Depuis l’obtention des premiers résultats de la mission Cassini Huygens, les aérosols de Titan présentent un intérêt astrobiologique car leur caractérisation permet d'évaluer la chimie prébiotique qui a eu lieu sur la Terre primitive. Mieux comprendre les propriétés physico-chimiques des aérosols de Titan est important pour les scientifiques. Le laboratoire via l'analyse des propriétés des tholins (l'analogue des aérosols de Titan) permet de surmonter les difficultés d’analyser les aérosols de Titan directement. Dans ce travail de thèse, l'objet de la recherche est l’analyse des tholins produits par l’expérience PAMPRE. La technique d’analyse Pyr-GC-MS a été utilisée pour caractériser la composition et la structure de tholins. La stabilité thermique et le changement des propriétés en fonction de la température ont été réalisés par l'étude de la dégradation thermique. Enfin, l'évolution des aérosols organiques après leur précipitation sur la surface de Titan a également été étudiée selon la méthode GC-MS d’analyse des tholins. Les résultats obtenus peuvent être utilisés pour interpréter les données recueillies par des observations de Titan de la terre ou par la sonde Cassini-Huygens, afin de mieux caractériser le satellite et son évolution. / Since the achievement of the first results from the Cassini Huygens mission, Titan’s aerosols present an astrobiological interest as their characterization enables to evaluate the prebiotic chemistry that occurred on the primitive Earth. To better understand the physical chemistry of the aerosols of Titan is important for scientists. The laboratory via analyzing the properties of tholins (analogues of Titan’s aerosols) overcomes the difficulties for analyzing Titan’s aerosols directly. In this thesis work, the research object is tholins produced by the PAMPRE experiment. Pyr-GC-MS analysis technique was used to characterize the composition and structure of tholins. The thermal stability and the properties change with the temperature have been realized by thermal degradation study. Finally, the evolution of organic aerosols after precipitation on the surface of Titan was also investigated through GC-MS analysis of tholins. The results obtained can be used to interpret data collected by observations of Titan from Earth or by the Cassini-Huygens probe, to better characterize the satellite and its evolution.

A necessidade básica de corte de têxteis nos formatos convenientes ao posterior das peças dentro da indústria da confecção determinou o desenvolvimento dos diversos tipos de processos de corte atualmente existentes. Estes processos podem ser classificados em três grupos principais: corte mecânico, corte por laser e híbrido mecânico-térmico. O corte mecânico, que se utiliza de um agente de corte tal como faca, serra, prensa, etc., é de longe o mais empregado, devido principalmente seu baixo custo. Embora perfeitamente adequado para uma grande variedade das aplicações existentes, possui limitações específicas. O corte mecânico é adequado para cortes simultâneo de várias camadas de tecidos sobrepostas embora a velocidade de corte seja baixa. O processo de corte por laser tem sua principal vantagem na ausência de forças de corte sobre o material, permitindo um corte preciso. Além disso, permite altas velocidades de avanço. Suas principais desvantagens são o preço do equipamento e a impossibilidade de corte de várias camadas sobrepostas de tecido. O corte mecânico-térmico tem emprego bem mais limitado e consiste na degradação do material através do contato de uma ferramenta aquecida. Para têxteis tem sido usado até agora para seccionamento reto. A proposta aqui apresentada é de um novo processo de corte de têxteis apropriado ao retalhamento de tecidos dispostos em camadas sobrepostas que emprega um processo híbrido de degradação térmica do material combinada à ação mecânica de gumes de corte. Este processo consiste na utilização de uma fresa de topo eletricamente aquecida, que em decorrência da pequena área da seção transversal do circuito elétrico no comprimento de corte, da elevada resistividade elétrica do seu material e do valor elevado da corrente elétrica que o atravessa, tem a temperatura nesta região bastante elevada devido ao calor gerado pelo efeito Joule. Esta energia será absorvida pelo meio material que circunda a ferramenta, provocando a degradação localizada das fibras têxteis. Uma campânula cobre a região do contato entre a ferramenta e o tecido e em seu interior é injetado gás nitrogênio como forma de criar-se uma atmosfera inerte que iniba a combustão do tecido. O mecanismo de corte pode então ser sucintamente descrito como uma degradação térmica do material seguido da remoção