Les balles de céréales, à savoir l'enveloppe autour du grain, ont récemment retenu l'attention des scientifiques afin d'entrer dans la formulation de biocomposites. En effet, ces sous-produits de l'agriculture ont un coût négligeable, sont perpétuellement renouvelables et disponibles en volume important dans le Monde et leur fin de vie est assurée par leur biodégradabilité. Leurs compositions chimiques et leurs propriétés thermiques et mécaniques sont similaires à celles des fibres naturelles.Dans cette thèse, deux types de balles de riz et deux types de balles de Petit Epeautre ont été étudiées à travers leur microstructure, leur composition chimique, leurs propriétés mécaniques et thermiques. Les balles ont été incorporées dans une matrice bio-sourcée et biodégradable, à savoir le poly(acide lactique) (PLA) pour donner des biocomposites dont les propriétés d'usage ont été étudiées. Il apparaît que les balles céréalières peuvent devenir un candidat potentiel intéressant pour le renforcement du PLA moyennant une amélioration de l'adhésion à l'interface entre les balles et le PLA.Afin d'améliorer cette interface, les balles ont été traitées par une solution alcaline (NaOH) et par des agents de couplage de type organosilane (3-aminopropyltriéthoxysilane et 3- glycidoxypropyltrimethoxysilane). Le traitement alcalin a permis de retirer une grande partie des hémicelluloses, de la lignine, de la cire et de la silice présentes dans les balles. La dissolution de ces constituants a provoqué une plus forte hygroscopicité des balles et se traduit par de plus faibles propriétés mécaniques des biocomposites. Le couplage traitement alcalin/traitement silane semble apporter une amélioration des performances plus importantes que le traitement silane seul. Ce traitement de surface a davantage d'impact sur la balle de Petit Epeautre que sur la balle de riz.L'évolution des propriétés d'usage des biocomposites à base de balles de riz au cours de différents vieillissements (thermique, hydro-thermique, cyclages hygro-thermiques, UV) a été étudiée. Les résultats montrent que l'évolution microstructurale induite par les vieillissements influence significativement les propriétés des biocomposites. La dégradation des biocomposites se traduit par une diminution de la masse moléculaire moyenne du PLA. La réorganisation de ces macromolécules augmente sensiblement le taux de cristallinité du matériau. Ceci induit un changement de la couleur, de la stabilité dimensionnelle des pièces et des propriétés mécaniques du PLA et des biocomposites qui dépend essentiellement de la température de vieillissement par rapport à la température de transition vitreuse du PLA. Il apparaît que l'ajout de balles accélère la dégradation du PLA. Dans le cas d'un vieillissement hydro-thermique au-dessus de la température de transition vitreuse du PLA, une réduction de cette dégradation a été mise en évidence par l'utilisation de certains traitements de surface des balles. / The cereal husks, namely the envelope around the grain, have recently attracted the attention of scientists for biocomposites development, because they are low-cost, renewable, biodegradable, and available in abundant volume throughout the world. Their chemical composition and their thermal and mechanical properties are similar to the natural fibers.In this work, two types of rice husk and two types of Einkorn wheat husk were studied through their microstructure, chemical composition, mechanical and thermal properties. The husks have been incorporated into a bio-sourced and biodegradable matrix, namely poly (lactic acid) (PLA) to produce biocomposite which functional properties were studied. It appears that the husks can be good candidates for strengthening the PLA through improved adhesion at the interface between the husks and the PLA.To improve the husks/PLA interface, the husks were treated with an alkaline solution (NaOH) and organosilane coupling agents, such as 3-aminopropyltriethoxysilane and 3 - glycidoxypropyltrimethoxysilane. The alkaline treatment has removed much of hemicelluloses, lignin, wax and silica present in the husks. The dissolution of these components resulted in a higher hygroscopicity of husks and lower mechanical properties of biocomposites. The coupling between an alkaline treatment and a silane treatment seems to provide better properties than the silane treatment alone. This surface treatment has a greater impact on the Einkorn wheat husks than on rice husksThe variations of the functional properties of rice husks based biocomposites during different ageings (thermal ageing, hydro-thermal ageing, hygro-thermal cycled ageing, UV ageing) was studied. The results show that the microstructural changes induced by ageing significantly influence the properties of biocomposites. Biocomposites degradation results in a decrease of the average molecular weight of PLA. The reorganization of these macromolecules significantly increases the degree of crystallinity of the material. This causes a change in color, dimensional stability of devices and mechanical properties of PLA and biocomposites which essentially depends on the ageing temperature regards to the glass transition temperature of PLA. It appears that the addition of husks accelerates the degradation of PLA. In the case of a hydro-thermal ageing performed above the glass transition temperature of the PLA, a reduction of this degradation was demonstrated by the use of specific surface treatments of husks.

