Thermal protection systems (TPS) are components designed to protect the internal and external areas of a rocket motor from high temperatures. There has been studies in Brazil of resin-based polybutadiene hydroxylated (HTPB) loaded with asbestos since the 1970s. Nevertheless, asbestos has been banned in several countries because it is severely harmful to the human health. In this context, the development of asbestos free in flexible thermal protection (FTP) is extremely important. This study evaluates the use of Expanded Perlite (PExp) as an asbestos substitute. Lower densities were observed, which become a very interesting achievement for the aerospace field. Samples with 5 phr of Expanded Perlite showed similar results when comparing with 47 phr of fillers in PTF reference on oxy-acetylene torch test, and a reduction about 20 % of mass loss rate in test with solid propellant, thus showing that Expanded Perlite can replace asbestos in FTP.

ABSTRACT Fourier transform infrared spectroscopy techniques, associated or not to others, are a well-studied subject used for characterizing polymers/energetic materials that have been employed mainly in aerospace industries. However, the infrared analyses are usually qualitative and performed using the mid-infrared. This paper discusses the Fourier transform infrared spectroscopy qualitative and quantitative methodologies, coupled or not with thin layer chromatography and thermogravimetric analysis, for characterization of aerospace polymer systems, in some cases, using mid-infrared, near-infrared and far-infrared regions, by traditional accessories and the latest generation spectra mode, universal attenuated total reflection. This short review was made based on methodologies developed during the last two decades and published by many scientific and industrial research groups, emphasizing studies usually carried out in the last five years. A critical assessment and future trends were included.

ABSTRACT: Iron oxide is a mineral compound that shows different polymorphic forms, including hematite (α-Fe2O3), magnetite (Fe3O4) and maghemite (γ-Fe2O3). Solid propulsion technology nanoparticulate materials, such as hematite and maghemite, exhibit high performance on thermal decomposition of ammonium perchlorate. The enhanced catalytic effect of metallic iron oxide nanoparticles is attributed to their particle size, more active sites and high surface area, which promotes more gas adsorption during thermal oxidation reactions. Nowadays, metallic iron nanoparticles can be synthesized via numerous methods, such as co-precipitation, sol-gel, microemulsion, or thermal decomposition. Although there are data on these synthetic methods in the literature, there is a lack of details related to nanoparticulate oxides and to their characterization techniques. In this context, this short review based on scientific papers, including data from the last two decades, presents methods for obtaining nanoparticulate iron oxides as well as the main aspects of the different characterization techniques and also about the decomposition aspects of these nanomaterials. Morphologies and structures of iron oxides can be characterized through transmission electron microscopy, scanning electron microscopy, X-ray powder diffraction, and Fourier transform infrared spectroscopy. As for textural properties, they are usually determined by physical adsorption techniques.

A possibilidade de interação entre o sistema à base do polímero de azoteto de glicidila e da dinitramida de amônio (GAP/ADN) foi avaliada, por FT-IR, nas regiões do infravermelho médio (MIR) e infravermelho próximo (NIR). O sistema GAP e perclorato de amônio (GAP/AP), utilizando oxidante mais usual, foi analisado por MIR. Maiores alterações espectrométricas foram observadas para o sistema GAP/ADN. Foi observado um alargamento de bandas para ambos os sistemas na região entre 3100-3500cm-1, sugerindo interações entre os grupos OH do GAP e NH4+ do ADN ou AP. A diminuição da intensidade da banda do grupo N3 do GAP e o aumento de intensidade do nitroílo (NO2+) do ADN também foram notados, sugerindo interação entre esses grupos no sistema GAP/ADN.

FT-IR spectroscopy, in the mid-infrared (MIR) and near infrared (NIR) regions, was used to investigate possible interactions in the polymer system made with glycidyl azide and ammonium dinitramide (GAP/ADN). The GAP and ammonium perchlorate (GAP/AP) system with the most usual oxidizer was studied by MIR. Major spectrometric changes were observed for the GAP/ADN system, with a broadening of the bands in the region between 3100-3500cm-1, pointing to interactions between OH groups from GAP and NH4+ groups from ADN or AP. Also noted were a decrease in band intensity for the N3 group in GAP and an increased intensity of nitronium (NO2+) of ADN, suggesting interaction between these groups in the GAP/ADN system.

Abstract Over the last two decades, many routes have been proposed to synthesize ammonium dinitramide (ADN). However, most of them lie in routes in which reactants are too expensive for large-scale production. In this sense, the use of ordinary reactants is of paramount importance in this case. The aim in this synthesis consists on nitrating a starting reactant in a reaction known as nitration. Both the nitrating agent and the starting reactant should preferably be ordinary, narrowing the possibility of having realistic options for them. The most ordinary nitrating agent consists of a mixture of sulfuric and fuming nitric acids. Therefore, the breakthrough must come from the suitable choice of the starting reactant. However, so far, the only viable reaction relies on the use of sulfamate salts. Even though the process with this kind of salt has been largely commercially developed, only few information are available in the literature to properly address issues emerged from it. In this study, an attempt is made to enlighten some effects on the product caused by modifications in the route conditions. Characterization of the resulting products was confirmed by FT-IR in the region of MIR and NIR. The characteristic bands employed to identify ADN in the region of middle infrared were: 3129 and 1384 cm-1 (NH4+); 1537, 1344, 1209, and 1177 cm-1 (NO2); 1032, 954 cm -1 (N3); 828, 762 and 732 cm-1(NO2). The near infrared analysis pointed out few bands at 5185 and 4672 cm-1 in NH combination bands region. The resulting middle infrared spectrum was compared to the reference found in the literature for this product. The results show excellent agreement with the expected product.