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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThis paper presents evaluations of stability and rheological behavior of aqueous foam formulations. The stability of these systems was evaluated by the Ross-Miles method, using halflife measurements, and was studied as a function of the type and concentration of surfactants, polymers and salts. The effect of contaminants such as crude oil is also examined. A capillary tube viscometer was used to perform the rheological studies. The effect of variables such as quality of the foam, pressure system, tube diameter and polymer type is shown. Results were corrected for wall slip effect and normalized by using equalized volume corrections. Results indicated that the sensitivity of the foam to contamination with oil and salts depends on the chemistry of the foaming agent system and crude oil used. The rheological evaluations showed that the flow behavior is highly dependent on the foam quality for a given pressure, the chemistry of polymer and the tube diameter.

Context: Tetra Pak® is a common material used for the production of food containers. Currently, those containers are recycled by physical separation of the cellulose fibers through a hydro pulped process, but sometimes separating the individual components is not economically viable. This work evaluates an al­ternative process to obtain composites from recycled Tetra Pak®. Methodology: Tetra Pak® used containers were co­llected and cut into small pieces at the laboratory. Then, the containers were hot-pressed to obtain sheets in a manual hydraulic press by using different confi­gurations. Samples were cut, and their tensile stren­gth was evaluated (ASTM D3039). Failure analysis of samples was carried out by FE-SEM to identify issues related to processing and to understand the differen­ces in mechanical properties. Results: The results showed that the lowest tensile strength was 9.5 MPa (type I sample) and the highest tensile strength was 37.4 MPa (type III sample). Conclusions: The results of mechanical tests show that this material can be used for non-structural purposes in the building industry. Failure analysis shows that fiber pull-out and delamination are the most impor­tant failure mechanisms in type I samples. For type III sample, failure was produced by a sequence of intralaminar fractures

En este artículo se presentan los resultados de una investigación sobre el uso del polvo de vidrio como remplazo del feldespato en la fabricación de gres porcelánico. Se prepararon mezclas en donde el polvo de vidrio sustituyó al feldespato en dos volúmenes distintos (25% y 50%). Especímenes de las pastas obtenidas fueron moldeados, secados y cocidos. Las propiedades físicas (densidad aparente, porosidad, absorción, entre otras) y mecánicas (resistencia a flexión) de los especímenes cocidos estándar (V0) se compararon con las de especímenes cocidos en donde el material fundente fue sustituido en la formulación por polvo de vidrio en porcentajes de 25% y 50% (V25 y V50). Se encontró que la adición de polvo de vidrio en las formulaciones ocasionaba disminución en la resistencia a la flexión e incremento en los valores de absorción de agua. Sin embargo, la acción fundente del polvo de vidrio disminuyó la temperatura de sinterización respecto a la mezcla estándar en 150 °C para remplazos de 50% y 25%, respectivamente. Mediante MEB se evidenció en la microestructura de las piezas cocidas (V0, V25 y V50) la presencia de cristales de mullita primaria, adyacentes a cristales de mullita secundaria (agujas elongadas).