Approved for public release, distribution is unlimited / The extreme strain, strain rate and temperature gradients during Friction Stir Processing (FSP) render measurement of key parameters in the stir zone infeasible with common methods. The objective of this research was to separate the effects that temperature and deformation in an experimental study of the microstructure and mechanical properties of Ni-AL bronze (NAB). This was accomplished by subjecting as-cast NAB material to several isothermal annealing and quenching treatments as well as isothermal hot rolling processes. Sufficient material was generated to provide results and data for subsequent optical microscopy, tensile, & hardness tests. All results were then compared to similar data collected from previous works completed here at Naval Postgraduate School and with other DARPA FSP program participants. During the course of this work correlations were drawn between FSP material and the material subjected to isothermal hotworking, which may enhance our understanding of the roles that various FSP process parameters have on the microstructural transformation sequence within this material. The hot-rolling study conducted here suggests that FSP process parameters leading to severe deformation at temperatures between 950-1000 C in the NAB material provides high ductility (elongation approximately 28%) with moderate strengths. / Lieutenant, United States Coast Guard

O edentulismo acomete grande parcela da população mundial, especialmente os idosos, gerando perda da função mastigatória, desordens nutricionais, estética desfavorável e redução da qualidade de vida. Como alternativa a esses problemas, as overdentures implanto retidas tem representado uma modalidade de tratamento eficiente para reabilitação da mandíbula. Assim, o presente estudo teve por objetivo desenvolver e avaliar a efetividade de dois modelos de mini-implantes dentários e um componente protético, cápsula de retenção para overdentures mini-implante retidas. Para tal, um total de 30 mini-implantes (n=10) foram utilizados: modelo comercial Intra-Lock® System, experimental rosqueado e experimental helicoidal. Ambos os mini-implantes desenvolvidos no estudo foram confeccionados em titânio Grau IV, nas dimensões de Ø 2,0 mm x 10 mm de comprimento e submetidos a tratamento de superfície nanométrico. O desempenho dos mesmos foi comparado ao modelo comercial selecionado quanto à estabilidade primária, por meio de torque de inserção e ensaio de arrancamento e à distribuição de tensões, através dos métodos fotoelástico e de correlação de imagens digitais (CID). Foram realizados carregamentos puntiformes axiais e oblíquos (inclinação de 30º do modelo), com cargas de 100 N para a fotoelasticidade e de 250 N axial e 100 N oblíquo para a CID. Para análise do componente protético foi utilizado o teste de resistência à fadiga. 60 cápsulas (n=20): Poliacetal, Politetrafluoretileno (PTFE) e o-ring convencional (Intra-Lock®) foram capturadas aos pares, com resina acrílica e submetidas a 3625 ciclos de inserção/remoção, simulando 30 meses de uso da overdenture. A deformação interna e externa dos componentes foi avaliada por meio de Estereomicroscópio Óptico. Os dados obtidos foram submetidos a ANOVA e teste de Tukey (&alpha;=0,05). O torque de inserção (TI) e ensaio de arrancamento apresentaram significância estatística para todos os modelos (p<0,05), sendo o TI maior para o mini-implante rosqueado e a força máxima de arrancamento para o modelo Intra-Lock®. Quanto à análise de tensões por meio da fotoelasticidade verificou-se de maneira geral, maiores tensões no terço médio e apical dos mini-implantes. O mesmo padrão foi observado para a CID, porém, neste caso, com tensões significativamente maiores (p<0,05) para os mini-implantes rosqueados na condição de carregamento axial, para o oblíquo não foram encontradas diferenças significativas (p>0,05). Quanto à análise dos componentes protéticos, a cápsula de poliacetal apresentou a maior retenção (p<0,05), seguida do o-ring e PTFE. Menor deformação foi observada para o o-ring (p<0,05) e maior deformação interna (p<0,05), após a realização da fadiga, para o poliacetal. O mini-implante rosqueado apresentou de modo geral estabilidade primária e distribuição de tensões comparável ao modelo comercial avaliado. O componente protético de poliacetal demonstrou superioridade em relação ao o-ring da Intra-Lock® quanto à força de retenção e apesar da maior deformação interna sofrida, sugere-se sua substituição após no mínimo 30 meses de uso da overdenture / Edentulism affects a large part of the world population, especially the elderly, generating loss of masticatory function, nutritional disorders, unfavorable esthetics and reduction of quality of life. As an alternative to these problems, overdentures implant retained have represented an efficient treatment modality for mandibular rehabilitation. Thus, the present study aimed to develop and evaluate the effectiveness of two models of dental mini-implants and a prosthetic component, retention caps for overdentures mini-implant retained. To do this, a total of 30 mini-implants (n=10) were used: Intra-Lock® System commercial model, experimental threaded and experimental helical. Both mini-implants developed in the study were made in Titanium Grade IV, in the dimensions of Ø 2.0 mm x 10 mm in length and submitted to a nanometric surface treatment. Their performance were compared to the commercial model