Thesis (PhD)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: As there is inadequate control of the hydrothermal synthesis technique used to date in the synthesis of zeolite A membranes, the feasibility of a new synthesis approach was investigated, namely the static transverse synthesis method. The former technique involved (i) thorough mixing of the chemical components, (ii) gel-formation and ageing and (iii) heat treatment. The proposed new method for zeolite A synthesis concerns the use of two individual nutrient pools (AI and Si) on opposite sides of a porous medium (a-alumina tube). Diffusion of these two nutrients towards each other, due to concentration differences, results in their contact in the porous medium (crystallisation front), leading to gel formation and eventual zeolite crystal growth. By means of the new static transverse synthesis technique the application of very high nutrient concentrations (O.72g NaOH, 80.0g H20, 8.26g NaAI02 and 15.48g Na2Si03), contrary to what is used in conventional hydrothermal synthesis techniques (11.23g NaOH, 54.82g H20, 0.61g NaAI02 and 3.63g Na2Si03), is now possible. The advantage of using high nutrient concentrations lies in the fact that supersaturation exists immediately after gel formation occurs. Supersaturation is a prerequisite for grain growth, which, in tum, is the only way in which a very thin (4-6 urn), continuous (pinhole-free) zeolite crystal layers can be prepared. A variety of support materials have been used to provide the mechanical stability for zeolite membranes, because the chemical/physical interaction between a zeolite synthesis solution and the support also plays a role in the formation of a zeolite membrane. Hence, zeolite A crystal growth on four different types of supports was evaluated and the a-alumina tube proved to be the best support for zeolite A crystal growth. An exploratory study into the upgrading of the static transverse synthesis to a continuousflow synthesis was also undertaken. The nutrients were continuously passed over the opposite surfaces (internal and external) of the porous a-alumina tube. In this way the nutrients could be replenished throughout the synthesis. It was possible to make zeolite A membranes using this technique, although these membranes were not an improvement on the membranes produced with the STS method. The zeolite A crystal population in and on the surface of the porous supports was determined by scanning electron microscopy (SEM). The zeolite A crystallinity, symmetry and morphology were characterised using x-ray diffraction PCRD). The zeolite lattice vibrations, structure sensitive and structure insensitive vibrations were determined by infra red spectroscopy (IR). The wettability of the alumina support was determined by dynamic contact angle measurements. The zeolite A membranes prepared by the static transverse synthesis were tested for their helium permeance. They were also subjected to pervaporation experiments at 45°C, using a water/ethanol mixture (5 wt% water) and it was found that the fluxes varied between 0.2 -0.4 kg/m2h and the separation factors varied between 5000 and 16000. These results compare very favourably with results reported in the literature. In conclusion, the possibilities created by using a combination of membranes and catalysis, both on bench scale and in industry, are reviewed. / AFRIKAANSE OPSOMMING: Weens onvoldoende beheer oor die hitte behandeling sintese tegniek wat tans vir die sintese van zeoliet-A-membrane gebruik word, is die haalbaarheid van 'n nuwe sintese tegniek, nl. die statiese sydelingse sintese-metode, ondersoek. Eersgenoemde tegniek behels (i) deeglike vermenging van die chemiese komponente, (ii) jelvorming en -veroudering en (iii) hittebehandeling. Die voorgestelde nuwe sintese tegniek vir die bereiding van ondersteunde zeoliet-A-membrane behels die plasing van twee aparte voedingsbronne (Al en Si onderskeidelik), aan teenoorgestelde kante van 'n poreuse medium (a-aluminabuis). Diffusie van hierdie twee komponente na mekaar, agv konsentrasieverskille, veroorsaak dat die twee oplossings in die poreuse medium met mekaar in aanraking kom (kristallisasie front). Dit lei dan tot jelvorming en uiteindelik zeolietkristal groei. Met die nuwe sydelingse sintesetegniek is die aanwending van baie hoë konsentrasies van die voedingsbronne (O.72g NaOH, 80.0g H20, 8.26g NaAI02 en 15.48g Na2Si03) nou moontlik. Dit is in teenstelling met die konvensionele hitte behandelingstegnieke (11.23g NaOH, 54.82g H20, O.61g NaAl02 en 3.63g Na2Si03). Die voordeel van hoë voedingsbronkonsentrasies is dat oorversadiging onmiddelik na jelvorming bereik word. Absolute oorversadiging is 'n voorvereiste vir partikelgroei, wat op sy beurt die enigste manier is om baie dun (4-6 urn), aaneenlopende zeolietkristallae te verkry. 