Orientador: Julio Roberto Bartoli / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-12T05:46:37Z (GMT). No. of bitstreams: 1 PampaQuispe_NoeBenjamin_D.pdf: 4048674 bytes, checksum: 584228b9ad826cb07274497b4df107b0 (MD5) Previous issue date: 2007 / Resumo: Nanocompósitos poliméricos são novos materiais de grande interesse devido à sua favorável relação custo/benefício com a incorporação de pequenas quantidades de carga mineral, aumentado sua resistência térmica, retardante de chama e propriedades mecânicas dos polímeros. O processamento por fusão tem sido empregado com sucesso na preparação de nanocompósitos de polímero e argila usando diversos termoplásticos (commodities e de especialidade). Neste trabalho, poli[tereftalato de butileno], PBT, de reciclagem primária foi reforçado com argilas do tipo montmorilonita organicamente modificadas (MMT). O processo de preparação a partir do fundido, em extrusora de rosca dupla, foi empregado para obter compostos de PBT reciclado e MMT, em função da velocidade de rotação e tipo de nanoargila. Análises morfológicas de Difração de Raios-X (DRX) e Microscopia Eletrônica de Transmissão (MET) sugerem uma esfoliação parcial ou inicial da argila na matriz de PBT reciclado quando se usa a Cloisite 25A, menos organofílico, mas uma intercalação usando a Cloisite 20A. Análises de DMTA (modo de flexão), TGA e reológicas também foram sensíveis em mostrar diferenças entre os tipos de MMT e o efeito da rotação da rosca da extrusora ou taxa de cisalhamento usadas. Corpos de prova moldados por injeção foram preparados para caracterização mecânica. Foi verificada uma melhoria no módulo de elasticidade sob tração dos nanocompósitos de PBT reciclado quando comparado ao composto virgem e ao reciclado sem cargas, em especial usando a argila organicamente modificada Cloisite 25A. / Abstract: Polymeric nanocomposites are novel materials of huge interest due to their favorable cost/performance ratio with low amount of nanofillers, increasing thermal resistance, flame retardancy and mechanical properties of polymers. Polymer clay nanocomposite systems were successfully prepared by melt compounding using several thermoplastics (commodities and specialties). In this work, primary recycled poly(butylenes terephtalate), PBT, is being used to be reinforced with organic modified montmorillonite clays (MMT). Melt compounding with a twin-screw extruder was used to prepare recycled PBT/MMT compounds as a function of screw speed and grade of nanoclay. Morphological analysis X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) suggested that a partial or initial exfoliation of the nanoclay in the PBT compounds was achieved when using the grade Cloisite 25A, less organophylic, but an intercalation when using Cloisite 20A. DMTA (flexural mode), TGA and rheological characterizations were also sensitive to show differences between organoclay grades and the effect of screw speed or shear rate used. Injection molded specimens were prepared for mechanical characterization. It was found that tensile modulus of the recycled PBT nanocomposites was improved when compared to the virgin and recycled net PBT, specially using the organoclay grade Cloisite 25A. / Doutorado / Ciencia e Tecnologia de Materiais / Doutor em Engenharia Química

