Yes / The tribological performance of the piston assembly of an automotive engine is highly influenced by the complex flow mechanisms that supply lubricant to the upper piston rings. As well as affecting friction and wear, the oil consumption and emissions of the engine are strongly influenced by these mechanisms. There is a significant body of work that seeks to model these flows effectively. However, these models are not able to fully describe the flow of lubricant through the piston assembly. Some experimental studies indicate that droplets of lubricant carried in the gas flows through the piston assembly may account for some of this. This work describes an investigation into the nature of lubricant misting in a fired gasoline engine. Previous work in a laboratory simulator showed that the tendency of a lubricant to form mist is dependent on the viscosity of the lubricant and the type and concentration of viscosity modifier. The higher surface area-to-volume ratio of the lubricant if more droplets are formed or if the droplets are smaller is hypothesised to increase the degradation rate of the lubricant. The key work in the investigation was to measure the size distribution of the droplets in the crankcase of a fired gasoline engine. Droplets were extracted from the crankcase and passed through a laser diffraction particle sizer. Three characteristic droplet size ranges were observed: Spray sized (250–1000 μm); Major mist (30–250 μm); and Minor mist (0.1–30 μm). Higher base oil viscosity tended to reduce the proportion of mist-sized droplets. The viscoelasticity contributed by a polymeric viscosity modifier reduced the proportion of mist droplets, especially at high load.

No

Today, the focus lies on the state of the environment and how we can choose more sustainable alternatives to oil based materials. One material of interest is microfibrillated cellulose (MFC).The microfibril exhibits interesting properties, which one is its excellent barrier properties, that is expected to come in good use for the conversion to a more sustainable society. It is believed that the use of biobased barriers will increase with these new materials and MFC is showing promising results. But in order to develop the material to its full potential, it is important to investigate how MFC behaves in different situations, which can be examined with rheological measurements. The aim of the thesis is to examine how the rheological properties of suspensions containing MFC are affected by temperature and time storing and how the learning from this work can be used for influencing dispersion properties. Four samples were investigated, containing different amounts of MFC and modified waxy maize starch. The samples were analyzed with a dynamic rotational rheometer (Kinexus Pro +) with a splined cup and bob. The following steps were included in the method development used in this work: sample preparation, the repeatability, rest time and statistical analysis. An oscillatory shear and steady shear measurement was performed on the samples, and selected samples were studied with microscopy. The results show that the temperature has affected the samples. The shear viscosity of all samples decreased with increasing temperature and the samples followed the temperature dependence of Arrhenius' equation. For samples containing MFC, the structure was affected, and the initial viscosity was not recovered. The complex viscosity did also decrease at the beginning to then suggestively increase, creating a stronger network at higher temperatures. With the raised temperature the bonding between the fibrils became weaker, which in turn made the dispersion less viscous. Then, depending on the applied force, the shear viscosity and complex viscosity acted differently. To conclude, both the shear viscosity and the complex viscosity in these dispersions containing MFC are dependent on the temperature and time storing. By the learnings from this work, a method has been developed to understand how to use temperature and storing time to lower the shear viscosity and lower, or increase, the complex viscosity. / Idag ligger det ett stort fokus på miljöns tillstånd och hur vi kan välja mer hållbara alternativjämfört med oljebaserade material. Ett material av intresse är mikrofibrillerad cellulosa (MFC).Denna mikrofibrill besitter intressanta egenskaper, varav en är enastående barriäregenskaper,som förväntas komma till