Análise comparativa entre propriedades mecânicas, termofísicas e geométricas de tijolos produzidos pelos fornos caieira e abóbada

In the State of Rio Grande do Norte potteries are distributed in several counties in the four meso, which are: West Potiguar, Center Potiguar, Agreste Potiguar and East Portiguar. The ceramics, mostly, are responsible for products used in construction as bricks, tiles and white brick and wood used as fuel. This paper had a primary focus in the region of Seridó. The furnaces in this region, used to manufacture bricks are configured Caieira and Valt, in most of them using principles rustic, usually operated in an empirical way, using principles of control rather primitive, predominantly visual control. The focus of this study was to analyze the differences in the thermophysical, mechanical and geometric characteristics of bricks produced by Caieira and vault furnaces, using the NBR 15720 and the evaluation of energy efficiency in both furnaces. Thermophysical characteristics were analyzed through tests to determine the water absorption obtained from the difference between dry mass and wet mass of the sample and analysis of the thermal gradient, the mechanical characteristics from determination of the compressive strength of ceramic brick popularly known as bricks and also analyzed the geometrical characteristics of the bricks in order to verify the homogeneity of manufacturing. The tests showed that the energy difference of the two furnaces is not considered responsible for a significant difference in the properties of the products

Estudo das propriedades mecânicas de biocompósitos de polipropileno reforçados com fibras naturais

This research presents an approach to the addition of curauá fibers and licuri fibers in a polypropylene resin matrix, such as an alternative proposal to reinforce the polymeric composites. Fiber content of 0 %, 5 %, 10 %, and 20% were analyzed for verification of their mechanical properties comparing them, inclusive with the properties of polypropylene. The grainulated biocomposites had been prepared in an extrusora. The test bodies had been molded by injection and submitted to the mechanical essays uniaxial traction, flexion on three points, impact, in addition to thermal tests (HDT). These biocomposites had been also subjected the essay physicist-chemistry index of fluidity (IF). It was observed that the biocomposites of PP with 20% curauá, obtained bigger increase in the modulus of elasticity and a bigger reduction in the resistance to the impact. In the mechanical behavior, for all the biocomposites, these were increases in values of the limit of drainage and tension of rupture, when tested by uniaxial traction, as they added the fibers. Another important point was the increase of the resistance the flexion. It was also noted that the addition of fibers reduced the thermal degradation of the mixture natural fibers / polypropylene.

Avaliação do comportamento tribológico de compósitos poliéster/fibra de vidro utilizando resíduos de poliéster/fibra de vidro e carbonato de cálcio como carga

The use of composite materials and alternative is being increased every day, as it becomes more widespread awareness that the use of renewable and not harmful to the environment is part of a new environmentally friendly model. Since its waste (primarily fiberglass) can not be easily recycled by the difficulty that still exists in this process, since they have two phases mixed, a polymeric matrix thermoset difficult to recycle because it is infusible and phase of fiber reinforcements. Thermoset matrix composites like Polyester + fiberglass pose a threat due to excessive discharge. Aiming to minimize this problem, aimed to reuse the composite Polyester + fiber glass, through the wastes obtained by the grinding of knifes and balls. These residues were incorporated into the new composite Polyester/Fiberglass for hot compression mold and compared tribological to composites with filler CaCO3, generally used as filler, targeting a partial replacement of CaCO3 by such waste. The composites were characterized by thermal analysis (TGA, DSC and DMA), by the surface integrity (roughness determination, contact angle and surface energy), mechanical properties (hardness) and tribological tests (wear and coefficient of dynamic friction) in order to evaluate the effect of loads and characterize these materials for applications that can take, in the tribological point of view since waste Polyester + fiberglass has great potential for replacement of CaCO3

Estudo da fibra de coco como reforço em tijolo de solocimento

To take care of to the demand of the new constructions in the low income communities and to develop the production of a strengthened alternative brick with staple fibers of coconut, capable to contribute mainly with the recycling of the green and mature coconut in the urban and agricultural lexes, this research was developed, to confection bricks of soil-cement with coconut fiber. Ecologically correct material and of low cost, since the greenhouse use of or oven for burning will be manufactured without. The study it presents a set of tables and graphs that prove good indices found in the values of the density, water absorption, axial compressive strength and isolation term acoustics, with evidential results that make possible the production in industrial character with press mechanics or the place of the workmanship with manual form. The preparation of coconut staple fibers was made of natural form without use of chemical products not to deprive of characteristics the properties mechanical physicist-chemistries and of the same ones. The sixty bricks produced in simple and manual press had been carried through in four lots of fifteen units. The mixture of aggregates was made in four different traces composites for: ground erinaceous, cement, fiber of dry coconut and water; the bricks had been compact in the press and cured in natural way under an area covered during the minimum time of seven days

