L'objectif de ce travail était d'étudier l'impact du mode de préparation et de la formulation de bioplastiques transparents issus d'huile de soja sur leur structure et leurs propriétés thermiques et mécaniques. Nous nous sommes plus particulièrement intéressés à l'huile de soja époxydée (ESO), qui a ensuite été acrylée et co-polymérisée avec méthacrylate de méthyle (MMA) en présence ou non de nano-particules de dioxyde de titane. Deux méthodes de préparation d'ESO ont été comparées. La première a fait appel à une époxydation chimique en présence de peroxyde d'hydrogène et d'acide formique. L'acide sulfurique a été utilisé comme catalyseur pour la production de peracides, ces oxydants forts générant ensuite des époxydes par attaque des doubles liaisons des acides gras de l'huile. La seconde consistait en une époxydation chimio-enzymatique, les peracides étant alors générés dans des conditions douces de pH et de température par catalyse enzymatique en présence d'H2O2 et d'huile. Deux types de lipases ont été utilisées comme biocatalyseurs : la lipase de Candida antarctica (Novozyme 435) et la lipase/acyltransférase de C. parapsilosis. Un contrôle de la réaction a permis d'obtenir des produits à différents degrés d'époxydation (50 et 75  3 %). Les effets du mode d'époxydation, du degré d'acrylation et des teneurs en MMA et TiO2 sur les propriétés des bioplastiques obtenus ont été étudiés par FTIR, RMN 1D et 2D, DMTA, TGA et par mesure des propriétés mécaniques.Mots-clés : Biocomposite, Bioplatique, Nanocomposite, Huile de soja époxydée et acrylée (AESO), Dioxyde de titane (TiO2), Biocatalyse, Lipase / The aim of this research to study the effect the production method and the formulation of transparent soybean oil-based bioplastics on their structure and their thermal and mechanical properties. We focused on epoxidized soybean oil (ESO), that was acrylated and copolymerized methyl methacrylate (MMA) with and without titanium dioxide (TiO2). Two methods of ESO preparation were compared. The first used chemical epoxidation in the presence of H2O2 and formic acid, using sulfuric acid as a catalyst to produce peracids as strong oxydants for the epoxidation. The second one was a chemo-enzymatic method where the peracids were generated in mild conditions by an enzyme in the presence of H2O2. Two types of lipases were selected as biocatalysts for the chemo-enzymatic epoxidation: Novozyme®435 and a non-commercial lipase/acyltransferase (CpLIP2). The reaction was controlled so as to obtain different degrees of epoxidation (DOE), i.e. 50+/-3 mol% and 75+/-3 mol%, from both methods. Acrylated ESO (AESO) was chemically synthesized by acrylation of ESO and acrylic acid. Then AESO was copolymerized with MMA and cured to form a rigid polymer using 1 wt% of benzoyl peroxide as a free radical initiator. A nanocomposite was prepared by blending AESO-co-PMMA with 0.1-0.2 wt% nano-TiO2 (particle size 2-5 nm). The effect of degree of acrylation, MMA content and titanium dioxide content on structural, tensile and thermal properties of the obtained bioplastics were studied using Fourier transform infrared spectrometer (FTIR), 1D and 2D NMR, dynamic mechanical thermal analysis (DMTA), thermogravimetric analysis (TGA) and mechanical properties determination.

M.Sc. (Chemistry) / Please refer to full text to view abstract.

Supercritical CO2 foam processing of biopolymers represents a green processing route to environmentally friendly media and packaging foams. Mater-Bi, a multiconstituent biopolymer of polyester, starch and vegetable oils has shown much promise for biodegradation. The polymer, however, is not foamable with CO2 so blended with another polymer which is. Polycaprolactone is a biopolymer with potential of 4000% change in volume with CO2. Thus we investigate blends of Mater-Bi (MB) and polycaprolactone (PCL) foamed in supercritical CO2 using the batch process. Characterization of the foamed and unfoamed samples were done using X-ray diffraction (XRD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Micrographs of the samples from the SEM revealed that the cell size of the foams reduced and increased with increase in MB concentration and increase in the foaming temperature respectively. Mechanical tests; tensile, compression, shear and impact were performed on the foamed samples. It was noted that between the 20-25% wt. MB, there was an improvement in the mechanical properties. This suggests that at these compositions, there is a high interaction between PCL and MB at the molecular level compared to other compositions. The results indicate that green processing of polymer blends is viable.