god användning i omställningen till ett mer hållbart samhälle. Det tros att biobaserade barriärer kommer att användas mer i dessa nya material och här visar MFC lovande resultat. Men för att kunna utveckla materialet till sin fulla potential är det viktigt att undersöka hur MFC beter sig i olika situationer, som kan undersökas genom reologiska mätningar. Syftet med arbetet är att undersöka hur de reologiska egenskaperna för suspensioner innehållande MFC påverkas av temperatur och lagringstid samt hur lärdomen från det här arbetet kan användas för att påverka dispersionsegenskaper. Fyra prover undersöktes,innehållande olika mängd MFC och modifierad majsstärkelse. Proverna analyserades med en dynamisk rotations reometer (Kinexus Pro +) med räfflad kopp och bob. Följande steg ingick i metodutvecklingen som användes i detta arbete: provberedning, repeterbarhet, vilotid och statistisk analys. En oscillerande skjuvning och jämn skjuvmätning utfördes på de olika proverna samt att utvalda prover studerades med mikroskopi. Resultatet visade att temperaturen hade påverkat proverna. Skjuvviskositeten för alla prover minskade med en ökande temperatur och proverna följde temperaturberoendet av Arrhenius ekvation. För prover innehållande MFC påverkades strukturen och startviskositeten återficks inte. Den komplexa viskositeten minskade också till en början för att sedan suggestivt öka, vilket skapade ett starkare nätverk vid högre temperaturer. Med en högre temperatur blev bindningarna mellan fibrillerna svagare, vilket bidrog att dispersionerna blev mindre viskösa. Beroende på den applicerade kraften, verkade skjuvviskositeten och den komplexa viskositeten olika. Slutsatsen var att både skjuvviskositeten och den komplexa viskositeten i dessa prover innehållande MFC beroende av temperaturen och lagringstid. Från lärdomen av arbetet har en metod tagits fram för att kunna använda temperatur och lagringstid för att sänka skjuvviskositeten och sänka, eller öka, den komplexa viskositeten.

"The present work is a study of the low inertia spreading dynamics of initially spherical viscous droplets on a planar interface. The droplets are affected by gravity, surface tension and viscous forces and are modeled as two-dimensional axisymmetric bodies. The main focus of this study is the examination of the dependence of droplet stability, equilibrium shape and fluid motion within the drop on the relative magnitude of these forces. The dynamics are modeled using the unsteady, non-linear Navier-Stokes equations for an incompressible fluid. The spreading of a droplet on a solid surface is modeled with both a no-slip and a partial-slip boundary condition. In addition, the spreading of a droplet on another identical drop (two-drop problem) is modeled to study the problem without the contact point singularity. The governing equations are solved numerically using the Mixed Galerkin Finite Element formulation, augmented by the use of the Newton-Raphson iteration scheme to effectively treat the non-linearities of the problem. The Generalized Eulerian Lagrangian formulation is adopted for the treatment of the moving free surface of the droplet. Computations are performed for capillary numbers ranging from 0.01 to 100 and for Reynolds numbers from 0.005 to 50, where the velocity scale is based on the droplet radius and the gravitational acceleration. For the droplet spreading on a solid surface, three distinct behaviors are observed~: for low Reynolds numbers and sufficiently high capillary numbers, droplets deform to a stable, equilibrium shape; for higher Reynolds numbers, an oscillatory droplet behavior occurs; at still higher Reynolds numbers, the droplets shatter. Very often, a recirculation is induced near the contact point just before the droplet shatters, which is also observed for the case of stable oscillating droplets. When a partial-slip boundary condition is applied, it is observed that the stability of the droplet and the rate at which the droplet attains the static contact angle depend strongly on the velocity of slip of the droplet with respect to the solid surface at the contact point. For the two-drop problem, only two distinct behaviors are observed: for low Reynolds numbers and high capillary numbers, the droplet retains a near-spherical shape and remains stable; while for higher Reynolds numbers, the droplet deforms to a high extent and becomes unstable."

No description available.

