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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
271

Studies On HTPB Based Copolyurethanes As Solid Propellant Binders : Characterization And Modeling Of Network Parameters

Sekkar, V 11 1900 (has links) (PDF)
No description available.
272

Characterization of a Degradable Polar Hydrophobic Ionic Polyurethane Using a Monocyte/Endothelial Cell Co-culture (in vitro) and a Subcutaneous Implant Mouse Model (in vivo)

McDonald, Sarah M. January 2011 (has links)
A degradable/polar/hydrophobic/ionic (D-PHI) polyurethane with properties intended to promote tissue regeneration in a small diameter peripheral artery vascular graft was evaluated for cell biocompatibility and growth. Films were cast in polypropylene 96 well plates for monocyte/endothelial cell (EC) co-culture in vitro studies and porous scaffold discs were implanted in an in vivo subcutaneous mouse model. After 7 days in culture the co-culture demonstrated cell adhesion and growth, low esterase activity (a measure of degradative potential and cell activation), no detectable release of pro-inflammatory cytokine (tumour necrosis factor -α) but measurable anti-inflammatory interleukin (IL)-10. The EC and the co-culture expressed the EC biomarker CD31, whereas the monocyte monoculture did not. Cytokine array analysis of the in vivo characterization of D-PH supported an anti-inflammatory phenotype of cells at the site of the implant. Levels of IL-6 significantly decreased over time while IL-10 was significantly higher at 6 weeks post implant. TNF-α levels did not change significantly from 24 hours onwards, however the trend was towards lesser amounts following the initial time point. Histological analysis of the explanted scaffolds showed excellent tissue ingrowth and vascularization. A live/dead stain showed that the cells infiltrating the scaffolds were viable. Both the in vitro and in vivo results of this thesis indicate that D-PHI is a good candidate material for tissue engineering a peripheral artery vascular graft.
273

Développement de trois différents types de matériaux innovants à base de tannins / Developmentof three different innovative tannin-based materials

Thébault, Marion 16 December 2014 (has links)
Les tannins sont des extraits chimiques présentant une alternative naturelle aux produits chimiques de type phénol ou résorcinol issus du pétrole. Ils sont déjà utilisés industriellement pour la synthèse d’adhésifs utilisés pour la fabrication de produits à base de bois tels que les panneaux de particules et les contreplaqués, mais généralement en utilisant toujours du formaldéhyde comme durcisseur pour améliorer leur pouvoir collant. Les premiers types de produits développés dans cette thèse sont des résines adhésives pour fabriquer des panneaux de particules, synthétisées à partir de tannins de Pin Radiata et d’autres aldéhydes moins nocifs obtenus en faisant réagir de l’huile de tournesol avec de l’ozone puis avec agent réducteur. L’étude s’est portée sur les conditions de l’ozonolyse, dont les paramètres étaient nombreux, et sur les analyses des huiles obtenues, puis sur la synthèse de résines à partir de solutions de tannins. Certaines de ces résines ont été utilisées pour fabriquer des panneaux de particules qui ont été testés en cohésion interne sèche. Puis le sujet s’est orienté vers le développement de mousses rigides à base de tannins et d’alcool furfurylique dans le cadre d’un projet industriel multi-matériaux. Plusieurs formulations ont été testées pour atteindre les objectifs d’un cahier des charges, dont la finalité était d’obtenir en premier lieu des panneaux de mousse homogènes de basse densité avec de bonnes propriétés mécaniques. L’innovation apportée a été de produire ces mousses dans une presse à panneaux. Enfin, une nouvelle façon de fabriquer des polymères polyuréthanes à base de tannins a été testée en utilisant des produits chimiques moins nocifs en remplacement des isocyanates habituellement utilisés dans l’industrie. La synthèse s’est fait d’abord par une étape de carbonatation des groupes hydroxyles des tannins, puis par une réaction avec l’hexamethylènediamine. Les analyses spectrométriques montres que les produits obtenus possèdent bel et bien des liaisons uréthanes. L’étude débouché sur l’exploration de l’utilisation de tannins réagis avec de l’ammoniac pour le remplacement de l’hexaméthylènediamine afin d’obtenir de nouveaux polyuréthanes « non isocynates » avec encore plus de produits biosourcés et plus respectueux de l’environnement / Tannins are chemical extracts which represent a natural alternative to chemicals as phenol or resorcinol which are from oil resources. They are already used industrially for the synthesis of adhesives used for the manufacture of wood-based products such as particleboards and plywood, but generally always used with formaldehyde as a hardener to improve their mechanical strengths. The first products developed in this thesis are adhesive resins for the manufacture of particleboards, synthesized from Radiata Pine tannins and less hazardous aldehydes obtained by reacting sunflower oil with ozone then with a reducing agent. The study has focus first on the conditions of the ozonolysis, whose parameters are numerous, and the analysis of the oils obtained, then on the synthesis of resins with solutions of tannins. Some of these resins have been used to manufacture particleboards that have been tested in dry internal bond strength. Then the subject has been oriented toward the development of rigid tannin/furanic-based foams as part of an industrial multi-material project. Several formulations have been tested to achieve the objectives of a specification, whose first purpose is to obtain foam panels homogeneous, low in density and with good mechanical properties. The innovation has been to make these foams in a particleboard press. Finally, a new route to manufacture tannin-based polyurethane polymers has been tested by using less hazardous chemicals in replacement of isocyanates, conventionally used in the industry. The synthesis is made by a first carbonatation step of tannins hydroxyl groups and then by a reaction with hexamethylenediamine. Spectrometric analyzes have shown that the products obtained do have urethane linkages. The study led to the exploration of the use of tannins reacted with ammonia to replace hexamethylenediamine to obtain new "non isocynates" polyurethanes with more bio-based and environment-friendly chemicals
274

