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1
Robinson, Leslie A. (Leslie Anne) 1982. "Structural opportunities of ETFE (ethylene tetra fluoro ethylene)". Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/31127.
Testo completoAbstract (sommario):
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2005.Includes bibliographical references (leaves 53-54).
An exploration of ETFE (ethylene tetra fluoro ethylene) foil cushions was performed in its use for building cladding. ETFE foil cushions consist of alternating layers of ETFE film and air cavities. An inflation system pressurizes the foil cushions prestressing the film layers to carry applied load. The ETFE cushion system is an extremely lightweight plastic offering considerable advantages over traditional cladding materials. ETFE foil cushions are self-cleaning, highly transparent to light, resistant to weathering and can be manufactured in almost any shape and size. Incorporating ETFE into a building's cladding results in a more efficient and low maintenance structure. ETFE foil cushions are successfully being implemented in cladding for botanical gardens, zoo buildings, and swimming pools. ETFE is currently finding its place as an effective alternative to glass in more traditional buildings as roofing for courtyards, atria, and shopping malls.
by Leslie A. Robinson.
M.Eng.
2
Glikman, Jean-François. "Oxydation photo-thermique des copolymeres ethylene-acetate de vinyle, ethylene-acrylate d'ethyle, ethylene-acide acrylique". Clermont-Ferrand 2, 1987. http://www.theses.fr/1987CLF21050.
Testo completoAbstract (sommario):
Irradiation sous vide et dans l'air. La vitesse d'apparition des produits de photooxydation depend du type de copolymere. Cinetique et mecanisme. Mise en evidence de la labilite croissante de l'atome d'hydrogene tertiaire situe en position alpha des groupes substituants quand on passe de l'acetate a l'ethylate et a l'acide. Influence de charges et de stabilisants
3
Mbarawa, M., W. Lee, YW Nam e SH Chung. "Ethylene propane and ethylene ester synergistic effects on soot formation". R&D Journal of the South African Institution of Mechanical Engineering, 2007. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1000860.
Testo completoAbstract (sommario):
In this study, the synergistic elfects of ethylene-propane
and ethylene-dimethyl ester (DME) mirtures on soot
formation were investigated experimentully using u coflow
dilfusion flame burnen The soot volume fraction,
soot particle diameter and number density were measured
and compured to the homogenous mixture. Addition
of DME and propane to the ethylene fuel increased
soot volume fraction in the ethylene flames. The ethylene-
propnne has more pronounced synergistic ffict in
compsrison to the ethylene-DME flame* This is due
to the fact that during the decomposition of propane
some methyl radicals are generated, The reuctions
related to these methyl radicals promote the formation
of propargyl rodiculs and conseqaently the formation
of benzene through propargyl self-reaction and finally
to the soot formation. Althoagh DME decomposition
produces methyl, the C-O bond in the DME removes
some carbon from the reaction puth that produces soot,
Hence the soot formation in ethylene-DME mixture is
much slower than that in ethylene-propane mixtuFe,
4
Shaikh, Yacoob. "Towards Selective Ethylene Tetramerization". Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23161.
Testo completoAbstract (sommario):
There is an increasing trend towards advancing the understanding and development of ethylene oligomerization catalysts, both in academia and industry. The metal of choice in this chemistry is invariably chromium, which has shown great versatility in selective trimerization/tetramerization, non-selective oligomerization and polymerization of ethylene. While much success has been achieved in ethylene trimerization, the same con not be said about tetramerization catalysis. Aminophosphine based ligands have demonstrated their ability towards selective 1-octene production, however, the popular PNP catalyst is able to achieve only 70% selectivity. In order to explore the possibility of developing and enhancing the selectivity of chromium based ethylene tetramerization catalyst, this thesis work was undertaken. The ligand systems we chose for our work were bidentate aminophosphine based (PN(CH2)nNP), which has yielded interesting selective oligomerization. Subtle modifications were found to result in drastic changes in selectivity, from tetramerization (PN(CH2)3NP) to trimerization (PN(CH2)2NP). We managed to successfully develop the first truly selective (over 90%) 1-octene catalyst with polymer-free behavior. Further modifications on the ligand framework, where one atom of Si was used to link the two NP units, resulted in non-selective oligomerization, in which case we determined that the oxidation-state of chromium is a key player. We explored other modifications on our selective ligands in which one of the arms on the bidentate ligand was replaced with a base-donor amine, phosphine or pyridine, and resulted in interesting selectivity changes. The final modification that we tested was a novel N(CH2)2P ligand and found it to be a highly active, non-selective oligomerization catalyst.
5
Auden, Noel Geraint. "Ethylene-vinyl acetate copolymers". Thesis, Lancaster University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239046.
Testo completo
6
Porter, Andrew J. R. "The regulation of ethylene biosynthesis by the ethylene-forming enzyme in plant tissues". Thesis, University of Reading, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259342.
Testo completo
7
Burgess, Steven K. "Fundamentals of transport in poly(ethylene terephthalate) and poly(ethylene furanoate) barrier materials". Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54887.
Testo completoAbstract (sommario):
The increasing use of polymeric materials in food packaging applications is due to many factors; however, most are related to cost. While poly(ethylene terephthalate) (PET) is currently the industry standard for soft-drink bottles, more stringent requirements on the barrier properties to oxygen are needed for PET to expand further into more demanding markets (i.e., juice, etc). The current work examines the fundamental oxygen and carbon dioxide permeation and sorption properties of amorphous, caffeine antiplasticized PET and amorphous poly(ethylene furanoate) (PEF), which is a new biologically sourced polyester that exhibits significantly enhanced performance compared to petroleum-sourced PET. The fundamental transport data reported herein at 35°C illustrate that amorphous PEF exhibits significant reductions in permeability for oxygen (11X), carbon dioxide (19X), and water (2X) compared to amorphous PET. Such impressive barrier enhancements are unexpected since PEF exhibits a higher free volume compared to PET. Further investigation into the fundamental chain motional processes which contribute to penetrant diffusion, as probed via dynamic mechanical and solid-state NMR methods, reveals that the polymer ring-flipping motions in PEF are largely suppressed compared to those for PET. Such behavior allows for rationalization of the reduced transport properties compared to PET. Additional characterization techniques (i.e., thermal, mechanical, density, etc.) are used to develop a more complete understanding of PEF and caffeine antiplasticized PET, with the ultimate goal of relating these properties to penetrant transport.
8
Ndiripo, Anthony. "Comparative study on the molecular structure of ethylene/1-octene, ethylene/1-heptene and ethylene/1-pentene copolymers using advanced analytical methods". Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/96889.
Testo completoAbstract (sommario):
Thesis (MSc)--Stellenbosch University, 2015.ENGLISH ABSTRACT: Linear low density polyethylene (LLDPE), one of the fastest growing types of polyethylene, is made from the copolymerisation of ethylene and higher 1-olefin comonomers. 1-octene is the comonomer of choice as it gives mechanically better LLDPEs as compared to other 1-olefins. Recently, a shortage of 1-octene has been observed in the global market. Considering the fact that ethylene/1-heptene (EH) copolymers may have properties that are very similar to those of ethylene/1-octene (EO), replacing 1-octene with 1-heptene as the comonomer in the manufacture of commercial linear low density polyethylene (LLDPE) is a viable option. In order to do so, evaluation of microstructural and mechanical properties of both types of resins and their comparison were carried out first. Several LLDPE resins were synthesised using Ziegler-Natta (ZN) and metallocene type catalysts. The LLDPE resins were made using varying amounts of the comonomer to obtain copolymers of different compositions. Ten of the ZN-LLDPE resins became the core focus of the present study. Carbon-13 nuclear magnetic resonance spectroscopy (13C NMR) showed the differences in the compositions of both the EH and EOresins. Crystallisation analysis fractionation (CRYSTAF), differential scanning calorimetry (DSC) and high temperature high performance liquid chromatography (HT-HPLC) revealed the presence of at least two fractions within the EH and EO copolymers which varied in quantity and chemical composition as the comonomer content was increased. The fractions were identified as being the copolymer (of ethylene and the comonomer) and polyethylene. Comparisons of the EH and EO CRYSTAF and HPLC data showed similarities in the microstructures of the resins. Preparative-temperature rising elution fractionation (prep-TREF) was used to obtain several fractions from each resin for quantification and analyses. DSC, HT-HPLC, CRYSTAF, and 13CNMR revealed close similarities in the fractions of EH and EO copolymers with comparable comonomer contents. It also was revealed that TREF fractionations are influenced by the bulk resin comonomer content. EH and EO copolymers demonstrated high similarities in tensile strength and Young’s modulus at comonomer contents of < 3 mol %. Minor differences in the mentioned properties at comonomer content of > 3 mol % were attributed to the slightly better ability of 1-octene at reducing crystallinity as compared to 1-heptene as well as small differences in the comonomer contents of the test samples. The results of the study suggest that 1-heptene can be used in the place of 1-octene in the commercial manufacture of LLDPE.
