No description available.

Thesis (Ph. D.)--Institute of Paper Chemistry, 1976. / Includes bibliographical references (p. 129-133).

O cenário energético mundial traz à tona a necessidade da busca por fontes renováveis que contribuam de maneira positiva para a diminuição de emissões de gases nocivos, como o CO2. Neste contexto estudos como o presente constituem importante contribuição para o melhor entendimento destas questões ambientais, para tanto o mesmo teve como objetivo avaliar o efeito de pré-tratamento com solução alcalina aquosa (mercerização, NaOH 20%, 20 g.L-1, temperatura ambiente, 5h) sobre a sacarificação, via hidrólise ácida e enzimática de fibras lignocelulósicas de curauá (Teor de: umidade 8,2% ±0,2, cinzas 2,0% ±0,1, holocelulose 85,9% ±0,7, hemiceluloses 15,5% ±0,2, α-celulose 70,4% ±0,2, lignina total de 9,4% ±0,3 e índice de cristalinidade (Ic) 69,4%. Alíquotas retiradas durante a mercerização foram caracterizadas, por exemplo, a alíquota referente a 2h apresentou as seguintes propriedades: α-celulose 81,6% ±0,2, lignina total 3,2% ±0,3 e índice de cristalinidade (Ic) 75,5%. Análises de microscopia eletrônica de varredura (MEV), comprimento e espessura médio (MorFi) mostraram, ao longo da mercerização, aumento de rugosidade e fragmentos aderidos a superfície da fibra, e diminuição de comprimento e espessura. Fibras não tratadas e tratadas (2h) foram submetidas a hidrólise ácida (1:30 vol./massa, H2SO4 a 24%, 80°C, 6h), onde as fibras não reagidas foram separadas do licor via filtração, e caracterizadas por difração de raios X, MEV, MorFi, e os açúcares do licor e produtos de decomposição foram analisados via Cromatografia líquida de alta eficiência (CLAE). Os resultados da hidrólise ácida com a fibra mercerizada, apresentaram maior produção de glicose (fração celulósica) e diminuição dos teores de xilose e arabinose, (fração hemicelulósica). A glicose atingiu teor máximo de 2,68 g.L-1, no entanto para a hidrólise com a fibra não tratada atingiu um máximo de 1,3 g.L-1, com formação em baixa escala de produtos de decomposição (HMF e furfural). Fibras de partida e mercerizada também foram submetidas a hidrólise enzimática (48h, enzimas celulase comercial-Accellerase 1500, 0,5mL/g). Alíquotas das polpas não reagidas e licor foram extraídas durante a reação, e caracterizadas conforme descrito para hidrólise ácida. Microscopias mostraram que houve aumento da rugosidade e da abertura dos feixes de fibras nas fibras mercerizadas. Os valores de Ic apresentaram aumento inicial e posterior queda indicando hidrólise da fração não cristalina da celulose seguida da fração cristalina. O comprimento e espessura médio das fibras, sofreram diminuição, sendo mais acentuada na hidrólise com a fibra mercerizada e mais intenso para a espessura. Houve formação de glicose e xilose e não houve formação de produtos de decomposição como ocorrido na hidrólise ácida. A fibra não tratada apresentou um máximo de 12,0 g.L-1 de glicose e 2,30 g.L-1 de xilose, já a fibra mercerizada apresentou máximos de 17,5 g.L-1, 1,36 g.L-1 de glicose e xilose respectivamente, indicando aumento de 45% de glicose e diminuição de 56% de xilose. Esta investigação do efeito da mercerização sobre a sacarificação da fibra de curauá forneceu informações importantes para o aprofundamento deste estudo, assim como indicou que o curauá pode posteriormente se tornar fonte de produção de etanol de