'n Verskeidenheid van draermateriale is al gebruik om meganiese stabiliteit aan zeolietmembrane te verleen, aangesien die chemiese/fisiese interaksie tussen die zeolietsintese-oplossing en die draermateriaal 'n rol speel in die vorming van die zeolietmembraan. Om hierdie rede is die groei van zeoliet-A-kristalle op vier verskillende tipes draermateriale ondersoek en die a-aluminabuis is as die beste draermateriaal vir zeoliet-A-kristalgroei bewys. 'n Aanvanklike studie na die moontlike opgradering van die statiese sydelingse sintese na aaneenlopende vloeisintese is ook onderneem. In hierdie studie is die voedingsbronne deurlopend oor die teenoorgestelde oppervlaktes (intern en ekstern) van die poreuse a-aluminabuis gepomp. Sodoende kon die voedingstowwe voortdurend tydens die sintese aangevul word. Dit was moontlik om zeoliet-A-membrane met behulp van hierdie tegniek te maak, alhoewel hierdie membrane nie 'n verbetering was op dié wat deur middel van die statiese sydelingse sintesetegniek gemaak is nie. Die teenwoordigheid van die zeoliet-A-kristalle op die verskillende oppervlaktes van die poreuse buis is met behulp van 'n skandeerelektronmikroskoop (SEM) bepaal. Die zeoliet-A-kristalliniteit, -simmetrie en -morfologie is met behulp van x-straaldiffraksie (XRD) gekarakteriseer. Die zeolietlatwerk-, struktuursensitiewe- en struktuuronsensitiewe vibrasies, is met behulp van infrarooispektroskopie (IR) en die benatbaarheid van die aluminabuis met dinamiese kontakhoekbepalings bepaal. Die zeoliet-A-membrane berei met die statiese sydelingse sintese-metode is vir helium-deurlaatbaarheid getoets en ook aan pervaporasie eksperimente by 45°C, deur gebruik te maak van 'n water/etanol mengsel (5 wt% water), onderwerp. Daar is gevind dat vloei tussen 0.2 - 0.4 kg/mh en dat skeidingsfaktore tussen 5000 en 16000 gevarieer het. Hierdie resultate vergelyk baie goed met die resultate in die literatuur. Samevattend word 'n oorsig gegee van die moontlikhede wat geskep word deur membraanskeidingstegnologie te kombineer met katalise op laboratorium- en industriële skaal.

Thesis (PhD)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: This dissertation describes work done on Fischer- Tropsch ionomeric waxes. The waxes are characterized with respect to the method of manufacture, the mechanism of the oxidation process, the saponification, the physical properties, the rheological properties, the morphology and the water absorption of the waxes. Different methods of physical and mechanical analysis are used to prove at which concentration level, for each type of cation tested arid for each type of oxidized and grafted wax prepared, the formation of multiplets and clusters within the Fischer- Tropsch ionomeric waxes takes place. An understanding of multiplet and cluster formation in Fischer- Tropsch ionomeric waxes is essential as these morphological phenomena control the mechanical and physical behaviour of the Fischer- Tropsch ionomeric waxes. The ability to be able to analyse the Fischer- Tropsch ionomeric waxes for multiplet and cluster formation should allow one to predict the physical and mechanical behaviour of the Fischer- Tropsch ionomeric waxes in practical applications. / AFRIKAANSE OPSOMMING: Hierdie skripsie beskryf werk gedoen op Fischer-Tropsch ionomeries wasse. Die wasse is gekarakteriseer ten opsigte van die vervaardigingsmetode, die meganisme van oksidasie, die verseping, hulle fisiese en reologiese eienskappe, hulle morfologie en water absorpsie. Verskillende metodes van fisiese en meganiese analiese is gebruik om te bewys by watter konsentrasie, vir 'n spesifieke katioon en vir 'n spesifieke geoksideerde of entwas, wanneer veelvoud of tros-vorming plaasvind. Die vermoë om te verstaan hoe en wanner veelvoude en trosse in Fischer- Tropsch ionomeries wasse vorm is van kardinale belang, aangesien die fisiese en meganiese eienskappe van die Fischer- Tropsch ionomeries wasse direk beinvloed word deur die vorming van veelvoude en trosse. Die vermoë om Fischer- Tropsch ionemeries wasse te kan analiseer vir veelvoud en tros vorming is voordelig om Fischer- Tropsch ionomeries wasse se meganiese en fisiese eienskappe in praktiese aanwendings te voorspel.

