Preparation and Properties of Various Molecular Weights Poly(oxyalkylene)-amine bearing DGEBA Epoxy Functionalizing Multiwalled Carbon Nanotube /Polypropylene Composite Bipolar Plates for Polymer Electrolyte Fuel Cells (PEMFCs)

Multiwalled carbon nanotubes (MWCNTs) were covalently modified with different molecular weights 400 and 2000 poly(oxyalkylene)-amine bearing DGEBA epoxy (POA400-DGEBA and POA2000-DGEBA) oligomers via a grafting method. The weight-average molecular weights of POA400-DGEBA and POA2000-DGEBA were measured as 1623 and 9231 with polydispersity indices (PDIs) of 2.3 and 1.6, respectively. The oxidized MWCNTs (MWCNTs-COOH) were converted to the acid chloride-functionalized MWCNTs, followed by the reaction with POA-DGEBAs to prepare the MWCNTs/POA400-DGEBA and MWCNTs/POA2000-DGEBA. FTIR and high resolution X-ray photoelectron spectra (XPS) revealed that the POA-DGEBAs were covalently attached to the surface of MWCNTs. The weight of grafted polymer chains was determined by thermogravimetric analysis. The morphology of MWCNTs/POA-DGEBA was observed by TEM. The POA400-DGEBA coated on the MWCNTs was thicker and more uniform. However, the coating of POA2000-DGEBA on the MWCNTs showed a worm-like bulk substance and the MWCNT surface was bare. In addition, this study also investigated the electrical, mechanical and single fuel cell properties of MWCNTs/polypropylene nanocomposite bipolar plates prepared by melt blending process for PEMFCs. The flexural strength and the electrical conductivity of the nanocomposite bipolar plates were 59 % and 505 % higher than those of the original composite bipolar plates by adding 8 phr of MWCNTs/POA400-DGEBA. The maximum current density and power density of the single cell test for the nanocomposite bipolar plate with 4 phr MWCNTs/POA400-DGEBA were 1.32 Acm and 0.533 Wcm, respectively. The overall performance confirms the functionalized MWCNTs/polypropylene nanocomposite bipolar plates are suitable for PEMFC application and meet the D.O.E. (Department of Energy, USA) targets.