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A hydrogel film, poly-3,4-ethylenedioxythiophene (PEDOT):polystyrenesulfonate (PSS), containing an ionic liquid, is used as an air–cathode for a metal-air battery and its performance is investigated. This work presents the development of the air–cathode and the characterization of its physical, chemical and mechanical properties. Moreover, in view of wearable batteries, these air-cathodes are implemented within a flexible aluminium-air battery. It contains an aluminium anode, an electrolyte made of cellulose paper imbibed with an aqueous sodium chloride solution and the PEDOT:PSS air–cathode. Characterisation tests showed that the ionic liquid did not change the air–cathode chemically, while the electric conductivity increased considerably. The anode has an acceptable purity and was found to be resistant against self-corrosion. Discharge tests showed operating voltages up to 0.65 V, whereas two batteries in series could deliver up to 1.3 V at a current density of 0.9 mA cm−2 for almost a day, sufficient for monitoring and medical devices. Several discharge tests with current densities from 0.25 up to 2.5 mA cm−2 have presented operating lifetimes from 10 h up until over a day. At a current density of 2.8 mA cm−2, the operating voltage and lifetime dropped considerably, explained by approaching the limiting current density of about 3 mA cm−2, as evidenced by linear sweep voltammetry. The batteries showed high specific energies up to about 3140 Wh kg−1. Mechanical tests revealed a sufficient stretchability of the air–cathode, even after battery discharge, implying an acceptable degree of wearability. Together with the reusability of the air–cathode, the battery is a promising route towards a low-cost viable way for wearable power supply for monitoring medical devices with long lifetimes and high specific energies. Optimization of the air–cathode could even lead to higher power applications.

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This paper aims to investigate the effect of the addition of mineral oil and pyrolytic carbon black on crosslinking the natural rubber and the mechanical properties of the crosslinked products. A rheometer determined curing characteristics at a temperature of 150 °C. The mechanical properties of prepared vulcanized composites were determined. By adding mineral oil to rubber compounds, the vulcanization reaction starts later, and it takes slightly more time to achieve the optimal vulcanization time. The addition of mineral oil to the rubber mixture achieves better dispersion of pyrolytic carbon blacks in the matrix and thus increases the physical interaction between the filler and rubber. Pyrolytic carbon black (pCB) is obtained by recycling waste products and contains a higher proportion of impurities. Due to impurities, PCB has a smaller surface area for the physical adsorption of rubber molecules than standard carbon black, and it can be assumed that this has led to a decrease in the crosslinking density. The addition of mineral oil to rubber compounds results in a slight reduction in mechanical properties. The type of carbon black has a much more significant influence on the mechanical properties of vulcanized composites based on natural rubber.

Hyperbranched alkyds based on trimethylolpropane, dimethylol propionic acid and castor oil were synthesized. The process implied preparing the three samples with ZnO nanoparticles in an amount of 0, 1, and 3 wt%. Commercial melamine resin was used as a crosslinking agent. Curing was carried out firstly in a drying oven at the 120 °C for half an hour, and afterward for seven days at room temperature. Thermal properties, physico-mechanical characteristics, and chemical resistance of cured coated were determined. An increasing amount of the ZnO nanoparticles in hyperbranched alkyd resins leads to the improvement of the properties of the cured coating. Based on the results, it was concluded that the hyperbranched alkyds with ZnO nanoparticles could be employed as binders in environment-friendly coatings due to lower viscosity (less content of organic solvent) compared to conventional alkyd resins.