Дисертації з теми "Vinyl chlorides"
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1
Datta, Gopal K. "Heck Reactions with Aryl Chlorides : Studies of Regio- and Stereoselectivity." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-9202.
2
Gaikwad, Parikshit S. "Chemically deposited optical fiber humidity sensor." Master's thesis, Mississippi State : Mississippi State University, 2003. http://library.msstate.edu/etd/show.asp?etd=etd-06092003-141607.
3
Forrest, Martin J. "Characterisation of vinyl chloride oligomers." Thesis, Loughborough University, 1988. https://dspace.lboro.ac.uk/2134/27931.
Анотація:
A low molecular weight fraction was obtained from a mass polymerised PVC resin by using diethyl ether Soxhlet extraction followed by either preparative gel filtration or solvent fractionation. A gas chromatography - mass spectroscopy (GC-MS) analysis of this fraction revealed that, in addition to vinyl chloride (VC) oligomers, it contained a large number of other compounds, in particular a large concentration of phthalates. By using adsorption liquid chromatography it was possible to remove the phthalates, along with other contaminants having a similar or greater polarity, from the low molecular weight PVC fraction.
4
Fairbrass, Sheila Ann. "Surface deterioration of poly(vinyl chloride)." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322083.
5
Ogilvy, Norman. "Vinyl chloride precipitation polymerisation : charge effects." Thesis, University of Edinburgh, 1985. http://hdl.handle.net/1842/11229.
6
Dorobantu, Ioana-Miruna. "Vinyl chloride polymerization in microdroplet reactor." Thesis, Toulouse, INPT, 2012. http://www.theses.fr/2012INPT0037/document.
Анотація:
La polymérisation du chlorure de vinyle est une réaction très fréquente dans l’industrie des polymères, conduisant à l’obtention d’un matériau plastique très commun, connu sous le nom de PVC (polychlorure de vinyle). Ses applications concernent principalement l’industrie des constructions néanmoins d’autres domaines sont également touchés. La complexité de ce procédé de polymérisation est due à la nature toxique du monomère, à la maitrise du transfert de chaleur ou au maintien de l’agitation. Le control de ces variables de procédé influence de manière directe les caractéristiques finales du produit. Même si la polymérisation en suspension du chlorure de vinyle a été largement étudiée dans des réacteurs de type batch, il y a un manque de données au niveau de la cinétique et de la physicochimie d’une goutte de monomère pendant la réaction. L’objectif de ces travaux est de proposer un dispositif microstructuré permettant d’obtenir des gouttes monodisperses ayant un diamètre de 200 µm environ, chacune étant considérée comme un réacteur de polymérisation. Une fois identifiés les verrous liés au système eau/chlorure de vinyle en microréacteur, la réaction de polymérisation a été décrite de manière qualitative par visualisation des gouttes/grains de polymère. Des mesures Raman non-invasives en temps réel ont été réalisées sur une goutte immobile de chlorure de vinyle, cela permettant d’accéder aux valeurs des constantes cinétiques. Un modèle théorique en bon accord avec les résultats expérimentaux a été proposé afin de simuler le degré de conversion de la réaction. Les caractéristiques morphologiques des grains de PVC obtenus en microréacteur présentent des particularités intéressantes en termes d’agglomération des particules primaires ou porositéVinyl chloride suspension polymerization is a common reaction in polymer industry allowing to obtain one of the world wide most used plastics, known as PVC (polyvinyl chloride). Its applications involve mostly the construction industry but other domains are also concerned. This polymerization process is highly complex due to the toxic nature of the monomer, the good manage of heat transfer and agitation. The control of these process variables directly impacts the characteristics of the final product. Even though the suspension polymerization of vinyl chloride has been extensively studied in batch reactors, there is a lack of data regarding the kinetics or the physicochemistry of a single monomer droplet during the reactions. The aim of this present work is to propose a microstructured device which enables obtaining monodisperse droplets within 200 µm in diameter, each one being considered as a polymerization reactor. After a good acknowledgement of the vinyl chloride/water system in microchannel the polymerization reaction was qualitatively described by means of droplet/polymer grain visualization. Real-time non-invasive Raman measurement has been performed on stationary vinyl chloride monomer droplets and has provided values of kinetic constants. A theoretical model was proposed, simulating the reaction conversion in good agreement with the experimental values. The morphologic characteristics of the PVC grains obtained in microreactor presented interesting features in terms of primary particle agglomeration or porosity
7
Sham, C. K. "Studies of poly (vinyl chloride)/polyacrylate blends." Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37850.
8
Zaikov, Vadim Guennadievich. "A study of poly(vinyl chloride) microstructure." W&M ScholarWorks, 1997. https://scholarworks.wm.edu/etd/1539623916.
Анотація:
High-field {dollar}\sp{lcub}13{rcub}{dollar}C and {dollar}\sp1{dollar}H NMR spectroscopies were used to investigate some unusual features of the molecular microstructure of poly(vinyl chloride) (PVC).;Several model monochloroalkenes were synthesized in order to determine {dollar}\sp{lcub}13{rcub}{dollar}C shift increments for the replacement of H by Cl at positions that are near an isolated internal double bond. These increments then were used to predict the {dollar}\sp{lcub}13{rcub}{dollar}C shifts of the internal allylic chloride structure in PVC. The predictions were not satisfactory, because, as expected, the increments were not additive.;It was shown that during conventional VC polymerization, the chloroallylic chain end (-CH{dollar}\sb2{dollar}CH=CHCH{dollar}\sb2{dollar}Cl) does not copolymerize with the monomer and is not destroyed by a mechanism involving allylic rearrangement, macroradical addition, and chlorine-atom {dollar}\beta{dollar}-scission to produce a -CHClCH{dollar}\sb2{dollar}CH=CHCH{dollar}\sb2{dollar}CHCl- structure. Nevertheless, that mechanism was found to operate during the preparation of a special type of PVC (made at 0{dollar}\sp\circ{dollar}C with (t-Bu){dollar}\sb2{dollar}Mg initiation) which contained the rearranged chain end, -CH{dollar}\sb2{dollar}-CHClCH=CH{dollar}\sb2,{dollar} at an abnormally high concentration.;During the preparation of PVC under subsaturation VC pressures, small amounts of a 1,3-di(2-chloroethyl) branch structure were found to be formed by a "double backbiting" mechanism involving two intramolecular H abstractions in succession. The presence of this structural defect was established by the 125.77-MHz {dollar}\sp{lcub}13{rcub}{dollar}C NMR spectra of reductively dechlorinated PVC specimens. at 55-80{dollar}\sp\circ{dollar}C, the two backbites leading to the defect differ substantially in relative rate, in that the backbiting:addition rate ratio is larger for the second backbite by a factor of 15-16, irrespective of temperature. No evidence was obtained for the presence of the 2-ethyl-n-hexyl branch structure that would have resulted from double backbiting by an alternative route. These findings were confirmed by spectral comparisons with the {dollar}\sp{lcub}13{rcub}{dollar}C shifts of two separately synthesized models, 9,11-diethylnonadecane and 9-(2-ethyl-n-hexyl)heptadecane.;Polymerizations of VC were performed in the presence of two potential transfer agents, trans-1-chloro-2-hexene and trans-1,5-dichloro-2-pentene. Preliminary examination of the resulting polymers by high-field NMR provided evidence for the destruction of the -CH{dollar}\sb2{dollar}CH=CHCH{dollar}\sb2{dollar}Cl chain end, during polymerization, by a mechanism involving H abstraction to form the -CH{dollar}\sb2{dollar}CH=CHC{dollar}\sp{lcub}\cdot{rcub}{dollar}HCl radical, followed by the addition of that species to VC in order to give the -CH{dollar}\sb2{dollar}CH=CHCHClCH{dollar}\sb2{dollar}- structure.
