| Summary: | 博士 === 中原大學 === 機械工程研究所 === 96 === Fuel cells constitute one of the most promising sources of clean energy and bipolar plate is an important component of a fuel cell. Electrically conductive polymer composites for molding of bipolar plates, has the advantages of lightweight, low cost, chemical stability, and ease of fabrication. They will can alternative to graphite and metal-based material if one can improve the conductivity of polymer composite.
In this study, bipolar plates without channel were injection molding using PC polymer filled with a few carbon fiber to investigate the fiber orientation and distribution from molding condition. Then the plates with and without channels were convectional injection molding (CIM) and injection-compression molding (ICM) using PPS polymer filled with 50 wt% carbon fiber (and different content of graphite) under different molding parameters was addressed. The effect of molding methods (CIM and ICM) and processing parameters including mold temperature, melt temperature, injection velocity, and packing pressure on the electrical conductivity performance were analyzed and correlated. Meanwhile, influence of fiber orientation and distribution from molding conditions was evaluated. How flow channel design affects the conductivity distribution was also studied as well. The in-plane conductivity and through-plane resistance of the bipolar plate was done by four-point probe apparatus and micrograph was done via SEM. In addition, 3D-CAE simulation for fiber orientation and dispersion phenomenon during filling process was also investigated and compared with injection molding experiment.
The results showed that through-plane resistance and in-plane conductivity of the bipolar plate can drop 53% and improve 48%, respectively, when the better molding condition was chosen (mold temperature 210℃, melt temperature 330℃,injection velocity 60mm/s, packing pressure 150MPa) for CIM. In addition, when ICM with 0.8 mm initial open gap, it can decreases 38% and increases 61% for through-plane resistance and in-plane conductivity, respectively. At a graphite level of 20 wt%, the in-plane conductivity can reached 156S/cm and it has been achieved the DOE target. As channel is perpendicular to filling direction for ICM, the in-plane conductivity can reached 183S/cm.
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