segunda geração. / The global energy scenario brings to light the need for the search for renewable sources that contribute positively to the reduction of harmful gases emission, such as CO2. In this context, studies such as the one herein constitute an important contribution to a better understanding of these environmental issues. The purpose of this study was to evaluate the effect of the alkaline pre-treatment (mercerization, NaOH 20%, 20 g.L-1, room temperature, 5h) on saccharification, via acid and enzymatic hydrolysis of curauá lignocellulosic fibers (moisture content 8.2% ± 0.2, ashes 2.0% ± 0.1, holocellulose 85.9% ±0.7, hemicellulose 15.5% ±0.2, α-cellulose 70.4% ± 0.2, total lignin 9.4% ± 0.3 and crystallinity index, (Ic, 69.4%). Aliquots removed during mercerization were characterized. For example, the aliquot referring to 2h had the following properties: α-cellulose 81.6% (± 0.2), total lignin 3.2% (± 0.3) and crystallinity index (Ic) 75.5%. Analyses of scanning electron microscopy (SEM), length and average thickness (MorFi) showed increased roughness and fragments adhered to the fiber surface and a decrease in length and thickness throughout the mercerization. Untreated and treated fibers (2h) were subjected to acid hydrolysis (1:30 vol./M.H2SO4 24%, 80°C, 6h), in which the unreacted fibers were separated from the liquor via filtration, and then characterized by X-ray diffraction, MEV, MorFi; liquor sugars and decomposition products were analyzed via High Performance Liquid Chromatography (HPLC). The results of the acid hydrolysis with the mercerized fiber presented higher glucose production (cellulose fraction) and decreased xylose and arabinose contents (hemicellulosic fraction). The maximum glucose content obtained was 2.68 g.L-1, while for the hydrolysis with the untreated fiber the maximum was 1.3 g.L-1, in which there was low-scale formation of decomposition products (HMF and furfural). No mercerized and mercerized fibers were also subjected to enzymatic hydrolysis (48h, commercial cellulase enzymes-Accellerase 1500, 0.5mL / g). Aliquots of the unreacted pulps and liquor were extracted during the reaction, and then characterized as described for acid hydrolysis. Microscopies showed that there was an increase in roughness and in the opening of fiber bundles in the mercerized fibers. The crystallinity indexes showed an initial increase and a subsequent decrease indicating hydrolysis of the non-crystalline fraction of the cellulose followed by the crystalline fraction. The length and average thickness of the fibers decreased, which was more accentuated in the hydrolysis with the mercerized fiber and more intense as for the thickness. There was formation of glucose and xylose and there was no formation of decomposition products as occurred in acid hydrolysis. For the untreated fiber, a maximum glucose of 12.0 gL-1 and 2.30 gL-1 of xylose was obtained, whereas the mercerized fiber presented a maximum of 17.5 gL-1, 1.36 gL-1 of glucose and xylose respectively, indicating a 45% increase in glucose and a 56% decrease in xylose. This investigation of the effect of mercerization on the saccharification of the curauá fiber provided important information for further studies, as well as indicating that the curauá can later become a source of second generation ethanol production. Keywords: Curauá Fiber. Mercerization. Acid and Enzymatic Hydrolysis. Glucose.

