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  • Multifunctional polymer foams with carbon nanoparticles

     de Sousa Pais Antunes, Marcelo; Velasco Perero, Jose Ignacio
    Progress in polymer science
    Date of publication: 2014-03
    Journal article

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    Increasingly demanding industry requirements in terms of developing polymer-based components with higher specific properties have recently aroused a great interest around the possibility of combining density reduction through foaming with the addition of small amounts of functional nanosized particles. Particular interest has been given to the creation of lightweight conductive polymers by incorporating conductive carbon-based nanoparticles, related to processing improvements in attaining homogeneous nanoparticle dispersion and distribution throughout the polymer as well as new processes that enable a higher control and throughput of highly pure carbon nanoparticles, which could overcome some of the common problems of conductive polymers, such as high cost and poor mechanical properties. This review article considers the use of carbon nanoparticles in polymer foams, initially focusing on the important aspects of foam preparation, the main results found in the literature about conductive polymer composites containing carbon nanoparticles, as well as the main polymer foaming processes and types of foams. The main section is dedicated to the properties of multifunctional polymer foams with carbon nanoparticles, with special focus being given to the electrical and transport properties of these materials.

  • Diffusion of CO2 in polymer nanocomposites containing different types of carbon nanoparticles and nanoclays for solid-state microcellular foaming applications

     de Sousa Pais Antunes, Marcelo; de Redondo Realinho, Vera Cristina; Gedler, Gabriel; Arencón Osuna, David; Velasco Perero, Jose Ignacio
    Journal of nano research
    Date of publication: 2014-01
    Journal article

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    This work considers the study of the diffusion of carbon dioxide in polypropylene and amorphous polymers containing carbon nanoparticles, particularly carbon nanofibres and graphene, as well as nanoclays, to be used in microcellular foaming. The diffusion of CO2 out and into the nanocomposites was studied during high pressure CO2 dissolution, as the amount of CO2 dissolved into the nanocomposite and CO2 desorption rate are crucial in order to have a proper control of foaming. Comparatively, platelet-like nanoparticles slowed down the desorption of CO2 out of the nanocomposites by means of a physical barrier effect, enabling a higher concentration of CO2 to remain in the polymer and be used in foaming. As a consequence of the higher amount of CO2 retained in the polymer and the cell nucleation effect promoted by the nanoparticles, polymer nanocomposite foams presented finer microcellular structures, in the case of PMMA even submicrocellular, and higher specific moduli and electrical conductivities when compared to their pure counterparts.

  • Thermal stability and fire behaviour of flame retardant high density rigid foams based on hydromagnesite-filled polypropylene composites

     de Redondo Realinho, Vera Cristina; Haurie Ibarra, Laia; de Sousa Pais Antunes, Marcelo; Velasco Perero, Jose Ignacio
    Composites Part B: Engineering
    Date of publication: 2014-03
    Journal article

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    The present work deals with the development of new rigid polypropylene composite foams filled with high amounts of flame-retardant systems based on synthetic hydromagnesite, a basic magnesium carbonate obtained from an industrial by-product. A partially-interconnected cellular structure with a cell size around 100 micrometers was obtained for the hydromagnesite-filled PP foams. A 40% reduction of this cell size was observed when a small amount of a combination of montmorillonite and graphene layered nanoparticles was added to the hydromagnesite. The combination of hydromagnesite with an intumescent additive (ammonium polyphosphate) and layered nanoparticles led to improved thermal stability. In particular, the intumescent additive delayed the beginning of the thermal decomposition temperature and the layered nanoparticles split the second step of thermal decomposition in a third peak observed at higher temperatures. Improved flame retardancy, measured by means of cone calorimetry, was observed in the samples containing the intumescent additive. A novel normalized parameter, called foam efficiency ratio (FER), which takes into account the expansion ratio of the foam and the relation of its fire properties with that of the base solid, was also analyzed.

  • Polycarbonate foams with tailor-made cellular structures by controlling the dissolution temperature in a two-step supercritical carbon dioxide foaming process

     Gedler, Gabriel; de Sousa Pais Antunes, Marcelo; Velasco Perero, Jose Ignacio
    Journal of supercritical fluids
    Date of publication: 2014-04
    Journal article

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    Closed-cell polycarbonate foams were prepared using a two-step foaming process, which consisted of the initial dissolution of supercritical CO2(scCO2) into PC foaming precursors and their later expansion by heating using a double contact restriction method. The effects of the parameters of both CO2 dissolution and heating stages on the cellular structure characteristics as well as on the physical aging of PC in the obtained foams were investigated. A higher amount of CO2 was dissolved in PC with increasing the dissolution temperature from 80 to 100 ºC, with similar CO2 desorption trends and diffusion coefficients being found for both conditions. PC foams displayed an isotropic-like microcellular structure at a dissolution temperature of 80 ºC. It was shown that it is possible to reduce their density while keeping their microcellular structure with increasing the heating time. On contrary, when dissolving CO2 at 100 ºC and later expanding, PC foams presented a cellular morphology with bigger cells and with an increasingly higher cell elongation in the vertical growth direction with increasing the heating time. Comparatively, PC foams obtained by dissolving CO2 at 100 ºC presented a more marked physical aging after CO2 dissolution and foaming, although this effect could be reduced and ultimately suppressed with increasing the heating time.

    Closed-cell polycarbonate foams were prepared using a two-step foaming process, which consisted of the initial dissolution of supercritical CO2(scCO2) into PC foaming precursors and their later expansion by heating using a double contact restriction method. The effects of the parameters of both CO2 dissolution and heating stages on the cellular structure characteristics as well as on the physical aging of PC in the obtained foams were investigated. A higher amount of CO2 was dissolved in PC with increasing the dissolution temperature from 80 to 100 ºC, with similar CO2 desorption trends and diffusion coefficients being found for both conditions. PC foams displayed an isotropic-like microcellular structure at a dissolution temperature of 80 ºC. It was shown that it is possible to reduce their density while keeping their microcellular structure with increasing the heating time. On contrary, when dissolving CO2 at 100 ºC and later expanding, PC foams presented a cellular morphology with bigger cells and with an increasingly higher cell elongation in the vertical growth direction with increasing the heating time. Comparatively, PC foams obtained by dissolving CO2 at 100 ºC presented a more marked physical aging after CO2 dissolution and foaming, although this effect could be reduced and ultimately suppressed with increasing the heating time.

