Fluoroplastic- and Bio-Based Composites Materials for PEM Fuel Cells Bipolar Plates

Abstract

Conductive polymer composite materials for polymer electrolyte membrane fuel cells bipolar plates have been successfully prepared from renewable plant biomass sources and copolymers of tetrafluoroethylene with vinylidenefluoride. The composites are based on various conductive fillers (natural, oxidized and colloidal graphite’s) and polymer binder (the 5-HMF synthesis by-product or fluoroplastic). The influences of type and content of binder and type of conductive filler on the mechanical properties and conductivity were investigated. Conductivity of the composites decreases with increasing of polymer content, but its mechanical properties changes inversely. Composite based on 5-HMF by-products (content 30 wt.%) and colloidal graphite as a filler meets the DOE requirements for a mechanical strength. Flexural and compressive strengths were 25 and 32 MPa, respectively. Composites based on fluoroplastic 32 (content 30 wt.%) and fluoroplastic 42 (content 20 wt.%) with colloidal graphite as a filler and fluoroplastic 42 (content 20 wt.%) with nature graphite have flexural strength values close to the target value of DOE and amounted to 24, 17 and 19 MPa, respectively. Interfacial contact resistance depends to a greater extent on the nature of the filler and is maximum for composites based on natural graphite. Composites based on fluoroplastic 42 at any filler content correspond to the requirements DOE ≤ 0.01 ohm∙cm2. Composite based on 5-HMF synthesis by-product (resin) and fluoroplastic with conductive filler (colloidal graphite) shows a great potential application as bipolar plates for PEMFCs.