Dissertations / Theses: 'Vinyle Acetate'

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Glikman, Jean-François. "Oxydation photo-thermique des copolymeres ethylene-acetate de vinyle, ethylene-acrylate d'ethyle, ethylene-acide acrylique." Clermont-Ferrand 2, 1987. http://www.theses.fr/1987CLF21050.

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Irradiation sous vide et dans l'air. La vitesse d'apparition des produits de photooxydation depend du type de copolymere. Cinetique et mecanisme. Mise en evidence de la labilite croissante de l'atome d'hydrogene tertiaire situe en position alpha des groupes substituants quand on passe de l'acetate a l'ethylate et a l'acide. Influence de charges et de stabilisants

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Morel, Aurélie. "Synthèse et comportement auto-associatif des copolymères poly(acetate de vinyle)-b-poly(acide acrylique) et de leurs dérivés hydrolysés." Montpellier 2, 2004. http://www.theses.fr/2004MON20162.

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Dhuiège, Benjamin. "Acylation des nanocelluloses en milieu aqueux par transestérification des esters de vinyle et utilisation comme charge dans le caoutchouc naturel." Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0645/document.

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Ce travail de thèse a pour objectif d’élaborer de nouveaux matériaux composites (élastomères, adhésifs) en utilisant les nanocelluloses (NCC et NFC) comme renforts mécaniques biosourcés. Une méthode de fonctionnalisation des nanocelluloses en conditions aqueuses a d’abord été développée, dans le but ultime d’améliorer leur compatibilité avec les matrices polymères. La réaction, basée sur la transestérification des esters de vinyle, a été optimisée à partir de l’acétate de vinyle utilisé comme réactif modèle. Le greffage en conditions basiques s’est avéré efficace, mais a également conduit à la formation de poly(acétate de vinyle) (PVAc) comme produit secondaire. Pour pallier à ce problème, un deuxième protocole en conditions neutres a également été développé, mais des rendements moins bons ont été obtenus dans ce cas. Les nanocelluloses non modifiées et acétylées ont ensuite été dispersés dans une matrice caoutchouc naturel (NR) afin d’étudier l’impact de cette charge sur les performances thermomécaniques du matériau cru ou vulcanisé. Une amélioration des propriétés mécaniques a pu être observée en présence de NCC ou NFC, mais l’acétylation des nanoparticules n’a pas conduit à de meilleures performances. Enfin, une valorisation du PVAc produit lors de l’acétylation des nanocelluloses en conditions aqueuses basiques a été proposée. La dispersion des NCC acétylés dans le PVAc polymérisé in-situ a en effet permis de produire des composites aux propriétés améliorées. L’utilisation ultérieure de ces composites comme charge (mélange-maître) dans des matrices NR ou EVA a été discutée
The objective of this research work consists in the elaboration of novel composite materials (elastomers, adhesives) using nanocelluloses (CNC and NFC) as biobased reinforcing fillers. A method allowing the functionalization of nanocelluloses in aqueous conditions was first developed, with the aim of ultimately improving their compatibility with polymer matrices. The reaction, based on the transesterification of vinyl esters, was optimized with vinyl acetate selected as model reactant. The grafting performed in basic aqueous conditions was efficient, but also led to the formation of poly(vinyl acetate) as a by-product. To limit this problem, a second protocol in neutral aqueous conditions was also developed, but lower yields were obtained in that case. The unmodified and acetylated nanocelluloses were then dispersed in a natural rubber matrix (NR), to study the impact of this filler on the thermomechanical performances of the crude and vulcanized material. An improvement of the mechanical properties was observed in the presence of NCC or NFC, but the acetylation of the nanoparticles did not enhance further the performances. Finally, a valorization of the PVAc produced during the acetylation of the nanocelluloses in basic aqueous conditions was proposed. The dispersion of the acetylated NCC in the PVAc polymerized in-situ indeed led to the production of composites with improved properties. The subsequent utilization of these composites as filler (master batch) in NR or EVA matrices was discussed

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Atanase, Léonard-ionut. "Contribution à l'étude des complexes Poly (vinyle alcool - vinyle acétate) / tensioactifs anioniques : caractéristiques colloïdales des nanogels et extension aux copolymères à blocs." Thesis, Mulhouse, 2010. http://www.theses.fr/2010MULH3728.

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Les copolymères poly (acétate de vinyle-co-alcool vinylique), désignés par PVA, sont des tensioactifs macromoléculaires obtenus par hydrolyse partielle de poly (acétate de vinyle)(PVAc). Si les propriétés tensioactives des PVA ont pu être corrélées aux caractéristiques moléculaires il n'en est par de même en ce qui concerne les associats du type nanogels présents dans les solutions aqueuses. L'objectif de cette thèse était de caractériser les nanogels par des techniques telles que la diffusion dynamique de la lumière, la chromatographie d'exclusion stérique et la viscosimétrie. 9 PVA, de degrés d'hydrolyse de 73 à 88 mole% et de degrés de polymérisation de 650 à 2500 ont été étudiés. Il est apparu que les nanogels présent dans les PVA de DH =73 mole% et formés par interactions hydrophobe-hydrophobe entre séquences acétate ont des tailles entre 20-40 nm, avec des fractions volumiques de l'ordre de 20-30%. La désagrégation des nanogels par formation de complexes avec des tensioactifs anioniques du type SDS et SDBS a ensuite été démontrée. En faisant appel à la technique de fractionnement par « point de trouble » il est apparu que les chaînes les plus riches en acétate et en particulier celles ayant des longueurs des séquences acétate importantes complexent plus de SDS.Des « copolymères modèles » du type copolymères diblocs PVAc-b-PVOH comportant une séquence hydrophobe PVAc et une hydrophile PVOH ont pu être préparés par polymérisation RAFT, suivie par une réaction click. Une étude préliminaire de la micellisation de tels copolymères a permis de montrer la très grande analogie entre micelles de copolymères à blocs PVAc-b-PVOH et les nanogels de PVA examinés précédemment
Poly (vinyl acetate-co-vinyl alcohol) copolymers, designated by PVA, are macromolecular surfactants obtained by partial hydrolysis of poly (vinyl acetate) (PVAc). If the surfactant properties of PVA have been correlated with molecular characteristics it is not the same for the colloidal aggregates in aqueous solutions so-called nanogels. The objective of this thesis was to characterize the nanogels using techniques such as dynamic light scattering, size exclusion chromatography and viscometry.9 PVA with degrees of hydrolysis between 73 and 88 mole% and polymerization degrees of 650 to 2500 were studied. It appeared that the nanogels, formed by hydrophobic-hydrophobic interactions between acetate sequences, are the size in the range of 20 to 40 nm with volume fractions between 20 and 30%. The disaggregation of nanogels by complex formation with anionic surfactants such as SDS and SDBS was further demonstrated. By using the "cloud point" fractionation technique it appeared that SDS is complexed by the sequences with high acetate content and in particular those with significant lengths of acetate sequences.As a model system diblock copolymers PVAc-b-PVOH containing a PVAc hydrophobie sequence and a PVOH hydrophilic sequence were prepared by RAFT polymerization, followed by a click reaction. A preliminary micellization study of these copolymers showed a very strong analogy between PVAc-b-PVOH block copolymer micelles and PVA nanogels discussed above

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Dommanget, Cédric. "Polymérisation radicalaire contrôlée : le défi de l'éthylène." Thesis, Lyon 1, 2013. http://www.theses.fr/2013LYO10216/document.

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Les travaux présentés dans cette thèse portent sur le contrôle de la polymérisation radicalaire de l'éthylène à basse pression (200 bar) et basse température (70 °C) et sur la synthèse de copolymères à blocs contenant au moins un segment de polyéthylène. Quatre techniques de polymérisation, couramment utilisées en ingénierie macromoléculaire, ont été étudiées : NMP, CMRP, RAFT/MADIX et ESCP. Nos études sur le nitroxyde SG1 (NMP) et le bis(acétylacétonate) de cobalt (CMRP) ont montré que ces composés sont inefficaces pour contrôler la polymérisation de l'éthylène. Un comportement inattendu du bis(acétylacétonate) de cobalt a cependant été mis en évidence. Il semblerait que ces complexes de cobalt favorisent les réactions de couplage entre les radicaux propagateurs. En revanche, la première polymérisation radicalaire contrôlée de l'éthylène a été atteinte grâce à l'utilisation de xanthates (RAFT/MADIX). Les polyéthylènes synthétisés possèdent des masses molaires qui augmentent linéairement avec la conversion et des dispersités faibles. Le caractère pseudo-vivant de la réaction a été démontré par la synthèse de copolymères à blocs poly(acétate de vinyle)-b-polyéthylène. L'utilisation de nitrones (ESCP) a également permis l'introduction d'une fonction réactive au centre des chaînes de polyéthylène et la synthèse de copolymères triblocs de type ABA, où les blocs latéraux A sont en polystyrène ou polyacrylate et le bloc central B est en Polyéthylène
The work presented in this thesis displays the controlled radical polymerization of ethylene at low temperature (70 °C) and low pressure (200 bar) and the synthesis of block copolymers featuring polyethylene segments. Four polymerization techniques, commonly used in macromolecular engineering, were studied: NMP, CMRP, RAFT/MADIX and ESCP. Our investigation of the use of SG1 nitroxide (NMP) and cobalt (II) acetylacetonate (CMRP) as controlling agents demonstrated their inability to control the polymerization of ethylene. Nonetheless, an unexpected reaction with cobalt (II) acetylacetonate was observed. The coupling reaction between propagating radicals appeared to be favored by the presence of this compound. On the other hand, the first controlled polymerization of ethylene was successfully achieved by using xanthate (RAFT/MADIX). A linear increase of molecular weight with conversion and low polydispersities were observed for the produced polyethylenes. The reaction was demonstrated to be a pseudo-living polymerization by the synthesis of block copolymers poly(vinyl acetate)-b-polyethylene. In addition, midchain-functionalized polyethylenes and ABA type block copolymers, with polystyrene or polyacrylate as the A block and polyethylene as the B block, were also prepared using nitrone based polymerization technique (ESCP)

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Atanase, Léonard-Ionut. "Contribution à l'étude des complexes Poly (vinyle alcool - vinyle acétate) / tensioactifs anioniques : caractéristiques colloïdales des nanogels et extension aux copolymères à blocs." Phd thesis, Université de Haute Alsace - Mulhouse, 2010. http://tel.archives-ouvertes.fr/tel-00562063.

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Les copolymères poly (acétate de vinyle-co-alcool vinylique), désignés par PVA, sont des tensioactifs macromoléculaires obtenus par hydrolyse partielle de poly (acétate de vinyle)(PVAc). Si les propriétés tensioactives des PVA ont pu être corrélées aux caractéristiques moléculaires il n'en est par de même en ce qui concerne les associats du type nanogels présents dans les solutions aqueuses. L'objectif de cette thèse était de caractériser les nanogels par des techniques telles que la diffusion dynamique de la lumière, la chromatographie d'exclusion stérique et la viscosimétrie. 9 PVA, de degrés d'hydrolyse de 73 à 88 mole% et de degrés de polymérisation de 650 à 2500 ont été étudiés. Il est apparu que les nanogels présent dans les PVA de DH =73 mole% et formés par interactions hydrophobe-hydrophobe entre séquences acétate ont des tailles entre 20-40 nm, avec des fractions volumiques de l'ordre de 20-30%. La désagrégation des nanogels par formation de complexes avec des tensioactifs anioniques du type SDS et SDBS a ensuite été démontrée. En faisant appel à la technique de fractionnement par " point de trouble " il est apparu que les chaînes les plus riches en acétate et en particulier celles ayant des longueurs des séquences acétate importantes complexent plus de SDS.Des " copolymères modèles " du type copolymères diblocs PVAc-b-PVOH comportant une séquence hydrophobe PVAc et une hydrophile PVOH ont pu être préparés par polymérisation RAFT, suivie par une réaction click. Une étude préliminaire de la micellisation de tels copolymères a permis de montrer la très grande analogie entre micelles de copolymères à blocs PVAc-b-PVOH et les nanogels de PVA examinés précédemment.