  • Multifunctional nanocomposite foams based on polypropylene with carbon nanofillers

     de Sousa Pais Antunes, Marcelo; Gedler, Gabriel; Velasco Perero, Jose Ignacio
    Journal of cellular plastics
    Date of publication: 2013-05
    Journal article

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    This work considers the preparation and characterization of polypropylene foams with variable concentrations of graphene and carbon nanofibres, focussing on the influence of the foaming process and the nanofillers on the microstructural and dynamic-mechanical- thermal properties of the foams. Great differences were found in terms of foam morphology depending on the type of foaming process, with foams prepared by physical foaming showing a vertically deformed cell structure, while chemical foams presented an isotropic-like cellular structure. The addition of graphene resulted in foams with higher cell densities and more uniform cellular structures when compared to the ones with nanofibres. All these considerations are of extreme importance, as some of the most promising applications of these polymer foams require a good electromagnetic interference shielding efficiency, which greatly depends on the developed foam morphology.

    This work considers the preparation and characterization of polypropylene foams with variable concentrations of graphene and carbon nanofibres, focussing on the influence of the foaming process and the nanofillers on the microstructural and dynamic-mechanical- thermal properties of the foams. Great differences were found in terms of foam morphology depending on the type of foaming process, with foams prepared by physical foaming showing a vertically deformed cell structure, while chemical foams presented an isotropic-like cellular structure. The addition of graphene resulted in foams with higher cell densities and more uniform cellular structures when compared to the ones with nanofibres. All these considerations are of extreme importance, as some of the most promising applications of these polymer foams require a good electromagnetic interference shielding efficiency, which greatly depends on the developed foam morphology.

  • Analysis and thermo-mechanical characterization of mixed plastic wastes

     Sanchez Soto, Miguel Angel; Maspoch Ruldua, Maria Lluïsa; Velasco Perero, Jose Ignacio
    Polymer-Plastics technology and engineering
    Date of publication: 2013
    Journal article

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  • Influence of foaming process on the structure-properties relationship of foamed LDPE/silica nanocomposites

     Saiz Arroyo, Cristina; Rodríguez Pérez, Miguel Ángel; Velasco Perero, Jose Ignacio; de Saja, José Antonio
    Composites Part B: Engineering
    Date of publication: 2013-05
    Journal article

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    In this paper LDPE/silica nanocomposites are foamed by two different processes. First one is the pressure quench method which is based on the use of a physical blowing agent and second one is the improved compression moulding technique. As the latter process uses a chemical blowing agent, both types of foamed nanocomposites will provide very useful information about the relationship between foaming process-microstructure and macroscopic properties. Results have revealed how silica nanoparticles are able to act as nucleating sites during foaming step in both processes; however, the optimum amount of particles strongly depends on the foaming route. Thermal and mechanical properties of solid and foamed nanocomposites have been analyzed by means of thermogravimetric analysis and compression tests. Results have revealed that nanosilica particles act as effective nucleating agents, not only reducing cell size and increasing cell density but also achieving more homogeneous cellular structures. Thermal and mechanical properties are improved due to the presence of silica nanoparticles. It has been found that the improvement degree reached for samples produced using chemical blowing agents is greater than that achieved for samples produced using physical blowing agents.

  • Addition of flame retardants in epoxy mortars: thermal and mechanical characterization

     Haurie Ibarra, Laia; Lacasta Palacio, Ana Maria; Ciudad Alvarez, Aleix; de Redondo Realinho, Vera Cristina; Velasco Perero, Jose Ignacio
    Construction & building materials
    Date of publication: 2013-05
    Journal article

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    In this work we have studied the effect of different flame retardants on the fire behavior and mechanical properties of epoxy mortars. Flame retardants acting under different mechanisms of action have been compared: phosphate flame retardants as well as magnesium hydroxides and carbonates. Besides the commercial flame retardants we have also used a magnesium basic carbonate obtained from an industrial by-product. The use of an alternative based on an industrial by-product combines an economic and sustainable solution. Different formulations of flame retarded epoxy mortars have been prepared and characterized. The obtained results prove the effectiveness of the tested flame retardants on the improvement of the fire properties of the epoxy mortars without a significant decrease on their mechanical properties.

  • Graphene-induced crystallinity of bisphenol A polycarbonate in the presence of supercritical carbon dioxide

     Gedler, Gabriel; de Sousa Pais Antunes, Marcelo; Velasco Perero, Jose Ignacio
    Polymer
    Date of publication: 2013-11-01
    Journal article

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    Changes in the crystallinity of polycarbonate (PC) induced by the simultaneous presence of 0.5 wt% graphene nanoplatelets (GnP) and supercritical carbon dioxide (sc-CO2) were examined by means of Raman spectroscopy, WAXS, SAXS and DSC. Composites were prepared by melt-mixing, compression-molding and dissolving sc-CO2 at high pressure and temperature. It was found that dissolved CO2 induced the formation of an ordered non-crystalline phase in PC during slow cooling under pressure. A fast depressurization and cooling did not cause such an effect in the resultant foams. GnP induced a higher crystallinity in PC, especially when combined with sc-CO2, even during fast depressurization and cooling. Raman spectroscopy enabled to correlate changes in the PC vibration modes with the presence of ordered phases, as well as to detect interactions between GnP and PC. Additionally, evidence of GnP exfoliation in the composites could be explained by the intensity reduction of the (002) graphite diffraction peak.

