In the present work, we studied a "Mixed Alkaline-Earth Effect", i.e. the non-linear behaviour showed by the glass transition temperature as well as by the compressive strength of glasses of the CaO-MgO-Al 2 O 3 -SiO 2 system, when a part of the CaO contained in them was substituted by a BaO/SrO mixture, in variable molar proportions. An important factor for the occurrence of this phenomenon was the difference in atomic weight, ionic radii and field strength of the Ba 2+ and Sr 2+ ions in comparison with those corresponding to the Ca 2+ ion. Another factor considered was the likely occurrence of a microphase separation caused by the addition of BaO and/or SrO, together with the presence of F -and Mg 2+ in the glasses. Other glass properties studied as a function of the CaO substitution level were density, glass molar volume, oxygen molar volume, packing fraction, and chemical resistance in neutral, basic and acidic aqueous media. In general, the structural reinforcement of the glass network caused by the partial substitution of CaO by a BaO/SrO mixture was accompanied by an improvement in the alkaline resistance of the materials, which were found to be suitable for applications in corrosive environments, especially in basic media. En el presente trabajo, se estudia el comportamiento no lineal mostrado por la temperatura de transición vítrea y por la resistencia a la compresión de vidrios del sistema CaO-MgO-Al 2 O 3 -SiO 2 , cuando una parte del CaO contenido en los mismos es sustituido por una mezcla de BaO/SrO, en relación molar variable. Factores importantes para que se de este comportamiento son la diferencia entre pesos atómicos, radios iónicos e intensidad de campo de los iones Ba 2+ y Sr 2+ y los del propio ión Ca 2+. Otro factor considerado ha sido la probable existencia de una separación de microfases originada por la adición de BaO y/o SrO, junto con la presencia de flúor y magnesio en los vidrios. Otras propiedades estudiadas, en función del CaO sustituido, han sido la densidad, el volumen molar del vidrio, el volumen molar del oxígeno, la fracción de empaquetamiento, y la resistencia química en medios acuosos neutros, básicos y ácidos. En general, el refuerzo estructural del retículo vítreo causado por la sustitución parcial del CaO por una mezcla de BaO/SrO viene acompañada por una mejora en la resistencia alcalina, lo que hace que estos materiales sean adecuados para aplicaciones en ambientes corrosivos y especialmente en medios básicos.
ResumenSe propone un método para separar la fibra de los componentes principales del envase de cartón para líquidos y para evaluar las ventajas y desventajas del empleo de esta materia prima como fuente de fibras secundarias en la fabricación de papel. La resistencia mecánica del envase postconsumo se reduce por hidratación utilizando NaOH. Este proceso destruye los puentes de hidrógeno que unen fibra-fibra. El procedimiento permite rescatar 92% de fibra existente en el envase, por ello este material se ubica como potencial alternativa de fuente de fibra secundaria para la fabricación de papel. El material recuperado registra un alto contenido de material adhesivo (stickies), aunque es factible reducir esta cantidad a niveles que permiten su utilización en la fabricación de papel. AbstractA new method is proposed for separating fiber material from the main components of cartonboard commonly used for storing liquids and for evaluating the advantages and disadvantages of this material as fiber sources for paper manufacture. The mechanical resistance of the cartonboard has been reduced by hydration using NaOH to accelerate the process. This process destroys hydrogen bonding that joint fiber-fiber. The process allows recovering 92% of the existing fiber in the carton packaging , which makes this material a potential alternative as fibber source for the manufacture of paper. The recovered material contains a high quantity of stickies, although it is possible to reduce this amount to levels that allows using the recovered fiber in paper manufacture.
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