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Papers by Enrique Blázquez

Polymers

Composites based on an L-rich poly(lactic acid) (PLLA) and MCM-41, either neat or modified with a... more Composites based on an L-rich poly(lactic acid) (PLLA) and MCM-41, either neat or modified with a silver (MCM-41@Ag), are achieved by solvent casting, being next processed by compression molding. Ag is mainly embedded as nanowires within the hybrid MCM-41@Ag particles, enabling its antimicrobial character. In these composites, the PLLA thermal stability, nucleation efficiency, and mechanical response are dependent on the MCM-41 nature and, to a lesser extent, on its content. Thus, differences in transitions of the PLLA matrix are noticed during cooling at 10 °C/min and in the subsequent heating when composites with neat or modified MCM-41 are compared. A very remarkable nucleation effect is played by pristine MCM-41, being inferior when MCM-41@Ag is incorporated into the PLLA. Wide angle X-ray scattering (WAXS) measurements using synchrotron radiation and performed under variable-temperature conditions in the composites containing MCM-41@Ag indicate that during cold crystallization,...

Polymers

Different amounts of carbon nanotubes (CNT) have been incorporated in materials based on poly(vin... more Different amounts of carbon nanotubes (CNT) have been incorporated in materials based on poly(vinylidene fluoride) (PVDF) by solvent blending followed by their further precipitation. Final processing was performed by compression molding. The morphological aspects and crystalline characteristics have been examined, additionally exploring in these nanocomposites the common routes described in the pristine PVDF to induce the β polymorph. This polar β phase has been found to be promoted by the simple inclusion of CNT. Therefore, coexistence of the α and β lattices occurs for the analyzed materials. The real-time variable-temperature X-ray diffraction measurements with synchrotron radiation at a wide angle have undoubtedly allowed us to observe the presence of the two polymorphs and determine the melting temperature of both crystalline modifications. Furthermore, the CNT plays a nucleating role in the PVDF crystallization, and also acts as reinforcement, increasing the stiffness of the n...

Microporous and Mesoporous Materials

Macromolecular Materials and Engineering

espanolEl uso de dispositivos medicos para la administracion de farmacos, suero o sangre constitu... more espanolEl uso de dispositivos medicos para la administracion de farmacos, suero o sangre constituye una herramienta importante en el tratamiento de pacientes con distintas dolencias. Estos dispositivos tienen, por lo general, como material base el poli(cloruro de vinilo) (PVC), cuya flexibilidad esta condicionada por la adicion de plastificantes. El mas ampliamente utilizado para este fin ha sido el bis(2-etilhexil) ftalato (DEHP). Sin embargo, numerosos estudios han mostrado los perjuicios asociados a su uso, debido a su toxicidad. Estos examenes han conducido a su prohibicion y busqueda de alternativas para su empleo como plastificantes. Este trabajo pretende analizar las nuevas tendencias que se han implementado para el desarrollo de dispositivos mas seguros. La evaluacion de estos materiales puede permitir la identificacion de compuestos mas respetuosos con la salud y el medio ambiente, y contribuir a la sustitucion del DEHP en una gran cantidad de aplicaciones EnglishThe use of...

Molecules

In this study, nanocomposites based on polypropylene are synthesized by the in situ polymerizatio... more In this study, nanocomposites based on polypropylene are synthesized by the in situ polymerization of propene in the presence of mesoporous SBA-15 silica, which acts as a carrier of the catalytic system (zirconocene as catalyst and methylaluminoxane as cocatalyst). The protocol for the immobilization and attainment of hybrid SBA-15 particles involves a pre-stage of contact between the catalyst with cocatalyst before their final functionalization. Two zirconocene catalysts are tested in order to attain materials with different microstructural characteristics, molar masses and regioregularities of chains. Some polypropylene chains are able to be accommodated within the silica mesostructure of these composites. Thus, an endothermic event of small intensity appears during heating calorimetric experiments at approximately 105 °C. The existence of these polypropylene crystals, confined within the nanometric channels of silica, is corroborated by SAXS measurements obtained via the change i...

