This thesis is concerned primarily with the curing of epoxy resin and the effect of gamma-irradiation on the electrical properties of epoxy resin systems. The particular systems examined were a diglycidyl ether of bisphenol A (DGEBA, Ciba Geigy MY750) epoxy resin cured using one of two hardeners. These were a hydroxyalkylated polyamine (Ciba Geigy HY956) and a dodecenyl-succinicanhydride (DDSA) with an accelerator of benzyldimethylamine. Different methods of examining the curing of the epoxy resin system have been carried out including differential scanning calorimetry (DSC), infrared spectroscopy (I.R.), dielectric measurements, volume resistivity measurements and thermally stimulated discharge current. The results of dielectric relaxation measurements obtained during the curing of the epoxy resin system were interpreted on the basis of a model considering the growing polymer molecules to be in solution, the solvent being the unreacted monomer and hardener. The investigation of the effect of gammairradiation on the electrical properties (conduction mechanism and dielectric behaviour) of the epoxy resin system was achieved by examining the electrical properties of the fully cured epoxy resin system before and after irradiation and the results compared. To establish the electrical properties of the fully cured epoxy resin system before and after irradiation, a series of experiments which provide information about the conduction mechanism, the dielectric properties, the infrared spectra (I.R.) and the glass transition temperature (Tg) obtained from (DSC) measurements were carried out. For the epoxy resin system MY750/HYS56, it was found that the D.C. conductivity, dissipation factor and capacitance values increase, whereas the glass transition temperature (Tg) and the activation energy, E, obtained from D.C. measurements decreased for the irradiated samples. Furthermore, a modification in the I.R. spectrum in the 1600 to 1800 cm⁻¹ range due to the formation of carbonyl groups (C = O) in the irradiated sample has been observed. However in the case of epoxy resin system MY750/DDSA, it was found that the dissipation factor and capacitance values decrease, whilst the glass transition temperature (Tg) and the activation energy obtained from dielectric measurements increased for the irradiated samples.

Three types of composite resins, classified as conventional, microfilled and hybrid resins were compared with respect to surface characteristics, effect on the gingival margin, marginal adaptation and clinical durability in anterior cavities. The surface characteristics were studied in in vitro systems by means of scanning electron microscopy. Fillings prepared in vivo were evaluated regarding surface characteristics, marginal conditions, color stability and the effect on the develop­ment of gingivitis and caries. Microfilled resins were superior to the conventional and hybrid composites with regard to the possibility of obtaining and retaining a smooth surface. The number of porosities varied greatly between the composites investigated and could not be related to the type or curing method used in their manufacture. Marginal defects in the form of chip fractures and fractures in the resin parallel to the resin/enamel border were seen more frequently in the microfilled composite fillings than in the conventional and hybrid resins. The severity of the defects increased with time. There was a great variation in clinical behaviour within each resin group. The dif­ference in surface characteristics between the three composites did not result in clinically measurable differences in amount of plaque on and degree of gingivitis around the composite fillings neither during a period of normal home care nor during an experimental gingivitis period. Recurrent caries was the major single reason for replacement. Patients with a greater number of caries risk factors clearly showed a higher caries increment, especially around composite fillings. The short­comings of the three composite resin types indicate that no material as yet meets the demands of an all purpose material. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1987, härtill 7 uppsatser.</p> / digitalisering@umu

No description available.

This thesis examines the feasibility of manufacturing small marine propellers from continuous fibre reinforced polymer composite materials. An appraisal of some current applications of composite materials in the marine industry is given, together with the moves shown towards the use of composites in the area of propeller design. It has been shown that manufacturing propellers in composite materials is theoretically more cost effective than traditional materials. The manufacturing route investigated is Resin Transfer Moulding, where some detailed investigations have highlighted some of the critical processing parameters necessary for successful production of laminates suitable for propellers and other high performance marine structures. A thorough testing programme of 4 novel designs of composite propeller is reported. Trials at sea on university run vessels has enabled many hours use to be logged, which has shown the fitness for purpose of propellers made from glass reinforced, epoxy composite. Experimental tank testing has helped to shape the remainder of the research by identifying the possibility of using hydroelastic tailoring to improve the efficiency of the propeller when a variety of operating conditions are required from the propulsion system. Further experience is required with respect to the the tooling construction and the life assessment of the propeller. To facilitate appropriate modelling of the propeller, spreadsheet based load prediction models have been used. Finite element analysis (FEA) was used to model the elastic characteristics of one particular design of novel composite propeller. This indicated that traditional geometries may be too stiff to allow significant performance advantages from the anisotropy of the material. However the potential does exist for modified propeller geometries made from composite to give some performance benefit. For specific applications, small marine propellers made from continuous glass fibre reinforced epoxy composite are likely to yield cost savings over traditional propeller materials.

