Thermoset fire retardant nanocomposites

Building and Fire Research Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 

Flame Retardant Polymer Nanocomposites, edited by Alexander B. Morgan and Charles A. Wilkie Copyright 2007 lohn WHey Sons, Inc. 

This characteristic also greatly affects the flammability of polymeric nanocomposites through three main mechanisms  

High-aspect-ratio nanoparticles, reassembling on the polymer surface during combustion, create an intercalated carbonaceous-silicate residue that lowers the rate of diffusion of the degradation products by a labyrinth effect.  

The large surface area for nanofiller-polymer contact enhances catalytic effects such as the catalysis of charring reactions or radical trapping mechanisms.  

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Zammarano, M. 2007. Thermoset fire retardant nanocomposites. In Flame Retardant Polymer Nanocomposites, Eds. A. Morgan and C. Wilkie, New York John Wiley Sons. 

In 1976 Unitika Ltd, Japan, first presented the potential flame retardant properties of polyamide 6 (PA6)/layered silicate nanocomposites. However, not until more recent studies did the serious evaluation of the flammability properties of these materials begin when Gilman et al. reported detailed investigations on flame retardant properties of PA6/layered silicate nanocomposite. From this pioneering work many attempts have been made to study the flammability properties of polymer/layered silicate nanocomposites. A wide range of polymers has been employed to provide either intercalated or exfoliated nanocomposites, which exhibit enhanced fire retardant properties. These include various thermoplastic and thermosetting polymers, such as polystyrene (PS), high impact polystyrene (HIPS), poly(styrene-co-acrylonitrile) (SAN), acrylonitrile-butadiene-styrene (ABS), polymethyl methacrilate (PMMA), " polypropylene 14,15,19-22 polyethylene is, 19,23-27 poly(ethylene-... 

Thermosetting nanocomposites exhibit a reduced rate of heat release compared to neat polymer. However, the approach to nanocomposites itself is not sufficient to comply with the actual fire test standards. For this reason, traditional flame retardants are currently used in combination with nanofillers, and researchers are focusing on the individuation of synergistic systems. As an alternative to the most common cationic clays, anionic clays show improved performance in terms of flame retardancy. Epoxy nanocomposites based on anionic clay exhibit unique self-extinguishing behavior in a UL-94 horizontal burning test never observed before in a pure nanocomposite. The formation of a continnous intu-mescent ceramic layer on the surface of a polymer during combustion reduces the heat release rate to a higher extent than do montmorillonite nanocomposites. 

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