Um problema importante na heveicultura é o seu longo período de imaturidade. A explotação precoce pode reduzi-lo, porém, o seu efeito a longo prazo não é bem conhecido. O objetivo do presente estudo foi de investigar a factibilidade da explotação precoce da seringueira e avaliar diferentes sistemas de explotação. Foram explotadas árvores com perímetro do tronco entre 36 e 41 cm e sua produção e crescimento comparados com daqueles em plantas sem explotação. Quando todas as plantas do experimento atingiram perímetro de tronco de aproximadamente 45 cm, foram explotadas pelo sistema convencional 1/2S d/3 6d/7 10m/y ET 2.5% La/Pa 1/1 5/y. O delineamento experimental adotado foi inteiramente casualizado, com uma planta por parcela. O experimento 1 foi conduzido em Nhandeara-SP, com 25 repectições por tratamento, durante 17 meses de explotação precoce e três anos de explotação convencional. Os sistemas de explotação precoce foram: tratamento 1, 1/4S d/3 6d/7 10m/y ET 2.5% La/Pa 1/1 5/y, sangria matinal; tratamento 2, 1/2S d/7 6d/7 10m/y ET 2.5% La/Pa 1/1 5/y, sangria matinal; tratamento 3, 1/2S d/7 6d/7 10m/y ET 2.5% La/Pa 1/1 5/y, sangria vespertina; tratamento 4 6PI 70x1 d/2 6d/7 10m/y ET 5% Ga 1/1 10/y, sangria matinal. No experimento 2, conduzido em Rio Claro-SP, com 20 repetições, durante um ano de explotação precoce e um ano de convencional, repetiu-se o tratamento 1. As produções obtidas no experimento 1, na fase de explotação precoce, foram similares entre os tratamentos 1, 2 e 4, com aproximadamente 1,2 kg de borracha por árvore, porém significativamente menor no tratamento 3, com aproximadamente 0,9 kg por árvore. Durante o mesmo período as produções em g por árvore por sangria foram maiores no tratamento 2 (22,6 g) e 3 (18,82 g), do que no tratamento 1 (14,41 g) e 4 (8,97 g), diminuindo com o aumento da frequencia de sangria. A produção acumulada, nos 4,5 anos de explotação precoce e convencional, foi maior no tratamento 1 (7,92 kg) do que no controle (5,95 kg). Os outros tratamentos de explotação precoce tiveram um resultado intermediário. O incremento do perímetro do tronco durante a fase precoce foi significativamente menor nos tratamentos 3 e 4, em comparação com os outros tratamentos e o controle. Entretanto, durante a fase convencional, o incremento de perímetro de tronco de todos os tratamentos foi comparável ao do controle. O índice de colheita teve valores similares em todos os sistemas de explotação precoce, porém o tratamento 1 resultou em um valor para o \"fator de perda de biomassa\" (k) muito menor do que o dos outros tratamentos (entre 0,109 e 0,1794). No experimento 2, a produção obtida durante a explotação precoce foi de aproximadamente 0,85 kg por árvore. Durante o mesmo período, a produção por árvore por corte foi de 13,31 g e comparável com aquela do experimento 1. As produções obtidas durante o primeiro ano de explotação convencional no tratamento 1 (1,52 kg) e no controle (1,15 kg) foram bastante similares àquelas dos mesmos tratamentos no experimento 1, respectivamente, 1,53 kg e 1,08 kg. Durante as fases precoce e convencional, o incremento de perímetro de tronco foi igual no tratamento 1 e no controle. O coeficiente de colheita no tratamento 1 foi similar àquele observado no experimento 1, enquanto que o \"fator de perda de biomassa\" (k) foi maior. As principais conclusões foram: 1. O sistema de explotação precoce do tratamento 1 possibilita uma produção prévia de borracha, a níveis satisfatórios, mantendo um crescimento adequado das plantas. Pela sua capacidade, em ambientes diferentes, de produção precoce sem prejuízo permanente para as plantas, pode ser recomendado para uso em seringais comerciais. 2. Os sistemas de explotação precoce dos tratamentos 2, 3 e 4 possibilitam uma produção prévia de borracha, a níveis satisfatórios, porém reduzem o crescimento das plantas. / One major problem of rubber cultivation is the long immature period. Premature exploitation may reduce it, however, its long term effects are not fully understood. The aim of this study was to investigate the feasibility of premature exploitation of rubber, and evaluate different exploitation systems. Trees of about 36 to 41 cm of girth were tapped with premature exploitation systems, and their yield and growth were compared to untapped control trees. When all experimental trees reached approximately 45 cm of girth, they were converted to conventional tapping 1/2S d/3 6d/7 10m/y ET 2.5% La/Pa 1/1 5/y. The experiments were arranged in a complete randomized design, with one tree per plot. Experiment 1 was carried out in Nhandeara-SP, with 25 replications for each treatment, during 17 months of premature and three years of conventional exploitation. The premature systems included: treatment 1, 1/4S d/3 6d/7 10m/y ET 2.5% La/Pa 1/1 5/y, morning tapping; treatment 2, 1/2S d/7 6d/7 10m/y ET 2.5% La/Pa 1/1 5/y, morning tapping; treatment 3, 1/2S d/7 6d/7 10m/y ET 2.5% La/Pa 1/1 5/y, afternoon tapping; treatment 4 6PI 70x1 d/2 6d/7 10m/y ET 5% Ga 1/1 10/y, morning tapping. In experiment 2, carried out in Rio Claro-SP, with 20 replications, during one year of premature and one year of conventional tapping, treatment 1 was repeated. In experiment 1, yield obtained during premature exploitation, was similar between treatment 1, 2 and 4, with about 1.2 kg of rubber per tree, but significantly lower in treatment 3 with approximately 0.9 kg per tree. During the same period, yield in terms of g per tree per tapping, was higher in treatment 2 (22.6 g) and 3 (18.82 g), than in treatment 1 (14.41 g) and 4 (8.97 g), declining with increased tapping frequency. Cumulative yield obtained over 4,5 years of premature and conventional exploitation was higher in treatment 1 (7.92 kg) than in the control (5.95 kg). The other treatments with premature exploitation had an intermediate result. The girth increment during premature phase was significantly lower in treatment 3 and 4, compared to other treatments and control. However, during the conventional phase, girth increment of all treatments was comparable to the control. Harvest index values were similar in all premature exploitation systems, but treatment 1 resulted in a much lower value (0.019) for the \'factor of biomass loss\' (k) than the other treatments (0.109 to 0.1794). In experiment 2, yield obtained during premature exploitation in treatment 1 was approximately 0.85 kg per tree. During the same period, yield per tree per tapping was 13.31 g thus comparable to that in experiment 1. Yields obtained during the first year of conventional exploitation in treatment 1 (1.52 kg) and in control (1.15 kg) were very similar to the yields in those treatments in experiment 1, respectively 1.53 kg and 1.08 kg. During premature and conventional phases girth increment was equal in treatment 1 and control. Harvest index in treatment 1 was similar to that in experiment 1, whereas the \'factor of biomass loss\' (k) was higher (0.098). The main conclusions were: 1. The premature exploitation system of treatment 1 gives a reasonable yield and maintains appropriate tree growth. Because its capacity, in different environments, to antecipate yield without permanent damage to the trees, this system may be recommended for use in commercial rubber plantations. 2. The premature exploitation systems of treatments 2, 3 and 4 give reasonable yield, but cause growth retardation.