AFRIKAANSE OPSOMMING: Lineêre lae digtheid poliëtileen (LLDPE), een van die vinnigste groeiende poliëtileen tipes, word produseer deur die ko-polimerisasie van etileen en ‘n hoër 1-olefien ko-monomeer. 1-okteen is die ko-monomeer wat die meeste gebruik word aangesien dit LLDPE met die beste meganiese eienskappe produseer. Daar is egter ‘n tekort aan 1-okteen in die globale mark. Aangesien etileen/1-hepteen (EH) kopolimere moontlik soortgelyke eienskappe het as etileen/1-okteen (EO), kan 1-okteen moontlik vervang word deur 1-hepteen as ‘n komonomeer in die produksie van LLDPE. Om dit te doen is die meganiese en mikrostrukturele eienskappe van beide polimere geëvalueer. Verskeie LLDPE polimere is gesintetiseer met behulp van Ziegler-Natta (ZN) en metalloseen kataliste. Die komonomeer inhoud is gevarieer om LLDPE polimere te produseer met verskillende komposisie. Tien van die gesintetiseerde ZN-LLDPE polimere is gekies en is die kernfokus van die huidige studie. 13-Koolstof kern magnetiese resonans spektroskopie (13C KMR) het die variasie in ko-monomeer inhoud bevestig van beide die EH en EO polimere. Kristallisasie analise fraksioneering (CRYSTAF), differensiële skandeer kalorimetrie (DSC) en 'n hoë temperatuur hoë verrigting vloeistof chromatografie (HT-HPLC) het die teenwoordigheid van ten minste twee fraksies binne die EH en EO ko-polimeer bevestig wat ‘n variasie in hoeveelheid en chemise samestelling getoon het met ‘n toename van die ko-monomeer inhoud in die ko-polimeer. CRYSTAF en HT-HPLC data het getoon dat hierdie fraksies in EH en EO ooreenkomstige mikrostrukturele gedrag getoon het. Preparatiewe temperatuur styging elueering fraksioneering (prep-TREF) is gebruik om die polimere te fraksioneer om sodoende kwantitief die poliëtileen fraksies te verky en te analiseer. Verdere analise van die fraksies deur DSC, HT-HPLC, CRYSTAF en 13C KMR het getoon dat die fraksies, bekom van die EH en EO kopolimere met vergelykbare ko-monomeer inhoud, baie dieselfde eienskappe toon. Die analises het ook getoon dat die TREF fraksionering beinvloed word deur die ko-monomeer inhoud van die oorspronklike ko-polimeer.
9
Resnick, Josephine Stockton. "Reversion-to-ethylene-sensitivity1 a novel regulator of ethylene receptor function in Arabidopsis thaliana /". College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/4142.
Testo completoAbstract (sommario):
Thesis (Ph. D.) -- University of Maryland, College Park, 2006.Thesis research directed by: Cell Biology & Molecular Genetics. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
10
Nehring, Ramlah Bliss. "Characterization of ETHYLENE INSENSITIVE SIX and the ENHANCER OF ETHYLENE INSENSITIVE in Arabidopsis thaliana". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3262184.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of California, San Diego, 2007.Title from first page of PDF file (viewed April 9, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 102-117).
11
Lu, Xuehong. "Structure of random copolymers of poly(ethylene terephthalate) and poly(ethylene naphthalene-2,6-dicarboxylate)". Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338271.
Testo completo
12
Ozbek, Murat Olus. "Computational Study Of Ethylene Epoxidation". Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613856/index.pdf.
Testo completoAbstract (sommario):
This work computationally investigates the partial oxidation of ethylene (i.e. ethylene epoxidation) using periodic Density Functional Theory (DFT) on slab models that represent the catalyst surfaces. The mechanical aspects of the reaction were investigated on silver surfaces, which are industrially applied catalysts, for a wide range of surface models varying from metallic surfaces with low oxygen coverage to oxide surfaces. For comparison, the metallic and oxide phases of copper and gold were also studied. On these surfaces, the reaction paths and the transition states along these paths for the selective and non-selective reaction channels were obtained using the climbing image nudged elastic band (CI-NEB) method.
In order to answer the question &ldquowhat is the relation between the surface state and the ethylene oxide selectivity?&rdquo
metallic (100), (110) and (111) surfaces of Cu, Ag and Au
and, (001) surfaces of Cu2O, Ag2O and Au2O oxides were studied and compared. For the studied metallic surfaces, it was found that the selective and non-selective reaction channels proceed through the oxametallacycle (OMC) intermediate, and the product selectivity depends on the relative barriers of the these channels, in agreement with the previous reports. However for the studied metallic surfaces and oxygen coverages, a surface state that favors the ethylene oxide (EO) formation was not identified. The studied Au surfaces did not favor the oxygen adsorption and dissociation, and the Cu surfaces favored the non-selective product (acetaldehyde, AA) formation. Nevertheless, the results of Ag surfaces are in agreement with the ~50% EO selectivity of the un-promoted silver catalyst. The catalyst surface in the oxide state was modeled by the (001) surfaces of the well defined Cu2O, Ag2O and Au2O oxide phases. Among these three oxides, the Cu2O is found not to favor EO formation whereas Au2O is known to be unstable, however selective for epoxidation. The major finding of this work is the identification of a direct epoxidation path that is enabled by the reaction of the surface oxygen atoms, which are in two-fold (i.e. bridge) positions and naturally exist on (001) oxide surfaces of the studied metals. Among the three oxides studied, only Ag2O(001) surface does not show a barrier for the formation of adsorbed epoxide along the direct epoxidation path. Moreover, the overall heat of reaction that is around 105 kJ/mol agrees well with the previous reports. The single step, direct epoxidation path is a key step in explaining the high EO selectivities observed. Also for the oxide surfaces, the un-selective reaction that ends up in combustion products is found to proceed through the OMC mechanism where aldehyde formation is favored. Another major finding of this study is that, for the studied oxide surfaces two different types of OMC intermediates are possible. The first possibility is the formation of the OMC intermediate on oxygen vacant sites, where the ethylene can interact with the surface metal atoms directly. The second possibility is the formation of a direct OMC intermediate, through the interaction of the gas phase ethylene with the non-vacant oxide surface. This occurs through the local surface reconstruction induced by the ethylene. The effect of Cl promotion was also studied. Coadsorption of Cl is found to suppress the oxygen vacant sites and also the reconstruction effects that are induced by ethylene adsorption. Thus, by preventing the interaction of the ethylene directly with the surface metal atoms, Cl prevents the OMC formation, therefore the non-selective channel. At the same time Cl increases the electrophilicity of reacting surface oxygen. The direct epoxidation path appears to be stabilized by coadsorbed oxygen atoms. Thus, we carry the discussions on the silver catalyzed ethylene epoxidation one step further. Herein we present that the EO selectivity will be limited in the case of metallic catalyst, whereas, the oxide surfaces enable a direct mechanism where EO is produced selectively. The role of the Cl promoter is found to be mainly steric where it blocks the sites of non-selective channel.
