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The intent of this research was to enhance our knowledge of aqueous phenolformaldehyde resin cure as it is affected by the elevated water vapor pressures that occur during hot-pressing of a wood-based composite. Microdielectric spectroscopy (DEA) was used to monitor the cure reaction, and thermomechanical analysis (TMA), swelling tests and scanning electron microscopy (SEM) techniques were used to characterize the final resin-network. Microdielectric results showed that as the water vapor pressure of the sy stem increases the time to gelation increases. It was also found that the injection of saturated water vapor sharply decreased the gelation time when compared to the other water vapor environmental conditions. In addition, it was found that the higher the water vapor pressure the lower the residual ion viscosity. Thermomechanical analysis and swelling test experiments showed that as the water vapor pressure increases the glass transition temperature and the cross-link density of the cured resin-network decreases. Considerable differences in the morphology of the network were found using SEM. Thus, it can be established that during the curing process under elevated water vapor pressures of a liquid phenol-formaldehyde adhesive some water is trapped into the resin network and it is acting as a plasticizer. A theoretical approach to model the cure kinetics of phenol-formaldehyde has been developed. The model is based on the occurrence of two simultaneous processes (condensation polymerization and evaporation of water) and on the concentration dependency of the activation energy of polymerization. / Ph. D.

Orientador: Michelle Leali Costa / Coorientadora: Cirlene Fourquet Bandeira / Banca: Edson Cocchieri Botelho / Banca: Bruno Ribeiro / Resumo: Com os avanços tecnológicos na engenharia, em particular na engenharia de materiais, materiais híbridos e materiais compósitos são desenvolvidos a cada ano. A busca do material adequado (alta resistência aliado ao baixo peso), novas oportunidades para estruturas de alto desempenho e com baixa massa específica, vem favorecendo o desenvolvimento em diversos setores, dentre estes o setor aeroespacial. Dando continuidade a esses avanços, o presente trabalho tem como um dos objetivos a caracterização de uma resina benzoxazina comercial XU 35610, via técnicas de infravermelho (FT-IR), termogravimetria (TGA) e calorimetria exploratória diferencial (DSC), e posteriormente estabelecer um ciclo de cura para a mesma utilizando técnicas de análise térmica. Com o ciclo de cura definido processou-se a resina junto com fibra de carbono via moldagem por compressão a quente com o objetivo de produzir um compósito de fibra de carbono/resina benzoxazina. Este compósito foi caracterizado por técnicas de análise térmica (TGA e DSC), inspeção visual, avaliação por ultrassom e microscopia óptica. De posse deste compósito, estudou-se o comportamento da mecânica da fratura via ensaios de ILSS (Interlaminar Shear Strenght) e ENF (End-notched Flexure - Mode II), bem como por análise dinâmico-mecânica (DMA). Para os compósitos produzidos, observou-se por inspeção visual, que o laminado apresenta-se sem trincas e delaminações. Os resultados mostram que os compósitos de fibra de carbono/resina benzoxazina... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The technological advancements in engineering, particularly in materials engineering, hybrid materials and composite materials have been developed every year. The search for suitable material (high resistance combined with low weight), new opportunities for high performance structures with low specific weight, has favored the development in several sectors, among them the aerospace sector. The present work has as one of the objectives the characterization of a commercial benzoxazine resin XU 35610, via infrared techniques (FT-IR), thermogravimetry (TGA) and differential scanning calorimetry (DSC) and subsequently establishes a cure cycle for the polymer matrix using thermal analysis techniques. Since the curing cycle has defined the resin was processed along with carbon fiber by hot compression molding with the objective of producing a carbon fiber / benzoxazine resin composite. This composite was characterized by thermal analyses (TGA and DSC), visual inspection, ultrasonic evaluation and optical microscopy. In possession of this composite, the behavior of fracture mechanics was studied by ILSS (Interlaminar Shear Strenght) and ENF (End-notched Flexure - Mode II) as well as dynamic-mechanical analysis (DMA). The laminated was evaluated by visual inspection, in order to identify cracks and delaminations. The results show that carbon fiber/benzoxazine composites showed good consolidation, a glass transition temperature of 158°C and good thermal stability (measured by TGA) at a... (Complete abstract click electronic access below) / Mestre