9
He, Jianzhong. "Complete reductive dechlorination of chloroethenes to ethene and isolation of Dehalococcoides Sp. Strain BAV1." Diss., Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04082004-180217/unrestricted/he%5Fjianzhong%5F200312%5Fphd.pdf.
10
Chuang, Adina Shiang Mattes Timothy E. "Proteomic investigations of vinyl chloride-assimilating bacteria from pure cultures to the environment /." [Iowa City, Iowa] : University of Iowa, 2009. http://ir.uiowa.edu/etd/347.
11
Damron, Fredrick Heath. "Characterization of vinyl chloride degrading bacteria from a serial anaerobic chloroethene bioreactor." Huntington, WV : [Marshall University Libraries], 2006. http://www.marshall.edu/etd/descript.asp?ref=662.
12
Christin, Orane. "Synthèse totale de l’énacyloxine IIa, un antibiotique d’origine naturelle au mécanisme d’action original." Electronic Thesis or Diss., Université Paris Cité, 2023. http://www.theses.fr/2023UNIP5197.
Анотація:
Isolée en 1982 par l'équipe de Watanabe à partir de la souche bactérienne Frateuria sp. W-315, l'énacyloxine IIa est un antibiotique polyénique présentant une forte activité contre les bactéries à Gram positif et à Gram négatif, ainsi qu'une activité plus faible contre les champignons. Ce polycétide se compose d'une chaîne linéaire de 23 carbones portant 6 centres stéréogènes, parmi lesquels un est chloré. Il comprend également un pentaène fragile doté d'un chlorure de vinyle, ainsi qu'un cyclohexane possédant 3 centres stéréogènes. L'énacyloxine IIa est une molécule dont la complexité laisse entrevoir de nombreux défis synthétiques. La rétrosynthèse envisagée repose sur un découpage en trois fragments A, B et C, suivi de leur assemblage à l'aide de réactions d'estérification et d'aldolisation de Mukaiyama. Une première voie de synthèse a été élaborée pour le fragment B C1-C16. Cette dernière implique une réaction clé de chloroallylation d'alcynes en présence de palladium(II), conduisant à la formation sélective du chlorure de vinyle (Z). Elle est suivie d'un couplage croisée allène-alcyne catalysé par un couple Pd(II)/Cu(I), et enfin, d'une étape d'élimination 1,2 visant à achever la formation de la chaîne polyénique. La synthèse du fragment A C1'-C6' repose, quant à elle, sur une réaction de métathèse cyclisante, une réaction de carbonylation catalysée par du Pd(0), et une séquence d'hydrogénation/isomérisation de l'acrylate formé afin de générer le troisième centre stéréogène du fragment. D'autre part, le fragment C C17-C23 est obtenu à l'aide d'une étape clé de chloration en position alpha d'un aldéhyde, catalysée par la L-prolinamide, ce qui engendre sélectivement le centre stéréogène chloré souhaité. Finalement, l'assemblage des fragments B et C a été réalisé avec succès grâce à une réaction d'aldolisation diastéréosélective de Mukaiyama, nous permettant d'accéder à la chaîne fonctionnalisée C1-C23 de l'énacyloxine IIa naturelle. Ce manuscrit présente également les premières tentatives d'assemblage des fragments A et BIsolated in 1982 by Watanabe et al. from soil bacteria Frateuria sp. W-315, enacyloxin IIa is a polyenic antibiotic displaying a strong activity against both Gram-positive and Gram-negative bacteria as well as a slight activity against fungi. This rather complex polyketide consists of a 23 carbons linear chain bearing 6 stereogenic centers, whose one is chlorinated, alongside a conjugated chlorinated penta-ene attached to a cyclohexane with 3 stereogenic centers. The structural complexity of this target induces a high degree of synthetic difficulty involving the synthesis of the fragile polyene unit or the control of the halogenated carbon stereochemistry. Our retrosynthetic plan features the synthesis of fragments A, B and C prior to their assemblage through esterification and aldol reactions. The synthetic strategy developed for fragment C1-C16 relies on a key Pd(II)-catalyzed alkyne chloroallylation, resulting in the selective formation of the (Z)-vinyl chloride, followed by a Pd(II)/Cu(I)-catalyzed alkyne hydrocarbation of allenes and a final 1,2-elimination step to complete the polyenic chain formation. The synthesis of fragment A C1'-C6' relies on a ring closure metathesis, a Pd(0)-catalyzed carbonylation reaction, and a hydrogenation/isomerization one-pot sequence of the acrylate formed to generate the third stereogenic center. On the other hand, fragment C C17-C23 is obtained through a key L-prolinamide-catalyzed '-chlorination of aldehydes, resulting in the stereoselective formation of the desired chlorinated stereogenic center. Finally, the successful assemblage of fragments B and C was achieved through a diastereoselective Mukaiyama aldol reaction, providing access to the C1-C23 skeleton peculiar to the enacyloxin family. This manuscript also presents initial attempts to assemble fragments A and B
13
Zerfa, Mohamed. "Vinyl chloride drop behaviour in suspension polymerisation reactors." Thesis, Loughborough University, 1994. https://dspace.lboro.ac.uk/2134/6737.
Анотація:
The suspension polymerisation of vinyl chloride is the main industrial process used for the production of PVC. One of the key operations in this process is liquid-liquid agitation. The stability of the dispersion formed by such a system depends upon a number of parameters that have to be controlled. The present study clarifies drop behaviour in dispersion of vinyl chloride monomer, using poly(vinyl alcohol) stabilisers, before and during polymerisation. In order to carry out our experiments, a11. capacity pressurised reactor system connected to an external microscopic optical cell was designed along with a reflux system. Parameters affecting the initial VCM dispersion, prior to suspension polymerisation, such as residence time, agitation speed, volume fraction and type and concentration of suspending agent have been studied in some details and a correlation relating the Sauter mean diameter (D32) to the vessel geometry, the volume fraction and the Weber number has been proposed. Studies of drop coalescence using a tracer ( dye ) under different experimental conditions showed that the rate of coalescence between non-polymerising VCM droplets was relatively slow, proportional to the agitator speed and decreased by increasing PVA concentration. The PVA adsorption on VCM droplets during both dispersion and polymerisation was also studied. It was found that during polymerisation the rate of adsorption was relatively high at the early stages. The individual mechanisms of the droplets formation and subsequent droplet agglomeration processes in suspension polymerisation were also investigated. It was found that the method of addition of initiator was very important as it affects the morphology as well as the conversion of the final product. The influence of the condenser operation in the suspension polymerisation of vinyl chloride and its effects on the mechanism of droplet formation were also studied and the fate of monomer droplets returning from the condenser were investigated. The external morphology of the final PVC particles was studied using scanning electron microscopy (SEM) technique.
