Matéria (Rio de Janeiro), Volume: 25, Issue: 3, Published: 2020
  • Pre-Publication of Papers in the Matéria Journal Editorial

    Miranda, Paulo Emílio V. de
  • Valorization of wood shavings waste for the production of wood particulate composites Articles

    Faria, Douglas Lamounier; Lopes, Thamirys Andrade; Mendes, Lourival Marin; Guimarães Júnior, José Benedito

    Abstract in English:

    ABSTRACT The aim of this work was to evaluate the physical and mechanical properties of particleboards using particles from wood shaving at three urea-formaldehyde adhesive contents: 6, 9 and 12% (dry mass basis). The particleboards were produced with nominal density of 0.70 g.cm-3, pressing cycle with temperature of 160 °C, pressure of 3.92 MPa and time of 8 minutes. The properties of water absorption (WA), thickness swelling (TS), both after 2 and 24 hours, apparent density, compression ratio, perpendicular traction, modulus of elasticity (MOE) and modulus of rupture (MOR) in static bending, Janka hardness and screw withdrawal resistance were evaluated. The results of the tests indicated that with the increase of the adhesive content from 6 to 12%, there was no significant statistical difference for the average values of apparent density and compression ratio, being 0.621 g.cm-3 and 1.234, respectively, and the WA and the TS are decreased after 2 and 24 hours. There was a gain of 93% for the MOR property and 64% for the MOE property with the increase of the adhesive content. For perpendicular traction, the highest mean value was 0.67 MPa, referring to the panels with 12% of adhesive. For Janka hardness, the treatments with contents of 9 and 12% of adhesive presented the highest average values being of 21.60 and 25.26 MPa, respectively. In general, the use of wood shavings is feasible for the production of particleboards with a 12% adhesive content.
  • Influence of the cooling temperature on the mass variation and mechanical resistance of injected ABS Artigos

    Silva, Fabiano Aparecido; Cozza, Ronaldo Câmara

    Abstract in Portuguese:

    RESUMO Peças de ABS injetadas e submetidas a diferentes temperaturas de resfriamento podem apresentar variações em sua massa e diferentes níveis de resistência mecânica. O objetivo deste trabalho é estudar a influência da temperatura de resfriamento sobre a variação mássica e resistência mecânica de peças produzidas em ABS por injeção. Com isso, inicialmente, corpos-de-prova em forma de engrenagem foram produzidos sob diferentes condições de resfriamento. Em seguida, a variação mássica dos corpos-de-prova foi analisada com o auxílio de uma balança analítica. Para a verificação da resistência mecânica do material estudado, foi projetado e construído um dispositivo mecânico, o qual possibilitou a aplicação de um carregamento ativo entre dois corpos-de-prova. Pelos resultados obtidos, foi possível observar que, com a diminuição da temperatura de resfriamento, houve um aumento de massa e resistência mecânica das peças injetadas.

    Abstract in English:

    ABSTRACT Injected ABS parts submitted to different cooling temperatures can present variations on their mass and different levels of mechanical resistance. The purpose of this work is to study the influence of the cooling temperature on the mass variation and mechanical resistance of injected ABS parts. Thereby, initially, specimen with gear shape have been produced under different cooling conditions. Then, the mass variation of the specimen has been analysed with the help of an analytical balance. To verify the mechanical resistance of the studied material, was designed and constructed a mechanical device, which made possible the application of an active loading on two specimens. By obtained results, it was possible observe that with the decrease of the cooling temperature, there was an increase on the mass and mechanical resistance of the injected ABS parts.
  • Extraction of acetaldehyde from mineral water using 2,4- dinitrophenylhydrazine as derivatizing agent Articles

    Ali, Ghulam

    Abstract in English:

    ABSTRACT Acetaldehyde generated, when PET bottles of water are deposited at high temperature for long period of time. The acetaldehyde produced, transferred into the mineral water and alter the organoleptic properties of water. Acetaldehyde is also a possible carcinogen and mutagen. In the present research work, acetaldehyde in mineral water was derivatized with 2, 4-dinitrophenyl hydrazine (DNPH), extracted by solid phase extraction (SPE) using octadecyl silane oxide (C18) and finally investigated by gas chromatography (GC). Acetaldehyde-2, 4-dinitropheyl hydrazone (A-DNPH) formed after derivatization which were adsorbed on the surface of C18. Solvent acetonitrile was used for the elution of A-DNPH from the solid phase extraction (SPE) column. Effect of storage time and light on the migration of acetaldehyde was investigated and found the mineral water stored for longer period of time in sun light change their organoleptic properties due to migration of acetaldehyde into water.
  • Thermal properties of acrylonitrile-butadienestyrene (ABS) composites reinforced with silica nanoparticles (SiO2) modified cellulose Artigos

    Lustosa, Emanuela Camargo de Barros; Menezzi, Cláudio Henrique Soares Del; Luz, Sandra Maria da; Raabe, Joabel; Jesus, Luiz Carlos Correia de; Leão, Rosineide Miranda; Zattera, Ademir José

    Abstract in Portuguese:

    RESUMO O objetivo deste trabalho foi caracterizar os compósitos produzidos com o terpolímero acrilonitrila-butadieno-estireno (ABS) reforçados com fibras de polpa celulose modificadas com nanopartículas de sílica (SiO2). Primeiramente, as fibras foram modificadas utilizando o processo sol-gel, tendo como precursor da sílica o ortosilicato de tetraetila (TEOS). Adicionalmente, duas concentrações de TEOS e dois tempos de reação foram utilizados para produzir dois tipos de fibras modificadas, FT1 e FT2, logo depois, foi determinado o rendimento de cada processo de modificação. As fibras foram caracterizadas por meio da microscopia eletrônica de varredura (MEV), análise termogravimetria (TGA) e sua derivada (DTG). Depois da obtenção das fibras os compósitos de acrilonitrila-butadieno-estireno reforçados com 10 e 20% (m/m) de fibras de polpa celulose branqueada não modificadas (FNT) e modificadas com nanopartículas de sílica (FT1 e FT2) foram obtidos por extrusão e posteriormente por injeção, depois os compósitos foram caracterizados quanto à densidade, análise térmica (TGA/DTG), temperatura de deflexão térmica (HDT) e a temperatura de amolecimento VICAT. A adição de fibras, de modo geral, proporcionou incremento para a temperatura de deflexão térmica HDT e temperatura de amolecimento VICAT, sendo mais acentuado quando o teor de fibras passou de 10% para 20%. No entanto, o aumento do teor de fibras de 10% para 20%, em comparação ao ABS puro provocou diminuição da temperatura de início de degradação e provocou aumento da densidade.

    Abstract in English:

    ABSTRACT The aim of this study was to evaluate thermal properties of composites made with terpolymer acrylonitrile-butadiene-styrene (ABS) reinforced with silica nanoparticles (SiO2) modified cellulose. Primarily, the fibers were modified using the sol-gel process and the tetraethyl ortosilicate (TEOS) as precursor. In addition, two concentrations of TEOS and two reaction times were used to produce two types of modified fibers, FT1 and FT2 fibers, then was determined the yield of modification process. The fibers were characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and its derivative (DTG). The acrylonitrile-butadiene-styrene composites reinforced with 10 and 20% (w/w) unmodified cellulose pulp fibers (FNT) and silica nanoparticles modified (FT1 and FT2) were obtained by extrusion process and subsequent injection. The composites were characterized in terms of density, thermogravimetric (TGA / DTG), thermal deflection temperature (HDT) and VICAT softening temperature. In general, the addition of fibers provided an increase for HDT and VICAT, being more pronounced when the fiber content increased from 10% to 20%. However, in comparison with ABS the increasing of fiber content from 10% to 20%, caused a decrease in Tonset and caused an increase in density.
  • Tribological and mechanical properties of biobased reinforcement in a friction composite material Articles

    Vivek, S; L S, Jayakumari; S, Stephen Bernard; G, Suresh; Md, Javeed Ahmed; S, Arulmurugan

    Abstract in English:

    ABSTRACT This work presents the function of biobased ingredients (palm fiber) as reinforcement in brake pad materials. Reinforcement in brake lining improvise wear stability, wear resistance and friction optimization under a dynamic set of operating variables such as braking force, sliding speed, braking duration and braking temperature. The effect of palm fiber on physical, mechanical and tribological properties of brake pad composite is evaluated. The percentage of palm fiber is gradually increased from 2% to 12% at an interval of 2% as an alternate of rockwool fiber by varying the pressure and speed in a pin on disc tribometer. By increasing the pressure, 8% and 10% shows high friction stability at all speeds. The results show that the raise in the palm fiber quantity increases the hardness, specific gravity and heat swell and the properties, loss on ignition and porosity decreases. The SEM descriptions of the composite indicated that the smaller micro voids occurred in the sample having low palm fiber. Weight gain in the composites were also observed by exposing them in salt water, water and oil.
  • Properties evaluation of semi-crystalline and amorphous polymers injected in AISI P20 molds repaired by welding Articles

    Junkes, Rafael; Howarth, Janaina Lisi Leite; Becker, Daniela; Bond, Danielle

    Abstract in English:

    ABSTRACT >Injection molds can fail after a certain period of use, which may compromise the final part’s integrity and quality, but that can be solved using welding repair processes. This work aimed to investigate the influence of AISI P20 molds repaired by Gas Tungsten Arc Welding (GTAW) and Nd-YAG laser-welding processes on the properties of injection-molded parts with semi-crystalline (polypropylene) and amorphous (polycarbonate and acrylonitrile butadiene and styrene terpolymer) thermoplastics. Welds were prepared by machining 0.8 mm-deep 40 mm x 5 mm grooves to be filled by GTAW and Nd-YAG laser-welding deposits, in order to simulate the repair of AISI P20 molds. All polymers were injected into weld-repaired and unrepaired molds, and then evaluated in terms of microstructure, crystallinity degree, mechanical properties and gloss. The results suggest that the repaired region for both studied welding processes, despite the difference in hardness of the weld region, does not significantly affect the properties of semi-crystalline and amorphous injected polymers.
  • Hydroxylation of sunflower, corn and crambe oils and chemical characterization of the obtained vegetable polyols Artigos

    Nascimento, Bárbara Zon; Costa, Ana Paula Oliveira

    Abstract in Portuguese:

    RESUMO Neste trabalho foram sintetizados e caracterizados polióis vegetais a partir do óleo de girassol, milho e crambe. Os polióis foram obtidos a partir da modificação química dos óleos vegetais pela reação de hidroxilação direta com o sistema perácido in situ (ácido fórmico e peróxido de hidrogênio) na proporção molar (óleo/ácido/peróxido) de 1,0:3,0:1,5, temperatura de 85 ºC, tempo de reação de 6 h com agitação mecânica. Os produtos foram caracterizados quanto à viscosidade, densidade, espectroscopia na região do infravermelho (FTIR), índice de hidroxila (IOH), índice de iodo (II) e acidez (IA). O poliol com as melhores propriedades foi obtido a partir do óleo de girassol, com IOH de 72,88 mg de KOH/g de amostra, II de 11,87 g de I2/g de amostra, IA de 16,13 mg de NaOH/g de amostra e viscosidade de 1096,4 mPa.s. O poliol de crambe apresentou valores de IOH de 40,80 mg de KOH/g de amostra, II de 78,18 g de I2/g de amostra, IA de 4,25 mg de NaOH/g de amostra e viscosidade de 649,9 mPa.s. Por fim, o poliol de milho apresentou IOH de 37,40 mg de KOH/g de amostra, II de 62,47 g de I2/g de amostra, IA de 54,62 mg de NaOH/g de amostra e viscosidade de 486,8 mPa.s. A aplicação da técnica de FTIR nos polióis vegetais obtidos permitiu a análise qualitativa dos grupos hidroxilas pelo aparecimento de uma banda alargada na faixa de 3400-3500cm-1, característica desse grupo funcional. Foi possível sintetizar os polióis vegetais a partir da reação de hidroxilação dos óleos estudados e os produtos apresentam potencial para serem usados na síntese de poliuretanos flexíveis, aumentando-se o valor agregado das matérias-primas estudadas.

    Abstract in English:

    ABSTRACT In this work, vegetable polyols were synthesized and characterization from sunflower’s, corn’s and crambe’s oils. The polyols were obtained from the chemical modification of the vegetable oils by the direct hydroxylation reaction with the peracid system in situ (formic acid and hydrogen peroxide) in the molar ratio (oil/acid/peroxide) of 1,0:3.0:1,5, temperature of 85 ºC, reaction time of 6 h with mechanical agitation. The products were characterized by viscosity, density, infrared spectroscopy (FTIR), hydroxyl number (IOH), iodine value (II) and acidity level (IA). The polyol with the best properties was obtained from sunflower oil, with IOH of 72.88 mg KOH/g of sample, II of 11.87 g I2/g sample, IA of 16.13 mg of NaOH/g sample and viscosity of 1096.4 mPa.s. The crambe polyol presented IOH of 40.80 mg KOH/g of sample, II of 78.18 g of I2/g sample, IA of 4.25 mg of NaOH/g of sample and viscosity of 649.9 mPa.s. Finally, the corn polyol presented IOH of 37.40 mg of KOH/g of sample, II of 62.47 g of I2/g of sample, IA of 54.62 mg of NaOH/g of sample and viscosity of 486.8 mPa.s. The application of the FTIR technique in the obtained polyols allowed the qualitative analysis of the hydroxyl groups by the appearance of a wide band in the range of 3400-3500cm-1, characteristic of this functional group. It was possible to synthesize the vegetable polyols from the hydroxylation reaction of the studied oils and the products have potential to be used in the synthesis of flexible polyurethanes, increasing the added value of the raw materials studied.
  • An experimental methodology to determine the parameters of the compression molding process of composite materials made of recycled thermoplastic and recovered wood Artículos

    Tupia, Walter; Brañez Haro, Luz Elena; Arribasplata, Adan; Acosta, Julio

    Abstract in Spanish:

    RESUMO El objetivo de esta investigación es determinar los parámetros del proceso de sinterizado de materiales compuestos plástico-madera (CPM) fabricados mediante moldeo por compresión y con mejores propiedades desde el punto de vista de ingeniería. La estructura de este artículo es, en sí misma, una propuesta de metodología experimental para obtener CPM a partir de partículas de termoplásticos reciclados y maderas recuperadas. Ésta incluye la caracterización de los materiales y pruebas de moldeo por compresión, para determinar en una primera etapa la temperatura y tiempo de sinterizado y, en una segunda, el contenido y tamaño de las partículas de madera. Empleando madera capirona recuperada (MCR) y polipropileno reciclado (PPR), se evalúan dichos parámetros mediante ensayos en muestras moldeadas. Para este caso, los parámetros hallados son: 50 min de permanencia en horno a 190 °C, 30% y 70% en volumen de MCR y PPR respectivamente y partículas de MCR de 0,98 mm a 1,90 mm de tamaño.

    Abstract in English:

    ABSTRACT The objective of this research is to determine the sintering process parameters of wood-plastic composite materials (WPC) manufactured by compression molding and with better properties from an engineering point of view. The structure of this article is, by itself, a proposal of experimental methodology to obtain WPC from recycled thermoplastic particles and recovered wood. This methodology includes the characterization of both starting materials and compression-molding tests, to determine in a first stage the temperature and time of sintering and, in a second stage, the content and size of the wood particles. Using recovered capirona wood (RCW) and recycled polypropylene (RPP); these parameters are evaluated by standardized tests on molded samples. For this case, the parameters are: 50 min of time into the oven at 190 °C, 30% and 70% in volume of RCW and RPP respectively and RCW particles from 0,98 mm to 1,90 mm of size.
  • Influence of the molybdenum content in cobalt and molybdenum catalysts supported on magnesium oxide for the production of carbon nanotubes Artigos

    Goulart, Thayana; Smarzaro, Juliana; Esteves, Laura M.; Oliveira, Hugo

    Abstract in Portuguese:

    RESUMO O desenvolvimento dos processos de produção de nanotubos de carbono é amplamente estudado com o objetivo de melhorar a produção, pureza e qualidade do produto. Entre os processos de produção de nanotubos, a deposição química em fase vapor sobre catalisadores é o método mais empregado para produção em larga escala, pois este permite controlar, de modo eficiente, os parâmetros reacionais. Catalisadores de CoMo/MgO com baixa concentração de cobalto, 5% em massa, e três diferentes concentrações de molibdênio, 5, 10 e 20%, foram preparados pelo método de impregnação seca para estudar o efeito do molibdênio na síntese de nanotubos de carbono. As caracterizações dos catalisadores e dos nanotubos puderam demonstrar as relações entre as propriedades catalíticas e as características dos nanotubos. Os catalisadores com maior concentração de molibdênio apresentaram maior formação de espécies CoMoO4 e MgMoO4 indicando maior interação do cobalto e do suporte com o molibdênio. A elevada concentração de molibdênio nos catalisadores prejudicou a taxa de formação dos nanotubos e a menor grau de grafitização.

