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Thesis (MScIng)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: Spherical wax particles with diameters of 5 μm and less are known to enhance the properties of powder and solvent-based coatings. Conventional methods, including spray freezing and jet milling, yield only 15 – 20 % of particles within this desired size range. Recently, supercritical fluids have been used in the micronisation of a variety of polymers, pharmaceuticals and other inorganic solids. Of these processes, the Rapid Expansion of Supercritical Solutions (RESS) involves the expansion of a solid dissolved in a supercritical fluid over a nozzle. In the process the solubility of the solid is drastically decreased to yield high supersaturated conditions, resulting in a multitude of small and stable wax nuclei. The technique is known to produce small, solvent free particles with a narrow size distribution. In this project, the RESS technique was applied to two commercial Fischer-Tropsch waxes: Paraflint C80 and Paraflint C105. Propane was selected as supercritical solvent due to its increased solvent power for paraffin wax compared to other conventional supercritical solvents such as carbon dioxide and ethane. From theoretical studies, nozzle geometry, as well as nozzle inlet temperature, pressure and concentration was identified as the parameters most likely to influence the size and shape of the wax particles. Porous plate nozzles were chosen as expansion device due to lower pressure drop and higher flow rate of the expanding solution compared to conventional capillary nozzles. Pre-expansion conditions of 125 to 160 ºC and 125 – 180 bar were investigated. Wax concentrations up to 5 weight % were expanded through porous plate nozzles with pore sizes of 15, 25 and 60 μm. It was found that small particles, less than 5 μm in size could readily be produced for the whole range of parameters investigated. Average particle sizes of less than 2 μm were found in virtually all cases. The C80 particles tended to be less smooth and of more angular shape than C105 particles. It is argued that the higher fraction of low weight compounds softens the C80 wax particle surface, making them more susceptible to deformation and coagulation. Experimental studies confirmed that a combination of lower temperature and higher pressure (175 bar and 130 ºC) increases the chances for the formation of spherical particles. This combination corresponded to conditions furthest away from the dew point of the solution. The 25 μm porous plate nozzle gave better results than the other nozzles, indicating that the characteristics of the nozzle could play a more important role than the pore size. SEM images indicated that this nozzle has a larger porosity, which could have resulted in lower pressure drops compared to the other nozzles. Higher wax concentration did seem to give smaller individual particles, but particle shape visibly deteriorated as the concentration increased. From experiments with C105 wax, at these optimal conditions, it seems as if a maximum concentration between 4 and 5 % is achievable, above which the particle shape became flak-like with rough edges. Due to limitations of the batch experimental set-up, especially regarding the reaching of steady state, it is strongly recommended that the obtained results be verified on pilot plant scale, where longer spray times can be achieved. The RESS process for wax micronisation on industrial scale needs to be critically examined and higher pressure and solvent recycling costs would need to be weighed up against the lower wax recycling required to obtain the desired