No description available.

No description available.

La présente étude a démontré l'effet de certains additifs sur les propriétés de vieillissement des composites élastomères. Dans les travaux actuels des colorants, des pigments à hautes performances et des liquides ioniques conducteurs ont été utilisés comme additifs pour obtenir des composites à base d'élastomère, caractérisés par une meilleure résistance aux intempéries et au vieillissement et avec de bonnes propriétés mécaniques. Les propriétés mécaniques des composites d'éthylène – norbornène, ont confirmé que les colorants avec des substituants fortement donneurs d'électrons, apportent une meilleure et plus efficace protection contre le vieillissement dans le spectre solaire, que la plupart des stabilisants commerciaux utilisés dans la technologie des polymères. La partie suivante de la thèse a porté sur l'impact des liquides ioniques hydrophile et hydrophobe à base d'imidazolium dans les caoutchoucs butadiène-acrylonitrile. L'influence de la nature de l'anion (thiocyanate SCN, bis (trifluorométhylsulfonyl)imide TFSI) et de la longueur de la chaîne alkyle du cation (éthyl, hexyl) des liquides ioniques à base d'imidazolium sur la cinétique de durcissement, sur les propriétés mécanique et morphologique, sur la conductivité ionique et sur la tenue aux intempéries des composites en caoutchouc nitrile a été étudiée. Il a été constaté que l'addition de liquides ioniques hydrophobes à base d'imidazolium – TFSI – en quantité de 2,5 à 5 phr, améliore le plus efficacement les propriétés mécaniques ainsi que la conductivité ionique des matériaux composites NBR et présente un effet positif sur la matrice de caoutchouc pendant l'exposition à l'extérieur / The present study demonstrated the effect of some additives on aging properties of elastomer composites. In the current work solvent dyes, high performance pigments and conductive ionic liquids were employed as additives to obtain elastomer composites, characterized by enhanced weathering aging resistance and good mechanical properties. In the first part of the investigation, selected solvent dyes mainly with anthraquinone chromophores and high performance pigments, which exhibited high light and temperature resistance, were applied in ethylene-norbornene cyclic olefin and acrylonitrile butadiene rubber and then subjected to aging process. The mechanical properties as well as surface analysis of ethylene-norbornene composites, confirmed that solvent dyes, provided better efficient protection against aging in full sun spectrum, than most investigated commercial stabilizers used in polymer technology. Next part of thesis was focused on impact of hydrophilic and hydrophobic imidazolium ionic liquids on acrylonitrile-butadiene rubber. The influence of (thiocyanate, SCN;bis(trifluoromethylsulfonyl)imide, TFSI) anion type and the length of alkyl chain (from ethyl to hexyl) for the cations of imidazolium ionic liquids on the curing kinetic, mechanical, morphological, ionic conductivity and weathering properties of nitrile rubber composites was investigated. It was found, that the addition of hydrophobic TFSI-based imidazolium ILs in quantity 2.5-5 phr, the most effectively improved, mechanical properties and ionic conductivity of the NBR composites and exhibit some positive effect on rubber matrix during outdoor exposure

No description available.

