Neste trabalho foram obtidos nanocompósitos de polipropileno (PP) e argilas. Três tipos de PP com índices de fluidez de 1,5; 2,2 e 37,9 g/10min (230ºC/216kg) foram utilizados. O PP com maior índice de fluidez é um produto modificado com peróxido. Essas amostras de PP foram misturadas ao masterbatch da Nanocor nanoMax®-PP. Concentrações de masterbatch variando de 3 a 12% em peso foram utilizadas. Os compósitos foram obtidos em uma extrusora dupla rosca e em um misturador. O Masterbatch foi caracterizado por fluorescência de raios X, difração de raios X (DRX) e por espectroscopia no infravermelho (FTIR). Os compósitos foram caracterizados por DRX, microscopia ótica (MO) e de transmissão (MET), e reologicamente. A caracterização reológica foi realizada conduzindo ensaios de varredura de tempo e ensaios de Cisalhamento Oscilatório de Pequena Amplitude (COPA) no regime de viscoelasticidade linear. Ensaios utilizando uma matriz cônica que permite a avaliação da viscosidade elongacional foram também conduzidos. Com essa matriz foi também possível a avaliação da viscosidade de cisalhamento dos compósitos para taxas de cisalhamento que correspondem a regime de viscoelasticidade linear. Os resultados da caracterização do Masterbatch mostraram que este consiste de uma mistura de polipropileno enxertado com anidrido maleico e uma argila do tipo esmectita, predominantemente montmorilonita (MMT). O espaçamento basal das argilas nos compósitos obtidos foi maior do que aquele da argila no masterbatch para todos os compósitos, diminuindo com o aumento da concentração de masterbatch no compósito. A viscosidade dos compostos obtidos aumentou com o tempo durante os ensaios de varredura de tempo devido a variações morfológicas. Essas variações foram mais importantes quando a freqüência utilizada no ensaio era menor. Essas variações foram correlacionadas com a evolução da morfologia dos compostos em função do tempo. O módulo de armazenamento obtido nos ensaios de COPA a baixas frequências para os compósitos foi maior do que o módulo dos polímeros puros para concentrações de argila acima de 6%. Esse aumento do módulo foi muito mais intenso para o PP de maior índice de fluidez. Os ensaios de caracterização reológica utilizando a matriz cônica mostraram que os nanocompósitos não seguem a Regra de Cox-Merz e que para o PP de maior índice de fluidez a viscosidade elongacional aumenta com o aumento da concentração de masterbatch. / In this work nanocomposites of polypropylene (PP) were obtained. Three types of PP with melt flow rates of 1,5; 2,2 e 37,9 g/10min (230ºC/216kg) were used. The PP with the largest melt flow rate is a product modified with peroxide. These samples were mixed with PP masterbatch Nanocor nanoMax ®-PP. Masterbatch in different concentrations ranging from 3 to 12 wt%. The composites were obtained using a twin screw extruder and internal mixer. The masterbatch was characterized by X-ray fluorescence, X-ray diffraction (XRD) and infrared spectroscopy (FTIR). The composites were characterized by XRD, optical microscopy (OM) and transmission (TEM) and rheologically. The rheological characterization was made carrying out time sweep, small amplitude oscillatory shear (SAOS) tests in order to study the rheological behavior on the linear viscoelastic regime. Tests using a conical diewith which it is possible to measure elongational viscosity were also conducted. The shear viscosity at high shear rates was evaluated using a slit die The characterization results showed that the masterbatch is a mixture of polypropylene grafted with maleic anhydride and a smectite type clay, predominantly montmorillonite (MMT). The basal spacing of clay in the composites was greater than that of the clay within the masterbatch for every composites. It was shown to decrease with increasing concentration of masterbatch in the composite. The viscosity of composites increased during the time sweep experiments. This evolution of viscosity was attributed to changes of morphology of the composites. These variations were more important when the frequency used in the test was lower. The storage modulus obtained during COPA at low frequencies for composites was higher than the modulus of the pure polymers when the clay content was above 6%. This increase in modulus was greater for the lower melt flow index PP The rheological tests performed using the slit die showed that Cox-Merz rule was not valid for the composites. The elongational viscosity was shown to increase with increasing concentration of masterbatch.

