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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Self-assembling metal coatings from phosphated and silicone-modified polyurethane dispersions

Mequanint, Kibret 03 1900 (has links)
Dissertation (Ph.D.)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: Self-emulsifiable and self-assembling nano-particle phosphated and siloxane-modified polyurethane dispersions, for use in metal coatings, were synthesised from a new phosphate monomer, a carboxylate monomer, a polysiloxane macroglycol and a . cycloaliphatic diisocyanate, and characterised. Crosslinked nano-particles of acrylic-modified, self-assembling, phosphated polyurethane dispersions with better water swell resistance were obtained using the phosphated nanoparticles as the 'seed' to polymerise monofunctional and multifunctional acrylic monomers in the dispersed phase. This was done by reacting 2-hydroxyethyl methacrylate end-capped polyurethane with monofunctional and multifunctional acrylate monomers in the dispersed phase. Phase inversion of the polyurethane resin from an organic solvent into dispersion was accompanied by three stages, as studied by viscosity and conductivity measurements. In an attempt to modify existing synthesis procedures of the traditional polyurethane acrylic dispersions for which organic solvents are used, polymerisable acrylic monomers were used as diluents during the urethane-forming reaction. This resulted in overcoming the limitations of the existing process. Particle-size analysis indicated that the above dispersions had smaller particle sizes, narrower distributions and better hydrophobicity than any reported to date. Aqueous vinylterminated phosphated polyurethane dispersions were studied for their viscosity behaviour under shear and showed Newtonian behaviour. The polyurethane dispersions were evaluated for their hydrolytic stability with respect to the location of the ionic groups on the segments. Greater hydrolytic stability was obtained when the ionic groups were on the urethane hard segment. The polyurethane dispersionsresponded well to UV curing, a curing technique that has not received much attention to date. The surface and interface analyses of the self-assembling coatings obtained from the phosphated and siloxane-modified polyurethane dispersions showed increased silicon enrichment at the coating/air interface and phosphorus enrichment at the metal/coating interface. Results of dynamic contact angle studies proved the poor wettability of the coatings, as shown by the increase in contact angle by probe liquids. Dynamic thermogravimetry studies of the phosphate-containing polyurethanes showed a decrease in activation energy with increasing phosphate content. This is a good indication that phosphate-containing polyurethanes could be used as fire retarding coatings that comply with fire limit regulations. / AFRIKAANSE OPSOMMING: Self-emulgeerbare en selfsamestellende, nanopartikel, fosfaat- en siloksaanbevattende poliuretaandispersies, vir gebruik as deklae vir metale, is gesintetiseer en gekarakteriseer. Die uitgangstowwe vir die ~ bereiding was 'n splinternuwe fosfaatmonomeer, 'n karboksilaatmonomeer, 'n polisiloksaanglikol en 'n siklo-alifatiese diisosianaat. Deur die polimerisasie van die monofunksionele en multifunksionele akriel-monomere in die dispergeerde fase in te ent met die fosfaat-bevattende nanopartikels, is kruisgebinde nanopartikels van akrielgemodifiseerde, selfsamestellende, fosfaatbevattende poliuretaandispersies met goeie waterswelweerstand berei. Dit is bewerkstellig deur poliuretaan, met reaktiewe hidroksietiel-endgroepe, te reageer met monofunksionele akrilaatmonomere in die gedispergeerde fase. Fase-omkering van die poli-uretaanhars uit die organiese oplosmiddel, tot in dispersie, het in drie stappe plaasgevind. Dit is bepaal deur viskositeit en konduktiwiteit. Bestaande metodes van sintese Vir tradisionele poli-uretaanakrieldispersies, waarvoor organiese oplosmiddels gebruik is, is gewysig om die beperkinge van die bestaande metodes te oorkom. Suskes is behaal met die gebruik van polimeriseerbare akrielmonomere as verdunningsmiddels in die uretaanvormingsreaksie. Partikelgrootte-analises het getoon dat die verkreë dispersies kleiner partikelgroottes, nouer verspreidings en beter hidrofobisiteit gehad het as enige wat tot dusver beskryf is. Die viskositeit van die wateroplosbare, vinielgetermineerde, fosfaatbevattende poliuretanandispersies is onder afskuiwing bepaal en het Newtoniese gedrag getoon. Die hidrolitiese stabiliteit van die poli-uretane, met betrekking tot die posisie van die ioniese groepe in die segmente, is bepaaL ..Die polimere met die ioniese groepe in die harde segment van die poli-uretaan het hoër hidrolitiese stabiliteit vertoon. Kruisbinding (verharding) deur middel van UV, wat tot dusver min aandag geniet het, was baie suksesvol. Analises van die oppervlakte en die tussenvlak van die selfsamestellende deklaag, wat van die fosfaat- en siloksaanbevattende dispersies berei is, het verhoogde siloksaanverryking by die deklaag/lug tussenvlak en verhoogde fosfaatverryking by die metaal/deklaag tussenvlak getoon. Resultate van dinamiese kontakhoekstudies het bewys dat die deklae swak benat is, dws daar was 'n toename in die kontakhoek deur peilvloeistowwe. Termogravimetriese studies het getoon dat daar 'n afname was in die aktiveringsenergie van die fosfaatbevattende poli-uretane met 'n toenemende fosfaatinhoud. Hierdie feit dui daarop dat hierdie poli-uretane moontlik as brandvertragende deklae gebruik kan word.
2