Microelectromechanical systems (MEMS) based artificial sensory hairs for flow sensing have been widely explored, but the processes involved in their fabrication are lithography intensive, making the process quite expensive and cumbersome. Most of these devices are also based on silicon MEMS, which makes the fabrication of out-of plane 3D flow sensors very challenging. This thesis aims to develop new fabrication technologies based on Polymer MEMS, with minimum dependence on lithography for the fabrication of piezoresistive 3D out-of-plane artificial sensory hairs for sensing of air flow. Moreover, the fabrication of a flexible sensor array is proposed and new materials are also explored for the sensing application. Soft lithography based approaches are first investigated for the fabrication of an all elastomer device that is tested in a bench top wind tunnel. Micromolding technologies allow for the mass fabrication of microstructures using a single, reusable mold master that is fabricated by SU-8 photolithography, reducing the need for repetitive processing. Polydimethylsiloxane (PDMS) is used as the device material and sputter deposited gold is used as both the piezoresistive as well as the electrode material for collection of device response. The fabrication results of PDMS to PDMS metal transfer micromolding (MTM) are shown and the limitations of the process are also discussed. A dissolving mold metal transfer micromolding process is then proposed and developed, which overcomes the limitations of the conventional MTM process pertinent to the present application. Testing results of devices fabricated using the dissolving mold process are discussed with emphasis on the role of micro-cr  acking as one failure mode in elastomeric devices with thin film metal electrodes. Finally, a laser microfabrication based approach using thin film Kapton as the device material and an electrically conductive carbon-black elastomer composite as the piezoresistor is proposed and demonstrated. Laminated sheets of thick and thin Kapton form the flexible substrate on which the conductive elastomer piezoresistors are stencil printed. Excimer laser ablation is used to make the micro-stencil as well as to release the Kapton cantilevers. The fluid-structure interaction is improved by the deposition of a thin film of silicon dioxide, which produces a stress-gradient induced curvature, strongly enhancing the device sensitivity. This new approach also enables the fabrication of backside interconnects, thereby addressing the commonly observed problem of flow intrusion while using conventional interconnection technologies like wire-bonding. Devices with varying dimensions of the sensing element are fabricated and the results presented, with smallest devices having a width of 400 microns and a length of 1.5 mm with flow sensitivities as high as 60 Ohms/m/s. Recommendations are also proposed for further optimization of the device.

Cette thèse se concentre sur la préparation et l'étude des composites élastomères chargés avec des particules lamellaires et des liquides ioniques. Ces composites sont caractérisés par des propriétés mécaniques améliorées, une diminution du gonflement par les solvants, une faible perméabilité aux gaz ainsi que par une amélioration de la conductivité ionique. Les propriétés de structure et de surface différentes des charges lamellaires, telles que le rapport d'aspect des particules, la surface spécifique et l'activité de surface ont été analysées comme les facteurs impactant le renforcement du caoutchouc nitrile (NBR) et du caoutchouc nitrile carboxylé (XNBR). Une attention particulière a été portée aux systèmes XNBR contenant des hydroxydes doubles lamellaires (MgAI-HDL), qui varient en fonction du rapport Mg / Al et de morphologie de particules. L'application simultanée de MgAI-HDL en tant que charge et en tant qu'agent de réticulation dans XNBR ne fournit pas uniquement un produit écologique sans oxyde de zinc mais également un composite élastomère ionique avec de meilleures propriétés mécaniques, de barrière et de transparence. Cette thèse considère également les applications potentielles des liquides ioniques en tant qu'additifs multifonctionnels dans les composites élastomères afin d'obtenir une bonne dispersion des charges minérales dans une matrice polymère ainsi qu'une amélioration de la conductivité ionique des matériaux composites. La concentration optimale et le type de liquides ioniques ont été sélectionnés pour obtenir un bon compromis entre les propriétés mécaniques et la conductivité des matériaux composites de caoutchouc / This thesis focused on the preparation and the study of elastomer composites filled with layered fillers with improved mechanical properties, decreased swelling in solvents, increased UV stability and reduced gas permeability. The layered minerals were investigated not only in terms of their use as reinforcing fillers for rubbers but also as crosslinking agents, gas barrier and UV stability enhancers. The layered fillers tested belong to a class of cationic clays (natural and synthetic hectorite), anionic clays (hydrotalcites or magnesium aluminum layered double hydroxides MgAI-LDHs) and graphene-based materials. Different structural and surface properties of layered fillers were investigated as factors impacting the reinforcement of acrylonitrile-butadiene rubber (NBR) and carboxylated acrylonitrile-butadiene rubber (XNBR). Special attention has been devoted to the XNBR systems containing MgAI-LDHs varying in Mg / AI ratios, layers aspect ratios and particles morphologies. It was reported that the simultaneous application of MgAI-LDH as a filler and as a crosslinking agent in XNBR provides not only environmentally friendly, zinc-oxide free product but also ionic elastomer composite with improved mechanical, barrier and transparent properties. This thesis considers also the potential application of imidazolium ionic liquids as dispersing agents in rubber matrix, plasticizers and ionic conductivity enhancers. The optimal concentration and type of ionic liquids were selected for obtaining a good compromise between mechanical and conductivity properties of rubber composites