Thesis (MSc)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: This work involves the study of the effects of Reversible Addition-Fragmentation Chain Transfer (RAFT) agents on the emulsion polymerization of styrene. The feasibility of RAFT as a method for obtaining controlled radical polymerizations in emulsion systems is also investigated. Both seeded and ab initio systems were studied with three RAFT agents of varying structure. Inhibition and retardation effects on addition of various amounts of the RAFT agents to the emulsion systems were observed and the trends noticed. The effect of the RAFT agents on the average number of radicals per latex particle was calculated from reaction rates. The effect of the RAFT agent on the molecular weight and the molecular weight distribution was monitored by gel permeation chromatography. Exit of free radicals from the latex particles proves to be a major feature in the studied RAFT emulsion systems. Fragmentation of the RAFT agent in the latex particles, gives rise to free radical species that can exit from the particle and enter other particles where they can either terminate instantaneously or propagate. The exit and termination processes presumably result in both the inhibition and retardation of the emulsion polymerizations. A linear increase in Mn with conversion is observed, however the low concentration of RAFT agent in the latex particles is responsible for the obtained number average molecular weights being much higher than predicted. The low concentrations of RAFT agents in the latex particles is also responsible for the broad molecular weight distributions that are obtained. Reaction conditions for RAFT experiments should to be chosen so that the effects of exit processes are minimized and that the RAFT agent is primarily situated in the latex particles. These conditions must be met if the RAFT process is to be successful as a method of controlled radical polymerization in emulsions. / AFRIKAANSE OPSOMMING: Hierdie navorsing behels die studie van die effek van In bygevoegde addisie-fragmentasie kettingsoordragsreagent (RAFT1) op die emulsie polimerisasie van stireen. Die uitvoerbaarheid van RAFT as 'n metode om gekontroleerde radikale polimerisasies in emulsiesisteme te verkry is ook ondersoek. Eksperimente met drie RAFTkettingoordragsreagente van gevarieerde strukture is uitgevoer in beide seeded en ab initia sisteme. Die effek van die RAFT-reagent op die inhibisie en vertraging van die emulsie polimerisasie is waargeneem en die invloed van RAFT op die gemiddelde aantal radikale per partikel is bepaal. Die ontwikkeling van die molekulêre massa en die molekulêre massadistribusie is waargeneem deur middel van gel permeasie- kromatografiese tegnieke. Die ontsnapping van vrye radikale vanuit die partikels was 'n belangrike faktor in RAFT emulsiesisteme wat ondersoek is. Hierdie radikale is gegenereer deur die fragmentasie van die oorspronklike RAFT-reagent. Fragmentasie van die RAFT-reagent in die lateks partikels lei tot die vorming van vrye radikale spesies wat uit een partikel kan ontsnap en ander partikels kan binnedring waar dit onmiddellik kan termineer of propageer. Die ontsnappings- en terminasieprosesse van vrye radikale lei oënskynlik tot die inhibering en vertraging van die emulsie polimerisasie. 'n Lineêre verhoging in die gemiddelde molekulêre massa tydens konversie is waargeneem, alhoewel die Mn-waardes baie hoër was as wat verwag is. Die verskil kan toegeskryf word aan die klein hoeveelhede van die RAFT-reagent wat in die partikels teenwoordig is. Hierdie lae RAFT-konsentrasies is ook verantwoordelik vir die breë molekulêre massa distribusie wat waargeneem is. Vir die RAFT-proses om suksesvol te wees in gekontroleerde radikale polimerisasies in emulsies, moet reaksie kondisies so gekies word dat die ontsnapping van vrye radikale tot 'n minimum beperk word en die RAFT-reagent hoofsaaklik in die lateks partikels teenwoordig is.