13
Law, D. "Aspects of ethylene epoxidation catalysis". Thesis, University of Liverpool, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333563.
Testo completo
14
Tan, S. A. "The mechanism of ethylene epoxidation". Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383935.
Testo completo
15
Sozynski, Jan Maria. "Synthesis of Novel Ethylene Antagonists". Thesis, Curtin University, 2022. http://hdl.handle.net/20.500.11937/89600.
Testo completoAbstract (sommario):
In search of more user-friendly ethylene antagonists, synthesis of water soluble cycloproparenes and [1,2,3]triazolo[1,5-a]pyridines were targeted for this study. A series of precursors to water soluble cycloproparenes were synthesised, however all decomposed in the final reaction. Functionalised analogues of [1,2,3]triazolo[1,5-a]pyridines were prepared and demonstrated some anatgonism of ethylene action in a series of chemical reactivity and preliminary in vivo assays.
16
Billuart, Guilhem. "Free radical emulsion polymerization of ethylene". Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10033.
Testo completoAbstract (sommario):
Les travaux présentés dans cette thèse portent sur la polymérisation radicalaire de l'éthylène en émulsion, dans des conditions douces (P < 250 bar et T < 90 °C). Tout d'abord, l'homopolymérisation de l'éthylène a été étudiée. Des latex stables de polyéthylène présentant des taux de solide relativement élevés (30 %) ont été obtenus. Pour cela, deux systèmes différents d'amorçage et de stabilisation (cationique et anionique) ont été employés. Ces latex peuvent trouver des applications comme revêtements hydrophobes (par exemple du papier). L'étude des propriétés thermiques des latex a mis en évidence des phénomènes de cristallisation du polyéthylène à basse température, dû à son confinement dans les nanoparticules. Cela a une forte influence sur les morphologies finales des particules. D'autre part, la copolymérisation radicalaire de l'éthylène en émulsion a été étudiée. Les comonomères utilisés sont le styrène, l'acrylate de butyle, le méthacrylate de méthyle et l'acétate de vinyle qui différent par leur solubilité dans l'eau et leurs rapports de réactivité de copolymérisation avec l'éthylène. La composition des copolymères obtenus influence leurs propriétés thermiques (Tg, Tf). Des latex stables de copolymères de compositions variées ont pu ainsi être synthétisés. Ce travail en homo- et copolymérisation a souligné la complexité des milieux de polymérisation en émulsion impliquant un monomère gazeux supercritique comme l'éthylèneIn this work, the free radical emulsion polymerization of ethylene under mild conditions (P < 250 bar and T < 90 °C) was investigated. Ethylene homopolymerization was first studied. Stable polyethylene latexes of significantly high solids content (30 %) were produced. This was achieved by the use of two different initiating and stabilizing systems (cationic and anionic). These latexes could be applied as hydrophobic coatings (e.g. on paper). Investigation of the thermal properties of the latexes evidenced crystallization phenomena at low temperatures, owing to PE confinement in the nanoparticles, which strongly impacted their final morphologies. Free radical emulsion copolymerization of ethylene was then studied. The investigated comonomers were styrene, butyl acrylate, methyl methacrylate and vinyl acetate. They differ in their reactivity ratios to ethylene and their water solubility. The composition of the obtained copolymers had a strong influence on their thermal properties (Tg, Tm). Stable latexes containing copolymers of various compositions were thus synthesized. This work on homo- and copolymerization evidenced the complexity of the polymerization media involving a gaseous supercritical monomer such as ethylene
17
Wysocki, Clare L. "Reinforcement of Ethylene Propylene Rubber (EPR) and Ethylene Propylene Diene Rubber (EPDM) by Zinc Dimethacrylate". University of Akron / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=akron1145038716.
Testo completo
18
Audouin, Hugo. "Transformation de l'éthylène par les complexes du titane : de la géométrie des complexes à la production sélective d'hexène-1". Thesis, Lyon, École normale supérieure, 2015. http://www.theses.fr/2015ENSL1018/document.
Testo completoAbstract (sommario):
Les α-oléfines jouent un rôle très important en tant qu'intermédiaires réactionnels dans l'industrie chimique et pétrochimique. Leur utilisation principale est la production de diverses qualités de polyéthylène dans lequel l'α-oléfine est engagée en tant que co-monomère (butène-1, hexène-1 et octène-1). Les systèmes capables de dimériser, trimériser voir tétramériser sélectivement l'éthylène en α-oléfines supérieures, utilisent principalement le titane et le chrome. Du fait de la toxicité potentielle du chrome, la recherche industrielle et académique s’oriente de plus en plus vers des systèmes à base de titane.Notre objectif dans ce contexte était d’étudier le potentiel des systèmes « phénoxy-tridente » du Ti(IV) pour la trimérisation sélective de l’éthylène en hexène-1. De nombreux systèmes de formules générales [(ArO-X-L)TiCl3] (X=O,P,N et L=O,P,N) ont ainsi été isolés et caractérisés. L’étude de leurs propriétés électroniques et stériques et ses conséquences sur leurs performances en oligomérisation/polymérisation de l’éthylène ont été discutées. Elles mettent en évidence la criticité de l’ensemble des paramètres à la fois électroniques et structuraux du ligand. Un seul système de cette famille est capable de produire sélectivement de l’hexène-1, les autres conduisant à la polymérisation de l’éthylène.Une étude DFT associée à une étude expérimentale des propriétés redox des précurseurs catalytiques ou encore du comportement hémilabile des ligands mis en jeu, nous a conduit à proposer un mécanisme identifiant la phase d’activation comme l’élément clé permettant d’orienter les systèmes étudiés vers la polymérisation ou la production sélective d’hexène-1Linear α-olefins (LAOs) are crucial importance for the chemical and petrochemical industry as they are highly valuable feedstock for a variety of process mainly as co-monomer for the production of different grade of polyethylene (1-butene, 1-hexene and 1-octene). Some systems and predominantly chromium and titanium systems have performed selective dimerization, trimerization and tetramerization of ethylene to higher α-olefins. For toxicity reasons, industrial and academic research focus more and more on titanium-based systems.Our objective in this context was the study of potential “tridentate phenoxy” systems of Ti(IV) for selective trimerization of ethylene to 1-hexene. Numerous systems with general formula [(ArO-X-L)TiCl3] (X=O,P,N and L=O,P,N) were described and characterized. The study of electronic and steric properties and their consequences on catalytic performances in oligomerization/polymerization of ethylene were discussed. They showed the criticity of all electronic and structural parameters of ligands. Only one system of this family is able to produce selectively 1-hexene, others give mainly polyethylene.DFT study associated with an experimental study of redox properties on catalytic precursors or the hemilabile behavior of ligands involved, led us to propose a mechanism identifying the activation phase as the key to switch between polymerization or selective trimerization of ethylene
19
Fakhrnasova, Dina. "Rational and statistical approaches in enhancing yield of ethylene carbonate in urea transesterification with ethylene glycol". Doctoral thesis, Universitat Rovira i Virgili, 2016. http://hdl.handle.net/10803/364779.
