Fernando Villafane

@uva.es

Química Inorgánica
UNiversidad de Valladolid



           

https://researchid.co/fervilla
1

Scopus Publications

Scopus Publications

  • Reaching a near zero radiative heat transfer by the inclusion of modified multiwalled-carbon nanotubes (MWCNTs) in polyurethane-polyisocyanurate aerogels
    Beatriz Merillas, Tomás Enrique Gómez Álvarez-Arenas, Fernando Villafañe, and Miguel Ángel Rodríguez-Pérez
    Elsevier BV

  • 1,2-Azolylamidino ruthenium(ii) complexes with DMSO ligands: electro- and photocatalysts for CO<inf>2</inf> reduction
    Murphy Jennings, Elena Cuéllar, Ariadna Rojo, Sergio Ferrero, Gabriel García-Herbosa, John Nganga, Alfredo M. Angeles-Boza, Jose M. Martín-Alvarez, Daniel Miguel, and Fernando Villafañe
    Royal Society of Chemistry (RSC)
    Ru(ii) 1,2-azolylamidino-DMSO complexes are herein described. Their electrochemical behavior in CO2 media is consistent with CO2 electrocatalyzed reduction, whereas photocatalytic CO2 reduction experiments lead to CO and trace amounts of formate.

  • Polyurethane foam scaffold for silica aerogels: effect of cell size on the mechanical properties and thermal insulation
    B. Merillas, A. Lamy-Mendes, F. Villafañe, L. Durães, and M.Á. Rodríguez-Pérez
    Elsevier BV

  • Super-Insulating Transparent Polyisocyanurate-Polyurethane Aerogels: Analysis of Thermal Conductivity and Mechanical Properties
    Beatriz Merillas, Fernando Villafañe, and Miguel Ángel Rodríguez-Pérez
    MDPI AG
    A family of transparent polyisocyanurate-polyurethane (PUR-PIR) aerogels with an interesting combination of physical properties were synthesized. First, their textural properties were analyzed aiming to study catalyst influence on the final porous structures and densities. Their thermal conductivities were measured at different temperatures allowing observation of a clear trend relating the initial formulation with the porous structure and reaching values as low as 12 mW/mK, the lowest found in the literature for aerogels based on this polymer matrix. Contributions to thermal conductivity were calculated, improving the understanding of the porous structure-insulating performance relationship. Moreover, their mechanical properties were studied (elastic modulus, stress at different strains and elastic behavior). The aerogels showed tunable stiffness (elastic modulus from 6.32 to 0.13 MPa) by changing the catalyst concentration and significant elasticity. Thus, super-insulating transparent PUR-PIR aerogels with tailored mechanical properties were obtained opening a wide range of potential applications in the energy, building, automotive and aeronautical sectors, among others. The exceptional insulation of silica aerogels was reached at the same time that their general brittleness was improved while keeping good transparency to visible light (85%, 650 nm). Therefore, these aerogels may constitute an alternative to silica aerogels.

  • Silica-Based Aerogel Composites Reinforced with Reticulated Polyurethane Foams: Thermal and Mechanical Properties
    Beatriz Merillas, Alyne Lamy-Mendes, Fernando Villafañe, Luisa Durães, and Miguel Ángel Rodríguez-Pérez
    MDPI AG
    In this work, silica aerogel composites reinforced with reticulated polyurethane (PU) foams have been manufactured having densities in the range from 117 to 266 kg/m3 and porosities between 85.7 and 92.3%. Two different drying processes were employed (ambient pressure drying and supercritical drying) and a surface modification step was applied to some of the silica formulations. These composites, together with the reference PU foam and the monolithic silica aerogels, were fully characterized in terms of their textural properties, mechanical properties and thermal conductivities. The surface modification with hexamethyldisilazane (HMDZ) proved to improve the cohesion between the reticulated foam and the silica aerogels, giving rise to a continuous network of aerogel reinforced by a polyurethane porous structure. The samples dried under supercritical conditions showed the best interaction between matrixes as well as mechanical and insulating properties. These samples present better mechanical properties than the monolithic aerogels having a higher elastic modulus (from 130 to 450 kPa), a really exceptional flexibility and resilience, and the capacity of being deformed without breaking. Moreover, these silica aerogel-polyurethane foam (Sil-PU) composites showed an excellent insulating capacity, reaching thermal conductivities as low as 14 mW/(m·K).