  • Application of layered nanoparticles in the micromechanical reinforcement and flame retardancy of polymer foams

     de Redondo Realinho, Vera Cristina; de Sousa Pais Antunes, Marcelo; Velasco Perero, Jose Ignacio
    Date of publication: 2013
    Book chapter

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    One of the key objectives of nanotechnology is to develop our knowledge to manipulate matters at nanoscale level to create novel, smart, cost effective and eco-friendly macrostructures to improve quality of human life. Recent advancement in development of nano-materials and structures motivate engineers to design nano-modified smart, effective, high performance and sustainable macro-units. This volume contains recent research progresses on development and application on construction based nanomaterials, market potential, problems regarding conventional building system and nanostructures characterized by higher potency, greater robustness and resilience, increased speed of construction, and lessened environmental impact. It contains vivid discussion on methods, mechanical properties, electrical and resistive properties, thermal conductive and damping properties of nanomaterials like titanium dioxide and carbon nanotubes, ultra high pressure ¿sensitive cement based composites and their potential applications. Authors lucidly and ornately discussed about self cleaning rods, fabrics, electricity generating coatings, heating/ cooling installation systems, micro-electromechanical systems (MEMS) in automobiles, development of nano based structures for disaster protection, waste and pollutant treatment, aviation and land transportation systems, and their applications. Nanotechnology not only finds its use in building highways, dams, bridges and flyovers, but also in making eco-friendly and smart nano-surfaces in ceramics and glasses which currently holds a very potential market globally. This volume will not only expand the knowledge and enhance the analytical ability of the students and researchers, but also help the industrial scientists, engineers, constructors and developers, to address many unsolved problems regarding production and characterisation of construction materials and their prospective applications.

    A great deal of attention has been given in the last years to the study of the influence of incorporating nanosized particles and particularly nanoparticles with a flat-like morphology such as nanoclays or layered double hydroxides, in the properties of polymer nanocomposites. The high aspect ratio of these nanofillers could result in improved interactions with polymer molecules at low filler concentrations, maintaining some of the main advantages of polymer composites such as reduced density. These improved interactions could lead to mechanical improvements or enable to regulate polymer nanocomposites' properties such as transport properties or even improve their intrinsically low flame retardancy. Recently, polymer foam preparation and characterization has gained a lot of attention, as foams have been shown to extend the range of properties and thus possible applications of polymers. The combination of foaming with the incorporation of nanosized particles (polymer nanocomposite foams) could further extend the material's properties, as nanoparticles could have a direct effect in the cellular structure of the foamed material and thus in its final properties. This chapter pretends to give a review of the most recent studies carried out on the influence of layered nanoparticles, focusing on silicate nanoclays and layered double hydroxides, on the mechanical and flame retardancy properties of polymer foams, with the final goal of developing multifunctional lightweight materials with improved properties for applications in sectors such as construction or automotive.

  • Foamed polypropylene for industrial applications

     de Sousa Pais Antunes, Marcelo; Velasco Perero, Jose Ignacio
    Date of publication: 2013
    Book chapter

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    There is a great deal of industrial interest in the development of increasingly lighter materials based on polymer foams with improved specific properties for the most varied purposes, from flexible foams for packaging to rigid ones for structural applications. Due to its good combination of properties and reduced cost, foamed polypropylene (PP) could come as a good option. Depending on the base material, foam density and developed cellular structure and microstructure, PP foams may cover a wide range of characteristics and properties which, combined with the incorporation of functional fillers, could ultimately result in the development of multifunctional lightweight materials. This chapter presents a review of the most recent developments in polypropylene foams, starting out by the commercially available PP grades thought out for foaming applications, the different types of PP-based foams depending on their characteristics and final uses, from low-density flexible foams for cushioning and packaging to medium-high density foams for structural purposes, and the main industrial foaming processes, going from melt-like foaming to solid-state chemical and physical foaming. Recent developments in the field of PP foams are also considered, focusing on the combination of cellular structure control via foaming and the incorporation of micro and nanosized functional fillers, with the ultimate objective of developing PP-based foams with a wide range of properties and unique characteristics, from electrically conductive foams through the incorporation of conductive carbon-based nanofillers to foams with direction-dependent transport properties.

    There is a great deal of industrial interest in the development of increasingly lighter materials based on polymer foams with improved specific properties for the most varied purposes, from flexible foams for packaging to rigid ones for structural applications. Due to its good combination of properties and reduced cost, foamed polypropylene (PP) could come as a good option. Depending on the base material, foam density and developed cellular structure and microstructure, PP foams may cover a wide range of characteristics and properties wich, combined with the incorporation of functional fillers, could ultimately result in the development of multifunctional lightweight materials. This chapter presents a review of the most recent developments in polypropylene foams, starting out by the commercially available PP grades thought out for foaming applications, the different types of PP-based foams depending on their characteristics and final uses, from low-density flexible foams for cushioning and packaging to medium-high density foams for structural purposes, and the main industrial foaming processes, going from melt-like foaming to solid state chemical and physical foaming. Recent developments in the field of PP foams are also considered, focusing on the combination of cellular structure control via foaming and the incorporation of micro and nanosized functional fillers, with the ultimate objective of developing PP-based foams with a wide range of properties and unique characteristics, from electrically conductive foams through the incorporation of conductive carbon-based nanofillers to foams with direction-dependent transport properties.

  • Mechanical¿viscoelastic characterization in nanocomposites

     de Redondo Realinho, Vera Cristina; de Sousa Pais Antunes, Marcelo; Arencón Osuna, David; Velasco Perero, Jose Ignacio
    Date of publication: 2013-06
    Book chapter

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  • Two-step supercritical carbon dioxide dissolution foaming of Bisphenol A polycarbonate: effects of the heating stage parameters on foam characteristics

     Gedler, Gabriel; de Sousa Pais Antunes, Marcelo; Sanchez Soto, Miguel Angel; Maspoch Ruldua, Maria Lluïsa; Velasco Perero, Jose Ignacio
    International Conference on Diffusion in Solids and Liquids
    Presentation's date: 2013-06-25
    Presentation of work at congresses

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    Caracterización mecánica, térmica y a fuego de aerogeles arcilla/polímero modificados con partículas  Open access

     Sanchez Soto, Miguel Angel; Wang, Liang; Martinez Benasat, Antonio; Velasco Perero, Jose Ignacio; Santana Pérez, Orlando Onofre; Maspoch Ruldua, Maria Lluïsa
    Congreso Nacional de Materiales Compuestos
    Presentation's date: 2013-07-03
    Presentation of work at congresses

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    Los aerogeles son una clase de materiales que se caracteriza por su extrema ligereza y alto contenido de aire. En este trabajo se han preparado diferentes aerogeles polímero/arcilla (PVOH/Na+-MMT) mediante un proceso simple de congelación y liofilización. Mediante esta técnica se han preparado aerogeles modificados conteniendo diferentes agentes ignifugantes en forma de partículas. La adición de dichos agentes causó un ligero incremento de la densidad aparente. Las propiedades mecánicas en compresión tanto a baja como a alta velocidad en general se vieron ligeramente reducidas debido a una menor unión entre el polímero y la arcilla. La excepción fue la muestra modificada con Al(OH)3 que incrementó la rigidez de los compuestos y la tensión a máxima deformación. En cuanto a las propiedades térmicas, la presencia de polifosfato de amonio (APP) o de silica gel (SG) redujo notablemente la velocidad de descomposición de los aerogeles en el rango de temperaturas entre 250ºC y 650ºC, sin embargo, la temperatura de inicio de descomposición no se vio sensiblemente alterada. El comportamiento a fuego se analizó mediante calorimetría de cono y los resultados han indicado que tanto la presencia de Al(OH)3 como de APP retardan la combustión del sistema y reducen la tasa de liberación de calor.

