http://hdl.handle.net/2117/3716 2013-05-24T00:27:47Z http://hdl.handle.net/2117/19379 Title: Unexpected differences between thermal and photoinitiated cationic curing oa a diglycidyl ether of bisphenol. A modified with a multiarm star poly (styrene)-b-poly (e-caprolactone) polymer Authors: Morancho Llena, José María; Cadenato Matia, Ana María; Ramis Juan, Xavier; Morell, Mireia; Fernández Francos, Xavier; Salla Tarragó, José María; Serra, Àngels Abstract: The effect of adding a multiarm star poly(styrene)-b-poly("-caprolactone) polymer on the cationic thermal and photoinitiated curing of diglycidyl ether of bisphenol A was studied. This star-polymer decelerated the thermal curing of diglycidyl ether of bisphenol A and modified the final structure of the epoxy matrix. The photocuring was influenced significantly by the addition of the multiarm star. When the proportion of this modifier added was 5%, much more time was necessary for complete photocuring (160 min at 40ºC). In the presence of 10% of modifier, the degree of photocuring reached was very low (0.196 at 120°C). A subsequent thermal post-curing was necessary to cure completely the system. During photocuring in presence of poly(styrene)-b-poly("-caprolactone), the formation of dormant species, which are reactivated when the temperature increases, takes places. The kinetics of the thermal curing and the photocuring was analyzed using an isoconversional method due to the complexity of the reactive process. Applying this method, it has been confirmed the dependence of activation energy on the degree of conversion. The fracture morphology analyzed by scanning electron microscopy exhibited a second phase originated during photocuring by the presence of the modifier. 2013-05-23T10:48:39Z http://hdl.handle.net/2117/18689 Title: Modification of epoxy-anhydride thermosets using a hyperbranched poly(este-amide): I. Kinetic study Authors: Fernández Francos, Xavier; Rybak, Andrzej; Sekula, Robert; Ramis Juan, Xavier; Serra, Angels Abstract: An epoxy-anhydride formulation used for the coating of electrical devices was modified with a commercially available hyperbranched poly(ester-amide), HybraneS2200, in order to improve the thermal degradability of the resulting thermoset and thus facilitate the recovery of substrate materials after use of the component. The curing kinetics of the unmodified and modifiedformulationswerestudied in detail with differential scanning calorimetry,Fourier transform infrared spectroscopyand rheology. The results suggest that S2200 gets incorporated into the network structure and the curing kinetics are accelerated by the presence of hydroxyl groups from S2200. 2013-04-08T10:48:27Z http://hdl.handle.net/2117/17636 Title: Study on dielectric, mechanical and thermal properties of polypropylene (PP) composites with ground tyre rubber (GTR) Authors: Mujal Rosas, Ramón María; Orrit Prat, Jordi; Ramis Juan, Xavier; Marín Genescá, Marcos; Rahhali, Ahmed 2013-02-11T14:57:40Z http://hdl.handle.net/2117/17612 Title: Aplicaciones eléctricas del acrilonitrilo butadieno estireno (ABS) reforzado con neumáticos fuera de uso (GTR) Authors: Mujal Rosas, Ramón María; Orrit Prat, Jordi; Ramis Juan, Xavier; Marín Genescá, Marcos 2013-02-08T13:57:52Z http://hdl.handle.net/2117/17370 Title: The use of dihydrazides as latent curing agents in diglycidyl ether of bisphenol A coatings Authors: Tomuta, Adrian; Ramis Juan, Xavier; Ferrando, Francesc; Serra, Angels Abstract: Dihydrazides of different structure were synthesized and tested as curing agents for DGEBA epoxy coatings. By calorimetric studies their latent characteristics were proved and the kinetics of the curing studied. The temperatures of activation are usually dependant on the melting point of the dihydrazide. The acceleration by base and Lewis acids was proved, but the latent character was diminished. FTIR/ATR allowed characterizing the final structures of the thermosets and confirming that the fully cured was achieved. The thermal stability of the materials and their thermomechanical characteristics were evaluated by TGA and DMTA, respectively. Mechanical properties of the thermosets were also determined. 