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Polymeric
Nanocomposites
Nanocomposites are a new class of composites, that are particle-filled
polymers for which at least one dimension of the dispersed particles is in
the nanometer range. Over the
last decade, the utility of layered silicate nanoparticles as additives to
enhance polymer performance has been established.
Nanoscale fillers result in physical behavior that is dramatically
different from that observed for conventional microscale counterparts.
For instance, increased moduli, gas barrier, increased strength and
reduced thermal expansion coefficients are observed with only a few
percent additions of nanofiller; thus maintaining polymeric processability,
cost and clarity.
The
following are two potential projects in this area:
Emulsion
polymerization offers a viable, flexible route for nanocomposite
fabrication from nanoscale spheres, rods and plates.
Combining emulsion generated polymer particles that are ionically
stabilized in aqueous solution with a dispersion of nanoparticles of
opposite sense results in an interfacial exchange reaction and
co-precipitation. As shown in
Fig. 2, the idea is to make a few percentage of the surfactants, which
have positive charges, with double bonds so that the surfactant molecules
can be copolymerized. The
resulting macromolecules, which will carry certain amounts of charges,
will then co-precipitate with charged exfoliated clay particles or charged
rigid rod macromolecules, to make polymer/layered silicate nanocomposites
or rigid rod molecular composites.
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Protect
polymeric materials against aggressive space environment through
nanocomposite
Polymers
are very attractive and desirable materials for use in space
applications, in particular for addressing multi-functional
requirements. With
modifications these materials could potentially solve many of the
weight-based and process-based problems plaguing the space industry
and offer new capabilities for future systems.
Polymers are remarkable materials but there are, as with any
material, problems associated with their use, especially in a harsh
space environment. Degradation
is a most prominent concern with using polymers in space, and the
existence of atomic oxygen in Low Earth Orbit (LEO) is one of the
major reasons of degradation.
This research is to investigate the “Multi-functional
(self-passivating/self-rigidizing/self-healing) polymeric materials
for space survivable structures based on polymer/layered silicate
nanocomposites”. The
previous results showed that Nylon 6/layered silicate nanocomposites
are able to self-generate a silicate passivation layer upon exposure
to oxygen plasma. The
resulting layer is strongly interferometric.
The thickness of the layer varies from a few hundred nanometers
to one micron, and chemical composition of the layer is nearly
completely inorganic. The
formation of the layer is due to the preferential oxidation of the
polymer (Nylon 6) from the nanocomposite, and the corresponding
deposition of the nanoscale layered silicate on the surface.
The structure of the inorganic layer is turbostratic, with the
average distance between silicate layers of about 1 to 4 nanometers.
After the passivation layer forms, the degradation of the
polymer underlying can be significantly retarded during exposure to
oxygen plasma. Thus,
nanocomposite may potentially be used to protect the degradation of
polymers, especially against atomic oxygen in low earth orbit.
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