Abstract Wood–cement composites are interesting materials for structural and isolation purposes. Dimensional stability, economic factors and resistance to environmental degradation are features that can be exploited for housing... more
Abstract Wood–cement composites are interesting materials for structural and isolation purposes. Dimensional stability, economic factors and resistance to environmental degradation are features that can be exploited for housing components. The main inconvenient affecting its manufacture is the incompatibility between wood and cement, caused by setting inhibitory substances present in woods. Wood treatments are multivariable processes required for the appropriate cement setting reaction on wood surfaces. Treatment conditions affect the mechanical properties of the resulting composites. This work evaluates the simultaneous influence of the variables ruling three widely used wood treatments – water extraction, degradation by alkaline hydrolysis and retention of inhibitory substances – on the mechanical properties of wood fibers and of resulting wood–cement composites. Populus Euroamericana wood fibers and Portland cement were selected as case materials. The alkaline hydrolysis was found as the most effective treatment for the suppression of inhibitory substances and the highest decrease on mechanical properties of resulting composites. Empirical relationships describing the dependence of the compressive modulus of elasticity and compression strength of wood–cement composites with the wood treatment variables are presented.
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Abstract Wood–cement composites are interesting materials for structural and isolation purposes. Dimensional stability, economic factors and resistance to environmental degradation are features that can be exploited for housing... more
Abstract Wood–cement composites are interesting materials for structural and isolation purposes. Dimensional stability, economic factors and resistance to environmental degradation are features that can be exploited for housing components. The main inconvenient affecting its manufacture is the incompatibility between wood and cement, caused by setting inhibitory substances present in woods. Wood treatments are multivariable processes required for the appropriate cement setting reaction on wood surfaces. Treatment conditions affect the mechanical properties of the resulting composites. This work evaluates the simultaneous influence of the variables ruling three widely used wood treatments – water extraction, degradation by alkaline hydrolysis and retention of inhibitory substances – on the mechanical properties of wood fibers and of resulting wood–cement composites. Populus Euroamericana wood fibers and Portland cement were selected as case materials. The alkaline hydrolysis was found as the most effective treatment for the suppression of inhibitory substances and the highest decrease on mechanical properties of resulting composites. Empirical relationships describing the dependence of the compressive modulus of elasticity and compression strength of wood–cement composites with the wood treatment variables are presented.
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Argentina es un país bicontinental y marítimo; bicontinental porque comprende parte del continente sudamericano y parte del continente antártico, y marítimo porque posee legítimos derechos soberanos sobre una extensa superficie marítima... more
Argentina es un país bicontinental y marítimo; bicontinental porque comprende parte del continente sudamericano y parte del continente antártico, y marítimo porque posee legítimos derechos soberanos sobre una extensa superficie marítima del Atlántico Sudoccidental. Las Islas Malvinas constituyen el primer eslabón emergente de la prolongación argentina desde el continente sudamericano hacia el continente antártico, por ello es clave su dominio. En 1982 la Argentina recuperó las Islas Malvinas luego de una prolongada usurpación por parte del Reino Unido de Gran Bretaña; la respuesta británica le impuso una guerra en la que durante 74 días fuerzas argentinas defendieron el territorio insular recuperado; 649 compatriotas fueron muertos en esos combates, de los cuales 54 son santafesinos. En estos 36 años de posguerra, los Veteranos de Guerra de Malvinas santafesinos han avanzado en su organización en centros diseminados por toda la geografía provincial, crearon una federación provincial...
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The pattern of alkaline impregnation of eucalyptus and pinewood under industrial conditions, i.e. presteaming and pressurized impregnation, is analyzed. Difference between the external and central zones in the log section for 8-year-old... more
The pattern of alkaline impregnation of eucalyptus and pinewood under industrial conditions, i.e. presteaming and pressurized impregnation, is analyzed. Difference between the external and central zones in the log section for 8-year-old Eucalyptus grandis and between earlywood and latewood of 25-year-old Pinus elliotti wood are examined. Profiles of content and concentration of alkali as well as profiles of liquid content and acetyl group content are experimentally determined. Results show that an impregnation front is established inside wood, which separates an intact inner zone from an external swollen zone. After presteaming, an important amount of liquid enters the wood under the pressurized impregnation. Wood is almost saturated by liquid. Earlywood of pine reaches a liquid content of 2.5g/g wood. It is suggested that, at the beginning of the impregnation, the liquid arrives at the core of a chip but the alkali does not. The described characteristics results useful to analyze t...
