The idea of recycling waste materials from such different sectors as textile or automotive has... more The idea of recycling waste materials from such different sectors as textile or automotive has been popular for decades, but today's recycling methods often produce poor quality products that are difficult to reuse. In the specific case of thermoset composites the problem is even greater, since once the resin is cured its dissolution is not possible and therefore the recovery of the original fiber and resin becomes practically unfeasible. This work presents recyclable thermoset composites made with fabrics obtained from waste textiles and epoxy or polyurethane resins, whose crosslinking is based on reversible bonds, which confers them the ability to be dissolved in a specific agent, so that both the fiber and the resin can be recovered for subsequent reuse. Taking into account the particularities of the starting raw materials, the manufacturing parameters of the composites and the resin dissolution conditions have been studied and optimized. The work is part of the European p...
Resumen del trabajo presentado al APS March Meeting, celebrado en Baltimore, Maryland (USA) del 1... more Resumen del trabajo presentado al APS March Meeting, celebrado en Baltimore, Maryland (USA) del 14 al 18 de marzo de 2016.
By aging, we draw glassy polymer films to a thermodynamic state, the ideal glass, with the entrop... more By aging, we draw glassy polymer films to a thermodynamic state, the ideal glass, with the entropy of the crystal.
L'objet de cette étude est l'élaboration de matériaux polymères nanocomposites transparen... more L'objet de cette étude est l'élaboration de matériaux polymères nanocomposites transparents à matrice polycarbonate, pour des applications dans des domaines tels que la lunetterie ou le vitrage automobile. L'incorporation de nanoparticules au sein du polycarbonate a été envisagée afin de lui conférer certaines propriétés mécaniques telles qu'une plus grande rigidité, une meilleure stabilité dimensionnelle, une résistance à la rayure plus importante, tout en conservant sa transparence. Le maintien de la transparence du matériau passe d'une part par l'utilisation de particules nanométriques présentant un indice de réfraction proche de celui de la matrice et d'autre part par une trés bonne dispersion de ces particules au sein de la matrice polymère. Ainsi différents types de nanoparticules minérales ont d'abord été sélectionnés puis incorporés dans la matrice polycarbonate. L'évaluation des performances de ces nanocomposites en termes de transparence...
We have monitored the physical aging of poly (methyl methacrylate)(PMMA)∕ silica nanocomposites, ... more We have monitored the physical aging of poly (methyl methacrylate)(PMMA)∕ silica nanocomposites, namely the slow evolution occurring to the structure of glasses below the glass transition temperature (Tg), following the time evolution of the enthalpy as measured by differential scanning calorimetry (DSC). We have systematically varied the concentration of silica to provide insight about the influence of the ratio area of silica∕ volume of PMMA on the physical aging process. Our results clearly indicate that physical aging speeds up with ...
The aim of this work is to study the effect of gold nanoparticles on the segmental dynamics, glas... more The aim of this work is to study the effect of gold nanoparticles on the segmental dynamics, glass transition (Tg) and physical aging of polystyrene (PS). To do so, PS/gold nanocomposite samples containing 5 and 15 wt% of 60 nm spherical gold nanoparticles, surface-treated with thiolated-PS, were prepared. The segmental dynamics of PS, as measured by means of broadband dielectric spectroscopy (BDS), was found to be unchanged in the presence of gold nanoparticles. Conversely, the calorimetric Tg of PS ...
ABSTRACT Physical aging is an ubiquitous phenomenon in glassy materials and originates from the f... more ABSTRACT Physical aging is an ubiquitous phenomenon in glassy materials and originates from the fact that they are generally out-of-equilibrium. Due to the technological and fundamental implications, this phenomenon has been deeply investigated in the last decades especially in glassy polymers. Here we provide a critical review of the latest hot debated themes in the field of physical aging in polymers and polymer nanocomposites. We first summarize the fundamental aspects of physical aging, highlighting its relation with the polymer segmental mobility. A review of the methods employed to monitor physical aging is provided too, in particular those probing the time dependent evolution of thermodynamic variables (or related to) and those probing the (quasi)instantaneous polymer segmental mobility. We subsequently focus our attention on the two following debated topics in the field of physical aging of polymers: i) the fate of the dynamics and thermodynamics of glassy polymers below the glass transition temperature ($T_g$), i.e. the temperature below which physical aging occurs; ii) the modification of physical aging induced by the presence of inorganic nanofillers in polymer nanocomposites. In respect to the former point particular attention is devoted to recent findings concerning possible deviations from the behavior normally observed above $T_g$ of both dynamics and thermodynamics deep in the glassy state. Regarding the effect of the presence of nanofillers on the rate of physical aging, the role of the modification of the polymer segmental mobility and that of purely geometric factors is discussed with particular emphasis on the most recent advances in the topic. The modification of the rate of physical aging in other nanostructured systems, such as polymer thin films, is discussed with particular emphasis on the analogy in terms of large amount interface with polymer nanocomposites.
