Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-07-28T15:26:06Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) DISSERTAÇÃO BIB CENTRAL SALIM ARRUDA.pdf: 4318932 bytes, checksum: a6d753eb3af831ca1aa8c18f6f631669 (MD5) / Made available in DSpace on 2016-07-28T15:26:06Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) DISSERTAÇÃO BIB CENTRAL SALIM ARRUDA.pdf: 4318932 bytes, checksum: a6d753eb3af831ca1aa8c18f6f631669 (MD5) Previous issue date: 2016-02-26 / PRH-L8 Petrobrás / O acúmulo de resíduos plásticos em aterros sanitários, rios e ilhas, além da contaminação da fauna e da flora com esses dejetos, acarretou uma pesquisa intensa em materiais biodegradáveis que possam substituir os tradicionais materiais sintéticos advindos do petróleo. Os polímeros biodegradáveis são uma opção que vem sendo constantemente estudada e que pode, em um futuro próximo, competir com os polímeros a base de petróleo. O Poli (3-hidroxibutirato) (PHB) é um polímero produzido por bactérias que utilizam a sacarose da cana de açúcar ou do milho como fonte de alimento. O PHB possui características interessantes como biodegradabilidade, sustentabilidade, plasticidade e sua durabilidade. Porém, ele possui um maior custo, além de ser duro e quebradiço e termicamente instável durante o processamento. Portanto, torna-se necessário o estudo da cristalização do PHB atrelado a fibras de babaçu, com o intuito de diminuir o custo do compósito, além de buscar melhorias nas propriedades térmicas, como cristalinidade relativa, taxa de cristalização, temperatura do pico de cristalização, entre outras variáveis. Neste trabalho foram estudados os parâmetros de cristalização a partir do fundido para o sistema PHB/20% fibra de babaçu conduzidos a diferentes taxas de resfriamento (2, 3, 4, 6, 8, 12, 16 e 24 °C/min) e fluxo de nitrogênio a 50 mL/min e, posteriormente, esses parâmetros de cristalização, como a granulometria, tempo de processamento e diferentes partes do babaçu, foram comparados para as diferentes taxas de resfriamento. Uma segunda análise foi realizada para os parâmetros de cristalização a frio conduzidos a diferentes taxas de aquecimento. A partir do tratamento de dados obtidos para os parâmetros de cristalização a partir do fundido, realizou-se a modelagem cinética para os modelos de Pseudo-Avrami, Ozawa e Mo. Entre as modelagens, o modelo de Pseudo-Avrami apresentou a melhor correlação com os dados experimentais com erro relativo de aproximadamente 5%. O modelo de Ozawa apresentou um erro em torno de 8% e Mo aproximadamente 10%. A análise da energia de ativação foi realizada a partir do Método Isoconversional de Friedman, obtendo energias de ativação negativas, indicativo que há reações complexas na cristalização a partir do fundido para o sistema PHB/20% fibra de babaçu. / The accumulation of plastic waste in landfills, rivers and islands, as well as the contamination of fauna and flora with these wastes, led to intensive research into biodegradable materials that can replace traditional synthetic materials. Biodegradable polymers are an option that has been constantly studied and that may, in the near future, compete with petroleum-based polymers. Poly (3-hydroxybutyrate) (PHB) is a polymer produced by bacteria that use sucrose from sugar cane or corn as a food source. PHB has interesting features such as biodegradability, sustainability, plasticity and durability. However, it has a high cost, in addition to being hard and brittle and thermally unstable during processing. Therefore, it was found convenient to study the crystallization of PHB/20% babassu compounds, with the intention of reducing the cost of the composite, in addition to seeking improvements in thermal properties such as relative crystallinity, crystallization rate, peak crystallization temperature, etc. In this work, the parameters of melt crystallization were studied for PHB/20% babassu compounds driven at different cooling rates (2, 3, 4, 6, 8, 12, 16 and 24°C/min) under a nitrogen flow of 50 ml/min. Subsequently, crystallization parameters determined in compounds prepared with different filler particle size, processing times, and different parts of babassu, were compared for different cooling rates. A second analysis was performed for the parameters of cold crystallization conducted at different heating rates. A kinetic analysis of data obtained for melt crystallization, using Pseudo-Avrami, Ozawa, and Mo models was performed. Among the models studied, Pseudo-Avrami showed the best correlation with experimental data, with relative error about 5%. The Ozawa model presented a discrepancy around 8% and Mo approximately 10%. The activation energy was estimated using the isoconversional Friedman method, obtaining negative activation energies, which suggests that there are complex reactions involved in the crystallization from the melt in the system PHB/20% babassu.