O cenário energético mundial traz à tona a necessidade da busca por fontes renováveis que contribuam de maneira positiva para a diminuição de emissões de gases nocivos, como o CO2. Neste contexto estudos como o presente constituem importante contribuição para o melhor entendimento destas questões ambientais, para tanto o mesmo teve como objetivo avaliar o efeito de pré-tratamento com solução alcalina aquosa (mercerização, NaOH 20%, 20 g.L-1, temperatura ambiente, 5h) sobre a sacarificação, via hidrólise ácida e enzimática de fibras lignocelulósicas de curauá (Teor de: umidade 8,2% ±0,2, cinzas 2,0% ±0,1, holocelulose 85,9% ±0,7, hemiceluloses 15,5% ±0,2, α-celulose 70,4% ±0,2, lignina total de 9,4% ±0,3 e índice de cristalinidade (Ic) 69,4%. Alíquotas retiradas durante a mercerização foram caracterizadas, por exemplo, a alíquota referente a 2h apresentou as seguintes propriedades: α-celulose 81,6% ±0,2, lignina total 3,2% ±0,3 e índice de cristalinidade (Ic) 75,5%. Análises de microscopia eletrônica de varredura (MEV), comprimento e espessura médio (MorFi) mostraram, ao longo da mercerização, aumento de rugosidade e fragmentos aderidos a superfície da fibra, e diminuição de comprimento e espessura. Fibras não tratadas e tratadas (2h) foram submetidas a hidrólise ácida (1:30 vol./massa, H2SO4 a 24%, 80°C, 6h), onde as fibras não reagidas foram separadas do licor via filtração, e caracterizadas por difração de raios X, MEV, MorFi, e os açúcares do licor e produtos de decomposição foram analisados via Cromatografia líquida de alta eficiência (CLAE). Os resultados da hidrólise ácida com a fibra mercerizada, apresentaram maior produção de glicose (fração celulósica) e diminuição dos teores de xilose e arabinose, (fração hemicelulósica). A glicose atingiu teor máximo de 2,68 g.L-1, no entanto para a hidrólise com a fibra não tratada atingiu um máximo de 1,3 g.L-1, com formação em baixa escala de produtos de decomposição (HMF e furfural). Fibras de partida e mercerizada também foram submetidas a hidrólise enzimática (48h, enzimas celulase comercial-Accellerase 1500, 0,5mL/g). Alíquotas das polpas não reagidas e licor foram extraídas durante a reação, e caracterizadas conforme descrito para hidrólise ácida. Microscopias mostraram que houve aumento da rugosidade e da abertura dos feixes de fibras nas fibras mercerizadas. Os valores de Ic apresentaram aumento inicial e posterior queda indicando hidrólise da fração não cristalina da celulose seguida da fração cristalina. O comprimento e espessura médio das fibras, sofreram diminuição, sendo mais acentuada na hidrólise com a fibra mercerizada e mais intenso para a espessura. Houve formação de glicose e xilose e não houve formação de produtos de decomposição como ocorrido na hidrólise ácida. A fibra não tratada apresentou um máximo de 12,0 g.L-1 de glicose e 2,30 g.L-1 de xilose, já a fibra mercerizada apresentou máximos de 17,5 g.L-1, 1,36 g.L-1 de glicose e xilose respectivamente, indicando aumento de 45% de glicose e diminuição de 56% de xilose. Esta investigação do efeito da mercerização sobre a sacarificação da fibra de curauá forneceu informações importantes para o aprofundamento deste estudo, assim como indicou que o curauá pode posteriormente se tornar fonte de produção de etanol de segunda geração. / The global energy scenario brings to light the need for the search for renewable sources that contribute positively to the reduction of harmful gases emission, such as CO2. In this context, studies such as the one herein constitute an important contribution to a better understanding of these environmental issues. The purpose of this study was to evaluate the effect of the alkaline pre-treatment (mercerization, NaOH 20%, 20 g.L-1, room temperature, 5h) on saccharification, via acid and enzymatic hydrolysis of curauá lignocellulosic fibers (moisture content 8.2% ± 0.2, ashes 2.0% ± 0.1, holocellulose 85.9% ±0.7, hemicellulose 15.5% ±0.2, α-cellulose 70.4% ± 0.2, total lignin 9.4% ± 0.3 and crystallinity index, (Ic, 69.4%). Aliquots removed during mercerization were characterized. For example, the aliquot referring to 2h had the following properties: α-cellulose 81.6% (± 0.2), total lignin 3.2% (± 0.3) and crystallinity index (Ic) 75.5%. Analyses of scanning electron microscopy (SEM), length and average thickness (MorFi) showed increased roughness and fragments adhered to the fiber surface and a decrease in length and thickness throughout the mercerization. Untreated and treated fibers (2h) were subjected to acid hydrolysis (1:30 vol./M.H2SO4 24%, 80°C, 6h), in which the unreacted fibers were separated from the liquor via filtration, and then characterized by X-ray diffraction, MEV, MorFi; liquor sugars and decomposition products were analyzed via High Performance Liquid Chromatography (HPLC). The results of the acid hydrolysis with the mercerized fiber presented higher glucose production (cellulose fraction) and decreased xylose and arabinose contents (hemicellulosic fraction). The maximum glucose content obtained was 2.68 g.L-1, while for the hydrolysis with the untreated fiber the maximum was 1.3 g.L-1, in which there was low-scale formation of decomposition products (HMF and furfural). No mercerized and mercerized fibers were also subjected to enzymatic hydrolysis (48h, commercial cellulase enzymes-Accellerase 1500, 0.5mL / g). Aliquots of the unreacted pulps and liquor were extracted during the reaction, and then characterized as described for acid hydrolysis. Microscopies showed that there was an increase in roughness and in the opening of fiber bundles in the mercerized fibers. The crystallinity indexes showed an initial increase and a subsequent decrease indicating hydrolysis of the non-crystalline fraction of the cellulose followed by the crystalline fraction. The length and average thickness of the fibers decreased, which was more accentuated in the hydrolysis with the mercerized fiber and more intense as for the thickness. There was formation of glucose and xylose and there was no formation of decomposition products as occurred in acid hydrolysis. For the untreated fiber, a maximum glucose of 12.0 gL-1 and 2.30 gL-1 of xylose was obtained, whereas the mercerized fiber presented a maximum of 17.5 gL-1, 1.36 gL-1 of glucose and xylose respectively, indicating a 45% increase in glucose and a 56% decrease in xylose. This investigation of the effect of mercerization on the saccharification of the curauá fiber provided important information for further studies, as well as indicating that the curauá can later become a source of second generation ethanol production. Keywords: Curauá Fiber. Mercerization. Acid and Enzymatic Hydrolysis. Glucose.

Puisque cette thèse présente deux études indépendantes sur les nanocristaux de cellulose, le résumé a été divisé en deux sections qui font référence aux chapitres II et III, respectivement.Investigation morphologique et structurelle des nanocristaux de cellulose I et II préparés par hydrolyse à l'acide sulfuriqueLe but du travail de recherche présenté dans le chapitre II était de produire, de caractériser et de comparer les CNC obtenus à partir de la pâte de bois d'eucalyptus en utilisant trois méthodes différentes: i) l'hydrolyse classique à l'acide sulfurique (CN-I), ii) l'hydrolyse acide de la cellulose précédemment mercerisée par traitement alcalin (MCN-II), et iii) la solubilisation de la cellulose dans l'acide sulfurique et la recristallisation subséquente dans l'eau (RCN-II). Les trois types de CNC préparés présentent des morphologies et des structures cristallines différentes. Lorsque les conditions d'hydrolyse acide sont mises en place de telle sorte que les domaines cristallins dans la pâte de bois initial et la cellulose mercerisée (WP et MWP, respectivement) sont préservés (60 wt% H2SO4, 45°C, 50 min), les nanocristaux résultants conservent la nature fibrillaire des fibres d’origine (c'est-à-dire que l'axe de la chaîne est parallèle au grand axe des particules aciculaires) et leur type allomorphe initial (I pour WP et II pour la MWP). Dans les deux cas, les particules sont principalement composées de quelques cristallites élémentaires liées latéralement. Les nanocristaux unitaires dans les CNC préparés à partir de cellulose mercerisée (MCN-II) sont plus courts, mais plus larges que ceux préparés à partir des fibres de cellulose I (CN-I). Si des conditions plus sévères sont considérées (64 wt% H2SO4, 40°C, 20 min), ce qui entraîne la dépolymérisation et la dissolution de la cellulose native, les chaînes courtes recristallisent en rubans de Cell-II lors de la régénération dans l'eau à température ambiante. Dans ces rubans tortueux, l'axe de la chaîne serait perpendiculaire au grand axe du nanocristal et parallèle à son plan basal.La structure moléculaire et cristalline unique des nano-rubans implique qu'un nombre plus élevé d'extrémités de chaîne réductrice sont situées à la surface des particules, ce qui peut être important pour des modifications chimiques subséquentes et pour de potentielles applications spécifiques telles que