Morphology and properties of perfluorosulfonic acid polymer/perfluorocarboxylic acid polymer blend membranes

Abstract

A melt-extruded method has been used to prepare blend membranes of Perfluorosulfonic Acid Polymer (PFSA) and Perfluorocarboxylic Acid Polymer (PFCA) with different combination ratios. Fourier Transform Infrared (FT-IR) and X-ray Diffraction (XRD) analyses have showed that the chemical structure and crystallization behaviour of both polymers remained unchanged in the blend membrane, and the crystallinity has been increased for the blend membrane with a higher weight fraction of PFCA. According to the results obtained from Scanning Electron Microscope (SEM), PFSA and PFCA polymers are well compatible, forming mixed aggregates containing both sulphonyl and carboxyl ions. Surprisingly, a membrane containing a 50:50 ratio of PFSA/PFCA has showed microphase separation, and it possesses the smallest ionic cluster size among all the blend membranes prepared, as illustrated by the Small Angle X-Ray Scattering (SAXS) analysis. In addition, when the PFCA content was increased, the ion exchange capacity (IEC) for blend membranes remained the same, while their water uptake and proton conductivity have decreased rapidly. Compared with the PFSA/PFCA two-layered membrane, this PFSA/blend/PFCA membrane not only maintained respectable electrolysis property, also exhibited significantly higher peel strength, especially after the hydrolization process; plus, it has showed excellent resistance to the peeling damage under the operational conditions of chlor-alkali electrolytic cells. POLYM. ENG. SCI.,

Revisiting Chlor-Alkali Electrolyzers: from Materials to Devices

“…Wang et al [92] studied the effect of blend layers with different ratios of PFSA to PFCA on the performance of composite membranes. The distribution morphology of the blend membrane has a great influence on its ion transport performance and water absorption capacity.…”

In-Depth Study on the Effects of Impurity Ions in Saline Wastewater Electrolysis

“…However, Buddhi et al [ 23 ] reported that the electrolysis efficiency of the NaCl solution was better with trace amounts of Mg 2+ in it, demonstrating the complexity of the ion effects under different electrolyte environments. In fact, the impurity ions were usually limited to very low concentrations to ensure the H 2 /Cl 2 production efficiency for either water electrolysis or saturated NaCl solution electrolysis [ 24 , 25 , 26 ]. In detail, the concentration of SO 4 2− should be no higher than 0.05 mol/L for the purpose of 30% NaOH solution production and much lower for 42% or 50% NaOH solution production [ 27 ] in the chlor-alkali industry.…”

Effect of hydration on morphology of thin phosphonate block copolymer electrolyte membranes studied by electron tomography

“…TEM and scanning transmission electron microscopy (STEM) has been widely used to directly image the morphology and distributions of acid groups in dry thin films of sulfonated ionomers. [ 45‐52 ] However, the analyses of 2‐D projection were limited by overlapped features in the thin film, (thickness is much larger than acid group size), and electron beam damage. [ 37,53 ] Low‐dose imaging and STEM tomography 3D reconstructions enabled the quantitative characterization of the location and size distribution of sulfur‐rich clusters in a free‐standing dry polystyrene sulfonate‐ b ‐polymethylbutylene (PSS‐ b ‐PMB) thin film.…”