Synthèse et caractérisation des particules électrophorétiques pour les encres électroniques

Les écrans électrophorétiques sont un nouveau moyen de communication avec un gros potentiel de développement et d application. Pour répondre aux exigeances, l encre électronique, qui est le fondement des écrans électrophorétiques doit présenter des propriétés bien ciblées. Dans cette thèse sont décrites la synthèse et la caractérisation des particules électrophorétiques, ainsi que leur intégration dans les encres électroniques, le but du travail étant le contrôle du fonctionnement des encres électroniques, d etablir les facteurs déterminants pour leurs caractéristiques optiques et électriques. Après une étude électro-optique préliminaire du système électrophorétique, on a essayé de bien comprendre et d utiliser les avantages offertes par certaines méthodes de synthèse et de faire le meilleur choix du matériel de départ. La synthèse des particules structurées a été réalisée par différentes techniques de polymèrisation en système hétérogène: polymèrisation par dispersion, par suspension et précipitation, en système direct et inverse. Des techniques originales de polymèrisation ont été proposées et testées. La recherche a été focalisée vers l obtention d un meilleur taux de charge par particule et sur la stabilisation stérique pour éviter l aggrégation irréversible qui empêcherait le bon fonctionnement de l écran. Cette stabilisation a été effectuée grâce aux tensioactifs non-ioniques greffés à la surface des particules. Un pas important vers l amélioration du système a été la diminution du courant résiduel global en éliminant l excess du surfactant de la formulation d encre. Du point du vue optique, la recherche a été centrée sur les possibilités de préparation des particules électrophorétiques colorées soit par incorporation des colorants par différentes methodes, soit par encapsulation du pigment, ainsi que sur l ajustement des paramètres du système afin d obtenir le meilleur résultat.Electrophoretic displays are a new communication device with a great potential for application and development. To meet all requirements, the electronic ink - the active principle of electrophoretic displays, has to exhibit certain characteristics, therefore its composition and the chemical nature of its constituents are of great importance.This thesis presents the synthesis and characterization of electrophoretic particles, as well as their integration in electrophoretic inks. The objective and challenges were to obtain a better understanding of the mechanisms involved in the electrophoretic system.After an intensive preliminary electro-optical study of the electrophoretic system, the effort was made to understand and to exploit the advantages that certain synthetic methods offered, with a good choice of starting electrophoretic material. The synthesis of multistructured particles was achieved by different heterogeneous polymerization techniques: dispersion, suspension and precipitation, in directsystem (oil-in-water) and in inverse system (water-in-oil). Attention was focused on improved colloidal stability provided by particle-attached block copolymers, on the reduction of the overall residual current by elimination of excess surfactant from the dispersion formulation and on the ways to obtain faster electrophoretic response times. In this context, novel synthetic techniques have been proposed and tested. From optical contrast point of view, the research was centered on the possibilities to improve the coloration of the electrophoretic particles either by pigment encapsulation to obtain light scattering particles, or by particle dyeing to obtain light absorbing particles and on adjusting the display parameters in order to obtain the best outcome.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF

Improving the cleanability of melamine-formaldehyde-based

Decorative laminates based on melamine formaldehyde (MF) resin impregnated papers are used at great extent for surface finishing of engineered wood that is used for furniture, kitchen, and working surfaces, flooring and exterior cladding. In all these applications, optically flawless appearance is a major issue. The work described here is focused on enhancing the cleanability and antifingerprint properties of smooth, matt surface-finished melamine-coated particleboards for furniture fronts, without at the same time changing or deteriorating other important surface parameters such as hardness, roughness or gloss. In order to adjust the surface polarity of a low pressure melamine film, novel interface-active macromolecular compounds were prepared and tested for their suitability as an antifingerprint additive. Two hydroxy-functional surfactants (polydimethysiloxane, PDMS-OH and perfluoroether, PF-OH) were oxidized under mild conditions to the corresponding aldehydes (PDMS-CHO and PF-CHO) using a pyridinium chlorochromate catalyst. With the most promising oxidized polymeric additive, PDMS-CHO, the contact angles against water, n-hexadecane, and squalene increased from 79.8°, 26.3° and 31.4° for the pure MF surface to 108.5°, 54.8°, and 59.3°, respectively, for the modified MF surfaces. While for the laminated MF surface based on the oxidized fluoroether the gloss values were much higher than required, for the surfaces based on oxidized polydimethylsiloxane the technological values as well as the lower gloss values were in agreement with the requirements and showed much improved surface cleanability, as was also confirmed by colorimetric measurements

Numerical analysis and simulation of the heat recovery from wastewater using heat exchanger

The problem of global warming and the reduction of energy consumption have led to an evolutionary progress of research directed towards finding as many solutions as possible to these environmental issues. Firstly, this paper presents the background information on the role of wastewater as a source of heat for the future. Next, the paper includes the analysis elements that define a system for recovering thermal energy from wastewater. The main objective was to identify the parameters that determine the heat transfer. It has started from a conceptual model of the technological system that involves inputs and outputs characterized by technological, physical-chemical, measurable or imposed properties. In the second part this paper presents a numerical model elaborated for the analysis and simulation of the main physical processes, the mass and heat transfer, which underlie the operation of the heat pipe heat exchangers (HPHE). The numerical simulation of heat and mass transfer in the HPHE is computed by using Delphi 7 solver program. This program contained a series of sub-programs for the meshing of the field occupied by the HPHE, another subprogram for solving the meshing equations and the third for post processing. The design of HPHE is the key to provide a heat exchanger system to work proficient as expected. Finally, the result is used to optimize and improving heat recovery systems of the increasing demand for energy efficiency in residential buildings or industry