Orientador: Fernando Alvarez / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-24T22:24:16Z (GMT). No. of bitstreams: 1 Antunes_ViniciusGabriel_M.pdf: 3019304 bytes, checksum: 07f935b74d9527a192ce26b38e17afda (MD5) Previous issue date: 2014 / Resumo: Os tratamentos de superfície a plasma são amplamente usados em diversas áreas de tecnologia, tais como: indústria metalmecânica, microeletrônica, plástico e medicina, para o crescimento de filmes finos, camadas protetoras em instrumentos e ferramentas de corte, funcionalização de superfícies plásticas, tecidos sintéticos, esterilização de instrumentos cirúrgicos e plasma reativo em semicondutores. Há alguns anos, uma nova família de filmes duros e protetores com baixo atrito compostos por nanoestrururas, tem sido intensamente pesquisada por apresentar propriedades particularmente interessantes, do ponto de vista da físico-química básica, como possíveis aplicações tecnológicas em que a demanda por desgaste, altas temperatura, e resistência mecânica são necessárias. A deposição de filmes finos, constituídos por nanocompósitos, e a compreensão de propriedades (mecânicas, elétricas, ópticas) desses novos materiais, gera um leque de possíveis aplicações tecnológicas. A partir de tais premissas, focalizamos o objetivo do trabalho em estudar a obtenção e caracterização das propriedades físico-químicas de filmes finos nanoestruturados (nanocompósitos), que contêm compostos de Ti, C, N, e O, utilizando a técnica de Deposição Química pela Decomposição do precursor líquido tetraetóxido de titânio (Ti(OC2H5)4) (PECVD, na sigla em inglês). Ressalta-se que o interesse em obter esses materiais, a partir do reagente em questão, reside no fato de que ele poderia substituir o uso de outros precursores de difícil manuseio, tais como o tetracloreto de titânio (TiCl4), o qual é normalmente utilizado em numerosas aplicações de deposições de filmes compósitos, mediante a técnica de PECVD, e cujo subproduto da reação gera reagentes altamente corrosivos. Em resumo, este trabalho contempla a caracterização da composição química, micro e nano estrutura de compósitos que contêm os compostos mencionados, em função das variáveis mais importantes de deposição. O presente estudo foi bem sucedido em obter nanocompósito e correlacionar a dependência das ligações químicas do material com os parâmetros mais importantes de deposição / Abstract: Plasma surface treatments are widely used in several technological areas (e.g., metallurgic industry, microelectronic, plastic industry, medicine) in order to obtain hard coatings on cutting tools and instruments, funtionalization of plastics and synthetic materials used in the textile industry, sterilization of chirurgic instruments, etching by reactive plasma in the semiconductor industry, etc. Recently, a new family of coatings deposited by plasma assisted techniques owing interesting physical chemical properties such as super-hardness, low friction and wear resistant, temperature and corrosion resistant, known as nano-composites, have been intensely studied.The objectives of this work is developing a nano composite containing Ti, C, N e O and understand as far as possible its physical and chemical properties. The material is obtained by plasma assisted enhanced chemical deposition (PECVD) using Titanium(IV) ethoxide ( (Ti(OC2H5)4) and N as precursors of the reaction. The importance of the attempt to use the cited precursor resides in the fact that it is a friendly liquid without corrosive o major toxic effects, as the normal precursors used in the actual industrial process (e.g., titanium tetrachloride, TiCl4). Summarizing, this work is focusing the research in the deposition and study of the physical and chemical properties of thin films nano composites obtained from Titanium(IV) ethoxide precursor. The study shows that the deposition procedure allows obtaining a material containing nanoscopics size crystallites of the compounds cited above. Finally, the relation of the material properties with the more important deposition parameters is discussed and presented / Mestrado / Física / Mestre em Física

Orientadores: Ana Rita Morales, Maria Aparecida Marin-Morales / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-22T13:30:08Z (GMT). No. of bitstreams: 1 Souza_PatriciaMoraesSinohara_M.pdf: 5897831 bytes, checksum: ff702db4dd4540ec41606b5fd8a007e3 (MD5) Previous issue date: 2013 / Resumo: Neste estudo, foram preparados nanocompósitos de PLA e argilas organofílicas Cloisite 20A e Cloisite 30B, pelo método de intercalação do fundido. Os materiais foram caracterizados mediante Difração de Raios-X (DRX), Microscopia Eletrônica de Transmissão (MET), Análise Termogravimétrica (TGA) e Calorimetria Diferencial Exploratória (DSC). A influência das argilas organofílicas no processo de biodegradação do PLA foi avaliada pela quantificação da taxa de mineralização do PLA e dos nanocompósitos pela norma ISO 14855-2, em condições simuladas de compostagem. Também foi avaliada a influência das argilas no processo de degradação hidrolítica do PLA, pela análise visual e monitoramento de peso molecular após os períodos de 15 e 30 dias de degradação em composto. Diante da falta de informação relacionada à ecotoxicidade de polímeros biodegradáveis, a avaliação de efeitos citotóxicos, genotóxicos e mutagênicos do composto orgânico após a degradação dos materiais foi realizada empregando o bioensaio com o organismo teste Allium cepa. Os nanocompósitos preparados apresentaram estrutura intercalada, evidenciada pela análise de DRX. As micrografias obtidas por MET permitiram a observação de diferentes níveis de dispersão, incluindo regiões esfoliadas. Foram verificadas, após