This thesis is motivated by the use of full-depth, precast, prestressed concrete panels to facilitate deck replacement of composite bridges. The shear pockets required in using convention shear stud connections, however, can cause durability problems. The objective of this study is to investigate the possibility of eliminating the use of shear studs, and adhesively bond the concrete and steel sections. The feasibility of the developed polyurethane adhesive joint is defined based on the serviceability and ultimate limit states. The joint must have sufficient stiffness that additional deflection due to slip must not be excessive. The adhesive and bond must also have sufficient strength to allow the development of the full plastic capacity of the composite section. The use of the developed adhesive joint in typical composite bridges was found to be feasible. The behaviour under live load was found to be close to a fully composite section.

Tissue engineering of the annulus fibrosus (AF) is challenging due to its complex lamellar structure. Polyurethane scaffolds have shown promise in AF tissue engineering. The current study examines whether matrix protein coatings (collagen type I, fibronectin, or vitronectin) would enhance cell attachment and promote cell and collagen orientation that more closely mimics native AF. The results demonstrate that the greatest cell attachment occurred with fibronectin (Fn)-coated scaffolds. Cells on Fn-coated scaffolds were also aligned parallel to scaffold fibers, a process that involved α5β1 integrin, determined by integrin-specific blocking antibodies. The inhibition of this integrin reduced AF cell spreading and alignment and the changes in cell shape were regulated by the actin cytoskeleton, demonstrated using cytochalasin D inhibitor. Cells on Fn-coated scaffolds formed fibrillar Fn, synthesized significantly more collagen, and showed alignment of type I collagen that more closely mimics native AF therefore facilitating the development of the tissue in vitro.

Although termites serve the ecologically important function of converting dead trees into organic matter, they annually cause damage worth billions of dollars to human structures such as houses, power poles and bridges throughout the world. This led to the development of various chemical and physical measures that primarily aimed at preventing the termites from causing damage to wooden structures. While the adverse effects of the chemical methods on the environment and human health has made them widely unacceptable, physical methods are costly and difficult to implement. There is a specific need to develop an environment friendly, cost effective, easily applicable and durable alternative barrier that would effectively protect a wide range of wooden structures. This study aims at designing and developing an eco-friendly, robust and easy to apply barrier material to protect wooden structures. Ether polyurethane (EPU) was chosen as the base material considering its toughness, resilience, hydrolytic stability due to the presence of ether group and easy applicability on large, irregular surfaces. EPU was upgraded to a ‘termite effective’ material by the incorporation of a synthetic pyrethroid, Bifenthrin®. Bifenthrin® was chosen over other termiticides due to its less pervasive nature to the environment along with its repellent/ killer effect on termites. The EPU/ Bifenthrin® system incorporates the specific features of durability of the polymer and slow release of Bifenthrin®, making it more acceptable to the environment and public health. Termite damage resistance of EPU was analyzed by testing the polymer, along with various other polymers (HDPE, PP, PVC and Nylon), with Coptotermes acinaciformes and correlating the termite properties (mandibular force, hardness) with those of the polymeric materials (surface and tensile properties). EPU resisted termite damage, though its softer form incurred 5 times more material damage than the robust cast type. EPUs with high values of hardness incurred ~40% less damage than HDPE and were comparable with the damages on PP. The depth and width of termite damage on HDPE was 5 and 4 times, respectively, than that of PVC. This part of the study inferred that, although hardness of polymeric materials helps prevent termite damage, toughness and resilience too can make it difficult for termites to find a pathway through the material. XPS, FTIR, termite mortality bioassays in an applied setting and elusion tests of Bifenthrin® from EPU in water, acetone and soil were employed to understand the interaction of EPU with Bifenthrin®. Water and soil were chosen as test mediums due to their practical nature. These studies confirm that Bifenthrin® at concentrations as low as 0.5 wt% enriches the surface of EPU due to preferential migration of CF3 group to the surface of EPU. Furthermore, Bifenthrin® incorporated in EPU does not compromise its insecticidal activity and diffuses in a controlled manner at the rate of ~10–8 cm2 s–1 and ~10–7 cm2 s–1 when kept in water and soil media respectively. The durability of EPU/ Bifenthrin® system was analyzed by conducting degradation studies on EPU. The effect of Bifenthrin® on the ageing of EPU was also investigated. The studies involved ageing of the system in natural and accelerated conditions and validating the results by use of Arrhenius models. The sub-soil conditions do not degrade EPU beyond the oxidative levels as the activation energy required to cause changes in properties of EPU are unphysically small (0.02 kJ mol-1). It was found that EPU can sustain its physical integrity for 12 years at room temperature and Bifenthrin® may remain in a 5 mm thick barrier material for up to 10 years. The effect of Bifenthrin® on the tensile properties of EPU is negligible. Studies to analyze the performance of the barrier material, involved testing of timber coated with the EPU/ Bifenthrin® system under real-life conditions against termites in field trials located at two tropical locations in Northern Queensland. EPU/ Bifenthrin® system with nominal concentrations of Bifenthrin® incurred no damage when the concentration of Bifenthrin® was above 0.07 wt% in EPU. The degradation of Bifenthrin® under sub-soil conditions is unlikely. Given that favourable characteristics of EPU and Bifenthrin® the design and development an effective and long-lasting termite barrier material seems feasible.

