Organic coatings are frequently applied to metals, often in circumstances where there is a need to protect the substrate from corrosion or to improve the aesthetic quality of a product. Increasingly, coatings are also expected to provide additional functionality, such as anti-bacterial properties. Concurrent with the need to satisfy ever more demanding specifications, coating formulators are being obliged to comply with stringent environmental legislation. A research area which may benefit the development of coating formulations is that of nanocomposite synthesis, in which the composite additives have at least one dimension in the nanometre size range. The current research has sought to modify a waterborne organic coating primer with two types of nano-sized additives: layered clays and titanium dioxide nanoparticles. Dispersion of the particles at loadings up to 5% w/w was achieved by ball milling and the modified coatings were subjected to numerous tests to ascertain the effect of the additives. Titanium dioxide was found to improve the tribological properties and corrosion resistance of the coatings, while the addition of magnesium aluminium hydroxycarbonate (hydrotalcite) layered clay had a deleterious effect. Some coatings exhibited a cracked morphology, although no correlation between particle loading and the presence of cracks could be determined. A preliminary investigation into substrate preparation was also conducted. This ensured that the degree of cleanliness of the hot-dip galvanized substrates was both satisfactory and consistent.

Lactose is used in many food/pharmaceutical products, despite powders containing amorphous lactose being difficult to handle because they tend to be sticky and are prone to crystallization and powder caking. There is therefore a market for lactose powder with improved functionality to facilitate powder handling. The aim of the proposed project was to produce a value-added, free-flowing and non-caking lactose powder that can be easily blended into other dairy products, such as dry-powder soups or drinks, and non-dairy products such as chocolate bars. The principle of particle coating during spray drying (in-situ coating), which exploits the phenomenon of solute segregation of different components within the drying droplet, was used for the purpose of producing such powders. In this work, spray-dried lactose powders containing low concentrations of edible additives, such as proteins, polymers or fat, were produced in order to investigate the ability of these additives to accumulate at the droplet surface during drying to form a coating that improves powder functional properties and limits powder caking. This thesis presents the results of the trials necessary to develop these coated powder by the use of an

Since metals in general, and steels in particular, are vital construction materials in our modern society, the corrosion protection of said materials is of great importance, both to ensure safety and to reduce costs associated to corrosion. Previously, chromium (VI) and other harmful substances were effectively used to provide corrosion protection to steel, but since their use was heavily regulated around year 2000, no coating has yet been developed that, in a fully satisfactory manner, replaces their corrosion protective properties.In this thesis, the use of hydrophobic and superhydrophobic surface coatings as part of corrosion protective coating systems has been studied. Since the corrosion mechanism relies on the presence of water to take place, the use of a superhydrophobic coating to retard the penetration of water to an underlying metal surface is intuitive. The evaluation of corrosion protective properties of the hydrophobic and superhydrophobic surfaces was performed using mainly contact angle measurements and electrochemical measurements in severely corrosive 3 wt% NaCl water solution.First, the differences in corrosion protection achieved when employing different hydrophobic wetting states were investigated using a model alkyl ketene dimer wax system. It was found that superhydrophobicity in the Lotus state is superior to the other states, when considering fairly short immersion times of less than ten days. This is due to the continuous air film that can form between such a superhydrophobic surface and the electrolyte, which can retard the transport of electrolyte containing corrosive ions to the metal surface to the point where the electrical circuit is broken. Since corrosion cannot occur unless an electrical current