The goal of this research study was to create an artificial annulus fibrosus similar to that of the natural intervertebral disc, as well as find preliminary results for vertebral endplate connection and nucleus pulposus internal pressure, for the correction of disc degeneration in the spine. The three-part composite samples needed to demonstrate good shock absorption and load distribution while maintaining strength and flexibility, and removing the need for metal in the body, something of which no current total disc replacement or spinal fusion surgery can offer. For this study, the spinal disc was separated into its three different components, the annulus fibrosus, the nucleus pulposus, and the vertebral endplates, each playing a vital role in the function of the disc. Two low-cost materials were selected, a Covestro polyurethane and cellulose nanocrystals, for the purpose of creating a polymer composite spinal disc implant. A methodology was established for creating the cast composite material for use as an annulus fibrosus, while also investigating its mechanical properties. The same composite material was used to acquire preliminary results for vertebral endplate connection to the synthesized annulus, however no additional material was used to determine or mimic the mechanical properties of these endplates, due to time constraints. Also because of time constraints, the nucleus used in this study was only comprised of water with no other additives for preliminary testing since the natural nucleus is comprised of about 80-90% water. These properties were then compared to the mechanical properties of the natural disc, so that they could be finely tuned to emulate the natural disc. It is shown in this study that the composite material, when swelled in water, was able to mimic the annulus fibrosus in tensile strength and modulus, however showed higher compressive strength and modulus than ideal. The samples also did not undergo any permanent deformation within the realm of force actually introduced to the natural disc. The vertebral endplates showed decent adhesion to the synthesized annulus, however there were slight defects that became failure concentrators during compression testing. The nucleus showed promising results maintaining good internal pressure to the system causing better compressive load distribution, with barreling of the samples. / Master of Science / Spinal disc degeneration is a very prevalent problem in today’s society, effecting anywhere from 12% to 35% of a given population. It usually occurs in the lumbar section of the spine, and when severe enough, can cause bulging and herniation of the intervertebral disc itself. This can cause immense lower back pain in individual’s stricken with this disease, and in the US, medical costs associated with lower back pain to exceed $100 billion. Current solutions to this problem include multiple different treatment options of which, spinal fusion surgery and total disc replacement (TDR) are among the most common. Although these treatments cause pain relief for the majority of patients, there are multiple challenges that come with these options. For example, spinal fusion surgery severely limits the mobility of its patients by fusing two vertebrae together, disallowing any individual movement, and TDR can cause hypermobility in among the vertebrae and offer little to no shock absorption of loads. Therefore, a better treatment option is needed to relieve the pain of the patients, as well as maintain equal motion, shock absorption, and load cushioning to that of the normal intervertebral disc and remaining biocompatible. The goal of this research study was to create a three-component system, like that of the natural intervertebral disc, for the use of spinal disc replacement and to replace current options. The fabricated system was comprised of the three components found in the natural intervertebral disc; the annulus fibrosus, the nucleus pulposus, and the vertebral endplates. Because the system will need to go in-body, the materials used were all characterized as biocompatible materials; the polyurethane currently being used in medical devices and implants, and the cellulose nanocrystals (CNCs) coming from natural cellulose in sources such as wood and plants. The results determined that the mechanical properties of the system can be fine-tuned in order to mimic the natural strength and cushioning capabilities of the natural disc, based on CNC content added to the polyurethane, and when all three components of the system are added together, the compressive stress-strain is most similar to the natural disc in compression. However, the system did show failure in the connection between the annulus fibrosus and vertebral endplates, causing herniation of the nucleus similar to the initial problem attempting to be solved. For this, more ideal fabrication methods should be researched in the future including 3D printing techniques, injection molding, and roll milling. As well as alternate fabrication techniques, cell grow and viability should be determined to show that cells don’t die once the system in implanted.

