Breathable water-repellent garments are common products on the outdoor market. There are many recommendations on how to wash and waterproof your garment in order to make sure that its water-repellence is cared for, but the advice given by different sources is inconsistent. Are expensive products really necessarily or are regular laundry products just as good? What waterproofing agents should one use in order to insure that the water-repellent layer is restored? Four different water-repellent wash-in products were tested on polyester and polyamide fabrics. Seven laundry products and two water-repellent wash-in products were tested on jackets with dendrimer based finishes and untreated polyamide fabrics. The results were evaluated by spray testing according to ISO EN 24920 and sessile drop tests. Not all wash-in products offer good water-repellence on polyamide and polyester fabrics. Two laundry detergents decreased the water-repellence of the jackets. The laundry detergents did not affect the function of wash-in waterproofing agents on the jackets. The water-repellence of one wash-in product was affected by the use of two different detergents on untreated fabric / Program: Textilingenjörsutbildningen

Inspired by a planar partitioning problem involving multiple unbounded chambers, this thesis investigates using classical techniques what can be said of the existence, uniqueness, and regularity of minimizers in a certain free-endpoint isoperimetric problem. In two cases, a full existence-uniqueness-regularity result is proved using a convexity technique inspired by work of Talenti. The problem studied here can be interpreted physically as the identification of the equilibrium shape of a sessile liquid drop in half-space (in the absence of gravity). This is a well-studied variational problem whose full resolution requires the use of geometric measure theory, in particular the theory of sets of finite perimeter. A crash course on the theory required for the modern statement of the equilibrium shape theorem is presented in an appendix. / Thesis / Master of Science (MSc)

No description available.

Povrchy inorganických materiálov, zvlášť kovov alebo kovových oxidov, ktoré sú často charakteristické vysokou povrchovou energiou, sú zvyčajne kontaminované adsorbovanými organickými molekulami. Tieto molekuly majú na povrchy zväčša nepriaznivý vplyv, do značnej miery napríklad ovplyvňujú funkcionalitu a výkonnosť polovodičov a znemožňujú, prípadne sťažujú prevedenie povrchových úprav na povrchoch kovov aj keramík. Taktiež majú nepriaznivý vplyv na priľnavosť. Adsorbované častice spôsobujú znižovanie hydrofilicity povrchu. Hydrofilicita, adhezivita a zmáčavosť povrchu sa veľmi dobre posudzujú prostredníctvom merania kontaktného uhlu. V tejto práci je značná pozornosť venovaná práve meraniu statického kontaktného uhlu. [10] Samotné meranie kontaktného uhlu je možné vykonať rôznymi spôsobmi, v tejto práci bol však použitý najvhodnejší prístup, a to metódou „sessile-drop“, teda pokladanej alebo depozitovanej kvapky na meraný povrch. K meraniu bol využitý klasický „sessile-drop goniometer“, teda aparatúra, ktorá pozostávala z nastaviteľného stojanu na vzorky, nad ktorým bol umiestnený zdroj svetla, a objektívu fotoaparátu, ktorý bol prepojený s kamerou zabudovaného smartfónu. Meranie prebiehalo tak, že kvapka s objemom 3L destilovanej superčistej vody bola depozitovaná na povrch substrátu pomocou mikroinjekčnej