selected for primary stability by means of insertion torque and pullout test and stress distribution using photoelastic and digital image correlation (DIC) methods. Axial and oblique punctiform loads (30º inclination of the model) were performed, with loads of 100 N for photoelasticity and 250 N axial and 100 N oblique for DIC. For the analysis of the prosthetic component, the fatigue strength test was used. 60 capsules (n=20): Polyacetal, Polytetrafluoroethylene (PTFE) and conventional O-ring (Intra-Lock®) were captured in pairs with acrylic resin and subjected to 3625 insertion/removal cycles, simulating 30 months of overdenture use. The internal and external deformation of the components was evaluated using an Optical Stereomicroscope. Data were submitted to ANOVA and Tukey\'s test (&alpha;=0.05). The insertion torque (IT) and pullout test were statistically significant for all models (p<0.05), with IT being highest for the threaded mini-implant and maximum pulling force for the Intra-Lock® model. As for stress analysis by photoelasticity, it was generally observed that there were higher tensions in the middle and apical third of the mini-implants. The same pattern was observed for the DIC, but in this case, with significantly higher stresses (p<0.05) for the mini-implants threaded in the axial loading condition, no significant differences were found for the oblique (p>0.05). As for the analysis of prosthetic components, the polyacetal caps presented the highest retention (p<0.05), followed by o-ring and PTFE. Lower deformation was observed for o-ring (p<0.05) and greater internal deformation (p<0.05), after fatigue, for polyacetal. The threaded mini-implant generally showed primary stability and strain distribution comparable to the commercial model evaluated. The polyacetal prosthetic component showed superiority over the Intra-Lock® o-ring for the retention force and despite the greater internal deformation suffered, it is suggested to replace it after at least 30 months of overdenture use

O estudo avaliou a efetividade de tratamentos de superfície na modificação superficial e adesão da zircônia ao cimento resinoso; a estabilidade de união após ciclagem termomecânica entre coroas metal free com copings em zircônia ou coroas monolíticas em zircônia e pilares personalizados do mesmo material, submetidos a tratamento superficial, e a influência destes na sobrevida dos sistemas protéticos após fadiga termomecânica acelerada. A pesquisa foi desenvolvida em 2 etapas. Na primeira, discos de zircônia foram distribuídos em sete grupos (n=6): G1 (Rocatec); G2 (ácido hidrofluorídrico 40%, 210 segundos); G3 (ácido hidrofluorídrico 40%, 210 segundos + Rocatec); G4 (nanopartícula ZrO2); G5 (nanopartícula SiO2); G6 (nanopartícula SiO2ZrO2); G7 (nanopartícula SiO2ZrO2 + silano). Uma amostra por grupo (n=1) foi analisada por espectroscopia infravermelho (FTIR), difração de raios-x (DRX) e microscopia eletrônica de varredura (MEV). As demais, submetidas a microscopia confocal a laser (n=5) para determinação da rugosidade superficial (Ra) e teste de cisalhamento. Molhabilidade e energia de superfície foram desenvolvidas em triplicata (n=3). G1, G3, G5 e G7 apresentaram valores de resistência ao cisalhamento superiores aos demais. Os melhores resultados definiram os tratamentos da etapa seguinte. Na segunda etapa, 162 análogos de implante conexão tipo Morse foram utilizados. Sobre eles, instaladas bases de titânio conectando pilar de zircônia ao análogo. Os 162 pilares foram distribuídos em 2 grupos de acordo com o ensaio: ciclagem termomecânica ou fadiga termomecânica acelerada. Para cada ensaio, duas modalidades restauradoras foram planejadas (Mono - coroa monolítica em zircônia, Pren - coping em zircônia + cobertura de vitrocerâmica fluorapatita). Pilares foram distribuídos a depender do tratamento recebido: MonoRo (Rocatec), MonoSi (nanopartícula SiO2), MonoSiZr (nanopartícula SiO2ZrO2 + silano). Grupo Pren recebeu os mesmos tratamentos. Sobre pilares, foram cimentadas coroas. Coroas monolíticas, copings e pilares foram obtidos via CAD/CAM. A adesão foi quantificada por teste de resistência à tração após ciclagem termomecânica (n=9) (2x106 ciclos, 2Hz, 120N e ciclos térmicos de 5º-55ºC). Valores de resistência à tração e padrões de falha obtidos foram registrados. Não foram encontradas diferenças significantes entre grupos para resistência à tração, mas o comportamento médio da força foi diferente nos grupos dependendo da falha. Sobrevida dos conjuntos foi analisada após fadiga termomecânica acelerada (n=18) (cargas progressivas a cada 2x104 ciclos de 80, 120, 160, 200, 240, 280 e 320N em 5Hz até 14x104 ou a falha, com ciclos térmicos de 5º- 55ºC). Resistência à fadiga foi comparada pela probabilidade de sobrevivência em cada intervalo. Padrões de falha foram classificados em ambos testes e amostras representativas de cada falha analisadas em MEV. MonoRo e MonoSiZr são semelhantes e têm maior probabilidade de sobrevivência que os demais. Pertencer a PrenSiZr, MonoSi, PrenRo ou PrenSi diminui a probabilidade de sobrevivência. / The study evaluated the effectiveness of surface treatments in surface modification and zirconia adhesion to resin cement; the bonding stability after thermomechanical cycling between free metal crowns with zirconia copings or monolithic zirconia crowns and customized abutments of the same material, subjected to surface treatments, and their influence in the survival of