We performed a systematic study on the recoverable enthalpy in several glass-forming polymers. We... more We performed a systematic study on the recoverable enthalpy in several glass-forming polymers. We found that after prolonged isothermal physical aging the enthalpy reaches a plateau with values substantially larger than than those corresponding to the enthalpy state extrapolated from the melt state. Enthalpy recovery experiments after up-jumps indicate that the enthalpy state corresponding to the plateau found after simple down-jump experiments is restored after long-term aging. This result is interpreted considering the plateau in the ...
A method of preparing a transparent polymer material includes mixing mineral nanoparticles select... more A method of preparing a transparent polymer material includes mixing mineral nanoparticles selected from nanoparticles of alkaline-earth metal carbonates, alkaline-earth metal sulfates, metallic oxides, oxides of metalloids, and siloxanes, and a composition A including at least one thermoplastic polymer in the molten state selected from polycarbonate (PC), polystyrene (PS) and polymethyl methacrylate (PMMA) in order to obtain a master-batch, the mixture of step i) including at least 25% and at most 75% by weight of the mineral nanoparticles. The ...
Abstract: The glass transition temperature ($ T_g $) of polymer thin films has been a subject of ... more Abstract: The glass transition temperature ($ T_g $) of polymer thin films has been a subject of controversy in the last two decades.(Pseudo) thermodynamic determinations of $ T_g $ generally suggest a significant depression, whereas the molecular mobility is found to be unchanged. The present study clarifies this apparent controversy by assuming that the $ T_g $ in thin films is determined not only by the molecular mobility but also by the thickness of the film. This hypothesis is supported by the analysis of literature results on polystyrene ...
The idea of recycling waste materials from such different sectors as textile or automotive has... more The idea of recycling waste materials from such different sectors as textile or automotive has been popular for decades, but today's recycling methods often produce poor quality products that are difficult to reuse. In the specific case of thermoset composites the problem is even greater, since once the resin is cured its dissolution is not possible and therefore the recovery of the original fiber and resin becomes practically unfeasible. This work presents recyclable thermoset composites made with fabrics obtained from waste textiles and epoxy or polyurethane resins, whose crosslinking is based on reversible bonds, which confers them the ability to be dissolved in a specific agent, so that both the fiber and the resin can be recovered for subsequent reuse. Taking into account the particularities of the starting raw materials, the manufacturing parameters of the composites and the resin dissolution conditions have been studied and optimized. The work is part of the European p...
Resumen del trabajo presentado al APS March Meeting, celebrado en Baltimore, Maryland (USA) del 1... more Resumen del trabajo presentado al APS March Meeting, celebrado en Baltimore, Maryland (USA) del 14 al 18 de marzo de 2016.
By aging, we draw glassy polymer films to a thermodynamic state, the ideal glass, with the entrop... more By aging, we draw glassy polymer films to a thermodynamic state, the ideal glass, with the entropy of the crystal.
L'objet de cette étude est l'élaboration de matériaux polymères nanocomposites transparen... more L'objet de cette étude est l'élaboration de matériaux polymères nanocomposites transparents à matrice polycarbonate, pour des applications dans des domaines tels que la lunetterie ou le vitrage automobile. L'incorporation de nanoparticules au sein du polycarbonate a été envisagée afin de lui conférer certaines propriétés mécaniques telles qu'une plus grande rigidité, une meilleure stabilité dimensionnelle, une résistance à la rayure plus importante, tout en conservant sa transparence. Le maintien de la transparence du matériau passe d'une part par l'utilisation de particules nanométriques présentant un indice de réfraction proche de celui de la matrice et d'autre part par une trés bonne dispersion de ces particules au sein de la matrice polymère. Ainsi différents types de nanoparticules minérales ont d'abord été sélectionnés puis incorporés dans la matrice polycarbonate. L'évaluation des performances de ces nanocomposites en termes de transparence...
