Thèses : « Depolymerization of cellulose fibres »

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Bélanger, Karine. « Controlled depolymerization and decrystallization of cellulose-rich substrates into glucose ». Mémoire, Université de Sherbrooke, 2005. http://savoirs.usherbrooke.ca/handle/11143/1483.

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The energy needs are increasing rapidly throughout the world. To fulfill this need, new environmentally friendly energy sources must be developed. Production of bio-ethanol from lignocellulosics, a renewable resource, has a favorable life cycle compared to actual fossil fuels or to bio-ethanol from starch.The main difficulty is to obtain the sugars from the rigid cellulose matrix characteristic of lignocellulosics.The sugars would then be fermented into ethanol. Scientists generally follow two approaches to develop the sugar production process from lignocellulosics, (1) acid hydrolysis and (2) enzymatic hydrolysis. Both approaches produce high glucose recoveries; however, both processes have been, so far, economically unattractive and rely, as the corn-linked process, on subsidies. This project attempts to develop improved methods that make the sugar production from lignocellulosics economically attractive.The acid hydrolysis process is based on the ASTM E1758-95 method, referred to as"Determination of carbohydrates in biomass by HPLC". Our innovation has been to modify the"swelling" and hydrolysis steps inherent in the ASTM method, by using a mediator to produce a more concentrated solution of sugars.The experiment presented in this thesis proves that that proposed innovation is technically feasible. However, the economical feasibility of our innovation hinges upon the recovery and recycling of the acid and mediator.The enzymatic hydrolysis innovation is based on using the substrates produced by steam treatment and evaluating whether or not their enzymatic hydrolysis is preferred (less enzymes and less time) over processes with pre-treated but non-fractionated substrates or in relation to high-purity cellulose as the ultimate standard. Our research shows that time and enzymatic loading are the main factors controlling the hydrolysis. When compared with these two factors, the type of substrate has little effect on enzymatic hydrolysis. From this information, it can be deduced that crystallinity is the key limiting step and barrier to enzymatic activity.

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Yeoh, Sang Ju. « Electrospun cellulose fibres from kraft pulp ». Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/12930.

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Cellulose, the most abundant biomass extractable from wood, was generated in fibre form from kraft pulp by electrospinning, a fibre-producing process using electrostatic forces. Kraft pulping is the most dominant pulping technique in North America. Kraft pulp fibres (diam. 30μm) have a tensile strength of 700MPa and elastic modulus of 20GPa. In comparison, individual cellulose nanofibrils (diam. 5nm) have a tensile strength of 10GPa and elastic modulus of 150GPa. The strength displayed by cellulose nanofibrils suggests that the smaller fibre diameter could lead to a lower probability of including smaller flaw sizes in the fibre. Electrospinning has been successfully demonstrated as a one-step process to produce cellulose fibres directly from kraft pulp, thereby showing great potential for reducing cost and making the fibre-producing process more environmental friendly. Based on SEM and XRD, the electrospun fibres have a fibrillation-free, nano-filament structure with a seemingly cellulose I crystal structure, indicating significant potential for making crystalline cellulose fibres directly from kraft pulp. Contact angle measurements show that the electrospun fibres appear more hydrophobic than kraft pulp. The mechanical properties of the electrospun fibres have a large variation, suggesting the need for further process optimization. The ability to produce cellulose fibres directly from kraft pulp with improved moisture resistance and mechanical properties could potentially result in the development of more high value-added products for the Canadian pulp and paper industry, and perhaps even globally.

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Bengtsson, Andreas. « Carbon fibres from lignin-cellulose precursors ». Licentiate thesis, KTH, Träkemi och massateknologi, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-244756.

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It is in the nature of the human species to find solutions of complex technical problems and always strive for improvements. The development of new materials is not an exception. One of the many man-made materials is carbon fibre (CF). Its excellent mechanical properties and low density have made it attractive as the reinforcing agent in lightweight composites. However, the high price of CF originating from expensive production is currently limiting CF from wider utilisation, e.g. in the automotive sector. The dominating raw material used in CF production is petroleum-based polyacrylonitrile (PAN). The usage of fossil-based precursors and the high price of CF explain the strong driving force of finding cheaper and renewable alternatives. Lignin and cellulose are renewable macromolecules available in high quantities. The high carbon content of lignin is an excellent property, while its structural heterogeneity yields in CF with poor mechanical properties. In contrast, cellulose has a beneficial molecular orientation, while its low carbon content gives a low processing yield and thus elevates processing costs. This work shows that several challenges associated with CF processing of each macromolecule can be mastered by co-processing. Dry-jet wet spun precursor fibres (PFs) made of blends of softwood kraft lignin and kraft pulps were converted into CF. The corresponding CFs demonstrated significant improvement in processing yield with negligible loss in mechanical properties relative to cellulose-derived CFs. Unfractionated softwood kraft lignin and paper grade kraft pulp performed as good as more expensive retentate lignins and dissolving grade kraft pulp, which is beneficial from an economic point of view. The stabilisation stage is considered the most time-consuming step in CF manufacturing. Here it was shown that the PFs could be oxidatively stabilised in less than 2 h or instantly carbonised without any fibre fusion, suggesting a time-efficient processing route. It was demonstrated that PF impregnation with ammonium dihydrogen phosphate significantly improves the yield but at the expense of mechanical properties. A reduction in fibre diameter was beneficial for the mechanical properties of the CFs made from unfractionated softwood kraft lignin and paper grade kraft pulp. Short oxidative stabilisation (<2 h) of thin PFs ultimately provided CFs with tensile modulus and strength of 76 GPa and 1070 MPa, respectively. Considering the high yield (39 wt%), short stabilisation time and promising mechanical properties, the concept of preparing CF from lignin:cellulose blends is a very promising route.
Det ligger i människans natur att hitta lösningar på komplexa tekniska problem, samt att alltid sträva efter förbättringar. Utvecklingen av nya material är inget undantag. Ett av flera material utvecklade av människan är kolfiber. Dess utmärkta mekaniska egenskaper samt låga densitet har gjort det attraktivt som förstärkningsmaterial i lättviktskompositer. Det höga priset på kolfiber, vilket härstammar ur en kostsam framställningsprocess, har förhindrat en mer utbredd användning i exempelvis bilindustrin. Det dominerande råmaterialet för kolfiberframställning är petroleumbaserad polyacrylonitril (PAN). Användandet av fossila råvaror och det höga priset på kolfiber förklarar den starka drivkraften att hitta billigare och förnyelsebara alternativ. Lignin och cellulosa är förnyelsebara makromolekyler som finns tillgängliga i stora kvantiteter. Det höga kolinnehållet i lignin gör det mycket attraktivt som råvara för kolfiberframställning, men dess heterogena struktur ger en kolfiber med otillräckliga mekaniska egenskaper. Däremot har cellulosa en molekylär orientering som är önskvärd vid framställning av kolfiber, men dess låga kolinehåll ger ett lågt processutbyte som i sin tur bidrar till höga produktionskostnader. Det här arbetet visar att många av de problem som uppstår med kolfiber från respektive råvara kan kringgås genom att utgå från blandningar av desamma. Prekursorfibrer från blandningar av kraftlignin och kraftmassa från barrved tillverkade med luftgapsspinning konverterades till kolfiber. Utbytet för kolfibrerna som framställdes var mycket högre än vid framställning från endast cellulosa. Ofraktionerat barrvedslignin och kraftmassa av papperskvalitet presterade lika bra som de dyrare retentatligninen och dissolvingmassan, vilket är fördelaktigt ur ett ekonomiskt perspektiv. Stabilisering är det mest tidskrävande processteget i kolfibertillverkning. I det här arbetet visades det att prekursorfibrerna kunde stabiliseras på kortare än två timmar, eller direktkarboniseras utan någon sammansmältning av fibrerna. Detta indikerar att en tidseffektiv produktion kan vara möjligt. Impregnering av prekursorfibrerna med ammoniumdivätefosfat ökade utbytet avsevärt, men med lägre mekaniska egenskaper som bieffekt. Kolfibrernas mekaniska egenskaper ökade vid en diameterreduktion. En kort oxidativ stabilisering under två timmar i kombination med tunna prekursorfibrer gav kolfiber med en elasticitetsmodul på 76 GPa och dragstyrka på 1070 MPa. Att göra kolfiber från blandningar av lignin och cellulosa är ett lovande koncept om det höga utbytet (39%), den korta stabiliseringstiden samt de lovande mekaniska egenskaperna tas i beaktande.

QC 20190226

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Hilgert, Jakob [Verfasser], Ferdi [Akademischer Betreuer] Schüth et Martin [Akademischer Betreuer] Muhler. « Mechanocatalytic depolymerization of cellulose and subsequent hydrogenation / Jakob Hilgert. Gutachter : Ferdi Schüth ; Martin Muhler ». Bochum : Ruhr-Universität Bochum, 2015. http://d-nb.info/1079843728/34.

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Li, Yingjie. « Emulsion electrospinning of nanocrystalline cellulose reinforced nanocomposite fibres ». Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/30474.

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Cellulose is the most abundant renewable and biodegradable natural polymer. Cellulose can release nanocrystalline cellulose (NCC). NCC is light-weight, biodegradable and strong. The strength of NCC is about 10 GPa, which is almost three times stronger than commercial high performance fibre such as Kevlar® and Spectra®. In order to realize the utmost translation of NCCs’ extraordinary properties to higher order structures, it is necessary to accomplish a well-controlled alignment and tailored distribution of NCCs within a matrix. However, it is challenging to achieve this goal since NCCs tend to agglomerate in matrix materials. To address this problem in the present study, NCC water- in-oil (W/O) emulsions were prepared, consisting of a drop phase of NCC aqueous suspension and a continuous phase of immiscible poly (lactic acid) (PLA) solution. NCC W/O PLA emulsions were electrospun into NCC reinforced nanocomposite fibres. The concept of emulsion electrospinning of NCCs is based on that (1) NCC can be stably and uniformly dispersed in the intermediate medium water; (2) NCC aqueous suspension can be dispersed in the form of droplets into the immiscible solutions of PLA solution system; and (3) the well dispersed NCC / PLA emulsion can be electrospun into fibres. In this work, to better control electrospinning of NCC/PLA emulsions, we started with electrospinning of W/O PLA emulsions consisting of a drop phase of distilled water and a continuous phase of hydrophobic PLA solution. This emulsion formulation for electrospinning was optimized using response surface methodology (RSM) to identify the optimal conditions for W/O PLA electrospinning. After optimizing the W/O PLA emulsion electrospinning process, the feasibility of the emulsion electrospinning of NCC W/O PLA was confirmed and the emulsion electrospun 5% NCC/ 8% PLA random fibre mats and aligned fibre yarns were collected. The distribution and alignment of NCCs in fibres were verified. The morphology, structure and properties of resultant fibres were characterized. The mechanism of the formation of fibre structure (core-shell and hollow) was also proposed and validated by the study of emulsion droplet size effect on fibre structure.

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Qi, Haisong, Jianwen Liu, Yinhu Deng, Shanglin Gao et Edith Mäder. « Cellulose fibres with carbon nanotube networks for water sensing ». Royal Society of Chemistry, 2014. https://tud.qucosa.de/id/qucosa%3A36157.

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Electroconductive cellulose-based fibres were fabricated by depositing multi-walled carbon nanotubes (MWNTs) on the surface using a simple and scalable dip coating. The morphology, mechanical properties and conductive properties of the resultant MWNT–cellulose fibres were investigated by scanning electron microscopy, tensile testing and electrical resistance measurement, respectively. The resistance (RL) of the single MWNT–cellulose fibre can be controlled in a wide range of 50–200 000 kΩ cmˉ¹ by varying the conditions of dip coating. The sensing behaviour of these fibres to liquid water was investigated in detail. The results showed that they exhibit rapid response, high sensitivity and good reproducibility to water, with a relative electrical resistance change of about 100–8000% depending on the initial resistance. It was proposed that the disconnection of MWNT networks caused by swelling effects of the cellulose fibres is the dominant mechanism. Moreover, the sensitivity of the MWNT–cellulose fibres to an electrolyte solution was also investigated.

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Benoit, Maud. « Dépolymérisation catalytique de la cellulose couplée à des techniques d’activation non thermiques ». Thesis, Poitiers, 2012. http://www.theses.fr/2012POIT2270.

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Avec la disparition progressive des réserves de carbone fossile, un intérêt tout particulier est aujourd’hui porté sur la valorisation de la biomasse notamment la cellulose. Elle représente une source importante (1,3 Millions de tonnes) et peu onéreuse (< 10 €/kg) de carbone renouvelable. L’utilisation de la cellulose en tant que matière première pour la chimie fine apparait comme une solution attractive tant sur le plan économique qu’environnemental. Néanmoins, la présence de liaisons hydrogène intra et extra réseau lui confère une stabilité élevée (forte cristallinité) la rendant insoluble dans les solvants organiques usuels et dans l’eau. Ainsi, l’hydrolyse de ce polymère en glucose ou oligosaccharides, en présence d’un catalyseur solide est limitée par les interactions catalyseur/cellulose. C’est pourquoi, des prétraitements de la cellulose sont souvent utilisés permettant alors d’augmenter les interactions avec les catalyseurs solides. Toutefois, les méthodes développées dans la littérature sont coûteuses ou néfastes pour l’environnement. L’objectif de cette étude est le développement d’activations physiques de la cellulose, respectueuses de l’environnement, permettant l’hydrolyse de ce polymère en présence d’un catalyseur solide. L’activation de la cellulose est effectuée par ultrasons ou par plasma atmosphérique non thermique. Ces méthodes d’activation permettent d’augmenter considérablement le rendement en glucose en modifiant i) la taille des particules et/ou ii) le degré de polymérisation et/ou iii) la cristallinité de la cellulose. Enfin, à partir des sucres issus de la dépolymérisation de la cellulose, le 5- hydroxyméthylfurfural (molécule plateforme) peut être obtenu. Cette synthèse sera étudiée et plus particulièrement la nature du solvant, qui impacte la sélectivité de cette réaction. Lors de ces travaux, un intérêt tout particulier est porté sur l’utilisation de glycérol et de carbonate de glycérol en tant que solvant
With the depletion of fossil carbon resources, biomass (including cellulose) is widely introduced in the chemical industry, as a renewable source of carbon. Cellulose is a huge reservoir (1,3 Million tons) of cheap (< 10 €/kg) and non-edible carbon. So use cellulose as raw material has many advantages, as much as economic plan than environmental one. However, due to important inter and intra hydrogen bonds network, cellulose is highly crystalline and thus insoluble in common solvents (including water) and recalcitrant to hydrolysis by heterogeneous catalysis, due to solid/solid interactions. A preliminary step consists in the activation of cellulose to enhance the solid/solid interactions. However, the pretreatments used in the literature are limited by the cost, corrosiveness, and toxicity. The aim of this study is to develop physical pretreatments of cellulose in order to be environmentally friendly and promote cellulose/catalyst interactions. In this manuscript, two physical methods of cellulose activation will be explored. The first involves a sonic treatment and the second implies non-thermal atmospheric plasma technology. These methods lead to an increase of the glucose yield due to the change of i) the particle size, or/and ii) the degree of polymerization or/and iii) the cristallinity. From carbohydrate obtained via the depolymerisation of cellulose, 5-hydroxymethylfurfural (platform molecule) is achieved. This synthesis, including dehydration of fructose, will be studied and especially, the nature of the solvent which is a key point ofthis conversion will be discussed. In this work glycerol or glycerol carbonate-based media were studied, as co-solvent from renewable carbon

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Le, Moigne Nicolas. « Mécanismes de gonflement et de dissolution des fibres de cellulose ». Phd thesis, École Nationale Supérieure des Mines de Paris, 2008. http://tel.archives-ouvertes.fr/tel-00353429.

