Carlos Arthur Ferreira

Electroactive poly(aromatic amine) films for iron protection in sulfate medium

Polyaniline (PANil and poly(1,5-diaminonaphthalene) (PDAN) films can be deposited on iron from aqueous sulfuric acid. The films exhibit electroactive properties similar to those of PANi and PDAN generated on platinum. Electrosynthesis performed in the presence of both monomers leads to a composite film which presents excellent adhesion properties on iron. The composite film imparts a form of anodic protection for at least 9 days in pH 4 sulfate medium.

Electrochemical synthesis and characterization of poly(5-amino-1-naphthol) on mild steel electrodes for corrosion protection

Abstract The electrodeposition of poly(5-amino-1-naphthol) films on mild steel from aqueous perchloric acid is reported. The polymer films are very adherent to the surface and present the same structure as in the case of Pt electrode. The test for corrosion protection of the polymer-coated iron samples was done in acidic solutions (0.4xa0M NaCl+0.1xa0M HCl).

Studies on the properties of rice-husk-filled-PP composites: effect of maleated PP

Rice husk is a by-product of rice milling process that usually finds inadequate final disposal (burning, land filling). Thermoplastics composites filled with rice husk flour are materials that offer an alternative for using this agricultural resource viewing the production of low dense materials with some specific properties. In this work composites of polypropylene (PP) and rice husk flour (RHF) were prepared by melt extrusion. Maleic anhydride-modified PP (MAPP) was added as a coupling agent. It was verified that tensile strength decreased with filler loading. The presence of MAPP improved this property showing a strong dependence on the MAPP/RHF ratio (MAPP/RHF = 0.03 produced the best results). The density of the composites slightly increased with filler and coupling agent in comparison to pure PP. The presence of MAPP diminished more than 20% water uptake in highly-loaded composites.

Hybrid polythiophene–clay exfoliated nanocomposites for ultracapacitor devices

Exfoliated nanocomposites of poly(3,4-ethylenedioxythiophene) (PEDOT) and montmorillonite (MMT) have been prepared by in situ anodic polymerization, concentrations of clay ranging from 5% w/w to 50% w/w being included in the aqueous polymerization medium. The morphology, electrical conductivity, adherence, thermal stability, charge storage, specific capacitance, electrostability, doping level and band gap have been determined for the different PEDOT–MMT nanocomposites and compared with those of pristine PEDOT. Many of these properties have been found to depend on both the concentration of clay and the thickness (micrometric or nanometric) of the generated films. Types I and II ultracapacitors have been fabricated using nanometric and micrometric films of PEDOT and PEDOT–MMT. The properties of such devices have been characterized and compared with those reported in the literature for ultracapacitors fabricated using nanocomposites of PEDOT and other inorganic materials. Both nanometric and micrometric type II ultracapacitors, which correspond to an asymmetric configuration of PEDOT and PEDOT–MMT films, have been found to present the better properties (e.g. the specific capacitance for nanometric and micrometric devices is 429 and 116 F g−1, respectively), evidencing the favorable effect of the clay. Finally, the effects of the electrochemical degradation on the ultracapacitors have been rationalized using electrochemical impedance spectroscopy.

Preparation and physical characterization of a sulfonated poly(styrene-co-divinylbenzene) and polypyrrole composite membrane

The properties of cation-exchange membranes based on polymeric composites of sulfonated poly(styrene-co-divinylbenzene) and polypyrrole (Ppy) are discussed. The amount of Ppy in the composites depends on the oxidant solution concentration used in the synthesis. Comparing composite membranes, the highest electronic conductivity and the best thermal stability were obtained for the composite membrane with the greatest content of Ppy. The membranes were thermally stable up to 250°C. As could be seen by SEM, Ppy is homogeneously distributed in the sulfonated poly(styrene-co-divinylbenzene) matrix. Consequently, composite membranes swell in water much less than base membrane alone. Ion-exchange capacity (IEC) does not change with pyrrole polymerization.