Les résines phénoliques de type résole présentent des propriétés applicatives et thermiques adaptées à l'élaboration de matériaux composites pour l'industrie aérospatiale. En particulier, ces résines peuvent être polymérisées en plusieurs étapes et présentent des propriétés de charbonnement très élevées. Seulement, ces résines sont principalement synthétisées à partir de formaldéhyde et de phénol. Ces précurseurs sont classés Cancérigène Mutagène Reprotoxique (CMR) respectivement de catégorie 1B et 2 et sont issus de ressources pétrolières. Du fait de cette classification CMR et de la raréfaction des ressources pétrolières, la société SAFRAN-Herakles souhaite substituer le formaldéhyde par des précurseurs non classés CMR et d'origine renouvelable. Les précurseurs aldéhyde aromatiques issus des lignines, 4-hydroxybenzaldéhyde, vanilline et syringaldéhyde, ne sont pas toxiques et peuvent être issus d'une ressource renouvelable abondante et bon marché, les lignines. Néanmoins, nous avons montré que ces trois précurseurs bio-sourcés ne sont pas réactifs en synthèse de résines résole. Nous avons également montré que le formaldéhyde doit être substitué par des précurseurs dialdéhyde aromatiques réactifs pour synthétiser des résines phénoliques avec d'excellentes propriétés de charbonnement. Ainsi, nous avons mis au point deux méthodes de fonctionnalisation pour transformer ces composés aldéhyde aromatiques bio-sourcés en de tels précurseurs dialdéhyde aromatiques réactifs. Les précurseurs obtenus ont ensuite été utilisés en synthèses de résines résole sans formaldéhyde et bio-sourcées. Après caractérisation de ces résines, nous avons enfin identifié des précurseurs donnant accès à des résines résole bio-sourcées avec des propriétés de charbonnement supérieures aux résines formophénoliques actuelles. En résumé, ces nouveaux précurseurs aldéhyde bio-sourcés représentent des alternatives prometteuses à l'usage de formaldéhyde pour la synthèse de résines résole avec des propriétés cibles pour des applications dans l'industrie aéropatiale. / Resol-type phenolic resins present applicative and thermal properties suitable for applications such as composite manufacture in aeropatial industry. Especially, resols can be polymerized stage-wise and present after curing high char yield properties. However, those resins are typically synthesized from formaldehyde and phenol. Those precursors are both classified as Carcinogenic Mutagenic Reprotoxic (CMR), respectively 1B and 2, and are petrobased. Because of this classification and of the fossil feedstock depletion, SAFRAN-Herakles wants to substitute formaldehyde by non-toxic and biobased aldehyde precursors. Aromatic aldehyde precursors such as 4-hydroxybenzaldehyde, vanillin and syringaldehyde are interestingly non-toxic and can be produced from the cheap and abundant lignins. Nevertheless, we have shown that those precursors are not reactive in resol synthesis conditions. Also, we have shown that difunctional and reactive aromatic aldehyde precursors are suitable for the synthesis of high char yield resins. Then, we have designed two functionalization methods to turn the biobased aldehyde precursors into difunctional and reactive ones. Finally, those precursors have been used for the synthesis of biobased resols without formaldehyde. Those new resins can be polymerized stage-wise and present higher char yield properties than the current formophenolic resins. Hence, those new biobased aldehyde precursors represent promising alternatives to formaldehyde for the synthesis of resols with target properties for aerospatial industry applications.

Thesis (M.S.)--Mississippi State University. Department of Chemistry. / Title from title screen. Includes bibliographical references.

