistance and stiffness. In the 
field of laser sintering (LS), these materials are less common so far. In order to extend the available 
material variety for the LS process, new ceramic-filled Polyamide 613 powders are investigated
within the scope of this work. Here, the resulting properties from two different powder production 
methods are compared. One filled powder is produced by dry blending and the other powder with 
the same filler and filling ratio is produced by encapsulating the filler particles inside the polymer 
particles within the dissolution-precipitation process. It was found that encapsulating the filler 
particles can provide certain benefits for the processability, for example an improved powder 
flowability or better filler dispersion. However, encapsulating the filler also alters the thermal 
properties of the precipitated powder.}},
  author       = {{Kletetzka, Ivo and Neitzel, Fabian and Schmid, Hans-Joachim}},
  booktitle    = {{Proceedings of the 34th Annual International Solid Freeform Fabrication Symposium}},
  editor       = {{Beaman, Joseph}},
  location     = {{Austin}},
  publisher    = {{Laboratory for Freeform Fabrication and University of Texas}},
  title        = {{{Assessing the Impact of the Powder Production Method on Ceramic-filled Polyamide Composites made by Laser Sintering}}},
  volume       = {{34}},
  year         = {{2023}},
}

@inproceedings{51218,
  abstract     = {{Polymer composites represent the industry standard in injection molding for the production of plastic components with increased requirements in terms of heat resistance and stiffness. In the field of laser sintering (LS), these materials are less common so far. In order to extend the available material variety for the LS process, new ceramic-filled Polyamide 613 powders are investigated within the scope of this work. Here, the resulting properties from two different powder production methods are compared. One filled powder is produced by dry blending and the other powder with the same filler and filling ratio is produced by encapsulating the filler particles inside the polymer particles within the dissolution-precipitation process. It was found that encapsulating the filler particles can provide certain benefits for the processability, for example an improved powder flowability or better filler dispersion. However, encapsulating the filler also alters the thermal properties of the precipitated powder. }},
  author       = {{Kletetzka, Ivo and Neitzel, Fabian and Schmid, Hans-Joachim}},
  booktitle    = {{Proceedings of the 34th Annual International Solid Freeform Fabrication Symposium}},
  editor       = {{Beaman, Joseph}},
  keywords     = {{Additive Manufacturing, Laser Sintering, Filled Materials, Composites, Polyamide 613}},
  location     = {{Austin}},
  title        = {{{Assessing the Impact of the Powder Production Method on Ceramic-filled Polyamide Composites made by Laser Sintering}}},
  doi          = {{https://doi.org/10.26153/tsw/50931}},
  year         = {{2023}},
}

@inproceedings{46862,
  abstract     = {{The high flammability of components manufactured by laser sintering (LS) using standard polyamide 12 (PA12) powder still severely restricts their use in industries such as electronics, aviation, and transportation. A key factor for the further establishment of LS is the expansion of the material portfolio with, for example, refreshable and halogen-free flame-retardant (FR) powder materials. Accordingly, various halogen-free FRs are investigated in this work and evaluated with respect to their use in LS. First, their decomposition behavior and mode of action are examined. Subsequently, the additives are dry blended with PA12 to investigate properties relevant for LS, such as particle morphology, thermal behavior and melt viscosity. Afterwards, test specimens for UL94 vertical flame-retardancy tests are produced by processing the dry blends on an EOS P3 LS system. Finally, the process stability of the process-aged powder blends is investigated by again examining the thermal behavior and melt viscosity.}},
  author       = {{Neitzel, Fabian and Kletetzka, Ivo and Schmid, Hans-Joachim}},
  booktitle    = {{Proceedings of the 34th Annual International Solid Freeform Fabrication Symposium}},
  editor       = {{Beaman, Joseph}},
  keywords     = {{Additive Manufacturing, Laser Sintering, Flame Retardant, Polyamide 12}},
  location     = {{Austin}},
  title        = {{{Halogen-Free Flame Retardant Powder Materials for Laser Sintering: Evaluation and Process Stability Analysis}}},
  doi          = {{https://doi.org/10.26153/tsw/50926}},
  year         = {{2023}},
}

@article{46815,
  abstract     = {{In this work, the influence of the filler–matrix adhesion on the tensile properties of laser-sintered parts built with Polyamide 613 filled with glass beads was investigated. For this purpose, dry blends of glass beads with and without organosilane coupling agents and polyamide powder were prepared and processed into tensile specimens on an EOS P396 laser sintering system. The samples were tested both in the dry state and after an accelerated conditioning in a climate chamber. Furthermore, finite element method (FEM) simulations were performed to model the extreme cases of optimum adhesion and no adhesion. By correlating the tensile tests with the simulation results and by analyzing the fracture surfaces, it was shown that the filler–matrix adhesion is sufficient in the dry state but is strongly degraded by conditioning. Even the presence of various organosilane thin films could not prevent a strong deterioration of the filler–matrix adhesion and the associated deterioration of the mechanical properties. Since a comparison with an injection-molded sample of the same polymer filler combination shows identical behavior after conditioning, it is assumed that this problem is not limited to additively manufactured parts.}},
  author       = {{Kletetzka, Ivo and Kosanke, Maren and Meinderink, Dennis and Neßlinger, Vanessa and Grundmeier, Guido and Schmid, Hans-Joachim}},
  issn         = {{2363-9512}},
  journal      = {{Progress in Additive Manufacturing}},
  keywords     = {{Industrial and Manufacturing Engineering}},
  publisher    = {{Springer Science and Business Media LLC}},
  title        = {{{Influence of the filler–matrix adhesion and the effects of conditioning on tensile properties of laser-sintered parts built with polyamide–glass bead dry blends}}},
  doi          = {{10.1007/s40964-023-00501-z}},
  year         = {{2023}},
}