Numerical analysis and simulation of the heat recovery from wastewater using heat exchanger

The problem of global warming and the reduction of energy consumption have led to an evolutionary progress of research directed towards finding as many solutions as possible to these environmental issues. Firstly, this paper presents the background information on the role of wastewater as a source of heat for the future. Next, the paper includes the analysis elements that define a system for recovering thermal energy from wastewater. The main objective was to identify the parameters that determine the heat transfer. It has started from a conceptual model of the technological system that involves inputs and outputs characterized by technological, physical-chemical, measurable or imposed properties. In the second part this paper presents a numerical model elaborated for the analysis and simulation of the main physical processes, the mass and heat transfer, which underlie the operation of the heat pipe heat exchangers (HPHE). The numerical simulation of heat and mass transfer in the HPHE is computed by using Delphi 7 solver program. This program contained a series of sub-programs for the meshing of the field occupied by the HPHE, another subprogram for solving the meshing equations and the third for post processing. The design of HPHE is the key to provide a heat exchanger system to work proficient as expected. Finally, the result is used to optimize and improving heat recovery systems of the increasing demand for energy efficiency in residential buildings or industry

High-gloss surfaces by powder coating and hot pressing of veneered particle board

In the powder coating of veneered particle boards the highly reactive hybrid epoxy/polyester powder transparent Drylac 530 Series from TIGER Coatings GmbH & Co. KG, Wels, Austria was used. Curing is accelerated by a mixture of catalysts reaching curing times of 3 min at 150 °C or 5 min at 135 °C which allows for energy and time savings making Drylac Series 530 powder suitable for the coating of temperaturesensitive substrates such as MDF and wood

Powder coating of veneered particle board surfaces by hot pressing

The powder coating of veneered particle boards by the sequence electrostatic powder application –powder curing via hot pressing is studied in order to create high gloss surfaces. To obtain an appealingaspect, veneer Sheets were glued by heat and pressure on top of particle boards and the resulting surfaceswere used as carrier substrates for powder coat finishing. Prior to the powder coating, the veneeredparticle board surfaces were pre-treated by sanding to obtain good uniformity and the boards werestored in a climate chamber at controlled temperature and humidity conditions to adjust an appropriate electrical surface resistance. Characterization of surface texture was done by 3D microscopy. The surfaceelectrical resistance was measured for the six veneers before and after their application on the particleboard surface. A transparent powder top-coat was applied electrostatically onto the veneered particleboard surface. Curing of the powder was done using a heated press at 130◦C for 8 min and a smooth, glossy coating was obtained on the veneered surfaces. By applying different amounts of powder thecoating thickness could be varied and the optimum amount of powder was determined for each veneer type

Developments and trends in powder coating of heat-sensitive substrates

Powder coatings provide several advantages over traditional coatings: environmental friendliness, freedom of design, robustness and resistance of surfaces, possibility to seamlessly all-around coating, fast production process, cost-effectiveness. In the last years these benefits of the powder coating technology have been adopted from metal to heat-sensitive natural fibre/ wood based substrates (especially medium density fibre boards- MDF) used for interior furniture applications. Powder coated MDF furniture parts are gaining market share already in the classic furniture applications kitchen, bathroom, living and offices. The acceptance of this product is increasing as reflected by excellent growth rates and an increasing customer base. Current efforts of the powder coating industry to develop new powders with higher reactivity (i.e. lower curing temperatures and shorter curing times; e.g. 120°C/5min) will enable the powder coating of other heat-sensitive substrates like natural fibre composites, wood plastic composites, light weight panels and different plastics in the future. The coating could be applied and cured by the conventional powder coating process (electrostatic application, and melting and curing in an IR-oven) or by a new powder coating procedure based on the in-mould-coating (IMC) technique which is already established in the plastic industry. Extra value could be added in the future by the functional powder toner printing of powder coated substrates using the electrophotographic printing technology, meeting the future demand of both individualization of the furniture part surface by applying functional 3D textures and patterns and individually created coloured images and enabling shorter delivery times for these individualized parts. The paper describes the distinctiveness of powder coating on natural fibre/ wood based substrates, the requirements of the substrate and the coating powder

Importance of Visual Estimation of Coronary Artery Stenoses and Use of Functional Evaluation for Appropriate Guidance of Coronary Revascularization—Multiple Operator Evaluation

Background: Visual estimation (VE) of coronary stenoses is the first step during invasive coronary angiography. The aim of this study was to evaluate the accuracy of VE together with invasive functional assessment (IFA) in defining the functional significance (FS) of coronary stenoses based on the opinion of multiple operators. Methods: Fourteen independent operators visually evaluated 133 coronary lesions which had a previous FFR measurement, indicating the degree of stenosis (DS), FS and IFA intention. We determined the accuracy of FS prediction using several scenarios combining individual and group decision, considering IFA as deemed necessary by the operator or only in intermediate lesions. Results: The accuracy of VE in predicting FS was largely variable between operators (average 66.1%); it improved significantly when IFA was used either as per operator’s opinion (86.3%; p p p = 0.166). The poorest accuracy of VE for FS was obtained in intermediate DS lesions (59.1%). Conclusions: There are significant inter-observer differences in reporting the degree of DS, while the accuracy of VE prediction of FS is also largely dependent on the operator, and the worst performance is obtained in the evaluation of intermediate DS