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Le but de ces travaux était d'étudier les mécanismes de gonflement et de dissolution des fibres de cellulose en faisant varier la qualité du solvant (N-methylmorpholine-N-oxide avec différentes quantités d'eau et solutions aqueuses de NaOH à 8%), les conditions de dissolution, comme la tension, et l'origine des fibres (coton, bois, fibres régénérées ou dérivées). Les mécanismes de gonflement et de dissolution ont été étudiés par des observations microscopiques à haute résolution. Une séparation sélective des fractions solubles et insolubles a été réalisée par centrifugation. La distribution de masse molaire, la cristallinité, la composition en sucre, l'allomorphie et la quantité de chaque fraction ont été analysées. A partir de ces résultats, nous avons pu mieux décrire les mécanismes de gonflement et de dissolution des fibres de cellulose et ainsi identifier les principaux paramètres gouvernant la dissolution. Nos résultats montrent que les caractéristiques structurales et moléculaires des fibres de cellulose ainsi que les paramètres de procédés doivent être mieux contrôlés afin d'améliorer la dissolution. (i) Les paramètres de procédés concernent la convection du solvant et la possibilité de mouvements des fibres dans le solvant, (ii) les paramètres structuraux concernent la suppression des parois externes, la déstructuration des parois internes et la suppression sélectives des hémicelluloses, (iii) les paramètres moléculaires concernent la thermodynamique, comme la longueur des chaînes, la cristallinité mais aussi l'amélioration de la mobilité conformationelle des chaînes.

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Ly, El Hadji Babacar. « Nouveaux matériaux composites thermoformables à base de fibres de cellulose ». Phd thesis, Grenoble INPG, 2008. http://tel.archives-ouvertes.fr/tel-00268828.

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Cette étude s'inscrit dans le cadre de la recherche de solutions alternative à l'utilisation des matières fossiles et à la pollution que les matériaux issus de cette filière (les emballages plastiques par exemple) peuvent causer. L'objectif est de préparer de nouveaux matériaux composites à base de matière première issue de ressources renouvelables tels que les biopolymères. Notre choix s'est orienté vers l'utilisation de fibres de cellulose et de polymères thermoplastiques biodégradables. La préparation de ces matériaux composites nécessite de compatibiliser, ou de copolymériser, les fibres et la matrice. Pour arriver à cette fin, des modifications chimiques sont effectuées sur l'un des constituants par le biais d'agents de couplage bi-fonctionnels (dianhydrides, diisocyanates, silanes et polyoléfines fonctionnalisés). La mise en œuvre des matériaux se fait par des techniques utilisées en industries plastiques (extrusion, coulée-évaporation ou "solvent casting"). La biodégradabilité et les propriétés thermomécaniques de ces matériaux, avant et après vieillissement des matériaux, sont étudiées.

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Quajai, Sirisart, et soj@kmitnb ac th. « Biopolymer Composite based on Natural and Derived Hemp Cellulose Fibres ». RMIT University. Applied Sciences, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20061222.111612.

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The aim of this research was to study the effect of pre-treatment and modification processes on the properties of hemp cellulose fibre for biopolymer composites application. Hemp fibres have been modified by various extraction, swelling, chemical and enzymatic treatments. The morphology and mechanical properties of the modified fibres have been measured. Biopolymer composites have been prepared using the modified fibres and matrices of cellulose acetate butyrate and cellulose solutions derived from hemp. The first fibre treatment employed was acetone extraction and mercerization. A low pressure acrylonitrile grafting initiated by azo-bis-isobutylonitrile was performed using alkali treated fibre. The AN grafted fibres had no transformation of crystalline structure as observed after mercerization. The mechanical properties performed by a single fibre test method were strongly influenced by the cellulose structure, lateral index of crystallinity, and fraction of grafting. Bioscouring of hemp using pectate lyase (EC 4.2.2.2), Scourzyme L, was performed. Greater enzyme concentration and a longer treatment improved the removal of the low methoxy pectin component. Removal of pectate caused no crystalline transformation in the fibres, except for a slight decline in the X-ray crystalline order index. Smooth surfaces and separated fibres were evidence of successful treatment. The shortening of fibre by grinding and ball-milling was introduced to achieve a desired fibre size. An increase in the milling duration gradual ly destroyed the crystalline structure of the cellulose fibres. An increase in solvent polarity, solvent-fibre ratio, agitation speed and drying rate resulted in the rearrangement of the ball-milled cellulose crystalline structure to a greater order. The thermal degradation behaviour of hemp fibres was investigated by using TGA. The greater activation energy of treated hemp fibre compared with untreated fibre represented an increase in purity and improvement of structural order. The all hemp cellulose composites were prepared by an introduction of fibres into 12% cellulose N-methyl-morpholine N-oxide (NMMO) solution and water-ethanol regeneration. A broadening of the scattering of the main crystalline plane, (002) and a depression of the maximum degradation temperature of the fibres were observed. These revealed a structural change in the fibres arising from the preparation. The mechanical properties of composites depended on size, surface area, crystallinity and the structural swelling of the fibres. Composites of cellulose acetate butyrate (CAB) and modified hemp fibres were prepared. Composites containing pectate lyase enzyme treated fibres showed better mechanical property improvement than untreated and alkali treated fibres respectively.

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Budd, J. « The adsorption of aluminium from aqueous solution by cellulose fibres ». Thesis, University of Reading, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379304.

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Fernandes, Susana Cristina de Matos. « Novel materials based on chitosan, its derivatives and cellulose fibres ». Doctoral thesis, Universidade de Aveiro, 2010. http://hdl.handle.net/10773/3222.

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Doutoramento em Química
O presente trabalho tem como principal objectivo o desenvolvimento de novos materiais baseados em quitosano, seus derivados e celulose, na forma de nanofibras ou de papel. Em primeiro lugar procedeu-se à purificação das amostras comerciais de quitosano e à sua caracterização exaustiva em termos morfológicos e físicoquímicos. Devido a valores contraditórios encontrados na literatura relativamente à energia de superfície do quitosano, e tendo em conta a sua utilização como precursor de modificações químicas e a sua aplicação em misturas com outros materiais, realizou-se também um estudo sistemático da determinação da energia de superfície do quitosano, da quitina e seus respectivos homólogos monoméricos, por medição de ângulos de contacto Em todas as amostras comerciais destes polímeros identificaram-se impurezas não polares que estão associadas a erros na determinação da componente polar da energia de superfície. Após a remoção destas impurezas, o valor da energia total de superfície (gs), e em particular da sua componente polar, aumentou consideravelmente. Depois de purificadas e caracterizadas, algumas das amostras de quitosano foram então usadas na preparação de filmes nanocompósitos, nomeadamente dois quitosanos com diferentes graus de polimerização, correspondentes derivados solúveis em água (cloreto de N-(3-(N,N,N-trimetilamónio)-2- hidroxipropilo) de quitosano) e nanofibras de celulose como reforço (celulose nanofibrilada (NFC) e celulose bacteriana (BC). Estes filmes transparentes foram preparados através de um processo simples e com conotação ‘verde’ pela dispersão homogénea de diferentes teores de NFC (até 60%) e BC (até 40%) nas soluções de quitosano (1.5% w/v) seguida da evaporação do solvente. Os filmes obtidos foram depois caracterizados por diversas técnicas, tais como SEM, AFM, difracção de raio-X, TGA, DMA, ensaios de tracção e espectroscopia no visível. Estes filmes são altamente transparentes e apresentam melhores propriedades mecânicas e maior estabilidade térmica do que os correspondentes filmes sem reforço. Outra abordagem deste trabalho envolveu o revestimento de folhas de papel de E. globulus com quitosano e dois derivados, um derivado fluorescente e um derivado solúvel em água, numa máquina de revestimentos (‘máquina de colagem’) à escala piloto. Este estudo envolveu inicialmente a deposição de 1 a 5 camadas do derivado de quitosano fluorescente sobre as folhas de papel de forma a estudar a sua distribuição nas folhas em termos de espalhamento e penetração, através de medições de reflectância e luminescência. Os resultados mostraram que, por um lado, a distribuição do quitosano na superfície era homogénea e que, por outro lado, a sua penetração através dos poros do papel cessou após três deposições. Depois da terceira camada verificou-se a formação de um filme contínuo de quitosano sobre a superfície do papel. Estes resultados mostram que este derivado de quitosano fluorescente pode ser utilizado como marcador na optimização e compreensão de mecanismos de deposição de quitosano em papel e outros substratos. Depois de conhecida a distribuição do quitosano nas folhas de papel, estudou-se o efeito do revestimento de quitosano e do seu derivado solúvel em água nas propriedades finais do papel. As propriedades morfológicas, mecânicas, superficiais, ópticas, assim como a permeabilidade ao ar e ao vapor de água, a aptidão à impressão e o envelhecimento do papel, foram exaustivamente avaliadas. De uma forma geral, os revestimentos com quitosano e com o seu derivado solúvel em água tiveram um impacto positivo nas propriedades finais do papel, que se mostrou ser dependente do número de camadas depositadas. Os resultados também mostraram que os papéis revestidos com o derivado solúvel em água apresentaram melhores propriedades ópticas, aptidão à impressão e melhores resultados em relação ao envelhecimento do que os papéis revestidos com quitosano. Assim, o uso de derivados de quitosano solúveis em água em processos de revestimento de papel representa uma estratégia bastante interessante e sustentável para o desenvolvimento de novos materiais funcionais ou na melhoria das propriedades finais dos papéis. Por fim, tendo como objectivo valorizar os resíduos e fracções menos nobres da quitina e do quitosano provenientes da indústria transformadora, estes polímeros foram convertidos em polióis viscosos através de uma reacção simples de oxipropilação. Este processo tem também conotação "verde" uma vez que não requer solvente, não origina subprodutos e não exige nenhuma operação específica (separação, purificação, etc) para isolar o produto da reacção. As amostras de quitina e quitosano foram pré-activadas com KOH e depois modificadas com um excesso de óxido de propileno (PO) num reactor apropriado. Em todos os casos, o produto da reacção foi um líquido viscoso composto por quitina ou quitosano oxipropilados e homopolímero de PO. Estas duas fracções foram separadas e caracterizadas.
The purpose of this study was to develop new materials based on chitosan and its derivatives and cellulose, in the form of nanofibres or paper sheet. Firstly, the commercial chitosan samples were thoroughly characterized in terms of morphology and physicochemical aspects. Because of conflicting reports and unrealistic literature values, and because of the use of chitosan as mixtures component, or as precursor for chemical modifications, a systematic study of the surface energy of chitin, chitosan and their respective monomeric counterparts was carried out using contact angle measurements. All the commercial samples of these polymers were shown to contain non-polar impurities that gave rise to enormous errors in the determination of the polar component of their surface energy. After their thorough removal, the value of the total surface energy (gs), and particularly of its polar component, increased considerably. Well characterized chitosan samples were then used to prepare transparent nanocomposite films based on different chitosan (CH) matrices (two chitosans with different DPs and corresponding water-soluble derivatives (N-(3-(N,N,Ntrimethylamonium)- 2-hydroxypropyl) chloride chitosan), nanofibrillated cellulose (NFC) and bacterial cellulose (BC) were prepared by a fully green procedure by casting a water based suspension of CH, NFC and BC. Different contents of NFC (up to 60%) and BC (up to 40%) were dispersed in 1.5% (w/v) CH solutions. The films were characterized by several techniques, namely SEM, AFM, X-ray diffraction, TGA, tensile assays, dynamic mechanical analysis and visible spectroscopy. The films obtained were shown to be highly transparent, displayed better mechanical properties than the corresponding unfilled chitosan films and showed increased thermal stability. Another approach involved the coating of E. globulus based paper sheets with chitosan and two different chitosan derivatives, a fluorescent and a watersoluble derivative, on a pilot-size press machine. First, a fluorescent chitosan derivative was deposited layer-by-layer onto conventional paper sheets and its distribution, in terms of both spreading and penetration, was assessed by emission measurements. The results showed that, on the one hand the surface distribution was highly homogeneous and, on the other hand, the penetration of chitosan within the paper pores ceased after a three-layer deposit, beyond which any additional coating only produced an increase in its overall thickness and film-forming aptitude. These results show that this modified chitosan can be used as probe to optimize and understand the mechanism of the deposition of chitosan onto paper and other substrates. Then, the effect of chitosan and chitosan quaternization on the final properties of chitosan-coated papers was investigated. Different coating weights were attained by the deposition of 1-5 coating layers. The morphological, mechanical, surface, barrier and optical properties as well as the paper ageing and printability of the ensuing coated papers were investigated and assessed. In general, both chitosan and water-soluble chitosan coatings had a positive impact on the final properties of the coated papers, which was quite dependent on the number of deposited chitosan layers. The results obtained also showed that the water-soluble chitosan coated papers presented superior optical properties, inkjet print quality and better results on ageing measurements than chitosan coated papers. Therefore, the use of water-soluble chitosan derivatives on paper coating processes represents an interesting and sustainable strategy for the development of new functional paper materials or for the improvement of the end-user properties of paper products. Finally, chitin and chitosan were converted into viscous polyols through a simple oxypropylation reaction, with the aim of valorising the less noble fractions or by-products of these valuable renewable resources. This process bears “green” connotations, given that it requires no solvent, leaves no byproducts and no specific operations (separation, purification, etc.) are needed to isolate the entire reaction product. Chitin or chitosan samples were preactivated with KOH and then reacted with an excess of propylene oxide (PO) in an autoclave. In all instances, the reaction product was a viscous liquid made up of oxypropylated chitin or chitosan and PO homopolymer. The two fractions were separated and thoroughly characterized.

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Hernandez, Zurine. « Conditions required for spinning continuous fibres from cellulose nano-fibrils ». Thesis, Edinburgh Napier University, 2012. http://researchrepository.napier.ac.uk/Output/5286.

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The thesis describes a programme of work to develop a novel cellulose based fibre. The most important innovative step in this work lies in the manufacture of the fibre from a chiral nematic suspension of plant based cellulose nano-fibrils. In the course of the project a number of key steps have been addressed in the development process. These included: • Developing a method for extraction of nano-fibrils from wood and cotton based pulp and filter paper; • Development of concentrated chiral nematic suspensions of the nano-fibrils suitable for extrusion (spinning); • Spinning a continuous fibre or filament; • Fibre characterization. A key objective of the work was to understand the factors that could contribute to nematic order of the nano-fibrils in the fibre and produce a high strength fibre. The fibres developed showed reasonably good strength potential and good stiffness properties with the best fibres having a tenacity of between 40 and 100 cN/tex and an initial modulus of 5000-6000 cN/tex. These values fall midway between lyocell and Kevlar. Two patents have to date been published based upon the developments described in this work (Turner et al., 2010, 2011). However, the work highlighted a number of gaps in current knowledge that prevented development of the full potential strength properties of these fibres. These included: • Incomplete knowledge of the gel conditions required to achieve complete alignment of the fibrils in the spinning process; • Challenges in being able to draw the fibre sufficiently during spinning to produce target fibre diameters of 5-10μm; • The linear density of the spun fibres had a key impact on fibre strength. It was only when linear density values dropped below 1 tex (1g/km) that a significant increase in fibre strength occurred. Factors that had an important impact on linear density included solids content of the suspension, zeta potential, extrusion rate and fibre drying temperature. All these factors relate directly to the mobility of the cellulose nano-fibrils and their subsequent ability to align under flow during spinning. The thesis can be seen as a first phase in an ongoing process to develop a new approach to the manufacture of cellulose based industrial textile fibres.

