El polidimetilsiloxano (PDMS) es un polímero amorfo en base inorgánica con grupos pendientes que le imparten hidrofobicidad que es ampliamente utilidado en aplicaciones biomédicas. Debido a la baja energía superficial del PDMS, su adhesión es pobre. En algunas aplicaciones biomédicas (catéteres, prótesis) se requiere adhesión para lo cual se modifica superficialmente. Los plasmas generados en condiciones de no-equilibrio, también llamados plasmas fríos, han sido utilizados en el tratamiento superficial de PDMS para aumentar su energía superficial, pero las modificaciones producidas son poco estables, produciéndose una rápida recuperación de la hidrofobicidad (hydrophobic recovery). La estabilidad de las modificaciones superficiales del PDMS depende de las características del plasma utilizado para su tratamiento, por lo que el objetivo de la tesis doctoral se centra en la utilización de diferentes tipos de plasmas fríos para modificar las propiedades superficiales de PDMS de manera que simultáneamente se aumente su estabilidad y se mejore su adhesión. Otro aspecto innovador en el estudio consiste en la discriminación y optimización de las condiciones de tratamiento con plasma utilizando un diseño estadístico de experimentos, lo que he permitido modelar el efecto del tratamiento con plasma de superficies de PDMS empleando los ángulos de contacto y la química superficial como variables respuesta. Se ha estudiado el efecto de los diferentes tipos de plasma en la hidrofobicidad y la energía superficial del PDMS mediante medidas de ángulo de contacto. Las modificaciones en la química superficial han sido evaluadas usando espectroscopia infrarroja en modo de reflectancia total atenuada (FTIR-ATR) y espectroscopia fotoelectrónica de rayos X (XPS), mientras que los cambios en la morfología y nanorugosidad superficial se monitorizaron usando microscopía electrónica de barrido (SEM) y microscopía de fuerza atómica (AFM). Las propiedades de adhesión del PDMS se evaluaron mediante ensayos de adhesión en pelado en T y de cizalla a solape simple, utilizando un adhesivo sensible a la presión (PSA) en base acrílica para uso médico. Estas propiedades fueron además monitorizadas en función del tiempo tras el tratamiento con plasma para determinar la estabilidad de las modificaciones producidas. En general, el tratamiento superficial de PDMS con plasma produce oxidación de las cadenas de polisiloxano por sustitución de los grupos metilo por grupos hidroxilo, lo que aumenta la polaridad y la energía superficial, incrementando las propiedades de adhesión. Se produce el entrecruzamiento de cadenas mediante condensación de los grupos hidroxilo, formando una delgada capa superficial con estructura de sílice. Cuando las características del plasma son demasiado agresivas aparecen grietas superficiales favoreciendo la recuperación hidrofóbica por difusión de especies apolares desde el seno del PDMS hacia la superficie, así como por la reorientación de los nuevos grupos polares en la superficie hacia el seno del material. Este fenómeno se minimiza optimizando las condiciones de tratamiento empelando un diseño estadístico de experimentos. En sistemas de generación de plasma a baja presión, tratamientos con baja potencia durante largos tiempos mejoran la funcionalización de la superficie del PDMS, y el uso de mezclas de argón y oxígeno como gas plasmógeno resulta más efectivo que el empleo de los gases puros; la presión de trabajo tiene un papel fundamental en la estabilidad de las modificaciones producidas. En sistemas de antorcha de plasma atmosférico el tiempo de tratamiento y la distancia de la boquilla a la superficie son los parámetros más relevantes en la oxidación superficial del PDMS, mientras que en sistemas de plasma atmosférico de doble barrera dieléctrica, el voltaje, el tiempo de tratamiento y la distancia entre electrodos son las variables críticas en la efectividad del tratamiento superficial. Finalmente, la deposición de monómeros mediante antorcha de plasma permite generar nanoestructuras superficiales en el PDMS aportándole características de superhidrofobicidad.

No description available.

