Papers by Mercedes Pastor Blas
Dedicated to Prof. Dr. rer. nat. Jü rgen Caro on the occasion of his 70th birthday Polypyrrole (P... more Dedicated to Prof. Dr. rer. nat. Jü rgen Caro on the occasion of his 70th birthday Polypyrrole (PPy) has been prepared by oxidative polymerization of pyrrole and used as a raw material for the preparation of N-doped activated carbons. Thus, PPy has been pyrolyzed at 900°C and then activated with steam under different activation conditions (time and temperature). This has allowed for the preparation of activated carbons with different porosity development and nitrogen content, as well as distinctive distribution of nitrogen species. It has been observed that the presence of nitrogen functionalities favors water adsorption at low relative pressures but, at relative pressures higher than 0.5 it is determined by the porosity development.
Activated carbons doped with nitrogen and/or sulfur have been obtained by pyrolysis followed of s... more Activated carbons doped with nitrogen and/or sulfur have been obtained by pyrolysis followed of steam activation of a sulfur containing polymer (polythiophene) and two nitrogen-containing polymers (polyaniline and polypyrrole). These polymers were synthesized by oxidative chemical polymerization in aqueous media of their corresponding monomers. The influence of the steam activation on the textural properties and surface chemistry of the carbons has been evaluated and their catalytic activity has been determined in the hydrogenation reaction of 1-chloro-4-nitrobenzene. The degree of conversion in the reaction depends on the development of adequate porosity in the activated carbon (which is determined by the activation conditions) together with the presence of heteroatoms that act as active catalytic sites, with S showing considerably greater effectiveness than N. A compromise between an acceptable level of doping with sulfur and an adequate porosity is necessary, which has been achieved in a carbon obtained from polythiophene pyrolyzed at 900 • C and steam activated at 800 • C for 4 h, with a specific surface area of 742 m 2 /g and S content of 1.71 at%.
Nitrogen-doped carbons were obtained by the pyrolysis of polyaniline (PANI), which had been previ... more Nitrogen-doped carbons were obtained by the pyrolysis of polyaniline (PANI), which had been previously synthesized by chemical oxidative polymerization of aniline at two different temperatures (0 and 25 • C). A series of activation treatments with steam under different experimental conditions were carried out in order to develop carbon porosity. It has been shown that the experimental polymerization conditions greatly affect the properties of the N-doped carbons and their reactivity to the steam activation treatment. Carbons were characterized by N 2 adsorption at − 196 • C, CHNS Elemental Analysis and XPS and their hydrophilicity/hydrophobicity were assessed by water adsorption measurements. The carbons prepared from PANI synthesized at 0 • C showed a more developed porosity and specific surface area than those obtained from PANI synthesized at 25 • C. The increase in the activation temperature produces the loss of the nitrogen heteroatom. Adsorption of water and toluene depends on the amount of surface nitrogen atoms as well as on the pore structure developed in the carbon.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
El objetivo inicial de esta red es que profesores del Area de Conocimiento de Quimica Inorganica ... more El objetivo inicial de esta red es que profesores del Area de Conocimiento de Quimica Inorganica de la Universidad de Alicante iniciaran un debate sobre los contenidos de dicha area de conocimiento que deberian incluirse en los futuros planes de estudios. Sin embargo, pronto surgio el problema de la indefinicion y de la falta de informacion, en esos momentos, sobre como quedarian dichos planes de estudios. Asi, se acordo trabajar en esta primera etapa sobre la metodologia a utilizar, tomando como base la usada actualmente. La definicion de los contenidos y su estructuracion debera abordarse en una segunda etapa, cuando la nueva situacion se encuentre mas clarificada. De esta forma, se analizo la metodologia utilizada en diferentes asignaturas de las titulaciones de Licenciado en Quimicas y de Ingeniero Quimico, se debatio sobre sus ventajas e inconvenientes y se propusieron nuevas metodologias y tecnicas de ensenanza que pudieran ser utiles en el nuevo marco.
International Journal of Adhesion and Adhesives, 2005
... others [13], [14], [15] and [16]. However, a few studies dealing with the corona discharge tr... more ... others [13], [14], [15] and [16]. However, a few studies dealing with the corona discharge treatment of rubbers have been published [17]. A recent paper byRomero-Sánchez et al. [18] analyzed the modifications produced by ...
Información del artículo Red de Química Inorgánica.