Woods other than the traditional oak wood have been studied for their applicability to winemaking, aiming to produce wider ranges of wine flavours with a distinctiveness associated with New Zealand. Prior studies with woods other than oak have shown that unpleasant flavours from infusion of some woods could be linked to the presence of resin. The main thrust of this research was to test the hypothesis that any wood free of resin would be suitable for flavouring wine since all trees are composed of the same major constituents. The study involved various organic solvent extractions to remove resins from manuka, macrocarpa, totara, kahikatea, radiata pine, gorse, and American oak, prior to toasting and wine infusion. The woods were cut to a defined chip dimension, and Soxhlet-extracted with dichloromethane before toasting to 200 and 210°C for two and three hours, respectively. These were the light and heavy toasts. In discriminative triangle trials comparing unextracted with resin-extracted infusion treatments in unwooded chardonnay at the two toasting levels, the 50 panellists could distinguish a difference in only three of the 14 trials. The exceptions were manuka heavy toast (P < 0.01), and both macrocarpa toasts (P < 0.05). The remaining 11 trials did not elicit significant levels of correct judgements from the panellists. The mass of resin recovered ranged from 1% (gorse) to 11 % (manuka), but there was no relationship between the quantity of resin and the discrimination results. Other parameters relating to the wood chips were measured in parallel to the discrimination trials. Colour changes in untoasted woods due to resin extraction were usually statistically significant but minor. Colour changes were unrelated to weight losses due to extraction. Light and heavy toasting resulted in significant and often major changes in colour parameters due to resin extraction. However there was no clear pattern of change and thus had no meaningful outcomes. In the discrimination trials, subtleties of the responses to macrocarpa and manuka, suggested that not all resin was extracted by the single extraction with dichloromethane. A further extraction of toasted chips not used for infusion showed that resinous matter was still present in all woods, although pyrolytic generation of dichloromethane-soluble matter could not be excluded. These collective results prompted an exhaustive extraction of wood chips prior to a hedonic trial with manuka, macrocarpa, and American oak. The solvents in sequence were dichloromethane, hexane and diethyl ether. Each extracted some resinous matter, clearly showing that the single dichloromethane extraction prior to the discrimination trials left some resin in the chips, potentially affecting wine flavour. The triple-extracted woods were light toasted and infused in wine destined for a hedonic trial in six retail wine shops, for which the overall statistical significance was P < 0.001. The 121 consumers found that the unwooded chardonnay (control) was most favoured whereas the wine infused with macrocarpa was very significantly the least favoured. Its dislike was clearly caused by presence of its resin in the wine and/or because of a very low flavour threshold for that resin. The manuka treatment was numerically the most favoured ahead of American oak, but not significantly so. The resins extracted at various points of this study were also evaluated by panellists focusing on descriptive qualities. These descriptions and the results of the discrimination and hedonic trials led to the conclusion that variation in wine flavour when infused with toasted wood was in most cases not related to the occurrence of resin in woods. Finally, future research possibilities have been described, with an emphasis of the most potentially useful wood, manuka.

Woods other than the traditional oak wood have been studied for their applicability to winemaking, aiming to produce wider ranges of wine flavours with a distinctiveness associated with New Zealand. Prior studies with woods other than oak have shown that unpleasant flavours from infusion of some woods could be linked to the presence of resin. The main thrust of this research was to test the hypothesis that any wood free of resin would be suitable for flavouring wine since all trees are composed of the same major constituents. The study involved various organic solvent extractions to remove resins from manuka, macrocarpa, totara, kahikatea, radiata pine, gorse, and American oak, prior to toasting and wine infusion. The woods were cut to a defined chip dimension, and Soxhlet-extracted with dichloromethane before toasting to 200 and 210°C for two and three hours, respectively. These were the light and heavy toasts. In discriminative triangle trials comparing unextracted with resin-extracted infusion treatments in unwooded chardonnay at the two toasting levels, the 50 panellists could distinguish a difference in only three of the 14 trials. The exceptions were manuka heavy toast (P < 0.01), and both macrocarpa toasts (P < 0.05). The remaining 11 trials did not elicit significant levels of correct judgements from the panellists. The mass of resin recovered ranged from 1% (gorse) to 11 % (manuka), but there was no relationship between the quantity of resin and the discrimination results. Other parameters relating to the wood chips were measured in parallel to the discrimination trials. Colour changes in untoasted woods due to resin extraction were usually statistically significant but minor. Colour changes were unrelated to weight losses due to extraction. Light and heavy toasting resulted in significant and often major changes in colour parameters due to resin extraction. However there was no clear pattern of change and thus had no meaningful outcomes. In the discrimination trials, subtleties of the responses to macrocarpa and manuka, suggested that not all resin was extracted by the single extraction with dichloromethane. A further extraction of toasted chips not used for infusion showed that resinous matter was still present in all woods, although pyrolytic generation of dichloromethane-soluble matter could not be excluded. These collective results prompted an exhaustive extraction of wood chips prior to a hedonic trial with manuka, macrocarpa, and American oak. The solvents in sequence were dichloromethane, hexane and diethyl ether. Each extracted some resinous matter, clearly showing that the single dichloromethane extraction prior to the discrimination trials left some resin in the chips, potentially affecting wine flavour. The triple-extracted woods were light toasted and infused in wine destined for a hedonic trial in six retail wine shops, for which the overall statistical significance was P < 0.001. The 121 consumers found that the unwooded chardonnay (control) was most favoured whereas the wine infused with macrocarpa was very significantly the least favoured. Its dislike was clearly caused by presence of its resin in the wine and/or because of a very low flavour threshold for that resin. The manuka treatment was numerically the most favoured ahead of American oak, but not significantly so. The resins extracted at various points of this study were also evaluated by panellists focusing on descriptive qualities. These descriptions and the results of the discrimination and hedonic trials led to the conclusion that variation in wine flavour when infused with toasted wood was in most cases not related to the occurrence of resin in woods. Finally, future research possibilities have been described, with an emphasis of the most potentially useful wood, manuka.