a incorporação das argilas organofílicas, a redução da estabilidade térmica e o aumento do grau de cristalinidade do PLA, pelas análises de TGA e DSC, respectivamente. Com relação às medidas de mineralização, notou-se que a argila Cloisite 20A não apresentou influência significativa na biodegradação do PLA. Por outro lado, a argila Cloisite 30B levou à redução dos valores de mineralização comparados com o polímero puro, o que pode estar relacionado à atividade antimicrobiana de seu agente modificador. Na avaliação da degradação hidrolítica, notou-se que a presença de argilas organofílicas pode diminuir a taxa de degradação, possivelmente pela atuação de suas camadas como barreira. Ainda assim, mesmo no caso dos nanocompósitos, a redução do peso molecular foi significativa indicando que o processo de compostagem é favorável para a cisão de cadeia do polímero nos materiais em estudo. Na análise realizada por meio do bioensaio com o organismo teste Allium cepa, foi verificado que, após a degradação do PLA e dos nanocompósitos, o composto orgânico apresentou redução do índice mitótico e aumento da indução das alterações cromossômicas, de forma estatisticamente significativa em relação ao controle negativo do ensaio (água destilada). Pela comparação dos resultados obtidos para os nanocompósitos em relação ao polímero puro, não foram verificadas diferenças estatisticamente significativas. Os tipos de aberrações cromossômicas observadas indicam um efeito genotóxico dos materiais, possivelmente relacionado a uma ação aneugênica dos produtos de degradação do PLA / Resumo: Neste estudo, foram preparados nanocompósitos de PLA e argilas organofílicas Cloisite 20A e Cloisite 30B, pelo método de intercalação do fundido. Os materiais foram caracterizados mediante Difração de Raios-X (DRX), Microscopia Eletrônica de Transmissão (MET), Análise Termogravimétrica (TGA) e Calorimetria Diferencial Exploratória (DSC). A influência das argilas organofílicas no processo de biodegradação do PLA foi avaliada pela quantificação da taxa de mineralização do PLA e dos nanocompósitos pela norma ISO 14855-2, em condições simuladas de compostagem. Também foi avaliada a influência das argilas no processo de degradação hidrolítica do PLA, pela análise visual e monitoramento de peso molecular após os períodos de 15 e 30 dias de degradação em composto. Diante da falta de informação relacionada à ecotoxicidade de polímeros biodegradáveis, a avaliação de efeitos citotóxicos, genotóxicos e mutagênicos do composto orgânico após a degradação dos materiais foi realizada empregando o bioensaio com o organismo teste Allium cepa. Os nanocompósitos preparados apresentaram estrutura intercalada, evidenciada pela análise de DRX. As micrografias obtidas por MET permitiram a observação de diferentes níveis de dispersão, incluindo regiões esfoliadas. Foram verificadas, após a incorporação das argilas organofílicas, a redução da estabilidade térmica e o aumento do grau de cristalinidade do PLA, pelas análises de TGA e DSC, respectivamente. Com relação às medidas de mineralização, notou-se que a argila Cloisite 20A não apresentou influência significativa na biodegradação do PLA. Por outro lado, a argila Cloisite 30B levou à redução dos valores de mineralização comparados com o polímero puro, o que pode estar relacionado à atividade antimicrobiana de seu agente modificador. Na avaliação da degradação hidrolítica, notou-se que a presença de argilas organofílicas pode diminuir a taxa de degradação, possivelmente pela atuação de suas camadas como barreira. Ainda assim, mesmo no caso dos nanocompósitos, a redução do peso molecular foi significativa indicando que o processo de compostagem é favorável para a cisão de cadeia do polímero nos materiais em estudo. Na análise realizada por meio do bioensaio com o organismo teste Allium cepa, foi verificado que, após a degradação do PLA e dos nanocompósitos, o composto orgânico apresentou redução do índice mitótico e aumento da indução das alterações cromossômicas, de forma estatisticamente significativa em relação ao controle negativo do ensaio (água destilada). Pela comparação dos resultados obtidos para os nanocompósitos em relação ao polímero puro, não foram verificadas diferenças estatisticamente significativas. Os tipos de aberrações cromossômicas observadas indicam um efeito genotóxico dos materiais, possivelmente relacionado a uma ação aneugênica dos produtos de degradação do PLA / Abstract: In this study, nanocomposites of PLA with organoclays Cloisite 20A and Cloisite 30B were prepared by the melt intercalation method. The materials were characterized by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC). The influence of organoclays in the biodegradation process of PLA was assessed by quantifying the rate of mineralization according to ISO 14855-2, in simulated composting conditions. The influence of clays on the hydrolytic degradation process of PLA was also investigated by visual analysis and monitoring of molecular weight after periods of 15 and 30 days of degradation in organic compost. Given the lack of information related to ecotoxicity of biodegradable polymers, the assessment of citotoxic, genotoxic and mutagenic effects of the organic compost, after the materials degradation, was carried out using the bioassay with Allium cepa as test organism. The nanocomposites presented an intercalated structure, evidenced by XRD analysis. The TEM micrographs allowed the observation of different dispersion levels, including exfoliated regions. After incorporation of organoclays, a reduction of thermal stability and an increasing in the degree of crystallinity of the PLA were observed by TGA and DSC