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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

INCORPORATION OF BIO-BASED MOLECULES IN SILICONES THROUGH MICHAEL ADDITIONS

Lu, Guanhua 24 November 2023 (has links)
Silicone stands as an indispensable material for numerous applications; however, its high energy-cost synthesis poses significant environmental challenges. To address these concerns, bio-based silicone has gained considerable attention, showcasing its potential to dilute energy density while offering inherent functional benefits. Despite promising prospects, existing incorporation methods often involve protecting groups, rare metal catalysts, and multistep synthesis, which contradict green chemistry principles. The aza- Michael reaction emerges as a superior choice due to its high atom economy and mild reaction conditions. However, it still suffers from prolonged reaction times, hindering its overall efficiency and sustainability. This thesis utilizes self-activated beta-hydroxy acrylates to greatly enhance aza-Michael kinetics, achieving a 3-fold rate enhancement in solvent-free silicone synthesis. This fast aza-Michael reaction acts as the platform for the incorporation of Vitamin C and amino acids into silicone materials. Vitamin C-modified silicone demonstrates the potential for controlled antioxidant activity release, while amino acid-functionalized silicones are synthesized using choline amino acid ionic liquids, presenting a protecting-group-free and solvent-free synthesis method. Moreover, the synthesized choline amino acid-functional polymers and elastomers are investigated for their dielectric properties revealing promising potential for dielectric elastomer actuator applications. These innovative methods offer green alternatives for incorporating hydrophilic biomolecules into hydrophobic silicone systems, providing new functionalities that address both environmental and functional requirements. / Thesis / Doctor of Science (PhD)
2

Étude des voies de dépolymérisation chimique des tanins condensés : vers une production industrielle de composés phénoliques biosourcés / Study of the different ways of the chemical depolymerization of condensed tannins for an industrial production of biosourced phenolic compounds

Roumeas, Laurent 18 December 2013 (has links)
La substitution des composés carbonés d'origine fossile par des matières premières renouvelables représente un enjeu majeur et stratégique pour l'environnement, l'économie, et la santé publique. Nous nous sommes particulièrement intéressés au cas des dérivés du phénol, largement utilisés dans le domaine des matériaux synthétiques (résines, plastiques). Des travaux antérieurs ont démontré le potentiel des monomères de flavanols, sous-unités constitutives des chaines polymériques des tanins condensés comme substituts aux phénols issus de la pétrochimie, tels que le bisphénol A, l'objectif du présent travail a été de contribuer au développement d'une voie industrielle d'accès à de tels composés par dépolymérisation des tanins condensés (proanthocyanidines), une ressource végétale abondante mais actuellement peu exploitée pour ce type d'applications. Cette dépolymérisation peut être obtenue par rupture de la liaison interflavanique en milieu acide et piégeage des carbocations formés par un réactif nucléophile. Différentes stratégies et conditions ont été étudiées pour mieux comprendre le rôle de l'acide, du nucléophile, du solvant et l'impact de la température sur la réaction de dépolymérisation. Les stratégies sélectionnées, menées sur un dimère B2 pur servant de modèle et sur un extrait industriel de tanins de pépins de raisins blancs issus de marcs à l'échelle du gramme, ont été comparées en termes de rendement, de cinétique, de stabilité des produits, et de facilité de mise en œuvre et de traitement dans la perspective d'une production à plus grande échelle respectant au mieux les objectifs du développement durable et les contraintes de l'industrialisation. / The substitution of fossil carbon by renewable raw materials is a major strategic challenge for the environment, economy and public health. Our thesis focuses on the utilisation of phenol derivatives, which are widely used in the field of synthetic materials (resins, plastics). Previous studies have demonstrated the potential of plant flavanol monomers as substitutes for petrochemical phenols such as bisphenol A. The objective of this work was to contribute to the development of an industrial access to such compounds by depolymerization of condensed tannins (proanthocyanidins), an abundant plant resource currently untapped for such applications. Depolymerization can be performed by breaking the interflavan bonds in acidic medium and scavenging the released carbocations by a nucleophilic reagent. Various strategies and conditions were studied and compared to better understand the role of the acid, the nucleophile and the solvent and temperature in the depolymerisation reaction. The selected strategies, applied on a pure B2 dimer used as a model and an industrial seed tannins extract from white grape pomace at the gram scale, were compared in terms of performance, kinetics, product stability, ease of implementation and work-up in the context of a larger scale production complying with the objectives of sustainable development and the constraints of industrialization.
3

