Dissertations / Theses on the topic 'Vinyl acetate'
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1
Auden, Noel Geraint. "Ethylene-vinyl acetate copolymers." Thesis, Lancaster University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239046.
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Croot, Robert Arthur. "The characterisation and adsorption of vinyl alcohol vinyl acetate copolymers." Thesis, University of Bristol, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303767.
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De, Bruyn Hank. "The Emulsion Polymerization of Vinyl Acetate." Thesis, The University of Sydney, 1999. http://hdl.handle.net/2123/381.
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Abstract This work investigates the kinetics of the emulsion polymerization of vinyl acetate. Several aspects of this system have been clarified, including the induced decomposition of persulfate, retardation by oxygen and entry by, and analysis of, the aqueous phase oligomeric radicals. It has been shown that the retardation period observed in the emulsion polymerization of VAc can be explained by the effect of traces of oxygen (< 10-6 M) on the entry efficiency of the initiator-derived aqueous-phase oligomeric radicals. Comparison of rates of polymerization in V and persulfate -initiated polymerizations together with electrospray mass spectrometry of aqueous phase oligomers, has shown that the mechanism for the induced decomposition of persulfate by vinyl acetate is chain transfer to initiator from aqueous-phase oligomeric radicals. A value has been determined for the rate coefficient for transfer to initiator, by fitting literature data to a model based on this mechanism. The reported independence of the rate of polymerization from the monomer concentration in the emulsion polymerization of vinyl acetate has been investigated. Possible explanations for this behaviour have been proposed and tested in this work, by measuring radical-loss rates directly with y-relaxation techniques. Although the Y relaxations were found to be affected by experimental artefacts, it has been demonstrated that rapid exit is not responsible for the high radical-loss rates in this system. The major artefact identified in the y relaxations was the significant effect of relatively small exotherms on relaxation behaviour, Methodologies were developed for correcting affected data and for avoiding exotherms under certain conditions. Arrhenius parameters were determined for the rate coefficient for chain transfer to monomer using the In^M method, which utilises the whole MWD. This section of the work is incomplete, for reasons detailed in chapter 5. However, as a preliminary indication it was found that the frequency factor was 106.38 M-1 s-1 and the activation energy was 38.8 kJ mol-1.
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De, Bruyn Hank. "The Emulsion Polymerization of Vinyl Acetate." University of Sydney, Chemistry, 1999. http://hdl.handle.net/2123/381.
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Abstract This work investigates the kinetics of the emulsion polymerization of vinyl acetate. Several aspects of this system have been clarified, including the induced decomposition of persulfate, retardation by oxygen and entry by, and analysis of, the aqueous phase oligomeric radicals. It has been shown that the retardation period observed in the emulsion polymerization of VAc can be explained by the effect of traces of oxygen (< 10-6 M) on the entry efficiency of the initiator-derived aqueous-phase oligomeric radicals. Comparison of rates of polymerization in V and persulfate -initiated polymerizations together with electrospray mass spectrometry of aqueous phase oligomers, has shown that the mechanism for the induced decomposition of persulfate by vinyl acetate is chain transfer to initiator from aqueous-phase oligomeric radicals. A value has been determined for the rate coefficient for transfer to initiator, by fitting literature data to a model based on this mechanism. The reported independence of the rate of polymerization from the monomer concentration in the emulsion polymerization of vinyl acetate has been investigated. Possible explanations for this behaviour have been proposed and tested in this work, by measuring radical-loss rates directly with y-relaxation techniques. Although the Y relaxations were found to be affected by experimental artefacts, it has been demonstrated that rapid exit is not responsible for the high radical-loss rates in this system. The major artefact identified in the y relaxations was the significant effect of relatively small exotherms on relaxation behaviour, Methodologies were developed for correcting affected data and for avoiding exotherms under certain conditions. Arrhenius parameters were determined for the rate coefficient for chain transfer to monomer using the In^M method, which utilises the whole MWD. This section of the work is incomplete, for reasons detailed in chapter 5. However, as a preliminary indication it was found that the frequency factor was 106.38 M-1 s-1 and the activation energy was 38.8 kJ mol-1.
5
Clough, Norman E. "Thermodynamics of ethylene-vinyl acetate copolymer blends." Thesis, Durham University, 1994. http://etheses.dur.ac.uk/5489/.
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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.
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Tongcher, Oychai. "Novel routes to stereoregular poly(vinyl acetate)." Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620688.
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Cauich-Rodriguez, Juan Valerio. "Hydrogels based on poly(vinyl alcohol-vinyl acetate) blends for biomedical applications." Thesis, Queen Mary, University of London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267577.
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Kumar, Dheeraj. "Synthesis of vinyl acetate on palladium-based catalysts." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1747.
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Hatzinikolaou, Theodosios A. "Adhesion of ethylene vinyl acetate copolymers to metals." Thesis, University of Bath, 1985. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355114.
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The 180° peel strength of four ethylene vinyl acetate copolymers with varying V.A. content was measured (Pol A: 28%, Pol B: 18%, Pol C: 12% and Pol D: 9.5% by weight). The polymers were applied as hot-melts with or without an inextensible fabric support on: (a) mild steel etched in hydrochloric acid; (b) chemically polished copper and; (c) oxidised copper with a fibrous topography. The peel loads for a given polymer decreased from oxidised copper to etched steel to polished copper. For a given substrate the peel loads generally decreased from polymer A to polymer D with a peak for polymer C. This trend was correlated to similar trends obtained in mechanical tests like the tearing energy, strain energy density and tensile strength to failure. The fractured parts of the bond were examined with a scanning electron microscope. There was microscopic evidence of an analogy between the peel load and the observed extent of polymer deformation in the fractured surfaces where the ductilty of the particular polymer and the topography of the substrate were clearly depicted. Contact angle measurement showed a cohesive type of failure in all cases. X-ray photo-electron spectroscopy and multiple internal reflection infra-red spectroscopy provided evidence of polymer oxidation by the substrate, mostly significant in the case of etched steel. The energy balance approach was employed in order to analyse the peel test results further. The polymers response to the imposed mechanical deformations during peeling was shown to control the measured peel load. For the unbacked samples the major energy loss mechanism is the stretching of the freed strip. The much higher peel loads of the backed samples were attributed to energy losses around the peel front. Finally, plastic bending of the polymer was found to account for a relatively smaller part of the total input energy for both backed and unbacked samples.
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Haley, Roger David. "Surface chemistry of the vinyl acetate catalytic system." Thesis, University of Cambridge, 1999. https://www.repository.cam.ac.uk/handle/1810/272089.
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Edakkara, A. J., J. J. Mathen, J. Sebastian, G. Ramalingam, and G. P. Joseph. "Electrical Behaviour of Polyethylene Vinyl Acetate / ZnO Nanocomposite." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35634.
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Recently, nanoscale materials have attracted material scientists because of their unique size depend-ent magnetic, optical, electrical and thermal properties. Homogeneous dispersion of nanoparticles in the polymer matrix and control of their size are vital to achieve many of these properties. In the present work, Zinc Oxide (ZnO) nanoparticles were prepared by solvothermal route. Chemical replacement reaction was chosen for the homogeneous dispersion of prepared ZnO nanoparticles into polymer matrix. Zinc oxide is an inorganic material with a large direct band gap (3.34 eV), high exciton binding energy (60 meV) and having a unique combination of properties. In inorganic/polymetric composite, the semiconducting nanoclusters enhances the electrical and thermal properties. The dielectric properties of the composites were studied using HIOKI 3532-50 LCR Hitester. The dielectric constant was found to increase with in-creasing the concentration of nano filler. DC electrical conductivity as a function of temperature was stud-ied using Keithley picoammeter 6485.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35634
12
Wood, Timothy John. "An adsorption study of vinyl alcohol/vinyl acetate copolymers on polystyrene by quartz microbalance." Thesis, University of Bristol, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261278.
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Mathen, J. J., A. J. Augustine, J. Sebastian, J. Madhavan, and G. P. Joseph. "Synthesis and Characterization of Polyethylene Vinyl Acetate / ZnSe Nanocomposite." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35635.
