Visando o desenvolvimento de materiais biodegradáveis para embalagens, blendas de amido/quitosana estruturadas com nanopartículas de montmorilonita (MMT) ou nanofibras de bambu (NFBs) em concentrações de (0,0; 0,5 e 1,0) g de NPs/100 g de polímero foram obtidas pelas técnicas de casting e extrusão. Os bionanocompósitos obtidos das duas técnicas foram caracterizados, bem como foi avaliada a influência da dispersão das nanopartículas sobre as principais propriedades físico-químicas dos bionanocompósitos. Para os filmes produzidos de blendas de amido/quitosana por casting, foram avaliadas as proporções de (5/0; 3,75/0,25; 2,5/2,5; 1,25/0,75 e 0/1) g/100 g base polímero, e a adição dos reforçadores na solução filmogênica. Observou-se uma dispersão assim como uma intercalação satisfatória da MMT nos bionanocompósitos, confirmadas pelas mudanças da cristalinidade devido ao deslocamento do pico característico de 7,2 º para 5,2 º; e os filmes estruturados com NFBs apresentaram variações nas frequências vibracionais dos arranjos moleculares indicando a formação de ligações fortes entre as blendas e os reforçadores. A partir da extrusão da mistura de homo pellets e pellets masterbatch, das blendas de amido/quitosana nas proporções de (100/0; 75/25 e 50/50) g/100 g, foram obtidos compósitos em processo contínuo os quais exibiram propriedades qualitativas satisfatórias assim como mudanças de cristalinidade e interações moleculares. Em relação às propriedades mecânicas, os bionanocompósitos apresentaram um aumento da resposta à tensão assim como da elongação e módulo de elasticidade em relação às concentrações dos reforçadores em cada umas blendas avaliadas. Por outro lado, tanto a formação das blendas como as interações dos reforçadores modificaram significativamente a rede tridimensional dos filmes em relação à taxa de transferência de vapor de água, obtendo-se valores de (155 e 139) g m-2 d-1 para os compósitos obtidos da blenda amido/quitosana 100/0 estruturados com (0,5 e 1,0) g MMT/100 g, respectivamente. Os valores de PVA obtidos são inferiores aos reportados por produtos comerciais como o (PBS) Bionolle™ (330 g m-2 d-1) e (PBAT) Ecoflex® (272 g m-2 d-1). Neste trabalho foi possível desenvolver um material promissor com características diferenciadas e alta aplicabilidade no setor de embalagens biodegradáveis para uso industrial. / Aiming at the development of biodegradable packaging materials, starch/chitosan blends structured with montmorillonite nanoparticles (MMT) or bamboo nanofibers (NFBs) at concentrations of (0.0,0.5 and 1.0) g NPs/100 g of polymer were obtained by the casting and extrusion techniques. The obtained bio-nanocomposites were characterized, as well as, how the dispersion of nanoparticles influenced the main physicochemical properties of the films. For the films from starch/chitosan blends produced by the casting method, the proportions of (5/0, 3.75/0.25, 2.5/2.5, 1.25/0.75 and 0/1) g/100 g based on polymer, were tested and the introducing of the reinforcers into filmogenic solution were evaluated. Satisfactory dispersion and exfoliation of MMT in bio-nanocomposites were confirmed by changes of crystallinity due to displacement of the characteristic peak from 7.2 ° to 5.2 °. In the same way, films structured with NFBs showed variations of the vibrational frequencies of the molecular arrangements indicating strong bonds between the polymer blends and the reinforcers. By the extrusion from the mixture of homo pellets and masterbatch pellets, from starch/chitosan blends at proportions of (100/0, 75/25 and 50/50) g/100 g, the obtained films have exhibited changes of the crystallinity and the molecular interactions. In relation to mechanical properties, the films presented increase of the tension response as well as the elongation and modulus of elasticity in relation to the reinforcer concentration in each evaluated blend. On the other hand, the formation of polymer blends and the interactions of reinforcers with the matrix changed significantly the three-dimensional network and consequently the water vapor transmission (WVT). Films produced from starch/chitosan 100/0, nanostructured with (0.5 and 1.0) g MMT/100 g, exhibited lower values of WVT 155 e 139) gm-2 d -1, respectively, when compared to commercial products such as Bionolle ™ (PBS) 330 g m-2 d-1) and (PBAT) Ecoflex® (272 g m-2 d-1). In this work, it was possible to develop a promising material with desired characteristics in the biodegradable packaging sector with wide application in the industry.