Cellulose is one of the most abundant biopolymers on earth and is an important commodity for industries such as the pulp and paper industry. Cellulose is deposited into the plant cell walls by a complex of membrane bound enzymes known as cellulose synthases. A number of cellulose synthase (CesA) genes, which encode for different cellulose synthase proteins, have been identified from plant species such as Eucalyptus, Populus and Arabidopsis. Mutant and expression profile analysis of the CesA genes indicated that a set of three CesA genes are associated with secondary cell wall formation, while a different set of CesA genes are associated with primary cell wall formation. The aim of this study was to investigate the transcriptional regulation of the different members of the CesA gene family in Eucalyptus. The promoter regions were comparatively analysed with the orthologous regions in Arabidopsis and Populus using bioinformatics tools to identify putative regulatory motifs that playa role in CesA genes regulation. Six Eucalyptus CesA gene promoters were isolated using genome walking. The Eucalyptus promoter regions and the orthologous promoter regions from Populus and Arabidopsis were analysed using TSSP (Transcriptional start site plant promoter prediction) and NNPP (Neural network promoter prediction) software packages. The software packages predicted the transcriptional start sites of the genes and the core regulatory elements such as the TATA-box and initiator elements. The in silico results were compared among species and it was found that the predicted transcriptional start sites and the core elements of the CesA gene promoters showed substantial structural conservation. The promoter regions were used in a comparative in silico analysis with the orthologous promoter regions from Arabidopsis and Populus to identify putative regulatory motifs. This is the first study in which the promoters of the CesA gene family are characterized in Arabidopsis, Populus and Eucalyptus. Three software packages (Weeder, POCO and MotifSampler) were used to analyse the promoter regions and identify over-represented motif sequences. A number of key stem-specific and xylem-specific motifs such as the AC-motif and G-box motif were identified as well as a number of novel motifs. Although all of the predicted motifs identified here will have to be functionally tested, the results of this study provide a good map for directed deletion studies and functional testing of the CesA promoters. / Dissertation (MSc (Genetics))--University of Pretoria, 2009. / Genetics / unrestricted