Orientador: Renivaldo José dos Santos / Banca: Flavio Camargo Cabrera / Banca: John Fredy Franco Baquero / Resumo: O uso de materiais alternativos para inovação tecnológica, em específico para compósitos de borracha natural, são cada vez mais explorados; materiais reforçantes conhecidos como "cargas", comumente utilizados na indústria de borracha, são objetos de pesquisa para que sejam substituídos parcialmente por cargas alternativas ou residuais; sabe-se que o negro de carbono (NC) é estabelecido no mercado como uma das melhores cargas reforçantes. A presente dissertação de mestrado buscou uma forma alternativa para substituição do NC (tipo N-762) pelo carbonato de cálcio ultrafino (CC) comercial tratado com 2% de Chartwell C-515-71HR (agente de acoplamento) fornecido pela Aodran Ltda. Ainda, foram feitos estudos da reticulação dos compósitos produzidos, caracterização e comparação das propriedades dos compósitos vulcanizados. Os compósitos foram desenvolvidos com 50 phr de carga (CC/NC), variando a proporção de NC e CC. As propriedades mecânicas, térmicas e morfológicas foram analisadas por meio das seguintes técnicas: reometria, análises térmicas (DSC, TG, DMA), espectroscopia por infravermelho FT-IR, microscopia eletrônica de varredura (MEV), ensaios mecânicos (tensão x deformação, resistência à abrasão, dureza) e densidade de ligações cruzadas. Os resultados de tração na ruptura revelaram uma substituição de até 30 phr de NC em que o compósito CC30/NC20 (17,56 MPa) superou os valores de CC0/NC50 (16,83 MPa) além do aumento de 48% em relação a elongação na ruptura. As analises térmic... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The use of alternative materials for technological innovation, specifically for natural rubber composites, are increasingly explored; reinforcing materials known as "fillers", commonly used in rubber industry, are the subject of research to be partially replaced by alternative or residual fillers; it is known that carbon black (CB) is established on the market as one of the best reinforcing fillers. The present master's dissertation sought an alternative form of substitution of the NC (type N-762) by the commercial ultra-fine calcium carbonate (CC) treated with 2% of Chartwell C-515-71HR (coupling agent) supplied by Aodran Ltda. Also, the crosslinking of the composites produced, characterization and comparison of the properties of the vulcanized composites were made. The composites were developed with 50 phr of load (CC/CB), varying the ratio of CB and CC. The mechanical, thermal and morphological properties were analyzed using the following techniques: rheometry, thermal analysis (DSC, TG, DMA), FT-IR infrared spectroscopy, scanning electron microscopy (SEM), mechanical (stress x strain, abrasion and hardness) and crosslink density. The results of tensile at break revealed a substitution of up to 30 phr of CB in which the composite CC30/CB20 (17,56 MPa) exceeded the values of CC0/CB50 (16,83 MPa) in addition to the increase in 48% over elongation at break. Thermal analyzes revealed satisfactory thermal stability of the material. The results showed in general that the new mat... (Complete abstract click electronic access below) / Mestre