Biomass is the only renewable carbon source that can compete with fossil energy sources in terms of production of materials, chemicals and fuels. Biomass can be transformed into charcoal, liquid and gas through pyrolysis, i.e. pure thermal decomposition. By changing the pyrolysis conditions either solid, liquid or gaseous fractions can become the main product and pyrolysis is thus a very versatile process. Pyrolysis is also the first step in combustion and gasification, two important thermal processes in our society. The importance of biomass pyrolysis has led to extensive research in this area but due to the complexity of the process there is still no general understanding of how to describe biomass pyrolysis, which is essential in order to optimize thermal processes. The research presented in this thesis thus aims at finding a simple yet accurate way to model the decomposition rate of biomass during pyrolysis. Thermogravimetric analysis, a well known method that is simple to use, was chosen to collect the experimental data used for kinetic evaluation. The reaction kinetics were derived using two different model-free, isoconversional methods, i.e. the non-linear form of the Friedman method and the incremental, integral method ofVyazovkin. By using these two methods and experimental data, complete reactionrate expressions could be derived for commercial cellulose, Norway spruce and seven different samples originating from kraft cooking, the most common process to produce pulp for the paper industry. The derivation of model-free rate expressions have never been performed before for these materials and since the rate expressions are model-free, no assumptions or knowledge about the pyrolysis reactions were required. This is a great advantage compared to the commonly used model-fitting methods that rely on information about these aspects. All therate expressions were successful in predicting mass-loss rates at extrapolated pyrolysis conditions. This is a clear indication of the soundness of the methodologypresented in this thesis. / Biomassa är den enda förnybara kolkällan som kan konkurrera med fossila energikällor när det gäller produktion av material, kemikalier och bränslen. Biomassakan omvandlas till biokol, bioolja och gas med hjälp av pyrolys, dvs termisk nedbrytning. Genom att variera de processförhållanden som råder under pyrolysen kan man få antingen fast, flytande eller gasfasiga ämnen som huvudprodukt, något som gör pyrolys väldigt flexibelt. Utöver detta är pyrolys även betydelsefull vid förbränning och förgasning, två viktiga processer i dagens samhälle. Vikten av biomassapyrolys har resulterat i omfattande forskning inom området men pga biomassas komplexa natur råder det ännu ingen enighet gällande hur biomassapyrolys bör modelleras. Detta försvårar utveckling och optimering av termiska processer matade med biomassa. Forskningen som presenteras i denna avhandling fokuserar således på att finna en enkel men noggrann metod för att beskriva hastigheten med vilken biomassa bryts ned under pyrolys. Termogravimetrisk analys, en vanligt förekommande metod som är enkel att använda, valdes för att samla in experimentell data som kan användas för att undersöka hastigheten för termisk nedbrytning, dvs kinetiken. Två olika metoder som på engelska går under benämningen “model-free” och “isoconversional” har använts, nämligen den icke-linjära formen av Friedmans metod och den stegvisa, integrala metoden som utvecklats av Vyazovkin. Genom att använda dessa två metoder och experimentell data kunde kompletta reaktionshastighetsuttryck tas fram för kommersiell cellulosa, gran och sju olika material framställda genom sulfatprocessen, den