Universiẗat, Diss., 2000--Dortmund. / Dateiformat: PDF.

Heavy metals, despite their essential roles as minerals in biological systems, pose a significant threat to human health and the environment due to their toxic properties. Even at low concentrations, heavy metals such as lead, mercury, arsenic, and cadmium can cause adverse effects on humans and animals. Consequently, stringent regulations have been established to limit heavy metal concentrations in water resources. However, existing laboratory-based analytical methods for heavy metal detection are time-consuming, expensive, and require skilled personnel. The current detection limit required by several health organizations around the globe is below 10 ppb for Lead, Mercury, Chromium, and Arsenic. The current state of the art which can accomplish low levels of detection is either expensive to operate or incapable of achieving the required trace level sensing. This thesis aims to address the need for a simple, cost-effective, and portable method for detecting heavy metals in water. The thesis begins by reviewing the current state-of-the-art heavy metal sensing methods, highlighting their limitations and the requirement for sample preconcentration. Various preconcentration techniques are discussed, emphasizing their performance parameters and advancements in trace-level detection. Furthermore, the thesis identifies the gaps in current technology, particularly in the context of developing a reliable and user-friendly method for testing heavy metal concentrations in drinking and surface waters. The primary objective of this thesis is to develop a preconcentration-based colorimetric method for detecting heavy metals in water. This method aims to overcome the limitations of existing techniques by offering high sensitivity and a limit of detection below regulatory ranges without the need for complex equipment or extensive sample preparation. The thesis contributes to the advancement of the state-of-the-art by providing a simplified, portable, and efficient solution for in-line detection of heavy metal contamination in water resources. This has been achieved through the design and deployment of sensor utilizing a novel architecture, measuring heavy metal ions down to the sub ppb level. we were able to detect ions such as copper and Lead at concentrations below 0.5 ppb with a limit of detection (LOD) of 0.14 ppb. Overall, this thesis combines knowledge from the fields of analytical chemistry, sensor technology, and environmental science to address the pressing need for a practical and accessible method for monitoring heavy metal concentrations in water. By achieving this goal, the research will contribute to safeguarding public health and promoting sustainable water resource management. / Thesis / Doctor of Philosophy (PhD) / Heavy metals can be found naturally and are needed in small amounts for our bodies to function properly. However, many heavy metals are toxic and can cause serious health problems even at very low concentrations. These metals can contaminate water sources through activities like mining and improper waste disposal. Currently, detecting heavy metals in water requires expensive equipment and skilled experts in a laboratory setting. This process is time-consuming and not easily portable for on-site testing. The existing methods also have limitations such as low sensitivity or the need for complex procedures. This thesis aims to improve the way we detect harmful heavy metals in water. The goal of this thesis is to develop a simpler and more sensitive method for detecting heavy metals in water. The focus is on using color-changing dyes that react to the presence of heavy metal ions. However, these dyes often have detection limits higher than what is considered safe, so the thesis also explores ways to concentrate the samples to improve sensitivity. By addressing these challenges, the thesis aims to contribute to the development of a reliable and easy-to-use method for testing heavy metal concentrations in drinking and surface waters, helping to protect public health and identify potential sources of contamination.

No description available.