Although termites serve the ecologically important function of converting dead trees into organic matter, they annually cause damage worth billions of dollars to human structures such as houses, power poles and bridges throughout the world. This led to the development of various chemical and physical measures that primarily aimed at preventing the termites from causing damage to wooden structures. While the adverse effects of the chemical methods on the environment and human health has made them widely unacceptable, physical methods are costly and difficult to implement. There is a specific need to develop an environment friendly, cost effective, easily applicable and durable alternative barrier that would effectively protect a wide range of wooden structures. This study aims at designing and developing an eco-friendly, robust and easy to apply barrier material to protect wooden structures. Ether polyurethane (EPU) was chosen as the base material considering its toughness, resilience, hydrolytic stability due to the presence of ether group and easy applicability on large, irregular surfaces. EPU was upgraded to a ‘termite effective’ material by the incorporation of a synthetic pyrethroid, Bifenthrin®. Bifenthrin® was chosen over other termiticides due to its less pervasive nature to the environment along with its repellent/ killer effect on termites. The EPU/ Bifenthrin® system incorporates the specific features of durability of the polymer and slow release of Bifenthrin®, making it more acceptable to the environment and public health. Termite damage resistance of EPU was analyzed by testing the polymer, along with various other polymers (HDPE, PP, PVC and Nylon), with Coptotermes acinaciformes and correlating the termite properties (mandibular force, hardness) with those of the polymeric materials (surface and tensile properties). EPU resisted termite damage, though its softer form incurred 5 times more material damage than the robust cast type. EPUs with high values of hardness incurred ~40% less damage than HDPE and were comparable with the damages on PP. The depth and width of termite damage on HDPE was 5 and 4 times, respectively, than that of PVC. This part of the study inferred that, although hardness of polymeric materials helps prevent termite damage, toughness and resilience too can make it difficult for termites to find a pathway through the material. XPS, FTIR, termite mortality bioassays in an applied setting and elusion tests of Bifenthrin® from EPU in water, acetone and soil were employed to understand the interaction of EPU with Bifenthrin®. Water and soil were chosen as test mediums due to their practical nature. These studies confirm that Bifenthrin® at concentrations as low as 0.5 wt% enriches the surface of EPU due to preferential migration of CF3 group to the surface of EPU. Furthermore, Bifenthrin® incorporated in EPU does not compromise its insecticidal activity and diffuses in a controlled manner at the rate of ~10–8 cm2 s–1 and ~10–7 cm2 s–1 when kept in water and soil media respectively. The durability of EPU/ Bifenthrin® system was analyzed by conducting degradation studies on EPU. The effect of Bifenthrin® on the ageing of EPU was also investigated. The studies involved ageing of the system in natural and accelerated conditions and validating the results by use of Arrhenius models. The sub-soil conditions do not degrade EPU beyond the oxidative levels as the activation energy required to cause changes in properties of EPU are unphysically small (0.02 kJ mol-1). It was found that EPU can sustain its physical integrity for 12 years at room temperature and Bifenthrin® may remain in a 5 mm thick barrier material for up to 10 years. The effect of Bifenthrin® on the tensile properties of EPU is negligible. Studies to analyze the performance of the barrier material, involved testing of timber coated with the EPU/ Bifenthrin® system under real-life conditions against termites in field trials located at two tropical locations in Northern Queensland. EPU/ Bifenthrin® system with nominal concentrations of Bifenthrin® incurred no damage when the concentration of Bifenthrin® was above 0.07 wt% in EPU. The degradation of Bifenthrin® under sub-soil conditions is unlikely. Given that favourable characteristics of EPU and Bifenthrin® the design and development an effective and long-lasting termite barrier material seems feasible.