Thesis (MSc)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: A novel approach to conducting controlled free radical polymerization in aqueous systems using Reversible Addition-Fragmentation Chain Transfer (RAFT) has been studied. When conducting RAFT in aqueous systems, reaction conditions must be chosen such that monomer transport across the aqueous-phase is either eliminated or facilitated. This is to prevent the formation of the red layer associated with RAFT in emulsions. The formation of the red layer is ascribed to the inability of waterinsoluble, dithiobenzoate-endcapped oligomers to be sufficiently transported across the aqueous phase. The novel approach in this study focussed on eliminating monomer transport and comprises two fundamental steps: the synthesis of dithiobenzoate-encapped oligomers in bulk followed by miniemulsification of these oligomers to yield a polymerizable miniemulsion. Dithioesters that act as chain transfer agents in the RAFT -process were synthesized in situ, thereby eliminating laborious and time-consuming organic purification procedures of dithioesters. In situ formation of the RAFT-agents involved conducting the reaction between di(thiobenzoyl) disulfide and conventional azo-initiators of differing structures in the presence of monomer. The structure of the chosen azo-initiator played a role in the efficiency of the RAFT process when the reaction was conducted in the presence of monomer to control the free radical polymerization process. Synthesis of the oligomers was performed by heating di(thiobenzoyl) disulfide and a selected azo-initiator, in the presence of monomer for a specific reaction duration in bulk. After the reaction was stopped, these oligomers were then miniemulsified by adding water, surfactant and cosurfactant, followed by the application of shear to form the resulting mini emulsion. The free radical polymerization of the dithiobenzoate-endcapped oligomers in the miniemulsion proceeded in a controlled manner with molecular weight increasing in a linear fashion with increasing conversion, while polydispersities remained low. The familiar red layer formation associated with RAFT polymerization in conventional emulsions was not observed under these conditions. The effects of changing the cosurfactant (hydrophobe) as well as changing the degree of polymerization of the emulsified oligomers were also investigated and described. / AFRIKAANSE OPSOMMING: Hierdie studie is geloods om 'n nuwe benadering tot die beheerde vry-radikaal polimerisasie in water gebaseerde sisteme te ondersoek. Daar is spesifiek gekyk na die uitvoer van die RAFT (Reversible Addition-Fragmentation Chain Transfer) proses in emulsies. Wanneer RAFT in emulsies toegepas word, moet die toestande waaronder die reaksie uitgevoer word, versigtig opgestel word. Die toestande moet so gekies word dat die vervoer van monomere deur die waterfase óf geëlimineer word óf gefasiliteer word. Dit word gedoen om die faseskeiding in die vorm van 'n rooi laag, wat so kenmerkend van RAFT -polimerisasie in emulsies is, te voorkom. Hierdie faseskeiding vind plaas omdat die vervoer van ditiobensoaat endgroep-bevattende oligomere deur die waterfase tydens interval II, moeilik is a.g.v. hulle oplosbaarheid in water. Die nuwe benadering wat hier bestudeer is, het twee basiese stappe. Eerstens word die ditiobensoaat endgroep-bevattende oligomere in bulk gesintetiseer. Dit word gevolg deur die emulsifisering van die oligomere. Hierna vind verdere polimerisasie van die oligomere plaas deur die dormante oligomere te heraktiveer. Die ditio-esters wat as kettingoordrag agente optree in die RAFT proses, word in situ gesintetiseer. Hierdie modifikasie sny tydrowende organiese suiweringsmetodes uit. Die in situ RAFT agente word gesintetiseer deur di(tiobensoïel) disulfied met verskillende konvensionele azo-inisieerders te laat reageer. Die struktuur van die spesifieke azoinisieerder het wel 'n rol gespeel in die effektiwiteit van die RAFT proses om molekulêre massa te beheer as bg. reaksie in die teenwoordigheid van monomere uitgevoer is. Die sintese van die oligomere is gedoen deur di(tiobensoïel) en 'n azo-inisieerder te verhit in die teenwoordigheid van monomere. Die reaksie is gedoen in bulk en die graad van polimerisasie van die oligomere is beheer deur die reaksie te stop by verskillende tydstippe. Nadat die bulk reaksie gestop is, is hierdie oligomere ge-emulsifiseer deur die oligomere te meng met 'n seep, hidrofoob en water. Hierdie mengsel word dan onderwerp aan 'n vermengingskrag om 'n polimeriseerbare mini-emulsie te vorm. Die voortsetting van die polimerisasie van die oligomere in die mini-emulsie het op 'n beheerde wyse verloop, m.a.w. molekulêre massa wat linieêr toeneem met stygende omsetting. Polidispersiteit indekse van die polimere het deurentyd laag gebly in die stabielste sisteme. Onder hierdie toestande was daar geen kenmerkende rooi laagvorming te bespeur nie. Die effekte wat die verandering van die hidrofoob, asook die verandering van die graad van polimerisasie van die oligomere op die sisteem gehad het, is onder andere ook ondersoek en beskryf.