We have monitored the physical aging of poly (methyl methacrylate)(PMMA)∕ silica nanocomposites, ... more We have monitored the physical aging of poly (methyl methacrylate)(PMMA)∕ silica nanocomposites, namely the slow evolution occurring to the structure of glasses below the glass transition temperature (Tg), following the time evolution of the enthalpy as measured by differential scanning calorimetry (DSC). We have systematically varied the concentration of silica to provide insight about the influence of the ratio area of silica∕ volume of PMMA on the physical aging process. Our results clearly indicate that physical aging speeds up with ...
The aim of this work is to study the effect of gold nanoparticles on the segmental dynamics, glas... more The aim of this work is to study the effect of gold nanoparticles on the segmental dynamics, glass transition (Tg) and physical aging of polystyrene (PS). To do so, PS/gold nanocomposite samples containing 5 and 15 wt% of 60 nm spherical gold nanoparticles, surface-treated with thiolated-PS, were prepared. The segmental dynamics of PS, as measured by means of broadband dielectric spectroscopy (BDS), was found to be unchanged in the presence of gold nanoparticles. Conversely, the calorimetric Tg of PS ...
ABSTRACT Physical aging is an ubiquitous phenomenon in glassy materials and originates from the f... more ABSTRACT Physical aging is an ubiquitous phenomenon in glassy materials and originates from the fact that they are generally out-of-equilibrium. Due to the technological and fundamental implications, this phenomenon has been deeply investigated in the last decades especially in glassy polymers. Here we provide a critical review of the latest hot debated themes in the field of physical aging in polymers and polymer nanocomposites. We first summarize the fundamental aspects of physical aging, highlighting its relation with the polymer segmental mobility. A review of the methods employed to monitor physical aging is provided too, in particular those probing the time dependent evolution of thermodynamic variables (or related to) and those probing the (quasi)instantaneous polymer segmental mobility. We subsequently focus our attention on the two following debated topics in the field of physical aging of polymers: i) the fate of the dynamics and thermodynamics of glassy polymers below the glass transition temperature ($T_g$), i.e. the temperature below which physical aging occurs; ii) the modification of physical aging induced by the presence of inorganic nanofillers in polymer nanocomposites. In respect to the former point particular attention is devoted to recent findings concerning possible deviations from the behavior normally observed above $T_g$ of both dynamics and thermodynamics deep in the glassy state. Regarding the effect of the presence of nanofillers on the rate of physical aging, the role of the modification of the polymer segmental mobility and that of purely geometric factors is discussed with particular emphasis on the most recent advances in the topic. The modification of the rate of physical aging in other nanostructured systems, such as polymer thin films, is discussed with particular emphasis on the analogy in terms of large amount interface with polymer nanocomposites.
We performed a systematic study on the recoverable enthalpy in several glass-forming polymers. We... more We performed a systematic study on the recoverable enthalpy in several glass-forming polymers. We found that after prolonged isothermal physical aging the enthalpy reaches a plateau with values substantially larger than than those corresponding to the enthalpy state extrapolated from the melt state. Enthalpy recovery experiments after up-jumps indicate that the enthalpy state corresponding to the plateau found after simple down-jump experiments is restored after long-term aging. This result is interpreted considering the plateau in the ...
A method of preparing a transparent polymer material includes mixing mineral nanoparticles select... more A method of preparing a transparent polymer material includes mixing mineral nanoparticles selected from nanoparticles of alkaline-earth metal carbonates, alkaline-earth metal sulfates, metallic oxides, oxides of metalloids, and siloxanes, and a composition A including at least one thermoplastic polymer in the molten state selected from polycarbonate (PC), polystyrene (PS) and polymethyl methacrylate (PMMA) in order to obtain a master-batch, the mixture of step i) including at least 25% and at most 75% by weight of the mineral nanoparticles. The ...
Abstract: The glass transition temperature ($ T_g $) of polymer thin films has been a subject of ... more Abstract: The glass transition temperature ($ T_g $) of polymer thin films has been a subject of controversy in the last two decades.(Pseudo) thermodynamic determinations of $ T_g $ generally suggest a significant depression, whereas the molecular mobility is found to be unchanged. The present study clarifies this apparent controversy by assuming that the $ T_g $ in thin films is determined not only by the molecular mobility but also by the thickness of the film. This hypothesis is supported by the analysis of literature results on polystyrene ...
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