Thesis (M.S.)--University of Michigan, 2004. / Includes bibliographical references.

Thesis (M.S.)--University of Michigan, 2003. / Includes bibliographical references.

Thesis (M.S.)--University of Michigan, 2002. / Includes bibliographical references.

Made available in DSpace on 2014-06-11T19:28:58Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-07-12Bitstream added on 2014-06-13T19:58:26Z : No. of bitstreams: 1 michida_sma_me_sjc.pdf: 1742951 bytes, checksum: 280b4986bb5daf3b8e21e366847dde92 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O objetivo desta pesquisa foi avaliar a resistência à microtração de uma resina composta indireta, tratada com ácido fluorídrico em diferentes tempos de condicionamento, após termociclagem, a um cimento resinoso. Um padrão em resina acrílica (6 x 6 x 6 mm) foi moldado com polivinilsiloxano obtendo-se um molde para a confecção de 30 blocos de resina composta indireta (RCI) (Vita VMLC). Os blocos foram divididos em 6 grupos (n=5): G1 (controle negativo): sem HF; G2: HF 60 s; Grupo 3: HF 90 s; G4: HF 120 s; G5: HF 180 s; G6 (controle positivo): silicatização (Cojet Sand). As superfícies de RCI receberam aplicação de silano (Monobond-S) e adesivo (Excite DSC) e foram cimentados, aos seus respectivos blocos de resina composta direta (RCD) confeccionados da mesma forma que os de RCI, com cimento resinoso dual. Os conjuntos RCI/cimento/RCD foram armazenados em água destilada (37ºC/24 hs) e cortados em máquina de corte para obtenção dos palitos (n=9). As amostras foram submetidas à termociclagem (6000 ciclos, 5ºC a 55ºC, 30 s) e , ao teste de microtração na máquina de ensaio universal (EMIC). ANOVA (a=0.05) mostrou que os valores de resistência adesiva (MPa) não foram afetados pelo tratamento de superfície (p>0.001). Foi verificado que em G5 (41,86 mais ou menos 7,01b) houve diferença estatisticamente significante em relação a G1 (35,64 mais ou menos 4,95a); e, G2 (40,20 mais ou menos 5,63a), G3 (40,96 mais ou menos 5,18a), G4 (40,61 mais ou menos 3,17a) tiveram diferenças estatisticamente significantes em relação ao G6 (47,38 mais ou menos 6,12b) (teste de Dunnet). Concluiu-se que o tratamento de superfície da RCI com HF... / The aim of this study was to evaluate the microtensile bond strength of an indirect composite resin, after surface treatment with hydrofluoridric acid in different periods of etching time and thermocycling, to a resin cement. An acrylic block (6 x 6 x 6mm) was molded with polivinilsiloxane obtaining a mold to build 30 blocks of indirect composite resin (ICR) (Vita VMLC) The blocks were divided in 6 groups (n=5): G1 (negative control): without HF; G2: HF 60s; Group 3: HF 90s; G4: HF 120s; G5: HF 180s; G6 (positive control): sandblasting (Cojet Sand). On the ICR block surface was applied silane (Monobond-S), adhesive system (Excites DSC) and it was cemented to direct composite resin (DCR) blocks, built on the same way that the ICR blocks were made, with dual resin cement. The ICR/cement/DCR were stored in distilled water (37ºC/24hs) and cut in machine obtaining 9 samples (n=9). They were submitted to thermocycling (6000 cycles, 5ºC to 55ºC, 30s) and to the microtensile bond strength test in an universal machine (EMIC). ANOVA (a=0.05) showed that the bond strength (Mpa) was not affected by the surface treatment (p>0.001). It was verified that G5 (41.86 mais ou menos 7.01b) was statistically different from G1 (35.64 mais ou menos 4.95a); and G2 (40.20l5.63a), G3 (40.96l5.18a), G4 (40.61 mais ou menos 3.17a) was statistically different from G6 (47.38 mais ou menos 6.12b) (Dunnet test). It was concluded that the ICR surface treatment with HF... (Complete abstract click electronic access below)