Resumo: Países tropicais, como o Brasil, são depositários de uma grande variedade de fontes de polissacarídeos vegetais conhecidos e outros ainda não explorados que possuem grande potencial em aplicações industriais. Alguns estudos reportam a possibilidade de aplicação industrial da goma exsudada do cajueiro em substituição à goma arábica devido à semelhança estrutural e química. Neste estudo propôs-se caracterizar comparativamente algumas propriedades destas duas gomas, antes e após dois tratamentos de extrusão termoplástica. Nos resultados de composição centesimal as amostras de goma de cajueiro in natura e processadas destacaram-se pelo alto teor de fibra solúvel. Por outro lado, apresentaram menor teor de minerais que a goma arábica. Por meio da análise de viscosidade rápida, foi observado que este parâmetro aumentou nas amostras de goma arábica processadas, enquanto nas amostras processadas de goma de cajueiro houve redução. Nos resultados da análise de difração de raios X predominou-se a conformação amorfa das cadeias poliméricas de ambas as amostras. A partir dos parâmetros avaliados, a goma de cajueiro poderia ser indicada como substituta da goma arábica. Palavras-chave: Goma de cajueiro, goma arábica, extrusão. Cashew Gum (Anacardium occidentale): Evaluation of Chemical and Physical Changes by Thermoplastic ExtrusionAbstract: Tropical countries such as Brazil are rich in a great variety of plant sources of polysaccharides, some of which are not known or explored yet and could have great potential in industrial applications. Some studies report the possible industrial application of cashew gum as substitute for Arabic gum owing to their structural similarity. This study aimed at comparing properties of these gums before and after two treatments of thermoplastic extrusion. The cashew gum raw and processed was found to possess high content of soluble fibers and low ash content, also exhibiting a lower content of minerals in comparison with Arabic gum. The rapid viscosity increased upon processing for Arabic gum, while it decreased for cashew gum. With x-ray diffraction we confirmed the amorphous conformation of the polymer chains of both samples. From the parameters evaluated, we conclude that cashew gum could be used as a replacement for Arabic gum.

Graphene nanoplatelets (GNP) is noncovalently functionalized with imidazolium-, pyridinium-, and vinyl-pyridinium-based ionic liquids containing bromide or bis(trifluoromethyl-sulfonyl)imide (TFSI) as the counteranions, and used to prepare poly (methyl methacrylate) (PMMA) nanocomposites by solution casting approach followed by compression molding technique. The PMMA composites loaded with 1.9 and 1.8 wt% of GNP in PMMA/GNP composite and PMMA/GNP/ionic liquids, respectively, were characterized by melting viscosity, thermogravimetric analysis and AC electrical conductivity (σ AC). The microwave absorption properties at the X-band (8.2-12.4 GHz) frequency were measured for systems with 1 mm thickness using the metal-backed configuration. PMMA nanocomposites loaded with GNP/N-dodecyl-4-vinyl-pyridinium.

Polyaniline doped with dodecylbenzene sulfonic acid (PAni.DBSA) was prepared by inverse emulsion polymerization of aniline in toluene medium in the presence of silica (SiO2) nanoparticles. The presence of cetyltrimethylammonium bromide (CTAB) during the aniline polymerization results in hybrid material with smaller particle size, as indicated by dynamic light scattering analysis and scanning electron microscopy. Also the electrical conductivity of such hybrid is one order higher, as compared with that prepared without CTAB. Moreover, more ordered PAni chain is obtained as indicated by the red shift of the π–polaron transition band observed by UV–vis spectroscopy and higher crystallinity observed by X‐ray diffraction analysis. Anti‐corrosive properties of carbon steel substrate coated with epoxy resin containing 5 wt % of PAni.DBSA and the corresponding SiO2‐based hybrid materials were evaluated in 3.5% NaCl solution by electrochemical impedance spectroscopy. The coating resistance increases by one order for the epoxy system containing PAni.DBSA/SiO2 hybrid prepared in the presence of CTAB, thus confirming the anticorrosion efficiency of this hybrid. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45505.