Thesis (MSc)--Stellenbosch University, 2001 / ENGLISH ABSTRACT: The effect of various organic reducing agents, in the. form of monosaccharide reducing sugars, on the rate of atom transfer radical polymerization (ATRP) of n-butyl methacrylate and methyl methacrylate is reported in this study. The addition of the reducing sugars has a positive effect on the rate of ATRP. Up to 100% increase in the rate of polymerization was recorded, in some cases. These organic reducing agents have little effect on the molecular weight and molecular weight distribution of the polyin-butyl methacrylate) and polydispersity indexes remain well below 1.2. The molecular weight of the poly(methyl methacrylate), when glucose and galactose are added to the reaction mixture, compares well with the theoretical expected values. An explanation for these observations is the ability of the reducing sugars to reduce part of the Cu(II) species, that serves to deactivate the growing radicals, to Cu(I), thereby ensuring a shift in the equilibrium between active and dormant chains in the direction of the former and a resulting increase in the rate of polymerization. uvNIS spectroscopy and cyclic voltammetry were used to investigate the mechanism behind the polymerization rate enhancement. / AFRIKAANSE OPSOMMING: In hierdie studie word die effek van verskeie organiese reduseermiddels, in die vorm van monosakkaried reduserende suikers, op die tempo van polimerisasie van ATRP gerapporteer. Hierdie reduserende suikers het 'n positiewe effek op die polimerisasie tempo. In sommige gevalle word 'n toename van 100% in die polimerisasie tempo waargeneem. Die organiese reduseermiddels het 'n minimale effek op die molekulere massa en molekulere massa verspreiding (in meeste gevalle minder as 1.2) van die poly(n-butiel metakrielaat). In die geval van die poly(metiel metakrielaat), wanneer glukose en galaktose by die reaksie mengsel gevoeg word, stem die molekulere massas goed ooreen met die teoreties voorspelde molekulere massas. Die waargenome toename in die polimerisasie tempo kan toegeskryf word aan die vermoe van die reduserende suikers om die Cu(II), wat dien om die groeiende radikale te deaktiveer, gedeeltelik te reduseer na Cu(l). Hierdeur word verseker dat die ewewig tussen die aktiewe en dormante kettings in die rigting van die eersgenoemde verskuif word, wat dus aanleiding gee tot 'n toename in die polimerisasie tempo. Ultraviolet spektroskopie en sikliese voltammetrie is ook gebruik om lig te werp op die meganisme agter die toename in die tempo van polimerisasie.

Thesis (MSc)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: Aqueous polyurethane (PU) dispersions were synthesized for the use in paper coatings. These PUs contained a polyester polyol soft segment (content of 60-70%) and a urethane hard segment (content of 30-40%). This was followed by grafting using four different grafting agents. 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-CHOCA) and 2-phosphonobutane-1 ,2,4- tricarboxylic acid (PSTCA), while the urethane hard segment consisted of hydrogenated 4,4-diphenylmethane diisocyanate, dimethylolproponic acid (OMPA), 3-hydroxypivalic acid (HPA) and hydroxyethylene methacrylate (HEMA). The grafting agents used were lauryl methacrylate (LMA), n-butyl methacrylate (n-SMA), methyl methacrylate (MMA) and styrene. Two different polyester polyols were synthesized, one containing 10% phosphate and the other none. The polyols were characterized in terms of their acid value, hydroxyl value and molecular mass. The PUs synthesized from the polyol containing 0% phosphate were grafted with LMA, while the phosphate-containing