is flowing, this is a very efficient way of suppressing corrosion.An air layer on an immersed superhydrophobic surface is, however, not stable over long time, and to investigate long-term corrosion protection using hydrophobic coatings a polydimethylsiloxane formulation containing hydrophobic silica nanoparticles was developed. This system showed enhancement in corrosion protective properties with increasing particles loads, up until the point where the particle load instead causes the coating to crack (at 40 wt%). The conclusion is that the hydrophobicity of the matrix and filler, in combination with the elongatedivdiffusion path supplied by the addition of particles, enhanced the corrosion protection of the underlying substrate.To further understand how hydrophobicity and particle addition affect the corrosion protective properties of a coating a three layer composite coating system was developed. Using this coating system, consisting of a polyester acrylate base coating, covered by TiO2 particles (with diameter &lt; 100 nm) and finally coated with a thin hexamethyl disiloxane coating, it was found that both hydrophobicity and particles are needed to reach a great enhancement in corrosion protective properties also for this system. / Eftersom metaller, och då särskilt stål, är viktigta konstruktionsmaterial i vårt moderna samhälle är korrosionsskydd av stor betydelse, både för att garantera säkerhet och för att minska kostnader som uppkommer i samband med korrosion. Tidigare har sexvärt krom och andra skadliga ämnen använts för att på ett effektivt sätt skydda stål från korrosion, men efter att deras användning kraftigt reglerades runt år 2000 har ännu ingen beläggning utvecklats som helt kan ersätta krombeläggningarna med avseende på funktion.I denna avhandling har hydrofoba och superhydrofoba ytbeläggningar och deras möjliga applikation som en del av ett korrosionsskyddande beläggningssystem studerats. Eftersom korrosionsmekanismen är beroende av närvaron av vatten, är användandet av en superhydrofob beläggning för att fördröja transporten av vatten till den underliggande metallytan intuitiv. De korrosionsskyddande egenskaperna hos superhydrofoba ytbeläggningar utvärderades här främst med hjälp av kontaktvinkelmätningar och elektrokemisk utvärdering i korrosiv lösning bestående av 3 vikts% NaCl i vatten.Först undersöktes skillnaden i korrosionsskydd som uppnås vid användandet av ytbeläggningar med olika hydrofoba vätningsregimer med hjälp av ett modellsystem bestående av ett alkylketendimer vax. Det konstaterades att superhydrofobicitet i Lotusregimen är överlägset bättre än de andra hydrofoba vätningsregimerna, i alla fall när man ser till relativt korta exponeringstider, typiskt mindre än tio dagar. Detta beror på att den kontinuerliga luftfilm som kan bildas på en sådan typ av superhydrofob yta kan minska transporten av elektrolyt (som innehåller korrosiva joner) till metallytan till den grad att den elektriska kretsen bryts. Eftersom korrosion inte kan ske utan en sluten elektrisk krets är detta ett mycket effektivt sätt att förhindra korrosion från att ske.Ett luftskikt på en superhydrofob yta nedsänkt i vatten är dock inte stabilt under lång tid. För att undersöka möjligheten till korrosionsskydd under längre tid med hjälp av hydrofoba beläggningar utvecklades en hydrofob ytbeläggning bestående av polydimetylsiloxan och hydrofoba nanopartiklar av kiseldioxid. Detta system visade en förbättring av korrosionsskyddet vid ökat partikelinnehåll upp till den koncentration (40 wt%) där i stället sprickbildning i ytbeläggningen observerades. Från detta system kunde slutsatsen dras att matrisens och partiklarnasvihydrofobicitet i kombination med den längre diffusionsvägen som partiklarna orsakade förbättrade korrosionsskyddet av den underliggande metallen.För att ytterligare förstå hur hydrofobicitet och partikeltillsatser påverkar en ytbeläggnings korrosionsskyddande egenskaper har dessutom ett treskikts kompositbeläggningssystem utvecklats. Genom att använda detta beläggningssystem, som består av en basbeläggning av polyesterakrylat, ett lager TiO2-partiklar (med en diameter på &lt;100 nm) slutligen belagt med ett tunt ytskikt bestående av hexametyldisiloxan så kunde slutsatsen dras att både en hydrofob matris och partiklar behövs för att nå en markant förbättring av ytbeläggningens korrosionsskyddande egenskaper. / <p>QC 20151015</p>