mecânica dos seus resíduos pelas arestas de corte da ferramenta. Apropriado para o corte de várias camadas de tecido sobrepostas, sua maior vantagem está em sua capacidade de corte de figuras complexas que apresentem curvaturas bastante acentuadas. A combinação de um processo mecânico com o de degradação térmica permite que as forças de corte sejam baixas, garantindo desse modo a precisão do corte. Uma das áreas que possivelmente se beneficiaria deste tipo de equipamento seria o de confecção de roupas infantis, que utiliza extensivamente o recorte de figuras estampadas. Inicialmente pensado para o corte de têxteis de fibras naturais observou-se que o emprego acarretava a impregnação das peças com um persistente odor de queimado, o que se constitui uma restrição ao emprego do processo em artigos de vestuário e do lar. Contudo, no caso de têxteis sintéticos foi observado um desempenho bastante apreciável e que tenha como limitação apenas a soldagem das peças sobrepostas, o que pode ser evitado com a introdução de folhas de papel entre elas. Dos resultados obtidos no processo de corte observou-se que o seu desempenho é comparável a de outras tecnologias já estabelecidas, realçando-se que este processo pode ser certamente otimizado com o emprego de dispositivos que o levem a operar nas condições de maior rendimento e de outras medidas que diminuam as restrições atuais. / The basic necessity of cutting textiles into convenient forms for later processing within the confection industry has determined the various cutting methods in existence. These processes may be classified in three principle groups: mechanical cutting, laser cutting and hybrid mechanical-thermal cutting processes. Mechanical cutting, in which knives, saws, presses, etc. are employed, is by far the most used, due principally to the low costs involved. Although perfectly adequate for wide variety of applications, it possesses specific limitations. Mechanical cutting is adequate for straight cuts or of not very pronounced curvature and is efficient for over-layed simultaneous cuts, although the cutting velocity is low. The laser cutting process has as its principal advantage the lack of cutting forces on cut the material. As well as high advance speeds. The principal disadvantages are the price of the equipment and the impossibility of cutting various layers of material at the same time. Mechanical-thermal cutting is much less used and consists of the degradation of the material on contact with the heated cutter. The proposal here presented is of a new process of textile cutting of overlaid layers of material through the use of a hybrid process of thermal degradation of the material combined with the mechanical action of the cutting-edges. This process consists of the use of an electrically heated vertical mill which, as a result of the small cross-section of the electrical circuit formed by the length of the cut, the high resistivity of the material and of the electrical current that runs through it, possesses a high temperature in this region due the Joule effect. This energy is absorbed by the material that touches the cutting surface provoking the localized degradation of the textile fibers. A bell form covers the region of contact between cutter and material and nitrogen is injected into this space, being an inert gas that inhibits combustion of the material. The mechanism of the cut may thus be described as the thermal degradation of the material followed by the mechanical removal of the material and its residues by the tool cutting edges. Suitable for the cutting of various layers of material, the major advantage of this method is its capacity of cutting complex forms that include accentuated curvatures. The combination of mechanical process with thermal degradation permits low cutting forces, thus guaranteeing the precision of the cut. One area of use that could possibly benefit from this type of equipment is the confection of children and infant clothing, which makes extensive use of the cutting of printed designs. Initially intended for the cutting of natural textile fibers, the method is restricted to use for articles for home use due to the persistent burn odor observed during tests. For synthetic textiles was observed a good performance although occurs the edge welding of over-Iayed pieces. This may be evicted by the introduction of paper sheets between the fabric layers. The results of the tests show the performance of this process is comparable with others established technologies. However this process may be optimized with the use of devices that make the equipment to operate in the conditions of high efficiency and others that reduce the current restrictions.