Företaget Nobel Biocare tillverkar tandimplantat. Då tandimplantat används i munnen är den medicinska nivån hög och strikt. För att benet runt implantatet ska läka snabbare används en saltlösning på tandimplantaten. Saltlösningen appliceras i nuläget genom ett saltbad och sen ett justeringssteg för att avlägsna överflödigt salt. Detta arbete är en förstudie för att hitta en eller flera metoder som skulle kunna lösa denna process på ett enklare sätt.En fördjupad undersökning av sprayningsmetoder, sköljlackering samt physical vapor deposition gjordes för att finna eventuellt fungerande lösningar. Slutligen utvärderades dessa metoder för att föreslå en kandidat för prototypstudier. / The Company Nobel Biocare is a producer of dental implants. As implants are used in the mouth the medical restrictions are high. A saline solution is used to help the bone around the implants heal faster. The saline solution is currently applied using a salt bath followed by an adjustment step to remove superfluous salt.This report describes a pre-study to find one or more methods that could simplify the salt application. The focus was on spraying methods, flow coating and physical vapor deposition. Finally, a ranking was done to suggest the top candidate for prototype testing.

Considering the pervasive presence of chlorides in concrete bridge decks, bridge engineers have a critical responsibility to perform proper and effective preventive maintenance and rehabilitation operations. Bridge engineers often perform scarification and overlay (SO) procedures on concrete bridge decks to minimize the corrosion of reinforcing steel due to chloride ingress. Given the need to develop guidelines for the initial timing of SO treatments, the specific objectives of this research were to collect information from several department of transportation (DOT) personnel about their SO procedures and, subsequently, to determine the recommended timing of initial SO procedures on concrete bridge decks for preventing the accumulation of corrosion-inducing levels of chlorides and extending deck service life. A questionnaire survey of state DOTs was conducted, and numerical modeling of SO treatments was performed. Simulations involving both decks with and without stay-in-place metal forms (SIPMFs) were performed. Numerical modeling was performed for each unique combination of variables through a service life of 50 years to determine the recommended initial timing of SO treatment in each case. The research results show that, overall, bridge decks without SIPMFs can endure longer delays in SO treatment timing than those with SIPMFs; in all cases, the absence of SIPMFs extended the amount of time before an SO treatment was needed. For decks with SIPMFs, the allowable delay in SO timing ranged from 2 to 6 years, while on decks without SIPMFs the allowable delay in SO timing ranged from 6 to 18 years. These delays are only 1 to 3 years longer than allowable delays associated with placement of surface treatments investigated in previous research. On average, the period of additional delay allowed before an SO treatment is required in decks with SIPMFs was 2 years with each additional 0.5 in. of OCD. In decks without SIPMFs, the presence of a greater OCD had a more pronounced effect on the latest recommended timing of treatment than in the decks with SIPMFs; an average additional delay period of 5 years was obtained with each additional 0.5 in. of OCD in decks without SIPMFs. Together with the findings of this research and the specific properties of the bridge deck under scrutiny, engineers can determine the appropriate timing of rehabilitation procedures to prevent or mitigate corrosion of the steel reinforcement of a bridge deck and ensure the usability of the deck for its intended service life. Although the conditions studied in this research were consistent with bridges located in the state of Utah, bridge decks that exist in similar environments and that are subjected to similar treatments of deicing salts as part of winter maintenance could exhibit similar properties to the decks simulated in this research. Engineers should carefully consider the results of this research and implement proper timing of SO treatments on their respective bridge decks to protect against and minimize the effects of corrosion due to chloride ingress.