A local company instituted a new chemical procedure in their spray phosphating system used in the pretreatment of large components for industrial racking systems. An inorganic conversion coating is deposited on the workpiece surface during phosphating and this prepares the surface to receive an organic top-coat. The organic coating is applied to the workpiece surface in the form of a powder and cured to form a continuous film about 80 u.m thick. The solution chemistry of the phosphating system was monitored by sampling and chemical analysis and taking direct reading instrumental measurements on the process and rinse solutions. The process was also evaluated using the results of a waste minimisation audit. This involved gathering data on composition, flow rates and costs of inputs and outputs of the process. Two types of information were collected and used during the audit, namely chemical monitoring (concentration levels of Na, Fe, Zn, Mo, Mn and Cr and measurements of conductivity, TDS, SS and pH) and water usage data on the Phosphating Line and existing data (raw materials, workpieces and utility inputs as well as domestic waste, factory waste and scrap metal outputs). The data were analysed using four established waste minimisation techniques. The Scoping Audit and the Water Economy Assessment results were determined using empirically derived models. The Mass Balance and the True Cost of Waste findings were obtained through more detailed calculations using the results of the chemical analysis. The results of the audit showed that the most important area for waste minimsation in the Phosphating Line was the (dragged-out phosphating chemicals present in) wastewater stream. According to the scoping audit, water usage had the third highest waste minimisation potential behind powder and steel consumption for the entire powder coating process. While the scoping audit and the specific water intake value showed that water consumption for the process was not excessive, it did not indicate that the pollution level in the rinse waters was high. Further, drag-out calculations showed that drag-out volumes were typical of those found in the metal finishing industry. However the presence of high levels of metal species in the rinse waters was highlighted through the chemical monitoring of the Phosphating Line. The True Cost of Waste Analysis estimated potential financial savings for the effluent stream at about R8000 for a period of 105 days. However this does not take into consideration the cost of the liability associated with this stream when exceeding effluent discharge limits (given in the Trade Effluent Bylaws) or of the chemical treatment necessary to render this stream suitable for discharge to sewer. Intervention using only "low-cost-no-cost" waste minimisation measures was recommended as a first step before contemplating further areas for technical or economic feasibility studies. However, a further study involving monitoring the sludge was recommended in order to establish the potential financial savings offered by this waste stream. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.

This work investigated the protection of mechanism of organic coatings on steel exposed to 3&percnt; sodium chloride solution at 50&deg;C, coupled with the use of electrochemical impedance spectroscopy (EIS) to monitor progress of corrosion and degradation of coating. Unlike Walter, EIS measurement was conducted at 50&deg;C as well as after cooling, and measurements at intermediate temperatures have been used to characterize the dependence of the process involved. The proposition that corrosion rate is controlled by the ionic resistance of an organic coating has been tested. EIS results were fitted to a model circuit and changes in the film resistance and charge-transfer resistance with temperature were analyzed to deduce activation energies for the processes involved. Surprisingly, the calculated activation energy for coating resistance is significantly lower than the activation energy for the charge transfer resistance. This suggests that ion conduction in the coating, as apparent in an AC measurement, cannot be controlling the corrosion rate. Potentiostatic pulse tests on coated metal enable iR-corrected polarization curves to be plotted at different temperatures. From this, the activation energy determined from the corrosion currents also higher matches the higher activation energy value calculated from the charge transfer resistance. However, measurements of coating resistance on free films of the same coating also generate higher activation energy values, leaving two possible models that can account for the results.