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In the not too distant past, polymer scientists and technologists expanded their horizons from consum-er products to the high technology arena, particularly notable in opto - electronic applications. Ethylene Vinyl Acetates (EVA) are popular because of their superior adhesion to most substrates as well as their ease of formulation. Its High transparency is a key attribute for photovoltaic cell encapsulation. It is ex-pected that with the addition of ZnSe nano fillers, EVA becomes a high refractive index polymer (HRIP) with refractive index 2.5 and posses anti-reflective property. In this work, ZnSe nanoparticles were syn-thesised by solvo-thermal method. Nano – Composite matrices based on polyethylene vinyl acetate / ZnSe were prepared by chemical replacement mechanism. Refractive index of prepared polymer nanocomposites were calculated from dielectric study using Hioki 3532-50 LCR HITESTER at various frequencies and temperatures. The presence of nano filler enhanced the refractive index and it varied with frequency and temperature. UV-Vis-NIR Spectra of the samples enable to determine the bandgap and was found to de-crease with increasing the concentration of nano fillers dispersed in polymer matrix. I-V characteristics of the nanocomposites were plotted at various concentrations of nano fillers and at various temperatures.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35635
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Bailly, Nathalie. "N-vinylpyrrolidone-vinyl acetate block copolymers as drug delivery vehicles." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/20133.
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Thesis (PhD)--Stellenbosch University, 2012.ENGLISH ABSTRACT: The primary aim of this study was to investigate the feasibility of the amphiphilic block copolymer poly((vinylpyrrolidone)-b-poly(vinyl acetate)) (PVP-b-PVAc) as a vehicle for hydrophobic anti-cancer drugs. PVP-b-PVAc block copolymers of constant hydrophilic PVP block length and varying hydrophobic PVAc block lengths were synthesized via xanthate-mediated controlled radical polymerization (CRP). The methodology consisted of growing the PVAc chain from a xanthate end-functional PVP. In an aqueous environment the amphiphilic block copolymers selfassembled into spherical vesicle-like structures consisting of a hydrophobic PVAc bilayer membrane, a hydrophilic PVP corona and an aqueous core. The self-assembly behaviour and the physicochemical properties of the self-assembled structures were investigated by 1H NMR spectroscopy, fluorescence spectroscopy, transmission electron microscopy (TEM) and dynamic and static light scattering. Drug loading studies were performed using a model hydrophobic drug, clofazimine, and a common anti-cancer drug paclitaxel (PTX) to evaluate the potential of the PVP-b-PVAc block copolymers for drug delivery,. Clofazimine and PTX were physically entrapped into the hydrophobic domain of the self-assembled PVP-b-PVAc block copolymers via the dialysis method. The drug-loaded PVP-b-PVAc block copolymers were characterized regarding particle size, morphology, stability and drug loading capacity in order to assess their feasibility as a drug vehicle. The polymer vesicles had a relatively high drug loading capacity of 20 wt %. The effect of the hydrophobic PVAc block length on the drug loading capacity and encapsulation efficiency were also studied. Drug loading increased with increasing the hydrophobic PVAc block length. The effect of the drug feed ratio of clofazimine and PTX on the drug loading capacity and encapsulation efficiency were also investigated. The optimal formulation for the drug-loaded PVP-b-PVAc was determined and further investigated in vitro. The size stability of the drugloaded PVP-b-PVAc block copolymers was also assessed under physiological conditions (PBS, pH 7.4, 37 °C) and were stable in the absence and presence of serum. PVP-b-PVAc block copolymers were tested in vitro on MDA-MB-231 multi-drug-resistant human breast epithelial cancer cells and normal MCF12A breast epithelial cells to provide evidence of their antitumor efficacy. In vitro cell culture studies revealed that the PVP-b-PVAc drug carrier exhibited no cytotoxicity towards MDA-MB-231 and MCF12A cells, confirming the biocompatibility of the PVP-b-PVAc carrier. In vitro cytotoxicity assays using clofazimine-PVPb- PVAc formulations showed that when MDA-MB-231 cells were exposed to the formulations, an enhanced therapeutic effect was observed compared to the free drug. Cellular internalization of the PVP-b-PVAc drug carrier was demonstrated by fluorescent labeling of the PVP-b-PVAc carrier. Fluorescence microscopy results showed that the carrier was internalized by the MDAMB- 231 cells after 3 hours and localized in the cytoplasm and the perinuclear region. Overall, it was demonstrated that PVP-b-PVAc block copolymers appear to be promising candidates for the delivery of hydrophobic anti-cancer drugs.
AFRIKAANSE OPSOMMING: Die studie is gebaseer op die gebruik van amfifieliese blokkopolimere van poli((Nvinielpirolidoon)- b-poli(vinielasetaat)) (PVP-b-PVAc) as potensiële geneesmiddeldraers. PVP-b-PVAc blokkopolimere van konstante hydrofiliese bloklengte en verskillende hydrofobiese bloklengte is voorberei via die RAFT/MADIX-proses. Blokkopolimere met vinielasetaat is vanaf poli(N-vinielpirolidoon) met ‘n xantaatendfunksie voorberei. In ‘n wateromgewing vorm die PVP-b-PVAc blokkopolimere vesikel strukture met ‘n hydrofobiese membraan en ‘n hydrofiliese mantel. Die fisies-chemiese eienskappe van die PVP-b-PVAc blokkopolimere is gekarakteriseerd met gebruik van KMR spektroskopie, fluoresent spektroskopie, transmissie elektronmikroskopie (TEM) en dinamiese en statiese lig verstrooiing. Die potensiaal van PVP-b-PVAc as ‘n geneesmiddeldraer is ondersoek deur gebruik te maak van die hydrofobiese geneesmiddel, clofazimine, en ‘n anti-kanker geneesmiddel, paclitaxel. Clofazimine en paclitaxel is ge-inkapsuleer in die hydrofobiese gedeelte van die blokkopolimere via die dialise-metode. Clofazimine-PVP-b-PVAc en paclitaxel-PVPb- PVAc blokkopolimere is gekarakteriseerd met betrekking tot die partikel grootte, morfologie, stabiliteit en laai kapasitiet om die PVP-b-PVAc blokkopolimere as geneesmiddeldraers te evalueer. Die PVP-b-PVAc geneesmiddeldraer het ‘n relatiewe hoë laai kapsiteit van 20 gew % aangetoon. Die invloed van die bloklengte op die laai kapasitiet is ook ondersoek en beskryf. ‘n Toename in die laai kapasitiet is gesien met ‘n toename in die hydrofobiese bloklengte. Die invloed van die hoeveelheid geneesmiddel op die laai kapasitiet en die inkapsuleer doeltreffendheid is ook ondersoek. Die optimale formulasie is gevind en verder gebruik vir in vitro studies. Die stabiliteit van die geneesmiddeldraer in fisiologiese omstandighede (pH 7.4, 37 °C) is ook beskryf. Resultate toon aan dat die sisteem stabiel is onder hierdie omstandighede in die afwesigheid en aanwesigheid van serum. In vitro eksperimente is op MCF12A epiteel-borsselle en MDA-MB-231 epiteelborskankerselle getoets om die anti-tumoraktiwiteit te ondersoek. Resultate toon aan dat die PVP-b-PVAc geen sitotoxiese effek op die selle het nie, wat aandui dat die polimere bioverenigbaar is. Verder is dit bewys dat die PVP-b-PVAc geneesmiddel formualsie ’n hoër sitotoxisiteit besit as die vry-geneesmiddel. Fluoresent studies het aangetoon dat die geneesmiddeldraer na 3 uur opgeneen word deur MDA-MB231 selle en gelokaliseerd is in die sitoplasma en in die omgewing van die kern van die selle. In die algemeen is dit aangetoon dat PVP-b-PVAc blokkopolimere potensiële kandidate vir die lewering van hydrofobiese geneesmiddels is.
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Guo, Haochen. "RECYCLING THERMOPLASTIC EVA (POLYETHYLENE-CO-VINYL ACETATE) WITH IMPROVED PROPERTIES." Case Western Reserve University School of Graduate Studies / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case1585673886043802.
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Jovanovic, Renata. "Butyl acrylate/vinyl acetate emulsion copolymerization: Reaction monitoring and property evaluation." Thesis, University of Ottawa (Canada), 2001. http://hdl.handle.net/10393/9102.
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Several aspects of butyl acrylate/vinyl acetate (BA/VAc) polymerizations were investigated in this thesis. Polymerization process monitoring is a key factor in obtaining high quality products with prespecified properties. Therefore, a considerable part of this work was devoted to the real-time monitoring of BA/VAc emulsion polymerization reactions. An Attenuated Total Reflectance - Fourier Transform Infrared (ATR-FTIR) spectroscopy sensor was used for monitoring conversion and copolymer composition. Due to the novelty of this technique, in the first part of the study, the suitability of this technique for polymerization monitoring was investigated. In the second part of this thesis, the knowledge obtained from the off-line monitoring of the solution polymerizations was employed for the real time monitoring of six high-solids BA/VAc emulsion polymerizations. Finally, the latexes obtained in the second part of this thesis were characterized for a variety of polymer properties of interest to adhesive industry. Among the properties investigated were particle size, rheology, dynamic mechanical properties of the dry polymers and the shear and tensile strength of adhesive bonds when hard maple wood is used as a substrate. (Abstract shortened by UMI.)