  • Improving the Insulating Capacity of Polyurethane Foams through Polyurethane Aerogel Inclusion: From Insulation to Superinsulation
    Beatriz Merillas, Fernando Villafañe, and Miguel Ángel Rodríguez-Pérez
    MDPI AG
    A novel synthesis of polyurethane foam/polyurethane aerogel (PUF–PUA) composites is presented. Three different polyurethane reticulated foams which present the same density but different pore sizes (named S for small, M for medium, and L for large) have been used. After the characterization of the reference materials (either, foams, and pure aerogel), the obtained composites have been characterized in order to study the effect of the foam pore size on the final properties, so that density, shrinkage, porous structure, mechanical properties, and thermal conductivity are determined. A clear influence of the pore size on the density and shrinkage was found, and the lowest densities are those obtained from L composites (123 kg/m3). Moreover, the aerogel density and shrinkage have been significantly reduced through the employment of the polyurethane (PU) foam skeleton. Due to the enhanced mechanical properties of polyurethane aerogels, the inclusion of polyurethane aerogel into the foam skeleton helps to increase the elastic modulus of the foams from 0.03 and 0.08 MPa to 0.85 MPa, while keeping great flexibility and recovery ratios. Moreover, the synthesized PUF–PUA composites show an excellent insulating performance, reducing the initial thermal conductivity values from 34.1, 40.3, and 50.6 mW/(m K) at 10 °C for the foams S, M, and L, to 15.8, 16.6, and 16.1 mW/(m K), respectively. Additionally, the effect of the different heat transfer mechanisms to the total thermal conductivity is herein analyzed by using a theoretical model as well as the influence of the measurement temperature.

  • A New Methodology Based on Cell-Wall Hole Analysis for the Structure-Acoustic Absorption Correlation on Polyurethane Foams
    Beatriz Merillas, Fernando Villafañe, and Miguel Ángel Rodríguez-Pérez
    MDPI AG
    Polyurethane foams with a hybrid structure between closed cell and open cell were fabricated and fully characterized. Sound absorption measurements were carried out in order to assess their acoustic performance at different frequency ranges. The cellular structure of these systems was studied in detail by defining some novel structural parameters that characterize the cell wall openings such as the average surface of holes (Sh), the number of holes (h), and the area percentage thereof (%HCW). Therefore, these parameters allow to analyze quantitatively the effect of different structural factors on the acoustic absorption performance. It has been found that the parameters under study have a remarkable influence on the normalized acoustic absorption coefficient at different frequency ranges. In particular, it has been demonstrated that increasing the surface of the holes and the percentage of holes in the cell walls allows increasing the acoustic absorption of these types of foams, a promising statement for developing highly efficient acoustic insulators. Additionally, we could determine that a suitable minimum value of hole surface to reach the highest sound dissipation for these samples exists.

  • Optical Properties of Polyisocyanurate–Polyurethane Aerogels: Study of the Scattering Mechanisms
    Beatriz Merillas, Judith Martín-de León, Fernando Villafañe, and Miguel Ángel Rodríguez-Pérez
    MDPI AG
    Highly transparent polyisocyanurate–polyurethane (PUR–PIR) aerogels were synthesized, and their optical properties were studied in detail. After determining the density and structural parameters of the manufactured materials, we analyzed their optical transmittance. It was demonstrated that the catalyst content used to produce the aerogels can be employed to tune the internal structure and optical properties. The results show that the employment of lower catalyst amounts leads to smaller particles forming the aerogel and concomitantly to higher transmittances, which reach values of 85% (650 nm) due to aerogel particles acting as scattering centers. Thus, it was found that the lower this size, the higher the transmittance. The effect of the sample thickness on the transmittance was studied through the Beer–Lambert law. Finally, the scattering mechanisms involved in the light attenuation were systematically evaluated by measuring a wide range of light wavelengths and determining the transition between Rayleigh and Mie scattering when the particles were larger. Therefore, the optical properties of polyurethane aerogels were studied for the first time, opening a wide range of applications in building and energy sectors such as glazing windows.

