References of "Calberg, Cédric"
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See detailOrganomodification of montmorillonite in supercritical carbon dioxide
Naveau, Elodie ULg; Calberg, Cédric ULg; Detrembleur, Christophe ULg et al

in Applied Clay Science (2011), 51(4), 467-772

The use of organo-montmorillonite as nanofiller for the preparation of polymer nanocomposites still attracts a lot of attention both on experimental and industrial scale. In order to enlarge the range of ... [more ▼]

The use of organo-montmorillonite as nanofiller for the preparation of polymer nanocomposites still attracts a lot of attention both on experimental and industrial scale. In order to enlarge the range of organo-montmorillonites available for this application, supercritical carbon dioxide (scCO2) was used as a medium for the organomodification process. This environmentally friendly solvent showed a great potential to obtain ready-to-use organo-montmorillonite powders. Intercalation with high degrees of exchange was obtained when the surfactants (alkyl ammonium, phosphonium, and imidazolium salts) were in the liquid state at the reaction temperature. The addition of a small quantity of co-solvent enabled the intercalation of solid surfactants, such as those bearing hydroxyl or carboxyl groups. Basal spacings of montmorillonite modified in scCO2 corresponded to those measured for organo-montmorillonite prepared in the wet process. A detailed investigation of the reaction conditions was finally performed in order to up-scale the process. [less ▲]

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See detailStudy of photocatalytic decomposition of hydrogen peroxide over ramsdellite-MnO2 by O2-pressure monitoring
Páez Martínez, Carlos ULg; Liquet, Dimitri ULg; Calberg, Cédric ULg et al

in Catalysis Communications (2011), 15

The catalytic and photocatalytic activities of ramsdellite type manganese oxide, R-MnO2 were studied from the initial rate of decomposition of H2O2 in aqueous solution. The kinetic study was followed by ... [more ▼]

The catalytic and photocatalytic activities of ramsdellite type manganese oxide, R-MnO2 were studied from the initial rate of decomposition of H2O2 in aqueous solution. The kinetic study was followed by the production of O2 via gas pressure monitoring (O2-monitored method), in the dark and under visible light irradiation (λ≥400 nm), at 20 °C. Experimental data showed that the rate of H2O2 decomposition, under visible light irradiation and in the dark, obeys the first order kinetic law.While in the dark the H2O2 decomposition rate bymass unit was around 6.88 mmol g−1 s−1, under visible light irradiation theH2O2 decomposition rate achieved a maximal value of 15.13 mmol g−1 s−1. The increase in the H2O2 decomposition, by effect of the visible light, was observed in ranges of catalyst concentrations from 16 to 374 mg L−1. These results reflect the potential of R-MnO2 as a photoactive catalyst, being a consequence of presumed photoreduction of Mn4+centers. [less ▲]

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See detailExtrusion foaming of poly(styrene-co-acrylonitrile)/ clay nanocomposites using supercritical CO2
Urbanczyk, Laetitia; Alexandre, Michaël ULg; Detrembleur, Christophe ULg et al

in Macromolecular Materials and Engineering (2010), 295(10), 915-

Supercritical CO2 has been used as a blowing agent to foam poly(styrene-co-acrylonitrile)-based materials in a single screw extruder specially adapted to allow fluid injection. The cellular morphology ... [more ▼]

Supercritical CO2 has been used as a blowing agent to foam poly(styrene-co-acrylonitrile)-based materials in a single screw extruder specially adapted to allow fluid injection. The cellular morphology depends on foaming temperature, more regular cells being obtained with decreasing extrusion temperature. In a second step, a natural and an organomodified nanoclay have been added for the purpose of imparting some flame resistance to the foamed material. The filler efficiency in reducing sample combustion rate appeared to be dependent on its delamination level inside the matrix and better results were obtained when the organomodified clay was first delaminated in the polymer in an efficient twin screw extruder using water assistance, prior to foaming in the single screw extruder. [less ▲]

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See detailBatch foaming of SAN/clay nanocomposites with scCO2: A very tunable way of controlling the cellular morphology
Urbanczyk, Laetitia ULg; Calberg, Cédric ULg; Detrembleur, Christophe ULg et al

in Polymer (2010), 51(15), 3520-3531

This paper aims at elucidating some important parameters affecting the cellular morphology of poly(styrene-co-acrylonitrile) (SAN)/clay nanocomposite foams prepared with the supercritical CO2 technology ... [more ▼]

