Mechanical responses in the length direction and thickness direction of quaternary 1,4‐diazabicyclo‐[2.2.2]‐octane polysulfone alkaline anion‐exchange fuel‐cell membranes

Abstract

A quaternary 1,4-diazabicyclo-[2.2.2]-octane polysulfone (QDPSU) alkaline anion-exchange fuel-cell membrane was synthesized. Nanoindentation and uniaxial tension methods were used to test the mechanical properties of this membrane in both the thickness direction and length direction at 26 C and 40% relative humidity. We found that the QDPSU membrane exhibited remarkable viscoelastic properties with significant loading rate-dependent behavior and time-dependent behavior (creep-relaxation). The value of compression creep rates and compression relaxation rates of the QDPSU membrane were measured to be about 0.2 by a spherical indenter and changed very little with different holding loads. Compared with Nafion, a most widely used fuel-cell membrane, the QDPSU alkaline anion-exchange membrane showed a better creep resistance. During the nanoindentation fatigue test, the variation of depths with the indentation cycles were divided into a rising primary region, a steady-state secondary region, and a continuous declining region. This was different from the uniaxial tension fatigue test. The cross-scale and cross-direction mechanical study from this work will help provide new evidence for bridging the gap between nanoindentation and uniaxial tensile testing.

Temperature‐dependent mechanical performance of Nafion® 212 proton exchange membrane under uniaxial and biaxial loading

“…Proton exchange membrane fuel cells (PEMFCs) have broad potential applications in the areas of new energy equipment and environmental protection, owing to their robust energy utilization efficiency and low emissions. [1][2][3][4][5][6] Wang et al 7 developed a low-temperature anion exchange membrane by incorporating imidazoliummodified metal-organic frameworks to enhance its alkaline stability. Liu et al 8 utilized a spin-coating method to fabricate novel multilayered membranes.…”

Study on characterization methods of the deformation properties of soft material polydimethylsiloxane using the indentation test

“…Up to now, many works have been carried out on the indentation test of soft materials [31][32][33][34]. The results are usually related to various factors, such as different shape indenters (pyramidal indenter, spherical indenter and flat-ended indenter), load and material thickness [35][36][37][38][39][40][41][42][43][44][45][46]. The indentation test on polydimethylsiloxane was carried out to characterize its mechanical properties using the pyramidal indenter and spherical indenter [47].…”

“…A molecular dynamics model was established to study the effect of different molecular weights on the mechanical properties of polydimethylsiloxane [48][49][50][51][52][53]. In addition, the thickness of soft materials is one of the essential factors, especially in the flexible electronics field, and it is integral to select the soft materials of appropriate thickness [39,54,55]. However, there are few studies focused on the effect of thickness on soft materials' mechanical properties, and most of them have ignored this point.…”