Multiwalled carbon nanotubes functionalized with 7-octenyltrichlorosilane and n-octyltrichlorosilane: dispersion in Sylgard®184 silicone and Young’s modulus

Journal of Materials Science (Impact Factor: 2.31). 07/2009; 44(13):3476-3482. DOI: 10.1007/s10853-009-3464-1

ABSTRACT Sylgard®184/multiwalled carbon nanotube (MWNT) composites have been prepared by in situ polymerization using purified and functionalized
multiwalled carbon nanotubes (f-MWNTs) as fillers. Surface modification of the MWNTs has been carried out by silanization
with 7-octenyltrichlorosilane (7OTCS) and n-octyltrichlorosilane (nOTCS). The modification and dispersion of the carbon nanotubes in composites were characterized by X-ray photoelectron spectroscopy
(XPS), transmission electron spectroscopy (TEM), and high-resolution transmission electron spectroscopy (HRTEM). Young’s modulus
results were derived from indentation testing. It is shown that the terminal-vinyl group of 7OTCS molecules plays an essential
role for both the dispersion of the f-MWNTs in the composite and its mechanical properties. At loading as low as 0.2wt%,
the Young’s modulus is shown to increase up to 50%. This is interpreted as resulting from a combination of the good compatibility
in the forming silicone matrix of the MWNTs coated with a siloxane network, on the one hand, and the covalent links created
between the terminal-vinyl groups and the host matrix in formation, on the other hand.

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    ABSTRACT: The effects of surface-functionalized and pristine multiwall carbon nanotubes (MWCNT) on the bulk and adhesion properties of silicone nanocomposites were investigated. The MWCNTs surface functionalization was carried out by silanization of methacryloxy or vinyl-based silanes. The nanocomposites were prepared using solvent mixing which enhanced distribution and dispersion of the MWCNTs in the high-viscosity silicone matrix. The quality of dispersion was evaluated using scanning electron microscopy (SEM) indicating good dispersion state. It was found that the optimal concentration of both treated and untreated MWCNTs in the nanocomposites was 1 wt.%. Above this threshold value, the nanocomposites properties were reduced. Furthermore, the silane treatment of the MWCNTs was proven to be an effective process that resulted in a significant increase in the nanocomposites properties compared to the neat polymer, leading to higher storage modulus simultaneously with up to 27% improvement in the tensile strength and elongation, 20–30% reduction in the thermal expansion coefficient, 220–300% enhancement in crystallinity (enthalpy of fusion), and up to 56% improvement in the lap shear strength. SEM analysis indicated that significant changes in the fracture morphologies occurred due to higher energy absorption in the case of silane-treated MWCNTs. It was concluded that incorporation of silane-treated MWCNTs is an effective route to reinforce and increase the toughness of silicone-based adhesives.
    Journal of Adhesion Science and Technology 04/2014; 28(17). · 1.09 Impact Factor
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    ABSTRACT: Surface modification of oxidized carbon nanotubes (O-CNTs) with silicon based anchoring groups (R-SiR′3R-SiR′3) is a relatively uncommon approach of the CNTs functionalization. Hydrosilane derivatives constitute an attractive subclass of compounds for silanization reactions on the CNTs surface. In this work, we report on the ZnCl2 catalytically controlled reaction (hydrosilane dehydrogenative cross-coupling, DHCC) of fluorinated hydrosilane probes with the carboxylic functions present on the surface of oxidized multi-wall carbon nanotubes. Carbon nanotubes functionalized with essentially alcohol groups are also used to compare the selectivity of zinc chloride toward carboxylic groups. To assess the efficiency of functionalization, X-ray Photoelectron Spectroscopy is used to determine the qualitative and quantitative composition of the different samples. Solubility tests on the oxidized and silanized MWNTs are also carried out in the framework of the Hansen Solubility Parameters (HSP) theory to apprehend at another scale the effect of DHCC.
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