The purpose of this research was to determine the effects of cellulose nanocrystals (CNCs), as potential additives, on the properties and performance of phenol–formaldehyde (PF) adhesive resin. The steady-state viscosity of a commercial PF resol resin and three CNC–resin mixtures, containing 1–3 wt % CNCs, based on solids content, was measured with a rheometer as a function of shear rate. The viscosity of the PF resin itself was independent of shear rate. The viscosity–shear rate curves of the CNC–resin mixtures showed two regions, a shear thinning region at lower shear rates and a Newtonian region at higher shear rates. The low-shear-rate viscosity of the resin was greatly increased by the CNCs. The structure of the CNC–resin mixtures under quiescent conditions was analyzed by polarized light microscopy. The mixtures contained CNC aggregates, which could be disrupted by ultrasound treatment. The curing progressions of the resin and CNC–resin mixtures were analyzed by non-isothermal differential scanning calorimetry (DSC). The DSC curves showed two exotherms followed by an endotherm. The energy of activation for the first exotherm was reduced by the CNCs whereas the energy of activation for the second exotherm was not affected by the CNCs. Increasing CNC contents caused higher degrees of reaction conversion during the first curing stage and a greater loss of sample mass, attributed to formaldehyde release during resin cure. For analysis of the mechanical properties during and after cure, sandwich-type test specimens were prepared from southern yellow pine strips and the resin and CNC–resin mixtures. The mechanical properties of the test specimens were measured as a function of time and temperature by dynamic mechanical analysis (DMA). The time to incipient storage modulus increase decreased and the rate of relative storage modulus increase increased with increasing CNC content. The ultimate sample stiffness increased with increasing CNC content for CNC contents between 0 and 2 wt %, which was attributed to mechanical reinforcement of the resin by the CNCs. At a CNC content of 3 wt %, the ultimate sample stiffness was lower than at a CNC content of 2 wt % and the second tan δ maximum occurred earlier in the experiment, indicating an earlier onset of vitrification. The lower ultimate sample stiffness was attributed to premature quenching of the curing reactions through CNC-induced depression of the vitrification point. For analysis of the fracture performance, double cantilever beam test specimens were prepared from southern yellow pine beams and the resin and CNC–resin mixtures, using different hot-pressing times. Fracture energies were measured by mode I cleavage tests. Bondline characteristics were analyzed by light microscopy. At a hot-pressing time of 10 min, the fracture energy decreased with increasing CNC content, whereas it stayed constant for CNC contents between 1 and 3 wt % at a hot-pressing time of 8 min. The bondlines of resin mixtures containing CNCs exhibited voids, whereas those of the pure resin did not. CNCs had both benefitial and detrimental effects on the properties and performace of PF resin. / Master of Science

The objective of this research is to develop a water-based processing method for incorporating large filler loadings into nanocomposite systems. Specifically, cellulose nanocrystal/poly(vinyl alcohol) (CNC/PVA) nanocomposite aqueous suspensions and films were processed and characterized at CNC loadings up to 67 wt.% with respect to polymer concentration. Both aqueous suspended and freeze-dried CNCs were studied with this method. Two methods for incorporating the CNCs were investigated: solution processing and batch mixing of aqueous suspensions. The materials produced by these methods were characterized using rheology of aqueous suspensions and a method for understanding the morphology of these aqueous suspension through rheological characterization was developed. The CNC/PVA suspensions were dried and the structure of the film studied using x-ray diffraction, Fourier transform infrared spectroscopy, and differential scanning calorimetry. With regard to characterization of polymer structure by these methods, PVA crystallinity was seen to increase with increasing CNC loading. Finally, dynamic mechanical analysis and micro-tensile testing were conducted on consolidated films and CNCs were seen to increase modulus, yield stress but decrease strain at failure. Biodegradation studies were also conducted and CNCs were seen to increase the biodegradation characteristics of PVA. While the general trends in experimental data were the same, differences in properties between systems made with solution processing and batch mixing were observed, attributed to differences in the CNC dispersion. Overall, results indicated that this methodology is feasible for the industrially scalable production of highly loaded nanocomposites.