Etude expérimentale et numérique du comportement hygrothermique de blocs préfabriqués en béton de chanvre / Experimental and numerical study of the hygrothermal behavior of precast hemp concrete blocks

Seng, Billy 07 September 2018 (has links)
Le béton de chanvre est un matériau de construction biosourcé pouvant répondre aux problématiques environnementales actuelles. Utilisé comme matériau de remplissage avec une bonne capacité isolante, il possède également la capacité de réguler l'humidité relative intérieure. Son comportement hygrothermique complexe résulte notamment de performances thermiques et hydriques interdépendantes. La prédiction de ces effets est réalisée à l'aide de modélisation et simulation de transferts hygrothermiques. Toutefois, l'utilisation de données d'entrée les plus représentatives possibles de la réalité est nécessaire. Les méthodes de caractérisation courantes ont souvent été développées pour des matériaux conventionnels et peuvent montrer des limites dans le cas de matériaux biosourcés. L'objectif principal de ces travaux est de déterminer les propriétés hygrothermiques d'un bloc de béton de chanvre préfabriqués à l'échelle industrielle, de mieux appréhender cette caractérisation et de décrire son comportement hygrothermique via des simulations numériques. Le matériau étudié est formulé à partir d'un liant pouzzolanique et de granulats de chènevotte. Une partie de ce travail de thèse a donc porté sur la caractérisation des propriétés physiques, thermiques et hydriques du béton de chanvre étudié ainsi que sur les méthodes de mesure. Pour chaque paramètre hygrothermique étudié, plusieurs méthodes ont été confrontées afin d'en évaluer l'impact. Dans la mesure du possible, l'influence de la température et de l'humidité sur les différents paramètres a également été estimée. Un modèle de transferts hygrothermiques est proposé avec une évaluation d'ordre de grandeur dans le cas du béton de chanvre à partir des propriétés de la littérature. Ce modèle est appliqué à une étude expérimentale à l'échelle de la paroi, dans une enceinte bi-climatique, mettant en avant l'impact de la sorption et du changement de phase sur les transferts de chaleur. En ce qui concerne les propriétés thermiques, l'étude expérimentale à l'échelle du matériau met en évidence l'impact significatif du protocole expérimental sur le résultat de mesure, en particulier pour la chaleur massique. Pour les propriétés hydriques, les essais mettent en avant l'intérêt de réaliser une étude paramétrique de type round-robin sur les matériaux biosourcés. [...] / Hemp concrete is a bio-based construction material able to meet current sustainable issues. Used as filling and insulating material, it has the capacity to regulate the indoor relative humidity. Its complex hygrothermal behavior results on interdependent thermal and hydric performances. The prediction of the hygrothermal effect is performed through heat and moisture transfer modeling and simulation. However, the use of representative inputs is necessary. Standard characterization methods have often been developed for usual building material and can show some limitations in the case of bio-based material. The main objective of these works is to determine the hygrothermal properties of a precast hemp concrete produced at industrial scale, have a better understanding of this characterization and describe its hygrothermal behavior through numerical simulations. The studied material is based on pozzolanic binder and hemp aggregates. One part of this work deals with the characterization of the physical, thermal and hydric properties of the studied material and with the measurement methods. For each hygrothermal properties, several methods have been confronted. If possible, the temperature and humidity influences have been appraised. A heat and moisture transfer model is proposed with a scale analysis based on hemp concrete properties from the literature. This model has been applied to wall scale experiments highlighting the impact of sorption and phase change phenomena on the heat transfers. With regards to the thermal properties, the experimental study at material scale highlights the significant impact of the experimental protocol on the result of the measure, particularly for the specific heat capacity. For hydric properties, the studies put forward the interest of performing a parametric round-robin test dedicated to bio-based materials. An air permeability measurement protocol designed for regular concrete has been adapted in order to evaluate the performance of a very permeable material such as the hemp concrete. The numerical model is validated on a test from a standard and a test from the literature. It manages to describe test with usual ambient solicitations performed in the bi-climatic chamber.
4

Étude expérimentale et numérique de solutions basées sur les éco-matériaux pour la rénovation thermique du patrimoine bâti urbain / Experimental and numerical study of bio-based insulation systems for the thermal refurbishment of historic dwellings in urban areas