Gears are an important part of many machines. This thesis is a study in how new mechano-chemical surface treatments can be used to improve the efficiency in gear transmissions, specifically those relating to electric vehicles. The primary equipment used for this research is the FZG-test rig, a rig dedicated for the evaluation of lubricant and gear behaviour. To achieve an understanding of the effects of surface treatment, how gear contacts interact, and how geometry affects the efficiency, a substantial background study was performed, mixing various fields of knowledge and incorporating results from previous projects utilizing the FZG-test rig. Throughout the experimental phase of the project many goals had to be adjusted based on various problems encountered. Notable gear wear was observed in addition to the fact that many of the examined gears fell outside some of the specified manufacturing tolerance requirement. As a result, the data acquired from the testing is inconclusive. It is not possible to clearly establish the correlation between the effects of the new surface treatments method and efficiency due to the uncertainty in the interaction between lack of quality and a previously untested lubricant. These results are however still of benefit as to establish future test conditions and to identify the potential problems with FZG-testing. / Kugghjul är en viktig del i många maskiner. Denna rapport är en studie i hur nya mekaniska-kemiska ytbehandlingar kan tillämpas för att förbättra effektiviteten i kugghjulstransmissioners, specifikt för tillämpning i elektriska fordon. Den centrala utrustningen som använts i denna undersökning är en FZG-testrigg, en testrigg vars huvudsakliga uppgift är utvärdering av smörjmedel och kugghjulsbeteende. För att uppnå en förståelse av effekterna av ytbehandlingar, hur kugghjulskontakter interagerar, och hur kugghjulsgeometri påverkar effektiviteten, har en betydlig bakgrundstudie genomförts. Denna studie blandade flera olika kunskapsområden, samt resultat från tidigare projekt som även tillämpande FZG-testriggen. I projektets experimentella fas krävdes justeringar i flera av projektets mål på grund av problem som uppstod. Betydlig nötning kunde identifieras i samband med att flera av kugghjulen var utanför de nödvändiga tillverknings toleranskraven. I följd av detta är data från experimenten som utfördes icke-slutgiltiga. Det är inte möjligt att med säkerhet etablera ett samband mellan effekterna av den nya metoden av ytbehandling och effektivitet på grund av den osäkerhet som uppstår via kvalitetsbrister och ett smörjmedel som tidigare ej testats på KTH. Detta är fortfarande viktiga positiva resultat för att kunna etablera framtida test förhållanden och identifiera möjliga problem i experiment med FZG-testriggen.

Mechanical performance characteristics were compared for 100% polyester treated and untreated weft-knitted mesh fabric that are used to contain dry-ageing hams, commonly referred to as ham nets. The treated net was coated with a patent-pending food-grade chemical solution (40% Propylene Glycol + 1% Propylene Glycol Alginate + 1% Carrageenan) to control ham mites. Both treated and untreated ham nets were compared for mechanical performance characteristics based on the following standards: abrasion resistance (ASTM D4966), elastic recovery (BS EN 14704-1:2005), breaking strength (ASTM D5034-09), and bursting strength (ASTM D3786). Results indicate that the coating had minimal to no impact on the mechanical performance characteristics of ham nets. SEM images also showed no negative effect on the fiber morphology due to the applied chemical solution. Findings support the use of treated ham nets to increase the end-use functionality and provide stakeholders an option for integrated pest management without compromising performance needs.

At present the automotive industry is due to an EU directive, replacing hexavalent chrome on vehicles. This is an extensive job as hexavalent chrome is used all over the vehicle and to large extent on fasteners (screws, nuts, rivets etc.). Chrome (VI) is used as a passivating layer on mainly zinc-iron. When replacing the hexavalent chrome with a chrome (VI) free product, the passivating properties are reduced. One of the alternatives is to replace the zinc-iron coating with a zinc-nickel coating. This coating shows great promise from the corrosion resistance point of view. Zinc-nickel is a cathodically protecting coating, and will in principle dissolve to protect the substrate from corrosion. It is therefore important to understand how, and at what rates nickel is released from zinc-nickel coatings when exposed to a chloride-rich automotive environment. The potential environmental impact of nickel needs to be evaluated before Scania can introduce this alternative as corrosion protection. Tests by Scania have previously shown that contact allergy is not an issue for zinc-nickel coatings with Cr (III) passivation. Nickel release rates corresponding to 0,12 mg m-2yr-1 for zinc-15 % nickel coatings at a pH of 4,2 were determined from an accelerated corrosion test. Based on these values, less than 1 kg of nickel per year would be released from the Scania rolling stock if Scania were to introduce zinc-nickel coatings preferably on fasteners. This value is low compared to other sources of nickel release. In order to evaluate the toxicity of the released nickel, information about the chemical speciation, i.e. chemical forms, is needed. Total or dissolved metal are not good predictors of ecotoxicity of metals. Chemical speciation and bioavailability must be incorporated in toxicity testing. Total or dissolved metal may be used as a worst case approximation.

