Caracterització de la fibra Henequén per ser utilitzada com a reforç en materials compostos

La generació massiva de residus plàstics constitueix actualment un gravíssim problemamediambiental. Una de les estratègies desenvolupades per pal•liar-lo consisteix en el reciclatge delsresidus plàstics i la seva posterior utilització en diferents aplicacions en sectors com la construcció.La incorporació de reforços en el material reciclat millora les seves propietats mecàniques. Unpossible reforç són les fibres d'origen vegetal o biofibres, que, a més de millorar tècnicament elproducte, presenten avantatges econòmics i ambientals. Les biofibres són un bon competidor contrales fibres reforçants tradicionals com la fibra de vidre ja que presenten un baix cost, baixa densitat i,per tant, bones propietats específiques, menys equip de processament, alta suavitat,biodegradabilitat i són ecològicament sostenibles, ja que es produeixen a partir de recursos naturals.En aquest treball es fan servir fibres provinents de la pinya de Henequén. Aquestes fibres són unsubproducte del procés per a l’obtenció del licor de Henequén i es volen fer servir com a reforç enmaterials compostos.Ja s’han fet estudis sobre la fibra de Henequén que creix a Mèxic. Aquest projecte s’emmarca dinsuna col•laboració entre la Universitat de Girona i la Universitat Cubana de Holguin, per tal d’estudiarla fibra de Henequén que creix a Cuba

Instrumentació i anàlisi de dades d'assaigs de bigues de formigó armades amb barres de FRP

Estudi experimental del comportament de bigues de formigó armades amb barres de materials compostos de matriu polimèrica (FRP)

Research on the suitability of organosolv semi-chemical triticale fibers as reinforcement for recycled hdpe composites

The main objective of this research was to study the feasibility of incorporating organosolv semi-chemical triticale fibers as the reinforcing element in recycled high density polyethylene (HDPE). In the first step, triticale fibers were characterized in terms of chemical composition and compared with other biomass species (wheat, rye, softwood, and hardwood). Then, organosolv semi-chemical triticale fibers were prepared by the ethanolamine process. These fibers were characterized in terms of its yield, kappa number, fiber length/diameter ratio, fines, and viscosity; the obtained results were compared with those of eucalypt kraft pulp. In the second step, the prepared fibers were examined as a reinforcing element for recycled HDPE composites. Coupled and non-coupled HDPE composites were prepared and tested for tensile properties. Results showed that with the addition of the coupling agent maleated polyethylene (MAPE), the tensile properties of composites were significantly improved, as compared to non-coupled samples and the plain matrix. Furthermore, the influence of MAPE on the interfacial shear strength (IFSS) was studied. The contributions of both fibers and matrix to the composite strength were also studied. This was possible by the use of a numerical iterative method based on the Bowyer-Bader and Kelly-Tyson equations

Instrumentació i anàlisi de dades d'assaigs de bigues de formigó armades amb barres de FRP

Estudi experimental del comportament de bigues de formigó armades amb barres de materials compostos de matriu polimèrica (FRP)

Consumo e dinâmica ruminal da fibra em detergente neutro em bovinos em pastejo no período das águas recebendo suplementação com nitrogênio não-proteico e/ou proteína verdadeira

Objetivou-se avaliar o efeito de diferentes relações entre proteína verdadeira e nitrogênio não-proteico sobre o consumo e a dinâmica de trânsito e degradação ruminal da fibra em detergente neutro (FDN) da forragem em bovinos em pastejo durante o período das águas. Foram utilizados cinco novilhos mestiços Holandês × Zebu, castrados, com peso corporal inicial de 335±35 kg fistulados no rúmen e no abomaso. Os tratamentos foram: controle (somente pasto); e suplementos com ureia; com 2/3 de compostos nitrogenados oriundos da ureia e 1/3 de compostos nitrogenados oriundos da albumina; com 1/3 de compostos nitrogenados oriundos da ureia e 2/3 de compostos nitrogenados oriundos da albumina; e com albumina. Foram fornecidos 200 g/dia de proteína bruta (PB) a partir dos suplementos. O experimento foi conduzido segundo delineamento em quadrado latino 5 × 5, com cinco períodos experimentais de 15 dias. Não foram observados efeitos da suplementação sobre o consumo voluntário, com exceção do consumo de PB, que aumentou com a suplementação. A substituição da ureia por albumina nos suplementos teve efeito linear sobre o consumo de PB. Os consumos dos demais componentes da dieta não foram afetados pela composição dos suplementos. Nenhum efeito foi observado sobre a taxa de passagem ruminal de compostos fibrosos. O fornecimento de suplementos ampliou, em média, a estimativa da taxa comum de latência e degradação da FDN. Contudo, não houve efeito da alteração na composição dos suplementos sobre este parâmetro. A suplementação de bovinos com fontes de compostos nitrogenados degradáveis no rúmen proteicos ou não-proteicos durante o período das águas não afeta o consumo voluntário de pasto.

