Telechelic associating polymer networks consist of polymer chains terminated by endgroups that have a different chemical composition than the polymer backbone. When dissolved in a solution, the endgroups cluster together to form aggregates. At low temperature, a strongly connected reversible network is formed and the system behaves like a gel. Telechelic networks are of interest since they are representative for biopolymer networks (e.g. F-actin) and are widely used in medical applications (e.g. hydrogels for tissue engineering, wound dressings) and consumer products (e.g. contact lenses, paint thickeners). In this thesis such systems are studied by means of a molecular dynamics/Monte Carlo simulation. At first, the system in rest is studied by means of graph theory. The changes in network topology upon cooling to the gel state, are characterized. Hereto an extensive study of the eigenvalue spectrum of the gel network is performed. As a result, an in-depth investigation of the eigenvalue spectra for spatial ER, scale-free, and small-world networks is carried out. Next, the gel under the application of a constant shear is studied, with a focus on shear banding and the changes in topology under shear. Finally, the relation between the gel transition and percolation is discussed.

Paraffin is used as a main household energy source for cooking, lighting and heating by low-income communities in South Africa. It is highly inflammable and spillages from paraffin can be considered as one of the major causes of fires that lead to the destruction of dwellings in the informal settlement. The situation is made worse due to the close proximity of the dwellings to each other which cause the fires to spread very quickly from one dwelling to the next leaving suffering and most often death in its wake (Schwebel et al., 2009:700). It has been shown by Muller et al. (2003:2018) that most of the informal rural communities use paraffin in non-ventilated and windowless environments and this causes major respiratory problems. The government has made a huge effort towards replacing paraffin as main cooking fuel in rural and informal settlements with ethanol gel. Ethanol gel is a healthier, safer alternative to paraffin because ethanol gel does not burn unless it is contained within a cooking device that concentrates the flame. It also fails to emit lung irritants or other dangerous chemical vapours when burned indoors (Bizzo et al., 2004:67). Commercial ethanol gels are manufactured with imported gelling agents that make their costs unaffordable to the rural poor communities. It is the objective of this study to determine whether gelling agents extracted from the local endemic species of cactacea viz. Opuntia fiscus-indica and Cereus Jamacaru can be used to synthesise ethanol gel comparable or better than the commercial gels. The two species chosen have been declared pests (Nel et al., 2004:61) and are continuously uprooted from arable land and burned by local farmers (Van Wilgen et al., 2001:162) This study showed that Opuntia ficas-indica stems gave a better cellulose yield (15.0 ± 6.7 wt. %) than Cereus Jamacaru (11.5 ± 7.8wt %). Chemical composition analyses and FT-IR analyses showed that the hemicelluloses and lignin were completely removed from the extracted cellulose and the extraction was more effective for Opuntia ficasindica than for Cereus Jamacaru. Ethanol gel produced by using the extracted cellulose, as was investigated during this study, was compared to commercial gels with respect to viscosity, burn time, calorific values and residue and a good comparison was obtained. / Thesis (M.Sc. Engineering Sciences (Chemical Engineering))--North-West University, Potchefstroom Campus, 2012.

Paraffin is used as a main household energy source for cooking, lighting and heating by low-income communities in South Africa. It is highly inflammable and spillages from paraffin can be considered as one of the major causes of fires that lead to the destruction of dwellings in the informal settlement. The situation is made worse due to the close proximity of the dwellings to each other which cause the fires to spread very quickly from one dwelling to the next leaving suffering and most often death in its wake (Schwebel et al., 2009:700). It has been shown by Muller et al. (2003:2018) that most of the informal rural communities use paraffin in non-ventilated and windowless environments and this causes major respiratory problems. The government has made a huge effort towards replacing paraffin as main cooking fuel in rural and informal settlements with ethanol gel. Ethanol gel is a healthier, safer alternative to paraffin because ethanol gel does not burn unless it is contained within a cooking device that concentrates the flame. It also fails to emit lung irritants or other dangerous chemical vapours when burned indoors (Bizzo et al., 2004:67). Commercial ethanol gels are manufactured with imported gelling agents that make their costs unaffordable to the rural poor communities. It is the objective of this study to determine whether gelling agents extracted from the local endemic species of cactacea viz. Opuntia fiscus-indica and Cereus Jamacaru can be used to synthesise ethanol gel comparable or better than the commercial gels. The two species chosen have been declared pests (Nel et al., 2004:61) and are continuously uprooted from arable land and burned by local farmers (Van Wilgen et al., 2001:162) This study showed that Opuntia ficas-indica stems gave a better cellulose yield (15.0 ± 6.7 wt. %) than Cereus Jamacaru (11.5 ± 7.8wt %). Chemical composition analyses and FT-IR analyses showed that the hemicelluloses and lignin were completely removed from the extracted cellulose and the extraction was more effective for Opuntia ficasindica than for Cereus Jamacaru. Ethanol gel produced by using the extracted cellulose, as was investigated during this study, was compared to commercial gels with respect to viscosity, burn time, calorific values and residue and a good comparison was obtained. / Thesis (M.Sc. Engineering Sciences (Chemical Engineering))--North-West University, Potchefstroom Campus, 2012.