la biodétection et la bio-imagerie. Donc, cette étude permet de mieux comprendre la structure cristalline et la morphologie de la CNC obtenue par régénération à l'acide sulfurique.Propriétés mécaniques de nanocomposites de caoutchouc naturel renforcé avec des nanocristaux de cellulose à facteur de forme élevé extraits de la coque de sojaDans cette étude, les CNCs ont été isolés des coques de soja à partir d’un traitement par hydrolyse avec de l'acide sulfurique. Ces CNCSH ont été utilisés comme phase de renfort dans une matrice NR par casting à différents taux de charge, à savoir 1, 2.5 et 5% en poids. Les effets des CNCSH sur la structure ainsi que sur les propriétés thermiques et mécaniques du NR ont été étudiés. Par exemple, en ajoutant seulement 2,5% en poids de CNC, le module de conservation en traction du nanocomposite à 25 °C est environ 21 fois plus élevé que celui de la matrice NR non chargée. Cet effet de renfort est supérieur à celui observé pour les CNCs extraits d'autres sources. Il peut être attribué non seulement au facteur de forme élevé de ces CNCs, mais aussi à la rigidité du réseau percolant de nanoparticules formé au sein de la matrice polymère. De plus, il a été constaté que la sédimentation des CNC pendant la mise en œuvre du film nanocomposite par casting joue un rôle crucial sur les propriétés mécaniques. Une contribution importante de ce travail est de mettre en évidence l'importance de la sédimentation des CNCs, pendant l'étape d'évaporation sur les propriétés mécaniques des nanocomposites, ce qui est rarement mentionné dans la littérature. / Since this thesis presents two independent studies on cellulose nanocrystals, the abstract was divided in two sections referring to chapters II and III, respectively.Comprehensive morphological and structural investigation of cellulose I and II nanocrystals prepared by sulfuric acid hydrolysisCellulose nanocrystals (CNCs) were produced from eucalyptus wood pulp using three different methods: i) classical sulfuric acid hydrolysis (CN-I), ii) acid hydrolysis of cellulose previously mercerized by alkaline treatment (MCN-II), and iii) solubilization of cellulose in sulfuric acid and subsequent recrystallization in water (RCN-II). The three types of CNCs exhibited different morphologies and crystal structures that were characterized using complementary imaging, diffraction and spectroscopic techniques. CN-I corresponded to the type I allomorph of cellulose while MCN-II and RCN-II corresponded to cellulose II. CN-I and MCN-II CNCs were acicular particles composed of a few laterally-bound elementary crystallites. In both cases, the cellulose chains were oriented parallel to the long axis of the particle, although they were parallel in CN-I and antiparallel in MCN-II. RCN-II particles exhibited a slightly tortuous ribbon-like shape and it was shown that the chains lay perpendicular to the particle long axis and parallel to their basal plane. The unique molecular and crystal structure of the RCN-II particles implies that a higher number of reducing chain ends are located at the surface of the particles, which may be important for subsequent chemical modification. While other authors have described nanoparticles prepared by regeneration of short-chain cellulose solutions, no detailed description was proposed in terms of particle morphology, crystal structure and chain orientation. Was provide such a description in the present document.Mechanical properties of natural rubber nanocomposites reinforced with high aspect ratio cellulose nanocrystals isolated from soy hullsCellulose nanocrystals (CNCs) were isolated from soy hulls by sulfuric acid hydrolysis. The resulting CNCs were characterized using TEM, AFM, WAXS, elemental analysis and TGA. The CNCs have a high crystallinity, specific surface area and aspect ratio. The aspect ratio (around 100) is the largest ever reported in the literature for a plant cellulose source. These CNCs were used as a reinforcing phase to prepare nanocomposite films by casting/evaporation using natural rubber as matrix. The mechanical properties were studied in both the linear and non-linear ranges. The reinforcing effect was higher than the one observed for CNCs extracted from other sources. It may be assigned not only to the high aspect ratio of these CNCs but also to the stiffness of the percolating nanoparticle network formed within the polymer matrix. Moreover, the sedimentation of CNCs during the evaporation step was found to play a crucial role on the mechanical properties.

