Physicochemical properties and surface morphology of heterogeneous ion-exchange membranes after temperature modification
Changes in physicochemical properties of heterogeneous ion-exchange membranes as a result of prolonged exposure of elevated temperatures are caused by changes of their microstructure due to the partial destruction of the ion-conductive and inert polymers. The most significant changes in the structure due to temperature effects on the heterogeneous ion-exchange membranes: an increase in macroporosity; increase in the share and the linear dimensions of the ion exchangers; the development of micro-relief and an increase in surface roughness factor were found by the microscopic analysis methods using the original authoring software. The revealed microstructure changes explain the reasons for increasing the water content of the membranes against the backdrop of a partial loss of their exchange capacity. By comparative analysis of physico-chemical and structural properties of strongly anion-exchange membranes after temperature modification it was established that lowering of the total exchange capacity and the relative contribution of degradation reactions in loss of capacity for strongly basic groups fall with decreasing of polymer matrix crosslinking degree and increasing specific water capacity of membranes.