Flammability and thermal stability of polymer layered silicate nanocomposites

Flammability and thermal stability of polymer/ layered silicate nanocomposites 

Plastics and textiles find many uses and add greatly to the quality of modem day life. However, a major problem arises because most of the polymers on which these materials are based are organic and thus flammable. Most deaths due to fire are caused by inhalation of smoke and toxic combustion gases, carbon monoxide being the most common, and serious injuries can result from exposure to the heat involved. What is of major interest in the plastics and textiles industries is not the fact that their products bum but how to render them less likely to ignite and, if they are ignited, to bum much less efficiently. The phenomenon is termed flame retardance . 

Contrary to what many people think, PLSNs are not a recent discovery. One of the earliest systematic studies of the interaction between a clay mineral and a macromolecule dates backs to 1949, when Bower described the absorption of DNA by montmorillonite. Even in the absence of X-ray diffraction (XRD) evidence, this finding implied insertion of the macromolecule in the lamellar structure of the silicate. In the case of synthetic polymers, Uskov found in 1960 that the softening point of polymethylmethacrylate derived by polymerisation of methylmethacrylate was raised by montmorillonite modified with octadecyl-ammonium, while in the following year Blumstein obtained a polymer inserted in the structure of a montmorillonite by polymerising a previously inserted vinyl monomer. In 1965 Blumstein first reported the improved thermal stability of a PMMA/clay nanocomposite. He showed that PMMA inserted between the lamellae of montmorillonite clay resisted thermal degradation under conditions that would otherwise completely degrade pure PMMA.  

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- 

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