Orientador: Adriana Vitorino Rossi / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-19T14:28:20Z (GMT). No. of bitstreams: 1 Coelho_AlineGuadalupe_M.pdf: 2011995 bytes, checksum: 9c482d314d20b2ffa92f0b204911224f (MD5) Previous issue date: 2011 / Resumo: Antocianinas (ACYS) são corantes naturais que conferem cor a folhas, flores e frutas, são derivados glicosilados do cátion flavílio, da classe dos flavonóides e apresentam potencial para uso como corante, além de atividade antioxidante e terapêutica. Essas características estimulam buscar formas de viabilizar a utilização desses corantes na indústria de diversos segmentos, além de fomentar pesquisas acerca de sua estabilidade. Nesse trabalho, realizou-se o estudo da degradação térmica de extratos de ACYS, obtidos de uva (Vitis vinifera L. 'Brasil') e jabuticaba (Myrciaria Cauliflora). Os padrões das ACYS majoritárias para cada fruta malvidina-3-glicosídeo e cianidina-3-glicosídeo foram utilizados como referência. Foram realizados ensaios de estabilidade, para extratos obtidos a 25, 55 e 85 °C, com pH ajustado para 3,0 e mantido natural, armazenados sob-refrigeração ou a temperatura ambiente. Além disso, foram realizados ensaios de degradação acelerada a 55 e 85 °C com monitoramento espectrofotométrico e análises dos extratos e padrões iniciais e degradados por UHPLC-MS. Os ensaios de estabilidade dos extratos foram monitorados por até 170 dias. Foi verificado o efeito da baixa temperatura de armazenamento, para a estabilidade dos extratos de uva, enquanto para os extratos de jabuticaba foram verificados também o efeito da diminuição do pH, e do aumento da concentração. Os estudos da degradação térmica indicaram o aumento da velocidade da degradação das ACYS, com o aumento da temperatura. As análises de UHPLC-MS dos extratos degradados indicaram que a temperatura de degradação não altera a rota de degradação das ACYS nas amostras. As reações de degradação dos padrões seguem ajustes de segunda ordem com energias de ativação de 95,2±0,1 e 89,34±0,05 kJ mol, e tempos de meia vida de 78 ± 2 e 4,2± 0,1 e 58,7 e 3,8±0,4 horas para degradação a 55 e 85 °C da cianidina-3-glicosídeo e malvidina-3-glicosídeo, respectivamente / Abstract: Anthocyanins (ACYS) are natural dyes that give color to leaves, flowers and fruits, they are glycosylated derivatives of flavylium cation, the class of flavonoids and have potential for use as a dye, as well as antioxidant activity and therapy. These features facilitate finding ways to encourage the use of these dyes in various industry segments, and foster research about its stability. In this work, we carried out the study of thermal degradation of ACYS extracts obtained from grape (Vitis vinifera L. 'Brazil') and jabuticaba (Myrciaria cauliflora). Standards of the ACYS (malvidin-3-glucoside and cyanidin-3-glucoside) present in major quantity in each fruit were used as a reference. Stability tests over time, for extracts obtained at 25, 55 and 85 ° C, with pH adjusted to 3.0 and maintained course, and stored under refrigeration, were performed at room temperature. Further tests were carried out in order to determine accelerated degradation at 55 and 85 °C and were analyzed through spectrophotometry. Inicial and degraded standards were analyzed by UHPLC-MS. Monitoring of the extracts was performed for up to 170 days, and the effect of storage temperature for stabilization of grape extracts was verified. In case of jabuticaba extracts, the effect of lower pH, the concentration of the extracts was also verified in addition to storage temperature. The thermal degradation studies indicated that the increased speed of degradation of ACYS with increasing temperature. The UHPLC-MS analysis of degraded extracts to indicate, that the degradation temperature does not change the route of degradation of samples. The standards degradation reaction followed fit second order adjustment with activation energies of 95.2±0.1 and 89.34±0.05 kJ mol, half-life of 78±2, and 4.2± 0.1 and 58.7±0.4 and 3.8 hours to decay to 55 and 85° C of cyanidin-3-glucoside and malvidin-3-glucoside, respectively / Mestrado / Quimica Analitica / Mestre em Química

No description available.

