Understanding the dynamics of water in solid-state polymer electrolytes (e.g., Nafion) is important for a variety of applications ranging from membrane-based water purification to hydrogen fuel cells. In this study, the dynamics of water in Nafion was investigated at both low and high humidities with time-resolved Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy; a technique that provides a molecular fingerprint of both the diffusant and the polymer simultaneously in real time. At low humidities (0-22% RH), an extended initial time lag resulted in non-Fickian behavior, where dynamic infrared data provided evidence for a reaction between water and sulfonic acid. A diffusion-reaction model was developed and predicted this anomalous behavior, where the time lag was a function of water content. At high humidities (0-100% RH), a slow approach to steady state resulted in non-Fickian behavior, where dynamic infrared data provided evidence of water-induced relaxation in the polymer backbone. A diffusion-relaxation model was developed and regressed well to both the polymer relaxation and water diffusion data, where only one fitting parameter was used for each data set to determine both a relaxation time constant and diffusion coefficient. This approach differs significantly from previous work on non-Fickian behavior in glassy polymers, which, consisted of regressing gravimetric data to models with a minimum of six fitting parameters. Not only do the diffusion coefficients from these two models compare well with Fickian diffusion coefficients from experiments with small water concentration gradients, but also the results in this study provide physical insight into the transport mechanisms of water and relaxation phenomena in solid-state polymer electrolytes.
This review describes the state-of-the-art of material derived from the forest sector with respect to its potential for use in the packaging industry. Some innovative approaches are highlighted. The aim is to cover recent developments and key challenges for successful introduction of renewable materials in the packaging market. The covered subjects are renewable fibers and bio-based polymers for use in bioplastics or as coatings for paper-based packaging materials. Current market sizes and forecasts are also presented. Competitive mechanical, thermal, and barrier properties along with material availability and ease of processing are identified as fundamental issues for sustainable utilization of renewable materials.
The representation of solubility isotherms of gases and vapors in glassy polymers has been
analyzed through the use of a thermodynamic model, nonequilibrium lattice fluid, recently
introduced. The possible use of the model as a predictive tool for gas solubility in glassy polymers
has been discussed in previous works for the special cases in which the polymer density in pseudo-equilibrium conditions is known from experimental measurements. In this paper, a different
use of the model is presented in which the polymer density at different sorption conditions is
not known from direct experimental measurements and is thus treated as a correlation
parameter, following the typical linear dilation isotherm. The solubility isotherms thus obtained
by the model have been compared with several experimental data, obtaining a rather satisfactory
representation of the sorption isotherms, through use of two fitting parameters, at most.
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