    Abstract in English:

    ABSTRACT The development of carbon nanotubes production has been subject of research seeking higher carbon yields and selective processes towards materials with superior purity and quality. Among the methods for nanotube synthesis, the catalytic route is a viable option for large-scale production, since it allows a more effective control of reaction. CoMo/MgO catalysts with low loading of cobalt, 5 wt.%, and three different loading of molybdenum, 5, 10 and 20 wt.%, were prepared by incipient wetness impregnation for high yield and pure carbon nanotubes. A detailed characterization of the catalysts and nanotubes indicated a relationship between their properties. Catalysts prepared with higher molybdenum loading showed higher formation of MgMoO4 and CoMoO4 indicating an enhanced interaction of MgO and cobalt with molybdenum. Excess of molybdenum in the catalyst caused a decrease in carbon yield and produced nanotubes with a lower degree of graphitization.
  • Ultra high molecular weight polyethylene doped with iron through high energy mechanical alloying Articles

    Borges, José Flávio Marcelino; Mugnaine, Michele; Camilo Junior, Alexandre; Borges, Fabiana Cristina Nascimento; Cintho, Osvaldo Mitsuyuki

    Abstract in English:

    ABSTRACT Doping polymers with metallic materials can improve significantly its use. Ultra high molecular weight polyethylene is known for its high resistance to abrasion and impact, and also for its friction coefficient, which is significantly lower than that of commercial steel and most polymeric materials. Therefore, this material presents high industrial demand despite its processing difficulty due to its high viscosity. One kind of polymer processing which has been widely used recently is the high energy mechanical alloying. This method provokes significant changes in the material, such as crystalline structure transformation, amorphization, formation of metastable phases, and nanostructuring, among others. In order to investigate the influence of iron dopant in structural characteristics of polymeric matrix, ultra high molecular weight polyethylene were doped with low concentrations (between 0.1 at.% and 1 at.%) of iron using the method of high energy mechanical alloying. The samples composition was characterized by X-Ray Diffraction Mössbauer Spectroscopy. A theoretical molecular modeling was carried out to simulate the iron presence in polymeric cell, which is in good agreement with the experimental results. Therefore, there is evidence that part of the iron promotes a crossed bond between the polymeric chains.
  • Multi-scale analysis of the two-dimensional problem of plates submitted to shear loadings and considering phase debonding Artigos

    Fernandes, Gabriela Rezende; Pituba, José Julio de Cerqueira; Furtado, Amanda Soares

    Abstract in Portuguese:

    RESUMO O presente trabalho trata da simulação do comportamento mecânico de microestruturas dúcteis reforçadas por inclusões elásticas e a repercussão de seu comportamento na resposta macromecânica de estruturas submetidas a carregamentos predominantes de cisalhamento. Para tanto, uma modelagem baseada em conceitos de homogeneização computacional utilizando um acoplamento direto entre escalas e do MEC/MEF é utilizado. Também, o fenômeno de descolamento de fase é levado em conta com o uso de modelo de fratura e contato onde a abertura da fratura por escorregamento é considerada. Por outro lado, a ductilidade da matriz metálica é representada pelo modelo de Von Mises. As análises numéricas são realizadas em duas etapas: uma primeira, em nível de microestrutura e, em seguida, é realizada a análise de uma chapa através do acoplamento direto entre as escalas. Contata-se coerência dos resultados encontrados nas micro e macro escalas com a utilização da modelagem proposta.

    Abstract in English:

    ABSTRACT The present work deals with numerical analyses on mechanical behavior of ductile microstructures reinforced by elastic inclusions and the consequences upon micromechanical behavior of structures submitted to shear loadings. For this proposal, a proposed modeling based on computational homogenization technique using full coupling between scales and BEM/FEM is used. Also, the phase debonding is taken into account by using cohesive fracture and contact models where the opening sliding phenomenon is considered. On the other hand, the ductility of the metallic matrix is represented by Von Mises model. Initially, the numerical analyses are performed only at microstructural level and then a full coupled multi-scale analysis of a plate is considered, showing coherence between the micro and macro scale results.
  • Blends rheological properties of copolymer polypropylene/recycled polypropylene from industrial containers Artigos

    Luna, Carlos Bruno Barreto; Silva, Wallisson Alves da; Araújo, Edcleide Maria; Siqueira, Danilo Diniz; Oliveira, Akidauana Dandara Brito de

    Abstract in Portuguese:

    RESUMO Neste estudo, foram avaliadas blendas de polipropileno copolímero (PPCop)/polipropileno reciclado (PPRec), proveniente de baldes industriais pós-consumo, em três proporções diferentes (80:20; 60:40 e 40:60% em peso). As blendas foram avaliadas por índice de fluidez, reometria de torque e reologia em regime dinâmico-oscilatório. Os resultados de índice de fluidez indicaram que a mistura de material reciclado com o PPCop promove uma diminuição da massa molar, em comparação ao PPCop. Por reometria de torque, verificou-se que as blendas melhoraram a processabilidade em comparação ao PPCop. Além disso, as blendas apresentaram estabilidade ao longo do processamento, indicando ausência de degradação para as condições de processos utilizadas. Por meio dos ensaios em regime dinâmico-oscilatório, observou-se que, em baixas frequências (< 1 rad/s), o PPCop e as blendas (PPCop/PPRec) apresentam um comportamento de fluido Newtoniano, enquanto que, para frequências maiores que 1 rad/s, um comportamento de fluido pseudoplástico. Os valores dos pontos de intersecção (G’ = G”) das curvas de módulo de armazenamento (G’) e de módulo de perda (G’’), em função da frequência angular (ω), indicaram que as blendas apresentaram uma redução da massa molar, sendo mais pronunciada na composição contendo 60% de PPRec. Os resultados reológicos das blendas PPCop/PPRec foram de grande relevância, uma vez que permitem analisar o comportamento de blendas contendo material reciclado.

    Abstract in English:

    ABSTRACT In this study, blends of copolymer polypropylene (PPCop /recycled polypropylene (PPRec) from industrial containers after consumption were evaluated in three different ratios (80:20, 60:40 and 40:60 wt.%). The blends were evaluated by melt flow index, torque rheometry and rheology in a dynamic oscillatory regime. The results from the melt flow index indicated that the blending of recycled material with PPCop causes a decrease in the molecular weight as compared to PPCop. By torque rheometry, it was verified that the blends showed improved processability in relation to PPCop. Also, the blends showed stability throughout the processing, indicating absence of degradation due to the process conditions used. By the dynamic-oscillatory regime tests, it was observed that, at low frequencies (<1 rad/s), the PPCop and the blends (PPCop / PPRec) demonstrated a Newtonian fluid behavior, whereas, at frequencies greater than 1 rad/s, a pseudoplastic fluid behavior was observed. The values of the intersection points (G ‘= G”) of the storage modulus curves (G’) and loss modulus (G’), as a function of the angular frequency (ω) indicated that the blends showed a reduction of the molecular weight, which was more pronounced in the composition containing 60% PPRec. The rheological results of the PPCop / PPRec blends were of great relevance, since they allowed the analysis of the blends behavior containing recycled material.
  • Light-Curing Units, Photoinitiators System, and Monomers on Physico-Mechanical Properties of Experimental Composite Resins Articles

    Prezotto, Gustavo Furlan da Silva; Lima, Weverteon Soares de; Vitti, Rafael Pino; Silva, Ariel Farias da; Sinhoreti, Mário Alexandre Coelho; Brandt, William Cunha

    Abstract in English:

    ABSTRACT This study evaluated the physico-mechanical properties of experimental composite resins made with different resin matrix and light-curing units. Experimental composite groups were divided according to monomers (BisGMA + TEGDMA-BT and BisGMA + BisEMA + UDMA + TEGDMA-BBUT) and photoinitiator system (camphorquinone-CQ and 1-phenyl-1,2-propanedione-PPD). A quartz tungsten halogen (QTH) or light-emitting diode (LED) were used to light cure all materials. Knoop microhardness (n = 10) was determined using Knoop microhardness test. Compressive strength, diametral tensile strength, and Young modulus (n = 7) were obtained using a universal testing machine at crosshead speed of 1.0 mm/min. The data were submitted to a three-way ANOVA and the Tukey post-hoc test (α = 0.05). QTH presented the highest total irradiance values and similar total radiant exposure to LED. For the compressive strength test, BT-PPD light-cured with LED group showed the lowest mean value. BT-CQ light-cured with LED group exhibited the lowest diametral tensile strength results. The BBUT-composite resins presented lowest Young modulus values, with no statistical difference between light-curing units (QTH and LED) and photoinitiators system (CQ and PPD). Application of QTH or LED in BT-based composite resins with PPD photoinitiator generated suitable results regarding the physico-mechanical properties.
  • On the encapsulation materials for ion-selective electrodes Artículos

    Silveyra, Josefina M.; Ureña, Andrea; Garrido, Juan Manuel Conde

    Abstract in Spanish:

    RESUMEN Los electrodos selectivos de iones (ISEs) con membranas de vidrios calcogenuros son sensores capaces de detectar iones de metales pesados en soluciones electrolíticas. Su uso in-situ y repetido plantea grandes desafíos a la selección del material para encapsular la membrana sensible. La falla en el encapsulado inutiliza al sensor, que debe ser descartado. Sin embargo, no existe hasta ahora estudios reportados sobre este componente crítico de los sensores. El material encapsulante debe aislar al contacto eléctrico de la solución circundante, tener un bajo nivel de absorción de la solución y de los iones en solución, así como mantener sus propiedades invariables por largos períodos de tiempo. Los requisitos del material dependerán también de la geometría de la membrana, ya sea en bulk o en forma de película delgada. Con el fin de facilitar nuevas investigaciones en la temática de los ISEs, estudiamos cinco materiales encapsulantes disponibles comercialmente en la región latinoamericana (Poxipol transparente, Vaicel, Wilpox APV 3C, Wilpox Doming P-5 y Araldite CY-248 + HY-956). Analizamos los requisitos de estabilidad y confiabilidad evaluando las siguientes propiedades: viscosidad, tiempo de curado, dureza, calidad superficial, formación de burbujas, respuesta al pulido mecánico, reacción con pintura de Ag, efecto del agua y de soluciones de limpieza y almacenamiento. Encontramos que, tomando los cuidados necesarios, las resinas epoxi Wilpox APV 3C y Araldite CY-248 + HY-956 son las más idóneas para encapsular membranas de vidrios calcogenuros en bulk, mientras que la resina epoxi Wilpox APV 3C y la resina acrílica Vaicel resultan ser las mejores candidatas para el caso de las membranas en forma de película delgada.

    Abstract in English:

    ABSTRACT Ion-selective electrodes (ISEs) built with chalcogenide glass membranes are sensors capable of detecting heavy metal ions in electrolytic solutions. Using ISEs in-situ and repeatedly can be challenging not only to the sensitive membrane, but to the material used to encapsulate the electrical contact between the membrane and the metallic wire. If the encapsulation fails, the sensor must be discarded. Despite how critical these issues are on this sensor component, no studies on the requirements and selection of the encapsulation material have been reported so far. This material must isolate the electrical contact of the surrounding solution, have a low level of absorption of the solution and the ions in the solution, as well as keep its properties stable in the long-term. The material requirements will also depend on the geometry of the membrane, either bulk or thin film. To stimulate further research and development in the field of ISEs, we investigated five encapsulating materials commercially available in the Latin American region (transparent Poxipol, Vaicel, Wilpox APV 3C, Wilpox Doming P-5 and Araldite CY-248 + HY-956). We analyzed the encapsulation requirements to enable stable and reliable ISEs by evaluating the following properties: viscosity, curing time, hardness, surface quality, formation of bubbles, effect of mechanical polishing, reaction to Ag paint, effect of water, and cleaning and storage solutions. We found that, under the proper conditions, Wilpox APV 3C and Araldite CY-248 + HY-956 epoxy resins are the most suitable materials to encapsulate bulk chalcogenide glass membranes, while Wilpox APV 3C epoxy resin and Vaicel acrylic resin turn out to be the best candidates for thin film membranes.
  • Evaluation of physical properties of six forest wood species Artigos

    Schulz, Henrique Römer; Gallio, Ezequiel; Acosta, Andrey Pereira; Gatto, Darci Alberto

    Abstract in Portuguese:

    RESUMO Este estudo tem como objetivo, avaliações e correlações entre propriedades físicas da madeira, sendo estas, massa especifica básica, teor de umidade, absorção de água, perda de massa em 50°C e 100°C, contração linear máximo (β), coeficiente de anisotropia de contração (Ca β), inchamento linear máximo (α) e coeficiente de anisotropia de inchamento (Ca α), sendo analisado para as madeiras das seguintes espécies: Corymbia citriodora, Corymbia maculata, Eucalyptus dunnii, Eucalyptus grandis, Eucalyptus saligna e Eucalyptus tereticornis. Para isso, foram confeccionados corpos de prova de 20 mm x 20 mm x 15 mm. Para as análises físicas, os corpos de prova foram submersos em água até a saturação, condicionados sob temperatura de 20°C com umidade relativa (UR) de 65% e secos em estufa (100 ± 3°C). Foram coletados dados de massa e dimensões desses corpos de prova em cada uma dessas etapas, para posterior cálculo das propriedades tecnológicas. Observou-se que as madeiras das sete espécies apresentaram diferença significativa. Analisando-se as propriedades de perda de massa a 100°C e massa específica básica, como também, anisotropia para inchamento (Ca α) e contração (Ca β), apresentam uma correlação significativa, sendo diretamente proporcional. A massa específica básica e absorção de água, perda de massa a 100°C e absorção de água, Coeficiente de Anisotropia de Contração (Ca β) e absorção de água, apresentaram correlações significativas, sendo essas propriedades inversamente proporcionais. As madeiras do gênero Corymbia apresentaram valores médios de propriedades tecnológicas, superiores às do gênero Eucalyptus, destacando a madeira Corymbia citriodora.