Minimizing adhesion of ice has been the subject of extensive studies for applications such aircraft wings, wind turbine blades spacecraft, power transmission wires, while a growing interest concerns coatings for aerospace applications. The work described here describes progress for coatings and ice release test method development over the last few years. Major achievements include: (1) New Rigid Adherent-Resistant Elastomers (RARE), (2) A new Epoxied Cylinder (EC) adhesion test, (3) Validation of an ice release test, and (4) Study of ice adhesion strength on coating thickness for a PDMS elastomer. Rigid Adhesion-Resistance Elastomers (RARE) are comprised of 3F 1 terminated with triethoxysilane moieties and linear 3F polyurethane (U-3F). Hybrid compositions U-3F-x are designated by polyurethane weight percent “x”. Interestingly, RARE coatings spontaneously “self-stratify” during coating deposition and cure. Cured RARE coatings are comprised of (1) a nanoscale surface layer with low work of adhesion, (2) a low modulus mesoscale and (3) a tough U-3F bulk, where “Mesoscale” is defined as a near surface region with a depth ~ 1000 nm. An EC adhesion test was developed to evaluate the fouling release characteristics of RARE. EC adhesion testing was devised by using the commercially available instrument, TA RSA-3. The TA RSA-3 is well suited for these tests as the 3.5 kg load cell facilitates accurate measurements. This test gives peak force (Ps) for EC removal. A striking compositional dependence was found for EC adhesion. A U-3F-50 hybrid coating had the lowest adhesion (Ps = 0.078 MPa) with good toughness (6.2 MPa). Bulk and surface characterization together with adhesion measurements established U-3F-x hybrid coatings, and U-3F-50 in particular, as new fluorous rigid adherent-resistant elastomers (RARE) that are tough, oil resistant, and optically transparent. Inspired by the Epoxied Cylinder (EC) adhesion test, a laboratory method for ice adhesion measurement with a commercially available instrument was established in the Wynne Laboratory. This is the first laboratory ice adhesion test that does not require a custom built apparatus. The temperature controlled chamber on TA RSA-3 is an enabling feature that is essential for the test. The method involves removal of an ice cylinder from a polymer coating with a probe and the determination of peak removal force (Ps). To validate the test method, the strength of ice adhesion was determined for a prototypical glassy polymer, poly(methyl methacrylate). The distance of the probe from the PMMA surface has been identified as a critical variable for Ps. The new test provides a readily available platform for investigating fundamental surface characteristics affecting ice adhesion. In addition to the ice release test, PMMA coatings were characterized using DSC, DCA and TM-AFM. This new laboratory ice release test was then employed to obtain the thickness dependence of ice adhesion for Sylgard 184, a filled polydimethylsiloxane elastomer. A correlation between ice adhesion and coating thickness (t) was found, that follows a relationship developed by Kendall over 40 years ago for removal of a rigid object from an elastomer. In particular, a nearly linear relationship between peak removal stress (Ps) and 1/t1/2 was found, with Ps decreasing from 550 kPa to 100 kPa with coating thickness increasing from 12 μm to 800 μm. While work of adhesion, which is related to surface free energy, is recognized as an important factor that can affect ice release, the results reported herein show that coating thickness can override this single parameter for elastomeric substrates. Base on the result, a general model is proposed for the removal of ice from low modulus elastomers (~10 MPa).

El objetivo de esta revisión fue recopilar información sobre las técnicas de Sellado Dentinario Inmediato (SDI) y Resin Coating (RC) como incremento de las fuerzas de adhesión. Asimismo, el siguiente trabajo describe las principales características de cada técnica, así como sus ventajas y desventajas. / The aim of this review was to collect information about the Immediate Dental Sealing (IDS) and Resin Coating (RC) techniques to achieve an increase in bond strengths. Also, this article describes its main characteristics as well as advantages and disadvantages. / Trabajo académico

No presente trabalho foram obtidos e caracterizados filmes finos de SnO2 e SnO2:Sb preparados pelo processo sol-gel. Estes filmes foram estudados através da influência do número de camadas nas suas propriedades ótico-eletroquímicas. Foi observado que a densidade de carga para um filme de SnO2:Sb de 5 camadas foi de 40 mC/cm2, tornando-se um excelente candidato como contra-eletrodo para aplicação em janelas eletrocrômicas. Os filmes de SnO2 e SnO2:Sb também foram estudados utilizando técnicas eletroquímicas: cronoamperometria e voltametria cíclica cujo o enfoque na análise foi o de intercalação de lítio em função da carga inserida. As medidas de transmissão ótica na região de ultravioletainfravermelho próximo revelaram que estes filmes possuem leve coloração azul, evidenciadas