2013-01-15T12:06:46Z http://hdl.handle.net/2117/17368 Title: Study of the thermal degradation of bioactive sol–gel coatings for the optimization of its curing process Authors: Hernández-Escolano, Miriam; Ramis Juan, Xavier; Jiménez-Morales, A; Juan-Díaz, M; Suay, Julio Abstract: A set of materials has been prepared by sol–gel process containing different quantities of hydroxyapatite (0, 2.5 and 5% HAp w/w) using as silica precursors glycidyloxypropyltrimethoxysilane (GPTMS) and triethoxyvinylsilane (VTES). In order to optimize the curing process to obtain sintherized systems (inorganic network) or hybrid systems (organic–inorganic) a TG and FTIR studies have been developed and degradation kinetic triplet parameters were obtained (the activation energy, pre-exponential factor, and function of degree of conversion). The kinetic study was analyzed by means of an integral isoconversional non-isothermal procedure (model free), and the kinetic model was determined by the Coats–Redfern method and through the compensation effect (IKR). All the systems followed the n = 6 kinetic model. The addition of HAp increases the thermal stability of the systems. The isothermal degradation was simulated from non-isothermal data, and the curing process could be defined to obtain the two types of materials. Temperature under 250 °C allows the formation of hybrids networks 2013-01-15T11:31:24Z http://hdl.handle.net/2117/17363 Title: Determinació de la calor de combustió d’una closca d’arròs Authors: Morancho Llena, José María; Salla Tarragó, José María; Cadenato Matia, Ana María; Martín Godoy, José Luis; Montserrat Jordà, José; Ramis Juan, Xavier Abstract: Determinació mitjançant una bomba calorimètrica de la calor de combustió d'una closca d'arròs. 2013-01-15T09:52:50Z http://hdl.handle.net/2117/16485 Title: Elastomeric epoxy nanocomposites: Nanostructure and properties Authors: Lipinska, Magdalena; Hutchinson, John M. Abstract: In polymer layered silicate nanocomposites, significant differences have been reported between the effects of the nano-reinforcement on rigid and elastomeric nanocomposites. In this paper, we have studied elastomeric nanocomposites based upon DGEBA epoxy resin filled with montmorillonite (MMT) and cured with a long-chain polyoxypropylene diamine, for comparison with analogous rigid nanocomposites. Ultrasonic mixing was used to disperse the MMT in the matrix to improve homogeneity and decrease the agglomerate size. Two different methods of nanocomposite preparation were used in which the MMT was first swollen with either the curing agent or the epoxy before the addition of, respectively, DGEBA or diamine. A better dispersion of the nanoclay in the matrix and a greater amount of intercalation occurred when the MMT was first swollen with the diamine. The effect of MMT concentrations up to 8 wt.% on the mechanical behaviour of the epoxy/MMT nanocomposites was investigated. It was found that the addition of MMT increased the tensile strength and modulus, although SAXS and TEM indicated that a significant fraction of the clay layers were not exfoliated. Nevertheless, the addition of the clay resulted in changes in the fracture surfaces, as indicated by SEM, consistent with the tensile results and indicative of toughening. 2012-09-14T08:49:01Z http://hdl.handle.net/2117/16165 Title: New epoxy thermosets with improved toughness by adding hyperbranched polymer modifiers Authors: Serra, Àngels; Flores, Marjorie; Foix, David; Ramis Juan, Xavier; Ferrando, Francesc; Fernández Francos, Xavier 2012-07-02T09:20:55Z http://hdl.handle.net/2117/16154 Title: Improvement of mechanical properties of epoxy/anhydride coatings using sepiolite and a hyperbranched polyster Authors: Serra, Àngels; Foix, David; Rodríguez, María Teresa; Ferrando, Francesc; Ramis Juan, Xavier Abstract: Epoxy resins are one of the most successful thermosetting materials when it comes to industrial application, and their uses embraces adhesives, coatings, encapsulation of electronic components and matrices of composite materials among others. The explanation to the extended usage of such materials can be found in the excellent properties they present in terms of chemical and thermal stability, heat distortion, high stiffness and versatility among others.1 However, they present also some drawbacks that limit their range of applications. One of the most significant is their poor impact resistance, since due to their high crosslinking density epoxy resins are inherently brittle coatings. In order to overcome this lack on toughness, the use of nanofillers have attracted great interest, both in academic and industrial fields, because they often exhibit dramatic improvements in mechanical properties of polymer matrix even at very low loadings.2 Another strategy recently adopted is the use of hyperbranched polymers (HBP) as chemical modifiers of epoxy resins.3,4 If the HBP is homogeneously dispersed in the matrix it introduces flexibility to the network resulting in an improvement in toughness. The particularity of this strategy is the fact that it is accomplished without compromising other properties of the material such as its Tg or hardness, and also without dramatically increasing the viscosity of the curing mixture. Here we present the combination of the two strategies in order to improve toughness. The influence on the curing process and in the final thermomechanical properties of both additives has been studied and finally some mechanical properties have been determined. The results have been correlated with the morphology of the materials. 