Study of nanocomposites prepared from polyamides and biodegradable polyesters and poly(ester amide)s

Premi extraordinari doctorat curs 2011-2012, àmbit d’Enginyeria IndustrialPolymer clay nanocomposites of polyamides and biodegradable polymers with three kinds of organomodified clays were prepared by different techniques (in situ polymerization, solution casting, and melt mixing). The polymers used in this research were nylons 56, 65 and 47 and the biodegradable polymers: poly (glycolic acid-alt-6-hydrohexanoic acid) and poly(glycolic acid-alt-6-aminohexanoic acid). The development of biodegradable nanocomposites with improved or modified material properties is an interesting topic since these new materials are expected to replace already existing biodegradable and non-biodegradable commodity plastics in some specific applications.This project aims to study the influence of clay particles incorporated in a polymer matrix on the crystallization processes, the study of the in situ polymerization kinetics of mixtures of clays and monomers of biodegradable polymers, as well as the influence of nanoparticles on the thermal behavior and morphologic parameters. Even-odd, and odd-even polyamides were chosen to study the Brill transition and to prepare nanocomposites with organomodified clays. These polyamides have a peculiar structure where hydrogen bonds are established along two different directions. X-ray diffraction as well as SAXS-WAXD synchrotron experiments were employed to study the structural changes induced by temperature, during heating and cooling. Different organomodified clays were used to prepare nanocomposites, which final structure was found to be dependent on the preparation method. Nanocomposites derived from biodegradable polymers were characterized by means of X-ray diffraction and transmission electron microscopy. Morphological studies showed that the extent of clay dispersion depended on the clay type and on the preparation technique. Hence, exfoliated and intercalated nanocomposites could be obtained. The final nanocomposite structure was found to have a great influence on both cold and hot crystallization processes. Hence, the crystallization rate increased and decreased with respect to the neat polymer when intercalated and exfoliated structures were respectively obtained. The kinetics of the polymerization process was also studied by means of FTIR and SAXS-WAXD. The results indicate that the presence of the organomodified clay had a remarkable effect on the kinetic parameters.Award-winningPostprint (published version

Synchrotron radiation studies on even-odd and odd-even nylons

Aliphatic polyamides derived from odd diamine or odd dicarboxylic acid units cannot adopt a conventional sheet structure when molecular chains have an all trans conformation. However, typical fiber diffraction patterns of this sheet structure were observed in several polyamides derived from odd units such as nylons 65 and 56. Consequently, a new structure based on the establishment of intermolecular hydrogen bonds along two different directions was postulated. Real-time temperature dependence of X-ray diffraction patterns for nylons 65 and 56 was studied by synchrotron radiation to gain understanding of the Brill transition usually occurring in polyamides. Significant differences were found between the temperature dependence of both nylons, although a transition towards a monoclinic structure characterized by a single equatorial reflection around 0.425-0.420 nm was observed to occur at high temperatures. This transition was reversible for nylon 65 only. In this case, a characteristic hysteresis effect was found.Peer ReviewedPostprint (published version

Desarrollo de una propuesta para la construcción de una planta piloto para el reciclaje de los componentes de las baterías níquel-cadmio