Yes / Polyamide 6 (PA6) is an important engineering thermoplastic, very widely used but prone to thermal degradation during extrusion at temperature not far from its melt temperature (220 oC). Typically, and as measured in this study, PA6 extruded at temperature of 300 oC shows a 40% decrease in tensile modulus compared to non-extruded PA6. To rebuild PA6 molecular weight, the easiest and cheapest method is to use an appropriate chain extender. Many chain extenders have been used in the past but they are essentially suited to nucleophile induced degradation, targeting split PA6 chains carboxyl COOH and amine NH2 end groups. What has been lacking are effective chain extenders for thermally only induced degradation, i.e. for the practical cases where the PA6 is thoroughly dried before extrusion. For such a case, the degradation reaction mechanism dictates that the solution is to develop chain extenders that target the split PA6 chains amide CONH2 groups not the carboxyl COOH and amine NH2 end groups. As amide groups strongly react with anhydride functionalities, we test the effectiveness of a novel chain extender, Joncryl® ADR 3400, a styrene maleic anhydride copolymer with multiple, repeating anhydride functionality. Assessment of chain extension in this study is done as with previous work, using rheology, mechanical and thermal properties of PA6 extruded on its own and with the chain extender. The viscoelastic data conclusively show the efficacy of such chain extender with more than 10 fold changes in the comparative values of the extruded sample storage modulus G' and as much as an 85% increase in the tensile modulus. / Republic of Turkey, Ministry of National Education. University of Bradford

Le traitement thermique est basé sur la modification chimique des biopolymères par thermodégradation, en évitant l'ajout de produits chimiques. Ce traitement améliore la stabilité dimensionnelle et la durabilité fongique du bois. Ces améliorations se font au détriment des propriétés mécaniques qui ont tendance à s'affaiblir. Aujourd'hui, plusieurs types de procédés sont utilisés. Ils se distinguent entre autre par la nature du milieu dans lequelle se déroule le traitement. La durabilité de ce nouveau matériau bois est liée au degré de thermodégradation, dépendant des conditions et de l'intensité du traitement. Un pilote de traitement par conduction, travaillant sous vide ou sous azote, mesurant la masse en dynamique est utilisé afin de mieux comprendre l'influence de l'atmosphère. Les résultats obtenus montrent que l'utilisation du vide permet d'éliminer, de l'enceinte de traitement, les produits volatils formées au cours du traitement conduisant à des taux de lignine de Klason plus faibles du fait de la non recondensation des produits de dégradation. Cette limitation de recondensation des produits volatiles engendre des pertes de masse, pour une même intensité de traitement plus faibles, confirmés par des taux de polysaccharides plus élevés pour un traitement sous vide. Des études de cinétiques des réactions de thermodégradation ont confirmé la plus grande sensibilité des feuillus vis-à-vis de la thermodégradation (comparé aux résineux). De plus, ces analyses ont permis d'identifier les principaux produits de thermodégradation du bois qui varient en fonction de l'intensité du traitement et a permis de montrer une thermosensibilité plus importante de la lignine que de l'holocelluloses pour la gamme de températures utilisée. Le fruit de ces travaux est donc une progression significative des connaissances de bases sur les mécanismes de thermodégradation et leurs relations avec les paramètres de traitement / Thermal treatment is based on biopolymer chemical degradation by heat transfer, without additional chemical products impregnation. This process improves the dimensional stability and the decay resistance of wood. These improvements come at the expense of wood mechanical properties of wood which weak. Several types of heating processes exist currently differing mainly by the nature of the inert atmosphere used during treatment. The durability of this new wood material is correlated to the degree of polymers thermal degradation depending on the conditions and the treatment intensity. A conducting heat treatment pilot using nitrogen or vacuum and allowing dynamic record of mass loss is used to understand better the atmosphere influence. The results show that utilization of vacuum permit the elimination of volatile products formed during heat treatment and accumulated in oven, leading to lower extractives and Klason lignin contents due to the non recondensation of thermal degradation products. Limitation of the formation of recondensation products generates