Orientador: Vivaldo Silveira Jr / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-03T02:14:18Z (GMT). No. of bitstreams: 1 Mendes_AlexandreConsul_M.pdf: 28710433 bytes, checksum: dd88ab66a072eb5070a05416b953f5c6 (MD5) Previous issue date: 2003 / Resumo: O trabalho a seguir apresenta as principais ferramentas necessárias para o controle do processo de extrusão baseado na densidade e umidade do produto extrusado úmido. Para facilitar a compreensão da aplicação do controle avançado, revisa-se alguns conceitos básicos da teoria clássica de controle. Devido à complexidade deste processo, orientado pela transformação bio-polimérica da matéria-prima farino-lipídico-protéica a certa umidade ao longo da extrusora, são retomados alguns conceitos de estatística, a fim de compor um modelo experimental para as principais variáveis independentes e de processo na extrusão. Estudou-se a relação estatística significativa entre as variáveis independentes: vazão de farinha, vazão de vapor, vazão de água e rotação de helicóide do extrusor e as variáveis de processo: densidade e umidade do produto extrusado úmido, temperatura de saída e pressão de saída da extrusora. Para o completo entendimentos destas relações, são correlacionados as variações dos teores de umidade, lipídios, proteínas e carboidratos da farinha a ser extrusada. Ainda como importante parâmetro industrial é realizado o balanço de energia para o processo em questão através da energia mecânica específica ('SME') e energia térmica específica ('STE'). Devido à aplicação industrial deste trabalho, o controle da densidade e umidade do produto extrusado úmido é na verdade baseado no controle da relação empírica entre a temperatura e pressão na saída da extrusora. Dessa forma, o custo de instalação e precisão, enfatizando a necessidade de repetibilidade na medida de temperatura e pressão de saída, se tomam muito mais viáveis quando os mesmos são comparados com a medida de densidade e umidade para o produto extrusado na saída da extrusora. Equipamentos para a medida precisa de densidade para produtos sólidos-úmidos aplicam princípio nuclear e para a medida de umidade são empregados instrumentos com sofisticados espectros de infravermelho associados a sistemas óticos internos. A fim de estudar-se a viabilidade deste modelo, foi realizado um planejamento composto central (4 variáveis independentes), com pontos axiais e a inclusão de alguns pontos aleatórios de interesse prático, a fim de obter-se um modelo mais robusto. Para tanto foram avaliadas três receitas típicas na indústria de rações de animais, a fim de representar-se a maioria dos produtos comerciais recomendados para cachorros e gatos. Através do conhecimento profundo das variáveis de processo, utilizou-se alguns experimentos para o entendimento do processo quanto à natureza da resposta, como a linearidade e a variação da resposta com o tempo. Estes experimentos informaram sobre o comportamento das curvas de reação para as variáveis independentes isoladamente. Atendendo a necessidade para a aplicação de estratégias de controle não lineares e/ou neurais o processo demonstrou-se com resposta em um único sentido com a perturbação, não linear e variante com o tempo. Este estudo foi comprovado pela aplicação da teoria de controle para processos lineares com perturbações lineares isoladas. Finalmente, é utilizado o conhecimento adquirido no estudo do processo de extrusão e da avaliação da curva resposta experimental das perturbações isoladas para o projeto de um algorítimo de controle baseado na estratégia de controle MIMO 2 x 2. Este controle foi testado através do controlador neuro-adaptativo 'Model Free Adaptive' (MFA), demonstrando resultados preliminares satisfatórios para o controle simultâneo da temperatura e pressão de saída de um extrusor de eixo simples, empregando como variáveis manipulativas a proporção de vapor / água e a vazão de farinha de alimentação respectivamente para as variáveis de processo citadas / Abstract: The present study informs about the main features of extrusion control processes, based on product-wet density and moisture. To comprehend the study, some background of the classic control theory is provided. The process complexity, provided by formation of a bio-polymer from carbohydrate-lipid-protein raw materials, requires analysis using statistical concepts to build an experimental model for the principal extrusion process variables. Significant statistical relationships were evaluated between the following independent variables: meal feed rate, steam feed rate, water feed rate and extruder screw speed; and dependent variables: wet product density and moisture, extruder die temperature and die pressure. The process energy and mass balance were described using the Specific Mechanical Energy ('SME') and Specific Thermal Energy ('STE') concepts. To facilitate the industrial application of this study, the wet density and moisture control is evaluated by an experimental empirical relationship between die temperature and die pressure. Die temperature and die pressure measurements are more feasible when compared with wet product density and moisture measurements due to ease of installation and measurement precision. Suitable equipment for the wet-solid product density measurements apply the nuclear principle, where safety is a concern; and moisture measurements use sophisticated devices with any combination of infrared and optical systems. In order to evaluate the model application, a box experimental design was used with four independent variables, star points and some random points resulting from extrusion operation experience. Three typical dry recipes used in the pet food industry were tested, representing the majority of retail products for dogs and cats. Applying the knowledge of extrusion process variables, several experiments were run to understand the process responses, such as linearity and control parameters. These experiments showed the influence of isolated independent variables to the dependent variables. The process was characterized by presenting a one way, non-linearity and time varying response, suitable for non-linear and neural controllers. Classic control theory was applied to evaluate each perturbation. The knowledge gained from an extrusion process and experimental response curve analysis from isolated perturbation was applied to build a control algorithm based on MIMO 2 X 2 control strategy. This model was tested by the neural-adaptive ' Model Free Adaptive' (MFA) controller. Initial satisfactory results were observed from the simultaneous control of die temperature and die pressure on a single screw extruder, using as manipulative variables the ratio of steam / water and the meal feed rate respectively / Mestrado / Mestre em Engenharia de Alimentos

No description available.