analysis, respectively. In respect to the mineralization, it was noted that the clay Cloisite 20A showed no significant influence on the biodegradation of PLA. On the other hand, the clay Cloisite 30B led to decreased levels of mineralization compared to the polymer, which may be related to an antimicrobial activity of its modifying agent. In the evaluation of hydrolytic degradation it was verified that the presence of organoclays can decrease the rate of degradation possibly by the action of its layers as a barrier. Nevertheless, even in the case of nanocomposites, the molecular weight reduction was significant, indicating that the composting process is favorable to the chain scission of the polymer in the studied materials. In the analysis performed by the bioassay using the test organism Allium cepa, it was verified that after degradation of PLA and the nanocomposites, the organic compost showed an reduction of the mitotic index and an increasing in the induction of chromosomal abnormalities. These results were statistically significant in relation to negative control (distilled water). By comparing the results obtained for the nanocomposites in relation to pure polymer, there were no statistically significant differences. The types of chromosomal aberrations observed indicate a possible genotoxic effect of materials, which may be related to an aneugenic action of the degradation products of PLA / Abstract: In this study, nanocomposites of PLA with organoclays Cloisite 20A and Cloisite 30B were prepared by the melt intercalation method. The materials were characterized by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC). The influence of organoclays in the biodegradation process of PLA was assessed by quantifying the rate of mineralization according to ISO 14855-2, in simulated composting conditions. The influence of clays on the hydrolytic degradation process of PLA was also investigated by visual analysis and monitoring of molecular weight after periods of 15 and 30 days of degradation in organic compost. Given the lack of information related to ecotoxicity of biodegradable polymers, the assessment of citotoxic, genotoxic and mutagenic effects of the organic compost, after the materials degradation, was carried out using the bioassay with Allium cepa as test organism. The nanocomposites presented an intercalated structure, evidenced by XRD analysis. The TEM micrographs allowed the observation of different dispersion levels, including exfoliated regions. After incorporation of organoclays, a reduction of thermal stability and an increasing in the degree of crystallinity of the PLA were observed by TGA and DSC analysis, respectively. In respect to the mineralization, it was noted that the clay Cloisite 20A showed no significant influence on the biodegradation of PLA. On the other hand, the clay Cloisite 30B led to decreased levels of mineralization compared to the polymer, which may be related to an antimicrobial activity of its modifying agent. In the evaluation of hydrolytic degradation it was verified that the presence of organoclays can decrease the rate of degradation possibly by the action of its layers as a barrier. Nevertheless, even in the case of nanocomposites, the molecular weight reduction was significant, indicating that the composting process is favorable to the chain scission of the polymer in the studied materials. In the analysis performed by the bioassay using the test organism Allium cepa, it was verified that after degradation of PLA and the nanocomposites, the organic compost showed an reduction of the mitotic index and an increasing in the induction of chromosomal abnormalities. These results were statistically significant in relation to negative control (distilled water). By comparing the results obtained for the nanocomposites in relation to pure polymer, there were no statistically significant differences. The types of chromosomal aberrations observed indicate a possible genotoxic effect of materials, which may be related to an aneugenic action of the degradation products of PLA / Mestrado / Ciencia e Tecnologia de Materiais / Mestra em Engenharia Química

Orientadores: Ana Rita Morales, Leila Peres / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-22T15:46:33Z (GMT). No. of bitstreams: 1 Cruz_CarolinaVertuMarinhoda_M.pdf: 4798053 bytes, checksum: 65af0005636fd070fa8ddccf682f09f9 (MD5) Previous issue date: 2013 / Resumo: O trabalho teve como objetivo estudar o desempenho de filmes flexíveis de nanocompósitos visando aplicação na área de embalagens. Partindo-se de uma blenda típica do mercado, de polietileno de alta densidade - PEAD, com polietileno de baixa densidade linear - PEBDL, foram preparados nanocompósitos com uma argila montmorilonita organofílica comercial. Na primeira parte experimental foi elaborado, em uma extrusora de dupla rosca, um concentrado ou masterbatch de argila montmorilonita com resina compatibilizante à base de polietileno de baixa densidade linear enxertado com anidrido maléico - PEBDL-AM e partir deste concentrado foram feitos filmes com uma blenda de PEAD e PEBDL com o objetivo de se obter uma estrutura esfoliada da argila na matriz polimérica. A morfologia do concentrado e dos filmes de nanocompósitos foi caracterizada por Difração de Raios-X e Microscopia Eletrônica de Varredura - MET, bem como foram avaliadas as propriedades de barreira ao gás oxigênio e vapor d'água e as propriedades mecânicas dos filmes produzidos. A partir da análise dos resultados da primeira parte experimental, executou-se a segunda parte experimental, onde se mudaram as condições de processamento e a formulação do masterbatch visando uma melhor dispersão da