Specifically binding ions induce the transition of anionic polyacrylate coils from extended conformation to collapsed globules passing through a cascade of intermediate states when solution conditions approach the L-type precipitation threshold. It is the conformation of these intermediate states on surfaces and in solution which is at the focus of this thesis. In comparing the surface and solution conformations of intermediate states, we were able to qualitatively and quantitatively underline the effects of sample history. Two types of quantitative comparisons have been emphasized. In real space, the radius of gyration values of adsorbed molecules have been evaluated incorporating fully the x, y and z axes. These values have been compared with radius of gyration values of the very same sample solution obtained using SLS. In reciprocal space, a novel image processing protocol has been used to generate the 2D form factor curve wherein the correlation maxima have been compared with corresponding maxima obtained for the very same sample solution using small angle scattering techniques like the SANS. The influence of bivalent ions, respectively, Strontium, Lead and Calcium, on the shape of polyacrylate coils is studied. In the last case, temperature has been introduced as a secondary parameter to shed further light on the mechanism by which polyelectrolytebivalent ion complexation takes place. Both scattering and AFM experiments reveal formation of necklace-like structures as intermediates for NaPA-Sr2+ system. Since the mol. wt. of the NaPA coils used was relatively large in this case, adsorption on mica surfaces was strong. Under such conditions, the molecules undergo a z collapse upon flux drying but do not get altered in x and y directions. The ratio Rg(AFM)/Rg(SLS) was found to be in the range 0.7-0.9. The remaining (insignificant) differences in the Rg Abstract ii values arise due to the fact that AFM gives the square root of number averaged mean squared radius of gyration while SLS gives the square root of z-averaged mean squared radius of gyration. The differences in radius of gyration values observed in solution and on surfaces were more prominent for NaPA-Pb2+ system. Again, although both scattering and AFM reveal necklace-like structures as intermediates, the ratio Rg(AFM)/Rg(SLS) was now found to be nearly 0.6. The fact that Rg(AFM) is the square root of number averaged and Rg(SLS) is the square root of z-averaged mean squared radius of gyration, alone cannot explain this low value. Since the mol. wt. of NaPA coils used in this case was quite low, adsorption on mica surfaces was weak. Under such conditions, the molecule does not only undergo a z collapse upon flux drying, but also shrinks in the x and y directions due to capillary forces. Finally, with NaPA-Ca2+ system, the picture did not show a one-to-one correspondence between solution and surface conformations at all. In fact, it showed a one-step-ahead correspondence. As already stated, the coil to globule transition was induced by increasing the equilibration temperature from 15°C to 30°C in this case. SANS could not identify any necklace-like intermediates in solution at the equilibration temperature of 15°C while AFM scans at this temperature showed the beginning of formation of pearls. Likewise, at the equilibration temperature of 30°C, SANS could identify necklace-like intermediates in solution with a large majority of dumbbells while AFM scans at this temperature showed a mix of dumbbells, sausage-like structures and globules. Indeed, we were witnessing an accelerated coil to globule transition on surfaces as compared to the situation in solution resulting in a pre-emption in the formation of intermediate states on surfaces. Since the ratio Rg(AFM)/Rg(SLS) (given the square root of number averaged and the square root of z-averaged mean Abstract iii squared values respectively) at the equilibration temperature of 30°C showed a range of 0.7-0.9 indicating strong adsorption of the relatively high mol. wt. NaPA coil on mica surfaces, our suspect were the substrate-sample interaction forces. The AFM scans were therefore analysed with 2D form factor curves, a better protocol when no assumptions about the shape of adsorbed molecules are made a priori, to trace the effects of sample history. The thesis establishes the general utility of AFM to capture the essential features of a collapsing coil which the very coil exhibits in solution. The shape of the coil on surface and in solution may not be exactly the same, yet reveal the same characteristics. The comparative advantages and disadvantages of salt pre-treated mica surfaces and chemically modified mica surfaces have been brought out. Finally, a definitive new insight is gained as regards the mechanism of coil collapse induced by specifically binding ions. The entropic nature of the process as well as the visualized shape of the collapsing intermediates does not support a mechanism along an electrostatically driven shrinking with linear, rod-like arrays of pearls as intermediates. On a molecular level, it is the liberation of water molecules and Na+ ions which promotes binding of bivalent ions to COO- residues. This binding in turn increases the hydrophobicity of the polyacrylate chains. As a consequence, the chains shrink due to an increased propensity for polymerpolymer contacts (and finally precipitate).

