Tensile behavior of Nafion and sulfonated poly(arylene ether sulfone) copolymer membranes and its morphological correlations

Abstract

The tensile stress–strain behavior of Nafion 117 and sulfonated poly(arylene ether sulfone) copolymer (BPSH35) membranes were explored with respect to the effects of the strain rate, counterion type, molecular weight, and presence of inorganic fillers. The yielding properties of the two films were most affected by the change in the strain rate. The stress–strain curves of Nafion films in acid and salt forms exhibited larger deviations at strains above the yield strain. As the molecular weight of the BPSH35 samples increased, the elongation at break improved significantly. Enhanced mechanical properties were observed for the composite membrane of BPSH35 and zirconium phenylphosphonate (2% w/w) in comparison with its matrix BPSH35 film. The stress‐relaxation behavior of Nafion and BPSH35 membranes was measured at different strain levels and different strain rates. Master curves were constructed in terms of plots of the stress‐relaxation modulus and time on a double‐logarithm scale. A three‐dimensional bundle‐cluster model was proposed to interpret these observations, combining the concepts of elongated polymer aggregates, proton‐conduction channels, and states of water. The rationale focused on the polymer bundle rotation/interphase chain readjustment before yielding and polymer aggregate disentanglements and reorientation after yielding. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1453–1465, 2006

Constitutive response and mechanical properties of PFSA membranes in liquid water

“…This behavior includes an initial linear (Hookean) regime, followed by the onset of nonlinearity (which can be associated with the initiation of yield ing) and strain-induced hardening at larger strains [1][2][3]6,30]. A modified form of the G'Sell-Jonas (GJ) constitutive model for semicrystalline polymers accurately describes the experimental tensile test data obtained at various humidities, especially at low strains and low humidities [30].…”

“…have been shown to cause significant changes in the measured physical [18.23.25.26) and mechanical properties [6,[27][28][29]. The mechanical response of Nafion ® membranes 1 at various degrees of swelling has recently been a focus of a number of studies [1][2][3]5,6,[27][28][29][30]. The con stitutive response of PFSA-based membranes swollen at various temperatures and hydration levels for various ions were inves tigated by Kawano et al [6] and Kundu et al [29] based on measurements from a dynamic mechanical analyzer.…”

“…Experimen tal data on the temperature and humidity dependent tensile stress-strain response was reported by Tang et al [1] and later by Solasi et al [2] for Nafion ® 112 and 111 membranes, respectively. Liu et al [3] studied the tensile loading and stress-relaxation behav ior of vapor-equilibrated Nafion ® 117 membranes, examining the effects of strain rate and counterion type. Solasi et al [27] developed a viscoplastic model to reproduce the experimental results for the strain-rate dependence and the stress-relaxation behavior of the membrane.…”

Fast low-voltage electroactive actuators using nanostructured polymer electrolytes

“…S3). This implies that the creation of well-defined ionic channels within the self-assembled polymer matrix was beneficial for achieving improved bending performance owing to the formation of less tortuous ion pathways facilitating fast and efficient ion transport across the polymer layers 43,48 . In particular, the confinement of ions within nanoscale channels leads to the increment of the local concentration of ions, lowering of the activation barrier for ion conduction because of the close proximity of ions 49 .…”

“…Note that the Young's moduli of conventional sulphonated polymers are reported as 0.2-1 GPa (ref. 43). Figure 1b shows the chemical structure of ionic liquids used in the present study.…”