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Palma, Mauri Sergio Alves. "Polimerização de acetato de vinila em emulsão de modo contínuo em coluna pulsada de pratos perfurados." Universidade de São Paulo, 2002. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-27082013-122010/.

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Processos industriais de polimerização em emulsão são usualmente realizados em reatores tipo tanque agitado em batelada (ou semi-batelada) ou em contínuo (CSTR). Reatores contínuos tem a vantagem de serem comparativamente de menor porte, e propiciarem melhor controle da qualidade do produto pela redução de variações de batelada a batelada. Reatores tipo CSTR podem exibir oscilações periódicas e autosustentadas de conversão, de tamanho e concentração de partículas. Estas oscilações podem ser minimizadas nos reatores tubulares pulsados devido à diminuição da dispersão axial em relação aos reatores do tipo CSTR. Na presente tese, desenvolveu-se um novo tipo de reator tubular, a Coluna Pulsada de Pratos Perfurados, CPPP, para uso no processo de polimerização contínua do acetato de vinila em emulsão. O reator é operado com escoamento pulsado e contém pratos perfurados como dispositivos internos. Inicialmente foram realizados ensaios de distribuição de tempos de residência, em um reator montado em vidro, com o objetivo de caracterizar o escoamento no reator CPPP quanto ao grau de mistura axial. Os dados foram interpretados usando o modelo de escoamento pistonado com dispersão axial. Valores do coeficiente de dispersão axial foram medidos e correlacionados para diferentes condições de freqüência e amplitude de pulsação, vazão, espaçamento entre pratos, e viscosidade do fluido. Verificou-se que o grau de mistura axial pode ser variado em faixas relativamente amplas pela manipulação da freqüência e amplitude de pulsação. Foi também montado um reator em aço inox e encamisado, com as mesmas dimensões, onde foram realizados ensaios de polimerização em emulsão de acetato de vinila, medindo-se a conversão e a distribuição de tamanhos de partículas (DTP), na saída do reator em regime transiente e permanente, e também ao longo do reator em regime permanente. Verificou-se que as condições operacionais (tempo médio de residência e grau de dispersão axial) influenciam várias características do produto, como, a conversão, tamanho médio e concentração de partículas, porém, não influencia, significativamente, a viscosidade da emulsão produzida, para a receita da reação de polimerização e as condições operacionais estudadas. Os resultados experimentais foram interpretados usando um modelo matemático do reator, o qual foi estabelecido com base em um modelo cinético publicado na literatura para o processo de polimerização em emulsão de acetato de vinila em batelada. Tal modelo foi adaptado incluindo-se os termos convectivos e dispersivos nas equações de balanço de massa, e resolvido numericamente. Foram ajustados apenas dois parâmetros neste modelo, para todas as condições operacionais estudadas e os resultados simulados reproduziram adequadamente o comportamento das principais variáveis de processo para a condição de regime permanente. O novo tipo de reator contínuo apresentado neste trabalho mostrou-se ser possível obter altas conversões em tempos médios de residência da ordem ou mesmo inferiores aos do processo em batelada e atingir regime permanente de operação em um a dois tempos médios de residência. O reator é eficiente, robusto, construtivamente simples, de fácil limpeza e manutenção, e mostrou-se promissor para utilização industrial em processo de polimerização em emulsão de acetato de vinila.
Industrial emulsion polymerization processes are usually carried out in stirred tanks operated in batch/semibatch or in continuous mode (CSTR). In comparison to batch processes, continuous reactors present several advantages such as lower volumes and better quality control by reducing batch-to-batch variations. Continuous emulsion polymerization in CSTR may exhibit sustained oscillations in conversion, particle size and particle concentration. Such oscillations may be reduced in pulsed tubular reactors due to less axial mixing. In this thesis a new type of tubular reactor, called Pulsed Sieve Plate Column, PSPC, was developed for the continuous process of vinyl acetate emulsion polymerization. This reactor is operated using oscillatory pulsed flow and uses perforated plates as internals. Residence time distribution runs were carried out in a glass reactor in order to characterize the axial mixing and flow patterns in the PSPC. The data were treated using the axially dispersed plug flow model. Axial dispersion coefficient was measured for different conditions of pulse frequency and amplitude, flow rate, plate spacing and viscosity. It was found that the degree of axial mixing can be varied in wide ranges by manipulating pulsation frequency and/or amplitude. Vinyl acetate continuous emulsion polymerization runs were carried out in a jacketed stainless steel reactor (with the same size of the glass reactor). Monomer conversion and particle size distribution was measured both at the reactor exit in transient state and along the reactor length at steady-state. It was found that average residence time and degree of axial mixing affect process and product quality variables, such as monomer conversion, mean particle size and concentration, but did not affect the viscosity of the emulsion produced, for the recipe and conditions used. A mathematical model for the reactor was developed. The model used, based on a well-known kinetic model previously developed in the literature for batch emulsion polymerization, was adapted to the continuous tubular reactor by adding the dispersion and convective terms to the balance equations. The model was numerically solved. Only two parameters were adjusted in this model and the simulated results showed excellent agreement with the experimental results, for steady state conditions. The proposed tubular reactor allows to reach high monomer conversion with similar or even lower residence time than those in batch processes and reaches steady state operation in just one to two mean residence times. The reactor is efficient, easy-to-built, easy-to-clean, robust and promising for use in industrial continuous emulsion polymerization of vinyl acetate.

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Hashimoto, Patrícia Kazuyo. "Complexos de Mn(II) e Fe(II) coordenados a bases de Schiff Bidentadas derivadas de cicloalquilaminas como mediadores da OMRP de acetato de vinila /." Presidente Prudente, 2018. http://hdl.handle.net/11449/154400.

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Orientador: Beatriz Eleutério Goi
Coorientador: Valdemiro Pereira de Carvalho Júnior
Banca: Pedro Ivo da Silva Maia
Banca: Ana Maria Pires
Resumo: Nas últimas décadas, a polimerização radicalar controlada (CRP) tem se tornado muito importante, pois permite a síntese de macromoléculas de arquiteturas específicas com um controle sobre as propriedades químicas e físicas. Sendo assim, este trabalho apresenta a síntese de novos complexos de Mn(II) e Fe(II) coordenados à ligantes bases de Schiff bidentados, que são resultantes da condensação do salicilaldeído com as seguintes cicloalquilaminas: (1) Ciclopentilamina, (2) Cicloexilamina, (3) Cicloeptilamina e (4) Ciclooctilamina, de forma que estes possam ser utilizados como mediadores da polimerização radicalar mediada por organometálicos. Os ligantes foram caracterizados pelas seguintes técnicas: espectroscopia de ressonância magnética nuclear de hidrogênio (RMN de 1H), espectroscopia de absorção na região do ultravioleta-visível (UV-Vis) e espectroscopia vibracional na região do infravermelho (FTIR). Já os complexos de Mn(II) e Fe(II) foram caracterizados pelas técnicas de FTIR, UV-Vis, voltametria cíclica (VC) e ponto de fusão (p.f.). Os estudos cinéticos de polimerização foram realizados para os complexos de manganês e ferro. O complexo [MnIIbis(N-Salicilideno-Ciclopentilamina)], Mn(L1)2, apresentou um melhor controle na polimerização do acetato de vinila com menores valores de polidispersidade e a curva de massa molecular (Mn) mais próxima aos valores da curva teórica. Já os complexos de ferro mediadores apresentaram um comportamento mais similar, não havendo muita...
Abstract: In the last decades, controlled radical polymerization (CRP) has become very important, since it facilitates the synthesis of macromolecules of specific architectures with excellent control over the chemical and physical properties. Thus, this work presents the synthesis of new Mn(II) and Fe(II) complexes coordinated with the bidentate Schiff bases ligands, which are the result of the condensation of salicylaldehyde with cycloalkylamines: (1) cyclopentylamine, (2) cyclohexylamine, (3) cycloheptylamine and (4) cyclooctylamine, so that they can be used as mediators of radical polymerization mediated by organometallic (OMRP). The ligands synthesized were characterized by proton nuclear magnetic resonance (1H-NMR) spectroscopy, ultraviolet-visible (UV-Vis) absorption spectroscopy and Fourier-transform infrared spectroscopy (FTIR) techniques. The synthesized Mn(II) and Fe(II) complexes were studied by FTIR, UV-Vis, cyclic voltammetry (CV) and melting point (m.p.). Kinetic polymerization studies were performed for the manganese and iron complexes. The [MnIIbis (N-Salicylidene-Cyclopentylamine)], Mn(L1)2, complex showed a better control in the polymerization of vinyl acetate with lower values of polydispersity and the molecular mass curve (Mn) closer to the values of the theoretical curve. However, the iron mediator complexes presented a more similar behavior, not having much difference in the kinetic curves
Mestre

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Raihane, Mustapha. "Copolymérisation du méthyl cyanure de vinylidène (MVCN) avec l'acétate de vinyle et des styrènes substitués : synthèses, microstructures, propriétés et dégradation thermique." Saint-Etienne, 1993. http://www.theses.fr/1993STET4017.

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Le méthyl cyanure de vinylidène (MVCN) est un nouveau monomère préparé en une seule étape selon la méthode de Knoevenagel à partir de produits commerciaux. Ce monomère n'homopolymérise pas. Sa copolymérisation avec l'acétate de vinyle et des styrènes substitués est effectuée par voie radicalaire. Ces copolymères ont été caractérisés par les méthodes classiques d'analyse (IR, RMN, GPC, DSC, microanalyse. . . ). La microstructure de ces copolymères a été aussi étudiée par RMN #1h et #1#3C pour déterminer la répartition des stéréoséquences dans ces copolymères. Le mécanisme de copolymérisation a été aussi étudié en utilisant le modèle terminal et le modèle pénultième. L'application de la méthode de Fineman-Ross et celle de Kelen-Tudos a permis de déterminer les paramètres d'Alfrey et Price du MVCN. La solubilité de ces copolymères a été étudiée, les paramètres de solubilité de trois copolymères ont été mesurés. L'étude des propriétés diélectriques du P(MVCN-FS) ET P(MVCN-CLS) a montré un phénomène de relaxation au-dessus de TG. Ces propriétés sont en accord avec les propriétés thermiques. L'étude thermique de ces copolymères a mis en évidence les mécanismes de décomposition en température, leur stabilité thermique et certains paramètres cinétiques tels que l'énergie d'activation et la constante de vitesse de réaction ont été calculées. Deux modèles (autocatalytique et dépolymérisation) ont été vérifiés

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Franco, Cilene Meinberg. "Pesquisa experimental sobre a polimerização via radical livre com iniciadores mono e difuncional." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266156.