This paper aims at elucidating some important parameters affecting the cellular morphology of poly(styrene-co-acrylonitrile) (SAN)/clay nanocomposite foams prepared with the supercritical CO2 technology. Prior to foaming experiments, the SAN/CO2 system has first been studied. The effect of nanoclay on CO2 sorption/desorption rate into/from SAN is assessed with a gravimetric method. Ideal saturation conditions are then deduced in view of the foaming process. Nanocomposites foaming has first been performed with the one-step foaming process, also called depressurization foaming. Foams with different cellular morphology have been obtained depending on nanoclay dispersion level and foaming conditions. While foaming at low temperature (40 °C) leads to foams with the highest cell density (1012–1014 cells/cm3), the foam expansion is restricted (d0.7–0.8 g/cm3). This drawback has been overcome with the use of the two-step foaming process, also called solid-state foaming, where foam expansion occurs during sample dipping in a hot oil bath (d0.1–0.5 g/cm3). Different foaming parameters have been varied, and some schemes have been drawn to summarize the characteristics of the foams prepared – cell size, cell density, foam density – depending on both the foaming conditions and nanoclay addition. This result thus illustrates the huge flexibility of the supercritical CO2 batch foaming process for tuning the foam cellular morphology. [less ▲]

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See detail“One-pot” dispersion ATRP and alkyne-azide Huisgen’s 1,3-dipolar cycloaddition in supercritical carbon dioxide: towards the formation of functional microspheres
Grignard, Bruno ULg; Calberg, Cédric ULg; Jérôme, Christine ULg et al

in Journal of Supercritical Fluids (2010), 53(1-3), 151-155

Functional polymers were successfully prepared in scCO2 by combining alkyne-azide 1,3-dipolar Huisgen’s cycloaddition and dispersion ATRP in a “one pot” process using new perfluorinated polymeric amino ... [more ▼]

Functional polymers were successfully prepared in scCO2 by combining alkyne-azide 1,3-dipolar Huisgen’s cycloaddition and dispersion ATRP in a “one pot” process using new perfluorinated polymeric amino-based ligands that had a dual role, i.e. the complexation of the copper catalyst and the stabilization of growing particles. [less ▲]

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See detailPreparation of fire-resistant poly(styrene-co-acrylonitrile) foams using supercritical CO2 technology
Urbanczyk, Laetitia ULg; Bourbigot, Serge; Calberg, Cédric ULg et al

in Journal of Materials Chemistry (2010), 20

This work deals with the preparation and characterization of fire-resistant poly(styrene coacrylonitrile) (SAN) foams containing (organo)clays and/or melamine polyphosphate (MPP) as fire retardants using ... [more ▼]

This work deals with the preparation and characterization of fire-resistant poly(styrene coacrylonitrile) (SAN) foams containing (organo)clays and/or melamine polyphosphate (MPP) as fire retardants using supercritical CO2 as the foaming agent. The additives dispersion was first characterized with X-ray and transmission electron microscopy (TEM) analyses. Their presence clearly affected the cellular morphology, as observed by scanning electron microscopy (SEM). Then, the peak of heat release rate (PHRR) and total heat evolved (THE) were determined with a cone calorimetry test, performed on each foamed sample as a function of the foam density. Incorporation of clay (3 and 5 wt%) in the exfoliated state into the SAN foam clearly led to a significant decrease of PHRR, while intercalated and aggregated clay had a lower effect. Similar results were obtained with 10 and 20 wt% of MPP. The best results were obtained when exfoliated clay and MPP were combined, with a PHRR drop as large as 75%, thanks to the synergistic action of both additives. The magnitude of PHRR drop, related to the fire resistance, was found to be in direct relationship with the cohesiveness of the protective carbonaceous layer formed at the sample surface during combustion. Clay and MPP, when added together, are thus believed to favour the formation of a highly cohesive protective layer able to act as an efficient shield against the flame, despite the fact that the sample is originally composed of ~90% of voids. [less ▲]

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See detailMorphology and properties of SAN-clay nanocomposites prepared principally by water-assisted extrusion
Mainil, Michaël; Urbanczyk, Laetitia ULg; Calberg, Cédric ULg et al

in Polymer Engineering & Science (2010), 50(1), 10-21

An efficient extrusion process involving the injection of water while processing was used to prepare poly(styrene-co-acrylonitrile) (SAN) / clay nanocomposites with a high degree of nanoclay delamination ... [more ▼]