  • Characterization and Properties of Water-Blown Rigid Polyurethane Foams Reinforced with Silane-Modified Nanosepiolites Functionalized with Graphite
    Mercedes Santiago-Calvo, María Carracedo-Pérez, María Luisa Puertas, Antonio Esteban-Cubillo, Julio Santaren, Fernando Villafañe, and Miguel-Ángel Rodríguez-Pérez
    MDPI AG
    In the present study, a promising flame retardant consisting of 80 wt% silane-modified nanosepiolites functionalized with 20 wt% graphite (SFG) is used to obtain a synergistic effect principally focussed on the thermal stability of water-blown rigid polyurethane (RPU) foams. Density, microcellular structure, thermal stability and thermal conductivity are examined for RPU foams reinforced with different contents of SFG (0, as reference material, 2, 4 and 6 wt%). The sample with 6 wt% SFG presents a slightly thermal stability improvement, although its cellular structure is deteriorated in comparison with the reference material. Furthermore, the influence of SFG particles on chemical reactions during the foaming process is studied by FTIR spectroscopy. The information obtained from the chemical reactions and from isocyanate consumption is used to optimize the formulation of the foam with 6 wt% SFG. Additionally, in order to determine the effects of functionalization on SFG, foams containing only silane-modified nanosepiolites, only graphite, or silane-modified nanosepiolites and graphite added separately are studied here as well. In conclusion, the inclusion of SFG in RPU foams allows the best performance to be achieved.

  • Transparent Polyisocyanurate-Polyurethane-Based Aerogels: Key Aspects on the Synthesis and Their Porous Structures
    Beatriz Merillas, Judith Martín-de León, Fernando Villafañe, and Miguel A. Rodríguez-Pérez
    American Chemical Society (ACS)
    The effect of the catalyst concentration on the synthesis and textural properties of polyisocyanurate-polyurethane aerogels is analyzed. The use of different catalyst amounts allows obtaining low-density aerogels (0.10−0.16 g/cm) with high porosities (85−91%). Their porous structures were analyzed by scanning electron microscopy and nitrogen adsorption−desorption isotherm. A noticeable decrease in the size of the scattering centers, particles and pores, was achieved when reducing the catalyst amount. In some samples, the small size of these features, much smaller than the wavelength of visible light, causes a bare light dispersion, leading to the first transparent polyisocyanurate-polyurethane aerogels. Light transmittance measurements at 532 nm have been made showing high values (ca. 76% for 1 mm thick samples) for the formulations with the smallest particle and pore sizes. These aerogels presenting optical transparency have many potential applications such as solar collectors, glazing systems for insulating windows, and sensors, among others.

