A computational study has been carried out to investigate smoldering ignition and propagation in polyurethane foam. The onedimensional, transient, governing equations for smoldering combustion in a porous fuel are solved accounting for improved solid-phase chemical kinetics. A systematic methodology for the determination of solid-phase kinetics suitable for numerical models has been developed and applied to the simulation of smoldering combustion. This methodology consists in the correlation of a mathematical representation of a reaction mechanism with data from previous thermogravimetric experiments. Geneticalgorithm and trail-and-error techniques are used as the optimization procedures. The corresponding kinetic parameters for two different mechanisms of polyurethane foam smoldering kinetics are quantified: a previously proposed 3-step mechanism and a new 5-step mechanism. These kinetic mechanisms are used to model one-dimensionalsmoldering combustion, numerically solving for the solid-phase and gasphase conservation equations in microgravity with a forced flow of oxidizer gas. The results from previously conducted microgravity experiments with flexible polyurethane foam are used for calibration and testing of the model predictive capabilities. Both forward and opposed smoldering configurations are examined. The model describes well both opposed and forward propagation. Specifically, the model predicts the reaction-front thermal and species structure, the onset of smoldering ignition, and the propagation rate. The model results reproduce the most important features of the smolder process and represent a significant step forward in smoldering combustion modeling.

Os cateteres intravasculares são aliados indispensáveis na prática da medicina moderna, particularmente em unidades de terapia intensiva (UTIs). Pelo Cateter Venoso Central (CVC) pacientes que ficam muito tempo internados recebem medicação e alimentação sendo, no entanto, importante fonte de infecção da corrente sanguínea primária. Os CVC\'s de poliuretano podem ter sua superfície modificada pela incorporação de titânio e prata (Ti/Ag) que possuem características antimicrobianas conhecidas desde a antiguidade. A incorporação das nanopartículas de prata sobre o polímero pode ser feita com o uso da radiação ionizante, que também irá esterilizar o material. Assim, este trabalho tem por objetivo utilizar a radiação ionizante para incorporação de nanopartículas de prata em Cateter Venoso Central (CVC) a fim de adquirir propriedades antibactericidas. Para isto utilizou-se o CVC Pellethane 2363-65D, termoplástico de poliuretano elastômero (TPU), óxido de titânio puro, sintetizado pelo processo sol-gel e nanopartículas de prata (NpAg_925). A irradiação para incorporação da prata foi com dose de 25 kGy e com taxa de dose de 1,03 kGy/h em um irradiador \"Gammacel 220\" de 60Co. Posteriormente, os cateteres foram esterelizados com dose de 25 kGy. Pode-se concluir que a incorporação da prata pelo processo de irradiação foi possível e que este processo não afeta a estrutura do polímero, o que é importante para a correta inserção do cateter venoso central no corpo do paciente. Observou-se que o método sol-gel, para deposição do titânio na superfície do CVC, não foi homogênea, dificultando a incorporação da prata que depende do titânio neste processo. Os testes de análise antimicrobiana não indicaram atividade antimicrobiana nos cateteres revestido com titânio e prata, acredita-se que a metodologia escolhida seja inadequada para o tipo de análise. / Intravascular catheters are indispensable allies in the practice of modern medicine, particularly in intensive care units (ICUs). Central Venous Catheter (CVC) patients who are hospitalized for a long time receive medication and feeding, however, being an important source of infection of the primary bloodstream. Polyurethane CVCs may have their surface modified by the incorporation of titanium and silver (Ti/Ag) which have antimicrobial characteristics known from antiquity. The incorporation of the silver nanoparticles on the polymer can be done with the use of ionizing radiation, which will also sterilize the material. Thus, this work aims to use ionizing radiation to incorporate silver nanoparticles in Central Venous Catheter (CVC) in order to acquire antibacterial properties. For this purpose CVC Pellethane 2363-65D, thermoplastic elastomer polyurethane (TPU), pure titanium oxide, synthesized by the sol-gel process and silver nanoparticles (NpAg_925) were used. Irradiation for incorporation of silver was at a dose of 25 kGy and at a dose rate of 1.03 kGy/h in a \"Gammacell 220\" irradiator of 60Co. Subsequently, the catheters were sterilized at a dose of 25 kGy. It can be concluded that the incorporation of silver by the irradiation process was possible and that this process does not affect the structure of the polymer, which is important for the correct insertion of the central venous catheter into the patient\'s body. It was observed that the sol-gel method, for deposition of the titanium on the surface of the CVC, was not homogeneous, making difficult the incorporation of the silver that depends on the titanium in this process. The antimicrobial analysis tests did not indicate antimicrobial activity in catheters coated with titanium and silver, it is believed that the chosen methodology is inadequate for the type of analysis.