Orientador: Gustavo Paim Valença / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-26T07:00:33Z (GMT). No. of bitstreams: 1 Duarte_JulianaCanto_D.pdf: 4804028 bytes, checksum: 8a14cd7e6bdf26f6d7000302437af726 (MD5) Previous issue date: 2014 / Resumo: Foram realizadas fermentações em batelada do sorbitol, sacarose, glicerol e glicose por Propionibacterium acidipropionici livre em biorreatores. As fermentações do sorbitol forneceram a maior concentração final de ácido propiônico (39,5±5,2 g L-1) e as fermentações da glicose forneceram a menor concentração final de ácido propiônico (23,9±2,1 g L-1). Apenas as fermentações do glicerol produziram n-propanol e sua concentração final foi de 1,7±0,1 g L-1, além disso, o ácido acético não foi produzido nas fermentações do glicerol. As fermentações da sacarose forneceram a maior concentração final de ácido acético (10,9±0,0 g L-1). O maior valor de produtividade do ácido propiônico foi obtido nas fermentações do sorbitol (0,60 g L-1 h-1). Fermentações do sorbitol e da sacarose em batelada utilizando células de P. acidipropionici livres e imobilizadas em montmorilonita K10 foram realizadas em três ciclos sequenciais com reciclo celular. As concentrações finais de ácido propiônico para as fermentações do sorbitol com células livres foram 39,5±5,2; 35,8±1,4 e 34,4±1,9 g L-1 e para células imobilizadas foram 33,1±0,7; 37,2±0,6 e 36,6±0,4 g L-1, para o primeiro, segundo e terceiro ciclos sequenciais, respectivamente. O maior valor de produtividade e de rendimento do ácido propiônico nas fermentações do sorbitol foi obtido para o primeiro ciclo com células livres: 0,60 g L-1 h-1 e 0,613 g g-1, respectivamente. As concentrações finais de ácido propiônico para as fermentações da sacarose com células livres foram 33,4±0,3; 31,3±0,9 e 31,1±0,1 g L-1 e para células imobilizadas foram 26,9±0,6; 29,1±0,3 e 29,5±0,8 g L-1 para o primeiro, segundo e terceiro ciclos sequenciais, respectivamente. A produtividade e o rendimento do ácido propiônico foram maiores no primeiro ciclo para células livres: 0,48 g L-1 h-1 e 0,409 g g-1, respectivamente. Foram realizadas co-fermentações de glicose:glicerol em duas razões mássicas (1:1 e 2:1) em batelada utilizando P. acidipropionici livre e imobilizada em montmorilonita K10. Apenas nas co-fermentações foi observada a produção do ácido lático e trealose além dos ácidos acético, succínico e propiônico. A maior concentração final de ácido propiônico foi obtida para as co-fermentações glicose:glicerol de razão mássica 2:1 com células de P. acidipropionici livres (31,4±0,3 g L-1) e a menor concentração final foi obtida nas co-fermentações de razão mássica 1:1 para células imobilizadas (23,9±0,8 g L-1). O ácido acético foi produzido apenas nas co-fermentações de razão mássica 2:1 para células livres (0,3±0,4 g L-1) e imobilizadas (1,1±0,2 g L-1). A maior concentração final de ácido lático foi obtida nas co-fermentações de razão mássica 1:1 para células livres (10,5±0,3 g L-1) e a menor concentração final foi obtida nas co-fermentações de razão mássica 2:1 para células livres (0,9±0,6 g L-1). A maior concentração final de trealose foi obtida nas co-fermentações de razão mássica 2:1 para células imobilizadas (12,1±0,1 g L-1) e a menor concentração final foi obtidas nas co-fermentações de razão mássica 2:1 para células livres (6,7±1,0 g L-1). O maior valor de produtividade e de rendimento do ácido propiônico foram obtidos nas co-fermentações de razão mássica 2:1 para células livres: 0,45 g L-1 h-1 e 0,412 g g-1, respectivamente / Abstract: Batch fermentations of sorbitol, sucrose, glycerol and glucose by free cells of Propionibacterium acidipropionici were conducted in bioreactors. Sorbitol fermentations yield the major final propionic acid concentration (39.5±5.2 g L-1) while glucose fermentations yield the minor result (23.9±2.1 g L-1). Only glycerol fermentations yield n-propanol (1.7±0.1 g L-1), furthermore, acetic acid was not generated in glycerol fermentations. In the other hand, sucrose fermentations yield great acetic acid final concentration (10.9±0.0 g L-1). The major propionic acid productivity was got in sorbitol fermentations (0.60 g L-1 h-1). Sorbitol and sucrose batch fermentations