Tyrimo objektas ir metodai: poliakrilo rūgšties polimerų hidroalkoholinių gelinių pagrindų tyrimas. Hidroalkoholinių gelinių pagrindų klampa buvo nustatyta taikant viskozimetrijos metodą, skaidrumas nustatytas spektrofotometrijos metodu. Tyrimais buvo įvertinta karbomero rūšies, alkoholio tipo, koncentracijos ir neutralizatoriaus tipo įtaka klampai, skaidrumui, elektrolitų tolerancijai ir stabilumui. Darbo tikslas: pagaminti skirtingus poliakrilo rūgšties polimerų hidroalkoholinius gelinius pagrindus, siekiant ištirti ir įvertinti alkoholio tipo, koncentracijos, neutralizatoriaus įtaką šių gelinių pagrindų fizikinėms savybėms. Darbo uždaviniai: parengti poliakrilo rūgšties polimerų hidroalkoholinių gelinių pagrindų sudėtis ir pagaminti pagrindus; ištirti polimero rūšies, alkoholio tipo ir koncentracijos įtaką drėkinimo laikui; įvertinti polimero rūšies, alkoholio tipo ir koncentracijos bei neutralizatoriaus įtaką pagrindų klampos ir skaidrumo savybėms; nustatyti elektrolitų poveikį klampai; įvertinti gelių stabilumą. Išvados: trumpiausiu drėkinimo laiku pasižymėjo Carbopol® UtrezTM 10 karbomerai 10 % etilo alkoholyje. Carbopol® UtrezTM 10 polimero geliai pasižymi didesne klampa, o Carbopol® UtrezTM 20 – geresniu skaidrumu ir tolerancija elektrolitams. Skaidrumas, klampa ir klampa pridėjus elektrolitų atvirkščiai proporcinga alkoholio koncentracijai. Nustatyta, kad kai alkoholio koncentracija 10 % klampa didesnė su izopropanoliu, kai 30 arba 50 % - su etanoliu. Taip pat... [toliau žr. visą tekstą] / Object and methods: the investigation of hydroalcoholic gelic bases of polyacrylic acid polymers. The viscosity was determined by viscosimetric method, clarity – by spectrophotometric method. The influence of type of carbomer, type and concentration of alcohol and type of neutralizer were evaluated on viscosity, clarity and stability of the different polyacrylic acid polymer hydroalllcoholic gelic bases. Objective: to prepare compositions of hydroalcoholic gelic bases of polyacrylic acid polymers and produce the bases; to investigate the influence of type of polymer and type and concentration of alcohol on wetting time; to evaluate the influence of type of the polymer, type and concentration of the alcohol, and neutralizer on viscosity and clarity properties of gelic bases; to determine the effect of electrolyte on viscosity; to evaluate the stability of gelic bases. Results: the shortest wetting time was found to Carbopol® UtrezTM 10 polymers in 10 % ethyl alcohol. Gels of the Carbopol® Ultrez 10™ has a higher viscosity and Carbopol® UtrezTM 20 has a better clarity and tolerance to electrolytes. The clarity, viscosity and viscosity after electrolytes addition are inversely related to concentration of alcohol. A viscosity study showed that the base containing 10 % alcohol concentration has a higher viscosity with isopropanol and the base containing 30 or 50 % alcohol concentration has a higher viscosity with ethanol. Also gels of Carbopol® UtrezTM 10 neutralized with... [to full text]

