No description available.

No description available.

Made available in DSpace on 2016-03-15T19:37:01Z (GMT). No. of bitstreams: 1 Marcio Rubens Xavier Bartholomei.pdf: 4061609 bytes, checksum: da657a031051b1f1a9571a34df2312ba (MD5) Previous issue date: 2010-05-07 / The bakery uses forms of carbon steel coated with nonstick layer and these forms have a lifespan of 10,000 cycles of production (3 years to 3.5 years) and are expensive. In order to reduce this cost, these industries could replace conventional forms by forms of a commercial liquid crystal polymer, Vectra E540i. The present study evaluated the mechanical and physicochemical properties of this polymer, in view of this replacement, without prejudice to the quality of the bread obtained. Because of the need to use forms in an oven at high temperature, the samples were subjected to heat treatment at various temperatures above and below the temperature of cooking in the oven and then observed the effect of temperature on tensile strength and hardness of the material. Tests of degradation by ultraviolet (UV) were also conducted and found its effect on the tensile strength and impact. In these laboratory tests, the resistance of the forms and quality of bread were tested in a pilot plant. The results show that there is no degradation after constant exposure to UV radiation for 80 days and the tensile strength and impact were not affected. There were no significant changes in mechanical properties due to heating. It was observed that no major changes in mechanical properties due to heating in the polymer are subjected during its passage in the oven. At these temperatures, the mechanical properties mentioned are lower than expected. In a pilot scale, the quality of bread has not changed. From this study, the Company may decide to continue using the current metallic forms or replace them with forms of liquid crystal polymer Vectra E540i. / As indústrias de panificação usam formas de aço carbono revestidas com camada antiaderente sendo que estas formas têm uma vida útil de 10.000 ciclos de produção (3 anos a 3,5 anos) e tem custo elevado. Com o intuito de diminuir este custo, estas indústrias poderiam substituir as formas convencionais por formas a base de um polímero de cristal líquido comercial, Vectra E540i. Neste trabalho foram avaliadas as propriedades mecânicas e físico-químicas deste polímero, tendo em vista esta substituição, sem prejuízo da qualidade do pão obtido. Devido à necessidade de se usar as formas num forno com temperaturas elevadas, as amostras foram submetidas a tratamento térmico em várias temperaturas, acima e abaixo das temperaturas do cozimento no forno e, posteriormente, foi verificado o efeito da temperatura na resistência à tração e na dureza do material. Também foram realizados ensaios de degradação por radiação ultravioleta (UV) e verificou-se seu efeito sobre a resistência a tração e impacto. Além destes ensaios laboratoriais, a resistência das formas e a qualidade do pão foram testadas numa planta piloto. Os resultados mostram que não há degradação frente à radiação UV, após exposição constante durante 80 dias, bem como as resistências à tração e ao impacto não foram afetadas. Observou-se que não há grandes alterações nas propriedades mecânicas devido ao aquecimento em que o polímero é submetido durante a sua passagem dentro do forno. Amostras aquecidas em temperaturas acima de 275ºC apresentaram a formação de bolhas visíveis a olho nu, sugerindo degradação térmica do polímero. Nestas temperaturas, as propriedades mecânicas citadas apresentam valores inferiores aos esperados. Em escala piloto, a qualidade do pão não se alterou A partir deste estudo a Empresa poderá tomar a decisão de continuar a utilizar as atuais formas metálicas ou substituir por formas a base do polímero de cristal líquido comercial Vectra E540i.

In dieser Grundlagenstudie wird evaluiert wie präzise 3D-Gesichtsaufnahmen eines Patientenkollektivs mit einer Lippen-, Kiefer-, Gaumenspalte mit dem 3D-Bildaufnahmesystem Vectra M3 (Canfield) und der Analysesoftware Facial Analysis Tool (FAT), entwickelt in der Abteilung MKG der Universität Leipzig, analysiert werden können. Im ersten Studienabschnitt werden 3D-Gesichtsaufnahmen von 3 Patienten und einem Modellkopf erstellt und für 62 manuell festgelegte Landmarken (LM) 10-mal die x-, y-, z-Koordinaten bestimmt. Die statistisch ermittelten prozentualen Variationskoeffizienten und die FAT-Beurteilungen der Messdaten werden graphisch verglichen und zeigen eine gute Übereinstimmung. Die Präzision der LM-Positionierungen ist Landmarken-abhängig Im zweiten Abschnitt werden an 91 Patienten mit unterschiedlichen Spaltdiagnosen jeweils 146 Distanzen aus LM und auch konstruierten Punkten mittels FAT ermittelt. Die prozentualen Variationskoeffizienten der Messdaten der Patientenkollektive werden nach Spaltdiagnose (beid-, rechts-, linksseitiger LKG-Spalte und Minimalvarianten), nach Geschlecht und Alter (≤ , >16 Jahre) graphisch ausgewertet. Die Variationskoeffizienten der Distanzen innerhalb einer Patientengruppe sind vergleichsweise hoch, insbesondere im Nasen- / Mundbereich mit kleinen Distanzen. Eine Differenzierung nach Geschlecht und Alter ist nicht möglich. Im dritten Abschnitt werden Symmetrieindizes für 36 Distanzen von den nach Spaltdiagnose gruppierten 91 Patienten errechnet und graphisch ausgewertet. Die Patienten mit einer einseitigen Anomalie weisen im Nasen- / Mundbereich eine erhöhte Asymmetrie auf. Bei den Patienten mit rechtsseitiger LKG-Spalte sind die Distanzen in der rechten Gesichtshälfte des fehlgebildeten Bereichs im Mittel größer als in der linken, bei linksseitiger LKG-Spalte sich diese Verhältnisse umgekehrt.