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Okpe, Owoicho. "Alumina trihydrate as a fire retardant for ethylene vinyl acetate copolymer." Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339740.
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Khan, Shadeed. "Controlled Release of Fluoride from Poly(ethylene-co-vinyl acetate) Films." VCU Scholars Compass, 2009. http://scholarscompass.vcu.edu/etd/1928.
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The development of aesthetically unattractive white spots is a concern for patients undergoing fixed orthodontic treatment. Due to poor oral hygiene during treatment, accumulation of plaque around orthodontic brackets causes bacterial fermentation reactions producing acids that dissolve the mineral enamel. Such dissolution results in white spot formation, an early sign of dental caries. In principal, to inhibit the appearance of these spots during treatment, fluoridated elastomeric o-rings might be employed. Once placed around brackets, these o-rings should release fluoride therapeutically for at least 30 days, after which the orthodontist may replace them. At the present time, such fluoride-releasing o-rings are not available. In this study, model materials for fluoride-releasing elastomeric o-rings were developed. These materials were fluoride-impregnated poly(ethylene-co-vinyl acetate) (PEVA) films. In vitro release studies of these films were conducted, assessing their capacity to deliver fluoride within therapeutic range (1.2 ≤ µg F/ring/day ≤ 51.4) for 30-45 days. Optimal sample and experimental parameters, including (1) fluoride loading in the film (wt% F), (2) overcoat thickness, and (3) temperature that provided therapeutic release, were determined. At 37°C, favorable release was observed for the following: (1) films with overcoat thickness of 0.14 mm and fluoride loadings of 3.9 wt% and 5.7 wt% and (2) films with overcoat thickness of 0.27 mm and fluoride loading of 5.7 wt%. These results are important in providing fundamental guidance for the development of o-rings that combat white spot formation among orthodontic patients.
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Yao, Hongyang. "Microstructures of poly(vinyl acetate) studied by nuclear magnetic resonance spectroscopy." W&M ScholarWorks, 1997. https://scholarworks.wm.edu/etd/1539623911.
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Carbon-13 NMR spectroscopy was used to investigate the microstructures of poly(vinyl acetate) prepared by solution polymerization in benzene. A series of aromatic compounds was synthesized in order to model the structures formed via chain transfer to solvent. The peaks near 126.5 and 128.5 ppm in the spectra of the polymer samples were assigned to a 1-phenyl-(2n + 1)-multi-acetoxyalkane (where n = 1, 2, 3, etc.) microstructure. The concentration of that structure obtained from NMR spectra was correlated with the concentration calculated from reported kinetic data.;Chain transfer to benzene was shown to occur by addition of the macroradical to benzene, followed by rearomatization involving loss of a hydrogen atom. No evidence was obtained for a transfer mechanism involving hydrogen abstraction from benzene, and the copolymerization of benzene with vinyl acetate also was shown to be absent. The transfer mechanism actually established accounts for the unexpectedly large transfer constant of benzene in vinyl acetate polymerization. General mechanisms are proposed for the solution polymerization of vinyl acetate in aromatic solvents.
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Nare, Keith Dumisani. "Formulation development and thermorheological properties of crumb rubber/eva modified bitumen." Thesis, Nelson Mandela Metropolitan University, 2016. http://hdl.handle.net/10948/11974.
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The study deals with the formulation development and thermorheological properties of crumb rubber/ethylene vinyl acetate (EVA) modified bitumen with the aim of optimizing the amount of crumb rubber and EVA loadings in bitumen based on thermorheological parameters complex shear modulus, phase angle and rutting parameter. In the modified binders EVA offers plastomer properties whereas the crumb rubber confers elasticity to the bitumen. 13.75% crumb rubber and 2.5% EVA loadings based on aging indices gave the best optimized mixture. The thermorheological behaviour of the best optimized mixture was compared to industrial grade EVA (AP-1) and crumb rubber (AR-1) modified bitumen. Improving aging behaviour of the bitumen was evaluated using four antioxidants: carbon black, hydrated lime, Irganox 1010 and Irgafos 168. The least aging indices at 58˚C and 64˚C were obtained from a 1:1:1 Irganox 1010/hydrated lime/carbon black mixture. SARA (saturates, aromatics, resins and asphaltene) analysis gave the chemical background for application of antioxidants to reduce the propensity of short term aging. To further improve the EVA/crumb rubber optimized mixture for workability FT wax (Sasobit®) was assayed at loadings from 0-2.5%. This was done to match the EVA content and maintain the original maximum loading of 2.5% in the optimized mixture. The phase change abilities of FT wax owing to the high latent heat enabled co-crystallization with the EVA with the elastomeric backbone of crumb rubber acting as support material. The energy-sustainability nexus was found to have worked at less than 1% loading of FT wax in the EVA/crumb rubber modified bitumen. Response surface methodology approach to all the sections of work was used to come up with the optimized mixtures based on rheological parameters complex shear modulus, phase angle and rutting parameter at test temperature 64˚C. The interaction chemistry of bitumen, crumb rubber, EVA and FT wax was found to be first and second order in all cases involving individual contributions and co-interaction amongst the factors. Project costing for each section of work (optimizing section, antioxidant section and FT wax section) was conducted involving the raw materials used, equipment used, labour involved and other costs incurred for all the project work.
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Oghide, Godwin O. "Miscibility studies of poly (methyl acrylate) poly (vinyl acetate) and poly (vinyl acetate)/ poly (vinylidene fluoride) blends using differential scanning calorimetry and fourier transform infra red spectroscopy." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 1985. http://digitalcommons.auctr.edu/dissertations/3294.
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The miscibility of poly (methyl acrylate)/poly (vinyl acetate) (PMA/PVAc) and poly (vinyl acetate)/poly(vinylidene fluoride) (PVAc/PVF2) blends has been studied. Films of compositions 100/0, 80/20, 60/40, 50/50, 40/60, 20/80, and 0/100 (w/w) were cast for each system. Films of PMA/PVAc were found transparent and those of the PVAc/PVf2 were slightly opaque. While all the compositions of the PMA/PVAc exhibit single sharp Tgs, as measured with the differential scanning calorimeter, almost all of those of the PVAc/PVF2 exhibit s1 ng1 e broad TgS. By the single Tg criterion, the PVA/PVAc and PVAc/PVF2 systems are miscible in all proportions. Fourier transform infra-red spectroscopy spectra indicate molecular interaction complex involvement in the two systems. Evidence for such interaction was found to be significant in the 80% PMA/20% PVAc and 20% PVAc/80% PVF2 compositions.
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Poormahdian, Saïd. "Emulsion copolymerization of vinyl acetate and butyl acrylate in a tubular reactor." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0028/NQ48892.pdf.
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Olsen, Donald Grant. "A study in plantwide control of a vinyl acetate monomer process design." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/MQ65065.pdf.
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Lange, Hanna. "Emulsion polymerization of vinyl acetate with renewable raw materials as protective colloids." Thesis, KTH, Skolan för kemivetenskap (CHE), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-41019.
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Emulsion polymerizations of vinyl acetate (VAc) were performed by fully or partially replacing poly(vinyl alcohol) (PVA) with renewable materials as protective colloids or by adding renewable materials, as additives or fillers, to the emulsions during or after polymerization. The purpose of the study was to increase the amount of renewable materials in the emulsion. A total of 19 emulsions were synthesized. Different recipes were used for the synthesis. The following renewable materials were studied; hydroxyethyl cellulose (HEC) with different molecular weights, starch and proteins. HEC and starch were used as protective colloids. Proteins were used as additives or fillers. Cross-linking agent A and Cross-linking agent B were used as cross-linking agents. A total of 26 formulations were pressed, either cold or hot. The synthesized emulsions were evaluated with respect to pH, solids content, viscosity, minimum film formation temperature (MFFT), glass transition temperature (Tg), particle size and molecular weight (Mw). The tensile shear strengths of the emulsions were evaluated according to EN 204 and WATT 91. It was possible to fully, or partially, replace PVA as protective colloid with renewable materials. It was also possible to use renewable materials as additives or fillers in the emulsions. The emulsions obtained properties that differed from the reference. Generally, emulsions with HEC as protective colloid showed lower viscosity and slightly higher MFFT, Tg and molecular weight than emulsions with PVA as protective colloid. Larger particle sizes than the reference were obtained for emulsions containing PVA combined with renewable materials. The emulsion with starch as protective colloid exhibited the largest particle size. 10 formulations passed the criteria for D2. The emulsions where PVA was fully or partially replaced with HEC or starch showed a water resistance similar to the reference (around D2). The addition of protein did not decrease the water and heat resistance compared to the reference. Addition of protein after polymerization increased the water resistance (D2) compared to addition during polymerization. Addition of cross-linking agents did not increase the water resistance further. Two formulations passed the criteria for D3. The emulsion in the first formulation had PVA as protective colloid and protein B was added during polymerization. The emulsion in the second formulation had HEC as protective colloid. To both of these emulsions, protein A was added after polymerization, as a filler, combined with Cross-linking agent B as cross-linking agent before hot pressing. The first formulation also showed a good heat resistance (passed the criteria for WATT 91).