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Summary The impregnation pattern of alkali in fresh Cottonwood is analysed. Isothermal process, medium alkali-concentration, temperature below 100°C and tangential direction are considered. The degree of deacetylation in the wood is taken... more
Summary The impregnation pattern of alkali in fresh Cottonwood is analysed. Isothermal process, medium alkali-concentration, temperature below 100°C and tangential direction are considered. The degree of deacetylation in the wood is taken as an indicator of the whole chemical action of the alkali. Profiles of alkali concentration, alkali content, liquid content and acetyl content in the wood are experimentally determined. The results show that wood behaves rather like a glassy polymeric solid placed in contact with a solvent. An advancing boundary zone is established which separates an intact inner part from the outer swollen zone. Alkali concentration and acetyl groups content profiles can approximately be described by a model used to analyse the reaction of solids: the shrinking core model. The chemical reaction in the front is the controlling mechanism. The swelling of the cell walls together with the occupation of the hollow cavities of the wood by the liquor make it possible fo...
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Se estudia la relación estructura-toxicidad de los bifenilos policlorados (PCBs) con efecto dioxina con fines didácticos utilizando herramientas informáticas de fácil acceso. Analizando los datos de los 209 congéneres, mediante... more
Se estudia la relación estructura-toxicidad de los bifenilos policlorados (PCBs) con efecto dioxina con fines didácticos utilizando herramientas informáticas de fácil acceso. Analizando los datos de los 209 congéneres, mediante combinaciones de filtros se define el grupo de 12 PCBs con TEF, mostrando que el número y posición de las sustituciones con cloro cumplen las condiciones (orto ≤ 1, meta ≥ 2 y para = 2). El análisis mediante filtrado, tabla dinámica y diagramas, evidencia también que los PCBs con TEF tienen un ángulo diedro ≤ 56o y que a menor ángulo corresponde mayor TEF. Para visualización de los distintos casos se generaron imágenes tridimensionales de PCBs usando Gabedit, interfase gráfica libre, a partir de coordenadas de centros atómicos obtenidas mediante simulador diseñado en planilla de cálculo. Las metodologías aplicadas y los modelos obtenidos son simples, de fácil uso, muy útiles para educación y potencialmente aplicables a otras familias químicas.
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... Acknowledgements The authors thank to Dr. Armando Borgna for valuable discussions and criticism of the manuscript and to Elsa Grimaldi for the lin-TIME = 30 mln Ο Experimental data Ο Calculated points 10 Fig. 6. Acetyl content after... more
... Acknowledgements The authors thank to Dr. Armando Borgna for valuable discussions and criticism of the manuscript and to Elsa Grimaldi for the lin-TIME = 30 mln Ο Experimental data Ο Calculated points 10 Fig. 6. Acetyl content after 30 min treatment vs. ...
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Se informan logros alcanzados en la incorporación de TICs de visualización y modelado molecular en el inicio de carreras de grado de la Facultad de Ingeniería Química, UNL. A partir de 2008 desarrollamos una serie de actividades:... more
Se informan logros alcanzados en la incorporación de TICs de visualización y modelado molecular en el inicio de carreras de grado de la Facultad de Ingeniería Química, UNL. A partir de 2008 desarrollamos una serie de actividades: promovimos la instalación de doble booteo en los gabinetes informáticos, seleccionamos e instalamos software libre de visualización y modelado molecular, dictamos un ciclo de charlas y realizamos talleres para estudiantes y docentes. Estas actividades iniciales lograron despertar un imprescindible interés y generar el involucramiento y compromiso de docentes que permitieron proponer y respaldar actualizaciones curriculares que incluyen estas TICs tanto en asignaturas optativas como del tercio inicial. La modificación curricular más importante es la realizada en la asignatura Informática que se dicta para los ingresantes de todas las carreras de la FIQ. En el primer cuatrimestre de 2011 se incluyó el Gabedit, interfaz gráfica con un avanzado constructor de m...