Elimination of SF6 from transmission system equipment

Cai, Xiaolei January 2013 (has links)
Sulphur hexafluoride gas is the dominant insulation and interruption material in high voltage gas insulated substation. Its usage remains a concern of transmission system operators owing to the global warming potential of the gas. The work carried out in this thesis aims to find the environment-friendly materials that can replace SF6. These candidates are required to have a strong dielectric strength for high voltage busbar insulation and well arc extinguishing capability necessary for high voltage circuit breaker.A range of alternative insulation types including CF3I gas and its mixture, high pressure air and solid insulating foam are considered as substitute of SF6. Theoretical studies on the dimensions of busbars used in substations are carried out for these options. The dimension of the dielectric system and its ampacity of respect system are calculated using heat transfer models considering their boiling point and proper working pressure which is related with the dielectric strength of some gas.On the other hand, SF6 gas circuit breaker is extremely popular on the medium and high voltage power networks owning to its effective arc extinguishing performance. It would be ideal if a substitute material could be found for SF6 as an interruption material. Biodegradable oil PTFE ablation, other gas candidates including N2, CF3I are investigated as possible replacement of SF6 through literature study.The usage of vacuum circuit breaker is eventually capable to operate in high voltage transmission system. Simulations have been carried out with software ATP/EMTP to investigate the influence of different characteristics of vacuum circuit breaker including chopping current level, the dielectric strength of vacuum gap and the opening time. And then the probability of overvoltages when vacuum circuit breakers installed is studied by statistical study in MATLAB.
275

Physico-chimie de matériaux à base d'élastomères modifiés hyperélastiques / Physical chemistry of materials based on modified hyperelastic elastomers