An efficient extrusion process involving the injection of water while processing was used to prepare poly(styrene-co-acrylonitrile) (SAN) / clay nanocomposites with a high degree of nanoclay delamination. The usefulness of water-assisted extrusion is highlighted here, in comparison with classical extrusion and roll mill processes. Cloisite® 30B (C30B), a montmorillonite clay organomodified with alkylammonium cations bearing 2-hydroxyethyl chains, and pristine montmorillonite were melt blended with SAN (25wt% AN) in a semi-industrial scale extruder specially designed to allow water injection. XRD analysis, visual and TEM observations were used to evaluate the quality of clay dispersion. The relationship between the nanocomposite morphology and its mechanical and thermal properties was then investigated. The superiority of the SAN/C30B nanocomposite extruded with water has been evidenced by cone calorimetry tests and thermogravimetric measurements (TGA). These analyses showed a substantial improvement of the fire behavior and the thermal properties, while a 20% increase of the Young modulus was recorded. [less ▲]

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See detailNew perfulorinated macroligand for the implementation of dispersion atom transfer radical polymerization in sc CO2
Grignard, Bruno ULg; Calberg, Cédric ULg; Jérôme, Christine ULg et al

Poster (2009, September 17)

Due to an increasing need for polymers with well-defined architecture (diblock-, graft-, star-shaped copolymers), molecular weight and/or functional end-groups, the use of controlled radical ... [more ▼]

Due to an increasing need for polymers with well-defined architecture (diblock-, graft-, star-shaped copolymers), molecular weight and/or functional end-groups, the use of controlled radical polymerization (CRP) in scCO2 has started to gain attention. Among all the controlled processes, Atom Transfer Radical Polymerization has emerged as a robust tool for the preparation of polymers with well-defined molecular weight, architecture and chain-end functionality. In a very recent paper, we reported the first efficient dispersion ATRP of methyl methacrylate (MMA) in scCO2 using a fluorinated polymeric ligand that had a dual role, i.e., the complexation of the copper salt and the stabilization of PMMA growing particles. In this contribution, we extended this new system to the dispersion ATRP of styrene2, to the synthesis of diblock copolymers beads2 or to the preparation of PMMA particles by AGET ATRP. Because both ATRP and alkyne-azide Huisgen’s 1,3-dipolar cycloaddition relies on the use of a Cu(I) catalyst, synthesis of pyrene end-functionalized polymers by simultaneous dispersion ATRP and click reaction was also investigated in supercritical carbon dioxide. Finally, the immobilization of these new macroligands onto an inorganic support leads to the formation of pseudo-homogeneous catalyst that were successfully used to prepare CO2-soluble perfluorinated methacrylate and depending on the molecular weight and TEDETA composition of the macroligand, results obtained by supported ATRP without addition of Cu(II) as deactivator are identical to those obtained by homogeneous ATRP. [less ▲]

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See detailOrganoclays prepared in supercritical CO2: implication of onium stability on the properties of PA6 nanocomposites
Naveau, Elodie ULg; Calberg, Cédric ULg; Detrembleur, Christophe ULg et al

Conference (2009, June 23)

The organomodification of layered silicates via our patented supercritical CO2 ion-exchange process, enables the use of a large variety of surfactants, among which phosphonium and ammonium ions of the ... [more ▼]

The organomodification of layered silicates via our patented supercritical CO2 ion-exchange process, enables the use of a large variety of surfactants, among which phosphonium and ammonium ions of the very same structure. The as-obtained organoclays were melt blended with PA6 and the morphology as well as the fire properties of the nanocomposites were studied. With the same degree of nanodispersion, longer ignition times were observed with phosphonium-modified clays compared to ammonium-modified clays. [less ▲]

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See detailProduction of polymer/clay nanocomposite foams with improved fire behaviour using supercritical fluid technology
Urbanczyk, Laetitia ULg; Calberg, Cédric ULg; Detrembleur, Christophe ULg et al

Poster (2009, June 19)

In this study, supercritical CO2 is successfully used as foaming agent to prepare poly(styrene-co-acrylonitrile) (SAN) foams containing a low amount of well-dispersed nanoclay (5wt%). This kind of ... [more ▼]