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The main shortcoming of the papermaking properties of recycled fibres refers mainly to the hornification effect, as a consequence of drying during papermaking. An alkaline treatment is potentially useful to reverse this effect. The... more
The main shortcoming of the papermaking properties of recycled fibres refers mainly to the hornification effect, as a consequence of drying during papermaking. An alkaline treatment is potentially useful to reverse this effect. The present paper discusses the consequences of alkaline and alkaline peroxide treatments on unbleached recycled softwood kraft pulp (Kappa number: 92). A 3 factorial experimental design was applied, on considering the following factors: a) total alkaline charge and b) total peroxide charge. The chemical oxygen demand values were used for evaluating the material loss. It was found out that the delignifying effect of alkali was enhanced by peroxide addition. The alkaline treatment reduced freeness and improved the papermaking properties, such as tensile strength, Concora crush strength and short column compressive strength. Also, the addition of peroxide increased the papermaking properties even more, while the material loss caused a considerable increase in t...
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Persistent Organic Pollutants (POPs) are a group of highly-toxic considered compounds that cause serious effects on human health and the environment. It currently represents a topic of great impact and international concern. Within the... more
Persistent Organic Pollutants (POPs) are a group of highly-toxic considered compounds that cause serious effects on human health and the environment. It currently represents a topic of great impact and international concern. Within the project "Visualization and molecular modelling of organic high polymers of industrial interest", the three-dimensional molecular models of some of these components were initially obtained using the free software Gabedit, a 3D molecule editor. Afterwards, information on nomenclature, chemical structure, and model coordinate files were incorporated and a database was designed using the PostgreSQL free motor to store this data. Later, the free interactive Jmol applet was added. It allows for animated representation of molecular models and a portal was created to access this information. Having started with PCBs, followed by the dioxins and furans, i.e. about 400 POPs, the challenge now is to complete and make available the twelve groups of comp...
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En 2011 se incluyo en forma experimental el Gabedit – un editor libre de moleculas en 3D – en los contenidos de la asignatura Informatica que se imparte para alumnos ingresantes de la Facultad de Ingenieria Quimica, UNL. A principios de... more
En 2011 se incluyo en forma experimental el Gabedit – un editor libre de moleculas en 3D – en los contenidos de la asignatura Informatica que se imparte para alumnos ingresantes de la Facultad de Ingenieria Quimica, UNL. A principios de 2012, se aprobo esta actualizacion curricular estableciendo un nuevo escenario de ensenanza-aprendizaje con el objetivo de acelerar la incorporacion de TIC de visualizacion y modelado molecular en todas las carreras de la FIQ. Las libertades de la licencia del software seleccionado permitieron instalarlo en todos los gabinetes informaticos garantizando condiciones de libre disponibilidad con alta incidencia en todas las actividades de docencia y promoviendo iniciativas de actualizacion, aplicacion y desarrollo con estas herramientas. En el primer cuatrimestre de 2012 se implemento una encuesta orientada a sondear el impacto en los alumnos de dicho editor de moleculas, en terminos de usabilidad y herramienta didactica que les favoreceria la construcci...
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Se informan logros alcanzados en la incorporación de TICs de visualización y modelado molecular en el inicio de carreras de grado de la Facultad de Ingeniería Química, UNL. A partir de 2008 desarrollamos una serie de actividades:... more
Se informan logros alcanzados en la incorporación de TICs de visualización y modelado molecular en el inicio de carreras de grado de la Facultad de Ingeniería Química, UNL. A partir de 2008 desarrollamos una serie de actividades: promovimos la instalación de doble booteo en los gabinetes informáticos, seleccionamos e instalamos software libre de visualización y modelado molecular, dictamos un ciclo de charlas y realizamos talleres para estudiantes y docentes. Estas actividades iniciales lograron despertar un imprescindible interés y generar el involucramiento y compromiso de docentes que permitieron proponer y respaldar actualizaciones curriculares que incluyen estas TICs tanto en asignaturas optativas como del tercio inicial. La modificación curricular más importante es la realizada en la asignatura Informática que se dicta para los ingresantes de todas las carreras de la FIQ. En el primer cuatrimestre de 2011 se incluyó el Gabedit, interfaz gráfica con un avanzado constructor de m...
