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See detailEffect of clay modification on the mechanism of local deformations in PA6 nanocomposites
Dominkovics, Zita; Naveau, Elodie ULg; Jérôme, Christine ULg et al

in Macromolecular Materials and Engineering (2013), 298(7), 796-805

PA nanocomposites are prepared from clays organophilized with a phosphonium and an ammonium salt, and sodium montmorillonite is used as reference. The analysis of mechanical and micromechanical properties ... [more ▼]

PA nanocomposites are prepared from clays organophilized with a phosphonium and an ammonium salt, and sodium montmorillonite is used as reference. The analysis of mechanical and micromechanical properties of the composites reveal that several micromechanical deformation processes occur in the PA/MMT composites. The matrix cavitates at relatively small stress. Processes related to non-exfoliated clay structural units are initiated at larger stresses. Sound is emitted mainly by the fracture of particles, but debonding may also occur. The plastic deformation of the matrix dominates at larger stresses and deformations. The various local deformations are independent of each other and composite properties are not determined by silicate related processes but by the deformation of the matrix. [less ▲]

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See detailEffect of silica-coated poly(butyl methacrylate)-block-poly(methyl methacrylate) double-shell particles on the mechanical properties of PMMA composites
Chakkalakal, G. L.; Alexandre, Michaël ULg; Boschetti-de-Fierro, Adriana et al

in Macromolecular Materials and Engineering (2012), 297(9), 887-893

Silica nanoparticles with average diameters of 12nm are grafted with PBMA-b-PMMA double shells through typical ATRP from a Si12-g-(PBMA)Br macroinitiator using 2-BriB as the initiator. A commercially ... [more ▼]

Silica nanoparticles with average diameters of 12nm are grafted with PBMA-b-PMMA double shells through typical ATRP from a Si12-g-(PBMA)Br macroinitiator using 2-BriB as the initiator. A commercially available PMMA homopolymer is used for the preparation of composites with unmodified, silane-modified and double-shell-modified silica particles. Good mechanical properties are obtained for silica double shell containing systems. The silica content in double shell particle systems is varied from 0 to 2.5 wt%. A significant improvement in impact properties is observed. The surface-modified silica particles are characterized by ATR-FTIR, NMR, GPC, and thermal analysis. TEM analysis is used to analyze the nature of dispersion of particles in the composites. [less ▲]

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See detailNanostructured polymer blends: from core/shell nanoobjects to continuous three-phase morphologies
Lei, Liangcai; Detrembleur, Christophe ULg; Jeusette, Mélanie et al

in Macromolecular Materials and Engineering (2011), 296(2), 122-130

A PS-b-PIP-b-PMMA copolymer has been melt-blended with homo-PMMA with a similar molecular weight as the PMMA block. For a 50:50 wt.-% mixture, the components form 3D bicontinuous lamellae. Upon annealing ... [more ▼]

A PS-b-PIP-b-PMMA copolymer has been melt-blended with homo-PMMA with a similar molecular weight as the PMMA block. For a 50:50 wt.-% mixture, the components form 3D bicontinuous lamellae. Upon annealing at 190 °C, a more regular network is observed, which consists of PMMA and 55 nm-thick bilayered lamellae of triblock copolymer, both being continuous. This co-continuity persists even when of the homo-PMMA is twice that of the PMMA block in the copolymer. For 30:70 and 20:80 wt.-% copolymer/homopolymer pair, the copolymer forms cylindrical and spherical phases, respectively. Blends have also been prepared by solvent casting. Large domains of copolymer interconnected by few lamellae are observed in the 50:50 blend that reorganize into a bicontinuous network upon annealing. [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 detailEnd-grained wood-polyurethane composites, 1 Synthesis, morphology and characterization
Persenaire, Olivier; Alexandre, Michaël ULg; Degée, Philippe et al

in Macromolecular Materials and Engineering (2004), 289(10), 895-902

In order to improve the dimensional stability of end-grained wood upon environmental humidity variations, a two-step procedure was thoroughly Studied which involved the osmotic impregnation of native ... [more ▼]

In order to improve the dimensional stability of end-grained wood upon environmental humidity variations, a two-step procedure was thoroughly Studied which involved the osmotic impregnation of native poplar wood by PEG, followed by the reactive impregnation with HMDI, leading to polymer chain extension and polyurethane formation. It came out that the efficiency of PEG and/or polyurethane grafting within ligno-cellulosic cell walls was intimately related to parameters such as concentration of the PEG impregnation bath, PEG molar mass, time and temperature of impregnation steps. Based on the different sample characterizations, Soxhlet extraction and density measurements, it came out that adequate experimental conditions are to carry out osmotic impreanation at 20degreesC for 24 h starting from an aqueous solution of PEG([PEG] = 0.5mol(.)L(-1) and (M) over bar (nPEG) = 400 or 1000) and reactive impregnation in bulk with a large excess of HMDI at 20degreesC for 2 h. Combining scanning electron microscopy and mercury porosimetry demonstrated the selective impregnation of cell wall and wood rays which were collapsed in native wood and expanded in wood polyurethane composites. [less ▲]

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