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Palma, Mauri Sergio Alves. "Polimerização de acetato de vinila em emulsão de modo contínuo em coluna pulsada de pratos perfurados." Universidade de São Paulo, 2002. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-27082013-122010/.
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Processos industriais de polimerização em emulsão são usualmente realizados em reatores tipo tanque agitado em batelada (ou semi-batelada) ou em contínuo (CSTR). Reatores contínuos tem a vantagem de serem comparativamente de menor porte, e propiciarem melhor controle da qualidade do produto pela redução de variações de batelada a batelada. Reatores tipo CSTR podem exibir oscilações periódicas e autosustentadas de conversão, de tamanho e concentração de partículas. Estas oscilações podem ser minimizadas nos reatores tubulares pulsados devido à diminuição da dispersão axial em relação aos reatores do tipo CSTR. Na presente tese, desenvolveu-se um novo tipo de reator tubular, a Coluna Pulsada de Pratos Perfurados, CPPP, para uso no processo de polimerização contínua do acetato de vinila em emulsão. O reator é operado com escoamento pulsado e contém pratos perfurados como dispositivos internos. Inicialmente foram realizados ensaios de distribuição de tempos de residência, em um reator montado em vidro, com o objetivo de caracterizar o escoamento no reator CPPP quanto ao grau de mistura axial. Os dados foram interpretados usando o modelo de escoamento pistonado com dispersão axial. Valores do coeficiente de dispersão axial foram medidos e correlacionados para diferentes condições de freqüência e amplitude de pulsação, vazão, espaçamento entre pratos, e viscosidade do fluido. Verificou-se que o grau de mistura axial pode ser variado em faixas relativamente amplas pela manipulação da freqüência e amplitude de pulsação. Foi também montado um reator em aço inox e encamisado, com as mesmas dimensões, onde foram realizados ensaios de polimerização em emulsão de acetato de vinila, medindo-se a conversão e a distribuição de tamanhos de partículas (DTP), na saída do reator em regime transiente e permanente, e também ao longo do reator em regime permanente. Verificou-se que as condições operacionais (tempo médio de residência e grau de dispersão axial) influenciam várias características do produto, como, a conversão, tamanho médio e concentração de partículas, porém, não influencia, significativamente, a viscosidade da emulsão produzida, para a receita da reação de polimerização e as condições operacionais estudadas. Os resultados experimentais foram interpretados usando um modelo matemático do reator, o qual foi estabelecido com base em um modelo cinético publicado na literatura para o processo de polimerização em emulsão de acetato de vinila em batelada. Tal modelo foi adaptado incluindo-se os termos convectivos e dispersivos nas equações de balanço de massa, e resolvido numericamente. Foram ajustados apenas dois parâmetros neste modelo, para todas as condições operacionais estudadas e os resultados simulados reproduziram adequadamente o comportamento das principais variáveis de processo para a condição de regime permanente. O novo tipo de reator contínuo apresentado neste trabalho mostrou-se ser possível obter altas conversões em tempos médios de residência da ordem ou mesmo inferiores aos do processo em batelada e atingir regime permanente de operação em um a dois tempos médios de residência. O reator é eficiente, robusto, construtivamente simples, de fácil limpeza e manutenção, e mostrou-se promissor para utilização industrial em processo de polimerização em emulsão de acetato de vinila.Industrial emulsion polymerization processes are usually carried out in stirred tanks operated in batch/semibatch or in continuous mode (CSTR). In comparison to batch processes, continuous reactors present several advantages such as lower volumes and better quality control by reducing batch-to-batch variations. Continuous emulsion polymerization in CSTR may exhibit sustained oscillations in conversion, particle size and particle concentration. Such oscillations may be reduced in pulsed tubular reactors due to less axial mixing. In this thesis a new type of tubular reactor, called Pulsed Sieve Plate Column, PSPC, was developed for the continuous process of vinyl acetate emulsion polymerization. This reactor is operated using oscillatory pulsed flow and uses perforated plates as internals. Residence time distribution runs were carried out in a glass reactor in order to characterize the axial mixing and flow patterns in the PSPC. The data were treated using the axially dispersed plug flow model. Axial dispersion coefficient was measured for different conditions of pulse frequency and amplitude, flow rate, plate spacing and viscosity. It was found that the degree of axial mixing can be varied in wide ranges by manipulating pulsation frequency and/or amplitude. Vinyl acetate continuous emulsion polymerization runs were carried out in a jacketed stainless steel reactor (with the same size of the glass reactor). Monomer conversion and particle size distribution was measured both at the reactor exit in transient state and along the reactor length at steady-state. It was found that average residence time and degree of axial mixing affect process and product quality variables, such as monomer conversion, mean particle size and concentration, but did not affect the viscosity of the emulsion produced, for the recipe and conditions used. A mathematical model for the reactor was developed. The model used, based on a well-known kinetic model previously developed in the literature for batch emulsion polymerization, was adapted to the continuous tubular reactor by adding the dispersion and convective terms to the balance equations. The model was numerically solved. Only two parameters were adjusted in this model and the simulated results showed excellent agreement with the experimental results, for steady state conditions. The proposed tubular reactor allows to reach high monomer conversion with similar or even lower residence time than those in batch processes and reaches steady state operation in just one to two mean residence times. The reactor is efficient, easy-to-built, easy-to-clean, robust and promising for use in industrial continuous emulsion polymerization of vinyl acetate.
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Hashimoto, Patrícia Kazuyo. "Complexos de Mn(II) e Fe(II) coordenados a bases de Schiff Bidentadas derivadas de cicloalquilaminas como mediadores da OMRP de acetato de vinila /." Presidente Prudente, 2018. http://hdl.handle.net/11449/154400.
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Orientador: Beatriz Eleutério GoiCoorientador: Valdemiro Pereira de Carvalho Júnior
Banca: Pedro Ivo da Silva Maia
Banca: Ana Maria Pires
Resumo: Nas últimas décadas, a polimerização radicalar controlada (CRP) tem se tornado muito importante, pois permite a síntese de macromoléculas de arquiteturas específicas com um controle sobre as propriedades químicas e físicas. Sendo assim, este trabalho apresenta a síntese de novos complexos de Mn(II) e Fe(II) coordenados à ligantes bases de Schiff bidentados, que são resultantes da condensação do salicilaldeído com as seguintes cicloalquilaminas: (1) Ciclopentilamina, (2) Cicloexilamina, (3) Cicloeptilamina e (4) Ciclooctilamina, de forma que estes possam ser utilizados como mediadores da polimerização radicalar mediada por organometálicos. Os ligantes foram caracterizados pelas seguintes técnicas: espectroscopia de ressonância magnética nuclear de hidrogênio (RMN de 1H), espectroscopia de absorção na região do ultravioleta-visível (UV-Vis) e espectroscopia vibracional na região do infravermelho (FTIR). Já os complexos de Mn(II) e Fe(II) foram caracterizados pelas técnicas de FTIR, UV-Vis, voltametria cíclica (VC) e ponto de fusão (p.f.). Os estudos cinéticos de polimerização foram realizados para os complexos de manganês e ferro. O complexo [MnIIbis(N-Salicilideno-Ciclopentilamina)], Mn(L1)2, apresentou um melhor controle na polimerização do acetato de vinila com menores valores de polidispersidade e a curva de massa molecular (Mn) mais próxima aos valores da curva teórica. Já os complexos de ferro mediadores apresentaram um comportamento mais similar, não havendo muita...
