Browsing by Author "Markaide, N."
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Item Alternative rigidisation method for inflatable structures(2008) Markaide, N.; Marcos, J.; Zubillaga, O.; Tecnalia Research & Innovation; SISTEMAS FOTOVOLTAICOSThermally rigidised thermoset composites and UV rigidised composites are methods that have been widely studied in inflatable structures. However, these methods based on chemical rigidisation present some awbacks, as for example the influence of space environment in polymerisation and thus, in final properties obtained in the composite. Alternative and promising methods are passive cooled thermoplastics. The aim of this project has been to conduct further research in this new rigidisation technology. A study of different materials has been performed based on the final properties required in space conditions, but also properties specifically needed for folding, inflation and rigidisation steps. Thus, the approach has been planned in two phases. The first phase covers a material study and testing at coupon level, which has allowed the optimisation of the rigidisation process. The second phase deals with the manufacturing, testing and validation of a reduced size breadboard, consisting of a solar array composed by two lateral flexible solar panels (membranes) supported by a central rigidisable boom.Item Development of unsaturated polyester matrix - Carbon Nanofibers Nanocomposites with Improved Electrical Properties(2010-08-01) Monti, M.; Terenzi, A.; Natali, M.; Gaztelumendi, I.; Markaide, N.; Kenny, J. M.; Torre, L.; POLIMEROSIn this work, the dispersion of carbon nanofibers (CNFs) in an unsaturated polyester (UP) resin was performed by mean of the calendering process. The calendering process allows to obtain good dispersion of the nanoparticles, and, with respect to the other techniques, is also possible to scale it up at the industrial level. Optimization of the calendering conditions for the processing was carried out as a first step of this study. Optimization, in this case, means to reach the best dispersion level, as rapidly as possible and with the lowest amount of styrene evaporation. The dispersion level reached was investigated by the technique of scanning electron microscopy. The investigation on electric conductivity of the nanocomposites at different CNF concentrations has revealed that the electrical percolation threshold exists at around 0.3 wt %, where electrical conductivity switches from 10-13 to 10-7 S/cm. The rheologicalcharacterization has been performed to verify if the improved electrical properties are obtained at the expense of loss of workability, that is a significant increase of viscosity. Eventually, a mechanical characterization was carried out. VC 2010 Wiley Periodicals, Inc.Item The influence of mechanical dispersion of MWCNT in epoxy matrix by calendering method: Batch method versus time controlled(2013-05) Jiménez-Suárez, A.; Campo, M.; Gaztelumendi, I.; Markaide, N.; Sánchez, M.; Ureña, A.; POLIMEROSThe calendering approach has proved to be an effective alternative to chemical dispersion routes, but knowledge on the effectiveness of the different calendering parameters and methods used is still lacking. This study compared two different calendering methods widely used in the literature to evaluate possible differences in their dispersion effectiveness and their effect on the main properties of the nanocomposites being used. The nanocomposites' thermal, electrical, mechanical and thermomechanical properties were evaluated to exhaustively analyze the influence of each calendering method on these properties. Slight differences were observed in the dispersion effectiveness of the two methods analyzed, and behavioral differences were found in the nanocomposites with high and low nanoreinforcement contents.Item Rheological characterization of tetraglycidyl 4,4′-diaminodiphenylmethane/m-phenylene diamine systems(1992-03) Imaz, J. J.; Markaide, N.; Jurado, M. J.; Corcuera, M. A.; Mondragon, I.; Tecnalia Research & InnovationAn epoxy resin/hardener system, TGDDM/m-PDA, has been studied. A series of isothermal rheological runs provided information about the kinetics of curing over a temperature range. Both important parameters of the curing reaction (resin/hardener stoichiometry and temperature) were varied and their influence on viscosity was investigated. The dependence of viscosity on temperature was described by using Williams-Landel-Ferry treatment and the gelation process was studied using viscosity profiles during curing cycles.Item Specific rheological and electrical features of carbon nanotube dispersions in an epoxy matrix(2010-05) Chapartegui, M.; Markaide, N.; Florez, S.; Elizetxea, C.; Fernandez, M.; Santamaría, A.; POLIMEROSThe rheological analysis of epoxy pre-polymer/MWCNT dispersions indicates that a physical network is formed. This is destroyed with an imposed shear, giving a viscoplastic and shear thinning behavior. Such destruction is not reflected in dynamic viscoelastic experiments, due to the very rapid recovery of the MWCNT network in the pre-polymer matrix. This responds to the observed lower electrical than rheological percolation threshold. Electrical conductivity results fulfill electron hopping/tunnelling mechanism, which implies a tube-tube distance close to 5. nm. However, rheological percolation requires nanotubes should touch each other, since no polymer chains are implied in the network.