The current socio-economic and environmental context worldwide, with different actors and needs, requires continued progress towards energy efficiency and environmental improvements in order to create a sustainable future, and this implies a scientific and technologic effort to achieve the proposed goals. Transport by propulsive systems based on reciprocating internal combustion engines (ICE) is one of the major agents affecting future environmental sustainability. Included in the wide research done in this area, one of the options considered is the use of low viscosity oils (LVO) as an option for increasing ICE efficiency. This technology presents a modest contribution to the efficiency target, but the excellent cost-effectiveness ratio and ease of application to current and future vehicle parc are two reasons that has driven towards research into the use of these oils. The low viscosity oils base their contribution to improving energy efficiency by reducing mechanical losses associated with viscous friction in hydrodynamic regime. This in turn reduces energy consumption to operate the system, and it is associated with a reduction of pollutant emissions for the same performance. The hypotheses of application of LVO are well founded, but there are a number of uncertainties surrounding the application of low viscosity oils in MCIA today. On one hand, it is possible to expect a modification of the ICE tribological performance, as well as changes in lubricant performance which ultimately could lead to a reduction in the period of useful life, an early lubrication failure or other consequences difficult to predict. Also, a reduction in viscosity may increase wear production, so there is also an interest in the remote diagnosis of lubricated system status. In this Thesis a concise review of the state-of-the-art has been done applied to ICE tribology and lubricating oils, with special interest in the low viscosity oils development. Then, a series of different studies have been performed to deepen the understanding of oil performance and its influence on ICE wear, supported by a set of physico-chemical analytical techniques applied to diagnose the state of the lubricating oil. The different results obtained show that the application of low viscosity oils in ICE is a viable alternative, since the results obtained in the various tests validate the different hypotheses done, and it opens a line of research possibilities around future enhancements and technology development. / La situación actual a nivel mundial, enmarcada en un contexto socioeconómico y medioambiental complejo, con diferentes actores y necesidades presentes, requiere un avance continuo hacia la eficiencia energética y las mejoras medioambientales de cara a poder crear un futuro sostenible, así como de un esfuerzo científico y tecnológico para poder alcanzar los objetivos propuestos. El transporte mediante sistemas propulsivos basados en motores de combustión interna alternativos (MCIA) es uno de los grandes agentes que afectan a la sostenibilidad medioambiental futura. Dentro de la profunda investigación que se realiza en éste ámbito, una de las opciones estudiadas es la del uso de aceites de baja viscosidad (LVO) como opción para el aumento de la eficiencia de los MCIA. Esta tecnología presenta una aportación modesta al objetivo de eficiencia energética, pero la excelente relación coste-beneficio y la facilidad de aplicación al parque automovilístico actual y futuro son dos razones que han impulsado a la industria hacia la investigación en el uso de estos aceites. Los aceites de baja viscosidad basan su aportación a la mejora de la eficiencia energética en la reducción de las pérdidas mecánicas asociadas a la fricción viscosa en régimen hidrodinámico. Así, se consigue reducir el consumo de energía utilizado para hacer funcionar el sistema, y lleva asociada una reducción de las emisiones contaminantes para el mismo desempeño. La hipótesis de aplicación de los aceites de baja viscosidad están bien fundamentadas, pero existen una serie de incertidumbres alrededor de la aplicación de los aceites de baja viscosidad en MCIA a día de hoy. Por un lado, es posible esperar una modificación del comportamiento tribológico en el propio MCIA, así como una variación del propio comportamiento del lubricante que en último lugar podría provocar una reducción del período de vida útil del mismo, un fallo temprano de lubricación u otras consecuencias difíciles de prever. Además, la bajada de viscosidad puede aumentar el fenómeno de desgaste, por lo que existe también un interés en la cuantificación y diagnóstico de manera continua y remota del estado del sistema lubricado. Así, en esta Tesis se ha realizado un conciso trabajo de revisión del estado del arte de la tribología aplicada a MCIA y de los aceites lubricantes, poniendo especial interés en el desarrollo de la idea de los aceites de baja viscosidad. A continuación, y