Submitted by Juliana Bovi de Oliveira null (juliana_bovi@hotmail.com) on 2016-04-28T03:07:28Z No. of bitstreams: 1 Dissertação de Mestrado - Juliana B Oliveira.pdf: 3628116 bytes, checksum: 38a7295f033a2a9bda4b4118db7acee0 (MD5) / Approved for entry into archive by Felipe Augusto Arakaki (arakaki@reitoria.unesp.br) on 2016-05-02T11:57:44Z (GMT) No. of bitstreams: 1 oliveira_jb_me_guara.pdf: 3628116 bytes, checksum: 38a7295f033a2a9bda4b4118db7acee0 (MD5) / Made available in DSpace on 2016-05-02T11:57:44Z (GMT). No. of bitstreams: 1 oliveira_jb_me_guara.pdf: 3628116 bytes, checksum: 38a7295f033a2a9bda4b4118db7acee0 (MD5) Previous issue date: 2016-03-08 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Nos últimos anos, reforços constituídos de nanoestruturas em carbono, tais como nanotubos de carbono, fulerenos, grafenos e nanofibras de carbono, vêm sendo muito pesquisados devido às suas elevadas propriedades mecânicas, elétricas e térmicas. Uma vez que, as nanofibras de carbono consistem em um reforço contínuo (ou na forma de mantas) de elevada área superficial específica, associado ao fato de que estas podem ser obtidas a um baixo custo e em grandes quantidades, estas vêm se mostrando vantajosas quando comparadas aos tradicionais nanotubos de carbono. Assim, as nanofibras de carbono são ótimas candidatas para a obtenção de materiais avançados, podendo estas serem utilizadas como reforços em compósitos com diversas aplicações, tais como em implantes neurológicos e ortopédicos, como suportes de catalisadores, artefatos para aplicações aeroespaciais, dentre outras. Desta forma, o objetivo principal deste trabalho é a produção de nanofibras de carbono, empregando como precursora a manta de poliacrilonitrila (PAN) obtida pelo processo de eletrofiação via solução polimérica, com posterior utilização como reforço em compósitos poliméricos. Neste trabalho, uma manta de poliacrilonitrila com nanofibras de diâmetro de aproximadamente (375 ± 85) nm foi obtida por eletrofiação, sendo esta posteriormente carbonizada. A massa residual resultante do processo de carbonização foi de aproximadamente 38% em massa, com uma redução de 50% nos diâmetros das nanofibras após a queima das mantas de PAN, sendo que as mesmas apresentaram um rendimento de 25%. Na análise da estrutura cristalina do material carbonizado, verificou-se que o material apresentou uma desorganização estrutural. E a partir do ensaio de condutividade elétrica da manta carbonizada, concluiu-se que o material se comporta como um semi-condutor. O compósito de nanofibras de carbono/resina epóxi processado apresentou módulo de elasticidade de (3,79 ± 0,48) GPa, temperatura de transição vítrea (Tg) na faixa de 108,9 a 135,5°C, e um coeficiente de expansão térmica linear entre a faixa de 68 x 10-6/°C e 408 x 10-6/°C. / In recent years, reinforcement consisting of carbon nanostructures, such as carbon nanotubes, fullerenes, graphenes, and carbon nanofibers has been very researched due to its mechanical, electrical and thermal properties, besides having good thermal conductivity, mechanical resistance and high surface area. Since the carbon nanofibers comprise a continuous reinforcing with high specific surface area, associated with the fact that they can be obtained at a low cost and in large amounts, they have shown to be advantageous compared to traditional carbon nanotubes. Thus, the carbon nanofibers are excellent candidates in order to obtain advanced materials, and these can be used as reinforcements in composites with several applications such as for example, neurological and orthopedic implants, integrates in catalysts systems, devices for aerospace applications, among others. So, the main objective of this work is the processing of carbon nanofibers, using PAN as a precursor, obtained by the electrospinning process via polymer solution, with subsequent use for applications as reinforcement in polymer composites. In this work, PAN nanofibers were produced by electrospining with a diameter of approximately (375 ± 85) nm. The resulting residual weight after carbonization was approximately 38% in mass, with a diameters reduction of 50%, and the same showed a yield of 25%. From the analysis of the crystallinity structure of the carbonized material, it was found that the material presented a disordered structure. From the electrical conductivity results of the specimens, it was concluded that the material behaves as a semi-conductor. The epoxy resin/carbon nanofiber composite presented an elastic modulus value of (3.79 ± 0.48) GPa, a glass transition temperature (Tg) in the range from 108.9 to 135 5 ° C and a linear thermal expansion coefficient within the range of 68 x 10-6/°C and 408 x 10-6/°C.