No description available.

No description available.

<p>Diffusion of liquids into and through polymers is an important factor that negatively may influence the durability or lifetime of a polymer structure used in industrial applications. In this work two types of polymers, a liquid crystalline polymer (LCP, Vectra A950) and various thermoset resins as used in fibre reinforced plastics (FRP) process equipment were studied with regard to barrier properties, chemical resistance and long-term performance. LCP are known for their outstanding chemical resistance and barrier properties. FRP used in process equipment may be a cost-efficient solution in chemically aggressive environments where standard carbon or stainless steel cannot be used due to its limited corrosion resistance. Transport properties of typical industrial environments were determined for the LCP and the influence of annealing and orientation was investigated to study whether the barrier properties can be improved. The possibility to use LCP as cost-effective lining for FRP was explored. Special focus was put on the diffusion of water and its effect on long-term transport properties and stability of thermoset resins as the performance of FRP is strongly related to the diffusion of water. </p><p>The results showed that Vectra A950 was suitable for organic solvent and non-oxidising acid environments. Its transport properties were gravimetrically determined and found to be 10 to 102 times lower than that of a high barrier fluoropolymer of type FEP. The degree of molecular packing increased with annealing time both below and above the melting point. Below the melting point this was – at least – partly due to crystal formation whereas above the melting point other mechanisms were involved. The effects of annealing and orientation on the transport properties in LCP were, however, very small or not significant and probably significantly longer annealing times are required. LCP has potential to be used as lining material for FRP as the use of an LCP-lining substantially reduced the permeability of and the solute sorption in a bisphenol A epoxy-based vinyl ester resin. The bonding strength was improved significantly by a combined abrasive and oxygen plasma treatment.</p><p>The long-term sorption of water in thermoset resins including bisphenol A epoxy-based vinyl ester, novolac-based vinyl ester, urethane modified vinyl ester and bisphenol A polyester resins was found to increase with exposure time whereas the diffusion coefficient was not significantly affected. It was shown that the presence of water induced relaxation processes that were considered to be the primarily reason for the increase in sorption coefficient in comparison to degradation processes, such as hydrolysis, causing osmotic processes. A general relationship for the estimation of the sorption coefficient at 80ºC in dependence of the water activity and the sorption coefficient at unit activity independent of the resin type was established.</p>

In dieser Grundlagenstudie wird evaluiert wie präzise 3D-Gesichtsaufnahmen eines Patientenkollektivs mit einer Lippen-, Kiefer-, Gaumenspalte mit dem 3D-Bildaufnahmesystem Vectra M3 (Canfield) und der Analysesoftware Facial Analysis Tool (FAT), entwickelt in der Abteilung MKG der Universität Leipzig, analysiert werden können. Im ersten Studienabschnitt werden 3D-Gesichtsaufnahmen von 3 Patienten und einem Modellkopf erstellt und für 62 manuell festgelegte Landmarken (LM) 10-mal die x-, y-, z-Koordinaten bestimmt. Die statistisch ermittelten prozentualen Variationskoeffizienten und die FAT-Beurteilungen der Messdaten werden graphisch verglichen und zeigen eine gute Übereinstimmung. Die Präzision der LM-Positionierungen ist Landmarken-abhängig Im zweiten Abschnitt werden an 91 Patienten mit unterschiedlichen Spaltdiagnosen jeweils 146 Distanzen aus LM und auch konstruierten Punkten mittels FAT ermittelt. Die prozentualen Variationskoeffizienten der Messdaten der Patientenkollektive werden nach Spaltdiagnose (beid-, rechts-, linksseitiger LKG-Spalte und Minimalvarianten), nach Geschlecht und Alter (≤ , >16 Jahre) graphisch ausgewertet. Die Variationskoeffizienten der Distanzen innerhalb einer Patientengruppe sind vergleichsweise hoch, insbesondere im Nasen- / Mundbereich mit kleinen Distanzen. Eine Differenzierung nach Geschlecht und Alter ist nicht möglich. Im dritten Abschnitt werden Symmetrieindizes für 36 Distanzen von den nach Spaltdiagnose gruppierten 91 Patienten errechnet und graphisch ausgewertet. Die Patienten mit einer einseitigen Anomalie weisen im Nasen- / Mundbereich eine erhöhte Asymmetrie auf. Bei den Patienten mit rechtsseitiger LKG-Spalte sind die Distanzen in der rechten Gesichtshälfte des fehlgebildeten Bereichs im Mittel größer als in der linken, bei linksseitiger LKG-Spalte sich diese Verhältnisse umgekehrt.