a lower mass loss for same treatment intensity and explains the lower polysaccharides degradation during a vacuum process. Fine chemical analyses and the study about thermal degradation reaction kinetics have allowed confirming the higher sensibility of hardwood than softwood to thermal degradation. In addition, these analyses have permitted the volatile thermal degradation products identification related to the treatment intensity. Subsequently, results have shown a higher thermal sensibility of lignin than holocelluloses for temperatures below 230°C. This work is a significant increase in basic knowledge about the mechanisms of wood thermal degradation and their relations with the processing parameters

Aqueous amine solutions loaded with CO2 were degraded in stainless steel sealed containers in forced convection ovens. Amine loss and degradation products were measured as a function of time by cation chromatography (IC), HPLC, and IC/mass spectrometry. A full kinetic model was developed for 15-40 wt% MEA (monoethanolamine) with 0.2 – 0.5 mol CO2/mol MEA at 100°C to 150°C. Experiments using amines blended with MEA demonstrate that oxazolidone formation is the rate-limiting step in the carbamate polymerization pathway. With 30 wt% MEA at 0.4 mol CO2/mol MEA and 120°C for 16 weeks there is a 29% loss of MEA with 13% as hydroxyethylimidazolidone (HEIA), 9% as hydroxyethylethylenediamine (HEEDA), 4% as the cyclic urea of the MEA trimer, 1-[2-[(2-hydroxyethyl)amino]ethyl]-2-imidazolidone, 3% as the MEA trimer, 1-(2-hydroxyethyl)diethylenetriamine, and less than 1% as larger polymeric products. In the isothermal experiments, thermal degradation was slightly more than first order with amine concentration and first order with CO2 concentration with an activation energy of 33 kcal/mol. In a modeled isobaric system, the amount of thermal degradation increased with stripper pressure, but decreased with an increase in amine concentration and CO2 concentration due to a reduction in reboiler temperature from the changing partial pressure of CO2. Three-fourths of thermal degradation in the stripper occurred in the reboiler due to the elevated temperature and long residence time which offset the decrease in CO2 concentration compared to the packing. The amount of degradation for other amines tested starting with the least degraded include; cyclic amines with no side chains < long chain alkanolamines < alkanolamines with steric hindrance < tertiary amines < MEA < straight chain di- and triamines. Piperazine and morpholine had no measurable thermal degradation under the conditions of this experiment and were the most resistant to thermal degradation. Diethyelenetriamine and HEEDA had the largest amount of degradation with over 90% loss at 135°C for 8 weeks. / text

The replacement of artificial with natural dyes is one of the most challenging research fields in the food production area. Recent studies have shown that some frequently used synthetic colours, called the “Southampton 6 Colours” may be linked with hyperactivity in children. The purpose of this work is to analyse the degradation behaviour of black carrot, a natural, red dye commonly used for colouring food products, and subsequently improve its stability during heat and storage conditions. The stability of the black carrot mixture to heat exposure was investigated at a range of pH values by heat-treating aqueous solutions in a domestic oven at around 180oC to maintain the temperature at 100oC and the powdered material in a furnace at 180oC (typical baking conditions). 1H NMR (800 MHz) spectroscopy was used for the assignment of the aromatic chemical shifts of the black carrot mixture by overlaying them with the characterised 1H NMR chemical shifts of the individual components separated by RP-HPLC. Integration of high-resolution 1H NMR (800 MHz) spectra was used to follow the relative degradation of each of the components. Different procedures for the complexation of black carrot with metal oxides were developed, for which colourants of different colour shades were prepared. Spectroscopic techniques were used to follow the degradation of the complexes which were heat-treated at 180oC. Nano-scale investigation of the metal oxide powders was also carried out. The optimised colourants were tested on a bench scale and subsequently on an industrial scale in food pilot procedures. The successful complexes produced were found to be more heat stable compared to the commercial black carrot dye. The developed technologies are cheap and easy-to-produce methods to create intense heat and storage stable coloured pigments which can be used for the replacement of existing artificial dyes during food processing.

