Montmorillonite reinforced polymers are a new development in the area of nanocomposite materials. Since reinforcement of epoxy is important to the development of high strength adhesives and composite matrices, the introduction of montmorillonite to epoxy is of interest. Compositional effects on epoxy reactivity, on molecular relaxation, and on mechanical properties were investigated. Change in reactivity was determined by Differential Scanning Calorimetry. Tensile properties at room temperature indicated improved modulus and retention of strength of the epoxy matrix but a decreased elongation to failure. Depression of dry nanocomposite glass transition was observed for nanocomposites beyond 5% by weight montmorillonite. Samples that were saturated with water showed lower moduli due to the epoxy matrix. The greatest moisture absorption rate was found at 7%, the least at 3%.

Étant donné son origine, le bois reste biodégradable et a besoin d'être protégé contre les agents abiotiques et biotiques afin d'avoir une longue durée de service. Les associations entre les tanins et l'acide borique peuvent être considérés comme un traitement innovant et respectueux de l'environnement. Ces formulations aqueuses de tannins et d'acide borique augmentent la rémanence du bore dans le bois traité. De plus, le bore est partiellement fixé au réseau polymère de tannins autocondensés dans le bois et garde suffisamment de mobilité pour garder son efficacité biologique. Ces associations ont été testées pour une application en extérieur, au-dessus et dans le sol, et pour leurs propriétés ignifugeantes. Une première formulation de tannin-hexamine et acide borique a montré une efficacité certaine face aux dégradations biologiques et au feu. Le comportement au vieillissement naturel et artificiel, au lessivage à l'échelle du laboratoire, ainsi que l'efficacité biologique résultante, de bois traité par ces associations a été étudié. Les résultats montent que ces trois vieillissements mènent à des performances biologiques différentes, toutes liées à la teneur en bore résiduelle. Une formulation tannin-bore dite améliorée, contenant du ɛ-caprolactame pour rendre le réseau polymère plus flexible (et éviter les craquelures comme dans la première formulation) a été étudiée pour les mécanismes chimiques mis en jeu, la résistance biologique au-dessus et dans le sol, et la résistance au feu. Le polymère à base de tannin acquiert une structure plus élastique après incorporation de ɛ-caprolactame, comme démontré par des analyses FT-IR. La résistance biologique du bois traité procure une résistance à long terme en extérieur, même dans le sol. L'effet de protection au feu est moins intéressant que pour la première formulation, mais reste toute de même plus important que pour le témoin. Afin d'améliorer l'efficacité des associations entre bore et tannins, l'élaboration de bois contenant un polymère nano-composite (Wood Tannin NanoComposite, WTNC) utilisant tannins, acide borique et montmorillonite a été étudiée. Des analyses FT-IR et XRD on permit d’identifier des nanoparticules d'argiles dans le WTNC. Par ailleurs, des traces de montmorillonite dans les parois du bois ont été observées en microscopie électronique à balayage. Par comparaison avec des témoins, la résistance à la compression du WTNC est plus importante, l'absorption d'eau et l'aptitude au collage du WTNC dépend de l'essence utilisée (pin sylvestre vs. Hêtre), la stabilité dimensionnelle du WTNC est légèrement abaissée et sa mouillabilité significativement réduite. La résistance à l'attaque de champignons et termites est améliorée dans des proportions variables selon que l'on utilise du pin sylvestre ou du hêtre. Les performances anti-feu des WTNC sont affectées différemment en fonction de l'essence de bois utilisée et des paramètres considérés. Cette étude analyse aussi les impacts environnementaux de la production de produit de préservation tannin-bore (pour la première formulation) et compare aussi les impacts du berceau à la tombe dans le cadre d'une analyse de cycle de vie de bois traité par cette formulation, en comparaison avec 2 formulations industrielles et du béton. Il apparaît que même si ces associations tannin-bore peuvent être encore étudiées plus avant et plus finement du point de vue chimique, pour leurs performances biologiques (vis-à-vis d'insectes coléoptères, essais de champ avec des termites, moisissures…), ainsi que pour leur profil éco-toxicologique, elles ont montré de réelles améliorations du bois dans les domaines de la résistance biologique et de la résistance au feu. / Due to its origins, wood remains biodegradable and needs to be protected against abiotic and biotic agents for a long service life. Tannin-boron associations can be considered as an innovative preservative formulation and environmentally-friendly treatment. These waterborne associations of tannins and boric acid increase the permanence of boron in the wood. Furthermore, boric acid is partly fixed to the network of autocondensed tannin in the