Orientador: André Luiz Barboza Formiga / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-22T00:53:19Z (GMT). No. of bitstreams: 1 Rollo_PedroMartinsdeAlmeida_M.pdf: 27184092 bytes, checksum: f3fc542db91febabadab91c184ba101d (MD5) Previous issue date: 2012 / Resumo: Este trabalho apresenta o estudo da funcionalizacão do polímero poliacrilonitrila a partir da hidrólise alcalina do material em meio homogêneo e os fatores que controlam essa reação. Uma investigação sistematica foi realizada para compreender o mecanismo reacional e a dependência da concentracão de base e de H2O com a composição final do polímero modificado. Estudos espectroscópicos assistidos por cálculos teóricos permitiram concluir que ambos os fatores possuem influência na reacão e que o produto formado depende do procedimento de modificacão empregado. Aborda-se também como a funcionalizacão das cadeias poliméricas altera as propriedades físico-químicas e mecânicas do material. É evidenciado que há uma mudança na cristalinidade do material, que por sua vez altera propriedades mecânicas do mesmo. O comportamento das cadeias poliméricas em solução também sofre modificações relevantes, sendo evidenciadas por viscosimetria de soluções diluídas. Por último, utiliza-se a poliacrilonitrila hidrolisada na preparação de membranas assimétricas por inversão de fase, com o intuito de comparar as propriedades das membranas de materiais modificados com membranas de material não modificado / Abstract: The work here reported deals with the alkaline hydrolysis of polyacrylonitrile in homogeneous medium and the experimental conditions that influence the reaction. A systematic investigation of the reaction mechanism was conducted, allowing to understand the influence of the concentration of base and H2O on the hydrolyzed product composition. Spectroscopic studies combined with theoretical calculations led to conclude that both factors have a noteworthy influence on the modified product. It is also reported an investigation on how the chemical functionalization alters the physico-chemical and mechanical properties of the material. It is noticed a significant change in the crystallinity of the material, that leads to changes on the mechanical properties for itself. The hydrodynamic properties of the polymer in solution also underwent significant changes with hydrolysis, this being evidenced by a rheological study. Lastly, hydrolyzed polyacrylonitrile was applied to membrane preparation by the method of non-solvent induced phase separation, with the intention to compare membranes of hydrolyzed materials with non-hydrolyzed ones / Mestrado / Quimica Inorganica / Mestre em Química

Philosophiae Doctor - PhD / Organic and inorganic pollutants are two broad classes of pollutants in the environment with their main sources from waste waters that are indiscriminately dumped from chemical related industries. Among the organic pollutants are dyes that come as effluents from the textile industries. Toxic metals are the main inorganic pollutants with their sources from industries such as mining, electroplating, batteries etc. The presence of both classes of pollutants in the aquatic environment poses a serious threat to aquatic organisms and humans who depend on these waters for domestic purpose. Therefore, this research focused on the fabrication of materials and designing of methods for removal of both classes of pollutants from their aqueous solutions.