  • Analysis of the foaming window for thermoplastic polyurethane with different hard segment contents
    Mercedes Santiago-Calvo, Haneen Naji, Victoria Bernardo, Judith Martín-de León, Alberto Saiani, Fernando Villafañe, and Miguel Ángel Rodríguez-Pérez
    MDPI AG
    A series of thermoplastic polyurethanes (TPUs) with different amounts of hard segments (HS) (40, 50 and 60 wt.%) are synthesized by a pre-polymer method. These synthesized TPUs are characterized by Shore hardness, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD), dynamic mechanical thermal analysis (DMTA), and rheology. Then, these materials are foamed by a one-step gas dissolution foaming process and the processing window that allows producing homogeneous foams is analyzed. The effect of foaming temperature from 140 to 180 °C on the cellular structure and on density is evaluated, fixing a saturation pressure of 20 MPa and a saturation time of 1 h. Among the TPUs studied, only that with 50 wt.% HS allows obtaining a stable foam, whose better features are reached after foaming at 170 °C. Finally, the foaming of TPU with 50 wt.% HS is optimized by varying the saturation pressure from 10 to 25 MPa at 170 °C. The optimum saturation and foaming conditions are 25 MPa and 170 °C for 1 h, which gives foams with the lowest relative density of 0.74, the smallest average cell size of 4 μm, and the higher cell nucleation density of 8.0 × 109 nuclei/cm3. As a final conclusion of this investigation, the TPU with 50 wt.% HS is the only one that can be foamed under the saturation and foaming conditions used in this study. TPU foams containing 50 wt.% HS with a cell size below 15 microns and porosity of 1.4–18.6% can be obtained using foaming temperatures from 140 to 180 °C, saturation pressure of 20 MPa, and saturation time of 1 h. Varying the saturation pressure from 10 to 25 MPa and fixing the foaming temperature of 170 °C and saturation pressure of 1 h results in TPU foams with a cell size of below 37 microns and porosity of 1.7–21.2%.

  • Nanoparticles addition in pu foams: The dramatic effect of trapped-air on nucleation
    Beatriz Merillas, Fernando Villafañe, and Miguel Ángel Rodríguez-Pérez
    MDPI AG
    To determine the effect of nanoclays and trapped air on the formation of rigid polyurethane foams, three different production procedures were used. To study the influence of mixing at atmospheric pressure, two approaches were carried out employing either an electric or a magnetic stirrer. The third approach was executed by mixing under vacuum conditions with magnetic stirring. The samples thus obtained were characterized, and the effect of trapped air into the reactive mixtures was evaluated by analyzing the cellular structures. Different levels of trapped air were achieved when employing each manufacturing method. A correlation between the trapped air and the increase in the nucleation density when nanoclays were added was found: the cell nucleation density increased by 1.54 and 1.25 times under atmospheric conditions with electric and magnetic stirring, respectively. Nevertheless, samples fabricated without the presence of air did not show any nucleating effect despite the nanoclay addition (ratio of 1.09). This result suggests that the inclusion of air into the components is key for improving nucleation and that this effect is more pronounced when the polyol viscosity increases due to nanoclay addition. This is the most important feature determining the nucleating effect and, therefore, the corresponding cell size decreases.

  • Luminescent cis-Bis(bipyridyl)ruthenium(II) Complexes with 1,2-Azolylamidino Ligands: Photophysical, Electrochemical Studies, and Photocatalytic Oxidation of Thioethers
    Elena Cuéllar, Alberto Diez-Varga, Tomás Torroba, Pablo Domingo-Legarda, José Alemán, Silvia Cabrera, Jose M. Martín-Alvarez, Daniel Miguel, and Fernando Villafañe
    American Chemical Society (ACS)
    New 1,2-azolylamidino complexes cis-[Ru(bipy)2(NH=C(R)az*-κ2N,N)](OTf)2 (R = Me, Ph; az* = pz, indz, dmpz) are synthesized via chloride abstraction after a subsequent base-catalyzed coupling of a nitrile with the previously coordinated 1,2-azole. The synthetic procedure allows the easy obtainment of complexes having different electronic and steric 1,2-azoylamidino ligands. All of the compounds have been characterized by 1H, 13C, and 15N NMR and IR spectroscopy and by monocrystal X-ray diffraction. Photophysical studies support their phosphorescence, whereas their electrochemistry reveals reversible RuII/RuIII oxidations between +1.13 and +1.25 V (vs SCE). The complexes have been successfully used as catalysts in the photooxidation of different thioethers, the complex cis-[Ru(bipy)2(NH=C(Me)dmpz-κ2N,N)]2+ showing better catalytic performance in comparison to that of [Ru(bipy)3]2+. Moreover, the significant catalytic performance of the dimethylpyrazolylamidino complex is applied to the preparation of the drug modafinil, which is obtained using ambient oxygen as an oxidant. Finally, mechanistic assays suggest that the oxidation reaction follows a photoredox route via oxygen radical anion formation.