wood and keeps sufficient mobility to maintain its biological action. These associations have been investigated for their outdoor applications, both above and in-ground, as well as for their ability for fire protection. An original formulation of tannin-hexamine and boric acid, has shown efficiency against biological attack and fire degradation. The natural and artificial weathering behaviour, and laboratory scale leaching, of such treated wood have been investigated, and followed by biological tests. The results showed that the weatherings led to different performances, always linked with the amount of remaining boron. An advanced tannin-boron formulation including ɛ-caprolactam to make the polymer network more flexible (and avoiding cracks as noticed for the original formulation) was studied for the chemical mechanisms, biological resistance above and in-ground, fire retardancy. The tannin polymer acquires a more elastic structure after adding ɛ-caprolactam, as seen with FT-IR analyses. The biological resistance of the treated wood provided a long lasting protection against degradation in outdoor exposures, and even in ground contact. However, fire retardant effect of this advanced tannin-boron preservative was negatively influenced with comparison to the original tannin-boron formulation, but still better than control. In order to improve the associations between boron and tannin for wood protection, the conception of wood polymer nanocomposite using tannin, boric acid and montmorillonite tentatively carried out. The analyses of FT-IR and XRD have investigated to identify nanoclay in Wood Tannin Nanocomposite (WTNC). Meanwhile, the trace of montmorillonite in wood cell is also captured by SEM. By comparison with control, compression strengths of WTNC samples increase; water absorption and gluing ability of WTNC depend on the wood species used (Scot Pine vs. Beech); dimensional stability of WTNC is slightly decreased, and wettability was significantly decreased. Fungal and termite resistance of WTNC are improved to different extends if Scots pine or beech samples are used. Fire performances of WTNC is affected differently depending on the wood species used and the parameters considered. This study also analyses the environmental impacts of producing tannin-boron (TB) preservative (the original formulation) and comparatively introduces the cradle-to-grave life cycle environmental impacts (LCA) of TB-treated timber as landscaping materials, compared with 2 industrial formulations and concrete.Even if all these tannin-boron association systems developed still need to be improved for some point of their chemistry, biological performances (coleoptera insects, field tests with termites, molds…), as well as for their eco-toxicological profile, they have shown to improve the biological and fire resistance of the wood.

No description available.

During the last years rubber nanocomposites obtained by incorporating anisotropic clay nanoparticles within a rubber matrix to tailor material properties have attracted steadily growing interest. However, one main complication preventing rubber-clay nanocomposites from many potential applications is the difficulty to achieve a high degree of exfoliation particularly in case of melt mixing or compounding (using mixing equipment like internal mixer, two roll mills which can be up-scaled in industry). Albeit commercially available organomodified montmorillonite clays (OMt) are fairly compatible with the polar rubber like Acrylo-nitrile butadiene rubber (NBR), carboxylated nitrile rubber (XNBR), chloroprene rubber (CR) etc., its dispersion in non-polar rubbers like natural rubber (NR), is rather unsatisfactory. Incorporation of only 5 phr of OMt in NR by mechanical mixing leads to very poor dispersions with larger aggregates. Large agglomerates of OMt were observed with bare eyes throughout the matrix. Even in the TEM micrographs, highly agglomerated structures of clay particle were observed. A high degree of exfoliation of such clay is achieved in NR utilizing the so called ‘Propping-open approach’ where stepwise expansion of interlayer spacing of Mt took place. A series of long chain fatty acids (C16-C22) are intercalated into the interlayer space of OMt and a gradual expansion of the interlayer space were observed as the chain length of the fatty acid increased. Wide angle X-ray diffraction (WAXD), Fourier transform infrared spectroscopy (FTIR) and contact angle measurement indicated successful intercalation of the fatty acids into the interlayer space of the clay minerals. Since the fatty acid containing 22 carbon atoms has the largest interlayer distance among the modified samples studied, it has been selected for further study to understand the reinforcing behavior in NR matrix. An unusual mechanical percolation behavior of EOMt nanoparticles was observed in a NR matrix. The value of the mechanical percolation threshold (φp) and the fractal nature of nanoparticle clusters were determined through an analysis of the experimental