striekačky. Cieľom tejto práce bolo nielen stanoviť kontaktné uhly a porovnať ich hodnoty medzi rôznymi typmi materiálov navzájom a po upravách tepelného a/lebo chemického charakteru. Vyhodnotené údaje zachycovali zmeny, ku ktorým došlo na povrchoch daných keramických materiálov pri adsorpcii organických molekúl. Proces tepelnej úpravy (kalcinácia na teplote 800°C, následne pokles na teplotu 600°C, po celkovú dobu 16 hodín) bol aplikovaný na všetkých typoch vzoriek, kde niektoré sa medzi sebou líšili teplotou slinovania. Ihneď po kalcinácii boli vzorky podrobené meraniu kontaktných uhlov, z ktorého jasne vyplynulo, že hydrofilicita a zmáčavosť povrchu sa zvýšila. Tento jav bol pozorovaný na všetkých vzorkách, a na všetkých vzorkách sa hodnoty kontaktného uhlu líšili veľmi významne od hodnoty, ktorá bola získaná v tzv. primárnom meraní. Všetky detailné hodnoty a vyhodnotené výsledky sú posudzované v časti diskusia. Ďalšou úpravou povrchu, ktorá bola vykonaná na vybraných vzorkách, bolo čistenie povrchu etanolom. Proces bol opäť realizovaný na všetkých vzorkách. Potom, ako boli zrealizované všetky merania na kalcinovaných vzorkách, boli všetky tieto vzorky ponorené do etanolu na približne 2 hodiny. Po vybratí vzoriek a ich osušení na vzduchu boli uskutočnené ďalšie merania kontaktných uhlov. Výsledky priniesli opäť rozdielne hodnoty v porovnaní s predchádzajúcimi meraniami a sú rozvinuté v časti diskusia.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: See item for full text / AFRIKAANSE OPSOMMING: Sien item vir volteks

The surface response of a polymer substrate to external stimuli such as initial wetting is controlled by the outermost molecular layer. Thus, changes on the nanoscale may be engaged to control macroscale wetting behavior. Our work has predominantly focused on surface modification of conventional polyurethane coatings (HMDI-BD-PTMO). Studies on network constrained phase separation and facile polydimethylsiloxane surface functionalization led to the discovery of a simpler one-step and more general approach to functional polymer surfaces that we have designated as “Bottle-Brush Nanoglass” (BB-NG) after the two principle components: (a) a polyoxetane soft block “spine” with side chain “A” bristles and triethoxysilyl chain ends and (b) an alkoxysilane that together with BB chain ends comprise precursors to a “nanoglass”, NG phase. This paper focuses on the extent of modification for a conventional aliphatic polyurethane using a range of fluoropolyoxetane (poly(trifluoroethoxymethyl-methyl oxetane) diol) or 3F diol based modifier concentrations. Upon generating a blend of the polyurethane with the modifier, the BB-NG which is a minor constituent of the blend, phase separates to provide the topmost layer of the coating. Initial results demonstrate that the modified polymer coatings exhibit an expected increase in contact angles with water. Wetting behavior was characterized using the sessile drop technique as well as Dynamic Contact Analysis (DCA, Wilhelmy Plate). Surface composition as well as near surface topology and morphology are characterized by X-ray Photoelectron Spectroscopy (XPS) and Tapping Mode Atomic Force Microscopy (TM-AFM) respectively. Contrast in phase images reflect the surface modulus and viscoelasticity, from which physical form or compositional differences may be deduced. These characteristics have also been explored in our study by hardness tests via nanoindentation.