Les résines phénoliques, sont entre autres utilisées dans l’industrie du bois pour la fabrication de panneaux de particules ou de contreplaqués, après des étapes d'encollage, d'imprégnation et/ou de pressage à chaud. Elles sont principalement obtenues par polymérisation par étapes (polycondensation) à partir de formaldéhyde et de phénol. Ces deux matières premières de base sont actuellement des produits issus de la pétrochimie.Ce travail de thèse Cifre, en partenariat avec la société Rolkem, spécialisée dans la conception et la fabrication de résines phénoliques de type résol, a pour objectif la réduction de l’utilisation de matières pétrochimiques via la substitution du phénol par une bioressource telle que la lignine. Cette dernière a une structure phénolique et une similarité structurelle avec le réseau des résines phénoliques, elle est abondante dans la nature et disponible. Pour atteindre l’industrialisation de ces nouvelles résines biosourcées, une étude sur la compréhension des mécanismes réactionnels qui gouvernent le procédé a été menée avant d’optimiser le protocole permettant l’incorporation de la lignine dans les résines.Il a été possible de remplacer jusqu’à 50%m du phénol par de la lignine organosolve et de réduire la concentration initiale en formaldéhyde. En utilisant une lignine Kraft il a été possible de remplacer jusqu’à 75%m du phénol et de réduire jusqu’à 30%m du formaldéhyde utilisé, par rapport aux résines classiques de référence, tout en respectant le cahier des charges imposé par Rolkem. Ces résultats ont été possibles grâce à des suivis cinétiques des procédés et des études de réactivité de la lignine. Grâce à ces travaux de thèse, le transfert d’échelle des résines biosourcées du laboratoire au pilote industriel a été possible, tout en respectant les contraintes industrielles telles que la productivité, la qualité, la sécurité et l’environnement. De plus, les essais industriels de collage de contreplaqués réalisés sont conformes aux prérequis.En complément des objectifs fixés par le projet, et de manière plus académique, la réactivité de la lignine vis-à-vis du formaldéhyde a été étudiée en chauffage conventionnel et sous irradiation microonde. Cette étude complémentaire permet de corréler la réactivité lignine-formaldéhyde et mode de chauffage et d’atteindre spécifiquement des produits issus de réactions d’addition ou de condensation. / Phenolic resins, may be used in the wood industry for the manufacture of particle boards or plywood, after gluing, impregnation and/or hot-pressing steps. They are mainly obtained by step polymerization (polycondensation) from formaldehyde and phenol. These two raw materials are currently petrochemicals.This thesis work, supported by Rolkem, a company specialized in the design and manufacture of resol type phenolic resins, aims to reduce the use of non-biobased materials by replacing phenol with lignin exhibiting a phenolic structure and a structural similarity with the network of phenolic resins. Lignin is abundant in the environment and easily available. To achieve the industrialization of these new biobased resins, a study on the understanding of the reaction mechanisms has been carried out to favor the incorporation of lignin within the resins. It has been possible to replace up to 50wt.% of the phenol with organosolve lignin and to reduce the initial concentration of formaldehyde at the same time. 75wt.% substitution has been achieved using a Kraft lignin by reducing up to 30wt.% of the formaldehyde concentration as compared to conventional resins. The new biobased resins respect the Rolkem specifications. Thanks to this work results, the scale transfer of biobased resins from the laboratory scale to the industrial pilot was possible, while respecting industrial constraints such as productivity, quality, safety and environment. In addition, the industrial plywood bonding tests were in accordance with the prerequisite.In addition to the above objectives the reactivity of BiolignineTM with formaldehyde has been studied under conventional heating and microwave irradiation. This complementary study allows the correlation of the lignine-formaldehyde reactivity and the heating modes to specifically reach products resulting from addition or condensation reactions.