@inproceedings{45783,
  author       = {{Kletetzka, Ivo}},
  location     = {{Berlin}},
  title        = {{{Tensile Testing for Polymer AM - Best Pratice at the DMRC}}},
  year         = {{2023}},
}

@article{43046,
  abstract     = {{In the laser sintering technology, the semi-crystalline polymer material is exposed to elevated temperatures during processing, which leads to serious material ageing for most materials. This has already been investigated intensively by various authors. However, the ageing of the material at ambient temperatures during shelf life has not been the focus so far. The need to analyse the shelf life can be derived from an ecological and economic point of view. This work is focusing on the shelf life of PA2200 (PA12). To reduce the potential influences of powder production fluctuations, two different powder batches stored for 5.5 years and 6.5 years are investigated and compared to a reference powder produced 0.5 years before these investigations. Multiple powder analyses and part characterisations have been performed. A significant yellowing and molecular chain length reduction can be derived from the measurement results. Whereas the influence on mechanical part performance was minor, the parts built with the stored powders are more yellowish. As it is most likely that this is due to the consumption of polyamide stabilisers, it can be assumed that these parts will be subject to significantly faster ageing. Therefore, it is still not recommended to use the stored powders for critical parts or light intense and humid environments.}},
  author       = {{Klippstein, Sven Helge and Kletetzka, Ivo and Sural, Ilknur and Schmid, Hans-Joachim}},
  journal      = {{The International Journal of Advanced Manufacturing Technology }},
  keywords     = {{Selective laser sintering, Shelf life, Polyamide 12, powder, PA2200, material ageing}},
  publisher    = {{Springer}},
  title        = {{{Influence of a prolonged shelf time on PA12 laser sintering powder and resulting part properties}}},
  doi          = {{https://doi.org/10.1007/s00170-023-11243-1}},
  year         = {{2023}},
}

@inproceedings{30220,
  abstract     = {{In this work, the influences of spherical fillers on the processing properties and the resulting mechanical properties of laser sintered components are investigated. For this purpose, micro glass spheres, hollow glass bubbles and mineral spheres are dry blended to the matrix polymers polyamide 613 and polypropylene with a filling ratio of 20 and 40 vol%. First, relevant properties of the blends, such as powder flowability, thermal behavior and melt viscosity, are investigated. Based on the results, processing parameters are then developed for the LS process and the mechanical properties of the components are investigated. The aim is to be able to tailor the mechanical properties of LS components by adding fillers and thus to create new application areas for additively manufactured components. }},
  author       = {{Kletetzka, Ivo and Gawlikowicz, Roland and Schmid, Hans-Joachim}},
  booktitle    = {{Proceedings of the 33th Annual International Solid Freeform Fabrication Symposium}},
  location     = {{Austin}},
  publisher    = {{Laboratory for Freeform Fabrication and University of Texas}},
  title        = {{{Effects of spherical fillers on the processability and mechanical properties of PA613 and PP-based LS dry blends}}},
  doi          = {{http://dx.doi.org/10.26153/tsw/44558}},
  volume       = {{33}},
  year         = {{2022}},
}

@inproceedings{32874,
  author       = {{Kletetzka, Ivo and Klippstein, Sven Helge and Schmid, Hans-Joachim}},
  booktitle    = {{Proceedings of the 33th Annual International Solid Freeform Fabrication Symposium}},
  location     = {{Austin}},
  publisher    = {{Laboratory for Freeform Fabrication and University of Texas}},
  title        = {{{Shelf Life of Polyamide 12 (PA2200) Laser Sintering Powder}}},
  doi          = {{http://dx.doi.org/10.26153/tsw/44555}},
  volume       = {{33}},
  year         = {{2022}},
}

@inproceedings{31871,
  author       = {{Kletetzka, Ivo and Klippstein, Sven Helge}},
  booktitle    = {{3D-DRUCK HAUTNAH - Der Einfluss einer Zukunftstechnologie auf unser Leben }},
  location     = {{Paderborn}},
  publisher    = {{Universität Paderborn}},
  title        = {{{Pulver im 3D-Druck - von Mascarabürsten bis zum Interieur eines Mini-Coopers (Vortrag)}}},
  year         = {{2022}},
}

@inproceedings{24160,
  abstract     = {{In automotive and other fields of application media-carrying components often have complex, flow-optimized geometries and are made of plastics for reasons of weight and cost. Therefore, the laser sintering technology is predestinated to manufacture these components as it offers a very high degree of design freedom and good mechanical properties.
For industrial applications the long-term properties of the SLS material in contact with liquid media are important and were therefore investigated for PA12, PP and PA613. Hereby, different media such as motor oil or Glysantin based coolant were tested with different temperatures and immersion times of up to 26 weeks. The mechanical properties were tested after immersion and compared to injection molded samples. Furthermore, laser sintering design guidelines for media-carrying components were developed. These guidelines for instance include the minimum wall thickness to ensure media tightness and the removal of powder from channels with a high length to diameter ratio.}},
  author       = {{Kletetzka, Ivo and Kummert, Christina and Schmid, Hans-Joachim}},
  booktitle    = {{Proceedings of the 32nd Annual International Solid Freeform Fabrication Symposium}},
  location     = {{Austin}},
  publisher    = {{Laboratory for Freeform Fabrication and University of Texas}},
  title        = {{{Laser Sintering Design Guidelines for media transmitting Components}}},
  doi          = {{http://dx.doi.org/10.26153/tsw/17548}},
  volume       = {{32}},
  year         = {{2021}},
}