Thesis (M.S.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains xi, 71 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 69-71).

Thesis (M.S.)--University of Texas at El Paso, 2009. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (Ph.D)--Polymer, Textile and Fiber Engineering, Georgia Institute of Technology, 2010. / Committee Chair: Jacob. Karl; Committee Member: Griffin. Anselm; Committee Member: Tannenbaum. Rina; Committee Member: Thio. Yonathan S; Committee Member: Yao. Donggang. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (Ph.D)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009. / Committee Chair: Perry, Joseph W.; Committee Member: Kippelen, Bernard; Committee Member: Lyon, L. Andrew; Committee Member: Marder, Seth R.; Committee Member: Whetten, Robert L. Part of the SMARTech Electronic Thesis and Dissertation Collection.

A presente dissertação tem por objetivo apresentar um estudo quanto à influência da adição de nanocargas nas proprie!dades térmicas, morfológicas, físicas e anticorrosivas de tintas em pó base resina epóxi. Nanocompósitos poliméricos aplicados a tinta em pó com teores de 2 e 4 % de montmorilonita organofílica (OMMT) (p/p) foram obtidos no estado ·fundido em extrusora dupla-rosca co-rotante, em diferentes velocidades de processamento. As tintas em pó foram aplicadas em substratos de aço-carbono por pulverização eletrostática. Os resu ltados obtidos demonstram que os parâmetros utilizados para a cura em estufa (200 °C por 1 O minutos) das tintas foram satisfatórios, não sendo observados picos exotérmicos nos termogramas de calorimetria exploratória diferencial (DSC). As análises térmicas demonstraram que a incorporação de OMMT resultou no aumento da temperatura de máxima degradação para as amostras antes da cura, e apresentou pouca influência nos revestimentos após a cura, apresentando ainda redução da reatividade (b.Hreação) das tintas em pó base epóxi com o aumento da velocidade de processamento, de 200 para 400 rpm. As análises morfológicas de difração de raios X (DRX) e microscopia eletrônica de transmissão (MET) indicaram a presença de estruturas com predominância esfoliada para os nanocompósitos, com boa dispersão da OMMT na matriz epóxi. A incorporação dos teores de 2 % (p/p) de OMMT, para ambas as velocidades de! processamento, resultou em revestimentos com melhores propriedades de resistência ao impacto, resistência a flexibil idade e de brilho. Os revestimentos obtidos com teores de 4 % de OMMT (p/p) apresentarem melhor desempenho quanto às propri1edades térmicas e resistência a corrosão, conforme análises de TGA e de exposição à névoa salina, respectivamente. As medidas de migração subcutânea realizadas após o ensaio de exposição à névoa salina indicaram revestimentos com melhores propriedades de barreira para as amostras com OMMT, corroborado pelos resultados de espectroscopia de impedância eletroquímica (ElE). / Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 2015-10-07T13:01:23Z No. of bitstreams: 1 Dissertacao Diego Piazza.pdf: 24298065 bytes, checksum: ceb0efa8d78e26b1bbd45581c9a739fe (MD5) / Made available in DSpace on 2015-10-07T13:01:23Z (GMT). No. of bitstreams: 1 Dissertacao Diego Piazza.pdf: 24298065 bytes, checksum: ceb0efa8d78e26b1bbd45581c9a739fe (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico, CNPq / The objective of this dissertation is to present a study of the influence of the addition of nanoclays on thermal, morphological, physical and anticorrosive properties of powder coatings epoxy resin based. Polymeric nanocomposites applied of powder coatings with leveis of 2 and 4 % of orgianophilic montmorillonite (OMMT) (w/w) were obtained in the melt state in extruder twin-screw co-rotation at different processing speeds. The powder coatings were applied to carbon steel substrates by electrostatic spraying. The results show that the parameters used for curing (200 °C for 10 minutes) the coatings were satisfactory, exothermic peaks were not observed in thermograms of differential scanning calorimetry (DSC). Thermal analysis showed that the incorporation of OMMT resulted in increasing the temperature of degradation maximum for the samples before curinn, and little influence in coatings after curing, also reduces the reactivity (~H reaction) of powder coatings based epoxy with increasing processing speed (400 rpm). The morphological analysis of X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicated the presence of predominantly exfoliated structures for the nanocomposites, with good dispersion of OMMT in the epoxy matrix. The incorporation of th~e leveis of 2 % of OMMT (w/w), for both processing speed, resulted in coatings with improved impact strength, endurance, flexibility and gloss. The coatings obtained with leveis of 4 % of OMMT (w/w) having better performance on the thermal proiPerties and corrosion resistance, as thermal analysis and exposure to salt spray, respectively. Measures of subcutaneous migration made after salt spray teslting indicated coatings with better barrier properties for samples with OMMT, with was corroborated by electrochemical impedance spectroscopy (EIS) results.

