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The Arrhenius parameters have been measured for the addition of the ethyl radical to methyl acrylate and its mono-methyl derivatives, methyl methacrylate, methyl cis-crotonate and methyl trans-crotonate. The energy of activation for each of these derivatives is significantly greater than for methyl acrylate, probably because of the adverse polar effect introduced by the methyl group. The activation energy for the addition to methyl methacrylate appears to be lower than for either the cis- or trans- methyl crotonate. This can probably be attributed to the fact that the ∝-methyl group can more effectively stabilise the adduct radical resulting from the addition of the ethyl radical to the methyl methacrylate, than the β-methyl group can in the case of crotonates. The pre-exponential factor is significantly smaller for each of the methyl crotonate isomers than for methyl methacrylate; partial shielding of the β-carbon atom of methyl crotonate is thus expressed by a steric factor rather than by an energy term. In terms of the rate constant for the addition reaction over the range 70°C to 160°C, methyl trans-crotonate is significantly more reactive than methyl cis-crotonate, and each isomer is only about one tenth as reactive as the vinyl compounds, methyl acrylate and methyl methacrylate, in which the site of radical attack is comparatively unobstructed. The cis-trans isomerisation of methyl crotonate is photo-sensitised by diethyl ketone illuminated by 3130 Å radiation in the gaseous phase; a mechanism of triplet state energy transfer is proposed for the process below 200°C; above 200°C an alternative mechanism involving the reversible addition of the ethyl radical to the double bond becomes the predominant process of isomerisation. / Science, Faculty of / Chemistry, Department of / Graduate

It was my purpose to study the role of acrylic paints and other products in the secondary high school and junior high school art curriculum in the area of painting, and related activities and to make a realistic evaluation of this medium. Because of its comparative newness and because of a general lack of knowledge of and experience with it, I felt such a study would fill a need relative to the utilization of acrylic products in the classroom. In preparation I read the material which was available on painting with acrylics'. The number of books published on the subject is limited. I talked with art teachers and found that many had only a cursory acquaintance with acrylics or had not used them at all. With this background I became involved in as many aspects of the use of acrylics in. the classroom as I could. A skeptic at first, I became increasingly enthusiastic as my work progressed. From my own experiences with acrylics, I devised some experiments which, for the most part, I took into the classroom and with which I involved students ranging from third grade to high school level. After my own experiences with acrylics as both artist and teacher, it is my conviction that acrylics can be invaluable in the art curriculum, and that they can be most helpful in providing a significant contemporary approach to the fundamentals of painting and other techniques. There are five chapters and an appendix in this thesis report. The first chapter provides an introduction to the acrylic products, with a brief summary of their-development as a fine arts medium, their cost, handling characteristics and their advantages and disadvantages. The second chapter is concerned with the individual acrylic products and with equipment and supplies. Painting techniques and suggestions for the use of acrylics are discussed in the third chapter. Suggestions for additional uses in the related activities of collage, mosaic, printing, drawing, transparent design and other techniques are contained in the fourth chapter. In the fifth chapter I state my conclusions concerning the medium. Photographs of student work and my work are included as a supplement to the text. A list of local suppliers and a list of manufacturers are included in the appendix, as well as photographs of my thesis paintings.

Indiana University-Purdue University Indianapolis (IUPUI) / The purpose of this laboratory study was to determine whether etching of flat bovine enamel surfaces with a 50 per cent aqueous solution of phosphoric acid for 60 seconds increases the bonding of a conventional restorative acrylic resin and a new polycarboxylate cement. The test specimens were subjected to 24 hours, 30 days and six months storage in water and then subjected• to temperature stress cycling and intermittent tensile stress cycling. A tensile test was used to measure the bond strength of both materials. The results of the Newman-Keul's test showed that pretreating the enamel surface with 50 per cent phosphoric acid significantly increased the bonding of the restorative resin, and that the cavity sealer supplied by the manufacturer further improved the resin attachment to enamel surfaces previously etched with phosphoric acid. The bonding of the resin to acid-etched enamel surfaces pretreated with or without the cavity sealer was unaffected by prolonged storage in water, temperature stress cycling, and intermittent tensile stress cycling. However, a significant reduction in the adhesion of the acrylic resin to polished-enamel surfaces pretreated with or without the cavity sealer was observed when the test specimens were subjected to the same testing conditions. The data obtained for the polycarboxylate cement test specimens showed that etching of the enamel surface with phosphoric acid also provided slightly higher adhesive values than the control specimens. Results obtained revealed that prolonged storage in water, and temperature and mechanical stress cycling did not affect the adhesion of the polycarboxylate cement to acid-etched enamel surfaces. However, thermal and mechanical stress cycling after prolonged storage in water appeared to decrease the adhesion of the cement to polished enamel surfaces. When Ca45 was used to assess the marginal seal of resin restorations placed into acid-etched Class V cavity preparations in extracted human teeth, the autoradiographs showed that etching of the cavity preparations with 50 per cent phosphoric acid improved the marginal seal of the restorative resin after one-week storage in water. When both the acid-etched and control restorations were thermal stress cycled 2500 times at a 40°C temperature differential, a slight improvement in the marginal seal of the acid-etched restorations was observed.

