Tensile mechanical properties of sulfonated poly(ether ether ketone) (SPEEK) and BPO<sub>4</sub>/SPEEK membranes

Reyna-Valencia, Alejandra; Kaliaguine, Serge; Bousmina, Mosto

doi:10.1002/app.22417

Cited by 60 publications

(38 citation statements)

References 21 publications

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“…Thus, the refractive index of the films is lower under ambient conditions as compared to under dry nitrogen. The presence of the sulfonic acid groups in SPEEK makes the material highly hydrophilic and causes the polymer films to swell and plasticize in the presence of water vapor [36,37]. Because the refractive index of liquid water, 1.33, is lower than that of the polymer, the swollen films have a lower overall refractive index.…”

Section: Resultsmentioning

confidence: 99%

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

2015

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The thickness, the refractive index, and the optical anisotropy of thin sulfonated poly(ether ether ketone) films, prepared by spin-coating or solvent deposition, have been investigated with spectroscopic ellipsometry. For not too high polymer concentrations (B5 wt%) and not too low spin speeds (C2000 rpm), the thicknesses of the films agree well with the scaling predicted by the model of Meyerhofer, when methanol or ethanol are used as solvent. The films exhibit uniaxial optical anisotropy with a higher in-plane refractive index, indicating a preferred orientation of the polymer chains in this in-plane direction. The radial shear forces that occur during the spin-coating process do not affect the refractive index and the extent of anisotropy. The anisotropy is due to internal stresses within the thin confined polymer film that are associated with the preferred orientations of the polymer chains. The internal stresses are reduced in the presence of a plasticizer, such as water or an organic solvent, and increase to their original value upon removal of such a plasticizer.

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Section: Resultsmentioning

confidence: 99%

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

2015

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“…Although this design exhibited good protonic conductivity of around 0.11 S.cm -1 , the swelling ratio was slightly higher than what was achieved in [298] (~12.9% at 100°C). The difference between these two swelling ratios maybe attributed to the degree of sulfonation applied during membrane preparation as pointed out by Reyna-Valencia et al [236].…”

Section: Membrane Swellingmentioning

confidence: 88%

Degradation aspects of water formation and transport in Proton Exchange Membrane Fuel Cell: A review

Ous

Arcoumanis

2013

Journal of Power Sources

137

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This is the accepted version of the paper.This version of the publication may differ from the final published version. Permanent repository link AbstractThis review paper summarises the key aspects of Proton Exchange Membrane Fuel Cell (PEMFC) degradation that are associated with water formation, retention, accumulation, and transport mechanisms within the cell. Issues related to loss of active surface area of the catalyst, ionomer dissolution, membrane swelling, ice formation, corrosion, and contamination are also addressed and discussed. The impact of each of these water mechanisms on cell performance and durability was found to be different and to vary according to the design of the cell and its operating conditions. For example, the presence of liquid water within Membrane Electrode Assembly (MEA), as a result of water accumulation, can be detrimental if the operating temperature of the cell drops to sub-freezing.The volume expansion of liquid water due to ice formation can damage the morphology of different parts of the cell and may shorten its life-time. This can be more serious, for example, during the water transport mechanism where migration of Pt particles from the catalyst may take place after detachment from the carbon support. Furthermore, the effect of transport mechanism could be augmented if humid reactant gases containing impurities poison the membrane, leading to the same outcome as water retention or accumulation.Overall, the impact of water mechanisms can be classified as aging or catastrophic. Aging has a longterm impact over the duration of the PEMFC life-time whereas in the catastrophic mechanism the impact is immediate. The conversion of cell residual water into ice at sub-freezing temperatures by the water retention/ accumulation mechanism and the access of poisoning contaminants through the water transport mechanism are considered to fall into the catastrophic category. The effect of water mechanisms on PEMFC degradation can be reduced or even eliminated by (a) using advanced materials for improving the electrical, chemical and mechanical stability of the cell components against deterioration, and (b) implementing effective strategies for water management in the cell.

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“…That paper shows that SPEEK films always exhibit optical anisotropy which is a result of the internal stresses present in the films, due to preferential orientations of the polymer chains [14]. The internal stresses and consequently, optical anisotropy in SPEEK films, decrease upon sorption of plasticizers, such as water or organic solvents [14,16]. Consequently, the increase of the relative humidity degree (RH %) of the surrounding ambient atmosphere, to which films are exposed after the formation procedure, results in an increased water vapor sorption and therefore, in depression of optical anisotropy.…”

Section: For Spectroscopic Ellipsometrymentioning

confidence: 88%

The effects of water on the morphology and the swelling behavior of sulfonated poly(ether ether ketone) films

et al. 2015

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Thin sulfonated poly(ether ether ketone) films swell excessively in water. The extent of water-induced swelling is shown to be correlated with the optical anisotropy of the films, due to two distinct phenomena. Firstly, the optical anisotropy is directly related to the amount of water taken up from the surrounding ambient atmosphere, and thus to amount of water present in the material just prior to swelling. Secondly, the optical anisotropy corresponds to internal stresses in the film that affect the free energy of the film, and thus the potential of the film to swell. The anisotropy vanishes upon sorption of liquid water and returns when the water is desorbed. When the water is completely removed, the film changes from more or less colorless to an intense yellow color that can be attributed to molecular assembly of the aromatic rings in the polymer backbone. The color change is reversible and occurs immediately upon exposure to low humidity. For films prepared in the absence of water, the lack of hydration of the sulfonic acid groups affects the microphase separation behavior of the polymer. This is manifested by an apparent lower propensity to water-induced swelling. The possibility to affect the properties of sulfonated polymer films by varying the hydration state of the polymer during preparation can have important implications for applications of such films.

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Tensile mechanical properties of sulfonated poly(ether ether ketone) (SPEEK) and BPO₄/SPEEK membranes

Cited by 60 publications

References 21 publications

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

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

Degradation aspects of water formation and transport in Proton Exchange Membrane Fuel Cell: A review

The effects of water on the morphology and the swelling behavior of sulfonated poly(ether ether ketone) films

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Tensile mechanical properties of sulfonated poly(ether ether ketone) (SPEEK) and BPO4/SPEEK membranes

Cited by 60 publications

References 21 publications

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

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

Degradation aspects of water formation and transport in Proton Exchange Membrane Fuel Cell: A review

The effects of water on the morphology and the swelling behavior of sulfonated poly(ether ether ketone) films

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Tensile mechanical properties of sulfonated poly(ether ether ketone) (SPEEK) and BPO₄/SPEEK membranes