Estudo comparativo das propriedades mecânicas em compósitos da fibra modal e poliester

In the present work, three composites with distinct reinforcements (polyester, modal e polyester + modal), all if a unsaturated orthophthalic polyester resin as matrix were used, in order to conduct a comparative study by mechanical tests and water absorption. The fibre mats were prepared in a mat preparatory by immersion developed in the Textile Engineering Laboratory. The composites were manufactured using a closed mould process by compression using an unsaturated orthophthalic polyester resin as matrix and 1% MEK (methyl ethyl ketone peroxide) as an initiator. In each composite twelve samples with the dimensions of 150x25x3 mm were cut randomly for the mechanical analysis (tension x extension, three points bending and water absorption and Scanning Electron Micsroscopy). The mechanical tests were carried out in the Laboratório de Metais e Ensaios Mecânicos UFRN . All the analyses were carried out according to the ASTM norms. The resultant samples from the mechanical analysis were subjected for the Scanning Electron Microscopy analysis. Based on the results obtained, it was observed that the reinforced composite with two fibres (modal + polyester) presented better results in comparison to the other two composites both in the tension/extension as well on the three point bending tests. In the water absorption test, it was possible to observe an equilibrium in the water absorption by the modal and polyester composite, due to the union of the two fibres. In the SEM images, the regions of rupture in the composites as well as the adsorption between the fiber and the matrix could be observed

Caracterização e análise das propriedades da fibra de Macambira (Bromelia Laciniosa)

Concern for the environment and the exploitation of natural resources has motivated the development of research in lignocellulosic materials, mainly from plant fibers. The major attraction of these materials include the fact that the fibers are biodegradable, they are a renewable natural resource, low cost and they usually produce less wear on equipment manufacturing when compared with synthetic fibers. Its applications are focused on the areas of technology, including automotive, aerospace, marine, civil, among others, due to the advantageous use in economic and ecological terms. Therefore, this study aims to characterize and analyze the properties of plant fiber macambira (bromelia laciniosa), which were obtained in the municipality of Ielmo Marino, in the state of Rio Grande do Norte, located in the region of the Wasteland Potiguar. The characterization of the fiber is given by SEM analysis, tensile test, TG, FTIR, chemical analysis, in addition to obtaining his title and density. The results showed that the extraction of the fibers, only 0.5% of the material is converted into fibers. The results for title and density were satisfactory when compared with other fibers of the same nature. Its structure is composed of microfibrils and its surface is roughened. The cross section has a non-uniform geometry, therefore, it is understood that its diameter is variable along the entire fiber. Values for tensile strength were lower than those of sisal fibers and curauá. The degradation temperature remained equivalent to the degradation temperatures of other vegetable fibers. In FTIR analysis showed that the heat treatment may be an alternative to making the fiber hydrophobic, since, at high temperature can remove the hemicellulose layer, responsible for moisture absorption. Its chemical constitution is endowed with elements of polar nature, so their moisture is around 8.5% which is equivalent to the percentage of moisture content of hydrophilic fibers. It can be concluded that the fiber macambira stands as an alternative materials from renewable sources and depending on the actual application and purpose, it may achieve satisfactory results

Influência da umidade nas propriedades mecânicas dos compósitos poliméricos híbridos (sisal/ vidro)

This study aims to evaluate the mechanical properties of polymer matrix composites reinforced with sisal fabric bidirectional tissue (Agave sisalana,) and E-glass fibers, containing the following configuration: a polymer matrix hybrid composite (Polyester Resin orthophalic) reinforced with three (3) layers of glass fibers and alternating-2 (two) layers of bidirectional sisal fabric, and finally a composite of polymer matrix reinforced with five (5) layers of glass fiber mat-type E. For this purpose as first step, the preparation of by sisal, since they are not on the market. The composites were made by manual lamination (Hand lay-up) and evaluated for tensile properties and three point bending both in the dry, and wet conditions aswele as immersed in oil. Macroscopic and microscopic characteristics of the materialsweve awalysed, after the completion of the mechanical tests. After the studies, it was proven that the sisal fiber decreases the tensile stiffness of the material above 50% for both situations studied the tensile strength of the material decreases by approximately 40% for the cases mentioned, and when compared to the specific strength stiffness values drop to 14.6% and 29.02% respectively for the dry state only. Constants for bending the values were are to approximately 50% to 25% for strength and stiffness of the material for the cases dry, wet and immersed in oil. Under the influence of tension fluids do not interfere in the stiffness of the material for the bending tests, the same does not occur with the resistance, and these values are modified only in the cases stiffness and flexural strength

