Preparation and characterization of PC/SBR heterogeneous cation exchange membrane filled with carbon nano-tubes

Polycarbonate (PC)/styrene–butadiene–rubber (SBR) blend heterogeneous cation exchange membranes were prepared by solution casting technique using tetrahydrofuran as solvent and cation exchange resin powder as functional groups agent. Multi-walled carbon nano-tube (MWCNT) was selected as inorganic filler additive. The effect of additive loading on properties of prepared membranes was studied. Sonication was used to help in appropriate dispersion of particles in the membranes matrix. SOM images showed uniform particles distribution in the prepared membranes resulted from sonication. Moreover, images revealed that the membranes have relatively uniform surface. The increase of MWCNT's concentration in the casting solution led to membrane water content improvement, although it decreased the ion exchange capacity. The ion permeability and flux, electrical conductivity and current efficiency of the prepared membranes all were decreased initially by increase of additive concentration up to 2 wt% and then they showed the increasing trend with higher increase in additive concentration from 2 to 8 wt%. Conversely, the membrane potential, permselectivity, transport number, energy consumption and mechanical strength of membranes showed opposite trends. Moreover, with more additive loading, the membrane oxidative stability was slightly decreased but its thermal stability was increased. The membrane with 8 wt% MWCNTs loading exhibited higher efficiency and suitable electrochemical properties in comparison with other prepared membranes in this research while its mechanical strength was lower than others.

Research highlightsThe incorporation of carbon nano-tubes into ion exchange membranes was utilized to enhance the mechanical, thermal and chemical stabilities of polymer matrixes at high temperature and strongly oxidizing environment. Moreover, the ultrasonic method was employed in membrane fabrication to achieve better homogeneity and uniform dispersion and distribution of particles in the membrane matrix and to obtain the balance between electrochemical properties and mechanical integrity. Excessive homogeneity and uniform distribution of resin particles, i.e. functional groups on the membrane surface and in the bulk of membrane matrix provide superior conducting regions for the membrane and improve their electrochemical properties.