Film formation and thermal transitions of polymers studied by atomic force microscopy

Meincken, Martina 03 1900 (has links)
Dissertation (PhD)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: The kinetics of drying and film formation of different polymeric latices were studied. Various theoretical models predict a strong dependency of the film formation characteristics on the particle size and morphology. This could be confirmed by experimental studies. The influence of particle size and morphology of differently structured latices on the film formation process was investigated by Atomic Force Microscopy (AFM) and Ultrasonic shear wave reflection. These two methods allow a comprehensive characterization of the drying and film formation process of emulsions. The studies confirmed the theoretical model, that the film formation behavior is influenced by the particle size and particle morphology. Furthermore the influence of different additives, such as coalescent solvents and rheology modifiers on the film formation behavior was investigated. As a second part of the studies, a novel technique was developed to measure thermal transitions of polymers with the AFM in the non-contact mode, using it as a Dynamic Mechanical Analyzer (DMA) on a local scale. The resonance frequency of the AFM cantilever was measured as a function of the temperature and thermal transitions of a polymer were clearly visible as changes in the resonance frequency / temperature response curve. Using the AFM in this mode allows the determination of the thermal properties of a material at a specific position on a sample, thereof on a macromolecular scale. A simple model was developed to explain the response of the cantilever caused by the transitions in the polymer and the related form of the frequency/temperature curves. This new technique adds a new dimension to standard thermal analysis techniques. It is now possible to resolve the individual thermal transitions of different polymer phases, for example in structured multiphase polymers. / AFRIKAANSE OPSOMMING: Die kinetika van droging en filmvorming van verskeie polimeriese lateksverbindingse is ondersoek. Verskeie teoretiese modelle voorspel 'n sterk afhanklikheid tussen die filmvormingseienskappe, partikelgrootte en morfologie. Hierdie afhanklikhede is eksperimenteel bevestig. Die invloed van partikelgrootte en morfologie van verskillende lateksstrukture op die filmvormingsproses is deur atoominteraksiemikroskopie (Eng: Atomic Force Microscopy, AFM) sowel as ultrasoniese skuifweerstandgolfrefleksie ondersoek. Hierdie twee metodes bied 'n deurslaggewende karakterisering van die droging en filmvormingsproses van emulsies. Resultate bevestig die teoretiese model, nl. dat filmvorming deur partikelgrootte en morfologie beïnvloed word. Die invloed van verskillende bymiddels, insluitend reologie-modifiseerders op filmvorming, is ook ondersoek. Vervolgens is 'n nuwe tegniek ondersoek om die termiese oorgange van polimere met behulp van die AFM in nie-kontak modus (deur dit as 'n dinamiese meganiese analiseerder (DMA) te gebruik) te bestudeer. Die resonansie-frekwensie van die AFM-hefboom is bepaal as 'n funksie van temperatuur. Termiese oorgange van 'npolimeer is duidelik waarneembaar as veranderinge in die resonansfrekwensie/ temperatuur responskurwe. Deur gebruik te maak van die AFM in hierdie modus kan die termiese eienskappe van 'n materiaal by 'n spesifieke posisie op die monster op molekulêre skaal bepaal word. 'n Eenvoudige model is ontwikkel om die oorgange in die polimeer, en gevolglik die vorm van die frekwensie/temperatuur kurwes, dmv. die respons van die hefboom, te verduidelik Hierdie nuwe tegniek gee 'n nuwe dimensie tot die standaard tegnieke van termiese analise tegnieke. Dit is nou moontlik om individuele termiese oorgange van verskeie polimeerfases, byvoorbeeld in gestruktureerde multifase polimere, te ondersoek en op te los
3

