In a series ofpreIiminary studies of urea-formaldehyde reactions, the influence of the U:F molar ratio, the temperature and the catalyst were investigated. Subsequently, in a more rigorous evaluation of the influence of four variables on urea-formaldehyde resin formation, viz., U:F molar ratio, pH, temperature and reaction time, a set of twenty reactions were performed using a statistical approach. The results indicate that high resin viscosity is best achieved by using a high U:F molar ratio (1:2) and conducting the reaction at 90°C. Several basic components produced in urea-formaldehyde reactions have been synthesised, characterised by NMR spectroscopy, silylated using bis(trimethylsilyl)trifluoroacetamide and analysed by low resolution mass spectrometry. The use oftriazones as cross-linking agents has been investigated, and a series of 5-substituted triazones have been prepared and their mass fragmentation patterns explored using a combination of low and high resolution mass spectrometry. In order to facilitate interpretation of ¹³C NMR data obtained for U-F resins, internal rotation in various urea derivatives was investigated using variable temperature ¹H and ¹³C NMR spectroscopic study. Signal splittings observed below 247 K have been rationalised in terms of various rotameric structures.

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Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 105-120). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 105-120). Also available on the Internet.

Indiana University-Purdue University Indianapolis (IUPUI) / Clinical studies on composite resins in Class II Resotrations place in adults indicate that wear is the predominant problem. However, little has been published on the use of composites for such restorations in primary teeth. The purpose of this study was to compare amalgam to composite resins in such restorations. Two composite resins (Adaptic and Radio-opaque Adaptic) served as the Experiemental material and amalgam, (Dispersalloy) was the control . One operator placed 57 sets, one restoration of each of the three materials per set, in 50 patients at the Riley Children's Hospital in Indianapolis. Evaluations were made at baseline, six months, one year, two years, and three years using the Ryge-USPHS criteria and by means of casts poured from elastomeric impressions. Results of the Ryge-USPHS criteria indicated no wear or color change of the composites after two years (p=N.S.). However, of the 49 sets that returned at one year, two composites had caries around the restoration. This particular observation was monitored at the three-year time interval and found not to increase around any other composite restorations. Composite restorations in posterior primary teeth compared equally to amalgam (Dispersalloy) for the first two years of the project. The loss of anatomic form was significant after three years (p=.05).

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No description available.

This creative project was a study of combining large-scale ceramics and polymer resin (Brandname: Bondo) vessels. This project came out of an earlier experiment combining metals and resin, and therefore the interest in combining clay and resin was a natural transition for me, since ceramics was my major focus. I had a definite interest in the challenge of marrying two very different materials; clay and resin, and by using this combination I would make vessels that were visually successful and engaged the viewer.The technical basis for all of the ceramic elements of the vessels is wheel throwing. The molds made for the resin parts of the piece were wheel thrown as well. This project was very unique and there was little documented technical information for me to rely on other than personal experimentation and ceramic knowledge.The visual elements of clay with its opaqueness, and resin with its translucent qualities offered great visual contrast. The use of color contrast between warm and cool colors became an important element of the pieces.From an expressive standpoint, I feel the form of the vessels is viewed as solid and confrontational, yet very compelling. The smooth surfaces and the lush vibrant colors compel the viewer to examine the forms. The pieces are commanding in size and strength, so the viewer is somewhat hesitant to view for too long. There is a visual push/pull, a contrast between these simple yet over-scaled layered forms that evokes an emotional push/pull as well. / Department of Art