Electrically conductive polyaniline (PANI)-coated electrospun poly(vinylidene fluoride) (PVDF) mats were fabricated through aniline (ANI) oxidative polymerization on electrospun PVDF mats. The effect of polymerization condition on structure and property of PVDF/PANI mats was investigated. The electrical conductivity and PANI content enhanced significantly with increasing ANI concentration due to the formation of a conducting polymer layer that completely coated the PVDF fibers surface.The PANI deposition on the PVDF fibers surface increased the Young modulus and the elongation at break reduced significantly. Attenuated total reflectance-Fourier transform Infrared spectroscopy revealed that the electrospun PVDF and PVDF/PANI mats display a polymorph crystalline structure, with absorption bands associated to the β, α, and γ phases.

In this study, composites based on polyurethane (PU) derived from castor oil and montmorillonite/ polypyrrole doped with dodecylbenzenesulfonic acid (MMt-PPy.DBSA) were developed. In order to investigate the potential use of these materials for electromagnetic shielding applications, the electrical and mechanical properties of PU/MMt-PPy.DBSA composites were determined and compared with composites containing neat PPy.DBSA. The electrical conductivity of PU/MMt-PPy.DBSA composites was found to be higher than those for PU/PPy.DBSA with a similar filler content. Additionally, with a higher conductive additive content, significant increases in the tensile stress (σ) and elastic modulus (E) were observed, suggesting that MMt-PPy.DBSA acts as reinforcing agent for the PU matrix. The electromagnetic interference shielding effectiveness (EMI SE) of composites is mainly dependent on the morphology and filler content. The PU/MMt-PPy.DBSA composite containing 25 wt % of MMt-PPy.DBSA showed a maximum EMI SE of-21 dB, which is similar to the value required for commercial applications (-20 dB). The results revealed that PU/MMt-PPy.DBSA composites are promising materials for electromagnetic shielding applications.

Resumo: Nanocompósitos de montmorilonita/polipirrol (MMT/PPy) foram preparados a partir da polimerização in situ do pirrol na presença de argila, bentonita sódica natural, (MMT-Na + ) em solução aquosa com ou sem surfactante aniônico, dodecil sulfato de sódio (SDS), utilizando-se o cloreto de ferro (III) hexahidratado (FeCl 3 .6H 2 O), como oxidante. A estrutura e propriedades dos nanocompósitos obtidos pela polimerização in situ do pirrol na presença de SDS (MMT/PPy.SDS) e sem surfactante (MMT/PPy) foram avaliadas e comparadas a partir da espectroscopia de infravermelho com transformada de Fourier (FTIR), difração de raios X (DRX), microscopia eletrônica de varredura (MEV), microscopia eletrônica de transmissão (MET), análise termogravimétrica (TG) e método padrão quatro pontas. Os difratogramas dos nanocompósitos revelaram que o espaçamento basal d 001 da MMT (1,42 nm) foi alterado para valores maiores, indicando a intercalação do PPy na MMT para ambos os nanocompósitos obtidos. Os difratogramas e as imagens de MET e MEV dos nanocompósitos de MMT/PPy.SDS confirmaram que a presença do SDS na reação promoveu, além da intercalação, esfoliação parcial da argila. Os nanocompósitos MMT/PPy.SDS apresentaram condutividade elétrica (9,50 S/cm) maior do que o nanocompósito de MMT/PPy (4,44 S/cm). A presença da argila melhorou de forma significativa a estabilidade térmica do PPy. Palavras-chave: Polipirrol, montmorilonita, nanocompósitos, condutividade elétrica. The Preparation of Montmorillonite/polypyrrole Nanocomposites: The Effect of Surfactant Incorporation on the Structure and PropertiesAbstract: Montmorillonite/polypyrrole (MMT/PPy) nanocomposites were prepared by the in situ polymerization of pyrrole in the presence of clay, natural sodium bentonite, (MMT-Na + ) in aqueous solutions with or without an anionic surfactant, sodium dodecyl sulfate (SDS), using Iron (III) chloride hexahydrate (FeCl 3 .6H 2 O) as oxidant. The structure and properties of the nanocomposites obtained by the in situ polymerization of pyrrole in the presence of SDS (MMT/PPy.SDS) and without surfactant (MMT/PPy) were compared and evaluated by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis and the four-point probe method. The XRD patterns of the MMT/PPy composites shows that the d 001 spacing in MMT (1.42 nm) was changed to higher values, indicating the intercalation of PPy on MMT for both nanocomposites. The XRD pattern, SEM and TEM images of the MMT/PPy.SDS nanocomposites confirmed that the presence of SDS in the reaction medium promoted, beyond intercalation, the partial exfoliation of the clay. The MMT/PPy.SDS nanocomposites showed electrical conductivity (9.50 S/cm) higher than the MMT/PPy nanocomposites (4.44 S/cm). The presence of the clay significantly improved the thermal stability of PPy.

In this work, non-woven mats of poly(vinylidene fluoride; PVDF) containing different weight fractions (2.5, 5, 10, and 12.5 wt%) of a nanostructured conductive additive based on montmorillonite-dodecylbenzenesulfonic acid-doped polypyrrole (Mt-PPy.DBSA) have been prepared by electrospinning. The effect of Mt-PPy.DBSA content on the properties of PVDF solution, mats morphology, thermo-mechanical, and electrical properties was investigated. Polymorphism of PVDF/Mt-PPy.DBSA mats was investigated by Fourier Transform Infrared (FTIR) spectroscopy. Moreover, the electromagnetic interference shielding effectiveness (EMI SE) and EMI attenuation mechanism was investigated. In order to perform a comparative study, nanocomposites with the same weight fraction of Mt-PPy.DBSA was also prepared by solution casting. The PVDF/Mt-PPy.DBSA mats display fibers with smaller diameters than neat PVDF, due to the increment in the ionic conductivity of the solution. The incorporation of the Mt-PPy.DBSA additive slightly improved electrical conductivity of the mats and they behave like as an electrically insulating material (10 −14 S cm −1), due to their porosity, that prevents the formation of a conducting network. Furthermore, the EMI SE of electrospun mats is practically null, indicating that they are almost transparent to magnetic waves. On the other hand, nanocomposites fabricated by solution casting display superior electrical conductivity (10 −2 S cm −1) and EMI SE reached values of −5 dB.

No abstract

No abstract

This article reports the potential use of Polypyrrole (PPy) particles as anticorrosive additive on an epoxy water-based paint to increase the corrosion protective property of aluminum-coated panels. AA1200 aluminum panels were painted using the electrophoretic deposition method and the coatings with different concentrations of PPy particles were tested. PPy particles were synthetized by oxidative polymerization of pyrrole (Py) with iron (III) chloride hexahydrate (FeCl 3 .6H 2 O) in the presence of dodecylbenzenesulfonic acid (DBSA). Electrically conducting PPy particles (6.5 S cm −1) were obtained with a size average of 154 nm. The as-prepared PPy particles were added into a water-based epoxy paint and AA1200 panels were coated via electrophoretic deposition method. The corrosion protective properties of e-coated AA1200 panels were evaluated by means of electrochemical impedance spectroscopy over prolonged exposure time in neutral non-aerated 0.1 M sodium chloride NaCl electrolyte. In particular, the addition of 0.4% by weight PPy has improved the coating corrosion protective property with respect to epoxy clearcoat and exhibited the highest value of impedance modulus at low frequency among the studied coatings.