14
McConnell, D. C. "Plastification of poly(vinyl chloride) by polymer blending." Thesis, Queen's University Belfast, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411152.
15
Lee, David W. "Thermal degradation of polymer blends containing poly(vinyl chloride) /." Online version of thesis, 1987. http://hdl.handle.net/1850/10287.
16
Gu, Zhongchun April. "Assessment of reductive dechlorination of vinyl chloride and characterization of enrichments that grow on vinyl chloride as the sole carbon and energy source /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/10169.
17
Payne, Lynda B. "The Dehydrochlorination Mechanism of the Internal Allylic Chloride Structure in Poly(Vinyl Chloride)." W&M ScholarWorks, 2000. https://scholarworks.wm.edu/etd/1539626253.
18
Wang, Chao. "Oxydation catalytique des composés organiques volatils à l’aide de catalyseurs de type oxyde." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1332.
Анотація:
Dans ce travail de recherche, des oxydes mixtes dopés par des métaux nobles ont été préparés et mis en œuvre dans la réaction d'oxydation catalytique du chlorure de vinyle (VC). Les catalyseurs d'oxyde composite de Co-Ce ont été préparés par des procédés sol-gel et testés pour l'activité d'oxydation du VC. L'analyse XPS a certifié que l'introduction de Ce favorisait la présence d'espèces de Co2 + et de Ce3 +, ce qui modifie l'environnement de coordination du réseau d'oxygène et génère plus de vacations d'oxygène. Les oxydes de cobalt modifiés par Ru ont été préparés et étudiés pour l'oxydation du VC. L'analyse XPS montre que le Ru4 + et le Co2 + modifie la concentration des espèces oxygènes sur la surface. Une proportion relative élevée de Co2+ et de Ru4+ perturbe également les lacunes en oxygène. Cela impacte l'activité catalytique et diminue la quantité de sous-produits chlorés. Des mousses cellulaires mésostructurées de phosphate de cobalt-SiO2 (CoPO-MCFs) ont été synthétisées avec succès par la méthode de croissance in situ. Les analyses XPS confirment une augmentation d'espèces d'oxygène de surface pour ce système catalytique. L'énergie apparente d'activation confirme cette tendance. L'influence de la morphologie des particules de Co3O4, sur l'activité catalytique du méthyl benzène et du chlorure de vinyle a été étudiée. Le Co3O4 cubique a montré une meilleure activité et une meilleure stabilité que celle de Co3O4 sphérique. La structure cubique, avec Co2 + exposée à la surface, est le site actif de l'oxydationIn this research works, composite oxides, noble metal supported oxides and noble supported MCFs were prepared, and their catalytic performances were investigated for the catalytic oxidation of vinyl chloride (VC). The Co-Ce composite oxide catalysts were prepared by citrate sol-gel methods, and tested for the activity of VC oxidation. The catalyst with high performance is the molar ratio of Co/Ce=7:3. The XPS analyse certified that the Ce introduction favored the presence of Co2+ and Ce3+ species, which changed the coordination environment of the oxygen lattice and generated more oxygen vacancies. At last, this catalyst exhibited a good performance and stability during 110 h of time on stream at 300 oC. Ru-modified cobalt oxides were prepared and studied for the VC oxidation. The XPS analyse certified that the Ru4+ will be in synergy with Co2+ concentration and this would also change the chemical coordination of oxygen on the surface. High relative proportion of Co2+ and Ru4+ will also devote to oxygen defects or vacancies. This would increased the catalytic activity and decrease the amount of chlorinated by-products.A novel heterostructured material, cobalt phosphate-SiO2 mesostructured cellular foams (CoPO-MCFs), was successfully synthesized by the in-situ growth method. The XPS confirmed a higher amount of surface oxygen species. The activation energy calculated from Arrhenius plots showed a lower value for VC oxidation. The influence of Co3O4 morphology, including cube and sphere, on catalytic activity of methylbenzene and vinyl chloride was studied. The Co3O4 cube had shown better activity and stability than that of the Co3O4 sphere. The cube structure, with Co2+ exposed on the surface, acted as the active site of the oxidation
19
Kakiuchi, Munetaka. "VISCOELASTIC PROPERTIES OF POLY (VINYL CHLORIDE) GELS AND SOLS." 京都大学 (Kyoto University), 2001. http://hdl.handle.net/2433/150247.
20
Brooks, S. R. "Photochemistry of metal salts in poly(vinyl chloride) film." Thesis, Bucks New University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374818.
21
Hobson, Rachel Jane. "The structure of poly(vinyl chloride) and poly(acrylonitrile)." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307019.
22
Clifton, Andrew. "Sonochemical modification of polyethylene and poly(vinyl chloride) surfaces." Thesis, University of Bath, 1993. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760647.
23
Kurta, Mykola. "Environmental and Energy Saving Technologies of Vinyl Chloride Production." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4352.
Анотація:
Recently, because of the increase of environmental concerns in process design, the need to enhance conversion to product and prevent generation of wasteful byproducts in the reactor network has become urgent. This prevents high cost treatment and separation costs downstream in the process. Therefore, in this thesis I focus on making production of vinyl chloride monomer (VCM) more efficient and on possible ways of industrial organochlorine waste (OCW) recycling. In particular, in the first experiment, we investigate how catalyst and its structure can affect product output.
Infrared spectroscopy and X-ray diffraction analysis were utilized to investigate the structure of the γ-Al2O3 carrier with CuCl2 catalyst on its surface. Structure of the two catalysts, HarshowX1 and MEDC-B, and their effect on the mechanism of ethylene oxidative chlorination reaction into 1,2-dichlorethane were studied. Differential thermal analysis and mass spectroscopy were applied to study the structure and the mechanism differences between the deposited and permeated CuCl2 catalysts.
The second experiment deals with ecological processing and recycling methods of wasteful byproduct that can be called chlororganic wastes. Typical waste products are 1,2-dichloroethane, 1,1,2-trichloroethane, vinylidene, and vinyl chloride monomer. Polymerization and copolymerization of typical waste products with their C5-C9 fraction resulted in non-toxic polymer products that can be used in construction and road-building industries. The possibility of joint chlorine and sulfide-containing chemical wastes recycling into polysulfide oligomeric products is discussed. This comprehensive recycling allows utilizing 80-90% of all wastes generated during synthesis of chlorinated products in the chemical industry.
The results of the studies aim to improve the conversion of ethylene to vinyl chloride and minimize the formation of byproducts.
24
Tse, Albert Sze-Kwong. "Impact modification of poly(vinyl chloride) with chlorinated polyethylene." Case Western Reserve University School of Graduate Studies / OhioLINK, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=case1054834010.
25
Liu, Xikun. "Aerobic vinyl chloride degradation at the microbial community level." Diss., University of Iowa, 2016. https://ir.uiowa.edu/etd/2238.
