Material compuesto de matriz polipropileno (PP) y fibra de cedro: influencia del compatibilizante PP-g-MA

Because the strength of the wood plastic composite (WPC) is based on the fiber-matrix interaction, we have studied the influence of a coupling agent to modify the plastic matrix with different proportions of maleic anhydride-grafted polypropylene (PP-g-MA). Therefore, the physical-mechanical properties of a novel series of WPC with 20% fiber by injection technique were evaluated. It is worth mentioningthat in the previous step to the injection process,these materials were mixed in a co-rotating twin screw extruder under mild conditions, because it was possible to reduce by 50% the residence time of the fiber with regard to polymer. The thermogravimetric analysis (TGA) results for the WPC extrudates showed the onset temperatures of degradation with intermediate values T10 of ~ 295 °C compared to the starting components (fiber, PP). The final product had  loss of ~ 3.4% associated with the second thermal process suffered material. The mechanical analysis showed an increase in tensile strength of 20.3% in the new WPC, while the flexural strength reached 46.2%. In the micro-structural analysis of the final products incorporating the fiber into the matrix was made using Scanning Electron Microscopy (SEM). Finally, the optimal mixing ratio necessary to achieve a significant increase in mechanical properties is determined.Debido a que la fuerza de los compuestos de madera y plástico (CMP) se basa en la interacción fibra-matriz, se ha estudiado la influencia del agente compatibilizante al modificar la matriz plástica con diferentes proporciones de polipropileno injertado con anhídrido maléico (PP-g-MA). Por lo tanto, se evaluaron las propiedades térmicas y mecánicas de una nueva serie de CMP con 20% de fibra mediante la técnica de inyección. Cabe mencionar que en la etapa previa al proceso de inyección, estos materiales fueron mezclados en una extrusora de doble husillo co-rotante, en condiciones suaves debido a que se logró disminuir en un 50% el tiempo de residencia de la fibra con respecto al polímero. Los resultados de los análisis termogravimétricos obtenidos de los productos extruidos de CMP presentaron una temperatura de degradación con valores intermedios de T10 ~295 °C respecto a los componentes de partida (Fibra, PP). Los productos finales presentaron una pérdida de ~3.4% asociada al segundo proceso térmico que sufrió el material. El análisis mecánico presentó un aumento en la resistencia a la tensión del 20.3% en el nuevo CMP, mientras que la resistencia a la flexión alcanzó un 46.2%. En el análisis micro-estructural de los productos finales se observó la incorporación de la fibra en la matriz mediante microscopia electrónica de barrido. Finalmente, se determinó la relación óptima de la mezcla para lograr un incremento significativo en las propiedades mecánicas

Discutindo a educação ambiental no cotidiano escolar: desenvolvimento de projetos na escola formação inicial e continuada de professores

A presente pesquisa buscou discutir como a Educação Ambiental (EA) vem sendo trabalhada, no Ensino Fundamental e como os docentes desta escola compreendem e vem inserindo a EA no cotidiano escolar., em uma escola estadual do município de Tangará da Serra/MT, Brasil. Para tanto, realizou-se entrevistas com os professores que fazem parte de um projeto interdisciplinar de EA na escola pesquisada. Verificou-se que o projeto da escola não vem conseguindo alcançar os objetivos propostos por: desconhecimento do mesmo, pelos professores; formação deficiente dos professores, não entendimento da EA como processo de ensino-aprendizagem, falta de recursos didáticos, planejamento inadequado das atividades. A partir dessa constatação, procurou-se debater a impossibilidade de tratar do tema fora do trabalho interdisciplinar, bem como, e principalmente, a importância de um estudo mais aprofundado de EA, vinculando teoria e prática, tanto na formação docente, como em projetos escolares, a fim de fugir do tradicional vínculo “EA e ecologia, lixo e horta”.Facultad de Humanidades y Ciencias de la Educació

Physicomechanical behavior of composites of polypropylene, and mineral fillers with different process cycles