Utilização do éster de soja como biolubrificante

The lubricants found in the market are of mineral or synthetic origin and harm to humans and the environment, mainly due to their improper discard. Therefore industries are seeking to develop products that cause less environmental impact, so to decrease mainly, operator aggression the Cutting Fluids became an emulsion of oil / water or water / oil. However, the emulsion was not considered the most suitable solution for environmental question, therefore the search for biodegradable lubricants and which no are toxic continues and so vegetable oils are seen, again, as a basis for the production of lubricants. The biggest problem with these oils is their oxidative instability that is intensified when working at high temperatures. The process transesterification decreases the oxidation, however changes some physical and chemical properties. Therefore soybean oil after the transesterification process was subjected to tests of density, dynamic viscosity, kinematic viscosity which is calculated from two parameters mentioned, flash point and acidity. Besides the physico-chemical test the soybean oil was subjected to a dynamic test in a tribometer adapted from a table vise, whose induced wear was the adhesive and ultimately was used as cutting fluid in a process of turning in two different materials, steel 1045 and cast iron. This latter test presented results below the mineral cutting fluid which it was compared in all tests, already in other experiments the result was satisfactory and other experiments not, so that chemical additives can be added to the oil analyzed to try equate all parameters and so formulate a biolubrificante not toxic to apply in machining processes of metalworking industry

Morfologia e propriedades mecânicas da fibra de sisal unidirecional e em sobreposição de compósito com resina epóxi

The composites manufactured with long fibres aligned in a single direction, and overlay has been shown to have better performance than the short fibers randomly distributed. In particular, the lignocellulosic fibers extracted from the sisal leaves, used in conjunction with the epoxy resin has attracted the attention of many researchers because the final properties of the system formed. In this work composites based on epoxy resin reinforced with sisal fibers were manufactured. The sisal fibres were treated with an alkaline solution of 0.06 mol/l NaOH. The treated, and untreated fibres were subjected to tension x extension tests. The composites were manufactured in the "Lossy" mold with the specifications of the samples to be produced (300x20x4 mm). The tension tests were carried out in accordance with the ASTM standards 3039 (for the composite aligned in a single direction) and ASTM D5573 (for composites in overlay), three point bending tests were performed according to ASTM D790. Analyzing the results of the tests of tension and three point bending tests, it was observed that the composites with the configuration of overlapping had the better elastic module in both tests. As to the maximum resistance to tension, the best result was the composites aligned in a single direction. Tests of absorption of water and micrographs are in progress

Estudo das propriedades físico-químicas do biodiesel e suas influências na deterioração dos elastômeros aplicados no sistema de injeção dos motores diesel

The biodiesel use has become important due to its renewable character and to reduce environmental impacts during the fuel burning. Theses benefit will be valid if the fuel shows good performance, chemistry stability and compatibility with engines. Biodiesel is a good fuel to diesel engines due to its lubricity. Then, the aimed of this study was to verify the physicalchemistry properties of biodiesel and their correlations with possible elastomers damage after biodiesel be used as fuel in an injection system. The methodology was divided in three steps: biodiesels synthesis by transesterification of three vegetable oil (soybean, palm and sunflower) and their physical-chemistry characterization (viscosity, oxidative stability, flash point, acidity, humidity and density); pressurized test of compatibility between elastomers (NBR and VITON) and biodiesel, and the last one, analyze of biodiesels lubricity by tribological test ball-plan( HFRR). Also, the effect of mixture of biodiesel and diesel in different concentrations was evaluated. The results showed that VITON showed better compatibility with all biodiesel blends in relation to NBR, however when VITON had contact with sunflower biodiesel and its blends the swelling degree suffer higher influences due to biodiesel humidity. For others biodiesels and theirs blends, this elastomer kept its mechanical properties constant. The better tribological performance was observed for blends with high biodiesel concentration, lower friction coefficient was obtained when palm biodiesel was used. The main mechanisms observed during the HFRR tests were abrasive and oxidative wear

Competitividade de diferentes atmosferas de plasma sobre as propriedades hidrofílicas em tecidos de polilático