Orientador: Maria do Carmo Gonçalves / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-27T15:15:24Z (GMT). No. of bitstreams: 1 Leite_LilianeSamaraFerreira_M.pdf: 4562587 bytes, checksum: 0ee5828360fc15cbd08b98c4070e5bd3 (MD5) Previous issue date: 2015 / Resumo: Nesse trabalho, nanocristais de celulose (CNC) foram obtidos por hidrólise de fibras de algodão, utilizando-se três diferentes ácidos: ácido sulfúrico, clorídrico e fosfórico. Micrografias obtidas por microscopia eletrônica de varredura (SEM) e transmissão (TEM) confirmaram que as condições de hidrólise empregadas foram adequadas para isolar seus nanocristais. No entanto, foi também possível observar a presença de uma pequena fração de fibras não totalmente hidrolisadas em todas as amostras analisadas. Imagens de microscopia óptica por luz polarizada (PLM) revelaram que o processo de secagem por liofilização dos CNC conduz à formação de aglomerados com dimensões micrométricas. Modificações químicas nas superfícies dos CNC, empregando-se ácido acético e cloreto de hexanoíla, foram conduzidas com o objetivo de diminuir o seu caráter hidrofílico. As modificações foram confirmadas por espectroscopia na região do infravermelho e por imagens de PLM das suspensões dos CNC. Compósitos de acetato de celulose (CA), reforçados com CNC, foram preparados por extrusão, utilizando-se dois procedimentos para a incorporação da carga na matriz: mistura direta e masterbatch, sendo esse último conduzido na tentativa de evitar a etapa de liofilização, onde ocorre a formação de aglomerados de nanocristais. Ensaios mecânicos mostraram que não houve aumento significativo nas propriedades mecânicas para os compósitos preparados por mistura direta. Entretanto, compósitos preparados por masterbatch apresentaram aumento no módulo de Young em torno de 5% e 14%, para composições contendo 10 e 15 % nanocristais em massa, respectivamente. Esses resultados evidenciam a importância das condições de hidrólise para obtenção das nanopartículas, como também da escolha do método de preparação do compósito de forma a promover a menor formação de aglomerados e melhor dispersão da carga na matriz / Abstract: In this work, cotton fiber cellulose nanocrystals (CNC) were obtained by acid hydrolysis using three different acids: sulfuric acid, hydrochloric acid and phosphoric acid. Scanning (SEM) and transmission (TEM) electron micrographs confirmed that the acid hydrolysis conditions used were efficient to isolate their nanocrystals. However, in all samples analyzed, it was possible to observe the presence of some partially hydrolyzed fibers. Polarized Light Microscopy (PLM) showed that the freeze-drying process led to the formation of small CNC agglomerates with micron dimensions. CNC surface functionalization was carried out with the purpose of reducing the hydrophilic character, by using acetic acid and hexanoyl chloride. Chemical modifications at the surface were confirmed by infrared spectroscopy and the hydrophilic character decrease was confirmed by PLM images of the functionalized CNC. Cellulose acetate composites, reinforced with CNC, were obtained by melt extrusion using two techniques for the introduction of reinforcing agent: direct mixing and masterbatch. The latter were carried out prevent CNC agglomeration formation due to the freeze-drying process. Mechanical tests showed that there was no significant increase in of the composites prepared by direct mixing mechanical properties. However, composites prepared from masterbatch showed a 5% and 14% increase in Young's modulus for 10 and 15 wt% CNC content, respectively. These results show the importance of the hydrolysis conditions on the nanoparticle synthesis, as well as the choice of an appropriate reinforcing agent load method so as to avoid agglomeration and increase load dispersion in the matrix / Mestrado / Mestra em Química

No description available.

No description available.

Yes / Polymer extrusion is an energy intensive production process and process energy e ciency has become a key concern in the current industry with the pressure of reducing the global carbon footprint. Here, knowledge of the pattern of energy usage and losses of each component in the plant is highly useful in the process energy optimization. Moreover, it is essential to maintain the melt quality while improving the energy e ciency in polymer processing. In this work, an investigation was made on the total energy consumption, drive motor energy consumption, power factor and the melt temperature profile across the die melt flow (as an indication of the melt thermal quality) of an industrial scale extruder with three di erent screw geometries, three polymer types and wide range of processing conditions (altogether 135 di erent processing situations were observed). This aims to widen the knowledge on process energy and thermal behaviors while exploring possible correlation/s between energy demand and melt quality (in terms of melt temperature fluctuations across the melt flow). The results showed that the level and fluctuations of the extruder’s power factor is particularly dependent upon the material being processed. Moreover, it seems that there is a relation between the level of energy demand of the heaters and the level of melt temperature fluctuations. While the extruder specific energy consumption decreases with increasing screw speed, specific energy consumption of the drive motor may have either increasing or decreasing behavior. Overall, this study provides new insights in a wide range on process energy demand and melt thermal quality in polymer extrusion. Moreover, further research is recommended to establish strong correlation/s between process energy consumption and melt thermal quality which should help to enhance process control and hence the product quality in single screw polymer extrusion.