<p>With the purpose of expanding our understanding on the main causes that make maintaining competitiveness a challenging issue for companies in an industry, a qualitative research is conducted in this thesis based on Porter theoretical framework (i.e. the five competitive forces model); thereby selecting a single case study with a Swedish rubber subcontractor. The findings show that the threat of new entrants, the rivalry among the existing rubber subcontractors, the bargaining power of carmakers, the bargaining power of suppliers and the role of the Swedish government all highly concern and challenge the competitiveness of the case company. However, given the fact that close substitute products to the case company’s product are absent from the market, their threat does not represent any distress for the competitiveness of the company.</p>

A thermal catalytic decomposition process has been developed to recycle used tire rubber. This process enables the recovery of useful products, such as hydrocarbons and carbon blacks. During the catalytic decomposition process, the tire rubber is decomposed into smaller hydrocarbons, which are collected in the process. The solid reaction residue, which normally consists of carbon black, catalysts, other inorganic rubber compound components, and organic carbonaceous deposits, was subjected to a series of treatments with the intention to recover the valuable carbon black and catalyst. The process economics depend strongly on the commercial value of the recovered carbon black and the ability to recover and recycle the catalysts used in the process. Some of the important properties of the recovered carbon black product have been characterized and compared with that of commercial-grade carbon blacks. The composition of the recovered carbon black was analyzed by TGA and EDX, the structure and morphology were studied through transmission electron microscopy (TEM), and the specific surface area was measured by BET nitrogen adsorption. The recovered products possess qualities at least comparable to (or even better than) that of the commercial-grade carbon black N660. Methods for increasing the market value of this recovered carbon black product are discussed. Anhydrous aluminum chloride (AlCl3) was used as the primary catalyst in the process. A catalyst recovery method based on the AlCl3 sublimation and recondensation was studied and found to be non-feasible. It is believed that the catalyst forms an organometallic complex with the decomposed hydrocarbons, such that it becomes chemically bonded to the residue material and hence not removable by evaporation. A scheme for the further study of the catalyst recovery is suggested.

With the purpose of expanding our understanding on the main causes that make maintaining competitiveness a challenging issue for companies in an industry, a qualitative research is conducted in this thesis based on Porter theoretical framework (i.e. the five competitive forces model); thereby selecting a single case study with a Swedish rubber subcontractor. The findings show that the threat of new entrants, the rivalry among the existing rubber subcontractors, the bargaining power of carmakers, the bargaining power of suppliers and the role of the Swedish government all highly concern and challenge the competitiveness of the case company. However, given the fact that close substitute products to the case company’s product are absent from the market, their threat does not represent any distress for the competitiveness of the company.

