Abstract Proton‐exchange membrane fuel cell vehicles offer a low‐carbon alternative to traditional oil fuel vehicles, but their performances still need improvement to be competitive. Raising their operating temperature to 120 °C will enhance their efficiency but is currently unfeasible due to the poor mechanical properties at high temperatures of the state‐of‐the‐art proton‐exchange membranes consisting of perfluorosulfonic acid (PFSA) ionomers. To address this issue, xx designed composite membranes made of two networks: a mat of hybrid fibers to maintain the mechanical properties filled with a matrix of PFSA‐based ionomer to ensure the proton conductivity. The hybrid fibers obtained by electrospinning are composed of intermixed domains of sulfonated silica and a fluorinated polymer. The inter‐fiber porosity is then filled with a PFSA ionomer to obtain dense composite membranes with a controlled fibers‐to‐ionomer ratio. At 80 °C, these obtained composite membranes show comparable performances to a pure PFSA commercial membrane. At 120 °C however, the tensile strength of the PFSA membrane drastically drop down to 0.2 MPa, while it is maintained at 7.0 MPa for the composite membrane. In addition, the composite membrane shows a good conductivity of up to 0.1 S cm −1 at 120 °C/90% RH, which increases with the ionomer content.
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Melt synthesis of sulfonated EPDM ionomers in batch and continuous processes
Zinc‐neutralized sulfonated EPDM ionomers (Zn‐SEPDM) were prepared by batch and continuous melt sulfonation processes, and the ionomer products were compared with ionomers synthesized by sulfonation of EPDM in homogeneous solution. The efficiency of a batch melt sulfonation using an intensive mixer as a reactor was comparable to that of the solution sulfonation process, but the efficiency of the melt sulfonation in a twin‐screw extruder was considerably lower, which was thought to be a consequence of a relatively short reaction residence time due to limitations of the equipment. Melt neutralization was not complete, which produced a dark colored product. However, the incomplete neutralization and the color of the product did not affect the mechanical properties of the melt sulfonated ionomers, which were comparable to those of ionomers made by conventional solution sulfonation. The metal sulfonate concentration alone determined the mechanical properties of the ionomer. Melt sulfonation of Zn‐SEPDM ionomers by batch or continuous melt processes appears to be a practical alternative to solution sulfonation, but further optimization of the melt sulfonation processes is needed to ensure uniform sulfonation and complete neutralization.
more » « less- PAR ID:
- 10455263
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Polymer Engineering & Science
- Volume:
- 60
- Issue:
- 12
- ISSN:
- 0032-3888
- Page Range / eLocation ID:
- p. 3216-3230
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Polymer electrolyte fuel cells (PEMFCs) are key to developing the hydrogen economy, particularly in the transportation sector. The focus on heavy-duty vehicles has driven research toward improving the efficiency and durability of catalyst layers and understanding the role of the ionomer binder. The characterization of these ionomers is important not only in their cast forms but also in inks and dispersions. Small-angle scattering (SAS) techniques have become one of the primary tools for analyzing ionomer systems in solution. While SAS can provide valuable structural information about ionomer aggregates, relevant size and shape information requires model fitting to obtain. While many scattering form factor models have been applied to uncover the behavior of aggregates in ionomer dispersions, the role of the fitting range in the fit quality has not been extensively discussed. In this work, we illustrate the effect of varying fitting ranges for three commonly used form factors.more » « less
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2018 ,135 , 45662.