Reversible addition-fragmentation transfer polymerization in heterogeneous aqueous media

McLeary, James Breton 04 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: The study presented in this dissertation had as primary aim to develop pathways to heterogeneous aqueous polymerizations that had living characteristics. To this end, the reversible addition fragmentation chain transfer (RAFT) process was investigated in predispersed and ab initio emulsions as well as homogeneous media. The synthesis of RAFT agents was carried out. The compounds prepared provided varied behaviour in reaction. In situ IH nuclear magnetic resonance (NMR) increased understanding of homogeneous RAFT mediated polymerizations. The early behaviour of RAFT mediated polymerizations led to the definition of initialization; a period before pre-equilibrium in a polymerization where degenerate behaviour occurs. Stable miniemulsion preparation methods were developed that provided living polymer latexes using high surfactant concentrations. The effect of surfactant concentration on particle size and latex stability was investigated. Living polymer characteristics were shown by the use of size exclusion chromatography, and 2- dimensional chromatography conclusively showed block polymer formation. In situ NMR spectroscopy of emulsions in deuterated water was used to provide evidence on the role of initiator solubility in polymerization. Secondary nucleation in high surfactant concentration miniemulsions systems was investigated using both particle size and molar mass analysis techniques and a means of eliminating secondary particle nulceation was shown through the use of aqueous phase radical traps. The role of the RAFT agent used in the polymerization was shown to be significant in determining the extent to which multiple polymer distributions formed in the polymerization in that radical exit from particles was affected. Finally, a new form of emulsion polymerization, which has been termed proto-seeded emulsion, has been developed. The proto-seed latex is formed by using a monomer whose polymer has chain length dependent water solubility. This process allows ab initio RAFT mediated emulsion polymerization to be conducted successfully without transport of RAFT agents in heterogeneous media. / AFRIKAANSE OPSOMMING: Die primerê doel in hierdie dissertasie is die ontwikkeling van roetes na heterogene water-gebaseerde polimerisasies met lewende eienskappe. Om hierdie doel te bereik is die omkeerbare addisie fragmentasie ketting oordrag proses (eng reversible addition fragmentation chain transfer (RAFT)) ondersoek in vooraf verspreide en direkte emulsies sowel as homogene media. Die sintese van RAFT agente is uitgevoer. Die verbindings wat voorberei is het verskillende einskappe in reaksies getoon. In situ IH kern magnetiese resonansie (KMR) het die kennis en begrip van homogene RAFT polimerisasies uitgebrei. Die vroeë gedrag van RAFT polimerisasies het tot die definisie van inisialisasie gelei; 'n periode voor die pre-ekwilibrium in 'n polimerisasie waartydens "degenerate" gedrag plaasvind. Stabiele miniemulsie voorbereidings metodes is ontwikkel wat lewende polimeer latekse verskaf het met gebruik van hoë seep konsentrasies. Die effek van seep konsentrasie op partikel grootte en lateks stabilitiet is ondersoek. Lewende polimeer eienskappe is bewys deur gebruik te maak van grootte-uitsluiting vloeistof chromatografie, en 2-dimensionele chromatografie het duidelik blok-polimeer vorming gewys. In situ KMR spektroskopie van emulsies in gedeutereerde water is gebruik om bewys te lewer van die rol van initieerder-oplosbaarheid in polimerisasie. Sekondêre nukleasie in hoë seep konsentrasie miniemuisie sisteme is ondersoek met die gebruik van beide partikel grootte sowel as molêre massa analise tegnieke. 'n Metode om sekondêre partikels te verhoed is verskaf deur gebruik te maak van waterfase radikaal lokvalle. Die rol van die RAFT agent in die polimeerisasie is beduidend in die graad van vorming van meer as een polimeer distribusie in die sin dat radikal uitgang van partikels beinvloed was. Ten slotte is 'n nuwe vorm van emulsie polimeerisasie ontwikkel wat proto-gesaaide emulsie genoem is. Die proto-gesaaide lateks is gevorm deur gebruik te maak van 'n monomeer waarvan die polimeer water-oplosbaarheid afhanklik is van die kettinglengte. Die proses laat ab initio RAFT emulsie polimerisasie toe om suksesvol uitgevoer te word sonder die vervoer van RAFT agente in heterogene media.
4