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Orientador: Liliane Maria Ferrareso Lona
Dissertação (mestrado) - Universidade Estadual de Campinas. Faculdade de Engenharia Quimica
Made available in DSpace on 2018-08-07T07:49:45Z (GMT). No. of bitstreams: 1 Franco_CileneMeinberg_M.pdf: 1835289 bytes, checksum: 8c7c34fee69d338538caffa2e9546741 (MD5) Previous issue date: 2006
Resumo: Iniciadores mono funcionais são largamente utilizados em polimerizações VIa radical livre. Muitas vezes, na busca de maiores produtividades, utilizam-se temperaturas de operação mais elevadas e/ou maiores concentrações iniciais de iniciador, que por conseqüência, geram polímeros com pesos moleculares mais baixos. O uso de iniciadores difuncionais permite o aumento da produtividade sem a redução no peso molecular do produto final, o que pode ser urna característica desejável. A pesquisa com iniciadores difuncionais é atual e de grande interesse industrial. O objetivo deste trabalho é analisar o efeito da funcionalidade do iniciador, no caso mono e difuncional, sobre a polimerização via radical livre, considerando corno caso estudo um polímero linear, o poliestireno, e um ramificado, o poli (acetato de vinila). Para isso, foram feitas, experimentalmente, reações de polimerização em ampolas de vidro (polimerização em massa), com o iniciador mono funcional (Luperox TBEC) e o di funcional (Luperox 531). Foram analisados também o efeito da temperatura de polimerização e a concentração de iniciador. Também neste trabalho é apresentado um estudo estatístico através de um Planejamento Fatorial, a fim de analisar o efeito das variáveis temperatura e concentração de iniciador na polimerização do estireno com iniciador difuncional. Observou-se, tanto para o estireno corno para o acetato de vinila, que quando utilizado o iniciador difuncional é possível obter conversões maiores, sem alterar o peso molecular médio mássico e numérico, sendo que em alguns casos pode se até obter um aumento no peso molecular. O uso de iniciador di funcional é também mais viável economicamente, pois apresenta melhores resultados frente ao monofuncional, mesmo quando utilizado em concentrações ou temperaturas menores do que as utilizadas com o iniciador mono funcional. É importante salientar o caráter inovador desta pesquisa, já que não foram encontrados, em literatura aberta, dados experimentais da polimerização do acetato de vinila (ou outro monômero que produza ramificações de cadeia longa) utilizando iniciadores difuncionais
Abstract: Monofunctional initiators are extensively utilized in free radical polymerization. In order to increase productivity, higher temperature or higher initial initiator concentration are used, therefore polymers with lower molecular weights are obtained. Bifunctional initiators increase the polymerization rate without decreasing the average molecular weight and this can be desirable. They are an important issue to be investigated and are of great interest to industries. The objective of this work is to analyze the effect of the functionality of the initiator, by using mono and bifunctional, in free radical polymerization, for linear polymer (poly styrene) and branched polymer (poly(vinyl acetate)). Polymerizations were experimentally performed in glass ampoules (bulk polymerization) using both mono(Luperox TBEC) and bi- (Luperox 531) functional initiators. The effects of temperature and initiator concentration were also analyzed for various polymerization conditions. This work includes a statistical study using the factorial design to analyze the effect of temperature and initiator concentration in styrene polymerization with bifunctional initiator. It is observed in this study, that high conversions with no effect in the molecular weigh of the dead polymer can be achieved using bifunctional initiators in the polymerization of styrene and vinyl acetate. In many cases, it is possible to obtain higher molecular weights. Bifunctional initiator can also be used to provide reduction costs to initiators. They showed better results than the monofunctional initiator when lower concentration or temperature lower were utilized.
Mestrado
Desenvolvimento de Processos Químicos
Mestre em Engenharia Química

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Carvalho, Antônio Carlos Sallarés de Mattos. "Desenvolvimento de processo contínuo de copolimerização em emulsão em reator tubular." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-02062008-135006/.

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Os processos industriais de polimerização em emulsão são normalmente realizados em reatores batelada ou semi batelada ou em tanques agitados contínuos (CSTR). Os reatores contínuos têm a vantagem de terem menor porte e de propiciarem melhor controle de qualidade do produto através da redução de variações de batelada a batelada. Além disso, as oscilações periódicas autosustentadas na conversão de monômero e no tamanho da partícula, que são normalmente observadas em reatores do tipo CSTR, podem ser minimizadas em reatores tubulares mediante o uso de dispositivos de mistura estáticos adequados combinados com escoamento pulsado (oscilatório). O objetivo deste trabalho é apresentar o desenvolvimento de uma copolimerização em emulsão de acetato de vinila e acrilato de butila em uma coluna pulsada com pratos perfurados (CPPP). A fim de aumentar a sua flexibilidade operacional, a coluna é composta de 5 seções, cada uma apresentando controles independentes de alimentação lateral e temperatura. Dependendo da estratégia de alimentação de monômero, pode-se notar uma deriva de composição durante o processo de copolimerização em emulsão do acetato de vinila e acrilato de butila devido às grandes diferenças entre estes monômeros em suas razões de reatividade e nas solubilidades na fase aquosa. Neste caso, a CPPP propicia diferentes possibilidades de alimentação que permitem controlar a composição do copolímero através da alimentação do monômero mais reativo ao longo da coluna. Por esta razão, foi avaliado neste estudo o efeito do número de correntes de alimentação sobre as propriedades do polímero. Diferentes números de correntes laterais de alimentação de monômero foram empregadas nos ensaios experimentais. Diferenças na uniformidade da composição do copolímero podem ser notadas dependendo do número de correntes laterais de alimentação aplicadas em cada teste. A fim de permitir variações de temperatura, somente a temperatura de entrada das camisas de resfriamento foi fixada. Para simular as reações foi utilizado um modelo matemático desenvolvido baseado no modelo de escoamento pistonado (plug-flow) axialmente disperso. No presente trabalho, um balanço de energia foi incluído ao modelo matemático anterior de modo que a influência de diferentes perfis de temperatura pudesse ser considerada. O efeito das correntes laterais de alimentação de monômero sobre as propriedades do copolímero puderam ser previstas com suficiente precisão pelas simulações do modelo, as quais foram também validadas pelos resultados experimentais. Com base nas simulações matemáticas, um perfil ótimo de alimentação pôde ser calculado e experimentalmente aplicado na CPPP permitindo a produção de um copolímero mais homogêneo. Os resultados também permitiram a validação do modelo matemático como uma ferramenta confiável na predição de ensaios experimentais. Além disso, as vantagens da CPPP puderam ser verificadas pelo seu desempenho adequado como reator tubular para processos contínuos de copolimerização em emulsão. Finalmente, os resultados indicaram a possibilidade de melhorias adicionais nas propriedades do polímero através do emprego de diferentes temperaturas e perfis de alimentação de outros reagentes ao longo da coluna.
Industrial emulsion polymerization processes are usually performed in batch or semi-batch stirred tanks, or in continuous stirred tank reactors (CSTR). Continuous reactors have the advantage of being smaller and providing a better product quality control by the reduction of the batch-to-batch variations. In addition, periodical self-sustained oscillations in monomer conversion and in particle size that are usually observed in CSTR can be minimized in tubular reactors presenting good radial mixing. Such conditions can be achieved in tubular reactors by using adequate static mixing devices combined with pulsed (oscillatory) flow. The aim of this work is to report the development of a continuous emulsion copolymerization of vinyl acetate and butyl acrylate performed in a pulsed sieve plate column (PSPC). In order to improve its operational flexibility, the column is composed of five sections, each one presenting independent lateral feed and temperature controls. Depending on the monomer feeding strategy, a composition drift can be noticed during the emulsion copolymerization process of vinyl acetate and butyl acrylate, due to the large differences in reactivity ratios and aqueous phase solubility between these monomers. In this case, the PSPC provides different operational feeding possibilities which allow controlling the copolymer composition by feeding the more reactive monomer along the column. For this reason, in this study the effect of the number of lateral feed streams on the polymer properties was evaluated. Different numbers of lateral monomer feed streams were employed in the experimental runs. Differences in the uniformity of the copolymer composition can be noticed along the reactor depending on the number of lateral feed streams applied in each test. In order to allow temperature variations, during each reaction only the inlet temperature of the cooling jackets was fixed. A developed mathematical model based on the axially dispersed plug-flow model was used to simulate the reactions. In the present study the energy balance was included in the mathematical model so that the influence of different temperature profiles could be taken into account. The effect of lateral monomer feed streams over the copolymer properties could be predicted with sufficient accuracy by model simulations which were also validated by the experimental results. Based on mathematical simulations, an optimal feeding profile could be calculated and experimentally applied in the PSPC allowing the production of a more homogeneous copolymer. The results also permitted the validation of the mathematical model as a reliable tool in the prediction of experimental runs. Furthermore, the advantages of the PSPC could be verified by its adequate performance as a tubular reactor for continuous emulsion copolymerization processes. Finally, the results indicate the possibility of further improvements in other polymer properties by employing different temperature and feeding profiles of other reagents along the column.

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12

Auden, Noel Geraint. "Ethylene-vinyl acetate copolymers." Thesis, Lancaster University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239046.

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13

Morin, Aurélie. "Controlled radical polymerization of vinyl esters and vinyl amides : experimental and theoretical studies." Thesis, Toulouse, INPT, 2013. http://www.theses.fr/2013INPT0117/document.

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Ces travaux de thèse portent sur la polymérisation radicalaire contrôlée (PRC) des esters et amides de vinyle. L’une des possibilités de contrôle est le piégeage dynamique réversible des chaînes radicalaires croissantes (P•) par un agent de contrôle (T) formant une espèce dormante (P─T’). La concentration en radicaux dans le milieu peut alors diminuer dramatiquement de sorte que les réactions indésirables de terminaisons soient négligeables et que le contrôle de la masse molaire des polymères soit atteint avec un faible indice de dispersité. L’utilisation de complexes métalliques, pouvant s’oxider et former une liaison métal-carbone, comme agent de piégeage des radicaux est une manière de réaliser ce contrôle. La PRC est alors appelée Polymérisation Radicalaire Contrôlée par voie Organométallique (OMRP). A ce jour, plusieurs métaux de transitions ont été utilisés avec plus ou moins de succès en OMRP. Lors de cette étude, nous avons synthétisé des complexes de cuivre(I) et testé leurs performances pour l’OMRP de l’acétate de vinyle et de l’éthylène. Nous avons également utilisé des outils de chimie théorique pour mieux comprendre pourquoi le cobalt(II) acétylacétonate est, jusqu’à aujourd’hui, le meilleur agent de contrôle pour la polymérisation de l’acétate de vinyle et des amides de vinyle. Grâce à la théorie de la fonctionnelle de densité (DFT), nous avons mis en lumière le rôle crucial de la coordination sur le cobalt des groupements carbonyles des monomères étudiés
This thesis focus on Controlled Radical Polymerization (CRP) of vinyl esters and vinyl amides. One of the possibilities to achieve this control is a dynamic reversible trapping of the growing radical chains (P•) by a controlling agent (T) to form a dormant species (P─T’). The radical concentration in the medium can be dramatically reduced so that the unwanted terminations are disfavored and polymers with controlled molecular weights and low dispersity can be obtained. A way to achieve this control is the use of metallic complexes, which can oxidize and form a metal-carbon bond, as trapping agent in the so-called Organometallic Mediated Radical Polymerization (OMRP). So far, different transition metals have been used with gretaer or smaller success. In this study, the synthesis of copper(I) complexes and their investigation for the vinyl acetate and ethylene polymerization under OMRP conditions were performed. We also used computational chemistry as a tool to better understand why the cobalt(II) acetylacetonate (Co(acac)2) has, so far, given the best results for either vinyl acetate or vinyl amides polymerization. Thanks to Density Functional Theory (DFT), the crucial role of the monomer carbonyl group coordination to cobalt was pointed out

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Bergerbit, Cédric. "RAFT polymerization of ethylene for the synthesis of polar-apolar olefin block copolymers." Thesis, Lyon, 2019. https://n2t.net/ark:/47881/m6s181w9.