  • (1,2-Azole)bis(bipyridyl)ruthenium(II) Complexes: Electrochemistry, Luminescent Properties, and Electro- And Photocatalysts for CO<inf>2</inf>Reduction
    Elena Cuéllar, Laura Pastor, Gabriel García-Herbosa, John Nganga, Alfredo M. Angeles-Boza, Alberto Diez-Varga, Tomás Torroba, Jose M. Martín-Alvarez, Daniel Miguel, and Fernando Villafañe
    American Chemical Society (ACS)
    New cis-(1,2-azole)-aquo bis(2,2'-bipyridyl)ruthenium(II) (1,2-azole (az*H) = pzH (pyrazole), dmpzH (3,5-dimethylpyrazole), and indzH (indazole)) complexes are synthesized via chlorido abstraction from cis-[Ru(bipy)2Cl(az*H)]OTf. The latter are obtained from cis-[Ru(bipy)2Cl2] after the subsequent coordination of the 1,2-azole. All the compounds are characterized by 1H, 13C, 15N NMR spectroscopy as well as IR spectroscopy. Two chlorido complexes (pzH and indzH) and two aquo complexes (indzH and dmpzH) are also characterized by X-ray diffraction. Photophysical and electrochemical studies were carried out on all the complexes. The photophysical data support the phosphorescence of the complexes. The electrochemical behavior of all the complexes in an Ar atmosphere indicate that the oxidation processes assigned to Ru(II) → Ru(III) occurs at higher potentials in the aquo complexes. The reduction processes under Ar lead to several waves, indicating that the complexes undergo successive electron-transfer reductions that are centered in the bipy ligands. The first electron reduction is reversible. The electrochemical behavior in CO2 media is consistent with CO2 electrocatalyzed reduction, where the values of the catalytic activity [icat(CO2)/ip(Ar)] ranged from 2.9 to 10.8. Controlled potential electrolysis of the chlorido and aquo complexes affords CO and formic acid, with the latter as the major product after 2 h. Photocatalytic experiments in MeCN with [Ru(bipy)3]Cl2 as the photosensitizer and TEOA as the electron donor, which were irradiated with >300 nm light for 24 h, led to CO and HCOOH as the main reduction products, achieving a combined turnover number (TONCO+HCOO-) as high as 107 for 2c after 24 h of irradiation.

  • Synergistic effect of expandable graphite and phenylphosphonic-aniline salt on flame retardancy of rigid polyurethane foam
    Pablo Acuña, Xuebao Lin, Mercedes Santiago Calvo, Zhubao Shao, Nerea Pérez, Fernando Villafañe, Miguel Ángel Rodríguez-Pérez, and De-Yi Wang
    Elsevier BV