Claude, Sophie 08 March 2018 (has links)
Concilier patrimoine et amélioration de la performance énergétique du bâti ancien est un défi pour de nombreux centres historiques. La Communauté d’Agglomération du Grand Cahors, qui finance ce travail de thèse à travers une convention CIFRE, a souhaité s’attaquer à cette problématique en valorisant des isolants bio-sourcés. Le choix du matériau et du système d’isolation sont essentiels car ils influencent à la fois la performance hygrothermique de la paroi, la qualité de l’air intérieur, le coût et l’empreinte carbone de la rénovation. Dans cette étude, nous nous sommes focalisé sur la performance hygrothermique de la paroi afin d’assurer que la mise en place d’une isolation par l’intérieur ne soit pas source de dégradations futures de la paroi. Pour cela, nous avons confronté différents outils et méthodes tels que la caractérisation physique des matériaux, une instrumentation in-situ dans deux appartements du centre ancien de Cahors et des simulations hygrothermiques alliant différents outils numériques. / Improving the energy efficiency of buildings is essential to reduce greenhouse gas emissions and mitigate against climate change. Historic dwellings represent a large part of the French building stock that needs to be refurbished. In the city center of Cahors, France, the old medieval dwellings are considered as valuable cultural heritage and internal insulation is often the only insulation technique that can be used when the architectural value of the exterior façade is to be preserved. This PhD thesis, funded by a CIFRE agreement with the Communauté d’Agglomération du Grand Cahors, studied the suitability of bio-based materials for the internal insulation of historical dwellings in urban area. The selection of the insulation material and the system is crucial because of its impact on the hygrothermal performance of the wall, the indoor air quality, the financial cost, and the carbon footprint of the refurbishment solution. In this study we focused on the hygrothermal performance of the walls to provide a reliable risk assessment in order to avoid hygrothermal failure. Due to the complexity of the problem and the lack of needed data, we ran a multi-scale study including both experimental (laboratory characterisation and building monitoring) and numerical modelling methods.
5

LERGJORD : Stampad lerjord som ett innovationsmaterial i Skåne / EARTHMADE : Rammed earth as innovation material in Scania

Dovberg, Ludvig, Tobias, Löfgren January 2021 (has links)
Lergjord is a thesis that puts emphasis on the possibility of innovation by using local biobased material in the building industry of Skåne in Sweden. The thesis examines if rammed earth can be used in the implementation of LFM30 (Translated into English: Local Sustainable Goals in Malmö by 2030). By use of qualitative research methods, views on rammed earth as a building technique was explored by three stakeholders. This research has concluded if rammed earth is possible in Skåne as a conventional material in the future. We (Ludvig Dovberg and Tobias Löfgren) have examined the practical aspect of rammed earth on Urban Living Lab in the municipality of Lund by the use of local clay material from excavation for an expansion of a new railway between Malmö and Lund in collaboration with Trafikverket. This thesis concludes that rammed earth is feasible with clay from the excavation masses through project LERGJORD. Also, due to the vast quantity of it the resource might be useful for future rammed earth projects in Skåne. However, the building technique itself has some major drawbacks such as time-consumption and the knowledge gap is easily addressed. Although, there has been a development of a pre-fabrication concept of the building technique in Germany since the late 1990s, that could be a solution to the problem. The thesis also concludes that  higher education and research is compulsory to establish a knowledge base for architects to work by. The case study showcased that a standardization of the material is needed to prevent vast material testing before being accepted for construction, like the Lehmbau-praxis in Germany. According to the material’s low impact in CO₂-emission and circularity this resourceful extraction could be of interest by the members of LFM30 to implement in the building industry of Skåne. / Lergjord är ett arbete som undersöker möjligheten till innovation genom att utnyttja lokala biobaserade material i Skåne i Sverige. Arbetet undersöker om stampad jordbyggnad kan användas för att genomföra de Lokala Färdplansmålen som Malmö Stad sätter fram till år 2030 (förk. LFM30). Genom kvalitativa forskningsmetoder undersöktes stampad lerjord som byggnadsteknik hos tre intressenter. Studien har sammanfattat möjligheten om hur stampad lerjord i Skåne kan bli ett konventionellt byggmaterial i framtiden. Vi (Ludvig Dovberg och Tobias Löfgren) har utvärderat den praktiska aspekten i stampad lerjord på Urban Living Lab i Lund med användandet av lokal lerjord från utgrävningar av tillbyggnation för järnvägsspår mellan Malmö och Lund i samarbete med Trafikverket. Arbetet visar att stampjordstekniken är möjlig med utvunnen lera från schaktmassorna mellan Lund och Malmö med hänvisning till projekt LERGJORD. Med tanke på den stora kvantitet av lera som finns kan denna utvinning vara användbar för andra projekt i Skåne. Hursomhelst, byggtekniken besitter på utmaningar såsom tidskrav och kunskapsluckan är tämligen lätt att adressera. Trots det, har ett prefabriceringskoncept inom byggtekniken utvecklats sedan slutet på 1990-talet i Tyskland, som kan vara en lösning på problemet. Arbetet tyder också på att högre utbildning och forskning krävs för att etablera en kunskapsbas som arkitekter kan arbeta vidare på. Fallstudien visar på att en standardisering av materialet krävs för att undvika långa och omständliga materialtester innan godkännande för konstruktion, likt Lehmbau-lagstiftningen i Tyskland. Materialets låga klimatpåverkan och cirkularitet gör det relevant för LMF30’s medlemmar att se vidare på alternativet för implementering i den skånska byggindustrin.
6