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La synthèse de copolymères à blocs, comprenant un bloc semi-cristallin de polyéthylène (PE) apolaire et un bloc polaire (poly(acétate de vinyle) (PAcV), poly(méthacrylate de méthyle) (PMAM), poly(oxide d’éthylène) (POE)) a été étudiée par polymérisation RAFT. L’étude préliminaire de l’homopolymérisation de l’éthylène en conditions relativement douces (T = 70 – 80 °C, P = 200 bar) a révélé que l’utilisation d’agents de transfert de chaîne (ATC) de type xanthates aromatiques conduit à une perte de fonctionnalité des extrémités de chaînes au cours de la polymérisation, conséquence directe de réactions de terminaison se produisant sur le radical intermédiaire. L’utilisation de dithiocarbamates aromatiques a permis de s’affranchir de ce mécanisme parasite et pour la première fois des chaînes de PE présentant une fonctionnalité de bout de chaîne proche de 100%. Des ATCs macromoléculaires polaires, obtenus avec les agents de transfert de chaînes identifiés au cours de l’étude préliminaire, ont ensuite été utilisés pour la synthèse de copolymères à blocs dans le carbonate de diméthyle (DMC), un solvant organique peu transférant. Le rôle clé de la thermodynamique du milieu de polymérisation (mélange DMC/éthylène supercritique à 200 bar) a alors été mis en évidence. En effet, les macro-ATCs sont insolubles dans un tel milieu, ce qui a conduit à la formation d’un mélange d’homopolymères. La diminution de la pression de polymérisation (P < 100 bar) a toutefois permis d’éviter ce phénomène et les copolymères PVAc-b-PE, PMMA-b-PE et PEO-b-PE attendus ont été obtenus. Des propriétés d’auto-assemblage ont été mises en évidence et des morphologies de type fibre ont été obtenues pour les copolymères PMMA-b-PE et PEO-b-PE synthétisés dans le DMC, permettant d’envisager un mécanisme de type auto-assemblage induit par la polymérisation (PISA). Le passage en milieu aqueux en utilisant le macro-ATC hydrosoluble PEO a permis l’observation de morphologies de type sphériques, vésicules ou encore ellipsoïdes selon le rapport molaire macro-ATC/amorceur utilisé
The synthesis of polar-apolar olefin block copolymers, combining a semi-crystalline polyethylene (PE) block and a polar block (poly(vinyl acetate) (PVAc), poly(methyl methacrylate) (PMMA), poly(ethylene oxide) (PEO)) was investigated by RAFT polymerization. A preliminary study on ethylene homopolymerization revealed parasite cross-termination reactions happening at the intermediate radical, resulting in the loss of chain-end fidelity when using aromatic xanthates as chain transfer agents (CTA) under relative mild conditions (T = 70 – 80 °C, P = 200 bar). The extent of cross-termination was greatly reduced with aromatic dithiocarbamates, and for the first time, PE chains with a high livingness were obtained. These first results were used to equip polar macromolecular CTAs (PVAc, PMMA, PEO), with selected aromatic xanthates and dithiocarbamates, that were further used for block copolymerization with ethylene in a low-transferring organic solvent (dimethyl carbonate, DMC). A critical influence of the ethylene pressure was evidenced as block polymerization at 200 bar could not be achieved due to solubility issues in the resulting supercritical DMC/ethylene mixture. This was circumvented by performing the block copolymerization below the supercritical point of the mixture (P < 100 bar) and well-defined PVAc-b-PE, PMMA-b-PE and PEO-b-PE copolymers were eventually obtained. The block copolymers were found to feature self-assembly properties and worm-like morphologies were observed for PMMA-b-PE and PEO-b-PE synthesized in DMC, hinting at a plausible polymerization-induced self-assembly (PISA) mechanism. The successful switch from DMC to water for the synthesis of PEO-b-PE copolymers enabled the observation of various particle morphologies: spheres, vesicles and ellipsoidal particles, depending on the initial macro-CTA:initiator molar ratio

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15

De, Bruyn Hank. "The Emulsion Polymerization of Vinyl Acetate." Thesis, The University of Sydney, 1999. http://hdl.handle.net/2123/381.

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Abstract This work investigates the kinetics of the emulsion polymerization of vinyl acetate. Several aspects of this system have been clarified, including the induced decomposition of persulfate, retardation by oxygen and entry by, and analysis of, the aqueous phase oligomeric radicals. It has been shown that the retardation period observed in the emulsion polymerization of VAc can be explained by the effect of traces of oxygen (< 10-6 M) on the entry efficiency of the initiator-derived aqueous-phase oligomeric radicals. Comparison of rates of polymerization in V and persulfate -initiated polymerizations together with electrospray mass spectrometry of aqueous phase oligomers, has shown that the mechanism for the induced decomposition of persulfate by vinyl acetate is chain transfer to initiator from aqueous-phase oligomeric radicals. A value has been determined for the rate coefficient for transfer to initiator, by fitting literature data to a model based on this mechanism. The reported independence of the rate of polymerization from the monomer concentration in the emulsion polymerization of vinyl acetate has been investigated. Possible explanations for this behaviour have been proposed and tested in this work, by measuring radical-loss rates directly with y-relaxation techniques. Although the Y relaxations were found to be affected by experimental artefacts, it has been demonstrated that rapid exit is not responsible for the high radical-loss rates in this system. The major artefact identified in the y relaxations was the significant effect of relatively small exotherms on relaxation behaviour, Methodologies were developed for correcting affected data and for avoiding exotherms under certain conditions. Arrhenius parameters were determined for the rate coefficient for chain transfer to monomer using the In^M method, which utilises the whole MWD. This section of the work is incomplete, for reasons detailed in chapter 5. However, as a preliminary indication it was found that the frequency factor was 106.38 M-1 s-1 and the activation energy was 38.8 kJ mol-1.

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De, Bruyn Hank. "The Emulsion Polymerization of Vinyl Acetate." University of Sydney, Chemistry, 1999. http://hdl.handle.net/2123/381.

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Abstract This work investigates the kinetics of the emulsion polymerization of vinyl acetate. Several aspects of this system have been clarified, including the induced decomposition of persulfate, retardation by oxygen and entry by, and analysis of, the aqueous phase oligomeric radicals. It has been shown that the retardation period observed in the emulsion polymerization of VAc can be explained by the effect of traces of oxygen (< 10-6 M) on the entry efficiency of the initiator-derived aqueous-phase oligomeric radicals. Comparison of rates of polymerization in V and persulfate -initiated polymerizations together with electrospray mass spectrometry of aqueous phase oligomers, has shown that the mechanism for the induced decomposition of persulfate by vinyl acetate is chain transfer to initiator from aqueous-phase oligomeric radicals. A value has been determined for the rate coefficient for transfer to initiator, by fitting literature data to a model based on this mechanism. The reported independence of the rate of polymerization from the monomer concentration in the emulsion polymerization of vinyl acetate has been investigated. Possible explanations for this behaviour have been proposed and tested in this work, by measuring radical-loss rates directly with y-relaxation techniques. Although the Y relaxations were found to be affected by experimental artefacts, it has been demonstrated that rapid exit is not responsible for the high radical-loss rates in this system. The major artefact identified in the y relaxations was the significant effect of relatively small exotherms on relaxation behaviour, Methodologies were developed for correcting affected data and for avoiding exotherms under certain conditions. Arrhenius parameters were determined for the rate coefficient for chain transfer to monomer using the In^M method, which utilises the whole MWD. This section of the work is incomplete, for reasons detailed in chapter 5. However, as a preliminary indication it was found that the frequency factor was 106.38 M-1 s-1 and the activation energy was 38.8 kJ mol-1.

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17

Croot, Robert Arthur. "The characterisation and adsorption of vinyl alcohol vinyl acetate copolymers." Thesis, University of Bristol, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303767.

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18

Zarrouki, Arthur. "Synthèse de polymères à base d'éthylène pour additiver les carburants." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1039.

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Les gazoles, carburant automobile préféré des français, sont « additivés » afin de permettre leur utilisation en hiver. Les n-paraffines présentes dans ces gazoles cristallisent en effet à basse température. Ces cristaux peuvent alors entraîner le colmatage des filtres protecteurs situés en amont du moteur. Des polymères à base d'éthylène, notamment les copolymères éthylène-acétate de vinyle (EVA), sont utilisés pour abaisser la température à laquelle les problématiques de filtration adviennent. Un nouveau procédé de copolymérisation radicalaire d'éthylène et d'acétate de vinyle, à plus basse pression et à plus basse température, que le procédé industriel actuel, a été développé au cours de cette thèse. Une grande variété d'EVA a ainsi été obtenue. Ils présentent des caractéristiques structurelles et une efficacité, pour le traitement des gazoles, similaires aux EVA commerciaux. Ce procédé a, par ailleurs, permis la synthèse d'autres co- et terpolymères de l'éthylène variant par la nature des comonomères polaires utilisés ou par l'architecture. Des modèles de copolymères EVA ont été également synthétisés par métathèse. La grande diversité d'additifs polymères à disposition combinée à des techniques d'analyse thermique et de diffusion des rayons X mises en oeuvre au plus proche de l'application (en particulier dans le gazole), ont permis de mieux appréhender leur mode d'action sur la cristallisation des n-paraffines. Les spécificités structurelles, des polymères, conditionnant leur efficacité pour le traitement de la tenue à froid des gazoles ont également pu être établies
The additivation of diesel fuels allows operating engines at low temperatures without filter blocking and thus fulfilling legal requirements. Ethylene based copolymers such as ethylene-vinyl acetate copolymers, made by free radical polymerization at high pressure (above 2000 bars) and high temperature (above 200 Â°C) are frequently used as middle distillate cold flow improvers (MDFI). A new free radical copolymerization process of ethylene and vinyl acetate in organic solvent media has been developed. This process gives access to polymers close to commercial MDFI additives under tremendous less drastic conditions (under 250 bars of ethylene and 70 Â°C). Thanks to this process, a wide diversity (variation of the nature of the polar unit, of polymer architectureâ€¦) of ethylene based polymers was obtained. Moreover, EVA model copolymers have been synthesized by metathesis. Thanks to these numerous and diverse ethylene based polymers combined with thermal analysis and X-ray scattering studies a better understanding of the operating mode of these additives in a diesel fuel has been achieved. The structural characteristics of the polymers enabling their effectiveness as diesel fuel cold flow improvers have also been established

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Alencar, Ana Ellen Valentim de. "Estudo das propriedades do cimento asfÃltico de petrÃleo modificado por copolÃmero de etileno e acetato de vinila(eva)." Universidade Federal do CearÃ, 2005. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=1439.

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CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior
Cimento AsfÃltico de PetrÃleo (CAP), caracterizado como CAP 50/60, oriundo do Campo Fazenda Alegre, no estado do EspÃrito Santo, foi modificado por adiÃÃo de CopolÃmero de Etileno e Acetato de Vinila (EVA). Na modificaÃÃo foram incorporadas amostras do copolÃmero EVA puro e proveniente do resÃduo da indÃstria de calÃados (EVAR). Os CAPS, polÃmeros e CAPS modificados, foram inicialmente caracterizados por espectroscopia no infravermelho (FTIR) e ressonÃncia magnÃtica nuclear (RMN). AnÃlise tÃrmica, como a termogravimetria (TG) e caloria exploratÃria diferencial (DSC), foi utilizada para o estudo da decomposiÃÃo tÃrmica, bem como para avaliar a estabilidade termoxidativa das amostras. Testes empÃricos como penetraÃÃo, ponto de amolecimento, susceptibilidade tÃrmica e retorno elÃstico, alÃm de viscosidade, tambÃm foram realizados para caracterizaÃÃo dos materiais. Os resultados indicaram que CAPS modificados apresentaram maior estabilidade em atmosfera oxidativa do que em atmosfera inerte. A anÃlise das curvas DSC revelou que os CAPS modificados mostraram-se mais resistentes Ã trincas tÃrmicas, quando submetidos a temperaturas mais baixas, que o CAP convencional. Os CAPS modificados foram mais resistentes Ã decomposiÃÃo oxidativa, quando foram submetidos ao envelhecimento simulado. A viscosidade do ligante modificado por adiÃÃo do polÃmero foi aumentada em relaÃÃo ao ligante puro. Diferentemente do CAP convencional, o CAP modificado por EVAR apresentou comportamento nÃo Newtoniano. Os ensaios empÃricos, relativos Ã penetraÃÃo, ponto de amolecimento, susceptibilidade tÃrmica e retorno elÃstico, mostraram que os CAPS modificados com EVAR, tiveram uma melhoria nas suas propriedades fÃsicas, em relaÃÃo aos CAPS nÃo modificados.
The Petroleum Asphaltic Cement characterized as CAP 50/60, produced at the state of EspÃrito Santo (Fazenda Alegre), was modified by addition of copolymers of ethylene vinyl acetate (EVA) and EVA from the footwearâs industry residue (EVAR). The original and modified CAPS were characterized by infrared spectroscopy (FTIR) and nuclear magnetic resonance (RMN). Thermal analysis,as thermogravimetry (TG) and differential scanning calorimetry (DSC), was used to evaluate the thermal stability of the samples. The characterization was also performed with empirical tests such as penetration, softening point, elastic recovery and viscosity. The main results indicated that polymer modified CAPS presented larger thermal stability in oxidative atmosphere than in inert atmosphere. The analysis of DSC curves revealed that modified CAPS, when submitted to lower temperatures, were more resistant to the thermal cracks than conventional CAP. Also modified CAPS showed to be more resistant to the thermal oxidative decomposition, when submitted to a simulated aging process. The viscosity of the polymer modified binder was increased in relation to the original binder. Polymer modified CAP EVAR presented non-Newtonian behavior, whereas Newtonian behavior was observed for unmodified CAP. It was observed that modifying the asphalt binder with a copolymer EVAR leads to an improvement in the physical properties in relation to the penetration, softening point, thermal susceptibility and elastic recovery

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20

Clough, Norman E. "Thermodynamics of ethylene-vinyl acetate copolymer blends." Thesis, Durham University, 1994. http://etheses.dur.ac.uk/5489/.