In this work, a development of composites of polypropylene [PP] with mineral fillers [M] of talc and calcium carbonate [CaCO3] by co-extrusion and injection techniques were carried out. In the preparation of the mixtures, was used the rheometric analysis to define the optimum temperature of the extrusion process, and a weight ratio of 80:20 PP: fillers was maintained, while for the injection molding process six generations of PP and its compounds were obtained to study the rheological, thermal, morphological and mechanical properties of the new series of PPnM composites formed from a recycled matrix and the PPMn series reprocessed compounds for up to six cycles. The results allowed correlating the changes due to the thermal history and the influence of adding the mineral fillers. The mechanical characterization in the reprocessed matrix indicated a 6.0% decrease in tensile strength and an increase in flexural strength of 9.9%. Likewise, the compounds showed an increase in tensile strength of 11.7%, while flexural strength reached 35.8%. From the thermogravimetric analysis, the degradation temperature in the matrix gradually decreased from 406.5 °C to 364.3 °C, for the sixth generation with respect to the virgin material by the injection process; meanwhile, for the compounds was maintained around 410 °C indicating an optimal interaction, these results could be contrasted with the colorimetric analysis. Finally, re-injection led to a significant decrease in the size of the talc and CaCO3 particles; the sizes were estimated from microstructural analysis from Scanning Electron Microscope.En este trabajo, se llevó a cabo el desarrollo de compuestos de polipropileno [PP] con cargas minerales [M] de talco y carbonato de calcio [CaCO3] mediante técnicas de coextrusión e inyección. En la preparación de las mezclas, se utilizó el análisis reométrico para definir la temperatura óptima del proceso de extrusión, y se mantuvo una relación 80:20 en peso de PP con las cargas, mientras que para el proceso de moldeo por inyección se obtuvieron seis generaciones de PP y sus compuestos para estudiar las propiedades reológicas, térmicas, morfológicas y mecánicas de las nuevas series de compuestos de PPnM formados a partir de una matriz reciclada y los compuestos reprocesados de la serie PPMn hasta seis ciclos. Los resultados permitieron correlacionar los cambios debidos al historial térmico y la influencia de incorporación de las cargas minerales. La caracterización mecánica en la matriz reprocesada indicó una disminución del 6,0% en la resistencia por tracción y un aumento de la resistencia por flexión del 9,9%. Así mismo, los compuestos mostraron aumento de la resistencia a la tracción del 11,7%, mientras que la resistencia a la flexión alcanzó el 35,8%. Por otro lado, la temperatura de degradación en la matriz disminuyó gradualmente de 406,5 °C hasta 364,3 °C, para la sexta generación con respecto al material virgen; mientras tanto, la temperatura de degradación de los compuestos se mantuvo alrededor de 410 °C indicando una óptima interacción, estos resultados se pudieron contrastar con el análisis colorimétrico. Finalmente, la re-inyección condujo a una disminución significativa del tamaño de las partículas de talco y CaCO3, los tamaños fueron estimados a partir del análisis microestructural mediante Microscopía Electrónica de Barrido (SEM)

Material compuesto de matriz polipropileno (PP) y fibra de cedro: influencia del compatibilizante PP-g-MA