An investigation into the nano-structure self assemblies of amphiphiles and their fixation by polymerization

McLeary, James Breton 04 1900 (has links)
Thesis (M.Sc.)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: This thesis is a written record of an investigation into the self-assembly of organic monomers in amphiphilic solutions. The polymerizable surfactant sodium 10-undecenoate was used alone and with different concentrations of styrene and methyl methacrylate monomers and phenyl acetophenone initiator to investigate single particle formation from a simple amphiphilic self-assembly. Reactions were carried out under either ultra-violet light or gamma irradiation. It was shown that copolymerization between the surfactant and the monomers did not occur to any significant extent. This meant that inclusion of easily modifiable carboxyl functionalities in the polymer by incorporation of the carboxylate surfactant could not be quantified. Star-like particles were found. The shape of the particles formed, was the result of surfactant self-assembly to create self-assembled particles rather than templating of polymeric material. Polymerization of the unsaturated surfactant particles occurred to low conversions only. Analyses of formed particles were carried out using scanning electron microscopy, transmission electron microscopy, atomic force microscopy, field emission scanning electron microscopy and light microscopy for structure observation. The techniques of energy dispersive analysis by x-rays, particle SIze analysis, differential scanning calorimetry, thermogravimetric analysis, Fourier transform infrared analysis, nuclear magnetic resonance, small angle x-ray scattering and inductively coupled plasma (for counter-ion analysis) were used for the gathering of physical data. / AFRIKAANSE OPSOMMING: Hierdie studie is 'n geskrewe rekord van 'n ondersoek van die self-aneensetting van organiese monomere in amfifiliese oplossings. In die ondersoek is die polimeeriseerbare seep natrium 10-undekenoaat alleen en saam met verskillende konsentrasies van monomere en feniel asetofenoon gebruik om enkelpartikel formasie vanaf 'n eenvoudige amfifiliese templaat te ondersoek. Reaksies is uitgevoer onder of ultra-violet lig, of gamma bestraling. Dit is bewys dat kopolimerisasie tussen die seep en die monomere me III emge merkwaardige hoeveelhede plaasgevind het nie. Dit beteken dat insluiting van maklik veranderbare karboksiel funksionele groepe in die polimeer deur middel van insluiting van die karboksilaat seep nie meetbaar was nie. Ster-vormige partikels is gevind. Dit is getoon dat die vorm van die partikels wat in die vroeëre werk verkry is, die resultaat van seep self-aaneensetting, eerder as templatering van polimeriese materiaal is. Polimerisasie van die seep partikels het net tot lae vlak van omskakeling plaasgevind. Analise van die gevormde partikels is uitgevoer deur middel van skandeer elektron mikroskopie; transmissie elektronmikroskopie; atomiese kragmikroskopie; veldemissie skandeer elektron mieroskopie en ligmikroskopie vir struktuur bepalings. Die tegnieke van energie dispersie analiese deur middel van x-strale; deeltjie grootte analise; differensiaal skandeer kalorimetrie; termogravimetriese analise; Fourier transformasie infra rooi analiese; kern magnetiese resonansie; klein hoek x-straal diffraksie en induktief-gekoppelde plasma (vir teenioon analise) is gebruik om fisiese data te versamel.
5

Synthesis, characterization and evaluation of macromonomers used to prepare rheology modifiers for possible improvement of the pigmentation of decorative coatings