Las baterías son los dispositivos de almacenaje portátil de energía más usados. Existen diferentes tipos, desde las primeras y más simples llamadas pilas voltaicas inventadas por Alessandro Volta en 1800, hasta las más complicadas, que desde entonces hasta la fecha han evolucionado, gracias a nuevas tecnologías y nuevos materiales, buscando siempre proporcionar la mayor densidad energética a un costo razonable. En primer lugar se desarrollaron las baterías, que consisten en un conjunto de pilas conectadas ya sea en serie o en paralelo, lo que aumenta la cantidad de energía que pueden proporcionar. Además de diferentes materiales en las baterías, se han desarrollado distintas formas de operación; se tienen las baterías primarias que se ocupan comúnmente en aparatos electrónicos con demanda moderada de energía, y las secundarias que proporcionan mayor cantidad de energía, gracias al aumento de su vida útil por sus ciclos múltiples de operación, pudiéndose cargar y descargar en diversas ocasiones. Aunque la vida de las baterías recargables es más larga, al igual que todas las baterías cuando ésta llega a su fin deben desecharse. Con la creciente demanda de energía portátil, a causa del avance tecnológico y desarrollo de aparatos portátiles, las baterías de desecho han aumentado en gran medida. En la actualidad se tienen problemas por la contaminación que generan, ya que entre sus componentes pueden estar metales pesados altamente tóxicos. Ejemplo de lo anterior son las baterías de níquel - cadmio (Ni-Cd), ambos metales son dañinos para la salud, principalmente el cadmio (Cd). Las empresas productoras de baterías se han visto obligadas a introducir técnicas de reciclaje de los componentes de las baterías, debido a presión legislativa y de los consumidores. Además han aparecido empresas que se dedican sólo al reciclaje de las baterías. Sin embargo los procesos industrializados no son económicamente convenientes para países en desarrollo como México debido a los altos requerimientos de energía. Las tecnologías de reciclaje sólo existen en los mismos países productores de baterías como: Estados Unidos, Suecia, Japón etc. Por lo que se han buscado métodos alternativos a los ya establecidos para el reciclaje, que demanden menor cantidad de energía y por lo tanto resulten económicamente viables en países en desarrollo. En diversos estudios se ha probado la factibilidad técnica, del uso de la hidrometalúrgia como alternativa para recuperar los metales presentes en las baterías de Ni-Cd. En el presente trabajo se busca establecer una secuencia de equipos para el reciclaje, mediante técnicas hidrometalúrgicas en combinación con otros procesos físicos. Se reporta la revisión bibliográfica realizada para validar los resultados de laboratorio, que además justifica las condiciones de diseño establecidas para la planta piloto. Se efectúo el diseño de equipo mediante un programa en excel (CADIPREBAT), el cual es una herramienta muy útil ya que cambiando los parámetros (o bases de diseño) se pueden obtener las dimensiones de equipo para cualquier cantidad de baterías a procesar o cambiar otro dato de entrada y observar los efectos en las dimensiones o diseño en general. Por último se llevó a cabo la evaluación económica para el proyecto de inversión en la planta piloto de reciclaje

Effects of a microbiological compound for the stabilisation of compactedoils on their microstructure and hydro-mechanical behaviour.

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Effects of a microbiological compound for the stabilisation of compactedoils on their microstructure and hydro-mechanical behaviour.

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Thermal stability studies on clay nanocomposites prepared from a degradable poly(ester amide) constituted by glycolic acid and 6-aminohexanoic acid

An intercalated nanocomposite of the organically modified montmorillonite Cloisite C25A and a degradable poly(ester amide) based on glycolic acid and 6-aminohexanoic acid units (poly(glc-alt-amh)) was prepared using a twin-screw co-rotating extruder. The non-isothermal degradation kinetics was investigated by thermogravimetric analysis (TG and DTG) in the temperature range of 50–600 ◦C at five heating rates (2, 5, 10, 20 and 40 ◦C/min) and compared with the neat polymer. Significant differences were found since the nanocomposite showed three degradation steps instead of the two decomposition processes detected in the pristine sample. The onset mass loss temperature decreased in the nanocomposite due to the presence of the organo-modifier compound, but the presence of the silicate layers significantly decreased the degradation rate at the last stages of decomposition. Kinetic analysis was performed using the Kissinger method and the isoconversional (Kissinger–Akahira–Sunose and Friedman) methods. The true kinetic triplets (E, A, f(˛)) were determined for the first two steps of degradation through the Coats–Redfern and the Invariant Kinetic Parameters methods. The results clearly indicated that the presence of the organo-modified clay modified the mechanisms of degradation.Peer ReviewedPostprint (published version

Modelling criteria for a microbiologically stabilised compacted soil in the framework of elastoplasticity.

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The preparation of cutback bitumens to ASTM specifications by blending readily available constituents

SIGLEAvailable from British Library Document Supply Centre- DSC:7768.29(TRRL-RR--104) / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Thermal stability studies on clay nanocomposites prepared from a degradable poly(ester amide) constituted by glycolic acid and 6-aminohexanoic acid

An intercalated nanocomposite of the organically modified montmorillonite Cloisite C25A and a degradable poly(ester amide) based on glycolic acid and 6-aminohexanoic acid units (poly(glc-alt-amh)) was prepared using a twin-screw co-rotating extruder. The non-isothermal degradation kinetics was investigated by thermogravimetric analysis (TG and DTG) in the temperature range of 50–600 ◦C at five heating rates (2, 5, 10, 20 and 40 ◦C/min) and compared with the neat polymer. Significant differences were found since the nanocomposite showed three degradation steps instead of the two decomposition processes detected in the pristine sample. The onset mass loss temperature decreased in the nanocomposite due to the presence of the organo-modifier compound, but the presence of the silicate layers significantly decreased the degradation rate at the last stages of decomposition. Kinetic analysis was performed using the Kissinger method and the isoconversional (Kissinger–Akahira–Sunose and Friedman) methods. The true kinetic triplets (E, A, f(˛)) were determined for the first two steps of degradation through the Coats–Redfern and the Invariant Kinetic Parameters methods. The results clearly indicated that the presence of the organo-modified clay modified the mechanisms of degradation.Peer Reviewe