Blend membranes of sulfonated poly (ether ether ketone) and thermoplastic poly (urethane) for fuel cells

Membranes used in polymer electrolyte membrane fuel cells (PEMFCs) have critical importance because their properties directly affect the performance of fuel cell. For this purpose, blend membranes based on sulfonated poly (ether ether ketone) (sPEEK)-thermoplastic poly (urethane) (TPU) were prepared by solution casting method in different compositions. Generally, sPEEK-TPU blend membranes were thermally resistant up to 190 °C due to the presence of sulfonic acid groups regardless blend composition. The proton conductivity (σ) of blend membranes significantly increased compared to TPU100. After 24 h in water, σ values of blend membranes were found to be 3.9–18.7 mS cm −1 and rose with sPEEK content. A similar trend was also observed for water uptake (WU %), sulfonation degree (DS %) and ion exchange capacity (IEC). While sPEEK100 membrane has a fragile structure, blending with TPU led to dense, uniform and defect-free membrane surface. Further, all the blend membranes had no obvious phase separation. sPEEK80-TPU20 showed good mechanical properties to be used in PEMFCs with good compatibility. Preliminarily, the methanol permeability of blend membrane containing 40% of sPEEK was found to be 1 × 10 −11 cm 2 s −1 . Unlike, the blend membranes deteriorated with methanol if sPEEK content was more than 40% in composition. The membrane selectivity value of sPEEK40-TPU60 was found to be 4.7× 10 8 S s/cm 3 .