Sprong, Ewan 03 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: There is a decrease in viscosity when universal colorants are added to the latex coating system. Two different routes were taken to investigate this problem. The first was to investigate the thickening mechanism of the coating system. For this purpose six different hydrophobically modified alkali-soluble (HASE) thickeners were synthesized. The second was to compile new color concentrate formulations. The HASE thickeners consist of acrylic acid and a second associative monomer. The associative monomer (macromonomer) contained a long chain hydrophilic segment, terminated with a hydrophobic group. The hydrophilic segment consists of polyethoxylation, situated between the ethylenic unsaturation at one end of the molecule and the terminal hydrophobe at the other end. Three different macromonomers were prepared by coupling the hydroxyl end groups of three commercially available nonionic surfactants with either acrylic acid or acryloyl chloride. A much higher yield of macromonomer was obtained when the nonionic surfactants were reacted with the acryloyl chloride. Six HASE thickeners were synthesized by means of free radical addition polymerization. The first three HASE thickeners had the same backbone length and each thickener containing one type of hydrophobic macromonmer. The hydrophobic macromonomers differed in the length of their repeating oxyethylene units. They contained either 20, 50 or 100 oxyethylene units. The next three HASE thickeners were very similar to the first three except that 5% of the acrylic acid in the backbone was substituted with a second, phosphated, macromonomer, meaning that these thickeners each contained two types of macromonomers. These thickeners were then introduced into a standard latex coating formulation. By comparing the rheology profiles of the different coatings it was possible to determine the thickening efficiencies of the different thickeners. These coatings were also evaluated for their viscosity stability when tinted with a universal colorant. The HASE thickeners containing the second phosphated macromonomer showed superior thickening efficiency. All six coatings showed excellent stability on tinting with a universal colorant. Following the second route of investigation, eight universal colorant formulations consisting of only one polymeric dispersant in each of the formulations as sole wetting and dispersing additive were made up. A commercially available universal colorant was used as standard against which the new formulations were tested. The colorants were tested for color strength, their compatibility with the different coating groups, and the rheology profiles of the tinted vs. untinted coating systems. The two colorant formulations that contained EFKA 4550 as the polymeric dispersant performed very well in all the coating groups. / AFRIKAANSE OPSOMMING: Daar is 'n afname in viskositeit wanneer universele kleurstowwe by die lateks-bedekkingsisteem gevoeg word. Twee verskillende roetes is gevolg om die probleem te ondersoek. Die eerste was om die verdikkingsmeganisme van die bedekkingsisteem te ondersoek. Vir die doel is ses verskillende hidrofobies gemodifiseerde alkali-oplosbare (HASE)-verdikkers gesintetiseer. Die tweede was om nuwe kleurkonsentraatformulerings saam te stel. Die HASE-verdikkers bestaan uit akrielsuur en 'n tweede assosiatiewe monomeer. Die assosiatiewe monomeer (makromonomeer) bevat 'n langketting-hidrofiliese segment, met 'n hidrofobiese endgroep. Die hidrofiliese segment bestaan uit herhalende oksi-etileen eenhede, tussen die etileniese onversadigdheid aan die een punt van die molekuul en die hidrofobiese endgroep aan die ander punt. Drie verskillende makromonomere is voorberei deur die koppeling van die hidroksiel-endgroepe van drie kommersieel beskikbare anioniese sepe met akrielsuur of akriloielchloried. 'n Baie hoër opbrengs van makromonomere is verkry toe die anioniese sepe met die akriloielchloried gereageer is. Ses HASE-verdikkers is gesintetiseer deur middel van vrye radikaal addisie polimerisasie. Die eerste drie HASE-verdikkers het dieselfde ruggraatlengte en elke verdikker bevat een tipe hidrofobiese makromonomeer. Die hidrofobiese makromonomere verskil in die lengte van hul herhalende oksi-etileen eenhede. Die hidrofobiese makromonomere bevat of 20, 50 of 100 oksietileen eenhede. Die volgende drie HASE-verdikkers stem baie ooreen met die eerste drie behalwe dat 5% van die akrielsuur in die ruggraat vervang is deur 'n tweede, fosfaatbevattende makromonomeer, wat beteken dat hierdie verdikkers elk twee tipes makromonomere bevat. Hierdie verdikkers is in 'n standaard lateks bedekking formulering gevoeg. Deur die vergelyking van die reologie profiele van die verskillende bedekkings was dit moontlik om die verdikkings effektiwitiet van die verskillende verdikkers te bepaal. Hierdie bedekkings is ook geevalueer vir hulle viskositeits stabiliteit as dit met 'n universele kleurstof gekleur word. Die HASE-verdikkers wat die tweede fosfaatbevattende makromonomeer bevat, het uitstekende verdikkings effektiwiteit getoon. Al ses bedekkings het uitstekende stabiliteit getoon tydens kleuring met 'n universele kleurstof. Deur die tweede roete van ondersoek te volg, is agt universele kleurstof formulerings wat bestaan uit slegs een polimeriese dispergeermiddel opgemaak. 'n Kommersieel beskikbare universele kleurstof is gebruik as standaard waarteenoor die nuwe formulerings getoets is. Die kleurstowwe is getoets vir kleursterkte, hul verenigbaarheid met die verskillende bedekkingsgroepe, en die reologie profiele van die gekleurde teenoor die ongekleurde bedekkingsisteme. Die twee kleurstof formulerings wat EFKA 4550 as die polimeriese dispergeer middel bevat, het baie goed gevaar in al die bedekkingsgroepe.
6