Os polímeros biodegradáveis, como o poliácido láctico (PLA) apesar de consolidado nos campos farmacêuticos, médico e biomédico como biomateriais úteis para aplicações variadas, porém, depende da necessidade de funcionalizar a sua superfície estudando suas propriedades tais como hidrofilidade e hidrofobicidade favorecendo a interação do polímero com os materiais de aplicação farmacêutica, médica e biomédica. Este trabalho tem como objetivo produzir um material com características diferentes em cada um de seus lados, sendo um lado hidrofílico e o outro hidrofóbico. O substrato têxtil utilizado neste estudo foi um tecido de malha de composição 100% PLA que é biodegradável e biocompatível, o que possibilita sua aplicação na área biomédica. Para modificação superficial foi utilizado o tratamento a plasma de baixa pressão. A técnica de modificação de superfície por plasma foi escolhida por ser uma tecnologia limpa, anticorrosiva e não tóxica ao contrario de muitos processos químicos convencionais utilizados na indústria têxtil, além disso, não afeta as propriedades de massa do substrato. Neste estudo, um lado da superfície do substrato foi tratado com plasma oxigênio, argônio e nitrogênio, para o trabalho de melhoria da hidrofilidade da superfície e metano para a hidrofobicidade da amostra. A espectroscopia de emissão ótica (OEE) foi utilizada para fazer o diagnóstico das espécies do plasma durante o tratamento. Após o tratamento a plasma as amostras foram caracterizadas por medidas de ângulo de contato, microscopia eletrônica de varredura (MEV), Espectroscopia de fotoelétrons de raios-X (XPS), Infravermelho com Transformada de Fourier (FTIR) de reflexão total atenuada (ATR), medidas da área de espalhamento do líquido e arraste vertical. Onde foi caracterizado o aumento e diminuição da molhabilidade das amostras tratadas por plasma bem como as variáveis que contribuíram para tal efeito. O tratamento das amostras de PLA com O2 + CH4 apresenta comportamento hidrofílico no lado tratado com O2, apresentando aumento de rugosidade e grupos funcionais e no lado tratado com CH4, apresentando a formação de um filme polimérico formado sobre a superfície da amostra. O tratamento com N2 + CH4 apresenta comportamento hidrofóbico, porém com variações no fluxo do CH4 tem-se um controle da molhabilidade na superfície das amostras, podendo ir de hidrofóbico a hidrofílico, neste tratamento as amostras apresentaram pequenas diferenças de molhabilidade entre os lados tratados com plasma de N2 e com plasma de CH4

Avaliação mecânica e microestrutural de compósitos de poliéster com adição de cargas minerais e resíduos industriais

With the current growth in consumption of industrialized products and the resulting increase in garbage production, their adequate disposal has become one of the greatest challenges of modern society. The use of industrial solid residues as fillers in composite materials is an idea that emerges aiming at investigating alternatives for reusing these residues, and, at the same time, developing materials with superior properties. In this work, the influence of the addition of sand, diatomite, and industrial residues of polyester and EVA (ethylene vinyl acetate), on the mechanical properties of polymer matrix composites, was studied. The main objective was to evaluate the mechanical properties of the materials with the addition of recycled residue fillers, and compare to those of the pure polyester resin. Composite specimens were fabricated and tested for the evaluation of the flexural properties and Charpy impact resistance. After the mechanical tests, the fracture surface of the specimens was analyzed by scanning electron microscopy (SEM). The results indicate that some of the composites with fillers presented greater Young s modulus than the pure resin; in particular composites made with sand and diatomite, where the increase in modulus was about 168 %. The composites with polyester and EVA presented Young s modulus lower than the resin. Both strength and maximum strain were reduced when fillers were added. The impact resistance was reduced in all composites with fillers when compared to the pure resin, with the exception of the composites with EVA, where an increase of about 6 % was observed. Based on the mechanical tests, microscopy analyses and the compatibility of fillers with the polyester resin, the use of industrial solid residues in composites may be viable, considering that for each type of filler there will be a specific application

Propagação de danos: importância da atualização dinâmica, efeitos da diluição e propriedades termodinâmicas

