Preparation, optimization and characterization of novel ion exchange membranes by blending of chemically modified PVDF and SPPO

Mixing two or more polymers results in various property combinations of the final material. Most polymer pairs are immiscible; consequently, the blends are not formed spontaneously. In this research, a new kind of homogeneous cation exchange membrane was prepared for new applications by blending polyvinylidene fluoride (PVDF) and sulfonated poly (2,6-dimethyl-1,4-phenylene oxide) (SPPO). Chemical reagents were used to modify PVDF powder and improve the miscibility between PVDF and SPPO. The degradation of the PVDF structure by chemical reagents was elucidated by FT-IR, and the miscibility between two polymers was clarified by X-ray diffraction (XRD). The blends were used for membrane preparation, and it was followed by characterization and optimization of the prepared membranes. The stability of the functional groups at different temperatures for three categories of PVDF/SPPO blend membranes in various drying conditions was studied by CHNOS elemental analyzer. Furthermore, the modified PVDF/SPPO blend cation exchange membranes were prepared in various blend ratios. The prepared membranes were characterized and optimized by the analysis of the general properties including water content, IEC (ion exchange capacity), membrane potential, permselectivity, energy consumption, membrane specific resistance, flux of ions and oxidative stability. The thermal behavior of the membranes was analyzed by differential scanning calorimetry (DSC).

► Cation exchange membranes were prepared by blending PVDF and SPPO.
► Modification of PVDF by KOH was found as superior method to increase miscibility.
► Membranes were characterized in various blend ratios.
► The membrane with 40% PVDF was found as superior membrane.