    Los aerogeles son una clase de materiales que se caracteriza por su extrema ligereza y alto contenido de aire. En este trabajo se han preparado diferentes aerogeles polímero/arcilla (PVOH/Na+-MMT) mediante un proceso simple de congelación y liofilización. Mediante esta técnica se han preparado aerogeles modificados conteniendo diferentes agentes ignifugantes en forma de partículas. La adición de dichos agentes causó un ligero incremento de la densidad aparente. Las propiedades mecánicas en compresión tanto a baja como a alta velocidad en general se vieron ligeramente reducidas debido a una menor unión entre el polímero y la arcilla. La excepción fue la muestra modificada con Al(OH)3 que incrementó la rigidez de los compuestos y la tensión a máxima deformación. En cuanto a las propiedades térmicas, la presencia de polifosfato de amonio (APP) o de silica gel (SG) redujo notablemente la velocidad de descomposición de los aerogeles en el rango de temperaturas entre 250ºC y 650ºC, sin embargo, la temperatura de inicio de descomposición no se vio sensiblemente alterada. El comportamiento a fuego se analizó mediante calorimetría de cono y los resultados han indicado que tanto la presencia de Al(OH)3 como de APP retardan la combustión del sistema y reducen la tasa de liberación de calor.

  • Combined effects of sc-CO2 and graphene nanoparticles on the crystallinity of bisphenol A polycarbonate

     Gedler, Gabriel; de Sousa Pais Antunes, Marcelo; de Redondo Realinho, Vera Cristina; Martinez Benasat, Antonio; Velasco Perero, Jose Ignacio
    International Symposium Frontiers in Polymer Science
    Presentation's date: 2013-05-23
    Presentation of work at congresses

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    There is still lack of information regarding changes in the microstructure of polycarbonate (PC) due to the addition of secondary phases and processing. In this work, PC composites with graphene were expanded using supercritical CO2 (sc-CO2). Raman spectroscopy, XRD and DSC demonstrated that the presence of graphene and CO2 induced PC¿s crystallization during saturation. Double melting behavior indicated the presence of crystals with different thermal stabilities. Saturation temperature, time and CO2 pressure had a direct effect on PC's melting temperature, indicating that processing parameters may be regulated to achieve different crystalline microstructures. Raman spectroscopy enabled to correlate changes in PC¿s crystallinity with processing conditions, showing that graphene and sc-CO2 favored the formation of an ordered non-crystalline phase. This induced crystallization, combined with graphene, led to composites with specific moduli that were up to 15% higher than that of unfilled PC.

  • Diffusion of CO2 in polymer nanocomposites containing different types of carbon nanoparticles and nanoclays for solid-state microcellular foaming applications

     de Sousa Pais Antunes, Marcelo; de Redondo Realinho, Vera Cristina; Gedler, Gabriel; Arencón Osuna, David; Velasco Perero, Jose Ignacio
    International Conference on Diffusion in Solids and Liquids
    Presentation's date: 2013-06-25
    Presentation of work at congresses

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  • Determinación de las curvas tensión-deformación verdaderas en polímeros

     Maspoch Ruldua, Maria Lluïsa; Loaeza, David; Martinez Benasat, Antonio; Arencón Osuna, David; de Sousa Pais Antunes, Marcelo; Velasco Perero, Jose Ignacio
    Encuentro del Grupo Español de Fractura
    Presentation's date: 2013-03-14
    Presentation of work at congresses

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  • Graphene in multifunctional polymeric materials

     de Sousa Pais Antunes, Marcelo; de Redondo Realinho, Vera Cristina; Gedler, Gabriel; Arencón Osuna, David; Velasco Perero, Jose Ignacio
    Jornada Internacional de Innovaciones Técnicas en Plástico
    Presentation's date: 2013-11
    Presentation of work at congresses

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    A highly topical subject in Materials Science considers the development of multifunctional materials with improved specific properties by combining the low density of polymers with the incorporation of functional nanofillers. This is the case of graphene, a two-dimensional nanosized material that has recently attracted a great interest due to its unique combination of properties and that has been shown to result in significant property enhancements when added into polymers even at extremely low concentrations. This presentation covers the most recent applications of graphene in polymer-based materials with the goal of developing multifunctional lightweight materials with a vast range of applications.

  • Thermal stability of polycarbonate-graphene nanocomposite foams

     Gedler, Gabriel; de Sousa Pais Antunes, Marcelo; de Redondo Realinho, Vera Cristina; Velasco Perero, Jose Ignacio
    Polymer degradation and stability
    Date of publication: 2012
    Journal article

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  • Thermal conductivity anisotropy in polypropylene foams prepared by supercritical CO2 dissolution

     de Sousa Pais Antunes, Marcelo; de Redondo Realinho, Vera Cristina; Velasco Perero, Jose Ignacio; Solórzano Quijano, Eusebio; Rodríguez-Pérez, Miguel Ángel; de Saja, José Antonio
    Materials chemistry and physics
    Date of publication: 2012-09
    Journal article

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  • Moulded polypropylene foams produced using chemical or physical blowing agents: structure¿properties relationship

     Saiz-Arroyo, Cristina; de Saja, José Antonio; Rodríguez Pérez, Miguel Ángel; Velasco Perero, Jose Ignacio
    Journal of materials science
    Date of publication: 2012
    Journal article

