La corrosion des canalisations métalliques pour le transport de gaz ou d’hydrocarbures est un problème critique qui peut avoir des répercussions financières et environnementales très importantes. Les revêtements polyoléfines tricouches sont largement utilisés pour préserver l’intégrité des structures. Ils sont constitués d’une sous couche mince époxy, d’une couche mince d’adhésif et d’une couche épaisse le plus souvent en polyéthylène. Ce système de revêtement bénéficie de très bonnes qualités d'adhérence. Néanmoins, des cas de décollements de ces revêtements à l’interface époxy/acier ont été constatés sur des pipelines en service depuis quelques années seulement, alors que la durée minimale de vie escomptée des tubes dans le sol est de quelques dizaines d’années. Ces décollements pourraient être dus à une dégradation progressive des liaisons interfaciales entre le primaire époxy et la surface métallique, associée à la présence de contraintes interfaciales importantes entre les différentes couches de l'assemblage. Cette étude vise alors d'une part à proposer des solutions permettant d’aboutir à la meilleure performance en vieillissement de la liaison adhésive, et d'autre part à quantifier les niveaux de contraintes au sein de la canalisation en acier revêtue depuis sa mise en œuvre, jusqu'à sa mise en service.Les liaisons interfaciales dépendant nécessairement de la préparation de surface de l’acier, des procédés de nettoyage ont été testés afin d’évaluer leur influence sur l’adhérence initiale et la durabilité des assemblages. Les préparations de surface permettent d'obtenir un degré de propreté et une rugosité. Ces deux éléments maximisent les forces de liaison et donc l'adhérence du revêtement. Le revêtement résiste alors mieux dans des environnements agressifs. Tous les procédés de nettoyage testés ont conduits à des niveaux de propreté équivalents du substrat en acier. Les essais effectués sur substrats polis miroir ont mis en évidence qu’une rugosité est nécessaire pour améliorer la durabilité des assemblages. La rugosité permet d'obtenir des adhérences supérieures à celles sur substrats polis miroir, de ralentir les effets du vieillissement humide et donc de prolonger la durée de vie du système. Il a été mis en évidence que les fortes rugosités étaient particulièrement bénéfiques pour les adhérences sèches. Par contre, au-delà d’une certaine rugosité, l’augmentation de la rugosité ne s’accompagne pas d’une amélioration significative de l’adhérence humide. Une étude sur l’apport des traitements de surface a aussi été menée. L’addition d’un traitement de surface a peu d’impact sur les adhérences initiales des assemblages, en comparaison avec une préparation de surface classique. Par contre les traitements de surfaces améliorent considérablement les adhérences humides, et donc la durabilité des assemblages. Notre travail prouve que le traitement aminosilane est un candidat potentiel en vue du remplacement du traitement toxique de chromatation, référence en matière de traitements de surface dans l'industrie des pipelines et dont l'utilisation sera interdite dans un futur proche compte tenu de l'évolution de la réglementation. Dans de bonnes conditions d'application et associé avec des primaires époxy appropriés, les adhérences sèches et humides obtenues avec les silanes sont comparables (voire supérieures) à celles de la chromatation.Par ailleurs, la modélisation par éléments finis du système tricouches a permis de préciser les niveaux de contraintes aux interfaces résultant de la mise en œuvre et de prévoir leur évolution au cours du temps et du vieillissement humide. / External Corrosion can weaken underground steel pipelines and render them unsafe for transporting oil or gas. Premature damage of this network could lead to dramatic financial and environmental consequences. Three layers polyolefin coatings composed by a fusion bonded epoxy, a modified polyolefin adhesive and a thick polyolefin topcoat, are the most widely systems used to preserve the structure integrity. This protective coating system presents excellent adhesion. Nevertheless, in some specific cases, loss of adhesion has been observed at steel/epoxy interface on operating pipelines on shorter period than their expected lifetime of about fifty years. This disbonding can be assigned to the progressive degradation of interfacial bonds between the epoxy primer and the metallic surface combined to substantial interfacial stresses between the different layers of the assembly. This study thus aims both to provide solutions to achieve the best ageing performance of the adhesive bond, and secondly to quantify the stress levels in a coated steel pipe since coating manufacturing to pipeline commissioning.Given that interfacial bonds depend necessarily on steel surface preparation, cleaning methods were compared to appraise their influence on assemblies dry and wet adhesion. Surface preparations allow to achieve a level of cleanness and to create a surface roughness. These two elements maximize binding forces and therefore the adhesion of the coating. The coating is thus more resistant to aggressive environments. All cleaning process have led to equivalent level of cleanness of steel substrate. Experiments carried out on mirror polished steel substrates highlighted that a surface roughness is necessary to improve joints durability. Roughness allows to obtain higher adhesion compared to mirror polished steel substrates, slows the effects of humid ageing and thus contributes to extend the durability of the system. It has been demonstrated that a high roughness is particularly beneficial for dry adhesion. By cons, beyond a certain roughness, increasing the surface roughness does not lead to significant improvement of wet adhesion. The benefits of surface treatments were also investigated. The addition of a surface treatment has little impact on dry adhesion in comparison with a conventional surface preparation. However, surface treatments substantially enhance the adhesion strength in wet stage, and therefore increase the durability of the assemblies. We also demonstrate that aminosilane surface treatments are competitive alternatives to traditional chromate conversion, which is the surface treatment of reference in pipeline industry, and whose use will be prohibited in a near future considering changes in legislation. Under good conditions of application and associated with appropriate fusion bonded epoxy, dry and wet adhesion obtained with silane surface treatments are comparable (or even higher ) than those obtained with chromate surface treatments.Furthermore, finite element modeling has allowed to specify interfacial stresses levels inside the assembly resulting from coating's manufacturing process and to predict their evolution over time and during wet ageing.