Abstract: In the last decades, controlled radical polymerization (CRP) has become very important, since it facilitates the synthesis of macromolecules of specific architectures with excellent control over the chemical and physical properties. Thus, this work presents the synthesis of new Mn(II) and Fe(II) complexes coordinated with the bidentate Schiff bases ligands, which are the result of the condensation of salicylaldehyde with cycloalkylamines: (1) cyclopentylamine, (2) cyclohexylamine, (3) cycloheptylamine and (4) cyclooctylamine, so that they can be used as mediators of radical polymerization mediated by organometallic (OMRP). The ligands synthesized were characterized by proton nuclear magnetic resonance (1H-NMR) spectroscopy, ultraviolet-visible (UV-Vis) absorption spectroscopy and Fourier-transform infrared spectroscopy (FTIR) techniques. The synthesized Mn(II) and Fe(II) complexes were studied by FTIR, UV-Vis, cyclic voltammetry (CV) and melting point (m.p.). Kinetic polymerization studies were performed for the manganese and iron complexes. The [MnIIbis (N-Salicylidene-Cyclopentylamine)], Mn(L1)2, complex showed a better control in the polymerization of vinyl acetate with lower values of polydispersity and the molecular mass curve (Mn) closer to the values of the theoretical curve. However, the iron mediator complexes presented a more similar behavior, not having much difference in the kinetic curves
Mestre
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Bambalaza, Sonwabo Elvis. "An investigation into the use of a ceramifiable Ethylene Vinyl Acetate (EVA) co-polymer formulation to aid flame retardency in electrical cables." Thesis, Nelson Mandela Metropolitan University, 2014. http://hdl.handle.net/10948/d1020159.
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The concept of a unique ceramifiable Ethylene vinyl acetate (EVA) based polymer composite was based on the incorporation of inorganic compounds such as aluminium hydroxide, calcium carbonate, muscovite mica, and calcined kaolinite within a 95 percent EVA/ 5 percent Polydimethylsiloxane (PDMS) polymer matrix such tha t upon heating to elevated temperatures of about 1000 oC, a solid end-product with ceramic-like properties would be formed. The ceramifiable EVA based polymer composite was developed to be used as electric cable insulation or sheath as the formation of a ceramic based material at elevated temperatures would provide flame retardant properties during fire situations. The flame retardant properties at elevated temperatures would ensure that the insulation remains at such temperatures due to some of the properties of the resultant ceramic such as reasonably high flexural strength, high thermal stability, non-reactivity and high melting point. During a fire this would ensure that flames would not be propagated along the length of the cable and also protect the underlying conducting wires from being exposed to the high temperatures of the fire. Its application as a cable insulation also required that the material functions as a cable insulator under ambient temperature conditions where the ceramifiable polymer composite should retain certain polymer properties such as the post-cure tensile strength (MPa), degree of polymer elongation (percent), thermal expansion, thermal slacking, limited oxygen index and electrical insulation. This study made use of a composite experimental design approach that would allow for the optimization of the amounts of the additives in the ceramifiable polymer composite giving both the desired mechanical properties of the material under normal operating temperatures as a polymer and also as a ceramic once exposed to elevated temperatures. The optimization of additives used in the ceramifiable polymer composite was done by using a D-optimal mixture design of experiments (DoE) which was analyzed by multiple linear regression.
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Lake, Richard Charles. "The identification of the fouling mechanism during the crossflow filtration of a model fermentation broth." Thesis, University of Surrey, 1996. http://epubs.surrey.ac.uk/842774/.
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Experiments have been conducted to identify the fouling mechanism during the crossflow filtration of a model yeast fermentation broth of Vinyl Acetate particles suspended in a Bovine Serum Albumin (BSA) solution. These have been conducted with filter modules, to obtain quantitative data for the rate and the extent of flux decline due to membrane fouling, and with filter coupons, to obtain quantitative data for the build up of the fouling layer with each individual system and the mixed system. The data from the individual systems have been analysed and then used to determine their fouling mechanisms; this information has been used to predict the fouling mechanism for the mixed system. Finally, this prediction has been compared to the actual fouling mechanism determined by analysis of the mixed system data. For the model particulate suspension, the fouling was due to the build up of a cake layer, as with dead end filtration; however, fouling was limited by membrane scouring. For the model macromolecular solution, a four part fouling mechanism was identified: initially aggregates formed within the pores; the concentration at the membrane surface increased until protein came out of solution as strands; the strands disappeared causing increased aggregation in the pores; finally, a mesh formed on the membrane surface. For the mixed system, fouling was due to the formation of a particle cake on the membrane surface with protein aggregates forming in the pores. The fouling kinetics could be predicted by considering the results from the individual systems; however, the fouling mechanism could not be predicted without using visualisation experiments due to the interactions between the particles and the macromolecules.
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Ferguson, Christopher James. "Core-shell polymers from styrene and vinyl acetate for use as wood adhesives." Thesis, University of Canterbury. Chemistry, 2000. http://hdl.handle.net/10092/5647.
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Techniques to produce core-shell morphology have been applied to the creation of poly(vinyl acetate) emulsions for use as wood adhesives. These strategies have been used to investigate the molecular origins of some of the shortcomings of poly(vinyl acetate) adhesives, and also to attempt to enhance the properties of these widely used adhesives. A model is presented to predict the incidence of particle formation, which was used to accurately predict that the polymerisation of vinyl acetate in the presence of large polystyrene seed particles would not be possible without the formation of secondary particles. Numerous attempts were made to reduce the incidence of secondary particle formation using the mechanistic basis of the model as a guide, without success. As a result, the inverse route to core-shell morphology was used to create the desired morphology. Microscopic characteristics that favoured the formation of particles containing one centrally located polystyrene core were investigated. Transmission electron microscopy techniques were developed to allow characterisation of the morphology produced in two-stage styrene-vinyl acetate polymerizations Latices having a range of morphologies, including the desired core-shell, were subjected to a range of physical tests to evaluate their performance as wood adhesives. The information gained from this testing was used to correlate performance between tests. The results have also been explained on the basis of microscopic structure.
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Khunniteekool, Chonlada. "Structure/property relationships of cross-linked polyethylene and ethylene vinyl acetate copolymer foams." Thesis, University of Manchester, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390453.
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Owens, Thomas Graham. "The promoting role of Au in the Pd-catalysed synthesis of vinyl acetate monomer." Thesis, University of St Andrews, 2007. http://hdl.handle.net/10023/352.
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Greenslade, Mark. "Electrochemical & catalytic study of graphite-supported palladium-gold catalysts for vinyl acetate synthesis." Thesis, Cardiff University, 2006. http://orca.cf.ac.uk/56151/.
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The chemistry of vinyl acetate synthesis from ethylene, acetic acid, and oxygen over palladium-gold catalysts has been investigated in a study which has concentrated on the use of cyclic voltammetry as a surface sensitive analytical technique. Three series of palladium-gold/graphite catalysts were prepared by slurry precipitation or by incipient wetness impregnation and by reduction with formaldehyde or hydrazine. These catalysts, which behaved similarly, contained metallic particles having bi-modal particle-size distributions and alloy compositions, as judged by X-ray diffraction, high resolution transmission electron microscopy, and energy dispersive X-ray analysis. Surface characterisation was achieved by cyclic voltammetry and X-ray photoelectron spectroscopy. In experiments intended to mimic the industrial LEAP process (in which potassium acetate is added to the reaction mixture) catalysts were treated with acetic acid or potassium acetate/acetic acid mixtures. Such treatments resulted in etching of the catalysts with consequent loss of palladium dissolution of the lost palladium as dimeric and trimeric palladium acetate complexes was confirmed by ultra-violet absorption spectroscopy. Such etching occurred at the surfaces of palladium-rich particles gold-rich particles were resistant to etching. Thus, the role of gold as a promoter is to stabilise the optimum alloy phase against loss of palladium. Reduction of palladium acetate complexes by ethylene led to plating of metallic palladium onto the surfaces of etched catalysts. Thus, a cycle of palladium dissolution and deposition occurred under reaction conditions leading to a redistribution of palladium between the catalyst particles. Palladium acetate forms complexes with acetic acid and water that are liquid at synthesis temperatures. Thus, even under gas-phase reaction conditions, a liquid-phase may be present in which palladium acetate complexes can facilitate the homogeneous catalysis of vinyl acetate synthesis. This investigation provides definitive evidence that the balance of heterogeneous and homogeneous synthesis is determined by the range of the palladium-gold alloy composition present at the surface of the active catalyst. Etching and dissolution would be avoided by suitably restricting this range, whereupon reaction would be confined to that achieved by heterogeneous catalysis.
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Brown, Nicole Robitaille. "Understanding the Role of N-Methylolacrylamide (Nma) Distribution in Poly(Vinyl Acetate) Latex Adhesives." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/26446.
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This work addresses the distribution of N-methylolacrylamide (NMA) units in crosslinking poly(vinyl acetate) (PVAc) adhesives. In this case, distribution refers to the three potential locations of polymerized NMA units in a latex: the water-phase, the surface of polymer particles, and the core of the polymer particles. The objective is to identify the distribution of NMA in three latices and to determine whether NMA distribution correlates with durability related performance. NMA distribution was studied via a series of variable temperature solution NMR experiments, while the durability-related performance was studied via mode I fracture mechanics tests.