En la asignatura "ICM" de la Licenciatura en Química, se ha realizado un estudio sobre la prepara... more En la asignatura "ICM" de la Licenciatura en Química, se ha realizado un estudio sobre la preparación, por parte de grupos de alumnos y alumnas, de trabajos colaborativos, con objeto de transformar el "proceso de enseñanza" en "proceso de aprendizaje". Cada grupo realizó un informe escrito y lo presentó al aula utilizando herramientas multimedia, mostrando la adquisición de competencias transversales. Los resultados de aprendizaje de contenidos, así como el desarrollo de competencias transversales obtenidos, mostraron una elevada implicación en su propio proceso de aprendizaje. Además, se realizó una evaluación "por iguales" mediante una encuesta anónima aunque, en algunos cursos, los resultados no fueron acordes con la valoración del profesor. En el presente curso se ha seleccionado un nuevo formato para la realización de los trabajos, una wiki. La gestión de la wiki se ha realizado dentro de un sistema de gestión del aprendizaje (LMS) como Moodle, que permite controlar la actividad realizada por cada miembro del grupo. En este caso, la "valoración por iguales" se realiza utilizando un sistema de voto mediante radiofrecuencia (RF) que produce una retroalimentación inmediata, además de facilitar la gestión de la evaluación, anteriormente realizada sobre papel, y la publicación de los resultados correspondientes en la web de la asignatura. Palabras clave: aprendizaje colaborativo, sistema de gestión del aprendizaje (LMS)-Moodle, wiki, voto mediante radiofrecuencia (RF), clicker.
Journal of Adhesion Science and Technology, 1997
Different amounts (5-30 wt% with respect to the polyurethane content in the adhesive) of a new fi... more Different amounts (5-30 wt% with respect to the polyurethane content in the adhesive) of a new filler, a partially defibrillated natural hydrated magnesium silicate (sepiolite), were added to solvent-based polyurethane (PU) adhesive formulations. The rheological, mechanical, surface, and adhesion properties of the PU adhesives obtained were measured. Increase in the amount of sepiolite added to PU adhesives led to an increase in viscosity and imparted thixotropy and pseudoplasticity to the adhesive solution. However, the addition of sepiolite produced an increase in storage and loss moduli and a decrease in the mechanical properties but did not affect the surface properties of the PU adhesive films. On the other hand, the immediate (measured 30 s after joint formation) T-peel strength of roughened or (roughened + chlorinated with 1 wt% trichloroisocyanuric acid solutions in 2-butanone) styrene-butadiene rubber/PU adhesive joints was greatly improved if the adhesive was filled with up to 10 wt% sepiolite. The T-peel strength measured 72 h after bond formation was similar for the joints prepared with PU adhesives without and with up to 10 wt% sepiolite. The joint strength decreased if the amount of sepiolite in the PU adhesive was 20-30 wt%, due to the poor mechanical properties and too high moduli of the adhesives. Some interactions between the sepiolite, the polyurethane, and/or the solvent seemed to be responsible for the improved properties of filled PU adhesives. These interactions were responsible for the increased storage and loss moduli and the displacement of Tg of the PU adhesive films to higher temperature when it contained sepiolite. Furthermore, the addition of a high amount of sepiolite changed the rheological behaviour of the PU to a solid, giving rigidity to the structure, which is responsible for the reduced adhesion in roughened rubber joints produced with polyurethanes containing 20-30 wt% sepiolite.
Journal of Adhesion Science and Technology, 1999
In order to improve their adhesion to polyurethane adhesives, three unvulcanized block styrene-bu... more In order to improve their adhesion to polyurethane adhesives, three unvulcanized block styrene-butadiene-styrene (SBS) rubbers with styrene contents between 33% and 55% were surface-treated with solutions of 2 wt% trichloro-isocyanuric acid (TCI) in ethyl acetate. The joint strength was estimated using T-peel tests and the failed surfaces were analyzed to assess the locus of failure. The failed surfaces were analyzed using ATR-IR spectroscopy, contact angle measurements, XPS, and SEM. An unexpected trend in the joint strength was obtained because the locus of failure depended on both the styrene content and the mechanical properties of each SBS rubber. A mixed mode of failure was obtained in joints produced with S 1 rubber (33 wt% styrene content), whereas failure in the chlorinated layer was observed with S3 rubber (55 wt% styrene content); cohesive failure in the adhesive was found for the joints produced with S2 rubber (44 wt% styrene content).
International Journal of Adhesion and Adhesives, 2003
A styrene-butadiene-styrene (S6) rubber was treated with corona discharge to increase its surface... more A styrene-butadiene-styrene (S6) rubber was treated with corona discharge to increase its surface energy and adhesion to polyurethane (PU) adhesive. The influence of the length of treatment (the speed of the upper plate was varied from 80 to 900 cm/ min) during corona discharge was analyzed. The corona energy applied to S6 rubber surface ranged from 0.4 to 4.6 J/cm 2 . The surface modifications produced as a consequence of the corona discharge were characterized immediately after treatment was carried out and were monitored by means of different surface analysis techniques, mainly contact angle measurements (ethylene glycol, 251C), ATR-IR spectroscopy, XPS and Scanning Electron Microscopy (SEM). T-peel tests of corona-discharge-treated S6rubber/polyurethane (PU) adhesive/leather joints (72 h after joint formation) were carried out to evaluate the influence of the surface modifications produced by the corona discharge on the adhesion properties of the treated S6 rubber.