prosthetic systems after accelerated thermomechanical fatigue. The research was developed in 2 stages. In the first, zirconia discs were distributed in seven groups (n = 6): G1 (Rocatec); G2 (hydrofluoric acid 40%, 210 seconds); G3 (hydrofluoric acid 40%, 210 seconds + Rocatec); G4 (nanoparticle ZrO2); G5 (SiO2 nanoparticle); G6 (SiO2ZrO2 nanoparticle); G7 (SiO2ZrO2 nanoparticle + silane). One sample per group (n = 1) was analyzed by infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The others were submitted to laser confocal microscopy (n = 5) for determination of surface roughness (Ra) and shear test. Wettability and surface energy were developed in triplicate (n = 3). G1, G3, G5 and G7 presented higher values of shear strength than the others. The best results defined the treatments of the next stage. In the second stage, 162 Morse type implant analogues were used. On them, installed a titanium base, connecting zirconia abutment to analog. The 162 abutments were distributed in 2 groups according to the test: thermomechanical cycling or accelerated thermomechanical fatigue. For each test, two restorative modalities were planned (Mono - monolithic zirconia, Pren - zirconia coping + vitroceramic fluorapatite revestment). Abutments were distributed depending on the treatment received: MonoRo (Rocatec), MonoSi (nanoparticle SiO2), MonoSiZr (nanoparticle SiO2ZrO2 + silane). The Pren Group received the same treatments. Crowns were cemented on abutments. Monolithic crowns, copings and abutments were obtained by CAD/CAM. The adhesion was quantified by tensile strength test after thermomechanical cycling (n = 9) (2x106 cycles, 2Hz, 120N and thermal cycles of 5º-55ºC). Values of tensile strength and obtained failure patterns were recorded. No significant differences were found between groups for tensile strength, but mean force behavior was different in groups depending on failure. The survival of the sets was analyzed after accelerated thermomechanical fatigue (n = 18) (progressive loads every 2x104 cycles of 80, 120, 160, 200, 240, 280 and 320N in 5Hz up to 14x104 or failure, with thermal cycles of 5º- 55ºC). Fatigue resistance was compared by the probability of survival at each interval. Failure patterns were classified in both tests and representative samples of each failure analyzed in SEM. MonoRo and MonoSiZr are similar and more likely to survive than the others. Belonging to PrenSiZr, MonoSi, PrenRo or PrenSi reduces the probability of survival.

O propósito deste estudo foi avaliar a resistência adesiva ao cisalhamento de um cimento resinoso à alumina densamente sinterizada testando o tratamento superficial feito pelo fabricante. O cimento utilizado foi o Multilink (Ivoclar Vivadent) e a alumina foi a Procera®Alumina (Nobel Biocare) constituída por 99,9 % de óxido de alumínio densamente sinterizado. Trinta e dois cilindros de alumina foram confeccionados pela Nobel Biocare, onde um dos extremos deste cilindro recebeu o tratamento superficial e o outro não. Para a aplicação do cimento resinoso sobre os cilindros de alumina, utilizou-se uma matriz de Teflon com um orifício central de 3,5mm de diâmetro por 3,0mm de profundidade. Foram determinados 4 grupos experimentais: Grupo 1 superfície sem tratamento; Grupo 2 superfície sem tratamento e com aplicação de adesivo; Grupo 3 - superfície com o tratamento realizado pelo fabricante; Grupo 4 superfície com tratamento realizado pelo fabricante e com adesivo. Após a aplicação do cimento nos 4 grupos, os espécimes foram armazenados em água deionizada a 37ºC durante 24h, sendo, em seguida, montados em uma máquina universal de ensaios para realização dos testes de resistência ao cisalhamento. Os resultados foram submetidos à análise de variância a dois critérios e ao teste de Tukey para comparação entre os grupos. A superfície tratada (grupo 3) apresentou valores significativamente maiores que todos os outros grupos. A presença do adesivo diminuiu a resistência adesiva quando aplicado na superfície tratada, mas não deu diferença significante quando aplicado na superfície sem tratamento. / The aim of this study was to investigate the shear bond strength between a resin cement and densely sintered alumina treated by the fabricant. The resin cement used was the Multilink (Ivoclar Vivadent) and the alumina the Procera®Alumina (Nobel Biocare) made with 99,9% of densely sintered aluminum oxide. Thirty two alumina cylinders were made by Nobel Biocare, and in one of the extremes was applied a own`s fabricant surface treatment. For the application of the cement, a Teflon matrix with a central hole (diameter of 3,5 mm and a height of 3,0 mm) was used. Four groups were created: Group 1 surface without treatment; Group 2 - surface without treatment and with adhesive; Group 3 surface with the own`s fabricant treatment; Group 4 - surface with the own`s fabricant treatment with adhesive. After the cement application, the specimens were stored in water at 37º C for 24 hours. Then the samples were placed in a universal testing machine for making the shear strength test. Statistical analysis was performed with two-way analysis of variance (ANOVA), and paired comparisons between groups were done with Tukey`s multiple comparison. Higher significant values were detected for Group 3 when compared with all the other groups. The adhesive decreased the shear bond strength when laid on the treated surface, and there were no difference when laid on the untreated surface.

