Resumo: O presente trabalho tem por objetivo oferecer subsídios para análise do ciclo de vida de assentos a base de fibra de coco com látex. Com esse intuito foi realizado um estágio junto a uma Unidade de beneficiamento e industrialização da fibra de coco, localizada na comunidade de Praia Grande, no município de Ponta de Pedras, Ilha do Marajó, no Estado do Pará. Nesse estágio foram coletados dados a respeito de todo o processo de beneficiamento da fibra de coco até a produção de mantas a base de fibra de coco com látex para aplicação em veículos. Através da Mercedes-Benz do Brasil, foram feitas amostragens dos materiais em estudo: fibra de coco, manta de fibra de coco com látex e espuma de poliuretano. É importante notar que a fibra de coco e suas mantas foram fornecidas pela Unidade de beneficiamento e industrialização de fibra de coco já citada e, a espuma de poliuretano foi fornecida pela Empresa Sanko de Diadema - SP. A partir dessas amostragens foram realizados ensaios de compressão e torção, apenas compressão, análise de metais e análise qualitativa do produtos formados na pirólise desses materiais, visando analisar assentos automobilísticos a base de fibra de coco com látex como um possível substituto da espuma de poliuretano. A partir deste estudo foi possível verificar que ambos os materiais sofrem deformação volumétrica após os ensaios de compressão e torção e, apresentam um comportamento de retorno ao seu volume inicial. No entanto, a espuma retorna praticamente 100% ao seu volume inicial enquanto a manta de fibra de coco com látex mantém uma deformação em torno de 10%. Quanto a análise qualitativa dos produtos formados na pirólise a 800oC desses materiais verificou-se que o fumo produzido pela pirólise da espuma de poliuretano é mais tóxico em relação ao produzido pela manta de fibra de coco com látex. / Abstract: The aim of this work is to present a contribution to the analysis of the life cycle of vehicles' seats made with a mixture of coconut fibres with latex. Part of the work was developed at a unit for manufacture and industrialization of coconut fibres, at the community of Praia Grande, town of Ponta de Pedras, Marajó Isle, Pará, Brazil. At the unit, information on the processing of the coconut fibre was collected, ranging from the raw material to the production of a mat of natural fibre with latex to be used in vehicles. The different materials involved in the study were analysed at the laboratories of Mercedes-Benz do Brazil: coconut fibre, the mat of natural fibre with latex, and polyurethane foam. The polyurethane foam was supplied by Sanko, from Diadema/SP. Once obtained the samples, they were submitted to tests of compression and torsion, compression only, analysis of heavy metals content, and qualitative analysis of products resulting from the incineration of the different materials. The coconut fibre plus latex composite was evaluated as a possible substitute for polyurethane foam in seats. Starting from this study it was possible to verify that both materials suffer volumetric deformation after the compression rehearsals and torsion and, they present a return behaviour to its initial volume. However, the foam comes back 100% practically to its initial volume while the mat of coconut fibre with latex maintains a deformation around 10%. As the qualitative analysis of the products formed in the pyrolysis to 800oC of those materials was verified that the fume produced by the pyrolysis of the polyurethane foam is more toxicant in relation to the produced by the mat of coconut fibre with latex. / Orientador: Alcides Lopes Leão / Coorientador: Jayme de Toledo Piza e Almeida Neto / Mestre

Many coatings only need to either be durable or fast drying, usually sacrificing long term stability in favor of quick setting, or vice versa. One coating type that cannot afford to sacrifice either performance feature is traffic paint. These paints are made up of a weak polycation, an anionic latex, and a volatile base which evaporates upon application. The high pH in the initial formulation deprotonates the polycation, rendering it charge neutral. However, upon evaporation, the resulting drop in pH allows for the electrostatic complexation between the polycation and the latex. The electrostatic interactions used in these formulations parallels that of complex coacervation, an associative liquid-liquid phase separation. In this thesis, we will take advantage of model coacervate systems to elucidate the design parameters necessary for the formulations to serve as paints. We used a series of simplified systems, starting with a system consisting of a weakly cationic homopolymer and weakly anionic homopolymer before moving on to anionic copolymers with decreasing charge density, and ultimately an anionic latex. We investigated the effects of pH, charge stoichiometry, and salt concentration for each of these systems, using turbidimetry and optical microscopy as a means of measuring the extent of coacervation. We determined that, the removal of 99.9% of the charge on our polymers was necessary for coacervation to no longer occur. This can be achieved using either salt or pH, however, salt may be preferable, due to the inherent hazardous properties of highly acidic or basic solutions. Very excitingly, we were able to observe coacervation with latex particles. To our knowledge, there are no known observations of polymer-particle coacervation prior to this study. These results suggest that the underlying physics and design principles associated with fast setting paints can be explored using complex coacervation, and that a much broader range of parameters can be used to control the setting of these materials, beyond just pH used in existing technology. Future efforts are still needed to better understand the effect that polymer chemistry has on the complexation of these materials, and how it also affects the mechanical and adhesive properties of coating produced by such formulations.

