Materials Science Forum Vols. 775-776

Abstract: Polypyrrole was synthesized onto aluminum surfaces by electrochemical polymerization technique using pyrrole monomer and phosphoric acid in aqueous medium. The influence of applied potential on the morphology of the films was studied by Scanning electron microscopy (SEM). The films displayed a cauliflower-like structure consisting of micro-spherical grains. This structure is related to dopant intercalation in the polymeric chain. The efficiency of these polymeric films to protecting aluminum alloy against corrosion was investigated by potentiodynamic polarization curves. It was also observed that the polymer roughness depend on the applied potential.

Abstract: Recent advances in biodegradable polymers have attracted a great interest not only in traditional areas such as biomedical and pharmaceutical industry, but also in packaging applications, articles and injected membranes. The aim of this work was to produce bio-nanocomposites poly (lactic acid) - PLA with bentonite clay. The bio-nanocomposites were produced by melt intercalation with incorporation of 1 to 3 wt% of organoclay. The degree of dispersion of clays in the polymer, and consequently the structure of bio-nanocomposites produced was evaluated by X-ray diffraction (XRD), and the thermal properties were studied by differential scanning calorimetry (DSC). XRD results indicated the formation of intercalated structures. It was observed the appearance of crystalline melting double peaks in bio-nanocomposites PLA.

Abstract: Coal extraction produces large amounts of wastewater containing coal powders, which could be used to produce coke. In this case, binder materials should be used to allow compression capacity to the mixture. This work aims to study the effect of binder addition in mixtures of coals containing different contents of coal powders to obtain coke. Compositions containing different amounts of coal powders were prepared by varying the nature and the contents of the binders to allow the pressing of powders. Study of the thermal behavior of these compositions was performed. The composition that showed the best results was then homogenized, pressed and heat treated. The final composition showed FSI about 4.5 and compressive strength of 5 MPa, demonstrating high potential for coke production from coal powder.

Abstract: The main objective of this work was to study the crystallization kinetics of glass-ceramic obtained from steel waste. Two compositions were melted at about 1350 °C. The obtained frits were dried and re-melted. Each composition was then wet ground, dried, and chemically characterized (X-ray fluorescence and atomic absorption spectrometry), structurally (X-ray diffraction), and thermally (thermal differential analysis). Then the powders were compacted and the samples were dried and heat treated in a kiln between 690 and 890 °C. After, the crystallized bodies were ground and the crystalline phases were identified by X-ray diffraction. Results showed that the main formed crystalline phases were magnetite, hematite, Fe_2.95Si_0.05O₄, and CaAl₂Fe₄O₁₀. The activation energies obtained by the Kissinger method were between 348 and 423 kJ.mol^-1, whereas the Avrami parameter was obtained between 0.76 and 1.1 indicating surface crystallization.

Abstract: A number of methods are available for characterization of the structural, physical, and chemical properties of natural fibers. Various methods are used for fiber identification like microscopic analysis, solubility, heating and burning technique density, staining etc. End-use property characterization methods often involve use of laboratory techniques which are adapted to simulate actual application as composite reinforcement. One of the techniques used on this kind of studies is the infrared spectroscopy. In fact, Fourier Transform Infrared (FTIR) spectroscopy is a valuable tool in the determination of functional groups actively interacting within a fiber. In this work, the banana fiber was evaluated by FTIR to reveal these functional groups and compare to similar works on other different types of banana fibers.

Abstract: The growing interest for natural materials as an environmentally friendly alternative for the substitution of energy intensive and non-sustainable synthetic materials, has motivated the use of lignocellulosic fibers as reinforcement of polymer composites. The malva fiber, a relatively unknown lignocellulosic fiber with potential for composite reinforcement, still needs to be characterized for possible engineer applications. Therefore, the present work analyzed the malva fiber by means of Fourier Transform Infra-red (FTIR) spectroscopy. The malva fiber FTIR spectrum revealed main absorption bands typical of any lignocellulosic fiber. However, some specific bands as well as bands broadening and intensity suggested particular activities for functional molecular groups in the malva fiber.

Abstract: Polymer matrix composites have been applied in components such as helmets and shielding for which toughness is a major requirement. A natural fiber presents interfacial characteristics with polymeric matrices that favor a high impact energy absorption by the composite structure. The objective of this work was then to assess the Izod impact resistance of polymeric composites reinforced with different amounts, up to 30% in volume, of a promising high strength natural fiber, the banana fiber. The results showed a remarkable increase in the notch toughness with the amount of incorporated banana fibers. This can be attributed to a preferential debonding of the fiber/matrix interface, which contributes to an elevated absorbed energy.

Abstract: Economical, technical and environmental advantages justify the substitution of glass fiber for lignocellulosic fibers in polymeric composites. However the uniformity of the glass fiber dimensions and composition contrast to the lignocellulosic fibers heterogeneity. In this work, a statistical analysis of the correlation between the diameter and the density of coir fiber using the Weibull methodology was performed. The diameter was obtained by profile projector measurements, while the density used precise determinations of the fibers mass and volume. The results revealed an inverse dependence between the coir fiber diameter and its density.

Abstract: Polyester composites reinforced with natural lignocellulosic fibers have attracted interest in several engineering areas due to their low cost, low energy consumption during fabrication in association with a number of possible applications. One of these applications is the replacement of traditional composites such as the fiberglass. Characterization of polyester composites incorporated with ramie fiber has recently been conducted for physical and mechanical properties. However, the effect of increasing temperature on these composites has not yet been fully investigated. Therefore, the objective of this study was to evaluate the thermogravimetric behavior of polyester composites reinforced with up to 30 vol% of ramie fibers. The analysis was conducted by TG and DTG techniques. The presence of ramie fibers induces sensible changes in the thermal stability of the polyester composites, showing a significant effect of the ramie fibers by reducing their temperatures of degradation.

Abstract: Dynamic-mechanical (DMA) tests have not yet been conducted in malva aligned fiber reinforcing polymeric composites. In this work, the temperature dependence of the DMA parameters in polyester matrix composites reinforced with up to 30% in volume of continuous and aligned malva fibers was investigated. These parameters were the storage and the loss modulus as well as the tangent delta. The investigation was conducted in the temperature interval from-20 to 180°C using a Perking-Elmer DMA equipment operating in flexural mode. The results showed that the incorporation of malva fibers tends to increase the viscoelastic stiffness of the polyester matrix. Sensible modifications in the glass transition temperature and the damping capacity of the structure were found with the amount of fiber in the composite. The molecular mobility of the polyester matrix is affected by its interaction with the malva fibers.