High-impact polystyrene/polyaniline membranes for acid solution treatment by electrodialysis : Preparation, evaluation, and chemical calculation

In this study different membranes were produced, aiming to evaluate their use in electrodialysis. These membranes were produced using conventional polymer (high-impact polystyrene) and polyaniline. The membrane characterization was done by FTIR spectroscopy, scanning electron microscopy (SEM), and thermogravimetry (TGA). The studies of the zinc and proton extraction ionic transport through the membranes were evaluated using a three-compartment cell. The results obtained using the produced membranes were compared to the results obtained with the commercial membrane Nafion 450. It was found that a synthesized membrane can be used to recover zinc in acid media. In addition, a preliminary computational essay about the structures of PAni and CSA is presented.

A New Oscillatory Electrochemical Phenomenon Observed in the Electropolymerization of Pyrrole in MeCN + N ( Bu ) 4 PF 6 on an Iron Electrode Studied by the Ring‐Disk‐Electrode Technique

A regular oscillatory behavior was observed during the electropolymerization of pyrrole on an iron electrode in aqueous acetonitrile containing tetrabutylammonium hexafluorophosphate. The periodicity, the amplitude, and the shape of the oscillations depend on the concentrations of the electrolyte species. In order to elucidate the mechanism of this oscillatory phenomenon, the ring-disk-electrode technique was used. A mechanism involving a catalytic oxidation of pyrrole by Fe 3+ ions produced during iron oxidation is proposed and discussed

Electroactive poly(aromatic amine) films deposited on mild steel

Abstract Polyaniline (PAni) and poly(1,5-diaminonaphthalene) (polyl,5-DAN) films can be deposited on mild steel from aqueous HCIO. This medium allows passivation of the substrate without preventing monomer oxidation. The films are uniform, with controlled thickness and exhibit electroactive properties between 0.3 V and 1.0 V SCE which are similar to those of PAni and poly(1,5-DAN) generated on platinum. Electrosynthesis performed in the presence of two monomers leads to a composite film which presents excellent adhesion properties on mild steel.

Castor oil and commercial thermoplastic polyurethane membranes modified with polyaniline: a comparative study

The study of conducting polymeric membranes is decisive in some areas, as in fuel cells and electrodialysis. This work aims the study of membranes using conventional and conductive polymers blends. Two types of polyurethane were used as conventional polymers, commercial thermoplastic polyurethane and polyurethane synthesized from castor oil and 4-4-dicyclohexylmethane isocyanate. Two kinds of conducting polymers were used, polyaniline doped with organic acid and a self doped polyaniline. The polymers and the membranes were characterized by electrical conductivity, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM). The synthesis of the membranes produced was proper, featuring a complete reaction, analyzed by FTIR. The membranes also showed good mechanical properties and thermal stability (≈ 220 °C). Among the membranes studied, the polyaniline doped with p-toluenesulphonic acid obtained higher thermal and viscoelastic properties. Thus they can be used in separation techniques using membranes.

Characterization of EVA residues from the shoe industry and post-consumer urban-waste polyethylenes

This paper presents a characterization of a crosslinked EVA residue (EVA-c) from expanded sheets used in the shoe industry and post-consumer urban-waste polyethylenes regarding their molecular (FTIR), mechanical (tensile and impact tests), morphological (SEM), thermal (DSC, TGA) and dynamic-mechanical (DMTA) properties. For comparison, the properties of the EVA-c and recycled polyethylenes are compared to respective virgin polymers. The recycled polyethylenes generally presented similar properties to the virgin ones. On the other hand, some EVA-c properties differed from virgin ones since it has a high degree of crosslinking and it therefore has a higher tensile modulus and lower elongation at break, notched Izod impact strength and hardness. Additionally, crosslinking was also found to modify the thermal properties (TGA and DSC) of EVA-c.