Os aços de alta resistência e baixa liga (ARBL) utilizados em tubos para linhas de transmissão, ou seja, transferência e transporte de petróleo e gás, são especificados pela American Petroleum Institute (API) através da norma API 5L. Neste trabalho foi realizado um estudo da influência da têmpera e da nitretação no comportamento mecânico do aço API 5L X56. A microestrutura, os compostos formados com a nitretação e os mecanismos de fratura foram analisadas usando microscopia óptica, difração de raios X e microscopia eletrônica de varredura respectivamente. As amostras foram caracterizadas mecanicamente por testes de microdureza, tração, impacto e fadiga. Os resultados revelaram que apenas a têmpera promoveu modificações severas na microestrutura em relação à como recebida, formando bainita, martensita e constituinte M-A. A camada nitretada apresentou profundidade de 25 ?m e formação dos nitretos Fe3N e Fe4N. Houve aumento da microdureza, resistência mecânica com os tratamentos, juntamente com a diminuição da tenacidade e também houve um melhoramento na vida em fadiga para as duas amostras tratadas termicamente e superficialmente. Os mecanismos de fratura variaram de dúctil à frágil e em fadiga foi observado que as trincas nuclearam a partir da superfície para todas as amostras. / The high strength and low alloy steel (HSLA) used in pipeline for line transmission, there is transference and transportation of oil and gas, they are specified by American Petroleum Institute (API) through norm API 5L. In this work it was conducted a study of the nitriding and quenching influence on the mechanical behavior of API 5L X56. The microstructure, compounds made with the nitriding and the mechanisms failure were analyzed using optical microscopy, X-ray diffraction and scanning electron microscopy respectively. The samples were mechanical characterized by microhardness, tensile, impact and fatigue test. The results revealed that only quenching treatment promoted severe modifications in microstructure in relation to as received, making up bainite, martensite and M-A constituent. The nitriding layer showed depth of 25 ?m and formation of Fe3N e Fe4N nitrides. There was an increasing of microhardness and mechanical strength with the treatments, along with the decreasing of toughness and there was also an improvement in fatigue life for the two samples heat e surface treated. The failure mechanisms varied from ductile to brittle and in fatigue was observed that the cracks nuclear from the surface to all samples.

Les matériaux polymères ont connu un essor considérable dans le milieu du bâtiment depuis de nombreuses années, du fait d'un large panel de propriétés. Ces matériaux sont cependant très sensibles à la température et peuvent être facilement inflammables, permettant le développement d'un incendie. Du fait de la mise en place de normes de plus en plus strictes, relatives à la sécurité vis-à-vis d'un feu, il est nécessaire de mettre au point des systèmes retardateurs de flamme de plus en plus performants.Le premier objectif de la thèse est d'étudier les mécanismes retardateurs de flamme de composites EVA/ATH, et en particulier l'effet barrière. La notion de compacité de la couche de particules a pu être mise en évidence via l'essai de compression oedométrique. La mesure de la résistance à la compression d'une poudre, ou d'un mélange, permet d'estimer l'efficacité de l'effet barrière dans le cas de composites EVA/ATH.Le second objectif s'est concentré sur la caractérisation de nouvelles charges pouvant améliorer le comportement au feu de l'EVA. Dans un premier temps, de la diatomite a été introduite, jouant le rôle d'agent de synergie avec l'ATH. Dans un second temps, de la colémanite et des fondants broyés ont été introduits afin d’améliorer la cohésion de la couche barrière et du résidu de combustion par vitrification. La colémanite s’est révélée être un retardateur de flamme efficace, du fait de la libération d’eau de façon endothermique, et d’une vitrification à haute température. Dispersés dans la masse, les fondants perturbent la formation de la couche barrière du fait de la coagulation des particules. En tant que couche supérieure d’un système coeur-peau, le fondant vitrifie lors du refroidissement de l’échantillon, assurant la cohésion du résidu, ainsi qu’un rôle de suppresseur de fumées.Finalement, le dernier objectif de la thèse est de traiter des ATH, afin d’améliorer les propriétés mécaniques et retardatrices de flamme de l’EVA. Des molécules de greffage ont été réalisées à partir de MAPC1. La présence d’un copolymère p(MMA-co-MAPC1(OH)2) à la surface des particules homogénéise la dispersion de l’ATH dans la matrice EVA, améliorant les propriétés d’allongement à la rupture du composite. Un homopolymère p(MAPC1(OH)2) permet également d’améliorer la dispersion et l’allongement à la rupture. De plus, les groupements phosphorés présents le long de la chaîne semblent capables d’agir en phase condensée en tant que promoteur de charbonnement, ainsi qu’en phase gazeuse par le biais de radicaux réactifs. / Polymeric materials are booming for many years in the building industry, due to a wide range of properties. However, those materials are particularly heat sensitive and may be easily flammable, contributing to the development of a fire. Because of the implementation of more strict standards related to fire safety, the elaboration of more and more efficient fire retardant systems is necessary.The first goal of this thesis is to study the fire retardant mechanisms of EVA/ATH composites, and particularly the barrier effect. The role of the packing fraction of the particles layer was assessed used the oedometric compression test. The measurement of the