Specifically binding ions induce the transition of anionic polyacrylate coils from extended conformation to collapsed globules passing through a cascade of intermediate states when solution conditions approach the L-type precipitation threshold. It is the conformation of these intermediate states on surfaces and in solution which is at the focus of this thesis. In comparing the surface and solution conformations of intermediate states, we were able to qualitatively and quantitatively underline the effects of sample history. Two types of quantitative comparisons have been emphasized. In real space, the radius of gyration values of adsorbed molecules have been evaluated incorporating fully the x, y and z axes. These values have been compared with radius of gyration values of the very same sample solution obtained using SLS. In reciprocal space, a novel image processing protocol has been used to generate the 2D form factor curve wherein the correlation maxima have been compared with corresponding maxima obtained for the very same sample solution using small angle scattering techniques like the SANS. The influence of bivalent ions, respectively, Strontium, Lead and Calcium, on the shape of polyacrylate coils is studied. In the last case, temperature has been introduced as a secondary parameter to shed further light on the mechanism by which polyelectrolytebivalent ion complexation takes place. Both scattering and AFM experiments reveal formation of necklace-like structures as intermediates for NaPA-Sr2+ system. Since the mol. wt. of the NaPA coils used was relatively large in this case, adsorption on mica surfaces was strong. Under such conditions, the molecules undergo a z collapse upon flux drying but do not get altered in x and y directions. The ratio Rg(AFM)/Rg(SLS) was found to be in the range 0.7-0.9. The remaining (insignificant) differences in the Rg Abstract ii values arise due to the fact that AFM gives the square root of number averaged mean squared radius of gyration while SLS gives the square root of z-averaged mean squared radius of gyration. The differences in radius of gyration values observed in solution and on surfaces were more prominent for NaPA-Pb2+ system. Again, although both scattering and AFM reveal necklace-like structures as intermediates, the ratio Rg(AFM)/Rg(SLS) was now found to be nearly 0.6. The fact that Rg(AFM) is the square root of number averaged and Rg(SLS) is the square root of z-averaged mean squared radius of gyration, alone cannot explain this low value. Since the mol. wt. of NaPA coils used in this case was quite low, adsorption on mica surfaces was weak. Under such conditions, the molecule does not only undergo a z collapse upon flux drying, but also shrinks in the x and y directions due to capillary forces. Finally, with NaPA-Ca2+ system, the picture did not show a one-to-one correspondence between solution and surface conformations at all. In fact, it showed a one-step-ahead correspondence. As already stated, the coil to globule transition was induced by increasing the equilibration temperature from 15°C to 30°C in this case. SANS could not identify any necklace-like intermediates in solution at the equilibration temperature of 15°C while AFM scans at this temperature showed the beginning of formation of pearls. Likewise, at the equilibration temperature of 30°C, SANS could identify necklace-like intermediates in solution with a large majority of dumbbells while AFM scans at this temperature showed a mix of dumbbells, sausage-like structures and globules. Indeed, we were witnessing an accelerated coil to globule transition on surfaces as compared to the situation in solution resulting in a pre-emption in the formation of intermediate states on surfaces. Since the ratio Rg(AFM)/Rg(SLS) (given the square root of number averaged and the square root of z-averaged mean Abstract iii squared values respectively) at the equilibration temperature of 30°C showed a range of 0.7-0.9 indicating strong adsorption of the relatively high mol. wt. NaPA coil on mica surfaces, our suspect were the substrate-sample interaction forces. The AFM scans were therefore analysed with 2D form factor curves, a better protocol when no assumptions about the shape of adsorbed molecules are made a priori, to trace the effects of sample history. The thesis establishes the general utility of AFM to capture the essential features of a collapsing coil which the very coil exhibits in solution. The shape of the coil on surface and in solution may not be exactly the same, yet reveal the same characteristics. The comparative advantages and disadvantages of salt pre-treated mica surfaces and chemically modified mica surfaces have been brought out. Finally, a definitive new insight is gained as regards the mechanism of coil collapse induced by specifically binding ions. The entropic nature of the process as well as the visualized shape of the collapsing intermediates does not support a mechanism along an electrostatically driven shrinking with linear, rod-like arrays of pearls as intermediates. On a molecular level, it is the liberation of water molecules and Na+ ions which promotes binding of bivalent ions to COO- residues. This binding in turn increases the hydrophobicity of the polyacrylate chains. As a consequence, the chains shrink due to an increased propensity for polymerpolymer contacts (and finally precipitate).

Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Polymethacrylates are well known adhesives and can carry specific functionality, but have the disadvantage that their flexible backbones impart limited thermal stability and mechanical strength. Polyurethanes (PUs) are finding increasing application and use in many industries due to their advantageous properties, such as a wide range of flexibility combined with toughness, high chemical resistance and excellent weatherability. PUs do however have some disadvantages, for instance, PU is considered an expensive polymer, especially when considered for solvent based adhesives. the focus of this study was to consider a largely unstudied area of PU chemistry, namely combining PUs with polymethacrylates. Two types of linear urethane macromers (UMs) UM1 and UM2 were synthesized by the polyaddition polymerization of 4,4'-methylenediphenyl diisocyanate (MDI) with ethylene glycol (EG), and MDI with neopentylglycol (NPG), via a pre-polymer method, followed by termination with 2-hydroxy ethylacrylate (2-HEA) and methanol (MeOH) to yield UMs having specific urethane chain lengths, and which have to be predominantly monofunctional. Structural identification of the UMs was verified by MALDI-TOF-MS, FTIR, 13C-NMR and 1HNMR spectroscopy.Various percentages of the respective UMs (0_55 wt % of methacrylate monomers) were then incorporated into polymethyl methacrylate (PMMA) and poly n-butyl methacrylate (PnBMA) backbones via solution free-radical copolymerization. The resulting methyl methacrylate-g-urethane and n-butyl methacrylate-g-urethane copolymers were characterized by 1H-NMR,13C-NMR, FTIR, SEC with double detectors (UV and RI), light scattering, UV-Vis, HPLC, TGA, DSC, DMA and TEM. Weight percentages of UM incorporated into the methyl methacrylate-g-urethane copolymers were calculated using FTIR, UV-Vis and 1H-NMR techniques. Phase separation which occurred between the urethane segment and methacrylate segment in the graft copolymerization products was investigated by DMA, DSC and TEM analysis. Microphase separation occurred in all PMMA-g-UM1 and PnBMA-g-UM1 copolymers: two glass transitions temperatures corresponding to the PMMA or PnBMA and UM1 fractions, respectively, were observed. On the other hand, DMA and DSC results showed that in most graft copolymer products the two respective component parts PMMA-g-UM2 or PnBMA-g- UM2 were compatible, because only one Tg was observed. Two glass transitions occurred for PMMA or PnBMA and UM2 when the amount of UM was increased to 55 wt % during copolymerization and microphase separation was evident in DSC, DMA and TEM measurements. Thermal stability and storage modulus (stiffness) of all the synthesized PMMA-g-urethane and PnBMA-g-urethane copolymers increased as the concentration of urethane macromonomer in the copolymerization feed increased, as confirmed in TGA and DMA results. The surface and adhesive properties of the synthesized graft copolymer were studied by measuring the static contact angle and peel strength. Adhesion increased as the content of UMs increased in the graft copolymer. The graft copolymers prepared using a high UM2 feed for both PMMA and PnBMA showed improved in adhesion compared to the pure methacrylate polymers. The adhesion was better for both leather and for vinyl. / AFRIKAANSE OPSOMMING: Polimetakrilate is bekende kleefstowwe. Hulle het egter die tekortkoming dat hulle buigbare ruggraat beperkte termiese en meganiese stabliteit besit. Poliuretane (PUs) word deesdae al hoe meer gebruik in baie nywerhede as gevolg van hulle baie voordele, insluitend hul wye buigsaamheid tesame met sterkte, hoë chemiese weerstand en uitstekende weerbaarheid. PUs het egter ’n paar nadele: hulle is baie duur, veral wanneer hulle gebruik word in oplosmiddel-gebaseerde kleefstowwe. Die doel van hierdie studie is om die kombinering van PUs met polimetakrilate te bestudeer, 'n onderwerp wat tot dusver baie min aandag-getrek het. Twee tipes liniêre uretaanmakromere (UMs), UM1 en UM2, is gesintetiseer deur gebruik te maak van poliaddisiepolimerisasie van 4,4'-metileendifeniel diisosianaat (MDI) met etileenglikol (EG), en MDI met neopentielglikol (NPG), via ‘n prepolimeermetode, gevolg deur terminering met 2-hidroksiëtielakrilaat (2-HEA) en metanol (MeOH). Die produk hiervan is UMs met spesifieke kettinglengtes (hoofsaaklik monofunksioneel). Die samestelling van die UMs is met behulp