Анотація:
Vinyl chloride (VC) is a human carcinogen and common groundwater contaminant in the United States. Some of the indigenous bacteria can utilize VC for their growth, which is important for bioremediation. As previous studies have been majorly focused on VC-degrading bacteria in pure cultures, we initiated the study to investigate the microbial community structure and interactions in more complicated systems, such as mixed-pure cultures and groundwater enrichment cultures. Finally, we extended our study into the field by investigating the diversity and abundance of functional genes in VC-assimilating pathways at six contaminated sites.
In our first study, Nocardioides was found to be the most dominant genus in Carver groundwater enrichment cultures via stable-isotope probing and 16S rRNA gene amplicon Illumina sequencing. As cross-feeding was observed, in the second study, mixed-pure culture experiment was conducted to explore the potential effects of VC-assimilating Nocardioides on other bacteria, which showed VC cometabolizer Mycobacterium strain JS622 would take up carbon from VC to sustain their growth when mixed with VC-assimilating Nocardioides sp. strain JS614. The third study was conducted with a different groundwater source from Fairbanks, AK, which again showed Nocardioides is dominant in the microbial community. A novel VC-assimilating Nocardioides sp. bacteria was isolated, named XL1. The putative genome of XL1 extracted from enrichment culture metagenome was 99% to 100% identical to strain JS614, with a plasmid genome bin similar to strain JS614 plasmid pNOCA01, though the morphology of strain XL1 was distinct from strain JS614. About 90% of the plasmid contigs could be mapped onto Nocardioides sp. strain JS614 plasmid with 100% identity, containing known aerobic ethene and VC degradation pathway genes encoding alkene monooxygenase and epoxyalkane: coenzyme M transferase (EaCoMT). Glutathione synthase and glutathione S-transferase genes, possibly involved in epoxide detoxification, were found in Polaromonas, Mesorhizobium and Pseudomonas-affiliated genome bins. The study also showed cultures adapted to VC faster after amended with ethene. The in-situ study (the fourth study) revealed 192 different EaCoMT T-RFs from six chlorinated ethene contamination sites via T-RFLP analysis, implicating higher EaCoMT diversity than previously known. Phylogenetic analysis revealed that a majority of the 139 cloned sequences (78.4%) grouped with EaCoMT genes found in VC- and ethene-assimilating Mycobacterium strains and Nocardioides sp. strain JS614. EaCoMT gene abundance was positively correlated with VC and ethene concentrations at the sites studied.
26
Kelsall, David Gerald. "A mathematical model for the suspension polymerisation of vinyl chloride." Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37740.
27
High, Jessica M. "Microcosm evaluation of vinyl chloride bio-oxidation under anaerobic conditions." Connect to this title online, 2008. http://etd.lib.clemson.edu/documents/1219865442/.
28
King, J. "Correlation of structure and mechanical properties of poly(vinyl chloride)." Thesis, University of Leeds, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355471.
29
Terranova, Steven Alfred. "Cross-Linking Additives as Smoke Suppressants for Poly(Vinyl Chloride)." W&M ScholarWorks, 1993. https://scholarworks.wm.edu/etd/1539625814.
30
Lo, Chung Keung. "Voltammetric and spectroscopic studies of dye-immobilised poly(vinyl chloride) membranes." HKBU Institutional Repository, 2003. http://repository.hkbu.edu.hk/etd_ra/425.
31
Allen, Matthew Robert. "Thermal desorption techniques for the analysis of trace level VOC's in landfill gas." Thesis, Nottingham Trent University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285725.
32
Lobry, Emeline. "Batch to continuous vinyl chloride suspension polymerization process : a feasibility study." Phd thesis, Toulouse, INPT, 2012. http://oatao.univ-toulouse.fr/11498/1/lobry.pdf.
Анотація:
Continuous processes present the benefit to be safer and more cost saving than batch processes. Many researches have been carried out in fine chemistry but few contributions refer to polymerization. We focus on the vinyl chloride suspension polymerization. This process has been extensively studied in batch with lots of improvement regarding the formulation and the technologies. This polymerization process is highly complex due to the toxic nature of the monomer, the good manage of heat transfer and stirring. Moreover the reaction step remains the only batch step of the PVC production. According to the PVC grain formation, the process can be divided into three steps (i) a liquid-liquid dispersion step in which the monomer droplet (30-50 µm) are generated and stabilized, (ii) a controlled agglomeration step of the reacting droplets exhibiting a sticky behaviour, (iii) a reaction step until the conversion rate is around 80-90% and the particles size is stable. In this study, the different technologies suitable for the different steps are pointed out. Based on the state of the art of the grain behaviour depending on the reaction conversion and on the literature concerning polymerization continuous process, static mixers and different co-current pulsed columns are proposed. Three technologies with different model system were chosen to study the liquid-liquid dispersion step. Static mixers allow the control of the droplet size under turbulent flow. In the range of the operating conditions, the dispersed phase concentration does not have a significant effect on the droplet size. The interfacial tension appears to be the most significant physico-chemical parameters. Correlation to predict the mean droplet size is proposed depending on different dimensionless numbers based on the hydrodynamics and on the systems: the Reynolds and Weber numbers. Given the promising results, static mixers are implemented at pilot scale to load the batch prior to polymerization. Their use demonstrates a noticeable reduction of the loading time and a better homogenisation of the different suspending agents and initiator inside the PVC grain. The two co-current pulsed columns design studied are the discs and doughnuts pulsed column and the COBR (continuous oscillatory baffled reactor, Nitech). For the first one, the effect of the packing materials (type and height), of the physico-chemical parameters (dispersed phase concentration, surfactant) and of hydrodynamic parameters (flowrate and oscillation conditions) on the droplet size are investigated where as for the second one the study is limited to the hydrodynamic parameters. A mean droplet size correlation is proposed based on the characteristic dimensionless numbers. The three continuous contactors used for liquid-liquid dispersion are compared in term of energy dissipation rate. The reaction is carried out in a continuous tubular reactor (the pulsed column). The column is suitable to transport solid-liquid suspension. Vinyl acetate suspension polymerization is performed to demonstrate the feasibility and particularly to study the encrusting and fouling problem. The first results are very promising.
33
Kann, Yelena. "Chemiluminescence studies of degradation and stabilization of plasticized poly(vinyl chloride)." Thesis, University of Sussex, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398359.
34
INAGAKI, TAKAO, HIROSHI MANO, AKIRA FUKUMURA, TSUNETO AOI, NOBUO SAKAMOTO, and HISAO HAYASHI. "Invasive Character of Malignant Endothelial Cells in Vinyl-Chloride-Induced Liver Angiosarcoma." Nagoya University School of Medicine, 1990. http://hdl.handle.net/2237/17511.
35
Ramacieri, Patricia. "Microstructure and kinetics of thermal degradation of alkene copolymers of vinyl chloride." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=72819.
36
Fontaine, Adam. "Degradation of poly(ε-caprolactone)-based 'green' plasticizers for poly(vinyl chloride)". Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=117014.
Анотація:
Poly(vinyl chloride) (PVC) requires the addition of large quantities of plasticizers in order to improve the flexibility and processability of the polymer. Since the plasticizer is not bound to the PVC polymer matrix, there is a tendency of the plasticizer to migrate into the surroundings. The most commonly used PVC plasticizer, di-2-ethylhexyl phthalate (DEHP), has become a ubiquitous environmental contaminant. As with other plasticizers, it may either accumulate or lead to the formation of metabolites, which resist further degradation and can themselves be toxic. Accordingly, there is incentive for the development of a 'green' plasticizer as a replacement to DEHP in order to minimize the environmental impact of PVC production and use. In this study, a method was developed to quantify the degradation of plasticizers used in PVC formulation or proposed as alternatives. The method is based on derivatization in order to lower the boiling points of the compounds and allow for analysis by gas chromatography (GC). Using this developed method, the biodegradation of two different families of potential 'green' plasticizers was considered. The biodegradation was assessed using Rhodococcus rhodochrous and evaluated based on the rate and completeness as well as the toxicity and stability of any observed metabolites. It was found that the poly([ε]-caprolactone)-based plasticizers containing octanoate-terminal groups degraded much more rapidly and completely than the benzoate-terminated ones. Furthermore, no metabolites were observed during the degradation of octanoate-terminated plasticizers while the benzoate-terminated plasticizers gave rise to metabolites which contributed substantial toxicity to the culture media. Under ideal conditions, these metabolites were shown to be biodegraded themselves. The methodology and data presented in this thesis can be used as a tool in selecting a 'green' plasticizer based on the degradation criteria, and aid in the selection of alternative plasticizers to DEHP.Le polychlorure de vinyle (PVC) requiert l'ajout important de plastifiant afin d'obtenir un polymère flexible et plus facile à mettre en forme. Comme ces plastifiants ne sont pas chimiquement liés à la matrice, ils ont toutefois tendance à migrer dans le milieu environnant. Le phtalate de diéthylhéxyle (DEHP) est le plastifiant le plus couramment utilisé et est maintenant un contaminant omniprésent. Tout comme d'autres plastifiants, il peut s'accumuler dans l'environnement ou se biodégrader et former des métabolites qui peuvent résister à la biodégradation et être potentiellement toxiques. Cette situation inquiétante a susciter l'intérêt envers le développement de plastifiants verts offrant une alternative au DEHP et permettant de minimiser l'impact environnemental de la production et de l'utilisation du PVC.Dans le cadre de l'étude présentée dans cette thèse, une méthodologie a été développée afin de permettre la quantification et le suivi de la biodégradation de plastifiants utilisé pour le PVC ou proposés comme alternatives. Cette méthode basée sur le dérivatisation permet la diminution du point d'ébullition des composés et l'analyse par chromatographie en phase gazeuse (GC). Cette méthode a été utilisée ici afin d'étudier la biodégradation de deux familles de composés proposés comme plastifiants verts. La biodégradation a été étudiée à l'aide de la bactérie Rhodococcus rhodochrous et évaluée en fonction de la cinétique et l'étendue de la dégradation ainsi que selon la formation de métabolites et la toxicité résiduelle. Les résultats ont démontré que les plastifiants à base de poly([ε]-caprolactone ayant des groupes terminaux octanoïque se biodégradent plus rapidement et que ceux ayant des groupes terminaux benzoïque. De plus, aucun métabolite n'a été détecté lors de la dégradation des plastifiants octanoïque alors que les plastifiants benzoïques ont formés des métabolites et engendré une toxicité résiduelle du milieu de culture. Dans des conditions idéales de biodégradation, les métabolites se sont dégradés. La méthodologie développée et les résultats présentés dans cette thèse seront utiles à la sélection de plastifiants verts offrant une alternative au DEHP.
37
Horrill, M. D. "The effect of suspending agents on the suspension polymerization of vinyl chloride." Thesis, Loughborough University, 1997. https://dspace.lboro.ac.uk/2134/7513.
Анотація:
The suspension polymerisation of vinyl chloride is the main industrial process used for the manufacture of PVC. The aim of this project was to study the suspension polymerisation of vinyl chloride monomer to form PVC. The work concentrated on the effects that the choice of suspension stabilisers (PVA's), pH and other environmental factors had on the properties of both the initial droplet suspension and the polymerising system throughout the course of the reaction. Experiments were carried out using a pressurised 11 stainless steel jacketed reactor connected to an external optical cell. Progress of the polymerisation was monitored optically by taking samples into the cell at regular intervals and examining them with a microscope which had an attached camera. Properties that were studied included the drop size and drop size distribution of the initial droplet suspension, the stabiliser take-up during the reaction and the particle size distribution, porosity and physical appearance of the polymer particles. The work showed that the choice of suspension stabiliser not only effected the drop size and drop size distribution of the initial suspension but also effected the properties and particle size of the final polymer product which was produced. The pH of the system was also discovered to effect both drop stability and the course of the polymerisation. Lowering the pH (
38
Matti, Y. Y. "The thermal degradation of vinyl chloride polymers and its relation to structure." Thesis, Cardiff University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372345.
39
Domike, Kristin Rebecca 1981. "The impact of improved materials in poly(vinyl chloride)-based endotracheal tubes." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28871.
Анотація:
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2004.Includes bibliographical references.
Endotracheal tubes (ETs) are used to aid artificial ventilation in millions of medical patients every year and are known to invoke the proliferative phase in the cell linings. The technical objective of this work was to investigate in vitro the interaction between epithelial cells and current poly(vinyl chloride)-based ET materials, as well as some ET samples embedded with materials intended to improve biocompatibility properties of the tubes. Cells were grown in wells with small samples of ETs and proliferation and migration were observed using phase microscopy. ETs appeared to increase cell growth wherever cells came into contact with the material. The cell morphology altered once in contact with the ET sample. Cell growth on and around the ETs with embedded material appeared to slow, but had significant visible changes in cell morphology. The need for continued research in this area of research and development and future steps are addressed. A proposal for starting a company around a safer material for use in endotracheal tubes was developed and showed significant barriers to entry for a small medical device company with a single product. Subsequently, the most appropriate approach for bringing a new ET to the market would be by way of a licensing with an existing manufacturer.
by Kristin Rebecca Domike.
M.Eng.
40
Soong, Sharon Yu-Wen. "Rate-dependent deformation behavior of poss-filled and plasticized poly(vinyl chloride)." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/38977.
Анотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2007.Includes bibliographical references.
Polymers are known to exhibit strong time-dependent mechanical behavior. In different temperatures or frequency regimes, the rate sensitivities of polymers change as various primary and secondary molecular mobility mechanisms are accessed. The incorporation of nanoparticles can potentially alter the molecular level structure of polymer, offering the opportunity to tailor the rate-dependent mechanical deformation and failure behavior of the polymer. This study focuses on polyhedral oligomeric silsesquioxanes (POSS) enhanced polymeric systems. POSS are hybrid organic-inorganic nano-scale molecules which consist of a silica cage with functional groups attached to the cage comers. Various binary and ternary polymer blends were produced by incorporating methacryl-POSS (C56I88,28Si8) (mPOSS) and dioctyl phthalate (DOP) into poly(vinyl chloride) (PVC) through melt blending. mPOSS was found to be miscible with PVC up to 15 wt% added. Both mPOSS and DOP plasticize PVC and reduce the [alpha]-transition temperature. While mPOSS also reduces the secondary ([beta]) transition temperatures in PVC, DOP was found to restrict the p-relaxation motions.
(cont.) The rate-dependent yield and postyield behavior was characterized in compression testing over a wide range of strain rate (10-4/s to [approx.] 4000/s). Due to the geometric and size distinctions between the two molecules, mPOSS and DOP have different influences on PVC local molecular motions, resulting in dissimilar mechanical behavior. A clear rate-dependent sensitivity transition in yield was observed in the pure PVC and PVC/mPOSS blends in the intermediate strain rate regime, which is attributed to the need for stress-assisted activation of [beta]-motions at high strain rates. A transition in rate sensitivity was also identified in high DOP content compounds; this transition is due to the [alpha]-transition. The potential of using POSS as a plasticizer for PVC was evaluated. Through the use of ternary compositions, the proportion of mPOSS in PVC was increased substantially. The T8 of appropriately formulated ternary PVC/mPOSS/DOP compounds can be reduced to near room temperature, and these materials exhibit desirable ductile behavior. A constitutive model was used to predict the large deformation behavior of the PVC compounds. The two-process model is shown to capture the rate-sensitivity transitions in yield and the large deformation stress-strain behavior at low and high strain rates.
by Sharon Yu-Wen Soong.
Ph.D.
41
Vale, Hugo. "Population Balance Modeling of Emulsion Polymerization Reactors : applications to Vinyl Chloride Polymerization." Lyon 1, 2007. http://www.theses.fr/2007LYO10034.
Анотація:
This thesis is a contribution to the development of population balance models of emulsion polymerization and, more particularly, to the modeling of particle formation and particle size distribution (PSD) in vinyl chloride emulsion polymerization. The rst part of the work is dedicated to the acquisition of experimental data. Ab initio polymerizations were done to obtain reliable data regarding the dependence of the particle number on the concentration of surfactant, as well as to analyze the effect of the initiator concentration, stirring rate, and monomer-to-water ratio upon the particle number and the polymerization kinetics. In addition, seeded polymerizations were carried out at different concentrations of seed latex and emulsifier in order to quantify the influence of these factors on the onset and extent of secondary particle formation. Moreover, the adsorption isotherms of SDS and SDBS on poly (vinyl chloride) latex particles were determined. The second part of the manuscript focuses on the development of the population balance model. A special feature of the model proposed in this work is the computation of the coupled radical number and particle size distributions by the zero-one-two population balance equations. Overall, the examples presented show that the model can capture the tendencies observed in the polymerizations with physically reasonable values of the unknown/ adjustable parameters. With respect to particle formation, it was seen that including the possibility of particle nucleation (homogeneous and micellar) by exited radicals helps to explain the high particle numbers observed and the fact that the initiator concentration has a negligible effect on the particle number. Moreover, it was demonstrated that particle coagulation must be taken into account in order to obtain plausible PSDs and to avoid the use of abnormally low values of the efficiency of radical entry into micelles. In the third and last part, two novel numerical methods for the solution of population balances of interest to emulsion polymerization systems are presented and discussedCette thèse est une contribution au développement de modèles mécanistiques de la polymérisation en émulsion et, plus particulièrement, une contribution à la modélisation de la formation des particules et de leur distribution de taille (DTP) lors de la polymérisation en émulsion du chlorure de vinyle. La première partie de l'étude est consacrée à l'obtention de données expérimentales. Des polymérisations ab initio ont été réalisées afin d'obtenir des données fiables sur l'effet de la concentration de tensioactif, concentration d'initiateur, vitesse d'agitation et rapport monomère/eau sur le nombre de particules formées et sur la cinétique de polymérisation. Des polymérisations ensemencées ont également été réalisées afin de déterminer l'influence de la quantité de semence et de la concentration de tensioactif sur la formation de particules par nucléation secondaire. Enfin, les isothermes d'adsorption du SDS et du SDBS sur des particules de latex de poly (chlorure de vinyle) ont été déterminées. La deuxième partie de l'étude concerne le développement et la validation du modèle de polymérisation. Celui-ci à la particularité d'utiliser les bilans de population propres aux systèmes ‘zéro-un-deux' pour déterminer la distribution jointe du nombre de radicaux et de la taille des particules. Dans l'ensemble, les résultats obtenus montrent que le modèle proposé est capable de décrire les principaux comportements retrouvés lors des polymérisations avec des valeurs physiquement plausibles des paramètres inconnus ou ajustables. Pour ce qui concerne la formation des particules, il s'avère que la prise en compte de la possibilité de nucléation (homogène ou micellaire) par les radicaux désorbés aide à expliquer les valeurs élevées du nombre de particules ainsi que l'effet négligeable de la concentration d'initiateur sur le nombre de particules. En autre, il est démontré que le phénomène d'agrégation des particules doit être pris en considération afin d'obtenir des DTPs cohérentes. Dans la troisième et dernière partie, deux nouvelles méthodes numériques pour la résolution de bilans de population d'intérêt pour la modélisation des systèmes de polymérisation en émulsion sont proposées et analysées
42
Bryant, William Stephen. "Mechanisms of Poly(Vinyl Chloride) Pyrolysis in the Presence of Transition Metals." W&M ScholarWorks, 1995. https://scholarworks.wm.edu/etd/1539626994.
43
Lintner, Carly Faye. "Exploring the diversity of vinyl chloride assimilating bacteria in enriched groundwater cultures." Thesis, University of Iowa, 2014. https://ir.uiowa.edu/etd/4676.
44
Dobson, Meredith Lynn. "Assessment of methanotroph presence and activity in dilute vinyl chloride contaminated groundwater." Thesis, University of Iowa, 2011. https://ir.uiowa.edu/etd/2860.
Анотація:
The extensive use of tetrachloroethene (PCE) and trichloroethene (TCE) as cleaning solvents has resulted in widespread contamination of groundwater systems with vinyl chloride (VC). VC, a known human carcinogen, is primarily formed in groundwater via incomplete anaerobic reductive dechlorination of PCE and TCE. Aerobic, methane-degrading bacteria (methanotrophs), which are capable of VC cometabolism while growing on methane, could be important in natural attenuation of VC plumes that escape anaerobic treatment. Real-time PCR (qPCR) represents an innovative approach for detecting and quantifying the presence and activity of these VC-degrading microbes. Immediate applications of this technique include use in a laboratory setting to help elucidate the potential bacterial-substrate interactions occurring in the subsurface environments at these contaminated sites; interactions that could ultimately affect the role of methanotrophs in VC degradation. This technique could also provide lines of evidence for natural attenuation of VC, thus support existing anaerobic bioremediation technologies that generate VC as a metabolic intermediate.