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The purpose of this study was to characterise the miscibility of several poly(ethylene-co-vinyl acetate), EVA, based polymer blends. EVA has many industrial applications and is often present as one of several polymeric components. Consequently, there is considerable interest in the thermodynamics of these blend systems. The thermodynamics of these blends was studied using several techniques: differential scanning calorimetry; phase contrast optical microscopy; small angle neutron scattering and wide angle X-ray scattering. Characterisation was also to include assessing the relative enthalpic and entropic thermodynamic contributions to the Rory-Huggins interaction parameter (%) of these blends. To determine the enthalpic interaction parameter, a "mixing calorimeter" was designed and constructed to measure accurately the "heat of mixing" values on blending these polymers. Free energy interaction parameters were determined from melting point depression and small angle neutron scattering measurements. In all the blends studied, the heat of mixing was endothermic and consequently, the enthalpic interaction parameters were positive i.e. unfavourable to miscibility. Miscibility in these blends can therefore only be achieved by a dominant entropic contribution, favourable to miscibility. Using phase contrast optical microscopy, both miscible and immiscible phase behaviour was observed in this series of blends. This shows good agreement with predictions of miscibility from heat of mixing, melting point and small angle neutron scattering measurements, based on the classical Flory-Huggins lattice theory. Wide angle X-ray scattering and differential scanning calorimetry results have associated miscible blends with crystallisation effects between the blend components. Small angle neutron scattering has been used to determine the concentration and temperature dependence of interaction parameters in a miscible blend. From these values the upper critical solution temperature (UCST) of the blend was predicted. The enthalpic contributions to these interaction parameters show good agreement with experimental values determined from heat of mixing measurements. It was concluded that the classical Flory-Huggins lattice theory (despite its many well documented Limitations) appears to be particularly suited to the thermodynamic characterisation of miscibility in these polymer blends.

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21

Tongcher, Oychai. "Novel routes to stereoregular poly(vinyl acetate)." Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620688.

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Oliveira, Mauricio Pinheiro de. "Síntesse de novos estabilizantes poliméricos do tipo poli(álcool vinilico-co-neo decanoato de vinila) para utilização na copolimerização em miniemulsão do acetato de vinila (VAc) com o neo-nonanoato de vinila (VEOVA-9)." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/97/97133/tde-04102012-120438/.

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Devido à importância industrial e tecnológica dos látices estabilizados com poli(álcool vinílico)/PVA e a dificuldade encontrada na etapa de polimerização em emulsão, na presença de monômeros hidrofóbicos e de PVA\'s com alto grau de hidrólise (>92%), a síntese de novos estabilizantes poliméricos derivados de PVA para utilização em reações de polimerização em emulsão e em miniemulsão se torna muito atraente e desafiadora. O objetivo principal deste trabalho foi sintetizar novos estabilizantes poliméricos do tipo poli(álcool vinílico-co-neodecanoato de vinila)/PVA-VV com alto grau de hidrólise e conseqüentemente com propriedades diferenciadas, para serem utilizados como estabilizantes nas reações de polimerização em emulsão e em miniemulsão do acetato de vinila (VAc) com o neo-nonanoato de vinila (VEOVA-9), visando a obtenção de adesivos com propriedades diferenciadas para colagem de madeiras. Os novos estabilizantes poliméricos foram obtidos em duas etapas: i) copolimerização em solução do VAc com o neo-decanoato de vinila (VEOVA-10); ii) hidrólise alcalina (NaOH/Metanol) do poli(acetato de vinila-coneodecanoato de vinila). As miniemulsões de VAc com VEOVA-9 com diferentes tipos de estabilizantes poliméricos foram preparadas em um homogeneizador de alta pressão do tipo \"Manton Gaulin\". Foi estudado o efeito dos estabilizantes poliméricos (PVA e PVA-VV) na etapa de emulsificação (diâmetro médio das gotas, polidispersão, estabilidade das miniemulsões) e na copolimerização em emulsão e em miniemulsão do VAc com o VEOVA-9, em processo batelada. O efeito do tipo de iniciador (persulfato de amônio/APS e hidroperóxido de tércio butila/TBHP e peróxido benzoato de tércio butila/TBPB, juntamente com o formaldeído sulfoxilato de sódio/SFS) na cinética da polimerização em miniemulsão do VAc com o VEOVA-9 foi estudado em processo semi-contínuo. A distribuição dos estabilizantes poliméricos (PVA e PVA-VV) entre a fase aquosa e a superfície das partículas de polímero (adsorvido/enxertado) foi determinada e correlacionada com a viscosidade e a estabilidade coloidal dos látices. Látices na condição ideal de cópia (1:1) das gotas de monômero para as partículas de polímero foram obtidos via polimerização em miniemulsão, apresentando propriedades diferenciadas, tais como, menores valores de viscosidade, menor concentração de coágulos e maior estabilidade de estocagem, em comparação com os látices obtidos em emulsão.
Due to the technological and industrial importance of latexes stabilized with poly(vinyl alcohol)/PVA and the difficulties related to the emulsion polymerization of hydrophobic monomers and the use of PVA having a high degree of hydrolysis (> 92%), the synthesis of new PVA based polymeric stabilizers for use in emulsion and miniemulsion polymerizations becomes very attractive and challenging. The aim of this work was to synthesize a new class of polymeric stabilizer, poly(vinyl alcohol-co-vinyl neo-decanoate)/PVA-VV, with a high degree of hydrolysis and differentiated properties to be used as stabilizers in the emulsion and miniemulsion copolymerization of vinyl acetate (VAc) with vinyl neo-nonanoate (VEOVA-9), that can be used as adhesive for wood bonding. New PVA based polymeric stabilizers with high degree of hydrolysis (94 - 98%) were synthesized in two steps: i) solution copolymerization of vinyl acetate (VAc) with vinyl neo-decanoate (VEOVA-10) and ii) alkaline hydrolysis (NaOH/Methanol) of poly(vinyl acetate-co-vinyl neodecanoate). Miniemulsions of VAc/VEOVA-9 were prepared using the different polymeric stabilizers in a \"Manton Gaulin\" high pressure homogenizer. The effect of different initiators (ammonium persulfate/APS or tert-butyl hydro peroxide/TBHP and tert-butyl peroxide benzoate/TBPB in the presence of sodium formaldehyde sulfoxylate/SFS) in the polymerization kinetic was evaluated. The effect of the type and concentration of polymeric stabilizer, in the emulsification step (average diameter of drops, stability of miniemulsions) as well in the polymerizations (rate of consumption of monomers, particle size and particles number) was investigated in this work. The partition of the polymeric stabilizers between the aqueous phase and the polymer particle surface (grafted/adsorbed) was determined and correlated with the viscosity and colloidal stability of latexes. Latexes with differentiated properties such as low-viscosity, lower grits content and improved storage stability, were obtained by miniemulsion polymerization with an ideal condition copy (1:1) of the monomer droplets to the polymer particles.

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Cauich-Rodriguez, Juan Valerio. "Hydrogels based on poly(vinyl alcohol-vinyl acetate) blends for biomedical applications." Thesis, Queen Mary, University of London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267577.

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Cazotti, Jaime Caetano. "Síntese e caracterização de látices híbridos de poli(acetato de vinila)/montmorilonita - PVAc/MMT para aplicação como adesivos." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/97/97136/tde-27082013-103950/.

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Este projeto de mestrado teve como objetivo a obtenção de látices híbridos constituídos de poli(acetato de vinila) (PVAc) e argila montmorilonita (MMT). O homopolímero de acetato de vinila foi sintetizado através da técnica de polimerização em emulsão na presença de diferentes tipos de argila, sendo empregada uma argila sódica (Na-MMT) e três argilas modificadas (o-MMT) com diferentes sais quaternários de amônio. Poli(álcool vinílico) (PVOH) foi utilizado como colóide protetor e persulfato de amônio (APS) como iniciador. Foi estudada a melhor condição para incorporação da argila na matriz polimérica, visando a esfoliação desta nanocarga, resultando desta maneira na formação de nanocompósitos com propriedades diferenciadas. A influência da presença das argilas foi avaliada em termos da velocidade de consumo de monômero, a qual foi acompanhada por gravimetria. Os látices foram caracterizados quanto ao diâmetro médio de partícula e polidispersidade pela técnica de espalhamento de luz (LS). O teor de coágulos do látex foi calculado por análise gravimétrica e a viscosidade analisada em um viscosímetro rotacional. Os filmes nanocompósitos foram caracterizados pelas técnicas de análise dinâmico-mecânica (DMA), análise termogravimétrica (TGA) e difração de raios X (DRX). A morfologia das partículas de látex foi avaliada por microscopia eletrônica de transmissão (MET).
The goal of this project was the preparation of hybrids latexes constituted by poly(vinyl acetate) (PVAc) and montmorillonite (MMT) clays. The poly(vinyl acetate) homopolymer was synthesized via emulsion polymerization in the presence of different types of clay, one sodium clay (Na-MMT) and organically modified clays (o-MMT) with different ammonium quaternary salts. Poly(vinyl alcohol) (PVOH) was used as protective colloid and ammonium persulfate (APS) as initiator. It was evaluated the best condition for the incorporation of the clay in the polymeric matrix, looking forward the exfoliation of the nanofiller, resulting in the formation of nanocomposites with new and improved properties. The influence of clay type and loading was evaluated in terms of latex stability and monomer consumption rate. The latexes were characterized in terms of particle size diameter and polydispersity by light scattering (LS) technique. Coagulum content was determined by gravimetric analysis and viscosity was analyzed in a rotational viscometer. Nanocomposite films were characterized by dynamic-mechanical analysis (DMA), thermogravimetric analysis (TGA) and X-ray diffraction (XRD). Latex particles morphology was evaluated by transmission electron microscopy (TEM).

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Kumar, Dheeraj. "Synthesis of vinyl acetate on palladium-based catalysts." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1747.

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Hatzinikolaou, Theodosios A. "Adhesion of ethylene vinyl acetate copolymers to metals." Thesis, University of Bath, 1985. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355114.