Yes / Extrusion is one of the fundamental production methods in the polymer processing industry and is used in the production of a large number of commodities in a diverse industrial sector. Being an energy intensive production method, process energy efficiency is one of the major concerns and the selection of the most energy efficient processing conditions is a key to reducing operating costs. Usually, extruders consume energy through the drive motor, barrel heaters, cooling fans, cooling water pumps, gear pumps, etc. Typically the drive motor is the largest energy consuming device in an extruder while barrel/die heaters are responsible for the second largest energy demand. This study is focused on investigating the total energy demand of an extrusion plant under various processing conditions while identifying ways to optimise the energy efficiency. Initially, a review was carried out on the monitoring and modelling of the energy consumption in polymer extrusion. Also, the power factor, energy demand and losses of a typical extrusion plant were discussed in detail. The mass throughput, total energy consumption and power factor of an extruder were experimentally observed over different processing conditions and the total extruder energy demand was modelled empirically and also using a commercially available extrusion simulation software. The experimental results show that extruder energy demand is heavily coupled between the machine, material and process parameters. The total power predicted by the simulation software exhibits a lagging offset compared with the experimental measurements. Empirical models are in good agreement with the experimental measurements and hence these can be used in studying process energy behaviour in detail and to identify ways to optimise the process energy efficiency.

Yes / Thermal stability is of major importance in polymer extrusion, where product quality is dependent upon the level of melt homogeneity achieved by the extruder screw. Extrusion is an energy intensive process and optimisation of process energy usage while maintaining melt stability is necessary in order to produce good quality product at low unit cost. Optimisation of process energy usage is timely as world energy prices have increased rapidly over the last few years. In the first part of this study, a general discussion was made on the efficiency of an extruder. Then, an attempt was made to explore correlations between melt thermal stability and energy demand in polymer extrusion under different process settings and screw geometries. A commodity grade of polystyrene was extruded using a highly instrumented single screw extruder, equipped with energy consumption and melt temperature field measurement. Moreover, the melt viscosity of the experimental material was observed by using an off-line rheometer. Results showed that specific energy demand of the extruder (i.e. energy for processing of unit mass of polymer) decreased with increasing throughput whilst fluctuation in energy demand also reduced. However, the relationship between melt temperature and extruder throughput was found to be complex, with temperature varying with radial position across the melt flow. Moreover, the melt thermal stability deteriorated as throughput was increased, meaning that a greater efficiency was achieved at the detriment of melt consistency. Extruder screw design also had a significant effect on the relationship between energy consumption and melt consistency. Overall, the relationship between the process energy demand and thermal stability seemed to be negatively correlated and also it was shown to be highly complex in nature. Moreover, the level of process understanding achieved here can help to inform selection of equipment and setting of operating conditions to optimise both energy and thermal efficiencies in parallel. / This work was funded through an inter-disciplinary research programme (Grant No. EP/G059330/1) by the EPSRC-UK. The technical assistance provided by Ken Howell, Roy Dixon and John Wyborn is greatly appreciated.

An iterative penalty finite element model is developed for the analysis of three-dimensional coupled incompressible fluid flow and heat transfer problems. The pressure is calculated by solving the momentum equation using known values of velocities, velocity gradients, and flow stresses from previous iteration. An iterative solution algorithm which employs the element-by-element data structure of the finite element equations is used to solve large systems of algebraic equations resulting from finite element models of real world problems. Three different iterative methods (ORTHOMIN, ORTHORES and GMRES) are implemented and tested to determine the efficiency of each algorithm terms of CPU time and storage requirements. Jacobi/Diagonal preconditioning is used to scale the system of equations and improve the convergence of the iterative solvers. The developed iterative penalty finite element model is extended to analyse three-dimensional manufacturing processes such as casting, extrusion and forming of metals. For numerical simulation of extrusion and forming, flow formulation is used since these operations involve large deformations. The viscosity of the metal at elevated temperatures is calculated from the flow stress. The formulation uses the enthalpy method to account for the transfer of latent heat during phase change. The fluid inside the mushy region (between liquid and solid regions) is assumed to obey D’Arcy’s law for flow through porous materials. The permeability of the material is determined as a function of liquid fraction. This forces the velocities in the solid region to zero. In the finite element model, the effects of convection during phase change of the material are included. A method for calculation of the movement of liquid metal-air interface during mold filling process is presented. The developed model predicts the location of the interface (defined by a pseudo-concentration value) by solving for its movement due to forced convection. Also during filling analysis, only the filled and interface elements are used for flow field calculations. / Ph. D.