Testo completoAbstract (sommario):
Aquest treball d’investigació aplica una aproximació racional per a la millora de les propietats del catalitzador emprat en la transesterificació de la urea amb etilenglicol (EG), per a la producció de carbonat d'etilè (EC) sobre òxids metàl•lics; i un enfocament estadístic per maximitzar la formació del producte desitjat. Per a l’aproximació racional, òxids metàl•lics singulars i mixtes amb combinacions elementals (Zn, Mg, Al, Fe), i amb una àmplia varietat de propietats àcid-base, han estat sintetitzats i avaluats per a la reacció de transesterificació. El rol de l’acidesa i la basicitat en les rutes de reacció identificades han estat clarificats en base a la selectivitat dels productes, i als paràmetres cinètics obtinguts a partir dels perfils de concentració dels reactius i dels productes per a cada ruta de reacció, mitjançant monitorització IR in situ i els subseqüents anàlisis multivariable. Les rutes de formació del EC són catalitzades favorablement mitjançant centres de reacció àcids, mentre que els centres bàsics catalitzen totes les rutes de reacció cap a productes indesitjats. No obstant això, els centres superficials estan obstruïts quan l’acidesa es massa elevada i, per tant, existeix un valor òptim per a la relació del total de centres àcids i bàsics, el qual permetrà obtenir un catalitzador eficient per a la reacció desitjada. L’òxid metàl•lic mixt basat en Zn i Fe amb una relació atòmica 3:1 ha estat identificat com el catalitzador òptim ja que posseeix propietats àcid-base equilibrades adequadament. Els estudis mecanístics han mostrat la formació d’espècies sobre la superfície del catalitzador - isocianats i cianats – indicant diferents mecanismes per a l’activació dels reactius. Els isocianats han estat observats, majoritàriament, sobre òxids basats en Mg, mentre que els òxids acídics així com els basats en Zn promouen la formació de cianat. A més a més, l’aproximació al disseny d’experiments (DoE) ha estat utilitzada per a identificar, d’una forma estadística, els paràmetres crítics de reacció i per a optimitzar dits paràmetres per als millors catalitzadors basats en Zn i Fe. Aquestes aproximacions han permès, de forma exitosa, l’obtenció de coneixements sobre els factors materials determinants en la reacció objectiu i assolir una selectivitat excel•lent per al EC i amb un rendiment elevatEn este trabajo se presenta: (i) un enfoque racional, con el objetivo de mejorar las propiedades de materiales como catalizadores para la transesterificación de urea mediante la conversión de etilenglicol (EG) a carbonato de etileno (EC) sobre óxidos metálicos y, (ii) un enfoque estadístico para maximizar el producto deseado. Para el enfoque racional se han sintetizado y evaluado diversas combinaciones elementales de óxidos metálicos individuales y mixtos (Zn, Mg, Al, Fe) con una variedad de propiedades ácido-base. Los roles de la acidez y la basicidad en el camino de la reacción se han clarificado en base a la selectividad de los productos y, a los parámetros cinéticos extraídos de los perfiles de concentración de los reactivos y de los productos en cada camino de la reacción, por medio de in situ IR monitoring y el posterior análisis multivariable. El camino hacia EC es catalizado favorablemente por sitios ácidos, mientras que los sitios básicos, catalizan todos los caminos hacia los productos no deseados. Sin embargo, los sitios superficiales son bloqueados cuando la acidez es demasiado alta. Existe un valor óptimo para la proporción de sitios ácidos y básicos, para que el catalizador sea eficiente en una reacción específica. La mezcla de óxidos metálicos consistente en Zn y Fe con una proporción atómica de 3:1 ha sido identificada como el catalizador óptimo con unas propiedades ácido-base equilibradas. Estudios mecanísticos, muestran la formación de diferentes especies sobre el catalizador - cianatos e isocianatos - indicando así, diferentes mecanismos para la activación de los reactivos. Los isocianatos se observan principalmente sobre óxidos básicos que contienen Mg. En cambio, la formación de cianatos, se observa en óxidos ácidos que contienen Zn. Además, un enfoque de diseño de experimentos (DoE) se ha utilizado para identificar estadísticamente los parámetros críticos de la reacción, así como, para optimizarlos con el propósito de encontrar el mejor catalizador compuesto por Zn y Fe. Estos enfoques, nos han permitido determinar con éxito, conocimientos acerca de los factores materiales determinantes para dicha reacción, además de obtener una excelente selectividad para EC (hasta un 99.6%) con un alto rendimiento.
This work employs (i) a rational approach to improve material properties as catalyst for urea transesterification with ethylene glycol (EG) to ethylene carbonate (EC) over metal oxides and (ii) a statistical approach to maximize the desired product. For the rational approach, single and mixed metal oxides with different elemental combinations (Zn, Mg, Al, Fe) with a variety of acid-base properties were synthesized and evaluated for the reaction. The roles of acidity and basicity in the identified reaction paths were clarified based on product selectivities and kinetic parameters extracted from the concentration profiles of reactants and products in every reaction path by means of in situ IR monitoring and subsequent multivariate analysis. The paths towards EC are favorably catalyzed by acidic sites, while basic sites catalyze all paths towards undesired products. However, surface sites are blocked when acidity is too high and there exists an optimum value for the ratio of total acidic and basic sites to be an efficient catalyst in the targeted reaction. Mixed metal oxide consisting of Zn and Fe at 3:1 atomic ratio was found to be the optimum catalyst with a well-balanced acid-base property. Mechanistic study showed formation of species over catalyst surface – isocyanates and cyanates– indicating different mechanism of reagent activation. Isocyanates were mostly observed over basic Mg-containing oxides, whereas acidic and Zn-containing oxides promote cyanate formation.Furthermore, design of experiments (DoE) approach was used to statistically identify critical reaction parameters and optimize them for the best Zn- and Fe- containing catalyst. These approaches successfully gained insights into the determining material factors for the reaction and afforded excellent EC selectivity (up to 99.6%) with high yield.
20
Bellahdeb, Fatima. "Compatibilisation of poly(ethylene terephthalate) and polyolefins with mixtures of phenoxy and acid functionalised ethylene copolymer". Thesis, Loughborough University, 1993. https://dspace.lboro.ac.uk/2134/12009.
Testo completoAbstract (sommario):
Polyethylene terephthalate (PET) and polyolefins, such as high density polyethylene (HDPE), are important commodity polymers. PET is widely used for fibres and fllms but is also an attractive material for moulded products, owing to its high melting point and solvent resistance. Crystalline PET, however, is brittle and susceptible to hydrolytic degradation through water absorption. Polyolefins, on the other hand, are tough materials with low water absorption but have a relatively low melting point. Blending these two materials is expected to produce an attractive combination of properties. Blending PET with polyolefins, however, produces coarse microstructures and poor mechanical properties due to the lack of compatibility of the two polymers. Compatibility is expected to improve by reducing the interfacial tension and increasing the adhesion between the two phases; the first will reduce the size of the dispersed phase, while the latter would improve the mechanical properties. Compatibilisation of immiscible blends can be achieved by blending suitable functionalised polymers capable of reacting with the two components and/or by adding a compatibilising agent, e.g. block and graft copolymers with units along the main chains that are miscible and capable of strong interactions, such as H-bonds, with the two polymers in the blend. In the present work, polyhydroxyether of bisphenol A (phenoxy), which is known to be compatible with polyesters [1,2] and anhydride/acid functionalised ethylene copolymers, i.e. copolymers and terpolymers of ethylene containing acrylic acid units or grafted maleic anhydride, as well as the corresponding sodium ionomers, were used as the base polymer components for the production of graft copolymer type of compatibilisers by reaction processing methods. Additives such as sodium ethoxide, sodium benzoate, sodium montanate and sodium p-toluene sulphonate were evaluated as reaction controller catalysts for potential interactions between the OH groups in the phenoxy and acid and/or anhydride groups in the ethylene copolymers. The extent of interactions between the compatibiliser components were characterised by solubility tests, Fourier transform infrared spectroscopy (FITR), rheological properties and optical microscopy. The efficiency of the compatibilisers was studied on blends of PET with several grades of HDPE differing in molecular weights, by scanning electron microscopy (SEM), rheological properties, differential scanning calorimetry (DSC), and by measuring the mechanical properties. The results show that the type of graft copolymers or co-ionomers of phenoxy with acid functionalised ethylene copolymers can be made and that sodium ethoxide is an effective catalyst for the production of these types of compatibilisers. These systems were found to be a very efficient compatibiliser for PET/HDPE blends as they produce fme dispersions and improve the mechanical properties. A correlation is found between the efficiency of the compatibilisers and the melt viscosity of the final blends. Furthermore this work has revealed that the further addition of sodium ethoxide to ionomers and ionomer based compatibilisers enhances considerably the nucleation of PET in the blend.