Submitted by Ronildo Prado (ronisp@ufscar.br) on 2017-08-23T14:10:16Z No. of bitstreams: 1 DissPICC.pdf: 9243099 bytes, checksum: d5c4984be722eda91236fbec51d566f6 (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-08-23T14:10:24Z (GMT) No. of bitstreams: 1 DissPICC.pdf: 9243099 bytes, checksum: d5c4984be722eda91236fbec51d566f6 (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-08-23T14:10:29Z (GMT) No. of bitstreams: 1 DissPICC.pdf: 9243099 bytes, checksum: d5c4984be722eda91236fbec51d566f6 (MD5) / Made available in DSpace on 2017-08-23T14:10:35Z (GMT). No. of bitstreams: 1 DissPICC.pdf: 9243099 bytes, checksum: d5c4984be722eda91236fbec51d566f6 (MD5) Previous issue date: 2017-02-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / New materials from cellulose have been developed, such as cellulose nanocrystals (CNC) and cellulose nanofibrils (CNF). Different morphologies of the cellulose can lead to the formation of films with different thermal, mechanical and optical properties in relation to conventional cellulose films. The objective of this work was to evaluate the effect of different dimensional scales of cellulose, micro and nanometric, on the production of cellulose films from two vegetable species and their thermal, mechanical, morphological and optical properties. Eucalyptus fibers and pineapple leave fiber (curauá) (PALF) were used as cellulosic fibers for this study. The films of eucalyptus and pineapple cellulosic fibers were prepared by filtration and casting, and the CNC and CNF films were obtained by continuous casting. The CNC and CNF films showed mechanical tensile strength in the order of 9 to 35 MPa higher than the films of cellulose fibers, regardless of the origin of the fiber. The continuous casting process produced CNC and CNF films that presented different mechanical resistance in the longitudinal direction of the process with respect to the transverse direction. This behavior may be related to how hydrogen bonds and mechanical anchorages occur between nanofibers. The thermal stability of the nanocellulose films was lower in the order of 20 to 150 ºC than in the films of fibers due to the routes of obtaining the CNC and CNF. Nanofiber films presented lower opacity in the order of 3 to 60% lower than the films of fibers due to the diameter of the nanocelluloses. Curauá fibers had the highest crystallinity index (Ic) reaching 87%. It is concluded that the properties studied were influenced by the type of nanocellulose (CNC or CNF), the origin of the cellulose (eucalyptus or pineapple), and the micro and nanometric scale of the fibers. / Novos materiais a partir da celulose tem sido obtidos, como os nanocristais de celulose (CNC) e as nanofibrilas de celulose (CNF). Diferentes morfologias da celulose podem levar a formação de filmes com propriedades térmicas, mecânicas e ópticas diferentes de filmes de celulose convencional. O objetivo deste trabalho foi avaliar o efeito de diferentes morfologias de fibras de celulose, micro e nanométricas, na obtenção de filmes - provenientes de duas espécies vegetais – e em suas propriedades térmicas, mecânicas, ópticas e morfológicas. Utilizou-se como fibras celulósicas para este estudo as fibras de eucalipto e fibras de folhas de abacaxi (curauá) (PALF). Os filmes de fibras celulósicas de eucalipto e de abacaxi foram confeccionados por filtragem e casting, e os filmes de CNC e CNF foram obtidos por continuous casting. Os filmes de CNC e CNF apresentaram resistência mecânica à tração, na ordem de 9 a 35 MPa superior aos filmes de fibras de celulose, independente da origem da fibra. O processamento por continuous casting produziu filmes de CNC e CNF que apresentaram resistência mecânica diferente no sentido longitudinal ao processo com relação ao sentido transversal. Este comportamento pode estar relacionado de que forma ocorrem às ligações de hidrogênio e os emaranhamentos mecânicos entre as nanofibras. A estabilidade térmica dos filmes de nanofibra foi menor na ordem de 20 a 150 ºC do que aos filmes de fibras devido às rotas de obtenção das CNC e CNF. Os filmes de nanofibra apresentaram menor opacidade, na ordem de 3 a 60% inferior, que os filmes de fibras devido ao diâmetro das nanofibras. As fibras de curauá apresentaram o maior índice cristalinidade (Ic) chegando a 87%. Conclui-se que a propriedades estudadas foram influenciadas pelo tipo de nanofibra (CNC ou CNF), pela origem da celulose (eucalipto ou abacaxi), e pela escala micro e nanométrica das fibras.