van die volgende gevorderde analitiese tegnieke bepaal: MALDI-TOFMS, FTIR, 13C-NMR en 1H-NMR. Verskillende hoeveelhede van die UMs (0_55 gewIing% metakrilaatmonomere) is dan in die polimetielmetakrilaat (PMMA) en poli-n-butielmetakrilaat (PnBMA) ruggrate geïnkorporeer deur middel van oplossing-vryradikaalpolimerisasie. Die samestelling van die kopolimeerprodukte, metiel-metakrilaat-g-uretaan en n-butiel-metakrilaat-g-uretaan, is met behulp van die volgende gevorderde analitiese tegnieke bepaal: 1H-NMR, 13C-NMR, FTIR, SEC met dubbele detektors (UV en RI), ligverstrooiing UV-Vis, HPLC, TGA, DSC, DMA en TEM. Die hoeveelheid UM geïnkorporeer in die metielmetakrilaat-g-uretaan kopolimere is bereken deur gebruik te maak van FTIR, UV-Vis en 1H-NMR data. Die faseskeiding wat plaasgevind het tussen die uretaansegment en die metakrilaatsegment in die produkte van die entpolimerisasie is met behulp van DMA, DSC en TEM ondersoek. In alle PMMA-g-UM1 en PnBMA-g-UM1 kopolimere het mikrofaseskeiding plaasgevind: twee verskillende glasoorgangstemperature vir die PMMA of PnBMA en UM1 fraksies is waargeneem. Hierteenoor het DMA en DSC resultate getoon dat in die meeste entkopolimeerprodukte (PMMA-g-UM2 of PnBMA-g-UM2) was die twee komponente verenigbaar, aangesien net een Tg waargeneem is. In die geval van die kopolimere waar die hoeveelheid UM in die kopolimerisasiereaksies tot 55 gew% verhoog is, is twee glasoorgangstemperature vir PMMA of PnBMA, en UM2 waargeneem. Mikrofaseskeiding is met behulp van DSC, DMA en TEM bewys. Termiese stabiliteit en stoormodulus (styfheid) van alle gesintetiseerde PMMA-g uretaan en PnBMA-g-uretaan kopolimere het toegeneem namate die uretaankonsentrasie in die kopolimerisasiereaksie toegeneem het soos deur middel van TGA en DMA resultate bewys is. Die oppervlakte- en kleefeienskappe van die bereide entkopolimere is bestudeer deur die statiese-kontakhoek en skilkrag te meet. Adhesie het toegeneem namate die UMinhoud toegeneem het. Die entkopolimere berei met hoë PMMA en PnBMA inhoud het uiteindelik beter adhesie getoon as die suiwer metakrilaatpolimere. Die adhesie was beter vir beide leer en viniel.

Lors du décollement d'un adhésif mou (tels que les adhésifs sensibles à la pression, dits PSA), des mécanismes complexes entrent en jeu à l'interface et dans l'épaisseur du film d'adhésif. Afin d¿optimiser ces adhésifs, il convient de maîtriser les transitions entre les différents modes de décollement. Nous avons étudié ces transitons grâce à des matériaux modèles. Nous avons réalisé une analyse quantitative d'expériences de décollement, en nous appuyant notamment sur une nouvelle technique d'analyse d'image. Nous avons également modélisé le comportement mécanique de nos matériaux en traction uniaxiale grâce à un modèle viscoélastique de Phan-Thien et Tanner (PTT) à deux modes. Ces études ont montré la forte hétérogénéité des mécanismes de décollement où des processus à l'interface et dans l'épaisseur de l'adhésif sont en compétition. Pour obtenir des PSA plus efficaces, nous avons donc optimisé leurs propriétés en introduisant un gradient dans les propriétés viscoélastiques du film selon leur épaisseur. Des systèmes bi-couches optimisés montrent d¿intéressantes propriétés, sur surface de forte ou de faible adhésion. Enfin, des adhésifs à gradient continu ont été réalisés et caractérisés via la diffusion d'un réticulant dans un film de polymère puis activation à un instant précis de la réaction de réticulation. / During the debonding of a soft adhesive (as are Pressure Sensitive Adhesives or PSA), complex mechanisms enter in competition at the interface and in the bulk of the adhesive film. In order to optimize these adhesives, it is crucial to understand the transitions between the different debonding modes. We studied these transitions using model materials and carried out a quantitative analysis of debonding experiments with a new image analysis method. We also modeled the mechanical behavior of our materials under uniaxial deformation by using a 2-modes Phan-Thien and Tanner (PTT) viscoelastic model. These studies showed the strong heterogeneity of the debonding mechanisms where process at the interface and in the bulk are in competition. To obtain more efficient PSA, we optimized their properties by introducing a gradient in the viscoelastic properties of the film along their thickness. Bi-layer optimized systems showed interesting properties on surfaces with high or low adhesion. Finally, adhesives with a continuous gradient were realized and characterized by the diffusion of a cross-linker in a polymer film followed by an activation of the cross-linking reaction at a given time