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The 180° peel strength of four ethylene vinyl acetate copolymers with varying V.A. content was measured (Pol A: 28%, Pol B: 18%, Pol C: 12% and Pol D: 9.5% by weight). The polymers were applied as hot-melts with or without an inextensible fabric support on: (a) mild steel etched in hydrochloric acid; (b) chemically polished copper and; (c) oxidised copper with a fibrous topography. The peel loads for a given polymer decreased from oxidised copper to etched steel to polished copper. For a given substrate the peel loads generally decreased from polymer A to polymer D with a peak for polymer C. This trend was correlated to similar trends obtained in mechanical tests like the tearing energy, strain energy density and tensile strength to failure. The fractured parts of the bond were examined with a scanning electron microscope. There was microscopic evidence of an analogy between the peel load and the observed extent of polymer deformation in the fractured surfaces where the ductilty of the particular polymer and the topography of the substrate were clearly depicted. Contact angle measurement showed a cohesive type of failure in all cases. X-ray photo-electron spectroscopy and multiple internal reflection infra-red spectroscopy provided evidence of polymer oxidation by the substrate, mostly significant in the case of etched steel. The energy balance approach was employed in order to analyse the peel test results further. The polymers response to the imposed mechanical deformations during peeling was shown to control the measured peel load. For the unbacked samples the major energy loss mechanism is the stretching of the freed strip. The much higher peel loads of the backed samples were attributed to energy losses around the peel front. Finally, plastic bending of the polymer was found to account for a relatively smaller part of the total input energy for both backed and unbacked samples.

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Haley, Roger David. "Surface chemistry of the vinyl acetate catalytic system." Thesis, University of Cambridge, 1999. https://www.repository.cam.ac.uk/handle/1810/272089.

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Edakkara, A. J., J. J. Mathen, J. Sebastian, G. Ramalingam, and G. P. Joseph. "Electrical Behaviour of Polyethylene Vinyl Acetate / ZnO Nanocomposite." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35634.

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Recently, nanoscale materials have attracted material scientists because of their unique size depend-ent magnetic, optical, electrical and thermal properties. Homogeneous dispersion of nanoparticles in the polymer matrix and control of their size are vital to achieve many of these properties. In the present work, Zinc Oxide (ZnO) nanoparticles were prepared by solvothermal route. Chemical replacement reaction was chosen for the homogeneous dispersion of prepared ZnO nanoparticles into polymer matrix. Zinc oxide is an inorganic material with a large direct band gap (3.34 eV), high exciton binding energy (60 meV) and having a unique combination of properties. In inorganic/polymetric composite, the semiconducting nanoclusters enhances the electrical and thermal properties. The dielectric properties of the composites were studied using HIOKI 3532-50 LCR Hitester. The dielectric constant was found to increase with in-creasing the concentration of nano filler. DC electrical conductivity as a function of temperature was stud-ied using Keithley picoammeter 6485. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35634

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Castanharo, Jacira Aparecida. "Preparação de microesferas poliméricas à base de estireno, acetato de vinila e divinilbenzeno com propriedades magnéticas." Universidade do Estado do Rio de Janeiro, 2011. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=2712.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Microesferas poliméricas magnéticas à base de estireno (STY), divinilbenzeno (DVB), acetato de vinila (VAc) e ferro foram preparadas via polimerização em suspensão e semissuspensão. Foram estudadas as influências da concentração de VAc adicionado na polimerização e a presença de ferro sobre as características das partículas poliméricas obtidas. Estas partículas foram caracterizadas por espectrometria de absorção na região do infravermelho (FT-IR), análise térmica (TGA/DTA), microscopia óptica (MO), microscopia eletrônica de varredura (SEM) e magnetometria de amostra vibrante (VSM). Foram obtidas com sucesso microesferas poliméricas com propriedades magnéticas à base de estireno, divinilbenzeno e acetato de vinila. Estes materiais apresentaram bom controle morfológico, com maior rendimento na faixa de 120 a 75 m. Apresentaram também boas propriedades magnéticas (22,62 a 73,75 emu/g) com comportamento próximo de materiais superparamagnéticos e boa estabilidade térmica (444 C)
Magnetic polymeric microspheres based on styrene (STY), divinylbenzene (DVB), ethylene vinyl acetate (VAc) and iron were prepared via suspension and half suspension polymerization. The influence of the concentration of VAc and iron added to the polymerization on the characteristics of polymeric particles obtained were studied. These particles were characterized by infrared spectrometry (FT-IR), thermal analysis (TGA / DTA), optical microscopy (OM), scanning electron microscopy (SEM) and vibrating sample magnetometry (VSM). Polymeric microspheres with magnetic properties based on styrene, divinylbenzene and vinyl acetate were obtained. These materials showed good morphological control and large yield range from 120 to 75 micrometers. They also showed comparable magnetic properties (from 22.62 to 73.75 emu/g) to superparamagnetic materials and good thermal stability (444 C)

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Mathen, J. J., A. J. Augustine, J. Sebastian, J. Madhavan, and G. P. Joseph. "Synthesis and Characterization of Polyethylene Vinyl Acetate / ZnSe Nanocomposite." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35635.

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In the not too distant past, polymer scientists and technologists expanded their horizons from consum-er products to the high technology arena, particularly notable in opto - electronic applications. Ethylene Vinyl Acetates (EVA) are popular because of their superior adhesion to most substrates as well as their ease of formulation. Its High transparency is a key attribute for photovoltaic cell encapsulation. It is ex-pected that with the addition of ZnSe nano fillers, EVA becomes a high refractive index polymer (HRIP) with refractive index 2.5 and posses anti-reflective property. In this work, ZnSe nanoparticles were syn-thesised by solvo-thermal method. Nano – Composite matrices based on polyethylene vinyl acetate / ZnSe were prepared by chemical replacement mechanism. Refractive index of prepared polymer nanocomposites were calculated from dielectric study using Hioki 3532-50 LCR HITESTER at various frequencies and temperatures. The presence of nano filler enhanced the refractive index and it varied with frequency and temperature. UV-Vis-NIR Spectra of the samples enable to determine the bandgap and was found to de-crease with increasing the concentration of nano fillers dispersed in polymer matrix. I-V characteristics of the nanocomposites were plotted at various concentrations of nano fillers and at various temperatures. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35635

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31

Wood, Timothy John. "An adsorption study of vinyl alcohol/vinyl acetate copolymers on polystyrene by quartz microbalance." Thesis, University of Bristol, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261278.

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Nare, Keith Dumisani. "Formulation development and thermorheological properties of crumb rubber/eva modified bitumen." Thesis, Nelson Mandela Metropolitan University, 2016. http://hdl.handle.net/10948/11974.

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The study deals with the formulation development and thermorheological properties of crumb rubber/ethylene vinyl acetate (EVA) modified bitumen with the aim of optimizing the amount of crumb rubber and EVA loadings in bitumen based on thermorheological parameters complex shear modulus, phase angle and rutting parameter. In the modified binders EVA offers plastomer properties whereas the crumb rubber confers elasticity to the bitumen. 13.75% crumb rubber and 2.5% EVA loadings based on aging indices gave the best optimized mixture. The thermorheological behaviour of the best optimized mixture was compared to industrial grade EVA (AP-1) and crumb rubber (AR-1) modified bitumen. Improving aging behaviour of the bitumen was evaluated using four antioxidants: carbon black, hydrated lime, Irganox 1010 and Irgafos 168. The least aging indices at 58˚C and 64˚C were obtained from a 1:1:1 Irganox 1010/hydrated lime/carbon black mixture. SARA (saturates, aromatics, resins and asphaltene) analysis gave the chemical background for application of antioxidants to reduce the propensity of short term aging. To further improve the EVA/crumb rubber optimized mixture for workability FT wax (Sasobit®) was assayed at loadings from 0-2.5%. This was done to match the EVA content and maintain the original maximum loading of 2.5% in the optimized mixture. The phase change abilities of FT wax owing to the high latent heat enabled co-crystallization with the EVA with the elastomeric backbone of crumb rubber acting as support material. The energy-sustainability nexus was found to have worked at less than 1% loading of FT wax in the EVA/crumb rubber modified bitumen. Response surface methodology approach to all the sections of work was used to come up with the optimized mixtures based on rheological parameters complex shear modulus, phase angle and rutting parameter at test temperature 64˚C. The interaction chemistry of bitumen, crumb rubber, EVA and FT wax was found to be first and second order in all cases involving individual contributions and co-interaction amongst the factors. Project costing for each section of work (optimizing section, antioxidant section and FT wax section) was conducted involving the raw materials used, equipment used, labour involved and other costs incurred for all the project work.

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Ildefonso, Jesner Sereni. "Análise da viabilidade técnica da utilização do copolímero etileno acetato de vinila (EVA) descartado pela indústria calçadista em misturas asfálticas (processo seco)." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/18/18143/tde-13032007-112426/.

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A presente dissertação teve por objetivo analisar o comportamento de misturas asfálticas modificadas, pelo processo seco, com o copolímero etileno acetato de vinila (EVA), resíduo sólido descartado pela indústria calçadista. Em razão das características do EVA, acredita-se que ele possa melhorar as características mecânicas de misturas asfálticas e a resistência ao desgaste. A maioria dos pesquisadores tem direcionado seus esforços em estudos de misturas asfálticas modificadas pelo processo úmido, porém, devido à natureza do resíduo analisado neste trabalho, optou-se pelo processo seco, que demanda menos energia por não necessitar de moagem do material. A pesquisa compreendeu o estudo de amostras de misturas asfálticas não envelhecidas e com envelhecimento de duas e quatro horas em estufa, com moldagem de corpos-de-prova para realização dos ensaios de resistência à tração por compressão diametral estática, módulo de resiliência por compressão diametral, fluência por compressão uniaxial estática e dinâmica, vida de fadiga e desgaste por abrasão (ensaio Cantabro). Os resultados mostram que a utilização deste resíduo aumentou a resistência das misturas à fadiga e ao desgaste de forma significativa, porém as misturas tornaram-se mais susceptíveis à deformação permanente. O tempo de envelhecimento de curto prazo se mostrou importante, pois aumentou a resistência das misturas à fadiga e à deformação permanente.
The main purpose of the present master thesis was to analyze the behavior of modified hot-mix asphalt, through the dry process, with the copolymer ethylene vinyl acetate (EVA) discarded by the footwear industry. Since the EVA characteristics, it is believed that it can improve hot-mix asphalt mechanic characteristics and the wear and tear resistance. Most of the researchers have been addressing efforts in studies on modified hot-mix asphalt by the wet process, however, due to the nature of the solid residue analyzed in this work, the dry process will demand less energy for not needing of grinding. The research evolved the study of samples of asphalt mixtures not aged and with aging of two and four hours in oven, submitted to indirect tension test, resilient modulus, static and dynamic creep, fatigue life and loss due to abrasion (Cantabro test). The results show that the use of this residue increased the resistance of the mixtures to the fatigue and loss of mass due to abrasion, however the mixtures became more susceptible to the permanent deformation. The short-time aging was shown important, because it increased the resistance of the mixtures to the fatigue and the permanent deformation.

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Bailly, Nathalie. "N-vinylpyrrolidone-vinyl acetate block copolymers as drug delivery vehicles." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/20133.

