Cellulose and silica were obtained from rice husk by a multi-step procedure. Three different strategies including different alkaline and bleaching steps were evaluated by Fourier transform infrared spectroscopy (FTIR) in order to choose the sequence that combines the better conditions to obtain both subproducts simultaneously. The effects of the different steps on the structure and morphology of original material treated by the selected procedure were analyzed by X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The results suggest that it is possible to obtain both by-products with a simple procedure, giving an added value to this waste. Experimental MaterialsRH was obtained as a residue of rice industries of Entre Ríos (Argentina). Rice husk was extensively washed with distilled water to remove dust and other impurities. This operation was carried out several times at room temperature under vigorous stirring. After successive washings, rice husk was dried in an air-circulated oven at 80±1 o C and then crushed for 10 min using a ball mill (Pulverisette 7, Fritsh, Alemania). The final moisture content of the material was
Conversión de un microscopio de polarización en un microscopio de matriz de Mueller. Aplicación a la medida de fibras textiles. ABSTRACT:This work reports the conversion of a commercial polarization microscope (Zeiss Jenaval) into an automatized Mueller matrix microscope. A Mueller matrix measurement provides the value of all the optical properties of a specimen (linear dichroism, linear birefringence, circular dichroism etc.) at a specific wavelength. In contrast to traditional polarization microscopes, which use white light and crossed polarizers to generate colored interference patterns that are analyzed by the microscope user and give only semi-quantitative results, here we demonstrate that it is possible to convert a polarization microscope into a Mueller microscope by only adding two motorized rotating compensators into the optical path without altering the optics or other opto-mechanical elements of the microscope. To our knowledge this is the most compact, fast and handy Mueller microscope ever developed. The performance of this new Mueller matrix microscope is illustrated with some birefringence measurements on textile fibers.Key words: microscopy, polarimetry, Mueller matrix, birefringence. RESUMEN:Este trabajo describe la conversión de un microscopio de polarización comercial (Zeiss Jenaval) en un microscopio de matriz de Mueller automatizado. Una medida de la matriz de Mueller proporciona todas las propiedades ópticas de una muestra (dicroísmo lineal, birrefringencia lineal, dicroísmo circular, etc) para una longitud de onda dada. Los microscopios de polarización tradicionales usan luz blanca y polarizadores cruzados para generar un patrón de colores interferencia que debe ser interpretado por el usuario del microscopio y proporciona resultados sólo semi-cuantitativos. En este trabajo demostramos que añadiendo dos compensadores rotatorios actuados por sendos motores es posible convertir un microscopio de polarización en un microscopio de matriz de Mueller sin alterar la óptica u otros elementos opto-mecánicos del microscopio. Creemos que este es el microscopio de matriz de Mueller más compacto, rápido y práctico que se ha desarrollado. El funcionamiento de este microscopio se demuestra con algunas medidas de birrefringencia en fibras textiles.Palabras clave: microscopía, polarimetría, matriz de Mueller, birrefringencia.
The aim of this work was to evaluate the influence of two kinds of bio- nano-reinforcements, cellulose nanocrystals (CNCs) and bacterial cellulose (BC), on the properties of castor oil-based waterborne polyurethane (WBPU) films. CNCs were obtained by the acidolysis of microcrystalline cellulose, while BC was produced from Komagataeibacter medellinensis. A WBPU/BC composite was prepared by the impregnation of a wet BC membrane and further drying, while the WBPU/CNC composite was obtained by casting. The nanoreinforcement was adequately dispersed in the polymer using any of the preparation methods, obtaining optically transparent compounds. Thermal gravimetric analysis, Fourier-transform infrared spectroscopy, field emission scanning electron microscopy, dynamical mechanical analysis, differential scanning calorimetry, contact angle, and water absorption tests were carried out to analyze the chemical, physical, and thermal properties, as well as the morphology of nanocelluloses and composites. The incorporation of nanoreinforcements into the formulation increased the storage modulus above the glass transition temperature of the polymer. The thermal stability of the BC-reinforced composites was slightly higher than that of the CNC composites. In addition, BC allowed maintaining the structural integrity of the composites films, when they were immersed in water. The results were related to the relatively high thermal stability and the particular three-dimensional interconnected reticular morphology of BC.
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