PUs were grafted with each of the all four grafting agents. The resulting dispersions were applied to paperboard, and then dried at a maximum temperature of 100°C. The PU-coated paperboard was characterized using the moisture vapour transmission rate (MVTR), and scanning electron microscopy (SEM) techniques. PU films (not supported by paper, stand alone) were prepared by heating the PU dispersion in Teflon holders up to 130°C for 6 hours. The dried films were then characterized by thermogravimatric analysis (TGA), differential scanning calorimetry (OSC), dynamic mechanical analysis (OMA) and Fourier transform infrared spectroscopy (FTIR). MVTR-analysis showed that the phosphated PU coatings had a minimum MVTR-value at 0% grafting, and that its overall MVTR-values were much lower than that of the non-phosphated PU coatings. SEM-analysis showed that the phosphated PU coatings had no pinholes at a maximum of 8% grafting, while the non-phosphated PU coatings showed pinholes at all levels of grafting. OMA-analysis showed that the phosphated PU samples had higher Tg's (Tg onset between O-S°C)than that of the non-phosphated PU samples (Tgonset below -SO°C). / AFRIKAANSE OPSOMMING: POLI-URETAAN DISPERSIES VIR PAPIER BEDEKKINGS Waterige poli-uretaan (PU) dispersies is gesintetiseer vir gebruik as papierbedekkings. Hierdie poli-uretane het 'n poliester poli-ol sagte segment (60-70% inhoud) en 'n uretaan harde segment (30-40% inhoud) bevat. Die poli-uretane is met vier verskillende ent-middels geêent. Trietielamien (TEA) is as neutraliseermiddel gebruik. Die poli-ester poli-ot segment het bestaan uit: neopentielglikol (NPG), adipiensuur, 1,4-sikloheksaandikarboksielssuur (1,4- SHDKS) en 2-fosfonobutaan-1 ,2,4-trikarboksielssuur (FSTKS). Die uretaan harde segment het bestaan uit: hidrogeneerde 4,4-difenielmetaandiisosianaat, dimetielpropioonsuur (DMPS), 3-hidroksipivaalsuur (HPS) en hidroksietileenmetakrilaat (HEMA). Laurielmetakrilaat (LMA), n-butielmetakrilaat (n-SMA), metielmetakrilaat (MMA) en stireen is as entmiddels gebruik. Twee verskillende poli-ester polihidroksie verbindings is gesintetiseer: een met 10% fosfaat en een met geen fosfaat, en gekarakteriseer in terme van hulle suurwaardes, hidroksiwaardes en molekulêre massas. Die PUs wat vanaf die fosfaat-bevattende poli-ol gesintetiseer is, is met LMA geêent, terwyl die fosfaat-bevattende PUs met al vier entmiddels geêent is. Papier (Eng. paperboard) is met hierdie dispersies bedek en by 100°C gedroog. Die PU-bedekte papier is gekarakteriseer in terme van vogdeurlaatbaarheidstransmissie (Eng: MVTR - the moisture vapour transmission rate), en skandeerelektonmikroskopie (SEM). PU-films wat nie deur papier gestut is nie is ook voorberei deur die verhitting van die PU dispersies in Teflon houers (130°C, 6 ure). Die droë films is daarna gekarakteriseer deur middel van termogravimetriese analise (TGA), differensiêle skandeerkalorimetrie (DSC), dinamiese meganiese analise (OMA) en Fourier-transformasie infrarooispektroskopie (FTIR). Resultate van MVTR analises het getoon dat die fosfaat-bevattende PU bedekkings 'n mimimum MVTR-waarde by 0% enting gehad het, en dat die totale MVTR waardes baie laer was as die van die nie-fosfaatbevattende bedekkings. SEM het gewys dat die fosfaat-PU bedekkings by 8% enting geen mikrogaatjies (Eng. pinholes) gehad net nie, terwyl die PU bedekings met geen fosfaat mikrogaatjies (Eng. pinholes) by alle vlakke van enting gehad het. OMA analises het getoon dat die monsters van die fosfaatbevattende PU hoër Tg waardes gehad het (Tg begin tussen 0 en 5 "C) as die nie-fosfaatbevattende PU monsters (Tg begin onder -50°C).