The objective of this research work was to develop a methodology for experimentally estimating the interfacial properties at slag-metal interfaces. From previous experiments carried out in the division, it was decided to use surface active elements like sulfur or oxygen to trace any motion at the interface. For this purpose the following experimental investigations were carried out. Firstly the density of slag was estimated using the Archimedes Principle and the Sessile Drop technique. The density of the slag would give the molten slag height required for the surface active element to travel before reaching the slag-metal interface. Diffusivity measurements were uniquely designed in order to estimate the sulfur diffusion through slag media. It was for the first time that the chemical diffusivity was estimated from the concentration in the metal phase. Experiments carried out validated the models developed earlier. The density and diffusivity value of sulfur in the slag was used to accurately capture the time for sulfur to reach the slag-metal interface. The oscillations were identified by calculating the contact angle variations and the interfacial velocity was estimated from the change in the surface area of the liquid iron drop. The interfacial tension was estimated from the contact angles and the interfacial dilatational modulus was calculated. Based on cold model experiments using water as well as mercury, an equation of the dependence of the interfacial shear viscosity on the interfacial velocity and interfacial tension was established. This paved way for the estimation of the interfacial shear viscosity at the slag-metal interface. The present study is expected to have a strong impact on refining reactions in pyometallurgical industries where slag/metal interfaces play an important role. From a fundamental view point, this provides a deeper insight into interfacial phenomena and presents an experimental technique to quantify the same. / QC 20101130

La maîtrise de la fabrication de films de suspension colloïdale par évaporation constitueencore à ce jour, un véritable verrou scientifique pour l’élaboration des matériaux. Le séchage desuspensions colloïdales entraine souvent des défauts de surface et de volume dans le film. Lorsque lesparticules sont molles, les films sont continus mais présentent des défauts de plissement de surface.Lorsque les particules sont dures (latex vitreux, silice..), le film se fissure et se délamine. Ces défautssont souvent liés aux contraintes résiduelles dans le gel à la fin du séchage qui sont dues à la pressioncapillaire causée par la déformation des ménisques d’eau à la surface des films. Par contre on neconnait pas encore l’échelle de taille où agit la contrainte ni la relation entre la contrainte et la périodedes craquelures.Dans ce travail de thèse, nous étudions la morphologie des craquelures dans des films dedivers mélanges de suspensions colloïdales, élaborés par séchage. Ces mélanges sont composés departicules dures (polystyrène et PBMA réticulés) et molles (PBA et PBMA). La structurenanométrique de ces mélanges est caractérisée par diffusion de neutron et par turbidité. Nousdisposons de mélanges avec diverses structures et divers états de dispersion. Certains mélangescontiennent des particules dispersées à l’échelle nanométrique (l’ordre de grandeur est celle de la tailledes particules - 50 nm) alors que d’autres contiennent des particules agrégées. L’étude de lamorphologie des craquelures est réalisée sur des gouttes sessiles avec séchage à la surface libre. Descraquelures radiales périodiques sont observées lors du séchage. Nous observons que la période descraquelures augmente avec l’augmentation de la fraction en particules molles et de la température maistoute en conservent la périodicité. Nous avons mis en évidence que le rapport : période des craqueluressur l’épaisseur des films λ/h est le seul paramètre qui décrit parfaitement la morphologie descraquelures pour un séchage au niveau d’une surface libre. Nous avons aussi démontré que ce rapportλ/h ne peut pas descendre au-dessous de 2 même dans le cas de particules vitreuses. Le séchage induitde fortes contraintes résiduelles dans le gel qui permettent à certaines fibres situées entre deuxcraquelures de délaminer radialement. Ce phénomène de délamination s’estompe avec la dissipationdes contraintes. Nous avons démontré que le modèle mécanique de Russel ne permet pas de décrire lapériode de craquelures loin de la contrainte critique. Nous proposons ainsi dans le cadre de notretravail, un autre modèle plus à même à caractériser la périodicité de ces craquelures. Nous avonsremarqué que les propriétés du substrat n'ont aucune incidence sur la morphologie des craquelures. Letaux d'évaporation modifie la morphologie des craquelures, où dans le cas d’un séchage rapide, onobtient des fibres décollées longues unidirectionnelles tandis que pour le cas d’un séchage lent, onassiste à la formation de craquelures non décollées avec apparition de craquelures secondairestransverses. / Controlling the production of colloidal suspension films by evaporation is still, nowadays, atruly scientific obstacle for materials development. The drying of colloidal suspensions leads often tosurface and volume defects in the film. When the particles are soft, films are continuous but haveseveral folding surface defects. However, when the particles are hard (glassy