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Diimide generated from the hydrazine/hydrogen peroxide/catalyst system can be used to hydrogenate unsaturated polymers in latex form. As an economical and environmentally benign alternative to the commercial processes based on hydrogen/transition metal catalysts, this method is of special interest to industry. This thesis provides a detailed description of the diimide hydrogenation process. Reaction kinetics, catalysts and gel formation mechanism have been investigated. <br /> <br /> Four main reactions and a mass transfer process form three parallel processes in this system: diimide is generated at the interface of the latex particles; diimide diffuses into the organic phase to saturate carbon-carbon double bonds; diimide may be consumed at the interface by hydrogen peroxide, and may also be consumed by the disproportionation reaction in the organic phase. The two side reactions contribute to the low hydrogenation efficiency of hydrogen peroxide. Slowing down hydrogen peroxide addition and using stable interfacial catalysts may totally suppress the side reaction in the aqueous phase. The actual catalytic activity of metal ions in the latex depends on the hydrogen peroxide concentration and the addition procedure of reactants. Cupric ion provides better selectivity for hydrogenation than ferric ion and silver ion do. Boric acid as a promoter provides improved selectivity for hydrogenation and faster diimide generation rate. The side reaction in the rubber phase results in low efficiency and gel formation. The rate constants of the four reactions in this system are estimated. <br /> <br />It is shown that the hydrogenation of nitrile rubber latex with an average particle diameter of 72 nm is mainly a reaction-controlled process. Diimide diffusion presents limitation upon hydrogenation at high hydrogenation degree range. Antioxidants can not effectively inhibit gel formation during hydrogenation. Hydrogenation of a core-shell latex with NBR as the shell layer should be able to achieve a higher efficiency, a higher degree of hydrogenation and a lower level of crosslinking.

Particle shape is evaluated on three scales corresponding to form, roundness and roughness. Shape at each of these scales uniquely influences material behavior. The shape of sand grains is largely formed as magma cools. Subsequent cleavage and abrasion change the roundness and roughness of particles. Published results indicate that particle shape influences several aspects of granular systems behavior including stiffness, strength, the evolution of strength anisotropy, dilation, and the development of strain localization. The crushing of granite creates a particulate material with a unique angular shape. A wide range of experimental studies implemented as part of this research permit assembling a unique database of material parameters and comparing the behavior of several crushed and natural sands. In general, the low roundness of crushed sands leads to higher maximum void ratios, lower small strain stiffnesses, and higher critical state friction angles than more rounded natural sands. It also impacts mortar strength and workability. Previous studies have emphasized size-controlled segregation. New experimental results show that differences in particle shape can also lead to segregation in a binary granular material. Round or spherical particles are more mobile than angular or flat particles. Then, the greater motion of round or spherical particles in a binary mixture subjected to horizontal or vertical vibration results in their segregation from their angular or flat neighbors. Particle shape may change significantly with stress in the case of soft particles. Therefore, the presence of shape-deformable particles decreases the stiffness of binary rigid-soft particle mixtures. However, macro-scale measurements with rigid-soft mixtures show higher stiffness than would be expected by volume averaging techniques. A subsequent microscale study shows the formation of backbone chains made of the rigid particles, partially supported by the soft particles which prevent the buckling of the load-carrying chains.

A thermal catalytic decomposition process has been developed to recycle used tire rubber. This process enables the recovery of useful products, such as hydrocarbons and carbon blacks. During the catalytic decomposition process, the tire rubber is decomposed into smaller hydrocarbons, which are collected in the process. The solid reaction residue, which normally consists of carbon black, catalysts, other inorganic rubber compound components, and organic carbonaceous deposits, was subjected to a series of treatments with the intention to recover the valuable carbon black and catalyst. The process economics depend strongly on the commercial value of the recovered carbon black and the ability to recover and recycle the catalysts used in the process. Some of the important properties of the recovered carbon black product have been characterized and compared with that of commercial-grade carbon blacks. The composition of the recovered carbon black was analyzed by TGA and EDX, the structure and morphology were studied through transmission electron microscopy (TEM), and the specific surface area was measured by BET nitrogen adsorption. The recovered products possess qualities at least comparable to (or even better than) that of the commercial-grade carbon black N660. Methods for increasing the market value of this recovered carbon black product are discussed. Anhydrous aluminum chloride (AlCl3) was used as the primary catalyst in the process. A catalyst recovery method based on the AlCl3 sublimation and recondensation was studied and found to be non-feasible. It is believed that the catalyst forms an organometallic complex with the decomposed hydrocarbons, such that it becomes chemically bonded to the residue material and hence not removable by evaporation. A scheme for the further study of the catalyst recovery is suggested.