Syfte: Syftet med föreliggande studie är  att undersöka högtranslucent zirkonias benägenhet till missfärgning beroende på ytbehandling och hur detta påverkar materialets färgstabilitet över tid. Material och metod: Totalt frästes och sintrades 40 cylindriska provkroppar av högtranslucent zirkonia. Provkropparna delades slumpmässigt in i grupp G (glansbrända provkroppar) och grupp P (mekaniskt polerade provkroppar). Ytbehandling utfördes genom mekanisk polering eller glansbränning. Därefter utsattes provkropparna för vätskeförvaring i svart kaffe eller svart te under 288 timmar. Provkropparna mättes med en dental spektrofotometer efter 72, 144, 216 och 288 timmar. Mätningarna utfördes tre gånger centralt på varje provkropp. Mätvärdena L*c*h och ΔEab användes för att beskriva och analysera eventuell missfärgning och färgskillnad hänvisat till NBS-klassificering. Resultat: Det fanns inte någon signifikant skillnad vad gäller missfärgning på högtranslucent zirkonia. Detta var oberoende ytbehandling och förvaring i svart kaffe eller svart te, under en tidsperiod som motsvarade ett års oral exponering. De mekaniskt polerade provkropparna som förvarades i svart te uppvisade störst färgskillnad, det högsta ΔE-värdet, efter 288 timmars förvaring. Resultatet visade på en liten färgförändring enligt NBS-klassificeringen. Slutsats: Ytbehandling genom polering eller glansbränning ger bra egenskaper när det gäller motstånd mot missfärgning. En glansbränd yta visar en tendens att inte påverkas av missfärgning lika mycket som en mekaniskt polerad yta. / Purpose: The purpose of the present study is to investigate the tendency of highly translucent zirconia to discolour depending on surface treatment and how this affects the color stability of the material over time. Material and method: A total of 40 cylindrical specimens of high translucent zirconia were milled and sintered. The specimens were randomly divided into group G (glazed specimens) and group P (mechanically polished specimens). Surface treatments were performed by mechanical polishing or glazing. Subsequently, the specimens were subjected to liquid storage in black coffee or black tea for 288 hours. The specimens were measured using a dental spectrophotometer after 72, 144, 216, and 288 hours. The measurements were performed three times centrally on each specimen. The L*c*h and ΔEab values were used to describe and analyze any discoloration and color difference referred to NBS classification. Results: There was no significant difference in discoloration of high-translucent zirconia. This was independent of surface treatment and storage in black coffee or black tea, for a period equivalent to one year of oral exposure. The mechanically polished specimens stored in black tea showed the highest ΔE value (color difference) after 288 hours of storage. However, the results showed a slight change according to the NBS classification. Conclusion: Surface treatment by polishing or burnishing gives good properties in terms of resistance to discoloration. A burnished surface shows a tendency not to be affected by discoloration as much as a mechanically polished surface.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Chip and spray surfacing seals has been widely used in South Africa as the preferred surface treatment for rural roads. The design of these seals has also experienced renewed interest and continuous development in several other countries over the past two decades. In South Africa seals are continually used as increasing attention is given to the periodic maintenance of existing surfaced roads. There is also a significant increase in the use of surfacing seals in North America as the need to develop more energy and resource efficient surfacing options becomes a priority. Despite this growing use of surface seals, the seal design and especially the selection of binder type and grade does not always follow scientific processes. Seals are often designed based on client preference, previous experience, material availability and industry trends. With an ageing road network and limited funding to ensure timeous maintenance, the focus in South Africa is moving towards more stringent and scientific design processes. The USA and Europe, forced by increasing traffic volumes and heightened performance demands, are moving towards performance- based specification to account for deficiencies in their current surface seal design methods. One of the major failure mechanisms of surface seals is ravelling which takes place when the binder and the aggregate bond becomes weak and are broken by the forces generated by traffic. This leads to loose aggregate on the road which in turns leads to bare surface patches and broken windscreens. To prevent and address this as part of the development of performance-based specifications, the need for a simple