Este trabalho teve como objetivo avaliar a influência da adição do plastificante trietilcitrato (TEC) nas propriedades térmicas e mecânicas de nanocompósitos poliméricos biodegradáveis à base de poli(hidroxibutirato-co-hidroxivalerato) (PHBV). Os nanocompósitos foram obtidos utilizando diferentes filossilicatos – montmorilonita não modificada (MMT), montmorilonita modificada organicamente (OMMT) e haloisita (HNT) – na proporção de 3% em massa, e TEC na proporção de 10% em massa, por meio de processamento no estado fundido. Ensaios de extração com solvente e exsudação, juntamente com microscopia eletrônica de varredura (MEV), sugeriram boa compatibilidade entre o TEC e o PHBV. Com relação à morfologia, micrografias de MEV mostraram alguns aglomerados em sistemas contendo MMT, o que foi confirmado pelo mapeamento realizado por espectroscopia de energia dispersiva de raios X (EDS). Para os demais sistemas, os resultados de MEV/EDS e de difração de raios X (XRD) sugeriram uma distribuição homogênea das nanopartículas pela matriz do PHBV, principalmente na presença do TEC. Os resultados de XRD também indicaram que a adição de nanopartículas e plastificante não causaram alterações na estrutura cristalina do PHBV. As curvas de calorimetria exploratória diferencial (DSC) mostraram que a temperatura de fusão diminuiu para todas as amostras, em comparação ao PHBV puro. A temperatura de cristalização aumentou para os nanocompósitos não plastificados e para o sistema PHBV/TEC/HNT, comportamento atribuído ao efeito nucleante das argilas. Além disso, os nanocompósitos em geral apresentaram-se mais cristalinos que o PHBV puro. Os ensaios da análise térmica dinâmico-mecânica (DMA) confirmaram o efeito de plastificação por meio da redução na temperatura de transição vítrea (Tg) de todas as amostras com TEC. Observou-se um aumento geral da resistência ao impacto, porém, este foi dependente do grau de dispersão das nanopartículas na matriz. O conjunto de resultados revelou o potencial da HNT quando comparada à MMT. De maneira geral, os nanocompósitos de PHBV plastificados apresentaram melhores características de processamento e desempenho mecânico, o que torna a adição de plastificantes uma alternativa para viabilizar a utilização deste polímero em diversas aplicações industriais. / Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 2015-11-19T15:32:19Z No. of bitstreams: 1 Dissertacao Suelen Dias Fagundes Brandolt - versão final.pdf: 3994012 bytes, checksum: d3659638633be206cdc3fa518208eb39 (MD5) / Made available in DSpace on 2015-11-19T15:32:19Z (GMT). No. of bitstreams: 1 Dissertacao Suelen Dias Fagundes Brandolt - versão final.pdf: 3994012 bytes, checksum: d3659638633be206cdc3fa518208eb39 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, CAPES. / The aim of this work was to evaluate the influence of the addition of a plasticizer – triethyl citrate (TEC) – on the thermal and mechanical properties of biodegradable polymer nanocomposites based on poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV). The nanocomposites were obtained using 3 wt% of different phyllosilicates – unmodified montmorillonite (MMT), organically modified montmorillonite (OMMT), and halloysite (HNT) – and 10 wt% of TEC by melt mixing. The exudation and solvent extraction tests, together with scanning electron microscopy (SEM), suggested a good compatibility between TEC and PHBV. The morphological analysis by SEM identified some agglomerated structures in the systems containing MMT. This result was confirmed by X-ray energy dispersive spectroscopy (EDS). For the other samples, the results of SEM/EDS and X-ray diffraction (XRD) suggested a homogeneous distribution of nanoparticles within the PHBV matrix, mainly in the presence of TEC. XRD results also indicated that the addition of nanoparticles and plasticizer did not change the crystalline structure of PHBV. The differential scanning calorimetry (DSC) indicated a reduction in the melting temperature of the samples compared to the neat PHBV. The crystallization temperature increased for the nanocomposites without TEC and for the PHBV/TEC/HNT system. This can be attributed to the nucleating effect of the clays. Moreover, the nanocomposites were more crystalline than the neat PHBV. Dynamic mechanical analysis (DMA) results confirmed the plasticizing effect by the reduction of the glass transition temperature (Tg) of all samples containing TEC. It was observed a general increase in the impact strength. However, this was dependent on the degree of dispersion of nanoparticles in the polymer matrix. The set of results revealed the potential of HNT when compared to MMT. In general, the plasticized nanocomposites exhibited better processing characteristics and mechanical performance, which makes the plasticizing an alternative to facilitate the use of this polymer in various industrial applications.