This project consists of two parts. One area of focus in the first part is understanding the interactions between a non-ionic, block copolymer type dispersant and hydrophobically-modified, ethoxylated urethane (HEUR) associative thickeners in water. The dispersant was mixed at various concentrations (0-2% by weight) with HEUR thickeners at 1% by weight concentration in the aqueous medium. This study is an integral part of our attempts to determine mechanisms of viscosity drop when colorant dispersions are added to latex tint base formulations thickened with associative thickeners. One of the HEUR thickeners is a product that has been available for over three decades (HEUR RM-825), whereas the other, HEUR RM-995 is a product recently introduced to minimize the tint base viscosity drop. The old HEUR showed a definitive viscosity maximum as a function of the dispersant concentration. However, the new generation product did not indicate a viscosity maximum within the dispersant concentration range studied; instead it showed a small, but linear increase in viscosity as dispersant level was increased. The next area of focus was on understanding the phase behavior, rheology, and interactions between polymer latex particles and a hydrophobically-modified, ethoxylated urethane (HEUR) associative thickener in water. The influence of the addition of surfactant in some of the systems was also studied. Several types of dispersions were made using two types of polymer latex, two associative thickeners, and two surfactants. Mixtures containing a small particle size acrylic latex and HEUR RM-825 exhibited the most interesting and complex phase behavior and rheology. In experiments wherein the latex particle volume fraction was kept constant, the addition of HEUR caused stable, followed by phase separated (syneresis) and stable mixtures as HEUR concentration was increased. The observed phase behavior is consistent with previous work reported by other investigators. However, detailed rheological data on systems such as these have not been reported, and this report presents the rheological data and correlate rheology with the phase behavior. The stable latex-HEUR mixtures at low HEUR levels show shear-thinning viscosity with well-defined low-shear Newtonian plateaus. As HEUR level is increased wherein syneresis is observed, erratic rheological profiles with shear-thickening are observed. When HEUR level is increased to a region where no syneresis is observed, low shear Newtonian plateaus re-appeared albeit at higher viscosities. The effects of added non-ionic and anionic surfactants on the dispersion are also studied. The main focus of the second part of this project is hybrid organic-inorganic photovoltaics. They have been the focus of recent studies due to their promising use in low-cost, flexible electronics, which can be processed from solution by printing and coating techniques. Understanding the rheology of these nanocomposites is essential in controlling shear flows during printing and application processes. Through rheology, we can determine different properties of poly(3-hexylthiophene) and dodecanethiol (DDT) modified zinc oxide (ZnO-DDT). Semiconductor nanowires such as ZnO have rigid or rod-like macromolecule geometry. Therefore, they have a tendency to have a lytropic liquid crystal (LLC) phase. LLC orders occur spontaneously in solutions with rod-shaped or anistropic objects from isotropic phase to nematic phase above a critical volume fraction which was studied using ZnO-DDT. The shear-induced alignment of the liquid crystal molecules was analyzed, serving as a guide for LLC printing. Furthermore by using this nanocomposite we are able to induced gelation using the ZnO-DDT nanowires in what is considered as a “good solvent,” dichlorobenzene. The kinetics of this gelation process was determined to be of first-order reaction kinetics. Furthermore, a mechanism of this gelation process is also presented.

Das neue (La)TeX. Vortrag UNIX-Stammtisch 09/94.

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Vortrag UNIX-Stammtisch 09/99

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