Studying the distribution of NMA required the use of isotopically labeled NMA. Both 15N-NMA and 13C, 15N-NMA were synthesized. Three NMA/vinyl acetate (VAc) latices were prepared. The NMA feed strategy was varied during each of the three emulsion copolymerizations. Latex characterization methods including differential scanning calorimetry (DSC), rheometry, particle size analysis, and scanning electron microscopy (SEM) were used to study the three latices.
The solution NMR method to identify NMA distribution was performed on untreated latices and on washed latices. Washing techniques included membrane dialysis and centrifugation. Results revealed that the three latices had different NMA distributions, and that the distributions were related to the expected differences in microstructure. Latex 3 had ~ 80% core-NMA, while Latex 2 had ~ 80% surface-NMA. Latex 1 had a high proportion of surface-NMA (~60%), but also had the highest proportion of water-phase NMA (~ 20%). This high proportion of water-phase NMA could be responsible for the unique morphology Latex 1 exhibited in SEM studies.
Mode I opening fracture mechanics studies were used to study adhesive performance. Specimens were analyzed after exposure to accelerated aging treatments. Latex 2 and Latex 3 exhibited very similar results, despite having very different NMA distributions. All three latices showed good durability related performance. In Latex 2 and Latex 3, the critical strain energy release rates (Gc) after accelerated aging treatments were statistically the same as the Gc of the control specimens. The most interesting finding was that the Latex 1 Gc values were significantly higher after accelerated aging. Latex 1 also had the highest proportion of water-phase NMA. Bondline images and SEM micrographs both indicated that the integrity of Latex 1 was least affected by the accelerated aging treatments.Ph. D.
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Badiee, Amir. "An examination of the response of ethylene-vinyl acetate film to changes in environmental conditions." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/33757/.
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Photovoltaics are used for the direct conversion of sunlight into electricity. In order to provide useful power, the individual solar cells must be connected together. This electrically connected and environmentally protected unit is termed a photovoltaic (PV) module. The structure of a PV module consists of a number of layers of various materials with different properties. The encapsulation material is one of the critical components of a PV module. It mechanically protects the devices and electrically insulates them, ideally for at least the 20-25 year lifetime of the modules. The lifetime of a PV module is generally limited by the degradation of the constituent parts. The materials degrade and cause a decrease in the efficiency leading to eventual failure, with the encapsulant being particularly susceptible to degradation. The most common encapsulant material is Ethylene Vinyl Acetate (EVA) the degradation of which leads to a significant drop in a PV module’s efficiency, durability and lifetime. EVA undergoes chemical degradation when it is exposed to environmental factors such as elevated temperature, humidity and Ultra Violet (UV) radiation. Although numerous works have been done in this field there is still a gap in knowledge to fully understand the degradation of EVA and develop a predictive tool. This work investigates the chemical degradation of an EVA encapsulant to understand the degradation mechanisms, develop a predictive model and correlate the degradation with changes in the structure and mechanical properties. To determine the effect of environmental stresses on EVA environmental conditions were simulated in the laboratory in order to accelerate the test program. The ageing was classified into three main groups, namely thermal ageing, UV ageing and damp-heat ageing. In order to investigate the effect of elevated temperature on the mechanical and thermal properties and also to study the thermal degradation, EVA sheets were aged in a dark laboratory oven at 85°C for up to 80 days. To investigate the impact of UV exposure on the properties and photodegradation of EVA the samples were exposed to UV radiation of 0.68 W/m2 at 340 nm and 50°C. To study moisture diffusion and the impact of absorbed moisture on the mechanical properties and morphology, EVA sheets were aged in an environmental chamber at 85°C-85% RH and using a potassium chloride (KCl) salt solution in a sealed chamber to obtain 85% RH at room temperature (22±3°C). Thermal analysis techniques including Differential Scanning Calorimetry (DSC), Thermo-gravimetric Analysis (TGA), Dynamic Mechanical Analysis (DMA) along with Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR) and Gravimetrics were used to investigate the structure, degradation kinetics and viscoelastic mechanical properties of the EVA as a function of ageing. The EVA was shown to have viscoelastic properties that were highly sensitive to the ambient temperature. Thermal ageing was shown to reduce the storage modulus due to the changes in the structure of the EVA and reduction in crystallinity. Over a longer time, chemical changes due to thermal activation also occurred, hence, these were insignificant compared with transient thermal effects. The activation energy of deacetylation was also shown not be affected by the ageing process. Investigation of photodegradation showed notable chemical changes as a result of UV exposure, with FTIR absorbance peaks related to carboxylic acid, lactone and vinyl exhibiting a sharp increase after UV irradiation. Differences in the ATR-FTIR spectra of the UV irradiated and non-irradiated samples showed that the intensity is depth dependant. DMA results showed UV ageing had a significant influence on the mechanical properties of the EVA and reduces the storage modulus. The predictive photodegradation model showed a good agreement on the UV irradiated surface with the experimental data where it did not agree well with the results on the non-irradiated side which could be due to the presence of UV absorber. The response of the EVA to damp heat was investigated at two conditions with same the RH level (85% RH) and different temperatures (room temperature and 85°C). The moisture diffusion coefficient was measured via gravimetry and Water Vapour Transmission Rate (WVTR) technique which were well-agreed. Results from DSC indicated that the crystallinity increased due to incorporation of moisture into the structure of the copolymer but decreased as ageing continued, showing the significant influence of elevated temperature and thermal degradation on the structure of EVA. A comparative study of the impact of the ageing on the structure and mechanical properties indicated that UV has a stronger degrading influence comparing to other degradation factors. DSC results also suggested that property changes could be connected to structural modifications. The impact of different degradation factors can be summarised as UV > T > DH.
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Collins, Stephen. "An investigation into the synthesis and characterisation of three materials based on poly (vinyl acetate)." Thesis, University of Sheffield, 2005. http://etheses.whiterose.ac.uk/3588/.
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An investigation into the synthesis of three types of material based on poly (vinyl acetate) was performed using three novel polymerisation techniques. The three techniques used were: i) the use of chain transfer to solvent; ii) the use of enzymes to catalyse the synthesis of block copolymers of vinyl acetate and c- caprolactone; iii) the synthesis of hyperbranched polymers of vinyl acetate and n- vinyl pyrrolidinone, monomers which both propagate through an unstabilised radical. The first technique has been widely used in order to synthesise polymers and oligomers with solvent derived endgroups. In this work polymers have been synthesised using isopropanol, 2-isopropoxy ethanol and 3-methyl-2-butanone as solvents. All of these have been shown to be active as chain transfer agents in previous studies. The second technique builds on previous work, performed in the field of enzymatic control of polymerisation reactions. Enzymes can be used to both synthesise monomers and catalyse the polymerisation of monomers. Hydroxy terminated poly (vinyl acetate) was used to control the polymerisation of 6- caprolactone, leading to the formation of block copolymers. The third technique involves the synthesis of hyperbranched poly (vinyl acetate) and poly (n-vinyl pyrrolidinone). This was achieved through the use of a polymerisable branching agent, also with the ability to act as a chain transfer agent. Through the use of this as a comonomer a hyperbranched polymer can be synthesised without the formation of a crosslinked gel.
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English, Hugh Edmund. "Molecular simulations of ethylene vinyl acetate for the improvement of the cold flow properties of diesel." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/molecular-simulations-of-ethylene-vinyl-acetatefor-the-improvement-of-the-cold-flow-propertiesof-diesel(735bf45e-acf0-4115-86a0-ea0c811c910a).html.
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Ethylene-vinyl acetate co-polymers are widely used as cold-flow improving additives in diesel fuels. Although their functionality is undisputed, the mechanisms of action at a molecular level are not fully understood. Theories that EVA acts as both a nucleating agent for small wax crystals and as a crystal growth inhibitor are generally acknowledged, however the understanding of the effect of structure on additive performance is limited. Studies have been carried out using molecular simulation techniques with the aims of improving the understanding of the interactions between EVA and diesel fuels, and assessing the potential of these methods for the analysis of different additive structures and fuel compositions. Firstly, the ability of Monte Carlo simulations to predict the chemical potentials of n-alkanes in organic solvents was studied. This information would be of use in determining the characteristics of different fuel compositions. It was found that the particle insertion method used becomes more efficient as the aspect ratio of the solvent increases relative to that of the solute. Despite the identification of expected linear trends in the chemical potential of n-alkanes, it was not possible to produce high quality quantitative data using this method. The effect of vinyl acetate spacing and solvent environment on the configuration of lone EVA molecules in the liquid phase was studied. Molecular dynamics showed that closely spaced vinyl acetate groups increase the tendency of the molecule to fold at that point, whilst molecules with 2 or 3 ethylene groups in between show resistance to folding. It was shown that n-hexane as a solvent produced more folded configurations than benzene and n-hexadecane respectively. Monte Carlo simulations were also performed but were largely unsuccessful. Finally, molecular dynamics simulations were performed to study the effect of different EVA structures on the spontaneous crystallisation of n-hexadecane, and the interaction of the EVA with the resulting structures at a molecular level. It was shown that different EVAs had varying effects on the crystallisation, with trends attributed to the spacing of the vinyl acetate groups and the length and position of extended aliphatic sections of the EVA molecules. One molecule, with evenly spaced side-groups and no extended aliphatic sections was shown to fully prevent the formation of any crystalline structure within the time of the simulation where all other EVA molecules allowed some degree of wax formation to occur.