and inexpensive technique for evaluating bitumen and bitumen emulsion bond strength development over time, as well as binder-aggregate compatibility, was identified. Although various tests exist for investigating adhesion between bituminous emulsions and aggregate chips most of the tests does not deliver the level of information required by the performance-based specifications. The Bitumen Bond Strength (BBS) test method was therefore developed with the aim to address some of the limitations encountered in evaluating bond strength between binders and aggregates. The BBS test (AASHTO TP-91, 2011) was developed by the University of Wisconsin – Madison (UWM) in partnership with the University of Ancona – Italy (UAI) and the University of Stellenbosch – South Africa (US) specifically for evaluating bond strength between aggregates and hot applied binders and emulsions, respectively. US became involved in BBS test efforts in 2008 to assist in the development and practical evaluation of the BBS test method. UAI contributed significantly to the development of the test apparatus through their work in conjunction with UWM. Due to time and resources available, the involvement of the US was limited to various discussion sessions, a study tour, the evaluation of the BBS test, and conducting a series of control tests. By using the Bitumen Bond Strength test it was possible to evaluate the practicality and repeatability of the developed procedure and the results measured was successfully used to evaluate the bond strength development of modified and unmodified bitumen emulsions on tillite and granite aggregates. It was also possible to correlate the results achieved at the University of Stellenbosch with results from the University of Wisconsin-Madison due to the fact that testing took place at both institutions. The development of the test and the inter-laboratory test results in essence reinforced the hypothesis that the BBS test protocol can be used to effectively evaluate bond strength of different emulsion types and aggregate types. Except for the loading rate which is a known critical influence, the emulsion type and curing intervals are both identified as the most significant other factors contributing to bond strength development. Aggregate type is also identified as a significant factor that will influence the bond strength development. Interactions between emulsion type and curing interval are identified as the most significant interaction. A lot of further validation test on the BBS test method is still required for the test to be integrated into a performance-based specification system for surface seals. / AFRIKAANSE OPSOMMING: “Chip and Spray” oppervlak seëls is die verkose seël tipe vir gebruik op Suid Afrikaanse plattelandse paaie. Die ontwerp van hierdie tipe seëls is ook tans besig om hernude aandag te trek in heelwat lande. In Suid Afrika word die tipe seël al meer gebruik soos die behoefte na herseël projeke op die verouderde pad netwerk groei . Daar is ook heelwat groei in die gebruik van “Chip en Spray” seëls in Noord Amerika aangesien daar n behoefte is om n meer energie en materiaal effektiewe seëls te gebruik. Ten spyte van die groeiende gebruik van hierdie seëls het daar min wetenskaplike ontwikkeling plaasgevind in the ontwerp daarvan. Seëls word meestal ontwerp gebaseer op klient voorkeur , ondervinding, materiaal beskikbaarheid en ook industrie norms. ‘n Verouderde pad netwerk dwing die Suid Afrikaanse industrie om meer deeglike en wetenskaplike ontwerp prosedures te volg. Die VSA en Europa word deur vinnig groeiende verkeersvolumes en verhoogte kwaliteits behoeftes gedwing om prestasie gebaseerde spesifikasies te ontwikkel. Een van die hoof defekte op seëls is klipverlies wat plaasvind as die verbinding tussen die bitumen en aggregaat verswak en gebreek word deur die kragte wat deur verkeer oorgedra word. Dit lei tot los klip op die pad wat weer tot skade aan voertuie lei. Om dit te voorkom en aan te spreek het die behoefte laat ontwikkel vir n maklike en goedkoop tegniek om te meet hoe sterk die verbinding is wat ontwikkel tussen verskillende bitumen, bitumen emulsies en aggregaat monsters. Alhoewel daar alreeds toetse bestaan wat kan toets hoe sterk die verbinding is , gee die meeste van die toetse nie die informasie wat benodig word deur die voorgestelde prestasie gedrewe spesfikasies nie. Die “Bitumen Bond Strength” (BBS) toets metode is daarom ontwikkel om die tekortkoming in die toets van die bitumen en aggregaat verdindinge aan te spreek. Die BBS toets (AASHTO TP-91, 2011) is ontwikkel by die Universiteit van Wisconsin – Madison (UWM) in vennootskap met die Universiteit van Ancona – Italy (UAI) en die Universiteit van Stellenbosch (US) , spesifiek om die die sterkte van die verbinding wat vorm tussen aggregaat en bitumen te meet. Die US het in 2008 betrokke