    Abstract in English:

    ABSTRACT This study aims at assessing and correlating physical properties of wood, such as basic specific mass, moisture content, water absorption, loss of mass at 50 ° C and 100 ° C, maximum linear contraction (β), coefficient of contraction anisotropy (Ca β), maximum linear swelling (α) and coefficient of swelling anisotropy (Caα), being analyzed for wood of the following species: Corymbia citriodora, Corymbia maculata, Eucalyptus dunnii, Eucalyptus grandis, Eucalyptus saligna and Eucalyptus tereticornis. For that, 20 mm x 20 mm x 15 mm specimens were prepared. For the physical analyzes, the specimens were submerged in water until saturated, conditioned at a temperature of 20 ° C with relative humidity (RH) of 65% and oven dried (100 ± 3 ° C). Mass data and dimensions of these specimens were collected in each of these stages, for later calculation of the technological properties. It was observed that the wood of the seven species presented significant difference. Analyzing the mass loss properties at 100 ° C and basic specific mass, as well as anisotropy for swelling (Ca α) and contraction (Caβ), they present a significant correlation, being directly proportional. The basic specific mass and water absorption, loss of mass at 100 ° C and water absorption, Coefficient of Contraction Anisotropy (Caβ) and water absorption, showed significant correlations, being these inversely proportional properties. The wood of the genus Corymbia presented average values of technological properties superior to those of the genus Eucalyptus, highlighting the wood Corymbia citriodora.
  • A study on the thermophysiological and tactile comfort properties of silk/lyocell blended fabrics Articles

    Adnan, Mariyam; Moses, Jeyakodi

    Abstract in English:

    ABSTRACT Certain investigations on the thermophysiological and tactile comfort properties of silk/lyocell blended fabrics have been carried out. A series of yarns were produced as 100% silk (S 100), 75% silk and 25% lyocell (S/L 75:25), 50% silk and 50% lyocell (S/L 50:50), 25% silk and 75% lyocell (S/L 25:75) and 100% lyocell (L 100) and converted to woven fabrics keeping the same fabric set. FTIR study on silk, lyocell and silk/lyocell blended fabrics show the characteristic functional groups for the respective fabrics. The effects of blend compositions on thermophysiological and tactile comfort properties were examined and the results show that thermal resistance of the fabrics containing silk has a higher value in comparison with lyocell-rich blends. Water vapour permeability, absorbency and wickability for lyocell and lyocell-rich blends are found to be superior as compared to 100% silk fabrics. With respect to drape, bending length and crease recovery the lyocell rich fabrics are good in comparison with 100% silk fabrics. The results are discussed using one way ANOVA with 5% significant level.
  • Investigating the use of wastes from the processing of eucalyptus wood for the compacted solid fuels production Artigos

    Silva, Alessandro de Paula; Andrade, Azarias Machado de; Dias Júnior, Ananias Francisco

    Abstract in Portuguese:

    RESUMO Este trabalho teve por objetivo analisar os carvões da casca, maravalha e serragem de Eucalyptus pellita, assim como os briquetes produzidos desses materiais, carbonizados em duas temperaturas. Para isso, a casca, maravalha e serragem oriundas do processamento mecânico foram carbonizados sob temperaturas de 400 ºC e 600 ºC. As propriedades físico-químicas dos carvões produzidos foram comparadas com as do lenho carbonizado nas mesmas temperaturas. Em seguida os resíduos carbonizados foram briquetados e analisados através da umidade de equilíbrio, massa específica aparente, taxa de degradação natural e forçada. A carbonização da casca da madeira de Eucalyptus pellita proporcionou aumentos significativos nos rendimentos gravimétricos em carvão. Houve uma relação positiva entre a temperatura de carbonização e a umidade de equilíbrio dos briquetes produzidos com os resíduos carbonizados. Os briquetes produzidos com o carvão da casca carbonizada a 400 ºC apresentaram elevado ritmo de degradação térmica.

    Abstract in English:

    ABSTRACT This study aimed to analyze the charcoals of bark, shavings and sawdust of Eucalyptus pellita, and the briquettes produced from these materials, carbonized at two temperatures. The bark, shavings and sawdust generated by mechanical processing were charred at temperatures of 400 °C and 600 °C. The physicochemical properties of the charcoals produced were compared with those of the carbonized wood at the same temperatures. Then the charred residues were briquetted and analyzed through equilibrium moisture, apparent specific mass, natural and forced degradation rate. Carbonization of the bark of Eucalyptus pellita wood increased the gravimetric yields in charcoal. There was a positive relationship between the carbonization temperature and the equilibrium moisture of the briquettes produced with the carbonized residues. The briquettes produced with charcoal from the carbonized bark at 400 ºC presented a high rate of thermal degradation.
  • Comparative Study Between Theoretical and Experimental Values of Dimensional Quantities for Tropical Brazilian Wood Articles

    Almeida, Tiago Hendrigo de; Ferro, Fabiane Salles; Almeida, Diego Henrique de; Christoforo, André Luis; Lahr, Francisco Antonio Rocco

    Abstract in English:

    ABSTRACT Brazil presents many wood species that are very useful in several sectors such as civil construction and furniture industry. Rational use of wood resources depends on the wood characterizations process, that can become easier using equations involving properties of interest. Some theoretical equations found in the literature were developed for primarily softwood from the northern hemisphere, but not checked regarding of their accuracy for tropical Brazilian wood species. This paper aims to confront four theoretical equations with the dimensional stability quantities of fifteen tropical Brazilian woods and test the accuracy of them for these wood species. Results showed that experimental values present greater variability than the ones provided by the theoretical equations. Kruskal-Wallis ANOVA performed showed that one of the four equations cannot be accurately used for tropical Brazilian wood species at 5% significance level.
  • Evaluation of two test methods for the strain measurement of interior paints Articles

    Radoevski, Aleksandar Milkov; Höflinger, Michael; Spitzenberger, Edmund; Ghanbari, Razmik-Roger; Kolbitsch, Andreas

    Abstract in English:

    ABSTRACT The appearance of structural cracks is nothing unusual neither in old nor in new buildings. The causes of these cracks range from improper selection and use of materials to faulty design, and can have serious consequences. In buildings in which the structural integrity is not endangered, cracking, especially in interior spaces, constitutes a significant impairment of the building’s serviceability. The repair costs for these cracks are often considerable. Fortunately, a cost-effective and lasting solution to this cracking problem can be found in the use of more elastic interior paints. In order to utilize this solution, it is essential to know the elastic properties of the paint; however, manufacturers often fail to provide adequate information in this respect. In addition, the European market lacks standardized procedures for quantitatively determining the elasticity of paint. By combining two independent mechanical test methods, it is attempted to obtain a quantitative determination of the strain of interior paints. The suitability and relevance of the test methods used is discussed on the basis of the results obtained. The tests used are the classical tensile test in accordance with DIN EN ISO 6892-1 and a modified 3-point bending test based on DIN EN ISO 178. In order to determine the strain, optical deformation analysis by means of digital image correlation (DIC) is used for both test methods.
  • Recycling of cliche waste from flexography printing for production of composites with applications for acoustic and thermal insulation Artigos

    Maciel, Elton; Nascimento, Eduardo do

    Abstract in Portuguese:

    RESUMO A flexografia é um método bastante utilizado na impressão de embalagens plásticas flexíveis, onde o clichê é uma placa de impressão resiliente fotopolimerizada. Os clichês são dificilmente reciclados, porque adquirem uma estrutura molecular reticulada, gerando também graves problemas ambientais no seu descarte final, logo que, apresentam um período de decomposição indeterminado. Consequentemente, as empresas precisam aterrar os clichês após o seu tempo de vida. Atualmente, não existem produtos ou métodos de reciclagem deste material. Portanto, o objetivo deste trabalho é reciclar os clichês descartados para a produção de placas para isolamento acústico e térmico. Desenvolveu-se um método de cominuição do material com uma adequada granulometria. As misturas feitas com clichê e PET triturado, prensados a uma temperatura de 350°C, obtiveram uma elongação de 22% até a ruptura com alta flexibilidade. Adicionou-se até 90% de clichê reaproveitado nas composições estudadas. O isolamento térmico do compósito foi 18% inferior ao de um laminado de madeira com espessura similar. Em contrapartida, o isolamento acústico com as placas de clichê mostrou um aumento de 30% na capacidade de isolamento acústico, principalmente na faixa de frequência acima de 2 kHz, mostrando uma potencial aplicação para isolamento.

    Abstract in English:

    ABSTRACT Flexography is a widely used method in flexible packaging printing, where the cliche is a resilient photopolymerized printing plate. Cliches are difficultly recycled, because they acquire a crosslinked molecular structure. This also generates serious environmental problems in the final discard, as soon as, it has an indeterminate period of decomposition. Companies need grounding the cliches after their lifetime. Currently, there are no products or methods for recycling of this material. Therefore, the aim of this work is the recycle of cliche waste for the production of plates for thermal and acoustic insulation. A method of comminution of the material with suitable particle size was developed. Composites produced with cliche and PET by means of press molding at 350°C, obtained high flexibility and elongation of 22% until rupture. Up to 90% of the cliche can be useful in the compositions studied. Thermal insulation of the composite was 18% lower than of a laminated wood plate with similarly thick. For other hand, acoustic insulation has increased by 30% with the composite plates, especially in the frequency range above 2 kHz, showing to a potential insulation application.
  • Microstructural development and oxygen ion mobility in Sr, Ba, and Ca-doped LaAlO3 perovskites Artigos

    Villas-Boas, Lúcia Adriana; Goulart, Celso Antonio; Souza, Dulcina Pinatti Ferreira de

    Abstract in Portuguese:

    RESUMO Materiais com estrutura do tipo perovskita têm sido extensamente investigados na tentativa de encontrar novos eletrólitos para Células a Combustível de Óxido Sólido que operem em baixas temperaturas. Dentre esses materiais destaca-se o LaAlO3 que, quando apropriadamente dopado, apresenta condutividade iônica considerável. Neste trabalho LaAlO3 puro e dopado com Sr, Ba e Ca foram estudados. O método utilizado para preparação dos pós foi o de reação no estado sólido. Análises microestrutural, estrutural e elétrica das amostras sinterizadas foram realizadas por microscopia eletrônica de varredura, difração de raios X e espectroscopia de impedância, respectivamente. Entre os diferentes tipos de dopantes, a amostra dopada com Sr foi a que apresentou maior condutividade, tanto do grão ( a 800°C) como total ( a 800°C). Em todas as amostras dopadas, a condutividade total é controlada pelo contorno de grão e as microestruturas são heterogêneas e o grau de heterogeneidade depende do dopante.

    Abstract in English:

    ABSTRACT Perovskite-type materials have been extensively investigated in the attempt to find new electrolyte materials for Solid Oxide Fuel Cell that work at low temperatures. Among these materials, LaAlO3 stands out for presenting considerable ionic conductivity when adequately doped. In this work, pure and Sr, Ba, and Ca-doped LaAlO3 were studied. The powders were prepared by solid state reaction. Microstructural, structural and electrical conductivity of sintered samples were analyzed by scanning electron microscopy, X-ray diffraction and impedance spectroscopy, respectively. Among the different kinds of dopants, Sr-doped sample presented the higher conductivity, for both the grain ( at 800°C) and total ( at 800°C) conductivity. In all doped samples, the total conductivity is controlled by the grain boundary, i.e., the grain boundary is more resistive than the grain, and the microstructures are heterogeneous and the degree of heterogeneity is determined by the dopant.
  • Effects of rice husk ash and wollastonite incorporation on the physical and thermal properties of refractory ceramic composites Articles

    Silva, Débora; Pachla, Eduardo; Marangon, Ederli; Tier, Marco; Garcia, Ana Paula

    Abstract in Portuguese:

    RESUMO O principal objetivo deste trabalho foi avaliar os efeitos da incorporação de cinza da casca de arroz e microfibras de wollastonita, adicionadas por substituição parcial de argila, nas propriedades físicas e térmicas de compósitos cerâmicos refratários. As matérias-primas foram caracterizadas quanto à composição química (FRX), composição de fases (DRX) e granulometria por laser. Os compósitos foram avaliados pelas propriedades físicas - porosidade aparente, densidade aparente, absorção de água, retração linear após sinterização e variação de massa - e propriedades térmicas - condutividade térmica e choque térmico. A cinza da casca de arroz utilizada no presente trabalho provou ter potencial como precursor cerâmico no desenvolvimento de refratários. A substituição da argila pela cinza e pelos diferentes percentuais de microfibra resultou em um aumento da absorção de água e da porosidade aparente e uma redução na retração linear de queima. O aumento da porosidade sugere que a reação de mulitização foi insuficiente. No que concerne o desempenho térmico, a condutividade térmica foi inversamente proporcional à porosidade e ao percentual de microfibra. Ademais, quanto maior foi o gradiente de temperatura de choque-térmico menor foi o número de ciclos resistidos pelos compósitos.

    Abstract in English:

    ABSTRACT The main objective of this work was to evaluate the effects of rice husk ash and wollastonite microfibers incorporation, added per clay partial substituition, on physical and thermal properties of refractory ceramic composites. The raw materials characterization occurred with respect to their chemical composition (XRF), phase composition (XRD) and granulometry by laser. The composites were avaluated by physical properties - apparent porosity, bulk density, water absorption, linear retraction after sinterization and mass variation - and thermal properties - thermal conductivity and thermal shock. The rice husk ash used in the present work proved to have potential as a ceramic precursor in the development of refractories. The clay substitution per ash and the microfiber different percentages resulted in an increase in water absorption and apparent porosity and a reduction in the linear retraction. The increase in porosity suggests that the mullitization was insufficient. Regarding the thermal performance, the thermal conductivity was inversely proportional to the porosity and the microfiber percentage. In addition, the higher the thermal-shock temperature gradient the lower was the number of cycles resisted by the composites.
  • Stabilized Guabirotuba Silt with waste from cellulose and paper industry Artigos

    Izzo, Ronaldo Luis dos Santos; Baldovino, Jair de Jesús Arrieta; Erbs, Alexandre; Lima, Danilo; Graupmann, Ölaf

    Abstract in Portuguese:

    RESUMO A resistência à compressão simples, a resistência à tração por compressão diametral e o Índice de Suporte de Califórnia (CBR) foram sistematicamente pesquisados para analisar o desempenho de um solo siltoso da região metropolitana de Curitiba (Brasil) estabilizado com cinza da indústria da produção de papel e com cal dolomítica hidratada. Uma série de ensaios de compactação na energia Proctor normal foram realizados para calcular os parâmetros ótimos de compactação das misturas solo-cinza-cal: peso específico seco máximo (γd-max) e teor de umidade ótimo (ωo). Foram adicionados e utilizados 4 teores de cinza de celulose (5%, 10%, 15% e 20% em relação à massa seca do solo) e um teor fixo de cal (L) de 5% baseado no consumo inicial de cal modificado, estabelecido a partir da interpretação das medidas de pH realizadas em várias misturas solo-cinza-cal. Os resultados demonstram que existe um aumento no teor de umidade ótimo e uma diminuição no peso específico seco máximo das curvas de compactação com o aumento do teor de cinza de celulose. Por outro lado, os ensaios de compressão simples, tração por compressão diametral e CBR revelam que existe um acréscimo nos valores de resistência mecânica das misturas até um teor de cinza de 15%. Em adição, a Espectroscopia por Dispersão de Energia (EDS) feita em uma mistura protótipo mostra que houve uma interação química entre o solo, a cal e as partículas menores da cinza de celulose. Finalmente, equações de dosagem que permitem estimar os valores da resistência das misturas foram desenvolvidas baseadas na relação semiempirica porosidade/cal (η/Liv) tendo em consideração a massa específica e o volume dos materiais, além da energia de compactação.