  • Luminescent Rhenium(I)tricarbonyl Complexes Containing Different Pyrazoles and Their Successive Deprotonation Products: CO<inf>2</inf>Reduction Electrocatalysts
    Beatriz Merillas, Elena Cuéllar, Alberto Diez-Varga, Tomás Torroba, Gabriel García-Herbosa, Sergio Fernández, Julio Lloret-Fillol, Jose M. Martín-Alvarez, Daniel Miguel, and Fernando Villafañe
    American Chemical Society (ACS)
    Cationic fac-[Re(CO)3(pz*H)(pypzH)]OTf (pz*H = pyrazole, pzH; 3,5-dimethylpyrazole, dmpzH; indazole, indzH; 3-(2-pyridyl)pyrazole, pypzH) were obtained from fac-[ReBr(CO)3(pypzH)] by halide abstraction with AgOTf and subsequent addition of the corresponding pyrazole. Successive deprotonation with Na2CO3 and NaOH gave neutral fac-[Re(CO)3(pz*H)(pypz)] and anionic Na{fac-[Re(CO)3(pz*)(pypz)]} complexes, respectively. Cationic fac-[Re(CO)3(pz*H)(pypzH)]OTf, neutral complexes fac-[Re(CO)3(pz*H)(pypz)], and fac-[Re(CO)3(pypz)2Na] were subjected to photophysical and electrochemical studies. They exhibit phosphorescent decays from a prevalently 3MLCT excited state with quantum yields (Φ) in the range between 0.03 and 0.58 and long lifetimes (τ from 220 to 869 ns). The electrochemical behavior in Ar atmosphere of cationic and neutral complexes indicates that the oxidation processes assigned to ReI → ReII occurs at lower potentials for the neutral complex compared to cationic complex. The reduction processes occur at the ligands and do not depend on the charge of the complexes. The electrochemical behavior in CO2 saturated media is consistent with CO2 electrocatalyzed reduction, where the values of the catalytic activity [icat(CO2)/icat(Ar)] ranged from 2.7 to 11.5 (compared to 8.1 for fac-[Re(CO)3Cl(bipy)] studied as a reference). Controlled potential electrolysis for the pyrazole cationic (3a) and neutral (4a) complexes after 1 h affords CO in faraday yields of 61 and 89%, respectively. These values are higher for indazole complexes and may be related to the acidity of the coordinated pyrazole.

  • Identification by NMR of key compounds present in beer distillates and residual phases after dealcoholization by vacuum distillation
    David Labrado, Sergio Ferrero, Isabel Caballero, Celedonio M Alvarez, Fernando Villafañe, and Carlos A Blanco
    Wiley
    BACKGROUND Nowadays, low alcohol and non-alcohol beer intake has increased due to the expanding concern on healthy diets. However, there are still appreciable differences between non-alcoholic beer and conventional beer, particularly regarding flavor. Vacuum distillation is commonly used to remove ethanol from the beer in industrial processes and it is herein used. RESULTS The presence of n-propanol, isobutanol, 3-methylbutanol, 2-methylbutanol, 2-phenylethanol, ethyl acetate, isoamyl acetate, and acetaldehyde, which are key compounds responsible for aroma and flavor of beer, have been analyzed in commercial beers and also in the corresponding distillates and residual phases after dealcoholization by using NMR. CONCLUSION The compounds present in each phase are identified by mono and bidimensional NMR spectra. A detailed description of which compounds are completely removed or remain present in the residue of the conventional beers studied is herein included. The presence of these compounds in dealcoholized beer would be beneficial in order to keep the aroma and flavor in dealcoholized beer. This article is protected by copyright. All rights reserved.

  • Long-term thermal conductivity of cyclopentane–water blown rigid polyurethane foams reinforced with different types of fillers
    Mercedes Santiago‐Calvo, Josías Tirado‐Mediavilla, José Luis Ruiz‐Herrero, Fernando Villafañe, and Miguel Ángel Rodríguez‐Pérez
    Wiley

  • X-ray radioscopy validation of a polyol functionalized with graphene oxide for producing rigid polyurethane foams with improved cellular structures
    Mercedes Santiago-Calvo, Saúl Pérez-Tamarit, Paula Cimavilla-Román, Victoria Blasco, Carolina Ruiz, Rodrigo París, Fernando Villafañe, and Miguel Ángel Rodríguez-Pérez
    Elsevier BV