A cost estimation of an industrial scale production of nanocellulose filaments utilizing PBCM and TRL : A case study at RISE Research Institutes of Sweden AB / Kostnadsestimering av produktionen för nanocellulosafilament på industriell skala genom användningen av PBCM och TRL : Fallstudie på RISE Research Institutes of Sweden AB

Zhang, Rui Liang, Rask, Lukas January 2019 (has links)
Producing the strongest bio-based material called nanocellulose, in the form of filaments, has shown to be technically feasible at lab-scale, but the production costs remain unknown. The research has focused on technical feasibility and less on costs, which is a common phenomenon when developing new technologies. Constructing a Process-Based Cost Model (PBCM) can link the technical aspects of a technology to its costs of production. However, the accuracy of such a model might be dependent on the data availability of the technology. In this study, the technology of producing nanocellulose filaments has been evaluated along the scale of Technology Readiness Level (TRL) to understand the maturity of the technology and a PBCM has been constructed to show the economic prerequisites for the production of nanocellulose filaments. The main results indicate that at TRL 4, with parts of TRL 5 fulfilled, parameters such as Capital Expenditures cannot be allocated to unit production cost, only Operational Expenditures. Therefore, the relevant cost elements become material and energy as these constitute the currently available data. The PBCM can thus be used to estimate the production costs of different scenarios while highlighting the areas of future research. In the empirical context of nanocellulose filament production, utilizing deionized water in the production is a more promising option compared to utilizing solvents as the cost of recovering the solvent becomes high. Furthermore, using deionized water also becomes more promising due to the fact that other scenarios have not yet been evaluated experimentally. However, as the technology matures and more data becomes available, the model accuracy will increase as more parameters can be included in the model and the basis increases for decisionmaking regarding techno-economic concerns of the technology. / Produktionen av världens starkaste biobaserade material, nanocellulosa i filamentform, har visat sig vara tekniskt möjligt på labbskala, men produktionskostnaderna är idag okända. Forskning som fokuserar mer på den tekniska genomförbarheten och mindre på produktionskostnader är ett vanligt förekommande fenomen i utveckling av ny teknologi. Genom att konstruera en processbaserad kostnadsmodell (PBCM) kan en teknologis tekniska aspekt länkas till dess produktionskostnader. Dock påverkas en sådan modells noggrannhet av datatillgängligheten för teknologin. I denna studie har teknologin för produktionen av nanocellulosa filament utvärderats längs med Technology Readiness Level (TRL) skalan för att förstå teknologins mognadsgrad. Därefter har en PBCM konstruerats för att visa de ekonomiska förutsättningarna för en produktion av nanocellulosafilamenten på industriell skala. Huvudresultaten indikerar att på TRL 4, med delar av TRL 5 uppfyllda, kan somliga parametrar såsom investeringskostnader inte allokeras till enhetsproduktionskostnaden, utan bara löpande kostnader. De relevanta kostnadselementen blir därför material och energi då dessa utgör den aktuellt tillgängliga datan. PBCM kan därför användas för att beräkna produktionskostnader av olika scenarion och lyfta fram områden för framtida forskning. I den empiriska kontexten av produktionen av nanocellulosafilament är användningen av avjoniserat vatten ett mer lovande alternativ jämfört med användningen av lösningsmedel då kostnaden för återvinningen av lösningsmedlet blir högt. Dessutom är användningen av avjoniserat vatten mer lovande eftersom övriga scenarion inte har testats experimentellt än. Allteftersom teknologin mognar och mer data blir tillgänglig, så kommer modellens noggrannhet öka då fler parametrar kan inkluderas i modellen och därmed kan underlaget öka för beslutsfattning gällande teknoekonomiska frågor om teknologin.
7

Laser Scattering for Fast Characterization of Cellulose Filaments / Laserspridning för Snabb Dimensionskarakterisering av Cellulosafilament