L’originalité de ce travail est d’étudier la contribution des nanocelluloses pour limiter deux défauts courant dans les papiers sécurités: le froissage et les “cornes”, où plis qui se manifestent dans les angles des papiers. Ces défauts sont principalement causés par une manipulation quotidienne de ces papiers à haute valeur ajoutée, et sont responsables d’une perte en qualité visuelle et mécanique ainsi que de troubles économiques. Les nanocellulose peuvent être divisées en deux différentes familles de matériaux : les nanofibrilles de celluloses (NFCs) et les nanocristaux de cellulose (NCCs). Les NFCs sont longues et flexibles et peuvent facilement s’enchevêtrer pour former un réseau cohésif maintenu par de nombreuses liaisons hydrogènes. Les NCCs sont des matériaux petits et rigides, et leurs impressionantes propriétés mécaniques font d’eux des candidats intéressants pour être utilisés en renfort de polymère. Dans cette étude, deux stratégies sont proposées pour incorporer ces deux types de nanocellulose dans la fabrication du papier sécurité. Premièrement, il est question d’introduire une couche de NFCs à l’intérieur du papier afin d’augmenter la résistance de ce papier au froissage. Ensuite, il est question d’imprégner ce papier avec de l’alcool polyvinylique renforcé par des NCCs afin d’augmenter la résistance aux cornes. Enfin, ces approches sont testées à l’échelle pilote et industrielle. / The original feature of this work is the use of nanocellulose for limiting two security paper defects: corner folds, also called “dog-ears”, and crumpling. These defects, caused principally by daily handling of these high added value documents, are responsible for a decrease of paper visual and mechanical quality and constitute an economic loss. Nanocellulose can be divided into two different families: cellulose nanofibrils (CNFs) and cellulose nanocrystals (CNCs). CNFs are long and flexible materials with the ability to entangle and form a network strongly maintained by hydrogen bonds. CNCs are short and rigid materials whose outstanding mechanical properties make them good candidates for reinforcement in a polymer matrix. In this study, two strategies are proposed to incorporate these two kinds of nanocellulose in the security paper process. First, it is question to introduce a CNF layer within the paper substrate in order to increase the paper crumpling resistance. Then, it is question to impregnate the paper with CNCs-reinforced polyvinyl alcohol (PVOH) in order to increase the dog-ears resistance. Finally, these approaches are tested at pilot and industrial scales.

Cette thèse s'intéresse à la préparation, par la technique de la lyophilisation, des aérogelsà base de celluloses et de charges minérales destinés à une utilisation potentielle dans le domainede l'isolation thermique. Le premier objectif de la thèse a été la caractérisation de différentescelluloses (cellulose (PBPD), nanocristaux (NCC) et nanofibrilles oxydées (NFCs)), les chargesminérales (principalement la zéolithe) et les différents aérogels résultants de différentescombinaisons des matériaux de départ utilisés. Nous avons utilisé pour la caractérisation desmatériaux de départ et des aérogels des techniques d'analyse telles que la diffraction des rayonsX (DRX), la BET, le MEB et le potentiel zêta. Nous avons également caractérisé les propriétésmécaniques des aérogels par des essais de compression et leurs propriétés de conductionthermique dans le régime non stationnaire par la technique du fil chaud. Il s’est avéré qu’unestructuration multi-échelles de ces différentes celluloses favorise la création de méso etnanoporosités au détriment de la macroporosité. Ceci favorise le confinement de l’air dans le bioaérogelpar effet de Knüdsen et améliore ses propriétés d’isolation thermique. D'autre part lesnanoparticules (organiques et inorganiques) permettent d'avoir des aérogels de très bonnespropriétés mécaniques. Le troisième objectif était d'essayer d'autres charges minérales (autres quela zéolithe) dans les différentes celluloses et d’explorer les propriétés morphologiques,structurales, thermiques et mécaniques. Cette étude a permis de montrer l'importance descaractéristiques morphologiques et géométriques des charges minérales dans le contrôle despropriétés physiques et mécaniques des aérogels bio-hybrides. / This thesis focuses on the preparation, using freeze drying technique, of aerogels madefrom cellulose and mineral fillers intended for potential use in the field of thermal insulation. Thefirst goal of this thesis was the characterization of different cellulose (cellulose (PBPD)nanocrystals (NCC) and oxidized nanofibrils (NFCs)), the inorganic filler (mainly zeolite) and theresulting aerogels prepared by various combinations. We used for the