In this work, we evaluated several PCR primer sets from the literature for use in methanotroph qPCR assays of groundwater samples. PCR primers targeting two functional genes involved in VC cometabolism, pmoA (sub-unit of particulate methane monooxygenase (pMMO)) and mmoX (sub-unit of soluble MMO (sMMO)), as well as 16S rRNA gene primers that targeted Bacteria, and Type I and Type II methanotrophs were tested. These assays were made quantitative by constructing standard curves with DNA from Methylococcus capsulatus (Type I) and Methylocystis sp. strain Rockwell (Type II). Primer sets were evaluated by comparing gene abundance estimated against known amounts of Type I and Type II methanotroph DNA. After primer validation, an effort to substantiate this methanotroph qPCR method was made by attempting to investigate methanotroph populations in groundwater samples from VC-contaminated sites. Some samples studied were also subjected to 16S rRNA gene pyrosequencing, allowing for relative abundance comparisons with qPCR analyses. Following our primer assessment experiments, effective primer sets were used to estimate the presence of methanotrophs at environmental sites in Soldotna, Alaska; Naval Air Station Oceana, Virginia Beach, Virginia; and Carver, Massachusetts. Results showed that methanotrophs were present in nearly all wells sampled from all environmental sites. Estimations of methanotroph relative abundance in environmental samples were determined by comparing the Type I and Type II primer estimates to those of the 16S universal primers. Methanotrophs in these groundwater samples ranged from 0.2% to 6.6% of the total bacterial population. Pyrosequencing analysis of the same samples showed methanotroph relative abundances that ranged from 1.7% to 54%. In groundwater samples where both DNA and RNA was extracted, the quantities of functional gene transcripts per gene copy was compared, revealing that the transcripts/gene ratio for both pmoA and mmoX was less than one, implying relatively low methanotroph activity. Analysis of mmoX environmental sample dissociation curves revealed a double peak, indicating possible non-specific PCR products. Our data suggests that most of the qPCR primer sets used in the environmental samples adequately detect methanotrophs, though the mmoX primers need to be further validated. These primer sets will be useful for supporting VC bioremediation strategies by providing a rapid, convincing, and cost effective alternative the enrichment culture technique currently employed. Comparison of qPCR and pyrosequencing analysis revealed biases in either one, or both techniques. Finally, our preliminary transcripts/gene data suggests that the methanotrophs at the Carver site are not actively expressing pMMO and sMMO genes above basal levels.
45
Zhao, Xiaobin. "Plasticised poly(vinyl chloride) : significance of plasticiser and surface modification for protein adsorption." Thesis, University of Strathclyde, 1999. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21257.
Анотація:
Plasticised poly(vinyl chloride)(PVC-P) remains the most widely used bloodcontacting biomaterial. With respect to the blood compatibility of PVC-P, the plasticiser plays a more important role than the PVC polymer itself, since the blood contacting surface is highly distributed with plasticiser. Therefore, the objective of this project was to study the significance of the plasticiser on protein adsorption onto PVC-P, where the features of plasticiser considered were plasticiser selection (nature of plasticiser), the plasticiser surface level and plasticiser surface distribution. To evaluate this, three types of medical grade PVC-P, plasticised with 2-diethylhexyl phthalate (DEHP), tri-(2-ethylhexyl) trimellitate (TEHTM) and n-butyryl-tri-n-hexyl citrate (BTHC) respectively in sheet form with the same softness, were selected. Protein adsorption was carried out using 1251 radiolabelled human fibrinogen and bovine serum albumin. The in vitro protein Imaterial contact was achieved with a modified 24-well incubation test cell. A reduced plasticiser surface level was obtained with methanol surface treatment. Surface characterisation was carried out using ATRFTIR and UV-spectrophotometer. Results obtained indicate that fibrinogen adsorption on PVC-P strongly correlates with the plasticiser surface level. A reduced plasticiser level can reduce fibrinogen adsorption and increase albumin adsorption. However, excess surface washing might lead to a surface topographical change, initiating an increased fibrinogen adsorption. Protein adsorption is also dependent on the plasticiser nature and plasticiser surface distribution. A high level of plasticiser does not necessarily mean a high reactivity towards fibrinogen adsorption. Based on this study, surface modification of PVC-P was carried out using cyclodextrins (CDs) by blending. The combination of CDs with polyethylene oxide (PEO) or polyethylene (PEO)-poly(propylene oxide) (PPO) triblock copolymer (pluronic surfactant) was also studied. Protein adsorption results indicate that the surface enriched CDs, CDIPEO, CD/Pluronic physical mixture or CD inclusion complex (CIC) can achieve a reduced protein adsorption. Finally, a possible mechanism was hypothesised and a proposal was made for a novel form of surface modification.
46
Varshney, Neil. "Lubrication effects on die plateout in lead stabilised rigid poly(vinyl chloride) extrusion." Thesis, Loughborough University, 2004. https://dspace.lboro.ac.uk/2134/24870.
Анотація:
Plateout is an extrusion defect that has caused formulators and processors major problems throughout the history of poly(vinyl chloride) (PVC) processing. It is an unwanted deposit that forms on the die, calibration and degassing sections of extrusion equipment that can cause unacceptable streaking and scoring on the final product through continued deposition. Extrusion companies must therefore periodically strip their equipment to stop excessive formation, but the downtime associated with this cleaning procedure is obviously costly. The purpose of this thesis is to develop an understanding of the lubrication mechanisms within lead stabilised rigid PVC compounds using polyethylene (PE) wax as a source for external lubrication, in order to make formulation recommendations to minimise plateout. Plateout samples supplied by commercial processors were analysed to identify deposit prone additives. Of the techniques investigated, laser ionisation mass analysis (LIMA), gas chromatography/mass spectrometry and infra-red spectroscopy by the diffuse reflectance infra-red Fourier transform (DRIFT) method identified calcium carbonate, titanium dioxide and dibasic lead phosphite as the bulk of die plateout. Additive interactions were investigated by differential scanning calorimetry (DSC) and hot-stage microscopy. Majority of the additives in a lead stabilised window profile formulation did not interact, but molten calcium stearate and normal lead stearate did not recrystallise when mixed together. To simulate commercial processes, a laboratory-scale twin-screw extruder equipped with a plateout sensitive die was used to analyse window profile formulations containing various homopolymer grades of PE wax and oxidised PE or high-density PE lubricants. Structural properties that influence physical properties such as melting point and viscosity were related to their tendency to plateout. The influence of calcium stearate and normal lead stearate dosage on lubrication and plateout performance was also investigated using experimental design.
47
Molefe, Dan Matlhomola. "Magnesium hydroxide derivatives as stabilisers and flame retardants for plasticised poly (vinyl chloride)." Thesis, University of Pretoria, 2015. http://hdl.handle.net/2263/53529.
Анотація:
The potential of magnesium hydroxide, hydromagnesite and layered double hydroxides (LDHs) as heat stabilisers and flame retardants for plasticised poly (vinylchloride) (PVC) was studied. These inorganic hydrated fillers feature flake-shaped particles with a strong tendency to agglomerate. Filler particles must be homogeneously distributed and individually dispersed in the polymer matrix in order to attain the best performance. For this reason the first step in the investigation was to explore the use of a stearic acid coating in order to improve the dispersability of these fillers in liquids. The platelet morphology-type flame retardants were coated with approximately a monolayer of stearic acid using a solvent technique. Compared to the uncoated powders, the BET surface area was lower, the powder packing density was improved, and the thickening effect on white oil was significantly reduced. The latter two observations were rationalised in terms of a reduction in the attractive interactions between the powder particles.