idag vanligast förekommande pappersmassaprocessen. Pyrolyskinetiken för dessa material har aldrig tidigare analyserats med dessa två metoder och fördelarna med metoderna gjorde det möjligt att bestämma hastighetsuttryck utan någon kunskap om de pågående reaktionerna. Detta är en viktig fördel jämfört med andra metoder som är beroende av sådan information. Alla framtagna reaktionshatighetsuttryck kunde användas för att framgångsrikt förutsäga minskningen av massa vid extrapolerade pyrolysförhållanden. Detta är en tydlig indikation på att metoden använd i denna avhandling fungerar väl. / <p>QC 20160524</p>

Les travaux de recherche présentés dans cette thèse sont orientés vers la compréhension des mécanismes réactionnels propres aux produits pétroliers tels que les lubrifiants et les graisses par analyse thermique. La technique d’analyse thermique principalement utilisée était la calorimétrie de réaction. Dans un premier temps, une étude approfondie de la réponse instrumentale a été conduite. Une nouvelle méthode d’étalonnage a été proposée en se basant sur l’étalonnage par effet Joule. Avec ce type de correction, une étude cinétique plus précise peut alors être conduite, elle permet en outre d’étudier la cinétique de mécanisme complexes comme celles rencontrées avec les produits pétroliers. Dans un second temps, l’étude de la neutralisation de l’acide sulfurique par un lubrifiant marin a été effectuée. Cette étude a permis de développer une méthode d’analyse de routine permettant de comparer l’efficacité d’un lubrifiant à neutraliser une quantité précise d’acide sulfurique. Il devient alors possible d’estimer le temps nécessaire pour neutraliser l’acide afin d’éviter qu’il n’endommage l’intégrité des parties métalliques sensées être protégées par le lubrifiant marin. Une étude cinétique du phénomène de neutralisation, par l’intermédiaire des méthodes isoconversionnelles, a permis d’avoir une indication sur le modèle réactionnel pilotant ce mécanisme. Pour finir, l’influence du choix des paramètres tels que la température, les vitesses de chauffe où les temps de cuisson de graisse, a été étudié par en mêlant des techniques d’analyses thermique et rhéologiques. / The research work presented in this thesis are oriented on the understanding of reactional mechanisms occurring in the field of oil products, such as lubricants and greases, by thermal analysis. The main thermal analysis technique used was the reaction calorimetry. Firstly, the instrumental response study of the calorimeter was led. A new calibration method have been proposed, this method is based on the calibration by Joule effect. From this correction, a more accurate kinetic evaluation can be done in order to study the complex mechanisms as those met with oil products. In a second time, the study of the neutralization of sulfuric acid by a marine cylinder lubricant was carried out. This work allowed to develop a routine analysis method to compare the lubricant ability to neutralize a precise amount of sulfuric acid. The time estimation is important to determine the frequency of lubricant replacement and to avoid the damage on the metallic parts. A kinetic study of the neutralization phenomena using isoconversional kinetic method, allowed to obtain the reactional model. Finally, the influence of parameters choice such as temperature, heating rate or cooking time have been evaluated by thermal and rheological analysis. Greases have been produced in a reaction calorimeter using a stirring system specifically developed. Information obtained allow to choose accurately the parameters used during the manufacturing processes in order to save time and decrease production costs.