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The presence of mineral oils in dry foodstuff was found to originate from the packaging materials, namely, paperboard manufactured from recovered fibres, and these oils subsequently migrate to the foodstuff via the vapour phase. The presence of mineral oils in food is of concern as it originates from the use of paper products not originally intended for food contact applications, i.e., before the paper is subjected to a suitable recycling process. These mineral oils consist of technical grade compounds which may contain aromatic compounds and other components with unknown toxicological effects. Although the related authorities are currently considering the safe and legal limits of these contaminants in foodstuffs, as well as establishing a standardised test method for monitoring mineral oils in food and packaging materials, paperboard manufacturers wish to ensure that their products are safe for food contact applications. Since recycling is unavoidable, particularly from an ecological and economical point of view, one of the proposed solutions the industry is focussing on is the use of a functional barrier towards mineral oils – be it an inner bag as a direct food-contact surface, or a barrier coating directly applied on the inner side of the paperboard. In this study, a permeation test method was established, and developed, to evaluate the transmission rate of a volatile organic compound, acting as a mineral oil simulant, through model paper and plastic packaging materials. This was correlated to the transmission rate of actual mineral oil through the packaging materials, and therefore used as a highly accelerated tool to characterise packaging materials in relation to their barrier properties. The test method, referred to as the “heptane vapour transmission rate,” was subsequently used to derive the required transport parameters’ characteristics of each of the tested materials, which enabled an evaluation of the potential shelf-life of the packaged product. This research demonstrated that barrier-coated paperboards have the ability to behave in the same way as, and often even better than, commercial plastic films, towards the migration of mineral oil. Detailed information on the interaction between the packaging materials and mineral oil simulant, n-heptane, was acquired from gravimetric sorption. Insight was obtained into a material’s ability to function as a mineral oil barrier. It was established that the quick and easy permeation method was sufficient for evaluating packaging materials as potential mineral oil barriers, and resulted in the determination of transport parameters that were higher than that obtained by sorption. The obtained transport parameters could therefore be considered a worst case scenario when predicting the package content shelf-life. / AFRIKAANSE OPSOMMING: Daar is voorheen bevind dat die teenwoordigheid van mineraalolies in droë voedsel afkomstig is van die verpakkingsmateriaal, naamlik karton, wat vervaardig is van herwonne papierprodukte, en daarna migreer die olies na die voedsel deur die gasfase. Die teenwoordigheid van hierdie mineraalolies in kos wek groot kommer aangesien dit afkomstig is van papierprodukte wat nie oorspronklik bedoel is vir voedselkontak voor die herwinningsproses nie. Die olies bestaan uit industriële graad mineraalolies wat moontlik aromatiese verbindings asook ander komponente bevat waarvan die toksiekologiese effekte onbekend is. Terwyl die betrokke owerhede tans besig is om die veilige en wettige grense van hierdie kontaminante in voedsel te oorweeg, asook die vestigting van 'n gestandaardiseerde toetsmetode vir die kontrole van mineraalolies in die voedsel-verpakkingsmateriaal-kombinasie, wil karton- en papiervervaardigers graag verseker dat hul produkte veilig is vir voedselkontak. Siende dat herwinning onvermydelik is vanuit 'n ekologiese en ekonomiese oogpunt, is een van die voorgestelde oplossings in die bedryf om te fokus op die gebruik van 'n funksionele keerfilm ten opsigte van mineraalolies, wat ‘n sakkie binne-in die karton, wat dien as die direkte kos-kontakoppervlak, of 'n keerlaag, wat direk aangewend word op die binnekant van die karton, kan behels. Hierdie studie ondersoek die daarstel en deursypelingsontwikkeling van 'n toetsmetode om die oordragtempo van 'n vlugtige organiese verbinding, wat optree as 'n mineraalolie simulant, deur middel van model papier- en plastiekverpakkingsmateriale, te evalueer. Dit stem ooreen met die oordragtempo van werklike mineraalolies deur die verpakkingsmateriaal en kan dus gebruik word as 'n hoogs versnelde instrument om verpakkingsmateriale te karakteriseer met betrekking tot hul keereienskappe. Die toetsmetode, die sogenaamde "heptaangasoordragtempo," is vervolgens gebruik om die vereiste oordragparameters af te lei wat kenmerkend is van elk van die geëvalueerde verpakkingsmateriale en wat sodoende gebruik kon word om die potensiële raklewe van die verpakte produk te bepaal. Hierdie navorsing het getoon dat kartonprodukte met ‘n keerlaag die vermoë het om dieselfde op te tree as kommersiële plastiekfilms en dikwels selfs beter, ten opsigte van die migrasie van mineraalolies. Gedetailleerde inligting oor die interaksie tussen die verpakkingsmateriale en mineraalolie simulant, n-heptaan, is verkry vanaf gravimetriese sorpsie. Dit gee insig in 'n materiaal se vermoë om te funksioneer as 'n mineraalolie-keermiddel. Daar is vasgestel dat die vinnige en maklike deurwerking metode voldoende is vir die evaluering van verpakkingsmateriale as potensiële mineraalolie-keermiddels, en verleen oordragparameters wat hoër is as dié verkry deur sorpsie. Hierdie oordragparameters kan dus as 'n ergste scenario vir die voorspelling van die raklewe van ‘n verpakte produk beskou word.