RESUMEN
This paper describes the use of an optical instrument, the Fabry-Perot interferometer, adapted to measure very low pressures. The interferometer consists of two high-reflectance flat mirrors placed one in front of another. In addition, a metallic chamber contains air or a gas. In one of the faces of the chamber, a flexible thin silicone membrane is attached and, over it, one of the mirrors is glued. The other mirror rests in a fixed mechanical mounting. Light crosses both mirrors and, when it leaves them, forms an interference pattern consisting of concentric circular fringes. When the pressure is increased/decreased within the chamber, a displacement of the fringes is observed due to the movement of the glued mirror. By measuring the fringe displacement and knowing the pressure, a calibration plot can be made. Minimum pressure measurements of about tens of Pascals were achieved.
RESUMEN
Intercalated and exfoliated nanocomposites based on HDPE and EPDM blends with an organoclay have been obtained through the addition of EPDM-g-MA as a compatibilizer. The combined effect of clay and EPDM-g-MA on the rheological behaviour is very noticeable with a sensible increase in viscosity which suggests the formation of a structural net of percolation induced by the presence of intercalated and exfoliated silicate layer. As deduced from rheological studies, a morphology based on nanostructured micro-domains dispersed in HDPE continuous phase is proposed for EPDM/HDPE blend nanocomposites. XRD and SEM analysis suggest that two different transport phenomena take simultaneously place during the intercalation process in the melt. One due to diffusion of HDPE chains into the tactoid and the other to diffusion of EPDM-g-MA into the silicate galleries.