Study On Continuous Compression Molding Process And Application Performance Of Resin/Graphite Proton Exchange Membrane Fuel Cell Bipolar Plates

Nowadays, energy conservation and environmental protection have been becoming direction of unremitting efforts of human under persecution of tense energy and environmental pollution. Considerable attention has focused on fuel cell due to its high efficiency, non-pollution, and convenience of utilization. The proton exchange membrane fuel cell (PEMFC) is the mainstream among fuel cell research at present. Bipolar plates, as one of the key components, accounts for80%,70%,60%of the volume, the quality, and the cost in PEMFC stack respectively. Therefore, breakthrough of material and process technology for the bipolar plate will contribute to commercialization of fuel cell. The continuous compression molding process and application performance of resin/graphite composite bipolar plates is both studied in this paper, and the optimization of raw material and the continuous compression molding process is expected to improve the application performance of the bipolar plates and production efficiency, and reduce production cost.In this paper, the material formula is first optimized, the phenolic resin with low cost and excellent performance is selected as the binder, the bending strength and electrical conductivity is selected as the optimization objective, the appropriate types of phenolic resin is confirmed; the phenolic resin content and graphite particle size is optimized in succession. The results show that:the type of phenolic resin is PF5120; the optimum phenolic resin content and graphite particle size is18wt%and-100mesh respectively, and the electrical conductivity and bending strength is142.7S/cm and51MPa respectively. On the basis of single plate compression forming mould designed by our task group, the continuous compression forming mould of resin/graphite composite bipolar is designed, and the bending strength and electrical conductivity is selected as the optimization objective, the continuous compression molding process of resin/graphite composite is studied. the results show that:the optimum continuous compression molding process of resin/graphite composite plate is as follows:the molding temperature is200℃、the molding time is30min、the molding pressure is30MPa, and the electrical conductivity and bending strength is115.8S/cm and39.2MPa respectively.On the basis of the research of continuous compression molding process, the high efficient formability of complex flow channels is studied, the mould surface smoothness, the influence of the selection of feeding temperature, the selection of demoulding methods, the demoulding temperature and the continuous compression molding process on the formability of resin/graphite composite bipolar plates, the optimum forming conditions of bipolar plates is obtained by the analysis of the surface roughness and the appearance quality. The results show that:the bipolar plate is easy to demould when the feeding temperature is at room temperature; the good formability can be obtained by taking silicon oil as the external release agent and znic stearate as the internal release agent, and the surface roughness of bipolar plates is579.53nm and647.37nm respectively; the flow channels of bipolar plates is clear and smooth, the optimum demoulding temperature is60℃～80℃. The optimum forming conditions is as follows:the molding temperature～200℃、the molding pressure30MPa、the single molding time～10min。The addition of internal release agent improves the formability of bipolar plates greatly, but affects the application performance of bipolar plates, therefore the effect of release agent on bending strength and electrical conductivity, the effect of different heat treatment on bending strength and electrical conductivity, and aging resistance, corrosion resistance, wettability of bipolar plates is studied. In order to improve the low conductivity due to the addition of internal agent. the resin/graphite composite bipolar plates reinforced by carbon nanotubes is studied. The results show that:the bending strength and electrical conductivity of composite both achieves the maximum,56.3MPa and97.5S/cm respectively as the znic stearate is2wt%; the heat treatment is no need to proceed due to the features of continuous compression molding; the aging resistance performance of bipolar plates is good by research of aging resistance test of30days, the bending strength reduce to44.1MPa, but it still exceeds the standard of American DOE, the conductivity remains unchanged basically; the surface contact angle of bipolar plates is88.95°, the wettability is good; the corrosion resistance is good, the gas impermeability is2.18×10-10m3. m-2·s-1·Pa-1; the bending strength and electrical conductivity of composite bipolar plates reinforced by carbon nanotubes both achieves the maximum,75.02MPa and118.19S/cm respectively as the carbon nanotubes content is2wt%; they all exceed the standard of American DOE.