Effect of mold temperature on the impact behavior and morphology of injection molded foams based on polypropylene polyethylene–octene copolymer blends

Producción CientíficaIn this work, an isotactic polypropylene (PP) and a polyethylene–octene copolymer (POE) have been blended and injection-molded, obtaining solids and foamed samples with a relative density of 0.76. Different mold temperature and injection temperature were used. The Izod impact strength was measured. For solids, higher mold temperature increased the impact resistance, whereas in foams, the opposite trend was observed. In order to understand the reasons of this behavior, the morphology of the elastomeric phase, the crystalline morphology and the cellular structure have been studied. The presence of the elastomer near the skin in the case of high mold temperature can explain the improvement produced with a high mold temperature in solids. For foams, aspects as the elastomer coarsening in the core of the sample or the presence of a thicker solid skin are the critical parameters that justify the improved behavior of the materials produced with a lower mold temperature.Ministerio de Economía, Industria y Competitividad (grant DI-15-07952

Foams with enhanced ductility and impact behavior based on polypropylene composites

Producción CientíficaIn this work, formulations based on composites of a linear polypropylene (L-PP), a long-chain branched polypropylene (LCB-PP), a polypropylene–graft–maleic anhydride (PP-MA), a styrene-ethylene-butylene-styrene copolymer (SEBS), glass fibers (GF), and halloysite nanotubes (HNT-QM) have been foamed by using the improved compression molding route (ICM), obtaining relative densities of about 0.62. The combination of the inclusion of elastomer and rigid phases with the use of the LCB-PP led to foams with a better cellular structure, an improved ductility, and considerable values of the elastic modulus. Consequently, the produced foams presented simultaneously an excellent impact performance and a high stiffness with respect to their corresponding solid counterparts.Unión Europea (Evolution project under grant 314744)Ministerio de Ciencia, Innovación y Universidades - Fondo Europeo de Desarrollo Regional (project RTI2018-098749-B-I00)Junta de Castilla y Leon (project VA275P18

Escalera hacia el cielo

El presente artículo recoge la investigación científica que realizaron tres profesores de matemáticas y tecnología acerca de la estabilidad de estructuras crecientes. Durante la misma dedujeron la posibilidad de construir una escalera, simplemente apoyando peldaños uno encima de otro, que pueda unir dos puntos a diferente altura y desplazados horizontalmente cualquier distancia por grande que esta sea. El resultado está basado en el desplazamiento del centro de gravedad según la sucesión semiarmónica que da origen a una curva especial de estabilidad. Esta investigación fue la base también para una experiencia realizada con alumnos de 1º Bachiller como aplicación del tema “Sucesiones”. ¿Es posible formar una escalera hasta el cielo simplemente colocando peldaños uno sobre otro sin ningún tipo de adherente

Freeze–thaw durability of cement-based geothermal grouting materials

The authors wish to express their gratitude to the Spanish Ministry of Economy and Competitiveness which funded this study through the research project BIA2009- 08272. Finally, authors wish to acknowledge the financial support provided by the research projects FICYT FC-10-EQUIP10-17 and BIA-2008-00058

Salarios y organización del trabajo en la minería del sureste español, 1850-1936

This paper analyzes the evolution of the workers’ wages in the mining operations of the southeast of Spain, where predominates a model of mining defined by the extreme division of property and a specific organization of labor relations. We reconstruct real wages series for the Sierra of Cartagena, one of the most representative area of this kind of productive organization. For deflating we have elaborated a Cost of Living Index mainly using documentation from hospitals in the area and the local government. Shopping baskets and published household budget surveys were used as weights. The wages were obtained from business documentation. Finally, results have been compared with other areas, delving into the features of the income of the study area. The purpose of this paper is explain differences across several mining business models and their implications in wages dynamics, trying to find the main factors behind these differences.Este trabajo analiza la evolución de los salarios de los trabajadores de las explotaciones mineras del sureste de España, espacio donde predominaba un modelo de minería caracterizado por la extrema división de la propiedad y una específica organización de las relaciones laborales. Se ha realizado una reconstrucción de los salarios reales en la Sierra de Cartagena- La Unión, una de las zonas más representativas de este tipo de organización productiva. Para deflactar hemos elaborado un índice del coste de la vida. La documentación que se ha utilizado en su confección procede principalmente de los hospitales de la zona, junto con documentación municipal. El conjunto se ha ponderado con cestas de la compra y presupuestos familiares de publicaciones de la época. En cuanto a los salarios, se ha utilizado documentación empresarial. Por último, se hace una comparación con los trabajos de otras zonas, profundizando en las características de los ingresos de la zona de estudio.Con todo ello nuestra aportación trata de profundizar en la línea de investigación consistente en comprobar y comparar los diferentes comportamientos socio-laborales de las distintas minerías existentes en el país y determinar cuáles han podido ser los factores que han influido en la pluralidad de comportamientos que se detectan

Crosslinked ethylene butyl acrylate copolymer foams with different cellular structure interconnectivity and tortuosity: Microstructure and physical properties

Producción CientíficaIn this work, the cellular structure, physical properties, and the structure–property relationship of several novel crosslinked ethylene butyl acrylate (EBA) foams with different cellular structure interconnectivity (low tortuosity and high tortuosity) have been analyzed and compared to that of closed cell EBA foams and to that of an open-cell polyurethane foam. The results have shown that these materials present interesting properties highly dependent on the tortuosity of the cellular structure. In particular, it has been proved that reducing the tortuosity allows enhancing the acoustic absorption, the oil uptake, and the cushioning behavior. On the other hand, increasing tortuosity allows improving the impact behavior. In addition, the new open-cell materials present an enhanced damping factor for low-frequency vibrations.Ministerio de Economía, Industria y Competitividad (grant DI-15-07952)Ministerio de Asuntos Económicos y Transformación Digital-FEDER, UE (project MAT2015-69234-R)Junta de Castilla y León (project VA275P18