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2006. / Rectangular components were produced by both standard injection moulding and by a process called Lomolding. Both moulding grade polypropylene homopolymer and glass-filled polypropylene were used. The effect of processing parameters on material properties, as measured by tensile and impact strength, and warpage were determined for both injection moulding and lomolding, for both unfilled and glass-filled polypropylene materials. Sampling of the components allowed for critical evaluation of processing parameters’ effect on material properties at points close to and distant from the injection point, as well as in the direction of materials flow and transverse to material flow. Glass-filled components were also evaluated in terms of glass fibre length and fibre distribution (post-injection). Overall conclusions could be drawn with respect to the 2 different processes and the materials used. It was seen, inter alia, that the specimen orientation had no effect on the mechanical properties when using unfilled polypropylene, but that the orientation of the glass fibres in the testing direction resulted in an increase in the tensile strength and the impact strength for the injection moulded samples. Similar results were seen for lomolded samples, except that the fibre orientation effects were different. In the same vein, other notable differences could be observed for samples produced by lomolding and injection molding. Fibre length and distributions obtained by polymer burn-off experiments served to help explain differences in properties of glass-filled products produced by the two processes.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2005. / Polymerization using the reversible addition-fragmentation chain transfer (RAFT) process affords a researcher control over the molecular weight and polydispersity of the final polymer. Research is being carried out globally, using heterogeneous RAFT systems, as these systems offer superior industrial possibilities. Many emulsion systems fail when incorporating RAFT agents due to phase separation and colloidal instability. Exchanging conventional emulsion polymerizations with predispersed polymerization systems (i.e. miniemulsions) has shown many improvements. Evidence of uncontrolled aqueous phase polymerization (i.e. not mediated by the RAFT process) has however been found. This behaviour is similar to polymerization in a conventional emulsion polymerization system, but is not expected in miniemulsion polymerization.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2006. / Polyurethanes (PUs) are finding increasing application and use in many industries due to their advantageous properties, such as a wide range of flexibility combined with toughness, high chemical resistance, excellent weatherability, and very low temperature cure. PUs do however have some disadvantages, for instance, PU is considered an expensive polymer, especially when considered for solvent based adhesives. A motivation for this study was to consider a largely unstudied area of PU chemistry by combining PUs with polyacrylates. Polyacrylates are well known adhesives and can carry specific functionality, but have the disadvantage that their flexible backbones impart limited thermal stability and mechanical strength. In this study PU was incorporated into acrylates in an effort to obtain acrylate-g-urethanes with good properties. The mode of incorporation chosen was urethane macromonomers (UMs), a hardly mentioned substance in literature, yet one deserving investigation. UMs having different urethane chain lengths (X) were synthesized by the polyaddition polymerization of toluene diisocyanate (TDI) and ethylene glycol (EG) by the prepolymer method, which was terminated by 2-hydroxy ethyl methacrylate (HEMA) and isopropanol. The UMs were characterized by Fourier-transform infrared spectroscopy (FTIR), proton NMR (1H NMR), carbon NMR (13C NMR), gel permeation chromatography (GPC), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). Various percentages of the respective UMs (0-40 wt % according to acrylate monomers) were then incorporated into methyl methacrylate (MMA) and into normal butyl methacrylate (n-BMA) backbones via solution free radical copolymerization. The resulting methyl methacrylate-urethane graft copolymers (PMMA-g-urethane) and normal butyl methacrylate-urethane graft copolymers (n-PBMA-g-urethane) were characterized by GPC, 1H NMR and 13C NMR, FTIR, TGA, and DMA. Phase separation between the urethane segment and acrylate segment in the yield of graft copolymerization products was investigated by DMA and transmission electron microscopy (TEM). As the concentration of the UMs in the free radical copolymerization feed increased, lower yields of both graft copolymers PMMA-g-urethane and n-PBMA-g-urethane were observed and more UM was incorporated into the PMMA and n-PBMA backbones. It also was found that the thermal stability of the PMMA-g-urethane and n-PBMA-gurethane copolymers increased with increasing UM concentration. DMA results showed that in most graft copolymer products the two respective component parts of PMMA-g-urethane or n-PBMA-g-urethane were completely compatible as only one Tg was observed. Two glass transitions, at temperatures of 22.0 and 76.0 oC, corresponding to the n-PBMA and urethane moieties, were observed when the chain length of the UMs was increased from X=4 to X=32 [the amount of this UM used in the copolymerization feed was increased to 40%, and microphase separation was indicated].