Browsing by Author "Gaztelumendi, I."
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Item Carbon nanotubes and graphene into thermosetting composites: Synergy and combined effect(2018-07-20) Prolongo, S. G.; Moriche, R.; Ureña, A.; Flórez, S.; Gaztelumendi, I.; Arribas, C.; Prolongo, M. G.; POLIMEROSThis work analyzes the morphology and behavior of hybrid composites reinforced with carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs). In order to avoid the weak interface of laminar nanofillers, GNPs were functionalized with amine groups. Different tendencies were observed as a function of the measured property. Storage modulus showed a synergic trend, being the stiffness of hybrid CNT/GNP/epoxy composites higher than the corresponding ones measured in neat epoxy composites reinforced with CNTs or GNPs. In contrast, the thermal and electrical conductivity increased with the nanofiller addition, the final value of the mentioned properties in the hybrid composites was strongly influenced by specific graphitic nanofiller. Neat GNP/epoxy composites showed the highest thermal conductivity, while neat CNT/epoxy composites presented the highest electrical conductivity. This behavior is explained by the observed morphology. All composites exhibited a suitable nanofiller dispersion. However, on hybrid GNP/CNT/epoxy composites, CNTs tend to be placed between nanoplatelets, forming bridges between nanoplatelets. This morphology implies a less effective electrical network, limiting the synergic effect in the properties, which requires percolation. In spite of this, the hybrid GNP/CNT/epoxy composites showed a better combination of properties than the neat composites.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 Enhancement of electrical conductivity of composite structures by integration of cnts via bulk resin and/or buckypaper films(European Conference on Composite Materials, ECCM, 2014) Gaztelumendi, I.; Chapartegui, M.; Seddon, R.; Flórez, S.; Pons, F.; Cinquin, J.; Korzhenko, A.; POLIMEROSThis work describes two approaches for the incorporation of Carbon Nanotubes (CNTs) in CFRP composites by infusion processing methods: firstly through the addition of the CNTs in the bulk resin to improve the electrical properties of the epoxy matrix prior to infusion [1], and secondly by the addition of CNT-based buckypaper (BP) in the CFRP structure for enhanced electrical properties [2]. Several laminates were manufactured with different formulations. A cross check of EC testing was carried out among different laboratories in order to compare different surface preparations and test methods. This characterization was completed with Scanning Electron Microscopy (SEM) analyses, in order to assess the presence of the filtering effect. In addition, ILSS tests were performed, comparing the results of the different formulations.Item Graphene and its application in polymer composites(European Conference on Composite Materials, ECCM, 2014) Flórez, S.; Chapartegui, M.; Bustero, I.; Gaztelumendi, I.; Mendizábal, M.; Iraola, B.; Atxaga, G.; Jurado, M.; POLIMEROS; PRINTEX; EXTREMAT; Tecnalia Research & InnovationThis paper looks at the development of graphene/polymer nanocomposites to be used as adhesives for Thermal Interface Materials (TIMs) and lightweight high performance CFRP composite laminates with conductive properties. The addition of graphene, even at a very low concentration level (usually less than 5%), into a polymeric matrix can significantly improve its thermal conductivity. The achievement of a good dispersion of graphene and the interfacial bonding of graphene and the polymer matrix is a key aspect. Different qualities of graphene material have been characterised and tested to obtain good dispersion in the polymer matrixes tested. High improvements in the thermal conductivity for both applications under study have been achieved.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 Natural fibre composites for automotive applications(2005) Rubio, A.; Elizetxea, C.; Calleja, N.; Gaztelumendi, I.; Gaballah, I.; Mishra, B.; Solozabal, R.; Tanaka, M.; POLIMEROS; Centros PRE-FUSION TECNALIA - (FORMER)The main advantage of the use of composite materials is related to their intrinsic lightweight. In this way, labour and transport costs will be strongly decreased, and the total weight of the manufactured part will be minimised. The reduction of weight implies a considerable reduction of fuel consumption with the consequent respect to the environment. Although glass fibres, as plastics, are not intrinsically harmful to the environment, some of their products can be dangerous or, at least, environment "unfriendly". The health hazards of dealing with glass fibres have been already mentioned. A second drawback of these materials regards their recyclability because it requires costly separation procedures. It is clear that from this point of view natural fibre offer more possibilities for a complete recyclability allowing the development of «eco-waste» technologies and products. This work has been carried out within the European Growth Project G5RD-CT1999-00147 "Eco-Efficient Technologies and Products based on Natural Fibre Composites-ECOFINA".