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Adams, K. V. « Dyeing of cellulose fibres : how the structure of cellulose and the dye molecules affect the dyeing process ». Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.595346.

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The understanding of the dyeing of cellulosic fibres has been limited by the lack of fundamental knowledge about the structures and processes that occur on the molecular scale. The work reported in this dissertation has begun to address some of the areas where greater insight into these structures and processes is required. This information can then be used as input into existing empirical models of the dyeing process used in industry. The solid state structure of various cellulosic fibres were investigated using carbon-13 cross polarisation/magic angle spinning nuclear magnetic resonance (¹³C CP/MAS NMR) spectroscopy. The percentage crystallinities and the proportions of the different crystalline forms of cellulose, Iα, Iβ and II, in each sample were calculated from lineshape analyses of the spectra. The presence of cellulose II in mercerised cotton was confirmed and it is proposed that the degree of mercerisation is indicated by the percentage crystallinity and the proportion of cellulose II present in the sample. The pulsed-gradient spin-echo (PGSE) NMR technique has been used to characterise the self-diffusion of water within various cellulose samples. A new model, defined by a three-component diffusivity, has been proposed to describe this diffusion and it is consistent with the known structures of various cellulosic fibres, such as native cotton and Tencel. It is also proposed that some of the variations in dyeability of cellulose fibres might be partially explained by the observed differences in the self-diffusion of water within the samples. The characterisation of the self-diffusion and aggregation of acid dyes in aqueous solution has been investigated for the first time using the PGSE NMR method. The results found agree well with the literature, and the main trends, such as an increase in the average aggregation number caused by a corresponding increase in dye molecular weight, dye concentration or addition of NaCl, were observable by this method. Finally, the self-diffusion of dye molecules within cotton fibres was investigated using the PGSE NMR technique. Not all dyes could be studied using this method as it was found that an increase in the affinity of the dye for the cotton fibre surface caused the dye molecules to be associated with fast relaxation times and therefore become 'invisible' to the NMR experiment. Major variations were apparent when comparing the diffusion of dye within the unmercerised and mercerised cotton. It is proposed that this difference is found because of the increased affinity of dyes towards the surface of mercerised cotton.

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Hardman, Susan Marion. « The mineralization of fibres in archaeological contexts ». Thesis, Cardiff University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320178.

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Utsel, Simon. « Surface modification of cellulose-based fibres for use in advanced materials ». Licentiate thesis, KTH, Fiber- och polymerteknik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-25245.

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The awareness of our need for a sustainable society has encouraged the search for renewable, high quality materials that can replace oil-based products. This, in combination with increased competition in the forest industry, has stimulated a lot of research into different types of wood-based materials where cellulose-rich fibres are combined with different types of polymers. There is hence a large need to develop efficient fibre modification techniques by which the fibres can be tailored to obtain specific properties. Furthermore, by modifying only the surface of fibers a significant change in properties can be achieved although only a relatively small amount of the total fibre material is modified. The potential impact of a surface modification increases tremendously when nano-sized fibres are used due to the larger interfacial area between the fibres and their surroundings. Interest in smaller building blocks in the nanometer range has continued to grow rapidly in recent years due to both the availability and preparation/synthesis of smaller building blocks and to the discovery of the high performance of these types of nanocomposites. In this thesis, three different types of surface modifications are presented as new tools to design the properties of new novel cellulose-based materials. In the first work, thermoresponsive nanocomposites have been assembled from specially designed thermoresponsive polymers and nanofibrillated cellulose. The polymers have one thermoresponsive block and one cationically charged block which can thus attach the polymer to an oppositely charged fibre/fibril surface. Multilayers were assembled with these polymers and the nanofibrillated cellulose utilizing the layer-by-layer technique, resulting in thin films with thermoresponsive behavior which for example could be used for controlled drug-release applications. In the second work, an amphiphilic block copolymer with one high molecular weight hydrophobic polystyrene block and one cationic block was synthesized for use as a compatibilizer between fibres and hydrophobic polymer matrices in composites. These polymers self-assemble into micelles in water with the hydrophobic part in the core of the micelle and the cationic part in the shell. Due to the cationic charges, these micelles adsorb to oppositely charged surfaces where the hydrophobic parts can be liberated on the surface by a heat treatment, leading to a new, less hydrophilic, surface with a contact angle close to that of pure polystyrene. Atomic force microscopy was used to measure the adhesive properties of a polymer-treated surface using a polystyrene probe at different temperatures and contact times. The adhesion increased with increasing contact time for the treated surfaces, probably due to entanglement between the polystyrene blocks at the treated surface and the probe. The relative increase in adhesion with contact time was higher at the lower temperature whereas the absolute value of the adhesion was higher at the higher temperature, most probably due to a larger molecular contact area. This odification technique could be utilized to make fibrebased composite materials with better mechanical properties. In the third work, click chemistry was used to covalently attach dendrons to cellulose surfaces and further to modify them with mannose groups to obtain specific interactions with Concanavalin A. The protein interactions were studied at different protein concentrations with a quartz crystal microbalance. The multivalent dendronized surface showed a 10-fold increase in sensitivity to the protein compared to a monovalent reference surface. This could be used to design more sensitive cellulose-based biosensors in the future.
Det finns idag en stor insikt av att vi behöver nya miljövänliga processer och produkter för att kunna skapa ett långsiktigt hållbart samhälle. Denna medvetenhet har stimulerat sökandet efter förnyelsebara, högkvalitativa material som kan ersätta oljebaserade produkter. I kombination med den ökande konkurrensen inom skogsindustrin, har detta stimulerat forskning inom olika typer av träbaserade material där cellulosarika fibrer kombineras med olika typer av polymerer så att vi använder vår förnyelsebara skogsråvara i så kallade högvärdesprodukter. Det finns därför ett stort behov av utveckling av effektiva tekniker för fibermodifiering där fibrer kan skräddarsys för att erhålla specifika egenskaper. Genom att endast modifiera fibrernas yta kan dessutom en markant förändring i egenskaper erhållas genom att endast modifiera en relativt liten del av det totala fibermaterialet. Den potentiella effekten av ytmodifiering ökar dessutom avsevärt när cellulosananofibriller används, eftersom gränsytan mellan fibrillerna och dess omgivning ökar dramatiskt när storleken minskar med flera tiopotenser. Intresset för mindre byggstenar i nanometerområdet har fortsatt att öka snabbt under de senaste åren, både tack vare tillgängligheten och ny teknik för tillverkning/syntes av mindre byggstenar, och insikter av de mycket goda egenskaper som den här typen av nanokompositer besitter. I föreliggande avhandling presenteras tre olika typer av fibermodifiering som kan användas som nya redskap för att skräddarsy egenskaper hos nya cellulosabaserade material. I det första arbetet har termoresponsiva nanokompositer byggts upp från specialtillverkade termoresponsiva polymerer och nanofibrillerad cellulosa. Polymererna har ett block som är termoresponsivt samt ett andra block som är katjoniskt laddat och därmed kan fästa polymeren till en motsatt laddad fiber/fibrillyta. Multiskikt byggdes upp med dessa polymer och den nanofibrillerade cellulosan genom att använda lager-på-lager tekniken, vilket resulterar i tunna filmer med termoresponsivt beteende som exempelvis skulle kunna användas för kontrollerad frisättning av läkemedel. I det andra arbetet har en amfifil block copolymer med ett högmolekulärt hydrofobt polystyrenblock och ett katjoniskt block syntetiserats för användning som kompatibilisator mellan fibrer och hydrofoba polymer matriser i fiber/fibrill förstärkta kompositer. Dessa polymerer självorganiseras i form av miceller i vatten med den hydrofoba delen i kärnan av micellen och den katjoniska delen i skalet. Eftersom micellerna har katjoniska laddningar adsorberar de till motsatt laddade ytor där de hydrofoba delarna kan frigöras på ytan efter en värmebehandling vilket leder till en ny, mindre vattenvätbar, yta. Ett atomkraftsmikroskop användes för att mäta de adhesiva egenskaperna mellan en polymerbehandlad yta och en polystyrenprob vid olika temperaturer och kontakttider. Adhesionen ökade med kontakttiden för de behandlade ytorna, troligtvis beroende på molekylär intrassling mellan polystyrenblock på den behandlade ytan och polystyrenproben. Den relativa adhesionsökningen, med ökad kontakttid, var högre vid den lägre temperaturen medan den absoluta adhesionskraften var högre vid den högre temperaturen, vilket troligen beror på en högre molekylär konataktyta vid den högre temperaturen. I det tredje arbetet användes klick-kemi för att kovalent fästa dendroner till cellulosaytor och vidare modifiera dem med mannosgrupper för att erhålla specifik växelverkan med Concanavalin A. Proteininteraktionerna studerades vid olika proteinkoncentrationer med hjälp av en kvartskristallmikrovåg. Den flervärda dendroniserade ytan visade en 10-faldig ökning i känslighet gentemot proteinet jämfört med den envärda referensytan. Detta skulle kunna användas för att skräddarsy känsligare cellulosabaserade biosensorer i framtiden.
QC 20101014

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Sinden, Jane. « The electrokinetic aspect of cellulose fibres used in the papermaking process ». Thesis, University of Reading, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244904.

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Coelho, Da Silva Mercês. « Contribution à l'étude des composites à base de fibres de cellulose ». Grenoble INPG, 2008. http://www.theses.fr/2008INPG0143.

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Ce travail de thèse traite de la caractérisation de différents sous-produits, d’une usine de pâte à papier, obtenus à partir d’eucalyptus et leur possible valorisation, comme matière première fibreuse. Ces trois résidus ont été caractérisés en terme de leur composition chimique, propriétés thermiques, structurales et morphologiques. Les résultats obtenus indiquent que ces déchets industriels peuvent être potentiellement utilisés comme matière première dans des applications à base de fibre. Ensuite, des mousses de polyuréthanes rigides (RPU) ont été préparées et les matériaux cellulaires obtenus ont été. L’introduction des fibres dans les mousses RPU n’a pas altéré leur stabilité thermique. L’utilisation des fibres de cellulose comme agent de renfort a augmenté leur résistance mécanique, propriétés d’isolation thermique et leur vitesse de biodégradation
This dissertation is a contribution of scientific knowledge on the characteristics of several by-products from a bleached eucalyptus kraft pulp mill and their possible valorisation as fibrous raw materials. The structural, thermal, and morphological investigations of these raw materials were carried out and the results obtained indicate that these industrial wastes can be used as potential raw materials in fiber-based applications. The introduction of the fibres into RPU did not alter their thermal stability, but enhanced their density. The use of cellulose fibres as reinforcing phase increased the resistance to compression of the resulting foam, enhanced their thermal insulation performances and their biodegradation rate

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Zhu, Chenchen. « Manufacturing of cellulose and chitin fibres using ionic liquids based solvents ». Thesis, University of Bristol, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.682729.

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Cellulose and chitin are considered to be the most abundant, sustainable and environmentally-friendly polymers. They are, however, not utilized for large-scale applications due to their poor solubility in most traditional solvents, which makes them difficult to extract and shape into a desired product. Ionic liquids can effectively dissolve cellulose and chitin with less environmental impact than the traditionally used solvents. In this thesis, a manufacturing method has been developed for regenerating cellulose and chitin fibres with good mechanical properties and multi functional properties, using ionic liquids as environmentally benign solvents. In the first part, the study focused on the dissolution of cellulose, regenerating continuous cellulose fibres through dry-jet wet spinning, and characterising fibres' properties. In the second part, the study focused on imparting multi-functionality on cellulose fibres, by dispersion of electrically conducting particles such as carbon nanotubes and carbon black. An experiment was designed with different extrusion and winding velocities to determine the factors affecting fibres' conductivities during fibre spinning. This study provided useful guidelines for improving the degree of nanotube dispersion in cellulose fibres, electrical conductivity of cellulose composite fibres and their potential for use in other applications, such as conducting textiles and implantable electrodes for stimulation of tissues. In the third part, the study focused on producing high modulus cellulose fibres from an optically birefringent solution of cellulose. The resulting fibres demonstrated high level of alignment of cellulose chains along the axis direction. This study has immense potential to reshape the composites industry by introducing sustainable, environmentally benign and renewable fibres with enhanced mechanical performance. In the last part, the same manufacturing method for cellulose was used for chitin in order to demonstrate the wider scope of the technique. This study will be potentially useful for medical applications of chitin fibres in tissue regeneration and for wound sutures.

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Dadach, Zin Eddine [Verfasser]. « Mechanism of Depolymerization of Cellulose in Low Sulfuric Acid Medium. Kinetic Investigation and Stochastic Simulation / Zin Eddine Dadach ». München : GRIN Verlag, 2018. http://d-nb.info/1180403568/34.

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De, Matos Fernandes Susana. « Novel materialsbased in chitosan, its derivates and cellulose fibers ». Pau, 2010. http://www.theses.fr/2010PAUU3010.