Diffusion of liquids into and through polymers is an important factor that negatively may influence the durability or lifetime of a polymer structure used in industrial applications. In this work two types of polymers, a liquid crystalline polymer (LCP, Vectra A950) and various thermoset resins as used in fibre reinforced plastics (FRP) process equipment were studied with regard to barrier properties, chemical resistance and long-term performance. LCP are known for their outstanding chemical resistance and barrier properties. FRP used in process equipment may be a cost-efficient solution in chemically aggressive environments where standard carbon or stainless steel cannot be used due to its limited corrosion resistance. Transport properties of typical industrial environments were determined for the LCP and the influence of annealing and orientation was investigated to study whether the barrier properties can be improved. The possibility to use LCP as cost-effective lining for FRP was explored. Special focus was put on the diffusion of water and its effect on long-term transport properties and stability of thermoset resins as the performance of FRP is strongly related to the diffusion of water. The results showed that Vectra A950 was suitable for organic solvent and non-oxidising acid environments. Its transport properties were gravimetrically determined and found to be 10 to 102 times lower than that of a high barrier fluoropolymer of type FEP. The degree of molecular packing increased with annealing time both below and above the melting point. Below the melting point this was – at least – partly due to crystal formation whereas above the melting point other mechanisms were involved. The effects of annealing and orientation on the transport properties in LCP were, however, very small or not significant and probably significantly longer annealing times are required. LCP has potential to be used as lining material for FRP as the use of an LCP-lining substantially reduced the permeability of and the solute sorption in a bisphenol A epoxy-based vinyl ester resin. The bonding strength was improved significantly by a combined abrasive and oxygen plasma treatment. The long-term sorption of water in thermoset resins including bisphenol A epoxy-based vinyl ester, novolac-based vinyl ester, urethane modified vinyl ester and bisphenol A polyester resins was found to increase with exposure time whereas the diffusion coefficient was not significantly affected. It was shown that the presence of water induced relaxation processes that were considered to be the primarily reason for the increase in sorption coefficient in comparison to degradation processes, such as hydrolysis, causing osmotic processes. A general relationship for the estimation of the sorption coefficient at 80ºC in dependence of the water activity and the sorption coefficient at unit activity independent of the resin type was established.

This thesis focuses on transport properties and durability of liquid crystalline polymers (LCP)and fibre reinforced plastics (FRP) with regard to application in industrial process equipment.In the first part of the study the possibility of using a thermotropic LCP of type Vectra A950as lining material for FRP process equipment was investigated. Its performance wascompared to that of a fluorinated ethylene propylene copolymer (FEP) with respect tochemical and permeation resistance. Transport property and chemical resistance data wereestablished for different types of LCP film (compression molded, uniaxially and biaxiallyoriented film) exposed to selected chemicals chosen to represent typical industrial processenvironments. Annealing of the LCP, which may reduce the disclination density and henceimprove the barrier properties, induced a crystallinity increase, but did not significantlyimprove the barrier and chemical resistance properties. Different surface treatments toincrease the bonding between the LCP and FRP were explored. The conclusion was that LCPhas potential to serve as lining material for FRP in contact with water, organic solvents andnon-oxidizing acid environments, although certain issues, such as jointing techniques, stillhave to be evaluated. The second part of the study focused on transport and long-termproperties of commercial thermoset and FRP materials for industrial process equipment inaqueous environments (50 – 95 °C, water activity 0.78 – 1, exposure time ≤ 1000 days). Thewater transport properties in different thermosets were related to their chemical structureusing the solubility parameter concept. The transport of water in the thermosets with differentchemical structures could be predicted from the water activity, regardless of the actual type ofionic or non-ionic solute in the solution. An empirical relationship, independent of boththermoset chemistry and temperature, was established to describe the water concentration inthe thermoset as a function of water activity and the water concentration in pure water. Inlong-term, the water concentration in the thermosets increased with exposure time. Thisseemed to be primarily related to stress relaxation processes induced by water absorption andcertain leaching effects. The effects of hydrolysis seemed to be small. The glass fibrereinforcement may to various extents affect the water transport properties by capillarydiffusion and additional absorption around fibre bundles. The extent of such processesseemed to depend on temperature, water activity and the type of thermoset and reinforcement.The present work may be a useful contribution to an increased understanding of water effectsand durability of FRP process equipment. However, open questions still remain for a morecomprehensive durability analysis. / QC20100629