latex, silica,...), the filmtends to crack and to be delaminated. These defects are often associated with residual stresses in thegel at the end of drying, due to the capillary pressure caused by the water menisci deformation at thefilm surface. Nevertheless, neither the size scale where constraint acts nor the relation between stressand cracking time were known.In this thesis we present the study of cracks morphology observed in films of differentcolloidal suspension mixtures obtained by a drying process. These mixtures are composed of hard(polystyrene crosslinked PBMA) and soft (PBA and PBMA) particles. The nanometric structure ofthese mixtures is obtained through neutron scattering and turbidity studies. We have mixtures withdifferent structures and different states of dispersion. While some mixtures contain dispersed particlesat a nanoscale, with an order of magnitude same as the particles size - 50 nm, some others containaggregated particles. The study of cracks morphology is performed on sessile drops by drying at thefree surface. Periodic radial cracks are observed during drying. We also observe that cracks periodincrease with the increment of soft particles fraction and temperature, but keeping constant itsperiodicity. We have demonstrated that the ratio: crack period between film thickness, i.e. λ/h, is theonly parameter that describes perfectly cracks morphology for a drying process at a free surface. Wealso demonstrated that this relation (λ/h) couldn’t decrease below 2 even in the case of glassy particles.Drying process induces high residual stresses in the gel, allowing to some fibers located between twocracks to delaminate radially. This delamination phenomenon fades with dissipation constraints. Wehave also established that the Russel’s mechanical model does not describe the period of cracks nearthe critical stress. Therefore, in this work we propose another model able to characterize theperiodicity of the cracks. We noticed that the properties of the substrate did not affect cracksmorphology. The evaporation rate changes the morphology of cracks, which in the case of a quickdrying it is possible to obtain unidirectional long loose fibers. However, for a slow drying, we arewitnessing the formation of not protruding cracks with the apparition of secondary transverse cracks.

L’imbibition est d’une importance fondamentale dans de nombreuses applications technologiques et intervient par ailleurs dans de nombreux phénomènes naturels (industrie textile, industrie pharmaceutique, érosion des sols ….). Malgré l’importance de ce phénomène, la description et la modélisation des mécanismes d’imbibition sont encore sujettes à discussion dans la littérature, en particulier, la prédiction des cinétiques d’imbibition à partir de la connaissance de la topographie du milieu poreux. L’objectif de ce travail de thèse a été de relier les cinétiques d’imbibition à la structure du milieu poreux imbibé. Pour cela, nous avons étudié l’imbibition capillaire (ou spontanée) en suivant une démarche expérimentale dans laquelle nous avons utilisé des substrats poreux modèles dont nous contrôlons le volume et la structure de pores. La configuration d’imbibition choisie dans ce travail est celle d’une goutte sessile (ou posée).Ces travaux ont permis de mettre en œuvre une technique de construction de pastilles macroscopiques, autosupportées et cohésives, par assemblage de microbilles de polymère. Ces systèmes modèles ont été utilisés pour étudier les cinétiques d’imbibition capillaire de liquides dans des supports tridimensionnels à structure de pores complexe en fonction de la taille des microbilles constituant la pastille poreuse, de la reconstruction thermique, de la perméabilité pour une structure poreuse bicouches et de la force capillaire. Ces études ont permis entre autres de mettre en évidence des régimes cinétiques et des transitions d’imbibition inattendues dans ces systèmes (régimes visqueux et inertiel). / Imbibition is of fundamental importance in many technological applications, and is also involved in many natural phenomena (textile industry, pharmaceutical industry, soil erosion ....). Despite the importance of this phenomenon, the description and modelling of imbibition mechanisms are still subject to discussion in the literature, in particular, the prediction of the kinetics of imbibition from the knowledge of the morphology of the porous medium.The aim of this thesis was to relate the imbibition kinetics with the structure of a model porous medium. For this, we studied the capillary imbibition (or spontaneous) following an experimental approach in which we used a model porous substrate with both a controlled porous volume and pore structure. The experimental configuration for studying this imbibition was that of a sessile drop. In this work we developed a technique for the fabrication of self-supported and cohesive macroscopic pellets of polymer microbeads. These model porous systems have been characterized for their internal structure and used to study the capillary imbibition kinetics as a function of i) the size of the microbeads, ii) the temperature of the thermal annealing, iii) the permeability in the case of bilayered porous structures and iv) the capillary force (concentration of ethanol in water, nature of the liquid). This approach allowed observing and discussing unexpected imbibition regimes and transitions (inertial and viscous regimes).