Este trabalho teve como objetivo avaliar a influência da adição do plastificante trietilcitrato (TEC) nas propriedades térmicas e mecânicas de nanocompósitos poliméricos biodegradáveis à base de poli(hidroxibutirato-co-hidroxivalerato) (PHBV). Os nanocompósitos foram obtidos utilizando diferentes filossilicatos – montmorilonita não modificada (MMT), montmorilonita modificada organicamente (OMMT) e haloisita (HNT) – na proporção de 3% em massa, e TEC na proporção de 10% em massa, por meio de processamento no estado fundido. Ensaios de extração com solvente e exsudação, juntamente com microscopia eletrônica de varredura (MEV), sugeriram boa compatibilidade entre o TEC e o PHBV. Com relação à morfologia, micrografias de MEV mostraram alguns aglomerados em sistemas contendo MMT, o que foi confirmado pelo mapeamento realizado por espectroscopia de energia dispersiva de raios X (EDS). Para os demais sistemas, os resultados de MEV/EDS e de difração de raios X (XRD) sugeriram uma distribuição homogênea das nanopartículas pela matriz do PHBV, principalmente na presença do TEC. Os resultados de XRD também indicaram que a adição de nanopartículas e plastificante não causaram alterações na estrutura cristalina do PHBV. As curvas de calorimetria exploratória diferencial (DSC) mostraram que a temperatura de fusão diminuiu para todas as amostras, em comparação ao PHBV puro. A temperatura de cristalização aumentou para os nanocompósitos não plastificados e para o sistema PHBV/TEC/HNT, comportamento atribuído ao efeito nucleante das argilas. Além disso, os nanocompósitos em geral apresentaram-se mais cristalinos que o PHBV puro. Os ensaios da análise térmica dinâmico-mecânica (DMA) confirmaram o efeito de plastificação por meio da redução na temperatura de transição vítrea (Tg) de todas as amostras com TEC. Observou-se um aumento geral da resistência ao impacto, porém, este foi dependente do grau de dispersão das nanopartículas na matriz. O conjunto de resultados revelou o potencial da HNT quando comparada à MMT. De maneira geral, os nanocompósitos de PHBV plastificados apresentaram melhores características de processamento e desempenho mecânico, o que torna a adição de plastificantes uma alternativa para viabilizar a utilização deste polímero em diversas aplicações industriais. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, CAPES. / The aim of this work was to evaluate the influence of the addition of a plasticizer – triethyl citrate (TEC) – on the thermal and mechanical properties of biodegradable polymer nanocomposites based on poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV). The nanocomposites were obtained using 3 wt% of different phyllosilicates – unmodified montmorillonite (MMT), organically modified montmorillonite (OMMT), and halloysite (HNT) – and 10 wt% of TEC by melt mixing. The exudation and solvent extraction tests, together with scanning electron microscopy (SEM), suggested a good compatibility between TEC and PHBV. The morphological analysis by SEM identified some agglomerated structures in the systems containing MMT. This result was confirmed by X-ray energy dispersive spectroscopy (EDS). For the other samples, the results of SEM/EDS and X-ray diffraction (XRD) suggested a homogeneous distribution of nanoparticles within the PHBV matrix, mainly in the presence of TEC. XRD results also indicated that the addition of nanoparticles and plasticizer did not change the crystalline structure of PHBV. The differential scanning calorimetry (DSC) indicated a reduction in the melting temperature of the samples compared to the neat PHBV. The crystallization temperature increased for the nanocomposites without TEC and for the PHBV/TEC/HNT system. This can be attributed to the nucleating effect of the clays. Moreover, the nanocomposites were more crystalline than the neat PHBV. Dynamic mechanical analysis (DMA) results confirmed the plasticizing effect by the reduction of the glass transition temperature (Tg) of all samples containing TEC. It was observed a general increase in the impact strength. However, this was dependent on the degree of dispersion of nanoparticles in the polymer matrix. The set of results revealed the potential of HNT when compared to MMT. In general, the plasticized nanocomposites exhibited better processing characteristics and mechanical performance, which makes the plasticizing an alternative to facilitate the use of this polymer in various industrial applications.

