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Flame Retardant Mechanism of the Nanotubes-Based Nanocomposites. Final Report.


pdf icon Flame Retardant Mechanism of the Nanotubes-Based Nanocomposites. Final Report. (6213 K)
Kashiwagi, T.

NIST GCR 07-912; Final Report; 68 p. September 2007.

Sponsor:

National Institute of Standards and Technology, Gaithersburg, MD

Keywords:

flame retardants; nanocomposites; nanotubes; flammability; polymethyl methacrylate

Abstract:

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.