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The adhesion and durability of model epoxy/silane/SiO2/Si bonded systems were investigated under various conditions, including the type of surface preparation, pH of the environmental media, temperature, cyclic thermal stress, and external applied stress. The fundamental debond mechanism was studied for bonded systems exposed to selected environments. The bond failure mode was characterized by examining the failed bond surfaces using X-ray photoelectron spectroscopy. The effectiveness of combining the oxygen plasma treatment and silane coupling agent (SCA) derivatization in adhesion promotion for an epoxy bonded to a silicon surface was evaluated in this research. SCAs with different amine functionalities were studied. The oxygen plasma treatment time was varied systematically to achieve a different extent of oxidation on the Si wafer. The surface chemistry/composition of various silane derivatized Si surfaces was investigated. The studies revealed that SCA interaction with the Si surface was enhanced by the oxygen plasma pre-treatment of the Si substrates. XPS surface analysis results showed that the SCA/SiO2 ratio did not correlate strongly with the increase in oxygen plasma pretreatment time. However, for Si surfaces treated for longer oxygen plasma pretreatment times, more silanol groups may be available to interact with the hydrolyzed silanol groups on silane, resulting in a stronger SCA-Si attachment. Three different tests were employed to determine adhesion and durability of the model epoxy/SCA/SiO2/Si bonded specimens. The immersion test qualitatively evaluates the bond durability for various systems exposed to different chemical and thermal conditions. Second, a novel probe test was used to quantitatively determine adhesion under critical debonding conditions for bonded specimens with different SCA preparations. A general trend of bond durability varied in the manner SCA-2 > SCA-3 > SCA-1 > no silane. Bond durability also increased for samples: model epoxy/SCA modified/O2 plasma treated/Si as the oxygen plasma pre-treatment time increased. Third, bond durability was studied using the wedge DCB (double cantilever beam) test under subcritical debonding conditions with environment-assisted crack growth as a function of applied strain energy release rate. Higher crack velocity and the absence of a Gthreshold value were noted in tests at 70 oC. The Gthreshold value increased as the strength of the interface increased and as the chemical aggressiveness of the environment decreased. For tests involving 25 oC -70 oC thermal cycling, only limited crack growth was found. / Ph. D.

Nowadays, when environmental concerns are becoming increasingly important are there great interest in natural materials and recyclability. The possibility of reusing materials with maintained mechanical properties are essential for sustainability. Today produced approximately 90,000 tons of natural fiber reinforced composites in Europe of those are 40,000 tons compression molded of which the automotive industry uses 95%. Natural fiber reinforced composites is recyclable and therefore interesting in many applications. Also, natural fiber reinforced composites is inexpensive, light in weight and shows decent mechanical properties which makes them attractive to manufactures. However, the problem with natural fiber reinforced composites is the poor adhesion between fiber and matrix, the sensitivity of humidity and their low thermal stability. Those problems could be overcome by addition of compatibilizer and reactive filler. This study will examine the technical requirement in order to develop a sustainable and recyclable biocomposite. It investigates the composition of matrix (polypropylene), fiber (flax), compatibilizer (maleic anhydride grafted polypropylene) and reactive filler (CaO) in order to obtain various combinations of stiffness, strength and processability. The two main methods used for preparing samples were compounding and injection molding. Results shows that 20 wt% flax was the optimal fiber content and that maleic anhydride grafted polypropylene is a very good compatibilizer by enhancing the strength significant. Surprisingly was the strength impaired due to the addition of CaO. The composition of 20 wt% flax, 1 wt% maleic anhydride grafted polypropylene and 79 wt% polypropylene is the technically most favorable composition.

La biofonctionnalisation de surfaces de silice est une étape cruciale dans de nombreux domaines de biotechnologie tels que la biodétection ou la bioséparation. Le contrôle de l’état de surface entre les supports solides des matériaux et les espèces biologiques permet d’améliorer leurs performances de reconnaissance. Dans ce travail, nous avons développés des organosilanes fonctionnels dendritiques de première et de seconde génération pour la modification chimique de surface. Ces organosilanes dendritiques de type RSiX3 (X= Cl ou OMe3 ou OEt3) ont été greffés de manière covalente sur des surfaces de silice ou des surfaces de nanoparticules superparamagnétiques de type core-shell (gamma-Fe2O3/SiO2). La qualité des greffages a été analysée par AFM et TEM. Ils ont également été caractérisés par infrarouge, angle de contact et zêtamétrie. Ces surfaces modifiées par des molécules dendritiques ont montré une capacité à immobiliser des molécules biologiques comme la protéine A ou des anticorps de lapin. / Biofunctionalization of silica surfaces represents a crucial step for many applications in biotechnology such as biosensing and bioseparation. Monitoring the surface modification of the materials supports can improve their performances for the recognition of biological species. In this work, we have developed functional dendritic organosilanes of first and second generation for chemical modification of surfaces. These dendritic organosilanes RSiX3 (X = Cl or OMe3 or OEt3) were covalently grafted on planar silica or on core-shell superparamagnetic nanoparticles surfaces (gamma-Fe2O3/SiO2). The grafted surfaces were analyzed by AFM and TEM. They were also characterized by Infrared, contact angle and zetametry. These modified surfaces by dendritic molecules have shown high ability to immobilize biological molecules such as protein A or rabbit antibodies.