Introdução: Produtos confeccionados a partir de materiais não biodegradáveis têm trazido um grande problema para a sociedade nos dias de hoje. A facilidade de utilização e manipulação dos produtos descartáveis leva a um aumento do consumo, podendo gerar danos para o meio ambiente, quando não há forma eficiente para o tratamento do mesmo. Materiais como fraldas, absorventes e curativos são exemplos de bens de consumo que apresentam Poliacrilato de Sódio, o qual é um polímero superabsorvente não biodegradável, como o principal constituinte destes produtos. O Poliacrilato de Sódio tornou-se muito conhecido a partir da década de 80 quando as fraldas descartáveis começaram a ser comercializadas. Atualmente, são consumidas aproximadamente 18 bilhões de fraldas todos os anos, apenas nos Estados Unidos. Devido aos impactos ambientais que este composto tem gerado, a ciência tem buscado polímeros que possam substituir o Poliacrilato de Sódio nas suas principais características, como superabsorção e alta cinética de intumescimento. Objetivo: No âmbito de desenvolver materiais que possam substituí-lo, buscou-se, neste trabalho, um monômero que apresentasse, em sua molécula, a presença de cadeia carboxílica a qual é a parte altamente hidrofílica. Metodologia: Neste trabalho, foi explorado o monômero de ácido Itacônico como possível substituinte do Poliacrilato de Sódio. Esta substância, além de ser caracterizada pela presença de estruturas hidrofílicas, também é biodegradável. Foram feitas análises de grau de intumescimento do material tanto na forma de gel quanto na forma microgel. A morfologia e a biodegradabilidade do material também foram estudadas. Concomitantemente, foi realizada a padronização do Poliacrilato de sódio para que este fosse utilizado como instrumento comparativo para a avaliação do grau de intumescimento, morfologia e degradabilidade. Hidrogéis de ácido itacônico foram assim analisados e avaliados com o hidrogel de poliacrilato de sódio e os resultados comparados. Resultados: Embora o grau de intumescimento do gel de ácido itacônico não tenha alcançado o mesmo grau de intumescimento do gel de poliacrilato de sódio, os resultados foram bons, uma vez que houve grande absorção de solução pelo gel de ácido itacônico. Além disso, sua biodegradabilidade mostrou resultados fascinantes pela rapidez de degradação e formação de fungos nas amostras. Contudo, são necessários mais estudos, uma vez que a reprodutibilidade do grau de intumescimento do gel 12,5% não foi satisfatória em outros experimentos. Outro obstáculo encontrado no estudo foi a necessidade de se obter uma técnica melhor para a análise da cinética de intumescimento dos géis dos polímeros usados no estudo. A seleção de um polímero ou monômero ideal deve ser caracterizada pela superabsorção, alta cinética de intumescimento, baixo custo, curto tempo de manipulação, baixa toxicidade e biodegradabilidade. Embora as pesquisas sobre o ácido itacônico ainda se encontram em andamento, ele é considerado uma substância promissora para o futuro dos materiais biodegradáveis. / Introduction:Products made from non-biodegradable materials have brought a major problem for society. The easiness of the utilization and manipulation of disposable products leads to an increased consumption, and, consequently, damages to the environment. Besides, most of the discharged of these materials have no efficient treatment affecting the modern society. Materials such as diapers, sanitary napkins and dressings are examples of consumer goods which contain in their main structure sodium polyacrylate, a non-biodegradable superabsorbent polymer. Since 1980, sodium polyacrylate has become well known when disposable diapers began to be marketed. Nowadays, superabsorbent components mainly diapers are consumed in large scale reaching about 18 billion diapers consumed every year only in the U.S. Due to the environmental impacts that sodium polyacrylate has generated, science has sought polymers that can replace sodium polyacrylate in its main features such as high swelling degree and swelling kinetics. Goal: In the ambit to develop materials that can replace sodium polyacrylate, this work focuses on a monomer that has in