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    Polypropylene (PP) foams have become essential items due to their excellent properties. Nevertheless, obtaining net-shaped PP foams with medium relative densities is a complicated issue. In this article, two processes able to produce moulded PP foams in this density range are presented. One of them is based on a modification of the pressure quench foaming method and therefore uses a physical blowing agent (CO2). The second one is the improved compression moulding technique which uses a chemical blowing agent (azodicarbonamide). PP foams with relative densities in the range between 0.25 and 0.6 and cylindrical shape were prepared using these foaming techniques. A common PP grade (instead a highly branched one) was used to obtain the samples, showing, that by combining the appropriate foaming technique, the adequate moulds, suitable blowing agent and proper foaming parameters, net-shaped PP foams with excellent properties can be produced starting from a conventional PP grade. Samples were characterized by analyzing their cellular structure and their mechanical properties. Results have showed that depending on the chosen foaming route isotropic or anisotropic structures with cell sizes ranging from 40 to 350 lm and open cell content in the range between 0 and 65% can be obtained. Moreover, mechanical properties are highly influenced by the production route and chemical composition of the foams. For instance, the stiffer materials at relative densities higher than 0.4 are the ones produced using the chemical blowing agent while at relative densities lower than 0.4 are the ones produced using the physical blowing agent.

  • Low energy impact indentation of a modified polyethylene terephthalate by instrumented falling weight

     Martinez Benasat, Antonio; Arencón Osuna, David; Navas, Javier; Velasco Perero, Jose Ignacio
    Journal of applied polymer science
    Date of publication: 2012-04-27
    Journal article

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  • Foaming behavior, cellular structure and physical properties of polybenzoxazine foams

     Ardanuy Raso, Monica; Rodríguez-Pérez, Miguel Ángel; de Saja, José Antonio; Velasco Perero, Jose Ignacio
    Polymers for advanced technologies
    Date of publication: 2012-04-10
    Journal article

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    In this paper, polymer foams based on a benzoxazine resin have been successfully prepared using azodicarbonamide (ADC) as a chemical blowing agent and have been characterized regarding their foaming behavior, cellular structure, and physical properties. The effect of the ADC on the curing process of the resin was analyzed using differential scanning calorimetry and blowing agent decomposition was followed by thermogravitmetric analysis (TGA). The characterization of the cellular structure of the foamed samples was done using scanning electron microscopy. The mechanical properties of the foams were determined using compression tests and the thermal conductivity was assessed using the transient plane source method. The results indicated that the curing process and gas release took place in a similar time interval. The foams showed an isotropic cellular structure with relative densities in the range 0.35–0.60, and showed compressive strengths and compressive moduli in the range of 10–70 MPa and 400–1100 MPa, respectively. Thermal conductivities were in the range of 0.06–0.12 W m−1K−1. The findings in this paper demonstrate the possibility of producing polybenzoxazine foams using a simple process in which curing and foaming take place simultaneously. In addition, the mechanical characterization of these materials indicates that they are suitable for structural applications.

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    Novel polycarbonate-graphene nanocomposite foams prepared by CO2 dissolution  Open access

     Gedler, Gabriel; de Sousa Pais Antunes, Marcelo; de Redondo Realinho, Vera Cristina; Velasco Perero, Jose Ignacio
    IOP Conference Series: Materials Science and Engineering
    Date of publication: 2012
    Journal article

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    Polycarbonate foams reinforced with 0,5 wt% of graphene were obtained by firstly melt-mixing the polycarbonate and graphene in an internal mixer, compression-moulding the melt-compounded grinded material and lastly dissolving CO2 inside a high pressure vessel. The CO2 desorption behaviour in the unfilled polycarbonate and nanocomposite was studied in terms of the CO2 saturation concentration and desorption diffusion coefficient, with the graphene-filled nanocomposite displaying a higher CO2 loss rate when compared to the neat polycarbonate. The cellular structure of the foams was found to be highly dependent on the saturation/foaming temperature, with smaller cell sizes being obtained with decreasing the temperature. Another parameter that had an important influence was the residual pressure, with higher residual pressure values resulting in foams with more uniform and regular cells.

    Originally published as "IOP Conference Series: Materials Science and Engineering", vol. 31, no 1, 2012. DOI:10.1088/1757-899X/31/1/012008. .

  • Optical expandometry: a technique to analyze the expansion kinetics of chemically blown thermoplastic foams

     Solórzano Quijano, Eusebio; de Sousa Pais Antunes, Marcelo; Saiz-Arroyo, Cristina; Rodríguez-Pérez, Miguel Ángel; Velasco Perero, Jose Ignacio; de Saja, José Antonio
    Journal of applied polymer science
    Date of publication: 2012-07
    Journal article

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    A novel technique to determine in situ the free expansion kinetics of chemically foamed thermoplastic foams, so-called optical expandometry, is presented in this work. This technique is based on the camera monitoring of a free-foaming material placed inside a furnace. Images are acquired under special illumination conditions to facilitate the later image processing. The present article explains the experimental set-up and the image processing methods used to determine the free volumetric expansion of different polyolefinbased foams. The results are compared with those obtained using thermo-mechanical analysis. In addition, several possible applications of this method are detailed, such as studying the effect of polymer rheology, foaming temperature, blowing agent content and the anisotropy of the expansion.

  • Study of the fracture behaviour of flexible polypropylene foams using the Essential Work of Fracture (EWF)

     Arencón Osuna, David; de Sousa Pais Antunes, Marcelo; Martinez Benasat, Antonio; Velasco Perero, Jose Ignacio
    Polymer testing
    Date of publication: 2012-04-01
    Journal article

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  • Vegetable fibres from agricultural residues as reinforcement in recycled polyolefin-based green foams

     Ardanuy Raso, Monica; de Sousa Pais Antunes, Marcelo; Velasco Perero, Jose Ignacio
    Waste management
    Date of publication: 2012-02
    Journal article

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  • Layered double hydroxides (LDHs) as functional fillers in polymer composites

     Velasco Perero, Jose Ignacio; Ardanuy Raso, Monica; de Sousa Pais Antunes, Marcelo
    Date of publication: 2012-10-31
    Book chapter

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  • Improvement of the fire behaviour of PCM in building applications

     Haurie Ibarra, Laia; Lacasta Palacio, Ana Maria; Fernandez Llado, Javier; de Redondo Realinho, Vera Cristina; Velasco Perero, Jose Ignacio
    International Conference on Energy Storage
    Presentation's date: 2012-05-17
    Presentation of work at congresses