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L’objectif de cette étude est de développer de nouveaux matériaux à base de chitosane, de ses dérivés et de fibres de cellulose, sous la forme de nanofibres ou de feuille de papier. Des échantillons de chitosane purifié ont été utilisées afin de préparer les films nanocomposites transparents à base de chitosane (CH) comme matrice (deux chitosanes avec différentes masses molaires et leurs dérivés solubles dans l'eau) et de cellulose nanofibrillaire (NFC) ou de cellulose bactérienne (BC). Les films obtenus sont très transparents; ils affichent de meilleures propriétés mécaniques que ceux à base de chitosane seul. Une autre démarche a consisté à revêtir des feuilles de papier à base d’E. Globulus avec le chitosane ou deux dérivés de chitosane, l'un fluorescent et l'autre soluble dans l'eau. Tout d'abord, un dérivé du chitosane fluorescent a été déposé couche par couche sur des feuilles de papier et sa distribution,a été évaluée. Les résultats montrent que, que la répartition en surface est très homogène et que la pénétration du chitosane dans les pores du papier cesse après un dépôt de trois couches, au-delà une augmentation de l'ensemble de ses épaisseurs et aptitude filmogène. Ensuite, l'effet du chitosane et de son dérivé soluble dans l'eau sur les propriétés finales des papiers a été étudié. En général, chitosane et le chitosane soluble dans l'eau ont un impact positif sur les propriétés finales des papiers couchés. Finalement, la chitine et le chitosane ont été convertis en polyols visqueux à travers une réaction d'oxypropylation simple , dans le but de valoriser les fractions les moins nobles ou les sous-produits de ces précieuses ressources renouvelables
The purpose of this study was to develop new materials based on chitosan and its derivatives and cellulose, in the form of nanofibres or paper sheet. . Chitosan samples were then used to prepare transparent nanocomposite films based on different chitosan (CH) matrices (two chitosans with different DPs and corresponding water-soluble derivatives) and nanofibrillated cellulose (NFC) and bacterial cellulose (BC). The films obtained were shown to be highly transparent, displayed better mechanical properties than the corresponding unfilled chitosan films and showed increased thermal stability. Another approach involved the coating of E. Globulus based paper sheets with chitosan and two different chitosan derivatives, a fluorescent and a water-soluble derivative, on a pilot-size press machine. First, a fluorescent chitosan derivative was deposited layer-by-layer onto conventional paper sheets and its distribution was assessed. The results showed that the surface distribution was highly homogeneous and the penetration of chitosan within the paper pores ceased after a three-layer deposit, beyond coating only produced an increase in its overall thickness and film-forming aptitude. Then, the effect of chitosan and chitosan quaternization on the final properties of chitosan-coated papers was investigated. In general, both chitosan and water-soluble chitosan coatings had a positive impact on the final properties of the coated papers. Finally, chitin and chitosan were converted into viscous polyols through a simple oxypropylation reaction, with the aim of valorizing the less noble fractions or by-products of these valuable renewable resources

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Doineau, Estelle. « Modification de fibres de lin par des nanocristaux de cellulose et du xyloglucane pour le développement de composites biosourcés hiérarchiques Adsorption of xyloglucan and cellulose nanocrystals on natural fibres for the creation of hierarchically structured fibres Hierarchical thermoplastic biocomposites reinforced with flax fibres modified by xyloglucan and cellulose nanocrystals Development of Bio-Inspired Hierarchical Fibres to Tailor the Fibre/Matrix Interphase in (Bio)composites ». Thesis, IMT Mines Alès, 2020. http://www.theses.fr/2020EMAL0007.

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Ce travail de thèse vise à développer un traitement de surface de fibres de lin pour l’amélioration des propriétés mécaniques de biocomposites à matrice polymère et renforts en lin. Cette modification de surface s’inspire des structures hiérarchiques présentes dans les systèmes biologiques (os, nacre ou bois), constitués de nano-objets permettant un meilleur transfert de charges dans ces matériaux. Cette présence d’objets de dimensions nanométriques permet notamment d’atteindre des valeurs de contrainte et ténacité élevées et de limiter la propagation de fissures. Dans ces travaux de recherche, des produits dérivés de la biomasse ligno-cellulosique, à savoir les nanocristaux de cellulose (CNC) et le xyloglucane (XG), ont été choisis pour leurs propriétés et leur affinité mutuelle afin de créer des fibres de lin hiérarchiques. Dans un premier temps, l’adsorption de XG et CNC sur les fibres de lin a pu être localisée et quantifiée grâce à des marqueurs fluorescents. De plus, des mesures de force d’adhésion en microscopie à force atomique ont révélé la création d’un réseau extensible XG/CNC sur la surface de la fibre. Par la suite, deux voies ont été proposées avec l’élaboration de biocomposites thermoplastiques (polypropylène/fibres de lin) et thermodurcissables (résine époxy/tissu de lin) utilisant ces fibres nanostructurées. Dans les deux cas, une augmentation du travail à la rupture a été mesurée en micro-tractions et/ou tractions uniaxiales, permettant une plus grande dissipation de l’énergie lors de la rupture. L’ensemble de ces travaux a permis d’évaluer le potentiel de différents renforts en lin hiérarchiques(tissu unidirectionnel ou fibres courtes)pour le développement de biocomposites structuraux avec un focus fait sur la zone d’interphase fibre / matrice
This thesis project aims at developing flax fibres surface treatment for the improvement of the mechanical properties of biocomposites with polymeric matrix and flax reinforcements. This surface modification is inspired by the hierarchical structures present in biological systems (bone, nacre or wood), composed of nano-objects which allow a better transfer of loads in these materials. This presence of nano-sized objects makes it possible to reach impressive strength and toughness values and to limit cracks propagation. In this project, products derived from lingo-cellulosic biomass, namely cellulose nanocrystals (CNC) and xyloglucan (XG), were chosen for their interesting properties and mutual affinity to create hierarchical flax fibres. In a first step, the adsorption of XG and CNC onflax fibres w as localized and quantified using fluorescent markers. In addition, atomic force microscopy measurements of adhesive force revealed the creation of an extensible XG/CNC netw ork on the fibre surface. Subsequently, two paths were proposed with the elaboration of thermoplastic (polypropylene/flax fibres) and thermoset (epoxy resin/flax fabric) biocomposites using these nanostructured fibres. In both cases, an increase of the work of rupture has been measured by micro-and/or uniaxial tensile tests, allowing dissipating more energy upon breakage. All this work has allowed evaluating the potential of different hierarchical natural reinforcements (unidirectional fabric or short flax fibers) for the development of structural biocomposites with a focus on the fiber/matrix interphase zone

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Plumejeau, Sandrine. « Croissance de TiO₂ en surface de fibres de cellulose pour l'élaboration de filtres photocatalytiques ». Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT230/document.

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La dépollution est aujourd’hui un enjeu majeur pour la protection de l’environnement et un développement durable. Les technologies membranaires et les procédés d’oxydation avancée jouent un rôle de plus en plus important dans le traitement de l'eau que ce soit pour la production d’eau potable que pour le traitement des eaux usées urbaines ou industrielles. La photocatalyse hétérogène est un procédé d’oxydation avancée permettant la génération des espèces très oxydantes comme les radicaux OH•, en présence d’eau et de dioxygène, lors de l’irradiation de certains solides semi-conducteurs au premier rang desquels on retrouve le dioxyde de titane. L’objectif final visé dans cette thèse est le développement de filtres photocatalytiques performants mis en œuvre dans des procédés hybrides couplant séparation et photodégradation. Le mode d’élaboration envisagé pour ces filtres photocatalytiques est basé sur une voie de synthèse en rupture utilisant un polymère biosourcé, la cellulose, à la fois comme réactif (source d’oxygène) et support mécanique pour la croissance de nanoparticules de TiO2 à partir de tétrachlorure de titane. La première partie de la thèse est dédiée à une revue bibliographique qui porte principalement sur les procédés membranaires et hybrides, le dioxyde de titane et ses propriétés photocatalytiques et sur les propriétés chimiques, structurales et microstructurales et l’évolution thermique de la cellulose. Après un descriptif des matériels et méthodes mis en œuvre dans l’étude expérimentale sont d’abord présentés et discutés les résultats obtenus sur la préparation et la caractérisation de poudres purement minérales, à base de TiO2, et de poudres composites TiO2-carbone. L’effet du dopage du TiO2 par différents métaux de transition afin d’améliorer ses propriétés fonctionnelles est ensuite examiné. Une simplification du procédé de synthèse consistant à éliminer tout usage de solvant est exposée dans le chapitre suivant. S’appuyant sur le savoir-faire précédemment acquis en matière de synthèse et sur les performances photocatalytiques préalablement mesurées, le dernier chapitre est consacré aux travaux préliminaires menés sur la préparation de filtres photocatalytiques et sur l’évaluation leurs performances fonctionnelles
The pollution is definitely a major issue for environmental protection and sustainable development. Membrane technologies and advanced oxidation processes play more and more a key-role in the treatment of water both for the production of drinking water and for the treatment of municipal and industrial wastewaters. Heterogeneous photocatalysis is an advanced oxidation process for generating highly oxidizing species such as OH• in the presence of water and dioxygen, under irradiation of some semiconducting solids like titania (TiO2). The targeted objective for this PhD work is the development of efficient photocatalytic filters to be implemented in hybrid processes coupling separation and photodegradation. The innovative route investigated for preparing such photocatalytic filters is based on the use of a bio-based polymer, i.e. the cellulose, both as reactant (oxygen source) and mechanical support for the growth of titania nanoparticles from titanium tetrachloride. The first part of the thesis is dedicated to a literature review mainly focused on membrane and hybrid processes, on titanium dioxide and its photocatalytic properties and on the chemical, structural, microstructural and thermal behaviour of cellulose. After a description of the experimental procedures, the second part of this manuscript is first dedicated to the presentation and the discussion of the experimental results on the preparation and characterization of pure titania powders and of TiO2-carbon composite powders. The effect of titania doping by different transition metals in order to improve its functional properties is then examined. Simplification of the synthesis process by removing any is described in the next chapter. From the previously developed know-how on synthesis and photocatalytic performance, the last chapter is devoted to preliminary work on the preparation of photocatalytic filters and on the assessment of their functional properties

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McGillen, J. G. « Studies on the wet spinning of cellulose fibres from novel solvent systems ». Thesis, University of Strathclyde, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372448.

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Gaffiot, Lauric. « Optimisation d’un procédé d’élaboration d’un composite à base de fibres naturelles ». Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAI056.

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Les matériaux composites constituent aujourd’hui un domaine très dynamique tant au niveau de l’industrie que de la recherche. Dans ce cadre, les renforts d’origines naturelles représentent une alternative intéressante aux fibres synthétiques de par leurs propriétés mécaniques élevées, leur faible densité et leur caractère biosourcé, afin de répondre à l’accroissement des niveaux de performances ciblés ainsi qu’aux exigences économiques et écologiques actuelles.Ces travaux s’inscrivent dans un projet regroupant laboratoires de recherche, fournisseurs et end-users, visant à développer un matériau composite unidirectionnel structural à base de fibre de lin pour une application sport et loisirs. Ainsi, les objectifs initiaux incluent le développement de différents traitements chimiques des fibres, afin de les laver, d’homogénéiser leurs propriétés mécaniques et d’améliorer l’adhésion fibre-matrice. Une stratégie originale a pour cela été élaborée, basée sur la réactivité et les propriétés physico-chimiques d’un agent de couplage biosourcé. Ce produit a montré un potentiel prometteur d’additif de renforcement des matériaux cellulosiques, notamment à l’état humide. De plus, sa réactivité avec des molécules compatibilisantes a permis de le fonctionnaliser pour promouvoir l’adhésion fibre-matrice.Les caractérisations menées aux différentes échelles de la fibre de lin ont ensuite montré la pertinence de ces traitements, qui renforcent les interfaces fibre-matrice et les fibres techniques à l’état humide. Les études mécaniques ont cependant soulevé de nombreuses problématiques expérimentales, et ont démontré que les spécificités morphologiques de ces objets et leur caractère naturel ne permettaient pas l’exploitation directe des mesures dans le cadre d’un tel projet de développement. Les axes de recherche se sont alors avant tout focalisés sur l’étude des matériaux composites. Ainsi, plusieurs verrous structuraux ont pu être identifiés. La qualité de l’imprégnation de ces renforts naturels, qui peut être influencée par la formulation des traitements et la mise en œuvre, est déterminante dans le développement du matériau à cause de la morphologie multi-échelles des fibres. L’orientation des fibres au sein des plis unidirectionnels s’est également avéré être un paramètre prépondérant, étroitement lié à l’architecture des renforts et aux procédés de traitements industriels.Les développements menés à la fois sur les traitements et sur la structure des composites ont ainsi permis de doubler les propriétés mécaniques des systèmes initiaux pour atteindre un module de rigidité de 30 GPa et une contrainte ultime d’environ 370 MPa en traction tout en limitant grandement la perte de résistance après vieillissement dans l’eau et en garantissant une déformation en flexion répondant au cahier des charges. Les évolutions réalisées ne permettent pas pour le moment d’envisager l’industrialisation de ce matériau, mais vont permettre le prototypage de produits finis
Nowadays, composite materials are a challenging and dynamic thematic for both industry and academic research. In this context, natural fibres are an interesting alternative to synthetic fibres thanks to their high mechanical properties, low density and biosourced origins in order to meet the requirements in terms of performance, costs and durability.This work take part into an industrial project that include research laboratories, suppliers and end-users. It aims at developing a unidirectional flax fibre composite material for sport and recreation application. The initial objectives of development focused on the surface optimization and the reinforcement, and the improvement of fibre-matrix adhesion. An original strategy has been set, based on the reactivity and the physico-chemical properties of métapériodate oxidized xyloglucan. This molecule has shown a promising effect of reinforcement on cellulosic materials, particularly in wet conditions. Besides, its reactivity with compatibilization agents allows different functionalization possibilities to increase fibre-matrix adhesion, encouraging its use as a coupling agent.The characterizations led on the different scales of flax fibre validated this strategy, as micro-mechanical tests showed adhesion improvement and mechanical properties of wet fibres had significantly increased. However, further mechanical investigations rose numerous experimental issues, and demonstrated that the specific morphology of these objects as well as their natural origins were major obstacles to measures exploitation in this kind of development project. So, the main research axis then focused on directly composite materials.Different structural problematics has been thus identified. Natural fibre impregnation, which can be influenced by treatments composition and elaboration process, has revealed itself has an important parameter linked to the multi-scale organization of flax. The fibre orientation in the unidirectional ply has been also identified as a key parameter that is affected by reinforcement architecture and industrial process of treatment.Those developments on treatments and composite structure led to a great increase of the material tensile properties to reach 30 GPa modulus and 370 MPa in strength, also improving its water ageing behaviour and its flexion ultimate strain. These promising enhancements are not sufficient in terms of overall mechanical performance and elaboration process to envisage an industrialization phase, but the prototyping of finished products will be realized

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Ulfstad, Louise. « Rheological study of cellulose dissolved in aqueous ZnCl2 : Regenerated cellulosic fibres for textile applications ». Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-28781.

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The most known regenerated cellulosic fiber is viscose, produced in a wet spinning process, but due to cost and environmental issues other processes have been developed. Lyocell fibers, produced in air-gap spinning, have superior dry and wet strenght and a lower environmental impact compared to viscose. Research in different cellulose solvent has increased significantly tha last decadess, due to an increased cotton price and a decreased paper production, providing more wood pulp to production of regenerated cellulosic fibers. Inorganic molten salt hydrates have the ability of dissolving cellulose for production of textile fibers. Aqueous zinc chloride was investigated at Swerea IVF from dissolution of cellulose to fiber spinning. Aqueous zinc chloride has a dissolving capacity of up to at least 13.5 % cellulose, possibly much higher. Dissolving concentration ZnCl2/water range from 65-76 % amd lowest possible ZnCl2 concentration increases as the cellulose concentration increases. Above around 68 % ZnCl2 results in a significantly increased viscosity due to a polymeric structure formed by zinc chloride, creating a network of cellulose-zinc complexes and causing a gel behaviour of the dope difficult to use in spinning processes. The dissolving capacity of 68 % ZnCl2 is only about 8 % cellulose, which is very low compared to other solvents used today e.g. Lyocell and ILs. Additions of 0.3 % CaCl2 or 0.05-0.1 % NaOH is used to decrease degradation of cellulose. The addition causes ans increased viscosity, which is either a result of less degradation of the interaction of the added molecules to zinc-cellulose complexes. Addition of NaOH results in a temperature dependent geleation at increased temperatures (75˚C and 80˚C), which also might be an effect of the interaction. Highest tensile strenght was reached for wet spun fibers coagulated in ethanol of 9.5 % cellulose with 0.1 % NaOH addition, with a tenacity of 13-15 cN/tex, elongation of 10-12 % and wet strenght 30 % of dry strenght. Beacuse of many disadvantages of zinc chloride as a solvent, e.g. degradation of cellulose, corrosivity and the viscosity and gel behaviour at cellulose concentrations of 9.5 % and 13.5 % cellulose, a future possibility of a conventional production of textile fibers appears to be quite limited.