by free and immobilized cells of P. acidipropionici in montmorillonite K10 were carried out in three sequential cycles with cell reuse. The final propionic acid concentrations to sorbitol with free cells were 39.5±5.2; 35.8±1.4 e 34.4±1.9 g L-1 and with immobilized cells were 33.1±0.7; 37.2±0.6 e 36.6±0.4 g L-1, to the first, second and third sequential cycles, respectively. The major propionic acid productivity was got in the first cycle with free cells to sorbitol fermentations (0.60 g L-1 h-1). The major propionic acid yield was 0.613 g g-1 in the first cycle to free cells. The final propionic acid concentrations to sucrose fermentations with free cells were 33.4±0.3; 31.3±0.9 e 31.1±0.1 g L-1 and to immobilized cells were 26.9±0.6; 29.1±0.3 e 29.5±0.8 g L-1 to the first, second and third sequential cycles, respectively. The propionic acid productivity was major in the first cycle to free cells (0.48 g L-1 h-1). The major propionic acid yield was 0.409 g g-1 in the first cycle to free cells. Batch co-fermentations of glucose and glycerol were also conducted in two different mass ratios (1:1 and 2:1 glucose:glycerol) by P. acidipropionici free and immobilized in montmorillonite K10. The major propionic acid final concentration was got in glucose:glycerol 2:1 mass ratio co-fermentations by free cells (31.4±0.3 g L-1) while the minor final concentration was got with co-fermentation 1:1 mass ratio to immobilized cells (23.9±0.8 g L-1). Acetic acid was got only in co-fermentations 2:1 mass ratio to free (0.3±0.4 g L-1) and immobilized (1.1±0.2 g L-1) cells. The major propionic acid productivity was got in co-fermentations 2:1 mass ratio to free cells (0.45 g L-1 h-1). The major propionic acid yield was got in co-fermentations 2:1 mass ratio to free cells (0.412 g g-1). Only co-fermentations yield lactic acid and trehalose. The major lactic acid final concentration was got in co-fermentations 1:1 mass ratio to free cells (10.5±0.3 g L-1) and the minor final concentration was got in co-fermentations 2:1 mass ratio to free cells (0.9±0.6 g L-1). The major trehalose final concentration was got in co-fermentations 2:1 mass ratio to immobilized cells (12.1±0.1 g L-1) and the minor final concentration was got in co-fermentations 2:1 mass ratio to free cells (6.7±1.0 g L-1) / Doutorado / Engenharia de Processos / Doutora em Engenharia Quimica

Orientadores: Júlio Roberto Bartoli, Marcos Akira D'Ávila / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-20T09:53:53Z (GMT). No. of bitstreams: 1 Galvan_Danieli_M.pdf: 5419216 bytes, checksum: 3bbb69d4a9a4e73278d7ed9781b01c43 (MD5) Previous issue date: 2012 / Resumo: O presente trabalho estudou a preparação e caracterização de híbridos de polímero-argila, tendo a poli(acrilonitrila-butadieno-estireno) (ABS) como matriz polimérica e duas argilas montmorilonitas organofílicas (MMTO) distintas e sua mistura binária 1:1 como fases dispersas. O objetivo foi avaliar os efeitos das variáveis: tipo de argila e processo nas propriedades físicas dos híbridos de ABS/MMTO. A seleção das argilas MMTO comerciais (Cloisite 30B e Cloisite 20A) baseou-se nas possíveis afinidades químicas de cada uma delas com as distintas fases do terpolímero ABS. Na preparação dos híbridos através do processo de intercalação no estado fundido, em extrusora com rosca-dupla co-rotacional, foi investigado o efeito do torque da rosca (ou tempo de residência na extrusora), na dispersão das argilas na matriz ABS. Os compostos obtidos foram caracterizados através de análises de difração de raios-X, termogravimetria, ensaios de tração uniaxial e resistência ao impacto, flamabilidade e análises reológicas do fundido em regime permanente e oscilatório em altas e baixas taxas de cisalhamento. A difração de raios-X indicou que os híbridos obtidos apresentavam estruturas intercaladas, que proporcionaram aumento nos módulos de elasticidade por tração e por cisalhamento (armazenamento e perda). As análises reológicas dos híbridos ABS mostram o surgimento de um caráter pseudo-sólido, em especial para os híbridos contendo a MMTO com maior afinidade química (Cloisite 30B) à fase SAN do terpolímero. Este comportamento indicaria uma provável dispersão em escala nanométrica da Cloisite 30B nos híbridos ABS, seja como único componente na fase dispersa ou na sua mistura binária com a Cloisite 20A. Este resultado caracterizaria os materiais obtidos como nanocompósitos. Melhorias significativas nas propriedades mecânicas de tração também foram verificadas nos híbridos a base de Cloisite 30B. Já os ensaios de rigidez ao impacto e as análises de estabilidade térmica não apresentaram resultados satisfatórios. Entretanto a adição de MMTO eliminou o gotejamento de material incandescente apresentado pelo ABS durante a queima (norma UL 94 HB). A utilização de um menor torque na rosca, ou seja, maior tempo de residência dos híbridos na extrusora, parece favorecer a dispersão/intercalação das argilas na matriz de ABS. Entretanto, o efeito deste fator foi confundido com variações na concentração nominal de argila / Abstract: This work studied the preparation and characterization of hybrids of polymer-clay, where the polymeric matrix was the poly(acrylonitrile-butadiene-styrene) (ABS) and two different organically modified montmorillonite (OMMT) and their mixture (1:1) were used as dispersed phase. The aim was evaluate the effect of kind of clay and process parameters on physical properties of ABS/OMMT hybrids. Two grades of commercial OMMT organoclay (Cloisite 20A and Cloisite 30B) were investigated, with distinct chemical affinities according to terpolymer phases, and a binary mixture of these clays. The hybrids were prepared by melt intercalation process, on a co-rotating twin-screw extruder, the effect of screw torque (or residence time on extruder) on clay dispersion in the polymeric matrix was investigated. The hybrids were characterized by analysis of X-ray diffraction, thermogravimetry, mechanical properties (uniaxial tensile and impact strength), flammability, and rheological analysis in steady and oscillatory states, at high and low shear rates. The X-ray diffractions indicated that the ABS hybrids present an intercalated structure, which improved the tensile elastic modulus and shear modulus (storage and loss). The rheological analysis of ABS hybrids shows the emergence of a pseudo-solid character, especially to the hybrids containing the OMMT with higher chemical affinity (Cloisite 30B) to SAN phase of the terpolymer. This behavior would indicate a probable nanometric scale dispersion of the Cloisite 30B on the hybrids of ABS, even in the single form or in a binary mixture, likely characterizing them as nanocomposites. Significant improvements in the tensile mechanical properties were also verified on the hybrids based on Cloisite 30B. Nevertheless the impact strength and thermal stability analysis did not show satisfactory results. The flammability test (UL 94 HB standard) of ABS hybrids showed a non-dripping effect of incandescent material during burning. The use of a lower screw torque, higher residence time of the hybrids on extruder, seems to favor clay dispersion/intercalation on the ABS matrix, however, the effect of this factor was confounded with some variations in the organoclay nominal content / Mestrado / Ciencia e Tecnologia de Materiais / Mestre em Engenharia Química

This thesis investigate the structure of cadmium sulfide (CdS) nanoparticles and its stabilization by a surfactant - cetyltrimethylamonnium cation CTA+ and further describe interactions among stabilized CdS nanoparticles and the surface of the layered clay mineral - montmorillonite with using the molecular simulation methods. Initial models of the CdS nanoparticles were build for both crystal structures (Greenockit (G) and Hawleyit (H)). The preferred orientations of the molecules of CTA+ for both crystal types of CdS nanoparticles were found with respect to minimum energy. Prefered orientation is monolayer for Greenockite and bilayer for Hawleyite. Models with the preferred orientation of the molecules of CTA+ were placed on the surface of montmorillonite and after optimization, adsorption energy of CdS nanoparticles with its envelope and montmorillonite surface was calculated. All results and used procedures were compiled in the form of practice for the subject Computational experiments in the theory of molecules I - NBCM100 taught at MFF UK in Prague.