L’extraction d’éléments d’intérêt (terres rares, métaux lourds, métaux de transition, radionucléides) de de minerais conventionnels ou non conventionnels (mines urbaines) et d’effluents industriel ou nucléaire est un enjeu majeure dans les procédés d’extraction, de recyclage et/ou de décontamination.Un grand nombre de solides organiques et inorganiques, chélatants ou échangeurs d’ions, ont été développés pour un tri ionique sélectif par procédé solide/liquide.L’introduction covalente de ligands spécifiques dans le squelette de la résine permet d’augmenter la sélectivité vis-à-vis d’une cible métallique par la nature des agents de complexation, leurs sites de chélation et leur rigidité.L’objectif de cette thèse recouvre d’une part la synthèse de systèmes chélatant réactifs, leur polymérisation pour la préparation des résines « super »chélatantes et d’autre part, l’évaluation des polymères pour l’extraction/séparation d’ions, les terres rares étant plus particulièrement ciblées.A partir de résines formo-phénolique incorporant du catéchol et la 8-hydroxyquinoléine qui sont des précurseurs phénoliques, nous avons pu montrer que la récupération sélective du germanium été possible vis-à-vis du silicium ou du zinc en fonction de leur proportion dans la matrice polymérique.La synthèse des précurseurs phénoliques intégrant des ligands comme l’acide diglycolamique et les diglycolamides a permis la mise en œuvre de résine pour la récupération des terres rares. Une étude sur la compréhension de la synthèse des résines ainsi que leurs performances d’extraction a ainsi été réalisée et a pu mettre en évidence le potentiel de ces résines pour la récupération et valorisation des terres rares.Une ouverture vers d’autres possibilités de synthèses de ce type de résines (matériaux poreux, sous forme de mousse…) est également proposée pour permettre d’augmenter les surfaces de contacts lors des extractions solide-liquide et ainsi augmenter les performances de ces matériaux. / Extraction of specific targeted species (rare earth, heavy metals, transition metals, radionuclides) from industrial (mining deposit and urban mining) and nuclear effluents is an important issue in the recycling and / or decontamination processes. A large number of organic and inorganic solids, chelating or ion-exchanging materials, have been developed for selective ionic separation by solid / liquid process. Metal-specific ligands incorporate in the structure of the resin itself is an interesting way to perform ion separation taking the advantage of the selectivity of chelating agents. The aims of this project are firstly the synthesis of chelating original systems and then prepare specific ion exchange resins.From formo-phenolic resins incorporating catechol and 8-hydroxyquinoline, we have been able to show that the selective recovery of germanium from silicon or zinc was possible, , depending on their proportion of each phenolic precursors in the polymeric matrix.The synthesis of the phenolic precursors integrating ligands such as diglycolamic acid and diglycolamides allowed the use of resin for the recovery of rare earths elemnets. A study on the understanding of the synthesis of resins as well as their performance of extraction was thus realized and was able to highlight the potential of these resins for the recovery and valorization of the rare earths elements.An opening towards other possibilities of synthesis of this type of resins (porous materials, in the form of foam, etc.) is also proposed in order to increase the contact surfaces during solid-liquid extractions and thus increase the performance of these materials.

No presente trabalho, tanino (macromolécula de origem natural) foi utilizado como substituinte de fenol na formulação de matriz fenólica usada na preparação de compósitos, o que é possível devido à presença de anéis fenólicos sua estrutura. Os compósitos de matriz taninofenólica (50% em massa de tanino) apresentaram propriedades mecânicas superiores aquelas dos compósitos de matriz fenólica, quando reforçados pelo mesmo tipo de fibra, mostrando que a substituição de material obtido em larga escala a partir de fonte fóssil (fenol) é viável e pode ser feita por material obtido de fonte renovável (tanino) sem comprometimento de propriedades. Ainda, avaliou-se para propriedades de compósitos com diferentes tipos de reforços (fibras e cargas) através de caracterizações via análise térmica (TG e DSC), análise dinâmico-mecânica, espectroscopia na região do infravermelho, resistência ao impacto, absorção de água e microscopia eletrônica de varredura. Os ensaios de resistência ao impacto indicaram uma melhora de propriedades mecânicas quando da incorporação de fibras vegetais (juta e coco) nos