Hydrazine and monomethylhydrazine are widely used as propellants in aerospace and defense industries. However these chemicals are volatile, carcinogenic, and sensitive to impact, which impose serious threats during their usage. In this thesis, we have demonstrated two novel ways to immobilize hydrazine chemicals. In one approach hydrazine, monomethylhydrazine have been gelled using carbon dioxide. Chemical and structural properties of these gels are studied by NMR (1H, 15N, 13C), diffusion-ordered NMR spectroscopy, and Cryo-HRSEM. Thermal reversibility of these gels is also demonstrated. In another approach, hydrazine, monomethylhydrazine and 1,1-dimethylhydrazine are reacted with 5-methyltetrazole to form ionic liquids. Synthesis of novel tetrazole monomers and polymers, .and new method for encapsulating sodium azide have also reported in this thesis

Le travail de cette thèse consiste à mettre au point des gels stimulables à partir d'un polymère hydrosoluble simple : la polyallylamine. Nous avons choisi d'utiliser la réaction réversible entre les acides boroniques et les diols pour former les points de réticulation (esters boroniques). La formation de ces esters boroniques a été étudiée pour deux systèmes modèles composés d'acide 4-carboxyphénylboronique et de cyclopentanediol ou de glucose. La fonctionnalisation de la polyallylamine est effectuée selon deux méthodes : les fonctions phénylboroniques par une réaction d'amidification via un agent de couplage carbodiimide. Les fonctions diol par une réaction d'ouverture du cycle de la gluconolactone. Cette deuxième réaction de greffage peut être réversible à pH élevé. Les mélanges de ces deux polymères permettent la formation de gels réversibles sur une large gamme de pH (pH>6). Cette efficacité de gélification, même à pH neutre, est attribuée à l'effet stabilisateur qu'exercent les fonctions amines du polymère sur les esters boroniques. Il a été également montré que les polymères greffés gluconamide peuvent facilement former des gels en présence de borax. La réaction entre une polyamine et la gluconolactone s'avère être une méthode simple et efficace pour conférer à ce type de polymère un pouvoir viscosifiant important lorsqu'il est combiné avec des dérivés portant des fonctionnalités acides boriques ou boroniques.

Firstly, the effect of pectin on acid milk gels in concentrated, quiescent systems was investigated by passive microrheology using two complementary techniques: diffusive wave spectroscopy (DWS) and multiple particle tracking (MPT). DWS, by allowing probing the mechanical properties of the network at high frequency, gave information on its microstructure. The addition of high methoxyl pectins was shown to change the network structure which has been explained by bridging of the casein micelles by the polymer as the system was undergoing acidification. On the other hand, the presence of low methoxyl pectin in the acid milk gel was shown to have no effect on the microstructure of the network at low concentration of polymer (0.1%w/w) which has been attributed to the sensitivity of this low DM pectin to calcium: LM pectin are trapped by calcium and not able to interact with casein micelles anymore. Multiple particle tracking was used to probe the effect of pectin on the heterogeneity of the system by following the distribution of the displacements of added micro beads at a given time lag during the gelation using the Van Hove distribution. Furthermore, the surface chemistry of the probes was modified in an attempt to control their location in the system. Finally, the mean square displacements of the casein micelles obtained by DWS and, of k-casein coated particles obtained by MPT were shown to give good agreement for the same acid milk system. Having established that the interaction between casein micelles and low methoxyl pectin is prevented by the pectin sensitivity to calcium, the effect of the pectin fine structure was investigated on the interaction between k-casein and pectin by surface plasmon resonance (SPR). The amount of pectin binding on a k-casein coated gold surface was shown to be strongly dependant on the pectin fine structure. It was concluded that small negative patches on the pectin backbone, likely to comprise of around two consecutive unmethylesterified galacturonic acid, are the most effective for pectin binding to k-casein. The effect of the direct interaction between pectin and k- casein on ‘calcium-free casein micelle mimics’ in pectin solution was then investigated using coated latex beads. A pectin structure with a limited number of negative patches on its backbone was also shown to limit the potential for destabilization via bridging.