Um dos sistemas de proteção de substratos metálicos mais comumente empregado na indústria é o de tintas. Os fatores favoráveis à utilização das tintas em pó incluem a não utilização de solventes, facilidades de processamento/aplicação e possibilidade de reaproveitamento do material que não aderiu na superfície da peça. As características térmicas, mecânicas e químicas da tinta são influenciadas principalmente pelo tipo de resina utilizada. As tintas em pó híbridas (epóxi/poliéster) visam conciliar a característica de resistência ao intemperismo e ação dos raios UV com as características de resistência química e mecânica. Nas tintas em pó podem ser adicionados nanocargas que tem por finalidade melhorar as propriedades térmicas, mecânicas e químicas dos revestimentos. Outra característica das nanocargas é o baixo custo financeiro, decorrente da utilização de uma menor quantidade de carga, com elevado nível de desempenho. Dentre as nanocargas utilizadas, pode-se citar a mica muscovita e a montmorilonita 30B (MMT 30B) que, quando incorporadas às tintas, mesmo em baixas concentrações, apresentam propriedades de barreira superiores que às cargas convencionais. Este trabalho tem por objetivo desenvolver e caracterizar uma tinta em pó híbrida contendo diferentes teores de mica muscovita e MMT 30B. Os argilominerais foram incorporados numa formulação padrão de tinta em pó híbrida nas proporções de 2, 4 e 6% (m/m), separadamente. Antes da aplicação da tinta, os substratos metálicos foram submetidos a um pré-tratamento de fosfatização com fosfato de zinco. Após isso, a tinta em pó foi aplicada em painéis com dimensões de 70 x 120 x 0,65 mm de aço carbono AISI 1010 através de pulverização eletrostática. Os argilominerais, a tinta em pó e o revestimento foram analisados empregando diferentes técnicas de caracterização, tais como análise granulométrica, análise termogravimétrica (TGA), calorimetria exploratória diferencial (DSC), espectroscopia de infravermelho por transformada de Fourier (FTIR) e microscopia eletrônica de varredura por emissão de campo (MEVFEG). O efeito da incorporação dos argilominerais nas propriedades físicas e de proteção à corrosão das tintas foi avaliado com ensaios de medida de brilho, aderência, flexibilidade, resistência ao impacto, impedância eletroquímica (EIE), exposição à névoa salina (NS) e ensaio de chama. Para todas as tintas contendo argilominerais foi constatado o aumento da dureza superficial e a redução de brilho com o aumento do teor do argilomineral, sendo este efeito mais pronunciado com a adição de 6% (m/m) de MMT 30B. A aderência da tinta ao substrato não foi alterada pela presença dos argilominerais. As tintas contendo mica muscovita apresentaram melhores resultados nos ensaios de resistência ao impacto e de flexibilidade quando comparados as tintas contendo MMT 30B, nas concentrações testadas. A amostra TH/6/MICA apresentou melhor resultado no ensaio de impedância eletroquímica em relação aos outros sistemas estudados. No ensaio de névoa salina todas as amostras apresentaram elevada proteção à corrosão. Não foram observados bolhas ou pontos de corrosão na superfície de nenhuma das amostras. Porém, no ensaio subsequente de migração subcutânea, a amostra TH/2/MMT 30B foi a que apresentou maior desplacamento. No ensaio de chama, as tintas com incorporação de mica muscovita apresentaram melhores resultados que as tintas com MMT 30B. Após a análise de todos os ensaios, conclui-se que a adição de mica muscovita na proporção de 4% resultou em uma tinta com melhores propriedades térmicas, mecânicas e químicas. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior. / One of metallic substrates protection systems most commonly used in the industry is the paint. Factors favorable to the use of powder coatings include non-use of solvents, processing facilities/application and the possibility of reuse of material that did not adhere to the surface of the pieces. The thermal, mechanical and chemical characteristics of the obtained paint are influenced principally by the type of resin used. Hybrid (epoxy/polyester) powder coatings aimed at reconciling the weathering resistance characteristic and action of UV rays with the chemical resistance and mechanical characteristics. In the powder coatings can be added nanofillers which aims to improve the thermal, mechanical and chemical coatings. Another feature of nanofillers is the low financial cost resulting from the use of a lesser amount of filler, with a high level of performance. Among the nanofiller used, it can be cited muscovite mica and montmorillonite 30B (MMT 30B) that, when incorporated into the coatings, even at low concentrations, have higher barrier properties than conventional fillers. This work aims to develop and characterize a hybrid powder coating containing different amounts of muscovite mica and MMT 30B. Clayminerals have been incorporated in a standard formulation hybrid powder coatings in proportions of 2, 4 and 6% (w/w). Before applying the coating, the metal substrates were subjected to a pretreatment phosphating with zinc phosphate. After this, the powder paint was applied to panels with dimensions 70 x 120 x 0.65 mm carbon steel AISI 1010 through electrostatic spraying. The clayminerals, the powder paint and coating were analyzed using various characterization techniques, such as particle size analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), infrared spectroscopy in Fourier transform (FTIR) and scanning electron microscopy for field emission (SEM-FEG). The effect of the incorporation of clayminerals in the physical properties and corrosion protection of coatings was evaluated with brightness measurement tests, adhesion, flexibility, impact resistance, electrochemical impedance spectroscopy (EIS), exposure to fog saline (NS) and flame test. For all coatings containing clayminerals was found to increase the surface hardness of the coating and reduced gloss with increasing clay content, this being more pronounced effect with the addition of 6% (w/w) of MMT 30B. The adhesion of the coating to the substrate was not altered by the presence of clayminerals. The coatings containing mica muscovite showed better results in impact resistance tests and flexibility when compared to coatings containing MMT 30B. The sample TH/6/MICA showed better results in the electrochemical impedance test in relation to other systems studied. In the salt spray test all samples showed high corrosion protection. There were no blistering or corrosion spots on the surface of any of the samples. However, in the subsequent test of subcutaneous migration, the sample TH/2/MMT 30B showed the greatest peeling. In the flame test, coatings with incorporation of muscovite mica showed better results than coatings with MMT 30B. After analyzing all the tests, it is concluded that the addition of muscovite mica in the proportion of 4% resulted in an paint with improved thermal, mechanical and chemical properties.

The effect of incorporation two clays; layered double hydroxides (LDH) and montmorillonite layered silicates (MLS) in linear low density polyethylene (PE) matrix was investigated. MLS and LDH were added of 5, 15, 30 and 60 weight percent in the PE and compounded using a Brabender. Ground pellets were subsequently compression molded. Dispersion of the clays was analyzed using optical microscopy, SEM and XRD. Both the layered clays were immiscible with the PE matrix and agglomerates formed with increased clay concentration. The thermal properties were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Both clays served as nucleation enhancers increasing recrystallization temperatures in the composites. Flame retarding properties were determined by using the flammability HVUL-94 system. LDH indicated better flame retarding properties than MLS for PE. The char structure was analyzed by environmental scanning electron microscopy. Mechanical properties were studied by tensile testing and Vickers microhardness testing apparatus.

Available instruments for viscosity and rheologic measurements necessitate disruption of the system under test prior to observations. Generally, the gel structure of a thixotropic clay must be disturbed by shaking, pouring into a container for testing, and again upon insertion into the sample of the bob, spindle or paddle of the instrument. Also, these instruments yield a single point reading which is only a final or average value, depending upon the instrument. The occurrences during the test itself cannot be observed. Accordingly? it seemed feasible to determine, if possible, what other rheologic factors are involved in the breakdown of ·the gel structure of a thixotropic clay dispersion. The objective of the study was to design and test an instrument which would not require disturbing the sample before testing, which would give minimal destruction of the sample upon entry of the test probe into the sample, and which would give complete permanent recordings throughout the time of testing.

This dissertation describes a new electrochemical synthesis of novel composite materials based on montmorillonite (MMT) clay and intrinsically conducting polyaniline (PANI). PANI was successfully incorporated into MMT galleries to form PANI−MMT nanocomposites. Electropolymerization of anilinium ions which are intercalated inside the clay layers have been carried out at a constant applied potential. The synthetic conditions have been optimized taking into account the effect of concentration of aniline, magnetic stirring and potential cycling. The resulting organic-inorganic hybrid material, PANI-MMT has been characterized by various physicochemical techniques. Results of elemental analysis show that nanocomposite contains only 10 % of conducting PANI. Formation of PANI inside the clay tactoid has been confirmed by the expansion of inter layer distance of MMT as revealed by X-ray diffraction studies. Relatively lower interlayer expansion for PANI-MMT than that of anilinium-MMT indicates the higher stereoregularity in PANI-MMT which has strong influence on electrical properties of nanocomposites. Infrared spectroscopy studies reveal the presence of physicochemical interaction, probably hydrogen bonding, between clay and polyaniline. Cyclic voltammetry studies indicate that presence of electroinactive clay does not influence the electrochemical activity of PANI. Electrochromic behaviour of PANI-MMT nanocomposites have been studied using in situ UV-Vis spectroscopy which reveals that electrochromism of PANI in the composite material has been retained. One of the main technological applications of conducting polymers, particularly PANI, is in the area of corrosion protection of active metals. PANI-MMT nanocomposites synthesized using the present method and a chemically synthesized PANI which is soluble in organic solvents have been used to protect C45 steel surface against corrosion. Corrosion studies have been performed using electrochemical impedance measurements(EIM)and anodic polarization studies. Electrochemical impedance data has been analyzed using a suitable equivalent circuit. Corrosion protection of steel offered by both PANI-MMT and organically soluble PANI is evident form the increase in the value of charge transfer resistance of the coated steel surfaces. Time dependent EIM measurements reveal that charge transfer resistance gradually decreases with time, however, the values are much higher than that of uncoated surfaces. Two capacitive loops, one at higher and another at lower frequencies, observed in the Nyquist plots have been assigned to the electrical properties of coating material (in the present case, PANI-MMT or soluble PANI) and electrochemical process at the interface, respectively. An anodic shift in the corrosion potential, a decrease in the corrosion rate and a significant increase in the polarization resistance indicate a significant anti-corrosion performance of both PANI-MMT nanocomposite and organically soluble PANI deposited on the protected steel surface. / Diese Dissertation beschreibt eine neue elektrochemische Synthese neuartiger Compositmaterialien basierend auf dem Tonmineral Montmorillonite (MMT) und intrinsisch leitfähigem Polyanilin (PANI). Die Elektropolymerisation von Aniliniumionen, welche in die Tonmineralschichten eingebaut sind, wurde bei einem konstanten Potenzial durchgeführt. Das resultierende organisch-anorganische Hybridmaterial PANI-MMT wurde mit verschiedenen physikochemischen Methoden charakterisiert. Die Ergebnisse der Elementaranalyse zeigen, dass nur 10 % des Nanocompositmaterials aus leitfähigem PANI bestehen. Die Vergrößerung des Zwischenschichtabstandes von