Electrochemical Properties of Chemically Treated Polyvinylchloride‐Based Heterogeneous Cation‐Exchange Membrane

Chemical treatment is a facile method for improving electrochemical properties of a heterogeneous ion‐exchange membrane. In this work, polyvinylchloride (PVC)‐based heterogeneous cation‐exchange membrane is prepared by a dry–wet phase inversion process. The membrane is treated with a sulfuric acid solution in a room and a high temperature (80 °C). Effects of the treatment procedure and hydrophilic additive on membrane electrochemical properties are investigated. Chemically treated PVC and PVC/additive heterogeneous cation‐exchange membranes show a change in membrane electrochemical properties in terms of water uptake (Wu), conductivity, ion‐exchange capacity (IEC), and permselectivity (Ps). In general, Wu and conductivity increase after the chemical treatment. Significant improvement is observed when a high temperature is used. Meanwhile, the conductivity is more pronounced for PVC/additive membranes. The improvement may be associated with an increase in hydrophilicity. A significant increase in IEC is also observed for modified PVC/additive membrane. This may be associated with the removal or leaching of the additive during the treatment which in turn increases the portion of ion‐exchange resins in the membrane. Most of the modified membranes show a decrease in Ps. It may be due to a decrease in the effectiveness of Donnan effect indicated by Donnan equilibrium constant (K+). POLYM. ENG. SCI., 59:E219–E226, 2019. © 2018 Society of Plastics Engineers     

Surface modification of ion‐exchange membranes: Methods,characteristics, and performance

Considerable effort has been made to improve ion‐exchange membrane (IEM) properties in order to achieve better performance of IEM‐based processes in various applications. Surface modification is one of the effective ways to improve IEM properties. Various methods have been used to modify IEM surfaces, for example, plasma treatment, polymerization, solution casting, electrodeposition, and ion implantation. These methods are able to produce a thin and fine distributed layer and also to modify the chemical structure of the surface. The new layer can be adsorbed, deposited, or chemically bonded on a membrane surface. By using these methods, IEM properties are improved, and the desired or specific characteristics such as high monovalent ion permselectivity, low fuel crossover, and anti‐organic‐fouling property can be obtained. In this paper, methods for surface modification of IEMs are reviewed. Moreover, the effects of modification on IEM properties and performance are discussed. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45540.     

Effect of hydrophilic additive and PVC polymerization degree on morphology and electrochemical properties of PVC‐based heterogeneous cation‐exchange membrane

Membrane solution composition is one of the important factors that determine properties of ion‐exchange membranes. In this study, PVC‐based heterogeneous cation‐exchange membranes were prepared by the solution casting method. Effects of a hydrophilic additive [poly(ethylene glycol), PEG400] and degree of polymerization of poly(vinyl chloride) (PVC) on the morphology and electrochemical properties of the cation‐exchange membranes were investigated. The results revealed that the hydrophilic additive can improve membrane properties, including water uptake (Wu), ion‐exchange capacity (IEC), conductivity, and permselectivity. The improvements might be associated with an increase in accessibility of functional sites in the membrane matrix due to a higher hydrophilicity, indicated by a reduction of water contact angle and the greater void fraction shown by scanning electron microscopy. However, the permselectivity slightly decreased when the additive concentration was increased further. Meanwhile, increasing the degree of polymerization and PVC concentration resulted in higher permselectivity and lower conductivity, which might be due to a better resin distribution and a lower void fraction. Overall, the prepared membranes had relatively good conductivities (up to ～2.5 mS/cm) and permselectivities (up to ～0.92). In general the conductivity increased with increasing Wu and IEC, while the permselectivity showed the opposite trends. This could be associated with the efficacy of Donnan exclusion indicated by the IEC/Wu ratio and the Donnan equilibrium constant of the cation (K⁺). © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46690.