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PubMed2006

Characterization and thermophysical properties of unsaturated polyester-layered silicate nanocomposites.

The thermophysical properties of unsaturated polyester (UPE) nanocomposites reinforced by organo-montmorillonite clay nanoplatelets are reported. The organo-clay nanoplatelets were sonicated in acetone for 2 hours to be dispersed in the UPE matrix. Vacuum extraction removed not only the acetone but also the styrene present in the UPE solution. The same mechanical and thermophysical properties of UPE were regained after adding the lost amount of styrene to the UPE solution. Both delaminated and intercalated clay morphologies were observed by transmission electron microscopy. It was found that the sonication process was effective to delaminate clay nanoplatelets for more homogeneous dispersion, dependent on organic chemical modifications for clay nanoplatelets. A higher storage modulus enhancement was obtained when the organo-clay nanoplatelets were delaminated and more homogeneously dispersed. The reinforcing effect of both delaminated and intercalated clay nanoplatelets was theoretically evaluated with the Halpin-Tsai equations. It was evaluated that the aspect ratio of delaminated clay nanoplatelets was approximately 150. The increase of the storage modulus below and above the glass transition temperature was achieved without reducing glass transition temperature and Izod impact strength with increasing clay content.

Materials Testing↗
PubMed2006

Modified electrodes prepared from ferrocene functionalized silicate xerogels: analysis of the electrochemical response in isotropic and fractal structural systems.

New xerogels functionalized by ferrocenes as redox probes have been prepared using various types of catalysis. The analysis of the electrochemical response in the case of modified electrodes allows us to get an insight into the gel nanostructure which has been found to be isotropic in the case of acidic catalysis, and fractal in the case of fluoride catalysis, provided that the amount of functionalized silanes is not too high. Indeed the results of electrochemical measurement prove that the fractality of functionalized hybrid silica is general in the case of basic catalysis, except in the case of very high functional moieties loading, where the electrode become essentially organic and isotropic. On the other hand, in the case of acidic catalysis, whatever the amount of organic material, the hybrid gel remains isotropic, and a classical electron pseudo-diffusive behaviour is observed. The diffusion coefficient values extracted from the current-time slopes do not vary monotonically with the amount of redox probe in the case of fractal xerogel structures, which is indicative that not all the functional moieties are electroactive in that case.

Electrochemistry↗