Análise das influências do branqueamento na retenção de caulim e nas propriedades do papel

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Reciclagem de poliestireno expandido: compósito com fibras de algodão para a confecção de placas de circuito impresso

In this work polymeric composites reinforced with cotton fibers, from the textile industry, were developed in order to manufacture printed circuit boards. It was used expanded polystyrene (EPS) as a thermoplastic matrix by melting it. For the obtention of 10% and 15% of fiber volume fraction in cotton fibers composites, it was used wasted cotton fibers as an incentive of recycling and reusing of the domestic and industrial wastes as well as for Expanded Polystyrene(EPS). The mechanical properties of the composites were evaluated by tensile and flexural strength from standardized test methods. Composites were characterized by a Scanning Electron Microscopy (SEM), Thermogravimetry (TG/DTG), Differential Scanning Calorimetry (DSC) and dielectric analysis. The analysis of the results showed that fiber in the composite directly influenced in the thermal and mechanical properties

Estudo da superfície de fibras de carbono após tratamento de implantação iônica por imersão em plasma (3IP)

In this work, plasma immersion ion implantation (PIII) treatments of carbon fibers (CFs) were performed in order to induce modifications of chemical and physical properties of the CF surface aimed to improve the performance of thermoplastic composite. The samples to be treated were immersed in nitrogen or air glow discharge plasma and pulsed at −3.0 kV for 2.0, 5.0, 10.0, and 15.0 min. After PIII processing, the specimens were characterized by atomic force microscopy (AFM), scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). After CFs treatments, the CF/Polypropylene (PP) composites were produced by hot pressing method. Surface morphology of as-received CFs exhibited some scratches aligned along the fibers due to the fiber manufacturing process. After both treatments, these features became deeper, and also, a number of small particles nonuniformly distributed on the fiber surface can be observed. These particles are product of CF surface sputtering during the PIII treatment, which removes the epoxy layer that covers as-received samples. AFM analyses of CF samples treated with nitrogen depicted a large increase of the surface roughness (Rrms value approximately six times higher than that of the untreated sample). The increase of the roughness was also observed for samples treated by air PIII. Raman spectra of all samples presented the characteristic D- and G-bands at approximately 1355 and 1582 cm−1, respectively. Analysis of the surface chemical composition provided by the XPS showed that nitrogen and oxygen were incorporated onto the surface. The polar radicals formed on the surface lead to increasing of the CF surface energy. Both the modification of surface roughness and the surface oxidation contributed for the enhancement of CF adhesion to the polymeric matrix. These features were confirmed ... (Complete abstract click electronic access below)

Incorporação da apatita na superfície da liga Ti30ta empregando tratamento alcalino associado à eletrofiação de fibras de PCL

Pós-graduação em Engenharia Mecânica - FEG

Compósitos de nanocelulose / PHBV: manta microfibrilica por eletrofiação

Pós-graduação em Engenharia Mecânica - FEG

Otimização do processo de soldagem por resistência elétrica em compósitos PEI/fibras contínuas para aplicações aeronáuticas

Pós-graduação em Engenharia Mecânica - FEG

Obtenção e caracterização de compósitos de benzoxazina/fibra de carbono

Pós-graduação em Engenharia Mecânica - FEG

Experimentação em química de compostos organometálicos: preparação do cloreto de dicarbonilciclopentadienilferro(II)

In this work, we describe a new method for obtaining [Fe(CO)2[(eta5-C5H5)Cl] employing simple techniques and low-cost reagents. It is worth mentioning that this method is faster than others reported in the literature. It was applied in laboratory classes for undergraduate students, exploring different concepts in organometallic chemistry and discussing the steps involved in the synthetic route.

Determinação do perfil de compostos voláteis e avaliação do sabor e aroma de bebidas produzidas a partir da erva-mate (Ilex paraguariensis)

Volatile compounds from green and roasted yerba mate were analyzed by gas chromatography/mass spectrometry and the flavor profile from yerba mate beverages was determined by descriptive quantitative analyses. The main compounds tentatively identified in green mate were linalool, alpha-terpineol and trans-linalool oxide and in roasted mate were (E,Z)-2,4-heptadienal isomers and 5-methylfurfural. Green mate infusion was qualified as having bitter taste and aroma as well as green grass aroma while roasted mate was defined as having a smooth, slightly burnt aroma. The relationship between the tentatively identified compounds and flavor must be determined by olfatometric analysis.

Carotenóides: propriedades, aplicações e biotransformação para formação de compostos de aroma

Carotenoids are widely distributed in nature, providing yellow, orange or red color in a great number of vegetables, microorganisms and in some animals. Carotenoids act as biological antioxidants and seem to play an important role in human health by protecting cells and tissues from the damaging effects of free radicals and singlet oxygen. Several authors describe the oxidative cleavage of carotenoids in flavor compounds as occuring through chemical or photochemical degradations or through biotechnological processes. Biotransformation of carotenoids seems to be a reasonable alternative to produce flavor compounds since these compounds are considered 'natural' ingredients. In this work we describe the properties of some carotenoids, as well as biotechnological approaches to obtain its oxyfunctionalized derivatives.