Neste trabalho investigamos aspectos da propagação de danos em sistemas cooperativos, descritos por modelos de variáveis discretas (spins), mutuamente interagentes, distribuídas nos sítios de uma rede regular. Os seguintes casos foram examinados: (i) A influência do tipo de atualização (paralela ou sequencial) das configurações microscópicas, durante o processo de simulação computacional de Monte Carlo, no modelo de Ising em uma rede triangular. Observamos que a atualização sequencial produz uma transição de fase dinâmica (Caótica- Congelada) a uma temperatura TD ≈TC (Temperatura de Curie), para acoplamentos ferromagnéticos (TC=3.6409J/Kb) e antiferromagnéticos (TC=0). A atualização paralela, que neste caso é incapaz de diferenciar os dois tipos de acoplamentos, leva a uma transição em TD ≠TC; (ii) Um estudo do modelo de Ising na rede quadrada, com diluição temperada de sítios, mostrou que a técnica de propagação de danos é um eficiente método para o cálculo da fronteira crítica e da dimensão fractal do aglomerado percolante, já que os resultados obtidos (apesar de um esforço computacional relativamente modesto), são comparáveis àqueles resultantes da aplicação de outros métodos analíticos e/ou computacionais de alto empenho; (iii) Finalmente, apresentamos resultados analíticos que mostram como certas combinações especiais de danos podem ser utilizadas para o cálculo de grandezas termodinâmicas (parâmetros de ordem, funções de correlação e susceptibilidades) do modelo Nα x Nβ, o qual contém como casos particulares alguns dos modelos mais estudados em Mecânica Estatística (Ising, Potts, Ashkin Teller e Cúbico)

Propriedades físicas de bicamadas magnéticas

The magnetic order of bylayers composed by a ferromagnetic film (F) coupled with an antiferromagnetic film (AF) is studied. Piles of coupled monolayers describe the films and the interfilm coupling is described by an exchange interaction between the magnetic moments at the interface. The F has a cubic anisotropy while the AF has a uniaxial anisotropy. We analyze the effects of an external do magnetic field applied parallel to the interface. We consider the intralayer coupling is strong enough to keep parallel all moments of the monolayer an then they are described by one vector proportional to the magnetization of the layer. The interlayer coupling is represented by an exchange interaction between these vectors. The magnetic energy of the system is the sum of the exchange. Anisotropy and Zeeman energies and the equilibrium configuration is one that gives the absolute minimum of the total energy. The magnetization of the system is calculated and the influence of the external do field combined with the interfilm coupling and the unidirectional anisotropy is studied. Special attention is given to the region near of the transition fields. The torque equation is used to study dynamical behavior of these systems. We consider small oscillations around the equilibrium position and we negleet nonlinear terms to obtain the natural frequencies of the system. The dependence of the frequencies with the external do field and their behavior in the phase transition region is analized

Obtenção de polímeros graftizados de quitosana e estudo das propriedades físico-químicas para aplicação na indústria do petróleo

Chitosan is a biopolymer derived from the shells of crustaceans, biodegradable, inexpensive and renewable with important physical and chemical properties. Moreover, the different modifications possible in its chemical structure generate new properties, making it an attractive polysaccharide owing to its range of potential applications. Polymers have been used in oil production operations. However, growing concern over environmental constraints has prompted oil industry to search for environmentally sustainable materials. As such, this study sought to obtain chitosan derivatives grafted with hydrophilic (poly(ethylene glycol), mPEG) and/or hydrophobic groups (n-dodecyl) via a simple (one-pot) method and evaluate their physicochemical properties as a function of varying pH using rheology, small-angle Xray scattering (SAXS), dynamic light scattering (DLS) and zeta potential. The chitosan derivatives were prepared using reductive alkylation under mild reaction conditions and the chemical structure of the polymers was characterized by nuclear magnetic resonance (1H NMR) and CHN elemental analysis. Considering a constant mPEG/Chitosan molar ratio on modification of chitosan, the solubility of the polymer across a wide pH range (acidic, neutral and basic) could only be improved when some of the amino groups were submitted to reacetylation using the one-pot method. Under these conditions, solubility is maintained even with the simultaneous insertion of n-dodecyl. On the other hand, the solubility of derivatives obtained only through mPEG incorporation using the traditional methodology, or with the ndodecyl group, was similar to that of its precursor. The hydrophilic group promoted decreased viscosity of the polymer solutions at 10 g/L in acid medium. However, at basic pH, both viscosity and thermal stability increased, as well as exhibited a pronounced pseudoplastic behavior, suggesting strong intermolecular associations in the alkaline medium. The SAXS results showed a polyelectrolyte behavior with the decrease in pH for the polymer systems. DLS analyses revealed that although the dilute polymer solutions at 1 g/L and pH 3 exhibited a high density of protonated amino groups along the polymer chain, the high degree of charge contributed significantly to aggregation, promoting increased particle size with the decrease in pH. Furthermore, the hydrophobic group also contributed to increasing the size of aggregates in solution at pH 3, whereas the hydrophilic group helped reduce their size across the entire pH range. Nevertheless, the nature of aggregation was dependent on the pH of the medium. Zeta potential results indicated that its values do not depend solely on the surface charge of the particle, but are also dependent on the net charge of the medium. In this study, water soluble associative polymers exhibit properties that can be of great interest in the petroleum industry