pela mudança do espectro UV-Vis em 8% entre estado colorido e descolorido; Por espectroscopia no infravermelho dos sóis, foi possível observar bandas características dos grupos de moléculas presentes em alcóxido, confirmando a formação do alcóxido de estanho enquanto dos precipitados apenas evidências da formação do óxido de estanho. As morfologias dos filmes estudadas por Microscopia Eletrônica de Varredura (MEV) e Microscopia de Força Atômica (AFM) demonstraram que o filme apresenta pequenos riscos, provavelmente devido a presença de Sb, e por AFM obtidas informações da rugosidade e do tamanho de grão, sendo estes valores de 100 nm e 104 nm respectivamente. A partir do espectro do filme por EDX foi possível confirmar a presença de estanho e antimônio nos filmes. A estrutura dos xerogéis e dos sóis para deposição dos filmes estudada por difração de raios-X é a casseterite. Por fim Análises Térmicas (DSC/TGA) demonstram que à 60oC um pico endotérmico correspondendo à liberação de água e uma perda da massa de 6,3 %, e na faixa de 450C um pequeno aumento da linha de base no sentido exotérmico atribuído a cristalização do SnO2:Sb na fase casseterite, com perda de massa de 33%. / In this study were obtained and characterized thin films of SnO2 and SnO2: Sb prepared by the sol-gel process. These films were studied through the influence of the number of layers in its optical-electrochemical properties. It was observed that the density of charge for a film of SnO2: Sb, 5 layers was 40 mC/cm2, making it an excellent candidate as counter-electrode for use in electrochromic windows. The films of SnO2 and SnO2: Sb also were studied using electrochemical techniques: chronoamperometry and cyclic voltammetry with a focus on analysis of intercalation of lithium according to load inserted. Measures of optical transmission in the ultraviolet region of near-infrared revealed that these films have light blue colour, highlighted by the changing spectrum of UV-Vis by 8% between state and colorful discolour; In the infrared spectroscopy, in solution has been possible to see bands characteristics groups of molecules present in alkoxide, confirming the formation of alkoxide of tin while the precipitated only evidence of the formation formation of tin oxide. The morphologies of the films studied by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) showed that the film presents little risk, probably because the presence of Sb, and the information obtained by the AFM roughness and the size of grain, and these values of 100 nm and 104 nm respectively. From the spectrum of the film by EDX were unable to confirm the presence of tin and antimony in the films. The structure of xerogel and solution for deposition of films studied by X-rays diffraction is the cassiterite. Finally Thermal Analysis (DSC / TGA) show that the 60oC a peak endothermical corresponding to the release of water and a loss of the mass of 6.3%, and in the 450ºC a small increase from baseline in the sense attributed range of exothermically the crystallization of SnO2:Sb during casseterite, with mass loss of 33%.

To evaluate the effect of cool roof coatings containing Expancel® thermoplastic microspheres on industrial buildings, a warehouse was built-up in the computer simulation software IDA-ICE. The warehouse was modelled in line with ASHRAE 90.1. 2004 ”Energy Standard for Buildings Except Low-Rise Residential Buildings”. Four different cases were set up where the coating of the roof was the only variable. Two coatings containing Expancel® microspheres - one white and one red coating were compared to the same white coating without Expancel® microspheres and the ”base case” where there is no coating at all. The same circumstances were also implemented in a practical laboratory test using a model warehouse with a detachable roof. Four interchangeable roofs with different roof coatings constitute the various cases in the laboratory tests. A ”sun” consisting of statically mounted IR light bulbs were constructed, as well as a cooling system to measure the difference in cooling effect (maintaining a constant indoor temperature) between the different cases as a result of the change in insolation. The results of the computational simulations show that for a warehouse placed in Houston, Texas about 50 MWh in combined heating and cooling energy can be saved yearly between the best and the worst case, a reduction of 6.2%. Changing the geographic placement of the warehouse to Tepic, Mexico the corresponding savings were determined to 83 MWh or 13.5%. A way of determining the yearly savings in heating and cooling amount for the warehouse with a generic roof coating, only knowing the SRI value of the coating, was developed. It was determined that for every unit-increment of the SRI value the yearly savings for the warehouse placed in Houston, Texas were 718 kWh and 0.1%. The corresponding savings for the warehouse placed in Tepic, Mexico were determined to be 1252 kWh and 0.22%. The laboratory tests showed that the indoor temperature of the model warehouse decreased by close to 16°C between the best and the worst case.