data based on a theory put forward by Huber and Vilgis. This phenomenon was discussed in terms of fractal dimensions of the nanoparticle cluster. The impact of filler dispersion and rubber-filler interactions on the viscoelastic behavior of NR nanocomposites was systematically investigated. Significant non-linear viscoelastic behavior (Payne effect) was observed at very low EOMt content. Kraus and Maier-Göritz models were utilized to interpret such non-linear viscoelastic behavior. The nanocomposites showed enormous improvement in different physic-mechanical properties in the presence of EOMt. Technical elastomers are generally filled with certain fillers (e.g. carbon black) in order to reinforce the rubber matrix for some typical applications like tires, conveyer belts etc. Such rubber goods are always exposed to cyclic stress and deformations attributed to their dynamic application. Under constant and repeated applied stress, cracks develop at a stress concentration point, which could lead to ultimate failure. Therefore, the crack initiation and propagation behavior in such rubber products is very fundamental and need proper attention. The role of EOMt nanoparticles on the microstructure and fracture mechanical behavior of CB filled NR composites was investigated. Using pure-shear test specimen tear fatigue analysis (TFA) tests under cyclic conditions were carried out to explicate the crack growth behavior of CB filled NR in the presence of EOMt. A significant reduction in crack growth rate was noticed in the presence of only 5 phr of EOMt. Furthermore, instrumented tensile-impact tests (IT-IT) were also performed for the characterization of the crack resistance of the materials under impact-like loading conditions. / Die Einarbeitung von nur 5 phr organisch modifizierten Montmorillonite (OMt) in Naturkautschuk (NR) durch mechanisches Mischen führt zu einer sehr schlechten Verteilung mit größeren Aggregaten. Große Agglomerate von OMt waren mit bloßem Auge in der NR Matrix sichtbar. Sogar in TEM Aufnahmen wurden stark agglomerierte Strukturen beobachtet. Ein hoher Grad der Exfolierung von diesem Clay in NR wird durch die Nutzung des so genannten ‘Propping-open’ Ansatzes erreicht, in dem eine stufenweise Aufweitung des Zwischenschichtabstandes des OMt stattfindet. Eine Reihe langkettiger Fettsäuren (C16 – C22) wurde in die Zwischenschicht des OMt eingefügt. Mit zunehmender Kettenlänge der Fettsäuren wurde eine allmähliche Aufweitung der Zwischenschicht beobachtet. Da OMt, der mit einer Fettsäure mit 22 Kohlenstoffatomen modifiziert wurde, den größten Zwischenschichtabstand aller untersuchten Proben hatte, wurde diese Fettsäure für die weiteren Untersuchungen ausgewählt, um das Verstärkungsverhalten in der NR Matrix zu verstehen. Ein ungewöhliches Perkolationsverhalten der expandierten OMt (EOMt) Nanopartikel wurde in einer NR Matrix beobachtet. Der Wert der mechanischen Perkolationsschwelle (φp) und die fraktale Natur der Nanopartikel Cluster wurden durch eine Analyse der experimentellen Daten bestimmt, wobei eine Theorie, die von Huber und Vilgis vorangetrieben wurde, zur Anwendung kam. Dieses Phänomen wurde in Bezug auf die fraktalen Dimensionen der Nanopartikel Cluster diskutiert. Die Einfluss von EOMt Nanopartikel auf die Mikrostruktur und das mechanische Bruchverhalten von russgefüllten NR Kompositen wurde untersucht. Unter Verwendung reiner Schertestproben wurden Rissermüdungsanalysen unter zyklischer Belastung ausgeführt, um das Risswachstumsverhalten von russgefülltem NR in der Gegenwart von EOMt zu untersuchen und zu erklären. Eine signifikante Reduktion der Rissausbreitungsrate wurde in Gegenwart von nur 5 phr EOMt erreicht. Des Weiteren wurden auch instrumentierte Schlagzugprüfungen zur Charakterisierung des Risswiderstandes von Materialien unter schlagartigen Belastungsbedingungen durchgeführt.

The influence of charge heterogeneity in nanoparticles such as montmorillonite layered silicates (MLS) and hybrid systems of MLS + carbon nanotubes was investigated in cured and uncured epoxy. Epoxy nanocomposites made with cation-exchanged montmorillonite clay were found to form agglomerates near a critical concentration. Using differential scanning calorimetry it was determined that the mixing temperature of the epoxy + MLS mixture prior to the addition of the curing agent critically influenced the formation of the agglomerate. Cured epoxy samples showed evidence of the agglomerate being residual charge driven by maxima and minima in the concentration profiles of thermal conductivity and dielectric permittivity respectively. A hybrid nanocomposite of MLS and aniline functionalized multi walled nanotubes indicated no agglomerates. The influence of environmentally and process driven properties on the nanocomposites was investigated by examination of moisture, ultrasound, microwaves and mechanical fatigue on the properties of the hybrid systems. The results point to the importance of charge screening by adsorbed or reacted water and on nanoparticulates.

