Sorption induced relaxations during water diffusion in S-PEEK

Abstract

This paper presents an analysis of the sorption kinetics of water vapor and liquid water in the glassy polymer sulfonated poly(ether ether ketone) (S-PEEK). Sorption isotherms are determined experimentally using a gravimetric sorption balance, and the relative contributions of Fickian diffusion and relaxational phenomena are quantified as a function of the water concentration in the polymer using the model of Hopfenberg and Berens.Analysis of the sorption isotherms and determination of the sorption kinetics prove the occurrence of both Fickian sorption behavior and relaxational phenomena already at very low water concentrations in the polymer. With increasing water concentration, the relative importance of relaxation phenomena increases, whereas the relative contribution of Fickian diffusion decreases.Based on the water vapor sorption kinetics only, the Fickian diffusion coefficient increases over two orders of magnitude with increasing water vapor concentration. Taking also the diffusion kinetics from liquid water sorption experiments into account reveals a change of even three orders of magnitude of the Fickian diffusion coefficient when the water concentration in the polymer increases.

Optical anisotropy, molecular orientations, and internal stresses in thin sulfonated poly(ether ether ketone) films

“…The subsequent slower reduction in thickness is related to polymer relaxation, which is a process with a much larger time constant. These observations are consistent with those of Potreck et al, who studied vapor sorption in SPEEK by mass uptake [35]. During desorption, the sample thickness decreased from an initial thickness of 333.8 to 284.7 nm at the end of the desorption process.…”

Membrane technologies for CO2 capture

“…When Figure 7 shows the CO 2 concentration in the thin ODPA PEI films as determined by ellipsometry using thin (0.5-3.8 µm) supported films. Matrimid® [12] and PEBAX® [39] are well known materials for CO 2 separation, whereas SPEEK has been considered for gas dehydration purposes [36,37]. The sorption isotherms for thin films of these materials are presented in Figure 9.…”

“…Combining Equations 2 and 3 and by taking into account that the product of solubility (S) and diffusivity (D) equals the permeability (P), this results in The equation P=D⋅S is generally known as the solution-diffusion model for transport of gases through dense polymeric membranes [37]. First the gas dissolves in the membrane material and then diffuses through the membrane.…”

“…Figure 3) with a sulfonation degree of 70% (y = 0.7; x = 0.3), was obtained from the sulfonation of PEEK, as described by Komkova et al [35]. SPEEK was recently identified as membrane material for the dehydration of (flue) gas streams with extremely high water vapor permeabilities combined with very high water vapor over N 2 and CO 2 selectivities [36,37]. PEEK was purchased from Victrex (United Kingdom) and sulfuric acid (95-98 wt %) was obtained from Merck, Germany.…”

“…Amino acids have the same functionality as alkanol amines (e.g. MEA), but in contrast to MEA they are expected to have a higher oxidative stability [35,37] and a better resistance to degradation [38]. In addition, they can be made non-volatile by adding a salt functionality, which significantly reduces the liquid loss and energy consumption associated to that [14,35,38].…”