Submitted by OTAVIO AUGUSTO TITTON DIAS (otaviotd@gmail.com) on 2017-02-07T12:19:37Z No. of bitstreams: 1 Otávio [rev. 06.02.17] - arquivamento.pdf: 3569255 bytes, checksum: d063af8c0f50bdd6bd8ea5a53186f094 (MD5) / Approved for entry into archive by LUIZA DE MENEZES ROMANETTO (luizamenezes@reitoria.unesp.br) on 2017-02-13T15:49:14Z (GMT) No. of bitstreams: 1 dias_oat_me_bot.pdf: 3569255 bytes, checksum: d063af8c0f50bdd6bd8ea5a53186f094 (MD5) / Made available in DSpace on 2017-02-13T15:49:14Z (GMT). No. of bitstreams: 1 dias_oat_me_bot.pdf: 3569255 bytes, checksum: d063af8c0f50bdd6bd8ea5a53186f094 (MD5) Previous issue date: 2016-12-12 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / As preocupações ambientais e o esgotamento dos combustíveis fósseis resultaram em um interesse crescente em materiais ambientalmente amigáveis, à base de polímeros naturais. Esforços estão sendo feitos para introduzir a lignina em compostos plásticos, tais como polipropileno, com o objetivo de produzir materiais com boas características mecânicas e, ao mesmo tempo, ambientalmente amigáveis. A lignina é uma matéria-prima amplamente disponível na natureza, que contém alta densidade de compostos aromáticos, os quais são atualmente, em sua maioria, derivados do petróleo. No entanto, grande parte da lignina é utilizada para geração de energia e pode ser um potencial agente poluidor se não destinada de forma adequada. Desse modo, é importante encontrar uma maneira econômica de converter esse polímero natural em materiais de alto valor agregado, como compósitos com alto desempenho mecânico e térmico. Neste estudo, compósitos de polipropileno e de lignina kraft de pinus (LKI) e de bagaço de cana (LBC) foram submetidos à extrusão, e os corpos de prova foram produzidos pelo processo de injeção. Os materiais produzidos foram analisados quanto às propriedades mecânicas, térmicas (TGA, DSC, HDT), química (FTIR), reológica (índice de fluidez) e morfológica (MEV). Os objetivos desta pesquisa foram desenvolver novos compósitos de polipropileno contendo lignina e proporcionar propriedades mecânicas comparáveis aos polipropilenos comerciais, além de obter compósito com alto grau de afinidade entre a lignina e o polipropileno. Os resultados mostraram que a incorporação de lignina na matriz de polipropileno originou, de maneira geral, compósitos com propriedades adequadas para vários segmentos industriais, especialmente aqueles em que características mecânicas e térmicas são cruciais, tais como a substituição de plásticos de engenharia e polipropileno com cargas minerais. / Environmental concerns and the depletion of fossil fuels resulted in a growing interest in environmentally friendly materials based on natural polymers. Efforts are being made to introduce the lignin in plastic composites such as polypropylene, in order to produce materials with good mechanical characteristics and at the same time environmentally friendly. Lignin is a biopolymer widely available which contains high density of aromatic compounds. Nowadays, the aromatic compounds are almost exclusively derived from petroleum. However, the lignin is used mainly to generate energy and can be a pollution potential if not properly treated. Lignin, however, can improve the performance of composites. Moreover, it is important to find an economical way to convert lignin into high value-added materials. In this study, blends of polypropylene, pine kraft lignin (LKI) and sugar cane bagasse lignin (LBC) were subjected to extrusion and the specimens were produced by injection process. The materials produced were analyzed for their mechanical, thermal (TGA, DSC, HDT), chemical (FTIR), rheological (melt flow index) and morphological (SEM) properties. The objective of this research was to develop new lignin-based polypropylene composite with mechanical properties comparable to commercial polypropylene. The results showed that the incorporation of lignin in polypropylene matrix resulted in composites, in general, with properties suitable for various industrial segments, especially those in which mechanical and thermal properties are crucial, such as the replacement of engineering plastics and polypropylene mineral filled.