nanocarga. Novos filmes foram preparados como o masterbatch e a blenda de PEAD e PEBDL e as mesmas propriedades da parte experimental I foram estudadas. As variáveis de processamento do masterbatch e o teor de argila influenciaram a dispersão da argila e os resultados de permeabilidade dos filmes obtidos. O modelo de Nielsen foi aplicado para estimar a razão de aspecto e para entender o grau de esfoliação da argila. Melhorias nas propriedades de barreira foram observadas, o que indica que os sistemas estudados mostram-se promissores para aplicações em embalagens flexíveis / Abstract: The objective of this work was to study the properties of a flexible film based in nanocomposites for packaging application. Assuming a typical blend of HDPE and LLDPE, nanocomposites were prepared with commercial organophilic clay. In the first experimental part, a masterbatch was prepared from a linear low density polyethylene modified with maleic anhydride and a montmorillonite clay. The masterbatch was diluted in a blend of high density polyethylene (HDPE) with linear low density polyethylene (LLDPE) and films were extruded. The objective was to obtain nanocomposites whitin an exfoliated structure of the clay in the polymer matrix. The nanocomposites morphologies were evaluated by X-ray diffraction and TEM. Besides, the properties of gas barrier to oxygen and water vapor and mechanical properties were also determined. Analyzing the results of the first experimental part, improvement on the clay dispersion based on the processing conditions was expected and the second experimental part was held. The conditions of processing and masterbatch formulation were changed. Dilutions were also made in the blend of HDPE / LLDPE for films preparation and the same properties of the experimental I were studied. Processing conditions and clay content affect the ability of the clay dispersion and the results of permeability. Nielsen's model was applied in order to measure the aspect ratio and to understand the clay exfoliation level. Improvements on the barrier properties were observed and the studied systems were shown to be promising for applications in flexible packaging / Mestrado / Ciencia e Tecnologia de Materiais / Mestra em Engenharia Química

Submitted in fulfillment of the requirements for the degree of Master in Engineering: Mechanical Engineering, Durban University of Technology, Durban, South Africa, 2017. / Despite the huge improvements made in the development of vehicle brake pad materials, problems such long stopping distances, noise pollution, and heat dissipation still continue to persist. In this regard, a novel polymer-based hybrid nanocomposite brake pad (HC) has been developed. Here, a combination of carbon-based materials, including those at a nanoscale, was used to produce the brake pad. The coefficient of friction, wear rate, noise level, and interfacial temperature was investigated and compared with that of a commercial brake pad material (CR). It was found that the brake pad performance varied with the formulation of each pad. Hybrid nanocomposite brake pads material exhibited superior performance in most tests when compared to the commercial brake pad. They exhibited a 65% lower wear rate, 55% lower noise level, 90% shorter stopping distance, and 71 % lower interfacial temperature than the commercial brake pad (CR). Furthermore, mechanical properties such as hardness, compressive strength, shear strength, and impact resistance were also evaluated. The material exhibited a 376% higher shear strength, 100% improved compressive strength, 77% greater modulus and 100% higher impact strength than the commercial brake pad. The hardness of both brake pads material was statistically comparable. Additionally, the thermal stability, degradation, water and oil absorption behaviour were measured. It was found that HC brake pad material exhibited a 100% lower water absorption and 80% oil absorption rate. The brake pads also exhibited a thermal stability within the brake pad standard maximum working temperature of 300 -400 0C. The superior performance of hybrid nanocomposite brake pad material observed was due to synergism between the carbon-carbon additives and uniform dispersion of carbon fiber as shown in Figure 4.16. Scanning electron microscopy study was subsequently performed on fracture and worn surfaces of the brake pads. The micrographs show changes in the structural formation after the incorporation of carbon based fillers. It also shows the smooth structure and uniform dispersion of the carbon fiber. The smooth surface of the worn brake pad is an indicative of a harder structure. No ploughing or score marks were evident. Hence, it was deduced that the reinforced had superior mechanical and tribological properties. These improved properties are suggestive of materials that may be successfully used for brake pad application. / M