Journal of Thermal Analysis and Calorimetry

Recycling of plastics is absolutely essential in a circular economy, especially in the case of co... more Recycling of plastics is absolutely essential in a circular economy, especially in the case of commodity polymers from fossil resources, like isotactic polypropylene (iPP). Therefore, evaluation of the factors that are decisive for an optimum performance of the recycled based materials becomes mandatory for the obtainment of new products with optimal properties. One of the most important aspects is the protection of the plastics materials not only against the external degradation agents, but also from the radicals generated during their previous service life. Accordingly, several materials have been prepared by extrusion based on virgin iPP with different amounts of the same polypropylene severely degraded, which has been used as model component to be recycled. Previous to the extrusion, a mixture of antioxidants was added to all the samples, and special attention has been paid to consumption of those additives during the extrusion. The results show an increasing reduction of antiox...

Journal of Composites Science

Several nanocomposites were prepared by extrusion from a commercial metallocene-type isotactic po... more Several nanocomposites were prepared by extrusion from a commercial metallocene-type isotactic polypropylene (iPP) and different amounts of two types of graphene (G) nanofibers: ones with a high specific surface, named GHS, and the others with a low specific surface, labeled as GLS. The number of graphene layers was found to be around eight for GLS and about five in the GHS. Scanning electron microscopy (SEM) images of the resultant iPP nanocomposites showed a better homogeneity in the dispersion of the GLS nanofibers within the polymeric matrix compared with the distribution observed for the GHS ones. Crystallinity in the nanocomposites turned out to be dependent upon graphene content and upon thermal treatment applied during film preparation, the effect of the nature of the nanofiber being negligible. Graphene exerted a noticeable nucleating effect in the iPP crystallization. Furthermore, thermal stability was enlarged, shifting to higher temperatures, with increasing nanofiber am...

Materials Today Communications

Polymers, 2022

Two L-rich polylactides (PLLA) with distinct contents in D isomer and their composites with an in... more Two L-rich polylactides (PLLA) with distinct contents in D isomer and their composites with an intermediate amount of mesoporous Santa Barbara Amorphous-15 (SBA-15) (about 9 wt.%) particles were attained by melt extrusion for the evaluation of the effect of content in D isomer and incorporation of mesoporous silica on the structural PLLA features and on their ultimate mechanical performance. For that, samples have been crystallized under dynamic and isothermal tests (from the melt and from the glassy states). The results from DSC and X-ray diffraction show obtainment of the pure α’ and α modifications at different intervals of crystallization temperature depending on the D steroisomer amount of the PLLA used. Furthermore, several phase transitions are observed depending on the crystallinity reached and the polymorphs developed during the isothermal crystallization from the glass: an additional cold crystallization, the α’/α transformation and the subsequent melting process, appearin...

espanolLos juguetes son uno de los objetos mas codiciados por los sectores mas jovenes de la soci... more espanolLos juguetes son uno de los objetos mas codiciados por los sectores mas jovenes de la sociedad. Sin embargo, su seguridad queda a menudo en entredicho debido a la venta de productos falsificados que no han pasado los controles aduaneros y no cumplen con la estricta normativa comunitaria que regula su comercializacion. Esta normativa garantiza que los productos que se venden con arreglo a sus disposiciones son seguros para los ninos y no entranan peligro para su salud. Este trabajo pretende poner de manifiesto las diferencias existentes entre los objetos originales y los fraudulentos. El analisis de la composicion del material hace posible la deteccion de sustancias quimicas no permitidas en los juguetes falsificados que no cumplen con las exigencias de la legislacion vigente EnglishToys are one of the objects most desired by the youngest sector of society. Their safety is, nevertheless, compromised due to sales of fake objects that have not passed the customs controls and do ...

Polymers, 2021

A study of different nanocomposites based on poly(ε-caprolactone) (PCL) and mesoporous SBA-15 sil... more A study of different nanocomposites based on poly(ε-caprolactone) (PCL) and mesoporous SBA-15 silica that were prepared by melt extrusion was carried out by analyzing the possible effect of this filler on the crystalline details of PCL, on its mechanical behavior, and on the eventual observation of the confinement of the polymeric chains within the hollow nanometric silica channels. Thus, simultaneous Small-Angle and Wide-Angle X-ray Scattering (SAXS/WAXS) synchrotron experiments at variable temperature were performed on these PCL nanocomposites with different mesoporous silica contents. The importance of the morphological and structural features was assessed by the changes that were observed during the mechanical response of the final materials, which determined that the presence of mesoporous particles leads to a noticeable reinforcing effect.