21
Whittaker, David J. "Ethylene Biosynthetic Genes in Actinidia Chinensis". Thesis, University of Auckland, 1997. http://hdl.handle.net/2292/2169.
Testo completoAbstract (sommario):
Actinidia chinensis, a diploid relative of kiwifruit, has valuable fruit characteristics, and varieties with superior flavour and marketable size have recently been selected in a classical breeding programme. However, the marketability of the fruit of A. chinensis and many other species of Actinidia is limited by poor fruit storage properties. Pioneering work in tomato has demonstrated that fruit ripening and senescence can be very effectively delayed by down-regulating genes required for biosynthesis of the phytohormone ethylene. The goal of this work was to isolate genes for ethylene biosynthesis in A. chinensis, characterise their expression, and to generate transgenic plants containing T-DNA constructs designed for ethylene downregulation. A small cDNA library was constructed from RNA isolated from the ripe fruit of A. chinensis. The library was screened for genes encoding each of the enzymes in the ethylene biosynthetic pathway, by probing with PCR products amplified from kiwifruit cDNA and with a cDNA clone previously isolated from kiwifruit. Three distinct cDNA clones encoding S-adenosyl-L-methionine (SAM) synthetase (ACSAM1, ACSAM2 and ACSAM3) were isolated from the library, together with two distinct 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase cDNA clones (ACAO1 and ACAO2). No ACC synthase cDNAs were detected in the library, indicating low transcript abundance. However, a partial ACC synthase cDNA (ACAS1) was amplified from ripe fruit using PCR techniques, and subsequently cloned in a plasmid vector. Phylogenetic analysis of SAM synthetase protein sequences from A. chinensis and other plant species indicates bifurcation of angiosperm SAM synthetase sequences into two main branches; ACSAM3 was assigned to a different branch from ACSAM1 and ACSAM2. The peptide sequence of ACAS1 shows higher homology to several auxin-inducible ACC synthase peptides than the product of the ethylene-inducible ACC synthase gene which is predominantly transcribed in ripening tomato fruit. RNAse protection assays were employed to estimate the relative transcript levels of each of the ethylene biosynthetic genes isolated from A. chinensis during ethylene-induced, post-harvest fruit ripening, and in immature fruit and floral samples. The response of the mature fruit to exogenous ethylene indicated a clear separation of ethylene sensitivity and ethylene production in A. chinensis. The application of exogenous ethylene correlated with increased transcript levels for all three SAM synthetase genes (ACSAM1, ACSAM2 and ACSAM3) and for the ACC oxidase gene family. Transcription of the ACC synthase gene ACAS1 was not affected by exogenous ethylene, but transcript levels increased during subsequent ethylene biosynthesis, consistent with this being a controlling step for the onset of ethylene production. One or more ACC oxidase transcripts increased significantly both prior to and during ethylene production. Only one of the SAM synthetase transcripts (ACSAM3) was induced during the late ethylene burst, and these transcripts were also abundant in floral tissues and young fruit. A role for SAM synthetase genes in the methionine salvage pathway is discussed. The expression patterns for ACAS1 and the ACC oxidase gene family arc consistent with the consensus view that the rate of ethylene biosynthesis in plant tissues is dependent on both ACC synthase and ACC oxidase activity levels. Therefore, with the aim of down-regulating ethylene biosynthesis in A. chinensis, expression cassettes containing ACAS1 and ACAO1 cDNAs, each controlled by a d35S promoter, were inserted in tandem into the Agrobacterium binary vector pCGN1549, in both the sense and antisense orientations. Leaf tissue from the ‘Earligold’ variety of A. chinensis was transformed with the resulting binary vectors, and transgenic plants were regenerated. PCR and Southern analysis indicated intact T-DNAs were integrated in at least half of the transformed plants, and Northern analysis detected mRNAs from one of the transgenes transcribed from both the sense and antisense constructs. No decrease in wound-induced ethylene biosynthesis was detected in the leaves of a small sample of these transgenic plants, and a larger number of transformants are now being grown for phenotypic screening. Down-regulation of ethylene biosynthesis may improve the storage properties and/or the shelf life of transgenic A. chinensis plants and may provide insights into the roles of ethylene in fruit ripening.Appendix 1 restricted at the request of the author
22
Matthews, Thomas R. "Surface properties of poly(ethylene terephthalate) /". Connect to Online Resource-OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=toledo1177515548.
Testo completoAbstract (sommario):
Thesis (M.S.Ch.E.)--University of Toledo, 2007.Typescript. "Submitted as partial fulfillment of the requirements for The Masters of Science Degree in Chemical Engineering." Bibliography: leaves 76-77.
23
Gibson, Edward James. "Studies on the ethylene forming enzyme". Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363887.
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24
Ince, J. E. "Formation of ethylene by Escherichia coli". Thesis, University of Kent, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355189.
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25
Mazeres, F. S. "Rubber toughening of poly(ethylene terephthalate)". Thesis, Cranfield University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305303.
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26
Erdemli, Ӧmer Can. "UV stabilisation of poly(ethylene terephthalate)". Thesis, University of Strathclyde, 2016. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=27455.
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27
Lamb, Michael James. "Fundamentals of heterogeneous selective ethylene oligomerisation". Thesis, Durham University, 2018. http://etheses.dur.ac.uk/12613/.
Testo completoAbstract (sommario):
Sequential treatment of a partially dehydroxylated oxide (i.e. SiO2, γ-Al2O3, or mixed SiO2-Al2O3) with solutions of Cr{N(SiMe3)2}3 (0.71 wt% Cr) and a Lewis acidic alkyl aluminium-based co-catalyst (Al/Cr = 15) affords initiator systems active for the oligo- and poly-merisation of ethylene. The influence of the oxide support, calcination temperature, co-catalyst, and reaction diluent on the catalytic performance of such oxide-supported chromium initiators have been investigated. The best performing combination {SiO2-600, modified methyl aluminoxane (MMAO-12), heptane} generates a mixture of hexenes (61 wt%; 79% 1-hexene), and polyethylene (PE; 16 wt%) with an overall activity of 2403 g gCr–1 h–1. The observed product distribution is rationalised by two competing processes: trimerisation via a supported metallacycle-based mechanism and polymerisation through a classical Cossee-Arlman-type chain growth pathway. This is supported by the indirect observation of two distinct chromium environments at the surface of silica by a solid-state 29Si direct excitation (DE) magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopic study of the Cr{N(SiMe3)2}x/SiO2-600 pro-initiator. A series of experimental parameters were tested to evidence their impact on the catalytic performance of the Cr{N(SiMe3)2}x/SiO2-600/MMAO-12 initiator at a constant ethylene pressure. These include varying chromium concentration, Al/Cr loadings, reaction temperature, ethylene working pressure, stirrer speed, reaction time, diluent volume, and the impact of potential promoters, namely 1,2-dimethoxyethane (1,2-DME) and Et2Zn.
28
Blevins, Lori A. "Ethylene glycol rapid methods of detection". Thesis, Kansas State University, 2015. http://hdl.handle.net/2097/18943.