Jaudouin, Olivier 13 December 2011 (has links)
Cette thèse vise à développer des matériaux destinés à remplacer les gants des boîtes à gants utilisées en milieu nucléaire confiné par des disques élastomères pouvant prendre la forme des mains lorsqu'un opérateur insère son bras et revenir à leur forme initiale lorsqu'il l'enlève. Le but du travail est de réaliser et d'étudier les propriétés physico-chimiques de matériaux capables de se déformer à plus de 2000 %, à être totalement élastique, à résister au déchirement et aux radiations. Dans un premier temps, une étude bibliographique a montré que les matériaux les plus susceptibles d'y répondre sont les élastomères thermoplastiques. Des matériaux de deux familles d'élastomères thermoplastiques ont donc été réalisés et étudiés. Les premiers sont les élastomères thermoplastiques polyuréthanes. L'influence de la stœchiométrie des monomères et de la structure chimique de différents allongeurs de chaînes sur les propriétés mécaniques a été étudiée. Il en ressort que ces matériaux sont trop visqueux pour répondre au cahier des charges mais une relation intéressante de linéarité entre la contrainte à l'écoulement et le taux de viscosité de l'ensemble de ces formulations a été observée. Les seconds matériaux sont des copolymères Styrène-Ethylène-Butylène-Styrène (SEBS). Les effets du procédé de mise en œuvre ainsi que l'incorporation de plastifiants, de nanoparticules ou de polyuréthane sur les propriétés mécaniques de ces matériaux ont été étudiés. Il a été mis en évidence que le procédé de mise en œuvre influence fortement les propriétés mécaniques et que l'ajout de nanoparticules et de polyuréthane permet d'améliorer certaines propriétés mécaniques. Globalement, les matériaux développés ont des propriétés très proches de celles de matériaux hyperélastiques. / The aim of this PhD work is to replace current gloves of gloveboxes used in nuclear area by elastomer discs which could take the shape of the arm of an operator and come back to their original shape when the arm is removed. The goal of the work is to design and study a material meeting the following specifications: at least 2 000 % strain at break, very high elastic properties, tear and radiation resistant. A bibliographic study showed that the most relevant materials are thermoplastic elastomers. As a consequence, two kinds of these materials were formulated. First ones are thermoplastic polyurethane elastomers. The influence of stoichiometric ratios and different chain extenders on mechanical properties was studied. These materials are too viscous to match the specifications but an interesting linear relation between flow stress and viscosity ratio was observed. Second ones are Styrene-Ethylene-Butylene-Styrene copolymers (SEBS). Studies on the influence of the process and incorporation of plasticizers, nanoparticules or polyurethane were carried out. It was highlighted that the process strongly influences mechanical properties and addition of nanoparticules or polyurethane can increase some of these properties. On the whole, the materials developed are very close to these of hyperelastic materials.
276

Aderência bacteriana e formação de biofilme aos fios de dermossustentação facial / Bacterial adherence and biofilm formation on facial lifting threads