Polymers, 2021

Several composites were prepared based on a polypropylene random copolymer (PPR) and different am... more Several composites were prepared based on a polypropylene random copolymer (PPR) and different amounts of date stone flour (DSF). This cellulosic fiber was silanized beforehand in order to reduce its hydrophilicity and improve the interfacial adhesion with the polymer. Other composites were also obtained, including a sorbitol derivative as an effective nucleant. Films made from these composites were prepared using two different thermal treatments, involving slow crystallization and rapid cooling from the melt. Scanning electron microscopy was used to evaluate the morphological features and the DSF particle dispersion within the PPR matrix. X-ray diffraction experiments and differential scanning calorimetry tests were employed to assess the crystalline characteristics and for the phase transitions, paying especial attention to the effects of the DSF and nucleating agent on PPR crystallization. An important nucleation ability was found for DSF, and evidently for the sorbitol derivativ...

Journal of Composites Science, 2021

In this study, nanocomposites based on polycaprolactone (PCL) and two types of mesoporous silicas... more In this study, nanocomposites based on polycaprolactone (PCL) and two types of mesoporous silicas, MCM-41 and SBA-15, were attained by melt extrusion. The effect of the silica incorporated within the PCL matrix was observed, firstly, in the morphological characteristics and degradation behavior of the resultant composites. DSC experiments provided information on the existence of confinement in the PCL–SBA-15 materials through the appearance of an additional small endotherm, located at about 25–50 °C, and attributed to the melting of constrained crystallites. Displacement to a slightly lower temperature of this endothermic event was observed in the first heating run of PCL–MCM-41 composites, attributed to the inferior pore size in the MCM-41 particles. Thus, this indicates variations in the inclusion of PCL chains within these two mesostructures with different pore sizes. Real-time variable-temperature small-angle X-ray scattering (SAXS) experiments with synchrotron radiation were cr...

Polymers

Composites based on an L-rich poly(lactic acid) (PLLA) and MCM-41, either neat or modified with a... more Composites based on an L-rich poly(lactic acid) (PLLA) and MCM-41, either neat or modified with a silver (MCM-41@Ag), are achieved by solvent casting, being next processed by compression molding. Ag is mainly embedded as nanowires within the hybrid MCM-41@Ag particles, enabling its antimicrobial character. In these composites, the PLLA thermal stability, nucleation efficiency, and mechanical response are dependent on the MCM-41 nature and, to a lesser extent, on its content. Thus, differences in transitions of the PLLA matrix are noticed during cooling at 10 °C/min and in the subsequent heating when composites with neat or modified MCM-41 are compared. A very remarkable nucleation effect is played by pristine MCM-41, being inferior when MCM-41@Ag is incorporated into the PLLA. Wide angle X-ray scattering (WAXS) measurements using synchrotron radiation and performed under variable-temperature conditions in the composites containing MCM-41@Ag indicate that during cold crystallization,...

Polymers

Different amounts of carbon nanotubes (CNT) have been incorporated in materials based on poly(vin... more Different amounts of carbon nanotubes (CNT) have been incorporated in materials based on poly(vinylidene fluoride) (PVDF) by solvent blending followed by their further precipitation. Final processing was performed by compression molding. The morphological aspects and crystalline characteristics have been examined, additionally exploring in these nanocomposites the common routes described in the pristine PVDF to induce the β polymorph. This polar β phase has been found to be promoted by the simple inclusion of CNT. Therefore, coexistence of the α and β lattices occurs for the analyzed materials. The real-time variable-temperature X-ray diffraction measurements with synchrotron radiation at a wide angle have undoubtedly allowed us to observe the presence of the two polymorphs and determine the melting temperature of both crystalline modifications. Furthermore, the CNT plays a nucleating role in the PVDF crystallization, and also acts as reinforcement, increasing the stiffness of the n...