geraak by die BBS toets studie om hulp te verleen met die ontwikkeling en praktiese evalueering van die BBS toets metode. As gevolg van tyd en personeel tekorte is die betrokkendheid by die US beperk tot verskeie besprekings sessies, n studie toer, die evalueering van die BBS toets sowel as die voltooing van n uitgebreide stel toetse. Deur die voltooing van eksperimente met die BBS toets was dit moontlik om die uitvoerbaarheid en herhaalbaarheid van die ontwikkelde prosedure te toets. Die resultate van die toetse is suksesvol gebruik om die ontwikkeling van die verbinding sterkte tussen gemodifiseerde en ongemodifiseerde bitumen emulsies en tilliet en graniet te definïeer en te evalueer. Dit was ook moontlik om die resultate van die Universiteit Stellenbosch en die Universiteit of Wisconsin-Madison suksesvol met mekaar te vergelyk aangesien toetse by beide die instansies voltooi is. Die ontwikkeling van die toets en die inter laboratorium toets resultate het dit moontlik gemaak om die hipotese te bevestig dat die BBS toets prosedure effektief gebruik kan word om die bitumen en aggregaat verdindinge te toets en te evalueer. Behalwe vir die tempo van die lading waarteen die aftrek sterkte getoets word , is die emulsie tipe en die nabehandeling tydperk beide geidentifiseer as die mees beduidende invloede wat bydrae tot die ontwikkeling van die verbinding sterkte. Die aggregaat tipe is ook geidentifiseer as n belangrike faktor wat die verbinding sterkte ontwikkeling sal beïnvloed. Die interaksie tussen die emulsie tipe en nabehandeling tydperk was geïdentifiseer as die mees beduidende interaksie. Daar sal wel nog heelwat eksperimente voltooi moet word met die BBS toets prosedure voordat dit volkome geïntegreer kan word as deel van n prestasie gebaseerde spesifikasie stelsel vir die ontwerp van seëls.

Un nouveau procédé propre et performant de préparation de surface reposant sur l'utilisation d'un jet d'azote sous très haute pression et basse température est développé. Comparativement aux techniques classiques de préparation de surface, ce nouveau procédé apporte des avantages environnementaux (pas de génération de déchets additionnels), techniques (modes d'action sur le revêtement à traiter) et énergétiques (consommation d'énergie). Cependant, le fonctionnement du procédé de traitement de surface en question, qui existe sous forme de prototype à l'heure actuelle, repose sur des bases empiriques et les phénomènes physiques qu'il met en jeu sont encore bien mal appréhendés. Pour comprendre ces phénomènes et les modéliser, une analyse numérique est présentée. Cette analyse s'inclut dans une stratégie d'étude qui vise à augmenter progressivement le degré de complexité de la modélisation. Un premier modèle vise à décrire l'évolution du fluide en temps et en espace en supposant un écoulement compressible visqueux et axisymétrique. Dans ce modèle, le fluide est considéré comme parfait. Une extension directe de ce modèle est ensuite présentée, elle propose de tenir compte des effets de fluide réel dans l'écoulement compressible monophasique. Ces modèles sont implémentés dans un code de calculs par volumes finis. Des cas tests sont étudiés afin de valider les modèles numériques. Une étude sur des configurations de type industrielles, représentatives des conditions d'utilisation du procédé de traitement de surface par jet d'azote, est ensuite menée / A new and efficient process of surface treatment is developed and exists in prototype form at present. The process aims at injecting an inert gas, such as nitrogen, at supercritical conditions through a nozzle. The jet resulting from the expansion of the fluid at high pressure and supercritical temperature impinges normally a flat surface. Alternatively to water jet technologies, which need expansive purification of water after use, and to other classical surface treatment process, this process provides environmental (no generation of additional waste), technical (action on the coating) and energetical (efficiency) benefits. However, the physical phenomena involved in the jet are still poorly understood at present. To understand and model these phenomena, numerical analysis is presented. This analysis is part of a study strategy that aims at gradually increasing the complexity of modeling. A first model aims at describing the evolution of the fluid in time and space, assuming a compressible axisymmetric viscous flow. In this model, the fluid is assumed perfect. A direct extension of this model is then presented where real fluid effects are taken into account in the compressible flow. These models are implemented in finite volume CFD code. Test cases are studied to validate the numerical models. A study of industrial-type configurations, representative of the conditions of use of the process of surface treatment by nitrogen is then conducted