Univ., Diss.--Dortmund, 2007.

Zugl.: Siegen, Univ., Diss., 2008

Universiẗat, Diss., 2002--Kassel. / Lizenzpflichtig.

Techn. Hochsch., Diss., 2005--Aachen.

Les polyHIPEs sont des matériaux cellulaires obtenus par polymérisation d’émulsions concentrées appelées HIPEs « High Internal Phase Emulsions ». La phase continue de l’émulsion contenant les monomères est le siège de la polymérisation permettant la création de la matrice solide. La phase dispersée engendre la porosité. Les matériaux polyHIPEs sont généralement synthétisés par polymérisation radicalaire. La variété des monomères utilisables est donc ainsi limitée. La majorité des polymères à haute performances étant obtenus par polycondensation, il serait d’un grand intérêt d’élargir la gamme des matériaux poreux de type polyHIPEs disponibles en utilisant cette technique. L’objectif de ce travail consiste à synthétiser des matériaux polyHIPEs obtenus par polycondensation ou polyaddition et à les caractériser. Réaliser une réaction de polymérisation par étape au sein d’une émulsion concentrée représente un vrai défi car ce type de réaction requiert généralement des conditions opératoires peu compatibles avec la stabilité des émulsions concentrées. Dans le cadre de ce travail, nous nous sommes intéressés à la synthèse de polyHIPEs de type polyuréthane et polyester. L’homogénéité de la morphologie de ces matériaux a été étudiée en faisant varier un certain nombre de paramètres tels que : la nature de l’émulsion (aqueuse ou non-aqueuse, stabilisée par des tensioactifs ou des particules), la nature des catalyseurs et les techniques de polymérisation. Ce travail a permis d’accéder pour la première fois à des matériaux polyHIPEs de type polyuréthane et polyester. Les résultats obtenus ouvrent la voie au développement dans ce domaine. / PolyHIPEs are cellular materials obtained by polymerization within HIPEs « High Internal Phase Emulsions ». The polymerization occurs in the continuous phase of the emulsion allowing the creation of a solid matrix. The dispersed phase induces the porosity. PolyHIPEs are generally obtained by free-radical polymerization which restricts the choice of monomers. The majority of high performance polymers are obtained by polycondensation therefore it will be a great interest to enhance the variety of polyHIPEs available by using this technique. The objective of this work consists to synthetize polyHIPEs using polycondensation or polyaddition. Performing a step-growth polymerization within emulsion is a great challenge because this kind of reaction requires conditions generally incompatible with the stability of HIPEs. In the context of this work, we focused on the synthesis of polyurethane and polyester polyHIPEs. The homogeneity of the morphology of the materials was studied by varying several parameters, such: the nature of the emulsion (aqueous or non-aqueous, stabilized by surfactants or particles), the nature of the catalysts and the polymerization techniques. This work opens the access for the first time to polyurethane and polyester polyHIPEs. The results obtained are a starting point for further development in this field.