Bruna de Arruda Leite 03 July 2008 (has links)
A flacidez e as rugas de expressão podem ser amenizadas com lifting facial ou implante no tecido subcutâneo da face de fios de poliuretano ou polipropileno. Sob determinadas condições microrganismos podem aderir sobre os fios e interagir com essas superfícies iniciando crescimento celular. O objetivo do presente estudo foi avaliar a aderência bacteriana aos fios de poliuretano e polipropileno por meio de microscopia eletrônica de varredura e métodos microbiológicos. Os fios foram seccionados em segmentos de 1,0 cm de comprimento e transferidos individualmente para tubos Falcon (50,0 mL) contendo caldo Mueller Hinton (15,0 mL), com 200 \'mü\'L da suspensão bacteriana (\'10 POT.8\' UFC/mL) preparada e, incubados por 1h e 30 minutos, 4, 24, 48, 72 e 120 horas. Após cada período de incubação, os corpos-de-prova foram lavados três vezes e introduzidos, separadamente, em 5,0 mL de solução salina esterilizada, sonicados a 40 kHZ por 8 minutos e homogeneizados em vortex por 10 segundos. Esta solução foi diluída (1/10 a 1/1000), da diluição 1/1000 uma alíquota de 0,1 mL foi plaqueada sobre Tryptic Soy Agar (TSA). As placas foram incubadas a 37 graus Celsius por 18 a 24 horas. Após o período de incubação, as células viáveis foram contadas e o resultado anotado em termos de unidades formadoras de colônia (UFC/mL). Os corpos-de-prova destinados à observação por microscópio eletrônico de varredura foram fixados em glutaraldeído, desidratados em séries de álcool, secos em centrífuga a vácuo metalizados com ouro. A avaliação quantitativa do crescimento de S. aureus sobre a superfície do poliuretano, após 1 hora e 30 minutos de contato, foi 4,0 \'+ OU -\' 0,0 log UFC/mL, S. epidermidis 4,07 \'+ OU -\' 0,10 log UFC/mL e P. aeruginosa 5,08 \'+ OU -\' 0,1410 log UFC/mL. Após 4-120 horas o número de células viáveis de S. aureus sobre a superfície do poliuretano foi 5,49 \'+ OU -\' 0,04 log UFC/mL, S. epidermidis 4,99 \'+ OU -\' 0,07 log UFC/mL e P. aeruginosa 6,52 \'+ OU -\' 0,03 log UFC/mL. A avaliação quantitativa do crescimento de S. aureus sobre a superfície do polipropileno, após 1 hora e 30 minutos de contato, foi 4,24 \'+ OU -\' 0,0 log UFC/mL, S. epidermidis 4,14 \'+ OU -\' 0,14 log UFC/mL e P. aeruginosa 5,77 \'+ OU -\' 0,05 log UFC/mL. Após 4 - 120 horas o número de células viáveis de S. aureus sobre a superfície do polipropileno o número de células viáveis de S. aureus foi de 5,96 \'+ OU -\' 0,07 log UFC/mL, S. epidermidis 4,96 \'+ OU -\' 0,06 log UFC/mL e P. aeruginosa 6,63 \'+ OU -\' 0,05 log UFC/mL. O número de células viáveis de S. aureus, S. epidermidis e P. aeruginosa sobre as superfícies de poliuretano e polipropileno foram significantemente diferentes (p<0,05). O biofilme foi observado sobre ambos fios (poliuretano e polipropileno) como demonstrado por meio de microscopia eletrônica de varredura. / Flabbiness and expression wrinkles can be helped by undergoing a face lifting or by implanting subcutaneous tissues of polyurethane or polypropylene threads. Under certain conditions microorganisms can attach themselves to the threads and interact with these surfaces initiating cellular growth. The goal of the present study was to evaluate bacterial attachment to polyurethane and polypropylene threads by means of scanning electron microscopy and microbiological method. The threads were sectioned into segments of 1.0 cm in length and inserted, one by one, into separated Falcon tubes (50 mL) containing Mueller Hinton broth (15 mL), with 200 \'mü\'L of the bacterial suspension (\'10 POT.8\' CFU/mL) prepared, and incubated for 1 hour and 30 minutes, at 4, 24, 48, 72 and 120 hour periods. After each incubation period, the coupons were rinsed three times and, inserted, one by one, into 5.0 mL of sterile physiological saline solution, sonicated at 40 kHz for 8 minutes and vortexed for 10 seconds. This solution was diluted three-fold (1/10 to 1/1000), from dilution the 1/1000 dilution an aliquot of 0.1 mL was plated onto Tryptic Soy agar (TSA). The plates were incubated at 37 Celsius degrees from 18 to 24 h. After the incubation periods, the viable bacteria were counted and the results noted in terms of colony forming units (CFU/mL). The coupons destined for scanning electron microscopy observations were fixed in glutaraldehyde, dehydrated in alcohol series, dried in vacuum centryfuge and metalized with gold. A quantitative evaluation was recorded of the growth of S. aureus on the surface of polyurethane, after 1h and 30 minutes of contact, the results shown 4.0 \'+ OU -\' 0.0 CFU/mL, S. epidermidis 4.07 \'+ OU -\' 0.1 CFU/mL and P. aeruginosa 5.08 \'+ OU -\' 0.14 CFU/mL. After 4 - 120 h the number of viable cells of S. aureus on polyurethane surfaces were 5.49 \'+ OU -\' 0.04 CFU/mL, S. epidermidis 4.99 \'+ OU -\' 0.07 CFU/mL and P. aeruginosa 6.52 \'+ OU -\' 0.03 CFU/mL. A quantitative evaluation was recorded of the growth of S. aureus on the surface of polypropylene after 1h and 30 minutes of contact, the results shown 4.24 \'+ OU -\' 0.20 CFU/mL, with S. epidermidis 4.14 \'+ OU -\' 0.1 CFU/mL and P. aeruginosa 5.77 \'+ OU -\' 0.05 CFU/mL. After 4 - 120 h the number of viable cells of S. aureus on polypropylene surfaces were 5.96 \'+ OU -\' 0.07 CFU/mL, S. epidermidis 4.96 \'+ OU -\' 0.07 CFU/mL and P. aeruginosa 6.63 \'+ OU -\' 0.05 CFU/mL. The number of viable cells of S. aureus, S. epidermidis, P. aeruginosa on polyurethane and polypropylene surfaces were significantly different (p<0.05). A biofilm was observed on both threads (polyurethane and polypropylene) as demonstrated by scanning electron microscopy.
277

Espumas poliuretânicas derivadas de óleo de mamona utilizadas na adsorção de bifenilas policloradas (PCBs) presentes em óleo mineral isolante / Polyurethane foam derived from castor oil used in adsorption polychlorinated biphenyls (PCBs) present in mineral insulating oil

Camargo, Marcio Antonio Ferreira 24 November 2010 (has links)
Os PCBs, do inglês Polychlorinated Biphenyls (bifenilas policloradas), é o nome genérico dado à classe de compostos organoclorados resultante da reação do grupo bifenila com cloro anidro na presença de catalisador. São tóxicos, persistentes, bioacumulativos e representam o risco de provocar efeitos nocivos à saúde humana e ao meio ambiente. Grandes quantidades de PCBs foram produzidos em vários países entre 1927 e 1977. Nos Estados Unidos a proibição ocorreu em 1977. Utilizados como fluidos dielétricos em transformadores elétricos e capacitores em todo o mundo, comercialmente conhecidos como Ascarel, dentre outras denominações, tais como Aroclor, Pyralene, Clorophen, Inerteen, Asbestol e Kneclor. Devido à alta toxicidade, a produção e comercialização dos PCBs foram proibidas no mundo todo a partir de 1980. No Brasil, transformadores que tiveram o óleo mineral isolante, contaminado por PCBs, estando em uso ou em armazenamento, segundo os critérios da Norma ABNT NBR 13882, a destinação final do óleo isolante deverá ser feita por incineração e ou descontaminação a valores inferiores a 50mg/kg. Neste trabalho realizado no Instituto de Química de São Carlos - Universidade de São Paulo, desenvolveu-se um procedimento para a descontaminação de óleo contaminado com valor conhecido acima de 50mg/kg, por percolação em coluna contendo espuma de poliuretano derivada de óleo de mamona, produzida pelo Laboratório de Química Analítica e Tecnologia de Polímeros (GQATP), obtendo-se uma redução de 55% dos níveis de PCBs em óleo contaminado. As espumas foram funcionalizadas com tiodiglicol e polissulfeto de amônio, obtendo-se respectivamente 24% e 11% de redução dos níveis de PCBs em óleo contaminado. Observou-se que a espuma de poliuretano produzida pelo GQATP, funciona como um adsorvente eficaz na remoção de PCBs, e que a utilização de n-hexano na dessorção da espuma, permite remover praticamente todos os PCBs adsorvidos. Portanto, esses tipos de espumas podem servir como adsorventes altamente eficazes na remoção dos PCBs presentes nos óleos minerais isolantes e, portanto, contribuir significativamente para a proteção do meio ambiente. / PCBs, (polychlorinated biphenyls), is the generic name given to the class of organochlorine compounds resulting from the reaction of the biphenyl group with anhydrous chlorine in the presence of catalyst. They are toxic, persistent, bioaccumulative and pose the risk of causing harm to human health and the environment. Large quantities of PCBs were produced in several countries between 1927 and 1977. In the United States the prohibition occurred in 1977. Used as dielectric fluids in electrical transformers and capacitors in the world, commercially known as Ascarel, among other names such as Aroclor, Pyralene, Clorophen, Inerteen, and Asbestol Kneclor. Due to high toxicity, production and marketing of PCBs have been banned worldwide since 1980. In Brazil, transformers that had insulating mineral oil, contaminated with PCBs, while in use or in storage, according to the criteria of the Standard NBR 13,882, the final destination of insulating oil should be by incineration or decontamination and the values below 50mg/kg. In a previous work carried out at the Chemistry Institute of Sao Carlos - University of Sao Paulo, a procedure was developed for the decontamination of oil contaminated with known value above 50 mg / kg of percolation column containing polyurethane foam derived from castor oil produced Laboratory of Analytical Chemistry and Technology of Polymers (GQATP), resulting in a 55% reduction in the levels of PCBs in contaminated oil. Foams were functionalized with thiodiglycol and Ammonium polysulfide, yielding respectively 24% and 11% reduction in the levels of PCBs in contaminated oil. It was observed that the polyurethane foam produced by GQATP function as an effective adsorbent for removal of PCBs, and that the use of n-hexane desorption of the foam allows to remove virtually all PCBs adsorbed. So these types of foam can serve as highly efficient adsorbents for the removal of PCBs present in the insulating mineral oil, and thus contribute significantly to environmental protection.
278

Étude de la réactivité des uréthanes et polyuréthanes : application aux dispositifs médicaux / Study of the reactivity of urethanes and polyurethanes : application to medical devices

Rhoné, Benoît 23 November 2016 (has links)
De nombreux dispositifs médicaux implantables sont utilisés chaque jour. Le contrôle de l'interface du dispositif avec les tissus vivants environnants doit encore être amélioré. De nombreux dispositifs médicaux implantés dans le corps sont le siège d’une ou plusieurs complications graves, telles que l'infection ou la thrombose. C’est notamment le cas des cathéters intraveineux. Dans ce contexte, nous avons cherché à développer une stratégie permettant de réduire les complications associées à leur utilisation, via l’immobilisation covalente de polymères sur les matériaux utilisés en implantation (polyuréthane). La réactivité des uréthanes a d’abord été étudiée, permettant d’identifier la réaction de transcarbamoylation comme outil efficace de modification des uréthanes et polyuréthanes en conditions douces. La réaction entre des poly(éthylène glycol) et la surface de polyuréthane, catalysée par des bases, a permis de rendre les surfaces de PU hydrophiles. Les conditions de modification ont été optimisées. Les surfaces ont été analysées: angle de contact, spectrométrie infrarouge, XPS et TOF-SIMS. Les surfaces modifiées ont montrées d’excellentes propriétés antiadhésives avec une diminution significative de l’adsorption protéique, de l’adhésion de cellules, de plaquettes et de bactéries. Les propriétés des surfaces modifiées ont été évaluées et comparées à d’autres systèmes. Cette stratégie est prometteuse pour la modification en une étape de surfaces de polyuréthane. Les tests in vitro montrent le potentiel de cette modification de surface pour obtenir un polyuréthane ayant une biocompatibilité accrue. / Many implantable medical devices (stents, catheters, cardiac valves…) are used everyday in many domains. The control of the interface between the medical device and the surrounding tissue is still to be improved. Many implanted devices are facing serious complications following implantation such as infections or thrombosis. These problematics are especially present for intravenous catheters used to administrate drugs. In this context, we investigated a way to strongly limit the problematics associated with their implantation, by covalently binding polymers at the surface, to reduce protein adsorption and cell adhesion on the materials used in implantation (polyurethane). The reactivity of urethanes was first studied, it allowed identifying the transcarbamoylation reaction as an efficient tool to modify urethanes and polyurethanes in soft reaction conditions. The reaction of poly (ethylene glycol) and the polyurethane surface, catalyzed by bases, allowed us to get hydrophilic polyurethane surfaces. Modification conditions were optimized to obtain a good covering of the surface with PEG. Surfaces were analyzed: contact angle, profilometry, infrared spectroscopy, XPS and TOF-SIMS. Modified surfaces showed excellent antiadhesive properties with a strong reduction of protein adsorption, cell and bacterial adhesion. The properties of modified surfaces were evaluated and compared to other systems. This strategy of modification is promising to allow one step modification of polyurethane surfaces. In vitro tests show the potential of this surface modification technique to obtain a polyurethane with enhance biocompatibility.
279

Investigations on post-processing of 3D printed thermoplastic polyurethane (TPU) surface