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Haire, Andrew Richard. "Probing the influence of bimetallic composition on the Pd/Au catalysed synthesis of vinyl acetate monomer." Thesis, University of St Andrews, 2010. http://hdl.handle.net/10023/1018.
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Scanning Tunnelling Microscopy (STM) was utilised together with the high resolution depth-profiling capabilities of Medium Energy Ion Scattering (MEIS), a technique traditionally associated with single crystal substrates, to probe the mean size and depth dependent composition profile of bimetallic PdAu nanoparticles on planar oxide surfaces as functions of the starting composition and annealing temperature. In order to fit composition profiles to experimental MEIS data, a new analysis tool has been designed that models the particles as flat-topped structures with a hexagonal base which can be divided into a number of shells, each shell corresponding to a particular ion pathlength inside the material. The reliability of this method will be discussed in detail. Fitting results show that the surface layers are always significantly enriched in Au compared to the bulk alloy composition. By comparing MEIS data for clean surfaces data for modified surfaces it was found that Pd generally segregates towards the particle surface on adsorption of acetic acid. The interaction of potassium acetate with Au/Pd{111} alloy surfaces of varying composition has been investigated using Temperature Programmed Desorption (TPD) and Reflection Absorption Infra Red Spectroscopy (RAIRS). At lower coverage, potassium acetate reacts reversibly with the surface to form CO and carbonate. Formation of surface acetate is observed on Pd-rich surfaces only. At higher coverage, acetate is the major surface species formed on all samples examined.
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Schofield, Wayne Christopher Edward. "Factors affecting the performance of magnesium hydroxide flame retardant fillers in an ethylene vinyl acetate copolymer." Thesis, Manchester Metropolitan University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297579.
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Garlet, Givanildo. "Aproveitamento de resíduos de E.V.A. (Ethylene Vinyl Acetate) como agregado para concreto leve na construção civil." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 1998. http://hdl.handle.net/10183/118243.
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O desenvolvimento de novos materiais para a construção civil a partir do aproveitamento de resíduos industriais, buscando a redução do custo das habitações e a preservação do meio ambiente, apresenta vantagens que vem despertando o interesse de pesquisadores e empresários em todo o mundo. Neste trabalho é descrito o estudo para o aproveitamento, na construção civil, do resíduo de E.V.A. (Ethylene Vinyl Acetate), polímero muito utilizado na indústria calçadista para a confecção de solados e palmilhas internas de calçados. Em virtude do grande volume gerado mensalmente este material vem se acumulando ao longo dos anos em áreas a céu aberto, causando diversos problemas ao meio ambiente. O emprego dos resíduos de EVA na construção, além de contribuir para a solução do problema ambiental, pode representar uma nova fonte de receita para empresas que exploram o uso deste material. Aproveitando a baixa massa unitária deste resíduo (± 180 kg/m3) o estudo foi direcionado para o desenvolvimento de um agregado leve, a ser usado na produção de concreto e de componentes de vedação para a construção civil. O material proveniente das fábricas de calçados foi triturado em um moinho, sendo ass1m obtido um agregado de EVA com determinada granulometria. Posteriormente foi conduzido um programa experimental, onde foram avaliadas as condições de trabalhabilidade e consistência necessárias à mistura fresca, bem como as propriedades físicas e mecânicas do concreto obtido, pela mistura de cimento, areia e agregado de EVA. Os resultados mostram um novo tipo de concreto leve, cuja principal propriedade é a grande ductilidade, devido às propriedades elásticas do agregado de EVA. Como aplicações em potencial são apontadas o uso como contrapiso de lajes entrepisos para atenuação do ruído de impacto, isolamento térmico, absorção acústica, além da possibilidade de produção de alguns artefatos de cimento, desde que a resistência à compressão seja adequada, na dosagem do concreto.The development of new construction materiais, using industrial wastes, can to reduce the cost of construction and preserve the environment. These advantages have been waking the interest of researchers around world. This work describes the studies to make use of E.V.A. (Ethylene Vinyl Acetate) wastes, which is a polymer very utilized to make soles in the shoes industry. The big amount of EVA wastes producted per month has been deposited in many earth sufaces, causing many environmental problems. Therefore utilizes these wastes can represent a new source of take for business enterprises. Furthermore, can contribute to solve the environmental problems. Due to the low weight of this material the studies were conducted to find out a new Lightweight aggregate to use in the civil construction. The first step was to grind the wastes from the factories to reduce them to an aggregate. Then was developed an experimental program where the physical and mechanical properties of the concrete obtained mixing cernent, sand and EVA aggregate were analyzed. The results shown a new Lightweight aggregate concrete that can be utilized to make non structural components for construction as thermal insulation of roofs, to reduce de impact noise between slabs of the multistory building and to acoustical absorption. The studies also conclude that the strength can be control through the concrete density in the project mix.
40
Franco, Cilene Meinberg. "Pesquisa experimental sobre a polimerização via radical livre com iniciadores mono e difuncional." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266156.
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Orientador: Liliane Maria Ferrareso LonaDissertação (mestrado) - Universidade Estadual de Campinas. Faculdade de Engenharia Quimica
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Resumo: Iniciadores mono funcionais são largamente utilizados em polimerizações VIa radical livre. Muitas vezes, na busca de maiores produtividades, utilizam-se temperaturas de operação mais elevadas e/ou maiores concentrações iniciais de iniciador, que por conseqüência, geram polímeros com pesos moleculares mais baixos. O uso de iniciadores difuncionais permite o aumento da produtividade sem a redução no peso molecular do produto final, o que pode ser urna característica desejável. A pesquisa com iniciadores difuncionais é atual e de grande interesse industrial. O objetivo deste trabalho é analisar o efeito da funcionalidade do iniciador, no caso mono e difuncional, sobre a polimerização via radical livre, considerando corno caso estudo um polímero linear, o poliestireno, e um ramificado, o poli (acetato de vinila). Para isso, foram feitas, experimentalmente, reações de polimerização em ampolas de vidro (polimerização em massa), com o iniciador mono funcional (Luperox TBEC) e o di funcional (Luperox 531). Foram analisados também o efeito da temperatura de polimerização e a concentração de iniciador. Também neste trabalho é apresentado um estudo estatístico através de um Planejamento Fatorial, a fim de analisar o efeito das variáveis temperatura e concentração de iniciador na polimerização do estireno com iniciador difuncional. Observou-se, tanto para o estireno corno para o acetato de vinila, que quando utilizado o iniciador difuncional é possível obter conversões maiores, sem alterar o peso molecular médio mássico e numérico, sendo que em alguns casos pode se até obter um aumento no peso molecular. O uso de iniciador di funcional é também mais viável economicamente, pois apresenta melhores resultados frente ao monofuncional, mesmo quando utilizado em concentrações ou temperaturas menores do que as utilizadas com o iniciador mono funcional. É importante salientar o caráter inovador desta pesquisa, já que não foram encontrados, em literatura aberta, dados experimentais da polimerização do acetato de vinila (ou outro monômero que produza ramificações de cadeia longa) utilizando iniciadores difuncionais
Abstract: Monofunctional initiators are extensively utilized in free radical polymerization. In order to increase productivity, higher temperature or higher initial initiator concentration are used, therefore polymers with lower molecular weights are obtained. Bifunctional initiators increase the polymerization rate without decreasing the average molecular weight and this can be desirable. They are an important issue to be investigated and are of great interest to industries. The objective of this work is to analyze the effect of the functionality of the initiator, by using mono and bifunctional, in free radical polymerization, for linear polymer (poly styrene) and branched polymer (poly(vinyl acetate)). Polymerizations were experimentally performed in glass ampoules (bulk polymerization) using both mono(Luperox TBEC) and bi- (Luperox 531) functional initiators. The effects of temperature and initiator concentration were also analyzed for various polymerization conditions. This work includes a statistical study using the factorial design to analyze the effect of temperature and initiator concentration in styrene polymerization with bifunctional initiator. It is observed in this study, that high conversions with no effect in the molecular weigh of the dead polymer can be achieved using bifunctional initiators in the polymerization of styrene and vinyl acetate. In many cases, it is possible to obtain higher molecular weights. Bifunctional initiator can also be used to provide reduction costs to initiators. They showed better results than the monofunctional initiator when lower concentration or temperature lower were utilized.