  • Identification and quantification of cell gas evolution in rigid polyurethane foams by novel GCMS methodology
    Anastasiia Galakhova, Mercedes Santiago-Calvo, Josias Tirado-Mediavilla, Fernando Villafañe, Miguel Ángel Rodríguez-Pérez, and Gisbert Riess
    MDPI AG
    This paper presents a new methodology based on gas chromatography-mass spectrometry (GCMS) in order to separate and quantify the gases presented inside the cells of rigid polyurethane (RPU) foams. To demonstrate this novel methodology, the gas composition along more than three years of aging is herein determined for two samples: a reference foam and foam with 1.5 wt% of talc. The GCMS method was applied, on one hand, for the accurate determination of C5H10 and CO2 cell gases used as blowing agents and, on the other hand, for N2 and O2 air gases that diffuse rapidly from the surrounding environment into foam cells. GCMS results showed that CO2 leaves foam after 2.5 month (from 21% to 0.03% for reference foam and from 17% to 0.03% for foam with 1.5% talc). C5H10 deviates during 3.5 months (from 28% up to 39% for reference foam and from 29% up to 36% for foam with talc), then it starts to leave the foam and after 3.5 year its content is 13% for reference and 10% for foam with talc. Air diffuses inside the cells faster for one year (from 51% up to 79% for reference and from 54% up to 81% for foam with talc) and then more slowly for 3.5 years (reaching 86% for reference and 90% for foam with talc). Thus, the fast and simple presented methodology provides valuable information to understand the long-term thermal conductivity of the RPU foams.

  • Improvement of thermal and mechanical properties by control of formulations in rigid polyurethane foams from polyols functionalized with graphene oxide
    Mercedes Santiago‐Calvo, Victoria Blasco, Carolina Ruiz, Rodrigo París, Fernando Villafañe, and Miguel Ángel Rodríguez‐Pérez
    Wiley

  • Impact of expandable graphite on flame retardancy and mechanical properties of rigid polyurethane foam
    Pablo Acuña, Mercedes Santiago‐Calvo, Fernando Villafañe, Miguel Angel Rodríguez‐Perez, Javier Rosas, and De‐Yi Wang
    Wiley

  • Influence of the characteristics of expandable graphite on the morphology, thermal properties, fire behaviour and compression performance of a rigid polyurethane foam
    Pablo Acuña, Zhi Li, Mercedes Santiago-Calvo, Fernando Villafañe, Miguel Rodríguez-Perez, and De-Yi Wang
    MDPI AG
    Three types of expandable graphite (EG) differing in particle size and expansion volume, are compared as flame retardant additives to rigid polyurethane foams (RPUFs). In this paper we discuss microstructure, thermal stability, fire behavior, and compression performance. We find that ell size distributions were less homogeneous and cell size was reduced. Furthermore, thermal conductivity increased along with EG loading. Thermogravimetric analysis (TGA) showed that EG only increased residue yield differently. The results indicate that a higher expansion of EG increased the limiting oxygen index (LOI) value, whereas a bigger particle size EG improved the rating of the vertical burning test (UL94). Results from the cone calorimeter test showed that a bigger particle size EG effectively reduced peak of heat release rate (pHRR). Furthermore, a higher expansion, led to a decrease in smoke production (TSP). The combination of both characteristics gives extraordinary results. The physical–mechanical characterization of the EG/RPUF foams revealed that their compression performance decreased slightly, mostly due to the effect of a bigger size EG.

  • Whole microwave syntheses of pyridylpyrazole and of Re and Ru luminescent pyridylpyrazole complexes
    Beatriz Merillas, Elena Cuéllar, Alberto Diez-Varga, Miryam Asensio-Bartolomé, Gabriel García-Herbosa, Tomás Torroba, Jose M. Martín-Alvarez, Daniel Miguel, and Fernando Villafañe
    Elsevier BV

  • Evaluation of the thermal conductivity and mechanical properties of water blown polyurethane rigid foams reinforced with carbon nanofibers
    Mercedes Santiago-Calvo, Josías Tirado-Mediavilla, Jens Chr. Rauhe, Lars Rosgaard Jensen, José Luis Ruiz-Herrero, Fernando Villafañe, and Miguel Ángel Rodríguez-Pérez
    Elsevier BV