Wax characterisation by instrumental analysis

Webber, Glenda Vanessa 12 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: Various companies produce waxes, which are used extensively in various applications, either as produced or as chemically or physically modified value-added products. They are used in the traditional candle industry and applications including hot melt adhesives, inks, plastics, polishes and emulsions for rust prevention or fruit coating. Insight into the properties of these waxes is required to assist the applications chemist in understanding the role of the wax component in a specific formulation. Analytical techniques such as differential scanning calorimetry (DSC), thermogravimetry (TG), rheometry, gel permeation chromatography (GPC), high temperature gas chromatography (HTGC) and infra-red spectroscopy (IR) were used to characterise Fischer Tropsch, polyethylene, natural and petroleum waxes. Property profiles were formulated by integrating the results from the various techniques. The results of traditional wax analyses (e.g. congealing point, melting point, penetration, density and viscosity) were also correlated to relevant analytical results obtained from the instrumental techniques. Structure-property relationships have been proposed. / AFRIKAANSE OPSOMMING: Verskeie maatskappye vervaardig wasse, wat in menige toepassings gebruik word - of direk, of as chemies- of fisies- veranderde produkte van hoër waarde. Benewens die tradisionele kersbedryf, word die wasse in toepassings soos warmsmeltkleefmiddels, ink, plastiek, roeswerende- en vrugtebedekkings- emulsies en politoere gebruik. Wetenskaplikes betrokke by die formuleering van wasse vir verskillende toepassings sal baat vind by beter inligting van waseienskappe en die rol van waskomponente in formulasies. Tegnieke, bv. differensialeskandeerkalorimetrie (DSC), termogravimetrie (TG), reologie, gelpermeasiechromotografie (GPC), hoëtemperatuurgaschromatografie (HTGC) en infrarooispektroskopie (IR), is gebruik om Fischer Tropsch-, polietileen-, petroleum- en natuurlike wasse te karakteriseer. Profiele van waseienskappe is geformuleer deur die integrasie van die data verkry van die verskillende analitiese tegnieke. Die resultate van tradisionële wasanalises (bv. stolpunt, smeltpunt, penetrasie, digtheid, viskositieit en olie-inhoud) word ook in verband gebring met die resultate van die instrumentele analises. Verbande tussen struktuur en waseienskappe word ook voorgestel.
7

Metallocene and Ziegler-Natta catalyzed polypropylene utilizing 1-heptene

Lutz, Marietjie 12 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: This study concerns the copolymerization of propylene with l-heptene. The percentage of l-heptene used as co-monomer in the polymerization reactions was varied from 5% to 20% in order to compare a variety of polymers with different percentages of comonomer incorporated. A variety of different catalysts were used for these polymerizations. Two metallocene catalysts were used: (A) the isospecific catalyst, rae- [ethylene bis(l-indenyl)]zirconium dichloride (rac-Et(Ind)2ZrCh2) and (B) the silylene-bridged catalyst, rac-Me2Si(2-MeBenz[ e]Ind)zZrCh2. Methylaluminoxane (MAO) was used as cocatalyst for these two metallocene catalysts. Another series of polymerization reactions was done using a Ziegler-Natta catalyst, namely TiCb/AlEt3/Si02. Characterization of the copolymers included usmg high temperature gel permeation chromatography (HTGPC) for molecular mass and molecular mass distributions, differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) to investigate the thermal and mechanical properties of the copolymers, nuclear magnetic resonance spectroscopy (NMR) for information concerning the microstructures of the copolymers and crystallization analysis fractionation (CRYSTAF) to investigate the short chain branching of the copolymers. Comparative studies were done on the different catalysts and the polymer properties. The synthesized polymers were also compared with copolymers of propylene with l-hexene and l-octene. / AFRIKAANSE OPSOMMING: Hierdie studie behels die kopolimerisasie van propileen met I-hepteen. Die persentasie van I-hepteen wat as komonomeer in die polimerisasie-reaksies gebruik is, is van 5% tot 20% gevarieer. 'n Verskeidenheid van verskillende kataliste is gebruik vir hierdie polimerisasies. Twee metalloseenkataliste is gebruik: (A) die isospesifieke katalis, rae- [etileen bis(l-indeniel)]zirconium dichloried (rac-Et(lnd)2ZrCh2) en (B) die silileengebrugde katalis, rac-Me2Si(2-MeBenz[e]Ind)2ZrCh2. Metielaluminoksaan (MAO) is as ko-katalis gebruik saam met bogenoemde twee metalloseenkataliste. 'n Ander reeks polimerisasie reaksies is gedoen waarin 'n Ziegler-Natta katalis gebruik is as aktiverende katalis, naamlik TiCi)/ AlEt3/Si02. Die karakterisering van die kopolimere sluit in: hoë temperatuur gel deurlatings chromatrografie (HTGPC) vir molekulêre massa en molekulêre massa verspreidings, differensiële skandering kalorimetrie (DSC) en dinamiese meganiese analisering (DMA) om sodoende die termiese en meganiese eienskappe van die polimere te ondersoek, kern magnetiese resonans spektroskopie (KMR) vir inligting in verband met die mikrostrukture van die kopolimere en kristallisasie analise fraksioneringstegniek (CRYSTAF) om die kort-kettingvertakkings van die kopolimere te ondersoek. Vergelykende studies IS op die verskillende katalisatore en die polimeereienskappe gedoen. Die gesintetiseerde polimere is ook met kopolimere van propileen met I-hekseen en l-okteen vergelyk.
8