A presente dissertação tem por objetivo apresentar um estudo quanto à influência da adição de nanocargas nas proprie!dades térmicas, morfológicas, físicas e anticorrosivas de tintas em pó base resina epóxi. Nanocompósitos poliméricos aplicados a tinta em pó com teores de 2 e 4 % de montmorilonita organofílica (OMMT) (p/p) foram obtidos no estado ·fundido em extrusora dupla-rosca co-rotante, em diferentes velocidades de processamento. As tintas em pó foram aplicadas em substratos de aço-carbono por pulverização eletrostática. Os resu ltados obtidos demonstram que os parâmetros utilizados para a cura em estufa (200 °C por 1 O minutos) das tintas foram satisfatórios, não sendo observados picos exotérmicos nos termogramas de calorimetria exploratória diferencial (DSC). As análises térmicas demonstraram que a incorporação de OMMT resultou no aumento da temperatura de máxima degradação para as amostras antes da cura, e apresentou pouca influência nos revestimentos após a cura, apresentando ainda redução da reatividade (b.Hreação) das tintas em pó base epóxi com o aumento da velocidade de processamento, de 200 para 400 rpm. As análises morfológicas de difração de raios X (DRX) e microscopia eletrônica de transmissão (MET) indicaram a presença de estruturas com predominância esfoliada para os nanocompósitos, com boa dispersão da OMMT na matriz epóxi. A incorporação dos teores de 2 % (p/p) de OMMT, para ambas as velocidades de! processamento, resultou em revestimentos com melhores propriedades de resistência ao impacto, resistência a flexibil idade e de brilho. Os revestimentos obtidos com teores de 4 % de OMMT (p/p) apresentarem melhor desempenho quanto às propri1edades térmicas e resistência a corrosão, conforme análises de TGA e de exposição à névoa salina, respectivamente. As medidas de migração subcutânea realizadas após o ensaio de exposição à névoa salina indicaram revestimentos com melhores propriedades de barreira para as amostras com OMMT, corroborado pelos resultados de espectroscopia de impedância eletroquímica (ElE). / Conselho Nacional de Desenvolvimento Científico e Tecnológico, CNPq / The objective of this dissertation is to present a study of the influence of the addition of nanoclays on thermal, morphological, physical and anticorrosive properties of powder coatings epoxy resin based. Polymeric nanocomposites applied of powder coatings with leveis of 2 and 4 % of orgianophilic montmorillonite (OMMT) (w/w) were obtained in the melt state in extruder twin-screw co-rotation at different processing speeds. The powder coatings were applied to carbon steel substrates by electrostatic spraying. The results show that the parameters used for curing (200 °C for 10 minutes) the coatings were satisfactory, exothermic peaks were not observed in thermograms of differential scanning calorimetry (DSC). Thermal analysis showed that the incorporation of OMMT resulted in increasing the temperature of degradation maximum for the samples before curinn, and little influence in coatings after curing, also reduces the reactivity (~H reaction) of powder coatings based epoxy with increasing processing speed (400 rpm). The morphological analysis of X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicated the presence of predominantly exfoliated structures for the nanocomposites, with good dispersion of OMMT in the epoxy matrix. The incorporation of th~e leveis of 2 % of OMMT (w/w), for both processing speed, resulted in coatings with improved impact strength, endurance, flexibility and gloss. The coatings obtained with leveis of 4 % of OMMT (w/w) having better performance on the thermal proiPerties and corrosion resistance, as thermal analysis and exposure to salt spray, respectively. Measures of subcutaneous migration made after salt spray teslting indicated coatings with better barrier properties for samples with OMMT, with was corroborated by electrochemical impedance spectroscopy (EIS) results.