Orientador: Marcos Akira d'Ávila / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-22T03:44:39Z (GMT). No. of bitstreams: 1 Salles_TaisHelenaCosta_M.pdf: 2536678 bytes, checksum: 358cfaf694adc91a715f58aabead529d (MD5) Previous issue date: 2013 / Resumo: A eletrofiação é reconhecida como uma técnica eficiente para a fabricação de microfibras e nanofibras de polímero, devido à sua versatilidade e potencial para aplicações em diversos campos. As aplicações notáveis incluem engenharia tecidual, biossensores, filtração, curativos, liberação controlada de fármacos e imobilização de enzimas. As nanofibras são geradas através da aplicação de um campo elétrico em uma solução polimérica. As fibras fiadas por este processo oferecem várias vantagens, como elevada área de superfície em relação ao volume, alta porosidade e a capacidade de manipular a composição de nanofibras, a fim de obter as propriedades e funções desejadas. Neste trabalho, a eletrofiação de blendas de gelatina com polivinilpirrolidona (PVP) para a fabricação de nanofibras foi investigada. Os polímeros foram fiados a partir de soluções contendo diversas concentrações de água e ácido acético. As soluções foram fiadas a uma tensão positiva de 29,0-29,2 kV, uma distância da ponta da agulha ao coletor de 10 cm, e uma vazão de 1 mL / h. Todas as soluções foram avaliadas quanto ao pH, condutividade elétrica, tensão superficial e viscosidade. Foram investigados os efeitos da concentração de ácido acético nas propriedades das soluções que por sua vez, influenciaram no processo de obtenção de fibras por eletrofiação. Foi observado que há uma correlação entre a concentração de ácido acético e a formação de fibras desse sistema, assim como a influência no diâmetro final das fibras. No presente estudo, uma matriz de nanofibras uniformes com diâmetro aproximado de 519, 355 e 154 nm foram produzidas via eletrofiação. A morfologia das membranas foi avaliada por Microscopia Eletrônica de Varredura (MEV). Foi realizada a análise térmica termogravimétrica (TGA) e avaliação de citotoxicidade, visando futuras aplicações em engenharia tecidual / Abstract: The electrospinning is recognized as an efficient technique for the fabrication of polymeric microfibers and nanofibers due to its versatility and potential for applications in many fields. Notable applications include tissue engineering, biosensors, filtration, wound dressings, controlled drug release and enzyme immobilization. The nanofibers are generated by applying an electric field in a polymer solution. The fibers spun by this process offers several advantages such as high surface area relative to volume, high porosity and the ability to manipulate the composition of nanofibers in order to obtain the desired properties and functions desired. In this work, the electrospinning blends of gelatin with polyvinylpyrrolidone (PVP) to fabrication nanofibers were investigated. The polymers were electrospun from solutions containing various concentrations of water and acetic acid. The solutions were electrospun at a positive voltage of 29.0 to 29.2 kV, a distance from the needle tip to the collector of 10 cm and a flow rate of 1 mL / h. All solutions were analyzed as your pH, electrical conductivity, surface tension and viscosity. We investigated the effects of acetic acid concentration on the properties of the solutions, on the other hand, influenced the process of obtaining fibers by electrospinning. It was observed that there was a correlation between the concentration of acetic acid and formation of fibers of that system, as well the influence on the final diameter of the fibers. In the present study, a matrix of nanofibers uniform with diameters of approximately 519, 355 and 154 nm had been produced by electrospinning. The morphology of the membranes was evaluated by Scanning Electron Microscopy (SEM). We made thermal analysis (TGA) and assessment of cytotoxicity, aiming future applications in tissue engineering / Mestrado / Materiais e Processos de Fabricação / Mestra em Engenharia Mecânica

Všeobecne, cieľom tejto diplomovej práce bola príprava a charakterizácia sieťovaných hyaluronových mikrovláken, ktoré by boli stabilné vo vodnom prostredí s vhodnými mechanickými vlastnosťami. Vlákna pripravené technikou zvlákňovania z roztoku boli sieťované pomocou roztoku so sieťovacím činidlom 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimidom alebo roztoku s dvoma sieťovacími činidlami 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimidom a N-hydroxysuccinimidom, vedúcim k amidácii a tvorbe esterových väzieb. Charakterizácia pripravených vzoriek je hlavným cieľom experimentálnej časti práce. Charakteristiky botnání boli vykonané na určenie stability vláken v troch rôznych roztokoch (s pH 7.4, 3 a 11). Na určenie termickej stability bola využitá termogravimetrická analýza a na stanovenie esterifikácie a amidácie bola použitá infračervená spektroskopia s Fourierovou transformáciou. Mechanické vlastnosti vláken boli študované pomocou testovania závislosti stress-strain. Ďalej boli testované reologické vlastnosti ako aj mikroštruktúra a povrch vláken pomocou skenovacieho elektrónového mikroskopu. Vlákna pred chemickým sieťovaním vykazovali nižšiu stabilitu vo všetkých troch roztokoch, termálna stabilita bola taktiež nižšia ako stabilita zosieťovaných vláken. Pre vlákna chemicky nemodifikované so sieťujúcim činidlom, sa objavil iba jeden typ píku pre esterifikáciu. Infračervené spektrum chemicky zosieťovaných vláken ukázalo prítomnosť dvoch píkov pre esterifikáciu, čo je prejavom efektivity sieťovacieho činidla. Amidácia bola tiež výraznejšia pri zosieťovaných vláknach, špeciálne pre vlákna sieťované dlhú dobu a v roztoku s vyššou koncentráciou sieťujúceho činidla. Kvôli nerovnomerným vláknam, mechanické vlastnosti nevykazovali žiadnu závislosť na sieťovaní. Štúdium reológie ukázalo, že viskozita vlákna rozpusteného vo vode je menej závislá na šmykovej rýchlosti ako prášok hyaluronanu sodného rozpusteného vo vode. Napriek mnohým rôznym metódam charakterizácie vláken, ktoré boli použité v tejto práci, je stále veľa možností pre lepšiu charakterizáciu a bližšie pochopenie tohto biopolymérneho materiálu.