Polymerisation of 1,5-hexadienes

Smit, Madri 12 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: In this study, the feasibility of the non-conjugated 1,5-hexadiene as monomer in metallocene catalised cyclopolymerizations was considered. Homopolymers and copolymers with ethylene, propylene, 1-pentene, 1-hexene and 2-methyl-1,5- hexadiene as comonomers were synthesised in the presence of Cp2ZrCh and rac-Et(lnd)2Zrh. The microstructure (stereoregularity and cyclisation) and number-average molecular weight were determined from NMR analysis. Crystalline oligomers with functional (eg -OH) and vinylidene end groups were obtained. / AFRIKAANSE OPSOMMING: Die studie behels die ondersoek rakende die gebruik van ongekonjugeerde 1,5- heksadieen as monomeer in metalloseengekataliseerde polimerisasies. Homopolimere, sowel as kopolimere van etlieen, propileen, 1-penteen, 1- hekseen en 2-metiel-1,5-heksadieen, is in die teenwoordigheid van Cp2ZrChen rac-Et(lnd)2ZrCI2 gepolimeriseer. Die mikrostruktuur (stereochemie en siklisering) en die getal-gemiddelde molekulêre gewig van die gesintetiseerde polimere is met behulp van KMR spektroskopie ondersoek. Die studie het getoon dat kristallyne oligomere met funksionele (bv -OH) en vinilideen endgroepe gesintetiseer is.
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New monomer for hydrophobic acrylic copolymers and their novel properties

De Vries, Andrew Robert 12 1900 (has links)
Thesis (DSc (Chemistry and Polymer Science))--University of Stellenbsoch, 2006. / The synthesis and characterization of a new tertiary alcohol (2-octyl-2-dodecanol) and “bushy-tailed”, hydrophobic acrylic monomer (2-octyl-dodecyl acrylate) from a 1-decene dimer (2-octyl-1-dodecene) precursor that was synthesized with metallocene technology is reported. Some preliminary applications of the newly synthesized 2-octyl-dodecyl acrylate were investigated. These applications included the use of 2-octyl-dodecyl acrylate as a reactive hydrophobe in mini-emulsion polymerizations, and as a reactive (internal) plasticizer. In an attempt to selectively dimerize 1-decene, the effect of various factors on the oligomerization of 1-decene was investigated. These factors include the following: i. Different temperatures: 5, 35, 70 and 90°C ii. Different co-catalyst [methylaluminoxane (MAO)] concentrations iii. Different catalysts: bis(cyclopentadienyl)zirconium dichloride (Cp2ZrCl2) and bis(cyclopentadienyl)hafnium dichloride (Cp2HfCl2) iv. Different reaction times. In all instances the final product obtained, under the abovementioned conditions, was a mixture of residual monomer, the dimer and trimer of 1-decene. These findings were corroborated with GC-MS and 1H-NMR spectroscopy. The isolation and further processing of the dimer of 1-decene (2-octyl-1-dodecene) was investigated. The efficiency, in terms of the final product-composition for the amount of catalyst used and reaction time, of Cp2ZrCl2 compared to bis(cyclopentadienyl)hafnium dichloride (Cp2HfCl2; hafnocene) as catalyst for the oligomerization of 1-decene is also reported on. The results obtained indicated that Cp2ZrCl2 is the more efficient catalyst for the oligomerization of 1-decene. The effect of different reaction times (1, 3, 6, 24 hours) on the final product-composition for the oligomerization of 1-decene was also investigated. Longer reaction times (24 hours) seemed to be excessive. A reaction time of 6 hours was optimal. The purified 1-decene dimer (2-octyl-1-dodecene) was converted to the new tertiary alcohol (2-octyl-2-dodecanol) using the oxymercuration-demercuration procedure. The 2-octyl-dodecyl acrylate was synthesized by the esterification of the tertiary alcohol with acryloyl chloride in the presence of triethylamine. The new tertiary alcohol and acrylate were characterized by FT-IR and 1H-NMR spectroscopy. Stable polymer latex particles were successfully synthesized with the novel reactive hydrophobe 2-octyl-dodecyl acrylate in the mini-emulsion polymerization of butyl acrylate, methyl methacrylate and styrene. Phase-separation experiments showed that the presence of 2-octyl-dodecyl acrylate in the dispersed phase retards Ostwald ripening. The novel acrylic monomer, 2-octyl-dodecyl acrylate, was copolymerized with styrene via conventional free radical polymerization. Both low and high molecular weight copolymers were prepared. Thermal analysis of the copolymers showed that 2-octyl-dodecyl acrylate does act as a reactive (internal) plasticizer. Blends of commercial virgin polystyrene and the synthesized low and high molecular weight copolymers were prepared. Partially miscible blends were obtained. Decreases in the glass transition temperatures of the blends compared to the virgin polystyrene were observed. The higher molecular mass styrene/2-octyl-dodecyl acrylate copolymers produced larger decreases in glass-transition temperatures.
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Synthesis and characterization of tailored polyurethane coatings