Nanokomposit innehållande högdensitetspolyeten och kolnanorör återvanns och analyseradesför att undersöka hur materialets egenskaper påverkas av återvinning. Kompositenproducerades med 3 viktprocent kolnanorör och återvanns tio gånger genom att extrudera ochmala ner materialet. Analyser gjordes efter varje cykel av extrudering. Dessutom utfördessimulerade tester med kontinuerlig extrudering i 20, 100 och 200 minuter motsvarande 10, 50och 100 cykler. Därav kunde nedbrytningen av kompositen efter längre tids bearbetninganalyseras. I projektet studerades ett referensmaterial bestående av den rena polymeren för attkunna jämföra resultat. Karaktärisering av materialen för att bestämma mekaniska egenskapergjordes med dragprovning, böjningstest och slagprovning. För att undersöka termiskaegenskaper användes Differential Scanning Calorimetry (DSC) och Gel PermeationChromatography (GPC) användes för att hitta molekylviktsändringar. Fourier TransformInfrared Spectroscopy (FTIR) utfördes för att identifiera materialet. Resultaten visade ingenstörre skillnad i egenskaper efter tio återvinningscykler, vilket indikerade att materialet harförmåga att behålla sina egenskaper vid återvinning. I de simulerade cyklerna minskade denoxidativa induktionstiden efter 50 och 100 cykler, vilket berodde på att antioxidanterkonsumerats under bearbetningen. Efter 50 simulerade cykler hade molekylvikten börjat sjunkaoch efter 100 cykler kunde en signifikant minskning obseveras, vilket tydde på attpolymerkedjorna förkortats under bearbetningen. För kompositen däremot var molekylviktenstabil, på grund av att kolnanorören skyddade polymeren vid nedbrytning. / Nanocomposite containing High Density Polyethylene (HDPE) and Carbon Nanotubes (CNTs)was reprocessed and characterised to investigate the effect on properties during recycling. Thecomposite was prepared with 3 wt-% CNTs and was recycled ten times by alternatereprocessing and grinding and thereafter the material was characterised. Furthermore, simulatedcycles with continuous processing at 20, 100 and 200 minutes were conducted, representing 10,50 and 100 cycles respectively, in order to investigate the degradation after longer time ofprocessing. In both trials, a reference material containing neat HDPE was studied. Thecharacterisation of the materials produced was conducted using tensile, flexural and charpyimpact testing for investigation of mechanical properties. Differential Scanning Calorimetry(DSC) was used for determining the thermal behaviour and Gel Permeation Chromatography(GPC) to find molecular weight changes. Fourier Transform Infrared Spectroscopy (FTIR) wasused for identification of the material. The results showed no major difference in propertiesafter ten recycling steps, which indicated that the material had the ability to retain its propertiesduring recycling. In the simulated cycles, the oxidative induction time was decreased after 50and 100 cycles, meaning that antioxidants had been consumed during processing. After 50cycles the molecular weight for the reference material was slightly decreased and after 100cycles significantly decreased, indicating chain scission of the polymer chains. For thecomposite the molecular weight was stable, due to that the carbon nanotubes protect thepolymer matrix during degradation.

Ces travaux de thèse portent sur le développement d’un dispositif de synthèse de nanoparticules (NPs) par une voie physique basée sur la pulvérisation laser d’une cible suivie d’une trempe du panache plasma ainsi formé. L’association de cette source à une enceinte d’ablation laser conventionnelle a permis de synthétiser des NPs d’argent et de vanadium empilées sur des substrats ou noyées dans des matrices synthétisées par ablation laser. Des analyses par microscopie électronique en transmission (MET) et microscope à force atomique (AFM) ont révélé des NPs cristallisées en vol, de forme sphérique et de tailles relativement monodisperses (~ 3 nm de diamètre) fonction de leur temps de séjour dans la cavité de nucléation. La réalisation de nanocomposites Al2O3 amorphe dopée par des NPs d’argent métallique de différentes tailles a montré l’influence de la taille de ces entités nanométriques sur la position et la largeur de la résonance plasmon de surface (RPS) du matériau nanostructuré. Les NPs gardent leur forme originelle après impact sur le substrat ce qui conduit à des empilements de nanoparticules fortement poreux (de l’ordre de 50%). Des NPs de dioxyde de vanadium ont pu être synthétisées par recuit d’empilements de NPs de vanadium. Du fait de leur individualité, les NPs de VO2 présentent une température de transition plus faible (~50°C) et une largeur d’hystérésis plus importante (~10-30°C) qu’un film mince (température de transition d’environ 68°C et largeur d’hystérésis d’environ 3°C). En associant un film mince synthétisé par PLD à un empilement de NPs il est alors possible de combiner leurs propriétés et d’obtenir un matériau nanocomposite présentant une transition par palier. / The work presented in this thesis is focused on the development of an experimental setup for the synthesis of nanoparticles (NPs) by a physical route, based on the laser vaporization of a target and followed by the rapid quenching of the plasma plume. Combining such a NP source with conventional laser ablation makes possible to synthesize silver and vanadium NPs in stacks on substrates or embedded in different matrices synthesized by laser ablation. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) analysis revealed crystallized spherical NPs relatively monodisperse in size (~ 3 nm in diameter) depending on the residence time in the nucleation cavity. The synthesis of amorphous Al2O3 nanocomposites doped with metallic silver NPs of different sizes showed the influence of the size on the position and the width of the surface plasmon resonance (SPR) of the nanostructured material. The NPs keep their original shape during impact on the substrate, leading to highly porous NPs stacks (approximately 50%). Vanadium dioxide nanoparticles (VO2 NPs) have been synthesized by annealing vanadium NPs stacks. Due to their individual behaviour, VO2NPs exhibit lower transition temperature (~ 50°C) and larger hysteresis width (~ 10-30°C) than thin films (transition temperature around 68°C and hysteresis width around 3°C). By coupling a PLD thin film and a NPs stack, it is possible to combine their properties and obtain a nanostructured material having a step transition.

