Ionic polymer metal composites (IPMCs) based on radiation grafted polystyrenesulfonıc acid onto poly (ethylene- alttetrafluoroethylene) (ETFE-g-PSSA)
Karahan, Bahar Burcu (2012) Ionic polymer metal composites (IPMCs) based on radiation grafted polystyrenesulfonıc acid onto poly (ethylene- alttetrafluoroethylene) (ETFE-g-PSSA). [Thesis]
Ionic polymer-metal composites (IPMCs), one of the electroactive polymers, have revealed remarkable properties with its large bending behavior and force response under applied low voltages. Nafion® has been used for the manufacturing IPMCs due to its high ionic conductivity and mechanical strength. However, high cost and limited thickness availability of Nafion® diminishes its demand. As a promising alternative to the Nafion® based IPMCs, radiation grafted poly(ethylene-alt-tetrafluoroethylene)- graft-polystyrenesulfonic acid (ETFE-g-PSSA) membrane based IPMCs have been fabricated successfully in this study. Poly(ethylene-alt-tetrafluoroethylene) (ETFE) is a hydrophobic polymer. In this study, hydrophilic properties were induced by radiation grafting followed by sulfonation. Radiation grafting, firstly creates active sites on the ETFE film by - irradiation with y[gamma]-rays. Secondly, polystyrenesulfonic acid side chains were grafted into ETFE film by grafting and with a subsequent sulfonation procedure. The introduction of sulfonic acid end groups supply hydrophilic properties to the hydrophobic base film. ETFE-g-PSSA membranes' properties were studied in terms of graft level, water uptake and ionic conductivity. Ionic polymer metal composites (IPMCs) were produced by electroless plating of platinum (Pt) onto both surfaces of ETFE-g-PSSA membranes. ETFE-g-PSSA based IPMCs strips showed an actuation performance under applied electric potentials. The superior actuation performance with higher displacement capabilities was achieved with respect to conventional Nafion® based IPMCs. The effect of grafting on actuation performance was investigated. In addition to these, different characteristics of ETFE-g- PSSA based IPMCs compared to the Nafion® based IPMCs were revealed. For ETFE-g- PSSA based IPMCs, an adaptation period to the applied electric field –prior to the first actuation of the tested sample- was observed such as the conditioning time in PEM (proton exchange membrane) fuel cells. Furthermore, the displacement capability was increased by the repeated actuation performances. Lastly, 5V and above applied potentials are affecting the displacement character of ETFE-g-PSSA based IPMCs widely. After application of 5V, in the next electromechanical tests, a reverse actuation character (actuation towards cathode and back-relaxation towards anode) was observed.
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