con el apoyo de un conjunto de técnicas analíticas físico-químicas aplicadas a diagnosticar el estado del aceite lubricante, se han planteado una serie de estudios desde diferentes ámbitos para poder profundizar en el conocimiento del comportamiento del aceite y de su influencia en el desgaste en MCIA. Los diferentes resultados obtenidos señalan que la aplicación de los aceites de baja viscosidad en MCIA es una alternativa viable y exitosa, ya que los resultados obtenidos en los diferentes ensayos realizados validan el comportamiento de esta opción, y abre una línea de posibilidades de investigación alrededor de futuras mejoras y de desarrollo de la tecnología. / La situació actual a nivell mundial, emmarcada en un context socioeconòmic i mediambiental complex, amb diferents actors i necessitats presents, requereix d'un avanç continu cap a l'eficiència energètica i les millores mediambientals de cara a poder crear un futur sostenible, així com d'un esforç científic i tecnològic per poder assolir els objectius proposats. El transport mitjançant sistemes propulsius basats en motors de combustió interna alternatius (MCIA) és un dels grans agents que afecten la sostenibilitat mediambiental futura. Dins de la profunda investigació que es realitza en aquest àmbit, una de les opcions estudiades és la de l'ús d'olis de baixa viscositat (LVO) com a opció per a l'augment de l'eficiència dels MCIA. Aquesta tecnologia presenta una aportació modesta a l'objectiu d'eficiència energètica, però l'excel¿lent relació cost-benefici i la facilitat d'aplicació al parc automobilístic actual i futur són dues raons que han impulsat a la indústria cap a la investigació en l'ús d'aquestos olis. Els olis de baixa viscositat basen la seva aportació a la millora de l'eficiència energètica en la reducció de les pèrdues mecàniques associades a la fricció viscosa en règim hidrodinàmic. Així, s'aconsegueix reduir el consum d'energia utilitzat per fer funcionar el sistema, i porta associada una reducció de les emissions contaminants per a l'obtenció del mateix resultat. Les hipòtesis d'aplicació dels olis de baixa viscositat estan ben fonamentades, però hi ha una sèrie d'incerteses al voltant de l'aplicació dels olis de baixa viscositat en MCIA a dia de hui. D'una banda, és possible esperar una modificació del comportament tribològic en el propi MCIA, així com una variació del propi comportament del lubricant que en últim lloc podria provocar una reducció del període de vida útil d'aquest, una fallada de lubricació primerenca o altres conseqüències difícils de preveure. A més, la baixada de viscositat pot augmentar el fenomen de desgast, pel que existeix també un interès en la quantificació i diagnòstic de manera contínua i remota de l'estat del sistema lubricat. Així, en aquesta Tesi s'ha realitzat un concís treball de revisió de l'estat de l'art de la tribologia aplicada a MCIA i dels olis lubricants, posant especial interès en el desenvolupament de la idea dels olis de baixa viscositat. A continuació, i amb el suport d'un conjunt de tècniques analítiques fisico-químiques aplicades a diagnosticar l'estat de l'oli lubricant, s'han plantejat una sèrie d'estudis des de diferents àmbits per poder aprofundir en el coneixement del comportament de l'oli i de la seva influència en el desgast en MCIA. Els diferents resultats obtinguts assenyalen que l'aplicació dels olis de baixa viscositat en MCIA és una alternativa viable, ja que els resultats obtinguts en els diferents assajos realitzats validen el comportament d'aquesta opció, i obre una línia de possibilitats d'investigació al voltant de futures millores i de desenvolupament de la tecnologia. / Miró Mezquita, G. (2017). Estudio del comportamiento y de la influencia en el desgaste de los aceites lubricantes de baja viscosidad en MCIA [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/78615

Thesis (MScMedSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The basic semen analysis plays a pivotal role in the diagnosis of male infertility and makes a significant contribution to the diagnostic process in andrology, gynecology and clinical urology. In 1902, the man considered to be ―the founding father of modern andrology‖ Edward Martin, proposed that an analysis of a semen sample should be incorporated into all infertility assessments. Following this suggestion in 1956, the scientist John MacLeod advanced the basic semen analysis from beyond a mere observation and introduced the importance of certain semen parameters such as morphology, motility and viscosity. The present day examination includes the analysis of certain established semen parameters, which can provide key information about the quality of a patient‘s semen and the functional competence of the spermatozoa. A semen analysis is also a valuable diagnostic tool in assessing possible disorders of the male genital tract and the secretory pattern of the male accessory sex glands. This