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[资源] Nanotube Firefighters

Nanotube Firefighters
When polymers are heated and reach the temperature at which they begin to decompose,
bubbles often form beneath the surface because the boiling points of the degradation products
are usually lower than the decomposition temperature of the parent polymer.The evolution
of these bubbles prevents the formation of a solid layer of char, which would insulate the
rest of the polymer from further heating.With
the advent of restrictions on halogenated
flame-retardant additives, nanoscale reinforcing
materials, such as clay particles, have been
investigated as alternatives.
Kashiwagi et al. have found that carbon
nanotubes and nanoparticles can also act both as
reinforcing materials and as flame retardants,
and in some cases can surpass the performance
of nanoclay materials. Coaxing the asymmetric
fibers into a continuous network structure is the
key to reducing bubbling. At fixed loads under
radiant heat, the best results were obtained
using single-walled carbon nanotubes (SWNTs),
which left a residue with an undulating surface
but no deep cracks. In contrast, multiwalled
carbon nanotubes (MWNTs) yielded only islands of protection, and neither carbon nanofibers
(CNF) nor carbon black particles helped very much. Flame retardancy was found to correlate with
rheology, because the best materials showed a gel-like response,which matches their ability to
form networks.

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[ Last edited by luo.henry on 2008-4-25 at 15:52 ]
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