Polymer nanocomposites represent a class of advanced, multifunctional materials, combining the attractive features of both nanomaterials and polymers. The level of dispersion of the nanoparticles directly controls the extent to which nanocomposites can maximize the unique attributes of their nano-scale fillers. However, as a consequence of the tendency of nanofillers to agglomerate, the anticipated superior properties of polymer nanocomposites are yet to be realised, and remain merely a theoretical prediction. As a result, the surface chemistry of nanofillers is often tailored to reduce the attractive interparticle interactions that promote agglomeration. This modification can also be used to enhance the interfacial interactions between the nanofiller and polymer matrices to achieve improved filler dispersion. Accordingly, this thesis addresses this challenge in nanocomposite technology by investigating the chemical surface functionalisation of various nanoparticles in order to produce polypropylene (PP) nanocomposites with superior electrical, mechanical and thermal properties. Part I describes covalent modification of nanosilica, microsilica, furnace Carbon Black (CB), acetylene black (ACB) and carbon nanotube (CNT) nanomaterials by carbene insertion and azo-coupling reactions, in a series of studies, in order to tailor their surfaces for application in polypropylene (PP) nanocomposites. The surface characterisation of the modified nanomaterials was assessed in detail using XPS, CHN, SSNMR, BET, ATR-IR and thermal analysis techniques. The surface grafting densities were estimated to be of the order of 10¹³ and 10¹⁴ molecules/cm² and additionally, SSNMR provided direct evidence of the diarylcarbene reaction to the silica surface. Following nanocomposite production with PP by solvent mixing methods, the macroscopic properties were studied demonstrating altered electrical, mechanical and thermal properties following assessment of the DC conductivity, dielectric properties, thermal analysis (TGA, DSC, DMA) and morphological measurements. In particular, the introduction to the CB surface of a diaryl complex with terminal dodecyl hydrocarbon chains demonstrated substantial improvements to the DC electrical and dielectric properties of the PP nanocomposites. Part II explores the non-covalent surface functionalisation of CB and ACB by the physisorption of the non-ionic surfactant Triton-X-100. Various protocols were developed in which an optimal surface loading for CB was determined by treatment at 0.024 mM(aq). In addition, the modification procedure was combined with the granulation protocol of ACB in an effort to evaluate the potential for industrial applications. The degree of surface functionalisation was extensively characterised by BET, XPS, thermal analysis, UV-Vis and ATR-IR analyses. PP nanocomposites produced by solvent and melt mixing methods demonstrated similar conductive properties following the nanoscale modification, however morphological, dielectric and thermal analysis indicated altered interfacial interactions demonstrating improved mechanical properties.