Micron size non-treated / silane coupling agent (SCA) treated serpentine filled acrylonitrile-butadiene-styrene (ABS) composite preparation and characterization of composites in terms of mechanical, thermal, flow properties and morphology were studied in this work. First step of the study was the size reduction of the as collected serpentine mineral. Secondly, three types of silane coupling agent treatments were applied to serpentine which were gamma-methacryloxypropyltrimethoxysilane (A-174), beta-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane (A-186) and gamma-mercapto-propyltrimethoxysilane (A-189). Non-treated and three different types of SCA treated serpentine minerals were melt mixed with ABS. Non-treated serpentine filled ABS composites had the serpentine weight fractions of 2%, 5%, 10% and 20%. On the other hand, SCA treated ones had serpentine weight fractions of 2%, 5% and 10%. Morphological analysis showed that SCA treatment was partly effective in interface interaction enhancement and A-186 gave the best results according to micrographs. There wasn&amp / #8217 / t any critical mechanical property loss up to 20% serpentine addition. Tensile tests revealed that SCA treatment increased the yield strength values of composites compared to non-treated serpentine filled composites. In accordance with morphological study, best result was obtained from 5% A-186 treated serpentine filled ABS as 12.9% improvement in yield strength value. Percent elongation at break values were increased with filler addition and greatest increase was observed in A-189 treated samples. Serpentine addition had no net effect on Young&amp / #8217 / s Modulus values. According to the impact testing results, A-189 treated samples had improved toughness compared to non-treated samples in accordance with elongation at break values. However increasing filler content resulted with decrease in impact strength values. DSC analysis showed that glass transion temperatures, especially for SCA treated samples, were decreased compared to neat ABS with filler addition. This result suggests that SCA may had the plasticizing effect on the composite. Flow properties of composites were not different from neat ABS up to 2% addition, when the filler concentration was further increased melt flow index values were dramatically decreased.

This study covers the recycling of waste poly(ethylene terephthalate) (PET) bottles through melt blending with low density polyethylene (LDPE) and polypropylene (PP). In general, polymer blends are known to be immiscible and incompatible with poor mechanical properties. This problem is due to the low intermolecular forces between the components of the immiscible blends. In order to enhance the interaction and compatibility between these matrices, some reactive or non-reactive copolymers were used. In this work / PET was treated with silane coupling agent (SCA) (low molecular weight reactive additive) for compatilization of LDPE-PP-PET blends. LDPE-PP-PET blends were prepared in different compositions (by weight) with and without silane coupling agent at high temperatures by a single screw extrusion and injection molding. Mechanical properties of treated and non-treated blends were studied in terms of tensile strength, strain at break and impact strength. Melt flow properties of blends were investigated by melt flow index. The impact fractured surfaces and thermal behaviour of the blends were examined with Scanning Electron Microscope (SEM) and Differential Scanning Calorimeter (DSC), respectively. Through out the studies, good adhesion between PET and LDPE-PP matrix was successfully achieved by the surface treatment of PET particles. The adhesion was also observed in SEM studies. Also the variation in mechanical properties was found to be highly dependent on the number of extrusion.