No description available.

Company Purtech in Dals-Ed manufactures molded polyurethane (PUR). Examples of products that include polyurethane are car seats. Robots are used to fill the molds with PUR and to apply the release agent (wax) in the empty molds. Turning from online programming into a graphical offline programming of release agent spraying robots is going to simplify the process by: Applying less of release agent to avoid polluting environment, to produce an easier removal of moulds, for the sake of homogeneous moulds and for economical saving in the cost of release agent Adaption of spraying paths to variation in production speed. Programming of complex spraying trajectories to deal with sharp geometrical subsurface Decreasing onsite programming time (when program a new workpiece or modify an old one); so that robots would be free for production. While turning into offline programming brought the challenges of: Impact of variation in the production speed Lack of 3D models of workcell’s equipments Robot joint configuration when paths and robtargets are in move. Physical Joint limits, Singularities & Reach limits Collisions within the cell space. At the end, the following objectives are successfully met: Adaption of spraying programs to variation in production speed by developing and embedding a method in those programs. Graphical offline generation of spraying trajectories and optimization of those trajectories to the Purtech condition of spraying allowed time for each carrier. Simulation of release agent spraying process; and producing of a well structured RAPID program that reflect the simulated process.

Thin polyurethane films have been widely used as erosion-resistant coatings on helicopter rotor blades. Published research has mainly focused on empirical studies that relate the mechanical properties such as rebound resilience and hardness of polyurethane to solid particle erosion resistance. However polyurethane possesses phase mixing at multiple scales and thus sand particle erosion resistance depends also on the micro structure and the phase mixing. Hence, it is very important to carry out detailed and systematic investigations to understand the step-by-step mechanism of erosion and how it relates to the polyurethane micro, meso, and macrostructure. Thermal transitions of the pristine films have been studied through Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA) yielding micro-scale information such as glass transition temperatures of the hard and soft segments and melting temperature of the soft segment. The next stage of our study involved sand particle erosion tests carried out at 500 mph, at an impact angle of 30 degrees. Test specimens were exposed to two different sand media at different mass loadings ranging from 0.1 to 20 g/cm^2. The tools of characterization used on the pristine polyurethane are once again used on the eroded specimens, with the goal to compare pre- and post- erosion results. The comparison of FTIR results on pre-eroded and eroded films reveal the removal of macromolecular bonds corresponding to soft segments in the micro scale. The reduction of the crystalline portion of the soft segment observed from DSC results supports the FTIR findings. Scanning electron microscopy (SEM) images of the eroded specimens are used to correlate the sequence of the damage due to erosion. The observations revealed that after initial ductile deformation of the soft segments on the surface, brittle cracks are formed on the hard segments. The increased exposure to sand particles leads to formation of fragments containing mainly soft segments with cracks in the hard segments propagating in a brittle manner. As exposure increases, cracks intersect and material on the surface gets removed which mainly contains the soft segments as revealed by the FTIR and DSC results.

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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.