Made available in DSpace on 2014-12-17T15:41:46Z (GMT). No. of bitstreams: 1 MoisesRCpdf.pdf: 4615723 bytes, checksum: 8e0d75d3465b34a6f59e81df4ba5830e (MD5) Previous issue date: 2009-02-04 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The present work aims the preparation of filmes of strontium-doped lanthanum manganite (perovskita) yttria-stabilized zirconia (LSM-SDC) films deposited on substrate of YSZ by means of spin coating technique having as principal objective their application to solid oxide fuel cells of intermediate temperature. La0,8Sr0,2MnO3 and Ce0,8Sm0,2O1,9 were obtained by modified Pechini method by use of gelatin which act as polymerization agent. The powders obtained were characterized by Xray fluorescence, X ray diffraction, electronic scanning microscopy and the superficial area by BET method. The results obtained by X-ray fluorescence showed that the route adopted for obtention of powders was effective in the obtention of the compositions with close values to the stoichiometrics. Ethyl cellulose was used as pore-forming agent and mixed with the LSM-SDC powders in weight proportions of 1:24, 2:23 and 1:9. The films were sintered at 1150 ?C for 4 h and characterized by X-ray diffraction and scanning electron microscopy technique (SEM) and atomic force. The phases quantification of the precursory powders and of the obtained films was carried through Rietveld method. According with the analysis of SEM, as the content of ethyl cellulose was increased, the pore distribution in films become more uniform and the pore size reduced. The methodology used for the obtention of the films was very efficient, considering a material was obtained with characteristics that were proper to the application as electrolyte/cathode system to solid oxide fuel cells / O trabalho trata da prepara??o de filmes de manganita de lant?nio dopado com estr?ncio (perovskita) c?ria dopada com sam?rio (LSM-SDC) sobre substrato de zirc?nia estabilizada com ?tria (YSZ) pela t?cnica spin coating, para utiliza??o em c?lulas a combust?vel de ?xido s?lido de temperatura intermedi?ria. Neste trabalho, La0,8Sr0,2MnO3 e Ce0,8Sm0,2O1,9 foram obtidos pelo m?todo Pechini modificado pelo uso de gelatina que atua como agente polimerizante e quelante. Os p?s obtidos foram caracterizados por fluoresc?ncia de raios-X, difra??o de raios-X, microscopia eletr?nica de varredura e determina??o da ?rea superficial pelo m?todo BET. Os resultados obtidos por fluoresc?ncia de raios-X mostraram que a rota adotada para obten??o dos p?s foi eficaz na obten??o da composi??o com valores pr?ximos ao estequiom?trico. A etilcelulose foi usada como agente formador de poros e foi misturada ao p?s de LSM-SDC em propor??es m?ssicas de 1:24, 2:23 e 1:9. Os filmes foram tratados termicamente a 1150 ?C por quatro horas e caracterizados estruturalmente pela t?cnica de difra??o de raios X e morfologicamente pelas t?cnicas de microscopia eletr?nica de varredura e for?a at?mica. A quantifica??o das fases dos p?s precursores e dos filmes obtidos foi realizada atrav?s do refinamento Rietveld. De acordo com a an?lise de MEV, quando a quantidade de etilcelulose foi aumentada, a distribui??o dos poros nos filmes tornou-se mais uniformes e o tamanho de poros reduzidos. A metodologia empregada para a obten??o dos filmes mostrou-se satisfat?ria, considerando que foi obtido um material com caracter?sticas apropriadas para a aplica??o como sistema eletrodo/eletr?lito em c?lulas a combust?vel de ?xido s?lido (SOFC)