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The effects of digestion variables alkali charge and temperature on bagasse defibrability and semichemical pulp properties are analyzed. A 3 x 4 factorial experimental design is applied for an alkali charge ranging from 8 to 11% NaOH and... more
The effects of digestion variables alkali charge and temperature on bagasse defibrability and semichemical pulp properties are analyzed. A 3 x 4 factorial experimental design is applied for an alkali charge ranging from 8 to 11% NaOH and a temperature ranging from 100 to 145°. Second order regression models show a strong effect of cooking temperature on the shives content and handsheet properties: burst resistance presents a maximum at an intermediate level while tear strength and shive content decrease and CMT crush resistance increases continuously as temperature is increased. The lowest alkali charge of the range leads to an acceptable CMT and offers the possibility of choosing, by cooking temperature, the shives content of the pulp and the best balance between tear and tensile resistances.
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Facultad de Ingenieria Quimica, Universidad Nacional del Litoral Santiago del Estero 2654, (S3000AOM) Santa Fe, Argentina (1) Instituto de Tecnologia Celulosica/PI:56-273, FIQ, UNL. vmarzocc@fiq.unl.edu.ar (2) Instituto de Catalisis y... more
Facultad de Ingenieria Quimica, Universidad Nacional del Litoral Santiago del Estero 2654, (S3000AOM) Santa Fe, Argentina (1) Instituto de Tecnologia Celulosica/PI:56-273, FIQ, UNL. vmarzocc@fiq.unl.edu.ar (2) Instituto de Catalisis y Petroquimica/PI:56-273, FIQ, UNL. mdamato@fiq.unl.edu.ar (3) Estudiante de Ingenieria Quimica/PI:56-273, FIQ, UNL. rodolfoleonarduzzi@gmail.com (4) Estudiante de Ingenieria Quimica//PI:56-273, FIQ, UNL. nvanzetti@gmail.com
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Achievements are reported in incorporating ICT molecular modeling and visualization at the beginning of undergraduate courses at Chemical Engineering Faculty, UNL. Since 2008, we have developed a series of activities: promoted dual boot... more
Achievements are reported in incorporating ICT molecular modeling and visualization at the beginning of undergraduate courses at Chemical Engineering Faculty, UNL. Since 2008, we have developed a series of activities: promoted dual boot installation in computer cabinets; select and install visualization and molecular modeling free software; issued a series of talks and conducted workshops for students and teachers. Through these initial activities it was possible to generate interest as well as the essential involvement and commitment of teachers that made it possible to propose and support curriculum updates that include these ICT both, in elective and in the initial core subjects. The most important curricular change has been made to the Informatics subject, which is dictated for entrants of all courses. During the first quarter of 2011, Gabedit, a graphic interface with advanced builder molecules, was introduced. Then, during the first quarter of 2012, it was extended to Jmol, wh...
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Esta publicacion informa sobre la experiencia acumulada en el diseno y la construccion de simuladores usando Planilla de Calculo por ingresantes de la Facultad de Ingenieria Quimica de la UNL durante el cursado de la asignatura... more
Esta publicacion informa sobre la experiencia acumulada en el diseno y la construccion de simuladores usando Planilla de Calculo por ingresantes de la Facultad de Ingenieria Quimica de la UNL durante el cursado de la asignatura Informatica. El alumno debe hallar un procedimiento de resolucion de un problema sin la computadora –introduciendo el concepto de algoritmopara luego volcarlo a la Planilla de Calculo y obtener un simulador eficiente y de facil construccion. De los sistemas fisicos evaluados seleccionamos el tema gases porque es basico, comun a todas las carreras, exige el uso de un sistema de unidades y es anterior al desarrollo de Planilla de Calculo. Se muestran algunas variantes de estos simuladores con distintos niveles de complejidad; el mas completo realiza calculos para diez gases ideales y reales usando la ecuacion de Van der Waals. Se aplican comandos, herramientas y procedimientos -incluido el grabador de macrossin acceder al codigo de programacion. Aun con poco ti...