Boualleg, Abdelmadjid January 2019 (has links)
Abstract The reduction of product development cycle time is a major concern in industries to remain competitive in the marketplace. Among various manufacturing technologies, 3D printing technology or also known as additive manufacturing (AM), has shown excellent potential to reduce both the cycle time and cost of the product due to its lower consumption of energy and material usage compared to conventional manufacturing. Fused deposition modeling (FDM) is one of the most popular additive manufacturing technologies for various engineering applications which has the ability to build functional parts having complex geometrical shapes in reasonable build time and can use less expensive equipment and cheaper material. However, the quality of parts produced by FDM has some challenges such as poor surface quality.   The focus of this study is improving the surface quality produced by Fused Deposition Modeling. The investigations include 3D printing study samples with optimum parameter settings and post-processing the sample’s surfaces by laser ablation. Taguchi’s design of the experiment is employed to identify the optimum settings of laser ablation the FDM surfaces. Laser power, laser speed and pulse per inch (PPI) are the laser settings considered in the study. Characterization of the samples are done using Dino-lite USB camera images and GFM Mikro-CAD fringe projection microscope is used to measure the surface roughness of the samples. Areal surface parameters are used to characterize and compare the surfaces of as printed and laser ablated. It is observed that the effect of laser ablation varies with respect to surfaces printed at different angles and laser-ablated with different settings. The surface roughness of laser-ablated surfaces is found to be lower than as-printed FDM surfaces.
280

Avaliação de painéis de partículas homogêneas empregando-se madeira de hevea brasiliensis e tectona grandis, aglutinadas com adesivo poliuretano derivado de óleo de mamona /

Gilio, Caroline Graminha. January 2020 (has links)
Orientador: Sergio Augusto Mello da Silva / Resumo: Estudos sobre florestas plantadas para aproveitamento de madeiras em vários setores industriais tem se intensificado no mundo. A utilização dessas madeiras no Brasil, além de garantir a sustentabilidade de espécies nativas, possibilita a produção de derivados de madeiras e o amplo emprego na construção civil. A Seringueira (Hevea brasilienses) e Teca (Tectona grandis) representam duas espécies de reflorestamento cultivadas no Brasil e que serão utilizadas neste trabalho para produção de painéis de partículas homogêneas. A Seringueira é utilizada para produção de borracha natural, entretanto, precisam ser substituídas ao final do ciclo de produção (25 a 30 anos) e, as árvores improdutivas são utilizadas para geração de energia. Com relação à Teca, espécie de origem asiática, sua madeira apresenta excelentes características de resistência e durabilidade e vem sendo empregada na construção civil de modo geral e para a produção de móveis. Vale ressaltar, que tanto a Seringueira quanto a Teca, adaptadas às condições edafológicas das regiões em que são reflorestadas, apresentam rápido crescimento e poderiam ser utilizadas para produção de painéis de partículas. Entretanto, para este trabalho, será considerada a utilização dessas espécies com mais de 20 anos, buscando-se avaliar a possibilidade de aproveitamento dessas para a produção de painéis de partículas aglutinadas com adesivo poliuretano derivado de mamona (PU-Mamona). Os painéis produzidos foram avaliados de acordo com NBR 1... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Studies on planted forests to use wood in various industrial sectors has intensified in the world. The use of these woods in Brazil, in addition to ensuring the sustainability of native species, enables the production of wood derivatives and wide employment in civil construction. The rubber tree (Hevea brasilienses) and Teca (Tectona grandis) represent two species of reforestation cultivated in Brazil and which are used in this work for the production of particleboards. The rubber tree is used for the production of natural rubber, however, it needs to be replaced at the end of the production cycle (25 to 30 years) and, the unproductive trees are used for power generation. Regarding Teca, a species of Asian origin, its wood has excellent resources of resistance and durability and has been used in civil construction in general and for furniture production. It is worth mentioning that both Seringueira and Teca, adapted to the edaphological conditions of the regions where they are reforested, show quick growth and are used for the production of particleboards. However, for this work, the use of these species with more than 20 years will be considered, looking for the possibility of using them for the production of agglutination panels with castor oil-based polyurethane adhesive (PU-Castor). The panels produced were evaluated according to NBR 14810 - 1 and 2: 2013 and international documents to verify their physical and mechanical properties, as well as, using scanning electron mi... (Complete abstract click electronic access below) / Mestre

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