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Exfoliation in NanoComposites: An Alternative Use of Acetone
Universidade Federal de Minas Gerais
Nanoclay
filled polymeric systems have been studied for many researchers who
concluded that polymeric systems’ mechanical and
thermal properties are greatly
enhanced with the addition of small amounts of nanoclay. However,
the exfoliation of these particles stills a problem for many
polymeric systems, especially for the epoxy systems. In this
specific case, as the resin presents high
viscosity, to exfoliate the nanoparticles an elevated temperature
must be reached. By heating the resin, its viscosity decreases
leading to a better exfoliation. However, when the hardener
is added at high temperature, in general
between 40 and 60 oC, the polymerization reaction is so
fast that can cause the nanoparticles precipitation or a non-uniform
exfoliation. To avoid it, an investigation using acetone as an
exfoliation vehicle is conducted. The epoxy system employed is the
ARALDITE 2000 (resin XR 1553/hardener HY 1246) from Huntsman and the
nanoclay used is montmorillonite clay (NANOMER I 30) from
Nanocor. Different dilutions of acetone and I30 were selected. This
solution is then exfoliated at
ARALDITE matrix up to 5% in weight. The nanocomposite preparation
involves not only the search for the ideal diluted solution nanoclay/acetone,
but also of a period of low heating and mixing to obtain a
homogeneous mixture. After cooling and degassing, the hardener is
added and the cure is processed. By controlling the amount of
remaining acetone, it is possible to control the nanocomposite
toughness and stiffness. Experiments have demonstrated that the
presence of acetone associated to nanoclays increases the
nanocomposite toughness. Indeed, it was observed that for large
concentrations of acetone, the nanocomposites get a
rubber-like behavior, while
an increase of stiffness is observed for small or quasi-null
nanoclay concentrations.
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Presented at the International Congress
of Nanotechnology, November 7-10, 2004 San Francisco, USA
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