Made available in DSpace on 2014-10-09T12:27:01Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:47Z (GMT). No. of bitstreams: 0 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP / FAPESP:06/54851-8

COSTA, Vanderson da Silva. Elaboração de novo produto gelificado à base de extrato hidrossolúvel da amêndoa da castanha de caju: estudo dos parâmetros sensoriais. 2013. 78 f. : Dissertação (mestrado) - Universidade Federal do Ceará, Centro de Ciências Agrárias, Departamento de Tecnologia de Alimentos, Fortaleza-CE, 2013 / Submitted by Nádja Goes (nmoraissoares@gmail.com) on 2016-06-30T14:11:28Z No. of bitstreams: 1 2013_dis_vscosta.pdf: 1081233 bytes, checksum: b4954dea317cbf8070be5051d6323fd0 (MD5) / Approved for entry into archive by Nádja Goes (nmoraissoares@gmail.com) on 2016-06-30T14:11:51Z (GMT) No. of bitstreams: 1 2013_dis_vscosta.pdf: 1081233 bytes, checksum: b4954dea317cbf8070be5051d6323fd0 (MD5) / Made available in DSpace on 2016-06-30T14:11:51Z (GMT). No. of bitstreams: 1 2013_dis_vscosta.pdf: 1081233 bytes, checksum: b4954dea317cbf8070be5051d6323fd0 (MD5) Previous issue date: 2013 / Considering the economic importance of cashews nuts for the state of Ceará, Brazil's main exporter of this product and the high percentage of broken kernels during processing Chestnut considerably decreases the profit-making in this sector, it is necessary to search for new alternatives for utilization of this raw material as a way of adding value to it. Thus , this research aimed to develop a product based on watersoluble extract of almond cashew (EHACC) and blend of guar gum/carrageenan (CG) using the orthogonal factorial design 2² with three central points and the technique of response surface for optimization of sensory characteristics. By applying affective sensory testing scale relative to the ideal and structured hedonic scale of nine points , the center point of the formulations with different percentages of sucrose were evaluated for selecting the optimal sucrose concentration by linear regression analysis , analysis of the ideality firmness and acceptance of attributes color, aroma, texture, flavor and overall impression . The formulations of the experimental design with the addition of the ideal percentage of sucrose were analyzed in relation to global hedonic acceptance and ideality of visual texture, manual and oral texture texture. The optimal concentration was 22 % sweetness of sucrose. There was a trend of increasing acceptance at the midpoint of a 0,3g/100mL guar/carrageenan in 50:50 experimental design. The visual texture evaluation showed that the higher the concentration of hydrocolloids, most ideality. In the evaluation of manual and oral texture none of the samples reached 70 % of ideality. Thus, the combination of quantity and proportion of the blend midpoint contributed to greater acceptance of gelled product features and good acceptance tested showed a potential for commercial success for future marketing of the product. / Considerando a importância econômica das amêndoas da castanha de caju para o estado do Ceará, o principal exportador brasileiro deste produto e o elevado percentual de amêndoas quebradas durante o beneficiamento da castanha que diminui consideravelmente a obtenção de lucro desse setor, faz-se necessária a busca por novas alternativas de aproveitamento desta matéria-prima como forma de agregação de valor a mesma. Dessa forma, esta pesquisa objetivou desenvolver um produto à base de extrato hidrossolúvel da amêndoa da castanha de caju (EHACC) e blenda de goma guar/carragena (GC) usando o delineamento ortogonal fatorial 22 com três pontos centrais e a técnica de superfície de resposta para otimização de características sensoriais. Através da aplicação de testes sensoriais afetivos de escala relativa ao ideal e escala hedônica estruturada de nove pontos, as formulações do ponto central com diferentes porcentagens de sacarose foram avaliadas para a seleção da concentração ideal de sacarose através análise de regressão linear, análise da idealidade da firmeza e aceitação dos atributos cor, aroma, textura, sabor e impressão global. As formulações do planejamento experimental com adição da porcentagem ideal de sacarose foram analisadas em relação à aceitação hedônica global e idealidade de textura visual, textura manual e textura oral. A concentração ideal de doçura ficou em 22% de sacarose. Observou-se uma tendência de aceitação crescente no ponto central do delineamento experimental correspondente a 0,3g/100mL de guar/carragena na proporção 50:50. A avaliação de textura visual mostrou que quanto maior a concentração de hidrocolóides, maior a idealidade. Na avaliação de textura manual e oral nenhuma das amostras alcançou 70% de idealidade. Assim, a combinação quantidade e proporção de blenda no ponto central contribuiu para uma maior aceitação do produto gelificado e a boa aceitabilidade das características testadas revelaram um potencial de sucesso comercial para uma futura comercialização do produto.

Made available in DSpace on 2014-10-09T12:37:37Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:11Z (GMT). No. of bitstreams: 1 05332.pdf: 2914455 bytes, checksum: c697ecb9e5304ef8da8ed2413bee9263 (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP