Estrategias de funcionalización de grafeno para el desarrollo de nanocompuestos de matriz termoplástica

Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Departamento de Química Inorgánica. Fecha de lectura:29-03-2019El objetivo principal de esta tesis es el desarrollo de nanocompuestos poliméricos multifuncionales basados en grafeno, con potencial aplicación en sectores como el de la automoción y el aeronáutico. Se investigan tres polímeros termoplásticos con propiedades muy diferentes pero todos de gran relevancia industrial: un elastómero termoplástico, poli(estireno-b-etileno-cobutileno- b-estireno) (SEBS), una poliolefina, polipropileno isotáctico (iPP), y un polímero de altas prestaciones, poli(éter éter cetona) (PEEK). Con la incorporación del grafeno se pretende obtener materiales con mejor estabilidad térmica y propiedades mecánicas, y que presenten conductividad eléctrica. En esta tesis se desarrollan estrategias de funcionalización del grafeno específicas para cada matriz termoplástica y se preparan nanocompuestos poliméricos empleando grafeno modificado y sin modificar como carga. Se estudia la influencia que la modificación química ejerce sobre la morfología de fases del nanocompuesto y sobre la estructura cristalina del material resultante. Del mismo modo, se evalúa la estabilidad térmica de cada uno de los sistemas obtenidos y se determinan sus propiedades mecánicas y eléctricas, para establecer la efectividad de la modificación química en la obtención de nanocompuestos con mejores propiedades. Los resultados indican mejoras en la dispersión del grafeno modificado con cadenas poliméricas cortas de naturaleza similar a la de la matriz polimérica objetivo. Esto da lugar, generalmente, a nanocompuestos con superior estabilidad térmica y mejores propiedades mecánicas y eléctricas en comparación con el empleo de grafeno sin funcionalizar. Además, algunos de los nanocompuestos de iPP y PEEK se exploraran para el desarrollo de materiales compuestos con jerarquía de refuerzo, donde se combina tejido continuo de fibra de carbono (refuerzo en la microescala) y grafeno (refuerzo en la nanoescala). Con la incorporación de grafeno al sistema multicapa convencional, es decir, fibra de carbono/polímero, se pretende mejorar las propiedades interlaminares del sistema, que son las principales causantes de su fallo mecánico. No obstante, la preparación de sistemas multicapa donde se combinan refuerzos en la micro- y nano-escala es muy complejo, ya que no solo hay que conjugar factores de dispersión e interacción de la nanocarga, sino que también se ven influenciados por factores como la viscosidad e impregnación de la fibra, siendo estos últimos de especial dificultad en el caso de emplear matrices termoplásticas.The main objective of the thesis research is the development of advanced polymer nanocomposites based on graphene, with the aim of producing multifunctional materials suitable to be used in demanding sectors such as the automotive and the aeronautic industry. Three thermoplastic polymer matrixes of important relevance for the industry are selected: a thermoplastic elastomer, poly(styrene-b-ethylene-co-butylene-b-styrene) (SEBS), a polyolefin, isotactic polypropylene (iPP) and a high performance polymer, poly(ether ether ketone) (PEEK). Graphene incorporation is aimed to simultaneously improve both thermal stability and mechanical properties, and also to provide the new material with electrical conductivity. In this thesis, specific strategies for graphene functionalization are developed according to the targeted polymer matrix and polymer nanocomposites with graphene or modified graphene are prepared. The aim is to investigate the influence that graphene modification exerts on nanocomposite phase morphology and on the crystalline morphology of the resulting material. Furthermore, the thermal stability of each system is assessed and their mechanical and electrical properties are determined, with the aim of evaluating the suitability of the graphene chemical modification to develop nanocomposites with enhanced properties. The results suggest that modifying graphene with short polymer chains similar in nature to those of the targeted polymer matrix improve its dispersion. As a result, nanocomposites with superior thermal stability and better mechanical and electrical properties than in the case of the non-functionalized graphene are typically produced. In addition, some iPP and PEEK nanocomposites are explored in the preparation of composite materials hierarchically reinforced with carbon fibre fabric (microscale reinforcement) and graphene (nanoscale reinforcement). The purpose of incorporating graphene to the conventional composite (fibre reinforced polymer composite) is to improve its interlaminar properties, which are the main cause of catastrophic failure in this type of systems. Nonetheless, the preparation of composite materials where micro- and nano-scaled reinforcements are combined is very complex, since not only the filler dispersion and its interaction with the matrix need to be considered, but additional parameters such as matrix viscosity and fibre impregnation are of special relevance, especially in the case of thermoplastic matrices.Financiada por el Ministerio de Economía, Industria y Competitividad (MAT2013-47898-C2-2-R

Catalytic performance of CuO/Ce0.8Zr0.2O2 loaded onto SiC-DPF in NOx-assisted combustion of diesel soot