termorrígidos fenólico e taninofenólico, além de mostrar que as fibras de juta reforçam as matrizes taninofenólicas mais eficientemente que as fibras de coco. As cascas da árvore de Acácia Negra, ricas em taninos, também foram utilizadas como agentes de reforço em compósitos na forma de fibras e cargas, obtidos através de desfibramento e pulverização, respectivamente. A utilização destes reforços, em diferentes proporções de massa, em compósitos de matriz taninofenólica (50% de tanino) levou a diferenças nas propriedades do compósito, com destaque para baixa absorção de água. Provavelmente, a presença de taninos no reforço e na matriz levou a intensas interações na interface fibra/matriz, diminuindo o número de vazios que podem alojar moléculas de água. As fibras de coco foram tratadas por ultra-som, a fim de avaliar a influência deste tratamento nas propriedades da fibra e dos compósitos reforçados por elas. As fibras de coco tratadas e não-tratadas foram caracterizadas quanto à composição química, índice de cristalinidade, ensaio de tração e microscopia eletrônica de varredura. Os resultados obtidos mostraram que o ultra-som é um tratamento promissor, pois modifica a morfologia da superfície das fibras sem levar à degradação química, sendo que a separação dos feixes de fibra que ocorre permite melhor interação fibra/matriz na interface, obtendo-se assim compósitos mais resistentes à água. Outros tratamentos utilizados em trabalhos anteriores a este, como mercerização, diminuem absorção de água dos compósitos por ela reforçados, ao custo de parcial degradação das fibras lignocelulósicas. No presente trabalho, materiais preparados a partir de matéria-prima oriunda de fontes renováveis foram processados, o que vem de encontro aos anseios atuais. Os compósitos obtidos têm potencial para aplicações não estruturais, por exemplo, em partes internas de veículos automotivos. / In the present work, tannin (macromolecule obtained from natural source) was used as substitute of phenol in the formulation of phenolic matrix composites, due to the presence of phenolic rings in its structure. The tanninphenolic matrix composites (50% w/w of tannin) presented mechanical properties better than those of phenolic matrix composites showing that substitution of material obtained in large scale from non-renewable source (phenol) can be done by material obtained from natural source (tannin) without compromising the properties of the composite. The tanninphenolic matrix composites reinforced by different reinforcing agents (fibers and particules) were characterized by different techniques: Izod impact strength, thermogravimetry (TG), differential scanning calorymetry (DSC), infrared spectroscopy (IV), dynamic-mechanical analysis (DMA) and scanning electron microscopy (SEM). The Izod impact strength showed an improvement of mechanical properties due to the incorporation of natural fibres (jute and coir) in the phenolic and tanninphenolic matrices and also the better reinforcement of these matrices by jute fibres, when compared to coir fibres. The barks of Acacia Mimosa (high content of tannin) were also used as reinforcing agents of the tanninphenolic matrices in the forms of fibres and particules. The presence of these reinforcing agents in the matrix led to differences in the properties of the composites, highlighted by its lower water uptake. The presence of tannins in both reinforcing agents and matrix enhanced the fiber/matrix interactions, lowering the voids that increase water uptake. The coir fibres were treated by ultrasound, in order to evaluate the influence of this treatment in the properties of the fibres and, therefore, the composites reinforced with them. Besides chemical composition, all the fibres were characterized by the following techniques: X-ray diffraction, tensile strengh, infrared spectroscopy (IV), and scanning electron microscopy (SEM). The results revealed that the ultrasound is a promising treatment of fibres for the processing of composites, because it modifies the morphology of the surface of fibres without leading them to chemical degradation. The separation of fiber beams allows enhancement of the fiber/matrix interactions, leading to composites with lower water absorption capacity. Other treatments, such as mercerization, for example, improved the impregnation of the fibres by the pre-polymer, leading to composites with better properties, at expenses of partial degradation of lignocellullosic fibres. In the present work, composites were prepared using material obtained from renewable source, according to the purpose of this work. The obtained composites presents potential for non-structural applications, such as, internal panels of cars, for example.