Testo completoAbstract (sommario):
Master of Veterinary BioscienceDepartment of Diagnostic Medicine/Pathobiology
Deon Van Der Merwe
Every year thousands of domestic animals are poisoned by ethylene glycol. Exposure is normally orally, but may be dermal, and poisonings are usually accidental and not malicious. Antifreeze, overwhelmingly the source of the ethylene glycol poisoning, is responsible for over 99% of reported cases. Storage, handling and proper disposal of ethylene glycol is extremely important in limiting access to this deadly product. Ethylene glycol exposures were involved in 1737 calls made to the American Society for the Prevention of Cruelty to Animals call center between 2006 and 2011. Dogs were involved in approximately 87% of exposures and cats in 13%. There were no seasonal or breed patterns. The most common clinical signs reported were neurological and gastrointestinal for both cats and dogs. Urinary calcium oxalate crystals were reported in 28.6% of exposed cats, and 21% of dogs. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was used to detect calcium oxalate crystals in wax-mounted kidneys from twenty total cases, ten of which were suspected ethylene glycol poisoning submitted to the Kansas State Veterinary Diagnostic Laboratory, and ten samples deemed negative by a pathologist using light microscopy. Pure calcium oxalate monohydrate was used as a reference, and a unique absorption peak was detected between wavenumbers 1290 cm[superscript]-1 and 1320 cm[superscript]-1. The drying of kidney tissues resulted in increased sensitivity for calcium oxalate. Crystal detection by the ATR-FTIR was compared to light microscopy. Bi-fringence of crystals allowed microscopic detection, but the ATR-FTIR specificity for the test was 100%, and sensitivity was 80% compared to traditional microscopy for ca-oxalate crystal identification. ATR-FTIR was also used to detect un-metabolized ethylene glycol in vomitus using wavenumbers 1084 cm[superscript]−1, 1039 cm[superscript]−1, and 882 cm[superscript]−1, but ethylene glycol was not detectable. Ethylene glycol concentrations in samples were much too low to be detected as ethylene glycol on the ATR-FTIR, as the limit of detection was not distinguishable until 5000 ppm using a serial dilution. These methods presented simple, reliable, quick, sensitive, stable, and highly adaptable tests for detection, diagnosis and treatment of ethylene glycol poisoning.
29
Jenkins, John A. Jr. "ULTRASONIC DECROSSLINKING OF CROSSLINKED POLY (ETHYLENE)". University of Akron / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=akron1177185317.
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30
Matthews, Thomas Robert. "Surface Properties of Poly(ethylene terephthalate)". University of Toledo / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1177515548.
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31
Venkatasubramaniam, Shyam. "Constitutive Modeling of Poly(Ethylene Terephthalate)". The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1417444300.
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32
Speiser, Fredy. "Oligomerisation of ethylene with Ni-complexes". Université Louis Pasteur (Strasbourg) (1971-2008), 2002. http://www.theses.fr/2002STR13221.
Testo completoAbstract (sommario):
Au cours de ce travail de thèse des nouvelles familles de ligands P-N, N-O bidentates et P-N tridentates ont étés préparés pour les utiliser en synthèse de complexes de Ni et Fe. Ces ligands possèdent un hétérocycle azoté à cinq ou six chaînons qui peut porter un groupement stériquement encombré et une fonctionnalité phosphorée dont la basicité peut être variée. La synthèse des complexes de Ni est réalisée dans des conditions très douces en faisant réagir des quantités équimolaires de ligand avec [NiCl2(DME)]. Les complexes préparés sont paramagnétiques de sorte qu'un grand nombre d'entre eux à dû être caractérisé par diffraction de rayons X. Leurs moments magnétiques en solution on été déterminés à l'aide de la méthode d'Evans. Les propriétés catalytiques des précatalyseurs de Ni mis au point se rapprochent à un système de dimérisation de l'éthylène, de sorte que le [NiCl2(PCy3)2], un catalyseur de dimérisation typique, a été choisi comme référence. On obtient une fréquence de rotation de 25108 mol C2H4 / mol Ni·h-1 avec une sélectivité de 75% pour les C4 (10% a-oléfine). Au-dessous de 6 équivalents d'AlEtCl2, le [NiCl2(PCy3)2] est inactif. Pour tous les complexes synthétisés, pendant ce travail, on observe des fréquences de rotation de 40000 à 174330 mol C2H4 / mol Ni·h-1 et des sélectivités pour les C4 de 65 à 92% (8 à 60% a-oléfine). La plupart des complexes de Ni préparés montrent de bonnes activités en présence de seulement 1,3 ou 2 équivalents d'AlEtCl2. Avec des cocatalyseurs non-halogénes, comme p. Ex. Le MAO, des sélectivités pour les a-oléfines de 60% peuvent être obtenuesNew families of bidentate P-N, N-O and tridentate P-N ligands were prepared and used in the synthesis of nickel and iron complexes. These ligands posses a five or six membered heterocycle which carries a sterically demanding substituent and a phosphorous moiety whose basicity can be varied. The synthesis of the complexes was realised under very mild conditions by reacting equimolar quantities of the ligand and [NiCl2(DME)]. All complexes were paramagnetic and therefore had to be characterised by X-ray diffraction. Their magnetic moments in solution were determined with the help of the Evan's method. [NiCl2(PCy3)2] a typical dimerisation catalyst, was chosen as reference as the catalytic properties of the prepared complexes were comparable to those of a typical dimerisation system. For the reference complex turnover frequencies of 25108 mol / C2H4 / mol Ni·h-1 with a selectivity of 75% for butenes (10 % a-olefin) were observed. Below 6 equivalents of AlEtCl2 [NiCl2(PCy3)2] was inactive. For all complexes which were synthesised turnover frequencies between 40000 and 174330 mol / C2H4 / mol Ni·h-1 and selectivities for C4 oligomers of 65 to 92% (8 to 60% a-olefin) were obtained. Most of the synthesised complexes show good activities in the presence of only 1,3 or 2 equivalents of AlEtCl2. When non-halogenated cocatalysts as e. G. MAO were applied a-olefin selectivities of 60% were obtained
33
Segouin, Frances H. "Crystallization kinetics of poly(ethylene oxide) /". Online version of thesis, 1994. http://hdl.handle.net/1850/11678.
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34
Bavarian, Neda. "Investigation of ethylene/propylene and ethylene/propylene/diene polymerization by Cp*TiMe3/B(C6F5)3 catalyst system". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0016/MQ52971.pdf.
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35
Bellam, Balaji Anand. "Effect of e-beam sterilization on polypropylene/ethylene propylene diene monomer and ethylene vinyl acetate thermoplastic elastomer". Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/52484/.
Testo completoAbstract (sommario):
Thermoplastic elastomer is one of the priority polymeric compound identified for promotion and further development, given the growing demand for a number of commercial industries such as automobile, construction, footwear, healthcare, medical and food packaging sectors. In this study polypropylene (PP)/ethylene propylene diene monomer (EPDM) based thermoplastic elastomers are preferred for improving their properties as it can serve as a good replacement for PP or EPDM material, bridging the gap between thermoset and thermoplastic materials. This study focuses to develop PP/EPDM which can resist changes or improve properties when exposed to E-beam radiation, as E-beam also offers sustainable sterilization at low cost. The PP/EPDM blends with mixing ratios of 80/20, 50/50 and 20/80 were melt blended with the process parameters optimized using Design of experiments (DOE). The effect of E-beam on mechanical properties, thermal stability, crystallization and dynamic mechanical properties over the dose of 0 to 100 kGy were studied. The blends with high EPDM content (20PP/80EPDM) showed improvement in tensile strength up to 36% (at 40kGy and 60kGy) and resistant to impact strength up to 100 kGy, at the expense of elongation at break. On the other hand, the blends with high PP content (80 PP/20 EPDM and 50 PP/50 EPDM) showed detrimental effects on mechanical properties at all radiation dose studied and found to be not compatible for E-beam sterilization. Further, ethylene vinyl acetate (EVA) was incorporated to PP/EPDM blends at 10EVA/40EPDM/50PP, 20EVA/30 EPDM/50PP, 30EVA/20 EPDM/50PP and 40EVA/10 EPDM/50PP ratios. The gel content analysis showed that the efficiency of crosslinking decreased with increase in EVA loading. However, the presence of EVA in ternary blend especially facilitated the induction of sufficient crosslinks leading to improvement in tensile strength (up to 29% at 60 kGy), impact strength (up to 15% at 80 kGy) and retention of stiffness and thermal properties under radiation at the expense of elongation at break. In order to develop antibacterial ternary blends, silver nanoparticles (AgNP) were added by varying the loading from 0.3wt% to 1wt%. The Ag-ternary blends showed enhancement in impact properties (up to 9%) at the expense of decrement in tensile properties due to the agglomeration of AgNP. When, exposed to E-beam radiation, the mechanical and thermal properties exhibited similar trend of increment and decrement across radiation dose similar to the blends without AgNP. While, 1% Ag blend composites showed bacteriostatic effect on Staphylococcus aureuson, no significant reduction of Pseudomonas aeruginosa bacteria was observed. All the blends, before and after sterilization showed no significant toxicity on HaCaT cells investigated using in vitro analysis. Thus, the blends showed an instinct that their application could be extended to manufacturing of healthcare products and food packaging sector, as they are biocompatible and can withstand E-beam sterilization as demanded by the respective application. Among all the blends ternary blends studied (that exhibited biocompatibility even after radiation), 20EVA/30EPDM/50PP without AgNP showed the highest tensile strength of 18.41 MPa and impact strength of 43.64 J/m. Only a slight increase in tensile and impact properties was witnessed upon addition of 20% EVA to PP/EPDM blend in comparison to the binary blend (50PP/50EPDM blend). However, unlike the binary blend (whose properties decreased upon radiation), the ternary blend (20EVA/30EPDM/50PP) showed improvement in tensile strength up to 29% at 60kGy and up to 15% increase in impact strength at 80kGy.