its molecule, the presence of carboxylic chain which is a highly hydrophilic part. Methodology: In this work it was searched the monomer of itaconic acid as a possible material to replace sodium polyacrylate. This monomer not only has hydrophilic structure in its molecule, but also is biodegradable. During the program, it was made analyses of swelling degree both in gel and in microgel forms. The morphology of its structure and the biodegradability were also studied. Concomitantly, it was made the standardization of sodium polyacrylate to be utilized as a comparative instrument assessing the high swelling degree, morphology and degradability. Itaconic acid hydrogels were analyzed and assessed and the outcomes compared with sodium polyacrylate. Results: Although the swelling degree of itaconic acid has not reached similar results to sodium polyacrylate, the results can still be considered good since the swelling degree of itaconic acid was high. Furthermore, its biodegradability showed excellent results due to the short time of degradation and fungus formation in all samples. However, more studies are necessary, inasmuch as the reproducibility of swelling degree of the itaconic acid 12.5% gel was not satisfactory enough in other experiments. Another obstacle encountered in the study has been the need for a more precise technique for the analysis of the swelling kinetics of the polymers used. The selection of an ideal polymer must present high swelling degree, high kinetics of swelling, low cost, short handling time, low toxicity and high biodegradability. Although the researches about the Itaconic acid have still been undertaken, it is considered a promising substance for the future of biodegradable material.

Introdução: Produtos confeccionados a partir de materiais não biodegradáveis têm trazido um grande problema para a sociedade nos dias de hoje. A facilidade de utilização e manipulação dos produtos descartáveis leva a um aumento do consumo, podendo gerar danos para o meio ambiente, quando não há forma eficiente para o tratamento do mesmo. Materiais como fraldas, absorventes e curativos são exemplos de bens de consumo que apresentam Poliacrilato de Sódio, o qual é um polímero superabsorvente não biodegradável, como o principal constituinte destes produtos. O Poliacrilato de Sódio tornou-se muito conhecido a partir da década de 80 quando as fraldas descartáveis começaram a ser comercializadas. Atualmente, são consumidas aproximadamente 18 bilhões de fraldas todos os anos, apenas nos Estados Unidos. Devido aos impactos ambientais que este composto tem gerado, a ciência tem buscado polímeros que possam substituir o Poliacrilato de Sódio nas suas principais características, como superabsorção e alta cinética de intumescimento. Objetivo: No âmbito de desenvolver materiais que possam substituí-lo, buscou-se, neste trabalho, um monômero que apresentasse, em sua molécula, a presença de cadeia carboxílica a qual é a parte altamente hidrofílica. Metodologia: Neste trabalho, foi explorado o monômero de ácido Itacônico como possível substituinte do Poliacrilato de Sódio. Esta substância, além de ser caracterizada pela presença de estruturas hidrofílicas, também é biodegradável. Foram feitas análises de grau de intumescimento do material tanto na forma de gel quanto na forma microgel. A morfologia e a biodegradabilidade do material também foram estudadas. Concomitantemente, foi realizada a padronização do Poliacrilato de sódio para que este fosse utilizado como instrumento comparativo para a avaliação do grau de intumescimento, morfologia e degradabilidade. Hidrogéis de ácido itacônico foram assim analisados e avaliados com o hidrogel de poliacrilato de sódio e os resultados comparados. Resultados: Embora o grau de intumescimento do gel de ácido itacônico não tenha alcançado o mesmo grau de intumescimento do gel de poliacrilato de sódio, os resultados foram bons, uma vez que houve grande absorção de solução pelo gel de ácido itacônico. Além disso, sua biodegradabilidade mostrou resultados fascinantes pela rapidez de degradação e formação de fungos nas amostras. Contudo, são necessários mais estudos, uma vez que a reprodutibilidade do grau de intumescimento do gel 12,5% não foi satisfatória em outros experimentos. Outro obstáculo encontrado no estudo foi a necessidade de se obter uma técnica melhor para a análise da cinética de intumescimento dos géis dos polímeros usados no