Carboxymethyl cellulose (CMC) is produced commercially in a two-stage process consisting of a mercerization stage, where the pulp is treated with alkali in a water alcohol solution, followed by an etherification stage in which monochloroacetic acid is added to the pulp slurry. In this thesis an extended mercerization stage of a spruce ether pulp was investigated where the parameters studied were the ratio of cellulose I and II, concentration of alkali, temperature and retention time. The influence of the mercerization stage conditions on the etherification stage, were evaluated as the degree of substitution (DS) of the resulting CMC and the filterability of CMC dissolved in water at a concentration of 1%. The DS results suggested that the NaOH concentration in the mercerization stage was the most important of the parameters studied. When the NaOH concentration in the mercerization step was low (9%), a high cellulose II content in the pulp used was found to have no negative impact on the DS of the resulting CMC compared with pulps with only cellulose I. However, when the NaOH concentration was high (27.5%), pulps with high content of cellulose II showed a lower reactivity than those with only cellulose I with respect to the DS of the CMC obtained after a given charge of NaMCA. The results obtained from the filtration ability study of CMC water solutions suggested that both the amount of cellulose II in the original pulp and the temperature had a negative influence on the filtration ability whereas the NaOH concentration in the mercerization stage had a positive influence. The filtration ability was assumed to be influenced highly by the presence of poorly reacted cellulose segments. A retention time between 1-48 h in the mercerization stage had no effect on either the DS or the filtration ability of the CMC. Using NIR FT Raman spectroscopy molecular structures of CMC and its gel fraction were analyzed with respect to the conditions used in the extended mercerization stage. Here it was found that the alkaline concentration had a very strong influence on the following etherification reaction. FT Raman spectra of CMC samples and their gel fractions prepared with low NaOH concentrations (9%) in the mercerization stage indicated an incomplete transformation of cellulose to Na-cellulose before carboxymethylation to CMC. Low average DS values of the CMC, i.e. between 0.42 and 0.50, were yielded. Such CMC dissolved in water caused very thick and semi solid gum-like gels, probably due to an uneven distribution of substituting groups along the cellulose backbone. FT Raman spectra of CMC mercerized with alkaline concentrations at 18.25 and 27.5% in the mercerization stage indicated, however, that all of the cellulose molecules were totally transferred to CMC of high DS, i.e. between 0.88 and 1.05. When dissolved in water such CMC caused gels when they were prepared from ether pulp with a high fraction of cellulose II.

Recovery of caustic solution from mercerizing wastewaters of a denim producing textile mill was performed by using membrane technologies. A comprehensive characterization study was conducted to develop the treatment scheme. Highly alkaline and warm condition of wastewater has induced using membranes made of Polyethersulfone (PES). Conducted pretreatment applications such as microfiltration, flocculation and centrifuge have been found unsuccessful to improve further treatment capacities. Hence recovery studies which are UF, NF and pilot-system membrane applications have been implemented without any pretreatment. Effects of TMP and CFV on UF and NF processes were investigated and optimum operating conditions have been defined. UF has accomplished almost complete caustic solution recovery beside high COD and color retentions 84 % and 94 % under 4.03 bar TMP and 0.79 m/s CFV at 20&plusmn / 2 0C. Because of higher capacity of NF membranes also in acid and alkali recovery area, NF process has been studied in addition to UF. NF has also provided nearly complete NaOH recoveries with 92 % COD and 98 % color retentions under 4.03 bar TMP and 0.79 m/s CFV at 20&plusmn / 2 0C. Furthermore temperature effect was also studies by repeating the same processes at 40&plusmn / 2 0C considering the real operating conditions. Temperature has affected the system performance positively with regards to flux increases with insignificant loses in recovery and retention capacities. Lastly a pilot plant study has been conducted and it was found successful despite some operational difficulties due to high inorganic content and temperature of wastewater.