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Randrembason, Vero. « Biocomposites amidon-cellulose : Elaboration, caractérisation et modélisation du comportement viscoélastique ». Montpellier 2, 2005. http://www.theses.fr/2005MON20009.

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Cuissinat, Céline. « Etude des mécanismes de gonflement et de dissolution des fibres de cellulose native ». Phd thesis, École Nationale Supérieure des Mines de Paris, 2006. http://pastel.archives-ouvertes.fr/pastel-00002729.

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La cellulose, polymère naturel appartenant à la famille des polysaccharides, est non fusible. Pour la mettre en forme, il est donc nécessaire soit de la dériver, soit de la solubiliser. L'objectif de notre travail est de préciser les mécanismes qui conduisent à la dissolution de la cellulose native. Cinq mécanismes sont observés lors de cette étude, basée sur des fibres de cellulose native d'origine diverse (coton, bois, ramie, jute, lin, chanvre, sisal et abaca). Chaque échantillon est observé dans une large gamme de systèmes aqueux (NMMO - eau à différentes teneurs en eau ou hydroxyde de sodium - eau - additif) et des liquides ioniques. Des données recueillies sur des échantillons dépourvus de leurs parois externes suite à un traitement enzymatique, ainsi que des dérivés cellulosiques, viennent compléter cette étude. Nous avons identifié cinq mécanismes de gonflement et de dissolution de fibres de cellulose native : Mode 1: dissolution rapide par désintégration de la fibre en fragments Mode 2: gonflement par ballonnement, dissolution de toute la fibre Mode 3: gonflement par ballonnement, dissolution partielle de la fibre Mode 4: gonflement homogène, non dissolution de la fibre Mode 5: pas de gonflement ni de dissolution (cas d'un système non solvant) Malgré les différences morphologiques entre toutes les fibres de cellulose testées et les dérivés cellulosiques, les mécanismes de gonflement et de dissolution restent similaires. Trois zones le long des fibres de cellulose sont définis lors d'un mécanisme impliquant un gonflement par ballonnement: les ballons, la membrane des ballons, les sections non gonflées (zones situées entre les ballons). Chacune de ces zones présentent un mécanisme de dissolution particulier. Le mode 2 est donc détaillé en 4 étapes. Les ballons sont des entités constituées d'une membrane (paroi primaire, plus une partie de la paroi secondaire), caractérisée par une structure hélicoïdale. La membrane est la partie de la fibre la plus difficile à dissoudre. Il est important de noter que la cellulose à l'intérieur des ballons est dissoute. Les mécanismes de gonflement et de dissolution ne sont pas liés à la nature chimique des agents solvants. La qualité du solvant influe évidemment sur le mode de dissolution induit, mais le facteur clé des mécanismes est la structure morphologique de la fibre.

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Hanley, Shaune J. (Shaune John). « Application of atomic force microscopy to cellulose, wood, kraft pulp fibres and paper ». Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40030.

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The surfaces of well characterised microfibrils from Ventricaria and Micrasterias denticulata (M.d.), wood sections, kraft pulp fibres and paper have been examined with both atomic force microscopy (AFM) and Tapping Mode atomic force microscopy (TM-AFM), under ambient conditions in both air and water. Artifacts and limitations inherent to these techniques in the study of microfibrils, pulp fibres and paper are discussed. AFM images of the surface of the highly crystalline cellulose microfibrils, Ventricaria and M.d., were obtained at molecular resolution under ambient conditions; the molecular images showed periodicities along the microfibril axis that correspond to those of the fibre and glucose unit repeat distances of cellulose, respectively. Images of the section surface of Black Spruce (Picea mariana) wood clearly show features of the underlying cell wall structure. The apparent lamellation, with periodicities from tens or nanometers down to 15 nm, were observed in radial sections of the middle secondary wall (S2). However, transverse sections of the same S2 layer did not show a lamellation independent of the knife direction. AFM images of unbeaten and beaten unbleached kraft pulp fibre surfaces indicate the orientation of the component microfibrils; fibrillar material attached to the surface of the beaten fibres was readily observed. Images from the scale of the fibre web down to the microfibril level in air and water show the dimensional changes of the paper surface and fibres. However, little or no change was seen at the microfibril level. The dimensions of the lamella in wood sections and the size of the microfibrils at both the surface of pulp fibres and the fibrillated material indicate that microfibrils as small as 1.5 nm across are present.

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Dolores, Gonzalo Mármol de los. « Low-alkalinity matrix composites based on magnesium oxide cement reinforced with cellulose fibres ». Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/74/74133/tde-17082017-113846/.

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A lower-alkalinity cement based on MgO and SiO2 blends is analysed to develop clinker-free Fibre Reinforced Cementitious Composites (FRCC) with cellulosic fibres in order to solve the durability problems of this type of fibres when used in FRCC with Portland cement. Hydration evolution from 7 to 28 days of different MgO-SiO2 formulations is assessed. The main hydration products are Mg(OH)2 and M-S-H gels for all the formulations studied regardless of age. Hardened pastes are obtained with pH values < 11 and good mechanical properties compared to conventional Portland cement. 60% MgO-40% SiO2 system is chosen as optimal for the development FRCC since is the most mechanical resistant and is less alkaline compared with 70% MgO-30% SiO2. FRCC based on magnesium oxide and silica (MgO-SiO2) cement with cellulose fibres are produced to study the durability of lignocellulosic fibres in a lower pH environment than the ordinary Portland cement (PC). Flexural performance and physical tests (apparent porosity, bulk density and water absorption) of samples at 28 days and after 200 accelerated ageing cycles (aac) are compared. Two types of vegetable fibres are utilised: eucalyptus and pine pulps. MgO-SiO2 cement preserves cellulosic fibres integrity after ageing, so composites made out of MgO-SiO2 exhibit significant higher performance after 200 cycles of accelerated ageing than Portland cement composites. High CO2 concentration environment is evaluated as a curing treatment in order to optimise MgO- SiO2 matrices in FRCC. Samples are cured under two different conditions: 1) steam water curing at 55°C and 2) a complementary high CO2 concentration (20% by volume). In carbonated samples, Mg(OH)2 content is clearly lowered while new crystals of hydromagnesite [Mg5 (CO3)4⋅(OH) 2⋅4H2O] are produced. After carbonation, M-S-H gel content is also reduced, suggesting that this phase is also carbonated. Carbonation affects positively to the composite mechanical strength and physical properties with no deleterious effects after ageing since it increases matrix rigidity. The addition of sepiolite in FRCC is studied as a possible additive constituent of the binding matrix. Small cement replacement (1 and 2% wt.) by sepiolite is introduced and studied in hardened cement pastes and, later, in FRCC systems. When used only in cement pastes, it improves Dynamic Modulus of Elasticity over time. Bending tests prove the outcome of this additive on the mechanical performance of the composite: it improves composite homogeneity. Ageing effects are reported after embedding sisal fibres in MgO-SiO2 and PC systems and submitting them to different ageing conditions. This comparative study of fibre degradation applied in different cementitious matrices reveals the real compatibility of lignocellulosic fibres and Mg-based cements. Sisal fibres, even after accelerated ageing, do neither suffer a significant reduction in cellulose content nor in cellulose crystallinity and crystallite size, when exposed to MgO-SiO2 cement. Fibre integrity is preserved and no deposition of cement phases is produced in MgO-SiO2 environment.
Um cimento de baixa alcalinidade à base de blendas de MgO e SiO2 é analisado para o desenvolvimento de Compósitos Cimentícios Reforçados com Fibras (CCRF) celulósicas sem clínquer para resolver os problemas de durabilidade de este tipo de fibras quando são usadas em CCRF com cimento Portland. A evolução da hidratação, desde 7 aos 28 dias, das diferentes formulações é avaliada. Os principais produtos hidratados são o Mg(OH)2 e o gel M-S-H para todas as formulações independentemente da idade estudada. As pastas endurecidas apresentam valores de pH < 11 e bom desempenho mecânico comparado com o cimento Portland convencional. O sistema 60% MgO-40% SiO2 é escolhido como a formulação ótima para o desenvolvimento de CCRF já que é a mais resistente e menos alcalina comparada com 70% MgO-30% SiO2. CCRF com cimento à base de óxido de magnésio e sílica (MgO-SiO2) e fibras celulósicas são produzidos para a análise da durabilidade das fibras lignocelulósicas em ambientes com valores de pH mais baixos comparados com o cimento Portland (PC). O desempenho mecânico a flexão e os ensaios físicos (porosidade aparente, densidade aparente e absorção de água) são comparados aos 28 dias e após de 200 ciclos de envelhecimento acelerado. O cimento à base de MgO-SiO2 preserva a integridade das fibras após o envelhecimento. Os compósitos produzidos com este cimento exibem melhores propriedades após 200 ciclos de envelhecimento acelerado que os compósitos produzidos com cimento Portland. Ambientes com alta concentração de CO2 são avaliados como tratamento de cura para otimizar as matrizes MgO- SiO2 nos CCRF. As amostras são curadas sob 2 condições diferençadas: 1) cura com vapor de água a 55oC e 2) cura com alta concentração de CO2 (20% do volume). As amostras carbonatadas apresentam teores reduzidos de Mg(OH)2 enquanto é produzida uma nova fase cristalina: hidromagnesita [Mg5 (CO3)4⋅(OH) 2⋅4H2O]. Após a carbonatação, o conteúdo de gel M-S-H é reduzido também, indicando uma carbonatação desta fase. A carbonatação aumenta a rigidez da matriz o que influi positivamente no desempenho mecânico e as propriedades físicas dos compósitos sem efeitos prejudiciais ao longo prazo. A adição de sepiolita em CCRF é estudada como possível adição na composição da matriz aglomerante. Baixos teores (1 e 2% em massa) de cimento são substituídos por sepiolita para o estudo das pastas de cimento hidratado e, posteriormente, dos compósitos. O Módulo Elástico Dinâmico das pastas é incrementado com o tempo pela adição de sepiolita. Os ensaios a flexão demostram que a adição de sepiolita melhora a homogeneidade dos compósitos. Reportam-se os efeitos das fibras de sisal após da exposição a sistemas MgO-SiO2 e PC e submetidas a diferentes condições de envelhecimento. Este estudo comparativo da degradação das fibras expostas a diferentes matrizes cimentícias mostra a compatibilidade das fibras lignocelulósicas com os cimentos à base de Mg. As fibras de sisal, inclusive após o envelhecimento acelerado, não apresentam nem redução significativa no conteúdo de celulose nem na cristalinidade da celulose assim como do tamanho de cristalito, quando expostas a cimentos MgO-SiO2.

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KHENFER, MOHAMMEDMOULDI. « Caractérisation structurale et rhéologique des ciments et plâtres renforcés de fibres de cellulose ». Bordeaux 1, 1990. http://www.theses.fr/1990BOR10800.

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Les ciments et platres renforces de fibres ont ete developpes dans le but de combattre la fragilite de ces materiaux seuls ; l'utilisation de fibres de cellulose comme renfort s'impose actuellement. L'objectif de cette etude est de realiser des materiaux de construction en plaques a base de platres ou de ciment, renforces de facon uniforme par des fibres de cellulose, ainsi que de caracteriser la structure et la rheologie de ces materiaux (durabilite, adherence fibre-matrice, fissuration, ).

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Jimenez, Saelices Clara. « Développement de matériaux super-isolants thermiques à partir de nano-fibres de cellulose ». Thesis, Lorient, 2016. http://www.theses.fr/2016LORIS417/document.

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L'objectif de cette thèse est la préparation d’aérogels biosourcés ayant des propriétés de super-isolation thermique. Pour cela, nous avons choisi de développer de nouveaux aérogels à base de nanofibres de cellulose (NFC). Les aérogels ont été préparés par lyophilisation. Dans un premier temps, une analyse des paramètres expérimentaux jouant un rôle sur la morphologie et les propriétés physico-chimiques des aérogels a été réalisée afin d’obtenir les meilleures propriétés d’isolation thermique. Avec une suspension de NFC à 2% en masse, sans ajout de sels et sans faire varier le pH, une lyophilisation réalisée dans des moules d’aluminium à une température de -80°C a permis d’obtenir des aérogels ayant une conductivité thermique de 0,024 W/m.K. Afin de diminuer cette conductivité thermique, nous avons choisi de réduire la taille des pores pour obtenir un effet Knudsen. Pour cela, une nouvelle technique de séchage a été proposée : la lyophilisation par pulvérisation. Les aérogels préparés dans les mêmes conditions expérimentales que précédemment avec cette technique ont des propriétés thermiques super-isolantes (0,018 W/m.K) grâce à la nano-structuration du réseau poreux. Finalement, un nouveau dispositif expérimental a été développé pour caractériser plus finement les propriétés thermiques des aérogels. C’est un dispositif transitoire impulsionnel qui permet d'estimer simultanément la contribution de la conduction solide et gazeuse, l'effet radiatif et la diffusivité thermique grâce à un modèle théorique simple. Ce dispositif permettra d’approfondir l’étude complexe du transfert thermique à travers des matériaux poreux semi-transparents tels que les aérogels
The objective of this thesis is the preparation of renewable aerogels having thermal super-insulating properties. To do it, we designed new aerogels from nanofibrillated cellulose (NFC) by freeze-drying. This technique is simple and has the advantage of not using organic solvents. First of all, the parameters playing a role on the aerogel morphology and physico-chemical properties of the aerogels were analyzed to get the best thermal insulating properties. Using 2 wt% NFC suspensions, without addition of salts, keeping the initial pH, the obtained freeze-dried aerogels in alumina molds at -80 °C have a thermal conductivity of 0.024 W/m.K. In order to reduce the pore size and to improve the thermal insulating properties by Knudsen effect, a new drying technique was proposed: the spray freeze-drying. Aerogels prepared in the same experimental conditions with this technique have thermal super-insulating properties (0.018 W/m.K) thanks to the nanostructuration of the porous network. Finally, a new device was designed to characterize more precisely the thermal properties of aerogels. This is an impulsive transient device, which can estimate simultaneously the contribution of solid and gas conduction, the radiative effect and thermal diffusivity using a simple theoretical model. This device will allow studying complex heat transfer through porous semi-transparent materials such as aerogels

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Khenfer, Mohammedmouldi. « Caractérisation structurale et rhéologique des ciments et plâtres renforcés de fibres de cellulose ». Bordeaux 1, 1990. http://www.theses.fr/1990BOR10645.

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Les ciments et platres renforces de fibres ont ete developpes dans le but de combattre la fragilite de ces materiaux seuls ; l'utilisation de fibres de cellulose comme renfort s'impose actuellement. L'objectif de cette etude est de realiser des materiaux de construction en plaques a base de platres ou de ciment, renforces de facon uniforme par des fibres de cellulose, ainsi que de caracteriser la structure et la rheologie de ces materiaux (durabilite, adherence fibre-matrice, fissuration, ).