    Abstract in English:

    ABSTRACT The unconfined compressive strength, the splitting tensile strength and the California Bearing Ratio (CBR) were systematically investigated to analyze the performance of a silt soil from the metropolitan region of Curitiba (Brazil) stabilized with cellulose ash and with hydrated dolomitic lime. A series of compaction tests on normal Proctor energy were performed to calculate the optimum compaction parameters of the soil- cellulose ash-lime mixtures: maximum dry unit weight (γd-max) and optimum moisture content (ωo). Four percentages of cellulose ash (5%, 10%, 15% and 20% in relation to the dry mass of the soil) were added and used, and a fixed content of lime (L) of 5% based on the modified initial consumption of lime and established from the interpretation of pH measurements performed on several soil-ash-lime mixtures. The results demonstrate that there is an increase in the optimum moisture content and a decrease in the maximum dry unit weight of the compaction curves with increasing the cellulose ash content. On the other hand, the tests of unconfined compression, splitting tensile and CBR show that there is an increase in the mechanical strength values of the blends up to an optimal content of 15%. In addition, Energy Dispersion Spectroscopy (EDS) made in a prototype blend shows that there was a chemical interaction between soil, lime and the smallest particles of cellulose ash. Finally, dosing equations that allow estimation of the strength values of the blends were developed based on porosity/lime index (η/Liv) considering the specific gravity and volume of the materials besides the compaction energy.
  • Static bending of glulam beams manufactured with rubber wood and epoxy adhesive Articles

    Faria, Douglas Lamounier; Lopes, Thamirys Andrade; Scatolino, Mário Vanoli; Soriano, Julio; Mendes, Lourival Marin; Guimarães Júnior, José Benedito

    Abstract in English:

    ABSTRACT The aim of this study was to evaluate the properties of Hevea brasiliensis wood wastes for production structural pieces of glued laminated (glulam) timber. Three trees with age close to 25 years and diameter at breast height (DBH) higher than 500 mm were obtained. The basic density of the wood were quantified, as well as the stiffness and the strength in static bending, shear strength and parallel compression to grain and hygroscopic equilibrium moisture. The beams of glulam were evaluated according to the modulus of elasticity (MOE), modulus of rupture (MOR) and delamination. Due to the bending properties MOR (75.14 MPa) and MOE (8166.79 MPa), as well as the shear strength (12.29 MPa) obtained, was concluded by the suitability of the rubber wood for the production of glulam beams. The composite beams presented values of MOR (75.14 MPa) and MOE (8166.79 MPa) compatible with species traditionally used in the production of glulam beams. The adhesive bond quality was verified by the delamination test, presenting delamination of 4.95 %, indicating its use for internal and external environments.
  • Physical-mechanical performance of reinforced gypsum composites with crushed multi-layer packaging Artigos

    Villela, Luciana Silva; Castro, Eliziane Denize de; Mesquita Júnior, Laércio; Veloso, Maria Cecillia Ramos de Araújo; Mendes, Rafael Farinassi; Mendes, Lourival Marin; Guimarães Júnior, José Benedito

    Abstract in Portuguese:

    RESUMO As embalagens multicamadas são utilizadas por um período de tempo bastante curto gerando um volume de descarte elevado. Por serem formadas por diferentes materiais devido suas diversas camadas, sua reciclagem é dificultada. Sendo assim, são importantes novas aplicações para essas embalagens pós-consumo, como por exemplo o seu reaproveitamento em compósitos. Neste contexto, o objetivo deste trabalho foi desenvolver e caracterizar compósitos à base de gesso reforçados com embalagens multicamadas trituradas. As proporções utilizadas para a incorporação dos reforços foram de 0%, 7,5%, 15%, 22,5% e 30% em substituição ao gesso. Foram produzidos corpos de prova (três repetições por tratamento) para avaliação das propriedades de absorção de água, umidade, massa específica aparente, compressão e flexão estática, os quais foram confeccionados com dimensões de 40 x 40 x 160 mm. Para o ensaio térmico, as dimensões foram de 200 x 200 x 20 mm. Os reforços adicionados levaram a um aumento em umidade e absorção de água, enquanto que, para massa específica aparente, condutividade térmica, resistência à flexão, resistência à compressão e rigidez na compressão houve decréscimo. A incorporação de embalagens multicamadas em compósitos de gesso mostrou ser uma alternativa viável, visto que, além de aplicar a logística reversa reutilizando estas embalagens que muitas vezes são descartadas no meio ambiente de maneira inadequada, gerando diversos impactos, ainda melhorou a propriedade térmica dos compósitos e diminuiu a densidade destes. Ademais, todas as porcentagens atenderam a normatização para resistência à flexão, e para a resistência à compressão, apenas a substituição de 30% não atendeu a normativa.

    Abstract in English:

    ABSTRACT The multilayer packages are used for a very short time generating a high discard volume. Because they are formed by different materials due to their several layers, their recycling is difficult. Therefore, new applications for these post-consumer packages are important, such as their reuse in composites. In this context, the objective of this work was to develop and characterize plaster based composites reinforced with crushed multilayer packages. The proportions used to incorporate reinforcements were 0%, 7.5%, 15%, 22.5% and 30%, replacing gypsum. Test specimens (three replicates per treatment) were produced to evaluate the properties of water absorption, moisture, apparent specific mass, compression and static bending, which were made with dimensions of 40 x 40 x 160 mm. For the thermal test, the dimensions were 200 x 200 x 20 mm. The added reinforcements led to an increase in moisture and water absorption, whereas, for apparent specific mass, flexural strength, compressive strength and stiffness in compression there was decrease. The incorporation of multilayer packages into plaster composites proved to be a viable alternative, since in addition to applying reverse logistics reusing these packages that are often discarded in the environment in an inadequate manner, generating several impacts, it also improved the thermal properties of the composites , their density decreased, all percentages complied with normalization for flexural strength, and for compression strength, only the 30% insertion did not meet the standards.
  • Thermoenergetic and luminous performance of a office building with the use of electrochromic glasses Artigos

    Porto, Joseane da Silva; Freitas, Julye Moura Ramalho de; Balboni, Raphael Dorneles Caldeira; Treichel, Suzana; Cunha, Eduardo Grala da; Mattos, Renie Santos de; Leitzke, Rodrigo Karini; Cholant, Camila Monteiro; Avellaneda, César Antonio Oropesa

    Abstract in Portuguese:

    RESUMO Este trabalho tem como objetivo analisar o desempenho termoenergético e luminoso de uma edificação com atividades características de escritórios com vidros eletrocrômicos através de estudo comparativo, considerando vidros comuns de 3mm e 6mm. Para a simulação computacional foi utilizado o programa EnergyPlus . Foram realizadas simulações com o vidro comum Clear 3mm e de 6mm e o vidro eletrocrômico Sage Glass 9mm com a finalidade de analisar a iluminação, o consumo de energia, e o nível de conforto térmico provenientes da climatização artificial e da ventilação natural, respectivamente. As simulações foram realizadas em duas zonas bioclimáticas, na zona bioclimática 2 (ZB 2) e na zona bioclimática 8 (ZB 8), onde utilizou-se os arquivos climáticos da cidade de Camaquã e da cidade de Manaus, respectivamente. Com os resultados obtidos foi possível observar que a edificação com vidros eletrocrômicos apresentou melhor nível de conforto térmico nas horas ocupadas, e que o consumo de energia para resfriamento diminui conforme o aumento da coloração principalmente na ZB 8, por se tratar de uma região com clima quente. Notou-se que na ZB 2 em alguns meses do ano o vidro eletrocrômico permanecia totalmente descolorido, já que a temperatura de setpoint era sempre maior que a temperatura externa. Também foi possível observar que é fundamental analisar a orientação solar para o melhor posicionamento das aberturas na edificação.

    Abstract in English:

    ABSTRACT This work aims to analyze the thermoenergetic and luminous performance of a building with office characteristic activities with electrochromic glasses through comparative study, considering common glasses of 3mm and 6mm. For the computational simulation were used the EnergyPlus software. Simulations were performed with the Clear common glass Clear of 3 mm and 6 mm and the electrochromic glass Sage Glass 9 mm with the purpose of analyzing the lighting, the energy consumption, and the level of thermal comfort coming from the artificial climatization and the natural ventilation, respectively. The simulations were performed in two bioclimatic zones, in bioclimatic zone 2 (ZB 2) and in bioclimatic zone 8 (ZB 8), where it was used the climate files from the city of Camaquã and the city of Manaus, respectively. With the results obtained it was possible to observe that the building with electrochromic glasses presented the best level of thermal comfort in the hours occupied, and that the energy consumption for cooling decreases as the coloration increases, especially in the ZB 8, since it is a region of warm weather. It was noted that in the ZB 2 in some months of the year, the electrochromic glass remains totally discolored, since the temperature of setpoint was always higher than the external temperature. It was also possible to observe that it is fundamental analyze the solar orientation for the best positioning of the building’s openings.
  • Solid surface composite materials manufactured from syrup of polymethyl methacrylate, alumina trihydrate and natural mineral fillers Artículos

    Seguin, Adan Arribasplata; Lizano, Kelly Lucas; Sánchez, Juan Rueda; Sullcahuamán, Julio Acosta

    Abstract in Spanish:

    RESUMEN Se desarrolló un material compuesto a partir de un jarabe de polimetilmetacrilato (PMMA), trihidróxido de aluminio (ATH) y cargas minerales naturales (CMN) con propiedades similares al material comercial Krion®. Con este propósito, se fabricaron materiales compuestos en dos etapas: En la primera etapa, se realizó la polimerización parcial, en masa, vía radicales libres del metacrilato de metilo (MMA) para obtener un jarabe de polimetilmetacrilato y se determinaron los parámetros de la polimerización necesarios para evitar el efecto de autoaceleración y, al mismo tiempo, lograr un jarabe de un porcentaje de conversión de PMMA capaz de evitar la sedimentación de partículas de ATH. En la segunda etapa, se fabricaron y caracterizaron diversas muestras de materiales compuestos a partir de la mezcla del jarabe de PMMA obtenido anteriormente, partículas de ATH y CMN, con el propósito de determinar los parámetros adecuados para lograr propiedades similares al Krion®. Se ha demostrado que, para evitar la autoaceleración y la sedimentación de ATH, se debe lograr un jarabe con un porcentaje de conversión de MMA en PMMA entre 20% y 25% en peso y la polimerización parcial debe realizarse con 0,1% en peso de peróxido de benzoilo (PBO) y 0,2% en peso de etilenglicol dimercaptoacetato (EGDM) a 85°C durante 90 minutos. Similarmente, para obtener propiedades similares al Krion®, los parámetros para la fabricación de un material compuesto de PMMA reforzado con partículas de ATH y CMN son: 40% jarabe / 60% ATH / %CMN variable según el tipo de carga, 0,1% en peso de PBO adicional, 2,0% en peso de etilenglicol dimetacrilato (EGDMA) y 13 horas de curado en un horno a 85°C. Las propiedades del material compuesto con solo ATH fabricado bajo estas condiciones son: 53 MPa de resistencia a flexión, 8054 MPa de módulo elástico en flexión y 91 HRM de dureza. La calidad estética mejora con la incorporación de CMN pero las propiedades mecánicas disminuyen.

    Abstract in English:

    ABSTRACT A composite material, which properties are similar to the commercial material Krion®, was manufactured using polymethyl methacrylate (PMMA) syrup, alumina trihydrate (ATH) and natural mineral fillers (CMN). For this purpose, composites have been manufactured in 2 stages: In first stage, free radical polymerization of methyl methacrylate (MMA) was carried out to obtain syrup of polymethyl methacrylate. Polymerization parameters were determined in order to avoid autoacceleration effect and to get syrup which PMMA conversion avoids precipitation of ATH particles. In second stage, composite samples were manufactured using the obtained syrup, ATH and CMN particles and, then, they were tested in order to determine suitable parameters to get similar properties to Krion®. It has been proved that syrup must have a MMA to PMMA conversion between 20% and 25% to avoid autoacceleration effect and precipitation of ATH particles. To obtain such syrup, polymerization must be carried out using 0,1% of benzoyl peroxide (PBO) y 0,2% of ethylene glycol dimercaptoacetate (EGDM) at 85°C during 90 minutes. Similarly, to get composites which properties are similar to Krion®, the manufacturing parameters of a PMMA composite reinforced with ATH and CMN particles are: 40% syrup / 60% ATH / %CMN variable according to the type of filler, 0,1% of additional PBO, 2,0% ethylene glycol dimethacrylate (EGDMA) y curing time 13 hours inside a furnace at 85°C. Properties of the composite that has been manufactured under these conditions and only contains ATH filler are: flexural resistance of 53 MPa, flexural elastic modulus of 8054 MPa and hardness of 91 HRM. Esthetic quality improves with the incorporation of CMN but mechanical properties decrease.
  • Improved fatigue performance of nanostructured bidirectional fiberglass-polyurethane composites under uniaxial state and high deformations Artículos

    Belardi, Alberto; Oyarzabal, Nicolás A.; Chiacchiarelli, Leonel Matías

    Abstract in Spanish:

    RESUMEN Se fabricaron placas de material compuesto con refuerzo en fibra de vidrio bidireccional [+/-45]4S y matriz poliuretano nanoestructurado usando la técnica de infusión asistida por vacío. Se utilizó nanosílice (NS) hidrofóbica con porcentajes del 1 y 2 % en peso. A pesar de la NS, la permeabilidad de la preforma no aumentó significativamente, obteniéndose valores elevados de Vf (52%) y una buena impregnación del refuerzo, comprobada mediante microscopía SEM. Los ensayos de tracción uniaxial cuasiestáticos presentaron una elevada deformación a rotura (emax>10%) y valores de resistencia última (RUTS) y módulo elástico (E) que disminuyeron en función del agregado de NS. Por el contrario, los ensayos de fatiga controlados por tensión indicaron que el agregado de NS hasta el 2% permitió mejorar la performance en fatiga. En concreto, los parámetros a y b del modelo empírico lineal aumentaron su valor absoluto en un 77 % y 92,7 %, respectivamente. Esta mejora se corroboró a través de la evaluación del módulo elástico residual. Finalmente, los laminados presentaron una acumulación inelástica de deformación (“ratchetting”), aspecto que fue evaluado para dos frecuencias, 0.2Hz y 2 Hz.

    Abstract in English:

    ABSTRACT Plates of composite material of bidirectional fiberglass [+/-45]4S and nanostructured polyurethane matrix were manufactured using the Vacuum Assisted Resin Infusion (VARI) technique. Hydrophobic nanosilica (NS) was used at 1 and 2 wt. % loading. Even though the use of NS, the permeability of the perform did not increase substantially, obtaining high Vf (52%) and a good impregnation, as visualized with SEM. Uniaxial tensile tests under quasi-static conditions presented high deformations to failure (emax>10%), tensile strengths (RUTS) and elastic moduli (E) which decreased as a function of increased NS loading. On the other hand, the stress-controlled fatigue testings revealed that the addition of NS up to 2 wt. % improved fatigue performance. Specifically, the a and b constants of the empirical lineal model presented an increase of 77% and 92.7%, respectively. This improvement was corroborated through the measurement of the residual elastic modulus. Finally, the laminates presented an accumulation of inelastic deformation (ratcheting), whereas this phenomena was studied for two frequencies, 0.2Hz and 2 Hz.
  • Comparative analysis of the thermal effect and wear suffered by a disc brake friction material subjected to Krauss bench tests with engine power variations and operating conditions. Artigos

    Pinto, Rafael Lucas Machado; Gutiérrez, Juan Carlos Horta; Menezes, Rodrigo Cardoso; Rubio, Juan Carlos Campos; Faria, Paulo Eustáquio

    Abstract in Portuguese:

    RESUMO Estudo que visa à análise comparativa dos efeitos térmicos e do desgaste sofridos pelo par tribológico de um sistema de freio durante ensaios realizados variando a potência motora de um banco de ensaio de freios. Como é conhecido, o mecanismo de freio é empregado para controlar a velocidade convertendo energia cinética e/ou energia potencial em energia térmica. Neste estudo, objetivou-se analisar os parâmetros de operação de um sistema de freio a disco para motocicletas utilizando-se um banco de ensaios baseado no procedimento Krauss, descrito pela norma ABNT NBR 6143/1995. Os ensaios experimentais foram conduzidos em duas etapas. Na primeira, o banco de ensaios foi equipado com um motor de 3cv de potência motora e utilizou-se um planejamento fatorial 23, em que os três fatores de controle considerados foram alterados deliberadamente em dois níveis cada. Para avaliar o desempenho do sistema de freio durante o processo de frenagem, analisaram-se três variáveis de resposta simultaneamente: temperatura final, coeficiente de atrito e desgaste das pastilhas de freio. Na segunda etapa, a potência motora foi aumentada para 10cv; analisou-se o efeito dos fatores pressão de contato e velocidade de escorregamento, que foram alterados em quatro níveis cada. Aqui foi analisada a variável de resposta desgaste das pastilhas de freio. Como resultado da análise comparativa realizada, foi possível constatar que os ensaios da segunda etapa mostraram um maior desgaste e aquecimento do material de atrito do mecanismo de freio estudado, o que promoveu redução do coeficiente de atrito em função do aumento da temperatura, especialmente acima de 300°C, fenômeno este conhecido na literatura como efeito fade de frenagem.