This work presents a comparative study between the catalytic performance of the 2% CuO/ceria-zirconia powder catalyst and the same catalyst supported on silicon carbide DPF (Diesel Particulate Filter) towards NO oxidation reaction and soot combustion reaction. The ceria-zirconia catalyst was prepared by the co-precipitation method and 2 wt% copper was incorporated by the incipient wetness impregnation method. The catalyst was incorporated onto the ceramic support using a simple and organic solvent-free procedure by a simply dipping the DPF into an aqueous solution of the catalyst. The powder catalyst has been characterized using N2 adsorption at −196 °C, XRD and Raman Spectroscopy; whereas the catalytic coating morphology has been evaluated by SEM and the mechanical stability by an adherence test. Both catalyst configurations were tested for NO oxidation to NO2 and for soot combustion under NOx/O2. The results revealed that incorporation of the very active copper/ceria-zirconia catalyst onto SiC-DPF has been successfully achieved by a simple coating procedure. Furthermore, the catalytic coating has shown suitable mechanical, chemical and thermal stability. A satisfactory catalytic performance of the catalytic-coated filter was reached towards the NO oxidation reaction. Moreover, it was proved that the catalytic coating is stable and the corresponding coated DPF can be reused for several cycles of NO oxidation without a significant decrease in its activity. Finally, it was verified that the loose-contact mode is a good choice to simulate the catalytic performance of this active phase in a real diesel particulate filter.The authors gratefully acknowledge the financial support of Generalitat Valenciana (PROMETEOII/2014/010 project), the Spanish Ministry of Economy and Competitiveness (CTQ2012-30703 project, UE-FEDER funding). S.Q.D. wishes to thank VIDI-University of Alicante her Master Thesis Grant

Impact of a home telehealth program after a hospitalized COPD exacerbation: a propensity score analysis

[Abstract] Introduction: Currently there is lack of data regarding the impact of a home telehealth program on readmissions and mortality rate after a COPD exacerbation-related hospitalization. Objective: To demonstrate if a tele-monitoring system after a COPD exacerbation admission could have a favorable effect in 1-year readmissions and mortality in a real-world setting. Methods: This is an observational study where we compared an intervention group of COPD patients treated after hospitalization that conveyed a telehealth program with a followance period of 1 year with a control group of patients evaluated during one year before the intervention began. A propensity-score analyses was developed to control for confounders. The main clinical outcome was 1-year all-cause mortality or COPD-related readmission. Results: The analysis comprised 351 telemonitoring patients and 495 patients in the control group. The intervention resulted in less mortality or readmission after 12 months (35.2% vs. 45.2%; hazard ratio [HR] 0.71 [95% CI=0.56-0.91] 0.71 [95% CI=0.56-0.91; p=0.007). This benefit was maintained after the propensity score analysis (HR=0.66 [95% CI=0.51-0.84]). This benefit, which was seen from the first month of the study and during its whole duration, is maintained when mortality (HR=0.54; 95% CI=[0.36-0.82]) or readmission (subdistribution hazard ratio [SHR] 0.66; 95% CI=[0.50-0.86]) are analyzed separately. Conclusion: Telemonitoring after a severe COPD exacerbation is associated with less mortality or readmissions at 12 months in a real world clinical setting

Monitoring the complex benthic habitat on semi-dark underwater marine caves using photogrammetry-based 3D reconstructions

Marine caves are dark environments considered a priority habitat for conservation included in the EU Habitats Directive (H8330). They harbor fragile benthic communities and represent a major reservoir of marine biodiversity. However, there is a lack of knowledge of these habitats due to the difficulties of creating detailed benthic maps and characterizing the biodiversity, structure, and dynamics of their communities. The uniqueness of marine caves fosters their popularity among recreational divers, who can cause disturbances through abrasion of the biota, resuspension of sediment, and accumulation of exhaled air bubbles in the caves' ceilings. This study aims to build a monitoring framework to characterize the structure and temporal dynamics of this complex habitat using Structurefrom- Motion (SfM) photogrammetry. SfM is a novel, non-invasive technique that allows a major advancement in the monitoring of changes in the cave’s community assemblages. This method relies on images acquired by 4K video footage to build fine-scaled 3D digital models of the substrate using overlapping imagery. For this study, we combined SfM photogrammetry and photo quadrats extracted from the video recordings. We evaluate the effectiveness of this methodology in a marine cave highly frequented by divers, located in Illa de l’Aire (Balearic Islands, Spain), and carried out two surveys before and after the diving season (2019-2021). As a result, we found a loss of 25 colonies of bryozoans with fragile skeletons, like Schizoretepora sp., and 8 individual sponges with globose morphotypes. Our results indicate that this methodology enables accurate and efficient monitoring of benthic communities in underwater caves that allow us to better understand their dynamics and, therefore, to develop the need management measures

MAPPING COMMUNITY INTEREST HABITATS IN THE COLUMBRETES ARCHIPELAGO, AN EXTRAORDINARY HOT SPOT OF BIODIVERSITY

The Columbretes Archipelago and their submerged surroundings are part of an unusual, Pleistocene volcanic field located in the Western Mediterranean designated as a Site of Community Importance (SCI) of the Natura 2000 Network. In the present study, 4 benthic habitats of community interest (1110, 1170, 1180 and 8330) have been identified by analyzing several sources of information. Generalized additive models (GAMs) have been used to model the potential distribution of reefs (1170) and maërl beds (1110). Our results highlight the diversity and extent of these habitats and allow comparisons to other marine SCIs of Spain. This can be attributed to the variability of the environment of this site. The Columbretes Islands combine a relatively shallow environment with volcanic structures, hydrothermalism with active degassing, current-driven sedimentary lobes and the influence of inland flows. Understanding high biodiversity spots is crucial as they offer natural laboratories to describe how ecosystems respond to the effects of global change. The knowledge obtained will be of paramount importance for the conservation of species and habitats. Furthermore, it will establish a baseline for future monitoring and assist in the development of effective management plans

Catalyzed Particulate Filter Regeneration by Platinum Versus Noble Metal-Free Catalysts: From Principles to Real Application

In this short review, results from previous investigations by our group regarding 2 % Cu/ceria–zirconia catalyst incorporated onto a lab-scale diesel particulate filter (DPF) were compiled and compared to recent results concerning commercial platinum/alumina incorporated onto a DPF, in order to explore their catalytic regeneration. Their behavior was compared to the corresponding powder catalytic activity. In this sense, NO oxidation to NO2 and NO/NO2 recycling efficiency on the soot combustion catalytic activity were investigated for different catalyst/soot ratios. The active phase incorporated onto the DPFs was checked to be mechanically stable and reproducible in terms of amounts. Results show that catalytic activity towards NO oxidation to NO2 remains essentially constant after several cycles for both DPF-supported catalysts. It was also found that soot combustion rates presented by Pt/alumina-DPF (in 1:3 soot/catalyst ratio) and CuO/ceria–zirconia-DPF (in 1:5 soot/catalyst ratio) are very similar. It reveals that this noble metal-free catalyst can be competitive compared to a commercial platinum-based one, regarding soot combustion reaction in a particulate filter.The authors gratefully acknowledge the Financial Support of Generalitat Valenciana (PROMETEOII/2014/010 Project), the Spanish Ministry of Economy and Competitiveness (CTQ2015-64801-R project, UE-FEDER funding). S.Q.D. wishes to thank VIDI-University of Alicante her Master Thesis Grant

Anhydride-based chemistry on graphene for advanced polymeric materials

Functionalization of graphene based on the coupling of acylium ions under conditions similar to Friedel-Crafts acylation is reported. The reaction is applied to the functionalization of graphene with low molecular weight polypropylene, and the resulting material when incorporated as a filler significantly enhances the electrical, mechanical and thermal performance of a commodity polymer like polypropylene.The authors thank the Spanish Government (MINECO) for nancial support (Projects: MAT2013-47898-C2-2-R and MAT2014-54231-C4-4P), a Ramon y Cajal Research Fellowship (H. J. S.) and a FPI studentships (S. Q. D). Also Mr David G´omez and Ms Isabel Muñooz (Characterization Service of the Institute of Polymer Science & Technology) are gratefully acknowledged for the SEM and Raman measurements, respectivelyPeer Reviewe

The role of molecular architecture on the viscoelastic properties of thermoreversible polyurethane adhesives

New polyurethane (PUR) adhesives containing covalent Diels-Alder (DA) bonds that can break and form with temperature have been recently developed for sustainable multilayer packaging. The understanding of the mechanical properties and in particular of creep in terms of molecular architecture appears of outmost importance in view of their applications and potential reutilization. Oscillatory shear rheometry shows a modulus decrease with temperature associated to bond breakage and the enhancement found upon cooling can be associated with network reconstruction. Analysis of storage modulus values above the glass transition and below the retro-DA reaction suggests a lower network crosslinking density with increasing adduct content. Room temperature indentation and shear rheometry tests reveal that DA bonds improve the modulus and reduce the resistance to linear viscoelastic flow. The modulus improvement can be associated to the enhanced chain rigidity introduced by the DA moieties and the reduced creep resistance seems to be related to the decrease of crosslinking density.This project has received funding from the Bio Based Industries Joint Undertaking (BBI-JU) under the European Union’s Horizon 2020 research and innovation program under grant agreement N◦ 837715. The authors wish to thank the MICINN (Ministerio de Ciencia e Innovacion), ´ Spain, for funding under grant PID2019-107710 GB-I00. The TEM-BIOPHYM Service at the IEM-CSIC is acknowledged for granting the use of the rheology facilities

Nanoindentation in Polymer-Based/graphene composites

POLY-CHAR 2019,Kathmandu, Nepal, May 19 - 23, 201