Because the strength of the wood plastic composite (WPC) is based on the fiber-matrix interaction, we have studied the influence of a coupling agent to modify the plastic matrix with different proportions of maleic anhydride-grafted polypropylene (PP-g- MA). Therefore, the physical-mechanical properties of a novel series of WPC with 20% fiber by injection technique were evaluated. It is worth mentioning that in the previous step to the injection process, these materials were mixed in a co-rotating twin screw extruder under mild conditions, because it was possible to reduce by 50% the residence time of the fiber with regard to polymer. The thermogravimetric analysis (TGA) results for the WPC extrudates showed the onset temperatures of degradation with intermediate values T10 of ~ 295 °C compared to the starting components (fiber, PP). The final product had a loss of ~ 3.4% associated with the second thermal process suffered material. The mechanical analysis showed an increase in tensile strength of 20.3% in the new WPC, while the flexural strength reached 46.2%. In the micro-structural analysis of the final products incorporating the fiber into the matrix was made using Scanning Electron Microscopy (SEM). Finally, the optimal mixing ratio necessary to achieve a significant increase in mechanical properties is determined.Debido a que la fuerza de los compuestos de madera y plástico (CMP) se basa en la interacción fibra-matriz, se ha estudiado la influencia del agente compatibilizante al modificar la matriz plástica con diferentes proporciones de polipropileno injertado con anhídrido maléico (PP-g-MA). Por lo tanto, se evaluaron las propiedades térmicas y mecánicas de una nueva serie de CMP con 20% de fibra mediante la técnica de inyección. Cabe mencionar que en la etapa previa al proceso de inyección, estos materiales fueron mezclados en una extrusora de doble husillo co-rotante, en condiciones suaves debido a que se logró disminuir en un 50% el tiempo de residencia de la fibra con respecto al polímero. Los resultados de los análisis termogravimétricos obtenidos de los productos extruidos de CMP presentaron una temperatura de degradación con valores intermedios de T10 ~295 °C respecto a los componentes de partida (Fibra, PP). Los productos finales presentaron una pérdida de ~3.4% asociada al segundo proceso térmico que sufrió el material. El análisis mecánico presentó un aumento en la resistencia a la tensión del 20.3% en el nuevo CMP, mientras que la resistencia a la flexión alcanzó un 46.2%. En el análisis micro-estructural de los productos finales se observó la incorporación de la fibra en la matriz mediante microscopia electrónica de barrido. Finalmente, se determinó la relación óptima de la mezcla para lograr un incremento significativo en las propiedades mecánicas

Physicomechanical behavior of composites of polypropylene, and mineral fillers with different process cycles

In this work, a development of composites of polypropylene [PP] with mineral fillers [M] of talc and calcium carbonate [CaCO3] by co-extrusion and injection techniques were carried out. In the preparation of the mixtures, was used the rheometric analysis to define the optimum temperature of the extrusion process, and a weight ratio of 80:20 PP: fillers was maintained, while for the injection molding process six generations of PP and its compounds were obtained to study the rheological, thermal, morphological and mechanical properties of the new series of PPnM composites formed from a recycled matrix and the PPMn series reprocessed compounds for up to six cycles. The results allowed correlating the changes due to the thermal history and the influence of adding the mineral fillers. The mechanical characterization in the reprocessed matrix indicated a 6.0% decrease in tensile strength and an increase in flexural strength of 9.9%. Likewise, the compounds showed an increase in tensile strength of 11.7%, while flexural strength reached 35.8%. From the thermogravimetric analysis, the degradation temperature in the matrix gradually decreased from 406.5 °C to 364.3 °C, for the sixth generation with respect to the virgin material by the injection process; meanwhile, for the compounds was maintained around 410 °C indicating an optimal interaction, these results could be contrasted with the colorimetric analysis. Finally, re-injection led to a significant decrease in the size of the talc and CaCO3 particles; the sizes were estimated from microstructural analysis from Scanning Electron Microscope

Search for narrow resonances using the dijet mass spectrum in pp collisions at s√=8 TeV

Results are presented of a search for the production of new particles decaying to pairs of partons (quarks, antiquarks, or gluons), in the dijet mass spectrum in proton-proton collisions at s√=8  TeV. The data sample corresponds to an integrated luminosity of 4.0  fb−1, collected with the CMS detector at the LHC in 2012. No significant evidence for narrow resonance production is observed. Upper limits are set at the 95% confidence level on the production cross section of hypothetical new particles decaying to quark-quark, quark-gluon, or gluon-gluon final states. These limits are then translated into lower limits on the masses of new resonances in specific scenarios of physics beyond the standard model. The limits reach up to 4.8 TeV, depending on the model, and extend previous exclusions from similar searches performed at lower collision energies. For the first time mass limits are set for the Randall–Sundrum graviton model in the dijet channel