characterization of thestarting materials and the aerogels analytical techniques such as x-ray diffraction (XRD), BET,SEM and the zeta potential. We also characterized the mechanical properties of the aerogels bycompression tests and their thermal conduction properties in the non-steady state by the hot wiretechnique. It has been found that multi-scale structure of these celluloses promotes the creation ofmeso and nanoporosities to the detriment of macroporosity. This promotes the confinement ofthe air in the bio-aerogel by Knudsen effect and improves their thermal insulation properties. Onthe other hand, the nanoparticles (organic and inorganic) allow the aerogels to have very goodmechanical properties. The third objective was to try other mineral fillers (other than the zeolite)in combination with the different cellulose and explore the morphological, structural, thermaland mechanical of the corresponding aerogels. This study has allowed showing the importance ofmorphological and geometrical characteristics of the mineral fillers in controlling physical andmechanical properties of the bio-hybrid aerogels.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / The use of cellulose nanocrystals (CN) as a reinforcing agent for polymeric matrices has attracted considerable attention because the cellulose nanocrystal-based nanocomposites typically exhibit thermal, mechanical and superior barrier properties compared to the pure polymer or conventional composites and additionally provide environmental benefits. In order to use these to the CN as a reinforcing agent polymer matrix, the thermal stability of these crystals is a key factor in that they can be used as effective reinforcement materials, since the thermoplastic processing temperatures often exceeds 200°C. In this work CN were obtained from different sources, cellulose of purified mango seed (PMS), eucalyptus kraft pulp (PK) and cellophane (CELL) by acid hydrolysis with HCl and H2SO4. The chemical compositon of PMS, PK and CELL used in the hydrolysis were determined for the levels of -cellulose, hemicelluloses, holocellulose, lignin and ash All NC were characterized by elemental analysis (C,H,N,S), x - rays diffraction (XRD), atomic force microscopy ( AFM ) and thermogravimetry analysis ( TGA ) . Through thermogravimetric analysis kinectic study of thermal decomposition of the CN was carried out, it was possible to determine the conversion ( ) of the thermal decomposition of each sample of NCC under different heating rates of 5 , 10 , 20 and 40 ° C.min-1 . Through these data was possible to estimate the activation energy involved in the thermal decomposition process by applying kinetic method ASTM E 1641 , and the kinetic method of Kissinger . / A aplicação de nanocristais de celulose (NCC) como agente de reforço para matrizes poliméricas tem atraído considerável atenção, pois os nanocompósitos baseados em NC geralmente exibem propriedades térmicas, mecânicas e de barreira superiores em relação ao polímero puro ou compósitos convencionais, e adicionalmente oferecem benefícios ambientais. Tendo em vista a utilização desses NCC como agente de reforço para matrizes poliméricas, a estabilidade térmica destes cristais é um fator chave para que os mesmos possam ser usados como materiais de reforço eficazes, uma vez que as temperaturas de processamento de termoplásticos muitas vezes excede os 200°C. Neste trabalho foram extraídos NCC de diferentes fontes, celulose de manga purificada (CP), celulose de polpa Kraft de eucalipto (PK) e celofane (CEL), através de hidrolise ácida com H2SO4 e HCl. As composições químicas dos CP, PK e CEL utilizadas na hidrólise foram determinadas quanto aos teores de -celulose, holocelulose, hemicelulose, lignina e cinzas. Todos os NCC foram caracterizados através de análise elementar (C,H,N,S), difração de raios-x, microscopia de força atômica (AFM) e análise termogravimétrica (TGA). Através das análises termogravimétricas, foi realizado o estudo cinético de degradação térmica dos NCC, onde foi possível se determinar a conversão ( da decomposição térmica para todas as amostras de nanocristais de celulose. E sob diferentes taxas de aquecimentos 5, 10, 20 e 40°C.min-1. Através desses dados pôde-se estimar a energia de ativação envolvida no processo de decomposição térmica aplicando-se os métodos cinéticos ASTM E 1641 e o método cinético de Kissinger. / Mestre em Química

CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Devido a busca e necessidade da aplicação de produtos sustentáveis, as blendas e os nanocompósitos a partir de biopolímeros surgem como uma proposta de uso em diversos campos tais como: embalagens, biomedicina e agricultura. Nesse sentido foram desenvolvidos blendas de goma de linhaça/ágar reticulados com glutaraldeído utilizando nanocristais de celulose como reforço, obtidos através do método “casting”. Testes preliminares foram realizados inicialmente variando a proporção de agente reticulante e plastificante além da variação de pH do meio, com o objetivo de promover ligações cruzadas na estrutura e consequente diminuição da hidrofilicidade do material. Seguiu-se o desenvolvimento das blendas em meio ácido fixando as proporções mássicas de aditivos (30% m/m de glicerol e 15% m/m de glutaraldeído em relação a massa final para cada filme), além de variar as proporções dos polímeros (75/25, 50/50 e 25/75 GL/AG). Os nanocompósitos foram obtidos a partir de cada formulação (blendas e amostras controles) com a adição de 2, 4 e 8% m/m de nanocristal de celulose (NC). Os filmes e blendas foram caracterizados pelas técnicas: Calorimetria Exploratória Diferencial, Análise Termogravimétrica, Difração de Raios-X e Infravermelho com Transformada de Fourier a fim de avaliar possíveis interações e organização do sistema. O estudo da reticulação das matrizes poliméricas, de suas blendas e dos nanocompósitos foram avaliados através da interação com a água pelo teste de solubilidade, absorção de vapor de água, ângulo de contato e permeabilidade ao vapor de água. A morfologia das amostras foi estudada por Microscopia Eletrônica de Varredura e por fim, o ensaio sob tração foi realizado para avaliação do desempenho mecânico das amostras. Os eventos endotérmicos observados nas curvas de DSC podem estar associados a novas interações estabelecidas no sistema. As curvas termogravimétricas apresentaram aumento da estabilidade térmica para os filmes controles e as blendas reticuladas em meio ácido. Os difratogramas de DRX apresentaram um padrão difuso de material tipicamente amorfo. Os espectros de FTIR não apresentaram bandas específicas de reticulação, apenas as existentes na estrutura original dos polissacarídeos. As imagens de MEV mostraram boa agregação e dispersão para as blendas e nanocompósitos. Os testes realizados de interação dos filmes com água mostraram que a reticulação em meio ácido levou a menor solubilidade para a formulação de goma de linhaça. A inserção de ágar bem como de NC contribuiu para uma menor absorção de água e melhora nas propriedades mecânicas. As formulações 50/502% NC e 50/504% NC apresentaram aumento da tensão na ruptura, elongamento e módulo de Young demonstrando assim resultados que justificam tanto a obtenção destas blendas quanto dos nanocompósitos. Além disso, com as diferentes morfologias obtidas nesse estudo é possível estender a faixa de aplicação para as formulações propostas. / Nowadays, due to the incentive and the requirement for the use of sustainable products, the blends and nanocomposites from biopolymers appear as a proposal for application in several fields, such as: packaging, biomedicine and agriculture. In this sense, flaxseed gum/agar blends were developed using glutaraldehyde as a crosslinker and cellulose nanocrystals as reinforcement, produced by casting method. Preliminary tests were fulfilled varying the amount of crosslinker agent and plasticizer, changing the pH of the medium in order to insert crosslinks in the polymer structure and consequently decrease the hydrophilicity of the samples. The development of the blends in acid medium by setting the mass proportions of additives (30 wt.% glycerol and 15 wt.% glutaraldehyde relative to the final mass for each film) and varying the polymers proportions (75/25, 50/50 and 25/75 GL/AG). The nanocomposites were obtained from each formulation (blends and control samples) with the addition of 2, 4 and 8% w/w of cellulose nanocrystals (NC). Films and blends were characterized by Differential Scanning Calorimeter, Thermal Gravimetric Analysis, X-ray Diffraction and Attenuated Total Reflectance with Fourier Transforms Infrared Spectroscopy techniques in order to assess possible interactions and organization of the system. The effect of the crosslinking in the polymer matrices, their blends and the nanocomposites were evaluated through the interaction with water by the solubility test, water vapor absorption, contact angle and water vapor permeability. The morphology of the samples was studied by the Scanning electron microscopy and, finally, the tensile test was performed to evaluate the mechanical performance of the samples. The endothermic events observed in the DSC curves may be associated with new interactions established in the polymeric systems. The thermogravimetric curves showed increased thermal stability for the control films and crosslinked blends in acid media. The X-ray diffractograms presented a diffuse pattern of the amorphous material. The infrared spectra did not present specific bands of crosslinking, only those being in the original