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Se estudia la relacion estructura-toxicidad de los bifenilos policlorados (PCBs) con efecto dioxina con fines didacticos utilizando herramientas informaticas de facil acceso. Analizando los datos de los 209 congeneres, mediante... more
Se estudia la relacion estructura-toxicidad de los bifenilos policlorados (PCBs) con efecto dioxina con fines didacticos utilizando herramientas informaticas de facil acceso. Analizando los datos de los 209 congeneres, mediante combinaciones de filtros se define el grupo de 12 PCBs con TEF, mostrando que el numero y posicion de las sustituciones con cloro cumplen las condiciones (orto ≤ 1, meta ≥ 2 y para = 2). El analisis mediante filtrado, tabla dinamica y diagramas, evidencia tambien que los PCBs con TEF tienen un angulo diedro ≤ 56o y que a menor angulo corresponde mayor TEF. Para visualizacion de los distintos casos se generaron imagenes tridimensionales de PCBs usando Gabedit, interfase grafica libre, a partir de coordenadas de centros atomicos obtenidas mediante simulador disenado en planilla de calculo. Las metodologias aplicadas y los modelos obtenidos son simples, de facil uso, muy utiles para educacion y potencialmente aplicables a otras familias quimicas
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The complex process of isothermal transversal impregnation is analyzed in detail. In it, the diffusing alkali reagent is considerably consumed. On the other hand, the wood is chemically and physically modified. During the impregnation, a... more
The complex process of isothermal transversal impregnation is analyzed in detail. In it, the diffusing alkali reagent is considerably consumed. On the other hand, the wood is chemically and physically modified. During the impregnation, a moderately defined reaction front that moves to the center of the chip is established. The deacetilation kinetics (main reaction) of eucalyptus wood, in conditions close
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ABSTRACT
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Summary In order to analyse the fundamentals of alkaline chemi-mechanical pulping of hardwoods, the chemical state of the wood was related to both the swelling level of fibres and the papermaking properties of pulp. Wafers of poplar wood... more
Summary In order to analyse the fundamentals of alkaline chemi-mechanical pulping of hardwoods, the chemical state of the wood was related to both the swelling level of fibres and the papermaking properties of pulp. Wafers of poplar wood were alkali treated following a factorial experimental design for two variables: temperature and alkali concentration. Treated wafers were hot defibrated in a 300-mm disk mill at 15% consistency, and then refined in PFI mill at 20% consistency. Results show how fibre swelling gradually increases as alkaline action is increased. The significant improvement in tensile and tear strength of the pulp can, in great part, be ascribed to the development of fibre bonding capacity. A limited effect of ion content on cell wall swelling was found. Swelling correlates well with deacetylation level, and is a major factor in determining the tensile strength and scattering ability of the pulp.
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When wood undergoes an acidic or alkaline chemical action or a moderate thermal action, acetyl groups are easily removed. As deacetylation favourably increases the accessibility of the cell wall and the fibre swelling, mechanical... more
When wood undergoes an acidic or alkaline chemical action or a moderate thermal action, acetyl groups are easily removed. As deacetylation favourably increases the accessibility of the cell wall and the fibre swelling, mechanical properties of wood and responses of wood to pulping are modified. In this paper, the importance of the deacetylation effects in alkaline pulping is highlighted. It is shown that it is very useful to analyse acetyl content profiles in eucalyptus wood for determining the level of alkali impregnation. Global deacetylation can be a parameter that can be practical for determination of the effectiveness of alkaline impregnation of chips. In alkaline chemi-mechanical pulping of poplar, the deacetylation level that takes place during pre-treatment can establish the bonding capacity of the pulp developed afterwards in the refiner. Acetyls can be very reactive under conditions of peroxide bleaching of chemi-mechanical pulps and, as a consequence of this reaction, alk...
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... Alkaline Wood Pretreatment at Low Temperature By Miguel Zanuttini, Miguel Citroni, MariaJulia Martinez and Victorio Marzocchi Institute of Cellulose Technology, Faculty of Chemical Engineering, Littoral National University, Santa Fe,... more
... Alkaline Wood Pretreatment at Low Temperature By Miguel Zanuttini, Miguel Citroni, MariaJulia Martinez and Victorio Marzocchi Institute of Cellulose Technology, Faculty of Chemical Engineering, Littoral National University, Santa Fe, Argentina. ...