    Abstract in English:

    ABSTRACT Study aiming at comparative analysis of the thermal effects and wear suffered by the tribological pair of a brake system during tests performed by varying the motor power of a brake test bench. As is known, the brake mechanism is employed to control speed by converting kinetic energy and/or potential energy into thermal energy. This study aimed to analyze the operating parameters of a motorcycle disc brake system using a test bench based on the Krauss procedure, described by ABNT NBR 6143/1995. Experimental tests were conducted in two steps. In the first one, the test bench was equipped with a 3hp engine of motor power and a 23 factorial design was used, in which the three control factors considered were deliberately changed at two levels each. To evaluate the performance of the brake system during the braking process, three response variables were analyzed simultaneously: final temperature, friction coefficient and brake pad wear. In the second stage, the motor power was increased to 10hp; The effect of contact pressure and sliding velocity factors, which were changed at four levels each, was analyzed. Here the brake pad wear response variable was analyzed. As a result of the comparative analysis, it was found that the tests of the second stage showed greater wear and heating of the friction material of the studied brake mechanism, which promoted a reduction of the coefficient of friction as a function of temperature increase, especially above 300 ° C, a phenomenon known in the literature as the braking fade effect.
  • Waterproofing of bottle gourd (Lagenaria siceraria) with castor oil polyurethane resin Articles

    Nejeliski, Danieli Maehler; Duarte, Lauren da Cunha

    Abstract in English:

    ABSTRACT Castor oil is widely used in chemical industry as raw material for paints, coatings, lubricants and a wide variety of other products. It is an important alternative to petrochemical feedstocks for the synthesis of polyurethanes (PU), besides being cost competitive and environmentally friendly alternative. It is used as a substitute for formaldehyde adhesives to produce composites and particleboards. Higher percentages of the resin tend to cause low water absorption and dimensional changes in the panels, so it has potential to use as waterproofing of natural materials. Bottle gourd is a fruit, used worldwide by different peoples as a raw material for the production of artifacts since many thousands of years. After the drying period, the inner part of the shell acquires characteristics similar to wood and the outer shell becomes impermeable. The objective of the work is increasing the durability and extend the useful life of the bottle gourd for use in the product design by waterproofing the material with polyurethane resin derived from castor oil. Untreated samples were compared with one and two layer resin samples. For the water absorption test, reference was made to standard NBR 15316: Medium density fiberboard. The analysis of the results was made through Scanning Electron Microscopy (SEM), water absorption test and contact angle. As a result, the application of the PU resin of castor oil reduced the water absorption indexes, and the samples with two layers of resin obtained the best results.
  • Analysis of the 3-Glycidoxypropyltrimethoxysilane (GPTMS) hydrolysis by infrared spectroscopy Articles

    Casagrande, Cézar Augusto; Jochem, Lidiane Fernanda; Repette, Wellington Longuini

    Abstract in English:

    ABSTRACT The study of silanes and polymers with special functions is increasing and the development of materials from silane-based polymers follows this trend. In this way, the hydrolysis of 3-Glycidoxypropyltrimethoxysilane (GPTMS) was studied as a function of the hydrolysis time in solutions with 50% of alcoholic solvents by infrared spectroscopy. It was verified that it was possible to analyze qualitatively and quantitatively the chemical reactions involving the hydrolysis / condensation of GPTMS and the main kinetics variations during the process. The results suggest that up to 30 minutes of hydrolysis, the predominant reactions are hydrolysis of the alkoxy groups, with the generation of the Si-OH groups and alcohol, in this case methanol. From 30 minutes, there is a large amount of silanols in the solution that tend to condense and form siloxane groups, which has this reaction accelerated from 60 minutes. Already, from 70-80 minutes, the reactions tend to decrease the kinetics, due to the absence of silanols and the hydrolysis / condensation process.
  • Mathematical model of a combustion chamber of a pirotubular boiler using the matlab-simulink tool Artículos

    Rivera, Andrea del Pilar Fabra; Jiménez, Francys Marcel Rodríguez; Santaella, José Ricardo Bermúdez; Rubio, Juan Carlos Campos

    Abstract in Spanish:

    RESUMEN En este artículo se presenta la implementación del modelo matemático de la cámara de combustión de una caldera piro-tubular, por medio del planteamiento de los balances de masa, energía y estequiométrico. Estos balances fueron descritos por los componentes de entrada (aire y combustible) que se presentan en la zona de combustión, basados en el concepto de mantener la relación estequiométrica entre ellos, los cuales, fueron simulados a través de las herramientas computacionales como el ESS y Matlab®, con el fin de determinar el comportamiento de los gases de combustión dependiendo del tipo de reacción química presentada. Así mismo, fue determinado la cantidad de carbonos e hidrógenos que componen los combustibles de estudio (ACMP y Keroseno), igualmente los kmol/s que componen al aire, con el objetivo de analizar su oxidación y determinar la producción de y . Finalmente, se realizó la respectiva comparación analizando los valores de presión y temperatura en los tres tipos de combustión, estequiométrica, con presencia de inquemados y con exceso de aire. El planteamiento del modelo matemático fue aplicado para los dos tipos de combustibles de estudio.

    Abstract in English:

    ABSTRACT This article presents the implementation of the mathematical model of the combustion chamber of a pyro-tubular boiler, by means of the approach of mass, energy and stoichiometric balances. These balances were described by the input components (air and fuel) that are presented in the combustion zone, based on the concept of maintaining the stoichiometric relationship between them, which were simulated through the computational tools such as the ESS and Matlab®, in order to determine the behavior of combustion gases depending on the type of chemical reaction presented. Likewise, it was determined the amount of carbons and hydrogens that make up the study fuels (ACMP and kerosene), as well as the kmol / s that compose the air, with the objective of analyzing its oxidation and determining the production of [CO]_(2,) H_2 O. Finally, the respective comparison was made analyzing the values of pressure and temperature in the three types of combustion, stoichiometric, with presence of unburned and with excess air. The approach of the mathematical model was applied for the two types of study fuels.
  • Characterization of the raw material with nanometric particle size used in the processing of the composite WC-10% Co Artigos

    Batista, Adriano Corrêa; Aguiar, Amanda Maia; Oliveira, Hellen Cristine Prata de; Assis, Paulo Santos

    Abstract in Portuguese:

    RESUMO O compósito WC-10%Co também conhecido como Metal Duro de Carbeto de Tungstênico (WC) com Cobalto (Co) é um dos materiais mais produzidas pela indústria fabricante de metal duro, entretanto busca-se o melhor entendimento sobre o efeito de parâmetros de processo sobre as suas características estruturais, especialmente no que diz respeito à formação de fases metaestáveis – fases η. Neste trabalho, usamos o método de Rietveld aliado a difração de raios X (DRX), a microscopia eletrônica de varredura (MEV) e o Brunauer – Emmett – Teller (BET) para investigar a estrutura das matérias-primas utilizadas na produção de metal duro. Os tamanhos das partículas assim como as morfologias identificadas para os pós de WC e Co são reflexos do seu processo de fabricação que, introduzem tensões residuais para o pó de WC, a baixa cristalinidade e significante parcela de amorfo para o pó de Co. Estas características foram identificadas com a difração de raios X em comparação com o padrão de difração obtido e os bancos de dados cristalográficos. Após o processo de mistura dos pós foram quantificadas as fases e identificados os efeitos desse processo sobre as células unitárias de cada fase. Este trabalho mostra que a rota de caracterização empregada, com o uso do método de Rietveld, é eficiente para analisar a estrutura desses materiais durante seu processamento. Foi possível observar que o processo de mistura utilizando equipamento de moagem de alta energia promove alteração na densidade das células unitárias do WC “empurrando” átomos de Co para dentro de sua estrutura. Isso pode vir a acelerar o processo de dissolução de grande parte das partículas de WC durante a sinterização, contribuindo para a formação acentuada das fases metaestáveis eta – η, prejudicando o equilíbrio entre as propriedades mecânicas de dureza e tenacidade à fratura tornando a ferramenta ou peça muito dura e pouco tenaz.

    Abstract in English:

    ABSTRACT The composite WC-10% Co is one of the materials most produced by the hardmetal fabrication industry. However, a better understanding of the effect of process parameters on their structural characteristics is sought, especially with respect to the formation of metastable phases - η. In this work, we used the Rietveld Method with X - Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Brunauer - Emmett - Teller (BET) to investigate the structure of the raw materials used in the production of hardmetal. The particle sizes as well as the identified morphologies for the WC and Co powders are reflections of their manufacturing process, which introduce residual stresses for WC powder, low crystallinity and a significant amorphous portion for Co powder. These characteristics were identified with XRD in comparison to the obtained diffraction pattern and crystallographic databases. After the powder mixing process, the phases were quantified and the effects of this process were identified on the unit cells of each phase. This work shows that the characterization route using the Rietveld Method is efficient to analyze the structure of these materials during their processing. It was observed that the mixing process using high energy milling equipment promotes a change in the density of WC unit cells by “pushing” Co atoms into their structure. This may accelerate the dissolution process of most WC particles during sintering. And contribute to the accentuated formation of metastable phases eta – η, damaging the balance between the mechanical properties of hardness and fracture toughness making the tool or piece very hard and not very tenacious.
  • Coprocessing of tailings of the Garimpo Areinha (Diamantina/MG) for red ceramics production Artigos

    Gurgel, Jayne Francielle Santana; Xavier, Stéffany Carolina Rocha; Amaral, Igor Brumano Coelho; Araújo, Amanda Dias; Reis, Arlete Barbosa dos

    Abstract in Portuguese:

    RESUMO A indústria extrativa mineral é responsável pela produção de rejeitos em larga escala que, quando descartados de forma incorreta, podem gerar danos à natureza e à saúde pública. Sabendo disso, estudou-se a viabilidade da adição de rejeitos de garimpo na produção de cerâmica vermelha, buscando-se uma alternativa sustentável para a utilização e descarte desses rejeitos. O rejeito usado para o trabalho foi extraído de três bacias de retenção na região do garimpo Areinha, em Diamantina-MG, e trata-se de lama composta basicamente por silicatos e metais pesados. Objetivou-se fabricar corpos de prova de cerâmica estrutural com adição desses rejeitos e avaliar suas propriedades tecnológicas, tais como: retração linear, perda ao fogo, estudo da cor, absorção de água, porosidade aparente e resistência à compressão simples. Em comparação aos corpos de prova produzidos com solo puro, os resultados apontaram importantes melhorias nessas propriedades com adição dos rejeitos, diminuindo a absorção de água e aumentando a resistência à compressão, apontando a viabilidade da sua utilização para incorporação dos rejeitos de mineração e estabilização de metais pesados.

    Abstract in English:

    ABSTRACT The mineral extractive industry is responsible for the production of large-scale waste which, when discarded incorrectly, can cause damage to nature and public health. Knowing this, the feasibility of the addition of tailings was studied in the production of red ceramics, seeking a sustainable alternative for the use and disposal of these wastes. The residue used for the work was extracted from three holding basins in the region of the Areinha gold mining, in Diamantina-MG, and is a mud composed of silicates and some heavy metals. The objective of this study was to manufacture structural test specimens with addition of these tailings and to evaluate their technological properties, such as: linear retraction, loss on ignition, color study, water absorption, apparent porosity and compressive strength. In comparison to the test specimens produced with pure soil, the results pointed out important improvements in these properties with addition of the tailings, reducing the water absorption and increasing the compressive strength, pointing out the viability of its use for the incorporation of the mining tailings and stabilization of heavy metals.
  • High temperature corrosion of stainless steel AISI 316L in molten nitrate salts based thermofluids for concentration solar plants Artículos

    Sandoval-Amador, Anderson; Jaimes-Campos, Angie Gimena; Mogollón-Sanabria, Astrid Xiomara; Estupiñán-Duran, Hugo Armando; Peña-Ballesteros, Darío Yesid

    Abstract in Spanish:

    RESUMEN Con el reciente auge de las energías amigables con el medio ambiente, surge la demanda de materiales capaces de resistir a ciertas condiciones de trabajo que exigen estos procesos, por ejemplo, la obtención de energía a partir de luz solar, en la cual el almacenamiento térmico es vital en el transcurso del funcionamiento de la planta. En el presente trabajo se evaluó la reacción que presenta el acero AISI 316L en contacto con sales fundidas de nitratos (Ca(NO3)2+NaNO3+KNO3 y LiNO3+KNO3+NaNO3), para ello se realizaron pruebas gravimétricas, con dos tipos de sales ternarias de nitratos a una temperatura de 600°C, evaluando la ganancia de masa en el acero, a su vez se realizaron estudios metalográficos, con el fin de evaluar el daño de la microestructura. Por medio de SEM y micrografías ópticas se observó la morfología de la capa y el daño del acero. La superficie donde se evidenció la mayor agresividad de daño por parte de la sal ternaria en el acero es la superficie del acero expuesta a la sal de litio. Los resultados de DRX arrojaron Fe0,612Ni0,388 y CrNi, como principales productos de corrosión del acero, demostrando así que la sal fundida con el componente de calcio es menos corrosiva para el acero usado en este proyecto.

    Abstract in English:

    ABSTRACT With the recent boom of environmentally friendly energies, the demand for materials capable of resisting certain working conditions demanded by these processes arises, for example, the obtaining of energy from sunlight, in which the Thermal storage is vital during the operation of the plant. In the present work, the reaction of AISI 316L steel in contact with molten nitrate salts (Ca (NO3)2 + NaNO3 + KNO3 and LiNO3 + KNO3 + NaNO3) was evaluated, gravimetric tests were carried out with Two types of ternary salts of nitrates at a temperature of 600°C, evaluating the gain of mass in the steel, in turn, were carried out metallographic studies, in order to evaluate the damage of the microstructure. By means of SEM and optical micrographs, the morphology of the layer and the damage caused to the steel was observed. The surface where the greater aggressiveness of damage by the ternary salt in the steel was evidenced is the surface of the steel exposed to the lithium salt. The results of DRX yielded Fe0.612Ni0.388 and CrNi, as the main steel corrosion products, demonstrating that the salt fused with the calcium component is less harmful to the steel used in this project.
  • Electrospun natural rubber fibers-based flexible conductive membranes Articles

    Dognani, Guilherme; Silva, André Antunes da; Cabrera, Flávio Camargo; Faita, Fabrício Luiz; Saénz, Carlos Alberto Tello; Bechtold, Ivan Helmulth; Job, Aldo Eloízo; Agostini, Deuber Lincon da Silva

    Abstract in English:

    ABSTRACT In recent years, the technique of electrospinning has been used to develop a novel class of micro- and nanoscale materials based on fibrous structures. Several polymers, in particular elastomers, that have been implemented in this process rely on properties such as elasticity, flexibility, biocompatibility, and low cost. Herein, we describe for the first time the electrospinning of natural rubber fibers without polymeric matrix to obtain self-standing non-woven mats and oriented elastomeric fibers. The fibers average diameters were approximately 5.5 µm. Polyaniline (PAni) was deposited on the membrane surface in order to enhance the conductive properties making easy the charge transportation. We have obtained biocompatible and flexible fibrous materials using natural rubber, this research opens up possibilities of using micro and nanofibers of only-natural rubber in many applications including sensors preparation.
  • Analysis of the performance of road subgrades using concepts of Pavement Mechanics Artigos

    Santos, Thaís Aquino dos; Pinheiro, Rinaldo José Barbosa; Specht, Luciano Pivoto; Brito, Lélio Antônio Teixeira

    Abstract in Portuguese:

    RESUMO O pavimento é considerado um sistema de múltiplas camadas finitas, sujeito às tensões, deformações e deslocamentos provenientes das solicitações cíclicas do tráfego. A fundação da estrutura deve apresentar capacidade de suporte compatível com a intensidade e frequência com a qual será solicitada. Sob essa perspectiva, o presente estudo avalia o desempenho de quatro solos com origens geológicas diferentes, usualmente encontrados em subleitos rodoviários no estado do Rio Grande do Sul, com base em princípios da Mecânica dos Pavimentos. A metodologia aplicada nesse estudo consistiu em simulações numéricas assistidas por dois programas computacionais: AEMC/SisPav e AASHTOWare Pavement ME Design. As análises mecanicistas foram realizadas para avaliar a resposta do solo frente à deformação resiliente e à resistência ao cisalhamento, importantes propriedades no emprego de solos em pavimentação. Os resultados mostraram que a deformação resiliente apresenta um papel preponderante no desempenho dos materiais, visto que, para os solos analisados, não há qualquer indício de ruptura por cisalhamento, tanto como material de subleito rodoviário como fundação de pavimentos de baixo volume de tráfego. Isso, porém não afasta a hipótese de altas deformações plásticas. Quanto à deformação resiliente, observou-se ainda a ineficácia do atual método de dimensionamento de pavimentos flexíveis, que não considera o módulo de resiliência dos materiais de pavimentação, resultando no predomínio de ruptura por fadiga, com exceção do solo denominado de CB que poderá levar o pavimento a ruptura por excesso de afundamento de trilha de roda.