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Solberg, Daniel. « Adsorption kinetics of cationic polyacrylamides on cellulose fibres and its influence on fibre flocculation ». Licentiate thesis, KTH, Fibre and Polymer Technology, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1665.

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The adsorption of cationic polyacrylamide (C-PAM) and silicananoparticles onto a model surface of silicon oxide wascompared with the adsorption of C-PAM to fibres and theirinfluence on flocculation of a fibre suspension. An increase inionic strength affects the polyelectrolyte adsorption indifferent ways for these two systems. With the silica surface,an increase in the ionic strength leads to a continuousincrease in the adsorption. However, on a cellulose fibre, theadsorption increases at low ionic strength (1 to 10 mM NaCl)and then decreases at higher ionic strength (10 to 100 mMNaCl). It was shown that the adsorption of nanoparticles ontopolyelectrolyte-covered surfaces has a great effect on both theadsorbed amount and the thickness of the adsorbed layer. Theresults showed that electrostatic interactions were thedominating force for the interaction between both the fibresand the polyelectrolytes, and between the polyelectrolytes andthe silica particles. Furthermore, at higher NaClconcentrations, a significant non-ionic interaction between thesilicon oxide surface/particles and the C-PAM was observed.

The adsorption rate of C-PAM onto fibres was rapid andquantitative adsorption was detected in the time range between1 and 8 s at polyelectrolyte addition levels below 0.4 mg/g.Conversely, an increase in the amount of added polymer leads toan increased polymer adsorption up to a quasi-static saturationlevel. However, after a few seconds this quasi-staticsaturation level was significantly lower than the level reachedat electrostaticequilibrium. The adsorbed amountof charges at full surface coverage after 1 to 8 s contact timecorresponded to only 2 % of the total fibre charge, whereasafter 30 minutes it corresponded to 15 % of the total fibrecharge. This shows that a full surface coverage at shortcontact times is not controlled by surface charge. Based onthese results, it is suggested that a combination of anon-equilibrium charge barrier against adsorption and ageometric restriction can explain the difference between theadsorption during 1 to 8 s and the adsorption after 30 minutes.With increasing time, the cationic groups are neutralised bythe charges on the fibre as the polyelectrolyte reconforms to aflat conformation on the surface.

The addition of a high concentration of C-PAM to a fibresuspension resulted in dispersion rather than flocculation.This behaviour is most likely due to an electrostericstabilisation of the fibres when the polyelectrolyte isadsorbed. Flocculation of the fibre suspension occurred at lowadditions of C-PAM. A maximum in flocculation was found ataround 50 % surface coverage and dispersion occurred above 100% surface coverage. It was also shown that for a given level ofadsorbed polymer, a difference in adsorption time between 1 and2 seconds influenced the flocculation behaviour. An optimum inflocculation at 50 % surface coverage in combination with theimportance of polymer reconformation time at these shortcontact times showed that the C-PAM induced fibre flocculationagrees with La Mer and Healys description of bridgingflocculation.

A greater degree of flocculation was observed with theaddition of silica nanoparticles to the fibre suspension thanin the single polyelectrolyte system. Flocculation increased asa function of the concentration of added nanoparticles until0.5 mg/g. At higher additions the flocculation decreased againand this behaviour is in agreement with an extended model formicroparticle-induced flocculation. An increase in flocculationwas especially pronounced for the more extended silica-2particles. This effect is attributed to the more extendedpolyelectrolyte layer, since the adsorbed amount wasessentially the same for both silica particles.

Finally it was found that fines from the wood fibres had asignificant effect on the flocculation. When fines were added,a greater degree of flocculation was detected. Furthermore, itwas also more difficult to redisperse the fibres with polymerin the presence of fines.

Keywords:Adsorption, bridging, cationic polymers,cellulose fibres, electrosteric stabilisation flocculation,ionic strength, nanoparticle, polyelectrolyte, reconformation,retention aids and silica

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Kong, Kenny. « Deformation micromechanics of process controlled cellulose fibres using Raman spectroscopy and X-ray diffraction ». Thesis, University of Manchester, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.545914.

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Raman spectroscopy has been used to follow the defonnation micromechanics of a range of process---controlled fibres. The fibres were solvent spun using a N-methylmorpholine N-{)xide/ cellulose system. Single fibres are defonned in tension, and it is shown that the 1095 cm-l and 1414 cm-l Raman bands, corresponding to the C-O stretch mode and the side group (C-O--H) along the chain respectively, shift towards a lower wavenumber upon the application of external tensile defonnation. The shift profile of the 1095 cm-' band is shown to be non-linear, following the shape of the stress-strain curve, and the initial shift rate is shown to be directly related to the stiffness of the fibre. This band shift rate with respect to strain is shown to increase with increasing crystall ine orientation. The 1414 cm·1 band also shifts non-linearly and rapidly reaches a plateau with both strain and stress. This is thought to be due to the breakdown of hydrogen bonding in the structure, and a potential cause of the yield point in the mechanics of the fibres. The crystalline modulus and orientation of regenerated cellulose are measured using a wide-angle X-ray diffraction method. The crystalline modulus appears to vary with fibres having different orientations. It is shown that whilst the c-spacing of crystals increases with tensile stress, the crystalline fraction reorients to the direction of the fibre axis. An average shear modulus for these fibres is detennined by placing the data on a master curve and fitting with a model equation. Structure-property relationships are derived from the molecular and crystal defonnation characteristics of cellulose fibres using Raman spectroscopy and X-ray diffraction. This represents, for the first time, a full analysis of the relationship between structure and mechanics. at a local scale, of these regenerated cellulose fibres. Using a set of hypotheses tested on the experimental data, it is possible to distinguish unifonn stress and unifonn strain beha"iourNo portion of work referred to within this thesis has been submitted in support of an application for another degree or qualification of this or any other uni\crsity. or other institution of learning

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Sjöstedt, Anna. « Preparation and characterization of nanoporous cellulose fibres and their use in new material concepts ». Doctoral thesis, KTH, Fiberteknologi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-155530.

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The overall objective of the work in this thesis is to better utilize the non-collapsed structure of the delignified wood-fibre cell wall in the preparation of new types of materials. In order to utilize the fibres in new materials, it is crucial to have a well-defined starting material and to know how it reacts to certain treatments of the fibres. A new robust method for measuring the average pore size of water-swollen fibres-rich in cellulose is presented. This method is based on solid-state NMR, which measures the specific surface area [m2/g] of water-swollen samples, and the fibre saturation point (FSP) method, which measures the pore volume [water mass/solid mass] of a water swollen sample. These results can be combined since they are both recorded on water-swollen fibres in the presence of excess water and neither is based on any assumption of any particular pore geometry. Delignifed wood fibres (chemical pulp fibres) have an open fibrillar structure, with approximately 20 nm thick fibril aggregates arranged in a porous structure with a specific surface area of 150 m2/g. This open structure was preserved in the dry state by a liquid-exchange procedure followed by careful drying in argon gas. The dry structure had a specific surface area of 130 m2/g, which implies that the porous structure was preserved in the dry state. New fibre-basedmaterials were prepared by two different strategies. The first strategy was to utilize the open nanoporous fibre wall structure for the preparation of nanocomposites. The nanoporous structure was used as a scaffold, allowing monomers to impregnate the structure and to be in-situ polymerized inside the fibre wall pores. Poly(methyl methacrylate) (PMMA) and poly(butylacrylate) (PBA) were synthesized inside the dry nanoporous fibre wall structure, and an epoxy resin was cured in never-dried fibres oxidized to different degrees by TEMPO. The composites prepared thus have a mixture of fibril aggregates and a polymer matrix inside the fibre wall. The structure and performance of the composite materials were evaluated both by high resolution microscopy and mechanically. Characterization of the composite showed that the polymer matrix was successfully formed inside the fibre wall pores. The structural changes caused by oxidation were preserved and utilized for the composite with the epoxy matrix. By tailoring the supramolecular structure of fibres in their water-swollen state, it was hence indeed possible to control the mechanical performance of the nanostructured fibre composites. The secondbstrategy used to prepare composites was to improve the thermoplastic properties of paper by adding polylactic acid (PLA) latex during the preparation of fibrebsheets. By the addition of PLA-latex, it was possible to form double curved sheets with a nominal strain at break of 21%.

QC 20141107

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Wilton, Anne Marie Gibbons. « The physical and dynamic characterisation of heterogeneously acetylated cellulose and of its interaction with dibutyl phthalate, plasticiser ». Thesis, University of Strathclyde, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260212.

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Nouaille, Régis. « Etude du métabolisme de Fibrobacter succinogenes S85 par RMN : synthèse d'oligosides et dégradation de fibres végétales ». Clermont-Ferrand 2, 2004. http://www.theses.fr/2004CLF22502.

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Fibrobacter succinogenes est une bactérie cellulolytique anaérobie stricte du rumen prédominante lorsque le regime du ruminant est riche en parois végétales lignifiées. Cette espèce bactérienne possède un système fibrolytique très efficace composé de nombreuses cellulases, hémicellulases et estérases dont l'organisation et l'action synergique sont mal connues. L'objectif de ce travail de thèse était d'une part d'approfondir nos connaissances sur le métabolisme des sucres et la synthèse d'oligosaccharides par F. Succinogenes S85, et d'autre part, d'analyser la cinétique de dégradation de la paille de blé par cette bactérie. Nous avons d'abord analysé la synthèse d'oligosides par des cellules au repos de F. Succinogenes métabolisant le glucose, le cellobiose ou la cellulose. Nous avons essentiellement utilisé l'outil RMN, approche originale qui a permis, parce qu'elle est utilisée in situ et sans a priori, de découvrir la synthèse de nouveaux oligosides : maltodextrines, maltodextrines-1P, dérivé du glucose-1P(X), et glucose substitué par une agycone (X2). L'apport majeur de notre travail est de montrer que les maltodextrines et les maltodextrines-1P peuvent être à la fois synthétisées, excrétées et dégradées par F. Succinogenes et peuvent provenir des sucres exogènes et du glycogène endogène via le maltotriose ou le glucose-1P généré par le glycogène phosphorylase. De plus, en fonction des substrats et de la physiologie des cellules (cellules au repos ou en croissance), d'importantes déviations métaboliques vers la synthèse de ces différents oligosides ont été observées. Nous n'avons pas observé d'accumulation extracellulaire de cellodextrines, quelque soit le substrat métabolisé et la condition physiologique. Enfin, nos résultats nous ont conduit à proposer un modèle de "système maltose" chez F. Succinogenes, différent de celui écrit par E. Coli. Dans le cadre de l'étude de la dégradation des fibres, l'approche originale a été de combiner l'utilisation de RMN liquide et solide afin de conserver intacts à la fois le système enzymatique au sein de la bactérienne, et le substrat analysé (paille de blé) dans sa complexité. Nous n'avons pas démontré de dégradation préférentielle des zones amorphes de la cellulose par rapport aux zones cristallines, ni de la cellulose par rapport aux hémicelluloses. Par ailleurs, nous avons montré que la première fois une action séquentielle des estérases et des xylanases de F. Succinogenes S85 au cours de la dégradation de la paille. Nous avons montré en particulier que l'acétyl-xylane estérase était plus active que l'arabinofuranosidase, elle-même plus active que l'alpha-glucuronidase, l'analyse des xylooligosaccharides libérés témoigne en outre de l'activité conjointe de xylanases des familles 10 et 11

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Caceres, Najarro Marleny. « Depolymèrization enzymatique d’Hydroxypropyl Methyl Cellulose (HPMC) pour la conception des nouveaux copolymères à blocs ». Thesis, Montpellier, Ecole nationale supérieure de chimie, 2015. http://www.theses.fr/2015ENCM0027/document.

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Parmi les bio-polymères issus des ressources renouvelables, les polysaccharides fournissent une alternative intéressante aux polymères de synthèse. Dans ce contexte, l’objectif de ce travail de thèse est basé sur la conception des copolymères amphiphiles pour la préparation de nouveaux biomatériaux. Ainsi, l’hydroxypropylméthylcellulose (HPMC) a été étudiée en raison de ses propriétés remarquables, dont la biocompatibilité, la biodégradabilité, la rétention d'eau et la gélification thermoréversible. Ces propriétés sont utiles pour de nombreuses applications telles que le relargage de médicament, la préparation des membranes et la formation de biomatériaux. L'hydrolyse enzymatique avec des endo cellulases issues de Trichoderma reesei a été étudiée pour produire des fragments d'HPMC ayant une masse molaire (Mw) entre 6000 et 30000 g mol-1. Les paramètres de l’activité enzymatique ont été étudiés en fonction de : la nature de substrat, le temps de réaction et la concentration de l'enzyme. Les polymères obtenus ont été comparés à ceux produits par hydrolyse acide. Il a été constaté que la structure des polymères issus d’un procédé d’hydrolyse, varie en termes de degré de substitution pour un même Mw. Cet effet donne lieu à différentes propriétés de gélification thermoréversible. Des copolymères amphiphiles tels que HPMC-b-poly (propylène glycol) et HPMC-b-PLA ont été préparés par amination réductrice et par couplage click thiol-ene, respectivement. Les propriétés d’agrégation ont été caractérisées par la diffusion de la lumière (DLS), le microscope électronique en transmission (TEM) et par la séparation de phase obtenue par la mesure du point de trouble
Following the concept of bio-refinery, we propose to produce small fragments of biopolymers that can be used further as building blocks to prepare novel polymeric architectures. In the case of polysaccharides, enzymatic hydrolysis enables to form reducing end groups after each cleavage on the polymer chain. Reaction by reductive amination affords the possibility to introduce polysaccharides fragments in a large variety of materials going from amphiphilic copolymers to more sophisticated devices. Hydroxypropyl methylcellulose (HPMC) was used in this work because of its remarkable properties including biocompatibility, biodegradability, water retention and thermoreversible gelation beneficial for many applications such as drug delivery, film and biomaterial formation. Enzymatic hydrolysis using endo cellulases from Trichoderma reesei was investigated to produce a library of HPMC fragments with molecular weight (Mw) from 6000 to 30000 g mol-1. Mw control was carried out by varying the procedure conditions including the nature of starting HPMC, reaction time and enzyme concentration. The obtained polymers were compared to those produced by acidic hydrolysis.According to the preparation conditions, the structure of short chain polymers regarding substitution degrees varied for the same Mw giving rise to different clouding temperature and thermoreversible gelation properties. Amphiphilic block copolymers HPMC-b-poly(propylene glycol) and HPMC-b-PLA were prepared by reductive amination and by the thiol-ene click reaction, respectively. Self-assembly properties of these novel block copolymer were characterized by dynamic light scattering (DLS), transmission electron microscope (TEM), and clouding point temperature

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Mtibe, Asanda, et Linda Linganiso. « Biocomposites from polyfurfuryl alcohol reinforced with microfibres and nanocellulose from flax fibres and maize stalks ». Thesis, Nelson Mandela Metropolitan University, 2016. http://hdl.handle.net/10948/12175.