Eletrodos compósitos à base de grafite/poliuretana foram preparados contendo diferentes quantidades de hexacianoferratos de cobre(II), cobalto(II) e ferro(III). Os complexos foram preparados de acordo como procedimentos descritos na literatura e caracterizados por análise elementar, análise térmica e espectrometria na região do infra-vermelho. A análise térmica mostrou que há 10 moléculas de água de hidratação no hexacianoferrato de cobre(II), 11 no hexacianoferrato de cobalto(II) e 16 no hexacianoferrato de ferro(III). Após desidratação ocorre decomposição exotérmica violenta dos complexos. No caso do cobre a decomposição se dá com formação de CuO seguida da degradação do Fe(CN)3 com formação de Fe2O3. Para o hexacianoferrato de cobalto(II) e o hexacianoferrato de ferro(III) a mistura de Co3O4/Fe2O3 e o Fe2O3, respectivamente, se formaram após uma única etapa de decomposição. Apenas os eletrodos preparados com os complexos de cobalto e cobre apresentaram sinais voltamétricos, enquanto que o complexo de ferro não respondeu, provavelmente devido à sua baixa solubilidade em água. As condições de preparação dos eletrodos, tais como composição, ordem de adição de reagentes, pH, eletrólito suporte e intervalo de potenciais foram otimizadas. Um mecanismo para explicar a não estabilização do sinal voltamétrico, mesmo após ciclagem de potencial foi proposto com base na baixa solubilidade dos sais em água e a sua imobilização no eletrodo sólido a qual dificulta a formação do filme de hexacianoferrato na superfície. Finalmente um método analítico para a determinação de piridoxina, usando o eletrodo de grafite/poliuretana modificado com hexacianoferrato de cobre(II) foi proposto, com base na redução de sinal do complexo, na presença do analito. Neste caso foi observada uma resposta linear entre 1,08 x 10-6 a 1,07 x 10-5 mol L-1, com limite de detecção de 8,78 x 10-7 mol L-1 (3 x S/N) e o método foi aplicado na determinação de piridoxina em duas formulações comerciais. Coeficientes de recuperação entre 98-120% foram observados sem interferência dos componentes das formulações e sem necessidade de renovação da superfície do eletrodo. / Graphite-poliurethane solid composite electrodes were prepared containing different amounts of copper(II), cobalt(II) and iron(III) hexacianoferrates. The complexes were synthesized according to procedures previously described and characterized using elemental analysis, infrared spectrometry and the thermal analytical techniques: thermogravimetry/derivative thermogravimetry and differential thermal analysis. The thermal analysis revealed that there are 10 hydration water molecules in the copper(II) hexacianoferrate, 11 in the cobalt(II) and 16 in the iron(III) complexes. After dehydration, a strong exothermal degradation occurred in all cases. The copper complex decomposed in two steps with generation of CuO, followed by degradation of the Fe(CN)3 and formation of Fe2O3. The cobalt(II) and iron(III) hexacianoferrates decomposed in a single step with generation of Co3O4/Fe2O3 mixture and Fe2O3 as residues respectively. Only the electrodes prepared with copper and cobalt complexes presented voltammetric signals, while the iron complexes did not responded, probably due to its very low solubility in water. The conditions for the electrode preparation such as composition, order of addition of the components supporting electrolyte, pH and useful potential window were optimized. A mechanism to explain the non-stabilization of the voltammetric signal even after 200 cycles has been proposed on the basis of the complexes solubility in water as well as the immobilization of the complex in the solid electrode that turns difficult the formation of the hexacianoferrate film on the electrode surface. Finally, a graphite polyurethane electrode modified with the Cu(II) hexacianoferrate has been used in the voltammetric determination of pyridoxine, based on the diminution of the voltammetric signal of the modifier in the presence of the analyte. In this case a linear dynamic range of 1.08 x 10-6 to 1.07 x 10-5 mol L-1, with a detection limit of 8.78 x 10-7 mol L-1 (3 x S/N). The proposed electrode was used in the determination of pyridoxine in two solid pharmaceutical formulations with recoveries of 98 - 120% without interference of the other substances present in the formulation and no adsorption on the electrode surface.