36
McDowell, Christopher Carroll. "Sorption and Transport of Acetone in Random Copolymers of Poly(ethylene terephthalate) and Poly(ethylene 2,6-naphthalate)". Raleigh, NC : North Carolina State University, 1998. http://www.lib.ncsu.edu/etd/public/etd-1741193984981/edf.pdf.
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Abedi, Ali Abdulhamid. "Economical analysis of a new gas to ethylene technology". Texas A&M University, 2003. http://hdl.handle.net/1969.1/6000.
Testo completoAbstract (sommario):
Ethylene is one of the most important petrochemical intermediates and feedstocks
for many different products. The motivating force of this work is to compare a new
process of ethylene production developed at Texas A&M University to the most common
processes. Ethylene is produced commercially using a wide variety of feedstocks ranging
from ethane to heavy fuel oils. Of them, the thermal cracking of ethane and propane
using a fired tubular heater is the most common process in the United States. In Europe
and Japan, where natural gas is not abundant, thermal cracking of naphtha using a fired
heater is the most common process. In addition to these processes; ethylene could also be
produced from crude oil by autothermic and fluidized bed techniques and from coal and
heavy oils by synthesis from carbon monoxide and hydrogen.
At Texas A&M University, a group of researchers developed a new process that
can convert natural gas into liquids (GTL) or to ethylene (GTE). This technology is a
direct conversion method that does not require producing syngas. When selecting a
process for ethylene production, the dominant factor is the selection of hydrocarbon
feedstocks. Based upon plant capacity of 321 million pounds of ethylene per year, this
study has shown that using natural gas, as a feedstock, is more economical than using
ethane, propane, naphtha, and other feedstocks. Therefore, it is more economical to convert natural gas directly to ethylene than separating ethane or propane from natural
gas and then converting it to ethylene. A process simulation package ProMax is used to
run the GTE process; and a software program, Capcost, is used to evaluate fixed capital
costs of the GTE process. Finally, the cost index is used to update the cost of the other
processes of ethylene production today.
38
Macqueron, Benoit. "Étude du comportement des systèmes catalytiques métallocène de néodyme / dialkylmagnésium pour la copolymérisation de l'éthylène avec le butadiène et fonctionnalisation des polymères synthétisés". Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10083.
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39
Dausen, David F. "Design of a premixed gaseous rocket engine injector for ethylene and oxygen". Thesis, Monterey, Calif. : Naval Postgraduate School, 2006. http://bosun.nps.edu/uhtbin/hyperion.exe/06Dec%5FDausen.pdf.
Testo completoAbstract (sommario):
Thesis (M.S. in Astronautical Engineering)--Naval Postgraduate School, December 2006.Thesis Advisor(s): Christopher M. Brophy. "December 2006." Includes bibliographical references (p. 97). Also available in print.
40
Elmi, Fardusa. "Elucidating ethylene-mediated physiology and biochemistry in selected climactic and non-climacteric fruits using e+® ethylene remover". Thesis, Cranfield University, 2013. http://dspace.lib.cranfield.ac.uk/handle/1826/10245.
Testo completoAbstract (sommario):
The presence of ethylene in a storage environment can undermine both quality and postharvest life of many fruits, often generating significant waste and associated economic losses. A demand for discovering alternative technologies capable of scavenging ethylene has led to the development of a new material, e+® Ethylene Remover, which has significant ethylene adsorption capacity. The material has been shown to remove ethylene to below physiologically active levels during fruit storage at 0-20 o C and consequently extend postharvest life for a variety of fresh produce types. Different formats incorporating e+® Ethylene Remover have been developed. Successful application of e+® Ethylene Remover in laboratory settings has created opportunities to test new formats of the product. To this end, work was conducted herein to attest whether e+® Ethylene Remover, which has been shown to maintain avocado (Persea americana cv. Hass) firmness in recent laboratory trials, could result in a meaningful extension of storage life in a commercial setting. It was shown that e+® Ethylene Remover coated sheets were a highly efficacious format for suppressing ethylene and extending storage life of imported avocado and pluot plums in a series of commercial trials. Moreover, the potency of the e+® Ethylene Remover treatment in retarding ethylene induced ripening was significantly enhanced when avocados were treated during the early stages of ripening. After a storage period of up to 31 days (5-6 o C), avocado fruits which had received an early treatment at source and then treated again in the laboratory were significantly more firm and greener compared to fruits treated following 5 weeks of transit alone . Strawberry is regarded as non-climacteric fruit; nevertheless, exogenous ethylene can negatively influence postharvest life. The low ethylene produced by non-climacteric fruits has been generally ignored and research reporting on the involvement of ethylene in these fruits is typically devoid in the literature. To this end, application of a highly sensitive laser based photoacoustic ethylene detector has revealed a possible role of ethylene in determining the postharvest life of strawberries. Moreover, fruit quality parameters including disease incidence, sugars, organic acids, phenolic compounds and plant phytohormones/metabolites were found to be profoundly affected by ethylene and likewise the removal of ethylene. Storage of strawberries in the presence of e+® Ethylene Remover was associated with lower disease incidence, significantly less red fruits and higher ascorbic acid content. In contrast, ethylene and 1-methylcyclopropene (1-MCP) treatments resulted in the higher postharvest disease. Ethylene-treated fruits were associated with lower level of sucrose and higher simple sugars (fructose and glucose) suggesting a role of ethylene in promoting the rate of senescence and concomitant reduced postharvest quality of strawberries. Changes in ABA, ABA metabolites and auxins within different tissues of ripe strawberry during storage were investigated. ABA was more abundant in the flesh than in the achenes, while auxins were undetectable in the flesh tissue. Auxins indole-3-acetic acid (IAA) and the conjugated form indole-3-acetylaspartic acid (IAAsp) were detected in high concentrations in the achenes and were affected by ethylene and storage length.
41
Kyaw, Poe Nandar. "Regulation of Ethylene Production and Postharvest Fruit Quality of Stone Fruit Using Different Formulations of New Ethylene Antagonists". Thesis, Curtin University, 2019. http://hdl.handle.net/20.500.11937/78297.
Testo completoAbstract (sommario):
Stone fruits are highly perishable due to their sensitivity to ethylene which limit their domestic and international trade. Different formulations of the anti-ethylene compounds 1H-cyclopropabenzene and 1H-cyclopropa[b]naphthalene were investigated to manage ethylene, extend postharvest life and maintain fruit quality. Fumigation and spray solutions containing ethanol prevented the deleterious effects of ethylene and maintained postharvest fruit quality of stone fruits. The development of spray solutions will allow these compounds to be used in future open-field applications.
42
Alyamac, Elif. "Impact Modified Poly(ethylene Terephthalate)-organoclay Nanocomposites". Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605092/index.pdf.
