Roth Benedikt, Frank Rainer, Kleffel Tobias, Schneider Kevin, Drummer Dietmar
Institute of Polymer Technology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Am Weichselgarten 10, 91058 Erlangen, Germany.
Polymers (Basel). 2022 Jul 8;14(14):2799. doi: 10.3390/polym14142799.
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.
近年来，与金属材料相比，聚合物电解质膜燃料电池（PEMFC）双极板应用中对聚合物复合溶液的需求持续增长，这得益于其显著的成本和寿命优势。这些复合材料的主要挑战在于，为确保双极板具有足够的导电性，需要较高的填料含量。随之而来的粘度增加以及同时提高的热导率，在可实现的流道长度与壁厚比（板长宽比）方面限制了传统注塑工艺。为了评估高度改性的导电聚合物材料体系能够在多大程度上加工成薄壁且尺寸稳定性高的双极板，已开发出一种具有动态模具温度控制的注射压缩成型工艺（ICM-DT）。为此，由聚丙烯（PP）和石墨片制备了一种复合材料。对该复合材料在填料含量、电导率以及压力和温度相关的凝固范围方面进行了表征。通过改变最大模具温度和压缩力进行了ICM-DT实验。此外，该工艺设计了多个压缩和减压步骤，以考虑复合材料可能的压力依赖性凝固。对板材在实现的板长宽比和流道相关的尺寸厚度稳定性方面进行了表征。结果表明，与文献中提供的传统注塑工艺相比，在最大填料含量下，板长宽比可提高多达125%。通过多阶段ICM-DT工艺，还能够优化厚度尺寸稳定性，在流道上的最大偏差为3%。