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This study is aimed at extracting cellulose and nanocelluloses (cellulose nanocrystals (CNCs) and cellulose nanofibres (CNFs)) from maize stalks and flax fibres. Both flax fibres and maize stalks are composed of cellulose, lignin, hemicellulose and extractives. The extraction of cellulose involves the removal of lignin, hemicellulose and extractives. The presence of these components in plant fibres hinders the extraction of cellulose and nanocelluloses. Prior to extraction of cellulose, the different concentrations (1 wt.%, 1.5 wt.% and 2 wt.%) of NaOH were optimised. However, chemical compositions and XRD results revealed that the treatment of flax fibres with 1.5 wt.% sodium hydroxide (NaOH) gives optimum results and this concentration was further selected for the extraction of cellulose. Cellulose was extracted by chemical treatments (sodium hydroxide (NaOH), sodium chlorite (NaClO2) and potassium hydroxide (KOH)) and a combination of chemical treatments and mechanical process (supermass colloider). The materials obtained after each treatment stage during the extraction process were characterised by different characterisation techniques such as Fourier transform infrared (FTIR) spectroscopy, environmental scanning electron microscopy (ESEM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The results from the aforementioned characterisation techniques confirmed that cellulose was successfully extracted from flax fibres and maize stalks. Cellulose nanocrystals (CNCs) were extracted by sulphuric acid hydrolysis accompanied with ultra-sonication from cellulose obtained from flax fibres and maize stalks. The extracted CNCs were rod-like material with diameters and lengths in nanoscale and microscale, respectively. On the other hand, cellulose nanofibres (CNFs) were extracted by mechanical process (supermass colloider). The extracted CNFs were web-like material with diameters and lengths in nanoscale and microscale, respectively. The dimensions of nanocelluloses were measured by atomic force microscopy (AFM). Their dispersion was investigated by light polarised microscopy. The extracted nanocelluloses and cellulose were used to produce nanopapers and micropaper. Nanopapers mimic the traditional paper, the only difference of the nanopapers is that they are produced from high aspect ratio nanomaterials. Both nanopapers and micropapers were prepared by solvent evaporating method. Their thermal, optical and mechanical properties were investigated and compared. The mechanical and thermal properties of nanopapers produced from CNFs were better than those produced from CNCs and micropapers. On the other hand, nanopapers produced from CNCs were more transparent in comparison to nanopapers produced from CNFs and micropapers. Cellulosic fibres have attracted a considerable attention in composite materials due to their high tensile strength and tensile modulus. This study is focused on the development of biocomposites of polyfurfuryl alcohol (PFA) by in-situ polymerisation in the presence of acid catalyst (p-toluene sulphonic acid). Biocomposites were produced by reinforcing PFA with flax fibres (untreated and treated), nanoparticles and CNCs. The biocomposites reinforced with CNCs and flax fibres showed an improvement in mechanical, thermal and thermo-mechanical properties. On the other hand, biocomposites reinforced with nanoparticles obtained from treated maize stalks showed an improvement in mechanical and thermal properties while biocomposites reinforced with nanoparticles obtained from untreated maize stalks showed lower mechanical properties and decreased thermal stability.

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Loffler, Steven Marc. « Dyeing of cellulose fibres : a case study in structure-transport relationships in heterogeneous porous media ». Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627033.

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Brännvall, Elisabet. « Aspects on Strenght Delivery and Higher Utilisation of the Strength Potential of Kraft Pulp Fibres ». Doctoral thesis, KTH, Träkemi och massateknologi, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4373.

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Studies on strength delivery and related fields have so far concentrated on finding the locations in the mill where fibres are damaged and what the damages consist of. However, fibres will invariably encounter mechanical stresses along the fibreline and in this thesis a new concept is introduced; the vulnerability of fibres to mechanical treatment. It is hypothesised that fibres with different properties have different abilities to withstand the mechanical forces they endure as they are discharged from the digester and transported through valves, pumps and various washing and bleaching equipment. In the thesis, results are presented from trials where pulps with significantly different hemicellulose compositions were high-intensity mixed at pH 13, 70°C and 10% pulp consistency and pulp strength evaluated. By varying alkalinity and temperature, pulps with different carbohydrate composition could be obtained. High alkali concentration and low temperature resulted in high glucomannan content and low xylan content, whereas cooking at low alkali concentration and high temperature rendered a pulp with low glucomannan and high xylan content. The high alkalinity pulp was stronger, determined as tear index at given tensile index. The pulp viscosity was also higher for this pulp. However, when the pulps were subjected to high-intensity mixing, the high alkalinity pulp lost in tear strength and the re-wetted zero-span tensile strength was substantially reduced. The pulp cooked at high alkalinity was thus interpreted as being more vulnerable to mechanical treatment than the pulp obtained by cooking at low alkalinity. Another pair of pulps was manufactured at high and low sodium ion concentrations, but otherwise with similar chemical charges. The pulp obtained by cooking at low sodium ion concentration became stronger, evaluated as tear index at a given tensile index and the curl index was substantially lower, 8% compared to 12% for the pulp cooked at a high sodium ion concentration. The viscosity was 170 ml/g higher for the pulp manufactured at low sodium ion concentration. When the pulps were subjected to high-intensity mixing, the tear strength of the pulp manufactured at high sodium ion concentration was reduced. The re-wetted zero-span tensile index decreased also after mixing. The pulp obtained by cooking at higher sodium ion concentration was thus interpreted as being more vulnerable to mechanical treatment than the pulp manufactured at lower sodium ion concentration. In the thesis, two reasons for the low strength delivery of industrially produced pulps compared to laboratory-cooked pulps are put forward. Since the ionic strength of mill cooking liquor systems is much higher than is normally used in laboratory cooking, this can partly explain the difference in strength between mill- and laboratory-cooked pulp. A higher sodium ion concentration was shown in this thesis work to give a pulp of lower strength. Secondly, it is suggested that the difference in retention time of the black liquor in laboratory cooking and continuous mill cooking systems can explain the difference in tensile strength between laboratory-cooked and mill-produced pulp. The black liquor in a continuous digester has a longer retention time in the digester than the chips. This gives a longer time for the dissolved xylan to degrade and, as a consequence, the xylan deposited on the mill pulp fibres will be more degraded than the xylan deposited on the laboratory-cooked pulp fibres. In the thesis, results are also presented from studies using different strength-enhancing chemicals. The fibre surfaces of bleached never-dried and once-dried pulp were modified by the polyelectrolyte multilayer technique using cationic and anionic starch. Although the pulps absorbed the same amount of starch, the never-dried pulp reached a higher tensile index than the once-dried pulp. When the starch-treated never-dried pulp was dried and reslushed it still had higher tensile index than the never-dried untreated pulp. The starch layers were thus able to counteract part of the hornification effect. The never-dried starch treated pulps were subsequently dried, reslushed and beaten. Pulp with starch layers had a better beatability evaluated as the tensile index obtained after given number of PFI revolutions than dried untreated pulp. Hence, there is a potential to increase the tensile index of market pulp by utilising the polyelectrolyte multilayer technique before drying. Addition of CMC to bleached mill pulp and laboratory-cooked pulp increased the tensile strength to the same degree for both pulps. CMC addition had a straightening effect on the fibres, the shape factor increased and this increased the zero-span tensile strength also.
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Devallencourt, Leriche Christine. « Caractérisation physico-chimiques de celluloses recyclées, de résines mélamine formaldéhyde et de composites résine/cellulose ». Rouen, 1997. http://www.theses.fr/1997ROUES055.

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Lorsqu’une résine mélamine formaldéhyde est introduite dans un substrat cellulosique, un matériau composite est obtenu. Dans ce travail, nous montrons que les propriétés mécaniques et le comportement à l'humidité de ce composite dépendent du taux de dilution, du PH de la solution de résine et de la température de traitement utilisée. Les méthodes expérimentales utilisées sont l'analyse thermogravimétrique (ATG), l'analyse thermogravimétrique couplée IRFT, la RMN du 13C, l'analyse mécanique dynamique et l'analyse enthalpique différentielle (AED). A l'aide de l'analyse ATG utilisée en mode isotherme, nous avons montré que les cinétiques de dégradation des celluloses recyclées sont d'ordre 1. Ce résultat nous a autorisés à utiliser le modèle cinétique de Broido (mode dynamique) et ainsi à trouver une méthode qui permet la quantification des constituants des celluloses de récupération en particulier les quantités relatives en pâte mécanique et chimique. A l'aide de l'ATG couplée IRFT, l'ATG en mode isotherme et en mode dynamique et l'AED, nous avons montré que les réactions d'auto condensation de la résine sont accélérées en PH acide lorsque cette résine est introduite dans la matrice cellulosique. Les mesures viscoélastiques montrent que des réactions de co-condensation peuvent avoir lieu pour des recuits à haute température lorsque le PH est neutre ou basique, tandis que pour les systèmes à PH acide les réactions d'auto condensation restent majoritaires. Enfin, l'étude en absorption d'eau sur les composites résine/cellulose recyclée (PH=7) montre un double mode d'absorption, du type Langmuir et Flory Huggins, dépendant du taux d'humidité relative. En présence de la résine mélamine formaldéhyde le comportement à l'humidité du composite se rapproche de celui d'un polymère dense.

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Kihlman, Martin. « Dissolution of cellulose for textile fibre applications ». Licentiate thesis, Karlstads universitet, Avdelningen för kemiteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-12798.

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This thesis forms part of a project with the objective of developing and implementing a novel, wood-based, process for the industrial production of cellulose textile fibres. This new process should not only be cost effective but also have far less environmental impact then current processes. Natural and man-made fibres are usually plagued with problems (e.g. economic and environmental) and are unsuitable in meeting growing demands. The focus of this thesis was therefore to investigate the dissolution of cellulose derived from various pulps in novel aqueous solvent systems. It was shown that cellulose could be dissolved in a NaOH/H2O solvent at low temperatures (<0°C) and that such an alkaline solvent can be improved regarding the solubility, stability and rheological properties of the cellulose dopes formed if different additives (salts or amphiphilic molecules) are used. The effect of different kinds of pretreatment (individually and combined) and the influence of pulp properties on cellulose accessibility and dissolution were also evaluated. These pretreatments affected, as expected, some characteristic properties of the pulps mainly by reducing the DP but also, for example, changing the composition of the carbohydrates. Not only did the pretreatment affect the solubility it also increased the stability of the cellulose dopes, resembling the effect of chemical additives to the NaOH system. According to multivariate data analysis it was established that, of the pulp properties analyzed, only the composition of carbohydrates and the DP had a significant influence on the solubility of the pulps used in this study. Finally, it was emphasized that the dissolution of cellulose pulps seemed to be controlled by a very complex interaction between both kinetic and thermodynamic parameters.
CelluNova

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Le, Roux Jérôme. « Modification des fibres cellulosiques : amélioration des propriétés hydrophiles des pâtes bisulfites ». Bordeaux 1, 2003. http://www.theses.fr/2003BOR12665.

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Les travaux de recherche portent sur l'amélioration des propriétés absorbantes des pâtes bisulfites. La cellulose est fonctionnalisée par oxydation ménagée, puis des essais de réticulation intra-fibres sont réalisés. Deux approches sont abordées pour réaliser l'oxydation, la première concerne une approche physique avec l'utilisation des plasmas froids oxygène et la deuxième une approche chimique avec l'utilisation d'oxydants en milieux aqueux. Deux systèmes de génération de plasmas ont été utilisés, le traitement corona sous pression atmosphérique et le plasma froid oxygène sous pression réduite. Les deux procédés mettent en avant des améliorations de la mouillabilité des pâtes corrélées à une diminution de l'angle de contact des fibres. L'oxydation chimique de la cellulose a été réalisée soit sur des alcools primaires soit sur des alcools secondaires. L'oxydation des alcools secondaires en acide carboxylique se fait par une séquence d'oxydation au periodate de sodium suivi d'un traitement au chlorite de sodium/peroxyde d'hydrogène. Concernant les alcools primaires, la fonctionnalisation est obtenue par un procédé électrochimique utilisant des oxydants radicalaires du type TEMPO. Dans les deux cas, les traitements sont significatifs et le compromis qualité fibreuse des pâtes/fonctionnalisation est respecté. Des essais de réticulation intra-fibres ont montré une amélioration des propríétés finales des pâtes défibrées à sec. Les performances des fibres modifiées ont été évaluées par des analyses physico-chimiques des pâtes, notamment, les différents tests papetiers liés à l'absorption et la rétention des liquides dans les réseaux fibreux.

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Gustafsson, Emil. « Tailoring Adhesion and Wetting Properties of Cellulose Fibres and Model Surfaces Using Layer-by-Layer Technology ». Doctoral thesis, KTH, Fiberteknologi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-155932.

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The versatile layer-by-layer (LbL) technique, for consecutive adsorption of polyelectrolytes and charged nanoparticles onto a substrate, was used to modify cellulose fibres and model surfaces for improved mechanical and wetting properties. In addition to being used to modify cellulose substrates, the LbL technique was also used to create cellulose surfaces suitable for high resolution adhesion measurements. LbL assembly of cellulose nanofibrils and polyethylenimine was used to prepare cellulose model surfaces on polydimethylsiloxane hemispheres which allowed for the first known Johnson-Kendall-Roberts (JKR) adhesion measurements between cellulose and smooth, well-defined model surfaces of cellulose, lignin and glucomannan. The work of adhesion on loading and the adhesion hysteresis were comparable for all three systems which suggest that adhesion between wood constituents is similar. The LbL technique was also used to decrease the hydrophilicity of paper, while improving the dry strength, by coating cellulose fibres with a polylallylamine hydrochloride (PAH) and polyacrylic acid (PAA) LbL film, followed by adsorption of anionic wax particles. Paper sheets made from the modified fibres were highly hydrophobic with a contact angle of 150°, while retaining, and in some cases improving, the tensile index of the paper. It was also observed that PAH/PAA modified sheets without the addition of wax became hydrophobic when heat treated. The mechanism behind the increased hydrophobicity was studied by the interface sensitive technique, vibrational sum frequency spectroscopy, which indicated that the increased hydrophobicity is a result of the reorientation of polymer chains to expose more hydrophobic CH2 and CH groups at the polymer-air interface. Paper sheets prepared from LbL-modified bleached softwood fibres using PAH and the biopolymer hyaluronic acid (HA) exhibited a 6.5% strain at break and a tensile index which was increased 3-fold compared to unmodified fibres. The wet adhesive properties of the PAH/HA system were studied by colloidal probe atomic force microscopy and correlated to film growth and viscoelastic behavior. The presence of background salt was a crucial parameter for achieving high adhesion but time in contact and LbL film thickness also strongly affected the adhesion. Finally, the wet adhesive properties of carboxymethylcellulose (CMC), which had been irreversibly adsorbed to regenerated cellulose, and polyvinylamine (PVAm) were evaluated by means of 90° peel tests. Strong wet adhesion was achieved for dried rewetted samples without any obvious chemical crosslinking, which was attributed to interdigitation and complex formation in PVAm-CMC films. This system also gave significant wet adhesion for non-dried systems at water contents around 45%.

QC 20141117

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Li, Qiang. « Growth of carbon nanotubes on electrospun cellulose fibres for high performance supercapacitors and carbon fibre composites ». Thesis, University of Exeter, 2018. http://hdl.handle.net/10871/34360.