structure of the polysaccharides. MEV images showed good aggregation and dispersion for blends and nanocomposites. Tests performed on the interaction of the films with water show that crosslinking in acid media led to a lower solubility for the flax gum formulation. The insertion of agar, as well as, the insertion of NC contributed to a lower water absorption and improvement in the mechanical tensile properties. The 50/502%NC and 50/504%NC formulations showed increased tensile rupture, Young's Modulus and elongation thus demonstrating results that justify both blends and nanocomposites originated from these. Moreover, with the different morphologies obtained in this study it is possible to extend the application range for the proposed formulations. / Dissertação (Mestrado)

Biobased all-cellulose composites (ACCs), in which the matrix and the reinforcement are made out of the same material, have gained a noticeable increased attention in recent years. Their successful application would solve the commonly faced challenges with natural fiber composites regarding their chemical antipathy between the hydrophilic fiber and the usually hydrophobic polymer matrix, while still keeping the advantages of being environmental friendly. Moreover, the use of man-made continuous regenerated cellulose fibers for this purpose could result in unidirectional all-cellulose composites with excellent mechanical properties. In this study, a new processing technique for unidirectional all-cellulose composites, reinforced with continuous regenerated cellulose nanocomposite fibers, has been developed, where the fibers are wound directly after the coagulation bath and then welded together while still being swelled in order to form all-cellulose composite sheets without the need of adding any additional solvent or chemicals. Scanning electron microscopy and tensile testing were used to investigate and compare the microstructure and mechanical properties, of a reference material without nanoreinforced fibers and two variants reinforced with 2 % cellulose nanocrystals (CNCs) and 2 % halloysite nanotubes (HNTs). Analysis revealed that transparent all-cellulose composites with a high compaction degree and minimal warpage during shrinkage, showing high mechanical properties could be made. However, the addition of nanoreinforcements did not lead to any improvements.

The goal of this work was to quantify the mechanical properties of cellulose nanocrystal (CNC)-based thin films using a polystyrene (PS) structuring approach. This structuring approach was used to biaxially wrinkle CNC-polymer and all-CNC films, in order to assess how changes in the film fabrication process affected the elastic modulus of these films. All films were prepared on pre-stressed PS substrates and structured by heating them above the glass transition temperature of PS, which caused the substrates to shrink and the films to wrinkle biaxially. CNC-polymer films were prepared using the layer-by-layer approach, where three parameters were modified to obtain films of varying compositions: 1) type of polymer (xyloglucan, XG, or polyethyleneimine, PEI), 2) polymer concentration (0.1 wt% or 1 wt%), and 3) film thickness (i.e., number of deposited bilayers). After these films were structured, their elastic moduli were calculated to be 70 ± 2 GPa for CNC-XG0.1, 72 ± 2 GPa for CNC-PEI0.1, and 32.2 ± 0.8 GPa for CNC-PEI1.0 films, indicating that the mechanical properties of CNC-polymer films changed with film composition. This structuring method was also found to provide a humidity-independent measurement of the modulus due to the irreversible nature of the wrinkling. Next, to prepare all-CNC films, CNC suspensions were evaporated under conditions designed to control the film thickness (using 0.005 wt% – 8 wt% CNC suspensions) and CNC nanoparticle orientation (chiral nematic, isotropic, or uniaxial). Suspensions were dried slowly under vacuum, quickly by heating, or by spin-coating to form films with chiral nematic, isotropic, or uniaxial (radial) CNC orientations, respectively. Following structuring, these wrinkled films showed unique morphologies that changed with nanoparticle orientation, suggesting that their mechanical properties are dependent on the CNC orientation within the films. The work presented in this thesis implies that the mechanical properties of films fabricated from hygroscopic bio-based nanomaterials can be assessed in a humidity-independent way by using the structuring method presented. Quantifying the mechanical properties of these films is critical to assess the potential applications of CNCs, where CNC-based materials may be used in developing paper-based electronics, extracellular matrix mimics, and plant cell wall mimics. / Thesis / Master of Science (MSc)