Flame Retardant Mechanism of the Nanotubes-Based Nanocomposites. Final Report.
Flame Retardant Mechanism of the Nanotubes-Based
Nanocomposites. Final Report.
NIST GCR 07-912; Final Report; 68 p. September 2007.
Sponsor:National Institute of Standards and Technology,
flame retardants; nanocomposites; nanotubes;
flammability; polymethyl methacrylate
This project was started from April 1, 2005 and is
ending on September 30, 2007 with a total budget of
$105,392. One weak aspect of synthetic polymer materials
compared with steel and other metals is that these
materials are combustible under certain conditions.
Thus, the majority of polymer-containing end products
must pass some type of regulatory test to assure public
safety from fire. Although halogenated flame retardants
are highly effective for reducing heat release rates of
commodity polymers, the future use of some of these
retardants is becoming highly questionable in Europe and
possibly worldwide. Therefore, new, highly effective
flame retardants are urgently needed as a possible
alternative to conventional halogenated flame
retardants. The main objective is to determine the flame
retardant (FR) effectiveness of various polymer/nanotube
nanocomposites and to understand their FR mechanisms.
Four different nanotubes are used; they are multi-walled
carbon nanotube (MWNT), single-walled carbon nanotube
(SWNT), carbon nano-fiber (CNF), and alumina silicate
nanotube (ASNT). The selected resins are polystyrene
(PS) and poly(methyl methacrylate) (PMMA). The study
consists of five parts aimed at understanding the FR
mechanisms of these nanocomposites, (1) effects of
nanotube type and of concentration of the nanotubes in
the nanocomposites, (2) effects of the dispersion
of the nanotubes in the nanocomposites, (3) effects of
molecular weight of the resin, and (4) effects of
viscoelastic characteristics of the nanocomposi tes, (5)
effects of aspect ratio (length divided by outer
diameter of tubes). A cone calorimeter and the nitrogen
gasification device are used for measuring flammability
properties of the samples. The results of the first, the
third, and the fourth parts were published in Nature
Materials and the paper is included in this report. The
results of the second part (effects of dispersion) were
published in Polymer and also the results of the fifth
part (effects of aspect ratio) are being published in
Polymer. Both papers are included in this report.
Finally, a review of flammability of carbon nanotube
based polymer nanocomposites was published as one of
chapters in "Flame Retardant Polymer Nanocomposites"
edited by A. Morgan and C. Wilkie, Wiley Interscience,
2007 and this review is also included in this report.
Nanocomposites based on ASNT with PMMA were prepared for
mass concentrations of 1%, 2% and 4% of ASNT. However,
ASNT was not well dispersed (translucent instead of
transparent) and special functional component was
attached to ASNT surface to improve the dispersion of
ASNT. Although some improvement in the dispersion of
ASNT was made, no significant reduction in flammability
properties of PMMA was observed.