information can help to determine the reproductive capacity of the male and can be used in conjunction with the partner to indicate the impact of male genital pathophysiology in the assessment of a couple‘s prospect for fertility. Patients attending the andrology laboratory at Tygerberg Academic Hospital for a semen analysis are referred based on primary, secondary or idiopathic infertility. Amongst these patients, an increase in semen viscosity has been observed over a period of time and created the need to assess the possible causes behind this trend. Despite viscosity being included in a routine spermiogram, it raises a considerable amount of concern as it is assessed semi-quantitatively. In the first part of this study, the possible correlation between seminal hyperviscosity and leukocytospermia was assessed. To achieve the most comprehensive assessment of viscosity, a new approach was used, which is a highly quantitative method to record viscosity in the international unit, centipoise (cP). The analysis of semen samples for possible leukocytospermia was approached by three methods the first of which was cytological. During this method granulocyte grading was performed on stained semen smears during the normal determination of morphology. The same approach was taken for the second method, whereby white blood cell concentrations were quantified with a leukocyte peroxidase test in the total sample group (n=200). Viscosity was compared between the samples classified as leukocytospermic positive or negative, according to the set reference values of the World Health Organisation (WHO). Correlation analysis between the two variables was also performed. In the biochemical approach of detecting leukocytospermia, an enzyme-linked immunoabsorbant assay (ELISA) was used to quantify the concentration of the extracellular polymorphonuclear (PMN) enzyme released from leukocytes. This test was performed on 124 randomly selected samples. All samples were fractionated before storage in liquid nitrogen, to allow for multiple assessments to be performed on each sample. The PMN elastase concentration was assessed against viscosity to investigate a possible correlation and relationship with the presence of leukocytospermia. All three methods of detecting possible infection showed a significantly positive relationship with increased viscosity in semen samples. The second approach in the study was to assess increased viscosity and leukocytospermia against parameters included in the spermiogram. An evaluation of hyperviscosity and its correlations to the various other semen parameters can allow for a detailed study into the effects that this anomaly may elicit. With the assessment of each of the sperm parameters against the leukocyte count and viscosity (cP), volume, concentration and morphology showed significance. To further the study, the third angle was to investigate a possible correlation between viscosity and the functional status of the male accessory sex glands. The biochemical approach of assessing the secretory patterns of the prostate and seminal vesicles against markers of infection can possibly further the understanding behind hyperviscous semen and leukocytospermia. Citric acid and fructose, secretory products of the prostate and seminal vesicles respectively, showed no significance when assessed against the leukocyte count and viscosity. However, this project was a pilot study and this approach offers an exciting avenue for further research. These research findings may provide a more comprehensive assessment of a man‘s fertility status. Seen in the context of patients attending the andrology laboratory of Tygerberg Academic Hospital, this is greatly needed as the majority of these patients cannot afford advanced assisted reproductive therapies. The introduction of a more accurate method of quantifying viscosity may possibly help to identify, diagnose and treat patients suffering from leukocytospermia in order to ultimately enhance their fertility potential. / AFRIKAANSE OPSOMMING: Die basiese semenanalise speel 'n belangrike rol in die diagnose van manlike infertiliteit en maak dus 'n betekenisvolle bydrae tot die diagnostiese proses in andrologie, ginekologie en kliniese urologie. In 1902 het Edward Martin, wat deur sommige navorsers as die vader van moderne andrologie beskou word, voorgestel dat 'n semenanalise deel moet vorm van alle infertiliteitsondersoeke. In 1956 het die wetenskaplike John MacLeod aanvoorwerk gedoen om die grondslag van 'n basiese semenanalise daar te stel, wat beteken het dat, in plaas van net 'n observasie studie te doen, 'n semenmonster kwantitatief analiseer moes word en dat parameters soos spermmorfologie, motiliteit en viskositeit as deel van die volledige analise gedoen moet word. Die hedendaagse analise sluit, behalwe die basiese semenparameters, ook inligting in oor die funksionele aspekte van spermatozoa. Die semenanalise is dus ook ‗n belangrike diagnostiese hulpmiddel om inligting rakende moontlike abnormaliteite in die manlike genitale traktus en die sekretoriese funksies van die manlike bykomstige geslagskliere te verskaf. Hierdie inligting kan help om 'n moontlike diagnose van die man se fertiliteitspotensiaal te maak. Terselftertyd kan dit ook tesame met die metgesel se reproduktiewe inligting meer lig werp op die impak van die man se genitale patofisiologie op die paartjie se fertilitetspotensiaal. Pasiënte wat die andrologielaboratorium van die Tygerberg Akademiese Hospitaal besoek word verwys op grond van primêre, sekondêre of idopatiese infertiliteit. Gedurende die laaste aantal jare is daar ‗n toename in voorkoms van verhoogde semenviskositeit onder hierdie groep pasiënte waargeneem. Dit het die behoefte laat ontstaan om die moontlike redes hiervoor te ondersoek. Ten spyte van die feit dat viskositeit deel vorm van die roetine semenanalise is dit tog kommerwekkend aangesien dit op 'n semi-kwantitatiewe manier bepaal word. In die eerste deel van hierdie studie is 'n moontlik korrelasie tussen seminale hiperviskositeit en leukositospermie ondersoek. Om die beste moontlike verwantskap te kon bepaal is 'n nuwe en hoogs kwantitatiewe metode gebruik om viskositeit in numeriese waardes volgens internasionale standaarde in centipoise (cP) te meet. Daar is van drie metodes gebruik gemaak om die teenwoordigheid van leukositospermie in 'n semenmonster te ondersoek. Die eerste metode was die sitologiese metode waar die teenwoordigheid van granulosiet op die gekleurde semensmeer tydens die standaard morfologie beoordeling bepaal word. Die tweede was deur middel van 'n leukosietperoksidase toets waarmee daar 'n kwantitatiewe telling gedoen kan word, soos teenwoordig in 'n voorbereide semenmonster. Hierdie twee bepalings is op die totale studiepopulasie van 200 pasiënte gedoen. Die viskositeit van monsters met of sonder die teenwoordigheid van leukositospermie, soos bepaal met die voorafgaande metodes en gebaseer op die WGO riglyne, is met mekaar vergelyk. Korrelasies is ook tussen hierdie twee veranderlikes en verskeie semenparameters van hierdie twee groepe gedoen. Die derde metode was 'n biochemiese ontleding met behulp van 'n ensiemgekoppeldeimmuunsorberende essai (ELISA) vir die bepaling van die ekstrasellulêre konsentrasie van polimorfonukleêre (PMN) elastase ensiem in die seminale plasma. Hierdie toets is op 124 lukraak gekose semenmonsters uitgevoer. Alle monsters is gefraksioneer voor berging in vloeibare stikstof om meervoudige analises van elke monster moontlik te maak. Die PMN elastase konsentrasies is vergelyk met die viskositeit van die semenmonsters vir 'n moontlike korrelasie en verwantskap met die teenwoordigheid van leukositospermie. Die resultate van al drie hierdie metodes, vir die moontlike bepaling van infeksie, het 'n betekenisvolle positiewe verwantskap met die toename in graad van viskositeit in semenmonsters aangetoon. Die tweede benadering van hierdie studie was om die viskositeitsgradering en die kwantitatiewe leukositopermie waardes te vergelyk met die semenparameters wat bepaal is tydens die semenanalise. Die doel van hierdie benadering was om enige verwantskap of effek van viskositeit asook die teenwoordigheid van witbloedselle op die semenparameters te ondersoek. Daar is betekenisvolle verwantskappe gevind tussen die viskositeitstatus van 'n semenmonster, die teenwoordigheid van witbloedselle en die semenparameters, soos motiliteit, morfologie en spermatosoa konsentrasie. Die derde benadering was om 'n ondersoek te doen na die moontlike verwantskap tussen viskositeit en die sekretoriese funksies van die manlike bykomstige geslagskliere, te wete die prostaat en seminale vesikula. Die biochemiese ondersoek na die sekresies van hierdie twee organe, naamlik fruktose en sitroensuur, is gedoen om te bepaal of die teenwoordigheid van infeksies van die manlike traktus, en waargeneem as leukositospermia, ook in verband gebring kan word met die viskositeitstatus van 'n semenmonster. Daar is geen verband gevind tussen die sekresies van hierdie twee kliere en die viskositeit van die semenmonsters nie. Aangesien hierdie deel van die studie net as 'n loodsprojek beskou is, is die biochemiese bepalings slegs op 'n beperkte aantal semenmonsters uitgevoer en kan hierdie tipe ondersoek as 'n moontlike verdere studie onderneem word. Hierdie navorsingsresultate kan lei tot ‗n meer omvattende assessering van mans se fertiliteitstatus. Dit is uiters noodsaaklik in die konteks van omstandighede van die pasiënte wat die andrologielaboratorium van die Tygerberg Akademiese Hospitaal besoek aangesien die meerderheid nie gevorderde in vitro behandeling kan bekostig nie. Die akkurate bepaling van 'n semenmonster se viskositeit kan dus moontlik waarde toevoeg tot die identifisering, diagnose en behandeling van pasiënte met leukositospermie om sodoende hulle fertiliteitspotensiaal te verbeter.