Microporous and Mesoporous Materials

Macromolecular Materials and Engineering

espanolEl uso de dispositivos medicos para la administracion de farmacos, suero o sangre constitu... more espanolEl uso de dispositivos medicos para la administracion de farmacos, suero o sangre constituye una herramienta importante en el tratamiento de pacientes con distintas dolencias. Estos dispositivos tienen, por lo general, como material base el poli(cloruro de vinilo) (PVC), cuya flexibilidad esta condicionada por la adicion de plastificantes. El mas ampliamente utilizado para este fin ha sido el bis(2-etilhexil) ftalato (DEHP). Sin embargo, numerosos estudios han mostrado los perjuicios asociados a su uso, debido a su toxicidad. Estos examenes han conducido a su prohibicion y busqueda de alternativas para su empleo como plastificantes. Este trabajo pretende analizar las nuevas tendencias que se han implementado para el desarrollo de dispositivos mas seguros. La evaluacion de estos materiales puede permitir la identificacion de compuestos mas respetuosos con la salud y el medio ambiente, y contribuir a la sustitucion del DEHP en una gran cantidad de aplicaciones EnglishThe use of...

Molecules

In this study, nanocomposites based on polypropylene are synthesized by the in situ polymerizatio... more In this study, nanocomposites based on polypropylene are synthesized by the in situ polymerization of propene in the presence of mesoporous SBA-15 silica, which acts as a carrier of the catalytic system (zirconocene as catalyst and methylaluminoxane as cocatalyst). The protocol for the immobilization and attainment of hybrid SBA-15 particles involves a pre-stage of contact between the catalyst with cocatalyst before their final functionalization. Two zirconocene catalysts are tested in order to attain materials with different microstructural characteristics, molar masses and regioregularities of chains. Some polypropylene chains are able to be accommodated within the silica mesostructure of these composites. Thus, an endothermic event of small intensity appears during heating calorimetric experiments at approximately 105 °C. The existence of these polypropylene crystals, confined within the nanometric channels of silica, is corroborated by SAXS measurements obtained via the change i...

Journal of Thermal Analysis and Calorimetry

Recycling of plastics is absolutely essential in a circular economy, especially in the case of co... more Recycling of plastics is absolutely essential in a circular economy, especially in the case of commodity polymers from fossil resources, like isotactic polypropylene (iPP). Therefore, evaluation of the factors that are decisive for an optimum performance of the recycled based materials becomes mandatory for the obtainment of new products with optimal properties. One of the most important aspects is the protection of the plastics materials not only against the external degradation agents, but also from the radicals generated during their previous service life. Accordingly, several materials have been prepared by extrusion based on virgin iPP with different amounts of the same polypropylene severely degraded, which has been used as model component to be recycled. Previous to the extrusion, a mixture of antioxidants was added to all the samples, and special attention has been paid to consumption of those additives during the extrusion. The results show an increasing reduction of antiox...

Journal of Composites Science

Several nanocomposites were prepared by extrusion from a commercial metallocene-type isotactic po... more Several nanocomposites were prepared by extrusion from a commercial metallocene-type isotactic polypropylene (iPP) and different amounts of two types of graphene (G) nanofibers: ones with a high specific surface, named GHS, and the others with a low specific surface, labeled as GLS. The number of graphene layers was found to be around eight for GLS and about five in the GHS. Scanning electron microscopy (SEM) images of the resultant iPP nanocomposites showed a better homogeneity in the dispersion of the GLS nanofibers within the polymeric matrix compared with the distribution observed for the GHS ones. Crystallinity in the nanocomposites turned out to be dependent upon graphene content and upon thermal treatment applied during film preparation, the effect of the nature of the nanofiber being negligible. Graphene exerted a noticeable nucleating effect in the iPP crystallization. Furthermore, thermal stability was enlarged, shifting to higher temperatures, with increasing nanofiber am...