[pt] O uso de fibras naturais como reforço em materiais compósitos vem ganhando destaque em diversos setores industriais, principalmente devido às restrições ambientais, que impõem requisitos legais relacionados ao uso de produtos sintéticos, visando a reutilização e substituição de matérias-primas não renováveis. As fibras naturais são biodegradáveis e apresentam propriedades e morfologia muito atraentes. Dentre elas, novas categorias de fibras estão sendo investigadas, como é o caso da fibra de piaçava, oriunda da palmeira Attalea funifera Martius. Sua fibra longa, lisa, resistente e de textura impermeável apresenta propriedades mecânicas semelhantes às fibras de coco, amplamente utilizadas pela indústria. Um dos desafios no uso dessas fibras como reforço em materiais compósitos é melhorar a interação entre a fibra e matriz polimérica, uma vez que as fibras naturais são hidrofílicas e as matrizes são hidrofóbicas, desenvolvendo interfaces fracas. Em alguns casos, tratamentos químicos específicos (por exemplo, o método de mercerização) podem melhorar esta interface, removendo parte da lignina e celulose de fibras, tornando a superfície rugosa compatível com a matriz polimérica. Neste trabalho, vários parâmetros foram avaliados através de MEV, microCT, FTIR e microscopia de varredura laser confocal (CLSM) da fibra de piassava antes e depois da mercerização em solução aquosa de NaOH a 10 por cento em peso. As análises permitiram avaliar que o tratamento alcalino promoveu uma limpeza profunda na superfície das fibras, removendo protrusões de sílicas do vegetal, com aumento do índice de cristalinidade, além de remover frações de lignina, hemicelulose, celulose, ceras e outras impurezas, causando desfibrilação do tecido. Também houve aumento da área superficial, rugosidade e porosidade das fibras após o tratamento químico. / [en] The use of natural fibers to reinforce composite materials has been gaining considerable notice in many industrial fields. This is mainly due to environmental restrictions, which impose legal requirements related to the use of synthetic products, aiming at the reuse and replacement of non-renewable raw materials, which cause less damage to the environment. Natural fibers are biodegradable, renewable resources with very attractive properties and morphology. Among them, new categories of fibers are being investigated, as the case of piassava fiber, from the palm of Attalea funifera Martius. Its long, smooth, sturdy and waterproof textured fiber has similar mechanical properties to the coconut fibers widely used in the industry. One of the challenges in using these fibers as reinforcement in composite materials is to improve the interaction between fiber and polymer matrix, since the natural fibers are hydrophilic and the matrices are hydrophobic, developing weak interfaces. In some cases, specific chemical treatments (eg the mercerization method) can improve this interface by removing part of the lignin and cellulose from fibers, making the rough surface compatible with the polymer matrix. In this work, several parameters were evaluated through MEV, microCT, FTIR and confocal laser scanning microscopy (CLSM) of piassava fibers, before and after mercerization with 10 percent by weight aqueous NaOH solution. The analyzes allowed to evaluate that the alkaline treatment promoted a deep cleaning on the surface of the fibers, removing protrusions of silica from the vegetable, besides removing lignin, hemicellulose, cellulose, waxes and other impurities, causing tissue defibrillation. Also, it was able to increase the surface area, roughness and porosity of the fibers after chemical treatment.

No description available.

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.