    Abstract in English:

    ABSTRACT The pavement is considered a system of multiple finite layers, subject to tensions, deformations and displacements from cyclical traffic demands. The foundation of the structure must have support capacity compatible with the intensity and frequency with which it will be requested. From this perspective, the present study evaluates the performance of four soils with different geological origins, usually found in road subgrades in the state of Rio Grande do Sul, based on the principles of Pavement Mechanics. The methodology applied in this study consisted of numerical simulations assisted by two computational programs: AEMC/SisPav and AASHTOWare Pavement ME Design. The mechanistic analyzes were performed to evaluate the soil response to resilient deformation and shear strength, important properties in the use of paving soils. The results showed that the resilient deformation has a preponderant role in the performance of the materials, since, for the analyzed soils, there is no evidence of shear rupture, both as a road subgrade material and as a foundation of low traffic pavements. This, however, does not rule out the hypothesis of high plastic deformations. Regarding the resilient deformation, it was also observed the inefficiency of the current flexible pavement design method, which does not consider the resilience modulus of the paving materials, resulting in the predominance of fatigue rupture, with the exception of the CB soil, which could lead to pavement to rupture by excessive wheel track rutting.
  • Evaluation of thermochemical and physicomechanical properties of three fast growing forest species Artigos

    Schulz, Henrique Römer; Acosta, Andrey Pereira; Gallio, Ezequiel; Barbosa, Kelvin Techera; Gatto, Darci Alberto

    Abstract in Portuguese:

    RESUMO As madeiras apresentam propriedades tecnológicas distintas, por ser material orgânico e heterogêneo, sendo necessário uma avaliação para o uso adequado. Sendo assim, o objetivo deste trabalho foi a avaliação de propriedades tecnológicas, sendo elas: massa especifica básica, massa especifica aparente a 12%, teor de umidade de equilíbrio, flexão estática (MOE e MOR), compressão paralela as fibras (Fc e Ec), análise colorimétrica, termogravimetria (TGA e DTG) e fourier transform infrared spectroscopy (FT-IR), das espécies de Corymbia maculata, Eucalyptus grandis, Pinus elliottii. Determinaram-se as propriedades tecnológicas conforme descrito nas normas ASTM D 2395-17 (2017) e ASTM D 143-94 (2014). Em relação as propriedades físico-mecânicas, as species apresentaram diferenças significativas baseadas em análises estatisticas, possuindo destaque a espécie de Corymbia maculata. Em relação a análise colorimétrica, foi verificado que a espécie Corymbia maculata possui uma coloração marrom-avermelhado, a espécie de Pinus elliottii amarelo com tonalidade clara, enquanto o Eucalyptus grandis avermelhada com tonalidade clara. Para o FT-IR foi constatado picos semelhantes entre as espécies, porém com intensidades distintas, sendo estes referentes as vibrações moleculares características dos componentes orgânicos da madeira. Por meio da análise termogravimétrica percebe-se que as espécies de Pinus elliottii e Corymbia maculata, apresentaram maior estabilidade térmica, quando comparadas ao Eucalyptus grandis, possuindo um menor percentual de perda de massa e um retardo de temperatura em relação ao pico máximo de degradação (DTG), próximo aos 400°C, sendo essas propriedades analisadas com testes ANOVA com significância de 5%. Sendo assim destaca-se uma heterogeneidade entre as espécies avaliadas nesse estudo, tanto do ponto de vista físico, mecânico, térmico e químico, fazendo-se necessário a caracterização de tais propriedades para o emprego correto destes materiais.

    Abstract in English:

    ABSTRACT The woods have distinct technological properties, as they are organic and heterogeneous material, requiring an assessment for proper use. Therefore, the objective of this work was the evaluation of technological properties, which are: basic density, apparent density at 12%, equilibrium moisture content, static flexion (MOE and MOR), parallel compression of the fibers (Fc and Ec), colorimetric analysis, thermogravimetry (TGA and DTG) and Fourier transform infrared spectroscopy (FT-IR), of the species of Corymbia maculata, Eucalyptus grandis, Pinus elliottii. The technological properties were determined as described in the ASTM D 2395-17 (2017) and ASTM D 143-94 (2014) standards. Regarding the physical-mechanical properties, the species showed significant differences based on statistical analysis, highlighting the species of Corymbia maculata. Regarding the colorimetric analysis, it was found that the species Corymbia maculata has a reddish-brown color, the Pinus elliottii species loves it with a light shade, while the Eucalyptus grandis reddish with a light shade. For FT-IR, similar peaks were found between species, but with different intensities, these being related to the molecular vibrations characteristic of the organic components of wood. Through thermogravimetric analysis, it can be seen that the species of Pinus elliottii and Corymbia maculata, presented greater thermal stability when compared to Eucalyptus grandis, having a lower percentage of mass loss and a delay in temperature in relation to the maximum peak of degradation ( DTG), close to 400 ° C, and these properties were analyzed with ANOVA tests with 5% significance. Thus, there is a heterogeneity among the species evaluated in this study, both from a physical, mechanical, thermal and chemical point of view, making it necessary to characterize these properties for the correct use of these materials.
  • Preliminary studies on the interesterification of soybean oil with methyl acetate catalyed by layered materials” Artigos

    Useda, Aligia Arrubia; Wypych, Fernando; Cordeiro, Claudiney Soares

    Abstract in Portuguese:

    RESUMO A substituição parcial do óleo diesel pelo biodiesel tem contribuído para o aumento da disponibilidade de glicerina no mercado mundial. Cerca de 10 m3 e glicerina são obtidos para cada 100 m3 de triacilglicerídeos (principal componente de óleos vegetais e gorduras animais) processados na principal rota tecnológica para produção do biodiesel, a transesterificação alcalina em meio homogêneo. Naturalmente, a glicerina obtida como coproduto no processo precisa ser aproveitada em processos complementares. Isso usualmente é possível após a glicerina passar por vários processos de purificação. Com a intenção de evitar tais processos complementes para aproveitamento da glicerina, estamos propondo a síntese do biodiesel por interesterificação do óleo de soja com acetato de metila, uma rota tecnológica que possibilita a obtenção da glicerina na forma de triacetina, ou seja, já quimicamente modificada. Os catalisadores utilizados no processo foram o hidróxido duplo lamelar (HDL) Zn2 Al/NO3 e o estearato de zinco comercial (EZ), um carboxilato lamelar. Ambos estes materiais lamelares ainda não haviam sido testados como catalisadores em reações de interesterificação. Foram obtidas conversões em ésteres metílicos de ácidos graxos de 50,8±4,2 % e 82,9±1,0 % (m m-1) utilizando os catalisadores EZ e HDL, respectivamente; quando as reações foram conduzidas utilizando 5 % de catalisador (m m-1), por 10 h de reação e razão molar acetato de metila: óleo de soja de 24:1.

    Abstract in English:

    ABSTRACT The partial replacement of diesel oil with biodiesel has contributed to the increased availability of glycerin on the world market. About 10 m3 of glycerol is obtained for every 100 m3 of triacylglycerides (main component of vegetable oils and animal fats) processed in the main technological route for biodiesel production, the alkaline transesterification in homogeneous medium. Of course, the glycerin obtained as a coproduct in the process needs to be harnessed in complementary processes. This is usually possible after the glycerin undergoes several purification processes. With the intention of avoiding such complementary processes, we are proposing the synthesis of biodiesel by interesterification of soybean oil with methyl acetate, a technological route that makes it possible to obtain glycerol in the form of triacetin, that is, already chemically modified. The catalysts used in the process were the layered double hydroxide (HDL) Zn2 Al/NO3 and the commercial zinc stearate (EZ), a layered carboxylate. Both these layered materials had not yet been tested as catalysts in interesterification reactions. Conversions were obtained in fatty acid methyl esters of 50.8 ± 4.2% and 82.9 ± 1.0% (m m-1) using the EZ and HDL catalysts, respectively; when reactions were conducted using 5% catalyst (m m-1), for 10 h reaction and molar ratio methyl acetate: soybean oil of 24:1.
  • Utilization of carbon nanotubes in hydrogen electrosynthesis from tropical fruit fermentation Articles

    Lopes, Adriana Carla de Oliveira; Abreu, Fabiane Caxico de

    Abstract in Portuguese:

    RESUMO O uso de combustíveis fósseis, especialmente petróleo e gás, acelerou nos últimos anos, o que está resultando na crise energética global. O processo biológico fermentativo é uma forma sustentável de produzir hidrogênio, já que pode utilizar, como substrato diversos tipos de resíduos industriais e domésticos ricos em carboidratos, como frutas, minimizando, mas não eliminando por completo, os problemas causados pelo descarte inadequado deste material. A partir de uma perspectiva de conservação de energia e uso de fontes renováveis para a geração de energia, este trabalho pretende contribuir para a identificação do uso de uma parcela de energia, atualmente inutilizada, otimizando a produção de hidrogênio a partir de uma célula de combustível microbiano. O nano material principal utilizado na eletrólise foi nanotubos de carbono (CNT) incorporados ao feltro de carbono (FC). Estudos de voltametria cíclica também foram realizados em três sistemas de eletrodos: eletrodo de carbono vítreo como eletrodo de trabalho, eletrodo de platina como eletrodo auxiliar e Ag / AgCl / Cl- como eletrodo de referência. Uma célula eletroquímica formada por dois compartimentos separados foi construída. Antes de iniciar o experimento de eletrólise, foi realizado um delineamento experimental utilizando a técnica de planejamento fatorial completo para analisar a influência das variáveis selecionadas para este estudo. As variáveis independentes selecionadas foram: Concentração de licor de frutas tropicais em % v/v, tipo de eletrodo de trabalho, tempo de eletrólise e pH do meio eletrolítico. A variável observada foi a concentração em %v/v do gás hidrogênio obtido na eletrólise. Após os resultados dos testes, concluiu-se que os nanotubos de carbono podem ser utilizados como eletrodo de trabalho, apresentando sucesso no processo de produção de hidrogênio e que o pH do meio eletrolítico exerce forte influência nesse processo. O presente trabalho foi concluído apresentando um caminho alternativo na produção de uma fonte de energia renovável.

    Abstract in English:

    ABSTRACT The use of fossil fuels, especially oil and gas, has accelerated in recent years, resulting in the global energy crisis. The fermentative biological process is a sustainable way to produce hydrogen, as it can use as a substrate various types of carbohydrate-rich industrial and household waste such as fruit, minimizing but not completely eliminating the problems caused by improper disposal of this material. From a perspective of energy conservation and use of renewable sources for energy generation, this work aims to contribute to the identification of the use of a currently unused portion of energy, optimizing hydrogen production from a fuel cell. microbial. The main nanomaterial used in electrolysis was carbon nanotubes (CNT) incorporated into carbon felt (CF). Cyclic voltammetry studies were also performed on three electrode systems: vitreous carbon electrode as working electrode, platinum electrode as auxiliary electrode and Ag / AgCl / Cl- as reference electrode. An electrochemical cell formed by two separate compartments was constructed. Before starting the electrolysis experiment, an experimental design was performed using the complete factorial design technique to analyze the influence of the variables selected for this study. The independent variables selected were: Tropical fruit liquor concentration in %v/v, type of working electrode, electrolysis time and pH of the electrolyte medium. The observed variable was the concentration in% v / v of the hydrogen gas obtained in the electrolysis. After the results of the tests, it was concluded that carbon nanotubes can be used as working electrode, presenting success in the hydrogen production process and that the pH of the electrolytic medium has a strong influence on this process. The present work was concluded presenting an alternative way in the production of a renewable energy source.
  • Polyester/paper composites: study of manufacturing techniques for product development Articles

    Porto, Jussara Smidt; Angrizani, Clarissa Coussirat; Calegari, Eliana Paula; Amico, Sandro Campos; Duarte, Lauren da Cunha

    Abstract in English:

    ABSTRACT Composite materials using vegetal fibers and industrial waste are being applied in different areas and structures, requiring, more and more, researches that highlight their characteristics. In this context, the study of manufacturing techniques becomes increasingly necessary in order to use the appropriate tools and obtain the best conditions of the materials. Thus, this article demonstrates the behavior of the materials, which used the polyester resin with ground paper residue to generate the two composites studied in this paper, Polyester/smaller paper (PO/ PME) and Polyester/large paper (PO/PMA). These two materials were molded by hot compression and subjected to manufacturing processes. Joinery equipment were chosen for the experimentation of cutting, drilling, screw insertion and sanding to analyze the performance of these composite materials. As a general result, it can be observed that the composites maintained their physical integrity, because the particles of the load remained well anchored in the matrix in the two composite materials tested, giving the finish an aspect without damages, cracks or imperfections after the operations. Therefore, it is concluded that the materials created can be submitted to the manufacturing techniques evaluated in this article, reinforcing previous studies that suggest its use in the development of products such as furniture, table tops, decorative objects and others. Thus, this study contributes to Designer has knowledge of the potential of the material and make the best use of it.
  • Obtaining the effective elastic constants under dynamic condition of hybrid laminate for aeronautical use Artigos

    Brito Júnior, Carlos Alberto Rios; Pardini, Luis Claudio; Ancelotti Júnior, Antônio Carlos

    Abstract in Portuguese:

    RESUMO O presente trabalho aborda a determinação das constantes elásticas efetivas de materiais compósitos estruturais de uso aeronáutico por meio de ensaio de vibração. O experimento foi conduzido em um aparato apropriado com interferômetro a laser. Inicialmente, foi realizado um ensaio de vibração do tipo livre para obtenção das frequências naturais intrínsecas à placa de compósito híbrido de alumínio aeronáutico com tecido prepreg de fibra de carbono/epóxi (CARALL). Do mesmo modo, verificou-se por meio deste método, o alumínio 2024 T3 que é uma liga metálica que pode ser aplicada em aeronaves. Tanto o alumínio quanto os compósitos foram modelados em aplicativo computacional (ANSYS) onde por meio do método de elementos finitos obtiveram-se frequências relacionadas aos seis primeiros modos de vibração. O alumínio aeronáutico apresentou uma maior precisão entre os materiais analisados em relação as suas frequências naturais. Em relação as constantes elásticas, a liga de alumínio 2024 T3 apresentou um módulo E1 de 71,3 GPa e um coeficiente de Poisson de 0,31. As constantes elásticas do CARALL foram determinadas como solução de um problema de otimização computacional descrita em linguagem própria contida em uma sub-rotina do ANSYS. Observou-se que o módulo de elasticidade principal e o coeficiente de Poisson são próximos dos valores encontrados numericamente pela regra da mistura (70 GPa e 0.3, respectivamente).