This study addresses the flexural performance of sandwich panels composed of a polyurethane foam core and glass fibre-reinforced polymer (GFRP) skins. Panels with and without GFRP ribs connecting the skins have been studied. While the motivation of the study was to develop new insulated cladding panels for buildings, most of the work and findings are also applicable to other potential applications such as flooring, roofing and light-weight decking. The study comprises experimental, numerical, and analytical investigations. The experimental program included three phases. Phase I is a comprehensive material testing program of the polyurethane core and GFRP skins and ribs. In Phase II, six medium size (2500x660x78 mm) panels with different rib configurations were tested in one-way bending. It was shown that flexural strength and stiffness have increased by 50 to 150%, depending on the rib configuration, compared to a panel without ribs. In Phase III, two large-scale (9150x2440x78 mm) panels, representing a cladding system envisioned to be used in the field, were tested under a realistic air pressure and discrete loads, respectively. The deflection under service wind load did not exceed span/360, while the ultimate pressure was about 2.6 times the maximum factored wind pressure in Canada. A numerical study using finite element analysis (FEA) was carried out. The FEA model accounted for the significant material nonlinearities, especially for the polyurethane soft core, and the geometric nonlinearity, which is mainly a reduction in thickness due to core softness. Another independent analytical model was developed based on equilibrium and strain compatibility, accounting for the core excessive shear deformation. The model also captures the localized deformations of the loaded skin, using the principals of beam-on-elastic foundation. Both models were successfully validated using experimental results. Possible failure modes, namely core shear failure, and compression skin crushing or wrinkling were successfully predicted. A parametric study was carried out to explore further the core density, skin thickness, and rib spacing effects. As the core density increased, flexural strength and stiffness increased and shear deformations reduced. Also, increasing skin thickness became more effective as the core density increased. The optimal density was 95-130 kg/m3. Reducing the spacing of ribs enhanced the strength up to a certain level; It then stabilized at a spacing of 2.9 times the panel thickness. / Thesis (Ph.D, Civil Engineering) -- Queen's University, 2010-09-21 16:29:00.315

Rigid polyurethane foam is a polymeric material which is widely used for thermal insulation in building construction and other applications. Given recent emphasis on energy conservation and efficiency, there has been continuous growth in its use over the years. This raises significant fire safety concerns since polyurethanes are inherently very flammable and prone to release toxic gases as the foam thermally decomposes and burns. To improve fire safety characteristics by reducing ignitability and flammability of the foams, various flame retardants (FR) have been introduced into base foam formulations. But with the introduction of FR agents, there has been rising concern within the fire safety community and general public regarding the overall benefits versus detrimental impacts of even commonly used FR agents. In the case of rigid polyurethane foam, however, such an assessment is difficult as there are few cross comparisons in the literature that detail the impacts of different concentrations of common fire retardants, such as brominated, phosphorus-based and expandable graphite agents, on the fire behavior, smoke development and toxic gas production for even single base foam formulations. The present experimental work focuses on a systematic evaluation of these factors using three common, commercial fire retardants added in concentrations of 0%wt, 10%wt and 20%wt to a single formulation of rigid polyurethane foam. Cone calorimeter and smoke density tests are used to simulate well ventilated and poorly ventilated fire conditions during material fire performance assessment, while FTIR, Novatech P 695 gas analyzers and TD-GC/MS methods are used to investigate the gases evolved during oxidative pyrolysis and combustion of the samples. Concentration measurements of principal fire gases such as CO, CO2, reduced O2, and NOx are combined with more detailed investigation of the volatile organic compounds generated during the fire testing. Use of gas absorption sampling followed by off-line Thermal Desorption/Gas Chromatography/Mass Spectrometry (TD-GC-MS) analysis for identification of toxic gases has proven of significant benefit in this application. The full set of data obtained provides a more comprehensive identification of the evolved products during three characteristic periods in the combustion process. As such, it expands current knowledge and provides valuable new insight and understanding of thermal degradation, combustion and smoke development, as well as overall fire performance, of fire retarded rigid polyurethane foams in well-ventilated and poorly ventilated environments.

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.