In this study, waterborne silicone-acrylic resin was produced by incorporating silane coupling agent onto the acrylic main chain by emulsion polymerization. After applying different emulsion polymerization processes, batch polymerization was selected to obtain the resultant resin. Thus finding the optimum conditions by investigating the parameters of monomer ratios, initiators, concentrations of initiators, temperature and time, the novel resin was synthesized. Water-dispersed silicone-acrylic resin was produced using butyl acrylate, butyl methacrylate, methyl methacrylate, 3-methacryloxypropyltrimethoxysilane and acrylic acid as a hydrophilic monomer. 2,2&#039 / -azobis[2-(2-imidazolin-2yl)propane]dihydrogen chloride as thermal initiator and t-butyl hydroperoxide / sodiummetabisulfite as redox couple initiator were selected as the best effective initiators for the production of silicone-acrylic resin. The reaction temperature of the preparation of silicone-acrylic resin was taken as 50&amp / #61616 / C maximum to prevent gelation and agglomeration. To understand the effect of silane coupling agent on the properties of the resin, a new resin was synthesized which did not contain any silane coupling agent and the properties of both resins were determined by FTIR spectroscopy, thermal analysis and mechanical tests. Their physical properties were also determined. The addition of 3-methacryloxypropyltrimethoxysilane to the main chain increased the hardness and the gloss values but slightly decreased the abrasion resistance value of the silicone-acrylic resin. All the samples showed superior flexibility. The produced polymer which contains silane coupling agent showed excellent adhesion properties on glass and metal plates.

No description available.

The influence of silane treated amorphous fumed silica fillers on properties of the cured epoxy was examined in the first part of the study. Silica particles were treated with 3- aminopropyldiethoxymethylsilane (APDS) and 3-aminopropyltriethoxysilane (APTS) coupling agents. The filler and coupling agents decreased the mobility of the polymer chains in the vicinity of the filler leading to an increase in the activation energy for the glass transition and an increase in cooperativity. Fumed silica did not significantly affect moisture diffusion properties. Next, a linear dilatometer was used to investigate the effects of cure conditions, mold types, and the presence of filler in the model epoxy. These studies revealed that there was substantial shrinkage in the cured epoxy on heating it through its glass transition region. The shrinkage was determined to be the result of stress in the epoxy generated during cure and could be minimized by curing at lower temperatures, followed by a postcuring heat treatment. Additional free volume in the sample increased the magnitude of the shrinkage by allowing increased stress release through increased network mobility. Decreasing the polymer mobility by adding fillers decreased the observed shrinkage. The influence of the model epoxy crosslink density was examined by varying the content of 1,4-butanediol in the model system. Addition of 1,4-butanediol led to a decrease in the modulus and glass transition temperature, which resulted in a reduction in residual stress and subsequent shrinkage. Moisture uptake increased with the addition of 1,4-butanediol due to an increase in the free volume of the epoxy. However, even with greater moisture uptake, the addition of 1,4-butanediol to the epoxy increased its adhesion to quartz by promoting lower residual stress and increased energy dissipation. These results indicate that bulk diffusion of water is not the controlling factor in adhesive degradation in this system. / Ph. D.

No description available.

The adhesion and durability of model epoxy/silane/SiO2/Si bonded systems were investigated under various conditions, including the type of surface preparation, pH of the environmental media, temperature, cyclic thermal stress, and external applied stress. The fundamental debond mechanism was studied for bonded systems exposed to selected environments. The bond failure mode was characterized by examining the failed bond surfaces using X-ray photoelectron spectroscopy. The effectiveness of combining the oxygen plasma treatment and silane coupling agent (SCA) derivatization in adhesion promotion for an epoxy bonded to a silicon surface was evaluated in this research. SCAs with different amine functionalities were studied. The oxygen plasma treatment time was varied systematically to achieve a different extent of oxidation on the Si wafer. The surface chemistry/composition of various silane derivatized Si surfaces was investigated. The studies revealed that SCA interaction with the Si surface was enhanced by the oxygen plasma pre-treatment of the Si substrates. XPS surface analysis results showed that the SCA/SiO2 ratio did not correlate strongly with the increase in oxygen plasma pretreatment time. However, for Si surfaces treated for longer oxygen plasma pretreatment times, more silanol groups may be available to interact with the hydrolyzed silanol groups on silane, resulting in a stronger SCA-Si attachment. Three different tests were employed to determine adhesion and durability of the model epoxy/SCA/SiO2/Si bonded specimens. The immersion test qualitatively evaluates the bond durability for various systems exposed to different chemical and thermal conditions. Second, a novel probe test was used to quantitatively determine adhesion under critical debonding conditions for bonded specimens with different SCA preparations. A general trend of bond durability varied in the manner SCA-2 > SCA-3 > SCA-1 > no silane. Bond durability also increased for samples: model epoxy/SCA modified/O2 plasma treated/Si as the oxygen plasma pre-treatment time increased. Third, bond durability was studied using the wedge DCB (double cantilever beam) test under subcritical debonding conditions with environment-assisted crack growth as a function of applied strain energy release rate. Higher crack velocity and the absence of a Gthreshold value were noted in tests at 70 oC. The Gthreshold value increased as the strength of the interface increased and as the chemical aggressiveness of the environment decreased. For tests involving 25 oC -70 oC thermal cycling, only limited crack growth was found. / Ph. D.

No description available.