Latex polymers serve as binders in a wide range of architectural paints and coatings. A latex is an aqueous colloidal dispersion of polymer particles that when dried above the polymer’s film formation temperature coalesces into a dry polymer film (Dragnevski, Routh, Murray, & Donald, 2010). The other main components of paint include associative thickeners, surfactants, pigments and fillers with the thickener being the primary area of focus for this study. The relatively simple system of latex, associative thickener and surfactant has been studied extensively. These studies have shown the mechanism of thickening for the associative thickener, and surfactant effects on both latex and thickener; however, there are few studies conducted for a fully-formulated system. The introduction of pigments, fillers, coalescing aids, functional amines, and other additives greatly increases the difficulty of research in this area. The addition of many additives ultimately affects the stability and physical properties of the end-product. Phase separation of the paints, also called syneresis, is a major concern of paint formulators because paints need to be as stable when left sitting in a paint-can for an extended period of time. The goal of this project is to essentially probe the areas of phase separation for some hydrophobically modified ethoxylated urethane (HEUR) thickened paint systems that are very similar to commercially used paint formulations. The probing of these phase separated regions includes the careful preparation of each paint sample, physical property testing, as well as new experimental development in the area of syneresis, rheology, followed by statistical analysis of data. Dispersion phase diagrams (DPDs) were first reported by Kostansek (2003) in a simple system of HEUR thickener, surfactant, and latex. They are a plot of the three possible dispersion states for an associative thickened system. These states include bridging flocculation which occurs at low levels of HEUR in which 50% or less of the latex particle surface is covered by the associative thickener. The second state is a good dispersion, which does not show any signs of flocculation. The third state is a mode of flocculation called depletion flocculation that occurs when the particle surfaces of the system are covered mostly with surfactant. The free associative polymer in the system is excluded from the free space in between particles, and the latex particles form aggregates (Otsubo, 1995). The three dispersion phases are then plotted with wt% HEUR on the continuous phase versus wt% surfactant on the continuous phase. The ideal end product for this project would be to use various combinations of latex, surfactant, and associative thickeners (ATs) to create multiple DPDs, which then could be used to troubleshoot formulations and samples in which flocculation is present. Each formulation was made using a thickening package of two non-ionic HEURs: a low-shear and high-shear thickener. Surfactant additions were made after the HEUR in small incremental amounts. Each DPD would consist of one surfactant, the previously stated combination of HEURs, and an all-acrylic latex. Three different surfactants were used in the study: two non-ionic surfactants, and an anionic surfactant. The first non-ionic surfactant was not studied in full as the other two surfactants due to time constraints. Two different all-acrylic latexes were used which varied in the particle size. The first latex studied, Acrylic-A, has an average particle size of 105 nm, and the second latex was Acrylic-B with 150 nm particle size. The TiO2 used in each DPD was surface treated and used in powder form. By the end of the project, 4 full-scale DPDs were made with the following combinations: Acrylic-A and a non-ionic surfactant, Acrylic-A and an anionic surfactant, Acrylic-B and a non-ionic surfactant, and Acrylic-B and an anionic surfactant. From these DPDs the mechanistic interactions of various components of the system could be made. The DPDs could also be used to troubleshoot problematic paints and even hypothesize new formulations.

Yes / The fracture resistance of polymethylmethacrylate (PMMA) as the most popular denture base material is not satisfactory. Different factors can be involved in denture fracture. Among them, flexural fatigue and impact are the most common failure mechanisms of an acrylic denture base. It has been shown that there is a correlation between the static strength and fatigue life of composite resins. Therefore, the transverse strength of the denture base materials can be an important indicator of their service life. In order to improve the fracture resistance of PMMA, extensive studies have been carried out; however, only a few promising results were achieved, which are limited to some mechanical properties of PMMA at the cost of other properties. This study aimed at optimizing the packing and processing condition of heat-cured PMMA as a denture base resin in order to improve its biaxial flexural strength (BFS). The results showed that the plain type of resin with a powder/monomer ratio of 2.5:1 or less, packed conventionally and cured in a water bath for 2 h at 95 °C provides the highest BFS. Also, it was found that the performance of the dry heat processor is inconsistent with the number of flasks being loaded.