resistance to compression of a powder, or a combination, can be used to estimate the efficiency of the barrier effect for EVA/ATH composites.The second goal has focused on the characterization of new fillers in order to improve the fire behavior of the EVA copolymer. Firstly, diatomite was introduced as a synergistic agent with ATH. In a second time, ground colemanite and glass frits were introduced in order to improve the cohesion of the barrier layer and the residue of combustion by vitrification. Colemanite seems to be an efficient fire retardant, because of the endothermic reaction associated with the release of structural water, and a vitrification at high temperature. When the glass frits are introduced in EVA/ATH composites, the formation of the barrier layer is disrupted because of the coagulation of particles. As an upper layer in a skin-core structure, the glass frit vitrifies during the cooling of the sample, improving the cohesion of the residue and acting as a smoke suppressor.Finally, the last goal of this thesis was to functionalize ATH, to improve mechanical and fire retardant properties of EVA. Surface treatment molecules were synthetized, based on a phosphonated monomer, the MAPC1. The presence of a p(MMA-co-MAPC1(OH)2) copolymer at the surface of particles improves the filler dispersion in the matrix, enhancing the elongation at break. The grafting using a p(MAPC1(OH)2) homopolymer also improves the filler dispersion and the elongation at break. Moreover, the phosphorus based functions along the molecular chain, seem to act in condensed phase as a char promoter, and in gaseous phase by means of reactive radicals.

Made available in DSpace on 2017-07-21T20:42:46Z (GMT). No. of bitstreams: 1 Danielle M Ferreira Madeira.pdf: 2830948 bytes, checksum: b0683133449a7aa9574bf79758c203d4 (MD5) Previous issue date: 2013-02-27 / The objective of this work was to study the surface adhesion of polyethylene on the liquid paper board. By using surface characterization, the chemical and physical interactions between the paper board and polyethylene were studied. Paper board samples were laminated with low density polyethylene with an extruder, in order to evaluate the adhesion forces of the following samples: 1) Paper board coating with different latex composition; 2) paper board bottom layer (brown side) with surface sizing (starch) and, 3) paper board bottom layer (brown side) without surface sizing (starch). It was also evaluated in the extruded samples treated with flame the polyethylene adhesion. The following analyses were used in other to characterize the paper board surface: 1) Contact angle analysis for surface energy determination, 2) Confocal laser scanning microscopy for surface roughness analysis and, 3) FTIR spectroscopy Attenuated Total Reflectance (ATR) to evaluate differences in the functional groups. The characterization results were correlated with the increase of polyethylene adhesion forces on the paper board surface. It was observed that flame treatment on the paper board surface increased the surface tension, thus increasing the adhesion forces of the polyethylene. In comparison to the styrene-butadiene latex, the styrene acrylic latex, which contains polar groups in its composition, improved the adhesion forces of the polyethylene with the paper board top layer (white side). For the paper board bottom layer (brown side) with no surface sizing, the polyethylene adhesion was superior when compared to the sized paper board. It can be explained by the increase on the surface smoothness of the paper which may interfere on the polyethylene adhesion. The flame treatment may have caused the oxidation of functional groups on the surface of the paper board, resulting in the surface tension increase and, consequently, increasing the polyethylene adhesion. The surface tension has shown to be an excellent indicator for polyethylene adhesion due to its linear correlation with polyethylene adhesion forces. On the other hand, it has not been observed difference on surface roughness on the studied samples. The FTIR-ATR technique has not been sensitive for the detection of chemical differences among the samples treated with and without flame. However, this technique can be used to verify the latex composition in the paper board coating. The Peel Test Method (180º) which is used to evaluate the adhesion force, presents more reliable results than the manual delamination test that depends on the analyst. / O objetivo deste trabalho foi estudar a adesão de polietileno à superfície do papel cartão utilizado na produção da embalagem Longa Vida. Através de técnicas de caracterização de superfície foram verificadas as interações químicas e físicas existentes entre o papel cartão e o polietileno. Amostras de papel cartão foram laminadas com polietileno de baixa densidade em uma extrusora para avaliar a força de adesão nas seguintes amostras: 1) “coating” do papel cartão com diferentes látex na composição da tinta de revestimento. 2) base do papel cartão (lado marrom) com colagem superficial com amido. 