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    Phase change materials (PCM) have been proved to be an effective tool to regulate indoor temperature fluctuations and reduce the energetic demand of buildings [1,2]. Paraffins are among the most common PCM used for thermal storage in building applications. A broad range of melting temperatures, with an elevated heat of fusion associated, can be obtained varying the length of the hydrocarbon chain that forms the paraffins. Furthermore, they exhibit numerous benefits such as the nearly absence of supercooling, chemical stability, low vapor pressure during the phase change and no phase segregation [3]. These paraffins can be incorporated in several forms to building materials like gypsum or concrete [4]. Despite all these advantages, one major concern regarding the paraffins as PCM is their possible contribution to flame propagation in case of fire [5]. Several authors have tried to improve this aspect by combining the paraffins with HDPE polymers to obtain a form-stable PCM [6]. Blends of paraffin and polyethylene usually contain some inorganic filler, which can act improving both the thermal conductivity as well as the flame retardancy of the system [3, 7]. Microencapsulated PCM or paraffins adsorbed in a substrate are designed to be incorporated directly into the building material and, therefore blending with HDPE is less interesting. Another possibility to increase the fire performance of the PCM is the addition of flame retardants directly into the matrix-PCM mixture. Paraffins usually present their combustion between 220-320ºC and therefore the flame retardants selected should act in this temperature range. In this work we have studied the effect of different loads of PCM on the fire behaviour of gypsum boards. In order to improve the fire behaviour of the gypsum-PCM system, two different types of flame retardants have been added. We have chosen two endothermic flame retardants: aluminium hydroxide (ATH) and a synthetic basic magnesium carbonate, hydromagnesite (HM), obtained from an industrial by-product. Both FR have an endothermic decomposition starting around 200ºC and can be found among the cheapest alternatives to achieve flame retardancy.

  • Influence of graphene nanoparticles on the thermal stability of polycarbonate nanocomposite foams

     Gedler, Gabriel; de Sousa Pais Antunes, Marcelo; de Redondo Realinho, Vera Cristina; Velasco Perero, Jose Ignacio
    International Conference on Modification, Degradation and Stabilization of Polymers
    Presentation's date: 2012-09-05
    Presentation of work at congresses

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  • Halogen-free flame retardant polyolefin foams

     de Redondo Realinho, Vera Cristina; de Sousa Pais Antunes, Marcelo; Santana Pérez, Orlando Onofre; Velasco Perero, Jose Ignacio
    International Conference on Foam Materials & Technology
    Presentation's date: 2012-09-12
    Presentation of work at congresses

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    Influencia de las nanocargas en las propiedades termomecánicas de espumas poliméricas  Open access

     de Sousa Pais Antunes, Marcelo; Gedler, Gabriel; de Redondo Realinho, Vera Cristina; Velasco Perero, Jose Ignacio
    Encuentro del Grupo Español de Fractura
    Presentation's date: 2012-03-22
    Presentation of work at congresses

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    Se presenta la influencia de nanopartículas y nanofibras sobre las propiedades termomecánicas de espumas poliméricas. A una formulación base polipropileno especial para espumación se le incorporaron nanocargas (silicatos laminares) y nanofibras de carbono al objeto de aportar a los materiales celulares resultantes características de multifuncionalidad (rigidezm retardancia a la llama y conductividad). En el presente trabajo se analizan los efectos que introducen las partículas incorporadas sobre las características termodinámicas de las espumas, a través de análisis térmico mecánico dinámico (DMTA), en relación con la composición de las espumas, con su densidad relativa y con su estructura celular. Los resultados han demostrado que la influencia de las nanopartículas y nanofibras añadidas al polímero base de la espuma alcanza, no sólo a su cristalidad, temperaturas de transición características o propiedades mecánicas, sino también a la generación de estructuras celulares más finas y homogéneas que las de sus homónimos de referencia sin partículas.

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    Espumas ignífugas de poliolefina libres de halógenos  Open access

     de Redondo Realinho, Vera Cristina; de Sousa Pais Antunes, Marcelo; Haurie Ibarra, Laia; Maspoch Ruldua, Maria Lluïsa; Velasco Perero, Jose Ignacio
    Congreso Nacional de Materiales
    Presentation's date: 2012-06-01
    Presentation of work at congresses

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    En el presente trabajo se han preparado y caracterizado espumas ignífugas de poliolefinas libres de halógenos. Se ha utilizado para ello una formulación comercial, empleada típicamente en la industria de cables, y se le ha añadido pequeños porcentajes másicos (entre 2 y 4%) de dos sistemas retardantes de llama: "sílice-borato de zinc" y manolaminillas de "montmorillonita y grafeno expandible". Durante la caracterización celular de las espumas, preparadas por espumación química utilizando como agente espumante azodicarbonamida, se ha constatado que la presencia de las nanopartículas promovía una estructura celular con tamaño de celda más pequeño. Mediante un análisis termogravimétrico, se ha observado un aumento del residuo inorgánico de la formulación base a temperaturas superiores a 500ºC. Esta observación puede ser debida, en cierta medida, a un efecto sinérgico entre ambos sistemas retardantes de llama, el cual promueve una mayor estabilidad térmica de la formulación base. Durante la caracterización del comportamiento frente al fuego mediante ensayos de cono calorimétrico, se ha constatado que el sistema "síliceborato de zinc" retarda en tiempo hasta ignición de la llama (mayores valores de TTI) y que la presencia de las nanopartículas disminuye el valor del PHRR (máxima tasa de liberación de calor).

  • The multi-scalar effect of incorporating nanofillers and cellulosic-based reinforcements into polyurethane foams: towards the development of low cost structural lightweight materials

     de Sousa Pais Antunes, Marcelo; Maspoch Ruldua, Maria Lluïsa; Velasco Perero, Jose Ignacio
    International Conference on Foam Materials & Technology
    Presentation's date: 2012-09-13
    Presentation of work at congresses

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  • Nucleation efficiency of talc in the foaming behavior and cellular structure of polyolefin-based foams: new perspectives for optimized lightweight materials

     Meli, Gilles; Abler, Caroline; Jouffret, Frédéric; de Sousa Pais Antunes, Marcelo; Gedler, Gabriel; Arencón Osuna, David; Velasco Perero, Jose Ignacio
    International Conference on Foam Materials & Technology
    Presentation's date: 2012-09-12
    Presentation of work at congresses

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    The research consisted in evaluating the nucleation efficiency of different types of talc (with different particle size distributions, morphologies and even surface modifications) in the foaming behaviour and cellular structure os polypropylene-based materials, with the objective of developing lightweight materials with improved stiffness and lower densities. Nucleation efficiency was first evaluated in talc filled PP foamed with a physical blowing agent inside a high pressure vessel. Depending on different talc characteristics, such a particle size distribution, surface area and morphology, cell density as much as doubled. Optimized foamed PP-talc composites prepared by injection-moulding using the MuCell process displayed further weight reductions for similar stiffness values.

