Mechanical properties of Nafion™ electrolyte membranes under hydrated conditions

Polymer electrolyte membrane fuel cells use a polymer membrane as the electrolyte to transport hydrogen ions from the anode to the cathode side. This paper reports a study of mechanical (stress-strain curves) and dynamic mechanical (temperature sweeps) properties of membranes made using Nafion™ under dry and hydrated conditions. Hydrating the membranes reduced the mechanical properties. Specifically there was significant change in the Young's modulus, yield strength, and transition temperatures of the different membranes tested. Presence of contaminant ions was studied through an ion exchange technique using selected ions (Na⁺, K⁺, Mg²⁺, Cu²⁺, Ni²⁺). Ion exchange in hydrated samples increased the stiffness of the material as well as the yield strength in order of increasing ionic radius. Transition onset temperatures observed on the mechanical damping of hydrated membranes also increased with the addition of ions.