THE CHARACTERIZATION OF SOME METHACRYLATE AND ACRYLATE HOMOPOLYMERS, COPOLYMERS AND FIBERS VIA DIRECT PYROLYSIS MASS SPECTROSCOPY &Ouml / zlem G&uuml / ndogdu, Suriye Ph.D., Department of Polymer Science and Technology Supervisor: Prof. Dr. Jale Hacaloglu December 2012, 177 pages Poly(methyl methacrylate) possesses many desirable properties and is used in various areas. However, the relatively low glass transition temperature limits its applications in textile and optical-electronic industries. Monomers containing isobornyl, benzyl and butyl groups as the side chain are chosen to copolymerize with MMA to increase Tg and to obtain fibers with PMMA. In this work, thermal degradation characteristics, degradation products and mechanisms of methacrylate homopolymers, poly(methyl methacrylate), poly(butyl methacrylate), poly(isobornyl methacrylate) and poly(benzyl methacrylate), acrylate homopolymers, poly(n-butyl acrylate), poly(t-butyl acrylate), poly(isobornyl acrylate), two, three and four component copolymers of MMA and fibers are analyzed via direct pyrolysis mass spectrometry. The effects of substituents on the main and side chains, the components present in the copolymers and fiber formation on thermal stability, degradation characteristics and degradation mechanisms are investigated. According to the results obtained, the depolymerization mechanism yielding mainly the monomer is the main thermal decomposition route for the methacrylate polymers, acrylate polymers degradation occurs by H-transfer reactions from the main chain to the carbonyl groups. However, when the alkoxy group involves

Although, several researches on synthesis and characterization of benzoxazines and polybenzoxazines have appeared in the literature, detailed studies on thermal characterization are still limited. In this study, polymerization and thermal degradation mechanisms of benzoxazines were investigated via direct pyrolysis mass spectrometry. Benzoxazine monomers prepared by reactions of phenol or bisphenol- A with aniline or methyl amine were analyzed to investigate the effects of the structures of phenyl and amine groups on both polymerization and thermal degradation behaviours. It has been proposed in the literature that polymerization of benzoxazines occurs by ring opening polymerization of oxazine ring / cleavage of O-CH2 bond of the oxazine ring and attack of n-CH2 group to phenol or bisphenol-A ring. However, the direct pyrolysis mass spectrometry analyses of polymerization and thermal degradation of benzoxazines pointed out that after the cleavage of O-CH2 bond of the oxazine ring, polymerization proceeded through opposing pathways. Strong evidences confirming coupling of (CH3)NCH2 or (C6H5)NCH2 groups yielding dimers involving diamine linkages were detected. Polymerization of the dimer by the reactions with the corresponding monomers was proposed. In case of benzoxazines based on bisphenol-A, the results indicated polymerization of the dimer ii by coupling of both of the oxazine rings. On the other hand, polymerization of the dimer through the ethylene units (vinyl polymerization) in case of benzoxazine monomer based on phenol and methyl amine was also noted. For polybenzoxazines based on aniline another polymerization pathway involved attack of radicals generated by cleavage of the oxazine ring to aniline ring. Multi-step thermal decomposition was observed for all the polybenzoxazines under investigation confirming the presence of units with different structures and stabilities.