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    Characterization of polycarbonate foam structures prepared by one-step SC-CO2 dissolution process  Open access

     Gedler, Gabriel; de Sousa Pais Antunes, Marcelo; de Redondo Realinho, Vera Cristina; Velasco Perero, Jose Ignacio
    International Conference on Foam Materials & Technology
    Presentation's date: 2012-09-12
    Presentation of work at congresses

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    In this communication polycarbonate foams were prepared by a supercritical CO2 dissolution one-step batch foaming process. Firstly, CO2 diffusion behavior in polycarbonate was studied by means of desorption experiments. The cellular structure of foams prepared under different foaming conditions was characterized through scanning electron microscopy. Different foaming temperatures as well as CO2 saturation pressures and times were applied. The foams displayed typical closed-cell structures with cell densities ranging from 3x10⁵ to 3x10⁶ cells/m³ and cell average sizes from around 70 to 150μm. Analysis by X-ray diffraction and differential scanning calorimetry seemed to suggest that slight crystallization took place because of the plasticizing effect of CO2 during saturation and foaming. Thermogravimetric analysis showed a higher thermal stability of the foams when compared to the compact polymer. The preliminary results shown in this work suggest the possibility of developing lightweight polycarbonate components with improved specific thermal properties through carefully controlling the foaming parameters.

    Electronic version of an article published as "FOAMS 2012: 10th International Conference on Foam Materials & Technology : Barcelona, Spain, September 12 - September 13, 2012". Society of Plastics Engineers.

  • Multifunctional nanocomposite foams based on polypropylene with carbon nanofillers

     de Sousa Pais Antunes, Marcelo; Gedler, Gabriel; Mudarra Lopez, Miguel; Velasco Perero, Jose Ignacio
    International Conference on Blowing Agents and Foaming Processes
    Presentation's date: 2012-05-09
    Presentation of work at congresses

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  • Comportamiento a fractura de láminas de espuma de polipropileno producidas mediante dos métodos diferentes de espumación

     Arencón Osuna, David; de Sousa Pais Antunes, Marcelo; Martinez Benasat, Antonio; Velasco Perero, Jose Ignacio
    Encuentro del Grupo Español de Fractura
    Presentation's date: 2012-03-22
    Presentation of work at congresses

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  • Esparto wool as reinforcement in hybrid polyurethane composite foams

     de Sousa Pais Antunes, Marcelo; Cano, Álvaro; Haurie Ibarra, Laia; Velasco Perero, Jose Ignacio
    Industrial crops and products
    Date of publication: 2011-11
    Journal article

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  • Microcellular Foaming of Layered Double Hydroxide-Polymer Nanocomposites

     Martinez Benasat, Antonio; de Redondo Realinho, Vera Cristina; de Sousa Pais Antunes, Marcelo; Maspoch Ruldua, Maria Lluïsa; Velasco Perero, Jose Ignacio
    Industrial & engineering chemistry research
    Date of publication: 2011
    Journal article

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    Microcellular foams of polystyrene (PS), poly(styrene-co-acrylonitrile) (SAN), and poly(methyl methacrylate) (PMMA) having organically modified layered double hydroxides (LDH) were prepared using a high-pressure CO2 dissolution foaming process and characterized both structurally and thermo-mechanically. The saturation concentration of CO2 was found to increase with the incorporation of LDH nanoparticles into the PMMA, while the opposite effect was observed in the PS and SAN nanocomposites with respect to the pure polymers. The CO2 desorption diffusion coefficient substantially decreased in the nanocomposites comparatively to the respective pure polymers. The incorporation of hydrotalcite (HT) into the polymers and subsequent foaming resulted in foams with finer and more isotropic cellular structures, related to a cell nucleation effect promoted by the particles. No significant differences were found among the several foamed nanocomposites. Both PS and SAN nanocomposite foams displayed higher glass transition temperatures than the respective unfilled ones, related to a higher amount of residual CO2 in the last, favoring plasticization. The contrary effect was observed inPMMA, attributed to a combined plasticizing effect promoted by the higher affinity of PMMA for CO2 and greater interaction with the organically modified HT platelets. Although no significant differences were found among the several nanocomposite foams and respective unfilled counterparts, the incorporation of HT limited the reduction observed in the specific storage moduli with foaming, related to a finer cellular structure induced by the HT particles.

  • Mechanical Properties and Morphology of Multifunctional Polypropylene Foams

     de Sousa Pais Antunes, Marcelo; de Redondo Realinho, Vera Cristina; Ardanuy Raso, Monica; Maspoch Ruldua, Maria Lluïsa; Velasco Perero, Jose Ignacio
    Cellular polymers
    Date of publication: 2011
    Journal article

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  • Mg-Al Layered double hydroxide nanoparticles. Evaluation of the thermal stability in polypropylene matrix

     Ardanuy Raso, Monica; Velasco Perero, Jose Ignacio
    Applied clay science
    Date of publication: 2011-02
    Journal article

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  • Fracture behaviour of flexible polyethylene foams for potential use in damping applications

     Velasco Perero, Jose Ignacio; de Sousa Pais Antunes, Marcelo; Arencón Osuna, David; Martinez Benasat, Antonio
    Applied mechanics and materials
    Date of publication: 2011-09
    Journal article

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    The application of the essential work of fracture (EWF) methodology for the fracture behavior characterization of closed-cell low density polyethylene flexible foams is discussed in the present paper. The thickness of the foamed sheet and the relative orientation of the initial crack were the main parameters studied. The interpretation of the results is carried out on the basis of the material microstructure and the applicability of the testing method.