Mestrado
Desenvolvimento de Processos Químicos
Mestre em Engenharia Química
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Langer, Filip. "Vliv okolních podmínek na recyklaci solárních modulů." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2021. http://www.nusl.cz/ntk/nusl-442429.
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This thesis is focused on experiments, goal of which is to separate protective glass apart from thin layer solar panel. This could lead to less expensive and more efficient recycling. We try to achieve the separation of the glass by thawing ethylene vinyl acetate layer, which serves as insulant and bonding material. Experiments are concluded in high temperature dryer and high temperature vacuum oven on samples of thin layer solar panel, which is for the purposes of experiments cut into same pieces by water jet cutting machine. The initiatory experiments in dryer and oven are to determine value of ethylene vinyl acetate thaw point in tested samples of panel. The thaw point is determined to be 340 °C. When exposed to this temperature, the ethylene vinyl acetate thaws enough for glass to be able to be extracted with minimal physical strength. The process is accompanied by fire destruction of tedlar layer and creation of exhaust gases. Following experiments in vacuum and nitrogen environment are to test their influence on thawing process. Exposing sample to temperature of 340 °C in vacuum led to no new results. Exposing sample to temperature of 340 °C in nitrogen environment prevented fire and achieved same level of thawing of ethylene vinyl acetate while creating less exhaust gases. Even though the fire was prevented, tedlar layer was still destroyed by the high temperature. Furthermore, particles of evaporated ethylene vinyl acetate condensed on surface of module in form of dust. Following experiments studied absorption of panel and influence of accessible solvents on thawing process. It was determined that panel is able to absorb approximately 2 % of acetone, 0,4 % of isopropyl alcohol and 0,11 % of distilled water in its own weight. Experiments with modules soaked in these solvents proved no new results in thawing process. By observing samples of ethylene vinyl acetate taken from module, thawed out of module after experiment in vacuum oven and dust condensed on surface of module after experiment in nitrogen environment, it was proven that the condensed dust is indeed ethylene vinyl acetate.
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Wittmar, Matthias. "Charge modified, comb-like graft polyesters for drug delivery and DNA vaccination synthesis and characterization of poly(vinyl dialkylaminoalkylcarbamate-co-vinyl acetate-co-vinyl alcohol)-graft-poly(D,L-lactide-co-glycolide)s /." [S.l.] : [s.n.], 2004. http://archiv.ub.uni-marburg.de/diss/z2004/0075/.
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Guclu, Mehmet. "Light Stability And The Effect Of Temperature On Mechanical Properties Of Polypropylene / Poly(ethylene-vinyl-acetate) Blends." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608535/index.pdf.
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The variation in properties of Polypropylene (PP) / Ethylene Vinyl Acetate (EVA) blends upon EVA content, temperature, and light stability were followed by using tensile testing, impact testing, and differential scanning calorimetry (DSC).
Young&rsquos modulus of the blends decreased with increasing drawing temperature and EVA content. The stress at break values of the blends slightly increased with EVA whereas decreased with drawing temperature. The percent strain at break values of the blends were found to increase abruptly by increasing EVA content and drawing temperature. These changes in the mechanical properties are the indication of compatibility. The impact tests were performed only at 0°
C, 25°
C and the impact strength increased with the temperature and EVA content, but none of the samples were broken at higher testing temperatures. The effect of stabilizer was very obvious because stabilizer-free samples failed after 400 hours whereas, the samples with stabilizer resisted up to 750 hours. Elongation values of the samples decreased because of increasing brittleness by UV irradiation. We also observed chain stiffening effect by crosslinking in all samples upon UV irradiation. Thermal analysis of the blends of the drawn samples showed an increasing trend of crsytallinity with increasing drawing temperature. Increasing drawing temperature made polymer chains more flexible because of the increasing chain mobility. These flexible chains were then oriented in one direction during tensile testing and therefore uniaxial crystallization occurred. The morphology of impact and tensile tests samples were also analyzed by scanning electron microscope (SEM). The fibrillation of pure PP is higher than the fibrillation of the blends.
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Rodriguez-Vazquez, Miguel. "Thermal and photo degradation and stabilisation of an ethylene vinyl acetate copolymer in the presence of air." Thesis, Manchester Metropolitan University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289615.
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Ting, Chin Jou, and 丁振洲. "Study the effect of poly(starch-g-vinyl acetate) on the mecha- nical properties of poly(vinyl cholride-ran-vinyl acetate)." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/29364460100088624424.
Full textAbstract:
碩士中原大學
化學工程研究所
82
Vinyl chloride-Vinyl acetate copolymer, generally is proc- essed for product in rigid or in flexual formula. When starch or its derivatives is filled in the formula will promote an effective biodegradable copolymer. In the rigid copolymer containning 12% vinyl acetate, wit- hin 15% of filler containned, tensile strength increase as following seqence of starch < graft copolymer < coarse graft copolymer. In the case of plasticizer added, flexual copolymer conta- inned 8% vinyl acetate, within 10% of filler containned, tens- ile strength increase as following sequence of starch = graft copolymer < coarse graft copolymer, and with containning 12% vinyl acetate,within the same 10% of filler containned, coarse graft copolymer was better than starch in both tensile streng- th and elongation. Under the same quantity of polyvinyl acetate side chain, rigid copolymer containning 12% vinyl acetate, generally shows higher water absorption than those containning 8% vinyl acet- ate, and under the case of same filler, more quantity of the filler, there are an higher water absorption. In the case of flexual copolymer, with same quantity of filler and the more the polyvinyl acetate side chain, the hig- her the water absorption, and the water absorption increased as following sequence of starch < coarse graft copolymer < graft copolymer.
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Dougherty, William R. "Miscibility of vinyl acetate-ethylene copolymers with vinyl chloride-ethylene copolymers /." Diss., 1999. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:9935160.
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wu, Chun-chang, and 吳俊璋. "A STUDY OF Vinyl acetate-CLAY NANOCOMPOSITES." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/dkwpzp.
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碩士國立臺北科技大學
有機高分子研究所
98
In the study, Nylon6 site are synthesized by ATRP. A new living free radical polymerization is used to exofoliate the Montmorillonite (PK802).The Montmorillonite are treated by 4-(N,N-Diethyl dithiocarbamyl methyl)benzyltrimethylammonium bromide. The Montmorillonite are exofolided by X-ray measurement(XRD). Finally, theolyacrylic acid clay nanocomposite are mixed with Nylon6 by twin-crew extruder. Theyare molded into test specimens by compression molding. It is found the tensile strengths increase almost twice of its original value when the clay content is 5 wt％ of the composites.,the thermal properties increase significantly after adding the clay. The thermal properties of Nylon6 nanocomposite were investigated by DSC measurement. Nanocomposites of PU-Clay、PC-Clay are studied in this research.
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Chen, Yun-ji, and 陳韻如. "Grafting Copolymerization of Vinyl Acetate onto Chitin." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/00184679975917294427.
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碩士國立臺灣大學
化學工程學系
86
The graft copolymer of vinyl acetate on chitin was synthesized by the use of cerium ammonium nitrate (CAN) as initiator. After the copolymerization reaction was complete, the ungrafted poly(vinyl acetate) was removed by the extraction process with acetone. The grafting percentage (GP(%)) and grafting efficiency (GE(%)) could then be calculated by the loss of weight in graft copolymer. The degradation behavior was studied by TGA and the thermal property was determined by DSC. The morphology of the graft copolymer was observed by TEM and SEM. The results indicated that at first GP and GE both increased .Then GP kept a constant value but GE started to decrease. Besides, the degradation behavior and the thermal property depended on the grafting percentage and the grafting efficiency of the graft copolymer. The possible mechanism was identified by TEM. The presence of homopolymer on the surface of graft copolymer and the differences between the ungrafted chitin and the graft copolymer were also observed by SEM.
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Budhlall, Bridgette M. S. "Grafting reactions in the emulsion polymerization of vinyl acetate using poly(vinyl alcohol) as emulsifier /." Diss., 1999. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:9955141.
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金家鳳. "Studies on chhitosan-g-poly(vinyl acetate)and chitosan-g-poly(vinyl alcohol)copolymers." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/89607313990826351109.
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