Flammability Properties of Polymer Nanocomposites With Single-Walled Carbon Nanotubes: Effects of Nanotube Dispersion and Concentration.
Flammability Properties of Polymer Nanocomposites With
Single-Walled Carbon Nanotubes: Effects of Nanotube
Dispersion and Concentration.
(975 K)
Kashiwagi, T.; Du, F.; Winey, K. I.; Groth, K. M.;
Shields, J. R.; Bellayer, S. P.; Kim, H.; Douglas, J. F.
Polymer, Vol. 46, No. 2, 471-481, January 2005.
Keywords:
nanocomposites; flammability; polymers; carbon;
nanotubes; dispersion; thermal stability; morphology
Abstract:
The effects of the dispersion and concentration of
single walled carbon nanotube (SWNT) on the flammability
of polymer/SWNT nanocomposites were investigated. The
polymer matrix was poly (methyl methacrylate) (PMMA) and
the SWNT were dispersed using a phase separation
('coagulation') method. Dispersion of SWNTs in these
nanocomposites was characterized by optical microscopy
on a micrometer scale. Flammability properties were
measured with a cone calorimeter in air and a
gasification device in a nitrogen atmosphere. In the
case where the nanotubes were relatively well-dispersed,
a nanotube containing network structured layer was
formed without any major cracks or openings during the
burning tests and covered the entire sample surface of
the nanocomposite. However, nanocomposites having a poor
nanotube dispersion or a low concentration of the
nanotubes (0.2% by mass or less) formed numerous black
discrete islands with vigorous bubbling occurring
between these islands. Importantly, the peak heat
release rate of the nanocomposite that formed the
network layer is about a half of those, which fornled
the discrete islands. It is proposed that the formation
of the discrete islands is due to localized accumulation
of the nanotubes as a result of fluid convection
accompanying bubble formation and rise of the bubbles to
the surface through the molten sample layer and bursting
of the bubbles at the surface. The network layer acts
as a heat sheild to slow the thermal degradation of
PMMA.