Journal of Adhesion Science and Technology, 2002
International Journal of Adhesion and Adhesives, 2001
Three thermoplastic block styrene}butadiene}styrene (TR) rubbers were treated with sulfuric acid ... more Three thermoplastic block styrene}butadiene}styrene (TR) rubbers were treated with sulfuric acid to improve their adhesion to polyurethane adhesives. T-peel test, scanning electron microscopy (SEM), contact-angle measurements (water, ethane diol), infra red spectroscopy (ATR-IR) and stress}strain experiments were used to analyze the nature of surface modi"cations produced in the rubber. The length of the treatment and the neutralization procedure (with and without ammonium hydroxide) were considered in this study. The treatment produced the sulfonation of the butadiene units of the rubber and the creation of highly conjugated C " C bonds, which produced a change in the color of the TR rubbers. The treatment also produced a decrease in the tensile strength and the elongation at break of the TR rubbers. This suggests that the treatment with sulfuric acid was not restricted to the rubber surface but also produced a bulk modi"cation. The lower the styrene content in the TR rubber, the more signi"cant modi"cations were produced on the surface. The styrene content (33}55 wt%) in three thermoplastic styrene}butadiene (TR) rubbers a!ected the extent, but not the nature of the surface modi"cations produced by treatment with sulfuric acid. The H SO treatment increased the T-peel strength of S1 and S2 rubber/polyurethane adhesive joints and produced a mixed failure mode (adhesion#cohesive failure in the rubber). Sulfonation of the TR rubbers is fast and needs only a 30 s immersion in sulfuric acid to produce high adhesion. Furthermore, the neutralization of the acidic surface with ammonium hydroxide is critical to assure an adequate durability of the adhesive joints.
International Journal of Adhesion and Adhesives, 1997
A sepiolite silicate was heat-treated at 550 and 1000°C to modify its structure, and was used as ... more A sepiolite silicate was heat-treated at 550 and 1000°C to modify its structure, and was used as a filler in a solvent-based polyurethane (PU) adhesive. The treated sepiolites were characterized by X-ray diffraction and infra-red spectroscopy, and it was observed that the water was irreversibly removed from the structure and pores of the sepiolite, changing the structure. The increase of temperature produced a collapse of the sepiolite structure. The rheological, mechanical, thermal and adhesion properties of the filled PU adhesives were measured. In general, the addition of treated sepiolite to PU adhesives resulted in a loss of adhesive properties with respect to the blank (PU adhesive with untreated sepiolite). The loss in properties was more noticeable as the treatment temperature increased. Thus the PU adhesives containing treated sepiolite had reduced rheological properties (lower viscosity, lower storage and loss moduli, and they did not provide thixotropy and pseudoplasticity to the solutions) with respect to the PU adhesive filled with untreated sepiolite. On the other hand, the addition of treated sepiolite decreased the mechanical and thermal mechanical properties of PU films. The T-peel strength of roughened and roughened+chlorinated (with l wt% trichloroisocyanuric acid in 2-butanone) styrene-butadiene rubber/PU adhesive joints was improved if the PU adhesive contained untreated sepiolite, but it decreased if the sepiolite was heat-treated. Interactions between the untreated sepiolite, the solvent and the polyurethane were responsible for the improved properties of PU adhesives. These interactions disappeared when the sepiolite was heattreated, because of the destruction of the structure of the sepiolite and the removal of surface silanol groups. © 1997 Elsevier Science Ltd (Keywords: A. polyurethane; A. solvent based; B. rubber; B. surface treatment; C. infrared spectra; C. dynamic mechanical analysis; C. rheology; D. viscoelasticity)
Surface and Interface Analysis, 2008
The interface produced between a chlorinated thermoplastic styrene-butadiene-styrene rubber and a... more The interface produced between a chlorinated thermoplastic styrene-butadiene-styrene rubber and a polychloroprene (PCP) adhesive has been studied and compared to the interface produced using a polyurethane (PU) adhesive. Chlorination of the rubber was produced by spin coating solutions of trichloroisocyanuric acid in methyl ethyl ketone. The adhesive solution was spin coated on to the chlorinated rubber and the interface between the chlorinated rubber and the adhesive was analyzed by infrared spectroscopy.Chlorination of the rubber produces cross-linking of the outermost chlorinated and oxidized rubber surface, which becomes insoluble in toluene. The chlorinated rubber chains are able to migrate through the chlorinated rubber/adhesive interface and produce a cross-linked interface. Similar interfaces are obtained with PU or PCP adhesive. However it is the addition of a thermoreactive phenolic tackifier resin to the PCP adhesive, which imparts appropriate rheological properties to the PCP adhesive, responsible for the increased adhesion properties. Copyright © 2008 John Wiley & Sons, Ltd.
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Papers by Mercedes Pastor Blas