Goal of this work was to measure dimensional changes of ion-exchange membranes and resins used in electrodialysis (ED) or electrodeionization (EDI) devices under the applied pressure and temperatures up to 60 °C in order to describe their behavior in real conditions of these processes. Regarding ion exchange resins, measurements of their compressibility were carried out with samples of gel strongly basic and strongly acidic pure resins, their mixture and macroporous strongly acidic resin. In

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... e of ion exchange membranes, their thickness changes under the influence of pressure and temperature were measured and long-term experiments were performed with the maximal applied pressure. To obtain a complete view, ED spacer frame foil properties were also examined in long-term experiments. For each experiment, the unique work methodology and measurement apparatus was proposed. It was found that each resin exhibited specific behavior under applied pressure and temperature. Furthermore, the important impact of temperature changes on ion exchange membranes and ED spacer foils was observed, and then, it was examined under the conditions of pressure load similar to that in real ED device. This work confirms that the research of mechanical properties of ion exchange materials has a great importance, mainly if it simulates real conditions in industrial ED and EDI modules. It can help in designing new or improved module components taking into account expected temperature or pressure changes of ion exchange materials.