Polymer composites bipolar plates for fuel cell

Bipolar plates (BPs) are a key component of proton exchange membrane fuel cells. They are designed to carry out many functions, such as carry current from cell to cell and prevent leakage of reactants and coolant. BPs application should present a balance of various physical and chemical properties[۱]. A set of targets has been established by the department of energy (DOI) for BPs. The most relevant properties are the electrical and the mechanical properties which should be satisfied for the fabrication of BPs[۲][۳]. In this study, pp composites with different contents of graphite (۵۰_۸۰ v%) were compounded by internal mixer and investigated for their application in fuel cells. We use two different graphite particle sizes and structures: ۵۹۵ μm which has flake like structure and ۴۴ μm which has spherical structure. Also, we use ۲ phr carbon Nano tube, ۲۰ nm, as reinforcement for both electrical conductivity and flexural strength The variation of the flexural strength of the pp/graphite and pp/graphite/carbon Nano tube with an increase in total filler content is shown in fig۱ Fig.۱. variation of the flexural strength of the pp/graphite and pp/graphite/carbon Nano tube with an increase in total fillerThe flexural strength of the graphite/PP composite initially increased with increasing graphite content in the range of ۲۲ MPa at ۵۰ v% loading to ۵۲ MPa at ۶۰ v% loading. However, beyond ۶۰ v% loading, the flexural strength of the composites decreased. The decrease in flexural strength at higher filler concentrations is due to the lack of sufficient PP to bind the fillers in the composites. As we use ۲ phr content of Carbon Nano tube, the flexural strength of compositeswere increased due to its high aspect ratio.The variation of the through-plane electrical conductivity with filler content is shown in table.۱ According to the table.۱, the reduced size of carbon nano tube and secondary graphite filler (۴۴μm) allows for filling voids between the first graphite filler (۵۹۵ μm) particles thus increasing thenumber of conductive paths and the bulk conductivity of the composite. Furthermore, carbonnano tube with spherical structure fills the voids between graphite with flake structure, helping toincrease electrical conductivity of the composite