Konstantinidou, Alexandra, Holmström, Saga, Hellberg, Susanna January 2022 (has links)
Cellulosananofibriller (CNFs) hör till naturens mest fundamentala byggstenar och förser naturliga material, såsom den yttre cellväggen i trä, med en otrolig styrka och styvhet. Genom att imitera träets arkitektur öppnas möjligheter upp för tillverkning av nya, biobaserade och lättviktiga strukturella material med mekaniska egenskaper som överskrider de för glasfiber, metaller och legeringar. Den ingenjörsmässiga utmaningen ligger i att framgångsrikt lyckas överföra de önskade mekaniska egenskaperna hos CNFs till filament som kan användas i material för dagligt bruk. Vid flödesfokuserad spinning av extraherade CNFs påverkar många parametrar den slutgiltiga funktionaliteten och kvaliteten hos de resulterande filamenten. För att optimera dessa processparametrar är mätning av de spunna filamentens dimensioner ett viktigt moment. Av särskilt intresse är filamentbredden, eftersom den är avgörande för de mekaniska egenskaperna. Karakterisering av filamentbredden är i dagsläget en mycket tidskrävande process där varje filament mäts manuellt i optiskt mikroskop. Det huvudsakliga målet med detta projekt är att effektivisera den nuvarande mätprocessen med avseende på både hastighet och noggrannhet med hjälp av laserspridning. I denna rapport visar vi på minst en halvering av nuvarande mättid vid användandet av en 3D-printad laseruppställning istället för ett optiskt mikroskop vid mätning av filamentbredd. Våra resultat indikerar att mätsäkerheten generellt är högre för lasermetoden jämfört med mikroskopin. Genomsnittliga standardavvikelser för mätvärden på tunnaste bredden från mikroskopi samt de två olika kurvanpassningsmetoderna vid lasermätning rapporteras vara 1.62, 0.85 (Curve fit) respektive 1.59 (Minima matching). Standardavvikelserna för tunnaste bredd korrelerar dock inte direkt mot metodernas noggrannhet eftersom de spunna filamenten uppvisar en stor variation i bredd längs med längden. En närmare jämförelse mellan mätvärden för matchade punkter på ideala och defekta filament demonstrerar att icke-uniforma och defekta filament påverkar mätnoggrannheten för laserspridningen negativt. Sammantaget stödjer våra resultat det faktum att ett tunnare filament resulterar i bättre upplösning och mindre mätfel vid mätning med laserspridning. Våra resultat visar på den stora potentialen för laserspridning som en mer effektiv mätmetod vid karakterisering av cellulosafilamentbredd. / Cellulose nanofibrils (CNFs) are one of nature’s most fundamental building blocks, providing incredible strength and stiffness to natural materials, such as the outer cell wall layer in wood. By mimicking the architecture of wood, possibilities opens up for the fabrication of new, biobased, light-weight structural materials with mechanical properties exceeding that of glassfibers, metals and alloys. However, the engineering challenge lies in successfully managing to translate the desirable mechanical properties of the CNFs into filaments that can be used in everyday life materials. Throughout the process of spinning the extracted CNFs into filaments, many factors and parameters affect the ultimate functionality and performance of the resulting filaments. Measuring the dimensions of the spun filaments is a crucial step in further optimizing process parameters. The width of the filament especially, impacts its mechanical performance. The characterization of the cellulose filament width is currently very time-consuming as each filament is manually measured using optical microscopy. The primary goal of this project is to make the current characterization process more effective, with respect to both accuracy and speed of measurement, by using laser scattering. In this report, we demonstrate a reduction by more than a half in measurement time using a 3D-printed laser scattering setup instead of an optical microscope when measuring filament width. Our results indicate that the certainty in measurement is generally higher for lase rscattering compared to optical microscopy. The mean standard deviations (SD) for the smallest widths estimated with optical microscopy and the two curve fitting methods used for the laser measurements are reported to be 1.62, 0.85 (Curve fit) and 1.59 (Minima matching) respectively. However, standard deviations for the thinnest width does not correlate directly to the accuracy of the methods since the spun filaments show a large variation in width along the length. A closer comparison between measurement values for matched points at ideal and non-uniform filaments demonstrate that the accuracy of the laser measurements are dependent on the uniformity of the filaments, with non-uniform filaments negatively impacting the accuracy. Our overall results supports the fact that a thinner filament gives a better resolution and smaller error when measuring with laser. Our results provide evidence for the great potential of laser scattering as a more efficient method for cellulose filament width determination.

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