Testo completoAbstract (sommario):
This study was conducted to investigate the effects of component concentrations and addition order of the components, on the final properties of ternary nanocomposites composed of poly(ethylene terephthalate), organoclay, and an ethylene/methyl acrylate/glycidyl methacrylate (E-MA-GMA) terpolymer acting as an impact modifier for PET.
In this context, first, the optimum amount of the impact modifier was determined by melt compounding binary PET-terpolymer blends in a corotating twin-screw extruder. The amount of the impact modifier (5 wt. %) resulting in the highest Young&rsquos modulus and reasonable elongation at break was selected owing to its balanced mechanical properties. Thereafter, by using 5 wt. % terpolymer content, the effects of organically modified clay concentration and addition order of the components on ternary nanocomposites were systematically investigated. Mechanical testing revealed that different addition orders of the materials significantly affected mechanical properties. Among the investigated addition orders, the best sequence of component addition (PI-C) was the one in which poly(ethylene terephthalate) was first compounded with E-MA-GMA. Later, this mixture was compounded with the organoclay in the subsequent run. Young'
s modulus of not extruded pure PET increased by 67% in samples with 5 wt. % E-MA-GMA plus 5 wt. % clay loading. The highest percent elongation at break was obtained as 300%, for the addition order of PI-C, with 1 wt. % clay content, which is nearly 50 fold higher than that obtained for pure PET. In X-ray diffraction analysis, extensive layer separation associated with delamination of the original clay structure occurred in PI-C and CI-P sequences with both 1 and 3 wt. % clay contents. X-ray diffraction patterns showed that, at these conditions exfoliated structures resulted as indicated by the disappearence of any peaks due to the diffraction within the consecutive clay layers.
43
Tolga, Asli. "Nanocomposites Based On Recycled Poly(ethylene Terepthalate)". Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/3/12606309/index.pdf.
Testo completoAbstract (sommario):
In this study, the effects of glycol type, organoclay type and concentration on the final properties of nanocomposites based on recycled poly(ethylene terephthalate) was investigated. For this purpose, first recycled PET was glycolysed and after that unsaturated polyester-montmorillonite nanocomposites were synthesized by using three different types of glycols (i.e. ethylene glycol (EG), propylene glycol (PG) and diethylene glycol (DEG)). As the first step, all the compositions were prepared by Cloisite 30B type of clay, and then for comparison of clay type, nanocomposites containing 1 wt. % of Cloisite 15A and Cloisite 25A type of clay were also synthesized. Morphological and mechanical analyses were performed for the characterization of the nanocomposites.
According to the results of XRD analysis, for all glycol types maximum intercalation was observed in Cloisite 30B containing samples. Exfoliated structures were obtained in the samples containing EG at 1 wt. % Cloisite 30B content and DEG at 3 wt. % Cloisite 30B content.
Mechanical tests showed that, for all properties, glycol type is the most effective experimental parameter. DEG based samples are the most flexible whereas PG based samples are the least flexible. EG and DEG based samples give maximum tensile strength and tensile modulus values at 1 wt. % clay loading. Samples prepared by DEG exhibited maxima in both flexural strength and modulus at 1 wt. % clay content. With respect to the organoclay type, Cloisite 30B containing samples gave the highest compatibility with the unsaturated polyester matrix as indicated by the tensile test results.
Organoclay type and content had no positive effect on the impact strength. Clay particles acted as stress concentrators and lowered the impact strength.
44
De, Bruyn John Roy. "The critical behaviour of ethylene and hydrogen". Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/28661.
Testo completoAbstract (sommario):
Optical techniques have been used to study the behaviour of ethylene and hydrogen near their liquid-vapour critical points. From measurements of the coexistence curve of ethylene over the reduced temperature range 1.5 x 10⁻⁶ < t < 4.5 x 10⁻², where t — (Tc — T)/Tc and Tc is the critical temperature, we find the critical exponent β = 0.327±.002 and the corrections-to-scaling exponent ∆ = 0.46±.02. Similar measurements for hydrogen over the range 3.2 x 10⁻⁵ < t < 7.0 x 10⁻² give β = 0.326 ± .002 and ∆ = 0.46 ± .02. Measurements of the compressibility of hydrogen give the critical exponent [Formula Omitted] = 1.19 ± .05 and the critical amplitude ratio [Formula Omitted] = 5.2 ± .4. With the exception of ∆, which is slightly lower than its predicted
value of 0.5, the results for these universal quantities are in agreement with theoretical predictions.
The leading coexistence curve amplitude for hydrogen, B₀ = 1.19±.03, is lower than the corresponding values for ethylene, B₀ = 1.56 ± .03, and for other room-temperature fluids. This decrease is in qualitative agreement with the predictions of a theory of quantum effects on critical behaviour. Measurements of the coexistence curve diameter for both fluids show an anomaly near the critical point having a form consistent with the predicted t¹⁻α temperature dependence. These results are in agreement with a recent theory of the effects of many-body forces on the diameter; the hydrogen data indicate that these forces are attractive in that fluid. This suggests that quantum mechanical exchange interactions are important near the critical point of hydrogen.Science, Faculty of
Physics and Astronomy, Department of
Graduate
45
Larsson, Andréas. "Biochip design based on tailored ethylene glycols /". Linköping : Division of Molecular Physics, Department of Physics, Chemistry and Biology, Linköping University, 2007. http://www.bibl.liu.se/liupubl/disp/disp2007/tek1111s.pdf.
Testo completo
46
Clough, Norman E. "Thermodynamics of ethylene-vinyl acetate copolymer blends". Thesis, Durham University, 1994. http://etheses.dur.ac.uk/5489/.
Testo completoAbstract (sommario):
The purpose of this study was to characterise the miscibility of several poly(ethylene-co-vinyl acetate), EVA, based polymer blends. EVA has many industrial applications and is often present as one of several polymeric components. Consequently, there is considerable interest in the thermodynamics of these blend systems. The thermodynamics of these blends was studied using several techniques: differential scanning calorimetry; phase contrast optical microscopy; small angle neutron scattering and wide angle X-ray scattering. Characterisation was also to include assessing the relative enthalpic and entropic thermodynamic contributions to the Rory-Huggins interaction parameter (%) of these blends. To determine the enthalpic interaction parameter, a "mixing calorimeter" was designed and constructed to measure accurately the "heat of mixing" values on blending these polymers. Free energy interaction parameters were determined from melting point depression and small angle neutron scattering measurements. In all the blends studied, the heat of mixing was endothermic and consequently, the enthalpic interaction parameters were positive i.e. unfavourable to miscibility. Miscibility in these blends can therefore only be achieved by a dominant entropic contribution, favourable to miscibility. Using phase contrast optical microscopy, both miscible and immiscible phase behaviour was observed in this series of blends. This shows good agreement with predictions of miscibility from heat of mixing, melting point and small angle neutron scattering measurements, based on the classical Flory-Huggins lattice theory. Wide angle X-ray scattering and differential scanning calorimetry results have associated miscible blends with crystallisation effects between the blend components. Small angle neutron scattering has been used to determine the concentration and temperature dependence of interaction parameters in a miscible blend. From these values the upper critical solution temperature (UCST) of the blend was predicted. The enthalpic contributions to these interaction parameters show good agreement with experimental values determined from heat of mixing measurements. It was concluded that the classical Flory-Huggins lattice theory (despite its many well documented Limitations) appears to be particularly suited to the thermodynamic characterisation of miscibility in these polymer blends.
47
Lewis, M. N. "Styrene-ethylene/butylene-styrene layered silicate nanocomposites". Thesis, Queen's University Belfast, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432525.
Testo completo
48
Agunloye, F. F. "Gelation of solutions of poly(ethylene terephthalate)". Thesis, University of Leeds, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234344.
Testo completo
49
Phillips, Julia. "Depolymerisation of poly(ethylene terephthalate) for recycling". Thesis, University of York, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245916.
Testo completo
50
Turin, Sandra. "Heterogenisation of zirconocene catalysts for ethylene polymerisation". Thesis, University of Southampton, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396178.
Testo completo