- 學位論文
高分子複合型燃料電池雙極板射出成型製程與流道配置對碳纖分佈之研究
Study on Injection Molding Process and Layout of Channel to Fiber istribution for Composite Polymer Bipolar of Fuel Cell
摘要
燃料電池是極具潛力的潔淨能源之一，而雙極板則是燃料電池中重要的組成元件，其成本佔了整體的五至六成。以添加導電性纖維之高分子複合材料搭配射出成型方式來成型雙極板，具有價位低且可大量生產等優點，因此可取代石墨或不?袗?等材料而漸漸展現其重要性。然目前很少有利用射出成型，對具添加導電性纖維之高分子複合材料，在成型參數及模穴的幾何形狀上，其纖維分佈與導電性之間的關係做一系統的相關研究。 在本研究中，選用添加4%碳纖之PC高分子複合材料，利用長寬皆各50 mm與厚2 mm之平板狀模仁與含流道之模仁(流道深0.5 mm、寬2 mm、長42 mm)，針對不同的射出速度(50、65以及80 mm/s三種射出速度)與流道配置方向(分別垂直與平行充填方向)來成型雙極板成品，並以掃描式電子顯微鏡(SEM)沿厚度方向上對纖維孔洞做一量測與分析，藉以探討射出速度與流道配置方向對纖維分佈的影響。而後再以添加30% 碳纖之PS高分子複合材料來成型並量測其電阻值，探討流道與充填方向對導電性之影響，實驗結果並與添加4%碳纖之PC高分子複合材料的成型品纖維分佈趨勢做一比較。 研究結果顯示，在各種熔膠射出速度的情況下，除了非常接近近澆口端與充填末端的纖維含量均非常少之外，其餘成型品部分則當射出速度較低時(50 mm/s)，纖維由近澆口端至充填末端分佈較為均勻。當射出速度由50增加至65以及80 mm/s時，纖維含量會由近澆口端之較多含量而逐漸向充填末端處減少(即分佈愈不均勻)，因此射速對於纖維分佈會有明顯的影響，速度慢時有較好的分佈性。在流道的配置方面，當流道垂直於充填方向時，會使纖維產生翻滾而糾結在一起，因此相較於與流道平行於充填方向的成型品相比，整體電導度可提高了約50%，且導電均勻度也有提升。本研究結果，可提供相關業者在雙極板流道佈置與進澆口位置設計時一重要參考準則。
並列摘要
The fuel cell is one of the extremely potential clean energy. The bipolar plate is an important component in the fuel cell, and its cost has accounted for about 50 to 60% of the whole. Injection molding of the bipolar plate using polymer composite of electric fiber becomes price competitive method and can be mass-produced. At present, there are few research on the relationship between fiber distribution and the electric conductivity for polymer composite with electric fiber using injection molding process. In this study, there are two designs of mold insert that one is a flat insert, the other is channel insert and the material is polycarbonate blended with 4% carbon fiber. For studying fiber distribution, the bipolar plate was molded using different filling velocity(50 mm/s, 65 mm/s and 80 mm/s) and channel layout direction, and the fiber distribution along the thickness-direction was measured by SEM to investigate the influence of filling velocity and channel layout on distribution. By obtaining the best fiber distribution at the results of previous experiment, influence of filling velocity and channel layout on resistance was investigated using polystyrene blended with 30% carbon fiber. The relationship between fiber distribution and resistance was studied. As the results, the fiber distribution is uniform at low velocity(50 mm/s), but the low concentrations of conductive fiber appear near gate and at the end of flow for all kinds of filling velocity. As filling velocity raises to 60 mm/s or 80 mm/s, the concentrations graduately reduce from gate to end of flow. Therefore the filling velocity influences fiber distribution. On the channel layout, as channel is perpendicular to filling direction, the fibers are rolled and banded together, and the conductivity can be improved about 50% compared with channel parallel to filling direction. This study can offer guide lines of channel layout and gate position for bipolar.