    Abstract in English:

    ABSTRACT This paper deals with the determination of the effective elastic constants of structural composite materials of aeronautical use by means of vibration test. The experiment was conducted in an appropriate apparatus with a laser interferometer. Initially, a free-vibration mode vibration test was performed to obtain the natural frequencies intrinsic to the hybrid composite plate (aeronautical aluminum lamina’s alternating to carbon fiber/epoxy fabric lamina’s) known as CARALL. Likewise, aluminum 2024 T3 which is a metallic alloy that can be applied in aircraft was verified by means of this method. Both the aeronautical aluminum and the hybrid composite were modeled in a computer application (ANSYS) where, through the finite element method, frequencies related to the first six modes of vibration were obtained. The aeronautical aluminum presented a greater precision between the materials analyzed in relation to their natural frequencies. Regarding the elastic constants, the 2024 T3 aluminum alloy presented an E1 modulus of 71.3 GPa and a Poisson’s ratio of 0.31. The CARALL elastic constants were determined as the solution of a computational optimization problem described in its own language contained in an ANSYS subroutine. It was observed that the main modulus of elasticity and Poisson’s coefficient are close to the values found numerically by the mixing rule (70 GPa and 0.3, respectively).
  • Polymerization depths of conventional and bulk fill composites photoactivated by different methods Articles

    Felipe, Willian Fernando; Oliveira, Weverteon Soares de; Miranda, Milton Edson; Olivieri, Karina Andréa Novaes; Vitti, Rafael Pino; Brandt, William Cunha

    Abstract in English:

    ABSTRACT The aim of this study was to evaluate the depth of cure of conventional (Filtek Z350 and Esthet-X HD) and bulk fill resins composites (Filtek bulk fill flow and SDR) using different photoactivation methods. Samples were made using five disc-shaped matrices (1 mm high and 8 mm central diameter) with interposed polyester strips. The samples were photoactivated using different methods [continuous high-irradiance light (LCA), continuous low-irradiance light (LCB), and soft-start (SS)], maintaining 24 J/cm2 radiant exposure. After 24h, Knoop microhardness test was performed at 5 depths (surface, 1 mm, 2 mm, 3 mm and 4 mm). The Knoop microhardness were analyzed by ANOVA two-way and Tukey’s test (5%). Conventional resins presented the highest results up to 2 mm depth, except for Esthet-X photoactived by LCB, which showed significant lower Knoop hardness from 2 mm depth. Bulk fill resins photoactivated with LCA and SS had the highest results in 4 mm depth. The LCA and SS photoactivation methods produce suitable photoactivation in conventional composites up to 2 mm and bulk fill up to 4 mm depth and the bulk fill composites present higher polymerization depth than conventional composites.
  • Preparation and characterization of absorbent materials based on glycerine and kaolin from caraí - Minas Gerais - Brasil Artigos

    Mendes, Wilker Tagner do Nascimento; Roa, Juan Pedro Bretas; Santos Filho, Edivaldo dos

    Abstract in Portuguese:

    RESUMO A produção de materiais absorvedores de água é um grande desafio para diversas aplicações nos setores agrícola, industrial, de energia, entre outros. No presente trabalho, foram preparados materiais a partir da reação de glicerina, caulim e ácido succínico, tendo ácido sulfúrico como catalisador. Foram utilizadas três razões molares para a mistura caulim:ácido succínico, 1:0, 1:1 e 0:1. Foram preparados materiais também em uma reação com o auxílio do Dean-stark, onde foram preparadas três amostras. Foram produzidos filmes de amido para facilitar a aplicação dos materiais obtidos. O FTIR confirmou a polimerização do ácido succínico com a glicerina, e a ancoragem do mesmo ao caulim. O que também pode ser evidenciado através do DRX. Os testes de absorção mostram que o material produzido pode ser utilizado como material absorvente, absorvendo cerca de 50 g de água por g de amostra.

    Abstract in English:

    ABSTRACT The production of water-absorbing materials is a major challenge for several applications in the agricultural, industrial and energy sectors, among others. In the present work, materials were prepared from the reaction of glycerin, kaolin and succinic acid, with sulfuric acid as a catalyst. Three molar ratios were used for the kaolin mixture: succinic acid, 1: 0, 1: 1 and 0: 1. Materials were also prepared in a reaction with the aid of Dean-stark, where three samples were prepared. Starch films were produced to facilitate the application of the materials obtained. The FTIR confirmed the polymerization of succinic acid with glycerin, and its anchoring to kaolin. What can also be evidenced through the DRX. Absorption tests show that the material produced can be used as an absorbent material, absorbing about 50 g of water per g of sample.
  • Effect of infill pattern in Fused Filament Fabrication (FFF) 3D Printing on materials performance Articles

    Cabreira, Vinicius; Santana, Ruth Marlene Campomanes

    Abstract in English:

    ABSTRACT Fused Filament Fabrication (FFF) is an Additive Manufacturing process popularized in the last decade due to its easiness of use and lower costs. However, despite its increasing popularity, the process itself has several gaps in knowledge, hindering further uses on more advanced objects. Also, the freedom of design allows significant variances in the printed parts, many influencing production and mechanical properties. This work studies the influences of the infill patterns in the mechanical response of printed parts. Using poly (lactic acid) (PLA), a widely used polymer in FFF process, the mechanical responses of parts printed with different infill patterns were analyzed. Rectilinear, Honeycomb, Triangle and Grid patterns were tested on impact resistance and tensile strength. Additionally, samples masses were measured and compared to the mechanical response. Results shown significant differences in the on tested properties. Tensile strength varied from 2.4 to 1.1 MPa, and impact resistance from 3.8 to 1.5 kJ/m2 Also, measured mass was found to be significantly higher on the Honeycomb pattern. Considering mechanical response from both tensile and impact tests along with printed mass, Rectilinear pattern can be considered the most advantageous from the economic point of view.
  • Structural characterization of sustainable geopolymers of steel slag LD and steel slag LF with KOH Artigos

    Pereira, Ana Paula dos Santos; Ramos, Flavio James Humberto Tommasini Viera; Silva, Marcelo Henrique Prado da

    Abstract in Portuguese:

    RESUMO A produção de compósitos à base de produtos derivados de resíduos industriais conduziu o presente estudo, agregando valor aos resíduos de indústrias metalúrgicas e siderúrgicas, o que é revertido em bem à sociedade. Os materiais geopoliméricos podem ser uma das soluções para a destinação dos resíduos industriais gerados por esses setores. O objetivo do estudo foi investigar a relação entre sólido/líquido para produção de corpos-de-prova obtidos pela reação de geopolimerização, utilizando escória de aciaria de convertedor e de panela, ou seja, processo de Linz Donawitz (LD) e de ladle furnace (LF), respectivamente. As amostras dos resíduos foram sintetizadas a partir de uma solução alcalina de hidróxido de potássio 8 M (KOH), nas proporções de 1.2; 1.4 e 1.6 g/v (sólido/líquido). As análises de composição química, estabilidade térmica, microestrutura, quantificação de fases cristalinas e porosidade foram realizadas por espectroscopia de fluorescência de raios X (FRX), espectroscopia de infravermelho por transformada de Fourier (FTIR), análise termogravimétrica (TGA), microscopia eletrônica de varredura com fonte de emissão de campo (MEV-FEG), difratometria de raios X (DRX) e determinação de densidade pelo princípio de Arquimedes. Os resultados indicaram que os geopolímeros obtidos a partir das escórias de aciaria geraram peças com estabilidade dimensional e altas possibilidades de aplicações como materiais de engenharia. Observou-se que a razão solido/líquido foi um ponto importante na síntese dos compósitos, uma vez que as amostras com razão 1.6 apresentaram um aspecto com maior coesão entre as partículas e maiores valores de densificação em relação às amostras com razões 1.2 e 1.4.

    Abstract in English:

    ABSTRACT Production of composites based on derivative products of industrial wastes was presented in this study, which aggregate value to metallurgical, steelmaker wastes of the industries, and this is reversed in beneficial effects to society. Geopolymeric materials can be a solution to industrial residues generated for these sectors. The objective of study was the investigation between a solid/liquid relationship to production of specimens obtained from geopolymerization reaction, using steelmaking slags by process of Linz Donawitz (LD) and ladle furnace (LF), respectively. Samples of the residues were synthesized from an alkaline solution of 8M potassium hydroxide (KOH) in the 1.2, 1.4 and 1.6 g/v proportions (solid/liquid). Analyses of chemical composition, thermal stability, microstructure, amount of crystallinity phases and porosity were evaluated to XRF, FTIR, TGA, SEM-FEG and Archimedes’ principle obtained by reaction geopolymerization through the steelmaking slags (LF and LD), respectively. The results indicated that obtained geopolymers from steelmaking slags developed specimens with dimensional stability and high possibilities of applications, as engineering materials. The results indicate that the solid / liquid ratio is an important point in the geopolymerization process, since the 1.6 samples presented a more cohesive appearance and higher densification values than the 1.2 and 1.4 samples.
  • Structure and properties of starch and flour of four Brazilian sweet potatoes (Ipomoea batatas) cultivars Articles

    Souza, Alana Gabrieli de; Viana, Daniel José Silva; Santos, Alexandre Soares dos; Andrade Júnior, Valter Carvalho de; Rosa, Derval dos Santos

    Abstract in English:

    ABSTRACT Starch is the most natural polymer used in the food and non-food industry. Sweet potato is among the world’s most important, versatile and underexploited food crops; its composition depends on the planting strategy, climatic conditions, cultivar, geographic region, soil quality, and other. The physical-chemical characteristic and functional properties depends also of the amylose, amylopectin ratio and the molecular components of amylose and amylopectin. In this study, the structural and physicochemical properties of starches from four sweet potato genotypes cultivated in Brazil were compared. Starch granules of roots of sweet potato all exhibited oval and irregular shapes with granule sizes ranging from 8 to 30 µm. Amylose contents of roots of sweet potato starches differed from 9.7 to 15.1%. Ratios of 1045/1022 and 1022/995 cm-1 of Fourier transform infrared spectra varied in the range of 0.8114–0.8558 and 0.9046–0.9347, respectively, which means that the genotypes present different structure ordering. Also, the digestibility, swelling power, and solubility showed some differences between the starches, probably due to the differences in amylose and amylopectin contents and granules sizes. The different genotypes showed similar thermal stability. Our study indicated the sweet potato genotypes are greatly influenced the amylose content, structure order, the degree of short-range order, granule size, digestibility, swelling power and solubility of sweet potato genotypes.
  • Synthesis, Characterization and Catalytic Evaluation of Cobalt and Niobium Oxide Solids Modified with Alkaline Earth Metals Articles

    Sena, Maiana Pinheiro; Lima, Simone Pereira de; Carvalho, Luciene Santos; Ruiz, Doris; Ballarini, Adriana; Martins, André Rosa

    Abstract in English:

    ABSTRACT Cobalt and niobium oxide solids modified with alkaline earth metals (Mg, Ca, and Sr) were synthesized and characterized to compare the second element effect on the catalyst structural and chemical properties. The materials were prepared by co-precipitation of cobalt nitrate and niobium oxalate solutions using ammonium hydroxide as precipitating agent. The samples were characterized by XRD, SEM, Ra-man, BET, TPR, ammonia TPD and cyclohexane dehydrogenation reaction (CHD). Results showed that Mg, Ca or Sr addition changed cobalt niobate crystalline structure, leading to alkaline earth metal nio-bates with lower crystallinity. It was observed that Mg, Ca or Sr increased the solids acidity and changed cobalt niobate reduction behavior so that the lowest amount of metallic cobalt was obtained when Mg was incorporated. Modifiers also decreased cobalt niobate dehydrogenation activity. This effect was higher with Mg or Sr addition.
  • Characterization and evaluation of thermoresponsive Ecovio®/PNIPAAm electrospun fibers Artigos

    Pascoalino, Liege Aguiar; Souza, Ricardo Luiz de; Marques, Nívia do Nascimento; Curti, Priscila Schroeder

    Abstract in Portuguese:

    RESUMO Neste trabalho foram obtidas fibras eletrofiadas de blendas de Ecovio® e de poli(N-isopropilacrilamida) de alta massa molar (Ecovio®/PNIPAAm AMM) e de baixa massa molar (Ecovio®/PNIPAAm BMM). As fibras de blendas de Ecovio®/PNIPAAm AMM foram obtidas a partir de soluções com concentração de 10% e nas proporções mássicas de 100/0, 85/15, 70/30, 50/50 e 0/100. As fibras de Ecovio®/PNIPAAm BMM foram obtidas a partir de soluções de Ecovio® a 20% com adição 1%, 2%, 3% ou 10% de PNIPAAM BMM. As fibras eletrofiadas foram caracterizadas pelas técnicas de microscopia eletrônica de varredura (MEV), espectroscopia de infravermelho com transformada de Fourier usando acessório de reflectância atenuada (FTIR-ATR) e de medidas de molhabilidade das superfícies das fibras em função da temperatura. Verificou-se que a adição de PNIPAAm AMM às soluções das blendas de Ecovio®/PNIPAAm favoreceu a eletrofiabilidade das soluções, pois as fibras obtidas apresentaram morfologia esférica e ausência de contas, principalmente a partir da proporção mássica de PNIPAAm AMM de 30%. Além disso, a presença de PNIPAAm AMM tornou as fibras de Ecovio®/PNIPAAm termossensíveis. Esse resultado foi observado a partir das medidas de ângulo de contato da gota de água em função da temperatura, que mostraram que a molhabilidade dessas fibras aumentou em temperaturas abaixo de 32 oC e, em temperaturas acima de 32 oC, a molhabilidade diminuiu. Isso ocorreu devido à transição hidrofílica-hidrofóbica, característica do PNIPAAm na faixa de 32-35 °C. Por outro lado, não foi verificado o mesmo comportamento para as fibras de Ecovio®/PNIPAAm BMM, as quais tiveram uma melhora na molhabilidade com a adição de PNIPAAm BMM, mas não apresentaram o comportamento de termosssensiblidade, provavelmente devido ao menor tamanho das cadeias do PNIPAAm BMM, que não favoreceu a transição hidrofílica-hidrofóbica. Assim, provavelmente apenas as fibras eletrofiadas de Ecovio®/PNIPAAm AMM poderiam vir a apresentar potencial aplicação na área de crescimento/descolamento celular.

    Abstract in English:

    ABSTRACT In this work were obtained electrospun fibers from Ecovio® and poly (N-isopropylacrylamide) high molar mass (Ecovio®/PNIPAAm AMM) and low molar mass (Ecovio®/PNIPAAm BMM) blends. Ecovio®/PNIPAAm AMM blend fibers were obtained from solutions with a concentration of 10% and in the mass ratios of 100/0, 85/15, 70/30, 50/50 and 0/100. Ecovio®/PNIPAAm BMM fibers were obtained from 20% Ecovio® solutions with 1%, 2%, 3% or 10% addition of PNIPAAM BMM. The electrospun fibers were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy using attenuated reflectance enhancement (FTIR-ATR) and fiber surface wettability measurements. The addition of PNIPAAm AMM to the solutions of Ecovio®/PNIPAAm blends favored the electrospinning of the solutions, since the fibers obtained showed spherical morphology and absence of beads, mainly from the 30% mass ratio of PNIPAAm AMM. In addition, the presence of PNIPAAm AMM made Ecovio®/PNIPAAm fibers thermosensitive. This result was observed from water drop contact angle measurements as a function of temperature, which showed that the wettability of these fibers increased at temperatures below 32 ºC and at temperatures above 32 ºC decreased. This was due to the hydrophilic-hydrophobic transition characteristic of PNIPAAm in the 32-35 °C range. On the other hand, the same behavior was not observed for the Ecovio®/PNIPAAm BMM fibers, which had an improvement in wettability with the addition of PNIPAAm BMM, but did not exhibit the thermosensitivity behavior, probably due to the smaller size of the PNIPAAm BMM chains, which did not favor the hydrophilic-hydrophobic transition. Thus, it is likely that only the electrospun Ecovio®/PNIPAAm AMM fibers could have potential application in the area of cell growth/detachment.
  • Effect of adding endocarp residue tucumã (Astrocaryum Aculeatum) in High Impact Polystyrene (HIPS) Artigos

    Silva, Andrey Marcos Pinho da; Margalho, Daniel Esquerdo; Correia Junior, Darbens Silvio

    Abstract in Portuguese:

    RESUMO Este trabalho investigou o efeito da adição de resíduo do endocarpo de tucumã (Astrocaryum Aculeatum) em poliestireno de alto impacto. Foram obtidos corpos de prova por meio do processamento de injeção plástica, para a confecção dos corpos de prova, foram utilizados 2% e 4% em peso de resíduo (CPS2 e CPS4). Foram realizadas caracterizações térmicas (TG e DSC), mecânicas (ensaio de impacto e resistência em módulo de tração) e um estudo com espectrometria de infravermelho (FTIR). Portanto o estudo mecânico indicou uma menor resistência ao impacto e tração dos CPS2 e CPS4 comparados com o material puro (PSAI). O estudo térmico indicou que a estabilidade térmica é aprimorada com a incorporação do resíduo. Por meio da espectrometria de infravermelho (FTIR), foi possível verificar a perda de ligações de monossubstituição. De forma geral, foi possível observar uma boa adesão entre as partículas, notou-se o efeito compatibilizante da lignina residual, as interações resíduo-polímero provocaram alterações nas propriedades térmicas, mecânicas e espectroscópicas nos corpos de prova.