In this study, supercritical CO2 is successfully used as foaming agent to prepare poly(styrene-co-acrylonitrile) (SAN) foams containing a low amount of well-dispersed nanoclay (5wt%). This kind of nanofiller has an influence both on material cellular morphology and fire property. In fact, SAN foam filled with nanoclay has smaller cells and higher density compared to unfilled foam. Moreover, the nanocomposite foam burns more slowly and without producing any burning droplets, which is highly desirable when considering housing applications. [less ▲]

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See detailPreparation of living polymer microspheres by dispersion atom transfer radical polymerization in scCO2 using fluorinated macroligands
Grignard, Bruno ULg; Calberg, Cédric ULg; Jérôme, Christine ULg et al

Poster (2009, May 19)

Due to an increasing need for polymers with well-defined architecture (diblock-, graft-, star-shaped copolymers), molecular weight and/or functional end-groups, the use of controlled radical ... [more ▼]

Due to an increasing need for polymers with well-defined architecture (diblock-, graft-, star-shaped copolymers), molecular weight and/or functional end-groups, the use of controlled radical polymerization (CRP) in scCO2 has started to gain attention. Among all the controlled processes, Atom Transfer Radical Polymerization has emerged as a robust tool for the preparation of polymers with well-defined molecular weight, architecture and chain-end functionality. In a very recent paper, we reported the first efficient dispersion ATRP of methyl methacrylate (MMA) in scCO2 using a fluorinated polymeric ligand that had a dual role, i.e., the complexation of the copper salt and the stabilization of PMMA growing particles. In this contribution, we extended this new system to the dispersion ATRP of styrene, to the synthesis of diblock copolymers beads and the controlled synthesis of hyperbranched copolymers. Finally, because both ATRP and alkyne-azide Huisgen’s 1,3-dipolar cycloaddition relies on the use of a Cu(I) catalyst, synthesis of pyrene end-functionalized polymers by simultaneous dispersion ATRP and click reaction was also investigated in supercritical carbon dioxide. [less ▲]

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See detailSupercritical CO2 as an efficient medium for layered silicate organomodification: preparation of thermally stable organoclays and dispersion in polyamide 6
Naveau, Elodie ULg; Calberg, Cédric ULg; Detrembleur, Christophe ULg et al

in Polymer (2009), 50(6), 1438-1446

In this study, the preparation of organoclays via a new process using supercritical carbon dioxide is described. This method turns out to be very efficient with various surfactants, in particular nonwater ... [more ▼]

In this study, the preparation of organoclays via a new process using supercritical carbon dioxide is described. This method turns out to be very efficient with various surfactants, in particular nonwater-soluble alkylphosphonium salts. The influence of the surfactant as well as of the clay nature on the thermal stability of the organoclay is evaluated by thermogravimetric analysis. Phosphonium-based montmorillonites are up to 90 °C more stable than ammonium-based montmorillonites. Moreover, the use of hectorite adds another 40 °C of thermal stability to the phosphonium-modified clays. These organomodified clays have been melt-blended with polyamide 6 and morphology as well as fire properties of the nanocomposites are discussed, in terms of influence of the stability of organoclays. For the first time, comparison of nanocomposites based on clay organomodified by ammonium and phosphonium salts of the very same structure is reported. [less ▲]

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See detailSynthesis of polylactide/clay nanocomposites by in situ intercalative polymerization in supercritical carbon dioxide
Urbanczyk, Laetitia ULg; Ngoundjo, Fred; Alexandre, Michaël ULg et al

in European Polymer Journal (2009), 45(3), 643-648

Polylactide (PLA)/clay nanocomposites have been prepared by in situ ring-opening polymerization in supercritical carbon dioxide. Depending on the type of organoclay used, polylactide chains can be grafted ... [more ▼]

Polylactide (PLA)/clay nanocomposites have been prepared by in situ ring-opening polymerization in supercritical carbon dioxide. Depending on the type of organoclay used, polylactide chains can be grafted onto the clay surface, leading to an exfoliated morphology. Nanocomposites with high clay contents (30–50 wt.%), called masterbatches, have also been successfully prepared and were recovered as fine powders thanks to the unique properties of the supercritical fluid. Dilution of these masterbatches into commercial l-polylactide by melt blending has led to essentially exfoliated nanocomposites containing 3 wt.% of clay. The mechanical properties of these materials have been assessed by flexion and impact tests. Significant improvements of stiffness and toughness have been observed for the PLA/clay nanocomposites compared to the pure matrix, together with improved impact resistance. [less ▲]

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