Rheological Characterization of Nafion Dispersions

• Milo Barko, Chemical Engineering, Rowan Univeristy

• Mukund Kabra, Chemical Engineering, University of Delaware
• Norman Wagner, Chemical Engineering, University of Delaware

Nafion is a sulfonated fluoropolymer polyelectrolyte copolymer with the highest proton conductivity recorded in a polymer-based membrane. This material is ubiquitous in hydrogen fuel cells and other electrochemical applications. The mechanical properties of Nafion membranes are well documented, but the morphology of Nafion dispersions is not. Previous literature shows the structure of Nafion dispersions are influenced by the solvent, leading to several proposed morphological models. Nafion’s morphological dependence on dispersion solvent results in membranes cast from such dispersions to have different conductivities and material properties. This work aims to enhance the conductivity and material properties of films cast from Nafion dispersions by characterization of its rheology. Low boiling point solvents that yield optimal conductivity and material properties are ideal because the solvent must be evaporated below Nafion’s degradation temperature. The rheological data indicate that Nafion dispersions exhibit shear thinning behavior. However, the impact of shear on Nafion morphology, and any potential changes that persist after returning to a no shear state, are not yet fully understood. To investigate this Nafion films were cast at varying speeds. Although this work is preliminary, it serves as a proof of concept to demonstrate that films cast from different solvents exhibit distinct properties. These initial findings provide insight on the impact of  membrane processing conditions and suggest the potential for solvent selection to optimize the design and performance of Nafion-based materials.