Au cours de cette étude, il a été question de développer une méthodologie d’élaboration et d’évaluation de la qualité de l’interface fibre-matrice au sein d’un composite à matrice polyamide 12 renforcé par du verre. Un modèle macroscopique a été élaboré dans un premier temps sous forme d’un assemblage lame de verre/film polyamide 12, et plusieurs promoteurs d’adhésion, principalement des organosilanes, de fonctionnalités différentes et compatibles avec la matrice polyamide ont été testés. La qualité du greffage a pu être caractérisée grâce à des techniques d’analyses physico-chimiques adaptées (AFM, PM-IRRAS, mouillabilité,…), et la performance adhésive des assemblages a pu être évaluée par des tests mécaniques spécifiques (pelage, clivage). Dans une seconde étape, le protocole de dépôt décrit à l’échelle macroscopique a été adapté à l’échelle des fibres de verre, plus particulièrement à l’échelle mésoscopique des fibres optiques. Des essais mécaniques spécifiques à l’échelle microscopique (fragmentation) ont été réalisés afin d’évaluer la performance adhésive de l’interface dans les assemblages concernés. Une étude focalisée sur la compréhension des mécanismes interfaciaux a également été réalisée afin de clarifier la nature des interactions établies à l’interface fibre-matrice. Grâce aux différentes techniques de caractérisation physico-chimiques il a été possible de mettre en évidence l’influence de différents paramètres expérimentaux, tels que la durée du greffage, la densité de greffage et la chimie des surfaces traitées, sur la cristallisation de la matrice à l’interface. La dernière partie de ce travail de thèse concerne le passage à l’échelle du semi-produit sous forme de rubans. Des analyses des propriétés de l’interface ainsi que des caractéristiques mécaniques ont été réalisées. / During this study, the aim was to develop a methodology to elaborate and evaluate the quality of the fiber-matrix interface in a glass fiber reinforced polyamide 12 composite.At first, a macroscopic model was developed using a glass slide/polyamide 12 film assembly. Several organosilane adhesion promoters with different features and compatible with the polyamide matrix were tested. The grafting quality was characterized through appropriate physico-chemical analytical techniques (AFM, PM-IRRAS, Wetting…), and the adhesive performance of the assemblies was evaluated by specific mechanical tests (Peel test, Wedge test). In a second step, the deposition procedure described in macroscopic scale has been adapted to the glass fibers’ scale, more particularly to optical fibers. Specific mechanical tests were performed (fragmentation test) to assess the adhesive performance at the interface of the concerned assemblies.A study focused on the understanding of the interfacial mechanisms was also conducted to clarify the nature of the interactions established at the fiber-matrix interface. Thanks to the different physico-chemical characterization techniques, it has been possible to demonstrate the influence of various experimental parameters such as the surface treatment time, the grafting density and the chemistry on the treated surfaces on the crystallization of the matrix at the interface. The last part of this work concerns the transition to the semi-scale form of ribbons. The analysis of the interface’s properties and the mechanical characteristics has been investigated.