Local minima and the saddle points separating them in the energy landscape are known to dominate the dynamics of biopolymer folding. Here we introduce a notion of a “folding funnel” that is concisely defined in terms of energy minima and saddle points, while at the same time conforming to a notion of a “folding funnel” as it is discussed in the protein folding literature.

Ceramic membranes (CM) are robust membranes attributed with high production, long life span and stability against critical conditions. While capital costs are high, these are partially offset by lower operation and maintenance costs compared to polymeric membranes. Like any other low-pressure membrane (LPM), CM faces problems of fouling, low removal of organic matter and poor removal of trace organic compounds (TOrCs). Current pretreatment approaches that are mainly based on coagulation and adsorption can remove some organic matter but with a low removal of the biopolymers component which is responsible for fouling. Powdered activated carbon (PAC) accompanied with a LPM maintains good removal of TOrCs. However, enhanced removal of TOrCs to higher level is required. Submicron powdered activated carbon (SPAC), obtained after crushing commercial activated carbon into very fine particle, and novel activated carbon (KCU 6) which is characterized with larger pores and high surface area were employed. A pre-coating approach, which provides intimated contact between PAC and contaminants, was adopted for wastewater and (high DOC) surface water treatment. For seawater, in-line coagulation with iron III chloride was adopted. Both SPAC and KCU 6 showed good removal of biopolymers at a dose of 30 mg/L with > 85 % and 90 %, respectively. A dose of 40 mg/L of SPAC and 30 mg/L KCU 6 pre-coats were successful used in controlling membrane fouling. SPAC is suggested to remove biopolymers by physical means and adsorption while KCU 6 removed biopolymers through adsorption. Both KCU 6 and SPAC attained high removal of TOrCs whereas KCU 6 showed outstanding performance. Out of 29 TOrCs investigated, KCU 6 showed > 87 % TOrCs rejection for 28 compounds. In seawater pretreatment, transparent exopolymer particles (TEP) were found to be an important foulant. TEP promoted both reversible and irreversible fouling. TEP are highly electronegative while alumina CM is positively charged which support strong TEP–alumina binding. The influence of TEP fouling was minimized with a low dose of 0.5 – 1 mg/l Fe coagulant. Bacteria were almost completely removed; Silt Density Index (SDI) value was maintained to 2 % per minute and a constant permeate turbidity of 0.05 NTU was achieved.

No description available.

Interest in using renewable raw materials to prepare biobased monomers, polymers, and materials is rapidly increasing. The goal of the research described is to develop branched polyesters of plant oil fatty acids, using different core pol yo ls (i.e. sucrose, dipentaerythritol, and tripentaerythritol) and plant oils (i.e. linseed, safflower, and soybean), into curing systems that have potential uses in applications such as coatings, composites, and adhesives. This study is mainly focused on the use of sucrose as the core polyol in the soyate resins. Sucrose esters and their derivatives have a compact structure, high density, and high functionality-double bonds, epoxides, or hydroxyls. When considering the use of sucrose ester compounds to form cross linked materials, the rigid core of sucrose can potentially impart hardness to the thermoset, and the high functionality can lead to rapid gelation and high cross link density. Thus, these novel biobased resins using sucrose esters of plant oils have the potential to be a significant advance in biobased resin technology, as well as to be competitive with the conventional petroleum-based resins.