The presence of pharmaceuticals and personal care products (PPCPs) in the environment has become a matter of concern during the last decade. Increased production of PPCPs along with their increased use has led to release of these compounds in the environment via various routes. PPCPs includes large group of compounds including veterinary and human antibiotics, analgesics and anti-inflammatory drugs, psychiatric drugs, β-blockers, X-ray contrasts, and steroid hormones, etc. Many of the compounds used in PPCPs have been shown to possess adverse effects to living organisms and act as endocrine disrupting agents (ECDs). This dissertation includes the investigation of the occurrence of antibiotic compounds added to personal care product and the transformation of hormones used in pharmaceuticals such as contraceptives. The results obtained in this study can provide information on the fate and transformation of the studied compounds once released in the environment. An analytical method employing sonication extraction and HPLC-ESI-MS detection was developed. The developed method was used to detect antibiotic compounds triclosan (TCS) and triclocarban (TCC) in biosolids-applied soil and biosolids. Both TCS and TCC were detected at high concentrations in biosolids and at lower concentrations in biosolids-applied soil. TCS and TCC concentrations decreased in biosolids composts and in biosolids-applied soil collected at deeper depths. The developed method was able to provide efficient detection limits and reliable quantification of target compounds. A molecularly imprinted polymer (MIP) was synthesized to achieve efficient clean-up of TCS and TCC from biosolids-applied soil and biosolids samples using 4,4’- DBP-4-vp-EGDMA. The motivation behind this project was to be able to eliminate the use of expensive instruments such as LC-MS and employ easily available instruments such as LC-UV. The synthesized MIP was able to achieve efficient clean-up and allowed quantification and identification of TCS and TCC in a complex matrix. Transformation of hormones such as 17β-estradiol, estriol, ethynlestradiol, estrone and testosterone was studied by employing Fe (III)-saturated montmorillonite catalysts. The use of Fe (III) – saturated montmorillonite as a catalyst proved be to very efficient in transformation of the studied hormones. Complete removal of hormones was observed in aqueous environment. LC-UV was used for detection and quantification of hormones.

Ao contrário de muitos polímeros, as resinas fenólicas se caracterizam por possuir um grande número de aplicações por conta de sua superior resistência ao fogo e baixa emissão de fumos e ao seu excelente nível de resistência térmica e química, além de seu baixo custo. No entanto, devido à sua estrutura tridimensional, caracterizada pelo alto grau de reticulação, este tipo de resina apresenta baixas tenacidade e resistência à fratura. Com isso, para garantir seu bom desempenho, faz-se necessário promover modificações em sua formulação ou acrescentar agentes de reforço de modo a compensar essas deficiências resultantes de sua estrutura. São inúmeros os materiais que, usualmente, são incorporados à matriz fenólica. Além da preparação de blendas poliméricas em que uma das fases consiste em um elastômero ou um termoplástico, a introdução de agentes de reforço como materiais fibrosos também são utilizados. São exemplos de agentes de reforço: fibras vegetais, fibras de vidro e de carbono, negro de fumo, argilas entre outros. A mistura de polímeros e argilas pode levar à formação de nanocompósitos de modo a obter excelentes combinações de resistência à fratura, tenacidade, condutividade, resistência ao calor e redução da permeabilidade a gases e líquidos quando comparados com o polímero puro. Neste trabalho, argilas do tipo montmorilonita modificadas foram utilizadas como agente de reforço na preparação de filmes de nanocompósitos de matriz fenólica com o objetivo de melhorar as propriedades mecânicas deste material polimérico quando comparado com o material puro. A resina fenólica utilizada neste trabalho é a do tipo resol, utilizada comercialmente para a formulação de vernizes para revestimento de embalagens metálicas. No estudo foram utilizadas três argilas comerciais: Cloisite® sódica (Na) e argilas Cloisite® modificadas com sais quaternários de alquilamônio, de códigos 15A e 30B, objetivando verificar qual apresentaria melhor compatibilidade com a matriz fenólica. Para a preparação de filmes poliméricos uniformes, isentos de defeitos como bolhas, foi feita, de forma preliminar, a seleção de um ciclo de cura apropriado. Como a formação de bolhas é intrínseco à cura da resina fenólica resol, a definição de um esquema de tratamento térmico de cura apropriado constituiu-se em etapa crítica no processo de preparação dos compósitos de resina fenólica/argila montmorilonita modificada. Os filmes curados isentos de defeitos foram caracterizados por difração de raios X, análise termomecânica dinâmica (DMA) e calorimetria exploratória diferencial (DSC). Os resultados das análises de DRX mostraram para os compósitos preparados com as argilas modificadas 15A e 30B manutenção e até mesmo redução do espaçamento basal da estrutura cristalina das argilas, indicando não ter ocorrido intercalação do polímero nessas argilas; enquanto que para a argila Cloisite® Na ocorreu aumento do espaçamento basal. Os resultados de DMA mostraram para a maioria das amostras aumento no módulo de armazenamento em baixa e alta temperatura. Por último, a análise de DSC mostrou redução na temperatura de transição vítrea nos compósitos preparados com as argilas modificadas 15A e 30B, e elevação na composição de 5% da argila Cloisite® Na. Os resultados indicam o potencial de reforço mecânico de resinas fenólicas com argilas lamelares do tipo montmorilonita sem a necessidade de modificação química. / Unlike most polymers, phenolic resins are characterized by having a large number of applications because of its superior fire resistance and low emission of smoke and its excellent level of thermal and chemical resistance, and low cost. However, due to its three dimensional structure, characterized by a high degree of crosslinking, this type of resin has low toughness and fracture resistance. Thus, to ensure their good performance, it is necessary to make enhancements in their formulation or adding strengthening agents so as to compensate for these deficiencies due to its structure. There are numerous materials that usually are incorporated into the phenolic matrix. Besides the preparation of polymer blends in which one phase consists of an elastomer or a thermoplastic, the introduction of agents such as fibrous reinforcement is also used. Examples of reinforcing agents: vegetable fibers, glass and carbon fibers, carbon black, clay and others. The mixture of polymer clays may cause the formation of nanocomposites in order to obtain excellent combination of fracture strength, toughness, conductivity, heat resistance and reduced permeability to gases and liquids when compared with the pure polymer. In this work, modified montmorillonite clays were used as a reinforcing agent in the preparation of nanocomposite films of phenolic matrix with the aim of improving the mechanical properties of polymer materials when compared with the pure material. The phenolic resin used in this work is that of the resol type, used commercially for the formulation of varnish for coating metal containers. The study used three types of commercial clay: Cloisite® sodium (Na) and Cloisite® clays modified with quaternary alkylammonium salts, codes 15A and 30B in order to verify which present better compatibility with the phenolic matrix. For the preparation of uniform polymeric films, free of defects such as bubbles, was preliminarily selected a suitable cure cycle. As the bubble formation is intrinsic to the cure of resol phenolic resin, the definition of a heat treatment scheme is a critical step in the process of preparing composites of phenolic resin/montmorillonite clay. The cured films free of defects were characterized by X-ray diffraction (DRX), dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). The results of XRD analysis showed the composites prepared with the modified clays 15A and 30B maintained and even reduced the basal spacing within the clay crystal structure, indicating not having occurred polymer intercalation of the clay; for the Cloisite® Na clay DRX has shown increased basal spacing. DMA results showed for most of the samples increase in storage modulus at low and high temperatures. Finally, DSC analysis showed a reduction in glass transition temperature of the composites prepared with the modified clays 15A and 30B, and an increase in the composition of 5% in the Cloisite® Na clay. The results indicate the potential of enhancement of phenolic resins mechanical properties with layered clays of montmorillonite without chemical modification.

Nanocompósitos poliméricos foram preparados por meio da incorporação de 1, 2, 5 e 10% das argilas montmorilonita organofílicas Cloisite 15A e 30B em poliamida-6, pelo método de fusão numa extrusora dupla rosca. Em seguida, foram reprocessados numa extrusora mono-rosca gerando folhas pelo método balão e caracterizados por meio de técnicas espectroscópicas, de análise térmica e difração de raio-X. Os estudos mostraram a formação de nanocompósitos com uma boa dispersão e esfolheamento, principalmente em concentrações de argila inferiores a 5%. Nas amostras com 5 e 10%, nanocompósitos intercalados também foram observados. Portanto, quando a concentração de argila aumenta no nanocompósito, fica cada vez mais difícil obter nanocompósitos totalmente esfoliados. Além disso, verificou-se que a incorporação de 1% da Cloisite 15A ou 30B induzem a cristalização do polímero, predominando a fase γ nos filmes. Entretanto, a medida que a concentração de argila aumenta a fração de fase amorfa tende a aumentar, provavelmente em decorrência da diminuição da velocidade do processo de recristalização em torno de 194 ºC, que gera a fase cristalina γ. Foi demonstrado a presença de um excesso de surfactante em uma das argilas organofílicas, tanto na parte exterior dos tactóides como na região interlamelar, aumentando o espaçamento basal e facilitando o processo de intercalação/esfolheamento. Todavia, o excesso de surfactante interfere nos processos de incorporação pois sofrem decomposição em temperaturas relativamente baixas (200 ºC) enquanto o cátion amônio intercalado se decompõe a 240 ºC. De fato, os estudos realizados comprovam que o surfactante tem influência direta sobre as propriedades das argilas organofílicas e grande importância no processo de incorporação. Melhorias significativas foram observadas nas propriedades de barreira a gases e mecânicas, principalmente com relação a resistência a tração, que aumenta a medida que se aumenta a concentração de argila. As propriedades de perfuração não foram significativamente modificadas, mas também verificou-se um aumento significativo da estabilidade mecânica em função da temperatura. Porém, a absorção de umidade interfere negativamente tanto nas propriedades mecânicas quanto na de barreira a gases, sendo que a Cloisite 15A é menos suscetível que a Cloisite 30B, provavelmente devido ao cátion de amônio quaternário ser mais hidrofóbico. Assim, os filmes de nanocompósitos de poliamida- 6/argila devem ter aplicações diversas na indústria de embalagens / Polymeric nanocomposites were obtained by incorporation of 1, 2, 5 e 10% of the organophilic clays Cloisite 15A e 30B in polyamide-6, using a twin-screw extruder and the melting process. Then, the pellets were reprocessed as films in a single-screw extruder coupled with the blow method, and those materials were characterized by means of spectroscopic, thermal and X-ray difraction techniques. The results were consistent with the formation of nanocomposites with excellent dispersion and exfoliation, especially when the concentration of clay was below 5%. In the samples containing 5 e 10%, the presence of tactoids were observed showing the formation of intercalated nanocomposites as well. Thus, as the concentration of organophillic clay increases, the fraction of completely exfoliated clay decreased. Furthermore, the incorporation of clays (Cloisite 15A or 30B) in concentrations as low as 1% induced the crystallization of polyamide-6, such that it was found in the films predominantly in the γ phase. However, as the concentration of clay increases there is a steady increase of the amorphous phase, probably due to the decrease of the rate of the recrystallization process at 194 ºC, responsible for the formation of the γ phase. Also, the presence of an excess of surfactant was confirmed for both, Clositite 15A and 30B, around the tactoids and in the interlamelar space also, increasing the basal distance and facilitating the intercalation/exfoliation process. However, such an excess interfere in the nanocomposite preparation process since decomposes at relatively low temperatures (200 ºC) while the intercalated quaternary ammonium cation decomposes at 240 ºC. In fact, we showed that the structure of the surfactant directly influences the properties of the organophilic clays, and has strong influence on the nanocomposite preparation process. Significant improvements in the barrier effect to gases and in the mechanical properties were noticed for the nanocomposites, particularly on the resistance to traction and on the mechanical stability as a function of temperature, but the resistance to perforation didnt change significantly as the concentration of clay increased. The absorption of water by the nanocomposites influenced negatively the mechanical properties and the barrier effect as well. However, the nanocomposites prepared with Cloisite 15A were less susceptible than those obtained with Cloisite 30B, probably because the quaternary ammoniun salt in the first one is more hydrophobic and repels more effectively the water molecules

Nanocompósitos poliméricos foram preparados por meio da incorporação de 1, 2, 5 e 10% das argilas montmorilonita organofílicas Cloisite 15A e 30B em poliamida-6, pelo método de fusão numa extrusora dupla rosca. Em seguida, foram reprocessados numa extrusora mono-rosca gerando folhas pelo método balão e caracterizados por meio de técnicas espectroscópicas, de análise térmica e difração de raio-X. Os estudos mostraram a formação de nanocompósitos com uma boa dispersão e esfolheamento, principalmente em concentrações de argila inferiores a 5%. Nas amostras com 5 e 10%, nanocompósitos intercalados também foram observados. Portanto, quando a concentração de argila aumenta no nanocompósito, fica cada vez mais difícil obter nanocompósitos totalmente esfoliados. Além disso, verificou-se que a incorporação de 1% da Cloisite 15A ou 30B induzem a cristalização do polímero, predominando a fase γ nos filmes. Entretanto, a medida que a concentração de argila aumenta a fração de fase amorfa tende a aumentar, provavelmente em decorrência da diminuição da velocidade do processo de recristalização em torno de 194 ºC, que gera a fase cristalina γ. Foi demonstrado a presença de um excesso de surfactante em uma das argilas organofílicas, tanto na parte exterior dos tactóides como na região interlamelar, aumentando o espaçamento basal e facilitando o processo de intercalação/esfolheamento. Todavia, o excesso de surfactante interfere nos processos de incorporação pois sofrem decomposição em temperaturas relativamente baixas (200 ºC) enquanto o cátion amônio intercalado se decompõe a 240 ºC. De fato, os estudos realizados comprovam que o surfactante tem influência direta sobre as propriedades das argilas organofílicas e grande importância no processo de incorporação. Melhorias significativas foram observadas nas propriedades de barreira a gases e mecânicas, principalmente com relação a resistência a tração, que aumenta a medida que se aumenta a concentração de argila. As propriedades de perfuração não foram significativamente modificadas, mas também verificou-se um aumento significativo da estabilidade mecânica em função da temperatura. Porém, a absorção de umidade interfere negativamente tanto nas propriedades mecânicas quanto na de barreira a gases, sendo que a Cloisite 15A é menos suscetível que a Cloisite 30B, provavelmente devido ao cátion de amônio quaternário ser mais hidrofóbico. Assim, os filmes de nanocompósitos de poliamida- 6/argila devem ter aplicações diversas na indústria de embalagens / Polymeric nanocomposites were obtained by incorporation of 1, 2, 5 e 10% of the organophilic clays Cloisite 15A e 30B in polyamide-6, using a twin-screw extruder and the melting process. Then, the pellets were reprocessed as films in a single-screw extruder coupled with the blow method, and those materials were characterized by means of spectroscopic, thermal and X-ray difraction techniques. The results were consistent with the formation of nanocomposites with excellent dispersion and exfoliation, especially when the concentration of clay was below 5%. In the samples containing 5 e 10%, the presence of tactoids were observed showing the formation of intercalated nanocomposites as well. Thus, as the concentration of organophillic clay increases, the fraction of completely exfoliated clay decreased. Furthermore, the incorporation of clays (Cloisite 15A or 30B) in concentrations as low as 1% induced the crystallization of polyamide-6, such that it was found in the films predominantly in the γ phase. However, as the concentration of clay increases there is a steady increase of the amorphous phase, probably due to the decrease of the rate of the recrystallization process at 194 ºC, responsible for the formation of the γ phase. Also, the presence of an excess of surfactant was confirmed for both, Clositite 15A and 30B, around the tactoids and in the interlamelar space also, increasing the basal distance and facilitating the intercalation/exfoliation process. However, such an excess interfere in the nanocomposite preparation process since decomposes at relatively low temperatures (200 ºC) while the intercalated quaternary ammonium cation decomposes at 240 ºC. In fact, we showed that the structure of the surfactant directly influences the properties of the organophilic clays, and has strong influence on the nanocomposite preparation process. Significant improvements in the barrier effect to gases and in the mechanical properties were noticed for the nanocomposites, particularly on the resistance to traction and on the mechanical stability as a function of temperature, but the resistance to perforation didnt change significantly as the concentration of clay increased. The absorption of water by the nanocomposites influenced negatively the mechanical properties and the barrier effect as well. However, the nanocomposites prepared with Cloisite 15A were less susceptible than those obtained with Cloisite 30B, probably because the quaternary ammoniun salt in the first one is more hydrophobic and repels more effectively the water molecules

Ao contrário de muitos polímeros, as resinas fenólicas se caracterizam por possuir um grande número de aplicações por conta de sua superior resistência ao fogo e baixa emissão de fumos e ao seu excelente nível de resistência térmica e química, além de seu baixo custo. No entanto, devido à sua estrutura tridimensional, caracterizada pelo alto grau de reticulação, este tipo de resina apresenta baixas tenacidade e resistência à fratura. Com isso, para garantir seu bom desempenho, faz-se necessário promover modificações em sua formulação ou acrescentar agentes de reforço de modo a compensar essas deficiências resultantes de sua estrutura. São inúmeros os materiais que, usualmente, são incorporados à matriz fenólica. Além da preparação de blendas poliméricas em que uma das fases consiste em um elastômero ou um termoplástico, a introdução de agentes de reforço como materiais fibrosos também são utilizados. São exemplos de agentes de reforço: fibras vegetais, fibras de vidro e de carbono, negro de fumo, argilas entre outros. A mistura de polímeros e argilas pode levar à formação de nanocompósitos de modo a obter excelentes combinações de resistência à fratura, tenacidade, condutividade, resistência ao calor e redução da permeabilidade a gases e líquidos quando comparados com o polímero puro. Neste trabalho, argilas do tipo montmorilonita modificadas foram utilizadas como agente de reforço na preparação de filmes de nanocompósitos de matriz fenólica com o objetivo de melhorar as propriedades mecânicas deste material polimérico quando comparado com o material puro. A resina fenólica utilizada neste trabalho é a do tipo resol, utilizada comercialmente para a formulação de vernizes para revestimento de embalagens metálicas. No estudo foram utilizadas três argilas comerciais: Cloisite® sódica (Na) e argilas Cloisite® modificadas com sais quaternários de alquilamônio, de códigos 15A e 30B, objetivando verificar qual apresentaria melhor compatibilidade com a matriz fenólica. Para a preparação de filmes poliméricos uniformes, isentos de defeitos como bolhas, foi feita, de forma preliminar, a seleção de um ciclo de cura apropriado. Como a formação de bolhas é intrínseco à cura da resina fenólica resol, a definição de um esquema de tratamento térmico de cura apropriado constituiu-se em etapa crítica no processo de preparação dos compósitos de resina fenólica/argila montmorilonita modificada. Os filmes curados isentos de defeitos foram caracterizados por difração de raios X, análise termomecânica dinâmica (DMA) e calorimetria exploratória diferencial (DSC). Os resultados das análises de DRX mostraram para os compósitos preparados com as argilas modificadas 15A e 30B manutenção e até mesmo redução do espaçamento basal da estrutura cristalina das argilas, indicando não ter ocorrido intercalação do polímero nessas argilas; enquanto que para a argila Cloisite® Na ocorreu aumento do espaçamento basal. Os resultados de DMA mostraram para a maioria das amostras aumento no módulo de armazenamento em baixa e alta temperatura. Por último, a análise de DSC mostrou redução na temperatura de transição vítrea nos compósitos preparados com as argilas modificadas 15A e 30B, e elevação na composição de 5% da argila Cloisite® Na. Os resultados indicam o potencial de reforço mecânico de resinas fenólicas com argilas lamelares do tipo montmorilonita sem a necessidade de modificação química. / Unlike most polymers, phenolic resins are characterized by having a large number of applications because of its superior fire resistance and low emission of smoke and its excellent level of thermal and chemical resistance, and low cost. However, due to its three dimensional structure, characterized by a high degree of crosslinking, this type of resin has low toughness and fracture resistance. Thus, to ensure their good performance, it is necessary to make enhancements in their formulation or adding strengthening agents so as to compensate for these deficiencies due to its structure. There are numerous materials that usually are incorporated into the phenolic matrix. Besides the preparation of polymer blends in which one phase consists of an elastomer or a thermoplastic, the introduction of agents such as fibrous reinforcement is also used. Examples of reinforcing agents: vegetable fibers, glass and carbon fibers, carbon black, clay and others. The mixture of polymer clays may cause the formation of nanocomposites in order to obtain excellent combination of fracture strength, toughness, conductivity, heat resistance and reduced permeability to gases and liquids when compared with the pure polymer. In this work, modified montmorillonite clays were used as a reinforcing agent in the preparation of nanocomposite films of phenolic matrix with the aim of improving the mechanical properties of polymer materials when compared with the pure material. The phenolic resin used in this work is that of the resol type, used commercially for the formulation of varnish for coating metal containers. The study used three types of commercial clay: Cloisite® sodium (Na) and Cloisite® clays modified with quaternary alkylammonium salts, codes 15A and 30B in order to verify which present better compatibility with the phenolic matrix. For the preparation of uniform polymeric films, free of defects such as bubbles, was preliminarily selected a suitable cure cycle. As the bubble formation is intrinsic to the cure of resol phenolic resin, the definition of a heat treatment scheme is a critical step in the process of preparing composites of phenolic resin/montmorillonite clay. The cured films free of defects were characterized by X-ray diffraction (DRX), dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). The results of XRD analysis showed the composites prepared with the modified clays 15A and 30B maintained and even reduced the basal spacing within the clay crystal structure, indicating not having occurred polymer intercalation of the clay; for the Cloisite® Na clay DRX has shown increased basal spacing. DMA results showed for most of the samples increase in storage modulus at low and high temperatures. Finally, DSC analysis showed a reduction in glass transition temperature of the composites prepared with the modified clays 15A and 30B, and an increase in the composition of 5% in the Cloisite® Na clay. The results indicate the potential of enhancement of phenolic resins mechanical properties with layered clays of montmorillonite without chemical modification.