MMT, die bei Röntgendiffraktometrieuntersuchungen beobachtet wurde, lässt auf die Bildung von PANI innerhalb der Tonmineral-Taktoide schließen. IR-spektroskopische Untersuchungen deuten auf das Vorhandensein von Wechselwirkungen physikochemischer Art, wahrscheinlich Wasserstoffbindungen zwischen dem Tonmineral und Polyanilin, hin. Untersuchungen mit zyklischer Voltammetrie zeigten, dass die Anwesenheit von elektroinaktivem Tonmineral die elektrochemische Aktivität von PANI nicht beeinflusst. Das elektrochrome Verhalten von PANI-MMT Nanocompositen wurde mit UV-Vis-Spektroskopie untersucht, wobei sich herausstellte, dass das elektrochrome Verhalten vom PANI im Compositmaterial erhalten bleibt. Eines der technologischen Hauptanwendungsgebiete von leitfähigen Polymeren, insbesondere von PANI, ist der Korrosionsschutz von aktiven Metallen. PANI-MMT Nanocomposite die mit der angegebenen Methode (elektrochemisch) synthetisiert wurden und chemisch synthetisiertes in organischen Medien lösliches PANI wurden zum Korrosionsschutz von C45 Stahl eingesetzt. Die Korrosionsuntersuchungen wurden mit Hilfe von elektrochemischen Impedanzmessungen (EIM) und anodischen Polarisationsuntersuchungen durchgeführt. Der von PANI-MMT und von in organischen Medien löslichem PANI gebotene Korrosionsschutz ist wahrscheinlich auf die Zunahme des Ladungsdurchtritts widerstandes der beschichteten Stahloberfläche zurückzuführen. Die anodische Verschiebung des Korrosionspotenzials, eine Verringerung der Korrosions-geschwindigkeit und eine deutliche Zunahme des Polarisationswiderstandes sind eindeutige Hinweise für das Antikorrosionsvermögen von PANI-MMT und auch von in organischen Medien löslichem PANI, welche auf der zu schützenden Stahloberfläche abgeschieden wurden.

Amino derivatives of polycyclic aromatic hydrocarbons are well-known chemical carcinogens which should be carefully monitored in our environment. They are amenable to anodic oxida- tion on suitable solid or paste electrodes. This fact was exploited for voltammetric determina- tion of 4-aminobiphenyl on unmodified carbon paste electrode and carbon paste electrodes modified by montmorillonite and sepiolite. The optimum pH of BR buffer for measurement on unmodified carbon paste electrode is pH 2, pH 10 for CPE-SEP and pH 11 for CPE-MMT. It was possible to increase sensitivity of the determination using adsorptive stripping voltam- metry on modified electrodes. The optimum time for accumulation of 4-aminobiphenyl is 5 minutes. The limits of quantification of the order of 10−6 mol dm−3 were obtained for each electrode. After accumulation, the limits of quantification decreased to the 10−7 mol dm−3 . The newly developed method was tested for the determination of 4-aminobiphenyl in model sam- ples of drinking and river water, reaching limits of quantification of the order of 10−7 mol dm−3 .

The compacted bentonites are used as buffer and backfill materials for engineering barriers for high-level nuclear waste repositories located underground. For this purpose, it is very important to evaluate the swelling characteristics of this clay. The swelling capacity is one of the most important properties of the bentonite clay. The swelling behaviour is due two mechanisms, the crystalline swelling and the osmotic swelling. These mechanisms produce an increase in the distance between the layers of montmorillonite which is one component of bentonite. The result of the swelling capacity is the swelling pressure. It has been studied in several investigations. The results of experimental tests have been collected and compared in this thesis, considering only the Na-dominant bentonite and sand and distilled water as test solution. The experimental tests show that there is only an unique relation between different bentonites in the Na-dominant bentonite and sand mixture swollen depending on its final dry density. Also, the relation between the swelling pressure and the clay void ratio shows the mechanism of the swelling pressure. On the other hand, a mechanistic model is used to predict the swelling pressure of fully saturated bentonite and sand mixture in distilled water. Firstly, it has been compared with the results of experimental tests and it should be pointed out that the model gives good predictions. In addition, the model has been used to make sensitivity analysis with different parameters of bentonite. The most important conclusions in this section show that the swelling pressure mainly depends on the distance among particles. Also, the sensitivity analyses indicate which parameters should be fitted more carefully for future studies to validate this model with different bentonites.