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Thesis (PhD)--Stellenbosch University, 2012.
ENGLISH ABSTRACT: The primary aim of this study was to investigate the feasibility of the amphiphilic block copolymer poly((vinylpyrrolidone)-b-poly(vinyl acetate)) (PVP-b-PVAc) as a vehicle for hydrophobic anti-cancer drugs. PVP-b-PVAc block copolymers of constant hydrophilic PVP block length and varying hydrophobic PVAc block lengths were synthesized via xanthate-mediated controlled radical polymerization (CRP). The methodology consisted of growing the PVAc chain from a xanthate end-functional PVP. In an aqueous environment the amphiphilic block copolymers selfassembled into spherical vesicle-like structures consisting of a hydrophobic PVAc bilayer membrane, a hydrophilic PVP corona and an aqueous core. The self-assembly behaviour and the physicochemical properties of the self-assembled structures were investigated by 1H NMR spectroscopy, fluorescence spectroscopy, transmission electron microscopy (TEM) and dynamic and static light scattering. Drug loading studies were performed using a model hydrophobic drug, clofazimine, and a common anti-cancer drug paclitaxel (PTX) to evaluate the potential of the PVP-b-PVAc block copolymers for drug delivery,. Clofazimine and PTX were physically entrapped into the hydrophobic domain of the self-assembled PVP-b-PVAc block copolymers via the dialysis method. The drug-loaded PVP-b-PVAc block copolymers were characterized regarding particle size, morphology, stability and drug loading capacity in order to assess their feasibility as a drug vehicle. The polymer vesicles had a relatively high drug loading capacity of 20 wt %. The effect of the hydrophobic PVAc block length on the drug loading capacity and encapsulation efficiency were also studied. Drug loading increased with increasing the hydrophobic PVAc block length. The effect of the drug feed ratio of clofazimine and PTX on the drug loading capacity and encapsulation efficiency were also investigated. The optimal formulation for the drug-loaded PVP-b-PVAc was determined and further investigated in vitro. The size stability of the drugloaded PVP-b-PVAc block copolymers was also assessed under physiological conditions (PBS, pH 7.4, 37 °C) and were stable in the absence and presence of serum. PVP-b-PVAc block copolymers were tested in vitro on MDA-MB-231 multi-drug-resistant human breast epithelial cancer cells and normal MCF12A breast epithelial cells to provide evidence of their antitumor efficacy. In vitro cell culture studies revealed that the PVP-b-PVAc drug carrier exhibited no cytotoxicity towards MDA-MB-231 and MCF12A cells, confirming the biocompatibility of the PVP-b-PVAc carrier. In vitro cytotoxicity assays using clofazimine-PVPb- PVAc formulations showed that when MDA-MB-231 cells were exposed to the formulations, an enhanced therapeutic effect was observed compared to the free drug. Cellular internalization of the PVP-b-PVAc drug carrier was demonstrated by fluorescent labeling of the PVP-b-PVAc carrier. Fluorescence microscopy results showed that the carrier was internalized by the MDAMB- 231 cells after 3 hours and localized in the cytoplasm and the perinuclear region. Overall, it was demonstrated that PVP-b-PVAc block copolymers appear to be promising candidates for the delivery of hydrophobic anti-cancer drugs.
AFRIKAANSE OPSOMMING: Die studie is gebaseer op die gebruik van amfifieliese blokkopolimere van poli((Nvinielpirolidoon)- b-poli(vinielasetaat)) (PVP-b-PVAc) as potensiële geneesmiddeldraers. PVP-b-PVAc blokkopolimere van konstante hydrofiliese bloklengte en verskillende hydrofobiese bloklengte is voorberei via die RAFT/MADIX-proses. Blokkopolimere met vinielasetaat is vanaf poli(N-vinielpirolidoon) met ‘n xantaatendfunksie voorberei. In ‘n wateromgewing vorm die PVP-b-PVAc blokkopolimere vesikel strukture met ‘n hydrofobiese membraan en ‘n hydrofiliese mantel. Die fisies-chemiese eienskappe van die PVP-b-PVAc blokkopolimere is gekarakteriseerd met gebruik van KMR spektroskopie, fluoresent spektroskopie, transmissie elektronmikroskopie (TEM) en dinamiese en statiese lig verstrooiing. Die potensiaal van PVP-b-PVAc as ‘n geneesmiddeldraer is ondersoek deur gebruik te maak van die hydrofobiese geneesmiddel, clofazimine, en ‘n anti-kanker geneesmiddel, paclitaxel. Clofazimine en paclitaxel is ge-inkapsuleer in die hydrofobiese gedeelte van die blokkopolimere via die dialise-metode. Clofazimine-PVP-b-PVAc en paclitaxel-PVPb- PVAc blokkopolimere is gekarakteriseerd met betrekking tot die partikel grootte, morfologie, stabiliteit en laai kapasitiet om die PVP-b-PVAc blokkopolimere as geneesmiddeldraers te evalueer. Die PVP-b-PVAc geneesmiddeldraer het ‘n relatiewe hoë laai kapsiteit van 20 gew % aangetoon. Die invloed van die bloklengte op die laai kapasitiet is ook ondersoek en beskryf. ‘n Toename in die laai kapasitiet is gesien met ‘n toename in die hydrofobiese bloklengte. Die invloed van die hoeveelheid geneesmiddel op die laai kapasitiet en die inkapsuleer doeltreffendheid is ook ondersoek. Die optimale formulasie is gevind en verder gebruik vir in vitro studies. Die stabiliteit van die geneesmiddeldraer in fisiologiese omstandighede (pH 7.4, 37 °C) is ook beskryf. Resultate toon aan dat die sisteem stabiel is onder hierdie omstandighede in die afwesigheid en aanwesigheid van serum. In vitro eksperimente is op MCF12A epiteel-borsselle en MDA-MB-231 epiteelborskankerselle getoets om die anti-tumoraktiwiteit te ondersoek. Resultate toon aan dat die PVP-b-PVAc geen sitotoxiese effek op die selle het nie, wat aandui dat die polimere bioverenigbaar is. Verder is dit bewys dat die PVP-b-PVAc geneesmiddel formualsie ’n hoër sitotoxisiteit besit as die vry-geneesmiddel. Fluoresent studies het aangetoon dat die geneesmiddeldraer na 3 uur opgeneen word deur MDA-MB231 selle en gelokaliseerd is in die sitoplasma en in die omgewing van die kern van die selle. In die algemeen is dit aangetoon dat PVP-b-PVAc blokkopolimere potensiële kandidate vir die lewering van hydrofobiese geneesmiddels is.

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Guo, Haochen. "RECYCLING THERMOPLASTIC EVA (POLYETHYLENE-CO-VINYL ACETATE) WITH IMPROVED PROPERTIES." Case Western Reserve University School of Graduate Studies / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case1585673886043802.

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36

Jovanovic, Renata. "Butyl acrylate/vinyl acetate emulsion copolymerization: Reaction monitoring and property evaluation." Thesis, University of Ottawa (Canada), 2001. http://hdl.handle.net/10393/9102.

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Several aspects of butyl acrylate/vinyl acetate (BA/VAc) polymerizations were investigated in this thesis. Polymerization process monitoring is a key factor in obtaining high quality products with prespecified properties. Therefore, a considerable part of this work was devoted to the real-time monitoring of BA/VAc emulsion polymerization reactions. An Attenuated Total Reflectance - Fourier Transform Infrared (ATR-FTIR) spectroscopy sensor was used for monitoring conversion and copolymer composition. Due to the novelty of this technique, in the first part of the study, the suitability of this technique for polymerization monitoring was investigated. In the second part of this thesis, the knowledge obtained from the off-line monitoring of the solution polymerizations was employed for the real time monitoring of six high-solids BA/VAc emulsion polymerizations. Finally, the latexes obtained in the second part of this thesis were characterized for a variety of polymer properties of interest to adhesive industry. Among the properties investigated were particle size, rheology, dynamic mechanical properties of the dry polymers and the shear and tensile strength of adhesive bonds when hard maple wood is used as a substrate. (Abstract shortened by UMI.)

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Okpe, Owoicho. "Alumina trihydrate as a fire retardant for ethylene vinyl acetate copolymer." Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339740.

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Khan, Shadeed. "Controlled Release of Fluoride from Poly(ethylene-co-vinyl acetate) Films." VCU Scholars Compass, 2009. http://scholarscompass.vcu.edu/etd/1928.

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The development of aesthetically unattractive white spots is a concern for patients undergoing fixed orthodontic treatment. Due to poor oral hygiene during treatment, accumulation of plaque around orthodontic brackets causes bacterial fermentation reactions producing acids that dissolve the mineral enamel. Such dissolution results in white spot formation, an early sign of dental caries. In principal, to inhibit the appearance of these spots during treatment, fluoridated elastomeric o-rings might be employed. Once placed around brackets, these o-rings should release fluoride therapeutically for at least 30 days, after which the orthodontist may replace them. At the present time, such fluoride-releasing o-rings are not available. In this study, model materials for fluoride-releasing elastomeric o-rings were developed. These materials were fluoride-impregnated poly(ethylene-co-vinyl acetate) (PEVA) films. In vitro release studies of these films were conducted, assessing their capacity to deliver fluoride within therapeutic range (1.2 ≤ µg F/ring/day ≤ 51.4) for 30-45 days. Optimal sample and experimental parameters, including (1) fluoride loading in the film (wt% F), (2) overcoat thickness, and (3) temperature that provided therapeutic release, were determined. At 37°C, favorable release was observed for the following: (1) films with overcoat thickness of 0.14 mm and fluoride loadings of 3.9 wt% and 5.7 wt% and (2) films with overcoat thickness of 0.27 mm and fluoride loading of 5.7 wt%. These results are important in providing fundamental guidance for the development of o-rings that combat white spot formation among orthodontic patients.

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39

Yao, Hongyang. "Microstructures of poly(vinyl acetate) studied by nuclear magnetic resonance spectroscopy." W&M ScholarWorks, 1997. https://scholarworks.wm.edu/etd/1539623911.

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Carbon-13 NMR spectroscopy was used to investigate the microstructures of poly(vinyl acetate) prepared by solution polymerization in benzene. A series of aromatic compounds was synthesized in order to model the structures formed via chain transfer to solvent. The peaks near 126.5 and 128.5 ppm in the spectra of the polymer samples were assigned to a 1-phenyl-(2n + 1)-multi-acetoxyalkane (where n = 1, 2, 3, etc.) microstructure. The concentration of that structure obtained from NMR spectra was correlated with the concentration calculated from reported kinetic data.;Chain transfer to benzene was shown to occur by addition of the macroradical to benzene, followed by rearomatization involving loss of a hydrogen atom. No evidence was obtained for a transfer mechanism involving hydrogen abstraction from benzene, and the copolymerization of benzene with vinyl acetate also was shown to be absent. The transfer mechanism actually established accounts for the unexpectedly large transfer constant of benzene in vinyl acetate polymerization. General mechanisms are proposed for the solution polymerization of vinyl acetate in aromatic solvents.

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40

Bambalaza, Sonwabo Elvis. "An investigation into the use of a ceramifiable Ethylene Vinyl Acetate (EVA) co-polymer formulation to aid flame retardency in electrical cables." Thesis, Nelson Mandela Metropolitan University, 2014. http://hdl.handle.net/10948/d1020159.

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The concept of a unique ceramifiable Ethylene vinyl acetate (EVA) based polymer composite was based on the incorporation of inorganic compounds such as aluminium hydroxide, calcium carbonate, muscovite mica, and calcined kaolinite within a 95 percent EVA/ 5 percent Polydimethylsiloxane (PDMS) polymer matrix such tha t upon heating to elevated temperatures of about 1000 oC, a solid end-product with ceramic-like properties would be formed. The ceramifiable EVA based polymer composite was developed to be used as electric cable insulation or sheath as the formation of a ceramic based material at elevated temperatures would provide flame retardant properties during fire situations. The flame retardant properties at elevated temperatures would ensure that the insulation remains at such temperatures due to some of the properties of the resultant ceramic such as reasonably high flexural strength, high thermal stability, non-reactivity and high melting point. During a fire this would ensure that flames would not be propagated along the length of the cable and also protect the underlying conducting wires from being exposed to the high temperatures of the fire. Its application as a cable insulation also required that the material functions as a cable insulator under ambient temperature conditions where the ceramifiable polymer composite should retain certain polymer properties such as the post-cure tensile strength (MPa), degree of polymer elongation (percent), thermal expansion, thermal slacking, limited oxygen index and electrical insulation. This study made use of a composite experimental design approach that would allow for the optimization of the amounts of the additives in the ceramifiable polymer composite giving both the desired mechanical properties of the material under normal operating temperatures as a polymer and also as a ceramic once exposed to elevated temperatures. The optimization of additives used in the ceramifiable polymer composite was done by using a D-optimal mixture design of experiments (DoE) which was analyzed by multiple linear regression.

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41

Lake, Richard Charles. "The identification of the fouling mechanism during the crossflow filtration of a model fermentation broth." Thesis, University of Surrey, 1996. http://epubs.surrey.ac.uk/842774/.