estudo. A seleção de um polímero ou monômero ideal deve ser caracterizada pela superabsorção, alta cinética de intumescimento, baixo custo, curto tempo de manipulação, baixa toxicidade e biodegradabilidade. Embora as pesquisas sobre o ácido itacônico ainda se encontram em andamento, ele é considerado uma substância promissora para o futuro dos materiais biodegradáveis. / Introduction:Products made from non-biodegradable materials have brought a major problem for society. The easiness of the utilization and manipulation of disposable products leads to an increased consumption, and, consequently, damages to the environment. Besides, most of the discharged of these materials have no efficient treatment affecting the modern society. Materials such as diapers, sanitary napkins and dressings are examples of consumer goods which contain in their main structure sodium polyacrylate, a non-biodegradable superabsorbent polymer. Since 1980, sodium polyacrylate has become well known when disposable diapers began to be marketed. Nowadays, superabsorbent components mainly diapers are consumed in large scale reaching about 18 billion diapers consumed every year only in the U.S. Due to the environmental impacts that sodium polyacrylate has generated, science has sought polymers that can replace sodium polyacrylate in its main features such as high swelling degree and swelling kinetics. Goal: In the ambit to develop materials that can replace sodium polyacrylate, this work focuses on a monomer that has in its molecule, the presence of carboxylic chain which is a highly hydrophilic part. Methodology: In this work it was searched the monomer of itaconic acid as a possible material to replace sodium polyacrylate. This monomer not only has hydrophilic structure in its molecule, but also is biodegradable. During the program, it was made analyses of swelling degree both in gel and in microgel forms. The morphology of its structure and the biodegradability were also studied. Concomitantly, it was made the standardization of sodium polyacrylate to be utilized as a comparative instrument assessing the high swelling degree, morphology and degradability. Itaconic acid hydrogels were analyzed and assessed and the outcomes compared with sodium polyacrylate. Results: Although the swelling degree of itaconic acid has not reached similar results to sodium polyacrylate, the results can still be considered good since the swelling degree of itaconic acid was high. Furthermore, its biodegradability showed excellent results due to the short time of degradation and fungus formation in all samples. However, more studies are necessary, inasmuch as the reproducibility of swelling degree of the itaconic acid 12.5% gel was not satisfactory enough in other experiments. Another obstacle encountered in the study has been the need for a more precise technique for the analysis of the swelling kinetics of the polymers used. The selection of an ideal polymer must present high swelling degree, high kinetics of swelling, low cost, short handling time, low toxicity and high biodegradability. Although the researches about the Itaconic acid have still been undertaken, it is considered a promising substance for the future of biodegradable material.

abstract: In this study, two novel sorbents (zeolite 4A and sodium polyacrylate) are tested to investigate if utilizing ultrasonic acoustic energy could decrease the amount of time and overall energy required to regenerate these materials for use in cooling applications. To do this, an experiment was designed employing a cartridge heater and a piezoelectric element to be simultaneously providing heat and acoustic power to a custom designed desorption bed while measuring the bed mass and sorbent temperature at various locations. The results prove to be promising showing that early in the desorption process ultrasound may expedite the desorption process in zeolite by as much as five times and in sodium polyacrylate as much as three times in comparison to providing heat alone. The results also show that in zeolite desorption utilizing ultrasound may be particularly beneficial to initiate desorption whereas in sodium polyacrylate ultrasound appears most promising in the after a temperature threshold is met. These are exciting results and may prove to be significant in the future as more novel heat-based cooling cycles are developed. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2018