In the last decades, there has been a trend towards bio-inspired approaches for the formation of nanocoatings as well as to accomplish energy-intensive industrial separations in a more sustainable fashion. Solvent Resistant Nanofiltration (SRNF) is a pressure driven technology where the operation conditions are moderate and additional waste streams are minimized, making this a favorable energy efficient approach for challenging molecular separations such as purification of active pharmaceutical ingredients, production of specialty chemicals and in the petrochemical industry just to mention a few examples, where this technology can be currently applied. The overall performance of SRNF membranes is determined by solute/solvent interactions with the membrane top layer. Therefore, the modification of the membrane surface becomes crucial to obtain high-performance SRNF membranes, as well as exploring novel and green approaches to improve the separation properties of SRNF membranes, without sacrificing their permeation properties. One alternative for the fabrication of the thin-films in SRNF membranes proposed in this work is the use of biopolyphenolic molecules. Among the many classes of phenolic biomolecules, plant phenols are capable of binding and cross-linking due to their strong interfacial activity. Here, the successful optimization of the interfacial polymerization reaction for the manufacture of SRNF membranes is demonstrated by replacing the common toxic amines used for this method with natural occurring bio-polyphenols such as dopamine, tannic acid, morin hydrate and catechin. These bio-polyphenols can be found in mussels, date fruits, guava fruits and green tea respectively and they were used to form a selective thin film on top of a crosslinked polyacrylonitrile or a cellulose support. These membranes have shown an exceptional performance and resistance towards harsh solvent environments. Due to the incorporation of natural compounds for the manufacture, they provide a cost-effective alternative for industrial separations due to the ease of chemical modification and preparation, which is potentially easy to scale up at low cost taking advantage of the natural compounds for their manufacture.

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Thermocouples are one of the most commonly used instruments for thermometry at elevated  temperatures. As of today, there are only a few types of thermocouples that are built to withstand a temperature beyond 1600 °C,however they usually have a temperature measurement uncertainty of around 1% at these high temperatures. Beyond the 1600 °C temperature span, most high temperature thermocouples tend to drift in the measurements, causing it to output a faulty and inaccurate read of the actual temperature. This thesis explores the usage of carbon fibers as a material to be used in thermocouples, by the combination of two dissimilar carbon fibers. Polyacrylonitrile (PAN) and rayon based fibers were used up to a temperature of 200 °C, where the output voltage of the thermocouple was logged. The study shows a promising and stable linear output of the electromotive force for this type of thermocouple using commercially available carbon fibers at lower temperatures. A comparison is made between the commonly used thermocouples type K and S, results shows that the carbon thermocouple have around 21% of the thermoelectrical efficiency of that of a type K or S thermocouple at 25 °C. For the case of its functionality at higher temperatures, similar graphite material has been studied through literature and found a potential increase in the thermoelectrical stability at higher temperatures beyond 2000 °C, which show that carbon-based thermocouples are well suited for high temperature measurements. / Termoelement är ett av de mest använda instrumenten för temperaturavläsning vid upphöjda temperaturer. Idag finns det bara några få typer av termoelement som är byggda för temperaturer över 1600 ℃, däremot innehar dom vanligtvis en temperaturmätnings osäkerhet på cirka 1% vid dessa höga temperaturer. Över 1600 ℃ temperaturintervallet har de flesta högtemperatur termoelement en tendens att skifta i mätningarna vilket orsakar en felaktig och inexakt mätning av den faktiska temperaturen. Denna avhandling undersöker användningen av kolfiber som ett material för användning i termoelement, genom kombinationen av två olika grafitfibrer. Polyacrylonitrile- (PAN) och Rayon-baserade fibrer användes i en sammansatt kombination upp till en temperatur av 200 ℃, där spänningen mättes mot temperaturen. Studien visar en lovande och stabil linjär effekt av dess elektromotoriska spänning för denna typ av termoelement med kommersiellt tillgängliga kolfibrer vid lägre temperaturer. En jämförelse görs mellan de vanliga termoelementen av typ K och S vid rumstemperaturer, resultaten visar att grafittermoelementen har cirka 21% av den termoelektriska effektiviteten hos den för en typ K eller S termoelement vid 25 ℃. När det gäller dess funktionalitet vid högre temperaturer har liknande grafitmaterial studerats och funnit en potentiell ökning av den termoelektriska stabiliteten vid högre temperaturer över 2000 ℃, vilket visar att grafitbaserade termoelement gör sig väl lämpade för högtemperaturmätningar.