    Abstract in English:

    ABSTRACT This work investigated the effect of adding residue from the tucumã (Astrocaryum Aculeatum) endocarp in high impact polystyrene. Specimens were obtained through plastic injection processing, to make the specimens, 2% and 4% by weight of waste (CPS2 and CPS4) were used. Thermal (TG and DSC), mechanical (impact test and tensile strength tests) and a study with infrared spectrometry (FTIR) were performed. Therefore, the mechanical study indicated a lower impact and traction resistance of CPS2 and CPS4 compared to pure material (HIPS). The thermal study indicated that thermal stability is improved with the incorporation of the residue. Through infrared spectrometry (FTIR), it was possible to verify the loss of monosubstitution bonds. In general, it was possible to observe a good adhesion between the particles, the compatibilizing effect of the residual lignin was noted, the residue-polymer interactions caused changes in the thermal, mechanical and spectroscopic properties in the specimens.
  • Reuse of waste printed circuit boards as fillers in polypropylene composites Artigos

    Schneider, Eduardo Luis; Grassi, Guilherme Dias; Amico, Sandro Campos; Chaves, Rodrigo de Andrade; Mazzuca, Daniel Claro; Robinson, Luiz Carlos

    Abstract in Portuguese:

    RESUMO As placas de circuito impresso (PCIs) são as partes mais valiosas dos resíduos eletrônicos, pois possuem uma considerável quantidade de metais com potencial de recuperação. Processos de reciclagem com o intuito de recuperar metais de PCIs têm despertado interesse ultimamente. Contudo, uma fração destes resíduos não é completamente aproveitada e tem destino incerto, como ocorre para a fração não-metálica e o pó gerados durante os processos de recuperação de metais. O foco deste estudo foi o emprego do pó gerado nos processos de cominuição mecânica, separação granulométrica, magnética e eletrostática de PCIs controladoras e indicadoras de temperatura de câmaras frias, para obter compósitos de matriz de polipropileno (PP) com diferentes teores de pó de PCIs, 5, 10 e 20% em massa. Os materiais foram pesados, misturados, moldados por injeção e posteriormente caracterizados por ensaios de tração, dureza Shore D, espectroscopia de infravermelho, análise termogravimétrica e microscopia eletrônica de varredura. Os resultados dos ensaios de tração e dureza indicaram propriedades levemente superiores às do PP puro, exceto para a deformação na ruptura, que foi reduzido em até 2,7 vezes para a amostra com 20% de resíduo. O desenvolvimento de compósitos utilizando o pó de PCIs se mostrou viável em aplicações onde as propriedades resistência à tração, rigidez e dureza são determinantes, mesmo para um elevado teor de resíduo (20%) agregado.

    Abstract in English:

    ABSTRACT Printed Circuit Boards (PCBs) are the most valuable parts of e-waste because they have a considerable amount of metals with recovery potential. Recycling processes aimed at recovering metals from PCBs have aroused great interest recently. However, there is a fraction of this waste that is not utilized and has uncertain destination, e.g. the non-metallic fraction and the dust generated during metal recovery processes. The focus of this study was to employ the powder generated in the mechanical comminution, granulometric, magnetic and electrostatic separation processes of controller and temperature indicator PCBs of cold rooms to obtain polypropylene (PP) matrix composites with distinct PCBs powder content, 5, 10 and 20% in weight. The sample was collected during the mechanical comminution processes. The materials were weighed, mixed, injection molded and later characterized using tensile tests, Shore D hardness, infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. Results of the tensile and hardness tests showed properties slightly superior to pure PP, except for strain at break, which was reduced up to 2.7 times for the sample with 20% of residue. In all, the development of composites using the powder of PCBs was considered feasible for applications where tensile strength, stiffness and hardness are important, even for a large amount of residue added (20%).
  • Determination and analysis of fracture toughness on fiber-metal laminates composite materials Artículos

    Asta, Eduardo; Cambiasso, Francisco; Balderrama, Juan; Ríos, Juan

    Abstract in Spanish:

    RESUMEN La determinación de la tenacidad a la fractura en materiales compuestos híbridos, laminados fibra-metal, FML (Fiber Metal Laminates) resulta muy importante para poder realizar un análisis de integridad estructural que permita estimar la tolerancia al daño y la resistencia remanente del material frente a la propagación de una fisura. Dicha evaluación debe realizarse tanto en estructuras aeronáuticas como navales que utilizan compuestos FML del tipo CARALL (CArbon Reinforced Aluminum Laminates). En este trabajo se presenta la determinación experimental de la tenacidad a la fractura en términos de los parámetros J y CTOD utilizando probetas compactas C(T) en dos tipos de material compuesto laminado con láminas de aluminio 6061-T0 en un caso y láminas de aluminio 1050 en otro y fibras de carbono NCT-301, embebidas en resina epoxi, para ambos materiales. Los resultados indican que la adaptación de las técnicas de ensayo de tenacidad a la fractura elasto-plástica, aplicando la norma ASTM E1820, son aceptables para la determinación de la tenacidad a la fractura J en compuestos del tipo CARALL. Dicha caracterización es necesaria para el desarrollo de un programa de evaluación de daño tolerable tanto a nivel de diseño como para un análisis de significación de defectos a partir de resultados de ensayos no destructivos sobre este tipo de materiales compuestos.

    Abstract in English:

    ABSTRACT The determination of fracture toughness in hybrid composite materials, fiber-metal laminates(FML) is very important in order to make a structural integrity analysis that allows estimating damage tolerance and the remaining strength of the material against crack propagation. This evaluation should be carried out in both aeronautical and naval structures that use FML composites, CARALL type (CArbon Reinforced Aluminum Laminates). This paper presents the experimental determination of fracture toughness in terms of parameters J and CTOD using compact C (T) specimens in two types of composite material laminated with 6061-T0 aluminum sheets in one case and sheets 1050 aluminum in another and carbon fibers NCT-301, embedded in epoxy resin, for both materials. The results indicate that the use of the elasto-plastic fracture toughness test techniques, applying ASTM E1820, are acceptable for the determination of the fracture toughness J in CARALL type materials. Such characterization is necessary for the development of a tolerable damage assessment program both at the design level and for a defect significance analysis based on the results of non-destructive tests on this type of composite materials.
  • Analysis of epoxy based paint efficiency in expanded clay lightweight concrete protection of sulfuric acid attack Artigos

    Abreu, Felipe de Souza; Ribeiro, Carmen Couto; Pinto, Joana Darc Silva; Oliveira, Danielle Meireles; Ribeiro, Sidnea Eliane Campos; Figueiredo, Ênio José Pazini

    Abstract in Portuguese:

    RESUMO Este trabalho tem como objetivo realizar uma análise da eficiência da tinta de base epoxídica utilizada como proteção superficial do concreto leve com argila expandida submetido ao ataque por ácido sulfúrico (H2SO4). Ataques ácidos externos podem promover reações expansivas e a degradação acelerada, comprometendo assim a durabilidade das estruturas de concreto leve. Dentre as proteções desenvolvidas, as tintas têm um importante destaque, por possuírem boa aderência à superfície do concreto, serem resistentes ao intemperismo e à fotodegradação, além de apresentar boa estabilidade química. O desempenho da tinta de base epoxídica foi avaliado por meio de inspeção visual e de ensaios de resistência à compressão, absorção de água e perda de massa do concreto antes e após ataque químico. A avaliação por inspeção visual demonstrou que os corpos de prova de concreto leve com proteção superficial epoxídica apresentaram uma diminuição da perda de coesão da pasta causada pelo ataque. Os resultados dos ensaios de absorção de água, de perda de massa e de resistência mecânica demonstraram o bom desempenho da tinta de base epoxídica, impedindo a penetração do agente agressivo nos concretos protegidos. A pesquisa permite concluir que a proteção epoxídica reduz significativamente o impacto causado pelo ácido sulfúrico ao concreto e que pode garantir a durabilidade das estruturas confeccionadas com concretos leves de argila expandida.

    Abstract in English:

    ABSTRACT The purpose of this study is to analyze the efficiency of epoxydic base paint used as a protective coating on expanded clay lightweight concrete under sulfuric acid (H2SO4) attack. External attacks can promote expansions and accelerated degradation, reducing the concrete durability. Developed protections, such as paints have an important performance result, because they have good adhesion to the concrete surface, weathering and photodegradation resistant, besides provide a good chemical stability. The performance of epoxydic paint was assessed through visual inspection, compressive strength test, water absorption and mass losses before and after chemical attack. The visual inspection demonstrated that the epoxy-coated lightweight concrete specimens had a clear reduction in the loss of cohesion of the paste caused by the attack. The teste results of regarding water absorption, mass loss and mechanical strength showed the good performance of the epoxydic base paint, preventing the penetration of the aggressive agent on protected concretes. This research shows that epoxydic protection reduces the impact of external acid attacks on concrete and can improve the durability of expanded clay lightweight concrete structures.
  • Evaluation of the physical, chemical and mechanical properties of starch/PVA/bentonite clay films modified with glycidyl methacrylate Artigos

    Carvalho Neto, Alberto Gonçalves Vieira de; Santos, Dayse Iara dos; Rissato, Sandra Regina; Saeki, Margarida Juri; Favaro, Silvia Luciana; Radovanovic, Eduardo; Pellosi, Diogo Silva

    Abstract in Portuguese:

    RESUMO Filmes constituídos por amido de mandioca, álcool polivinílico (PVA) e argila Bentonita (BNT) e glicerol como plastificante foram obtidos utilizando o método casting. A fim de aumentar a compatibilidade dos polímeros ao mineral e sua hidrofobicidade, estes foram posteriormente modificados quimicamente utilizando metacrilato de glicidila (GMA) para a substituição dos grupamentos hidroxilas por vinílicos. Este procedimento gerou filmes com excelente estabilidade a sorção de água e permeabilidade ao vapor de água 15% menor quando comparados coms os filmes sem modificação química. Adicionalmente, esta estratégia também resultou na melhora de 25% na resistência a tração, mantendo o mesmo módulo de Young mas, com uma leve diminuição na estabilidade térmica (início de degradação 14ºC menor). A adição da argila BNT gera filmes compósitos com propriedades, mecânicas, térmicas e físicas diferenciadas, contudo há uma dependência entre a quantidade de reforço e a distribuição estrutural das lamelas de argila na matriz. As modificações químicas foram comprovadas por RMN H1, FTIR, DRX e os filmes foram caracterizados por DRX, sorção e permeabilidade a água, ensaios mecânicos (tração, alongamento e módulo de Young) e TGA. A utilização de 1% m/m deste reforço gera compósitos com BNT estruturalmente esfoliado, independentemente da prévia modificação com metacrilato de glicidila. Já a formulação com 5% m/m gerou filmes compósitos intercalados. Qualquer outro teor de reforço exibe estruturas lamelares aglomeradas (empacotadas). Destaca-se que nas formulações reforçadas com 1% de argila, houve melhora em cerca 30% na resistência a tração com permeabilidade a água 60% menor, para cargas maiores de argila. Estes fatos apontam que as modificações propostas neste trabalho geraram propriedades promissoras para a produção de materiais de embalagem biodegradáveis.

    Abstract in English:

    ABSTRACT Films constituted by cassava starch, polyvinyl alcohol (PVA) and Bentonite clay (BNT) and glycerol as plasticizer were obtained using the casting method. In order to increase the compatibility of the polymers with the mineral and its hydrophobicity, they were subsequently chemically modified by replacing the hydroxyl groups with vinyls using glycidyl methacrylate (GMA). This procedure generated films with excellent water sorption stability and 15% lower water vapor permeability. This strategy also resulted in a 25% improvement in tensile strength, maintaining the same Young’s modulus and slight decrease in thermal stability (onset of degradation 14 ° C lower). The addition of BNT clay generates composite films with different mechanical, thermal and physical properties, however, there is a dependence between the amount of reinforcement and the structural distribution of the clay lamellae in the matrix. The chemical modifications were confirmed by H 1 NMR, FTIR, XRD and the films were characterized by XRD, sorption and water permeability, mechanical tests (traction, stretching and Young’s modulus) and TGA. The use of 1% w / w of this reinforcement generates composites with structurally exfoliated BNT, independently of the previous modification with glycidyl methacrylate. The formulation with 5% m / m generated intercalated composite films. Any other reinforcing content exhibits agglomerated (packaged) lamellar structures. It is noteworthy that in the formulations reinforced with 1% clay, there was an improvement of about 30% in tensile strength with 60% lower water permeability, for higher clayey loads. These facts indicate that the modifications proposed in this work have generated promising properties for the production of biodegradable packaging materials.
  • Comparative analysis of depositions of graphene oxide films by ultrasonic and conventional spray Artigos

    Lima, Andreza Menezes; Santos, Thebano Emílio de Almeida; Medeiro, Rodrigo Amaral de; Cruz, Leila Rosa de Oliveira; Pinheiro, Wagner Anacleto

    Abstract in Portuguese:

    RESUMO A técnica de deposição de filmes por spray destaca-se por sua versatilidade, simplicidade e eficiência. Neste trabalho, dois equipamentos de spray distintos foram empregados para produção de filmes de óxido de grafeno: o primeiro, um equipamento industrial para produção por método ultrassônico e o segundo, uma adaptação realizada com um aerógrafo, um solenoide, um circuito elétrico e um programa em linguagem C++, denominado de método convencional. Os filmes obtidos foram caracterizados com respeito à espessura, resistividade elétrica, transmitância e morfologia. As amostras produzidas pelo método convencional apresentaram menores espessuras e maiores transmitâncias, sendo, desse modo, mais adequadas para aplicações optoeletrônicas. Já as menores resistências de folha foram obtidas pelo método de spray ultrassônico. A morfologia dos filmes aponta melhor uniformidade para as amostras obtidas por meio da técnica ultrassônica. A análise comparativa dos resultados indicou que o equipamento convencional, apesar de ser muito mais simples e de baixo custo, foi capaz de alcançar resultados tão satisfatórios quanto os obtidos em um equipamento industrial de spray ultrassônico. A grande vantagem do equipamento industrial está na possibilidade de produção de várias amostras simultaneamente, enquanto o convencional adaptado tem como benefício a rapidez, possibilidade de deposição com folhas de óxido de grafeno maiores e acessibilidade da produção e operação do sistema.

    Abstract in English:

    ABSTRACT The spray technique for thin film deposition stands out for its versatility, simplicity and efficiency. In this work, two different spray techniques, conventional and ultrasonic, were used for the production of graphene oxide films, the first one was an industrial equipment for ultrasonic spray production and the second, an adaptation performed with an airbrush, a solenoid, a circuit electric and a program in C ++ language, called conventional spray. The films obtained were characterized with respect to thickness, electrical resistivity, transmittance and morphology. The samples produced by the conventional method presented thicknesses and transmittances more suitable for electronic applications, since the smaller sheet resistances were obtained by the ultrasonic spray method. The morphology of the films shows a better uniformity for the samples obtained by means of the ultrasonic spray technique. The comparative analysis of the results indicated that the conventional spray equipment, although much simpler and low cost, was able to achieve results as satisfactory as those obtained in an industrial ultrasonic spray equipment. The great advantage of the industrial equipment is the possibility of producing several samples simultaneously, while the conventional spray adapted has the benefit of speed, deposition possibility with larger graphene oxide sheets and accessibility of the production and operation of the system.
  • ERRATA Errata

Laboratório de Hidrogênio, Coppe - Universidade Federal do Rio de Janeiro, em cooperação com a Associação Brasileira do Hidrogênio, ABH2 Av. Moniz Aragão, 207, 21941-594, Rio de Janeiro, RJ, Brasil, Tel: +55 (21) 3938-8791 - Rio de Janeiro - RJ - Brazil
E-mail: revmateria@gmail.com