The objective of the study is to improve the interfacial adhesion between the wood fibers and thermoplastic matrix. Efforts were also directed towards improving manufacturing processes so as to realize the full potential of wood fibers as reinforcing fillers. Chemical coupling plays an important role in improving interfacial bonding strength in wood-polymer composites. A novel compatibilizer with isocyanate functional group was synthesized by grafting m-Isopropenyl –α –α –dimethylbenzyl-isocyanate (m-TMI) onto isotactic polypropylene using reactive extrusion process. The compatibilizer was characterized with respect to its nature, concentration and location of functional group, and molecular weight. There are two main process issues when blending polymers with incompatible filler: (1) creating and maintaining the target morphology, and (2) doing so with minimum degradation of fillers. A 28mm co-rotating intermeshing twin screw extrusion system was custom built and the design optimized for (1) blending biological fibers with thermoplastics, and (2) for melt phase fictionalization of thermoplastics by reactive extrusion. To assess the effect of inclusion of wood fibers in polypropylene composites, a series of polypropylene wood fiber/wood flour filled composite materials having 10 to 50 wt % of wood content were prepared using the co-rotating twin screw extrusion system. m-TMI-g-PP and MAPP were used as coupling agents. Addition of wood fibers, at all levels, resulted in more rigid and tenacious composites. The continuous improvement in properties of the composites with the increasing wood filler is attributed to the effective reinforcement of low modulus polypropylene matrix with the high modulus wood filler. Studies on were also undertaken to understand effect of particle morphology, type and concentration of coupling agent, and effect of process additives on mechanical properties. Composites prepared with m-TMI-grafted-PP were much superior to the composites prepared with conventionally used maleated polypropylene in all the cases. Non-destructive evaluation of dynamic modulus of elasticity (MoE) and shear modulus of wood filled polypropylene composite at various filler contents was carried out from the vibration frequencies of disc shaped specimens. The vibration damping behaviour of the composite material was evaluated. MoE and shear modulus were found to increase whereas damping coefficient decreased with the increasing filler content. Knowledge of moisture uptake and transport properties is useful in estimating moisture related effects such as fungal attack and loss of mechanical strength. Hence, a study was undertaken to asses the moisture absorption by wood filled polypropylene composites. Composites prepared with coupling agents absorbed at least 30% less moisture than composites without compatibilizer. Thermo-gravimetric measurements were also carried out to evaluate the thermal stability and to evaluate kinetic parameters associated with thermal degradation of wood fiber and wood flour filled polypropylene composites. The moisture absorption and thermal behaviour are described based on analytical models. High efficiency filler-anchored catalyst system was prepared by substituting of hydroxyl groups present on the cellulosic filler. The process involves immobilizing the cocatalyst onto the cellulosic filler surface followed by addition of metallocene catalyst and then polymerization of ethylene using this filler supported catalyst. The polymerization and composite formation takes place simultaneously. All the polymerization reactions were carried out in a high-pressure stirred autoclave. Effect of temperature, ethylene pressure, and cocatalyst to catalyst ratios (Al/TM ratios) were also studied. Studies on kinetics of polymerization showed that, higher Al/Zr ratio and higher temperature lead to higher polymerization rates but lower the molecular weight. A model incorporating effect of reaction parameter on polymerization rates has been developed.

Made available in DSpace on 2014-08-20T14:30:12Z (GMT). No. of bitstreams: 1 Tese _Luciano_de_Vargas_ Habekost.pdf: 2287600 bytes, checksum: 421084441401a2957e40573944b6a691 (MD5) Previous issue date: 2011-01-14 / The objective of this study was to investigate the influence of nanoparticle loading and the use of silane (TSPM), phosphate (PAM) or carboxylic (CAM) methacrylates as coupling agents on key properties of experimental resin luting agents. An experimental photocurable resin blend composed with 50 wt% of Bis-GMA and 50 wt% of TEGDMA was obtained. To study the influence nanoparticle loading, five different experimental resin luting agents were prepared with a total mass fraction of 60% of inorganic fillers. Silanated 2-μm barium borosilicate glass microparticles and 7-nm silica nanoparticles were used; the mass fraction of nanoparticles was set at 0 (control), 1 (G1), 2.5 (G2.5), 5 (G5) and 10% (G10). To study the influence of coupling agents, the resin blend was loaded with a 60% mass fraction of inorganic fillers (59/1 mass ratio of micro/nanoparticles) of Ba-B-Al-Si glass and colloidal silica coated with 5 wt% of TSPM, PAM or CAM; no filler treatment was performed in the control group. The properties evaluated were flexural strength () and modulus (Ef), Knoop hardness number (KHN), and film thickness (FT). Dispersion/interaction of particles with the resin phase was assessed by scanning electron microscopy (SEM).The degree of conversion (DC) was evaluated only to study the influence of coupling agents. Data were submitted to statistical analysis (5%). Results for nanoparticle loading: for , G1 > G2.5 = G5 = G10, and control > G10. For Ef, G2.5 > control = G1 > G5 > G10. For KHN, G5 = G10 > control = G1 = G2.5. For FT, control = G1 < G5 = G10, and G2.5 < G10. Incorporation of nanoparticles was associated with observation of clusters in the SEM analysis. Results for different coupling agents: for  and Ef, TSPM > CAM > control > PAM. For KHN, TSPM > CAM > PAM = control. For FT, TSPM < control < CAM < PAM. The SEM analysis revealed clustering of nanoparticles for all groups and better interaction between the organic-inorganic phases for TSPM and CAM. No significant differences in DC were observed. The results demonstrated that moderate incorporation of silanated silica nanoparticles may improve the properties of hybrid resin cements. However, mass fraction above 2.5% had a detrimental effect on the luting agent properties and the increase of clusters is associated with the increase of nanoparticles. The use of TSPM generated agents with improved properties as compared with the acidic methacrylates, with CAM showing better performance than PAM. The use of PAM generated agents with properties usually poorer compared with the material with no coupling agent. / O objetivo deste estudo foi investigar a influência da incorporação de nanopartículas e o uso de silano (TSPM), monômero ácido fosfatado (PAM) ou monômero ácido carboxilado (CAM) como agentes de união nas propriedades de cimentos resinosos experimentais. Uma matriz resinosa fotopolimerizável modelo foi desenvolvida com 50% de Bis-GMA e 50% de TEGDMA. Para observar o comportamento da incorporação de nanopartículas, cinco cimentos resinosos experimentais foram preparados pela adição de 60% (em massa) de micropartículas de bário borosilicato de vidro (2μm) e nanopartículas de sílica coloidal (7nm). As nanopartículas foram utilizadas nas seguintes proporções (em massa): 0 (controle), 1 (G1), 2.5 (G2.5), 5 (G5) e 10% (G10). Para estudar a influência dos agentes de união, 60% (em massa) de partículas inorgânicas (59/1 de micro/nanopartículas) de vidro de Ba-B-Al-Si e sílica coloidal, cobertas com 5% de TSPM, PAM ou CAM, foram acrescidas à matriz resinosa; o grupo controle foi composto por partículas não tratadas. As propriedades avaliadas foram resistência flexural (), módulo de elasticidade (Ef), número de dureza Knoop (KHN) e espessura de película (FT).A dispersão/interação das partículas com a fase resinosa foi avaliada com microscópio eletrônico de varredura (MEV). O grau de conversão (DC) foi avaliado somente para estudar a influência dos diferentes agentes de união. Os dados foram submetidos à análise estatística (5%). Resultados para incorporação de nanopartículas: para , G1 > G2.5 = G5 = G10 e controle > G10. Para Ef, G2.5 > controle = G1 > G5 > G10. Para KHN, G5 = G10 > controle = G1 = G2.5. Para FT, controle = G1 < G5 = G10 e G2.5 < G10. Nas análises em MEV, a presença de aglomerados foi associada à incorporação de nanopartículas. Resultados para a utilização de diferentes agentes de união: para e Ef, TSPM > CAM > controle > PAM. Para KHN, TSPM > CAM > PAM = controle. Para FT, TSPM < controle < CAM < PAM. As análises em MEV revelaram aglomerados de nanopartículas em todos os grupos e melhor interação entre as fases orgânica/inorgânica para TSPM e CAM. Não foram observadas diferenças para o DC. Os resultados demonstraram que a incorporação moderada de nanopartículas de sílica silanizada pode beneficiar as propriedades dos cimentos resinosos híbridos. Entretanto, proporções de nanopartículas acima de 2,5% possuem um efeito prejudicial nas propriedades destes cimentos, e seu aumento está associado com o aumento da presença de aglomerados. O uso de TSPM gerou cimentos com melhores propriedades quando comparado ao uso de monômeros ácidos, o CAM demonstrou melhor desempenho que o PAM. O uso do PAM gerou cimentos com propriedades inferiores a cimentos sem a utilização de agentes de união.

Adding layered double hydroxides (LDHs) to polymer compounds has been shown to make them more resistant to corrosion and improve their physical and chemical properties. However, the main challenge lies in the compatibility between inorganic LDH fillers and organic polymer matrices. The incompatibility between these two is due to differences in polarity and surface properties, which makes dispersion of LDHs within the polymer very difficult, negatively affecting the final material's performance and characteristics. In this work, Zn-Al-NO3 LDH particles were synthesized through co-precipitation method and then modified by decavanadate via the anion exchange process. Then, a silane coupling agent was used to functionalize intercalated LDH particles to make them more hydrophobic; this helped the particles to disperse well inside epoxy coating, which ultimately resulted in better corrosion inhibition performance for the coating. The concentration effect of silane coupling agent on LDHs' surface grafting was also studied using various concentrations of 3-aminopropyltriethoxy silane (APTES). Compositional and structural characterization study on revealed more insight into how the surface treatments worked. Finally, to modify LDHs, sodium dodecyl sulfate was inserted in LDH structure, then APTES molecules were grafted on the dodecyl sulfate intercalated LDHs' surface. These organic intercalation and grafting steps made LDHs more suitable with acrylic resin to form uniform composite mixture through solvent solution mixing. The thermal stability of acrylic coating improved by adding modified hybrid LDH fillers and elevation in decomposition temperature was confirmed using thermogravimetric analysis.