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Experiments have been conducted to identify the fouling mechanism during the crossflow filtration of a model yeast fermentation broth of Vinyl Acetate particles suspended in a Bovine Serum Albumin (BSA) solution. These have been conducted with filter modules, to obtain quantitative data for the rate and the extent of flux decline due to membrane fouling, and with filter coupons, to obtain quantitative data for the build up of the fouling layer with each individual system and the mixed system. The data from the individual systems have been analysed and then used to determine their fouling mechanisms; this information has been used to predict the fouling mechanism for the mixed system. Finally, this prediction has been compared to the actual fouling mechanism determined by analysis of the mixed system data. For the model particulate suspension, the fouling was due to the build up of a cake layer, as with dead end filtration; however, fouling was limited by membrane scouring. For the model macromolecular solution, a four part fouling mechanism was identified: initially aggregates formed within the pores; the concentration at the membrane surface increased until protein came out of solution as strands; the strands disappeared causing increased aggregation in the pores; finally, a mesh formed on the membrane surface. For the mixed system, fouling was due to the formation of a particle cake on the membrane surface with protein aggregates forming in the pores. The fouling kinetics could be predicted by considering the results from the individual systems; however, the fouling mechanism could not be predicted without using visualisation experiments due to the interactions between the particles and the macromolecules.

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42

Langer, Filip. "Vliv okolních podmínek na recyklaci solárních modulů." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2021. http://www.nusl.cz/ntk/nusl-442429.

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This thesis is focused on experiments, goal of which is to separate protective glass apart from thin layer solar panel. This could lead to less expensive and more efficient recycling. We try to achieve the separation of the glass by thawing ethylene vinyl acetate layer, which serves as insulant and bonding material. Experiments are concluded in high temperature dryer and high temperature vacuum oven on samples of thin layer solar panel, which is for the purposes of experiments cut into same pieces by water jet cutting machine. The initiatory experiments in dryer and oven are to determine value of ethylene vinyl acetate thaw point in tested samples of panel. The thaw point is determined to be 340 °C. When exposed to this temperature, the ethylene vinyl acetate thaws enough for glass to be able to be extracted with minimal physical strength. The process is accompanied by fire destruction of tedlar layer and creation of exhaust gases. Following experiments in vacuum and nitrogen environment are to test their influence on thawing process. Exposing sample to temperature of 340 °C in vacuum led to no new results. Exposing sample to temperature of 340 °C in nitrogen environment prevented fire and achieved same level of thawing of ethylene vinyl acetate while creating less exhaust gases. Even though the fire was prevented, tedlar layer was still destroyed by the high temperature. Furthermore, particles of evaporated ethylene vinyl acetate condensed on surface of module in form of dust. Following experiments studied absorption of panel and influence of accessible solvents on thawing process. It was determined that panel is able to absorb approximately 2 % of acetone, 0,4 % of isopropyl alcohol and 0,11 % of distilled water in its own weight. Experiments with modules soaked in these solvents proved no new results in thawing process. By observing samples of ethylene vinyl acetate taken from module, thawed out of module after experiment in vacuum oven and dust condensed on surface of module after experiment in nitrogen environment, it was proven that the condensed dust is indeed ethylene vinyl acetate.

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43

Oghide, Godwin O. "Miscibility studies of poly (methyl acrylate) poly (vinyl acetate) and poly (vinyl acetate)/ poly (vinylidene fluoride) blends using differential scanning calorimetry and fourier transform infra red spectroscopy." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 1985. http://digitalcommons.auctr.edu/dissertations/3294.

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The miscibility of poly (methyl acrylate)/poly (vinyl acetate) (PMA/PVAc) and poly (vinyl acetate)/poly(vinylidene fluoride) (PVAc/PVF2) blends has been studied. Films of compositions 100/0, 80/20, 60/40, 50/50, 40/60, 20/80, and 0/100 (w/w) were cast for each system. Films of PMA/PVAc were found transparent and those of the PVAc/PVf2 were slightly opaque. While all the compositions of the PMA/PVAc exhibit single sharp Tgs, as measured with the differential scanning calorimeter, almost all of those of the PVAc/PVF2 exhibit s1 ng1 e broad TgS. By the single Tg criterion, the PVA/PVAc and PVAc/PVF2 systems are miscible in all proportions. Fourier transform infra-red spectroscopy spectra indicate molecular interaction complex involvement in the two systems. Evidence for such interaction was found to be significant in the 80% PMA/20% PVAc and 20% PVAc/80% PVF2 compositions.

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44

Poormahdian, Saïd. "Emulsion copolymerization of vinyl acetate and butyl acrylate in a tubular reactor." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0028/NQ48892.pdf.

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45

Olsen, Donald Grant. "A study in plantwide control of a vinyl acetate monomer process design." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/MQ65065.pdf.

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46

Lange, Hanna. "Emulsion polymerization of vinyl acetate with renewable raw materials as protective colloids." Thesis, KTH, Skolan för kemivetenskap (CHE), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-41019.

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Emulsion polymerizations of vinyl acetate (VAc) were performed by fully or partially replacing poly(vinyl alcohol) (PVA) with renewable materials as protective colloids or by adding renewable materials, as additives or fillers, to the emulsions during or after polymerization. The purpose of the study was to increase the amount of renewable materials in the emulsion. A total of 19 emulsions were synthesized. Different recipes were used for the synthesis. The following renewable materials were studied; hydroxyethyl cellulose (HEC) with different molecular weights, starch and proteins. HEC and starch were used as protective colloids. Proteins were used as additives or fillers. Cross-linking agent A and Cross-linking agent B were used as cross-linking agents. A total of 26 formulations were pressed, either cold or hot. The synthesized emulsions were evaluated with respect to pH, solids content, viscosity, minimum film formation temperature (MFFT), glass transition temperature (Tg), particle size and molecular weight (Mw). The tensile shear strengths of the emulsions were evaluated according to EN 204 and WATT 91. It was possible to fully, or partially, replace PVA as protective colloid with renewable materials. It was also possible to use renewable materials as additives or fillers in the emulsions. The emulsions obtained properties that differed from the reference. Generally, emulsions with HEC as protective colloid showed lower viscosity and slightly higher MFFT, Tg and molecular weight than emulsions with PVA as protective colloid. Larger particle sizes than the reference were obtained for emulsions containing PVA combined with renewable materials. The emulsion with starch as protective colloid exhibited the largest particle size. 10 formulations passed the criteria for D2. The emulsions where PVA was fully or partially replaced with HEC or starch showed a water resistance similar to the reference (around D2). The addition of protein did not decrease the water and heat resistance compared to the reference. Addition of protein after polymerization increased the water resistance (D2) compared to addition during polymerization. Addition of cross-linking agents did not increase the water resistance further. Two formulations passed the criteria for D3. The emulsion in the first formulation had PVA as protective colloid and protein B was added during polymerization. The emulsion in the second formulation had HEC as protective colloid. To both of these emulsions, protein A was added after polymerization, as a filler, combined with Cross-linking agent B as cross-linking agent before hot pressing. The first formulation also showed a good heat resistance (passed the criteria for WATT 91).

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47

Rocha, Beatriz Aline Riga [UNESP]. "Síntese de ligantes diimínicos para obtenção de complexos organocobalto(III) para polimerização radicalar mediada por cobalto." Universidade Estadual Paulista (UNESP), 2017. http://hdl.handle.net/11449/149815.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Neste trabalho objetivou-se a síntese e caracterização de oito complexos de cobalto(II) que fossem aptos a atuarem como agentes controladores na Polimerização Radicalar Mediada por Cobalto do monômero acetato de vinila. Através da modulação da esfera de coordenação destes complexos com a alteração dos efeitos estéricos e eletrônicos promovidos pela coordenação de ligantes α-diiminas, buscou-se estabelecer parâmetros para propor a forma como estes complexos mediam a CMRP do referido monômero. Os complexos foram divididos em dois grupos, objetivando uma avaliação mais eficiente da forma como os efeitos estéricos e eletrônicos interferem na capacidade controladora dos mesmos. Após a variação sistemática das proporções molares entre complexo, iniciador e monômero encontrou-se na proporção [Co]/[AIBN]/[VAc] = 1/3,25/542 os resultados mais satisfatórios deste trabalho. O uso de DMSO fora prejudicial para os complexos 2a-c, porém fez com que os complexos 2d-h apresentassem melhorias, reduzindo seus valores de polidispersidade e aumentando as massas moleculares dos polímeros. O complexo 2b fora escolhido como o melhor controlador do grupo do efeito estérico, por reunir em si as características estérias e eletrônicas que o fizeram apresentar os menores valores de polidispersidade (Đmáx = 1,43). Com relação ao grupo de complexos do efeito eletrônico, fora o complexo 2f que, devido à maior estabilidade estrutural conferida ao complexo por seu substituinte cicloexil, apresentara as menores polidispersidades de seu grupo, entre 1,12 e 1,58.
This work aimed the synthesis and characterization of eight cobalt(II) complexes which could be able to act as controlling agents in vinyl acetate radical polymerization mediated by cobalt. By modulating the coordination sphere of these complexes, modifying the steric and electronic effects offered by the α-diimine ligands, we sought to establish parameters to propose how these complexes mediate the CMRP of vinyl acetate. The complexes were split in two groups in way to assess efficiently how the electronic and steric effects can affect the controlling capacity of the CoII(α-diimine).A systematic variation of the molar ratio such as [Co]/[initiator] and [Co]/[monomer] made it possible to choose [Co]/[initiator]/[monomer] = 1/3.25/542 as the ratio that provided certain level of control. The addition of DMSO was detrimental to the complexes 2a-c, but caused an improvement to the activity of complexes 2dh, reducing their polydispersity values and increasing the molecular weights of the polymers. Complex 2b was chosen as the best controller of the steric effect group, its steric and electronic characteristics made possible to reach the lowest polydispersity of its group (Đmax = 1.43).Regarding to the group of complexes of the electronic effect, it was the complex 2f that had the smallest polydispersity of its group, between 1.12 and 1.58, due to the greater structural stability conferred to the complex by its cyclohexyl substituent.

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48

Ferguson, Christopher James. "Core-shell polymers from styrene and vinyl acetate for use as wood adhesives." Thesis, University of Canterbury. Chemistry, 2000. http://hdl.handle.net/10092/5647.

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Techniques to produce core-shell morphology have been applied to the creation of poly(vinyl acetate) emulsions for use as wood adhesives. These strategies have been used to investigate the molecular origins of some of the shortcomings of poly(vinyl acetate) adhesives, and also to attempt to enhance the properties of these widely used adhesives. A model is presented to predict the incidence of particle formation, which was used to accurately predict that the polymerisation of vinyl acetate in the presence of large polystyrene seed particles would not be possible without the formation of secondary particles. Numerous attempts were made to reduce the incidence of secondary particle formation using the mechanistic basis of the model as a guide, without success. As a result, the inverse route to core-shell morphology was used to create the desired morphology. Microscopic characteristics that favoured the formation of particles containing one centrally located polystyrene core were investigated. Transmission electron microscopy techniques were developed to allow characterisation of the morphology produced in two-stage styrene-vinyl acetate polymerizations Latices having a range of morphologies, including the desired core-shell, were subjected to a range of physical tests to evaluate their performance as wood adhesives. The information gained from this testing was used to correlate performance between tests. The results have also been explained on the basis of microscopic structure.

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49

Khunniteekool, Chonlada. "Structure/property relationships of cross-linked polyethylene and ethylene vinyl acetate copolymer foams." Thesis, University of Manchester, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390453.

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50

Owens, Thomas Graham. "The promoting role of Au in the Pd-catalysed synthesis of vinyl acetate monomer." Thesis, University of St Andrews, 2007. http://hdl.handle.net/10023/352.

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Dissertations / Theses on the topic 'Vinyle Acetate'

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