Yes / Interpolymer complex formation of poly(acrylic acid) with other macromolecules can occur via several mechanisms that vary depending on the pH. At low pH the protonated acid functional group can form bonds with both donor and acceptor moieties, resulting in desolvated structures consisting of two polymers. Complexes were formed in dilute solutions of PAA, functionalised with acenaphthylene, with a range of other polymers including: poly(NIPAM); poly(ethylene oxide) (PEO); poly(dimethylacrylamide) (PDMA); poly(diethyl acrylamide) (PDEAM) poly(vinyl alcohol) (PVA) and poly(vinyl pyrolidinone) (PVP). Fluorescence anisotropy was used to demonstrate complex formation in each case by monitoring the reductions in segmental motion of the chain as the complexes formed. Considerations of the molecular structures of the complexing moieties suggest that solvation energies and pKas play an important role in complex formation.

I stand in awe of nature's beauty. The natural forms and colors of my subjects inspire me to create paintings and three-dimensional clay pieces. As I marvel at God's handiwork, my soul is enriched by the pure sight of His canvas. The rich bright colors of the organic shapes compel me to visually interpret what I experience as an expression of who and what I am, and what I want others to see. My intent is to focus on the elements of the subject matter where the color, shape, and form dominate the space.

Artists generally begin their craft by relating to what is most familiar to them. It is in this comfort zone that my journey into painting began. From my first painting of the Chrysler Building in New York City to the countryside in Tuscany, my work tells the story of my travels. When I began to create jewelry that contained elements of my paintings, I expanded on the concept of documenting my travels. Further experimentation with new materials used in jewelry making allowed me to create a visual correlation between my paintings and my wearable jewelry.

O objetivo deste trabalho foi avaliar as alterações dimensionais de resinas acrílicas submetidas a diferentes tipos de processamento avaliados ao nível condilar. As condições experimentais foram introduzidas em três etapas. Na etapa A, as resinas acrílicas (Clássico, Ondacryl, Acron MC, Lucitone e QC-20) foram incluídas em muflas contendo muralha de gesso, prensadas na fase plástica e submetidas a cinco ciclos de acrilização. Na etapa B, as resinas acrílicas utilizadas foram a QC-20 e a Lucitone, utilizando três tipos de muralha (gesso, silicone (ZETALABOR) e filme de silicone (VIPISIL)), e duas fases de reação química da resina acrílica na prensagem (fluida e plástica). Na etapa C, foi utilizada a resina Acron MC com dois ciclos de polimerização (90W por treze minutos e 500W por três minutos) variando-se, ainda, o tipo de muralha como na etapa B. Para o estudo, foram confeccionadas 5 próteses totais para cada grupo. Ao final, obtiveram-se 23 grupos totalizando 115 próteses totais superiores. Mediu-se a variação posicional do ramo superior do articulador TT antes e após os processamentos, tendo por base a orientação oclusal da máxima intercuspidação. Tal variação foi registrada através de gesso tipo IV vertido em espaço ao redor das esferas condilares, previamente providos por meio de espaçadores utilizados antes do processamento. Foram medidas três distâncias em cada esfera condilar (superoinferior, anteroposterior e mediolateral) resultando em 690 medidas que variaram de 0 a 3 mm, com média de 0,79 mm e desvio padrão de 0,59 mm. Ocorreu alteração em 687 medidas, sendo que houve diferença entre os grupos, estatisticamente significante, principalmente para a distância anteroposterior do lado esquerdo, na variável resina. Conclui-se que, as alterações dimensionais de resinas alteraram as posições das esferas condilares. / The objective of this study is to evaluate the dimensional acrylic resin alterations submitted to different types of processing evaluated to the level of the condyle. The experimental conditions were introduced in three stages. In stage A , the acrylic resins (Classic, Ondacryl, Acron MC, Lucitone and QC-20) were enclosed in flasks contend plaster wall, pressed in the plastic phase and submitted to five cycles of acrylization. In stage B, the QC-20 and the Lucitone were used with three types of wall (plaster, silicone (ZETALABOR) and silicone film (VIPISIL)), and with two phases of chemical reaction of the acrylic resin (fluid and plastic). In stage C, the resin Acron MC with two cycles of polymerization was used (90W for thirteen minutes and 500W for three minutes) by changing the type of wall as in stage B. For the study, 5 complete dentures for each group were made. At the end of the experiment, 23 groups were obtained, totalizing 115 superior complete dentures. Positional variation of the upper member of the articulator T.T.was measured before and after the processing, based on the maximum intercuspidation orientation. Such variation was registered by using plaster type IV shed in the space around of the condyle spheres, previously provided by means of spacers used before the processing. Three distances in each condyle sphere were measured (superoinferior, anteroposterior and mediolateral) resulting in 690 measures that varied from 0 to 3 mm, with average of 0,79 mm and shunting line standard of 0,59 mm. An alteration in 687 measures occurred and there was difference between the groups statistically significant, mainly for the anteroposterior distance on the left side. The conclusion was that the dimensional resin alterations modified the positions of the condyle spheres