Materials Today Communications

Polymers, 2022

Two L-rich polylactides (PLLA) with distinct contents in D isomer and their composites with an in... more Two L-rich polylactides (PLLA) with distinct contents in D isomer and their composites with an intermediate amount of mesoporous Santa Barbara Amorphous-15 (SBA-15) (about 9 wt.%) particles were attained by melt extrusion for the evaluation of the effect of content in D isomer and incorporation of mesoporous silica on the structural PLLA features and on their ultimate mechanical performance. For that, samples have been crystallized under dynamic and isothermal tests (from the melt and from the glassy states). The results from DSC and X-ray diffraction show obtainment of the pure α’ and α modifications at different intervals of crystallization temperature depending on the D steroisomer amount of the PLLA used. Furthermore, several phase transitions are observed depending on the crystallinity reached and the polymorphs developed during the isothermal crystallization from the glass: an additional cold crystallization, the α’/α transformation and the subsequent melting process, appearin...

espanolLos juguetes son uno de los objetos mas codiciados por los sectores mas jovenes de la soci... more espanolLos juguetes son uno de los objetos mas codiciados por los sectores mas jovenes de la sociedad. Sin embargo, su seguridad queda a menudo en entredicho debido a la venta de productos falsificados que no han pasado los controles aduaneros y no cumplen con la estricta normativa comunitaria que regula su comercializacion. Esta normativa garantiza que los productos que se venden con arreglo a sus disposiciones son seguros para los ninos y no entranan peligro para su salud. Este trabajo pretende poner de manifiesto las diferencias existentes entre los objetos originales y los fraudulentos. El analisis de la composicion del material hace posible la deteccion de sustancias quimicas no permitidas en los juguetes falsificados que no cumplen con las exigencias de la legislacion vigente EnglishToys are one of the objects most desired by the youngest sector of society. Their safety is, nevertheless, compromised due to sales of fake objects that have not passed the customs controls and do ...

Polymers, 2021

A study of different nanocomposites based on poly(ε-caprolactone) (PCL) and mesoporous SBA-15 sil... more A study of different nanocomposites based on poly(ε-caprolactone) (PCL) and mesoporous SBA-15 silica that were prepared by melt extrusion was carried out by analyzing the possible effect of this filler on the crystalline details of PCL, on its mechanical behavior, and on the eventual observation of the confinement of the polymeric chains within the hollow nanometric silica channels. Thus, simultaneous Small-Angle and Wide-Angle X-ray Scattering (SAXS/WAXS) synchrotron experiments at variable temperature were performed on these PCL nanocomposites with different mesoporous silica contents. The importance of the morphological and structural features was assessed by the changes that were observed during the mechanical response of the final materials, which determined that the presence of mesoporous particles leads to a noticeable reinforcing effect.

Polymers, 2021

Several composites were prepared based on a polypropylene random copolymer (PPR) and different am... more Several composites were prepared based on a polypropylene random copolymer (PPR) and different amounts of date stone flour (DSF). This cellulosic fiber was silanized beforehand in order to reduce its hydrophilicity and improve the interfacial adhesion with the polymer. Other composites were also obtained, including a sorbitol derivative as an effective nucleant. Films made from these composites were prepared using two different thermal treatments, involving slow crystallization and rapid cooling from the melt. Scanning electron microscopy was used to evaluate the morphological features and the DSF particle dispersion within the PPR matrix. X-ray diffraction experiments and differential scanning calorimetry tests were employed to assess the crystalline characteristics and for the phase transitions, paying especial attention to the effects of the DSF and nucleating agent on PPR crystallization. An important nucleation ability was found for DSF, and evidently for the sorbitol derivativ...

Journal of Composites Science, 2021

In this study, nanocomposites based on polycaprolactone (PCL) and two types of mesoporous silicas... more In this study, nanocomposites based on polycaprolactone (PCL) and two types of mesoporous silicas, MCM-41 and SBA-15, were attained by melt extrusion. The effect of the silica incorporated within the PCL matrix was observed, firstly, in the morphological characteristics and degradation behavior of the resultant composites. DSC experiments provided information on the existence of confinement in the PCL–SBA-15 materials through the appearance of an additional small endotherm, located at about 25–50 °C, and attributed to the melting of constrained crystallites. Displacement to a slightly lower temperature of this endothermic event was observed in the first heating run of PCL–MCM-41 composites, attributed to the inferior pore size in the MCM-41 particles. Thus, this indicates variations in the inclusion of PCL chains within these two mesostructures with different pore sizes. Real-time variable-temperature small-angle X-ray scattering (SAXS) experiments with synchrotron radiation were cr...