particles. / AFRIKAANSE OPSOMMING: Sferiese was partikels met ’n deursnee van 5 μm en minder is bekend daarvoor dat dit die eienskappe van ’n verskeidenheid van poeier en oplosmiddel-gebaseerde deklae verbeter. Alledaagse metodes, waaronder sproeivries- en maalprosesse soos straalmaling, lewer slegs sowat 15 – 20 % van die partikels binne die gewenste partikelgrootte. In die afgelope tyd is superkritiese vloeistof mikroniseringsprosesse gebruik om ’n verskeidenheid van polimere, farmaseutiese en ander anorganiese stowwe te mikroniseer. Die sogenaamde “Rapid Expansion of Supercritical Solutions (RESS)”– proses behels die ontspanning van ’n oplossing van die vaste stof en ’n superkritiese oplosmiddel oor ’n spuitstuk. In die proses verlaag die oplosbaarheid van die vaste stof drasties, sodat hoë superversadigde vlakke in ’n baie kort tydperk bereik word om ’n menigte klein en stabiele was kerne te vorm. Die tegniek is bekend daarvoor om fyn, oplosmiddelvrye partikels met ’n nou partikelgrootteverspreiding te lewer. In hierdie projek is die RESS-proses ondersoek om twee Fischer-Tropsch wasse, C80 en C105, te mikroniseer. Propaan is as oplosmiddel gekies weens die verhoogde oplosbaarheid van paraffienwasse daarin vergeleke met ander konvensionele superkritiese oplosmiddels soos koolsuurgas en etaan. Poreuse skywe is as spuitstukke verkies weens die feit dat hoër vloeitempos en laer drukvalle oor hierdie spuitstukke verkry kan word. Na ’n teoretiese ondersoek is spuitstukgeometrie, asook die temperatuur, druk en konsentrasie by die spuitstukinlaat geïdentifiseer as die prosesparameters wat die partikelgrootte en –verspreiding die waarskynlikste sal beïnvloed. Daar is besluit om die spuitstukinlaatkondisies van 125 tot 160 ºC en 125 tot 180 bar te ondersoek. Waskonsentrasie tot en met 5 massa % is deur poreuse skywe met gemiddelde poriegroottes van 15, 25 en 60 μm ontspan. Klein waspartikels, met gemiddelde partikelgroottes van minder as 2 μm is in feitlik al die gevalle verkry. Die C80 waspartikels het geneig om minder glad en meer hoekig as die C105 partikels te wees. Hier word vermoed dat die hoër hoeveelheid lae massa komponente die C80 waspartikeloppervlak versag en dit meer vatbaar maak vir vervorming en koagulasie. Eksperimentele studies het getoon dat ’n kombinasie van laer temperature en hoër drukke (175 bar en 130 ºC) by die spuitstukinlaat die kanse vir sferiese partikels vergroot. Hierdie temperatuur/druk kombinasie val saam met toestande verder weg van die doupunt van die oplossing. Sover dit die spuitstukke aanbetref, het die 25 μm poreuse skywe beter resultate as die ander spuitstukke gelewer. Hier word vermoed dat die fisiese eienskappe van die spuitstuk ’n meer prominente rol as die poriegrootte speel. SEM foto’s het getoon dat hierdie spuitstuk ’n groter porositeit, wat ’n laer druikval tot gevolg kon gehad het, in vergelyking met die ander spuitstukke. Dit blyk asof hoër waskonsentrasies lei tot kleiner individuele partikels, maar die vorm en oppervlak daarvan het sigbaar verswak by hoër konsentrasie. Vanuit eksperimente met C105 was, by die bovermelde optimale kondisies, wil dit voorkom asof ’n maksimum konsentrasie tussen 4 en 5 % haalbaar is, voordat die partikels ’n vlokkierige vorm met ruwe oppervlak aangeneem het. Weens die beperkinge van die eksperimentele opstelling, word dit ten sterkste aanbeveel dat die resultate op loodsaanlegskaal, waar langer sproeitye moontlik is, bevestig word. Die RESS-proses behoort krities ondersoek te word en die hoër druk en oplosmiddel hersirkuleringskoste moet opgeweeg word teenoor die voordele van die laer was hersirkulering benodig om die gewenste partikels te lewer.

