11 research outputs found

    Nanocomposites at Elevated Temperatures: Migration and Structural Changes

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    The possible effect of temperature stability of organic layered silicates (OLSs) on the structure and flammability behavior of polymer/montmorillonite (MMT) nanocomposites has been discussed in a previous publication. Above 200°C, the OLS begins to decompose, and the nanocomposite structure is gradually destroyed even before pyrolysis and combustion. Data on the decomposition of polymer/OLS mixtures upon isothermal thermogravimetric analysis (TGA) experiments are presented, and include rates and energies of activation at a range of temperatures from 200 to 400°C. Decomposition of OLSs in the presence of polymer is discussed in view of the decomposition of clay, pristine surfactant, and OLS. Accumulation of clay by migration to the surface of samples at a range of temperatures is indicated by X-ray diffraction (XRD) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) measurements on the isothermally heated samples. Mechanistic considerations concerning changes in the structure of the nanocomposite, the decomposition of OLS, and migration of clay will be presented. Copyright © 2006 John Wiley & Sons, Ltd

    Improving the flame retardancy of flax fabrics by radiation grafting of phosphorus compounds

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    International audienceTwo phosphorus-based molecules were grafted onto flax fibers through electron beam irradiation in order to impart flame retardancy to flax fabrics. Fabrics were impregnated by dipping them into a solution containing a phosphonated monomer: dimethyl(methacryloxy)methyl phosphonate (MAPC1) or dimethylvinyl phosphonate (MVP). Then fabrics were irradiated at a dose ranging between 10 and 100 kGy. The grafting efficiency was found to be dependent on the molecule concentration in the impregnation solution, on the radiation dose and on the nature of the monomer. In particular, it has been observed that MAPC1 is grafted only onto the surface while MVP is also grafted into the bulk leading to high phosphorus content (4 wt%). Flame retardancy of the modified flax fibers, fabrics and polyester thermoset composites containing these fabrics were also investigated. High phosphorus content allows fabrics to achieve self-extinguishing behavior. The flammability of composites in cone calorimeter test is also reduced, even if the thermoset is not flame retarded itself

    Pd Nanoclusters in CC Coupling Reactions: Proof of Leaching

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    A simple experiment based on exclusion of Pd nanoclusters was used to identify the true catalytic species in cluster-catalyzed Heck cross-couplings. A special reactor was used in which two compartments are separated by a nanoporous membrane that allows the passage of Pd atoms and ions but not of Pd nanoclusters. The results show that the real catalysts in the Heck coupling of n-butyl acrylate with iodobenzene are species leached from the Pd nanoclusters
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