No presente trabalho, tanino (macromolécula de origem natural) foi utilizado como substituinte de fenol na formulação de matriz fenólica usada na preparação de compósitos, o que é possível devido à presença de anéis fenólicos sua estrutura. Os compósitos de matriz taninofenólica (50% em massa de tanino) apresentaram propriedades mecânicas superiores aquelas dos compósitos de matriz fenólica, quando reforçados pelo mesmo tipo de fibra, mostrando que a substituição de material obtido em larga escala a partir de fonte fóssil (fenol) é viável e pode ser feita por material obtido de fonte renovável (tanino) sem comprometimento de propriedades. Ainda, avaliou-se para propriedades de compósitos com diferentes tipos de reforços (fibras e cargas) através de caracterizações via análise térmica (TG e DSC), análise dinâmico-mecânica, espectroscopia na região do infravermelho, resistência ao impacto, absorção de água e microscopia eletrônica de varredura. Os ensaios de resistência ao impacto indicaram uma melhora de propriedades mecânicas quando da incorporação de fibras vegetais (juta e coco) nos termorrígidos fenólico e taninofenólico, além de mostrar que as fibras de juta reforçam as matrizes taninofenólicas mais eficientemente que as fibras de coco. As cascas da árvore de Acácia Negra, ricas em taninos, também foram utilizadas como agentes de reforço em compósitos na forma de fibras e cargas, obtidos através de desfibramento e pulverização, respectivamente. A utilização destes reforços, em diferentes proporções de massa, em compósitos de matriz taninofenólica (50% de tanino) levou a diferenças nas propriedades do compósito, com destaque para baixa absorção de água. Provavelmente, a presença de taninos no reforço e na matriz levou a intensas interações na interface fibra/matriz, diminuindo o número de vazios que podem alojar moléculas de água. As fibras de coco foram tratadas por ultra-som, a fim de avaliar a influência deste tratamento nas propriedades da fibra e dos compósitos reforçados por elas. As fibras de coco tratadas e não-tratadas foram caracterizadas quanto à composição química, índice de cristalinidade, ensaio de tração e microscopia eletrônica de varredura. Os resultados obtidos mostraram que o ultra-som é um tratamento promissor, pois modifica a morfologia da superfície das fibras sem levar à degradação química, sendo que a separação dos feixes de fibra que ocorre permite melhor interação fibra/matriz na interface, obtendo-se assim compósitos mais resistentes à água. Outros tratamentos utilizados em trabalhos anteriores a este, como mercerização, diminuem absorção de água dos compósitos por ela reforçados, ao custo de parcial degradação das fibras lignocelulósicas. No presente trabalho, materiais preparados a partir de matéria-prima oriunda de fontes renováveis foram processados, o que vem de encontro aos anseios atuais. Os compósitos obtidos têm potencial para aplicações não estruturais, por exemplo, em partes internas de veículos automotivos. / In the present work, tannin (macromolecule obtained from natural source) was used as substitute of phenol in the formulation of phenolic matrix composites, due to the presence of phenolic rings in its structure. The tanninphenolic matrix composites (50% w/w of tannin) presented mechanical properties better than those of phenolic matrix composites showing that substitution of material obtained in large scale from non-renewable source (phenol) can be done by material obtained from natural source (tannin) without compromising the properties of the composite. The tanninphenolic matrix composites reinforced by different reinforcing agents (fibers and particules) were characterized by different techniques: Izod impact strength, thermogravimetry (TG), differential scanning calorymetry (DSC), infrared spectroscopy (IV), dynamic-mechanical analysis (DMA) and scanning electron microscopy (SEM). The Izod impact strength showed an improvement of mechanical properties due to the incorporation of natural fibres (jute and coir) in the phenolic and tanninphenolic matrices and also the better reinforcement of these matrices by jute fibres, when compared to coir fibres. The barks of Acacia Mimosa (high content of tannin) were also used as reinforcing agents of the tanninphenolic matrices in the forms of fibres and particules. The presence of these reinforcing agents in the matrix led to differences in the properties of the composites, highlighted by its lower water uptake. The presence of tannins in both reinforcing agents and matrix enhanced the fiber/matrix interactions, lowering the voids that increase water uptake. The coir fibres were treated by ultrasound, in order to evaluate the influence of this treatment in the properties of the fibres and, therefore, the composites reinforced with them. Besides chemical composition, all the fibres were characterized by the following techniques: X-ray diffraction, tensile strengh, infrared spectroscopy (IV), and scanning electron microscopy (SEM). The results revealed that the ultrasound is a promising treatment of fibres for the processing of composites, because it modifies the morphology of the surface of fibres without leading them to chemical degradation. The separation of fiber beams allows enhancement of the fiber/matrix interactions, leading to composites with lower water absorption capacity. Other treatments, such as mercerization, for example, improved the impregnation of the fibres by the pre-polymer, leading to composites with better properties, at expenses of partial degradation of lignocellullosic fibres. In the present work, composites were prepared using material obtained from renewable source, according to the purpose of this work. The obtained composites presents potential for non-structural applications, such as, internal panels of cars, for example.