The present work was initiated to investigate the surface- and interfacial phenomena for iron and slag/iron systems. The aim was to understand the mechanism of the effect of surface active elements on surface and interfacial properties. In the present work, the adsorption of oxygen and sulfur on iron surface as well as adatom surface movements were studied based on the ab initio method. BCC iron melting phenomena and sulfur diffusion in molten iron were investigated by Monte Carlo simulations. The impact of oxygen potential on interfacial mass transfer was carried out by X-ray sessile drop method. Firstly, the structural, electronic and magnetic properties as well as thermodynamic stability were studied by Density functional theory (DFT). The hollow site was found to be the most stable adsorption site both for oxygen and sulfur adsorbed on iron (100) surface, which is in agreement with the experiment. The relaxation geometries and difference charge density of the different adsorption systems were calculated to analyze the interaction and bonding properties between Fe and O/S. It can be found that the charge redistribution was related to the geometry relaxation. In addition, the sulfur coverage is considered from a quarter of one monolayer (1ML) to a full monolayer. It was found that the work function and its change Δφ increased with S coverage, in very good agreement with experiment. Due to a recent discussion regarding the influence of charge transfer on Δφ, it is shown in the present work that the increase in Δφ can be explained by the increasing surface dipole moment as a function of S coverage. S strongly interacts with the surface Fe layer and decreases the surface magnetic moment as the S coverage increases. Secondly, a two dimensional (2D) gas model based on density functional calculations combined with thermodynamics and statistical physics, was proposed to simulate the movement of the surface active elements, viz. oxygen and sulfur atoms on the Fe(100) surface. The average velocity of oxygen and sulfur atoms was found to be related to the vibration frequencies and energy barrier in the final expression developed. The calculated results were based on the density function and thermodynamics & statistical physics theories. In addition, this 2D gas model can be used to simulate and give an atomic view of the complex interfacial phenomena in the steelmaking refining process. A distance dependent atomistic Monte Carlo model was developed for studying the iron melting phenomenon as well as effect of sulfur on molten iron surface. The effect of boundary conditions on the melting process of an ensemble of bcc iron atoms has been investigated using a Lennard-Jones distance dependent pair potential. The stability of melting process was energetically and spatially analyzed under fixed wall and free surface conditions and the effects of short and long-range interactions were discussed. The role of boundary conditions was significantly reduced when long-range interactions were used in the simulation. This model was further developed for investigating the effect of sulfur on molten iron surface. A combination of fixed wall and free surface boundary condition was found to well-represent the molten bath configuration while considering the second nearest neighbor interactions. Calculations concerning the diffusion of sulfur on molten surface were carried out as a function of temperature and sulfur concentration. Our results show that sulfur atoms tended to diffuse away from the surface into the liquid bulk and the diffusion rate increased by increasing temperature. Finally, impact of oxygen potential on sulfur mass transfer at slag/metal interface, was carried out by X-ray sessile drop method. The movement of sulfur at the slag/metal interface was monitored in dynamic mode at temperature 1873 K under non-equilibrium conditions. The experiments were carried out with pure iron and CaO-SiO2-Al2O3-FeO slag (alumina saturated at the experimental temperature) contained in alumina crucibles with well-controlled partial pressures of oxygen and sulfur. As the partial pressure of oxygen increased, it was found that interfacial velocity as well as the oscillation amplitude increased. The thermo-physical and thermo-chemical properties of slag were also found to influence interfacial velocity. / QC 20101123