In the last decade, carbon nanotubes (CNTs) and Graphene nanoplatelets (GNPs) have attracted a lot of attentions in various polymeric and ceramic composite systems, in an effort to improve their mechanical and functional properties. Al2O3 has attracted considerable interests in ceramics community, in particular as a matrix material for composite fabrications. The high stiffness, excellent thermal stability and chemical resistance of Al2O3 make it practically a very important engineering material, and if we can overcome its brittleness issue, its applications will be much wider. Adding CNTs as a reinforcement to the Al2O3 matrix to improve the toughness is one of the most promising methods. Similarly, GNPs have recently also been shown to be very promising for the same purpose. It has been demonstrated that by adding a mixture of the 2D-GNPs and 1D-CNTs into a polymer matrix, the toughest or strongest man-made ropes have been made. However, the homogenous dispersion of CNTs or GNPs is more of a challenge in a ceramic matrix than in polymeric matrices, owing to the tendency of CNT agglomerations and more steps are needed to completely transfer the useful properties of CNTs and GNPs into ceramics. In this thesis, nanocomposites of Al2O3 reinforced with a hybrid of GNTs (a blend of GNPs and CNTs) were first fabricated. The hybrid GNT reinforcements were mixed with the Al2O3 using a wet chemical technique under ultrasonic treatment. The effects of varied GNT contents on the microstructural features and mechanical properties of the nanocomposites were then investigated. It is found that the well-dispersed GNT fillers resulted in high sintered densities (>99%) in the composites, whilst the fracture mode alteration, grain refinement and improved flexural strength of the composites are all associated with the inclusion of CNTs and GNPs. The average fracture toughness of the nanocomposites reached up to 5.7 MPa·m1/2, against 3.5 MPa·m1/2 of the plain Al2O3, and the flexural strength improved from 360 MPa to 424 MPa respectively, at a hybrid addition of 0.5 wt% GNPs and 1 wt% CNTs. The toughening mechanisms attributed with the unique morphologies and structures of the GNT fillers were also discussed based on analyses on the morphology, grain sizes and fracture mode. The effects of hot-pressing (HP) and spark plasma sintering (SPS) methods on the grain size, microstructural features, and mechanical behaviour of GNT-reinforced Al2O3 nanocomposites were then comprehensively studied. Identical overall reinforcement contents at various GNP/CNT ratios were selected to prepare the composites using both HP and SPS. Highly densified samples (>98%) were obtained at 1650°C under 40 MPa in Ar atmosphere, with dwell times of 1 h and 10 min for HP and SPS respectively. Both types of sample showed a mixture of inter- and trans-granular fracture behaviour. A 50% grain size reduction was observed for samples prepared by HP, compared with the SPS samples. Both types of samples achieved a high flexural strength and fracture toughness of > 400 MPa and 5.5 MPa·m1/2, respectively, whilst the properties of the SPS samples peaked at relatively lower GNT contents than those of the HP samples. Based on analyses of the morphology, grain sizes and fracture mode, similar toughening mechanisms for both types of sample were observed, involving the complex characteristics of the combined GNT fillers. The tribological performance of the HPed pure Al2O3 and its composites containing various hybrid GNT contents was further evaluated under different loading conditions using a ball-on-disc method. Benchmarked against the pure Al2O3, the composite reinforced with a 0.5 wt% GNP exhibited a 23% reduction in the friction coefficient along with a promising 70% wear rate reduction, and a hybrid reinforcement consisting of 0.3 wt.% GNPs + 1 wt.% CNTs resulted in even better performance, with a 86% reduction in the wear rate. The extent of damage to the reinforcement phases caused during wear was studied using Raman spectroscopy. The wear mechanisms for the composites were analysed according to the mechanical properties, brittleness index and microstructural characterization. The combination between GNPs and CNTs contributed to the excellent wear resistance properties for the hybrid GNT-reinforced composites. The GNPs played an important role in the formation of a tribofilm on the worn surface by exfoliation; whereas the CNTs contributed to the improvement in fracture toughness and prevented the grains being pulled out during the tribology test. Finally, Graphene Oxide (GO) was used to replace the GNPs in the hybrid, to prepare Al2O3-GONT nanocomposites, by adopting a new sol-gel processing, in addition to powder mixing. It has been found that sol-gel process leads to an impressive grain size reduction of 62%, the fracture toughness and flexural reached 6.2 MPa·m1/2 and 420 MPa (i.e. 70% and 14% improvement), respectively, than those of pure Al2O3, which even marginally outperformed the previously optimised Al2O3-GNP nanocomposites by 8% in fracture toughness. The success of our new sol-gel strategy opens up new opportunities for choosing hybrid reinforcements for the fabrication of advanced ceramic nanocomposites.

Master of Science / Department of Chemistry / Kenneth J. Klabunde / In this study, low molecular weight nanocomposites of L-lactic acid were synthesized with Commercial, Nanoactive®, and Nanoactive Magnesium Oxide Plus®, each of which differs in both surface area and shape. Synthesis of the composites was carried out by refluxing the nanoparticles in a solvent suspension. Both methanol and 1-propanol were used during this work. Heating was necessary in order to achieve adequate dispersion of the particles before adding L-lactic acid. Upon addition of the lactic acid monomer, the reactants were refluxed for a total of 3 hours, followed by evaporation of the excess solvent. The products were characterized via DSC, TGA, FTIR, [superscript]1H and [superscript]13C NMR, UV-Vis, XRD, and TEM. Additionally, titrations were performed with the reactants to ensure the particles were not being consumed by the acid regardless of their size. The results of this study indicate that condensation reactions are the primary polymerization route of lactic acid and polymerization appears to initiate on the surface of the magnesium oxide particles, resulting in physically unique composites of lactic acid and magnesium oxide.