The viscosity of white oil slurries containing 25 wt.% solids showed shear-thinning non-Newtonian behaviour. The coated powders showed significantly lower viscosities at low shear rates although the difference diminished at high shear rates. The lower viscosities shown by the coated powders indicate that the surface modification facilitated the break-up of agglomerates and aided the dispersion of individual particles in the fluid.
The thermal decomposition of these hydrated fillers is central to their flame retardant action. At elevated temperatures they endothermically release inert gases. The latter dilute the atmosphere surrounding the burning sample while the endothermic decomposition cools the substrate. These two effects are responsible for the flame retardant action of these fillers. The detailed behaviour of the present samples was studied using thermogravimetric analysis and spectroscopic methods. The decomposition mechanisms, proposed in the literature for these flame retardants, were confirmed. This includes the mass loss, enthalpy of decomposition, and the nature of evolved gases for temperatures up to 1 000 °C. The magnesium hydroxide decomposed endothermically at temperatures well above 250 °C releasing only steam. The LDH decomposed between 225 ºC and 450 ºC and the hydromagnesite between about 220 °C and 500 °C. Both initially released water vapour followed by carbon dioxide.
Next the utility of the magnesium hydroxide, hydromagnesite and LDH as combination heat stabilisers and flame retardants for plasticised PVC was studied. Emulsion grade PVC was plasticised with 100 parts per hundred parts of resin (phr) diisononyl phthalate (DINP) and filled with 30 parts per hundred parts of resin (phr) filler additive. Thermomat static heat stabilities were determined at 200 °C by following the time dependence of hydrogen chloride evolution. Fire retardancy was studied using a cone calorimeter at a radiant flux of 35 kW m-2. The layered double hydroxide outperformed the other fillers with regard to improving heat stabilisation and also with respect to most fire retardancy indices.
Since the layered double hydroxide performed best it was decided to see whether slight composition variations could improve performance. Derivatives of the standard LDH compound ([Mg0.667Al0.333(OH)2](CO3)0.167·0.44H2O) were synthesised using a hydrothermal method. Again, emulsion grade PVC was plasticised with 100 phr diisononyl phthalate and stabilised with 30 phr of the LDH filler additive derivatives. The heat stability and fire resistance of these compounds were studied. Heat stabilities were determined at 200 °C. The dynamic heat stability tests were performed on the plastisols using the torque rheometer method. Static heat stability was evaluated on the fused compounds. It was evaluated from discoloration profiles of strips exposed for various lengths of time to high heat in a Metrastat oven. The time dependence of hydrogen chloride evolution was followed with a Metrohm Thermomat instrument. The conventional LDH provided the best dynamic heat stability. However, partial replacement of the magnesium with copper significantly delayed the release of volatile HCl. If instead the replacement was done using zinc, better colour retention was achieved.
The fire performance was determined at a radiant flux of 35 kWm?2 in a cone calorimeter. The conventional magnesium-aluminium LDH lowered the peak heat release rate of the plasticised PVC from 623 ± 8 kW m?2 to 389 ± 9 kW m?2 and reduced the smoke release by 37 %. Partial replacement of the aluminium with iron resulted in a red pigmented additive that was more effective as a flame retardant reducing the peak heat release rate (pHRR) to as little as 253 ± 5 kW m?2. This additive also showed better smoke suppression (reduction of 44 %) but the best smoke suppression was achieved by replacing part of the magnesium with copper reduction by 49 %).Thesis (PhD)--University of Pretoria, 2015.
Chemistry
PhD
Unrestricted
48
LeBlanc, Ronald Paul 1961. "Transformation of methane and vinyl chloride by methanotrophic bacteria in unsaturated soil columns." Thesis, The University of Arizona, 1991. http://hdl.handle.net/10150/278055.
Анотація:
A model for the transformation of methane or vinyl chloride by methanotrophic bacteria in unsaturated sand columns was proposed. The model was based on Michaelis-Menten kinetics. The columns were successful in transforming methane and vinyl chloride at a remarkably high rate. Vinyl chloride was transformed only in the obligate presence of methane, as the two are in competition for the enzyme responsible for transformation. The model was highly sensitive to estimated methanotrophic biomass concentration. Water content was not inhibitory between 0.04 and 0.39 volumetric water content. Interphase mass transport limitation was not apparent at influent methane concentrations >> Km .
49
Tran, Hoang Vi. "The Influence of Microstructure on the Thermal Degradation Behavior of Poly(vinyl Chloride)." W&M ScholarWorks, 1997. https://scholarworks.wm.edu/etd/1539626102.
50
Ge, Xianlong. "Synthetic and mechanistic studies of poly(vinyl chloride) and some other chlorinated polymers." W&M ScholarWorks, 2003. https://scholarworks.wm.edu/etd/1539623417.
Анотація:
Unlike vinyl chloride, 1,2-dichloroethylene (DCE) experienced dimerization under free-radical conditions. Chain transfer to DCE by beta-Cl elimination was shown to be the major reason for its nonpolymerization.;During the chlorination of alkyl chlorides with molecular chlorine, the involvement of a bridged intermediate led to the formation of vicinal chlorides as the major products. The yields of geminal chlorides increased significantly in the presence of solvents that form complexes with chlorine atoms, but such solvents also decreased the reactivity of the chlorination. Thus the chlorination of poly(vinyl chloride) (PVC) in the presence of complexing solvents was not a useful method for the synthesis of poly(1,2-dichloroethylene).;Polyacetylene (PA) was prepared by the methods of both Shirakawa and Luttinger. The PA's were chlorinated with Cl2 to form white polymers that were, however, not chlorinated completely, in that double bonds were invariably left in the polymer backbone. The chlorinated PA's had a much higher glass transition temperature than PVC but were much less thermally stable, apparently owing to the presence of allylic chloride groups.;Ring-opening metathesis polymerization (ROMP) followed by addition chlorination with Cl2 provided an approach to the preparation of a series of new polymers that could be interesting technologically. However, experiments with model compounds showed that the addition chlorination of conjugated double bonds or the double bonds of allylic dichlorides is frequently slow and incomplete. The chlorination of ROMP polymers made from cyclopentadiene, 1,3-cyclooctadiene, and 1,3,5-cyclooctatriene also did not proceed to completion, and the chlorination of the -(CH=CHCHClCHCl)n- polymer made from cis-3,4-dichlorocyclobutene did not occur at all.;Polyene sequences formed during the thermal degradation of PVC were found to interact with HCl in order to form an ion pairs whose thermal excitation produces triplet cation diradicals. These diradicals abstract methylene hydrogen atoms from PVC, and the ensuing beta-Cl scission forms internal allylic chloride structural defects that quickly lose HCl. as a result, the autoacceleration of thermal dehydrochlorination occurs.;A "Plasticizer thiol", 2-ethylhexyl 3-mercaptobenzoate, was confirmed to be an excellent thermal stabilizer for PVC and was suggested by preliminary experiments to function via a mechanism involving both the nucleophilic displacement of labile chloride and addition to double bonds.