Thesis (PhD)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: Alkali-soluble rheology modifiers are commercially synthesised via conventional freeradical polymerisation processes. This results in the end product having certain limitations; there is poor control over the molar mass, molar mass distribution and chain architecture of the polymer chains. These limitations can be overcome by using a controlled/living free radical polymerisation process, for example the RAFT process. This alternate method of synthesis was used here to prepare model alkali-soluble rheology modifiers. The structure/property relationships of model alkali-soluble rheology modifiers synthesised via the RAFT process were studied. Model alkali-soluble rheology modifiers of different molar masses and chain architectures (block, co- and ter-polymers) were successfully synthesised by the RAFT polymerisation of methyl methacrylate, methacrylic acid and various hydrophobic macromonomers. The different types of alkali-soluble rheology modifiers were synthesised in solution and in miniemulsion. Each of the two systems had certain advantages and disadvantages. The conversion limit of reactions in solution was about 60 % and reaction times were much slower than those of the miniemulsion reactions. Higher final conversions were recorded for miniemulsion reactions, reactions were faster and no solvent removal was required. Unfortunately it was not possible to synthesise all the different types of associative rheology modifiers investigated here in a miniemulsion system. The latex solutions thickened with conventional rheology modifiers (co-polymers) show very contrasting behaviour (rheology profile and dynamic properties) to that of the latex solutions thickened with the associative rheology modifiers (ter-polymers). The AB block copolymers gave the latex solutions rheology results between those obtained with conventional rheology modifiers and those with the associative rheology modifiers. Varying the number of ethylene oxide spacer units in the hydrophobic macromonomers of the associative rheology modifiers had a significant influence on the rheology properties of the latex and alkali solutions. As the number of ethylene oxide spacer units was increased from 20 to 100 there was a significant increase in the zero-shear viscosity of the latex solutions thickened with the associative rheology modifiers. Contrasting results were obtained for the polymer solutions (no latex present), where the use of the associative rheology modifiers containing the highest number (EO = 100) of ethylene oxide spacer units resulted in solutions with the lowest viscosity, but the rheology modifiers containing the 50 ethylene oxide spacer units gave the highest steady shear viscosity. / AFRIKAANSE OPSOMMING: Alkali-oplosbare reologie-modifiseerders word kommersieël gesintetiseer d.m.v. konvensionele vrye-radikaal polimerisasieprosesse. Hierdie prosesse lewer gewoonlik 'n eindproduk met sekere tekortkominge, a.g.v. swak beheer oor molekulêre massa, molekulêre massa-verspreiding, en polimeerkettingstruktuur (Eng. chain architecture). Hierdie tekortkominge kan oorbrug word deur gebruik te maak van 'n beheerde/lewende vrye-radikaal polimerisasieproses, soos byvoorbeeld die RAFT-proses (Eng. RAFT: reversible addition-fragmentation chain transfer polymerisation). Hierdie alternatiewe metode is in die studie gebruik om model alkali-oplosbare reologiemodifiseerders te sintetiseer. Die struktuur-eienskapverhoudings van die model alkali-oplosbare reologie modifiseerders wat d.m.v. die RAFT-proses gesintetiseer is, is bestudeer. Model alkali-oplosbare reologiemodifiseerders van verskillende molekulêre massas en kettingstrukture (blok, ko- en ter-polimere) is suksesvol gesintetiseer d.m.v. RAFT-polimerisasie van metielakrilaat, metakrielsuur en hidrofobiese makromonomere. Die verskillende alkali-oplosbare reologiemodifiseerders is in organiese oplosmiddel sowel as in mini-emulsie gesintetiseer. Elkeen van die sisteme het sekere voordele en nadele getoon. In die reaksies wat in organiese oplosmiddels gedoen