M. Tech. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology. / Electrospinning is a method that has gained more attention due to its capability in spinning a wide variety of polymeric fibers and nanoparticles embedded in polymer fibers. Polymer blending has been considered the most appropriate way for creating new materials with fused properties which improve poor chemical, mechanical, thermal and dynamic mechanical properties of each polymer. Hence, in this study, electrospinning technique was used to fabricate polyacrylonitrile (PAN) nanofibers at concentrations of (10, 12 and 14 wt%) and cellulose acetate (CA) nanofibers at concentrations of (14, 16 and 18 wt%). 10wt% of PAN and 16 wt% of CA were blended together and the optimum blend ratio was found to be 80/20 PAN/CA. TiO2 nanoparticles (0.2 and 0.4 wt%) were incorporated into CA nanofibers and (1, 2 and 3 wt%) were incorporated into PAN and PAN/CA blended polymers, respectively. Applied voltages of 20, 22 and 24 kV were varied at a spinning distance of 15cm and the optimum voltage for the fabrication of composite was 22 kV. The sol-gel method was used to synthesise the TiO2 nanoparticles at different calcination temperatures of 400, 500 and 600 ºC. The fabricated composite nanofibers were tested for antibacterial and photocatalytic activities. The synthesised nanomaterials were characterized using SEM, TEM, EDX, UV-Vis, PL, FTIR spectroscopy, XRD and TGA. The absorption and emission spectra illustrated the formation of TiO2 nanoparticles and the increase in absorption band edges. TEM showed the spherical morphology of the nanoparticles with average diameter of 12.2 nm for nanoparticles calcined at 500 ºC. SEM illustrated the diameter and morphology of the nanofibers and composites with the average diameter of 220, 338, 181, 250, 538, 294 nm for PAN, CA, PAN-TiO2, CA-TiO2, PAN/CA and PAN/CA-TiO2, respectively. XRD revealed anatase phase as the dominant crystalline phase of the synthesised nanoparticles. FTIR spectroscopy and EDX signified that the formation of composite nanofibers and the presence of TiO2 nanoparticles corresponded to the Ti-O stretching and Ti-O-Ti bands on the FTIR spectra. The antimicrobial activity of the composite nanofibers were tested against E. coli, S. aureus and C. albicans microorganisms. The photocatalytic activity of the nanomaterials was tested using methyl orange dye. PAN/CA-TiO2 composite nanofibers revealed the greatest antibacterial activity against selected microorganisms as compared to the other nanocomposites. PAN/CA-TiO2 nanocomposite (44%) showed greater rate of photodegradation of methyl orange than PAN-TiO2 nanofibers (28%) and TiO2 nanoparticles (12%) under visible light irradiation.

Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Polyacrylonitrile, (PAN), polymers are of interest due to their many unique characteristics in comparison to most other fibre forming polymers. The focus of this study was the effect of electrospinning variables and additives on their unusual thermal properties and internal molecular morphology with the objective of improving the performance of this fibre in industrial application, or at least contributing to the understanding of how the fibre processing variables affect the thermal performance. The process of electrospinning was used to process samples of PAN fibres with additives in order to determine their effect on the molecular orientation and crystallinity of the resultant nano- and micronsized fibres. The effect of additives in the forms of low molecular weight oligomers, blends of conductive polymers and nanoparticles and conductive salts (mainly copper and lithium based) on the molecular structure and thermal properties is reported. In addition the effect of certain electrospinning processing variables such as the PAN polymer grade, the type of solvent, the temperature, the spinning voltage and the spinning distance were evaluated in terms of their effect on the resultant fibre molecular structure. The crystallinity and molecular orientation are quantified using various analytical techniques including: Fourier-Transform Infra-Red Spectroscopy (FTIR); Differential Scanning Colorimetry; (DSC) Thermal Gravimetric Analysis, TGA, Scanning and Transmission Electron Microscopy; Wide-Angle X-ray Diffractometry, XRD, Small-angle Neutron Scattering; SANS, Solid-state 13C Nuclear Magnetic Resonance Spectroscopy; NMR, and Electron-spin Resonance Spectroscopy, ESR. The researcher has ascertained in this study that the orientation of electrospun PAN is comparable to that in commercial wet-spun fibres when the electrospinning field strength is greater than 0,75 kV per cm. The process of electrospinning leads to chemical degradation of the PAN polymer only previously noted by other fibre scientists after heating PAN fibres to more than 280 C. This is due to the high mechanical stress on the high surface area electospun fibres spun into an oxygen rich air atmosphere. The addition of certain salts, particularly lithium chloride and copper nitrate, to the PAN electrospinning dope by the researchers produced fibres with improved thermal stability in comparison to the control PAN samples with no additives. In addition these salts lower the endotherm for the production of carbonized fibres from PAN fibres and will therefore make more structured, stronger, high tenacity carbon fibres. The XRD revealed that through the addition of certain salts to disrupt the dipole interations in PAN, that fibres with a 2D hexagonal crystal structure can be electrospun and have a structure similar to wet spun PAN. It is shown that fibres in a non-aligned electrospun mat have a 3D crystal structure and lower molecular orientation that wet spun fibres. Some industrial applications of electrospinning using PAN fibres are developed and reported. / AFRIKAANSE OPSOMMING: Polyakrilonitrielpolimere (PAN) is van belang weens die baie unieke eienskappe wat hulle het in vergelyking met die meeste ander vesel-vormende polimere. Die fokus van hierdie studie op die effek van verskeie veranderlikes en byvoegmiddels op hul buitengewone termiese eienskappe en interne molekulêre morfologie, met die doel om die werksverrigting van hierdie vesel in industriële toepassings te verbeter, of ten minste by te dra tot die begrip van hoe die vesel-prosesveranderlikes die termiese werksverrigting beïnvloed. Die elektrospinproses is gebruik om monsters van PAN met bymiddels te prosesseer om vas te stel wat die effek sou wees op die molekulêre oriëntering en kristalliniteit van die gelewerde nano- en mikrongrootte vesels. Verslag word gelewer oor die effek van bymiddels in die vorm van oligomere met „n lae molekulêre gewig, mengsels van geleidende polimere en verskillende nano-partikels en geleidende soute (meestal koper- en litium-gebaseerd). Die effek van sekere veranderlikes in die elektrospinproses, soos die PAN polimeer-graad, die temperatuur, die tipe oplosmiddel, die spin-spanning en spin-afstand, is geëvalueer in terme van hulle effek op die vesels wat gelewer word. Die kristalliniteit en molekulêre oriëntering word gekwantifiseer deur verskeie analitiese tegnieke te gebruik, onder meer: Fourier-Transform Infrarooispektroskopie; Differensiële Skandeerkolorimetrie; Termiese Gravimetriese Ontleding; Skandeeringelektronmikroskopie; Transmissie Elektron Mikroskopie; Wye-hoek X-straal Diffraktometrie; Klein-hoek Neutronstrooiing; Vaste-toestand 13C Kern Magnetiese Resonansiespektroskopie; en Elektronspin Resonansiespektroskopie. Dit is in hierdie studie vasgestel dat die oriëntering van elektro-gespinde PAN vergelykbaar is met kommersiële nat-gespinde vesels as die elektro-spin veldsterkte groter is as 0,75 kV per cm. Die elektro-spin proses lei tot chemiese degradasie van die PAN polimeer, wat voorheen slegs deur ander vesel-wetenskaplikes waargeneem is nadat PAN tot meer as 280 C verhit is. Dit word veroorsaak deur die hoë meganiese spanning op die hoë-oppervlakarea vesels wat in „n suurstofryke lug-atmosfeer gespin word. Die byvoeging van sekere soute, veral litiumchloried en kopernitraat, by die PAN elektro-spin spinlak (dope) deur die navorser het vesels gelewer met verbeterde termiese stabiliteit in vergelyking met die kontrole PAN-monsters sonder bymiddels. Verder verlaag hierdie soute die endoterm vir die produksie van gekarboniseerde vesels uit PAN-vesels, en dit sal daarom meer gestruktureerde, sterker koolstofvesels met hoë taaiheid lewer. X-straaldiffraksieanalise het gewys dat gewone elekrospin vesels ‟n driedimensionele struktuur het maar as gevolg van die byvoeging van sekere soute, wat die dipoolinteraksies in PAN opbreek, dat vesels wat 'n soortgelyke tweedimensionele struktuur het as dié van groot skaalse kommersiële nat-spin vesels, maklik d.m.v. die elektrospinproses berei kan word. Enkele nywerheidstoepassings van elektrospin is ontwikkel, en beskryf.