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The production of cellulose derived hybrid carbon nanofibre (CNF)/carbon nanotubes (CNTs) electrodes for the fabrication of supercapacitors and carbon fibre composites was investigated. The CNTs were grown via a floating catalyst chemical vapor deposition (CVD) method on the top surface of electrospun cellulose derived CNFs. These CNF and CNF/CNTs samples were then used as electrodes to produce liquid electrolyte-based supercapacitors. The growth of CNTs leads to an improvement of electrochemical performance compared to the plain CNFs. This improvement is due to the grown CNTs enlarging the reactive sites through enhanced surface area and porosity, and thereby increasing the conductivity of the system. CNTs have been also grown onto CNFs containing ferrocene and SiC particles. Composites were fabricated by combining the fibres and CNTs grown fibres with model polymers. The stress transfer properties of these materials have been estimated using an in situ Raman spectroscopic method by observing the shift of the Raman band during the tensile deformation of model polymer composites. Using this method, the elastic modulus of CNF/SiC/CNTs fibres has been estimated to be 208 ± 26 GPa. No shifts in the peak positions of bands relating to the carbon structure were obtained for in situ Raman spectroscopic studies of the CNF/CNTs fibres made from the ferrocene embedded fibres. This was thought to be due to the low yield of CNTs on the surface of the fibres. Furthermore, CNF/CNTs electrode-based structural supercapacitors, combining a solid electrolyte with the carbonized fibres, have been produced. These CNF/CNTs electrodes have a better capacitive performance than the plain CNF electrodes. There was a decrease in this performance with increased curing time of the resin, from 2 to 24 h, due to a lack of charge carrier mobility in the latter samples. A Raman spectroscopic study of the deformation of the carbon structures showed that the G-band shift towards a lower wavenumber position for the CNF and CNF/CNTs samples processed at a carbonization temperature of 2000 °C. Moduli of these fibres were estimated to be ~145 GPa and ~271 GPa, respectively, suggesting the growth of CNTs not only enhances the capacitive performance but also the mechanical properties of the structural supercapacitors. No Raman bend shift was found for the CNFs and CNF/CNTs samples processed below a carbonization temperature of 2000 °C, e.g. 900 °C and 1500 °C. This is because the graphitic structures are not well developed at carbonization temperatures below 1500 °C.

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Mortimer, Simon. « Etude de la structuration des fibres Lyocell ». Université Joseph Fourier (Grenoble), 1995. http://www.theses.fr/1995GRE10033.

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Le but de cette these est d'etudier la formation des fibres produites a partir des solutions de cellulose dans le n-oxyde de n-methylmorpholine et de trouver des moyens pour modifier les proprietes de ces fibres, notamment leur tendance a fibriller. Dans une premiere partie, le systeme de filage de ces fibres est introduit, suivi par une explication des methodes de mesure en-ligne du developpement du diametre et de la birefringence des fibres. Ensuite, on utilise ces techniques pour suivre l'evolution de la structure d'une fibre des la filiere jusqu'a la fibre sechee. La structure finale est comparee avec celles d'autres fibres cellulosiques. Dans les quatrieme et cinquieme chapitres l'influence sur la formation de la fibre de plusieurs parametres du procede est etudie, tels que le taux d'etirage, la vitesse de filage, le diametre de la filiere et l'air entre la filiere et le bain de precipitation. Finalement, on developpe des methodes pour le filage des fibres ayant une faible tendance a fibriller, utilisant les parametres de filage, dont les plus importants sont l'air et le taux d'etirage

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Sandberg, Birgersson Paulina. « Transparent paper : Evaluation of chemical modification routes to achieve self-fibrillating fibres ». Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-281347.

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Transparenta papper tillverkade av cellulosa nanofibriller (CNF), visar stor potential att kunna ersätta petroleumbaserade plaster inom många användningsområden, till exempel för mat- och varuförpackningar. CNF, även känt som nanocellulosa, kombinerar viktiga cellulosaegenskaper, med unika egenskaper hos nanomaterial. Denna kombination av egenskaper möjliggör tillverkning av ett pappers-liknande material som uppvisar både utmärkta mekaniska egenskaper och hög transparens. Användningen av nanocellulosa är dock förknippad med diverse utmaningar, för att materialet ska kunna bli kommersiellt slagkraftigt. En av de främsta utmaningarna är nanocellulosas höga affinitet för vatten och dess höga specifika yta som försvårar hanteringen av materialet. Avvattningen av nanocellulosadispersioner, för att tillverka transparenta papper, kan ta upp till flera timmar. För att övervinna detta hinder, har avdelningen för Fiberteknologi vid KTH tillsammans med BillerudKorsnäs AB, nyligen utvecklat en metodik för att skapa så kallade själv-fibrillerande fibrer (SFFer). Dessa fibrer möjliggör en snabbavvattnad papperstillverkningsprocess med makroskopiska vedbaserade fibrer, som efter tillverkning av pappret omvandlas till ett nanocellulosapapper, det vill säga ett nanopapper. För att erhålla SFFer krävs det att höga koncentrationer av karboxyl- och aldehydgrupper introduceras i cellulosafibrerna. Införandet av dessa funktionella grupper, möjliggör självfibrilleringen då SFFerna utsätts för moderata alkali-koncentrationer. I den ursprungliga studien som utfördes av Gorur m.fl., introducerades de funktionella grupperna med hjälp av sekventiell TEMPO- och periodatoxidation. I detta examensarbete, har alternativa kemiska metoder för att introducera samma kemiska funktionalitet som TEMPO-periodatsystemet undersökts. Huvudsyftet med arbetet är att besvara frågan: Hur påverkar olika kemiska behandlingar vid SFF tillverkningen, de kemiska och fysikaliska egenskaperna hos de modifierade fibrerna, samt de slutgiltiga pappersegenskaperna? För att besvara frågan, preparerades fibrer med liknande karboxyl- och aldehydinnehåll med hjälp av följande tre kemiska metoder: 1) TEMPO- följd av periodatoxidation (detta kommer att användas som referenssystem); 2) periodat- följd av kloritoxidation; 3) karboxymetylering följd av periodatoxidation. Egenskaperna hos fibrerna undersöktes med avseende på aldehyd- och karboxylinnehåll, avvattningspotential och förmåga att självfibrillera. Papper tillverkades med hjälp av en vakuumfiltreringsuppställning och följande egenskaper undersöktes hos pappret: mekaniska egenskaper (dragstyrka, brottsyrka och Young’s modul); optiska (transparens och ytreflektion); samt syrgaspermeabilitet. De erhållna fibrerna från samtliga tre kemiska modifieringar visade på självfibrillerande egenskaper i alkaliska lösningar. Detta beteende styrker hypotesen att ett strategiskt införande av ett högt karboxyl- och aldehydinnehåll leder till självfibrillerande fibrer. Transparenta papper tillverkade av fibrer som utsatts för TEMPO-periodatoxidation samt klorit-periodatoxidation, visade på utmärkta mekaniska egenskaper, hög transparens och bra barriäregenskaper - jämförbara med vad som vanligen kan noteras hos papper tillverkat av nanocellulosa. Samtliga egenskaper förbättrades ytterligare efter fibrillering av fibrerna i papperen. De karboxymetylerade-periodatoxiderade materialet, å andra sidan, uppvisade andra egenskaper jämfört med de två, tidigare nämnda, metoderna. TEMPO-periodat- och periodat-klorit-pappersmassan var halvgenomskinlig och geléliknande, medan den karboxymetylerade-periodatoxiderade massan var mer lik det omodifierade materialet. Detsamma gällde det tillverkade pappret som liknade ett konventionellt papper. Det var inte heller möjligt att åstadkomma en fibrillering av det karboxymetylerade-periodatoxiderade-pappret som utsattes för behandling med alkaliska lösningar. Avvattningstiden vid papperstillverkningen varierad mellan 4 och 60 sekunder, och karboxymetylering-periodat oxidation visade på snabbast avvattningstid. Den förlängda avvattningstiden i jämförelse med studien utförd av Gorur m.fl., tros främst bero på att ett filtreringsmembran med mindre porer användes på vakuumfiltreringsuppställningen, istället för en avvattningsvira som tidigare använts. Sammanfattningsvis så har det visat sig möjligt att tillverka självfibrillerande fibrer med hjälp av samtliga tre undersökta kemiska modifieringar. SFFer möjliggör tillverkning av snabbavvattnade transparenta nanocellulosapapper och visar på så vis på hög potential att kunna ersätta olje-baserade plaster till många förpackningsapplikationer.
Transparent papers made from cellulose nanofibrils (CNF), derived from e.g. wood, show great potential to replace petroleum-based plastics in many application areas, such as packaging for foods and goods. CNF, also known as nanocellulose, combine important cellulose properties with the unique features of nanoscale materials, gaining paper-like materials with outstanding mechanical properties and high transparency. However, nanocellulose faces various challenges in order to make the products commercially competitive. One of the main challenges is accompanied with nanocelluloses’ high affinity for water, which makes processing difficult. Dewatering of a nanocellulose dispersion in order to produce transparent paper may take up to several hours. To overcome this obstacle, the Fibre technology division at KTH Royal Institute of technology and BillerudKorsnäs AB have recently developed a new concept of self-fibrillating fibres (SFFs). This material enables fast-dewatering papermaking using fibres of native dimensions and conversion into nanocellulose after the paper has been prepared. In order to obtain SFFs, proper amounts of charged groups and aldehyde groups need to be introduced into the cellulose backbone. When SFFs are exposed to high alkali concentration, i.e. > pH=10, the fibres self-fibrillates into CNFs. In the original study, the functional groups were introduced through sequential TEMPO oxidation and periodate oxidation. In this work, alternative chemical routes have been examined to prepare SFFs with the same functional groups as introduced with the TEMPO-periodate system. The aim of the thesis has been to answer: how does different chemical routes to prepare transparent nanopaper made from SFFs affect the chemical and physical properties of the modified fibres, as well as the final physical properties of the transparent papers? To answer the question, fibres with similar carboxyl and aldehyde contents were prepared using three chemical routes: 1) TEMPO oxidation followed by periodate oxidation (which was used as reference system); 2) periodate oxidation followed by chlorite oxidation; 3) carboxymethylation followed by periodate oxidation. The properties of the fibres were examined regarding aldehyde and carboxyl content, dewatering potential and self-fibrillating ability. Papers were produced using a vacuum filtration set-up and the properties investigated were the mechanical; tensile strength, strain at failure and Young’s modulus, the optical properties; transparency and haze, as well as the oxygen permeability. In order to investigate the impact of the fibrillation of the papers, the properties were measured for both unfibrillated and fibrillated samples. Furthermore, the gravimetric yield after each chemical modification procedure was examined, as well as the dewatering time during sheet making. Fibres obtained from all three chemistries demonstrated self-fibrillating properties in alkaline solutions. This strengthens the hypothesis that the strategical introduction of aldehydes and carboxyl groups is the main feature responsible for the self-fibrillating ability of the fibres. Transparent papers made from fibres treated through TEMPO-periodate oxidation and periodate-chlorite oxidation showed excellent mechanical, optical and barrier properties, comparable to those seen in nanocellulose papers. The properties were further increased after fibrillation. The carboxymethylated-periodate oxidized fibres, on the other hand, behaved differently from the others. While the TEMPO-periodate and periodate-chlorite pulp was semi-translucent and gel-like, the carboxymethylated-periodate oxidized fibres resembled more the unmodified material. Likewise, the properties of those papers resembled conventional paper and no fibrillationwas experienced after immersing the papers in alkaline solution, according to the same protocol developed for the other two chemistries. The dewatering time during sheet making ranged from 4–60 seconds (carboxymethylation-periodate oxidation showing the fastest dewatering rates). The increased dewatering time compared to earlier studies is believed to mainly be due to the use of a filtration membrane on the vacuum filtration set-up, instead of a metallic wire with larger pores. Overall, SFFs was successfully produced using three different chemical routes. SFFs enables production of fast-dewatering transparent nanocellulose papers that shows the potential to replace oil-based plastics in many packaging applications.

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Piotrowski, Violaine. « Protéines de soie de Bombyx ou d’araignée, naturelles ou modifiées, et fibres de cellulose comme renfort in situ de composites bioinspirés ». Thesis, Lille 1, 2020. http://www.theses.fr/2020LIL1R033.

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Les composites synthétiques sont constitués d’une résine et d’un renfort par des fibres industrielles courtes ou longues. Les fibres longues tissées ou stratifiées permettent d’obtenir le meilleur renforcement possible, mais nécessitent un processus industriel long et complexe pour la mise en oeuvre des composites. Les fibres courtes peuvent, elles, être mélangées directement dans la résine et permettent de former un composite en une seule étape par photopolymérisation ou polymérisation thermique. Cependant les propriétés mécaniques de tels composites sont de loin inférieures à celles obtenues par renforcement à fibres longues. L'alternative étudiée dans cette thèse est le renforcement de composites par biomimétisme c’est-à-dire par des fibres longues naturelles introduites sous forme d’un liquide homogène et qui redeviennent des fibres lors de la mise en œuvre du composite. Ce procédé pourrait permettre la conception de composites avec un renforcement macroscopique avec la facilité de production des composites à fibres courtes. Dans ce projet de thèse, deux types de biopolymères ont été étudiés : la cellulose (et son dérivé l’acétate de cellulose), un polysaccharide très souvent utilisé pour le renforcement de composite et les protéines de soie (fibroïne H, MaSp1) qui sont parmi les fibres naturelles les plus résistantes. La fibroïne H a été extraite de cocons frais du vers à soie Bombyx mori et la protéine de soie d'araignée MaSp1 de Nephila clavipes a été produite par génie biologique dans E. coli. Des liquides ioniques polymérisables et un tensioactif photoclivable, permettant de solubiliser de manière réversible les biomolécules, ont été synthétisés. Des films renforcés à partir de liquide ionique et de biomolécules ont été synthétisés et caractérisés. Enfin des composites renforcés par des microfibres industrielles ou des fibres biologiques ont été produits. La mesure des propriétés mécaniques a démontrée un renforcement supérieur par les fibres biologiques
Synthetic composites consist on a resin and a reinforcement by short or long industrial fibers. Laminated or woven long fibers provide the best possible reinforcement but require a long and complex industrial process for the processing of the composites. Short fibers can be mixed directly into the resin and can form a composite in a single step by photopolymerization or by thermal polymerization. However, the mechanical properties of such composites are considerably lower compared to those obtained by long-fiber reinforcement. The alternative studied in this thesis is the reinforcement of composites by biomimicry, i.e. by natural long fibers introduced as a homogeneous liquid, which become fibers at a solid state during the composites manufacturing process This process could provide the design of composites with macroscopic reinforcement using the ease of production for short fibers composites. In this thesis project, two types of biopolymers were studied: cellulose (and its derivative cellulose acetate), a polysaccharide often used for composite reinforcement, and silk proteins (fibroin H, MaSp1) which are one of the most resistant natural fibers. Fibroin H was extracted from fresh cocoons of the Bombyx mori silkworm and the spider silk protein MaSp1 from Nephila clavipes was produced by bioengineering in E. coli. Polymerizable ionic liquids and a photocleavable surfactant, able to reversible solubilize of biomolecules, were synthesized. Reinforced films from ionic liquids and biomolecules were synthesized and characterized. Finally, composites reinforced with industrial microfibers or biological fibers have been manufactured. The measurement of mechanical properties demonstrated superior reinforcement by biological fibers

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Thèses sur le sujet « Depolymerization of cellulose fibres »

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