Tato dizertační práce je napsána jako termoanalytická studie humifikovaných substrátů, tj. huminových látek a půdních vzorků, získaných z několika různých zdrojů tak, aby byl pokryt co nejširší rozsah primárních charakteristik. Práce hledá lineární korelace (s využitím Pearsonova korelačního koeficientu) mezi kinetikou termo-oxidační degradace (sledovanou pomocí termogravimetrie (TGA) a vyjádřenou konverzním časem stanoveným neizotermickou izokonverzní metodou) a standardními charakteristikami, jako je množství aromatického a karboxylového uhlíku přítomného v huminových látkách stanoveného spektroskopií nukleární magnetické rezonance (NMR). Hlavním cílem této práce je objasnit proces termo-oxidační degradace humifikované části přírodní organické hmoty a hledat závislosti mezi primární a sekundární strukturou huminových látek. Dalším úkolem je nalezení korelace mezi termogravimetrickým úbytkem hmotnosti půdních vzorků a jejich mikrobiální stabilitou měřenou v laboratorních experimentech jakožto půdní respirace (tedy uvolňování oxidu uhličitého). Účelem je zjistit, zdali vzájemné propojení vůbec existuje, a objasnit jaké druhy procesů, které provázejí půdní respiraci, je možné jednoduše odhalit pomocí TGA. Výsledky práce skýtají detailnější pohled na termickou analýzu půdních vzorků a jiných humifikovaných materiálů. Hlavním přínosem této práce je prezentace vyskytujících se aplikací termické analýzy pro charakterizaci půdní organické hmoty a dále také příspěvek k rozvoji aplikací technik termické analýzy v půdní vědě.

This diploma thesis is focused on issues concerning the stability of selected vegetable oils which are used in cosmetic industry. The stability of eight oils without additives were determined by a differential scanning calorimeter. In the first phase, the temperatures of oil degradation were determined for different rates of heating, i.e. nonisothermal stabilities. They were consequetly used to calculate isothermal stabilities alias induction periods. The calculation of induction periods was completed by using integral isoconversional methods, which applied four different temperature functions. One of the temperature functions corresponded to Arrhenius equation while the others to non-Arrhenius functions. The confrontation of induction periods under standart conditions showed that an optimal temperature function to calculate oil stabilities is one of the non-Arrhenius functions in exponential form. We can state that all oils are degraded by similar, if not the same, mechanism. The specified stabilities, in periods of months, have proved the importance of using stabilizers and other additives in the commercial and technological use of vegetable oils.

<p>Additive manufacturing of gun propellants is an emerging and promising field which addresses the limitations of conventional manufacturing techniques. Gun propellants are manufactured using wetted extrusion, which uses volatile solvents and dies of limited and constant geometries. On the other hand, additive techniques are faced with the challenges of maintaining the gun propellant’s energetic content as well as its structural integrity during high pressure combustion. The work presented in this thesis demonstrates the feasibility of producing functioning gun propellant grains using vibration-assisted 3D printing, a novel method which has been shown to extrude extremely viscous materials such as clays and propellant pastes. At first, the technique is compared to screw-driven additive methods which have been used in printing gun propellant pastes with slightly lower energetic content. In chapter two, diethylene glycol dinitrate (DEGDN), a highly energetic plasticizer, was investigated due to its potential to replace nitroglycerin in double base propellants with high nitroglycerin content. A novel isoconversional method was applied to analyze its decomposition kinetics. The ignition and lifetime values of diethylene glycol dinitrate were obtained using the new isoconversional method, in order to assess the safety of using the plasticizer in a modified double base propellant. In chapter three, a modified double base propellant (M8D) containing DEGDN was additively manufactured using VAP. The printed strands had little to no porosity, and their density was nearly equal to the theoretical maximum density of the mixture. The strands were burned at high pressures in a Crawford bomb and the burning was visualized using high speed cameras. The burning rate equation as a function of the M8D propellant as a function of pressure was obtained. Overall, this work shows that VAP is capable of printing highly energetic gun propellants with low solvent content, low porosity, with high printing speeds, and which have consistent burning characteristics at high pressures. </p>

<p dir="ltr">Additive manufacturing (AM) of gun propellants is an emerging and promising field which addresses the limitations of conventional manufacturing techniques. Overall, this thesis is a body of work which serves to bridge the gap between fundamental research and application of additively manufactured gun propellants.</p>