is, is slegs 60 % van die monomere ingebou in die polimeerkettings en die tydsduur van hierdie reaksie was heelwat langer as by die wat uitgevoer is in mini-emulsie. Meer as 60 % van die monomere is omgeskakel na polimeer tydens die reaksies wat in mini-emulsie uitgevoer is, die reaksietempo was vinniger en dit was nie nodig om die organiese oplosmiddel te verwyder nie. Ongelukkig was dit nie moontlik om al die verskillende tipes assosiatiewe-reologiemodifiseerders (Eng: associative rheology modifiers) in miniemulsie te sintetiseer nie. Die lateks wat met konvensionele reologiemodifiseerders (ko-polimere) verdik is, het kontrasterende eienskappe (reologie-profiel en dinamiese eienskappe) getoon teenoor die van die lateks-oplossings wat met assosiatiewe-reologiemodifiseerders (ter-polimere) verdik is. Die AB-tipe blok ko-polimere gee reologieresultate vir die lateks-oplossings wat lê tussen die wat bepaal is vir konvensionele reologieodifiseerders en assosiatiewe reologiemodifiseerders. Variasie in die aantal etileenoksiedeenhede in die hidrofobiese makromonomere van die assosiatiewe reologiemodifiseerders het 'n betekenisvolle invloed op die reologie-eienskappe van die lateks, sowel as die alkali-oplossings gehad. Namate die aantal etileenoksiedeenhede van 20 tot 100 vermeerder is, het 'n betekenisvolle verhoging in die "zero-shear " viskositeit van die lateks oplossings wat met die assosiatiewe reologiemodifiseerders verdik is voorgekom. Teenstrydige resultate is verkry vir die polimeeroplossings met geen lateks teenwoordig nie: die assosiatiewe reologiemodifiseerders met die hoogste aantal etieleenoksiedeenhede (EO = 100) het die laagste viskositeitsresultate opgelewer en die reologiemodifiseerders met slegs 50 etieleenoksiedeenhede het die hoogste viskositeitsresultate gelewer.

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The mass transfer area of nine structured packings was measured as a function of liquid load, surface tension, liquid viscosity, and gas rate in a 0.427 m (16.8 in) ID column via absorption of CO₂ from air into 0.1 mol/L NaOH. Surface tension was decreased from 72 to 30 mN/m via the addition of a surfactant (TERGITOL[trademark] NP-7). Viscosity was varied from 1 to 15 mPa·s using poly(ethylene oxide) (POLYOX[trademark] WSR N750). A wetted-wall column was used to verify the kinetics of these systems. Literature model predictions matched the wetted-wall column data within 10%. These models were applied in the interpretation of the packing results. The packing mass transfer area was most strongly dictated by geometric area (125 to 500 m²/m³) and liquid load (2.5 to 75 m³/m²·h or 1 to 30 gpm/ft²). A reduction in surface tension enhanced the effective area. The difference was more pronounced for the finer (higher surface area) packings (15 to 20%) than for the coarser ones (10%). Gas velocity (0.6 to 2.3 m/s), liquid viscosity, and channel configuration (45° vs. 60° or smoothed element interfaces) had no appreciable impact on the area. Surface texture (embossing) increased the area by 10% at most. The ratio of effective area to specific area (a[subscript e]/a[subscript p]) was correlated within limits of ±13% for the experimental database: [mathematical formula]. This area model is believed to offer better predictive accuracy than the alternatives in the literature, particularly under aqueous conditions. Supplementary hydraulic measurements were obtained. The channel configuration significantly impacted the pressure drop. For a 45°-to-60° inclination change, pressure drop decreased by more than a factor of two and capacity expanded by 20%. Upwards of a two-fold increase in hold-up was observed from 1 to 15 mPa·s. Liquid load strongly affected both pressure drop and hold-up, increasing them by several-fold over the operational range. An economic analysis of an absorber in a CO₂ capture process was performed. Mellapak[trademark] 250X yielded the most favorable economics of the investigated packings. The minimum cost for a 7 m MEA system was around $5-7/tonne CO₂ removed for capacities in the 100 to 800 MW range. / text