Nos últimos anos, a irradiação por micro-ondas tem sido cada vez mais usada na síntese de varias moléculas orgânicas, devido a uma série de vantagens que essa nova tecnologia apresenta. Até o momento, existem poucos estudos sobre polimerizações assistidas por micro-ondas e menos ainda sobre a modificação de polímeros usando essa nova fonte de energia. Polímeros heterocíclicos contendo anéis azóicos, como o tetrazol possuem interesse acadêmico e comercial devido as suas várias aplicações. Nesta Dissertação foi estuda a modificação química da poliacrilonitrila pela incorporação em sua cadeia polimérica de 10% de grupos tetrazol empregando-se a irradiação de micro-ondas e o método convencional (térmico). Foram utilizados um forno de micro-ondas doméstico e um reator de micro-ondas monomodo nas reações assistidas por micro-ondas. As reações em reator foram realizadas em vaso aberto, em solução (DMF) ou em massa, sendo variado o tempo e a temperatura reacional, bem como a potência do equipamento. Os copolímeros produzidos foram caracterizados por espectroscopia na região do infravermelho (FTIR) e os teores de grupos tetrazol incorporados na PAN foram determinados por titulometria de neutralização. A poliacrilonitrila foi modificada quimicamente com sucesso tanto no forno doméstico quanto no reator de micro-ondas, como foi verificado pela sua análise de FTIR. Pela determinação do grau de incorporação de grupos tetrazol nos polímeros concluiu-se que, para a reação em solução, nas temperaturas mais elevas, bem como em uma potência maior, o teor de heterocíclico incorporado no polímero está muito próximo do valor obtido pelo método convencional. Já as reações conduzidas em massa apresentaram graus de incorporação inferiores as das feitas em solução. / In recent years, microwave irradiation has been increasingly used in the synthesis of various organic molecules, due to a number of advantages that this technology presents. To date, few studies on polymerization assisted by microwave and even less about the modification of polymers using this new source of energy. Polymers containing heterocyclic ring azoles such as tetrazole have academic and commercial interest due to their various applications. This thesis has been studying the chemical modification of polyacrylonitrile by its incorporation into the polymer chain, 10% of tetrazole groups employing the irradiation of microwave and conventional method (thermal). We used a domestic microwave oven and a reactor monomode microwave to assisted reactions in the microwave. The reactions were performed in reactor open cup in solution (DMF) or in bulk, and varied the reaction time and temperature, and power equipment. The copolymers were characterized by infrared spectroscopy (FTIR) and the concentrations of tetrazole groups incorporated into the PAN were determined by neutralization titration. The polyacrylonitrile was chemically modified with success both at home and in the oven microwave reactor, as verified by his analysis of FTIR. By determining the degree of incorporation of tetrazole groups in the polymers it was concluded that, for the reaction in solution at higher temperatures, as well as a higher power, the content of heterocyclic incorporated into the polymer is very close to the value obtained by the conventional method. The reactions were conducted in mass lower degree of incorporation of the solution made.