Up to now, laser-sintered components have been barely used by industries such as aerospace and transport industry due to high flammability. By the use of flame retardants, the flammability of laser-sintered parts should be reduced to extend their range of possible applications. This paper aims to investigate the influence of halogen-free phosphinate-based flame retardants on process-relevant characteristics and process behavior, as well as mechanical and physical properties. Most importantly, the flammability of the material should be reduced. Two different types of phosphinate-based fillers were used in a concentration between 10 and 25 wt % in combination with the matrix material polyamide 12 (PA12). Thermal, optical, and powder properties of the mixtures were analytically investigated. Furthermore, the mechanical characterization of the sintered specimen was carried out. The addition of filler in laser sintering changes the process behavior and properties of the component. With this investigation, the correlation among flame retardants, process-relevant characteristics, process behavior, and resulting part properties was derived for the first time. Finally, a mixture of 15–20 wt % of flame retardant leads to the best trade-off between flame retardancy and mechanical properties.

In recent years, the demand for polymer compound solutions for the application of bipolar plates in polymer electrolyte membrane fuel cells (PEMFC) has increased continuously due to significant cost and lifetime advantages compared to metallic solutions. The main challenge of the compounds is the high filler content required to ensure sufficient electrical conductivity of the bipolar plates. The associated increase in viscosity and simultaneously increased thermal conductivity limit the conventional injection molding process in terms of achievable flow path length to wall thickness ratios (plate aspect ratio). In order to evaluate the extent to which highly modified electrically conductive polymer material systems can be processed into thin-walled and highly dimensionally stable bipolar plates, an injection compression molding process with dynamic mold temperature control (ICM-DT) has been developed. For this purpose, a compound was prepared from polypropylene (PP) and graphite-flakes. The compound was characterized with respect to the achieved filler content, the electrical conductivity, as well as the pressure- and temperature-dependent solidification range. The ICM-DT experiments were carried out by varying the maximum mold temperature and the compression force. In addition, the process was designed with multiple compression and decompression steps to account for a possible pressure-dependent solidification of the compound. The plates were characterized with respect to the achieved plate aspect ratio and the flow-path-dependent dimensional thickness stability. It was shown that the plate aspect ratio could be increased by up to 125% with the maximum filler content compared to conventional injection molding processes provided in the literature. With the multi-stage ICM-DT process, it was also possible to optimize the thickness dimensional stability with a maximum deviation of 3% over the flow path.

High‐frequency heating processes are widely used in industry, for example, for food processing, wood drying, or plastic welding. A recent development in this field uses radio‐frequency heating to fuse particle foam beads to complex components. The aim of using the modified process is to reduce the energy consumption of particle foam fusion. Within this process, the molds used must be electrically insulating to ensure the building of an electrical field. For this purpose, mold made of two different plastics were analyzed. Additional to the dielectric, mechanical, and thermal expansion, the thermal conductivity of the mold materials are of great interest. Although welding is finished quickly, cooling to the demolding temperature is comparably long. To achieve shorter cooling and therefore shorter process times, the mold materials were modified by two different thermal conductive but electrically insulating fillers. By the use of the thermally optimized mold materials, a reduction in cooling time of up to 40% was possible. At the same time, the heating step was hardly affected. Mechanical properties were enhanced while thermal expansion was reduced.

Due to its chemical structure and the resulting dielectric properties, the processing of the commonly used particle foam material, expanded polypropylene (ePP), is limited. Processing within the radio-frequency welding process is therefore only possible with the use of processing aids. In this paper, a new approach for the use of a solid and dielectric heatable coating for the production of three-dimensional welded components out of ePP is presented. For this purpose, three different types of water-soluble polymer polyvinyl alcohol (PVA) were analyzed as potential coating materials. The thermal and dielectric properties of the coating were further adjusted by a modification with glycerol. The maximum amount of glycerol tested was 25% by volume. It influences both the temperature development in the radio-frequency (RF) welding process as well as the adhesive bond between the ePP foam particles. It is shown that the 120 °C approach in the RF welding process resulted in a cohesive bond between the coating layers. In this way, bonded plates can be produced. In mechanical tests with compression of 20%, the manufactured plates show sufficient load capacity. Furthermore, it can be shown that a separation of PVA and ePP by type, and thereby a separation of the foam particles, is possible with the use of hot water. This might open a new way for recycling of particle foams.

The steam chest molding process is currently state of the art concerning the generation of three‐dimensional polymeric foam components made from particle foams. An adaption of the high‐frequency welding process shows advantages regarding the required energy and the used water. Due to the low dielectric loss factors of the most common foam materials (PE, PP, and PS), they cannot be heated sufficiently by an electric field. To enable heating of these foams, the particles may be coated with a second material that shows a high dielectric loss. The possible heat development of the modified particles was simulatively investigated. To ensure a realistic simulation, the properties of the used materials are analyzed beforehand. The heating simulation shows clear dependence regarding the particle size and the shell thickness. By a suitable combination, sufficient heating is achievable. For single particles, an irregular temperature distribution is calculated, mainly caused by the difference of permittivity resulting in a local variation of electrical flux density. Bigger particles and thicker shells will result in faster heating ramps and higher overall temperatures. The additional calculation regarding a particle–particle interaction shows a homogenization of the temperature distribution across the particle surface.