3) base do papel cartão (lado marrom) sem colagem superficial com amido. Nas amostras extrusadas também foi avaliada a adesão de polietileno quando a superfície do papel cartão foi tratada com chama. Análise do ângulo de contato para obtenção da energia superficial, microscopia confocal a laser, para verificar efeitos na rugosidade superficial, e análise de infravermelho (ATR – reflectância total atenuada), para avaliar diferenças dos grupos funcionais, foram também utilizadas para a caracterização da superfície do papel cartão. O resultado da caracterização foi correlacionado com aumento das forças de adesão de polietileno à superfície do papel cartão. Para os casos estudados, observou-se que o tratamento de superfície feito com chama no papel cartão aumentou a energia superficial, elevando assim a força de adesão ao polietileno. O uso de látex estireno-acrílico, que apresenta grupos polares na composição, também propiciou melhor adesão de polietileno na cobertura (lado branco do papel cartão) comparado ao látex estireno-butadieno. Para a base do papel cartão (lado marrom) sem a colagem superficial, a adesão de polietileno se mostrou superior à condição com colagem, pois esta gera maior nivelamento da superfície, deixando a base do papel cartão mais lisa, dificultando assim a adesão de polietileno. Os tratamentos de superfície com chama podem ter causado a oxidação da superfície do papel cartão, gerando assim um aumento de grupos polares na superfície, aumentando a energia superficial da mesma e, consequentemente, melhorado a adesão de polietileno. A energia superficial pode ser vista como um excelente indicativo para adesão de polietileno, pois se verificou uma correlação linear onde quanto maior a energia superficial do papel cartão, maior a força de adesão ao polietileno. Por outro lado, a rugosidade superficial não mostrou diferenças entre as amostras estudadas. A técnica de infravermelho (ATR) não foi sensível para detectar diferenças químicas entre os tratamentos com e sem chama. No entanto, esta técnica pode ser utilizada para verificar a composição, quanto ao tipo de látex, usado na tinta de revestimento do papel cartão. O método Peel Test em 1800, usado para avaliar a força de adesão, apresenta resultados mais confiáveis do que somente a avaliação através da delaminação manual, que depende muito do analista e sua percepção.

Cette thèse vise à étudier le comportement multiéchelle (nano-, micro- et macroscopique) des composites, basé sur une étude fine utilisant les techniques les plus modernes pour comprendre les interfaces et les quantifier. Deux séries de renforts sur une échelle micrométrique, des fibres de carbone (CF) et des matériaux à base de graphène ont été utilisées ici. Pour améliorer l'interaction entre les nanorenforts et la matrice polymère, deux voies principales ont été utilisées dans cette thèse : l'oxydation des renforts et la greffe de nanotubes de carbone sur leur surface.L'étude en elle-même a été menée à une échelle microscopique pour étudier la résistance interfaciale entre une fibre de carbone (CF) et la matrice époxy, avec des essais de traction effectués in situ dans la chambre d'un microscope à double colonne MEB-FIB (microscope électronique à balayage couplé à un faisceau d'ions focalisé). Le faisceau d'ions a été utilisé pour découper une éprouvette de traction du composite contenant à la fois de l'époxy et de la CF. Le champ de tractiona été appliqué via le nanomanipulateur et l'essai a été observé via les deux colonnes ionique et électronique (sous deux angles de vue différents) et a permis d'estimer le champ de déformation, et donc la résistance interfaciale au moment de la rupture. Une expérience similaire a été menée sur un composite où les renforts sont des nanoplaquettes de graphène.Enfin, l'étude en microscopie électronique en transmission de la région de l'interface entre l'époxy et les renforts a révélé la présence d'une interphase et a permis de mesurer son épaisseur et donner une indication de sa nature. À cette fin, une analyse EELS (spectroscopie par pertes d'énergie des électrons) a été effectuée, permettant de mesurer la densité de l'échantillon très localement (taille de sonde de l'ordre du dixième de nanomètre) en travers ou parallèlement à l'interface. Un scénario sur les modes de liaison chimique entre les deux milieux en fonction du traitement de surface utilisé permet d'expliquer la nature des interphases observées. / This thesis aims to investigate the multiscale (nano-, micro-, and macro-scopic) behavior of the composites based on a fine investigation using the most modern techniques, to understand the interfaces and to quantify them. Two series of reinforcements on a micrometer scale, carbon fibers (CFs) and graphene-based materials, were studied here. To improve the interactions between these nanofillers and the surrounding polymer matrix, two major routes were used in this thesis: the oxidation of the fillers and the grafting of carbon nanotubes on their surface.The study itself was conducted on a microscopic scale on the interfacial strength between CFs and the epoxy matrix, with tensile tests carried out in-situ in the chamber of a double-column FIB-SEM microscope (scanning electron microscope coupled to a focused ion beam). The ion beam was used to mill a thin bond-shaped tensile specimen of composite containing both an epoxy and a CF part. Thetensile stress field was applied using the nanomanipulator and the test was observed both via the ionic and the electronic columns (with two different angles of view) to estimate the strain field, hence the interfacial strength when the failure is observed. A similar experiment was led on a composite with GNPs.Finally, the transmission electron microscopy (TEM) study of the interface region between the epoxy and the graphene-based nanofillers revealed the existence of an interphase and allowed to measure its thickness and give an indication of its nature. For this purpose, an EELS (electron energy-loss spectroscopy) analysis was carried out, making it possible to measure the density of the sample very locally (probe size of the order of a tenth of a nanometer) across or parallelly to an interface. A scenario on the chemical bonding modes between the two media as a function of the surface treatment used makes it possible to explain the nature of the observed interphases.

