High-temperature stability of hydrocarbon-based Pemion® proton exchange membranes: A thermo-mechanical stability study

Abstract

In this work, the ex-situ thermo-mechanical stability of Pemion® – a commercial mechanically-reinforced sulfo-phenylated polyphenylene-based proton exchange membrane – is investigated across a wide range of temperature (30–120 °C) and relative humidity (RH) (10–90%) conditions versus a commercial mechanically-reinforced PFSA material (r-PFSA). The Young's modulus and strain hardening of Pemion® are found to be temperature-independent, whereas r-PFSA exhibits significant decay above 90 °C. Pemion® maintains acceptable resistance against yielding within the tested range, while small mechanical stress values (e.g., 1 MPa) can cause spontaneous yielding in r-PFSA above 110 °C. The modulus of resilience for the r-PFSA membrane is also predicted to approach zero at elevated hygrothermal conditions, rendering them unsuitable for higher operating temperatures. Thermal transition and decomposition of samples are studied using DSC and TGA as well. Overall, Pemion® shows appreciable stability at hygrothermal ambience close to high-temperature PEMFC operating targets, i.e., 110–120 °C and 40–50% RH, likely due to its rigid-rod polyphenylene backbone with reduced intermolecular mobility.