  • Broad-band electrical conductivity of carbon nanofibre-reinforced polypropylene foams

     de Sousa Pais Antunes, Marcelo; Mudarra Lopez, Miguel; Velasco Perero, Jose Ignacio
    Carbon
    Date of publication: 2011
    Journal article

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    The influence of foaming a semi-crystalline polymer reinforced with different concentrations of carbon nanofibres (0–20 wt.%) on the formation of an electrically conductive network was studied at room temperature using an impedance analyzer over a wide interval of frequencies (from 10−2 to 106 Hz). Composites were prepared by melt-compounding using a twin-screw extruder, and later chemically foamed. Although composite materials displayed lower conductivities than expected, assuming a percolative behavior, foaming promoted a tunnel-like conduction at lower CNF concentrations than in the solids. At higher CNF concentrations, no great improvements were achieved as tunneling conduction decreased with increasing local crystallinity. Foams showed electrical conduction characteristics typical of a conductive random-distributed fibre-like system, while the behavior of the solids was closer to a system of spherical particles, related to CNF aggregation. The anisotropic cellular structure of the 20 wt.% CNF composite foamed by a physical foaming process disrupted the preferential in-plane CNF orientation attained during solid preparation, with these foams showing higher through-plane conductivity and more isotropic electrical properties than the chemically-foamed ones. It has been demonstrated that foaming PP–CNF composites resulted in the formation of a conductive network at lower CNF concentrations than in the solids, with foams showing the potential for use in conductive high-performance lightweight composite systems.

  • Characterization of highly filled magnesium hydroxide-polypropylene composite foams

     de Sousa Pais Antunes, Marcelo; Velasco Perero, Jose Ignacio; Haurie Ibarra, Laia
    Journal of cellular plastics
    Date of publication: 2011
    Journal article

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  • Influence of the electric arc furnace dust in the physical and mechanical properties of EVA-polyethylene-butene blends

     Niubo Eslava, Maria; Fernández Renna, Ana Inés; Haurie Ibarra, Laia; Capdevila, X.G.; Chimenos Ribera, Josep Maria; Velasco Perero, Jose Ignacio
    Materials science and engineering A. Structural materials properties microstructure and processing
    Date of publication: 2011-05-24
    Journal article

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    This study assesses the processing behaviour and mechanical properties of different thermoplastic polymers filled with Electric Arc Furnace Dust (EAFD). Design of Experiments (DoE) approach enabled the evaluation of the influence of each component and the interactions between them. There were prepared different composite formulations varying the content of EAFD. The mechanical properties and the melt flow index (MFI) of composites were selected as output responses and the effect of CaCO3, BaSO4 and EAFD fillers as well as different polymer matrixes were evaluated. It was observed that slight variations in the formulation yield to a broad range of response values. Polyethylene-co-vinyl acetate (EVA) concentration showed a significant effect on all responses. It was found that the presence of EAFD increased fluidity and decreased the elasticity modulus and the elongation at break. In addition, when added with barite, the presence of EAFD caused an increase of the tensile strength.

  • Influence of nanoclay concentration on the CO2 diffusion and physical properties of PMMA montmorillonite microcellular foams

     de Redondo Realinho, Vera Cristina; de Sousa Pais Antunes, Marcelo; Martinez Benasat, Antonio; Velasco Perero, Jose Ignacio
    Industrial & engineering chemistry research
    Date of publication: 2011-11-08
    Journal article

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  • Low energy impact indentation of an epoxy-carbon fiber laminate

     Martinez Benasat, Antonio; Xiang, Gao; Arencón Osuna, David; Velasco Perero, Jose Ignacio
    Polymers and polymer composites
    Date of publication: 2011-08-01
    Journal article

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  • Characterization of rigid polypropylene-based microcellular foams produced by batch foaming processes

     Velasco Perero, Jose Ignacio; de Sousa Pais Antunes, Marcelo; de Redondo Realinho, Vera Cristina; Ardanuy Raso, Monica
    Polymer engineering and science
    Date of publication: 2011
    Journal article

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    The properties of polypropylene (PP) foams can be extended by controlling the cellular structure and adding functional fillers. PP-based microcellular foams having an interesting combination of mechanical and transport properties were prepared by two different batch foaming processes. The batch processes employed were a semisolid state CO2 dissolution physical foaming process and a chemical one based on the dissolution of the gases generated by the thermal decomposition of a chemical blowing agent in the molten state. The role of the cellular structure and nanofillers (5 wt% of organoclay and 10–20 wt% of cellulosic fibers) on the foam properties and CO2 diffusion rate was discussed. Foams with expansion ratios around 3 but different cell structures were prepared and studied concerning their structural characteristics. For unfilled foams prepared by CO2 dissolution, the microcellular structure resulted in the highest values of the specific storage modulus. A fraction of organically-treated montmorillonite dispersed into the PP matrix resulted in superior mechanical properties due to the combined effect of a finer cell structure and inherent higher stiffness of the silicate layers. Despite displaying an opencell structure, foams reinforced with high contents of cellulosic fibers showed increased specific storage moduli with respect to the unfilled foams

  • Essential work of fracture (EWF): a useful tool for the fracture toughness characterization of particulate polyolefin composites

     Arencón Osuna, David; de Sousa Pais Antunes, Marcelo; Velasco Perero, Jose Ignacio
    Date of publication: 2011-01-03
    Book chapter

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    The characterization of the fracture toughness of polyolefin composites filled with inorganic particles is commonly solved by means of standardized testing procedures based wherther on the Linear Elastic Fracture Mechanics (LEFM) and the Elastic-Plastic Fracture Mechanics approaches. Fracture parameters as Kc, Gc and Jc are obtained and managed as "material" parameters in plain strain conditions. Nevertheless, particulate polyolefin composites are often in form of film or sheet, making difficult to achieve the specimen size criteria for fracture toughness characterization under plain strain conditions. In such cases, the concept os Essential Work of Fracture (EWF) is nowadays being increasingly applied and considered as a reliable way of fracture toughness determination for this kind of composites. The EWF has traditionally been used for fracture characterization of metals and ductile polymers under plain stress conditions, and most recently applied to ductile particulate composites. In the present chapter, the application of the EWF testing method to the particulate polyolefin composites is reviewed analyzed with regard to the variables of the testing method and the composite characteristics, such as the polyolefin nature and its ductility , the reinforcing particle characteristics and concentration, and the interfacial adhesion level, among others.