2012-06-28T10:23:38Z http://hdl.handle.net/2117/16118 Title: The Use of Matlab in the study of the glass transition and vitrification in polymers Authors: Hutchinson, John M.; Fraga Rivas, Iria 2012-06-21T11:59:43Z http://hdl.handle.net/2117/16040 Title: Identification of nanostructural development in epoxy polymer layered silicate nanocomposites from the interpretation of differential scanning calorimetry and dielectric spectroscopy Authors: Román Concha, Frida Rosario; Calventus Solé, Yolanda; Colomer Vilanova, Pere; Hutchinson, John M. Abstract: The effect of nanoclay on the non-isothermal cure kinetics of polymer layered silicate nanocomposites based upon epoxy resin is studied by calorimetric techniques (DSC and TGA) and by dielectric relaxation spectroscopy (DRS) in non-isothermal cure at constant heating rate. The cure process takes place by homopolymerisation, initiated anionically using 3 wt% dimethylaminopyridine (DMAP), and the influence of the nanoclay content has been analysed. Interesting differences are observed between the nanocomposites with 2 wt% and 5 wt% clay content. At low heating rates, these samples vitrify and then devitrify during the cure. For the sample with 2 wt% clay, the devitrification is accompanied by a thermally initiated homopolymerisation, which can be identified by DRS but not by DSC. The effect of this is to improve the exfoliation of the nanocomposite with 2 wt% clay, as verified by transmission electron microscopy, with a corresponding increase in the glass transition temperature. These observations are interpreted in respect of the nanocomposite preparation method and the cure kinetics. 2012-06-14T11:27:05Z http://hdl.handle.net/2117/15728 Title: Competency assessment in engineerign courses at the Universitat Politècnica de Catalunya in Spain Authors: Martínez Martínez, María del Rosario; Amante García, Beatriz; Cadenato Matia, Ana María Abstract: Presented in this study are the evidences and details of the tools used to assess and monitor projects assigned to student groups within the context of three subjects of the Universitat Politècnica de Catalunya (UPC, BarcelonaTech, Spain). During the process, the aim was to integrate generic competencies: teamwork, and oral and written effective communication. To facilitate learning throughout the process, follow-up meetings of teacher and student groups were held. Monitoring of progress was carried out in conjunction with a feedback process that enabled continuous improvement. The main conclusions from an analysis of the results are: 1) the projects developed were of higher quality; 2) motivation and student involvement was higher; and 3) greater satisfaction was experienced by the participating students and teachers. 2012-04-16T08:25:02Z http://hdl.handle.net/2117/15056 Title: El puzle como actividad de evaluación en el aula en grupos numerosos Authors: Cadenato Matia, Ana María; Martínez Martínez, María del Rosario Abstract: La presente comunicación expone cómo se ha utilizado la técnica del puzle como actividad de evaluación en el aula con el doble objetivo de realizar una evaluación continua e introducir la competencia del trabajo en equipo en grupos numerosos. La experiencia se ha venido desarrollando desde el curso 2007-08 en dos asignaturas troncales, Química I y Termodinámica, de la titulación de Ingeniería Industrial, en la Escuela Técnica Superior de Ingeniería Industrial de Barcelona, de la Universidad Politécnica de Cataluña (ETSEIB-UPC). Esta técnica, al igual que todas las de aprendizaje cooperativo, transfiere parte de la responsabilidad del aprendizaje al alumnado, que es uno de los principales objetivos del cambio a que aspira la implantación del EEES en el mundo universitario. Se ha constatado una gran participación en esta actividad y se ha valorado la percepción del alumnado por medio de cuestionarios de incidencias críticas (CuIC), encuestas de opinión y de satisfacción al final del curso (SEEQ). Se puede extraer como conclusión que esta actividad ha servido para mejorar significativamente el aprendizaje, tal como se deduce del análisis de los resultados académicos. 2012-02-10T11:24:33Z http://hdl.handle.net/2117/14962 Title: Evidencias e instrumentos para la evaluación del aprendizaje por competencias Authors: Martínez Martínez, María del Rosario; Cadenato Matia, Ana María; Amante García, Beatriz 2012-02-06T12:31:13Z