Les procédés de traitement de surface tels que le grenaillage sont utilisés pour introduire des contraintes résiduelles de compression dans les matériaux métalliques. Cela permet de prévenir l'initiation et la propagation des fissures afin d'augmenter la durée de vie en fatigue des pièces mécaniques. Les limites et inconvénients des procédés actuels généralement utilisés pour cette fin sont connus et ont été mis en avant dans plusieurs études. Il s'agit d'une modification importante de l'état de surface (rugosité), une profondeur traitée limitée, des difficultés de mise en œuvre, etc. Aussi, de nouveaux procédés permettant d'obtenir des résultats équivalents voire meilleurs tout en évitant ces problèmes suscitent un intérêt grandissant. Le traitement de surface par cavitation (cavitation peening) et la mise en compression par impulsions électromagnétiques font partie de ces procédés innovants dont la modélisation a fait l'objet de cette thèse. Le traitement de surface par cavitation consiste à générer un jet d'eau submergé contenant des bulles de cavitation et dirigé vers la surface à traiter. La principale difficulté dans la modélisation du cavitation peening est la détermination du chargement mécanique sur la surface provenant de l'implosion des bulles de cavitation. L'effondrement des bulles peut se faire de manière sphérique ou non-sphérique suivant leur proximité de la paroi solide. Des modèles analytiques et numériques ont donc été élaborés pour étudier la dynamique des bulles et déterminer l'onde de pression due à une bulle sphérique d'une part, et la pression d'impact du micro-jet (bulle asphérique) d'autre part. Ces deux types de sollicitations ont été comparés et un modèle macroscopique pour le traitement par cavitation a été dérivé, en s'appuyant sur une simulation numérique du jet de cavitation. Une comparaison avec des résultats expérimentaux a été effectuée et a montré la pertinence du modèle proposé. En ce qui concerne le traitement par impulsions électromagnétiques, il consiste à générer un puissant champ magnétique transitoire par induction dans la pièce de matériau conducteur. Les contraintes résiduelles proviennent de la déformation plastique créée par les forces de Laplace à l'intérieur du matériau. Un modèle numérique couplant l'électromagnétisme et la mécanique des solides a été mis en place pour la simulation du procédé. Grâce à une étude d'optimisation, ce modèle a permis d'obtenir les paramètres électriques nécessaires pour arriver à mettre en compression des matériaux de type alliage de base nickel ou d'aluminium par cette méthode. Les profondeurs de la mise en compression calculées sont théoriquement par calcul plus élevées que celles obtenues avec les méthodes classiques de traitement de surface. Une étude de l'influence des différents paramètres a été faite et a montré que le procédé peut être contrôlé de manière relativement aisée en variant l'intensité et la pseudo-fréquence du courant traversant l'inducteur. / Surface treatments methods like shot peening are used to introduce compressive residual stresses in metallic materials. The compressive stresses prevent the initiation and growth of cracks and hence improve the fatigue life of mechanical parts. The drawbacks and limitations of the existing processes generally used for this purpose are known and have been highlighted in many studies. These are, among others, an important surface modification (roughness), a limited compressive depth, difficulties in execution, debris and contamination problems, etc. Therefore, the interest in new surface treatment methods, which permit to obtain equivalent or even better compressive results while avoiding the previous problems, are growing. Cavitation peening and electromagnetic pulse peening are part of these innovative processes which modeling is the aim of this PhD thesis. Cavitation peening is a process of surface treatment which acts by the generation of cavitation bubbles near the workpiece surface. The modeling of this process is challenging because of the complexity of cavitation phenomenon and the main problematic point is the determination of the mechanical loading on the material due the bubbles collapse. In this thesis, an approach of modeling for cavitation peening based on the study of the dynamics of cavitation bubbles is proposed. Spherical and aspherical collapse of bubbles near a solid surface are studied by some numerical and analytical models. These two sources of loading pressures have been compared and a macroscopic model for cavitation peening have been derived by associating the numerical simulation of the cavitation jet and the localization of the cavitation zone. The comparison between the final residual stress profile calculated with the proposed model and the experimental results were satisfactory. Electromagnetic pulse peening (EMP) is a contactless process of surface treatment which could be used to introduce compressive residual stresses in conductive materials, by the generation of a high transient electromagnetic field. Laplace forces induced in the material by magnetic induction are the source of the material plastic deformation and compressive residual stresses introduction. To predict the EMP results, a numerical model have been built for the process simulation. The model, based on finite element method, coupled successfully electromagnetic and mechanical phenomena by using a sequential-coupled approach. It was proven theoretically, by the study of a reference case, that compressive residual stresses could be induced in metallic materials like nickel-based (Inconel) or aluminum alloys by the means of the present process. It was also shown by the calculations that much higher compressive depths than those of conventional peening processes could be achieved. The parametric study exhibited the influence of the maximum current intensity and frequency which affect both the compressive depth and the maximum residual stress.