The development of a "cradle-to-cradle" mindset with both material performance during utilization and end of life disposal is a critical need for both ecological and economic considerations. The main limitation to the use of the biopolymers is their mechanical properties. Reinforcements are therefore a good alternative but disposal concerns then arise. Thus the objective of this dissertation is to investigate a biopolymer nanocomposite where the filler is a synthetically prepared layer double hydroxide (inorganic interface); and a biopolymer paper (organic interface) based coating or laminate. The underlying issues driving performance are the packing density of the biopolymer and the interaction with the reinforcement. Since the polyhydroxyalkanoates or PHAs (the biopolymers used for the manufacture of the nanocomposites and coatings) are semicrystalline materials, the glass transition was investigated using dynamic mechanical analysis (DMA) and dielectric spectroscopy (DES), whereas the melt crystallization, cold crystallization and melting points were investigated using differential scanning calorimetry (DSC). Fourier transform infrared (FTIR) spectroscopy was used to estimate crystallinity in the coated material given the low thermal mass of the PHA in the PHA coating. The significant enhancement of the crystallization rate in the PHA nanocomposite was probed using DSC and polarized optical microscopy (POM) and analyzed using Avrami and Lauritzen-Hoffman models. Both composites showed a significant improvement in the mechanical performance obtained by DMA, tensile and impact testing. The degradation and decomposition of the two composites were investigated in low microbial activity soil for the cellulose paper (to slow down the degradation rate that occurs in compost) and in compost. An in-house system according to the American Society for Testing and Materials ASTM D-98 (2003) was engineered. Soil decomposition showed that PHA coating into and onto the cellulose paper can be considered to be a useful method for the assessment of the degradability of the biopolymer. PHA nanocomposite showed enhanced compostability.

Understanding the deformation mechanism in nanocomposites is critical to realizing a host of next-generation technologies like stretchable electronics, three-dimensional multifunctional surfaces, and nanoscale machines. Graphene’s unparalleled mechanical strength and stability – owing to its two-dimensional geometry, high intrinsic strength, and Young’s modulus – have opened up new opportunities to engineer composites of higher strength-to-weight ratios for various practical applications. The ability of graphene (Gr) to act as a strength enhancer depends on the interface interactions and the composite’s microstructure. Here we demonstrate a microstructure design of Cu-Gr-Cu nanolaminate that enhances the composite’s load-bearing capacity, improves the composite’s strength, and reduces its coefficient of friction. The mechanical and frictional properties of Cu-Gr-Cu nanolaminate were probed using the nanoindenter. A series of nanoindentations performed on Cu-Gr-Cu nanolaminate exhibit an effective yield strength of 320 MPa and effective flow strength of 0•.5 GPa. Scratch tests performed on the free surface of the Cu-Gr-Cu nanolaminate show a considerable decrease in the coefficient of friction from 0.3 to 0.2. The cantilever bending test performed on Cu-Gr-Cu nanolaminate showed an increase in flow strength and strain hardening compared to Cu-Cu. The enhancement in the mechanical and friction properties of Cu-Gr-Cu nanolaminate suggests a build-up of dislocations at the Cu-Graphene interface. FEA simulations of the nanoindentation on Cu-Gr-Cu nanolaminate confirm the effectiveness of graphene as a barrier to plastic deformation. The pile-up of dislocations at the Cu-Graphene interface implies large plastic strain gradients near the interface. We developed a strain gradient plasticity computational model of the beam bending experimental system based upon Gudmundson’s higher-order theory and implemented it as a user element in ABAQUS. A set of material parameters is identified that reproduce the experimental for