Seboa, Sharrief 12 1900 (has links)
Thesis (DSc (Chemistry and Polymer Science))--University of Stellenbosch, 2005. / Aqueous polyurethane (PU) dispersions were synthesized for use in paper coatings. These PUs contained a polyester polyol soft segment (content of between 65 to 75%) and a urethane hard segment (content of between 30 to 35%). Triethylamine (TEA) was used as the neutralizing agent. The polyester polyol segment consisted of neopentyl glycol (NPG), adipic acid, 1,4-cyclohexane dicarboxylic acid (1,4-CHDCA) and 2-phosphonobutane- 1,2,4-tricarboxylic acid (PBTCA), while the urethane hard segment consisted of toluene diisocyanate (TDI), dimethylolproponic acid (DMPA) and ethylene glycol (EG) as a chain extender for increasing the hard segment content. Waxes and fillers were incorporated into the PU coating mixtures to investigate their effect on the barrier properties of the PU. Two types of fillers were used: nano-fillers and micro-fillers. The nano-fillers used included the Cloisite nano-clays NC15A, NC93A and NC30B, and the micro-fillers used included talc, kaolin clay and barium sulfate. Two different polyester polyols were synthesized: one containing a phosphate and the other containing no phosphate. The polyols were characterized in terms of their acid value, hydroxyl value and molecular mass. The PUs synthesized from the polyol containing no phosphate showed unfavourable barrier properties compared to results achieved with the phosphate-containing PU. The PU dispersions were applied to paperboard, and then dried at a maximum temperature of 130oC for 15 to 60 seconds, depending on the coating volume. The PU-coated paperboard was characterized primarily by determining the moisture vapour transmission rate (MVTR), and by scanning electron microscopy (SEM). PU films (stand alone, not supported by paper) were prepared by heating the concurrent PU dispersion in Teflon holders over three different temperature stages (60, 90 and 120oC) for about 2 days. The dried films were then characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy. The PU coatings showed self-assembly properties, which were affected primarily by the ionic content (comprising of DMPA, PBTCA and excess TEA) and emulsion viscosity. These self-assembly properties were analyzed by static contact angle (SCA) and MVTR measurements. It was found that the final coating properties were affected by the self-assembly mechanism of the PU. Generally, the phosphated PU coatings had lower MVTR values than the non-phosphated PU coatings. SEM analysis showed that the phosphated PU coatings had no pinholes, while the non-phosphated PU coatings had pinholes. DMA analysis showed that the phosphated PUs had higher Tg values than the non-phosphated PUs. Further, the inclusion of the phosphate monomer increased the emulsion stability and the compatibility between the hard and soft segments of the PU. Also, the exfoliated PU nanocomposites at 1% filler loading gave much better MVTR results compared to the PU microcomposites. It also rendered the coating to be non-blocking, with minimal change in MVTR.

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