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.

Thesis (M.S.)--University of Michigan, 1958.

Submitted in fulfillment of the requirements for the Master's of Technology: Chemistry, M L Sultan Technikon, 1999. / Saturated long chain hydrocarbons, such as paraffin waxes, have a large variety of applications. These applications may, however, be restricted by certain properties of the wax such as brittleness and in compounding. Cross-linking of the long chains in waxes may provide improved physical properties and hence a wider application of these waxes / M

Montan wax has been extracted from the lignite deposits of Germany since the early part of the twentieth century, The wax was named by von Boyen (1901), The word Montan is derived from the Latin term montanus meaning "of a mountain," The wax has found extensive uses in polishes, insulating materials, candles, explosives, and special applications in the rubber industry, The increased demand for waxes for industrial uses and the limited supply of domestic origin has made the study of the sources and characteristics of domestic waxes desirable, California lignite has been shown to be a valuable source of Montan wax, The object of this research is to improve upon the physical and chemical properties of the extracted wax,

Waxes have many potential uses but large-scale application is hampered by their virtual insolubility. By grafting the wax with a polyethylene glycol segment to form an alcohol ethoxylate, the solubility of the wax in commercial solvents is significantly increased. Alcohol ethoxylates are produced by the polymerisation addition of ethylene oxide onto an oxidised wax. Current methods of alcohol ethoxylate production from alcohols lead to wide ethylene oxide addition distribution and large quantities of residual alcohol. The objective of this study is to provide a method for narrowing the ethylene oxide distribution and to reduce the residual alcohol content. It is proposed to concentrate the alcohol ethoxylate in a post-production separation process using supercritical fluid extraction. The system is modelled to contain three pseudo-components: an alkane, an alcohol and an alcohol ethoxylate. Propane is selected as the supercritical solvent of choice due to the large solubility difference between the alkane and polyethylene glycol. Lower molecular weight alkane phase equilibrium data with propane is abundant but extrapolation to higher molecular weights requires further investigation as it may be complicated by molecular folding. Molecular folding occurs in crystalline polyethylene and high molecular weight normal alkanes but information regarding molecular folding in solution is inconclusive. A model is proposed for molecular folding of normal alkanes in supercritical solution. A high molecular weight alkane mixture is synthesised and phase equilibrium measurement with propane are conducted. A lower molecular weight alkane mixture is used to prove the application of the principle of congruency to high-pressure phase equilibria. In the high wax mass fraction region the measurements are between the no-folding and once-folded relationship, indicating the possibility of partial molecular folding. In the mixture critical and low wax mass fraction region the measurements are similar to the non-folding relationship. Molecular folding in solution is thus dependent on the solution concentration. No phase equilibria measurements exist for propane with either high molecular weight alcohols or alcohol ethoxylates. Measurements of propane with an alcohol mixture show total solubility below 140barA for temperatures up to 408K. Measurements of propane with an alcohol ethoxylate at temperatures between 378 and 408K shows that for an alcohol ethoxylate mass fraction between 0.025 and 0.5 pressures greater than 275barA are required for solubilisation. When comparing the solubility of the three pseudo-components, the alkane is the most soluble followed by the alcohol. The alcohol ethoxylate is the least soluble. A counter-current supercritical extraction process is proposed for the concentration of the alcohol ethoxylate. Pilot plant tests were conducted and the proposed set-up shows good separation. An estimate of the energy requirements shows that heating and cooling constitute the majority of the energy required but with the use of heat integration it can be reduced by approximately 33%. This work thus shows that the proposed process is both technically and economically viable. Although this work has provided a method for concentrating the alcohol ethoxylate, the process has not been optimised yet and future work includes the fine-tuning of this process.

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.

Partially hydrogenated oil (PHO) has no longer GRAS status. However, PHO is one of the important ingredients in bakery and confectionary industry and therefore the food industry is seeking for an alternative fat to replace PHO. Waxes have shown promise to fulfill that demand because of its easy availability and cheap in price. Waxes with high melting points (> 40 °C) help in the crystallization process when mixed with low melting point oils. A crystalline network is formed in this wax/oil crystallization process where liquid oil is entrapped in wax crystal network. A new material is formed which is neither completely solid nor completely liquid; it’s called semisolid material. This wax/oil semisolid material is formed physically; there are no chemical processes or treatments involved. This material has a potential use in the lipid industry due to its resemblance to the properties of commercial margarine or similar lipids. BW has shown softer crystalline network formation compared to SFW and RBW. It is understood that presence of higher wax ester in SFW and RBW leads to stronger crystalline material formation. Blending waxes of different chemical composition (e.g. BW: wax ester, hydrocarbon, fatty acids, di-esters, hydroxyl esters. RBW: 100% wax ester) shows differences in physical characteristics at different blending proportions. HIU technology helps in delaying phase separation of crystals in low concentration (0.5 and 1% wt. basis) of wax/oil system. Our overall wax crystallization study has shown that there are different physical characteristics of wax/oil semi-solid system based on different parameters and processing conditions such as wax concentration, wax and oil type, cooling rate, storage temperature, high intensity ultrasound. The hypothesis of this dissertation is that chemical composition of waxes and vegetable oils and also processing conditions affect wax crystallization and physical properties of wax/oil materials.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 85-87). Also available via the Internet.